Mechanistic Insights and Design Strategies for Hydrogel/Aerogel Sorbents in Remediation of Per- and Polyfluoroalkyl Substances

TL;DR

This paper reviews hydrogel and aerogel sorbents for removing harmful PFAS chemicals from water, focusing on their design, mechanisms, and challenges.

Contribution

The paper provides a comprehensive review of underexplored hydrogel/aerogel sorbents and their mechanisms for PFAS remediation.

Findings

Hydrogels are highly effective PFAS adsorbents due to their porous structure and functionalization potential.

Adsorption mechanisms include ionic, hydrophobic, hydrogen bonding, and F–F interactions.

Challenges include large-scale production and the need for ionic fluorogel and thermosensitive hydrogel development.

Abstract

Per- and polyfluoroalkyl substances (PFAS) have been
used for several
decades in various sectors, including aerospace, construction, the
military, and the production of goods, among others. This widespread
use has significantly contaminated water bodies globally. Several
government agencies and organizations are trying to develop advanced
technologies such as oxidation, membrane filtration, adsorption, and
ion-exchange resin to capture these chemicals and thus mitigate their
impacts. Adsorption has proven to be a highly attractive method for
removing PFAS, involving activated carbon, silica, bioadsorbents,
anion-exchange resin, hydrogels, and nonion exchange polymers. Among
different adsorbents, hydrogels are the most effective adsorbents
for removing these forever chemicals due to their highly porous structure,
reuse and regeneration ability, and ease of functionalization with
specific groups for effective binding with PFAS molecules. Keeping
in view their tremendous potential, this Review critically reviews
the potential of underexplored hydrogel/aerogels-based sorbents developed
from synthetic polymers as well as biopolymers. The use of different
cross-linkers, co-monomers, inorganic and organic additives, and surface
functionalization techniques on the PFAS removal ability of the resulting
hydrogels/aerogels under varying pH, background species concentration,
PFAS concentration, and temperature was thoroughly discussed. Furthermore,
the underlying adsorption mechanisms (ionic, hydrophobic, hydrogen
bonding, and F–F interactions) of hydrogels and aerogels for
PFAS adsorption from a molecular perspective were also examined. Finally,
the challenges inhibiting the large-scale production of these adsorbents
and the scope of ionic fluorogel and thermosensitive hydrogels have
also been thoroughly reviewed.

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