MXPA97003639A - Use of a reticulated matrix impregnated with solvents for recovery of me - Google Patents

Abstract

A composition comprising a highly crosslinked porous body derived from a water soluble hydrogel polymer, the porous body is characterized in that it has a three-dimensional open cell lattice structure, a density of less than about 1.0 gram per cubic centimeter, a surface area equal to or greater than about 300 square meters per gram, a compressive strength equal to or less than a yield of about 10 percent at 21.09 kilograms per square centimeter and an average pore diameter of less than about 500 angstrom units, wherein the polymer of hydrogel is selected from the group consisting of alginates, gums, starch, dextrins, agar, gelatin, casein, collagen, polyvinyl alcohol, polyethylene imine, acrylate polymers, starch / acrylate copolymers and mixtures and copolymers thereof, and an extractant of metal. The composition can be used to remove and / or recover metal ions from aqueous streams. A process for recovering metal ions from an aqueous metal ion solution including the steps of impregnating a metal extractant into the porous body described above and contacting the aqueous ion solution with the impregnated porous body in order to remove the metal ions from it and separate the ions from the porous body impregnates

Description

"USE OF A RETICULATED MATRIX IMPREGNATED WITH SOLVENT FOR METAL RECOVERY" BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a carrier impregnated with liquid ion-specific extractants, and a metal recovery process using the impregnated carrier.

DESCRIPTION OF THE PREVIOUS TECHNIQUE The concept of using porous resins as polymeric carriers for ion-specific liquid extractants has been known since as early as the 1970s. See Patent Application South African Number 5637 (1971) and the article by A.

Warshawsky, 83 Trans. Inst. Min. Metal. C101 (1974) ["Warshawsky I"]. Typical concerns associated with using these solvent impregnated resins include: 1) the possibility of loss of solubility of the entrapped solvent; 2) the limitations of mass transfer due to limited interfacial contact with the treatment current; and 3) the characteristics of the basic pore structure of the polymeric support. See A. Warshawsky, Ion Exchange and Solvent Extraction, Ch. 3, page 229 (New York, 1981) ["Warshawsky II"]. More specifically, the average pore diameter of the appropriate resins should be large enough to accommodate the extractant-organic complex, but not so large as to subject the immobilized extractant to excessive loss of elevated hydrodynamic pressure. These resins should also exhibit little or no shrinkage or swelling when exposed to solutions of very different pH values and salt concentrations, which is an inconvenience associated with known resins such as styrenic polymer resins and cross-linked styrene-divinylbenzene resins . See Warshawsky II at 229. Although the solubility losses can be minimized by careful selection of the extractants and diluents, the selection of the polymeric support plays the final role in determining the commercial viability of a solvent / resin system. Hydrometallurgy, the extraction of metals from an aqueous solution is a process that is gaining importance as the quality of metal-carrying ores available in the world declines. See D.S. Flett, 83 Trans. Inst. Min. Metal. C30 (1974). In order to selectively extract metal ions from aqueous ore leached materials, commercial hydrometallurgical operations currently use liquid-liquid processes (solvent extraction). In general, these processes typically consist of a multiple-capped mixer-setter section where the metal-bearing leached material emulsifies with an immiscible organic extractant. The organic and aqueous phases are then allowed to separate and the organic phase, which now contains the extracted metal, is transferred to a purification section where the metal value is recovered for subsequent purification. These solvent extraction processes have several inherent limitations: (1) a large capital investment is required for the construction of the plant, (2) large losses of organic reagents are incurred by vaporization into the atmosphere, by retention due to separation of phase deficient and by solubility of organic extractants in the aqueous phase, (3) phase separation is difficult and impossible at lower operating temperatures and (4) a relatively large track of equipment is required. It would be desirable to provide an improved, environmentally safe metal extractive composition that exhibits not only higher dimensional stability in different solvents, but also has improved porosity characteristics to accommodate the needs of metal recovery applications. It would also be desirable to provide an economically safe environmental metal recovery process that maximizes the mass transfer contact area between the treatment stream and the extractant.

COMPENDIUM OF THE INVENTION According to the present invention, there is provided a composition comprising: a) a highly crosslinked porous body derived from a water soluble hydrogel polymer, the porous body being characterized by having a three-dimensional reticular cell structure of open cells, a density of less than of about 1.0 gram per cubic centimeter, a surface area equal to or greater than 300 square meters per gram, a compressive strength equal to or less than a yield of about 10 percent to 21.09 kilograms per square centimeter and an average pore diameter of less than about 500 angstrom units, wherein the hydrogel polymer is selected from the group consisting of alginates, gums, starch, dextrins, agar, gelatin, casein, collagen, polyvinyl alcohol, polyethylene imine, acrylate polymers, starch copolymers / acrylate and mixtures of copolymers thereof; and b) a metal extractant. The metal extractants can be selected from the group consisting of cationic extractants, anionic extractants, neutral extractants and mixtures thereof. Another aspect of this invention provides a process for recovering metal ions from an aqueous solution containing metal ions comprising: a) impregnating a metal extractant within a highly porous, crosslinked body derived from a soluble hydrogel polymer in water, the porous body is characterized by having a three-dimensional reticular structure of open cells, a density of less than about 1 gram per cubic centimeter, a surface area equal to or greater than about 300 square meters per gram, an equal compressive strength ao less than a yield of about 10 percent at 21.09 kilograms per square centimeter and an average pore diameter of less than about 500 angstrom units, wherein the hydrogel polymer is selected from the group consisting of alginates, gums, starch, dextrins , agar, gelatin, casein, collagen, polyvinyl alcohol, polyethyleneimine, acrylate polymers, starch / acrylate copolymers and mixtures and copolymers thereof to form a porous body impregnated with a metal extractant. b) contacting the aqueous solution with the porous body impregnated with a metal extractant to remove the metal ion from the aqueous solution; and c) separating the metal ions from the impregnated porous body with a metal extractant. The porous body used both in the composition and in the process of the present invention exhibits numerous beneficial properties, including rigidity, very large pore volume, high surface area, excellent strength characteristics. Therefore, when the porous body is used in combination with the metal extractant, the possibility of losing the metal extractant or the "solvent" component trapped therein during the metal extraction, and the interfacial and through contact is reduced. therefore the mass transfer, with the treatment current is maximized. In addition, the composition of this invention has excellent dimensional stability, regardless of the amount of exposure to solutions of varying pH values and salt concentrations.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood and the additional advantages will become apparent when reference is made to the following detailed description of the invention and the accompanying drawings, in which: Figure 1 is a schematic drawing illustrating a porous body used in this invention and its three-dimensional reticular structure of open cells. Figure 2 is a graph illustrating the performance of the copper penetration of the freshly impregnated ketoxime of Example 2 in terms of concentration of copper effluent (C / Co), the ratio of the concentration observed to the feed concentration (1 gram per liter) versus column fraction volumes. Figure 3 is a graph illustrating the debugging operation of the impregnated resin of the Example 3 in terms of the copper level (grams-copper / liter of acid) versus the volumes of the fraction of the column. Figure 4 is a graph illustrating the results of the longevity study of the impregnated resin described in Example 4 in terms of copper capacity of the resin versus cycles (hundreds) of the simulated recovery operation. Figure 5 is a graph illustrating the characteristics of the pressure drop of the impregnated resin of Example 5 in terms of the inlet pressure (kilograms per square centimeter) versus the flow rate of the water treatment (gpm / 9.29 square centimeters) ).

