Biosorption of Cadmium and Manganese Using Free Cells of Klebsiella sp. Isolated from Waste Water

Abstract

In the present study, we evaluated a bacterium that was isolated from waste water for its ability to take up cadmium and manganese. The strain, identified both biochemically and by its 16S rRNA gene sequence as Klebsiella, was named Yangling I2 and was found to be highly resistant to heavy metals. Surface characterization of the bacterium via SEM revealed gross morphological changes, with cells appearing as biconcave discs after metal exposure rather than their typical rod shape. The effects of pH, temperature, heavy metal concentration, agitation and biomass concentration on the uptake of Cd(II) and Mn(II) was measured using atomic absorption spectrophotometry. The results showed that the biosorption was most affected by pH and incubation temperature, being maximized at pH 5.0 and 30°C, with absorption capacities of 170.4 and 114.1 mg/g for Cd(II) and Mn(II), respectively. Two models were investigated to compare the cells' capacity for the biosorption of Cd and Mn, and the Langmuir model based on fuzzy linear regression was found to be close to the observed absorption curves and yield binding constants of 0.98 and 0.86 for Cd and Mn, respectively. This strain of Klebsiella has approximately ten times the absorption capacity reported for other strains and is promising for the removal of heavy metals from waste water.

Fig 1. The growth curves of Klebsiella sp. Yangling I2 in the presence of different initial concentrations of Cd(II).

Initial pH = 5.0, biomass concentration = 1.0 g/L, and contact time = 26 h.

Fig 2. The growth curves of Klebsiella sp. Yangling I2 in the presence of different initial concentrations of Mn(II).

Initial pH = 5.0, biomass concentration = 1.0 g/L, and contact time = 26 h.

Fig 3

(A) SEM images of Klebsiella sp. Yangling I2, (B) Klebsiella sp. Yangling I2 equilibrated with 4mM Cd(II), and (C) Klebsiella sp. Yangling I2 equilibrated with 20mM Mn(II).

Fig 4. Effect of pH on the absorption of Cd(II) by Klebsiella sp. Yangling I2.

Initial ion concentration = 2 mM, biomass concentration = 1.0 g/L, and contact time = 26 h.

Fig 5. Effect of pH on the absorption of Mn(II) by Klebsiella sp. Yangling I2.

Initial ion concentration = 10 mM, biomass concentration = 1.0 g/L, and contact time = 20 h.

Fig 6. Effect of incubation temperature on the absorption of Cd(II) by Klebsiella sp. Yangling I2.

Initial ion concentration = 10 mM, initial pH = 5.0, and contact time = 26 h.

Fig 7. Effect of incubation temperature on the absorption of Mn(II) by Klebsiella sp. Yangling I2.

Initial ion concentration = 10 mM, initial pH = 5.0, and contact time = 20 h.

Fig 8. Effect of initial ion concentration on the absorption of Cd(II) by Klebsiella sp. Yangling I2.

Initial pH = 5.5, biomass concentration = 1.0 g/L, and contact time = 26 h.

Fig 9. Effect of initial ion concentration on the absorption of Mn(II) by Klebsiella sp. Yangling I2.

Initial pH = 5.0, biomass concentration = 1.0 g/L, and contact time = 20 h.

Fig 10. Effect of agitation speed on the absorption of Cd(II) by Klebsiella sp. Yangling I2.

Initial ion concentration = 2 mM, initial pH = 5.5, and contact time = 26 h.

Fig 11. Effect of agitation speed on the absorption of Mn(II) by Klebsiella sp. Yangling I2.

Initial ion concentration = 10 mM, initial pH = 5.0, and contact time = 20 h.

Fig 12. Effect of biosorbent density on the absorption of Cd(II) by Klebsiella sp. Yangling I2.

Initial ion concentration = 2 mM, initial pH = 5.5, and contact time = 26 h.

Fig 13. Effect of biosorbent density on the absorption of Mn(II) by Klebsiella sp. Yangling I2.

Initial ion concentration = 10 mM, initial pH = 5.0, and contact time = 20 h.

Fig 14. Effect of contact time on the uptake of Cd(II) and Mn(II) by Klebsiella sp. Yangling I2.

Fig 15. (A) Langmuir isotherm based on fuzzy linear regression for the absorption of cadmium. (B) Langmuir isotherm based on fuzzy linear regression for the absorption of manganese. (C) Freundlich isotherm based on fuzzy linear regression for the absorption of cadmium. (D) Freundlich isotherm based on fuzzy linear regression for the absorption of manganese.