The process of vanadium migration and silicon extraction by alkaline leaching from high silicon stone coal under reduction conditions

Abstract

It is difficult to utilize stone coal with a vanadium grade of below 0.7%. With the aim of effectively utilizing the silicon and vanadium in stone coal, the vanadium concentration and silicon extraction processes by alkaline leaching under reducing conditions were investigated. The effect of NaOH mass fraction, temperature and the amount of hydrazine hydrate on the leaching process was researched. Moreover, the laws of phase transformation and the migration process of vanadium were revealed. The results show that the dissolution of quartz resulted in the exposure of muscovite and goldmanite, but the phase of muscovite and goldmanite was not damaged. Under the optimal operation conditions (25% mass fraction of NaOH, liquid-solid ratio 2:1 at 200 °C for 4 hours), 90.14% of silicon was removed. At the same time, the modulus of sodium silicate product reached 1.88 and the content of V2O5 enriched from 0.5% to 2.51%. In addition, V(IV) was partially reduced to V(III) by adding hydrazine hydrate in an amount of 10% by mass. V(IV) migrated from the liquid phase to the alkali leaching slag, and the recovery of vanadium increased from 89.48% to 94.43%. All the obtained results suggest an efficient process for separation and extraction of vanadium and silicon.