Efficient Removal of Per- and Polyfluoroalkyl Substances from Water with Zirconium-Based Metal–Organic Frameworks

Abstract

Per-and polyfluoroalkyl substances (PFASs) are an emerging class of contaminants raising increased levels of concern due to their toxic, bioaccumulative, and persistent nature. Current solutions for removing PFAS from contaminated water rely on adsorption-based methods where commonly used sorbents, for example, activated carbons and ion-exchange resins, exhibit low adsorption capacity and a long equilibration time. Motivated by the generally deficient performance of these current materials, this work addresses the need for the discovery of advanced sorbents for high capacity and efficient PFAS removal. The zirconium-based metal−organic framework (MOF) NU-1000 was characterized for the adsorption of three perfluorosulfonic acids (PFSAs, C4−C8) and six perfluorinated carboxylic acids (PFCAs, C1−C9) from aqueous solutions. The results indicate that NU-1000 exhibits outstanding adsorption capacities of 400−620 mg/g for PFSAs and 201−604 mg/g for PFCAs coupled with ultrafast adsorption kinetics featuring equilibrium times of <1 min. Complementary density functional theory calculations reveal that the PFAS@MOF adsorption mechanism is dominated by a combination of hydrogen bonding, electrostatic, and hydrophobic non-covalent PFAS−MOF interactions. Excellent regeneration and reusability characteristics were found, particularly nearly quantitative removal and recovery rates of NU-1000 after five consecutive adsoption and desorption cycles of PFAS. Additional adsorption testing using PFAS-contaminated groundwater samples obtained from U.S. Air Force bases revealed impressive PFAS removal rates of 75−98% within 10 min regardless of the presence of co-contaminants. To the best of our knowledge, the suite of herein presented PFAS sorption characteristicscapacity, kinetics, regeneration, and reusabilitysignificantly outperforms other current sorbents, rendering NU-1000 as a promising platform for the rapid and effective removal of PFAS from aqueous media.

Installation of synergistic binding sites onto porous organic polymers for efficient removal of perfluorooctanoic acid

“…This corresponds to the capture of 1.75 PFOA per NDMB group in PAF-1-NDMB (consisting of 0.79 NDMB in 1 g PAF-1-NDMB as illustrated above), thereby implying the great accessibility of PAF-1-NDMB for PFOA. As far as we know, the maximum uptake capacity of PAF-1-NDMB is unprecedented among all adsorbent materials reported thus far for PFOA adsorption, including NU-1000 (507 mg g −1 ) 10 , DFB-CDP (33 mg g −1 ) 16 , MIL-101 (Cr) (460 mg g −1 ) 20 , MWNTs (140 mg g −1 ) 51 , FCX4-P (188.7 mg g −1 ) 52 , UiO-67 (700 mg g −1 ) 53 , AC (52.8 mg g −1 ) 54 , all-silica Beta (β) (371 mg g −1 ) 55 , resins (1500 mg g −1 ) 23 , 56 . Although the PAF-1-NDMB exhibited a BET surface area of only 108 m 2 g −1 , it demonstrated a superior uptake capacity due to the efficacious functionalization.…”

“…Among various technologies used for PFAS removal from contaminated water such as oxidative 6 , UV irradiation 7 , sonochemical 8 , and electrochemical methods 9 , adsorption is highly favored owing to its simplicity and high efficiency in the purification process of contaminated water 10 . Thus, a wide range of adsorbents have been investigated for PFAS elimination from polluted waters.…”

Influence of Defects and Linker Exchange on Removal of Phosphate Using MOFs with the Node Structure M6(OH)4(O)4 for M = Hf, Zr, or Ce

“…Well known in this class are UiO-66, DUT-69, NU-1000, and MOF-808, among others. ,, These MOFs contain a variety of topologies, metal analogues, coordinating ligands, and connectivity, resulting in a broad range of chemical and physical properties. Experimental studies have shown their successful utilization for usage in various applications, − such as those previously mentioned. However, a complete theoretical description of the processes involved in these applications is an active area of research, which can be utilized to design the next-generation MOF-based technologies with higher efficiency.…”

Systematic Study on the Removal of Per- and Polyfluoroalkyl Substances from Contaminated Groundwater Using Metal–Organic Frameworks

“…Metal–organic frameworks (MOFs) are porous, crystalline materials composed of inorganic nodes and organic linkers that assemble into multidimensional lattices through coordination bonds. − The unique characteristics of MOFs such as ultra-high surface areas and pore volumes combined with their structural tunability render them as promising candidates for the adsorption and/or separation of small molecules. − Rapid adsorption kinetics are commonly found within such applications, making MOFs particularly promising candidate materials for water remediation. For example, MOFs have been proven to be effective in removing a wide range of pollutants from water including heavy metals, dyes, and pharmaceuticals. ,, However, the application of MOFs for PFAS removal is underexplored . The few existing PFAS@MOF studies focus on the adsorption of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), two well-known long-chain perfluoroalkyl acids (PFAA), but the performance of MOFs on short-chain PFAS is unclear. − Furthermore, there are nearly 5000 different types of PFAS and the role of their charge state, chain length, and head group functionality on the adsorption behavior using MOFs is largely unknown.…”