A basic investigation was conducted in batch conditions to remove a hazardous heavy metal, cadmium from aqueous solutions utilizing lyophilized cell mass of two cadmium resistant bacteria, Leucobcter sp. KUCd3 and Ralstonia mannitolilytica KUCd7 separately, as biosorbents. Irrespective of initial Cd concentration of solution, both the biosorption reactions took 80 min to attain equilibrium at neutral pH and 28°C following pseudo-second order kinetics which indicated their chemisorption nature. Though the specific metal biosorption enhanced with increasing initial Cd concentration of the solution, Cd removal efficiency reduced. Maximum Cd removal efficiency of the biomasses of KUCd3 (91.8%) and KUCd7 (95.8%) was observed at 10mg/L of Cd concentration. While Cd adsorption isotherm of KUCd3 biomass followed ‘Langmuir model’of monolayer sorption on a homogeneous surface, adorption by KUCd7 biomass could be described better through ‘Freundlich model' of heterogeneous absorption principle. The values of separation factor between 0 to 1 and high surface coverage revealed that these reactions were favourable with considerable amount of Cd sorption sites on both these biosorbents. Therefore, KUCd3 showed maximum cadmium sorption capacity of 108.7mg/g with the Cd binding affinity of 0.083L/mg and KUCd7 having Cd binding affinity of 0.054L/mg exhibited maximum cadmium sorption capacity of 84.75mg/g as biosorbents. SEM-EDAX analysis documented cell surface morphology of KUCd3 and KUCd7 and presence of bound Cd on it. FTIR analysis revealed the involvement of different anionic functional groups presenton bacterial cell envelopin Cd2+ entrapment. From the in-vitro analysis it can be concluded that the individual call biomasses of Ralstonia mannitolilytica KUCd7 and Leucobcter sp. KUCd3 are the potent biosorbent those can be explored for cadmium removal from contaminated water body.
