Research Articles

the combination of increased specific surface area, electrostatic forces, and hydrophobic interactions, thus compensating for the loss of optical properties resulting from LC refining. The mechanical hydraulic force generated by the high refining energy disturbed the FWA retention. Therefore, high refining energy could improve the adsorption of FWAs when they are added after refining, but for better performance, the refining energy should be controlled and lowered. In addition, small amounts of calcium salt added after refining can also ameliorate the adsorption of FWAs.

Transformation of the hemicellulose fraction in an environmentally benign manner to deliver high value-added chemicals is critical for the integrated utilization of biomass. Amongst all the chemicals derived from hemicellulose, furfural (produced by hydrolysis of xylan into xylose and successive dehydration of the latter) is a promising option. In this manuscript, a catalytic approach for converting xylan and xylose into furfural co-catalyzed by choline chloride-citric acid·H2O, a deep eutectic solvent (DES) synthesized from biorenewable building blocks, and trivalent metal chloride was developed. Choline chloride-citric acid·H2O acted as both reaction medium and Brønsted acid catalyst. Both monophasic route and biphasic route (with methyl isobutyl ketoneas extractant for in situ extraction of furfural) were proposed. The highest furfural yields obtained from xylose and xylan in monophasic approach were 59.3% and 54.2%, respectively, at 140 °C, and these values increased to 73.1% and 68.6% when biphasic system was applied for the reaction. Moreover, in biphasic system, choline chloride-citric acid and metal chloride could be recycled and reused for 5 runs with stable catalytic ability.

Magnetic chitosan composite microparticles (MCCPs) were successfully prepared using a simple one-step co-precipitation method and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM). The experimental results showed that the particles possessed a honeycomb-like porous structure and had super-paramagnetic properties, with a saturation magnetization of about 33.3 emu/g. Congo red (CR), an anionic azo dye, was used to investigate the adsorption properties of the MCCPs. The adsorption kinetics data and isotherms produced from these experiments indicated that CR adsorption onto the MCCPs was best fitted with a pseudo-second-order kinetic equation and was well described by the Langmuir model. Thermodynamic parameters such as the changes in Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were also estimated; the results revealed that the adsorption process was spontaneous and endothermic. The regeneration studies demonstrated that the MCCPs can be used as a reusable adsorbent for CR adsorption from aqueous solution. The molecular similarity between chitosan and cellulose suggests that the present results might serve as a model of what might be achieved with a cationic derivative of cellulose.

The wood industry continues to strive to reduce production costs and increase productivity to remain competitive. Knowledge of the effect of wood cutting parameters on power consumption could increase energy efficiency, reducing operating costs and increasing profitability. Measuring power consumption also provides information about other variables, such as tool edge wear, occurrence of catastrophic failures, and other parameters that affect the quality of the sawn boards and the momentary efficiency of the breakdown process. In this work, power consumption during sawing of Pinus sylvestris L. using a double arbor circular saw was investigated. Both climb-sawing and counter-sawing were considered. The experiments were carried out under normal production circumstances in two Swedish sawmills. The relationship between cutting parameters and theoretical power consumption was investigated. The experimental power consumption increased by 11 to 35% during an 8-h shift, mainly due to an increase in the tooth radius. Additionally, this study showed that climb-sawing consumed more power than counter-sawing.

Green vein is one of the most severe defects that affect wild cherry (Prunus avium L.). It consists of green streaks that alter the typical color and uniformity of the cherry wood, causing considerable value losses. A colorimetric analysis was performed on wild cherry clones using the CIE L*a*b* system, and the influences of environmental and genetic factors on green vein as well as the effects of the presence of green vein on the physical properties of the wood were investigated. Discriminant analysis shows that the color parameter that best discriminated green vein were low values of L* and a*. The cloning effect was the most important, but the environment also played an important role in the development of green vein. Finally, the presence of green vein was found to mainly affect the longitudinal shrinkage of wood and, to a lesser extent, wood density. These same features are typical of tension wood, to which green vein was strictly linked, as confirmed by some preliminary anatomical observations.

In this study, four species of wood-rot fungi—Piptoporus betulinus, Fomes fomentarius, Irpex lacteus, and Coriolus versicolor—were compared regarding their ability to degrade the wood of white birch and used to assess the degradation mechanisms. Chemical analyses were conducted following the Chinese national standard methods and included Fourier transform infrared spectroscopy (FTIR). The wood samples were inoculated with the four wood-rot fungi for a predetermined duration in the wood-decaying test. In the wood weight loss test, both F. fomentarius and P. betulinus showed the greatest reduction, but through different mechanisms: F. fomentarius mainly decomposed lignin, whereas P. betulinus mainly acted on cellulose. F. fomentarius, I. lacteus, and C. versicolor exhibited a shift at 3417 cm^-1 related to O-H stretching in hydroxyl groups, along with decreased absorption at 3410, 3406, and 3405 cm^-1, most likely due to the degradation of the related functional groups of lignin side chains. The wood decayed by P. betulinus displayed a change in the relative position of cellulose-associated bands at 1161 and 898 cm^-1. F. fomentarius can be considered a potential agent for the biopulping of white birch because of its high ability to degrade lignin, high holocellulose content, low content of 1% NaOH, and ethanol-benzene extractives.

Cationic dry strength agents (DSAs) are commonly used for paper strengthening. However, before they are applied, another chemical called an anionic trash catcher (ATC) is often used to pretreat pulp to neutralize the negative dissolved and colloidal substances (DCS), increasing the effectiveness of the subsequently added cationic DSA. However, in many cases, the negativity of the fibers is also neutralized by the ATC. Under such circumstances, it remains unclear to what degree the effectiveness of the DSA will be affected. In this paper, a deinked pulp was first pre-treated with a polyamine ATC; then, the effectiveness of two subsequently-added DSAs, anionic polyacrylamide (APAM) and cationic polyacrylamide (CPAM), were compared. Results showed that when the ATC was used alone, it deteriorated paper formation, resulting in a decrease of paper strength. When the DSAs were used alone, the CPAM was effective but the APAM was not. However, when the ATC was used to pretreat the pulp, the effectiveness of the CPAM clearly decreased, while that of the APAM clearly increased. The reason for this could be that the adsorption of APAM onto fibers was promoted by the pretreatment of ATC, possibly through the formation of an ATC and APAM polyelectrolyte complex.

The wet strength of handsheets subjected to dipping treatment by solutions such as glyoxal with Zn(NO3)2 as a catalyst, chitosan, and the crosslinking system of glyoxal and chitosan is studied in this paper. The crosslinking system achieved better wet strength performance than glyoxal or chitosan alone and slightly better than the sum of glyoxal and chitosan in the case of a curing temperature between 90 and 130 oC. However, handsheets treated by this crosslinking system became more brittle, which was shown by the reduction of folding endurance of the handsheets with increasing wet strength. The capillary rise and contact angle of the treated handsheets showed certain relations to their wet strength when the above solutions were used to improve the wet strength of the handsheets. The physical changes of the treated handsheets can provide evidence to explain the mechanism of wet strength development.

A simple electroless Ni-Cu-P plating process for preparing an EMI-shielding and corrosion-resistant wood-based composite has been developed. The effects of solution pH value on the metal deposition, surface resistivity, chemical composition, anti-corrosion properties, and crystal structure of the coatings were studied. The coatings were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. When the solution pH was increased from 8.5 to 10.0, the metal deposition increased decreased. Chemical composition indicated that the nickel deposition increased, whereas the opposite effect was obtained on copper and phosphorus elements with a pH increase from 9.0 to 10.0, and the crystal structure of the Ni-Cu-P coatings changed from an amorphous state to a microcrystalline one. Tafel curves of the Ni-Cu-P coatings prepared at pH 9.0 or 9.5 showed that they had excellent anti-corrosion properties in a 3.5 wt% NaCl solution. The morphology of the coating containing 69.86% Ni – 7.65% Cu – 22.49% P is superior to that with 75.99% Ni – 6.60% Cu – 17.41% P after corrosion tests. The plated birch veneers exhibited electromagnetic shielding effectiveness higher than 58 dB in frequencies ranging from 9 KHz to 1.5 GHz, and the coating firmly adhered to the wood surface.

A novel cationic amphiphilic lignin derivative with high surface activity was prepared from kraft lignin via the introduction of dehydroabietyl groups as lipophilic groups and diethylenetriamine groups as hydrophilic groups by the Mannich and ketone-amine condensation reactions. Solubility, surface tension, hydrophilic-lipophilic balance (HLB) values, foamability, and zeta potential were used to evaluate the basic physico-chemical properties of the cationic amphiphilic lignin derivative. The experiments show that the solubility of the cationic amphiphilic lignin derivative is 2.10 wt%, the critical micelle concentration is 5.0 g·L^-1, the surface tension is 29.85 mN·m^-1 at a concentration of 5.0 g·L^-1, the HLB value is 12, and the foam volume is 11.1 mL initially and 8.0 mL after standing for 5 min in an aqueous solution at pH 2.0.