Extraction Of Cellulose Nanocrystals Research Articles

Natural acidic deep eutectic solvent to obtain cellulose nanocrystals using the design of experience approach

In this study, a new approach to optimize the cellulose nanocrystals (CNCs) extraction using acidic natural deep eutectic solvents (NADES) was introduced using, for the first time, design of experiment method. Choline chloride:oxalic acid dihydrate with a molar ratio of 1:1 was used to extract CNCs. Then, three most important parameters were varied to design the experiment: (i) cotton fibre concentrations, (ii) temperature and (iii) treatment time. Two outcomes were studied: the CNC yield and the crystallinity. The mathematical model for crystallinity perfectly described the experiments, while the model for CNC yield provided only a tendency. For a reaction time of 6 h at 95 °C with a fibre concentration of 2 %, the expected optimum CNC yield was approximately 35.5 ± 2.7 % with a crystallinity index of 80 ± 1 %. The obtained experimental results confirmed the models with 43.6 ± 1.9 % and 81 ± 1 % for the CNC yield and the crystallinity index, respectively. This study shows that it is possible to predict the CNC yield CNC and their crystallinity thanks to predictive mathematical models, which gives a great advantage to consider in the near future a scale up of the extraction of cellulose nanocrystals using this original family of green solvents.

Lignocellulose nanocrystals from sugarcane straw

Efficient use of the entire lignocellulosic biomass is important for biorefinery sustainability, especially considering the extraction of high value-added products, such as nanocellulosic materials. This work investigates the feasibility of using sugarcane straw as a feedstock to obtain lignocellulose nanocrystals (LCNCs). Together with bagasse, the straw is a residue from the processing of sugarcane in the ethanol/sugar mills, but its effective use remains to be further studied. An organosolv pretreatment process was first applied to the straw for partial removal of the lignin and hemicellulose contents (reductions of 72.2 and 62.1 %, respectively) and to increase the surface area (observed by scanning electron microscopy and atomic force microscopy). Acid hydrolysis carried out for different reaction times, with or without mechanical treatment, resulted in high yields of sugarcane straw LCNCs (40–64 % of the total mass). X-ray diffraction analyses showed that the crystallinity of the LCNCs increased from 65 to 80 %, with an estimated average elementary crystallite size of 3.3 nm. The aspect ratios of the LCNCs were determined by AFM and ranged from 18.0–30.1. The onset of thermal degradation of the LCNCs occurred between 145 and 191 °C. The findings demonstrated the effective extraction of cellulose nanocrystals with residual lignin from sugarcane straw, opening the possibility of obtaining high value-added nanomaterials and contributing to the sustainability of future lignocellulosic biomass biorefineries.

Extraction of cellulose nanocrystals from microcrystalline cellulose for the stabilization of cetyltrimethylammonium bromide-enhanced Pickering emulsions

The cellulose nanocrystals (CNCs) synthesized by sulfuric acid hydrolysis are highly hydrophilic and prone to form the agglomerations due to the hydrogen bonding, which limit their applications in the formulations of Pickering emulsions. For this reason, we selected microcrystalline cellulose (MCC) as the raw material for the extraction of CNCs through sulfuric acid hydrolysis and hydrogen peroxide oxidation, and then combined the surfactants of cetyltrimethylammonium bromide (CTAB) and CNCs to prepare the (O/W) Pickering emulsions by high-speed shearing method. The physicochemical properties of the resultant CNCs were evaluated by scanning electron microscopy (SEM), atomic force microscope (AFM), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). The formed emulsions were characterized by fluorescent microscope (FM). And the effects of the CTAB concentration, pH and ionic strength on the stability of the formed Pickering emulsions were also investigated. Experimental results showed that the sulfuric acid hydrolysis of MCC induced the removal of the amorphous components and the cleavage of the crystalline microfibrils, making CNCs exhibit the curled and rod-like shape with the average hydrodynamic diameter of 460.5 nm (PDI = 0.585), zeta potential of -34.1 mV and the crystallinity index (CrI) of 77.3 %, which revealed good colloidal properties. In addition, the optimal emulsification conditions for CTAB concentration, pH and ionic strength were respectively 0.5 CMC, 11 and 20∼60 mmol/L. On the basis of the above results, the Pickering emulsions stabilized by CTAB/CNCs complex may have potential for large applications in foods, cosmetics and medicines.

