Photocatalytic degradation of diclofenac using TiO2-SnO2 mixed oxide catalysts

The complex nature of diclofenac limits its biological degradation, posing a serious threat to aquatic organisms. Our present work aims to eliminate diclofenac from wastewater through photocatalytic degradation using TiO2-SnO2 mixed-oxide catalysts under various operating conditions such as catalyst loading, initial diclofenac concentration and initial pH. Different molar ratios of Ti-Sn (1:1, 5:1, 10:1, 20:1 and 30:1) were prepared by the hydrothermal method and were characterized. The results indicated that addition of Sn in small quantity enhances the catalytic activity of TiO2. Energy Band gap of the TiO2-SnO2 catalysts was found to increase with an increase in Tin content. TiO2-SnO2 catalyst with a molar ratio of 20:1 was found to be the most effective when compared to other catalysts. The results suggested that initial drug concentration of 20 mg/L, catalyst loading of 0.8 g/L and pH 5 were the optimum operating conditions for complete degradation of diclofenac. Also, the TiO2-SnO2 catalyst was effective in complete mineralization of diclofenac with a maximum total organic carbon removal of 90% achieved under ultraviolet irradiation. The repeatability and stability results showed that the TiO2-SnO2 catalyst exhibited an excellent repeatability and better stability over the repeated reaction cycles. The photocatalytic degradation of diclofenac resulted in several photoproducts, which were identified through LC-MS.