【作者】 刘勇；

【导师】 李晖；

【作者基本信息】 四川大学 ， 应用化学， 2007， 博士

【摘要】 利用自然界天然自净化功能，寻求与环境相协调的、绿色环保的污染治理与环境修复方法已成为当前人们关注的焦点。其中，自然界广泛存在的天然粘土矿物，由于其具有比表面积大、吸附性能好、储量丰富、来源广泛、处理工艺相对简单的特点，因此在环境对重金属污染的自净化中起着重要作用，是目前重金属废水处理的研究热点。蛭石是天然粘土矿物的一种。有关蛭石在环境方面的应用研究发展很快，但在金属离子的废水处理及含磷废水处理方面的研究还很不深入，仅有一些零散及初步的研究报道，尚缺乏系统的、全面的、深入的研究。针对以上问题，本文以新疆尉犁细粒蛭石为研究对象，综合运用环境化学、分析化学、矿物学等学科的知识，采用多种分析手段，对该蛭石进行了结构鉴定研究；并将原蛭石用于吸附金属离子Pb²⁺、Ag⁺、Ni²⁺、Cd²⁺，系统研究了蛭石吸附单一及混合金属离子的动力学和热力学机理；进而制备了两类具有重要应用前景的新型吸附材料，即羟基铝柱撑蛭石和CaCl₂改性蛭石，将其用于磷酸盐吸附，并对吸附过程的影响因素及吸附机理进行了详细探讨。吸附剂本身的结构性质，是决定该吸附剂吸附潜力的关键。通过扫描电镜（SEM）、傅立叶变换红外光谱分析（FT-IR）、热重分析（TG）、X射线衍射方法（XRD）对新疆尉犁蛭石进行了结构鉴定。结果表明，该蛭石属于Na、Ca混合型的层状硅酸盐矿物，既含有独立的蛭石成分，也含有水金云母成分，属于V（蛭石）+P（金云母）／V型无序矿物。为了计算新疆尉犁蛭石矿中蛭石和金云母的混层比，建立了以参比强度为基础的XRD定量分析新方法，该方法优于传统的分晶层定量方法。同时，首次通过MS modeling软件构建了新疆尉犁蛭石矿中的纯蛭石模型和水金云母模型及其粉末衍射模拟XRD谱图，表明该蛭石矿确实是纯蛭石和水金云母的混合体，弥补了定性分析中因缺乏粉末衍射卡PDF而无法进行相分析的不足。在对蛭石结构进行系统研究基础上，将原蛭石用于吸附金属离子Pb²⁺、Ag⁺、Ni²⁺、Cd²⁺，系统研究了蛭石吸附单一金属离子的动力学和热力学机理。结果表明：蛭石对Pb²⁺的吸附动力学可用拟一级速率方程和拟二级速率方程表示，蛭石对单一离子Ag⁺、Ni²⁺、Cd²⁺的吸附动力学可用拟二级速率方程来描述，计算值与实测值吻合甚好，室温下相关系数（R²）均达到0.99以上。蛭石对4种金属离子的吸附速率大小分别为：Ag⁺＞Pb²⁺＞Cd²⁺＞Ni²⁺。蛭石对单一离子Pb²⁺、Ag⁺、Ni²⁺、Cd²⁺的吸附等温线均符合Langmuir和Freundlich等温方程式，室温下相关系数（R²）分别达到0.9以上。且4种金属离子按其吸附容量大小的排序为Pb²⁺＞Cd²⁺＞Ag⁺＞Ni²⁺。考察了温度对蛭石吸附单一离子Pb²⁺、Ag⁺的影响。温度升高，蛭石对单一离子Pb²⁺、Ag⁺的平衡吸附量均增大，说明该吸附反应是吸热反应。首次求得了蛭石吸附Pb²⁺、Ag⁺的焓变（△H）、熵变（△S），及不同温度下的吉布斯自由能变化（△G），弥补了目前关于温度对蛭石吸附金属离子的影响尚无定量描述方法的不足。同时，蛭石吸附不同金属离子(如Pb²⁺、Ag⁺、Ni²⁺、Cd²⁺)前后的XRD分析表明，蛭石吸附不同的金属离子，其晶面间距d₀₀₁呈现不同值。这是由于金属离子的电子构型、电价及半径不同造成的。蛭石吸附Pb²⁺后的热重分析（TG）和X光电子能谱分析（XPS）表明，吸附到蛭石上的Pb（Ⅱ）存在多种形态，如Pb-O-Si、Pb-OH、Pb（OH）等。基于上述实验结果，进一步研究了二元金属离子体系(Pb²⁺／Ag⁺、Pb²⁺／Ni²⁺、Pb²⁺／Cd²⁺、Ag⁺／Ni²⁺、Ag⁺／Cd²⁺、Ni²⁺／Cd²⁺)，三元金属离子体系(Pb²⁺／Ag⁺／Ni²⁺、Pb²⁺+／Ag²⁺／Cd²⁺、Pb²⁺／Ni²⁺／Cd²⁺、Ag²⁺／Ni²⁺／Cd²⁺)和四元金属离子体系(Pb²⁺／Ag⁺／Ni²⁺／Cd²⁺)在蛭石上的竞争吸附行为。结果表明：蛭石对4种金属离子的竞争吸附能力大小顺序为：Pb²⁺＞cd²⁺＞Ni²⁺＞Ag²⁺。且各混合体系中蛭石对Pb²⁺的吸附均符合Langmuir等温方程式。在溶液pH值、蛭石的粒径、用量等外界条件一致的情况下，影响蛭石对金属离子吸附能力的主要因素是金属离子自身的因素，如离子水合能、离子半径、有效水合半径、电价、电负性等。蛭石对4种金属离子的竞争吸附速率大小依次为Ag⁺＞Pb²⁺＞Ni²⁺＞Cd²⁺。拟二级速率方程能很好的描述蛭石对各金属离子的吸附动力学，实验数据与方程吻合甚好，相关系数（R²）均达到0.98以上。为了提高蛭石对Ag⁺的吸附容量，将蛭石进行热改性和酸改性。结果表明：蛭石经不同温度灼烧处理后，随着灼烧温度从100℃升高到600℃，其d₀₀₁值逐渐变小，阳离子交换容量（CEC）逐渐减小到几乎为0。蛭石经100℃灼烧处理后，其吸附Ag⁺的能力较原蛭石强。而蛭石经200℃、300℃、600℃灼烧处理后，其对Ag⁺的吸附率越来越低，说明蛭石吸附Ag⁺的能力变差。经100℃处理的蛭石对Ag⁺的吸附等温线均符合Langmuir和Freundlich方程，室温下相关系数（R²）分别达到0.999和0.975。蛭石经不同浓度HCl处理后，随着HCl浓度增大，蛭石的d₀₀₁衍射峰强度明显降低，半峰宽明显增大，直至该衍射峰消失。阳离子交换容量（CEC）也逐渐减小到几乎为0。蛭石经0.1mol／L HCl处理后，其对Ag⁺的吸附能力较原蛭石强，0.2000 g改性蛭石对100 mg／L Ag⁺的吸附率达到77.08％，比原蛭石对Ag⁺的吸附率增大了10％。随着HCl浓度增大，其对Ag⁺的吸附能力反而降低。经0.1 mol／L HCl处理的蛭石对Ag⁺的吸附等温线均符合Langmuir和Freundlich方程，室温下相关系数（R²）分别达到0.997和0.961。由于原蛭石对磷酸盐的吸附能力较弱，将原蛭石改性，首次制备了两类对磷酸盐有较好吸附效果的新型吸附材料，即羟基铝柱撑蛭石和CaCl₂改性蛭石，系统研究了其制备方法和吸附磷酸盐机理。结果表明：将新疆尉犁蛭石矿依次经过HNO₃酸化，600℃灼烧，草酸酸化，NaCl交换5次后，增加Si／Al比值，使其层电荷降低。再用Keggin离子插层，得到了18（?）的羟基铝柱撑蛭石。进而将此改性蛭石用于磷酸盐废水处理，实验了不同pH值下改性蛭石吸附磷酸盐的效果，并与原蛭石作比较。结果发现，pH3条件下，改性后的蛭石对磷酸盐的吸附率最大，达到11.51％，比原蛭石提高了约3倍。其吸附机理主要为将原蛭石进行羟基铝柱撑改性后，Keggion离子进入层间，其中的Al-OH基团可与H₂PO₄^-离子发生离子交换反应：Al-OH+H₂Po₄^-→Al-OPO₃H₂+OH^-另外，除了离子交换反应外，羟基铝插层后游离出的少量Al³⁺会与磷反应生成磷酸铝沉淀，以及蛭石表面的-Si-OH、-Al-OH等基团与磷的络合反应等。建立了CaCl₂改性蛭石吸附磷酸盐的新方法，讨论了溶液pH值、温度、时间对吸附效果的影响，探讨了吸附机理，并与原蛭石作比较。