Volume 11 Issue 3

Nanostructured cellulose was successfully prepared from native cellulose using a homogeneous catalytic H2SO4 hydrolysis pathway in the presence of Cr(III)- and Mn(II)-transition metal salts as the co-catalyst. The effect of transition metal salts with different valence states (Cr3+ and Mn2+) on the physicochemical properties (chemical characteristics, crystallinity index, nano-structure, thermal stability, and morphology) of prepared nanocellulose was investigated. Interestingly, TEM micrographs showed that the Cr(III)-treated and Mn(II)-treated nanocellulose exhibited a web-like nanostructured-surface with average diameters of 44.7 ± 13.2 nm and 58.4 ± 15.3 nm, respectively. XRD study revealed that the crystallinity of nanocellulose was increased because the catalytic degradation of the less crystalline regions of cellulose occurred at a faster rate than its crystalline phases. Cr(III)-treated nanocellulose was capable of rendering a higher crystallinity index (75.6 ± 0.1%) compared with Mn(II)-treated nanocellulose (72.3 ± 0.4%). Furthermore, a dynamic light scattering (DLS) study revealed that Cr(III)-treated nanocellulose showed a smaller distribution range (92% at 14 to 135 nm) compared with Mn(II)-treated nanocellulose (92% at 607 nm). A higher valence state for the Cr(III)-cation, with a trivalent state (+3), rendered a more effective hydrolysis reaction compared with the Mn(II)-cation, with a divalent state (+2), for preparing the nanocellulose.

With the decreased demand for pulp and paper worldwide, the reorganization of pulp and paper mills for cellulosic sugar production is possible. To maximize cellulosic sugar production from the wood pulp with minimum resources, the effects of pH, buffer system, temperature, enzyme loadings, pulp concentrations, and mixing modes on enzymatic hydrolysis were investigated, one factor at a time. Temperature played an important role in enzymatic hydrolysis. When the temperature was lower than 45 °C, the sugar production declined dramatically to almost half of the maximum value. Increasing enzyme dosage, increasing pulp concentration, and adding xylanase increased sugar production. The intermittent manual mixing mode generated higher concentrations of sugars and could be used for large-scale production. At pilot-scale, the diverted pulp for the pulping process was directly hydrolyzed without any treatment, and the residue after hydrolysis was hydrolyzed by adding fresh enzymes. This study provides insight on economically feasible enzymatic hydrolysis of wood pulp at large-scale cellulosic sugar production.

During pretreatment, the pretreatment pH often plays an important role in removing hemicelluloses and lignin for improving the conversion of biomass to sugars. In this study, corn stover was subjected to magnesium bisulfite pretreatment (MBSP) under various pH conditions. The obtained data showed that the hemicelluloses and lignin were solubilized by MBSP, which led to changes in the structural and chemical properties of the pretreated material. The pretreatment pH could alter the existing forms of SO2, and magnesium bisulfite was the most effective reagent for removing lignin. A relatively neutral MBSP (pH 5.13) not only considerably improved the enzymatic hydrolysis yield (80.18%), but also produced a large amount of high-value xylo-oligosaccharides in the spent liquor. Furthermore, only the hemicellulose removal showed a linear relationship with the enzymatic hydrolysis yield. These results suggest that removal of all the lignin might not be necessary to improve the hydrolysis efficiency.

Peanut hull residues were considered for the manufacturing of particleboards. Various concentrations of two types of adhesive—polymeric diphenylmethane diisocyanate (MDI) and urea-formaldehyde (UF)—were separately combined with four types of peanut hull particles (fine, mixed, coarse particles, and peanut hull powder) to manufacture particleboards with a certain target density. The confidence level of the effect of the selected production parameters on the physical and mechanical properties of the panels was evaluated. The results showed that increasing the adhesive mass percentage significantly improved the dimensional stability of the boards. A better mechanical performance was achieved for the MDI-bonded boards compared with the UF-bonded boards. Superior bonding between the MDI adhesive and the peanut hulls with different particle geometries was also observed; the peanut hull powder and coarse particles were unsuitable for the manufacturing of panels, due to the risk of an internal blowout. The water resistance of the panels was poor, whereas the mechanical strength of the peanut hull particleboard met the class M-1 requirement of the ANSI A208.1 (2009) standard for wood particleboard.

