Surface-modified biopolymers for removing mixtures of per- and polyfluoroalkyl substances from water: Screening and removal mechanisms

Green, renewable, and sustainable materials are needed for removing per-and polyfluoroalkyl substances (PFASs) in water. Herein, we synthesized and tested alginate (ALG) and chitosan (CTN) based and poly-ethyleneimine (PEI) functionalized fibers/aerogels for the adsorption of mixtures of 12 PFASs (9 short-and long -chain PFAAs, GenX, and 2 precursors) from water at an initial concentration of 10 mu g/L each. Out of 11 bio-sorbents, ALGPEI-3 and GTH CTNPEI aerogels had the best sorption performance. Through detailed character-ization of the sorbents before and after PFASs sorption, it was revealed that hydrophobic interaction was the dominant mechanism controlling PFASs sorption while electrostatic interactions played a minor role. As a result, both aerogels had fast and superior sorption of relatively hydrophobic PFASs from pH 2 to 10. Even at extreme pH conditions, the aerogels retained their shape perfectly. Based upon the isotherms, the maximum adsorption capacity of ALGPEI-3 and GTH-CTNPEI aerogels towards total PFASs removal was 3045 and 12,133 mg/g, respectively. Although the sorption performance of the GTH-CTNPEI aerogel toward short chain PFAS was less than satisfactory and varied between 70 and 90% in 24 h, it may find its use in removing relatively hydrophobic PFAS at high concentrations in complex and extreme environments.

Automated summary

The researchers synthesized and tested alginate and chitosan based fibers/aerogels, as well as poly-ethyleneimine functionalized fibers/aerogels, for the adsorption of 12 PFASs from water. The ALGPEI-3 and GTH CTNPEI aerogels showed the best sorption performance, with hydrophobic interaction being the dominant mechanism. These aerogels exhibited fast and superior sorption of hydrophobic PFASs and retained their shape even at extreme pH conditions. The maximum adsorption capacity of ALGPEI-3 and GTH-CTNPEI aerogels for total PFASs removal was found to be 3045 and 12,133 mg/g, respectively. A rating of 8 out of 10 is given for the importance of this study.