Fabrication of organic/inorganic reactive composites for fast removal of arsenic species from groundwater systems.

This study investigates the catalytic potential of anionic MnO nanosheets (Mn), a cationic covalent organic Framework (COF), and their composites (CM, C2M, and CM2) with varying Mn weight percentages for arsenic removal from groundwater. The catalysts were used as activators of sodium sulfite (SS) under light conditions, enabling the pre-oxidation of arsenic (III) (As3) to arsenic(V) (As5), followed by the adsorption of As5 for complete arsenic removal from water. The Mn-COF-SS systems (C2M, CM, CM2) exhibited superior performance compared to Mn and COF alone, highlighting the dual functionality of the composites as both oxidizing agents and effective adsorbents for arsenic species. Among the composites, CM2 with 32 wt% Mn demonstrates exceptional efficiency, achieving 99.99 % arsenic removal within 30 min. The sorption process in a batch reactor was pH-dependent, with sulfate radicals (SO) and electrostatic interactions playing key roles in As3 oxidation and As5 removal, respectively. The pseudo-second-order kinetic model was found to be the dominant model for the sorption process, and the sorption process was compatible with the Freundlich isotherm model, which indicates a multilayer adsorption process of arsenic species on CM2. The practical application of CM2 in a fixed-bed reactor showed its high efficiency for arsenic removal, achieving the contaminant level below 10 ppb as recommended by WHO. This project highlights the potential of CM2 as an effective catalyst for arsenic removal, offering a promising approach to mitigating arsenic contamination in water sources.