WO2019036767A1 - Percrystallisation method and porous material for use therein - Google Patents

Percrystallisation method and porous material for use therein Download PDF

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Publication number
WO2019036767A1
WO2019036767A1 PCT/AU2018/050903 AU2018050903W WO2019036767A1 WO 2019036767 A1 WO2019036767 A1 WO 2019036767A1 AU 2018050903 W AU2018050903 W AU 2018050903W WO 2019036767 A1 WO2019036767 A1 WO 2019036767A1
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Prior art keywords
layer
porous material
pores
porous
carbon
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PCT/AU2018/050903
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French (fr)
Inventor
Christelle YACOU
Joe Diniz DA COSTA
Julius MOTUZAS
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The University Of Queensland
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Priority claimed from AU2017903432A external-priority patent/AU2017903432A0/en
Application filed by The University Of Queensland filed Critical The University Of Queensland
Publication of WO2019036767A1 publication Critical patent/WO2019036767A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0018—Evaporation of components of the mixture to be separated
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0018—Evaporation of components of the mixture to be separated
    • B01D9/0027—Evaporation of components of the mixture to be separated by means of conveying fluid, e.g. spray-crystallisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/021—Carbon
    • B01D71/0211—Graphene or derivates thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0039—Inorganic membrane manufacture
    • B01D67/0067—Inorganic membrane manufacture by carbonisation or pyrolysis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/14—Dynamic membranes
    • B01D69/141—Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes
    • B01D69/148—Organic/inorganic mixed matrix membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/021—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/024—Oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0077—Screening for crystallisation conditions or for crystal forms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
    • B01J20/3234—Inorganic material layers
    • B01J20/3236—Inorganic material layers containing metal, other than zeolites, e.g. oxides, hydroxides, sulphides or salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
    • B01J20/3234—Inorganic material layers
    • B01J20/324—Inorganic material layers containing free carbon, e.g. activated carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D2009/0086—Processes or apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2221/00—Applications of separation devices
    • B01D2221/06—Separation devices for industrial food processing or agriculture
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2221/00—Applications of separation devices
    • B01D2221/10—Separation devices for use in medical, pharmaceutical or laboratory applications, e.g. separating amalgam from dental treatment residues
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/26—Further operations combined with membrane separation processes
    • B01D2311/2673—Evaporation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes
    • B01D2325/021—Pore shapes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
    • B01D61/362—Pervaporation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0018—Evaporation of components of the mixture to be separated
    • B01D9/0022—Evaporation of components of the mixture to be separated by reducing pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0018—Evaporation of components of the mixture to be separated
    • B01D9/0031—Evaporation of components of the mixture to be separated by heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/42—Materials comprising a mixture of inorganic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/46—Materials comprising a mixture of inorganic and organic materials
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F2001/5218—Crystallization

