【作者】 杜沛；

【导师】 可欣；

【作者基本信息】 沈阳航空航天大学 ， 安全技术及工程， 2011， 硕士

【摘要】 工业文明给社会带来了快速发展,但在发展同时产生的“三废”物质也对环境造成了严重的破坏从而进一步影响动植物和人类的健康。土壤是人类赖以生存的资源,土壤的重金属铬污染目前受到相当大的关注。土壤林洗法是一种具有发展潜力的土壤重金属污染去除技术。特别是土壤淋洗修复技术中的原位修复具有技术应用简单、效率高和成本少等优点,因此对于土壤淋洗修复技术的研究是非常具有应用前景的。本研究主要选择的是有机酸作为土壤淋洗剂,包括柠檬酸、酒石酸、草酸。通过振荡淋洗试验从pH值、淋洗浓度、淋洗时间等因素考察有机酸的淋洗效果,分析淋洗效果的成因,并通过人工螯合剂EDTA的淋洗效果加以对比,通过形态分级试验考察淋洗前后铬在土壤中形态的变化。另外,进一步通过多级淋洗试验和土柱淋洗试验探讨了有机酸淋洗重金属铬的机理,并通过形态分级试验考察多级淋洗土样形态变化和土柱淋洗土样的形态变化,从机理上进一步解释有机酸淋洗技术的优势。通过淋洗液pH值对重金属铬去除率的影响试验得到柠檬酸、酒石酸、草酸的适宜淋洗pH值为4,EDTA淋洗的适宜pH值范围较广从3到7都可以适用;通过淋洗液浓度对重金属铬去除率的影响试验得到柠檬酸、酒石酸的最优淋洗浓度为0.4mol·L^-1,草酸的最优淋洗浓度为0.8 mol·L^-1,EDTA的最优淋洗浓度为0.1 mol·L^-1,并对浓度试验的数据进行回归分析;通过解吸动力学试验得到三种有机酸和EDTA的适宜的淋洗时间为24小时,并用质量转移方程对试验数据加以拟合。综合上述试验得出柠檬酸与其他两种有机酸相比淋洗效果稍好些。对振荡淋洗试验、多级淋洗试验柠檬酸淋洗的土壤样品形态分级,试验获得的数据表明本研究的土壤样品中铬以残余态为主,其次是交换态和碳酸盐结合态,柠檬酸对重金属铬的残余态去除效果很好,其次是具有生物可利用性的交换态和碳酸盐结合态。在土柱淋洗试验中,测得了该土样在土柱环境下的孔隙体积为200ml,用1孔隙体积作为单位淋洗体积。选择柠檬酸作为主要的有机酸淋洗剂,EDTA和蒸馏水作为对比,由振荡淋洗试验得出的适宜淋洗pH值和淋洗浓度以及时间作为淋洗条件,通过间歇式淋洗和连续式淋洗两种方式,考察三种淋洗剂的淋洗效果,再对柠檬酸淋溶土样进行形态分级试验,并将形态分级数据与振荡淋洗形态分级数据对比,考察两种试验的优缺点,同时也考察了土柱淋洗试验对于生物可利用性形态的去除效果,数据表明,残余态的去除效果与振荡淋洗试验相似,交换态和碳酸盐结合态间歇淋洗方式和连续淋洗方式的去除率与振荡淋洗试验相比淋洗效果更好,且连续式优于间歇式土柱淋洗。更多还原

【Abstract】 Industrial civilization has brought about a rapid development for society. However,“three wastes”produced by industry also caused severe damage to the environment which will further affect the flora, fauna and human health while in the development. Soil is the survival resources of human. Chromium contaminated in soil is also subject to considerable concern. Soil washing metheod is a development potential of the soil heavy metals pollution removal techniques, especially for soils for a high sand content. Leaching of soil remediation technologies, especially in situ remediation technology applications has advantages of simple, efficient and cost less. Therefore, leachting of soil remediation technologies for the research is very promising.The organic acid is chose as soil eluent, including citric acid, tartaric acid, oxalic acid. Through the oscillation leaching test, we can investigate the effect of leaching and analyze the cause of the effect by pH, leaching concentration and leaching time. At the same time, artificial chelator EDTA is used to compare the effect of leaching. The fractionation test is used to investigate morphological changes of chromium in the soil before and after the leaching tests. In addition, multi-stage leaching and soil column leaching are further carried out to investigate the mechanism of chromium leaching by organic acid. Meanwhile, through fractionation tests, morphological changes of multi-stage leaching and soil column leaching are investigated and the advantages of organic acid leaching technology are further explained.Through the pH test, we can get suitable pH 4 for citric acid, tartaric acid and oxalic acid leaching. The suitable pH value for EDTA is broadly from 3 to 7. Through the concentration test, we can get the best leaching concentration of citric acid and tartaric acid is 0.4 mol·L^-1, the best leaching concentration of oxalic acid is 0.8 mol·L^-1, the best leaching concentration of EDTA is 0.1 mol·L^-1. Meanwhile the regression analysis is used in concentration tests data. Through dynamic test, the suitable leaching time for three organic acids and EDTA are all 24 hours, and the mass transfer equation would be used for fitting the experimental data. The experiments show that citric acid is a little better than the other two organic acid in the leaching effect. The fractionation tests are used in leaching test, multi-stage leaching to obtain tests data. These data show that the chromium form of soil sample in this study is main residual fraction, followed by exchangeable and carbonate. The citric acid has good leaching effect on residual fraction, followed by the exchangeable and carbonate which have biological availability.In soil column leaching experiment, the pore volume in the column environment of the soil sample is measured and it’s 200ml. One pore volume is a unit of leaching volume. Citric acid is selected as organic acid, EDTA and distilled water are as contrasts. The pH, leaching concentration and leaching time which are obtained from oscillation tests are as leaching conditions. Through intermittent and continuous leaching, the leaching effect of three eluent is investigated. Fractionation is used next to the soil sample which is leached by citric acid. This fractionation data is compared with the data from oscillation test so that we can investigate advantages and disadvantages of the two tests. Meanwhile, we can investigate the removal effect of the form that has biological availability for column leaching. The experiment data show that the removal effect of residual is similar to oscillation leaching. Exchangeable and carbonate in the intermittent and continuous column leaching are better than oscillation leaching. And continuous leaching is better than intermittent leaching.更多还原