Designing zeolites for the removal of aqueous PFAS: a perspective

Zeolites possess unique sieving properties that offer a high selectivity for removing pollutants, such as per- and polyfluoroalkyl substances (PFAS). However, there are limited studies examining the efficacy of zeolites as PFAS sorbents. Previous literature explores the effects of certain frameworks and the silica alumina ratio (SAR), and only one study has shown the effect of silanol defects on the hydrophobicity of the adsorbent. Since most zeolites are synthesized in hydroxide media, this leads to formation of silanol defects, which increase hydrophilicity with a greater effect than the inclusion of non-Si T atoms. It is critical that specific characterizations be performed to demonstrate the specific effects of different properties of the zeolites. In particular, synthesis, modification, and/or repair in fluoride media can be used to increase the hydrophobicity of zeolites by reducing silanol defects, and increasing Lewis acidity.

Keywords: Zeolites; Aqueous adsorption; PFAS; Hydrophobic interaction; Silica–alumina ratio.