The present invention relates to a process for extracting one or more metals selected from the group consisting of Ge, Ga, In, As, Sb, Bi, Pt, Pd, Ni and Co from an acid aqueous solution containing said one or more metals, according to which the acid aqueous solu¬ tion is contacted with a solid ion exchanger at a pH at which the ion exchanger absorbs said one or more metals, said ion-exchanger resulting from the reaction of a carrier material, containing NH- and/or NH2-groups that are able to react with aldehydes, with

(a) an aldehyde and

(b) 8-hyurox quinυliιιe and/or an δ-hydroxyqumolme derivative, and possibly (c) a swelling agent and/or a solvent.

Such a process is described in SU-A-407922. In this known process indium is extracted from sulfuric acid solutions of pH 1.05 and 2.9 by contacting the solutions with an ion exchanger resulting from the reaction of crosslinked polymers having primary or secon- dary aminogroups with formaldehyde and 8-hydroxyquinoline in water or alcohol, the aminated crosslinked polymers themselves resulting from either the condensation of amines with epichlorohydrin or the amination of chloromethylated styrene-divinylbenzene-copolymers.

The aim of the present invention is to provide a process such as defined herebefore, which gives better extraction results than the prior art process.

Therefore, according to the invention use is made of an ion exchanger resulting from the said reaction, when the carrier mate¬ rial is one that is obtainable by amidoalkylation, preferably by imidoalkylation with an ester or an ether of a N-hydroxyalkylimide, of a crosslinked styrene-copylomer and by subsequent hydrolysis of the amido- or imidoalkylation product.

Preferred modes of carrying out the process of the invention are described in the hereto attached claims 2-29. The process of the invention is particularly useful for extrac¬ ting Ge, Ga and/or In from ZnS0 solutions used in the electrowin- ning of zinc, for separating As, Bi and Sb impurities from sulfuric

acid solutions and for separating Pt or Pd impurities from AgNOβ solutions used in the electrorefining of silver.

As to the preparation of the ion exchanger used in the process of the present invention, the following should be noted. The carrier material contains preferably at least one reactive group of the general formula

- (CH ₂ ) _n - NH - R ¹ (I)

wherein

R*-* = H or a possibly substituted and possibly unsaturated alkyl- , cycloalkyl- or alicyclic rest with 1 to 10 C-atoms - preferably methyl - or a possibly substituted aromatic rest with 6 to 10 C- atoms and n - 1 or 2.

Carrier materials, wherein R-*- = H and n = 1, are especially preferred. A acroporous aminomethylated styrene-divinylbenzene- copolymer is used as a preferred carrier material.

The carrier material can be prepared by a Friedel-Crafts reac- tion of a crosslinked, water-insoluble organic polymer containing aromatic nuclei, with an imidoalkylation agent in the presence of a swelling agent for the polymer and of an acid catalyst and by subse¬ quent hydrolysis of the imidoalkylated polymer in accordance with DE-PS 2161628 and DE-PS 2418976. The esters of N-hydroxyalkylimides with lower aliphatic car- boxylic acids (DE-PS 2418976) as well as bis-(dicarbonimidoalkyl)- ethers (DE-PS 2161628) can be used as imidoalkylation agents.

As N-hydroxyalkylimides which can be used there should be mentioned the di-methylimides and di-ethylimides of aliphatic C -C6 dicarboxylic acids and of aromatic o-dicarboxylic acids. The N- hydroxymethylimides are preferably used.

The crosslinked, water-insoluble organic polymers containing aromatic nuclei is preferably an aromatic vinyl compound of the type obtained by the copolymerisation of monovinyl and polyvinyl com- pounds. Such copolymers are known per se and are obtained by known methods. The copolymer may be either microporous, i.e. has a gel

structure, or macroporous.

Preferred copolymers are those which consist of a major amount of aromatic monovinylcompounds and of a minor amount of aromatic or aliphatic polyvinyl compounds. Suitable swelling agents for the polymer are, above all, halo- genated hydrocarbons or polar organic solvents such as nitro com¬ pounds.

Suitable catalysts include the usual Friedel-Crafts catalysts, such as AICI3 or FeCl3 and, especially, sulphuric acid. The reaction of the organic polymer with the ester of the N- hydroxyalkylimide is carried out at temperatures of 0-150°C. The ester is used in such quantities that there are from 0.5 to 4 mols of ester per mol of aromatic nuclei in the polymer. The catalyst is generally used in quantities ranging from 0.1 to 1.5 mol per mol of ester.

