Abstract: A cobaltic oxide hydrate is mixed with spent sulfate electrolyte and the slurry is sparged with air to liberate any entrained chloride ions as gaseous chlorine. Thereafter a reducing agent is used to enable dissolution of the cobalt and obtaining of a chloride-free solution from which, after purification, cobalt can be electrowon.

Abstract: A process for selectively extracting and ultimately recovering copper from acidic chloride solutions containing the same wherein an acidic chloride solution containing copper is initially contacted with an extractant to selectively extract copper, as copper chloride, therefrom. The loaded extractant is contacted with a suitable aqueous stripping solution to strip copper therefrom. Thereafter, the pregnant aqueous stripping solution is contacted with an active hydrogen ion exchange extractant, such as hydroxy oxime, a beta diketone or mixture thereof dissolved in an inert organic carrier solvent. The active hydrogen ion exchange extractant selectively extracts copper from the pregnant aqueous stripping solution with hydrochloric acid being formed.

Abstract: Disclosed is a process for separating precious metals such as gold or platinum from acidic solutions having a pH below about 3, which comprises the steps of:(a) adding a sufficient amount of a heavy metal chelate (e.g., zinc or iron) of 2-mercaptopyridine-N-oxide to the acidic solution to cause at least a portion of the precious metals in the solution to transchelate with the heavy metal chelate of 2-mercaptopyridine-N-oxide and then to form precipitates in the solution; and(b) separating the precipitated precious metal chelates of 2-mercaptopyridine from the acidic solution.

Abstract: Spent aqueous liquor containing cyanide, as from ore treatment, is passed through a bed of suitable anion-exchange resin to segregate the cyanide, which is subsequently recovered in regeneration of the resin by weak alkaline solution. Both the eluted cyanide and the alkaline regenerant are recycled, if desired, for further ore treatment. A most important benefit of such procedure is nearly complete elimination of cyanide as a component of the treatment effluent. Free cyanide may be separated from complexed cyanides when present by using weak alkaline regenerant to elute the free cyanide from the resin and stronger alkaline regenerant to elute the complexed cyanides.

Abstract: Metal values of ferromanganese nodules harvested from ocean floors are placed in aqueous solution suitable for partition as by selective extraction with chelating agents by treating the nodules with aqueous solutions which contain oxalic acid or mixture of oxalic acid with a strong acid. These unique reagents may be used alone or in combination with other reducing, complexing or acidic treating agents.

Abstract: Platinum, palladium, rhodium, ruthenium, iridium and other metals are recovered from aqueous media containing precious metal ions in solution by contacting the metal-containing solution with blood meal to collect the metals in concentrated insoluble form in the blood meal, and recovering the thus collected metals from the resulting metals-loaded blood meal.

Abstract: There is disclosed a process for recovering nickel (II), copper (II) and cobalt (II) from an ammoniacal-ammonium sulfate leach liquor. This process includes the step of adjusting the pH of the leach liquor prior to co-extracting the nickel and the copper values. Cobalt is recovered as cobalt (II) by reduction of cobalt (III) to cobalt (II) following by an extraction step.

Abstract: Improved solvent-extractants for the selective recovery of metal values from acidic aqueous media comprise solutions of 5-alkylbenzotriazoles in water-immiscible organic solvents. Extraction efficiency is enhanced by addition to the solvent-extractant of alkyl aromatic sulfonic acids, alkyl phosphoric acids or carboxylic acids. Especially important applications for the improved solvent-extractants are in the recovery of copper (II) from cobalt (II), copper (II) from nickel (II), copper (II) from iron (III), copper (II) from zinc (II), nickel (II) from cobalt (II), nickel (II) from zinc (II), nickel (II) from iron (III), iron (III) from magnesium (II), and cobalt (II) from zinc (II).

Abstract: An extractant system comprising (a) a high molecular weight alkylaromatic sulfonic acid and (b) a chelating amine having a pKa of from about 3 to about 9 in a solvent which is essentially immiscible with water, said system being useful for the selective extraction of desired metals, e.g., cobalt, nickel or copper ions from aqueous acidic ore leach liquors.

Abstract: A process is described for regenerating a spent ammoniacal etching solution containing copper values. The process comprises extracting copper from the spent etching solution by means of an organic solution containing a reagent which is capable of selectively extracting copper ions from the spent etching solution. The process also comprises extracting copper from the washing water originating from the etching process.

