Reactive Nitrogen Species Generated by Gas–Liquid Dielectric Barrier Discharge for Efficient Degradation of Perfluorooctanoic Acid from Water

Abstract

Perfluorooctanoic acid (PFOA) poses a serious threat to the ecological environment and biological health because of its ubiquitous distribution, extreme persistence, and high toxicity. In this study, we designed a novel gas–liquid dielectric barrier discharge (GLDBD) reactor which could efficiently destruct PFOA. PFOA removal efficiencies can be obtained in various water matrices, which were higher than 98.0% within 50 min, with energy yields higher than 114.5 mg·kWh–1. It was confirmed that the reactive species including e–, ONOOH, •NO2, and hydroxyl radicals (•OH) were responsible for PFOA removal. Especially, this study first revealed the crucial role of reactive nitrogen species (RNS) for PFOA degradation in the plasma system. Due to the generation of a large amount of RNS, the designed GLDBD reactor proved to be less sensitive to various water matrices, which meant a broader promising practical application. Moreover, influential factors including high concentration of various ions and humic acid (HA), were investigated. The possible PFOA degradation pathways were proposed based on liquid chromatograph–mass spectrometer (LC-MS) results and density functional theory (DFT) calculation, which further confirmed the feasibility of PFOA removal with RNS. This research, therefore, provides an effective and versatile alternative for PFOA removal from various water matrices.

Electrosorption, Desorption, and Oxidation of Perfluoroalkyl Carboxylic Acids (PFCAs) via MXene-Based Electrocatalytic Membranes

“…Then, C 7 F 15 O • is subdivided into the C 6 F 13 • radical and COF 2 ; COF 2 could rapidly react with water to finally form CO 2 and HF. By this continuous repeating CF 2 -unzipping cycle, the chain scission defluorination process eventually converts PFOA to H 2 O, CO 2 , and HF. , Most importantly, the pathway of Ti 3 C 2 O 2 is the most favorable among the three different models, which also indicates that the O-terminated surface is much more effective than Cl- and F-terminated surfaces.…”

Degradation of Perfluorooctanoic Acid by Chlorine Radical Triggered Electrochemical Oxidation System

“…In the absence of R·, Δ G was 693.34 kJ mol –1 , which was consistent with the results of Zhu et al. (694.88 kJ mol –1 ) . Therefore, it was difficult to initiate the degradation of PFOA without R·.…”

“…Excitingly, the Cl· mediated generation of C 7 F 15 COO· achieved the lowest Δ G (65.57 kJ mol –1 ), much lower than that of ·OH. It has been reported that SO 4 •– and NO 2 · can degrade PFOA with additional energy input such as light or heat. − The DFT calculations showed that the Δ G values for SO 4 •– (93.07 kJ mol –1 ) and NO 2 · (173.10 kJ mol –1 ) were higher than that of Cl·. Furthermore, the Δ G ‡ of a single electron transfer reaction was obtained according to the Marcus theory.…”

“…In the absence of R•, ΔG was 693.34 kJ mol −1 , which was consistent with the results of Zhu et al (694.88 kJ mol −1 ). 74 Therefore, it was difficult to initiate the degradation of PFOA without R•. According to Figure 4 and Table S9 (SI), the reaction between ClO• and C 7 F 15 COO − had the highest ΔG (169.29 kJ mol −1 ), with the reaction between •OH and C 7 F 15 COO − having the second highest ΔG (162.65 kJ mol −1 ).…”

Emerging investigator series: contributions of reactive nitrogen species to transformations of organic compounds in water: a critical review

“…However, ferulic acid, which reacts with ˙NO 2 with a rate constant of 7.4 × 10 8 M −1 s −1 and with ˙OH with a rate constant of approximately 10 10 M −1 s −1 , 57 has been used as a ˙OH and ˙NO 2 scavenger in a handful of studies probing the role of ˙NO 2 in contaminant transformation. 58–60 Flavanone, which acts as a radical scavenger in the human body, has been used as a scavenger in experiments assessing the role of ˙NO, 61 although flavonoids also react with ˙OH. 62 While scavengers can provide evidence for a role of RNS by inhibiting RNS reactions, quantifying the roles of ˙OH and RNS in organic compound transformation requires estimates of steady-state reactive intermediate concentrations.…”