Original Article

Co-smelting of waste printed circuit boards with copper concentrate: slag regulation and metal enrichment

¹ State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, PR China
² School of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, PR China

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Received: 4 November 2025
Accepted: 2 June 2026

Abstract

Waste printed circuit boards (WPCBs) are rich in valuable metals but contain large amounts of non-metallic fractions, leading to high slag viscosity and high flux consumption when smelted alone. This study proposed a co-smelting approach for WPCBs with copper concentrate, leveraging existing oxygen-enriched copper smelting technology. The effects of CaO addition, oxygen concentration, and Fe/SiO₂ ratio on copper content in the slag were investigated through thermodynamic calculations and co-smelting experiments. The results showed that CaO enlarged the liquidus region and reduced slag viscosity, but excessive addition formed high-melting-point phases such as Ca₂SiO₄. An appropriate Fe/SiO₂ ratio reduced slag viscosity, but an excessively high ratio increased the liquidus temperature. With a WPCBs to copper concentrate mass ratio of 1:10, 4 wt.% CaO addition, 60% oxygen concentration, and an Fe/SiO₂ ratio of 1.4 in the slag, the copper content in the slag decreased to 0.52 wt.%, while the magnetite content reached 19.26 wt.%. Magnetite enrichment around matte particles, which formed a wrapping layer was identified as the main cause of mechanical copper entrainment. This study provides theoretical support for the industrial application of co-smelting WPCBs with copper concentrate.