GB2460064A

GB2460064A - A method of forming a permanently magnetic absorbent composite material

Info

Publication number: GB2460064A
Application number: GB0808793A
Authority: GB
Inventors: Maria Catherine Tabiner
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-05-15
Filing date: 2008-05-15
Publication date: 2009-11-18
Also published as: GB0808793D0

Abstract

A composition of and method for forming an inorganic absorbent composite with permanent magnetic properties for magnetic separation of the composite from a liquid, vapour or gas being treated is disclosed. Wherein a preformed inorganic substrate (substrate) is mixed with a magnetic or magnetisable iron particle or particles and with an organic binding agent to form a composite mixture that when dried and subjected to pyrolysis of the bionding agent to form carbon bridges at a temperature below the curie temperature of the magnetic component forms composite particles in which the porous structure or solid structure substantially the same as that of the substrate prior to pyrolysis with regard to porosity, pore and particle size. The substrate has attached to its surface magnetic particles. The attachment is made by forming a carbon bridge between the substrate and magnetic particle. The resultant composite has controlled permanent magnetic properties dependent on the retentive magnetism of the type of magnetic material used or concentration of the magnetic particles attached to the substrate. The specific absorption qualities and porosity of the substrate particle are largely unaffected by the attachment of the carbon bridge and magnetic particles. The magnetic particles may be of any particle size below 20 micron, fine particle size, even micro powdered or nanoparticles, and still yield magnetic properties sufficient for magnetic agglomeration and separation. In a particular aspect of the invention, the substrate can be any commercial grade of inorganic absorber such as carbon or activated carbon which has been tailored during its manufacture for specific absorption properties. Other inorganic absorbent substrates can also be used examples are but are not limited to titanium dioxide, zeolite or clays who's structure and absorption properties have been tailored for specific absorption character in application. Also compositions of and methods for forming inorganic absorbent composites with permanent magnetic properties for magnetic separation of the composite from a liquid, vapour or gas being treated are disclosed. Wherein a organic substrate precursor is mixed with a magnetic or magnetisable iron particle or particles to form a composite mixture that when dried and subjected to pyrolysis below the curie temperature of the magnetic component forms composite absorbent particles in which a porous structure may be introduced by the process of pyrolysis. The substrate particle formed during pyrolysis has attached to its surface magnetic particles. The attachment is made by forming a carbon bond between the substrate and magnetic material during pyrolysis. Also disclosed is the addition of an organic binding agent to the mixture, which forms carbon bridges during the pyrolysis stage.

Description

Description:

BACKGROUND OF THE INVENTION

Porous inorganic materials are used to remove any number of materials from liquids and gasses either for the recovery of values or for the purification of a wide range of substances. They are used in the water, food, mining, automotive, chemicals, pharmaceutical and environmental industries. A common application of this type of material is to adsorb ions, complexes and molecules from aqueous solutions. An example would be activated carbon which has been used to extract metal ions or organic pollutants, either to purify the water, and/or to recover valuable material.

In water treatment applications, adsorbing media such as activated carbon are commonly used for removing organic molecules and heavy metals. These pollutants, which can range from natural organic molecules to synthetic types and heavy metals must be removed to render the water suitable for use and to comply with environmental regulations. In the case of activated carbon this is often accomplished by contacting the polluted water with the activated carbon. The treated water and the activated carbon are then separated, and the activated carbon is either disposed of as in the case of powdered activated carbon or treated in the case of granular activated carbon to remove the absorbed species and re-establish the capacity of the carbon. The water is often contacted with the carbon by passing the watel through fixed beds of the carbon. However, some operational efficiency can be derived by mixing the water and carbon in, for example, a stirred tank or fluidised bed. However, this requires separation of the carbon by mechanical screening or settlement * : to separate the carbon particles from the treated water. In the case of *..* powdered activated carbon this can be time consuming and impractical due to the low density of the particle and fine size. *

The adsorptive properties of porous adsorbents such as activated carbon are *: a consequence of the highly developed micro porous structure and of the surface functional groups generated during their production process.

Commercial grades of carbon have been tailored by successive development * for specific adsorption properties; this has resulted in a wide range of types being manufactured. Adsorption onto activated carbon is a diffusion-controlled process, where the size of the carbon particles plays an important role. In general adsorption capacity and adsorption kinetics increase as the size of the activated carbon particles decrease. In spite of the advantages that fine activated carbon particles offer in terms of adsorption capacity and adsorption kinetics, conventional carbon-recovery circuits tend to use granular activated carbon particles that are significantly coarser than the ground powdered version. This is due to the difficulty of effective separation of the loaded powdered activated carbon from the wet slurry phase by settlement, filtering or mechanical screening.

As the most important factor influencing adsorption rate is particle size of the adsorbent and the adsorption rate of a carbon particle is diffusion limited it is known that with <0.045 mm carbon powder 90% of adsorption is over in the first 15 seconds. With granules of 3 mm to 5 mm in diameter several hours contact time is necessary to reach 90% of capacity. This high adsorption rate of powdered activated carbon makes its use very attractive where long contact times are either not desired or impractical.

Granular activated carbon, the form more widely used, has the advantage that it can be used in an adsorption bed or in a column for both up flow and down flow operation, provided the flow rates are not excessive. Its main disadvantage is the relatively slow adsorption rate necessitating contact times in the order 15 to 30 minutes. Thus, a column has to be made large enough to provide the required contact time, and necessitates the use of large quantities of excess carbon.

Powdered carbon has the great advantage of rapid adsorption rate over granular carbon, but it is difficult to handle and to separate from solution and provisions for settling and/or flocculation have to be made for satisfactory recovery. This negatively impacts the primary advantage obtained from increased adsorption rate. Furthermore, the settled adsorbent is usually quite voluminous, making handling and disposal of it difficult and therefore expensive.

The present invention relates to a permanent magnetically tailor able adsorbent composite of low specific gravity or density. In one particular aspect, the present adsorbent reduces the normal settling time of for example carbon powders several fold without an externally applied magnet field.

The present invention is directed to modifying existing commercial adsorbents without impacting on their ability to absorb and remove specific pollutants, i.e. in the case of carbon it relates to that of a commercial carbon which is modified to have a high magnetic agglomeration rate and settling rate without changing significantly the bulk specific gravity, porosity or absorption capacity of the commercial grade of carbon used. In the case of carbon the composite : **. adsorbent consists essentially of a substrate carbon core, which is an inert porous particle, partially encapsulated with magnetic iron oxide particles bonded to the substrate surface or porous structure by a carbon bridge. The carbon surface remains largely open and porous and its absorptive properties essentially unaffected by the binding of the magnetic particles. S *

A second aspect of the invention is directed to modifying activated carbon precursors to render them permanently magnetic. Upon activation critically at a temperature below the Curie temperature of the magnetic component this produces an activated carbon which has been modified to have a high magnetic agglomeration rate and settling rate due to the permanent magnetic nature of the composite. In this case the composite adsorbent consists essentially of a substrate of porous activated carbon core, which is an inert porous particle, partially encapsulated with magnetic iron oxide particles bonded to the substrate surface or porous structure. The carbon surface via pyrolysis may become open and porous and its absorptive properties can then be modified and functionalized without essentially affecting the composites magnetic character.

Magnetic carbons have been previously made by others and patented by mixing or coating carbon with a magnetic precursor or solution from which one can be precipitated, usually this precipitate is magnetite. A problem with these materials is that the magnetic material is widely dispersed into the carbon particle pores or the carbon sits across substantially most or all of the surface.

This is inherent in these compositions and cannot be avoided, since the magnetite is used in only a minor amount to impart the magnetic property without impacting on the absorbing capacity of the carbon. Thus, depending on the particular composition, the magnetic material is dispersed throughout a matrix as small particles within the carbon material, or concentrated upon the surface. Significantly the natural or synthetically precipitated magnetite has low remnant magnetism and can be considered to be paramagnetic rather than permanently magnetic once activation has been performed at temperature above its curie temperature. When these materials are used in absorption and separation processes permanent magnets must be used to first attract the particles and subsequently separate them. They cannot be separated by virtue of their ability to form magnetic flocculated structures in which each particle attracts and bonds to another particle. This is inherently a disadvantage as external magnetic sources must be used. When these materials are abraded, carbon fines are formed that are either free of magnetic material due either to their pores not containing enough magnetic material or due to loss of that material from the carbon surface and they can not then be magnetically separated. Thus, magnetic separation requires that the particles remain relatively large to maintain their magnetic separation properties and are not abraded either intentionally or by process to maintain their magnetic separation. Once formed the non-magnetic fines cannot be magnetically recovered. Thus, the recovery requires relatively large carbon * particles, the same as in mechanical screening, and fine carbon particles * cannot be recovered.

: **. Other approaches to make magnetic carbons have also involved combining carbon procurers with magnetic materials and forming through either mechanical means or through pyrolysis a magnetic composite. However those which are compounded at room temperature do not bond the particles together permanently and are restricted to forming particles at a size greater * than 1mm unless they become separated in application. Those formed at high temperature form magnetic cores with a carbon shell and are not able to directly magnetically agglomerate by direct attachment of their magnetic component. Significantly they can also lose from their magnetic core structure some of the carbon coating which is a disadvantage as these are not magnetic and are lost from the process thus reducing the absorption capacity of the media.

