Structure and Properties of Novel Fibers Spun from Cellulose in NaOH/Thiourea Aqueous Solution

Influence of natural cellulose on hydroxyl radical generation by abiotic oxidation of pyrite under acidic conditions

Natural cellulose is one of the most important substances coexisting on the surface of pyrite. Oxidation of pyrite produces hydroxyl radicals (•OH). In this study, a pyrite-cellulose binary system was constructed with natural cellulose to investigate the effect of cellulose on the mechanism of •OH generation via oxidation of pyrite, and the mechanism for abiotic oxidative •OH production by pyrite under the influence of cellulose was investigated with oxidation and quenching experiments and characterization techniques. It was demonstrated that cellulose was chemisorbed onto the pyrite surface and some of the Fe(II) on the pyrite surface was masked, thus inhibiting the reaction between pyrite and O2 and decreasing the •OH production level from 33.54 to 22.48 μM under oxic conditions. In addition, the cellulose caused SS bond breakage, resulting in defects on the pyrite surface, which oxidized H2O to produce •OH in anoxic conditions. Therefore, under anoxic conditions, cellulose promoted the production of •OH and increased the •OH content from 11.85 to 14.78 μM. In addition to •OH, pyrite oxidation also produced SO42-. The amount of SO42- produced by a single pyrite crystal was less than that produced in the pyrite-cellulose system in all cases, and the amount produced under oxic conditions was approximately 10 times greater than that produced under anoxic conditions. More sulfate production indicated more sulfur intermediates during the reaction, such as S2O32-, which may decompose to produce S0 or Sn2- adsorbed on pyrite and decrease the amount of •OH produced. During the oxidation of pyrite by H2O2, cellulose competed with pyrite to react with H2O2, which inhibited the reaction between pyrite and H2O2 and decreased •OH production. Therefore, natural cellulose influenced the abiotic oxidation of pyrite to produce •OH.

Application of cellulose to chromatographic media: Cellulose dissolution, and media fabrication and derivatization

As the cornerstone of chromatographic technology, the development of high-performance chromatographic media is a crucial means to enhance the purification efficiency of biological macromolecules. Cellulose is a popular biological separation medium due to its abundant hydroxyl group on the surface, easy modification and, weak non-specific adsorption. In this paper, the development of cellulosic solvent systems, typical preparation methods of cellulosic chromatographic media, and the enhancement of chromatographic properties of cellulosic chromatographic media by polymeric ligand grafting strategies and their mechanism of action are reviewed. Ultimately, based on the current research status, a promising outlook for the preparation of high-performance cellulose-based chromatographic media was presented.

KOH/thiourea aqueous solution: A potential solvent for studying the dissolution mechanism and chain conformation of corn starch

Non-derivatizing, high-efficiency and low-toxicity solvents are important for studying the dissolution behavior and potential applications of starch. In this study, we investigated the starch dissolution mechanism and molecular conformation in KOH/thiourea aqueous solutions and compared these with KOH/urea and KOH aqueous solutions. Solubility analysis revealed that the KOH/thiourea solution demonstrates a better ability to dissolve corn starch than KOH/urea and KOH solutions. Rheological behavior and dynamic and static light scattering indicated that starch is stable in KOH/thiourea solution and exists as a regular star structure. Fourier transform infrared spectroscopy, ¹³C NMR, and molecular dynamics simulations indicated that hydrated K⁺ and OH^- destroy the strong starch hydrogen bond interactions; thiourea hydrate self-assembles into a shell surrounding the starch-KOH complex through interaction with KOH, whereas there is no direct strong interaction between urea and KOH. Therefore, adding thiourea to a KOH solution can promote dissolution and prevent self-aggregation of the starch chain.

Utilization of Cellulose to Its Full Potential: A Review on Cellulose Dissolution, Regeneration, and Applications

As the most abundant natural polymer, cellulose is a prime candidate for the preparation of both sustainable and economically viable polymeric products hitherto predominantly produced from oil-based synthetic polymers. However, the utilization of cellulose to its full potential is constrained by its recalcitrance to chemical processing. Both fundamental and applied aspects of cellulose dissolution remain active areas of research and include mechanistic studies on solvent-cellulose interactions, the development of novel solvents and/or solvent systems, the optimization of dissolution conditions, and the preparation of various cellulose-based materials. In this review, we build on existing knowledge on cellulose dissolution, including the structural characteristics of the polymer that are important for dissolution (molecular weight, crystallinity, and effect of hydrophobic interactions), and evaluate widely used non-derivatizing solvents (sodium hydroxide (NaOH)-based systems, N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl), N-methylmorpholine-N-oxide (NMMO), and ionic liquids). We also cover the subsequent regeneration of cellulose solutions from these solvents into various architectures (fibers, films, membranes, beads, aerogels, and hydrogels) and review uses of these materials in specific applications, such as biomedical, sorption, and energy uses.

