Fabrication of poly(γ-glutamic acid)-coated Fe₃O ₄ magnetic nanoparticles and their application in heavy metal removal

In this study, poly(γ-glutamic acid)-coated Fe₃O ₄ magnetic nanoparticles (γ-PGA/Fe₃O₄ MNPs) were successfully fabricated using the co-precipitation method. Fe ₃O₄ MNPs were also prepared for comparison. The average size and specific surface area results reveal that γ-PGA/Fe ₃O₄ MNPs (52.4 nm, 88.41 m²·g ^-1) have smaller particle size and larger specific surface area than Fe₃O₄ MNPs (62.0 nm, 76.83 m²·g ^-1). The γ-PGA/Fe₃O₄ MNPs can remove over 99% of Cr³⁺, Cu²⁺ and Pb²⁺, and over 77% of Ni²⁺ in deionized water, much higher than γ-PGA and Fe ₃O₄ MNPs, attributed to the larger specific surface area of γ-PGA/Fe₃O₄ MNPs. With the solution pH higher than 6.0, γ-PGA/Fe₃O₄ MNPs demonstrate better removal activity. The adsorption isotherm of γ-PGA/Fe₃O ₄ MNPs for Cr³⁺ fits the Freundlich model well, with the adsorption capacity of 24.60 mg·g^-1. γ-PGA/Fe ₃O₄ 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, γ-PGA/Fe₃O ₄ MNPs have great potential applications in water treatment.