Volume 14 Issue 4

It is important to remove excessive concentrations of boric acid from water because it can lead to environmental problems. However, current adsorbents are limited in separating boric acid from water due to their low desorption capability and poor selectivity for boric acid. In this study, the authors developed a functional cellulosic paper via crosslinking cellulose and tannic acid with chitosan to efficiently and reversibly remove boric acid from water. The adsorption capacity reached 769 mg/m2 according to the Langmuir model. The corresponding desorption rate of the chitosan/tannic acid-modified paper exceeded 80% in the whole flow rate region ranging from 15 to 250 mL/h. The reversible adsorption and desorption of boric acid were attributed to the formation and dissociation of the borate bond between the tannic acid and boric acid, respectively, at different pH values. This study improved the selectivity, batch adsorption, expensive carriers, and desorption difficulties of existing boric acid adsorption materials. This approach offers a new way to design highly efficient adsorption/desorption materials by constructing reversible chemical bonds for removal of other pollutants.

Glue laminated timber is currently manufactured using classical adhesives such as resorcinol formaldehyde and phenol resorcinol formaldehyde. These are proven structural adhesives; however their long cure times and rising costs are creating opportunities for newer technology adhesives. One such class are the structural polyurethanes with decreased spread rates and faster curing times. Their limitation lies in their inability to adhere timbers of densities exceeding 800 kg/m3. When used on species including the southern pines (Pinus spp.) with a high frequency of latewood, they delaminate after accelerated weathering tests due to stresses imposed on the glue line during the drying process. Surface incision has been trialed in this study to increase the penetration of polyurethane adhesives and reduce glue line stresses. The study shows that incisions to a depth of 2 mm decreases delamination when compared to matched samples with no incisions. The significant increase in glue line surface area may result in stress reduction as the more compliant adhesive may distribute the stresses better across the glue line. Furthermore, microscopic analysis suggests that the incisions are reducing glue line stress through crack propagation into the timber pointing to the possibility of increased timber compliance at the glue line.

Cellulose nanocrystals (CNCs) were fabricated using rubber wood (RW) as the raw material via acid hydrolysis followed by ultrasonication. The CNCs samples were then grafted with succinic anhydride to obtain modified CNCs, hereafter called CS. The CS samples were subsequently coated with a cationic surfactant, cetyltrimethyl ammonium bromide, and the obtained samples were named as CC. The morphology, chemical structure, and thermal stability of the RW, CNCs, CS, and CC samples were characterized using transmission electron microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis, respectively. Finally, the drug release performance was investigated using CC as the drug carrier and hesperidin, a hydrophobic drug, as the model drug. The drug release mechanism was also considered. The results of this study identified a new route for the high-value utilization of RW and also demonstrated that RW could be used as a novel substrate for the construction of cellulose-based hydrophobic drug delivery systems.

High fertilizer inputs augment the reactive nitrogen level in soil, air, and water. Unused reactive nitrogen acts as a pollutant and harms natural resources. This study focused on the thermal processing of corn starch into a coating material using disodium tetraborate and urea. The processed corn starch was coated over granular urea in a vertical bed coating reactor. The chemically modified starch, when compared with native starch, exhibited better stability and mechanical strength over time. The modified starch looked like a weak gel, and its loss modulus was dominated by the storage modulus. However, for native starch, the viscous component dominated the elastic component, especially at lower angular frequencies. The nitrogen release from the coated urea was remarkably slower than the uncoated one. A small difference in the peak and final starch viscosities in the presence of urea and borate revealed low thermal cracking of the starch molecules. The surface of the granular urea that was coated with chemically modified corn starch was uniform, dense, hard, and least porous. The uncoated urea granules became released into water in 6 min under gentle shaking, whereas the coated urea took almost 32 min to completely release.

Cross-laminated timber (CLT) is a bio-based building material that enables rapid construction and buildings with low embodied energy. Despite its comparative maturity in European markets, relatively little information regarding process design and economics for the manufacture of cross-laminated timber is available in the literature. Two techno-economic analyses were conducted to quantify the mill-gate cost of cross-laminated timber. The cross-laminated timber manufacturing process was described, and costs were analyzed for two facility scales. Cross-laminated timber produced at the large-scale facility using lumber priced at an average value for the northwest United States has a minimum selling price of $536/m3. Sensitivity analyses were used to define the impact of plant size, asset utilization, lumber price, plant capital cost, material waste, and other variables on minimum selling price. The cost of cross laminated timber rises quickly when a facility is not fully utilized. The second-ranking cost controlling variable is lumber price, while energy prices have minimal influence. The price of cross laminated timber can be optimized by locating a facility near low-cost lumber. The lowest-price region analyzed was the southeast United States using Southern Pine, which reduced the cost of cross laminated timber to $518/m3.

