EP1656201A1

EP1656201A1 - Arsenic-adsorbing ion exchanger

Info

Publication number: EP1656201A1
Application number: EP04735569A
Authority: EP
Inventors: Reinhold Klipper; Andreas Schlegel; Wolfgang Podszun; Rüdiger Seidel
Original assignee: Lanxess Deutschland GmbH
Current assignee: Lanxess Deutschland GmbH
Priority date: 2003-06-13
Filing date: 2004-06-01
Publication date: 2006-05-17
Also published as: US20060273014A1; WO2004110623A1; DE10327110A1; CN1835803A; US20060173083A1; JP2006527078A

Abstract

The invention relates to a method for producing an ion exchanger carrying carboxyl groups and containing iron oxide/iron oxyhydroxide, said method being characterised in that a) a bead-type ion exchanger containing carboxyl groups in an aqueous suspension is brought into contact with iron-(III)-salts, or a`) an aminomethylated, cross-linked polystyrol bead polymer in an aqueous suspension is brought into contact with iron-(III)-salts and chloroacetic acid, and b) the pH values of the suspensions obtained in steps a) or a`) are adjusted to between 3 and 14 by adding alkali hydroxides or alkaline-earth hydroxides, and the obtained ion exchangers containing iron oxide/iron oxyhydroxide are isolated according to known methods. The invention also relates to such ion exchangers, and to the use thereof for the adsorption of heavy metals, especially arsenic.

Description

Arsenic adsorbing ion exchangers

The present invention relates to a method for producing iron oxide / iron oxyhydroxide-containing carboxyl group-carrying ion exchangers, which is characterized in that

a) a pearl-shaped carboxyl group-containing ion exchanger in aqueous suspension with iron (III) salts in contact or

a ') an aminomethylated, crosslinked polystyrene bead polymer in aqueous suspension with iron (III) salts and with chloroacetic acid and

b) the suspensions obtained from stages a) or a ') are adjusted to pH values in the range from 3 to 14 by adding alkali metal or alkaline earth metal hydroxides and the iron oxide / iron oxyhydroxide-containing ion exchangers obtained are isolated by known methods.

The requirements for the purity of drinking water have increased significantly in recent decades. Health authorities in numerous countries have developed limit values for heavy metal concentrations in water. This also affects arsenic.

Under certain conditions, arsenic compounds can be leached out of rocks and thus get into the groundwater. Arsenic occurs in natural waters as an oxidic compound with trivalent and pentavalent arsenic. It shows that the species H ₃ AsO ₃ , H ₂ AsO ₃ ^" , H ₂ AsO ₄ ^" , HAsO ₄ ^{2 "} mainly occur at the pH values prevailing in natural waters.

Easily absorbable As compounds are highly toxic and carcinogenic.

In many regions of the USA, India, Bangladesh, China as well as in South America there are partly high concentrations in the groundwater.

Numerous medical studies now prove that pathological skin changes (hyperkeratoses) and various types of tumors can develop in people who have been exposed to such stress for a long time as a result of chronic arsenic poisoning.

Based on medical studies, the World Health Organization recommended in 1992 that a limit value for arsenic in drinking water of 10 μg / L be introduced worldwide. In many European countries and in the USA, this value is still exceeded. In Germany 10 μg / L have been observed since 1996, in EU countries the limit of 10 μg / L applies from 2003, in the USA from 2006.

Ion exchangers are used in a variety of ways to purify raw water, waste water and aqueous process streams. They are particularly effective in softening and desalination. Chelate resins are preferably used in hydrometallurgy for the adsorption of metal, in particular heavy metal or noble metal ions and their compounds from aqueous solutions or organic media.

However, they do not show the desired and necessary selectivity for all ions. Arsenic ions in particular cannot be sufficiently removed with ion exchangers / chelate resins.

I. Rau et al, Reactive & Functional Polymers 54, (2003) 85-94 describe the removal of arsenate ions with chelate resins with iminodiacetic acid groups which have been chelated with iron (III) ions. In their manufacture, the chelate resin is coated with iron (III) ions in the acid form with iminodiacetic acid groups (chelated). An iron oxide / iron oxy hydroxide phase, which is highly specific for arsenic, is not formed here, since care is taken not to exceed the pH value of 2 when coated with Fe (III) ions (same document, page 87).

