Production and purification of UO3 from rock phosphate deposits and its characterization

Abstract EN

This study was carried out mainly to produce uranium trioxide (U03), matching standard commercial specifications from rock phosphate deposits in Uro and Kurun at eastern part of the Nuba Mountains.

A simplified hydrometallurgical procedure has been adopted for production of yellow cake from the ore.

The powdered ore sample was leached with concentrated H2SO4 acid with and without addition of KCIO3 as an oxidant.

The crude yellow cake was precipitated from the resulting green solution of phosphoric acid as Na2U207 and (NH4)2U207 and subsequently purified by TBP extraction (tributylphosphate) and hydrogen peroxide as U04.

2H2O.

TBP purified product was dried and calcined to UO3 Whereas U04.2H20 was dried and reduced to UO3 by Na2S203.

Prior to precipitation of crude yellow cake, Fe in the phosphoric acid solution was precipitated using magnesia.

Elemental analysis has shown that the ore is rich in Ca and deficient in elements of potential interest such as Fe, Cu and Zn.

j Uranium content in ore, phosphoric acid and purified yellow cake (U03) obtained with different precipitants was analyzed usinq alpha-spectrometry.

On the average, the activity concentration of uranium in ore corresponds to 82 ± 42 ppm (0.

01 %).

From the data of pregnant liquor, it was observed that the addition of KC103 as an oxidant improves the dissolution of uranium from the ore by almost 20 %.

Data has also indicated that the yellow cake purified by hydrogen peroxide exhibit higher concentration of uranium by 45.5 % over the one purified by TBP extraction.

Undesirable impurities in yellow cake as dictated by the function to which it is intended for were analyzed and compared with international standard specifications set for commercial products.

Uranium as U3Os was found to be 53 % in yellow cake initially obtained as ammonium diuranate and purified by hydrogen peroxide and .3.8 % in one which is purified by TBP extractipnv With the exception of Cr, the values of the other critical impurities (V, Mn, Co, Cu, Sr, Zr, Pb, Fe, CI, Br, I) in U03 precipitated by hydrogen peroxide are either typical or lower than those internationally specified as standards for commercial products.

Among the impurities considered Cd, Th and Mo were undetectable.

The most salient point to be mentioned here regarding impurities is that Cd, which is most undesirable in yellow cake because of its high neutron absorbing cross section, was undetectable in both types of yellow cakes (i.e.

purified by TBP extraction and by hydrogen peroxide).