Electrospun NiO, ZnO and composite NiO–ZnO nanofibers/photocatalytic degradation of dairy effluent

Among the food wastes, the dairy effluent (DE) is considered to be the most polluting one because of the large volume of wastewater generated and its high organic load. Photocatalytic degradation of DE and organic dye methylene blue (MB) was studied using Zinc oxide nanofibers (ZnO NFs), Nickel oxide nanofibers (NiO NFs) and composite Zinc oxide–Nickel oxide nanofibers (ZnO–NiO NFs). These nanomembranes were characterized in SEM, TEM, XRD and UV studies. The pristine nanofiber membranes were smooth and continuous, with an average diameter of about 400 nm, and held their nanofibrous morphology even after calcination of 600 °C and more than 3 h of photocatalytic degradation of DE and MB dye. The ZnO NFs and NiO NFs were effective materials for degradation of DE and MB dye. NiO NFs and ZnO NFs showed a maximum degradation of 70% and 75% in DE and 50% and 60% in MB dye respectively, after 3 h. The significant enhancement of degradation in the composite ZnO–NiO NFs is attributed to the photoactivity of material under visible light irradiation. The composite ZnO–NiO NFs eliminated 40% of DE and 65% of MB dye, after 1 h and maximum degradation of 80% DE after 3 h and 100% MB dye after 90 min. Overall, this study also shows that the nanofibrous morphology strongly enhances the surface activity of the ZnO–NiO photocatalyst when utilized to degrade DE and MB dye at room temperature.