Research Articles

Black liquor (BL) can be regarded as the energy and alkali resource of the pulping mill. In this work, the effects of the characteristics of black liquor derived from the alkali-oxygen pulping of rice straw were studied. Through analyses of the chemical and physical properties, especially the thermodynamics properties, which depend on suspended matter and alkalinity, it was shown that the removal of the suspended matter from the black liquor could effectively improve its thermodynamic properties, particularly in making its solids content reach up to more than 56% at the turning point of its viscosity. Moreover, sodium salt played an important role in the presence of macromolecules and silica in the BL. When the BL was adjusted to pH = 11 with NaOH, the filtered BL had the lowest silica content, the highest volumetric isothermal expansivity (VIE), was more susceptibility to thermal cracking, and was more suitable for processing for alkali recovery.

The kinetics of cellulose decomposition in ionic liquid was investigated using microcrystalline cellulose as a raw material. Curve fitting of cellulose degradation kinetic data was carried out by MATLAB. Experimental results demonstrated that the cellulose decomposition rate constant, k1, was less than the constant for glucose decomposition to 5-hydroxymethylfurfural (5-HMF), k2, in the ionic liquid system, gaining a larger gap with increasing temperature. Results indicated that cellulose degradation is a slow reaction compared with glucose decomposition, which controls the speed of the overall reaction steps. CrCl3 increased the rate constant of cellulose and glucose degradation to almost the same degree, thus achieving simultaneous conversion of cellulose, glucose, and 5-HMF. Compared with other reaction systems, the ionic liquid system considerably reduced activation energy. Regression analysis of kinetic data indicated that the catalytic decomposition reactions of cellulose, glucose, and 5-HMF are all first-order reactions.

The conversion of lignocellulosic biomass into fine chemicals and polymers has been gaining attention recently. Regenerated lignocellulose beads (RLBs) were prepared by an emulsification/precipitation technique, using wheat straw as a raw material and [Bmim]Cl as a solvent. The morphology and properties of the obtained beads were characterized. The RLBs were perfectly spherical, with a porous microstructure, and had a huge specific surface area (142.4 m2/g). Their components were similar to that of wheat straw; however some chemical and crystal changes of these components occurred during the preparation process. Eighty percent of the beads were in the size range between 24.4 to 149.6 μm, and the mean particle size was 84.7 μm. Furthermore, the beads possessed good thermostability in the temperature range between ambient temperature and 200 °C. This work demonstrated the feasibility of the production of RLBs using lignocellulosic biomass and provided a new direction for high-valued utilization of lignocellulosic agricultural residues.

Bioethanol is a renewable energy source, and its production from agricultural wastes, such as banana and pineapple peels, is an economical approach. Enzymatic hydrolysis experiments were performed using a simultaneous saccharification and co-fermentation (SSCF) method. Banana and pineapple wastes inoculated with Aspergillus terreus and Kluyveromyces marxianus produced the maximum ethanol concentrations of 0.35 g/L and 0.27 g/L, respectively. Furthermore, logistic unstructured and incorporated models described well the growth of microorganism, product formation, and substrate utilization during SSCF system with high R2 and low RMSD.

Natural, renewable, and non-toxic lignin-based resin was synthesized through copolymerization with monomeric N-vinyl-2-pyrrolidone (VP) in the presence of benzoyl peroxide (BPO) as the free radical initiator. Glyoxalated lignin was used as the feedstock. The mechanism of copolymerization between the glyoxalated alkali lignin and VP monomer was determined through Fourier-transform infrared spectroscopy (FT-IR). The optimum amount of VP monomer used and the reflux time required in the synthesis process were determined through thermogravimetric analysis (TGA). In the presence of BPO, copolymerization between glyoxalated alkali lignin and VP monomer was accomplished via the formation of ether linkages in a condensation reaction at pH 7.0. More ether linkages were formed with higher amounts of VP monomer and longer reflux times. The addition of VP monomer into glyoxalated alkali lignin increased its thermal stability. FT-IR and TGA indicated that 0.012 moles of VP monomer and an 8-h reflux time were optimum conditions for the synthesis of glyoxalated alkali lignin-polyvinylpyrrolidone resins.

