Post-sulfonation of cellulose nanofibrils with a one-step reaction to improve dispersibility

Antibiotic delivery in the presence of green AgNPs using multifunctional bilayer carrageenan nanofiber/sodium alginate nanohydrogel for rapid control of wound infections

This study constructed bilayer nano-hydrogels using solvent casting and electrospinning techniques. The first layer consisted of a hydrogel containing sodium alginate and gellan gum, while the second layer was a carrageenan/polyvinyl alcohol nanofibrous membrane. The nanohydrogels were prepared with different doses of doxycycline antibiotic (0.12, 0.06, 0.03 g) and a fixed amount of silver nanoparticles (0.012 g), which were synthesized using the green method including Capparis spinosa leaf extract. The films were tested for their mechanical properties, swelling behavior, XRD, and FTIR, and their morphology was characterized using SEM. The biological properties of the nanohydrogels were also extensively assayed. X-ray diffraction analysis showed peak 111 for silver nanoparticles. Incorporating silver nanoparticles significantly enhanced nanohydrogels' mechanical and antibacterial properties and improved their ability to heal wounds. Nanohydrogels exhibited biodegradability, biocompatibility, anti-inflammatory properties (57.63 %), and high cell viability (>85 %) in laboratory conditions. The study confirmed that wound dressings containing doxycycline with controlled release are highly effective against pathogenic bacteria and prevent the formation of biofilms (92 %). The rats in-vivo study demonstrated that 100 % wound closure was achieved in nanohydrogels containing SA/GG/PVA/CAR/AgNPs/DOX0.12 after 14 days. The films could potentially lead to the development of new treatments against bacterial infections and inflammatory conditions of wounds.

Nanocellulose-based hydrogels as versatile materials with interesting functional properties for tissue engineering applications

Tissue engineering has emerged as a remarkable field aiming to restore or replace damaged tissues through the use of biomimetic constructs. Among the diverse materials investigated for this purpose, nanocellulose-based hydrogels have garnered attention due to their intriguing biocompatibility, tunable mechanical properties, and sustainability. Over the past few years, numerous research works have been published focusing on the successful use of nanocellulose-based hydrogels as artificial extracellular matrices for regenerating various types of tissues. The review emphasizes the importance of tissue engineering, highlighting hydrogels as biomimetic scaffolds, and specifically focuses on the role of nanocellulose in composites that mimic the structures, properties, and functions of the native extracellular matrix for regenerating damaged tissues. It also summarizes the types of nanocellulose, as well as their structural, mechanical, and biological properties, and their contributions to enhancing the properties and characteristics of functional hydrogels for tissue engineering of skin, bone, cartilage, heart, nerves and blood vessels. Additionally, recent advancements in the application of nanocellulose-based hydrogels for tissue engineering have been evaluated and documented. The review also addresses the challenges encountered in their fabrication while exploring the potential future prospects of these hydrogel matrices for biomedical applications.

Sulfonic acid functionalized cellulose-derived (nano)materials: Synthesis and application

The preparation/application of heterogeneous (nano)materials from natural resources has currently become increasingly fascinating for researchers. Cellulose is the most abundant renewable polysaccharide on earth. The unique physicochemical, structural, biological, and environmental properties of this natural biopolymer have led to its increased application in many fields. The more desirable features of cellulose-based (nano)materials such as biodegradability, renewability, biocompatibility, cost-effectiveness, simplicity of preparation, environmentally friendly nature, and widespread range of applications have converted them into promising compounds in medicine, catalysis, biofuel cells, and water/wastewater treatment processes. Functionalized cellulose-based (nano)materials containing sulfonic acid groups may prove to be one of the most promising sustainable bio(nano)materials of modern times in the field of cellulose science and (nano)technology owing to their intrinsic features, high crystallinity, high specific surface area, abundance, reactivity, and recyclability. In this review, the developments in the application of sulfonated cellulose-based (nano)materials containing sulfonic acid (-SO3H) groups in catalysis, water purification, biological/biomedical, environmental, and fuel cell applications have been reported. This review provides an overview of the methods used to chemically modify cellulose and/or cellulose derivatives in different forms, including nanocrystals, hydrogels, films/membranes, and (nano)composites/blends by introducing sulfonate groups on the cellulose backbone, focusing on diverse sulfonating agents utilized and substitution regioselectivity, and highlights their potential applications in different industries for the generation of alternative energies and products.

