改性胡敏素钝化修复重金属污染土壤的研究

发布时间：2018-04-20 20:23

本文选题：土壤污染 + 重金属　；参考：《广东工业大学》2015年硕士论文

【摘要】：土壤重金属污染具有隐蔽性、难降解性、生物积累性等特点,治理难度大、成本高。累积在土壤中的重金属不仅能够破坏土壤微生物群落结构,抑制农作物的生长,造成粮食减产,还能通过食物链不断传播并在生物体内富集,最终威胁人类健康。我国土壤重金属污染形势严峻,农田土壤的重金属污染已经严重威胁到了我国的粮食安全和人民群众的生命健康。原位钝化技术是修复重金属污染土壤的重要手段之一。原位钝化技术是指通过向土壤中施加一些有机或无机的化学物质,改变土壤理化性质,或使加入的化学物质与土壤中的重金属发生物理化学反应,从而改变重金属在土壤中的赋存形态,降低其在土壤环境中的生物有效性和迁移性,达到修复污染土壤的技术。与其他修复技术相比,该方法具有修复效果好、修复周期短、成本低廉、操作简单等特点,特别在修复重金属复合污染土壤方面具有明显优势。本文以环境友好的腐殖质类物质-胡敏素为基质,开发经济高效环保的土壤钝化剂材料,并对其用于土壤重金属污染修复开展了基础性的理论和技术研究。主要包括下列内容：1.采用碱提法从泥炭土中分离出来性质稳定的胡敏素,并通过吸附平衡实验研究了胡敏素对模拟土壤溶液中的重金属Cd(Ⅱ)、Pb(Ⅱ)、Cu(Ⅱ)的吸附动力学和热力学特性,并研究了pH、溶液电解质浓度、土壤溶液中小分子有机酸浓度等条件对胡敏素吸附重金属效果的影响。结果表明,胡敏素表面含有大量含氧活性官能团；其对三种重金属的吸附能力顺序为Cd(Ⅱ) Cu(Ⅱ)Cd(Ⅱ),且对Cd(Ⅱ)、Cu(Ⅱ)的吸附符合Freundlich模型,对Pb(Ⅱ)的吸附符合Langmuir模型；胡敏素对重金属的吸附动力学符合二级动力学方程；随着pH的升高,胡敏素对重金属的吸附量迅速增加；溶液中的电解质离子和酒石酸都能够抑制胡敏素对重金属的吸附；胡敏素对实际农田土壤溶液中重金属的钝化能力优于对模拟溶液的钝化能力。2.通过土壤钝化实验,研究了添加胡敏素对污染土壤中铜和铅的生物有效性的影响和重金属赋存形态的转化。结果表明,添加胡敏素可显著降低重金属的浸出浓度。当投加2%的胡敏素5天后,土壤中重金属铜和铅的浸出浓度分别下降45.16%和56.97%。投加胡敏素后能迅速钝化土壤中的重金属,进一步延长钝化时间对钝化效果影响不大。尿素、硫酸铵、磷酸二氢钾可显著提高胡敏酸对铅的钝化效果,浸出浓度分别下降了29.36%、23.57%、28.69%,但对铜的影响不明显。进一步的研究表明投加2%的胡敏素钝化处理30天后土壤中交换态铜和铅的所占的比例由原来的15.68%和15.79%下降到了0.48%和1.22%,而有机态铜和铅的比例则由5.35%和10.93%上升到了13.24%和27.32%,表明胡敏素可以促进可交换态重金属向有机态和残渣态转化。3.用巯基乙酸和乙酸酐对胡敏素进行巯基化改性,从而获得巯基胡敏素。通过傅里叶红外和热重分析研究了巯基化胡敏素的化学结构特点。通过吸附平衡实验研究了巯基化胡敏素对土壤溶液中重金属Cd(Ⅱ)的吸附热力学特性。最后通过土壤钝化实验比较了巯基胡敏素和胡敏素对重金属复合污染土壤的修复效果。结果表明：改性后胡敏素表面具有较多的羧基官能团。与胡敏素相比,巯基化胡敏素在2578cm-1处出现了典型的巯基官能团(S-H)的吸收峰,表明胡敏素表面巯基官能团的存在；在不同温度下巯基胡敏素对Cd(Ⅱ)的吸附等温线更符合Langmuir方程,在298K条件下,巯基胡敏素对Cd的理论饱和吸附量为8.9081 mg·g-1,而胡敏素的理论饱和吸附量为6.5335mg·g-1,表明在胡敏素表面增加巯基数量显著提高了其对镉的吸附能力；吸附热力学参数表明巯基胡敏素对Cd(Ⅱ)的吸附为自发吸热反应。随着温度升高,△G的绝对值增加,吸附剂的饱和吸附量也相应增大。在钝化剂投加量为2.5%的情况下,钝化处理十天后,巯基胡敏素对土壤中镉、铅、铜三种重金属的钝化率分别为44%、65%、50%。对镉的钝化率显著提高了12%,而对铅和铜的钝化效果没有明显变化胡敏素是一种优良的土壤重金属钝化剂,巯基化胡敏素对重金属Cd的吸附效果明显提高。巯基胡敏素适用于对受中低浓度重金属复合污染农田的修复,具有广阔的应用前景。
[Abstract]:Heavy metal pollution in soil has the characteristics of concealment, difficult degradation and bioaccumulation. The heavy metals in soil can not only destroy the soil microbial community structure, inhibit the growth of crops, cause grain production, but also can be continuously spread through the food chain and enriched in the organism, eventually threatening the human beings. The situation of heavy metal pollution in soil is serious in our country. Heavy metal pollution in farmland has seriously threatened the food safety of our country and the life and health of the people. In situ passivation technology is one of the important means to repair heavy metal contaminated soil. In situ passivation technology is to apply some organic or inorganic chemicals into the soil. To change the physical and chemical properties of soil, or to change the physical and chemical reactions between the chemicals added and the heavy metals in the soil, to change the form of the heavy metal in the soil, to reduce its bioavailability and mobility in the soil environment, to achieve the remediation of contaminated soil. The effect is good, the repair cycle is short, the cost is low, and the operation is simple, especially in the restoration of heavy metal compound contaminated soil. This paper uses the environmentally friendly humus material Hu Minsu as the matrix to develop the economically efficient and environmentally friendly soil passivating agent, and carries out the foundation for the remediation of soil heavy metal pollution. The main contents of the study are as follows: 1. the stability of Hu Minsu was separated from peat soil by alkali extraction, and the adsorption kinetics and thermodynamic properties of the heavy metals Cd (II), Pb (II), Cu (II) in the simulated soil solution were studied by adsorption equilibrium experiment, and the concentration of pH and electrolyte concentration was studied. The effects of the concentration of medium and small molecular organic acids on the adsorption of heavy metals on the adsorption of heavy metals on the Hu Minsu surface show that the Hu Minsu surface contains a large number of oxygen active functional groups, and the adsorption capacity of the three heavy metals is Cd (II) Cu (II) Cd (II), and the adsorption