结果表明：将蛭石进行CaCl₂改性后，改性蛭石对磷浓度为20mg／L的磷酸盐的吸附率达到98.5％。不同pH值条件下，CaCl₂改性蛭石对磷酸盐的吸附率明显高于原蛭石。pH＜10时，改性蛭石对磷酸盐的吸附率≤5.0％。pH＞10后，吸附率明显增大，出现突跃，在pH=12时达到最高值。原蛭石对磷酸盐的吸附率变化趋势与CaCl₂改性蛭石类似，但是各pH值下对磷酸盐的吸附率均较改性蛭石低。pH＜10时原蛭石对磷酸盐的吸附率≤1.5％。pH＞10.5后，吸附率明显增大，出现突跃，在pH=12时达到最高值。CaCl₂改性蛭石及原蛭石对磷酸盐的吸附动力学行为均符合拟一级动力学方程和拟二级动力学方程，室温下相关系数（R²）均在0.98以上。拟一级动力学方程计算所得的改性蛭石及原蛭石吸附磷酸盐的总的反应速率常数分别为0.1289 min^-1和0.07765 min^-1；拟二级动力学方程计算所得的改性蛭石及原蛭石吸附磷酸盐的反应速率常数分别为0.2809 g·mg^-1·min^-1和0.2273 g·mg^-1·min^-1。说明CaCl₂改性蛭石吸附磷酸盐的速率较原蛭石快。CaCl₂改性蛭石及原蛭石对磷酸盐的吸附平衡均符合Lamgmuir和Freundlich等温方程式，室温下其与两类方程的相关系数（R²）均达到0.9以上。且随着温度升高，两种蛭石对磷酸盐的最大吸附量Q_max甜逐渐增大，CaCl₂改性蛭石从10℃的11.29mg／g增加到60℃的12.79 mg／g，原蛭石从10℃的3.856 mg儋增加到60℃的5.000mg／g。说明CaCl₂改性蛭石对磷酸盐的吸附能力比原蛭石对磷酸盐的吸附能力强得多。求得了CaCl₂改性蛭石和原蛭石吸附磷酸盐的△H分别为4.072 kJ／mol、128.7 kJ／mol；△S分别为25.72 J／mol·K、461.7 J／mol·K；CaCl₂改性蛭石吸附磷酸盐的△G分别为-3.289 kJ／mol（10℃）、-3.537 kJ／mol（30℃）、-4.140 kJ／mol（45℃）、-4.549 kJ／mol（60℃）；原蛭石吸附磷酸盐的△G分别为-1.52 kJ／mol（10℃）、-10.64 kJ／mol（30℃）、-21.74 kJ／mol（45℃）、-22.72 kJ／mol（60℃）。表明两种蛭石对磷酸盐的吸附反应均是自发进行的，温度越高，自发进行的程度越大。且两种蛭石对磷酸盐的吸附反应是吸热反应，温度升高，有利于反应的进行。原蛭石及改性蛭石对磷酸盐的吸附作用除了物理吸附外，还存在化学吸附，如蛭石中的Ca²⁺与磷酸盐结合生成磷灰石，温度升高降低了反应的活化能，有利于形成化学键，利于化学吸附。更多还原

【Abstract】 Natural self-purification, a potential mechanism in nature whereby mankind and the earth are interrelated with each other, has been playing an increasingly important role in the field of harnessing contamination and remedying environment. Metal pollutants treatment by natural clay minerals is based on the law of nature and reflects natural self-purification function in the inorganic world. Vermiculite is one of the natural clay minerals, which is relatively cheap and easily available in China. Although previous researches have highlighted the utility of this very low cost and environmentally friendly vermiculite in the removal of heavy metals and phosphates from wastewater, little attention has been paid to the mechanisms of kinetics and the thermodynamics for the metal adsorption on natural vermiculite and for the phosphate adsorption on the modified vermiculite.Therefore, the objective of this paper was to investigate the structure characteristics of the vermiculite supplied by the Weili mine of Xinjiang by using kinds of analysis methods based on the knowledge of environmental chemistry, analysis chemistry and mineralogy. Moreover, the kinetics and thermodynamics mechanisms of Ag⁺, Pb²⁺, Cd²⁺ and Ni²⁺ adsorption on natural vermiculite were studied. Furthermore, two new kinds of adsorption materials of Al-pillared vermiculite and CaCl₂ modified vermiculite were prepared, and phosphates sorption experiments were carried out for the two modified vermiculites to investigate sorption behaviors and mechanisms of phosphates.The structure of an adsorbent is the key to decide itsadsorption ability. By using SEM, FT-IR, TG and XRD methods, the structure characteristics of the vermiculite were investigated, which indicated that the vermiculite is not pure vermiculite but a mixture of hydrobiotite and vermiculite. In