Gels for Removal and Adsorption

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

Deadline for manuscript submissions: closed (15 July 2023) | Viewed by 29229

Special Issue Editors


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Guest Editor
Key Laboratory of Bio-Based Material Science and Technology, Ministry of Education, Northeast Forestry University, Harbin 150040, China
Interests: wood bionics; cellulose-based functional material; selective adsorption; supramolecular material
Advanced Medical Care and Protection Technology Research Center, Key Laboratory of Bio-Fibers and Eco-Textiles, Qingdao University, Qingdao 266071, China
Interests: organic polymer materials for environmental pollution control; wetting/capillary; oil/water separation; microplastics absorption; drugs absorption/release
Key Laboratory of Bio-Based Material Science and Technology, Ministry of Education, Northeast Forestry University, Harbin 150040, China
Interests: wood functionalization; bionic; nano materials design
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, China
Interests: aerogels; cellulose; adsorbents; biomacromolecule; functional nanomaterials

Special Issue Information

Dear Colleagues,

Gels (aerogels, hydrogels, etc.), which are typically constructed in the forms of sponges, membranes, films, rods, fibers, etc., hold huge potential in the adsorption and removal of substances because of their abundant and tunable porous structure, lightweight properties, and programmable surface groups, which are beneficial to specifically and efficiently capture targeted substances.

This Special Issue is focused on the application of gels for adsorption and removal. The targeted substances include but are not limited to gaseous, liquid, and solid states. The gaseous matters can be poisonous gases (e.g., SOx, NOx, and CO), greenhouse gases (e.g., CO2, freon, and CH4), etc. The liquid matters include wastewaters containing oils, heavy metal ions, radioactive materials, dyes, and antibiotics. The targeted solids are represented by a variety of particulates (e.g., haze, dust, microorganisms). This Special Issue also welcomes research on the adsorption and removal of other special states of matter, such as plasmas, supercritical materials, liquid crystals, and superconductive materials. Therefore, the collected articles should not only focus on the preparation and characterizations of gels, but also their adsorption and removal properties. More importantly, the adsorption and removal mechanisms of gels, especially structure-activity relationships, should also be highlighted. This Special Issue also covers gels for the absorption and controlled release of drugs in postoperative repair dressing and wound healing. For these applications, the gels have to be constructed responsively or intelligently geared towards certain environmental stimulation, such as pH, light, magnetic field, electric field, and temperature for controlled drug release. The publication of original research articles, rapid communications and reviews in this Special Issue will make an important contribution to developing gels for removal and adsorption.

We look forward to the submission of new studies on gel development and application for adsorption and removal. Submissions of experimental and field studies are both welcomed.

Note: If you would like to contribute a related paper, please consider our 2nd Edition: Gels for Removal and Adsorption (2nd Edition)

Dr. Daxin Liang
Dr. Ting Dong
Dr. Yudong Li
Prof. Dr. Caichao Wan
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 2600 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

  • aerogels
  • hydrogels
  • membranes
  • films
  • adsorbents
  • removal
  • environmental science
  • novel gels
  • wastewater treatment
  • microplastic adsorption
  • drug adsorption/release

Published Papers (16 papers)

