WO2014027175A1

WO2014027175A1 - Separation of components within fluids

Info

Publication number: WO2014027175A1
Application number: PCT/GB2013/051861
Authority: WO
Inventors: Nigel Willis Brown; Edward P. L. Roberts; Andrew Kenneth CAMPEN; David Sanderson; Michael Geoffrey CONTI-RAMSDEN
Original assignee: Arvia Technology Limited
Priority date: 2012-08-17
Filing date: 2013-07-12
Publication date: 2014-02-20
Also published as: GB201214745D0

Abstract

A method for the treatment of a fluid containing a first organic component and an inorganic component or a second organic component of different molecular structure to the first organic component. The method comprises contacting the fluid within a treatment unit with an adsorbent material with a preferential affinity for one of the components over the other of the components. In this way, the one component is adsorbed on to the adsorbent material leaving the other component within the fluid. The method further involves electrochemically regenerating the adsorbent material within the treatment unit and discharging the fluid containing the other component from the treatment unit for further treatment, re-use or to the environment.

Description

SEPARATION OF COMPONENTS WITHIN FLUIDS

The present invention relates to a method for the treatment of a fluid to separate organic components of the fluid from inorganic components or from other organic components of differing molecular structure.

Many processes generate waste fluids containing a mixture of organic and inorganic species which must be handled using methods which are both economically and environmentally acceptable. Despite attempts to improve methods by which such fluids are treated, one of the most common methods is simply to dispose of them, for example, by discharge into the environment or incineration. As a result, any potentially useful components of the fluids cannot be re-used and are simply lost. This is undesirable from an economic perspective for many reasons, not least in circumstances where the waste fluid contains species of relatively high commercial value. It is also undesirable from an environmental perspective because opportunities to recycle resources are being missed and unnecessary levels of potential contaminants are being released to the environment.

By way of example, brine or salt water is commonly used to regenerate ion-exchange resins used to remove Natural Organic Matter (NOMs) from water. The NOMs cause colour in drinking waters and are the precursors of disinfection by-products generated through chlorination. Ion-exchange resins remove NOMs from water by concentrating them on to a surface of the resin. After a period of time the resin is fully loaded and there is a need for the resin to be regenerated. This is achieved by contacting the loaded resin with a strong brine solution, e.g. 10 - 15 % sodium chloride (NaCI). The sodium and chloride ions of the brine solution displace the NOMs and in doing so transfer the pollutant from the ion-exchange resin to the brine solution producing a highly polluted brine solution. At present, these highly polluted solutions are simply disposed of. As a result, a fresh batch of brine must be used each time to regenerate an ion-exchange resin, which is unduly costly and environmentally undesirable. The environmental benefits of using the process to treat brine water include the reduction in transportation associated with chemical deliveries to site and waste removal from site.

By way of a further example, phosphoric acid is employed in a wide range of applications ranging from the cleaning and etching of materials to electrolytic processes and use as a food additive. As a result, many different phosphoric acid- containing waste streams require handling in an economically and environmentally acceptable manner. Such waste streams often contain organic pollutants, such as phenolic compounds, which require careful handling.

Further examples of contaminated fluids requiring treatment are radioactive contaminated organic solvents and scintillants. Destruction of the organic component would allow the radioactive species to be treated using existing technologies. Unfortunately existing technologies find it difficult to treat radioactive contaminated organic compounds.

Inorganic and organic components that are combined within a single structure, for example chelating agents or organo-metallic compounds, also currently lack a cost effective means of separation.

Chelating agents are chemicals, according to ASTM-A-380, "that form soluble, complex molecules with certain metal ions, inactivating the ions so that they cannot normally react with other elements or ions to produce precipitates or scale". This is achieved by several bonds being formed between the metal and the organic compound (see Formula 1 ). Typical metals that can be chelated include Cadmium, Chromium, Copper, Nickel and Lead. Chelating compounds are used in a wide variety of industries and for a wide range of applications, for example as water softeners, in detergents, shampoos and as food preservatives, in medical treatments and for recovery of precious metals. They can be difficult to remove from wastewater using existing technologies.

Formula 1 - Metal EDTA (Ethylenediaminetetraacetic acid) Chelate

An additional use of these compounds is as cleaning agents within the nuclear industry, to solubilise radioactive contaminants in pipework prior to maintenance and handling. Destruction of the organic chelate would allow the release of the inorganic radioactive contaminant which can be treated using existing technologies. Unfortunately, there is currently no efficient way to achieve this. In addition there is a need to handle chelating compounds found in detergents used in laundering materials or in soil washing. During laundering, a wastewater is produced which usually requires disposal and which could contain a range of organic and inorganic components. Removal of the organic components would allow the inorganic components of value (for example, caustic) to remain in the water and the water to be recycled for further use. Additionally, when a valuable or toxic inorganic species is known to be present on the laundry, the washing process would transfer these to the fluid phase (possibly through the use of organic chelating agents). If an efficient method existed the organic and inorganic components could then be separated. Unfortunately this is not currently the case.

An example of a commonly used organo-metallic compound is Tri-butyl Tin (TBT) which is widely used in anti-fouling paints, wood preservation chemicals and antifungal agents in textiles. Fluids containing TBT are extremely toxic and cannot be discharged to water courses. If the TBT complex could be separated from aqueous solution the treated water could be considered for re-use or discharged. The inorganic component could then be separated from the organic component for re-use or separate treatment. As with the metal chelates described above, there are currently no efficient methods to achieve the desired separation.

A further example of where an improved separation technique would be of benefit is the treatment of water for agricultural purposes, particularly hydroponics. In this case a range of nutrients are provided for plant growth via the circulation of water. This water can only be circulated for a limited time due to the dangers of building-up organics, for example leaves, which are a food for micro-organisms. Re-circulation of the water containing microorganisms could also circulate pathogens to the plants. Treatment to remove the organics would allow the water to be re-circulated for longer, along with the inorganic nutrients that it contained; it might even be possible to destroy micro-organisms and pathogens during treatment.

In addition to the above, many processes generate waste fluids containing a variety of organic components of differing molecular structure. It is often the case that organic components of specific molecular structure are resistant to standard treatment methods meaning that these methods cannot be relied upon to remove all of the organic components of a waste fluid to the required discharge limits. Furthermore, it is also often the case that standard treatment methods are inhibited by organic components of specific molecular structure. An example of the preferential removal of certain organic components from a liquid containing a mixture of organic components is exemplified in "Olive oil wastewater treatment with the use of an electrolysis system"; C J Israilides, A G Vlyssides, V N Mourafeti, G Karvouni; Bioresource Technology; 61 (1997) 162-170. Aromatic organic components have an inhibitive effect on biological water treatment processes. Treatment to preferentially remove the aromatic organic components before biological water treatment would increase the efficiency of the biological water treatment of the liquid containing the remaining aliphatic organic components. Unfortunately, there is currently no efficient way to achieve this.

A further example is the treatment of industrial waste water or drinking water. Endocrine disruptors (EDCs) are common aromatic organic pollutants found in waste waters or drinking water. EDCs are well known for their detrimental health and environmental impacts; are resistant to standard treatment processes; and many EDCs are included in the Stockholm Convention on Persistent Organic Pollutants. Treatment to preferentially remove the EDCs either before or after the standard treatment process would ensure that the waste fluid contained sufficiently low concentrations of EDCs to conform to regulatory discharge limits. Unfortunately, there is currently no efficient way to achieve this.

Another example is the treatment of contaminated "heavy water" (deuterium oxide). Heavy water is commonly used as a moderator in certain types of nuclear reactor and can become contaminated with radionuclides and organics (such as oil, acetone, methanol and ethylene glycol) at unacceptable levels from a few parts per million and above during use. During routine refurbishment and maintenance of these reactors the contaminated heavy water must be replaced, thus generating quantities of contaminated heavy water as waste. Currently there are no efficient treatment processes to achieve treatment of such waste heavy water.

