Patent Number: 047909609
Section: claims

1. Process for selectively stripping cesium ions from a strongly acid aqueous radioactive waste solution in which a precipitation agent is added to the aqueous solution and the resulting precipitate, containing the Cs.sup.+ ions, is separated from the solution, comprising: adding to the solution a sodium or lithium tetraphenylborate having electron-attracting substituents on the phenyl rings as the precipitation agent, said precipitation agent being a compound which is disubstituted in the 2,4 positions of each of the phenyl rings, or is fourfold substituted in the 2,3,5,6, positions of each of the phenyl rings, or is fivefold substituted in the 2,3,4,5,6 positions of each of the phenyl rings, and wherein the substituents are fluorine atoms. 2. Process according to claim 1, wherein the precipitation reaction takes place at a temperature between 239.degree. K. and 303.degree. K. 3. Process according to claim 1, wherein the precipitation agent is added in excess. 4. Process according to claim 3, wherein the precipitation agent is added in the amount of from 1.2 times to 5 times the stoichiometrically needed amount with regard to the Cs.sup.+ concentration of the solution. 5. Process according to claim 1, wherein the solution containing the cesium ions (a) is adjusted to a Cs.sup.+ concentration in the range from 10.sup.-1 to 10.sup.-1 mol/l,  (b) the precipitation agent is added to the solution from step (a) and the resulting precipitate is separated off. 6. Process according to claim 5, wherein steps (a) and (b) are repeated at least once to achieve a desired decontamination of Cs-137, with the repetition of step (a) being conducted by adding inactive cesium as carrier to adjust the Cs.sup.+ concentration. 7. Process according to claim 1, wherein the separation of the precipitate from the solution occurs by means of extraction with an organic solvent. 8. Process according to claim 7, wherein the solvent is chloroform, diethyl ether/ligroine (b.p. 40.degree.-60.degree. C.) 2:1 (vol./vol.), 4-methyl-2-pentanone (5% by volume in chloroform), or 4-methyl-2-pentanone (5% by volume in toluol). 9. Process according to claim 1, wherein the precipitation is conducted in the presence of an acid concentration of 3 to 6 mol/l. 10. Process according to claim 1, wherein the precipitation is conducted in the presence of an acid concentration in the range of 1 to 6 mol/l.