Caesium selective resin

Abstract

The invention relates to ion exchangers laden with transition metal hexacyanoferrate complexes, to processes for the production thereof and to the use of these ion exchangers for removal and purification of cesium ions.

Claims

1. An ion exchanger comprising: polymers having functional groups of formula (I) ##STR00004## wherein: represents a polystyrene copolymer scaffold; and R.sup.1 and R.sup.2 are identical or different and independently of one another represent methyl and/or ethyl, and where a degree of substitution as indicated by a ratio of unsubstituted to alkylated amino groups is 1.1 to 1.6, and at least one cobalthexacyanoferrate complex.

2. The ion exchanger as claimed in claim 1, wherein the ion exchanger contains cobalthexacyanoferrate complex in an amount of 0.5 wt % to 10 wt % based on the dry weight of the ion exchanger.

3. The ion exchanger as claimed in claim 1, wherein the ion exchanger has an iron content of 0.5 wt % to 10 wt % based on the dry weight of the ion exchanger.

4. The ion exchanger as claimed in claim 1, wherein the polystyrene copolymer scaffold represents a styrene/divinylbenzene crosslinked copolymer.

5. The ion exchanger as claimed in claim 1, wherein the polymer of the ion exchanger is macroporous.

6. The ion exchanger as claimed in claim 1, wherein the cobalthexacyanoferrate complex is cobalt hexacyanoferrate (II) complex.

7. A process for producing the ion exchangers according to claim 1, the process comprising contacting an ion exchanger containing polymer having functional groups of formula (I) ##STR00005## wherein .sup.a represents a polystyrene copolymer scaffold, and R.sup.1 and R.sup.2 are identical or different and independently of one another represent methyl and/or ethyl, with at least one transition cobalt salt, and at least one alkali metal or ammonium hexacyanoferrate in an aqueous medium and wherein and a degree of substitution indicated by a ratio of unsubstituted to alkylated amino groups is 1.1 to 1.6.

8. The process for producing the ion exchanger as claimed in claim 7, wherein the process comprises: a) converting monomer droplets composed of at least one monovinylaromatic compound and at least one polyvinylaromatic compound and at least one initiator into a bead polymer, b) phthalimidomethylating the bead polymer from step a) with phthalimide derivatives, c) converting the phthalimidomethylated bead polymer from step b) into an aminomethylated bead polymer, d) optionally reacting the aminomethylated bead polymer by alkylation to afford ion exchangers having tertiary amino groups, e) loading the ion exchanger from step c) or step d) with at least one divalent or trivalent cobalt metal salt in an aqueous medium to produce a transition metal-containing ion exchanger, and f) reacting the transition cobalt-metal-containing ion exchanger from step e) with at least one alkali metal or ammonium hexacyanoferrate.

9. The process for producing the ion exchanger as claimed in claim 7, wherein the transition metal salts in step e) are selected form the group consisting of cobalt (II) sulfate, cobalt (II) chloride, cobalt (II) bromide, cobalt (III) sulfate, cobalt (III) chloride, cobalt (III) bromide, cobalt (II) nitrate, cobalt (III) nitrate, and hydrates and mixtures thereof.

10. The process for producing the ion exchanger as claimed in claim 7, wherein the alkali metal hexacyanoferrate in step f.) is selected from the group consisting of potassium hexacyanoferrate (II), potassium hexacyanoferrate (III), sodium hexacyanoferrate (II), sodium hexacyanoferrate (III), and hydrates and mixtures thereof.

11. The use of the ion exchangers as claimed in claim 1 for removal and purification of cesium ions.

Description

EXAMPLES

Example 1

(1) 1a) Production of a Monodisperse, Macroporous Bead Polymer Based on Styrene, Divinylbenzene and Ethyistyrene

(2) A 10 l glass reactor is initially charged with 3000 g of demineralized water, 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 commixed. The mixture is temperature-controlled to 25 C. Subsequently, with stirring, a mixture of 3200 g of microencapsulated monomer droplets having a narrow particle size distribution composed of 3.6 wt % of divinylbenzene and 0.9 wt % of ethyistyrene (employed in the form of a commercial isomer mixture of divinylbenzene and ethyistyrene comprising 80% divinylbenzene), 0.5 wt % of dibenzoyl peroxide, 56.2 wt % of styrene and 38.8 wt % of isododecane is added, wherein the microcapsule consists of a formaldehyde-hardened complex coacervate composed of gelatin and a copolymer of acrylamide and acrylic acid, and 3200 g of aqueous phase having a pH of 12 are added.

