Liquid-Liquid Phase Separation of Fe-Cu-Pb Alloy and Its Application in Metal Separation and Recycling of Waste Printed Circuit Boards

The pyrolysis processing was carried out on the waste printed circuit boards (WPCBs) of mobile phones to dissociate metals from non-metals and obtain mixed metals with Fe, Cu and Pb as main components. Based on the main compositions of Fe, Cu and Pb, the liquid-liquid phase separation behavior of (Fe0.4Cu0.6)(100-x)Pb-x ternary alloy has been studied experimentally. The results show that the liquid-liquid phase separation of L -> L(Fe)+L(Cu, Pb) may occur during the ternary Fe-Cu-Pb alloy melt cooling in the miscibility gap. After the liquid L(Fe) solidified, the secondary liquid-liquid phase separation L(Cu, Pb)-> L(Cu)+L(Pb) takes place in the residual L(Cu, Pb) liquid phase, finally resulting in a three-zone separation structure. On the basis of the behavior of the liquid-liquid phase separation, a self-organized hierarchical separation system has been designed to separate and recycle these mixed metals from WPCBs. The enrichment behavior of the minor components like Cr, Au and Cd in the separation system was explored. The effect of super-gravity level on the metal separation and recycling rates has been discussed. As a result, a new harmless route has been established to recycle metal resources in WPCBs.