Kinetics of vanadium leaching from black shale in non-oxidative conditions

The leaching kinetics of vanadium from black shale under non-oxidative conditions was presented and compared with that under oxidative conditions. The effects of agitation speed, sulphuric acid concentration, temperature and particle size were determined. The morphology of the solid particles during leaching indicated that no product layer formed on the particles. The grain model with pore diffusion control provided a good description of vanadium leaching kinetics. The model gave an activation energy of 55·6 kJ mol⁻¹, and reaction order 0·37 with respect to sulphuric acid due to diffusion and chemical reactions occurring in parallel in the porous solids. The linear relationship K_D∝1/r₀² found for the apparent rate constant, where r₀ is initial particle radius, also supported a diffusion controlled process. The apparent activation energy was 40% larger for leaching under non-oxidative conditions than for leaching under oxidative conditions, indicating that an oxidising atmosphere had a positive effect on vanadium leaching.