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The kinetics of copper dissolution in acetonitrile-water mixtures

Couche, Raymond A. (1986) The kinetics of copper dissolution in acetonitrile-water mixtures. PhD thesis, Murdoch University.

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Abstract

This thesis is concerned with the dissolution of copper in acetonitrile-water solutions. The literature relating to the dissolution of metals is first reviewed, commencing with a brief history and the applications of metal dissolution reactions.

The mechanism of these reactions is discussed largely from an electrochemical viewpoint. Because hydrodynamics are of importance in all heterogeneous systems the relevant literature concerning the rotating disc electrode (RDE) and rotating cylinder electrode (RCE) is reviewed.

A rapid electrochemical technique for measuring the kinetics of metal dissolution reactions was developed. This was based on plating a thin film of copper on to a polished noble metal substrate (RDE or RCE) and then measuring the time for dissolution of the copper (Stripping) in a reactant solution. The reaction time was determined by recording the mixed potential of the reaction, and noting the instant when the potential suddenly increased to the redox potential at the noble metal, which occurred when the thin film was completely stripped. The use of this technique is described and the results used in conjunction with other electrochemical data to evaluate the dissolution of copper in acidified acetonitrile-water solutions of iron(III) and copper(II).

The iron(III)/copper(0) reaction was shown to be diffusion controlled and the diffusion coefficients of iron(III) were determined as a function of acetonitrile and iron(III) concentrations.

Copper(II) was shown to be an "auto contaminant" in the electrochemical reduction of copper(II) and in the copper(II)/ copper(O) dissolution. Blocking of the copper surface occurred quite rapidly at high copper(II) concentrations and high rotation speeds. Consequently, only at low copper(II) concentrations and rotation speeds was it possible to obtain a satisfactory estimate of the copper(II) diffusion coefficient. The copper(II)/copper(0) dissolution reaction was more complex than the corresponding iron(III)/copper(0) reaction.

The stripping technique was used to investigate the hydrodynamic regimes of the active rotating cylinder and four regimes were identified namely, Taylor vortex, wavy vortex. transition and full turbulence. No data were obtained for the laminar regime which exists only at very low rotation speeds.

The stripping technique was also used to carry out some exploratory measurements on some variations of the rotating cylinder reactor. These included the case where the cylinder was baffled, where the outer cylinder was reactive, and where a turbine was used in place of the smooth rotating cylinder. In each case a relationship between the apparent rate constant and rotation speed was obtained.

Item Type: Thesis (PhD)
Murdoch Affiliation: School of Mathematical and Physical Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: repository@murdoch.edu.au. Thank you.
Supervisor(s): Parker, Jim and Ritchie, Ian
URI: http://researchrepository.murdoch.edu.au/id/eprint/51622
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