Visible light dye degradation over fluorinated mesoporous TiO2 − WO3 − Bi2O3/SiO2 nanocomposite photocatalyst-adsorbent using immersion well reactor

Abstract

Mesoporous silica-supported TiO2−WO3−Bi2O3 nanocomposites were prepared using wet impregnation and hydrophobically modified via a simple fluorination process using ammonium fluoride (NH4F) as the fluorination agent. The photocatalytic performance of the materials was evaluated in a triple-walled immersion well reactor for removal of Rhodamine B (RhB) dye using visible light. The bulk structures and surface properties of the materials were characterized by XRD, FE-SEM, HR-TEM, SAED pattern, EDS, N2 adsorption-desorption, FTIR, Zeta potential, DRS, PL, and water contact angle measurements. The FTIR spectra exhibited the incorporation of TiO2 nanoparticles and the fluoride ion into the fluorinated nanocomposites. Water contact angle and Zeta potential measurements of fluorinated samples indicated the enhanced surface hydrophobicity, the changes in point of zero charge (PZC) toward lower pH, and the increased negative surface charge. The performance of the TSWBi nanocomposites varied appreciably upon surface fluorination (TSWBi-F1) and displayed 93% RhB removal after only 30 min of visible light irradiation. RhB was adsorbed on the TSWBi-F1 and therefore, the material acts as both an adsorbent and photocatalyst simultaneously. Fluorinated SiO2 support was an excellent adsorbent, providing better sites for surface enrichment and adsorption of RhB molecules, while TiO2 nanoparticles promoted by WO3 and Bi2O3 behaved as visible light-active photocatalytic sites that could successfully degrade the RhB molecules adsorbed by the adjacent fluorinated SiO2 nanoparticles. Furthermore, the highly accessible surface area and mesoporous texture of the TSWBi-F1 could render more adsorptive and photocatalytic active centers and efficient mass transport of reacting molecules, respectively.