A Tunable Porous β-Cyclodextrin Polymer Platform to Understand and Improve Anionic PFAS Removal

Area of Science:

• Polymer Chemistry
• Environmental Science
• Materials Science

Background:

• Cross-linked polymers with β-cyclodextrin (β-CD) show potential for removing per- and polyfluoroalkyl substances (PFASs) from water.
• Existing β-CD adsorbents have limitations in structural definition, hindering performance optimization and mechanistic studies.
• Poorly defined structures and side reactions complicate understanding of PFAS adsorption mechanisms in current β-CD polymers.

Purpose of the Study:

• To develop a new β-CD polymer platform with a well-defined structure for improved PFAS removal.
• To investigate the adsorption mechanisms of PFASs on novel β-CD-based materials.
• To create versatile β-CD polymers amenable to rational design for water purification.

Main Methods:

• Synthesized a discrete β-CD monomer by attaching styrene groups to β-CD.
• Utilized radical polymerization to create three β-CD polymers using styrene and methacrylate comonomers.
• Evaluated PFAS removal efficiency in nanopure water and a salt matrix at low adsorbent loadings.

Main Results:

• Achieved high specific surface areas and isolated yields (>93%) for the synthesized β-CD polymers.
• Demonstrated nearly 100% removal of eight anionic PFASs at 1 mg L⁻¹ adsorbent loading using a cationic β-CD polymer.
• Identified that long-chain PFAS adsorption involves hydrophobic and electrostatic interactions, while short-chain PFASs primarily use electrostatic interactions in salt matrices.

Conclusions:

• The new β-CD polymer platform provides a versatile approach for rational design and performance enhancement.
• The developed cationic β-CD polymer shows exceptional efficiency for anionic PFAS removal at significantly lower loadings than previous materials.
• This work advances the understanding of PFAS adsorption mechanisms and offers a promising strategy for developing tailored adsorbents for micropollutant removal.