Insight into the extraction and characterization of cellulose nanocrystals from date pits

This study aims to extract and characterize cellulose nanocrystals (CNCs) from date pits (DP), an agricultural solid waste. Two methods were used and optimized for the cellulose nanocrystals (CNCs) extraction, namely the mechanical stirrer method (CNCs₁) and the Soxhlet apparatus method (CNCs₂) in terms of chemical used, cost, and energy consumption. The results showed that scanning electron microscopy revealed the difference in the morphology as they exhibit rough surfaces with irregular morphologies due to the strong chemical treatments during the delignification and bleaching process. Moreover, transmission electron microscopy analysis for CNCs reveals the true modification that was made through sulfuric acid hydrolysis as it presents cellulose microfibrils with a packed structure. Fourier transform infrared proved that the CNCs were successfully extracted using the two methods since most of the lignin and hemicellulose components were removed. The crystallinity index of CNCs₁ and CNCs₂ was 69.99%, and 67.79%, respectively, and both presented a high yield of CNCs (≥10%). Ultimately, both techniques were successful at extracting CNCs. Based on their cost-effectiveness and time consumption, it was concluded that method 1 was less expensive than method 2 based on the breakdown of the cost of each step for CNCs production.     

Cellulose nanocrystals from native and mercerized cotton

Cellulose - Nanocelluloses occur under various crystalline forms that are currently being selectively used for a wide variety of high performance materials. In the present study, two cellulose...     

Extraction and characterization of natural cellulosic fiber from Passiflora foetida stem

This article presents a comprehensive characterization study of natural cellulosic fiber extracted from Passiflora foetida vine stem. The chemical composition of the obtained P. foetida fibers (PFFs) comprised high cellulose (77.9 wt%) and low lignin (10.47 wt%) content and had distinctly higher crystallinity (67.36%) of cellulose, which was determined by an X-ray diffractometer. The PFFs exhibited good tensile strength of 248?942 MPa associated with elongation (1.38?4.67%) during tensile testing. Thermogravimetric analysis revealed that the PFFs are thermally stable up to 320°C with kinetic activation energy of 85.46 kJ mol^?1; hence they ensure their suitability as a reinforcing phase in composites for potential applications.     

Phytochemical profiling,in vitro biological activities,and in-silico molecular docking studies of Typha domingensis

A comparative study between methanolic extract and n-hexane fraction of Typha domingensis (Typhaceae) was conducted for the evaluation of phytochemical potential, in vitro biological activities, and in-silico molecular docking studies. The phytochemical composition was estimated by total phenolic and total flavonoid contents, and by GC–MS analysis. Several biological activities were performed such as antioxidant assays (ABTS, FRAP, DPPH, & CUPRAC), enzyme inhibition activity (Tyrosinase, Acetylcholinesterase & Butyrylcholinesterase), thrombolytic activity, and antimicrobial activity (antibacterial & antiviral) to evaluate the medicinal importance of Typha domingensis. The results of the comparative study showed that methanolic extract has more total phenolic and total flavonoid contents (95.72 ± 5.76 mg GAE/g, 131.66 ± 7.92 mg QE/g, respectively) as compared to n-hexane fraction which confirms its maximum antioxidant potential (ABTS 114.31 ± 8.17, FRAP 116.84 ± 3.01, DPPH 283.54 ± 7.3 & CUPRAC 284.16 ± 6.5 mg TE/g). In the case of in vitro enzyme inhibition study and thrombolytic activity, better results were observed for methanolic extract. Almost similar antimicrobial patterns were observed for both methanolic extract and n-hexane fraction of Typha domingensis. The major bioactive phytochemicals identified by GC–MS were further analyzed for in-silico molecular docking studies to determine the binding affinity between ligands and the enzymes. The docking study indicated that most of the bioactive compounds showed a better binding affinity with enzymes as compared to the standard compounds (kojic acid & galantamine). The results of this study recommended that Typha domingensis has promising pharmaceutical importance and it should be further analyzed for the isolation of bioactive phytochemicals which may be useful for the treatment of several diseases.     