Definitions

  • the present invention relates to a method for producing a solid material using percrystallisation and to a porous material for use in a percrystallisation process.
  • Crystallisation is an important industrial process generating a wide range of products throughout the world. Examples include sugar, which is staple in food consumption, lysozyme as an antibacterial agent used in food and pharmaceutical, intermediate metal compounds in metal extraction, such as nickel sulfate hydrate in hydrometallurgy. A large number of other products are also produced using crystallisation processes.
  • Brine processing is employed worldwide for the production of lithium, potassium and magnesium, which are global commodities with a combined annual worth in excess of $200 billion per year. Lithium is extensively used in batteries, potassium is widely used as a component of fertilizers for agricultural activities and magnesium has several applications ranging from health to metal alloying. Brine processing and recovery is also becoming a matter of consideration in water desalination, driven by environmental concerns and economic forces, particularly that the recovery value of discharged salts could exceed by a factor of 10 the value of the potable water produced.
  • the emerging coal seam gas (CSG) industry in Australia is facing strong scrutiny in the processing of saline CSG water to comply with best zero liquid discharge (ZLD) practices.
  • solar evaporation ponds are used in certain applications.
  • solar evaporation is a very slow process which takes on the order of 12-18 months to dry mineral brines, even in arid regions. Further, large areas of land are required for the solar evaporation ponds.
  • the present invention is directed to a method for producing a solid material from a solution and a porous material having mesoporous porosity for use in the method, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.
  • the present invention in one form, resides broadly in a method for producing a solid material from a solution containing one or more dissolved species or products dissolved in solvent, the method comprising the steps of providing the solution to one side of a porous material, the porous material having pores in the mesoporous and/or macroporous pore size range, wherein solution comprising the solvent and the dissolved species or products passes through the porous material, and evaporating at least part of the solvent from the other side of the porous material, characterised in that a solid material is crystallised and recovered from the other side of the porous material.
  • the method comprises evaporating solvent from the other side of the porous material at substantially the same rate or faster than a rate of solvent passing through the porous material to form a solid material on the other side of the porous material.
  • the porous material has at least a layer comprising an inorganic layer having mesoporous pores or macroporous pores and/or a carbon layer having mesoporous pores or macroporous pores, or a mixed matrix having mesoporous pores or macroporous pores comprising carbon and another material.
  • the porous material has at least a layer comprising an inorganic layer having mesoporous pores and/or a carbon layer having mesoporous pores, or a mixed matrix comprising carbon and another material having mesoporous pores.
  • the porous material has at least a layer comprising an inorganic layer having macroporous pores or a carbon layer having macroporous pores, or a mixed matrix comprising carbon and another material having macroporous pores.
  • the porous material comprises a porous polymer.
  • a mesoporous material is a material containing pores with diameters between 2 and 50 nm, according to IUPAC nomenclature.
  • IUPAC defines microporous material as a material having pores smaller than 2 nm in diameter and macroporous material as a material having pores larger than 50 nm in diameter.
  • the porous material is not a microporous material.
  • the material is a macroporous material having a pore size in the range of from 50nm to 1 ,000nm, or 50nm to 500nm, or 50 nm to 250nm, or 50nm to 200nm, or 50nm to 150m, Or 50nm to 125nm, or 50nm to 1 lOnm.
  • the present invention provides a method for producing a solid material from a solution containing one or more dissolved species or products dissolved in solvent, the method comprising the steps of providing the solution to one side of a porous material, the porous material having pores in the mesoporous and/or macroporous pore size range, wherein solution comprising the solvent and the dissolved species or products passes through the porous material, and evaporating at least part of the solvent from the other side of the porous material, characterised in that a solid material is crystallised and recovered from the other side of the porous material wherein the porous material has porosity such that it retains molecules having a molecular weight of greater than 100,000 Daltons and the layer has pores of larger than 2nm.
  • the porous material may be as described with reference to the first aspect of the present invention.
  • the process of the present invention utilises a porous material having at least a layer comprising an inorganic layer or region having mesoporous pores and/or a carbon layer or region having mesoporous pores.
  • the porous material comprises an inorganic porous material having at least a layer comprising an inorganic layer having mesoporous pores and/or macroporous pores and/or a carbon layer having mesoporous pores and/or macroporous pores and a substrate having pore sizes larger than pores in the layer, and the at least one layer having mesoporous pores.
  • the layer comprising an inorganic layer having mesoporous pores and/or a carbon layer having mesoporous pores comprises a layer formed on a surface of the substrate, or comprises a plurality of layers formed on a surface of the substrate.
  • the majority of the pores of the mesoporous layer are between 2 to 50 nm in diameter, even more preferably between 2 to 30 nm, still more preferably between 2 to 10 nm.
  • the porous material is a porous inorganic membrane that comprises a hierarchical membrane comprising layers with pores at different length scales including the micro-, meso- and macroporous range.
  • the porous inorganic membrane may be a stratified asymmetric membrane having layers with pore sizes differing from those layers in which they are in contact with.
  • the porous material comprises a porous inorganic substrate coated with a layer of inorganic material.
  • This porous material may be produced by coating one side of a porous inorganic substrate with one or more layers of inorganic material.
  • the one or more layers of inorganic material may be coated onto the substrate by way of coating with a sol or a gel, followed by calcination and/or carbonisation.
  • the porous inorganic substrate may have large pores than the layer of inorganic material.
  • the layer of inorganic material may have mesoporous pores.
  • the porous material may comprise a porous substrate that has one or more layers of carbon thereon.
  • the one or more layers of carbon may be formed by an impregnation method in which a carbonaceous liquid or a carbonaceous solution is impregnated onto one side of the porous substrate, followed by carbonising the carbonaceous material to form the carbon layer.
  • the carbonaceous liquid or carbonaceous solution comprises a solution in which a carbonaceous material is dissolved.
  • the carbonaceous solution may comprise a dissolved saccharide in water.
  • the carbonaceous liquid may comprise a resin, such as a phenolic resin or a polymer precursor.
  • the one or more layers of carbon may have mesoporous pores.
  • the one or more layers of carbon may have macroporous pores.
  • the one or more layers of carbon may have mesoporous pores and macroporous pores.
  • the layer comprises a mixed matrix membrane containing carbon and MOFs (metallic organic frameworks).
  • MOFs metal organic frameworks
  • the layer may be formed by impregnating and/or coating a carbonaceous liquid containing MOFs into a substrate, followed by carbonisation.
  • the layer may have mesoporous pores or macroporous pores or mesoporous pores and macroporous pores.
  • the process of the present invention can be used to produce a wide range of products. Indeed, the present inventors believe that most products that are presently made by conventional crystallisation processes can be made by the process of the present invention.
  • Products that may be made by the process of the present invention include mineral salts, food additives, pharmaceuticals and chemical products.
  • Some examples of specific products that can be made by the present process include chloride salts (such as nickel chloride, magnesium chloride, potassium chloride, lithium chloride and sodium chloride), nitrate salts (such as nickel nitrate), crystalline acids (such as ascorbic acid), pharmaceuticals and vitamins (such as vitamin C) and food additives (such as sodium lactate).
  • the solution that is supplied to the process of the present invention may comprise an aqueous solution containing dissolved material.
  • the solution that is supplied to the process of the present invention may comprise a non-aqueous solution containing dissolved material.
  • the porous material used in the process of the present invention may have a flat geometry (such as a sheet or a plate) or the porous material may be in a tubular form, or in the form of hollow fibres, or capillary fibres. If a porous material of tubular shape is used, the tube may be open at both ends or it may be closed at one end.
  • the porous material may comprise a flat porous substrate that has a layer of the mesoporous inorganic material or a layer of mesoporous carbon material thereon or therein.
  • the porous material may comprise a tubular article in which a tubular porous substrate has a layer of the mesoporous inorganic material or the mesoporous carbon material thereon or therein.
  • the layer of the mesoporous material may be coated on the inner shell of the tubular substrate, or it may be coated on the outer shell of the tubular substrate.
  • the porous membrane may form at least one wall of a hollow membrane chamber.
  • the process of the present invention may be conducted as a batch process.
  • the process of the present invention may be conducted as a continuous process.
  • the process of the present invention comprises a batch process in which the solution is fed to an inner part of a tubular porous material and crystals of material grow on an outer part of the tubular porous material, with the crystals growing in batches and being removed from the outer part of the tubular porous material by a drying process or microwave irradiation.
  • the crystals are removed from the outer part of the tubular porous material by mechanical action.
  • the crystals can be ejected from the tubular porous material by microwave irradiation.
  • the process of the present invention comprises a continuous process in which the solution is fed to an inner part of a tubular porous material and crystals of material grow on an outer part of the tubular porous material, with the crystals continuously growing and being removed from the outer part of the tubular porous material during operation of the process.
  • the crystals fall off the outer part of the tubular porous material under their own weight.
  • the process further comprises applying a vacuum to the other side of the porous material.
  • Applying a vacuum to the other side of the porous material promotes evaporation of the solvent passing through the porous material and can increase the rate of crystallisation.
  • the present inventors have found that vacuum speeds up the crystallisation process, thus increasing crystal production rates.
  • crystallisation also occurred at ambient pressures and temperatures, i.e. with no vacuum applied to the permeate side.
  • the level of pressure on the permeate side of the porous material may range from ambient pressure (typically 1 atm) down to very low vacuum pleasures below 1 Torr. (these pressures are given as absolute pressures, not gauge pressures).
  • the process further comprises heating the solvent passing through or that has passed through the porous material. Again, heating the solvent passing through the porous material promotes evaporation of the solvent passing through the porous material, which can increase the rate of crystallisation.
  • the solvent passing to the porous material is heated to a temperature within the range of from ambient temperature up to the boiling point of the solvent.
  • the solution is heated prior to passing through the membrane. The solution may be heated using waste heat, solar ponds, microwave radiation, or conventional heating technologies.
  • the solution that is supplied to the porous material is pressurised. In another embodiment, the solution is supplied under ambient pressure.
  • the process of the present invention provides a percrystallisation process in which crystals are formed on and recovered from the filtrate side or permeate side of the porous material. As mentioned above, this is quite distinct to all prior art percrystallisation processes known to the inventors, in which the crystals are formed on and recovered from the retentate side of the porous membrane.
  • the percrystallisation process in accordance with the present invention can deliver a range of crystal shapes and sizes.
  • the percrystallisation process can result in the formation of small cubic crystals with side dimensions ranging from 10 to 20 ⁇ , in addition to polymorph crystals, or in the formation of small polymorph and cubic crystal, or in the formation of elongated polymorph crystals, or in the formation of small flakes, or in the formation of very small crystals almost like needle- geometries, or in the formation of filaments.
  • the present invention also relates to a porous material for use in the process of the first aspect of the present invention.
  • the present invention provides a porous material for use in a percrystallisation process, the porous membrane comprising a porous substrate having a layer thereon or therein, the layer comprising an inorganic layer having mesoporous pores and/or macroporous pores, and/or a carbon layer having mesoporous pores and/or macroporous pores or a mixed matrix having mesoporous pores and/or macroporous pores comprising carbon and another material, the porous substrate having a porous structure having pores that are larger than mesoporous pores.
  • the present invention provides a porous material having at least a layer comprising an inorganic layer and/or a carbon layer and/or a mixed matrix comprising carbon and another material, wherein the layer has porosity such that it retains molecules having a molecular weight of greater than 100,000 Daltons and the layer has pores of larger than 2nm.
  • the layer comprises a mixed matrix having mesoporous pores comprising carbon and another material, wherein the mixed matrix comprises a composite of carbon and MOFs (metal-organic framework material).
  • MOFs metal-organic framework material
  • the layer having mesoporous pores or macroporous pores is relatively thin and the substrate is relatively thick.
  • the layer having mesoporous porosity has a thickness of from 0.5 to 5 ⁇ and the substrate as a thickness of from 100 ⁇ to 5 cm.
  • the substrate provides mechanical strength. Accordingly, the thickness of the substrate may vary widely, bearing in mind that the substrate should have a minimum thickness that provides for the minimum acceptable strength for the porous material.
  • the thickness of the substrate may vary widely, depending upon the particular substrate and the size of the structure. For example, porous inorganic hollow fibres could have a thickness in the range of from 200 ⁇ to 1 mm. Conventional substrate tubes that may be purchased commercially may have a thickness of from 1.5 to 2 mm. The thickness of the substrate may increase as the diameter of the tube increases. Other thicknesses are also included in the present invention.
  • the porous material has a layer having mesoporous pores and the majority of the pores of the mesoporous layer are between 2 to 50nm in diameter, even more preferably between 2 to 30 nm, still more preferably between 2 to 10 nm.
  • the mesoporous layer comprises an inorganic material or carbon.
  • the inorganic material may comprise a metal oxide, such as a titanium oxide, a zirconium oxide or an aluminium oxide, or a mixture of these metal oxides.
  • the inorganic material comprises ⁇ -alumina. Porous mixed metal oxides may also be used.
  • the mesoporous layer comprises carbon.
  • the carbon may comprise porous graphite, porous graphene, agglomerates of carbon nanotubes, agglomerates of carbon fibres, and the like.
  • a porous carbon membrane may be applied to the substrate.
  • the substrate may comprise a porous inorganic material, such as a porous metal oxide material or a porous metal.
  • the substrate may comprise titanium dioxide, zirconium dioxide, aluminium oxide, or a mixture of two or more thereof. Other metal oxide substrates or mixed metal oxide substrates may also be used.
  • the substrate may comprise a porous metal substrate, such as a porous stainless steel substrate. Other metals may also be used.
  • the porous material has a layer of carbon and the layer of carbon has macroporous pores.
  • the layer of carbon may also include mesoporous pores.
  • the substrate has a porosity that includes pore sizes that are larger than the pores included in the mesoporous layer.
  • the bulk of the pores in the substrate may be sized at 50nm or larger, or lOOnm or larger, or 500nm or larger.
  • the substrate may have a relatively regular pore size with a narrow pore size distribution, or it may have a relatively irregular or random pore size with a broad pore size distribution.
  • the substrate is formed using sol-gel synthesis, followed by firing or sintering, and the mesoporous layer is formed by dipping the substrate in a sol.
  • the solid material is in the form of a flat sheet or a flat plate.
  • the solid material is in the form of a tube or a pipe.
  • the tube or pipe may have an inner diameter of from less than 0.25mm to 0.5 - 1.0 cm or even larger.
  • the substrate may comprise a commercially available material and the diameter can be any diameter that is commercially available.
  • the solid material is in the form of porous hollow fibres.
  • the fibres may have an inner diameter of less than 0.25 mm. It is believed that using smaller tubes in the percrystallisation process is preferable to increase the surface area to volume ratio.
  • a plurality of tubes or pipes or hollow fibres are used.
  • the present inventors believe that, in some embodiments, providing a solid material having a layer of inorganic material or carbon, with that layer having mesoporous porosity and/or macroporous porosity is important in the present invention.
  • the present inventors have found that using a porous material having pore sizes of less than 2nm would not result in the formation of crystals, presumably because the pore sizes are too small for the dissolved material in solution to pass through the pores.
  • using porous material having pore sizes that are too large is believed to allow the solution to fully permeate through the porous material without any retention of salts or other dissolved materials in the pores, thereby effectively flooding the other side of the porous material and preventing formation of crystals.
  • the present inventors have also found that mesoporous metal oxides materials worked well for batch processes whereas carbon mesoporous materials worked well for continuous processes.
  • the present inventors have found that it is preferred that where the porous material contains a layer of inorganic oxide, the layer of inorganic oxide has mesoporous pores.
  • the porous material comprises a layer of carbon
  • the present inventors have found that layer of carbon can have mesoporous pores or macroporous pores, preferably with a maximum pore size not exceeding 500nm or not exceeding 250nm.
  • Figure 1 shows an SEM image of a mesoporous titania membrane (3-5 nm pores) coated on ⁇ -alumina interlayer on a -alumina substrate used in batch processes;
  • Figure. 2 shows a graph of crystallisation rate of chloride salts (LiCl, NaCl, C1, CaCl 2 , MgCl 2 , MnCl 2 , MnC12, CuCk, NiCh) (feed concentration of 3mol/L salt at 20 C, pervaporation time 10 min, microwave power lOOOw, microwave time 2 min) for a batch process;
  • chloride salts LiCl, NaCl, C1, CaCl 2 , MgCl 2 , MnCl 2 , MnC12, CuCk, NiCh
  • Figure 3 shows graphs of water and percrystallised salt flux as a function of (A) temperature with feed solutions of NaCl 17.5 wt% and (B) salt feed concentration with feed temperature at 37 C for a continuous process;
  • Figure. 4 shows a graph of crystallisation rate of KC1, MgCl 2 and NiCh (17.5 wt% at 37 C), oxalic acid and vitamin C (2.5 wt% at 37C)for a continuous process;
  • Figure 5 shows a schematic diagram for a postulated mechanism for the
  • Figure 6 shows micrograph images of NaCl, KC1, MgCl 2 , NiCl 2 , oxalic acid and vitamin C obtained using percrystallisation in accordance with embodiments of the present invention
  • Figure 7 (a) shows carbon mass content in membrane material after carbonisation as a function of sucrose concentration used for dip-coating; and Figure 7 (b) shows SEM images of the cross-section of carbonised sucrose membranes using 20 Wt%, 30 Wt%, 40 Wt , and 50 Wt% in Example 10;
  • Fig. 8 (a) shows water and nickel fluxes as a function of the sucrose concentration used for dip coating (20-50 Wt%), using a feed concentration of 40 g(Ni) L "1 and a temperature of 40°C. Nickel flux given as mass of metallic nickel permeated as nickel sulphate; and Figure 8(b) shows nickel production percentage contribution of total mass production as a function of sucrose concentration;
  • Fig. 9 (a) shows water and nickel fluxes as a function of feed concentration used for dip coating (10-100 g L "1 ), using a membrane dip-coated in 20 Wt% sucrose and a temperature of 40 °C. Nickel flux given as mass of metallic nickel permeated as nickel sulphate; and figure 9 (b) shows nickel production percentage contribution of total mass production as a function of feed concentration; [0071] Fig. 10 (a) shows water and nickel fluxes as a function of operation temperature used for dip coating (30-60°C), using a membrane dip-coated in 20 Wt sucrose and a feed concentration of 40 g L "1 . Nickel flux given as mass of metallic nickel permeated as nickel sulphate; and figure 10(b) shows nickel production percentage contribution of total mass production as a function of operation temperature;
  • Fig. 11 (a) shows XRD patterns of nickel sulphate crystals produced by different dip- coating concentrations, with the 40 and 50 Wt% produced crystals showing hexahydrate diffractions
  • Figure 11(b) shows XRD patterns of nickel sulphate crystals produced by different feed concentration, only 100 g L "1 showing hexahydrate diffractions
  • Figure 11(c) shows XRD patterns of crystals produced by different operating temperature, with 50 °C showing hexahydrate peaks;
  • Fig. 12 shows SEM images of percrystallised products from different tests in Example 10.
  • Figure 13 shows SEM photomicrographs showing the crystal morphology of the paracetamol crystals produced in example 11, with figure 13 (a) showing the crystals produced using a membrane made from a 5% sucrose solution, figure 13 (b) showing the crystals produced using a membrane made from a 10% sucrose solution, figure 13 (c) showing the crystals produced using a membrane made from a 20% sucrose solution, and figure 13 (d) showing the crystals produced using a membrane made from a 30% sucrose solution;
  • Figure 14 shows SEM photomicrographs of paracetamol crystals collected after (a) 5 min, (b) 2h, and (c) 18h of operation from the membrane surface in Example 12.
  • Figure 15 shows SEM images of the cross-sections of carbonised sucrose membranes at a) 650°C, b) 700°C and c) 750°C;
  • Figure 16 shows mercury porosimetry data (a) pore size distribution and (b) accumulated pore volume for the carbon membranes obtained at 650, 700 and 750 °C;
  • Figure 17 show a graph of NaCl and water fluxes as a function of the membrane carbonisation temperature (650, 700 and 750 °C) at a permeate pressure of 18 mbar;
  • Figure 18 shows a graph of NaCl and water fluxes as a function of permeate operating pressures (18, 22 and 26 mbar) for a membrane carbonised at 750 °C;
  • Figure 19 shows SEM pictures and corresponding histograms of NaCl particles produced by percrystallisation as a function of membrane's carbonisation temperature.
  • Percrystallisation conditions 18 mbar permeate pressure, feed solution temperature at 37°C and NaCl concentration of 17.5 wt%;
  • Figure 20 shows SEM pictures and corresponding histograms of NaCl particles produced by percrystallisation at various operating pressures and using a carbon membrane (carbonised at 750°C).
  • Percrystallisation conditions feed solution temperature at 37°C and NaCl concentration of 17.5 wt%;
  • Figure 21 shows XRD patterns of NaCl crystals produced by percrystallisation with sucrose derived membranes carbonised at 650, 700 and 750°C;
  • Figure 22 shows graphs of (a) NaCl crystallite size versus pore volume and (b) water flux versus pore volume for sucrose membranes carbonised at various temperatures;
  • Figure 23 shows graphs of NaCl particle size versus water flux (a) for the sucrose membrane carbonised at various temperatures and tested at 18 mbar, and (b) for sucrose membranes carbonised at 750 °C and tested at various pressures.
  • pore diameter (d p ) and membrane materials were key parameters which enables the desired percrystallisation properties to be obtained.
