Research Articles

Water contamination by heavy metal ions is a worldwide problem. In this work, a type of hydrogel, based on hemicellulose, was prepared via graft copolymerization. The reaction time and cost were reduced by modifying the traditional preparation process. The hemicellulose-based hydrogel was an opaque, smooth, well-distributed, and high resilience hydrogel. To better understand the application of hemicellulose-based hydrogel as an absorbent for the removal of Pb(II) (lead nitrate) from heavy metal contaminated water, the hydrogel was used to adsorb Pb(II) from aqueous solution. The various factors that influenced the Pb(II) removal efficiency were studied, including concentration and temperature. The results showed that the hemicellulose-based hydrogel was assessed as an ideal absorbent towards Pb(II), showing maximum monolayer adsorption capacity of 5.88 mg/g. The Pb(II) adsorption isotherm was determined to further understand the adsorption mechanism. The results demonstrated that the adsorption of the hemicellulose-based hydrogel on Pb(II) belongs to the monolayer adsorption and that adsorption conforms to the Langmuir model better than the other model. It revealed that the adsorption process of Pb(II) on hemicellulose-based hydrogel was spontaneous and endothermic in nature. The hemicellulose-based hydrogel was proven as a good material for potential application.

Novel thermoplastic composites filled with wheat straw (WS) and enzymatic-hydrolysis lignin (EHL) were developed and characterized. The three-dimensional melt blending system of WS, EHL, and high-density polyethylene (HDPE) was optimized via orthogonal experiments. The mechanical properties and melt index of the composites were measured and the optimum ratio of the composites was determined. Based on the optimum ratio of the composites’ blending system, identified through compounding granulation and extrusion molding process links, pilot products of the composites were produced. The thermal behavior, polar groups, and surface structures of the fibers and developed thermoplastic composites were assessed by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) analysis, respectively. The addition of EHL, an abundant renewable resource, improved the dispersity of the matrix as well as the mechanical and thermal properties of the composites. The results provide a theoretical basis for the application and development of new composites and illustrate a potential industrial application of EHL.

Time and motion studies are often used to evaluate the performance of various product systems. However, traditional studies are characterized by a series of technical limitations, and they require many resources. This study tested the capability of a low-cost Global Positioning System (GPS) receiver and an accelerometer unit to automate the field data collection for characterizing motor-manual felling of willow short rotation coppices. The results were promising. By thresholding the acceleration data, the running and stopped engine states were accurately separated. Also, by combining the GPS speed with the acceleration data, followed by threshold setting and data visualization in the Geographic Information System software, detailed time categories, such as productive, working, and non-working times, could be separated. The methods described herein could be used to manage long-term field data collection, as such operations are affected by many operational factors.

Most research on biomass-filled plastic composites (BFPCs) mainly focuses on their formulation and physical/mechanical properties, but studies on the connection performance of BFPCs are very rare. However, such performance is vital in the quality assessment of BFPCs products and plays an important role in improving product quality and promoting its application in the field of architecture and furniture. Therefore, the behavior of L-type BFPCs structure under the interaction of fatigue-creep was investigated. Results suggested that the fatigue-creep curve is a typically three-region curve at 80% and 60% failure load, and only first two stages at 40% failure load. But the damage caused by fatigue-creep interaction was not a simple superposition. Fatigue damage dominated when the holding time was short, and creep damage occupied a dominant position gradually when the holding time was longer. In addition, the lifespan of the BFPC component increased initially and then decreased as holding time increased. The component joint exhibited the least integrated damage when the holding time was 60 s and the lifespan was longer.

Magnesium hydroxide (Mg(OH)₂) nanosheets were explored as an effective material for the restoration and conservation of paper-based cultural archives and compared with the commonly used Ca(OH)₂ nanoparticles. The (Mg(OH)₂) nanosheets were applied to filter paper as a reference, as well as to new and old paper samples. The effectiveness of Mg(OH)₂ nanosheets was evaluated by (i) a pH test of the surface and the bulk extracts, (ii) measuring the alkaline reserve and correlating it with the enhancement in life expectancy, and (iii) in terms of mechanical strength. The alkaline reserve test indicated an increase in the alkaline buffer, which resulted in markedly reduced acidic content of the samples. It was inferred from the improved properties that Mg(OH)₂ nanosheets coated the paper as a lamination sheet and protected it as the first line of defense against acidic environmental attack. Moreover, its presence within the paper acted as an alkaline reserve and also as reinforcement in the form of an inorganic nanosheet. The results suggest that the nanosheets are an innovative, compatible, and efficient material for the consolidation and restoration of old and new paper samples.

