Research Articles

The colour change of wood has been the topic of numerous research activities worldwide. This study investigates the colour change of Robinia (Robinia pseudoacacia L.) and two hybrid poplars, namely Pannónia poplar (Populus x euramericana cv. Pannónia) and I-214 poplar (Populus x euramericana cv. I-214). The sapwood and heartwood were investigated separately for each of the poplars. The heartwood of Robinia was also investigated. The timbers were dried in a climate chamber at four different temperatures (20 °C, 40 °C, 60 °C, and 80 °C), as the relative humidity was reduced in 5 steps (95%, 80%, 65%, 40%, and 20%) at each temperature. The colour co-ordinates L*, a*, and b* were measured according to the CIELab system. Differences in terms of colour change between wood species and sapwood versus heartwood are discussed in the paper. The effect of wood moisture content and heat on the colour co-ordinates is provided. The colour of Robinia is more sensitive to heat than poplar.

This study aimed at determining the chemical composition of bio-oil from giant cane (Arundo donax L.), as well as its performance as a wood preservative. The performance was determined through water absorption, tangential swelling, and resistance to fungi and termites. Bio-oil was obtained by pyrolysis at 450 to 525 ºC. The yield of liquid, char, and gas was determined to be 45, 30, and 25%, respectively. The most abundant chemical compounds found in the bio-oil were acids, ketones, furans, benzenes, phenols, sugars, and guaiacols. Scots pine sapwood was impregnated with the obtained bio-oil at concentrations of 10 and 20%. Additionally, treated samples were impregnated with epoxidized linseed oil to study its effect on bio-oil leachability. The retention of the giant cane bio-oil was in the range of 50 to 100 kg m-3. Leached samples were exposed to white- and brown-rot fungi, according to European standard EN 113. Wood impregnated with only cane oil demonstrated a durability that classifies the treatment as very effective (mass loss less than 3%). Epoxidized linseed oil treatment significantly reduced water absorption of the treated samples with bio-oil and further improved the durability. A termite test showed that bio-oil was also effective against Reticulitermes flavipes.

Absorbent foams were produced at both the gram scale and the kilogram scale by treating bleached softwood kraft pulp fibers to TEMPO oxidation, followed by washing, fiber disintegration, and freeze drying. Two reaction temperatures and three different dosages of primary oxidant were evaluated to find suitable oxidation conditions. It was found that the absorption and retention capacities were 50 to 70% lower for kilogram-scale foams than for gram-scale foams. SEM studies showed that the kilogram-scale foams had larger pores than the gram-scale foams; this explains the major differences in absorption and retention. The oxidation treatments performed in both scales resulted in a major increase in the amount of carboxylate groups and a major decrease in DPV, but only minor differences in these factors were found in a comparison between pulps from gram- and kilogram-scale experiments. However, the kilogram-scale dispersing equipment appeared to cause more fiber cutting, while the equipment used in the gram-scale experiments promoted the liberation of microfibrils to a greater extent. Furthermore, in both the gram- and kilogram-scale samples, a high dosage of primary oxidant and a low oxidation temperature were found to maximize the retention of liquid.

Cationizations of galactomannan- and xylan-type hemicelluloses were performed in a solid state, with 2,3-epoxypropyltrimethylammonium chloride (ETA) as the cationic reagent under alkaline conditions. By this method, the reaction efficiency was significantly increased for all hemicellulose types, up to 90% in the case of xylan. The consumption of reagents was reduced by a factor of ten when compared to the reaction in liquid phase, while comparable values of the degree of substitution (DS) were obtained. By reducing the number of purification steps, the consumption of solvents was limited, and high mass yields were preserved. By all aspects, this method constitutes an economical and environmental gain for the cationization reaction of hemicelluloses. Native hemicelluloses and their cationic derivatives were tested as additives to the pulp slurry in order to increase the dry strength of the paper formed. The cationization of hemicelluloses had a beneficial effect on the mechanical properties of paper, with a supplementary gain of properties compared to the unmodified polysaccharides. Cationic derivatives of a DS 0.3 gave the best results for both polysaccharides, with the galactomannan-type being more efficient than the xylan-type with a 90% increase of the burst index.

The vibrational properties of eight resonance boards made from Picea glehnii, Picea jezoensis, Picea spinulosa, and Picea sitchensis were analyzed. The modulus of elasticity and the vibration transmission velocity of the resonance board, the modulus of elasticity of the beam samples cut from the edge of the resonance board, and the vibration response time of the soundboard (TL, TR: times for the longitudinal and radial directions, respectively) were calculated. After the resonance boards were incorporated into the pianos, the sound intensity of loud (LL) and soft playing (LS), sound length (S), and the dynamic range of volume (Vd) were measured. Then the influence of the vibrational properties of the resonance board on the acoustical quality of a piano was investigated preliminarily, and the results showed that the acoustical quality would improve notably with improvements in the vibrational properties in the y-direction of the resonance board, and that the TR affected acoustical quality more obviously than did TL.

