Production Of Cellulose Nanocrystals Research Articles

Benchmarking Cellulose Nanocrystals Part II: New Industrially Produced Materials.

The demand for industrially produced cellulose nanocrystals (CNCs) has been growing since 2012, when CelluForce Inc. opened its inaugural demonstration plant with a production capacity of 1 tonne per day. Currently, there are 10 industrial CNC producers worldwide, each producing a unique material. Thus, academic researchers and commercial users alike must consider the properties of all available CNCs and carefully select the material which will optimize the performance of their desired application. To support these efforts, this article presents a thorough characterization of four new industrially produced CNCs including sulfated CNCs from NORAM Engineering and Constructors Ltd. (in cooperation with InnoTech Alberta and Alberta-Pacific Forest Industries Inc.) and Melodea Ltd., as well as carboxylated CNCs from Anomera Inc. and Blue Goose Biorefineries Inc. These materials were benchmarked against typical lab-made, sulfated CNCs. While all CNCs were similar in size, shape, crystallinity, and suspension quality, the sulfated CNCs had a higher surface charge density than their carboxylated counterparts, leading to higher colloidal stability. Additionally, significant differences in the rheological profiles of aqueous CNC suspensions, as well as CNC thermal stability and self-assembly behavior, were observed. As such, this article highlights both the subtle and significant differences between five CNC types and acts as a guide for end-users looking to optimize the performance of CNC-based materials.

Co-production of ethanol and cellulose nanocrystals through self-cycling fermentation of wood pulp hydrolysate

A promising approach to help offset production costs for the cellulosic ethanol industry is to improve ethanol productivity while simultaneously generating value-added by-products. This study reports integration of an advanced fermentation approach (self-cycling fermentation) with the production of cellulose nanocrystals. Specifically, wood pulp was enzymatically hydrolyzed to yield dissolved sugars, which were fed to a self-cycling fermentation system for ethanol production, and residual solids were used for cellulose nanocrystals production via acid hydrolysis. Self-cycling fermentation achieved stable ethanol production for 10 cycles with significantly greater productivity than batch operation: ethanol volumetric productivity increased by 63–95% and annual ethanol productivity by 96 ± 5%. Additionally, the enzyme hydrolysis approach employed did not impede ethanol fermentation, and the cellulose nanocrystals generated displayed properties consistent with previous studies. Taken together, these results highlight the potential of this co-production strategy to produce both cellulosic ethanol and cellulose nanocrystals from a single feedstock.

An environmentally friendly and economical strategy to cyclically produce cellulose nanocrystals with high thermal stability and high yield

FeCl3 solution was used as a new solvent to develop a green and recyclable strategy to produce CNCs. Specifically, FeCl3 polarizes water molecules to generate H+ and catalyzes the hydrolysis of the amorphous area of cellulose.

Enzymatically produced cellulose nanocrystals as reinforcement for waterborne polyurethane and its applications

Waterborne polyurethanes (WBPUs) have been proposed as ecofriendly elastomers with several applications in coatings and adhesives. WBPU’s physicochemical properties can be enhanced by the addition of cellulose nanocrystals (CNCs). The way CNCs are isolated has a strong effect on their properties and can determine their role as reinforcement. In this work, CNCs produced using ancestral endoglucanase (EnCNCs) were used as reinforcement for WBPU and compared with CNC produced by sulfuric acid hydrolysis (AcCNC). The enzymatic method produced highly thermostable and crystalline CNCs. The addition of small contents of EnCNCs improved the thermomechanical stability and mechanical properties of WBPUs, even better than commercial AcCNCs. Besides, WBPU reinforced by adding EnCNCs was studied as a coating for paper materials, increasing its abrasion resistance and as electrospun nanocomposite mats where EnCNCs helped maintaining the morphology of the fibers.

Upgrading Euphorbia Antisyphilitica fiber compost: A waste material turned into nanocrystalline cellulose

The utilization of organic industrial wastes as source for production of cellulose nanocrystals (CNCs) is very attractive and has a huge advantage in comparison with traditional sources as plants, bacterial or commercial cellulose (MCC), because it has the potential of increasing the value chain of these materials. The aim of this study is to analyze the utilization of Euphorbia Antisyphilitica bagasse, a waste of the wax industry, as source for CNC’s prepared by two different techniques, namely acid hydrolysis and TEMPO mediated oxidation. Cellulose extraction was performed by a treatment with aqueous NaOH followed by a bleaching process with NaClO. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and conductometric titration. The CNCs samples have a diameter of around 17 nm and a length between 220 and 310 nm with a degree of crystallinity above 70 % and a very different thermal behavior depending of the isolation method. On one hand charge densities are 2.135 e/nm² and 1.933 e/nm², on the other hand root-mean-square roughness is around 2.1 and 2.3 nm (films were deposited on a glass surface), depending on the isolation technique.

