Volume 5 Issue 2

In this study it was shown that the enzymatic removal of xylan from ECF-bleached birch kraft pulp enhances the water removal from the pulp, especially in the late stages of pulp drying. The effect of xylanase treatments on dewatering was clarified by using a moving belt former (MBF), a press simulator (MTS), and an IR-drying equipment, to simulate and to measure dewatering properties on wire, press and drying sections of a paper machine. The xylanase treatment slightly increased the pulp freeness indicating improved pulp drainage properties. At the moving belt former, however, no significant changes that would indicate enhanced dewatering in forming were observed. The xylanase treatments slightly enhanced the dewatering in wet pressing and furthermore, at the thermal drying the xylanase treatment had a positive effect on the dry solid content (DSC) development, and time to reach the 95% dry solids content was reduced by up to 15%. This was also confirmed by the decrease in the fiber saturation point (FSP) values and the amount of bulk water. Our results indicate that the xylanase treatment affected the water-binding xylan in the fiber cell wall, yielding enhanced dewatering properties, without deteriorating the pulp and paper properties.

Self-assembled multilayers were fabricated from lignosulfonate (LS) and poly(diallyldimethylammonium chloride) (PDAC), and the adsorption and desorption behaviors of LS on the LS/PDAC multilayers under different pH conditions were intensively investigated. Results showed that the adsorption and desorption behaviors were controlled by electrostatic attraction, hydrophobic interaction, and changes in the microstructure, which depended on solution pH. Lignosulfonates exist as colloids in solutions at low pH because of a hydrophobic interactions, and the LS colloids adsorbed on the PDAC layer because of electrostatic attraction. LS colloids started to disassociate at pH 3.5, resulting in an abrupt rise of the adsorption rate, a sharp decrease of the adsorbed amount, and a steep reduction in the surface roughness. Desorption behaviors of LS multilayers were related to the pH values of both LS dipping solution for self-assembly and the immersing solution for post-preparation treatment. Desorption of LS could be induced by a weakening of electrostatic attraction or hydrophobic interaction. A significant desorption occurred only when LS colloids dissociated in the multilayers. LS colloids were harder to dissociate in the multilayers than in the solutions because of electrostatic attraction between LS and PDAC.

Bagasse from early species of Saccharum officinerum-Co 89003 has 71.36% useful, long, and thick-walled fibers with good slenderness ratio, but the rigidity coefficient is less than that of Eucalyptus tereticornis and Leucaena leucocephala. The kink index and kink per mm length are lower in bagasse fiber than E. terticornis, which gives rise to fewer weak points in the fiber. Low alcohol–benzene soluble substances in bagasse induce less pitch problems and favor more homogeneity in the paper. Lignin content in bagasse is comparable to Eucalyptus globulus and Leucaena leucocephala, but α-cellulose, and pentosans are slightly lower. A higher proportion of carbon content compared to hydrogen and oxygen increases the energy value of bagasse. It produces 42.2% pulp yield of kappa number 28.2 at optimum cooking conditions, such as active alkali 12% (as Na2O), temperature 150oC, and time (at temperature) 60 min. An addition of 0.1% anthraquinone at the optimum condition improves pulp yield by 2.6% and mitigates kappa number by 3.9 units.

Wheat straw was used to produce medium-density fiberboard (MDF). The chemical and physical characteristics of fractionated size-reduced wheat straw were investigated. The pH, pH-buffering capacity, ash, and silicon content increased as wheat straw particle size decreased. Ash of the finest straw, <0.2 mm, had high ash (15%) and silicon (18%) contents. The outer and inner parts of size-reduced straw were analyzed using scanning electron microscopy (SEM). The SEM micrographs revealed a complex ultrastructure containing a notable portion of thin-walled cells approximately 1 µm thick. Pressurized defibration of size-reduced wheat straw produced lignocellulosic fibers nearly 1.0 mm long combined with approximately 24% of small particles and dust. The high water uptake of straw-based MDF was significantly reduced using melamine-modified urea-formaldehyde (UF) resin and removing wheat straw particles and dust by screening. UF resin was added at levels of 12.5%, 13.1%, and 14%. In terms of water resistance, 12-mm-thick straw MDF displayed thickness swelling below 10%, acceptable according to the EN 622-5 MDF standards. It was concluded that manufacturing wheat straw MDF entails straw size reduction (hammer-milling), removing small particles and dust, and adding melamine-modified UF resin to attain necessary MDF quality standards.

Long chain omega-3 fatty acids such as eicosapentaenoic acid (EPA) are essential for the regulation of critical biological functions in humans and other mammals. EPA production via solid state fermentation of sunflower press cake was investigated using eight fungal strains representing the genus Mortierella. During this study the effect of supplementing the sunflower press cake substrate with 10% (w/w) linseed oil was studied with regard to the supplement’s impact on EPA production and the polyunsaturated fatty acid profile of the fermented substrate. The addition of the linseed oil improved the EPA yield of most strains, leading to a reduction in the average arachidonic acid:EPA ratio from 50.68 to 3.66. The ratio of polyunsaturated to saturated fatty acids was increased significantly (t=5.75, p=0.05) by the addition of linseed oil, with higher desaturation levels among the 20-carbon fatty acids. The strains that produced the highest levels of EPA on sunflower press cake supplemented with linseed oil were Mortierella alpina Mo 46 and Mortierella basiparvispora Mo 88, which produced 6.4 mg and 5.8 mg EPA per g of sunflower press cake, respectively.

