Water treatment by photodegradation on orthorhombic antimony sulfide powder and effect of key operational parameters using methyl orange as a model pollutant

Abstract

Photocatalytic treatment of colored wastewaters containing methyl orange was achieved using visible light active Sb2S3 photocatalyst powder. Antimony chloride and sodium sulfide were used as antimony and sulfur precursors, respectively, for the synthesis of Sb2S3 powder by the hydrothermal method. The temperature of the Teflon lined autoclave was maintained at 105, 150 and 200°C for varying times of 4, 6 and 12h and corresponding phase evolution was studied by X-ray diffraction. XRD showed well crystalline single phase orthorhombic Sb2S3 powder synthesized at the different temperatures of autoclave maintained for different times. From the view point of time and temperature efficiency, Sb2S3 powder synthesized at 105°C/4h was selected for further characterization and photocatalytic studies. Well grown spherical particles were observed under scanning electron microscope. Material was found to be thermally stable in temperature range of 25–1000°C. Vibrational modes of metal-sulfur bonds were observed at wave numbers below 1000cm−1 in the Fourier transform infrared spectrum at room temperature. BET surface area of the material was 65m2/g as obtained through N2 adsorption experiments. The well characterized material was used for the degradation studies of methyl orange and the effect of various factors such as, pH, concentration of the solution, time, temperature and quantity of catalyst was investigated. Lower MO concentrations were degraded better and lower pH favored the degradation. The catalyst dosage had direct relationship with the degradation rate up to a certain limit. Pseudo first rate constant of 0.0012min−1 was calculated from the fitting of kinetic data. Degradation rate increased with the increase in reaction temperature. Degradation mechanism was designed based on the characterization and photocatalytic studies.