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Eco-Friendly Gels for Adsorption
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Eco-Friendly Gels for Adsorption

A special issue of Gels (ISSN 2310-2861). This special issue belongs to the section "Gel Processing and Engineering".

Deadline for manuscript submissions: 25 September 2025 | Viewed by 7762

Special Issue Editors

Dr. Elena Ungureanu

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Guest Editor
Faculty of Horticulture, “Ion Ionescu de la Brad” Iasi University of Life Sciences, 700490 Iasi, Romania
Interests: natural compounds; biomaterials; hydrogels; biodegradable polymers; biocide systems; agrogels; hybrid materials; heavy metals; biosorption; biomass conversion; metallogels; gel filtration chromatography
Prof. Dr. Valentin Popa

E-Mail Website
Guest Editor
Faculty of Industrial Chemistry, “Gheorghe Asachi” Technical University of Iasi, 73 Prof. Dr. Docent Dimitrie Mangeron Blv., 700050 Iasi, Romania
Interests: natural aromatic compounds; lignocellulose; biogels; polyphenols; biofuels; wastewater treatment; biomass; biorefinery; biodegradable composites; phytochemicals; nanomaterials; phytoremediation; fermentation; adsorption; antioxidant activity; heavy metals; natural fibers; hydrogels; biopolymers; medicinal gels

Special Issue Information

Dear Colleagues,

We invite submissions for a Special Issue of Gels focusing on “Eco-Friendly Gels for Adsorption”.

The purpose of this Special Issue is to present the latest developments and innovations in the development and application of environmentally friendly gels with proven adsorption applications. We welcome original research articles, authoritative reviews, and short communications investigating the design, characterization, and environmentally friendly gels for adsorbing pollutants, contaminants, and other target molecules from a variety of sources within aqueous or non-aqueous environments. Topic of interests includes gels derived from natural, renewable, and biodegradable materials; green synthesis methods; methods of characterization; adsorption mechanisms; the removal of heavy metals, organic contaminants, and emerging pollutants; and more. Contributions regarding practical applications in water purification and environmental mitigation and demonstrating the scalability, cost-effectiveness, and feasibility of simple real-world gel adsorbents are particularly encouraged.

This ultimate goal of the current Special Issue aims to provide a shared open-source platform for technicians and researchers to change perspectives and contribute to sustainable adsorption development technology using the most advanced eco-friendly gels.

Dr. Elena Ungureanu
Prof. Dr. Valentin Popa
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Gels is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • gels/biogels/agrogels/hydrogels
  • adsorption
  • adsorbents/bioadsorbents
  • polymers
  • heavy metal ions
  • biocides
  • dye
  • pollutants
  • environmental science
  • wastewater remediation
  • wastewater treatment
  • renewable resources
  • biodegradable materials

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Further information on MDPI's Special Issue policies can be found here.

Published Papers (6 papers)

