Characterization of cadmium biosorption by inactive biomass of two cadmium-tolerant endophytic bacteria Microbacterium sp. D2-2 and Bacillus sp. C9-3.

Abstract

In this study, two cadmium-tolerant endophytic bacteria (Microbacterium sp. D2-2 and Bacillus sp. C9-3) were employed as biosorbents to remove Cd(II) from aqueous solutions. The influence of initial pH, initial Cd(II) concentration, adsorbent biomass, temperature and contact time on Cd(II) removal were investigated. Results showed that the Langmuir isotherms were found to best fit the equilibrium data, and the maximum biosorption capacities were found to be 222.22 and 163.93 mg/g at a solution pH of 5.0 for Microbacterium sp. D2-2 and Bacillus sp. C9-3, respectively. The biosorption kinetics followed well pseudo-second-order kinetics. Fourier transform infrared spectroscopic analysis suggested that the hydroxyl, carboxyl, carbonyl and amino groups on Microbacterium sp. D2-2 and Bacillus sp. C9-3 biomass were the main binding sites for Cd(II). The results presented in this study showed that Microbacterium sp. D2-2 and Bacillus sp. C9-3 are potential and promising adsorbents for the effective removal of Cd(II) from aqueous solutions.