Ion exchanger for winning metals of value

Abstract

The present invention relates to the use of monodisperse, macroporous anion exchangers of type I or type II in hydrometallurgical processes for winning metals of value.

Description

The present invention relates to the use of monodisperse, macroporous anion exchangers of type I or type II in hydrometallurgical processes for winning metals of value. Type I denotes resins whose adsorbing sites are quaternary ammonium groups which are substituted by alkyl groups. Type II denotes resins in which the quaternary ammonium groups have not only alkyl group(s) but at least one hydroxyalkyl group.

BACKGROUND OF THE INVENTION

Due to increasing industrialization in many parts of the world and globalization, the demand for numerous metals of value such as cobalt, nickel, zinc, manganese, copper, gold, silver and also uranium has increased considerably in recent years. Mining companies and producers of industrial metals are attempting to satisfy this increasing demand by means of various measures. These include improving the production processes themselves.

The metals of value relevant for industrial use are present in ore-bearing rocks which are mined. The ore which is then present in relatively large lumps is milled to give small particles. The materials of value can be leached from these rock particles by a number of methods. The customary technique is hydrometallurgy, also referred to as the wet method. If appropriate, the ore is subjected to a pretreatment to produce soluble compounds (roasting, pyrogenic treatment) and these are converted by means of acids or alkalis into aqueous metal salt solutions. The choice of solvent is determined by the type of metal, the form in which it is present in the ore, the type of accompanying rock in the ore (gangue) and the price. The most widely employed solvent is sulphuric acid, and hydrochloric acid, nitric acid and hot concentrated sodium chloride solutions are also possible. In the case of ores having acid-soluble accompanying materials, for example, copper ammoniacal solutions can also be used, sometimes also under high pressure and elevated temperature (pressure leaching). Sodium hydroxide is used for the winning of aluminium oxide; in the case of noble metals, alkali metal cyanide solutions are used. As an alternative, the winning of the metals in hydrometallurgy can also be carried out by precipitation or displacement by means of a less noble metal (cementation), by means of reduction by hydrogen or carbon monoxide under high pressure (pressure precipitation) or by electrolysis using insoluble electrodes or by crystallization (sulphates of copper, of zinc, of nickel or of thallium), by conversion (precipitation) into sparingly soluble compounds such as hydroxides, carbonates or basic salts by means of chalk, milk of lime or sodium carbonate solution.

U.S. Pat. No. 6,350,420 describes, for example, the treatment of the ore particles with mineral acids such as sulphuric acid at high temperatures (e.g. 250-270° C.) under superatmospheric pressure (high pressure leaching). This gives a suspension (slurry) of the fine ore particles in sulphuric acid, in which the leached metals are present in the form of their salts in more or less concentrated form.

As an alternative, the leaching of the metals from the rock can also be effected by other methods. The type of process used depends on a number of factors, for example on the metal content of the ore, on the particle size to which the crushed ore has been milled or on apparatus conditions, to name only a few.

In the heap leaching process, relatively coarse ore particles having a low metal content are used.

In the agitation leaching process, finer ore particles (about 200 μm) having high metal contents are used in the leaching process.

However, the atmospheric leaching process or the biooxidation process is also used for dissolving the metals from the ore. These processes are cited, for example, in U.S. Pat. No. 6,350,420.

The size of the milled ore particles to be used in these processes is in the range from about 30 to about 250 μm. Because of the small size of the particles and the large amount of rock, a classic filtration of the particles from the aqueous phase on filters is very costly. Separation by the gravitation principle in decanters by settling of the solid phase in very large stirred vessels is usually employed industrially. To obtain good separation and a solution of materials of value which is largely free of particles, stirred vessels having a diameter of 50 metres and more are used and a plurality of these are employed in series. Large amounts of water are required and these are very expensive since many mines are located in regions in which water is scarce (deserts). In addition, it is often necessary to use filtration media which are expensive and pollute the environment to achieve better removal of the particles.

In hydrometallurgical plants and mines which are operated in large numbers worldwide for the winning of materials of value such as gold, silver, nickel, cobalt, zinc and other metals of value, the process steps of filtration and clarification account for a large proportion of the capital cost of the plant and the ongoing operating expenses.

Great efforts are therefore made to replace the abovementioned expensive process steps by other less capital-intensive processes. New processes of this type are carbon in pulp processes for silver and gold and the resin in pulp (R.I.P.) process for gold, cobalt, nickel, manganese.

For example, U.S. Pat. No. 6,350,420 describes an R.I.P. process for the winning of nickel and cobalt. A nickel-containing ore is treated with mineral acids in order to leach out the materials of value. The suspension obtained by means of the acid treatment is admixed with ion exchangers which selectively adsorb nickel and cobalt. The laden ion exchangers are separated from the suspension by means of screens.

