Silica-Coated Magnesium Ferrite Nanoparticles/Glutaraldehyde-Cross-Linked Polyethylenimine Composite Adsorbent for Ultrahigh Remediation of 2,4-Dichlorophenoxyacetic Acid

The emerging contaminant 2,4-dichlorophenoxyacetic acid (2,4-D) has been shown to have harmful effects on the environment and human health. These contaminants present a critical challenge in water remediation. Herein, a magnetic composite composed of silica-coated magnesium ferrite nanoparticles and glutaraldehyde-cross-linked polyethylenimine polymer (i.e., MgFe₂O₄@SiO₂/GA-PEI composite) was synthesized to use as an effective adsorbent for the removal of 2,4-D. The successful preparation of the MgFe₂O₄@SiO₂/GA-PEI composite using the optimal synthesis condition was confirmed through XRD, TGA-DTG, FTIR, zeta potential analysis, solid-state ¹³C NMR, TEM, SEM, EDS, VSM, and organic functional group tests. The adsorption behavior of 2,4-D by this composite was systematically investigated. The results showed that the MgFe₂O₄@SiO₂/GA-PEI composite exhibited not only pH-dependent adsorption behavior but also an ultrahigh adsorption capacity (∼1631 mg g^-1) for 2,4-D. The efficient adsorption of 2,4-D is due to the large numbers of functional groups (i.e., hydroxy and amines) in the obtained composite. Furthermore, the electrostatic interaction between the composite and 2,4-D molecules significantly influenced the adsorption behavior. The reusability test indicated that the MgFe₂O₄@SiO₂/GA-PEI composite revealed the effective adsorption of 2,4-D after five adsorption-desorption cycles. This newly designed heterogeneous magnetic hybrid composite provides a unique foundation to perform ultrahigh removal capacity, easy separation, and reusability for harmful pesticide 2,4-D in water remediation.