Efficient separation of black shale-hosted vanadium induced by formation of kalunite-jarosite solid solution in two-stage pressurized acid leaching coupled with lixivium recycling

Abstract

Black shale-hosted vanadium deposit is an important species of nontraditional mineral resources. The green efficient separation of black shale-hosted vanadium has attracted lots of researchers’ attention. In the paper, two-stage pressurized acid leaching coupled with lixivium recycling was investigated and clarified. Results showed that this coupling technics endowed selective leaching of vanadium under the optimized conditions that were liquid to solid ratio of 1.5 mL/g, leaching time of 120 min, sulfuric acid addition of 12.5 vol%, the first-stage temperature of 180 °C and second-stage temperature of 150 °C. From the first stage to the second stage, the muscovite has been almost dissolved, which guaranteed high vanadium recovery. Through recycling the second-stage lixivium, the first-stage pH value was controlled below pHTθ of Eq. (5) (0.27, 180 °C) and above pHTθ of Eq. (6) (−0.88, 180 °C) and Eq. (7) (−2.83, 180 °C), triggering the isomorphous precipitation of Fe and Al as kalunite-jarosite solid solution. Once fresh sulfuric acid solution touched the first-stage residue, the kalunite-jarosite solid solution can still be stably remained and discharged. The leached Fe and Al ions were directionally gathered to the first stage and precipitated as kalunite-jarosite solid solution. Recent data collected from this coupling technics suggests that the asynchronous dissolution-precipitation of V, Al and Fe was achieved during acid leaching of the black shale.