【作者】 赵迎新；

【导师】 冯传平；

【作者基本信息】 中国地质大学（北京） ， 环境科学与工程， 2013， 博士

【摘要】 水体中Cr(VI)污染主要来源于制革、电镀、冶金等工业废水的不合理排放。过量的Cr(VI)对生物体有致癌性和致畸性，严重威胁着人类的健康。目前运用于Cr(VI)去除的方法有很多，如化学沉淀、离子交换、膜技术、以及吸附法等。其中，吸附法凭借其操作简单、实用高效、可重复利用性等优点成为应用最广泛的除Cr(VI)技术。在众多的吸附材料中，粘土矿物类吸附剂是备受关注的一种。在本研究中，具备多孔性、渗透性和吸附性的日本火山灰堆积物—赤玉土，首次被用于水溶液中Cr(VI)的吸附。实验采用序批式方法，探讨了吸附时间、溶液初始pH值、吸附剂投加量等对天然赤玉土吸附水溶液中Cr(VI)的影响。结果显示，天然赤玉土对Cr(VI)的吸附可在180min内达到平衡，吸附的最佳pH条件为2。当溶液初始Cr(VI)浓度为50.0mg/L，吸附剂投加量为5g/L时，实验最大Cr(VI)吸附量为4.29mg/g。天然赤玉土对Cr(VI)的吸附数据符合Freundlich等温线模型和伪二级动力学模型，吸附机理主要是化学吸附过程。与其他天然粘土矿物对比表明，天然赤玉土吸附Cr(VI)的开发潜力较大。为了提高Cr(VI)吸附量并拓宽应用范围，本研究采用HCl作为改性剂制得HCl改性赤玉土（CMAC）。实验通过研究主要因素如pH、共存离子等对吸附效果的影响评价了CMAC的Cr(VI)吸附性能。CMAC的pH适用范围可扩大至2~11，Cr(VI)的实验最大吸附量可达到7.47mg/g。吸附过程符合伪二级动力学方程，说明吸附反应是化学过程。吸附等温线拟合结果显示，CMAC对Cr(VI)的吸附与Langmuir模型拟合度较差，与Freundlich模型和Dubinin-Radushkevich模型更吻合，说明吸附发生在异相介质表面。CMAC在多种离子共存的状态下，仍具有较高的Cr(VI)离子选择性。无机盐作为改性剂也被应用于天然赤玉土的改性。在5种无机盐离子Al3+、Fe3+、Ca2+、Mg2+、和Mn2+中，Fe3+的改性效果最佳。在Fe3+改性赤玉土（FeAC）的研究中，析因分析法用于吸附影响因素贡献效率的评价和实验过程的优化。结果分析得出，对于Cr(VI)吸附量，溶液初始Cr(VI)浓度是最重要的因素，其次依次为吸附剂投加量和吸附时间，溶液初始pH对吸附结果不产生影响。在初始Cr(VI)浓度为400.0mg/L，吸附剂投加量为1g/L时，Cr(VI)吸附量可达到22.74mg/g。实验数据符合伪二级动力学方程和Freundlich等温线模型。热力学研究表明，FeAC对水溶液中Cr(VI)的吸附是易发、自动的吸热反应。在相同条件下，将天然赤玉土、CMAC、FeAC分别用于实际含Cr(VI)制革废水的处理发现，三者对Cr(VI)的去除率分别为23.1%，38.9%，和94.5%，FeAC的吸附效果最佳。总之，天然赤玉土、CMAC、FeAC均对溶液中Cr(VI)有良好的吸附性能，其中FeAC具有改性方法简单、成本低廉、效率高、适应性强等多重优点，在处理实际工业废水的应用中效果最佳。更多还原

【Abstract】 In aqueous systems, chromium（VI） is usually discharged from the industries ofleather tanning, electroplating, production of steel and alloys, etc. Exceed Cr（VI） iscarcinogenic and mutagenic to living organisms and seriously threaten human health.Various technologies such as chemical precipitation, ion exchange, membranetechnologies, adsorption, etc are available for Cr （VI） removal. Nowadays, adsorptionhas become the most versatile and widely used technology for its operation simplicity,availability, and recyclability. Among numerous adosrbents, mineral materials arecompetitive and concerned by public.In this study, a volcanic clay originated in Japan-Akadama clay, with goodproperties of porosity, permeability, and affinity, was used for Cr （VI） removal fromaqueous solution. Batch experiments were carried out to investigate the effect ofcontact time, initial pH, and adsorbent dose on Cr （VI） adsorption. Results showedthat Cr （VI） adsorption on natural Akadama clay reached equilibrium in180min. Theoptimum pH was2. The maximum adsorption capacity was4.29mg g-1at an initialconcentration of50.0mg L-1and adsorbent dosage of5g L-1. The equilibrium datafitted Freundlich isotherm better than Langmuir isotherm, and they were wellexplained by pseudo-second-order kinetic model. Adsorption mechanism analysisproved that electrostatic adsorption dominated the removal process. Results from thisstudy demonstrated that natural Akadama clay had the potential to be an efficientadsorbent for Cr （VI） removal compared to other natural mineral adsorbents.In order to improve the adsorption capacity of Cr （VI） and widen the adsorptionconditions, HCl-modified Akadama clay （CMAC） was developed as an adsorbent forthe treatment of Cr （VI） contaminated wastewater. The influence of pH, coexistingions etc. were evaluated by batch experiments. Wide pH ranges of2¹1were foundto be suitable for Cr （VI） adsorption onto CMAC. The maximum experimentaladsorption capacity of7.47mg g-1was obtained. The kinetic data fittedpseudo-second-order model better than pseudo-first-order model, indicating the Cr（VI）adsorption was mainly a chemical process. The Cr （VI） adsorption process well fittedthe Freundlich isotherm model and Dubinin-Radushkevich isotherm model ratherthan the Langmuir isotherm model, revealing that heterogeneous adsorption occurred onto CMAC. CMAC had a high selectivity for Cr （VI） ions in presence of coexistingions.Inorganic salts were also used to modify the original Akadama clay. Among Al3+,Fe³⁺, Ca²⁺, Mg²⁺, and Mn²⁺, Fe³⁺performed the best modification effect on Akadamaclay, and the adsorption capacity of Cr （VI） onto Fe-modified Akadama clay （FMAC）was greatly enhanced. A factorial design methodology was applied to evaluate theimportance of parameters and to optimize the adsorption process. Results revealedthat initial concentration is most important for the adsorption capacity, followed byadsorbent dose, and contact time, but pH of the solution had no effect on theadsorption of Cr （VI）. The maximum experimental adsorption capacity of Cr （VI）onto FMAC has been found to be22.74mg g-1at a dose of1.0g L-1with initial Cr（VI） concentration of400.0mg L-1. The experimental data was found to followpseudo-second order model and Freundlich isotherm model. Thermodynamic studiesindicated that the adsorption reaction was spontaneous and endothermic in nature.Under the same conditons, natural Akadama clay, CMAC, and FeAC wereapplied to treat Cr（VI） containing waster discharged from leather tannery. Resultsrevealed that the Cr（VI） removal efficiencies were23.1%,38.9%, and94.5%,respectively. FeAC had the optimum adsorption efficiency.In conclusion, natural Akadama clay, CMAC, and FMAC could be effectivelyused as adsorbents for Cr （VI） removal from wastewater. Among them, FMAC,presenting the best performance based on its simple operation, low cost, wide pHconditions, and high adsorption capacity, could be considered in practical application.更多还原