凹凸棒三维网络制备及其对重金属离子和有机污染物的吸附性能研究

Attapulgite(ATP) is a kind of crystalloid hydrous magnesium-aluminum silicate mineral, having a special laminated chain structure with high specific surface area and ion exchange capacity which lead it to be applied as an excellent adsorption material. The nanometer sized ATP crystals present in the shape of needles, fibers or fibrous clusters. However, the rod-like ATP crystals usually pack together closely to form agglomerates, which reduces their adsorption capability due to the decrease of the effective contact areas of the crystals. .This proposal aims at preparing novel, nanoporous ATP-based 3D networks as efficient aborbent materials. To this end, we scheme to design and synthesize a series of bi- or trifunctional organic compounds or oligomers, which act as the spacer molecules to isolate the agglomerated ATP crystals and covalently react with the surface-silanol groups of ATP crystals to form 3D network structures. The effect of molecular length of various orgainc compounds on the specific surface area and pore size of the 3D networks will be thoroughly investgated by experimental research combined with computational simulation. Based on these works, the studies on adsorption performance of the 3D networks for heavy metal ions and organic pollutants in water are developed to reveal an insight into fundamental understanding of various influence factors including ion exchange capacity of the ATP crystals, chemical properties of the spacer molecules and 3D structures of the as-prepared networks. It is possible that the implementation of the proposed project will not only invent a kind of efficient adsorption material with high adsorption performance, but also open a new way for value-increment of ATP resources.

凹凸棒粘土属层链状构造的含水铝镁硅酸盐，具有较高的离子交换容量，是优良的金属离子吸附材料，其纳米尺寸的晶体呈针状、纤维状集合体。但由于其纳米尺寸的棒晶高度团聚，影响了棒晶与金属离子的有效接触从而降低了吸附性能。本项目拟通过设计、合成一系列具有双官能团或三官能团的有机分子或低聚物作为间距分子，通过与凹凸棒棒晶表面的硅羟基进行化学反应使棒晶相互分离，制备以共价键修饰的、具有纳米孔径的凹凸棒三维网络结构。探讨不同有机分子的尺寸对凹凸棒三维网络结构的孔结构、比表面积的影响，在此基础之上开展凹凸棒三维网络结构对水相中的不同重金属离子及有机污染物的吸附性能研究，揭示凹凸棒晶体本身的离子交换容量、间距分子的化学性质以及三维网络的空间结构对其吸附性能产生的影响以及何种影响。项目的实施不但有可能得到对重金属离子、有机污染物具有高吸附容量的凹凸棒三维网络吸附材料，而且为凹凸棒粘土资源的高值化利用开辟新的途径。

凹凸棒粘土属层链状构造的含水铝镁硅酸盐，具有较高的离子交换容量，是优良的吸附材料，其纳米尺寸的晶体呈针状、纤维状集合体。但由于其纳米尺寸的棒晶高度团聚，影响了棒晶与金属离子或有机污染物的有效接触从而降低了吸附性能。本项目利用一系列具有双官能团的有机分子或低聚物（PAA、PAM、PEG、吡啶等）作为间距分子，通过与凹凸棒棒晶表面的硅羟基进行化学反应使棒晶相互分离，制备以共价键修饰的、具有纳米孔径的凹凸棒三维网络多孔吸附材料。相对于ATP原土，ATP基多孔材料对油/有机物的吸附能力有了大幅度提高。通过聚二甲基硅氧烷气相沉积法（CVD）、硅烷偶联剂改性等方法对多孔材料进行疏水改性，应用于模拟废水的选择性分离。研究了三维网络中有机物吸附量和网络结构的孔体积、比表面积等参数，以及间距分子尺寸、化学结构对凹凸棒三维网络结构的影响。由聚乙二醇PEG制得的多孔材料，其比表面积、孔体积、平均孔径均大于聚丙烯酸PAA制得的多孔材料。以CaCO3、NaCl等无机盐为模板剂与凹凸棒高温烧结后酸溶，制得了海绵状的吸附材料，其表面润湿性可调控，对重金属离子具有良好的吸附性能。利用吡啶和过氧化二苯甲酰改性凹凸棒处理亚甲基蓝废水，在实验条件范围内，凹凸棒吸附材料对亚甲基蓝的吸附符合准二级动力学方程，并且用Langmuir等温方程能更好的描述吸附过程。