The ion exchangers used in U.S. Pat. No. 6,350,420 are resins which are described in U.S. Pat. No. 4,098,867 and U.S. Pat. No. 5,141,965. Suitable resins are accordingly Rohm & Haas IR 904, a strong base macroporous anion exchanger, Amberlite XE 318, Dow XFS-43084, Dow XFS-4195 and Dow XFS-4196.

The ion exchangers described in U.S. Pat. No. 4,098,867 and U.S. Pat. No. 5,141,965 contain variously substituted aminopyridine, in particular 2-picolylamine, groups. All ion exchangers described there display a heterodisperse bead diameter distribution. In U.S. Pat. No. 5,141,965, the ion exchangers display bead diameters in the range 0.1-1.5 mm, preferably 0.15-0.7 mm, most preferably 0.2-0.6 mm. The ion exchangers described in U.S. Pat. No. 4,098,867 display bead diameters in the range 20-50 mesh (0.3 mm-0.850 mm) or larger diameters.

Rohm & Haas IR 904, a strong base macroporous anion exchanger, and Amberlite XE 318 are likewise heterodisperse ion exchangers having bead diameters in the range 0.3-1.2 mm. In the examples, screens having mesh openings of 30 or 50 mesh (=300 to 600μ mesh opening) are used to separate the laden ion exchangers from the rock particles and the leached solution.

In the case of uranium as material of value, it is mined either by open cast methods or underground. In the case of underground mining, mechanical cutting and, in the case of ores having a low uranium content, in-situ leaching are used. The uranium present in the ore is separated by physical and chemical processes from the remaining rock (liberated). For this purpose, the ore is comminuted (crushed, finely milled) and the uranium is leached out. This is achieved by means of acid or alkali with addition of an oxidant in order to convert the uranium from the very sparingly soluble chemical 4-valent state into the readily soluble 6-valent form. In this way, up to 90 percent of the urnanium present in the ore can be recovered (see www.nic.com.an/nip.htm).

Undesirable accompanying materials are removed from the slurry/solution obtained in a plurality of purification steps by means of decantation, filtering, extraction, etc.

The uranyl ions are removed from the purified solution using anion exchangers.

The first publication DE 26 27 540 (=U.S. Pat. No. 4,233,272) discloses a process for the selective separation of uranium by means of an ion exchanger from acidic solutions which additionally contain nickel, iron, arsenic, aluminium and magnesium. A chelating cation exchanger is used here, with both uranyl UO₂²⁺ and U⁴⁺ ions being separated off using 8-12% strength sulphuric acid.

U.S. Pat. No. 4,430,308 describes a process for the winning of uranium by means of a heated ion exchanger, with type II resins, for example Duolite 102 D®, Ionac A-550®, Ionac A-651®, IRA 410®, IRA 910® and Dowex 2®, being able to be used for this purpose. All of these are heterodisperse, gel-like or macroporous ion exchangers based on styrene and divinylbenzene as crosslinker.

DD 245 592 A1 describes a process for removing uranium by means of anion exchangers, characterized in that heterodisperse anion exchangers which are prepared by reaction of crosslinked alkyl acrylate copolymers with polyamines are used.

DD 245 368 A1 relates to a process for separating off and recovering uranium, in particular in the form of its uranium sulphato complexes by means of heterodisperse ion exchangers which are prepared from (methyl)acrylic ester copolymers and polyamines from the series of hydroxyethyl-polyethylenepolyamines. Furthermore, DD 261 962 A1 discloses a process for preparing heterodisperse ion exchangers having amino groups and ortho-hydroxyoxime groups. In Example 1c of this document, uranium is present in the form of anionic uranyl sulphato complexes and is bound on a heterodisperse anion exchanger which has been prepared by the process mentioned.

DE 101 21 163 A1 describes a process for preparing heterodisperse chelating exchangers which contain chelating groups of the formula —(CH)_nNR₁R₂ and are used for removing the heavy metals or noble metals, for instance uranium. The patent DE 34 28 878 C2 discloses a process for recovering uranium in an extractive reprocessing procedure for irradiated nuclear fuels. In this process, use is made of base heterodisperse anion exchangers based on polyalkyleneepoxypolyamine having tertiary and quaternary amino groups of the chemical structure R—NH⁺(CH₃)₂Cl⁻ and R—NH⁺(CH₃)₂(C₂H₄OH)Cl⁻.

A disadvantage of the ion exchanger used in the prior art for the winning of uranium and also those for the winning of cobalt or nickel is the nonuniform loading of the ion exchanger with uranyl ions, which leads to considerable losses. Due to the ion exchangers used, the separation of the laden ion exchanger beads from the slurry via a screen results in further product losses because part of the beads is lost through the sieve because of their small diameter. The consequences are losses both of metal of value, for example uranium, but also of ion exchanger beads. Furthermore, the washing out of fine ore particles remaining from the digestion process from the fine beads is very time consuming and requires large amounts of water. Finally, the ion exchangers to be used according to the prior art cause high pressure drops and the nonuniform loading of the ion exchanger beads result in broad mixing zones in the eluates in the elution of the metal of value from the beads, which are disadvantageous for further uranium winning.

