Efficient removal of arsenite through oxidation and adsorption on MWCNTs-decorated Ce-Mn binary oxide nanoparticles

Pre-oxidizing trivalent arsenic (As(III)) to pentavalent arsenic (As(V)) and removing it by in-situ adsorption is an ideal choice for reducing the toxicity of arsenic-containing groundwater. In this study, a series of threedimensional multifunctional mesoporous composites based on hydrated cerium oxide were prepared by chelating manganese oxide and hydrated cerium oxide, and then anchored on multi-walled carbon nanotubes (MWCNTs). Under the same reaction conditions, the removal performance of the three composites for As(III): CeMn@9CNTs (83.37%) > CeMn-3 (63.40%) > HCO (56.90%). MWCNTs played an important role in enhancing As(III) adsorption by CeMn-3: (i) Increasing the specific surface area and regulating the average pore size of the pristine CeMn-3. (ii) Preventing Ce-Mn oxide agglomeration. (iii) Electronic shuttle for metal valence transitions. The removal efficiency of arsenic by CeMn@9CNTs was hardly affected by pH (3.0-9.0) and ion concentration (0.001-0.1 M). Except for the high concentration of phosphate, inorganic anions such as sulfate, chloride, carbonate had no obvious interference. The pseudo-secondary kinetic and Langmuir adsorption model fitted better with the experimental data. The good regeneration performance and high adsorption capacity indicated that CeMn@9CNTs has the potential to remove As(III) through pre-oxidation-adsorption in an aqueous environment.