Kinetics study of the dissolution of black mass material using oxalic acid as a leaching agent

Artikel i vetenskaplig tidskrift, 2025

This study investigates the dissolution mechanisms of black mass by employing oxalic acid as a leaching agent at different temperatures. The concentration of oxalic acid and the solid-to-liquid ratio of the leaching are maintained
at a fixed molar ratio of 1:2.5. This work aims to study the impact of the leaching temperature on the
kinetics and the leaching residue composition or morphology. The findings confirm that increasing the temperature
significantly enhances the rate of lithium dissolution from the black mass; 6 h is needed to reach a
dissolution equilibrium at 30 ◦C against less than 30 min at 80 ◦C. The dissolution rate is shown to be chemically
controlled, with a pseudo-homogeneous model of 2nd and 3rd order, and the Avrami model best fitting the
experimental data. The energy of activation was determined via the Avrami model to be at 76 kJ/mol. Additionally,
this study identifies the anionic oxalate complexes formed in the aqueous solution during the leaching
process, which is essential to developing an adequate purification method for the leachate. Finally, residues are
characterized using various techniques, including XRD, SEM-EDS, and particle size analysis, which revealed that
oxalate precipitate is formed majorly in the bulk of the solution as a disordered (Co,Ni,Mn)C2O4 ⋅2 H2O phase.