Aqueous degradation kinetics of pharmaceutical drug diclofenac by photocatalysis using nanostructured titania–zirconia composite catalyst

Abstract

Diclofenac (DCF) is an anti-inflammatory pharmaceutical drug, and its presence in a trace amount in waste water makes severe environmental pollution. The degradation of DCF was investigated by a photocatalytic process in presence of ultra violet irradiation at room temperature using titania and titania-zirconia nanocom- posite catalysts in a batch reactor. The composite catalyst was prepared by sol-gel method and characterized by X-ray diffraction, transmission electron microscopy as well as BET surface area analyzer. The effect of various process parameters such as catalyst loading, initial concentration of DCF and pH of the experimental solution was observed on the degradation of DCF. The titania-zirconia nanocom- posites exhibited reasonably higher photocatalytic activity than that of anatase form of titania without zirconia. The maximum removal of DCF of about 92.41 % was achieved using Zr/Ti mass ratio of 11.8 wt% composite catalyst. A rate equation was proposed for the degradation of DCF using the composite catalyst. The values of rate constant (kc) and adsorption equilibrium constant (K1) were found to vary with the catalyst content in the reaction mixture.