Becanova Jitka, Saleeba Zachary S S L, Stone Aidan, Robuck Anna R, Hurt Robert H, Lohmann Rainer
Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, United States.
School of Engineering, Brown University, Providence, RI, United States.
Environ Sci Nano. 2021 Oct 1;8(10):2894-2907. doi: 10.1039/d1en00517k. Epub 2021 Aug 10.
Aquatic contamination by per- and polyfluorinated alkyl substances (PFAS) has attracted global attention due to their environmental and health concerns. Current health advisories and surface water regulatory limits require PFAS detection in the parts per trillion (ppt) range. One way to achieve those low detection limits is to use a reliable passive sampling-based monitoring tool for PFAS, as exists for numerous nonpolar persistent organic pollutants. Here we introduce a new graphene-based hydrogel monolith and describe its synthesis, chemical functionalization, property characterization, and testing as a PFAS equilibrium passive sampler. The graphene monoliths were self-assembled by hydrothermal treatment from graphene oxide (GO) aqueous dispersions to produce free standing cylinders of ~563 mm volume consisting of ~4 wt-% thin-walled porous graphene and ~96 wt-% water. The uptake of 23 PFAS was measured on the as-produced monoliths, and equilibrium partition coefficients (K), were derived for longer chain (C≥8) perfluoroalkyl acids (PFAA) and neutral precursors such as sulfonamides (log K range 1.9 - 3.6). To increase the K for shorter chain PFAA, the monoliths were chemically modified by a new diazonium-based grafting reaction that introduces positive surface charge without damage to the graphenic backbone. Introduction of benzylamine moieties through the diazonium intermediate switches zeta potential at pH 7 from -45mV (as-produced graphene) to + 5mV. This modification increased the sorption of short and middle chain PFAA by ten-fold (e.g. log K for PFBA increased from 1.3 to 2.2), thereby improving the functionality of the passive sampler device for a wider range of PFAS. Field deployments demonstrated that the graphene monoliths were capable of detecting key PFAS in the Delaware River.
全氟和多氟烷基物质（PFAS）对水体的污染因其对环境和健康的影响而受到全球关注。当前的健康建议和地表水监管限值要求在万亿分之一（ppt）范围内检测PFAS。实现这些低检测限的一种方法是使用一种可靠的基于被动采样的PFAS监测工具，就像对许多非极性持久性有机污染物所做的那样。在这里，我们介绍一种新型的基于石墨烯的水凝胶整体柱，并描述其合成、化学功能化、性能表征以及作为PFAS平衡被动采样器的测试。石墨烯整体柱通过水热处理由氧化石墨烯（GO）水分散体自组装而成，生成体积约为563立方毫米的独立圆柱体，其由约4重量%的薄壁多孔石墨烯和约96重量%的水组成。在制备好的整体柱上测量了23种PFAS的吸收情况，并得出了长链（C≥8）全氟烷基酸（PFAA）和中性前体如磺酰胺的平衡分配系数（K）（log K范围为1.9 - 3.6）。为了提高短链PFAA的K值，通过一种新的基于重氮的接枝反应对整体柱进行化学修饰，该反应引入正表面电荷而不破坏石墨烯骨架。通过重氮中间体引入苄胺部分可使pH为7时的ζ电位从-45mV（制备好的石墨烯）转变为+5mV。这种修饰使短链和中链PFAA的吸附增加了十倍（例如，PFBA的log K从1.3增加到2.2），从而改善了被动采样器装置对更广泛PFAS的功能。现场部署表明，石墨烯整体柱能够检测特拉华河中的关键PFAS。
