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24 pages, 6651 KiB

Open AccessArticle

Application of Activated Carbons Obtained from Polymer Waste for the Adsorption of Dyes from Aqueous Solutions

by Katarzyna Jedynak and Barbara Charmas

Materials 2024, 17(3), 748; https://doi.org/10.3390/ma17030748 - 4 Feb 2024

Cited by 2 | Viewed by 669

Abstract

Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, [...] Read more.

Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, and then the physical activation of the obtained material with CO₂, was developed. Dyes such as methylene blue (MB) and malachite green (MG) are commonly applied in industry, which contaminate the water environment to a large extent and have a harmful effect on living organisms; therefore, adsorption studies were carried out for these cationic dyes. The effects of the activation time on the physicochemical properties of the activated materials and the adsorption capacity of the dyes were investigated. The obtained microporous adsorbents were characterized by studying the porous structure based on low-temperature nitrogen adsorption/desorption, scanning electron microscopy (SEM-EDS), elemental analysis (CHNS), Raman spectroscopy, X-ray powder diffraction (XRD), infrared spectroscopy (ATR FT-IR), thermal analysis (TG, DTG, DTA), Boehm’s titration method, and pH_pzc (the point of zero charge) determination. Moreover, adsorption studies (equilibrium and kinetics) were carried out. The maximum adsorption capacities (q_{m exp}) of MB and MG (349 mg g⁻¹ and 274 mg g⁻¹, respectively) were identified for the obtained material after 8 h of activation. The results show that the use of waste CDs as a carbon precursor facilitates the production of low-cost and effective adsorbents. Full article

(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)

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13 pages, 5932 KiB

Open AccessArticle

Investigation of Ionic Polymers’ Stabilizing and Flocculating Properties in Dispersed Activated Carbons Systems

by Marlena Gęca, Małgorzata Wiśniewska and Piotr Nowicki

Materials 2024, 17(3), 693; https://doi.org/10.3390/ma17030693 - 1 Feb 2024

Viewed by 655

Abstract

Activated carbons obtained via the thermochemical treatment of lemon balm and mint herbs were applied for ionic polymers adsorption, which directly affects the stability of these types of aqueous suspensions. The examined carbonaceous materials were characterized by well-developed specific surface area (approximately 1000 [...] Read more.

Activated carbons obtained via the thermochemical treatment of lemon balm and mint herbs were applied for ionic polymers adsorption, which directly affects the stability of these types of aqueous suspensions. The examined carbonaceous materials were characterized by well-developed specific surface area (approximately 1000 m²/g) and mesoporous structure. The adsorbed amounts of anionic poly(acrylic acid) and cationic polyethyleneimine from one-component solutions reached significant levels, but the efficiency of adsorption of these compounds from binary solutions slightly decreased. Moreover, the ionic polymers showed stabilizing properties towards the activated carbons suspensions. For both adsorbents, the most stable suspensions were systems containing both types of polymeric macromolecules with different ionic characters. This was due to the occurrence of electrosteric and depletion stabilization mechanisms. Furthermore, the zeta potential and size of particle aggregates were also influenced by the presence of polymers in the aqueous suspensions of activated carbons. Full article

(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)

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13 pages, 1933 KiB

Open AccessArticle

Chain Reduction of CHCl₃ Photocatalyzed by SPEEK/PVA Films Swollen in Air-Saturated HCO₂Na Solutions

by Radini Dissanayaka, Md Safiqul Islam and G. Mills

Materials 2023, 16(20), 6629; https://doi.org/10.3390/ma16206629 - 10 Oct 2023

Viewed by 486

Abstract

Thin cross-linked films containing sulfonated poly(ether etherketone), SPEEK, and poly(vinyl alcohol), PVA, served as efficient photocatalysts for the reduction of CHCl₃ when swollen in air-saturated solutions of formate buffers were photolyzed with 350 nm photons. The phototransformation generated CH₂Cl₂ [...] Read more.

Thin cross-linked films containing sulfonated poly(ether etherketone), SPEEK, and poly(vinyl alcohol), PVA, served as efficient photocatalysts for the reduction of CHCl₃ when swollen in air-saturated solutions of formate buffers were photolyzed with 350 nm photons. The phototransformation generated CH₂Cl₂, CO₂ and Cl⁻ as products. The utilization of the continuous extraction method coupled with in situ potentiometry enabled kinetic determinations of the reaction progress. Quantum yields of halide ion formation, ϕ(Cl⁻), larger than 1 were obtained in the presence of air. These findings, together with the occurrence of a post-irradiation Cl⁻ formation, indicated that the photoreduction took place via a chain process. Reductions photoinitiated by swollen films exhibited ϕ(Cl⁻) values between 3 and 20 times higher than the reactions induced in solutions containing the two polymers. Also, the dependencies of ϕ(Cl⁻) on CHCl₃ or HCO₂⁻ concentration diverged significantly from the trends observed using solutions. Most findings are consistent with the occurrence of a reaction mechanism involving SPEEK radicals, •CO₂⁻ and •CHCl₂ as chain carriers. Full article

