Chlorinated Byproduct Formation during the Electrochemical Advanced Oxidation Process at Magnéli Phase Ti4O7 Electrodes
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-08-25 |
| Journal | Environmental Science & Technology |
| Authors | Meng‐Hsuan Lin, Devon Manley Bulman, Christina K. Remucal, Brian P. Chaplin |
| Institutions | University of Wisconsin–Madison, University of Illinois Chicago |
| Citations | 83 |
Abstract
Section titled “Abstract”This research investigated chlorinated byproduct formation at Ti<sub>4</sub>O<sub>7</sub> anodes. Resorcinol was used as a model organic compound representative of reactive phenolic groups in natural organic matter and industrial phenolic contaminants and was oxidized in the presence of NaCl (0-5 mM). Resorcinol mineralization was >68% in the presence and absence of NaCl at 3.1 V/SHE (residence time = 13 s). Results indicated that ∼4.3% of the initial chloride was converted to inorganic byproducts (free Cl<sub>2</sub>, ClO<sub>2</sub><sup>-</sup>, ClO<sub>3</sub><sup>-</sup>) in the absence of resorcinol, and this value decreased to <0.8% in the presence of resorcinol. Perchlorate formation rates from chlorate oxidation were 115-371 mol m<sup>-2</sup> h<sup>-1</sup>, approximately two orders of magnitude lower than reported values for boron-doped diamond anodes. Liquid chromatography-mass spectroscopy detected two chlorinated organic products. Multichlorinated alcohol compounds (C<sub>3</sub>H<sub>2</sub>Cl<sub>4</sub>O and C<sub>3</sub>H<sub>4</sub>Cl<sub>4</sub>O) at 2.5 V/SHE and a monochlorinated phenolic compound (C<sub>8</sub>H<sub>7</sub>O<sub>4</sub>Cl) at 3.1 V/SHE were proposed as possible structures. Density functional theory calculations estimated that the proposed alcohol products were resistant to direct oxidation at 2.5 V/SHE, and the C<sub>8</sub>H<sub>7</sub>O<sub>4</sub>Cl compound was likely a transient intermediate. Chlorinated byproducts should be carefully monitored during electrochemical advanced oxidation processes, and multibarrier treatment approaches are likely necessary to prevent halogenated byproducts in the treated water.