New approaches for efficient removal of some radionuclides and iron from rare earth liquor of monazite processing

In this article, new two approaches (A and B) are created for the efficient removal of the technically enhanced radium isotopes (²²⁸Ra, ²²⁶Ra and ²²³Ra), long-lived radioisotope of lead (²¹⁰Pb), thorium (Th⁴⁺) and iron (Fe³⁺) from the rare earth chloride (RECl₃) liquor produced during the monazite processing. In the first approach 'A,' elimination of the undesired species is achieved using a synergistic admixture of sulfate–sulfide solution (SO₄²⁻/S²⁻ admixture), while the second approach 'B' is performed using an iodate solution (IO₃⁻) as a selective precipitating agent. The results indicated that 14% of radionuclides and Th(IV), 12% of Ln(III) and 40% of Fe(III) were removed from the RECl₃ liquor at pH 3. In the first approach 'A,' the average percentage removal (%R) of all the undesired species reached ~ 96% using sulfate–sulfide admixture (0.058/0.04 mol/L). In the second approach 'B,' the average % R of all undesired species is improved and increased to ~ 99% using potassium iodate solution of 0.155 mol/L. Therefore, iodate solution is considered as an efficient and selective agent for the removal of Ra isotopes, ²¹⁰Pb, Th(IV) and Fe(III) from RECl₃ liquor without loss in Ln(III) at the optimized conditions. In this respect, promising results are obtained for the purification and production of Ln(III) using iodate solution or sulfate–sulfide admixture. Finally, the proposed two approaches are considered to be efficient not only to minimize the radiological human risks but also to eliminate the interfering of Th and Fe ions, to produce highly purified lanthanides from monazite ore.