高盐环境氯酚氧化降解体系中有机卤代物生成机制与毒性评价研究

发布时间：2018-06-02 10:08

本文选题：高盐氯酚废水 + Co/PMS　；参考：《东华大学》2017年博士论文

【摘要】：氯酚废水主要来源于炼油、炼焦、造纸、医药、印染、化工等行业,其排放量大,对环境造成极大的威胁,因而氯酚废水的无害化处理成为国内外学者关注的热点问题。近年来,基于硫酸根自由基(SO4·-)的高级氧化技术因其反应速度快、限制条件少,处理效率高等优点,被认为是未来可能应用于处理氯酚类等有机污染物的新型技术。但是,在对氯酚废水成分的考察中发现,其成分通常较为复杂,除含有高浓度的酚类污染物外,又含有大量的盐分。高浓度的盐不仅会对有机物降解动力学产生影响,且生成的活性物种与有机物反应还可能产生毒性更大的有机卤代物(AOX),在高级氧化体系大规模运用之前,我们需对其进行谨慎评估。因此,开展高级氧化体系处理高盐氯酚废水时有机卤代物的生成机制以及毒性评价研究具有十分重要的意义。本文选择了几种典型的氯酚,包括2,4,6-三氯酚(TCP)、邻间对氯苯酚(2-CP、3-CP、4-CP)、2,4,6-三溴酚(TBP)、4-溴-2-氯-苯酚(BCP),研究了它们在含盐体系中的氧化降解行为,重点分析了它们在基于单过氧硫酸氢盐(PMS)和过二硫酸盐(PS)的高级氧化体系中形成的AOX及其转化机制。此外,还系统的评估了氯离子的存在对氯酚降解过程中AOX生成及生物毒性的影响。主要结论如下:(1)对比Co/PMS和UV/H_2O_2体系降解TCP发现,Cl-的存在对Co/PMS体系中AOX的生成影响显著,AOX生成量随着Cl-浓度(0~300mM)的增加而升高;在UV/H_2O_2体系中,Cl-浓度的升高对体系中AOX生成量几乎无影响。在酸性条件下,两个体系中AOX生成量均会随pH降低而升高。对比Cl-存在时的体系中的中间产物发现,均会检测到多种高毒性有机氯代副产物,如2,3,4,6-四氯苯酚、2,3,4,5-四氯苯酚和2,3,5,6-四氯苯酚等。采用发光细菌法对污染物降解前后的生物毒性进行分析,Cl-的存在使Co/PMS体系中溶液的生物毒性明显增强且在180 min反应时间内一直保持在较高的毒性范围。无论是否添加Cl-,UV/H_2O_2体系中溶液的急性毒性随反应时间逐渐降低。(2)利用UV/PS体系降解单氯酚(MCPs)的研究表明,PS浓度与MCPs的降解性能具有正相关作用;向体系中加入0~300 mM的Cl-对MCPs的降解速率无明显影响。通过对中间产物定性和定量分析,无论体系中是否添加Cl-,均会检测到多种高毒性有机氯代副产物,且在4-CP的降解中检测到更多种类的有毒有机卤代物。在此基础上对4-CP在UV/PS体系中的降解途径进行了推测。在AOX的测定中发现,Cl-的存在对UV/PS体系中AOX影响显著,尤其是对4-CP。AOX值在60 min内随反应时间变化逐渐下降,但是从60 min开始,这种减小趋势明显减弱,呈现出一种反常的增加现象。通过对UV/PS降解MCPs过程中急性生物毒性的分析可知,溶液对发光细菌的抑制率随时间逐渐增加,急性毒性逐渐增强。(3)通过外加Cl-和微量Br-来模拟卤素离子在高盐废水处理时可能发生的反应及其环境意义。研究发现,PMS可以与卤素离子(Cl-、Br-)发生双电子转移反应,使Cl-和Br-分别被氧化为活性氯物种Cl2/HOCl和HOBr/OBr-,而这些活性卤代物种可以促使卤代酚发生降解,且卤素离子浓度的增加有利于卤代酚的降解。在酸性条件下,pH的增加有利于卤代酚的降解,同时pH也会影响中间产物的种类。在PMS/Br-体系中,4 h内TCP的矿化率仅为2.3%;在PMS/Cl-体系中,TBP的矿化率随反应时间而升高,但在4 h内的矿化率也只有22.9%。通过GC-MS和UPLC-QTOF-MS对中间产物定性和定量分析,卤代酚降解过程中会生成多种高毒性有机卤代物,包括多氯代苯酚、多溴代苯酚、氯溴同体的芳香类物质,且多数有毒有机副产物自生成开始直至测定结束都维持在很高的水平。即使是微量的Br-(0.1 m M)也能够导致多种有毒有机溴代产物的产生。本研究对基于PMS高级氧化体系在含盐废水方面的实际应用具有一定的指导意义。在评价PMS高级氧化体系对含盐废水的处理效果时,除了考虑氯离子的影响外,溴离子的影响也不容忽视。(4)选取既含有氯取代基又有溴取代基的BCP作为模型污染物,开展了其在Co/PMS体系中的降解研究。研究表明,BCP的降解速率随着底物浓度的升高而下降,随着PMS浓度、Co2+浓度以及溶液初始pH的升高而增大。不同浓度的Cl-对BCP的降解速率有不同的影响(双重作用):当氯离子浓度小于5 mM时BCP降解速率随Cl-浓度的增加而逐渐降低,外加氯离子抑制了反应的进行。接下来,反应速率常数会随着氯离子浓度(5~50 m M)的继续增加缓慢提高,在50 mM之后,反应速率常数增加更为明显,此时外加氯离子对反应呈现促进作用。随着Cl-浓度增加,BCP的矿化度受到明显抑制。通过GC-MS产物鉴定可知,在氯离子存在下,随着BCP的降解,生成了多种氯代副产物,但是未发现有多溴代物的生成。这可能与卤取代基的电负性相关(FClBrI),即卤代基的电负性越强,卤代有机物越容易氧化脱卤。
[Abstract]:Chlorophenol wastewater mainly comes from oil refining, coking, papermaking, medicine, printing and dyeing, chemical industry and other industries. It has a large emission and a great threat to the environment. Therefore, the harmless treatment of chlorophenol wastewater has become a hot issue for scholars both at home and abroad. In recent years, the advanced oxidation technology based on the radical sulfate radical (SO4 -) has a fast reaction speed and limit the strip. It is considered to be a new technology for the treatment of chlorophenols and other organic pollutants in the future. However, in the investigation of the composition of chlorophenol wastewater, it is found that the composition is usually more complex and contains a large amount of salt in addition to high concentration of phenolic pollutants. High concentration of salt will not only degrade organic matter. The reaction of the active species to the organic matter may produce more toxic organic halogen (AOX). Before the large-scale application of the