Uranium extraction from laboratory-synthesized, uranium-doped hydrous ferric oxides

Area of Science:

• Geochemistry
• Environmental Science
• Materials Science

Background:

• Uranium (U) extractability from synthetic uranium-hydrous ferric oxide (HFO) coprecipitates is influenced by mineral ripening.
• Mineral ripening is hypothesized to decrease uranium lability, affecting its environmental mobility and remediation strategies.

Purpose of the Study:

• To evaluate the effect of mineral ripening duration on uranium extractability from HFO coprecipitates.
• To investigate the influence of adjunct anions (silicate and phosphate) on uranium lability.
• To characterize the mineralogical and morphological changes during the ripening process.

Main Methods:

• Coprecipitation of uranyl (UO2(2+)) with HFO, with and without silicate or phosphate.
• Sequential extraction of uranium and iron over a 2-year period.
• Analysis using Micro-X-ray diffraction, Mössbauer spectroscopy, and scanning electron microscopy.

Main Results:

• Uranium extractability decreased with extended mineral ripening time for all HFO coprecipitates.
• The presence of silicate and phosphate altered uranium extractability, with phosphate-containing samples remaining largely amorphous.
• Micro-X-ray diffraction and microscopy confirmed the transformation of amorphous material to crystalline goethite and hematite, indicating mineral ripening and increased particle size.

Conclusions:

• Mineral ripening significantly reduces uranium lability and extractability from HFO coprecipitates.
• Adjunct anions play a role in stabilizing amorphous phases and influencing uranium retention.
• Understanding these processes is crucial for managing uranium-contaminated sites and developing effective remediation techniques.