Kinetic and thermodynamic studies on methylene blue biosorption using corn-husk

Abstract

A low-cost waste biomass derived from corn plant (husk) was tested as an alternative to other expensive treatment options, for the removal of methylene blue (MB), from aqueous solutions. The effects of different experimental parameters, such as biosorbent dosage, dye concentration, contact time, and temperature, on the adsorption process were investigated. An optimum value of discoloration was observed at pH 6.0 and 2 g L⁻¹ biomass dosage. The amount of dye removed per adsorbent unit decreased with increasing adsorbent dosage, temperature, and increased with increasing contact time, and concentration. Experimental data were modeled using first-order, pseudo-second-order, Elovich, and intraparticle diffusion kinetics models. The adsorption kinetics of MB could be described by the pseudo-second order reaction model. The experimental data were fitted to: Langmuir, Freundlich, Temkin, Redlich–Peterson, Toth, and Sips isotherm models and the best fitting was obtained with the Sips model. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) obtained revealed that MB adsorption is a spontaneous, exothermic and physical process. The obtained results indicated that corn husk as a low-cost biomaterial is an attractive candidate for the removal of basic dye MB from aqueous solutions.