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This study introduces a mechanistic model for the recovery of lithium and cobalt from LiCoO$_2$ during acidic-reductive leaching, utilizing HCl and H$_2$O$_2$. The model incorporates various factors such as particle size, acid concentration, and film passivation effects, providing insights into the dynamics of Co$_3$O$_4$ film formation and dissolution. Validation against experimental data reveals the model's effectiveness at lower acid concentrations, while highlighting areas for further refinement, particularly at higher HCl levels.
Recovery rates of lithium and cobalt can be significantly impacted by the presence of H$_2$O$_2$ and the formation of passivating films during leaching processes.
We developed a new mechanistic model for lithium and cobalt recovery during acidic-reductive leaching from LiCoO$_2$. The system considers HCl as an acid and H$_2$O$_2$ as a reducing agent. The model tracks conversion of LCO, the particle radius, the acid, H$_2$O$_2$, formation-dissolution dynamics of Co$_3$O$_4$ film, the film thickness, recovery of lithium and cobalt, and moles of O$_2$. We introduced the film passivation effects for reduced recovery in the absence of H$_2$O$_2$. We validated the model against the experimental data of recovered Li and Co reported in literature at three acid concentrations (0.5 M, 1.5 M, and 2.5 M) and four H$_2$O$_2$ concentrations (0%, 0.2%, 0.4%, and 0.6% (v/v)). The model works reasonably well at 0.5 M and 1.5 M HCl for the 0% and 0.6% concentrations of H$_2$O$_2$. At 2.5 M HCl, the model over-predicts the data in the presence of H$_2$O$_2$, while it works well at 0% H$_2$O$_2$. We suggest pathways for further improvements in the model. The comprehensive mechanistic modelling framework for the leaching with a full list of the equations, the parameters, and the variables, reported for the first time, can be extended to other cathode chemistries and acid-reductive leaching systems.