Aqueous exfoliation and dispersion of monolayer and bilayer graphene from graphite using sulfated cellulose nanofibrils

Amphiphilic sulfated cellulose nanofibrils were synthesized with yields in excess of 99% by sulfation of dissolving pulp cellulose using chlorosulfonic acid in anhydrous N,N-dimethyl formamide followed by high-speed blending. The sulfation level was stoichiometrically tunable to between 1.48 and 2.23 mmol g-1. The optimized SCNF demonstrated the ability to act as an effective dispersant for graphene produced via exfoliation in aqueous media, allowing for the production of aqueous stabilized graphene with 3.9 ± 0.3 wt% graphite to graphene conversion and suspended solids comprised of 19.5 ± 1.5 wt% graphene. Graphene exfoliated with SCNF was observed to consist exclusively of mono- and bilayers, with 42% of sheets being monolayer. Furthermore, it was demonstrated that SCNF defibrillation and graphene exfoliation could be combined into a single one-pot process.

Assessment of Cellulose Nanofiber-Based Elastase Biosensors to Inflammatory Disease as a Function of Spacer Length and Fluorescence Response

Inflammatory disease biomarker detection has become a high priority in point-of-care diagnostic research in relation to chronic wounds, with a variety of sensor-based designs becoming available. Herein, two primary aspects of biosensor design are examined: (1) assessment of a cellulose nanofiber (CNF) matrix derived from cotton ginning byproducts as a sensor transducer surface; and (2) assessment of the relation of spacer length and morphology between the CNF cellulose backbone and peptide fluorophore as a function of sensor activity for porcine pancreatic and human neutrophil elastases. X-ray crystallography, specific surface area, and pore size analyses confirmed the suitability of CNF as a matrix for wound care diagnostics. Based upon the normalized degree of substitution, a pegylated-linker connecting CNF transducer substrate to peptide fluorophore showed the greatest fluorescence response, compared to short- and long-chain alkylated linkers.

Synthesis, Characterization, and Adsorptive Characteristics of Radiation-Grafted Glycidyl Methacrylate Bamboo Fiber Composites

In the present study, a biosorbent was prepared through the radiation-induced graft polymerization (RIGP) technique by using a glycidyl methacrylate (GMA) monomer. Functionalized bamboo materials were used for grafting. The grafting percentage (G %) of GMA on bamboo fibers was assessed based on the optimization of the absorbed dose and concentration of the monomer. The chemical modification of the polymerized product into the sulfonated form of the grafted biopolymer was carried out by using sodium sulfite solution. The modification of the biopolymer at various stages was analyzed by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. By performing scanning electron microscopy (SEM), the morphological changes of the prepared biopolymer were analyzed. The temperature stability of the synthesized material was assessed by the thermogravimetric analysis (TGA) technique. The prepared sulfonated biosorbent was used in the batch adsorption study for the uptake of copper. We examined a variety of variables, including pH, adsorbent dosage, and time. The adsorption kinetics were studied using pseudo-first-order (PFO) and pseudo-second-order (PSO) models. Adsorption isotherms and thermodynamic parameters were also applied to study the adsorption capacity of the biosorbent. The maximum copper adsorption capacity was found to be 198 mg g-1 from the Langmuir isotherm. Copper adsorption followed PSO kinetics (R2 = 0.999). This inexpensive and eco-friendly biosorbent removed 96% of copper ions from the solution.