Production routes to tailor the performance of cellulose nanocrystals

Cellulose nanocrystals (CNCs) are bio-based, high aspect ratio nanoparticles that are industrially produced in tonne-per-day quantities across the globe. CNCs can be used to improve the performance of a large range of materials such as emulsions and foams, biomedical devices, electronics and sensors, high-viscosity fluids and polymer composites. Their ability to do so, however, is highly dependent on the way they are produced. In this Review, we assess the properties of CNCs from more than 30 production routes and 40 biomass sources to help CNC users select the right material for their desired application. CNCs produced by various methods are evaluated against three target properties: colloidal stability, size and crystallinity index. Alternative production routes and/or starting materials are suggested to overcome challenges associated with CNC use, including increasing compatibility with hydrophobic materials, resistance to thermal degradation and colloidal stability in high ionic strength environments. Additionally, we discuss industrial production of CNCs, as well as considerations for increasing the yield and reducing the environmental impact of these processes. Overall, this Review guides researchers and CNC users towards a deeper understanding of how production processes can be modified to control CNC properties and subsequently tailor their performance. Cellulose nanocrystals are rigid rod-shaped nanoparticles that show promise as additives in composites, emulsions, foams and biomedical devices and as rheological modifiers. In this Review, the authors guide end users towards selecting cellulose sources and production routes that optimize the performance of cellulose nanocrystals in their intended application.

Enzymatic extract of Aspergillus fumigatus CCT 7873 for hydrolysis of sugarcane bagasse and generation of cellulose nanocrystals (CNC)

In this study, cellulose nanocrystals (CNC) were produced from untreated and pretreated sugarcane fibers through enzymatic hydrolysis using a crude cellulolytic extract produced by the fungus Aspergillus fumigatus CCT 7873 using semi-solid fermentation (SSF). The fibers were characterized in terms of cellulose, hemicellulose, and lignin contents and crystallinity index. The CNC generated during the enzymatic hydrolysis using a sugarcane fiber pretreated with 4% NaOH and an enzymatic loading of 7.5 FPU g−1 of bagasse were characterized by atomic force microscopy (AFM). The results showed that after the hydrolysis time of 48 h, spherical-like particles with a good size distribution and a mean diameter of 61 nm were obtained. In this study, we produced cellulose nanocrystals (CNC) from untreated and pretreated sugarcane fibers through enzymatic hydrolysis using a crude cellulolytic extract produced by the fungus Aspergillus fumigatus CCT 7873 using semi-solid fermentation (SSF). In fact, the main novelty of this manuscript is the fact that it accompanies the formation of CNC, by means of atomic force microscopy (AFM). It is noteworthy that there are few manuscripts with this approach in the literature. In addition, this was performed during the cultivation of a fermentation broth containing cellulases produced by an enzymatic extract of the fungus Aspergillus fumigatus CCT 7873 using SSF. Thus, CNC, a highly added value product, can be obtained from lignocellulosic residues, which is a renewable and low-cost source. The results showed that, during the cultivation, there is a variation in the size distribution of the CNC and that, for the hydrolysis time of 48 h, a good size distribution was obtained for the CNC with about 61 nm in diameter, presenting a spherical shape.

Production of cellulose nanocrystals from pineapple crown fibers through alkaline pretreatment and acid hydrolysis under different conditions

In the growing search for sustainability, nanocellulose has stood out, since it is obtained from natural fibers, a renewable and biodegradable source, being able to promote the reuse of agricultural waste. Due to their high availability and low cost, residues from pineapple consumption become a viable alternative for the nanocellulose production process, which has not been explored so far. In this sense, the work aimed to produce nanocellulose from pineapple crowns, via acid hydrolysis, promoting the study of different process conditions, to define which methods obtained better results. The fibers were pretreated by mercerizing with sodium hydroxide and bleaching with hydrogen peroxide and sodium hydroxide. This was followed by hydrolysis with sulfuric acid to obtain the nanoparticles. Chemical characterization and scanning electron microscopy were performed on the crude and bleached fibers, and transmission electron microscopy on the produced nanocellulose. The treatments were effective in reducing lignin and hemicellulose in the fiber, and microscopy proved the production of cellulose nanoparticles, with an average width equal to 10.38nm. Therefore, the results confirmed the potential of the process used to obtain nanocellulose from the pineapple crowns.