DETAILED DESCRIPTION OF THE INVENTION As mentioned above, the present invention provides a composition comprising highly porous high strength crosslinked bodies derived from hydrogel polymers and a metal extractive compound. Hydrogel polymers are water-soluble polymeric materials that absorb water to form free-flowing gel-like substances, pregels. See related copending US Patent Application Serial Number 08 / 148,110 filed November 4, 1993, which is a continuation in part of the copending application Serial Number 27,975 filed March 8, 1993 which is a continuation in part of the application Serial Number 811,757 filed on December 20, 1991 (now abandoned), all of which are incorporated by reference herein. The pregels are solidified or coagulated to form porous gels that are self-supporting and then crosslinked with an appropriate crosslinking agent to form the high strength porous bodies used in the present invention. Porous hydrogel bodies have a three-dimensional reticular cell structure of open cells, for example, as illustrated in Figure 1. The term "reticular" as used herein refers to an open structure of the cross-linked polymer. Figure 1 illustrates a section of the three-dimensional reticular cell structure of a porous body of this invention. The porous body 10 has pores 11 that form a continuous network of pores. The porous hydrogel bodies of the present invention have a low density of less than about 1.0 gram per cubic centimeter, preferably, less than or equal to about 0.5 gram per cubic centimeter, more preferably less than or equal to about 0.3 gram per cubic centimeter. cubic centimeter, and especially preferably, less than or equal to 0.2 gram per cubic centimeter. In other preferred embodiments, the density is equal to or less than 0.15 gram per cubic centimeter and especially preferably less than about 0.1 gram per cubic centimeter or less than about 0.05 gram per cubic centimeter. However, preferably, the bodies have a minimum density that is at least sufficient to maintain the three-dimensional network structure of the body. In many preferred embodiments of the invention, the bodies have a density of at least 0.01 gram per cubic centimeter, and preferably at least 0.02 gram per cubic centimeter. The porous bodies of this invention also have excellent surface area characteristics, which present a considerable factor in the usefulness of the porous bodies and articles formed thereof. For example, its elevated exposed surface area, greater than that of the other available materials, can be obtained for fixation or absorption of active agents and the like. An increase in the surface area per unit weight of a material often minimizes the amount of material needed to perform a desired function. For example, the ability of a given amount of a material to function as an absorbent can be seen as a function of the amount of absorption per unit weight of the material. The greater the surface area per unit weight, the better the material will function as an absorbent.

The three-dimensional lattice bodies of porous open cells present have a surface area of at least about 30 square meters per gram. Preferably at least about 50 square meters per gram and especially preferably at least about 100 square meters per gram. In particularly preferred embodiments, the surface area is at least about 150 square meters per gram, more preferably at least about 200 square meters per gram and particularly preferably at least about 300 square meters per gram. The open cell nature of the porous bodies of this invention can also be partially car- ried out by the pore volume and the pore diameter. The porous bodies present have a pore volume of at least about 1 cubic centimeter per gram, preferably, at least about 1.5 cubic centimeters per gram and more preferably, at least about 2.0 cubic centimeters per gram. In the particularly preferred embodiments, the pore volume is at least about 2.5 cubic centimeters per gram, more preferably at least about 3.0 cubic centimeters per gram and especially preferably at least about 4.0 cubic centimeters per gram . The pore diameter can vary considerably to achieve a given pore volume. In general, the open cell lattice structure of the porous bodies has an average pore diameter of at least about 50 angstrom units (A). In preferred embodiments, the average pore diameter is at least about 100 angstrom units and more preferably at least about 200 angstrom units. In particularly preferred embodiments, the average pore diameter is at least about 250 angstrom units, preferably at least about 300 angstrom units, and especially preferably at least about 350 angstrom units. In alternately preferred embodiments, the average pore diameter ranges from about 50 angstrom units to about 500 angstrom units. In the alternative embodiments of the invention, the average pore diameter of the porous bodies can be varied to accommodate specific applications or different sieve materials. A method for controlling the average pore diameter of the present porous bodies involves changing their density as will be discussed further below. It is important to note that with a density that decreases from porous bodies, their average pore diameter tends to increase. Alternatively, the pore diameter can be controlled using a "phantom" mold or a printing technique. The "phantom mold" or printing technique involves adding to the gel a material (before, during or after gelation) which can then be removed from the gelled material. The phantom material leaves gaps when it is removed. It can be removed by conventional techniques known in the art, such as dissolution or chemical etching. In spite of their relatively low density, the bodies and articles formed thereof possess characteristics of beneficial resistance. The cross-linked three-dimensional reticular cell structure is believed to provide a large amount of strength. The porous bodies have a compressive strength such that the body does not separate or crush when subjected to pressure. The porous bodies of this invention have a relatively low limit. The compression limit corresponds to the stress-strain curve for a given amount of pressure applied to a material of known dimensions. This curve reflects the amount of compression that results from the applied pressure.

See Sibyl, A Guide to Materials Characterization and Chemical Analysis, 273-275 (1988). The porous bodies of the present invention have a compressive strength equal to or less than the limit of 75 percent at 21.09 kilograms per square centimeter, preferably equal to or less than 50 percent limit at 21.09 kilograms per square centimeter, greater preference equal to or less than the limit of 25 percent to 21.09 kilograms per square centimeter and especially preferred equal to or less than about 10 percent limit to 21.09 kilograms per square centimeter. In alternative embodiments, the compressive strength is equal to or less than about 10 percent of the limit at 70.30 kilograms per square centimeter. The polymers suitable for the invention present are natural and synthetic polymers containing a hydroxyl group and other synthetic polymers that form hydrogels when they are solubilized in water or other aqueous solvents, such as aqueous solutions of acid or base and mixtures of water and solvents. organic Polymers containing the appropriate hydroxyl group include natural polymers, such as polysaccharides, e.g., alginates, gums, carrageenin, starch, dextrins, chitosan and agar, proteins, v.gr, gelatins, casein and collagen; synthetic polymers, e.g., polyvinyl alcohols, vinyl alcohol copolymers, starch / acrylate copolymers; and mixtures and copolymers thereof. Alginate is the general name given to alginic acid and its salts. The alginates are composed of D-mannosyluronic acid and residues of L-glucopyranosyluronic acid, and are harvested commercially from algae. Exemplary suitable alginates are the alkali metal salts of alginic acid, and most preferably sodium alginate. The gums are polysaccharides extracted from plants and are illustrative of the appropriate gums, guar gum and locust bean gum. Carrageenan is a colloid extracted from carrageenin and dextrins are polymers of D-glucose. Illustrative of the appropriate vinyl alcohol polymers are saponified polyvinyl acetate, preferably having at least about 70 mole percent of the hydrolyzed acetate group to be readily soluble in water, and appropriate vinyl alcohol copolymers including copolymers of vinyl alcohol / ethyleneimine and vinyl alcohol / acrylate copolymers. Other synthetic hydrogel polymers suitable for the present invention include acrylate polymers, polyalkylene amides, polyalkenimides, polyacrylamides, and mixtures and copolymers thereof. Illustrative of the appropriate acrylate polymers are the monovalent polymers eg, Na +, K +, Li +, Cs + or divalent, e.g., Mg + 2, Ca + 2, Sr + 2, Ba + 2, Cu + 2 , Cs + 2, Pb + 2, Zn + 2, Fe + 2, Ni + 2, the metal salts of the polymers derived from acrylic acid, methacrylic acid, methyl methacrylic acid, ethyl methacrylic acid; and polymers derived from hydroxyethyl methacrylate, hydroxyethoxyethyl methacrylate, methoxyethyl methacrylate, methoxyethoxyethyl methacrylate, propylene aminoethyl methacrylate and glycol methacrylate. Suitable polyalkyleneimides include polyethylene imide and the like. Alginic acid is the hydrogel polymer that is preferably used in the present invention. The starting concentration of the hydrogel polymer directly affects the density of the porous bodies. As the concentration of the polymer in the solution increases, the density of the porous body increases. An effective amount of a gel-forming polymer is added. An "effective amount" is within the range of polymer concentrations between the minimum concentration that is high enough to form a gel and the maximum concentration that is low enough to be completely soluble in the gelling solvent. The effective amount of each polymer will vary with the selected density of the porous body. As usual, the proper concentration of the polymer for the present invention is between about 0.02 percent to about 15 percent, preferably between about 0.5 percent to about 12 percent and especially preferably between about 1 percent to about 10 percent . In order to solidify or coagulate the polymer solution, which will also sometimes be referred to as "pregel", it may be necessary to use a gelling agent. Some gel forming polymers do not require a gelling agent as discussed further below. In general, the polymer solution is exposed to an aqueous solution and an effective amount of the gelling agent. The effective amount as used in this respect is the amount of the gelling agent that is sufficient to solidify or coagulate the polymer solution such that its shape or configuration is maintained. The subclasses and appropriate amounts of the gelling agent will depend on the polymer. The gelling agents are well known in the art and each gel can be prepared by conventional techniques known in the art.