There is a need in the art for permanently magnetic porous absorbents such as magnetic activated carbon that have controlled and tuneable magnetic properties. Where the magnetic property is bound to the surface and attached across the surface of the carbon substrate so that when magnetised it retains high remnant magnetism and allowing particles to agglomerate by direct contact between the magnetic components bound to the surface. There is also a need in the art to allow for the production from commercially available absorbents their magnetic analogues which are not subject to restrictions of particle size or porosity or post activation which can be used within tailored and proven applications to take advantage of their chemistry. The use of permanently magnetic forms of magnetite or other magnetic materials with tuneable remnant magnetism would be an advantage. Such materials are commercially available in the form of pigments of magnetite, ferrites and gamma ferric oxide. Binding of these materials to the surface of an absorber would allow enhanced recovery largely independent of the particle size of the absorbing substrate and totally eliminate the need for screening. Smaller activated carbon particles (even powdered, micro powdered or nano powdered) could then be used to exploit kinetic and adsorption capacity advantages of small particles. This invention allows the simple production of such materials. * ** *S * * ** I* * S *5S* * ** *. S S*S

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Summary of the Prior-art.

United States Patent 2,479,930 discloses a process of precious metals recovery from ores using a magnetic activated carbon that can be recovered from solution using a magnetic separator.

United States Patent 4,260,523 discloses a method for forming a magnetized active carbon composition that consists essentially of mixing 100 parts of active carbon and 5-100 parts by weight of a magnetized ferromagnetic material, and compressing the mixture to form pellets. The magnetic particles are not bound or bonded to the surface of the carbon but are simple mechanically attached after being processed at room temperature. This is a disadvantage in application for example in water they become detached. The loss of the magnetic component will cause the particles to become demagnetised which is a considerable disadvantage.

United States Patent 4,201,831 describes a physical mixture of a magnetic particulate material and a solution of organic material which when dried and heated will decompose into "elemental" carbon, to produce a magnetic adsorbent composite. In this case the magnetic material is encapsulated with carbon. This does not allow the magnetic component to directly contact the magnetic component of another particles. This is a disadvantage as it slows the magnetic agglomeration rate of the particles reduces the strength of magnetic attachment and reduces the settlement rate when used in liquid separation systems in the absence of an external magnetic field. Furthermore the carbon can become detached from the magnetic core producing carbon particles which are not magnetic which is a disadvantage.

United state patent 4,284, 511 describes a process in which a physical mixture of magnetic particle and charcoal granule is used. The material is * .** produced by the process cited in US 4201831 to a size range 1 -2 mm. This size range is a disadvantage in fluidised systems due to the low surface area available for absorption when compared to powdered systems below 1mm International Application No PCT/2002/006065 describes a process in which a * carbonaceous precursor is infused from a solution of iron salts. The iron salts are treated to form a magnetic precursor. When the mixture is then carbonised it yields a magnetic activated carbon of small size. This magnetic carbon can be used to advantage due to its high surface area and small particle size. This application requires the carbon to be produced insitu from a carbonaceous precursor that must be infused with magnetic precursor and cannot be applied to ready made carbon forms such as commercially available forms tailored for specific applications. Additionally it does not allow preformed magnetic particles to be used of predetermined magnetic strength and is restricted to those that can be precipitated which is a disadvantage.

The magnetic material is dispersed throughout the carbon and is not of high remnant magnetism which reduces the magnetic particle to magnetic particle attraction in the absence of an external magnetic field. This is a clear disadvantage in applications such a fluid counter current systems when the degree of magnetic flocculation determines the settling rate of the particles for a given up flow velocity.

The above patents all disclose magnetic carbons formed from mixtures including magnetic materials. As discussed above, these compositions usually require that the carbon particles retain a relatively large size to ensure that the magnetic property is retained in the particle.

For the activated carbon materials used in a solution, such as in United States Patents 2,479,930 and 4,201,831, the handling of the carbon produces carbon fines, as the particles are abraded. These carbon fines usually have not retained any of the magnetic material and cannot be separated by a magnetic field. This results in the loss of the carbon and any material that was adsorbed upon the carbon.

International Application PCT/2002/006065 and US Patent 4,284,511 allow for smaller particle size but do not allow for commercial carbon grades to be used. This composition requires a route is followed that excludes commercially available activated carbons some of which are specifically tailored for specific removal of contaminants.

In co pending U.S. Patent application, Ser. No. 726,960, entitled "Magnetic Adsorbent Composite" filed Sept. 27, 1976 in the names of George M. J. Slusarczuk and Ronald E. Brooks and assigned to the assignee hereof, there is disclosed a magnetic adsorbent composite composed of a magnetic substrate particle which is non-reactive under conditions of use and which is encapsulated with adherent activated carbon.

* ,. In co pending U.S. Patent application, Ser. No. 726,962 entitled "Magnetic Adsorbent And Flocculent" filed Sept. 26, 1976, now abandoned in favor of Ser. No. 830,115 filed Sept. 2, 1977 in the names of George M. J. Slusarczuk and Ronald E. Brooks and assigned to the assignee hereof, there is disclosed a method for simultaneous removal of soluble and insoluble impurities from polluted liquids by adding thereto a magnetic adsorbent composite powder which adsorbs soluble organic impurities and a flocculent which flocculates suspended solid impurities and the magnetic powder and magnetically settling * the flocculated mixture. **

* In co pending U.S. Patent application, Ser. No. 726,961 entitled "Ferrite Flocculating System" filed Sept. 27, 1976 now U.S. Pat. No. 4,193,866 in the names of George M. J. Slusarczuk and Ronald E. Brooks and assigned to the assignee hereof, there is disclosed a method for removal of insoluble suspended impurities from polluted liquids by adding thereto a magnetic ferrite powder suspend able therein and a polyethyleneimine flocculent which flocculates suspended solid impurities and the magnetic powder producing a dense flocculated mixture. These patents prefer to form the carbon as an exterior coat surrounding the magnetic core. These are at a disadvantage to the invention reported here as they limit they type and range of carbon used to those that can be made insitu by pyrolysis. No ready made commercial grades can be used, furthermore they require post activation of the carbon to establish full absorption capacity.

International Application No PCT/US2004/042434 describes a magnetic carbon made by compounding a carbon precursor namely bituminous coal with a binder coal tar pitch and magnetite powder. The mixture is screened and then compacted and crushed before heating in an oxidising atmosphere at 450C. The resulting oxidised iron containing coal particulate is then gasified in steam at 925C to produce an iron containing porous activated carbon absorbent. Inherent in this method is that the carbon must be activated after the incorporation of the magnetic component at a temperature higher than the curie temperature of the magnetite used which is 575C. It is well known above this temperature the magnetite in the presence of oxygen is converted to hematite. Additionally even in the absence of oxygen above this temperature the ordering of the crystal structure is also altered resulting in a shift from ferrimagnetic or ferromagnetic to paramagnetic. Once the material is cooled it will not exhibit ferromagnetism or ferrimagnetism but rather anti ferromagnetism as hematite.

This patent claims other magnetic materia's can be used in the same process, however as the activation temperature is above their curie temperature it is unavoidable they will undergo changes to their crystal structure. This is a clear disadvantage in that susceptibility to a magnetic source will be altered and the remnant magnetism of the magnetic component will be significantly altered. Materials produced by this method can therefore only be separated by the use of external magnetic source. This is clear disadvantage and fundamentally a difference and disadvantage to the invention described in this application which allows for permanently magnetic carbons of high remnant magnetism to be produced from activated carbons which do not require * .* activation at high temperatures once they have been made magnetic. * * * * .* is''

The invention in this application is unique as it allows for the production of permanently magnetic composite particles from any commercially available * absorbents such as activated carbon of any particle size or tailored porosity 4. by direct blending with a magnetic or magnetisable particle in the presence of a binder which can subsequently be carbonised to bond the substrate porous particle to the magnetic or magnetisable particle. The absorbent is modified in this way and renders it to become a magnetic composite. The composites have magnetic particles bonded to a porous substrate particle in such a way as to leave the substrate surface open. The substrate particle is not significantly altered by particle size, porosity, surface area and absorption capacity. The magnetic particles are not altered with regard to their structure, ferrimagnetism or ferromagnetism maintaining their ability to hold remnant magnetism and be permanently magnetic. This is because they are heated to a maximum temperature that is below the curie temperature of the magnetic component to carbonise the organic binder or components. Furthermore the handling of the magnetic composite does not produce abraded particles that have not retained their magnetic character or create loss of the substrate or material absorbed upon the substrate. The composite is unique in that it has tailored and controlled remnant magnetism Additionally the invention in this application is unique as it allows for the production of permanently magnetic composite particles with controlled remnant magnetism from any single or combination of potential activated carbon precursor such as but not limited to powdered corn or wheat starch or powdered wood or coal of any particle size by direct attachment with a magnetic or magnetisable particle which during the process of pyrolysis is carbonised to bond the substrate particle to the magnetic or magnetisable particle. The carbon precursor is modified in this way and renders it to become upon magnetisation a magnetic carbon composite. The structure of the particle is unique, the core of the particle is carbon and the surface carries magnetic particles across it. The composites have magnetic particles bonded to a porous or solid substrate particle in such a way as to leave the substrate surface open. The substrate particle is not significantly altered by particle size except to the extent that during pyrolysis it decomposes to lose volatile organic compound hydrogen and oxygen and introduce porosity with increased surface area and absorption capacity. Furthermore the handling of the magnetic composite does not produce abraded particles that have not retained their magnetic character or create loss of the substrate or material absorbed upon the substrate. By correct choice of magnetic particle the carbon can be then be activated or functionalised without the loss of magnetic property by methods normally used to create the activation such as steam or acid treatment.