An object of the present invention is to obviate or mitigate one or more of the problems outlined above.

A further object of the present invention is to address problems associated with current methods for treating fluids containing mixtures of organic and inorganic components or fluids containing mixtures of organic components of differing molecular structure, such as one or more of those discussed in the above examples. A first aspect of the present invention provides a method for the treatment of a fluid containing a first organic component and an inorganic component or a second organic component of different molecular structure to the first organic component, the method comprising: contacting the fluid within a treatment unit with an adsorbent material with a preferential affinity for one of said components over the other of said components such that said one component is adsorbed on to the adsorbent material leaving the other component within the fluid; and electrochemically regenerating the adsorbent material within the treatment unit and discharging said fluid containing said other component from said treatment unit for further treatment, re-use or to the environment.

A second aspect of the present invention provides apparatus for the treatment of a fluid containing an organic component and an inorganic component or a second organic component of different molecular structure to the first organic component, the apparatus comprising a treatment unit for fluid to be contacted by an adsorbent material with a preferential affinity for one of said components over the other of said components; two electrodes connected to the treatment unit which are controllable to electrochemically regenerate said adsorbent material following contact with said fluid; and means for discharging the fluid containing said other component from the treatment unit for further treatment, re-use or to the environment.

By selecting an appropriate adsorbent material with a preferential affinity for one component (e.g. the first organic species) over the other, i.e. non-preferentially adsorbed, component (e.g. the inorganic species or the second organic species) the two components can be easily and conveniently separated from one another while allowing the fluid containing the residual component (i.e. the component not adsorbed on to the adsorbent material) to be re-used, subjected to separate treatment processes or released to the environment if appropriate. In the case where the two components to be separated are organic species of differing molecular structure, the method enables the treated fluid containing the non-adsorbed component to be subjected to standard treatment processes without the risk of the selectively adsorbed component inhibiting the standard treatment processes, or simply discharging the fluid containing the non-adsorbed component directly to the environment within the relevant discharge limits. Many waste fluids, such as brine that has been used to regenerate an ion-exchange resin, a phosphoric acid solution containing phenolic compounds or any of the other examples of the first aspect of the present invention outlined above, contain an organic pollutant or contaminant, which is unwanted, in combination with one or more inorganic species (e.g. NaCI or phosphoric acid) which would be desirable to re-use from a cost and environmental point of view. The first aspect of the present invention thus provides a means by which such fluids can be stripped of their unwanted organic contaminants to effectively regenerate the original fluid (e.g. brine or phosphoric acid) so that it can be re-used.

To maximise the uptake of a preferred organic component and minimise the uptake of one or more other organic components the following factors should be considered:

• the size, shape and morphology of the adsorbent material and therefore its inherent selectivity for one or more organic components;

• the mass of adsorbent material used; and

• for fluids of varying concentration of organic components, the contact time of the fluid and the adsorbent material, including the flow rate of the fluid through the adsorbent when a continuous rather than a batchwise process is being carried out.

The environmental and economic benefits provided by the present invention are further enhanced by virtue of the fact that the adsorbent material is subjected to electrochemical treatment within the treatment unit to regenerate the adsorbent material ready to contact a further supply of fluid in need of treatment.

The present invention thus provides a simple, convenient and environmentally acceptable method to treat and/or regenerate contaminated fluids which avoids many of the disadvantages associated with existing systems.

Reference is made throughout to the treatment of fluids. It will be appreciated that the methods and apparatus according to the various aspects of the present invention are particularly suitable for the treatment of liquids, but that they may also be employed, where appropriate, to treat gases.

Adsorbent materials suitable for use in the method of the present invention are solid materials capable of convenient separation from the fluid phase and capable of electrochemical regeneration. The material may be used in powder, flake or granular form. Whilst the particle size may not be critical, the optimum size is likely to depend on the settlement and regeneration properties. Generally, the material used and particularly the particle size is a compromise between ease of separation, electrochemical regeneratability and surface area.

Preferred adsorbent materials comprise particulate carbon-based adsorbent materials, such as unexpanded intercalated graphite. A single form of carbon-based material may be used or multiple component materials comprising a combination of two or more different types of material may be used in which at least one component is carbon-based. Particularly preferred materials include unexpanded graphite intercalation compounds (UGICs). Preferred UGICs include a bi-sulphate intercalated product, which can be formed by chemically or electrochemically treating graphite flakes in oxidising conditions in the presence of sulphuric acid. A preferred UGIC is in flake form, and typically has a composition of at least 95% carbon, and a density of around 2.225 gem^"3. Flake graphite can be used as the starting materials for producing UGICs with significantly lower carbon contents (80% or less). These compounds can also be used, but are likely to result in slightly higher voltages across the treatment unit. Other elements may also be present within the UGIC, depending on the initial composition of the flake graphite and the chemicals used to convert the flakes into intercalated form.

In single component adsorbent materials a typical particle size is around 0.25 - 0.75 mm. Significantly larger particle sizes can be employed, such as up to around 5 mm, when multiple component adsorbent materials are employed. This larger particle size is preferable to aid in the separation of the adsorbent material from the treatment fluid. Very fine particles (< 50 microns) can be used as the adsorbent material since these can be separated from the fluid phase easily if an organic polymer is used as a flocculent. This organic flocculent can then be destroyed by regeneration. The use of other materials of lower electrical conductivity and density would benefit from larger particles. Typical individual UGIC particles suitable for use in the present invention have electrical conductivities in excess of 10,000 Ω^"1 cm^"1. It will be appreciated however that in a bed of particles this will be significantly lower as there will be resistance at the particle/particle boundary. Hence it is desirable to use as large a particle as possible to keep the resistance as low as possible. It will be appreciated that a large number of different UGIC materials have been manufactured and that different materials, having different adsorptive properties, can be selected to suit a particular application of the method of the present invention.

The capability of materials to undergo electrochemical regeneration will depend upon their electrical conductivity, surface chemistry, electrochemical activity, morphology, electrochemical corrosion characteristics and the complex interaction of these factors.

A degree of electrical conductivity is necessary for electrochemical regeneration and a high electrical conductivity can be advantageous. Additionally, the kinetics of the electrochemical oxidation of the adsorbate must be fast. The kinetics depend upon the electrochemical activity of the adsorbent surface for the oxidation reactions that occur when the contaminant is destroyed. Additionally, electrochemical regeneration will generate corrosive conditions at the adsorbent surface. The electrochemical corrosion rate of the adsorbent material under regeneration conditions should be low so that the adsorption performance does not deteriorate during repeated cycles of adsorption and regeneration. Additionally, some materials can passivate upon attempted electrochemical regeneration, often due to the formation of a surface layer of non-conducting material. This may occur, for example, as a result of the polymerisation of the contaminant on the surface of the adsorbent. Additionally, electrochemical destruction of the contaminants on the adsorbent material will generate reaction products which must be transported away from the surface of the adsorbent material. The ability for the adsorbent material being regenerated to successfully transport the products away from the surface of the adsorbent material will depend upon both the surface structure and chemistry of the adsorbent material.

It will be appreciated that preferred adsorbent materials for the present invention will desirably have an ability to adsorb organic components. The ability of the material to absorb is not essential. The process of adsorption works by a molecular interaction between the contaminant and the surface of the adsorbent. By contrast, the process of absorption involves the collection and at least temporary retention of a contaminant within the pores of a material.

By way of example, expanded graphite is known to be a good absorber of a range of contaminants (e.g. up to 86 grams of oil can be 'taken-up' per gram of compound) whereas UGICs have no absorption capacity. UGICs can adsorb, but the adsorption capacity is low as the specific surface area is low (e.g. up to 7 milligrams of oil can be 'taken-up' per gram of compound per adsorption cycle). These figures demonstrate a difference of four orders of magnitude between the take-up capacity of expanded graphite and that of UGICs. The selection of UGICs for use in the present invention arises from carefully balancing its high regeneratability against its relatively low take- up capacity.

Research has determined that preferred adsorbent materials for use in the selective removal of one or more organic components from one or more other organic components in the fluid should have different adsorption affinities for the different organic components, which will be dependent, at least in part, upon the molecular structure of the various organic components. By way of example, the adsorption affinity of flake UGICs is different for organic components of differing solubility and chemical functionality.

It has been established that the adsorption affinity of flake UGICs for aliphatic organic components is indirectly proportional to the solubility of the organic components, i.e. the adsorption affinity of UGICs for aliphatic organic components with a low solubility is higher than that for aliphatic organic components with a high solubility. Furthermore, it has been determined that the adsorption affinity of flake UGICs for aromatic organic components is dependent upon the nature and number of aromatic substituents on the aromatic ring of the organic component. Moreover, further tests have determined that the adsorption affinity of flake UGICs for aromatic organic components with a halogen-type substitution on the aromatic ring of the organic component increases with the number of substituted halogen groups. Further testing has shown that the adsorption affinity of flake UGICs for aromatic organic components compared to that for aliphatic organic components of the same solubility is much higher, meaning that the aromatic organic component will be preferentially adsorbed over the aliphatic organic component.

Without wishing to be bound by any particular theory, the devisors of the present invention propose that the driving force for the variation in adsorption affinity of flake UGICs towards organics of different molecular structure is the presence of different types of surface onto which the organic components are adsorbed. The edges of the flake UGIC particles have a rough morphology which is anticipated to have a high adsorption affinity for aliphatic organic components. The basal planes of the flake UGIC particles have a large flat surface, which is anticipated to have a high adsorption affinity for aromatic organic components. The preferential adsorption of flake UGICs for aromatic organic components over aliphatic organic components of the same solubility is anticipated to be due to the larger ratio of basal plane surface area to rough edge surface area on a typical flake UGIC particle. If the shape of a flake particle is generalised to a disk of constant thickness, the ratio of the surface area of the basal plane to rough edge surface area can be estimated. As the size of the particle is increased, the surface area of the basal plane increases proportionally with the square of the diameter, whilst the surface area of the rough edge increases proportionally with the diameter; leading to an increased ratio of the basal plane surface area to the rough edge surface area. Consequently, it will be appreciated that increasing the size the particle would further encourage the adsorption affinity of UGICs for aromatic organic components.

The various aspects of the present invention can each be carried out continuously, semi-continuously or on a batch basis. Thus, fluid in need of treatment can be continuously passed through the treatment zone, such as a reservoir, containing appropriate levels of adsorbent, or individual volumes of fluid to be treated can be contacted by the adsorbent as a batch, with the adsorbent material being regenerated during treatment of the respective batch or between batch treatments as appropriate. Suitable apparatus for carrying out the process in a continuous, semi- continuous or batch-wise manner is described in International patent publication nos WO2007/125334, WO2009/050485, WO2010/128298, WO2013/054101 , published UK patent application no. GB1 1 1991 1 .4 and unpublished UK patent application no. GB1212676.9.

In a first preferred embodiment of the method and apparatus according to the present invention, continuous separation of the components in the fluid can be achieved during passage of the fluid containing the components through a bed of the adsorbent material in the treatment unit at a flow rate which is sufficiently high to pass the fluid through the bed of adsorbent material but below the flow rate required to fluidise the bed of adsorbent material. An electric current is passed through the adsorbent material within the treatment unit to regenerate the adsorbent material. The electric current is preferably passed through the adsorbent material while the fluid is passing through the bed of adsorbent material in the treatment unit, i.e. adsorption and electrochemical regeneration are preferably effected simultaneously. In a continuous or semi-continuous process the flow rate of the fluid through the treatment unit can be determined and controlled to facilitate efficient separation of different components of the fluid.

In a related preferred embodiment, it is preferred that the apparatus of the second aspect of the present invention comprises a bed of the adsorbent material, the electrodes being operable to pass an electric current through said bed to regenerate the adsorbent material, and means to admit the fluid into said bed to contact said adsorbent material at a flow rate which is sufficiently high to pass the fluid through the bed but below the flow rate required to fluidise the bed of adsorbent material.

Controlling the flow rate of the fluid entering the adsorbent material bed so as to pass the fluid through the bed but ensure the adsorbent material remains within the bed for regeneration enables the adsorption and regeneration processes to be carried out simultaneously within the same bed of adsorbent material. The adsorbent material can adsorb the desired component(s) from the fluid whilst, within the same adsorbent bed, an applied electric current causes gaseous products derived from the adsorbed component(s) to be released from the adsorbent material thereby regenerating the adsorbent material and restoring its ability to adsorb further quantities of the or each component.

Contacting of the fluid with the adsorbent material may be achieved through controlled agitation of the adsorbent. Controlled agitation may be achieved by feeding one, or more preferably multiple, parallel jet streams of the fluid under pressure to the adsorption bed. Each individual stream of fluid will generate a cylindrical or funnel shaped passage of the fluid through the adsorbent bed, drawing particulate adsorbent material from the lower region of the adsorbent bed and carrying it upward through the adsorbent bed. A downward flow of adsorbent material is produced around the upward flow of fluid and entrained adsorbent material thereby defining a discrete, endless stream of adsorbent material within the adsorbent bed flowing along an endless path.

During the upward passage of fluid and entrained adsorbent material, the adsorbent material separates one or more components from the fluid by a process of adsorption whereby said one or more components attach to the surfaces of the particles of the adsorbent material. When the upward passage of fluid and particulate adsorbent is at the top of the adsorbent bed, the fluid containing the non-adsorbed component(s) will cumulate or build-up in a fluid reservoir above the adsorbent bed and the adsorbent material will remain within the adsorbent bed. The fluid containing the non-adsorbed component(s) is free or substantially free of used adsorbent material and can then be released as desired via the outlet feed. The degree to which the component(s) to be adsorbed has or have been removed from the fluid can be monitored by taking one or more samples of the accumulated fluid from the fluid reservoir, and the fluid subjected to further treatment if necessary.

As the endless streams of adsorbent material are established in the adsorbent bed the electrodes can be operated to pass an electric current through the adsorbent bed. The regions of adsorbent material flowing downwards possess a sufficiently high enough density to be sufficiently electrically conductive to facilitate electrochemical regeneration of the adsorbent material. This oxidises the adsorbed component(s), releasing them in the form of, for example, carbonaceous gases and water when one or more organic components are the preferentially adsorbed component(s), thereby regenerating the adsorbent material and restoring its ability to adsorb further quantities of the component(s) that are to be removed from the fluid.

The electrodes preferably extend across the full height and width of the adsorbent bed to maximise their proximity to adsorbent particles loaded with adsorbed component(s) in need of regeneration. The electrodes will typically be provided on opposite sides of the adsorbent bed. A plurality of electrodes may be disposed along each side. Alternatively, multiple electrodes may be installed horizontally to allow different currents to be applied at different heights across the adsorbent bed during operation. By way of example, at the top of the adsorbent bed the adsorbent material may be fully loaded with adsorbed species, such that a larger regeneration current would be required than at the bottom of the adsorbent bed where substantial regeneration of the adsorbent material will already have occurred.

In use, a voltage can be applied between the electrodes, either continuously or intermittently, to pass current through the adsorbent material and regenerate it in the manner described in "Electrochemical regeneration of a carbon-based adsorbent loaded with crystal violet dye"; N W Brown, E P L Roberts, A A Garforth and R A W Dryfe; Electrachemica Acta 49 (2004) 3269-3281 and "Atrazine removal using adsorption and electrochemical regeneration"; N W Brown, E P L Roberts, A Chasiotis, T Cherdron and N Sanghrajka; Water Research 39 (2004) 3067-3074.

