Degradation of polymer additives during long-term Zn electrowinning

Hiroaki Nakano, Satoshi Oue, Hisaaki Fukushima, Shigeo Kobayashi, Kazuhiko Nishina

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    The time dependence of molecular weight of gelatin, the cathode potential, and the morphology of deposited Zn were investigated during long-term electrolysis of Zn to evaluate the degradation of gelatin and polyethylene glycol (PEG) added to the electrolyte for Zn electrowinning. Gelatin and PEG acted as a polariser for Zn deposition, shifting the cathode potential to a less noble direction. The polarisation caused by the additives gradually decreased with an increase in electrolysis duration. The effective duration of additives depended significantly on molecular weight, and was longer in PEG-containing solution than in a gelatin-containing solution. Gel permeation chromatog-raphy revealed that the molecular weight of gelatin in an electrolyte decreased in with an increase in electrolysis duration. In particular, the molecular weight of gelatin decreased more rapidly at the anode than at the cathode. The decrease in molecular weight of gelatin by electrolysis brought about a shift of the cathode potential to a more noble direction, showing that the molecular weight of degraded gelatin was related to the deposition potential of Zn. Even in the case without electrolysis, the molecular weight and polarisation effect of gelatin decreased with a lapse of time. On the other hand, the morphology and the crystal orientation of Zn obtained by long-term electrolysis corresponded to the change of the cathode potential with time regardless of the kinds of additives. With an increase in the cathodic polarisation, the deposits showed the smaller grains with preferred orientation of {1010}. The morphology and the crystal orientation of deposited Zn became similar to that in the additive-free solution when the polarisation was decreased as a result of the degradation of additives.

    Original languageEnglish
    Title of host publicationProceedings - European Metallurgical Conference, EMC 2009
    Pages1097-1110
    Number of pages14
    Volume3
    Publication statusPublished - Dec 1 2009
    Event5th European Metallurgical Conference, EMC 2009 - Innsbruck, Austria
    Duration: Jun 28 2009Jul 1 2009

    Other

    Other5th European Metallurgical Conference, EMC 2009
    Country/TerritoryAustria
    CityInnsbruck
    Period6/28/097/1/09

    All Science Journal Classification (ASJC) codes

    • Metals and Alloys

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