Enhanced Uranium Extraction via Charge Dynamics and Interfacial Polarization in MoS2/GO Heterojunction Electrodes.

The removal of uranyl ions (UO2 2+) from water is challenging due to their chemical stability, low concentrations, complex water matrix, and technical limitations in extraction and separation. Herein, a novel molybdenum disulfide/graphene oxide heterojunction (MoS2/GO-H) is developed, serving as an effective electrode for capacitive deionization (CDI). By combining the inherent advantages of electroadsorption and electrocatalysis, an innovative electroadsorption-electrocatalysis system (EES) strategy is introduced. This system utilizes interface polarization at the MoS2 and GO interface, creating an additional electric field that significantly influences carrier behavior. The MoS2/GO-H electrode, with its extraordinary adsorption capacity of 805.57 mg g-1 under optimal conditions, effectively treated uranium-laden wastewater from a mine, achieving over 90% removal efficiency despite the presence of numerous competing ions at concentrations significantly higher than UO2 2+. Employing density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, it is found that the MoS2/GO-H total charge density at the Fermi level, enhanced by interfacial polarization, surpasses that of separate MoS2 and GO, markedly boosting conductivity and electrocatalytic effectiveness.

Biomimetic Photocatalytic System Designed by Spatially Separated Cocatalysts on Z-scheme Heterojunction with Identified Charge-transfer Processes for Boosting Removal of U(VI).

Designing highly efficient photocatalysts with rapid migration of photogenerated charges and surface reaction kinetics for the photocatalytic removal of uranium (U(VI)) from uranium mine wastewater remains a significant challenge. Inspired by natural photosynthesis, a biomimetic photocatalytic system is assembled by designing a novel hollow nanosphere MnOx @TiO2 @CdS@Au (MTCA) with loading MnOx and Au nano particles (Au NPs) cocatalysts on the inner and outer surfaces of the TiO2 @CdS. The spatially separated cocatalysts efficiently drive the photogenerated charges to migrate in opposite directions, while the Z-scheme heterogeneous shell further separates the interfacial charges. Theoretical calculation identifies multiple consecutive forward charge transfers without charge recombination within MTCA. Thus, MTCA could efficiently remove 99.61% of U(VI) after 15 min of simulated sunlight irradiation within 3 mmol L-1 NaHCO3 with 0.231 min-1 of the reduction rate constant, outperforming most previously reported photocatalysts. MTCA further significantly removes 91.83% of U(VI) from the natural uranium mining wastewater under sunlight irradiation. This study provides a novel approach to designing an ideal biomimetic photocatalyst for remediating environmental pollution.