Research Articles

Applications of cellulose-based materials that require high-purity cellulose as a feedstock are becoming increasingly common. However, reported methods for hemicellulose removal are comparatively complicated. In this study, a Lewis base-enhanced high-temperature liquid water (HTLW) treatment was used to purify cellulose. The variation of carbohydrate content, average degree of polymerization (DP), and the crystalline index of specimens of the purified cellulose were investigated. After primary HTLW treatment, the alpha-cellulose content of specimens increased distinctly; also, the alkali solubility decreased. The DP of the specimens decreased dramatically after HLTW treatment. The incorporation of a Lewis base was beneficial for maintaining DP and for removing hemicellulose selectively. Simultaneously, the results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) showed that the chemical and crystal structure of the specimens were unchanged. Based on the experimental results, Lewis base-enhanced HTLW is a promising method to prepare high-purity cellulose.

Eco-friendly composites can be prepared by substituting man-made synthetic fibres with various types of cellulosic fibres. Sugar palm-derived nanocrystalline cellulose is a potential substitute. The most important factor in determining a good nanofiller reinforcement agent that can be used in composites is the character of the nanofiller itself, which is affected during a preliminary treatment. Thus, to gain better nanofiller properties, the delignification (NaClO2 and CH3COOH) and mercerization (NaOH) treatments must be optimized. The main objective of this study was to identify the effects of the delignification and mercerization treatments on sugar palm fibre (SPF). In addition, the characteristics of the SPF for the preparation of the hydrolysis treatment to produce nanocrystalline cellulose (NCC) for reinforcement in polymer composites were examined. Sugar palm cellulose (SPC) was extracted from the SPF, and its structural composition, thermal stability, functional groups, and degree of crystallinity were determined via field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD), respectively. The density, moisture content, chemical composition, and structure of the SPC were also analysed.

The catalytic hydrogenation of furfural was studied over a series of Ni-B, Co-B, and Ni-Co-B amorphous alloy catalysts that were prepared by the chemical reduction method using KBH4 and NaBH4 as reducing agents. These catalysts were characterized by N2 adsorption/desorption, XRD, XPS, FE-SEM, and TEM. The results showed that NaBH4 had a much stronger reduction ability to enhance the surface concentration of the metallic active sites for furfural hydrogenation and electron transfer capability, leading to much higher hydrogenation activity. In the Ni-Co-B amorphous alloy catalyst, the equilibrium between the isolated Ni-B/Co-B active sites and the combined Ni-Co-B active sites was important in regulating furfural conversion and products distribution.

Ammonium persulfate (APS) oxidation was employed to isolate carboxyl cellulose nanocrystals (CNCs) from hybrid poplar residue. Structure changes resulting from APS oxidation were investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The further oxidation of the ensuring CNCs with sodium periodate manifested selective oxidation of hydroxyl groups at the C6 position of cellulose into carboxyl groups during APS oxidation. The introduction of active carboxyl groups resulted in lower thermal stability. Transmission electron microscopy (TEM) and width distribution showed that the produced CNCs ranged from 10 nm to 24 nm. Carboxyl CNCs with a yield of 63.2% were isolated via APS oxidation, and they were suitable for large-scale CNCs production.

Six varieties of Erianthus arundinaceus were assessed as potential energy crops and compared with switchgrass. Bioethanol and biomethane were produced as well. The chemical composition, elemental composition, and heating values were close to those of switchgrass except for a higher cellulose content. All varieties scored higher than 110, suggesting excellent potential as an energy crop. Pretreatment resulted in almost complete hydrolysis and achieved a higher glucose yield. In particular, E33 and E19 yielded 337.4 g and 332.4 g glucose, respectively, from 1.0 kg of feedstock compared with 312.1g/kg for switchgrass. E33, E49, and E19 exhibited a higher ethanol yield of 144.2 g/kg, 146.9 g/kg, and 149.6 g/kg feedstock, respectively, at a solids loading of 15%. No obvious influences could be observed on anaerobic digestion performances. A 16.3%, 14.6%, 14.0%, and 13.1% higher yield on cumulative methane could be obtained from E17, E23, E33, and E6, respectively, compared to switchgrass. Bioethanol and biomethane could be maximally obtained from E19 (6820 kg/ha) and E17 (3916 m3/ha), respectively. Thus, they are specially recommended for bioethanol and biomethane production, respectively. E33 can be suggested as a flexible variety for yielding relatively high bioethanol (6008 kg/ha) and biomethane (3409 m3/ha).

