Mechanical and thermal properties of carboxymethyl fibers (CMF)/PVA based nanocomposite membranes

Double-skeleton interpenetrating network-structured alkaline solid-state electrolyte enables flexible zinc-air batteries with enhanced power density and long-term cycle life

The alkaline solid-state electrolytes have received widespread attention for their good safety and electrochemical stability. However, they still suffer from low conductivity and poor mechanical properties. Herein, we report the synthesis of double-network featured hydroxide-conductive membranes fabricated by polyvinyl alcohol (PVA) and chitosan (CS) as the double-skeletons. Then, we implanted quaternary ammonium salt guar hydroxypropyltrimonium chloride (GG) as the OH- conductor for high-performance electrochemical devices. By virtue of the unique stripe-like structure shared from the double skeleton with a high degree of compatibility and stronger hydrogen bond interactions, the polyvinyl alcohol/chitosan-guar hydroxypropyltrimonium chloride (PCG) solid-state electrolytes achieved optimal thermal stability (> 300 °C), mechanical property (∼ 34.15 MPa), dimensional stability (at any bending angle), and high ionic conductivity (13 mS cm-1) and ion mobility number (tion ∼ 0.90) compared with chitosan-guar hydroxypropyltrimonium chloride (CG) and polyvinyl alcohol-guar hydroxypropyltrimonium chloride (PG) electrolyte membrane. As a proof-of-concept application, the "sandwich"-type zinc-air battery (ZAB) assembled using PCG membrane as the electrolyte realized a high open-circuit voltage (1.39 V) and an excellent power density (128 mW cm-2). Notably, in addition to its long-term cycle life (30 h, 2 mA cm-2) and stable discharge plateau (12 h, 5 mA cm-2), it could even enable a flexible ZAB (F-ZAB) to readily power light-emitting diodes (LED) at any bending angle. These merits afford the PCG membrane a promising electrolyte for improving the performance of solid-state batteries.

A review of cellulose-based derivatives polymers in fabrication of gas separation membranes: Recent developments and challenges

Due to low-cost, sustainability and good mechanical stability, cellulose-based materials are frequently used in fabrication of polymeric gas separation membrane as potential carbohydrate polymers to substitute traditional petrochemical-based materials. In this review, the performance of cellulose-based polymeric membranes i.e. cellulose acetate, cellulose diacetate, cellulose triacetate, ethyl cellulose and carboxymethyl cellulose in the separation of different gases were investigated. This review paper provides the main features and advantages in the fabrication of cellulose-based gas separation membranes. The influence of the functionalization of cellulose on gas separation and permeability performance of related membranes is considered. Influence of different modification procedures such as blending with polymers, nanomaterials and ionic liquids on the gas separation ability of cellulose-based membranes were reviewed. Moreover, a brief inquiry of the potential of cellulose-based gas separation membranes for industrial applications, by examining the performance of different cellulose derivatives and identifying potential strategies for membrane modification and optimization are given, along with the current restrictions and the future perspectives are discussed.

Polyvinyl Alcohol/Nafion®-Zirconia Phosphate Nanocomposite Membranes for Polymer Electrolyte Membrane Fuel Cell Applications: Synthesis and Characterisation

PVA (polyvinyl alcohol)-ZrP (PVA/ZrP) and Nafion®/PVA-ZrP nanocomposite membranes were synthesised using the recasting method with glutaraldehyde (GA) as a crosslinking agent. The resulting nanocomposite membranes were characterised using a variety of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results of SEM revealed well-distributed zirconia phosphate (ZrP) within the membrane matrix, and the SEM images showed a uniform and dense membrane structure. Because ZrP nanoparticles are hydrophilic, the Nafion®/PVA-ZrP nanocomposite membrane had a higher water uptake of 53% at 80 °C and higher 0.19 S/cm proton conductivity at room temperature than the commercial Nafion® 117 membrane, which had only 34% and 0.113 S/cm, respectively. In comparison to commercial Nafion® 117 membranes, PVA-ZrP and Nafion®/PVA-ZrP nanocomposite membranes had a higher thermal stability and mechanical strength and lower methanol crossover due to the hydrophilic effect of PVA crosslinked with GA, which can make strong hydrogen bonds and cause an intense intramolecular interaction.

