Photocatalytic degradation of diclofenac using TiO2–SnO2 mixed oxide catalysts

Abstract

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 TiO<inf>2</inf>–SnO<inf>2</inf> 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 TiO<inf>2</inf>. Energy Band gap of the TiO<inf>2</inf>–SnO<inf>2</inf> catalysts was found to increase with an increase in Tin content. TiO<inf>2</inf>–SnO<inf>2</inf> 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 TiO<inf>2</inf>–SnO<inf>2</inf> 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 TiO<inf>2</inf>–SnO<inf>2</inf> 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. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group.