Volume 8 Issue 4

The effects of refining history and recycling times of NSSC pulp as a representative of semi-chemical pulps were studied. The results indicated that NSSC behaved as would be expected for a chemical pulp in all aspects. In fact, increasing the recycling cycles decreased the apparent density, tensile index, burst index, tear index, water retention value (WRV), and increased the hornification. In the current research, 400 mL CSF was judged to be the most suitable treatment among the refining levels considered. In the case of virgin pulp 400 mL CSF yielded better results than 500 mL CSF in all aspects (apparent density, tensile index, burst index, tear index, WRV and hornification). Also, there was not much difference with 300 mL CSF in these properties. Generally, a refining history of 400 mL CSF gave rise to the least negative influence on different properties compared to 500 and 300 mL CSF in 1st, 2nd, and 3rd recycling cycles of NSSC.

This study explored the effect of processing parameters on surface roughness as a result of aesthetic designs processed on walnut, chestnut, and beech wood edge-glued panels (EGPs) by CNC (computer numerical control) router. To accomplish this, the average roughness value (Ra) on an engraved surface in a Ying-Yang design treated on the material was measured. Using analysis of variance (ANOVA), the feed rate, spindle speed, step-over, and axial depth of cut factors; surface roughness factors; and the interactions between these factors were found to form significant differences at the level of 95%. At the end of the study, the Ra value was lower in walnut and beech EGPs (3.423 μm and 4.316 μm, respectively) and higher in chestnut EGPs (5.005 μm).

The use of mineral fillers in cellulosic paper products can result in cost/energy savings and improvement of paper properties. However, the increase in filler addition levels is hampered by the negative impact of fillers on paper strength, poor filler retention, etc. As an attempt to improve the use of fillers in papermaking, filler modification with the combination of cationic starch and carboxymethyl cellulose was preliminarily explored in this mini-study. This concept was compared with filler modification with either cationic starch or carboxymethyl cellulose. The combination of cationic starch with carboxymethyl cellulose resulted in improved attachment of the starch to the filler, possibly suggesting the in-situ formation of polymer complexes with lower solubility than starch. With respect to filler retention, tensile strength, brightness, and opacity of the filled paper, the combined use of cationic starch and carboxymethyl cellulose resulted in a modified filler material with modestly better performance, in comparison to filler modification with either cationic starch or carboxymethyl cellulose. The combined use of a cationic polymer and an anionic polymer to modify fillers may provide an alternative approach to improving the use of mineral fillers in the paper industry.

Biochars produced from thermochemical conversions of biomass were evaluated by temperature programmed oxidation (TPO). This technique, used to characterize carbon deposits on petroleum cracking catalysts, provides information on the oxidative stability of carbonaceous solids, where higher temperature reactivity indicates greater structural order, an important property for biochar applications. Differences between TPO profiles of biochars generated by fast pyrolysis of soy straw, barley straw, switchgrass, bamboo, and various woods demonstrated that the oxidative stabilities of the biochars are dependent on the starting biomass. Biochars from softwood and hardwood feedstocks were also processed by torrefaction and gasification to assess the impact of the thermoprocessing method on the TPO data. Results from these TPO analyses showed that the biochars produced under higher temperature conditions afford biochars that are more oxidation resistant. Biochars produced from pine wood (softwood) were consistently more resistant to oxidation compared to their hardwood counterparts. This exploratory study represents the first application of TPO to biochars.

To better understand how moisture content (MC) affects the longitudinal compressive mechanical properties of bamboo, mechanical tests on both the macroscopic and cellular levels were performed on Moso bamboo (Phyllostachys pubescens Mazei ex H. de Lebaie) at different MCs. At the macroscopic level, the compressive modulus of elasticity (CMOE) was determined using a common mechanical tester, while the indentation modulus of elasticity (EIT) and the hardness (HIT) of the bamboo fiber cell walls were obtained using nanoindentation. The results showed that CMOE, EIT, and HIT were all negatively correlated with the change in MC below the fiber saturation point (FSP) with strong linear relationships. However, the CMOE was found to be more sensitive to a change in MC than was EIT, which indicated that the bamboo was more sensitive to MC at the macro level than at the cellular level, at least in terms of longitudinal compression stiffness. Moreover, EIT was found to be much less sensitive to a change in MC than was HIT, which may explain why the longitudinal compression strength of bamboo was much more sensitive to changes in MC than was the compression modulus of elasticity on the macro scale.

The feasibility of the combination of fungal with mild acid pretreatments of Glycyrrhiza uralensis residue (GUR) for enzymatic hydrolysis and oil production was studied. Combined pretreatment with Phanerochaete chrysosporium and 2.5% sulfuric acid was shown to be more effective than the acid-only pretreatment. Subsequently, the residue obtained from acid hydrolysis was subjected to enzymatic hydrolysis to generate fermentable sugars for oil production by Chlorella protothecoides. The reducing sugar yield of enzyme hydrolysate from co-treated GUR was 1.08- to 1.71-fold higher than that obtained from acid-treated GUR under the same conditions. The highest cell dry and oil yield from co-treated GUR reached 4.16 and 1.66 g/L dry weight, respectively, values which were 2.1- and 3.32-fold higher than those using glucose as a carbon source. This study suggested that combined pretreatment with P. chrysosporium and 2.5% sulfuric acid is an effective strategy for enhancing enzymatic hydrolysis and microalgal oil production from GUR.

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.