The effects of an alkali treatment with NaOH (5%, 10%, and 15%) was studied relative to the tensile and flexural mechanical properties of Colombian coffee silverskin fiber (CCSF)/polyester biocomposites. The CCSF was treated with NaOH for 30 min and then dried at 50 °C for 5 h. Laminates with a 35.1% volume fraction of fiber were prepared using a hand lay up manufacturing technique. Scanning electron microscopy was used to study the fiber morphology. The results revealed that the specific maximum tensile and flexural strengths increased by 36.3% and 25.1%, respectively, the specific tensile and flexural moduli increased by 31.6% and 147.0%, respectively, and the tensile toughness was 67.9% higher compared with the untreated biocomposite. The flexural toughness decreased by 62.0%. The results suggested that mercerization is an effective method to treat CCSF/polyester biocomposites.

To compare the properties of different plant fiber/soybean protein adhesive composites, six types of plant fibers (rice straw, wheat straw, peanut straw, rice husk, wheat husk, and peanut shell) were selected as reinforced materials, and soybean protein adhesive was used as the adhesive. Six types of different bio-composites were prepared by the compression molding process. The Fourier transform infrared (FTIR) spectra, mechanical properties, moisture absorption, and thermal stability of the composites were measured. The tensile cross-section microstructure of the composites was examined. Results showed that the peanut straw/soybean protein adhesive composite contained more hydrophilic groups. The wheat fiber-based composites possessed more hydrogen bonds, leading to the best binding interface compatibility and mechanical properties. The wheat straw/soybean protein adhesive composite had the highest tensile strength, flexural strength, and impact strength, which were 337.7%, 638.6%, and 483.4%, compared to those of the rice husk/soybean protein adhesive composite, respectively. The peanut shell/soybean protein adhesive composite’s equilibrium moisture content was the lowest (8.70%). The rice husk/soybean protein adhesive composite had the highest equilibrium moisture content (14.23%), and the best thermal stability as the initial temperature of pyrolysis was 283.4 °C and the residual mass was 34.45%.

This study examined the thermal conductivity as a function of specific gravity and moisture content for laminated strand lumber (LSL) and red spruce. As part of a larger study of heat and mass transfer in cross-laminated timber panels using laminate comprised of both LSL and spruce, the authors measured the thermal conductivity at four moisture content levels. The results showed that the LSL had a higher thermal conductivity value across the entire moisture content range tested. The average difference was just over 8% and the range for both LSL and spruce was from 0.081 W /m-K to 0.126 W / m-K. Comparisons with published solid wood thermal conductivity values across the range were good. There were no reported values of LSL thermal conductivity at various moisture content levels.

Laccase treatment of prehydrolysis liquor (PHL) produced in a kraft-based dissolving pulp production may allow for purification of its hemicelluloses. In this work, a magnetic support of magnetic silica particle (Fe3O4/SiO2) was synthesized to immobilize laccase from Trametes versicolor. The laccase treatment led to increases in the molecular weight of lignin, which facilitated its removal from PHL. The results showed that laccase activity remained at 65% after seven successive recycle runs. The combination of 10 wt.% fresh immobilized laccase and 90 wt.% recycled immobilized laccase at the overall dosage of 1 U/mL led to 34% lignin removal, irrespective of the recycling runs. The laccase treatment caused 13 wt.% sugar losses from PHL. Based on the results, a process for removing lignin from PHL was proposed based on the application and recovery of an immobilized laccase system.

TEMPO-media oxidation and laccase have been successfully used in fiber degumming, but the combination of the two methods in the hemp degumming process has not yet been reported. In this paper, an alternative and efficient way for the pretreatment of hemp degumming was proposed as a combination of TEMPO-media oxidation with laccase and was a TEMPO-laccase system. A chemical composition analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were applied to systematically analyze and compare the degumming efficiency between the TEMPO-laccase system and other pretreatments. The results showed that after the TEMPO-laccase system degumming process, a clean and smooth surface of the degummed fibers could be observed and the non-cellulosic materials were greatly removed without any crystalline transformation. The hemp fibers after the TEMPO-laccase system degumming process had the most desirable linear density of 6.64 dtex and a tenacity value of 3.41 cN/dtex. This new pretreatment had a considerable effect on hemp degumming, which holds promise for use of high-value textiles.