Biosorptive removal of copper and cobalt from aqueous solutions: Shewanella spp. put to the test

Biosorption of copper and cobalt by Shewanella spp. was investigated in this study. The biosorption capabilities of Shewanella spp. for copper and cobalt were monitored at different ion concentrations (0.002 M, 0.07 M and 0.2 M), biomass dosages (50, 100 and 150 (×10⁴ CFU/ml)) and pH (values 2-8) in batch mode. At optimum concentration (0.002 M/3.86 gl^-1), biosorbent dosage (150 × 10⁴ CFU/ml) and solution pH 6.5, Shewanella spp. recorded maximum copper and cobalt uptakes of 38% and 27%, respectively. The kinetic data obtained at different concentrations suggested that the biosorption rate was fast and in most cases the biosorption took place within 8 h followed by a slow attainment of equilibrium and the Langmuir sorption model fitted the data well with very high correlation efficiencies (>0.95). The results obtained in this study suggest that biosorbents, with further research, can in future be viewed as suitable sorbents in the recovery of precious metals such as copper after being discharged as effluent or as a result of mineral processing. In managing water resources, it is important that metallic species such as copper and cobalt be removed from water or reduced to acceptable levels since these metal species may cause ill-health effects to humans and livestock if the required concentration levels are exceeded. The required levels should fall within with World Health Organization (WHO) water quality guidelines and the water quality standards for various purposes (e.g. agriculture, drinking, domestic, water-reuse) as prescribed by individual countries.