Sequential recovery of copper, nickel, gold, silver and zinc from WPCBs of obsolete mobile phones through hydrometallurgical recycling

Abstract

Waste printed circuit board (WPCB) of an obsolete mobile phone is a valuable source of base and precious metals. Alternatively, WPCBs also contain various lethal and toxic constituents which introduce ecological impacts while landfilling and incineration. Recycling WPCB is essential to reduce the environmental effects and to recover valuable metals. This article employs a hydrometallurgical route for the sequential recovery of copper, nickel, gold, silver and zinc from WPCBs through leaching, solvent extraction and cementation processes. Initially, the metal clads of WPCBs are used for the leaching of copper, nickel and other base metals without any selective dissolution of gold and silver. Optimal results revealed that dilute nitric acid at room temperature provides effective leaching (99.9%) of copper, nickel and zinc by leaving precious metals gold and silver in the residue. The utilization of phenolic oxime as a solvent extraction reagent revealed the selective recovery of copper and nickel from the leach liquor individually. The availed residue is dissolved in the halide salts in the presence of acidic conditions showing the quantitative dissolution of gold and silver. Solvent extraction with amide-based reagents recovered gold by leaving the silver-rich raffinate. A cementation technique with copper powder is implemented for the precipitation of silver. The proposed approach delivers an effective, eco-friendly and economically feasible process for the sequential recovery of metallic values from WPCBs of obsolete mobile phones.