This adsorber is therefore not able to remove arsenic ions from aqueous solutions except for the necessary residual amounts.

There is therefore a need for new ion exchangers or adsorbers in pearl formings which are highly specific for arsenic ions and which have a lower pressure drop, no abrasion, high mechanical and osmotic stability, and a significantly lower pressure drop than the ion exchangers according to the prior art in column processes and moreover besides arsenic can also adsorb other heavy metals.

The object of the present invention is now to provide an ion exchange resin for the removal of pollutants, preferably heavy metals, in particular arsenic, from liquids, preferably aqueous media or gases, and to provide a process for its production.

It has now been found a process for the preparation of iron exchangers containing iron oxide / iron oxyhydroxide containing carboxyl groups, which is characterized in that a) a pearl-shaped carboxyl group-containing ion exchanger in aqueous suspension with iron (III) salts in contact or

a ") an aminomethylated, crosslinked polystyrene bead polymer in aqueous suspension with iron (HI) salts and with chloroacetic acid and

b) the suspensions obtained from stages a) or a ^Λ ) are adjusted to pH values in the range from 3 to 14 by adding alkali metal or alkaline earth metal hydroxides and the iron oxide / iron oxyhydroxide-containing ion exchanger obtained is isolated by known methods.

In the case of the pearl-shaped carboxyl group-containing ion exchanger, steps a) and b) can optionally be carried out several times in succession. As an alternative to the iron (III) salt, iron (II) salts can also be used which are wholly or partially oxidized to iron-IH salts in the reaction medium by known oxidation processes.

The bead polymers obtained are colored brown and, in contrast to the prior art mentioned above, are distinguished by the formation of a highly specific iron oxide / iron oxy hydroxide phase for the adsorption of heavy metals, preferably arsenic.

According to the invention, heterodisperse or monodisperse carboxyl group-containing ion exchangers or heterodisperse or monodisperse aminomethylated polystyrene bead polymers can be used.

In the present application, monodisperse ion exchangers are referred to as bead-shaped resins in which at least 90% by volume or mass of the particles have a diameter which lies in the interval with the width of + 10% of the most common diameter around the most common diameter.

For example, resin beads with the most common diameter of 0.5 mm are at least 90% by volume or mass in a size interval between 0.45 mm and 0.55 mm, with resin beads with the most common diameter of 0.7 mm are at least 90 Volume or mass% in a size interval between 0.77 mm and 0.63 mm.

Weakly acidic ion exchangers based on cross-linked pory (meth) acrylic acid are suitable as carboxyl group-containing ion exchangers for process step a). Crosslinked (meth) acrylic acid esters and (meth) acrylonitrile are used to produce the same. - A -

As (meth) acrylic acid esters, unsaturated aliphatic (meth) acrylic acid esters, in particular methyl acrylic acid, ethyl acrylic acid and methyl methacrylate are used. Unsaturated aliphatic nitriles of the formula (I) are used as (meth) acrylonitrile.

Unsaturated, aliphatic nitriles are characterized by the general formula (I),

wherein

A, B and C are each independently for. Are hydrogen, alkyl or halogen.

For the purposes of the present invention, alkyl means straight-chain or branched alkyl radicals having 1 to 8 carbon atoms, preferably having 1 to 4 carbon atoms. Halogen in the sense of the present invention means chlorine, fluorine and bromine.

Preferred nitriles for the purposes of the present invention are acrylonitrile or methacrylonitrile, acrylonitrile is particularly preferably used.

Divinyl group-bearing aliphatic or aromatic compounds are used as crosslinkers. These include divinylbenzene, hexadiene 1.5, octadiene 1.7, 2,5-dimethyl-1,5-hexadiene and divinyl ether.

