【作者】 周井刚；

【导师】 郭正元； 蔡信德；

【作者基本信息】 湖南农业大学 ， 环境工程， 2009， 硕士

【摘要】 本文以废弃电镀厂址污染土壤修复为研究中心,通过研究不同光源对污染土壤中氰化物的处理,重金属污染土壤淋洗剂筛选及淋洗条件优化,以及淋洗修复技术对土壤健康和质量的生态效应,为同类污染土壤修复提供理论和应用基础,本论文的主要内容如下:利用紫外光和日光分别对污染土壤中氰化物进行处理。结果表明:对两种处理方法而言,污染土壤中总氰化合物量随着时间的增加而降低;紫外光24h、日光5d处理后,总氰化物的去除率分别达到24.8%和33.9%。通过重金属振荡淋洗的试验,比较了EDTA、CaCl₂、HCl、柠檬酸钠溶液四种淋洗剂对污染土壤中五种重金属Cr、Ni、Zn、Cu、Pb的去除能力。同时研究了EDTA浓度、pH、淋洗时间对重金属去除效果的影响,并利用一级反应动力学模型对试验数据进行拟合。结果表明:EDTA去除五种重金属的能力远远大于其他三种淋洗剂。柠檬酸钠、HCl、CaCl₂对污染土壤中多金属的去除率顺序为Cr>Zn>Ni>Cu>Pb,而同等条件下EDTA的去除率顺序为Zn>Cu>Cr>Ni>Pb。在研究条件下,EDTA为0.05mol/L、pH=7、液土比=10:1、淋洗时间为18h的条件下能达到对污染土壤重金属最大去除率,去除率分别Zn85.3%、Cu 21.7%、Pb 16.8%、Ni 7.8%、Cr 6.3%。模型拟合结果表明,转移系数最大的是Cr,其次是Cu、Pb、Zn,最后是Ni,说明在土壤淋洗过程中Cr最先达到质量转移的平衡状态,然后是Cu、Pb、Zn,最后是Ni。利用Na₂S溶液对EDTA淋洗废水进行处理,结果表明:Na₂S量为1.21mmol、pH为13的条件下达到对EDTA淋洗废水中重金属最大的去除率,去除率分别为Pb 98.7%、Cu 100.0%、Cr 2.3%、Ni 6.7%、Zn 97.3%。重金属絮凝剂A、B对EDTA淋洗废水中Cr、Ni都有较好的去除率,其中絮凝剂B的处理效果好于A。在絮凝剂B添加体积为1.3 ml,pH为7时,Cr、Ni去除率分别为95.1%、96.4%,EDTA淋洗废水在经过Na₂S和重金属絮凝剂一次处理后,其回收的EDTA溶液对土壤重金属仍然有一定的去除能力。其中,回收的EDTA溶液对土壤中Zn的去除能力在80%以上,而对其它四种元素的去除能力较低。用蚕豆根尖微核试验、油菜种子发芽率、蚯蚓回避行为试验对淋洗前后土壤的健康进行初步评价。结果表明:油菜种子发芽率和蚯蚓净回避率发生了显著负向效应,而蚕豆根尖微核率在淋洗前后的土壤中没有产生显著性差异,污染土壤经淋洗后其生态毒性没有发生显著性的变化。总之,围绕着重金属与氰化物复合污染土壤淋洗修复展开的系列研究表明,紫外光和日光都可以有效地去除污染土壤中的氰化物含量;EDTA作为一种常用的化学淋洗剂能够有效地去除污染土壤中的多金属。对淋洗前后的污染土壤进行的生物效应评价表明,淋洗后的土壤的质量健康会发生一些变化,不对土壤健康状况造成显著性的影响。因此多金属污染土壤淋洗修复是一种对土壤生物影响微小的可行的修复方法。更多还原

【Abstract】 The central point of the research is electroplated waste remediation. In this paper, we investigated the destruction of weak acid dissociable cyanide （WAD cyanide） and total cyanide with UV radiation and sunlight respectively. In addition we screened the elutriant and optimized the eluting technics. In the last, the ecological effect with the method of eluting repairation was investigated too. The major conclusions obtained were listed as follows:The both of percentage removal of total cyanide concentration from contaminated soil increases with the increase of contact time with UV radiation and sunlight respectively. The maximal removal efficiency of total cyanide achieves 24.8% after 24h with UV radiation, 33.9% after 5 days with sunlight respectively. However, photolysis of UV radiation or sunlight not only ineffectively decontaminate WAD cyanide, but also the concentration of this pollutant may increase in these progresses, resulting in much more potential ecological dangerous.A batch experiment was conducted to investigate the removal efficiency of Cr, Pb, Cu, Ni and Zn by HCl, CaCl₂, citric and EDTA. In addition,we examine the effects of different EDTA concentrations, pH, and washing duration of EDTA on removal of heavy metals from contaminated soil and empirical model was employed to describe the kinetics of heavy metals dissolution and desorption. The results showed that the removal ability of EDTA on heavy metals was much higher than those of other 3 extractants. Removal percentages of heavy metals due to extracting of HCl, CaCl₂ and citric were in a sequence of Cr>Zn>Ni>Cu>Pb, while removal percentages of heavy metals due to extracting of EDTA werw in a sequence of Zn>Cu>Cr>Ni>Pb.At 0.05mol/L and pH 7 of EDTA and within 18h, the removal rate of test heavy metals was the maximum, being 85.3% for Zn, 21.7% for Cu, 16.8% for Pb, 7.8% for Ni, 6.3% for Cr. The mass transfer coeffient was in the order of Cr > Cu >Pb >Zn >Ni.We investigated the recycling of EDTA used for the removal of trace metals from electroplated waste. The results of batch experiments showed that Na₂S was capable of separating the metals Pb,Cu and Zn from waste water containing EDTA. At 1.21mmol and pH 13 of EDTA, the removal rate of heavy metals was the maximum, being 98.74% for Pb, 100% for Cu, 2.3% for Cr, 6.7% for Ni, 97.3% for Zn. Both macromolecule heavy metal flocculant A and B were capable of removal the metals Ni and Cr and the removal ability of B on heavy metals was much higher than A. At 13ml and pH 7 of macromolecule heavy metal flocculant B and within 1h, the removal rate of Ni and Cr were 96.4% and 95.1%, respectively. After reusing the reclaimed EDTA one time, the successive washing cycle enhanced the removal of heavy metals from contaminated soils and the removal rate of Zn was more than 80%, while the others removal rate were little.In order to evaluate the influence of method of eluting repairation on soil quality, we researched the micronucleus frequencied in Vicia faba root tips cells, avoidance behavior of earthworms and inhibition rates of seed germination of rape. The results showed that avoidance rates of earthworms and inhibition rates of seed germination of rape can emerge slight negative effect. Thus, the eluting repairation may enhance the ecotoxicity of soil and the soil quality may deteriorated.In summary, the result indicates that both UV radiation and sunlight effectively decontaminated total cyanide. In addition, as a useful extractant,EDTA can effectively remove heavy metals from contaminated soil and Na₂S was capable of separating the metals Pb, Cu and Zn from waste water containing EDTA, but ineffectively separating the metals Ni and Cr. It is necessary to evaluate the biological effect of eluting repairation to soil quality, and the conclusion is that elution can influence soil health, and result in the deterioration of soil quality.更多还原