Cadmium (II) and nickel (II) biosorption by Bacillus laterosporus (MTCC 1628)

• Gram positive bacteria Bacillus laterosporus (MTCC 1628) was used as a biosorbent for the removal of toxic cadmium (II) and nickel (II) ions from aqueous solution.
• Bacillus laterosporus showed higher adsorption capability for the removal of cadmium (85.47 mg/g) than nickel 44.44 mg/g, demonstrating the sequence of selectivity, in the order of decreasing electronegativity and increasing ionic radius.
• Owing to its high metal uptake potential, high biosorption rate and reusability, it can be concluded that Bacillus laterosporus is a promising biosorbent for removal of Cd(II) and Ni(II) from aqueous solutions.

Biosorption of heavy metals is a promising technology that involves removal of toxic metals from industrial waste streams and natural waters. The study describes the sorption of cadmium (II) [Cd (II)] and nickel (II) [Ni (II)] by dead biomass of Bacillus laterosporus, MTCC 1628. The biosorption conditions for the removal of Cd (II) and Ni (II) were examined by studying the effect of pH, contact time, biosorbent dosage and initial metal ion concentration. Shake flask studies yielded adsorption equilibrium in almost 120 min, for both the metals. It was found from Langmuir model that the maximum adsorption capacity for Cd (II) and Ni (II) ions was 85.47 mg/g and 44.44 mg/g respectively. Kinetic evaluation of the experimental data showed that the biosorption process followed pseudo-second order kinetics. Thermodynamic analysis showed that biosorption is an endothermic process with ΔH° of 5.45 kJ/mol for Cd (II) biosorption and 24.33 kJ/mol for Ni (II) biosorption. The surface characteristics of B. laterosporus biomass before and after metal biosorption were analyzed by using scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDAX) to study the changes in surface morphology and elemental constitution of the adsorbent. B. laterosporus exhibited a higher and better potential biosorbent for the removal of Cd (II) as compared to Ni (II) from aqueous solution.