Research

12 pages, 6851 KiB

Open AccessArticle

Electrochemical Crosslinking of Alginate—Towards Doped Carbons for Oxygen Reduction

by Jelena Rupar, Armin Hrnjić, Snežana Uskoković-Marković, Danica Bajuk-Bogdanović, Maja Milojević-Rakić, Nemanja Gavrilov and Aleksandra Janošević Ležaić

Polymers 2023, 15(15), 3169; https://doi.org/10.3390/polym15153169 - 26 Jul 2023

Viewed by 743

Abstract

Electrochemical crosslinking of alginate strands by in situ iron oxidation was explored using a potentiostatic regime. Carbon-based materials co-doped with iron, nitrogen, and/or sulfur were prepared via electrolyte composition variation with a nitrogen-rich compound (rivanol) or through post-treatments with sodium sulfide. Nanometer-sized iron [...] Read more.

Electrochemical crosslinking of alginate strands by in situ iron oxidation was explored using a potentiostatic regime. Carbon-based materials co-doped with iron, nitrogen, and/or sulfur were prepared via electrolyte composition variation with a nitrogen-rich compound (rivanol) or through post-treatments with sodium sulfide. Nanometer-sized iron particles were confirmed by transmission and field emission scanning electron microscopy in all samples as a consequence of the homogeneous dispersion of iron in the alginate scaffold and its concomitant growth-limiting effect of alginate chains. Raman spectra confirmed a rise in structural disorder with rivanol/Na₂S treatment, which points to more defect sites and edges known to be active sites for oxygen reduction. Fourier transform infrared (FTIR) spectra confirmed the presence of different iron, nitrogen, and sulfur species, with a marked difference between Na₂S treated/untreated samples. The most positive onset potential (−0.26 V vs. saturated calomel electrode, SCE) was evidenced for the sample co-doped with N, S, and Fe, surpassing the activity of those with single and/or double doping. The mechanism of oxygen reduction in 0.1 M KOH was dominated by the 2e⁻ reduction pathway at low overpotentials and shifted towards complete 4e⁻ reduction at the most negative explored values. The presented results put forward electrochemically formed alginate gels functionalized by homogeneously dispersed multivalent cations as an excellent starting point in nanomaterial design and engineering. Full article

(This article belongs to the Special Issue Emerging Marine Biopolymer-Based Materials: Extraction to Application)

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18 pages, 3553 KiB

Open AccessArticle

Studies of the Tarragon Essential Oil Effects on the Characteristics of Doped Hydroxyapatite/Chitosan Biocomposites

by Daniela Predoi, Simona Liliana Iconaru, Carmen Steluta Ciobanu, Mariana Stefania Raita, Liliana Ghegoiu, Roxana Trusca, Monica Luminita Badea and Carmen Cimpeanu

Polymers 2023, 15(8), 1908; https://doi.org/10.3390/polym15081908 - 16 Apr 2023

Cited by 2 | Viewed by 1364

Abstract

Due to the emergence of antibiotic-resistant pathogens, the need to find new, efficient antimicrobial agents is rapidly increasing. Therefore, in this study, we report the development of new biocomposites based on zinc-doped hydroxyapatite/chitosan enriched with essential oil of Artemisia dracunculus L. with good [...] Read more.

Due to the emergence of antibiotic-resistant pathogens, the need to find new, efficient antimicrobial agents is rapidly increasing. Therefore, in this study, we report the development of new biocomposites based on zinc-doped hydroxyapatite/chitosan enriched with essential oil of Artemisia dracunculus L. with good antimicrobial activity. Techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) were used in order to evaluate their physico-chemical properties. Our studies revealed that biocomposite materials with nanometric dimension and homogeneous composition could be obtained through an economic and cost-effective synthesis method. The biological assays demonstrated that ZnHA (zinc-doped hydroxyapatite), ZnHACh (zinc-doped hydroxyapatite/chitosan) and ZnHAChT (zinc-doped hydroxyapatite/chitosan enriched with essential oil of Artemisia dracunculus L.) did not exhibit a toxic effect on the cell viability and proliferation of the primary osteoblast culture (hFOB 1.19). Moreover, the cytotoxic assay also highlighted that the cell morphology of the hFOB 1.19 was not altered in the presence of ZnHA, ZnHACh or ZnHAChT. Furthermore, the in vitro antimicrobial studies emphasized that the samples exhibited strong antimicrobial properties against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Candida albicans ATCC 10231 microbial strains. These results are encouraging for the following development of new composite materials with enhanced biological properties that could promote the osteogenic process of bone healing and also exhibit good antimicrobial properties. Full article

