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

Abstract

Novel magnetic sodium alginate-based biopolymer Fe 3 O 4 @SA-Fe was successfully prepared by the cross-linking reaction of sodium alginate (SA) and Fe(III) ions and adding magnetic ferric oxide (Fe 3 O 4 ), 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 Fe 3 O 4 @SA-Fe polymer gel beads exhibited super-high adsorption property and good stability when the mass concentrations of SA, Fe(III) ions and Fe 3 O 4 are 16, 12.5 and 7 g/L at room temperature respectively. The adsorption rates of two dyes by Fe 3 O 4 @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 Fe 3 O 4 @SA-Fe. A green magnetic biosorbent Fe 3 O 4 @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.

Synthesis and Characterization of Dual-ion-Crosslinked Magnetic Sodium Alginate-Based Fe-SA-Y@Fe3O4 Biogel Composite with Ultrastrong Performance for Azo Dye Removal

“…Concurrently, some white particles were found to be dispersed on the surface of gel beads, which should be the solid Fe3O4. The same phenomena were also observed in the previous reports [27,28]. Furthermore, according to the EDS results of element distribution presented in Fig.…”

“…Moreover, a reduction in pseudo-second-order rate constant (k2) with temperature increase indicated the exothermic adsorption. Similar phenomenon has also been reported [28].…”

Innovative environment-friendly liquid fertilizer bead from sodium alginate coating with IPN membrane derived from natural rubber and cassava starch

“…[31] Besides, it was found that the new signal peak of SAB and CSAB appeared at 582 cm − 1 , which should be assigned to the Ca-O bond. A similar behavior of the formation of SA bead with Fe 3 O 4 was also revealed by Lv and Li [32], reporting that the new peak appeared at around 586 cm − 1 (Fe-O bond), and suggested that Fe 3 O 4 was also involved in the polymerization. The wide band of the -OH group in St is seen at 3313 cm − 1 for the IPN NR/St, while the bands at 1660, 1539, and 1452 cm − 1 are ascribed to C = C and C-O stretching and -CH 3 deformation, respectively.…”

A Dual Physical Cross‐Linking Strategy to Construct Tough Hydrogels with High Strength, Excellent Fatigue Resistance, and Stretching‐Induced Strengthening Effect

“…There are no peaks could be observed in Fe2p spectra of SA 0 HA and SA 1.2 HA gels, as shown in Figure S2b,c S2d, Supporting Information), which correspond to Fe 2+ and Fe 3+ , respectively, indicating the presence of both bidentate coordinates and tridentate coordinates between Fe 2+ /Fe 3+ and -COO − . [66] These results confirmed the successful introduction of Fe in SA 1.2 HA-Fe 0.2 DPC hydrogel, indicating an effective penetration of Fe 3+ into the hydrogel during immersion and the formation of IC between Fe 3+ and -COO − , which gave rise to the construction of HA/IC DPC network. This result was further confirmed by energy dispersive spectrometer (EDS) [67,68] (Figure 9c,d; Figure S3, Supporting Information).…”