Production of Cellulose Nanocrystals from Australian Wood Sources.

Two Australian native wooden sources (Acacia Mangium and Eucalyptus Globulus) derived pulps were explored as raw feed stocks to prepare the valuable nanomaterial of cellulose nanocrystals (CNC). After bleaching and acid hydrolysis, cellulose nanocrystals were successfully produced with high yields of approximately 60% for both kraft pulps. According to the characterization of SEM and AFM, the as prepared CNC had a rod like structure with the length and diameter in the range of 200~1000 nm and 10~100 nm, respectively based on the initial wooden source. XRD confirmed the crystalline structure of the resulting CNC. Further characterisation by TGA showed that the chemical treatment of the wood pulp had impact upon the thermal stability, evidenced by a lower onset temperature of the thermal decomposition of CNC.

Particle Size Distributions for Cellulose Nanocrystals Measured by Transmission Electron Microscopy: An Interlaboratory Comparison.

Particle size is a key parameter that must be measured to ensure reproducible production of cellulose nanocrystals (CNCs) and to achieve reliable performance metrics for specific CNC applications. Nevertheless, size measurements for CNCs are challenging due to their broad size distribution, irregular rod-shaped particles, and propensity to aggregate and agglomerate. We report an interlaboratory comparison (ILC) that tests transmission electron microscopy (TEM) protocols for image acquisition and analysis. Samples of CNCs were prepared on TEM grids in a single laboratory, and detailed data acquisition and analysis protocols were provided to participants. CNCs were imaged and the size of individual particles was analyzed in 10 participating laboratories that represent a cross section of academic, industrial, and government laboratories with varying levels of experience with imaging CNCs. The data for each laboratory were fit to a skew normal distribution that accommodates the variability in central location and distribution width and asymmetries for the various datasets. Consensus values were obtained by modeling the variation between laboratories using a skew normal distribution. This approach gave consensus distributions with values for mean, standard deviation, and shape factor of 95.8, 38.2, and 6.3 nm for length and 7.7, 2.2, and 2.9 nm for width, respectively. Comparison of the degree of overlap between distributions for individual laboratories indicates that differences in imaging resolution contribute to the variation in measured widths. We conclude that the selection of individual CNCs for analysis and the variability in CNC agglomeration and staining are the main factors that lead to variations in measured length and width between laboratories.

Preparation of nanocellulose by hydrolysis catalysedusing salts with different Fe valency

The production of cellulose nanocrystals (CNCs) from vegetable fibres and residues has been intensely investigated due to the properties of high crystallinity and specific surface area of these nanofillers. The most common method of obtaining CNCs is by acid hydrolysis with inorganic acids; however, this method can lead to uncontrolled depolymerisation of the cellulose. Thus, this article examines the use of Lewis acids (FeSO4, Fe2(SO4)3 and FeCl3) as co-catalysts in the acid hydrolysis process and compares their impact on the yield, reduction of particle size and crystallinity index of the CNCs. The results show that the presence of Fe2(SO4)3 and FeCl3 improved the yield (50 and 27%, respectively) and decreased the particle size (632 and 66 nm, respectively) of the CNCs obtained in the hydrolysis process. On the other hand, the crystallinity index values were similar to that of microcrystalline cellulose (MCC), which was probably due to the severe conditions of the hydrolysis process that was used. The scanning transmission microscopy (STEM) images showed a spherical morphology for the CNCs obtained by both inorganic acid and Lewis acids; once again, this was probably due to the severe hydrolysis conditions. Thus, the presence of Lewis acids in the hydrolysis process makes it more efficient because it increases the efficiency of the hydrolysis in a less corrosive environment and with less probability of depolymerisation of the cellulose.

Cellulose nanocrystals from blueberry pruning residues isolated by ionic liquids and TEMPO-oxidation combined with mechanical disintegration

In the last years, Chile has increased the production of blueberries; consequently, a large number of lignocellulosic residues derived from the harvesting and pruning are being generated. These residues are commonly burned, therefore increasing CO2 emissions. This study focuses on the extraction of two added-value products from blueberry pruning residues (BPRs), cellulose nanocrystals (CNC-IL) isolated using ionic liquid (IL) 1-ethyl-3-methylimidazolium [emim][Cl], and carboxylated nanocellulose (TOCNC), isolated with (2,2,6,6-tetramethylpiperidine-1-yl) oxyl or TEMPO reagent combined with a mechanical disintegration process. These products were characterized by zeta potential (ζ), FTIR, XRD, TGA, AFM, and conductometric titration. Results show oval-shaped CNC-IL particles with lengths of 46.1 ± 9.3 nm; meanwhile, TOCNC were rod-like shaped particles, with lengths of 120.3 ± 30.6 nm. These BPRs showed a promising potential to produce cellulose nanocrystals (CNCs) with different surface properties, opening a new alternative for the production of cellulose nanomaterials (CNMs) with promising applications in colloidal formulations, coatings, among others.

