GB2170492A

GB2170492A - Composite materials

Info

Publication number: GB2170492A
Application number: GB08601504A
Authority: GB
Inventors: Dr Edward Sydney Lane
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1985-01-25
Filing date: 1986-01-22
Publication date: 1986-08-06
Also published as: GB8601504D0; GB2170492B; GB8501881D0

Abstract

A composite material comprising an organic liquid retained within a matrix of an inorganic material, is prepared in accordance with the present invention by a process which includes hydrolysing, in the presence of the organic liquid, a compound capable of producing the matrix of the inorganic material thereby to produce the composite material. The organic liquid may be, for example, a solvent extraction liquid or an oil. Alkyl silicates, alkyl titanates and aluminium alkoxides are examples of compounds capable of forming the matrix.

Description

SPECIFICATION Composite materials The present invention relates to composite materials and their production.

According to one aspect of the present invention there is provided a process for the preparation of a composite material comprising an organic liquid retained within a matrix of an inorganic material, which includes hydrolysing, in the presence of the organic liquid, a compound capable of producing the matrix of the inorganic material thereby to produce the composite material.

According to another aspect the present invention provides a composite material comprising an organic liquid retained within a matrix of an inorganic material.

The matrix may be considered to be a network structure in which the organic liquid is retained.

The matrix may retain some residual organic groups, where the compound is an organic compound, but it will be essentially of inorganic material.

Preferably a liquid mixture containing the organic liquid and the compound is treated to cause the hydrolysis.

Also it is preferred in one embodiment that the organic liquid is maintained in intimate contact with the compound during hydrolysis by effecting the hydrolysis in a liquid with which the liquid mixture is substantially immiscible.

The organic liquid may be selected from a wide range depending upon the desired composite material and may be, for example, an organic solvent such as TBP or an oil. Optionally the hydrolysis may be carried out in the presence of a "filler" (e.g. Kaolin or Kieselguhr).

It is preferred that the compound is one capable upon hydrolysis of producing, as the matrix, an inorganic material comprising a network structure of a hydrous oxide polymer or gel. The compound is preferably an organic compound containing an element, or elements, appropriate to the inorganic material to be prepared as the matrix.

By "element, or elements, appropriate to the inorganic material to be prepared" it will be understood that the organic compound is chosen on the basis of the element, or elements, it is required to obtain in the matrix of inorganic material. For example, if it is desired to produce a silica matrix the organic compound chosen for hydrolysis can be an organic silicon compound (e.g. an alkyl silicate).

It is possible to arrange for the matrix to be such that the organic liquid is accessible to species brought into contact with the composite material.

For example, where the organic liquid is a water insoluble organic extraction agent (e.g. TBP), it will not be readily leachable from the composite material into water, but due to interconnected porosity in the matrix it can still be accessible to species (e.g. extractable cations) in solutions contacted with the composite material and, therefore able to extract the species from such solutions.

The accessibility of the organic liquid to species brought into contact with the composite material may be modified by the extent to which the matrix is "open" or "closed". Thus, for example by drying the composite material it is possible to reduce the accessibility of the organic liquid because drying tends to close the matrix (i.e. cause the network structure to become less "open"). Conversely, e.g. by not drying, the matrix is not "closed" and the accessibility of the organic liquid may be retained.

The process of the present invention can be applied to produce composite material in selected physical configurations (e.g. microspheres). Thus, for example, the hydrolysis of the compound can be carried out whilst the compound is dispersed in droplet form such that the composite material comprises microspheres. Preferably, the hydrolysis is carried out in the presence of a protective colloid.

By "protective colloid" it is meant a substance capable of inhibiting aggregation of selected physical configurations (e.g. microspheres) of composite material produced by hydrolysis. Generally such protective colloids are water soluble compounds having groups capable of sorption onto the surface of the material. Examples of protective colloids that may be used in accordance with the present invention are polyvinyl alcohols, water soluble cellulose ethers, dextran and hydroxy alkylated natural gums such as hydroxy alkylated guar gum. Monomeric compounds such as glucose, glycerol and triethanolamine may also be used as protective colloids.

In the preparation of a composite material having a silica matrix in accordance with the present invention, of the organic silicon compounds available we prefer to use alkyl silicates. Of the alkyl silicates that may be used in accordance with the present invention we prefer to use ethyl silicate (i.e. tetraetholxysilane) e.g. as obtainable from or mixtures of this compound with ethyl polysilicate (e.g. those commercially available from Monsanto Chemicals Ltd. such as the mixture sold under the Trade Name Silester OS).