  • Salt crystals could be formed in mesoporous titania, gamma-alumina and carbon membranes, but not for other membranes such as microporous (d p ⁇ 2 nm) silica and carbon molecular sieves.
  • macroporous membranes having pores larger than mesoporous pores did not form crystals.
  • micropores were too small to store hydrated salt ions with radius of C1 ⁇ -H 2 0 (6.64 A) and Na + -H 2 0 (7.16 A), whilst pore wetting occurred in macropores as the salt solution fully permeated through the membrane without any retention of salts.
  • the present inventors have postulated that the instantaneous percrystallisation of salts in the membranes is schematically idealised in Fig. 5. Under pervaporation, a wet thin-film is formed on the surface of the membrane. Under the testing conditions, flooding did not occur suggesting that mesopores were modulating the flow of solution from the feed side to the wet thin-film on the permeate side of the membrane. This causes heat transfer improvement of thin-films, thus promoting evaporation close to the apparent solid-liquid-vapour contact line. For instance, we observed that percrystallisation occurred even at atmospheric conditions, due to the evaporation of water.
  • Permeation testing was conducted in a cross flow set up when the solution was fed via the inner shell of the tube.
  • the permeate stream via the outer shell of the tube was collected in a beaker and the mass was continuously recorded using an electronic scale.
  • the collected permeate solution was analysed using a Shimadzu UV- 2700 UV-vis spectrometer to determine the concentration of PVP against calibration curves.
  • EXAMPLE 4 Preparation of mesoporous ⁇ -alumina membranes
  • the substrates were pre-calcined at 1000 °C for 8 h with a ramp rate of 5 °C min -1 to improve the mechanical strength and to remove any organic impurities.
  • the a-alumina substrates were coated with three ⁇ -alumina layers, which were derived from an aluminium oxide (10%) in water sol with an average colloidal particle size of 0.05 ⁇ (Alfa Aesar). Dip coating was used at a dip and withdrawal speed of 5 cm min "1 , and holding time of 1 min.
  • the membranes were calcined in air at 500 °C at a ramping rate and cooling rate of 1 °C min "1 , and a holding time of 1 hour.
  • the final membrane coated on a ⁇ -alumina tube had up to 3 ⁇ -alumina top-layers.
  • titania membranes were prepared on the top of the ⁇ -alumina membranes as described above and following the same coating methods adopted for the ⁇ -alumina as interlayers.
  • the final membrane coated on a ⁇ -alumina tube had 3 ⁇ -alumina interlayers and 3 titania top-layers.
  • Titania was synthesised from a sol-gel method. Briefly, titanium(IV) propoxide (TTP,TiCi2H280 4 , 98%, Sigma-Aldrich) was added drop-wise into a solution of double distilled water and hydrochloric acid under vigorous stirring. Then the mixture was maintained in a water bath at 30 °C for 3 hours. The molar ratio of final sol was
  • TTP:HC1:H 2 0 1: 1:22.
  • the sol was dried in a temperature controlled oven at 60 °C for 3 h.
  • the dried gel was treated at 150°C(heating rate ofl °C min "1 , dwell time of 1 h) to ensure the consolidation of theTi02matrix and then calcined at 350 °C (heating rate of 1 °C min "1 , dwell time of 1 h) to confer a gentle thermal effect on the mesostructure of the T1O2 matrix.
  • Carbon membranes were prepared by an impregnation method with various saccharides as an organic precursor.
  • the saccharides were commercial food grade sugar (glucose, fructose, maltose and sucrose).
  • the solid sugar was dissolved in deionised water at 10- 40%wt concentration.
  • the contact time between the tube and sugar solution varied between 1 min to 4 hours.
  • vacuum pressures up to less than 1 Torr
  • the coated substrate was dried for 15 hours in an oven at 60°C.
  • the impregnated saccharide in the substrate was carbonised in an argon atmosphere at 700°C for 8 hours at heating and cooling rate of 5°C min "1 .
  • Phenolic resin Resinox IV- 1058 was used as precursor to prepare carbon membranes.
  • a dip coating method was used, where a substrate was immersed into the phenolic resin solution for 1 min of holding time with 10 cm min "1 dipping and withdrawal rate. After dip coating, the membrane was immediately exposed to a vacuum pressure ( ⁇ 1 Torr) via the inner shell of the tube for a desired time (from 30 to 1200 s).
  • the coated membranes were cured in an oven at 60 °C for 24 hours and carbonised in an inert nitrogen atmosphere with a ramping and cooling rate of 5 °C min "1 up to 700 °C and a dwell time of 2.5 h.
  • the solutions containing ZIF-8 were well mixed in centrifuge tube, followed by sonication for -60 minutes.
  • a dip coating method was used, where a substrate was immersed into the phenolic resin solution for 1 min of holding time with 10 cm min "1 dipping and withdrawal rate. After dip coating, the membrane was immediately exposed to a vacuum pressure ( ⁇ 1 Torr) via the inner shell of the tube for a desired time (from 30 to 1200 s).
  • the coated membranes were cured in an oven at 60 °C for 17 hours and carbonised in an inert nitrogen atmosphere following several steps as follows: 20°C (dwell time of 20 minutes) ramp to 120 °C (rate of 5 °C min "1 ), 120°C (dwell time 60 minutes), ramp to 450°C (rate of 5 °C min "1 ), 450°C (dwell time 4 hours), cooling down to room temperature (rate ⁇ 7 °C min "1 ), 25°C.
  • the percrystallisation method is accordance with embodiments of the present invention can deliver a range of shapes and sizes obtained in continuous membrane
  • micrograph images Fig. 6 show the formation of small cubic NaCl crystals with side dimensions ranging from 10 to 20 ⁇ , in addition to polymorph NaCl crystals.
  • C1 formed crystal similarly to NaCl, though NiCk resulted in larger and elongated polymorph crystals.
  • Vitamin C also formed very small crystals almost like needle-geometries, whilst oxalic acid percrystallised as filaments. MgCk resulted in the formation of small flakes.
  • Membrane coating solutions were prepared by dissolving 20, 30, 40 and 50 Wt % sucrose (>99.8% Chem-supply) respectively into demineralised water. The sucrose solutions were mixed, followed by 30 minutes of sonication. The solutions were then used to dip-coat a- alumina substrates (Ceramic Oxide Fabricators, Australia). The substrates were of a mean pore size of 0.1 microns. The total length of the substrates was ⁇ 4 cm in length, 1 and 0.45 cm in external and internal diameters, respectively. Dip-coating was performed on the outer layer of the a-alumina support. The tube was submerged in a solution for three minutes with a subsequent withdrawal from the solution.
  • the submersion and retraction speed was -31 cm min .
  • a vacuum was applied through the inside of the sucrose-coated support ( ⁇ 1.3 mbar), causing a partial impregnation of the thin-film onto the a-alumina tube. The partially
  • impregnated supports were dried overnight at 60°C, before being carbonised in an inert nitrogen atmosphere at 750°C.
  • the heating and cooling ramps were 5 K min "1 with a dwell time of 4 h once 750°C was reached.
  • the membranes' surfaces were coated with Protek type N blue solvent cement at the ends to create a seal, so the ends of the membranes can be used for mounting onto a percrystallisation system, leaving ⁇ 3 cm active membrane surface for testing.
  • Morphology of the produced membranes were analysed by scanning electron microscope (SEM), using a Jeol JSM-7001F SEM with a hot (Schottky) electron gun, with an acceleration voltage of 5 kV.
  • Nickel sulphate solutions were prepared by dissolving amounts of N1SO4.6H2O (> 98% Chem-Supply) in demineralised water to acquire the desired concentrations (10, 40, 70, and 100 g L "1 ) in order to test applicability of percrystallisation for production of solid nickel sulphate when using different feed concentrations.
  • the solutions were heated to a desired temperature (30, 40, 50, and 60 °C) and fed through the inner shell of the membrane unit, using a peristaltic pump with a flow rate of ⁇ 31.1 L h "1 to reduce potential concentration and temperature polarisation.
  • a Buchner flask was utilised as a container for the membrane, and as a crystal collection chamber.
  • the crystallisation collection chamber was connected to a cold trap
  • a measured amount of percrystallised nickel sulphate was removed from the crystal collection chamber in order to be used for SEM and XRD analysis, while the rest was dissolved in a known volume of water. The solution was used to determine the production rate of crystalline nickel sulphate via the use of conductivity. The mass of the produced water was used to determine the water production rates during percrystallisation.
  • the collected nickel sulphate powder was analysed by SEM imaging. TGA, analysis was used in order to quantify the mass of dry nickel sulphate was removed. This was done by heating the powder up to 800°C with a heating rate of 10 K min-1 and cooling rate of 20 K min "1 in air.
  • Fig. 7a shows the mass loss of the crushed membrane materials as a function of the concentration of the dipping solution.
  • the mass loss associated with the concentration of the dipping solution increases almost linearly, as the concentration increases. This finding indicates that the carbon content deposited on the a-alumina support is proportional to the sucrose concentration of the dipping solution.
  • Fig. 7b shows the morphology of the cross-section of the prepared membranes. In the figure, a film of carbon material can be observed, with the thickness increasing as the sucrose concentration of the dipping solution increases from 20 wt % to 50 wt %.
  • Fig. 8a shows the fluxes of water and the flux of metallic nickel produced by the crystallisation of nickel sulphate as a function of the sucrose concentration used during dipping of the supports, using an operating temperature of 40°C and a concentration of 40 g L "1 nickel.
  • the initial finding is that all the prepared membranes in this work were able to be used for percrystallisation of nickel sulphate. What is observed is observed is decreasing trend in both water and nickel production as the precursor solution used in producing the membranes increases in concentration. This finding is well-aligned with the visual observations of the membranes in Fig. 8b.
  • Fig. 8b shows the production ratio of nickel production over the total mass production.
  • the ideal ratio of nickel production would be 4.3% of the total mass production.
  • the production ratio of nickel was calculated to be within the experimental error of the 4.3% mark, meaning that the system is non-selective to either water or nickel, which is desirable for a percrystallisation process. This means that there is no accumulation of water or nickel sulphate on the permeate site.
  • Fig. 9a shows the nickel and water production rates of the best performing membrane as a function of the feed concentration. It can be observed that the water production rates decreases as the concentration of nickel sulphate increases, while the opposite is true for the nickel production rates.
  • Fig. 10b illustrates how much the nickel production contributes to the total mass production. It can be observed that the production ratio increases linearly with the black squares being the observed production fraction, while the blue circles is the ideal production ratio. It can again be observed that the membrane is non- selective, even at different solute concentrations.
  • Fig. 1 la presents the production rates of nickel and water, using the best performing membrane, with a nickel concentration of 40 g L "1 while varying the operating temperature. A near linear trend in water and nickel production rates can be observed, while the production ratio in Fig. 10b confirms that the process is non-selective during operation.
  • Fig.l 1 shows the XRD patterns attained by the products.
  • a key finding in the based on the diffractograms is that the solutes produced by membranes prepared with sucrose concentrations of 40 and 50 Wt %, by the feed concentration of 100 g L "1 , or using a feed temperature of 50°C exhibited diffraction peaks consistent with nickel sulphate hexahydrate and nickel sulphate heptahydrate. The remaining samples only consisted of peaks consistent with nickel sulphate heptahydrate.
  • hexahydrate crystals by usage of the membranes produced at higher sucrose concentrations can be explained by the decreased water production rates, as shown in Fig. 8 a.
  • the lower water flux would be caused by a lower transport of solution to the surface of the membrane unit, meaning that less water needs to evaporate per unit of time to attain dry solute.
  • the vacuum pump is operating with a constant output and because of this, more water could be removed. This which would allow for the formation of some hexahydrate crystals during percrystallisation.
  • a similar explanation can be used when explaining why a nickel feed concentration of 100 g L "1 allowed for production of hexahydrate nickel sulphate crystals.
  • the apparent activation energy for water production was calculated to be 15 kJ mol -1 , while the apparent activation energy for nickel production was found to be 16 kJ mol "1 .
  • the apparent energy of activation for both evaporation of water and percrystallisation of nickel sulphate are both in the range of mass transport-controlled reactions and in the range of diffusion controlled reactions in water.
  • sucrose derived carbon membranes can be used for percrystallisation of hydrometallurgical products like nickel sulphate. It was shown how percrystallisation potentially can be used to tune hydration states of percrystallised products by varying different conditions; increases in carbon content in the membrane allowed for production of nickel sulphate with a lower hydration state, by constricting the flow of solution to the surface. Increases in feed concentrations allowed for a similarly lower trans -membrane transport of water, allowing for the production of hexahydrate crystals. And by increasing the driving force for evaporation through higher operating temperatures would allow for the formation of lower hydration states, assuming that the vacuum levels could be maintained at the same low levels.
  • the apparent activation energies for both water and nickel production was estimated to be in the range of a diffusion or mass-transport limited process.
  • Membrane made from 5% sucrose solution - ethanol flux of 20.22, paracetamol flux of 0.49;
  • Membrane made from 20% sucrose solution - ethanol flux of 16.01, paracetamol flux of 0.89;
  • Membrane made from 30% sucrose solution - ethanol flux of 21.54 and paracetamol flux of 1.04.
  • paracetamol was crystallised using percrystallisation under the following conditions:
  • This example investigates the morphological features of porous carbon membranes and operation effects for the percrystallisation of NaCl.
  • the carbon membranes were prepared by dip coating of a-alumina tubes in a sucrose solution, followed by a post vacuum-assisted impregnation and carbonisation in an inert gas atmosphere.
  • the carbonisation temperature played an important role, as the highest pore volume and wet contact angle were achieved at the highest carbonisation temperature of 750 °C.
  • this created hydrophobic carbon membranes delivering the highest water flux of 33 L m "2 h "1 (NaCl 17.5 wt%) and NaCl flux of 6.9 kg m "2 h 1 .
  • the solvent (water) and the solute (NaCl) crystals were separated in a single-step in a wet thin-film formed on the permeate face of the membrane under pervaporation conditions, delivering almost pure water (>99%) and dry NaCl crystals.
  • the carbon membrane with the highest water flux delivered the smallest NaCl crystallite sizes, the smaller particle sizes, and the narrowest particle size distribution ( ⁇ 2 ⁇ ). This was attributed to the fast water evaporation rate from the wet thin-film, as crystal growth rate was reduced and NaCl particle aggregation was restricted.
  • a finer control of NaCl crystallite and particle size was achieved by tailoring the morphological features of the carbon membranes and operating at the lowest vacuum pressure.
  • sucrose membranes were carbonised in inert gas from 600 to 750 °C and assessed for the percrystallisation of a NaCl (17.5 wt%) solution under various permeated vacuum pressures.
  • the morphology of the carbon membranes was characterised by mercury porosimetry, wet contact angle and SEM analysis.
  • the membranes were tested for both water permeation and NaCl percrystallisation.
  • the formed NaCl particles were analysed statistically using SEM images, and the crystallite sizes were determined by XRD analyses.
  • Solutions were prepared by dissolving 20 wt% sucrose (>99.8%, Chem-supply) into demineralised water which was sonicated for 30 min. Subsequently, the sonicated solution was used for dip coating of tubular a-alumina substrates (Ceramic Oxide Fabricators, Australia) with a mean pore size of 0.1 ⁇ . Both ends of the tube were glazed, and the effective membrane are dimensions were ⁇ 3 cm in length, 1 and 0.45 cm external and internal diameters, respectively. Dip coating was carried out on the outer shell of the a-alumina tube. The tube was inserted into the solution for 3 min dip time, followed by a withdrawal from the solution at speed of ⁇ 31 cm min "1 .
  • the coated tube Upon withdrawal, the coated tube was exposed to a vacuum pressure ( ⁇ 1.3 mbar) via the inner shell for 5 min. This allowed for a partial impregnation of the coated thin-film into the a- alumina tube.
  • the membranes were dried overnight in an oven at 60°C.
  • the dry sucrose membranes where then carbonised in an inert nitrogen atmosphere at three different temperatures (650, 700 and 750 °C), using heating and cooling rates of 5 °C min "1 and a dwell time of 4 h at the highest temperature.
  • TGA Thermo-gravimetric analysis
  • Thermogravimetric analysis shows the mass loss of the sucrose sol under inert nitrogen atmosphere during carbonisation. There is a steep 60% mass loss from 200 to 300 °C. This mass loss is associated with the release of H 2 , CO, CH 4 , and C0 2 during the pyrolysis (carbonisation) of sucrose. From 400 to 800 °C, the mass loss greatly reduces, around -14% only, thus indicating the loss of oxygenated groups in sucrose.
  • the XRD patterns of the sucrose samples carbonised at high temperatures show that although all the patterns are similar, it is observed that the resolution of the peak at 2 ⁇ 43° becomes less broader as the carbonisation temperature increased to 750°C, a clear indication of structural evolution toward a more ordered structure.
  • the water contact angles reveal similar values of 107° for carbonisation temperatures at 650 to 700°C, though it increased to 118° as the carbonisation temperature was raised to 750 °C. All the contact angles values are > 90°, which demonstrates that the carbonised sucrose is indeed hydrophobic, and the increase in the contact angle from 107° to 118° indicates that hydrophobicity has increased. This can be associated to the continuous mass loss at the highest temperatures, suggesting further removal of organic groups from the carbonised sucrose. These organic groups tend to cluster water molecules in carbon structures, and the absence of these groups increased carbon hydrophobicity. These results are also in line with the XRD patterns, as a minor change towards graphitisation tends to increase hydrophobicity.
  • Figure 15 displays the SEM images for the cross section of the carbonised sucrose membranes.
  • a carbon film with a thickness in the range of 6-12 ⁇ is clearly observed in Fig. 15a for the membrane carbonised at 650°C.
  • This carbon film forms a top-layer (on the outer shell of the tube) with good adhesion and partial infiltration into the a-alumina substrate.
  • This morphology is attributed to two-step coating strategy used in this work.
  • the first coating step corresponds to the contact of the sugar solution with a dry porous ceramic oxide substrate. This caused initial high capillary forces, and the liquid solution is immediately drawn into the substrate (spontaneous liquid imbibition within the pores) induced by the wetting force.
  • Fig. 16a shows a narrow pore size distribution between ⁇ 0.11 and -0.05 ⁇ . Contrary to this, the carbonisation temperature played an important role as the total pore volume increased with temperature as displayed in Fig. 16b.
  • sucrose filled the a-alumina pores (inter-particle space) during impregnation porosity is developed during the carbonisation process. This is evidenced by the mass loss attributed to sucrose's oxygenated groups as ascertained by TGA analysis.
  • Fig. 17 shows that both fluxes of NaCl and water increased as a function of the carbonisation temperatures used to prepare the membranes. For instance, the water fluxes increased by 27% from 26 to 33 L m ⁇ h "1 , while NaCl by 12% from 6.2 to 6.9 kg m ⁇ h "1 , as the carbonisation temperature was raised from 650 to 750 °C, respectively.
  • the carbonisation temperature was found to affect the morphological features and surface interaction of the carbon membrane, as revealed by the mercury porosimetry and contact angle experiments, in addition to the SEM observations.
  • the high water fluxes in this example are also much higher than those obtained in pervaporative desalination using inorganic membranes operating at higher temperatures and lower NaCl feed concentration such as 22.9 L m "2 h “1 for cobalt oxide silica membranes (7.5 wt% at 60 °C) [32], 25.4 L m “2 h “1 for carbon alumina membranes (3.5 wt% at 75 °C) [33] and 9.2 L m “2 h “1 for hybrid carbon silica membranes (15 wt% at 60 °C) [34].
  • This great performance of the carbonised sucrose membranes for pure water recovery proved to be a bonus for using this technology to crystallise solutes whilst recovering the solvent.
  • Fig. 19 presents SEM images of the dry NaCl crystals recovered at the end of the percrystallisation tests.
  • the first general trend is that the membrane with the higher carbonisation temperature induced NaCl crystals morphological changes.
  • the crystals produced by the membrane carbonised at 650 °C shows fairly regular particles with near cubic shapes.
  • the structure of the crystals became irregular and more inter-grown.
  • crystals shapes were less defined and more agglomerated.
  • the histograms in Fig. 19 display average particle sizes of 2.8, 2.65 and 0.76 ⁇ for the carbonised membranes at 650, 700 and 750 °C, respectively.
  • the membrane carbonised at 650°C yield large number of NaCl particles between 1-3 ⁇ in size, though also producing a small number of larger particles and skewing the distribution to a higher particle size average.
  • the membrane carbonised at 700°C predominantly delivered particles between 1-2 ⁇ in size, whilst a wider spread of particle size distribution is observed.
  • the membrane carbonised at 750°C produced particles significantly different in terms of both particle sizes ( ⁇ 1 ⁇ ) and size distribution. Indeed, the majority of the particle sizes are fairly well distributed around the mean value (0.76 ⁇ ).
  • the morphology of the dry NaCl crystals was also affected by the vacuum pressure as displayed in the SEM images in Fig. 20. It is clearly observed that the particle sizes became more regular and their shape better defined as the operating pressure is increased, with the particles obtained at 18 mbar having the most irregular morphology.
  • the particles formed at 22 mbar show a more regular and cubic structure compared to those produced at 18 mbar, though particles with a non-regular shape were also observed.
  • NaCl crystals are generally regular in shape, thus conforming to a cubic structure.
  • the histograms in Fig. 20 reveal mean particle sizes of 0.76, 10.95 and 7.4 ⁇ for NaCl obtained at 18, 22 and 26 mbar, respectively.
  • Fig. 21 displays the XRD patterns of the NaCl particles produced using membranes carbonised at different temperatures. All the XRD patterns are almost identical in peak positions. There are two major peaks at 2 ⁇ 31 and 45°, and several minor peaks at 20 28, 54, 56, 66, 75 and 83°. Based on the XRD patterns, the NaCl particles are assigned to a cubic (Fm-3m) structure with space group number 225 (pdf file 01-077-2064). The only difference between the patterns is a slight increase of the peak intensities as a function of the carbonisation temperature of the membranes.
  • Fig. 23a shows a linear relationship between NaCl particle size and water flux, where a fine control in average particle size is demonstrated for the membrane carbonised at 750 °C. As this membrane delivered the highest water flux, it formed the smaller particle sizes as well as a narrow particle size distribution.
  • Fig. 23b shows the effect of permeate vacuum pressure on the formation of NaCl particle size. It seems that there is a need for a breakthrough condition as once permeate vacuum pressure is sufficiently low, particle sizes decrease noticeably. Again the finest particle size control is obtained at the highest water flux, which in this case is associated with the highest driving force for the lowest vacuum pressure at the permeate side.
  • This example demonstrates the versatility of carbon membrane percrystallisation as a technology for the production of crystalline products with specific quality requirements.
  • membrane structure By differentiating membrane structure, it was possible to tune particle size, morphology, and crystallite size of produced NaCl crystals. Variations of operating pressures were less sensitive to NaCl particle size control until a sufficiently low permeate vacuum pressure was set, where a breakthrough condition for fine particle size was attained.
  • the finer control of NaCl crystallite size, particle size and narrower particle distribution ( ⁇ 2 ⁇ ) was achieved with the membrane carbonised at the highest temperature of 750 °C. This membrane carbonisation temperature conferred the highest pore volume, and in turn the highest water flux.

