One-pot hydrothermal synthesis of MnO2/zeolite composite and its efficacy in Sr2+ removal

In this study, MnO 2 /zeolite composites (MnO 2 @Z4As) were synthesized via a one-pot self-assembly reaction using low-cost kaolinite minerals as the starting material. The successful embedding of MnO 2 nanoparticles within the zeolite matrix was confirmed through structural characterization. The highest capacity for Sr 2+ adsorption was observed for MnO 2 @Z4A-9 at 177.49 mg/g, representing a 39.96% increase compared to zeolite 4A (Z4A) alone. The process displayed characteristics consistent with the Langmuir model and pseudo-second-order kinetic behavior, indicating that the adsorption was monolayer chemisorption. However, competing ions, such as Ca 2+ and Na + , significantly hindered Sr 2+ adsorption. In seawater, MnO 2 @Z4A-9 removed 98.4% of Sr 2+ at a 10 g/L dosage. The dual adsorption mechanism of Sr 2+ adsorption on MnO 2 @Z4As has been elucidated, comprising ion exchange with Na + in the zeolite and the hydroxyl complexation with MnO 2 . This study offers a cost-effective strategy for Sr 2+ removal from seawater.