The gelation of the polymer solution is carried out over time. The amount of time required depends on the diffusion rate of the gelling agent. The viscosity of the gel, which depends on the concentration of the polymer, usually regulates the time interval necessary for the movement of the gelling agent through the gel. The higher the concentration of the polymer, the longer the diffusion time required will be. The gelation may also involve a molecular rearrangement of the polymer. To some degree, the re-accommodation will occur simultaneously with the diffusion of the gelling agent through the gel, but may also continue after the complete diffusion of the gelling agent. It is believed that without diffusion of the gelling agent through the gel, shrinkage or crushing of the gel may occur during the downstream process steps to form the porous bodies. With the initiation of shrinkage, the density may increase (as the surface area decreases) to a point above the desired level. The selection of the gelling agent depends on the polymer used. The gelling agent can be any agent that is reactive with the polymer to solidify or coagulate the pregel. For alginate, an inorganic material or an organic cationic material is used to ionically bind the carboxylic acid residues of the alginate polymer yarns. Dicathionic or polycationic materials are preferred because of their ability to ionically bind the carboxylic acid residues of two adjacent polymer strands. Sodium alginate can also be gelled using organic acids or inorganic materials, such as di- or polycationic metals. The organic acids used to gel the alginate, e.g., sodium alginate, can vary widely. Illustrative of these acids are acetic acid, propanic acid, butanoic acid, benzoic acid, oxalic acid, malonic acid, succinic acid, adipic acid, glutaric acid, maleic acid, ophthalmic acid and the derivatives thereof. Preferably, a dicathionic metal or a dicarboxylic acid is used in order to bond two polymer strands together. Suitable cationic ions include ionic forms of the following: Al, Ba, Ca, Mg, Sr, Cr, Cu, Fe, Mn and Zn. Most transition metals in the cationic form of X2 + or more can also be employed. Preferably, the cationic metal is a cationic form of Ca, Ba or Cu. For gums, gelling agents including sodium borate, inorganic acids, organic acids, such as boric acid and bases, are suitable. Other polymers such as agar, carrageenin, gelatin and casein do not require any additional gelling agent since they can be gelled by heat treatment. The pregel solution is heated to a temperature high enough to melt the polymers followed by cooling to form a gel. For example, a solution of aqueous gar will form a gel when heated to a temperature of at least 80 ° C and followed by cooling until gelation occurs. The polyvinyl alcohol and the starch / acrylate copolymers also do not require any additional agents or processes to form gels. Gels are formed when their aqueous solutions are exposed to an appropriate crosslinking solvent such as acetone. Rapid cooling is an alternative to using a gelling agent. This process can be used in addition to the treatment with the gelling agent or any other gelling technique. The rapid cooling technique involves forming a pregel or gel and dropping the pregel or gel in a solvent bath that has been cooled to a temperature at which the gelling solvent does not freeze, but which coagulates the polymer. For hydrogel materials, in general, water alone is not suitable as a gelling solvent for the rapid cooling technique, since the water will freeze and will not spread. Therefore, a water / organic solvent mixture is used. In the case of alginate, water / ethylene glycol, which has at least about 25 percent ethylene glycol or organic solvent can be used as the gelling solvent. The pregel or gel is then placed in an acetone-cooled bath, which then replaces the water / ethylene glycol solvent. The gels can be manufactured in any desired configuration. The configuration can be carried out by any conventional method known in the art. A solution of the polymer can be placed in a mold of any desired configuration and then gelled in the mold. For example, a layer of a polymer solution can be placed on a flat surface to form a sheet. A polymer solution can be squeezed through an opening to form a fiber, filament or tube or can be dropped into a gelling solvent to form granules. In this way you can obtain any desired configuration (tubes, cubes, rectangular configurations, spheres, such as beads, granules, sheets that may be in the shape of the membrane). In accordance with the present invention, the solidified or coagulated gels are further subjected to a crosslinking process to increase their physical strength and to preserve the porous structure of the gels. The gels are prepared for crosslinking by placing the initial gelling solvent, i.e. water, with a crosslinking solvent. The gelling solvent can be directly replaced with a crosslinking solvent. Alternatively, if the crosslinking solvent is not miscible in the gelation solvent, one or more intermediate solvents may be used. An appropriate intermediate solvent is miscible in both the gelation solvent and the crosslinking solvent. The crosslinking solvent must also be non-reactive with the polymer and the crosslinking agent. In general, the surface tension of the crosslinking solvent may be less than or greater than or equal to the surface tension of the gelling solvent. Preferably, the gelling solvent has a surface tension essentially equal to the gelation solvent. This would avoid the need for exchanges of the solvent through a concentration gradient as discussed infra. In the alternative embodiments, the crosslinking solvent has a surface tension that is less than that of the gelation solvent. In these embodiments, the gelling solvent may have a surface tension that is less than or greater than that of the intermediate solvent. In more preferred embodiments, the crosslinking solvent has a surface tension that is less than about 25 dynes per centimeter. In further preferred embodiments, the crosslinking agent has a surface tension equal to or less than about 50 dynes per centimeter. In particularly preferred embodiments, the crosslinking solvent has a surface tension equal to or less than about 40 dynes per centimeter. In more particularly preferred embodiments, the crosslinking solvent has a surface tension equal to or less than about 30 dynes per centimeter. Illustrative of the crosslinking solvents useful for the present invention are acetone, chloroform, dimethylsulfoxide, toluene, pyridine and xylene. In many preferred embodiments, the crosslinking solvent is an aprotic organic solvent. In general, the gelling solvent must be removed essentially if not completely from the gel before crosslinking, if the selected crosslinking agent is reactive with the gelling solvent, since the reaction between the gelling solvent and the crosslinking agent tends to decrease the crosslinking. For example, the water was a hydrogel polymer that will react with a crosslinking agent such as toluene diisocyanate (TDI). The replenishment of the gelling solvent by a crosslinking solvent is generally referred to herein as a solvent exchange step. The effective exchange towards the crosslinking solvent from the initial gelling solvent may comprise one or more exchanges of the gelation solvent with a solvent or intermediate solvents before the replacement of the intermediate solvent with the crosslinking solvent. Preferably, the solvent exchange process comprises replacing the initial gelling solvent with an intermediate low surface tension solvent, e.g., acetone. The intermediate solvent is selected such that it is miscible both in the gelling solvent and in the subsequent intermediate solvent or crosslinking solvent. Preferably, the intermediate solvent has a surface tension that is less than that of the gelling solvent. In more preferred modes, the intermediate solvent has a surface tension of less than about 75 dynes per centimeter. In additional preferred embodiments, the intermediate solvent has a surface tension equal to or less than about 50 dynes per centimeter. In particularly preferred embodiments, the intermediate solvent has a surface tension equal to or less than about 40 dynes per centimeter. In more particularly preferred embodiments, the intermediate solvent has a surface tension that is equal to or less than about 30 dynes per centimeter. It will be noted that if the crosslinking solvent has a surface tension greater than that of the gelling solvent and an intermediate solvent is used. Then the intermediate solvent preferably has a surface tension that is less than the surface tension of the crosslinking solvent and higher than the surface tension of the gelation solvent. If more than one intermediate solvent is used, then the intermediate solvent needs only to be miscible with the solvents used previously and subsequently. For example, the water can first be exchanged with acetone, which is miscible both in water and in the subsequent crosslinking solvent, such as toluene. Acetone is one of the preferred intermediate solvents due to several reasons. Acetone can be easily obtained and is relatively harmless and is also soluble in water and toluene. Other suitable intermediate solvents that may be used include alcohols, e.g., methanol, ethanol, propanol and butanol, esters; e.g., methyl and ethyl acetate; ketones, e.g., methylethyl ketone and others such as dimethylsulfoxide, dimethylformamide, methylene chloride, ethylene chloride, tetrahydrofuran, dioxane and the like. As is known in the art, the pores of porous gels derived from hydrogel polymers are crushed to form dense solids having a limited porosity when the gelling solvent is removed, i.e., when dehydrated. Furthermore, it has been found that when the gelling solvent is abruptly replaced with a crosslinking solvent having a considerably different surface tension and a polar characteristic, a large portion of the pores of the gels, especially the fine pores, are crushed to form gels less porous The crushing of the pores not only significantly decreases the surface area and increases the density of the porous bodies, but also reduces their dimensional stability and physical resistance. The crushed pores prevent access of the crosslinking agent resulting in uncrosslinked portions in the gel, which are free to swell and shrink. In order to maintain the porous gel structure without causing shrinkage or crushing of the gel during the removal of the gelling solvent, care must be taken when replacing the gelling solvent with an intermediate solvent. Frequently, the use of a number of gradual solvent exchanges can be beneficial by using the same intermediate solvent at increased concentrations. This exchange of solvent is referred to herein as solvent exchange through a concentration gradient. The concentration gradient is used for the gradual decrease of the surface tension of the liquid inside the gel. An effective concentration gradient is a range of changes in the concentration of the intermediate solvent or crosslinking which prevents significant crushing of the gel structure and prevents considerable shrinkage of the gel. In general, although not necessarily, at least a solvent exchange is carried out; many of the preferred embodiments employ more than one solvent exchange. Desirably, the number of steps used and the amount of organic waste generated in each batch of exchanges should be minimized. The intermediate waste can be reused, redistilled or separated to recover the solvents. For each step of solvent exchange, a sufficient period of time must be allowed for the replacement of the solvent to reach equilibrium. The equilibrium is the point at which the concentration of the replenishing solvent within the gel is in equilibrium with the concentration of the replenishing solvent on the outer surface of the gel. Intermediate solvents are usually a mixture of the intermediate solvent and the gelling solvent until 100 percent of the intermediate solvent is exchanged. The initial concentration of the intermediate solvent (or the crosslinking solvent if an intermediate solvent is not used) may contain from about 5 percent to about 25 volume percent of the intermediate solvent and then solvent exchanges through the concentration gradient can be effected by increasing the interval of 10 percent by volume or higher. In preferred embodiments, the intermediate solvent is initially employed in a concentration ranging from about 10 percent to 25 volume percent, and the concentration is then increased in ranges of about 15 percent to about 25 volume percent. Incremental increases from about 20 percent to about 25 percent by volume are particularly preferred to minimize the number of solvent exchanges. Once the essentially complete exchange of the intermediate solvent has been carried out by the initial gelling solvent, the intermediate solvent can usually be exposed directly to 100 percent of the crosslinking agent. Even though the theory holds that for most hydrogel polymers no gradient is required for the exchange of the intermediate solvent to the crosslinking solvent, there may be a situation where a concentration gradient is used for the exchange of the intermediate solvent and a crosslinking solvent. Other techniques can be used to prepare the gel for crosslinking. These can be used in addition to or instead of the solvent exchange processes. Sometimes it may be preferable to carry out at least one solvent exchange in relation to these techniques. Illustrative of these alternative techniques are freeze drying and supercritical fluid extraction. Freeze drying is advantageous since a solvent exchange process should not be necessary. On the other hand, the extraction of supercritical fluid can also be beneficial since the water can be exchanged by the method with or without the need for exchanges of intermediate solvent. Freeze drying is a well-known process that is frequently used in the food industry. The material to be dried by freezing is first cooled to less than the freezing temperature of the solvent, followed by vacuum drying as is known in the art. The resulting freeze dried hydrogel structure is placed directly in a crosslinking solvent to crosslink. As the freeze drying process does not retain the porous gel structure well, it may be necessary to add surfactant examples, elastomeric additives or polyols to the pregel composition in order to prevent crushing of the pores during the freeze drying process . Supercritical fluid extraction involves extractions of the gelling solvent or the high pressure intermediate solvent using supercritical CO2 in the liquid phase. Supercritical CO2 is non-polar and can replace the solvent present in the gel. When the pressure is released, the CO2 evaporates from the porous material. The technique can be used in a manner analogous to that which has been described for the preparation of inorganic aerogels. After freeze drying or supercritical extraction, the dried material is exposed to a crosslinking agent which can be provided in solution or in the gas phase, to form a cross-linked porous body. The solvent for the crosslinking agent can vary widely. This solvent or gas acts as a carrier vehicle for the crosslinking agent. Obviously, the carrier vehicle must be inert to the gel material and capable of solubilizing the crosslinking agent. The supercritical fluid extraction method can be a preferred method for producing materials of very low density, that is, less than about 0.05 gram per cubic centimeter. The selection of the crosslinking agent will vary with the polymer and the amount of the crosslinking agent will vary with the amount of polymer present in the gel and the amount of crosslinking desired. The crosslinking agent can be reactive with the functional groups present in the polymer. Polymers suitable for use in the present invention have a variety of functional groups, such as -OOH, -OSO3 and -NH2 in their basic polymer structure, as well as the hydroxyl functional group. Of these groups, the hydroxyl group is preferably focused for the crosslinking process. The degree of crosslinking can be varied to suit the needs of each application. The solvent exchange process of the gradient of the present invention which prevents crushing of the gel pores can facilitate up to 100 percent crosslinking of all available functional groups present on the surface of the porous gels. The porous bodies of the present invention which are highly crosslinked exhibit high considerable stability, expansion capacity or swelling minimal chemical integrity excellent even when exposed to different solvents. Preferably, up to 75 percent of the functional groups of the hydrogel polymer are crosslinked; more preferably, up to 85 percent crosslink; and especially preferably, up to 100 percent of at least one functional group of the hydrogel polymer is crosslinked. Since, as is known in the art, the maximum molar concentration of the available functionalities can be calculated empirically for a given starting concentration of each selected polymer, the approximate amount of the crosslinking agent necessary to achieve the desired level of crosslinking It can be easily determined.