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13 pages, 3872 KiB  
Article
Effective Removal of Cu2+ Ions from Aqueous Media Using Poly(acrylamide-co-itaconic acid) Hydrogels in a Semi-Continuous Process
by Jorge Alberto Cortes Ortega, Jacobo Hernández-Montelongo, Rosaura Hernández-Montelongo and Abraham Gabriel Alvarado Mendoza
Gels 2023, 9(9), 702; https://doi.org/10.3390/gels9090702 - 30 Aug 2023
Cited by 1 | Viewed by 1105
Abstract
Adsorption is one of the most crucial processes in water treatment today. It offers a low-cost solution that does not require specialized equipment or state-of-the-art technology while efficiently removing dissolved contaminants, including heavy metals. This process allows for the utilization of natural or [...] Read more.
Adsorption is one of the most crucial processes in water treatment today. It offers a low-cost solution that does not require specialized equipment or state-of-the-art technology while efficiently removing dissolved contaminants, including heavy metals. This process allows for the utilization of natural or artificial adsorbents or a combination of both. In this context, polymeric materials play a fundamental role, as they enable the development of adsorbent materials using biopolymers and synthetic polymers. The latter can be used multiple times and can absorb large amounts of water per gram of polymer. This paper focuses on utilizing adsorption through hydrogels composed of poly(acrylamide-co-itaconic acid) for removing Cu2+ ions dissolved in aqueous media in a semi-continuous process. The synthesized hydrogels were first immersed in 0.1 M NaOH aqueous solutions, enabling OH ions to enter the gel matrix and incorporate into the polymer surface. Consequently, the copper ions were recovered as Cu(OH)2 on the surface of the hydrogel rather than within it, allowing the solid precipitates to be easily separated by decantation. Remarkably, the hydrogels demonstrated an impressive 98% removal efficiency of the ions from the solution in unstirred conditions at 30 °C within 48 h. A subsequent study involved a serial process, demonstrating the hydrogels’ reusability for up to eight cycles while maintaining their Cu2+ ion recovery capacity above 80%. Additionally, these hydrogels showcased their capability to remove Cu2+ ions even from media with ion concentrations below 100 ppm. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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17 pages, 16329 KiB  
Article
Alleviating Effect of a Magnetite (Fe3O4) Nanogel against Waterborne-Lead-Induced Physiological Disturbances, Histopathological Changes, and Lead Bioaccumulation in African Catfish
by Afaf N. Abdel Rahman, Basma Ahmed Elkhadrawy, Abdallah Tageldein Mansour, Heba M. Abdel-Ghany, Engy Mohamed Mohamed Yassin, Asmaa Elsayyad, Khairiah Mubarak Alwutayd, Sameh H. Ismail and Heba H. Mahboub
Gels 2023, 9(8), 641; https://doi.org/10.3390/gels9080641 - 8 Aug 2023
Cited by 8 | Viewed by 1226
Abstract
Heavy metal toxicity is an important issue owing to its harmful influence on fish. Hence, this study is a pioneer attempt to verify the in vitro and in vivo efficacy of a magnetite (Fe3O4) nanogel (MNG) in mitigating waterborne [...] Read more.
Heavy metal toxicity is an important issue owing to its harmful influence on fish. Hence, this study is a pioneer attempt to verify the in vitro and in vivo efficacy of a magnetite (Fe3O4) nanogel (MNG) in mitigating waterborne lead (Pb) toxicity in African catfish. Fish (n = 160) were assigned into four groups for 45 days. The first (control) and second (MNG) groups were exposed to 0 and 1.2 mg L−1 of MNG in water. The third (Pb) and fourth (MNG + Pb) groups were exposed to 0 and 1.2 mg L−1 of MNG in water and 69.30 mg L−1 of Pb. In vitro, the MNG caused a dramatic drop in the Pb level within 120 h. The Pb-exposed group showed the lowest survival (57.5%) among the groups, with substantial elevations in hepato-renal function and lipid peroxide (MDA). Moreover, Pb exposure caused a remarkable decline in the protein-immune parameters and hepatic antioxidants, along with higher Pb residual deposition in muscles and obvious histopathological changes in the liver and kidney. Interestingly, adding aqueous MNG to Pb-exposed fish relieved these alterations and increased survivability. Thus, MNG is a novel antitoxic agent against Pb toxicity to maintain the health of C. gariepinus. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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24 pages, 3673 KiB  
Article
Self-Assembling Peptide-Based Magnetogels for the Removal of Heavy Metals from Water
by Farid Hajareh Haghighi, Roya Binaymotlagh, Laura Chronopoulou, Sara Cerra, Andrea Giacomo Marrani, Francesco Amato, Cleofe Palocci and Ilaria Fratoddi
Gels 2023, 9(8), 621; https://doi.org/10.3390/gels9080621 - 1 Aug 2023
Cited by 6 | Viewed by 1407
Abstract
In this study, we present the synthesis of a novel peptide-based magnetogel obtained through the encapsulation of γ-Fe2O3-polyacrylic acid (PAA) nanoparticles (γ-Fe2O3NPs) into a hydrogel matrix, used for enhancing the ability of the hydrogel to [...] Read more.