Cellulose-based adsorbents for solid phase extraction and recovery of pharmaceutical residues from water

Cellulose has attracted interest from researchers both in academic and industrial sectors due to its unique structural and physicochemical properties. The ease of surface modification of cellulose by the integration of nanomaterials, magnetic components, metal organic frameworks and polymers has made them a promising adsorbent for solid phase extraction of emerging contaminants, including pharmaceutical residues. This review summarizes, compares, and contrasts different types of cellulose-based adsorbents along with their applications in adsorption, extraction and pre-concentration of pharmaceutical residues in water for subsequent analysis. In addition, a comparison in efficiency of cellulose-based adsorbents and other types of adsorbents that have been used for the extraction of pharmaceuticals in water is presented. From our observation, cellulose-based materials have principally been investigated for the adsorption of pharmaceuticals in water. However, this review aims to shift the focus of researchers to the application of these adsorbents in the effective pre-concentration of pharmaceutical pollutants from water at trace concentrations, for quantification. At the end of the review, the challenges and future perspectives regarding cellulose-based adsorbents are discussed, thus providing an in-depth overview of the current state of the art in cellulose hybrid adsorbents for extraction of pharmaceuticals from water. This is expected to inspire the development of solid phase exraction materials that are efficient, relatively cheap, and prepared in a sustainable way.

Graft onto approaches for nanocellulose-based advanced functional materials

The resurgence of cellulose as nano-dimensional 'nanocellulose' has unlocked a sustainable bioeconomy for the development of advanced functional biomaterials. Bestowed with multifunctional attributes, such as renewability and abundance of its source, biodegradability, biocompatibility, superior mechanical, optical, and rheological properties, tunable self-assembly and surface chemistry, nanocellulose presents exclusive opportunities for a wide range of novel applications. However, to alleviate its intrinsic hydrophilicity-related constraints surface functionalization is inevitably needed to foster various targeted applications. The abundant surface hydroxyl groups on nanocellulose offer opportunities for grafting small molecules or macromolecular entities using either a 'graft onto' or 'graft from' approach, resulting in materials with distinctive functionalities. Most of the reviews published to date extensively discussed 'graft from' modification approaches, however 'graft onto' approaches are not well discussed. Hence, this review aims to provide a comprehensive summary of 'graft onto' approaches. Furthermore, insight into some of the recently emerging applications of this grafted nanocellulose including advanced nanocomposite formulation, stimuli-responsive materials, bioimaging, sensing, biomedicine, packaging, and wastewater treatment has also been reviewed.

A post-sulfonated one-pot synthesized magnetic cellulose nanocomposite for Knoevenagel and Thorpe-Ziegler reactions

The development of biodegradable and active cellulosic-based heterogeneous catalysts for the synthesis of different organic compounds would be attractive in pharmaceutical and petrochemical-related industries. Herein, a post-sulfonated composite of one-pot synthesized magnetite (Fe3O4) and cellulose nanocrystals (CNCs) was used as an effective and easily separable heterogeneous catalyst for activating the Knoevenagel and Thorpe-Ziegler reactions. The composite was developed hydrothermally from microcrystalline cellulose (MCC), iron chlorides, urea, and hydrochloric acid at 180 °C for 20 h in a one-pot reaction. After collecting the magnetic CNCs (MCNCs), post-sulfonation was performed using chlorosulfonic acid (ClSO3H) in DMF at room temperature producing sulfonated MCNCs (SMCNCs). The results confirmed the presence of sulfonated Fe3O4 and CNCs with a hydrodynamic size of 391 nm (±25). The presence of cellulose was beneficial for preventing Fe3O4 oxidation or the formation of agglomerations without requiring the presence of capping agents, organic solvents, or an inert environment. The SMCNC catalyst was applied to activate the Knoevenagel condensation and the Thorpe-Ziegler reaction with determining the optimal reaction conditions. The presence of the SMCNC catalyst facilitated these transformations under green procedures, which enabled us to synthesize a new series of olefins and thienopyridines, and the yields of some isolated olefins and thienopyridines were up to 99% and 95%, respectively. Besides, the catalyst was stable for five cycles without a significant decrease in its reactivity, and the mechanistic routes of both reactions on the SMCNCs were postulated.

