Preparation of Novel Magnetic Sodium Alginate-Ferric(III) Gel Beads and Their Super-Efficient Removal of Direct Dyes fro

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ORIGINAL PAPER

Preparation of Novel Magnetic Sodium Alginate-Ferric(III) Gel Beads and Their Super-Efficient Removal of Direct Dyes from Water Ting Lv1,2 · Beigang Li1,2  Accepted: 16 November 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract Novel magnetic sodium alginate-based biopolymer F ­ e3O4@SA-Fe was successfully prepared by the cross-linking reaction of sodium alginate (SA) and Fe(III) ions and adding magnetic ferric oxide (­ Fe3O4), and characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), Fourier Transform-Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Vibrating Sample Magnetometer (VSM), respectively. The effects of preparation and adsorption conditions on the adsorbent were investigated by adsorbing Congo red (CR) and Direct red 23 (DR 23) dyes. The results showed that the synthesized ­Fe3O4@SA-Fe polymer gel beads exhibited super-high adsorption property and good stability when the mass concentrations of SA, Fe(III) ions and ­Fe3O4 are 16, 12.5 and 7 g/L at room temperature respectively. The adsorption rates of two dyes by ­Fe3O4@SA-Fe were very fast at 298 K, and the time required to reach the equilibrium was very short, which was 30 min for CR and 60 min for DR 23. Moreover, the dye removal efficiencies were over 99.4% and 95.2% in a wide pH range of 2.0 ~ 9.0 for CR and 2.0 ~ 10.0 for DR 23, respectively. The adsorption process could be accurately described by the pseudo-second-order rate model, which were mostly controlled by intra-particle diffusion. The fitting results of isothermic data by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models revealed that the equilibrium data completely obeyed the Langmuir model and the obtained maximum adsorption capacities of CR and DR 23 were 3333 and 1429 mg/g at 298 K, respectively. FTIR, UV-Vis and XPS analysis indicated that the electrostatic adsorption, hydrogen bonding and ligand exchange promoted the interaction between dye molecules and ­Fe3O4@SA-Fe. A green magnetic biosorbent ­Fe3O4@SA-Fe gel beads with simple preparation method and high-cost performance can be used for super-efficient purification of high-concentration dye effluent and quickly separated from the aqueous phase and recovered, which would have a good application prospect. Keywords  Sodium alginate · Magnetism · Ferric iron · Biopolymer · Dye adsorption

Introduction Over the years, a large amount of dye wastewater has been produced due to the wide application of various dyes in food, textile printing and dyeing, leather, paper, plastic and other fields [1]. Without treatment or incomplete treatment, the colored dye wastewater discharged into the environmental water body can bring serious water environmental pollution * Beigang Li [email protected] 1



Chemistry & Environment Science College, Inner Mongolia Normal University, Hohhot 010022, People’s Republic of China



Inner Mongolia Key Laboratory of Environmental Chemistry, Hoh