Mass balance and economic study of a treatment chain for rare earths, base metals and precious metals recovery from used smartphones

In the present study, a comprehensive hydrometallurgical process was developed for the recovery of several types of metals from used cell phone printed circuit board assemblies. The overall process is divided into four stages of selective leaching of rare earth elements (REE), copper, nickel, silver and finally gold. After solubilization, the metals were purified using precipitation, solvent extraction, electrodeposition, and cementation techniques. Laboratory pilot-scale tests of the complete smart phone printed circuit board processing line showed REE, copper, nickel, silver, and gold recovery efficiencies of 78.0 %, 98.8 %, 81.8 %, 100 % and 96.1 %, respectively. The purity of the products obtained is evaluated at 94.8 % for rare earth oxides (70.0 % Nd2O3, 18.5 % Pr2O3, 2.8 % Dy2O3 and 2.4 % Sm2O3), 99.8 % for elemental copper, 94.3 % for nickel oxide, 93.8 % for silver and 89.3 % for gold. A scenario involving the installation of a plant processing 1 t/h of waste was evaluated using SuperPro Designer software. For a total investment of $53.22 million and an operating cost of $18.23 million per year, the main revenue is $65.77 million per year, with a return on investment of 91.6 % and a payback period of 1.1 years.