Photocatalytic Activity of Semiconductor Oxide, Titanium Dioxide - Tungsten Trioxide Nanocomposite Material in Visible Light

Florence Achieng Masese; Shem Wandiga; Vincent Madadi; Damaris Mbui

Florence Achieng Masese Department of Chemistry, University of Nairobi
Shem Wandiga Department of Chemistry, University of Nairobi
Vincent Madadi Department of Chemistry, University of Nairobi
Damaris Mbui Department of Chemistry, University of Nairobi

Keywords: Mineralization, Recycling, Characterization, Semiconductor, Nanocomposite, Visible radiation

Abstract

A range of recalcitrant organic pollutants are introduced into environment from industrial wastewater causing global water quality risks. The study aimed to investigate the efficacy of synthesized coupled titanium (IV) oxide photocatalysts in the degradation of methylene blue, serving as a model pollutant representative of dyes and recalcitrant organic compounds in water sources. An innovative method was made use of to synthesize a semiconductor oxide, titanium dioxide coupled with tungsten trioxide nanocomposite, at room temperature in molar ratios of 1:1, 1:4, and 4:1. The synthesised nanoparticles were characterised using Brunnauer-Emmett-Teller analysis, X-ray diffraction, Ultra Violet-Visible spectroscopy and Fourier transform infrared. Photocatalytic degradation of methylene blue in aqueous solution under to visible light radiation and the performance of coupled TiO₂/WO₃ nanocomposite were evaluated. The effects of pH, catalyst loading and concentration on degradation of methylene blue was also assessed. Nanocomposite ratio of 1:1, catalystic loading of 0.25g/50 mL and 20 ppm methylene blue solution tested at pH 2 and pH 12 yielded optimal degradation results, with efficiency of 87.8% after 30 minutes exposure to visible light. The degree of mineralization of methylene blue evaluated using closed reflux colorimetric method, yielded 86% organic matter reduction in 3 hours. Reusability of titanium dioxide coupled with tungsten trioxide nanocomposite tested through 4 cycles of treatments using equimolar solutions of methylene blue yielded degradation efficiency of 93%, 90% 88% and 87% for cycles 1, 2, 3 and 4 respectively, suggesting photocatalyst stability and efficiency. Titanium dioxide coupled with tungsten trioxide was successfully synthesized. Under optimal conditions, the photocatalyst degraded 20 ppm of methylene blue. This demonstrates that coupling titanium dioxide with tungsten trioxide enhances the photo-absorption of titanium dioxide, thereby increasing its effectiveness in treating contaminated domestic water.