Hydrotalcite Colloidal Stability and Interactions with Uranium(VI) at Neutral to Alkaline pH
Chris Foster1, Samuel Shaw1, Thomas S Neill1
1Research Centre for Radwaste Disposal and Williamson Research Centre, Department of Earth & Environmental Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 15, 2022
Summary
Stable colloidal hydrotalcite can transport uranium (VI) during nuclear decommissioning. This study shows hydrotalcite effectively removes uranium across pH 7-11.5, forming pseudo-colloids via surface precipitation or uranyl carbonate species.
Area of Science:
- Nuclear chemistry
- Environmental science
- Materials science
Background:
- Nuclear fuel reprocessing generates radioactive sludge containing uranium.
- Magnox fuel corrosion produces hydrotalcite, a layered double hydroxide (LDH).
- Colloidal hydrotalcite may mobilize radionuclides like uranium during decommissioning.
Purpose of the Study:
- Investigate hydrotalcite colloidal stability and uranium (VI) sorption.
- Determine uranium mobility under neutral to alkaline conditions.
- Understand uranium interactions with hydrotalcite for nuclear waste management.
Main Methods:
- Multi-technique approach including X-ray absorption spectroscopy (XAS) and luminescence.
- Studied hydrotalcite colloidal stability across pH 7-11.5.
- Varied U(VI) surface loadings from 0.01-1 wt %.
Main Results:
- Hydrotalcite formed stable colloidal suspensions between pH 7 and 11.5.
- >98% of U(VI) was removed by hydrotalcite, irrespective of pH and loading.
- U(VI) sorption involved surface precipitation (alkaline) or uranyl carbonate formation (circumneutral).
Conclusions:
- Hydrotalcite acts as a transport vector for U(VI), forming pseudo-colloids.
- Sorption mechanisms are pH and concentration-dependent.
- Findings are crucial for predicting uranium behavior in nuclear decommissioning scenarios.
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