[Studies on biosorption of Pd2+ by bacteria]

Area of Science:

• Environmental Microbiology
• Bioremediation
• Materials Science

Background:

• Palladium (Pd2+) is a valuable but often scarce heavy metal.
• Efficient methods for palladium recovery and removal from industrial wastewater are crucial.

Purpose of the Study:

• To screen and identify bacterial strains with high palladium (Pd2+) adsorption capabilities.
• To characterize the biosorption process of Pd2+ using the selected bacterial strain.

Main Methods:

• Screening of bacterial strains for Pd2+ adsorption.
• Identification of the optimal strain using biochemical and genetic methods.
• Optimization of biosorption conditions (pH, biomass concentration, initial Pd2+ concentration, temperature, time).
• Analysis of adsorption mechanisms using Transmission Electron Microscopy (TEM) and Infrared (IR) spectroscopy.

Main Results:

• The bacterial strain R08, identified as Bacillus licheniformis, demonstrated strong Pd2+ adsorption.
• Optimal biosorption occurred at pH 3.5, with rapid, non-temperature-dependent kinetics.
• A maximum biosorptive capacity of 224.8 mg/g was achieved under specific conditions (200 mg/L Pd2+, 0.4 g biomass/L, pH 3.5, 30°C, 45 min).
• TEM revealed the reduction of Pd2+ to Pd0 nanoparticles by the biomass.
• IR analysis suggested the involvement of carboxyl (-COO-) and phosphate (HPO(4)2-) functional groups in Pd2+ adsorption.

Conclusions:

• Bacillus licheniformis strain R08 is a promising biosorbent for efficient removal and potential recovery of palladium from aqueous solutions.
• The biosorption mechanism involves both adsorption and reduction of Pd2+ ions, mediated by cell wall functional groups.