Volume 14 Issue 3

A two-step statistical method was developed with two main objectives. One objective was to utilize plantation forest wastes for edible fungi (Pleurotus ostreatus CICC 14012) cultivation and the second was to maximize the laccase activity in the substrates to facilitate hemicellulose extraction. A total of eight forestry wastes were studied using this method. Among these, Pinus massoniana sawdust, Acacia confusa leaves, and Populus tomentosa leaves were selected and optimized to formulate an ideal culturing substrate. As a result, a laccase activity of 125.7 U/g and mycelium growth rate of 1.19 mm/d were achieved with a 30-d cultivation period and without the addition of foodstuffs or agricultural residues. The physical and chemical changes in the cultivated substrate were measured through a combination of morphology and spectroscopy analyses. The findings led to the selection of a liquid hot water treatment, which was optimized through comparative analysis among different conditions. With this technique, a maximum hemicellulose recovery ratio of 68.8% was achieved with treatment at 170 °C for 50 min. The number average and weight average molecular weights of the extracted hemicellulose were 1920 and 4289, respectively.

A new bio-composite pipe structure named bamboo winding composite pipe (BWCP) was made of bamboo slivers, and its mechanical performance was investigated. Bamboo winding composite pipe that is lightweight and has high strength mechanical properties can be used in water conveyance projects as a green alternative to traditional pipeline materials. Continuous lengths of bamboo slivers were reinforced with resin matrix, which were then fed through a mechanical arch-shaped winder to fabricate the BWCP. The specific ring stiffness of BWCP was comparable to that of fiberglass reinforced plastic pipe (GFRP). The BWCP density was 46.1% to 54.9% lower than that of GFRP. The BWCP exhibited a typical ductile failure and underwent significant deformation before fracture, with the pipe radial deflection at nearly 30%, which is nine times higher than that of brittle fracture failure of GFRP. The interlaminar shearing properties of the BWCP were higher in the structural layer reinforced by bamboo than that of the inner layer made of polyurethane. The BWCP was comparable to most materials used in the pipe industry, exhibiting light weight and high strength.

Modified dicyandiamide formaldehyde polymer (MDDF) and calcined bentonite were used to produce a MDDF-bentonite microparticle retention system. The authors investigated its retention, drainage-aid effect, and its mechanism through measuring the pulp charge density, particle size of the fine particles, and other factors. The results revealed that under neutral conditions and the addition of 0.08% MDDF and 0.3% bentonite, the initial floc was broken via high-speed shearing. Meanwhile, the inorganic filler was added, and the retention effect of the MDDF-bentonite system was close to that of the cationic polyacrylamide (CPAM)-bentonite system. The MDDF-bentonite system exhibited a patch-bridging mechanism. First, the authors added cationic polymer to form a sizeable initial floc, which was then dispersed at high shear force. Then, the authors added inorganic fillers with opposite charges. A smaller floc with more compact structure reformed and was distributed on the wet paper sheet so that more fillers and fine fibers remained on the paper, thus improving the retention efficiency. Because the charge density of MDDF is higher than that of CPAM, the addition of MDDF enabled the pulp system to become closer to the isoelectric point, and the drainage effect was better than that of CPAM.

To improve the penetration of adhesives on finely fluffed poplar veneer (FFPV), a 3% NaOH solution was used to treat FFPV heartwood and sapwood. The treated FFPVs were made into engineered wood composites, otherwise known as scrimbers, with phenol-formaldehyde (PF) resin. The static contact angle and the resin weight gain rate of the FFPV were tested. The shear strength of the FFPV scrimbers was investigated, and the bonding interface was characterized by fluorescence microscopy. The results revealed that the static contact angle of the treated FFPV decreased, but the resin weight gain rate increased. The shear strength of the treated FFPV scrimbers was lower than that of the untreated scrimbers. Fluorescence microscopy revealed that the bondline morphology of the treated FFPV scrimbers changed, with a thinner bondline, a deeper penetration distance, and a smaller glue stain. This result illustrated that alkali treatment can enhance the penetration of PF resin on the FFPV effectively, while excessive penetration of the adhesive should be avoided to ensure adequate bonding properties of the scrimber.

Wood powder/polyethylene composites (WP/PE) were surface treated by plasma discharge and bonded with epoxy resin and acrylic ester adhesives, respectively. The finite element model of the single lap bonded joints of WP/PE was established through the elastic-plastic finite element method, and the influences of adhesive and lap length on the stress distribution in the adhesive joints were analyzed. The results showed that polar oxygen-containing groups were introduced to the WP/PE surface with the plasma treatment, which improved the bonding properties. The peak values of Mises equivalent stress, peel stress, and shear stress of the bonded joints were mainly concentrated at the end of the bond joint. The peak values of the stress in the lap zone of the high-modulus epoxy resin-bonded joints were higher than those of the low-modulus acrylic ester-bonded joints. With an increased length of the joints, the Mises equivalent stress peak value at the end increased slightly, the peeling stress peak value decreased slightly, and the shear stress peak value changed little. The elastic modulus of the adhesive had a great influence on the stress distribution, and the change in the lap length was not remarkable enough to improve the stress distribution of the adhesive joint.

