Showing papers in "Bioresources in 2010"

Nanocomposites of poly(lactic acid) reinforced with cellulose nanofibrils

Abstract: A chemo-mechanical method was used to prepare cellulose nanofibrils dispersed uniformly in an organic solvent. Poly(ethylene glycol) (PEG 1000) was added to the matrix as a compatibilizer to improve the interfacial interaction between the hydrophobic poly(lactic acid) (PLA) and the hydrophilic cellulose nanofibrils. The composites obtained by solvent casting methods from N,N-Dimethylacetamide (DMAc) were characterized by tensile testing machine, atomic force microscope (AFM), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FT-IR). The tensile test results indicated that, by adding PEG to the PLA and the cellulose nanofibrils matrix, the tensile strength and the elongation rate increased by 56.7% and 60%, respectively, compared with the PLA/cellulose nanofibrils composites. The FT-IR analysis successfully showed that PEG improved the intermolecular interaction, which is based on the existence of inter-molecular hydrogen bonding among PLA, PEG, and cellulose nanofibrils.

Composting as a way to convert cellulosic biomass and organic waste into high-value soil amendments: a review

Abstract: Plant-derived cellulosic materials play a critical role when organic wastes are composted to produce a beneficial amendment for topsoil. This review article considers publications dealing with the science of composting, emphasizing ways in which the cellulosic and lignin components of the composted material influence both the process and the product. Cellulose has been described as a main source of energy to drive the biological transformations and the consequent temperature rise and chemical changes that are associated with composting. Lignin can be viewed as a main starting material for the formation of humus, the recalcitrant organic matter that provides the water-holding, ion exchange, and bulking capabilities that can contribute greatly to soil health and productivity. Lignocellulosic materials also contribute to air permeability, bulking, and water retention during the composting process. Critical variables for successful composting include the ratio of carbon to nitrogen, the nature of the cellulosic component, particle size, bed size and format, moisture, pH, aeration, temperature, and time. Composting can help to address solid waste problems and provides a sustainable way to enhance soil fertility.

Preparation and characterization of PVA composites with cellulose nanofibers obtained by ultrasonication.

Abstract: Cellulose nanofibers were obtained from microcrystalline cellulose (MCC) by the action of hydrodynamic forces associated with ultrasound. Nanofibers isolated from MCC by applying different ultrasonication conditions were characterized to elucidate their morpho-structural features by field emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, and dynamic light scattering. Several differences were observed regarding the size of the nanofibers obtained in different ultrasonic conditions, but no significant changes in the crystalline structure of cellulose nanofibers were detected. The obtained cellulose fibers were used at low levels (1 to 5 wt.%) as reinforcements in a poly(vinyl alcohol) (PVA) matrix. The mechanical and thermal properties of the PVA/cellulose fibers nanocomposites films were determined. The tensile strength and modulus of the PVA film were significantly improved by the addition of cellulose nanofibers. Slightly higher onset degradation temperatures were obtained for PVA composites in comparison to neat PVA, showing an increase of the thermal stability caused by the addition of cellulose fibers.

Luffa cylindrica as a lignocellulosic source of fiber, microfibrillated cellulose and cellulose nanocrystals

Abstract: In this work the annual plant called Luffa cylindrica (LC) has been characterized and used to prepare macroscopic lignocellulosic fibers and cellulosic nanoparticles, viz. microfibrillated cellulose (MFC) and whiskers, each of which can be used as a reinforcing phase in bionanocomposites. The morphological, chemical, and physical properties of LC fibers were first characterized. The contents of lignin, hemicellulose, and other constituents were determined, and scanning electron microscopy (SEM) observations were performed to investigate the surface morphology of the LC fibers. Sugars contents were determined by ionic chromatography, and it was shown that glucose was the main sugar present in the residue. MFC and whiskers were prepared after chemical treatments (NaOH and NaClO2), purifying cellulose by eliminating lignin and hemicellulose. Transmission electron microscopy (TEM) and SEM made it possible to determine the dimensions of LC whiskers and MFC. Tensile tests were carried out to investigate the mechanical properties of LF nanoparticles.

