Abstract
In pyrometallurgical processes refining copper, the main source of loss in the conversion stage is from slag. This paper reports on research work treating converter slag containing high percentages of copper (36 wt%) using ammonium hydroxide at room temperature. Variables analyzed are solution pH, agitation, temperature, NH4OH concentration and particle size. Results showed that the hydronium ion resulting from ammonium hydroxide dissociation was the main oxidant of copper compounds in slag, such as CuO, Cu2O and Cu, with the exception of CuFeO2. The particles contain a large amount of microcracks (porosity) in their refractory structure (analyzed by compositional image capture (BSE)). Thus, the diffusion of the leaching solution through the microcracks making contact with the copper oxides would be allowed. Leaching mechanisms were corroborated by X-ray diffraction and scanning electron microscopy analysis. Increasing temperature and NH4OH concentration while decreasing particle size obtained higher copper recoveries, reaching values of 84.8%. Under the same conditions, the main impurity (iron) was minimal (<2%). Solution pH also affected slag leaching. Agitation of the solution positively affected the rate of copper extraction. Leaching kinetics of the leaching solution through the porosity formed in the slag was analyzed under the intraparticle diffusion model. The reaction order was 1.2 with respect to the concentration of ammonium hydroxide and the model was inversely proportional to the square of the particle radius. The activation energy obtained was 42.3 kJ/mol for temperature range 283 to 333 K.
Highlights
Metallurgical treatment of metallic sulfides is generally carried out by means of high temperature methods, usually pyrometallurgy
It should be noted that working without agitation (0 rpm) an extraction value of 11.1% was achieved. This value is important because copper extraction from converter slag still occurs, even without stirring the solution
This is mainly due to the leaching solution diffusing throughout the slag via microcracks [18]
Summary
Metallurgical treatment of metallic sulfides is generally carried out by means of high temperature methods, usually pyrometallurgy. The results obtained at 523 K (250 ◦ C), 90 psi PO2 and times between 900 and 1200 s (15 to 20 min) yielded between 95–97% extraction of Ni, Co and Cu, each In another approach, the Taguchi method was used to determine optimum conditions for dissolving copper from converter slags [6] saturated with Cl2 gas. Metals 2020, 10, x FOR PEER REVIEW chloride solution [13], complex copper in ammonia-ammonium chloride solution [14], malachite ore in ammonium solutions [15], tenorite and cuprite in ammonium mediaore [16,17] Ammonia such as malachitenitrate in ammonia/ammonium carbonate system [12], oxidized copper in ammonium leaching has not[13], been carried copper out forin converter slags. Main with objective of this research to leach a slag from a Peirce-Smith converter using ammonium hydroxide (NH4 OH) under different working conditions as an alternative to leaching
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
