Ammonium phosphomolybdate-modified UiO-66 as an efficient adsorbent for the selective removal of 137Cs from radioactive wastewater

Abstract

137Cs is a radioactive pollutant in the production of wastewater from nuclear power plants. In this study, a rapid and simple in-situ synthesis new method was employed to prepare a novel AMP-functionalized UiO-66 composite material for the selective capture of 137Cs from low-level radioactive wastewater. Characterization techniques such as SEM-EDS, FTIR, XRD, TG, and BET were used to confirm the successful loading of AMP on the surface of UiO-66. UiO-66/AMP showed a good removal effect in pH4-11. At pH7, the effects of different parameters, such as the initial Cs concentration, the ratio of the amount of adsorbent to the volume of solution, and the adsorption time were investigated. The adsorption efficiency is 96.7%, the maximum adsorption capacity is 94.9 mg/g and has fast adsorption kinetics (90% Cs+ removal within 5 min). The adsorption data conformed to the pseudo-second-order kinetic model and Langmuir isotherm model, suggesting a monolayer homogeneous adsorption process. XPS helps confirm that the adsorption mechanism is the ion exchange between Cs+ and NH4+ ions. Particularly, in the adsorption experiments of 137Cs, UiO-66/AMP demonstrated good selectivity (KdCs: 5.8 × 103 ∼ 1.26 × 104 mL/g) towards trace Cs+ in a mixed ion solution with a molar ratio of 1 (Cs): 2.18 × 1015 (Na): 4.6 × 1014 (K): 2 × 1014 (Mg): 2 × 1014 (Ca), indicating its potential for selective capture of 137Cs from low-level liquid waste (LLLW).