The solution to the problem and thus subject matter of the present invention is the use of monodisperse, macroporous, intermediate base or strong base anion exchangers of type I or type II in the winning of metals of value.

The monodisperse anion exchangers to be used according to the invention are preferably used in hydrometallurgical processes, particularly preferably in resin in pulp processes (R.I.P. processes) or in in-situ leaching processes or in the work-up of water containing metals of value.

SUMMARY OF THE INVENTION

The invention therefore also relates to a process for winning metals of value from hydrometallurgical processes, preferably in R.I.P. processes or in in-situ leaching processes or for the work-up of water containing metals of value, characterized in that monodisperse, macroporous intermediate base or strong base anion exchangers of type I or type II, preferably of type II, are used.

Compared to the ion exchangers used in the prior art, the monodisperse, macroporous, intermediate base or strong base anion exchangers of type I or type II to be used according to the invention surprisingly display significantly higher adsorption rates for the metals of value, in particular for uranium, low pressure drops, have small mixing zones and require significantly smaller amounts of water.

In a particularly preferred embodiment, the monodisperse, macroporous intermediate base or strong base anion exchangers of type I or type II to be used according to the invention serve to adsorb uranium from aqueous solutions into which it has been leached by means of strong acids. When leached by means of strong acids or by means of concentrated sodium carbonate solutions, the uranium is preferably present as the uranyl ion (UO₂²⁺), particularly preferably as uranyl chloride, uranyl phosphate, uranyl acetate, uranyl carbonate, uranyl sulphate or uranyl nitrate, among which uranyl sulphate obtainable by leaching of the uranium-containing rock by means of sulphuric acid is particularly preferred.

The invention therefore particularly preferably provides for the use of monodisperse, macroporous intermediate base or strong base anion exchangers of type I or type II, in particular of type II, for the adsorption of uranyl ions from the salts of uranium with strong acids or with sodium carbonate, particularly preferably from uranyl sulphate or uranyl carbonate.

The preparation of monodisperse ion exchangers is known to those skilled in the art. A distinction is made between, apart from the fractionation of heterodisperse ion exchangers by sieving, essentially two direct preparation methods, namely injection or jetting and the seed feed process in the preparation of the precursors, the monodisperse bead polymers. In the case of the seed feed process, a monodisperse feed which can be produced, for example, by sieving or by jetting is used.

For the purposes of the present patent application, the term monodisperse refers to substances in which the uniformity coefficient of the distribution curve is less than or equal to 1.2. The uniformity coefficient is the ratio of the parameters d 60 and d 10. D 60 describes the diameter at which 60% by mass of the particles in the distribution curve are smaller and 40% by mass are larger or equal. D 10 refers to the diameter at which 10% by mass of the particles in the distribution curve are smaller and 90% by mass are larger or equal.

The monodisperse bead polymer, viz. the precursor of the ion exchanger, can be prepared, for example, by reacting monodisperse, optionally encapsulated monomer droplets comprising a monovinylaromatic compound, a polyvinylaromatic compound and also an initiator or initiator mixture and in the case of the present invention a porogen in aqueous suspension. To obtain macroporous bead polymers for preparing macroporous ion exchangers, the presence of a porogen is absolutely necessary. Prior to the polymerization, the optionally encapsulated monomer droplet is doped with a (meth)acrylic compound and subsequently polymerized. In a preferred embodiment of the present invention, microencapsulated monomer droplets are therefore used for the synthesis of the monodisperse bead polymer. The various methods of preparing monodisperse bead polymers both by the jetting principle and by the seed feed principle are known to those skilled in the art from the prior art. Reference may at this point be made to U.S. Pat. No. 4,444,961, EP-A 0 046 535, U.S. Pat. No. 4,419,245 and WO 93/12167.

The functionalization of the monodisperse bead polymers obtainable according to the prior art to give monodisperse, macroporous anion exchangers of type I or type II is likewise known to those skilled in the art from the prior art.

Thus, EP-A 1 078 688 describes the preparation of monodisperse macroporous anion exchangers by the phthalimide process, in which

a) monomer droplets comprising at least one monovinylaromatic compound and at least one polyvinylaromatic compound and, in the case of the present patent application, a porogen and/or optionally an initiator or an initiator combination are reacted to give a monodisperse, crosslinked bead polymer,

b) this monodisperse, crosslinked bead polymer is amidomethylated by means of phthalimide derivatives,

c) the amidomethylated bead polymer is converted into an aminomethylated bead polymer and

d) the aminomethylated bead polymer is finally alkylated.

