Comparative determination of uranium in rock phosphates and columbite by ICP-OES, alpha & gamma spectrometry

During this work selective separation of uranium from rock phosphate and columbite mineral was done before its quantitative estimation by using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Uranium from the rock phosphate and columbite was extracted by sodium peroxide fusion followed by leaching in 2 M HNO3. To avoid spectral interference in the estimation of uranium by ICP-OES, the selective separation of uranium from the leachate was carried out by using two different extractants, 30% Tributyl Phosphate (TBP) in CCl4 and an equi-volume mixture of Di(2-ethylhexyl) phosphoric acid (D2EHPA) & TBP in petrofin. Uranium was stripped from the organic phase by using 1 M ammonium carbonate solution. Determination of uranium by ICP-OES was done after dissolving the residue left after evaporation of ammonium carbonate solution in 4% HNO3. The concentration of the uranium observed in the rock phosphates samples was 40–200 µg/g whereas in columbite samples the concentration range was 100–600 µg/g. Uranium concentration evaluated by ICP-OES was complimented by gamma & alpha spectrometry. Concentration of uranium evaluated by gamma spectrometry in case of rock phosphate and columbite was in close agreement with the uranium content obtained by ICP-OES. Uranium determination by alpha spectrometry showed only minor deviation (1–2%) from the results obtained by ICP-OES in case of rock phosphates whereas in case of columbites results are off by 20–30%.