The fluid in need of treatment must be contacted by the adsorbent material for a sufficient period of time to achieve satisfactory separation of the various components, i.e. transfer of target component(s) from the liquid to the adsorbent material. Satisfactory contact time is ensured by controlling the velocity of the fluid through the adsorbent bed. This depends upon the initial velocity of the fluid injected into the tank and the density and height of the adsorbent bed.

The maximum velocity of the fluid within the adsorbent bed is just below the velocity that would cause fluidisation of the adsorbent particles. Fluidisation is produced when the velocity of the fluid is above the sedimentation rate of the adsorbent particles. The sedimentation rate of the adsorbent particles can be calculated according to Stokes's law and depends upon particle size, particle density and particle shape. The minimum velocity of the fluid is the velocity required to define an endless path along which the adsorbent material can flow within the adsorbent bed. Paths of adsorbent material are produced when the adsorbent bed is of a low enough density to allow free movement of the adsorbent material. However, the efficiency of the adsorbent bed to undergo electrochemical regeneration depends upon a high density of adsorbent material within the adsorbent bed. Thus, the velocity of the fluid through the adsorbent bed and the density of the adsorbent bed are interdependent and each parameter should be optimised while taking into account the other parameter.

Removal of the treated fluid from the fluid reservoir may be effected in any convenient way. For example, one or more pumps may be used to cause the treated liquid to flow out of the fluid reservoir for storage or any desirable further use. Alternatively or additionally, removal may be effected by control of valves or partitions in between the fluid reservoir and an adjacent vessel, such as a storage tank. For fluids originally containing particularly high levels of the component(s) to be adsorbed and removed, it may be desirable to pass some or all of the treated fluid from the fluid reservoir back through the adsorbent bed for further treatment. The need for doing so may be determined by reference to test samples of the treated fluid leaving the fluid reservoir. This could be used as a 'fail-safe' mechanism, which could be used, for example, during the initial stages of a treatment cycle at a new location or when treating a new source of fluid, or simply when a heavily contaminated fluid is to undergo treatment and it is particularly important that the resulting treated fluid is substantially free of the original contaminant for health and safety reasons.

By controlling the volume and the rate of the contaminated fluid allowed to flow into the adsorbent bed and the flow of fluid out of the fluid reservoir, it is possible to operate the method and apparatus of the present invention in a batchwise manner, a continuous manner or a semi-continuous manner.

It is desirable to have an optimum distribution of openings in a plate underneath the adsorbent bed to allow for the creation of an optimum number of discrete, endless streams of adsorbent material upon injection of the fluid to be treated into the adsorbent bed. If the openings are too close together, the circuits will interfere and potentially disrupt each other, creating an unpredictable motion of adsorbent material or an accumulation of adsorbent material and fluid at the top of the adsorbent bed. If the openings are too far apart, adsorbent material in between the upward jets of fluid may become stagnant, resulting in wasted energy through passing current through part of the adsorbent bed without adsorbed component(s). This could be eliminated by putting inert material (plastic) to replace any dead spots, which could be used as guides to direct the adsorbent material towards the openings in the plate.

In a second preferred embodiment of the present invention, a batch-wise separation can be achieved such that fluid to be treated within the treatment unit is essentially stationary, save for agitation to aid distribution of the adsorbent material throughout the fluid. Conveniently, the electrodes are located within the treatment unit so that used adsorbent material that has already contacted fluid can be regenerated within the treatment unit by passing an electric current through the adsorbent material to release from the adsorbent material gaseous products derived from the preferentially adsorbed components formerly present in the fluid. In use, a voltage can be applied between the electrodes, either continuously or intermittently, to pass current through the adsorbent material and regenerate it in the manner described in "Electrochemical regeneration of a carbon-based adsorbent loaded with crystal violet dye"; N W Brown, E P L Roberts, A A Garforth and R A W Dryfe; Electrachemica Acta 49 (2004) 3269-3281 and "Atrazine removal using adsorption and electrochemical regeneration"; N W Brown, E P L Roberts, A Chasiotis, T Cherdron and N Sanghrajka; Water Research 39 (2004) 3067-3074. When a batch-wise process is carried out such that the fluid to be treated is essentially stationary rather than flowing through the treatment unit it may be desirable to physically agitate the adsorbent material within the treatment zone to assist distribution of the adsorbent material in the fluid and adsorption of contaminants from the fluid. The physical agitation may be provided in any convenient manner, such as by use of a mechanical mixer, but is most conveniently provided by delivery to the treatment unit of pressurised fluid, e.g. air and/or a quantity of fluid in need of treatment.

A cathode is preferably housed in a separate compartment defined by a conductive membrane which enables a catholyte to be pumped through the compartment, whilst protecting the cathode from direct contact with the adsorbent material.

In a third preferred embodiment of the present invention, separation can be achieved in a batch-wise or continuous manner in apparatus that facilitates pH control, without a separate cathode compartment, through the periodic reversal of the direction of the electric current, as described in unpublished UK patent application no GB1212676.9. The fluid to be treated is contacted with the adsorbent material as in the first and second embodiments of the invention discussed above, but in this embodiment the adsorbent material is provided in first and second treatment zones separated by a porous membrane in the treatment unit and electrochemical regeneration of the adsorbent material is effected separately in each treatment zone by first applying an electric current in one direction through the adsorbent material in the two treatment zones and then reversing the direction of the applied electric current, a method which facilitates pH control of the fluid undergoing treatment and the resulting fluid containing the non-adsorbed components.

Accordingly, in the method according to the first aspect of the present invention it is preferred that the treatment unit comprises first and second treatment zones separated by a porous membrane, each treatment zone provided with a bed of the adsorbent material, and the method comprises admitting the fluid into at least one of said first and second treatment zones so as to contact the adsorbent material provided in said at least one treatment zone, and operating electric current feeders to pass an electric current in one direction through the adsorbent material within each treatment zone to electrochemically regenerate the adsorbent material in said at least one treatment zone. In a first version of the third embodiment, the fluid may be admitted into both of said first and second treatment zones so as to contact the adsorbent material provided in each respective treatment zone before operation of the electric current feeders, in which case the method further comprises distributing the adsorbent material in the fluid within each treatment zone, allowing the adsorbent material to settle within each treatment zone, and operating the electric current feeders to pass an electric current in one direction through the adsorbent material within each treatment zone to electrochemically regenerate the adsorbent material in one of said treatment zones and operating the electric current feeders to reverse the direction of the electric current applied to the adsorbent material in each treatment zone to electrochemically regenerate the adsorbent material in the other of said treatment zones.

Apparatus to put this version of the third embodiment into effect preferably includes a treatment unit which defines first and second treatment zones separated by a porous membrane, the adsorbent material being provided in said first and second treatment zones, an agitator operable to distribute the adsorbent material in the fluid contained in each of the first and second treatment zones, a first electric current feeder operably connected to the adsorbent material in the first treatment zone and a second electric current feeder operably connected to the adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the adsorbent material in the first and second treatment zones in one direction to regenerate the adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the adsorbent material in the first and second treatment zones to regenerate the adsorbent material in the other of the first and second treatment zones.

Operation of the apparatus and/or method according to the first version of the third embodiment enables the maintenance of a low pH in the treatment unit, which is the optimal pH level for this type of treatment process. Moreover, low pH conditions are preferable when treating organic waste containing radionuclides because many radionuclides are more soluble in acidic conditions than netural or alkaline conditions.