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Abstract

A method for producing a solid material from a solution containing one or more dissolved species or products dissolved in solvent, comprises providing the solution to one side of a porous material, the porous material having at least a layer comprising an inorganic layer having mesoporous pores and/or a carbon layer having mesoporous pores, or a mixed matrix having mesoporous pores comprising carbon and another material, and evaporating at least part of the solvent from the other side of the porous material, characterised in that a solid material is crystallised and recovered from the other side of the porous material. The porous material may comprise a layer having porosity such that it retains molecules having a molecular weight of greater than 100,000 Daltons and the layer has pores of larger than 2nm. Unlike previous crystallization methods using membranes in which crystals are recovered from the retentate side of the membrane, crystals are recovered from the permeate side of the porous material in the present invention.

Description

Percrystallisation method and porous material for use therein TECHNICAL FIELD
[0001] The present invention relates to a method for producing a solid material using percrystallisation and to a porous material for use in a percrystallisation process.
BACKGROUND ART
[0002] Crystallisation is an important industrial process generating a wide range of products throughout the world. Examples include sugar, which is staple in food consumption, lysozyme as an antibacterial agent used in food and pharmaceutical, intermediate metal compounds in metal extraction, such as nickel sulfate hydrate in hydrometallurgy. A large number of other products are also produced using crystallisation processes.
[0003] Essentially crystallisation involves removing (such as by evaporation) a liquid solvent and concentrating a solute once sufficiently super-saturated, which crystallises into a solid phase. The majority of the technologies used in crystallisation are mature and have been optimised based on energy intensive thermal processes to improve the evaporation rates of solvents.
[0004] Brine processing is employed worldwide for the production of lithium, potassium and magnesium, which are global commodities with a combined annual worth in excess of $200 billion per year. Lithium is extensively used in batteries, potassium is widely used as a component of fertilizers for agricultural activities and magnesium has several applications ranging from health to metal alloying. Brine processing and recovery is also becoming a matter of consideration in water desalination, driven by environmental concerns and economic forces, particularly that the recovery value of discharged salts could exceed by a factor of 10 the value of the potable water produced. The emerging coal seam gas (CSG) industry in Australia is facing strong scrutiny in the processing of saline CSG water to comply with best zero liquid discharge (ZLD) practices.
[0005] There are several mature technologies utilised by industry to process brines which invariably involve evaporating water and concentrating the salts. Adsorption methods have low production efficiencies due to the low capacity of the current adsorbents. Reverse osmosis membranes are ideal for concentrating saline waters up to brine concentrations. However, osmotic pressures quickly become too high causing mechanical collapse of the membranes in addition to the excessive energy requirements of high pressure pumping. Thermal processes can deliver fast evaporation rates, but are energy intensive and require high capital investment.
[0006] To avoid high energy costs, solar evaporation ponds are used in certain applications. However, solar evaporation is a very slow process which takes on the order of 12-18 months to dry mineral brines, even in arid regions. Further, large areas of land are required for the solar evaporation ponds.
[0007] A less energy intensive technology, which promotes nucleation and crystallisation rates, is membrane crystallisation. Membrane crystallisation remained a dormant field for almost a century following the initial observations of Kober in 1917. It is only in the last 20 years that membrane crystallisation has gained practical interest owing to the development of novel polymeric membranes. In one example, Drioli's group used polypropylene membranes to recover sodium chloride, magnesium sulfate hydrate [Mariah et al. 2014] and lithium chloride [Quist- Jensen et al. 2016]. In another example, Fane and co-workers [Chen et al. 2014] used polyvinylidene fluoride membranes to generate NaCl crystals from a reverse osmosis plant to avoid environmental impacts caused by the disposal of brines.
[0008] To date, membrane crystallisation technology has been solely based on organic membranes and generally used as contactors or as in a membrane and stirring tank configuration [Chabanon et al. 2016]. In both cases, polymeric membranes allow for the permeation of liquids only, thus causing super-saturation, nucleation and crystallisation in the retentate side of the membrane. Subsequently, there is a need for two further processing steps to filter and dry the crystal particles [Horst et al. 2015] and the rate of the process is slow. Therefore, breakthrough technologies are required to tackle the low production efficiencies, sluggish timeframes, high energy and capital expenditure, and large plant footprint.
[0009] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.
SUMMARY OF INVENTION
[0010] The present invention is directed to a method for producing a solid material from a solution and a porous material having mesoporous porosity for use in the method, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.
[0011] With the foregoing in view, the present invention in one form, resides broadly in a method for producing a solid material from a solution containing one or more dissolved species or products dissolved in solvent, the method comprising the steps of providing the solution to one side of a porous material, the porous material having pores in the mesoporous and/or macroporous pore size range, wherein solution comprising the solvent and the dissolved species or products passes through the porous material, and evaporating at least part of the solvent from the other side of the porous material, characterised in that a solid material is crystallised and recovered from the other side of the porous material.
[0012] In one embodiment, the method comprises evaporating solvent from the other side of the porous material at substantially the same rate or faster than a rate of solvent passing through the porous material to form a solid material on the other side of the porous material.
[0013] In one embodiment, the porous material has at least a layer comprising an inorganic layer having mesoporous pores or macroporous pores and/or a carbon layer having mesoporous pores or macroporous pores, or a mixed matrix having mesoporous pores or macroporous pores comprising carbon and another material.
[0014] In one embodiment, the porous material has at least a layer comprising an inorganic layer having mesoporous pores and/or a carbon layer having mesoporous pores, or a mixed matrix comprising carbon and another material having mesoporous pores.
[0015] In one embodiment, the porous material has at least a layer comprising an inorganic layer having macroporous pores or a carbon layer having macroporous pores, or a mixed matrix comprising carbon and another material having macroporous pores.
[0016] In one embodiment, the porous material comprises a porous polymer.
[0017] Throughout this specification, a mesoporous material is a material containing pores with diameters between 2 and 50 nm, according to IUPAC nomenclature. IUPAC defines microporous material as a material having pores smaller than 2 nm in diameter and macroporous material as a material having pores larger than 50 nm in diameter.
[0018] In one embodiment, the porous material is not a microporous material.
[0019] In one embodiment, the material is a macroporous material having a pore size in the range of from 50nm to 1 ,000nm, or 50nm to 500nm, or 50 nm to 250nm, or 50nm to 200nm, or 50nm to 150m, Or 50nm to 125nm, or 50nm to 1 lOnm.
[0020] In a second aspect, the present invention provides a method for producing a solid material from a solution containing one or more dissolved species or products dissolved in solvent, the method comprising the steps of providing the solution to one side of a porous material, the porous material having pores in the mesoporous and/or macroporous pore size range, wherein solution comprising the solvent and the dissolved species or products passes through the porous material, and evaporating at least part of the solvent from the other side of the porous material, characterised in that a solid material is crystallised and recovered from the other side of the porous material wherein the porous material has porosity such that it retains molecules having a molecular weight of greater than 100,000 Daltons and the layer has pores of larger than 2nm.
[0021] In the second aspect of the present invention, the porous material may be as described with reference to the first aspect of the present invention.
[0022] Unlike prior art percrystallisation processes in which the crystallised material is recovered from the retentate side of the porous material (which is the side of the porous material that is in contact with the solution), in the process of the present invention, the crystallised material is recovered from the filtrate or permeate side of the porous material (which is the other side of the porous material to the side that is in contact with the solution). In some embodiments, the process of the present invention utilises a porous material having at least a layer comprising an inorganic layer or region having mesoporous pores and/or a carbon layer or region having mesoporous pores.
[0023] In one embodiment, the porous material comprises an inorganic porous material having at least a layer comprising an inorganic layer having mesoporous pores and/or macroporous pores and/or a carbon layer having mesoporous pores and/or macroporous pores and a substrate having pore sizes larger than pores in the layer, and the at least one layer having mesoporous pores.
[0024] In one embodiment, the layer comprising an inorganic layer having mesoporous pores and/or a carbon layer having mesoporous pores comprises a layer formed on a surface of the substrate, or comprises a plurality of layers formed on a surface of the substrate.
[0025] In one embodiment, the majority of the pores of the mesoporous layer are between 2 to 50 nm in diameter, even more preferably between 2 to 30 nm, still more preferably between 2 to 10 nm.
[0026] In one embodiment the porous material is a porous inorganic membrane that comprises a hierarchical membrane comprising layers with pores at different length scales including the micro-, meso- and macroporous range.
[0027] In a further embodiment the porous inorganic membrane may be a stratified asymmetric membrane having layers with pore sizes differing from those layers in which they are in contact with.
[0028] In one embodiment, the porous material comprises a porous inorganic substrate coated with a layer of inorganic material. This porous material may be produced by coating one side of a porous inorganic substrate with one or more layers of inorganic material. The one or more layers of inorganic material may be coated onto the substrate by way of coating with a sol or a gel, followed by calcination and/or carbonisation. The porous inorganic substrate may have large pores than the layer of inorganic material. The layer of inorganic material may have mesoporous pores.
[0029] In one embodiment, the porous material may comprise a porous substrate that has one or more layers of carbon thereon. The one or more layers of carbon may be formed by an impregnation method in which a carbonaceous liquid or a carbonaceous solution is impregnated onto one side of the porous substrate, followed by carbonising the carbonaceous material to form the carbon layer. In one embodiment, the carbonaceous liquid or carbonaceous solution comprises a solution in which a carbonaceous material is dissolved. For example, the carbonaceous solution may comprise a dissolved saccharide in water. In another embodiment, the carbonaceous liquid may comprise a resin, such as a phenolic resin or a polymer precursor. The one or more layers of carbon may have mesoporous pores. The one or more layers of carbon may have macroporous pores. The one or more layers of carbon may have mesoporous pores and macroporous pores.
[0030] In another embodiment, the layer comprises a mixed matrix membrane containing carbon and MOFs (metallic organic frameworks). In this embodiment the layer may be formed by impregnating and/or coating a carbonaceous liquid containing MOFs into a substrate, followed by carbonisation. The layer may have mesoporous pores or macroporous pores or mesoporous pores and macroporous pores.
[0031] The process of the present invention can be used to produce a wide range of products. Indeed, the present inventors believe that most products that are presently made by conventional crystallisation processes can be made by the process of the present invention. Products that may be made by the process of the present invention include mineral salts, food additives, pharmaceuticals and chemical products. Some examples of specific products that can be made by the present process include chloride salts (such as nickel chloride, magnesium chloride, potassium chloride, lithium chloride and sodium chloride), nitrate salts (such as nickel nitrate), crystalline acids (such as ascorbic acid), pharmaceuticals and vitamins (such as vitamin C) and food additives (such as sodium lactate).
[0032] Other products, such as proteins (including antibodies, enzymes, peptides) from solution including serum, water or other, may also be crystallised from solution using the process of the present application.
[0033] The solution that is supplied to the process of the present invention may comprise an aqueous solution containing dissolved material. The solution that is supplied to the process of the present invention may comprise a non-aqueous solution containing dissolved material.
[0034] The porous material used in the process of the present invention may have a flat geometry (such as a sheet or a plate) or the porous material may be in a tubular form, or in the form of hollow fibres, or capillary fibres. If a porous material of tubular shape is used, the tube may be open at both ends or it may be closed at one end. The porous material may comprise a flat porous substrate that has a layer of the mesoporous inorganic material or a layer of mesoporous carbon material thereon or therein. The porous material may comprise a tubular article in which a tubular porous substrate has a layer of the mesoporous inorganic material or the mesoporous carbon material thereon or therein. The layer of the mesoporous material may be coated on the inner shell of the tubular substrate, or it may be coated on the outer shell of the tubular substrate.
[0035] In one embodiment, the porous membrane may form at least one wall of a hollow membrane chamber.
[0036] The process of the present invention may be conducted as a batch process. The process of the present invention may be conducted as a continuous process.
[0037] In one embodiment, the process of the present invention comprises a batch process in which the solution is fed to an inner part of a tubular porous material and crystals of material grow on an outer part of the tubular porous material, with the crystals growing in batches and being removed from the outer part of the tubular porous material by a drying process or microwave irradiation. In one embodiment, the crystals are removed from the outer part of the tubular porous material by mechanical action. In another embodiment the crystals can be ejected from the tubular porous material by microwave irradiation. [0038] In one embodiment, the process of the present invention comprises a continuous process in which the solution is fed to an inner part of a tubular porous material and crystals of material grow on an outer part of the tubular porous material, with the crystals continuously growing and being removed from the outer part of the tubular porous material during operation of the process. In one embodiment, the crystals fall off the outer part of the tubular porous material under their own weight.
[0039] In one embodiment, the process further comprises applying a vacuum to the other side of the porous material. Applying a vacuum to the other side of the porous material promotes evaporation of the solvent passing through the porous material and can increase the rate of crystallisation. The present inventors have found that vacuum speeds up the crystallisation process, thus increasing crystal production rates. However, crystallisation also occurred at ambient pressures and temperatures, i.e. with no vacuum applied to the permeate side.
Accordingly, the level of pressure on the permeate side of the porous material may range from ambient pressure (typically 1 atm) down to very low vacuum pleasures below 1 Torr. (these pressures are given as absolute pressures, not gauge pressures).
[0040] In one embodiment, the process further comprises heating the solvent passing through or that has passed through the porous material. Again, heating the solvent passing through the porous material promotes evaporation of the solvent passing through the porous material, which can increase the rate of crystallisation. In some embodiments, the solvent passing to the porous material is heated to a temperature within the range of from ambient temperature up to the boiling point of the solvent. In another embodiment, the solution is heated prior to passing through the membrane. The solution may be heated using waste heat, solar ponds, microwave radiation, or conventional heating technologies.
[0041] In one embodiment, the solution that is supplied to the porous material is pressurised. In another embodiment, the solution is supplied under ambient pressure.
[0042] The process of the present invention provides a percrystallisation process in which crystals are formed on and recovered from the filtrate side or permeate side of the porous material. As mentioned above, this is quite distinct to all prior art percrystallisation processes known to the inventors, in which the crystals are formed on and recovered from the retentate side of the porous membrane.
[0043] The present inventors have found that embodiments of the percrystallisation process in accordance with the present invention can deliver a range of crystal shapes and sizes. For example, the percrystallisation process can result in the formation of small cubic crystals with side dimensions ranging from 10 to 20 μιη, in addition to polymorph crystals, or in the formation of small polymorph and cubic crystal, or in the formation of elongated polymorph crystals, or in the formation of small flakes, or in the formation of very small crystals almost like needle- geometries, or in the formation of filaments.
[0044] The present invention also relates to a porous material for use in the process of the first aspect of the present invention.
[0045] According to a third aspect, the present invention provides a porous material for use in a percrystallisation process, the porous membrane comprising a porous substrate having a layer thereon or therein, the layer comprising an inorganic layer having mesoporous pores and/or macroporous pores, and/or a carbon layer having mesoporous pores and/or macroporous pores or a mixed matrix having mesoporous pores and/or macroporous pores comprising carbon and another material, the porous substrate having a porous structure having pores that are larger than mesoporous pores.
[0046] In a fourth aspect, the present invention provides a porous material having at least a layer comprising an inorganic layer and/or a carbon layer and/or a mixed matrix comprising carbon and another material, wherein the layer has porosity such that it retains molecules having a molecular weight of greater than 100,000 Daltons and the layer has pores of larger than 2nm.