(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)

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14 pages, 4043 KiB

Open AccessArticle

Evaluation of Cytotoxicity of Hyaluronic Acid/Chitosan/Bacterial Cellulose-Based Membrane

by Duangkamol Dechojarassri, Tomoki Okada, Hiroshi Tamura and Tetsuya Furuike

Materials 2023, 16(14), 5189; https://doi.org/10.3390/ma16145189 - 24 Jul 2023

Viewed by 878

Abstract

Novel wound dressing materials are required to non-cytotoxic with a viable cell ratio of above 92%. Herein, the cytotoxicity of hyaluronic acid/chitosan/bacterial cellulose-based (BC(CS/HA)) membranes are evaluated and compared to that of alginate/chitosan/bacterial cellulose-based (BC(CS/Alg)) membranes was investigated. Multilayer membranes with up to [...] Read more.

Novel wound dressing materials are required to non-cytotoxic with a viable cell ratio of above 92%. Herein, the cytotoxicity of hyaluronic acid/chitosan/bacterial cellulose-based (BC(CS/HA)) membranes are evaluated and compared to that of alginate/chitosan/bacterial cellulose-based (BC(CS/Alg)) membranes was investigated. Multilayer membranes with up to ten CS/HA or CS/Alg layers were prepared using the layer-by-layer (LBL) method. Scanning electron microscopy showed that the diameters of the fibers in the BC(CS/Alg) and BC(CS/HA) membranes were larger than those in a BC membrane. The cytotoxicity was analyzed using BALB-3T3 clone A31 cells (mouse fibroblasts, 1 × 10⁴ cells/well). The BC(CS/HA)₅ and BC(CS/HA)₁₀ membranes exhibited high biocompatibility, with the cell viabilities of 94% and 87% at 5 d, respectively, compared to just 82% for the BC(CS/Alg)₅ and BC(CS/Alg)₁₀ membranes with same numbers of layers. These results suggested that BC(CS/HA)₅ is a promising material for wound dressings. Full article

(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)

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18 pages, 5900 KiB

Open AccessArticle

Use of Insect-Derived Chitosan for the Removal of Methylene Blue Dye from Wastewater: Process Optimization Using a Central Composite Design

by Ilham Ben Amor, Hadia Hemmami, Salah Eddine Laouini , Soumeia Zeghoud, Mourad Benzina, Sami Achour, Abanoub Naseef, Ali Alsalme and Ahmed Barhoum

Materials 2023, 16(14), 5049; https://doi.org/10.3390/ma16145049 - 17 Jul 2023

Cited by 7 | Viewed by 1462

Abstract

Insects are a readily available source of chitosan due to their high reproductive rates, ease of breeding, and resistance to changes in their ecosystem. This study aimed to extract chitosan from several widespread insects: Blaps lethifera (CS-BL), Pimelia fernandezlopezi (CS-PF), and Musca domestica [...] Read more.

Insects are a readily available source of chitosan due to their high reproductive rates, ease of breeding, and resistance to changes in their ecosystem. This study aimed to extract chitosan from several widespread insects: Blaps lethifera (CS-BL), Pimelia fernandezlopezi (CS-PF), and Musca domestica (CS-MD). The study was also extended to using the obtained chitosans in removing methylene blue dye (MB) from wastewater. The source of the chitosan, the initial concentration of MB dye, and the reaction time were chosen as the working parameters. The experiments were designed using a central composite design (CCD) based on the dye removal efficiency as the response variable. The experimental work and statistical calculation of the CCD showed that the dye removal efficiency ranged from 35.9% to 88.7% for CS-BL, from 18.8% to 47.1% for CS-PF, and from 10.3% to 29.0% for CS-MD at an initial MB concentration of 12.79 mg/L. The highest methylene blue dye removal efficiency was 88.7% for CS-BL at a reaction time of 120 min. This indicates that the extraction of chitosan from insects (Blaps lethifera) and its application in dye removal is a promising, environmentally friendly, economical, biodegradable, and cost-effective process. Furthermore, the CCD is a statistical experimental design technique that can be used to optimize process variables for removing other organic pollutants using chitosan. Full article

(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)

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15 pages, 3424 KiB

Open AccessArticle

The Influence of Industrial Environmental Factors on Soft Robot Materials

by Dan Mihai Rusu, Olivia Laura Petrașcu, Adrian Marius Pascu and Silviu Dan Mândru

Materials 2023, 16(8), 2948; https://doi.org/10.3390/ma16082948 - 7 Apr 2023

Viewed by 1085

Abstract

This work aims to identify the effects that a series of environmental factors, specific to the industrial conditions, have on the materials in the structure of soft robots and, therefore, on soft robotics systems. The purpose is to understand the changes in the [...] Read more.

