InterPore2026

Up-flow foam fractionation and down-flow filtration for enhanced PFAS removal by adsorption at air-water and solid-water interfaces

22 May 2026, 09:35

15m

Oral Presentation (MS06) Interfacial phenomena across scales MS06

Speaker

Edo Boek (Queen Mary University of London)

Description

PFAS (per- and polyfluoroalkyl substances) have emerged as environmentally persistent compounds in water resources, of global concern due to their mobility, bioaccumulation, and toxicity. In this work, we demonstrate two unique pilot-scale experimental platforms to evaluate the efficiency of different adsorption mechanisms for enhanced PFAS removal: 1) down-flow filtration through fixed-bed granular sorbent porous media [1] and 2) up-flow foam fractionation by bubbling air through water filled reactors [2-5]. Both up-flow foam-fractionation and down-flow filtration reactors were designed and built in collaboration with our drinking water industry collaborators.

We examine the capacity of the foam and granular media to adsorb and remove PFAS from contaminated water sources. First, methyl orange (MO) dye is used as a model contaminant analogue, with CTAB as a co-surfactant, to mimic PFAS surface activity. The choice of this analogue facilitates easy real-time UV-Vis spectroscopy analysis of contaminant concentration in the effluent and supports further method development for breakthrough analysis.
For the downflow reactors, Granular Activated Carbon (GAC) materials were examined as porous sorbents. 2D imaging and subsequent machine learning analysis were used to analyse the size and shape of the GAC materials, to find a relation between adsorption performance and granular morphological properties.
For the upflow reactors, we consider enhanced stabilisation of the foam fractionation process by colloidal particles, as co-stabilisers along with CTAB surfactants. For this purpose, we ball-milled a GAC sorbent (Filtrasorb TL380) and an organo-clay sorbent (Fluro-Sorb 400, FS) [1] to colloidal size. Using UV-Vis analysis, we observe that both GAC and organoclay colloidal particles enhance contaminant removal.

Figure 1 shows the temporal evolution of MO concentration and removal efficiency in the down-flow GAC column over 25 min. The influent concentration of 0.043 g L⁻¹ was reduced to 0.006 g L⁻¹ after 5-min (86.0 % removal) and reduced further to 0.004 g L⁻¹ after 15-min (90.7 % removal), corresponding to one empty bed contact time (EBCT). A transient decrease in performance was observed at 20 min, where removal efficiency dropped to 80.1 % (0.009 g L⁻¹), attributed to partial pore saturation and internal mass-transfer re-equilibration. Based on these findings, a backwashing unit and improved flow distribution system were implemented in the column design to regenerate adsorption sites and mitigate localised clogging, with future experiments expected to achieve higher and more stable removal efficiencies.
Figure 2a shows foam stability vs. time in the up-flow foam fractionation reactor. This demonstrates that the particle-stabilised CTAB foam lifespans are longer than that of CTAB-only foam. This is especially true after 50 min, observing that colloidal particles help foam stabilisation and almost double the foam lifespan. Furthermore, Figure 2b shows that CTAB/particle-stabilised foams improve removal efficiency vs. CTAB-stabilised foam by ~20 %. After a 45-min foaming process, the removal of MO in water for CTAB is 76.4 %, while the addition of GAC and FS colloidal particles increases the MO removal efficiency to 84.5 and 91.3 % respectively.
We conclude that combinations of up- and downflow reactors are promising methods for PFAS removal from water resources.