【作者】 张静；

【导师】 李保山；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2010， 硕士

【摘要】 多氯联苯(polychlorinated biphenyls, PCBs)是目前国际上关注的12种持久性有机污染物(persistent organic pollutants, POPs)中最具有代表性的一类。由于其稳定的理化性质及疏水性,多氯联苯污染土壤的修复成为目前环境保护领域研究的热点之一。本文对零价金属铁镁混合粉末对多氯联苯污染土壤的修复效果进行了研究,取得了很好的结果。本文的主要工作如下：1.研究了金属Fe-Mg混合粉末对土壤中多氯联苯的降解效果及其他反应条件对降解效果可能造成的影响。当金属混合粉末Fe和Mg的摩尔比为2：3,混合粉末添加量(wt)：污染土壤量(wt)=1：500,室内光及室温条件(20℃)下反应24h,污染土壤中多氯联苯的降解率达到98.10%。本研究中的降解方法还受到电解质溶液、反应时间、光照条件和温度等因素的影响。由实验结果可知,降解效率随着反应时间的延长不断提高,在反应开始的6h提高速率最快,到24h能达到98%以上；人工添加电解质溶液后,相同作用时间内获得的降解效率更高；直接光照有利于多氯联苯的降解,在反应最初的6-8h作用明显；在20℃-50℃的情况下,温度升高不利于多氯联苯的降解,20℃时,修复效果最好,降解效率为96.32%；Fe-Mg摩尔比在0.2-0.67的范围变化时,降解效率几乎没有变化；从2：3扩大到1：1时,降解率有所下降,1：1时的降解率为93.29%。2.研究了金属Fe-Mg混合粉末对土壤中多氯联苯的降解机理。结果表明,在金属混合粉末作用下,多氯联苯脱氯降解,生成了两种新的产物：对异丙基甲苯和2,6-二(三甲基硅氧基)苯甲酸三甲基硅酯,其毒性均低于多氯联苯本身的毒性。以上研究表明,零价金属铁镁混合粉末对多氯联苯污染土壤是一种有效的修复方法,为今后的PCBs污染土壤修复提供了较高的参考价值。更多还原

【Abstract】 Polychlorinated biphenyl (PCB) is the most typical kind of 12 types of persistent organic pollutants (POPs) that people have always been paying attention to. Remediation of PCB-contaminated soil has been one of the hotspot researches for its extremely stable physical-chemical property. This paper has investigated the effect of zero-valent metallic mixed powder by iron and magnesium for repairing PCB-contaminated soils and has obtained good results. The main researches of the paper were as follows.1. Investigating the degradation effect of PCB-contaminated soils by metallic mixed powder composed of iron and magnesium and reaction parameters that may have influences on removal efficiency. Removal rate of PCBs can be up to 98.10% in 24h under the conditions of Fe-Mg ration was 2:3 and power-soil ratio (wt%) was 1:500, in room with room temperature (20℃). The influences by electrolyte solution, reaction time, direct sunlight and temperature on the effect of remediation have also been studied. According to the experimental results, it can be seen that removal rate was increasing with the extension of reaction time and it could be up to 98% in 24h; addition of extra electrolyte solution could lead to better remediation effect in the same reaction time; direct sunlight has been proved to be helpful in the degradation process, especially in the first 6-8h; raising temperature was adverse to the degradation effect when temperature was ranging from 20℃to 50℃, it could get the highest removal rate 96.32% as temperature was controlled to 20℃. Ratio of Fe-Mg was ranging from 0.2-0.67 without any obvious change of removal efficiency, when it was raised from 0.67-1, removal rate has decreased and was 93.29% as the ratio was 1.2. Investigating the mechanism of degradation. Result has indicated that two products were found after degradation process of PCBs, one was para-cymene, the other was trimethylsilyl 2,6-bis (trimethylsilyloxy) benzoate, toxicity of both were less than polychlorinated biphenyls.Researches above demonstrated that zero-valent metallic mixed powder by iron and magnesium is an effective technique for remediation of PCB-contaminated soils and that, it provides a reference for remediation of PCB-contaminated soils in future.更多还原