期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 -, 期 -, 页码 -出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.2c09237
关键词
Electro-oxidation; electro-synthesis; ferrate; ozone; boron-doped diamond; nickel-doped antimony tin oxide
Difficulties arise in applying conventional water treatment technologies to small and remote systems due to economic scale and practicability issues. Electro-oxidation (EO) emerges as a promising oxidation technology for these applications, degrading contaminants through direct, advanced, and/or electrosynthesized oxidant-mediated reactions. Ferrates, particularly Fe(VI)/(V)/(IV), are of interest and recently their circumneutral synthesis has been demonstrated using boron-doped diamond (BDD) electrodes. This study investigates ferrate synthesis using various high oxygen overpotential (HOP) electrodes (BDD, NAT/Ni-Sb-SnO2, and AT/Sb-SnO2).
Difficulties arise related to the economy-of-scale and practicability in applying conventional water treatment technologies to small and remote systems. A promising oxidation technology better suited for these applications is that of electro-oxidation (EO), whereby contaminants are degraded via direct, advanced, and/or electrosynthesized oxidant-mediated reactions. One species of oxidants of particular interest includes ferrates (Fe(VI)/(V)/ (IV)), where only recently has their circumneutral synthesis been demonstrated, using high oxygen overpotential (HOP) electrodes, namely boron-doped diamond (BDD). In this study, the generation of ferrates using various HOP electrodes (BDD, NAT/Ni-Sb- SnO2, and AT/Sb-SnO2) was investigated. Ferrate synthesis was pursued in a current density range of 5-15 mA cm-2 and initial Fe3+ concentrations of 10-15 mM. Faradaic efficiencies ranged from 11-23%, depending on operating conditions, with BDD and NAT significantly outperforming AT electrodes. Speciation tests revealed that NAT synthesizes both ferrate(IV/V) and ferrate(VI), while the BDD and AT electrodes synthesized only ferrate(IV/V) species. A number of organic scavenger probes were used to test the relative reactivity, including nitrobenzene, carbamazepine, and fluconazole, whereby ferrate(IV/V) was significantly more oxidative than ferrate(VI). Finally, the ferrate(VI) synthesis mechanism by NAT electrolysis was elucidated, where coproduction of ozone was found to be a key phenomenon for Fe3+ oxidation to ferrate(VI).
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