Volume 13 Issue 3

The use of mineral fillers in the paper industry has attracted much attention due to its low cost and ability to improve optical properties and printability. Besides the filler characteristics, paper properties, such as bulk, tensile, and opacity, are greatly affected by filler distribution in the z-direction. Therefore, optimization of filler distribution is an effective way to maximize the value of fillers. In this work, a filler distribution factor (Fc) was proposed to quantitatively describe the concentrated degree of filler distribution in the z-direction. The reduction in Fc resulted in an increase in paper bulk, porosity, and opacity, due to the generation of more interfaces between fibers and fillers. When filler particles were concentrated in one layer (Fc = 1), the tensile strength of the filled paper increased between 26 to 40% in comparison to the paper with various Fc values. For a given Fc, better tensile and opacity properties were achieved by increasing filler concentration on the surface layer of paper.

A totally chlorine free (TCF) bleaching sequence was studied for an acid sulfite pulp mill that produces dissolving pulps. Laboratory analyses of the last two bleaching stages, an oxidant-reinforced alkaline extraction stage (EOP), and a subsequent pressurized peroxide with oxygen stage (PO), were performed on a eucalypt pulp that had been delignified by an ozone (Z) stage in the pulp mill. The goal was to predict the optimal costs and operational conditions for the (EOP)(PO) partial bleach sequence for three different specialty pulp products. Four independent variables affecting the pulp quality properties were examined for each stage (i.e., reaction temperature, reaction time, NaOH dosage and H2O2 dosage). The dependent variables were various pulp properties, such as intrinsic pulp viscosity, alpha-cellulose content, kappa number, and GE brightness. Three scenarios were considered to optimize the bleaching process, which related to a regenerated cellulose product (viscose) that is widely commercialized, and to two novel products (nanocrystalline cellulose (NCC) and nanofibrillated cellulose (NFC). Statistical response surface models indicated that the bleaching behavior of the ozone-treated pulp could be represented by second-order polynomial equations. These non-linear optimization models predict cost savings of 62.2%, 73.4%, and 63.3% for producing viscose, NCC, and NFC pulp grades, respectively.

High biomass loading is a key technique to reduce the pretreatment cost of lignocellulosic biomass. In this work, various biomass species such as bagasse, erianthus, cedar, and eucalyptus were pretreated using an ionic liquid, 1-ethyl-3-methylimidazolium acetate, at different biomass loadings, particularly focusing on a high loading region. Cellulose structural changes in pretreated biomass were investigated via X-ray scattering and 13C solid-state nuclear magnetic resonance (SSNMR) spectroscopy. The structural behaviors roughly fell into two categories, corresponding to either grassy (bagasse and erianthus) or woody (cedar and hardwood) biomass. The grassy biomass gradually transformed from cellulose-I to cellulose-II in a monotonic manner against the biomass loading. In contrast, the transformation in the woody biomass occurred abruptly as solids was decreased within the high loadings range (50 wt% to 33 wt%). Below 33 wt%, a reformation of cellulose-I from cellulose-II proceeded readily. In terms of cellulose crystallinity, erianthus as well as bagasse showed a minimum value at 25 wt% loading, whereas the crystallinity for the woody biomass did not possess such a clear minimum. Acid hydrolysis of these pretreated biomass was also conducted and the relationship between the reactivity and the cellulose structural changes was discussed.

Furfural residue (FR), a solid waste from the furfural production industry, is rich in cellulose and lignin. It has great potential for producing bio-fuels and bio-chemicals through pyrolysis. To examine the effects of heating programs on the product distribution of FR pyrolysis, stepwise and one-step pyrolysis processes were compared using a commercial Py-GC/MS system. During the stepwise pyrolysis, the acids had a maximum yield at 300 °C, while the outputs of the ketones/aldehydes, furans, esters, alcohols, and sugars were the most abundant at 350 °C. The production of aromatics increased, whereas the nitrogen-containing compounds decreased as the temperature increased from 300 °C to 500 °C. The relative percentages of the aromatics and furans from the one-step pyrolysis were much higher than those from the stepwise pyrolysis. In contrast, the acids, sugars, alcohols, nitrogen-containing compounds, and alkanes/olefins from the stepwise pyrolysis were higher than those from the one-step pyrolysis at 500 °C. The kinetic analysis showed that the activation energy of the FR was reduced from between 212 and 214 kJ/mol to between 189 and 191 kJ/mol as the degree of conversion (α) increased from 20% to 60%, before increasing from 191 kJ/mol to 478 kJ/mol as α further increased from 70% to 90%.

With the use of Paulownia wood as a substrate and a vacuum impregnation method, CaCO₃/wood composites were prepared. The XRD results showed that a variety of types of calcium carbonates coexisted in the composite and the elevated temperature was favorable for the aragonite type. The SEM results showed the modified wood retained the original wood structure and that CaCO₃ was uniformly distributed in the wood cell cavity and clung to the wood cells. The mechanical testing results showed that the mechanical properties of all the composites were obviously improved; the maximum value of strength of compression (SC) and modulus of elasticity (MOE) of the CaCO₃/wood composites were 32.23 MPa and 0.92 GPa, respectively, values 44.2% and 53.3% higher than those of the original wood. The maximum value of proportional limit (PL) of the composites was 29.4 MPa (38.5% increase from original wood). A cone calorimeter was used to investigate the flame retardation properties of CaCO₃ on the composites. The value of the heat release rate and total heat release of composites were lower than those of the original wood; the CaCO₃ wood composites showed good flame retarding effects.

