The effect of interaction between Bacillus subtilis DBM and soil minerals on Cu(II) and Pb(II) adsorption

The effects of interaction between Bacillus subtilis DBM and soil minerals on Cu(II) and Pb(II) adsorption were investigated. After combination with DBM, the Cu(II) and Pb(II) adsorption capacities of kaolinite and goethite improved compared with the application of the minerals independently. The modeling results of potentiometric titration data proved that the site concentrations of kaolinite and goethite increased by 80% and 30%, respectively after combination with DBM. However, the involvement of functional groups in the DBM/mineral combinations resulted in lower concentrations of observed sites than the theoretical values and led to the enhancement of desorption rates by NH₄NO₃ and EDTA-Na₂. The DBM-mineral complexes might also help to prevent heavy metals from entering DBM cells to improve the survivability of DBM in heavy metal-contaminated environments. During the combination process, the extracellular proteins of DBM provided more binding sites for the minerals to absorb Cu(II) and Pb(II). In particular, an especially stable complexation site was formed between goethite and phosphodiester bonds from EPS to enhance the Pb(II) adsorption capacity. So, we can conclude that the DBM-mineral complexes could improve the Cu(II) and Pb(II) adsorption capacities of minerals and protect DBM in heavy metal-contaminated environments.