Experimental Study on the Phase Equilibrium of Copper Matte and Silica-Saturated FeOx-SiO2-Based Slags in Pyrometallurgical WEEE Processing

Abstract

The effects of the amphoteric and basic oxides alumina and lime on the phase equilibria of copper matte and silica-saturated slags were investigated at 1300°C and P SO 2 = 0.1 atm in a controlled CO-CO 2 -SO 2 -Ar gas atmosphere using a high-temperature isothermal equilibration technique followed by rapid quenching. The equilibrium phase compositions were obtained by Electron Probe X-ray Microanalysis. The relationship between the copper concentration in matte and the oxygen partial pressure, iron, and sulfur in matte was quantified. The pure iron-silicate slag exhibited the highest copper loss in slag, although the addition of alumina and lime decreased its value by approximately a quarter and a half, respectively, at a matte grade of 65 wt pct Cu. In contrast, copper and sulfur were highly distributed in the matte phase, and their deportment to the matte was favored by addition of alumina and lime.

Equilibrium of Copper Matte and Silica-Saturated Iron Silicate Slags at 1300 °C and $$ P_{{{\text{SO}}_{ 2} }} $$ of 0.5 atm

“…Detailed information about the experimental methodology used has been described previously. [11][12][13][14][15] The partial pressure of SO 2 was held constant at 0.5 atm in all experiments. To create the designed O 2 and S 2 partial pressures in the gas mixture for different target matte grades, the gas flow rates were calculated by MTDATA [36] software using the SGTE pure substances database.…”

“…The silica-saturated iron silicate slags were prepared by mixing Fe 2 O 3 (99.998 wt pct) and SiO 2 (99.995 wt pct) from Alfa Aesar and Al 2 O 3 (99.99 wt pct) and CaO (99.9 wt pct) from Sigma-Aldrich. [14,15] All gases used in this study were supplied by AGA-Linde (Finland) with purities > 99.97 vol pct. For each experiment, approximately 0.1 g copper matte mixture with an equal amount of slag mixture was pressed into a pellet before being placed into a silica crucible.…”

“…The sample pellet was annealed under different gas atmospheres for 4 hour to get uniform matte and slag compositions, as suggested in our previous study. [14,15] It should be noted that all experiments were duplicated for increased reliability (4 9 2 9 3 = 24 in total). The equilibrated samples were quenched into ice-water mixture so that the phases presented at high temperature and their compositions were attained at room temperature.…”

“…A careful literature review indicated that phase equilibria of copper matte and slag over the past few decades have been studied mainly under the SO 2 partial pressure of 0.1 atm [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] related to air blowing, while only limited data were reported for the equilibria under higher P SO 2 . [18][19][20][21][22][23] Roghani et al [19][20][21][22] investigated the phase equilibria of copper matte and different slags with the presence of trace elements at 1250°C to 1300°C and P SO 2 of 0.1, 0.5, and 1 atm.…”

“…In our previous works, [11][12][13][14][15] matte-slag equilibria at silica saturation have been studied at P SO 2 = 0.1 atm and t = 1250°C to 1300°C with the presence of different trace elements. Therefore, the objective of the present study was to enrich the experimental thermodynamic data for equilibrium phase relations of copper matte and different silica-saturated FeO x -SiO 2 , FeO x -SiO 2 -Al 2 O 3 , and FeO x -SiO 2 -Al 2 O 3 -CaO slags at 1300°C and high P SO 2 of 0.5 atm.…”