A large number of well-known chemical crosslinking agents are available for use in the crosslinking step. Illustrative of the crosslinking agents are the diamines and polyamines which crosslink the hydroxyl and / or carboxylic residues together with the basic structure of the hydrogel polymer. For the purposes of this invention, the diisocyanate compounds are preferred. The diisocyanate compounds may be aliphatic, cycloaliphatic, or aromatic. Aromatic diisocyanates, such as the 2,4-tolylene diisocyanates, 4,4-diphenylmethane diisocyanate, and 1,4-phenylene diisocyanate, are exemplary of the preferred embodiments. Other suitable agents for crosslinking the hydroxyl residue include, for example, diacid halides, such as adipic acid halide salts, glutaric acid or succinic acid, diepoxides, epichlorohydrin, aldehydes, dialdehydes, trimetaphosphates, vinyl sulfones, trimethylolmelamine, of melamine and formaldehyde, urea and formaldehyde and dihalogenated aliphatics. Specific examples of these compounds include urea of bis (hydroxymethyl) ethylene, N, N'-methylenebisacrylamide, and s-triazine of 1,3,5-trichlor and 1,3,5-triacyl. The crosslinking process is carried out over time, and the amount of time required for crosslinking depends on the diffusion of the crosslinking agent through the gel. The crosslinking process can be carried out at any temperature above the freezing temperature and below the boiling temperature of the crosslinking solvent. Preferably, the crosslinking process is carried out at an elevated temperature lower than the boiling temperature of the crosslinking solvent in order to accelerate the process. Upon completion of the crosslinking process, the crosslinking solvent is removed from the gel bodies by a variety of conventional techniques, such as draining the liquid from the solid crosslinked product. Vacuum evaporation is another appropriate technique. Suitably, the solid crosslinked material is then dried under reduced pressure at a temperature of at least 20 ° C to evaporate volatile solvents or crosslinking agents that have remained from the crosslinked gel bodies. The porous bodies present exhibit numerous beneficial properties including low density and large surface area as well as high pore volume and excellent resistance characteristics. In addition, the porous bodies have excellent dimensional stability even after dehydration and rehydration, especially at high levels of crosslinking at these levels which are not possible to achieve using the solvent exchange processes of the prior art. The numerous beneficial properties of the bodies provide a material with many uses, such as active agent support materials. A major advantage of the porous bodies used in this invention and the articles formed thereof is the diversity of chemical modification that can be carried out in the gel former prior to, during or after isolating the cross-linked porous body from open cells. The aforementioned functional groups present in the polymers suitable for use in the present invention can be chemically modified using conventional methods. The number of functional groups available for chemical modification depends on the number of functional groups that have been involved in the cross-linking. With less crosslinking, more functional groups will be available for chemical modification. Alginic acid contains a considerable number of carboxyl groups, for example, which are easily derived by numerous reagents. Even if they are crosslinked in these materials using specific hydroxyl reagents such as diisocyanates, a sufficient amount of free hydroxyls from the process can survive intact and must be accessible for further reaction.

