Photocatalytic degradation of nitro-aromatic explosives using visible-light-activated WO3: Optimization and catalyst modification

Nitro-aromatic explosives are hazardous, stable, and carcinogenic pollutants in industrial wastewaters. Photocatalytic degradation is one of the most efficient methods for the treatment of these types of pollutants. In this work, the degradation of p-nitrophenol (PNP) as a typical nitro-aromatic pollutant was studied using the synthesized catalyst WO3 under visible light irradiation. The synthesized catalyst was characterized using X-ray diffraction, field-emission scanning electron microscopy, and diffuse reflection spectroscopy. The effect of the operational parameters on the process efficiency, such as initial pH, initial concentration of PNP, catalyst dose, reaction temperature, calcination temperature (CT), and light source type, was studied. The effect of different morphologies of WO3 on the process efficiency was also evaluated. The results show that, under the optimum condition (pH = 11.5, catalyst dosage = 1000 mu g/ml, and CT = 700 degrees C) at T =25 degrees C and for initial PNP concentration of 20 mu g/ml, the process can degrade and mineralize PNP by about 90% and 40.16%, respectively, after 240min. Under the obtained optimum condition, mineralization of 2,4,6-trinitrotoluene as a nitro-aromatic explosive was evaluated, and 28% mineralization was observed after 240min. The electrical energy consumption of the process was also assessed, and under the optimum condition, it was calculated as 602.3 and 94.0 kWh/m(3) for the metal halide lamp and light-emitting diode, respectively.