SEPARATION OF ADJACENT RARE EARTH ELEMENTS USING SOLVENT EXTRACTION

Industrial rare earth separation facilities utilize the phosphonic acid PC88A for solvent extraction processes. Separation of adjacent lanthanides using solvent extraction is especially costly and difficult due to their chemical similarities. Process improvements provide significant positive impacts on regulatory and economic challenges associated with these difficult separations. The separation of praseodymium and neodymium has been of particular interest recently due to current and forecasted future demand for high purity neodymium. Laboratory solvent extraction testing combined with MATLAB modeling has been used to develop and test solvent extraction flowsheets to separate high purity neodymium from a 25 wt % praseodymium and 75 wt % neodymium mixture. The flowsheet chemistry is based on the current industrial extractant, PC88A. Mixer-settler flowsheet testing with PC88A has shown that greater than 99% purity neodymium can be produced with a neodymium scrub solution in a 12-stage scrubbing circuit. An overall flowsheet concept has been designed, tested, and evaluated to simultaneously produce didymium and high purity neodymium. The methods and processes developed in this research can be applied to all of the rare earth elements (REE) in the lanthanide series to develop a modeling capability.