Suitable divinyl ethers are compounds of the general formula (II)

^ o ^{/ Rχ} o (ID

wherein

R stands for a radical of the series C _n H _{2n 3} (C _m H _2m -O) pC _ni H _2m or CH ₂ -C ₆ H ₄ -CH ₂ and n> 2, m = 2 to 8 and p> 1 ,

Suitable polyvinyl ethers in the case of n> 2 are trivinyl ethers of glycerol, trimethylolpropane or tetravinyl ether of pentaerythritol.

Divinyl ethers of ethylene glycol, di-, tetra- or polyethylene glycol, butanediol or poly-THF or the corresponding tri- or tetravinyl ethers are preferably used. Particularly preferred are the divinyl ethers of butanediol and diethylene glycol as described in EP-A 11 10 608.

The reaction (saponification) of the acrylic polymer-containing bead polymers can be carried out with acids or alkalis.

Descriptions of the manufacture of weakly acidic ion exchangers are given in Ulimann's Encyclopedia of Industrial Chemistry (Ullmann's Encyclopaedia of Industrial Chemistry), 5th edition volume 14, page 393 ff; US-A 2,885,371, DDR Patent 79,584, US-A 3427262 and EP-A 11 10 608.

In process step a) it is also possible to use carboxyl group-containing chelation exchangers which contain aminoacetic acid and / or iminodiacetic acid groups. Chelate resins with acetic acid groups are preferably prepared by functionalizing crosslinked styrene / divinylbenzene bead polymers.

EP-A 0 980 711 and EP-A 1 078 690 describe the reaction of crosslinked heterodisperse or monodisperse crosslinked bead polymers based on styrene / divinylbenzene using the phthalimide process to form chelate resins with groups of acetic acid. The content of both documents is included in the present application.

Alternatively, US Pat. No. 4,444,961 describes, for example, a reaction of crosslinked, macroporous bead polymers by the chloromethylation process to give chloromethylated bead polymer and the subsequent reaction with iminodiacetic acid to form chelate resins with acetic acid groups, the content of which is included in the present application.

According to the invention, macroporous ion exchangers are preferably used.

Macroporous bead polymers can be formed, for example, by adding inert materials (porogens) to the monomer mixture during the polymerization. Organic substances which dissolve in the monomer but dissolve or swell the polymer poorly (precipitants for polymers), for example aliphatic hydrocarbons (paint factories Bayer DBP 1045102, 1957; DBP 1113570, 1957), are particularly suitable as such.

An aminomethylated, crosslinked polystyrene bead polymer suitable for process step a ¹ ) can be prepared, for example, as follows: First, the amidomethylation reagent is prepared. For this purpose, for example, phthalimide or a phthalimide derivative is dissolved in a solvent and mixed with formalin. A bis (phthalimido) methyl ether is then formed from this with elimination of water. The bis (phthalimido) methyl ether can optionally be converted to the phthalimido ester. Preferred phthalimide derivatives are phthalimide itself or substituted phthalimides, for example methylphthalimide.

Inert solvents are used as solvents which are suitable for swelling the polymer, preferably chlorinated hydrocarbons, particularly preferably dichloroethane or methylene chloride. Further details can be found in EP-A 0 980 711 and EP-A 10 78 690.

In a preferred embodiment of the present invention, the bead polymer is condensed with phthalimide derivatives. Oleum, sulfuric acid or sulfur trioxide is used as the catalyst.

The cleavage of the phthalic acid and the aminomethyl is effected in this case by treating the phthalimidomethylated crosslinked bead polymer with aqueous or alcoholic solutions of an alkali hydroxide such as sodium hydroxide or potassium hydroxide at temperatures between 100 and 250 ⁰ C, preferably 120-190 ⁰ C. The concentration the sodium hydroxide solution is in the range from 10 to 50% by weight, preferably 20 to 40% by weight. This process enables the production of crosslinked bead polymers containing aminoallςyl groups with a substitution of aromatic nuclei greater than 1.

The resulting aminomethylated polymer beads can be washed with deionized water without alkali.

All soluble iron (III) salts can be used as iron (III) salts in process step a) or a '), in particular iron (III) chloride, sulfate, nitrate are used.

All soluble iron (II) salts can be used as iron (II) salts, in particular iron (II) chloride, sulfate, and nitrate are used. The iron (IΙ) salts in the suspension in process step a) or a ') are preferably oxidized by air.

