Heterogeneous photocatalysis of a dye solution using supported TiO ₂ nanoparticles combined with homogeneous photoelectrochemical process: Molecular degradation products

Treatment of a dye solution containing C.I. Basic Red 46 (BR46) by homogeneous photoelectro-Fenton (PEF) combined with heterogeneous photocatalytic process was studied. The investigated photocatalyst was TiO₂ nanoparticles (Degussa P-25) immobilized on glass plates. Carbon nanotube-polytetrafluoroethylene (CNT-PTFE) electrode was used as cathode. Response surface methodology (RSM) was employed to assess individual and interactive effects of the four key factors (initial amount of Fe(III), initial concentration of the dye, reaction time and applied current) in PEF/UV/TiO ₂ process. Analysis of variance (ANOVA) showed a high coefficient of determination value (R² = 0.935) and satisfactory prediction second-order regression. Graphical response surface and contour plots were used to locate the optimum point. The optimum initial amount of Fe(III), initial dye concentration, reaction time and applied current were found to be 0.1 mM, 15 mg/L, 35 min and 300 mA, respectively. The observed experimental response was 88.89 of decolorization efficiency in optimum conditions of variables. The total organic carbon (TOC) measurements showed 99.2% mineralization of 15 mg/L dye at 6 h using PEF/UV/TiO₂ process. GC-MS analysis verified the identity of intermediates. The electrical energy consumption for the photo- electrochemical process was evaluated.