氮掺杂介孔炭凝胶的制备及其对工业废水中PFOS的吸附/脱附机理研究

As known, nitrogen-containing aromatic compounds can enhance the sorption of perfluorooctanesulphonate (PFOS), and carbon gel is an adsorbent with big surface area and large mesopore size and broad mesopore size distribution. Based on the above characteristics, we intend to prepare nitrogen-doped mesoporous carbon gel, which will be applied to the sorption of PFOS from wastewater. Firstly, nitrogen-doped mesoporous carbon gel are prepared using sol-gel method plus surfactant templating approach by adjusting the ratio of raw materials and aging parameters to increase its proportion of mesopore and surface properties. The raw materials contain resorcin, methanol, catalyzer and nitrogen-containing compounds (cetyl trimethyl ammonium bromide, tetraethylenepentamine and melamine). Secondly, the nitrogen-doped mesoporous carbon gel is used to sorb PFOS from wastewater. Sorbent type, structure, surface properties and dosages are the main factors to evaluate the sorption process by mesoporous carbon gel, and then to optimize the preparation process of nitrogen-doped mesoporous carbon gel vice versa. Finally, compared the kinetic and thermodynamic experiments of sorption/desorption of PFOS with the crystal chemical characteristics of nitrogen-doped mesoporous carbon gel, we will reveal the sorption/desorption mechanism of PFOS onto nitrogen-doped mesoporous carbon gel as well as the relationship between structure and sorption abilities. The deep studies of this research would provide theory foundation for its use in getting over the PFOS risks from industrial wastewater. Meanwhile, a new material, new technology and new method are supplied for the efficient removal of PFOS in the industrial wastewater.

本课题基于含氮芳香化合物对全氟辛烷磺酸（PFOS）的吸附增强作用，以及炭凝胶吸附材料比表面积大、介孔丰富、吸附速率快和再生容易的的特点，制备了氮掺杂介孔炭凝胶吸附材料用于废水中PFOS的吸附。本研究采用表面活性剂模板法+溶胶-凝胶法，通过调整原料配比（间苯二酚、甲醛、催化剂）及含氮化合物（十六烷基三甲基溴化铵、四乙烯五胺、三聚氰胺）用量等，考察对氮掺杂介孔炭凝胶的结构、表面化学性质的影响；其次研究氮掺杂介孔炭凝胶对废水中PFOS的吸附性能，重点考察吸附剂类型、结构、表面性质、用量等对废水中PFOS的去除效果，评价该工艺的可行性，并指导氮掺杂介孔炭凝胶的制备工艺优化；最后结合等温吸附实验，借助光谱、能谱等分析手段，揭示氮掺杂介孔炭凝胶吸附/脱附PFOS的机理及吸附构效关系。本课题的开展可为解决工业废水中难消除的PFOS隐提供理论基础，并为废水中PFOS的高效去除提供新材料、新技术和新方法。

基于含氮官能团对全氟辛烷磺酸基化合物（perfluorooctanesulphonate，PFOS）的吸附增强作用，以及炭凝胶吸附材料比表面积大、介孔丰富，具有吸附速率快和再生容易的特点，本课题采用表面活性剂模板法+溶胶-凝胶法，通过调整原料配比（间苯二酚、甲醛、催化剂）及含氮化合物（十六烷基三甲基溴化铵、四乙烯五胺、三聚氰胺）种类和用量等，制备了一系列氮掺杂介孔炭凝胶吸附材料，并研究了其对废水中PFOS的吸附/脱附机理。首先，在水:环己烷体积比为1:1的溶剂体系中，间苯二酚和碳酸钠的摩尔比（R/C）为1000:1，选择氮源为三聚氰胺且用量为0.05 g时所制备的氮掺杂介孔炭干凝胶（MCX1000-0.05）对PFOS的吸附效果是最佳。炭凝胶的用量、吸附时间、温度、溶液pH和离子强度对吸附容量均有一定影响。炭凝胶MCX1000和MCX1000-0.05对PFOS的吸附符合伪二级动力学模型（R2>0.99），吸附等温线可用Langmuir模型较好地拟合（R2>0.99）。其主要吸附机理是PFOS分子与吸附剂上的羟基、羧基、氨基等官能团之间存在静电作用、氢键作用以及范德华力作用；比表面积和介孔体积越大，吸附性能越强；且含氮官能团显著增强了其对污染物的吸附能力。低温有利于MCX1000对PFOS的吸附，最大吸附量可达185 mg/g；相反，高温有利于MCX1000-0.05对PFOS的吸附，最大吸附量高达232 mg/g。化学试剂（强酸、强碱、乙醇、丙酮）对吸附饱和后的炭凝胶的脱附效果均不理想，仍需继续寻找合适的脱附试剂或方法进行吸附剂的脱附再生研究。综合上述结果，本研究为解决工业废水中难消除的PFOS隐患提供了一定的理论基础，为工业废水中PFOS的高效吸附去除提供了新材料、新技术。