Comparative Evaluation of Plant-Mediated Zinc Oxide and Titanium Dioxide Nanoparticles for Photocatalytic Degradation of Industrial Dyes in Wastewater

Abstract

Water pollution caused by industrial dyes has become a significant environmental challenge due to the persistence, toxicity, and non-biodegradable nature of synthetic colorants. Conventional wastewater treatment methods often fail to completely degrade such pollutants, leading to the accumulation of hazardous compounds in aquatic ecosystems. In this context, nanotechnology-based approaches, particularly metal oxide nanoparticles, have emerged as efficient alternatives for dye removal. The present study focuses on the comparative evaluation of plant-mediated zinc oxide (ZnO) and titanium dioxide (TiO₂) nanoparticles for the photocatalytic degradation of industrial dyes in wastewater.

The nanoparticles were synthesized using environmentally friendly green synthesis techniques involving plant extracts rich in phytochemicals such as flavonoids, phenolics, and alkaloids. These biomolecules act as reducing and stabilizing agents, eliminating the need for toxic chemicals in nanoparticle fabrication. The synthesized ZnO and TiO₂ nanoparticles were characterized using UV–Visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) to determine their optical properties, crystalline structure, morphology, and functional groups.

The photocatalytic activity of the nanoparticles was evaluated using model dye pollutants such as methylene blue and congo red under controlled laboratory conditions. Experimental parameters including pH, catalyst dosage, contact time, and initial dye concentration were optimized to assess degradation efficiency. The comparative analysis revealed that both ZnO and TiO₂ nanoparticles exhibit significant photocatalytic performance, with degradation efficiencies exceeding 85% under optimal conditions. However, variations in efficiency were observed depending on operational parameters and light exposure conditions.