of Cd (II), Cu (II) conforms to the Freundlich model, and the adsorption of Pb (II). The adsorption kinetics of heavy metals conforms to the Langmuir model, and the adsorption kinetics of heavy metals conforms to the two stage kinetic equation; with the increase of pH, the adsorption of heavy metals by Hu Minsu increases rapidly; both the electrolyte ions and tartaric acid in the solution can inhibit the adsorption of heavy metals by the huminin and the blunt of the heavy metals in the actual farmland soil solution by Hu Min. The ability of chemical passivation.2. is better than the passivation ability of simulated solution. The effect of adding Hu min Su on the bioavailability of copper and lead in contaminated soil and the transformation of heavy metal forms are studied. The results show that the leaching concentration of heavy metals can be significantly reduced by adding Hu Minsu. The heavy gold in the soil when adding 2% of the humin 5 days later. The leaching concentration of copper and lead decreased by 45.16% and 56.97%. added humin to passivate the heavy metals in the soil quickly. Further prolonging the passivation time had little effect on the passivation effect. Urea, ammonium sulfate and potassium dihydrogen phosphate could significantly increase the passivation effect of Hu Min acid on lead, and the leaching concentration decreased by 29.36%, 23.57%, 28.69% respectively. The effect of copper was not obvious. Further studies showed that the proportion of exchangeable copper and lead in soil dropped from 15.68% and 15.79% to 0.48% and 1.22% after 30 days of passivation treatment, while the proportion of organic copper and lead increased from 5.35% and 10.93% to 13.24% and 27.32%, indicating that humin could promote exchangeable. The sulfhydryl thioacetic acid and acetic anhydride were modified by mercapto acetic acid and acetic anhydride to obtain mercapto thiothiothiothiothiothiothiothiothiothiothiothiothiothiothiothiothiothiothiothiothiohydrin (.3.). The chemical structure of thimercapmeryl humin was studied by Fourier transform infrared and thermogravimetric analysis. The heavy metal Cd in soil solution was studied by adsorption equilibrium experiment. The effect of sulfhydryl huminin and huminin on the remediation of heavy metal contaminated soil was compared with the soil passivation experiment. The results showed that the surface of Hu Minsu had more carboxyl functional groups after the modification. Compared with humin, the mercapto Hu Minsu had a typical sulfhydryl group (S-) at 2578cm-1. The absorption peak of H shows the existence of the Hu Minsu surface sulfhydryl functional group; the adsorption isotherm of thiol humin to Cd (II) at different temperatures is more consistent with the Langmuir equation. Under the 298K condition, the theoretical saturation adsorption of thiol humin to Cd is 8.9081 mg. G-1, while Hu Minsu's theoretical saturated adsorption amount is 6.5335mg. G-1, indicating that in Hu Minsu The adsorption capacity of cadmium was significantly increased by the increase of the number of sulfhydryl groups on the surface. Adsorption thermodynamic parameters showed that the adsorption of thiol huminin to Cd (II) was spontaneous endothermic reaction. With the increase of temperature, the absolute value of delta G increased and the adsorption capacity of adsorbents increased correspondingly. Under the condition of passivating agent 2.5%, the passivation treatment was treated after ten days, The passivation rate of three heavy metals of cadmium, lead and copper in soil was 44%, 65%, respectively, and the passivation rate of cadmium was increased by 12%, while the passivation effect of 50%. on lead and copper had no obvious change. The effect of huminin was a good heavy metal passivating agent. The adsorption effect of mercapto Hu Minsu on heavy metal Cd was obviously improved. It is suitable for remediation of farmland contaminated by low and heavy metals and has broad application prospects.

【学位授予单位】：广东工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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