In this study, we present the synthesis of a novel peptide-based magnetogel obtained through the encapsulation of γ-Fe2O3-polyacrylic acid (PAA) nanoparticles (γ-Fe2O3NPs) into a hydrogel matrix, used for enhancing the ability of the hydrogel to remove Cr(III), Co(II), and Ni(II) pollutants from water. Fmoc-Phe (Fluorenylmethoxycarbonyl-Phenylalanine) and diphenylalanine (Phe2) were used as starting reagents for the hydrogelator (Fmoc-Phe3) synthesis via an enzymatic method. The PAA-coated magnetic nanoparticles were synthesized in a separate step, using the co-precipitation method, and encapsulated into the peptide-based hydrogel. The resulting organic/inorganic hybrid system (γ-Fe2O3NPs-peptide) was characterized with different techniques, including FT-IR, Raman, UV-Vis, DLS, ζ-potential, XPS, FESEM-EDS, swelling ability tests, and rheology. Regarding the application in heavy metals removal from aqueous solutions, the behavior of the obtained magnetogel was compared to its precursors and the effect of the magnetic field was assessed. Four different systems were studied for the separation of heavy metal ions from aqueous solutions, including (1) γ-Fe2O3NPs stabilized with PAA, (γ-Fe2O3NPs); (2) Fmoc-Phe3 hydrogel (HG); (3) γ-Fe2O3NPs embedded in peptide magnetogel (γ-Fe2O3NPs@HG); and (4) γ-Fe2O3NPs@HG in the presence of an external magnetic field. To quantify the removal efficiency of these four model systems, the UV-Vis technique was employed as a fast, cheap, and versatile method. The results demonstrate that both Fmoc-Phe3 hydrogel and γ-Fe2O3NPs peptide magnetogel can efficiently remove all the tested pollutants from water. Interestingly, due to the presence of magnetic γ-Fe2O3NPs inside the hydrogel, the removal efficiency can be enhanced by applying an external magnetic field. The proposed magnetogel represents a smart multifunctional nanosystem with improved absorption efficiency and synergic effect upon applying an external magnetic field. These results are promising for potential environmental applications of γ-Fe2O3NPs-peptide magnetogels to the removal of pollutants from aqueous media. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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29 pages, 23004 KiB  
Article
The Development of Fe3O4-Monolithic Resorcinol-Formaldehyde Carbon Xerogels Using Ultrasonic-Assisted Synthesis for Arsenic Removal of Drinking Water
by Sasirot Khamkure, Prócoro Gamero-Melo, Sofía Esperanza Garrido-Hoyos, Audberto Reyes-Rosas, Daniella-Esperanza Pacheco-Catalán and Arely Monserrat López-Martínez
Gels 2023, 9(8), 618; https://doi.org/10.3390/gels9080618 - 30 Jul 2023
Viewed by 1218
Abstract
Inorganic arsenic in drinking water from groundwater sources is one of the potential causes of arsenic-contaminated environments, and it is highly toxic to human health even at low concentrations. The purpose of this study was to develop a magnetic adsorbent capable of removing [...] Read more.
Inorganic arsenic in drinking water from groundwater sources is one of the potential causes of arsenic-contaminated environments, and it is highly toxic to human health even at low concentrations. The purpose of this study was to develop a magnetic adsorbent capable of removing arsenic from water. Fe3O4-monolithic resorcinol-formaldehyde carbon xerogels are a type of porous material that forms when resorcinol and formaldehyde (RF) react to form a polymer network, which is then cross-linked with magnetite. Sonication-assisted direct and indirect methods were investigated for loading Fe3O4 and achieving optimal mixing and dispersion of Fe3O4 in the RF solution. Variations of the molar ratios of the catalyst (R/C = 50, 100, 150, and 200), water (R/W = 0.04 and 0.05), and Fe3O4 (M/R = 0.01, 0.03, 0.05, 0.1, 0.15, and 0.2), and thermal treatment were applied to evaluate their textural properties and adsorption capacities. Magnetic carbon xerogel monoliths (MXRF600) using indirect sonication were pyrolyzed at 600 °C for 6 h with a nitrogen gas flow in the tube furnace. Nanoporous carbon xerogels with a high surface area (292 m2/g) and magnetic properties were obtained. The maximum monolayer adsorption capacity of As(III) and As(V) was 694.3 µg/g and 1720.3 µg/g, respectively. The incorporation of magnetite in the xerogel structure was physical, without participation in the polycondensation reaction, as confirmed by XRD, FTIR, and SEM analysis. Therefore, Fe3O4-monolithic resorcinol-formaldehyde carbon xerogels were developed as a potential adsorbent for the effective removal of arsenic with low and high ranges of As(III) and As(V) concentrations from groundwater. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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13 pages, 2690 KiB  
Article
Superhydrophobic/Superoleophilic PDMS/SiO2 Aerogel Fabric Gathering Device for Self-Driven Collection of Floating Viscous Oil
by Feng Liu, Xin Di, Xiaohan Sun, Xin Wang, Tinghan Yang, Meng Wang, Jian Li, Chengyu Wang and Yudong Li
Gels 2023, 9(5), 405; https://doi.org/10.3390/gels9050405 - 12 May 2023
Viewed by 1414
Abstract
The persistent challenge of removing viscous oil on water surfaces continues to pose a major concern and requires immediate attention. Here, a novel solution has been introduced in the form of a superhydrophobic/superoleophilic PDMS/SiO2 aerogel fabric gathering device (SFGD). The SFGD is [...] Read more.
