Volume 12 Issue 4

A green method of synthesizing silver nanoparticles (AgNPs) with corn straw acting as reducing agents was used to prepare antibacterial paper. An ammonia solution, corn straw, and soluble starch were used as the silver precursor, reducing agent, and capping agent, respectively. The optimal condition for synthesizing AgNPs was obtained by varying the reactant ratio, temperature, and reaction time. The AgNPs were characterized by ultraviolet-visible (UV-vis) spectroscopy, X-ray diffraction (XRD), spray analyzer, and transmission electron microscopy (TEM). The obtained AgNPs were almost spherical and they were redispersed well in ethanol after centrifugation. Importantly, the prepared AgNPs were better applied in preparing antibacterial paper. After careful measurements, the mechanical properties and the antibacterial ability of the antibacterial paper were good. Therefore, the method of using corn straw as a reducing agent combined with AgNPs, to prepare antibacterial paper, is feasible. This method is noteworthy because corn straw is an underutilized material.

Low-temperature plasma treatment technology is an efficient and environmentally friendly surface treatment technology that has been extensively studied for the surface chemical modification to pulp fibers. In this study, Eucalyptus alkaline peroxide mechanical pulp (APMP) fibers were modified using a low-temperature plasma generator. The tensile index of the fibers after low-temperature plasma treatment under different conditions was measured and analyzed to evaluate the relationship between the plasma treatment conditions and the physical strength improvement of APMP. It was revealed that factors such as gas source (oxygen, argon, and nitrogen gases), discharge power, vacuum level, and modification time affected the physical strength properties of APMP. In addition, the change in carboxyl group content in the pulp fibers after low-temperature plasma treatment was measured using the Headspace Gas Chromatography (HS-GC) method. The carboxyl content in the fiber increased remarkedly after low-temperature plasma treatment, which was beneficial for improving the physical strength properties of paper made from the APMP.

Ordered mesoporous TiO2, loaded on walnut shell-based activated carbon, was prepared via sol-gel and ultrasonic-assisted technology. The obtained composites (M-TiO2/AC) were characterized via X-ray diffraction, N2 adsorption-desorption isotherms, and Fourier transform infrared spectroscopy. The adsorption–photocatalytic reduction capabilities were calculated using the removal rate of Acid Red 18 solution via UV spectrophotometry. The specific area of M-TiO2/AC increased from 563 m2·g-1 to 881 m2·g-1, compared to TiO2/AC. The removal rate was 92.3% when the Acid Red 18 with a concentration of 80 mg·L-1 was subjected to illumination for 2 h with 0.15 g of M-TiO2/AC. Under this condition the removal rate of Acid Red 18 solution by M-TiO2/AC was higher than that of TiO2/AC (83.7%), or AC (73.1%), which was attributed to the regular mesoporous structure, pore-pore synergistic amplification, and TiO2 photocatalysis. Acid Red 18 might be oxidized and decomposed into small molecular substances, such as CO2 and H2O, by strong oxidizing free hydroxyl radicals provided during the photocatalytic process by M-TiO2. The adsorption and photocatalytic processes followed the pseudo-second-order kinetic model. Internal diffusion and external diffusion processes influenced the adsorption rate.

Biocomposites composed from polyvinyl alcohol (PVOH)/palm kernel shell powder (PKSP) were prepared via a solution casting method. Halloysite nanotubes (HNTs) were used to gradually replace PKSP to study the effect of hybrid fillers and also to compare the properties of PVOH/PKSP biocomposites with a commercial filler, HNTs. The effect of HNTs’ addition on the biocomposites was investigated based on mechanical properties, physical properties, and its biodegradability. The incorporation of HNTs in the biocomposites enhanced the tensile properties. Scanning electron microscopy (SEM) studies revealed that better filler and matrix interaction was achieved after the incorporation of HNTs. Moreover, the water absorption and water vapour transmissibility (WVT) of biocomposites decreased. The biodegradability of biocomposites filled with HNT was lower compared to the biocomposites filled with PKSP.

Grinding wheels made from an easily-prepared and industrialized thermosetting PFL resin (phenol, formaldehyde, and alkali lignin) with aluminum oxide particles were prepared (i.e., PFL grinding wheel). The mechanical properties of these grinding wheels were characterized by their Brinell hardness, compression strength, and abrasiveness. The curing and heat resistance properties of the PFL resin were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results indicated that the new PFL resin with 30% of the phenol replaced by alkali lignin exhibited excellent heat resistance. When using alkali lignin to replace a portion of the phenol, the curing temperature of phenol-formaldehyde resin (PF) was increased. Scanning electron microscopy (SEM) of the PFL grinding wheel showed no pores and cracks in the composite when compared to laboratory prepared PF grinding wheels; PFL grinding wheels had high hardness and compression resistance. Furthermore, the PFL grinding wheel exhibited abrasiveness that was comparable to the PF grinding wheel during laboratory tests.

