A Mineralogical Investigation on Volatilization of Impurity Elements from Cu-Rich Polymetallic Concentrates During Roasting in Inert Atmosphere

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.

Redistribution of Minor and Trace Elements During Roasting of Cu-Rich Complex Concentrate in Inert Atmosphere

“…The mineralogical composition of the initial Garpenberg concentrate obtained through QEMSCAN is presented in Figure 6(a). It was pointed out in an earlier study [22] that the proportion of tetrahedrite (Ttr) in the Garpenberg concentrate is significantly higher than that of the other sulfosalts-bournonite and meneghinite, also found in it. Ttr exhibited a wide variation in its Ag-content, whereas, Ag-Sb had specifically approx.…”

“…The epoxy mount of the initial concentrate was additionally analysed in QEMSCAN (Model-QEMS-CAN 650, FEI with W-filament and two Brukar XFlash 5030 EDS detectors) at Boliden Mineral AB, Boliden, Sweden. Details of this measurement are mentioned in Prasad et al [22] 4. Laser-ablation ICP-MS The initial concentrate and the melt-nugget microstructures were also analyzed in a Laser-Ablation ICP-MS (henceforth referred as LA-ICP-MS) setup.…”

“…[11][12][13][14][15][16][17][18][19][20] Our recent publications reported the observations related to sulphide mineralogical interactions in context of roasting, based on the experiments performed with Cu-rich complex concentrates. [21][22][23] Pertinent findings from the geological literature such as the existence of solid-solution phases in the CuS-ZnS-FeS system [12,13] and liquid phases in the PbS-CuS-Sb 2 S 3 system [14,15] could very well explain the mineralogical transformations observed during the roasting of multiple complex concentrates.…”

“…Similar to the mineral crystallizations in ore bodies, roasting of complex concentrates also involves the formation of new solid and liquid phases. [21,22] Such physicochemical changes can stimulate redistribution of the minor and trace elements, originally residing in distinct mineral phases in the complex concentrate. Detailed characterization of complex concentrates together with their roasted calcine to determine the elemental redistributions is missing, which is the focus of the current study.…”