Cellulose fiber biodegradation in natural waters: river water,brackish water,and seawater

Cellulose, the main component of plant cell walls, is degradable in nature. However, to the best of our knowledge, this is the first report that compares the biodegradability of cellulose fibers with different structures in natural waters. River water, brackish water, and seawater were collected from the Kamo River and Osaka Bay, Japan. Biodegradation of cellulose fibers with different structures and crystallinities, ramie, mercerized ramie, and regenerated cellulose fibers in the collected natural water was investigated in the dark at 20 °C for 30 days. The primary and aerobic ultimate biodegradability were evaluated by weight loss and biochemical oxygen demand (BOD) tests, respectively. In the weight-loss test, cellulose fibers were found to be degraded by more than 50% in any natural water within 30 days. However, in the BOD test, biodegradation was diminished, with values of 40%, 20–30%, and 2–10% in river water, brackish water, and seawater, respectively. These results indicate that cellulose fibers are easily degraded into fine fragments, but it is difficult to cause their ultimate decomposition into water and carbon dioxide. Existence of such a tendency in the degree of biodegradation among the cellulose fibers remains unclear. The molecular weight of cellulose fibers in natural water was also measured during their degradation. The degradation behavior in river water and seawater was observed to be different from that in brackish water. The results thus obtained indicate that the microorganisms and enzymes that degrade cellulose fibers differ depending on the natural water, which influences the degree and mechanism of biodegradation.

     

Cellulose nanocrystals from lignocellulosic feedstock: a review of production technology and surface chemistry modification

Fossil fuel substitutes are being developed to combat the ecological impact and rapid exhaustion of petroleum-based products. Being the most abundant polymer on Earth, cellulose-based products are renewable and sustainable. Cellulose nanocrystals (CNCs) are derived from cellulosic-based materials, have good physicochemical properties, and can be used to produce numerous products. CNC synthesis and their applications have been extensively studied; however, they remain limited to laboratory-scale as several challenges hinder its commercial-scale production. Herein, the suitability of nanocrystalline isolation methods, including chemical, enzymatic, ionic liquids, and deep eutectic solvents, for mass production is evaluated. Poor re-dispersion of CNCs is a major challenge that hinders its utilization in many applications. Hence, surface chemistry modification of CNCs have also been reviewed. It has been concluded that the CNC isolation method and surface modification technique significantly impacts its cost, morphology, and physicochemical properties. This review paper presents the challenges often faced in the conversion of bench-scale studies into commercial production of nanocrystalline cellulose. Hence, this paper gives all the necessary information on the important aspects of raw material selection, nanocellulose isolation process selection, and suitable surface modification method together in a single review article. Readers will be able to identify the possible research gaps for future research studies.

     

Cellulose microfibrils from banana farming residues: isolation and characterization

Cellulose microfibrils have been prepared from banana rachis using a combination of chemical and mechanical treatments. The morphology and structure of the samples were characterized using transmission electron microscopy, atomic force microscopy, and X-ray diffraction. Fourier-transformed infrared spectroscopy (FTIR) was used to characterize the chemical modifications of the samples after each treatment. Suspensions of bundled or individualized 5-nm-wide microfibrils were obtained after homogenization (PH) whereas an organosolv (PO) treatment resulted in shorter aggregates of parallel cellulose microcrystallites. The sharper rings in the X-ray diffraction pattern of the PO-treated sample suggest a higher crystallinity due to a more efficient removal of hemicelluloses and dissolution of amorphous zones by the acid treatment. Both microfibrils and microcrystals prepared by both methods can be used as reinforcing filler in nanocomposite materials.     

Extraction,modification, and characterization of natural ligno-cellulosic fiber strands from napier grass

Napier grass is a high-productivity perennial grass that is a very important forage for animals in the tropics. In this research work, fiber strands from Napier grass were extracted and the effect of acetic acid treatment on their chemical composition, morphological and structural changes, and tensile and thermal properties was studied. The acid treatment was carried out using glacial acetic acid solution at three different concentrations (5, 10, and 15%) for 2 h. Chemical analysis indicated lowering of amorphous hemicellulose content on acid treatment. FT-IR spectroscopic studies revealed variation of functional groups on acid treatment. Scanning electron micrographs indicated roughening of the surface of the fiber strands due to the removal of the hemicellulose layer on acid treatment. X-ray diffraction analysis indicated an increase in crystallinity of the fiber strands on acid treatment. The thermal stability and tensile properties of the fiber strands increased on acid treatment. This fiber has competitive advantages when evaluated with other natural fibers and can be developed further as a potential reinforcement in polymer matrix composites.     

