Bacteria immobilisation on hydroxyapatite surface for heavy metals removal

Area of Science:

• Environmental Science
• Microbiology
• Materials Science

Background:

• Heavy metal contamination in aqueous streams poses significant environmental and health risks.
• Hydroxyapatite (HAp), derived from natural sources like fish bones, shows potential for heavy metal adsorption.
• Bacterial strains with inherent heavy metal resistance can contribute to bioremediation strategies.

Purpose of the Study:

• To evaluate the efficacy of immobilizing selected bacterial strains on hydroxyapatite (HAp) for heavy metal removal.
• To assess the synergistic effect of bacterial-HAp composites in adsorbing zinc (Zn(II)) and cadmium (Cd(II)) from aqueous solutions.
• To compare the adsorption capacities of individual bacterial strains and HAp with their combined application.

Main Methods:

• Selected bacterial strains (Pseudomonas fluorescens S3X, Microbacterium oxydans EC29, Cupriavidus sp. 1C2) were immobilized on natural hydroxyapatite (HAp).
• The adsorption capacity of HAp, bacterial strains, and their composites was tested using solutions containing Zn(II), Cd(II), or both.
• Adsorption efficiency was quantified by measuring metal concentrations before and after treatment.

Main Results:

• A significant synergistic effect was observed, with bacterial-HAp composites exhibiting higher heavy metal adsorption than HAp or bacteria alone.
• For single metal solutions, the composite of Cupriavidus sp. (1C2) with HAp showed a nearly four-fold increase in Zn(II) adsorption capacity (0.433 mmol/g).
• The composite of Microbacterium oxydans (EC29) with HAp demonstrated a nearly three-fold increase in Cd(II) adsorption capacity (0.090 mmol/g).
• Synergistic effects were more pronounced at higher metal concentrations for single-metal solutions and at lower concentrations for mixed-metal solutions.

Conclusions:

• Immobilization of specific bacterial strains onto HAp creates highly effective biosorbents for heavy metal removal.
• The bacterial-HAp composites offer a promising, sustainable solution for remediating zinc and cadmium contamination in water.
• The choice of bacterial strain is crucial for optimizing the removal of specific heavy metals.