Simplified determination of lignin content in hard and soft woods via uv-spectrophotometric analysis of biomass dissolved in ionic liquids

Abstract: A new simple and safe method for quantifying lignin content in lignocellulosic biomass is described. The approach consists of measuring the absorbance of a solution of whole biomass dissolved in the ionic liquid 1-n-butyl-3-methyl imidazolium chloride, [Bmim][Cl], at 440 nm via ultraviolet- (UV-) visible spectrophotometry. An extinction coefficient for a lignin standard, highly pure lignin isolated from biomass through an organosolv process, is used in conjunction with the Beer-Lambert Law to calculate the lignin concentration. Principal component analysis (PCA) of Fourier Transform-Infrared (FTIR) spectra collected for several different lignin standards was performed to understand the differences in their chemical structure and composition (e.g., the relative amounts of syringyl and guaiacyl units). A rapid FTIR analysis of the whole biomass sample with unknown lignin content is required to assist in the proper selection of the lignin standard for the subsequent spectrophotometric analysis. The proposed method was tested and validated on two biomass types: Yellow poplar and Southern pine. The spectrophotometric approach yielded lignin contents for Yellow poplar and Southern pine of 25.7 ± 1.1% and 26.7 ± 0.7%, respectively, which are comparable to the values obtained by a standard wet chemical protocol, 25.1% ± 0.7 and 26.6 ± 0.4%, respectively.

Deacidification for the conservation and preservation of paper-based works: a review.

Abstract: Embrittlement threatens the useful lifetime of books, maps, manuscripts, and works of art on paper during storage, circulation, and display in libraries, museums, and archives. Past studies have traced much of the embrittlement to the Bronsted-acidic conditions under which printing papers have been made, especially during the period between the mid 1800s to about 1990. This article reviews measures that conservators and collection managers have taken to reduce the acidity of books and other paper-based materials, thereby decreasing the rates of acid-catalyzed hydrolysis and other changes leading to embrittlement. Technical challenges include the selection of an alkaline additive, selecting and implementing a way to distribute this alkaline substance uniformly in the sheet and bound volumes, avoiding excessively high pH conditions, minimizing the rate of loss of physical properties such as resistance to folding, and avoiding any conditions that cause evident damage to the documents one is trying to preserve. Developers have achieved considerable progress, and modern librarians and researchers have many procedures from which to choose as a starting point for further developments.

Isolation and characterization of cellulose and lignin from steam-exploded lignocellulosic biomass

Abstract: The isolation of cellulose from different lignocellulosic biomass sources such as corn cob, banana plant, cotton stalk, and cotton gin waste, was studied using a steam explosion technology as a pre-treatment process for different times followed by alkaline peroxide bleaching. The agricultural residues were steam-exploded at 220 oC for 1-4 min for the corn cob, 2 and 4 min for the banana plant, 3-5 min for the cotton gin waste, and for 5 min for the cotton stalk. The steamed fibers were water extracted followed by alkali extraction and finally peroxide bleaching to yield cellulose with different degrees of crystallinity. The degree of polymerization of the cellulose fraction ranged from 167.4 to 1615.7. Longer residence time of the steam explosion led to an increase in cellulose crystallinity. The ten isolated cellulose samples were further characterized by SEM, FT-IR, and thermal analysis. Four lignin preparations were also obtained from steam-exploded corn cob, banana plant, cotton stalk, and cotton gin waste after alkali treatment. The SEM micrographs of the lignin showed different morphological structure for the different agricultural residues. The FT-IR and TGA analyses showed that the steam pre-treatment led to an extensive cleavage of ether bonds, condensation reactions, and some demethylation of aromatic methoxyl groups in the lignin structure. The thermal stabilities of the isolated lignins were different for different agricultural residues.

Structural changes evidenced by ftir spectroscopy in cellulose materials after pre-treatment with ionic liquid and enzymatic hydrolysis

Abstract: Attempts were made to enhance the hydrolysis of Asclepias syriaca (As) seed floss and poplar seed floss (PSF) by cellulase after pre-treatment with ionic liquids. Two ionic liquids, namely 1-butyl-3-methylimidazolium chloride [BMIM]Cl and 1-ethyl-3-methylimidazolium tetrachloroaluminate [EMIM]Cl-AlCl3, were used. In comparison with conventional cellulose pretreatment processes, the ionic liquids were used under a milder condition corresponding to the optimum activity of cellulase. Hydrolysis kinetics of the IL-treated cellulose materials was significantly enhanced. The initial hydrolysis rates for IL-treated cellulose materials were greater than those of non-treated ones. The structural modifications of hydrolyzed cellulose materials were analyzed using FTIR spectroscopy.

