Purification of nuclear wastes by novel inorganic ion exchangers

Abstract

Several ion exchange materials were compared to evaluate their sorption performance for the purification of two samples of real radioactive waste effluents. Four synthetic titanosilicates, ETS-10, ETS-4, AM-4 and Na₂Ti₂O₃SiO₄·2H₂O, a layered manganese oxide and its M-exchanged forms (where M = H⁺, Na⁺, Ca²⁺) and an antimonysilicate sample were the ion-exchange materials screened. The experiments were carried out by the batch method and the results expressed in terms of distribution coefficients. Variation in the magnitude, and mechanism, of the sorption of the nuclides onto the exchangers was ascribed to structural differences (some were layered compounds and others were frameworks with well defined pores capable of ion-sieving), and their ion exchange properties. The results also reflected the vital influence of the pH of the nuclear waste solutions in controlling the sorption process. They performed better in a slightly acidic media. Antimony-125, silver-110m and cobalt-60 (and cobalt-57) were best taken up by H-birnessite because of its special exchange sites and optimum ion exchange characteristics. Antimonysilicate and Na₂Ti₂O₃SiO₄·2H₂O showed a high affinity for radiocaesium.