The first and second treatment zones may be defined within the treatment unit so as to be provided at any desirable location with respect to the treatment unit and with respect to one another provided the porous membrane defines an interface between the two treatment zones. It will be appreciated that the treatment unit may define two or more treatment zones with a porous membrane defining an interface between neighbouring treatment zones. The porous membrane may be configured to prevent the adsorbent material from passing between the first and second treatment zones but to permit water and/or ionic species to pass between the first and second treatment zones. In a preferred embodiment, the treatment unit contains two parallel or side-by-side beds of the adsorbent material. Each treatment zone may be provided with a dedicated agitator to agitate the adsorbent material contained within its respective treatment zone. The agitator may be adapted to fluidise the adsorbent material. The or each agitator preferably comprises one or more nozzles, inlets or apertures defined by a wall, preferably the base, of the respective treatment zone through which a fluid under pressure can be admitted into the adsorbent material retained in the respective treatment zone, fluid may be air and/or aqueous organic waste liquid requiring treatment.

In the third embodiment, when the electric current is fed through the beds of adsorbent material the bed adjacent to the positive electric current feeder may be considered to behave as an anode and the bed adjacent to the negative electric current feeder may be considered to behave as a cathode. It is preferable to maintain the applied electric current in this first direction for a sufficient period of time to oxidise components adsorbed on to the adsorbent material from the fluid undergoing treatment and to thereby regenerate the adsorbent material. During this process aqueous protons are produced in the bed behaving as an anode and aqueous hydroxide ions are produced in the bed behaving as the cathode. Reversal of the direction of the applied current switches the formerly positive current feeder so that it is a negative current feeder and the formerly negative current feeder so that it is positive. As a result, the bed of adsorbent material that formerly behaved as an anode now behaves effectively as a cathode and the bed that formerly behaved as a cathode now behaves as an anode. This then enables components from the fluid that have been adsorbed on to the adsorbent material in the bed now acting as an anode to be oxidised and the adsorbent material in that bed regenerated.

The steps of distributing the carbon-based adsorbent material in the aqueous organic waste liquid and allowing the carbon-based adsorbent material to settle may be repeated one or more times to remove target components from the fluid prior to operating the first and second electric current feeders to reverse the direction of the current applied to the adsorbent material. Alternatively or additionally, the steps of distributing the adsorbent material in the fluid and allowing the adsorbent material to settle may be repeated one or more times to remove components from the fluid prior to removing the treated fluid from the treatment unit.

The current feeders may be operated to provide any desirable pH in the treated fluid. For example they may be operated to provide an alkaline pH, i.e. a pH greater than 7. Alternatively, in a preferred embodiment the current feeders are operated to provide an acidic pH, i.e. a pH of less than 7, in the treated liquid, more preferably a pH of around 1 to 4 in the treated liquid.

Charged inorganic species may be generated during the passage of the electric current through the carbon-based adsorbent material in the first and second treatment zones. The current feeders may be operated to minimise the electrodeposition of said charged inorganic species on the current feeders during operation.

The electric current may be passed through the carbon-based adsorbent in each direction for a similar time period or different time periods may be employed. Where different time periods are employed for each direction, the time period over which the electric current is applied in either direction may vary throughout the period over which treatment is being effected or it may remain the same.

It will be appreciated that the ability to treat fluids whilst periodically reversing the direction of the electric current provides a method with significant advantages as compared to prior art methods, even those described in UK patent no. GB2470042 and International patent application WO2010/149982, which themselves represented significant advances over earlier methods. The third embodiment enables the apparatus to operate without an external chemical dosing tank because the periodic reversing of the electric current maintains a consistent pH within the treatment system. Another advantage is that a variety of different materials can be used for the porous membrane or divider as compared to the systems described in UK patent no. GB 2470042 and International patent application WO2010/149982. Consequently, more stable materials with a larger pore diameter can be used if desired. The benefit of using a material with a larger pore diameter is that it offers a lower electrical resistance and therefore a lower voltage across the beds of adsorbent material. A further advantage is that it can operate at low power and therefore low operating cost, without the presence of an isolated catholyte compartment. That being said, since a low voltage across the beds of adsorbent material is preferable it may still be desirable to add an electrolyte to the bed of adsorbent material behaving as the high surface area cathode. A further advantage is that they allow a simplification of the complex electrode assemblies previously employed. Another advantage is that the potential build-up of electrodeposited inorganic components from the fluid undergoing treatment is reduced or eliminated by periodically reversing the applied current.

At different stages of the regeneration period, the electric current can be adjusted. For example, at the beginning of the regeneration period, only a very thin layer of the loaded adsorbent material will have settled so a smaller electric current is required than later in the regeneration period when a substantial quantity of the loaded adsorbent material will have settled. By way of a further example, at the beginning of a regeneration period, the particles of the adsorbent material are fully loaded with components and so a larger electric current is required than later in the regeneration period when a substantial amount of the adsorbed components will have already been oxidised.

It will be appreciated that this version of the third embodiment shares features with the second preferred embodiment described above. Accordingly, preferred features of the second preferred embodiment may be applied to this version of the the third preferred embodiment.

Alternatively, in a second version of the third embodiment, a quantity of the fluid may be admitted into said first treatment zone to contact the adsorbent material in the first treatment zone at a flow rate which is sufficiently high to pass the fluid through the bed of adsorbent material but below the flow rate required to fluidise the bed of adsorbent material before operation of the electric current feeders, the method further comprising operating the electric current feeders to pass an electric current in one direction through the adsorbent material within each treatment zone to electrochemically regenerate the adsorbent material in the first treatment zone, admitting a further quantity of the fluid into said second treatment zone to contact the adsorbent material in the second treatment zone at a flow rate which is sufficiently high to pass the fluid through the bed of adsorbent material but below the flow rate required to fluidise the bed of adsorbent material, and operating the electric current feeders to reverse the direction of the electric current applied to the adsorbent material in each treatment zone to electrochemically regenerate the adsorbent material in the second treatment zone. In apparatus to put this version of the third embodiment into effect it is preferred that the treatment unit defines first and second treatment zones separated by a porous membrane, the adsorbent material being provided in said first and second treatment zones, a pump operable to admit a quantity of the fluid selectively into each of said first and second treatment zones to contact the adsorbent material in the respective treatment zone at a flow rate which is sufficiently high to pass the fluid through the adsorbent material but below the flow rate required to fluidise the adsorbent material, a first electric current feeder operably connected to the adsorbent material in the first treatment zone and a second electric current feeder operably connected to the adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the adsorbent material in the first and second treatment zones in one direction to regenerate the adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the adsorbent material in the first and second treatment zones to regenerate the adsorbent material in the other of the first and second treatment zones.

The second version of the third embodiment is directed primarily at continuous methods for treating fluids where it may be preferred to operate so that the pH of the treated fluid is closer to neutral.

The apparatus preferably comprises one or more spaced inlets through which the contaminated liquid is admitted under pressure into the bed of adsorbent material. The apparatus may comprise a plurality of said inlets spaced apart by a sufficient distance to establish a corresponding plurality of discrete liquid flow paths through the adsorbent bed. The spacing of the plurality of inlets is preferably sufficient to define a region around each liquid flow path through which adsorbent material that has adsorbed contaminant can flow so as to define a discrete, endless stream of adsorbent material within the bed of adsorbent material.

In a preferred embodiment the apparatus comprises a reservoir in fluid communication with the adsorbent bed, the reservoir being adapted to receive fluid from the bed which has been contacted by the adsorbent material.

The steps admitting fluid to each treatment zone and then applying an electric current of varying direction may be repeated any desirable number of times to remove the desired amount of target component(s) in the fluid undergoing treatment. Application of the electric current is preferably effected while the fluid is passing through its respective bed of adsorbent material. As a result of the manner in which the fluid to be treated is admitted into each treatment zone the treated fluid accumulates in a region above the beds of adsorbent material in the treatment zones.

