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. 2025 Mar 16;11(3):211.
doi: 10.3390/gels11030211.

Simultaneous Removal of Heavy Metals and Dyes on Sodium Alginate/Polyvinyl Alcohol/κ-Carrageenan Aerogel Beads

Affiliations

Simultaneous Removal of Heavy Metals and Dyes on Sodium Alginate/Polyvinyl Alcohol/κ-Carrageenan Aerogel Beads

Taesoon Jang et al. Gels. .

Abstract

Industrial textile wastewater containing both heavy metals and dyes has been massively produced. In this study, semi-interpenetrating polymer network structures of sodium alginate (SA)/polyvinyl alcohol (PVA)/κ-carrageenan (CG) aerogel beads were synthesized for their simultaneous reduction. The SA/PVA/CG aerogel beads were synthesized through a cost-effective and environmentally friendly method using naturally abundant biopolymers without toxic cross-linkers. The SA/PVA/CG aerogel beads were spheres with a size of 3.8 ± 0.1 mm, exhibiting total pore areas of 15.2 m2/g and porous structures (pore size distribution: 0.04-242.7 μm; porosity: 93.97%) with abundant hydrogen bonding, high water absorption capacity, and chemical resistance. The adsorption capacity and mechanisms of the SA/PVA/CG aerogel beads were investigated through kinetic and isotherm experiments for heavy metals (Cu(II), Pb(II)), cationic dye (methylene blue, MB), and anionic dye (acid blue 25, AB)) in both single and binary systems. The maximum adsorption capacities of the SA/PVA/CG aerogel beads based on the Langmuir model of Cu(II), Pb(II), and MB were 85.17, 265.98, and 1324.30 mg/g, respectively. Pb(II) showed higher adsorption affinity than Cu(II) based on ionic properties, such as electronegativity and hydration radius. The adsorption of Cu(II), Pb(II), and MB on the SA/PVA/CG aerogel beads was spontaneous, with heavy metals and MB exhibiting endothermic and exothermic natures, respectively.

Keywords: aerogel bead; dye; heavy metal; polyvinyl alcohol; semi-interpenetrating polymer network; sodium alginate; κ-carrageenan.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
FE-SEM images of surface (a,b) SA, (c,d) SA/PVA, (e,f) SA/CG, and (g,h) SA/PVA/CG beads and cross-section images of (i,j) SA, (k,l) SA/PVA, (m,n) SA/CG, and (o,p) SA/PVA/CG beads.
Figure 2
Figure 2
Characteristics of the SA/PVA, SA/CG, and SA/PVA/CG aerogel beads: (a) FT-IR spectra, (b) water absorption efficiency, (c) and adsorption capacity for Cu(II), Pb(II), and MB.
Figure 3
Figure 3
Adsorption of single pollutants (Cu(II), Pb(II), MB, or AB) onto the SA/PVA/CG aerogel beads: (a) kinetic and isotherm data for (b) Cu(II) (C0 = 10–125 mg/L), (c) Pb(II) (C0 = 10–125 mg/L), and (d) MB (C0 = 10–500 mg/L).
Figure 4
Figure 4
Effect of pH on (a) Cu(II), Pb(II), and MB adsorption using the SA/PVA/CG aerogel beads and distribution of (b) Cu(II), (c) Pb(II), and (d) MB.
Figure 5
Figure 5
Effect of temperature on (a) Cu(II), (b) Pb(II), and (c) MB adsorption using the SA/PVA/CG aerogel beads.
Figure 6
Figure 6
Adsorption kinetic data for single and binary systems using the SA/PVA/CG beads: (a) Cu(Ⅱ), (b) Pb(Ⅱ), (c) MB, and (d) AB.
Figure 7
Figure 7
XPS spectra for the SA/PVA/CG aerogel beads (a) before and after the adsorption of single pollutants (Cu(II), Pb(II), MB, or AB), (b) after the adsorption of two pollutants, (c) the Cu 2p region after Cu(II) adsorption, (d) the Pb 4f region after Pb(II) adsorption, (e) high-resolution version of the Cu 2p region, and (f) high-resolution version of the Pb 4f region in the Cu–Pb system.
Figure 8
Figure 8
Predicted adsorption mechanism of single and binary system using the SA/PVA/CG aerogel beads.
Figure 9
Figure 9
Synthesis procedure of the SA-based aerogel beads.

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