Examples of other compounds suitable for use in accordance with the present invention to produce a matrix of an inorganic material are alkyl titanates (e.g. tetrabutyl titanate as available from BDH Ltd.) and aluminium alkoxides (e.g. aluminium isoproproxide).

By using two or more compounds it is possible, in accordance with the present invention, to prepare a matrix comprising an inorganic material containing a variety of elements. Thus, for example, by using a mixture of an alkyl silicate and an alkyl titanate it is possible to produce a siliceous matrix containing titania. Similarly by using a mixture of an alkyl silicate and an aluminium alkoxide it is possible to pro duce a siliceous matrix containing alumina.

The compound, organic liquid, protective colloid and a hydrolysing agent for hydrolysing the compound can be combined in a number of ways. Thus for example in one embodiment of the present invention in accordance with which microspheres of composite material may be produced, a liquid mixture of the compound and the organic liquid is dispersed in a liquid containing a protective colloid and a hydrolysing agent to achieve the hydrolysis.

In accordance with the immediately preceding embodiment the liquid is preferably an aqueous solution ofthe protective colloid and hydrolysing agent.

Also, for example, in another embodiment a liquid mixture of the compound and the organic liquid is dispersed in a liquid containing a protective colloid, and a hydrolysing agent is added subsequently.

In the immediately preceding embodiment of the invention the liquid is preferably an aqueous solution of the protective colloid.

In the above embodiments an organic additive may be mixed with the compound or with the organic liquid prior to contacting them together to improve their miscibility. For example, xylene can be added to a mixture of a heavy oil and orethosilicate to increase their miscibility.

The hydrolysing agent can be a base such as ammonium hydroxide solution. A wide range of concentrations of this solution can be used, but in general we have found that it is not usually necessary to employ solutions having > 30% ammonia by weight.

As alternatives to ammonium hydroxide, basic amines may be used as hydrolysing agent (e.g. morpholine, cyclohexylamine, dicyclohexylamine, benzyl-dimethylamine, and related compounds, and trieth anolamine, monoethanolamine and hydrazine).

It will be appreciated that where a base is used as a hydrolysing agent the process is operating under alkaline pH conditions.

It has been found in accordance with the invention that in some circumstances a diluent can be employed to assist in achieving a homogeneous system of compound-capable of producing the matrix and organic liquid during hydrolysis. The diluent may be miscible with the organic liquid such as, for example, to facilitate the formation-of a single phase containing the diluent, the compound capable of producing the matrix and the organic liquid to be retained in the matrix.

Such a diluent can be, for example, an organic diluent compatible with the compound capable of producing the matrix and the organic liquid (i.e. does not undergo any unwanted chemical reactions therewith). Suitable organic diluents are for example: hydrocarbons (e.g. toluene, benzene, hexane or heptane and mixtures thereof), halogenated hydrocarbons (e.g. chloroform, metrhylchloroform, 1,1,1-trichloroe- thane and carbon tetrachloride), esters (e.g. ethyl acetate), alcohols (such as n-hexanol 2-ethyl hexanol and isopropanol) and glycols (e.g. polypropylene glycol 400 or 1035 ex BDH Ltd).

Where water is present in the reactants used in carrying out the present invention (e.g. where the protective colloid is used in an aqueous solution) it will be appreciated that an inorganic material matrix as obtained after the hydrolysis step will generally be in the form of an hydrous gel which may also contain some protective colloid and/or some hydrolysing agent, and/or some diluent if used.

In accordance with another embodiment of the invention, it is possible to introduce further elements (e.g. metal species) during the hydrolysis, by carrying out the hydrolysis step in the presence of an element capable of forming an ammine. The element can be present as an ammine complex in an excess of the complexing ammine or of ammonia. Suitable elements for introduction into the inorganic material matrix in this way are, for example, copper, zinc, silver, chromium and nickel. The inorganic material matrix prepared in this way then includes ammine groups (e.g. metal ammine groups).

