Visible-Light-Induced Photocatalytic Degradation of Methyl Orange by Cobalt (II) Thiosemicarbazone Complexes

Abstract

A series of p-substituted isonitrosoacetophenone-4-phenylthiosemicarbazone cobalt(II) complexes were synthesized and investigated for their photocatalytic activity toward the degradation of methyl orange (MO), a common azo dye pollutant in industrial wastewater. The synthesized complexes were characterized using elemental analysis, molar conductance, magnetic susceptibility, UV–Visible spectroscopy, FTIR spectroscopy, and TG–DTA. Photocatalytic degradation studies were carried out under visible-light irradiation using a tungsten filament lamp. The effects of irradiation time, catalyst dosage, and catalyst reusability were systematically evaluated. The cobalt(II) complexes exhibited efficient photocatalytic activity, resulting in significant degradation of methyl orange under the optimized reaction conditions. The enhanced catalytic performance is attributed to the favourable redox properties of cobalt(II) and the chelating nature of the thiosemicarbazone ligands, which facilitate the generation of reactive oxygen species during the photocatalytic process. The catalysts also demonstrated good stability and reusability over successive cycles. These findings indicate that the synthesized cobalt(II) complexes are efficient and environmentally benign photocatalysts with potential applications in the treatment of dye-contaminated wastewater.