Nickel recovery from treated nickel sludge by cyclic voltammetry under varying cathode materials in an electrowinning bath

Abstract

Nickel is famous for being the electroplating element due to its corrosion resistance. However, after a certain period of time, the nickel electroplating solution needs to be disposed of, but the disposal cost is expensive. Thus, electrowinning is preferred instead of disposing of the electrowon nickel ions out of the sludge from the electroplating solution. This study aimed to evaluate electrowinning parameters that maximize nickel recovery from treated nickel sludge using the ideal commercial cathode material type for kinetic studies. During the study, determination of the best cathode material type, optimization by using Design of Experiment (DOE)-Box-Bhenken Design on applied potential, pH, and contact time, and characterization of cathodes’ surface morphology with deposited nickel have been conducted. Results show that graphite cathode recovered 56.74% followed by nickel metal (55.90%) and AISI 304 stainless steel (50.66%) at expected optimal electrowinning conditions of pH 5, 0.5 V and 3 hours. However, nickel deposits on graphite contain impurities and are difficult to extract. Thus, after considering commercialization aspects in the Analytical Hierarchy Process and the Technique for Order of Preference by Similarity to Ideal Solution (AHP-TOPSIS), the nickel cathode is the best. The optimal electrowinning conditions by using DOE are pH 6, 0.5 V and 1 hour with a maximum nickel recovery of 70.18%. The morphological characterization evidenced smooth, polycrystalline surfaces that become altered as the Ni grains increase. The electrochemical process has been discussed based on Nernst, Tafel, Anson and Butler Volmer equations. Overall, the nickel cathode has demonstrated significant potential as an ideal commercial cathode for nickel recovery.