Contacting of the fluid with the adsorbent material may be achieved through the controlled agitation of the adsorbent. Controlled agitation may be achieved by feeding one, or more preferably multiple, parallel jet streams of the fluid under pressure to the bed of adsorbent material via inlets. Each individual stream of fluid will generate a cylindrical or funnel shaped passage of fluid through the adsorbent bed, drawing particulate adsorbent material from the lower region of the adsorbent bed and carrying it upward through the adsorbent bed. A downward flow of adsorbent material is produced around the upward flow of fluid and entrained adsorbent material thereby defining a discrete, endless stream of adsorbent material within the adsorbent bed flowing along an endless path.

The control of the flow rate and path of the fluid entering the adsorbent bed so as to pass the liquid through the bed but ensure the adsorbent material remains within the bed for regeneration enables the adsorption and regeneration processes to be carried out simultaneously within the same bed of adsorbent material. The adsorbent material can adsorb one or more components from the organic whilst, within the same adsorbent bed, an applied electric current causes gaseous products derived from the adsorbed component(s) to be released from the adsorbent material thereby regenerating the adsorbent material and restoring its ability to adsorb further quantities of the target component(s).

After a first cycle of adsorption and electrochemical regeneration has taken place the pump is controlled to cease admitting fluid to the first treatment zone and instead to admit fluid to the second treatment zone containing the adsorbent material. The direction in which the electric current is applied via the electric current feeders is reversed so that the bed of adsorbent material that was previously behaving as the cathode now behaves as the anode and the bed of adsorbent material that was previously behaving as the anode behaves as the cathode. Any fluid containing aqueous hydroxide species is mobilised by the incoming stream of fluid and mixes with the acidic treated fluid in the region above the beds of adsorbent material to form a neutral, treated fluid. Aqueous proton and hydroxide species are then produced in the beds of adsorbent material in the second and first treatment zones respectively such that the pH neutralising effect continues with the or each subsequent reversal in direction of the applied current and change in the treatment zone into which the fluid to be treated is admitted. In this way, a net neutral pH is achieved in the treated fluid without the need for any after-treatment steps to adjust the pH of the treated fluid, such as a chemical dosing system. The process of optimisation to ensure a treated fluid with the desired pH is obtained depends upon the cycle time employed, i.e. the length of time between each change in current direction and treatment zone to which the fluid to be treated is admitted, the concentration of the component(s) in the fluid to be treated, and the volume of fluid in the fluid reservoir. In a preferred embodiment the current feeders and the pump are operated to provide a pH of approximately 7 in the treated fluid.

It will be appreciated that the second version of the third embodiment shares many features with the first preferred embodiment described above. Accordingly, preferred features of the first preferred embodiment may be applied to this version of the third preferred embodiment.

Preferably the method according to the first aspect of the present invention is effected using operational parameters which have been selected after considering the concentration and/or type of component(s) to be removed.

The time period over which the fluid within the treatment unit is contacted by the adsorbent material is preferably around 5 to 60 minutes, more preferably around 15 to 30 minutes. An advantage of the present invention is that it enables contact times of this order to be used, which are lower than many prior art processes.

It is preferred that the time period over which electrochemical regeneration of the adsorbent material is carried out is around 5 to 1440 minutes, more preferably around 10 to 300 minutes. In the embodiments where the direction of the applied electric current is periodically reversed to regenerate adsorbent material in one treatment zone followed by regeneration of the adsorbent material in another treatment zone within the treatment unit, i.e. the third preferred embodiment, the above-defined regeneration times may apply to the application of an electric current in one direction before the direction is reversed, the time period over which a single cycle of regeneration is effected, i.e. the time over which an electric current is applied in one direction plus the time over which an electric current is applied in the opposite direction, or the total time period over which an electric current is applied irrespective of the number of times the direction of the applied electric current is reversed.

Any suitable electric current density may be applied to the adsorbent material in the treatment unit to effect the desired level of electrochemical regeneration. An electric current density of 1 to 30 mAcm^"2 may be employed, more preferably an electric current density of around 6 to 20 mAcm^"2 may be employed.

A further operational parameter to consider is the charge passed per mg of COD removed from the fluid. It is preferred that the charge passed is around 12 to 50 Cmg^" ¹ , more preferably around 12 to 20 Cmg^"1 , and most preferably around 12 Cmg^"1.

A preferred embodiment of the present invention will now be exemplified with reference to the treatment of brine used to regenerate ion-exchange filters.

Apparatus suitable to remove organic contaminants, such as NOM, from salt water or brine which has contacted a used ion-exchange resin using a continuous, semi- continuous or batch process is described in International patent publication nos WO2007/125334, WO2009/050485, WO2010/128298, WO2013/054101 , published UK patent application no. GB1 1 1991 1 .4 and unpublished UK patent application no. GB1212676.9. For the present example, apparatus similar to that described in WO2013/054101 is employed in which the brine to be treated is passed through a treatment unit, within which is provided a bed of carbon-based adsorbent material, whilst an electric current is simultaneously applied to the bed of adsorbent material to regenerate said adsorbent material. The apparatus described in the aforementioned patent applications is modified to provide means to discharge decontaminated fluid containing the inorganic species, preferably to a recovery zone in the form of a reservoir for further treatment, storage or immediate re-use.

Ion-exchange resins remove NOM from water by concentrating it on to a surface of the resin. Once the resin is fully loaded it must be regenerated, typically by exposure to a strong brine solution (10 - 15% NaCI). The NOM is displaced from the resin by the sodium and chloride ions which results in the NOM transferring to the brine solution and producing a highly polluted brine solution in need of further treatment.

When the apparatus of the present invention is ready for use, an adsorbent material is loaded into the treatment unit in the required amount. Polluted brine is then delivered to the treatment unit through one or more inlets at a flow rate which is sufficiently high to pass the fluid through the bed of carbon-based adsorbent material but below the flow rate required to fluidise the bed of carbon-based adsorbent material.

Controlling the flow rate of the contaminated liquid entering the adsorbent material bed so as to pass the liquid through the bed but to ensure the adsorbent material remains within the bed for regeneration enables the adsorption and regeneration processes to be carried out simultaneously within the same bed of adsorbent material. The adsorbent material can adsorb contaminants from the contaminated liquid whilst, within the same adsorbent bed, an applied electric current causes gaseous products derived from the adsorbed contaminant to be released from the adsorbent material thereby regenerating the adsorbent material by anodic oxidation of the adsorbed NOM and restoring its ability to adsorb further quantities of the NOM.

Above the treatment unit is a fluid reservoir in which the brine that has passed through the treatment zone, from which the NOMs have been removed, comes to rest. Within the fulid reservoir are one or more discharge outlets from which the brine can be discharged, after treatment, to a recovery reservoir for further treatment, storage or re-use.

In a preferred arrangement the recovery reservoir contains one or more further used ion-exchange resins in need of decontamination to remove adsorbed NOM. Following regeneration of the ion-exchange resin the re-polluted brine can then be recycled and regenerated again using the method described above. In this way a continuous process can be set up to enable a single volume of brine to regenerate a plurality of ion-exchange resins thereby cutting waste and driving down costs. In an alternative preferred arrangement the recovery reservoir can be used to store regenerated brine ready for further use on or off-site as and when required.

As noted above in a second embodiment, the method may be used for the separate treatment of individual volumes of fluid. In this variant, the treatment unit is filled with fluid for treatment to the required level, and then a sufficient quantity of the adsorbent material provided to the treatment unit to complete the treatment. The fluid is then removed and a fresh charge of fluid delivered to the reservoir. The adsorbent material will normally be regenerated and recycled during the treatment process. A further preferred embodiment of the present invention will now be exemplified with reference to the selective removal of EDCs during the treatment of industrial waste water.