Cellulose nanocrystals and related nanocomposites: Review of some properties and challenges

Cellulosic nanoparticles with high Young's modulus, crystallinity, specific surface area, and aspect ratio can be found in the natural structure of plant fibers. Indeed, lignocellulosic fibers consist of semicrystalline cellulose nanofibrils embedded in an amorphous matrix mainly composed of lignin and hemicelluloses. These nanostructures give the mechanical strength to higher plant cells, and are biodegradable, renewable, resistant, and widely available to produce nanocomposites with low density, and improved and controlled mechanical, optical, and barrier properties. Nanoparticles can be extracted from cellulose using a top‐down mechanically or chemically assisted deconstructing strategy, and owing to their highly reactive surface ensuing nanomaterials can be chemically modified to tailor their properties for a wide range of applications. This review is limited to cellulose chemically extracted nanocrystals and aims to provide an overview about several aspects that involve this material, including sources, properties, challenges, and perspectives. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 791–806     

Extraction and characterization of new natural lignocellulosic fiber Cyperus pangorei

This research is focused on the study of the physical, chemical, mechanical, and thermal properties of a newly identified natural stem fiber, Cyperus pangorei. The chemical composition of Cyperus pangorei fibers (CPF) such as cellulose, lignin, ash, moisture, and wax contents was evaluated. Besides these, the fiber density was determined and the apparent diameter was measured using an optical microscope. Further, tensile, thermal, XRD, and FT-IR studies were performed to evaluate the suitability of the fiber as a reinforcement. The surface topography of CPF was analyzed using scanning electron microscopy (SEM). Encouraging properties such as increased stiffness, fiber texture, and higher thermal stability suggest the suitability of CPF as reinforcement in polymer matrices.     

Cellulose nanocrystals from bleached rice straw pulp: acidic deep eutectic solvent versus sulphuric acid hydrolyses

The present work aims to investigate the feasibility of oxalic acid-choline chloride deep eutectic solvent (OA-ChCl DES), which serves as a promising green solvent that utilized in the acidic deep eutectic solvent (DES) hydrolysis. Oxalic acid-choline chloride DES cellulose nanocrystal (OA-ChCl DES CNC) was isolated from the bleached DES treated pulp (BP) through the acidic DES hydrolysis using 1:1 molar ratio of OA-ChCl DES. The functional groups, crystallinity index, morphological structure, particle size, zeta potential, thermal stability and surface chemistry of the OA-ChCl DES CNC were compared with the sulphuric acid cellulose nanocrystal (SA-CNC) that prepared via sulphuric acid hydrolysis. The findings revealed the presence of negatively charged carboxyl groups on OA-ChCl DES CNC surface after the acidic DES hydrolysis. The physicochemical analyses verified that the OA-ChCl DES CNC was in nano-sized range with polydispersity index (PdI) of 0.56, indicating slightly monodispersed nanoparticles. A stable OA-ChCl DES CNC colloidal suspension with zeta potential value of ?52.1?±?5.2 mV was obtained. The OA-ChCl DES CNC outweighed the SA-CNC in term of thermal stability (288 °C) despite having a slightly lower crystallinity index (76.7%). In fact, the OA-ChCl DES CNC with a yield of 55.1% was achieved through the acidic DES hydrolysis, suggesting that the OA-ChCl DES was capable of promoting efficient cleavage of strong hydrogen bonds in BP.

Graphic abstract

     

Cellulose nanocrystals as promising adsorbents for the removal of cationic dyes

Cellulose nanocrystals (CNCs) prepared from cellulose fibre via sulfuric acid hydrolysis was used as an adsorbent for the removal of methylene blue (MB) from aqueous solution. The effects of pH, adsorbent dosage, temperature, ionic strength, initial dye concentration were studied to optimize the conditions for the maximum adsorption of dye. Adsorption equilibrium data was fitted to both Langmuir and Freundlich isotherm models, where the Langmuir model better described the adsorption process. The maximum adsorption capacity was 118 mg dye/g CNC at 25 °C and pH 9. Calculated thermodynamic parameters, such as free energy change (ΔG = ?20.8 kJ/mol), enthalpy change (ΔH = ?3.45 kJ/mol), and entropy change (ΔS = 0.58 kJ/mol K) indicates that MB adsorption on CNCs is a spontaneous exothermic process. Tunability of the adsorption capacity by surface modification of CNCs was shown by oxidizing the primary hydroxyl groups on the CNC surface with TEMPO reagent and the adsorption capacity was increased from 118 to 769 mg dye/g CNC.     

