Microwave-Assisted Bioprocess for Zinc Oxide Nanoparticles Synthesis Using Melaleuca quinquenervia Extract: A Sustainable Approach for Wastewater Dye Removal and Antimicrobial Valorization

This study presents an eco-friendly and rapid green synthesis of zinc oxide nanoparticles (ZnO NPs) using Melaleuca quinquenervia leaf extract (MQLE) as a dual reducing and capping agent under microwave assistance. The synthesis process was highly optimized, achieving completion in only 75.5 min, which was significantly faster than conventional green synthesis methods. Physicochemical characterization using XRD, EDS, and DLS confirmed the formation of phase-pure ZnO NPs with an average crystallite size of 26.6 ± 0.03 nm and a hydrodynamic diameter of 82.5 ± 0.02 nm. FTIR analysis verified the presence of plant-derived polyphenolic compounds on the nanoparticle surface, which demonstrated stability up to 11 months. The bio-capped ZnO NPs showed superior antioxidant capacity and broad-spectrum antimicrobial activity, and biogenic ZnO NPs effectively inhibited multidrug-resistant strains such as MRSA (methicillin-resistant Staphylococcus aureus) and CRAB (Carbapenem-resistant Acinetobacter baumannii). Furthermore, the synthesized ZnO nanoparticles indicated effective removal of organic dyes under visible-light irradiation. These findings highlight the potential of MQLE-mediated green synthesis as an alternative approach for ZnO nanoparticle preparation and suggest its possible applicability in environmental remediation. Further assessment of overall processing time, product yield, and energy consumption is needed to establish its cost-effectiveness and sustainability.