This work aims to identify the effects that a series of environmental factors, specific to the industrial conditions, have on the materials in the structure of soft robots and, therefore, on soft robotics systems. The purpose is to understand the changes in the mechanical characteristics of silicone materials, with the aim of transferring soft robotics applications from the sphere of services in the industrial field. Distilled water, hydraulic oil, cooling oil, and UV rays are the environmental factors considered in which the specimens were immersed/exposed for 24 h according to ISO-62/2008. The analysis was carried out on two of the most widely used materials in the field, belonging to the category of silicone rubber, which were subjected to uniaxial tensile tests on the strength testing machine Titan 2 Universal. The results show that the greatest impact on the characteristics of the two materials was when exposed to UV rays, while the other media tested had relatively little impact on the mechanical and elastic properties (tensile strength, elongation at break, and tensile modulus) of these materials. Full article

(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)

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15 pages, 5563 KiB

Open AccessArticle

Degradation of Carbon Fiber-Reinforced Polymer Composites in Salt Water and Rapid Evaluation by Electrochemical Impedance Spectroscopy

by Hanlu Zhang, Fabao Kong, Yuchao Dun, Xueping Chen, Quankai Chen, Xuhui Zhao, Yuming Tang and Yu Zuo

Materials 2023, 16(4), 1676; https://doi.org/10.3390/ma16041676 - 17 Feb 2023

Cited by 2 | Viewed by 1457

Abstract

The electrochemical impedance spectroscopy and weight gain tests were performed on carbon fiber/vinyl ester and carbon fiber/bismaleimide composites in 3.5% NaCl solution to study the electrochemical and water absorption behaviors. The microstructure morphology and the flexural property of the composites in the long-term [...] Read more.

The electrochemical impedance spectroscopy and weight gain tests were performed on carbon fiber/vinyl ester and carbon fiber/bismaleimide composites in 3.5% NaCl solution to study the electrochemical and water absorption behaviors. The microstructure morphology and the flexural property of the composites in the long-term exposure process were analyzed with the scanning electron microscope and four-point bending tests. The results revealed that after long-time immersion (>200 d), the water absorption of the two composites is less than 0.5%. This has little effect on the microstructural integrity, only with slight damage on the fiber/resin interfaces, but results in a significant decrease (about 84%) in the composite flexural property. The variation of the water absorption percentage shows good consistency with that of the resin capacitance (Q_c) and is negatively related to the variation of the resin resistance (R_po) and the low-frequency impedance (|Z|_0.01Hz) of the composites. A good linear relationship exists between the variations of phase angles in the middle-frequency range (0.1−10 Hz) and the |Z|_0.01Hz. The phase angle at 10 Hz (θ_10Hz) may be suggested as a suitable parameter to rapidly evaluate the performance of carbon fiber-reinforced polymer composites, just like for evaluating the protective performance of polymer-coated metals in the literature. Full article

(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)

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Review

Jump to: Research

27 pages, 2527 KiB

Open AccessReview

Preparation and Functionalization of Polymers with Antibacterial Properties—Review of the Recent Developments

by Monika Parcheta and Magdalena Sobiesiak

Materials 2023, 16(12), 4411; https://doi.org/10.3390/ma16124411 - 15 Jun 2023

Cited by 1 | Viewed by 1723

Abstract

The presence of antibiotic-resistant bacteria in our environment is a matter of growing concern. Consumption of contaminated drinking water or contaminated fruit or vegetables can provoke ailments and even diseases, mainly in the digestive system. In this work, we present the latest data [...] Read more.

The presence of antibiotic-resistant bacteria in our environment is a matter of growing concern. Consumption of contaminated drinking water or contaminated fruit or vegetables can provoke ailments and even diseases, mainly in the digestive system. In this work, we present the latest data on the ability to remove bacteria from potable water and wastewater. The article discusses the mechanisms of the antibacterial activity of polymers, consisting of the electrostatic interaction between bacterial cells and the surface of natural and synthetic polymers functionalized with metal cations (polydopamine modified with silver nanoparticles, starch modified with quaternary ammonium or halogenated benzene). The synergistic effect of polymers (N-alkylaminated chitosan, silver doped polyoxometalate, modified poly(aspartic acid)) with antibiotics has also been described, allowing for precise targeting of drugs to infected cells as a preventive measure against the excessive spread of antibiotics, leading to drug resistance among bacteria. Cationic polymers, polymers obtained from essential oils (EOs), or natural polymers modified with organic acids are promising materials in the removal of harmful bacteria. Antimicrobial polymers are successfully used as biocides due to their acceptable toxicity, low production costs, chemical stability, and high adsorption capacity thanks to multi-point attachment to microorganisms. New achievements in the field of polymer surface modification in order to impart antimicrobial properties were summarized. Full article

(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)

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