Recent advances in qualitative and quantitative characterization of nanocellulose-reinforced nanocomposites: A review

Nanocellulose has received immense consideration owing to its valuable inherent traits and impressive physicochemical properties such as biocompatibility, thermal stability, non-toxicity, and tunable surface chemistry. These features have inspired researchers to deploy nanocellulose as nanoscale reinforcement materials for bio-based polymers. A simple yet efficient characterization method is often required to gain insights into the effectiveness of various types of nanocellulose. Despite a decade of continuous research and booming growth in scientific publications, nanocellulose research lacks a measuring tool that can characterize its features with acceptable speed and reliability. Implementing reliable characterization techniques is critical to monitor the specifications of nanocellulose alone or in the final product. Many techniques have been developed aiming to measure the nano-reinforcement mechanisms of nanocellulose in polymer composites. This review gives a full account of the scientific underpinnings of techniques that can characterize the shape and arrangement of nanocellulose. This review aims to deliver consolidated details on the properties and characteristics of nanocellulose in biopolymer composite materials to improve various structural, mechanical, barrier and thermal properties. We also present a comprehensive description of the safety features of nanocellulose before and after being loaded within biopolymeric matrices.

Harnessing Nature's Ingenuity: A Comprehensive Exploration of Nanocellulose from Production to Cutting-Edge Applications in Engineering and Sciences

Primary material supply is the heart of engineering and sciences. The depletion of natural resources and an increase in the human population by a billion in 13 to 15 years pose a critical concern regarding the sustainability of these materials; therefore, functionalizing renewable materials, such as nanocellulose, by possibly exploiting their properties for various practical applications, has been undertaken worldwide. Nanocellulose has emerged as a dominant green natural material with attractive and tailorable physicochemical properties, is renewable and sustainable, and shows biocompatibility and tunable surface properties. Nanocellulose is derived from cellulose, the most abundant polymer in nature with the remarkable properties of nanomaterials. This article provides a comprehensive overview of the methods used for nanocellulose preparation, structure-property and structure-property correlations, and the application of nanocellulose and its nanocomposite materials. This article differentiates the classification of nanocellulose, provides a brief account of the production methods that have been developed for isolating nanocellulose, highlights a range of unique properties of nanocellulose that have been extracted from different kinds of experiments and studies, and elaborates on nanocellulose potential applications in various areas. The present review is anticipated to provide the readers with the progress and knowledge related to nanocellulose. Pushing the boundaries of nanocellulose further into cutting-edge applications will be of particular interest in the future, especially as cost-effective commercial sources of nanocellulose continue to emerge.

One-pot synthesis of magnetic cellulose nanocrystal and its post-functionalization for doxycycline adsorption

The composite of magnetite (Fe₃O₄) and cellulose nanocrystal (CNC) is considered a potential adsorbent for water treatment and environmental remediation. In the current study, a one-pot hydrothermal procedure was utilized for magnetic cellulose nanocrystal (MCNC) development from microcrystalline cellulose (MCC) in the presence of ferric chloride, ferrous chloride, urea, and hydrochloric acid. The x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy analysis confirmed the presence of CNC and Fe₃O₄, while transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis verified their respective sizes (< 400 nm and ≤ 20 nm) in the generated composite. To have an efficient adsorption activity for doxycycline hyclate (DOX), the produced MCNC was post-treated using chloroacetic acid (CAA), chlorosulfonic acid (CSA), or iodobenzene (IB). The introduction of carboxylate, sulfonate, and phenyl groups in the post-treatment was confirmed by FTIR and XPS analysis. Such post treatments decreased the crystallinity index and thermal stability of the samples but improved their DOX adsorption capacity. The adsorption analysis at different pHs revealed the increase in the adsorption capacity by reducing the basicity of the medium due to decreasing electrostatic repulsions and inducing strong attractions.

