Environmentally Friendly Magnetic Nanoparticles for Efficient Removal of Methylene Blue and Cr(VI) from Water

The poor environmental friendliness, low adsorption capacity and nonreusability of adsorbents are still challenging for the removal of pollutants in aqueous solution. Herein, novel polypeptide-functionalized silica-coated magnetic nanoparticles (PS-MNPs), Fe3O4@SiO2@PLL nanoparticles, with good environmental friendliness, excellent adsorption capability and economic reusability were designed and prepared for efficient removal of methylene blue (MB) and Cr(VI) ion (Cr2O72-). The chem-physical properties of Fe3O4@SiO2@PLL nanoparticles, such as chemical structure, nanosize, nanomorphology, crystalline structure, magnetization and thermo-oxidative degradation behavior were fully investigated in this study. In addition, the adsorption properties of the Fe3O4@SiO2@PLL nanoparticles for MB and Cr(VI) ion in aqueous solution were explored by batch adsorption experiments. Based on the experimental results, the Fe3O4@SiO2@PLL nanoparticles demonstrated excellent adsorption capacity for removal of both MB and Cr(VI) ion that the theoretical maximum adsorption capacities of the nanoparticles were 301.2 mg.g(-1) for MB and 164.7 mg.g(-1 )for Cr(VI), respectively. The adsorption process could be better fitted by pseudo-second-order model, and matched well with the Langmuir isotherm equation. Moreover, the Fe3O4@SiO2@PLL nanoparticles could be easily regenerated by desorbing metal ions and organic dyes from the adsorbents with appropriate eluents, and showed good adsorption capacity after five recycles. In brief, the as-prepared PS-MNPs exhibited improved environmental friendliness, excellent adsorption properties and high regeneration efficiency, which could be used as a potential adsorbent for different kinds of contaminants removal.