Green Synthesis of ZnO Nanoparticles Mediated by Lippia alba and Their Application in the Degradation of Organic Contaminants.

Abstract

Water pollution by industrial organic dyes is a serious issue that significantly affects humans, as well as the flora and fauna of aquatic ecosystems. One of the most frequently used methods in recent years to address this problem is photocatalysis. This technique employs solar or UV energy to induce chemical reactions between nanoparticles (NPs) and the pollutant molecules. There are various methods for synthesizing NPs, but green synthesis is a highly viable and environmentally friendly alternative, as it replaces hazardous or toxic materials with natural options like plants, peels, roots, or microorganisms. In this study, green synthesis was employed to produce zinc oxide (ZnO) NPs using the plant Lippia alba as a reducing agent. The NPs were characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA), ultraviolet-visible spectroscopy (UV-Vis), and Fourier-transform infrared spectroscopy (FTIR). Additionally, the NPs were used to evaluate their effectiveness in the degradation of four different organic dyes under ultraviolet light. The results showed that the synthesized NPs had an average size of 10.1 nm and quasi-spherical shape, good resistance to thermal degradation, and exhibited molecular vibrations characteristic of ZnO functionalized with organic compounds. In the photocatalytic degradation tests, 98% of methylene blue (MB) was degraded after 180 minutes, 94% of methyl orange (MO) after 180 minutes, 100% of methylene red (MR) after 100 minutes, and 100% of Congo red (CR) after 60 minutes. The use of L. alba enables the production of ZnO NPs with high efficiency in pollutant degradation, supporting their potential application on an industrial scale.