| Summary: | 碩士 === 國立高雄科技大學 === 環境與安全衛生工程系 === 107 === Nano-semiconductor particles assisted photocatalysis is an innovative process widely applied to organic wastewater purification. There have been numerous research results indicate that this kind of photocatalytic oxidation processes are able to decompose many organic pollutants in a short reaction time. Among the ever tested photocatalysts, titanium dioxide (TiO2) is one of the most common one, because it has many superior properties including highly reactive, inexpensive, low toxic, stable and widely available. But there is one drawback for TiO2 limiting its potential application, which is the recombination rates of the photo-generated electron and hole pairs of it are too fast to result in low quantum efficiencies. Thus, developing an convent modification for the TiO2-assisted photocatalysis process is attracting many research efforts in recent studies.
Accordingly, this study aimed to develop an electric magnetic field assisted photocatalytic oxidation processes for wastewater treatment by enhancing TiO2 activity. A home-made magnetic system supportively working with a typical TiO2-assited photocatalytic process was tested. A commercially available TiO2 powder, Degussa P-25, was used as the photocatalyst in the study. A typical dying compound, methyl orange, was tested as a target compound. Besides, there were several experimental parameters including solution pH levels, types and intensities of irradiated light sources, and intensity of applied magnetic fields, examined in the study.
There are some important findings demonstrated by this investigation. The TiO2-assisted photocatalysis of methyl orange basically followed the first-order reaction kinetics. Fast photocatalysis of methyl orange was observed under the illumination of near-UV light (λ= 365 nm), but slow degradation rate for it was detected while using visible blue light (λ= 470 nm) as an only light source. Higher photocatalytic rates for methyl orange were observed in more acid conditions (e.g., pH= 3) because that it was more easily adsorbed by the photocatalysts in lower-pH conditions. In addition, it is observed higher degradation rates while irradiated light intensity was higher. For the contribution of magnetic fields to the photocatalytic reaction rates, the degradation rate of methyl orange was proportional to magnetic intensity up to 140 mT. The higher photocatalytic reaction rate for methyl orange was achieved by the assistance of an additional magnetic field, especially in pH= 3 solution, which altered the recombination rates of electron-hole pairs under the effects of magnetic fields.
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