Development of novel iota carrageenan-g-polyvinyl alcohol polyelectrolyte membranes for direct methanol fuel cell application

Green heterogeneous catalyst based on cross-linked carrageenans for direct conversion of fructose to ethyl levulinate

Ethyl levulinate (EL) is a biomass-derived compound, capable of being converted to an array of costly compounds and therefore is attracted by many researchers. In the present study, κ and ι-carrageenan grafted methylenebisacrylamide (MBA) catalysts (κC-g-MBA and ιC-g-MBA) were prepared and applied to convert fructose to EL. FT-IR spectroscopy, XRD of both low-angle and wide-angle, N2 adsorption-and-desorption, FESEM, and TGA were used to identify the catalysts. From the catalysts, κC-g-MBA and ιC-g-MBA revealed the desirable results for EL with 80 and 82 % yields, respectively. The various parameters like reaction temperature, time, catalyst quantity, and the original fructose quantity were studied. Furthermore, experimental design was employed to create the ideal conditions for the reaction temperature 180 °C for the reaction, 5 h for the duration of the reaction, and 50 mg of catalyst for EL chosen. In addition, the catalyst's capability for reuse was explored and the catalyst was used repeatedly without a significant change in the catalyst activity.

Adsorption and antibacterial studies of a novel hydrogel adsorbent based on ternary eco-polymers doped with sulfonated graphene oxide developed from upcycled plastic waste

A novel ternary blended polymer composed of cost-effective and readily available polymers was synthesized using poly (vinyl alcohol) (PVA), iota carrageenan (IC), and poly (vinyl pyrrolidone) (PVP). Sulfonated graphene oxide (SGO), prepared from recycled drinking water bottles, was utilized as a doping agent. Varying amounts (1-3 wt%) were combined into the polymer matrix. The produced hydrogel film was examined as a potential adsorbent hydrogel film for the removal of methylene blue (MB) and Gentamicin sulfate (GMS) antibiotic from an aqueous solution. The experimental results demonstrate that the presence of SGO significantly increased the adsorption efficiency of PVA/IC/PVP hydrogel film. The antimicrobial tests revealed that the PVA/IC/PVP-3% SGO hydrogel film exhibited the most potent activity against all the tested pathogenic bacteria. However, the adsorption results for MB and GMS showed that the addition of 3 wt% SGO resulted in a removal percentage that was a two fold increase in the removal percentage compared with the undoped PVA/IC/PVP hydrogel film. Furthermore, the response surface methodology (RSM) model was utilized to examine and optimize several operating parameters, including time, pH of the solution, and initial pollutant concentration. The adsorption kinetics were better characterized by the pseudo-second-order kinetics model. The composite film containing 3 wt% SGO had a maximum adsorption capacity of 606 mg g-1 for MB and 654 mg g-1 for GMS, respectively. The generated nanocomposite hydrogel film demonstrated promising potential for application in water purification systems.

Green Synthesis of Cation Exchange Membranes: A Review

Cation exchange membranes (CEMs) play a significant role in the transition to a more sustainable/green society. They are important components for applications such as water electrolysis, artificial photosynthesis, electrodialysis and fuel cells. Their synthesis, however, is far from being sustainable, affecting safety, health and the environment. This review discusses and evaluates the possibilities of synthesizing CEMs that are more sustainable and green. First, the concepts of green and sustainable chemistry are discussed. Subsequently, this review discusses the fabrication of conventional perfluorinated CEMs and how they violate the green/sustainability principles, eventually leading to environmental and health incidents. Furthermore, the synthesis of green CEMs is presented by dividing the synthesis into three parts: sulfonation, material selection and solvent selection. Innovations in using gaseous SO3 or gas-liquid interfacial plasma technology can make the sulfonation process more sustainable. Regarding the selection of polymers, chitosan, cellulose, polylactic acid, alginate, carrageenan and cellulose are promising alternatives to fossil fuel-based polymers. Finally, water is the most sustainable solvent and many biopolymers are soluble in it. For other polymers, there are a limited number of studies using green solvents. Promising solvents are found back in other membrane, such as dimethyl sulfoxide, Cyrene™, Rhodiasolv® PolarClean, TamiSolve NxG and γ-valerolactone.

