Novel Fluxing Strategy for Enhanced Impurity Element Removal in Copper Scrap Refining Processes

Abstract The direct production of high-purity copper from copper scrap is a promising approach for its recycling and addressing the supply–demand gap of copper. To enable more efficient production of high-purity copper, the distribution equilibria of trace elements (e.g., Fe, Ni, Pb, Sn, Sb, and Zn) between copper alloy and different flux systems (CaO–SiO 2 –FeO x , CaO–SiO 2 –FeO x –Al 2 O 3 , CaO–SiO 2 –FeO x –Na 2 O, CaO–SiO 2 –Na 2 O–P 2 O 5 , CaO–SiO 2 –Na 2 O–B 2 O 3 ) were investigated at 1200 ºC and $${\text{p}}_{{{\text{o}}_{{2}} }}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>p</mml:mtext> <mml:msub> <mml:mtext>o</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> </mml:msub> </mml:math> of 10 –7.0 to 10 –4.5 atm. The slag-to-metal distribution coefficients followed the order Sb &lt; Ni &lt; Pb &lt; Sn &lt; Fe (Zn), indicating that antimony and nickel are the most challenging impurities to remove during fire refining. Based on the findings, a novel fluxing strategy was developed using the CaO–SiO 2 –FeO x –Al 2 O 3 flux system at 1200 °C and high oxygen partial pressures up to $${\text{p}}_{{{\text{o}}_{{2}} }}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>p</mml:mtext> <mml:msub> <mml:mtext>o</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> </mml:msub> </mml:math> = 10 –4.5 atm. Under such conditions, recycled copper purities of 99.5 wt% can be achieved after single-step refining. This analysis indicates that high-grade copper comparable to Standard Grade Electrolytic Copper (Cu% ≥ 99.9 wt%) can be attained through fire-refining alone by adjusting flux dosage, applying multiple refining stages, and using selected copper scrap. Graphical Abstract