Removing cationic and zwitterionic compounds extends DEXSORB®’s value proposition to treat polyfluorinated alkyl substances (PFAS) in drinking water The superior performance of the company’s polymer formulation was reported on September 14, 2020 in Environmental Science & Technology.
Concern over PFAS in drinking water and their associated health effects are widespread and well-known. Most attention has been focused on PFOA, PFOS and other anionic (negatively charged) PFAS compounds. Nearly 20 States have adopted or are adopting their own maximum contaminant levels, some as low as 8ppt for PFOA and 10ppt for PFOS, and others with limits of 20ppt for combinations of up to six PFAS compounds. But, many of the industrial processes and products that contain PFOA and PFOS also include a variety of other PFAS classes made up of cationic, zwitterionic and nonionic compounds, which are also finding their way into drinking water.
Per- and polyfluoroalkyl substances (PFASs) occur in groundwater as mixtures of anionic, cationic, zwitterionic, and nonionic species, although few remediation technologies have been evaluated to assess the removal of different types of PFASs. In this study, the performance of three β-cyclodextrin polymers (CDPs), an anion-exchange (AE) resin, and a cationexchange (CE) resin was evaluated for the removal of anionic, zwitterionic, and nonionic PFASs from water. It was found that a CDP with a negative
surface charge rapidly removes all zwitterionic PFASs with log KD values ranging between 2.4 and 3.1, and the CE resin rapidly removes two zwitterionic PFASs with log KD values of 1.8 and 1.9.
The CDPs with a positive surface charge rapidly remove all anionic PFASs with log KD values between 2.7 and 4.1, and the AE resin removes all anionic PFASs relatively slowly with log KD values between 2.0 and 2.3. All adsorbents exhibited variable removal of the nonionic PFASs and some adsorption inhibition at higher pH values and in the presence of groundwater matrix constituents. The findings provide insight into how adsorbents can be combined to remediate groundwater contaminated with complex mixtures of different types of PFASs.
Ching, C., Klemes, M. J., Trang, B., Dichtel, W. R., & Helbling, D. E. (2020). β-Cyclodextrin Polymers with Different Cross-Linkers and Ion-Exchange Resins Exhibit Variable Adsorption of Anionic, Zwitterionic, and Nonionic PFASs. Environmental Science & Technology. doi:10.1021/acs.est.0c04028
This is not the first time that Cyclodextrin News reports on the dervelopment of Cyclopure adsorbents. See also: