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根据同时平衡原理以及质量守恒定律,绘制了在不同的游离总钙浓度下Ca-V(Ⅴ)-H2O体系25℃时的热力学平衡图,并进行了热力学分析。结果表明,随着溶液pH值的增大,体系中依次出现V2O5、Ca(VO3)2、Ca2V2O7、Ca3(VO4)2、Ca3(VO4)2+Ca(OH)2、Ca(OH)2六个沉淀稳定区。当沉钒反应平衡后液游离总钙浓度为0.01mol/L时,在pH=5.1~9.8范围内,钒以Ca(VO3)2形式沉淀,钒浓度最低可降至2.2×10-3 mol/L;在pH=9.8~10.3范围内,钒以Ca2V2O7形式沉淀,钒浓度最低可降至1.2×10-2 mol/L;在pH=10.3~12.6范围内,钒以Ca3(VO4)2形式沉淀,钒浓度最低可降至2.4×10-4 mol/L,沉钒效果最佳。当游离总钙浓度为0.01~1.0mol/L时,理论最佳沉钒pH值基本维持在11.0~12.6。
According to the principle of simultaneous equilibrium and the law of conservation of mass, the thermodynamic equilibrium diagram of Ca-V (Ⅴ) -H2O system at 25 ℃ under different free total calcium concentration was plotted and the thermodynamic analysis was carried out. The results show that with the increase of the pH of the solution, V2O5, Ca (VO3) 2, Ca2V2O7, Ca3 (VO4) 2, Ca3 (VO4) 2 + Ca (OH) 2 and Ca (OH) A sedimentation area. When the concentration of total free calcium was 0.01mol / L, vanadium precipitated as Ca (VO3) 2 in the range of pH = 5.1 ~ 9.8, and the concentration of vanadium decreased to 2.2 × 10-3 mol / L, vanadium precipitated as Ca2V2O7 in the pH range of 9.8 ~ 10.3, the lowest vanadium concentration could be reduced to 1.2 × 10-2 mol / L, and vanadium precipitated as Ca3 (VO4) 2 in the range of pH = 10.3 ~ 12.6 , The lowest vanadium concentration can be reduced to 2.4 × 10-4 mol / L, Vanadium vanadium optimum. When the free total calcium concentration was 0.01-1.0 mol / L, the optimal theoretical vanadium pH was maintained at 11.0-12.6.