Ca²⁺-Facilitated Adhesion of Bacteria on the Na-Montmorillonite Surface

The adhesion of bacteria on clay surfaces strongly affected their migration and distribution in soil and water. Bacterial adhesion experiments on the Na-montmorillonite (Na-MMT) surface were conducted to determine the role of Na-MMT in the bacterial adhesion process and to prove the validity of the isotherm and kinetic theory for the bacterial surface adhesion in the presence of Ca²⁺ ions. Batch adhesion experiments with bacteria on the Na-MMT surface were carried out with varying time frames, temperatures, bacterial concentrations, and Ca²⁺ ion concentrations. The adhesion capacity of Na-MMT significantly correlated with the Ca²⁺ ion concentration, temperature, time frame, and bacterial concentration when Ca²⁺ ions were present. The adhesion morphology of the bacteria onto the Na-MMT surface, observed through the zeta-potential and atomic force microscopy (AFM), additionally demonstrated that the bacterial adhesion onto the Na-MMT surface was dominated by the nonelectrostatic force.