Synthesis of carboxyl-functionalized magnetic nanoparticle for the removal of methylene blue

In this paper, carboxylated ethylenediamine functionalization Fe3O4@SiO2 nanoparticles (Fe3O4@SiO2-EDA-COOH NPs) have been developed in order to remove methylene blue (MB) from aqueous solution. The chemical structure, morphology and magnetic characteristics of the magnetic composite nanoparticles were characterized by Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), High resolution transmission electron microscopy (HR-TEM), Scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). To explore the truth, some methylene blue adsorption influenced factors of initial concentration, contact time and solution pH were at length investigated. The results showed that the absorption capacity depended strongly on pH, and the maximum adsorption value for MB (43.15 mg/g) was obtained at pH 10. In addition, the equilibrium was attained within 60 min, and the adsorption kinetics and adsorption isotherms data can be well accorded with pseudo-second-order kinetic model and Freundlich isotherm model, respectively. Most importantly, remarkable enhancement in adsorption capacity for MB is achieved than other reported adsorbents. It is worth noting that adsorbents can be quickly recovered from aqueous solution by external magnet. Finally, the plausible adsorption mechanism was briefly discussed. Our results suggest that novel nanoparticle Fe3O4@SiO2-EDA-COOH is a promising adsorbent in improving adsorption performance of MB from aqueous solution.