Optimization of biosorption of Zn(II) ions from aqueous solutions with low-cost biomass Trametes versicolor and the evaluation of kinetic and thermodynamic parameters
The optimum biosorption conditions for removing Zn(II) ions from aqueous solutions by naturally powdered Trametes versicolor were successfully evaluated through a multi-step response surface methodology. The conducted experiments were based on a central composite design. The most influential factors on the biosorption process were initial pH (5-6.7), temperature (18-30 degrees C), and initial Zn(II) concentration (30-70mg L-1). Based on the statistical analysis, the optimum conditions for Zn(II) biosorption were found to be 5.74, 24.57 degrees C, and 60.95mg L-1 for initial pH, temperature and Zn(II) concentration, respectively. Under these optimum conditions, the maximum amount of biosorbed Zn(II) ions was 43.87mg Zn(II) per g dry cells. The proposed quadratic model fits very well to the experimental data. Furthermore, a Dubinin-Radushkevich isotherm model described the biosorption of Zn(II) ions on the biosorbent better than the common isotherm models, while kinetic studies showed that Zn(II) biosorption matched pseudo-second-order kinetics. Moreover, thermodynamic parameters, such as the changes in free energy, enthalpy, and entropy, were also calculated for the biosorption of Zn(II) ions onto T. versicolor. It was concluded that naturally powdered T. versicolor is a suitable biosorbent for the removal of Zn(II) ions from aqueous solutions.