The porous body of the present invention is impregnated with metal extractants selective for the metal of specific interest. Examples of these metal extractants include cationic extractants, anionic extractants, neutral extractants and mixtures thereof. The active metal extractants suitable for use in this invention are liquid complexing agents which are preferably homogeneously dispersed in the carrier medium present and exhibit a strong affinity to the carrier, i.e., the agent may be capable of forming a resistant or complexes with functional groups, such as hydroxyl groups, present through the carrier surface. Alternatively, the hydrophobic interaction of the organic metal extractant with the body of the crosslinked carrier is sufficient to fix the metal extractant within the present carrier body, especially when the capillary forces of the pores within the body of the crosslinked carrier are taken into account. Suitable extractants for use in the composition and process of the present invention may have cationic, anionic or neutral charges. See C. K. Gupta, and others Hydrometallurgy in Extraction Processes, 74-92 (1990)] "Gupta"]. More specifically, a number of suitable acidic extractants having cationic charges are also characterized by their ability to chelate the metal ion, for example oxines, diketones, oximes including those described in U.S. Patent Nos. 4,544,532 and 4,507,268, both of which are incorporated herein by reference, and the like and mixtures thereof, each of which contains chemical functionalities, both acidic and basic. When these acidic extractants are contacted with white metals in solution in accordance with the process of the present invention, the extractants and the metal interaction to form chelated salts. This interaction demonstrates the selectivity and remarkable affinity for metals possessed by these extractants. For example, hydroxyoxime extractants, such as those obtained from AlliedSignal Inc., of Morristonwn, New Jersey, under the "MOC" factory name, exhibit a pH-dependent ability to selectively recover copper in the presence of ion. ferric. Ketoximes are preferably used to form chelated salts in weak acid solutions, whereas aldoximes are especially preferred when strong acid solutions are used. Other cationic extractants suitable for use in the present invention include non-chelating extractants such as carboxylic, phosphoric and alkyl phosphonic acid, wherein the alkyl group contains between about 1 and about 12, preferably between about 4 and 8 carbon atoms . The interaction between the extractants of the non-chelating group and the target metals is more complicated than that which occurs with the extractants of the chelation group but is generally based on the charge ratios. Metal ions such as white metals are extracted in the order of their basicity, with improvements in their extraction capacity that are evident as the metal becomes more basic. Another suitable class of metal extractants includes the anionic extractants, such as the tertiary and quaternary amine agents which are selected from the group consisting of methyltraprylammonium chloride, methyltrioctylammonium chloride, 1-octanemonium, N-methyl-N, N-chloride. - dioctyl, tricaprylmethylammonium chloride, tricaprylmethylammonium chloride, and trioctylmethylammonium chloride. These anionic extractants can be obtained from Henkel Corp., of Minneapolis, Minnesota, under the factory names "Aliquat" or "Alamine". Neutral extractants, including several solvating agents that function by coordination with the metal in solution while simultaneously displacing the water molecules associated with that metal, are also suitable. This interaction results in the formation of a neutral complex that is sequestered within the hydrophobic environment that is provided by the neutral solvent impregnated with the body of the porous carrier of the present invention. Examples of neutral extractants include tributyl phosphate (TBP), methyl iso-butyl ketone (MIK), mixtures thereof, and the like. A summary of the different kinds of metal extractants including typical manufacturers and uses, ie, the type of metal that can be extracted from a specific solution using a particular extractant, is given in Tables 1 to 3. See also Gupta in 78-82. TABLE 1: CATIONICQS EXTRACTANTS TYPE TYPE OF MFR TYPICAL USE FACTORY NO-QUELACION Carboxylic Acid Naphthenic Acid Shell Chemical Cu Ni Solution Carboxylic Acid Versatile Acid Shell Chemical Cu Ni Solution Phosphoric Acid DEHPA Mobil Chemicals U Solution ("PSA") PSA; Ni solution co PSA HOSTAREX Hoechst A.G. Zn of solution; PA-216 antimony, and other metals of Group IIIB ("Rare Earth") solution Acid PC-88A Daihachi Ni solution of Phosphonic Chemical Co; ("PSNA") Rare Earths solution : "PSNA") CYANEX CNX Cytec Industries Co of CYANEX 272 Ni solution CHELATION Kelex 100 Sherex Chemicals Cu of MOC 45 oxime solution Allied Signal Cu of Extraction Inc. of solutions; Cu or Ni or Co of Ammoniacal Solution oxime LIX 64 Henkel Corp. Extraction of Cu solutions; Cu or Ni or Co of Ammoniacal Solution Oxime LIX 63 Henkel Corp. Extraction of Cu solution oxime Series P-5000 Acorga Ltd. Extraction of Cu solution ß-diketone Hostarex DK-16 Hoechst, A.G. Extraction of Cu or Zn from Ammoniacal Solution ß-diketone LIX 51 Henkel Corp. Cu or Co solution ß-diketone LIX 54 Henkel Corp. Cu or Co of solution TABLE 2: ANIONIC EXTRACTANTS TYPE NAME OF MFR TYPICAL USE FACTORY Primary Amine Primene JN-T Rohm & Haas Fe of Sulphate Solution Amina LA-1 and LA-2 Rohm & Haas U of Secondary solution: Sulfate n-lauryl alkyl-Co of Methylamine Solution Chloride Amina Adogen 283 Sherex chemicals U of Secondary Solution: Sulfate; Co-di-tridecylamine Chloride Solution Amina Alamine 336 Henkel Corp. U or V or Mo or W Tertiary: tricaprylamine Sulfate solution Amina Hostarex- A 327 Hoechst A.G. Co or CU Tertiary: Chloride Solution Amina Adopts 364 Sherex Chemicals platinum, Tertiary palladium: and such tri- ("PGM metals") isooctylamine solution.