Abstract: Certain sulfonylhydrazines, metal complexes thereof and solutions of said compounds in essentially water-immiscible, liquid hydrocarbon solvents are disclosed. The sulfonylhydrazines have the general structural formula:R--SO.sub.2 NHNH--R.sub.1wherein R and R.sub.1 are as defined in the specification and claims hereof. Particular metal values are recovered from their aqueous solutions by using sulfonylhydrazines dissolved in essentially water-immiscible, liquid hydrocarbon solvents. The extraction process involves contacting the metal value containing aqueous solution with the solution of the sulfonylhydrazines in essentially water-immiscible, liquid hydrocarbon solvent and stripping the metal from the loaded organic phase.

Abstract: Certain sulfonamidothiadiazoles, metal complexes thereof and solutions of said compounds in essentially water-immiscible, liquid hydrocarbon solvents are disclosed. The sulfonamidothiadiazoles have the general structural formula: ##STR1## wherein R and A are as defined in the specification and claims hereof. Particular metal values are recovered from their aqueous solutions by using sulfonamidothiadiazoles dissolved in essentially water-immiscible, liquid hydrocarbon solvents. The extraction process involves contacting the metal value containing aqueous solution with the solution of the sulfonamidothiadiazole in essentially water-immiscible, liquid hydrocarbon solvent and stripping the metal from the loaded organic phase.

Abstract: Dioxime extractants having the following general formula: ##STR1## where R and R' may be any of a variety of organic hydrocarbon radicals such as aliphatic, alkyl and aryl radicals. R and R' may also be hydrogen. Preferably R is an unsaturated hydrocarbon or branch chain alkyl group containing from about 3 to 20 carbon atoms and R' is hydrogen or an unsaturated hydrocarbon or branch chain alkyl group containing from about 1 to 10 carbon atoms. Preferably, there is a difference of about 3 to 10 carbon atoms between R and R' resulting in dissymmetry of the resulting dioxime molecule. Preferably, the dioximes also contain a total of about 5 to 32 carbon atoms. Representative compounds are methyl octyl dioxime and methyl hexyl dioxime.Organic preparations containing such dioximes are useful for the extraction of copper, nickel and cobalt metal values from acid or basic aqueous solution.

Abstract: A method for processing a hydroxide sludge residue to separate and recover the nonferrous metal values therefrom including the steps of(1) concentrating the residue and acidifying and heating the concentrated residue to produce a solution containing the nonferrous metal values;(2) removing the copper from the solution by liquid-liquid extraction;(3) separating the chromium, aluminum, residual portions of iron, as well as the remaining calcium from the copper-free solution by high temperature pressure hydrolysis to obtain the metals as the hydrated oxides or basic sulfates;(4) removing zinc and nickel from the remaining solution by liquid-liquid extraction;(5) processing the individual nonferrous metal fractions to isolate and recover the metal values in a conventional manner.By using this process, the nonferrous metal values can be easily separated in a relatively high state of purity from the hydroxide sludge wastes.

Abstract: Disclosed in the present invention is a process for selectively separating and recovering cobalt by liquid-liquid extraction from an aqueous solution containing cobalt such as those obtained by leaching a cobalt-containing ore with an acid by utilizing an organic solvent containing an alkyl ester of alkylphosphonic acid as the extractant.

Abstract: Certain sulfonamidophenols, metal complexes thereof and solutions of said compounds in essentially water-immiscible, liquid hydrocarbon solvents are disclosed. The sulfonamidophenols have the structural formula: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are as defined in the specification and claims hereof. Particular metal values are recovered from their aqueous solutions by using sulfonamidophenols dissolved in essentially water-immiscible liquid hydrocarbon solvents. The extraction process involves contacting the metal value containing aqueous solution with the solution of sulfonamidophenol in essentially water-immiscible liquid hydrocarbon solvent and stripping the metal values from the loaded organic phase.

