Superparamagnetic core-shell polymeric nanocomposites for efficient removal of methylene blue from aqueous solutions

摘要

Ultrafine well-dispersed Fe_3O_4 magnetic nanoparticles (NPs) were directly prepared in an aqueous solution using controlled co-precipitation method. The Fe_3O_4-poly(acrylamide-co- sodium acrylate) core-shell magnetic nanogels are prepared by solution polymerization of acrylamide (AM) and sodium acrylate (AA-Na) monomers in the presence of Fe_3O_4NPs, N, N'-methylenebisacrylamide (MBA) as a cross-linker, N, N, N',N'-tetramethylethylenediamine and potassium peroxydisulphate (KPS) as the redox initiator system. The novel Fe _3O_4-poly(acrylamide-cosodium acrylate) core-shell magnetic nanocomposite hydrogels are prepared by in situ free radical co-polymerization of AM and AA-Na in an aqueous dispersion of nanogel particles using MBA as the cross-linker and KPS as the initiator. The as-prepared nanocomposite hydrogels are characterized by Fourier transform infrared spectroscopy spectra, X-ray powder diffraction and transmission electron microscopic measurements. The mean particle size of the synthesized magnetite (Fe_3O_4) NPs was approximately 8 nm. The diameter of the stabilized polymer-coated Fe _3O_4 nanogels is approximately 11 nm. The surface morphology of the nanocomposites has been studied by scanning electron microscopy and atomic force microscopy. The Fe_3O_4- poly(acrylamide-co-sodium acrylate) nanocomposites have been extensively investigated for the removal of basic dyes from aqueous solutions. Results of batch experiments showed that these adsorbents exhibited high sorption capacities towards methylene blue (MB). Experimental data were analyzed using first-order kinetics, pseudo-second-order kinetics and intra-particle diffusion models. The kinetics followed a pseudo-second-order equation. Equilibrium isotherm data were analyzed according to Langmuir and Freundlich equations. The thermodynamic parameters for the adsorption of MB onto the nanocomposite hydrogels were also calculated. Regeneration of nanocomposite adsorbents can be easily achieved.