Amina Aliquat 336 Henkel Corp. V or Cr or Cu Quaternary: of solution Methyl-prilyl ammonium aqueous chloride Amina Adogen 464 Sheres Chemicals Rare Earths Quaternary: methyltricapril-ylammonium chloride solution Amina Hoe S 2706 Hoechst, A.G. Cr203, V05, and Quaternary: other metals (R3N + CH3) C1 ~ in oxyanionics where R is a solution. alkyl having from about 8 to about 10 carbon atoms TABLE 3. NEUTRAL EXTRACTANTS TYPE NAME OF MFR TYPICAL USE FACTORY Acid Ester TBP Union Carbide Fe Phosphoric Solution Cl Albright & U of solution; Wilson Daihachi Rare Earths Solution.

TOPO American oxide Uv extraction ^ Phosphine Cyanamid from Albright & H3P04 with DEHP ilson MIBK Ketone N / A Hf solution of Methyl-Zr isobutyl Au of Cl solution.

Alkyl- Di-n-hexyl- N / A Pd of solutions Sulphides of Cl sulfides As used herein, "Oxyanionic metals" refers to oxygen-containing metal ions containing negatively charged complexes, such as chromic oxide, chromium trioxide (VI), arsenic oxide (III), vanadium oxide (V), uranyl sulfate, uranyl nitrate and the like. Any of the methods of impregnating the active agent known in the art as being suitable for loading the chromatographic resins can be employed to impregnate the carrier of the present invention. Illustrative methods include the dry impregnation method and the wet impregnation method. In the dry impregnation method, a dilute active agent is contacted with the carrier, and then the diluent is slowly evaporated. This method is described, for example, in Warshawsky I., which is incorporated herein by reference. In the wet impregnation method, an active agent, which is diluted in a precalculated amount of the diluent, is contacted with the polymer carrier until the liquid phase is absorbed by the carrier. This method is described, for example, as described, for example, in Warshawsky II, which is incorporated herein by reference. In the preferred embodiment, the first porous carrier is completely degassed using an organic solvent of low surface energy, such as acetone or hexane. Preferably, the carrier of the porous body is exposed to a volumetric excess, i.e., from about 10 percent to about 150 percent and preferably from about 25 percent to about 50 percent of the selective metal extractant that can be dissolve in an appropriate diluent such as kerosene, at concentrations ranging from 10 percent to 99.99 percent, preferably from 45 percent to 55 percent, based on the total weight of the diluent and the extractant. The modifiers can optionally be added to the solvent in order to prevent the formation of the third phase and improve the solubility of the metal complex. Examples of these modifiers include long chain alkyl alcohols such as octanol or isodecanol, or other extractants that belong to the neutral category such as tributyl phosphate (TBP). Other suitable modifiers include nonylphenol, 2-ethylhexanol and the like. The excess liquid is then removed from the impregnated resin by conventional filtration methods well known in the art. A person skilled in the art can readily determine without undue experimentation that the resin impregnated with solvent should be dried for a sufficient period of time to achieve the desired predetermined solvent content of the resin. Small amounts of bulk liquid, i.e., less than about 4 liters (1 gallon) remaining in a fully impregnated porous material can empty the slurry of wet impregnated resin into a funnel of coarse porosity contained in an empty flask. lateral arm fixed to the vacuum medium that generates a pressure of approximately 64 KPa to approximately 78 KPa. Excessive bulk fluid is then allowed to be drawn into the flask by applying vacuum. The partially dried impregnated porous carrier can then be dried by placing the partially dried material in a vacuum oven and heating to a temperature of from about 30 ° C to about 100 ° C under pressure of about 64 Kpa to about 78 KPa for a sufficient period of time to achieve the desired degree of dryness. In a preferred embodiment, the porous carrier is dried to an extractant content of from about 10 percent to about 15 percent based on the total weight of the impregnated body. The content of the extractant can then be determined using well-known physical techniques such as thermogravimetric analysis.