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Research

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20 pages, 8566 KiB  
Article
Simultaneous Removal of Heavy Metals and Dyes on Sodium Alginate/Polyvinyl Alcohol/κ-Carrageenan Aerogel Beads
by Taesoon Jang, Soyeong Yoon, Jin-Hyuk Choi, Narae Kim and Jeong-Ann Park
Gels 2025, 11(3), 211; https://doi.org/10.3390/gels11030211 - 16 Mar 2025
Viewed by 1391
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Eco-Friendly Gels for Adsorption)
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23 pages, 15720 KiB  
Article
Composite Sorbents Based on Chitosan Polymer Matrix and Derivatives of 4-Amino-N′-hydroxy-1,2,5-oxadiazole-3-carboximidamide for Uranium Removal from Liquid Mineralized Media
by Anna I. Matskevich, Konstantin V. Maslov, Veronika A. Prokudina, Daria D. Churakova, Oleg Yu. Slabko, Dmitry K. Patrushev, Nikita S. Markin and Eduard A. Tokar’
Gels 2025, 11(1), 24; https://doi.org/10.3390/gels11010024 - 1 Jan 2025
Viewed by 837
Abstract
Composite adsorbents based on a natural biopolymer matrix of chitosan, to which 4-amino-N′-hydroxy-1,2,5-oxadiazole-3-carboximidamide and its Se derivative were attached, were synthesized. A complex of physicochemical analysis methods indicates that the direct introduction of a matrix with high ionic permeability into the reaction mixture [...] Read more.
Composite adsorbents based on a natural biopolymer matrix of chitosan, to which 4-amino-N′-hydroxy-1,2,5-oxadiazole-3-carboximidamide and its Se derivative were attached, were synthesized. A complex of physicochemical analysis methods indicates that the direct introduction of a matrix with high ionic permeability into the reaction mixture contributes to the formation of homogeneous particles of composite with developed surface morphology, which enhances the kinetic and capacitive parameters of uranium sorption in liquid media. It has been established that the direct introduction of a matrix with high ionic permeability into the reaction mixture contributes to the formation of homogeneous particles with a developed surface morphology, which enhances the kinetic and capacitive parameters of uranium sorption in liquid media. The synthesized materials had increased sorption-selective properties towards uranium in the pH range from 4 to 9 under static sorption conditions. The formation of the Se derivative of amidoxime during its attachment to the polymer matrix (Se-chit) contributes to the creation of a more chemically stable and highly effective adsorbent, compared to the direct binding of 4-amino-N′-hydroxy-1,2,5-oxadiazole-3-carboximidamide with chitosan (43AF-chit). The optimal parameters for the synthesis of materials were established. It was demonstrated that the ratio of amidoxime to chitosan should be within the range of 2:1 to 1:2. As the mass content of chitosan increases, the material gradually dissolves and transforms into a gel, resulting in the formation of liquid radioactive waste with a complex chemical composition. It was found that the kinetic sorption parameters of composite materials increase 2–10 times compared to those of non-composite materials. The sorption capacity of uranium in solutions with pH 6 and pH 8 can reach approximately 400–450 mg g−1. Under dynamic sorption conditions, the effective filtration cycle values (before uranium slips into the filtrate ≥ 50%) improve significantly when transitioning from a non-composite adsorbent to a composite one: increasing from 50 to 800 b.v. for pH 6 and from 2700 to 4000 b.v. for pH 8. These results indicate that the synthesized sorbents are promising materials for uranium removal from liquid media, suitable for both purification and the recovery of radionuclides as valuable raw materials. Full article
(This article belongs to the Special Issue Eco-Friendly Gels for Adsorption)
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20 pages, 6946 KiB  
Article
Composite Sorbents Based on Polymeric Se-Derivative of Amidoximes and SiO2 for the Uranium Removal from Liquid Mineralized Media
by Anna I. Matskevich, Konstantin V. Maslov, Veronika A. Prokudina, Daria D. Churakova, Vladimir V. Korochencev, Oleg Yu. Slabko, Evgenij A. Eliseenko and Eduard A. Tokar’
Gels 2025, 11(1), 14; https://doi.org/10.3390/gels11010014 - 27 Dec 2024
Viewed by 589
Abstract
A new composite material with enhanced sorption-selective properties for uranium recovery from liquid media has been obtained. Sorbents were synthesized through a polycondensation reaction of a mixture of 4-amino-N’-hydroxy-1,2,5-oxadiazole-3-carboximidamide (hereinafter referred to as amidoxime) and SiO2 in an environment of organic solvents [...] Read more.
A new composite material with enhanced sorption-selective properties for uranium recovery from liquid media has been obtained. Sorbents were synthesized through a polycondensation reaction of a mixture of 4-amino-N’-hydroxy-1,2,5-oxadiazole-3-carboximidamide (hereinafter referred to as amidoxime) and SiO2 in an environment of organic solvents (acetic acid, dioxane) and highly porous SiO2. To establish optimal conditions for forming the polymer sorption-active part and the synthesis as a whole, a series of composite adsorbents were synthesized with varying amidoxime/matrix ratios (35/65, 50/50, 65/35). The samples were characterized with FT-IR, XRD, SEM, EDX, XRFES spectroscopy and TGA. Under static conditions of uranium sorption, the dependence of the efficiency of radionuclide recovery from mineralized solutions of various acidities on the ratio of the initial components was established. In the pH range from 4 to 8 (inclusive), the uranium removal efficiency exceeds 95%, while the values of the distribution coefficients (Kd) exceed 104 cm3g−1. It was demonstrated that an increase in the surface development of the sorbents enhances such kinetic parameters of uranium sorption as diffusion rate by 10–20 times compared to non-porous materials. The values of the maximum static capacity exceed 700 mg g−1. The enhanced availability of adsorption centers, achieved through the use of a porous SiO2 matrix, significantly improves the kinetic parameters of the adsorbents. A composite with optimal physicochemical and sorption properties (amidoxime/matrix ratio of 50/50) was examined under dynamic conditions of uranium sorption. It was found that the maximum dynamic sorption capacity of porous materials is four times greater compared to that of a non-porous adsorbent Se-init. The effective filter cycle exceeds 3200 column volumes—twice that of an adsorbent with a monolithic surface. These results indicate the promising potential of the developed materials for uranium sorption from liquid mineralized media under dynamic conditions across a wide pH range. Full article
(This article belongs to the Special Issue Eco-Friendly Gels for Adsorption)
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24 pages, 5225 KiB  
Article
A Natural Carbon Encapsulated in Gellan-Based Hydrogel Particles Designed for Environmental Challenges
by Camelia-Elena Tincu (Iurciuc), Mihaela Hamcerencu, Marius Sebastian Secula, Corneliu Sergiu Stan, Cristina Albu, Marcel Popa and Irina Volf
Gels 2024, 10(11), 713; https://doi.org/10.3390/gels10110713 - 5 Nov 2024
Viewed by 1012
Abstract
This article reports the obtention of a new gellan-based hydrogel linked with Fe3+ and loaded with a natural micro/nanostructured carbon designed as a contaminant’s removal from wastewater. Hydrogels are known for their water-retaining properties, high binding capacity, and eco-friendly features. The new [...] Read more.
This article reports the obtention of a new gellan-based hydrogel linked with Fe3+ and loaded with a natural micro/nanostructured carbon designed as a contaminant’s removal from wastewater. Hydrogels are known for their water-retaining properties, high binding capacity, and eco-friendly features. The new material is expected to behave as one cost-effective and efficient sorbent, including natural carbon structures with various functional groups. The encapsulation efficiency ranges between 89% and 95%. The obtained hydrogel particles were characterized using FT-IR spectroscopy and scanning electron microscopy techniques. The hydrogel particles’ water stability was evaluated by measuring the transmittance for 10 days, and the capacity to retain water was assessed by determining the swelling degree (Q%). The results showed that hydrogel particles are stable (the transmittance value is higher than 97.8% after 10 days), and their properties are influenced by the cross-linking degree, the amount of the carbon particles encapsulated, and the concentration of gellan. For example, the Q% values and encapsulation efficiency increased when the cross-linking degree, the carbon microstructure quantity, and the gellan concentration decreased. The new hybrid material can retain Pb(II) ions and diclofenac molecules, and could be used in different adsorption–desorption cycles. Full article
(This article belongs to the Special Issue Eco-Friendly Gels for Adsorption)
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20 pages, 5258 KiB  
Article
Tuning Antioxidant Function through Dynamic Design of Chitosan-Based Hydrogels
by Manuela Maria Iftime, Gabriela Liliana Ailiesei and Daniela Ailincai
Gels 2024, 10(10), 655; https://doi.org/10.3390/gels10100655 - 13 Oct 2024
Cited by 1 | Viewed by 979
Abstract
Dynamic chitosan-based hydrogels with enhanced antioxidant activity were synthesized through the formation of reversible imine linkages with 5-methoxy-salicylaldehyde. These hydrogels exhibited a porous structure and swelling capacity, influenced by the crosslinking degree, as confirmed by SEM and POM analysis. The dynamic nature of [...] Read more.
Dynamic chitosan-based hydrogels with enhanced antioxidant activity were synthesized through the formation of reversible imine linkages with 5-methoxy-salicylaldehyde. These hydrogels exhibited a porous structure and swelling capacity, influenced by the crosslinking degree, as confirmed by SEM and POM analysis. The dynamic nature of the imine bonds was characterized through NMR, swelling studies in various media, and aldehyde release measurements. The hydrogels demonstrated significantly improved antioxidant activity compared to unmodified chitosan, as evaluated by the DPPH method. This research highlights the potential of developing pH–responsive chitosan-based hydrogels for a wide range of biomedical applications. Full article
(This article belongs to the Special Issue Eco-Friendly Gels for Adsorption)
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Review

