Removal of Strontium From Nuclear Waste

Removal of Strontium From Nuclear Waste

Author: ChemViews

The development of safe and highly selective methods for removing 90Sr, with a half-life of approx. 30 years, from nuclear waste and the environment is critical for sustainable use of nuclear power. The chemical similarity of calcium, strontium, and barium makes this a very challenging problem for synthetic ion exchange materials and phytoremediation systems alike.

Derk Joester, Northwestern University, Evanston, IL, USA, and colleagues show that the desmid green algae Closterium moniliferum separates Ca2+, Sr2+, and Ba2+ during biomineralization. Using synchrotron X-ray fluorescence (SXRF) microscopy, they were for the first time able to quantify the composition of BaSO4 crystals mineralized in the terminal vacuoles of the desmid. Sr sequestration occurs via co-precipitation of Sr with barite.

The researchers were able to manipulate medium conditions to increase the Sr content of crystals deposited by desmids by more than two orders of magnitude, to a maximum of 45 mol%. At the same time very little calcium is incorporated into the crystal.
Permanent removal of Sr from solution could be ensured simply by harvesting cells after crystal precipitation and isolating crystals by filtration and/or ashing.

The unusual ability of desmids to selectively sequester Sr into an inert inorganic form, combined with the potential for engineering the system to increase Sr incorporation, may offer a unique alternative to traditional methods for 90Sr remediation. The implications of this work range from direct bioengineering of desmids for waste or environmental clean up, to bio-inspired materials for separation technology.

Image (C) Wiley-VCH

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