Increasing the recovery and selectivity of U, U, and U extraction with tri-n-butyl phosphate in mine tailing samples with a high copper content.

Abandoned Cu mine tailings may be associated high concentrations of U. However, the presence of stable cations such as Cu, Fe, Al, Ca, or Mg, etc. in high concentrations can reduce the chemical efficiency of the liquid-liquid extraction method with tri-n-butyl phosphate (TBP); it can also inhibit the electrodeposition of U on the stainless steel planchet where the sample is measured. In this work we studied an initial stage of complexation with ethylenediaminetetraacetic acid (EDTA) and a back extraction with different solutions: HO, NaCO, and (NH)CO at room temperature and at 80 °C. The sensitivity of the method was 4.9·10 Bq for U and U, and 2.3·10 Bq for U. The validation of the method achieved 95% of the results when using a |ζ-score| ≤ ± 2.0 and a relative bias (RB[%]) ≤ ± 20% as the acceptance criteria. The recoveries obtained with the proposed method were higher than those achieved with the extraction method without initial complexation and re-extraction with HO for water samples. Finally, this method was applied in practice to study the tailing of an abandoned Cu mine and the activity concentrations of U and U were compared with those obtained by gamma spectrometry for Th and U. The means and variances of both methods showed no significant differences between these two isotopes.