By-product distribution and cytotoxicity assessment of ZnO-assisted photocatalytic degradation of reactive blue 250 dye

This research examined the effectiveness and feasibility of utilizing ultraviolet (UV) assisted photo-catalysis to treat wastewater effluents from textile production containing reactive blue 250 (RB 250) dye. Molecular oxygen and active species like O₂ ^•-, HO₂ ^•, H₂O₂ and ^•OH play crucial roles in the degradation process. Additionally, the degradation of dyes is influenced by several factors, including dye concentration, duration of UV irradiation, pH levels, concentration of H₂O₂, and the catalyst. The concentration of H₂O₂ and catalyst dose for the decolorization was studied at 0.6 mL and 0.5 g respectively. The discoloration was higher at low dye concentration, high H₂O₂ concentration, acidic conditions and high catalyst concentration. The maximum degradation (97 %) of RB 250 dye was obtained in the presence of zinc oxide nanoparticles within 90 min. The extent of decolorization of the dye was determined by UV-Vis spectroscopy. Fourier transform infrared spectroscopy (FTIR) was employed to analyze the changes in functionalities after degradation. The disappearance of characteristic peaks associated with specific groups within the dye molecule confirmed the extensive degradation of RB 250 dye. LCMS analysis was conducted to examine the intermediates and a mechanistic degradation pathway was subsequently proposed. The cytotoxicity of the irradiated dye samples was evaluated through a hemolytic test both pre and post-treatment. The findings suggest that the UV/H₂O₂/ZnO treatment represents a promising approach for effectively degrading RB 250 dye.