Research Articles

Three formaldehyde-based resins were prepared: urea-formaldehyde (UF) resin without melamine modifier (named UF0 resin) and melamine-urea-formaldehyde (MUF) resins with melamine modifier added at two different synthesis stages (named MUF1 resin and MUF2 resin). The effects of the melamine addition stage on the performance and curing behavior of MUF resin were studied. Three-ply plywood bonded by these adhesives was manufactured, and its bond strength and formaldehyde emissions were measured. The curing behavior and functional groups of the resins were measured by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). Their activation energies were calculated using the Kissinger equation and the Kissinger-Akahira-Sunose (KAS) method. The results showed that melamine addition and the addition stage had significant influences on the characteristics of resins. The plywood bonded by MUF1 resin showed the highest bond strength and the lowest formaldehyde emissions. The activation energies of UF0 resin, MUF1 resin, and MUF2 resin were significantly different; the values were 99.44 kJ/mol, 105.75 kJ/mol, and 150.65 kJ/mol, respectively. According to the FT-IR spectra, the amount of methylene and methylene-ether bonds in cured MUF2 resin was the lowest, which meant that the cross-linking degree of MUF2 resin was the lowest.

To use wood-based panels as a final product, they must undergo surface finishing via various processes, such as low pressure laminate (LPL), polyvinyl chloride (PVC), coating paper (CP), direct coating (DC), or veneer overlay/UV coating (VO-UVC). Tests were conducted to look for any reduction of formaldehyde emissions and in combustion behaviors with the use of five different surface finishing methods. To determine formaldehyde emissions, the desiccator method was used according to the Korean Standard KS M 1998. The combustion behaviors of wood-based panels were investigated using a cone calorimeter. The formaldehyde emissions of VO-UVC were lower than those of the other methods. In the burning tests, the heat release rate (HRR) with DC was higher than that with the other methods. The mass loss rate (MLR) when the product with DC was burned was higher than that for the other finishing materials.

Zygomycetes fungi are able to produce ethanol, and their biomass may hold a high market value, making them interesting microorganisms from a biorefinery perspective. In the present study, the inhibitor tolerance of the Zygomycetes fungus Rhizopus sp. was evaluated and compared with a flocculating strain of Saccharomyces cerevisiae. The inhibitors furfural, 5-hydroxymethylfurfural [HMF], acetic acid, and levulinic acid and the phenolic compounds catechol, guaiacol, and vanillin were applied in different combinations in a semi-synthetic medium. Glucose uptake and conversion of HMF in the presence of inhibitors were analyzed for the two organisms, and it appeared that the inhibitor resistances of Rhizopus sp. and S. cerevisiae were comparable. However, in the presence of catechol (0.165 g L^-1), guaiacol (0.186 g L^-1), and vanillin (0.30 g L^-1), the glucose uptake by S. cerevisiae was only 3.5% of its uptake in a medium without inhibitors, while under equal conditions, Rhizopus sp. maintained 43% of its uninhibited glucose uptake.

Biochar (BC) amendments might decrease the bioavailability of metals in soils that are contaminated with heavy metals. In general, soil microbial communities are sensitive to changes in soil property changes. Microbial communities were tested in a Cd- and Pb-polluted paddy field in southern China. BC was applied as a basal soil amendment before rice transplantation in 2009. The BC was applied at rates of 0, 10, 20, and 40 tons per hectare. Soil heavy metal fractions with sequential extraction procedure, soil microorganisms, and enzymes were monitored in 2011. The soil pH and soil organic carbon (SOC) were significantly increased by 2% to 5% and 16% to 51% under BC amendment, respectively. Compared to the non-BC treatment, the cadmium (Cd) and lead (Pb) acid-soluble fraction concentrations were significantly decreased by 15.3% to 26.7% and 18.2% to 30.9%. The Cd and Pb reducible fraction were decreased by 13.5% to 25.6% and 21.9% to 23.53%.The Cd and Pb oxidizable fraction by 15.4% to 69.2% and 22.7% to 29.3% with BC application, respectively. The populations of actinomycetes and fungi were increased by 19.0% to 38.5% and 3.7 to 9.3 times, respectively. Meanwhile, BC significantly increased the cellulose, urine enzyme, neutral phosphatase, and sucrase activities by 117.4% to 178.3%, 31.1% to 37.6%, 29.7% to 193.8%, and 36.5% to 328.6%, respectively. BC amendment offers a basic option to reduce Cd and Pb bioavailability and change the fractions. The BC also increases microorganism quantity and soil enzyme activity.

Moisture content (MC) has an important effect on the performance of wood in service. In an attempt to rapidly and non-destructively acquire the MC of heat-treated wood, a radio frequency-type moisture meter was used to take the MC of 170, 185, and 200 °C heat-treated Manchurian ash and Mongolian pine wood samples as well as reference (conventional kiln-dried) samples. A linear regression analysis was applied to assess the relationship between the MC values obtained using the meter and those obtained using the oven-dry method by fitting the data points according to the least squares method. From the results of the high coefficients of determination of the regression equation, it was concluded that the meter could be effectively used to obtain the MC of heat-treated wood. Finally, to ensure the simple and reliable application of the meter, the meter correction factors corresponding to each species and heat treatment temperature were calculated and listed.

