We are developing and characterizing a novel perstraction process for the removal of perfluorinated compounds (PFAS) from water. The process utilizes a membrane barrier between an organic solvent and a PFAS-contaminated water stream. The membrane barrier is required in this process, since significant foaming or emulsion formation occurs at the interface between organic solvents and PFAS-contaminated water. For this project, we are synthesizing membranes using polydimethylsiloxane (PDMS), which is a hydrophobic material. The inclusion of nanoparticles within the PDMS can vary the properties of the membrane, and so we have investigated the effects of various nanoparticles imbedded in PDMS membranes on the absorption of selected solvents and perfluorooctanoic acid (PFOA). We have found that nanoparticles imbedded into the PDMS membrane significantly increase the absorption of PFOA, a selected representative of PFAS compounds. The objectives of this project are to design, construct, and assess the performance of a prototype perstraction system. Ancillary objectives are to:<br/>(1) determine the partition coefficients of PFOA between water and selected solvents; (2) determine the solubility and diffusivity of the selected solvents in PDMS membranes; (3) assess the effects of selected nanoparticles on the solubility and diffusivity of selected solvents in PDMS and on the uptake of PFOA in PDMS (both extent of PFOA uptake and kinetics of the uptake).  Perstraction testing devices were designed and fabricated, and preliminary results have been obtained to demonstrate its feasibility. The partition of PFOA between water and selected organic solvents is being assessed. Three different alcohols (1-butanol; 1-hexanol; 1-octanol) and two different alkanes (hexane and cyclohexane) are being used for the proposed research to assess whether the carbon chain length in the alcohol and chemical structure of the solvent will impact the partition of PFOA between water and the solvent. Our preliminary efforts support the significance of pH of the PFOA solutions on uptake and permeation of PFOA by PDMS, where the ionized form of the PFOA is much less absorbed into PDMS. However, the solubility of PFOA in selected solvents is less affected by the pH.

Perstraction : A novel membrane-assisted liquid-liquid extraction method for removing PFAS from water

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ACS Fall 2022

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