Synthesis of nitrogen-doped titania for photocatalytic oxidation-reduction of bisphenol-A in industrial wastewater

Abstract

Photocatalysis has been a focused research area for several decades. This technology possesses many advanteges over conventional water treatment method. The most commonly used material in photocatalysis is titanium dioxide (titania). In this study, different nitrogen-doped titania were synthesized by simple sol-gel method with varying initial parameters during the synthesis process. These samples and commercial product P25 were characterized by a range of methods like XRD, UV-Vis DRS, FTIR and BET to study their physical and optical properties. Their photoactivities were determined by the degradation rate of Bisphenol A. It was observed that using tube furnace with nitrogen flow for calcination of samples from organic precursors is not suitable. Sulfation of amorphous titania significantly increased the surface area and favoured the crystallization process. Vacuum freeze dryer created samples with smaller apparent density than those using normal vacuum dry as the drying method for precipitated gels. Higher calcination temperature led to a decrease in photoactivity and unexpectedly, smaller crystallite size. All synthesized samples showed lower photoacitivity than P25 under UV irradiation. A hypothesis was proposed that synthesized catalysts underwent pyrolysis inside the furnace and thus formed an organic substance layer around the titania structure. Removal efficiency of about 20% Bisphenol A was obtained with some synthesized samples under visible irradiation. It is recommended that further studies on adsorption capacity and different parameters of photocatalytic oxidation process should be carried out in the future.