Response Surface Approach for the Biosorption of Cr6+ Ions by Mucor racemosus

Response surface methodology (RSM) employing the Box-Behnken design was used to optimize the biosorption of chromium (Cr6+) by Mucor racemosus in submerged culture. The initial Cr6+ concentration (20-100 mg/L), pH (3.0-7.0), biomass dosage (5.0-9.0 mg), and time of sorption (2.0-6.0 h) were chosen as the process variables for the optimization. Two response values were chosen, i.e., sorption capacity (mg/g) and sorption percentage are optimized. A four-factor-three-level Box-Behnken design was used to evaluate the effects of these parameters on the sorption percentage. A second-order quadratic model suggested the optimum conditions (initial Cr6+ concentration 100 mg/L, pH of 5.0, biomass dosage of 5.0 mg, and time of sorption 4 h) resulted in the improvement of sorption of Cr6+ from 12.47 to 49.98% as well as the improvement of the sorption capacity from 0.1036 to 0.5 mg/g. Analysis of variance (ANOVA) for the above-mentioned response variables yielded a high coefficient of determination (R-2) value of 0.9985 and 0.9025 for the sorption capacity and sorption percentage, respectively. The desirability plot and overlay plot suggested the significance of the designed model. This is the first report on Cr6+ sorption by M. racemosus using statistical experimental design employing RSM.