Study on Vanadium Leaching from Vanadium and Ferro-Titanium Concentrate Using Calcified Roasting Pellets and Sulfuric Acid at Constant pH

This study proposed a selective leaching method to address the challenge of excessive iron (Fe) leaching during a sulfuric acid treatment of magnetite pellets, which complicates the subsequent extraction and precipitation of vanadium (V). The approach involved constant-pH sulfuric acid leaching of calcined and roasted vanadium–titanium (V–Ti) magnetite pellets to enhance V recovery while minimizing Fe dissolution. A comparison between constant-pH leaching and conventional heap leaching was conducted. The results showed that, under optimal leaching conditions, the V leaching rate remained largely unchanged, while the Fe leaching rate was significantly reduced compared with conventional heap leaching. Specifically, under optimal conditions—acid concentration of 2 mol/L, liquid–solid ratio of 1:3, temperature of 90 °C, and leaching time of 360 h—the V leaching rate reached 72.21%, while the Fe leaching rate remained as low as 0.91%. Additionally, the valence states of V and Fe in the pellets before and after leaching, as well as the main phase compositions during the leaching process, were analyzed. The results indicated that the primary phases in the calcined and roasted pellets remain unchanged before and after leaching, and most of the V and nearly all divalent Fe were effectively leached.