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26 pages, 6273 KiB  
Review
Adsorption of Bisphenol A from Water Using Chitosan-Based Gels
by Ludmila Aricov and Anca Ruxandra Leontieș
Gels 2025, 11(3), 180; https://doi.org/10.3390/gels11030180 - 5 Mar 2025
Viewed by 1057
Abstract
The comonomer bisphenol A (BPA) finds applications in the plastics industry, where it is used in the production of polycarbonates, plastics, PVC, thermal paper, epoxy and vinyl ester resins, and polyurethane. The water, with which many of these materials come into contact, is [...] Read more.
The comonomer bisphenol A (BPA) finds applications in the plastics industry, where it is used in the production of polycarbonates, plastics, PVC, thermal paper, epoxy and vinyl ester resins, and polyurethane. The water, with which many of these materials come into contact, is one of the main sources of human exposure to BPA. When ingested or touched, BPA can damage organs, disrupt the endocrine and immune systems, generate inflammatory responses, and be involved in genotoxic processes. Therefore, the need to develop effective techniques for removing BPA from aqueous environments is imperative. This paper provides a comprehensive review regarding the effective removal of BPA from water, focusing on the performance and adsorption mechanisms of various adsorbents based on chitosan and chitosan composites. The chemical and physical factors, adsorption kinetics and models governing the adsorption process of BPA in chitosan materials are also examined. This review outlines that, despite considerable progress in the absorption of bisphenol using chitosan gels, further research is necessary to assess the efficacy of these adsorbents in treating real wastewater and in large-scale manufacture. Full article
(This article belongs to the Special Issue Eco-Friendly Gels for Adsorption)
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