Volume 15 Issue 3

Pretreatment of steam-exploded poplar by Fenton oxidation was used to effectively biodegrade lignin. The structure of lignin samples (LS from steam-exploded poplar and LSF from samples further treated by Fenton oxidation) obtained by enzymatic hydrolysis during pretreatment were characterized and compared. The results showed that the demethoxy reaction occurred in the process of Fenton oxidation. GPC results indicated that the weight average molecular weight (Mw) of LSF did not change significantly, indicating that that there was no significant condensation during Fenton oxidation pretreatment. Heteronuclear single quantum coherence nuclear magnetic resonance (HSQC NMR) results suggested that the proportion of the three-unit basic structural units of poplar (H, G, and S) were significantly changed during Fenton oxidation process, and more lignin S units were removed than lignin G units. The content of β-O-4 linkages was lower in LSF (74.0%, as a fraction of β-O-4 + β-5 + β-β) than in LS (78.2%), which indicated that β-O-4 linkages were destroyed to a certain extent during Fenton oxidation process, and the content of total lignin interunit linkages including β-O-4, β−β, and β-5 linkages over total lignin aromatic subunits (Ar%) in LSF was higher, reaching 49.9%.

Polymers and polymer composites are susceptible to premature failure due to formation of cracks and microcracks throughout their service. Evolution of cracks and microcracks induces catastrophic material failure. Hence, detection/diagnostics, as well as effective repair of cracks and microcracks, is essential to ascertain performance reliability, cost efficiency, and safety for polymer structures. Upon adopting the Paris relation for empirical data, this study incorporated a mathematical model after weighing in cracks initiation and propagation in rice husk (RH) polymer structures, along with the several viable techniques for life prediction and fracture observation. The specimens contained 35% RH fibres and were produced via an injection molding process. Fatigue cracks were evaluated for stresses between 80 and 90% from ultimate tensile strength (UTS) for R = 0.1, 0.3, and 0.5. The outcomes signified that the increment in R value enhanced the growth rate of the crack. Upon elaborating the fracture analysis, this study discusses in detail both fracture mechanics and formation.

Castor plant is used commonly for oil extraction and biodiesel synthesis. However, the residues during pruning are not being used effectively. These residues have the potential to be used as feedstock to produce bioethanol and other by-products. The present work assessed the eco-friendly autohydrolysis pretreatment of castor plant pruning residues at different severity factors (R0), applying a range of temperatures from 100 °C to 200 °C. The hydrolysis of pretreated solids was carried out using a commercial cellulases complex at different solid and enzyme loadings. The enzymatic hydrolysate with a higher glucose concentration was further subjected to fermentation using Saccharomyces cerevisiae ATCC 4126. The results showed an efficient xylan hydrolysis (77.5%) and a preservation of glucan up to 83% in the solids pretreated at an R0 of 5.78. The enzymatic hydrolysis of the pretreated solids at an R0 of 5.78 showed a glucose release of 2.9-fold higher than non-pretreated material. In the hydrolysate fermentation, a maximum ethanol production of 50.5 g/L was achieved (equivalent to 6.4% v/v), corresponding to a conversion efficiency of 98% and a biomass-to-ethanol conversion yield of 93.0 g of ethanol per kilogram of feedstock.

To characterize a suitable biomass for alkaline peroxide treatment, four types of lignocellulosic biomass (rice straw, two Miscanthus spp., and Japanese cypress) were characterized using thermogravimetric analysis. Before the alkaline peroxide treatment, rice straw had the lowest initial thermal degradation temperature and Japanese cypress had the highest. After alkaline peroxide treatment, this trend was reversed, such that the highest initial thermal degradation temperature was for alkaline-peroxide treated rice straw. Hemicellulose and lignin content significantly affected the thermal degradation behavior and alkaline peroxide treatment efficiency. Among the four lignocelluloses, raw rice straw exhibited the highest reducing capability, whereas the treated rice straw exhibited the lowest reducing capability. Surface morphology and crystallinity indicated that when the rice straw was subjected to AP treatment at room temperature for 10 min, crystalline cellulose microfibrils were exposed and concentrated on the surface. Thus, among the samples tested, rice straw was found to be the most suitable biomass for alkaline peroxide treatment.

To fabricate homogeneous bamboo fiber reinforced thermoplastic composites, polypropylene (PP) fiber and 3-aminpropyltriethoxysilane (APTES) modified bamboo fibers were first formed into mats by non-woven air paving technology, and then the composites were created by hot-pressing the mats. The modification of BFs was characterized by XPS and FTIR analyses, and the results confirmed that APTES had been grafted onto the surfaces of BFs. The effects of concentrations of APTES on the mechanical, physical, morphological, and thermal properties of the bamboo-polypropylene composites were examined by tests of bending strength, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and water absorption. The analysis of physical and mechanical properties revealed improved mechanical properties and water resistance (3 wt% of APTES). SEM images were used to assess the influence of modification treatment on the properties of the composites. The results confirmed that the modification of APTES improved the interfacial adhesion between BFs and PP matrix. DSC results indicated the melting point of composites decreased with an increase in concentration of APTES up to 3 wt%, while the melting point of composites increased when the concentration of APTES was higher than 3 wt%.