The persistent challenge of removing viscous oil on water surfaces continues to pose a major concern and requires immediate attention. Here, a novel solution has been introduced in the form of a superhydrophobic/superoleophilic PDMS/SiO2 aerogel fabric gathering device (SFGD). The SFGD is based on the adhesive and kinematic viscosity properties of oil, enabling self-driven collection of floating oil on the water surface. The SFGD is able to spontaneously capture the floating oil, selectively filter it, and sustainably collect it into its porous fabric interior through the synergistic effects of surface tension, gravity, and liquid pressure. This eliminates the need for auxiliary operations such as pumping, pouring, or squeezing. The SFGD demonstrates exceptional average recovery efficiencies of 94% for oils with viscosities ranging from 10 to 1000 mPa·s at room temperature, including dimethylsilicone oil, soybean oil, and machine oil. With its facile design, ease of fabrication, high recovery efficiency, excellent reclaiming capabilities, and scalability for multiple oil mixtures, the SFGD represents a significant advancement in the separation of immiscible oil/water mixtures of various viscosities and brings the separation process one step closer to practical application. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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12 pages, 3533 KiB  
Article
Biomass Chitosan-Based Tubular/Sheet Superhydrophobic Aerogels Enable Efficient Oil/Water Separation
by Wenhui Wang, Jia-Horng Lin, Jiali Guo, Rui Sun, Guangting Han, Fudi Peng, Shan Chi and Ting Dong
Gels 2023, 9(4), 346; https://doi.org/10.3390/gels9040346 - 18 Apr 2023
Cited by 3 | Viewed by 1321
Abstract
Water pollution, which is caused by leakage of oily substances, has been recognized as one of the most serious global environmental pollutions endangering the ecosystem. High-quality porous materials with superwettability, which are typically constructed in the form of aerogels, hold huge potential in [...] Read more.
Water pollution, which is caused by leakage of oily substances, has been recognized as one of the most serious global environmental pollutions endangering the ecosystem. High-quality porous materials with superwettability, which are typically constructed in the form of aerogels, hold huge potential in the field of adsorption and removal of oily substances form water. Herein, we developed a facile strategy to fabricate a novel biomass absorbent with a layered tubular/sheet structure for efficient oil/water separation. The aerogels were fabricated by assembling hollow poplar catkin fiber into chitosan sheets using a directional freeze-drying method. The obtained aerogels were further wrapped with -CH3-ended siloxane structures using CH3SiCl3. This superhydrophobic aerogel (CA ≈ 154 ± 0.4°) could rapidly trap and remove oils from water with a large sorption range of 33.06–73.22 g/g. The aerogel facilitated stable oil recovery (90.07–92.34%) by squeezing after 10 sorption-desorption cycles because of its mechanical robustness (91.76% strain remaining after 50 compress-release cycles). The novel design, low cost, and sustainability of the aerogel provide an efficient and environmentally friendly solution for handling oil spills. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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16 pages, 7626 KiB  
Article
The Use of Hydrogels in the Treatment of Metal Cultural Heritage Objects
by Elodie Guilminot
Gels 2023, 9(3), 191; https://doi.org/10.3390/gels9030191 - 2 Mar 2023
Cited by 8 | Viewed by 2477
Abstract
Currently gels are widely used in the restoration of paintings, graphic arts, stuccowork and stonework, but their use in metal restoration is less widespread. In this study, several polysaccharide-based hydrogels (agar, gellan and xanthan gum) were selected for use in metal treatments. The [...] Read more.
Currently gels are widely used in the restoration of paintings, graphic arts, stuccowork and stonework, but their use in metal restoration is less widespread. In this study, several polysaccharide-based hydrogels (agar, gellan and xanthan gum) were selected for use in metal treatments. The use of hydrogels allows to localize a chemical or electrochemical treatment. This paper presents several examples of treatment of metal objects of cultural heritage, i.e., historical or archaeological objects. The advantages, disadvantages and limits of hydrogel treatments are discussed. The best results are obtained for the cleaning of copper alloys via associating an agar gel with a chelating agent (EDTA (ethylenediaminetetraacetic acid) or TAC (tri-ammonium citrate)). The hot application allows to obtain a peelable gel, particularly adapted for historical objects. Electrochemical treatments using hydrogels have been successful for the cleaning of silver and for the dechlorination of ferrous or copper alloys. The use of hydrogels for the cleaning of painted aluminum alloys is possible but it has to be coupled with mechanical cleaning. However, for the cleaning of archaeological lead, the cleaning using hydrogels was not very effective. This paper shows the new possibilities of using hydrogels for the treatment of metal cultural heritage objects: agar is the most promising hydrogel. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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18 pages, 4490 KiB  