Langmuir-Blodgett films of cellulose nanocrystals: preparation and characterization

The goal of this work is the preparation of monolayers of cellulose I nanocrystals providing flat crystalline cellulose surfaces. Suspensions of cellulose nanocrystals were prepared by hydrolyzing ramie and tunicin fibers with sulfuric acid. Due to surface grafted sulfate groups, the negatively charged, rod-like cellulose nanocrystals were found to form stable layers at the air-water interface in the presence of a cationic amphiphilic molecule such as dioctadecyldimethylammonium (DODA) used in this work. These layers were formed at different cellulose-DODA weight ratios, compressed and analyzed by tensiometry, ellipsometry and Brewster angle microscopy. At low cellulose concentrations the layers are discontinuous, becoming dense and homogeneous upon reaching a critical weight ratio, which depends on the aspect ratio of the cellulose nanocrystals. After transfer onto silicon wafers, the surface composition and morphology as well as the thickness of the films were examined by X-ray photoelectron spectroscopy, ellipsometry and atomic force microscopy. The results indicate that they are monolayer films, well structured, relatively smooth and pure. These films offer a crystalline and easily reproducible model cellulose surface.     

Extraction and characterization of cellulose nanocrystals from post-consumer wood fiberboard waste

This study investigates the potential of wood wastes, specifically post-consumer fiberboards, as a new source for cellulose nanocrystals (CNC). This underused resource has currently no commercially viable way to recycle it and so the volumes of fiberboard waste are growing rapidly. A sequential chemical fractionation was used to separate the three main constituents of wood, namely cellulose, hemicelluloses and lignin, and the non-wood components present in fiberboards, such as resins and finishes (e.g. varnishes, paints, plastics, laminates, etc.). Most of the non-cellulosic components and non-wood elements were removed by an alkali treatment followed by bleaching, resulting in a cellulosic fraction which is suitable for the further isolation of CNC by an acid hydrolysis step. The intermediate and final products were characterized by chemical composition, microscopic, spectroscopic and X-ray diffraction methods. The CNC obtained from wood waste are totally devoid of traces of contaminants and possess comparable characteristics and quality to those extracted from virgin wood fibers. The results indicate that fiberboard wastes can be used as promising alternative source for nanocelluloses production.     

Cloud-point extraction of nodularin-R from natural waters

A cloud-point extraction (CPE) technique for the determination of a cyanobacterial hepatotoxin, nodularin-R, in aqueous media using a cationic surfactant, tricaprylmethylammonium chloride (Aliquat-336), was developed. Cloud-point phase separation of Aliquat-336 at ambient temperature was induced by the addition of sodium sulfate. The Aliquat-336/Na₂SO₄ CPE system displayed large preconcentration factor, F_C, for nodularin-R. At the operational CPE conditions, F_C of 709.2 was achieved. Distribution constant, K_D, of the distribution of nodularin-R between the surfactant-rich and aqueous phases of the CPE system was estimated to be (4.94±0.8)×10³. Coupled to liquid chromatography with UV detection, the CPE method offered a detection limit of 330 pg ml⁻¹ (in freshwater)/1.3 ng ml⁻¹ (in seawater) and a repeatability of 6.4% (in freshwater) (n=7, P<0.05) for nodularin-R in a sample of 25 ml. The CPE is a rapid process and no cleanup step is required. Effects of pH, natural abundant anion (chloride) and dissolved organic matters (DOM, humic acid, HA) on the extraction efficiency were evaluated. A double CPE technique was developed to overcome interferences encountered in the analysis of environmental samples. Applicability of the new method to the determination of nodularin-R in real coastal marine water samples has also been demonstrated.     