Lespedeza bicolor (L. bicolor) is used for medicinal purposes because of its various biological and pharmacological activities. In this study, the effects of L. bicolor ethanol extract on the treatment of vitiligo were investigated. The determination of melanin content in melanocytes was measured using B16 melanoma cells and C57BL/6J Ler-vit/vit mice. Finally, the quercetin content in L. bicolor were qualitatively analyzed using HPLC. The results obviously indicated that the L. bicolor extract enhanced melanogenesis and increased tyrosinase activity in cultured melanoma cells and C57BL/6J Ler-vit/vit mice. Treatment with L. bicolor extract led to a higher content of melanin and eumelanin in C57BL/6J Ler-vit/vit mice hair than in control (untreated) mice, which demonstrated the therapeutic effect of hair-graying associated with vitiligo. There was a notable increase in melanocytes in the skin of C57BL/6J Ler-vit/vit mice treated with L. bicolor extract compared with the control. L. bicolor extract was a potent tyrosinase and melanin synthesis activator in B16 melanoma cells. C57BL/6J Ler-vit/vit mice treated with L. bicolor extract had significantly higher melanin content in hair than the untreated control. The results suggest that L. bicolor extract is a potential alternative treatment for improvement of vitiligo.

Kenaf (Hibiscus cannabinus) produces a highly versatile fiber with a variety of uses, but it also produces sizable amounts of core materials that have fewer value-added applications. One possible use for the plant core is in plastic composites, but developing suitable interactions between the hydrophobic plastic and the hydrophilic kenaf core is difficult. In this study, the potential for using various kenaf core pre-treatments was explored using high-density polyethylene (HDPE). While the pre-treatments changed the pectin content and lignin content, the increase or decrease depended on the pre-treatment methods. Pretreatments of core particles with 1% NaOH for 60 min or 1% HCl for 30 min markedly improved the mechanical properties of a 60/40 kenaf/HDPE mixture, although the pre-treatment had little effect on resistance to fungal attack. The results suggest that pectinase enzyme or cellulase enzyme pretreatment time should be shortened to 30 min or 60 min.

An electroanalytical technique was devised using oil palm-based cellulose and hydroxyapatite as modifiers to carbon electrodes for Pb(II) ions detection in an aqueous system. The cyclic voltammetry scan suggested increased active binding sites and faster electron transfer with quasi-reversible redox peaks with a larger anodic current peak and smaller oxidation potential values. The optimal conditions were attained using 10% modifier at pH 2 in 0.1 M HCl, −1.2 V deposition potential, 270 s deposition time, 25 Hz frequency, 0.020 V amplitude, rotation speed of 700 rpm, and the step potential of 0.005 V. The square wave anodic stripping voltammetry established at optimum level exhibited excellent selectivity and stability from 10 ppb to 100 ppb for Pb(II) ions detection. Sharp anodic peaks were observed at -0.48 V for Pb(II) ions with the detection limit of 0.095 ± 0.32 ppb and limit of quantitation of 0.32 ± 0.32 ppb.

Plastic formation from wood has recently attracted immense attention as a new method of producing three-dimensional materials by only one press. In this study, hydroxyl groups in (block-shaped) wood were replaced with ester groups to realize plastic formation. FT-IR measurements indicated that most of the hydroxyl groups in the block-shaped wood were replaced by ester groups after 4 h of treatment. The thermal properties of the esterified wood were investigated; the modulus of elasticity decreased remarkably when heated. Particularly, propionylated wood demonstrated a distinct softening point at relatively low temperatures, demonstrating its thermoplasticity. Additionally, the propionylated wood was stretched extensively by pressing with heat, showing its fluidity. Observation of the end grain of the esterified wood samples after pressing revealed that slippage occurred between the cells, resulting in the bulk flow of the wood. Finally, plastic formation using propionylated wood as the raw material was attempted, and a cup-shaped three-dimensional product was successfully formed. Contact angle measurements demonstrated that the cup-shaped molded product exhibited high water resistance. Thereafter, re-forming was attempted, using crushed fragments of the cup-shaped molded product, and a plate-shaped product was successfully re-formed. Thus, esterification is a promising method for increasing fluidity in solid wood, helping to enable its utilization in plastic forming.

Ionic liquids (ILs) pretreatment is shown to improve the pulp bleachability and modify the physical strength of the hardwood pulp during the oxygen-chlorine dioxide-hydrogen peroxide (ODP) bleaching. The pretreatment enhanced lignin removal in ODP bleaching, resulting in decreased lignin content of the pretreated pulp. The brightness and strength properties were improved. In particular, the folding strength was increased by 153% relative to the control when the pulp was pretreated by [TEA][HSO4]. The analysis of scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction confirmed the enhancement of delignification in ILs pretreatment by the removal of hemicellulose and lignin on pulp fibers’ surface, and the well-preserved fiber framework of the hardwood pulp fibers during ODP-bleaching.