Theoretical Modeling and Experimental Evaluation of Vanadium Recovery from Mechanical Activation-Assisted Vanadium Titano-Magnetite Ore (NH 4 ) 2 C 2 O 4 Leaching

Recovering vanadium from vanadium titanium-magnetite (VTM) ore using (NH 4 ) 2 C 2 O 4 is a clean hydrometallurgical process, but the drawback is the low recovery and slow kinetics due to the formation of inhibitor. A novel energy-efficient mathematical model was derived for green leaching of VTM in which the mechanical activation (MA) removed the inhibitor “δ” (formation of impermeable product layer of CaC 2 O 4 ) covering the reacting core of the CaV 2 O 6 leaching process in (NH 4 ) 2 C 2 O 4 solution. Before the MA processing, the formation of the CaC 2 O 4 layer affects the kinetics (slow) and NH 4 VO 3 leachability (low recovery). The dissolution rate enhancement and economic importance (in terms of leaching kinetic/recovery) of mechanical activation (MA) pretreatment in hydrometallurgical processing cannot be overemphasized. It is shown from the experimental and developed mathematical model results that the rotating speed of the ball mill (ω b ) has a significant effect on the NH 4 VO 3 recovery. At 360 rpm, the experimental result gave an 82% optimum recovery rate and a reaction rate constant of 0.01889s −1 with close correlation with the present models at 82.8% and 81% for liquid-to-solid layer diffusion and chemical reaction controls, respectively, with a reaction rate constant of 0.018883s −1 . The close correlation between the experimental recovery rate results and the diffusion recovery rate model result justifies that the leaching process is diffusion control shrinking core kinetic with experimentally measured activation energy ( E a ) value of 19.502 kJ/mol . This present model proved that MA enhances the dissolution rate regardless of the formation of a passivation layer on the material and best describes the kinetics of the MA hydrometallurgical processes compared to the shrinking core model.