The iron (II) salts or iron (III) salts can be used in bulk or as aqueous solutions.

The concentration of the iron salts in aqueous solution is freely selectable. Solutions with iron salt contents of 10 to 20% by weight are preferably used.

The dosage of the aqueous iron salt solution is not critical in terms of time. Depending on the technical circumstances, this can be done as quickly as possible. 0.1 to 2 mol, preferably 0.5 to 1.3 mol, of alkali metal or alkaline earth metal hydroxides are used per mol of iron salt used.

0.1 to 1.5 mol, preferably 0.3 to 0.8 mol, of iron salt are used per mol of carboxyl group in the ion exchanger.

In process step a '), aminorαethylated, crosslinked bead polymers are loaded with iron (III) ions in aqueous suspension and additionally reacted with chloroacetic acid in an alkaline medium to give a bead polymer which contains both chelating iminoacetic acid groups and iron oxide / iron hydroxide.

2 to 3 moles of chloroacetic acid, preferably 2 to 2.5 moles of chloroacetic acid, are used per mole of aminomethyl groups in the aminomethylated ion exchanger.

The chloroacetic acid, preferably monochloroacetic acid, is metered in over a period of 2 to 6 hours, preferably 3 to 5 hours. Chloroacetic acid is dosed at temperatures between 60 and 100 ⁰ C, preferably at temperatures between 75 and 95 ° C.

The suspensions obtained from process steps a) and a ') have a pH of <3.

The pH value in process step b) is adjusted using alkali or alkaline earth hydroxides; especially potassium hydroxide, sodium hydroxide or calcium hydroxide. ^'

The pH value range in which iron oxide / iron oxyhydroxide groups are formed is in the range between 3 and 14, preferably 3 and 8, particularly preferably between 4 and 7.

0.1 to 2 mol, preferably 0.5 to 1.3 mol, of alkali metal or alkaline earth metal hydroxide are used per mol of iron salt used.

The substances mentioned are preferably used as aqueous solutions.

The concentration of the aqueous alkali metal hydroxide or alkaline earth metal hydroxide solutions can be up to 50% by weight. Aqueous solutions with an alkali hydroxide or alkaline earth hydroxide concentration in the range from 10 to 20% by weight are preferably used.

The rate of dosing of the aqueous solutions of alkali or alkaline earth hydroxide depends on the level of the desired pH value and the technical conditions. For example, 60 minutes are required. After the desired pH has been reached, stirring is continued for 0.1 to 10 hours, preferably 1 to 4 hours.

The aqueous solutions of alkali or alkaline earth hydroxide are metered in at temperatures between 15 and 95 ° C., preferably at 20 to 50 ° C.

Per milliliter or carboxyl Ammomethylgruppen-carrying ion exchange resin are used from 0.5 to 3 ml of deionized water to .a ^'good stirrability to reach the resin.

Without proposing a mechanism for the present application, in process step b) it is likely that the pH change in the pores of the ion exchange resins leads to the formation of FeOOH compounds which have freely accessible OH groups on the surface. The arsenic removal then probably takes place via an exchange OH ^" for HAsO ₄ ^2" or H ₂ AsO ₄ ^" with the formation of an AsO-Fe bond.

Equally capable of ion exchange are also to HAsO ₄ ^{2 "} or H ₂ AsO ₄ ^" isostructural ions such as z. B. H ₂ PO ₄ ^" , VO, MoO, WO, SbO anions.

According to the invention, NaOH or KOH is preferably used as the base. However, any other base which leads to the formation of FeOH groups can also be used, such as NH ₄ OH, Na ₂ CO ₃ , CaO, Mg (OH) ₂ etc.

Isolating in the sense of the present invention means separating the ion exchanger from the aqueous suspension and cleaning it. The separation takes place according to the measures known to those skilled in the art, such as decanting, centrifuging, filtering. The cleaning is carried out by washing with, for example, deionized water and can include a classification for separating fine or coarse fractions. Optionally, the iron oxide / iron oxyhydroxide-containing ion exchangers can be dried, preferably by reduced pressure and / or more preferably at temperatures between 20 ⁰ C and 18O ⁰ C.

