W（Ⅵ）­V（Ⅴ）­H2O体系钨钒分离的热力学分析

摘要

通过热力学计算绘制25℃时W(Ⅵ)­V(Ⅴ)­H2O系中存在的离子随pH、钨、钒浓度变化的热力学平衡图，并总结其变化规律。通过热力学分析，从理论上寻找到钨、钒在混合溶液中存在形式上的差异，并据此提出钨钒分离的技术路线。钒形成聚合离子的能力强于钨。在pH约为8.5~9.0的条件下，溶液中绝大部分的钒以聚合离子形式存在，而钨则几乎全部为单核离子，利用该差异通过合理的分离手段即可实现二者的有效分离；而在钨、钒浓度均较低时，体系会在pH较低的条件下形成VO2+离子，而此时钨的存在形式全部为阴离子，因而，采用阳离子萃取剂或阳离子树脂可望选择性地将VO2+从溶液中分离。%The thermodynamic equilibrium diagrams were drawn for the distribution of species at different pH and concentrations in the W(Ⅵ)­V(Ⅴ)­H2O system at 25 ℃. The difference of existing forms between W and V in the mixed solution was found by the theoretical analysis, and accordingly the technical routes for separation of W and V were presented. The results show that the polymeric ability of VO43-is stronger than that of WO42-. At the pH range of 8.5-9.0, most of VO43-transform to polymeric anions, while almost all W ions still exist as the form of monomeric WO42-. This difference makes it possible that W and V can be separated efficiently by a proper method. In the solution with low concentration of W and V, VO2+ ions are formed under low pH conditions, while W ions exist as the form of anions. Consequently, VO2+ions can be selectively separated by the cation extraction agent or exchange resin.