Zhi Yue, Zhao Xiaoqing, Shuai Ao, Jia Yonghui, Cheng Xinyi, Lin Shihong, Xiao Feng, Han Le, Chai Hongxiang, He Qiang, Liu Caihong
Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing 400044, PR China.
Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235-1831, United States; Department of Chemical and Bimolecular Engineering, Vanderbilt University, Nashville, TN 37235-1831, United States.
Water Res. 2025 Mar 15;272:122931. doi: 10.1016/j.watres.2024.122931. Epub 2024 Dec 7.
Nanofiltration (NF) effectively removes per- and polyfluoroalkyl substances (PFAS) from water but struggles with short-chain PFAS (i.e., those containing less than 6 perfluorinated carbons) due to size exclusion inefficiency. In this study, we developed layer-by-layer assembled NF membranes with PDADMAC/PSS terminal bilayers varying in chain lengths, hydrophilicity, and charge, and systematically assessed their removal of 16 representative PFAS species. The mechanisms between long-chain and short-chain PFAS were investigated and optimal strategies for enhancing PFAS selectivity were developed. Results demonstrated that the (PDADMAC/PSS) membrane achieved the highest removal (86.1%-98.1%) for short-chain PFAS, including PFBA-PFHpA (C4-C6), PFBS (C4), PFMOPrA (C3), PFMOBA (C4), and GenX (C5), while effectively removing (>99.9%) long-chain counterparts (≥C7). As feed water pH increased from 3.5 to 9.0, average PFAS rejection rose from 16.6% to 32.0%, revealing more negative charged membrane surface endow stronger electrostatic repulsion, particularly for short-chain anionic PFAS. In addition, we also tested the PFAS removal efficacy of (PDADMAC/PSS) membrane using real sewage plant effluent. Compared to the pristine membrane, the (PDADMAC/PSS) membrane exhibited improved removal for most PFAS, with removal efficiencies ranging from 82.5% for PFOA to 96.7% for PFOS. The most significant improvements were observed in C4 compounds like PFBA and PFBS (increased by 6.0-11.5%). Our study suggests that PFAS removal efficiency by NF highly depends on size exclusion, with short-chain anionic PFAS more likely affected by electrostatic repulsion. Membrane surface manipulation can enhance selectivity, aiding in predicting NF treatment effectiveness for specific PFAS compounds.
纳滤（NF）能有效去除水中的全氟和多氟烷基物质（PFAS），但由于尺寸排阻效率低，对短链PFAS（即含少于6个全氟碳的物质）的去除效果不佳。在本研究中，我们制备了具有不同链长、亲水性和电荷的聚二烯丙基二甲基氯化铵/聚苯乙烯磺酸钠（PDADMAC/PSS）末端双层的层层组装纳滤膜，并系统评估了它们对16种代表性PFAS的去除效果。研究了长链和短链PFAS之间的作用机制，并制定了提高PFAS选择性的最佳策略。结果表明，（PDADMAC/PSS）膜对短链PFAS（包括PFBA - PFHpA（C4 - C6）、PFBS（C4）、PFMOPrA（C3）、PFMOBA（C4）和GenX（C5））的去除率最高（86.1% - 98.1%），同时能有效去除（>99.9%）长链对应物（≥C7）。随着进水pH从3.5增加到9.0，PFAS的平均截留率从16.6%上升到32.0%，表明膜表面电荷越负，静电排斥越强，尤其是对短链阴离子PFAS。此外，我们还使用实际污水处理厂出水测试了（PDADMAC/PSS）膜对PFAS的去除效果。与原始膜相比，（PDADMAC/PSS）膜对大多数PFAS的去除效果有所改善，去除效率从PFOA的82.5%到PFOS的96.7%不等。在C4化合物如PFBA和PFBS中观察到最显著的改善（提高了6.0 - 11.5%）。我们的研究表明，纳滤对PFAS的去除效率高度依赖于尺寸排阻，短链阴离子PFAS更容易受到静电排斥的影响。膜表面调控可以提高选择性，有助于预测纳滤对特定PFAS化合物的处理效果。
