(中南大学 冶金与环境学院,长沙 410083)
摘 要: 根据配位化学的热力学平衡原理,绘制Co2+-H2O体系的羟基配合离子的浓度pc-pH图、配离子分率αn-pH图(lgαn-pH图)和Co(OH)2的条件溶度积pPs-pH图。pc-pH图描述Co(OH)2(s)溶解平衡时钴的总离子平衡浓度与pH值的关系。当pH值为10~13时,Co(OH)2(s)的溶解度最小;αn-pH图指出各种羟基配离子分率与pH值的关系,在不同pH值条件下,钴离子形成不同种类的羟基配离子;溶液中主要存在Co(OH)+、Co(OH)3-、Co(OH)42-、Co4(OH)44+这4种羟基配离子以及少量Co(OH)2和Co2(OH)3+。pPs-pH图显示了Co(OH)2(s)的条件溶度积与对应pH值之间的关系:当pH值为9~11时,Co(OH)2(s)的条件溶度积最小。
关键字: 配位化学;溶解平衡;羟基配离子分率;条件溶度积
(1. School of Metallurgy and Environment, Central South University, Changsha 410083, China)
Abstract:Based on the thermodynamic equilibrium principle of complex chemistry, the diagrams for the concentration of complex ions pc-pH, the ratio of Co2+ hydroxyl complex ions αn-pH, conditional solubility product of the hydrate to pH in the Co2+-H2O system were drawn, respectively. The relationship between the equilibrium concentration of total cobalt ions and pH value was shown in Co2+-H2O system, when the dissolution of Co(OH)2 is in equilibrium.The solubility of Co(OH)2 is the least at pH value of 10-13. The relationship of hydroxyl complex ions and pH value is shown in the diagram of αn-pH, the cobalt ions will turn into different hydroxyl complex ions according to different pH values. There are Co(OH)+, Co(OH)3-, Co(OH)42- and Co4(OH)44+ existing in the Co2+-H2O system, and a little of Co(OH)2 and Co2(OH)3+. The diagram for the conditional solubility product pPs-pH indicates that the pPs reaches the minimum value at pH value ranging from 9 to 11.
Key words: complex chemistry; solubility equilibrium; complex ions ratio; conditional solubility product