Source separation of V and Fe by two-stage selective leaching during V extraction from stone coal

A method of two stage selective leaching for separation of V and Fe during V extraction from stone coal was developed. In the primary procedure stone coal was roasted in an inert atmosphere at 900 degrees C for 1 h, and then the roasted product was leached for Fe removal in 7% (vol%) H2(S)O(4) at 30 degrees C for 30 min when the liquid-to-solid ratio (L/S) was 3 : 1 mL g(-1). The Fe removal residue was then leached under the conditions of 20% (vol%) H2SO4, L/S= 2 : 1 mL g(-1), at 95 degrees C for 4 h. In the first stage, 98.1% Fe could be removed from the roasted product with only 2.0% V loss. In the second stage, a 97.8% V leaching efficiency was obtained, which was 10.4% higher than the leaching efficiency of the roasted product using one-stage leaching. Based on the different solubilities in acid of muscovite and FeS, the decomposition product of pyrite at high temperature in an inert atmosphere, this method admirably prevented Fe from entering the V leaching liquor, realizing source separation of V and Fe during V extraction from stone coal.