低温等离子体等技术降解水中氯苯酚的研究

发布时间：2019-03-19 15:20

【摘要】：含氯苯酚化合物的废水是比较常见而且数量众多的废水之一,具有相当高的生物毒性和富集性,既难降解又容易在生物体内积累,对生物体的安全造成了极大的威胁。传统的物理法、化学法和生化法很难降解氯苯酚类化合物,因此,针对氯苯酚化合物降解的高级氧化技术越来越受到重视。低温等离子体技术是集臭氧氧化、高能电子辐射和紫外光光解等作用于一体,同时具有物理效应和化学效应的新型高级氧化技术。在介质阻挡放电过程中会产生具有强氧化性的羟基自由基(·OH)等活性粒子,是低温等离子氧化技术的关键。该技术具有反应速度快、有机物降解彻底等优点,应用前景广阔。首先,本实验以2,4,6-三氯苯酚为目标降解物,采用介质阻挡放电方式进行降解处理,通过质谱扫描和氯离子定性实验确定2,4,6-三氯苯酚降解处理后,会进行脱氯反应生成2,4-二氯苯酚。然后,以2,4-二氯苯酚为主要降解目标,研究了起始电压、初始浓度、初始pH、起始电导率等因素对其降解效率的影响。结果表明,在2,4-二氯苯酚初始浓度为50 mg/L,起始电压为75 V,初始pH为5.32的条件下处理120 min,2,4-二氯苯酚的去除率可达76.13%。为进一步提高去除率,向溶液中加入催化剂(Fe2+、H2O2、TiO2、10%I-TiO2),催化剂的存在不同程度的提高了2,4-二氯苯酚的去除率,这是因为催化剂存在时增加了溶液中·OH的数量。在TiO2存在时,2,4-二氯苯酚的去除率可以提升到83.68%,随着10%I-TiO2的引入,去除率又增加到了90.59%。为了验证·OH的作用,在溶液中加入自由基清除剂(叔丁醇、二丙醇),2,4-二氯苯酚的去除率随着二者浓度的增大而不断减小,在二者浓度很大时仍有一部分2,4-二氯苯酚被降解,说明·OH是起主要作用氧化剂,在放电过程中仍有其他氧化物质产生。溶液pH和TOC随放电时间的增加而减小。最后,通过紫外可见分光光度计和质谱扫描(MS)定性和定量表征了的2,4,6-三氯苯酚和2,4-二氯苯酚及其降解产物,分析了降解产物的结构和2,4-二氯苯酚的降解过程。实验结果表明,低温等离子体能有效降解溶液中的2,4,6-三氯苯酚和2,4-二氯苯酚并将其转化为其他中间产物,这一研究为低温等离子体技术在氯苯酚废水处理方面的实际应用提供了一定的理论指导。
[Abstract]:The waste water containing chlorophenol compounds is one of the most common and abundant wastewater, which has high biotoxicity and enrichment. It is difficult to degrade and accumulate easily in vivo, which poses a great threat to the safety of organisms. The traditional physical, chemical and biochemical methods are difficult to degrade chlorophenol compounds. Therefore, more and more attention has been paid to the advanced oxidation technology for the degradation of chlorophenol compounds. Low temperature plasma technology is a new advanced oxidation technology, which integrates ozone oxidation, high energy electron radiation and UV photolysis, and has both physical and chemical effects. In the process of dielectric barrier discharge (DBD), active particles such as hydroxyl radical (OH) are produced, which is the key technology of low temperature plasma oxidation. The technology has the advantages of fast reaction speed and complete degradation of organic matter, and has a wide application prospect. Firstly, 2,4,6-trichlorophenol was degraded by dielectric barrier discharge (DBD). The degradation of 2,4,6-trichlorophenol was determined by mass spectrometry and qualitative analysis of chloride ion. Dechlorination takes place to produce 2,4-dichlorophenol. Then, taking 2,4-dichlorophenol as the main degradation target, the effects of initial voltage, initial concentration and initial conductivity of pH, on the degradation efficiency were studied. The results show that when the initial concentration of 4-dichlorophenol is 50 mg/L, the initial voltage is 75 V, and the initial pH is 5.32, the removal rate of dichlorophenol can reach 76.13% when the initial concentration of 4-dichlorophenol is 50 min,2,4-. In order to further improve the removal rate of 2,4-dichlorophenol, the presence of catalyst (Fe2, H2O2, TiO2, 10% IxTiO2) increased the removal rate of 2,4-dichlorophenol. This is because the presence of the catalyst increases the amount of OH in the solution. In the presence of TiO2, the removal rate of 2,4-dichlorophenol can be increased to 83.68%, and with the introduction of 10%I-TiO2, the removal rate of 2,4-dichlorophenol can be increased to 90.59%. In order to verify the effect of OH, the free radical scavenger (tert-butanol, dipropanol) was added to the solution, and the removal rate of 2,4-dichlorophenol decreased with the increase of both concentrations. A part of 2,4-dichlorophenol is still degraded when the concentration of OH is very high, which indicates that DCP is the main oxidant, and other oxidation substances are still produced during the discharge process. 4-dichlorophenol is still degraded in the concentration of 2,4-dichlorophenol. The solution pH and TOC decrease with the increase of discharge time. Finally, 2,4,6-trichlorophenol and 2,4-dichlorophenol and their degradation products were characterized by UV-vis spectrophotometer and mass spectrometry scanning (MS). The structure of the degradation products and the degradation process of 2,4-dichlorophenol were analyzed. The experimental results show that the low temperature plasma can effectively degrade 2,4,6-trichlorophenol and 2,4-dichlorophenol and convert them into other intermediate products. This study provides some theoretical guidance for the practical application of low temperature plasma technology in chlorophenol wastewater treatment.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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