Response Surface Modeling and Optimization of Effective Parameters for Zn(II) Removal From Aqueous Solution Using Gracilaria Corticata

Biosorption of Zn(II) from aqueous solution by biomass marine alga, namely Gracilaria corticata was investigated in this paper. Four independent variables, including initial zinc concentration (50-150 mg L^-1), initial solution pH (3-7), contact time (10-50 min), and biomass amount (1-2 g/100mL) were studied in the biosorption process. Optimization of the process conditions for maximizing Zn(II) removal from aqueous solutions by Gracilaria corticata was carried out using Box-Behnken design, including response surface methodology (RSM) based on 27 different experimental data. The optimal operating conditions for 95.0% removal of Zn(II) were as follows: initial zinc concentration of 100 mg L^-1, initial solution pH of 5, contact time of 30.5 min, and biomass amount of 2 g/100 mL. In addition, the equilibrium isotherms were described by investigation of Langmuir and Freundlich isotherms. The Freundlich adsorption isotherm model well matched the experimental data (R^2 = 0.981). The kinetic data fitted pseudo-second order model with a correlation coefficient of 0.9953. Gracilaria corticata was found to be well applicable for zinc removal based on the experimental results.