Abstract: A process for recovering heavy metal ions or heavy metal ions and halogen values from a solution comprising a lower aliphatic monocarboxylic acid, which comprises the steps of:(1) contacting a lower aliphatic carboxylic acid solution containing heavy metal ions or heavy metal ions and halogen values with an anion exchange resin, at least 60% of the ion-exchange groups of said anion exchange resin being in the bromide or chloride state, while the water concentration in the lower aliphatic monocarboxylic acid solution has been adjusted to a level lower than 20% by weight, thereby to adsorb the heavy metal ions or the heavy metal ions and the halogen values on the anion exchange resin; and(2) desorbing the adsorbed heavy metal ions or the adsorbed heavy metal ions and the adsorbed halogen values from the anion exchange resin by elution with an eluent.

Abstract: Certain sulfonylthiosemicarbazides, metal complexes thereof and solutions of said compounds in essentially water-immiscible, liquid hydrocarbon solvents are disclosed. The sulfonylthiosemicarbazides have the general structural formula: ##STR1## wherein R and R.sup.1 are as defined in the specification and claims hereof. Particular metal values are recovered from their aqueous solutions by using sulfonylthiosemicarbazides dissolved in essentially water-immiscible, liquid hydrocarbon solvents. The extraction process involves contacting the metal value containing aqueous solution with the solution of the sulfonylthiosemicarbazide in essentially water-immiscible, liquid hydrocarbon solvent and stripping the metal from the loaded organic phase.

Abstract: A method is provided for extracting at least one of the trivalent ions Fe and Al from an acid solution. The method comprises uniformly mixing the acid solution with a liquid organic extractant comprising an organophosphorus compound and an alkylaromatic sulfonic acid dissolved in a water-immiscible organic solvent, the extractant being selective to the solvent extraction of said trivalent ions under acidic conditions. The molar ratio of the sulfonic acid to the organophosphorus compound is controlled over a range of about 1:4 to 10:1 and the mixing carried out for a time sufficient to effect solvent extraction of said trivalent ions and provide a raffinate substantially impoverished in said trivalent ions and a loaded extractant containing said trivalent ions, following which the loaded extractant is separated from the raffinate.

Abstract: A process for extracting metal values from aqueous solutions of metal salts which comprises the steps of contacting the aqueous solution with a solution in a water-immiscible organic solvent of one or more o-hydroxyaryloximes containing at least 3 aliphatic or alicyclic carbon atoms and which are strong metal extractants and one or more alkylphenols optionally containing one chlorine atom or one cyano group, separating from the aqueous phase the solvent phase containing metal in the form of a complex with the o-hydroxyaryloxime contacting the solvent phase with an aqueous mineral acid, and separating the solvent phase from the aqueous phase containing metal in the form of a salt with the mineral acid.

Abstract: A liquid-liquid extraction process is disclosed, in which an aqueous solution, containing metal ions, is contacted with an organic liquid substantially insoluble in water. The organic liquid contains two water-insoluble reagents, viz. a diester of dithiophosphoric acid and an organic phosphate, in a preferred volume ratio of between 1:10 and 2:1. The organic liquid may also contain a diluent for the reagents.

Abstract: A system of multiple extraction in which each of the metal elements extracted is bonded to the extractant with a different degree of intensity. To reduce impurities in each metal recovery stage, a bleed stream from each recovery stage is cascaded backwards. In general, the backward cascade disposes of the bleed stream from the most tightly bonded species by recycling it to any preceeding stage of a less tightly bonded species.An example of a process for recovering copper and nickel from an aqueous leach solution containing these values is given. In this type of process, ammonia, copper and nickel are first coextracted onto an organic extractant (oxime). Ammonia is stripped first. In a nickel recovery circuit, nickel values are selectively stripped from the oxime with acid, pure nickel is electrowon, and the acidic, nickel-barren raffinate from the electrowinning cell is recirculated.

Abstract: Aqueous nickel chloride solutions containing such impurities as copper, iron, and zinc, and optionally, cobalt, and having an acid concentration ranging from about 0.2 N to 4 N HCl together with a total chloride concentration of about 4 N to 11 N are purified of said impurities by solvent extraction with an organic extractant of essentially tributyl phosphate (TBP) dissolved in a water-immiscible organic solvent, the solvent extraction being carried out at a selected concentration of TBP and a selected volume ratio of organic to the aqueous solution effective to produce a nickel raffinate substantially impoverished in said impurities.

