Abstract
Background: Recently, hydrophilic carbon-coated magnetite (Fe3O4/C) has been prepared and applied in adsorption and separation sciences. Although there have been some works on preparation and application of Fe3O4/C in adsorption and separation sciences, little work has been carried out on protein adsorption and desorption on Fe3O4/C. Herein, the present work investigated the equilibrium and kinetics of protein (lysozyme) adsorption on Fe3O4/C NPs.
Methods: Fe3O4/C NPs were prepared by hydrothermal method. Effects of pH, initial lysozyme concentrations, and ionic strength on adsorption performance of Fe3O4/C NPs were investigated. Desorption of lysozyme from the Fe3O4/C was examined using 0.5M NaH2PO4, 0.5M NaCl and 1.5M NaSCN, respectively. Results: Fe3O4 and Fe3O4/C NPs with uniform particle size were of quasi-spherical shapes and the dominant diameters of them were about 300 nm and 330 nm, respectively. A coating thickness of carbon on surface of the Fe3O4/C NPs was about 15 nm. Fe3O4/C NPs exhibited typical superparamagnetic characteristics with the maximal saturation magnetization of 73.8 emu/g. Fe3O4/C NPs had a maximum adsorption of lysozyme at pH 9. The adsorption kinetics data fitted well into the pseudo-second-order model while the adsorption equilibrium results were best described by the Langmuir model. Conclusion: Fe3O4/C NPs were prepared by hydrothermal reaction and applied to adsorb lysozyme. The maximum adsorption of lysozyme on Fe3O4/C NPs arose at pH 9. Adsorption equilibria could be reached within 40 min. Adsorption kinetics of lysozyme on Fe3O4/C NPs could be expressed by pseudo-second order model. Langmuir isotherm fitted with experimental data best. The theoretical maximum adsorption capacity of Fe3O4/C NPs for lysozyme was 76.34 mg/g. The best desorption rate was about 32.7%.Keywords: Adsorption, Carbon coated Fe3O4 nanoparticles, Isotherm, Kinetics, Lysozyme, Magnetic separation.
Graphical Abstract