Article
Bamboo Nanocellulose/Montmorillonite Nanosheets/Polyethyleneimine Gel Adsorbent for Methylene Blue and Cu(II) Removal from Aqueous Solutions
by Xuelun Zhang, Feng Li, Xiyu Zhao, Jiwen Cao, Shuai Liu, You Zhang, Zihui Yuan, Xiaobo Huang, Cornelis F. De Hoop, Xiaopeng Peng and Xingyan Huang
Gels 2023, 9(1), 40; https://doi.org/10.3390/gels9010040 - 4 Jan 2023
Cited by 6 | Viewed by 2277
Abstract
In recent years, the scarcity of pure water resources has received a lot of attention from society because of the increasing amount of pollution from industrial waste. It is very important to use low-cost adsorbents with high-adsorption performance to reduce water pollution. In [...] Read more.
In recent years, the scarcity of pure water resources has received a lot of attention from society because of the increasing amount of pollution from industrial waste. It is very important to use low-cost adsorbents with high-adsorption performance to reduce water pollution. In this work, a gel adsorbent with a high-adsorption performance on methylene blue (MB) and Cu(II) was prepared from bamboo nanocellulose (BCNF) (derived from waste bamboo paper) and montmorillonite nanosheet (MMTNS) cross-linked by polyethyleneimine (PEI). The resulting gel adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), etc. The results indicated that the MB and Cu(II) adsorption capacities of the resulting gel adsorbent increased with the solution pH, contact time, initial concentration, and temperature before equilibrium. The adsorption processes of MB and Cu(II) fitted well with the fractal-like pseudo-second-order model. The maximal adsorption capacities on MB and Cu(II) calculated by the Sips model were 361.9 and 254.6 mg/g, respectively. The removal of MB and Cu(II) from aqueous solutions mainly included electrostatic attraction, ion exchange, hydrogen bonding interaction, etc. These results suggest that the resulting gel adsorbent is an ideal material for the removal of MB and Cu(II) from aqueous solutions. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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9 pages, 2220 KiB  
Article
Functional Aerogels Composed of Regenerated Cellulose and Tungsten Oxide for UV Detection and Seawater Desalination
by Yanjin Tang, Yuhan Lai, Ruiqin Gao, Yuxuan Chen, Kexin Xiong, Juan Ye, Qi Zheng, Zhenxing Fang, Guangsheng Pang and Hoo-Jeong Lee
Gels 2023, 9(1), 10; https://doi.org/10.3390/gels9010010 - 25 Dec 2022
Viewed by 1847
Abstract
Functional aerogels composed of regenerated cellulose and tungsten oxide were fabricated by implanting tungsten-oxide nanodots into regenerated cellulose fiber. This superfast photochromic property benefitted from the small size and even distribution of tungsten oxide, which was caused by the confinement effect of the [...] Read more.
Functional aerogels composed of regenerated cellulose and tungsten oxide were fabricated by implanting tungsten-oxide nanodots into regenerated cellulose fiber. This superfast photochromic property benefitted from the small size and even distribution of tungsten oxide, which was caused by the confinement effect of the regenerated cellulose fiber. The composite was characterized using XRD and TEM to illustrate the successful loading of tungsten oxide. The composite turned from pale white to bright blue under ambient solar irradiation in five seconds. The evidence of solar absorption and electron paramagnetic resonance (EPR) demonstrated the fast photochromic nature of the composite and its mechanism. Furthermore, carbon fiber filled with preferential growth tungsten-oxide nanorods was obtained by annealing the photochromic composite in a N2 atmosphere. This annealed product exhibited good absorption across the whole solar spectrum and revealed an excellent photothermal conversion performance. The water evaporation rate reached 1.75 kg m−2 h−1 under one sun illumination, which is 4.4 times higher than that of pure water. The photothermal conversion efficiency was 85%, which shows its potential application prospects in seawater desalination. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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10 pages, 3267 KiB  
Article
Nanocellulose-Linked MXene/Polyaniline Aerogel Films for Flexible Supercapacitors
by Liying Xu, Wenxuan Wang, Yu Liu and Daxin Liang
Gels 2022, 8(12), 798; https://doi.org/10.3390/gels8120798 - 5 Dec 2022
Cited by 7 | Viewed by 1683
Abstract
In the development of energy supply systems for smart wearable devices, supercapacitors stand out owing to their ability of quick and efficient energy supply. However, their application is limited due to their low energy density and poor mechanical energy. Herein, a strategy for [...] Read more.
