PHOTOCATALYTIC PERFORMANCE OF TiO₂/ZNO COMPOSITES FOR EFFICIENT DEGRADATION OF METHYL ORANGE DYE: STRUCTURAL AND OPTICAL PROPERTIES

Abstract

Semiconductor-based photocatalysts, such as ZnO and TiO₂, are widely studied for the degradation of organic dyes in wastewater due to their stability and cost-effectiveness. However, ZnO alone suffers from rapid electron-hole recombination, limiting its photocatalytic performance, while TiO₂ is limited by UV-only activation. Herein, TiO₂/ZnO composites were synthesized with varying TiO₂ loadings (5 wt.%, 10 wt.%, and 15 wt.%) using an ultrasonic-assisted chemical mixing method. The structural, morphological, and optical properties were comprehensively characterized using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL). SEM showed that the 10 wt.% TiO₂/ZnO composite exhibited the most uniform dispersion and porous morphology. FTIR confirmed Ti–O–Zn bond formation, while PL spectra indicated that 10 wt.% TiO₂ incorporation achieved the lowest emission intensity, signifying reduced recombination. Photocatalytic degradation of methyl orange (5 mg/L) under UV irradiation (6 Watt, λ = 325 nm) demonstrated that the 10 wt.% TiO₂/ZnO composite achieved the highest efficiency (89.2 %) with a rate constant, k of 0.02106 min⁻¹, surpassing pure ZnO (82.6 %) and pure TiO₂ (74.4 %). In contrast, 15 wt.% TiO₂/ZnO composite caused agglomeration and increased recombination, lowering activity. These results confirm that optimization of TiO₂ loading enhances heterojunction formation, promotes charge separation, and, consequently, enhances photocatalytic efficiency. The findings indicate that TiO₂/ZnO composites with controlled composition hold great potential for sustainable wastewater treatment.