Photodegradation of Rhodamine B and Phenol Using TiO2/SiO2 Composite Nanoparticles: A Comparative Study

Abstract

Organic pollutants found in industrial effluents contribute to significant environmental risks. Degradation of these pollutants, particularly through photocatalysis, is a promising strategy ensuring water purification and supporting wastewater treatment. Thus, photodegradation of rhodamine B and phenol under visible-light irradiation using TiO2/SiO2 composite nanoparticles was within the main scopes of this study. The nanocomposite was synthesized through a wet impregnation method using TiO2 and SiO2 nanopowders previously prepared via a facile sol–gel approach and was fully characterized. The obtained results indicated a pure anatase phase, coupled with increased crystallinity (85.22%) and a relative smaller crystallite size (1.82 nm) in relation to pure TiO2 and SiO2 and an enhanced specific surface area (50 m2/g) and a reduced energy band gap (3.18 eV). Photodegradation of rhodamine B upon visible-light irradiation was studied, showing that the TiO2/SiO2 composite reached total (100%) degradation within 210 min compared to pure TiO2 and SiO2 analogues, which achieved a ≈45% and ≈43% degradation rate, respectively. Similarly, the composite catalyst presented enhanced photocatalytic performance under the same irradiation conditions towards the degradation of phenol, leading to 43.19% degradation within 210 min and verifying the composite catalyst’s selectivity towards degradation of rhodamine B dye as well as its enhanced photocatalytic efficiency towards both organic compounds compared to pure TiO2 and SiO2. Additionally, based on the acquired experimental results, ●O2−, h+ and e− were found to be the major reactive oxygen species involved in rhodamine B’s photocatalytic degradation, while ●OH radicals were pivotal in the photodegradation of phenol under visible irradiation. Finally, after the TiO2/SiO2 composite catalyst was reused five times, it indicated negligible photodegradation efficiency decrease towards both organic compounds.