Recovery of vanadium from black shale

The recovery of vanadium from a black shale from Guizhou Province of China was performed using a three-step process, which consists of a leaching step in the H2SO4-HF-NaClO system under atmospheric pressure, the vanadium separation from leachate by solvent extraction and stripping, followed by precipitation of ammonium vanadate and thermal decomposition. Under the optimum leaching conditions of 100 g/L sulfuric, 15 g/L hydrofluoric acid, 1.5 g/L NaClO, 6 h leaching at 90 degrees C and oxygen partial pressure of 1 200 kPa, and the liquid-to-solid ratio of 2, about 91% vanadium extraction is achieved. The vanadium extraction yields of solvent and stripping are 99.83% and 97.66% when using 10% (volume fraction) P204, 5% TBP and 85% sulfonated berosene as organic phase and 15% (mass fraction) sulphuric acid as stripping agent. After thermal decomposition the purity of powder vanadium pentoxide products is 99.18% and the overall vanadium recovery is over 81% in the whole process.