In contrast to this ether/oleum variant, the preparation of monodisperse macroporous anion exchangers by the phthalimide process using the ester variant is known from EP-A 0 046 535. Here, the encapsulated bead polymer comprising macroporous, divinylbenzene-crosslinked polystyrene is converted without prior removal of the capsule wall into a strongly basic anion exchanger by the process described in U.S. Pat. No. 3,989,650 by means of amidomethylation using phthalimidomethyl acetate, alkaline hydrolysis and quaternization using chloromethane.

In an alternative embodiment, the monodisperse macroporous anion exchangers used according to the invention can also be prepared by the chloromethylation process described in EP 0 051 210 B2, in which the bead polymers are haloalkylated by means of chloromethyl methyl ether and the haloalkylated polymer is reacted with ammonia or primary amines such as methylamine or ethylamine or a secondary amine such as dimethylamine at temperatures of from 25° C. to 150° C.

The monodisperse macroporous anion exchangers of type I or type II to be used according to the invention can be synthesized by means of these three variants.

The macroporosity required for the anion exchangers to be used according to the invention is obtained as indicated above by the use of porogen during the preparation of the bead polymer precursor. Suitable porogens are organic solvents which do not readily dissolve or swell the polymer obtained. Examples are hexane, octane, isooctane, isododecane, methyl ethyl ketone, butanol or octanol and their isomers. Porogens are in particular organic substances which dissolve in the monomer but do not readily dissolve or swell the polymer (precipitants for polymers), for example aliphatic hydrocarbons (Farbenfabriken Bayer DBP 1045102, 1957; DBP 1113570, 1957).

As an alternative to aliphatic hydrocarbons, it is also possible, according to U.S. Pat. No. 4,382,124, to use alcohols having 4 to 10 carbon atoms as porogens for preparing monodisperse, macroporous bead polymers based on styrene-divinylbenzene. Furthermore, an overview of the preparative methods for macroporous bead polymers is given there.

The distinction between type I and type II anion exchangers has been described in U.S. Pat. No. 4,430,308. For the purposes of the invention, type I resins are resins whose adsorbing sites are quaternary ammonium groups which are substituted by alkyl groups, preferably by C₁-C₄-alkyl groups, particularly preferably by methyl groups.

In contrast thereto, type II resins are ones in which the quaternary ammonium groups have not only alkyl group(s) but also at least one hydroxyalkyl group, preferably a hydroxy-C₁-C₄-alkyl group. The type II resins are preferably ones which have methylenehydroxyalkyldimethylammonium groups as functional groups, with the hydroxyalkyl group having one or two carbon atoms. The type II anion exchangers which are preferably used according to the invention can be prepared by means of the three above-described variants using tertiary amines, preferably dimethylethanolamine or dimethylmethanolamine, as amine.

Metals of value to be isolated according to the invention by means of the monodisperse, macroporous anion exchangers are preferably metals of main groups III to VI and of transition groups 5 to 12 of the Periodic Table of the Elements. Preference is given to winning mercury, iron, titanium, chromium, tin, lead, cobalt, nickel, copper, zinc, cadmium, manganese, uranium, bismuth, vanadium, the platinum group elements ruthenium, osmium, iridium, rhodium, palladium, platinum and also the noble metals gold and silver. According to the invention, particular preference is given to using the monodisperse, macroporous anion exchangers for winning uranium.

Preferred processes for the use of the monodisperse, macroporous anion exchangers to be used according to the invention are resin in pulp processes or in-situ leaching processes, particularly preferably in-situ leaching processes, or the work-up of any water containing metals of value.

The monodisperse, macroporous anion exchangers to be used according to the invention are used in appropriate plants of exploration companies. In the case of the winning of uranium which is particularly preferred according to the invention, the pages http://www.uraniumsa.org/processing/insitu.leaching.htm, http://www.nrc.gov/materials/fuel-cycle-fac/ur-milling.htm or IAEA-TECDOC-1239, “Manual of acid in situ leach uranium mining technology” of the IAEA (International Atomic Energy Agency) of August 2001 give examples of possible configurations of apparatus of existing mines which employ the in-situ leaching process.

As indicated above, the monodisperse, macroporous anion exchangers of type I or type II, in particular of type II, to be used according to the invention surprisingly display a significantly higher adsorption rate for the abovementioned metals of value, in particular for the winning of uranium from in-situ leaching processes, compared to the prior art.