Flexible cellulose-based piezoelectric composite membrane involving PVDF and BaTiO3 synthesized with the assistance of TEMPO-oxidized cellulose nanofibrils

High-performance flexible barium titanate (BaTiO3)-based piezoelectric devices have gained much attention. However, it is still a challenge to prepare flexible polymer/BaTiO3-based composite materials with uniform distribution and high performance due to the high viscosity of polymers. In this study, novel hybrid BaTiO3 particles were synthesized with assistance of TEMPO-oxidized cellulose nanofibrils (CNFs) via a low-temperature hydrothermal method and explored for their application in piezoelectric composites. Specifically, Ba2+ was adsorbed on uniformly dispersed CNFs with a large amount of negative charge on their surface, which nucleated, resulting in the synthesis of evenly dispersed CNF-BaTiO3. The obtained CNF-BaTiO3 possessed a uniform particle size, few impurities, high crystallinity and dispersity, high compatibility with the polymer substrate and surface activity due to the existence of CNFs. Subsequently, both polyvinylidene fluoride (PVDF) and TEMPO-oxidized CNFs were employed as piezoelectric substrates for the fabrication of a CNF/PVDF/CNF-BaTiO3 composite membrane with a compact structure, displaying the tensile strength of 18.61 ± 3.75 MPa and elongation at break of 3.06 ± 1.33%. Finally, a thin piezoelectric generator (PEG) was assembled, which output a considerable open-circuit voltage (4.4 V) and short-circuit current (200 nA), and could also power a light-emitting diode and charge a 1 μF capacitor to 3.66 V in 500 s. Its longitudinal piezoelectric constant (d 33) was 5.25 ± 1.04 pC N-1 even with a small thickness. It also exhibited high sensitivity to human movement, outputting a voltage of about 9 V and current of 739 nA for only a footstep. Thus, it exhibited good sensing property and energy harvesting property, presenting practical application prospects. This work provides a new idea for the preparation of hybrid BaTiO3 and cellulose-based piezoelectric composite materials.

Understanding Nanocellulose-Water Interactions: Turning a Detriment into an Asset

Modern technology has enabled the isolation of nanocellulose from plant-based fibers, and the current trend focuses on utilizing nanocellulose in a broad range of sustainable materials applications. Water is generally seen as a detrimental component when in contact with nanocellulose-based materials, just like it is harmful for traditional cellulosic materials such as paper or cardboard. However, water is an integral component in plants, and many applications of nanocellulose already accept the presence of water or make use of it. This review gives a comprehensive account of nanocellulose-water interactions and their repercussions in all key areas of contemporary research: fundamental physical chemistry, chemical modification of nanocellulose, materials applications, and analytical methods to map the water interactions and the effect of water on a nanocellulose matrix.

Recent advances and future perspective on nanocellulose-based materials in diverse water treatment applications

Over the past few years, nanocellulose and its derivatives have drawn attention as promising bio-based materials for water treatment applications due to their high surface area, high strength, and renewable, biocompatible nature. The abundance of hydroxyl functional groups on the surfaces of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) enables a broad range of surface modifications which results in propitious nanocomposites with tunable characteristics. In this context, this review describes the continuously developing applications of nanocellulose-based materials in the areas of adsorption, catalysis, filtration, and flocculation, with a special emphasis on the removal of contaminants such as heavy metals, dyes, and pharmaceutical compounds from diverse water systems. Recent progresses in the diverse forms of application of nanocellulose adsorbents (suspension, hydrogel, aerogel, and membrane) are also highlighted. Finally, challenges and future perspectives on emerging nanocellulose-based materials and their possible industrial applications are presented and discussed.

