Effect of various oxidants in a photocatalysis/filtration system for the treatment of contaminants

Abstract

This study was conducted to investigate the effect of a photocatalysis/oxidant system for the treatment of humic acid and hazardous heavy metals in aqueous solutions. Hydrogen peroxide, ozone, and potassium peroxodisulfate were tested as oxidants. The effect of oxidant concentration was conducted with a pH of 7, a UV intensity of 64 W, and a TiO2 dosage of 0.3 g L−1. The oxidant addition in the UV/TiO2 system enhanced the degradation efficiency of humic acid and hazardous heavy metals compared to no addition of an oxidant. The addition of oxidants over the amounts of H2O2 50 mg L−1, O3 20 g m−3, and K2S2O8 50 mg L−1 inhibits the system efficiency. The negative effect of higher oxidant concentrations likely results from OH radical quenching caused by the excess oxidant. Therefore, the optimal dosages of oxidants such as a hydrogen peroxide, ozone, and potassium peroxodisulfate were found to be 50 mg L−1, 20 g m−3, and 50 mg L−1, respectively. The degradation efficiency of UV/TiO2/oxidant systems for the removal of humic acid and hazardous heavy metals was much greater in the UV/TiO2/H2O2 system using H2O2 as an oxidant.