Gels | Special Issue : Removing Hazardous Materials from Water Using Polymer Hydrogel

Research

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11 pages, 2911 KiB

Open AccessArticle

The Removal of Hydrophobic Matter from Thermosensitive Poly[oligo(ethylene glycol) Monomethyl Ether Acrylate] Gel Adsorbent in Alcohol–Water Mixtures

by Syed Ragib Safi, Toshiki Kaneko, Katsuhiro Nakahara, Takehiko Gotoh and Takashi Iizawa

Gels 2022, 8(4), 200; https://doi.org/10.3390/gels8040200 - 23 Mar 2022

Cited by 2 | Viewed by 2567

Abstract

A thermosensitive gel that exhibits lower critical solution temperature (LCST) becomes hydrophilic at low temperatures and hydrophobic at high temperatures in water. A system for absorbing hydrophobic organic matters that exploits this property has been reported. While washing the gel at a low [...] Read more.

A thermosensitive gel that exhibits lower critical solution temperature (LCST) becomes hydrophilic at low temperatures and hydrophobic at high temperatures in water. A system for absorbing hydrophobic organic matters that exploits this property has been reported. While washing the gel at a low temperature with a good solvent is a possible method for removing the adsorbed matter, a process that then shrinks the gel is also required. Herein, we focused on poly[oligo(ethylene glycol) mono(m)ethyl ether acrylate] (POEGA) gels as thermosensitive gels suitable for use in this system. POEGAs are known to contain poly(ethylene glycol) (PEG) units in their side chains and exhibit upper critical solution temperature (UCST) behavior in aliphatic alcohols. By exploiting this property, we developed a method for removing hydrophobic matters that accumulate in these gels; we also evaluated the LCST and UCST behavior of POEGA gels in alcohol–water mixtures, and measured the LCSTs of these gels in water and their UCSTs in some alcohols. Full article

(This article belongs to the Special Issue Removing Hazardous Materials from Water Using Polymer Hydrogel)

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18 pages, 4485 KiB

Open AccessArticle

Arsenate Removal from Aqueous Media Using Chitosan-Magnetite Hydrogel by Batch and Fixed-Bed Columns

by Ilse Paulina Verduzco-Navarro, Eduardo Mendizábal, José Antonio Rivera Mayorga, Maite Rentería-Urquiza, Alejandro Gonzalez-Alvarez and Nely Rios-Donato

Gels 2022, 8(3), 186; https://doi.org/10.3390/gels8030186 - 17 Mar 2022

Cited by 4 | Viewed by 1971

Abstract

The removal of arsenate ions from aqueous solutions at near-neutral pH was carried out using chitosan-magnetite (ChM) hydrogel beads in batch systems. Equilibrium isotherms and kinetic studies are reported. Obtained equilibrium and kinetic data were fitted to mathematical models, estimating model parameters by [...] Read more.

The removal of arsenate ions from aqueous solutions at near-neutral pH was carried out using chitosan-magnetite (ChM) hydrogel beads in batch systems. Equilibrium isotherms and kinetic studies are reported. Obtained equilibrium and kinetic data were fitted to mathematical models, estimating model parameters by non-linear regression analysis. Langmuir model was found to best fit equilibrium data; a maximum adsorption capacity of 66.9 mg As/g was estimated at pH 7.0. Pseudo-first order kinetic model was observed to best fit kinetic data. The pH of the solution was observed to increase with increasing contact time, which is attributed to protonation of amine groups present in the hydrogel. Protonation of functional groups in the ChM sorbent yields a higher number of active sites for arsenate removal, being as this a process that can’t be overlooked in future applications of ChM hydrogel for the removal or arsenate ions. Chitosan-magnetite and ChM-arsenate interactions were determined by XPS. Arsenate removal using fixed-bed column packed with ChM was carried out, reporting a non-ideal behavior attributed to pH increase of the effluent caused by proton transfer to ChM hydrogels. Full article

(This article belongs to the Special Issue Removing Hazardous Materials from Water Using Polymer Hydrogel)

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11 pages, 1762 KiB

Open AccessArticle

Removal of Acetic Acid from Bacterial Culture Media by Adsorption onto a Two-Component Composite Polymer Gel

by Junya Kato, Takehiko Gotoh and Yutaka Nakashimada

Gels 2022, 8(3), 154; https://doi.org/10.3390/gels8030154 - 2 Mar 2022

Cited by 2 | Viewed by 2920

Abstract

Organic acids, including acetic acid, are the metabolic products of many microorganisms. Acetic acid is a target product useful in the fermentation process. However, acetic acid has an inhibitory effect on microorganisms and limits fermentation. Thus, it would be beneficial to recover the [...] Read more.

