Removal of cadmium and zinc ions from aqueous solution by living Aspergillus niger

The potential of living Aspergillus niger to remove cadmium and zinc from aqueous solution was investigated. Effects of pH, initial concentration, contact time, temperature and agitation rate on the biosorption of Cd(II) and Zn(II) ions were studied. The optimum adsorption pH value for Cd(II) and Zn(II) were 4.0 and 6.0. The best temperature and agitation rate were in the range of 25-30 degrees C and 120 r/min for all metal ions. Under the optimal conditions, the maximum uptake capacities of Cd(II) and Zn(II) ions are 15.50 mg/g and 23.70 mg/g at initial concentrations of 75 mg/L and 150 mg/L, respectively. Biosorption equilibrium is established within 24 h for cadmium and zinc ions. The adsorption data provide an excellent fit to Langmuir isotherm model. The results of the kinetic studies show that the rate of adsorption follows the pseudo-second order kinetics.