The method of production is unique in that it allows for simple large scale production and use of permanently magnetic composite particles from readily * ** available commercial absorbents or absorber precursors which have been tailored for specific applications in a wide range of purification processes. * * .1* * .*

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SUMMARY OF THE INVENTION AND EXAMPLES

The present invention provides a magnetic absorbent wherein magnetic material is intimately or essentially dispersed over and bonded to the surface of the porous particle such as activated carbon particles. This absorbent or precursor used can be small fines which by this process can be made directly permanently magnetic. The magnetic absorbent of the invention has a controlled variable magnetic property and a fine particle size. If a commercial absorber such as activated carbon is used as the precursor it will maintain the same kinetic properties and adsorption capacity relative to it carbon content.

The present invention is a composition and process wherein magnetic material is intimately and essentially homogeneously combined with a solid or porous material such as an activated carbon and bonded to its surface. This allows a permanent magnetic property to be retained even in small powder particles and allows magnetic flocculation and separation for these small particles. The process of the invention in the case of carbon involves the intimate mixing or combining of a carbon, commercial activated carbon or with a precursor used for the production of activated carbon directly with magnetic material precursor.

1. Magnetic composite made by direct attachment and bonding of magnetic particles to the surface of an activated carbon.

The magnetic precursor is initially contacted with a binding agent at a concentration which coats all or part of the magnetic precursor. The carbon substrate and the magnetic precursor are intimately mixed and integrated by suitable means and then the mixture is heated to a temperature were the binding material initially softens or melts or flows forming a bridge between the substrate and the magnetic precursor particles at the point at which their * ,, surfaces contact. The bonded mixture is then heated to higher temperature below the Curie temperature of the magnetic component in an inert ** atmosphere. During this process the binding agent is carbonised forming a carbon bridge between the magnetic precursor and the substrate.

* *. A preferred embodiment of the invention is where the magnetic precursor is mixed with an organic binder which is readily carbonised at temperatures ** below 500C such as starch or sugars or types of synthetic polymer or surfactant. When the coated magnetic precursor is then mixed together with the inorganic absorbent such as carbon, upon pyrolysis (carbonization) * treatment the ferromagnetic material binds to the carbon through the carbonisation of the bonding agent. By this method the surface and porous character of the carbon is largely unaffected allowing commercial absorbents typically manufactured for specific adsorption qualities or particle size to be used. In this method in the case of carbon the carbon may be a porous material that readily allows the softening or flow of the heated binder to attach to the surface of the carbon and become adhered onto its porous structure, thus establishing the bond between the magnetic precursor and carbon substrate. This bridge between the substrate and the magnetic precursor when carbonised forms a carbon bridge binding the composite structure together.

The porous carbon is mixed into the magnetic particle coated with binder for sufficient time to integrate enough magnetic material onto the porous carbon material so that when the porous material is heated and the mixture carbonized the activated carbon has gained sufficient magnetic precursor particles to allow it to be easily ground to the original substrate particle size without loss of magnetic quality.

The binder may also be a carbon containing material that melts and becomes liquid and allows or enhances mixing with the magnetic material. The binder may soften or melt sufficient to allow a bridge to form between the magnetic material and the carbon material in the product prior to carbonisation. Suitable materials include starches, sugars and molasses, and low melting, low density plastics such as polyols and poly vinyl alcohol, and all categories of surfactant.

The binder or dispersant may be a material that is soluble in water or other solvent, thus dissolving and coating from solution the magnetic precursor.

Such materials include sugars, molasses and other soluble carbohydrates that are by-products of the food and paper manufacturing industries. Also suitable are water or solvent-soluble plastic materials such as polymers copolymers and surfactants. It may be the binder is added at a concentration to coat the surface of the magnetic precursor as a monolayer, bi-layer or multiples off and aid it's wetting onto the surface of the substrate. This concentration is within the skill of a practitioner to determine. It is preferred that the concentration of the binder should be adjusted to minimise the concentration of binder residing freely in the bulk liquid, this concentration is within the skill of a practitioner to determine.

The magnetic precursor may be any suitable compound that contains iron in * ** any suitable form, which may be, but not limited to ferric iron, ferrous iron, or elemental iron.

Suitable magnetic precursors include, for example, compounds that are soluble in water which form ions of iron solution. These include, but are not * ** limited to ferric and ferrous salts, such as ferrous chloride, ferric chloride, ferric nitrate, ferrous sulphate, ferric sulphate, and ferric citrate. These soluble *:. compounds can be dissolved to form a solution and used to precipitate as a magnetic material in the presence of the binder which in a fine particle form can be used to soak onto the carbon material. In this manner it is integrated onto the porous carbon substrate by the soaking the carbon substrate in a suspension of the precipitated compound and binder.

It is preferred that solid iron based materials are used either directly or with a binder coating or dispersed or suspended into a liquid together with a binder such as a surfactant or a starch to form a homogeneous solid or liquid mixture or suspension. Examples of solid iron materials are iron oxides (such as magnetite (Fe304)), commercially available pigments such as gamma ferric oxide or magnetite. Alternatively ferrite powders such as barium,strontium or cobalt ferrite can be used or mixtures of any of the aforementioned. It is preferred that the material should be capable of having high remnant magnetism or tuneable remnant magnetism once exposed to a saturation magnetic source.

The magnetic particles are preferred to be of an average size that is between a 0.05% to 30% of the average size of the carbon substrate particle.

The magnetic composite particles of the invention comprise a carbon substrate which may be a commercially available porous activated carbon with the ferromagnetic material dispersed upon and bonded onto the surface of the substrate. The dispersion is essentially on a particulate level leaving most of the substrate surface open and unmodified. The composite product has a tuneable remanent magnetization as a consequence of the specific magnetic properties of the magnetic precursor or combinations of magnetic precursor chosen. For this reason the use of external magnetization to induce separation is unnecessary.

In the case of magnetic carbon the small particle size of the magnetic composite results in higher loading capacity of the adsorbed material and faster adsorption kinetics than prior-art activated carbons which cannot be used at such small particle size without the loss of fine non magnetic particles or magnetic particles which have inherently a low degree of magnetism. It allows any commercial grade of carbon or activated carbon to be magnetically modified and unlike prior art is not limited to that which is formed during pyrolysis of precursor materials.

For the present invention, particle size of the magnetic composite produced can be largely that of the size of the absorber chosen as the substrate. A particle size between about imicron to 300 micron has been found suitable for magnetic separation, but particles sizes well outside of this range may be suitable depending upon the application. This size is generally included in the * ** range considered powdered and micro granular. Smaller sized particles are also subject to magnetic separation, but smaller sizes require higher loadings of magnetic material and so are disadvantaged by a reduction in carbon content and absorption capacity by weight. In current studies of the invention, * *. average particle size for the carbon substrate has been between 1 and 500 microns, typically the carbon substrate has a particle size range of 5 to 300 microns.

In extraction of pollutants the present invention will result in shorter absorber contact times, faster adsorption kinetics than that of the traditional absorbers *** currently used in industry. The magnetic properties of the absorber will permit loaded absorber to be recovered from slurry or sludges by any suitable magnetic separation method, such as a wet high intensity magnetic separator or magnetic drum separator, instead of the current screening process.

Uniquely the permanent magnetic nature of the individual particle allows for each particle to attract other particles and be recovered from low viscosity liquids via magnetic agglomeration and flocculation without the need for an external magnetic source.

For water purification applications, practice of the present invention will introduce more flexibility in how in the case of carbon the activated carbon is contacted with the water, allowing mixed systems, instead of fixed bed systems, and dramatically increase the amount of powdered activated carbon that can be used to achieve the desired purification. Separation and reuse of the activated carbon from the water can be directly by magnetic flocculation of the particles or from coagulated sludges achieved by known magnetic separation technologies.

In summary, the advantages of the present invention derive from firstly the very small particle size of the magnetic activated absorber resulting in higher adsorption kinetics than that of conventional granular absorbing media.

Second, because the absorber is permanently magnetic with tuneable remnant magnetism, it can easily be separated from streams to which it has been added, even from those that contain solids and reused. Thirdly this invention allows modification to all commercial grades of absorbers such as activated carbon or other inorganic particles used for absorption without affecting their designed capacities, such improvements have significant economic impact on plant design and operation. Fourthly the composite absorbers have tuneable remnant magnetism which can be established to allow for easy dispersion in mixed systems.

The improved adsorption capacity and kinetics can also result in further advantages. Generally, during the process of adsorbing material from the solution, the concentration of the material in solution will be reduced much quicker, and in a continuous process the concentration will typically be much lower. Based on chemical principles, this will alter the equilibrium and the driving forces for reactions involving the adsorbed material and favour counter current systems over co current or pure mixed systems.

* ,. In the case of magnetic activated carbon particles of the invention they may be used in any application where activated carbon is required and where separation of the activated carbon is required. These include any application where liquids are treated with activated carbon and the carbon is then : ** separated from the liquid. The magnetic activated carbon may also be used in gas treatment applications where separations of the carbon from another process material, such as another particulate adsorbent or catalyst, are required. In counter current systems the tuneable remnant magnetism of the invention is essential in allowing the system to be operated in the absence of S.....

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**...* * Counter current flow of the magnetic particles against the liquid being treated and the separation of the particles is then accomplished by direct magnetic agglomeration of the surface bound magnetic component. Since small particle (powdered) particles can be separated, the choice of particle size of the activated carbon is dependent upon the magnetic separation process and the amount and type of magnetic material bonded to the substrate, which allows greater flexibility in optimizing the size for adsorption or other properties.

