探討光電觸媒之氫氧自由基檢測方法及其產率

The study on the measurement method and yield of hydroxyl radical by photo/electro catalysis

許家綺(Jia-Chi Hsu)

指導教授 ： 章日行

朝陽科技大學/理工學院/環境工程與管理系/碩士(2011年)

摘要

高級氧化程序（Advanced Oxidation Processes, AOPs）為近年來較常使用的廢水處理技術，因其具有反應快速、不受污染物濃度限制，且能有效產生氫氧自由基（Hydroxyl radical, OH‧），達到快速氧化水中有機物之優點，故廣泛地運用於環境污染處理。在眾多AOPs技術中，以往多著重於Fenton法及光催化反應法，對於電觸媒技術（Electrocatalysis）著墨較少，特別對於電觸媒系統產生氫氧自由基之研究仍有待深入探討，因此，本研究主要驗證在光觸媒及電觸媒系統下，氫氧自由基之生成反應。試驗以反應時間、電解質種類、能量、pH及極板種類為操作參數，依據試驗結果瞭解二種系統在不同條件下對氫氧自由基生成之影響，進而估算二種系統單位面積的OH‧產率。

本試驗利用4-羥基苯甲酸（4-HBA）作為氫氧自由基捕捉劑，4-羥基苯甲酸可與氫氧自由基反應生成3,4-二羥基苯甲酸（3,4-DHBA），穩定存在的3,4-DHBA在水溶液中穩定即可作為氫氧自由基濃度指標。由試驗結果得知，光、電觸媒系統產生之氫氧自由基約於操作30 sec後達到穩定，本研究兩系統的OH‧濃度分別為4.58×10-3 M及6.58×10-3 M。在電解質方面，當光觸媒系統以硫酸鈉（Na2SO4）、電觸媒系統以硝酸鈉（NaNO3）為電解質之操作條件，其氫氧自由基之生成效果最佳。在能量輸入方面，兩系統生成之OH‧濃度皆與所施予之能量呈現正向的關係。另外，當pH在鹼性條件下有利於氫氧自由基之生成，其產率遠高於中性及酸性條件。而觸媒極板則以二氧化鈦之生成濃度為最佳，光、電觸媒系統之生成濃度最高分別可達7.69×10-3 M 及1.57×10-2 M。在本研究採用之光、電觸媒系統之最佳操作條件下，單位面積/能量所測得之氫氧自由基產率為：光觸媒系統為3.9×10-5 M W-1cm-2、電觸媒系統為4.5×10-5 M W-1cm-2，以電觸媒產生OH‧的效率較高。

關鍵字

二氧化鈦 ； 電觸媒 ； 光觸媒 ； 氫氧自由基 ； 高級氧化程序

並列摘要

Advanced Oxidation Processes (AOPs) is one of the most effective techniques for decomposing organic pollutants, owing to their extremely fast degradation and no restrict of pollutant concentration. Therefore, these techniques have been frequently used for wastewater treatment recently. Hydroxyl radicals can be produced effectively by the catalytic materials in the aquatic system. In the past, most researthes focued on the Fenton and photocatalytic reaction. For other kind of AOPs the electrocatalysis, there are few studies on the hydroxyl radicals production of electrocatalysis. This study investigated the reaction of hydroxyl radicals in the photocatalytic and electrocatalyst system. Based on different operation parameters (reaction time, electrolyte, energy, pH and electrode materials), the hydroxyl radicals production of the photocatalytic and electrocatalyst system were estirnated.

The 4-hydroxybenzoic acid (4-HBA) was served as a trapping reagent to determine the concentration the concentration hydroxyl radicals. The 4-HBA reacts with OH‧ to from 3,4-dihydroxybenzoic acid (3,4-DHBA), which can be used as an indicatiors of OH‧concentration. Results showed that the equilibrium concentration of derivatives (3,4-DHBA) could be reached after 30-second reaction in photocatalytic and electrocatalyst system, respectively. The concentration of OH‧ was about 4.58×10-3 M and 6.58×10-3 M under 1-min operation of photo and electro catalysis, respectively. The electrolyte of Na2SO4（photocatalytic）and NaNO3（electrocatalyst）was relatively appropriate for producing OH‧. In addition, production rate of OH‧ possessed linear correlation with energy application. High pH conditions were beneficial to the production of OH‧ in comparison with pH neutrality and acidity. The highest OH‧concentration of 7.69×10-3 M and 1.57×10-2 M could be obtained by using the TiO2 electrode. The yield rate of OH‧in the photocatalytic and electrocatalyst system was about 3.9×10-5 M W-1cm-2 and 4.5×10-5 M W-1cm-2 respecfirely, based on the same electrode area and energy application.

並列關鍵字

photocatalytic ； titanium dioxide ； electrocatalyst ； hydroxyl radical ； Advanced Oxidation Processes

參考文獻

12. 游非庸，「Photo-Fenton相關程序氫氧自由基生成及分解染料之研究」，博士學位論文，私立淡江大學水資源及環境工程學系，新北市(2010)。

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