Fabrication of Poly(γ-glutamic acid)-coated Fe3O4 Magnetic Nanoparticles and Their Application in Heavy Metal Removal

In this study, poly(gamma-glutamic acid)-coated Fe3O4 magnetic nanoparticles (gamma-PGA/Fe3O4 MNPs) were successfully fabricated using the co-precipitation method. Fe3O4 MNPs were also prepared for comparison. The average size and specific surface area results reveal that gamma-PGA/Fe3O4 MNPs (52.4 nm, 88.41 m(2) . g(-1)) have smaller particle size and larger specific surface area than Fe3O4 MNPs (62.0 nm, 76.83 m(2) . g(-1)). The gamma-PGA/Fe3O4 MNPs can remove over 99% of Cr3+, Cu2+ and Pb2+, and over 77% of Ni2+ in deionized water, much higher than.-PGA and Fe3O4 MNPs, attributed to the larger specific surface area of gamma-PGA/Fe3O4 MNPs. With the solution pH higher than 6.0, gamma-PGA/Fe3O4 MNPs demonstrate better removal activity. The adsorption isotherm of gamma-PGA/Fe3O4 MNPs for Cr3+ fits the Freundlich model well, with the adsorption capacity of 24.60 m(2) . g(-1). gamma-PGA/Fe3O4 MNPs are strongly attracted by permanent magnet, so it is easy to separate them completely from water. With their high efficiency for heavy metal removal and easier separation, gamma-PGA/Fe3O4 MNPs have great potential applications in water treatment.