However, the present invention also relates to the products obtainable by the process according to the invention, namely iron oxides / iron oxyhydroxide-containing carboxyl-bearing ion exchangers obtainable by contacting them

a) a pearl-shaped carboxyl group-containing ion exchanger in aqueous suspension with iron (III) salts or a ') an aminomethylated, crosslinked polystyrene bead polymer in aqueous suspension with iron (III) salts and with chloroacetic acid and

b) ^" Adding alkali metal or alkaline earth metal hydroxides to the suspensions obtained from steps a) or a ') and adjusting a pH in the range from 3 to 14 and isolating the iron oxide / iron oxyhydroxide-containing ion exchangers obtained by known methods.

Surprisingly, the iron exchangers / iron oxyhydroxide-containing ion exchangers according to the invention not only adsorb arsenic in its various forms but also heavy metals such as cobalt, nickel, lead, zinc, cadmium, copper.

The iron oxide / iron oxyhydroxide-containing ion exchangers according to the invention can be used for cleaning drinking water from wastewater streams from the chemical industry and from waste incineration plants. Another application of the ion exchanger according to the invention is the purification of leachate from landfills.

The iron oxide / iron oxyhydroxide-containing ion exchangers according to the invention are preferably used in devices suitable for their tasks.

The invention therefore also relates to devices through which a liquid to be treated can flow, preferably filtration units, particularly preferably adsorption containers, in particular filter adsorption containers, containing ion exchangers containing iron oxide / iron oxyhydroxide, obtainable by the process described in this application, for removing heavy metals, in particular arsenic, from aqueous solutions Media, preferably drinking water or gases are used. The devices can e.g. connected to the sanitary and drinking water supply in the household.

According to the invention, the ion exchangers containing iron oxide / iron oxyhydroxide can be used in combination with other adsorbents, such as activated carbon. The present invention therefore also relates to devices through which a liquid to be treated can flow, which in addition to iron oxide / iron oxyhydroxide-containing ion exchangers contain further adsorbents.

To measure the adsorption of arsenic (III) and arsenic (V) in a 5L PE bottle (L = liter) 3L of an aqueous solution of NaAsO ₂ or Na ₂ HAsO ₄ with the specified concentration of approx. 2-3 mg / L arsenic treated with 3 g of the sample to be examined and the bottle in motion on rotating rollers added. The adsorption rate of As ions on iron hydroxide over a certain period of time is given.

Examples

example 1

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

3000 g of fully demineralized water are 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 is added and mixed. The mixture is heated to 25 ⁰ C. A mixture of 3200 g of microencapsulated monomer droplets with a narrow particle size distribution of 3.6% by weight of divinylbenzene and 0.9% by weight of ethylstyrene (used as a commercially available mixture of isomers of divinylbenzene and ethylstyrene with 80% divinylbenzene), 5% by weight of dibenzoyl peroxide, 56.2% by weight of styrene and 38.8% by weight of isododecane (technical isomer mixture with a high proportion of pentamethylheptane), the microcapsule consisting of a complex coacervate of gelatin and a copolymer which is hardened with formaldehyde There is acrylamide and acrylic acid, and 3200 g of aqueous phase with a pH of 12 are added. The average particle size of the monomer droplets is 460 μm.

The batch is polymerized with stirring by increasing the temperature according to a temperature program at 25 ^° C. and ending at 95 ^° C. The mixture is cooled, washed over a 32 μm sieve and then dried in vacuo at 80 ^° C. 1893 g of a spherical polymer having an average particle size of 440 μm, a narrow particle size distribution and a smooth surface are obtained.

The polymer is chalky white when viewed from above and has a bulk density of approx. 370 g / l.

