Production Of Cellulose Nanofibrils Research Articles

Influence of TEMPO on preparation of softwood nanofibrils and their hydrogel network properties

From an economic and environmental perspective, the use of less chemicals in the production of cellulose nanofibrils (CNFs) is advantageous. In this study, we investigated the oxidation (TEMPO/NaClO2/NaClO, pH 6.8) of softwood (SW) particles with varying amounts of TEMPO (16, 8 or 0 mg g−1 of wood). Following, TEMPO-oxidized SW nanofibrils (TO-SWNFs) were obtained by nanofibrillation and their size, morphology, and crystallite size were assessed. Hydrogel networks of TO-SWNFs were prepared and mechanical properties were measured in dH2O and phosphate buffered saline (PBS) to compare their performance for possible biomedical applications such as wound dressings. The results reveal that the presence of TEMPO is of importance for TO-SWNF network properties, presenting higher eq. H2O absorption (≈2500 %) and elongation at break (≈10 %) with good wet strength (≈180 kPa). In addition, a decrease in use of TEMPO catalyst from 16 to 8 mg g−1 of wood is possible, without detrimental effects on hydrogel network properties (dH2O absorption ≈ 2000 %, elongation at break ≈ 13 %, wet strength ≈ 190 kPa) related to applications as wound dressings.

Ultrasound-assisted extraction of bioactives as a strategic step for chemical pretreatments in nanocellulose production from acerola by-products

Acerola by-products (AB) have been used as raw material for extracting active compounds; however, there were no studies related to the use of the remaining acerola by-product (RAB) from this extraction. This portion still has fibers and can be used for the production of cellulose nanofibrils (CNFs); therefore, the main objective of this study was to evaluate the production of CNFs using AB and RAB and to investigate whether the extraction can be a treatment step before bleaching/acid hydrolysis. AB and RAB were characterized before and after being chemically treated (AB_CT and RAB_CT, respectively). The fibers extracted from the RAB showed the highest cellulose contents (RAB: 36.6 % and RAB_CT: 69.9 %), suggesting that the extraction process had an impact on by-product defibrillation. The same trends were observed for CNFs produced by acid hydrolysis. CNFs based on RAB showed higher yield (CNF_RAB: 25.2 % and CNF_RAB_CT: 24.2 %), higher crystallinity index (CNF_RAB: 68.3 % and CNF_RAB_CT: 71.7 %) and higher thermal stability compared to CNFs extracted from AB and AB_CT. This study proved that it is feasible to use by-products after removing the active compounds for CNF production without other pre-treatments or in association with chemical treatment to obtain more crystalline and thermally stable CNFs.

Upscaling cellulose oxidation: Integrating TEMPO-mediated oxidation in a pilot-plant twin-screw extruder for cellulose nanofibril production

(TEMPO)-mediated oxidation (TMO) is a widely recognized pretreatment for producing highly fibrillated cellulose nanofibrils (CNFs) because of its efficiency and selectivity. However, the challenges of scaling up this process is limiting its implementation. This study explores enhancing the production of oxidized pulps (OPs) by performing the TMO reaction within a pilot-plant twin-screw extruder (TSE). This approach aims to oxidize large volumes of cellulose at high concentrations while simultaneously applying a soft mechanical fibrillation, making the upscaling process more sustainable and feasible. OPs and CNFs were characterized and compared to those obtained from the traditional TMO pretreatment in a stirred reactor as well as those pretreated by mechanical TSE. Results demonstrate that TMO within the TSE is more efficient and increase the yield fibrillation using 0.8, 0.08 and 2 mmol/g pulp of NaBr, TEMPO and NaClO, respectively. Multiple TSE steps decrease polymerization degree, enhance the process yield, and reduce the number of large fibers. Gradual addition of oxidants in multiple TSE steps prevents harsh reaction conditions and avoids yellowing of the final products.

