Vanadium leaching from carbonaceous shale using fluosilicic acid

Vanadium leaching from carbonaceous shale using H2SiF6 as a leaching aid was investigated. The results showed that vanadium leaching efficiency could reach up to 80% when the shale was leached by 15% H2SO4 and 8% H2SiF6 at 95 degrees C for 16 h with the liquid-solid ratio of 1 mL/g. In comparison, the efficiency was 80% with 20% H2SiF6 at 95 degrees C for 8 h and only 51% for 30% H2SO4 at 95 degrees C for 24 h at the same liquid-solid ratio. Samples treated by H2SO4 and H2SiF6 were characterized by XRD showing that the crystal structure of illite bearing vanadium was mostly collapsed. The satisfactory performance of H2SiF6 was attributed to the generation of HF which would easily destroy the stable structure of illite. (C) 2011 Elsevier B.V. All rights reserved.