Volume 4 Issue 3

Pulp fibers’ bleaching technology has been developing mainly by applying increasingly intensive delignification in the cooking department and implementation of elemental-chlorine-free chemicals in the bleaching department. The resulting effluents load is still considerable, and the environmental consequences largely depend on the effectiveness of wastewater treatment. Now it is well established that pulp fibers’ surface layers contain comparatively higher amounts of residual lignin, heteroaromatic compounds, and other lignin-like substances. Based on this knowledge an approach is proposed for consideration. As the pulp fibers’ refining process also includes the peeling of fiber wall surface layers, it could be useful to perform such refining first, followed by appropriate screening techniques before the pulp bleaching. The main objection to this approach is related to efficient utilization of the fines, i.e., fractions of the surface layers.

The study was carried out to find out the differences in the chemical composition of wheat straw obtained from three different regions of India, to compare their susceptibility to fungal degradation, and subsequently to evaluate the correlation between lignin loss and improvement in in vitro digestibility. Four Phlebia species were used to degrade different wheat straw samples during 30 days of incubation. In wheat straw obtained from central zone of India, most of the fungi were more selective in ligninolysis, with a moderate loss in total organic matter. The best found fungus, P. brevispora,enhanced the in vitro digestibility from 172 to 287 g/kg in north western, 165 to 275 g/kg in north eastern, and 145 to 259 g/kg in central zone with a respective loss of 163, 129, and 105 g/kg in total organic matter. Other three fungi P. fascicularia, P. floridensis, and P. radiata were also able to enhance the in vitro digestibility of all the wheat straw samples up to a significant extent. The study demonstrated that selective ligninolytic behaviour of fungi is influenced by the overall composition of wheat straw as governed by geographic location.

Two morphologically different pulps, a long-fiber jute pulp from a soda-AQ process and a short-fiber Trema orientalis pulp from a kraft process, were evaluated and compared for their reinforcing potential. T. orientalis pulp needed less beating energy than jute pulp at the same drainage resistance. Addition of jute fiber pulp to the T. orientalis pulp increased tear strength. Sheet density of pulp blends was increased with the increase of beating degree of both pulps and the proportion of T. orientalis pulp. Tensile index and burst index of blended pulp were increased when the beating degree and proportion of T. orientalis pulp increased.

The aim of the present investigation was to characterize a xylanase-producing Fusarium solani isolate and to optimize cultural conditions for xylanase enzyme production from free and immobilized cells. Screening of Fusarium solani isolate was based on the diameter of the clear zone formation in oat spelt xylan agar plates. Fusarium solani isolate F7 was selected and optimized for xylanase enzyme production using cheaper substrates such as wheat straw, rice straw, rice bran, and wood husk. Maximum enzyme activity was observed in wheat straw (78.32 U ml-1 for free cells and 94.68 U ml-1 for immobilized cells). Optimum pH and temperature for xylanase activity were found to be 5.5 and 30°C at 3% substrate concentration for free cells and 5.0 and 30°C at 3% substrate concentration for immobilized cells. In the purification step, 75% ammonium sulphate saturation was found to be suitable, giving maximum xylanase activity. Production of xylanase was greater from immobilized cells than from free cells. Purified xylanase from free cells yielded a single band with a molecular weight of 89kDa, while it was 92.8kDa for immobilized cells. The use of wheat straw as a major carbon source is particularly valuable, because oat spelt xylan is very expensive. The Fusarium solani F7 isolate proved to be a promising microorganism for xylanase production.

Pine sawdust pyrolysis was carried out respectively using microwave and conventional electrical heating at different temperatures in order to understand the properties of pyrolytic products from microwave pyrolysis of biomass. Less char material was obtained by microwave pyrolysis compared to conventional heating at the same temperature. While comparing the components of the pyrolytic gases, it was revealed that the microwave pyrolysis gas usually had higher H2 and CO contents and lower CH4 and CO2 contents than those obtained by conventional pyrolysis at the same temperature. The texture analysis results of the microwave pyrolysis chars showed that the chars would melt and the pores would shrink at high temperatures, and hence, the specific surface areas of the chars decreased with increasing temperature. Similarly, the reactivity of the char was remarkably reduced when the microwave pyrolysis temperature exceeded 600°C.

