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全氟和多氟化合物(PFASs)在过去几十年里被广泛用于含氟聚合物生产过程中的添加剂、疏水疏油剂以及泡沫灭火剂中的补充组分等。这类物质在环境中非常稳定,具有环境持久性和生物累积性,对生物体带来潜在危害。在这些物质中,全氟辛酸(PFOA),全氟辛烷磺酸(PFOS)和相关衍生物在全世界范围引起了极大的关注,并受到多个国家、地区机构以及组织的监管。因此,如何有效移除该类型物质成了近年来大家关注的热点。目前,高效吸附是应对此类物质污染问题最有效的方法之一,已有的吸附剂类型包括多孔无机材料、有机框架材料、多孔高分子材料等。这些材料或是通过尺寸作用,或是通过氢键作用,亦或是通过正负电荷作用来实现吸附。然而,该类吸附方式在实际应用时仍有许多问题需要解决。例如:(1)在自然环境中(湖水、海水等)还存在浓度数千倍于PFOA、PFOS的背景离子,它们也会被非选择性的吸附剂吸收,大大降低了对于含氟小分子的吸附效率;(2)由于同种电荷的排斥作用,基于电荷作用的吸附材料难以吸附不同电荷的含氟小分子。因此,开发出对PFASs呈现高选择性和高亲和力的吸附剂材料仍然是一项挑战。
复旦大学陈茂课题组长期致力于光控的可控/活性自由基聚合(photo-CRP)研究,尤其在光催化含氟单体可控聚合领域取得了一系列研究进展[1-4]。去年,他们在采用“引发剂原位异化”策略制备超高分子量含氟聚合物的过程中,发现超高分子量含氟纳米颗粒对含氟小分子具有高选择性的吸附性能[1]。因而,他们设想制备含氟小球吸附PFOA、PFOS等物质。考虑到纳米颗粒在使用中分离、回收的成本较高,他们进一步使用无金属的两步串联光控自由基聚合方法开发出了一种多氟化纳米粒子嵌入的水凝胶(图1),利用高性能且易于获得的聚合物材料实现了对PFASs的循环吸附[5]。共价交联的聚合物网络提供了一种可拉伸至其原始尺寸数倍的多分散水凝胶,从而促进了该材料在应用过程中的快速分离、再生和循环利用。在该合成过程中,以水和少量乙醇为溶剂、可见光为能源,所有单体均完全转化。多氟化的纳米颗粒和PFASs之间基于氟-氟作用的高度选择性识别使吸附过程受pH水平和背景离子的影响较小,从而将可吸附PFASs的类型扩展到中性、阴离子、阳离子和两性离子物种。该类吸附剂在不同环境条件下均表现出高吸附性能,并且对高浓度至环境相关浓度(10 mg/L至1 μg/L)的PFASs均展现出出色的去除效率(图2)。这一研究成果为PFASs的污染治理提供了新策略。
图 1 (a)两步串联photo-CRP过程的合成路线;(b)室温下水膨胀纳米氟核水凝胶(FCH)材料的应力-应变曲线;(c)拉伸性能,包括拉伸强度、断裂伸长率和杨氏模量;(d)拉伸多氟化钠米粒子嵌入的水凝胶(FCH2)的光学图像[5]
Figure 1. (a) Synthetic route of the two-step tandem photo-CRP process; (b) Stress-strain curves of the water-swollen FCH materials measured at room temperature; (c) Tensile properties including tensile strength, elongation at break and Young’s modulus; (d) Optical images of stretching FCH2[5]
图 2 用FCH2去除水溶液中的PFASs:(a)不同条件下从水溶液中以及正癸酸(DA)和无机盐离子IOSs(包括MgSO4,KNO3和NaCl)中去除PFOA;(b)不同浓度PFOA条件下,用FCH2和聚丙烯酰胺水凝胶(PAAH)去除PFOA(#1表示ρ(PFOA)=1 μg/L,ρ(DA)=20 mg/L,ρ(IOSs)=100 mg/L);(c)FCH2对不同PFASs的去除[5]
Figure 2. Removal of PFASs from aqueous solutions with FCH2: (a) Removal of PFOA from aqueous solutions at different conditions(DA is decanoic acid.IOSs is inorganic salts,including MgSO4,KNO3 and NaCl ); (b) Removal of PFOA with FCH2 and poly(acrylamide) hydrogel (PAAH) at diffferent concentrations of PFOA(#1 represents ρ(PFOA)=1 μg/L,ρ(DA)=20 mg/L,ρ(IOSs)=100 mg/L); (c) Removal of different PFASs with FCH2[5]
串联光照可控自由基聚合制备纳米氟核水凝胶:助力含氟小分子的水相分离
Fluorous-Core Nanoparticle-Embedded Hydrogel Synthesized via Tandem Photo-Controlled Radical Polymerization: Facilitating the Separation of Perfluorinated Alkyl Substances from Water
