冠醚溶剂萃取碱金属

SOLVENT EXTRACTION OF ALKALI METAL WITH CYCLIC POLYETHERS

用大环多醚溶剂萃取碱金属和碱土金属阳离子已有不少报道。大环多醚与碱金属的阳离子能形成稳定的络合物。在这类络合物中,金属阳离子处于多醚环孔穴的中心,依靠离子-偶极静电作用相互结合。被络合的阳离子的直径和多醚环孔径的吻合程度是影响络合物稳定性的主要因素。通过多醚对碱金属和碱土金属萃取行为的研究。

The distribution ratio of picric acid between organic and aqueous phases in the solvent extraction of alkali metal with DBC, 18C6 is determined and the effect of polyether equilibrium concentration and picric acid concentration of aqueous phases on the distribution ratio studied. The plots of the distribution ratio of K+, Rb+, Cs+ between organic and aqueous phases against equilibrium concentration of DBC-18C6 and picric acid give slope Values of approximatly 1. The polyether cation complex is found to be 1:1:1 in stoichio-metry. The extractability of complex cation-picrate ion pairs decreases in this sequence: K+>Rb+>.Cs+. The values of the equilibrium constants of the complex formation decreases as the sizes of the alkali metal cations increase.