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

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 acti-vator: 5 wt%, activation time: 30 min, sulfuric acid concentration: 12 vol%, leaching time: 6 h, leaching tem-perature: 95 degrees 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 Si-F and Al-F bonds. This behavior induced a beneficial reaction surface on muscovite with a low energy barrier for subsequent leaching. During the leaching process, the weakened Si-O and Al-O bonds could be more easily broken by H+ attack, thus accelerating muscovite dissolution and boosting the vanadium leaching efficiency.