Fast pyrolysis of lignins

Abstract: Three lignins: Indulin AT, LignoboostTM, and Acetocell lignin, were characterized and pyrolyzed in a continuous-fed fast pyrolysis process. The physical and chemical properties of the lignins included chemical composition, heat content, ash, and water content. The distributed activation energy model (DAEM) was used to describe the pyrolysis of each lignin. Activation energy distributions of each lignin were quite different and generally covered a broad range of energies, typically found in lignins. Process yields for initial continuous-fed fast pyrolysis experiments are reported. Bio-oil yield was low, ranging from 16 to 22%. Under the fast pyrolysis conditions used, the Indulin AT and LignoboostTM lignin yielded slightly more liquid product than the Acetocell lignin. Lignin kinetic parameters and chemical composition vary considerably and fast pyrolysis processes must be specified for each type of lignin.

Polyethersulfone composite membrane blended with cellulose fibrils

Abstract: Polyethersulfone (PES) is a common material used for ultrafiltration (UF) membranes, which has good chemical resistance, high mechanical properties, and wide temperature tolerances. The hydrophobic property of the PES membrane seriously limits its application. Cellulose fibrils are composed of micro-sized and nano-sized elements, which have high hydrophilicity, strength, and biodegradation. A composite membrane was prepared by the phase inversion induced by an immersion process. The characteristics of the composite membrane were investigated with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and atomic force microscopy (AFM). The pure water flux of the composite membrane increased dramatically with the increase of cellulose firbils. Mean pore size and porosity were significantly increased. Both mechanical properties and hydrophilicity were enhanced due to the addition of the cellulose firbils.

Chemical and thermal characterization of three industrial lignins and their corresponding lignin esters

Abstract: Corn stover and rice straw lignin samples received from ethanol pilot plants, along with softwood kraft lignin samples, were characterized using pyrolysis GC-MS, 13C CP/MAS NMR spectroscopy, and permanganate oxidation degradation. The lignins were then esterified using 1-methylimidazole as a catalyst in a pyridine-free reaction, and the thermal properties of the products were evaluated. Solid state NMR showed the rice straw lignin contained 18% residual polysaccharides. Pyrolysis GC-MS showed the softwood kraft, corn stover, and rice straw lignins to be G – type, H/G/S – type, and G/S – type, respectively. However, some discrepancy was apparent between the pyrolysis and permanganate oxidation studies as to the ratios of the monomeric make-up of the lignins. The kraft and rice straw lignins were determined to have high degrees of condensation, while the corn stover lignin was uncondensed. Little to no increase in solubility was noticed for corn stover or rice straw lignin esters in organic solvents. Glass transition temperatures (Tg) of the lignin derivatives were determined by a combination of differential scanning calorimetry, dynamic mechanical analysis, and parallel plate rheometry.

Analysis of the chemical composition and morphological structure of banana pseudo-stem

Abstract: An analysis of the chemical composition and anatomical structure of banana pseudo-stem was carried out using Light Microscopy (LM), Scanning Electron Microscopy (SEM), and Confocal Laser Scanning Microscopy (CLSM). The chemical analysis indicated there is a high holocellulose content and low lignin content in banana pseudo-stem compared with some other non-wood fiber resources. These results demonstrate that the banana pseudo-stem has potential value for pulping. In addition, we report for the first time from using LM and CLSM that banana stems possess a structure involving helicoidal fibers separated by barrier films.

Chemical modification effect on the mechanical properties of hips/ coconut fiber composites

Abstract: Lignocellulosic fibers from green coconut fruit were treated with alkaline solution (NaOH 10%m/v) and then bleached with sodium chlorite (NaClO2) and acetic acid (CH3COOH). Alkali-treated and bleached fibers were mixed with high impact polystyrene (HIPS) and placed in an injector chamber in order to obtain specimens for tensile tests. Specimens of HIPS/alkali-treated and bleached coconut fiber composites were tested in tensile mode, and the fracture surfaces of the composites were analyzed by scanning electron microscopy. Untreated, alkali-treated, and bleached coconut fibers were analyzed by scanning electron microscopy and X-ray diffraction. Alkaline treatment was effective for removing the extractives and increasing the roughness of surfaces, while the bleaching treatment intensified the effect of alkaline treatment, while increasing the crystallinity index and surface energy of fibers. Results of tensile tests showed that the addition of 30% alkali-treated and bleached fibers reinforcing the HIPS matrix provided considerable changes in the mechanical properties of composites in comparison with the pure HIPS. On the other hand, chemical treatments were not totally effective for improving the adhesion between the fiber and matrix, as was observed in the analysis of the fracture surfaces of composites materials.

