Effect of mechano-chemical activation with NaF on improved acid leaching of vanadium-bearing shale

Abstract

Vanadium extraction from vanadium-bearing shale by direct acid leaching is currently restricted owing to the inefficient release of vanadium from mica, which consumes a large amount of acid. To overcome this limitation, this study developed a mechano-chemical activation-assisted acid-leaching process. Further, the effects of the mechano-chemical activation parameters on the vanadium-bearing shale and vanadium dissolution in an acid system were examined using the following conditions: ball-to-pulp ratio: 50 to 1, pulp density: 50%, NaF activator: 5 wt%, activation time: 30 min, sulfuric acid concentration: 12 vol%, leaching time: 6 h, leaching temperature: 95 °C. These conditions increased the vanadium leaching efficiency from 82.3% to 90.3%. The mechano-chemical activation treatment exposed the fresh muscovite surface, promoting the preferential adsorption of fluoride to form stable SiF and AlF bonds. This behavior induced a beneficial reaction surface on muscovite with a low energy barrier for subsequent leaching. During the leaching process, the weakened SiO and AlO bonds could be more easily broken by H+ attack, thus accelerating muscovite dissolution and boosting the vanadium leaching efficiency.