Direct electron transfer mediated electrochemical activation of persulfates by reticulated vitreous carbon (RVC) cathode

• Published in: Journal of environmental chemical engineering Vol. 12; no. 5; p. 113416
• Main Authors: Liu, Zhongda, Kajtazi, Ardiana, Lynen, Frédéric, Askari, Najmeh, Dewil, Raf, Ladas, Spyridon, Kyriakou, Georgios, Katsaounis, Alexandros
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-10-2024
• Subjects: Acid orange 7; Electrochemical activation; H2O2 generation; Peroxymonosulfate; Reticulated vitreous carbon; Acid orange 7; Peroxymonosulfate; Reticulated vitreous carbon; H2O2 generation; Electrochemical activation
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2024.113416

The electrochemical activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) for pollutant degradation has gained increasing attention. In this work, reticulated vitreous carbon (RVC) electrodes were prepared at a low cost and investigated for the cathodic activation of PMS/PDS for Acid Orange 7 degradation. The RVC was characterized by SEM, TGA, XRD, Raman spectroscopy, XPS, EIS, and compression test. The superior activity outperformed previous reports in terms of low current density operation (1–10 mA/cm2), high degradation rates (0.13–0.49 min−1), low energy consumption (0.03–0.23 kWh/m3/order) without involvement of catalysts. The process was optimized for current density, PMS dosage, pollutant concentration, pH, water matrix, and supporting electrolyte. Under the optimal current density (3 mA/cm2), the addition of 0.5 mM of PMS boosted the degradation rate by 9.6 times to 0.4470 min−1 and reduced the electrical energy consumption by 90.1 % to 0.0243 kWh/m3/order in 50 mM of Na2SO4. Moreover, up to 117 mg/L of H2O2 was produced in 1 hour by the reduction of oxygen, with current efficiencies between 78–24 %. The process showed little deterioration in 10 cycles, worked for a variety of pollutants, and was not affected by the water matrix. The H-cell experiments confirmed that 90 % degradation took place on the cathode. Scavenging experiments and electrochemical tests suggested that the transitional state of PMS* and O2•− mediated the direct electron transfer mechanism for AO7 degradation. Eighteen degradation products were identified by HPLC-MS and categorized into 4 degradation pathways. Finally, their toxicity was assessed by the ECOSAR programme.
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•Low-cost electrochemical activation of persulfates was achieved with RVC cathode.•The transition state PMS* and O2•− mediated a direct electron transfer mechanism for AO7 degradation.•A small dosage of PMS (0.5 mM) enhanced the degradation by 9.6 times with 10 % energy consumption.•PMS addition altered the formation of degradation products and lowered the toxicity.•The process showed high durability and wide applicability for diverse pollutants.