Fibrous Aerogels for Solar Vapor Generation

Solar-driven vapor generation is emerging as an eco-friendly and cost-effective water treatment technology for harvesting solar energy. Aerogels are solid materials with desirable high-performance properties, including low density, low thermal conductivity, and high porosity with a large internal surface, which exhibit outstanding performance in the area of solar vapor generation. Using fibers as building blocks in aerogels could achieve unexpected performance in solar vapor generation due to their entangled fibrous network and high surface area. In this review, based on the fusion of the one-dimensional fibers and three-dimensional porous aerogels, we discuss recent development in fibrous aerogels for solar vapor generation based on building blocks synthesis, photothermal materials selection, pore structures construction and device design. Thermal management and water management of fibrous aerogels are also evaluated to improve evaporation performance. Focusing on materials science and engineering, we overview the key challenges and future research opportunities of fibrous aerogels in both fundamental research and practical application of solar vapor generation technology.

Sulfated Cellulose Nanofibrils from Chlorosulfonic Acid Treatment and Their Wet Spinning into High-Strength Fibers

This paper presents the proof of concept for a facile sulfation-disintegration approach toward generating sulfated cellulose nanofibrils (SCNF) via direct sulfation of rice straw cellulose with chlorosulfonic acid (HSO₃Cl) followed by blending. The direct sulfation of cellulose with chlorosulfonic acid (HSO₃Cl) was optimized at acid ratios of 1-1.5 HSO₃Cl per anhydroglucose unit (AGU) and short reaction times (30-60 min) at ambient temperature to produce SCNF with tunable charges of 1.0-2.2 mmol/g, all in impressively high yields of 94-97%. SCNF were characterized via AFM, TEM, FTIR, and XRD. SCNF lengths (L: 0.75-1.24 μm) and widths (W: 3.9-5.9 nm) decreased with harsher sulfation, while heights (H: 1.23-1.32 nm) remained relatively static. The SCNF had uniquely anisotropic cross sections (W/H: 3.0-4.7) and high aspect ratios (L/H: 568-984) while also exhibiting amphiphilicity, thixotropy, and shear thinning behaviors that closely followed a power law model. Aqueous SCNF dispersions could be wet spun into organic and mixed organic/ionic coagulants, producing continuous fibers possessing an impressively high tensile strength and Young's modulus of up to 675 ± 120 MPa and 26 ± 5 GPa, respectively.

Lignocellulose nanocrystals from pineapple peel: Preparation, characterization and application as efficient Pickering emulsion stabilizers

In this study, the pineapple peel treated with different degrees of delignification was used to isolate lignocellulose nanocrystals (LCNC) by sulfuric acid hydrolysis. Controlling delignification treatments can adjust the morphology and structure of pineapple peel and the retention of lignin, thereby achieving the regulation of the properties of LCNC, such as morphology, crystallinity, hydrophobicity and rheological properties. The results of atomic force microscope (AFM), confocal laser scanning microscopy (CLSM), UV/visible (UV-Vis) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the presence of lignin in LCNC, showing a rod-like structure with the distribution of lignin. Regulating delignification of pineapple peel can adjust the average length (310 ∼ 460 nm), diameter (19 ∼ 38 nm), crystallinity (61% ∼ 71%) and hydrophobicity (contact angle 84° ∼ 60°) of the obtained LCNC by acid hydrolysis, and influence the performance of its stabilized Pickering emulsions. This work confirms that the properties of LCNC can be controlled through adjusting delignification degree, possessing great significance for the high value utilization of lignocellulosic agricultural waste.

