Enhancing efficiency and photocatalytic activity of TiO2-SiO2 by combination of glycerol for MO degradation in continuous reactor under solar irradiation

This study evaluated the photocatalytic performance of a combination of TiO2-SiO2 film and glycerol for the degradation of methyl orange (MO) dye in wastewater passing through a continuous-flow reactor. A sol-gel TiO2-SiO2 film was synthesized and coated on glass beads as a thin layer using a conventional dip-coating technique. Our XRD and SEM analyses demonstrated that the TiO2-SiO2 nanoparticles contain an anatase (alpha-TiO2) phase, which enhanced photocatalytic properties. The obtained film was white in color, with a thickness of 0.9-1.2 mm, according to the amount of TiO2-SiO2 that was deposited on the glass beads, which ranged from 1.8 to 2.1 g/l. The photocatalytic activities of the film was evaluated using a continuous-flow reactor, where the effects of initial pH, hydraulic retention time (HRT), UV intensity, glycerol concentration, and initial MO concentration were investigated. Optimized operating conditions were obtained with an initial pH of 7, glycerol concentration of 0.5 g/L, HRT of 7 min, UV intensity exceeding 20 W/m(2), and an initial MO concentration of 10 mg/L, which resulted in 91% dye removal efficiency from the water. The correlation between photocatalytic degradation using TiO2-SiO2 in combination with glycerol, and irradiation time, exhibited a pseudo-first-order model.