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 Fe 3 O 4 @catechol/PEI were fabricated simply by co -polymerization of catechol and branched polyethylenimine (PEI) onto Fe 3 O 4 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 Fe 3 O 4 @catechol/PEI was investigated. The adsorption results showed that the removal of anionic dyes by Fe 3 O 4 @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 146.2   mg·g −   1 , respectively. Furthermore, the anionic dyes could be selectively absorbed from dye mixtures containing anionic and cationic dyes. After adsorption, Fe 3 O 4 @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.