Organic acids, including acetic acid, are the metabolic products of many microorganisms. Acetic acid is a target product useful in the fermentation process. However, acetic acid has an inhibitory effect on microorganisms and limits fermentation. Thus, it would be beneficial to recover the acid from the culture medium. However, conventional recovery processes are expensive and environmentally unfriendly. Here, we report the use of a two-component hydrogel to adsorb dissociated and undissociated acetic acid from the culture medium. The Langmuir model revealed the maximum adsorption amount to be 44.8 mg acetic acid/g of dry gel at neutral pH value. The adsorption capacity was similar to that of an ion-exchange resin. In addition, the hydrogel maintained its adsorption capability in a culture medium comprising complex components, whereas the ion-exchange did not adsorb in this medium. The adsorbed acetic acid was readily desorbed using a solution containing a high salt concentration. Thus, the recovered acetic acid can be utilized for subsequent processes, and the gel-treated fermentation broth can be reused for the next round of fermentation. Use of this hydrogel may prove to be a more sustainable downstream process to recover biosynthesized acetic acid. Full article

(This article belongs to the Special Issue Removing Hazardous Materials from Water Using Polymer Hydrogel)

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10 pages, 4052 KiB

Open AccessArticle

TiO₂ Nanoparticle-Loaded Poly(NIPA-co-NMA) Fiber Web for the Adsorption and Photocatalytic Degradation of 4-Isopropylphenol

by Hideaki Tokuyama and Ryosuke Hamaguchi

Gels 2022, 8(2), 137; https://doi.org/10.3390/gels8020137 - 21 Feb 2022

Cited by 4 | Viewed by 1844

Abstract

A TiO₂ nanoparticle-loaded polymer fiber web was developed as a functional material with the ability to adsorb and photo-catalytically degrade organic pollutants in aquatic media. A linear copolymer of N-isopropylacrylamide (primary component) and N-methylol acrylamide (poly(NIPA-co-NMA)) was prepared, [...] Read more.

A TiO₂ nanoparticle-loaded polymer fiber web was developed as a functional material with the ability to adsorb and photo-catalytically degrade organic pollutants in aquatic media. A linear copolymer of N-isopropylacrylamide (primary component) and N-methylol acrylamide (poly(NIPA-co-NMA)) was prepared, and composite fibers were fabricated by electrospinning a methanol suspension containing the copolymer and commercially available TiO₂ nanoparticles. The crosslinking of the polymer via the formation of methylene bridges between NMA units was accomplished by heating, and the fiber morphology was analyzed by electron microscopy. 4-Isopropylphenol generated by the degradation of bisphenol A—one of the endocrine-disrupting chemicals—was used as the model organic pollutant. As poly(NIPA) is a thermosensitive polymer that undergoes hydrophilic/hydrophobic transition in water, the temperature-dependence of the adsorption and photocatalytic degradation of 4-isopropylphenol was investigated. The degradation rate was analyzed using a pseudo-first-order kinetic model to obtain the apparent reaction rate constant, k_app. The enhancement of the photocatalytic degradation rate owing to the adsorption of 4-isopropylphenol onto thermosensitive poly(NIPA)-based fibers is discussed in terms of the ratio of the k_app of the composite fiber to that of unsupported TiO₂ nanoparticles. Based on the results, an eco-friendly wastewater treatment process involving periodically alternated adsorption and photocatalytic degradation is proposed. Full article

(This article belongs to the Special Issue Removing Hazardous Materials from Water Using Polymer Hydrogel)