EXAMPLES

Example 1

a) Preparation of the monodisperse, macroporous bead polymer based on styrene, divinylbenzene and ethylstyrene

3000 g of deionized water were placed in a 10 l glass reactor and a solution of 10 g of gelatin, 16 g of disodium hydrogenphosphate dodecahydrate and 0.73 g of resorcinol in 320 g of deionized water was added and mixed in. The temperature of the mixture was brought to 25° C. A mixture of 3200 g of microencapsulated monomer droplets having a narrow particle size distribution and comprising 3.6% by weight of divinylbenzene and 0.9% by weight of ethylstyrene (used as commercial isomer mixture of divinylbenzene and ethylstyrene containing 80% of divinylbenzene), 0.5% by weight of dibenzoyl peroxide, 56.2% by weight of styrene and 38.8% by weight of isododecane (industrial isomer mixture having a high proportion of pentamethyl-heptane) was subsequently added while stirring, with the microcapsule comprising a formaldehyde-cured complex coacervate of gelatin and a copolymer of acrylamide and acrylic acid, and 3200 g of an aqueous phase having a pH of 12 are added. The mean particle size of the monomer droplets was 460 μm.

The mixture was polymerized while stirring by increasing the temperature according to a temperature programme commencing at 25° C. and finishing at 95° C. The mixture was cooled, washed on a 32 μm sieve and subsequently dried at 80° C. under reduced pressure. This gave 1893 g of a spherical polymer having a mean particle size of 440 μm, a narrow particle size distribution and a smooth surface.

The polymer was chalky white in appearance and has a bulk density of about 370 g/l.

1b) Preparation of the amidomethylated bead polymer

2400 ml of dichloroethane, 595 g of phthalimide and 413 g of 30.0% strength by weight formalin were placed in a reaction vessel at room temperature. The pH of the suspension was adjusted to 5.5-6 by means of sodium hydroxide. The water was subsequently removed by distillation. 43.6 g of sulphuric acid were then added. The water formed was removed by distillation. The mixture was cooled. At 30° C., 174.4 g of 65% strength oleum was added, followed by 300.0 g of monodisperse bead polymer prepared according to process step 1a). The suspension was heated to 70° C. and stirred at this temperature for a further 6 hours. The reaction liquor was taken off, deionized water was added and residual amounts of dichloroethane were removed by distillation.

Yield of amidomethylated bead polymer: 1820 ml

Elemental composition determined by analysis: carbon: 75.3% by weight; hydrogen: 4.6% by weight; nitrogen: 5.75% by weight.

1c) Preparation of the aminomethylated bead polymer

851 g of 50% strength by weight sodium hydroxide solution and 1470 ml of deionized water were added to 1770 ml of amidomethylated bead polymer from Example 1b) at room temperature. The suspension was heated to 180° C. and stirred at this temperature for 8 hours.

The bead polymer obtained was washed with deionized water.

Yield of aminomethylated bead polymer: 1530 ml

The total yield, extrapolated, was 1573 ml

Elemental composition determined by analysis: carbon: 78.2% by weight; nitrogen: 12.25% by weight; hydrogen: 8.4% by weight.

Number of mol of aminomethyl groups per litre of aminomethylated bead polymer: 2.13

Number of mol of aminomethyl groups in the total yield of aminomethylated bead polymer: 3.259

A statistical average of 1.3 hydrogen atoms per aromatic ring originating from the styrene and divinylbenzene units were replaced by aminomethyl groups.

1d) Preparation of a monodisperse, macroporous anion exchanger having dimethylaminomethyl groups=type I

1995 ml of deionized water and 627 g of 29.8% strength by weight formalin solution were added to 1330 ml of aminomethylated bead polymer from Example 1c) at room temperature. The mixture was heated to 40° C. It was subsequently heated to 97° C. over a period of 2 hours. A total of 337 g of 85% strength by weight formic acid were added at this temperature. The pH was subsequently set to 1 by means of 50% strength by weight sulphuric acid over a period of 1 hour. At pH 1, the mixture was stirred for another 10 hours. After cooling, the resin was washed with deionized water and freed of sulphate and converted into the OH form by means of sodium hydroxide solution.

Yield of resin having dimethylamino groups: 1440 ml

The total yield, extrapolated, is 1703 ml

The product contains 2.00 mol of dimethylamino groups/litre of resin.

The total number of mol of dimethylamino groups in the total yield of product having dimethylamino groups was 3.406.

Example 2

Preparation of a monodisperse intermediate base macroporous anion exchanger having dimethylaminomethyl groups and trimethylaminomethyl groups=type I

1220 ml of bead polymer bearing dimethylaminomethyl groups from Example 1d), 1342 ml of deionized water and 30.8 g of chloromethane were placed in a reaction vessel at room temperature. The mixture was heated to 40° C. and stirred at this temperature for 6 hours.

Yield of resin bearing dimethylaminomethyl groups and trimethylaminomethyl groups: 1670 ml

The extrapolated total yield was 2331 ml.

Of the nitrogen-containing groups of the product, 24.8% were present as trimethylaminomethyl groups and 75.2% were present as dimethylaminomethyl groups.

The utilizable capacity of the product was: 1.12 mol/litre of resin.

Stability of the resin in the original state: 98 perfect beads in 100

Stability of the resin after the rolling test: 96 perfect beads in 100

Stability of the resin after the swelling stability test: 98 perfect beads in 100

94 percent by volume of the beads of the final product had a size in the range from 0.52 to 0.65 mm.