Potential of NIR spectroscopy for predicting cellulose nanofibril quality in commercial bleached Kraft pulp of Eucalyptus

Multivariate models were developed to classify cellulose nanofibril (CNF) fibrillation by a quality index from near infrared (NIR) spectra. Commercial pulps of Eucalyptus spp. were used to produce cellulose nanofibrils by means of a fibrillator mill. After each of the five passes through the mill, samples were collected and analyzed for energy consumption and fiber classification. As a standard, pulps were oxidized with TEMPO reagent followed by a single pass through the mill to compare the resulting quality of CNFs produced by each method. NIR spectra of CNFs were associated with quality indices determined by conventional laboratory analyses that included morphology, turbidity, mechanical properties, X-ray diffraction and quality index measurements. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were applied to the spectral and experimental data. Fibrillator milling to obtain CNFs was efficient and resulted in gel formation following the third pass through the mill. NIR spectroscopy combined with PLS-DA was used successfully to create a model to classify quality of CNFs with 96 % certainty in 3 wt% solutions. These findings suggest that NIR spectroscopy holds promise for estimating CNF quality in suspension, particularly in real-time industrial applications where reliable estimates are crucial.

Production and Characterization of Cellulose Nanofibrils from Cotton Noil Waste

HighlightsCotton noil is a waste short fiber from the cotton yarn industry.Cellulose nanofibrils were produced by ball-milling and high-pressure homogenization processes.The width of nanofibrils ranged from 50 to 70 nm, with about 80% crystallinity index.The 5% CNF had a tensile strength of about 25 MPa and can be used as a reinforcing material.Abstract. Cellulose nanofibrils (CNF), the nanostructured cellulose, are promising nanomaterials for bio-based barrier coating and packaging applications. In this study, we investigated the production of cellulose nanofibrils from cotton noil, a waste short-fiber from the cotton yarn industry. The cotton noil fibers were subjected to ball milling for 10 min and dispersed in water to prepare slurries with three different concentrations (1%, 5%, and 10% w/v). Then, the slurry was passed through a high-pressure homogenizer at 700 bar pressure for 14 cycles or until the fibers were fibrillated into CNF hydrogels. The CNF with 1% and 5% concentrations had an average width of 70 and 52 nm, respectively, while the 10% CNF concentration had a mix of both nanofibrils and microfibrils due to inconsistent fibrillation. Fourier Transform InfraRed (FTIR) spectroscopy and X-ray diffraction techniques on the isolated CNFs demonstrated that the manufacturing process did not affect the cellulose molecular structure or crystallinity. The tensile strength of CNF from 5% concentration was about 25 MPa. This simple manufacturing method can be applied to utilize cotton noil fibers to produce CNF for various applications. Keywords: Ball milling, Cellulose nanofibrils, Cotton noil, Homogenization, Tensile strength.

Improving sustainability of cellulose nanofibrils production: FTIR spectroscopy for online control of the synthesis of recyclable magnetic TEMPO catalyst

2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) and its derivatives are well-established catalysts for various oxidation processes, despite its hazardous nature, causing harm to aquatic ecosystems. Thus, the reuse of TEMPO with a sustained high activity has gained significant importance for its industrial application, which has led to the development of supported TEMPO catalyst. In this context, the efficiency of the support process acquires high relevance. Therefore, this research is aimed at the improvement of the TEMPO supported on silica magnetically modified with Fe3O4 through the application of an online Fourier transform infrared spectroscopy (FTIR) probe to monitor its synthesis. FTIR effectively controlled the synthesis of supported TEMPO, by tracking online the concentration of 3-aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate (TEOS). Additionally, the presence of Fe3O4 particles in the core of the catalyst allowed its convenient recovery and subsequent reuse. Furthermore, the supported TEMPO catalyst was successfully applied in the oxidation of cellulose to produce nano/microfibrils. The carboxyl groups of the initial untreated cellulose increase from 0.05 mmol/g to 0.68 mmol/g with the supported TEMPO catalyst in presence of sodium hypochlorite and sodium bromide at 50 °C.

Sustainable upcycling of sugarcane bagasse into nanofibrillated cellulose utilizing novel green solvents and high intensity ultrasonication

Nanofibrillated cellulose (NFC) are versatile materials with applications spanning from advanced composites to water treatment innovations. Production of NFC using biopolymers found in agricultural waste residues holds importance due to their environmentally friendly nature, providing viable substitute for non-renewable petroleum resources. From the perspective of sustainable economy, this article focuses on utilizing agricultural waste, sugarcane bagasse (SCB) for the production of nanofibrillated cellulose using green approach. Here, we synthesized four different types of acidic natural deep eutectic solvents (NADES) and investigated their potential as pretreatment agents synergistically with acetosolv, aiming to enhance cellulose recovery from SCB. The pretreatment step led to significant yield of cellulose (84.4 %) using Gly-CA NADES and acetosolv combination. The yields in case of Xyl-CA (82.2 %), Gly-TA (75.6 %) and Xyl-TA (68.9 %) were relatively lower. Subsequent implementation of high-intensity ultrasonication (HIU) process resulted in rapid nanofibrillation of fibres with minimal cellulose loss. The morphological and particle size analyses of the produced NFC samples using SEM, TEM and DLS revealed that they exhibited heterogeneity with lengths varying from 25 to 80 nm and widths varying from 5 to 10 nm, indicating a high efficiency of disintegration. The qualitative analysis of NFCs was also investigated by employing XRD, FTIR and TGA/DTG that further determined that the structure of NFCs remained unaltered even after subjecting it to various treatment methods. Thus, the study signifies a holistic approach to resource recovery and promoting sustainable and environmentally friendly biomass conversion processes.