Self-extinguished and flexible cation exchange membranes based on modified K-Carrageenan/PVA double network hydrogels for electrochemical applications

It is highly desired and yet challenging to develop eco-friendly cation exchange membranes with a combination of good mechanical, electrochemical, and biocompatible properties with a rational economic efficiency for given applications. In this study, new biocompatible double network (DN) hydrogels were prepared based on a blend of modified K-Carrageenan (KC) and polyvinyl alcohol (PVA). Acrylic acid (AA)-grafted KC (KC-g-(PAA)) and (AA-co-tertbutyl acrylate (TBA))-grafted KC (KC-g-P(AA-co-TBA)) were synthesized through an in situ free radical copolymerization. The grafted copolymers were blended with PVA and mixed with ZrOCl₂/KCl and glutaraldehyde (Glu) as the physical and chemical cross-linkers, respectively to produce KC-g-P(AA)/PVA and KC-g-P(AA-co-TBA)/PVA DN hydrogels. The membranes were prepared by a solution casting method. Various techniques were carried out to compare the structural, thermal, mechanical, flammability, and electrochemical properties of the membranes with those of the cross-linked KC, PVA, and KC/PVA membranes. The KC-g-P(AA-co-TBA)/PVA DN membrane showed more desirable properties as the cation exchange membrane with water uptake of 70.7 %, ion exchange capacity of 0.47 meq H⁺ /g, the ionic conductivity of 1.99 × 10^-2 S/cm², and elongation at break of 71.8 %. The prepared biopolymer membrane is very cost-effective and self-extinguished with admissible conductivity for electrochemical applications.

Modified Cellulose Proton-Exchange Membranes for Direct Methanol Fuel Cells

A direct methanol fuel cell (DMFC) is an excellent energy device in which direct conversion of methanol to energy occurs, resulting in a high energy conversion rate. For DMFCs, fluoropolymer copolymers are considered excellent proton-exchange membranes (PEMs). However, the high cost and high methanol permeability of commercial membranes are major obstacles to overcome in achieving higher performance in DMFCs. Novel developments have focused on various reliable materials to decrease costs and enhance DMFC performance. From this perspective, cellulose-based materials have been effectively considered as polymers and additives with multiple concepts to develop PEMs for DMFCs. In this review, we have extensively discussed the advances and utilization of cost-effective cellulose materials (microcrystalline cellulose, nanocrystalline cellulose, cellulose whiskers, cellulose nanofibers, and cellulose acetate) as PEMs for DMFCs. By adding cellulose or cellulose derivatives alone or into the PEM matrix, the performance of DMFCs is attained progressively. To understand the impact of different structures and compositions of cellulose-containing PEMs, they have been classified as functionalized cellulose, grafted cellulose, acid-doped cellulose, cellulose blended with different polymers, and composites with inorganic additives.

Sustainable Microbial and Heavy Metal Reduction in Water Purification Systems Based on PVA/IC Nanofiber Membrane Doped with PANI/GO

Effective and efficient removal of both heavy metal pollutants and bacterial contamination from fresh water is an open issue, especially in developing countries. In this work, a novel eco-friendly functional composite for water treatment application was investigated. The composite consisted of electrospun nanofiber membrane from blended polyvinyl alcohol (PVA)/iota carrageenan (IC) polymers doped with equal concentrations of graphene oxide (GO) nanoparticles and polyaniline (PANI). The effectiveness of this composite as a water purification fixed-bed filter was optimized in a batch system for the removal of cadmium (Cd⁺²) and lead (Pb⁺²) ions, and additionally characterized for its antimicrobial and antifungal properties and cytotoxicity effect. The fiber nanocomposite exhibited efficient antibacterial activity, with maximum adsorption capacity of about 459 mg g⁻¹ after 120 min for Cd⁺² and of about 486 mg g⁻¹ after 90 min for Pb⁺². The optimized conditions for removal of both metals were assessed by using a response surface methodology model. The resulting scores at 25 °C were 91.4% (Cd⁺²) removal at 117 min contact time for 89.5 mg L⁻¹ of initial concentration and 29.6 cm² membrane area, and 97.19% (Pb⁺²) removal at contact time 105 min for 83.2 mg L⁻¹ of initial concentration and 30.9 cm² nanofiber composite membrane. Adsorption kinetics and isotherm followed a pseudo-second-order model and Langmuir and Freundlich isotherm model, respectively. The prepared membrane appears to be promising for possible use in domestic water purification systems.