Example 3

Preparation of a monodisperse strong base macroporous anion exchanger having hydroxyethyldimethylaminomethyl groups=type II

1230 ml of the resin having dimethylaminomethyl groups prepared as described in Example 1d) and 660 ml of deionized water were placed in a reaction vessel. 230.5 g of 2-chloroethanol were added thereto over a period of 10 minutes. The mixture was heated to 55° C. A pH of 9 was set by pumping in 20% strength by weight sodium hydroxide solution. The mixture was stirred at pH 9 for 3 hours, the pH was subsequently set to 10 by means of sodium hydroxide solution and the mixture was stirred at pH 10 for a further 4 hours. After cooling, the product was washed with deionized water in a column and 3 bed volumes of 3% strength by weight hydrochloric acid were then filtered through.

Yield: 1980 ml

The utilizable capacity of the product was: 0.70 mol/litre of resin.

Stability of the resin in the original state: 96 perfect beads in 100

Stability of the resin after the rolling test: 70 perfect beads in 100

Stability of the resin after the swelling stability test: 94 perfect beads in 100

94 percent by volume of the beads of the end product had a size in the range from 0.52 to 0.65 mm.

Example 4

Preparation of a heterodisperse, strong base macroporous anion exchanger having trimethylammonium groups based on styrene-divinylbenzene according to the prior art

4a) Preparation of the bead polymer—use of the initiator dibenzoyl peroxide

1112 ml of deionized water, 150 ml of a 2% strength by weight aqueous solution of methylhydroxyethylcellulose and 7.5 gram of disodium hydrogenphosphate×12 H₂O were placed in a polymerization reactor at room temperature. The total solution was stirred at room temperature for one hour. The monomer mixture comprising 59.61 g of 80.53% strength by weight divinylbenzene, 900.39 g of styrene, 576 g of isododecane and 7.70 g of 75% strength by weight dibenzoyl peroxide was subsequently added. The mixture was firstly left to stand at room temperature for 20 minutes and was then stirred at room temperature at a stirring speed of 2000 rpm for 30 minutes. The mixture was heated to 70° C., stirred at 70° C. for a further 7 hours, then heated to 95° C. and stirred at 95° C. for a further 2 hours. After cooling, the bead polymer obtained was filtered off and washed with water and dried at 80° C. for 48 hours.

The diameter of the beads was in the range from 0.32 to 0.71 mm.

4b) Preparation of the amidomethylated bead polymer

1331 ml of 1,2-dichloroethane, 493.9 g of phthalimide and 347.4 g of 29.6% strength by weight formalin were placed in a reaction vessel at room temperature. The pH of the suspension was adjusted to 5.5-6 by means of sodium hydroxide. The water was subsequently removed by distillation. 36.2 g of sulphuric acid were then added. The water formed was removed by distillation. The mixture was cooled. At 30° C., 132.3 g of 65% strength oleum was added, followed by 317.1 g of heterodisperse bead polymer prepared according to process step 4a). The suspension was heated to 70° C. and stirred at this temperature for a further 6.5 hours. The reaction liquor was taken off, deionized water was added and residual amounts of dichloroethane were removed by distillation.

Yield of amidomethylated bead polymer: 1410 ml

Elemental composition determined by analysis: carbon: 76.8% by weight; hydrogen: 5.0% by weight; nitrogen: 5.4% by weight.

4c) Preparation of the aminomethylated bead polymer

1515.75 g of 24.32% strength by weight sodium hydroxide solution were added to 1385 ml of amidomethylated bead polymer from Example 4b) at room temperature. The suspension was heated to 180° C. over a period of 2 hours and stirred at this temperature for a further 8 hours.

The bead polymer obtained was washed with deionized water.

Yield of aminomethylated bead polymer: 1200 ml

Elemental composition determined by analysis: carbon: 79.3% by weight; nitrogen: 11.2% by weight; hydrogen: 8.4% by weight; balance oxygen.

Aminomethyl group content of the resin: 2.34 mol/l

A statistical average of 1.17 hydrogen atoms per aromatic ring originating from the styrene and divinylbenzene units were replaced by aminomethyl groups.

4d) Preparation of the heterodisperse, strong base, macroporous anion exchanger having trimethylammonium groups

1160 ml of aminomethylated bead polymer from Example 4c) were introduced into 1950 ml of deionized water in an autoclave at room temperature. 501.6 g of chloromethane were added and the suspension was heated to 40° C. At 40° C., the suspension was stirred at a stirring speed of 200 rpm for a further 16 hours. The autoclave was cooled and vented. The resin was filtered off on a sieve, washed with water and transferred to a column. 200 ml of 5% strength by weight aqueous sodium chloride solution were added while swirling. The resin was subsequently classified to remove soluble and solid constituents.

