钼酸钙酸分解热力学分析及其应用

针对钼酸钙的酸分解过程，根据同时平衡和物质守恒原理，应用现有热力学数据绘制298 K时CaMoO₄-H₂SO₄/HCl-H₂O系部分溶解组分的浓度对数——pH图.利用热力学平衡图对钼酸钙酸分解的工艺过程进行研究.结果表明，CaMoO₄-H₂SO₄-H₂O系在整个pH范围可以分为3个稳定区，pH在0~3.5时为H₂MoO_4(s)、CaSO_4(s)稳定区，pH在3.5~4.5时为H₂MoO_4(s)、CaSO_4(s)、CaMoO_4(s)稳定区，pH在4.5~7.0时为CaMoO_4(s)稳定区；CaMoO₄-HCl-H₂O系在整个pH范围可以分为3个稳定区，pH在0~2.9时为H₂MoO_4(s)稳定区，pH在2.9~4.5时为H₂MoO₄(s)、CaMoO_4(s)的稳定区，pH在4.5~7.0时为CaMoO_4(s)稳定区.根据热力学分析结果可以推断，钼酸钙容易被酸分解，相比于硫酸浸出钼酸钙，盐酸浸出钼酸钙过程无CaSO₄产出，减少浸出产物包裹钼酸钙.验证实验表明，盐酸对钼酸钙的分解效果优于硫酸，采用HCl浓度为2.4 mol/L的稀盐酸，浸出液固比V_L /W_S=10 mL/g，在25 ℃浸出45 min，钼的浸出率达到98.56 %. 

Thermodynamic study on acid decomposition of calcium molybdate and its application

According to the laws of simultaneous equilibria and mass conservation, the lgC-pH diagram of a CaMoO₄-H₂SO₄/HCl-H₂O system was established on the basis of the modynamic date at 298 K. Thermodynamic analysis was carried out to show the effect of technical conditions on acid decomposition of CaMoO₄. The results show that there are three stable areas of various solid phases of the CaMoO₄-H₂SO₄-H₂O system in the pH range of 0~7.0. The first one is H₂MoO_4(s) and CaSO_4(s) (0 < pH < 3.5), the second one is H₂MoO_4(s) CaMoO_4(s) and CaSO_4(s) (3.5 < pH < 4.5), and the third one is CaMoO_4(s) (4.5 < pH < 7.0). There are three stable areas of various solid phases of the CaMoO₄-HCl-H₂O system in the pH range of 0~7.0. The first one is H₂MoO_4(s) (0 < pH < 2.9), the second one is H₂MoO_4(s) and CaMoO_4(s) (2.9 < pH < 4.5), and the last one is CaMoO_4(s) (4.5 < pH < 7.0). Thermodynamics analysis results show that calcium molybdate is easily decomposed by acid; compared with the sulfuric acid leaching process, hydrochloric acid leaching calcium molybdate does not produce CaSO₄, which reduces leaching product covered by calcium molybdate. The experiment proves that compared with hydrochloric acid, calcium molybdate is a kind of better leaching agent, and the leaching of molybdenum reaches 98.56 % at 25 ℃ for 45 min with HCl concentration of 2.4 mol/L at a VL/WS ratio of 10 mL/g.