Solvent extraction separation of light rare earth elements from heavy rare earth elements: ICP-AES determination of rare earth elements and yttrium in xenotime mineral

Xenotime mineral is the main source of yttrium which is used for making crystals of the yttrium-aluminium garnet (YAG), yttrium-iron-garnet (YIG), phosphors (Eu:YO3) to create red colour in television and several other high-tech industrial applications. The chemical composition of the mineral is YPO4, with Y and P as major elements with minor quantities of certain heavy rare earth elements (HREE) like Dy, Er and Yb. The light rare earth elements (LREE) especially the first three members La, Ce and Pr are often present at very low level, therefore, their direct accurate ICP-AES determination is difficult due to the spectral interference caused by the presence of mg/ml amounts of Y and phosphate, besides changing the plasma characteristics at that salt load level. In the literature their values are often not quoted due to the difficulty in accurate determination. This paper summarises the method developed for the separation of bulk of the HREE from LREE in xenotime mineral which facilitate spectral interference free ICP-AES determination REE and Y particularly La, Ce and Pr. (author)