“Hydrometallurgical Separation and Purification of some Rare Earth Elements from Monazite Ore”

Abstract

In the first part of this thesis, a real high grade monazite sample (92%) was characterized and analyzed by XRF technique. The obtained results showed that monazite mineral composed mainly of three categories of elements. The actual concentration of these groups were 35.1% of REEs-oxide, 5.7% of the nuclear elements (as ThO2 > U3O8) and 48% of other elements (metal oxide). Radiological hazard indices were investigated for monazite sample and its respective hydroxide cake (after digestion with NaOH). The results indicated that the activity concentration was contributed to radium-isotopes (228Ra, 226Ra, 223Ra) and lead (210Pb) was extremely above the exemption limit (1000 Bq/kg) and worldwide average. The second part of this work aims for selective solvent extraction of thorium (IV), zirconium (IV), iron (III) and cerium (III) from aqueous sulphate medium using different basic and acidic extractants. In a single element system, Th(IV) was extracted by the primary amines (Octylamine and tert.Octylamine), the acidic extractnts [di-(2-ethylhexyl) phosphoric acid (D2EHPA) and (bis(2,4,4-trimethyl pentyl) phosphinic acid (Cyanex 272))]. Moreover, secondary amine (N-methylaniline) is effective for Fe(III) extraction while, the primary amines are suitable for Zr(IV) extraction. Ce(III) can be extracted with the primary amines and D2EHPA. In a mixed elements system, Th(IV) was extracted firstly with Cyanex 272 (65%) at pH 1 followed by the extraction of Fe(III) with N-methylaniline (95%), then Zr(IV) was precipitated at pH 2.5 (84%) while Ce(III) remains in the final aqueous phase.