Research Articles

Kinetics of the oxidation of D-xylose, a hemicellulose model compound, by chlorine dioxide was studied under simulated bleaching conditions. The final reaction product, chloroacetic acid, which is a type of adsorbable organic halogen (AOX), was detected by gas chromatography-mass spectrometer (GC-MS). The kinetic equation was expressed as dW/dt = 2.36e-560/T[H+]0.05[ClO2]0.11X0.92. The reaction exhibited first-order kinetics, with a good agreement between the experimental and modelling data. The reaction activation energy was 4.66 kJ.mol-1. Thus, the process is not controlled by a chemical reaction, but rather, it is controlled by hemicellulose properties. These results might have potential for resolving the major problems of environmental pollution in elemental chlorine-free (ECF) bleaching of pulp.

Increasing global paper consumption has fostered the search for new alternative non-wood fiber sources. The aquatic weeds Cyperus digitatus, Cyperus iria, and Scirpus grossus were analysed for their fiber characteristics and chemical composition, and the processed fibers were transformed into handmade paper. The selected species yielded medium-length fibers (0.92 mm to 1.03 mm), which were thin-walled with a lumen diameter (3.37 µm to 5.26 µm) wider than cell wall thickness (2.73 µm to 2.97 µm). In terms of fiber derived values, the selected species possessed a slenderness ratio of 86.5 to 113.1 (favourable, > 30) and flexibility coefficient of 35.2 to 47.6 (favourable, within the range 50 to 70), which was classified as rigid fiber. The species also contained high cellulose, 42.1% to 44.8% (favourable, > 40%) and hemicellulose content, 42.8% to 45.6% (favourable, within the range of 30% to 50%), and low lignin content, 10.6% to 11.8% (favourable, < 12%). Handmade paper of Cyperus digitatus possessed relatively high tensile strength (2.61 ± 0.15 kN/m) and breaking length (1.20 ± 0.07 km) among studied species. Comparison with other non-wood fibers indicated that the studied plants fibers can be used for production of paper plates, paperboard, and decorative paper.

A functional ionic liquid 1-butyl-3-vinylimidazolium iodide ([BuVyIm]I) was synthesized, and it exhibited the features of both decay resistance and leaching resistance after in-situ polymerization within wood. Treated wood specimens of Cryptomeria japonica were evaluated in this preliminary study using leaching tests with distilled water and decay tests for 12 weeks with brown rot fungi Fomitopsis palustris. The [BuVyIm]I polymerized by 100 kGy 60Co gamma irradiation was retained in wood after 10 wash and dry cycles, whereas nearly all of the [BuVyIm]I was washed out in the cases of 10 kGy and no irradiation. The decay testing of these specimens showed that sapwood had a different decay resistance depending on the strength of gamma irradiation used, whereas the treated heartwood did not support fungal growth. The results of this study imply that [BuVyIm]I polymerized by 100 kGy gamma irradiation have potential for wood preservation.

Polyvinyl alcohol/palm kernel shell powder biocomposites were prepared by using a solution casting method. To enhance the properties, the crosslinking agent glutaraldehyde (GA) was added to the composition. The effect of the crosslinking agent on the biocomposite was studied based on the change in the tensile properties, physical properties, and biodegradability. The optimum GA content was found to be 2 phr because the tensile properties tended to decrease with higher GA contents. The water absorption percentages and water vapour transmissibility decreased until the GA content reached 2 phr and then increased. It was found that the biodegradability of the film decreased when GA was added.

Concerns regarding the disposal, degradability, and recycling of synthetic fibres used in composite materials have highlighted the need for eco-friendly materials. This article focuses on fabrication and characterization of the fibre metal laminate (FML) reinforced with carbon, flax, and sugar palm fibres in order to reduce the environmental impact without compromising the strength requirements. Out of autoclave (OOA) manufacturing processes, including hand lay-up and hot compression molding, were employed to fabricate the FML. Tensile, compressive, inter-laminar shear strength (ILSS), and fatigue properties of the fabricated FML were studied. The results indicate that tensile properties and compressive strength for flax based FML (CFC) was superior and 23% higher than CSC while 5% higher than the hybrid CFSSFC configuration. CFSSFC outperformed CFC and CSC in the inter-laminar shear strength by showing 6.5% and 25% increment in magnitude. In case of fatigue, CFC showed excellent fatigue resistance by withstanding high fatigue loads and lasted up to 10⁴ cycles before failure. Delamination between the metal/composite plies was observed in fractured samples under all the mechanical loads.

