Green catalytic process for in situ oxidation of Arsenic(III) in concentrated streams using activated carbon and oxygen gas.

Arsenic(III) oxidation is a critical pre-treatment step for overall arsenic immobilization in concentrated industrial arsenic streams. Activated carbon (AC) catalysis is a green, economical and efficient method to oxidize As(III) from waters with high arsenic concentration prior to its removal through precipitation or adsorption. This research investigates AC-catalyzed oxidation process for oxidizing aqueous solutions of As(III) and proposed the possible reaction pathway. Batch tests were performed and efficient oxidation of 2.0 g/L acidic As(III) solution have been induced on AC surfaces in the presence of oxygen. The in-situ formation of reactive oxygen species on carbon surfaces and arsenic adsorption onto AC play important roles in As(III) oxidation. The kinetics of adsorption and catalyzed oxidation has been studied and the samples were characterized using ICP-OES, Zeta potential, TEM coupled with EDX and XPS techniques. A systematic reaction pathway was proposed, and reusability of AC has confirmed the economic viability of the proposed green process. This study offers a promising and facile solution for As(III) oxidation from waste water, mining and metal industrial waste streams under ambient conditions for arsenic immobilization.