In some preparations we have found it advantageous to use a hydrolysis promoting agent to effect hydrolysis in relatively short reaction times (e.g. ~ 1 hour). Examples of hydrolysis promoting agents are: Ammonium salts (e.g. ammonium halides, carbonate acetate, chloracetate and quaternary ammonium salts) and betaines. It has been found that quaternary ammonium salts of the kind disclosed in the Complete Specification of B.P. No. 1,303,353 can be used as hydrolysis promoting agents.The quaternary ammonium salts disclosed may be represented by the formula:

where X- is a halide ion and R2, R2, R3 and R4 each are aliphatic, aryl, alkoxy ether radicals or heterocyclic radicals, with at least two of the foregoing groups being lower alkyl (i.e. containing < 12 C atoms) and art least one of the foregoing groups being an aliphatic radical containing at least 12 C atoms, an aryl, a heterocyclic or an alkyl ether radical. In B.P. Specification No. 1,303,353 "aryl" is used broadly to refer to a hydrocarbon residue containing an aromatic ring.

The quaternary ammonium salts of the above general formula disclosed in B.P. 1,303,353 are (cationic) surface active agents It has been found, however, that quaternary ammonium salts containing small alkyl groups (e.g. tetramethyl-ammonium halides) which normally are devoid of surface active properties are effective in promoting hydrolysis of, for example, alkyl silicates in aqueous amine solutions.

The use of a hydrolysis promoting agent may be omitted, it has been found that this generally means that the reaction time is longer or that more vigorous reaction conditions or a more reactive hydrolysing agent is required.

The choice of reagents used, and particularly the choice of hydrolysing agent and hydrolysis promoting agent (if used), may be used to influence the nature of the microspheres produced in accordance with the present invention.

The hydrolysing agent should be sufficiently basic to hydrolyse the compound within practically convenient periods of time.

Generally combinations of reagents (i.e. the compound, organic liquid, protective colloid, hydrolysing agent and hydrolysis promoting agent (if used), are chosen in accordance with the present invention such that during hydrolysis there is the minimum formation of water soluble substances (e.g. water soluble polysilicic acids), which would pass into any aqueous media present.

Preferred hydrolysing agents are cyclohexylamine, dicyclohexylamine, benzyl dimethylamine, morpholine and ammonia, and preferred hydrolysis promoting agents are the quaternary ammonium salts Hyamine 2389 (ex BDH Ltd.), tetramethyl ammonium bromide and tetraethyl ammonium bromide. (Hyamine 2389 is an approximately 50% by weight solution of methyldodecyl benzyl trimethyl ammonium chloride and methyl dodecyczylene bistrimethylammonium chloride. "Hyamine" is a Trade Name of Rohn and Haas).

For large (up to - 1000 m) microsphere production it has been found that it is convenient to use cyclohexylamine as the hydrolysing agent in combination with a lower alkyl ammonium halide (i.e. alkyl = methyl or ethyl) as the hydrolysis promoting agent. For small (o.1 - 20 Am diameter) microsphere production it has been found that it is convenient to use cyclohexylamine in combination with longer chain quaternary ammonium salts (e.g. having at least one chain of about 12 C atoms, e.g. Hyamine 2389).

It will be appreciated that the behaviour of various combinations of reagents differ. However, satisfactory combinations of reagents can be easily confirmed by simple experimentation.

The size of microspheres produced in accordance with the present invention can be, for example, in the size range of < 1 Am to 1000 m. In addition to the influence of the choice of reagents of the size of microspheres (as hereinbefore mentioned) the size can be influenced, where agitation is employed to disperse the compound and organic liquid therefor) in droplet form, by the degree of agitation used. Also the presence of surface active agents may be used to influence interfacial surface tension and hence the size of droplets. The usual effect of the addition of a surfactant is to reduce the size of microspheres produced. Both ionic and non-ionic surfactant may be used. Examples of cationic surfactant are the quaternary ammonium salts hereinbefore disclosed and an example of an anionic surfactant is Sarkosyl O (ex Geigy Chemical Co. Ltd., England).An example of a non-ionic surfactant is Tergitol NPX (alkyl phenyl ether of polyethylene glycol, ex BDH Ltd., England).Since certain hydrolysis promoting agents may have surface active properties, (e.g. quaternary ammonium salts as hereinbefore disclosed) it will be appreciated that in some circumstances the hydrolysis promoting agent can have a dual function (i.e. in promoting hydrolysis and influencing size.

