عنوان مقاله [English]
An attempt was made to isolate bacterial strains capable of removing strontium biologically. In this study ten different water samples collected from Neydasht spring in the north of Iran and then the bacterial species were isolated from the water samples. The initial screening of a total of 50 bacterial isolates resulted in selection of one strain. The isolated strain showed a maximum adsorption capacity with 55mg strontium/g dry wt. It was tentatively identified as Bacillus sp. according to the morphological and biochemical properties, and called strain GT-83. Our studies indicated that Bacillus sp. GT-83 is able to grow aerobically in the presence of 50mM SrCl2, but its growth was inhibited at high levels of strontium concentrations. The biosorption capacity of Bacillus sp. GT-83 depends strongly on the pH solution. Hence the maximum strontium sorption capacity of Bacillus sp. GT-83 was obtained at pH 10, independent of absence or presence of MgCl2 of different concentrations. Strontium-salt biosorption studies were also performed at this pH values. The equilibrium biosorption of strontium was elevated by increasing the strontium concentration, up to 250mg/l for Bacillus sp. GT-83. The maximum biosorption of strontium was obtained at temperatures in the range of 30-35˚C. The Bacillus sp. GT-83 biosorbed 97mg strontium/g dry wt at 100mg/l initial strontium concentration without MgCl2. When MgCl2 concentration increased to
15%(w/v), these values dropped to 23.6mg strontium/g dry wt at the same conditions. Uptake of strontium within 5 min of incubation was relatively rapid and the absorption continued slowly thereafter.