Volume 13 Issue 1

By using renewable inexpensive plant-derived materials such as lignin and furfuryl alcohol, a new bio-based, easily-prepared, and industrially suitable thermosetting grinding wheel named lignin-furanic grinding wheel (LFG) was prepared and characterized. Cross-linking between lignin and furfuryl alcohol under acidic conditions was established by carbon-13 nuclear magnetic resonance (13C-NMR) and electrospray ionization mass spectrometry (ESI-MS). In addition, as the results of thermomechanical analysis (TMA) and thermogravimetric analysis (TGA) suggested, the lignin-furanic resin exhibited high resistance to heat, and the glass transition temperature (Tg) as high as 170 °C. The new lignin-based grinding wheel presented no pores or cracks in the surface and it had a high hardness and compression resistance compared to the commercial phenolic grinding wheel (PG). Moreover, it exhibited high abrasiveness, and the cutting time for a metal tube was shorter than that of PG.

This work focuses on optimization of the laminated lap-joint lengthening technology that is used to produce large-size bamboo bundle laminated veneer lumber (BLVL). A three-factor Box-Behnken design was developed in which lap-joint length (x1), board density (x2), and thickness of lap veneer (x3) were the three factors. Multi-objective optimization of response surface model was used to obtain 17 optimum Pareto solutions by a genetic algorithms method. The mechanical properties of BLVL predicted using the model had a strong correlation with the experimental values (R2 = 0.925 for the elastic modulus (MOE), R2 = 0.972 for the modulus of rupture (MOR), R2 = 0.973 for the shearing strength (SS)). The interaction of the x1 and x3 factors had a significant effect on MOE. The MOR and shearing SS were significantly influenced by the interaction of x2 and x3 factors. The optimum conditions for maximizing the mechanical properties of BLVL lap-joint lengthening process were established at x1 = 16.10 mm, x2 = 1.01 g/cm3, and x3 = 7.00 mm. A large-size of BLVL with a length of 14.1 m was produced with the above conditions. Strong mechanical properties and dimensional stability were observed.

The objective of this work was to simulate the stresses produced during the drying of Eucalyptus nitens wood due to variations in the moisture content. The methodology involved experimental determination and simulation of drying stresses caused by the development of internal moisture content gradients. Modeling of the moisture transport was based on the concept of an effective diffusion coefficient. The mathematical model for stress-strain, and for moisture diffusion into the wood, was constituted by a system of second-order nonlinear partial differential equations with variable coefficients, which were numerically integrated by the control volume based on the finite element method (CVFEM). For validation purposes, tests were realized for evaluating deformations, stress drying, and moisture gradients that were produced during the drying of Eucalyptus nitens. The results showed satisfactory agreement between the experimental and simulated values, indicating an effective simulation.

To ascertain the applicability of the isoamyl nitrite-assisted sulfanilic acid sulfonation method, a series of carbon precursors (sucrose-derived disordered mesoporous carbon, ordered mesoporous carbon CMK-3, glucose-based hydrothermal carbon, and activated carbon) were utilized in attempts to synthesize carbon-based solid acids. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, elemental analysis (EA), and temperature-programmed desorption of ammonia (NH3-TPD) were applied to characterize the catalysts. The carbon-based solid acids were applied in the dehydration of xylose and corn stover to evaluate their catalytic performance. Sucrose-derived disordered mesoporous carbon (C-CCA) and ordered mesoporous carbon CMK-3 were successfully sulfonated by isoamyl nitrite-assisted sulfonation, while glucose-based hydrothermal carbon (HGC) and activated carbon (AC) were unsuccessful. Compared with ordered mesoporous carbon CMK-3 solid acid (S-CMK-3), sucrose-derived disordered mesoporous carbon solid acid (ISC-CCA) showed better performance for the production of furfural. The reusability of ISC-CCA for furfural production from xylose during 5 runs was favorable. Using pure water and ISC-CCA as a solvent and catalyst, from corn stover, achieved a furfural yield of 43.1% at 190 °C in 4 h.

Enzymatic hydrolysis of lignocellulosic biomass is the key step for controlling the cost of bioethanol production. However, the non-productive adsorption of cellulase onto lignin in biomass severely hampers the enzyme activity and hydrolysis efficiency. Thus, understanding the adsorption mechanism of cellulase onto lignin is critical for the development of enzyme mixtures and enzymatic hydrolysis. In this investigation, cellulase, β-glucosidase (BG), and xylanase adsorption onto lignin from eucalyptus and bamboo, extracted by alkali and hydrotropic techniques, were compared. The physico-chemical properties of the four types of isolated lignin were detected. Langmuir isotherms were used to interpret the cellulase adsorption kinetics of the lignin. The hydrophobicity was found to be the major factor that affected the cellulase adsorption affinity of lignin. The surface charge was important for the adsorption of BG and xylanase onto the lignin. A comparison was made between hydrotropic and alkali lignin, and the hydrotropic lignin from eucalyptus had the highest cellulase adsorption capacity and lowest BG and xylanase adsorption capacities.

