Investigation of Uranium Binding Forms in Some German Mineral Waters

Cryogenic time-resolved laser-induced fluorescence spectroscopy (cryo-TRLFS) was successfully used to identify uranium binding forms in some German mineral waters of extremely low uranium concentrations (< 2.0 µg/L). The measurements were performed at low temperature of 153 K. The spectroscopic data showed a prevalence of aquatic species Ca2UO2(CO3)3 in all investigated waters, while other uranyl–carbonate complexes, viz, UO2CO3(aq) and UO2(CO3)22- only existed as minor species. The pH value, alkalinity (CO32-), and the main water inorganic constituents, specifically Ca2+ concentrations, showed a clear influence on uranium speciation. Thermodynamic calculations of the main uranium binding form in the investigated waters indicated a good agreement with spectroscopy.