Abstract

Optimization of a chromium biosorption process was performed by varying three independent variables pH (0.5 to 3.5), initial chromium ion concentration (10 to 30 mg/L), and Yarrowia lipolytica dosage (2 to 4 g/L) using a Doehlert experimental design (DD) involving response surface methodology (RSM). For the maximum biosorption of chromium ion in an aqueous solution by Y. lipolytica, a total of fifteen experimental runs were set and the experimental data fitted to the empirical second-order polynomial model of a suitable degree. The analysis of variance of the quadratic model demonstrates that the model was highly significant. The model showed that chromium uptake in aqueous solution was affected by all the three variables studied. The optimum values of the variables were found to be 2.07, 18.76 mg/L and 3.39 g/L for pH, initial chromium ion concentration and biomass dosage, respectively at contact time of 30 min. At these optimal conditions, the maximum percentage biosorption of chromium was predicted to be 41.59. The experimental values were in good agreement with predicted values and the correlation coefficient was found to be 0.9891. Therefore, it is apparent that the DD involving RSM not only gives valuable information on interactions between the variables but also leads to identification of feasible optimum values of the studied variables.

Key words: Biosorption, Doehlert experimental design, response surface methodology, Yarrowia lipolytica.