In the development of energy supply systems for smart wearable devices, supercapacitors stand out owing to their ability of quick and efficient energy supply. However, their application is limited due to their low energy density and poor mechanical energy. Herein, a strategy for the preparation of flexible supercapacitors is reported, which is based on the fabrication of aerogel films by simultaneously utilising cellulose nanofiber (CNFs) as an MXene intercalation material and polyaniline (PANI) as a template material. CNFs, which can form hydrogen-bonded networks, enhance the mechanical properties of MXene from 44.25 to 119.56 MPa, and the high electron transport properties of PANI endow MXene with a capacitance of 327 F g−1 and a resistance of 0.23 Ω. Furthermore, the combination of CNFs and PANI enables a 71.6% capacitance retention after 3000 charge/discharge and 500 folding cycles. This work provides a new platform for the development of flexible supercapacitors. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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18 pages, 3318 KiB  
Article
Cr(III) Ion-Imprinted Hydrogel Membrane for Chromium Speciation Analysis in Water Samples
by Ivanka Dakova, Penka Vasileva and Irina Karadjova
Gels 2022, 8(11), 757; https://doi.org/10.3390/gels8110757 - 21 Nov 2022
Cited by 5 | Viewed by 1676
Abstract
Novel Cr(III)-imprinted poly(vinyl alcohol)/sodium alginate/AuNPs hydrogel membranes (Cr(III)-IIMs) were obtained and characterized and further applied as a sorbent for chromium speciation in waters. Cr(III)-IIMs were prepared via solution blending method using blends of poly(vinyl alcohol) and sodium alginate as film-forming materials, poly(ethylene glycol) [...] Read more.
Novel Cr(III)-imprinted poly(vinyl alcohol)/sodium alginate/AuNPs hydrogel membranes (Cr(III)-IIMs) were obtained and characterized and further applied as a sorbent for chromium speciation in waters. Cr(III)-IIMs were prepared via solution blending method using blends of poly(vinyl alcohol) and sodium alginate as film-forming materials, poly(ethylene glycol) as a porogen agent, sodium alginate stabilized gold nanoparticles (SA-AuNPs) as a crosslinking and mechanically stabilizing component, and Cr(III) ions as a template species. The physicochemical characteristics of pre-synthesized AuNPs and obtained hydrogel membranes Cr(III)-IIM were studied by UV-vis and FTIR spectroscopy, TEM and SEM observations, N2 adsorption–desorption measurements, and XRD analysis. The mechanism of the adsorption process toward Cr(III) was best described by pseudo-first-order kinetic and Langmuir models. Experiments performed showed that quantitative retention of Cr(III) is attained in 20 h at pH 6 and temperature 40 °C. Under the same conditions, the adsorption of Cr(VI) is below 5%. A simple and sensitive analytical procedure was developed for the speciation of Cr in an aquatic environment using dispersive solid phase extraction of Cr(III) by Cr(III)-IIM prior to selective Cr(VI) measurement by ETAAS in the supernatants. The detection limits and reproducibility achieved for the Cr speciation analysis fulfill the requirements for their monitoring in waters under the demand of the Water Framework Directive. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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10 pages, 1345 KiB  
Article
Metal Oxide Hydrogel Composites for Remediation of Dye-Contaminated Wastewater: Principal Component Analysis
by Nimer Murshid, Omar Mouhtady, Mahmoud Abu-samha, Emil Obeid, Yahya Kharboutly, Hamdi Chaouk, Jalal Halwani and Khaled Younes
Gels 2022, 8(11), 702; https://doi.org/10.3390/gels8110702 - 30 Oct 2022
Cited by 13 | Viewed by 1939
Abstract
Water pollution is caused by multiple factors, such as industrial dye wastewater. Dye-contaminated water can be treated using hydrogels as adsorbent materials. Recently, composite hydrogels containing metal oxide nanoparticles (MONPs) have been used extensively in wastewater remediation. In this study, we use a [...] Read more.
Water pollution is caused by multiple factors, such as industrial dye wastewater. Dye-contaminated water can be treated using hydrogels as adsorbent materials. Recently, composite hydrogels containing metal oxide nanoparticles (MONPs) have been used extensively in wastewater remediation. In this study, we use a statistical and artificial intelligence method, based on principal component analysis (PCA) with different applied parameters, to evaluate the adsorption efficiency of 27 different MONP composite hydrogels for wastewater dye treatment. PCA showed that the hydrogel composites CTS@Fe3O4, PAAm/TiO2, and PEGDMA-rGO/Fe3O4@cellulose should be used in situations involving high pH, time to reach equilibrium, and adsorption capacity. However, as the composites PAAm-co-AAc/TiO2, PVPA/Fe3O4@SiO2, PMOA/ATP/Fe3O4, and PVPA/Fe3O4@SiO2, are preferred when all physical and chemical properties investigated have low magnitudes. To conclude, PCA is a strong method for highlighting the essential factors affecting hydrogel composite selection for dye-contaminated water treatment. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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12 pages, 3981 KiB  
Article
Design of Economical and Achievable Aluminum Carbon Composite Aerogel for Efficient Thermal Protection of Aerospace
by Yumei Lv, Fei He, Wei Dai, Yulong Ma, Taolue Liu, Yifei Liu and Jianhua Wang
Gels 2022, 8(8), 509; https://doi.org/10.3390/gels8080509 - 17 Aug 2022
Cited by 2 | Viewed by 1725
Abstract
