Decolorization of textile dyes by TiO2 -based photocatalyst using polyol as electron donor

Abstract

Decolorization of textile dyes including 2,6-dichlorophenolindophenol (DCIP), congo red (CR) and methyl orange (MO) by using TiO2-based photocatalyst in the presence of polyols such as glycerol and ethylene glycol was investigated. Polyols were used as sacrificial electron donors (SEDs). The results showed that the polyols improved the rate and yield of a light-induced decolorization of dyes in comparison with a photocatalytic reaction without polyols. A possible reaction mechanism of dye decolorization by the photocatalyst in the presence of electron donors was proposed. TiO2 photocatalyst absorbed light to generate electrons (e-) and holes (h+). The electrons and holes were prevented from recombining by the presence of SEDs. The free electrons and holes then involved in decolorization processes through reduction or oxidation reactions. The effects of TiO2 catalyst amounts, irradiation time and polyol concentrations on dye decolorization were investigated. The decolorization efficiency significantly increased with the increasing irradiation time, SED concentrations and certain amounts of TiO2.