柠檬酸和EDTA对重金属复合污染土壤的浸提效果研究

发布时间：2019-06-07 12:22

【摘要】：重金属主要来源于污灌、化肥农药的大量使用、矿山和工业生产产生的“三废”、城市垃圾和大气沉降物等。重金属进入土壤后,不能被微生物降解,只能发生迁移和转化等,其污染具有隐蔽性、长期性和不可逆性的特点。它们会污染水体和空气,影响作物和生物的生长,并通过食物链危害人体健康和生命。土壤重金属污染受到人们的日益关注。如何修复重金属污染土壤,降低重金属污染带来的危害,已成为环保领域的重要研究内容。众多修复技术中土壤淋洗修复技术作为一种快速有效的污染土壤治理技术越来越受到重视。本研究以浙江富阳某炼铜厂附近受Cd、Cu、Pb和Zn复合污染土壤为研究对象,采用振荡、静置和超声三种不同浸提方式,以柠檬酸和EDTA为浸提剂,通过研究两种浸提剂分别在不同浸提方式下对重金属的去除效果,筛选出最佳浓度、处理时间以及超声功率,并采用Tessier连续提取法分析柠檬酸浸提前后土壤中四种重金属形态的变化。以期为复合重金属污染土壤淋洗修复提供科学理论依据。主要研究结果如下:1.柠檬酸处理对四种重金属均具有良好的去除效果。无论哪种浸提方式,均是以Zn去除效果最好,Cd效果最差而Cu和Pb效果相当,但是在低浓度时,Pb去除率低于Cd。无论哪种浸提方式,Pb和Zn去除率均随着柠檬酸浓度的增加而增加,但增幅随之减少,Cu的去除率则先增加后基本保持不变,而Cd变化不明显。2.通过比较柠檬酸浸提前后土壤中重金属形态分布的变化,柠檬酸能够很大程度上改变土壤中重金属的形态分布,主要去除以可交换态和碳酸盐结合态形式存在的Cd以及以碳酸盐结合态和铁锰氧化物结合态形式存在的Cu、Pb和Zn。3.EDTA处理对四种重金属也具有较好的去除效果。三种浸提方式中Cu和Pb的去除率均高于Cd和Zn。其中以Pb的去除效果最好,去除率高达99%。除了Cd去除率在振荡浸提中基本保持不变,四种重金属的去除率变化规律一致,均是随着EDTA浓度的增加而呈现出先升高后下降的趋势。4.从柠檬酸和EDTA处理对Cd、Cu、Pb和Zn四种重金属的去除率分析得出,柠檬酸和EDTA浸提实验中最佳振荡时间均为4 h,最佳静置时间均为24 h,最佳超声功率均为500 W和超声时间均为30 min。综合考虑成本和去除率后,三种浸提方式中选用0.2 mol·L-1柠檬酸连续浸提两次为最优条件。而EDTA振荡浸提和超声浸提时最佳浓度均为0.03 mol·L-1,静置浸提时为0.07 mol·L-1。由此可见,在同等去除效果的条件下,应用超声波后,相对于振荡浸提和静置浸提,浸提时间大大减少。因此,超声波辅助浸提土壤中重金属效果较好,具有一定的应用前景。
[Abstract]:Heavy metals mainly come from sewage irrigation, the extensive use of chemical fertilizers and pesticides, the "three wastes" produced by mining and industrial production, municipal solid waste and atmospheric sedimentation, and so on. After heavy metals enter the soil, they can not be degraded by microorganisms, but can only be migrated and transformed. The pollution has the characteristics of concealment, long-term and irreversibility. They pollute water and air, affect the growth of crops and organisms, and endanger human health and life through the food chain. People pay more and more attention to heavy metal pollution in soil. How to repair heavy metal contaminated soil and reduce the harm caused by heavy metal pollution has become an important research content in the field of environmental protection. Among many remediation technologies, soil leaching remediation technology has been paid more and more attention as a rapid and effective remediation technology of contaminated soil. In this study, the soil polluted by Cd,Cu,Pb and Zn near a copper smelting plant in Fuyang, Zhejiang Province was taken as the research object. Three different extraction methods, oscillatory, static and ultrasonic, were used and citric acid and EDTA were used as extractants. The removal efficiency of heavy metals by two kinds of extractants under different extraction methods was studied, and the optimum concentration, treatment time and ultrasonic power were selected. The changes of four heavy metals in soil before and after citric acid extraction were analyzed by Tessier continuous extraction. In order to provide scientific theoretical basis for leaching and remediation of soil polluted by compound heavy metals. The main results are as follows: 1. Citric acid treatment has a good effect on the removal of four kinds of heavy metals. No matter which extraction method, the removal effect of Zn is the best, the effect of Cd is the worst, but the effect of Cu and Pb is the same, but at low concentration, the removal rate of Pb is lower than that of Cd.. No matter which extraction method, the removal rates of Pb and Zn increased with the increase of citric acid concentration, but the increase decreased, the removal rate of Cu increased at first and then remained basically unchanged, but the change of Cd was not obvious. 2. By comparing the morphological distribution of heavy metals in soil before and after citric acid extraction, citric acid can change the speciation and distribution of heavy metals in soil to a great extent. The removal of Cd in the form of exchangeable and carbonate bound states and the treatment of Cu,Pb and Zn.3.EDTA in the form of carbonate bound state and iron manganese oxide bound state also have good removal effect on four kinds of heavy metals. The removal rates of Cu and Pb in the three extraction methods were higher than those of Cd and Zn.. Among them, the removal effect of Pb is the best, and the removal rate is as high as 99%. Except that the removal rate of Cd remained basically unchanged in oscillatory extraction, the removal rate of four kinds of heavy metals changed the same, and all of them increased at first and then decreased with the increase of EDTA concentration. 4. The removal rates of Cd,Cu,Pb and Cd,Cu,Pb by citric acid and EDTA treatment were analyzed. the results showed that the optimum shaking time and static time of citric acid and EDTA extraction were 4 h and 24 h, respectively. The optimum ultrasonic power is 500W and the ultrasonic time is 30 min.. After considering the cost and removal rate, 0.2 mol 路L ~ (- 1) citric acid was selected as the optimal condition for the three extraction methods. The optimum concentration of EDTA oscillatory extraction and ultrasonic extraction was 0.03 mol 路L ~ (- 1), and that of static extraction was 0.07 mol 路L ~ (- 1). It can be seen that under the condition of the same removal effect, the extraction time is greatly reduced compared with the oscillatory extraction and the static extraction after the application of ultrasonic wave. Therefore, ultrasonic assisted extraction of heavy metals in soil has a good effect and has a certain application prospect.
【学位授予单位】：浙江农林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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