Research Articles

Lignin preparations from kraft and sulfite pulping, steam explosion, and enzyme saccharification processes were assessed as substrates for lignin polymerization catalyzed by Trametes hirsuta laccase (ThL). Oxygen consumption associated with laccase catalyzed oxidation of the selected lignins was measured using a microplate-based oxygen assay. Laccase-induced changes in the molecular masses of the lignin polymers were assessed with aqueous-alkaline size exclusion chromatography (SEC) and changes in monomeric phenolics by reverse-phase high pressure liquid chromatography (HPLC). Obtaining consistent results in the lignin-laccase assay system required careful pH monitoring and control. All lignin preparations were oxidized by ThL, the rate being highest for steam-exploded eucalypt and lowest for enzyme-saccharified lignin. Comparing lignins, higher lignin-laccase reactivity was correlated with lower lignin molecular mass and higher amounts of monomeric phenolics. Solubility was not an indicator of reactivity. Steam-exploded and lignosulfonate-treated pine preparations were further fractionated by ultrafiltration to determine what molecular mass fractions were the most reactive in ThL catalyzed oxidation. Both retentate (> 3kDa), and to a lesser degree permeate (< 3kDa), fractions were reactive.

The aim of this study was the development of an eco-friendly dye that may be used in furniture, woodworking, and upper surface treatment, with no ill effects to human health. The plant dyestuff was extracted from pomegranate skin (Punica granatum) and black mulberry (Morus nigra) using an ultrasonic method at different rates. The extraction percentage ratios were, by weight in distilled water, 25%, 30%, 35%, 40%, 45%, and 50% and were applied to Scotch pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis L.) through an immersion method. After that, the determination of color change under the accelerated weathering conditions and the feasibility as the upper surface stain of this dyestuff were studied. The values of total color change of the natural dye samples that were applied to the test material were determined after accelerated weathering processes lasting 50, 100, and 150 h, according to ISO 2470. The results showed the best color stability in Oriental beech wood that was treated with 30% pomegranate skin or black mulberry extract as well as Scotch pine wood that was treated with 25% pomegranate skin extract or 50% black mulberry extract. Exactly the same ΔE* values were obtained with the same dyestuff and same wood type, indicating close color stability behaviors. According to the results, both pomegranate skin (Punica granatum) and black mulberry (Morus nigra) can be used to color wood materials.

The surface characteristics of wood veneer are inevitably influenced by hot compression treatment, which is crucial to bonding ability in the production of veneer-based composites such as plywood and laminated veneer lumber (LVL). The objective of this study was to investigate the effect of compression at the temperature of 120 °C on the surface roughness, surface element compositions, and surface free energy (SFE) of poplar veneer. The results showed that the surface roughness of veneer decreased with increasing compression ratio (CR). X-ray photoelectron spectroscopy (XPS) analysis indicated that the oxygen to carbon atoms ratio (O/C ratio) of the veneer surface decreased, while the carbon C1 to C2 atoms ratio (C1/C2 ratio) increased due to hot compression. The SFE of veneer increased by 12% at the CR level of 11%. The improvement in wettability was mainly due to the interfacial contact area increase of the hydrophilic veneer and the decrease in hydrophobic air in the liquid-veneer interface as the CR level increased.

Response surface methodology (RSM) was employed to optimize dilute alkaline pretreatment conditions for the maximum glucose yield of poppy stalk, with respect to NaOH concentration (1.0 to 3.5%, w/v), pretreatment temperature (50 to 100 °C), and pretreatment time (10 to 110 min). Recovery of glucan ranged from 61.02% to 99.14%, based on the initial glucan in the raw material. The highest lignin removal (43.43%) was obtained at the pretreatment conditions of 90 °C and 3.50% NaOH for 90 min. The optimum pretreatment conditions for maximum glucose yield after enzymatic hydrolysis were found to be 2.40% w/v NaOH, 70 min, and 80 °C. Under these conditions, experimental glucose and xylose yields were 499.35 mg/g glucan and 498.66 mg xylose/g xylan, respectively.

A lignin-based quaternary amine anion exchanger (LQAE) modified from raw lignin was synthesized after the reaction with epichlorohydrin and triethylamine using an NaOH solution as the basic solvent. The reaction mechanism of the experiment was explored and validated. Effect of reaction conditions on the preparation of LQAE were investigated. The performance of the LQAE was characterized by FTIR, SEM, and elemental analysis. The adsorption rate and yield were the measurable indicators, and when the NaOH concentration was 6 M, the nitrate adsorption capacity and the yield were 36.7 mg nitrate/g anion exchanger lignin and 123.6%, respectively.