In this work, the possibility of using neutral sulfite semi-chemical (NSSC) bagasse pulp mixed with hardwood chemimechanical pulp (CMP) and bleached softwood kraft pulp (BSKP) was investigated with the aim of reducing hardwood and BSKP consumption. The bagasse NSSC pulp had a digester yield of about 73% and was unbleached. It was refined by a PFI mill to 400 mL CSF, but in the case of the hardwood CMP and imported long fiber pulp, the final refined freeness were selected to be 350 and 500 mL CSF. Handsheets were made (60 gm^-2), and their strength indices and optical properties were measured. Results of this research on a laboratory scale indicated that using bagasse NSSC pulp mixed with hardwood CMP to make newsprint with acceptable quality is possible, and this process will also noticeably reduce the consumption of imported long fiber pulp and wood for producing the grades of paper usually made from CMP.

In this study, blended paper was prepared by blending synthetic polyethylene (PE) via a disintegration technique. The produced paper was targeted to resist water or moisture. Unbleached kenaf whole stem pulp was used as the main source of fibre in making the paper. The pulp was blended with two types of PE: low-branched (LB) and high-branched (HB) polymers. To study the effect of PE addition to the paper, the water absorbency and mechanical properties were characterized. The pulp to PE mixtures were prepared at ratios of 9:1, 8:2, 7:3, 6:4, and 5:5. Scanning electron microscopy (SEM) showed that the PE was melted between the fibre linkages. The Cobb test determined that the blended paper absorbed less than 20 g/m2 of water within 60 s. The best water contact angle successfully achieved was at 84°, which is almost hydrophobic. The mechanical properties, such as tensile strength and tear strength, were in the range of accepted standard requirements. The obtained results indicated that blending via a disintegration technique can be applied in the process of making water-resistant paper. The produced paper is suitable for the manufacturing of water-resistant corrugated packaging materials.

Three kinds of wheat straw black liquor were extracted by alkaline solution at 25 °C, 100 °C, and 165 °C, and were precipitated by the stepwise addition of acid to pH 10.5, 9.0, and 2.0, respectively. The corresponding three lignin fractions were isolated. The characteristics of these lignin fractions were investigated, and their impacts on anti-oxidant properties were evaluated. The pH 10.5 fractions with low lignin content, low phenolic hydroxyl content, and high lignin molecular weight showed very poor radical scavenging ability. The pH 9.0 and 2.0 fractions with high phenolic hydroxyl contents exhibited excellent radical scavenging ability. The major portion of the degraded lignin was precipitated in the pH 2.0 fraction, resulting in a lower molecular weight and higher phenolic hydroxyl content as compared to the pH 10.5 and pH 9.0 fractions. The high extraction temperature degraded more lignin and generated more phenolic hydroxyl groups. Therefore, the lignin fractions extracted at 165 °C exhibited the best radical trapping potential as compared to the lignin extracted at 100 °C and 25 °C. The coefficients of DPPH· removal for the lignin fractions were ordered in sequence by phenolic hydroxyl content, methoxyl content, molecular weight, E+T content, and NO yield of lignin. The lignin fraction extracted at higher temperature and precipitated at lower pH had the best radical scavenging ability.

In the present study, jatropha oil cake (JOC), a waste produced from processing jatropha seeds for biodiesel production, has been investigated for the removal of nickel (II) from aqueous solutions. Jatropha oil cake contains different functional groups that can participate in the metal ion complexation. Jatropha oil cake is used in its natural form (JOCN) as well as in its immobilized form (JOCB). Batch experiments were performed for adsorption of Ni (II) by JOCN and JOCB. Parameters affecting the adsorption, such as the effect of adsorbent dose, pH, the initial concentration of metal ion, agitation speed, and contact time, were studied for the maximum removal efficiency. Removal efficiency was found to be 62% and 63% for Ni (II) at pH 6.2 in its natural and immobilized forms, respectively. Maximum adsorption occurred within an hour for Ni (II) with JOCN and 90 min for JOCB. The equilibrium data was analyzed using Langmuir and Freundlich isotherms.

Biomass catalytic fast pyrolysis is one of the most promising technologies for the production of renewable aromatics and olefins directly from solid biomass. In this study, catalytic pyrolysis experiments were carried out on biomass in a fluidized bed reactor using typical metal-loaded (Mg, K, Fe, Ga, and Ni) ZSM-5 zeolites as catalysts. The effects of catalysts on the product distribution and bio-oil components were investigated to determine the cheapest and most efficient metal-loaded catalyst. The results showed that bio-oil yields with metal-loaded catalysts (40 to 43.4 wt.%) were a little lower than that of pure ZSM-5 (46.4 wt.%). Metal-loaded catalysts produced more CO2 and CO than did pure ZSM-5. Fe/ZSM-5 produced the highest yield of CO2 (13.8 wt.%), as well as the highest yield of olefins (2.7 wt.%). Fe/ZSM-5 showed the same catalytic characteristics as Ga/ZSM-5 (aromatic hydrocarbon proportion in bio-oils of more than 80%), but it is much cheaper than Ga/ZSM-5.