Abstract: Multivalent heavy metal ions are removed from metal plating waste streams by passing them through an unexpanded vermiculite cation exchange column. The column is effective to remove copper, zinc, and nickel ions and mixtures thereof. Where cyanide and cyanide-metal complexes are also present in the plating waste stream, the stream is pretreated to destroy the cyanide and cyanide complexes prior to passage through the ion exchange column.

Abstract: Certain sulfonamidoquinolines and metal complexes thereof both of which are soluble in essentially water-immiscible organic solvents. The sulfonamidoquinolines have the structural formula ##STR1## where the R, R.sup.1 and R.sup.2 groups and m and n are as defined in the specification and claims hereof. Solutions of the sulfonamidoquinolines and the metal complexes thereof in essentially water-immiscible organic solvents.

Abstract: 7-Ethyl-undeca-2,4-dione as a chelation collector for the liquid-liquid extraction of transition metals from dilute ammoniacal leach solutions thereof exhibits the combination of requisite physical and dynamic properties marking an industrially attractive reagent for this purpose.

Abstract: The invention relates to the re-extraction of a metal from an organic extraction solution in which the metal is present as a metal chloride complex bonded to an extractant. The organic extraction solution is contacted with an aqueous solution, to transfer metal ions and chloride ions to the aqueous solution. Sulphuric acid is added to the aqueous solution, which is subsequently heated to drive off hydrogen chloride and water. Metal sulphate is removed from the acidified aqueous solution.

Abstract: A process for the removal of heavy metals uranium and transition metals other than noble transition metals from solution by contacting the solution with the product obtained by reacting an inorganic solid eg. silica gel containing surface hydroxyl groups with a silicon compound of defined formula containing a free thiol group or a free amino group and either an --OR group or a halogen atom under conditions which effect reaction between the hydroxyl group and the --OR group or halogen atom thereby bonding the silicon compound to the inorganic solid.

Abstract: An ion exchange resin having functional groups of the formula :- ##STR1## wherein :- A and B, independently of each other, represent groups forming together with the attached carbon and nitrogen atoms, an optionally substituted five or six membered heterocyclic ring which may embody a further heteroatom and wherein at least one of such heterocyclic rings is an aromatic ring; R* may be totally absent or it may represent an optionally substituted alkyl radical and Z represents a resin to which the functional groups are attached.

Abstract: Process for extraction and separation of metals utilizing the advantages of liquid-liquid extraction with cation exchangers without requiring the equivalent addition of alkali. The process is based on a combination of leaching the metal-containing raw materials with an organic acid (cation exchanger) and a subsequent use of the formed metal cationic complex in a liquid-liquid extraction process. In the said extraction process, the organic solution of metal complexes is used to recover and separate metal ions from an aqueous solution of metal salts.

Abstract: Solvent-extraction processes to recover metal values are improved by use as a component of the solvent-extractant of didodecylnaphthalene sulfonic acid. Especially important applications for the improved solvent-extractant which can include a .alpha.-hydroxy oxime are in the separation recovery of copper, nickel, zinc and cobalt and the selective separation of these metals, one from the other, and from iron, in acidic aqueous media.

Abstract: An extraction process is described for the selective separation of bivalent metal ions belonging to the group Cu, Co, Ni and Zn in aqueous solution of Cu- and Ni-ions, Cu- and Zn-ions or Cu- and Co-ions, wherein there is used as the extraction medium one or more unsaturated fatty acids, optionally in solution and/or in admixture with saturated fatty acids and an aliphatic oxime.

Abstract: Mercury and copper ions may be removed very selectively from aqueous solutions by means of a metal-chelating resin consisting of a polymer produced by the condensation of a phenolic component comprising one or more phenols, formaldehyde, and a diamino component comprising one or more di-(secondary amino) compounds under neutral conditions. The resin is prepared by condensing approximately equimolar quantities of a phenolic component comprising one or more phenols, and a diamino component comprising one or more di-(secondary amino) compounds with approximately twice the molar quantity of formaldehyde under Mannich reaction conditions.

Abstract: A process for treating a pyrite concentrate containing silver, copper and zinc to recover the metals contained therein is disclosed. The process includes the partial roasting of the concentrate to open the pyrite matrix to solution penetration followed by hydrometallurgical steps, including ferric sulphate leaching, reduction leaching, solid-liquid separation and metal extraction steps, to recover the copper and zinc separately and silver in concentrated form.