Construction of Marigold-like Poly(vinyl alcohol) Microspheres for Catalytic Microreactors

It has long been pursued to develop polymer microspheres with various special morphologies and structures for better results in applications such as catalysis, drug delivery, and bioscaffolds. However, it remains a challenge to develop a facile method to produce poly(vinyl alcohol) (PVA) microspheres with special morphologies. Herein, a micron-sized marigold-like poly(vinyl alcohol) (CE-PVATPA) microsphere was engineered and fabricated by a feasible strategy, that is, emulsification-cross-linking, freeze-drying, and secondary acetal reaction steps. The morphological evolution of microspheres was systematically investigated under different conditions, and the procedure of constructing PVA microspheres with stabilizing marigold-like structures was proposed. More importantly, a specially structured PVA microsphere microreactor synergistically loading palladium metal nanoparticles (CE-PVATPA@Pd) for the heterogeneous catalyst 4-nitrophenol (4-NP) could be further demonstrated, which indicated high catalytic activity and excellent recyclability. The resultant stabilized fabricating method is promising to provide valuable guidance for the design and fabrication of a high-performance PVA microsphere microreactor.

Efficiency evaluation of titanium oxide nanocomposite membrane in adsorption of chromium from oil effluents

Reverse osmosis and nanofiltration (NF) are the essential physical separation technologies used to remove contaminants from liquid streams. A hybrid of nanofiltration and forward osmosis (FO) was used to increase the removal efficiency of heavy metals in synthesized oil effluents. Thin-film nanocomposite (TFN) membranes were synthesized by applying surface polymerization on a polysulfone substrate to use in the forward osmosis process. The impact of different membrane fabrication conditions such as time, temperature, and pressure on effluent flux, the effect of different concentrations of the heavy metal solution on adsorption rate and sedimentation rate, the impact of TiO₂ nanoparticles on the performance and structure of forward osmosis membranes were investigated. The morphology, composition, and properties of TiO₂ nanocomposites made by the infrared spectrometer and X-ray diffraction (XRD) were studied. Kinetic modeling and Langmuir, Freundlich, and Tamkin relationships were used to draw adsorption isotherms and evaluate adsorption equilibrium data. The results indicated that pressure and temperature directly affect water outlet flux, and time affects it indirectly. Evaluating the isothermal relationships revealed that chromium adsorption from the TFN 0.05 ppm membrane and thin-film composite (TFC) membrane follows the Langmuir model with correlation coefficients of 0.996 and 0.995, respectively. The significant removal of heavy metals and the acceptable amount of water flux demonstrated the appropriate potential of the titanium oxide nanocomposite membrane, which can be used as an effective adsorbent to remove chromium from aqueous solutions.

A charged nanocomposite membrane via co-deposition of gallic acid and polyethyleneimine-silver for improving separation and antibacterial properties

Pharmaceuticals have been continuously detected from surface water and groundwater. In order to improve the rejection performance of pharmaceuticals by a nanofiltration membrane (NF), a positively charged membrane was prepared by co-deposition of natural gallic acid and polyethyleneimine on the polyacrylonitrile hydrolysis membrane. Effects of gallic acid concentration, polyethylene imine concentration, reaction time, and the molecular weight of polyethylene imine were documented. The physical and chemical properties of the membrane were also investigated by surface morphology, hydrophilicity, surface charge, and molecular weight cut-off. The optimized membrane had a molecular weight cut-off of about 958 Da and possessed a pure water permeability of 74.21 L·m^-2·h^-1·MPa^-1. The results exhibited salt rejection in the following order: MgCl₂ > CaCl₂ > MgSO₄ > Na₂CO₃ > NaCl > Na₂SO₄, while the rejection ability of pharmaceuticals is as follows: amlodipine > atenolol > carbamazepine > ibuprofen, suggesting that the positively charged membrane has enhanced retention to both divalent cations and charged pharmaceuticals. In addition, the antibacterial membrane was obtained by loading silver nanoparticles onto the positively charged membrane, which greatly improved the antibacterial ability of the membrane.

Study on cellulose nanofibers/aramid fibers lithium-ion battery separators by the heterogeneous preparation method

In this study, a heat-resistant and high-wettability lithium-ion batteries separator (PI-CPM-PI) composed of cellulose nanofibers (CNF) and aramid fibers (PMIA chopped fiber/PPTA pulp) with the reinforced concrete structure was fabricated via a traditional heterogeneous paper-making process. CNF played crucial roles in optimizing the pore structure and improving the wettability of PI-CPM-PI separator. The effects of composition on separator properties were investigated and the results indicated that the optimal compositions were 0.5 wt% CNF, 0.5 wt% PMIA chopped fiber/PPTA pulp (ratio of 5:5), 0.05 wt% diatomite and 1.5 wt% polyimide. Relevant tests demonstrated that the performance advantages of PI-CPM-PI separators were exhibited at the wettability and thermal stability compared to the commercial separator (PP). Additionally, batteries assembled with PI-CPM-PI separators showed excellent electrochemical and cycling performance (ionic conductivity of 1.041 mS.cm^-1, the first discharge capacity of 158.2 mAh.g^-1 at 0.2C and capacity retention ratio of 99.76 % after 100 cycles).

