title: Dye adsorption characteristics of magnetite nanoparticles coated with a biopolymer poly(γ-glutamic acid).
abstract: Magnetite nanoparticles coated with an anionic biopolymer poly(γ-glutamic acid) (PGA-MNPs) were synthesized and characterized for their methylene blue dye adsorption capability. Both bare- and dye-loaded PGA-MNPs were characterized by FTIR, TEM and VSM measurements, revealing the PGA-MNPs to be superparamagnetic with average particle diameter being 12.4 nm and magnetization value 59.2 emu/g. The synthesized PGA-MNPs were stable in deionized, tap and river waters as well as in acidic and basic media. Redlich-Peterson and Langmuir models precisely described the isotherm and the maximum adsorption capacity was 78.67 mg/g. A pseudo-second-order equation best predicted the kinetics with a maximum adsorption attained within 5 min. Incorporation of sodium or calcium ions reduced the dye adsorption, while a raise in pH enhanced adsorption and a complete desorption occurred at pH 1.0. Dye removal mechanism by PGA-MNPs was probably due to electrostatic interaction through exchange of protons from side-chain α-carboxyl groups on PGA-MNPs surface.
authors.affiliation: Department of Food Science, Fu Jen University, Taipei 242, Taiwan.
authors.forename: B Stephen
authors.initials: BS
authors.lastname: Inbaraj
authors.forename: B H
authors.initials: BH
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D004396:Coloring Agents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D060306:Magnetometry; D046529:Microscopy, Electron, Transmission; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D013054:Spectrophotometry, Atomic; D017550:Spectroscopy, Fourier Transform Infrared; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D004396:Coloring Agents; D058185:Magnetite Nanoparticles; D014874:Water Pollutants, Chemical; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid