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

The solubility behavior of the ammonium metavanadate–ammonium molybdate–ammonium acetate 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.

本研究探究了偏钒酸铵-钼酸铵-乙酸铵体系的溶解行为，并评估了采用乙酸铵（NH₄OAc）从偏钒酸铵（ammonium metavanadate, AMV）中选择性浸出钼的可行性。本研究采用Box-Behnken设计响应面法对浸出参数进行优化，确定的最优工艺条件为：乙酸铵浓度143 g·L⁻¹、浸出温度36 ℃、pH值8以及液固比10。在采用低钼偏钒酸铵（ammonium metavanadate, AMV，质量分数<2%）的实验中，电感耦合等离子体（Inductively Coupled Plasma, ICP）分析证实钼的脱除率超过99.99%。X射线衍射（X-ray Diffraction, XRD）与扫描电子显微镜（Scanning Electron Microscopy, SEM）表征结果显示，钒的回收率≥99.5%，产物纯度高于99.7%。傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy, FTIR）分析揭示了钒、钼物种随pH值的转变行为。动力学研究表明，该浸出过程主要受扩散控制，钼的活化能Eₐ(Mo)为9.4 kJ·mol⁻¹，钒的活化能Eₐ(V)为38.7 kJ·mol⁻¹。此外，杂质含量超过临界阈值的偏钒酸铵样品可通过多段浸出工艺实现有效提纯。另外，浸出液中富集的杂质可通过钙化沉淀法回收，进而延长乙酸铵溶液的使用寿命。