Photocatalytic Degradation of Methylene Blue Dye Using Green-Synthesized Zinc Oxide from Terminalia catappa Leaf Extract

Department of Chemical Engineering, College of Engineering and Architecture, Mapúa Malayan Colleges Laguna, Cabuyao, Laguna, Philippines, 4025

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Abstract

This study presents a sustainable route for synthesizing zinc oxide (ZnO) materials using zinc sulfate heptahydrate and Terminalia catappa leaf extract via a low-temperature precipitation method. The biosynthesis leveraged phytochemicals as natural reducing and stabilizing agents, eliminating the need for hazardous chemicals. Energy-dispersive X-ray spectroscopy (EDS) indicated the presence of Zn and O elements, with notable oxygen enrichment (68.49 atom %), which may be associated with surface-bound organic species. The photocatalytic performance of the synthesized ZnO was evaluated through the degradation of methylene blue (MB) dye under UV irradiation. A maximum degradation efficiency of 75.35 % was achieved with 15 mg of ZnO after 60 minutes. Visual trends confirmed significant MB removal across ZnO-treated groups compared to the control, although inter-dosage differences showed a plateauing behavior beyond the 5 mg dosage. While detailed crystallinity and optical properties were not assessed, these findings underscore the potential of T. catappa–mediated ZnO as a low-cost, eco-friendly photocatalyst for dye-contaminated wastewater. The synthesis approach supports green chemistry goals and contributes to the development of sustainable functional materials for environmental remediation.