A novel-green adsorbent based on betaine-modified magnetic nanoparticles for removal of methyl blue.

A potential adsorbent based on betaine-modified magnetic iron oxide nanoparticles (BMNPs) was successfully synthesized by facile method, characterized and applied for methyl blue (MB) removal from aqueous solution. The characterization results of FTIR, transmission electron microscopy (TEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) showed that the prepared nanoparticles could be well dispersed in water and exhibited excellent superparamagnetism. These properties imply the potential to recycle BMNPs from wastewater through magnetic field. In the adsorption process, the effects of main experimental parameters such as pH of MB solution, initial concentration of MB, contact time, and adsorption capacity for MB were studied and optimized. These results demonstrated that large amounts of quaternary ammonium groups existing on the surface of BMNPs could promote absorption of MB via electrostatic forces. Additionally, the adsorption kinetics of MB was found to follow a pseudo-second-order kinetic model and the adsorption equilibrium data fitted very closely to the Langmuir adsorption isotherm model. The maximum adsorption capacity for MB was calculated to be 136mgg at room temperature. Moreover, the BMNPs showed good reusability with 73.33% MB adsorption in the 5th cycle.