Removal of Zwitterionic PFAS by MXenes: Comparisons with Anionic, Nonionic, and PFAS-Specific Resins

Abstract

Zwitterionic per- and polyfluoroalkyl substances are increasingly detected in aquatic environments. The magnitude of their concentration and increased frequency of detection worldwide raise questions on their presence in drinking water and associated health risk. Scientific knowledge on the identification of treatment technologies to effectively capture such zwitterionic PFAS from contaminated water sources remains largely unknown. In this study, we investigated the application of anionic organic scavenger ion exchange (IX) resins (A860), nonionic IX resins (XAD 4 and XAD 7), PFAS-specific resins (A694 and A592), and Ti3C2 MXenes (novel two-dimensional metal carbides) for the removal of select fluorotelomer zwitterionic PFAS from natural waters. The cumulative removal of zwitterionic PFAS at pH ∼ 7 follows the order: Ti3C2 MXenes > A694 > A592 > A860 > XAD 4 ∼ XAD 7. Ti3C2 MXenes were able to capture >75% of the total influent zwitterionic PFAS and the performance remained consistent in natural and synthetic water. Ti3C2 MXenes also exhibited efficient regeneration (>90% recovery) with 0.4 M Na2SO3 solution, while the regeneration efficacy of other IX resins generally remained below 20%. Treatment with ∼180 J/cm2 UV dosage in the 0.4 M Na2SO3 regenerant brine solution yielded >99.9% reduction in the zwitterionic PFAS concentration indicating that UV–sulfite systems exhibit promising potential for the treatment of zwitterionic PFAS concentrates.

Thermal Phase Transition and Rapid Degradation of Forever Chemicals (PFAS) in Spent Media Using Induction Heating

“…PFASs generally resist degradation, posing considerable challenges to established water treatment and waste disposal practices. The removal and degradation of PFASs from water can be achieved by various approaches, such as photocatalytic degradation, − reductive defluorination, − enhanced adsorption, − electrochemical approaches, − supercritical water oxidation, − plasma , and nonthermal plasma, , and hydrothermal methods assisted with base − and aprotic solvents . However, much fewer options are available to handle solid materials containing PFASs. , In this study, we have demonstrated that the innovative approach of induction heating can significantly degrade PFASs in spent media within a short period.…”

Sources, Fate, and Detection of Dust-Associated Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS): A Review

“…Similarly, high-performance or ultra-high-performance liquid chromatography (HPLC or UHPLC) was also employed by many researchers, as shown in Table 3. In terms of mass spectrometry, the most commonly reported spectrometers for PFAS also included triple quadrupole (QqQ), quadrupole time-of-flight (QTOF), and quadrupole-orbitrap in positive or negative electrospray ionization (ESI) modes [86][87][88][89]. Typically for atmospheric or dust samples, gas chromatography mass spectrometry (GCMS) equipped with electron impact (EI) [38], electron capture negative ion (ECNI) [90], and mass selector detector (MSD) [91] have been used by researchers.…”

Thinking green with 2-D and 3-D MXenes: Environment friendly synthesis and industrial scale applications and global impact

“…This new family of 2D materials known as MXenes are derived from selective etching of their precursor MAX phase, realizing unique characteristics as a result of quantum confined electrons [11]. Despite being in their infancy, MXenes have gained explosive attention among researchers of almost all genres, namely microelectronics [12], tribology [13], battery electrodes [14], conductive inks [15], biomedicine [16,17] and solar thermal desalination [18,19]. Often regarded as 'wonder materials' MXenes are flexible, miniaturized, optically transparent layered structures with the chemical formula M n+1 X n T 2 where M denotes early transition metals, X is a carbon and/or nitrogen, and T is a surface termination functional group [20][21][22][23].…”