查看文章

Bulk Cd adsorption isotherm experiments, thermodynamic equilibrium modeling, and Cd K edge EXAFS were used to constrain the mechanisms of proton and Cd adsorption to bacterial cells of the commonly occurring Gram-positive and Gram-negative bacteria, Bacillus subtilis and Shewanella oneidensis, respectively. Potentiometric titrations were used to characterize the functional group reactivity of the S. oneidensis cells, and we model the titration data using the same type of non-electrostatic surface complexation approach as was applied to titrations of B. subtilis suspensions by Fein et al. (2005). Similar to the results for B. subtilis, the S. oneidensis cells exhibit buffering behavior from approximately pH 3–9 that requires the presence of four distinct sites, with pK_a values of 3.3±0.2, 4.8±0.2, 6.7±0.4, and 9.4±0.5, and site concentrations of 8.9(±2.6)×10⁻⁵, 1.3(±0.2)×10⁻⁴, 5.9(±3.3)×10⁻⁵, and 1.1(±0.6)×10⁻⁴ …