Styrene-Functionalized Cyclodextrin Polymers for Enhanced PFAS Water Purification

SHORT DESCRIPTION

For water treatment providers, this advanced styrene-functionalized cyclodextrin polymer rapidly adsorbs PFAS contaminants using optimized host–guest interactions and scalable synthesis.

• William Dichtel*
  • Weinberg College of Arts and Sciences, Department of Chemistry
• Damian Helbling
• Jieyuan Wang
• Zhi-wei Lin

NU Tech ID  NU 2024-080

IP STATUS
PCT Patent application pending (WO 2025/240894).

DEVELOPMENT STAGE
TRL-5 Prototype Validated in Relevant Environment: Demonstrated effective PFAS removal in laboratory and simulated wastewater conditions.

BACKGROUND
Per- and polyfluoroalkyl substances (PFAS) are fluorinated surfactants used across industrial processes and consumer products from firefighting foams and textiles to food packaging and cosmetics. Decades of manufacture and use have contaminated water resources worldwide, and their bioaccumulative nature, toxicity at chronic low-level exposure, and near-indestructible carbon–fluorine bonds have earned them the label “forever chemicals.” The U.S. EPA has classified PFOA and PFOS as likely human carcinogens and set enforceable drinking-water limits of 4 parts per trillion each, with a health-based goal of zero reflecting that no exposure level is considered safe. Exposure is linked to kidney and testicular cancer, thyroid and liver effects, elevated cholesterol, and immune suppression. Current solutions like conventional adsorbents which entail activated carbons, ion-exchange resins, and inorganic minerals are widely deployed but suffer from moderate-to-low affinity for PFAS (especially short-chain species), rapid breakthrough of mobile short-chain compounds, and fouling by natural organic matter and inorganic constituents in real water. As short-chain PFAS become more prevalent, mobile, and resistant to removal, there is a pressing need for a new class of high-capacity, selective, and durable adsorbents that capture the full range of anionic PFAS at trace, regulation-relevant concentrations.

ABSTRACT
Northwestern researchers have developed a styrene-functionalized β-cyclodextrin mesoporous polymeric material that adsorbs PFAS from water. Styrene-functionalized beta-cyclodextrin (StyDex) monomers are copolymerized with tunable cationic comonomers (alkylammonium- or alkylphosphonium-substituted aryl/biaryl groups) via free-radical polymerization to yield permanently porous, insoluble adsorbents with Brunauer–Emmett–Teller (BET) surface areas exceeding 200 m2/g .The cyclodextrin cavity provides strong host–guest binding while the cationic comonomers add electrostatic affinity for anionic PFAS. The materials remove PFAS, including perfluorocarboxylic acids (PFCAs), perfluorosulfonic acids (PFSAs), and GenX from water at loadings as low as 1 mg/L , and can be tailored by comonomer choice to target additional cationic and neutral micropollutants. Batch experiments and rapid small-scale column tests confirmed superior PFAS removal kinetics and equilibrium performance compared to conventional adsorbents. The method leverages radical polymerization to enable versatile and scalable synthesis, achieving enhanced performance through a balance of hydrophobic interactions and ionic accessibility.

APPLICATIONS

• Municipal and industrial drinking-water treatment: Effective PFAS removal in drinking water systems to meet EPA limits (4 ppt PFOA/PFOS).
• Groundwater and wastewater remediation: Clean-up of contaminated groundwater and surface water and AFFF-impacted sites.
• Portable filtration devices: Point-of-use and point-of-entry water filtration cartridges and media for integration in consumer and emergency water filters.
• Industrial wastewater treatment: Reduction of PFAS levels in process effluents.
• Capture of short-chain PFAS that break through conventional carbon and resin beds.
• Removal of GenX (HFPO-DA) and other emerging fluorinated replacements.
• Broad application for removal of other micropollutants (cationic, neutral, and anionic organics) after tuning.

ADVANTAGES

• Broad-spectrum capture of long- and short-chain anionic PFAS in one material.
• Rapid PFAS adsorption: Achieves faster contaminant removal compared to traditional adsorbents.
• Enhanced removal efficiency: Optimized host–guest interactions boost adsorption performance.
• Trace-level performance: high removal at adsorbent doses as low as 1 mg/L.
• Permanently mesoporous: BET surface area >200 m2/g for fast, high-capacity uptake.
• Robust and scalable synthesis: Utilizes a facile and reliable one-step radical polymerization for cost-effective production with >85–99% yields, sustainable CD feedstock.
• Robust performance: Maintains efficiency across diverse water conditions and contaminant loads.
• Modular & tunable: comonomer chemistry precisely tailors the binding environment for removal of other micropollutants (cationic, neutral, and anionic organics).
• Outperforms conventional solutions: higher affinity and less prone to fouling than carbons/resins.

PUBLICATIONS

• Lin, Z.-W et al., Structural Features of Styrene-Functionalized Cyclodextrin Polymers That Promote the Adsorption of Perfluoroalkyl Acids in Water. ACS Appl. Mater. Interfaces, May 20, 2024

KEYWORDS
PFAS, water purification, cyclodextrin polymer, styrene-functionalized, adsorption, environmental remediation, scalable synthesis, host–guest interactions, cleantech