Oxidation vs. agglomeration: impact of graphene oxidation on self-interactions and PFAS capture

Abstract

Per- and polyfluoroalkyl substances (PFAS), also known as “Forever Chemicals”, are a class of compounds characterized by their extremely stable C–F bonds. These molecules possess desirable properties, which has led to their widespread use in industry and household products. PFAS have been found in waterways around the world. This is concerning because PFAS have also been found to have negative health impacts on the human population. It is essential that effective adsorbent materials are developed to remove PFAS from the environment. Carbon nanomaterials such as graphene oxide are often used for water remediation and filtering purposes. Pure graphene is hydrophobic, but the presence of hydroxyl, epoxy, and carboxyl groups increases its hydrophilicity. Meanwhile, PFAS have hydrophobic tail groups and hydrophilic head groups. This work is focused on determining how the extent of oxidation in graphene oxide impacts the capture of amphiphilic PFAS. Seven graphene oxide flakes are examined which contain an oxygen coverage of 0.0, 2.4, 5.2, 7.6, 10.9, 14.5, and 17.5% oxygen by mass. In addition to becoming more hydrophilic as the oxygen content increases, the self-interaction between flakes also changes. Both factors play a role in how the materials interact with PFAS. Graphene oxide flakes with 5.2% and 7.6% oxygen by weight exhibited the highest PFAS-affinity out of all flakes studied herein.