Abstract
BackgroundPhotodegradation of trichloroethylene (TCE) in aqueous solution under simulated solar light irradiation was studied under different experimental conditions to determine the reaction mechanism and kinetics that control TCE degradation using bismuth oxybromide (BiOBr) in the presence of sulfite. Photocatalysts were synthesized to be more responsive to visible light under simulated solar light and particular attention was focused on the reactive specie formed by reaction of the sulfite on the surface of BiOBr under simulated sunlight.ResultDegradation rate of TCE was greatly enhanced by the presence of sulfite, and the enhancement increased with sulfite dose to a maximum that was retained at higher sulfite doses. Degradation rate of TCE was also affected by other factors, such as initial TCE concentration, BiOBr dose, and solution pH. In addition, the cycling performance of BiOBr was examined, and the amount of TCE degraded was almost constant over increasing cycle numbers when initial sulfite concentration was high enough to maintain a suitable sulfite concentration throughout the experiment. When TCE was degraded by BiOBr in the presence of sulfite under simulated sunlight irradiation, the major by-product measured was the non-hazardous chloride ion, and dechlorination efficiency was about 58%.ConclusionThis study extended the use of a potential effective photocatalyst (BiOBr) to a semi-volatile organic contaminant (TCE), not limited to mainly focus on organic dyes, and evaluated the use of sulfite as a hole scavenger in order to enhance the degradation of TCE without needing to manipulate the structure of BiOBr. The active species being responsible for TCE degradation in BiOBr/TCE/sulfite system under simulated solar light was the sulfite radical (SO3·−), and the photocatalytic activity of BiOBr did not decrease over a number of treatment cycles when SIV dose was sufficient.
Highlights
Photodegradation of trichloroethylene (TCE) in aqueous solution under simulated solar light irradiation was studied under different experimental conditions to determine the reaction mechanism and kinetics that control TCE degradation using bismuth oxybromide (BiOBr) in the presence of sulfite
This study extended the use of a potential effective photocatalyst (BiOBr) to a semi-volatile organic contaminant (TCE), not limited to mainly focus on organic dyes, and evaluated the use of sulfite as a hole scavenger in order to enhance the degradation of TCE without needing to manipulate the structure of BiOBr
The active species being responsible for TCE degradation in BiOBr/TCE/sulfite system under simulated solar light was the sulfite radical (SO3·−), and the photocatalytic activity of BiOBr did not decrease over a number of treatment cycles when S IV dose was sufficient
Summary
Photodegradation of trichloroethylene (TCE) in aqueous solution under simulated solar light irradiation was studied under different experimental conditions to determine the reaction mechanism and kinetics that control TCE degradation using bismuth oxybromide (BiOBr) in the presence of sulfite. The final products of TCE degradation by AOPs include chloride, formic acid, dichloroacetic acid, monochloroacetic acid, glyoxylic acid, monochloroacetylene, dichloroacetylene, formaldehyde, dichloroacetaldehyde, and oxalic acid. Phillips and Raupp [16] suggested that hydroxyl radical or hydroperoxide radical initialized the photocatalytic reaction of TCE and measured dichloroacetaldehyde an intermediate. Glaze et al [17] have proposed two pathways for TCE photodegradation; a reductive pathway involving conduction band electrons and an oxidative pathway leading to mineralization. They found dichloroacetaldehyde (DCAAD), dichloroacetic acid (DCAA), and trichloroacetic acid (TCAA) as products. Yamazaki-Nishida et al [3] proposed a mechanism including an initial reaction with hydroxyl radicals and monochloroacetate as an intermediate. Fan and Yates [2] have investigated the photooxidation of TCE on TiO2 using infrared spectroscopy and the intermediate they identified was dichloroacetyl chloride (HCl2CCOCl)
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