Briefly stated, the present process comprises providing a activated carbon substrate particle having a minimum specific gravity of less than 0.5 to a maximum of 4 and a minimum size of about 1 000nm or above diameter admixing with a magnetisable iron oxide such as a ferrite, alpha iron oxide of magnetite which has been coated with an organic binder. The binder at a temperature ranging from about 500 C. to about 1000° C. at atmospheric pressure first softens and melts forming a bridge between the carbon substrate and magnetisable particle. At higher temperatures but below the currie temperature of the magnetic component the binder decomposes to yield elemental carbon and gaseous product of decomposition. Upon decomposition he substrate carbon particle and magetisable iron oxide form a substantially composite mixture in which the magnetic particle is bound to the carbon substrate through a carbon bridge. Simply milling the resulting composite produces a magnetic carbon adsorbent composite of predetermined size which is substantially that of the in particle size of the carbon precursor.

The substrate particle of the present adsorbent composite is a low density porous material which functions with respect to its absorptive and physical properties in substantially the same way as the precursor material.

The magnetic particulate coating bonded to the carbon is an insoluble and non-toxic material which is inert under aqueous and oxidizing conditions and which functions with respect to its magnetic and physical properties in substantially the same way as the precursor material.

Specifically, it is a material which is non-reactive under the conditions used to prepare the adsorbent composite and non-reactive under the conditions of use as an adsorbent. The inert magnetic particle has a specific gravity ranging for most applications from about 2.0 to about 10.0. The bonded magnetic * *. precursor particle size range from about 100 Angstroms in diameter to about microns in diameter. Representative of such materials is very fine magnetic sand such as finely ground naturally occurring hematite and magnetite which is an iron oxide ore with specific gravity 4.9-5.3 Typical metal : ** powders useful as topographic materials are magnetic metal alloy powders such as cobalt ferrite, selenium ferrite, barium ferrite, gamma iron oxide or synthetic magnetite.

: The binding material is an organic compound such as a molasses, starch, * S sugar, polymer, copolymer or any type of surfactant which is a solid or liquid at room temperature and which softens, melts, f'ows and decomposes progressively as temperature is increased within a range from about 50° C. to about 1000°C but below the currie temperature of the magnetic component to yield elemental carbon and gaseous product of decomposition. Typical of such organic materials is yeast flour, sugar, molasses, coal tar, pitch, asphalt and various uncross linked organic polymers and copolymers such as poly acrylic acid or poly vinyl alcohol, copolymers with polymeric acids and bases or acrylonytrile and polyamides and surfactants of the generic types nonionic, cationic, anionic or amphoteric.

In carrying out the present process, the magnetic precursor particles are admixed with the organic binder or dispersing agent to form a substantially thorough mixture. It is preferable if the binder can also act as a dispersion agent on the magnetisable particles. The particular amount of organic binding material used is determined largely by the number of magnetic particles and their surface area. This is dependent of the degree of magnetism required to be imparted to the composite, the minimum amount of magnetic precursor used is that amount which would ensure attraction to an electro or permanent magnet including other magnetized particles of the composite material.

Generally, to insure sufficient magnetic attraction for separation the organic binder and magetisable material should be used in an amount significantly less than the substrate particles, i.e. from about a 1 -40% volume of substrate particles. These is no particular limit on the maximum amount of organic binder to be used but it is preferred this should be used to provide dispersion of the magnetic precursor and coating of its surface only.

A number of techniques can be used to produce a substantially thorough or uniform mixture of the organic binder and magnetic material. In one technique the organic binder in powder form is admixed with the magnetic particles by conventional means such as a milling to form a substantially thorough mixture and then melted. In another technique the organic binder can be heated to melt it and in molten form it is admixed with the magnetic particles by suitable means. Alternatively, the organic binder can be dissolved in a solvent such as water or another organic solvent and the resulting solution admixed by known techniques such as spray drying with the substrate particles to form a uniform mixture. In each instance, the resulting mixture is heated to the decomposition temperature of the organic binder to yield elemental carbon and the gaseous product or products of decomposition are diffused away. The decomposition is preferably carried out in an oxygen-free atmosphere such as nitrogen. The resulting magnetic carbon-substrate composite particle in dry form is easily * ** milled to a predetermined size producing the present flowable adsorbent * S.. composite. Grinding of the mass can be carried out by a number of conventional techniques such as by means of dry ball milling. A fine sizing using sieves will separate any undesirable agglomerates i.e., those not : ** ground to the optimum desired size. It is a particular attraction of this invention in that the grinding to a fine powered is done easily requiring little energy and producing few none magnetic particles.

*....: On decomposition of the organic binding material, elemental carbon is * S produced which adheres or bonds itself between the surface of the substrate particle and the magnetic precursor particles. The bonding agent becomes sufficiently activated to be useful as an adsorbent in its own right but the absorbing properties of the substrate particle are not materially affected and may be preferred. The bond between the substrate surface, the surface magnetic particle and elemental carbon is sufficiently strong so that the composite can be handled for gas and liquid adsorption applications without significant loss of activated carbon or break up of the magnetic particle substrate bond. The extent to which the composite is activated depends largely on the particular carbon selected for inclusion in the composite as the substrate. In the present invention by a sufficiently activated carbon to be useful it is meant an activated carbon having a minimum surface area of about 20 square meters per gram as measured by means of a gas adsorption or in iodine number of at least about 50. Such large surface areas indicate a porous structure which provides the adsorption means. If desired the present adsorbent composite can be treated by a number of techniques to establish or increase its activation, or if necessary to reactivate it. One such technique is to heat the adsorbent composite in steam. The invention also provides for the use of solid substrates such as solid carbon which may be preferred due to their higher density.

The adsorbent composite is composed of a substrate particle such as activated carbon ranging in size from about l000nm to about 0.6 millimeters in diameter which is partially encapsulated with magnetic particles or clusters of magnetic particles adhered to the substrate surface by a carbon bond or bridge. The surface of the substrate is open, porous and substantially the same as in its premodified form.

The size and the weight or density of the present adsorbent composite depends on its particular application. It has a minimum specific gravity of about 0.20. The present adsorbent composite can be a single particle composed of substrate particle partially encapsulated with magnetic particles or aggregates of particles or one substrate particle attached to a single magnetic particle.

In contrast to powdered substrates such as in the case of carbon which as a fine powder settles very slowly, the present magnetic adsorbent composite can be tailored to have a range of settlement rates at the same equivalent size dependent on the type, quantity and remnant magnetism of the magnetic particles attached to its surface. Specifically, the present adsorbent can provide the same rate of adsorption as powdered carbon and can be recovered by magnetic flocculation without major provisions for settling from * * liquids it is dispersed within. Alternatively it can be separated from the same liquids or sludge's by attraction to permanent magnets or electromagnets used for separation The present magnetic adsorbent composite is particularly useful as fluidized * ** adsorption media in a column for up flow operation utilizing flow rates which would be excessive for granular carbon or powdered carbon of the same size :. resulting in faster adsorption rates in significantly shorter periods of time. For example, when the flow of water upwardly through a granular carbon bed in a column is increased to a certain critical velocity, it fluidizes the bed washing it out of the column and to discharge. With the present tailor able magnetic : adsorbent composite, the critical velocity for granular carbon and powdered carbon of the same size can be significantly exceeded even with fluidization of the bed.

For a given size of adsorbent composite, the binding the substrate of a magnetic precursor particle or agglomerate will change the specific density or specific gravity of the adsorbent composite but not significantly alter its adsorption capacity. An increase in the proportion of the magnetic component increases the remnant magnetism of the composite and therefore the magnetic attraction and settling rate of the resulting composite and its ability to attract other magnetic particles to form a magnetic agglomerate or floc or its attraction to a magnetic source.

SpecificaUy, the present adsorbent composite with particularly high adsorption capacity is one with as fine a size as possible since the smaller the particle size the larger is the surface area available for adsorption.

After the present composite is used, its adsorption properties can be regenerated by methods available for regeneration of regular or commercial powdered or granular activated carbon. These must be performed at a temperature below the Curie temperature of the magnetic component.

Examples of this type of regeneration are but not limited to steam, acid and base regeneration, Regeneration can also be carried out biologically or through electrochemical means at ambient temperatures or moderate temperature below 150C. Heating methods such induction heating can also be used.

Examples of magnetic composite made using activated carbon.

Example la

6gms Black iron oxide Type Colorana CM-5D, Specification Particle size 250nm (median SEM) Magnetic properties Hc, Coercivity Hc (Oe) 390 Remnant (emu/g) 76 Saturation (emu/g) 31 Are mixed with 2gms of soluble starch powder (BDH) and milled together under nitrogen atmosphere in a Hosokawa Mechanofusion AMS-MINI for * ** lOmins. Operating rotor speed is at 6000rpm. During this process the iron oxide becomes coated with the soluble starch S...

S" The mixture is removed to a beaker and is added to 3gms of powdered

: *. activated carbon Type Norit Azo Specification **

Particle size >l50micron 33 % mass >106 micron 58% mass >74 micron 72% mass : >53 micron 81% mass * >37 micron 37% mass Surface area (BET) m2/g 700 Density g/ml 0.34 The powders are further mixed in the beaker with a spatula for another two minutes to ensure a thorough mix on the powders is achieved.

Water is added to wet the mixture to a paste and it again is mixed using a spatula for a further five minutes The mixture is transferred into a metal container and is then heated at 5CImin to 200C in an oven under a nitrogen atmosphere. This temperature is held for mins at 200C after which the temperature is increased at 5C/min to 450C and again held for 1 hour. The mixture is then cooled and the resulting power/cake milled for 30 seconds in a pestle and mortar to break up any agglomerated material and sieved using a series of Endecotes laboratory sieves to classify the composite particle size below 1 50micron.

Samples of powders were then imaged using a scanning electron microscope to determine their structure.

