本研究利用紫外光發光二極體為光源，藉由光觸媒同時催化三價砷的氧化和六價鉻的還原，探討各項實驗操作變因(如：光強度、水溶液pH值、照光週期、初始濃度、自由基抑制劑、共存離子、重複性測試)對三價砷的氧化和六價鉻的還原速率之影響。並透過BET、XRD、SEM、UV-vis DRS和界達電位，進行光觸媒的物化特性之分析。
研究結果顯示，在酸性條件下，與六價鉻和三價砷溶液相比，在六價鉻與三價砷的混合溶液中，三價砷的氧化速率顯著增加，而六價鉻的還原速率有些微降低。此外混合溶液在酸性條件下，通過光催化作用對六價鉻和三價砷的氧化還原反應速率明顯高於鹼性條件。提升光強度會稍微提高六價鉻和三價砷的氧化還原反應速率，但最終會受到溶液中共存離子的影響。觀察到吸附在二氧化鈦表面的六價鉻和三價砷幾乎分別被光氧化還原為三價鉻和五價砷。此外，藉由實驗趨勢推論速率限制步驟為介面電子轉移，並透過推導動力學方程可以很好地模擬六價鉻和三價砷在紫外光發光二極體光催化之氧化還原反應速率。

The reduction of Cr(VI) and oxidation of As(III) in aqueous solution by As(III)/Cr(VI)/TiO2 process was studied under various light intensities, solution pH values, periodic illumination, initial concentration, radical inhibitors, co-existing ions, and recyclability testing. The characterizations of photocatalyst were analyzed by Brunauer-Emmett-Teller surface area measurement (BET), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), UV-vis diffuse reflectance spectra (UV-vis DRS) and zeta potential. Compared to the Cr(VI) and As(III) solution, the oxidation rate of As(III) drastically increases and Cr(VI) slightly decreases in the mixed solution of Cr(VI) and As(III) at pH 3, respectively. The redox reaction rates of Cr(VI) and As(III) by photocatalysis were significantly higher for acidic solutions than those for alkaline solutions. Increasing the light intensity would slightly increase the redox reaction rates of Cr(VI) and As(III), but was ultimately influenced by the co-existing ions present in solutions. The Cr(VI) and As(III) adsorbed on the surface of TiO2 were observed to be photoreduced to Cr(III) and As(V) almost completely. Moreover, the experimental results indicate that the interfacial charge transfer step was rate-determining. Consequently, the photocatalytic redox reactions of Cr(VI) and As(III) by the UV-LED process could be well modeled by the kinetic equation.

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