Wood fiber sludge is a by-product of the pulp and paper industry, and 750,000 tons are generated per year in Finland. When aqueous fiber sludge (solid matter content 10 to 20%) is modified with water and enzymes, it is called biotechnologically modified fiber sludge (BMFS). So far, native fiber sludge has been only a waste material in Finland, but according to a new waste law, its waste tax is 70 € per ton. According to the present EU and Finnish strategies on waste materials, circular economy, and material-efficiency, all waste must be utilized primarily as material (reuse, recycling) and secondarily as energy. For these reasons, it is very important to develop new eco-, cost- and material-efficient utilization methods for this aqueous “pure waste” instead of landfilling and combustion. Continuing earlier experiments, which proved that BMFS is a good and efficient binding agent for combustion pellets, BMFS was studied in new utilization applications such as bedding pellets for horses as well as a road and horse riding hall dust binding agent. In laboratory measurements and field experiments, BMFS is a very efficient dust-binding agent and effective binding agent for bedding pellets.

Smart hydrophobic-hydrophilic self-switching cellulosic materials were synthesized by regioselective functionalization of cellulose in green Ionic Liquids (ILs). The thermal analysis indicated that the introduction of a macromolecular structure including a trityl or heptafluorobutyric group onto the cellulose chain increased the thermal stability of the cellulose derivatives. Wetting contact angle of the surface decreased from 103° to 73° as the holding time increased at ambient conditions (19.8 °C, 65%). After wetting, the surface free energy increased from 11.03 to 34.09 J·m, of which the polarity component increased from 60.92% to 94.19%. The XPS analysis indicated that the content of oleophobic-hydrophobic CF3-CF2-CF2-CO- groups at the exposed surface decreased after wetting, while the hydrophilic HOOC- groups increased, which verified the self-switching process between the hydrophobic and hydrophilic properties within the cellulosic materials. The self-switching characteristic means that the biodegradable cellulosic materials have suitable selectivities for high-impact applications in various fields.

The use of raw boron minerals (i.e. tincalconite, colemanite, and ulexite) was evaluated to increase the fire performance of wood plastic composites (WPCs) in comparison with commercially available fire retardants (FRs). Cone calorimetry and limited oxygen index tests were performed to evaluate the fire properties of WPC specimens. Artificial weathering and 3-point bending tests were also performed on the test specimens loaded with the highest loading level of FRs. The most important decrease in the heat release rate values was 42% and 40% in the magnesium hydroxide- and colemanite-added WPCs at a loading level of 15% (w/w), respectively. Incorporation of colemanite and ulexite into the WPCs increased the limited oxygen index levels by nearly 13% at the same loading level. An increase was observed in the peak heat release rate values in all of the WPC specimens after accelerated weathering. All of the FRs had statistically improved MOE values compared with the control WPC specimens. In particular, the incorporation of zinc borate and borax increased the MOE values by approximately 48% and 42%, respectively. Similar to the effect on the MOE values, zinc borate and borax improved the modulus of rupture the most (approximately 18%).

Green liquor (GL) combined with ethanol (GL-ethanol) was selected to pretreat sugarcane bagasse (SCB). The results showed that the maximum lignin removal of 85.2% was achieved at 160 °C and a GL loading of 1.5 mL/g-dry substrate. The glucose yield of pretreated SCB increased with increased pretreatment temperature, and the maximum glucose yield of 97.7% was reached from SCB pretreated at 160 °C. Simons’ stain (SS) showed that the glucose yield was affected by cellulose accessibility instead of lignin content when lignin removal was > 70%. The cellulase adsorption isotherm fitted by the Langmuir model showed that the strength of interaction between the cellulase and substrate of GL-ethanol-100/1.5 (100 °C, 1.5 mL GL/g-dry substrate) was declining with increased pH. The adsorption was pH-dependent, and negatively controlled by the pH value. Electrostatic interactions can account for the pH-dependency of cellulase adsorption.

This paper presents the shades of color of Quercus robur L. wood obtained in the processes of thermal treatment and color modification by saturated water vapor, with temperatures: t_I = 112.5 ± 2.5 °C for t = 5.5 h (mode I), t_II = 127.5 ± 2.5 °C for t = 6.5 h (mode II), and t_III = 137.5 ± 2.5 °C for t = 7.5 h (mode III).  The color of oak wood by thermal treatment in mode I changes minimally with mild browning in the CIE-L*a*b* color space: L* = 65.5 ± 1.7; a* = 8.8 ± 0.4; b* = 20.7 ± 0.5. A brown shade with coordinates: L* = 56.8 ± 1.3; a* = 9.3 ± 0.5; b* = 19.4 ± 0.5 is achieved in mode II. Oak wood thermally modified by mode III acquires an original brown-gray color with the color coordinates: L* = 47.5 ± 2.1; a* = 9.4 ± 0.5; b* = 17.1 ± 1.1. The irreversible changes in the color of the oak wood, achieved by some of the color modifications of wood using saturated water steam, extend the possibilities of its use in the field of building-joinery, the artistic field, and the field of design.