Research Articles

Cellulose was extracted from kenaf core powder by a series of bleaching processes and subsequently dissolved using an alkaline LiOH/urea solvent at low temperatures. The produced cellulose solution was mixed with polyvinyl alcohol (PVA) with different ratios of cellulose/PVA and coagulated to produce regenerated transparent films. The films were then air dried to produce transparent film. The effects of PVA content on tensile index, transparency, pore size, and printability of the films were studied. A slight reduction of 7% on the tensile index of the film was observed when the content of PVA increased to 10%. Nevertheless, the addition of 10% of PVA increased the porosity of the regenerated cellulose/PVA film, while the transparency of the film increased by 10%. The films were color-printed using a laser printer and can be recycled, in which the printed ink can be removed easily from the films with higher amount of PVA content. In addition, the films can be reprinted repeatedly several times.

Two tropical biomass species, teak (Tectona grandis) and obobo (Guarea thompsonii), were obtained in the form of sawmill waste from Nigeria and evaluated to determine their potential for gasification. Pyrolysis and gasification kinetics of the samples were investigated using a thermogravimetric analyser (TGA) at temperatures of 900 ºC and 1,000 ºC. Four iso-conversional methods, one peak temperature method, and two model-fitting methods were employed to determine the kinetic parameters, i.e. the apparent activation energy Ea, and pre-exponential factor A. Values of the gasification kinetic rate constant K were determined using two gas-solid reaction models: the volumetric reaction model (VRM) and the shrinking core model (SCM). The values obtained for all three kinetic parameters showed good agreement with values derived for samples of non-tropical wood.

Xylan-degrading enzymes from Aspergillus niger and Hypocrea orientalis were characterized by enzyme activity assays and protein profiling with SDS-PAGE and LC-MS/MS. The hydrolysis of Miscanthus xylan by xylan-degrading enzymes from A. niger, H. orientalis, and Trichoderma reesei were comparatively studied by HPLC analysis. It was found that the glycoside hydrolase families 10 xylanase was the main xylanase secreted by H. orientalis and A. niger when using corn cob and wheat bran as inducers. Compared to the enzymes from T. reesei,the enzymes from A. niger showed better efficiency in the hydrolysis of Miscanthus xylan into monosaccharides. Nevertheless, the enzymes from H. orientalis were more preferable for the hydrolysis of Miscanthus xylan into xylo-oligosaccharides (XOS), especially xylobiose and xylotriose. Miscanthus xylan degradation was significantly influenced by the activities of β-xylosidase and α-L-arabinofuranosidase. Xylan-degrading enzymes with high ratios of β-xylosidase and α-L-arabinofuranosidase are necessary for the efficient conversion of Miscanthus xylan into monosaccharides. However, xylan-degrading enzymes with low β-xylosidase activity and high α-L-arabinofuranosidase activity were required for producing XOS.

Ring width represents the total width of cells in a growing season. Relatively few studies have identified which of the parameters, cell number, size, or wall thickness is the greater contributor to variations in ring width. It is difficult to clearly explain the relationship between the climate in which a tree is located and the ring growth. In this study, the ring width and various tracheid characteristics (radial lumen diameter, double wall thickness, and number) in 298 rings of Picea crassifolia wood were investigated. Tree rings were quantitatively categorized based on their width into large, medium, and narrow classes. The tracheid number and lumen diameter were strongly correlated with annual ring width. The tracheid number had the strongest effect on the ring width. The effect of the tracheid number was three times larger than that of the lumen diameter. More earlywood cells were formed in larger rings, while larger earlywood cells were produced in years when narrow rings were formed. Wall thickness had no appreciable effect on ring width. The results of this study help to understand the relationship between the climate and the ring growth from the tree physiology perspective, when ring width is used as a climate proxy.

Changes in longitudinal stress wave velocity measured during the drying process of Cathay poplar (Populus cathayana) wood at different moisture contents were investigated. The test was performed at five different positions from bark to pith on each part. Five bars, cut successively from bark to pith with different fiber proportions, were also tested. The corrected velocity was calculated by dividing the velocity by the fiber proportion to negate any possible effects of wood structure on the velocity. The results showed that the longitudinal stress wave velocity decreased with increasing moisture content. Such trends were more obvious when the moisture content was lower than the fiber saturation point (FSP). The longitudinal stress wave velocity increased with increasing fiber proportion. A linear relationship between the corrected velocity and the moisture content was observed. This linear relationship was similar to the relationship between the relative velocity and the moisture content.

