Removal of PFOS using polypropylene coated with amphiphilic cyclodextrins

Per- and polyfluoroalkyl substances (PFAS) are a group of manmade organofluoride compounds, which are
bio accumulative, environmentally persistent and toxic to humans [1]. Membranes with low molecularweight cut-off (NF and RO) have shown high retention of PFAS. However, the filtration is energy intensive
and has low water recovery [2]. The use of higher molecular-weight cut-off membranes (UF and MF)
combined with the selective adsorbent cyclodextrins, should offer the possibility of a selective PFAS capture
with both highly efficient removal, low energy consumption and complete water recovery. The modification
of polymeric materials with cyclodextrins can be obtained by a simple and fast coating method [3].
Amphiphilic cyclodextrins (ACDs) with different degree of substitution (DS) were synthesised and immobilized
on non-woven polypropylene cloth by dip coating for 10s in a mixture of ACD, ethanol and water.
Ethanol/water ratios of 20/80, 70/30 and 90/10 were investigated for each ACD, representing an unstable
suspension, stable suspension and solution, respectively. The removal of perfluorooctanesulfonic acid (PFOS)
was investigated in a static adsorption experiment, where the removed concentration after 1h was
determined. It was demonstrated that the ACD coated polypropylene has a PFOS removal which is
approximately 25 times higher than the non-coated polypropylene.