Cd^(2+)-H_2O系羟合配离子配位平衡

Equilibrium of hydroxyl complex ions in Cd^(2+)-H_2O system

根据配位化学热力学平衡原理,绘制了Cd2+-H2O系配合离子浓度pc—pH图、镉羟合配离子分率αn—pH图及Cd(OH)2条件溶度积pKS—pH图。pc—pH图描述了Cd(OH)2(s)溶解平衡时,镉的总离子平衡浓度与pH的关系。当pH为9.84～13.31时,Cd(OH)2的溶解度最小;αn—pH图指出了各种羟合配离子分率与pH关系,每种羟合配离子都对应有其存在的最佳pH范围。Cd(OH)2(s)的条件溶度积pKS—pH图表明:当pH值在9.5～10.5范围内,Cd(OH)2(s)的条件溶度积最小。研究结果可为中和水解法去除废水中镉等技术提供理论依据。

Abstract： The diagrams for the concentration of complex ions pc-pH, the ratio of cadmium hydroxy complex ions a pH and the conditional solubility product of Cd（OH）2 to pH value in Cd^2＋-H2O system were drawn, respectively. The relationship between the equilibrium concentration of total cadmium ions and pH value was shown in Cd^2＋-H2O system, when the dissolution of Cd（OH）2 is in equilibrium. The solubility of Cd（OH）2 is the least at pH value of 9.84-13.31. The diagram for pKs-pH shows that each hydroxy complex ion existing in this system is dependent upon an optimized pH value. The diagram for the conditional solubility product pKs-pH indicates that the pKs reaches the minimum value at pH value ranging from 9.5 to 10.5. The results can provide a theoretical basis for the technology on removal of cadmium ion from the wastewater by neutralized hydrolyzation method.