The reaction can be carried out by initially preparing the ester of the N-hydroxyalkylimide in the swelling agent and swelling the polymer in this solution, whereafter the acid catalyst is added and the mixture is brought to the reaction temperature. On comple- tion of the acylimidoalkylation reaction the acyl radical is split off from the reaction products in a known manner, by subjecting the acylimidoalkylation product to alkaline or acid hydrolysis.

Preferred carrier materials are a inomethyl-polystyrene-divi- nylbenzene resins with a nitrogen content of 8-12 wt. % in the dry material and with a degree of crosslinking of 2-12 %, preferably 4- 8 %, and useful capacities of 1.5-3.5 equivalent/1, preferably 2.5- 3 equivalent/1, in accordance with DE-PS 2418976.

The aldehydes, which can be used for preparing the ion exchan¬ ger that is used in the process of the present invention, are those which are suited to undergo the Mannich-reaction with the amino¬ groups of the carrier material and 8-hydroxyquinolines according to formula III. These are aldehydes of the general formula :

0 (ID

in which R--- stands for hydrogen, an alkylrest with 1-4, especially 1-2 C-atoms or a possibly substituted aromatic hydrocarbon rest with 6-10 C-atoms, such as propionaldehyde, butyraldehyde, iso-butyralde¬ hyde, especially formaldehyde, acetaldehyde and benzaldehyde.

The 8-hydroxyquinolines, which can be used for preparing the ion exchanger used in the process of the present invention, are those of the general formula III

in which R^ -= H or a halogen atom or -SO3H and R*- ^* - H or CH3.

Very suitable compounds are those wherein R* ■= H or chlorine and R ⁵ - H.

The synthesis of the ion exchanger is normally carried out in the presence of a swelling agent and/or a solvent. Suitable swel¬ ling agents and/or solvents are water, to which acids and bases may be added, as well as C-_-C4-alcohols, especially methanol and ethanol.

The synthesis itself consists in reacting the carrier materials (M) with aldehydes and 8-hydroxyquinolines by a Mannich reaction :

The synthesis is carried out in the reaction conditions which are well known for carrying out Mannich-reactions. The aminomethy- lation of 8-hydroxyquinolines of formula III then occurs almost selectively at the 7-position. Preferably, the carrier material is allowed to swell in a sol¬ vent or a solvent mixture before the reaction.

The reaction temperature can lie, dependent on the nature of the components, between 20-100°C, preferably between 20-80°C and particularly between 50-70°C. The reaction time can amount up to 48 h;as a rule, however, it lies between 5 and 24 h.

The molar ratio aldehyde : 8-hydroxyquinoline can vary betw en 2:1 and 1:1, but is preferably about 1-1.5:1. The quantities of aldehyde and 8-hydroxyquinoline depend on the reactive aminogroups that are accessible on the carrier material. They are preferably used in such quantities that all accessible aminogroups undergo the Mannich-reaction. In most cases, a ratio aminogroups : 8-hydroxy- quinoline of 1:1 to 1:1.5 will be sufficient.

On completion of the reaction the resin is separated, washed with water, possibly in the presence of bases or acids, and/or sol- vents. The resin, which is so freed from not converted soluble reaction components, can be used directly for the extraction process.

Examples of the preparation of ion exchangers that can be used in the process of the present invention :

4 different a inomethylated styrene-divinylbenzene resins (I, II, III and IV), to be used as carrier materials, were prepared in accordance with DE-PS 2418976, example 2, such as described here- under for resin I :

354 g of N-hydroxymethylphtalimide, dissolved in 1100 g of dichlo- roethane, are heated for 5 hours to reflux temperature with 227 g of acetic acid anhydride. 150 g of resin beads made of a macroporous styrene polymer crosslinked with 6 % divinylbenzene are swollen in this ester solution for 1 hour at 60°C. 240 g of concentrated sul¬ phuric acid are then added dropwise over a period of 1 hour at reflux temperature and the reaction mixture is then stirred at the

4

same temperature for 20 hours. After the reaction product has been separated off, it is suspended in 1000 ml of a 10 % aqueous ammonia solution. The residues of dichloroethane are removed from this sus¬ pension by azeotropic distillation. The reaction product is then separated off and hydrolyzed by heating for 10 hours at 180°C with i 40 % sodium hydroxyde solution in an autoclave. After filtration and washing the aminomethyl-polystyrene-divinylbenzene resin I is obtained.

