Heterogeneous photoelectro-Fenton using ZnO and TiO2 thin film as photocatalyst for photocatalytic degradation Malachite Green

Abstract

Titanium dioxide (TiO2) and zinc oxide (ZnO) particles as photocatalysts are known to be effective in the degradation of various organic pollutants. Here we use a simple way of preparing an active TiO2 thin film for Malachite Green (MG) elimination from an aqueous solution based on a combination of advanced oxidation processes (electro Fenton and photocatalytic degradation) under UV wavelengths irradiation. The TiO2 and ZnO as nano-photocatalytic material as thin layers on the glass surface are applied. For the characterization of synthesized ZnO and TiO2 paste, SEM, TEM and XRD were used. The effects of operational variables on the degradation of MG were studied by central composite design (CCD). The results showed that MG was degraded by the TiO2 and ZnO pastes in photoelectro-Fenton system under UV irradiation at optimum conditions with 79.4 and 97.5% degradation efficiency, respectively, which reaction constant of thin film ZnO was 1.96 times as high as that of the TiO2 paste in the mentioned system. The optimum degradation conditions for thin film ZnO were as follows: pH of 3, 30 mg/L of initial MG concentration, 200 mA of electrical current, 0.4 mmol/L of FeCl3, and 16 min of contact time. In addition, the degradation rates of MG by both photocatalysts in the photoelectro-Fenton system could be explained in terms of the Langmuir-Hinshelwood pseudo-first-order kinetic equation.