Selective separation of molybdenum impurity from NH4VO3 via ammonium acetate-mediated solid-liquid phase control

The solubility behavior of the CH3COONH4-(NH4)2MoO4-NH4VO3-H2O system was investigated, and the feasibility of selectively leaching molybdenum from AMV using ammonium acetate (NH₄OAc) was evaluated. A Box-Behnken-designed response surface methodology was employed to optimize the leaching parameters, with the optimal conditions identified as NH₄OAc concentration of 143 g·L⁻¹, leaching temperature of 36 °C, pH 8, and liquid-to-solid ratio of 10. In experiments using low-molybdenum AMV (<2 wt%), ICP analysis confirmed a molybdenum removal efficiency exceeding 99.99%. XRD and SEM characterization demonstrated a vanadium recovery rate of ≥99.5% and a product purity above 99.7%. FTIR analysis revealed the pH-dependent transformation of vanadium and molybdenum species. Kinetic studies indicated that the leaching process is primarily diffusion-controlled, with activation energies of Eₐ(Mo) = 9.4 kJ·mol⁻¹ and Eₐ(V) = 38.7 kJ·mol⁻¹. Furthermore, AMV samples exceeding the critical impurity threshold were effectively purified via a multi-stage leaching process. Additionally, impurities accumulated in the leachate can be recovered through calcification precipitation, thereby extending the service life of the NH₄OAc solution.