Development of cellulose-based polymeric structures using dual functional ionic liquids

Carboxylate ionic liquids (ILs) combining benzethonium (BE) and didecyldimethylammonium (DDA) as cations have been explored to be used for the first time as dual functional solvents for microcrystalline cellulose (MCC) dissolution and, subsequently development of polymeric structures. Considering that some ILs can remain in the polymeric structures after phase inversion, these ILs can offer advantages such as antibacterial/antimicrobial response and ability to disrupt H-bonds. In this context, all tested ILs have been able to dissolve MCC up to a concentration of 4% (w/w), resulting in different polymeric structures, such as gel-like or films, depending on the type of IL and the ratio between MCC and IL. Furthermore, FTIR spectroscopy showed that some IL remains in the polymeric structures, which can enhance their application in the biomedical field.

Production of rayon fibres from cellulosic pulps: State of the art and current developments

The increasing demand for cellulosic fibres is continuously driven by the growing earth population and requirements of the textile industry. The annual cotton production of ca. 25 million tons is no longer enough to meet the market demands. This market gap of cellulosic fibres is progressively filled by regenerated cellulosic fibres derived from the dissolving pulp. The conventional industrial process of viscose production is far from being environmentally friendly due to the use of hazardous reagents. Alternatively, new trends in the production of regenerated fibres are related to the direct dissolution of cellulose in appropriate environmentally sound recyclable solvents, allowing high quality rayon fibres. This article reviews the sources of dissolving pulps used for the production of viscose and its quality parameters related to the performance of viscose production. The prospective cellulose regeneration processes, both commercialized and under development, are reviewed regarding current and future developments in the area.

Characterization the structural property and degradation behavior of corn starch in KOH/thiourea aqueous solution

Finding an efficient and eco-friendly solution for starch dissolution has attracted considerable attentions in recent years. This study investigated the structural characteristics, and degradation behavior of corn starch in KOH/thiourea aqueous solution by the comparison with DMSO/LiBr and 1-allyl-3-methylimidazolium chloride (AMIMCl). Results showed that KOH/thiourea solution was an effective solvent for corn starch dissolution (30 min with 97.01% solubility). X-ray diffraction (XRD) and ¹³C CP-MAS NMR spectroscopy revealed that native crystallinity of the corn starch was altered by all tested solvents, especially DMSO/LiBr and AMIMCl. Conversely, this new solvent did not change the primary molecular structure, chain-length distribution, or thermal stability of starch, compared with the native starch. Furthermore, KOH/thiourea solution was more suitable for measuring the molecular weight of corn starch, with a weight-average molecular weight (M_w) of 7.18 × 10⁷ g/mol. Therefore, KOH/thiourea solution is a promising novel solvent for starch dissolution and structural exploration.

Circulatory Management of Polymer Waste: Recycling into Fine Fibers and Their Applications

In modern society, it is impossible to imagine life without polymeric materials. However, managing the waste composed of these materials is one of the most significant environmental issues confronting us in the present day. Recycling polymeric waste is the most important action currently available to reduce environmental impacts worldwide and is one of the most dynamic areas in industry today. Utilizing this waste could not only benefit the environment but also promote sustainable development and circular economy management. In its program statement, the European Union has committed to support the use of sorted polymeric waste. This study reviews recent attempts to recycle this waste and convert it by alternative technologies into fine, nano-, and microscale fibers using electrospinning, blowing, melt, or centrifugal spinning. This review provides information regarding applying reprocessed fine fibers in various areas and a concrete approach to mitigate the threat of pollution caused by polymeric materials.

Cellulose modification and shaping – a review

This review aims to present cellulose as a versatile resource for the production of a variety of materials, other than pulp and paper. These products include fibers, nonwovens, films, composites, and novel derivatized materials. This article will briefly introduce the structure of cellulose and some common cellulose derivatives, as well as the formation of cellulosic materials in the micro- and nanoscale range. The challenge with dissolution of cellulose will be discussed and both derivatizing and nonderivatizing solvents for cellulose will be described. The focus of the article is the critical discussion of different shaping processes to obtain a variety of cellulose products, from commercially available viscose fibers to advanced and functionalized materials still at the research level.

