Biosorption and desorption of copper (II) ions by Bacillus sp.

Batch biosorption experiments were conducted to investigate the removal of Cu2+ ions from aqueous solutions by a series of bacterial strains isolated from a local activated sludge process. The characteristics of 12 isolates were identified and examined for their ability to bind Cu2+ ions from aqueous solution. Among the isolates, two species exhibited biosorption capacity >40 mg of Cu/g of dry cell. Isotherms for the biosorption of copper on bacterial cells were developed and compared, and the equilibrium data fitted well to the Langmuir and Freundlich isotherm models. The biosorption of copper increased significantly with increasing pH from 2.0 to 6.0 regardless of the species. More than 90% of copper sorbed on the cells of Bacillus sp. could be recovered by washing with 0.1 M HNO3 for 5 min. The performance of two different desorption processes was also tested and compared. The results show that five biosorption and desorption cycles are a better operation process than five successive biosorptions followed by one desorption to remove and recover copper from aqueous solution. The biosorbent could be used for at least five biosorptions and desorption cycles without loss of copper removal capacity. It can be concluded that the activated sludge or sludge-isolated bacteria could be a potential biosorbent for copper removal.