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

In the present study, the removal and immobilization of 137Cs from aqueous waste solutions and a simulated waste was investigated. Two inorganic ion-exchange complexes: di-potassium hexacyanocobalt(II)-ferrate(II), K2CoFe(CN)6·xH2O (KCFC), and ammonium-12-molybdophosphate [(NH4)3PMo12O40·aq] (AMP), were charged separately into porous nylon bags (sorption bags) of 5 µm 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 137Cs. The sorption bag technique showed promising results for the removal of 137Cs from aqueous waste solutions. The KCFC bags showed the highest 137Cs removal (∼0.91 g g−1), at pH 8.5; AMP bags gave the highest 137Cs removal (∼0.97 g g−1) in 0.1 N HNO3 and 1.5 N HNO3, both with a waste: sorbent ratio of 80 cm3 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. 137Cs recovery from the used sorbents was ∼0.46 g g−1 using 6 N HCl as leachant for AMP, compared with ∼0.253 g g−1 for KCFC using 6 N NaCl. These results indicated stronger cesium immobilization in the KCFC complex. Copyright © 2003 Society of Chemical Industry