Insulation materials play an extremely important role in the thermal protection of aerospace vehicles. Here, aluminum carbon aerogels (AlCAs) are designed for the thermal protection of aerospace. Taking AlCA with a carbonization temperature of 800 °C (AlCA–800) as an example, scanning electron microscopy [...] Read more.
Insulation materials play an extremely important role in the thermal protection of aerospace vehicles. Here, aluminum carbon aerogels (AlCAs) are designed for the thermal protection of aerospace. Taking AlCA with a carbonization temperature of 800 °C (AlCA–800) as an example, scanning electron microscopy (SEM) images show an integrated three-dimensional porous frame structure in AlCA–800. In addition, the thermogravimetric test (TGA) reveals that the weight loss of AlCA–800 is only ca. 10%, confirming its desirable thermal stability. Moreover, the thermal conductivity of AlCA–800 ranges from 0.018 W m−1 K−1 to 0.041 W m−1 K−1, revealing an enormous potential for heat insulation applications. In addition, ANSYS numerical simulations are carried out on a composite structure to forecast the thermal protection ability of AlCA–800 acting as a thermal protection layer. The results uncover that the thermal protective performance of the AlCA–800 layer is outstanding, causing a 1185 K temperature drop of the structure surface that is exposed to a heat environment for ten minutes. Briefly, this work unveils a rational fabrication of the aluminum carbon composite aerogel and paves a new way for the efficient thermal protection materials of aerospace via the simple and economical design of the aluminum carbon aerogels under the guidance of ANSYS numerical simulation. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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14 pages, 3591 KiB  
Article
Extraction of Palladium(II) with a Magnetic Sorbent Based on Polyvinyl Alcohol Gel, Metallic Iron, and an Environmentally Friendly Polydentate Phosphazene-Containing Extractant
by Pavel Yudaev, Irina Butorova, Gennady Stepanov and Evgeniy Chistyakov
Gels 2022, 8(8), 492; https://doi.org/10.3390/gels8080492 - 8 Aug 2022
Cited by 13 | Viewed by 2816
Abstract
In this work, a highly efficient and environmentally friendly method for extracting palladium from hydrochloric acid media was developed. The method uses a magnetic sorbent carrying an organophosphorus extractant, which is not washed from the sorbent into the aqueous phase. The extractant was [...] Read more.
In this work, a highly efficient and environmentally friendly method for extracting palladium from hydrochloric acid media was developed. The method uses a magnetic sorbent carrying an organophosphorus extractant, which is not washed from the sorbent into the aqueous phase. The extractant was characterized by 1H, 13C, and 31P NMR spectroscopy and MALDI TOF mass spectrometry, and the palladium complex based on it was characterized by IR spectroscopy. According to an in vitro microbiological study, the extractant was non-toxic to soil microflora. It was established that the water uptake and saturation magnetization of the magnetic sorbent were sufficient for use in sorption processes. The sorption efficiency of palladium(II) with the developed sorbent can reach 71% in one cycle. After treatment of the spent sorbent with 5 M hydrochloric acid, palladium was completely extracted from the sorbent. The new sorbent is proposed for the extraction of palladium from hydrochloric acid media obtained by the leaching of electronic waste. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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8 pages, 824 KiB  
Article
Evaluation of the Adsorption Efficiency of Graphene Oxide Hydrogels in Wastewater Dye Removal: Application of Principal Component Analysis
by Omar Mouhtady, Emil Obeid, Mahmoud Abu-samha, Khaled Younes and Nimer Murshid
Gels 2022, 8(7), 447; https://doi.org/10.3390/gels8070447 - 18 Jul 2022
Cited by 10 | Viewed by 2011
Abstract
Industrial dye wastewater is one of the major water pollution problems. Adsorbent materials are promising strategies for the removal of water dye contaminants. Herein, we provide a statistical and artificial intelligence study to evaluate the adsorption efficiency of graphene oxide-based hydrogels in wastewater [...] Read more.
Industrial dye wastewater is one of the major water pollution problems. Adsorbent materials are promising strategies for the removal of water dye contaminants. Herein, we provide a statistical and artificial intelligence study to evaluate the adsorption efficiency of graphene oxide-based hydrogels in wastewater dye removal by applying Principal Component Analysis (PCA). This study aims to assess the adsorption quality of 35 different hydrogels. We adopted different approaches and showed the pros and cons of each one of them. PCA showed that alginate graphene oxide-based hydrogel (without polyvinyl alcohol) had better tolerance in a basic medium and provided higher adsorption capacity. Polyvinyl alcohol sulfonated graphene oxide-based hydrogels are suitable when higher adsorbent doses are required. In conclusion, PCA represents a robust way to delineate factors affecting hydrogel selection for pollutant removal from aqueous solutions. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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Review

