Removal and Oxidation of Arsenic from Aqueous Solution by Biochar Impregnated with Fe-Mn Oxides

We explored the preparation of Fe-Mn oxide-biochar composites and applied them for the removal of arsenic (As) from aqueous solutions. All composites exhibited high As removal efficiencies that increased with increasing pH within the investigated range (pH 3–7). According to the equation fitting for adsorption processes, F3M1BC18 (biochar:FeSO4:KMnO4, the weight ratios of 18:3:1) had the greatest sorption ability (Qm = 8.80 mg g−1), and the sorption process of F3M1BC18 was well fitted with Freundlich isotherm. In addition, FTIR and XPS analyses indicated that Fe oxides and Mn oxide particles on the outer sphere resulted in more oxidation of As(III) to As(V). The best-performing composite was characterized before and after adsorption using a range of instrumental techniques, which better identify the properties of F3M1BC18. Moreover, the physical properties, composition, and structures of the synthesized composites were investigated, and the As removal mechanism involving surface adsorption/oxidation was proposed with the high performance of Fe-Mn oxide-impregnated biochars, suggesting that these materials are well-suited for efficient water decontamination.