Abstract
We evaluated the potential sequestration of cesium (Cs+) by microalgae under heterotrophic growth conditions in an attempt to ultimately develop a system for treatment of radioactive wastewater. Thus, we examined the effects of initial Cs+ concentration (100–500 μM), pH (5–9), K+ and Na+ concentrations (0–20 mg/L), and different organic carbon sources (acetate, glycerol, glucose) on Cs+ removal. Our initial comparison of nine microalgae indicated that Desmodesmus armatus SCK had removed the most Cs+ under various environmental conditions. Addition of organic substrates significantly enhanced Cs+ uptake by D. armatus, even in the presence of a competitive cation (K+). We also applied magnetic nanoparticles coated with a cationic polymer (polyethylenimine) to separate 137Cs-containing microalgal biomass under a magnetic field. Our technique of combining bioaccumulation and magnetic separation successfully removed more than 90% of the radioactive 137Cs from an aqueous medium. These results clearly demonstrate that the method described here is a promising bioremediation technique for treatment of radioactive liquid waste.
Highlights
These results clearly demonstrate that the method described here is a promising bioremediation technique for treatment of radioactive liquid waste
Measurements of Cs+ uptake by these microalgae indicated that D. armatus SCK removed the greatest amount of Cs+ (63.9 μmol/g dry cell weight (DCW)), followed by Ettlia sp
Our results show that the bioaccumulation of Cs+ by D. armatus SCK was efficient at pH values between 5 and 9, and the greatest uptake and removal efficiency were at pH 9
Summary
These results clearly demonstrate that the method described here is a promising bioremediation technique for treatment of radioactive liquid waste. The release of radioactive cesium (137Cs) was a major concern because of its long half-life (30.2 years), high water solubility, and rapid uptake by terrestrial and aquatic organisms due to its chemical similarity to potassium (K+)[1,2] This accident has led to the search for new methods that can prevent the adverse effects of pollution by radioactive nuclides, especially 137Cs. Researchers have previously examined the effects of many chemical and biological techniques for removal of Cs+ and/or 137Cs from wastewater effluents. To the best of our knowledge, only a limited number of reports examined the use of microalgae for the bioaccumulation of environmental Cs+ Conventional separation techniques, such as chemical precipitation and ion exchange, are well-developed, but are expensive and inefficient when the environmental concentration of Cs+ is low.
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