The adsorption behavior and mechanism of perfluorochemicals on oxidized fluorinated graphene sheets supported on silica

Abstract

This is the first report on the fabrication of oxidized fluorinated graphene sheets supported on silica (OFG@silica) for the selective adsorption of perfluorochemicals (PFCs). To increase the affinity towards PFCs, oxidized fluorinated graphene (OFG) was grafted onto amino-terminated alkyl chain modified silica (NH₂-silica), thus producing a mixed-mode material combining fluorophilicity and hydrophobic affinity with anion-exchange properties. The adsorption behavior and mechanism of OFG@silica towards PFCs were explored using a solid phase extraction (SPE) method. For demonstration, several organic analytes including perfluorinated fatty acids (PFFAs), aromatic analytes and fatty acids (FAs) were employed as adsorbates. By analysing the physicochemical properties of analytes, we found that the adsorption amount of analytes was negatively correlated with their molecular acidity coefficient (pK_a) and positively correlated with their octanol–water distribution coefficient (log D) at pH 7, suggesting that the anion-exchange effect and hydrophobic affinity played a major role in adsorption. Moreover, compared with FAs, PFFAs exhibited a higher adsorption amount which benefited from fluorous–fluorous interactions between PFFAs and OFG@silica. These findings suggested that OFG@silica might be a potential adsorbent for the enrichment of PFCs.