Kinetic comparison of photocatalysis with H2O2-free photo-Fenton process on BiVO4 and the effective antibiotic degradation

Abstract

In order to eliminate the serious environment pollution and the super bacteria generation caused by antibiotics discharge, it is an urgently challenging task for effective degradation of antibiotics. Many advanced oxidation technologies including Fenton and photocatalytic reactions have been adopted to face with the challenge of this issue. Herein, we developed a H2O2-free photo-Fenton process using BiVO4 as a light absorbing semiconductor with the addition of Fe3+ to degrade antibiotic under a 300 W Xenon lamp and further comparably investigated the kinetics of H2O2-free photo-Fenton and photocatalytic reactions to degrade rhodamine B (Rh B) and rhodamine 6G (Rh 6G). The corresponding reaction mechanism was proposed based on detailed experiments and data analysis. Subsequently using norfloxacin (NOR) as a model, the H2O2-free photo-Fenton reactions were adopted to evaluate the effectiveness of antibiotic degradation with the optimized conditions of pH = 3.0 and the Fe3+ concentration of 100 mg/L. The results displayed that the H2O2-free photo-Fenton reaction on BiVO4 conformed to pseudo-first-order kinetics and exhibited excellent antibiotic removing performance, the degradation ratio of NOR reached 96% within 1 h. While its photocatalytic cousin abided by pseudo-zero-order kinetics and its degradation ratio was only 25% with the absence of Fe3+ under the same conditions. It is anticipated that this study can deepen the understanding of mechanism and kinetics between photo-Fenton with photocatalytic reactions on the same catalyst and the expansion of H2O2-free photo-Fenton reactions on other semiconductors has great potential in the treatment of wastewater containing various antibiotics.