The objective of this study was to investigate the impact performance of bamboo oriented strand board under different impact energy. Bamboo oriented strand board with two types of strand orientation distribution, both with mainly parallel aligned strand orientation (LVSL) and three-layer assembly with orthogonally oriented strands (BOSB), were prepared. The impact properties of the boards, both untreated and treated with submersion, were investigated at seven energy levels. Additionally, the damage morphology was characterized using an X-ray computed tomography (CT) scanner. The results indicated that BOSB provided a larger maximum load carrying capacity, and represented superior impact properties compared to LVSL. The shapes of force/energy–time history of BOSB and LVSL were different from projectile energy levels, and they were related to the specimen destruction forms via CT scanning. Moreover, CT scanning revealed that LVSL and BOSB exhibited similar damage behaviors, which mainly included delamination and fibers breakage. The dent depth of BOSB on the impact site was less than LVSL’s for touch types, and there was more internal fracture inside the layers of LVSL at relatively higher energy levels of 300 J and 450 J. Furthermore, BOSB still exhibited better impact performance than LVSL under the condition of submersion.

Approximately 18 million tons of soybean straw are produced annually in China, with its disposal becoming an increasingly serious problem. Moreover, the Chinese government has banned the open burning of agricultural straw for environmental reasons. One potential solution is to use soybean straw for lactic acid (LA) production, avoiding open burning and waste. In this study, a Ca-alginate-immobilized Lactobacillus casei strain was used to produce LA from soybean straw enzymatic hydrolysate. Optimized conditions for the production of LA were initially established, consisting of Ca-alginate beads made from 2.5% sodium alginate with a diameter of 2 mm and a fermentation process using a 10% inoculum at 30 °C for 30 h. Lactic acid productivity was increased with only a slight decrease in overall yield by raising the initial sugar concentration from 8 g L-1 to 35 g L-1. Finally, immobilized cells could be reused at least 10 times without a noticeable performance decrease. These results indicated that production of LA from soybean straw enzymatic hydrolysate is a sustainable and feasible method to utilize these resources.

Biorefinery lignin was carbonized under a carbon dioxide atmosphere at various temperatures viz., 500 °C, 600 °C, 700 °C, and 800 °C, separately. The results indicated that with increasing temperature, the mass yield decreased from 49.2% to 39.8%. Carbonization at a high temperature resulted in an increment of carbon (C) content and decreased both the hydrogen (H) and oxygen (O) contents. With the increase of carbonization severity, the ratios of O/C and H/C decreased mainly due to the demethanation, dehydration, and decarboxylation reactions. The carbonization resulted in the transformation of aromatic rings as well as the rearrangement of the aromatic polymers, and the enhancement of the thermal stability of the charcoal formed.

Cellulosic paper is widely used in various applications, such as for decoration and in cold-rolled stainless steel. The thermal stabilities of cellulosic fibers were investigated with a thermogravimetric analyzer. Additionally, the impact of mechanical refining on the heat resistance of cellulosic paper was evaluated by testing the tensile strength and brightness of the samples derived from pulp with various beating degrees. The morphology of the paper was characterized with scanning electron microscopy and the monose content of the pulp samples was determined with high performance liquid chromatography. The results showed that the different pulps had different thermal stabilities. Because of pulp refining, the heat tolerance was enhanced in terms of the strength and optical properties. Compared with the original papers, the tensile strength and brightness of the 40°SR papers on average increased by 217% and 114%, respectively, all evaluated after heating at 240 °C. Therefore, the heat tolerance of cellulosic paper can be tuned with pulp refining.

Virgibacillus pantothenticus, Bacillus cereus, and B. subtilis were screened from an activated sludge that had become acclimated to white water in the laboratory. The effects of the pH on the ability of biological treatment to reduce the biological oxygen demand of white water was studied for three dominant bacteria. The pH ranged from 4 to 8, and the optimum treatment efficiencies for white water treatments with the single dominant bacterium V. pantothenticus, B. cereus, and B. subtilis occurred at pH values of 5, 6, and 6, respectively. The results also indicated that the best treatment effect was achieved at a hydraulic retention time of 14 h. When each dominate species was tested under their optimum pH value and hydraulic retention time, the chemical oxygen demand removal rate was 67.7%, 77%, and 75.4%; the electrical conductivity decreased by 0.18 mS/cm, 0.93 mS/cm, and 0.51 mS/cm; and the cationic demand decreased by 69.7%, 70.0%, and 70.9% for V. pantothenticus, B. cereus, and B. subtilis, respectively. These results are helpful for promoting the practical application of dominant bacteria in white water treatment.