Morphological, chemical and thermal analysis of cellulose nanocrystals extracted from bamboo fibre

This work investigates the extraction of cellulose nanocrystals (CNC) from bamboo fibre as an alternative approach to utilize the waste bamboo fibre. In this study, bamboo fibre was subjected to acid hydrolysis for efficient isolation of CNC from bamboo fibre. The extracted CNC's were morphologically, characterized via Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The energy Dispersive X-rays (EDX) provided the elemental composition of the prepared CNC's and X-ray diffractometer (XRD) exhibited their crystallinity. The physiochemical analysis was done via Fourier Transform Infrared (FTIR); and their thermal analysis was revealed by Thermogravimetric Analysis (TGA) and Differential scanning calorimetry (DSC). As from their morphological investigations, rod like structures of CNC's were observed under SEM analysis with higher carbon content as demonstrated by EDX, while needle shaped CNC's were observed from TEM and AFM studies. Acid hydrolysis for 45 min resulted into higher degree of crystallinity and higher yield of CNC's about 86.96% and 22% respectively. Owing to higher quality of CNC's obtained as a result of efficient and modified techniques, these can find potential usage in nanocomposites for biomedical and food packaging application.

Efficient extraction of cellulose nanocrystals from waste Calotropis gigantea fiber by SO42-/TiO2 nano-solid superacid catalyst combined with ball milling exfoliation

Cellulose nanocrystals (CNC) was successfully extracted from natural Calotropis gigantea fiber (CGF) by a combined ball milling defibrillation and SO42−/TiO2 nano-solid superacid catalyst-assisted method. In the extraction process, natural Calotropis gigantea fibers were defibrillated layer by layer, subsequently, catalysis degraded by nano-solid superacid catalysis. The new extraction method avoids large amounts of acid pollution. The yield of CNC obtained from Calotropis gigantea fiber was 55.37 %. Rod-like CNC with an average length of 242.06 nm and width of 8.80 nm was obtained. The aspect ratio of the CNC (the length:width) was 27.5 times. The green method avoids the use of large amounts of sulfuric acid. The ball milling defibrillation combined with SO42−/TiO2 nano-solid superacid catalyst-assisted provides an efficient and sustainable manner to make full use of natural Calotropis gigantea fiber resources.

Surface characterization, mechanical and abrasion resistance of nanocellulose-reinforced wood panels

Cellulose nanocrystals (CNCs) are promising particles in the production of wood fibre nanocomposites, due to their high stiffness, mechanical strength and low density. Wood fibres are the main source of cellulose, thus allowing the direct extraction of CNCs. As an attempt to improve the quality of wood fibre panels, this work performed topographical, tribological and mechanical characterization of medium density fibreboard (MDF) reinforced with CNCs at different concentrations, by substituting from 2 to 6% of the urea formaldehyde resin by acidic CNCs. The results showed no significant differences in the topographic characteristics and abrasion wear rates due to the incorporation of CNCs, although a tendency to obtain rougher panels was observed. The addition of CNCs at low proportions affected negatively the adhesion between the resin and the fibres, compromising the mechanical properties of the panels. On the other hand, some properties such as the modulus of rupture and hardness showed a tendency to recover when the amount of CNCs increased from 2 to 6%. The analysis of the microstructure of the worn samples showed more severe wear in the regions of poor adhesion between the fibres and the resin.

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.

Eco-friendly extraction of cellulose nanocrystals from grape pomace and construction of self-healing nanocomposite hydrogels

Extensive grape pomace from red-winemaking may seriously pollute the environment and cause the waste of resources. Cellulose after fermentation in grape pomace is suitable as the source of extract outstanding cellulose nanocrystals (CNCs). Herein, CNCs were successfully extracted from grape pomace with an eco-friendly and facile deep eutectic solvent (DES). The green DES with the composition of lactic acid/choline chloride (the molar ratio was 2:1), were used to fabricate CNCs. Importantly, the obtained CNCs as a robust nanocomposite can be successfully utilized to prepare the self-healing nanocomposite hydrogels. After added of Fe(III) and borax, the excellent self-healing performance of the guar gum-based hydrogels were achieved by the reversible noncovalent bonding interaction. Specifically, the hydrogels showed good mechanical properties (the stress was about 0.95 MPa, the strain was about 170%) and self-healing ability (the self-healing efficiency was about 90.0%). These biologically self-healing nanocomposite hydrogels can greatly broaden the recycling and utilization of grape pomace.

The valorization of municipal grass waste for the extraction of cellulose nanocrystals.

