Formation of crystal film at interface in process of extraction of rare earth metals by D2EHPA

In the process of extraction of the rare earth metals europium and samarium by D2EHPA, we find that solid films form at the organic/aqueous interface. For extraction solution systems of europium and samarium, we specified con centration zones where the solid films should form, and show that the forma tion of the solid films occurs at the specific zones of hydrogen ion and ex tractant concentrations. We also determine the atomic constituents of the s olid films by inductively coupled plasma emission spectroscopy, and find th at the solid films are crystals composed of neutral 1:3 intermediate comple xes. We further investigate film formation in the extraction solution syste m that contains two lanthanide elements, europium and samarium, We determin e the atomic ratio of the solid film, and show that the atomic ratio takes the value which is near to that predicted from the separation coefficient i n the organic/aqueous solution system.