Wang Ri, Lin Zhi-Wei, Klemes Max J, Ateia Mohamed, Trang Brittany, Wang Jieyuan, Ching Casey, Helbling Damian E, Dichtel William R
School of Civil and Environmental Engineering, Cornell University, Ithaca, New York 14853, United States.
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
ACS Cent Sci. 2022 May 25;8(5):663-669. doi: 10.1021/acscentsci.2c00478. Epub 2022 May 16.
Cross-linked polymers containing β-cyclodextrin (β-CD) are promising adsorbents with demonstrated removal performances for per- and polyfluoroalkyl substances (PFASs) from contaminated water sources. Despite the promising performance of some β-CD-based adsorbents for PFAS removal, many of these materials are not amenable for rational performance improvement or addressing fundamental questions about the PFAS adsorption mechanisms. These ambiguities arise from the poorly defined structure of the cross-linked polymers, especially with respect to the random substitution patterns of the cyclodextrins as well as side reactions that modify the structures of some cross-linkers. Here, we report a new β-CD polymer platform in which styrene groups are covalently attached to β-CD to form a discrete monomer that is amenable to radical polymerization. This monomer was polymerized with styrene and methacrylate comonomers to provide three β-CD polymers with high specific surface areas and high isolated yields (all >93%). A β-CD polymer copolymerized with a methacrylate bearing a cationic functional group achieved nearly 100% removal for eight anionic PFASs (initial concentration of 1 μg/L for each compound) in nanopure water at an exceedingly low adsorbent loading of 1 mg L, as compared to previous cyclodextrin polymers that required loadings at least 1 order of magnitude higher to achieve an equivalent degree of PFAS removal. Furthermore, when the adsorbents were studied in a challenging salt matrix, we observed that long-chain PFAS adsorption was controlled by a complementary interplay of hydrophobic and electrostatic interactions, whereas short-chain PFASs primarily relied on electrostatic interactions. This approach demonstrates great promise for anionic PFAS removal, and we anticipate that new compositions will be tailored using the versatility of radical polymerization to simultaneously target PFASs and other classes of micropollutants in the future.
含有β-环糊精（β-CD）的交联聚合物是很有前景的吸附剂，已证明其对受污染水源中的全氟和多氟烷基物质（PFASs）具有去除性能。尽管一些基于β-CD的吸附剂在去除PFAS方面表现出良好的性能，但其中许多材料并不适合进行合理的性能改进，也无法解决关于PFAS吸附机制的基本问题。这些不明确性源于交联聚合物结构定义不明确，特别是环糊精的随机取代模式以及改变一些交联剂结构的副反应。在此，我们报告了一种新的β-CD聚合物平台，其中苯乙烯基团共价连接到β-CD上，形成一种适合自由基聚合的离散单体。该单体与苯乙烯和甲基丙烯酸酯共聚单体聚合，得到三种具有高比表面积和高分离产率（均>93%）的β-CD聚合物。与之前的环糊精聚合物相比，一种与带有阳离子官能团的甲基丙烯酸酯共聚的β-CD聚合物在极低的吸附剂负载量1 mg/L下，对纳米纯水中的八种阴离子PFAS（每种化合物的初始浓度为1 μg/L）实现了近100%的去除，而之前的环糊精聚合物需要至少高一个数量级的负载量才能达到同等程度的PFAS去除。此外，当在具有挑战性的盐基质中研究吸附剂时，我们观察到长链PFAS的吸附受疏水和静电相互作用的互补相互作用控制，而短链PFAS主要依赖静电相互作用。这种方法在去除阴离子PFAS方面显示出巨大的前景，我们预计未来将利用自由基聚合的多功能性来定制新的组合物，以同时针对PFAS和其他类别的微污染物。
