Bio-ceramsite technology is one of the most effective technologies in the pretreatment of drinking water. In this work, bio-ceramsite was fabricated byCitrobacter freundii (C. freundii) immobilization on the ceramsite. Thefi ndings of the current study suggest that the bio-ceramites showed biosorption abilities for Cd(II) and Pb(II) and the removal efficiency for Pb(II) is lower than Cd(II). The adsorption mechanism can be attributed to electrostatic attraction and covalent bond. The morphology of the cells changed after the adsorption of Cd(II) and Pb(II) due to the dissociation of the assembly of peptidoglycan and lipopolysaccharide. The fluorescence polarization has shown a significant decrease in membrane fluidity and an increase of permeability of cell membrane. The spectral profi le ofC. freundii suggests the alteration of carbonyl, amide and phosphonic groups on the cell membrane.