Statistical modeling and optimization of the cadmium biosorption process in an aqueous solution using Aspergillus niger

In this study, the process of cadmium biosorption on NaOH pretreated Aspergillus niger biomass was investigated in the batch mode. The effect of three independent variables, initial pH of solution (1.3–8.7), biomass dosage (0.1–7.5 g/l) and initial cadmium ion concentration (0.5–37.5 mg/l) on the biosorption process was determined and the process was then optimized by means of response surface methodology (RSM). The process was evaluated by cadmium removal efficiency as the process response. Twenty experiments designed by central composite design (CCD) were carried out and the process response was modeled using a polynomial equation as function of the variables. The optimum values of the variables were found to be 5.96, 30.0 mg/l and 1.6 g/l for initial pH, initial cadmium ion concentration and biomass dosage, respectively, at contact time of 1440 min. At optimal conditions, a biosorption capacity of 10.14 mg Cd(II)/g biomass was obtained corresponding to 82.2% cadmium removal efficiency. Under this condition, a desirability value of 0.903 was obtained, showing that the estimated function may represent the experimental model and give the desired conditions. According to these observations, biomass A. niger fungus particles with clean surface and high porosity may have application as biosorbent for heavy metal removal from industrial wastewater effluents.