The effect of mass transport on deposit quality in copper electrowinning

<p>"Roughness and nodulation of copper electrodeposits depend strongly on mass transfer conditions of copper ions to the electrode surface. Mass transfer properties in electrowinning electrolytes were first characterized. The effective diffusivity of cupric ion was measured with a rotating disk electrode in CuSO₄-H₂SO₄ electrolytes at temperatures relevant to electrowinning, with and without additives. Adding 20 mg L^-1 of chloride ion increased the measured diffusion coefficient, but commercial smoothing additives had little effect. An empirical formula to predict cupric diffusivity was generated for later use in mass transport modeling.</p> <p>Boundary layer thickness information for commercial cells was taken from the literature. The rotating cylinder Hull cell (RCHC) was then used to produce copper deposits with similar boundary layer thicknesses. The current distribution was calculated with a finite element method and a Fourier series. Nodulation appears at 20-50% of the limiting current density, and this was termed the permissible current density. The amount of nodulation, as well as surface roughness, increases with increasing current density. The simulated air sparged cell enabled current densities 2-3 times higher than the conventional electrowinning cell while still producing smooth deposits. Pulsed plating with three rectangular waveforms was also examined A pulse-rest waveform with a 50% duty cycle gave a finer deposit morphology. Pulse-reverse and pulse-rest-reverse waveforms were also used but were inferior to the pulse-rest deposits. Addition of a smoothing additive, Hydrostar 10, significantly reduced the amount of nodulation, but did not completely suppress it"--Abstract, p. iv</p>

Name thesis:degree_name

Ph. D. in Metallurgical Engineering

Grantor

Missouri University of Science and Technology

Author dc:creator

• Bauer, Joseph

• Additives
• Copper
• Current distribution
• Electrowinning
• Mass transport
• Pulse plating
• Engineering
• Materials Science and Engineering
• Metallurgy

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/3232

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-4237