Experimental investigation on time-dependent recycling behaviour of WPCBs in copper flash smelting conditions

Abstract

With the rapid development of technology, the depletion of limited existing resources as well as more and more serious environmental pollution problems, increasing attention in recent years has been drawn to the responsible processing of end-of-life (EoL) Waste Electrical and Electronic Equipment (WEEE). Waste Printed Circuit Boards (WPCBs) are one of the main components of WEEE, accounting for 40% of the total metal recovery value and they have nowadays become an important part of urban mining. Feeding WPCBs into existing pyrometallurgical processes is developing as an easy-to-adapt and efficient way to recycle them. To fulfil sustainability and circular economy targets, the thermodynamics, kinetics and distribution behaviour of WPCBs during the pyrometallurgical process are the key factors. This study employed a series of experiments to investigate the dynamic behaviour of WPCBs in copper flash smelting process. The kinetic data were obtained by employing a well-developed high temperature reaction–quenching technique followed by direct phase analyses with a scanning electron microscopy-energy dispersive X-ray detector (SEM-EDS), electron microprobe (EPMA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS). The industrial copper flash smelting process was firstly simulated on laboratory scale and investigated in this study by smelting industrial chalcopyrite concentrate and FeOx-SiO2 slag at a typical smelting temperature of 1300 °C in both air and argon atmospheres. Then WPCBs were added to this system to track their physical and chemical time-dependent behaviour. Moreover, two groups of WPCB elements (Ag, Au, Pt, Pd, and As, Sb, Bi) were separately added into the matte-slag system, and their time-dependent behaviour in different phases and distribution coefficients were concluded and also compared in detail with those of In, Sn, Ge, Te, La and Nd, which were also treated in the same system. Moreover, the kinetic data and distribution ratios of base metals as well as minor elements (Ag, Au, Pt, Pd, As, Sb, Bi) in the flash smelting process were obtained experimentally and calculated. They can be used in process development for the WPCB precious metal recycling process and, equally, when using complex copper concentrates with high As, Sb and Bi content. Furthermore, the results are essential for complementing CFD models to simulate the flash smelting process more precisely, which is of significance to achieve industrial visualization and artificial intelligence to satisfy the future requirements of Industry 4.0 and even 5.0.