Nanocellulose (NC) was prepared from cotton linter using ionic liquid (IL) 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO4) as both swelling agent and catalyst followed by high-pressure homogenization. Evidence suggested that the IL played a significant role with respect to hydrolysis of the linter cellulose. The effects of various reaction conditions on the NC preparation were investigated in this study. The successful conversion of the cotton to NC was analyzed, which showed that the prepared NC had a uniform rod-like shape that was 50 nm to 100 nm in diameter and 500 nm to 800 nm in length. The characterization of the NC by X-ray diffraction and thermogravimetric analysis revealed that the crystalline cellulose I structure was retained in the NC and it showed stable thermal properties. The recycled ionic liquid exhibited a slightly decreased cellulose hydrolysis ability. The application of [Bmim]HSO4 as both a catalyst and swelling agent introduced an effective and environmentally friendly method for NC production.

Torrefaction, a thermal treatment, was studied as a means to increase calorific properties in sawdust biomass for some wooden species from southeast Europe. Torrefaction of wood material in the form of sawdust waste is known to modify the biomass at the chemical level, especially hemicelluloses. Four wood species, namely beech, spruce, larch, and oak, were thermally treated as sawdust waste at temperatures of 200 °C, 220 °C, 240 °C, 260 °C, 280 °C, and 300 °C for different times of 3 min, 5 min, and 10 min. The results indicated an increase in the calorific value and calorific density with increased torrefaction temperature and time. From the economic point of view, the pellets obtained from torrefied sawdust had better properties than untreated ones. The value-added pellets could compete on the market with traditional fossil fuels.

Maleic anhydride grafted high-density polyethylene (MAH-HDPE) film was used instead of urea-formaldehyde resin adhesive to face wood-based panels (WBP) such as finger-jointed wood panel, medium-density fiberboard (MDF), high-density fiberboard (HDF), and three-ply plywood with decorative wood veneer. The effects of hot pressing conditions on the physical-mechanical performance (surface bonding strength, water immersion performance, and hot-cold cycling performance) of overlain veneered panels were evaluated. Rheology analysis, differential scanning calorimetry (DSC), and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) were used to study the characteristics of MAH-HDPE film. Scanning electron microscopy (SEM) was used to observe the microstructure of the bonding interface. The veneered board using MAH-HDPE film as adhesive showed excellent properties, especially on water resistant and weather resistant performance. The veneered boards with finger-joint wood panel substrate could meet the Chinese national standard of type I grade veneered board of GB/T 17657 (2006), and the optimum hot pressing parameter was under a pressure of 1.3 MPa at 160 °C for 4 min. The MAH-HDPE film also can be applied to various other wood-based substrate materials for preparing veneered board. No glue penetration was observed on the surfaces.

Changes of soil biological activity and microbial diversity were assessed after application of biochar in different doses. The biochar doses were determined based on the initial carbon content in the soil, and they were increased to 2.5%, 5%, 10%, 20%, 50%, and 100% in the experimental conditions. The experiment design also included a control condition, which was not treated with biochar. The basic biological activities in the soil, i.e., enzymatic activity and the content of carbon and nitrogen in the microbial biomass, were determined. Additionally, the functional biodiversity of soil microorganisms was assessed using the Biolog EcoPlates method. It was demonstrated that biochar added to the soil at the dose of 10 to 20% significantly increased soil biological activity and functional diversity. The biochar dose of 10 to 20% was the optimal dose for enhancement of soil biological activity. This dose induced a significant increase in the total carbon content in the microbial biomass, enzymatic activity, and the overall content of total and easily extractable glomalins. The highest values of the Shannon and AWCD indices were determined in soil supplemented with 5 to 20% of biochar.

Dissolved lignin in eucalyptus black liquor was obtained at five different reaction times (1 h to 5 h) throughout the main delignification process to reveal the structural changes of lignin and its contributions to pollution load at different degrees of delignification. During the delignification process, the lignin removal efficiency and Kappa number of the pulp had a clear linear relationship with the holding time at the highest temperature (170 C). This indicated that the degree of delignification to which the pulp could be regulated by the holding time. Condensation and degradation appeared to participate as two competitive reactions in the cooking process. The condensation structures of lignin increased remarkably in the first 3 h, which resulted in increased molecular weight. Then, the degradation of lignin became the main reaction at longer reaction times (4 h to 5 h), when the β-O-4’ and β–β’ bonds were dramatically broken. Furthermore, the lignin concentration in black liquor increased with delignification time, which had a positive correlation to chemical oxygen demand (CODcr) in black liquor. The proportion of CODcr produced by lignin increased remarkably in the decomposition stage of lignin, which revealed the importance of changes in the lignin structure during the delignification process to the pollution load.