Bioaccumulation and Biosorption of Stable Cesium and Cesium-137 by Oscillatoria homogenea Cyanobacterium

Abstract

: Removal of stable cesium and cesium-137 by living filamentous cells of Oscillatoria homogenea cyanobacterium from aqueous solution has been investigated. The removal levels of the stable cesium and cesium-137 were found to be 989ng Cs/mm3 biomass, and 2389 mBq 137Cs/mm3 biomass, respectively, after the contact time of 240 hours. The optimum pH for cesium uptake was 10±0.3. No significant change was observed at the pH values of 4, 6 and 8 for the cesium sorption by the cyanobacterium biomass. Increasing the cyanobacterium biomass caused more removal capacity. The maximum removal efficiency in the liquid culture containing 133 mg/L cesium and 20.53 mm3biomass/ml culturewas 5.75 mg/l. The removal efficiency were found to be 1.1% and 51.2% as the Cs-133 concentration, ranged beween 0.133 to 332.5 mg/l, respectively. At the 1200 Lux illumination, the maximum removal value was 1065 ng Cs/mm3 biomass, and in the presence of 332.5 mg/l cesium concentration (2.5 mmol/L), the sorption was obtained to be 4530 ng/mm3 biomass. The microprobe PIXE analysis and autoradiography technique were used to confirm the cesium sorption on the biomass. The sorption of the stable cesium and cesium-137 were fitted to Langmuir isotherm, and the model parameters were found to be qmax=854 ng Cs/mm3 biomass, 2272 mBq 137Cs/mm3 biomass, b=0.00011(R2=0.97), and b=0.000009 (R2=0.96), respectively.

Keywords

• biosorption
• bioaccumulation
• cesium-137
• cyanobacteria