Cobalt recovery from spent lithium-ion batteries using a rotating cylindrical electrode reactor

The cobalt electrodeposition from a leaching containing cathode-powdery of spent laptop lithium-ion batteries (LIBs) of different commercial brands, collected from local laptop repair shops, was investigated. Citric acid (0.14 M) and hydrazine (0.1 M) were employed as complexing and reducing agents in the leaching during 24 h. Cobalt, manganese and nickel concentrations in the leachate, obtained by the flame method in an atomic absorption spectrometer, are reported. A rotating cylindrical electrode reactor which consists of a rotating open bottom as cathode and a static outer cylindrical as anode was employed. The numerical flow patterns and cathode velocities that induce the presence of Taylor vortices inside and/or outside the cathode were investigated. RANS equations with the standard k−ε turbulence model and enhanced wall treatment was used. Electrical power measurements were performed to validate simulations. Cyclic voltammetry experiments with synthetic solutions were applied to determine the reduction potential of cobalt (found in −1.2 V vs SCE). Subsequently, electrolysis experiments were carried out at predetermined cathode speeds (50, 75, and 125 rpm), imposing a working cathodic potential of −1.2 V versus SCE during 12 h. Experimental results indicate that the best cobalt recovery rates and current efficiency coincide with the presence of Taylor vortices both inside and outside the cathode, i.e., at 50 rpm. The peak performance in cobalt recovery and current efficiency was recorded at 49 % and 47.3 %, respectively. Finally, the deposits obtained from each electrolysis test were removed from the cathode and analyzed via energy dispersive spectroscopy. The range of purity of Co obtained in the electrodeposit film were between 56.75 % and 74.8 %.