Recovery of Gold as Nanoparticles from Gold-Poor Au-Cu-Cl Solutions

Abstract

Electrochemical methods for preparing functional surfaces typically use optimized solutions where competing reactions do not need to be considered. However, with the increased demand for resource efficiency, selective deposition methods that can make use of more complex solutions are gaining importance. In this study, we show how gold recovery as nanoparticles from Au-Cu-Cl solutions can be assisted by electrochemically generated Cu1+ species. In the electrochemically assisted reduction (EAR) method, a low-energy electrochemical step is employed, followed by spontaneous gold reduction onto the electrode. The studied solutions mimic challenging hydrometallurgical process solutions where the ratio of gold (5 ppm) to copper (20 g/L) is low. In addition to selective gold recovery, by controlling the electrochemical pulse parameters, the loss of deposits due to corrosion could be minimized, current efficiency improved from ∼0 to >10%, and relatively narrow particle size distributions achieved (43 ± 10 nm), and this can be done even at a high (4.5 M) NaCl concentration.