Cobalt (II/III) oxide and tungsten (VI) oxide p-n heterojunction photocatalyst for photodegradation of diclofenac sodium under visible light

Abstract Diclofenac sodium salt (DFC) is one of the new and emerging pollutants emanating from pharmaceuticals which are essential for animals and humans detected in drinking water effluents. DFC removal is a concern as it has been implicated in adverse health effects to humans and the ecosystem. In this study, different nanocomposites of cobalt (II, III) oxide and tungsten (VI) oxide were evaluated for the degradation of diclofenac sodium salt (DFC) under visible light irradiation. The synthesized composites were characterized by different techniques such as SEM, XRD, UV–vis, BET, TEM, and PL and the degradation results were obtained as a function of pH. The synthesized nanocomposites had oxygen vacancies and absorbed visible light with a low bandgap of 2.61 eV. The decrease of the microstrain values of the composites demonstrated improved crystallinity which improved the lattice structural defects of the photocatalyst with 1.6 × 10 −3 dislocations/nm2 compared to pristine WO3 resulting in high catalytic efficiencies. The mineralization of DFC involved the highly oxidizing hydroxyl radicals with an efficiency of 98.7 % at pH 10.7. The enhanced performance of the catalyst was due to p-n heterojunction formation that reduced electrons and holes recombination and improved interaction between the metal oxide semiconductors. The nanocomposite is suitable for applications in mineralization of organic pollutants in water under visible light.