Co-polymerization of catechol and polyethylenimine on magnetic nanoparticles for efficient selective removal of anionic dyes from water

In the present study, novel magnetic adsorbents Fe3O4@catechol/PEI were fabricated simply by co-polymerization of catechol and branched polyethylenimine (PEI) onto Fe3O4 nanoparticles under alkaline condition, and characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometer (VSM). Adsorption of three different kinds of anionic dyes, methyl blue, orange G and amaranth, from aqueous solutions using Fe3O4@catechol/PEI was investigated. The adsorption results showed that the removal of anionic dyes by Fe3O4@catechol/PEI matched well with pseudo-second-order kinetic model and Langmuir isotherm model. The maximum adsorption capacities for methyl blue, orange G and amaranth were 344.8, 192.3, and 146.2mg·g−1, respectively. Furthermore, the anionic dyes could be selectively absorbed from dye mixtures containing anionic and cationic dyes. After adsorption, Fe3O4@catechol/PEI could be efficiently separated from the solution under the adscititious magnetic field and could be easily regenerated. This novel magnetic adsorbent is a promising candidate for removal of anionic dyes in the wastewater. [Display omitted] •A novel magnetic adsorbent Fe3O4@catechol/PEI was synthesized via a simple mussel-inspired method.•The Fe3O4 nanoparticles were covered by the catechol-PEI polymer layer.•The Fe3O4@catechol/PEI showed high adsorption capacities for anionic dyes.•The Fe3O4@catechol/PEI selectively removed anionic dyes from mixed dye aqueous solution.•The Fe3O4@catechol/PEI exhibited excellent magnetic response and reusability.