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Towards sustainable chlorate production: The effect of permanganate addition on current efficiency
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
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2018 (English)In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 182, p. 529-537Article in journal (Refereed) Published
Abstract [en]

Sodium dichromate is an essential solution additive for the electrocatalytic production of sodium chlorate, assuring selective hydrogen evolution. Unfortunately, the serious environmental and health concerns related to hexavalent chromium mean there is an urgent need to find an alternative solution to achieve the required selectivity. In this study sodium permanganate is evaluated as a possible alternative to chromate, with positive results. The permanganate additive is stable in hypochlorite-containing solutions, and during electrolysis a thin film is reductively deposited on the cathode. The deposit is identified as amorphous manganese oxide by Raman spectroscopic and X-ray diffraction studies. Using different electrochemical techniques (potentiodynamic measurements, galvanostatic polarization curves) we demonstrate that the reduction of hypochlorite is suppressed, while the hydrogen evolution reaction can still proceed. In addition, the formed manganese oxide film acts as a barrier for the reduction of dissolved oxygen. The extent of hydrogen evolution selectivity in hypochlorite solutions was quantified in an undivided electrochemical cell using mass spectrometry. The cathodic current efficiency is significantly enhanced after the addition of permanganate, while the effect on the anodic selectivity and the decomposition of hypochlorite in solution is negligible. Importantly, similar results were obtained using electrodes with manganese oxide films formed ex situ. In conclusion, manganese oxides show great promise in inducing selective hydrogen evolution, and may open new research avenues to the rational design of selective cathodes, both for the chlorate process and for related processes such as photocatalytic water splitting.

Place, publisher, year, edition, pages
Elsevier, 2018. Vol. 182, p. 529-537
Keywords [en]
Cathode selectivity, Chromate, Hydrogen evolution reaction, Hypochlorite, Industrial electrochemistry, Suppression of backreaction
National Category
Other Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-224551DOI: 10.1016/j.jclepro.2018.02.071ISI: 000428925300039Scopus ID: 2-s2.0-85043599672OAI: oai:DiVA.org:kth-224551DiVA, id: diva2:1191793
Funder
Swedish Energy Agency
Note

QC 20180320

Available from: 2018-03-20 Created: 2018-03-20 Last updated: 2018-04-19Bibliographically approved

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