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    Title: 以化學法與電化學法氧化分解有機反應性染料之探討
    Other Titles: Chemical and electrochemcial oxidation for organic dye decomposition
    Authors: 何志軒;Ho, Chih-hsuan
    Contributors: 淡江大學水資源及環境工程學系博士班
    陳俊成;Chen, Luke
    Keywords: 化學氧化;電化學氧化;有機反應性染料;氧化分解;反應動力;Chemical Oxidation;Electrochemical Oxidation;Reactive Blue 19;decomposition;Reaction kinetics
    Date: 2010
    Issue Date: 2010-09-23 17:55:24 (UTC+8)
    Abstract: 本研究針對有機反應性染料進行氧化裂解特性分析,主要針對三個部份進行研究。第一部分:化學氧化裂解反應:以強氧化劑氧化裂解有機反應性染料,並求出化學反應動力常數與反應級數,進而探討氧化過程中活化能與碰撞頻率。並利用LC-MS分析氧化裂解途徑與有機碎片。第二部份:利用電化學氧化方式,分別以間接法與直接法二種方式進行探討。間接電化學法目的在判斷電化學過程中產生之氧化劑含量與氧化裂解有機反應性染料特性,並與第一部份之化學法比較,同時研判直接電化學法未來應用在實際工場氧化裂解之可行性。第三部份:於反應槽中間加入4~5.5μm的硼矽酸玻璃材質之隔膜濾材,使電化學反應槽內區分為陽極部份與陰極部分,並分析項目與第二部份的電化學法相同。其中間接法分析,係取具有強氧化劑的陽極部分之電解液進行分析,並探討氧化有機反應性染料之特性。直接法部分即於反應槽陽極部分加入有機反應性染料,探討氧化效應,並與第二部分直接法進行比較。
    由化學法氧化研究結果顯示,商業用次氯酸鈉實際濃度僅為2.38±0.18 %,而混合OCl-與有機染料之化學氧化裂解反應動力,有機染料部分之反應級數為0.5級反應,OCl-部份之反應級數為1級反應,碰撞頻率為1.3884×1010與活化能Ea為76.604 kJ/mole。在低濃度OCl-裂解有機染料RB-19的色度去除率達80 %時,COD僅去除約8% ,藉由LC-MS鑑定確認其最初裂解途徑為C14H9N2O5S與C8H10NNaO6S2及C20H13NO2等三類主要有機染料片段。
    由電化學法研究結果顯示,利用間接電化學法程序確實能產生具有氧化能力之OCl-,可氧化裂解有機反應性染料。當操作條件在通電電壓越大與通電時間越久,其化學氧化裂解反應結果越好。當反應槽內添加2g/L NaCl電解質時,間接電化學法最大約產生6.5 mM OCl-與化學氧化程序中同濃度氧化劑比較,間接電化學法的反應動力速率比化學法反應速率快約2.8倍。電解質的添加含量為電化學產生氧化劑含量多寡的主要條件,間接電化學法在適當條件(電壓15伏特以上,通電時間20分鐘以上),Color與COD去除效率皆能達到100%。直接電化學法程序則能有效且快速氧化裂解有機反應性染料,當高電解質(2g/L NaCl)添加以及適當電壓(15伏特以上)與通電處理時間(5分鐘以上),Color去除率達100%以及COD去除率達83%以上,有效去除有機染料之Color與COD。
    以硼矽酸玻璃隔膜提昇電化學氧化裂解結果顯示,將硼矽酸玻璃隔膜置入電化學反應槽內,以間接電化學法或直接電化學法,皆能於陽極電解液部分產生具有氧化能力之氧化劑,所產生氧化劑主要為Cl2與HOCl。當電壓越大與通電時間越長,陽極電解液pH值呈現強酸,產生之氧化劑(Cl2、HOCl)含量越多,相對於氧化裂解有機染料強度越強。硼矽酸玻璃隔膜提昇間接電化學法的實驗結果顯示,雖產生具有氧化強度較大之氧化劑,其處理效果與沒有隔膜之電化學處理效果差異不大,但其操作過程因電流密度明顯降低,因此以操作成本面考量,該隔膜確實有助於提升電化學處理之效益。在直接電化學法實驗結果中,則能更有效且快速氧化裂解有機反應性染料,當有機反應性染料內添加電解質(2g/L NaCl),並提供通電電壓(20伏特)與處理時間(3分鐘),能有效去除染料之Color去除率達95%以上與COD去除率達70%以上。
    The goal of this study is to understand the decomposition of Reactive Blue C.I. 19 (RB 19) in oxidation processes, to acquire a kinetic model for reactor and process design, and to develop the process as a viable alternative to advanced oxidation processes (AOPs) for industrial waste effluent decolorization.. The study was divided into chemical oxidation, electrochemical oxidation and membrane enhanced electrochemical processes.
