ACCUMULATION OF URANIUM AT LOW CONCENTRATION BY THE GREEN-ALGA SCENEDESMUS-OBLIQUUS-34

Accumulation of UO22+ by Scenedesmus obliquus 34 was rapid and energy- independent and the biosorption of UO22+ could be described by the Fre undlich adsorption isotherm below the maximum adsorption capacity (75 mg g(-1) dry wt). The optimum pH for uranium uptake was between 5.0 si milar to 8.5. 0.1 similar to 2.0 M NaCl enhanced uranyl, while CU2+, N i2+, Zn2+, Cd2+ and Mn2+ competed slightly with uranyl. Pretreatment h ad an unexpected effect on biosorption. After being killed by 0.1 M HC l, S. Obliquus 34 showed 45% of the uptake capacity of the control in which fresh cells were suspended directly in uranyl solution, while th e pretreatment of cells by 0.1 M NaOH, 2.0 M NaCl, ethanol or heating decreased uptake slightly. Fresh S. obliquus 34 at 1.2 similar to 2.4 mg dry wt mL(-1) was able to decrease U from 5.0 to 0.05 mg L-1 after 4 similar to 6 equilibrium stages with batch adsorption. Deposited U c ould be desorbed by pH 4.0 buffer. It is suggested that U was captured by effective groups or by capillary action in the cell wall in the fo rm of [UO2OH](+).