Volume 12 Issue 4

A series of multifunctional water-soluble polymeric fluorescent whitening agents (PFWAs, 5a-f) based on 4,4′-diamino-stilbene-2,2′-disulfonic acid (DSD acid)-triazine structure were successfully synthesized using a nucleophilic substitution reaction with cyanuric chloride, DSD acid, amino compounds, polyethylene glycol (PEG), and/or polyvinyl alcohol (PVA) as raw materials. The structure of the PFWAs was characterized by FT-IR, and the substitution degree was calculated from the results of an elemental analysis. The optical properties of the PFWAs were measured by the UV-vis spectra and fluorescence spectra when the PFWAs were applied to paper fiber to serve the roles of light stabilizer, fluorescent whitener, and surface-sizing agent. Then the performance of the PFWAs on paper was evaluated by measuring the surface strength and smoothness of paper, brightness degree of paper, and the yellowness value (value of PC) of paper. The results indicated that the PFWAs had better light stability in water solution than that of a conventional fluorescent whitening agent (FWA) as a light stabilizer. According to the surface-sizing experiment and UV aging experiment, it was concluded that not only could the PFWAs enhance the surface strength and smoothness of paper, but also have a better effect on anti-UV aging than that of FWA as a light stabilizer and fluorescent whitener agent.

The diffusion properties of walnut (Juglans regia L.) and cherry (Prunus avium L.) wood perpendicular to the grain are presented. The wet and dry cup tests were carried out in normal climate conditions. Simultaneously, inverse analyses by means of the finite element (FE) method were conducted based on the experimental sorption data. The results show that the numerically derived diffusion model can predict the mass changes during the experiments with sufficient accuracy with a maximum global relative error of 0.43%. However, the numerically determined diffusion coefficients do not show an agreement with the experimental data.

Enzymatic saccharification is a key step in the green conversion of lignocellulose to biofuels and other products. A key deficiency in common biocatalytic systems, such as Trichoderma reesei, is the insufficient presence of β-glucosidase (BGL). This study intended to develop an efficient process of BGL production as an enhancement to the T. reesei system. The authors investigated the process optimization of BGL by the mutant strain Aspergillus niger C112, which was previously developed in the authors’ laboratory. The culture medium and process (carbon, nitrogen, temperature, and pH) were optimized for cost-effective BGL production, which led to a maximum BGL activity of 8.91 ± 0.35 U/mL. In addition, the dynamics of the physio-chemical parameters (zeta potential and dissolved organic matter) of the process were studied and showed good correlations to the yield of BGL. Furthermore, a three-dimensional excitation-emission matrix fluorescence spectroscopy was successfully applied for analyzing the component, origin, and dynamics of dissolved organic matter, which contributed to a further understanding and optimization of BGL production.

A new type of electric heating plywood used for indoor heating products was made using melamine resin adhesive film (MRAF) as the bonding material and carbon fiber paper (CFP) as the electric heating material. Hot-press pressure greatly affected the permeation of the adhesive into the CFP and bonding performance, resulting in a bonding strength above 1.8 MPa. The conducting path in the electric heating layer was the main factor affecting the drop rate of resistance (DRR). Pressure of around 1.3 MPa was beneficial in controlling power deviation. Use of the MRAF improved insulation and water resistance. The plywood exhibited a surface temperature difference of 6 °C under commonly used power. Temperature rise exhibited an exponential relationship with heating time, and surface equilibrium temperature had a linear relationship with power density. The plywood had good power stability because the maximum resistance changed by only 0.44% when electricity was overloaded for 24 h at a power density of 500 W/m2. Stable resistance was presented after power was cycled 40 times, and the maximum DRR was 1.25% after 120 power cycles. This scheme offers a simple process for large-scale manufacture of the adopted MRAF, which has good bonding performance and electric heating stability.

Hexenuronic acid (HexA) not only influences delignification, but it is also one of the major factors producing absorbable organic halogens (AOX) during the chlorine dioxide bleaching of pulps. The efficient removal of the HexA from cooked pulp is important to minimize the need for bleaching and the pollution load from the mill effluent. Response surface analysis (RSA) was applied to determine the optimal oxidative degradation conditions for HexA in bagasse pulp. Based on the previous single-variable test results, reaction temperature, pH, and reaction time were chosen as the independent variables, with the amount of degradation of HexA being the response value in the RSA. According to the central composite experimental design principles, the type of response surface methodology with three factors and three levels was adopted and analyzed to determine the significant factors and the strength of interactions between factors. The optimal conditions determined were as follows: a reaction temperature of 94.7 °C, a pH of 3.7, and a reaction time of 124 min, which resulted in the amount of degradation of HexA at 10.5 µmol/g.