Figure la shows an scanning electron micrograph of the composite product * * * * * * ** S... * S *SS* * *S * S S

S * S.55 * *

S

SSSS*S

S

Figure lb shows the energy dispersive x ray analysis (EDX) of the same image, highlighting the magnetite as white against the gray carbon. * ** * * * * ** S... * . **..

: *s.* Example lb S...

6gms Black iron oxide Type Colorana CM-5D, Specification Particle size 250nm (median SEM) Magnetic properties Hc, Coercivity Hc (Oe) 390 Remnance (emu/g) 76 Saturation (emu/g) 31 Are mixed with 2gms of soluble starch powder (BDH) and milled together under nitrogen atmosphere in a Hosokawa Mechanofusion AMS-MINI for lOmins. Operating rotor speed is at 6000rpm.

The mixture is removed to a beaker and is added to 1 Ogms of powdered

activated carbon Type Norit Azo Specification

Particle size >l5Omicron 33 % mass >106 micron 58% mass >74 micron 72% mass >53 micron 81% mass >37 micron 37% mass Surface area (BET) m2/g 700 Density g/ml 0.34 The powders are further mixed in the beaker with a spatula for another two minutes to ensure a thorough mix on the powders is achieved.

Water is added to wet the mixture to a paste and it again is mixed using a spatula for a further five minutes The mixture transferred into a metal container and is then heated at 5C/min to 200C in an oven under a nitrogen atmosphere. This temperature is held for 30 mins at 200C after which the temperature is increased at 5C/min to 450C and again held for 1 hour. The mixture is then cooled and the resulting power/cake milled for 30 seconds in a pestle and mortar to break up any agglomerated material and sieved using a series of Endecotes laboratory sieves to classify the composite particle size below l50micron.

Example ic

SI,' 6gms Black iron oxide Type Colorana CM-5D, Specification I,...

S... Particle size 250nm (median SEM) Magnetic properties :. Hc, Coercivity Hc (Oe) 390 Remanence (emu/g) 76 Saturation (emu/g) 31 *..* * * Are mixed with 2gms of soluble starch powder (BDH) and milled together under nitrogen atmosphere in a Hosokawa Mechanofusion AMS-MINI for lOmins. Operating rotor speed is at 6000rpm.

The mixture is removed to a beaker and is added to l6gms of powdered

activated carbon Type Norit Azo Specification

Particle size >l50micron 33 % mass >106 micron 58% mass >74 micron 72% mass >53 micron 81% mass >37 micron 37% mass Surface area (BET) m2/g 700 Density g/mI 0.34 The powders are mixed in the beaker with a spatula for another two minutes to ensure a thorough mix on the powders is achieved.

Example id

2g samples of the product of examples Ia, lb and lcwere each added to lOOmis of tap water in sealed conical flasks and shaken to disperse the composite. Into each flask was then inserted a Eclipse Magnetics 9000 gauss magnetic sample probe. Each composite is collected on the surface of the probe and magnetized. The clear water is then drained off and the another 500mls of tap water added. The mixture is then shaken for Iminute to disperse the composite and then allowed to stand. Every 30 second a lOmI sample of the water is removed and the turbidity recorded on a Hach 2700 * ,* turbidity meter. The same procedure was repeated using virgin Norit Azo powdered activated carbon. The results are as follows; **** * * **** Standing time NoritAzo la (NTU) lb (NTU) ic (NTU) sec Off scale 40.4 78.3 138 sec Off scale 37.5 49.7 87 sec Off scale 34 39 58 sec Off scale 31 34 49 * S SS** ___________________ ___________________ ___________________ ___________________ * 150 sec Off scale 29 32 42 sec Off scale 28 29 37 210 sec Off scale __________ 28 33 240 sec Off scale ____________ ____________ 31 270 sec Off scale ____________ ____________ 29 300 sec 96 ____________ ____________ 28 330 sec 87 ____________ ____________ ____________ 360 sec 80 ____________ ____________ ____________ lOmins 69 ___________ ___________ ___________ l5mins 61 ___________ ___________ ___________ L2omins 153 I I Off scale denotes a value beyond the limits of measurement of the turbidity meter.

The procedure was repeated but this time without inserting the Eclipse magnetics sampling probe and allowing the composite to remain unmagnetised. The results are; Standing time Norit Azo 1 a (NTU) lb (NTU) Ic (NTU) sec Off scale Off scale Off scale Off scale sec Off scale Off scale Off scale Off scale sec Off scale Off scale Off scale Off scale sec. Off scale Off scale Off scale Off scale sec Off scale Off scale Off scale Off scale sec Off scale Off scale Off scale Off scale 210 sec Off scale Off scale Off scale Off scale 240 sec Off scale Off scale Off scale Off scale 270 sec Off scale Off scale Off scale Off scale 300 sec 96 173 110 Off scale 330 sec 87 170 98 156 360 sec 80 160 82 110 lOmins 69 118 74 105 l5mins 61 75 62 98 mins 53 48 50 76 Off scale denotes a value beyond the limits of measurement of the turbidity meter.

Example le

1gm of material from examples I a, b and c were mixed with lOOmIs of water in which 15mg/I of humic acid (Aldrich) had been added.

1gm of virgin NoritAzo activated carbon was additionally place in lOOmis of : *. water containing 15mg/I of the same humic material. S...

The UV adsorption of the water containing the humic material was measured by filtering five mis of solution with a Gelman 0.45 micron membrane and placing a irni sample in a Thermo Scientific Genysis 10 UV spectrophotometer at a a wave length of 254nm.

S..... S *

The solutions of humic acid and carbon suspensions were then agitated for 2, and 10 minutes after which interval Smls of each was filtered through a Gelman 0.45 micron membrane and the solution measured for UV absorption by the method outlined.

The table below contains the results of the absorption tests for both virgin Norit Azo to the specification outlined in examples la,lband ic and the magnetically modified carbon as produced in examples Ia lb and Ic.

T Virgin Norit Sample la Sample lb Sample ic ______________ azo ___________ ____________ ______________ Raw untreated -0.890 0.890 0.890 0.890 0 sec ______________ ___________ _____________ ______________ 2 mins 0.602 0.724 0.658 0.621 mins 0.412 0.634 0.442 0.498 lOmins 0.311 0.521 0.321 0.313

Example if

The iodine number of Norit Azo activated carbon and the samples from examples Ia, lb and ic were measured using the method as detailed in BS EN 12902 2004 section 6.10, subsection 6.10.5.2.

The results are show as mg/g of sample used and as mg/g of Azo carbon contained within the sample. * *�

Sample Iodine number (mg/g Iodine number (mg/g ****. sample) Azo powdered carbon in ____________________ _____________________ sample).

: *. Norit Azo 585 585 Sample la 225 833 Sample lb 378 609 Samplelc 466 647 ** **.*

* : Example 2

****** * * Example la is repeated with the following modifications 7.8 cm3 of strontium ferrite powder Grade UMWF -4A (Unimagnet Industry Co Ltd) Particle size 750 nm -850nm Magnetic properties Br(mt) 400 HCB(KA/m) 294 HCJ/(KA/m) 318 (B.H) max (KJ/m3) 31.2 Are mixed with 2ogms of wheat starch powder and ground in a pestle and mortar until a uniform and consistent gray colour is achieved.

To the mixture is then added 58cm3 of powdered activated carbon Type Norit

Azo Specification

Particle size >l50micron 33 % mass >106 micron 58% mass >74 micron 72% mass >53micron 81%mass >37 micron 37% mass Surface area (BET) m2Ig 700 Density g/ml 0.34 The powders are further mixed in beaker with a spatula for another five minutes to ensure a through mix on the powders is achieved.

Water is added to the mixture to cause it become a thick paste. It is mixed for another five minutes.

The mixture transferred into a metal container and is then heated at 5C/min to 200C in an oven under a nitrogen atmosphere. This temperature is held for 30 mins at 200C after which the temperature is increased at 5C/min to 400C and again held for 1 hour. The mixture is then cooled and the resulting power/cake milled for 30 seconds in a pestle and mortar to break up any agglomerated material and sieved using a series of Endecotes laboratory sieves to classify *:*:: the composite particle size below l50micron.

Figure No 2a shows an SEM of the composite material. This clearly shows the open pore structure of the carbon substrate. * * * S...

S S..

*S bSSS * S

S

*SSSSS * . Figure No 2b shows the same micrograph using EDX, showing the open pore structure of the carbon but highlighting the iron ferrite material partially covering the surface and not blocking the pore structure but leaving it open. * p * * *. *6*4 * S * .* ) *6 * * . * *6 * I4

S

I. .555 * . 55.55. * *1

Example 3 * **

Example I is repeated with the following modifications **. * S

* * US 4 gms of gamma ferric oxide powder type HHO -3590 (Nano Chemonics) 3 SI * . S *,**

S

Particle size <imicron (SEM) *. 0.55 * Hc, Coercivity (Oe, 345 Br Gauss 2000 Bm 4050 Are mixed with 2gms of wheat starch powder and ground in a pestle and mortar until a uniform and consistent brown colour is achieved.

To the mixture is then added 8gm of powdered activated carbon Type Norit

Azo Specification

Particle size >l5Omicron 33 % mass >106 micron 58% mass >74 micron 72% mass >53 micron 81% mass >37 micron 37% mass Surface area (BET) m2Ig 700 Density g/mI 0.34 The powders are further mixed in beaker with a spatula for another five minutes to ensure a through mix on the powders is achieved.