It is also possible for either or both the hydrolysing agent (e.g. amine) and the hydrolysis promoting agent to perform the function of increasing the miscibility of the organic compound and the substance in addition to being a hydrolysing or hydrolysis promoting agent.

As hereinbefore disclosed where water is present in the reactants used in accordance with the present invention (e.g. where the protective colloid is used in an aqueous solution) it will be appreciated that an inorganic material matrix as obtained after the hydrolysis step will be generally in the form of an hydrous gel which may also contain some protective colloid and/or some hydrolysing agent, and/or some diluent (if used).

Also, by use of water insoluble hydrolysing agent (e.g. amines) or hydrolysis promoting agents (e.g.

quaternary ammonium salts) such as benzyl dimethylamine, Prime JMT and Aliquat 336, these agents can be retained in the composite material and thereby modify the structure thereof.

Composite materials prepared in accordance with the present invention are believed to have applications in a variety of fields.

Thus, for example, where the substance is an organic extraction agent the composite material can be used to extract species from solution as hereinbefore disclosed.

Accordingly, from another aspect the invention provides a process for the extraction of species from a fluid which includes the step of contacting the fluid with a composite material comprising a substance retained within a matrix of an inorganic material, said substance being capable of extracting the species from the fluid.

Another example of an application of the present invention is in the incorporation of substances in an inorganic matrix for facilitating handling or for storage or for disposal. Thus, for example, a liquid waste (e.g. a radioactive liquid waste) can be incorporated and entrapped within a solid composite material by carrying out the hydrolysis in the presence of the radioactive liquid waste. In one particular application of the present invention an organic liquid contaminated with radioactive material or an oil contaminated with a radioactive material may be incorporated or entrapped in a matrix formed by use of an alkyl silicate.

Thus the present invention provides, in one embodiment, a process for the incorporation of a liquid waste comprising hydrolysing an alkyl silicate in the presence of the liquid waste to produce a composite material comprising a liquid waste incorporated in a matrix of inorganic material.

-Composite material prepared in accordance with the immediately preceding embodiment may be- a solid granular product. The product may be dried (e.g. at room temperature) and may contain approx.

50% (by volume) of liquid waste (e.g. oil or organic liquid).

It has been found that liquid is not leached from such a product after prolonged contact with H2O at ambient temperature. Where a suitably high silica : oil ratio is used the product may be extruded or pressed (e.g. into pellets) without any substantial separation of the liquid. If desired the product (e.g. as pellets or dried granules) may be incorporated into a concrete or other storage material for storage.

It is also believed that the composite materials of the present invention also find application, for example, as antifouling and waterproofing agents.

For some applications the composite materials prepared in accordance with the present invention may be at least partially dried after the hydrolysis, for example, to facilitate handling (e.g. when the composite materials are in the form of microspheres the at least partially dried microspheres provide a free flowing product such as, for example, free flowing microspheres of a composite containing a substance for disposal). It is to be understood that where the composite materials are to be used in an aqueous environment (e.g. in the extraction of metals from aqueous solution) drying is unnecessary, and in some cases can be detrimental to the properties of the composite materials.

The invention further provides in another aspect a composite material produced by-a process in accordance with the invention.

The invention will now be further described, by way of example only, as foliows: Example 7 A mixture was made comprising Morpholine (5 ml), digoxin (0.5 g) and pyridine (5 mls) (as a solvent for the digoxin) and added to Silester OS+ (35 ml) to form a homogenous solution. This was added to a stirred solution (500 ml) of water containing 5 gm of a low viscosity polyvinyl alcohol to form a dispersion of organic droplets in aqueous solution. Hyamine (3 mls) (as hereinbefore mentioned) was added to the stirred system and the reaction allowed to proceed for one hour. The white microspheres thus formed were allowed to settle, decanted three times with an equal volume of water, filtered off and dried in air at room temperature.The product composite material comprised siliceous microspheres containing digoxin, which were very free-flowing.

(* Silester OS (Registered Trade Mark) is a mixture of tetraethyl orthosilicate and ethyl polysilicates produced by Monsanto Ltd. It has a S.G. of 1.07 at 15.5 and contains approximately 41% by weight of silica.) Example 2 25 mis of tributyl phosphate was mixed with 50 mls of Silester OS (see Example 1) and 3 mls of cyclohexylamine. The resulting mixture was poured into 250 mls of a rapidly stirred 1% solution of Moviol N85-88 in water. (Moviol (Registered Trade Mark of Fabwerke Hoechst AG) is a particular grade of polyvinyl alcohol). 2 grams of tetraethyl ammonium bromide was added to the stirred suspension; after 15 minutes the mixture was filtered through a glass frit, and the solid residue washed with water.There was no "breakthrough" of immiscible organic liquids to the filtrate and the filtered microspheroidal product comprised a composite material of tributyl phosphate in a siliceous matrix.