addition, a new method for computing the proportion of phlogopite and vermiculite crystal layer of phlogopite-vermiculite interstratified mineral from Weili mine of Xinjiang was established based on the analysis of XRD, which is better than the traditionai method of individual crystal layer chemical formula. Furthermore, the tridimentional models of the vermiculite layer and the hydrobiotite crystal layer of Weili vermiculite of Xinjiang were established firstly by the MS modeling software.Based on the systemic investigation of the structure characteristics of the vermiculite, the kinetics and thermodynamics mechanisms of Ag⁺, Pb²⁺, Cd²⁺, Ni²⁺ adsorption on natural vermiculite were studied. The kinetics of Pb²⁺ adsorption on vermiculite can be best described by pseudo-first order kinetics model and pseudo-second order kinetics model. The kinetics of Ag⁺, Cd²⁺ and Ni²⁺ adsorption on vermiculite Can be best described by pseudo-second order kinetics model. The adsorption capacities calculated by the model were consistent with those actual measurements, which the correlation coefficient （R²） was more than 0.99 at room temperature. The adsorption rates for metal ions were in the order of Ag⁺＞Pb²⁺＞＞Cd²⁺＞Ni²⁺. The adsorption isotherms for Ag⁺, Pb²⁺, Cd²⁺ and Ni²⁺ adsorption on vermiculite followed both Langmuir and Freundlich isotherm model, which the correlation coefficients （R²） were more than 0.9 at room temperature. The adsorption capacities for metal ions were in the order of Pb²⁺＞Cd²⁺＞Ag⁺＞Ni²⁺. Furthermore, the effects of temperature on the Pb²⁺, Ag⁺ adsorption on vermiculite were studied. Increase of temperature from 10℃to 80℃increased the sorption of Pb²⁺ and Ag⁺, indicating the process to be endothermic. Thermodynamic parameters such as change in enthalpy （△H）, change in entropy （△S）, and change in free energy （△G） at different temperature were firstly evaluated by applying the Van’t Hoff equations. In addition, the XRD patterns for vermiculite adsorbed different metal ions, such as Pb²⁺, Ag⁺, Cd²⁺, Ni²⁺ indicated that the d₀₀₁ space was different from one metal to another, which were related to many factors, such as electron conformation, ion charges and ionic radius. The TG and XPS for vermiculite adsorbed Pb²⁺ indicated that there were more Pb（Ⅱ） forms adsorption on vermiculite, such as Pb-O-Si, Pb-OH, Pb（OH）₂ and so on.Moreover, the competitive adsorption capacity of metal ions Ag⁺, Pb²⁺, Cd²⁺, Ni²⁺ in a binary, ternary and quadruple systems on vermiculite followed Pb²⁺＞Cd²⁺＞Ni²⁺＞Ag⁺. Such behaviors were determined by the ion charge, the hydrated ionic radius and the hydration energies of metal species. The adsorption equilibrium of Pb²⁺ in a binary, ternary and quadruple system on vermiculite can be described by the Langmuir isotherm model. The adsorption rate among the four metal ions adsorbed onto vermiculite followed Ag⁺＞pb²⁺＞Ni²⁺＞Cd²⁺. The pseudo-second order kinetics model best described the kinetics of four metals. The adsorption