Application of response surface methodology for the optimization of Ni2+ ions biosorption from aqueous solution using Sargassum filipendula

All the experiments were performed in batch mode for biosorption of Ni2+ ions from aqueous solution using Sargassum filipendula. All the process parameters of Ni2+ ions biosorption was optimized by using response surface methodology. The effect of four independent variables temperature (20 degrees C-40 degrees C), pH (3-6), initial Ni2+ ions concentration (50-150 mg/L) and biosorbent dosage (1.0-2.5 g/L) on biosorption of Ni2+ ions were studied. The biosorbent was characterized by using Fourier transform infrared spectroscopy, field emission electron microscopy, and energy dispersive X-ray spectroscopy. The optimized values of four variables were found as temperature of 41.5 degrees C, initial Ni2+ ions concentration of 83.18 mg/L, biosorbent dosage of 1.97 g/L and pH of 5.4 which resulted in 68.45% removal of Ni2+ ions. The Redlich-Peterson isotherm model was found to be the best fitted to experimental data of Ni2+ ions biosorption with higher value of R-2 and smaller value of Delta q%. The best fitted kinetic model was noticed as pseudo-first-order kinetic model (R-2 > 0.98) which shows that the rate limiting step was physisorption. Thermodynamic parameters (Delta G degrees = -0.097 to -4.060 kJ/mol, Delta H degrees = 79.175 J/mol, Delta S degrees = 0.270 J/mol K) of Ni2+ ions biosorption showed that the process was spontaneous, feasible and endothermic in nature. The biosorption and desorption efficiency were decreased up to 8.5% and 12%, respectively after four successive cycles. Therefore, the present study demonstrated that S. filipendula can be used as biosorbent for Ni2+ ions biosorption from the synthetic wastewater effectively and economically.