天然小分子有机酸和吲哚类物质诱导聚氯乙烯微塑料光还原脱氯的研究

Microplastics have raised wide concerns on their environmental transformation and behavior due to their increasing ecological risk. Polyvinyl chloride (PVC) is one of the largest productions, and its residual has become one major component of microplastics in the environments. Photochemical dechlorination in air is a well recognized ageing and degradation route for PVC polymers. However, limited information is available on the photochemical transformation process of PVC in aqueous systems. Low-molecular-weight organic acids (LMWOA, e.g., formic and oxalic acid) and indole/indole derivatives, widely distributed in natural waters, can be photolyzed into reductive carbon dioxide anion radical and hydrated electron, respectively, which exhibit great potential to accomplish photo-reductive dechlorination and interfacial erosion of PVC microplastics, thus accelerating the ageing and degradation procedure. In the present project, comprehensive investigation will be conducted for the photochemical degradation of PVC microplastics in the presence of LMWOA or indole/indole derivatives. This project aims to discover the relationship between dechlorination results and different LMWOA or indole/indole derivatives; to clarify the photochemical degradation and interfacial erosion process of PVC microplastics in the presence of LMWOA or indole/indole derivatives via multiple in situ characterization techniques; to reveal the effect of water chemistry on dechlorination by mediating water quality factors; to assess the sorption capacity of pristine and aged PVC microplastics for polar and nonpolar organic contaminants.

微塑料引发的生态风险日益增加，其环境转化和环境行为备受关注。聚氯乙烯（PVC）是目前产量最大的塑料之一，也是环境中常见微塑料的重要组分。PVC在空气中主要通过光化学脱氯过程发生老化降解，但在天然水体中的光化学过程尚不明确。天然水体中广泛存在着小分子有机酸和吲哚类物质，它们分别可在光照下产生强还原性的二氧化碳阴离子自由基和水合电子，极有可能引起PVC微塑料的光还原脱氯和界面侵蚀，进而加速其老化降解进程。基于此，本项目拟系统研究小分子有机酸和吲哚类物质存在下PVC微塑料在水溶液中的光化学降解过程，揭示不同小分子有机酸和吲哚类物质对PVC微塑料脱氯的作用规律；通过多种在线监测光谱技术，原位呈现小分子有机酸和吲哚类物质对PVC微塑料的脱氯机制和界面侵蚀过程；阐明环境因子对还原脱氯的复合影响；评估光解前后PVC微塑料对极性和非极性有机污染物的吸附载带能力。

实施期间，紧密围绕项目研究目标和任务，在（1）小分子有机酸和吲哚类物质诱导PVC微塑料光解脱氯的机理；（2)建立小分子有机酸或吲哚类物质与PVC微塑料的界面反应过程原位光谱监测技术；（3)揭示小分子有机酸和吲哚类物质对聚氯乙烯微塑料光解老化环境行为的影响。. 项目完成了考核指标主要包括：（1）阐明了微塑料尺寸、小分子有机酸/吲哚类物质结构、以及水质因子对小分子有机酸和吲哚类物质诱导PVC微塑料光解脱氯过程影响以及内在关联性；（2）建立了聚氯乙烯微塑料光解老化过程原位单颗粒红外和拉曼光谱表征技术，并探明了微塑料界面反应过程；（3）揭示了聚氯乙烯微塑料光老化行为对其环境行为的影响。综上所述，理论成果方面：阐明了小分子有机酸及其铁基络合物光生二氧化碳阴离子自由基诱导PVC微塑料光还原脱氯的机理及所发生的界面过程；阐明了吲哚及其衍生物光生水合电子诱导PVC微塑料光还原脱氯的机理及所发生的界面过程。. 目前，以第一/通讯作者共发表论文13篇，其中，SCI论文7篇，中文核心6篇。包括Water Research（3篇）、Chemical Engineering Journal（1篇）、Chemosphere（2篇）、Journal of Environmental Sciences（1篇）、环境化学（6篇）；授权国家发明专利1项，实用新型专利1项。培养博士生3名，硕士生3名。