Cellulose nanocrystals obtained from microcrystalline cellulose by p-toluene sulfonic acid hydrolysis,NaOH and ethylenediamine treatment

Cellulose nanocrystals (CNCs) were first isolated from microcrystalline cellulose (MCC) by p-toluene sulfonic acid (p-TsOH) hydrolysis. Cellulose II nanocrystal (CNC II) and cellulose III nanocrystal (CNC III) were then formed by swelling the obtained cellulose I nanocrystal (CNC I) in concentrated sodium hydroxide solutions and ethylenediamine (EDA) respectively. The properties of CNC I, CNC II and CNC III were subjected to comprehensive characterization by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results indicated that CNC I, CNC II and CNC III obtained in this research had high crystallinity index and good thermal stability. The degradation temperatures of the resulted CNC I, CNC II and CNC III were 300 °C, 275 °C and 242 °C, respectively. No ester bonds were found in the resulting CNCs. CNCs prepared in this research also had large aspect ratio and high negative zeta potential.

     

Cellulose and microcrystalline cellulose from rice straw and banana plant waste: preparation and characterization

As part of continuing efforts to prepare cellulose and microcrystalline cellulose (MCC) from renewable biomass resources, rice straw and banana plant waste were used as the available agricultural biomass wastes in Egypt. The cellulose materials were obtained in the first step from rice straw and banana plant waste after chemical treatment, mainly applying alkaline-acid or acid-alkaline pulping which was followed by hypochlorite bleaching method. The results indicate a higher α-cellulose content, 66.2 %, in case of acid-alkaline treatment for rice straw compared to 64.7 % in case of alkaline-acid treatment. A low degree of polymerization, 17, was obtained for the cellulose resulting from acid–alkaline treatment for banana plant waste indicating an oligomer and not a polymer, while it reached 178 in case of the cellulose resulting from alkaline–acid treatment for the rice straw. MCC was then obtained by enzymatic treatment of the resulting cellulose. The resulting MCC show an average diameter ranging from 7.6 to 3.6 μm compared to 25.8 μm for the Avicel PH101. On the other hand, the morphological structure was investigated by scanning electron microscopy indicating a smooth surface for the resulting cellulose, while it indicates that the length and the diameter appeared to be affected by the duration of enzyme treatment for the preparation of MCC. Moreover, the morphological shape of the enzyme treated fibers starts to be the same as the Avicel PH101 which means different shapes of MCC can be reached by the enzyme treatment. Furthermore, Fourier transform infrared spectroscopy was used to indicate characteristic absorption bands of the constituents and the crystallinity was evaluated by X-ray diffraction measurements and by iodine absorption technique. The reported crystallinity values were between 34.8 and 82.4 %, for the resulting cellulose and MCC, and the degree of crystallinity ranged between 88.8 and 96.3 % dependent on the X-ray methods and experimental iodine absorption method.     

Cellulose nanocrystals as biobased nucleation agents in poly-l-lactide scaffold: Crystallization behavior and mechanical properties

The mechanical strength of polymer scaffold is closely related to its crystallinity. In this work, cellulose nanocrystals (CNC) were incorporated into poly-l-lactide (PLLA) scaffold which was fabricated by selective laser sintering, aiming to improve the mechanical properties. CNC possesses numerous hydroxyl groups which might form hydrogen bond with PLLA molecular chains. The hydrogen bond induces the ordered arrangement of PLLA chain by using CNC as heterogeneous nucleating agent, thereby increasing crystallization rate and crystallinity. Results showed that PLLA scaffolds with 3 wt% CNC resulted in 191%, 351%, 34%, 83.5%, 56% increase in compressive strength, compressive modulus, tensile strength, tensile modulus and Vickers hardness, respectively. Encouragingly, with the incorporation of hydrophilic CNC, the PLLA/CNC scaffolds showed not only better hydrophilicity, but also faster degradation than PLLA. In vitro cell culture studies proved that the PLLA/CNC scaffolds were biocompatible and capable of supporting cell adhesion, proliferation and differentiation. The above results indicated that the PLLA/CNC scaffolds may therefore be a potential replacement in bone repair.     

硫脲表面修饰的ZnS:Cd纳米晶的合成及表征

采用硫脲做为表面修饰剂，合成了硫脲表面修饰的掺杂Cd^2＋的ZnS纳米晶（ZnS：CA／SC（NH2）2），用X射线粉末衍射、透射电子显微镜、红外光谱以及荧光光谱等手段进行了表征．实验结果表明，CA抖掺入了ZnS纳米晶中，硫脲分子中的S原子与该纳米晶表面的金属离子存在配位作用，ZnS：CA／SC（NH2）2纳米晶为分散性较好、平均粒径7nm的球形粒子且具有良好的荧光性质．