Preparation, characterization, adsorption kinetics and thermodynamics of novel magnetic chitosan enwrapping nanosized γ-Fe2O3 and multi-walled carbon nanotubes with enhanced adsorption properties for methyl orange

A novel magnetic composite bioadsorbent composed of chitosan wrapping magnetic nanosized γ-Fe2O3 and multi-walled carbon nanotubes (m-CS/γ-Fe2O3/MWCNTs) was prepared under relative mild conditions and was characterized. Adsorption of methyl orange (MO) onto m-CS/γ-Fe2O3/MWCNTs was investigated with respect to pH, initial MO concentration, coexisting anions and temperature. Results of characterizations indicated that magnetic nanosized γ-Fe2O3 and MWCNTs have been wrapped by crosslinked chitosan. Introduction of MWCNTs could obviously increase the adsorption capacity (qe) of MO onto bioadsorbent by 2.2 times. Kinetics data and adsorption isotherm were better fitted by pseudo-second-order kinetic model and by Langmuir isotherm, respectively. Values of activation parameters such as free energy (△G°), enthalpy (△H°) and entropy (ΔS°) were determined as 3.15-3.78 kJ mol−1, −9.94 kJ mol−1 and −20.65 J mol−1 k−1, respectively, indicating that the adsorption was feasible, spontaneous and exothermic process in nature. After adsorption, m-CS/γ-Fe2O3/MWCNTs could be effectively and fleetly separated by applying a magnetic field.