Abstract
Four different Cu-rich polymetallic concentrates are tested for volatilization of Sb and As during laboratory-scale roasting. The experiments are performed between 200 °C and 700 °C, at intervals of 100 °C and in an inert atmosphere. Sb volatilization is much less (maximum approximately 45 pct) than As volatilization (maximum approximately 95 pct) in these conditions at 700 °C. As volatilization is however limited from the concentrate having As mainly in a tetrahedrite solid solution ((Cu,Ag,Fe,Zn)12(Sb,As)4S13). Sb and As retained in the roasted calcine are found in the low-melting liquid phase, formed at approximately 500 °C. This melt phase gets enlarged and enriched in Sb with an increase in temperature. However, there is noticeable As volatilization from this melt phase with the temperature approaching 700 °C. Furthermore, there is an early and relatively high Sb volatilization from the concentrate having Sb substantially as gudmundite. Micron-scale elemental redistribution in gudmundite in the 350 °C roasted calcine confirms its transformation at this temperature. Other Sb minerals did not undergo any detectable transformation at this temperature, suggesting that the significant Sb volatilization starting between 300 °C and 400 °C was primarily from gudmundite. This benign attribute of gudmundite featured in this work in the context of roasting should also be relevant from the geometallurgical perspective during concentrate production, where concentrates bearing Sb are considered substandard for further Cu extraction irrespective of the Sb mineralogy.
Highlights
SULFIDE deposits of copper can broadly be classified as simple or complex
This article discusses the extent of As and Sb removal in the laboratory-scale roasting experiments presented in Prasad et al.,[6] where the complex concentrates experienced sintering during roasting in inert atmosphere
These experiments were performed in inert atmosphere to facilitate a fundamental study on the mineral assemblies in low oxidation potential roasting environments, which are considered favorable for the impurity volatilization.[47]
Summary
SULFIDE deposits of copper can broadly be classified as simple or complex. The simple Cu deposits generally comprise copper as the main base metal in the form of chalcopyrite, for instance, the Aitik deposit in northern Sweden.[1]. Some examples of complex polymetallic deposits in Sweden are Garpenberg,[2,3] Maurliden[4] and Rockliden.[5] Mineral processing of the ore from these complex deposits generates multiple concentrates, each being rich in a particular base or precious metal. Polymetallic Cu-rich concentrates bearing impurity elements are introduced into the pyrometallurgical extraction process by blending in small proportions with concentrates from the simpler deposits. This article discusses the extent of As and Sb removal in the laboratory-scale roasting experiments presented in Prasad et al.,[6] where the complex concentrates experienced sintering during roasting in inert atmosphere These experiments were performed in inert atmosphere to facilitate a fundamental study on the mineral assemblies in low oxidation potential roasting environments, which are considered favorable for the impurity volatilization.[47]. The possibility of substantial Sb volatilization from the specific minerals during roasting may be relevant information, at the stage of concentrate production during mineral processing
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