The phytochemical investigation, including fractionation and purification of 70% acetone extracts of Juglans sigillata seed husks, an agricultural residue, led to the isolation of five low-molecular weight galloyltannins. The structures of the extractives were elucidated as 1,2,6-tri-O-galloyl-β-D-glucose (1), 3,4,6-tri-O-galloyl-β-D-glucose (2), 2,3,4,6-tetra-O-galloyl-β-D-glucose (3), 1,2,3,4,6-penta-O-galloyl-β-D-glucose (4), and tannic acid (5), primarily based on their spectral (NMR and MS) and chemical evidence. Galloyltannins 1-5 showed strong inhibitory activity against mushroom tyrosinase, with IC50 values ranging from 35.27 to 76.37 μM; kojic acid, which was used as a positive control, had an IC50 value of 342.14 μM. It was further found that 1-5 inhibited melanin production and exhibited intracellular tyrosinase activity, as well as down-regulated mRNA and protein expression levels of tyrosinase, in B16F10 mouse melanoma cells. Therefore, the isolated extractives from seed husks of J. sigillata may serve as potential candidates for hyperpigmentation remediation and as skin-whitening agents in the cosmetics industry.

Activated carbon fiber is known as an excellent adsorbent material due to its well-developed pore structure. In this work, the porosity evolution of activated carbon fiber prepared from phenol liquefied wood with water steam activation at 650 to 800 °C for 20 to 260 min was examined by physical adsorption of N₂ at -196 °C. By the series of activation processes, the specific surface area and pore volume were increased with the increase of activation time, most significantly by activation at 750 °C for 20 to 180 min and by activation at 800 °C for 20 to 260 min. The microporosity was gently and progressively developed with increasing activation time at 650 to 700 °C, while it was sharply developed at the early stage of activations at 750 to 800 °C, and then tended to almost stabilize. The mesoporosity was well developed only by activation at 800 °C for longer than 100 min. The pore size distributions were principally ultramicropores (0.5 – 0.7 nm) during activations at 650 to 700 °C. By activations at 750 to 800 °C, the supermicropores (0.7 to 2.0 nm) as well as mesopores (2 to 4 nm) became progressively more important as the activation time was increased.

This study reports the preparation of a novel biomaterial from a forestry residue – Xanthoceras sorbifolia shell (XSS) – by solvent modification. The effects of acid and base (hydrochloric acerbic, acetic acid, sodium hydroxide, ammonia water) and some organic solvents (ethanol, acetone, ethyl acetate, chloroform, petroleum ether, and n-hexane) on the surface acidic functional groups (SAFGs) on XSS were investigated. The amount of SAFGs was quantified using acid and alkali chemical titration methods, and the characteristics of virgin XSS were compared with treated ones by FT-IR spectroscopy. It was found that acid solutions can increase the concentration of SAFGs, while alkaline solutions reduce it. The XSS treated in 0.5 M HCl has the largest number of total acidic functional groups and phenolic hydroxyl groups. The shell extracted with 2 M acetic acid has the highest concentration of carboxyl. The SAFG contents were remarkably increased by treatments with ethanol and acetone, due to the outstanding enhancement of phenolic hydroxyl. These changes in the SAFGs of XSS brought about by treatments with various solutions could be a theoretical foundation for modifying this residue to create a new type of highly efficient absorbent material.

Interactions between biomass constituents (cellulose, hemicelluloses, and lignin) under pyrolytic conditions have received more and more attention in recent years. A synthesized sample was prepared through mixing of cellulose and lignin with a mass:mass ratio of 1:1. The cellulose-lignin mixture (C-L-M) was heated from 20 to 800 °C using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer (TG-FTIR). The presence of the cellulose-lignin complex was theoretically confirmed by the suggestion of a hydrogen bond network between cellulose- and lignin-related oligomers through the density functional theory (DFT) method. To estimate the strength of the interaction between cellulose and lignin in different regions, correlation coefficients r were employed to nominate three regions: region I (20 to 305 °C), in which lignin and cellulose were pyrolyzed into oligomers without interacting with one another; region II (305 to 432 °C), which was deemed the intensive interaction region, with an r value of about 0.2; and region III (432 to 800 °C), in which the pyrolysis of cellulose ceased and only lignin was further degraded. A kinetic scheme was also proposed to model the co-pyrolysis of cellulose and lignin.

Functionalization of papermaking pulp fibers using inorganic particles was investigated as a novel approach. Different layered double hydroxide (LDH) particles were used in peroxide bleaching of thermomechanical pulp (TMP) and in oxygen bleaching of eucalyptus kraft pulp. LDH particles were also tested as binding sites for optical brightening agents (OBA) that are commonly used in paper production. The surface chemistry of LDH-treated pulps was examined using X-ray photoelectron spectroscopy (XPS) and apparent contact angle with water. Adsorbed LDH was not detected by XPS on the fiber surfaces after the bleaching trials, but it had a clear impact on the processes. LDH particles modified with terephthalate anions decreased the consumption of hydrogen peroxide and increased opacity by 3 units in TMP. Unmodified LDH particles enhanced the selectivity in oxygen delignification of kraft pulp, leading to 10% gain in ISO brightness and reduction of 2 units in Kappa number in comparison with conventional processes. Paper strength properties were unaffected in the presented system. After bleaching with LDH, the amount of anionic groups on pulp surfaces was increased. Also, the retention of OBA onto TMP fibers was improved with modified LDH particles. LDH proved to have great potential for current and prospective applications in pulp and paper manufacture.