Extremely efficient electrochemical degradation of organic pollutants with co-generation of hydroxyl and sulfate radicals on Blue-TiO2 nanotubes anode

• Published in: Applied catalysis. B, Environmental Vol. 257; p. 117902
• Main Authors: Cai, Jingju, Zhou, Minghua, Pan, Yuwei, Du, Xuedong, Lu, Xiaoye
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-11-2019; Elsevier BV
• Subjects: Anode effect; Anodizing; Boron-doped diamond; Chemical oxygen demand; Chemical reduction; Cogeneration; Contaminants; Current density; Electrochemical advanced oxidation processes; Electrochemical oxidation; Electrochemistry; Electrode materials; Energy consumption; Environmental degradation; Formic acid; Free radicals; Hydroxyl radical and sulfate radical; Hydroxyl radicals; Intermediates; Low currents; Nanotechnology; Nanotubes; Organic wastes; Oxidation; pH effects; Phenol degradation; Phenols; Pollutants; Sodium sulfate; TiO2nanotubes; Titanium dioxide; Wastewater treatment; X ray photoelectron spectroscopy; Hydroxyl radical and sulfate radical; TiO2nanotubes; Electrochemical advanced oxidation processes; Phenol degradation; Boron-doped diamond
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2019.117902

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•First prepared in formic acid, Blue-TNA had a better radical production activity than BDD.•Compared with BDD, Blue-TNA had a higher COD and TOC removal and a lower energy consumption.•Current, initial pH and Na2SO4 influenced the contribution of •OH and SO4•− to degradation.•Blue-TNA anode was stable in pollutants removal and could be regenerated easily.•Blue-TNA anode was promising and cost-effective for organic pollutants degradation.
Efficient anode materials are essential to electrochemical advanced oxidation processes (EAOPs) for organic wastewater treatment. In this regard, blue TiO2 nanotube arrays (Blue-TNA) anode was prepared for the first time in formic acid electrolyte by electrochemical self-doping and applied for electrochemical degradation of contaminants. Characterized by XPS, Raman and Mott-Schottky curves, the formation of Ti3+ on Blue-TNA was confirmed. This anode was more efficient and had a higher hydroxyl radical production activity (1.7 × 10−14 M) than BDD (9.8 × 10-15 M), inducing a higher TOC and COD removal of 100 mg/L phenol with a lower energy consumption of 9.9 kW h/(kg COD) at current density 2.5 mA/cm2, pH 5 in 0.1 M Na2SO4, account for the lower accumulation of degradation intermediates. Both •OH and SO4•- were responsible for the degradation on Blue-TNA anode, while their contributions differed greatly with that of BDD, and could be affected and regulated by the operating parameters like current density, initial pH and Na2SO4 concentration. Blue-TNA anode represented a relative stable performance for 5 cycles degradation of 100 mg/L phenol for each cycle of 300 min, and such an oxidation capacity could be easily regenerated by electrochemical reduction in formic acid. Blue-TNA anode had an excellent performance on the TOC removal and MCE especially at low current density of 2.5 mA/cm2 when compared with other anodes. Therefore, Blue-TNA anode is hopeful a promising and cost-effective anode for electrochemical oxidation.