The mixture transferred into a metal container and is then heated at 5C/min to 200C in an oven under a nitrogen atmosphere. This temperature is held for 30 mins at 200C after which the temperature is increased at 5C/min to 400C and again held for 1 hour. The mixture is then cooled and the resulting power/cake milled for 30 seconds in a pestle and mortar to break up any agglomerated material and sieved using a series of Endecotes laboratory sieves to classify the composite particle size below l50micron.

Example 4

Example 1 is repeated with the following change Carbon type is changed to grade SKi P57 (CPL carbons Ltd) Particle size d90 41.7 micron d75 28.8 micron d50 17.4 micron d25 10.3 micron dlO 69 micron iodine number 950mg/g S... * ..

Example 5

Example 2 is repeated with the following change *.S...

* * 29 cm3 of strontium ferrite powder Grade UMWF -4A (Unimagnet Industry Co Ltd) Particle size 750 nm -850nm Magnetic properties Br(mt) 400 HCB (KA/m) 294 HCJ/(KA/m) 318 (B.H) max (KJ/m3) 312 Are mixed with 2Ogms of wheat starch powder and ground in a pestle and mortar until a uniform and consistent gray colour is achieved.

To the mixture is then added 58cm3 of powdered activated carbon grade SKI P57 (CPL carbons Ltd) Particle size d90 41.7 micron d75 28.8 micron d50 17.4 micron d25 10.3 micron dIO 6.9 micron iodine number 950mg/g The powders are further mixed in beaker with a spatula for another five minutes to ensure a through mix on the powders is achieved. No water is added to the mixture The mixture transferred into a metal container and is then heated to 300C in an oven under a nitrogen atmosphere. This temperature is held for 30 mins after which the temperature is increased to 450C and again held for 1 hour.

The mixture is then cooled and the resulting free flowing power milled for 30 seconds in a pestle and mortar to break up any agglomerated material.

Example 6

Example 3 is repeated with the following modifications 4 gms of gamma ferric oxide powder type HHO -3590 (Nano Chemonics) * S. Particle size <Imicron (SEM) S... * S *...

Hc, Coercivity (Oe, 345 : *, Br Gauss 2000 Bm 4050 *5* Are mixed with 2gms of wheat starch powder and ground in a pestle and mortar until a uniform and consistent brown colour is achieved.

To the mixture is then added 8gm of powdered activated carbon Type Norit

Azo Specification

Particle size >l50micron 33 % mass >106 micron 58% mass >74 micron 72% mass >53 micron 81% mass >37 micron 37% mass Surface area (BET) m2/g 700 Density g/mI 0.34 The powders are further mixed in beaker with a spatula for another five minutes to ensure a through mix on the powders is achieved. No water is added to the mixture The mixture transferred into a metal container and is then heated to 300C in an oven under a nitrogen atmosphere. This temperature is held for 30 mins after which the temperature is increased to 450C and again held for 1 hour.

The mixture is then cooled and the resulting free flowing powder milled for 30 seconds in a pestle and mortar to break up any agglomerated material.

2. Magnetic composite made by direct attachment of magnetic particles to a carbon precursor.

The carbon particle precursor is contacted directly with magnetic or magnetisable particles at a concentration which coats the carbon powder precursor in such a way that part of its the surface remains open and free from magnetic particles. The carbon precursor substrate and the magnetic precursor are intimately mixed and integrated by suitable means and then the mixture is heated to a temperature were the organic material initially either softens or melts and then forms a adhesive bond between the substrate and the magnetic precursor particles at the point at which their surfaces contact.

The bonding in the absence of a binder is dependent on the compressive nature of the carbon precursor. Hard or crystalline materials which are not easily compressed and do not deform under mixing or heating to take up the magnetic particles may benefit from the inclusion of a binder, this is within the skill of the practitioner to determine. The bonded mixture is then heated at high temperature preferably in an inert atmosphere. During this process the substrate is carbonised below the curie temperature of the magnetic component forming a carbon bridge between the magnetic precursor and the * substrate. **** * *

A preferred embodiment of the invention is where the magnetic precursor is : ,* mixed with an organic particle which is readily carbonised such as but not limited to a powdered or fine organic polymer, starch, sugar, wood or other commonly used for activated carbon production. When the magnetic precursor is then mixed together with the organic carbon precursor upon : pyrolysis (carbonization) treatment, the ferromagnetic material binds to the * carbon through the carbonisation of the substrate or binder and substrate. By this method the surface of the organic substrate is modified and may become porous in character. In this method the substrate is any organic material which under processing allows the magnetic particle to attach to it directly or via a binder which during pyrolysis forms a permanent attachment. Suitable particles for the production of activated carbon are organic particles of sugars and derivatives, starches, wood, polymer latex particles examples of but not limited to poly vinyl alcohol, styrene,acrylates and acrylonitrile. By a combination of the softening of either the substrate or binder and its deposition during carbonisation and pyrolysis the magnetic precursor forms a bond to the surface of the carbon substrate and a composite is produced. To a degree this bond is enhanced by the coating of the magnetic particles by carbon formed by the decomposition of the substrate into volatile organic carbon and its condensation onto the surface of both particles in the pyrolysis process The exact amount of blending of components, degree of magnetization for separation is dependent upon several variables, including exact size, size distribution and composition of the carbon precursor particles, loading of magnetic particles onto the surface of the substrate and is within the skill of a practitioner to determine.

The magnetic precursor particle may be any suitable compound that contains iron in any suitable form, which may be, but not limited to ferric iron, ferrous iron, or elemental iron. Suitable magnetic precursors include, for example, compounds that are soluble in water which form ions of iron solution. These include, but are not limited to ferric and ferrous salts, such as ferrous chloride, ferric chloride, ferric nitrate, ferrous sulphate, ferric sulphate, and ferric citrate.

These soluble compounds can be dissolved to form a solution and used to precipitate as a para magnetic material in the presence of the binder which in a fine particle form can be used to soak onto the carbon material. In this manner it is integrated onto porous carbon material by the soaking the carbon precursor in the suspension of the precipitated compound and binder.

It is preferred they are solid iron based powders that can be applied directly or with a binder. Alternatively they can be simply dispersed or suspended into a liquid and applied in that form. Examples of solid iron materials are iron oxides (such as hematite (Fe203) and magnetite (Fe304)), commercially available pigments such as gamma ferric oxide or magnetite, alternatively ferrite powders such as barium strontium or cobalt ferrite or mixtures of can be used.

The magnetic particles either precipitated from solution or commercially * * available are to be of an average size that is between a 1% to 20% of the average size of the carbon substrate particle.

: *s** The magnetic composite particles of the invention comprise a porous or solid carbon substrate with the ferromagnetic material dispersed upon and bonded onto the surface of the substrate. The dispersion is essentially on a particulate level leaving most of the substrate surface open and unmodified. The composite product has a tuneable remanent magnetization as a consequence * of the specific magnetic properties of the magnetic precursor chosen and the degree of saturation magnetism it is exposed to.

In the case of magnetic carbon it allows any form of activated carbon precursor to be magnetically modified and unlike prior art results in a permanently magnetic composite of tuneable magnetic quality.

For the present invention, particle size of the magnetic composite produced can be largely that of the size of the precursor chosen as the substrate. A particle size between about 0.5micron to 200 micron has been found suitable for magnetic separation, but particles sizes well outside of this range may be suitable depending upon the application. This size is generally included in the range considered powdered and micro granular. Smaller sized particles are also subject to magnetic separation, but smaller sizes require higher loadings of magnetic material and so are disadvantaged by a reduction in carbon content and absorption capacity by weight. In current studies of the invention, average particle size for the carbon substrate has been between 0.8 and 150 microns, typically the carbon substrate has a particle size range of 0.5-300 microns.

In summary, the advantages of the present invention derive from firstly the very small particle size of the magnetic activated absorber. This results in higher adsorption kinetics than that of conventional granular absorbing media.

Second, because the absorber is permanently magnetic with high remnant magnetism, it can easily be allowed to self separate by magnetic agglomeration from streams to which it has been added, even from those that contain solids. Thirdly this invention allows modification to all grades activated carbon and their precursors commonly used in the production of activated carbon to be modified into their magnetic versions. Fourth the composite absorbers have densities which though greater those which would be produced without the attachment of the magnetic component can still be easily dispersed in mixed systems and do not require external magnetic fields to be applied to separate them.

The improved adsorption capacity and kinetics can also result in further advantages. Generally, during the process of adsorbing material from the solution, the concentration of the material in solution will be reduced much quicker, and in a continuous process the concentration will typically be much lower. Based on chemical principles, this will alter the equilibrium and the driving forces for reactions involving the adsorbed material and favour counter current systems over co current or pure mixed systems. * *.

In the case of magnetic activated carbon particles of the invention they may * be used in any application where activated carbon is required and where separation of the activated carbon is required. These include any application : *** where liquids are treated with activated carbon and the carbon is then separated from the liquid. The magnetic activated carbon may also be used in * : * gas treatment applications where separations of the carbon from another process material, such as another particulate adsorbent or catalyst, are required.

* Separation is then accomplished by direct magnetic agglomeration between particles or by attraction to a magnetic source. Since small particle (powdered) particles can be separated, the choice of particle size of the activated carbon is dependent upon the magnetic separation process and the amount and type of magnetic material bonded to the substrate, which allows greater flexibility in optimizing the size for adsorption or other properties.

