水环境中氧化石墨烯的转化和降解及其对有机污染物迁移归趋的影响

Upon exposure in aquatic environment, graphene oxide (GO) could be suspended and transported in water columns for some time, where transformation and degradation processes mediated by chemicals and sunlight would become important. And the surface properties and dispersion/composition of GO are altered during transformation and degradation, and will directly affect the fates and adsorption behavior with organic pollutants of GO. Therefore, the research of the transformation and degradation processes of GO in the environment is the key link for the determination of the environmental capacity and for the evaluation of the life cycle of GO sheets in the environment. This work is proposed to systematically study the microscopic morphology, surface properties and aggregation properties of GO during transformation and degradation in aqueous environment, under the influence of oxidizing/reducing substances and light, and the mechanisms of transformation and degradation of GO will be investigated. Additionally, the effect of coexisting cations and dissolved organic matter (DOM) to transformation and degradation of GO will also be studied. Hydrophobic organics and antibiotics will be used as model compounds to investigate the effect of transformation and degradation of GO on adsorption behavior, and the adsorption mechanism between GO and organic pollutants. This work will establish a fundamental and useful database for environmental behavior prediction and risk assessment of GO and organic pollutants.

氧化石墨烯（GO）进入水体环境中，能够在水体中稳定悬浮并迁移一定的时间，在化学物质及光照的影响下，GO会发生转化和降解，且其聚合状态及表面性质也会发生相应的变化，这些变化将直接影响GO的环境归趋以及GO与有机污染物之间的相互作用，对该过程的研究是确定其环境效应，并在此基础上进行生命周期评价的重要环节。本研究拟针对氧化/还原性物质、光照等环境条件作用下，悬浮态GO在转化和降解过程中的微观形态、表面性质和聚合状态等进行综合研究，分析转化和降解机理；同时，考察水体中共存阳离子和溶解有机质（DOM）对GO转化和降解行为的影响机制；在此基础上，以憎水性污染物和抗生素作为模型化合物，考察GO的转化和降解对有机污染物吸附行为的影响规律，阐明GO与有机污染物的吸附机理。本研究将为GO和有机污染物的环境行为预测和风险评估建立基础数据储备。

作为极具应用前景的碳纳米材料，石墨烯类纳米材料在环境、生物、医学和能源等领域得到越来越多的开发和应用。目前对于石墨烯类纳米材料的环境风险已经开展了很多研究，但是对于此材料在水环境中的转化过程及此转化过程对其吸附性能的影响了解甚少。为了揭示这一科学问题，本项目系统探索了氧化石墨烯（GO）在水环境中的转化过程和吸附性能变化。研究发现在水环境介质中还原剂或光照的作用下GO发生显著的还原并转化为还原态的氧化石墨烯。化学转化后的还原态氧化石墨烯（CGO）表面形成更多的褶皱，含氧官能团含量降低，表面更加疏水，且表面负电荷降低，导致其对抗生素类污染物吸附速率减慢同时吸附能力略有提高。而光转化后的还原态氧化石墨烯（PGO）表面形成褶皱并出现细小碎片，整体层数减少且形成更多的缺陷位点，含氧官能团（羟基和环氧基团）减少，导致其对多环芳烃类污染物的吸附速率降低同时吸附能力显著提高。溶解性有机质主要通过氢键、π-π作用和极性作用与GO发生交互作用，占据GO的可转化位点，并且造成光屏蔽作用，导致GO的转化被抑制。本项目揭示了GO的转化过程的性质变化和聚合状态变化规律，阐明了GO的化学转化和光转化机理以及转化对GO吸附特性的影响规律，研究结果为今后评估GO及其吸附的有机污染物的环境风险提供了基础数据。