At larger scales, a container such as a filter drier can be used to contact the extractant with the porous carrier in order to extract the excess extractant from the carrier and dry the impregnated carrier. Periodic purging of the filter drier with a dry gas such as an inert gas i.e., nitrogen, helium or argon, is preferred during the drying process. The resulting impregnated matrix is suitable for packaging in a contactor having the appropriate desired format such as a fixed bed, a moveable bed or an intermittent contactor, under conventional methods known in the art. These methods are described, for example, in Perry1 s Chemical Engineers' Handbook, 19-40 to 19-48 (New York, Fifth Edition, 1973). A fixed bed format is preferred in the present invention. In the process of the present invention, an aqueous stream containing different metal salts is passed over the contactor in order to selectively remove a specific metal from the aqueous stream, and in this way concentrate the metal within the impregnated porous matrix with the selective metal extractant. The aqueous stream can be fed, preferably without filtration or pretreatment and at room temperature, through the contactor either in an ascending or descending flow direction. Optionally, a jacketed column may be employed to allow thermostating at the optimum temperature desired for a specific application. Examples of metal salts that can be removed from an aqueous stream include copper, cobalt, chromium (III and VI), cadmium, nickel, zinc, platinum, palladium, gold, radium, vanadium, lead, zirconium, hafnium, tin, tantalum and other elements of transition. Other metal species that can be removed from the aqueous stream include rare earth elements. The extractant that is impregnated with the porous matrix defines the selectivity and affinity of the resin. The non-metallic components and the metals for the ocuals the metal extractant contained within the porous matrix has no affinity, they pass unimpeded through the contactor towards the waste. The metals that were sequestered within the selective metal extractant impregnated within the porous matrix can be recovered by passing an appropriate solution, i.e., a purification solution, above the contactor. The nature of this depuration solution depends entirely on the type of metal extractant impregnated within the porous matrix and on the characteristics of the coordinating-metal complex complex that is formed between the metal and the selective extractant. A person skilled in the art can easily determine which depuration solution should be used. For example, copper ions that have been sequestered by the ketoxime metal extractant impregnated into the porous matrix can be purified or displaced from the extractant by the use of aqueous sulfuric acid at a molar concentration of about 1.0 to about 2.0. , preferably from about 1.5 to about 1.75. The concentration of dilute sulfuric acid does not need to be pure and can therefore contain up to about 25 grams per liter of copper or other metals. Preferably, the sulfuric acid is diluted with water to about 100 grams per liter or up to about 200 grams per liter. Other suitable purifying agents for acidic extractants can be selected from the group of inorganic acids including hydrochloric acid, phosphoric acid, perchloric acid and mixtures thereof. Dilute sulfuric acid is the preferred purification solution for matrices impregnated with oxime extractants. The family of tertiary and quaternary amine metal extractants can also be purified using a broad range of generally basic salt solutions including ammonia, sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium chloride, ammonium nitrate, and mixtures of the above plus sodium chloride. The metal extractant impregnated within the porous matrix can usually be purified from it by modifications of the procedures known in the art. A person skilled in the art can easily bring to the optimum the process parameters, such as reagent concentrations, inclusion of cleaning and washing steps, additives, temperatures and flow rates to purify the desired amount of metal extractant from the matrix. The metal can be recovered from the metal-rich purification solution by current commercial methods of metal recovery. For example, well known methods are described in Gupta, Chapter 3. For example, copper can be recovered as copper metal (CuO) by the electroextraction process, a widely used technique that is well known in the literature and industrial practice Another common method for recovering the copper from the metal-rich sulfuric acid stripping solution is by allowing the highly concentrated copper sulfate in the stripping solution to crystallize, and then recovering the metal as crystalline copper sulfate.

The present composition and process can be useful in various applications where it is desirable to selectively recover or remove metals from an aqueous stream. Examples of these applications include, but are not limited to, the metal finishing industry, wastewater carrying metal from industrial processes, hydrometallurgy, and environmental remedy of groundwater and bodies of water. The composition and process of this invention overcome the various problems encountered in the metal recovery processes of the prior art. For example, a difficulty encountered by the prior art support means is that the support means have a low chemical affinity for the agents. Therefore, the agents are easily leached from the support medium during normal use. Because the composition of the present invention employs a support medium which has negligible mechanical strength and shrinkage and expansion and swelling, as well as an appropriate surface chemistry, the support means is capable of retaining the active agents over a period of time. longer time than the prior art support means. Therefore, when the present composition is incorporated in the process of this invention to remove metals from the mixed aqueous streams, not only can the metal removal efficiency in the composition be increased with respect to the prior art methods but also the process claimed advantageously will be operated on a continuous basis for a longer period of time without replacing the impregnated matrix. The following examples are only illustrative of the present invention and should not be considered as limiting in any way.

EXAMPLE 1: PREPARING THE IMPREGNATED SUPPORT A dried cross-linked alginate resin (ground to about 0.42 millimeter to about 0.26 millimeter (40 to 60 mesh)) having a density of 0.152 gram per cubic centimeter was exposed to a volumetric excess of MOC ™ -45, a copper extractant of selective ketoxime obtainable from AlliedSignal Inc., of Morristown, New Jersey. The mixture was then completely degassed at a temperature of about 60 ° C and a vacuum pressure of about 71 to 84 KPa (for about 16 hours.) The resulting impregnated resin was then dried to a predetermined solvent content of about 20 per cent. 30 percent based on the total weight of the impregnated resin by exposure to a constant air flow at ambient temperature and pressure in a vitrified funnel for about 2 to about 16 hours.The dry resin that flows freely then was packed into columns of multi-dimensional glass The final volumetric density of the impregnated resin was about 0.592 gram per cubic centimeter The amount of the ketoxime extractant in the impregnated resin was calculated as being about 74 percent based on the volume of the impregnated resin it was not measurably different from that of algin's starting material reticulated tie.

EXAMPLE 2: IMPREGNATION ANALYSIS The copper impregnation analysis was carried out by passing a solution of 1 gram per liter of copper sulphate through a jacketed glass column (2.5 centimeters x 30 centimeters) packed with from about 140 to about 145 milliliters of resin impregnated, which was prepared as described in Example 1. The column, which was equilibrated at 32 ° C, was packed with 0.42 millimeter to 0.26 millimeter (40 to 60 mesh) resin and the penetration of the solution flow rate of copper sulfate was approximately 5.7 bed volumes per hour. The effluent thereof was collected in volume fractions of the bed. As used herein, the term "bed volume fractions" means a fraction size equal to a bed volume. Both colorimetric and atomic absorption spectroscopy analyzes were used to determine the copper content of each fraction as described in the R.H. Muller and others, 28 Mikrochemie see. Mikrochim.Acta 209 (1940) and Slavin, W., "Atomic Absorption Spectroscopy", 25 Chemical Analysis 102-104 (1968), respectively. The results of the copper penetration analysis are shown in Figure 2. As seen in Figure 2, the good chromatographic performance of the impregnated matrix is illustrated by the rapid rise in copper concentration in the fractions of 33 to 42. The copper capacity of the resin was found to be about 41.4 grams of Cu per liter of resin or about 8 weight percent, which corresponds almost exactly to the theoretical capacity based on the amount of ketoxime immobilized in the packing material of the column. The utilization of the capacity or the percentage of total capacity that is achieved before the rejection of the significant copper by the resin is approximately 81 percent which implicitly corresponds to a good mass transfer operation.

EXAMPLE 3: DEPURATION ANALYSIS The operation of the copper solution was determined by purifying the copper from a fully charged column as described above in Example 2 using approximately 4 bed volumes of 1.75 M sulfuric acid at 57 ° C and a flow rate of approximately 5 bed volumes per hour. The fractions of the acid effluent were collected and analyzed for copper content using the methods described in Example 2 above. The results of the purification operation achieved with the resin impregnated with ketoxime are shown in Table 3. It can be seen from Figure 3 that more than 90 percent of the copper bound to the resin can be recovered in less than one column volume of effluent from acid. In addition, the maximum copper concentration observed reached 53 grams per liter and the concentration of copper in fractions 2 to 5 collected was greater than 35 grams per liter. This operation exceeds the requirements for final copper recovery by electroextraction.