[0047] In one embodiment the layer comprises a mixed matrix having mesoporous pores comprising carbon and another material, wherein the mixed matrix comprises a composite of carbon and MOFs (metal-organic framework material).
[0048] In some embodiments, the layer having mesoporous pores or macroporous pores is relatively thin and the substrate is relatively thick. In one embodiment, the layer having mesoporous porosity has a thickness of from 0.5 to 5 μιη and the substrate as a thickness of from 100 μηι to 5 cm.
[0049] In the porous material of embodiments of the present invention, the substrate provides mechanical strength. Accordingly, the thickness of the substrate may vary widely, bearing in mind that the substrate should have a minimum thickness that provides for the minimum acceptable strength for the porous material. The thickness of the substrate may vary widely, depending upon the particular substrate and the size of the structure. For example, porous inorganic hollow fibres could have a thickness in the range of from 200 μιη to 1 mm. Conventional substrate tubes that may be purchased commercially may have a thickness of from 1.5 to 2 mm. The thickness of the substrate may increase as the diameter of the tube increases. Other thicknesses are also included in the present invention.
[0050] In one embodiment, the porous material has a layer having mesoporous pores and the majority of the pores of the mesoporous layer are between 2 to 50nm in diameter, even more preferably between 2 to 30 nm, still more preferably between 2 to 10 nm.
[0051] In one embodiment, the mesoporous layer comprises an inorganic material or carbon. The inorganic material may comprise a metal oxide, such as a titanium oxide, a zirconium oxide or an aluminium oxide, or a mixture of these metal oxides.. In some embodiments, the inorganic material comprises γ-alumina. Porous mixed metal oxides may also be used.
[0052] In another embodiment, the mesoporous layer comprises carbon. The carbon may comprise porous graphite, porous graphene, agglomerates of carbon nanotubes, agglomerates of carbon fibres, and the like. A porous carbon membrane may be applied to the substrate.
[0053] The substrate may comprise a porous inorganic material, such as a porous metal oxide material or a porous metal. The substrate may comprise titanium dioxide, zirconium dioxide, aluminium oxide, or a mixture of two or more thereof. Other metal oxide substrates or mixed metal oxide substrates may also be used. The substrate may comprise a porous metal substrate, such as a porous stainless steel substrate. Other metals may also be used.
[0054] In one embodiment, the porous material has a layer of carbon and the layer of carbon has macroporous pores. The layer of carbon may also include mesoporous pores.
[0055] The substrate has a porosity that includes pore sizes that are larger than the pores included in the mesoporous layer. For example, the bulk of the pores in the substrate may be sized at 50nm or larger, or lOOnm or larger, or 500nm or larger. The substrate may have a relatively regular pore size with a narrow pore size distribution, or it may have a relatively irregular or random pore size with a broad pore size distribution.
[0056] In one embodiment, the substrate is formed using sol-gel synthesis, followed by firing or sintering, and the mesoporous layer is formed by dipping the substrate in a sol.
[0057] In some embodiments, the solid material is in the form of a flat sheet or a flat plate. In other embodiments, the solid material is in the form of a tube or a pipe. The tube or pipe may have an inner diameter of from less than 0.25mm to 0.5 - 1.0 cm or even larger. In some embodiments, the substrate may comprise a commercially available material and the diameter can be any diameter that is commercially available. In one embodiment, the solid material is in the form of porous hollow fibres. The fibres may have an inner diameter of less than 0.25 mm. It is believed that using smaller tubes in the percrystallisation process is preferable to increase the surface area to volume ratio. In some embodiments, a plurality of tubes or pipes or hollow fibres are used.
[0058] The present inventors believe that, in some embodiments, providing a solid material having a layer of inorganic material or carbon, with that layer having mesoporous porosity and/or macroporous porosity is important in the present invention. The present inventors have found that using a porous material having pore sizes of less than 2nm would not result in the formation of crystals, presumably because the pore sizes are too small for the dissolved material in solution to pass through the pores. Similarly, using porous material having pore sizes that are too large is believed to allow the solution to fully permeate through the porous material without any retention of salts or other dissolved materials in the pores, thereby effectively flooding the other side of the porous material and preventing formation of crystals. The present inventors have also found that mesoporous metal oxides materials worked well for batch processes whereas carbon mesoporous materials worked well for continuous processes. The present inventors have found that it is preferred that where the porous material contains a layer of inorganic oxide, the layer of inorganic oxide has mesoporous pores. In instances where the porous material comprises a layer of carbon, the present inventors have found that layer of carbon can have mesoporous pores or macroporous pores, preferably with a maximum pore size not exceeding 500nm or not exceeding 250nm.
[0059] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.
[0060] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.
BRIEF DESCRIPTION OF DRAWINGS
[0061] Various embodiments of the invention will be described with reference to the following drawings, in which:
[0062] Figure 1 shows an SEM image of a mesoporous titania membrane (3-5 nm pores) coated on γ-alumina interlayer on a -alumina substrate used in batch processes; [0063] Figure. 2 shows a graph of crystallisation rate of chloride salts (LiCl, NaCl, C1, CaCl2, MgCl2, MnCl2, MnC12, CuCk, NiCh) (feed concentration of 3mol/L salt at 20 C, pervaporation time 10 min, microwave power lOOOw, microwave time 2 min) for a batch process;
[0064] Figure 3 shows graphs of water and percrystallised salt flux as a function of (A) temperature with feed solutions of NaCl 17.5 wt% and (B) salt feed concentration with feed temperature at 37 C for a continuous process;
[0065] Figure. 4 shows a graph of crystallisation rate of KC1, MgCl2 and NiCh (17.5 wt% at 37 C), oxalic acid and vitamin C (2.5 wt% at 37C)for a continuous process;
[0066] Figure 5 shows a schematic diagram for a postulated mechanism for the
percrystallisation process for a continuous process in accordance with embodiments of the present invention;
[0067] Figure 6 shows micrograph images of NaCl, KC1, MgCl2, NiCl2, oxalic acid and vitamin C obtained using percrystallisation in accordance with embodiments of the present invention
[0068] Figure 7 (a) shows carbon mass content in membrane material after carbonisation as a function of sucrose concentration used for dip-coating; and Figure 7 (b) shows SEM images of the cross-section of carbonised sucrose membranes using 20 Wt%, 30 Wt%, 40 Wt , and 50 Wt% in Example 10;
[0069] Fig. 8 (a) shows water and nickel fluxes as a function of the sucrose concentration used for dip coating (20-50 Wt%), using a feed concentration of 40 g(Ni) L"1 and a temperature of 40°C. Nickel flux given as mass of metallic nickel permeated as nickel sulphate; and Figure 8(b) shows nickel production percentage contribution of total mass production as a function of sucrose concentration;
[0070] Fig. 9 (a) shows water and nickel fluxes as a function of feed concentration used for dip coating (10-100 g L"1), using a membrane dip-coated in 20 Wt% sucrose and a temperature of 40 °C. Nickel flux given as mass of metallic nickel permeated as nickel sulphate; and figure 9 (b) shows nickel production percentage contribution of total mass production as a function of feed concentration; [0071] Fig. 10 (a) shows water and nickel fluxes as a function of operation temperature used for dip coating (30-60°C), using a membrane dip-coated in 20 Wt sucrose and a feed concentration of 40 g L"1. Nickel flux given as mass of metallic nickel permeated as nickel sulphate; and figure 10(b) shows nickel production percentage contribution of total mass production as a function of operation temperature;
[0072] Fig. 11 (a) shows XRD patterns of nickel sulphate crystals produced by different dip- coating concentrations, with the 40 and 50 Wt% produced crystals showing hexahydrate diffractions; Figure 11(b) shows XRD patterns of nickel sulphate crystals produced by different feed concentration, only 100 g L"1 showing hexahydrate diffractions; and Figure 11(c) shows XRD patterns of crystals produced by different operating temperature, with 50 °C showing hexahydrate peaks;
[0073] Fig. 12 shows SEM images of percrystallised products from different tests in Example 10;
[0074] Figure 13 shows SEM photomicrographs showing the crystal morphology of the paracetamol crystals produced in example 11, with figure 13 (a) showing the crystals produced using a membrane made from a 5% sucrose solution, figure 13 (b) showing the crystals produced using a membrane made from a 10% sucrose solution, figure 13 (c) showing the crystals produced using a membrane made from a 20% sucrose solution, and figure 13 (d) showing the crystals produced using a membrane made from a 30% sucrose solution;
[0075] Figure 14 shows SEM photomicrographs of paracetamol crystals collected after (a) 5 min, (b) 2h, and (c) 18h of operation from the membrane surface in Example 12.
[0076] Figure 15 shows SEM images of the cross-sections of carbonised sucrose membranes at a) 650°C, b) 700°C and c) 750°C;
[0077] Figure 16 shows mercury porosimetry data (a) pore size distribution and (b) accumulated pore volume for the carbon membranes obtained at 650, 700 and 750 °C;
[0078] Figure 17 show a graph of NaCl and water fluxes as a function of the membrane carbonisation temperature (650, 700 and 750 °C) at a permeate pressure of 18 mbar;
[0079] Figure 18 shows a graph of NaCl and water fluxes as a function of permeate operating pressures (18, 22 and 26 mbar) for a membrane carbonised at 750 °C; [0080] Figure 19 shows SEM pictures and corresponding histograms of NaCl particles produced by percrystallisation as a function of membrane's carbonisation temperature.
Percrystallisation conditions: 18 mbar permeate pressure, feed solution temperature at 37°C and NaCl concentration of 17.5 wt%;
[0081] Figure 20 shows SEM pictures and corresponding histograms of NaCl particles produced by percrystallisation at various operating pressures and using a carbon membrane (carbonised at 750°C). Percrystallisation conditions: feed solution temperature at 37°C and NaCl concentration of 17.5 wt%;
[0082] Figure 21 shows XRD patterns of NaCl crystals produced by percrystallisation with sucrose derived membranes carbonised at 650, 700 and 750°C;
[0083] Figure 22 shows graphs of (a) NaCl crystallite size versus pore volume and (b) water flux versus pore volume for sucrose membranes carbonised at various temperatures; and
[0084] Figure 23 shows graphs of NaCl particle size versus water flux (a) for the sucrose membrane carbonised at various temperatures and tested at 18 mbar, and (b) for sucrose membranes carbonised at 750 °C and tested at various pressures.
EXAMPLES
EXAMPLE 1
[0085] In this example, the percrystallisation of salts on a membrane surface via a batch pervaporation process was investigated. The porous material that was used in the percrystallisation process was a mesoporous titania membrane (3-5nm pores) coated on γ- alumina interlay er on an a- alumina substrate (see figure 1) In this work, mineral brines were retained in the mesopores of the titania top-layer which crystallised on the surface of the membrane by evaporation and heat. Microwave irradiation proved to be a very effective method to crystallise and expel the mineral brines retained in the mesopores, improving the batch production rate by 24 times. Figure 2 shows the production rate of a number of chloride salts (LiCl, NaCl, KC1, CaCh, MgCb, MnCb, MnC12, CuCh, NiCh) exposed to microwave heating.
EXAMPLE 2
This example demonstrated that the brine permeates the inorganic membrane under vacuum and pervaporation and percrystallisation occur simultaneously in the permeate side as a continuous process. This is the first demonstration of membranes separating the solvent from solute in a single step. Fig. 3 shows that the fluxes of NaCl and water increased as a function of the feed brine temperature for a mesoporous carbon membrane. At the highest tested temperature of 37 °C, the salt flux reached 5.5 kg m"2 h"1. Under these testing conditions, one square metre of membrane are could produce up 48000 kg of NaCl per year. What is more remarkable is that the membrane delivered a water flux of 20.0 L m"2 h"1 for a hyper saline feed NaCl brine solution of 20 wt%. These results are within the range of reverse osmosis membranes of 19.7-28.0 L m"2 h"1 reported by Mattia and co-workers [Lee et al. 2011] for NaCl concentrations of 3.5 wt%.
Although the intention of this work is percrystallisation membranes, an added benefit is also dewatering hyper saline brines well beyond the capabilities of reverse osmosis which is the gold standard technology for desalination.
EXAMPLE 3
[0086] The percrystallisation of NaCl using inorganic membranes is shown to be efficient. For instance, the production of table salts using evaporation ponds is very slow even in a dry continent like Australia. The Whyalla plant uses 4000 hectares of salt pans to produce 18 kg m"2 per year using feed sea water (NaCl ~3.5 wt%). Under the same feed salt concentration at room temperature operation and using conditions similar to example 1 , inorganic membranes can produce 8400 kg m"2 per year. In other words, each lm2 of inorganic membranes could replace more than 450 m2 of evaporation ponds. What is more remarkable about this discovery is the flexibility of inorganic membranes to percrystallise a wide range of substances. Further experiments were conducted to demonstrate that the inorganic membranes percrystallised other mineral salts (KC1 , MgCh and NiCh), organic acids (oxalic acid) and ascorbic acid (vitamin C) as displayed in Fig. 2, noting high productions up to 55,000 kg 2 per year. This technology can be used in hydrometallurgical operations or mining wastewater to recover metal, with the added benefit of also recovering water and complying with new environmental regulations of zero liquid discharge. In addition, the present inventors believe that this novel technology can spearhead percrystallisation developments in wide range of fields of interest in the human endeavour, particularly in health and bio-crystallisation of proteins, food/flavour additives and pharmaceutical compounds.
[0087] Subsequent investigations showed that the pore diameter (dp) and membrane materials were key parameters which enables the desired percrystallisation properties to be obtained. Salt crystals could be formed in mesoporous titania, gamma-alumina and carbon membranes, but not for other membranes such as microporous (dp<2 nm) silica and carbon molecular sieves. Similarly, macroporous membranes having pores larger than mesoporous pores did not form crystals. It is believed that micropores were too small to store hydrated salt ions with radius of C1~-H20 (6.64 A) and Na+-H20 (7.16 A), whilst pore wetting occurred in macropores as the salt solution fully permeated through the membrane without any retention of salts.
[0088] Without wishing to be bound by theory, the present inventors have postulated that the instantaneous percrystallisation of salts in the membranes is schematically idealised in Fig. 5. Under pervaporation, a wet thin-film is formed on the surface of the membrane. Under the testing conditions, flooding did not occur suggesting that mesopores were modulating the flow of solution from the feed side to the wet thin-film on the permeate side of the membrane. This causes heat transfer improvement of thin-films, thus promoting evaporation close to the apparent solid-liquid-vapour contact line. For instance, we observed that percrystallisation occurred even at atmospheric conditions, due to the evaporation of water. During evaporation of water, salt concentrates on nucleation points along the wet thin-film. Upon nucleation and spontaneous crystallisation, concurrent separation of solids and liquid occurs in a single step, as the lighter water molecules evaporate from the wet thin-film while the heavier NaCl crystals fall under the effect of gravity or are otherwise removed. Therefore, it is believed that solvent (i.e water) evaporation from the wet thin-film on the permeate side of the membrane is the driving force for the instantaneous percrystallisation.
[0089] Molecular weight cut-off tests were carried out as one way to determine pore sizes. These tests showed that the carbonized sugar membranes had a molecular weight cut-off of around 360,000 Daltons (360 kDa). This value correlates to mesopores of 5nm for carbonised phenolic resin membranes. Molecular weight cut-off tests were carried out using an aqueous solution containing a single compound such as 36 or 400 kDa polyvinyl pyrrolidine (PVP) or 0.34 kDa sucrose. PVP or sucrose was mixed with deionised water to solutions of 0.3 wt%. A pressure vessel is used to maintain a pressure of 5 bar. Permeation testing was conducted in a cross flow set up when the solution was fed via the inner shell of the tube. The permeate stream via the outer shell of the tube was collected in a beaker and the mass was continuously recorded using an electronic scale. The collected permeate solution was analysed using a Shimadzu UV- 2700 UV-vis spectrometer to determine the concentration of PVP against calibration curves. The molecular weight cut-off was determined by the rejection (R) of the substance as R = [1-(CP-Cf)] X 100, where Cp and Cf are the concentration of PVP or sucrose in permeate and feed streams, respectively. Measurements were recorded at steady-state conditions with a minimum three measurements for each test. EXAMPLE 4 - Preparation of mesoporous γ-alumina membranes
[0090] Commercial a-alumina tubes (OD = 10 mm; ID=5 mm) were used as membrane substrates. The substrates were pre-calcined at 1000 °C for 8 h with a ramp rate of 5 °C min-1 to improve the mechanical strength and to remove any organic impurities. The a-alumina substrates were coated with three γ-alumina layers, which were derived from an aluminium oxide (10%) in water sol with an average colloidal particle size of 0.05 μιτι (Alfa Aesar). Dip coating was used at a dip and withdrawal speed of 5 cm min"1, and holding time of 1 min. Subsequently to each coating, the membranes were calcined in air at 500 °C at a ramping rate and cooling rate of 1 °C min"1, and a holding time of 1 hour. The final membrane coated on a α-alumina tube had up to 3 γ-alumina top-layers.
EXAMPLE 5 - Preparation of mesoporous titania membranes
[0091] The titania membranes were prepared on the top of the γ-alumina membranes as described above and following the same coating methods adopted for the γ-alumina as interlayers. The final membrane coated on a α-alumina tube had 3 γ-alumina interlayers and 3 titania top-layers. Titania was synthesised from a sol-gel method. Briefly, titanium(IV) propoxide (TTP,TiCi2H2804, 98%, Sigma-Aldrich) was added drop-wise into a solution of double distilled water and hydrochloric acid under vigorous stirring. Then the mixture was maintained in a water bath at 30 °C for 3 hours. The molar ratio of final sol was
TTP:HC1:H20=1: 1:22. The sol was dried in a temperature controlled oven at 60 °C for 3 h. The dried gel was treated at 150°C(heating rate ofl °C min"1, dwell time of 1 h) to ensure the consolidation of theTi02matrix and then calcined at 350 °C (heating rate of 1 °C min"1, dwell time of 1 h) to confer a gentle thermal effect on the mesostructure of the T1O2 matrix.
EXAMPLE 6 - Preparation of carbon membranes derived from saccharide
