Nitrogen-doped titanium dioxide supported on activated carbon for synergistic removal of aqueous organic pollutants

Abstract

In recent years, increasing global water scarcity has resulted in intense research to improve the quantity and quality of drinking water. Adsorption via activated carbon (AC) is a proven technology for water treatment and reclamation, while heterogeneous photocatalysis using titanium dioxide (TiO2) is highly energy-efficient in degrading and mineralizing various recalcitrant organic pollutants. Thus, the coupled adsorption-solar photocatalysis processes potentially present an environmentally-friendly and cost-effective treatment technology for water reclamation and reuse. This study therefore focused on developing a novel bifunctional adsorptive-photocatalytic material which was photoexcitable under solar light irradiation. In this study, various types of nitrogen-doped TiO2 supported on powdered AC (N-TiO2/AC) composites were synthesized via the modified sol-gel techniques. These include the composites prepared via single-stage calcination, two-stage calcination, and also facile techniques incorporating commercial titania P25 (N-P25-TiO2/AC). The composites were characterized using X-ray diffraction (XRD), porosimetry, UV-Vis spectrophotometry, electrophoretic mobility measurement, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy coupled with energy-dispersive X-ray (SEM/EDX), and transmission electron microscopy (TEM). Three aqueous recalcitrant organic pollutants of varying molecular properties, namely bisphenol-A (BPA), sulfamethazine (SMZ), and clofibric acid (CFA), were chosen as the model pollutants in this study.