Volume 16 Issue 3

Mechanical pulping of raw wood material is a highly energy intensive and pollution generating step in the papermaking process. This study focused on combined mechanical and xylanase treatment prior to the kraft pulping of E. tereticornis. A screened pulp yield of 49.1% (on oven-dry wood basis) with a Kappa number of 24.9 was obtained at the optimum cooking temperature of 160 °C without any pretreatment of the wood chips. After mechanical treatment (destructuring), a slightly higher screened pulp yield (49.4%) was obtained with a Kappa number of 24.2 at the cooking temperature of 145 °C with the same active alkali charge (15%). The optimum cooking temperature was further reduced to 140 °C for the destructured xylanase-treated wood chips. The xylanase treatment resulted in a 2% reduction in screened pulp yield due to hydrolysis of xylan. However, the Kappa number was reduced to 18.2 after xylanase pretreatment of the mechanically destructured wood chips. The combined pretreatment (destructured and xylanase treatment) of wood chips resulted in a reduction in cooking temperature by 20°C compared to untreated wood chips. Such a reduction in cooking temperature can effectively reduce steam consumption. The combined pretreatment improved the pulp brightness by 2.0 (ISO points) and physical strength properties, which included the tensile index, tear index, and burst index by 11.06%, 21.72%, and 21.79%, respectively, compared to the control.

A new coating method was developed, based on cellulose regenerated from an N-methylmorpholine N-oxide (NMMO) solution applied to paper. In particular, the purpose of this study was to compare the effectiveness of the “deep coating” method using cellulose regenerated from NMMO solution and the classic pulp refining process as methods to improve paper mechanical properties and overall quality. The “deep coating” name comes from the fact that the coating process is combined with subsequent heating of the coating before its final solidification. As a result of this operation, deep penetration of the cellulosic solution into the paper structure occurs. This increases the contact surface of the solution with the cellulosic fibers, which increases the strength properties of the paper structure. It was found that the cellulosic coating increased the apparent density of the paper, the tensile strength, the elongation, the resistance to bursting, and the double fold number. However, the coating also decreased the air permeability and the tear resistance of the paper samples. Despite some technological difficulties, this method could be an attractive solution in the case of a need for additional functionalization of a paper structure.

Knot detection is a challenging problem for the wood industry. Traditional methodologies depend heavily on the features selected manually and therefore were not always accurate due to the variety of knot appearances. This paper proposes an automated framework for addressing the aforementioned problem by using the state-of-the-art YOLO-v5 (the fifth version of You Only Look Once) detector. The features of surface knots were learned and extracted adaptively, and then the knot defects were identified accurately even though the knots vary in terms of color and texture. The proposed method was compared with YOLO-v3 SPP and Faster R-CNN on two datasets. Experimental results demonstrated that YOLO-v5 model achieved the best performance for detecting surface knot defects. F-Score on Dataset 1 was 91.7% and that of Dataset 2 was up to 97.7%. Moreover, YOLO-v5 has clear advantages in terms of training speed and the size of the weight file. These advantages made YOLO-v5 more suitable for the detection of surface knots on sawn timbers and potential for timber grading.

Wood swelling and shrinkage affect the cooperation among the elements of furniture and should be considered during design. This study investigated the influence of moisture changes to the effective diameter of holes drilled in narrow and in wide sides of pine blanks. The moisture content (MC) of all samples has been averaged to 11.3-11.8% (air-conditioning for 4 month with RH = 60 ± 1% and t = 20 ± 1 °C). The 12 mm holes were drilled in radial and tangential directions of the samples. The MC in half of the samples was increased to 17.4-17.9% (air-conditioning for 6 months with RH = 85% and t = 20 ± 1 °C), and the MC in the second half of the samples was decreased to 8.2% (air-conditioning for six months with RH = 35% and t = 20 ± 1 °C). There were nonuniform changes in MC of the samples. Air with RH = 85% increased the MC by 6%, air with RH = 35% decreased the MC by 3%. The effective diameters of the holes were more sensitive to a decrease in air RH than to an increase the air RH. The swelling changes of wood significantly reduced the effective hole diameter, while adsorption shrinkage changes in wood only slightly increased the effective diameters of the holes. The pine blanks swell and shrink asymmetrically, but the changes in the effective diameter of the holes are not correlated with these phenomena. They also have a different form for holes drilled in radial and tangential directions.

Physical and mechanical properties were evaluated for bamboo-oriented strand boards (BOSB) prepared with combinations of two contrasting bamboo species and bonded with phenol formaldehyde resin under various compression ratios. The strands from the culms of Gigantochloa pseudoarundinacea and Dendrocalamus asper bamboo were steam-treated at a temperature of 126 °C and a pressure of 0.14 MPa for 1 h and then washed with a 1% NaOH solution. Three-layer dual-species bamboo-oriented strand boards with a shelling ratio of 25 to 50 to 25 (face to core to back) were manufactured with different compression ratios using an 8% phenol formaldehyde adhesive and 1% paraffin. The slenderness ratio and aspect ratio were evaluated by measuring 100 random strands to determine uniformity. The solidity profiles of the dual-species bamboo-oriented strand boards (thickness direction) were relatively uniform. The modulus of rupture, modulus of elasticity, and internal bond values of the dual-species bamboo-oriented strand boards increased as the compression ratio increased, but the water absorption and thickness swelling decreased. The dual-species bamboo-oriented strand boards prepared with compression ratios of 1.44 to 1.25 and 1.54 to 1.33 met all the requirements of CSA standard 0437 (2011). The optimum compression ratio for the preparation of dual-species bamboo-oriented strand boards was 1.44 to 1.25.