capacities calculated by the model were consistent with those actual measurements, which the correlation coefficient （R²） were more than 0.98.In order to improve the adsorption capacity of Ag⁺ on vermiculite, the natural vermiculite was modified by heat-treatment and acid-treatment. After heated at different temperature, with temperature increasing from 100℃to 600℃, the cation exchanged capacity （CEC） of the vermiculite decreased to almost zero, and the peak of d₀₀₁ decreased in intensity. The adsorption capacity of Ag⁺ for the vermiculite heated at 100℃was higher than that for the untreated vermiculite, while the adsorption capacities of Ag⁺ for the vermiculite heated at 200℃, 300℃, 600℃respectively were lower than that for the untreated vermiculite. The Ag⁺ adsorption on the vermiculite heated at 100℃obeyed both Langmuir and Freundlich model, and the correlation coefficients （R²） were 0.999 and 0.975 at room temperature, respectively.In addition, after leached with different concentration of HCl, with HCl concentration increasing from 0.1mol/L to 2.0mol/L, the peak of d₀₀₁ for vermiculite decreased to dismiss in intensity, and the cation exchange capacity （CEC） decreased to almost zero. The adsorption capacity of Ag⁺ for the vermiculite leached with 0.1 mol/L HCl was 10% higher than that for the untreated vermiculite, while the adsorption capacities of Ag⁺ for the vermiculites leached with 0.5 mol/L, 1.0 mol/L, 2.0 mol/L HCl respectively were lower than that for the untreated vermiculite. The Ag⁺ adsorption on the vermiculite leached with 0.1 mol/L HCl obeyed both Langmuir and Freundlich model, and the correlation coefficients （R²） were 0.961 at room temperature, respectively.Because of the poor adsorption ability of phosphates on natural vermiculite, two new kinds of adsorption materials of Al-pillared vermiculite and CaCl₂ modified vermiculite were prepared. A new method for preparation of Al-pillared vermiculite using the natural vermiculite supplied from Weili mine of Xinjiang has been established. The natural vermiculite was submitted to a nitric acid treatment followed by calcination, oxalic acid treatment, and sodium form by ion exchange, which results in an increase of the framework Si/Al ratio, thus, the reduction of the layer change density, and the conversion of the vermiculite into a form of sodium-vermiculite. Then the 18A Al-pillared vermiculite was obtained by contact with the aluminum pillaring solution. Furthermore, phosphate sorption experiments were carried out for Al-pillared vermiculite and untreated vermiculite under different pH condition to investigate sorption behaviors and mechanisms of phosphates. The phosphate sorption maxima for the Al-pillared vermiculite were 11.51% at pH 3, which were higher by about 3 orders than those for natural vermiculite.A new method for CaCl₂ modified vermiculite adsorption phosphate has been established. The adsorption ratio of phosphate with P concentration of 20 mg/L on the 0.1g