Leaching of vanadium from LD converter slag using sulfuric acid

In order to extract vanadium from LD (Linz–Donawitz) converter slag of steelmaking plant, an alkaline roasting–acid leaching study was carried out and the effect of different parameters on the kinetics of vanadium dissolution was determined. The leaching residue was characterized by XRD, XRF and SEM/EDX analyzer. The maximum vanadium recovery of ca. 95% was achieved at the optimum leaching condition of 70 °C, S/L: 1/15, acid concentration: 3 M and leaching time: 150 min. It was shown that particle size has a significant effect on the dissolution of vanadium and maximum extraction was achieved at the finest size of below 0.850 mm. Dissolution of vanadium in sulfuric acid showed that there are two stages in the kinetics of leaching. In the first 15 min, a sharp increase in the amount of vanadium extracted was observed and at longer times, leaching became slower. Shrinking core model (SCM) was used to describe the kinetics of the slag acid leaching. SCM equations were modified to represent the long time leaching process in which the initial recovery of vanadium (at the beginning of long term period) is not zero. It was found that the kinetics of leaching at low temperature is controlled by chemical reaction for both short and long leaching periods. Rate of leaching is controlled by solid product diffusion regime at high temperature.