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

Abstract

A new activation technology for sulfite (S(IV)) using a perovskite CaCu3Ti4O12 (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 SO4•−, 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 SO4•− to be 4.29 × 10−14mol·L−1, which reacts with As(III) with a second-order reaction rate constant of 3.83 × 1010L·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.