[0092] Carbon membranes were prepared by an impregnation method with various saccharides as an organic precursor. The saccharides were commercial food grade sugar (glucose, fructose, maltose and sucrose). The solid sugar was dissolved in deionised water at 10- 40%wt concentration. Then the solution containing sugar was coated on the outer shell of a commercial α-alumina tubes (OD = 10 mm; ID=5 mm). The contact time between the tube and sugar solution varied between 1 min to 4 hours. Once the tube was removed from the sugar solution, vacuum pressures (up to less than 1 Torr) were applied to the inner shell from 1 to 10 min. Subsequently, the coated substrate was dried for 15 hours in an oven at 60°C. Finally, the impregnated saccharide in the substrate was carbonised in an argon atmosphere at 700°C for 8 hours at heating and cooling rate of 5°C min"1.
EXAMPLE 7 - Carbon membranes derived from phenolic resin
[0093] Phenolic resin Resinox IV- 1058 was used as precursor to prepare carbon membranes. The resin was mixed with methanol at 1: 10 wt% ratio and aged under stirring for 2 hours at room temperature. All membranes were coated on the outer shell of a commercial a-alumina tubes (OD = 10 mm; ID=5 mm). A dip coating method was used, where a substrate was immersed into the phenolic resin solution for 1 min of holding time with 10 cm min"1 dipping and withdrawal rate. After dip coating, the membrane was immediately exposed to a vacuum pressure (< 1 Torr) via the inner shell of the tube for a desired time (from 30 to 1200 s). Subsequently, the coated membranes were cured in an oven at 60 °C for 24 hours and carbonised in an inert nitrogen atmosphere with a ramping and cooling rate of 5 °C min"1 up to 700 °C and a dwell time of 2.5 h.
EXAMPLE 8 - Mixed Matrix Membranes (MMM) containing Carbon and MOFs (Metallic Organic Frameworks)
[0094] The preparation of the Carbon MOF MMM membranes followed the same procedures as for the carbon membrane above [Abd Mil et al. 2017]. Then a new procedure was developed to embed MOFs in a carbon matrix. The MOFs used was a ZIF-8 I synthesised whilst a phenolic resin was the carbon precursor. The phenolic resin ratio is variable, though the initial membranes were prepared with 50/50 wt ratio of phenolic resin to methanol, which was stirred to a couple of days to get the solution as homogenous as possible. Subsequently, the solution was further diluted with methanol at a ratio of 1:4 and ZIF-8 was added at different ratios. The initial ratios are listed as follows:
• Membrane 1: 4.03 g 50% solution, 16.05 g MeOH, 0.15008 g ZIF-8
• Membrane 2: 4.01 g 50% solution, 16.00 g MeOH, 0.02291 g ZIF-8
• Membrane 3: 4.03 g 50% solution, 16.05 g MeOH, 0.01433 g ZIF-8
[0095] The solutions containing ZIF-8 were well mixed in centrifuge tube, followed by sonication for -60 minutes. The well mixed solutions were coated on the outer shell of a commercial a-alumina tubes (OD = 10 mm; ID=5 mm). A dip coating method was used, where a substrate was immersed into the phenolic resin solution for 1 min of holding time with 10 cm min"1 dipping and withdrawal rate. After dip coating, the membrane was immediately exposed to a vacuum pressure (< 1 Torr) via the inner shell of the tube for a desired time (from 30 to 1200 s). Subsequently, the coated membranes were cured in an oven at 60 °C for 17 hours and carbonised in an inert nitrogen atmosphere following several steps as follows: 20°C (dwell time of 20 minutes) ramp to 120 °C (rate of 5 °C min"1), 120°C (dwell time 60 minutes), ramp to 450°C (rate of 5 °C min"1), 450°C (dwell time 4 hours), cooling down to room temperature (rate ~7 °C min"1), 25°C.
EXAMPLE 9
[0096] The percrystallisation method is accordance with embodiments of the present invention can deliver a range of shapes and sizes obtained in continuous membrane
percrystallisation. The micrograph images Fig. 6 show the formation of small cubic NaCl crystals with side dimensions ranging from 10 to 20 μιη, in addition to polymorph NaCl crystals. C1 formed crystal similarly to NaCl, though NiCk resulted in larger and elongated polymorph crystals. Vitamin C also formed very small crystals almost like needle-geometries, whilst oxalic acid percrystallised as filaments. MgCk resulted in the formation of small flakes.
EXAMPLE 10 - Nickel sulphate production
[0097] Membrane coating solutions were prepared by dissolving 20, 30, 40 and 50 Wt % sucrose (>99.8% Chem-supply) respectively into demineralised water. The sucrose solutions were mixed, followed by 30 minutes of sonication. The solutions were then used to dip-coat a- alumina substrates (Ceramic Oxide Fabricators, Australia). The substrates were of a mean pore size of 0.1 microns. The total length of the substrates was ~4 cm in length, 1 and 0.45 cm in external and internal diameters, respectively. Dip-coating was performed on the outer layer of the a-alumina support. The tube was submerged in a solution for three minutes with a subsequent withdrawal from the solution. The submersion and retraction speed was -31 cm min . After dip- coating, a vacuum was applied through the inside of the sucrose-coated support (<1.3 mbar), causing a partial impregnation of the thin-film onto the a-alumina tube. The partially
impregnated supports were dried overnight at 60°C, before being carbonised in an inert nitrogen atmosphere at 750°C. The heating and cooling ramps were 5 K min"1 with a dwell time of 4 h once 750°C was reached. After carbonisation, the membranes' surfaces were coated with Protek type N blue solvent cement at the ends to create a seal, so the ends of the membranes can be used for mounting onto a percrystallisation system, leaving ~3 cm active membrane surface for testing.
[0098] Morphology of the produced membranes were analysed by scanning electron microscope (SEM), using a Jeol JSM-7001F SEM with a hot (Schottky) electron gun, with an acceleration voltage of 5 kV.
[0099] As prepared membrane material was crushed and annealed in in a TGA (TGA-DSC1 Mettler Toledo) to determine the carbon content in the membranes. The heating rate was set to 10 K min"1 and the maximum temperature was set to 1000°C with an isotherm of 30 minutes, before cooling down to ambient temperature with a cooling rate of 20 K min"1. The annealing was carried out in atmospheric air to allow for complete combustion of carbon material.
[00100] Nickel sulphate solutions were prepared by dissolving amounts of N1SO4.6H2O (> 98% Chem-Supply) in demineralised water to acquire the desired concentrations (10, 40, 70, and 100 g L"1) in order to test applicability of percrystallisation for production of solid nickel sulphate when using different feed concentrations. The solutions were heated to a desired temperature (30, 40, 50, and 60 °C) and fed through the inner shell of the membrane unit, using a peristaltic pump with a flow rate of ~31.1 L h"1 to reduce potential concentration and temperature polarisation. A Buchner flask was utilised as a container for the membrane, and as a crystal collection chamber. The crystallisation collection chamber was connected to a cold trap
(submerged in liquid nitrogen), followed by an isolation valve and a vacuum pump. The percrystallised nickel sulphate crystals were collected in the Buchner flask, while the solvent, water, was collected in the cold trap.
[00101] A measured amount of percrystallised nickel sulphate was removed from the crystal collection chamber in order to be used for SEM and XRD analysis, while the rest was dissolved in a known volume of water. The solution was used to determine the production rate of crystalline nickel sulphate via the use of conductivity. The mass of the produced water was used to determine the water production rates during percrystallisation.
[00102] The collected nickel sulphate powder was analysed by SEM imaging. TGA, analysis was used in order to quantify the mass of dry nickel sulphate was removed. This was done by heating the powder up to 800°C with a heating rate of 10 K min-1 and cooling rate of 20 K min"1 in air. The dry powder was also studied by XRD to determine the crystalline structure of the percrystallised material. XRD was done, using a Rigaku Smartlab X-ray diffractometer at 45 kV, 200 mA, having a step increment of 0.02° and a step speed of 4°min-l with filtered Cu Ka radiation (λ=1.5418 A).
[00103] Fig. 7a shows the mass loss of the crushed membrane materials as a function of the concentration of the dipping solution. The mass loss associated with the concentration of the dipping solution increases almost linearly, as the concentration increases. This finding indicates that the carbon content deposited on the a-alumina support is proportional to the sucrose concentration of the dipping solution. Fig. 7b shows the morphology of the cross-section of the prepared membranes. In the figure, a film of carbon material can be observed, with the thickness increasing as the sucrose concentration of the dipping solution increases from 20 wt % to 50 wt %. These observations confirm that the deposited carbon material in the membrane increases with dipping solution, which allows for the formation of a thicker visual film of carbon material to be formed in the membrane.
[00104] Fig. 8a shows the fluxes of water and the flux of metallic nickel produced by the crystallisation of nickel sulphate as a function of the sucrose concentration used during dipping of the supports, using an operating temperature of 40°C and a concentration of 40 g L"1 nickel. The initial finding is that all the prepared membranes in this work were able to be used for percrystallisation of nickel sulphate. What is observed is observed is decreasing trend in both water and nickel production as the precursor solution used in producing the membranes increases in concentration. This finding is well-aligned with the visual observations of the membranes in Fig. 8b. This finding suggests that the lower carbon content in the membrane allows for the best modulation of solution permeation to the surface of the membrane unit, which allowed for the best permeation and evaporation performance. Fig. 8b shows the production ratio of nickel production over the total mass production. The ideal ratio of nickel production would be 4.3% of the total mass production. As seen in Fig. 8b the production ratio of nickel was calculated to be within the experimental error of the 4.3% mark, meaning that the system is non-selective to either water or nickel, which is desirable for a percrystallisation process. This means that there is no accumulation of water or nickel sulphate on the permeate site. Based on these findings, the best performing membrane was found to be the one prepared in the 20 wt% sucrose solution.
[00105] Fig. 9a shows the nickel and water production rates of the best performing membrane as a function of the feed concentration. It can be observed that the water production rates decreases as the concentration of nickel sulphate increases, while the opposite is true for the nickel production rates. Fig. 10b illustrates how much the nickel production contributes to the total mass production. It can be observed that the production ratio increases linearly with the black squares being the observed production fraction, while the blue circles is the ideal production ratio. It can again be observed that the membrane is non- selective, even at different solute concentrations.
[00106] Fig. 1 la presents the production rates of nickel and water, using the best performing membrane, with a nickel concentration of 40 g L"1 while varying the operating temperature. A near linear trend in water and nickel production rates can be observed, while the production ratio in Fig. 10b confirms that the process is non-selective during operation.
[00107] The produced solutes were analysed by SEM imaging and XRD. Fig.l 1 shows the XRD patterns attained by the products. A key finding in the based on the diffractograms is that the solutes produced by membranes prepared with sucrose concentrations of 40 and 50 Wt %, by the feed concentration of 100 g L"1, or using a feed temperature of 50°C exhibited diffraction peaks consistent with nickel sulphate hexahydrate and nickel sulphate heptahydrate. The remaining samples only consisted of peaks consistent with nickel sulphate heptahydrate. The production of hexahydrate crystals by usage of the membranes produced at higher sucrose concentrations can be explained by the decreased water production rates, as shown in Fig. 8 a. The lower water flux would be caused by a lower transport of solution to the surface of the membrane unit, meaning that less water needs to evaporate per unit of time to attain dry solute. The vacuum pump is operating with a constant output and because of this, more water could be removed. This which would allow for the formation of some hexahydrate crystals during percrystallisation. A similar explanation can be used when explaining why a nickel feed concentration of 100 g L"1 allowed for production of hexahydrate nickel sulphate crystals. The water concentration of this solution would be lower than the other solutions tested, meaning that less water would need to be removed from the surface of the membrane. An explanation for why the experiments at 50°C allowed for formation of crystals with a lower hydration state, would be the fact that the driving force for evaporation would be higher, thus faster removal of solvent would occur. An explanation for why the higher temperature of 60°C did not produce any detectable hexahydrate phase would be that the used vacuum pump was not able to remove the vapour efficiently enough.
[00108] These findings were supported by the morphological findings by SEM imaging, as shown in Fig. 12. The images shown illustrates that the morphology of all samples containing a mixture of heptahydrate and hexahydrate crystals are forming particles approximating a spherical morphology, some of which also shows the formation of pore cavities in the particles. All the samples only containing nickel sulphate in a heptahydrate phase on the other hand produces particles that are elongated/laminar in morphology. It can be argued that the sample produced by the 30 Wt % sucrose membrane and the sample produced by a feed concentration of 70 g L"1 are the least elongated/laminar because they could potentially contain an undetectable amount of hexahydrate phase. These findings suggest that through control of operating parameters and membrane characteristics it is possible to control the hydration states of the produced crystals. [00109] The apparent activation energy for evaporation and crystal formation were calculated by using the molar fluxes of water and nickel. The natural logarithm to the production rates were plotted as a function of one over the operating temperature. Using the slope, an apparent activation energy can be calculated. The apparent activation energy for water production was calculated to be 15 kJ mol-1, while the apparent activation energy for nickel production was found to be 16 kJ mol"1. The apparent energy of activation for both evaporation of water and percrystallisation of nickel sulphate are both in the range of mass transport-controlled reactions and in the range of diffusion controlled reactions in water.
[00110] This example demonstrates how sucrose derived carbon membranes can be used for percrystallisation of hydrometallurgical products like nickel sulphate. It was shown how percrystallisation potentially can be used to tune hydration states of percrystallised products by varying different conditions; increases in carbon content in the membrane allowed for production of nickel sulphate with a lower hydration state, by constricting the flow of solution to the surface. Increases in feed concentrations allowed for a similarly lower trans -membrane transport of water, allowing for the production of hexahydrate crystals. And by increasing the driving force for evaporation through higher operating temperatures would allow for the formation of lower hydration states, assuming that the vacuum levels could be maintained at the same low levels. The apparent activation energies for both water and nickel production was estimated to be in the range of a diffusion or mass-transport limited process.
[00111] The ability to tune hydration states of percrystallised product and the solute non- accumulating nature of percrystallisation have demonstrated how this technology have potential uses for zero-liquid discharge systems, especially in cases where polymorph control through control of operation conditions is desired.
EXAMPLE 11
[00112] In this example, the crystallisation of paracetamol using a percrystallisation technique was investigated. Membranes were prepared in a manner similar to that described in example 10. Sucrose solutions containing 5%, 10%, 20% and 30%, by weight, were used to produce the membranes. The membranes were carbonised at 750°C. Paracetamol (5%) in ethanol solution was used for crystallisation experiments. The experiments were performed at room temperature and the solution temperature was not controlled or monitored. The paracetamol crystals that were produced by percrystallisation were harvested using a vacuum system. The sample collection time was 20 minutes. Ethanol was collected in a cold trap cooled by liquid nitrogen. [00113] The following membrane performance was recorded:
Membrane made from 5% sucrose solution - ethanol flux of 20.22, paracetamol flux of 0.49;
Membrane made from 10% sucrose solution - ethanol flux of 17.42, paracetamol flux 0.76
Membrane made from 20% sucrose solution - ethanol flux of 16.01, paracetamol flux of 0.89; and
Membrane made from 30% sucrose solution - ethanol flux of 21.54 and paracetamol flux of 1.04.
[00114] The flux measurements given above were determined in the units of kg/(m2 hr).
[00115] The paracetamol crystals that have been produced in this example were analysed using FT-IR. The FT-IR spectrum showed that the materials produced in this example are identical to paracetamol purchased from commercially available sources. Therefore, the percrystallisation process has no influence on the structure of the paracetamol at a molecular level. Further testing revealed that there was no apparent difference in the thermal properties and crystallinity between the control paracetamol and the paracetamol crystalized using the pervaporation membranes.
[00116] A comparison of the crystal shapes with commercially available paracetamol products shows that the crystals are of generally similar shape, although the shape of the crystals can be influenced by the particular membrane that is used.
[00117] EXAMPLE 12
[00118] In this example, paracetamol was crystallised using percrystallisation under the following conditions:
5% paracetamol in ethanol solutions,
Solution was at 74°C,
Crystals collected from the surface of the membrane in air, and
Solution was circulated by a peristaltic pump to retain the same operational conditions
(concentration and temperature of the solution).
Paracetamol produced by pressure driven membrane per-crystallisation process at 74°C in air. SEM photomicrographs of the paracetamol crystals collected after (a) 5 min, (b) 2h and (c) 18h of operation from the membrane surface are shown in figures 14(a), (b) and (c), respectively. It is noted that the crystal size is dependent on the crystal contact time with the solution on the membrane surface.
[00120] EXAMPLE 13
[00121] This example investigates the morphological features of porous carbon membranes and operation effects for the percrystallisation of NaCl. The carbon membranes were prepared by dip coating of a-alumina tubes in a sucrose solution, followed by a post vacuum-assisted impregnation and carbonisation in an inert gas atmosphere. The carbonisation temperature played an important role, as the highest pore volume and wet contact angle were achieved at the highest carbonisation temperature of 750 °C. In turn, this created hydrophobic carbon membranes delivering the highest water flux of 33 L m"2 h"1 (NaCl 17.5 wt%) and NaCl flux of 6.9 kg m"2 h 1. The solvent (water) and the solute (NaCl) crystals were separated in a single-step in a wet thin-film formed on the permeate face of the membrane under pervaporation conditions, delivering almost pure water (>99%) and dry NaCl crystals. The carbon membrane with the highest water flux delivered the smallest NaCl crystallite sizes, the smaller particle sizes, and the narrowest particle size distribution (< 2 μιη). This was attributed to the fast water evaporation rate from the wet thin-film, as crystal growth rate was reduced and NaCl particle aggregation was restricted. A finer control of NaCl crystallite and particle size was achieved by tailoring the morphological features of the carbon membranes and operating at the lowest vacuum pressure.
