在本研究中，研究了Fe(III)存在下的UV/TiO2工藝對As(III)的光催化氧化和Cr(VI)的光還原反應，並考察了不同操作條件對反應的影響，如溶液pH值、UV光強度、Fe(III)、As(III)和Cr(VI)的初始濃度、無機鹽和活性自由基等。通過浸潤法製備了Ti薄膜載體上的TiO2光催化劑，並利用X射線衍射（XRD）、Brunauer-Emmett-Teller表面積測定（BET）、場發射掃描電子顯微鏡（FE-SEM）、zeta電位（pHpzc）、X射線光電子能譜（XPS）等方法對催化劑進行了表徵分析。
研究探討了Fe(III)在單一和混合金屬離子系統中對As(III)氧化和Cr(VI)還原在UV/TiO2工藝中的作用。在UV/TiO2/Cr(VI)/Fe(III)系統中，Fe(III)的存在促進了酸性介質中Cr(VI)的光還原反應，通過Fe(III)/Fe(II)氧化還原循環使Cr(VI)的光還原反應提高了34%。首次提出了基於Langmuir-Hinshelwood機理的雙位點動力學模型，該模型對UV/TiO2/Fe(III)工藝中Cr(VI)的光還原反應與實驗數據非常吻合。在UV/TiO2/As(III)/Fe(III)系統中，添加Fe(III)顯著提高了As(III)的氧化效率，將其從48.53%提高到94.51%。實驗結果表明，在無Fe(III)存在的水溶液中，光產生的正電子是As(III)氧化的主要活性自由基。然而，在酸性介質中，As(III)的氧化主要發生在溶液中，由於Fe(III)在UV照射下光解產生∙OH自由基。在UV/TiO2/As(III)/Cr(VI)系統中觀察到As(III)和Cr(VI)之間的競爭吸附效應，產生了負面影響。在酸性溶液中，在90分鐘內，添加Fe(III)使As(III)和Cr(VI)的同時去除率分別提高了55%和24%。在無Fe(III)存在時，光產生的正電子和電子主要貢獻於As(III)的氧化和Cr(VI)的還原反應。在Fe(III)存在下，Fe(II)的生成和∙OH自由基參與了UV/TiO2/As(III)/Cr(VI)系統的反應機制。利用Langmuir-Hinshelwood（L-H）動力學模型分析，光催化表面反應被證明是As(III)光氧化和Cr(VI)光還原的速率控制步驟。

In this study, the simultaneous photocatalytic oxidation of As(III) and reduction of Cr(VI) in the presence of Fe(III) was investigated by UV/TiO2 process under various operation conditions, such as solution pH, UV light intensity, initial concentrations of Fe(III), As(III), and Cr(VI), inorganic salts, and active radicals. The Ti film supported TiO2 was fabricated by the impregnation method, as photocatalysts for the redox system and the characterizations of catalyst were analyzed by X-ray diffraction (XRD), Brunauer- Emmett-Teller surface area measurement (BET), field emission scanning electron microscope (FE-SEM), zeta potential (pHpzc), X-ray photoelectron spectroscopy (XPS).
The role of Fe(III) in the As(III) oxidation and Cr(VI) reduction under UV/TiO2 process in single and simultaneous metal ions system were studied. In UV/TiO2/Cr(VI)/Fe(III) system, the presence of Fe(III) promoted the photoreduction of Cr(VI) by 34% in acidic medium through the Fe(III)/Fe(II) redox cycle. A dual-site kinetic model based on the Langmuir-Hinshelwood mechanism for Cr(VI) photoreduction by UV/TiO2/Fe(III) process is first proposed and well fitted with the experiment data. In UV/TiO2/As(III)/Fe(III), the oxidation of As(III) was enhanced significantly by adding Fe(III) from 48.53% to 94.51%. Experimental results indicated that photogenerated holes were the main active radical for the oxidation of As(III) in the absence of Fe(III) in aqueous solution. However, the oxidation of As(III) primarily occurred in the bulk solution by ∙OH radicals, which were produced from Fe(III) photolysis under UV irradiation in acidic medium. In UV/TiO2/As(III)/Cr(VI) system, a negative effect between As(III) and Cr(VI) was observed due to their competitive adsorption on TiO2 surface. The simultaneous removal of As(III) and Cr(VI) enhanced by 55% and 24% by adding Fe(III) in acidic solution under UV irradiation within 90 min. In the absence of Fe(III), photogenerated holes and electrons primarily attributed to the As(III) oxidation and Cr(VI) reduction, respectively. In the presence of Fe(III), the production of Fe(II) and ∙OH radicals took part in the reaction mechanism of UV/TiO2/As(III)/Cr(VI) system. The photocatalytic surface reaction was demonstrated as the rate-determining step for As(III) photooxidation and Cr(VI) photoreduction which was analyzed by the Langmuir-Hinshelwood (L-H) kinetic model.

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