This study investigated the feasibility of using photoheterotrophic microalga, Desmodesmus armatus SCK, for removal of cesium (Cs+) followed by recovery process using magnetic nanoparticles. The comparison of three microalgae results indicated that D. armatus SCK removed the most Cs+ at both 25 °C and 10 °C. The results also revealed that the use of microalga grown in potassium (K+)-starved condition improves the accumulation of Cs+. Heterotrophic mode with addition of volatile fatty acids (VFAs), especially acetic acids (HAc), also enhanced removal of Cs+ by K+-starved D. armatus SCK; maximum removal efficiency of Cs+ was almost 2-fold higher than that of cells grown without organic carbon source. The Cs+ taken up by this microalga was efficiently harvested using magnetic nanoparticles, polydiallyldimethylammonium (PDDA)-FeO3. Finally, this strain eliminated more than 99% of radioactive 137Cs from solutions of 10, 100, and 1000 Bq mL-1. Therefore, use of K+-starved microalga, D. armatus SCK, with VFAs could be promising means to remove the Cs from the liquid wastes.
Keywords: Cesium; Magnetic separation; Microalgae; Potassium starvation; Volatile fatty acid.
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