Reaction Kinetics and Mechanism of Visible Light Induced Photocatalytic Degradation of Pharmaceutical Drug, Diclofenac in Synthesized N-Doped Tio2 Suspension

The present study deals with investigations on reaction efficiency and mechanism of visible light induced N- doped TiO2 mediated photocatalytic degradation of pharmaceutical drug, diclofenac. The photocatalytic efficiency of the NT-450 for degradation of diclofenac was found to be 90.2% upon irradiation with white light for 120 min, by maintaining the pH of solution at 2 and the observed rate constant for the reaction is found to be 0.0140 min-1. The reaction mechanism of photocatalytic degradation of diclofenac was proposed on the basis of monitoring the temporal evolution of intermediates during the process and their identification by using analytical techniques viz. UV-Vis Spectrometry and Gas Chromatography–Mass Spectrometry (GC/MS). Ten intermediates were identified by GC/MS and plausible pathway for photocatalytic degradation was evolved. The photocatalytic oxidation process is initiated by the generation of hydroxyl free radical and further proceeded by the hydroxylation leading to hydroxylated products, cyclization, cleavage of C-N bond and ring opening. The detailed reaction mechanism for the degradation process has been established.