A novel Ag2O-TiO2-Bi2WO6/polyvinyl alcohol composite film with ethylene photocatalytic degradation performance towards banana preservation

In this research, the Ag₂O-TiO₂-Bi₂WO₆(ATB) ternary heterojunction photocatalyst was synthesized by hydrothermal and surface deposition method, and the ATB/PVA composite film with ethylene photocatalytic degradation performance was constructed by the casting method. The structure and properties of ATB and ATB/PVA films were characterized and applied to banana preservation. The results showed that the addition of ATB could improve the mechanical properties, thermal stability, oxygen and moisture resistance, and reduce the crystallinity and light transmittance of PVA films. Compared with TiO₂, Bi₂WO₆ and TB photocatalysts, ATB had the best photocatalytic degradation effect of ethylene under LED light. Compared with blank group, the ethylene concentration decreased by 17.17%. This was mainly attributed to the formation of heterostructure among Ag₂O, TiO₂ and Bi₂WO₆, which promoted the separation and transfer of photogenerated carriers. The ATB/PVA composite coating could effectively prevent the respiration of the bananas by inhibiting gas exchange and degrading ethylene, which reduced the weight loss, inhibited glycogen decomposition, improved the pulp hardness, increased titratable acid content, reduced the PPO activity, hindered the phenol oxidation and keep better apparent color of bananas. The safety study suggested that the ATB/PVA film is safe for bananas packaging application.

Preparation and Application of Nb2O5 Nanofibers in CO2 Photoconversion

Increasing global warming due to NOx, CO2, and CH4, is significantly harming ecosystems and life worldwide. One promising methodology is converting pollutants into valuable chemicals via photocatalytic processes (by reusable photocatalysts). In this context, the present work aimed to produce a Nb2O5 photocatalyst nanofiber system by electrospinning to convert CO2. Based on the collected data, the calcination at 600 ∘C for 2 h resulted in the best condition to obtain nanofibers with homogeneous surfaces and an average diameter of 84 nm. As a result, the Nb2O5 nanofibers converted CO2 mostly into CO and CH4, reaching values around 8.5 μmol g−1 and 0.55 μmol g−1, respectively.

Sustainable functionalized metal-organic framework NH2-MIL-101(Al) for CO2 separation under cryogenic conditions

In this study, a sustainable NH₂-MIL-101(Al) is synthesized and subjected to characterization for cryogenic CO₂ adsorption, isotherms, and thermodynamic study. The morphology revealed a highly porous surface. The XRD showed that NH₂-MIL-101(Al) was crystalline. The NH₂-MIL-101(Al) decomposes at a temperature (>500 °C) indicating excellent thermal stability. The BET investigation revealed the specific surface area of 2530 m²/g and the pore volume of 1.32 cm³/g. The CO₂ adsorption capacity was found to be 9.55 wt% to 2.31 wt% within the investigated temperature range. The isotherms revealed the availability of adsorption sites with favorable adsorption at lower temperatures indicating the thermodynamically controlled process. The thermodynamics showed that the process is non-spontaneous, endothermic, with fewer disorders, chemisorption. Finally, the breakthrough time of NH₂-MIL-101(Al) is 31.25% more than spherical glass beads. The CO₂ captured by the particles was 2.29 kg m^-3. The CO₂ capture using glass packing was 121% less than NH₂-MIL-101(Al) under similar conditions of temperature and pressure.

Sustainable mixed matrix membranes containing porphyrin and polysulfone polymer for acid gas separations

The synergetic effect of nitrogen-rich and CO₂-philic filler and polymer in mixed matrix-based membranes (MMMs) can separate CO₂ competently. The introduction of well-defined nanostructured porous fillers of pores close to the kinetic diameter of the gas molecule and polymer matrix compatibility is a challenge in improving the gas transportation characteristics of MMMs. This study deals with the preparation of porphyrin filler and the polysulfone (PSf) polymer MMMs. The fillers demonstrated uniform distribution, uniformity, and successful bond formation. MMMs demonstrated high thermal stability with a glass transition temperature in the range of 480-610 °C. The porphyrin filler exhibited microporous nature with the presence of π-π bonds and Lewis's basic functionalities between filler-polymer resulted in a highly CO₂-philic structure. The pure and mixed gas permeabilities and selectivity were successfully improved and surpass the Robeson's upper bound curve's tradeoff. Additionally, the temperature influence on CO₂ permeability revealed lower activation energies at higher temperatures leading to the gas transport facilitation. This can be granted consistency and long-term durability in polymer chains. These results highlight the unique properties of porphyrin fillers in CO₂ separation mixed matrix membranes and offer new knowledge to increase comprehension of PSf performance under various contents or environments.