(This article belongs to the Special Issue Emerging Marine Biopolymer-Based Materials: Extraction to Application)

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12 pages, 4326 KiB

Open AccessArticle

Preparation of Amphiphilic Chitosan-Loaded Bentonite Adsorbent and Its Performance in Removing Organic Matter from Coking Wastewater

by Zhou Zhu, Haiqun Kou, Yuchang Zhou, Xindian Lan, Meiying Yu and Haonan Chen

Polymers 2023, 15(6), 1588; https://doi.org/10.3390/polym15061588 - 22 Mar 2023

Viewed by 950

Abstract

An amphiphilic chitosan-loaded bentonite adsorbent (C18CTS−BT) was prepared for the efficient removal of organic matter from coking wastewater. The structure and surface morphology of adsorbents were characterized by FT−IR, XRD, and SEM. The removal of those organics by C18CTS−BT was investigated by comparing [...] Read more.

An amphiphilic chitosan-loaded bentonite adsorbent (C18CTS−BT) was prepared for the efficient removal of organic matter from coking wastewater. The structure and surface morphology of adsorbents were characterized by FT−IR, XRD, and SEM. The removal of those organics by C18CTS−BT was investigated by comparing the adsorption performances of C18CTS−BT with bentonite (BT) and chitosan-loaded bentonite (CTS−BT). The results showed that compared with BT and CTS−BT, C18CTS−BT showed the performance advantages of having a low dosage, wide pH range, and short adsorption equilibrium time. The optimized treatment process was as follows: the adsorbent dosage was 1.5 g·L⁻¹, the adsorption time was 60 min, and the pH of the system was 7.0. The chemical oxygen demand (COD) of the coking wastewater treated with BT, CTS−BT, and C18CTS−BT decreased from 342 mg·L⁻¹ in the raw water to 264 mg·L⁻¹, 218 mg·L⁻¹, and 146 mg·L⁻¹, corresponding to COD removal rates of 22.81%, 36.26%, and 57.31%, respectively. The results of GC−MS analysis also confirmed that C18CTS−BT could remove most of the organic compounds in coking wastewater, especially long−chain alkanes and their derivatives. The hydrophobic modification of the adsorbent material can effectively improve the removal performance of organic compounds from coking wastewater. Full article

(This article belongs to the Special Issue Emerging Marine Biopolymer-Based Materials: Extraction to Application)

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15 pages, 5879 KiB

Open AccessArticle

The Influence of Azidated Glycerol as a New Low Temperature Stabilizer on the Colloidal Properties of Natural Rubber Latex: For Latex Marine Transportation

by A. S. Siti Nuraya, A. A. Azniwati, A. Baharin, A. R. Azura and M. F. Yhaya

Polymers 2023, 15(3), 698; https://doi.org/10.3390/polym15030698 - 30 Jan 2023

Viewed by 1352

Abstract

Natural rubber latex (NRL) is normally transported to a destination in colloid/liquid form. It requires large storage containers such as drums and the probability of latex leakage during transportation is high. This is prevalent especially when transporting latex by sea. To prevent latex [...] Read more.

Natural rubber latex (NRL) is normally transported to a destination in colloid/liquid form. It requires large storage containers such as drums and the probability of latex leakage during transportation is high. This is prevalent especially when transporting latex by sea. To prevent latex spillage, the liquid form of NRL is transformed into solid/frozen latex by freezing. However, the coagulation/destabilization of NRL by freezing has been acknowledged as a problem for years. Therefore, this study proposed a new low temperature stabilizer named azidated glycerol (AG) to be incorporated in NRL liquid before the freezing process. AG was prepared by a chemical reaction of pure glycerol with sodium azide. NRL containing AG was then frozen at a temperature of −4 °C. After 24 h of freezing, the frozen latex was thawed at ambient temperature for 1 h followed by heating in a water bath at 40 °C for another 1 h. The regenerated latex was then allowed to stand at room temperature before testing. The effect of AG on the colloid properties before and after the freeze–thaw processes was studied. The production of AG was confirmed by the appearance of a peak in the range of 2160–2120 cm⁻¹, corresponding to N=N=N stretching, confirming the introduction of an azide group into the glycerol molecule. Modifying NRL with AG did not significantly influence the TSC of latex. Increasing the AG content up to 0.4 phr resulted in an increase in MST from 699 s to 828 s. An AG content of 0.2 phr resulted in the highest anionically stabilized latex as indicated by zeta potential values of −59.63 mV (before freezing) and −56.27 mV (after thawing). It is concluded that the AG produced in this study can be used as an anti-freeze stabilizer for NRL and is suitable for latex marine transportation. Full article

