Solubility and spinnability of cellulose-lignin blends in aqueous NMMO

Advances in regenerated cellulosic aerogel from waste cotton textile for emerging multidimensional applications

Rapid development of society and the improvement of people's living standards have stimulated people's keen interest in fashion clothing. This trend has led to the acceleration of new product innovation and the shortening of the lifespan for cotton fabrics, which has resulting in the accumulation of waste cotton textiles. Although cotton fibers can be degraded naturally, direct disposal not only causes a serious resource waste, but also brings serious environmental problems. Hence, it is significant to explore a cleaner and greener waste textile treatment method in the context of green and sustainable development. To realize the high-value utilization of cellulose II aerogel derived from waste cotton products, great efforts have been made and considerable progress has been achieved in the past few decades. However, few reviews systematically summarize the research progress and future challenges of preparing high-value-added regenerated cellulose aerogels via dissolving cotton and other cellulose wastes. Therefore, this article reviews the regenerated cellulose aerogels obtained through solvent methods, summarizes their structure, preparation strategies and application, aimed to promote the development of the waste textile industry and contributed to the realization of carbon neutrality.

A Review of the Preparation of Porous Fibers and Porous Parts by a Novel Micro-Extrusion Foaming Technique

This review introduces an innovative technology termed "Micro-Extrusion Foaming (MEF)", which amalgamates the merits of physical foaming and 3D printing. It presents a groundbreaking approach to producing porous polymer fibers and parts. Conventional methods for creating porous materials often encounter obstacles such as the extensive use of organic solvents, intricate processing, and suboptimal production efficiency. The MEF technique surmounts these challenges by initially saturating a polymer filament with compressed CO2 or N2, followed by cell nucleation and growth during the molten extrusion process. This technology offers manifold advantages, encompassing an adjustable pore size and porosity, environmental friendliness, high processing efficiency, and compatibility with diverse polymer materials. The review meticulously elucidates the principles and fabrication process integral to MEF, encompassing the creation of porous fibers through the elongational behavior of foamed melts and the generation of porous parts through the stacking of foamed melts. Furthermore, the review explores the varied applications of this technology across diverse fields and imparts insights for future directions and challenges. These include augmenting material performance, refining fabrication processes, and broadening the scope of applications. MEF technology holds immense potential in the realm of porous material preparation, heralding noteworthy advancements and innovations in manufacturing and materials science.

Direct dissolution of unbleached pulp from corncob and wheat straw in N-methylmorpholine-N-oxide

Lignocellulose, as a kind of abundant natural resource, continuously developed to convert high value-added biological products is of great significance. Herein, we report a N-methylmorpholine-N-oxide (NMMO) solvent system to completely dissolve unbleached pulp to prepare a renewable lignin-containing cellulose film. The viscosity of the completely dissolved cellulose solution was measured using a high-pressure rotary rheometer. The shear viscosity exceeded 85 Pa·s at a shear rate of 1.62 s-1. It exhibited shear-thinning non-Newtonian fluid behavior with increasing shear rate. CF-WS had excellent tensile strength (>73 MPa), and exhibited unique optical properties of high transmittance in the visible region and high shielding performance in the ultraviolet region. When the thickness is only 0.016 mm, the UV shielding rate exceeds 75 % (λ < 380 nm). The structure of the bioplastic was revealed by SEM, XPS, and Raman spectroscopy. Directly dissolving lignocellulose in NMMO aqueous solution is expected to yield bioplastics with high strength and biodegradability. It is a potential substitute for petrochemical plastics and provides a possible way for the utilization of agricultural waste.

Fabrication of biodegradable films with UV-blocking and high-strength properties from spent coffee grounds

Utilizing spent coffee grounds (SCG) to produce high value-added materials is attractive and meaningful. In this work, a multi-functional biomass film is prepared from SCG and dissolving pulp through a dissolution and regeneration process. Importantly, dissolving pulp as a reinforcing additive can significantly enhance the mechanical strength of the regenerated SCG film. The prepared composite films with SCG contents ranging from 33.33 wt% to 81.82 wt% demonstrate excellent optical and mechanical properties. The composite film with 66.67 wt% SCG exhibits outstanding UV blocking capability (99.43 % for UVB and 96.59 % for UVA) and high haze (69.22%); meanwhile, the composite film with 33.33 wt% SCG performs better mechanical strength (58.69 MPa tensile strength and 3.13 GPa Young's modulus) and superior biodegradability (fully degraded within 26 days by being buried in soil) than commercial plastic. This work generally introduces a facile and practical approach to converting waste SCG into promising materials in various fields.

