Research Articles

In order to design effective shredding machines dedicated to shredding wood-based waste, information about the mechanical properties of materials subjected to shredding is necessary. A number of mechanical properties of particleboard, oriented strand boards, and medium-density fibreboards in the aspect of shredding process have been experimentally determined in the article. The influence of material type, blade geometries, and cutting depth on cutting force and elasticity coefficient were analysed. Blade geometries reflect different phases of rotation of the cylindrical wood chipper’s knife. It has been shown that a knife with the most favourable geometry is characterized by the lowest values of the stiffness coefficient for each of the materials. This is the geometry of the cylindrical wood chipper’s knife exactly halfway into the cutting process. By contrast, the least favourable geometry is characterized by a knife corresponding to the beginning of the cutting process. Among the tested materials, the medium density board requires the most energy to change its structure, and the laminated particleboard requires the least. The presented results can be a set of input data necessary to model the work required to implement the cutting process, but also enable validation of existing cutting models.

Activated carbon from coconut shells is a low-cost, environmentally friendly material that is available for fabricating the electrodes for electric double-layer capacitance supercapacitors. As such, activated carbon derived from coconut shells was coated with Co₃O₄/CeO₂, and its electrical and ionic conductivity were evaluated. The ternary technique for selecting materials was systematically investigated with an economical process. The Co₃O₄/CeO₂ coating that was formed on the activated carbon coconut shells was deemed AC-Co₃O₄-CeO₂. The 90-05-05 composite was the best electrode for electric double-layer capacitance supercapacitors, resulting in high conductivity (0.62 x 10³ S·cm²), low series resistance and internal resistance (based on the Nyquist plot), and the charge-discharge was able to reach 0.56 V for 90 seconds (1A/g). Therefore, activated carbon coconut shells coated in Co₃O₄/CeO₂ can promote the necessary characteristics of electrodes needed for electric double-layer capacitance supercapacitors.

Recycling organic waste for use as fertilizer requires prior knowledge of mineral nitrogen (N) availability for crops. Estimation of soil N release or potentially mineralizable N is an important tool for the design of fertilization strategies that aim to minimize the use of N fertilizer. The aerobic incubation method is considered a standard technique to measure soil potential to mineralize N. In this study, alternative methods of aerobic incubation were evaluated to help overcome its limitations (long time and equipment). In this regard, biological methods (anaerobic incubation at 7 and 14 days) and chemical extraction (hot KCl) procedures were examined. To determine potentially mineralizable N, a silty clay loam soil was fertilized with spent mushroom substrates and anaerobic digestates from different origins (C/N ratio of 4 to 38). Based on the results, chemical extraction emerges as a reliable alternative to the aerobic incubation method, particularly when the C/N ratio of the organic residues ranges from 12 to 15. Moreover, its implementation in routine soil laboratories is straightforward and faster, and it does not require any special equipment.

A reactive hot-melt resin (polyurethane) was used to manufacture Guadua composites with a certain flexibility, high processing speed, good initial rigidity, and high temperature performance. These composites can support a moderate tensile stress, allow for large strains at low stresses, and have a low density and a working temperature range of -40 °C and 110 °C. During the flexural test, bamboo composites with reactive polyurethane matrix do not break or fail during the test. A polyurethane-based reactive hot-melt resin was characterized by tensile tests, Shore hardness tests, differential scanning calorimetry, and thermogravimetry. Besides, a composite material was made with Guadua fiber and polyester matrix, which had a greater strength in the test of tension and flexion, although it had a lower percentage of elongation than the composite material with reactive polyurethane. Guadua fiber can increase the strength by 266% of polyurethane matrix and 228% of polyester matrix.

Flavonoids were extracted from Phyllostachys heterocycla leaves by adopting microwave-assisted extraction technology. Based on the single factor experiment and Plackett-Burman design results, the extraction process of flavonoids was further optimized using the response surface methodology. The optimum conditions were as follows: an ethanol concentration of 78.1%, an extraction time of 24.9 min, and a microwave power of 559 W. Under these conditions, the extraction yield of flavonoids was 4.67%, which was in close proximity to the predicted value (4.70%) and higher than the extraction yield from traditional Soxhlet extraction (3.35%). Moreover, the possible extraction mechanisms of these two extraction methods were further derived to explain why the microwave-assisted extraction of flavonoids was more efficient compared with traditional Soxhlet extraction. Ultimately, the antioxidant activities in vitro of flavonoids from Phyllostachys heterocycla leaves were evaluated via DPPH and ABTS radical scavenging assay. The flavonoids from Phyllostachys heterocycla leaves exhibited excellent antioxidant activities in vitro and Phyllostachys heterocycla leaves could be a new natural source for developing antioxidants. Overall, the findings of this research could provide a theoretical reference for the further comprehensive development and utilization of bamboo resources.