Heavy metal’s release without treatment poses a significant threat to the environment. Heavy metals are non-biodegradable and persistent. In the present study the ash of water hyacinth (Eichhornia crassipes), was used to remove six metals from aqueous solutions through biosorption. Results of batch and column experiments showed excellent adsorption capacity. Removal of lead, chromium, zinc, cadmium, copper, and nickel was 29.83, 1.263, 1.575, 3.323, 2.984 and 1.978 µgg-1, respectively. The biosorptive capacity was maximum with pH >8.00. Desorption in µgg-1 of ash for lead, chromium, zinc, cadmium, copper, and nickel was 18.10, 9.99, 11.99, 27.54, 21.09, and 3.71 respectively. Adsorption/desorption of these metals from ash showed the potential of this technology for recovery of metals for further usages. Hydrogen adsorption was also studied with a Sievert-type apparatus. Hydrogen adsorption experiments showed significant storage capacity of water hyacinth ash.

Acacia hybrid (Acacia mangium x auriculiformis), a wood species of low dimensional stability which is used almost exclusively for pulp, paper, or as firewood, was heat treated in nitrogen at 210-230 ºC for 2 to 6 hours. The changes in color and anti-swelling efficiency (ASE) of wood after heat treatment were determined for the different heat treatment conditions. The results show that heat treatment mainly resulted in the darkening of wood tissues, and heat-treated wood had better dimensional stability than those of the control samples. Chemical modifications of wood components were determined by FT-IR analysis. Spectra indicated that the hydroxyl group content was reduced by increased treatment intensity. This result coincides with the increase in dimensional stability of heat-treated wood. Heat treatment of acacia hybrid wood shows an interesting potential to improve the quality and value for solid wood products from plantation-grown wood species.

This study investigates effects of six kenaf cultivars named Cubano, Niger, Cubano 2032, 9277, 7551, and 7566 and three harvesting time stages on the properties of pulp and handsheet paper made from kenaf. Six cultivars of an Iranian kenaf (Hibiscus cannabinus L.), were planted on 19 May 2007, and harvested after 85, 105, and 135 days. It was understood that with the increase of plant age, fiber yield increased. Maximum yield at each of three harvesting time stages was related to Niger. Consequently, if a high fiber yield is sought, Niger can be recommended, but for a paper with high strength properties, Cubano 2032 is strongly suggested. This cultivar produces a paper with significant burst, tear, breaking length and fold endurance even though its yield was somewhat lower than that of Niger at short harvesting times. Moreover, at second harvesting time stage, maximum strength properties of handsheets such as burst, tear, and breaking length, were seen in Cubano, though the fiber yield of this cultivar was a bit lower than Niger, but still more than Cubano 2032. We showed that a minor positive change in the handsheet properties could be achieved through harvesting kenaf at the third stage as compared to the first and second stages.

In order to study the thermal decomposition characteristics of hemicellulose, a highly efficient procedure was carried out to extract hemicellulose from corn stalk. Several different sugar units were observed by 13C NMR spectra to show the presence and species of hemicellulose. Following isolation of the hemicellulose, experimental research on its thermal behavior were carried out with a thermogravimetric analyzer under inert atmosphere at heating rates ranging from 10 to 50°C/min, and the kinetic parameters were calculated by the Kissinger and Ozawa methods, respectively. It was found that the thermal degradation of hemicellulose mainly occurred in the temperature range 180-340°C with a final residue yield of 24% at 700°C. An increase of the heating rate could slightly increase both the temperatures at which the peak weight loss rate was observed and the maximum value of weight loss rate. The activation energy (E) and the pre-exponential factor (lnA) obtained by the Kissinger and Ozawa methods were 213.3kJ mol-1, 211.6kJ mol-1 and 46.2min-1, 45.9min-1, respectively. Even though the data showed little difference, the fitting degree of the Ozawa method was better than that of the Kissinger method. The experimental results and kinetic parameters may provide useful data for effective design and improvement of thermochemical conversion units.

In order to prepare nanoparticles, corn cobs were treated with sodium hydroxide in the range 0-6 mole/litre (0-24% of sodium hydroxide on oven dry basis) at 165 oC for 1.5 h at a liquor to solid ratio of 4.5:1. The sample obtained at the optimised condition (4.5 mole/litre) was washed with deionised water, disintegrated, and filtered through 80 mesh screens. Powder thus obtained was delignified by acidified sodium chlorite and dried in a vacuum oven to constant weight. Dried powder was further separated by 270 mesh screens. An average particle size approximately equal to 22 nm was observed by Transmission Electron Microscopy (TEM). Its crystallinity was determined by XRD analysis. The aggregated particle size was observed in the micron range by Scanning Electron Microscopy (SEM).