Use of electrodialysis to remove silver ions from model solutions and wastewater

The feasibility of the removal of Ag+ ions in a model solution and a sample of rinse water provided from an industrial plating plant was investigated in a batch electrodialysis system. The experiments were carried out using two different types of ion-exchange membranes. The effects of applied potential, pH value and initial silver concentration on the duration of electrodialysis and energy consumption were examined. Full removal of Ag+ ions was achieved from model solutions and the sample of rinse water. The most convenient applied voltage and energy consumption values to remove silver ions are reported. These results will be useful for designing and operating different capacities of electrodialysis plants for recovering Ag+ ions.

It was found in this work that the removal of silver ions from wastewater can be carried out effectively by applying electrodialysis. This method has advantages such as not using chemicals or causing sludge problems. In addition to these advantages, the operation cost of this method can be reduced because of the recovery of silver, which is one of the valuable heavy metals, either deposited on the cathode or concentrated in the cathode compartment. Moreover, besides the recovery of silver, the removal of the cyanide complex of silver and free cyanide from the wastewater, which gave rise to severe problems of water pollution, occurred in the anode compartment. With these advantages, ED of Ag+ ions from plating rinse water may become economically competitive in addition to being environmentally desirable, particularly when solutions are very diluted. From this point of view, a study based on the experimental data produced by using an optimized ED cell having thinner compartments working in a continuous mode is to be performed and will be reported in the near future.