富含纳米气泡的粘土基生物吸附剂的制备及与水相中PFOS/PFOA的界面相互作用过程及机制

Sorption is an effective technology to remove perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) from aqueous solution. Hydrophobic partition into organic matters has been considered to be responsible for sorption of PFOS and PFOA on the surface of hydrophobic sorbents. However, the long C-F chain in PFOS and PFOA is not only hydrophobic but also oleophobic, which is inconsistent with the sorption mechanism as mentioned above. Moreover, the removal of the isomers of PFOS and PFOA is scarce. The typical clays (montmorillonite and sepiolite) and biopolymer (chitosan and zein) will be used to synthetise the biocomposites. At the same time, the third phase gas bubbles will be introduced at the solid-liquid interface by in-situ and ex-situ generating of nanobubbles to prepare the biocomposites full of nanobubbles as supersorbents for PFOS and PFOA. The influences of mineral structure, the ratio of clay and biopolymer, the synthesis method and environmental factors on the formation of nanobubbles at the interface and the sorption property of PFOS and PFOA will be studied. Molecular imprinting will be used to separate selectively the main isomers of PFOS and PFOA. The nanobubbles will be observed by Nanosight and atomic force microscope (AFM). X-ray absorption near edge structure (XANES) technique and the quantum chemical calculation will be applied to scrutinize the interface behavior and interaction process between sorbents and PFOS/PFOA. The relationship between sorbent structure, active sites and sorption property will be established.

吸附可有效去除水中全氟辛烷磺酸/羧酸盐（PFOS/PFOA），但其疏水分配至有机相的吸附机制与C-F链疏水疏油的特性相矛盾，且其同分异构体的污染治理技术几乎还是零报道。本研究拟选择典型粘土矿物和生物聚体，采用异位和原位纳米气泡生成法，在固液界面引入气相，调控界面气泡的大小及数量，制备富含纳米气泡的生物吸附剂，实现对水相中PFOS和PFOA的“超”吸附。考察矿物结构特征、原材料比例、环境因子等对界面纳米气泡赋存状态及对PFOS/PFOA吸附性能的影响；结合分子印迹技术实现对直链和主要支链异构体的选择性分离。除常规表征手段分析吸附前后材料的微结构变化外，采用纳米颗粒分析仪、原子力显微镜等技术观测体相和界面纳米气泡的赋存状态；运用量子化学方法计算X射线吸收近边结构理论光谱，从分子水平深入认识PFOS和PFOA与吸附剂界面间的相互作用过程及机制，建立吸附剂结构特征、活性位点与吸附性能之间的关系。

吸附技术在有效去除水相中污染物方面得到了广泛的应用。本项目制备了具有不同亲疏水性的功能材料，并针对性地去除典型污染物。我们发现采用不同尺寸的TiO2和低表面能物质全氟硅烷构造的超疏水性材料对PFOS的吸附效果不佳，但对水体中的油污染却表现了优异的快速去除性能；通过热解天然有机-无机杂化材料蟹壳碳制备所得的生物炭富含钙，因此其针对高、低浓度的抗生素类污染物金霉素表现出了特异性的去除效果，比如，对低浓度的金霉素主要通过吸附作用，而富钙生物炭在高浓度的金霉素中产生游离的钙离子，其与金霉素形成络合物，因此絮凝作用是去除高浓度CTC的主要机理。