Example Ia '

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

3000 g of fully demineralized water are placed in a 10 L glass reactor and a solution of 10 g of gelatin, 16 g of di-sodium hydrogenphosphate dodecahydrate and 0.73 g of resorcinol in 320 g of deionized water are added and mixed. The mixture is heated to 25 ° C. A mixture of 3200 g of microencapsulated monomer droplets with a narrow particle size distribution of 8.0% by weight of divinylbenzene and 2.0% by weight of ethylstyrene (used as a commercially available mixture of isomers of divinylbenzene and Ethyl styrene with 80% divinylbenzene), 0.5% by weight of dibenzoyl peroxide, 52.0% by weight of styrene and 37.5% by weight of isododecane (technical isomer mixture with a high proportion of pentamethylheptane), the microcapsule consisting of a Formaldehyde-hardened complex coacervate consists of gelatin and a copolymer of acrylamide and acrylic acid, and 3200 g of aqueous phase with a pH of 12 are added. The average particle size of the monomer droplets is 460 μm.

The batch is polymerized with stirring by increasing the temperature according to a temperature program at 25 ° C. and ending at 95 ° C. The mixture is cooled, washed over a 32 μm sieve and then dried in vacuo at 80 ^° C. 1893 g of a spherical polymer having an average particle size of 440 μm, a narrow particle size distribution and a smooth surface are obtained.

Ib) Preparation of the amidomethylated bead polymer

2373 g of dichloroethane, 705 g of phthalimide and 505 g of 29.2% by weight formalin are initially introduced at room temperature. The pH of the suspension is adjusted to 5.5 to 6 with sodium hydroxide solution. The water is then removed by distillation. Then 51.7 g of sulfuric acid are added. The resulting water is removed by distillation. The batch is cooled. At 30 ⁰ C. 189 g of 65 wt .-% oleum and then 371.4 g of monodisperse polymer beads produced by process step Ia) or Ia ') metered. The suspension is heated to 70 ^° C. and stirred at this temperature for a further 6 hours. The reaction broth is drawn off, deionized water is metered in and residual amounts of dichloroethane are removed by distillation.

Yield of amidomethylated bead polymer: 2140 ml

Elemental analysis composition:

Carbon: 75.3% by weight;

Hydrogen: 4.9% by weight;

Nitrogen: 5.8% by weight;

Rest: oxygen. Ic) Preparation of the aminomethylated bead polymer

1019 g of 45% strength by weight sodium hydroxide solution and 406 ml of fully demineralized water are metered into 2100 ml of amidomethylated bead polymer at room temperature. The ^'suspension is heated to 180 ⁰ C and stirred for 6 hours at this temperature.

The bead polymer obtained is washed with deionized water.

Yield of aminomethylated bead polymer: 1770 ml

The total yield - extrapolated - is 1804 ml

Elemental analytical composition: nitrogen: 11.75% by weight

From the elemental analytical composition of the aminomethylated bead polymer it can be calculated that, on a statistical average, 1.17 hydrogen atoms per aromatic nucleus - originating from the styrene and divinylbenzene units - were substituted by aminomethyl groups.

Id) Preparation of the ion exchanger with chelating iminodiacetic acid groups

1180 ml of aminomethylated polymer beads from Example Ic) are metered into 1890 ml of completely deionized water at room temperature. 729.2 g of sodium salt of monochloroacetic acid are metered into this suspension. The mixture is stirred at room temperature for 30 minutes. Then the pH of the suspension is adjusted to pH 10 with 20% by weight sodium hydroxide solution. The suspension is heated to 80 ^° C. in 2 hours. The mixture is then stirred at this temperature for a further 10 hours. During this time, the pH is kept at 10 by controlled addition of sodium hydroxide solution.

The suspension is then cooled. The resin is washed free of chloride with deionized water.

Yield: 2190 ml

Total resin capacity: 2.39 mol / 1 resin

Example 2

Production of a chelate resin of the iminodiacetic acid type loaded with iron oxide / iron oxyhydroxide 400 ml of the chelating resin produced according to Example 1 with iminodiacetic acid groups are containing with 750 ml of aqueous iron (III) chloride solution, which 103.5 g of iron (III) chloride per liter, and added 750 mL of deionized water and 2.5 ^■ Stirred for hours at room temperature. A pH of 6 is then set with 10% strength by weight sodium hydroxide solution and held for 2 hours.

The ion exchanger is then filtered off through a sieve and washed with deionized water until the process is clear.