This study was performed to determine the impact of impregnation materials on the Brinell hardness of varnished wood materials. For this purpose, test specimens prepared from Scotch pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis Lipsky), which met the requirements of ASTM D 358, were impregnated according to ASTM D 1413-07 with borax, boric acid, zinc chloride, and di-ammonium phosphate by a vacuum technique. After impregnation, the surfaces were coated by cellulosic, synthetic, and polyurethane varnishes in accordance with ASTM D 3023. The Brinell hardness of the specimens after the varnishing process was determined in accordance with ASTM D 4366. According to the result of the tests, the highest Brinell hardness (135.40 kpm/m²) was determined in oriental beech samples, cut tangentially, impregnated with di- ammonium phosphate, and varnished with polyurethane. The lowest Brinell hardness (23.20 kpm/m²) was determined in Scotch pine control samples, cut radially and synthetically varnished.

This paper presents the results of a study to use virgin wood and OCC fiber for particleboard production. Three-layer boards, with wood and OCC fiber on the surface, were fabricated. The type of applied furnishes at surface layers, moisture, and adhesive content were considered as variables, and their effects on roughness of manufactured particleboards were examined. The panels were produced with 10% and 12% urea formaldehyde (UF) adhesive at 10% and 14% moisture content. The surface characteristics were investigated. The results indicated that wood and OCC fiber utilization on the surface layer gave smoother surfaces than a control board with fine wood particles on its surface. The surface roughness decreased as adhesive and moisture content increased.

This study concerns the structural change of lignin during auto-catalyzed ethanol-water pulping of aspen by 1H-NMR. The results showed that the linkages of alkyl-aryl ether of lignin, such as the α-ether linkages (α-O-4) and the β-ether linkages (β-O-4), were broken and the alkyl part formed carbenium at the Cα and Cβ of the aliphatic branch. Meanwhile, the aryl part of ether accepted one H+ and formed phenol. Because of the electronegative effect originating from the electron cloud of phenyl, partial carbenium of Cβ was rearranged. Due to its ether or hydroxyl linkage, rearranging to Cβ, the Cα was changed into carbenium and formed a new β-O-4 alkyl-aryl ether. The β-O-4 alkyl-aryl ether was not stable and broken further. So the large molecule of lignin was disintegrated into a smaller one and dissolved into ethanol. Finally, the α+ carbenium reformed α-O-4 linkages of ether with phenol.

To develop low-cost and environmentally friendly polymeric materials for enrichment, separation, and remediation of metal ions from water, graft copolymers based on cellulose extracted from pine needles were synthesized by grafting of 2-hydroxy methacrylate (HEMA) alone and with comonomers acrylic acid, acrylamide, and acrylonitrile by benzoyl peroxide initiation. The effects of change in concentrations of monomer and initiator, reaction time and temperature; and nature and composition of solvent system on graft yield and grafting efficiency were evaluated. At the optimum reaction conditions evaluated for the grafting of HEMA alone, comonomers as acrylamide, acrylic acid, and acrylonitrile at their five different concentrations were also co-grafted along with HEMA onto cellulose backbone polymer. Graft copolymers were further functionalized by partial hydrolysis, and were characterized by water uptake, FTIR, and elemental analysis. Sorption of Fe2+, Cu2+ and Cr6+ ions on graft copolymers were investigated to define their end-uses in separation technologies.

The response to refining of wheat straw and eucalyptus pulps as well as the relationships between refining, fiber properties, and paper properties are described in this paper. Pulps were bleached applying different bleaching sequences and thereafter refined to varying degrees. Pulp and fiber properties were investigated and set into relation to the final sheet properties. The results show that wheat straw pulps respond to refining more easily than eucalyptus pulps and that the differences are due mainly to morphological and ultrastructural differences as well as fines content and xylan content. The development of strength properties of the different pulps was found to be strongly correlated to the number of dislocations, i.e. weak points in the fiber wall, as well as to the morphological appearance of the pulp fibers after refining. A higher initial number and a faster development of dislocations together with the creation of large amounts of fines explain the slower and lower development of strength properties of wheat straw pulps than of eucalyptus pulps. Removal of fines from wheat straw pulps improved not only the drainability of the pulp suspension but also the mechanical and optical sheet properties. This indicates that the fines in the wheat straw pulps act mainly as filler with low bonding properties. The fact that fractionated D(EOP)D wheat straw pulps can deliver good mechanical sheet properties at very good drainability with no or only minor refining is very interesting when evaluating the potential of replacing or partially replacing eucalyptus with domestic Chinese raw materials in furnishes for production of different paper products.