Design of Promising Green Cation-Exchange-Membranes-Based Sulfonated PVA and Doped with Nano Sulfated Zirconia for Direct Borohydride Fuel Cells

The direct borohydride fuel cell (DBFC) is a low-temperature fuel cell that requires the development of affordable price and efficient proton exchange membranes for commercial purposes. In this context, super-acidic sulfated zirconia (SO₄ZrO₂) was embedded into a cheap and environmentally friendly binary polymer blend, developed from poly(vinyl alcohol) (PVA) and iota carrageenan (IC). The percentage of SO₄ZrO₂ ranged between 1 and 7.5 wt.% in the polymeric matrix. The study findings revealed that the composite membranes’ physicochemical features improved by adding increasing amounts of SO₄ZrO₂. In addition, there was a decrease in the permeability and swelling ratio of the borohydride membranes as the SO₄ZrO₂ weight% increased. Interestingly, the power density increased to 76 mW cm⁻² at 150 mA cm⁻², with 7.5 wt.% SO₄ZrO_2, which is very close to that of Nafion117 (91 mW cm⁻²). This apparent selectivity, combined with the low cost of the eco-friendly fabricated membranes, points out that DBFC has promising future applications.

Novel scaffold based graphene oxide doped electrospun iota carrageenan/polyvinyl alcohol for wound healing and pathogen reduction: in-vitro and in-vivo study

Wound healing is a complicated multicellular process that involves several kinds of cells including macrophages, fibroblasts, endothelial cells, keratinocytes and platelets that are leading to their differentiation towards an anti-inflammatory response for producing several chemokines, cytokine and growth factors. In this study, electrospun nanofiber scaffold named (MNS) is composed of polyvinyl alcohol (PVA)/iota carrageenan (IC) and doped with partially reduced graphene oxide (prGO) that is successfully synthesized for wound healing and skin repair. The fabricated MNS was tested in case of infection and un-infection with E. coli and Staphylococcus and in both of the presence and in the absence of yeast as a natural nutritional supplement. Numerous biochemical parameters including total protein, albumin, urea and LDH, and hematological parameters were evaluated. Results revealed that the MNS was proved to be effective on most of the measured parameters and had exhibited efficient antibacterial inhibition activity. Whereas it can be used as an effective antimicrobial agent in wound healing, however, histopathological findings confirmed that the MNS caused re-epithelialization and the presence of yeast induced hair follicles growth and subsequently it may be used to hide formed head wound scar.

Organic-Inorganic Novel Green Cation Exchange Membranes for Direct Methanol Fuel Cells

Commercializing direct methanol fuel cells (DMFC) demands cost-effective cation exchange membranes. Herein, a polymeric blend is prepared from low-cost and eco-friendly polymers (i.e., iota carrageenan (IC) and polyvinyl alcohol (PVA)). Zirconium phosphate (ZrPO4) was prepared from the impregnation–calcination method and characterized by energy dispersive X-ray analysis (EDX map), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM), then incorporated as a bonding and doping agent into the polymer blend with different concentrations. The new fabricated membranes were characterized by SEM, FTIR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and XRD. The results revealed that the membranes’ physicochemical properties (oxidative stability, tensile strength) are enhanced with increasing doping addition, and they realized higher results than Nafion 117 because of increasing numbers of hydrogen bonds fabricated between the polymers and zirconium phosphate. Additionally, the methanol permeability was decreased in the membranes with increasing zirconium phosphate content. The optimum membrane with IC/SPVA/ZrPO4-7.5 provided higher selectivity than Nafion 117. Therefore, it can be an effective cation exchange membrane for DMFCs applications.

