Studies on promising cell performance with H2SO4 as the catholyte for electrogeneration of Ag2+ from Ag+ in HNO3 anolyte in mediated electrochemical oxidation process
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Electrochemical performance of a divided cell with electrogeneration of Ag2+ from Ag+ in 6 M HNO3 anolyte has been studied with 6 M HNO3 or 3 M H2SO4 as the catholyte. This work arose because in mediated electrochemical oxidation (MEO) processes with Ag(II)/Ag(I) redox mediator, HNO3 is generally used as catholyte, which, however, produces NO x gases in the cathode compartment. The performance of the cell with 6 M HNO3 or 3 M H2SO4 as the catholyte has been compared in terms of (i) the acid concentration in the cathode compartment, (ii) the Ag+ to Ag2+ conversion efficiency in the anolyte, (iii) the migration of Ag+ from anolyte to catholyte across the membrane separator, and (iv) the cell voltage. Studies with various concentrations of H2SO4 catholyte have been carried-out, and the cathode surfaces have been analyzed by SEM and EDXA; similarly, the precipitated material collected in the cathode compartment at higher H2SO4 concentrations has been analyzed by XRD to understand the underlying processes. The various beneficial effects in using H2SO4 as catholyte have been presented. A simple cathode surface renewal method relatively free from Ag deposit has been suggested.
KeywordsMediated electrochemical oxidation Ag2+ electrogeneration from Ag+ H2SO4 catholyte Ag+ migration Ag deposit Surface analysis Cell performance
This work was supported by the Korean Ministry of Environment as “The Eco-technopia 21 project”, and the Ministry of Commerce, Industry and Energy (MOCIE) through Regional Innovation Centre (RIC), and the Korea Research Foundation and The Korean Federation of Science and Technology Society’s Grant funded by the Korea Government (MOEHRD, Basic Research Promotion Fund). One of the authors (KCP) wishes to thank the authorities of the University of Madras, Chennai-600 005, India for granting sabbatical leave.
- 1.Steele DF (1990) Platinum Met Rev 34:10Google Scholar
- 7.Nelson N (2002) Platinum Met Rev 46:18Google Scholar
- 10.Matheswaran M, Balaji S, Chung SJ, Moon IS (2007) J Ind Eng Chem 13:231Google Scholar
- 17.Plieth WJ (1978) In: Bard AJ (ed) Encyclopedia of electrochemistry of the elements, vol 8. Dekker, New York, p 440Google Scholar
- 18.Latimer WM (1952) The oxidation potentials of the elements and their potentials in aqueous solutions. Prentice-Hall, New YorkGoogle Scholar
- 19.Miles FD (1961, 1963) Nitric acid, manufacture and uses. Oxford University Press, OxfordGoogle Scholar
- 22.Yuan S, Hu S (2004) Electrochim Acta 49:4287Google Scholar
- 23.Lide DR (ed) (2006) CRC handbook of chemistry and physics, 87th edn. pp 8–119, CRC Press, Taylor and Francis, Boca Raton, FLGoogle Scholar
- 25.Furlong DN, Yates DE, Healy TW (1981) In: Trasatti S (ed) Electrodes of conductive metallic oxides, Part B, pp 367–432, Elsevier, AmsterdamGoogle Scholar