Boric Acid as A Low-Temperature Graphitization Aid and Its Impact on Structure and Properties of Cellulose-Based Carbon Fibers

In the present paper, a scalable, economically feasible, and continuous process for making cellulose-based carbon fibers (CFs) is described encompassing precursor spinning, precursor additivation, thermal stabilization, and carbonization. By the use of boric acid (BA) as an additive, the main drawback of cellulose-based CFs, i.e., the low carbon yield, is overcome while maintaining a high level of mechanical properties. This is demonstrated by a systematic comparison between CFs obtained from a BA-doped and an un-doped cellulose precursor within a temperature range for carbonization between 1000 and 2000 °C. The changes in chemical composition (via elemental analysis) and physical structure (via X-ray scattering) as well as the mechanical and electrical properties of the resulting CFs were investigated. It turned out that, in contrast to current opinion, the catalytic effect of boron in the formation of graphite-like structures sets in already at 1000 °C. It becomes more and more effective with increasing temperature. The catalytic effect of boron significantly affects crystallite sizes (La, Lc), lattice plane spacings (d002), and orientation of the crystallites. Using BA, the carbon yield increased by 71%, Young's modulus by 27%, and conductivity by 168%, reaching 135,000 S/m. At the same time, a moderate decrease in tensile strength by 25% and an increase in density of 14% are observed.

Dissolution mechanism of cellulose in a benzyltriethylammonium/urea deep eutectic solvent (DES): DFT-quantum modeling, molecular dynamics and experimental investigation

In this paper, a benzyltriethylammonium/urea DES was investigated as a new green and eco-friendly medium for the progress of organic chemical reactions, particularly the dissolution and the functionalization of cellulose. In this regard, the viscosity-average molecular weight of cellulose (M̄w) during the dissolution/regeneration process was investigated, showing no significant degradation of the polymer chains. Moreover, X-ray diffraction patterns indicated that the cellulose dissolution process in the BTEAB/urea DES decreased the crystallinity index from 87% to 75%, and there was no effect on type I cellulose polymorphism. However, a drastic impact of the cosolvents (water and DMSO) on the melting point of the DES was observed. Besides, to understand the evolution of cellulose-DES interactions, the formation mechanism of the system was studied in terms of H-bond density and radial distribution function (RDF) using molecular dynamics modeling. Furthermore, density functional theory (DFT) was used to evaluate the topological characteristics of the polymeric system such as potential energy density (PED), laplacian electron density (LED), energy density, and kinetic energy density (KED) at bond critical points (BCPs) between the cellulose and the DES. The quantum theory of atoms in molecules (AIM), Bader's quantum theory (BQT), and reduced density gradient (RDG) scatter plots have been exploited to estimate and locate non-covalent interactions (NCIs). The results revealed that the dissolution process is attributed to the physical interactions, mainly the strong H-bond interactions.

Lignin microparticles-reinforced cellulose filter paper for simultaneous removal of emulsified oils and dyes

The presence of multiple pollutants in wastewater, often with complex interactions, poses a significant challenge for conventional membranes to effectively remove multiple pollutants simultaneously. Herein, a lignin microparticles-reinforced cellulose filter paper (FP@AL-LS-DA) was fabricated via an aldol condensation between lignin and cellulose filter paper and cross-linking with dopamine hydrochloride (DA), which showed desired rejection of oil-in-water emulsions and dyes. Characterizations revealed that the addition of lignin and DA effectively narrowed the pore size (from 4.45 μm to 2.01 μm) and enhanced the rigidity and stability of the cellulose filter paper, thus making it not easily damaged in the water environment and showing excellent tolerance to strong acid and high-salt environments. The oil-in-water emulsions removal efficiency was higher than 99 % even after ten times usage, and the oil flux was kept stable at 52.54 L·m^-2·h^-1, indicating that FP@AL-LS-DA had outstanding reusability and stability. Remarkably, FP@AL-LS-DA showed excellent removal efficiency (>99 %) for complex pollutants containing dyes and oil-in-water emulsions. In this work, we demonstrate a lignin microparticles-reinforced cellulose filter paper that is simple to prepare and can efficiently separate oil-in-water emulsions and remove dyes.

