Effects of different exogenous cadmium compounds on the chemical composition and adsorption properties of two gram-negative bacterial EPS.

Three different Cd(II) compounds were used to regulate Pseudomonas aeruginosa and Alcaligenes faecalis EPS (extracellular polymeric substances). The purpose of this study was to improve the content of EPS protein and the adsorption capacity of Cd(II) by different Cd(II) compounds. The results showed that Cd(NO) had the best stress/induction effect on the two strains. Under the best stress/induction, the protein in EPS of the two strains increased most obviously, and the adsorption capacity of Cd(II) was increased by more than 40%. Under these conditions, the kinetics of the adsorption process of Cd(II) by Cd(NO)-EPS (EPS produced by Alcaligenes faecalis under Cd(NO) stress) could be well fitted by the Langmuir isotherm model, and the theoretical maximum adsorption amount of 1111.11 mg/g EPS could be obtained. The results of 3D-EEM, FTIR and XPS indicated that proteins, especially CO, CN and NH in proteins, played a major role in the removal of Cd(II) by Cd(NO)-EPS. The results of this study show that the addition of Cd(NO) can effectively regulate the content of chemical components, especially the content of protein, and thus greatly improve the removal efficiency of heavy metals, which shows great application prospects in the prevention and control of heavy metal pollution.