Resin yield: 380 ml

The Fe content of the loaded ion exchange beads was determined titrimetrically to be 14.4%.

Powder diffractograms identify α-FeOOH as the crystalline phase.

13.1 g of the ion exchanger, of which about 3.0 g is FeOOH, were brought into contact with an aqueous solution of Na ₂ HAsO ₄ and the decrease in the As (V) concentration was recorded over time.

Example 3

Production of a weakly acidic ion exchanger with carboxyl groups containing iron oxide / iron oxyhydroxide

300 ml of a weakly acidic ion exchanger with carboxyl groups, prepared according to EP-AI l 10 608, with 1500 ml of aqueous iron (III) chloride solution, which contains 103.5 g of iron (III) chloride per liter, and with 750 ml of deionized Water added. This mixture is stirred for 2.5 hours at room temperature. A pH of 6 is then set with 10% strength by weight sodium hydroxide solution and held for 120 minutes.

The ion exchanger is then filtered off through a sieve and washed with deionized water until neutral or until the process is clear. Resin yield: 240 ml

% By weight of iron in the resin: 12.0

Powder diffractograms identify α-FeOOH as the crystalline phase.

Example 4

Production of an iron oxide / iron oxyhydroxide-containing chelate resin of the iminodiacetic acid type

500 ml of an aminomethylated bead polymer prepared according to Example Ic are introduced into 375 ml of deionized water. 750 ml of aqueous iron (III) chloride solution containing 103.5 g of iron (III) chloride per liter are added. The suspension is heated to 90 ^° C. At 90 ^° C., 268 g of monochloroacetic acid are metered in within 4 hours. The pH is adjusted to 9.2 with 50% by weight aqueous KOH solution. When the dosing has ended, the temperature is heated to 95 ° C .; the pH is adjusted to 10.5 and the mixture is stirred for a further 6 hours at 95 ° C. and pH 10.5.

After cooling, the resin is filtered off and washed neutral with deionized water.

Resin content: 750 ml

% By weight of iron in the resin: 1.2

Powder diffractograms identify α-FeOOH as the crystalline phase.

Claims

claims

1. A process for the preparation of an iron oxide / iron oxyhydroxide-containing carboxyl group-bearing ion exchanger, characterized in that

a) ^• brings a pearl-shaped carboxyl group-containing ion exchanger in aqueous suspension into contact with iron (III) salts or

a) an aminomethylated, crosslinked polystyrene bead polymer in aqueous suspension with iron (III) salts and with chloroacetic acid and

b) the suspensions obtained from stages a) or a ^{^} ) are adjusted to pH values in the range from 3 to 14 by adding alkali metal or alkaline earth metal hydroxides and the iron oxide / iron oxyhydroxide-containing ion exchanger obtained is isolated by known methods.

2. Contact iron oxide / iron oxyhydroxide-containing carboxyl group-bearing ion exchangers obtainable by contact

a) a pearl-shaped carb.oxyl group-containing ion exchanger in aqueous suspension with iron (III) salts or

&) an aminomethylated, crosslinked polystyrene bead polymer in aqueous suspension with iron (III) salts and with chloroacetic acid and

b) addition of alkali or alkaline earth metal hydroxides to the suspensions obtained from steps a) or a ')

and setting a pH in the range from 3 to 14 and isolating the iron oxide / iron oxyhydrogen oxide ion exchanger obtained by known methods.

3. Use of the iron oxide / iron oxyhydroxide-containing ion exchanger for adsorbing pig metals, preferably arsenic, cobalt, nickel, lead, zinc, cadmium, copper.

4. Devices, preferably filtration units, containing iron oxide / iron oxyhydroxide-containing ion exchangers according to claim 2, characterized in that they are used to remove heavy metals, preferably arsenic, from aqueous media or gases. ^■

5. Use of the iron oxide / iron oxyhydroxide-containing ion exchanger according to claim 3, characterized in that these are used in combination with other adsorbents.

6. The devices according to claim 4, characterized in that they contain, in addition to the iron oxide / iron oxyhydroxide-containing ion exchangers, further adsorbents.

7. Use of the devices according to claims 4 or 6 in the sanitary and drinking water supply.