可变电荷土壤对重金属的吸附研究
摘 要
近代工农业的发展，天然水环境的污染日益严重。作为水体中的主要污染物之一，重金属越来越受到人们的普遍关注。不可降解性、迁移性小以及易土壤中富集等特点，经水、植物等介质最终影响人类健康。
本文主要研究了可变电荷土壤对重金属的单相吸附及影响其的相关因素。以Cu2+为目标污染物，通过改变环境因素如温度、pH、离子强度等因素，来确定可变电荷土壤对Cu2+吸附的最佳条件，并通过Zeta电位测定仪监测可变电荷土壤吸附Cu2+的表面电荷变化来探究其吸附机理。
本文研究结果表明：
（1）pH：可变电荷土壤吸附铜离子的吸附率基本上与pH值成正比例关系，有着明显的增长，但是当pH增加到一定值时，吸附率增长速度变缓。
（2）离子强度：随着离子强度的提高，可变电荷土壤对于铜离子的吸附效果明显降低。 （3）有机酸：酒石酸对于可变电荷土壤吸附铜离子的影响效果最好，依次是草酸、对照组；土壤中Cu2+的吸附随着投加量的增加而增加，但是随着投加量的提高，增速明显变缓。
（4）重金属：重金属离子存在下会抑制可变电荷土壤吸附Cu2+效果：且抑制顺序为： Cd2+> Hg2+；
（5）热力学：随着温度升高，吸附量增大，可能原因是吸附是一个吸热过程。Langmuir模型在描述可变电荷土壤对铜离子的吸附行为上要优于Freundlich模型。
（6）动力学：可变电荷土壤对重金属的吸附速度很快，在2.0h左右吸附基本达到平衡。可变电荷土壤吸附铜离子的动力学原理符合假二次动力学模型。
关键词：可变电荷土壤；铜离子；吸附
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Abstract
With the development of modern industry and agriculture, the pollution of water environment becomes worse. People pay more attention to heavy metals, which is the one of the main pollutants. With the characteristics of non-degradation, little mobility and easy to enrichment in soil, heavy metals will ultimately affect human health though water, plants and other media.
This paper mainly studies the variable charge soils’ single-phase adsorption of heavy metals and the affecting factors. Cu2+ as the target pollutant, this experiment changes the environmental factors such as temperature, pH, ionic strength and so on, to determine which is the best condition for the variable charge soils adsorbing Cu2+. Through the Zeta potential analyzer, we monitor the surface charge of variable charge soils to explore the adsorption mechanism.
In this paper,
(1) pH: the adsorption rate of variable charge soils adsorbing Cu2+ is essentially proportional to the pH value, but when the pH increases to a certain value, the adsorption rate of growth becomes small.
(2) Ionic strength: with the increase of ionic strength, the effect on Cu2+ adsorption by variable charge soils significantly reduces.
(3) Organic acid: the effect of tartaric acid for Cu2+ adsorption by variable charge soils is the best, followed by oxalic acid and the control group; the adsorption rate of Cu2+ increases with the dosage increasing; but as the dosage increased, the growth rate significantly becomes small.
(4) Heavy metals: The presence of heavy metals inhibit the adsorption of Cu2+ by variable charge soils, the effect on Cu2+’s adsorption by variable charge soils: Cd2+> Hg2+.
(5) Thermodynamics: as the temperature increases, the adsorption capacity increases; this may means the adsorption is an endothermic process. Langmuir and Freundlich models are used to describe the adsorption isotherms. Results indicate that Langmuir model is fit to experimental data well.
(6) Kinetics: the adsorption of variable charge soils on heavy metals is very fast, in about 2.0h adsorption equilibrium is achieved. The pseudo-second-order kinetic model is applied to
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describe the kinetic data. The experimental data agrees with pseudo-second-order kinetic model well.
Keyword: Variable charge soil, Copper ion, adsorption
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目录
摘 要 .................................................................... I Abstract ................................................................. II 第一章 绪论 ............................................................... 1
1.1研究背景 ....................................................................................................................................... 1 1.2国内外研究现状 ........................................................................................................................... 2 1.3水环境重金属污染现状 ............................................................................................................... 2 1.3.1国内水环境重金属污染现状 ................................................................................................ 3 1.3.2国外水环境重金属污染现状 ................................................................................................ 3 1.4重金属在可变电荷土壤/水界面的吸附机理及其影响因素 ...................................................... 4 1.4.1重金属在可变电荷土壤/水界面的吸附机制....................................................................... 4 1.4.2 重金属在可变电荷土壤吸附的影响因素 ........................................................................... 5 1.5研究意义及内容 ........................................................................................................................... 6
第二章 实验材料、设备和方法 ............................................... 7
2.1实验试剂与仪器 ........................................................................................................................... 7 2.1.1实验试剂与材料 .................................................................................................................... 7 2.1.2实验仪器 ................................................................................................................................ 7 2.2试验方法 ....................................................................................................................................... 8 2.2.1供试土样 ................................................................................................................................ 8 2.2.2土壤基本性质的测定 ............................................................................................................ 8 2.2.3影响因素实验 ........................................................................................................................ 8 2.2.4吸附热力学研究方法 ............................................................................................................ 9 2.2.5吸附动力学研究方法 ............................................................................................................ 9 2.3实验分析方法 ............................................................................................................................... 9 2.3.1标准曲线 ................................................................................................................................ 9
第三章 土壤样品基本性质的表征 ............................................ 11
3.1 XRF ............................................................................................................................................... 11 3. 2零点电位的确定（pHZPC） ........................................................................................................ 11 3. 3土壤样品基本性质的测定结果 ................................................................................................ 12 3.4 FT-IR红外光谱测定 .................................................................................................................... 12
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