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摘要: 全氟和多氟化合物,特别是全氟辛酸(PFOA)和全氟辛烷磺酸(PFOS)对多个国家和地区的水资源造成了污染。目前这类有机污染物处理技术在成本和效率方面存在的局限性,促使人们开发更高选择性和高亲和力的吸附剂。近期,复旦大学陈茂研究员团队报道了一种通过可见光催化的无金属串联光控自由基聚合得到的多氟纳米颗粒镶嵌的水凝胶吸附剂。这种吸附剂材料对于各种电性的全氟或多氟化小分子均表现出了优异的吸附性能,且在没有明显性能损耗的基础上可完成5次以上的吸附-解吸附循环。该方法为去除水中的PFOA、PFOS等全氟或多氟化小分子提供了新策略。Abstract: Per- and polyfluorinated alkyl substances (PFASs), notably perfluorooctanoic acid (PFOA), contaminate many ground and surface waters and are environmentally persistent. The cost and performance limitations of current PFAS removal technologies motivate efforts to develop adsorbents with high selectivity and affinity. Recently, Chen’s group at Fudan University reported a fluorous-core nanoparticle-embedded hydrogel (FCH) synthesized by the metal-free tandem photo-controlled radical polymerization under visible-light irradiation. This FCH material exhibits outstanding adsorption performance on PFASs with different electronic characteristics including neutral, anionic, cationic and zwitterionic ones. Moreover, the adsorption performance of the FCH material is barely affected even after more than five adsorption-desorption cycles. These results demonstrate the promise of the FCH material for treating PFAS-contaminated water.
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图 1 (a)两步串联photo-CRP过程的合成路线;(b)室温下水膨胀纳米氟核水凝胶(FCH)材料的应力-应变曲线;(c)拉伸性能,包括拉伸强度、断裂伸长率和杨氏模量;(d)拉伸多氟化钠米粒子嵌入的水凝胶(FCH2)的光学图像[5]
Figure 1. (a) Synthetic route of the two-step tandem photo-CRP process; (b) Stress-strain curves of the water-swollen FCH materials measured at room temperature; (c) Tensile properties including tensile strength, elongation at break and Young’s modulus; (d) Optical images of stretching FCH2[5]
图 2 用FCH2去除水溶液中的PFASs:(a)不同条件下从水溶液中以及正癸酸(DA)和无机盐离子IOSs(包括MgSO4,KNO3和NaCl)中去除PFOA;(b)不同浓度PFOA条件下,用FCH2和聚丙烯酰胺水凝胶(PAAH)去除PFOA(#1表示ρ(PFOA)=1 μg/L,ρ(DA)=20 mg/L,ρ(IOSs)=100 mg/L);(c)FCH2对不同PFASs的去除[5]
Figure 2. Removal of PFASs from aqueous solutions with FCH2: (a) Removal of PFOA from aqueous solutions at different conditions(DA is decanoic acid.IOSs is inorganic salts,including MgSO4,KNO3 and NaCl ); (b) Removal of PFOA with FCH2 and poly(acrylamide) hydrogel (PAAH) at diffferent concentrations of PFOA(#1 represents ρ(PFOA)=1 μg/L,ρ(DA)=20 mg/L,ρ(IOSs)=100 mg/L); (c) Removal of different PFASs with FCH2[5]
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