Biosorption of Strontium from Aqueous Solution by the New Strain of Bacillus sp. Strain GT-۸۳

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 ۵۰ bacterial isolates resulted in selection of one strain. The isolated strain showed a maximum adsorption capacity with ۵۵mg strontium/g dry wt. It was tentatively identified as Bacillus sp. according to the morphological and biochemical properties, and called strain GT-۸۳. Our studies indicated that Bacillus sp. GT-۸۳ is able to grow aerobically in the presence of ۵۰mM SrCl۲, but its growth was inhibited at high levels of strontium concentrations. The biosorption capacity of Bacillus sp. GT-۸۳ depends strongly on the pH solution. Hence the maximum strontium sorption capacity of Bacillus sp. GT-۸۳ was obtained at pH ۱۰, independent of absence or presence of MgCl۲ 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 ۲۵۰mg/l for Bacillus sp. GT-۸۳. The maximum biosorption of strontium was obtained at temperatures in the range of ۳۰-۳۵˚C. The Bacillus sp. GT-۸۳ biosorbed ۹۷mg strontium/g dry wt at ۱۰۰mg/l initial strontium concentration without MgCl۲. When MgCl۲ concentration increased to ۱۵%(w/v), these values dropped to ۲۳.۶mg strontium/g dry wt at the same conditions. Uptake of strontium within ۵ min of incubation was relatively rapid and the absorption continued slowly thereafter.