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

Abstract

Magnetic sodium alginate(SA)-based biogel composite Fe-SA-Y@Fe3O4 macroparticles were polymerized by co-crosslinking of yttrium(III) and iron(III) ions according to the optimized preparation conditions and characterized by various modern analytical techniques. The results show that the biogel beads have unique cauliflower-shaped surface and sensitive magnetic response. Fe-SA-Y@Fe3O4 composite was used for the removal of Direct Red 13 (DR 13) and Direct Black 19 (DB 19) dyes from water. The adsorption capacities and removal efficiency can reach 2487 mg/g and 99.5% for DR-13 and 2992 mg/g and 99.7% for DB-19 respectively within the equilibrium time of 60 min at 298K and pH 2.0, and decrease slightly with pH up to 10.0. The kinetic and equilibrium adsorption data followed the Pseudo-second-order rate model and Langmuir isothermal model well, respectively. Electrostatic adsorption, various H-bonding and complexation were largely involved in dye adsorption processes with spontaneous and exothermic character by the biogel beads, which were explained by thermodynamic studies, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), respectively. Fe-SA-Y@Fe3O4 gel composite with ultrahigh adsorption capacity and fast magnetic separation will be a promising eco-friendly biobased adsorbent for the superefficient purification of practical azo-dye effluents.Keywords: Sodium alginate  Yttrium(III)-Iron(III) ions  Azo dyes adsorption  Magnetism  Biogel composite

Preparation and Superstrong Adsorption of a Novel La(Ⅲ)-Crosslinked Alginate/Modified Diatomite Macroparticle Composite for Anionic Dyes Removal from Aqueous Solutions

“…The four peaks belonging to La 3d 5/2 and La 3d 3/2 at 834.9 and 837.7 eV, 851.6 and 854.7 eV in the high-resolution XPS spectra of La 3d ( Figure 6 d) shifted slightly toward the low-field and the peak area ratios reduced to 0.9:1 and 0.6:1 after dye adsorption, respectively. The above changes in binding energy and peak area further suggest that the various O−containing active groups and La(III) ions in the CPAM-Dia/SA-La gel spheres have chemical and hydrogen bond interactions with −N=N−, −NH 2 , −OH and aromatic rings in dye molecules [ 35 ], which is also consistent with the FT−IR and UV−vis analytical results.…”

“…In the CPAM-Dia/SA-La spectrum, the stretching vibration peaks of −OH and C=O and the asymmetric stretching vibration peak of −COO − were shifted to 3440, 1692 and 1611 cm −1 , respectively, while the symmetric stretching vibration peak of −COO − became larger in the peak area. This is because the O−containing active groups on the composite participated in the interaction with dye anions [ 35 ], showing the successful synthesis of the CPAM-Dia/SA-La composite.…”

“…After further EDS analysis of the samples (see Figure 2 h), compared with the element distribution of CPAM-Dia, a La element with a content of 4.27% appeared in the CPAM-Dia/SA-La gel spheres, while the content of the Si element decreased from 35.67 to 4.19%, further showing that the La(III) ions in solution underwent a cross-linking polymerization reaction with SA to form a CPAM-Dia/SA-La gel composite with a three-dimensional network structure [ 35 ]. The surface scan analysis of CPAM-Dia/SA-La ( Figure 2 i–m) reveals that the O, La, Si, and N elements are evenly distributed in the composite, indicating the successful preparation of the target composite.…”

“…However, the experimental results were not the case when the solution pH is equal to or less than 10 ( Figure 3 b). This should be due to various hydrogen bonding between gel spheres with abundant −COOH and −OH groups and dye anions with −N=N−, −NH, −OH and aromatic rings and possible complexation between unsaturated La(III) on the surface of gel spheres and reactive functional groups in dye anions [ 25 , 35 , 36 , 37 ]. The q e (mg/g) and R (%) values of CPAM-Dia/SA-La gel spheres for AB 113 and CR were, respectively 2696 and 1477 mg/g, 92.4 and 93.3% under natural pH (7.08 and 9.94, respectively) of dye solutions.…”

“…The asymmetric stretching vibration absorption peaks of −COO − in the CPAM-Dia/SA-La FT−IR spectrum were displaced from 1610 to 1618 cm −1 and 1629 cm −1 after AB 113 and CR adsorption in the CPAM-Dia/SA-La-AB 113 and CPAM-Dia/SA-La-CR FT−IR spectra, respectively, while the stretching vibration absorption peaks of C=O shifted from 1692 cm −1 to 1701 and 1701 cm −1 , respectively. The intensity of the −COO − symmetric vibration peak at 1384 cm −1 also changed [ 35 ], this may be caused by H−bonding between the adsorbent and the dye molecules. This indicates that the chemical reaction occurred in the adsorption process of each dye.…”