Electrochemical recovery of cobalt using nanoparticles film of copper hexacyanoferrates from aqueous solution.

Nanoparticles film of copper metal hexacyanoferrates (CuHCF) was fabricated to electrochemically separate Co2+ in aqueous solutions under various conditions such as applied potential, solution pHs, initial concentrations, contact time and coexisting ions. Results showed that the removal efficiency conducted in reduction potential was obviously higher than that in oxidation potential. The optimal pH for Co2+ adsorption occurred at 8.0. Coexisting ions studies revealed that Co2+ could be removed from aqueous solutions containing Li+, Cu2+ and Al3+. Considering that cobalt and lithium are the main metallic elements in LiCoO2, the effect of different ionic strengths (IS) of LiNO3 (0.5, 1, 2, 5, 10) on adsorption was further investigated. Results showed that IS of LiNO3 had little impact on the removal efficiency of Co2+, which indicated the potential of selective recovery of cobalt from LiCoO2 in spent lithium-ion batteries. X-ray energy-dispersion spectroscopy (EDS) confirmed that the Co2+ could be adsorbed effectively onto CuHCF film. The adsorption was well described by Langmuir isotherm and the maximum sorption capacity is 218.82 mg/g. The kinetic rate of Co2+ adsorption was rapid initially and attained equilibrium within 60 min, and the data well fitted the Redlich-Peterson and the Elovich model, implying a chemisorption dominated process.