Address short-chain PFAS contamination in water with nanofibrous adsorbent/filter material from electrospinning

Per- and polyfluorinated alkyl substances (PFAS) have been widely manufactured and used in consumer products. Due to easy deprotonation of head group and high strength of C-F bond, PFAS are water soluble and extremely stable in our environment. Significant accumulation of PFAS in water bodies has started as early as beginning of their production in the late 1940s. Recent study confirmed PFAS occurrence and accumulation in all human tissues and demonstrated harmful health effects. Upon environmental regulations as well as health advisories, industry quickly shifted to short-chain PFAS, e.g. hexafluoropropylene oxide dimer acid and its ammonium salt (GenX), to replace traditional long-chain PFAS, e.g. perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). According to the recent fact sheet by U.S. Environmental Protection Agency (EPA) in October 2021, however, GenX turns out to be more toxic than people originally thought and has shown health effects on liver, kidney, immune system, etc. upon animal tests. On June 15, 2022, U.S. EPA released final health advisory for GenX, which is just 10 ppt. Thus, there is an urgent need to develop novel adsorbents for highly effective GenX remediation from water.
Up to date there are just a few reports on remediation of GenX from water despite of its popular use. Herein we present our research at North Carolina A&T State University, the largest HBCU in the nation, on how to use common and economic polymer in form of nanofibrous membrane with handy chemical surface modification as innovative adsorbent/filter material for effective and scalable GenX remediation from water. For the first time, we compared GenX removal capability of electrospun polyacrylonitrile (ESPAN) and amidoxime surface-functionalized ESPAN (ASFPAN) nanofibrous membranes. By introducing amidoxime functional groups, the maximum GenX removal capacity (weight-normalized GenX removal) of the nanofibrous adsorbent/filter was almost doubled and reached ~0.6 mmol/g at pH 4, which is higher or comparable to most of reported adsorbents for GenX removal. Hydrophobic interaction and dipole-dipole interaction could be the GenX adsorption mechanism on ESPAN nanofibrous membrane while electrostatic interaction and surface hydrophilicity play major role in GenX adsorption on ASFPAN nanofibrous membrane. Our research shed light on the development of new adsorbent/filter materials for practical PFAS (especially short-chain PFAS) remediation from water.