Selection of High Flux Membrane for the Effective Removal of Short-Chain Perfluorocarboxylic Acids

Abstract

Nowadays persistent perfluorohexanoic acid (PFHxA) ubiquity in the environment is a result of its increasing use as substitute of longer chain perfluorocarboxylic acids. In this study, five nanofiltration (NF270, NF90) and reverse osmosis (XLE, BW30 and SW30XLE) membranes were analyzed in the separation of PFHxA at elevated concentrations (100 mg L–1) relevant in industrial effluents of the production of fluorinated polymers. Experiments assessed the influence of the operation pressure, pH, and ionic strength. The NF270 membrane achieved the highest permeate flux, although PFHxA rejection was typically the lowest of all membranes and was negatively affected in the acidic pH range. The NF90, XLE, and BW30 membranes achieved PFHxA observed rejections over 99%, but only NF90 and XLE membranes attained suitable water permeability. Finally, both XLE and NF90 membranes were selected to provide the lowest PFHxA concentration in the permeate (0.2 mg L–1 at 10 bar). However, when the ionic strength was further increased the electrostatic repulsion to perfluorohexanoate was weakened and the size exclusion mechanism contribution increased, thus making the membranes more permeable to PFHxA. Our results demonstrate that proper selection of NF/RO membranes is a critical issue for the design of treatments for industrial effluents containing short chain PFCAs.

Challenges in the PFAS Remediation of Soil and Landfill Leachate: A Review

“…Appleman et al [101] reported that NF removed PFOS, PFOA, PFDA, PFPeA, and PFBA to below-detection limits (with >97% removal efficiency) from artificial groundwater spiked with 1 µg/L of each PFAS; PFBS and PFHxS were present in extremely low concentrations (e.g., 10 and 20 ng/L, respectively) in the permeate. Soriano et al found that the NF90 membranes with a smaller pore size (0.34 ± 0.02 nm) rejected over 99% of PFHxA at 100 mg/L from the industrial effluents [102]. Their results showed that size exclusion and electrostatic interaction occurred simultaneously and affected the selectivity of PFHxA separation.…”

“…After membrane-treatment, PFAS were concentrated in the rejected water, which was about 15% of the treated water volume for RO [103]. Soriano et al showed an efficient removal of PFHxA (over 99%) using XLE and BW30, two types of RO membranes [102]. These results indicate that both NF and RO can be effective in treating PFAS of a wide range of molecular weights.…”

Amyloid fibril-based membranes for PFAS removal from water

“…Nanofiltration membrane is efficient in removing long-chain PFASs (removal rate: 85-99 %) but weak in rejecting short-chain PFASs (removal rate: 20-70 %) 47 . Reverse osmosis membrane, in general, has higher efficiency in removing both long-and short-chain PFASs, which can reach 99 % but at the expenses of significant energy consumption 48,49 . Moreover, weak removal efficiencies of short-chain PFASs were reported on many adsorbents, such as ion-exchange resins (11-90 %), biochar (the adsorption of PFBA is 75 % lower than the PFOA), and synthetic materials (eg.…”

An optimization model for the treatment of perfluorocarboxylic acids considering membrane preconcentration and BDD electrooxidation

“…The characteristics of two nanofiltration membranes, NF90 and NF270 commercialized by Dow Filmtec, were considered for this study. Both membranes were previously tested at laboratory scale (Soriano et al, 2019a(Soriano et al, , 2019b for the separation of PFHxA.…”

“…where Lp is the empirically determined membrane permeability (Soriano et al, 2019a(Soriano et al, , 2019b. The osmotic pressure difference (in psi) between both sides of the membrane is calculated according to Eq.…”