Trace elements sorption by bentonite in the presence of bacteria

Abstract

Sorption of lead and copper by calcium bentonite, living and destroyed cells of gram-positive bacteria Bacillus subtilis, as well as in systems including the clay mineral and one of the biotic components in the concentration range of the elements from 25 to 250 μM was studied. The effect of acidity on the biosorption of trace elements was shown. The maximum biosorption of lead and copper was observed at pH 6 and reached 0.72 and 0.52 mM/g of dry matter, respectively. At pH 6 the maximum biosorption by the destroyed cells was also observed — 0.81 mM/g of lead and 0.71 mM/g of copper. Accumulation of trace elements by living and destroyed cells significantly exceeded their sorption by calcium bentonite. In the ternary systems, including bentonite and bacterial cells or bentonite and cell debris, there was an increase in the sorption of lead and copper compared to bentonite alone. At the same time, the sorption of trace elements by a mixture of bentonite and cell fragments was lower than the additively calculated sorption by the individual components for both lead and copper at all concentrations studied. A similar pattern was observed for the system of living cells and bentonite for copper and living cells and bentonite for lead at low metal concentrations.