(3) The mixture is stirred and polymerized to completion by increasing the temperature in accordance with a temperature program commencing at 25 C. and terminating at 95 C. The mixture is cooled, washed over a 32 m sieve and then dried at 80 C. under reduced pressure. 1893 g of a spherical polymer having a narrow particle size distribution and a smooth surface are obtained.

(4) The polymer is chalky white in appearance and has a bulk density of about 370 g/I.

(5) 1b) Production of an Amidomethylated Bead Polymer

(6) 2218 ml of dichloroethane, 823 g of phthalimide and 569 g of 30 wt % formalin are initially charged 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. This is followed by metered addition of 60.4 g of sulfuric acid. The water formed is removed by distillation. The batch is cooled. At 30 C., 255 g of 65% oleum followed by 424 g of monodisperse bead polymer produced according to process step 1a) are metered in. The suspension is heated to 70 C. and stirred at this temperature for a further 6 hours. The reaction broth is drawn off, demineralized water is metered in and residual dichloroethane is removed by distillation.

(7) Yield of amidomethylated bead polymer. 2580 ml

(8) 1c) Production of an Aminomethylated Bead Polymer

(9) Metered into 2545 ml of amidomethylated bead polymer from 1b) at room temperature are 1454 g of 50 wt % sodium hydroxide solution and 1340 ml of demineralized water. The suspension is heated to 180 C. over 2 hours and stirred at this temperature for 8 hours.

(10) The obtained bead polymer is washed with demineralized water.

(11) Yield of aminomethylated bead polymer: 2155 ml

(12) Determination of amount of basic groups: 2.41 mol/liter of resin

(13) 1d) Production of a Bead Polymer Having Tertiary Amino Groups

(14) In a reactor 450 ml of deionized water, 900 ml of aminomethylated bead polymer from 1c) and 270 g of 30 wt % formalin solution are initially charged at room temperature. The suspension is heated to 40 C. The pH of the suspension is adjusted to pH 3 by metered addition of 85 wt % of formic acid. Over 2 hours the suspension is heated to reflux temperature (97 C.). During this time, the pH is maintained at 3.0 by metered addition of formic acid. Once reflux temperature has been reached the pH is adjusted to pH 2 initially by metered addition of formic acid, then by metered addition of 50 wt % sulfuric acid. The mixture is stirred at pH 2 for a further 30 minutes. A further 50 wt % sulfuric acid is then metered in and the pH is adjusted to pH 1. At pH 1 and reflux temperature stirring is continued for a further 10 hours.

(15) The batch is cooled, the resin is filtered-off on a sieve, washed with demineralized water and subsequently 2500 ml of 4 wt % aqueous sodium hydroxide solution are filtered through the resin. The resin is then washed with water.

(16) Volume yield: 965 ml

(17) Determination of amount of basic groups: 2.22 mol/liter of resin

(18) The degree of substitution is 1.3.

Example 2

(19) Production of a Cesium-Selective Ion Exchanger Based on an Aminomethylated Bead Polymer

(20) 19.7 g (0.07 mol) of cobalt(II) sulfate heptahydrate are dissolved in 350 mil demineralized water. 350 ml of aminomethylated bead polymer (0.625 mol) from Example 1d) are then added with stirring and stirred at room temperature for 1 h. A solution of 44.4 g (0.105 mol) of potassium hexacyanoferrate (II) trihydrate in 350 ml of deionized water is then added over one hour. The mixture is adjusted to pH=7 with 78% sulfuric acid and the suspension is stirred at pH=7 for 7 h.

(21) The suspension is placed on a sieve, the remaining reaction solution is allowed to run off and the ion exchanger is washed out with demineralized water on the sieve.

(22) Yield: 375 ml

(23) Cobalt content: 3.8 wt % (dry weight)

(24) Iron content: 5.5 wt % (dry weight)

Comparative Example 1

(25) (Use of a Strongly Basic Anion Exchanger Having Quaternary Ammonium Groups)

(26) Production of a Cesium-Selective Ion Exchanger Based on a Quaternized Aminomethylated Bead Polymer

(27) 44.4 g (0.105 mol) of potassium hexacyanoferrate (II) trihydrate are dissolved in 350 ml of water. 521 ml of a strongly basic anion exchanger (0.625 mol) are then added with stirring and the mixture is shaken at room temperature for 5 h. The suspension is placed on a sieve, the remaining reaction solution is allowed to run off and the ion exchanger is washed out with demineralized water on the sieve. The resin is then added to a solution of 19.7 g (0.07 mol) of cobalt (II) sulfate heptahydrate in 350 ml of deionized water and shaken at room temperature for 24 h. The suspension is placed on a sieve, the remaining reaction solution is allowed to run off and the ion exchanger is washed out with demineralized water on the sieve.