vermiculite modified by CaCl₂ was 98.5 %. The phosphate sorption to the untreated and CaCl₂ modified vermiculite strongly depended on pH. For the untreated vermiculite, the phosphate adsorption was lower under pH less 10.6. From pH 10.6 to pH 13, the phosphate adsorption increased largely. From pH 12 to pH 13, the phosphate adsorption reached a plateau value and remained constant, ranging from 66 % to 66.5 %. For the CaCl₂ modified vermiculite, the phosphate adsorption was higher than that the untreated vermiculite with different pH. At pH less 4, the phosphate sorption was 4 %. At pH 8.0, the phosphate sorption increased to 5%. From pH 9.5 to pH 13, the phosphate sorption increased sharply, reached 99% with pH-12. The kinetics of phosphate adsorption on CaCl₂ treated vermiculite and untreated vermiculite can be best described by pseudo-first order kinetics model and pseudo-second order kinetics model. The adsorption capacities calculated by the model were consistent with those actual measurements, which the correlation coefficient （R²） were more than 0.98. The overall rate constants for phosphate adsorbed on modified vermiculite and untreated vermiculite were 0.1289 min^-1 and 0.07765 min ^-1 respectively by pseudo-first order kinetics model. The rate constants calculated by pseudo-second order kinetics model for phosphate adsorption on modified vermiculite and untreated vermiculite were 0.2809 g·mg^-1·min^-1 and 0.2273 g·mg^-1·min^-1 respectively. The adsorption isotherms for CaCl₂ modified vermiculite and untreated vermiculite followed both Langmuir and Freundlich isotherm model, which the correlation coefficients （R²） were more than 0.9 at room temperature. Increase of temperature from 10℃to 60℃increased the sorption capacity of P from 11.29 mg/g to 12.79 mg/g by CaCl₂ modified vermiculite and from 3.856 mg/g to 5.000 mg/g by untreated vermiculite, indicating that CaCl₂ modified vermiculite was better than untreated vermiculite to remove phosphate. For the CaCl₂ modified vermiculite and untreated vermiculite, the△H were 4.072 kJ/mol, 128.7 kJ/mol respectively, which indicated that rise in temperature favored the adsorption and the adsorption process was an endothermic reaction in nature. The△S were 25.71 J/mol K, 461.7 J/mol K respectively, and the△G were negative at different temperature. It indicated that the adsorption was spontaneous in the nature and the spontaneous increased with increasing temperature. This observation can be explained by the fact that for the CaCl₂ modified vermiculite and untreated vermiculite, there are more than one mechanism for phosphate adsorption. Along with the usual physisorption, the chemisorption of phosphate at the active sites in the vermiculite surface, such as P precipitation induced by Ca²⁺ also took place. Increasing temperature not only increased the active surface centers available for adsorption, but also decreased the activation energy for the adsorption. All of these are favor to chemisorption.更多还原