Volatilization of Arsenic and Antimony from Tennantite/Tetrahedrite Ore by a Roasting Process

Samuelsson

2020

Four different Cu-rich polymetallic concentrates (additionally comprising Zn, Pb and impurity elements As, Sb) from various deposits in Sweden are examined, in particular for the sintering tendency during roasting in inert atmosphere. Experiments performed in a laboratory-scale roasting setup between 200 °C and 700 °C in intervals of 100 °C revealed that significant sintering initiates from 500 °C for all four concentrates. Two sintering mechanisms are determined from the examination of the sintered calcines: (1) solid-state assimilation of Cu-, Zn- and Fe-bearing main sulphide minerals to form a high-temperature solid solution, the iss phase belonging to the Cu-Fe-Zn-S system; (2) low-melting liquid phase formation due to partial melting of galena facilitated by the presence of impurity-bearing minerals, mainly the arsenopyrite and Sb sulphosalts such as tetrahedrite. Galena also forms a melt below 700 °C with the iss phase. Therefore, the presence of galena in polymetallic concentrates generally increases the susceptibility to early sintering. These experiments in inert atmosphere facilitate a fundamental study with practical relevance to the roasting in low oxidation potential environments, favourable for volatilization of impurity elements such as As and Sb.

Section: Introductionmentioning

confidence: 99%

A Mineralogical Investigation of Sintering in Cu-Rich Polymetallic Concentrates During Roasting in Inert Atmosphere

Samuelsson

2020

“…In Figure 5, As removal is shown to be higher than the Sb removal for most of the concentrates, owing to the low volatility of Sb from the sulfosalt minerals. [43] Previous experimental [28,32,53] and model-based theoretical studies [54] have also corroborated a high As volatilization of > 90 pct in inert atmosphere at 700°C from concentrates comprising As minerals such as enargite (Cu 3 AsS 4 ) [32,54] and tennantite (Cu 12 As 4 S 13 ). [28,53] In the current investigation, As content at 700°C was highest in the Maurliden concentrate, which also had the highest initial As content (Table IV).…”

Section: B Sb and As Volatilization During Roasting Experimentsmentioning

confidence: 84%

“…Alternatively, roasting of Cu-concentrates can also partially volatilize the impurity elements As and Sb. [21][22][23][24][25][26][27][28][29][30] Therefore, advancements in the roasting technology can also facilitate the increase in proportions of the complex concentrates in blends processed for pyrometallurgical Cu extraction.…”

Section: Introductionmentioning

confidence: 99%

“…There have also been investigations of As and Sb volatilization using complex concentrates as the starting material for laboratory-scale roasting. [21,24,[26][27][28][29][30]46] However, mineralogical transformations during the volatilization progress in roasted calcines are only moderately discussed. A detailed study of such transformations tracking the deportment of As and Sb in the mineral phases with an increase in temperature is missing, which is the focus of this work.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

McElroy

et al. 2021

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.

“…[13] Therefore, the volatilization of these elements from the sulfide concentrates during roasting have been studied in different controlled atmospheric environments. [14][15][16][17][18][19][20][21][22] However, the properties of volatilized and condensed Sb-and As-bearing species emanating from the sulfide concentrates during roasting have been rarely studied. Also, the effect of simultaneous release of volatile species by the other minerals such as pyrite present in the concentrate (comprising of labile sulfur [23] ) on the gas phase complexation behavior of Sb and As has not been investigated.…”

Section: Introductionmentioning

confidence: 99%

Volatilized and Condensed Sb- and As-Bearing Phases Produced During Roasting of Cu-Rich Complex Concentrate in Nitrogen Atmosphere with Oxygen in Traces

Samuelsson

2021

A Cu-rich complex sulpfide concentrate (containing Sb as sulphosalts and gudmundite, and As as arsenopyrite) is roasted in Nitrogen atmosphere carrying traces of oxygen ($${\text{p}}^{{\text{O}}_{2}} \approx {10}^{-5.3}\text{ bar)}$$ p O 2 ≈ 10 - 5.3 bar) . In situ measurements through QMS indicated that the volatilized species are mainly elemental sulfur, S2(g), and gaseous sulfur oxides. Sb- and As-bearing volatilized species could not be detected, owing to their low concentrations in the gas phase. Characterization studies through XRD and SEM-EDS confirmed that the condensates collected at room temperature during the roasting experiments comprised of (1) cyclo-octa sulfur, S8(s) and polysulfur oxides, Sn−xOx(s); (2) amorphous trisulfides of Sb and As; (3) and cubic crystalline trioxides of Sb and As. The solid phases in the condensate were found to be fine-sized (sub-micronic) and widely intermixed. Consequently, quantification of the solid phases in the condensates through direct measurement techniques like QEMSCAN was not possible. A novel approach of partial quantification of solid phases in the condensate through a stochastic model-based calculation approach is also presented. The model results suggested the occurrence of vapor-phase complexation of sulfides of Sb and As in the gas phase. Additional attributes of the volatilized species could be determined through a thermodynamic equilibrium calculation showing that the formation of the complex oxides, As4−nSbnO6(g), would be negligible compared to that of the complex sulfides, As4−nSbnS6(g).