(This article belongs to the Special Issue Emerging Marine Biopolymer-Based Materials: Extraction to Application)

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20 pages, 9717 KiB

Open AccessArticle

Enhanced Functional Properties of Bioplastic Films Using Lignin Nanoparticles from Oil Palm-Processing Residue

by Samsul Rizal, Tata Alfatah, H. P. S. Abdul Khalil, Esam Bashir Yahya, C. K. Abdullah, Eka Marya Mistar, Ikramullah Ikramullah, Rudi Kurniawan and R. D. Bairwan

Polymers 2022, 14(23), 5126; https://doi.org/10.3390/polym14235126 - 25 Nov 2022

Cited by 8 | Viewed by 2805

Abstract

The development of bioplastic materials that are biobased and/or degradable is commonly presented as an alleviating alternative, offering sustainable and eco-friendly properties over conventional petroleum-derived plastics. However, the hydrophobicity, water barrier, and antimicrobial properties of bioplastics have hindered their utilization in packaging applications. [...] Read more.

The development of bioplastic materials that are biobased and/or degradable is commonly presented as an alleviating alternative, offering sustainable and eco-friendly properties over conventional petroleum-derived plastics. However, the hydrophobicity, water barrier, and antimicrobial properties of bioplastics have hindered their utilization in packaging applications. In this study, lignin nanoparticles (LNPs) with a purification process were used in different loadings as enhancements in a Kappaphycus alvarezii matrix to reduce the hydrophilic nature and improve antibacterial properties of the matrix and compared with unpurified LNPs. The influence of the incorporation of LNPs on functional properties of bioplastic films, such as morphology, surface roughness, structure, hydrophobicity, water barrier, antimicrobial, and biodegradability, was studied and found to be remarkably enhanced. Bioplastic film containing 5% purified LNPs showed the optimum enhancement in almost all of the ultimate performances. The enhancement is related to strong interfacial interaction between the LNPs and matrix, resulting in high compatibility of films. Bioplastic films could have additional advantages and provide breakthroughs in packaging materials for a wide range of applications. Full article

(This article belongs to the Special Issue Emerging Marine Biopolymer-Based Materials: Extraction to Application)

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18 pages, 193791 KiB

Open AccessArticle

Hydrophobicity and Biodegradability of Silane-Treated Nanocellulose in Biopolymer for High-Grade Packaging Applications

by Indra Surya, C. M. Hazwan, H. P. S. Abdul Khalil, Esam Bashir Yahya, A. B. Suriani, Mohammed Danish and Azmi Mohamed

Polymers 2022, 14(19), 4147; https://doi.org/10.3390/polym14194147 - 03 Oct 2022

Cited by 7 | Viewed by 2393

Abstract

The growing concern about pollution produced by plastic waste and the consequent environmental dangers has led to increased interest in replacing plastics with sustainable and biodegradable alternatives. Biopolymers such as seaweed have been examined for their film-forming characteristics to make edible films for [...] Read more.

The growing concern about pollution produced by plastic waste and the consequent environmental dangers has led to increased interest in replacing plastics with sustainable and biodegradable alternatives. Biopolymers such as seaweed have been examined for their film-forming characteristics to make edible films for packaging applications. This study aimed to prepare biopolymeric packaging films through a solvent-casting process using natural red seaweed (Kappaphycus alvarezii) and kenaf cellulose nanofiber (CNF), followed by film surface treatment using silane. The hydrophobic properties of the seaweed/CNF biopolymer were examined through water solubility (WS), moisture absorption capacity (MAC), water vapor permeability (WVP), and contact angle (CA) measurements. Fourier transform infra-red (FT-IR) film spectra clearly showed successful modification of the seaweed film (SF) by silane and the incorporation of kenaf CNF over the surface of the seaweed film. The wettability-related analysis showed positive results in determining the modified film’s hydrophobicity properties. Film degradation analysis using the soil burial method showed a lower degradation rate for films with a higher CNF loading. Overall, the characterization results of the seaweed/CNF biopolymer film predicted hydrophobicity properties. The slow degradation rate was improved with surface modification using silane treatment and the incorporation of kenaf CNF filler with the seaweed matrix. As a result, we found that the seaweed/CNF biopolymer film could be used as high-grade packaging material in many potential applications. Full article