The purpose of the study was to link microbial community composition and chemical properties of various biomass and their resulting digestate residues for their potential use in biogas production or soil enrichment. The order of biogas production, graded from high to low was as follows: corn silage, grass silage, fruit waste, and dairy sewage sludge. Different bacterial families were predominant in different biomass. Corn silage deteriorated as a result of long-term air exposition and may serve as an efficient feedstock substrate for anaerobic digestion. A positive role in plant biocontrol microorganisms found in grass straw residues, and reasonable biogas yield obtained from this substrate suggests the use of grass straw for biogas production and its residues to enrich the soil. Due to potential threat of introducing pathogens into the soil within fruit waste or dairy sewage sludge, or soil acidification by fruit waste repeated use in field application, this biomass should be sanitized prior to soil application. Simultaneously, low biogas yields from fruit waste and dairy sewage sludge substrates make it necessary to transform them in anaerobic digestion with more energetic co-substrates. Tested residues may deliver a robust and wide range of methanogens as inoculum for further anaerobic digestion process.

This research focused on the production of a novel calcium silicate pigment made from pulverized coal fly ash and its application as a coating pigment in a size press for fiber replacement. Improved specific base paper properties of the newsprint was investigated. This novel coated fly ash based calcium silicate (FACS) pigment and conventional precipitated calcium carbonate (PCC) pigment was applied using a cylindrical laboratory coater. When a 4.3 gsm coat weight of FACS was used during the size press application, the brightness increased 10 points, whereas, when the coat weight of FACS was increased to 7.8 gsm, the brightness increased to 21 points as compared to base newsprint sheet; however, FACS brightness was lower than the PCC coated newsprint sheet. Also, there was a significant gain in other newsprint specific base properties when fly ash based pigment was used. This indicated that it is feasible to utilize a novel fly ash based pigment in the size press coating application to replace fiber in order to reduce production cost, improve specific base properties, and reduce environmental pollution. To the authors’ knowledge, this is the first study reporting the application of fly ash as a coating pigment for quality enhancement of newsprint.

The quantitative comparison of essential oils extracted from various parts of Cupressus funebris and Juniperus chinensis was studied. With increased height, the content of essential oils from branches decreased, while the content of essential oils from leaves increased for both species. A maximum amount of essential oils were found in the west and a minimum in the east of branches and leaves for the two species. Moreover, the content of essential oils in trees with a knot was higher than in those without a knot. The order of essential oil content was as follows: leaf > fine root > coarse root > bark > bough > branch > trunk in C. funebris, and leaf > fine root > bark > coarse root > bough > trunk > branch in J. chinensis. The essential oils extracted from various parts of C. funebris and J. chinensis were analyzed by gas chromatography-mass spectrometry. A total of 67, 33, 69, 65, and 69 components were identified from the roots, trunks, barks, branches, and leaves of C. funebris, respectively. A total of 72, 46, 79, 55, and 82 components were identified from the roots, trunk, bark, branches, and leaves of J. chinensis, respectively.

An easy and environmentally friendly strategy is shown for the synthesis of dialdehyde cellulose/silver nanoparticle composites using dialdehyde cellulose as reducing agent through the microwave-assisted hydrothermal method. The effects of the microwave heating time and temperature on the products were investigated by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). The dialdehyde cellulose was found to be an efficient reducing agent for silver ions, and the microwave heating time and temperature played a vital role in the morphologies of the silver nanostructures. The influences of different additional reductants such as ascorbic acid and glucose on the shapes, size-distribution, phase, and crystallinity of the samples were comparatively investigated in detail. This strategy is environmentally friendly, surfactant-free, without any other reducing or stabilizing agent chemicals, and the as-prepared dialdehyde cellulose/silver nanoparticles were more convenient to use in biomedical fields.

The feasibility of utilizing corn straws to produce butanol via fermentation with Clostridium acetobutylicum was evaluated. The supernatant of enzymatically hydrolyzed supernatant of steam-exploded corn straws was used as the raw material. A bacterial strain was selected from Clostridium acetobutylicum zzu-02 and Clostridium beijerinckii zzu-01, which was capable of fermenting the enzymatically hydrolyzed supernatant of steam-exploded corn straw to produce butanol with high yield. The optimal fermentation conditions for the selected strain with enzymatically hydrolyzed supernatant of steam-exploded corn straw were also investigated and they were determined as follows: sugar concentrations in enzymatically hydrolyzed solution of steam exploded corn straws, 57.5 g/L; initial pH, 6.3; the amount of added CaCO₃, 5g/L; the bacterial inoculation concentration to enzymatically hydrolyzed solution, 6%; fermentation temperature, 37 ^oC, the amounts of the added nutritional elements, i.e. yeast extract, CH₃COONH₄, KH₂PO₄, and C₆H₆N₂O, 0.8, 6.0, 0.5, and 0.25 g/L, respectively. Under these conditions, the butanol yield reached 9.88 g/L. Based on the butanol metabolism pathways, supplementation of a small amount of C₆H₆N₂O was found to effectively increase the yield of butanol production.