Electrospun Nanomaterials Based on Cellulose and Its Derivatives for Cell Cultures: Recent Developments and Challenges

The development of electrospun nanofibers based on cellulose and its derivatives is an inalienable task of modern materials science branches related to biomedical engineering. The considerable compatibility with multiple cell lines and capability to form unaligned nanofibrous frameworks help reproduce the properties of natural extracellular matrix and ensure scaffold applications as cell carriers promoting substantial cell adhesion, growth, and proliferation. In this paper, we are focusing on the structural features of cellulose itself and electrospun cellulosic fibers, including fiber diameter, spacing, and alignment responsible for facilitated cell capture. The study emphasizes the role of the most frequently discussed cellulose derivatives (cellulose acetate, carboxymethylcellulose, hydroxypropyl cellulose, etc.) and composites in scaffolding and cell culturing. The key issues of the electrospinning technique in scaffold design and insufficient micromechanics assessment are discussed. Based on recent studies aiming at the fabrication of artificial 2D and 3D nanofiber matrices, the current research provides the applicability assessment of the scaffolds toward osteoblasts (hFOB line), fibroblastic (NIH/3T3, HDF, HFF-1, L929 lines), endothelial (HUVEC line), and several other cell types. Furthermore, a critical aspect of cell adhesion through the adsorption of proteins on the surfaces is touched upon.

Preparation and Characterization of Regenerated Cellulose Membrane Blended with ZrO2 Nanoparticles

It is of great significance to search for efficient, renewable, biodegradable and economical membrane materials. Herein, we developed an organic-inorganic hybrid regenerated cellulose membrane (ZrO2/BCM) with excellent hydrophilic and anti-fouling properties. The membrane was prepared by introducing ZrO2 particles into an N-Methylmorpholine-N-oxide(NMMO)/bamboo cellulose(BC) solution system by the phase inversion method. The physi-chemical structure of the membranes were characterized based on thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD). The modified regenerated cellulose membrane has the excellent rejection of bovine serum albumin (BSA) and anti-fouling performance. The membrane flux of ZrO2/BCM is 321.49 (L/m2·h), and the rejection rate of BSA is 91.2%. Moreover, the membrane flux recovery rate after cleaning with deionized water was 90.6%. This new type of separation membrane prepared with green materials holds broad application potential in water purification and wastewater treatment.

Lignin enhances cellulose dissolution in cold alkali

Aqueous sodium hydroxide solutions are extensively used as solvents for lignin in kraft pulping. These are also appealing systems for cellulose dissolution due to their inexpensiveness, ease to recycle and low toxicity. Cellulose dissolution occurs in a narrow concentration region and at low temperatures. Dissolution is often incomplete but additives, such as zinc oxide or urea, have been found to significantly improve cellulose dissolution. In this work, lignin was explored as a possible beneficial additive for cellulose dissolution. Lignin was found to improve cellulose dissolution in cold alkali, extending the NaOH concentration range to lower values. The regenerated cellulose material from the NaOH-lignin solvents was found to have a lower crystallinity and crystallite size than the samples prepared in the neat NaOH and NaOH-urea solvents. Beneficial lignin-cellulose interactions in solution state appear to be preserved under coagulation and regeneration, reducing the tendency of crystallization of cellulose.