The study reports on the valorization of municipal grass waste (MGW) for the extraction of cellulose nanocrystals (CNCs), as an eco-friendly and sustainable low-cost precursor for cellulose nanomaterial production. The raw MGW was subjected to boiling in water pretreatment, and alkali and bleaching treatments for the extraction of cellulose fibers, followed by isolation of the CNCs through a conventional acid hydrolysis technique. Fourier transform infrared spectroscopy was used to analyze the cellulose fibers extracted while scanning electron microscopy and transmission electron microscopy images confirmed the presence of cellulose fibers and CNCs, respectively. The chemical composition of MGW was ascertained through the TAPPI-222 om-02 standard for lignin content and determination of α-cellulose. The diameters of CNCs are in the range of 5–15 nm with the length ranging from 100 nm to 500 nm, while a crystallinity index of 58.2% was determined from X-ray diffraction analysis. The production of CNCs from MGW is an avenue to convert green waste into a value-added product, in addition to reducing the volume of cumulative waste in the environment.

Characterization and Cellular Internalization of Spherical Cellulose Nanocrystals (CNC) into Normal and Cancerous Fibroblasts.

The aim was to isolate cellulose nanocrystals (CNC) from commercialized oil palm empty fruit bunch cellulose nanofibre (CNF) through sulphuric acid hydrolysis and explore its safeness as a potential nanocarrier. Successful extraction of CNC was confirmed through a field emission scanning electron microscope (FESEM) and attenuated total reflection Fourier transmission infrared (ATR-FTIR) spectrometry analysis. For subsequent cellular uptake study, the spherical CNC was covalently tagged with fluorescein isothiocyanate (FITC), resulting in negative charged FITC-CNC nanospheres with a dispersity (Ð) of 0.371. MTT assay revealed low degree cytotoxicity for both CNC and FITC-CNC against C6 rat glioma and NIH3T3 normal fibroblasts up to 50 µg/mL. FITC conjugation had no contribution to the particle’s toxicity. Through confocal laser scanning microscope (CLSM), synthesized FITC-CNC manifested negligible cellular accumulation, indicating a poor non-selective adsorptive endocytosis into studied cells. Overall, an untargeted CNC-based nanosphere with less cytotoxicity that posed poor selectivity against normal and cancerous cells was successfully synthesized. It can be considered safe and suitable to be developed into targeted nanocarrier.

Facile extraction of cellulose nanocrystals

A simple process for extracting cellulose nanocrystals (CNCs) is proposed that only uses high-pressure homogenization (HPH) controlling a process temperature. The proposed process was assessed and compared with normal production through acidic hydrolysis. Temperature-controlled HPH produced CNCs with high crystallinity, which linearly increased with increasing process temperature over 20 passes. The CNCs had uniform widths and lengths in the ranges of 4–14 nm and 60–320 nm, respectively. Undesirable chemical reaction can be avoided with the proposed process because no chemical was used to promote the CNC extraction. This method is an efficient and sustainable green approach to CNC production.

Extraction and characterization of nanocellulose crystals from cotton gin motes and cotton gin waste

Cellulose nanocrystals (CNC) have attracted a great deal of attention as an environmentally-friendly biorenewable resource for use as reinforcing agents in nanocomposites, polymers, gels, and emulsions. CNCs are typically prepared from extracted cellulose or highly refined cellulose products. The chemical refining process can alter the chemical and physical properties of the cellulose fibers prior to extraction of CNCs. Moreover, the method of isolation can also insert various functional groups onto the nanocellulose, affecting thermal stability and imparting different physical properties. Herein, two byproducts of the cotton industry, cotton gin motes and cotton gin waste, are investigated for the preparation of nanocelluloses. Cellulose was purified from these two post-process agroindustrial by-products and CNCs subsequently produced by sulfuric acid hydrolysis. Additionally, two acid hydrolysis methods were utilized to successfully extract CNCs from gin motes without chemical pretreatment. CNCs were obtained with diameters < 10 nm and lengths of ca. 100–300 nm resulting in high aspect ratios (12–33). Incorporating CNCs with these dimensions impart increased hydrophilicity to a substrate. The effect of post-extraction chemical treatments on crystallinity and morphology are discussed. The extracted nanocellulose derivatives were additionally characterized by FTIR, AFM, TGA, DLS, XRD and XPS. Differences in extraction method and chemical treatment resulted in different thermal properties and colloidal stability. Furthermore, this work provides a means of producing a high value commodity from inexpensive source materials such as cotton gin motes and cotton gin waste.

Banana fiber Cellulose Nano Crystals grafted with butyl acrylate for heavy metal lead (II) removal.