For determining the effects of meta-tolyl-N-methylcarbamate (MTMC, metolcarb) on Aphrophora costalis Matsumura (ACM) and the migration and leaching law of MTMC in soil, the thin-layer chromatography method was used. The characteristics of migration and leaching of MTMC in the dark brown soils, and the most critical influences such as soil type, pH, and amount of water were considered to evaluate the impact of leaching rate. The results showed that 25% MTMC diluted 1,000 times was most effective in controlling ACM, with a mortality reaching 87.8% by root irrigation, and a mortality of up to 94.4% by root burial. For dark brown soil, clay minerals are primarily quartz, as well as small amounts of agalmatolite, mica, and kaolinite. Adsorption of MTMC by dark brown soil begins within 2 h, which increases rapidly in capacity before 16 h, and tends to balance with a decrease in the gradient concentration after 16 h. The desorption capacity of MTMC exhibits a gradual increase within 2 h, showing a maximum around 12 μg·g-1, which tends to stabilize after 12 h. MTMC has moderate mobility in dark brown soil. This research has important practical significance for controlling tree diseases and insect pests and protecting the environment.

Crude sulfate turpentine (CST), a by-product of the kraft process, has commercial value that depends on the removal of sulfur compounds. The current study investigates desulfurization of CST using basic process steps for a paper mill at a pilot scale treatment. In another aspect, the sulfurous compounds in CST were removed by passing to the aqueous phase with terpin hydrate production, followed by α-terpineol conversion with citric acid catalysis. The goal was to design an environmentally friendly, low-cost, zero waste process and thereby refine the CST or byproducts to a quality that can produce chemical raw materials. Refining processes included hypochlorite oxidation, air oxidation, washing with water, and distillation. The sulfur content was decreased to 170, 106, and 29 ppm from respectively by 1260 ppm initial sulphur content of CST. The chlorine amount, due to treatment with hypochlorite oxidation, did not decrease with refining processes, even in distilled fraction. By obtaining α-terpineol from terpin hydrate, the sulfur compounds were completely removed. According to the GS-MS analysis results, distilled sulfate turpentine (DST) as the final product of the refining process of the CST sample increased the ratio with pinenes. On the other hand, with two reaction steps by obtaining terpin hydrate from CST and then α-terpineol, pinenes were converted to α-terpineol.

In both pulping and bleaching processes, lignin in the pulp fiber is degraded into smaller molecules that need to be rinsed away. However, despite the installation of automatic washing equipment, the small phenolic compounds among other lignin degradation products can hardly be completely removed from the brownstock. Among the myriad of small phenolic compounds degrading from lignin, some are water-soluble and highly reactive with bleaching reagents. To understand the impact of residual phenolic compounds from black liquor on pulp bleaching, six monomeric phenolic model compounds were tested in this study. Catechol and vanillin showed inhibitory effects on xylanase activity, while catechol, vanillin, and guaiacol interfered with the delignification reaction in the chlorine dioxide (D) and alkaline extraction (E) stages of the bleaching sequence, thereby preserving the integrity of cellulose in the pulp. Because the efficiency of xylanase and bleaching reagents is hindered by the presence of these phenolic compounds, higher operational cost and more bleaching reagents are needed, which are incompatible with modern environmental policies in the world. Nonetheless, the presence of remaining soluble phenolic compounds in the brownstock can improve the bleaching selectivity important for the production of high-quality pulp with less-degraded cellulose chains.

Hydroxypropylmethylcellulose (HPMC) is popularly known as a hydrocolloid for potential use as a biopolymer film. The films of HPMC exhibit brittleness, lacking flexibility, but they can provide a gas barrier. With the aim of improving the HPMC film properties, nanofibrillated cellulose (NFC) from the succulent plant Agave americana L was incorporated as reinforcement material using the solution casting method. The films were prepared with three different amounts of NFC with glycerol as a plasticizer. The incorporation of the NFC into the nanocomposite films showed a 1,000-fold reduction in the gas permeability. However, significant improvements in the tensile strength (TS), the elongation at break (EAB), and Young’s modulus (YM) were only observed with 1% NFC. A higher moisture content (24.5%) and a higher solubility (59.5%) were observed in the HPMC/NFC-1 film, which also exhibited the best biodegradability loss of the films that were observed with a 92.8% degradation rate in 15 d of soil burial studies. Therefore, the results evidence that the HPMC/NFC films might be potentially suitable as food wrap packaging on perishable produce of fruits and vegetables to maintain their quality attributes and prolong the storage life.

This paper presents the results of research on the treatment of secondary wood fibre semi-finished materials using a dry-grinding-type rotary cutting mill and the possibility of their use in finished products for various purposes. The physical phenomena, processes, and regularities of the treatment of secondary wood fibre materials in dry processing conditions were determined and evaluated. The influence of grinding plant design parameters on wood fibre quality indices was evaluated. Mechanical effects on wood fibre waste of face-cross cutting (cutting, crumpling, collapsing, and breaking) and the dry grinding environment (breaking, collision, defibering, and fibrillation) was studied. These phenomena contribute to the formation of external and internal fibrillation of secondary wood fibre and an increase in the specific surface area. This is achieved in the absence of high temperatures and pressure, in the absence of chemical additives, and without the application of water and vapour. The effectiveness of secondary wood fibre semi-finished material treatment was demonstrated under dry processing conditions, thus confirming the environmental and economic feasibility of this method.