Direct determination of uranium and co-extracted elements in the organic phases (D2EHPA/TOPO, TBP, TDA) in kerosene by TXRF technique

The total reflection X-ray fluorescence (TXRF) spectrometry was used for direct determination of uranium concentration in the organic phase di-(2-ethyl hexyl) phosphoric acid and trioctyl phosphine oxide (D2EHPA-TOPO)/kerosene, which resulted from first and second cycles of uranium extraction from wet-process phosphoric acid. The TXRF measurements were performed using gallium as an internal standard. A linear relationship between relative intensity of uranium vs. gallium (IU/SGa) against uranium concentration has been obtained. Four calibration curves, 0-5, 5-100, 100-1000 and 1000-7000 μg mL-1, according to uranium concentration in the studied samples, were constructed. The detection limit was found to be 0.15 μg mL-1. The effect of D2EHPA and TOPO concentration in kerosene on uranium determination was considered. The TXRF spectrometry was also applied for the multi-elemental analysis of the co-extracted impurities with uranium, such as (Fe, Ni, Cu and Zn) in the organic phase, and four calibration curves, 0-500 μg mL-1 Fe, 0-20 μg mL-1 Ni, 0-10 μg mL-1 Cu and 0-20 μg mL-1 Zn, according to Fe, Ni, Cu and Zn concentration in the studied samples were performed, respectively, using gallium as an internal standard. The obtained results using direct TXRF analysis method were in a very good agreement with those obtained by fluorometry method, which is suitable for aqueous solutions after stripping of uranium from the organic phase by 1 M Na2CO3