The adsorption effects, thermodynamics, and kinetics of formaldehyde-modified eucalyptus bark on Cr(VI) was investigated. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to verify the adsorption capacity difference between unmodified and modified eucalyptus bark. The results demonstrated that the surface area and active group content was increased by modification, which was conducive to the adsorption of Cr(VI). The effects of pH, time, temperature, initial Cr(VI) concentration, and adsorbent dosage and on adsorption were investigated. The optimal adsorption capacity was 16.50 mg.g-1 under the conditions of 50 mg.L-1 initial Cr(VI) concentration, pH 2.0, 3 g.L-1 adsorbent dosage, 50 °C, and 120 min. The fitting of kinetics indicated that the adsorption was governed by multiple factors. The thermodynamic parameters △H0 > 0 showed that the adsorption process was an endothermic reaction. The value △S0 > 0 indicated that liquid-solid interface disorder increased during the adsorption process and showed a good adsorption performance.

Wood foam cores manufactured from Eucalyptus fiber/epoxy adhesive and 4,4′ oxybis(benzene sulfonyl hydrazide) (OBSH), ethyl acetate (EA), and microsphere polymer bead (Expancel®) as foaming agents were investigated. A 10 phr of OBSH showed superior properties of the 0.50 g/cm3 wood foam and that 0.70 g/cm3 was the optimal density. Also, 17 phr of EA loading gave rise to the better mechanical properties and was considered the optimal content. The microsphere polymer bead did not achieve significant expansion under the conditions employed. Manufacturing of single (X1) and double (X2) layer of lightweight sandwich structures engineered woods with teak/glass fiber-reinforced polymer (GFRP) skins was studied. The enhancement of the sandwich structures’ properties was mainly contributed by the core and also by the added thin interlaminated GFRP layer. In X1 and X2 sandwich structures, with the same volume fraction of core(s), marginal improvement occurred in the properties, caused by the addition of the thin inter-layer of GFRP. Small contributions of the core properties on the sandwich structures were also demonstrated. The sandwich structure derived from the OBSH core was superior in mechanical properties and heat distortion temperature (HDT). The sandwich structure made from EA was unsuccessful in achieving water resistance.

Biomass densification elevates the bulk density of the biomass, providing assistance in biomass handling, transportation, and storage. However, the density and the chemical/physical properties of the lignocellulosic biomass are affected. This study examined the changes introduced by a briquetting process with the aim of subsequent processing for 2nd generation bioethanol production. The hydration properties of the unprocessed and briquetted wheat straw were characterized for water absorption via low field nuclear magnetic resonance and sorption balance measurements. The water was absorbed more rapidly and was more constrained in the briquetted straw compared to the unprocessed straw, potentially due to the smaller fiber size and less intracellular air of the briquetted straw. However, for the unprocessed and briquetted wheat straw there was no difference between the hygroscopic sorption isotherms, which showed that the amount of cell wall water was not affected by the briquetting process and that the sugar yield was similar after a combined hydrothermal pretreatment and enzymatic hydrolysis. The factors which offset the benefits introduced by the briquetting process need to be further examined to optimize the processing parameters and enzyme recipe for better use of the wheat straw biomass feedstock.

The influence of thermal modification by hot-compressing was investigated relative to the physical, mechanical, anatomical, crystallinity, and colour characteristics of poplar wood boards. The boards were modified by a hot-compressed method under various temperature stages. The physical and mechanical properties of hot-compressed poplar wood increased with increased pressing temperature. Likewise, the highest crystallinity index (68.7%) of X-ray diffraction (XRD) analyses was found in the samples pressed at 210 °C. Microscopic investigation, revealed that there were some structural deformations in early and late wood, annual ring, etc., of the compressed samples at 170 °C, 190 °C, and 210 °C. In a colour measurement test, it was determined that samples had different colour values in terms of temperature increase. The results achieved in this study demonstrated that the physical and mechanical properties of hot-compressed boards improved with increased press temperature. As a result, a thermal compression method could be preferred to advance end-usage features of low-density wood materials produced from fast-growing tree species like poplar, Douglas fir, spruce, yellow pine, eucalyptus, etc.

Regenerated cellulose (RC) membranes loaded with silver nanoparticles (AgNPs) were prepared in this study. Cellulose acted as a reducing agent, silver nitrate acted as an oxidizing agent, and N-methylmorpholine-N-oxide (NMMO) acted as a direct cellulose solvent. The AgNP-loaded RC membranes were obtained via the redox reaction between cellulose and silver nitrate. The results of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis suggest that AgNPs were reduced on the RC membranes during the dissolution and regeneration of cellulose. Atomic force microscopy (AFM) showed that the RC membranes exhibited high surface roughness, with a value of 7.19 nm. The Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) results demonstrated that the crystal lattice type of RC membranes changed from cellulose I to cellulose II, without any derivatization. The detection results of atomic absorption spectrometry (AAS) indicated that the silver content of the RC membranes increased with increasing silver nitrate solution concentration. Antibacterial experiments showed that the AgNP-loaded RC membranes exhibited good antibacterial properties with respect to both Escherichia coli and Staphylococcus aureus.