(28) Yield: 470 ml

(29) Cobalt content: 2.1 wt % (dry weight)

(30) Iron content: 2.9 wt % (dry weight)

Comparative Example 2

(31) (Use of a Weakly Basic Anion Exchanger with Tertiary Amine Groups)

(32) Production of a Cesium-Selective Ion Exchanger Based on a Weakly Basic, Heterodisperse Anion Exchanger Having Tertiary Amine Groups (IRA 96)

(33) 11.2 g (0.04 mol) of cobalt(II) sulfate heptahydrate are dissolved in 200 mil demineralized water. 200 ml of IRA 96 (0.28 mol) are then added with stirring and the mixture is stirred at room temperature for 1 h. A solution of 25.3 g (0.06 mol) of potassium hexacyanoferrate (II) trihydrate in 200 ml of deionized water is then added over one hour. The mixture is adjusted to pH=7 with 50% strength sulfuric acid and the suspension is stirred at pH=7 for 5 h.

(34) The suspension is placed on a sieve, the remaining reaction solution is allowed to run off and the ion exchanger is washed out with demineralized water on the sieve.

(35) Yield: 210 ml

(36) Cobalt content: 0.75 wt % (dry weight)

(37) Iron content: 3.4 wt % (dry weight)

Example 3 Determination of Uptake Capacity for Cesium

(38) To produce a Cs stock solution 139.4 mg of CsCl (22 mg/l of cesium), 276.6 mg of CaCl.sub.2 (20 mg/l of calcium) and 200 g of NaCl (40 g/l of cooking salt) are dissolved in 5 l of DM water, the pH is adjusted to pH=7 with sodium hydroxide solution.

(39) In each case 500 mg of the carefully patted-dry resin are added to 800 ml of the stock solution made up hereinabove. The mixture is shaken at room temperature and at 130 rpm for 24 h. The cesium concentration in the solution is then determined by atomic absorption spectroscopy (AAS).

(40) TABLE-US-00001 TABLE 1 Cs end Cs start concentration concentration Resin [mg/l] [mg/l] Separation [%] Example 2 22 0.6 97 Comparative 22 7.8 65 example 1

(41) It is apparent from the results of Table 1 that the resins according to the invention have an uptake capacity for cesium ions which is up to 32% higher than that of strongly basic anion exchangers having quaternary ammonium groups such as are disclosed for example in Journal of Hazardous Materials, 2009, Vol. 166, pp. 1148-1153.

(42) In addition, it is apparent from Comparative example 2 that weakly basic tertiary anion exchangers which have a degree of substitution above 85% and have been prepared using the chloromethylation process, for example IRA 96, take up cobalt (II) ions only in small amounts. By comparison the resin according to the invention takes up almost 5 times more cobalt (II) ions.

(43) Test Methods

(44) Determination of Amount of Basic Groups

(45) 100 ml of the aminomethylated bead polymer are shaken down in a tamping volumeter and subsequently washed into a glass column with demineralized water. 1000 ml of 2 wt % sodium hydroxide solution are passed through the column over 1 hour and 40 minutes.

(46) Demineralized water is then passed through until 100 ml of eluate admixed with phenolphthalein have a consumption of 0.1 N (0.1 normal) hydrochloric acid of not more than 0.05 ml.

(47) 50 ml of this resin are admixed in a beaker with 50 ml of demineralized water and 100 ml of 1 N hydrochloric acid. The suspension is stirred for 30 minutes and then transferred into a glass column. The liquid is drained off. A further 100 ml of 1 N hydrochloric acid are filtered through the resin for 20 minutes. 200 ml of methanol are then filtered through. All of the eluates are collected and combined and titrated with 1 N sodium hydroxide solution against methyl orange.

(48) The number of aminomethyl groups in 1 liter of aminomethylated resin computes according to the following formula: (200V)20=mol of aminomethyl groups per liter of resin, where V is the volume of the 1 N sodium hydroxide solution consumed in the titration.