Complete characterization of bagasse of early species of saccharum officinerum-co 89003 for pulp and paper making

Abstract: Bagasse from early species of Saccharum officinerum-Co 89003 has 71.36% useful, long, and thick-walled fibers with good slenderness ratio, but the rigidity coefficient is less than that of Eucalyptus tereticornis and Leucaena leucocephala. The kink index and kink per mm length are lower in bagasse fiber than E. terticornis, which gives rise to fewer weak points in the fiber. Low alcohol–benzene soluble substances in bagasse induce less pitch problems and favor more homogeneity in the paper. Lignin content in bagasse is comparable to Eucalyptus globulus and Leucaena leucocephala, but α-cellulose, and pentosans are slightly lower. A higher proportion of carbon content compared to hydrogen and oxygen increases the energy value of bagasse. It produces 42.2% pulp yield of kappa number 28.2 at optimum cooking conditions, such as active alkali 12% (as Na2O), temperature 150oC, and time (at temperature) 60 min. An addition of 0.1% anthraquinone at the optimum condition improves pulp yield by 2.6% and mitigates kappa number by 3.9 units.

Effect of heat treatment on the change in color

Abstract: Acacia hybrid (Acacia mangium x auriculiformis), a wood species of low dimensional stability which is used almost exclusively for pulp, paper, or as firewood, was heat treated in nitrogen at 210-230 oC for 2 to 6 hours. The changes in color and anti-swelling efficiency (ASE) of wood after heat treatment were determined for the different heat treatment conditions. The results show that heat treatment mainly resulted in the darkening of wood tissues, and heat-treated wood had better dimensional stability than those of the control samples. Chemical modifications of wood components were determined by FT-IR analysis. Spectra indicated that the hydroxyl group content was reduced by increased treatment intensity. This result coincides with the increase in dimensional stability of heat-treated wood. Heat treatment of acacia hybrid wood shows an interesting potential to improve the quality and value for solid wood products from plantation-grown wood species.

Techno-economical analysis of wood pellets production for U.S. manufacturers.

Abstract: Many companies in the U.S. are entering the wood pellets market due to the increasing importance of woody biomass utilization for energy purposes. Despite a 200% increase in U.S. production, it is difficult to obtain reliable information from the research community relative to the production costs, requirements, and market trends for wood pellets. Based on comprehensive investigations, a techno-economical model for the determination of production costs for U.S. manufacturers (internal market, with sell strategy based on bagged product) was developed, considering the most important technical and financial factors that affect pellet production. Outcomes from a case-study show that pellet production is profitable for U.S. manufacturers and distributors/retailers, with more revenue margin for retailers. Sensitivity analyses were performed, showing that a pellet plant is especially sensitive to changes to the cost of biomass and labor. In addition, changes in energy and CAPEX also affect the NPV and IRR of the project, but not as significantly as biomass and labor costs. Additional findings indicate that increasing the plant size especially increases CAPEX, with labor being the least increased cost factor; in addition, production factors have to be closely monitored for small-scale producers, due to increases in operational costs.

Characteristic of nanofibers extracted from kenaf core

Abstract: Cellulose nanofibers were isolated from kenaf core fibers by employing chemo-mechanical treatments. The morphologies and sizes of the fibers were explored with environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM). The results of chemical analysis showed that the cellulose contents of the bleached pulp fibers and nanofibers increased from 46% to 92% and to 94%, respectively. Most of the produced nanofibers had diameters in the range of 20 to 25 nm, whereas kenaf nanofibers ranged in diameter diameters from 10 to 75 nm. Fourier transform infrared spectroscopy (FTIR) analysis revealed the removal of lignin and the majority of the hemicelluloses from the kenaf core fibers. The thermogravimetric analysis (TGA), which was carried out to evaluate the thermal properties of the fibers, demonstrated that the thermal stabilities of these fibers were increased by the chemo-mechanical treatments. The results of X-ray analysis confirmed that chemical and mechanical treatments can improve the crystallinity of fibers.

