Biogenic Green Synthesis of Zinc Oxide Nanoparticles from Defatted Coconut Presscake for Wastewater Treatment

Abstract

Defatted coconut meat presscake is a by-product of coconut milk production, often discarded or used as low-value products, but has the potential to treat wastewater. This study aimed to characterize zinc oxide nanoparticles (ZnO NPs) synthesized from defatted coconut meat presscake and determine their effect on the degradation of contaminants in wastewater and antibacterial properties. The nanoparticles were synthesized via a co-precipitation method using zinc nitrate as a precursor and defatted coconut meat presscake extract as a reducing agent. The nanoparticles were characterized using FTIR (Fourier Transform Infrared Spectroscopy), FE-SEM (Field-Emission Scanning Electron Microscopy), XRD (X-ray diffraction), and TGA (Thermogravimetric Analysis). The ZnO NPs exhibited a hexagonal wurtzite structure with an average size of 54 nm. The photocatalytic degradation of methylene blue under UV light irradiation showed a degradation efficiency of 79.5% within 180 minutes. Treated wastewater with ZnO NPs at concentrations of 0.5, 1, and 5 mg/L showed a significantly reduced microbial load, with averages of 10.2×106, 8.3×106, and 3.8×106 CFU/mL, respectively, compared to untreated wastewater (16.5×106 CFU/mL), indicating the antimicrobial properties of ZnO NPs. Therefore, ZnO NPs synthesized from defatted coconut meat presscake extract offer an eco-friendly solution for efficiently treating wastewater from the food industry.