Zeolites possess unique sieving properties that offer a high selectivity for removing pollutants,such as perand 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.
Charles A.PongeDavid R.CorbinClarice M.SabolayMark B.Shiflett
With long-term production and widespread application,per-and polyfluoroalkyl substances(PFAS)have been detected in various media worldwide,including the atmosphere.Since the gradual restriction and phase-out of C8 perfluoroalkyl acids(PFAAs),environmental contamination by emerging PFAS substitutes such as short-chain PFAA homologues,perfluoroether carboxylic,and sulfonic acids has been reported.Although there has been extensive monitoring of emerging PFAS substitutes in the aquatic environment,few studies have conducted target analysis and nontarget screening(NTS)of emerging unknown PFAS in the atmosphere over the past decade.To fill the gap,this review focused on emerging PFAS in the atmosphere in addition to legacy PFAS.The reported sampling,pretreatment,and instrumental analysis methods for target analysis and NTS of both neutral and ionic PFAS in the atmosphere are summarized,along with the advantages and current limitations of different sampling and NTS methods for PFAS in the atmosphere.The global levels,composition,and spatiotemporal distribution characteristics of legacy and emerging PFAS in the atmosphere are summarized and their transport,transformation,and dry/wet deposition are elucidated.The review highlights the importance of developing and applying the all-in-one strategy integrating target,suspect screening,and NTS to gain insights into emerging PFAS in the atmosphere and provide a reference for future research.
