Relationship Between Reaction Rate of Perfluorocarboxylic Acid Decomposition at a Plasma–Liquid Interface and Adsorbed Amount

Abstract

SUMMARY Perfluorooctanoic acid (PFOA: C7F15COOH) in water is effectively decomposed by plasma generated at a gas–liquid interface. During the decomposition of PFOA, perfluorocarboxylic acids (PFCAs: normalCnnormalF2n+1 COOH ) with shorter carbon chains (n = 1–6) are generated as by‐products. Since these PFCAs are surfactants, they are adsorb onto the gas–liquid interface and show high surface concentrations. This study investigated the relationship between the adsorbed amount of PFCA and the rate of decomposition by a direct current plasma. The adsorbed amount of PFCA at the gas–liquid interface increased as the length of the carbon chain increased, resulting in a higher rate of decomposition. However, the reaction rate reached saturation at a certain adsorption amount, depending on the discharge current.

Enhancing Interface Reactions by Introducing Microbubbles into a Plasma Treatment Process for Efficient Decomposition of PFOA

“…The value was within analytical variations, confirming that it is not feasible to decompose PFOA only via the free radicals generated by collapsing microbubbles. Previous research has confirmed that in plasma treatment, most of the decomposition of PFOA occurs at the gas–liquid interface. , In our system, MBs form a dense foam layer at the top of the bulk solution phase, about 6 mm in height before the discharge treatment (Figure S5), while the concentration of PFOA in the foam layer was measured to be 71.2 mg/L for a bulk concentration of 30 mg/L, confirming significant PFOA enrichment. A separate test showed that the enrichment ratio increased from 1.5 to 7.6 times when PFOA concentration decreased from 50 to 5 mg/L.…”

Plasma-Based Water Treatment: Efficient Transformation of Perfluoroalkyl Substances in Prepared Solutions and Contaminated Groundwater

“…Unlike other AOPs, however, PWT involves the generation of radicals in situ and does not require significant chemical inputs. Additionally, plasma is capable of producing a broad range of reactive species (OH, O, H, O 3 , H 2 O 2 , e aq ), including strong oxidants and reductants. , Previous attempts have been made to utilize plasma to degrade PFASs; however, these involved the use of inefficient reactor types and DC discharges, which are less efficient than the pulsed discharges used in this study. − …”

Hydrophobic Surface Treatment of Carbon Black Nanoparticles in Isopropyl Alcohol Solution Using He/SF6 Atmospheric Plasma Jet

“…However, for the carbon black treated with the configuration in Figure 2(b), the contact angle increased significantly up to ∼140 with increasing the plasma treatment time to 180 s. When the APPJ is located outside of the carbon black nanoparticle solution, the plasma is difficult to react with the solution, therefore, it generally takes very long time (from tens of minutes to a few hours) for the plasma treatment and tends to modify the material surface hydrophilically by forming OH radicals as investigated by other researchers. [23][24][25][26][27][28][29][30][31][32][33][34] However, when the APPJ is located in the solution, due to more direct reaction of plasma with the solution, the modification of the carbon black nanoparticles was much faster than the plasma treatment at the outside of the solution.…”

“…[19][20][21][22] Therefore, until now, most of the researches on the modification of nanoparticles in the solution using the APPJ treatment have been concentrated in changing the properties of nanoparticles to more hydrophilic in the solvent with the -OH functional groups. [23][24][25][26][27][28][29][30][31][32][33][34] The solvents such as perfluorooctanoic acid, perfluorooctane sulfonate, etc. contain F atoms and tend to modify materials surface to be hydrophobic when they are dissociated by plasmas.…”