A graphene-based hydrogel monolith with tailored surface chemistry for PFAS passive sampling

Area of Science:

• Environmental Science
• Materials Science
• Analytical Chemistry

Background:

• Aquatic contamination by per- and polyfluorinated alkyl substances (PFAS) is a global concern due to environmental persistence and health risks.
• Current regulatory limits necessitate PFAS detection in the parts per trillion (ppt) range, demanding sensitive monitoring tools.
• Passive sampling offers a reliable method for monitoring persistent organic pollutants, but suitable tools for PFAS are needed.

Purpose of the Study:

• To develop and characterize a novel graphene-based hydrogel monolith for use as a passive sampler for PFAS.
• To evaluate the performance of the graphene monolith in detecting a wide range of PFAS in aquatic environments.

Main Methods:

• Graphene oxide (GO) dispersions were hydrothermally treated to self-assemble free-standing graphene hydrogel monoliths.
• The as-produced monoliths were tested for PFAS uptake, and equilibrium partition coefficients (K_SW) were determined.
• Chemical modification using a diazonium-based grafting reaction introduced positive surface charge to enhance short-chain PFAS sorption.

Main Results:

• The graphene monoliths demonstrated effective sorption for longer-chain perfluoroalkyl acids (PFAA) and neutral precursors (log K_SW range 1.9 - 3.6).
• Chemical modification significantly increased the sorption of short and middle-chain PFAA by tenfold (e.g., PFBA log K_SW increased from 1.3 to 2.2).
• Field deployments in the Delaware River confirmed the monoliths' capability to detect key PFAS at relevant environmental concentrations.

Conclusions:

• The developed graphene-based hydrogel monolith serves as a promising passive sampling tool for PFAS monitoring.
• Chemical functionalization enhances the sampler's efficacy for a broader spectrum of PFAS, including challenging short-chain compounds.
• This technology offers a reliable and sensitive method for assessing aquatic PFAS contamination, supporting regulatory compliance and environmental protection.