[00122] In this example, sucrose membranes were carbonised in inert gas from 600 to 750 °C and assessed for the percrystallisation of a NaCl (17.5 wt%) solution under various permeated vacuum pressures. The morphology of the carbon membranes was characterised by mercury porosimetry, wet contact angle and SEM analysis. The membranes were tested for both water permeation and NaCl percrystallisation. The formed NaCl particles were analysed statistically using SEM images, and the crystallite sizes were determined by XRD analyses. The
morphological features of the membranes were correlated to the membrane performance and the produced NaCl particles and crystals.
[00123] Solutions were prepared by dissolving 20 wt% sucrose (>99.8%, Chem-supply) into demineralised water which was sonicated for 30 min. Subsequently, the sonicated solution was used for dip coating of tubular a-alumina substrates (Ceramic Oxide Fabricators, Australia) with a mean pore size of 0.1 μιη. Both ends of the tube were glazed, and the effective membrane are dimensions were ~3 cm in length, 1 and 0.45 cm external and internal diameters, respectively. Dip coating was carried out on the outer shell of the a-alumina tube. The tube was inserted into the solution for 3 min dip time, followed by a withdrawal from the solution at speed of ~31 cm min"1. Upon withdrawal, the coated tube was exposed to a vacuum pressure (<1.3 mbar) via the inner shell for 5 min. This allowed for a partial impregnation of the coated thin-film into the a- alumina tube. The membranes were dried overnight in an oven at 60°C. The dry sucrose membranes where then carbonised in an inert nitrogen atmosphere at three different temperatures (650, 700 and 750 °C), using heating and cooling rates of 5 °C min"1 and a dwell time of 4 h at the highest temperature.
[00124] Mercury porosimetry was carried out on a Micromeritics AutoPore IV9500 to quantify pore size distribution and pore volumes of the membranes. Pressure values were used to calculate pore sizes according to the Washburn equation (assuming cylindrical pores) and a mercury contact angle of 154.9° for carbon. The maximum pressure applied was 415 MPa (4150 bar), corresponding to a pore size of 3.5 nm. The morphological features of the membranes were analysed by scanning electron microscope (SEM) using a Jeol JSM-7001F SEM with a hot (Schottky) electron gun and an acceleration voltage of 5 kV.
[00125] Pure carbon materials, produced by drying a sucrose sol followed by carbonisation, were also analysed by X-ray diffraction (XRD) and contact angle measurements. XRD analysis was carried out using a Rigaku Smartlab X-ray diffractometer at 45 kV and 200 mA, with step size of 0.02° and speed of 4°min_1 with filtered Cu radiation (λ = 1.5418 A). Contact angle measurements were determined by using an Andostar digital microscope Al and by placing water droplets on the surface of carbonised sucrose. Thermo-gravimetric analysis (TGA) was conducted on a TGA-DSC1 (Mettler Toledo) using an inert nitrogen gas at a flow rate of 60 mL min"1 and a heating ramp rate of 10 °C min"1.
[00126] Thermogravimetric analysis shows the mass loss of the sucrose sol under inert nitrogen atmosphere during carbonisation. There is a steep 60% mass loss from 200 to 300 °C. This mass loss is associated with the release of H2, CO, CH4, and C02 during the pyrolysis (carbonisation) of sucrose. From 400 to 800 °C, the mass loss greatly reduces, around -14% only, thus indicating the loss of oxygenated groups in sucrose. The XRD patterns of the sucrose samples carbonised at high temperatures show that although all the patterns are similar, it is observed that the resolution of the peak at 2Θ 43° becomes less broader as the carbonisation temperature increased to 750°C, a clear indication of structural evolution toward a more ordered structure. The water contact angles reveal similar values of 107° for carbonisation temperatures at 650 to 700°C, though it increased to 118° as the carbonisation temperature was raised to 750 °C. All the contact angles values are > 90°, which demonstrates that the carbonised sucrose is indeed hydrophobic, and the increase in the contact angle from 107° to 118° indicates that hydrophobicity has increased. This can be associated to the continuous mass loss at the highest temperatures, suggesting further removal of organic groups from the carbonised sucrose. These organic groups tend to cluster water molecules in carbon structures, and the absence of these groups increased carbon hydrophobicity. These results are also in line with the XRD patterns, as a minor change towards graphitisation tends to increase hydrophobicity.
[00127] Figure 15 displays the SEM images for the cross section of the carbonised sucrose membranes. A carbon film with a thickness in the range of 6-12 μιη is clearly observed in Fig. 15a for the membrane carbonised at 650°C. This carbon film forms a top-layer (on the outer shell of the tube) with good adhesion and partial infiltration into the a-alumina substrate. This morphology is attributed to two-step coating strategy used in this work. The first coating step corresponds to the contact of the sugar solution with a dry porous ceramic oxide substrate. This caused initial high capillary forces, and the liquid solution is immediately drawn into the substrate (spontaneous liquid imbibition within the pores) induced by the wetting force. Upon reaching equilibrium, the wetting force becomes less significant and further solution penetration into the porous substrate ceased. This first coating step results in the formation of a top-layer on the support surface with only shallow solution penetration into the porous substrate during the dip-coating process. The second coating protocol, induced by the applied vacuum pressure on the inner shell of the membrane tube, results in the drawing of the sucrose solution from the outer shell deeper into the substrate. This is evidenced by the carbon films with total thickness up to 12 μιη as observed in Fig. 15a. However, by increasing the carbonisation temperature to 700 °C, the visual appearance of the carbon film morphology changed (Fig. 15b) and became a very porous material once the carbonisation temperature reached 750 °C (Fig. 15c).
[00128] The morphological features of the carbonised sucrose membranes were analysed by mercury porosimetry. Fig. 16a shows a narrow pore size distribution between ~0.11 and -0.05 μιη. Contrary to this, the carbonisation temperature played an important role as the total pore volume increased with temperature as displayed in Fig. 16b. As sucrose filled the a-alumina pores (inter-particle space) during impregnation, porosity is developed during the carbonisation process. This is evidenced by the mass loss attributed to sucrose's oxygenated groups as ascertained by TGA analysis. The continuous mass loss as the carbonisation temperature increases from 700 to 750°C causes further morphological re-arrangement leading to a visually more porous structure as observed in the SEM image (Fig. 15). Therefore, the measured pore volume for the carbonised sucrose membranes in Fig. 16b matched well the SEM observations in Fig 15.
[00129] Fig. 17 shows that both fluxes of NaCl and water increased as a function of the carbonisation temperatures used to prepare the membranes. For instance, the water fluxes increased by 27% from 26 to 33 L m^ h"1, while NaCl by 12% from 6.2 to 6.9 kg m^ h"1, as the carbonisation temperature was raised from 650 to 750 °C, respectively. These results are consistent with the fact that the carbonisation temperature was found to affect the morphological features and surface interaction of the carbon membrane, as revealed by the mercury porosimetry and contact angle experiments, in addition to the SEM observations. These findings confirm the correlation that as pore volume increases, so does the water production rates. As percrystallisation is believed to essentially occur at the wet thin-film interface, increasing the water flux evaporated from the wet thin-film translates into higher NaCl percrystallised flux, in line with the results in Fig. 17.
[00130] In all experiments, the water collected in the cold trap was analysed and resulted in almost pure water (> 99%). These results confirm that the carbonised sucrose membranes were able to separate solvent (water) from solute (NaCl) in a single step separation process, a characteristic of the novel membrane percrystallisation process. This type of application is industrially very attractive, particularly for crystallisation processes where solvent recovery is a key point to reduce operational costs or to comply with strict environmental regulations such as zero liquid discharge. Notably, the very high water flux of 33 kg m"2 h_1 (NaCl 17.5 wt%) in Fig. 5 was aimed at solidification of NaCl instead of water purification. However, this value is higher than those of 20-28 L m~2 h"1 delivered by industrial reverse osmosis (RO) membranes with a much lower feed NaCl concentration of 3.5 wt%. The feed NaCl 17.5 wt% concentration used in this work would generate an osmotic pressure over 135 bar, well beyond the RO plant operation capabilities. In addition, the high water fluxes in this example are also much higher than those obtained in pervaporative desalination using inorganic membranes operating at higher temperatures and lower NaCl feed concentration such as 22.9 L m"2 h"1 for cobalt oxide silica membranes (7.5 wt% at 60 °C) [32], 25.4 L m"2 h"1 for carbon alumina membranes (3.5 wt% at 75 °C) [33] and 9.2 L m"2 h"1 for hybrid carbon silica membranes (15 wt% at 60 °C) [34]. This great performance of the carbonised sucrose membranes for pure water recovery proved to be a bonus for using this technology to crystallise solutes whilst recovering the solvent.
[00131] As the best performance in terms of water and NaCl fluxes was delivered by the membrane carbonised at 750 °C, this membrane was further tested to investigate the effect of the vacuum pressure in the permeate side. Fig. 18 shows that by increasing the pressure from 18 mbar to 26 mbar, the water flux reduced by 15% from 32 to 27 L m"2 h 1, and the NaCl flux also decreased by 8% from 6.8 to 6.2 kg m"2 h"1. These changes in fluxes are commensurate with the reduction of the driving force for water evaporation from the wet thin-film formed on the surface of the carbon membrane on the permeate side (outer shell). An interesting finding of this example was that percrystallisation ceased for vacuum pressures above 28 mbar where flooding on the permeate side occurred. In other words, a wet thin-film was no longer attained. In this situation, instead of dry NaCl crystals being ejected from the membrane surface and water being evaporated, large blobs of water and salt together were ejected and collected in the Buchner flask. This finding strongly suggests that both the carbon membrane morphological features and the vacuum pressure play a role in modulating the wet thin-film on the permeate face of the membrane where percrystallisation occurs. If the vacuum pressure is not low enough, then the water evaporation rate from the wet thin thin-film is lower than the permeation rate of the solution from the feed side to the wet thin-film in the permeate side. Under these conditions, excess solution started flooding the permeate side, which conferred unattainable conditions for the single-step NaCl crystallisation and water evaporation.
[00132] Fig. 19 presents SEM images of the dry NaCl crystals recovered at the end of the percrystallisation tests. The first general trend is that the membrane with the higher carbonisation temperature induced NaCl crystals morphological changes. For instance, the crystals produced by the membrane carbonised at 650 °C shows fairly regular particles with near cubic shapes. By raising the membrane's carbonisation temperature to 700 °C, the structure of the crystals became irregular and more inter-grown. For the highest carbonisation temperature of 750 °C, crystals shapes were less defined and more agglomerated. The histograms in Fig. 19 display average particle sizes of 2.8, 2.65 and 0.76μιη for the carbonised membranes at 650, 700 and 750 °C, respectively. The membrane carbonised at 650°C yield large number of NaCl particles between 1-3 μηι in size, though also producing a small number of larger particles and skewing the distribution to a higher particle size average. The membrane carbonised at 700°C predominantly delivered particles between 1-2 μιη in size, whilst a wider spread of particle size distribution is observed. The membrane carbonised at 750°C produced particles significantly different in terms of both particle sizes (< 1 μιη) and size distribution. Indeed, the majority of the particle sizes are fairly well distributed around the mean value (0.76 μιη).
[00133] The morphology of the dry NaCl crystals was also affected by the vacuum pressure as displayed in the SEM images in Fig. 20. It is clearly observed that the particle sizes became more regular and their shape better defined as the operating pressure is increased, with the particles obtained at 18 mbar having the most irregular morphology. The particles formed at 22 mbar show a more regular and cubic structure compared to those produced at 18 mbar, though particles with a non-regular shape were also observed. At the highest operating pressure of 26 mbar, NaCl crystals are generally regular in shape, thus conforming to a cubic structure. The histograms in Fig. 20 reveal mean particle sizes of 0.76, 10.95 and 7.4 μιη for NaCl obtained at 18, 22 and 26 mbar, respectively. There is a significant difference between all three size distributions, clearly evidencing the effect of operational pressure in the formation of NaCl particles. However, the size distribution curves of the particles obtained at 22 and 26 mbar can be considered as similar in the sense that outliers sizes (observed in all cases) are skewing the distribution to larger values (right side). Of particular interest are the particles formed at the lowest vacuum pressure (18 mbar). This lowest operating pressure produced the narrowest particle size distribution as compared to the wider values obtained at 22 and 26 mbar vacuum pressures.
[00134] The histograms in Figs. 19 and 20 confirms the formation of very small NaCl particles with sizes below 8 μηι for the membranes prepared 650°C and 700°C and even lower at 2.5 μιη for the membrane carbonised at 750 °C. For the latter, an increase of the vacuum pressure up to 26 mbar led to the formation of larger NaCl particles reaching 35 μιη. Nevertheless, these particle sizes are still one to two orders of magnitude smaller than those reported for polymeric membrane crystallisation with particle sizes of 20-200 μιη and 300-1000 μιη. Therefore, the membrane percrystallisation results in this work produced smaller NaCl particles with a narrower size distribution compared to those produced by polymeric membrane crystallisation. In other words, membrane percrystallisation offers a finer control for the production of NaCl crystals.
[00135] Fig. 21 displays the XRD patterns of the NaCl particles produced using membranes carbonised at different temperatures. All the XRD patterns are almost identical in peak positions. There are two major peaks at 2Θ 31 and 45°, and several minor peaks at 20 28, 54, 56, 66, 75 and 83°. Based on the XRD patterns, the NaCl particles are assigned to a cubic (Fm-3m) structure with space group number 225 (pdf file 01-077-2064). The only difference between the patterns is a slight increase of the peak intensities as a function of the carbonisation temperature of the membranes.
[00136] An interesting aspect of the above results is that there is a relationship between the membrane morphology and the size of crystallites. The latter was determined by applying the Scherrer equation to the XRD patterns in Fig. 21. The first relationship in Fig. 22a shows the evolution of crystallite sizes with the membrane pore volume, as determined by mercury porosimetry (Fig. 16a.). The second relationship in Fig. 22b shows the evolution of the measured water flux (Fig. 17) versus membrane pore volume. These results clearly show that the NaCl crystallite size decreases and water flux increases as a function of the membrane pore volume. These relationships explain that larger membrane pore volumes are able to transport more solution to the permeate face of the membrane where a wet thin-film is formed and percrystallisation of NaCl takes place. As the water flux increases, so does the water evaporation which in turn induces an increase in the supersaturation index of NaCl in the wet thin-film. Consequently, faster nucleation rates impact crystal growth rates and causes the formation of smaller crystals. This is the reason why crystallite sizes are smaller for the membranes delivering the highest water fluxes.
[00137] The effect of water flux on the NaCl particle size formation was also investigated based on the membrane carbonisation temperature and operating vacuum pressure. Fig. 23a shows a linear relationship between NaCl particle size and water flux, where a fine control in average particle size is demonstrated for the membrane carbonised at 750 °C. As this membrane delivered the highest water flux, it formed the smaller particle sizes as well as a narrow particle size distribution. Fig. 23b shows the effect of permeate vacuum pressure on the formation of NaCl particle size. It seems that there is a need for a breakthrough condition as once permeate vacuum pressure is sufficiently low, particle sizes decrease noticeably. Again the finest particle size control is obtained at the highest water flux, which in this case is associated with the highest driving force for the lowest vacuum pressure at the permeate side. These results suggest that at the highest water flux, water evaporation from the wet thin-film on the permeate face of the membrane is very fast that NaCl crystals have short time to agglomerate only before being ejected. As a consequence, higher water fluxes tend to yield smaller particles, contrary to lower water fluxes which allow more time for NaCl crystals clustering and forming larger particles.
[00138] This example demonstrates the versatility of carbon membrane percrystallisation as a technology for the production of crystalline products with specific quality requirements. By differentiating membrane structure, it was possible to tune particle size, morphology, and crystallite size of produced NaCl crystals. Variations of operating pressures were less sensitive to NaCl particle size control until a sufficiently low permeate vacuum pressure was set, where a breakthrough condition for fine particle size was attained. The finer control of NaCl crystallite size, particle size and narrower particle distribution (<2 μιη) was achieved with the membrane carbonised at the highest temperature of 750 °C. This membrane carbonisation temperature conferred the highest pore volume, and in turn the highest water flux. As NaCl percrystallisation occurred at the wet thin-film on the membrane face at the permeate side, the fast water evaporation rate enhanced nucleation and crystallisation. Under fast water evaporation rate, NaCl crystals were ejected from the membrane surface, thus reducing their particle aggregation and restricting the crystal growth. The morphological features of the carbon membranes played an important role in controlling percrystallisation process, in addition to tuning the particle size and crystallite size of NaCl. These are important parameters to spur the novel membrane percrystallisation technology to other industrial applications.
[00139] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers.
[00140] Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment.
Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.
[00141] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any)
appropriately interpreted by those skilled in the art.

