Solution Purification of Copper Electror

Typical copper electrorefining electrolyte contains tens of grams of copper, some nickel and a wide variety of impurities. Some of these impurities comprise trace amounts of dissolved precious metals like Ag, Pd and Pt that currently are not fully exploited. This study presents an electrochemical method to recover precious metals via a combined electrodeposition-redox replacement (EDRR) process, where energy is used only to deposit copper during the ED-step, while the RR-step relies on the spontaneous replacement of copper by the precious metals (i.e. cementation). In order to conduct the recovery successfully, process parameters such as deposition potential (EDE), deposition time (tDE), redox replacement time (tRR) and the number of cycles (n) was adjusted. Investigations performed in synthetic electrolyte (40 g/L Cu, Ag = 10 ppm) proved the possibility to recover a high purity silver. Short deposition times (tDE) were found to result in small Cu particles that provided a suitably high surface area for silver cementation. In addition, experiments performed in real industrial electrolytes containing 44 g/L Cu and 54 ppb Ag (Boliden Harjavalta, Pori), demonstrated that EDRR could attain Ag recoveries of between 46–67% in an energy efficient, additive-free manner.