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16 pages, 3144 KiB

Open AccessArticle

Novel Thermosensitive-co-Zwitterionic Sulfobetaine Gels for Metal Ion Removal: Synthesis and Characterization

by Eva Oktavia Ningrum, Takehiko Gotoh, Wirawan Ciptonugroho, Achmad Dwitama Karisma, Elly Agustiani, Zela Marni Safitri and Muhammad Asyam Dzaky

Gels 2021, 7(4), 273; https://doi.org/10.3390/gels7040273 - 17 Dec 2021

Cited by 3 | Viewed by 2512

Abstract

Zwitterionic betaine polymers are promising adsorbents for the removal of heavy metal ions from industrial effluents. Although the presence of both negative and positively charged groups imparts them the ability to simultaneously remove cations and anions, intra- and/or inter-chain interactions can significantly reduce [...] Read more.

Zwitterionic betaine polymers are promising adsorbents for the removal of heavy metal ions from industrial effluents. Although the presence of both negative and positively charged groups imparts them the ability to simultaneously remove cations and anions, intra- and/or inter-chain interactions can significantly reduce their adsorption efficiencies. Therefore, in this study, novel gels based on crosslinked co-polymers of thermosensitive N-isopropylacrylamide (NIPAAM) and zwitterionic sulfobetaine N,N-dimethylacrylamido propyl ammonium propane sulfonate (DMAAPS) were synthesized, characterized, and evaluated for ion removal. Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) analyses confirmed the success of the co-polymerization of NIPAAM and DMAAPS to form poly(NIPAAM-co-DMAAPS). The phase transition temperature of the co-polymer increased with increasing DMAAPS content in the co-polymer, indicating temperature-dependent amphiphilic behavior, as evidenced by contact angle measurements. The ion adsorption analyses of the poly(NIPAAM-co-DMAAPS) gels indicated that co-polymerization increased the molecular distance and weakened the interaction between the DMAAPS-charged groups (SO₃⁻ and N⁺), thereby increasing the ion adsorption. The results confirmed that, with a low concentration of DMAAPS in the co-polymer gels (~10%), the maximum amount of Cr³⁺ ions adsorbed onto the gel was ~58.49% of the sulfonate content in the gel. Full article

(This article belongs to the Special Issue Removing Hazardous Materials from Water Using Polymer Hydrogel)

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13 pages, 4365 KiB

Open AccessArticle

Synthesis of Oxidant Functionalised Cationic Polymer Hydrogel for Enhanced Removal of Arsenic (III)

by Yu Song, Takehiko Gotoh and Satoshi Nakai

Gels 2021, 7(4), 197; https://doi.org/10.3390/gels7040197 - 4 Nov 2021

Cited by 9 | Viewed by 1643

Abstract

A cationic polymer gel (N-[3-(dimethylamino)propyl]acrylamide, methyl chloride quaternary)(DMAPAA-Q gel)-supported oxidising agent (KMnO₄ or K₂Cr₂O₇) was proposed to remove As from water. The gel could adsorb arsenite, As(III), and arsenate, As(V), through the ion exchange [...] Read more.

A cationic polymer gel (N-[3-(dimethylamino)propyl]acrylamide, methyl chloride quaternary)(DMAPAA-Q gel)-supported oxidising agent (KMnO₄ or K₂Cr₂O₇) was proposed to remove As from water. The gel could adsorb arsenite, As(III), and arsenate, As(V), through the ion exchange method, where the oxidising agent oxidised As(III) to As(V). theoretically speaking, the amount of oxidant in the gels can reach 73.7 Mol%. The maximal adsorption capacity of the D-Mn gel (DMAPAA-Q gel carrying MnO₄⁻) and D-Cr gel (DMAPAA-Q gel carrying Cr₂O₇²⁻) for As(III) could reach 200 mg g⁻¹ and 263 mg g⁻¹, respectively; moreover, the As(III) removal rate of the gels could still be maintained above 85% in a neutral or weak acid aquatic solution. Studies on the kinetic and adsorption isotherms indicated that the As adsorption by the D-Mn and D-Cr gels was dominated by chemisorption. The thermodynamic parameters of adsorption confirmed that the adsorption was an endothermic process. The removal of As is influenced by the co-existing high-valence anions. Based on these results, the gels were found to be efficient for the As(III) adsorption and could be employed for the As(III) removal from the industrial wastewater. Full article

