重金属离子（Zn^2＋，Cu^2＋，Cd^2＋，Pb^2＋）-水系羟合配离子配位平衡研究

Thermodynamic equilibrium of hydroxyl complex ions in heavy metals（Zn^2＋,Cu^2＋,Cd^2＋,Pb^2＋）-H2O system

根据配位化学热力学平衡原理，绘制4种金属离子（Zn^2＋，Cu^2＋，Cd^2＋，Pb^2＋）-水系的pc-pH图、羟合配离子分率αn-pH图及4种金属氢氧化物条件溶度积与pH关系图。pc-pH图描述了4种金属氢氧化物在溶解平衡时，总离子平衡浓度与pH关系。Zn（OH）2（s），Cu（OH）2（s），Cd（OH）2（s）和Pb（OH）2（s）分别在pH为8．35-10．82，7．32—10．68，9．84-13．31和10．096-10．997时的溶解度最小。αn-pH图指出了各种羟合配离子分率与pH的关系，4种金属羟合配离子都有其最佳的存在pH范围。pPs—pH图指出了4种金属氢氧化物的条件溶度积与pH的关系，pH分别在8．0-9．0，7．0～9．0，9．5～10．5和10．3～11.2范围内Zn（OH）2（s），Cu（OH）2（s），Cd（OH）2（s）和Pb（OH）2（s）的条件溶度积最小。这些热力学图在中和水解法中的应用比电位—pH图更具实用价值，能为中和水解法处理各种重金属废水及湿法冶金除杂质提供更加严格的理论依据。

Diagrams for the concentration of complex ions pc-pH, the ratio of four kinds of heavy metals（Zn^2＋, Cu^2＋, Cd^2＋, Pb^2＋） hydroxyl complex ions αn-pH, conditional solubility product of their hydrates to pH in their system were drawn respectively based on the thermodynamic equilibrium principle of complex chemistry. The relationship between the equilibrium concentration of total heavy metal ions and pH is illustrated in Me^2＋-H2O system, when dissolution of hydrate is in equilibrium, The solubility of Zn（OH）2 is at the minimal level in pH range from 8.35 to 10.82, Cu（OH）2 from 7.32 to 10.68, Cd（OH）2 from 9.84 to 13,31, and Pb（OH）2 from 10.096 to 10.997. The diagram for αn-pH shows that each hydroxyl complex ion existing in the system depends on an optimized pH value. The diagram for the conditional solubility product pPs-pH indicates that PPs reaches the minimum in the pH range from 8.0 to 9.0 in Zn^2＋-H2O system, from 7.0 to 9.0 in Cu^2＋-H2O system, from 9.5 to 10.5 in Cd^2＋-H2O system and from 10.3 to 11.2 in Pb^2＋-H2O system. It is of greater practical value of these diagrams than that of potential-pH diagram, Moreover, it can offer more strict theoretical foundation for treatment of heavy metals-containing wastewater by neutralization and for purification of hydrometallurgy.