Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor

Abstract

“High-concentration” and “low-concentration” bench-scale batch plasma reactors were used to effectively degrade per- and polyfluoroalkyl substances (PFAS) at a high concentration (∼100 mg/L) and a low concentration (<1 μg/L), respectively, in ion exchange (IX) regenerant still bottom (SB) solutions. In the SBs, numerous PFAS were detected with a wide concentration range (∼0.01 to 100 mg/L; total oxidizable precursors (TOP) ∼4000 to 10000 mg/L). In the “high-concentration” plasma reactor, the concentrations of PFAS precursors and long-chain perfluoroalkyl acids (PFAAs) (≥6C for PFSAs and ≥8C for perfluorocarboxylic acids (PFCAs)) were decreased by >99.9% in 2 h, and short-chain PFAAs (<6C for perfluorocarboxylic acids (PFSAs) and <8C PFCAs) were decreased by >99% in 6 h of treatment. Subsequently, a “low concentration” plasma reactor was used to remove additional PFAAs. In this reactor, the addition of CTAB (cetrimonium bromide, a cationic surfactant) caused short-chain PFAAs, other than PFBA, to be removed to below detection limits in 90 min of treatment time. Overall, >99% of the TOP present in SBs was removed during the treatment. Fluorine recovery of 47 to 117% was obtained in six SB samples. Energy requirement (EE/O) for the treatment of PFOA and PFOS from SBs ranged from 380 to 830 kWh/m3.

Defluorination of Omega-Hydroperfluorocarboxylates (ω-HPFCAs): Distinct Reactivities from Perfluoro and Fluorotelomeric Carboxylates

“…Since hydrodefluorination cannot be avoided during UV/sulfite treatment, an oxidative post-treatment is usually required to cleave the remaining C–F bonds in H-rich residues. These mechanistic insights will benefit the development and understanding of PFAS treatment technologies such as photochemical degradation in homogeneous − and heterogeneous systems, − electrochemical degradation, − and plasma treatment, − where reductive and/or oxidative processes are involved. The HO • oxidation results also provide data to compare with similar reaction systems , and achieve a deeper mechanistic understanding.…”

Occurrence and removal of poly/perfluoroalkyl substances (PFAS) in municipal and industrial wastewater treatment plants

“…To degrade additional PFAAs, another plasma reactor was used for low concentrations. In this reactor, the authors added a cationic surfactant (cetrimonium bromide) which promoted the removal of short-chain PFAAs (below detection limits) in 1.5 h. Overall, .99% of PFAS from wastewater was removed during the treatment with corresponding fluorine recoveries of 47%-117% (Singh et al 2020b).…”

Near-Quantitative Defluorination of Perfluorinated and Fluorotelomer Carboxylates and Sulfonates with Integrated Oxidation and Reduction

“…The adverse health effects of long-chain PFAS have prompted a phase-out of C8-based chemicals and a shift toward short-chain alternatives. − A large variety of PFAS with various fluoroalkyl chain lengths and functional groups has been detected in the water environment worldwide. − Although carbon adsorption, ion exchange, and nanofiltration can rapidly remove PFAS from polluted water, − the concentrated PFAS in spent sorbents or membrane rejects require cost-effective destruction. Various PFAS destruction technologies have been under rapid development, such as wet oxidation, , plasma, , electrochemical, − photochemical, , and sonochemical , approaches. Most technologies utilize strong oxidative species (e.g., hydroxyl radical HO•, sulfate radical SO 4 – •, and semiconductor hole) and/or reductive species (e.g., hydrated electron e aq – ).…”

“…4−9 Although carbon adsorption, ion exchange, and nanofiltration can rapidly remove PFAS from polluted water, 10−13 the concentrated PFAS in spent sorbents or membrane rejects require cost-effective destruction. Various PFAS destruction technologies have been under rapid development, such as wet oxidation, 14,15 plasma, 16,17 electrochemical, 18−20 photochemical, 21,22 and sonochemical 23,24 approaches. Most technologies utilize strong oxidative species (e.g., hydroxyl radical HO•, sulfate radical SO 4 − •, and semiconductor hole) and/or reductive species (e.g., hydrated electron e aq − ).…”