    For chemical oxidation process, the reaction kinetics of RB 19 and sodium hypochlorite (NaOCl) was investigated. The decline of RB 19 was monitored continuously by an ultraviolet-visible range (UV-Vis) spectrophotometer to avoid sampling errors. The objective of this study is to develop a kinetic model for reactor and process design.
    For electrochemical oxidation, direct and indirect electrochemical oxidation methods were explored for their effectiveness on color removal and COD reduction. In the indirect electrochemical process oxidizing agent was produced and mixed with RB19-containing solutions to determine its efficiency on color removal and dye decomposition. For direct method, dye-containing solutions were treated in the electrochemical reactor. A thorough comparison was done among direct and indirect electrochemical processes, and chemical method.
    For membrane enhanced electrochemical oxidation, a borosilicate glass membrane (4.0 ~ 5.5 μm) was inserted into the electrochemical reactor, and divided the reactor into anode and cathode chambers. The reactor was test in both direct and indirect modes. For indirect operation, anolyte was used to treat RB19 in the synthetic dye bath. As for direct method, the synthetic dyebath was injected into the anode chamber for treatment. The results were compared with the previous study.
    The chemical oxidation results were in agreement with 0.5-order reaction kinetics with respect to the RB 19 concentration. The lumped rate constant of the pseudo-0.5-order reaction is proportional to the NaOCl concentration. The Arrhenius activation energy obtained from the slope of the best-fit line is 76.6 kJ/mol, with a corresponding preexponential factor of 1.3884 × 1010. The reaction rate is strongly affected by the pH of the solution. During the oxidation decomposition process, color was rapidly removed by the NaOCl but chemical oxygen demand (COD) resisted the treatment. A molar ratio of more than 44 is essential for OCl- to completely decompose the dye molecules thus remove COD from the solution. A system of liquid chromatography mass spectrometry (LC/MS) was used to determine the intermediates in the initial steps of the decomposition process.
    The results from electrochemical oxidation indicated that indirect method generates oxidation agent (OCl-) efficiently, and the OCl- effectively decomposes RB-19 in the solution. The key parameters of the process are applied voltage and operating time. A maximum concentration (6.5 mM OCl-) of oxidation agent was generated when 2 g/L NaCl solution was treated in the reactor at 20 volts DC for 30 minutes. It indicates that the amount of electrolyte determines the amount of oxidation agent that can be produced in the reactor. Color and COD reduction were 100% when the synthetic dyebath was treated with anolyte that was produced at 15 volts for 20 minutes. When directly treated in the anode chamber, color was completely removed in 5 minutes at 15 volts. Under the condition the decolorization efficiency was 100% while COD reduction was only 83%.
    The test result from the membrane enhanced electrochemical oxidation indicates that insert borosilicate glass membrane in the reactor significantly increased the oxidation potential of the anolyte. The oxidizing agent produced is believe to be the mixture of Cl2 and HOCl. The pH of anode solution was strongly acid (pH = 2) when operated under higher voltage for a long time. Decolorization efficiency of the membrane enhanced electrochemical oxidation was similar to that of the electrochemical oxidation. When treated the dyebath directly in the anode chamber color was completely remove in three minutes. However, under the same condition only 70% of the COD was removed.
    Appears in Collections:[水資源及環境工程學系暨研究所] 學位論文

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