The solvent extraction process of yttrium (III) from nitrate media by di(2-ethylhexyl) phosphoric acid (D2EHPA, represented as HA) has been studied as a first step to accomplish the homogeneous precipitation of yttrium oxalate from an organic metal loaded D2EHPA solution. The analysis of liquid-liquid distribution data at low metal concentrations determined YA3.2HA as the only metal organic species formed during the extraction, with a formation constant of logβ = 16.410±0.055. A polymerization of such organic metal species was observed at high metal loading of the organic phase. A comparison of these results with previous studies carried out in chloride or perchlorate media reveals a strong influence of the aqueous medium on the metal species formed in the organic phase, affecting mostly the stoichiometry of such species. The homogeneous precipitation of yttrium as yttrium oxalate using oxalic acid has been carried out as direct recovery of the metal from the organic solution. The observed precipitation-stripping kinetics has been related to the formation of organic yttrium species. The acidity of the stripping solution and the oxalic acid concentration also affects the kinetics and the precipitation yield. The morphology and particle size distribution of the powders obtained support the mentioned influence of the precipitation-stripping kinetics.
|Journal||Solvent Extraction and Ion Exchange|
|Publication status||Published - 1 Jan 1999|