Enhanced Uranium (VI) Removal by a Kaolin/MgAl-Layered Double Oxide Composite: Adsorption Performance and Mechanism

摘要: In this study, a Kaolin/MgAl layered double oxide (KaoL/MgAl-LDO) composite was successfully synthesized via an in-situ co-precipitation-hydrothermal-calcination method, and its adsorption performance toward U(VI) was systematically evaluated. Characterization results from XRD, FTIR, SEM, XPS, and BET indicated that MgAl‑LDO was uniformly loaded onto the kaolin surface, endowing the material with a typical mesoporous structure and a specific surface area of 102.98 m2∙g-1. Batch adsorption experiments revealed that at pH 4.0, the adsorption of U(VI) onto the material followed pseudo-second-order kinetics and the Langmuir isotherm model, with a maximum adsorption capacity of 436.68 mg∙g-1. Thermodynamic analysis confirmed the process to be spontaneous and endothermic. Combined analysis of XPS, FTIR, and XRD analyses revealed that the adsorption mechanism primarily stems from the synergistic effect between the “memory effect” of LDO and the inner sphere surface complexation of UO22+ with surface Mg/Al−OH sites. Moreover, the material maintained satisfactory adsorption performance in the presence of various coexisting ions and retained a removal efficiency of over 80% after five consecutive adsorption-desorption cycles. This study offers a novel strategy and provides experimental evidence for the development of efficient and stable adsorbents towards radionuclides.