Endocrine Disrputor Compounds (EDCs) are regularly found in industrial and agricultural waste water because they are a common by-product of some chemical and manufacturing processes and are a component of some pesticides and insecticides. They are well known for their detrimental health effects and are resistant to standard waste water treatment processes. There is a need for water treatment technologies that are efficient in the removal of EDCs so that discharge to the environment of the industrial waste water can be within regulatory discharge limits. There are a number of molecules that fit into the EDC category, for example DDT (dichlorodiphenyltrichloroethane) and PCB (polychlorinated biphenyl), both of which are included in the Stockholm Convention on Persistent Organic Pollutants. These molecules are halogen-substituted aromatic organic molecules.

Formula 2 - PCBs (polychlorinated biphenyl) Endocrine Disruptor

In treatment of industrial waste water, the majority of organic components within the fluid can be treated using standard water treatment techniques. However it has been found that EDCs are not removed from waste waters upon standard treatment. Furthermore, discharge to the environment of a number of aliphatic organic components does not offer a significant hazard to the environment and removal of all of the organics components of a waste water before discharge is not always necessary to conform to regulatory discharge limits. The present invention can selectively adsorb and remove the EDCs, leaving the remaining organic components for further treatment and/or discharge to the environment.

To effect maximum uptake of EDCs and minimum uptake of other organic components in a sample of waste water requiring treatment the following factors should be assessed:

• the mass of adsorbent material in the treatment unit; and • for waste waters of varying EDC concentration, the flow rate of the treatment fluid through the treatment unit and therefore the length of time that the adsorbent material is in contact with the waste water.

The mass of the adsorbent material in the treatment unit should be directly related to the concentration of the EDCs in the waste water. It will be appreciated that each adsorbent particle will adsorb a specific number of EDC molecules, depending upon the shape, size and morphology of the adsorbent material, and its ratio of basal plane surface area to rough edge surface area. Therefore, the total mass of the adsorbent material in the treatment unit should be calculated by considering the amount of EDC adsorbed per unit mass of adsorbent material and the concentration of the EDC present in the solution. By way of example, for waste waters with a low concentration of EDCs, the adsorbent material will initially preferentially remove the EDCs. However, if all of the EDCs are adsorbed and the waste water is still in contact with adsorbent material that has not adsorbed to complete capacity, the non-preferentially adsorbed components will instead be adsorbed, initiating unnecessary over treatment.

In circumstances where the concentration of EDCs in the waste water is variable, over or under treatment can be prevented by changing the speed at which the fluid moves through the adsorbent bed and therefore changing the contact time of the fluid and the adsorbent, in accord with the EDC concentration. For example, if the waste water has a high concentration of EDCs, it will be run through the treatment apparatus at a slower speed to ensure maximum take-up capacity of the adsorbent is achieved. If the waste water has a low concentration of EDCs, it will be run through the treatment apparatus at a faster speed to ensure only a minimum take-up capacity of the EDCs onto the adsorbent is achieved. It will be appreciated that the balance between contact time and flow rate can be optimised for any given application.

The selective removal of EDCs from industrial waste water can be achieved as described above using the same apparatus as that described above in relation to the use of brine to regenerate ion-exchange filters. Once the EDCs have been removed, the treated industrial waste water can then be subjected to further treatment or discharged to the environment, without the presence of the hazardous EDCs.

Another embodiment of the present invention involves the selective removal of organic components during the treatment of contaminated "heavy water" (deuterium oxide). For example, heavy water that has been used as a moderator in certain types of nuclear reactor. Heavy water becomes contaminated with radionuclides and organics (such as oil, acetone, methanol and ethylene glycol) at unacceptable levels from a few parts per million (ppm) and above during use. During routine refurbishment and maintenance of these reactors the contaminated heavy water must be replaced. This contaminated heavy water can be treated using the method and/or apparatus according to the present invention to remove the organic contaminants, making the heavy water available for re-use as a moderator or in a form that is more suitable for disposal than which is currently available by using existing treatment processes.

Preferred embodiments of the present invention will now be described by way of example only, with reference to the following Examples and Figures in which:

Figure 1 is a photograph of liquids treated using a preferred embodiment of the method according to the present invention. The photograph demonstrates the results of treating a 20% brine solution contaminated with NOMs over six cycles starting with the untreated liquid on the left-hand side of the photograph and culminated in the clear, treated liquid on the right-hand side of the photograph. The removal of colour from each sample is related to a reduction in NOM concentration;

Figure 2 is a graph of the absorbency across a range of wavelengths of UV/visible light exhibited by the initial untreated sample and the final sample after six treatment cycles;

Figure 3 is a photograph of liquids treated using a preferred embodiment of the method according to the present invention. The photograph demonstrates the results of treating a 10% brine solution contaminated with NOMs over seven cycles. The removal of colour from each sample indicates a reduction in NOM concentration; and

Figure 4 is a graph of the adsorptive uptake of phenol, an aromatic organic compound, in a binary mixture of aliphatic organic compounds of different solubility. EXAMPLES

Example 1

A 20 % brine solution, polluted with NOMs from the regeneration of an ion exchange resin, was treated using the batch-wise method of the present invention over six cycles. The adsorption, settlement and regeneration times used were 30, 5 and 30 minutes respectively. The photograph in Figure 1 demonstrates the reduction in colour after each round of treatment. This was corroborated using UV/visible spectrometry to demonstrate the removal of colour as shown in Figure 2.

Example 2

A 10 % brine solution, polluted with NOMs from the regeneration of an ion exchange resin was treated over seven cycles using the batch-wise method and apparatus of the present invention. The adsorption, settlement and regeneration times used were 30, 5 and 120 minutes respectively. The regeneration current was 14 A. The photograph in Figure 3 demonstrates the reduction in colour after each round of treatment.

Example 3

A 64 % phosphoric acid solution contaminated with phenol was treated using the batch-wise method and apparatus of the present invention over a number of cycles. The organic loading pre-treatment was 94,400 mg/l as measured by the chemical oxygen demand (COD). The fluid was slightly viscous and of a "golden" colour with a specific gravity of 1 .46 g/ml and a conductivity of 154 mS/cm.

The phosphoric acid was treated as a dilute solution with 0.5 % waste phosphoric acid mixed with phosphoric acid. This concentration was chosen as the high organic concentration and lower adsorptive capacity of the adsorbent material for phenol meant that the system was limited by the electrochemical regeneration capacity (i.e. the size of electrode used) and in this case the electrode used was only 7 cm by 7 cm. Hence to achieve detectable organic destruction within relatively few cycles, a low concentration of phenol was required.

Treatment of the diluted effluent achieved a removal rate of 1 1 mg of organic per cycle, as measured by COD (Table 1 ). Treatment COD Treatment COD Treatment COD Treatment COD

Cycle (mg/l) Cycle (mg/l) Cycle (mg/l) Cycle (mg/l)

0 460 4 430 9 420 14 300

1 540 5 470 10 410 15 360

2 450 6 370 12 360 16 330

3 490 8 360 13 330 17 280

Table 1 : Treatment of a phosphoric acid solution contaminated with phenol, over 17 cycles. The reduction in COD indicates a reduction in phenol concentration.

Example 4

An industrial effluent contaminated with a range of organics, including TBT, was treated using the batch-wise method and apparatus of the present invention. The organic loading pre-treatment was 6,100 mg/l, as measured by the COD. The solution was yellow/brown in colour, had a strong oily smell and had a total organic carbon content of 3,705 mg/l and a TBT content of 465 μ/Ι.

A 10 % dilute solution of the industrial effluent was treated over a number of cycles. The adsorption, settlement and regeneration periods used were 30, 5 and 30 minutes respectively. The regeneration current was 1 A.

Treatment of the diluted effluent achieved removal of organics, as measured by COD (Table 2). The TBT concentration before and after was analysed and a TBT reduction of 98% was achieved.

Table 2: Treatment of a 10 % industrial effluent solution contaminated with a range of organics, including TBT, over 8 cycles. The reduction in COD indicates a reduction in organic contaminant concentration. Example 5

An aqueous solution containing 10 ppm of phenol was mixed with three different aliphatic organic components, each with a different solubility, at different concentrations to demonstrate the preferential removal of an aromatic organic component in a binary matrix of aromatic and aliphatic organic components.

