Adsorptive removal of methylene blue and pharmaceutical effluents using biosynthesized zinc oxide nanoparticles

Zinc oxide nanoparticles (ZnO-NPs) were biosynthesized using Ocimum basilicum leaf extract via an eco-friendly, plant-mediated approach and applied for the adsorption of methylene blue dye and pharmaceutical effluent. The synthesized ZnO NPs were characterized using various techniques, including UV-Vis spectroscopy, X-ray diffraction transmission electron microscopy and energy-dispersive X-ray analysis. The characterization results demonstrated that round-shaped ZnO NPs were prepared with particle sizes of 10.24 nm. Key phytochemicals identified by GC-MS that participate in nanoparticle synthesis include hexanal, 1-octen-3-ol, eucalyptol, fenchone, benzenemethanol, octanal, and 9-Octadecenoic acid. The effluent decolorization efficiency decreased from 72.00 to 44.88%, whereas that of the dye dropped from 75.11 to 53.33%. When the contact time was increased from 5 to 100 min, the effluent decolorization efficiency increased from 46.67 to 76.89%, while that of the dye rose from 48.44 to 82.26%. A positive enthalpy change (ΔH = 14.76 and 23.28 kJ/mol for MB and pharmaceutical effluent) indicates that the reaction is endothermic. This indicates that the reaction requires heat input to proceed. This study provides a low-cost and sustainable approach for the remediation of pharmaceutical wastewater via the use of green-synthesized ZnO-NPs. The novelty of the work lies in the combined treatment of methylene blue and pharmaceutical effluent using Ocimum basilicum-mediated ZnO nanoparticles, which has not been previously reported.