One of the most common methods used to reinforce damaged paper is to apply a lining, using Japanese paper (JP). The reinforcing material must consolidate the paper without modifying its visual appearance. The unique properties of bacterial cellulose (BC) suggest that it could be efficiently used to reinforce degraded paper documents. The changes in the visual appearances of the printed commercial papers lined with BC and JP were examined in this study. Four commercial papers, coated and uncoated, were printed with cyan, magenta, yellow, and black offset inks. The printed samples were lined with BC and JP sheets. Print density, gloss, and CIELab coordinates were tested in the lined and unlined samples before and after aging. Lining with JP notably affected the print density and CIELab coordinates. The lining with BC resulted in lower decrements in color intensity. The gloss values of samples lined with BC differed widely amongst the papers, whereas in papers reinforced with JP these values never exceeded 6%. Subjecting the samples to an aging process did not markedly modify the results except for the BC-lined samples, in which color differences increased.

ATR-FTIR spectroscopy and conventional analysis techniques were performed to characterize the chemical structure of different coniferous (cedar, fir, Calabrian pine, and spruce) and deciduous (chestnut, oak, alder, and beech) tree barks. The cell wall components (holocellulose and lignin) and extractives of tree barks were determined using conventional analysis methods. Chemical analysis indicated that the polysaccharide contents of tree barks were very low compared to lignin and extractives content. Substantial dissolution of tree barks was brought about by 1% NaOH. FTIR analysis method is an easy and reliable way to determine the functional groups of tree bark components. The levels of carbohydrates and lignin, as determined by ATR-FTIR spectral analysis, were consistent with the results of conventional analysis. The highest content of lignin was in the alder species for the deciduous trees and in the cedar type for the coniferous trees.

Several different methods for the extraction, separation, and purification of wood constituents were combined in this work as a unified process with the purpose of achieving a high overall efficiency of material extraction and utilization. This study aimed to present a laboratory-scale demonstrator biorefinery that illustrated how the different wood constituents could be separated from the wood matrix for later use in the production of new bio-based materials and chemicals by combining several approaches. This study builds on several publications and ongoing activities within the Wallenberg Wood Science Center (WWSC) in Sweden on the theme “From wood to material components.” Combining the approaches developed in these WWSC projects – including mild steam explosion, membrane and chromatographic separation, enzymatic treatment and leaching, ionic liquid extraction, and fractionation together with Kraft pulping – formed an outline for a complete materials-biorefinery. The process steps involved were tested as integral steps in a linked process. The scale of operations ranged from the kilogram-scale to the gram-scale. The feasibility and efficiency of these process steps in a biorefinery system were assessed, based on the data, beginning with whole wood.

Cellulose nanofibers (CNFs) with an average diameter 8 nm were isolated from corncobs using a stepwise method that included steam-explosion pretreatment, alkaline treatment, sodium hypochlorite bleaching, high-speed blending, and ultrasonic treatment. This mechanochemical method used only two chemical reagents in low concentrations to remove non-cellulosic components. The removal of non-cellulosic components was confirmed by Fourier-transform infrared spectroscopy. X-ray diffraction revealed an increase in crystallinity during steam explosion and subsequent mechanochemical treatments. Pretreatment by steam explosion caused the partial hydrolysis of hemicellulose and loosened the structure of raw materials, which facilitated the subsequent chemical processes. The thermal stability and morphology of samples at different stages were also investigated. Steam explosion increased the thermal stability of hemicellulose and cellulose components, as it removed a fraction of hemicellulose. High-speed blending reduced the entanglement of cellulosic fibers and created uniform size. Ultrasonic treatment was used in the final step of nanoscale fibrillation. The method used in this study is environmentally friendly and has the potential to be applied at industrial scale.

In plywood manufacturing, the surface characteristics of veneers play a critical role in achieving appropriate bonding performance. An inactivated wood surface caused by oxidation or migration of wood extractives has been shown to lead to an insufficient bonding quality. In this study, inactivated birch and spruce veneer surfaces were activated with corona and chemical NaOH treatments. The effects of the treatments were determined by contact angle measurements and bond quality tests conducted with Automated Bonding Evaluation System (ABES). In addition, the mechanical properties of the plywood produced from the treated veneers were evaluated. The results showed that the corona treatment remarkably increased the wettability of the veneer surface and bond quality of both the spruce and birch veneers evaluated by ABES. The corona treatment also improved the mechanical properties of the birch plywood, but the spruce plywood properties were not affected as much. Soaking veneers in NaOH improved the wettability, but the bond strength was lower than that of the references.