钼酸钙酸分解热力学分析及其应用

Thermodynamic study on acid decomposition of calcium molybdate and its application

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CaMoO_4-H_2SO_4/HCl-H_2O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,CaMoO_4-H_2SO_4-H_2O系在整个pH范围可以分为3个稳定区,pH在0~3.5时为H_2MoO_(4(s))、CaSO_(4(s))稳定区,pH在3.5~4.5时为H_2MoO_(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;CaMoO_4-HCl-H_2O系在整个pH范围可以分为3个稳定区,pH在0~2.9时为H_2MoO_(4(s))稳定区,pH在2.9~4.5时为H_2MoO_(4(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CaSO_4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 m L/g,在25℃浸出45 min,钼的浸出率达到98.56%.

According to the laws of simultaneous equilibria and mass conservation,the lg C-pH diagram of a CaMoO4-H2SO4/HCl-H2O system was established on the basis of themodynamic 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 CaMoO4（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 Ca SO4,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/WSratio of 10 m L/g.