Abstract: New .beta.-diketones of the structure ##STR1## where R is phenyl or alkyl substituted phenyl, R' is alkyl, alkyl substituted phenyl or chloro substituted phenyl and R" is H or --CN with the provisos that; (1) when R is phenyl, R' is a branched chain alkyl group of at least seven carbon atoms and (2) when R is alkyl substituted phenyl, the number of carbon atoms in the alkyl substituent or substituents is at least 7 and at least one such alkyl substituent is branched chain. Process of recovering copper and nickel from their aqueous solutions by the use of the new .beta.-diketones.

Abstract: 12-alkyl-1,4,7,10-tetraazacyclotridecane of the formula ##STR1## wherein R is an alkyl group containing at least 8 carbon atoms. This compound can be used for capturing metal ions.

Abstract: A heavy metal ion adsorbent represented by the following general formula: ##STR1##wherein l, m, and n are 2 or 3, respectively; R is an alkyl group containing 4 to 6 carbon atoms which is substituted by an amino group in the .omega.-position; and A is hydrogen or a synthetic resin.

Abstract: A process is described for the recovery of copper values from an acidic aqueous solution containing copper values by means of liquid-liquid extraction, wherein the extractant is a mixture comprising a substantially water-immiscible organic solvent, one or more hydroxyoximes capable of extracting copper values, and one or more alpha, betadioximes of the anti-configuration. Novel alpha, beta-dioxime compounds are also disclosed.

Abstract: A process for treating a pyrite concentrate containing silver, copper, lead and zinc to recover the metals contained therein is disclosed. The process includes the partial roasting of the concentrate to open the pyrite matrix to solution penetration followed by various hydrometallurgical steps, including oxidation and reduction leaching, solid-liquid separation and metal extraction steps, to recover the copper and silver together, and the lead and zinc separately.

Abstract: The metal value separation efficiencies of alkyl aromatic sulfonic acid in solvent-extraction processes are enhanced by the addition to the solvent-extractant of a fused ring aromatic N-alkyl triazole and, optionally, an aliphatic .alpha.-hydroxy oxime. Especially important applications for the improved solvent-extractant are in the separation and recovery of copper from iron, cobalt from nickel, copper from cobalt, cobalt from zinc, nickel from zinc, zinc from iron, nickel from iron, copper from nickel, copper from iron and copper fron zinc.

Abstract: A method for treating nonferrous metal hydroxide sludge waste to separate and recover the nonferrous metals therein wherein the waste is first mixed with an alkali hydroxide or carbonate, dried, and then roasted and the water-insoluble residue in the roasted material is treated with sulfuric acid to produce an acid-insoluble residue and a sulfuric acid solution containing copper, aluminum and chromium and thereafter, separating the copper from this solution by liquid-liquid extraction and thereafter, separating the aluminium, chromium, zinc and nickel from the remaining solution by separate liquid-liquid extraction steps.

Abstract: Flow paths for liquids are disclosed in vessels, the paths oriented with electrodes which are electrically energized to establish electrostatic fields through the paths. One of the liquids is more polar than the other liquids in the paths. One of the fields is intense enough to generate the force to move drops of the polar liquid fast enough to shear the drops to smaller sizes and disperse the smaller drops. A second one of the fields is intense enough to generate the force to move the dispersed drops into coalescense. Various spacing and means of energizing the electrodes are disclosed to place the forces on the liquids in sequence and at different intensities.

Abstract: A process for treating very dilute solutions containing ecologically noxious heavy metal ions, in which the solutions are made acceptable for return to the environment, and the typically valuable heavy metal present in the solution is recovered at an economic profit. The dilute solution is flowed through an ion exchange resin, as a cross-linked polystyrene having quaternary ammonium functional groups which hold the heavy metal ions, allowing an ecologically benign effluent to return to the environment or the water to be re-used in industrial processing. Typically, an alkali metal halide is subsequently placed in contact with the resin to recover the heavy metal ion for subsequent reduction to a solid.

