Volume 15 Issue 4

The remediation effects of peanut shell biochar (HBC) and Mg-modified peanut shell biochar (MHBC) prepared under pyrolysis temperatures of 300 °C and 600 °C on Cd2+ polluted brown soil were investigated in a pot experiment. The results showed that the biochar treatment increased soil pH and decreased the bioavailable Cd2+ content in the soil. Compared with the control treatment (CK), the pH value increased by 0.32 to 2.5 upon treatment with 1% and 2% of HBC and MHBC. Bioavailable Cd2+ in the soil decreased by 5.64% to 21.33% with HBC. The MHBC presented better amendment effects than HBC; bioavailable Cd2+ in the soil decreased by 26.2% to 50.1% with the addition of MHBC. The addition of HBC and MHBC increased the shoot height and decreased the root length of the spinach. Moreover, they significantly decreased the accumulation of Cd2+ in the shoots and roots of the spinach. Compared to CK, the Cd2+ content in the shoots decreased by 7.0% to 46.8% upon treatment with 1% and 2% of HBC and MHBC, while the Cd2+ content in the roots decreased by 7.3% to 52.7%. The Cd2+ content in the shoots and roots was more greatly decreased with MHBC than with HBC.

This study evaluated the effects of coating Populus nigra wood with nanoclay by dip-coating and spin-coating. The samples were coated with nanoclay in concentrations of 3, 5, and 7%, and the products were compared with Abies alba wood as standard control for the morphological and moisture properties. Zycosil was also added into nanoclay as an adaptive material. The crystalline and morphological structures were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Performance parameters including water absorption, contact angle, density, and flexural resistance were investigated. Water absorption was decreased, but the density, flexural resistance, and contact angle were increased in nanoclay treatments compared with the P. nigra control group (P<0.05). The best performance properties were observed at a concentration of 7%. In sum, the concentration of 7% nanoclay in dip-coating decreased water absorption by 250% and increased water angle by 150%, density by 113%, and flexural resistance by 145% compared to P. nigra control group.

A synergistic effect was found between the electro-Fenton (E-Fenton) process and a white-rot enzyme (Trametes versicolor) system relative to the degradation of dealkaline lignin. The hydrogen peroxide produced by the E-Fenton process reacted with Fe2+ on the cathode to generate a large number of hydroxyl radicals. These hydroxyl radicals directly degraded various functional groups in lignin, which led to the quick initiation of lignin peroxidase (LiP) and manganese peroxidase (MnP) enzymatic hydrolysis and accelerated the progress of lignin biodegradation. In addition, the hydroxyl radicals produced by the Fenton reaction converted nonphenolic lignin into phenolic lignin, further promoting the ability of manganese peroxidase and laccase to degrade the lignin. Additionally, the Fe3+ secreted by white-rot fungi accelerated the regeneration of Fe2+ on the composite cathode, which sustained the lignin degradation system. In the synergistic system, mycelium growth was significantly improved, with the maximum growth amount reaching 2.3 g and the lignin degradation rate reaching 84.5%, the activity of the three enzymes increased with the increase of currents over 96 h. Among them, the activity of MnP increased significantly to 402 U/L.

Rubber wood was modified with both a combination of silica sol and glyoxal urea (S-GU), and a combination of silica sol and glyoxal melamine urea (S-GMU). The physico-mechanical properties were measured. Thermal properties, chemical molecular structure, and cellular morphology were analyzed via thermogravimetry (TG), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The weight percent gain (WPG) increased as the concentration of the impregnated aqueous solutions increased. The S-GMU treated wood exhibited a greater WPG than the S-GU treated wood at the same concentration. Anti-swelling efficiency (ASE), modulus of elasticity (MOE), and modulus of rupture (MOR) of treated wood increased as the WPG increased. The highest ASE value was 42.0%, for the S-20%GMU treated wood, which was higher than the S-20%GU treated wood. The MOR of the S-20%GMU treated wood was improved by 25%. Thermal analyses showed the thermostability of S-GMU treated wood increased. FTIR results indicated the presence of C-N and Si-O-Si bonds in the S-GMU treated wood, and the lignin and carbohydrates degraded to a certain extent. SEM imaging showed that the S-GMU was deposited in the cell lumen and cell wall. Therefore, this study produced evidence of an improvement in the physico-mechanical and thermal properties of S-GMU treated wood.

Alnus acuminata, Vochysia ferruginea, and Vochysia guatemalensis are three low-density wood species used for reforestation in Costa Rica. The goal of this work was to study a thermo-hydro-mechanical densification process and test the characteristics of densified wood of these species. Twelve densifying treatments based on temperature, compression time, and use/no use of steam were tested. The variables of the densification process and the properties of the densified wood were determined. The results showed that the densification percentage was over 80% for wood of A. acuminata and over 70% for wood of V. ferruginea and V. guatemalensis. In the three species, the densification process was influenced by initial density. The influence of temperature during the densification process affected the heating rate and color change. An increase in the modulus of elasticity and modulus of rupture in static bending and in the hardness of the densified wood relative to the normal wood was observed, as well as a clear positive correlation of the properties with final density and maximum load, the latter being highly correlated with initial density. This showed that initial density was significant in the densification process and affects wood properties.

