【作者】 祝春水；

【导师】 龚文琪； 孙振亚；

【作者基本信息】 武汉理工大学 ， 环境工程， 2004， 硕士

【摘要】 铁的（氢）氧化物，是土壤、沉积物和水体的常见组分。特别是针铁矿（α—FeOOH）是分布最广的表生矿物，是红土型矿石中的主要矿物成分，含量≥15％，也是我国东海、长江口和黄河口海域的各种水合氧化物中的主要成分，且具有稳定的化学性质和较高的比表面积，吸附性能良好，对阴、阳离子、重金属离子及有机螯合剂在地表环境中的迁移和沉淀有重要影响，因而具有十分重要的环境学意义。利用这样一种来自于天然的，因而具有良好的环境属性的物质来处理重金属废水，具有其它许多材料所不具备的环境协调性等方面的优势。 本研究进行了利用天然生物矿化针铁矿处理含铬模拟废水以及大冶有色金属公司的实际废水实验，旨在研究该针铁矿对重金属的吸附固定能力及机理，考察其作为吸附材料在废水处理及原位土壤修复中的可行性。 在本实验得出的最优条件下，吸附Cr₂O_<sup>2-与CrO₄^2-模拟废水的介质pH值为7.00，吸附Cr³⁺的介质pH值为5.50；当Cr₂O₇^2-、CrO₄^2-和Cr³⁺的初始浓度为10mg／L时，其去除率分别达到89.33％、88.27％和98.26％。用吸附了铬离子的针铁矿进行的二次吸附实验（条件同前）去除率达到80％左右，表明该针铁矿可以重复利用。淡水介质中的解吸实验（条件同吸附实验，样品吸附时的初始浓度为20mg／L）发现，Cr³⁺的解吸率为0.318％，CrO₄^2-则为9.64％，表明针铁矿对重金属离子具有较强的固定能力。 矿化合成样品吸附比较研究表明，表面较高浓度的有机大分子修饰FeOOH对CrO₄^2-的吸附行为与纯FeOOH存在明显差异。说明环境中针铁矿矿物与重金属离子的界面作用受到多糖、蛋白质等有机物的显著影响，同时它们的微结构也起剑重要作用，而比表面积并不是矿物吸附性能的决定因素。 光电子能谱研究表明，吸附Cr³⁺后样品的XPS谱图中出现了比较弱的N1s峰，说明有少量NO₃^-参与离子交换反应。对该N1s峰进行的退卷积处理表明N在针铁矿上发生了还原反应。对吸附Cr³⁺后的样品进行的XPS测试发现，铬的化学状态除有Cr（Ⅲ）外，主要为Cr（Ⅵ）。表明Cr³⁺在针铁矿表面发生了氧化反应。NO₃^-在针铁矿表面的还原作用有可能促进了Cr³⁺氧化为Cr（Ⅵ）。吸附Cr₂O₇^2-样品的XPS测试，则发现铬的化学状态除Cr（Ⅵ）外还有Cr（Ⅲ）出现，说明在吸附过程中Cr（Ⅵ）发生了还原反应。 SEM研究表明，针铁矿的微形貌及其中的粘土成分对铬离子的吸附都会有影响。草莓状颗粒上α-FeOOH含量较高，6价铬吸附量也较大，说明α-FeOOH对6价铬有较强的吸附能力；粘土含量较高的小颗粒则对Cr³⁺吸附能力较强。TEM／EDX、SEM／EDX及XPS分析发现铬的吸附存在不均匀性。更多还原

【Abstract】 Iron (oxy)hydroxide is a common consitutent of soils, sediments, and aquifers. As a iron (oxy)hydroxide, goethite (-FeOOH) is the most abundant mineral in the surface environment which accounts for 15% of weight in laterite. Goethite is also abundant in Dong hai, the estuaries of Yangtse River and Yellow river. Owing to its stable property, high surface areas and high reactivity, goethite has good performance as adsorbent and so has prominent effects on the transportation, transformation, and precipitation for a large number of cations, anions, metal ions, and organic chelates in subsurface environment. So, It has many advantages such as good and inimitable compatibility as a material for the treatment of heav-metal-containing waste water.In this research sorption and de-sorption studies were conducted to investigate the adsorption and binding efficiency for the chromium-containing model solution and factual waste water with the biomineralized goethite. The aim of this study was to probe the feasibility with it as sorbent material in enigeered system in plant and in situ environmental remediation.At the optimized conditions, the medium pH is 7.00 for CrO42- and Cr2O72-and 5.50 for Cr3+. When the initial concentration of chromium is 10 mg/L the removal ratio is 89.33%, 88.27%, and 98.26% respectively. Re-adsorption under the conditions ibidem got the removal ratio 80% indicated that the material can be utilized for several times. 0.318% and 9.64% desorption for Cr3+ and CrO42- were found with the specimens sorbed at the initial concention of 20mg/L under the condition same with adsorption showed a good binding ability of goethite for chromium.Comparison study of chromium adsorption with natural goethite and specimen biomineralized in systems with macromolecule organic substances found distinct difference in their behavior. So, it is concluded that the interface interaction between goethite and heavy metal ions was notably affected byorganic materials such as polysaccharide, protein and its microstructure also plays important role in it and the specific surface area isn’t the determinant factor.X-ray photoelectron spectroscopy (XPS) study of the specimem adsorbed with Cr3+ showing a weak Nls spectrum indicated the involving of NO3 in the sorption. The deconvolution of the Nls showed the deoxidization of NO3-. Apart of it, XPS analysis also found Cr (VI) chemical state besides Cr(III) which was the indication of the oxidation of. The deoxidization of NOs" may promote the oxidation of Cr (III). We also found Cr (III) in the XPS spectrum of the specimem adsorbed with C^O?2’ besides Cr (VI). This is the evidence of the deoxidization of Cr2O72-.Scanning electron microscope (SEM) study showed that the micropattern of goethite and clays intermingled in the specimem also had distinct effects on the sorption of chromium. High content of -FeOOH on strawberry-like particles corresponding to high content of Cr (VI) demonstrated the strong binding ability of goethite for Cr (VI). However, the binding ability of goethite for Cr(III) is weaker than clay containing A^Os in the form of kaolin. TEM/EDX, SEM/EDX and XPS studies found the adsorption of Cr(III) on goethite non-homogeneously.更多还原