DIRECT SPECTROPHOTOMETRIC DETERMINATION OF URANIUM IN GRANITE AFTER ITS SELECTIVE LEACHING USING LIXIVIANT REAGENTS WITHOUT ITS PRIOR SEPARATION.

A spectrophotometric determination of uranium in microgranite rock sample, Sela area, South Eastern Desert, Egypt, from its leach liquor using effective and efficient lixiviants for its selective leaching followed by its direct spectrophotometric determination using arsenazo (III) dye without prior separation, as solvent extraction or ion exchange, was proposed in the present work. Several lixiviants were studied for the selective leaching of uranium namely; citric acid, urea, ammonium acetate, ammonium carbonate, ammonium bicarbonate and ammonium nitrate. The selected ammonium bicarbonate and ammonium nitrate lixiviants gave high leaching efficiency of uranium beside the minimal dissolution concentrations of the concomitants hence lowering the matrix interfering effect of those elements during its determination. Several factors were studied for this purpose namely; the choice of proper lixiviant(s), solid to liquid ratio (S/L), leaching time, temperature, interfering matrix effect where their spectral interference on uranium was also studied. It was found that maximum leaching of uranium with the least concomitants was reached using 1M ammonium bicarbonate and 1M ammonium nitrate with percentage leaching efficiencies of 99.5% for both lixiviants. The optimized method was applied on three microgranite and two international certified samples BL-4a and DL-1a, where statistical evaluation showed that their average relative standard deviation was 0.61. - See more at: