Research Articles

The influence of the nano-zinc oxide amount was evaluated relative to the flammability behavior, as well as the morphological and mechanical properties of wood plastic composites (WPCs). The polymer amount was approximately 50 wt%, and the lignocellulose material was 50 wt%. Nano-zinc oxide was applied at six weight levels including, zero (control), 1, 2, 3, 4, and 5 phc. For all treatments, the maleic anhydride polyethylene (MAPE) amount was 2 phc. The WPCs were made using a mixture of nano zinc oxide, high-density polyethylene, and mixed hardwood flour injection molding method. The morphological and mechanical properties, such as flexural strength and modulus, were measured. Various tests were conducted with a cone calorimeter, including the amount of char residue, total smoke production, time to ignition, and heat release rate, according to ASTM E1354-92 (1992). The flexural strength and modulus of composites in samples with 5 phc nano-zinc oxide were 79.9% and 27.2% greater, respectively, than in samples without nano zinc oxide. Nano-zinc oxide enhancement to 5 phc increased the ignition time and char residue 105.1% and 121.7%, respectively, and decreased the burning rate and total amount of smoke production 20.3% and 46.0%, respectively. Scanning electron microscope results indicated the presence of nano-zinc oxide agglomerates in the sample.

Switchgrass harvested from saline soil was slowly pyrolyzed at 300, 500, and 700 °C in a fixed-bed reactor. The objective was to understand the characteristics and evaluate the potential values of the bio-oil, syngas, and biochar. The biochar yield (27.0% to 41.3%) decreased with increasing temperature, whereas the syngas yield (26.3% to 40.9%) increased. The bio-oil yield (30.8% to 34.1%) was highest when the switchgrass was pyrolyzed at 500 °C. Both the bio-oil and syngas had low value as direct fuels because of their low heating values. Compared with the biochars from the switchgrass grown in “sweet” soil, the biochars derived from the switchgrass grown in saline soil had higher values of ash (10.5% to 17.2%), mineral nutrients, and cation exchange capacity (CEC) (200.3 to 241.1 cmol/kg). These results suggested that the biochar generated in this study might have a better liming effect and improvement of soil fertility and crop growth as a soil conditioner, and lead to double wins in saline soil improvement and a new approach for switchgrass utilization.

Graphene was manufactured from commercial kraft lignin, and its forming mechanism, structure, and properties were investigated. A single factor test was employed to determine the optimum conditions of the production of graphene nanosheets. Kraft lignin was mixed with iron powders as catalyst with different weight ratios. The mixed carbon source and catalyst were thermally treated at 1000 °C and incubated for a period of time in a tubular furnace. The thermally treated carbon materials were analyzed by field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The preferable conditions for production of graphene nanosheets from kraft lignin were determined. The graphene fold structure was obtained after thermally treating for 90 min when the ratio of carbon source to iron was 3:1. The results revealed that folded lamellar graphene structure increased with greater holding time. Carbon nanotubes (CNTs) were observed after thermal treatment for 105 min. These results indicate the formation of graphite crystal structure and multi-layered graphene from kraft lignin in the presence of iron catalyst.

Kraft mill effluents treated by activated sludge show a reduction in acute toxicity. However, their discharges produce hormonal effects in an aquatic ecosystem, due to the sterols metabolites as androstenedione contained in the effluents. Daphnids bioassays are a powerful approach for determining toxicity. However, there are relative sensitivities depending on the species. The main objective of this study is to determine the sensitivity of D. magna and D. obtusa when exposed to kraft mill effluents, diethylstilboestrol (DES), and androstenedione (AED). The sensitivities were tested using acute bioassay exposed to kraft pulp mill. Moreover, the allometric growth rate of both daphnids affected by DES and AED regarding time were also evaluated for a period of nine days. Variation in the ratio between body length and body width – at the abdominal cavity – over time (k index) was evaluated. Results indicated that AED and DES compounds affected the allometric growth rate of daphnids. Specifically D. magna exhibited more sensitivity when it was exposed to kraft pulp mill.

Recently, an intermittent hot-pressing process had been developed and applied to produce bamboo bundle laminated veneer lumber (BLVL) joints with lengths of more than 6 m. According to our previous studies, there was a major difference in the physical and mechanical performance of hot-pressing joints and at adjacent positions on the lumber. In this paper, heat transfer and the effects of various aging temperatures on the mechanical performance of the joints of intermittent hot-pressed BLVLs were studied. During the hot-pressing process, there were noticeable different temperature changes on the board. In addition, degradation of the modulus of elasticity (MOE) and modulus of rupture (MOR) values on the joints was greater than that on the adjacent positions of the BLVLs, and the degradation increased with increasing aging temperature. Because of the low interfacial bonding strength of the joints caused by the pre-curing effect during the hot-pressing process, the MOR was more sensitive to hydrothermal conditions. Therefore, when BLVLs produced by intermittent hot-pressing are used as engineering components, the joints should be well-designed and arranged to avoid being used in the same cross-section.

