Diclofenac degradation using mont-La (6%)-Cu0.6Cd0.4S as photocatalyst under NUV-Vis irradiation. Operational parameters, kinetics and mechanism

We report the aqueous photodegradation -under NUV-Vis radiation-of diclofenac, a common non-steroidal anti-inflammatory drug found to be persistent in the environment, using mont-La(6%)-Cu0.6Cd0.4S, a nanocomposite prepared by simple cation exchange and impregnation method. Operational parameters relevant for the process have optimized: amount of catalyst, dissolved oxygen concentration, initial diclofenac concentration and pH. Heterogeneous suspensions of 1 g L-1 of mont-La(6%)-Cu0.6Cd0.4S nanocomposite allowed removal of ca. 92% of 10 mg L-1 solution of diclofenac at pH = 5.9 with natural dissolved oxygen from air within 240 min, meanwhile TOC removal was 67%. The photocatalytic process is adequately described by the Langmuir-Hinshelwood kinetic model, following apparent pseudo-first order kinetics. A suitable reaction mechanism has been proposed, based on the available kinetic evidences and the reaction products observed by HPLC-MS analysis.