(This article belongs to the Special Issue Emerging Marine Biopolymer-Based Materials: Extraction to Application)

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16 pages, 3499 KiB

Open AccessArticle

Chitosan and Sodium Alginate Implementation as Pharmaceutical Excipients in Multiple-Unit Particulate Systems

by Martina Čierna, Pavel Mučaji, Miroslava Špaglová, Mária Čuchorová and Oliver Macho

Polymers 2022, 14(14), 2822; https://doi.org/10.3390/polym14142822 - 11 Jul 2022

Cited by 4 | Viewed by 1907

Abstract

This study aimed to prepare and evaluate pellets containing acyclovir as a model drug. Pellets were prepared by the extrusion–spheronization process. Aqueous solutions of natural marine polymers (sodium alginate, chitosan) were compared to semi-synthetic hydroxypropyl methylcellulose (HPMC) in the role of binders. The [...] Read more.

This study aimed to prepare and evaluate pellets containing acyclovir as a model drug. Pellets were prepared by the extrusion–spheronization process. Aqueous solutions of natural marine polymers (sodium alginate, chitosan) were compared to semi-synthetic hydroxypropyl methylcellulose (HPMC) in the role of binders. The study focused on the characterization of the pellet properties that are crucial for the formulation of the final dosage form, such as in multi-unit pellet system (MUPS) tablets or hard gelatin capsules filled with the pellets. Finally, the mentioned dosage forms were tested for drug dissolution. The morphology of pellets observed by scanning electron microscopy correlated with the shape evaluation performed by dynamic image analysis. Sodium alginate pellets exhibited the lowest value of sphericity (0.93), and many elongated rods and dumbbells were observed in this batch. Chitosan pellets had the highest value of sphericity (0.97) and were also less rough on the surface. The pellets maintained a constant surface geometry during the dissolution studies; they only reduced in size. The most significant reduction in size and weight was assessed after 2 h of dissolution testing. This fact was in line with the drug release from pellets in capsules or MUPS tablets, which was massive during the first hour, in both cases. The dissolution profiles of all of the batches were comparable. Full article

(This article belongs to the Special Issue Emerging Marine Biopolymer-Based Materials: Extraction to Application)

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13 pages, 2501 KiB

Open AccessArticle

Properties Enhancement of Oil Palm Trunk Plywood against Decay and Termite for Marine Applications

by Atikah Che Ismail, Sabiha Salim, Paridah Md Tahir, Seng Hua Lee, Muhammad Aizat Abd Ghani, Syeed SaifulAzry Al Edrus and Fadhlin Qayyum Ahmad Faisal

Polymers 2022, 14(13), 2680; https://doi.org/10.3390/polym14132680 - 30 Jun 2022

Cited by 1 | Viewed by 1558

Abstract

Oil palm trunk (OPT) veneers have the potential to be used in the production of plywood for marine applications. However, OPT is not resistant to fungal decay and termites, limiting its use in the production of marine plywood. As a result, in this [...] Read more.

Oil palm trunk (OPT) veneers have the potential to be used in the production of plywood for marine applications. However, OPT is not resistant to fungal decay and termites, limiting its use in the production of marine plywood. As a result, in this study, phenolic resin treatment was used to improve the biological durability of OPT and produce marine grade equivalent (MGE) plywood. The OPT veneer was treated with medium molecular weight phenol formaldehyde (MmwPF) resin. The results showed that MmwPF resin with a solid content of 30% resulted in higher weight percent gain and polymer retention. Veneers treated with 30% MmwPF resin were then pressed for more than 10 min at temperatures above 140 °C. Dimensional stability, shear strength, bending strength, fungal decay resistance, and termite resistance were all tested on the plywood produced. The results of this study revealed that MGE plywood has satisfactory bonding quality and excellent biological durability. Good bending strength was recorded for the MGE plywood with modulus of rupture and modulus of elasticity ranged between 31.03 and 38.85 MPa and 4110 and 5120 MPa, respectively. Rubberwood, as a reference sample in this study, is not durable (Class 5) against white rot fungi and is moderately durable (Class III) against subterranean termite attacks. Interestingly, MGE plywood produced in this study was found very durable (Class 1) against white rot fungi. It is also durable (Class II) and very durable (Class I) against termite attacks, depending on the pressing parameters employed. Based on their outstanding bonding quality, bending strength, and biological durability, the study confirmed the feasibility of OPT plywood for marine applications. Full article

(This article belongs to the Special Issue Emerging Marine Biopolymer-Based Materials: Extraction to Application)

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