Issue 9, 2020

Advanced electrochemical oxidation for the simultaneous removal of manganese and generation of permanganate oxidant

Abstract

Emerging electrochemical systems, such as advanced electro-oxidation, provide a potentially powerful alternative to conventional oxidation processes which can often be unsuitable for small, remote and decentralised system applications. The one electro-oxidation process, which may be well suited for these applications, is the use of high oxygen overpotential boron-doped diamond (BDD) electrodes, as a pre-oxidation step for the removal of various raw water contaminants. While BDD electro-oxidation has been studied extensively for the abatement of organic micropollutants, its application as a pre-oxidation technology for the removal of soluble manganese (Mn2+) in source waters for drinking water supply, has not been reported to-date. In this study, we summarise the results of tests using a bench-scale electro-oxidation system and synthetic Mn2+ solutions in order to consider the simultaneous removal of manganese and the generation of permanganate. The results showed that total manganese was reduced by 9.1, 38.7 and 57.4% at current densities of 10, 40 and 80 mA cm−2, respectively, with an initial Mn2+ concentration of 39 μM. Increased Mn removal at higher current density was attributed to increased generation of, and reaction with, hydroxyl radicals, indicated by a direct proportional relationship between pseudo-first order reaction rate constants for methanol (˙OH radical scavenger) and current density. A mathematical model was developed to describe Mn removal under mass transport limitations, and was found to correlate well with experimental data. Finally, a completely novel synthesis pathway for the generation of permanganate species (Mn7+) is presented, whereby concentrations up to 0.9 μM were synthesised from Mn2+ in circumneutral conditions.

Graphical abstract: Advanced electrochemical oxidation for the simultaneous removal of manganese and generation of permanganate oxidant

Supplementary files

Article information

Article type
Paper
Submitted
22 mar 2020
Accepted
09 jul 2020
First published
10 jul 2020
This article is Open Access
Creative Commons BY-NC license

Environ. Sci.: Water Res. Technol., 2020,6, 2405-2415

Advanced electrochemical oxidation for the simultaneous removal of manganese and generation of permanganate oxidant

S. T. McBeath, D. P. Wilkinson and N. J. D. Graham, Environ. Sci.: Water Res. Technol., 2020, 6, 2405 DOI: 10.1039/D0EW00261E

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