含磷材料对污染土壤铅镉稳定化修复研究

发布时间：2018-06-12 08:31

本文选题：化学修复 + 铅　；参考：《湖南农业大学》2015年硕士论文

【摘要】：矿产资源的不适当开采与冶炼是引起环境重金属污染的一个主要方面,矿区重金属污染具有面积广、复合污染、含量高、潜伏性大、土壤肥力退化等特点。目前针对单一铅、镉的稳定修复研究较多,但多金属复合污染中铅镉同时钝化稳定修复的研究较少。本文通过筛选对矿区污染土壤中铅镉达到同时钝化的化学稳定剂,并对稳定剂进行复配,优化钝化修复的工艺参数以获得最佳的钝化效果,并对修复后土壤稳定性进行评价。主要的研究结果如下：(1)通过对磷酸盐类、工业废弃物类、粘土矿物类钝化剂进行筛选比对,首选Ca(H_2PO_4)_2与蒙脱石为主要稳定剂。通过单一与复配试验研究表明：单一Ca(H_2PO_4)_2对矿区土壤铅镉修复效果较好,有效态铅和镉的钝化率分别为70.05%和69.55%。1：1复合蒙脱石后,减少了50%的Ca(H_2PO_4)_2用量,对矿区土壤有效态铅和镉的钝化率分别为71.32%和65.10%。(2)矿区污染土壤铅镉最佳修复工艺参数为：复合磷基材料[Ca(H_2PO_4)_2:蒙脱石=1：1],添加量为5%,含水率为50%,陈化时间60d,对土壤中重金属铅镉有效态钝化效果分别为82.23%和70.08%。(3)通过Tessier五步形态分析表明,添加单一Ca(H_2PO_4)_2及复合磷基材料后土壤中铅离子态、碳酸盐结合态、铁锰氧化态浓度显著降低,残渣态铅含量显著增加；土壤中镉离子态、铁锰氧化态转变为稳定的有机结合态。证明磷基材料能明显将土壤重金属形态由生物有效态转化为有机态与残渣态等稳定态。(4)单一Ca(H_2PO_4)_2钝化,土壤稳定后pH值降低1.43～3.29个单位,复合磷基材料钝化后土壤pH值降低0.67～2.57个单位。土柱淋溶的试验结果表明：钝化后铅镉能有效控制在表层土壤,减少土壤铅径向迁移。复合磷基材料较单一Ca(H_2PO_4)_2相比,降低了砷的活化迁移,且深层土壤及淋溶液中磷含量无明显增加。(5)通过对钝化前后土壤进行XRD分析,结果表明：Ca(H_2PO_4)_2钝化修复后,土壤中铅镉生成较难溶的络合物。Ca(H_2PO_4)_2和蒙脱石复合钝化修复,使土壤铅镉生成难溶化合物Pb_3(PO_4)_2、Cd_3(PO_4)_2之外,更加降低了矿区土壤中PbAs_2O_6含量。
[Abstract]:Improper mining and smelting of mineral resources is one of the main aspects of environmental heavy metal pollution. Heavy metal pollution in mining area has the characteristics of wide area, complex pollution, high content, high latency, soil fertility degradation and so on. At present, there are many studies on the stabilization of single lead and cadmium, but there are few studies on the simultaneous passivation and stabilization of lead and cadmium in polymetallic complex pollution. In this paper, the chemical stabilizers of lead and cadmium in polluted soils of mining area were screened, and the stabilizer was compounded to optimize the technological parameters of passivation and repair to obtain the best passivation effect, and to evaluate the stability of the soil after restoration. The main results are as follows: (1) by screening and comparing the passivating agents of phosphate, industrial waste and clay minerals, CaH2PO4Snap2 and montmorillonite are preferred as the main stabilizers. The results of single and complex experiments show that the single CaH2POS4S _ 2 has a better effect on the remediation of lead and cadmium in the soil of the mining area. The passivation rates of available lead and cadmium are 70.05% and 69.55. 1: 1 respectively, and the amount of CaH2PO4 _ 4 _ 2 is reduced by 50% after the compound montmorillonite is composed of CaOH2PO-4# _ 2, and the passivation rates of available lead and cadmium are 70.05% and 69.55. 1: 1: 1 respectively. The passivation rate of available lead and cadmium in mine soil is 71.32% and 65.10% respectively.) the optimum technological parameters for the remediation of lead and cadmium in contaminated soil in mining area are as follows: compound phosphorus based material [CaH2PO4# _ 2: montmorillonite 1: 1], addition amount of 5, moisture content of 50, aging time of 60 days, and heavy weight to the soil. The passivation effects of the active state of lead and cadmium were 82.23% and 70.08%, respectively. The results of Tessier five-step speciation analysis showed that the passivation effect of lead and cadmium was 82.23% and 70.08% respectively. After the addition of single CaH2PO4K2 and the composite phosphorus base material, the concentration of lead ion, carbonate bound state, iron manganese oxide state and residual lead content in the soil decreased significantly, and the cadmium ion state and iron manganese oxide state in the soil changed into stable organic bound state. It was proved that the phosphorus based material could change the form of heavy metal from bioavailable state to organic state and residue state, etc.) the single CaH2PO4 / T _ 2 was passivated, and the pH value of soil was reduced by 1.43 ~ 3.29 units after stabilization. The soil pH value decreased by 0.67 ~ 2.57 units after passivation. The experimental results of soil column leaching showed that the passivated lead and cadmium could effectively control the surface soil and reduce the radial migration of lead in the soil. The composite phosphorous base material reduced the activation and migration of arsenic, and the phosphorus content in the deep soil and leaching solution was not significantly increased. Compared with the single Cah2PO4, the XRD analysis of the soil before and after passivation was carried out. The results showed that after passivated restoration, the content of phosphorus in the deep soil and leaching solution was not significantly increased. The complex of lead and cadmium in the soil, CaOH _ 2P _ 4C _ 2, and montmorillonite were passivated and repaired, which resulted in the formation of the insoluble compound Pb _ (3) O _ (4) O _ (4) O _ (4), and decreased the content of PbAs2O6 in the soil of the mining area.
【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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