Wood is a material widely used in various sectors of construction, such as in structures and building components. The volume of wood extracted from tropical forests has reached a considerable amount, and this wood is marketed with popular names without prior characterization. Wood density is an easy property to measure, and its use as an estimator of other properties is very common in this sector. This study investigated the possibility of the estimation of important quantities in dimensional stability of Brazilian tropical woods by using the density at 12% moisture content, anhydrous density, and basic density. Testing the ability to estimate radial, axial, tangential, and volumetric shrinkage, anisotropy coefficient, coefficient of volumetric rate of volumetric shrinkage, as well as the rate of volumetric swelling using the densities above, with linear, exponential, geometric, and logarithmic models, the best determination coefficient was: R² = 19.58%. The results were, in summary, that the variable density was not a good estimator of the dimensional stability of the wood.

A new type of biochar-SiO₂ core-shell particles (BCNPs) was successfully prepared via the sol-gel-sediment method. The characteristics of BCNPs were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). This novel filler was added to a polydimethylsiloxane (PDMS) matrix to prepare composite membranes to separate ethanol from water via pervaporation (PV). The effect of BCNPs on the performance of the membranes was researched. Experimental results showed that the addition of BCNPs led to remarkably improved PV performance of composite membranes. When a BCNPs content was 5 wt.% for a 10 wt.% ethanol solution at 40 °C, the best PV performances gained were the separation factor of 11.9 and the corresponding permeation flux of 227 g·m^-2·h^-1.

Utilizing biomass resources to synthesize water-absorbent resin has attracted global interest as a new research direction. Lignin, as the second most abundant renewable biopolymer in nature, is a strong candidate for use in renewable materials. In this study, water-absorbent resins were synthesized from lignosulfonate (LS) and acrylic acid (AA) by grafting copolymerization with an aqueous solution of potassium persulfate (KPS) as the initiator and N’N-methylene-bis-acrylamide (MBA) as a crosslinking agent. The optimum process parameters of lignosulfonate-grafted-polyacrylic acid resin (LS-PAA) were obtained via a single-factor method: AA 30 wt.%, LS 2.67 wt.% (to AA), cross-linker 0.03 wt.% (to AA), initiator 0.43 wt.% (to AA), and neutralization 65%. The optimum reaction temperature was 60 °C. Although lignin is a hydrophobic polymer, it has many reactive functional groups that can react with AA. It has been expected that adding lignins can change the cross-linking density by their three-dimensional structure, thus increasing the water absorbency. The LS-PAA resins were compared to other kinds of lignin derivatives including alkali lignin, lignocresol, lignoresorcinol, and lignopyrogallol under the same reaction conditions. The results showed that changing the types of lignin can change the resulting water absorbency. Lignopyrogallol-grafted-polyacrylic acid resin (LP-PAA) showed the highest water absorbency (2137 g/g).

The physical and mechanical properties were studied for fuel pellets made from a mixture of rice husk and Gmelina arborea wood particles. Pellet density, compressive strength, and abrasion resistance were used to evaluate pellet quality at various densification pressures and proportions of rice husk to wood particles. Pellet density and compressive strength increased from 850 to 1070 kg/m3 and 0.61 to 1.2 MPa, respectively, when densification pressure increased from 80 to 120 MPa. The abrasion resistance for all pellet samples in this study was < 2.0%. Proximate analyses of the fuel pellets showed that volatile matter, fixed carbon, and heating value were relatively high and increased with a higher proportion of wood particles. Ash levels were also high (1.3 to 17.8%), which could cause problems with emission and deposition during thermal conversion. In general, except for the ash content, the physical and mechanical properties of pellets made from rice husk and G. arborea wood particles in this study were within the acceptable limits to be used as fuel pellets for industrial heat applications.

The physical and chemical characteristics of several lignin-polyol blends were investigated by qualitative and quantitative methods from the view of biobased polyurethane applications. Four differently isolated biomass lignins from forestry and agricultural residues were blended with polyester polyol, and one was blended with polyethylene glycol. The isolated products were examined thoroughly to elucidate the subsequent lignin and polyol interactions during the premixing stage of biobased polyurethane formulation. Polyol was detected in lignin even after vigorous washings with several organic solvents and Soxhlet extraction. The experimental data coupled with two-dimensional heteronuclear multiple quantum coherence (HMQC) and nuclear magnetic resonance (NMR) spectroscopy confirmed the formation of ligno-polyols via strong intermolecular attractions, as well as some linkages between several lignin hydroxyl and polyol functional groups.