The combustion characteristics were evaluated for wood samples either untreated or treated with a piperazine-N-N´-bis(methylenephosphonic acid) flame retardant. Combustion properties were investigated using a cone calorimeter (ISO 5660-1 2002). The time to ignition of samples treated with the chemical additive was delayed by 193%, 124%, and 61% for maple, ash, and cypress, respectively, compared with the untreated samples. Compared with the untreated sample, the PHRR value was reduced by 20% for t-ash and by 2.6% for cypress, whereas it was increased by 0.28% for t-maple. The time of PHRR for the treated sample was shifted to 1605 s (698%), 470 s (45%), and 340 s (32%) for cypress, ash, and maple, respectively, compared with the untreated samples. The reduced PHRR value and postponed time to PHRR indicated that combustion was suppressed by the thicker char layer. The mean CO yield of t-ash and t-cypress was increased by 2.9% and 27%, respectively, compared with the untreated sample, but t-maple was reduced by 46% compared with maple. The mean CO2 yield of t-maple, t-ash, and t-cypress was decreased by 4%, 13%, and 37%, respectively, compared with the untreated sample. The combustion properties of treated wood were inhibited more than those of untreated wood.

This work investigates nano-fibrillated cellulose (NFC) as a component in mineral pigment paper coating. In this work, bleached Eucalyptus pulp was pretreated by TEMPO (2,2,6,6-tetramethyl-1-piperdinyloxy)-mediated oxidation. The oxidized pulp was then isolated to obtain NFC by sonication. Aqueous coating colors consisting of calcium carbonate, clay, carboxylated butadiene-styrene latex, additives, and NFC were prepared. The rheology of the coating colors and the surface properties of paper coated with NFC containing coating colors were determined. The rheological properties allowed NFC to be used in small amounts under laboratory conditions. Nano-fibrillated cellulose was found to improve the surface strength and smoothness of the coated paper. The water resistance of coated paper, on the other hand, decreased because of the hydrophilicity of NFC.

The aging resistance properties of poplar plywood prepared with soy protein-based adhesives were investigated. The shear strength of soybean meal/bisphenol epoxy resin (SM/EP) adhesive increased by 197.5% (surface layer) to 1.19 MPa and 153.5% (core layer) to 1.09 MPa compared to soybean meal (SM) adhesive. Wet-dry cycles of 25 ± 3 °C, 63 ± 2 °C, and 95 ± 2 °C accelerated the aging of poplar plywood with soy protein-based adhesive. After eight 25 ± 3 °C wet-dry cycles, the shear strength of plywood bonded with SM/EP adhesive was reduced to 0.88 MPa (surface layer) and 0.71 MPa (core layer). Furthermore, the shear strength of SM adhesive gradually decreased to 0 (surface and core layer) after six and five 25 ± 3 °C wet-dry cycles. The shear strength of SM/EP adhesives was reduced to 0.96 MPa and 0.79 MPa (surface and core layer) after eight 63 ± 2 °C wet-dry cycles, and 0.53 MPa and 0.27 MPa (surface and core layer) after eight 95 ± 2 °C wet-dry cycles. Vertical density profiles indicated that the decrease of shear strength could be attributed to several factors: The small molecules were dissolved, the molecular chains of the adhesives were hydrolyzed by water, and the interior and thermal stress destroyed the bonding structure.

The physicochemical properties of alkali lignin are crucial to its potential applications and recyclability, as it is one of the most important natural polymer materials. In this study, the solubility parameter (δ) of alkali lignin was determined using Hansen solubility parameters (HSP) theory and inverse gas chromatography (IGC). The δ of alkali lignin was determined by the IGC technique. Solute retention volumes (Vg0) of 6 solutes were determined using alkali lignin as the stationary phase. From 50 to 110 ºC, the δ of alkali lignin varied from 24.47 to 24.15 MPa1/2. Hansen solubility spheres were plotted using the data from the literature for the interactions of alkali lignin with 36 solutes to determine the three dimensional solubility parameter of alkali lignin at 25 to 100 ºC. These determined δ values were consistent with those calculated experimentally via IGC. Acetone was a moderate solvent for the alkali lignin.

A systematic study was conducted on P. pubescens by analyzing thermal characteristics of its rhizome and culm (1.5 m) at different ages, using various analyses such as X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetry (TG). For both the rhizome and culm of P. pubescens, the relative crystallinity (Cr) of cellulose increased and then appreciably decreased with increasing age, but the rhizome contained about 10% less Cr than culm. However, the glass transition temperature (Tg) of culm (268.8 to 273.8 °C) was higher than in the rhizome (213.9 to 219.4 °C). The extrapolated initial decomposition temperature (Te) of 1-, 3-, and 5-year-old rhizome were 263.7 °C, 266.1 °C, and 263.9 °C, respectively; the Te of culms of the same age were 289.7 °C, 282.8 °C, and 283.4 °C, respectively. Variance analysis showed no significant differences in the Te of either rhizome or culm of different ages. Taking the chemical characteristics into consideration, it was concluded that the rhizome has a stable composition and good heat resistance.