Zn-Cl^--NH₃-CO₂-3-H₂O系的热力学分析

来源期刊：中南大学学报(自然科学版)1998年第2期

论文作者：石西昌 赵瑞荣 蒋汉瀛

文章页码：91 - 94

关键词：热力学平衡; ZnO; ZnCO₃; NH₃;氯/浓度对数-pH图

Key words：thermodynamic equilibrium; ZnO; ZnCO₃; NH₃; chloride/logarithm concentration-pHdia-grams

摘    要：根据同时平衡原理和质量平衡原理,推导出Zn-Cl--NH₃-CO₂-3-H₂O系金属氧化物及碳酸盐在水溶液中热力学平衡的数学模型,计算并绘出该体系的浓度对数-pH图,研究了各配位体及pH值对该平衡体系的影响.当溶液有NH₃和Cl-存在时,ZnO的溶解度增大;NH₃的浓度对ZnO的溶解度的影响最大,因而不宜用氨水作为Zn²⁺的沉淀剂.当溶液中有CO₃^2-存在时,Zn的溶解损失小;即使溶液中含有一些NH₃,但溶液中Zn的总浓度还是比较小.当溶液中有CO₃^2-存在时不仅使Zn完全沉淀时的pH值降低了,而且pH值的范围也加宽了,因而可选用Na₂CO₃,(NH₄)₂CO₃等作为Zn²⁺的沉淀剂.根据溶液中[Cl-]T,[NH₃]T,[CO₃^2-]T的不同,通过这些浓度对数-pH图可以在理论上初步选择Zn²⁺沉淀的最佳pH值范围.

Abstract: According to the law of conservation of mass and the law of simultaneous equilibrium,the mathematics model of Zn-Cl--NH₃-CO₂-3-H₂O thermodynamic equilibrium system has been developed,and the logarithm concentration-pH(lgc-pH) diagrams of this system have been made.The effect of ligands and pH value was studied and discussed.The dissolvability of ZnO will be increase when NH₃ and Cl-exist in the solution.It is improper to use amonia as precipitator of Zn²⁺, because NH₃ can obviously increase the dissolvability of ZnO.The loss by solution of Zn is little when CO^2-₃exists in solution,even if some NH₃ exists in it.The pH of zinc deposition shows decrease and the range of pH is widened when CO^2-₃ exists in the solution.So we can choose Na₂CO₃,(NH₄)₂CO₃ etcas precipitators of Zn²⁺.According to the different [Cl^-]T,[NH₃]T,[CO^2-₃]T, we can choose optimum pH range of zinc deposition in the theory.