Removal and recovery of copper (II) ions by bacterial biosorption

Studies were conducted to investigate the removal and recovery of copper (II) ions from aqueous solutions by Micrococcus sp., which was isolated from a local activated sludge process. The equilibrium of copper biosorption followed the Langmuir isotherm model very well with a maximum biosorption capacity (q(max)) of 36.5 mg of Cu2+/g of dry cell at pH 5.0 and 52.1 mg of Cu2+/g of dry cell at pH 6.0. Cells harvested at exponential growth phase and stationary phase showed similar biosorption characteristics for copper. Copper uptake by cells was negligible at pH 2.0 and then increased rapidly with increasing pH until 6.0. In multimetal systems, Micrococcus sp. exhibited a preferential biosorption order: Cu approximate to Pb > Ni approximate to Zn. There is virtually no interference with copper uptake by Micrococcus sp. from solutions bearing high concentrations of Cl-, SO4(2-), and NO3- (0-500 mg/L). Sulfuric acid (0.05 M) was the most efficient desorption medium, recovering >90% of the initial copper sorbed. The copper capacity of Micrococcus sp. remained unchanged after five successive sorption and desorption cycles. Immobilization of Micrococcus sp. in 2% calcium alginate and 10% polyacrylamide gel beads increased copper uptake by 61%. Biomass of Micrococcus sp. may be applicable to the development of potentially cost-effective biosorbent for removing and recovering copper from effluents.