Facile synthesis of calcium peroxide modified mesoporous silica for enhanced uranium extraction from uranium tailings leachate

Herein, calcium peroxide modified mesoporous silica (CPMS) was successfully synthesized by a facile strategy and used for simultaneous adsorption and immobilization of U(VI) from uranium-containing wastewater. The batch uranium adsorption experiments reveal excellent adsorption performance of CPMS over a wide pH value. In comparison to calcium peroxide and mesoporous silica, the CPMS showed a great improvement in the removal capacity of uranium. As well, the pseudo-second-order model and Langmuir isotherm model provided a well description of adsorption kinetics and isotherm, respectively, which suggested the monolayer chemisorption governed the adsorption of CPMS for U(VI). In addition, the Langmuir isotherm model calculated the maximum adsorption capacity of CPMS for U(VI) up to 613.50 mg/g. Based on mechanistic studies of XPS, FT-IR, TEM and XRD, U(VI) is predominantly removed through synergistic adsorption of U(VI) by mesoporous silicon and immobilization of U(VI) by calcium peroxide as (UO2)O2•2 H2O (metastudtite). Furthermore, the efficient removal ability of CPMS for U(VI) in uranium tailings leachate was confirmed by column test, the U(VI) concentration of uranium tailings leachate can be reduced from 180.4 μg/L to 2.3 μg/L in 1895.2-bed volumes, which was well lower than the standard limit of WHO for U(VI) concentration in drinking water. This research provides a feasible approach and new idea for the efficient treatment of radioactive wastewater.