Direct characterization of cotton fabrics treated with di-epoxide by nuclear magnetic resonance

A non-acid-based, di-functional epoxide, neopentyl glycol diglycidyl ether (NPGDGE), was used to modify cotton fabrics. Direct characterization of the modified cotton was conducted by Nuclear Magnetic Resonance (NMR) without grinding the fabric into a fine powder. NaOH and MgBr₂ were compared in catalyzing the reaction between the epoxide groups of NPGDGE and the hydroxyl groups of cellulose. Possible reaction routes were discussed. Scanning electron microscopy (SEM) images showed that while the MgBr₂-catalyzed reaction resulted in self-polymerization of NPGDGE, the NaOH-catalyzed reaction did not. Fourier transform infrared spectroscopy (FTIR) showed that at high NaOH concentration cellulose restructures from allomorph I to II. NMR studies verified the incorporation of NPGDGE into cotton fabrics with a clear NMR signal, and confirmed that at higher NaOH concentration the efficiency of grafting of NPGDGE was increased. This demonstrates that use of solid state NMR directly on woven fabric samples can simultaneously characterize chemical modification and crystalline polymorph of cotton. No loss of tensile strength was observed for cotton fabrics modified with NPGDGE.

Biomass-Swelling Assisted Synthesis of Hierarchical Porous Carbon Fibers for Supercapacitor Electrodes

The preparation of porous materials from renewable energy sources is attracting intensive attention due to in terms of the application/economic advantage, and pore structural design is core in the development of efficient supercapacitors or available porous media. In this work, we focused on the transformation of natural biomass, such as cotton, into more stable porous carbonaceous forms for energy storage in practical applications. Biomorphic cotton fibers are pretreated under the effect of NaOH/urea swelling on cellulose and are subsequently used as a biomass carbon source to mold the porous microtubule structure through a certain degree of calcining. As a merit of its favorable structural features, the hierarchical porous carbon fibers exhibit an enhanced electric double layer capacitance (221.7 F g^-1 at 0.3 A g^-1) and excellent cycling stability (only 4.6% loss was observed after 6000 cycles at 2 A g^-1). A detailed investigation displays that biomass-swelling behavior plays a significant role, not only in improving the surface chemical characteristics of biomorphic cotton fibers but also in facilitating the formation of a hierarchical porous carbon fiber structure. In contrast to traditional methods, nickel foams have been used as the collector for supercapacitor that requiring no additional polymeric binders or carbon black as support or conductive materials. Because of the absence of additive materials, we can further enhance capacitance. This remarkable capacitive performance can be due to sufficient void space within the porous microstructure. By effectively increasing the contact area between the carbon surface and the electrolyte, which can reduce the ion diffusion pathway or buffer the volume change during cycling. This approach opens a novel route to produce the abundantly different morphology of porous biomass-based carbon materials and proposes a green alternative method to meet sustainable development needs.

Processing, characterization and hemostatic mechanism of a ultraporous collagen/ORC biodegradable composite with excellent biological effectiveness

To overcome the hemostatic limitations, ultraporous Col/ORC composites were prepared in this paper.

Effects of polymorphs on dissolution of cellulose in NaOH/urea aqueous solution

This study focused on the effect of cellulose crystal type on the dissolution of cellulose in aqueous NaOH/urea. Cellulose I, II, IIII, and IVI were prepared and characterized. Subsequently, the solubility of these cellulose samples in aqueous NaOH/urea was tested and the mechanism was determined by a combination of (1)H NMR spectroscopy and differential scanning calorimetry (DSC). The results indicated that, compared with the degree of polymerization (DP) and crystallinity index of cellulose, the cellulose crystal type had greater impact on cellulose dissolution. Specially, the solubility of the cellulose I, II, and III was progressively decreased, probably due to different hydrogen bond network and packing energy in it. The ability of cellulose I, II, III, and IV to form hydrogen bonds with sodium hydroxides was nearly the same, while gradually increased when cellulose preparations were associated with urea. Moreover, all the cellulose solutions showed good thermal stability.

Enhanced oxidized regenerated cellulose with functionalized multiwalled carbon nanotubes for hemostasis applications

The hemostatic effect of oxidized regenerated cellulose (ORC) was enhanced using aminated MWCNTs which covalently grafted to the surface of ORC. The aminated MWCNTs increases the water uptake and hemostatic effect of ORC gradually.