The lumber ofEucalyptusurophylla×E. camaldulensis was heat-treated at either 180, 190, 200, or 210 ºC for 3 h. According to the national forestry standard methods for evaluating the machining properties of lumber, the machining properties (including planing, sanding, boring, mortising, shaping, and turning) of heat-treated and untreated control samples were investigated. The results indicated that the machining properties of the lumbers were improved after heat treatment. In the machining comprehensive evaluation system (top score is 10 points), the scores of the control and heat-treated samples at 180, 190, 200, and 210 ºC were 4.74, 7.76, 8.08, 7.46, and 6.96 points, respectively. A temperature of 190 ºC was thus optimal for the comprehensive machining properties when heat-treatment was used to modify the machinability of E.urophylla×E.camaldulensis wood.

The chemical compositions of cotton stalk and bast are similar to those of hardwood and superior to those of grass fiber. With respect to the morphological characteristics of their fibers, cotton stalk is similar to hardwood and cotton bast is similar to softwood. The average length of cotton bast fibers is nearly triple that of cotton stalk fibers, and the length-to-width ratio is almost quadruple. Traditionally, cotton stalk and cotton bast are pulped together, which affects the quality and homogeneity of the pulp and complicates bleaching, limiting its use to low-grade paper. In this study, cotton bast and cotton stalk were separated and pulped individually by alkaline peroxide extrusion pulping (APEP). The orthogonal analytical method was used to determine the optimal pulping parameters. Compared to those obtained via the kraft pulp (KP) of cotton stalk as a whole, far superior yield and whiteness were obtained in APEP. Further, with APEP, lower amounts of chemicals and less energy were consumed and there was little pollution. The physical performance of APEP was slightly lower than that of KP. With respect to bast alone, the physical performance of APEP was almost as good as that of KP.

Ethanol production in a simultaneous saccharification and fermentation (SSF) process using waste textiles as feedstock was studied. The dissolution pretreatment of waste textiles in ortho-phosphoric acid resulted in at least 2 fold improvement in enzymatic hydrolysis rate and reducing sugar yield. The reducing sugars obtained from dyed or discolored waste textiles by cellulase hydrolysis demonstrated no inhibitory effect on ethanol fermentation activity of Zymomonas mobilis employed in SSF. SSF with a high waste textile loading (75 g L^-1) could still be operable due to the fast liquefaction of the pretreated substrate via enzymatic hydrolysis. Approximately 50 g L^-1 ethanol was achieved within 24 h. In addition to 100% cotton textiles, the 40/60 polyester/cotton (T/C) blend waste textile could also be pretreated under the same condition to achieve the comparable ethanol production yield (~0.4 g EtOH g^-1 glucose) from its cotton fraction in SSF.

ChineseAbutilon theophrasti fiber (AF) ranks first in the world for yield; however, its application in the textile field is limited due to its characteristics. In this study, AF was used to reinforce high-density polyethylene (HDPE). Mechanical property tests, observations of the internal combination, creep behavior, and resistance to accelerate ultraviolet (UV) aging were conducted on these composites with different mass ratios. The results showed that the addition of the fiber could improve the impact resistance of the AF/HDPE composites. However, when the additive fiber content was > 60%, the flexural properties and resistance to creep deformation of the composites significantly decreased. Under the same conditions, the hygroscopic properties of the composites increased. After exposure to accelerated UV aging, the flexural strength of the composites decreased, but their impact resistance slightly improved. Infrared analysis demonstrated that lignin and other botanical compositions induced oxidative degradation in the composites. When the fiber-to-HDPE mass ratio was 60:40, the properties of the material were optimal.

Agricultural production in Malaysia has been continually growing. Most of the agricultural waste has been discarded or burnt on land; however, these agricultural wastes can serve as a feedstock for biochar production, which contributes an insignificant net amount of carbon dioxide to the atmosphere after soil incorporation. Three kinds of primary biochar were used in this study: empty fruit bunch biochar (EFB), wood biochar (WB), and rice husk biochar (RHB). EFB and WB were produced by slow pyrolysis, whereas RHB was produced by gasification. This study aimed to understand how pyrolysis technologies of native feedstocks impact the chemical characteristics and short-term soil stability of biochar. The kinetic parameters of C-mineralization suggested a tri-phasic C-mineralization process (labile, unstable, and recalcitrant carbon). The estimates indicated the existence of a very labile C-fraction in RHB with a very small decay constant K3. Fourier transform infrared spectroscopy and X-ray diffraction showed the three phases of the biochar, from the microcrystalline C of the labile fraction to the largely amorphous intermediate C of the unstable fraction, and lastly the formation of turbostratic crystallite C in the recalcitrant fraction. It has been concluded that RHB had a higher degree of aromaticity and greater stability, and therefore should be more recalcitrant to biological and chemical degradation.