摘要
邻二氯苯(ortho-dichlorobenzene,o-DCB)在水体中具有低生物降解性和生物富集性的特点,被认为是最危险的环境污染物之一。为探讨臭氧/活性炭(O_3/GAC)体系对o-DCB作用机制,活性炭投加量、臭氧气体流量、p H值作为重要变量因素,文章分析了o-DCB浓度变化趋势及变化途径。结果表明:(1)GAC的投加更有利于o-DCB的去除,O_3/GAC体系的高去除率主要因为GAC的吸附和催化O_3分解的作用。(2)p H值对O_3/GAC体系对o-DCB去除效率有显著影响。p H为4.0时,o-DCB降解速率最慢,p H为8.0和10.0时,o-DCB的降解速率较快且相近,最终都能实现o-DCB的完全降解。(3)臭氧与活性炭联用具有较好的协同效应。碱性(p H值为8和10)条件下,p H对O_3/GAC体系影响更加显著,o-DCB的反应速率在O_3/GAC体系中显著增加,特别在p H值为10.0时,o-DCB反应速率达到0.15min,协同因子达到2.17。(4)腐殖酸、金属离子(Fe3+、Al3+)和自由基捕获剂对o-DCB在O_3/GAC体系中去除都有一定影响。在腐殖酸和o-DCB的共去除过程中,O_3/GAC联用工艺较单独O_3氧化工艺有较明显的优势;当Fe3+投加量在1~5 mg/L时,o-DCB去除效果增幅最为显著;叔丁醇投加极大的减缓了o-DCB的降解速度,证明了在O_3/GAC/Fe3+反应过程中·OH的生成。(5)o-DCB在O_3/GAC体系降解的中间产物分别是邻氯苯酚、苯酚、对苯二酚、邻苯二酚、邻苯醌、乙酸、甲酸等。由于Cl是邻对位定位基团,·OH易进攻其邻对位上的碳原子,迅速生成2,3-二氯苯酚和3,4-二氯苯酚,然后苯环上的氯原子相继被OH-亲核取代/消除,生成3-氯邻苯二酚等物质。o-DCB上的1个氯原子易被OH-亲核取代/消除后生成邻氯苯酚,邻氯苯酚的转化途径有2条。
Ortho-dichlorobenzene（o-DCB） is characterized by low biodegradability and bioaccumulation in water. It is considered to be one of the most dangerous environmental pollutants. In order to investigate the effect of O3/GAC system on oDCB, activated carbon dosage, ozone gas flow rate and p H value used as the important variable factors, the trend and variation of o-DCB concentration were analyzed. The results showed that the addition of GAC was more favorable for the removal of o-DCB, and the high removal rate of O3/GAC system was mainly due to the adsorption and catalytic O3 decomposition of GAC. p H has a significant impact on removal efficiency of o-DCB. At p H 4.0, the degradation rate of o-DCB was the slowest, and that of o-DCB was similar at p H 8.0 and 10.0. Ozone and activated carbon has a good synergistic effect. The effect of p H on the O3/GAC system was more significant at p H 8 and 10, and the reaction rate of o-DCB was significantly increased in the O3/GAC system. Especially, at p H 10.0, the o-DCB reaction was 0.15 min, and the synergistic factor reached 2.17.Humic acid, metal ions（Fe3＋, Al3＋） and free radical trapping agents have some influence on the removal of o-DCB in O3/GAC system. The effect of O3/GAC system was better than that of O3 on humic acid and o-DCB. When the dosage of Fe3＋was 15 mg/L, the removal of o-DCB was increased. The concentration of o-DCB was greatly reduced by the addition of tert-butanol, which proved that the formation of ·OH was in the process of O3/GAC/Fe3＋. The intermediate products of o-DCB degradation in O3/GAC system are o-chlorophenol, phenol, hydroquinone, catechol, o-benzoquinone, acetic acid, formic acid and so on. Cl is a para-to-position group, ·OH is liable to attack the carbon atoms in its ortho position to rapidly produce 2,3-dichlorophenol and 3,4-dichlorophenol, and then the chlorine atoms on the benzene ring are successively substituted with OHnucleophilic substitution/elimination to produce 3-chloro catechol and other substances. o-DCB on a
作者
雷彩虹
孙颖
杨英
赵素萍
LEI Caihong;SUN Ying;YANG Ying;ZHAO Suping(Hangzhou Polytechnic, Hangzhou 311402, China;Hebei University of Environmental Engineering, Qiahuangdao 464000, China)
出处
《环境科学与技术》
CAS
CSCD
北大核心
2018年第5期17-24,共8页
Environmental Science & Technology
基金
国家自然科学基金项目(51206782)
浙江省科技厅科技攻关项目(GG172106510708)
浙江省教育厅科研项目资助(Y201534093)
关键词
臭氧
活性炭
邻二氯苯
pH影响
降解途径
ozone
activated carbon
ortho-dichlorobenzene
pH
degradation pathway