advanced oxidation system, we need to evaluate it carefully. Therefore, the formation mechanism and toxicity evaluation of organic halogen in high chlorophenol wastewater treatment by advanced oxidation system Some typical chlorophenols, including 2,4,6- three chlorophenol (TCP), adjacent perchlorophenol (2-CP, 3-CP, 4-CP), 2,4,6- three bromophenol (TBP), 4- bromine -2- chloride phenol (BCP), are selected in this paper. Their oxidation degradation behavior in the salt containing system is studied. The emphasis is on their analysis based on the single peroxisate (PMS) and over two. AOX and its transformation mechanism in the high oxidation system of sulfate (PS). Furthermore, the effects of the existence of chlorine ions on the formation of AOX and the biological toxicity of chlorophenol degradation are systematically evaluated. The main conclusions are as follows: (1) the existence of Cl- is significant to the formation of AOX in Co/PMS system, AOX, as compared with the Co/PMS and UV/H_2O_2 system, AOX. The amount of formation increased with the increase of Cl- concentration (0~300mM); in the UV/H_2O_2 system, the increase of Cl- concentration had little effect on the AOX production in the system. Under the acidic condition, the AOX generation in the two systems would all increase with the decrease of pH. The intermediate products in the system when the Cl- existed, found that all kinds of high toxic organochlorine could be detected. By-products, such as 2,3,4,6- four chlorophenol, 2,3,4,5- four Chlorophenol and 2,3,5,6- four chlorophenol, were used to analyze the biological toxicity of the pollutants before and after the degradation of pollutants. The existence of Cl- significantly enhanced the biological toxicity of the solution in the Co/PMS system and kept in a higher toxicity range in the 180 min reaction time. In addition Cl-, the acute toxicity of the solution in the UV/H_2O_2 system decreased with the reaction time. (2) the study on the degradation of monchlorophenol (MCPs) by the UV/PS system showed that the concentration of PS had a positive correlation with the degradation performance of MCPs, and the Cl- of 0~300 mM to the system had no obvious effect on the degradation rate of MCPs. The qualitative and quantitative analysis of intermediate products had no effect. If Cl- is added to the system, a variety of highly toxic organochlorinated by-products can be detected, and more kinds of toxic organic halogenates are detected in the degradation of 4-CP. On this basis, the degradation pathway of 4-CP in the UV/PS system is speculated. In the AOX determination, the existence of Cl- has a significant influence on AOX in the UV/PS system, especially in the UV/PS system. The 4-CP.AOX value decreased with the reaction time in 60 min, but the decrease trend was obviously weakened from 60 min, which showed an abnormal increase. Through the analysis of the acute biological toxicity of UV/PS degradation in MCPs, the inhibition rate of the solution to luminescent bacteria was gradually increased with time, and the acute toxicity increased gradually. (3 ) by adding Cl- and micro Br- to simulate the possible reaction of halogen ions in the treatment of high salt waste water and its environmental significance. It is