Effect of Cooling Rate on base Metals Recovery from Copper Matte Smelting Slags

Authors: N. Tshiongo , R K.K. Mbaya , K Maweja, L.C. Tshabalala

Abstract:

Slag sample from copper smelting operation in a water jacket furnace from DRC plant was used. The study intends to determine the effect of cooling in the extraction of base metals. The cooling methods investigated were water quenching, air cooling and furnace cooling. The latter cooling ways were compared to the original as received slag. It was observed that, the cooling rate of the slag affected the leaching of base metals as it changed the phase distribution in the slag and the base metals distribution within the phases. It was also found that fast cooling of slag prevented crystallization and produced an amorphous phase that encloses the base metals. The amorphous slags from the slag dumps were more leachable in acidic medium (HNO3) which leached 46%Cu, 95% Co, 85% Zn, 92% Pb and 79% Fe with no selectivity at pH0, than in basic medium (NH4OH). The leachability was vice versa for the modified slags by quenching in water which leached 89%Cu with a high selectivity as metal extractions are less than 1% for Co, Zn, Pb and Fe at ambient temperature and pH12. For the crystallized slags, leaching of base metals increased with the increase of temperature from ambient temperature to 60°C and decreased at the higher temperature of 80°C due to the evaporation of the ammonia solution used for basic leaching, the total amounts of base metals that were leached in slow cooled slags were very low compared to the quenched slag samples.

Keywords: copper slag, leaching, amorphous, cooling rate

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1085311

References:

[1] Arslan, C. and F. Arslan, Recovery of copper, cobalt, and zinc from copper smelter and converter slags. Hydrometallurgy, 2002. 67(1-3): p. 1-7.
[2] Baghalha, M., V.G. Papangelakis, and W. Curlook, Factors affecting the leachability of Ni/Co/Cu slags at high temperature. Hydrometallurgy, 2007. 85(1): p. 42-52.
[3] Banza, A.N., E. Gock, and K. Kongolo, Base metals recovery from copper smelter slag by oxidising leaching and solvent extraction. Hydrometallurgy, 2002. 67(1-3): p. 63-69.
[4] Das, B., et al., An overview of utilization of slag and sludge from steel industries. Resources, Conservation and Recycling, 2007. 50(1): p. 40- 57.
[5] Gorai, B., R.K. Jana, and Premchand, Characteristics and utilisation of copper slag--a review. Resources, Conservation and Recycling, 2003. 39(4): p. 299-313.
[6] Kuo, Y., et al., Effect of water quenching and SiO2 addition during vitrification of fly ash: Part 1: On the crystalline characteristics of slags. Journal of Hazardous Materials, 2008. 152(3): p. 994-1001.
[7] Lin, K.L., and Chang, C.T. (2006). "Leaching characteristics of slag from the melting treatment of municipal solid waste incinerator ash." Journal of Hazardous materials,135(1-3), 296-302.
[8] Maweja, K., T. Mukongo, and I. Mutombo, Cleaning of a copper matte smelting slag from a water-jacket furnace by direct reduction of heavy metals. Journal of Hazardous Materials, 2009. 164(2-3): p. 856-862.
[9] Mukongo, T., et al., Zinc recovery from the water-jacket furnace flue dusts by leaching and electrowinning in a SEC-CCS cell. Hydrometallurgy, 2009. 97(1-2): p. 53-60.
[10] Piatak, N.M., R.R. Seal, and J.M. Hammarstrom, Mineralogical and geochemical controls on the release of trace elements from slag produced by base- and precious-metal smelting at abandoned mine sites. Applied Geochemistry, 2004. 19(7): p. 1039-1064.
[11] Saffarzadeh, A., et al., Characterization study of heavy metal-bearing phases in MSW slag. Journal of Hazardous Materials, 2009. 164(2-3): p. 829-834.
[12] Shen, H. and E. Forssberg, An overview of recovery of metals from slags. Waste Management, 2003. 23(10): p. 933-949.
[13] Tossavaine, M., Engstrom, F., Yang, Q., Menad, N., Lidstrom Larsson, M., and Bjorkman, B. (2007). " Characteristics of steel slag under different cooling conditions." Waste Management, 27(10), 1335-1344.