Surface modification of sugarcane bagasse cellulose and its effect on mechanical and water absorption properties of sugarcane bagasse cellulose/ hdpe composites

Abstract: Cellulose fibres from sugarcane bagasse were bleached and modified by zirconium oxychloride in order to improve the mechanical properties of composites with high density polyethylene (HDPE). The mechanical properties of the composites prepared from chemically modified cellulose fibres were found to increase compared to those of bleached fibres. Tensile strengths of the composites showed a decreasing trend with increasing filler content. However, the values for the chemically modified cellulose fibres/HDPE composites at all mixing ratios were found to be higher than that of neat HDPE. Results of water immersion tests showed that the water absorption affected the mechanical properties. The fracture surfaces of the composites were recorded using scanning electron microscopy (SEM). The SEM micrographs revealed that interfacial bonding between the modified filler and the matrix was significantly improved by the fibre modification.

Oil palm fibers as papermaking material: potentials and challenges

Abstract: This paper reviews the physical and chemical characteristics of fibers from the stem, fronds, and empty fruit bunches of oil palm tree in relation to their papermaking properties. Challenges regarding the use of this nonwood material for papermaking are raised, and possible solutions to them are given. A vision for the complete utilization of oil palm biomass is also outlined.

Storage of comminuted and uncomminuted forest biomass and its effect on fuel quality

Abstract: White birch was stored in the form of bundles, wood chips, and loose slash for a period of one year to examine the changes in biomass fuel properties. The samples were collected at regular quarterly intervals to measure moisture content, CNS content, ash content, and calorific value. Data loggers were also placed into the stored woody biomass to measure the temperature change inside the piles. After the first quarter of the storage period and continuing into the next three months of storage, the moisture content showed the most significant change. The moisture content of the biomass bundles increased from 29 % to above 80 % (db). The moisture content of the pile of wood chips covered with a tarp decreased from 51% to 26% and showed a continuous decline in moisture content to the end of storage period to an average range of 16.5% (db). However, the moisture content of uncovered wood chip pile was observed to continuously increase throughout the storage period, resulting in more than double in magnitude from 59% to 160% (db). The dry matter loss was higher in wood chip piles (8~27%) than in bundles (~3%). Among the other properties, there was slightly higher loss of calorific value in wood chips (~1.6%) as compared to bundles (~0.7%) at the end of one year.

Effect of lignin content on enzymatic hydrolysis of furfural residues.

Abstract: The enzymatic saccharification of pretreated furfural residues with different lignin content was studied to verify the effect of lignin removal in the hydrolysis process. The results showed that the glucose yield was improved by increasing the lignin removal. A maximum glucose yield of 96.8% was obtained when the residue with a lignin removal of 51.4% was hydrolyzed for 108 h at an enzyme loading of 25 FPU/g cellulose. However, further lignin removal did not increase the hydrolysis. The effect of enzyme loading on the enzymatic hydrolysis was also explored in this work. It was concluded that a high glucose yield of 90% was achieved when the enzyme dosage was reduced from 25 to 15 FPU/g cellulose, which was cost-effective for the sugar and ethanol production. The structures of raw material and delignified samples were further characterized by XRD and scanning electron microscopy (SEM).

Adsorption of cadmium(ii) ions from aqueous solution by tectona grandis l.f. (teak leaves powder)

Abstract: Batch adsorption studies were undertaken with the abundantly available waste biosorbent Tectona grandis L.f. leaf powder for removal of cadmium(II) from aqueous solutions. The adsorption experiments were performed under various conditions such as time, temperature, different initial Cd(II) concentrations, pH, adsorbent dosage, and adsorbent particle size. The data showed that in 30 minutes, 1 g of Tectona grandis L.f. could remove 86.73% of cadmium(II) from 50 mL aqueous solution containing 100 mg L -1 of Cd. The isothermal data fitted well to both Langmuir and Freundlich models for Cd(II) adsorption on Tectona grandis L.f. Using the Langmuir model equation, the monolayer sorption capacity of Tectona grandis L.f. was evaluated to be 29.94 mg g -1 . The optimum pH value was found to be 5.5. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. The dynamic data fitted well to the pseudo-second-order kinetic model. Cd(II) adsorption was only marginally affected in the temperature range of 30 to 50 o C. An SEM of Cd(II) loaded powder showed formation of agglomerates. The FTIR of Cd(II) loaded powder showed negative shift in the wave numbers.

