Roles of varying carbon chains and functional groups of legacy and emerging per-/polyfluoroalkyl substances in adsorption on metal-organic framework: Insights into mechanism and adsorption prediction

Hao Guo; Tongyu Hu; Xiaoman Yang; Zhaoyang Liu; Qianqian Cui; Chenchen Qu; Fayang Guo; Shun Liu; Andrew J Sweetman; Jingtao Hou; Wenfeng Tan

doi:10.1016/j.envres.2024.118679

Roles of varying carbon chains and functional groups of legacy and emerging per-/polyfluoroalkyl substances in adsorption on metal-organic framework: Insights into mechanism and adsorption prediction

Environ Res. 2024 Mar 20;251(Pt 2):118679. doi: 10.1016/j.envres.2024.118679. Online ahead of print.

Authors

Hao Guo¹, Tongyu Hu², Xiaoman Yang¹, Zhaoyang Liu³, Qianqian Cui⁴, Chenchen Qu¹, Fayang Guo⁵, Shun Liu⁶, Andrew J Sweetman⁷, Jingtao Hou¹, Wenfeng Tan¹

Affiliations

¹ State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
² Beijing Construction Engineering Environmental Remediation Co., Ltd., Beijing 100101, China.
³ State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: zhaoyangliu@mail.hzau.edu.cn.
⁴ Hubei Geological Survey, Wuhan 430034, China.
⁵ Institute of Resource and Environment, Henan Polytechnic University, Jiaozuo 454000, China.
⁶ The Seventh Geological Brigade of Hubei Geological Bureau, Yichang 443100, China.
⁷ Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.

PMID: 38518904
DOI: 10.1016/j.envres.2024.118679

Abstract

Metal-organic frameworks (MOFs) are promising adsorbents for legacy per-/polyfluoroalkyl substances (PFASs), but they are being replaced by emerging PFASs. The effects of varying carbon chains and functional groups of emerging PFASs on their adsorption behavior on MOFs require attention. This study systematically revealed the structure-adsorption relationships and interaction mechanisms of legacy and emerging PFASs on a typical MOF MIL-101(Cr). It also presented an approach reflecting the average electronegativity of PFAS moieties for adsorption prediction. We demonstrated that short-chain or sulfonate PFASs showed higher adsorption capacities (μmol/g) on MIL-101(Cr) than their long-chain or carboxylate counterparts, respectively. Compared with linear PFASs, their branched isomers were found to exhibit a higher adsorption potential on MIL-101(Cr). In addition, the introduction of ether bond into PFAS molecule (e.g., hexafluoropropylene oxide dimeric acid, GenX) increased the adsorption capacity, while the replacement of CF₂ moieties in PFAS molecule with CH₂ moieties (e.g., 6:2 fluorotelomer sulfonate, 6:2 FTS) caused a decrease in adsorption. Divalent ions (such as Ca²⁺ and SO₄^2-) and solution pH have a greater effect on the adsorption of PFASs containing ether bonds or more CF₂ moieties. PFAS adsorption on MIL-101(Cr) was governed by electrostatic interaction, complexation, hydrogen bonding, π-CF interaction, and π-anion interaction as well as steric effects, which were associated with the molecular electronegativity and chain length of each PFAS. The average electronegativity of individual moieties (named M_e) for each PFAS was estimated and found to show a significantly positive correlation with the corresponding adsorption capacity on MIL-101(Cr). The removal rates of major PFASs in contaminated groundwater by MIL-101(Cr) were also correlated with the corresponding M_e values. These findings will assist with the adsorption prediction for a wide range of PFASs and contribute to tailoring efficient MOF materials.

Keywords: Adsorption prediction; Emerging alternatives; Interaction mechanism; Legacy PFASs; MIL-101(Cr).