Example 3 This Example shows the use of a composite material in accordance with the present invention in the extraction of a species from solution.

Thus, a sample of the wet microspheres produced as in Example 2 was poured into a 1 cm diameter column and washed with 5M nitric acid. A solution of uranyl nitrate in 5M nitric acid was slowly run through the column and uranium containing species concentrated in a yellow band at the top of the column. This band could be moved slowly down the column by elution with further 5M nitric acid, or moved more rapidly by elution with 1M sulphuric acid.

Example 4 A mixture was formed by mixing 50 mls of Alamine* 336 with 50 mls of Silester OS (see Example 1) and 5 mls of cyclohexylamine. The resulting mixture was dispersed by stirring into 250 mls of water containing 0.15 g of Methocel 90 Hg 40 (registered Trade Mark of the Dow Chemical Co. - is a grade of hydroxypropyl methyl cellulose). 3 grams of tetraethylammonium bromide were added to the stirred dispersion (of organic droplets in aqueous solution) and the resulting mixture allowed to stir for one hour.

The mixture was filtered and solid microspheroidal (composite material) product washed with two bed volumes of water. This microspheroidal product contained Alamine 336 in a siliceous matrix. The amine was found to be accessible to solutions containing metal ions. The microspheroidal product was found to be capable of being dried to give a free--flowing powder. (*Alamine 336 is a tricaprylamine made by General Mills Inc.).

Example 5 A mixture was formed by mixing 50 ml Silester OS (see Example 1) with 5 ml of cyclohexylamine and 25 mls of LIX 64. (LIX 64 is a type of oxime made by General Mills Inc. mainly for the solvent extraction of copper; of USP 3,428,449). The mixture was added to a stirred solution (250 mls) comprising 0.15 grams of Methocel 90 HG 40 in water, and subsequently 2 grams of tetraethyl ammonium bromide was added. After 10 minutes continuous stirring the resulting solid composite material product (43 g) was filtered off and dried in air. This product was found capable of extracting copper when contacted with slightly acidic solutions containing copper ions. Since the composite product was for extraction purposes the drying step was omitted.

Example 6 A mixture of 20 mls of Silester OS (see Example 1), 10 mls of heavy mineral oil and 3 mls of polybutyl titanate was slowly poured into 250 mls of 5M aqueous ammonia. The mixture coagulated into lumps from which aqueous solution was decanted after 30 minutes. The solid residue was dried to a granular solid composite material, which was easily incorporated into a concrete mix without segregation of the oil.

Example 7 A mixture was formed from 30 mls of Silester OS (see Example 1), 10 mls of Silicone Fluid MS 200/50 cs (ex BDH) and 5 mls of benzyldimethylamine. The mixture added to 500 mls of water containing 1% by weight of polyvinyl alcohol to form a dispersion. 2 grams of tetramethyl ammonium bromide were added to the dispersion with stirring and the stirring continued for a further 30 minutes. The resulting mixture was then filtered and the solid residue composite material washed with water and dried in air (29 grams).

This microspheroidal composite material was readily incorporated into cement or concrete to confer waterproofing properties.

Example 8 A mixture was formed from 50 mls of Silester OS (see Example 1), 10 mls of dibutyltin dilaurate and 5 mls of cyclohexylamine. The mixture was poured into 250 mls of water containing 0.2 grams of Methocel 90 HG 40, 2 grams of Hyamine and 0.5 grams of Nonidet P40 solution with rapid stirring. The stirring was continued for a further 30 minutes. The resulting mixture was filtered through a glass frit and washed with a litre of water containing 0.5 grams of Nonidet P40 (nonionic surface active agent ex BDH).

The pressed, washed filter cake was dried in warm air to form an early friable cake of a composite mate rial comprising a microspheroidal silica matrix containing dibutyltin dilaurate. This composite material was incorporated into a paint system which confered antifouling properties to treated surfaces.