Removal of methylene blue by activated carbon produced from tea fruit peel (Camellia sinensis L.) residue using agents ZnCl2 (AC-1) and H3PO4 (AC-2) was investigated in this work. Mesoporous activated carbons with desirable surface areas and total pore volumes were obtained. Meanwhile, the characteristics of the activated carbon were examined. The effects of solution pH (2 to 10), contact time (0 to 480 min), and adsorbate dosage (0.5 to 3.5 g L-1) were studied. Equilibrium adsorption data were found to be in good agreement with the Langmuir isotherm model. The maximum monolayer adsorption capacities of methylene blue onto activated carbons were 291.5 and 342.5 mg g-1 for AC-1 and AC-2, respectively. The intraparticle diffusion model indicated that intraparticle diffusion was not the sole rate-determining step. The results demonstrated that the easily available tea fruit peel activated carbon is an excellent adsorbent for the removal of methylene blue from aqueous solutions.

Cellulosic fibers in Oil Palm Empty Fruit Bunches (OPEFB) are tightly packed with lignin, hemicelluloses, small depositions of wax, and inorganic elements. In the present work, eco-friendly reagents with low concentrations of 20% (v/v) formic acid and 10% (v/v) of 30% hydrogen peroxide were employed at 85 ºC for the extraction of cellulose from OPEFB. The yield of 64% (w/w) achieved was among the highest ever reported. Based on the XRD, the alpha-cellulose content was 93.7% with a high crystallinity of 69.9%. The average diameter was 13.5 μm with structural evidence of separated fibrils as investigated by FESEM. The TEM analysis suggested that the material was crystalline and its geometry was a monoclinic structure. The FTIR spectral peaks representing wax and hemicelluloses at 1735 cm-1 and 1375 cm-1, respectively, and lignin at 1248 cm-1 and 1037 cm-1, were not observed in the extracted OPEFB-cellulose spectra. Based on the TGA results, thermal stability at 325 ºC with a single degradation curve suggests the purity of OPEFB-cellulose.

Carboxymethyl cellulose (CMC)-assisted refining was shown, by means of tests with a PFI mill, to have potential to save energy compared with conventional refining techniques. Previously it was thought that the energy-saving effect of CMC-assisted refining was caused by resultant lubrication that reduced friction. In this work, the refined fiber of eucalyptus alkaline peroxide mechanical pulp was analyzed. The mechanism of CMC-assisted refining is that the cell wall is fibrillated to peel and weaken cell wall strength. Then CMC permeates into the cell wall and swells it, and the fiber becomes more pliable. CMC-assisted refining is helpful in maintaining fiber length through resultant hydration to avoid more fiber cutting. In this work, fiber morphological changes in the course of PFI refining for different numbers of revolutions were shown in relation to CMC-assisted refining. The purpose of the research was to determine whether energy savings could be achieved by CMC-assisted refining and to study its influence on fiber morphological development. The study showed a linear relationship between fiber length and energy consumption, as well as an exponential relationship between fines and fiber length. These results are helpful for obtaining ideal fiber morphology in pulp and paper making, man-made board, natural nano-fibers and specialty fibers, and the food industry.

An enhanced, xylose-utilizing strain of Rhizopus arrhizus was successfully developed via modification using media with increasing concentrations of xylose. Xylose, a relatively cheap monosugar that can be easily obtained from corncobs, rice straw, and vinasse, was the sole carbon source used for both the seed culture phase and the fermentation process. After modification, this newly improved strain showed tremendous industrial potential for fumaric acid production using xylose. The fumaric acid production increased to 28.48 g/L (parental strain was 13.23 g/L) at 8% initial xylose, a carbon:nitrogen ratio of 200, and a residence time of 7 days. The volumetric productivity was 169.52 mg/L (78.75 mg/L) per hour.

Synthesized amphipathic lignin derivatives comprised of acidic acid lignin (AL) with poly(ethylene glycol) diglycidyl ether (PEGDE), ethoxy-(2-hydroxy)-propoxy-poly(ethylene glycol) glycidyl ether (EPEG) or dodecyloxy-poly(ethylene glycol) glycidyl ether (DAEO) were added before the enzymatic saccharification of unbleached cedar pulp along with two commercially available cellulases, Meicelase and Genencor GC220. At the same filter paper unit (FPU) dosage, GC220 showed higher sugar yield than Meicelase. The difference was attributed to the composition of processive and non-processive endoglucanase activities per FPU; GC220 had higher such activities than Meicelase. The sugar yield was significantly improved by the addition of the lignin derivatives. In addition, residual activities after the saccharification were maintained at the higher level by their addition than with polyethylene glycol (PEG) 4000. In particular, EPEG-AL yielded the complete recovery of cellulase activity when using 20 FPU/g of substrate. It was found that the lignin derivatives were directly associated with Cel6A, one of cellulase components, whereas PEG 4000 was not. Thus, it is evident that the lignin derivatives are promising agents to improve the enzymatic saccharification of cellulase.