Potassium hexacyanocobalt ferrate and ammonium molybdophosphate sorption bags for the removal of Cs-137 from aqueous solutions and a simulated waste

In the present study, the removal and immobilization of Cs-137 from aqueous waste solutions and a simulated waste was investigated. Two inorganic ion-exchange complexes: di-potassium hexacyanocobalt(II)-ferrate(II), K2CoFe(CN)(6).xH(2)O (KCFC), and ammonium-12-molybdophosphate [(NH4)(3)PMo(12)O(40.)aq] (AMP), were charged separately into porous nylon bags (sorption bags) of 5mum pore diameter. The first complex (KCFC) was prepared in our laboratory. The second (AMP) was used for comparison. Easy handling and increased potential for reuse characterize the sorption bag technique. The KCFC complex was investigated by thermal gravimetric analysis (TGA) and differential thermal analysis (DTA), porosity, infra-red (IR) and X-ray powder diffraction (XRD). The chemical and structural investigations revealed that the KCFC complex has adequate ion-exchange capacity and high affinity for Cs-137. The sorption bag technique showed promising results for the removal of (CS)-C-137 from aqueous waste solutions. The KCFC bags showed the highest Cs-137 removal (similar to0.91 g g(-1)), at pH 8.5; AMP bags gave the highest Cs-137 removal (similar to0.97 gg(-1)) in 0.1 N HNO3 and 1.5 N HNO3, both with a waste: sorbent ratio of 80 cm 3 g(-1). Sorption data for both KCFC and AMP revealed a good fit to the Freundlich sorption isotherm. To assess the potential of sorption bags, the used bags were regenerated in different leachants and reused in further sorption investigations. Cs-137 recovery from the used sorbents was similar to0.46 g g(-1) using 6 N HCl as leachant for AMP, compared with similar to0.253 g g(-1) for KCFC using 6 N NaCl. These results indicated stronger cesium immobilization in the KCFC complex. (C) 2003 Society of Chemical Industry.