Handling trace elements in WEEE recycling through copper smelting-an experimental and thermodynamic study

Min Chen,Katri Avarmaa,Pekka Taskinen,Lassi Klemettinen,Radoslaw Michallik,Hugh O'Brien,Ari Jokilaakso

doi:10.1016/j.mineng.2021.107189

Abstract

Recycling of waste electrical and electronic equipment (WEEE) is attracting increasing attention, due to the presence of valuable metals and the risk of environmental emissions associated with WEEE disposal. In this study, the distributions of trace elements (Ag, Ni, Co, and Sn) between copper alloy and magnetite/wüstite-saturated iron silicate slags were investigated at 1200–1300 °C and PO2 of 10-10-10-6.5 atm, simulating the conditions of WEEE reprocessing through secondary copper smelting and converting. The high-temperature isothermal equilibration experiments were conducted in synthesized magnetite/wüstite crucibles under controlled CO-CO2 atmospheres followed by quenching in an ice-water mixture. The phase compositions and concentrations of the trace elements in copper alloy, magnetite/wüstite, and slag were determined by Electron Probe X-ray Microanalysis and Laser Ablation-High-Resolution Inductively Coupled Plasma-Mass Spectrometry. The distribution coefficients of all investigated trace elements between copper alloy and slag increased with decreasing oxygen partial pressure and increasing temperature. Ag distributed strongly into the copper alloy at all conditions, whereas Co mainly deported into the slag phase. Ni and Sn were concentrated in the alloy at lower PO2 and in the slag at higher PO2. Varying concentrations of Ni, Co, and Sn were also dissolved into the solid magnetite/wüstite phase.

Highlights

The rapid development of the electronic information industry and the rapid upgrading of electronic devices have resulted in a surge of waste electrical and electronic equipment (WEEE) (Marinello and Gamberini, 2021)
With a purpose of exploring the potential of recycling valuable metals from WEEE through secondary copper smelting and finding the optimal fluxing practices, the distributions of selected trace elements (Ag, Ni, Co, and Sn) between copper alloy and magnetite/wüstitesaturated iron silicate slags were investigated at 1200–1300 ◦C and PO2 of 10-10 to10-6.5 atm using the high-temperature equilibration followed by drop-quench technique and in situ phase composition analyses
It was found that silver was highly deported into the copper alloy, cobalt markedly distributed into the slag and magnetite/ wüstite phases

Summary

Introduction

The rapid development of the electronic information industry and the rapid upgrading of electronic devices have resulted in a surge of waste electrical and electronic equipment (WEEE) (Marinello and Gamberini, 2021). Compared with available primary cop per smelters, a wider variety of WEEE can be incorporated into the secondary copper smelters and subsequently produce copper as well as valuable side products of multiple precious and critical elements (Anindya et al, 2009). Among those secondary copper smelting routes, the processing of WEEE in TSL furnaces, like Ausmelt and Isasmelt technologies, are commonly used (Shuva et al, 2017). The precious and trace elements are introduced into the TSL furnace along with secondary materials like WEEE and the metals distribute in smelting and convert ing into metal, slag, and gas phases.

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Conclusion