Novel activation of sulfite by perovskite CaCu3Ti4O12 for As(III) oxidation: Kinetics and mechanism

A new activation technology for sulfite (S(IV)) using a perovskite CaCu 3 Ti 4 O 12 (CCTO) catalyst has been proposed to remediate the As(III) polluted water. When 0.05 g·L −1 CCTO and 0.4 mmol·L −1 S(IV) were mixed, 90.6% of As(III) could be removed in 30 min at an initial pH of 8.0. Dissolved oxygen played an indispensable role in the reaction. CCTO can interact with S(IV) via a heterogeneous catalytic route on its surface. Electrochemical characterization indicated that the electron transfer process between the surface Cu/ Ti atoms and S(IV) ions evoked the activation of S(IV), leading to the generation of SO 4 •− , which played a dominant role in the oxidation of As(III). Density functional theory (DFT) calculations have disclosed the spontaneous adsorption of sulfite on CCTO surface. A kinetics study determined the steady-state concentration of SO 4 •− to be 4.29 × 10 −14   mol·L −1 , which reacts with As(III) with a second-order reaction rate constant of 3.83 × 10 10   L·mol −1 ·s −1 . Furthermore, the CCTO catalyst was highly reusable, the structure of which did not significantly alter during the reaction. Therefore, the CCTO/S(IV) system is a promising and efficient advanced oxidation technique for the purification of As(III) in water.