Characterization of spray dried cellulose nanofibrils produced by a disk refining process at different fineness levels

Three types of wood pulp feedstocks including bleached softwood kraft, unbleached softwood kraft and old corrugated containers were disk refined to produce cellulose nanofibrils at different fineness levels ranging from 50 to 100%, and the resulting aqueous suspensions of cellulose nanofibrils were spray dried. The spray drying experiments were carried out to examine different processing conditions for the different CNF feedstock types and fines level at various suspension concentrations to produce dry samples with free-flowing powder morphologies. The fineness levels and solids contents of CNF suspensions were set to 80% or more and 1.8% or less, respectively. If the solids content of the CNF solutions was high and the fibrillation level was low, plugging was experienced in the spray head because of the high viscosity of the suspensions, resulting in production of poor-quality powders. In terms of reduction in processing energy, even if the CNF suspension solids content was increased to 1.5 wt.%, the powder quality and the production yields were excellent. It was confirmed that high-quality powder under 20 µm were produced at a 90% fibrillation level of all CNF feedstocks. The resulting dry CNF powders were characterized to determine particle size distributions and morphological properties via a scanning electron microscope and a laser diffraction particle size analyzer. The particle sizes were smaller at higher fibrillation levels and lower solids content of the CNF suspensions. The CNF suspension derived from bleached kraft pulp, the average particle size decreased by 43% and 33% with the lowered solids contents from 1.8 to 1%, and the increased fineness levels from 80 to 100%, respectively.

A facile route for concurrent fabrication and surface selective functionalization of cellulose nanofibers by lactic acid mediated catalysis

Celulose nanofibers are lightweight, recycable, biodegradable, and renewable. Hence, there is a great interest of using them instead of fossil-based components in new materials and biocomposites. In this study, we disclose an environmentally benign (green) one-step reaction approach to fabricate lactic acid ester functionalized cellulose nanofibrils from wood-derived pulp fibers in high yields. This was accomplished by converting wood-derived pulp fibers to nanofibrillated “cellulose lactate” under mild conditions using lactic acid as both the reaction media and catalyst. Thus, in parallel to the cellulose nanofibril production, concurrent lactic acid-catalyzed esterification of lactic acid to the cellulose nanofibers surface occured. The direct lactic acid esterification, which is a surface selective functionalization and reversible (de-attaching the ester groups by cleavage of the ester bonds), of the cellulose nanofibrils was confirmed by low numbers of degree of substitution, and FT-IR analyses. Thus, autocatalytic esterification and cellulose hydrolysis occurred without the need of metal based or a harsh mineral acid catalysts, which has disadvantages such as acid corrosiveness and high recovery cost of acid. Moreover, adding a mineral acid as a co-catalyst significantly decreased the yield of the nanocellulose. The lactic acid media is successfully recycled in multiple reaction cycles producing the corresponding nanocellulose fibers in high yields. The disclosed green cellulose nanofibril production route is industrial relevant and gives direct access to nanocellulose for use in variety of applications such as sustainable filaments, composites, packaging and strengthening of recycled fibers.