Abstract: Metals are removed from waste materials that contain an organic component and a bimetallic salt complex component that comprises complexes having the formula M.sub.I M.sub.II X.sub.n .multidot.Aromatic and/or the formula M.sub.I M.sub.II X.sub.n .multidot.M.sub.II OX.multidot.Aromatic, wherein M.sub.I is a Group I-B metal, M.sub.II is a Group III-A metal, X is halogen, n is the sum of the valences of M.sub.I and M.sub.II, and Aromatic is a monocyclic aromatic hydrocarbon or halogenated aromatic hydrocarbon having 6 to 12 carbon atoms by contacting the waste material with water and sufficient alkali metal hydroxide to form a hydrolysis mixture which has a pH above 5 and which separates into an upper organic phase and a lower aqueous phase. After separation of the phases, there is obtained a slurry of M.sub.I oxide, M.sub.I hydroxide, and/or M.sub.II hydroxide from which the metals can be recovered or which can be discarded in ways that are not damaging to the environment.

Abstract: Metals are recovered from waste materials that contain an organic component and a bimetallic salt complex component that comprises complexes having the formula M.sub.I M.sub.II X.sub.n.Aromatic and/or the formula M.sub.I M.sub.II X.sub.n.M.sub.II OX.Aromatic, wherein M.sub.I is a Group I-B metal, M.sub.II is a Group III-A metal, X is halogen, n is the sum of the valences of M.sub.I and M.sub.II, and Aromatic is a monocyclic aromatic hydrocarbon or halogenated aromatic hydrocarbon having 6 to 12 carbon atoms, by hydrolyzing the waste material with dilute hydrochloric acid to form a hydrolysis mixture that separates into an organic phase and an aqueous phase, and, after removing the organic phase, adding to the aqueous phase sufficient aluminum or another reducing metal to precipitate the Group I-B metal. After the precipitated metal has been removed from it, the aqueous solution is treated with sufficient base to precipitate the Group III-A metal hydroxyide, which is recovered from the aqueous solution.

Abstract: An integrated process for the recovery of copper from impure copper bearing materials is provided by leaching the copper bearing material with sulfuric acid to convert the copper value to the soluble copper sulfate, selectively extracting the copper value from the leach liquor by contacting the liquor with an organic extractant stripping the copper from the organic copper extractant by contacting with liquor of enhanced acid content resulting from a subsequent reduction step, thus regenerating the organic extractant, contacting and thus reacting the acidified copper containing solution with an organic solution of amine extractant to reduce its acid concentration to a desired level, and recovering the copper metal by reacting the copper containing solution of lowered acid content with sulfur dioxide.

Abstract: A method for recovering nonferrous metal values from hydroxide sludge wastes containing same by first chlorinating the aqueous waste to oxidize the chromium therein, separating the insoluble components therefrom and treating the resulting Cr(VI) solution in a fixed bed anion exchanger to separate the Cr(VI) from the solution, separating the copper from the aqueous solution by liquid-liquid extraction, separating the zinc from the copper-free solution by liquid-liquid extraction, precipitating and separating the aluminum in the form of hydroxide from the zinc-free solution and then separating the nickel from the aluminum-free solution by liquid-liquid extraction, and recovering the nonferrous metals from the respective solutions and precipitates by conventional procedures.

Abstract: A process is disclosed for the separation of copper from a copper-amine mixture. The process comprises contacting the copper-amine mixture with an acidic cation exchange resin in which substantially all of the acid groups have been exchanged with a metal ion that is above copper in the electromotive series.

Abstract: A process for extracting metal values from aqueous solutions of metal salts which comprises the steps of contacting the aqueous solution with a solution in a water-immiscible organic solvent of one or more o-hydroxyaryloximes containing at least 3 aliphatic or alicyclic carbon atoms and which are strong metal extractants and one or more alkylphenols optionally containing one chlorine atom or one cyano group, separating from the aqueous phase the solvent phase containing metal in the form of a complex with the o-hydroxyaryloxime contacting the solvent phase with an aqueous mineral acid, and separating the solvent phase from the aqueous phase containing metal in the form of a salt with the mineral acid.

Abstract: This invention provides a two-stage leaching procedure for manganese nodules for obtaining directly in one leaching stage the metal values other than manganese in one ammoniacal aqueous solution. The manganese nodules are reduced and then leached initially utilizing a solution of an ammonium salt, e.g., ammonium sulfate, to selectively leach out the manganese value, followed by a second stage leaching with an ammoniacal solution, to leach out the nickel, cobalt and copper values. The nickel, cobalt and copper values can then be individually separated from the second leach solution by liquid ion exchange extraction.