Briefly stated, the present process comprises providing a carbon precursor particle having a minimum specific gravity of less than 0.5 to a maximum of 4 and a minimum size of about 500nm or above admixing with a magnetisable iron oxide such as a ferrite, gamma iron oxide or magnetite. The organic activated carbon precursor at a temperature below the curie temperature of the magnetic component ranging from about 500 C. to about 1000° C. at atmospheric pressure first softens and forms a bridge between the substrate and magnetisable particle. At higher temperatures the organic activated carbon precursor and binder if used decomposes to yield elemental carbon and gaseous product of decomposition. Upon decomposition he substrate carbon particle and magetisable iron oxide form a substantially composite mixture in which the magnetic particle is bound to the carbon substrate through a carbonized bond. Milling the resulting composite produces a magnetic carbon adsorbent composite of predetermined size which is substantially that of the in particle size of the carbon precursor.

The substrate particle of the present adsorbent composite can be a low density porous material with high surface area. Alternatively it can be a solid material with low surface area.

The bonded magnetisable particle coating is an insoluble and non-toxic material which is inert under aqueous and oxidizing conditions and which functions with respect to its magnetic and physical properties in substantially the same way as the precursor material.

Specifically, it is a material which is non-reactive under the conditions used to prepare the adsorbent composite and non-reactive under the conditions of use as an adsorbent. The inert magnetic particle has a specific gravity ranging from about 2.0 to about 10, and for most applications the specific gravity ranges from about 2.0 to about 6.0. The surface bonded magnetic precursor particle size ranges from about 100 Angstroms in diameter to about 20 microns in diameter. Representative of such topographic materials is very fine magnetic sand such as finely ground naturally occurring magnetite which is an iron oxide ore with specific gravity 4.9-5.3 Typical metal powders useful as topographic materials are synthetic or processed magnetic metal alloy powders such as cobalt ferrite, selenium ferrite, barium ferrite, gamma iron * oxide or magnetite especially those types with potential of high remnant ***.

* * magnetism. ****

: *.., The carbon can be activated by conventional known means i.e. steam treatment without loss or separation of the magnetic component which remains bonded to the surface of the carbon with no loss of magnetic property.

*.**** * In carrying out the present process, the magnetic precursor particles are admixed with the organic carbon precursor to form a substantially thorough mixture. The particular amount of magnetic component used is determined largely by the size of the activated carbon precursor and the degree of magnetism and speed of separation required. The minimum amount of magnetic precursor used is that amount which would ensure attraction to an electro or permanent magnet including other magnetized particles of the composite material. Generally, to insure sufficient magnetic attraction for separation the magetisable material should be used in an amount significantly less by volume than the substrate particles, i.e. from about a 1 -50% volume of substrate particles.

A number of techniques can be used to produce a substantially thorough or uniform mixture of the organic binder and magnetic material. In one technique the organic binder in powder form is admixed with the magnetic particles by conventional means such as a milling to form a substantially thorough mixture. In another technique the organic precursor can be heated to melt it and in molten form it is admixed with the magnetic particles by suitable means. Alternatively, the organic material can be dissolved in a solvent such as water or an other organic solvent and the resulting solution admixed with the magnetic particles to form a uniform mixture and then dried in such a way as to form particles. In each instance, the resulting mixture is heated to the decomposition temperature of the organic component to yield elemental carbon and the gaseous product or products of decomposition. The decomposition is preferably carried out in an oxygen-free atmosphere such as nitrogen. The resulting magnetic carbon-substrate composite particle in dry form can used as produced or crushed to a reduced size producing a flowable adsorbent composite. Grinding of the mass can be carried out by a number of conventional techniques such as by means of dry ball milling. A fine sizing using sieves will separate any undesirable agglomerates i.e., those not ground to the optimum desired size. It is a particular attraction of this invention in that the grinding to a fine powered is not needed or done easily requiring little energy and producing no or very few none magnetic particles.

On decomposition of the organic material, elemental carbon and volatile carbon is produced which adheres or bonds the surface of the substrate particle to the magnetic precursor particles. The carbon becomes sufficiently activated to be useful as an adsorbent in its own right but the incorporation of an additional activation step is preferred. Activation methods known include activation electrochemically, at high temperature with steam, caustic and acids and can be accomplished by those experience in this process by known means. The bond between the substrate surface, the surface magnetic * particle is sufficiently strong so that the composite can be handled for gas and liquid adsorption applications without significant loss of activated carbon or break up of the magnetic particle substrate bond. The extent to which the : ,"* composite is activated depends largely on the particular process used to activate it. In the present invention by a sufficiently activated carbon to be useful it is meant an activated carbon or carbon having a minimum surface area of about 2 square meters per gram as measured by means of a gas *....: adsorption or in iodine number of at least about 50. If desired the present * adsorbent composite can be treated by a number of techniques to establish or increase its activation, or if necessary to reactivate it or create a porous structure. One such technique is to heat the adsorbent composite in steam at a temperature below the curie temperature of the magnetic component.

The adsorbent composite is composed of a substrate particle such as activated carbon ranging in size from about 500nm to about 600 micron in diameter which is partially encapsulated with magnetic particles or clusters of magnetic particles adhered to the substrate surface. The surface of the substrate is open, porous as a consequence of the pyrolysis.

The size and the weight or density of the present adsorbent composite depends on its particular application. It has a minimum specific gravity of about 0.20 and can range from about 600nm to about 0.6mm millimeters in diameter, but generally for most applications, it ranges from about 0.6 microns to about 500 microns in diameter. The present adsorbent composite can be a single particle composed of substrate particle partially encapsulated with magnetic particles or aggregates of particles or one substrate particle attached to a single magnetic particle. When substrate particles ranging from about 500nm to about 4 millimeters in diameter are used, the composite is frequently a cluster composed of a plurality of substrate particles within the matrix of surface bound magnetic particles.

In contrast to powdered substrates such as in the case of carbon which as a fine powder settles very slowly, the present magnetic adsorbent composite can be tailored to have a range of settlement rates at the same equivalent size dependent on the type and quantity of the magnetic particles attached to its surface. Specifically, the present adsorbent can provide the same rate of adsorption as powdered carbon and can be recovered by magnetic flocculation without major provisions for settling from liquids it is dispersed within. Alternatively it can be separated from the same liquids or sludge's by attraction to permanent magnets or electromagnets used for separation The present magnetic adsorbent composite is particularly useful as an fluidized adsorption media in a column for up flow operation utilizing flow rates which would be excessive for granular carbon or powdered carbon of the same size resulting in faster adsorption rates in significantly shorter periods of time. For example, when the flow of water upwardly through a granular carbon bed in a column is increased to a certain critical velocity, it fluidizes the bed washing it out of the column and to discharge. With the present tunable magnetic adsorbent composite, the critical velocity for granular carbon and powdered carbon of the same size can be significantly exceeded even with fluidization of the bed due to the permanent magnetic character and the composites ability to form magnetically assembled flocculated structures.

: .. For a given size of adsorbent composite, binding the substrate to a magnetic precursor particle or agglomerate will change the specific density or specific gravity of the adsorbent substrate but not significantly alter its adsorption capacity. An increase in the proportion or type of the magnetic component *.... increases its remnant magnetism of the composite and therefore the magnetic attraction and settling rate of the resulting composite and its ability to attract other magnetic particles to form a magnetic agglomerate or floc or its attraction to a magnetic source.

The present adsorbent composite is useful as an adsorbent for gaseous, liquid or dissolved contaminants in gaseous or liquid systems. Specifically, the present adsorbent composite with particularly high adsorption capacity is one with as fine a size as possible since the smaller the particle size the larger is the surface area available for adsorption.

Examples of magnetic carbon made using carbon precursors.

Example 6a

6gms Black iron oxide Type Colorana CM-2D, Specification Particle size 500nm (median SEM) Magnetic properties Hc, Coercivity Hc (Oe) 390 Remnant (emu/g) 76 Saturation (emu/g) 31 are mixed with 25gms of powdered wheat starch to the following specification Particle size -Endecotes laboratory sieves used to classify the particle size below l50micron.

The mixture is further milled together under nitrogen atmosphere in a Hosokawa Mechanofusion AMS-MINI for 5mins. Operating rotor speed is at 6000rpm. During this process the wheat starch becomes coated with black iron oxide.

The homogenized powder is then placed into a metal container and heated at 5C/min to 200C in an oven under a nitrogen atmosphere. This temperature is held for 30 mins at 200C after which the temperature is increased at 5C/min to 450C and again held for 1 hour. The mixture is then cooled and the resulting power/cake milled for 30 seconds in a pestle and mortar to break up any agglomerated material and sieved using a series of Endecotes laboratory sieves to classify the composite particle size below l5Omicron.

*... Figure 3a shows an SEM image of the resulting composite powder.

Figure 3b shows the same SEM image using EDX * ** * * * **** *

S * * * S

S

*ISS5* * *

Example 6b

The iodine number of the composite carbon from example 6a was measured using the method as detailed in BS EN 12902 2004 section 6.10, subsection 6.10.5.2.

The results are show as mg/g of sample used and as mg/g of sample.

Sample Iodine number (mg/g sample) Sample la 95 The iodine number of the sample can be increased by methods commonly used for activation, examples of which are but not restricted to steam or caustic activation. Where heat is employed in order to maintain the magnetic property this must not be to a temperature which is higher than the curie temperature 575-585 centigrade

Example 7a

6gms Black iron oxide Type Colorana CM-2D, Specification Particle size 500nm (median SEM) Magnetic properties Hc, Coercivity Hc (Oe) 390 Remanence (emu/g) 76 Saturation (emu/g) 31 Are mixed with 2gms of soluble starch powder (BDH) and milled together * under nitrogen atmosphere in a Hosokawa Mechanofusion AMS-MINI for lOmins. Operating rotor speed is at 6000rpm. During this process the iron oxide becomes coated with the soluble starch ** **** * The mixture is then added to 23grms of powdered Brazilian mahogany : . hardwood dust. This had been ground to a standard at which over 98% passed through a 212 micron sieve No 70.

