Removal of cadmium (II) in the aqueous solutions by biosorption of Bacillus licheniformis isolated from soil in the area of Tigris River

Abstract

Biosorption by dead bacteria is an alternative and effective method for the removal toxic elements from drinking water and waste water. The biosorption of Cd(II) from aqueous solutions was studied in a batch method by using dead bacteria Bacillus licheniformis sp. extracted from soil in the area of Tigris River. The Cd element analysis was determined using ICP-OES and AAS. The maximum adsorption capacity of biosorbent was determined, respectively, 24.51 mg/g for Cd element from Langmuir isotherm constants in the optimum conditions. The characterisation of B. licheniformis to describe behaviour of bacteria was determined such as adsorption isotherm, kinetic and thermodynamic data using FT-IR, TGA, DTA, SEM and EDX. The results suggested that the most equilibrium data of Cd(II) bioadsorption was best represented by the pseudo second-order equation and Langmuir isotherm model at different time-temperatures. The thermodynamic functions and activation energy was found to be ΔG°; −0,984 kJ/mol at 318 K, ΔH°; 15.48 kJ/mol, ΔS°; 39.08 kJ/mol and Ea; 23.24 kJ/mol and due to the ΔG°< 0, ΔH°> 0, ΔS°> 0, the reaction mechanism was determined to be physical adsorption and endothermic. This study shows that B. licheniformis sp. can be used as an effective method for the removal of Cd(II) from aqueous solutions.