Slag Cleaning Equilibria in Iron Silicate Slag–Copper Systems

Abstract

In this study, the equilibrium distributions of selected trace elements between molten iron-saturated copper alloy and selected iron silicate slags were measured, and the effects of silica fluxing on them. In addition to the copper and iron main components of the system, trace elements like antimony, gallium, germanium, gold, indium, and silver were added in experiments that spanned the temperature range of 1473-1573 K (1200-1300 °C). Experimental charges were quenched and prepared in polished mounts. In situ analyses of the resulting phases were made directly on the mounts without the need of phase separation prior to analysis. Electron probe X-ray microanalysis was used for concentrations at or above approximately 100 ppmw, and laser ablation-inductively coupled plasma-mass spectrometry for the lower concentrations in the slags. The very low slag concentrations of germanium, antimony, and indium obtained indicate that these elements can be removed from the slag by reduction, whereas gallium concentrations in the slag were high. Consequently, gallium removal from iron residues, such as zinc smelting jarosite, is difficult without volatilization. Based on the present observations, the industrial reduction processes for the treatment of smelting and refining slags as well as for the processing of iron residues, and extracting the reducible metal oxides and their metal values can be optimized. The target in fluxing should be to maintain the slag compositions with a silica concentration higher than about 28 wt%.

Integrating Flotation and Pyrometallurgy for Recovering Graphite and Valuable Metals from Battery Scrap

“…It was observed that the increasing silica concentration in the slag has an increasing effect on cobalt distribution coefficient. This information is in agreement with the study of Hellstén et al [37] on slag cleaning equilibria in iron silicate slag-copper system. According to their observations, Fe/SiO 2 ratio has a significant effect on trace elements distribution between metal alloy and the slag.…”

“…According to their observations, Fe/SiO2 ratio has a significant effect on trace elements distribution between metal alloy and the slag. Hellstén et al concluded that reduction of metal oxides can be optimized by adjusting SiO2 concentration in slag and the goal should be to maintain the slag compositions higher than about 28 wt% [37]. The previous study of Ruismäki et al together with the present study confirmed these findings, even though the silica concentration in the slag in this study was much higher, 35-43 wt% [24] versus 51-59 wt%, respectively.…”

“…However, at high silica concentrations, the viscosity of the slag increases, resulting in the decreasing reaction rates and the settling rate of particles through the slag layer [37,38]. As seen in Figure 10, the metal alloy is collected on top of the slag even after longer reduction times, as opposed to industrial practices, implying that the silica concentration may be too high for settling.…”

“…and CoO in the slag, on the other hand, decreases with increasing SiO2 concentration [37]. A high viscosity could also slow down the reduction rate by entraining the remaining oxides of the valuable metals in the slag as the concentration of the metals in the slag or metal alloy did not change significantly after 10 minutes.…”

Distribution Kinetics of Rare Earth Elements in Copper Smelting

“…However, in comparison to previous investigations, the concentrate used in our study contained much more zinc. The Fe/SiO 2 flux ratio was approximately 1.88, which corresponds to the orthosilicate composition, shown to be effective for minimizing the trace element losses into the slag [32]. The amounts of La and Nd oxides added to the mixture were both 5% of the mass of the concentrate.…”