氯代有機(jī)酸的電化學(xué)降解研究
發(fā)布時間：2019-02-09 07:18
【摘要】：本文采用電化學(xué)氧化和電化還原兩種方法研究了氯代有機(jī)酸的降解。接觸輝光放電電解(Contact Glow Discharge Electrolysis,CGDE)法是一種新型的電化學(xué)氧化方法,本文對CGDE氧化降解水中氯乙酸(Chloroacetic Acids,CAs)與氯丙酸(Chloropropionic Acids,CPAs)進(jìn)行了研究。對CAs的研究表明,隨著CAs的降解,總有機(jī)碳(Total Organic Carbon,TOC)的量也隨之減少,并且CAs上的氯原子發(fā)生脫氯反應(yīng)生成氯離子(Cl-)并釋放到溶液中。主要的中間產(chǎn)物為甲酸(Formic Acid,FA)。CAs的降解和TOC的去除皆符合一級動力學(xué)原理。CAs上連接的氯原子數(shù)越少,所對應(yīng)的CAs的降解與TOC的去除反應(yīng)速率越高。基于對反應(yīng)中間產(chǎn)物的檢測結(jié)果和動力學(xué)原理,討論了CAs在羥基自由基(·OH)等的連續(xù)作用下碳鏈裂解、Cl-脫除和二氧化碳生成的反應(yīng)途徑。CPAs的CGDE氧化降解過程與CAs相似。實(shí)驗結(jié)果表明,隨著CPAs的降解,TOC的量也隨之減少。CPAs上的氯原子被脫除,轉(zhuǎn)化為Cl-釋放到反應(yīng)溶液中。實(shí)驗中檢測出的主要中間產(chǎn)物有草酸(Oxalic Acid,OA)和FA,其它中間產(chǎn)物還有乙酸(Acetic Acid,AA)、氯乙酸(Monochloroacetic Acid,MCA)和丙二酸(Propanedioic Acid,PDA)。CPAs的降解和TOC的去除皆符合一級動力學(xué)原理。隨著CPAs的pKa值的增加,CPAs降解反應(yīng)速率常數(shù)也隨之增大,而TOC去除速反應(yīng)率常數(shù)基本不受pKa值影響。基于對反應(yīng)中間產(chǎn)物的檢測結(jié)果和動力學(xué)原理,提出了CPAs氧化降解主要是受到強(qiáng)氧化劑·OH的連續(xù)攻擊而引發(fā)CPAs的長碳鏈斷裂,進(jìn)而被氧化成二氧化碳、水和Cl-的反應(yīng)過程。本文還采用非電沉積法制備了鈀負(fù)載泡沫鎳陰極對三氯乙酸(Trichloroacetic Acid,TCA)進(jìn)行了恒電流電化學(xué)還原脫氯研究。考察了電解質(zhì)種類、電解質(zhì)濃度、電流密度、反應(yīng)溫度和鈀負(fù)載量此五種因素對TCA降解反應(yīng)的影響,并采用掃描電鏡(Scanning Electron Microscope,SEM)方法對制備的鈀負(fù)載泡沫鎳電極進(jìn)行了表征。實(shí)驗中發(fā)現(xiàn)當(dāng)條件為:20mM硫酸鈉為電解質(zhì),溫度為20℃,鈀負(fù)載量4.5mg/cm2,10mA恒電流電解240min時,TCA降解率達(dá)99.76%,氯原子脫除率達(dá)73.86%。反應(yīng)中檢測到了二氯乙酸(Dichloroacetic Acid,DCA)、MCA和AA三種中間產(chǎn)物,說明TCA電解還原脫氯反應(yīng)中氯原子以Cl-的形式逐個脫除。實(shí)驗中測得TCA還原反應(yīng)和符合一級動力學(xué)原理,反應(yīng)速率為0.0258min-1(R2=0.9955),同時溶液中TCA上未脫除氯原子濃度變化亦符合擬一級動力學(xué)原理,反應(yīng)速率為0.0072min-1(R2=0.9958)。
[Abstract]:The degradation of chlorinated organic acids was studied by electrochemical oxidation and electrochemical reduction. Contact glow discharge electrolysis (Contact Glow Discharge Electrolysis,CGDE) is a new electrochemical oxidation method. The degradation of chloroacetic acid (Chloroacetic Acids,CAs) and chloropropionic acid (Chloropropionic Acids,CPAs) in water by CGDE has been studied in this paper. The study of CAs showed that the amount of total organic carbon (Total Organic Carbon,TOC) decreased with the degradation of CAs, and the chlorine atom on CAs dechlorinated to form chloride ion (Cl-) and released into solution. The main intermediate product is formic acid (degradation of Formic Acid,FA). CAs and removal of TOC are in accordance with the first-order kinetic principle). The lower the number of chlorine atoms attached to CAs, the higher the rate of CAs degradation and TOC removal. Based on the detection results and kinetic principle of the intermediate products of the reaction, the carbon chain cleavage of CAs under the continuous action of hydroxyl radical (OH) et al was discussed. The process of CGDE oxidative degradation of CPAs is similar to that of CAs. The experimental results show that with the degradation of CPAs, the amount of TOC decreases. The chlorine atoms in CPAs are removed and converted into Cl- to be released into the reaction solution. The main intermediates detected in the experiment were oxalic acid (Oxalic Acid,OA) and other intermediate products of FA,: acetic acid (Acetic Acid,AA), chloroacetic acid (Monochloroacetic Acid,MCA) and malonic acid (Propanedioic Acid,. The degradation of PDA). CPAs and the removal of TOC accord with the first order kinetic principle. With the increase of pKa value of CPAs, the rate constant of CPAs degradation reaction increases, but the TOC removal rate constant is not affected by pKa value. Based on the detection results and kinetic principle of the intermediate products of the reaction, it is proposed that the oxidation degradation of CPAs is