Example 9 25 mls of tetraethylorthosilicate was added to a mixture of 3 mls of morpholine, 10 mls of tetra isopro pyltitanate and 15 mls of mineral oil and the resulting mixture poured into water. The mixture instantly solidified to a soft particulate gel. After standing for a further 30 minutes the gel was filtered off. No mineral oil appeared in the filtrate. The filter cake was dried to give a friable solid composite material suitable for inclusion in cement mixes etc. for storage/disposal of the oil.

Example 10 40 mls of Silester OS (see Example 1) was mixed with 10 mls of odourless Kerosene and 5 mls of di-2 ethylhexylphosphate and the resulting mixture was heated to reflux with stirring in 400 mls of an aqueous 0.5% by weight solution of Moviol 42-99. After 3 hours the refluxed mixture was cooled and filtered. The solid composite material product formed comprised siliceous spheres containing kerosene and di-2 ethylhexylphosphate and very little immiscible organic material was found in the aqueous filtrate. These spheres of composite material had the cationic ion-exchange properties normally associated with the solvent system of kerosene-di-2 ethylhexylphosphate.

Example ii 30 mls of Silester OS (see Example 1) and 10 mls of Alamine 336 (see Example 4) were stirred and refluxed in 400 mls of an aqueous 0.5% by weight solution of Moviol 42-99. As reaction proceeded solid spheres collected at the surface and were progressively removed. After washing the separated spheres of composite material had similar properties to those described in Example 4.

Example 12 A suspension of 30 g of Kaolin (B.P., light) in 50 ml Silester OS (see Example 1) and 3 ml cyclohexy lamine was prepared.

The suspension was added dropwise to 300 mls of a 1% aqueous solution of Methocel 90 HG 40 (see Example 4) (temperature monitored at 40"C) with slurry.

When the addition was completed and thorough dispersion had taken place, 5 mls of 50% aqueous solution of benzyl-trimethyl ammonium chloride were added and the mixture stirred for 30 minutes.

The resulting spheres were filtered off, washed successively with 2M HCI, water and industrial methylated spirits, and air dried. Subsequently the spheres were heated in a muffle furnace to 500"C.

The majority of the resulting spheres were of a size in the range 200 - 1000 (m diameter.

Example 13 A first mixture of water (50 ml), tetraethylammonium bromide (29) and Span 80 (1 ml) surfactant was added with stirring to a second mixture of Silester OS (80 mls), cyclohexylamine (20 mls) and vacuum oil (200 ml).

The resulting third mixture was gelled after 5 minutes stirring but remained stirable with an exotherm to 40"C.

The gelled mixture was scraped into trays and allowed to evaporate to dry in air at room temperature.

A week later the gelled mixture was a soft granular powder (256 g).

Example 14 A heavy lubricating oil (25 ml) was mixed with 25 mls of a mixture comprising 50 mls of Silester OS and 5 mls of cyclohexylamine. 25 mls of methylchloroform was added to make the mixture homogeneous. 5 ml of 5% by wt. solution of tetramethylammonium bromide in water was added and the system stirred until gelation occurred. There was a small quantity of liquid separating from the gel so a further 10 ml of the Silester OS cyclohexylamine mixture was added and the whole system restirred until gelled.

After evaporation of ethanol, methychloroform and water from the gel the residue comprised a fawn granular solid.

Claims

1. A process for the preparation of a composite material comprising an organic liquid retained within a matrix of an inorganic material, which includes hydrolysing, in the presence of the organic liquid, a compound capable of producing the matrix of the inorganic material thereby to produce the composite material.

2. A process as claimed in claim 1 wherein a liquid mixture containing the organic liquid and the compound is treated to cause the hydrolysis.

3. A process as claimed in claim 2 wherein the organic liquid is maintained in intimate contact with the compound during hydrolysis by effecting the hydrolysis in a liquid with which the liquid mixture is substantially immiscible.

4. A process as claimed in any one of the preceding claims wherein the hydrolysis is carried out in the presence of a filler.

5. A process as claimed in claim 4 wherein the filler is Kaolin or Kiselguhr.

6. A process as claimed in any one of the preceding claims wherein the compound is one capable upon hydrolysis of producing, as the matrix, an inorganic material comprising a network structure of a hydrous oxide polymer or gel.

7. A process as claimed in any one of the preceding claims wherein the compound is an organic compound containing an element, or elements, appropriate to the inorganic material to be prepared as the - matrix.