Insights into structure and properties of cellulose nanofibrils (CNFs) prepared by screw extrusion and deep eutectic solvent permeation

To achieve the balance on economy and ecology, it is indispensable to explore the greener and more inexpensive method for the production of cellulose nanofibrils (CNFs). Herein, a deep eutectic solvent (DES) system based on choline chloride (ChCl) and ethylene glycol (EG) was employed as the swollen solvent, combining with screw extrusion and permeant, to fabricate unmodified CNFs with high yield and thermal stability. The proposed method in this work was simple, convenient, and industrially viable. The hydrous DESs were applied in the process of CNFs preparation and dispersion to reduce the cost and viscosity of DES. To reveal the principle of CNFs preparation, the impact of sulfuric acid and water content of DES system on the chemical, physical, morphological, thermal, and dispersive properties of CNFs was systematically studied. Properties of the dispersed solvents were characterized by solvatochromic parameters and viscosity parameters to evaluate the potential influence on the preparation and dispersion of CNFs. In general, this work would play valuable guidance in realizing the preparation and dispersion of CNFs via a versatile DES solvent system, thus endowing cellulose materials high-value utilization.

Facile Preparation and Characteristic Analysis of Sulfated Cellulose Nanofibril via the Pretreatment of Sulfamic Acid-Glycerol Based Deep Eutectic Solvents

A deep eutectic solvent (DES) composed of sulfamic acid and glycerol allowed for the sustainable preparation of cellulose nanofibrils (CNF) with simultaneous sulfation. The reaction time and the levels of sulfamic acid demonstrated that fibers could be swelled and sulfated simultaneously by a sulfamic acid-glycerol-based DES and swelling also promoted sulfation with a high degree of substitution (0.12). The DES-pretreated fibers were further nanofibrillated by a grinder producing CNF with diameters from 10 nm to 25 nm. The crystallinity ranged from 53–62%, and CNF maintained the original crystal structure. DES pretreatment facilitated cellulose nano-fibrillation and reduced the energy consumption with a maximum reduction of 35%. The films prepared from polyvinyl alcohol (PVA) and CNF showed good UV resistance ability and mechanical properties. This facile and efficient method provided a more sustainable strategy for the swelling, functionalization and nano-fibrillation of cellulose, expanding its application to UV-blocking materials and related fields.

A review of nanocellulose as a new material towards environmental sustainability

Synthetic polymers, commonly referred to as plastics, are anthropogenic contaminants that adversely affect the natural ecosystems. The continuous disposal of long lifespan plastics has resulted in the accumulation of plastic waste, leading to significant pollution of both marine and terrestrial habitats. Scientific pursuit to seek environment-friendly materials from renewable resources has focused on cellulose, the primary reinforcement component of the cell wall of plants, as it is the most abundantly available biopolymer on earth. This paper provides an overview on the current state of science on nanocellulose research; highlighting its extraction procedures from lignocellulosic biomass. Literature shows that the process used to obtain nanocellulose from lignocellulosic biomass greatly influences its morphology, properties and surface chemistry. The efficacy of chemical methods that use alkali, acid, bleaching agents, ionic liquids, deep eutectic solvent for pre-treatment of biomass is discussed. There has been a continuous endeavour to optimize the pre-treatment protocol as it is specific to lignocellulosic biomass and also depends on factors such as nature of the biomass, process and environmental parameters and economic viability. Nanofibers are primarily isolated through mechanical fibrillation while nanocrystals are predominantly extracted using acid hydrolysis. A concise overview on the ways to improve the yield of nanocellulose from cellulosic biomass is also presented in this review. This work also reviews the techniques used to modify the surface properties of nanocellulose by functionalizing surface hydroxyl groups to impart desirable hydrophilic-hydrophobic balance. An assessment on the emerging application of nanocellulose with an emphasis on development of nanocomposite materials for designing environmentally sustainable products is incorporated. Finally, the status of the industrial production of nanocellulose presented, which indicates that there is a continuously increased demand for cellulose nanomaterials. The demand for cellulose is expected to increase further due to its increasing and broadening applications.