Volume yield: 1620 ml

Stability of the resin in the original state: 99% of whole beads

Stability of the resin after the rolling test: 96% of whole beads

Stability of the resin after the swelling stability test: 98% of whole beads

The diameter of the beads was in the range from 0.35 to 0.85 mm.

Example 5

Preparation of a monodisperse, strong base macroporous anion exchanger having trimethylammonium groups based on styrene-divinylbenzene

1513 ml of deionized water were placed in a reactor. 900 ml of aminomethylated bead polymer from Example 1c) and 263 ml of 50% strength by weight sodium hydroxide solution were added thereto at room temperature. 357 g of chloromethane are subsequently added and the suspension was heated to 40° C. The suspension was stirred at 40° C. for 16 hours and subsequently cooled to room temperature.

The suspension was poured onto a sieve and subsequently washed with deionized water. The anion exchanger was then introduced into a column provided with a glass frit. 1500 ml of 3% strength by weight aqueous HCl were filtered through. The anion exchanger was then classified by means of water to remove solid and dissolved particles.

Volume yield: 1560 ml

Stability of the resin in the original state: 99% of whole beads

Stability of the resin after the rolling test: 97% of whole beads

The diameter of the beads was in the range from 0.57 to 0.67 mm.

Example 6

Determination of the uptake capacity of a heterodisperse, strong base macroporous anion exchanger having trimethylammonium groups based on styrene-divinylbenzene

500 g of a zinc(II) chloride solution which was adjusted to pH 1 by means of hydrochloric acid were placed in a polyethylene bottle. The solution contained 4.2 g of zinc per litre of solution. 10 ml of a heterodisperse, strong base macroporous anion exchanger having trimethylammonium groups based on styrene-divinylbenzene were added to the solution. The mixture was stirred at room temperature for 24 hours.

Samples were taken after 5 hours and 24 hours and analysed to determine their zinc content.

Sample taken after 5 hours: zinc content=4.2 g of zinc per litre of solution—based on the initial concentration, 0% of zinc was taken up.

Sample taken after 24 hours: zinc content=4.1 g of zinc per litre of solution—based on the initial concentration, 2.5% of zinc was taken up.

Example 7

Determination of the uptake capacity of a monodisperse, strong base macroporous anion exchanger having trimethylammonium groups based on styrene-divinylbenzene

500 g of a zinc(II) chloride solution which was adjusted to pH 1 by means of hydrochloric acid were placed in a polyethylene bottle. The solution contained 4.2 g of zinc per litre of solution.

10 ml of a monodisperse, strong base macroporous anion exchanger having trimethylammonium groups based on styrene-divinylbenzene were added to the solution. The mixture was stirred at room temperature for 24 hours.

Samples were taken after 5 hours and 24 hours and analysed to determine their zinc content.

Sample taken after 5 hours: zinc content=3.5 g of zinc per litre of solution—based on the initial concentration, 16.7% of zinc was taken up.

Sample taken after 24 hours: zinc content=3.3 g of zinc per litre of solution—based on the initial concentration, 26.7% of zinc was taken up.

Methods of examination:

Number of perfect beads after preparation

100 beads are viewed under the microscope. The number of beads which have cracks or display spalling is determined. The number of perfect beads is the difference between the number of damaged beads and 100.

Determination of the stability of the resin after the rolling test

The bead polymer to be tested is distributed in a layer of uniform thickness between two plastic cloths. The cloths are placed on a firm, horizontal substrate and subjected to 20 cycles in a rolling apparatus. One cycle consists of one forward and back movement of the roller. After rolling, the number of unscathed beads in 100 beads is determined on representative samples by counting under the microscope.

Swelling stability test

25 ml of anion exchanger in the chloride form are introduced into a column. 4% strength by weight aqueous sodium hydroxide solution, deionized water, 6% strength by weight hydrochloric acid and once again deionized water are introduced in succession into the column, with the sodium hydroxide solution and the hydrochloric acid flowing downwards through the resin and the pure water being pumped through the resin from below. The treatment is sequenced by means of a control apparatus. One cycle takes one hour. 20 cycles are carried out. After the end of the cycles, 100 beads are counted out from the resin sample. The number of perfect beads which are not damaged by cracks or spalling is determined.

Utilizable capacity of strong base and intermediate base anion exchangers

1000 ml of anion exchanger in the chloride form, i.e. the nitrogen atom bears chloride as counterion, are introduced into a glass column. 2500 ml of 4% strength by weight sodium hydroxide solution are filtered through the resin over a period of 1 hour. The resin is subsequently washed with 2 litres debasified, i.e. decationized, water. Water having a total anion hardness of 25 degrees of German hardness is then filtered through the resin at a rate of 10 litres per hour. The eluate is analysed to determine the hardness and also the residual amount of silicic acid. Loading is complete at a residual silicic acid content of ≧0.1 mg/l.