Characterization of extracted lignin of bamboo (neosinocalamus affinis) pretreated with sodium hydroxide/urea solution at low temperature

Abstract: Ball-milled bamboo (Neosinocalamus affinis) was first treated under ultrasound at 20 oC in 95% ethanol solution for 0 to 50 min, dissolved in sodium hydroxide/urea solution (7% NaOH/12% urea) at –12 oC, and then extracted with ethanol and dioxane to isolate lignin. The structure of the isolated lignin was characterized with a set of wet chemical and spectroscopic methods, including UV, FT-IR, 13C NMR, and HSQC spectroscopies. The results showed that the lignin extracted from bamboo consisted of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) type lignins with minor cinnamate units. The predominate lignin inter-units were β-O-4´ ether linkages, followed by phenylcoumaran and a lower proportion of resinol and spirodienone. It was also found that the ester groups of lignin were cleaved during the pretreatment process with cold alkaline solution.

Techno-economic analysis: preliminary assessment of pyrolysis oil production costs and material energy balance associated with a transportable fast pyrolysis system.

Abstract: A techno-economic analysis was performed for a 100 dry-ton/day (90,719 kg/day) fast pyrolysis transportable plant. Renewable Oil International® LLC provided the life cycle cost of operating a 100 dry-ton/day fast pyrolysis system using southern pine wood chips as feedstock. Since data was not available from an actual large-scale plant, the study examined data obtained from an actual 15 dry-ton/day pilot plant and from several smaller plants. These data were used to obtain base figures to aid in the development of models to generate scaled-up costs for a larger 100 dry-ton/day facility. Bio-oil represented 60% of mass of product yield. The cost for the bio-oil from fast pyrolysis was valued at $0.94/gal. Energy cost bio-oil and char was valued at $6.35/MMBTU. Costs associated with purchasing feedstocks can drastically influence the final cost of the bio-oil. The assumed cost of feedstocks was $25/wet ton or $50/dry ton. This paper is part of a larger study investigating the economic and environmental impacts for producing bio-oil / biocide wood preservatives.

Study of cellulose paracrystallinity.

Abstract: The paracrystallinity of cellulose samples was studied with a complex of investigation methods including X-ray, NMR, sorption, calorimetry, and some others It was found that the paracrystalline fraction of cellulose is located on the surface of crystallites as thin monomolecular layers having an average thickness of 04 nm The paracrystalline surface layers have distorted and loose packing that is characterized by a high distortion parameter δp = 018, increased specific volume Vp=0664 cm3/g, and decreased specific gravity ρp= 151 g/cm3 The paracrystalline fraction of the crystallite can be quantified by the parameter (α), which has an expressed influence on some properties of cellulose Increasing of the α-value causes expansion of inter-plane distances in the C1 unit cell, as well as promotes mercerization and dissolution of cellulose

Ultrasound-catalyzed tempo-mediated oxidation of native cellulose for the production of nanocellulose: effect of process variables

Abstract: In this study application of ultrasound in oxidizing native cellulose for the production of nanocellulose has been explored for the first time. Bleached hardwood kraft pulp was oxidized with an ultrasound (US) catalyzed 2,2,6,6-tetramethylepiperidin-1-oxyl (TEMPO) system (US-TEMPO-system) at five different temperatures – 5, 15, 25, 35, and 45°C and two pH ranges, 8.5-9.0 and 10.0-10.5 – to obtain the optimum reaction conditions. The reaction pH and temperature have significant effect on the kinetics of the formation of carboxylate in the oxidized pulps and produce depolymerization at temperatures greater than 25°C. Formation of carboxylate on the cellulose chain is directly proportional to the NaBr concentration. The pulp oxidized by the US-TEMPO-system at 25°C had 10-15% more carboxyls and showed a ca. 10% increase in the nanocellulose yield when compared to the TEMPO-system without sono-catalysis.

Effect of chemical treatment on rice husk (RH) reinforced polyethylene (PE) composites.

Abstract: Rice husk reinforced polyethylene composites and their test specimens were manufactured using a single screw extruder and an injection molding machine respectively. Raw rice husk was chemically treated with benzene diazonium salt in alkali, acidic and neutral media separately. Both raw and treated rice husk were used as filler. Four levels of filler loading (25, 30, 35 and 40 wt%) were used during composite manufacturing. Microstructural analysis and mechanical tests were conducted. Alkali media treated specimens yielded the best set of mechanical properties, while raw rice husk specimens had the worst ones. Based on filler loading, 35% filler reinforced composites had the optimum set of mechanical properties among all composites manufactured.