EXAMPLE 4: STUDY OF LONGEVITY OF THE RESIN The expected duration of the impregnated resin was calculated by subjecting the resin material to many hundreds of simulated operating cycles. As used herein, the term "cycle" means exposing the impregnated matrix to a solution containing copper followed by exposure to an acid solution at a flow rate of 8.5 bed volumes per hour. The total duration of each complete loading and debugging cycle was 15 minutes. A 1 cm by 10 cm glass column with a jacket containing approximately 8 milliliters of a hydrophobic polymer support composed of a basic structure of polysaccharide highly crosslinked with toluene diisocyanate and impregnated with the extractant of Example 1 was exposed to: 1) five hundred cycles of water and sulfuric acid; 2) five hundred cycles of 1 gram per liter of copper sulfate and 1 M of sulfuric acid; and 3) seven hundred cycles of the acidic leaching solution (2.4 grams per liter of copper sulfate, 4.5 grams per liter of ferric sulfate with a pH of 2.1) and poor electrolyte copper sulfate (25 grams per liter in 1.75 M of acid). sulfuric). The copper capacity of the resin was checked at intervals of one hundred cycles in order to monitor the performance of the resin. An integrated Cole-Parmer computer-controlled pump system with solenoid-operated valves was used to synchronize the cycles and for flow generation. The results of the resin longevity study are shown in Figure 4. It can be seen from Figure 4 that there is no consistent loss of copper capacity that would have occurred after 1700 complete loading and debugging cycles. The total service duration of this column was more than five months. It is believed that a large amount of the observed longevity of the impregnated resin system can be attributed to the nature of the interaction between the organic metal extractant and the hydrophobic cross-linked polymer support. The ketoxime extractant is also highly hydrophobic in nature, as such demonstrates a great affinity for the polymeric support in relation to the aqueous feed solution. As a result of the hydrophobic interaction between the metal extrudate and the polymeric support, an extremely small amount of the extractant was lost to the effluent of the column. The initial solubility losses were of the order of about 1 part per million, based on the total organic carbon analysis. After equilibration, the organic loss towards the effluent was found to be lower than the detectable limits («0.5 ppm).

EXAMPLE 5: CHARACTERISTICS OF THE PRESSURE FALL A column (2.5 centimeters by 100 centimeters) packed with 0.42 millimeter to about 0.26 millimeter of impregnated resin as described in Example 1, was equipped with pressure calibrators at both the inlet and the outlet to determine the back pressure generated at the different flow regimes. The total depth of the packed bed of the column was approximately 1 meter. The water was pumped in the downflow direction at flow rates of approximately 0.118 to 0.365 meter per second. The characteristics of the pressure drop of the impregnated resin are shown in Figure 5. It can be seen in Figure 5 that a back pressure of only about .211 kilogram per square centimeter was observed in the column at nominal flow rates of 15 volumes of the bed per hour. Therefore, it is not anticipated that an excess of back pressure is a limiting factor in the design of commercial columns on a large scale. It will be seen that in the composition of this invention it provides for the effective removal of metal ions from aqueous solutions containing metal ions. It will be further seen that the process of this invention can be operated on a continuous basis for a considerable period of time without replacing the porous body, without losing a significant amount of trapped extractant within the porous body and without sacrificing the mass transfer capabilities of the composition used in it.

Claims (11)

R E I V I N D I C A C I O N E S:

1. A composition comprising: a) a highly crosslinked porous body derived from a water-soluble hydrogel polymer, the porous body being characterized as having a three-dimensional open cell lattice structure, a density of less than about 10 grams per cubic centimeter, surface area equal to or greater than about 30 square meters per gram, a compressive strength equal to or less than a limit of about 10 percent to 21.09 kilograms per square centimeter and an average pore diameter of less than about 500 angstrom units, wherein the hydrogel polymer is selected from the group consisting of alginates, gums, starch, dextrins, agar, gelatin, casein, collagen, polyvinyl alcohol, polyethylene imine, acrylate polymers, starch / acrylate copolymers and mixtures and copolymers of the same; and b) a metal extractant.

The composition according to claim 1, wherein the metal extractant is selected from the group consisting of cationic extractants, anionic extractants, neutral extractants and mixtures thereof.

3. The composition according to claim 2, wherein the cationic extractants are selected from the group consisting of diketones, oximes, oxines and mixtures thereof. .

The composition according to claim 3, wherein the oximes are selected from the group consisting of ketoximes, aldooximes and mixtures thereof.

The composition according to claim 2, wherein the cationic extractants are selected from the group consisting of alkylcarboxylic acid, phosphoric acid, phosphonic acid, sulfuric acid and mixtures thereof.

6. The composition according to claim 2, wherein the anionic extractants are selected from the group consisting of primary amines, secondary amines, tertiary amines and quaternary amines.

The conformational composition according to claim 6, wherein the anionic extractants are selected from the group consisting of methyltriphenyl ammonium chloride, methyltrioctylammonium chloride, 1-octanaminium, N-methyl-N, N-dioctyl chloride, tricaprylmethylammonium chloride , tricaprylmethylammonium chloride, trioctylmethylammonium chloride, n-laurylalkyl-methylamine, di-tridecylamine, tri-isooctylamine and mixtures thereof.

The composition according to claim 2, wherein the neutral extractants are selected from the group consisting of tributyl phosphate, phosphoric acid ester, phosphine oxide, methyl isobutyl ketone, alkyl sulfides and mixtures thereof.

9. A process for the recovery of metal ions from an aqueous solution containing metal ions comprising: a) impregnating a metal extractant into a highly porous cross-linked body derived from a water-soluble hydrogel polymer, the porous body is characterized in that it has a three-dimensional lattice structure of open cells, a density of less than about 1 gram per cubic centimeter, a surface area equal to or greater than about 30 square meters per gram, a compressive strength equal to or less than a yield from about 10 percent to 21.09 kilograms per square centimeter, and an average pore diameter of less than about 500 angstrom units, wherein the hydrogel polymer is selected from the group consisting of alginates, gums, starch, dextrins, agar, gelatins , casein, collagen, polyvinyl alcohol, polyethyleneimine, acrylate polymers, copolymers of midon / acrylate and mixtures and copolymers thereof in order to form a porous body impregnated with a metal extractant; b) contacting the aqueous solution with the porous body impregnated with the metal extractant to remove the metal ions from the aqueous solution; and c) separating the metal ions from the porous body impregnated with the metal extractant.

The process according to claim 9, wherein the extractant is selected from the group consisting of diketones, oximes, oxines, tertiary amines, quaternary amines and mixtures thereof.

11. The process according to claim 9, wherein the metal ions are separated from the porous body by passing a purification solution through the porous body. SUMMARY OF THE INVENTION A composition comprising a highly crosslinked porous body derived from a water soluble hydrogel polymer, the porous body is characterized in that it has a three-dimensional open cell lattice structure, a density of less than about 1.0 gram per cubic centimeter, an equal surface area ao greater than about 300 square meters per gram, a compressive strength equal to or less than a yield of about 10 percent at 21.09 kilograms per square centimeter and an average pore diameter of less than about 500 angstrom units, where the hydrogel polymer is selected from the group consisting of alginates, gums, starch, dextrins, agar, gelatin, casein, collagen, polyvinyl alcohol, polyethylene imine, acrylate polymers, starch / acrylate copolymers and mixtures and copolymers thereof; and a metal extractant. The composition can be used to remove and / or recover metal ions from aqueous streams. A process for recovering metal ions from an aqueous metal ion solution including the steps of impregnating a metal extractant into the porous body described above and contacting the aqueous ion solution with the impregnated porous body in order to remove the metal ions thereof and separate the ions from the impregnated porous body.