Redispersion and structural change evaluation of dried microfibrillated cellulose

Commercializing dried microfibrillated cellulose (MFC) has always been a challenge mainly due to the tendency of MFC to aggregate. In this study MFC samples were submitted to drying/redispersion cycles at different temperatures. Morphology, crystallinity and mechanical performance of films were analyzed throughout the cycles. Microscopy images, particle size and stability in water showed that aggregation happens more severely with 5 drying/redispersion cycles and at drying temperatures of 75 and 100 °C. Particles once-dried at 20 °C formed the same size and web-like structure as the MFC-control. Crystallinity and crystallite sizes increased with drying/redispersion cycles especially when dried at 75 and 100 °C, however drying/redispersion cycles also led to a reduction in mechanical performance due to aggregation. While oven-drying is not the most suitable method, milder action at room temperature once-drying led to suspension stability in water, morphology and mechanical properties close to never-dried MFC, which makes this treatment a feasible option to maintain cellulose quality.

Cross-Linked Nanocellulosic Materials and Their Applications

Nanocelluloses (NCs) have remarkable mechanical properties and contain abundant surface functional groups that can be modified or cross-linked with other materials. They have been widely used as an environment-friendly reinforcing agent in polymer composites. However, for applications that are carried out in humid environments or aqueous suspensions, hydrophilicity of NCs lower their mechanical integrity. Hence, cross-linking techniques have been investigated in recent years for preparing NC-based materials that are dimensionally stable under humid or aqueous environments and have better physicochemical properties. This Minireview examines the quickly growing field of cross-linked NC-based materials, which have many benefits including improved aqueous, structural, mechanical, and thermal stability. In addition, the potential application of cross-linked NC-based materials in adsorption of heavy metal is discussed.

Alkali Hydrolysis of Sulfated Cellulose Nanocrystals: Optimization of Reaction Conditions and Tailored Surface Charge

Cellulose nanocrystals (CNCs) are a biorenewable resource, which may be chemically modified to impart specific properties. Modified CNCs have found use in imaging applications, as rheology modifiers, polymer reinforcements, barrier and/or optical films, and nanocomposites. Nanoparticle dimensions of CNCs are typically 5-10 nm in width, with lengths of <100-300 nm. However, the physical properties are dependent upon the number and nature of the surface charge groups imparted during preparation. In the case of CNCs produced from sulfuric acid hydrolysis, the sulfated surface groups may be partially removed prior to further functionalization. This gives more available hydroxyls yet renders the CNCs less colloidally stable. Furthermore, conditions vary significantly and there is no consensus about the optimal conditions for partial removal of sulfate functionality or conditions developed to give specific surface charge. In the following, alkali hydrolysis of sulfate half-esters was quantified by conductometric titration of the strong acid groups, and using a design of experiments (DOE), optimal conditions were determined to produce CNCs with tailored surface charge.

A review on processing techniques of bast fibers nanocellulose and its polylactic acid (PLA) nanocomposites

The utilization of nanocellulose has increasingly gained attentions from various research fields, especially the field of polymer nanocomposites owing to the growing environmental hazardous of petroleum based fiber products. Meanwhile, the searching of alternative cellulose sources from different plants has become the interests for producing nanocellulose with varying characterizations that expectedly suit in specific field of applications. In this content the long and strong bast fibers from plant species was gradually getting its remarkable position in the field of nanocellulose extraction and nanocomposites fabrications. This review article intended to present an overview of the chemical structure of cellulose, different types of nanocellulose, bast fibers compositions, structure, polylactic acid (PLA) and the most probable processing techniques on the developments of nanocellulose from different bast fibers especially jute, kenaf, hemp, flax, ramie and roselle and its nanocomposites. This article however more focused on the fabrication of PLA based nanocomposites due to its high firmness, biodegradability and sustainability properties in developed products towards the environment. Along with this it also explored a couple of issues to improve the processing techniques of bast fibers nanocellulose and its reinforcement in the PLA biopolymer as final products.