Photosynthetic biomineralization of radioactive Sr via microalgal CO2 absorption

•Photosynthetic biomineralization of 90Sr was performed by microalgae.•Sr was crystallized as strontianite (SrCO3) at the biomass/liquid interface.•Chlorella vulgaris carried out the highest 90Sr removal ever reported.•Microalgal carbonating process is one of innovative ways to effectively remove Sr.

Water-soluble radiostrontium (90Sr) was efficiently removed as a carbonate form through microalgal photosynthetic process. The immobilization of soluble 90Sr radionuclide and production of highly-precipitable radio-strontianite (90SrCO3) biomineral are achieved by using Chlorella vulgaris, and the biologically induced mineralization drastically decreased the 90Sr radioactivity in water to make the highest 90Sr removal ever reported. The high-resolution microscopy revealed that the short-term removal of soluble 90Sr by C. vulgaris was attributable to the rapid and selective carbonation of 90Sr together with the consumption of dissolved CO2 during photosynthesis. A small amount of carbonate in water could act as Sr2+ sinks through the particular ability of the microalga to make the carbonate mineral of Sr stabilized firmly at the surface site.