mainly caused by the continuous attack of strong oxidant OH, which leads to the long carbon chain break of CPAs, which is then oxidized to the reaction process of carbon dioxide, water and Cl-. The electrochemical reduction dechlorination of trichloroacetic acid (Trichloroacetic Acid,TCA) by palladium supported nickel foam cathode was studied by non electrodeposition method. The effects of electrolyte type, electrolyte concentration, current density, reaction temperature and palladium loading on the degradation of TCA were investigated. The palladium-supported nickel foam electrode was characterized by SEM. It is found that the degradation rate of TCA is 99.76 and the removal rate of chlorine is 73.86 when sodium 20mM sulfate is used as electrolyte, temperature is 20 鈩，
本文編號：2418836
[Abstract]:The degradation of chlorinated organic acids was studied by electrochemical oxidation and electrochemical reduction. Contact glow discharge electrolysis (Contact Glow Discharge Electrolysis,CGDE) is a new electrochemical oxidation method. The degradation of chloroacetic acid (Chloroacetic Acids,CAs) and chloropropionic acid (Chloropropionic Acids,CPAs) in water by CGDE has been studied in this paper. The study of CAs showed that the amount of total organic carbon (Total Organic Carbon,TOC) decreased with the degradation of CAs, and the chlorine atom on CAs dechlorinated to form chloride ion (Cl-) and released into solution. The main intermediate product is formic acid (degradation of Formic Acid,FA). CAs and removal of TOC are in accordance with the first-order kinetic principle). The lower the number of chlorine atoms attached to CAs, the higher the rate of CAs degradation and TOC removal. Based on the detection results and kinetic principle of the intermediate products of the reaction, the carbon chain cleavage of CAs under the continuous action of hydroxyl radical (OH) et al was discussed. The process of CGDE oxidative degradation of CPAs is similar to that of CAs. The experimental results show that with the degradation of CPAs, the amount of TOC decreases. The chlorine atoms in CPAs are removed and converted into Cl- to be released into the reaction solution. The main intermediates detected in the experiment were oxalic acid (Oxalic Acid,OA) and other intermediate products of FA,: acetic acid (Acetic Acid,AA), chloroacetic acid (Monochloroacetic Acid,MCA) and malonic acid (Propanedioic Acid,. The degradation of PDA). CPAs and the removal of TOC accord with the first order kinetic principle. With the increase of pKa value of CPAs, the rate constant of CPAs degradation reaction increases, but the TOC removal rate constant is not affected by pKa value. Based on the detection results and kinetic principle of the intermediate products of the reaction, it is proposed that the oxidation degradation of CPAs is mainly caused by the continuous attack of strong oxidant OH, which leads to the long carbon chain break of CPAs, which is then oxidized to the reaction process of carbon dioxide, water and Cl-. The electrochemical reduction dechlorination of trichloroacetic acid (Trichloroacetic Acid,TCA) by palladium supported nickel foam cathode was studied by non electrodeposition method. The effects of electrolyte type, electrolyte concentration, current density, reaction temperature and palladium loading on the degradation of TCA were investigated. The palladium-supported nickel foam electrode was characterized by SEM. It is found that the degradation rate of TCA is 99.76 and the removal rate of chlorine is 73.86 when sodium 20mM sulfate is used as electrolyte, temperature is 20 鈩，
本文編號：2418836
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