Investigation of the factors affecting acid blue 256 adsorption from aqueous solutions onto red pine sawdust: equilibrium, kinetics, process design, and spectroscopic analysis

Abstract

Acid Blue 256 (AB256) dye was selected as the model. Textile effluents and linear and nonlinear regression procedures have been applied to the Langmuir, Freundlich, Tempkin, Dubinin–Radushkevich, and Redlich–Peterson isotherms for adsorption of the dye onto red pine (Pinus resinosa) sawdust. The effects of parameters were investigated and interaction was characterized by Fourier transform infrared (FTIR) spectroscopy and SEM/EDAX. Five isotherms were used, and the nonlinear method of the Langmuir isotherm equation was found to provide the closest fit to the equilibrium data. The monolayer adsorption capacity is 54.16 mg/g for AB256. The optimum conditions were found to be: adsorbent size 75–90 μm, initial pH 2, stirring rate 600 rpm, initial dye concentration 200 mg/l, biosorbent dose 1 g and temperature 25°C. All thermodynamic parameters suggested that AB256 adsorption onto red pine sawdust was a spontaneous, physisorption, and exothermic process. Kinetics was analyzed by four different kinetic equations using nonlinear regression analysis. The pseudo-second-order equation provided the best fit with experimental data.

Keywords:

• Acid Blue 256
• Acid dye
• Sawdust
• Nonlinear regression
• Adsorption

Acknowledgment

The author is most grateful to Dr Emrah Bulut for his comments on the first version of this manuscript and for several valuable suggestions that have been included in the final form.