Electrolytic recovery of nickel and copper from acid pickling solutions used to treat metal surfaces

The increased use of heavy metals in process industries often results in the generation of large quantities of wastewater (WW) and aqueous waste (AW) containing mixtures of heavy metals such as copper and nickel. This research focuses on the electrochemical recovery of copper and nickel from acid pickling solutions used to treat metal surfaces. Using hull cells, beaker plating, and electrolytic cells in pilot scale (capacity 30L), the most important parameters influencing the process have been identified (temperature, contact time, and current density). In total, about 60 tests were carried out on AW containing nickel and copper. The results of the tests carried out with copper-containing AW shows that removal yields are often higher than 50%; while the energy consumption is less than 15 kWh kg(-1) of metal deposited. The best removal efficiency (100%) was achieved by applying a current density of 6 A dm(-2) and the energy consumption was 2 kWh kg(-1). The tests carried out with AW containing nickel point out very low removal yields (<20%) and very high energy consumption (even exceeding 300 kWh kg(-1)). The best removal yield obtained, applying a current density of 3 A dm(-2), is 6.7% with an energy consumption of 40 kWh kg(-1) of metal removed. A costs analysis based on Metal Exchange value was carried out. The cost analysis suggests that the results, in terms of removal and recovery, obtained for these metals, in particular for copper, are very promising for an industrial application.