Biosynthesis of ZnO nanoparticles from plant extracts and using them to remove wastewater bacteria

Articles in Press

Document Type : Research Paper

Authors

1 College of Science, University of Babylon, 51001, Babylon, Iraq.

2 Environmental sciences, Al-Qasim Green University, 51001, Babylon, Iraq.

10.22103/jab.2026.26832.1852

Abstract

Objective
The aim of this study was to investigate the antibacterial efficacy of greenly synthesized zinc oxide nanoparticles (ZnO NPs). These nanoparticles were prepared using eucalyptus and green tea extracts for wastewater treatment applications. Another aim was to compare the antibacterial performance of plant extracts alone with ZnO nanoparticles used at different concentrations to determine their practical potential for wastewater disinfection.
Materials and Methods
Plant extracts were first evaluated as control treatments. aqueous extracts of Eucalyptus leaves and green tea as reducing and stabilizing agents were used to synthesize ZnO nanoparticles. The synthesized nanoparticles were applied to wastewater samples at two concentrations (0.5 g and 1 g per 100 mL). Controlled laboratory conditions were used to incubate treated samples before analysis. Antibacterial activity was assessed through total bacterial count reduction. Scanning electron microscopy (SEM) was used to observe surface morphology and structural damage of bacterial cells. Fourier transform infrared spectroscopy (FTIR) was performed to confirm nanoparticle formation and detect functional group changes.
Results
Compared to herbal extracts alone, we observed a significant reduction in total bacterial counts after treatment with ZnO nanoparticles. The removal efficiency increased in the following order: plant extract < 0.5 g ZnO nanoparticles < 1 g ZnO nanoparticles, indicating a clear dose-dependent response. SEM images demonstrated cell wall disruption, deformation, and reduced bacterial attachment on treated samples, especially at the higher nanoparticle concentration. FTIR analysis revealed a decrease in the intensity of organic and bacterial-related functional groups after treatment. This observation was along with the appearance of characteristic ZnO absorption bands. It confirmed successful nanoparticle synthesis and structural stability.
Conclusion
The results of this study showed that compared to plant extracts alone, ZnO nanoparticles synthesized by green method have better antibacterial activity. The antibacterial performance increased with concentration, demonstrating a strong concentration-effect relationship. According to the results of this study, it can be concluded that greenly synthesized ZnO nanoparticles can be proposed as an efficient, sustainable and environmentally friendly material for wastewater treatment and microbial control.

Keywords

References

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Available Online from 08 June 2026

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