Purification of nickel or cobalt ion containing effluents by electrolysis on reticulated vitreous carbon cathode

The study is aimed at improving a methodology to purify nickel or cobalt ion containing effluents by an electrochemical filter. Consequently, a cell with reticulated vitreous carbon (RVC) cathode for Ni and Co depletion was designed to analyze, at room temperature and pH equal to 6, flowrates and cathodic potentials able to affect the electrochemical process. Starting with Ni and Co initial concentration of 150 ppm, it is possible to reach a concentration lower than 0.1 ppm for both metals in less than 1 h, with a flowrate of about 1300 ml/min and for a catholyte volume of 1000 ml, under mass transport control conditions (for Ni - 1.1 V and for Co - 1.2 V cathodic potential versus Standard Calomel Electrode (SCE)). Moreover, the proposed work studied the process kinetics and fluid dynamics through the use of dimensionless relations such as Reynolds and Sherwood numbers. In addition considerations on current efficiency for reduction of both metal ions were done.