Electrolytic recovery of silver from low concentrated silver cyanide spent plating solutions

Cyanide silver solution containing 200 to 1000 mg L-1 silver ions were used for recovery studies. The nature of the silver deposit was studied using a Hull cell, and the current density range was selected for electrolysis to recover silver. A batch electrochemical reactor, consisting of a planar stainless steel cathode and platinum anode was used and silver was recovered at 0.04 to 0.2 A dm(-2). The effect of different initial silver concentrations on the electrochemical recovery of the metal was investigated as a function of electrolysis duration at various current densities. The cathode current efficiency and the energy consumption were determined for the solutions for various experimental conditions. Surface morphology and structure of the silver deposit was also studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that irrespective of the initial silver concentration, higher current efficiency and lower energy consumption can be achieved at a low current density. For a given current density, the energy consumption to recover silver is lower from relatively concentrated than from dilute solutions.