الفهرس 
Rare Earth ElementsOnly 14 pages are availabe for public view
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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.
Thirdly, the elimination process of the non-desired species (radionuclides, thorium and iron) in the RECl3 liquor before extraction and separation on trivalent lanthanides have been investigated and optimized by studying different effective parameters. The results indicated that activity concentration of radionuclides in RECl3 liquor was above the safe limits before separation of Ln(III). Adjustment of pH 3 of the RECl3 liquor leads to eliminate 14 % of radionuclides, 14%±1 of Th(IV), 40%±2 of Fe(III) and 12%±1 of Ln(III). About of 20-83% of Ln(III) were lost when the non-desired species removed by Na- or ammonium sulphate, or potassium chromate solution. The interference due to Fe(III) remained with Ln(III) when radionuclides and Th(IV) in the liquor eliminated using solutions of sulphuric acid (2.6 M) in presence of Ba, Pb or Ba/Pb-carriers. Fortunately, more than 95% of the non-desired species were successfully removed when the RECl3 liquor was treated by solutions of iodate (<0.16 M), sulphate/sulphide (0.058:0.04 M) admixture in presence of Ba/Pb-carrier (1:1).