Selective uptake of cesium by ammonium molybdophosphate (AMP)-calcium alginate composites

The uptake properties of Cs+ for ammonium molybdophosphate (AMR (NH4)(3)PMo (12)O(40)(.)3H(2)O) and its composite with alginate gel polymer have been s tudied by the batch and column methods. The free energy for the ion exchang e ([NH4+](ad)+Cs+ reversible arrow NH4+[Cs+](ad)) was found to have a relat ively low value of -9.7 kJ/mol compared to other inorganic ion exchangers, indicating high selectivity of AMP for Cs' ions. The fine crystals of AMP e xchanger were granulated with calcium alginate (CaALG) gel polymer as an im mobilization matrices. The uptake rate of Cs+ for AMP-CaALG composite was f airly fast and the uptake attained equilibrium within 3 h; the uptake was a bove 96% even in the presence of 5 M (=mol/dm(3)) NaNO3. The distribution c oefficient of Cs+, K-d,K-Cs, decreased in die order of coexisting ions, H> Na+ > K+ > NH4+. In a wide HNO3 concentration region of 10(-2)-5 M, the K -d,K-Cs value for the composite was around 10(4) cm(3)/g, while those for o ther elements, Na+, Sr+, Co2+, Eu3+ and Am3+, were less than 10(2) cm(3)/g. The uptake of Cs+ followed a Langmuir adsorption isotherm, and the uptake capacity of Cs+ increased with the content of AMP immobilized in the compos ite. The trace amounts of Cs in the presence of HNO3 were selectively adsor bed on the composite column.