Uranium speciation by time-resolved laser-induced fluorescence spectroscopy.

Area of Science:

• Environmental Chemistry
• Radiochemistry
• Spectroscopy

Background:

• Uranium(VI) speciation influences its environmental mobility and long-term stability.
• Understanding speciation in carbonate solutions is vital for nuclear waste disposal and contaminated site remediation.
• Alkaline conditions present challenges due to weak luminescence signals.

Purpose of the Study:

• To systematically investigate uranium(VI) speciation in aqueous carbonate solutions across a wide pH range.
• To identify and characterize uranyl complexes using luminescence properties.
• To provide insights into uranium behavior in cementitious environments relevant to geological repositories.

Main Methods:

• Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was employed.
• Measurements were conducted across a broad pH range (4.3-13.0) at room temperature.
• Luminescence lifetimes and emission spectra were analyzed to identify uranyl complexes.

Main Results:

• Distinct uranyl hydroxo and carbonato complexes were identified.
• Non-luminescent species were observed at high pH.
• TRLFS proved to be a robust tool for uranium quantification, showing luminescence intensity independent of pH and linearly correlated with concentration.

Conclusions:

• The study enhances understanding of uranium(VI) behavior in alkaline, carbonate-rich environments.
• Findings are applicable to nuclear waste management, particularly in deep geological repositories.
• Accurate speciation data improves predictions of uranium mobility and stability in contaminated areas.