Microscopic dissolution process of cellulose in alkaline aqueous solvents and its application in CNFs extraction - Investigating temperature as a variable

The target of this study is to gain a deeper understanding of the micro-dissolution process of cellulose in alkaline aqueous solutions and to develop a novel method for extracting cellulose nanofibrils (CNFs). Herein, the dissolution process of cellulose in alkaline aqueous solutions will be controlled by varying the temperature, and the undissolved cellulose will be analyzed to reveal the microscopic dissolution process of cellulose, and a novel process for extracting cellulose nanofibrils (CNFs) will be developed based on the findings. The crystalline structure of cellulose was gradually disrupted as the dissolution progressed, and the crystal form of cellulose changed gradually from cellulose I to cellulose II during the dissolution process, while all undissolved cellulose crystals remained as cellulose I. Cellulose, after its structure is disrupted during the dissolution process, will inevitably decompose into CNFs, and the microscopic dissolution process of cellulose follows a “top-down” dissolution sequence. The CNFs extraction method developed in this study can extract CNFs with high yield (>60 %) in a stable manner, as well as narrow particle size distribution, high crystallinity (>77 %), and good thermal stability. This study enhances the comprehension of the dissolution process of cellulose and paves a possible way for industrialization of CNFs production.

Recycling of TEMPO-mediated oxidation medium and its effect on nanocellulose properties

The potential of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)-mediated oxidation (TMO) to produce cellulose nanofibrils (CNFs) is hindered using costly and environmentally harmful catalysts, limiting its large-scale implementation. To promote sustainability, the TMO medium should be reused but there is a lack of knowledge on this process. The novelty of this research is the identification of the key parameters that affect the recirculation of the TMO medium, and their impact on the quality of the oxidized pulps and CNF products. Contrary to previous hypothesis, results show that the accumulation of salts is not a key parameter; instead, the pulp consistency during oxidation plays a vital role since concentrations higher than 10 g/L led to better CNF quality. Thus, reusing 75 % of the reaction medium, when high pulp consistency is used, does not alter the CNF properties. By reusing the reaction medium up to six times, the catalyst dose is dramatically reduced by >90 % for TEMPO and 80 % for NaBr, compared to the conventional process (0.1 mmol of TEMPO/g and 1 mmol of NaBr/g without medium reuse). Additionally, the high consistency oxidation enables a reduction of >80 % in the reaction time and effluent, and thus a threefold increase in CNF production.

Pre-treatment with calcium hydroxide and accelerated carbonation for cellulosic pulp fibrillation

Abstract In this study, the effect of different concentrations of calcium hydroxide (Ca(OH)2) was evaluated as a pre-treatment for accelerated carbonation and its influence on the fibrillation of cellulosic pulps to obtain nanofibrils, and its application as a coating agent for papers. Eucalyptus (EUC) and Pine (PIN) unbleached cellulosic fibers were submitted to pre-treatment with Ca(OH)2 at concentrations of 5 and 10% and subjected to accelerated carbonation, being subsequently mechanically fibrillated to produce cellulose nanofibrils (CNF). Pretreatment with calcium hydroxide followed by accelerated carbonation provided a 35% reduction in energy consumption. Cellulosic pulps EUC and PIN pretreated with calcium hydroxide showed higher fibrillation efficiency. There was a reduction in the cobb test values for papers coated with CNF in PIN. The WVP was lower for papers coated with CNF of EUC and control PIN. The CNF coating of EUC and PIN provided an oil barrier for the kit 11 solution. The CNF coating improved the dispersion of PVA and PVOH. The papers coated in this work have the potential to be used as packaging for fatty and oily foods or as a spreading agent for other industrial coatings.

Criteria for Assessing Sustainability of Lignocellulosic Wastes: Applied to the Cellulose Nanofibril Packaging Production in the UK

Extensive use of petrochemical plastic packaging leads to the greenhouse gas emission and contamination to soil and oceans, posing major threats to the ecosystem. The packaging needs, hence, are shifting to bioplastics with natural degradability. Lignocellulose, the biomass from forest and agriculture, can produce cellulose nanofibrils (CNF), a biodegradable material with acceptable functional properties, that can make packaging among other products. Compared to primary sources, CNF extracted from lignocellulosic wastes reduces the feedstock cost without causing an extension to agriculture and associated emissions. Most of these low value feedstocks go to alternative applications, making their use in CNF packaging competitive. To transfer the waste materials from current practices to the packaging production, it is imperative to assess their sustainability, encompassing environmental and economic impacts along with the feedstock physical and chemical properties. A combined overview of these criteria is absent in the literature. This study consolidates thirteen attributes, delineating sustainability of lignocellulosic wastes for commercial CNF packaging production. These criteria data are gathered for the UK waste streams, and transformed into a quantitative matrix, evaluating the waste feedstock sustainability for CNF packaging production. The presented approach can be adopted to decision scenarios in bioplastics packaging conversion and waste management.

