Volume 14 Issue 1

Wood is an environmentally friendly material for the construction of buildings, and it possesses great physical and mechanical properties. However, under certain circumstances, it needs to be protected from degradation. This can be achieved either by proper design or treatment. In this study, eastern white pine (Pinus strobus L.) and white spruce (Picea glauca (Moench) Voss) were impregnated with propiconazole and 3-iodo-2-propynyl butylcarbamate, which are two organic fungicides. Unlike most impregnation techniques, no pressure treatment was needed. Instead, an aqueous buffered amine oxide system was used to allow the fungicides to diffuse rapidly into the wood. Many combinations of fungicides and amine oxides, as well as different diffusion times were tested to study the effect of the treatment on the dimensional stability and resistance to decay fungi. It was found that only the amine oxide affected the dimensional stability of the treated wood, with anti-swelling and anti-shrinking efficiencies values up to 30%. Amine oxides and fungicides both had an impact on the weight loss caused by the brown rot fungi. The weight loss after 10 weeks of exposure to Rhodonia placenta was reduced by half when using amine oxides or fungicides, and it was completely inhibited when they were combined.

Biochar was derived from MgCl₂ and MgO pretreated sawdust and corn husks at 300 °C and 600 °C, respectively, to investigate the effects of exogenous minerals on the stability and sorption performance of the resulting biochar. Impregnation with Mg decreased carbon concentration, increased yield and ash concentration, and increased the pH values at the point of zero charge (pH_PZC) of the resulting biochar. The chemical stability of biochar oxidized by K₂CrO₇ was enhanced with increasing pyrolysis temperature and decreased with the pretreatment of MgCl₂ and MgO. Mg-impregnation enhanced carbon loss of the resulting biochar and increased the sorption capacity of biochar for CR significantly, which is potentially caused by electrostatic interaction and surface complexation. This study indicates that magnesium-impregnation significantly enhances the sorption performance of anionic contaminants and the pyrolysis temperature has a greater effect on the stability of the resulting biochar than the magnesium-impregnation.

Starch microcrystals have the advantages of native starch grains but with higher specific surface area and numerous active sites. In this study, tapioca starch microcrystals were made by sulfuric acid hydrolysis and then chemically modified with succinic anhydride in an aqueous alkaline medium. The succinylated starch microcrystals were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The adsorption properties of the succinylated starch microcrystals in aqueous solutions were studied at different time periods (1 to 60 min), pH (2 to 7), and metals concentration (100 to 2000 mg/L) for different divalent metal ions such as Cu(II), Zn(II), Cd(II), and Pb(II). The results showed that the starch microcrystals were successfully succinylated, and their adsorption equilibrium for divalent metal ions was reached within 1 min. The adsorption capacity in high metal concentration was 147.7 mg/g for Cu(II), 143.2 mg/g for Zn(II), 216.4 mg/g for Cd(II), and 216.0 mg/g for Pb(II)). The metal-adsorption of succinylated starch microcrystals followed the Freundlich isotherm.

The production of nanofibrillated cellulose (NFC) from bagasse was optimized through a novel green approach by combining an organosolv pretreatment with microgrinding. Bagasse was processed through organosolv pretreatment with trifluoroacetic acid (OPT) as a catalyst to provide precursor fibers with full control of chemical components for NFC production. The mass balance of the pretreated bagasse through OPT (OPTB) was determined by its chemical components and total organic carbon analysis. OPT was found to be an efficient and energy-saving strategy for recovering cellulose, as well as hydrolyzing hemicellulose and lignin. Noncellulosic contents in OPTB fibers were optimized to obtain a high NFC yield through microgrinding. The highest NFC yield relative to the mass of precursor fibers of 72% was achieved through mechanical defibrillation of the OPTB containing noncellulosic content of 29%, which generated nanofibrils with the average diameter of 9 nm. In biorefinery principles, OPT not only converted 57% of bagasse to solid cellulosic fibers for NFC preparation, but also 30% of bagasse to valuable bioproducts including the hemicellulose-derived xylose (19%) and lignin-derived organosolv lignin (11%). The combined OPT and microgrinding produced NFC and simultaneously extracted bioproducts from bagasse while using easily recoverable and low environmental impact reagents.

Genistein (GEN), a typical isoflavone compound, exhibits desirable pharmacological activities, such as antioxidation, anti-inflammatory, , and anti-cancer properties. However, the pharmaceutical application of GEN is limited because of its poor water solubility in aqueous systems. In this study, cellulose nanocrystals (CNCs) and cetyltrimethylammonium bromide (CTAB)-coated CNCs were used as carriers for GEN to improve its dissolution rate and antioxidant activity in aqueous systems. The CNC/GEN and CNC/CTAB/GEN nanocomposites were successfully prepared and characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray diffraction analysis. The results showed that the nanonized GEN performed better and its crystalline structure decreased because of the formation of the CNC/GEN and CNC/CTAB/GEN nanocomposites. The GEN dissolution rates in the CNC/GEN and CNC/CTAB/GEN nanocomposites increased to 72.1% and 92.5% at 120 min, respectively, compared with that of the original GEN (0.85%). Furthermore, the in vitro antioxidant activity of the GEN, which was evaluated by the hydroxyl radical scavenging efficiency, was remarkably enhanced. Based on the above results, CNCs as nanocarriers are a useful method for improving the dissolution and antioxidant activities of GEN in aqueous system.

