Reaction mechanisms of waste printed circuit board recycling in copper smelting : The impurity elements

Abstract

Feeding Waste Printed Circuit Boards (WPCBs) into existing pyrometallurgical processes is developing as an easy-to-adapt and efficient way to recycle them. To fulfill sustainability and circular economy targets, kinetics and distributions are the key factors when recovering metals and trace elements from WPCBs. We investigated the reaction mechanisms and distribution behavior of impurity elements Sb, As and Bi between copper matte and slag at a typical smelting temperature of 1300 °C both in air and argon atmospheres. Laboratory-scale heat-quench experiments indicated that vaporization can effectively eliminate arsenic in the matte phase, but not antimony or bismuth either in air or in an argon atmosphere. Sufficient contact time between the gas and matte phase is also needed to transfer the trace elements into gas and slag. In this work, kinetic data and distribution ratios of these impurity elements in the matte and slag phase were calculated. They can be used in process development for WPCB recycling and, equally, when using complex copper concentrates with high As, Sb, and Bi contents. The results also complement CFD models to simulate flash smelting processes more precisely.