Traditionally, the helmet shell has been used to provide protection against head injuries and fatalities caused by ballistic threats. In this study, because of the high cost of aramid fibres and the necessity for environmentally friendly alternatives, a portion of aramid was replaced with plain woven kenaf fibre, with different arrangements and thicknesses, without jeopardising the requirements demanded by U.S. Army helmet specifications. Furthermore, novel helmets were produced and tested to reduce the dependency on the ballistic resistance components. Their use could lead to helmets that are less costly and more easily available than conventional helmet armour. The hybrid materials subjected to ballistic tests were composed of 19 layers and were fabricated by the hot press technique using different numbers and configurations of plain woven kenaf and aramid layers. In the case of ballistic performance tests, a positive effect was found for the hybridisation of kenaf and aramid laminated composites.

Large quantities of volatile organic compounds (VOCs) are released from heat-treated bamboo during the manufacturing process of recombinant bamboo, which affects the environment and human health. In this study, bamboo was treated at 150 °C, 180 °C, and 210 °C for 3 h, and VOCs were collected every hour using a Tenax tube. The VOCs were analyzed with gas chromatography-mass spectrometry (GC-MS) to explore the effect of temperature and time on weight loss ratio, main components, and their relative proportions. The results showed that temperature considerably influenced weight loss ratio, and weight loss ratio increased rapidly at high temperature. Massive quantities of VOC were emitted during the first hour of treatment, and emissions decreased as the time and temperature increased. Terpenes were the primary component of the VOC emissions. Temperature and time exhibited minimal effects on the type of primary components, and the relative proportion of some components exhibited negligible changes over a range of temperatures and times.

Poplar wood was subjected to biological treatment with a white-rot fungus Trametes hirsuta C7784. The structural features of the lignin in the untreated and treated poplar wood samples were comparatively elucidated. Milled wood lignin (MWL) and residual enzymatic lignin (REL) fractions of each sample were sequentially isolated. The total pure yields of the isolated lignin fractions after white-rot fungus treatment exceeded 96% (based on the Klason lignin content), and thus, represented the whole lignin in the fungus-treated poplar wood. The structural features of the lignin fractions were quantitatively analyzed. β–O-4′ structures were the most prominent linkage in the biologically treated wood, and there were more present than in the untreated wood. To this effect, the lignin in the fungus-treated poplar wood was easily degraded and removed under mild conditions, which is essential for subsequent conversion processes.

Untreated and hot-water-extracted (HWE) Norway spruce (Picea abies) sawdust was cooked using the sulfur-free oxygen-alkali (OA) method under the following conditions: temperature, 170 °C; liquor-to-wood ratio, 5:1 L/kg; and NaOH charge, 19% on the oven-dry sawdust. In comparison with earlier studies conducted with birch sawdust, the spruce cooking yield data, together with the amount of the pulp rejects (78% to 86% for reference pulps from the initial feedstock and 73% to 83% for pulps from the HWE feedstock), revealed that the pretreatment stage prior to spruce OA pulping caused different effects on pulping performance. The analyses of the three main compound groups (i.e., lignin, volatile acids, and hydroxy acids) in black liquor indicated that slightly higher contents (25.5 to 45.9 g/L) of dissolved lignin were detected in black liquors originating from the HWE sawdust than in the black liquors from the reference material (27.2 to 39.6 g/L). In contrast, considerably lower (~20% decrease) volatile acid contents and similar or slightly decreased hydroxy acids contents were detected in the black liquors from the HWE sawdust.

The objective of this study was to provide fundamental parameters for the utilization of bamboo scrimber in the building structure field as a green building material. Both static tensile and compressive tests were conducted on bamboo scrimber, with 180 specimens for compressive tests and 173 specimens for tensile tests. The normal and lognormal distributions were selected to fit the experimental data. The design values were calculated according to the Chinese allowable stress design method and ASTM D2915 (2003). The results showed that both tensile strength (UTS) and compressive strength (CS) parallel to the fiber of bamboo scrimber were significantly higher than those of wood and other bamboo-based composite materials. Kolmogorov-Smirnov and chi-squared test results indicated that a lognormal distribution was a good fit for the UTS and CS except for the fitting result of UTS by the chi-squared test. The calculated design values of UTS and CS using ASTM D2915 (2003) were higher compared with those found using the Chinese allowable stress design method.

The physical properties of wheat straw treated with hydrothermal and chemical treatments were investigated using an electronic universal testing machine, Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The thermal stability of the wheat straw was also investigated using thermogravimetric analysis (TGA). The experimental results showed that the chemical treatment was a main factor governing the enzymatic saccharification of wheat straw. Different treatments of wheat straw had the same mass loss trend. The maximum mass loss occurred in the range between 250 and 400 °C for all straw samples. In this range, the wheat straw treated with NaOH showed an exothermic peak, while samples treated with the other treatments showed an endothermic peak. Chemical treatments disrupted the silicified waxy surface and destroyed the C-O bond. The internal structure of wheat straw treated with NaOH became porous and loose and exposed more accessible surface area of the cellulose to cellulase.