Deciphering Physicochemical Principles Guiding PFAS Adsorption and Thermal Degradation on Regenerable Waste-Derived...

Area of Science:

• Environmental Chemistry
• Materials Science
• Environmental Engineering

Background:

• Biochar shows promise for removing per- and polyfluoroalkyl substances (PFAS), but faces challenges with short-chain PFAS and regeneration.
• Diverse biochar properties complicate understanding PFAS removal mechanisms.

Purpose of the Study:

• Investigate the adsorption of long- and short-chain PFAS using 17 biochar materials with varying properties.
• Elucidate PFAS removal mechanisms, including the role of divalent cations and pore structure.
• Evaluate the regeneration potential and performance enhancement of spent biochar.

Main Methods:

• Comprehensive characterization of 17 biochar materials.
• Batch adsorption experiments for PFAS removal.
• Analysis of adsorption mechanisms involving hydrophobic/electrostatic interactions and cation bridging.
• Thermolysis-based reactivation of spent biochar and subsequent adsorption testing.

Main Results:

• Hydrophobic/electrostatic interactions and divalent cation bridging are crucial for PFAS adsorption.
• Micropore filling is significant for short-chain PFAS adsorption, which can be displaced by long-chain PFAS.
• Reactivation of biochar via 900 °C N2 thermolysis effectively removed PFAS and enhanced short-chain PFAS adsorption in subsequent cycles due to micropore formation.

Conclusions:

• Biochar pore structure and indigenous ionic species are key factors for selecting effective PFAS adsorbents.
• Engineered biochar adsorbents can be designed for simultaneous removal of both short- and long-chain PFAS.
• Effective reactivation strategies can improve the long-term performance of biochar for PFAS remediation.