共掺杂氧化石墨烯活化过硫酸盐降解水中防晒剂的研究

The occurrence of UV filters in water environments may pose a serious human and ecological health hazard. However, conventional processes in wastewater treatment plants are unable to effectively eliminate these emerging contaminants. Therefore, it is necessary to adopt appropriate advanced oxidation processes (AOPs) to remove them. Sulfate radical (SO4•−) based AOPs for environmental water remediation have recently become a hotspot, whereas the toxicity of the metal catalysts, for the activation persulfate to generate SO4•−, limited their applications. Employing metal-free nanocarbon materials as a catalyst, can completely prevent the potential toxic metal leaching and secondary contamination to water body. In particular, their catalytic activities can been further remarkably enhanced by heteroatoms doping. Graphene oxide (GO) contains a large number of oxygenic functional groups and thus is easier to be functionalized. Therefore in this study, firstly, carboxyl GO is chosen and co-doped with nitrogen, sulfur and phosphorous. From results of characterizations, the mechanisms of the enhancement in the GO catalytic performances are discussed. Secondly, the effects of various factors on the degradation of typical UV filters by persulfate are studied. Based on detected intermediates, the degradation mechanisms of the contaminants are proposed and justified by theoretical calculations of the frontier electron densities. Main research work in this paper will provide the scientific basis for green remediation of emerging contaminants in water.

水环境中防晒剂的污染可能对人体及生态健康造成潜在风险，但现有的城市污水处理厂处理工艺很难将其全部除去，因此需要采用高级氧化过程（AOPs）对其处理。而基于硫酸根自由基(SO4•−)的AOPs技术，目前正成为环境水体修复研究的热点。但是活化过硫酸盐产生SO4•−的金属催化剂的毒性问题，限制了其应用。而采用无金属的碳纳米材料作为催化剂，则可完全避免潜在的有毒金属浸出和对水体的二次污染。尤其是其催化活性可通过杂原子掺杂进一步提高。基于氧化石墨烯(GO)具有丰富的含氧官能团而更容易被改性，因此本研究首先以羧基化的GO为基础，制备氮、硫和磷原子共掺杂的GO催化剂，结合表征结果，研究共掺杂的GO催化性能提高的机理。其次，考察各种因素对降解典型防晒剂的影响，基于检测出的降解中间产物，研究其降解机理，并用计算的前线电子密度进行验证。本课题的研究将为水环境中新兴污染物的绿色修复提供依据和参考。

碳基材料是活化过硫酸盐的新兴催化剂，而非金属原子掺杂可进一步提高其活化性能。本项目中，创新性地对氧化石墨烯、还原氧化石墨烯、羧基化石墨烯等进行氮掺杂及氮硫共掺杂改性，得到了氮掺杂（rGO-N）及氮-硫共掺杂石墨烯（rGO-NS），并用于活化过硫酸盐(PMS)降解多种有机污染物（防晒剂BP-1和BP-4，以及化妆品、药品中常用防腐剂尼泊金甲酯等）。研究表明，与传统的氧化石墨烯（GO）及其氮掺杂或氮硫共掺杂材料（GO-N、GO-NS），及经典的金属催化剂（如Co3O4、Fe3O4）相比，rGO-N及rGO-NS对过硫酸盐有着卓越的活化效能。结合各种表征结果，以及自由基淬灭实验和电子顺磁共振试验表明，rGO-N及rGO-NS活化PMS主要遵循非自由基（单态氧1O2）路径，而不是过去认为的自由基活化路径，并且石墨氮和噻吩硫的掺杂对催化性能提升及其非自由活化路径有着重要的影响。此外，考察了各种反应因素的影响，包括催化剂用量、过硫酸盐浓度、反应温度、真实水体环境等。同时，根据测得的降解产物及前线轨道计算，提出了BP-1等可能的降解途径。最后，矿化和稳定性试验证实，共掺杂石墨烯可代替其它催化剂用于水环境修复。本研究对于新型非金属原子掺杂石墨烯材料的构建，及非自由基氧化去除防晒剂等新兴污染物开辟了新的思路。