Study on adsorption behavior of cesium using ammonium tungstophosphate (AWP)-calcium alginate microcapsules

A functional microcapsule was prepared by encapsulating the fine crystalline ammonium tungstophosphate (AWP) in calcium alginate polymer (CaALG). The characterization of AWP-CaALG microcapsule was examined by SEM and EPMA. The adsorption behavior of Cs(I), Rb(I), Sr(II), Pd(II), Ru(III), Rh(III), La(III), Ce(III), Dy(III) and Zr(IV) was investigated by the batch method. The batch experiments were carried out by varying the shaking times, HNO ₃ concentration, and initial concentration of metal ions. Relatively large K _d values above 10 ⁵ cm ³/g for Cs(I) were obtained in the range of 0.1-5 M HNO ³, resulting in a separation factor of Cs/Rb exceeding 10 ². In contrast, the K _d values of Sr(II), Pd(II), Ru(III), La(III), Dy(III), Ce(III) and Zr(IV) were considerably lower than 50 cm ³/g. The K _d value of Cs(I) decreased in the order of the coexisting ions, H ⁺ > Na ⁺ >> NH ₄ ⁺, and a linear relationship with a slop of about -1 was obtained between log K _d and log [NH ₄ ⁺] ([NH ₄ ⁺] > 0.01 M). The adsorption of Cs(I) was found to be controlled by chemisorption mechanism, and followed a Langmuir-type adsorption equation. A high uptake percentage of 99.4% for Cs(I) was obtained by using the dissolved solutions of spent fuel from FBR-JOYO (JAEA).