碳纳米纤维基材料的制备及其催化生成硫酸根自由基降解污染物研究

Due to the possession of unpaired electrons, free radicals are highly active in oxidization of various contaminants and pollutants, which consequently results in the onset of advanced oxidation processes. Degradation of organic contaminants with sulfate radicals generated by heterogeneous catalysis has become a hot spot in this research field, which is reflected in the increasing numbers of publications in peer-reviewed journals. After heterogeneous catalysis processes, toxic transition metals always dissolve to solution and it is also difficult to recover the nano size catalysts. In order to resolve these problems, synthesis of heterogeneous catalysts based on carbon nanofibers (CNFs), which have a relatively high specific surface and significantly large dimensions, is proposed in this project. The composite nanofibers would be manufactured by electrospinning the solution of polyacrylonitrile and transition metal salts and the composite CNFs heterogeneous catalysts can be obtained by the following stabilization and carbonization. The heterogeneous catalysts might also be prepared by wetness impregnation-thermal decomposition technique or immobilizing transition metal ions on the treated carbon nanofibers with ion-exchange method. The catalytic activities of these catalysts will be researched through comparing the degradation rate of organic contaminants with sulfate radicals generated by heterogeneous catalysis of peroxymonosulfate or persulfate. The leaching of transition metal ions from the catalysts will be tested and the recycling catalysis runs would be conducted. The performance of these heterogeneous catalysts will be evaluated and the catalysis mechanism might be proposed based on the above results and the characterization of the catalyst microstructures. The degradation mechanism of organic contaminants by sulfate radicals would be investigated by quenching studies for radical identification and analysis of the degradation products. This kind of advanced oxidation processes based on sulfate radicals might be impelled by synthesis of these heterogeneous catalysts and related mechanism researches.

非均相催化过硫酸盐产生硫酸根自由基降解有机污染物是高级氧化技术的研究热点之一。为了解决或改善非均相催化剂在反应中，金属离子溶出或不易回收等问题，提出了制备以具有超大长径比和比表面积的碳纳米纤维为载体的催化剂。 本课题主要拟用静电纺丝技术将金属盐与聚合物溶液混纺制备复合纳米纤维，并对其进行热稳定化和碳化处理，得到复合碳纳米纤维催化剂。本课题还拟采用常用的湿式浸渍-高温煅烧法和离子交换法，以碳纳米纤维为载体，制备其他两种非均相催化材料。以苯酚为目标污染物，对这三种催化剂活化过硫酸盐降解有机物的性能，以及催化剂的稳定性进行比较。结合材料表征结果，研究碳纳米纤维基材料的催化机理，并提出硫酸根自由基降解机理。本课题希望通过此类高催化活性、高稳定性和易于回收非均相催化剂的研制以及相关机理研究，促进硫酸根自由基类高级氧化剂技术的发展。

硫酸根自由基氧化电位高，能降解多数有机污染物，在较宽的pH范围内都具有较高的活性，其氧化产物对环境也比较友好，越来越多的研究关注其在高级氧化技术中的应用。项目组成员系统总结了硫酸根自由基在污染物控制技术中的应用现状；在比较了不同钴氧化物活化过一硫酸盐降解污染物特性的基础上，合成了系列负载型非均相催化剂（采用共纺法和湿式浸渍法制备了不同的碳纳米纤维基催化剂，以及用湿式浸渍法制备了凹凸棒石黏土基催化剂），并研究了其活化过一硫酸降解污染物的效率；进一步开发了高效且环境友好的均相硫酸根自由基降解体系，例如碱性活化过一硫酸和亚铁离子活化过二硫酸钠体系；同时，项目组成员积极探索新型功能化碳纳米材料及其使用领域，例如首次将具有大比表面积、强化学稳定性和吸附萃取能力的石墨烯通过化学键合的方法固定在坚固耐用的羟基化的钛合金丝上，并将该材料应用于固相微萃取技术中高效萃取不同水样中十五种邻苯二甲酸酯，并分析了北京市不同湖泊样品中邻苯二甲酸酯的浓度分布特征，该工作获得中国分析测试协会科学技术奖一等奖。在该项目资助下，截止2017年1月，已发表论文6篇，投稿1篇；申请发明专利3项；发表会议论文4篇，项目组成员参加国际和国内学术交流活动达到9人次，其中在中国化学会第二十九届学术年会上获得优秀墙报奖；有1名博士和5名硕士在项目资助下进行相关研究，3名硕士已经顺利毕业，其中一名学生获得国家奖学金和优秀毕业生。