Adsorption of 2,4-Dichlorophenoxyacetic acid and Methylene blue by magnesium Ferrite-based Nanoparticles

Abstract

The objective of this research is the investigation of adsorption behaviors of 2,4- dichlorophenoxyacetic acid (2,4-D) and methylene blue (MB) by magnesium ferritebased nanoparticles. The study on 2,4-D adsorption behavior using the aminefunctionalized magnesium ferrite nanoparticles (MgFe2O4–NH2 NPs) as adsorbents was firstly performed. The significant parameters affecting to the adsorption performance i.e., solvent types, adsorption time, initial pH of solution, adsorbent dose and solution temperature were investigated. The obtained results indicated the MgFe2O4–NH2 NPs provided a moderate adsorption efficiency (~56%, ~19 mg g-1) of 2,4-D under the optimum condition: 2,4-D in methanol at pH ~3, 30 mg of adsorbent, 60 min of adsorption time and 25oC of solution temperature. XPS spectra confirmed the existence of adsorbed 2,4-D molecules on adsorbent surface. In addition, the recycle test showed high reusability of MgFe2O4–NH2 NPs for 2,4-D adsorbent. The development of MgFe2O4– NH2 NPs by surface modification, coating with silica, to adopt as MB adsorbent was secondly performed. The silica coated MgFe2O4–NH2 NPs (MgFe2O4–NH2@SiO2 NPs) were prepared using a modified stöber method. After fully characterizations of the assynthesized MgFe2O4–NH2@SiO2 nanoadsorbent, investigation of MB adsorption behavior was conducted by adjusting the essential adsorption parameters such as initial pH of solution, initial MB concentration and adsorption time. The successful preparation of MgFe2O4–NH2@SiO2 NPs was confirmed by several characterization techniques: XRD, FTIR, TEM, SEM, EDS, VSM and zeta potential measurement. The highest adsorption efficiency of MB by MgFe2O4–NH2@SiO2 NPs (~86%, ~5 mg g-1) was performed under the optimal condition: 10 mg L-1 of MB solution at pH ~9 for 10 min. A quite low adsorption capacity of MB was occurred; however, rapid adsorption, good separation and reusability, and high stability were good characteristics to apply as the adsorbent for MB treatment. The key findings of this study indicated that MgFe2O4-based nanoparticles i.e., MgFe2O4–NH2 and MgFe2O4–NH2@SiO2 can be used as 2,4-D and MB adsorbents.