Jump to: Research

21 pages, 6616 KiB  
Review
Metal–Organic Framework Gels for Adsorption and Catalytic Detoxification of Chemical Warfare Agents: A Review
by Ye Zhang and Cheng-An Tao
Gels 2023, 9(10), 815; https://doi.org/10.3390/gels9100815 - 13 Oct 2023
Cited by 2 | Viewed by 1722
Abstract
Chemical warfare agents (CWAs) have brought great threats to human life and social stability, and it is critical to investigate protective materials. MOF (metal–organic framework) gels are a class with an extended MOF architecture that are mainly formed using metal–ligand coordination as an [...] Read more.
Chemical warfare agents (CWAs) have brought great threats to human life and social stability, and it is critical to investigate protective materials. MOF (metal–organic framework) gels are a class with an extended MOF architecture that are mainly formed using metal–ligand coordination as an effective force to drive gelation, and these gels combine the unique characteristics of MOFs and organic gel materials. They have the advantages of a hierarchically porous structure, a large specific surface area, machinable block structures and rich metal active sites, which inherently meet the requirements for adsorption and catalytic detoxification of CWAs. A series of advances have been made in the adsorption and catalytic detoxification of MOF gels as chemical warfare agents; however, overall, they are still in their infancy. This review briefly introduces the latest advances in MOF gels, including pure MOF gels and MOF composite gels, and discusses the application of MOF gels in the adsorption and catalytic detoxification of CWAs. Meanwhile, the influence of microstructures (pore structures, metal active site, etc.) on the detoxification performance of protective materials is also discussed, which is of great significance in the exploration of high-efficiency protective materials. Finally, the review looks ahead to next priorities. Hopefully, this review can inspire more and more researchers to enrich the performance of MOF gels for applications in chemical protection and other purification and detoxification processes. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption)
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