Interaction between bentonite and Bacillus litoralis strain SWU9

Abstract Mineral–microbe interactions are of high importance for understanding mineral formation and dissolution. This study presents experimental results on the mineral–bacteria interaction system between bentonite and a Gram-negative Bacillus strain isolated from soil in liquid culture. Glucose consumption and pH changes were monitored and the variation of Ca2 + and Mg2 + concentrations in the solution, released from montmorillonite and chlorite in bentonite, was investigated. The influence of soil bacteria on the interlayer space was studied by X-ray diffraction analysis. The results show that bentonite acted as a good buffering effect against the decrease of pH, which enhanced the activity of the soil bacteria and promote consumption of the glucose. The release of Ca2 + and Mg2 + displayed a rising tendency with the increase of the bentonite content. The regular release of Ca2 + and Mg2 + caused by the action of the soil bacteria could be summarized as (i) CB, the net-enhancing effect of element concentrations; and (ii) dB, the net-enhancing effect per unit mass of bentonite. With the decrease of the bentonite content, the basal spacing of montmorillonite increased from 1.486 nm to 1.769–2.021 nm, which was induced by the bacterial metabolism. The interlayer space of montmorillonite increased in the range of 0.283–0.534 nm with the decrease of mineral contents, and bacterial metabolism was responsible for this increase. The nanoparticle aggregation of mixture components was observed after the interaction between bacteria and bentonite, which may be explained by the release of Si4 +, Al3 +, etc. and coprecipitated into an amorphous precipitate.