【作者】 梁学峰；

【导师】 侯万国；

【作者基本信息】 山东大学 ， 环境工程， 2008， 硕士

【摘要】 进入21世纪以来,环境问题正日益引起全球关注,污染物的排放已经对生态安全和人类健康造成了严重的威胁,其中重金属污染的治理已经成为环境学科中的研究热点。在环境中的重金属,其在固/液界面的吸附与解吸是决定重金属地球化学过程和环境生态效应的根本问题。对这一基本现象的科学认识是了解重金属污染物的形态分布、迁移转化与最终归属以及开发污染土壤与废水修复治理技术的基础。现有的关于吸附研究的文献多采用带结构负电荷的材料作为吸附剂,荷结构正电荷材料与重金属相互作用的研究鲜有报道。本文选择带有结构正电荷的层状双金属氢氧化物（Layered double hydroxides,LDHs）为模型吸附剂,研究了重金属离子Pb（Ⅱ）在LDHs/H₂O界面上的吸附行为,考察多种影响因素,由此探讨结构电荷或由此而引起的界面相微观环境酸碱性对重金属吸附的影响规律,以期加深对吸附机理的认识。本文主要内容归纳如下:首先综述了重金属污染的现状、危害,重金属在固/液界面吸附宏观实验研究进展、微观吸附机理解释并简要介绍了层状双金属氢氧化物的特点与性能等。实验第一部分,合成了分子式为[Mg_0.72Fe_0.28（OH）₂]Cl_0.06（OH）_0.22的Mg-Fe型LDH,并研究了Pb（Ⅱ）在Mg-Fe型LDH上的吸附等温线、吸附动力学,考察了pH、电解质等因素对吸附的影响,并结合X射线衍射与红外光谱等方法探讨吸附机理。结果显示:Mg-Fe型LDH对Pb（Ⅱ）具有很强的吸附能力,其吸附动力学可以用准二级动力学方程和双指数动力学方程拟合,吸附等温线可以用S型等温线Aranovich-Donohue等温式拟合。Mg-Fe型LDH具有很强的pH缓冲能力,Pb（Ⅱ）溶液初始pH对最终吸附量无明显影响。支持电解质对吸附亦无明显影响。Pb（Ⅱ）在Mg-Fe型LDH上吸附的微观机理以生成碱式碳酸铅沉淀的表面沉淀为主,表面络合为辅,其中表面络合又可分为化学键合和静电键合。实验第二部分,合成了层间阴离子分别为Cl^-,NO₃^-,CO₃^2-,EDTA的四种不同Mg-Al型LDHs。阴离子对LDHs吸附Pb（Ⅱ）的能力有很大影响,其吸附能力大小顺序为:Mg₃Al-CO₃ LDH＞＞Mg₃Al-Cl LDH＞Mg₃Al-NO₃ LDH＞Mg₃Al-EDTALDH。Mg₃Al-CO₃ LDH对Pb（Ⅱ）的吸附机理可以解释为Pb（Ⅱ）在LDHs微界面碱性环境中与层间CO₃^2-作用生成碱式碳酸铅沉淀。Pb（Ⅱ）在Mg₃Al-Cl LDH和Mg₃Al-NO₃ LDH上的吸附可用Aranovich-Donohue等温式拟合,其吸附机理主要为Pb（Ⅱ）与LDH表面羟基的表面络合作用。Mg₃Al-EDTA LDH吸附Pb（Ⅱ）的主要机制为层间EDTA与Pb（Ⅱ）形成络合物从而完成吸附。实验第三部分,合成了Mg-Al-Fe型LDHs,其中电荷数维持恒定但Fe含量逐渐增加。研究发现可以用双指数动力学方程和准一级动力学方程拟合Pb（Ⅱ）在Mg-Al-Fe型LDHs上的吸附动力学,其吸附等温线可用Freundlich等温式较好地拟合。随着样品中Fe含量的增加,初始快速吸附阶段吸附速率变大,平衡吸附量增加。Pb（Ⅱ）在Mg-Al-Fe型LDHs上的吸附机制主要是通过LDHs在溶液中造成的局部微环境pH升高,致使生成碱式碳酸铅沉淀Pb₃（CO₃）₂（OH）₂。更多还原

【Abstract】 The environmental problems are attracting more and more attention all over the world now.The much pollutant may cause serious harm to ecological safety and human health,and the pollution of heavy metals is the focus of environmental science and technology.The adsorption/desorption behavior of heavy metals at the solid liquid interface is the fundamental which determines the geochemical process of heavy metals and environmental ecological effect.The scientific understanding of the basic phenomenon is the basis of understanding the speciation distribution,transport and fate of heavy metal pollutants and technology on remediation of contaminated soil and waste water treatment.At present most of the adsorption researches are based on the materials with negative charged,but few researches on the interaction of heavy metal cations with positive charged materials are reported.In this article positive charged material layered double hydroxides（LDHs）are chosen as model adsorbents to study the adsorption behavior of Pb（Ⅱ）on LDHs.The adsorption mechanisms are discussed and we hope to obtain the influence law of structural charge on heavy metal adsorption and deepen the cognition to the adsorption mechanism.In the summary part,firstly,the related contents of heavy metal such as properties and damage are introduced;secondly,the research progresses on macro adsorption experiments and the micro mechanisms are reviewed;thirdly,the basic knowledge of layered double hydroxides is introduced.In the section one of the experiment,Mg-Fe LDH with the formula [Mg_0.72Fe_0.28（OH）₂]Cl_0.06（OH）_0.22is prepared and the sorption behaviors of Pb（Ⅱ）on Mg-Fe LDH are studied including adsorption isotherm,adsorption kinetics,and various factors that affect the sorption behaviors such as pH,ionic strength.The sorption amount of Pb（Ⅱ）on Mg-Fe LDH is high and the sorption kinetics can be described by pseudo-second order kinetic model and double exceptional function model successfully.The sorption data can be fitted by Aranovich-Donohue isotherm which belongs to S type isotherm.The Mg-Fe LDH has a pH buffer capacity and the initial pH of the Pb（Ⅱ）solution has no effect on the final equilibrium sorption amount and the back electrolyte NaNO₃ also has no obvious effect on the sorption amount. Combined with XRD and FT-IR,the mechanisms of Pb（Ⅱ）sorption on Mg-Fe LDH are surface precipitation which is referred to the basic lead carbonate precipitation and surface complexation including chemical bonding and electric bonding.In the section two of the experiment,four kinds of Mg-Al LDHs with different anions Cl^-,NO₃^-,CO₃^2-,EDTA in the interlayer are prepared.The sorption amount of Pb（Ⅱ）on Mg₃Al-CO₃ LDH is high and the sorption mechanism is that Pb（Ⅱ）acted with CO₃^2-in the interlayer in the local basic environment in the LDHs/water interface to form the basic lead carbonate.The sorption amounts of Pb（Ⅱ）on Mg₃Al-Cl LDH and Mg₃Al-NO₃ LDH are less than that on Mg₃Al-CO₃ LDH and the sorption data can be described by Aranovich-Donohue isotherm.The sorption mechanism is the surface complexation which refers to Pb（Ⅱ）reacts with the hydroxyl on the surface of LDHs samples.The mechanism of Pb（Ⅱ）sorption on Mg₃Al-EDTA LDH is the complexation of Pb（Ⅱ）with EDTA in the interlayer.In the section three of the experiment,Mg-Al-Fe LDHs with the same charge but different Fe content are prepared.The sorption data can be described by Freundlich isotherm and pseuo-first order kinetic model.The mechanism is the surface precipitation of basic lead carbonate.With the increase of Fe content the sorption rate in kinetic experiment and the equilibrium sorption amount in the isotherm experiment increase.更多还原