Linseed oil and shellac are natural, environmentally friendly materials with good water repellency. They were used to impregnate Chinese ash wood at room temperature (20 °C) using a vacuum-pressure procedure (consisting of three cycles of 0.01 MPa for 1.5 h and atmospheric pressure for 1.5 h) to improve the dimensional stability of wood. The effects of the impregnation treatment on wood color changes, dimensional stability, moisture absorption, and morphological characteristics were evaluated. The linseed oil and shellac treatment improved the dimensional stability of wood. Linseed oil and shellac displayed good permeability in Chinese ash wood, with weight gains of 21.7% and 19.0%, respectively, after impregnation. The swelling coefficients of treated wood in the tangential and radial directions decreased by 15 to 22%, indicating that impregnation improved the dimensional stability of wood. Linseed oil and shellac solidified and occluded the pits within the wood interior to prevent moisture absorption. This method can be used to improve the dimensional stability of a variety of wood products, such as buildings, furniture, and landscape architecture.

Bamboo scrimber is a versatile material made by rolling and defibering bamboo into loose reticulate bundles (unbroken horizontally, loose longitudinally, and interlaced) that are subjected to drying, gluing, assembling, and hot pressing. In this study, to better understand the application value of bamboo scrimber in construction engineering, the axial compression properties of bamboo scrimber columns with solid, hollow, and I-shaped cross-sections were investigated. For each column type, three lengths of 1 m, 1.5 m, and 2 m (three specimens of each length) were selected and subjected to axial compression testing. The results demonstrated that the primary failure mode of solid bamboo scrimber columns was instability failure, whereas that of hollow and I-shaped columns was mainly debonding failure. Experimental data were further analyzed to better understand and model the failure mechanisms of bamboo scrimber columns. This study led to the establishment of a design formula for bamboo scrimber solid columns, the calculations of which matched well with the experimental results.

Wood materials for construction purposes can be attacked by various wood-destroying fungi. An ideal wood-preserving substance is supposed to be environment- and health-friendly. For this reason, the effects of the most relevant and non-toxic methylxanthines, such as caffeine and its metabolites theobromine and theophylline, on fungal growth, together with their degradability related to their properties were analyzed in this study. Agar tests with four wood-destroying fungal species (Serpula lacrymans, Coniophora puteana, Gleophyllum sepiarium, and Trametes versicolor) were performed after 28 days of substance exposure. Caffeine exhibited a 100% inhibitive effect on fungal growth, contrary to theobromine, which was not effective in that respect. Theophylline exhibited variable effects on the analyzed fungi. The analysis of degradability indicated the persistence of caffeine and theobromine, but theophylline was degraded up to 34%. The relation of toxicity to chemical structure of studied methylxanthines indicated the dipole moment and lipophilicity as important parameters affecting the antifungal properties. Both caffeine and theophylline are suitable potential candidates for antifungal active substances.

Factors affecting screw driving torques in plywood were investigated in this work. The factors were number of layers (7 and 9), pilot hole diameter (3.0 and 3.5 mm), pilot hole depth (60 and 80% of the thickness of specimen), and thickness of the metal plate (7.5 and 10 mm). Screw driving torques were studied in oriented strandboard, medium-density fiberboard, particleboard, and some wood-plastic composites. There is no such information about screw driving torques in plywood (PW). Therefore, this study focused on the plywood made of aspen (Populus tremula L.). The mean seating torque (SET) values ranged from 0.31 to 0.69 N∙m, whereas mean stripping torque (STT) values ranged from 0.50 to 4.7 N∙m. The ratios of STT/SET were between 2 and 5 in PW with seven layers, whereas the ratios were between 4 and 7 in PW with nine layers. The results indicated that the four main effects of SET and STT were statistically significant with p-values of ˂ 0.0001.

Kraft lignin (KL) was oxidized by peracetic acid, which is generated by mixing acetic acid and hydrogen peroxide, to produce polycarboxylates for use as a plasticizer for cement paste. Peracetic acid cleaves the aromatic ring structure of KL and introduces carboxylate groups with ring-opened chain structure. After oxidation, the water-soluble fraction (Cx-lig) was obtained, and the performance of the Cx-lig as a plasticizer was compared with two commercial plasticizers, lignosulfonate (LS) and polycarboxylate ether (PCE). In mortar table tests, the increase in cement fluidity with the Cx-lig was greater than with LS and PCE. Fourier-transform infrared spectroscopy, carbon-13 nuclear magnetic resonance, gel permeation chromatography, elemental analysis, and charge density analysis were used to determine the structure of the Cx-lig. Considering all the results, the Cx-lig had a polycarboxylate structure containing numerous carboxylate groups, and their high charge density was the key factor that caused the Cx-lig to increase the cement fluidity more than LS or PCE.