Reversible and Efficient Sequestration of Cesium from Water by the Layered Metal Thiophosphate K_(0.48)Mn_(0.76)PS_3·H_2O

摘要

Water body contamination with radioactive species is an important issue due to significant developments in nuclear energy. Cesium (~(137)Cs) radioisotope is a non-actinide fission product of uranium and plutonium that is long-lived. Hence, selective removal/capture of cesium is essential for managing radioactive waste. Herein, a detailed Cs~+ ion-exchange study on a potassium intercalated layered metal thiophosphate, K_(0.48)Mn_(0.76)PS_3·H_2O (K-MPS-1), is reported. The sorption of Cs~+ by K-MPS-1 follows the Langmuir model with a high capacity of 337.5 mgg~(-1) and high distribution coefficients in the order of about 104 mLg~(-1). K-MPS-1 can sequester Cs~+ efficiently, even from very low concentrations (ppb level). K-MPS-1 exhibits high cesium uptake over a broad pH range of 2-12 and the ion-exchange process reaches equilibrium within a short time (≈15 min), following pseudo-second-order kinetics. Moreover, K-MPS-1 demonstrates selectivity towards Cs~+ capture in the presence of complex solutions containing excess Na~+, Ca~(2+), and Mg~(2+) ions; this is due to favorable interactions between Cs (soft Lewis acid) and S (soft Lewis base). K-MPS-1 reversibly captures Cs~+ and it can be regenerated by treating Cs-MPS-1 with a solution of KCl.