Recent progress in cellulose-based electrospun nanofibers as multifunctional materials

Cellulose, the most abundant natural polymer, has good biocompatibility, biodegradability, and non-toxicity, which make it and its derivatives promising candidates for the fabrication of multifunctional materials, while maintaining sustainability and environmental friendliness. The combination of electrospinning technology and cellulose (and its derivatives) provides a feasible approach to produce nanostructured porous materials with promising functionalities, flexibility, renewability and biodegradability. At the same time, it enables value-added applications of cellulose and its derivatives that are derived from nature or even biomass waste. This review summarizes and discusses the latest progress in cellulose-based electrospun nanofibers, including their construction methods and conditions, various available raw materials, and applications in multiple areas (water treatment, biomaterials, sensors, electro-conductive materials, active packaging, and so on), which are followed by the conclusion and prospects associated with future opportunities and challenges in this active research area.

High-Strength Regenerated Cellulose Fiber Reinforced with Cellulose Nanofibril and Nanosilica

In this study, a novel type of high-strength regenerated cellulose composite fiber reinforced with cellulose nanofibrils (CNFs) and nanosilica (nano-SiO₂) was prepared. Adding 1% CNF and 1% nano-SiO₂ to pulp/AMIMCl improved the tensile strength of the composite cellulose by 47.46%. The surface of the regenerated fiber exhibited a scaly structure with pores, which could be reduced by adding CNF and nano-SiO₂, resulting in the enhancement of physical strength of regenerated fibers. The cellulose/AMIMCl mixture with or without the addition of nanomaterials performed as shear thinning fluids, also known as "pseudoplastic" fluids. Increasing the temperature lowered the viscosity. The yield stress and viscosity sequences were as follows: RCF-CNF² > RCF-CNF²-SiO₂² > RCF-SiO₂² > RCF > RCF-CNF¹-SiO₂¹. Under the same oscillation frequency, G' and G" decreased with the increase of temperature, which indicated a reduction in viscoelasticity. A preferred cellulose/AMIMCl mixture was obtained with the addition of 1% CNF and 1% nano-SiO₂, by which the viscosity and shear stress of the adhesive were significantly reduced at 80 °C.

Lignin-Based High-Performance Fibers by Textile Spinning Techniques

As a major component of lignocellulosic biomass, lignin is one of the largest natural resources of biopolymers and, thus, an abundant and renewable raw material for products, such as high-performance fibers for industrial applications. Direct conversion of lignin has long been investigated, but the fiber spinning process for lignin is difficult and the obtained fibers exhibit unsatisfactory mechanical performance mainly due to the amorphous chemical structure, low molecular weight of lignin, and broad molecular weight distribution. Therefore, different textile spinning techniques, modifications of lignin, and incorporation of lignin into polymers have been and are being developed to increase lignin's spinnability and compatibility with existing materials to yield fibers with better mechanical performance. This review presents the latest advances in the textile fabrication techniques, modified lignin-based high-performance fibers, and their potential in the enhancement of the mechanical performance.

Disassembly of lignocellulose into cellulose, hemicellulose, and lignin for preparation of porous carbon materials with enhanced performances

Lignocellulose is the primary component of many biomasses, including corn straw. Herein, lignocellulose in corn straw was disassembled into the individual polymers, cellulose, hemicellulose, and lignin via a mild and facile method. Subsequently, three porous carbon materials were prepared by carbonization and chemical activation of cellulose (PCCC), hemicellulose (PCHC), and lignin (PCLC). The three materials showed higher specific surface areas (2565.7, 2996.1, and 2590.3 m² g^-1) and higher porosities (1.4261, 1.5876, and 1.2406 cm³ g^-1) than that of PCCS, a porous carbon material derived from raw corn straw (1993 m² g^-1 and 1.19 cm³ g^-1). Of note, PCCC and PCHC exhibited higher adsorption (1025.5 and 950.1 mg g^-1) of brilliant green (BG), than PCCS (876.7 mg g^-1). Besides, the BG adsorption capacities of the designed materials were higher than that of most adsorbents, and 2-2.5 times higher than that of graphite oxide (416.7 mg g^-1). These study results indicate that the disassembly of lignocellulosic biomass into cellulose, hemicellulose, and lignin is an effective strategy for preparing various porous carbon materials with enhanced performances.