Impact of silica on cadmium cementation by zinc dust in a zinc SX/EW plant
Horsehead Metal Products is a zinc refinery in Mooresboro, NC, treating crude Waelz oxide (WOX) to produce special high-grade zinc by a hydrometallurgical process comprising leaching, zinc solvent extraction/electrowinning, melting and casting and bleed treatment. Cadmium removal by zinc-dust cementation plays an essential role in the bleed treatment circuit to prevent cadmium buildup in the circuit. Silica, though present at a low level of approximately 0.3 percent in the WOX feed material, had a significant impact on the efficiency of cadmium cementation with zinc dust, most likely due to the passivation of zinc dust particles with silica gel. Solid/liquid separation efficiency by filter press was also affected. To identify the source of the silica issues, silica levels were mapped throughout the circuit, and adjustments, including using pregnant leach solution as the feed to cementation, and pH control in the WOX leaching and neutralization were introduced to mitigate the issues created by silica gel in the circuit.
Key wordsSilica Silicon Silica gel Cementation Zinc Polyethylene oxide DADMAC WOX Waelz oxide
Unable to display preview. Download preview PDF.
- Ashman, D.W., Delong, O.J., and Jankola, W.A., 1993, “Silica Control During Zinc Calcine Leaching at Cominco’s Trail Operation,” International Symposium World Zinc 93, October, pp. 217–225.Google Scholar
- Cooper, R.M., 1998, “Silica Precipitation from Electrolytic Zinc Solutions,” Ph.D. Thesis, Curtin University of Technology, Australia.Google Scholar
- Iler, R.K., 1979, The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties and Biochemistry of Silica, John Wiley & Sons, Inc.Google Scholar
- Musadaidzwa, J.M., and Tshiningayamwe, E.T., 2009a, “Skorpion Zinc Solvent Extraction: The Upset Conditions”, The Journal of Southern African Institute of Mining and Metallurgy, Vol. 109, November, pp. 691–695Google Scholar
- Musadaidzwa, J.M., and Tshiningayamwe, E.T., 2009b, “SKORPION Zinc Solvent Extraction: The Upset Conditions,” The Southern African Institute of Mining and Metallurgy Base Metals Conference 2009, pp. 245–258Google Scholar
- Readett, D.J., and Miller, G.M., 1995, “The Impact of Silica on Solvent Extraction: Girilambone Copper Company, Case Study”, CMPS&F, Brisbane.Google Scholar
- Smethurst, A., 2014, “Colloidal Silica and Coagulation Polysil® Coagulant Product Introduction,” Huntsman Performance Product Presentation.Google Scholar
- Smethurst, A., Hearn, B., and Boskovic, S., 2015, “POLYSIL® Coagulants to Improve SX Conditions — A Practical Way to Reduce Colloidal Silica and Crud Formation,” SME Annual Conference & Expo Preprint, February 2015, Society for Mining, Metallurgy & Exploration, Englewood, CO, pp. 1–6.Google Scholar