Wood is flammable and consumes a lot of energy during processing. To improve this material, wood was pretreated via aluminum sulfate–sodium silicate synergistic impregnation combined with heat treatment. The wood before and after pretreatment was analyzed through the solids weight changes, thermogravimetric and differential thermogravimetric analyses, somke density, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The experimental results showed that the combined treatment could reduce the energy consumption of the heat treatment by catalyzed thermal degradation with aluminum-silicon synergistic impregnation. This procedure improved the thermal stability of the wood. Meanwhile, the combined treatment resolved the problem of increased smoke release caused by the impregnation of aluminum sulfate–sodium silicate modification reagents.

Constructed wetlands (CW) are being explored as an alternative treatment for boron removal. The efficiency of CW strongly depends on the substrate and plants used. A promising and inexpensive substrate is rice husk. This study explored the capacity of this residue to treat boron-rich wastewaters as main wetland substrate in laboratory constructed wetland microcosms. Two plants, Typha angustifolia and Puccinellia frigida, were used to evaluate their capacity to increase boron removal. It was found that CW removed ~40% of boron. Although both species presented high boron concentrations in their shoots (between 463 and 721 mg/kg), they did not enhance its removal. Interestingly, high sulfate removal was also observed, especially in non-vegetated cells (up to 68±18%), indicating that the presence of plants decreased their removal. Processes involved are probably biotic sulfate reduction and abiotic precipitation of sulfate minerals (hypothesis supported by PHREEQC modeling). Therefore, the performance of the system under continuous flow operation for a boron-and sulfate-rich wastewater indicates that rice husk has high potential as main media in CW for boron and sulfate removal.

Soda lignin-based activated carbons (AC) were successfully prepared through chemical curing with hexamethylenetetramine (HMTA), followed by carbonization and steam activation. The pore structure, surface chemical structure, and adsorption properties of the ACs were investigated. The obtained ACs exhibited a high specific surface area (S_BET) and total pore volume (V_total), which first increased and then decreased with an increasing HMTA concentration. The highest values were approximately 1800 m²/g and 1.0 mL/g, respectively. The S_BET and V_total were comparable or superior to those of ACs prepared with various activation methods reported in the literature. By increasing the HMTA concentration, the amount of graphitic carbon, which was the main compound on the surface of the ACs, decreased and then slightly increased, while the functional groups containing C-O showed the opposite tendency. Additionally, the great adsorption capacities of the ACs for methylene blue and iodine were mainly related to the carbonyl group chemical structure and pore structure.

Physico-chemical changes to ThermoWood produced from Norway spruce (Picea abies L.) with the dimensions 20 mm × 20 mm × 10 mm were evaluated as a function of thermal loading at a flame ignition temperature (FIT) and spontaneous ignition temperature (SIT). The extractives, cellulose, holocellulose, and lignin contents were determined by wet chemistry methods. Carbohydrates and cellulose changes were investigated by high-performance liquid chromatography and size exclusion chromatography. The dimensional characteristics of the fibers (length, width, and shape factor) were measured. After thermal loading, an increase in both the cellulose (FIT – 33.1%, SIT – 64.6%) and lignin (FIT – 28.3%, SIT – 63.4%) contents and a decrease in the extractives content (approximately 8% to 9%) were observed. The increase in the cellulose content was attributed to structural changes (carbonization and crosslinking). The lignin content increased because of condensation and its greater thermal stability compared with carbohydrates. After the thermal treatment, saccharides content was lower due to degradation of non-glucosic saccharides (mainly pentosans – 51.3%). The cellulose degree of polymerization decreased by 40.8% during thermal loading at the FIT and by up to 75.4% at the SIT. Thermal loading of ThermoWood samples caused a significant decrease of fibers average width.

In northern countries, engineered wood products are widely used for the construction industry. Recently, a concern has been raised regarding a slow freezing rate in green wood (of the order of 1 °C / h up to 25 °C) that could greatly reduce wood strength. Thus, logs processed during winter might produce lumber with a lower mechanical strength in service than those produced during summer. Therefore, the main objective of this study was to evaluate the influence of the freezing rate on the selected mechanical properties of balsam fir (Abies balsamea [L.] Mill). Three groups of 17 planks (20 mm x 20 mm x 1200 mm) were exposed to three freezing rates (10 °C/h, 5 °C/h, 1 °C/h) and another group was kept as a control group. After the freezing treatments, the planks were stored in a conditioning room at 20 °C and 65% relative humidity to obtain an equilibrium moisture content of 14%. Samples of 10 mm x 10 mm x 190 mm and 10 mm x 10 mm x 40 mm, for static bending and parallel compression to the grain tests were then prepared, respectively. The results showed that the freezing rate did not have any effect on the mechanical strength of balsam fir wood.