Preparation and characterization of bionanocomposite fiber based on cellulose and nano-SiO2 using ionic liquid

Microcrystalline cellulose (MCC)/nano-SiO2 composite fibers were processed from solutions in 1-allyl-3-methylimidazolium chloride (AMIMCl) by the method of dry-jet wet spinning. The oscillatory shear measurements demonstrated that the gel network formed above 10 wt% nano-SiO2 and the complex viscosity increased with increasing nano-SiO2. Remarkably, the shear viscosity of the nanofluids was even lower than solutions without nano-SiO2 under high shear rates. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that well-dispersed particles exhibit strong interfacial interactions with cellulose matrix. Measurements on wide-angle X-ray diffraction (WAXD) indicated that the regenerated cellulose and nanocomposite fibers were the typical cellulose II crystalline form, which was different from the native cellulose with the polymorph of Type I. The tensile strength of the nanocomposite fibers was larger than that of pure cellulose fiber and showed a tendency to increase and then decrease with increasing nano-SiO2. Furthermore, the nanocomposite fibers exhibited improved thermal stability.

Effect of heat treatment of digestion-resistant fraction from soybean on retarding of bile acid transport in vitro

In this study, we investigated the heat effect of digestion-resistant fraction (RF) from soybean on retarding bile acid transport in vitro. The RFs from soybean retarded bile acid transport. A raw, unheated RF of soybean (RRF-SOY) was significantly more effective than the heated RF of soybean (HRF-SOY). The RS1 which physically trapped in milled grains and inaccessible to digestive enzyme after 18 hrs incubation level of content in RRF-SOY was found to be as high as 24.1% and after heating the RS1 of HRF-SOY was significantly reduced to 16.8%. The X-ray diffraction pattern of RF from soybean was altered after heat treatment. The RFs from soybean were characterized by peak at diffraction angles of 12.0° and 20.0° corresponding to RS content. Cellulose contents of RRF-SOY was 5% higher than that of HRF-SOY and pentosan contents of RRF-SOY was 5% higher than that of HRF-SOY, too. Whereas the hemicellulose content of RRF-SOY was 13% lower than HRF-SOY.

Direct dissolution of cellulose in NaOH/thiourea/urea aqueous solution

Untreated cellulose was directly and quickly dissolved in NaOH/thiourea/urea aqueous solution. The mechanism of dissolution was investigated by SEM, WXRD and (13)C NMR. The components of this solvent cannot dissolve cellulose on their own, and the interactions between NaOH and urea, as well as between NaOH and thiourea, play an important role in improving the dissolution of cellulose. Moreover, (13)C NMR spectra proved that NaOH, thiourea, and urea were bound to cellulose molecules, which brings cellulose molecules into aqueous solution to a certain extent and prevents cellulose macromolecules from associating. (13)C NMR spectra of the cellulose solution show that this novel mixture is a direct solvent. Optical microscopy and CP MAS (13)C NMR were used to study the process of dissolution. The results reveal that cellulose is dissolved completely and that cellulose I (cotton linter) first changes to amorphous cellulose chains in solution, and then to cellulose II during regeneration. Moreover, a new, more effective dissolution method is proposed, as confirmed by dynamic rheology measurements.

Kinetics of Cellulose Regeneration from Cellulose−NaOH−Water Gels and Comparison with Cellulose−N-Methylmorpholine-N-Oxide−Water Solutions

The regeneration kinetics of cellulose from cellulose--NaOH--water gels immersed in a nonsolvent bath is studied in detail. Cellulose concentration, bath type, and temperature were varied, and diffusion coefficients were determined. The results were compared with data measured and taken from the literature on the regeneration kinetics of cellulose from cellulose--N-methylmorpholine-N-oxide (NMMO) monohydrate solutions. Different theories developed for the transport behavior of solutes in hydrogels or in porous media were tested on the systems studied. While the diffusion of NaOH from cellulose--NaOH--water gels into water has to be described with "porous media" approaches, the interpretation of NMMO diffusion is complicated because of the change of NMMO's state during regeneration (from solid crystalline to liquid) and the high concentration of NMMO in the sample. The activation energies were calculated from diffusion coefficient dependence on temperature for both systems and compared with the ones obtained from the rheological measurements. The activation energy of cellulose--NaOH--water systems does not depend on cellulose concentration or the way of measurement. This result shows that whatever the system is, pure NaOH--water solution, cellulose--NaOH--water solution, or cellulose--NaOH--water gel, it is NaOH hydrate with or without cellulose in solution, which is moving in the system. The swelling of cellulose in different nonsolvent liquids such as water or different alcohols during regeneration was investigated and interpreted using the Hildebrand parameter.