On-line version ISSN 2411-9717
Print version ISSN 0038-223X
J. S. Afr. Inst. Min. Metall. vol.111 n.5 Johannesburg May. 2011
T.A. Muhlare; D.R. Groot
Department of Materials Science and Metallurgical Engineering, University of Pretoria, South Africa
The use of electrolyte additives to smoothen cathode deposits during copper deposition is practised worldwide. These additives absorb on the cathode surface and take part in the electrochemical crystallization process. However, these additives also affect the quality of the cathodes when they are inadequately controlled.
Electrolyte additives used by Palabora are glue, thiourea, Avitone and chloride. Their effects were determined on cathode quality, the size of the current density region that gives the desired compact morphology, and current efficiency. This was done in a small-scale cell.
Small cells have different hydrodynamics from industrial-scale cells, which makes it difficult to simulate the operation of industrial cells in a laboratory. The approach used here was to use a rotating cylinder cathode to attain controlled hydrodynamics. The rotation speed was chosen to give a diffusion layer thickness that is similar to that of an industrial-scale cell.
It was shown that even fairly small changes in the additive levels can significantly affect the cathode morphology, and the current density range over which this morphology can be obtained.
Keywords: Copper, electrorefining, glue, thiourea, avitone and chloride
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1. ANDERSEN, T.N., BUDD, R.D., and STRACHAN, R.W. A Rapid Electrochemical Method for Measuring the Concentration of Active Glue in Copper Refinery Electrolyte Which Contains Thiourea. Metallurgical Transactions B, vol. 7B, 1976, pp. 333-338. [ Links ]
2. BISWAS, A. K. and DAVENPORT, W.G. Extractive metallurgy of copper, British Library, third edition, 1999, pp. 264-287. [ Links ]
3. BLECHTA, V.K., WANG, Z.Z., and KRUEGER, D.W. Glue analysis and behavior in Copper Electrolytes. Metallurgical Transactions B, vol. 24B, 1992, pp. 277-287. [ Links ]
4. CONARD, B.R., ROGERS, B., BRISEBOIS, R., and SMITH, C. Inco Copper Refinery Addition Agent Monitoring using Cyclic Voltammetry. Electrochemical plant practice, pp. 291-307. [ Links ]
5. DENI, R.M. 1994. The effect of addition agents on Cathodic Overpotential and cathode quality in copper electrorefining. Thesis, Laurentian University, Northeastern Ontario, 1994. [ Links ]
6. GOFFMAN, M. and JORDAN, T.L. 1985. Method of thiourea addition to electrolyte solutions useful for copper refining. Patent Amarillo, TX, US [ Links ]
7. KRZEWSKA, S., PAJDOWSKI, I., PODSIADLY, H., and PODSIADLY, J. Electrochemical Determination of Thiourea and Glue in the Industrial Copper Electrolyte. Metallurgical Transactions B, vol. 15B, 1984, p. 451-459. [ Links ]
8. MADORE, C., LANDOLT, D., HAßENPFLUG, C., and HERMANN, J.A. Application of the Rotating Cylinder Hull Cell to the measurement of Throwing Power and the monitoring of Copper Plating Baths, Plating and Surface Finishing, 1995, pp. 36-41. [ Links ]
9. MOATS, M.S., HISKEY, J.B., and COLLINS, D.W. The effect of copper, acid, and temperature on the diffusion coefficient of cupric ions in simulated electrorefining electrolytes. Hydrometallurgy, vol. 56, 2000, pp. 255-268. [ Links ]
10. Muresan, L., Varvara, S., Maurin, G., and Dorneanu, S. The effect of some organic additives upon copper electrowinning from sulphate electrolytes. Hydrometallurgy, vol. 54. 1999, pp. 161-169 [ Links ]
11. PRICE, D.C. and DAVENPORT, W.G. Physico-Chemical properties of copper electrorefining and electrowinning electrolytes. Metallurgical Transactions B, vol. 12B, 1981, pp. 639-643. [ Links ]
12. SABAN, M.D., SCOTT, J.D., and CASSIDY, R.M. 1991. Collagen Proteins in Electrorefining: Rate Constant for Glue Hydrolysis and Effects of Molar Mass on Glue Activity. Metallurgical Transactions B, vol. 23B. pp. 125-133. [ Links ]
13. SAFIZADEH, F., LAFRONT, A.M., GHALI, E., and HOULACHI, G. Hydrometallurgy. Monitoring the quality of copper deposition by statistical and frequency analyses of electrochemical noise, vol. 100, 2009, pp. 87-94. [ Links ]
14. STELTER, M. and BOMBACH, H. Process optimization in Copper Electrorefining. Advanced Engineering Materials. Wiley, vol. 6, no. 7, 2004. [ Links ]
* Paper written on project work carried out in partial fulfilment of B. Eng Metallurgical Engineering and presented at the Student Colloquium, November 2010