【作者】 饶正勇；

【导师】 李德亮；

【作者基本信息】 河南大学 ， 环境科学， 2012， 硕士

【摘要】 本文以中国铝业河南分公司拜耳法和烧结法赤泥为原料实验，用原子发射法、原子吸收法、滴定分析法测定出赤泥金属元素的含量，用红外光谱仪、差热分析仪、X射线衍射仪对赤泥表征分析，讨论赤泥内部结构；分别用十六烷基三甲基溴化铵（CTAB）和十八烷基三甲基溴化铵（STAB）对盐酸中和后的烧结法赤泥改性得到改性吸附剂CARM（CTAB Activated Red Mud）和SARM（STAB Activated Red Mud），用CARM和SARM对水溶液中Cr（Ⅵ）进行吸附性能研究，考察最佳吸附条件，结合吸附等温线、吸附动力学、吸附热力学探讨吸附机理。主要内容如下：（1）赤泥样品预处理后用酸法消解；对赤泥消解液进行ICP-AES全分析扫描，分析可能含有的金属元素并用ICP-AES法进行准确测定；Fe、Al、Ca、Mg、K、Na六种金属元素用AAS、滴定分析法作对比测定和加标回收实验验证；得到拜耳法赤泥中46种金属元素和烧结法赤泥中47种金属元素的具体含量；硅含量用重量法测定。（2）根据测定结果和赤泥在建筑材料中的应用以及赤泥金属元素的提取现状，对赤泥金属元素进行可利用分析，发现赤泥中很多金属元素都有一定的提取利用价值，但限于工业化技术因素和经济因素导致利用价值不大。总之，赤泥综合利用有多种方法，但当前的利用方法和提取工艺有待改进。（3）对赤泥做红外、热重、XRD表征，发现赤泥中有8%左右的羟基水，以结晶水、结合水和结构水的形态存在于赤泥复杂的矿物结构中；赤泥中有含CaCO3较多的矿物成分，这些矿物在580℃⁶80℃时分解放出CO2使拜耳法赤泥失重5%左右，烧结法赤泥失重10%左右；赤泥中的矿物组成比较复杂，主要有方解石、硅酸二钙、钙钛矿、钙霞石、水钙石榴石等。（4）烧结法赤泥表面有丰富的可交换阳离子，利用离子交换原理将阳离子表面活性剂CTAB中的阳离子基团C₁₆H₃₃（CH₃）₃N⁺和STAB中的阳离子基团C₁₈H₃₇（CH₃）₃N⁺结合到烧结法赤泥表面，达到扩充烧结法赤泥孔径增大烧结法赤泥比表面积的目的；两种改性剂CTAB和STAB的最佳改性浓度确定为0.5%和0.6%；改性后的CARM和SARM红外光谱图中发现CH₃^-（N⁺）和-CH₂-的特征峰，证明改性成功。（5）通过条件选择实验得到CARM和SARM吸附水溶液中Cr（Ⅵ）的最佳吸附条件；以CARM为吸附剂时，溶液初始pH值为2的酸性条件下吸附率最高，吸附30分钟可达吸附平衡，温度对吸附效果的影响不大，相同条件下随着Cr（Ⅵ）浓度的增加吸附量会有所上升；SARM吸附45分钟可达到平衡，其它条件和CARM相同。（6）在最佳实验条件下CARM和SARM对100mg/L的Cr（Ⅵ）的吸附率分别可以达到95%和97%以上，对20mg/L的Cr（Ⅵ）吸附率均可以到99%以上；原赤泥、CARM和SARM最大吸附量分别为4.658mg/g、22.03mg/g和25.16mg/g，说明改性后吸附量大幅增加，其中STAB的改性效果更好。（7）采用Langmuir和Freundlich两种等温吸附模型分析吸附等温线，分析结果表明，CARM吸附Cr（Ⅵ）的Langmuir等温吸附模型拟合qmax值为22.20mg/g和实验值22.03mg/g非常接近，线性关系为0.9997；SARM吸附Cr（Ⅵ）的Langmuir等温吸附模型拟合qmax值为25.21mg/g和实验值25.16mg/g非常接近，线性关系为0.9990；说明CARM和STAB对水溶液中Cr（Ⅵ）的吸附过程都符合以单分子吸附为主的Langmuir等温吸附模型。（8）吸附动力学分析中讨论了准一级动力学和准二级动力学模型，两个吸附过程的准一级动力学拟合出的qe的值分别为0.2165mg/g和0.9531mg/g，偏离实验值较大；CARM吸附Cr（Ⅵ）的准二级动力学模型拟合方程的R2为0.9999，qe理论计算值11.87mg/g和实验所得qe值11.86mg/g非常接近，SARM吸附Cr（Ⅵ）的准二级动力学模型拟合方程的R2为0.9999，qe理论计算值为11.96mg/g和实验所得qe值11.92mg/g也非常接近，说明CARM和STAB对Cr（Ⅵ）的吸附过程符合准二级动力学模型，两个吸附过程都是物理吸附和化学吸附共同作用的结果。（9）吸附热力学中计算出了CARM和STAB对Cr（Ⅵ）的吸附过程中吉布斯自由能△G0、吸附焓变值△H0和熵变值△S0，其中两个过程的△G0均小于0说明吸附可以自发进行；△H0分别为-21.75kJ/mol和^-16.48kJ/mol说明两个吸附都是属于放热反应，温度升高不利于吸附；△S0为-66.86J·mol^-1·K^-1和-48.76J·mol^-1·K^-1说明两个吸附反应都是总熵减小的过程。更多还原

【Abstract】 In this arcital, the Bayer red mud and sintering red mud were used as the experimental materials. Thedetermination of the metal element content in the two kinds of red mud are got using AES,AAS andtitration analysis method, characterized analysis to determine the internal structure using infraredspectroscopy, differential thermal analyzer and X-ray diffraction. Then we use CTAB and STAB to modifythe Sintering red mud which was neutralized by hydrochloric acid and the obtained adsorbents were namedas CARM and SARM.Then we use CARM and SARM to study the adsorption capability of Cr（Ⅵ） insolution, during this process, we investigate the optimum adsorption conditions and discuss the mechanismof adsorption in reference of the adsorption isotherms, adsorption kinetics and adsorption thermodynamics.The main research