Individual 15 ml samples of each solution were exposed to 1 g of adsorbent material in a sealed vial over a period of 60 minutes and the concentration of phenol in the solution was monitored to ascertain the loading of phenol on the adsorbent material. The loading of phenol as a function of the concentration and solubility of the three aliphatic organic components is demonstrated in Table 3 and Figure 4.

The adsorptive affinity for phenol is at a maximum when the binary matrix contains aliphatic organic components of a high solubility at low concentrations.

Table 3: The measurement of adsorption uptake of phenol in binary mixtures with aliphatic organic components of different solubility. The concentration of aliphatic organic components of different solubility required for 50 % reduction in adsorptive uptake of phenol at a phenol concentration of 10 ppm indicates the selectivity of the adsorbent for aromatic organic compounds over aliphatic organic compounds.

Claims

1 . A method for the treatment of a fluid containing a first organic component and an inorganic component or a second organic component of different molecular structure to the first organic component, the method comprising: contacting the fluid within a treatment unit with an adsorbent material with a preferential affinity for one of said components over the other of said components such that said one component is adsorbed on to the adsorbent material leaving the other component within the fluid; and electrochemically regenerating the adsorbent material within the treatment unit and discharging said fluid containing said other component from said treatment unit for further treatment, re-use or to the environment.

2. A method according to claim 1 , wherein the adsorbent material has a preferential affinity for the first organic component over the inorganic component or the second organic component.

3. A method according to claim 1 or 2, wherein the fluid containing the non- preferentially adsorbed component is discharged to a recovery zone in which said fluid can be subjected to further treatment, stored or re-used.

4. A method according to claim 3, wherein the recovery zone is in fluid communication with the treatment zone such that fluid from the recovery zone can be passed back to the treatment zone to be contacted with further adsorbent material.

5. A method according to any preceding claim, wherein the treatment unit comprises first and second treatment zones separated by a porous membrane, each treatment zone provided with a bed of the adsorbent material, and the method comprises admitting the fluid into at least one of said first and second treatment zones so as to contact the adsorbent material provided in said at least one treatment zone, operating electric current feeders to pass an electric current in one direction through the adsorbent material within each treatment zone to electrochemically regenerate the adsorbent material in said at least one each treatment zone.

6. A method according to claim 5, wherein the fluid is admitted into both of said first and second treatment zones so as to contact the adsorbent material provided in each respective treatment zone before operation of the electric current feeders, the method further comprising distributing the adsorbent material in the fluid within each treatment zone, allowing the adsorbent material to settle within each treatment zone, and operating the electric current feeders to pass an electric current in one direction through the adsorbent material within each treatment zone to electrochemically regenerate the adsorbent material in one of said treatment zones and operating the electric current feeders to reverse the direction of the electric current applied to the adsorbent material in each treatment zone to electrochemically regenerate the adsorbent material in the other of said treatment zones.

7. A method according to claim 5, wherein a quantity of the fluid is admitted into said first treatment zone to contact the adsorbent material in the first treatment zone at a flow rate which is sufficiently high to pass the fluid through the bed of adsorbent material but below the flow rate required to fluidise the bed of adsorbent material before operation of the electric current feeders, the method further comprising operating the electric current feeders to pass an electric current in one direction through the adsorbent material within each treatment zone to electrochemically regenerate the adsorbent material in the first treatment zone, admitting a further quantity of the fluid into said second treatment zone to contact the adsorbent material in the second treatment zone at a flow rate which is sufficiently high to pass the fluid through the bed of adsorbent material but below the flow rate required to fluidise the bed of adsorbent material, and operating the electric current feeders to reverse the direction of the electric current applied to the adsorbent material in each treatment zone to electrochemically regenerate the adsorbent material in the second treatment zone.

8. A method according to any one of claims 1 to 4, wherein the method comprises admitting the fluid into a bed of the adsorbent material at a flow rate which is sufficiently high to pass the fluid through the bed but below the flow rate required to fluidise the adsorbent material within the bed.

9. A method according to claim 8, wherein electrochemical regeneration of the adsorbent material is effected while the fluid is passing through the bed of adsorbent material.

10. A method according to any preceding claim, wherein the adsorbent material is physically agitated within the treatment zone to assist distribution of the adsorbent material in the fluid and adsorption of said one component from the fluid.

1 1 . A method according to claim 10, wherein the physical agitation is provided by delivery to the treatment zone of a pressurised fluid and/or fluid in need of treatment.

12. A method according to any preceding claim, wherein the adsorbent material comprises a particulate electrically conductive adsorbent material.

13. A method according to any preceding claim, wherein the adsorbent material comprises a particulate electrically conductive carbon-based adsorbent material.

14. A method according to any preceding claim, wherein the adsorbent material comprises unexpanded intercalated graphite.

15. A method according to any preceding claim, wherein the adsorbent material comprises activated carbon.

16. A method according to any preceding claim, wherein electrochemical regeneration of the adsorbent material is effected using an electric current density of around 1 to 30 mAcm^"2.

17. A method according to any preceding claim, wherein electrochemical regeneration of the adsorbent material is effected over a time period of around 5 to 1440 minutes

18. A method according to any preceding claim, wherein the fluid within the treatment unit is contacted by the adsorbent material for a time period in the range of around 5 to 60 minutes.

19. A method according to any preceding claim, wherein the charge passed per mg of COD removed from the fluid is around 12 to 50 Cmg^"1.

20. Apparatus for the treatment of a fluid containing an organic component and an inorganic component or a second organic component of different molecular structure to the first organic component, the apparatus comprising a treatment unit for fluid to be contacted by an adsorbent material with a preferential affinity for one of said components over the other of said components; two electrodes connected to the treatment unit which are controllable to electrochemically regenerate said adsorbent material following contact with said fluid; and means for discharging the fluid containing said other component from the treatment unit for further treatment, re-use or to the environment.

21 . Apparatus according to claim 20, wherein the treatment unit defines first and second treatment zones separated by a porous membrane, the adsorbent material being provided in said first and second treatment zones, an agitator operable to distribute the adsorbent material in the fluid contained in each of the first and second treatment zones, a first electric current feeder operably connected to the adsorbent material in the first treatment zone and a second electric current feeder operably connected to the adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the adsorbent material in the first and second treatment zones in one direction to regenerate the adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the adsorbent material in the first and second treatment zones to regenerate the adsorbent material in the other of the first and second treatment zones.

22. Apparatus according to claim 20, wherein the treatment unit defines first and second treatment zones separated by a porous membrane, the adsorbent material being provided in said first and second treatment zones, a pump operable to admit a quantity of the fluid selectively into each of said first and second treatment zones to contact the adsorbent material in the respective treatment zone at a flow rate which is sufficiently high to pass the fluid through the adsorbent material but below the flow rate required to fluidise the adsorbent material, a first electric current feeder operably connected to the adsorbent material in the first treatment zone and a second electric current feeder operably connected to the adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the adsorbent material in the first and second treatment zones in one direction to regenerate the adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the adsorbent material in the first and second treatment zones to regenerate the adsorbent material in the other of the first and second treatment zones.

23. Apparatus according to claim 20, wherein the apparatus comprises a bed of the adsorbent material, the electrodes being operable to pass an electric current through said bed to regenerate the adsorbent material, and means to admit the fluid into said bed to contact said adsorbent material at a flow rate which is sufficiently high to pass the fluid through the bed but below the flow rate required to fluidise the bed of adsorbent material.

24. Apparatus according to any one of claims 20 to 23, wherein said treatment unit is in fluid communication with a recovery reservoir which is adapted to receive fluid discharged from the treatment unit.