The present work deals with extraction of Cellulose Nano Crystals (CNCs) from Banana fiber using the steam explosion method. Extracted CNCs was grafted with butyl acrylate (BA) monomer with ceric ammonium nitrate (CAN) as an initiator. The prepared graft copolymer was analyzed using FTIR, XRD, SEM and EDAX. FTIR results indicate that the CH2 type of linkages was observed in the grafted copolymer showing effective formation of grafted copolymer. XRD results elucidate the changes in the crystalline behaviour of the prepared CNCs grafted butyl acrylate copolymer. SEM images of a prepared adsorbent was appeared to be heterogeneous and covered with clusters which will be suitable for adsorption. Batch adsorption studies was carried out for the removal of Pb(II) ions from the aqueous solution using the prepared copolymer. The parameters such as effect of pH, contact time, initial metal ion concentration and adsorbent dosage was investigated. From the observed results it was concluded that, the optimum pH: 5, contact time: 360 min, adsorbent dosage: 4 g/100 mL and initial metal ion concentration: 125 mg/L. The adsorption isotherm models of Pb(II) ions could be described very well by Freundlich model and the kinetic results revealed that pseudo-second-order kinetics showed a better fit.

Valorization and extraction of cellulose nanocrystals from North African grass: Ampelodesmos mauritanicus (Diss)

The aim of this research activity was based on the revalorization of Amplodesmos mauritanicus (Diss), an African grass largely presented in the Algerian territory. Diss stems were selected as native botanic material for the extraction of cellulose nanocrystals (CNC). Two different pretreatment steps were carried out to extract CNC from Amplodesmos mauritanicus stems and the following acidic hydrolysis procedure allowed to extract/obtain cellulose nanocrystals in aqueous suspension. The effect of the two different pretreatments, based essentially on chemical or enzymatic treatments, were deeply investigated and the properties compared. Field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were considered for the characterization of raw material, chemical or enzymatic treated Diss stems and CNC extracted from both chemical and enzymatic pretreated cellulose.

Improved mechanical properties of k-carrageenan-based nanocomposite films reinforced with cellulose nanocrystals

This work investigates the isolation of cellulose nanocrystals (CNC) from sugarcane bagasse (SCB) waste and the evaluation of their mechanical reinforcement capability for k-carrageenan biopolymer. The results from Atomic Force Microscopy and Transmission Electron Microscopy indicated the successful extraction of CNC from SCB following alkali, bleaching and acid hydrolysis treatments. The CNC displayed a needle-like structure with an average aspect ratio of 55. The surface functionality of the CNC was evaluated by Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy measurements. X-ray diffraction studies showed that the as-extracted CNC exhibit cellulose I crystalline structure, with a crystallinity index of 80%. The obtained CNC were dispersed into k-carrageenan biopolymer matrix at various CNC contents (1, 3, 5 and 8 wt%) and the prepared films were further characterized. The incorporation of CNC decreased the light transmittance values but enhanced the mechanical properties compared with the neat k-carrageenan film. Empirical Halpin-Tsai model was used to predict the CNC dispersion within k-carrageenan matrix. The obtained nanocomposite films have the potential to be used as food packaging material.

Efficiently Extracted Cellulose Nanocrystals and Starch Nanoparticles and Techno-Functional Properties of Films Made Thereof

Cellulose nanocrystals (CNC) and starch nanoparticles (SNP) have remarkable physical and mechanical characteristics. These properties particularly facilitate their application as high-performance components of bio-based packaging films as alternatives to fossil-based counterparts. This study demonstrates a time-efficient and resource-saving extraction process of CNC and SNP by sulfuric acid hydrolysis and neutralization. The yields of the hydrolyzed products were 41.4% (CNC) and 32.2% (SNP) after hydrolysis times of 3 h and 120 h, respectively. The nanoparticle dispersions were wet-coated onto poly(lactic acid) (PLA) and paper substrates and were incorporated into starch films. No purification or functionalization of the nanoparticles was performed prior to their application. Techno-functional properties such as the permeability of oxygen and water vapor were determined. The oxygen permeability of 5–9 cm3 (STP) 100 µm m−2 d−1 bar−1 at 50% relative humidity and 23 °C on PLA makes the coatings suitable as oxygen barriers. The method used for the extraction of CNC and SNP contributes to the economic production of these nanomaterials. Further improvements, e.g., lower ion concentration and narrower particle size distribution, to achieve reproducible techno-functional properties are tangible.

