Co^(2+)-H_2O体系羟基配离子配位平衡

Thermodynamic equilibrium of hydroxyl complex ions in Co^(2+)-H_2O system

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。

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 an-pH, conditional solubility product of the hydrate to pH in the C02＋ -H2O system were drawn, respectively. The relationship between the equilibrium concentration of total cobalt ions and pH value was shown in C02＋ -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 an-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）4^2- and C04（OH）4^4＋ existing in the C02＋ -H2O system, and a little of Co（OH）2 and C02（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.