Recovery of rare earths from nitric acid leach solutions of phosphate ores using solvent extraction with a new amide extractant (TODGA)

Abstract

The rare earths in phosphate ores are not effectively utilized and they cannot be directly extracted from leach liquor with the traditional extractants, such as organic phosphoric acid. This paper presents a new solvent extraction method for rare earths from nitric acid leaching of phosphate rock using N,N,N′,N′-tetraoctyl diglycol amide (TODGA) without interfering with the normal route for fertilizer production. When the concentration of extractant increased to 0.1 mol/L, the extraction rate of lanthanum, cerium, praseodymium, and neodymium have been found to be 98.1%, 99.1%, 98.8% and 98.6%, respectively. The recovery rate reached to 99.9% when a three-stage countercurrent extraction was carried out on the simulated leach solution. There was almost no extraction of other impurity ions and the rare earths could be separated with TODGA from Ca2+, PO43−, Fe3+, and Mg2+. The presence of phosphoric acid in solution enhanced the extraction of rare earth ions. The stripping of the loaded rare earth in the organic phase was readily carried out with water under room temperature with high efficiency. The mixed rare earth oxides (REO) with an assay of >95% could be recovered as a final product.