Ultrasound-assisted green synthesized ZnO nanoparticles with different solution pH for water treatment

Metal oxide nanoparticles (NPs), particularly ZnO NPs, have garnered significant attention in addressing global water-related challenges. This study introduces NPs agents for acidic water treatment by synthesizing ZnO nanostructures via ultrasound-assisted green synthesis utilizing Ginger extract. The research investigates the influence of solution pH on the physical properties of NPs and their photocatalytic efficiencies in treating acidic (pH = 5) and neutral (pH = 7) water through the photodegradation of methylene blue (MB) under ultraviolet (UV) illumination. Results indicate that the solution pH, varying between 7 and 13, significantly controls the morphologies of ZnO NPs, yielding hexagonal plates, barley-like structures, and nanoflakes. The band gap energies of the synthesized NPs are quite independent of the solution pH, but their crystallite sizes decrease with increasing pH values. Notably, ZnO NPs synthesized at pH = 11 exhibit the highest BET-specific surface area of 26.74 m²/g, correlating with their superior photocatalytic activity. The optimal degradation efficiencies of MB in acidic conditions (pH = 5) reach 93.54% and 86.04% when utilizing 10 and 5 mg of the irradiated photocatalyst, respectively, after a reaction time of 160 min. These findings underscore the potential of ZnO NPs as a cost-effective and environmentally sustainable solution for efficient acidic wastewater treatment.