Adsorption of Trace Elements by Bentonite in the Presence of Bacteria

Resumo

Abstract—The paper addresses the lead and copper adsorption by calcium bentonite, living and destroyed cells of the gram-positive bacteria Bacillus subtilis, as well as in systems including mineral and one of biotic component within the element concentration range of 25–250 μM. The effect of acidity on the biosorption of the studied trace elements is demonstrated. The maximum biosorption of lead and copper of 0.72 and 0.52 mM/g dry matter, respectively, is observed at рН 6. Biosorption by destroyed cells also reached maximum values at рН 6: 0.81 mM/g (Pb) and 0.71 mM/g (Cu). Accumulation of trace elements by living and destroyed cells is an order of magnitude more than their adsorption by calcium bentonite. Three-component bio-mineral systems, including bentonite and bacterial cells or bentonite and cell fragments, showed an increase of lead and copper adsorption as compared to bentonite. The adsorption of trace elements by a mixture of bentonite and cell fragments was lower than the additively calculated sorption by individual components both for lead and for copper at all studied concentrations. Similar tendency was observed in the bentonite–living cell system for copper and in the same system for lead at its low concentration in the sorption solution. The calculated sorption of lead by bentonite and cells was slightly lower than the experimental one, which can be explained by the formation of new specific sorption sites under the influence of living cells.