氯代有机酸的电化学降解研究
发布时间：2019-02-09 07:18
【摘要】：本文采用电化学氧化和电化还原两种方法研究了氯代有机酸的降解。接触辉光放电电解(Contact Glow Discharge Electrolysis,CGDE)法是一种新型的电化学氧化方法,本文对CGDE氧化降解水中氯乙酸(Chloroacetic Acids,CAs)与氯丙酸(Chloropropionic Acids,CPAs)进行了研究。对CAs的研究表明,随着CAs的降解,总有机碳(Total Organic Carbon,TOC)的量也随之减少,并且CAs上的氯原子发生脱氯反应生成氯离子(Cl-)并释放到溶液中。主要的中间产物为甲酸(Formic Acid,FA)。CAs的降解和TOC的去除皆符合一级动力学原理。CAs上连接的氯原子数越少,所对应的CAs的降解与TOC的去除反应速率越高。基于对反应中间产物的检测结果和动力学原理,讨论了CAs在羟基自由基(·OH)等的连续作用下碳链裂解、Cl-脱除和二氧化碳生成的反应途径。CPAs的CGDE氧化降解过程与CAs相似。实验结果表明,随着CPAs的降解,TOC的量也随之减少。CPAs上的氯原子被脱除,转化为Cl-释放到反应溶液中。实验中检测出的主要中间产物有草酸(Oxalic Acid,OA)和FA,其它中间产物还有乙酸(Acetic Acid,AA)、氯乙酸(Monochloroacetic Acid,MCA)和丙二酸(Propanedioic Acid,PDA)。CPAs的降解和TOC的去除皆符合一级动力学原理。随着CPAs的pKa值的增加,CPAs降解反应速率常数也随之增大,而TOC去除速反应率常数基本不受pKa值影响。基于对反应中间产物的检测结果和动力学原理,提出了CPAs氧化降解主要是受到强氧化剂·OH的连续攻击而引发CPAs的长碳链断裂,进而被氧化成二氧化碳、水和Cl-的反应过程。本文还采用非电沉积法制备了钯负载泡沫镍阴极对三氯乙酸(Trichloroacetic Acid,TCA)进行了恒电流电化学还原脱氯研究。考察了电解质种类、电解质浓度、电流密度、反应温度和钯负载量此五种因素对TCA降解反应的影响,并采用扫描电镜(Scanning Electron Microscope,SEM)方法对制备的钯负载泡沫镍电极进行了表征。实验中发现当条件为:20mM硫酸钠为电解质,温度为20℃,钯负载量4.5mg/cm2,10mA恒电流电解240min时,TCA降解率达99.76%,氯原子脱除率达73.86%。反应中检测到了二氯乙酸(Dichloroacetic Acid,DCA)、MCA和AA三种中间产物,说明TCA电解还原脱氯反应中氯原子以Cl-的形式逐个脱除。实验中测得TCA还原反应和符合一级动力学原理,反应速率为0.0258min-1(R2=0.9955),同时溶液中TCA上未脱除氯原子浓度变化亦符合拟一级动力学原理,反应速率为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，
本文编号：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，
本文编号：2418836
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