The properties of resin I are given in Table 1.

Resins II, III and IV (see Table 1) were prepared in an analogous way.

Table 1

*) according to elementary analysis **) the data relate to the moist resins (see DIN 54402, DIN 54408, DIN 54400)

(1) 314 g of the moist aminomethyl-polystyrene-divinylbenzene resin I (corresponding to 100 g of dry material) , 165 g of 8-hydroxy- quinoline and 470 ml of methanol are stirred for 1.5 hour at

60°C. 50.5 g of p-formaldehyde are then added and the stirring is continued for 5 hours at 60°C. The resin is filtered off. In order to remove not converted reaction components the resin is washed successively with 300 ml of respectively methanol, water, 4N H2SO4, water, 1.5 N NaOH and finally with water till the effluent is neutral.

The yield of moist resin is 350.6 g, corresponding to 201 g of dry material. The calculated 8-hydroxyquinoline content is 3.2 mol per kg dry resin (see table 2, resin A). The water content is 42.7 %. (2) The conversion of resin I such as described in example (1) is repeated with different reagent ratios, solvents and reaction times, whereby obtaining the resins Aa-Ad (see table 2).

Table 2

*) in accordance with DIN 54408

(3) Resins II, III and IV are converted in the same way as described in example (1) for resin I, whereby obtaining the resins B, C and D (see Table 3) .

Resins A, Aa, Ab, Ac, Ad, B, C and D are thus representative of the ion exchangers which can be used in the process of the present invention.

An ion exchanger to be used in the above discussed prior art process was prepared starting from a commercially available amina- tion product of chloromethylated macroporous polystyrene-divinyl- benzene resin with a nitrogen content of 6.3 %. This aminated resin was subjected to the Mannich-reaction as described in example (1), whereby obtaining ion exchanger E (see Table 3) .

Table 3

To be used in the process To be used in the of the invention prior art process

Resin

Starting resin II III IV Commercial macroporous aminotoβthyl-polystrene -divβnylbβnzene g 8-hydro_c quinoline 165 165 165 165 160 g formaldehyde 50.5 50.5 50.5 50.5 33

Solvent CH ₃ 0H CH3OH CH3OH CH3OH C ₂ H ₅ 0H

Reaction time h 5 5 5 S 40

Yield of dry material in g 201 147 171 213 131

Water content of the resin Z 42.7 46.4 38.3 30 58.3

Wt. per liter in g/ml* 0.81 0.77 0.78 0.87 0.75

Content Mo**- ^β -hydroxγquinoline 3.2 2.0 2.6 3.4 1.5 kg dry material

*) in accordance with DIN 54408

The process of the invention is illustrated by the following examples.

Example 1

The extraction of Ge, Ga, In, Sb, Bi, Pt, Pd, Ni and Co from acid solutions is carried out by one of the following methods : Method a :

A quantity of moist resin corresponding to 5 g of dry material is contacted for 3 minutes with 4 N H ₂ Sθ , then filtered off and washed until neutral with 2 1 of water. The resin is finally washed with solution 1 (see Table 4) and then stirred for 24 h in 110 ml of a solution of the metal (6 g/1 of metal ions in solution 1) . The metal content of the solution is determined before and after contact of the solution with the resin, by titration or by atomic absorption spectroscopy. Using these data, the metal loading of the resin in g M ⁿ⁺ /1 resin is calculated.

When the quantity of metal used in method a is not sufficient for saturating the resin with metal, then method b is used.

Method b :

One operates in the same way as in method a, but instead of using 110 ml of metal solution one uses 220 ml.

For the extraction of expensive metals one uses method c.

Method c :

One operates in the same way as in method a, but one uses a limited quantity of moist resin corresponding to 0.2 g of dry material and a solution of 1 m equivalent of metal in 50 ml of solution 1.

The results are given in Tables 4 and 4a.

Table 4

Table 4a

4

10

Example 2

The re-extraction of some metals from resin A is carried out as follows :

Resin A resulting from example 1 is poured into a column and washed with 200 ml of solution 1. The washwater is rejected. The resin is then treated with 500 ml of solution 2 (re-extraction) . The metal content of the obtained eluate is determined.

The re-extraction yield (in %) is calculated as follows :

(g of re-extracted metal : g of fixed metal) x 100.

The operation is carried out in downflow at a rate of 2-4 bed volumes per hour.

The results are given in Table 5.

Table 5