A graphene-based hydrogel monolith with tailored surface chemistry for PFAS passive sampling. Issue 10 (25th August 2021)

• Record Type: Journal Article
• Authors: Becanova, Jitka; Saleeba, Zachary S. S. L.; Stone, Aidan; Robuck, Anna R.; Hurt, Robert H.; Lohmann, Rainer
• Is Part Of: Environmental science. Volume 8:Issue 10(2021)
• Page Start: 2894
• Page End: 2907
• Publication Date: 2021-08-25
• Subjects: Environmental sciences -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/d1en00517k
• Languages: English
• ISSNs: 2051-8153

Abstract

Abstract : We introduce new PFAS passive sampling devices based on porous graphene monoliths grafted with cationic functional groups for broad-spectrum PFAS pre-concentration including short-chain anionic species. Abstract : 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 3 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 SW ), were derived for longer chain (C ≥ 8) perfluoroalkyl acids (PFAA) and neutral precursors such as sulfonamides (log K SW range 1.9–3.6). To increase the K SW 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 −45 mV (as-produced graphene) to +5 mV. This modification increased the sorption of short and middle chain PFAA by ten-fold ( e.g. log K SW 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.