As(III) Oxidation Mediated By Reactive Oxygen Species in-Situ-Generated from Pre-Photocharged TiO2 and WO3 Composite Catalyst Membrane Filters

Abstract

The photocatalytic oxidation system has been widely investigated as a pretreatment process for efficient removal of arsenic. However, its practical use for the arsenite (As(III)) oxidation is limited by several problems such as low oxidation efficiency under dark condition and difficult separation of catalysts from treated water. This study investigated light-charged TiO2 and WO3 (TW) composite-embedded inorganic membrane filter system as a practical method for preoxidative treatment of As(III) even without the addition of chemical oxidants under dark condition. And this study demonstrated that reactive oxygen species (ROSs ; O2 ·- and HO2 ·) in pre-photocharged TW composite catalyst membrane filter. TW membrane filters were charged under UV or simulated solar light (AM 1.5; 1 sun) irradiation and subsequently transferred to a once-through flow type system for testing As(III) oxidation in the dark condition. The As(III) oxidation efficiency increased with increasing photocharging time, weight ratio of WO3 and solution pH. These conditions enable the sufficient generation of ROSs via O2 reduction using electrons accumulated in TW during pre-photocharging for achieving the effective oxidation of As(III) in the dark condition. The oxidation capability of TW system was completely recovered after re-photocharging. TW-embedded membrane filter system can be easily reused after recharging process without the requirement of additional physical separation steps under ambient dark condition.