Novel Crosslinked Sulfonated PVA/PEO Doped with Phosphated Titanium Oxide Nanotubes as Effective Green Cation Exchange Membrane for Direct Borohydride Fuel Cells

A direct borohydride fuel cell (DBFC) is a type of low temperature fuel cell which requires efficient and low cost proton exchange membranes in order to commercialize it. Herein, a binary polymer blend was formulated from inexpensive and ecofriendly polymers, namely polyethylene oxide (PEO) and poly vinyl alcohol (PVA). Phosphated titanium oxide nanotube (PO₄TiO₂) was synthesized from a simple impregnation-calcination method and later embedded for the first time as a doping agent into this polymeric matrix with a percentage of 1-3 wt%. The membranes' physicochemical properties such as oxidative stability and tensile strength were enhanced with increasing doping addition, while the borohydride permeability, water uptake, and swelling ratio of the membranes decreased with increasing PO₄TiO₂ weight percentage. However, the ionic conductivity and power density increased to 28 mS cm^-1 and 72 mWcm^-2 respectively for the membrane with 3 wt% of PO₄TiO₂ which achieved approximately 99% oxidative stability and 40.3 MPa tensile strength, better than Nafion117 (92% RW and 25 MPa). The fabricated membrane with the optimum properties (PVA/PEO/PO₄TiO₂-3) achieved higher selectivity than Nafion117 and could be efficient as a proton exchange membrane in the development of green and low cost DBFCs.

Poly(Vinyl Alcohol) Recent Contributions to Engineering and Medicine

Poly(vinyl alcohol) (PVA) is a thermoplastic synthetic polymer, which, unlike many synthetic polymers, is not obtained by polymerization, but by hydrolysis of poly(vinyl acetate) (PVAc). Due to the presence of hydroxylic groups, hydrophilic polymers such as PVA and its composites made mainly with biopolymers are used for producing hydrogels that possess interesting morphological and physico-mechanical features. PVA hydrogels and other PVA composites are studied in light of their numerous application for electrical film membranes for chemical separation, element and dye removal, adsorption of metal ions, fuel cells, and packaging. Aside from applications in the engineering field, PVA, like other synthetic polymers, has applications in medicine and biological areas and has become one of the principal objectives of the researchers in the polymer domain. The review presents a few recent applications of PVA composites and contributions related to tissue engineering (repair and regeneration), drug carriers, and wound healing.

Synthesis and Characterization of Novel Green Hybrid Nanocomposites for Application as Proton Exchange Membranes in Direct Borohydride Fuel Cells

Organic–inorganic nanocomposite membranes for potential application in direct borohydride fuel cells (DBFCs) are formulated from sulfonated poly(vinyl alcohol) (SPVA) with the incorporation of (PO4-TiO2) and (SO4-TiO2) nanotubes as doping agents. The functionalization of PVA to SPVA was done by using a 4-sulfophthalic acid as an ionic crosslinker and sulfonating agent. Morphological and structural characterization by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) confirmed the successful synthesis of the doping agents and their incorporation into the polymer. The influence of PO4-TiO2 and SO4-TiO2 doping and their content on the physicochemical properties of the nanocomposite membranes was evaluated. Swelling degree and water uptake gradually reduced to 7% and 13%, respectively, with increasing doping agent concentration. Ion exchange capacity and ionic conductivity of the membrane with 3 wt.% doping agents were raised 5 and 7 times, respectively, compared to the undoped one. The thermal and oxidative stability and tensile strength also increased with the doping content. Furthermore, lower borohydride permeability (0.32 × 10−6 cm2 s−1) was measured for the membranes with higher amount of inorganic doping agents when compared to the undoped membrane (0.71 × 10−5 cm2 s−1) and Nafion®117 (0.40 × 10−6 cm2 s−1). These results pave the way for a green, simple and low-cost approach for the development of composite membranes for practical DBFCs.