found that PMS can have double electron transfer reaction with halogen ions (Cl-, Br-), and Cl- and Br- are oxidized to active chlorine species Cl2/HOCl and HOBr/OBr- respectively, and these active halogenated species can promote halogenation. The degradation of phenol and the increase of halogen ion concentration are beneficial to the degradation of halogenated phenol. Under the acidic condition, the increase of pH is beneficial to the degradation of halogenated phenols, while pH also affects the type of intermediate products. In the PMS/Br- system, the mineralization rate of TCP is only 2.3% in 4 h; in the PMS/Cl- system, the mineralization rate of TBP increases with the reaction time, but within 4 h. The mineralization rate is also only 22.9%. through GC-MS and UPLC-QTOF-MS for the qualitative and quantitative analysis of intermediate products. In the process of halogenated phenol degradation, a variety of highly toxic organic halogenates, including polychlorinated phenol, polybrominated phenol, and chlorinated bromide, are produced, and most of the toxic organic by-products are maintained from the beginning until the end of the determination. A very high level. Even a small amount of Br- (0.1 M M) can lead to the production of a variety of toxic organic brominated products. This study has a certain guiding significance for the practical application of the advanced oxidation system based on PMS in the salt containing wastewater. In evaluating the treatment effect of the PMS advanced oxidation system to the salt containing wastewater, the effect of the chloride ion is considered. In addition, the effect of bromine ion can not be ignored. (4) select BCP containing both chlorine substituent and bromine substituent as model pollutant, and carry out its degradation in Co/PMS system. The study shows that the degradation rate of BCP decreases with the increase of substrate concentration, and increases with the concentration of PMS, Co2+ concentration and the initial pH of the solution. The concentration of Cl- has different effects on the degradation rate of BCP: when the concentration of chlorine ion is less than 5 mM, the degradation rate of BCP gradually decreases with the increase of Cl- concentration, and the addition of chloride ions inhibits the reaction. The reaction rate constant will be slowly increased with the increase of the chloride concentration (5 ~50 m M), and after 50 mM, the reaction rate will be reversed. The increase of rate constant is more obvious. At this time, the addition of chloride ion has a promotion effect on the reaction. With the increase of Cl- concentration, the mineralization degree of BCP is obviously inhibited. Through the identification of GC-MS products, it is known that in the presence of chlorine ion, with the degradation of BCP, a variety of chlorinated by-products have been generated, but no polybrominated products are found. This may be with the halogen. The electronegativity correlation (FClBrI) of the substituents is that the stronger the electronegativity of halogenated groups, the easier the halogenated organic compounds are to oxidize dehalogenation.
【学位授予单位】：东华大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X703

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