Tannic acid-Fe complex derivative-modified electrode with pH regulating function for environmental remediation by electro-Fenton process

• Published in: Environmental research Vol. 204; no. Pt A; p. 111994
• Main Authors: Li, Yang, Lin, Ruoyun, Lv, Fangjie, Zhao, Xiaoyu, Yong, Tianzhi, Zuo, Xiaojun
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01-03-2022
• Subjects: Carbon felt cathode; Electro-Fenton; Electrodes; Environmental Restoration and Remediation; Ferric Compounds; Heterogeneous catalyst; Hydrogen Peroxide; Hydrogen-Ion Concentration; Oxidation-Reduction; pH regulator; Refractory organic pollutants; Tannins; Water Pollutants, Chemical - analysis; pH regulator; Heterogeneous catalyst; Electro-Fenton; Carbon felt cathode; Refractory organic pollutants
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2021.111994

A heterogeneous electro-Fenton (hetero-EF) system can effectively broaden the applicable pH range, although the decreased electrogeneration efficiency of H2O2 at elevated pH (especially neutral conditions) is unfavorable for the efficient removal of organic pollutants. Herein, a tannic acid-Fe complex derivative-modified carbon felt (TFD@CF) cathode was prepared for hetero-EF treatment of organic pollutants over a wide pH range. Interestingly, the as-prepared hetero-EF cathode could act as a pH regulator that acidified the solution over a wide pH range. As expected, the TFD@CF cathode exhibited excellent hetero-EF activity for the removal of diverse organic pollutants (such as methyl orange, methylene blue, sulfamerazine, bisphenol A and 2,4-dichlorophenoxyacetic acid) at neutral and even alkaline pH (removal efficiency >90 %). A total of 2.98 kWh kg−1 COD−1 with 83.2 % COD removal could be achieved by the TFD@CF cathode for the treatment of actual textile dyeing secondary wastewater. Electrochemical characterizations proved that the TFD@CF cathode had excellent electrochemical properties with improved electron transfer ability and a well-pronounced Fe(III) electroreductive response. Meanwhile, more acidic groups were newly generated during the electrochemical reaction (an increase of 30.1 %), thus dissociating more H+ into solution. The identification of reactive oxygen species suggested that OH and 1O2 could be responsible for the removal of organic pollutants in the TFD@CF EF system. These interesting findings may provide new insights into the design of multifunctional hetero-EF cathodes for the removal of refractory organic pollutants.
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•TFD@CF cathode was successfully prepared for hetero-EF treatment.•TFD@CF cathode could act as pH regulator to broaden the applicable pH range.•The hetero-EF activity of TFD@CF cathode was proved satisfactory at pH of 3–9.•TFD@CF cathode exhibited improved electron transfer ability compared with raw CF.•OH and 1O2 were the dominant reactive oxygen species in TFD@CF hetero-EF system.