The Mechanism of Immobilization of Cd(II) by Phosphate-Solubilizing Bacteria Bacillus sp. B19

The phosphorus provision and heavy metal toxicity are two main factors limiting the crop yield and quality in contaminated soils in South China. In order to find efficient and affordable methods of simultaneously enhancing phosphorus uptake and reducing cadmium uptake by plants, phosphate-solubilizing bacteria capable of Cd(II) immobilization were screened and the relevant process was investigated in this study. From cadmium-contaminated soil, we ultimately isolated one phosphate-solubilizing bacteria, Bacillus sp. B19, can dissolve tricalcium phosphate, aluminum phosphate, and iron phosphate when Cd(II) is added. By biosorption, bioaccumulation, and precipitation, Bacillus sp. B19 was able to solubilize phosphate while immobilizing Cd(II). Initial pH, contact time, and initial Cd(II) concentration could all have an impact on Bacillus sp. B19's ability to biosorb Cd(II). By using the Langmuir isotherm, the maximum Cd biosorption of strain B19 was determined to be 10.66 mg/g. Pseudo-second-order kinetic modeling provided a better explanation of the biosorption's kinetics. The Cd(II) biosorption by strain B19 was also investigated using zeta potential, scanning electron microscopy (SEM) combined with an energy dispersive spectrometer, and Fourier transform infrared spectroscopy (FTIR). When Cd(II) concentrations were low and high, strain B19's Cd(II) biosorption was primarily intracellular bioaccumulation and surface bioadsorption. Our findings show that strain B19 may be an effective option for immobilizing Cd(II) in soils contaminated with Cd, in addition to being a viable candidate for supplying nutrients.

Automated summary

This study screened and investigated phosphate-solubilizing bacteria capable of Cd(II) immobilization to find efficient methods of enhancing phosphorus uptake and reducing cadmium uptake by plants. Bacillus sp. B19 was isolated from cadmium-contaminated soil and showed the ability to solubilize phosphate while immobilizing Cd(II). Factors such as initial pH, contact time, and initial Cd(II) concentration affected the biosorption of Cd(II) by Bacillus sp. B19. The findings also provided insights into the kinetics and mechanisms of Cd(II) biosorption by strain B19 using various techniques such as zeta potential, SEM, and FTIR.