Cooperative Molecular Interaction-Based Highly Efficient Capturing of Ultrashort- and Short-Chain Emerging Per- and Polyfluoroalkyl Substances Using Multifunctional Nanoadsorbents

Abstract

The short-chain (C₄ to C₇) and ultrashort-chain (C₃ to C₂) per- and polyfluoroalkyl substances (PFAS) are bioaccumulative, carcinogenic to humans, and harder to remove using current technologies, which are often detected in drinking and environmental water samples. Herein, we report the development of nonafluorobutanesulfonyl (NFBS) and polyethylene-imine (PEI)-conjugated Fe₃O₄ magnetic nanoparticle-based magnetic nanoadsorbents and demonstrated that the novel adsorbent has the capability for highly efficient removal of six different short- and ultrashort-chain PFAS from drinking and environmental water samples. Reported experimental data indicates that by capitalizing the cooperative hydrophobic, fluorophilic, and electrostatic interaction processes, NFBS-PEI-conjugated magnetic nanoadsorbents can remove ∼100% short-chain perfluorobutanesulfonic acid within 30 min from the water sample with a maximum absorption capacity q _m of ∼234 mg g^-1. Furthermore, to show how cooperative interactions are necessary for effective capturing of ultrashort and short PFAS, a comparative study has been performed using PEI-attached magnetic nanoadsorbents without NFBS and acid-functionalized magnetic nanoadsorbents without PEI and NFBS. Reported data show that the ultrashort-chain perfluoropropanesulfonic acid capture efficiency is the highest for the NFBS-PEI-attached nanoadsorbent (q _m ∼ 187 mg g^-1) in comparison to the PEI-attached nanoadsorbent (q _m ∼ 119 mg g^-1) or carboxylic acid-attached nanoadsorbent (q _m ∼ 52 mg g^-1). In addition, the role of cooperative molecular interactions in highly efficient removal of ultrashort-chain PFAS has been analyzed in detail. Moreover, reported data demonstrate that nanoadsorbents can be used for effective removal of short-chain PFAS (<92%) and ultrashort-chain PFAS (<70%) simultaneously from reservoir, lake, tape, and river water samples within 30 min, which shows the potential of nanoadsorbents for real-life PFAS remediation.

Figure 1

(A–C) Scheme showing the synthetic process that we have used for the development of nonafluoro-butanesulfonyl (NFBS) and polyethylene imine (PEI)-conjugated Fe₃O₄ magnetic nanoparticle-based multifunctional magnetic nanoadsorbents. (D) Scheme showing the use of magnetic nanoadsorbents for the separation of short-chain and ultrashort-chain PFAS from water.

Figure 2

(A) TEM image from PEI-functionalized Fe₃O₄ magnetic nanoparticles. (B) SEM image from NFBS and PEI-conjugated magnetic nanoadsorbents. (C) Energy-dispersive X-ray spectroscopy (EDX) mapping data from nanoadsorbents. (D) EDX analysis showing particle constituents in nanoadsorbents. (E) XPS spectrum from the nanoadsorbent. (F) Picture showing that the nanoadsorbents can be used for the separation of emerging and legacy PFAS from water samples using a small bar magnet. (G) FTIR spectra from the nanoadsorbent. (H) X-ray diffraction (XRD) analysis from the nanoadsorbent. (I) Magnetic curve from the nanoadsorbent.

Figure 3

(A) Removal efficiency for short- and ultrashort-chain PFAS (1 μg/L) from drinking water using the NFBS and PEI-attached magnetic nanoadsorbent (1 mg/L). (B) Plot showing the time-dependent removal efficiency for short-chain PFAS using the nanoadsorbent. (C) Plot showing the time-dependent removal efficiency for short-chain PFBS from drinking water using different nanoadsorbents. (D) Plot showing how t/q_t varies with time for PFBS removal from drinking water. (E) Plot showing how 1/q_e varies with 1/C_e for PFBS removal from drinking water. (F) Plot showing the time-dependent removal efficiency for PFNA, PFPrS, and NFA using the nanoadsorbent. (G) Removal efficiency for short- and ultrashort-chain PFAS (1 μg/L) from drinking water using the PEI-attached magnetic nanoadsorbent (1 mg/L). (H) Removal efficiency for short- and ultrashort-chain PFAS (1 μg/L) from drinking water using the carboxy-attached magnetic nanoadsorbent (1 mg/L). (I) Plot showing pH-dependent PFBS removal efficiency using the nanoadsorbent.

Figure 4

(A) Removal efficiency for ultrashort-chain PFPrS (1 μg/L), atenolol (1 μg/L), and metformin (1 μg/L) from drinking water using the nanoadsorbent (1 mg/L). (B) Removal efficiency for short-chain PFBS (1 μg/L), aproxen (1 μg/L), and caffeine (1 μg/L) from drinking water using the nanoadsorbent (1 mg/L). (C) Removal efficiency for short-chain PFHxS (1 μg/L), diphenhydramine (1 μg/L), and oxytetracycline (1 μg/L) from drinking water using the nanoadsorbent (1 mg/L).

Figure 5

Removal efficiency of the nanoadsorbent (1 mg/L) for short- and ultrashort-chain PFAS samples prepared with water from different sources (Ross Barnett Reservoir water, tap water, Grenada lake water, and Mississippi River wa). (A) 1 μg/L emerging short-chain PFBS. (B) 1 μg/L short-chain PFHxS. (C) 1 μg/L ultrashort-chain PFPrS. (D) Mixture of 0.5 μg/L each of the short-chain PFBS and PFHxS. (E) Mixture of 0.5 μg/L of each of the ultrashort-chain PFPrS and TFA. (F) Mixture of 0.33 μg/L of each of the emerging PFBS, PFHxS, and GenX.