contents in this paper are as follows:（1） Treat the red mud samples by acid digestion after their pretreatment,then use ICP-AES qualitativeanalysis to make a full scanning of the digestion solution so as to determine whether a certain metalelement exist and its content by ICP-AES quantitative analysis, while Fe, Al, Ca, Mg, K and Na by AASwith titrimetry analysis method for comparison and standard recovery test for verification. We finally theaccurate contents of47kinds of metal elements of sintering red mud contains and46kinds of metalelements of the Bayer red mud in this study. In addition,silicon content in red mud is determined bygravimetric method.（2） According to the determination result and application of building materials as well as metalelements extracting statuses of red mud, we made a analysis of the potential utilization of the metalelements in red mud and it proves that many metal elements of the red have their certain amounts of extractvalue, but limited to the industrialized technical factors, there is little economic value. In short, there arevarious comprehensive utilization methods of red mud,but the current application ways and extractingtechnology still need to be improved.（3） The characterization of red mud was made by infrared spectroscopy, differential thermal analyzer andX-ray diffraction. It was found that the red mud contains about8%of the hydroxyl water which exists asthe form of crystal water, combined with the shape of the water and structural water present in the complexmineral structure of the red mud. Red mud contains the minerals which are rich in CaCO3, and these minerals break down at580℃⁶80℃and release CO2,which leads Bayer red mud about5%weight lossand sintering red mud about10%weight loss. The mineral composition of red mud are rathercomplicated,including mainly calcite, declaim silicate, perovskite, calcium nepheline, water calciumgarnet,etc.（4） The surface of Sintering red mud is rich in exchangeable cations, so the surface of Sintering redmud was combined with the cationic group C16H33（CH3）3N+from the cationic surfactant CTAB and thecationic group C18H37（CH3）3N+from the cationic surfactant STAB to the sintering of red mud surface byion exchange principle, this,as a result, achieves the purpose of expanding the aperture of the sintering redmud and increasing its surface area. CTAB and STAB are best modified when their concentration aredetermined as0.5%and0.6%. From the infrared spectra of CARM and Warmth peaks of CH3-（N+） and-CH2-were found and it is proved the modification was successful.（5） We got the best adsorption conditions of Cr（Ⅵ） by CARM and SARM through adsorptionexperimental conditions selection. With CARM for example, the highest adsorption rate can be obtainedwhen the initial acid condition is pH2; Adsorption equilibrium time is30minutes; the best adsorbentdosage is0.2g;Adsorption rate increases at lower temperature; with the same other conditions, adsorptioncapacity will increase with the concentration of Cr （Ⅵ）. All the mentioned conditions are same to theCARM except that the adsorption equilibrium time is45minutes.