Selective Uptake of Cesium by Ammonium Molybdophosphate (AMP)-Calcium Alginate Composites

The uptake properties of Cs+ for ammonium molybdophosphate (AMP, (NH 4 ) 3 PMo 12 O 40 .3H 2 O) and its composite with alginate gel polymer have been studied by the batch and column methods. The free energy for the ion exchange ([NH + 4 ] ad +Cs + NH + 4 +[Cs + ] ad ) was found to have a relatively 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 exchanger were granulated with calcium alginate (CaALG) gel polymer as an immobilization matrices. The uptake rate of Cs+ for AMP-CaALG composite was fairly fast and the uptake attained equilibrium within 3 h; the uptake was above 96% even in the presence of 5M (=mol/dm 3 ) NaNO 3 . The distribution coefficient of Cs+, Kd-Cs, decreased in the order of coexisting ions, H + >Na + >K+>NH + . In a wide HNO 3 concentration region of 10 -2 -5M, the K d,cs value for the composite was around 10 4 cm 3 /g, while those for other elements, Na + , Sr 2+ , Co 2+ , Eu 3+ and Am 3+ , 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 composite. The trace amounts of Cs + in the presence of HNO3 were selectively adsorbed on the composite column.