Production of cellulose nanocrystals integrated into a biochemical sugar platform process via enzymatic hydrolysis at high solid loading

This work evaluated the viability of integrating the isolation of cellulose nanocrystals (CNCs) via enzymatic hydrolysis at a high solid loading into the biochemical platform process for the production of sugars from sugarcane bagasse (SCB). SCB was first processed at a biochemical conversion pilot plant and bleached to yield a cellulose-rich pulp, which was enzymatically hydrolyzed at high solid and low enzyme loadings. The resulting hydrolysate had high sugar concentration (>120 g/L glucose) and the CNCs (20 nm in diameter) isolated directly from the hydrolysis residue showed superior properties (higher thermal stability, higher crystallinity index, and higher particle diameter uniformity) than the CNCs prepared from commercial bleached eucalyptus Kraft pulp. These findings demonstrate the technical viability of the proposed integrated process that combined with the high CNCs yield (approximately50%) and the no need for the costly ultrasonic dispersion treatment step to obtain nanoparticles can further contribute for improving the economic and environmental viability of the proposed enzyme-mediated isolation process.

Obtaining cellulose nanocrystals from pineapple crown fibers by free-chlorite hydrolysis with sulfuric acid: physical, chemical and structural characterization

Brazil is the second-largest world producer of pineapple and generates almost 45% of its initial mass in wastes after industrialization, mainly due to the inappropriate deposition of peel and crown, which contribute to environmental damage. In this study, pineapple crown fibers (PCF) residues were investigated as an essential alternative to produce cellulose nanocrystals (CNC). It was used a free-chlorite hydrolysis reaction combined with sulfuric acid using different times and acid concentrations to obtain CNC after obtaining of the bleached cellulose. CNC`s were characterized by zeta potential, TGA, XRD, FTIR, and TEM. The main results showed that the chemical treatments were efficient in the removal of amorphous components, increasing the fiber whiteness and the crystallinity index. The best result obtained was for a concentration of 64% of H2SO4 for two hours with values of particle size of c.a. 140 nm and Zeta potential of − 47.96 mV, validating the use of the PCF for CNC.

Selective Isolation Methods for Cellulose and Chitin Nanocrystals.

This Minireview focuses on the selective isolation methods for the preparation of cellulose nanocrystals (CNCs) and chitin nanocrystals (ChNCs). Various selective preparation strategies with specific preparation conditions and reaction mechanisms are summarized. In particular, these selective reaction routes include controlled acid hydrolysis and selective oxidations at specific positions of cellulose or chitin fibers as well as particular reaction sites of the repeating monosaccharide building blocks of their main chains. These lead to selective cleavage of the ordered and non-ordered regions of cellulose and chitin and result in efficient production of CNCs and ChNCs.

Nanocellulose from recycled indigo-dyed denim fabric and its application in composite films

In this study, nanocellulose was extracted from indigo-dyed denim fabric and the resultant nanocellulose properties were evaluated in comparison with those derived from bleached cotton fabric and wood pulp in order to investigate the potential of recycling denim waste for nanocellulose production and application. Sulfuric acid hydrolysis and (2,2,6,6-tetramethylpiperidin-1-yl) oxyl (TEMPO)-oxidation were utilized to produce cellulose nanocrystals (CNC) and cellulose nanofibers (TOCN), respectively. A stable CNC suspension with blue color was obtained after acid hydrolysis and the TEMPO process yielded colorless TOCN. The denim-derived nanocellulose possessed similar yield, morphology, size, crystallinity, and thermal stability to those derived from bleached cotton but higher crystallinity and thermal stability compared to the nanocellulose from wood pulp. When used to reinforce polyvinyl alcohol film, the blue indigo-CNC not only enhanced mechanical properties of the film but also provided the film with outstanding UV blocking.

Melt Processing of Cellulose Nanocrystal-Filled Composites: Toward Reinforcement and Foam Nucleation

Although the mass production of cellulose nanocrystals (CNC) shows the possibility of their use in scalable nanocomposite manufacturing, the low compatibility between the CNC-hydrophobic matrix and...

