PFAS removal by micro-nanobubble enhanced foam fractionation with chitosan

https://www.sciencedirect.com/science/article/abs/pii/S2214714426000681?via%3Dihub

• OTCS-MNBs achieved over 80% removal efficiency for PFOA/PFOS in natural waters.
• The OTCS-MNBs system demonstrated excellent pH adaptability and foam stability.
• The micro-nano bubbles-OTCS coupled foam fractionation system is reported for the first time to enhance PFAS removal.
•  A novel green cationic surfactant was synthesized to enhance the performance of foam fractionation

Effective removal of typical compounds like perfluorooctanoic acid (PFOA) 

and perfluorooctanesulfonic acid (PFOS) is crucial for drinking water safety. 

Foam fractionation shows promise for PFAS removal, but its efficacy is limited by

 the low PFAS concentrations in natural waters, which hinder interfacial adsorption 

and foam stability. This study synthesized a novel green surfactant, octanoyl 

chloride-modified chitosan (OTCS), and developed an enhanced foam fractionation

 system coupled with micro-nano bubbles technology (OTCS-MNBs) for the efficient

 removal of PFOA and PFOS. Compared to the OTCS-conventional air bubbles foam 

fractionation system OTCS (OTCS-CABs), the OTCS-MNBs system achieved removal

 efficiencies of 98.73% and 99.21% for PFOA and PFOS, respectively, representing improvements 

of 1.47-fold for PFOA and 1.29-fold for PFOS. The system demonstrated pH adaptability 

(pH 3–9) and excellent foam stability, with moderate ionic strength enhancing reaction 

kinetics through salting-out effects. Analysis revealed that micro-nanobubbles exhibited

 higher specific surface area, longer residence time, and superior resistance to coalescence 

compared to conventional bubbles, thereby providing more adsorption sites and sufficient

 contact time for PFAS. In practical water experiments conducted with four typical Chinese

 lakes and reservoir sources, the system achieved removal efficiencies exceeding 80% for

 PFOA/PFOS, demonstrating its potential for practical application in complex water conditions.

 This highly efficient and environmentally friendly foam fractionation process effectively 

mitigates the environmental and health risks associated with PFAS and provides valuable

 technical guidance for water treatment plants addressing emerging contaminant challenges

In this study, a micro-nano bubbles foam fractionation system coupled with octanoyl 

chloride–modified chitosan (OTCS–MNBs) was developed for the efficient removal of PFOA 

and PFOS from water. By introducing hydrophobic alkyl chains onto the chitosan backbone, 

OTCS provided dual hydrophobic–electrostatic binding sites, which, in synergy with the high

 surface area and stability of MNBs, significantly enhanced foam formation and pollutant 

enrichment at the gas–liquid interface.