Fish glue prepared from swim bladders has been used in China to glue wooden parts together since ancient times. It is also used as an important natural glue for wooden artifact and building restoration, musical instrument fabrication, as well as many other fields. Microorganism contamination is a major concern for fish glue preservation. In this research, fish glue was prepared from swim bladders using two methods, namely, heat treatment and enzymatic hydrolysis. Then, the molds that germinated in both samples were analyzed. Light microscope and scanning electron microscopy (SEM) observations of the molds’ hypha morphology identified Alternaria in both glue samples. The antimicrobial efficiencies of borax, sodium diacetate, and Antim AL-D (an organic/inorganic composite antimicrobial) were then compared. The results demonstrated that all antimicrobial agents in the research effectively inhibited Alternaria germination in both fish glue samples. A 0.3% (by weight) solution of Antim AL-D was sufficient for preserving fish glue. As for borax and sodium diacetate, the addition of a minimum of 1.0% was adequate to inhibit Alternaria growth. Results also revealed that the addition of Antim AL-D minimally affected the shear strength of glued wooden parts.

Genetic modification of plant lignin composition is an important strategy for improving biomass enzymatic digestibility without sacrificing the normal growth of the plant. However, the absence of fast and convenient methods for rapid determination of lignin composition has impeded corresponding research. Near-infrared reflectance spectroscopy (NIRS) analysis has potential as a solution for this dilemma, while the NIRS measurement for expediently assaying lignin composition in rice straws is still lacking. In this study, visible and near-infrared reflectance spectroscopy (VIS/NIRS) and modified partial least squares (MPLS) method were combined to develop calibration models for predicting the lignin monomer contents in a diverse rice population. Four optimal equations for predicting the content of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) lignin units and their total amount (H + S + G) were generated with acceptable determination coefficients for calibration (0.85 to 0.93), cross-validation (0.75 to 0.88), and external validation (0.82 to 0.88), and the ratio performance deviation (RPD, 2 to 3.01). This study was the first to demonstrate that VIS/NIRS could give a sufficiently accurate prediction of lignin monomer contents in rice and could be applied for rapid assessments of large-scale rice straw samples.

This research investigated the use of reclaimed rubber (RR) from waste tires to partially replace the rubber compound (RC) when making wood fiber-rubber composites (WRCs). Ninety panels of WRC containing RR were manufactured with RR contents of 0% to 40%, mixing times of 6 min to 14 min, and vulcanizing temperatures of 150 °C to 170 °C. There were three steps, which were the fiber-rubber mixing, tabletting, and vulcanization molding processes. Four regression equations for the tensile strength, elongation at break, hardness, and rebound resilience as functions of the RR content, mixing time, and vulcanizing temperature were derived, and a nonlinear programming model was developed to obtain the optimum panel properties. It was found that when the RR content was within 20%, the wood fibers were well encapsulated and embedded in the RC/RR blends, and the processability of the WRCs were improved by adding RR. The incorporation of RR into the WRCs increased the average tensile strength and hardness by 33.9% and 2.3%, respectively, while the swelling ratio in toluene and 24-h water absorption were reduced by 13% and 42%, respectively.

The potential of bamboo green (B), an abundant lignocellulosic residue from the bamboo processing industry, was evaluated to serve as an alternative fibrous raw material in the production of fiberboard. Urea-formaldehyde resin-bonded fiberboards were prepared from B, wood fiber (W), and a mixture of the two (BW). The board type depended on the mass fraction of B in fibrous raw materials (including B and W), which were 0%, 20%, 40%, 60%, 80%, and 100%. The analytical methods used to characterize fibers and fiberboards included X-ray diffraction, thermogravimetric analysis, dynamic mechanical analysis, contact angle analysis, physical-mechanical analysis, and scanning electron microscopy. Compared with W, B showed a higher crystallinity index and thermogravimetric stability, but lower surface hydrophilicity and weaker interactions with urea-formaldehyde resin. Compared with W fiberboards, B fiberboards possessed a lower interfacial adhesion but fibrous raw materials in B fiberboards were better dispersed; moreover, B fiberboard displayed a higher dynamic viscosity, thermogravimetric stability, surface wettability, water absorption, and flexural modulus, but lower thickness swelling and flexural strength. The fiberboards produced with BW had better performances than the fiberboards produced with B and W. The 40% B mass fraction resulted in BW fiberboards with the best physical-mechanical properties.

The wood anatomy and chemistry of a relatively lesser used wood species, known in Mozambique as nsangala (Millettia mossambicensis J. B. Gillett), was compared to overexploited species jambire (Milletia stuhlmannii Taub.) to provide diagnostic features for safe discrimination. The anatomical results showed that both species shared several similarities such as intervessel pitting size range (8 µm to 11 µm), rays composed of only procumbent cells, fiber dimensions (average length up to 1359 µm and wall thickness up to 10 µm), and banded axial parenchyma. The extractives and lignin content were higher in jambire, while the carbohydrates and acetyl contents were higher in nsangala. The main anatomical feature separating the two species was the porosity pattern with semi-ring porous wood of nsangala compared to the diffuse-porous structure of jambire. Jambire had wider vessel lumina (200 µm) and up to 3 vessels/mm² compared to nsangala vessel lumina of 86 µm and a frequency of 37 vessels/mm².