聚吡咯负载活性炭除氟特性及机理研究

Fluoride contamination in groundwater was a serious threat to drinking water safety and health of human. The traditional fluoride adsorption method using activated carbon has lots of problems, such as low adsorption efficiency, poor electrical conductivity and difficult to regeneration. Therefore, how to improve the electrochemical stability of activated carbon materials, chemical activity of surface functional groups and adsorption capacity of fluoride ions is one of the important contents for the defluorination research. To clarify and reveal the migration and transformation mode of fluoride ions on the adsorbent interface and interior is the emergency scientific problems to develop the mechanism research on defluorination. This project intends to choose the polypyrrole with high electrical conductivity, electrochemical stability and numbers of reactive nitrogen groups to load and modify the activated carbon materials. To explore the controllable synthesis method for polypyrrole loaded activated carbon material to remove fluoride. To reveal the structure and physicochemical properties of the polypyrrole load activated carbon materials before and after defluorination process by using X-ray diffraction, ultraviolet Raman spectroscopy, elemental analysis and mass spectrometry coupled analysis technologies. On this basis, to clarify the fluoride adsorption mechanism from the composition of chemical bonds and functional groups, pore size and microcrystalline structure characteristics, coupling effects of mass transfer environment by using the combination methods of the kinetics of shaking table and rapid static column simulation experiments. A new approach for treatment of fluoride pollution in groundwater will be provided.

地下水氟污染严重威胁人类的饮水安全和身体健康，传统活性炭吸附除氟方法存在处理效率低、导电性差、难再生等问题。因此，如何提高活性炭材料的电化学稳定性、表面官能团的化学活性和氟离子的选择吸附性是活性炭除氟研究的重要内容之一，阐明和揭示氟离子在吸附剂界面和内部的迁移、转化模式是开展除氟机理研究亟需解决的关键科学问题。本项目拟选用具备高电导率、电化学稳定性和大量含氮活性基团的聚吡咯负载改性活性炭；探讨高效除氟聚吡咯负载活性炭材料的可控合成方法；利用X射线衍射、紫外拉曼光谱、元素分析和质谱耦合分析等技术，揭示聚吡咯负载活性炭材料除氟前后的结构组成和物化特性；在此基础上，采用摇床动力学试验和静态快速柱模拟试验相结合的方法，从聚吡咯负载活性炭的化学键和官能团构成、孔径和微晶结构特征及其与传质环境因子的耦合作用等方面，阐明其吸附除氟机理。研究成果可以为我国地下水氟污染的治理和修复提供一条新途径。

近年来，地下水氟污染已经逐渐成为世界性问题而引起广泛关注，氟中毒严重威胁人们的身体健康。长期摄入过量的氟化物对人体具有致畸、致癌和致突变等反应。本研究筛选制备了具备高除氟效果的聚吡咯负载活性炭吸附材料（PPy/AC），发现活性炭材料表面的含氮官能团同PPy形成共轭结构，加强了材料的除氟性能。PPy/AC材料除氟性能实验表明，PPy/AC在溶液pH介于2.0~10.0时都具有较好的除氟效果，共存离子对PPy/AC的除氟影响较小。当氟浓度小于31.7 mg/L时，温度对氟吸附量几乎没有影响。Langmuir吸附等温线拟合结果显示，PPy/AC对氟的最大吸附容量为17.153 mg/g。采用多手段联用分析技术探讨了PPy/AC材料的除氟机理。热力学计算说明PPy/AC吸附除氟过程可以自发进行，且为吸热过程；吸附过程的吸附控速步骤为表面扩散以及颗粒内扩散过程中的介孔扩散过程；吸附动力学、D-R吸附等温线拟合以及共存离子的研究结果表明，PPy/AC吸附除氟的过程是内界相关的特异性化学吸附过程，主要为氟离子与氯离子之间的离子交换作用，以及氟离子同活性炭表面羟基官能团的静电吸引过程；Cl/N+值的降低、FTIR曲线的振动以及体系混乱度的增加证明了离子交换在该化学吸附过程中起到主要作用；XPS结果计算得到聚吡咯在活性炭表面形成三层聚合结构。本研究所开发出的聚吡咯负载活性炭吸附材料由于其成本低、适应性强，除氟效率高，操作简便等优点可以被考虑应用于实际的氟污染地下水治理中。