Maximizing production of cellulose nanocrystals and nanofibers from pre-extracted loblolly pine kraft pulp: a response surface approach

This study aims to optimize strong acid hydrolysis-based production of cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) from pre-extracted and fully bleached kraft pulp of loblolly pinewood, the most abundant and commercially significant softwood species in southeastern United States. The effect of four parameters, including acid concentration, temperature, duration and pulp particle size, on the yield and properties of CNCs was investigated using the central composite design (CCD) of response surface methodology (RSM) for process optimization. While CNC yield was significantly affected by acid concentration and hydrolysis temperature and was adequately explained by an empirical model, none of the characteristic properties of CNCs, including crystallinity index, surface charge and particle size, displayed any strong correlation to the process parameters within the experimental ranges tested. At different hydrolysis severities, we not only analyzed the waste streams to determine the extent of holocellulose degradation, but also evaluated the properties of leftover partially hydrolyzed pulp, called cellulosic solid residues (CSR), to gauge its potential for CNF production via mechanical fibrillation. Conditions that maximized CNC yields (60% w/w) were 60% acid concentration, 58 °C, 60 min and 40 mesh particle size. Twenty percent (w/w) of the pulp was degraded under these conditions. On the other hand, conditions that maximized CSR yields (60% w/w) were 54% acid, 45 °C, 90 min and 20 mesh particle size, which also produced 15% CNCs, caused minimal pulp degradation (< 5%) and imparted sufficient surface charge such that CSR was easily microfluidized into CNFs. Therefore, the strong acid hydrolysis process could be tuned to maximize the production of cellulose nanocrystals and nanofibers and obtain two products with different properties and applications through the process optimization.

Tomato plant residue as new renewable source for cellulose production: extraction of cellulose nanocrystals with different surface functionalities

With the aim of identifying new sources for cellulose manufacturing, post-harvest tomato plant residue (TPR) was proposed in this study as a viable and sustainable source for the extraction of cellulose derivatives, namely cellulose microfibers (CMF) and cellulose nanocrystals (CNC). Pure CMF with an average diameter of 20 µm were successfully produced by subjecting the raw TPR to chemical treatments and then characterized in terms of their morphology and physico-chemical characteristics. By subjecting CMF to sulfuric, phosphoric and citric/hydrochloric acid hydrolysis, sulfated CNC (S-CNC), phosphorylated CNC (P-CNC) and carboxylated CNC (C-CNC) have been successfully produced. This was done to produce CNC with different characteristics and surface functionalities depending on the inserted functional groups during the acid hydrolysis process. By using several characterization techniques, it was found that all the extracted CNC characterized by cellulose I structure, with a crystallinity index of 81–89, 81 and 78%, an aspect ratio of 40–49, 98 and 67 and zeta potential of − 27.8 to − 37.3, − 36.9 and − 22.3 mV for S-CNC, P-CNC and C-CNC, respectively. The determined thermal stability of all extracted CNC is relatively higher than that generally obtained for S-CNC from other sources, which suffer from limited thermal stability. The produced CNC with different surface functionalities formed stable colloidal suspensions in polar solvents such as water and dimethyl sulfoxide. The production of CMF and CNC from this underutilized waste has the potential to add value to the post-harvest tomato plant, which is produced annually as waste in vast quantities throughout the world, in addition to significantly reducing the volume of cumulative waste in the environment.

Oxidative treatments for cellulose nanofibers production: a comparative study between TEMPO-mediated and ammonium persulfate oxidation

In the recent years, several methods for producing cellulose nanofibers (CNF) have appeared. Depending on the type of treatment and its conditions, the source of cellulose and the fibrillation method, different properties and characteristics can be obtained. TEMPO-mediated oxidation has been extensively used for CNF production and it is considered as one of the most suitable treatments to obtain high-performance CNF with superior properties and reduced size. However, the recovery of the catalyst and its cost is still a challenge. In the recent years, the oxidation by means of ammonium persulfate (APS) has appeared as a potential alternative, although it is commonly used for cellulose nanocrystals production. The present work aims at comparing the properties of CNF obtained by means of TEMPO-mediated oxidation (TOCNF) and ammonium persulfate oxidation (APSCNF). For this, a similar oxidation degree was selected, adjusting the treatment conditions of both oxidative methods. The obtained results exhibited that similar properties can be obtained with different production costs associated. In addition, the APSCNF exhibited a significantly lower degree of polymerization and slightly higher transmittance, indicating the presence of higher crystalline regions. Finally, both types of CNF were tested over a recycled paper substrate, revealing that both APSCNF and TOCNF significantly increased the mechanical properties of paper with low effect on pulp drainability, representing a great advantage for the paper industry.