Investigation of processing methods for the recovery of gold, copper, and nickel values from RAM connectors

Random-access memory (RAM) can be a valuable source for metals such as Au, Cu, and Ni. The RAM connectors consist of end contacts (Cu, Ni, Au) and a fiber-reinforced Cu laminated structure. The study investigates two process routes involving leaching and pyrolysis (as a pre-or post-treatment). Various parameters (acid concentration, solid–liquid ratio, time, and H₂O₂ dosage) are evaluated during the direct leaching of connectors (without crushing) using HNO₃ and MSA. The optimal parameters are 4M MSA at solid-to-liquid ratio (S/L)- 1/20, at 50 °C for 180 min, resulting in Cu ~57.6% and Ni ~91% dissolution. Further, the Cu powder (98% purity) from the leach solution is recovered by chemical reduction using ascorbic acid. The rest of the Cu present as tracks in RAM strips is recovered by pyrolysis (550 °C, 1h) followed by density separation. Alternatively, pyrolysis is applied as a pre-treatment for organic decomposition and detachment of gold contacts. Subsequently, the gold contacts are leached to dissolve the Cu and Ni values at optimal conditions. However, the dissolution of Ni is hindered due to char formation (in the case of MSA leaching), and the final gold residue contains char as an impurity. Leaching followed by pyrolysis leads to 94% of copper (as Cu precipitate and Cu from tracks) and 97% of gold (as gold fingers) recovery in solid form, while nickel is recovered in the leach solution.

Graphical Abstract