Removal of iron and nickel from solutions by application of electrical fields

Metallic impurities such as Ni Fe, Cu ions in chromium plating solutions can be removed by electromigration followed by electrodeposition or coagulatiion using a porous pot, suspended in the bath and containing a lead cathode. In the same process, Cr(III) is oxidized to Cr (VI) at the insoluble lead anode leading to regeneration of the plating solution. Previous research and data from industrial operations have indicated the "porous pot" method could be a cost-effective and environmentally friendly method to continuously separate impurities and recycle spent chromium solutions. However, no data are available that relate the various concentrations of impurities to the extent and the rate of their removal. This investigation focused on the use of five suitable catholytes for the removal of impurities. Up to 60% nickel and 52% iron removal were observed in orthophosphoric acid and sodium monophosphate catholytes respectively. In addition to these two electrolytes, chromic acid appears to be a most suitable catholyte for purification when more than one metallic impurity is present in the spent solution.