To strengthen the dimensional stability of enzymatically treated corn stalk (ECS) biocomposites, hybrid modified lignosulfonate (HML) was used as a binder to fabricate reinforced ECS/HML composites with evaluation by response surface methodology. The effects of the preparation treatment on the enzymatic conditions, as well as the modified lignosulfonate dosage on the physicomechanical properties of the ECS/HML composites, were all evaluated. The optimum preparation parameters were determined via the Box-Behnken experimental design. High mass concentrations of laccase-vanillin and an appropriate modified lignosulfonate dosage for a relatively short enzymatic pretreatment time led to reduced residual stresses and improved dimensional properties. The optimum conditions that minimized thickness swelling (TS) and water adsorption (WA) without significantly compromising the biocomposite mechanical properties were determined to be 25 g/L laccase-vanillin, 118.8 min enzymatic pre-treatment time, and 15 wt% modified lignosulfonate. The ECS/HML composites that were treated under the optimal conditions resulted in an approximate 42% reduction in the dimensional properties without any significant decline in mechanical properties when compared to ECS panels. Unlike the loose structure of ECS biocomposites, the ECS/HML composites had a laminar shape with firm morphology.

With the aim of developing an efficient and inexpensive catalyst for the production of HMF from glucose, a solid Lewis acid catalyst γ-AlOOH, a common industrial catalyst with easy preparation and low price, was used as the sole catalyst to directly synthesize 5-hydroxymethylfurfural (HMF) from glucose in dimethyl sulfoxide. Various reaction parameters, such as catalyst loading, temperature, reaction duration, and solvent, were investigated. An impressive HMF yield of 61.2% was obtained at the reaction conditions of 130 °C for 3 h. Furthermore, HMF yields from other carbohydrates such as fructose (44.8%), cellulose (50.3%), maltose (53.6%) and sucrose (62.2%) could be achieved using γ-AlOOH as a catalyst. More importantly, the catalyst γ-AlOOH could be reused several times without the loss of its catalytic activities. After five reaction runs, an HMF yield of 57.2% was obtained.

Gasified rice husk carbon, which is a byproduct of power generation by gasification, can be converted to porous carbon (RHAC). This product is environmentally friendly, has excellent electrochemical performance, and represents a high value utilization of biomass resources. In this paper, the heterostructured nano composites were synthesized by a simple hydrothermal reaction. RHAC loaded sulfur-doped tin oxide was used to synthesize composites with a highly conductive porous structure, short ion/electron transport path, and enhanced pseudo capacitance kinetics. The specific capacitance of this composite was improved over that of biomass porous carbon RHAC. At a current density of 1.5 A/g, the specific capacitance of S-doped RHAC/SnO2 composite, RHAC/SnO2 composite, and RHAC were 215 F/g, 177 F/g, and 141 F/g, respectively. The current density was increased from 1 A/g to 5 A/g, and the specific capacity of the S-doped RHAC/SnO2 composite was maintained at 67% with good rate performance. At a current density of 0.4 A/g, the charge capacity was maintained at 78.5% after 5000 cycles of charge and discharge, indicating that the electrode has a long cycle life.

The antioxidant potential of extracts from spruce bark was studied after Soxhlet extraction with ethanol and n-hexane. Ethanol spruce bark extracts were pre-extracted with a mixture of ethanol and n-hexane in a ratio of 1:5. Residues of the extracts and pre-extracts were added to lard (200 mg/kg) to examine its influence on oxidation stability of lard. The composition of the bark extractives was analyzed by GC/MS. The highest antioxidant activity was observed in the original ethanol extracts (15.0 mmol/mg), which had greater antioxidant activity than alpha-tocopherol (13.9 mmol/mg). The n-hexane extract from the spruce bark had 70% less antioxidant activity than the ethanol extract. The high antioxidant activity of the ethanol extract was due to the presence of resin acids (35%) and stilbenes (12%). These antioxidant-active substances increased the oxidation stability of the lard by 5 h, while the n-hexane extract increased the oxidation stability by only 0.5 h. The spruce bark was found to be an alternative feedstock of compounds with potential for use in foodstuffs as antioxidant.

Organic solvent treatment of wood chips can be a key to converting pulp mills into pulp-producing biorefineries. Choosing an optimal solvent requires screening of numerous industrially relevant solvents. This work considers the delignification efficacy of several aqueous organic solvents for juvenile slash pine chips and correlates this efficacy to the lignin solubility. No correlation was shown between the pretreatment efficacy and solubility of ethanol-extracted lignin in organic solvents. At least 10% (v/v) water and 10% (v/v) organic solvent are required for effective delignification, and the different solvent delignification profiles for aqueous mixtures of 1,6 hexamethylene diamine, ethanol, 1-methylimidazole, tetrahydrofuran, and ethylene glycol were determined experimentally. No correlations were found between lignin solubility, Hansen solubility parameters, and delignification. Therefore, solubility measurements should not be a screen for lignin value prior to pulping. However, a 50% (v/v) organic solvent pretreatment at 200 °C for 2 h is a valuable screen to rank the delignification efficacy of organic solvents for further optimization.