8. A process as claimed in any one of the preceding claims wherein the composite material is prepared in selected physical configuration.

9. A process as claimed in any one of the preceding claims wherein the hydrolysis of the compound is carried out whilst the compound is dispersed in droplet form such that the composite material comprises microspheres.

10. A process as claimed in any one of the preceding claims wherein the hydrolysis is carried out in the presence of a protective colloid.

11. A process as claimed in claim 10 wherein the protective colloid is a polyvinyl alcohol, a water soluble cellulose ether, dextran, a hydroxy alkylated natural gum, glucose, glycerol or triethanolamine.

12. A process as claimed in any one of the preceding claims wherein the compound, organic liquid, protective colloid and a hydrolysing agent for hydrolysing the compound are combined.

13. A process as claimed in claim 12 wherein a liquid mixture of the compound and the organic liquid is dispersed in a liquid containing a protective colloid and a hydrolysing agent to achieve the hydrolysis.

14. A process as claimed in any one of claims 1 to 12 wherein a liquid mixture of the compound and the organic liquid is dispersed in a liquid containing a protective colloid, and a hydrolysing agent is added subsequently.

15. A process as claimed in any one of the preceding claims wherein an organic additive is mixed with the compound or with the organic liquid prior to contacting them together to improve their miscibility.

16. A process as claimed in any one of claims 12 to 15 wherein the hydrolysing agent is ammonium hydroxide solution.

17. A process as claimed in any one of claims 12 to 15 wherein the hydrolysing agent is a basic amine.

18. A process as claimed in claim 17 wherein the basic amine is morpholine, cyclohexylamine, dicyclohexylamine, benzyl-dimethylamine, triethanolamine, monoethanolamine or hydrazine.

19. A process as claimed in any one of the preceeding claims wherein a diluent is employed to assist in achieving a homogeneous system of compound capable of producing the matrix and organic liquid during hydrolysis.

20. A process as claimed in claim 19 wherein the diluent is a hydrocarbon, a mixture of hydrocarbons, a halogenated hydrocarbon, an ester, an alcohol or a glycol.

21. A process as claimed in any one of the preceding claims wherein the hydrolysis step is carried out in the presence of an element capable of forming an ammine thereby to introduce a further element

22. A process as claimed in any one of the preceding claims wherein a hydrolysis promoting agent is used.

23. A process as claimed in claim 22 wherein the hydrolysis promoting agent is an ammonium salt or a betaine.

24. A process as claimed in claim 23 wherein the ammonium salt is a quaternary ammonium salt.

25. A process as claimed in any one of the preceding claims wherein a surface active agent is used.

26. A process as claimed in any one of the preceding claims wherein the hydrolysis is carried out in the presence of a liquid waste thereby to incorporate and entrap liquid waste within a solid composite material.

27. A process as claimed in claim 26 wherein an alkyl silicate is hydrolysed in the presence of a liquid waste to produce a composite material comprising a liquid waste incorporated in a matrix of inorganic material.

28. A process as claimed in any one of claims 1 to 26 wherein the compound capable of producing the matrix is an alkyl silicate, an alkyl titanate or an aluminium alkoxide.

29. A process as claimed in any one of the preceding claims wherein the compound capable of producing the matrix is ethyl silicate.

30. A process as claimed in claim 28 wherein the compound capable of producing the matrix is tetrabutyl titanate.

31. A process as claimed in claim 28 wherein the compound capable of producing the matrix is aluminium isopropoxide.

32. A process as claimed in any one of claims 1 to 27 wherein a mixture of compounds capable of prqducing the matrix are used.

33. A process as claimed in any one of the preceding claims wherein the composite is in the form of microspheres having a size in the range of < 1 am to 1000 m.

34. A process as claimed in any one of the preceding claims wherein the composite material is dried after the hydrolysis.

35. A process for the extraction of species from a fluid which includes the step of contacting the fluid with a composite material comprising a substance retained within a matrix of an inorganic material, said substance being capable of extracting the species from the fluid.

36. A composite material comprising an organic liquid retained within a matrix of an inorganic material.

37. A process for the preparation of a composite material substantially as hereinbefore described, with reference to any one of Examples 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14.

38. A composite material substantially as hereinbefore described with reference to any one of Exam ples 1,2,3,4,5,6,7,8,9,10, 11,12,13 or 14.