Vanadium leaching from carbonaceous shale using fluosilicic acid

Abstract Vanadium leaching from carbonaceous shale using H 2 SiF 6 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% H 2 SO 4 and 8% H 2 SiF 6 at 95 °C for 16 h with the liquid–solid ratio of 1 mL/g. In comparison, the efficiency was 80% with 20% H2SiF6 at 95 °C for 8 h and only 51% for 30% H2SO4 at 95 °C for 24 h at the same liquid–solid ratio. Samples treated by H 2 SO 4 and H 2 SiF 6 were characterized by XRD showing that the crystal structure of illite bearing vanadium was mostly collapsed. The satisfactory performance of H 2 SiF 6 was attributed to the generation of HF which would easily destroy the stable structure of illite.