Claims

Claims
1. A method for producing a solid material from a solution containing one or more dissolved species or products dissolved in solvent, the method comprising the steps of providing the solution to one side of a porous material, the porous material having pores in the mesoporous and/or macroporous pore size range, wherein the solution comprising the solvent and the dissolved species or products passes through the porous material, and evaporating at least part of the solvent from the other side of the porous material, characterised in that a solid material is crystallised and recovered from the other side of the porous material.
2. A method as claimed in claim 1 comprising evaporating solvent from the other side of the porous material at substantially the same rate or faster than a rate of solvent passing through the porous material to form a solid material on the other side of the porous material.
3. A method as claimed in claim 1 or claim 2 wherein the porous material has at least a layer comprising an inorganic layer having mesoporous pores or macroporous pores and/or a carbon layer having mesoporous pores or macroporous pores, or a mixed matrix having mesoporous pores or macroporous pores comprising carbon and another material.
4. A method as claimed in claim 3 wherein the porous material has at least a layer comprising an inorganic layer having mesoporous pores and/or a carbon layer having mesoporous pores, or a mixed matrix comprising carbon and another material having mesoporous pores.
5. A method as claimed in claim 3 wherein the porous material has at least a layer comprising an inorganic layer having macroporous pores or a carbon layer having macroporous pores, or a mixed matrix comprising carbon and another material having macroporous pores.
6. A method as claimed in any one of the preceding claims wherein the material is a
macroporous material having pore sizes in the range of from 50nm to l,000nm, or 50nm to 500nm, or 50 nm to 250nm, or 50nm to 200nm, or 50nm to 150m, Or 50nm to 125nm, or 50nm to 1 lOnm.
7. A method for producing a solid material from a solution containing one or more dissolved species or products dissolved in solvent, the method comprising the steps of providing the solution to one side of a porous material, the porous material having pores in the mesoporous and/or macroporous pore size range, wherein solution comprising the solvent and the dissolved species or products passes through the porous material, and evaporating at least part of the solvent from the other side of the porous material, characterised in that a solid material is crystallised and recovered from the other side of the porous material wherein the porous material has porosity such that it retains molecules having a molecular weight of greater than 100,000 Daltons and the layer has pores of larger than 2nm.
8. A method as claimed in any one of the preceding claims wherein the porous material
comprises an inorganic porous material having at least a layer comprising an inorganic layer having mesoporous pores and/or macroporous pores and/or a carbon layer having mesoporous pores and/or macroporous pores and a substrate having pore sizes larger than pores in the layer, and the at least one layer having mesoporous pores.
9. A method as claimed in any one of the preceding claims wherein the layer comprises a layer comprising an inorganic layer having mesoporous pores and/or a carbon layer having mesoporous pores comprises a layer formed on a surface of the substrate, or comprises a plurality of layers formed on a surface of the substrate.
10. A method as claimed in claim 4 or claim 9 wherein a majority of the pores of the mesoporous layer are between 2 to 50 nm in diameter, or between 2 to 30 nm, or between 2 to 10 nm.
11. A method as claimed in any one of the preceding claims wherein the porous material is a porous inorganic membrane that comprises a hierarchical membrane comprising layers with pores at different length scales including the micro-, meso- and macroporous range.
12. A method as claimed in any one of claims 1 to 10 wherein the porous inorganic membrane is a stratified asymmetric membrane having layers with pore sizes differing from those layers in which they are in contact with.
13. A method as claimed in any one of the preceding claims wherein the porous material
comprises a porous inorganic substrate coated with a layer of inorganic material, the porous inorganic substrate having larger pores than the layer of inorganic material.
14. A method as claimed in claim 13 wherein the layer of inorganic material has mesoporous pores.
15. A method as claimed in any one of claims 1 to 12 wherein the porous material comprises a porous substrate that has one or more layers of carbon thereon, the one or more layers of carbon being formed by an impregnation method in which a carbonaceous liquid or a carbonaceous solution is impregnated onto one side of the porous substrate, followed by carbonising the carbonaceous material to form the carbon layer.
16. A method as claimed in claim 15 wherein the carbonaceous liquid or carbonaceous solution comprises a solution in which a carbonaceous material is dissolved or the carbonaceous liquid comprise a resin or a polymer precursor.
17. A method as claimed in claim 15 or claim 16 wherein the one or more layers of carbon have mesoporous pores, or the one or more layers of carbon have macroporous pores, or the one or more layers of carbon have mesoporous pores and macroporous pores.
18. A method as claimed in any one of claims 1 to 12 wherein the porous material comprises a substrate having a layer thereon, and the layer comprises a mixed matrix membrane containing carbon and MOFs (metallic organic frameworks), the layer being formed by impregnating and/or coating a carbonaceous liquid containing MOFs into a substrate, followed by carbonisation.
19. A method as claimed in claim 18 wherein the layer has mesoporous pores, or macroporous pores, or mesoporous pores and macroporous pores.
20. A method as claimed in any one of the preceding claims wherein the method is used to
produce mineral salts, food additives, pharmaceuticals and chemical products, chloride salts, nickel chloride, magnesium chloride, potassium chloride, lithium chloride and sodium chloride, nitrate salts, nickel nitrate, crystalline acids, ascorbic acid, vitamins, sodium lactate, proteins (including antibodies, enzymes, peptides) from solution including serum or water.
21. A method as claimed in any one of the preceding claims wherein the solution that is supplied to the method comprises an aqueous solution containing dissolved material or a non-aqueous solution containing dissolved material.
22. A method as claimed in any one of the preceding claims wherein the porous material has a flat geometry or the porous material is in a tubular form, or in the form of hollow fibres, or capillary fibres, or the porous material is of a tubular shape and the tube is open at both ends or is closed at one end.
23. A method as claimed in any one of the preceding claims wherein the layer of the mesoporous material is coated on an inner shell of a tubular substrate, or it is coated on an outer shell of a tubular substrate.
24. A method as claimed in any one of the preceding claims wherein the method is conducted as a batch process or as a continuous process.
25. A method as claimed in claim 24 wherein the method comprises a batch process in which the solution is fed to an inner part of a tubular porous material and crystals of material grow on an outer part of the tubular porous material, with the crystals growing in batches and being removed from the outer part of the tubular porous material by a drying process or microwave irradiation.
26. A method as claimed in claim 25 wherein the crystals are removed from the outer part of the tubular porous material by mechanical action or the crystals are ejected from the tubular porous material by microwave irradiation.
27. A method as claimed in claim 24 wherein the method comprises a continuous process in which the solution is fed to an inner part of a tubular porous material and crystals of material grow on an outer part of the tubular porous material, with the crystals continuously growing and being removed from the outer part of the tubular porous material during operation of the process.
28. A method as claimed in any one of the preceding claims wherein further comprising applying a vacuum to the other side of the porous material.
29. A method as claimed in claim 28 wherein an absolute pressure on the other side of the porous material ambient pressure of about 1 atm down to very low vacuum pleasures below 1 Torr.
30. A method as claimed in any one of the preceding claims further comprising heating the
solvent passing through or that has passed through the porous material.
31. A method as claimed in claim 30 wherein the solvent passing through the porous material is heated to a temperature within the range of from ambient temperature up to the boiling point of the solvent.
32. A method as claimed in claim 30 or claim 31 wherein the solution is heated prior to passing through the membrane.
33. A method as claimed in any one of the preceding claims wherein the solution that is supplied to the porous material is pressurised or the solution is supplied under ambient pressure.
34. A method as claimed in claim 1 or claim 2 wherein the porous material comprises a porous polymer.
35. A method as claimed in any one of the preceding claims wherein the porous material is not a microporous material.
36. A porous material for use in a percrystallisation process, the porous membrane comprising a porous substrate having a layer thereon or therein, the layer comprising an inorganic layer having mesoporous pores or macropores and/or a carbon layer having mesoporous pores macropores or a mixed matrix having mesoporous pores or macropores comprising carbon and another material, the porous substrate having a porous structure having pores that are larger than the pores in the layer.
37. A porous material having at least a layer comprising an inorganic layer and/or a carbon layer and/or a mixed matrix comprising carbon and another material, wherein the layer has porosity such that it retains molecules having a molecular weight of greater than 100,000 Daltons and the layer has pores of larger than 2nm.
38. A porous material as claimed in claim 36 or claim 37 wherein the layer having mesoporous porosity is relatively thin and the substrate is relatively thick.
39. A porous material as claimed in claim 38 wherein the layer having mesoporous porosity has a thickness of from 0.5 to 5 μιη and the substrate has a thickness of from 100 μιη to 5 cm.
40. A porous material as claimed in any one of claims 36 to 39 wherein a majority of the pores of the layer are mesoporous pores of between 2 to 50nm in diameter, or between 2 to 30 nm, or between 2 to 10 nm.
41. A porous material as claimed in any one of claims 36 to 40 wherein the layer comprises an inorganic material selected from a metal oxide, titanium oxide, zirconium oxide or an aluminium oxide, or a mixture of these metal oxides, or γ-alumina, or porous mixed metal oxides.
42. A porous material as claimed in any one of claims 36 to 40 wherein the layer comprises carbon and the carbon comprises porous graphite, porous graphene, agglomerates of carbon nanotubes, agglomerates of carbon fibres, or a porous carbon membrane may be applied to the substrate.
43. A porous material as claimed in any one of claims 36 to 42 wherein the substrate comprises a porous inorganic material selected from a porous metal oxide material or a porous metal.
44. A porous material as claimed in claim 43 wherein the substrate comprises titanium dioxide, zirconium dioxide, aluminium oxide, or a mixture of two or more thereof, or a mixed metal oxide substrate.
45. A porous substrate as claimed in claim 43 wherein the substrate comprises a porous metal substrate.
46. A porous material as claimed in any one of claims 36 to 45 wherein the substrate has a bulk of the pores in the substrate sized at 50nm or larger, or lOOnm or larger, or 500nm or larger.
47. A porous material as claimed in any one of claims 36 to 46 wherein the porous material is in the form of a flat sheet or a flat plate or the porous material is in the form of a tube or a pipe.
48. A porous material as claimed in any one of claims 36 to 47 wherein the layer comprises a layer of carbon and the layer of carbon has macropores.
49. A porous material as claimed in any one of claims 36 to 47 wherein the layer comprises a layer of carbon and the layer of carbon has mesopores.
50. A porous material as claimed in any one of claims 36 to 47 wherein the layer comprises a layer of inorganic material and the layer of inorganic material has mesopores.
PCT/AU2018/050903 2017-08-25 2018-08-24 Percrystallisation method and porous material for use therein WO2019036767A1 (en)

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CN113772764A (en) * 2020-06-09 2021-12-10 国家能源投资集团有限责任公司 Reinforced natural evaporation crystallization device and evaporation pond
CN116272922A (en) * 2023-02-15 2023-06-23 南宁师范大学 Preparation method of modified mesoporous cobalt-based composite material

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WO2011044582A1 (en) * 2009-10-09 2011-04-14 R.P. Scherer Technologies, Llc Apparatus for making crystals

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WO2011044582A1 (en) * 2009-10-09 2011-04-14 R.P. Scherer Technologies, Llc Apparatus for making crystals

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CN113772764A (en) * 2020-06-09 2021-12-10 国家能源投资集团有限责任公司 Reinforced natural evaporation crystallization device and evaporation pond
CN116272922A (en) * 2023-02-15 2023-06-23 南宁师范大学 Preparation method of modified mesoporous cobalt-based composite material

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