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Coupled effects of temperature and mass transport on the isotope fractionation of zinc during electroplating

Black, Jay R. and John, Seth G. and Kavner, Abby (2014) Coupled effects of temperature and mass transport on the isotope fractionation of zinc during electroplating. Geochimica et Cosmochimica Acta, 124 . pp. 272-282. ISSN 0016-7037. doi:10.1016/j.gca.2013.09.016.

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The isotopic composition of zinc metal electrodeposited on a rotating disc electrode from a Zn-citrate aqueous solution was investigated as a function of overpotential (electrochemical driving force), temperature, and rotation rate. Zn metal was measured to be isotopically light with respect to Zn^(+2) in solution, with observed fractionations varying from Δ^(66/64)Z_(nmetal-aqueous) = −1.0‰ to −3.9‰. Fractionation varies continuously as a function of a dimensionless parameter described by the ratio of observed deposition rate to calculated mass-transport limiting rate, where larger fractionations are observed at lower deposition rates, lower temperature, and at faster electrode rotation rates. Thus, the large fractionation and its rate dependence is interpreted as a competition between the two kinetic processes with different effective activation energies: mass-transport-limited (diffusion limited) kinetics with a large activation energy, which creates small fractionations close to the predicted diffusive fractionation; and electrochemical deposition kinetics, with a smaller effective activation energy, which creates large fractionations at low deposition rates and high hydrodynamic fluxes of solute to the electrode. The results provide a framework for predicting isotope fractionation in processes controlled by two competing reactions with different kinetic isotope effects.

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Additional Information:© 2013 Elsevier Ltd. Received 18 March 2013; accepted in revised form 14 September 2013; available online 27 September 2013. We thank Professor Edwin Schauble for his input and discussion of equilibrium isotope effects and Professor Jess Adkins for access to facilities at Caltech. We thank Jeffrey Crawford for assistance with the Zn electroplating experiments. This work was funded by the US Department of Energy: Division of Chemical Sciences, Geosciences, & Biosciences DE-FG02-10ER16136 (A.K.). Associate editor: Frederic Moynier
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Department of Energy (DOE) Division of Chemical Sciences, Geosciences, & BiosciencesDE-FG02-10ER16136
Record Number:CaltechAUTHORS:20131220-090628054
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Official Citation:Jay R. Black, Seth G. John, Abby Kavner, Coupled effects of temperature and mass transport on the isotope fractionation of zinc during electroplating, Geochimica et Cosmochimica Acta, Volume 124, 1 January 2014, Pages 272-282, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43109
Deposited By: Ruth Sustaita
Deposited On:20 Dec 2013 17:34
Last Modified:10 Nov 2021 16:32

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