Extraction of Cellulose Nanocrystals with Structure I and II and Their Applications for Reduction of Graphene Oxide and Nanocomposite Elaboration

The aim of the present study is to investigate the effect of the hydrolysis process on the properties of nanocrystalline cellulose (NCC) isolated from different precursors and the subsequent use of the extracted NCC for the reduction of graphene oxide (GO). The raw materials (almond and peanut shells) chosen for the isolation of cellulose were selected on the basis of their abundance and their poorly investigation in the production of NCC. Microcrystalline cellulose (MCC) was firstly extracted by alkali and bleaching treatments, then hydrolyzed under different processes to produce NCC polymorphs with structure I (NCC-I) and NCC structure II (NCC-II). The Fourier transform infrared spectroscopy, the X-ray diffraction (XRD) and the 13C NMR studies of the alkali and bleached products confirmed the formation of cellulose type I with high purity and good crystallinity, while scanning electron microscopy (SEM) showed micrometric fibers with lengths reaching 80 µm. Sulfuric acid treatment of these microfibers results in NCC type I or II, depending on the hydrolysis process. SEM of the NCC samples exhibited nanorods with diameter and aspect ratio in the range of 20–40 and 20–25 nm, respectively. Thermogravimetric analysis (TGA) of the MCC and NCC products indicated stable materials with a degradation temperature reaching 240 and 200 °C for MCC and NCC, respectively. The other part of our work concerns the use of the obtained cellulose nanocrystals (type II) for the preparation of reduced graphene oxide composite (NCC/RGO), to demonstrate the reducing properties of the isolated NCCII.

Alfa fibers as viable sustainable source for cellulose nanocrystals extraction: Application for improving the tensile properties of biopolymer nanocomposite films

Due to its renewability, availability and high cellulose content (≈45%), Alfa fibers (Stipa tenacissima) have been identified as a sustainable source for cellulose microfibers (CMF) and cellulose nanocrystals (CNC) production. Subjecting raw Alfa fibers to alkali, bleaching and sulfuric acid hydrolysis treatments allowed producing CMF and CNC with high yields. The fluorescence microscopy confirmed that CMF, with average diameter of 10 μm, were successfully obtained after bleaching treatments. TEM and AFM showed that the CNC exhibit needle-like shape with an average diameter and length of 5 ± 3 nm and 330 ± 30 nm, respectively, giving rise to an aspect ratio of about 66. XPS measurement confirmed the presence of sulfate groups on the surface of CNC with 2.04 sulfate groups per 100 anhydroglucose units, confirming the negatively charged surface of CNC, with zeta potential value of − 47.39 mV. XRD studies showed that CMF and CNC exhibit cellulose I structure with crystallinity index of 71% and 90%, respectively. FTIR and TGA analyses were used to identify the chemical composition and thermal stability changes during different chemical treatments, suggesting that all non-cellulosic compounds were removed after alkali and bleaching treatments. The obtained CNC were dispersed into three different biopolymer matrices, e.g. chitosan, alginate, and k-carrageenan, at various CNC loadings (1, 3, 5 and 8 wt%), to evaluate their ability to enhance the tensile properties of biopolymers and, at the same time, to produce new biopolymer-based nanocomposite films. It was found that the tensile properties of the as-produced nanocomposite films were largely improved with addition of CNC, resulting in mechanically strong and flexible ecofriendly nanocomposite films.

Facile and eco-friendly extraction of cellulose nanocrystalsviaelectron beam irradiation followed by high-pressure homogenization

Cellulose nanocrystals were preparedviashort-time pretreatment by electron-beam irradiation in the solid state and disintegration using high pressure homogenization.

Extraction and Characterization of Cellulose Nanocrystals from Tea Leaf Waste Fibers.

The aim was to explore the utilization of tea leaf waste fibers (TLWF) as a source for the production of cellulose nanocrystals (CNC). TLWF was first treated with alkaline, followed by bleaching before being hydrolyzed with concentrated sulfuric acid. The materials attained after each step of chemical treatments were characterized and their chemical compositions were studied. The structure analysis was examined by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). From FTIR analysis, two peaks at 1716 and 1207 cm−1—which represent C=O stretching and C–O stretching, respectively—disappeared in the spectra after the alkaline and bleaching treatments indicated that hemicellulose and lignin were almost entirely discarded from the fiber. The surface morphology of TLWF before and after chemical treatments was investigated by scanning electron microscopy (SEM) while the dimension of CNC was determined by transmission electron microscopy (TEM). The extraction of CNC increased the surface roughness and the crystallinity index of fiber from 41.5% to 83.1%. Morphological characterization from TEM revealed the appearance of needle-like shaped CNCs with average diameter of 7.97 nm. The promising results from all the analyses justify TLWF as a principal source of natural materials which can produce CNC.