Thermodynamic analysis of metals recycling out of waste printed circuit board through secondary copper smelting

Abstract

In this paper, a detailed thermodynamic analysis of processing of electronic waste (e-waste), particularly printed circuit boards (PCB), through secondary copper recycling (black copper smelting), was carried out. The mass balance flowsheets of two scenarios, i.e., the case of secondary copper recycling with (SCE1) and without (SCE2) addition of PCBs, have been developed and compared. From the perspective of recovery of copper (Cu), gold (Au), and silver (Ag); the thermodynamic analysis predicted that the process conditions at temperature of 1300 °C and oxygen partial pressure (pO2) of 10–8 atm are suitable for PCB processing through secondary copper smelting route. Under these conditions, no solid phases were predicted to form when the PCB addition is below 50 wt%. High PCB addition was predicted to produce high volume of slag in the process and more pollutants in the gas phase (Br-based gaseous compounds). The chemistry of the slag was also predicted to change that is shifting the liquidus temperature to a higher value due to the presence of aluminium (Al), silica (SiO2), and titanium dioxide (TiO2) in the feed coming from the PCB. The carbon content of the PCB potentially supplies additional heat and reductant (CO) in the process hence can partially replace coke in the feed material. The predicted recoveries of copper (Cu), gold (Au), and silver (Ag) from e-waste were 83.3, 96.5, and 88.5 wt% respectively.