Cao Jiefei, Feng Siyuan, Dolatabad Alireza Arhami, Zhi Yue, Deng Baolin, Liu Caihong, Lyu Xueyan, Christensen Charlotte S Q, Pignatello Joseph J, Ni Pan, Lin Shihong, Wei Zongsu, Xiao Feng
Department of Civil and Environmental Engineering, University of Missouri, Columbia, MO 65211, United States.
Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235-1831, United States.
Water Res. 2025 Aug 15;282:123758. doi: 10.1016/j.watres.2025.123758. Epub 2025 Apr 30.
We explored an underexplored area in water treatment by examining the removal of per- and polyfluoroalkyl substances (PFAS) from reverse osmosis/nanofiltration (RO/NF) brine. We first compared multiple RO/NF membranes, revealing that DK and NF270 showed sub-optimal removal (<90 %) of C4-C8 PFAS, SW30 had low flux (<15 L/m/h at 8 bar), and NFX exhibited significant adsorption of perfluorosulfonic acids (e.g., 8 µmol/m). To address the PFAS-enriched brine generated from membrane treatment, we further evaluated activated carbon (GAC) and anion-exchange (AIX) resin, both of which efficiently removed moderate- and long-chain PFAS from brine. Although AIX outperformed GAC, the ion exchange contribution was small for short-chain PFAS like perfluorobutanoic acid (PFBA, C4) but increased with chain length, driven by the hydrophobic effect facilitating the migration to near-surface regions of resins. Equilibrium batch experiments and thermodynamic modeling revealed a disproportionate salinity impact on PFAS adsorption by GAC, with short-chain PFAS (e.g., PFBA) experiencing more pronounced adsorption reduction than longer-chained homologs as NaCl concentrations increased. This reduction was driven by a significant change in a free energy component unrelated to the hydrophobic or electrostatic interactions, likely due to the competitive adsorption of Cl ions and short-chain PFAS anions or the formation of hydration shells around Na and Cl ions, obstructing the pathways for weakly hydrophobic PFAS (e.g., PFBA) within the GAC pore network. The salting-out effect was found to be unimportant. This study provides new insights into salinity-dependent sorptive removal of PFAS from high-ionic-strength water such as RO/NF brine.
我们通过研究从反渗透/纳滤（RO/NF）浓盐水中去除全氟和多氟烷基物质（PFAS），探索了水处理领域一个尚未充分研究的方面。我们首先比较了多种RO/NF膜，发现DK和NF270对C4 - C8 PFAS的去除效果欠佳（<90%），SW30通量较低（8巴时<15 L/m/h），而NFX对全氟磺酸表现出显著吸附（例如8 µmol/m）。为处理膜处理产生的富含PFAS的浓盐水，我们进一步评估了活性炭（GAC）和阴离子交换（AIX）树脂，二者均能有效去除浓盐水中的中长链PFAS。尽管AIX的性能优于GAC，但对于全氟丁酸（PFBA，C4）等短链PFAS，离子交换作用较小，不过随着链长增加而增大，这是由疏水效应促使其向树脂近表面区域迁移所驱动。平衡批次实验和热力学建模表明，盐度对GAC吸附PFAS有不成比例的影响，随着NaCl浓度增加，短链PFAS（如PFBA）的吸附减少比长链同系物更明显。这种减少是由与疏水或静电相互作用无关的自由能成分的显著变化驱动的，可能是由于Cl离子和短链PFAS阴离子的竞争吸附，或者是Na和Cl离子周围形成水合壳，阻碍了GAC孔隙网络中弱疏水性PFAS（如PFBA）的迁移途径。结果发现盐析效应并不重要。本研究为从RO/NF浓盐水等高离子强度水中盐分依赖型吸附去除PFAS提供了新见解。