Wood hemicellulose/chitosan-based semi-interpenetrating network hydrogels : mechanical swelling and controlled drug release properties

Abstract: The cell wall of most plant biomass from forest and agricultural resources consists of three major polymers, cellulose, hemicellulose, and lignin Of these, hemicelluloses have gained increasing attention as sustainable raw materials In this study, novel pH-sensitive semi-IPN hydrogels based on hemicelluloses and chitosan were prepared using glutaraldehyde as the crosslinking agent The hemicellulose isolated from aspen was analyzed for sugar content by HPLC, and its molecular weight distribution was determined by high performance size exclusion chromatography Results revealed that hemicellulose had a broad molecular weight distribution with a fair amount of polymeric units, together with xylose, arabinose, and glucose The effects of hemicellulose content on mechanical properties and swelling behavior of hydrogels were investigated The semi-IPNs hydrogel structure was confirmed by FT-IR, X-ray study, and the ninhydrin assay method X-ray analysis showed that higher hemicellulose contents yielded higher crystallinity Mechanical properties were mainly dependent on the crosslink density and average molecular weight between crosslinks Swelling ratios increased with increasing hemicellulose content and were high at low pH values due to repulsion between similarly charged groups In vitro release study of a model drug showed that these semi-IPN hydrogels could be used for controlled drug delivery into gastric fluid

Isolation and physico-chemical characterization of lignins from ultrasound irradiated fast-growing poplar wood

Abstract: Ultrasonic irradiation with organic solvents and alkaline extractions were carried out on a fast-growing poplar wood, triploid of Populus tomentosa Carr., in an attempt to develop efficient lignin isolation procedures. Four organosolv and three alkaline lignin fractions were successively isolated and comparatively characterized by sugar analysis, alkaline nitrobenzene oxidation, gel permeation chromatography (GPC), Fourier transform infra-red spectroscopy (FT-IR), quantitative 13C, and 2D HSQC nuclear magnetic resonance (NMR) spectroscopy, as well as thermogravimetric analysis (TGA). The results showed that the ultrasonic treatments and sequential extractions with three different concentrations of NaOH led to a release of 90.9% of the original lignin. The four organosolv lignin preparations obtained under the ultrasound-assisted extractions were degraded significantly and contained more carbohydrate and non-condensed syringyl units when compared to the three alkaline lignin preparations. Furthermore, the analyses confirmed that L5, the lignin preparation with the highest yield (44.6% of the original lignin), was partially acylated at the γ-carbon of the side-chain preferentially over syringyl units. The percentage of lignin acylation of β-O-4’ linkages was about 14%. The amount of β-O-4’, β-β’, and –OCH3 were estimated to be about 0.31/Ar, 0.06/Ar, and 1.73/Ar, respectively. The ratio of S/G was calculated to be 2.0.

Complete characterization of wheat straw (triticum aestivum pbw-343 l. emend. fiori & paol.) – a renewable source of fibres for pulp and paper making

Abstract: Triticum aestivum PBW-343 is grown in most of the regions of India, and it is one of the renewable sources most suitable for papermaking. Anatomical studies illustrate that vascular bundles near the periphery contain a strong sheath of sclerenchyma cells, which constitutes about 80% of the fibers. The total fibers in wheat straw are about 39.20%, and parenchyma and epidermal cells account for 32.10, and 23.56%, respectively, of the total cells. The dimensions of wheat straw fibers are: average fiber length 1.18 mm, fiber width 13.60 µm, lumen diameter 5.68 µm, and cell wall thickness 3.96 µm. The dimensions of non-fibrous cells are: parenchyma 445x124 µm, vessels 96x57 µm, and epidermal cells 390x38 µm, which lie between the corresponding values for rice straw, and bagasse. Flexibility coefficients and Runkel ratio of wheat straw fires are quite comparable to bamboo. The low lignin contents of wheat straw reflect that it requires mild cooking conditions; however, hemicelluloses are on higher side. Addition of AQ under optimum soda cooking conditions improves pulp yield by 0.75%, and lowers kappa number by 26.1%. Optimum strength properties are obtained at 45±1 oSR except tear index, which declines with increased refining. The fine contents are much higher, and relatively comparable to Eucalyptus tereticornis in terms of curl index and kinks per mm.