PFAS Removal from Water Using Foam Fractionation with Algae-Derived Biosurfactants

Abstract

Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants that occur throughout the water cycle, and European drinking water limits for them keep tightening. Foam fractionation concentrates PFAS into a small volume of foam by using their surface activity, but reaching the short-chain compounds takes a cationic co-surfactant on top of that. The one normally used, cetyltrimethylammonium bromide (CTAB), is toxic to aquatic life and poorly biodegradable. This work tests whether biosurfactants from algae can take its place.
Reverse-osmosis concentrate from a Dutch drinking water plant was treated in a 1 L batch column and analysed by LC-MS/MS across a 32-compound PFAS panel. Two algae were compared first, and the better of the two was then combined with three bio-based cationic co-surfactants. Spirulina held a foam for a full run and removed the short-chain PFBS at 32, 45 and 59% across its three doses, where Tetraselmis foam thinned within ten minutes and gave no removal above what bare bubbles achieve on their own. Neither alga matched CTAB on the short chains, because algal biosurfactants carry no positive charge. A bio-based cation closed that gap: PFBS rose from 48% with the alga alone to above 99%, beating the CTAB benchmark, while PFOS stayed above 85% in every run. LAE is the recommendation, as the only option classed as readily biodegradable. Every run in the second phase contained Spirulina, so whether the alga is still needed alongside a co-surfactant remains untested.