Application of a novel triple metal-nonmetal doped TiO2 (K-B-N-TiO2) for photocatalytic degradation of Linear Alkyl Benzene (LAB) industrial wastewater under visible light

In this work, novel triple metal-nonmetal doped TiO2 (K-B-N-TiO2) was synthesized by the sol-gel method. The structure and properties of the synthesized nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. Photocatalytic activity of the nanoparticles was assessed by degradation of linear alkyl benzene (LAB) industrial wastewater at different operating conditions. The effects of initial pH, photocatalyst loading, initial COD concentration and reaction time on the photocatalytic performance of the nanoparticles degrading LAB wastewater were determined by response surface methodology (RSM). The region of examination for the process was taken as the area enclosed by initial COD concentration (200-500 mg/l), catalysis loading (1-2 g/l), initial pH (3-11) and reaction time (1-8 h). The doping modes reduced recombination of photogenerated electrons and holes, and extended the absorption of TiO2 into the visible light. The photocatalyst properties of K-B-N-TiO2 were more effective than those of pure TiO2 and other modified single and double doped TiO2 (B-N, K-N, N, B and K-TiO2). The COD removal efficiencies by the photocatalysis were increased from pure TiO2 to multi-doped TiO2 in the following order; multi-doped TiO2 > single-doped TiO2 > pure TiO2. More than 55% and 81% of COD content of the LAB industrial wastewater was mineralized under visible light and UV irradiation, respectively at optimum condition (COD of 200 mg/l, catalyst loading of 1.5 g/l and pH of 3). The BOD5/COD ratio for the remaining COD was obtained to be about 0.4 which indicates higher biodegradability of the treated effluent in comparison with the raw wastewater.