2017 Volume 66 Issue 11 Pages 783-796
Ion-exchange and fractional precipitation using phosphorster coordination polymers have been studied to develop an environmental friendly lanthanide separation method, where only water is used as a solvent. In an ion-exchange system, high selectivity has been found in the lanthanide series. In addition, the selectivity changes depending on the ion exchange rate, which is likely to be caused by the contributions of both "electrostatic interaction between metal ions and phosphorester ligands" and "size matching of the ingoing ion to the framework of the coordination polymer". Such a mechanism may be feasible because the framework is formed by a lanthanide-selective phophoester and it is moderately rigid, which is not observed either in solvent extraction and conventional ion exchange systems. Furthermore, fabrication of phosphorester coordination polymers has been demonstrated: grain powders of phosphorester coordination polymer can be transformed to a monolithic structure through organogel formation and lypholization. As a consequence, the distribution coefficients and kinetic constant of ion exchange have been improved. Finally, successful fractional precipitation of Nd3+ and Dy3+ in an aqueous solution has been demonstrated.