Removal of Zwitterionic PFAS by MXenes: Comparisons with Anionic, Nonionic, and PFAS-Specific Resins

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment Technologies

Background:

• Zwitterionic per- and polyfluoroalkyl substances (PFAS) are increasingly detected in aquatic environments.
• Concerns exist regarding their presence in drinking water and potential health risks.
• Effective technologies for removing zwitterionic PFAS from water are largely unknown.

Purpose of the Study:

• To investigate the efficacy of various materials for removing zwitterionic PFAS from natural waters.
• To compare the performance of Ti3C2 MXenes, ion exchange resins, and PFAS-specific resins.
• To assess the regeneration potential of the studied materials.

Main Methods:

• Tested anionic organic scavenger ion exchange (IX) resins (A860), nonionic IX resins (XAD 4, XAD 7), PFAS-specific resins (A694, A592), and Ti3C2 MXenes.
• Evaluated zwitterionic PFAS removal efficiency at neutral pH.
• Assessed regeneration efficiency using sodium sulfite and UV treatment.

Main Results:

• Ti3C2 MXenes demonstrated the highest cumulative removal (>75%) of zwitterionic PFAS.
• Performance of Ti3C2 MXenes was consistent in both natural and synthetic waters.
• Ti3C2 MXenes showed efficient regeneration (>90% recovery), unlike other IX resins (<20%).
• UV-sulfite treatment of regenerant brine achieved >99.9% reduction in zwitterionic PFAS concentration.

Conclusions:

• Ti3C2 MXenes are highly effective for capturing zwitterionic PFAS from natural waters.
• The regeneration of Ti3C2 MXenes is significantly more efficient than traditional IX resins.
• UV-sulfite systems offer a promising approach for treating PFAS-laden concentrates.