The number of gram of CaO taken up by one litre of resin is determined from the amount of water filtered through the resin, the total anion hardness of the water filtered through and the amount of resin installed. The number of gram of CaO represents the utilizable capacity of the resin in the unit gram of CaO per litre of anion exchanger.

Volume change chloride/OH form

100 ml of anion exchanger bearing basic groups are rinsed into a glass column by means of deionized water. 1000 ml of 3% strength by weight hydrochloric acid are filtered through over a period of 1 hour and 40 minutes. The resin is subsequently washed free of chloride with deionized water. The resin is rinsed under deionized water in a tamping volumeter and jiggled in until the volume was constant—volume V1 of the resin in the chloride form.

The resin is again transferred into the column. 1000 ml of 2% strength by weight sodium hydroxide solution are filtered through. The resin is subsequently washed free of alkali with deionized water until the eluate has a pH of 8. The resin is rinsed under deionized water in a tamping volumeter and jiggled in until the volume is constant—volume V2 of the resin in the free base form (OH form).

Calculation: V1−V2=V3

V3:V1/100=swelling change chloride/OH form in %

Determination of the amount of basic aminomethyl groups in the aminomethylated, crosslinked polystyrene bead polymer

100 ml of the aminomethylated bead polymer are jiggled in on a tamping volumeter and subsequently rinsed into a glass column by means of deionized water. 1000 ml of 2% strength by weight sodium hydroxide solution are filtered through over a period of 1 hour and 40 minutes. Deionized water is subsequently filtered through until 100 ml of eluate admixed with phenolphthalein have a consumption of not more than 0.05 ml of 0.1 N (0.1 normal) hydrochloric acid.

50 ml of this resin are admixed with 50 ml of deionized water and 100 ml of 1 N hydrochloric acid in a glass beaker. The suspension is stirred for 30 minutes and subsequently introduced into a glass column. The liquid is drained. A further 100 ml of 1 N hydrochloric acid are filtered through the resin over a period of 20 minutes. 200 ml of methanol are subsequently filtered through. All eluates are collected and combined and titrated with 1 N sodium hydroxide against methyl orange.

The amount of aminomethyl groups in 1 litre of aminomethylated resin is calculated according to the following formula: (200−V)·20=mol of aminomethyl groups per litre of resin.

Determination of the degree of substitution of the aromatic rings of the crosslinked bead polymer by aminomethyl groups

The amount of aminomethyl groups in the total amount of the aminomethylated resin is determined by the above method.

The number of mol of aromatics present in the amount of bead polymer used, A in gram, is calculated from this amount by division by the molecular weight.

For example, 950 ml of aminomethylated bead polymer containing 1.8 mol of aminomethyl groups per litre are prepared from 300 gram.

950 ml of aminomethylated bead polymer contain 2.82 mol of aromatics.

1.8/2.81=0.64 mol of aminomethyl groups are then present per aromatic.

The degree of substitution of the aromatic rings of the crosslinked bead polymer by aminomethyl groups is 0.64.

Claims

1. A method of using monodisperse, macroporous anion exchangers of type I or type II for winning metals of value, wherein type I denotes resins whose adsorbing sites are quaternary ammonium groups which are substituted by alkyl groups, preferably C1-C4-alkyl groups, and wherein type II denotes resins in which the quaternary ammonium groups have not only alkyl group(s) but also at least one hydroxyalkyl group, preferably a hydroxy-C1-C4-alkyl group.

2. A method according to claim 1, wherein the metals of value belong to main groups III to VI or transition groups 5 to 12 of the Periodic Table of the Elements.

3. A method according to claim 2, wherein the metal of value is uranium.

4. A method according to any of claims 1 to 3, wherein the monodisperse macroporous anion exchangers are used in resin in pulp processes or in in-situ leaching processes or in the work-up of water containing metals of value.

5. A method according to claim 3, wherein the uranium is present as uranyl chloride, uranyl phosphate, uranyl acetate, uranyl carbonate, uranyl sulphate or uranyl nitrate.

6. A process for winning metals of value by the resin in pulp process or the in-situ leaching process or from water containing metals of value, wherein monodisperse, macroporous anion exchangers of type I or type II, preferably of type II, are used, and type I denotes resins whose adsorbing sites are quaternary ammonium groups which are substituted by alkyl groups, preferably C1-C4-alkyl groups, and type II denotes resins in which the quaternary ammonium groups have not only alkyl group(s) but also at least one hydroxyalkyl group, preferably a hydroxy-C1-C4-alkyl group.

7. A process according to claim 6, wherein the anion exchangers of type II are functionalized by tertiary amines, preferably dimethylethanolamine or dimethylmethanolamine.

8. A process according to claim 6 or 7, wherein metals of value of main groups III to VI and transition group 5 to 12 of the Periodic Table of the Elements are won.

9. A process according to claim 6, wherein uranium is won as metal of value.