The mixture is further milled together under nitrogen atmosphere in a Hosokawa Mechanofusion AMS-MINI for Smins. Operating rotor speed is at 6000rpm. During this process the wood dust starch becomes coated with black iron oxide/starch mixture.

The homogenized powder is then placed into a metal container and heated at 5C/min to 200C in an oven under a nitrogen atmosphere. This temperature is held for 30 mins at 200C after which the temperature is increased at 5C/min to 450C and again held for 1 hour. The mixture is then cooled and the resulting power/cake milled for 30 seconds in a pestle and mortar to break up any agglomerated material and sieved using a series of Endecotes laboratory sieves to classify the composite particle size below l50micron.

Example 7b

The iodine number of the composite carbon from example 7a was were measured using the method as detailed in BS EN 12902 2004 section 6.10, subsection 6.10.5.2.

The results are show as mg/g of sample used and as mg/g of sample.

Sample Iodine number (mg/g sample) Sample la 125 The iodine number of the sample can be increased by methods commonly used for activation, examples of which are but not restricted to steam or caustic activation. Where heat is employed in order to maintain the magnetic property this must not be to a temperature which is higher than the currie temperature 575-585 centigrade.

The composite magnetic carbon can be converted to any known functional activated carbon using known techniques providing this is undertaken at a temperature below the curie temperature of the magnetic component without interference to the permanent magnetic property of the composite.

It will be appreciated that this invention described herein is susceptible to variations and modifications other than those specifically described. It is to be * understood that the invention encompasses all such variations and **** modifications that fall within the spirit and scope. * *. * * . S... *

S. S... * * *

*..**.

Claims

Claims: What is claimed - 1. A permanently magnetic carbon composite formed through the process described in claim 2 having a minimum specific gravity of above 0.15 consisting essentially of a substrate particle of carbon partially encapsulated with magnetic particles. The said carbon capable of being preformed, porous or solid and bonded to said magnetic particle, particles or agglomerates. The said carbon substantially retaining its structure and form after compounding with the magnetic particles and binder and during subsequent carbonization of the binder. The resulting magnetic carbon composite having a particle size ranging from about Imicron to about 600 microns in diameter.
2. A method for producing an carbon composite particle with permanent magnetic properties as described in claim I comprising; integrating together a powdered magnetic precursor with an organic binder. The binder is solid or liquid at room temperature and which at a temperature below the curie temperature of the magnetic component ranging from 500 C. to 10000 C. at atmospheric pressure decomposes to yield elemental carbon and gaseous product of decomposition. Integrating the binder and magnetic material in such a way that the surface of the magnetic component is coated with binder and then further mixing with an activated carbon or carbon to allow the magnetic particles to partially encapsulate the carbon Heating the mixture in an inert atmosphere to a temperature below the curie temperature of the magnetic component and in doing so transforming the organic binder into a carbon bridge by pyrolysis and binding the activated carbon and magnetic particles to form solid composite particles of activated carbon, carbon and magnetic material. Milling the resulting composite particle agglomerate to produce said composite of a predetermined size ranging from about one micron to about 600 microns in diameter being substantially the same size as the substrate precursor. Subjecting the composite particles to saturation magnetism in such a way as to allow the particles to become permanently magnetic due to the high remnant magnetism of their magnetic component.The resulting composite yielding a permanently magnetic carbon substrate with tailored permanent magnetic properties unique in enhancing separation by magnetic particle to particle agglomeration or further enhanced by the useof an external magnetic field.
3. A process for producing a permanently magnetic adsorbent carbon composite having a minimum specific gravity of above 0.15 consisting essentially of substrate particle of carbon partially encapsulated with magnetic particles. The said carbon capable of being formed from a carbon precursor via pyrolysis and having a minimum surface area of about 2 square meters per gram and being adherently bonded to said magnetic particle, particles or agglomerates. The said carbon having either a solid or open porous structure.The magnetic carbon particles having a particle size ranging from about 0.5 micron to about 300 microns in diameter.
4 Providing a method in which the magnetic particles in claim 3 become adhered to the surface of the carbon precursor directly or by the use of an organic binder material which during pyrolysis below the curie temperature of the magnetic carbon becomes carbonized and bonds the carbon precursor surface and magnetic particle surface together. The carbon precursor is a solid at room temperature and which at a temperature ranging from about 500 C. to 10000 C. at atmospheric pressure decomposes to yield elemental carbon and gaseous product of decomposition. Admixing a plurality of said substrate particles with said magnetic particles to form a substantially uniform mixture, heating said mixture in a substantially oxygen-free atmosphere below the curie temperature of the magnetic component to decompose said organic precursor yielding elemental carbon and gaseous product of decomposition, and milling the resulting composite particle agglomerate to produce said composite of a predetermined size ranging from about 0.5 micron to about 300 microns in diameter. The resulting composite yielding a carbon substrate with tailored permanent magnetic properties useful in enhancing separation by magnetic particle to particle agglomeration or by the use of an externalmagnetic field.A method as in Claim 1, 2, 3, and 4 wherein the integrating is accomplished by direct milling and mixing of the components. Alternatively by providing a water insoluble magnetic material precursor, dispersing the water insoluble magnetic material precursor into an aqueous or non aqueous medium together with the soluble or insoluble organic binder. Further dispersing carbon into the mixture sufficiently that when it is dried a homogenous mixture is formed but in which the carbon surface remains open and the magnetic material is scattered sporadically over its surface as individual grains or clusters.4. A method as in Claim 1 2 3 and 4 wherein the integrating is accomplished by providing an organic binder that can be melted together with the magnetic material precursor to form a homogenous mixture and then applied to the carbon to partially encapsulate its surface.
5. A method as in Claim 1 2 3 and 4 wherein the integrating is accomplished by providing an organic binder precursor that can become adhered to the surface of the magnetic material precursor and the activated carbon by the process of pyrolysis below the curie temperature of the magnetic component to form a homogeneous mixture. Wherein said organic binder is by example but not limited to starch, sugar, steep asphalt, organic polymer or copolymer or surfactant of any type.
6. A composite carbon particle as described in claim 1, 2, 3 and 4 in which the magnetic material can be a natural magnetic mineral or commercial iron containing magnetic material. It is preferred the material is capable of high remnant magnetism examples of which are but not limited to all magnetic ferrites, magnetic minerals such as magnetite and synthetic magnetic pigments such as gamma ferric oxide and magnetite. The size of the magnetic particles being between ito 30 % of the size of the carbon particle and ranging in actual size from lOOnm to 20 microns.
7. A magnetic particle according to claims 1 2 3 and 4 in which the permanent magnetism can be tuned dependent on the concentration of magnetic material incorporated onto the surface of the composite and level of remnant magnetism as a consequence of saturation magnetism exposure.
8. A composite according to claims 1 2 3 and 4 wherein the substrate particle can be any porous or non porous carbon or activated carbon that is preformed. Furthermore the carbon can be fully activated with tailored absorption properties or functionality specific to the required duty. The composite can also be converted to any known functional activated carbon using known technologies without interference with the permanent magnetic property. It can also be the carrier for functional organic compounds, functional polymers such as ion exchangers, enzymes and chelating agents.The particle size of the carbon to be ideally less than 600 microns 8. A magnetic particle composite according to Claims 1 2 3 and 4 in which the substrate is an absorbing material other than carbon. Examples of which are but not limited to titanium dioxide, zeolite or clays.
9. A method of dispersing the permanently magnetic carbon or other as defined in claims 1, 2,3,4 and 8 in water containing a material to be removed that is capable of being adsorbed upon carbon or another absorber. The magnetic particle comprising magnetic material that is intimately dispersed and bonded over the surface of carbon or other absorber material at a particulate level. Subjecting the mixture of water and the permanently magnetic particle to agitation which when allowed to stand without agitation or under the influence of a magnetic field can form magnetic particle to particle agglomerates due to their inherent high remnant magnetism, enhancing the removal of the magnetic activated carbon or absorber by an increased rate of settlement.
10. A method as in Claim 9 wherein the activated carbon or absorber has a particle size less than about 600um.
11. A method as in Claim 9 wherein the material to be removed includes natural and synthetic organic compounds which are capable of being absorbed upon conventional activated carbon or other type of absorber.
12. A method as in Claim 9 wherein the material to be removed includes heavy metals of the type typically absorbed upon activated carbon or absorber.
13. A method for recovering gold cyanide complexes from solution comprising mixing an aqueous solution containing gold cyanide complexes with an activated carbon particle as described in claim 1. Adsorbing the gold cyanide complexes upon the magnetic activated carbon and subjecting the mixture of solution and the magnetic activated carbon to zero agitation to facilitate magnetic particle to particle agglomeration or flocculation. Additionally allowing the material to settle as a concentrated sludge and to then enhance the separation by applying an external magnetic field to attract the activated carbon and remove the activated carbon from the solution.
14. A method as in Claim 13 wherein the activated carbon has a particle size less than about 600 micron.
15. A method for recovering dissolved precious metals from solution comprising mixing an aqueous solution containing the precious metal in solution with a magnetic activated carbon particle comprising magnetic material that is intimately mixed and dispersed upon the surface of activated carbon material as described in claims 1 2 3 and 4. Subjecting the mixture of solution and the activated carbon to zero agitation to allow for magnetic particle to particle agglomeration or to a magnetic field under conditions to attract the magnetic activated carbon and remove the activated carbon from the solution.
16. A method as in Claim 15 wherein the activated carbon has a particle size less than about 600um.I