Investigation of the Bimodal Leaching Response of RAM Chip Gold Fingers in Ammonia Thiosulfate Solution

Oxidative thiosulfate leaching using Cu(II)-NH3 has been explored for both mining and recycling applications as a promising method Au extraction. This study seeks to understand the dissolution behavior of from waste RAM chips Cu(II)-NH3-S2O3 solution. In course this work, bimodal loss were observed in manner that we have not identified literature. Identification existence specific Au-Ni-Cu lamellar structure gold fingers by scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) revealed possibility interference between recovery Cu Ni. During leaching, co-extraction Ni was found predict negative impact on recovery, result chemical interactions interlayer. Decopperization pretreatment necessary remove pre-existing promote leaching. As part parameters, such Cu(II) concentration, aeration rates, ammonia concentrations, particle sizes, temperatures, investigated. A satisfactory 98% achieved 50 mM Cu(II), 120 mL/min rate, 0.5 M (NH3)2S2O3, 0.75 NH4OH (i.e., AT/AH ratio 0.67) 4 h residence time at room temperature (25 °C). However, there several high recoveries prior lixiviant. It main cause lower due precipitation or cementation reaction included sulfur species formation. Because composite response comprised maximum developed, termed proclivity, facilitate statistical analysis. Furthermore, explores provides suggestions improving under co-existing metals PCB materials.