(This article belongs to the Special Issue Removing Hazardous Materials from Water Using Polymer Hydrogel)

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21 pages, 4255 KiB

Open AccessArticle

Magnetic Cellulose-Chitosan Nanocomposite for Simultaneous Removal of Emerging Contaminants: Adsorption Kinetics and Equilibrium Studies

by Phodiso Prudence Mashile and Philiswa Nosizo Nomngongo

Gels 2021, 7(4), 190; https://doi.org/10.3390/gels7040190 - 30 Oct 2021

Cited by 10 | Viewed by 2031

Abstract

The presence of pharmaceuticals in water systems threatens both terrestrial and aquatic life across the globe. Some of such contaminants are β-blockers and anticonvulsants, which have been constantly detected in different water systems. Various methodologies have been introduced for the removal of these [...] Read more.

The presence of pharmaceuticals in water systems threatens both terrestrial and aquatic life across the globe. Some of such contaminants are β-blockers and anticonvulsants, which have been constantly detected in different water systems. Various methodologies have been introduced for the removal of these emerging pollutants from different waters. Among them, adsorption using nanomaterials has proved to be an efficient and cost-effective process for the removal of pharmaceuticals from contaminated water. In this this study, a firsthand/time approach applying a recyclable magnetic cellulose-chitosan nanocomposite for effective simultaneous removal of two β-blockers (atenolol (ATN)) and propranolol (PRP) and an anticonvulsant (carbamazepine (CBZ)) is reported. A detailed characterization of the eco-friendly, biocompatible cellulose-chitosan nanocomposite with magnetic properties was performed at various rates of synthesis using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and Fourier transform infrared (FTIR) spectroscopy. A N_2c adsorption-desorption test showed that the prepared nanocomposite is mesoporous, with a BET area of 112 m² g⁻¹. The BET isotherms results showed that the magnetic cellulose-chitosan nanocomposite has a pore size of 24.1 nm. The adsorption equilibrium of PRP and CBZ fitted with the Langmuir isotherm was consistent with the highest coefficient of determination (R² = 0.9945) and (R² = 0.9942), respectively, while the Sips model provided a better fit for ATN, with a coefficient of determination R² = 0.9956. The adsorption rate was accompanied by a pseudo-second-order kinetics. Moreover, the swelling test showed that up to 100 percent swelling of the magnetic cellulose-chitosan nanocomposite was achieved. Full article

(This article belongs to the Special Issue Removing Hazardous Materials from Water Using Polymer Hydrogel)

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Review

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23 pages, 3716 KiB

Open AccessReview

Hydrogel Adsorbents for the Removal of Hazardous Pollutants—Requirements and Available Functions as Adsorbent

by Yoshimi Seida and Hideaki Tokuyama

Gels 2022, 8(4), 220; https://doi.org/10.3390/gels8040220 - 3 Apr 2022

Cited by 32 | Viewed by 4937

Abstract

Over the last few decades, various adsorption functions of polymer hydrogels for the removal of hazardous pollutants have been developed. The performance of hydrogel adsorbents depends on the constituents of the gels and the functions produced by the polymer networks of the gels. [...] Read more.

Over the last few decades, various adsorption functions of polymer hydrogels for the removal of hazardous pollutants have been developed. The performance of hydrogel adsorbents depends on the constituents of the gels and the functions produced by the polymer networks of the gels. Research on hydrogels utilizing the characteristic functions of polymer networks has increased over the last decade. The functions of polymer networks are key to the development of advanced adsorbents for the removal of various pollutants. No review has discussed hydrogel adsorbents from the perspective of the roles and functions of polymer networks in hydrogels. This paper briefly reviews the basic requirements of adsorbents and the general characteristics of hydrogels as adsorbents. Thereafter, hydrogels are reviewed on the basis of the roles and functions of the polymer networks in them for the removal of hazardous pollutants by introducing studies published over the last decade. The application of hydrogels as adsorbents for the removal of hazardous pollutants is discussed as well. Full article

(This article belongs to the Special Issue Removing Hazardous Materials from Water Using Polymer Hydrogel)

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