In situ synchrotron X‐ray diffraction investigation of the evolution of a PbO2/PbSO4 surface layer on a copper electrowinning Pb anode in a novel electrochemical flow cell. (3rd February 2015)

• Record Type: Journal Article
• Authors: Clancy, Marie; Styles, Mark J.; Bettles, Colleen J.; Birbilis, Nick; Chen, Miao; Zhang, Yansheng; Gu, Qinfen; Kimpton, Justin A.; Webster, Nathan A. S.
• Is Part Of: Journal of synchrotron radiation. Volume 22:Part 2(2015)
• Page Start: 366
• Page End: 375
• Publication Date: 2015-02-03
• Subjects: Synchrotron radiation -- Periodicals; Free electron lasers -- Periodicals; 539.73505
• DOI: 10.1107/S1600577514027659
• Languages: English
• ISSNs: 0909-0495

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>This paper describes the quantitative measurement, by <italic>in situ</italic> synchrotron X‐ray diffraction (S‐XRD) and subsequent Rietveld‐based quantitative phase analysis and thickness calculations, of the evolution of the PbO<sub>2</sub> and PbSO<sub>4</sub> surface layers formed on a pure lead anode under simulated copper electrowinning conditions in a 1.6 <italic>M</italic> H<sub>2</sub>SO<sub>4</sub> electrolyte at 318 K. This is the first report of a truly <italic>in situ</italic> S‐XRD study of the surface layer evolution on a Pb substrate under cycles of galvanostatic and power interruption conditions, of key interest to the mining, solvent extraction and lead acid battery communities. The design of a novel reflection geometry electrochemical flow cell is also described. The <italic>in situ</italic> S‐XRD results show that β‐PbO<sub>2</sub> forms immediately on the anode under galvanostatic conditions, and undergoes continued growth until power interruption where it transforms to PbSO<sub>4</sub>. The kinetics of the β‐PbO<sub>2</sub> to PbSO<sub>4</sub> conversion decrease as the number of cycles increases, whilst the amount of residual PbO<sub>2</sub> increases with the number of cycles due to incomplete conversion to PbSO<sub>4</sub>. Conversely, complete transformation of PbSO<sub>4</sub> to β‐PbO<sub>2</sub> was observed in each cycle. The results of layer thickness calculations demonstrate a significant volume change upon PbSO<sub>4</sub> to β‐PbO<sub>2</sub> transformation.</p> </abstract>