Effect of phosphorylation on the production of cellulose nanofibrils from Eucalyptus sp

Effect of phosphorylation on the production of cellulose nanofibrils from Eucalyptus sp

Endo-Exoglucanase Synergism for Cellulose Nanofibril Production Assessment and Characterization.

A study to produce cellulose nanofibrils (CNF) from kraft cellulose pulp was conducted using a centroid simplex mixture design. The enzyme blend contains 69% endoglucanase and 31% exoglucanase. The central composite rotational design (CCRD) optimized the CNF production process by achieving a higher crystallinity index. It thus corresponded to a solid loading of 15 g/L and an enzyme loading of 0.974. Using the Segal formula, the crystallinity index (CrI) of the CNF was determined by X-ray diffraction to be 80.87%. The average diameter of the CNF prepared by enzymatic hydrolysis was 550-600 nm, while the one produced by enzymatic hydrolysis and with ultrasonic dispersion was 250-300 nm. Finally, synergistic interactions between the enzymes involved in nanocellulose production were demonstrated, with Colby factor values greater than one.

Oxidative treatment and nanofibrillation softwood kraft fibres with lytic polysaccharide monooxygenases from Trichoderma reesei and Podospora anserina

Cellulose oxidation and enzymatic treatments can be employed to reduce the energy consumption in production of cellulose nanofibrils (CNFs). Lytic polysaccharide monooxygenases (LPMOs) offer new biocatalytic tools for oxidative pretreatment of cellulosic fibres in this process. In this work the capability of LPMO enzymes to enhance fibrillation of bleached softwood kraft fibres was studied using two LPMO enzymes, i.e. C1/C4-oxidising AA9A from Trichoderma reesei (Tr AA9A) and C1-oxidising AA9E from Podospora anserina (Pa AA9E). The enzymatic treatments were carried out after mechanical pre-refining (grinding) of the pulp, which resulted in clear reduction of the intrinsic viscosity of the refined fibres compared to the previously published work, presumably due to better access of the enzymes on the fibre polysaccharides. The Tr AA9A treatments were carried out using different enzyme dosages (0.25–10 mg/g dry fibre) and fixed reaction time (24 h), resulting in fibres characterized by increased aldehyde content, which is in line with the C1/C4 oxidising activity of this enzyme. Comparison of the Tr AA9A to Pa AA9E with fixed enzyme dosage (2 mg/g dry fibre) and reaction time (24 h), showed that no remarkable increase in total charge of the cellulosic fibres could be obtained with either of the LPMO enzymes in these conditions. All the LPMO pretreatments improved fibrillation of mechanically refined fibres in microfluidization, seen as clearly lower residual fibre content and higher proportion nanosized material. In comparison of the Pa AA9E to Tr AA9A, clearly faster fibrillation was achieved with the Pa AA9E pretreatment. The mechanical and oxygen barrier properties of CNF films prepared from LPMO pretreated fibres were very similar to the reference CNF films while water vapour transmission rate was somewhat higher.

Cellulose nanofibril production by the combined use of four mechanical fibrillation processes with different destructuration effects

Cellulose nanofibril production by the combined use of four mechanical fibrillation processes with different destructuration effects

Response surface optimization of ionic liquid pretreatments for maximizing cellulose nanofibril production

Pretreatments with aqueous protic ionic liquid (PIL)–ethanolamine bis(oxalate) ([MEA][(HOA)(H2OA)]), combined with ultrasonic disintegration, were employed in cellulose nanofibril (CNF) production from pulp fibers.

Effects of residual pectin composition and content on the properties of cellulose nanofibrils from ramie fibers

In this study, a series of pretreatment methods (pectin extraction) were employed to prepare cellulose nanofibrils (CNFs) with different pectin composition and contents from ramie fibers. The comprehensive effects of residual pectin on the final properties of CNFs were investigated. The residual pectin did not have a significant effect on the size distribution of the obtained CNFs. While the presence of pectin led to higher zeta potential value, improved dispersion stability and enhanced storage modulus of the CNF dispersion, with the sodium carbonate extraction method showing the greatest impact. The possible mechanism for enhanced dispersion stability of CNFs is the formation of self-assembled hierarchical pectin-hemicellulose/lignin-cellulose nanostructures, offering abundant electrostatic repulsion and steric hindrance between the nanoparticles. This work provides guidelines for the tailored production of CNFs to meet the requirements for different applications.

Production of cellulose nanofibrils via an eco-friendly approach

Production of cellulose nanofibrils via an eco-friendly approach