School of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA.
Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
Water Res. 2024 Aug 15;260:121897. doi: 10.1016/j.watres.2024.121897. Epub 2024 Jun 6.
Perfluoroalkyl acids (PFAAs) are ubiquitous environmental contaminants of global concern, and adsorption processes are the most widely used technologies to remove PFAAs from water. However, there remains little data on the ways that specific water matrix constituents inhibit the adsorption of PFAAs on different adsorbents. In this study, we evaluated the adsorption of 13 PFAAs on two styrene-functionalized β-cyclodextrin (StyDex) polymers, an activated carbon (AC), and an anion-exchange resin (AER) in the absence and presence of specific water matrix constituents (16 unique water matrices) in batch experiments. All four adsorbents exhibited some extent of adsorption inhibition in the presence of inorganic ions and/or humic acid (HA) added as a surrogate for natural organic matter. Two PFAAs (C5-C6 perfluorocarboxylic acids (PFCAs)) were found to exhibit relatively weak adsorption and five PFAAs (C6-C8 perfluorosulfonic acids (PFSAs) and C9-C10 PFCAs) were found to exhibit relatively strong adsorption on all four adsorbents across all matrices. Adsorption inhibition was the greatest in the presence of Ca (direct site competition) and HA (direct site competition and pore blockage) for AC, NO (direct site competition) and Ca (chemical complexation) for the AER, and SO (compression of the double layer) for the StyDex polymers. The pattern of adsorption inhibition of both StyDex polymers were similar to each other but different from AC and AER, which demonstrates the distinctive PFAA adsorption mechanism on StyDex polymers. The unique performance of each type of adsorbent confirms unique adsorption mechanisms that result in unique patterns of adsorption inhibition in the presence of matrix constituents. These insights could be used to develop models to predict the performance of these adsorbents in real water matrices and afford rational selection of adsorbents based on water chemistry for specific applications.
全氟烷基酸（PFAAs）是具有全球关注的普遍存在的环境污染物，吸附工艺是最广泛用于从水中去除 PFAAs 的技术。然而，关于特定水基质成分如何抑制 PFAAs 在不同吸附剂上吸附的信息仍然很少。在这项研究中，我们在批处理实验中评估了 13 种 PFAAs 在两种苯乙烯功能化β-环糊精（StyDex）聚合物、一种活性炭（AC）和一种阴离子交换树脂（AER）上的吸附，同时存在和不存在特定的水基质成分（16 种独特的水基质）。在存在添加的无机离子和/或腐殖酸（HA）的情况下，所有四种吸附剂都表现出一定程度的吸附抑制作用，HA 作为天然有机物的替代品。两种 PFAAs（C5-C6 全氟羧酸（PFCAs））被发现吸附较弱，五种 PFAAs（C6-C8 全氟磺酸（PFSAs）和 C9-C10 PFCAs）被发现对所有四种吸附剂在所有基质中都表现出较强的吸附。在存在 Ca（直接位竞争）和 HA（直接位竞争和孔阻塞）的情况下，AC 的吸附抑制作用最大，在存在 NO（直接位竞争）和 Ca（化学络合）的情况下，AER 的吸附抑制作用最大，在存在 SO（双层压缩）的情况下，StyDex 聚合物的吸附抑制作用最大。两种 StyDex 聚合物的吸附抑制模式彼此相似，但与 AC 和 AER 不同，这表明 StyDex 聚合物上存在独特的 PFAAs 吸附机制。每种类型吸附剂的独特性能证实了独特的吸附机制，导致在存在基质成分的情况下吸附抑制的独特模式。这些见解可用于开发模型来预测这些吸附剂在实际水基质中的性能，并根据特定应用的水化学合理选择吸附剂。
