Low power degradation of perfluorooctane sulfonate (PFOS) in water using a nanosecond pulsed atmospheric pressure plasma

Abstract

The prevalence and persistence of perfluoroalkyl substances (PFAS) has led to significant concerns over the damage they can have on human health and the environment, particularly when they contaminate bodies of water. In this work, a plasma driven with high-voltage (20 kV) pulses of varying duration (50-400 ns) and frequency (0.5-10 kHz) is investigated for degrading perfluorooctane sulfonate (PFOS) in water. The concentration of PFOS in solution decreased with repeated passes through the reactor. Increasing the power consumption of the plasma, either by increasing the pulse width or the frequency, improved the rate of PFOS loss but decreased the energy efficiency. For instance, reducing the frequency of the pulse from 10 kHz to 500 Hz decreased the power consumption by over an order of magnitude while requiring about twice as much time to reduce 50% of the PFOS signal. Time-averaged emission spectroscopy showed that increasing the frequency decreased the average electron density of the plasma and while increasing the temperature of the reactor. In constrast, increasing the pulse width from 50 ns to 400 ns did not have a significant impact on the average electron density or the reactor temperature. Infrared (IR) measurements of the reactor indicated that changes in operating conditions caused only modest changes in reactor temperature. Spectroscopy revealed the presence of photons with energies >5 eV were also observed and could contribute to PFOS loss. This work shows that the main factor determining PFOS loss is the contact time between the plasma reactor and the solution, which implies the most energy efficient operating parameters for PFOS degradation comes from minimizing the duration and frequency of the high-voltage pulses to reduce power consumption.

Nanosecond pulsed discharge with plasma-functionalized TiO2 for the high efficiency degradation of tetracycline

“…Reactive species in tetracycline degradation. In the plasma-catalytic degradation system, reactive species that react with tetracycline molecules are induced by the plasma species via plasma-liquid interactions [5,6,9]. Therefore, plasma and liquid-phase active species are determined to investigate the mechanism of the tetracycline degradation by the NPG-LD coupled with catalysts.…”

“…Recently, nonthermal plasma has been considered as an efficient and eco-friendly approach for water treatment [2][3][4]. During the plasma-water interactions, free electrons with high energy and strong oxidizing species are produced at the gas-liquid interface, which then induces further liquid-phase reactions and results in the removal of organic pollutants [3,5,6]. To achieve a better degradation performance, some efforts have been attempted to increase the concentration of aqueous species by optimizing the plasma characteristics, forming microbubbles in the solution, and combining with a catalyst [6][7][8][9][10].…”

The role of helicity in PFAS resistance to degradation: DFT simulation of electron capture and defluorination

“…One set of techniques for the degradation of dilute PFAS in water is via the capture of hydrated electrons, e aq À . The sources of electrons vary and include the use of electrodes, 25 plasmas, [26][27][28][29] photochemical interactions with electron donors, [30][31][32][33] or radiolysis of the water. [34][35][36] As a recent review comprehensively covers, theoretical studies to elucidate the defluorination mechanisms complement the experimental work although identification of the elementary steps on the reaction pathway remains as recalcitrant as the molecules themselves.…”

“…One set of techniques for the degradation of dilute PFAS in water is via the capture of hydrated electrons, e aq − . The sources of electrons vary and include the use of electrodes, 25 plasmas, 26–29 photochemical interactions with electron donors, 30–33 or radiolysis of the water. 34–36…”

Effects of Non-Thermal Plasma on the Transition from Nano-Crystalline to Amorphous Structure in Water and Subsequent Effects on Viscosity

“…The non-equilibrium nature of non-thermal plasma can produce very high concentrations of chemically active species while keeping bulk temperatures as low as room temperature. These characteristics aid its use in material processing, for pollutant treatments, in biomedical applications, medicine, space craft sterilization, hydrogen sulfide mitigation, PFAS mitigation, agricultural applications, and beyond [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”