矿区污染土壤砷稳定化修复材料筛选及应用研究

发布时间：2018-02-01 23:03

本文关键词： 土壤砷污染修复稳定化复合材料　出处：《湖南农业大学》2015年硕士论文　论文类型：学位论文

【摘要】：伴随着我国经济的飞速发展,土地资源短缺的问题日益凸显,因此对污染场地进行修复和二次开发是减缓土壤短缺压力,实现土地可持续利用的重要手段。本文以某尾矿遗留重金属污染场地土壤为研究对象,筛选切实可行的砷稳定化修复材料。首先对单一稳定剂进行了筛选,然后通过正交实验确定修复效果最好的添加配比,并进行工艺参数的优化试验,包括Fe/As、pH、药剂添加量、土壤粒径、反应时间等；同时制定土壤修复建议方案,指导现场进行修复。主要试验结果如下：(1)本论文采用XRF、SEM以及Tessier连续提取法等方法对供试土壤的理化性质、微观形态和化学组成和砷的形态等进行了分析。结果表明：污染土壤土样略偏酸性,微观结构有明显的晶体颗粒；土壤结构成分复杂,砷、镉、铅的含量都比较高；其中砷有机物结合态(80.09%)和残渣态(17.96%)；有效态的总量只占到了2%左右,但由于污染土壤体积大,所以必须妥善处理,以免对周围生态环境造成危害。(2)矿物材料对土壤中砷的稳定能力表现为：强碱性赤泥弱碱性赤泥海泡石蒙脱石水滑石。稳定剂的梯度试验研究表明：砷的稳定效率跟赤泥的添加量呈正相关的趋势；稳定化后土壤中砷的浸出浓度随氧化钙的增加呈先减小后增大的趋势,但本试验表明在加入小于5%的CaO的情况下能降低土壤中As的浸出；随着Fe/As摩尔比的加大,砷的浸出浓度随之降低,砷的稳定化率先增加,后趋于平缓。正交试验结果表明,硫酸铁添加量影响最大,其次是氧化钙添加量,最后是赤泥添加量。即当CaO添加量为2%,砷铁比为1：2,赤泥添加量为1%时,土壤砷的稳定达到60%。8号复合稳定剂稳定化处理土壤后,镉的浸出浓度呈下降的趋势；当添加量小于6%时,对土壤中打的铅也能起到稳定效果；超过6%后,土壤中的铅部分被活化。因此应该将8号稳定剂的添加量控制在6%之内。(3)砷稳定化过程工艺参数优化：选择Fe：As摩尔比为2,供试土壤过12目筛,控制粒径小于1.38mm、实验陈化时间控制在3d做为试验的最优条件进行探究,砷的浸出浓度为1.38mg/L,砷的稳定化率为72.6%。(4)现场修复建议方案：通过前期稳定剂的筛选和综合比较,最终选定PMF复合材料(磷酸二氢钙、硫酸铁、赤泥为主要稳定剂,氧化钙为辅助剂)来对矿区土壤重金属复合污染进行修复。当稳定剂添加量达到6%时,铅隔砷的稳定化率均超过70%。
[Abstract]:With the rapid development of China's economy, the shortage of land resources is increasingly prominent, so the remediation and secondary development of contaminated sites is to alleviate the pressure of soil shortage. In this paper, a tailings residual heavy metal contaminated soil as the research object, screening feasible arsenic stabilization remediation materials. First, the single stabilizer was screened. Then the best proportion was determined by orthogonal experiment, and the optimum technological parameters were tested, including the pH of Fe / Asn, the amount of reagent added, the particle size of soil, the reaction time and so on. At the same time, a soil remediation proposal was made to guide site remediation. The main results are as follows: 1) XRF is adopted in this paper. The physicochemical properties, microscopic morphology, chemical composition and arsenic speciation of contaminated soil were analyzed by SEM and Tessier method. The results showed that the soil samples were slightly acidic. There are obvious crystal particles in the microstructure. The content of arsenic, cadmium and lead is relatively high. Among them, the arsenic organics bound state is 80.09% and the residue state is 17.96%; The total amount of available state is only about 2%, but due to the large volume of contaminated soil, it must be properly treated. To avoid harming the surrounding ecological environment. The stability of mineral materials to arsenic in soil is as follows: strong alkaline red mud, weak alkaline red mud, sepiolite, montmorillonite hydrotalcite. The stable efficiency of arsenic is positively correlated with the amount of red mud. The leaching concentration of arsenic in the stabilized soil decreased first and then increased with the increase of calcium oxide, but this experiment showed that the leaching of as in the soil could be reduced with the addition of less than 5% CaO. With the increase of the molar ratio of Fe/As, the leaching concentration of arsenic decreased, the stabilization of arsenic increased first, and then tended to smooth. The results of orthogonal experiment showed that the content of ferric sulfate was the most important factor. The second is the addition of calcium oxide, and finally the amount of red mud, that is, when the addition of CaO is 2, the ratio of arsenic to iron is 1: 2, and the amount of red mud is 1. After the stabilization of soil arsenic reached 60.8 complex stabilizer, the leaching concentration of cadmium decreased. When the addition amount is less than 6, the lead in the soil can also play a stable effect. When the amount of stabilizer No. 8 was controlled within 6%) the process parameters of arsenic stabilization were optimized: the molar ratio of Fe:As was 2. After 12 mesh sieve, the controlled particle size was less than 1.38 mm, the experimental aging time was controlled in 3 days as the optimum condition, the concentration of arsenic leaching was 1.38 mg / L. Arsenic stabilization rate is 72.6%) suggestion for site restoration: PMF composite material (calcium dihydrogen phosphate, ferric sulfate) is selected by screening and comprehensive comparison of pre-stabilizer. Red mud is the main stabilizer and calcium oxide is the auxiliary agent) to remediate the complex pollution of heavy metals in the soil of mining area. When the amount of stabilizer reaches 6, the stabilization rate of lead and arsenic is over 70%.
【学位授予单位】：湖南农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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