Magnetic lignin-based adsorbent (MLA) was successfully fabricated to remove methyl orange dye from aqueous solution. The synthesized MLA was characterized by means of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), N2 adsorption-desorption, scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). In the process of adsorption, influence factors and recycling performance were considered, and the adsorption mechanisms such as isotherm and kinetics were investigated. The result showed that the equilibrium data was consisted with the Langmuir model with a maximum adsorption capacity of 85.0 mg/g. The adsorption kinetics followed a pseudo-second-order model. Based the adsorption performance, MLA showed good recyclability. Therefore, these results demonstrate that MLA could offer a great potential as an efficient and reusable adsorbent in the wastewater treatments.

Coconut husk, rubberwood sawdust, and palm leaf base are cellulosic agricultural wastes that have potential to be processed to fiber as absorbing material. This study investigated characteristics (morphological, physiological properties, chemical composition, absorption capacity, and water absorption isotherms) of coconut, rubberwood, and palm fiber. Also, the study aimed to develop an antimicrobial sachet packaging to resist against foodborne pathogens (Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., and Escherichia coli) by adding lime oil (LO) emulsion or Litsea cubeba (LC) oil at 50 to 700 µL into the material (1 g) before, and then dried and placed in the 1-L seal box. Results showed that among the three, coconut performed the best in terms of releasing the essential oil (EO) emulsion against bacteria. Coconut could adsorb and release volatile LO or LC at the lowest concentrations (LO, 500 µL/L; LC, 300 µL/L) to inhibit bacteria compared with the other fibers (700 µL/L) at 35 °C. Results indicated that coconut has a low water absorption rate, which influenced the faster adsorption of EO emulsion in the beginning of the process; therefore, using low concentrations of EO in coconut for bacterial inhibition is possible. Coconut contains 34.5% lignin, 68.7% holocellulose, 37.6% cellulose, and 31.2% hemicellulose. Coconut is suitable as an alternative to the biocomposite material in developing a new antimicrobial packaging design.

Thermal, morphological, and mechanical properties of three-dimensional (3D) printed polylactic acid (PLA) composites reinforced with different amounts of waste pine sawdust were investigated. To determine the mechanical properties of the obtained filaments, test samples were produced using a 3D printer according to the mechanical test standards. The filaments that were produced from blends that contained the wood sawdust at the highest level (20%) could be printed via a 3D printer without any problems. According to the results obtained from the mechanical tests, a decrease in the tensile strength values of the composites was observed with the addition of wood sawdust into the neat PLA polymer. On the other hand, it was determined that the flexural strength values of the wood sawdust/PLA composites significantly increased with the addition of the wood sawdust. It was concluded that the waste pine sawdust is a reasonable reinforcement material for the production of composite filament for 3D printing applications and it can be compatibly extruded with PLA polymer. Thus, sawdust can be used as a value-added waste source for the production of high-quality 3D polymeric materials.

Poplar pretreated by steam explosion was used as an adsorbent to simulate the adsorption process of nickel ion in wastewater. The result of kinetics suggested that the pseudo-second-order model was well suited to describing the adsorption of nickel ion. Through controlled adsorption, steam-exploded poplar was recycled after Ni2+ adsorption and then reduced to carbon-supported nickel catalyst (NiC700). Spectrum analyses of Fourier transform infrared spectrometry (FTIR), X-ray diffractometry (XRD), X-ray photoelectron spectrometry (XPS), Brunauer Emmett-Teller (BET) surface area, and electrochemical tests were applied to study the properties of the NiC700 relative to the control carbonized materials having no Ni (C700). The FTIR analysis revealed that there were chemical interactions and ion changes between OH, C–H, C=O, and heavy metal ions in the bio-adsorption process of nickel. The surface area of NiC700 was 1480 m2/g. The presence of Ni nanoparticles in NiC700 after reduction was confirmed by the XRD and XPS analyses. Electrochemical impedance spectroscopy (EIS), photocurrent (IT), and Mott Schottky curve results revealed that the conduction band potential of NiC700 (ECB, NiC700) was -0.10 eV vs. RHE (reversible hydrogen electrode) as an n-type semiconductor, and the Ni-doped carbon fiber exhibited certain electrophotocatalytic activity due to the nickel modification.

The mechanism of lignin degradation via white rot fungi was studied. Phanerochaete chrysosporium and Pleurotus ostreatus were used for all the experiments, i.e., measuring the concentration and structure of alkali lignins and studying the effect of the substrate concentration and enzyme activity on the removal. Gas chromatography-mass spectrometry was performed on the reaction liquid of the lignin degradation enzyme system. Alkali lignin had a characteristic absorption spectrum with a peak at approximately 280 nm. Precipitation in the laccase (Lac) degradation system occurred earlier, as well as being more obvious than that in the manganese peroxidase (Mnp) degradation system. The maximum removal was 29.4% in the Mnp degradation system at a concentration of 40 mg/L. The removal increased in a concentration-dependent manner in the Lac degradation system. The increase in Mnp and Lac enzyme activity led to an increased alkali lignin removal. The removal of the control group was significantly lower than the experimental degradation systems. The degradation mainly produced organic acids, esters, and aromatic substances. In conclusion, white rot fungi could effectively remove alkali lignin, in which precipitation played a major role, followed by enzymolysis; the enzymolysis was associated with the alkali lignin concentration and enzyme activity.