Fong P, Chow A
Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2.
Talanta. 1992 Jul;39(7):825-36. doi: 10.1016/0039-9140(92)80103-k.
The extractability sequence of K(+) approximately Rb(+) > Cs(+) > Na(+) > Li(+) for the extraction with polyether foam suggests that the cation chelation mechanism might be operative. However, the same order was obtained for the extraction with 100% polypropylene oxide polyether foam which does not normally adopt a helical structure to form oxygen-rich cavities as easily or as effectively as polyethylene oxide to accommodate alkali metal ions. This result indicates that a hole-size/cation-diameter relationship may not be required for the high extraction of K(+). The extraction of alkali metal DPAs and hydroxides from methanol demonstrates the importance of the solvent effect. It indicates that the water-structure enforced ion-pairing (WSEIP) is the driving force for extraction of the ion-pairs. The extraction mechanism for ionic species can be described as an ion-pair extraction process. The overall effect of ion-pair formation in water and interaction of the extracted ions with foam appears to determine the extractability of the ions of the extractable ion-pair.
对于用聚醚泡沫进行的萃取，K(+)≈Rb(+)＞Cs(+)＞Na(+)＞Li(+)的萃取顺序表明阳离子螯合机制可能起作用。然而，对于用100%聚环氧丙烷聚醚泡沫进行的萃取也得到了相同的顺序，这种泡沫通常不像聚环氧乙烷那样容易或有效地形成富含氧的腔室以容纳碱金属离子的螺旋结构。该结果表明，对于K(+)的高效萃取可能不需要孔尺寸/阳离子直径关系。从甲醇中萃取碱金属二异丙胺和氢氧化物证明了溶剂效应的重要性。这表明水结构增强的离子对形成（WSEIP）是离子对萃取的驱动力。离子物种的萃取机制可描述为离子对萃取过程。水中离子对形成以及萃取离子与泡沫相互作用的总体效果似乎决定了可萃取离子对中离子的可萃取性。
