Experimental and CFD study of a dual-anode rotating electrochemical reactor for intensified cobalt recovery from spent lithium-ion batteries

This work investigates a dual-anode rotating cylindrical electrode for cobalt electrorecovery from spent lithium-ion batteries leachates (citric acid/hydrazine). RANS simulations (k–ε model with Enhanced Wall Treatment) were validated against power measurements. Simulations at cathode speeds of 50–1000 rpm identified 50, 75, and 125 rpm as speeds generating Taylor vortices inside and/or outside the cathode while minimizing energy consumption. At 50 and 125 rpm, vortices developed both inside and outside the cathode, and only outside at 75 rpm, with mixing times of 95.8, 146.7 and 184.8 s, respectively. Cathode wall shear stress ( τ w ) increased and homogenized with speed. Guided by CFD, macroelectrolysis was conducted at the same speeds for 12 h at -1.2 V vs. SCE, determined by cyclic voltammetry. Microelectrolysis confirmed diffusion-controlled electrodeposition, whereas macroelectrolysis of the multicomponent real leachate revealed bulk concentration gradients and mass-transfer limitations. The highest cobalt deposition rate and current efficiency (99%) occurred at 50 rpm. At 125 rpm, cobalt recovery (77%) and purity (90.1%) were maximized, with the lowest final specific energy consumption (8.53 kWh·kg⁻¹ Co). Higher speeds reduced particle size and improved deposit homogeneity. The dual-anode enables a coupled hydrodynamic–electrochemical regime where Taylor-vortex and τ w control mass transport and electrochemical performance.