Lab scale optimization and two-step sequential bench scale reactor leaching tests for the chemical dissolution of Cu, Au & Ag from waste electrical and electronic equipment (WEEE)

Abstract

Regulations force to Waste Electrical and Electronic Equipment (WEEE) management by recycling the materials by safe and suitable methods, due to generating massive amounts of WEEE. This research aims towards extract metals from waste random-access memory (RAM) devices in different solutions. In addition, the effect of different parameters such as reagent concentration, oxidant concentration and solid/liquid ratio were investigated with full factorial experimental design tests and analysis of variance (ANOVA). The results showed that the extraction of gold and silver was 96.81% and 99.02% respectively under the following conditions: concentration of 2% iodine and 3% hydrogen peroxide as oxidizing agent, 5% solid/liquid ratio and leaching period of 2 h. An increase of the hydrogen peroxide concentration increased gold and silver extraction. While about 79.30% silver was found to be extracted using 2 M sulfuric acid, 1.5 M ammonium persulfate, 5% solid/liquid ratio and leaching period of 5 h, 79.43% copper was extracted by using ammonia instead of sulfuric acid under the same conditions. Ammonium persulfate was found to be a good oxidizing agent for sulfuric acid and ammonia leaching, since it provided selective extraction of silver and copper respectively. Two-step sequential bench scale reactor leaching tests were conducted to extract copper (98.73%), gold (99.98%) and silver (96.90%) selectively with high extraction. Two-step leaching approach was concluded as the most appropriate method for selective extraction of targeted metals from waste RAM devices.