A novel use of TiO2 fiber for photocatalytic ozonation of
2,4-dichlorophenoxyacetic acid in aqueous solution |
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Authors: | GIRI Rabindra Raj OZAKI Hiroaki TAKANAMI Ryohei and TANIGUCHI Shogo |
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Institution: | 1. New Industrial R & D Center, Osaka Sangyo University, 3-1-1 Nakagaito, Daito City, 574-8530 Osaka, Japan 2. Department of Civil Engineering, Osaka Sangyo University, 3-1-1 Nakagaito, Daito City, 574-8530 Osaka, Japan |
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Abstract: | More efficient oxidation methods are needed to degrade especially newly emerging recalcitrant organic contaminants at low concentrations in the water environment. Reduced photonic efficiency of immobilized TiO2 is a major challenge in TiO2-assisted advanced oxidation processes (AOP). Mineralization of 2,4-dichllorophenoxyacetic acid (2,4-D) in low aqueous solution by O3/UV/TiO2 using the world's first high-strength TiO2 fiber was investigated and compared with O3UV/TiO2 and O3/TiO2 in laboratory batch experiments. The 2,4-D degradation and total organic carbon (TOC) removal followed pseudo first-order reaction kinetic, while their rates in O3/UV/TiO2 were respectively about 1.5 and 2.4 times larger than the summation of the values in O3 and UV/TiO2. The O3/UV/TiO2 was characterized by few aromatics with very low abundance, fast disappearance of aliphatics and more than 95% dechlorination. The discrepancies in organic carbon mass balance among the intermediates and 2,4-D were attributed mainly to few apparently major unidentified intermediates. The significantly enhanced 2,4-D mineralization in O3/UV/TiO2 was attributed to increased ozone dissolution followed by its decomposition, and reduced electron-hole recombination in presence of dissolved ozone resulting in a large number of hydroxyl radical (·OH) generation from more than one parallel path. The removal efficiencies of the systems can further be enhanced by optimizing design parameters, and O3/UV/TiO2 with the TiO2 fiber is promising to mineralize recalcitrant organic contaminants in water at low concentrations. |
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Keywords: | dechlorination degradation intermediates radicals TiO2 total organic carbon (TOC) |
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