（6） Under the optimal experimental conditions, Cr（Ⅵ） adsorption rate by CARM and SARM canreach over95%and97%when the initial concentration is100mg/L,while this value can be up to more than99%when the initial concentration of Cr（Ⅵ） is20mg/L. The maximum adsorption capacity of original redmud,CARM and SARM are4.658mg/g,22.03mg/g and25.16mg/g and it shows that red mud adsorptionquantity increases considerably after its modifition, while STAB better.（7） Adsorption isotherm was analyzed using Langmuir and Freundlich two adsorption isotherm modelanalysis, and the results show that the Langmuir isothermal adsorption model fitted qmaxvalue for theadsorption of Cr （Ⅵ） of CARM is22.20mg/g and it is very close to the experimental value of22.03mg/g,with linear relationship0.9997. Moreover, this value for SARM adsorption of Cr（Ⅵ） is25.21mg/g andvery close to its experimental value of25.16mg/g,too, with linear relationship value0.9990. In a word, it can be supposed that the adsorption processes of Cr（Ⅵ） of CARM and STAB from aqueous solution are inline with the Langmuir isotherm model based on single-molecule adsorption.（8） As for the analysis of adsorption kinetics,both of the pseudo first-order kinetics and dynamicsmodel of quasi two levels were discussed. The values of qefitted out from the pseudo-first order kineticwere0.2165mg/g and0.9531mg/g during the adsorption processes, with a vast deviation from theexperimental ones. However, for the adsorption of Cr （Ⅵ） by CARM,the value of R2in the quasi twolevels dynamic model fitting equation is0.9999, and theoretical calculation value of qeis11.87mg/g whichis very close to the experiment value of qe11.86mg/g. While for the adsorption of Cr （Ⅵ） by SARM，thevalue of R2in the quasi two level dynamic model fitting equation is also0.9999, and theoretical calculationvalue of qeis11.87mg/g which is very close to the experiment value of qe11.86mg/g,too. The resultsshow that, the adsorption processes of Cr （Ⅵ） by CARM and STAB meet quasi two level dynamic modelsand two adsorption processes is a joint action of both physical adsorption and chemical adsorption.（9） For adsorption thermodynamics, we calculated the Gibbs free energy△G0, adsorption enthalpyvalue△H0and entropy variable value△S0of CARM and STAB during the process of Cr（Ⅵ） adsorption.The△G0of the two processes are both less than zero and it can be determined the adsorption can bespontaneous. Delta△H0of two adsorption reaction are21.75kJ/mol and16.48kJ/mol accounting foradsorption reaction are-66.86J·mol^-1·K^-1and-48.76J·mol^-1·K^-1which prove that the two adsorptionreaction are both entropy reduction processes.更多还原