Volume 13 Issue 1

APMP (alkaline peroxide mechanical pulp) of bamboo was treated in NaOH-urea aqueous solution to modify the fiber properties. The effects of soaking time, fiber concentration, alkali dosage, freezing temperature, and freezing time were evaluated by single-factor experiments. The optimal conditions were determined as a soaking time of 10 min, a fiber concentration of 15%, an alkali dosage of 6%, a freezing temperature of -7 °C, and a freezing time of 40 min. Compared with the properties of untreated APMP, the tensile index of the treated APMP was increased by 64%, and the burst index was increased by 82%. The bulk was reduced by 15%, and the softness was increased by 18%. There was no obvious variation on the folding strength. According to the instrumental analysis, there were no significant effects on the structure in terms of functional groups, the crystalline region, or the fiber surface morphology; however, the variation on the fiber quality was more significant.

White poplar is an important biomass resource because of its high yield and fast-growing characteristics. Experiments were conducted to study the effects of microwave power, moisture content, and particle size on the heating rate and biochar yield. A Central Composite Design (CCD) was used to optimize the biochar yield. The CCD results showed that a maximum temperature-increasing rate of 2.71 °C/s was obtained with a microwave power of 2 kW and a small particle size of 100-mesh. High power, small size, and high moisture content would benefit the increase of the heating rate. An optimum biochar yield of 0.905 kg per kg poplar was obtained with a microwave power of 3 kW, moisture content of 1%, and temperature of 500 °C.

Four fiber fractions from poplar alkaline peroxide mechanical pulping, performed with refiner-chemical preconditioning (P-RC APMP), were used to estimate inter-fiber bonding capacity. The relationship between fiber characteristics and inter-fiber bonding capacities was investigated. The surface lignin content of the long fiber fraction was slightly lower than that of the short fiber fraction. Atomic force microscopy (AFM) images showed that the fiber surfaces were heterogeneous (i.e., different cell wall layers were exposed along the fiber surface). The fiber fractions that had lower surface lignin content had higher bonding capacities. Furthermore, modified PFI beating was used to peel the surface of the fibers. After the peeling treatment, the fiber surface charge increased remarkably, while the surface lignin concentration decreased considerably. The lignin and charge on the fiber surface are the two key factors for estimating the inter-fiber bonding capacities.

The primary and secondary amines of tetraethylenepentamine (TEPA) were N-methylated into tertiary amines through the Eschweiler-Clarke reaction. A straw-based tertiary amine-supported material (STA) was developed for SO2 removal, using a wet impregnation process. The effect of the adsorption conditions, such as the moisture content, flow rate, and adsorption temperature, as well as the regeneration performances were studied. Experimental results showed that STA has high SO2 adsorption capacity (approximately 100 mg/g) and can be regenerated at 100 °C. Furthermore, the adsorption of SO2 molecules on tertiary amine was studied using density functional theory (DFT). The most stable geometries of the adsorption structure in five possible positions, the geometric changes after the adsorption, and the corresponding adsorption energies were analyzed. The results showed that modified TEPA (M-TEPA) has four potential adsorbed sites (N(1,3,4,5)) with a small adsorption energy, indicating that the adsorption is weak. Moreover, the energy of the adsorbed SO2 on the N(1,3,4,5) is less than zero, indicating that the adsorption process is exothermic and spontaneous. The theoretical investigation agreed well with the experimental results.

Sequential submerged cultivation with different induction media as inducers of ligninolytic enzyme production by Pleurotus ostreatus strains was assessed by measuring laccase activities. An unconventional material, alkali lignin, was used for the first time as an inducer for different strains to enhance laccase activity. The P. ostreatus strains secreted similar but relatively high levels of laccase activity when the induction media contained alkali lignin with or without glucose. The laccase enzyme of different P. ostreatus strains in the different media exhibited large differences, and the wild strain YAASM 0568 exhibited enhanced production of laccase compared to other cultivated strains. The laccase activities of wild strain YAASM 0568 were nearly 3.4-, 3.3-, and 5.4-fold higher than that for cultivated strains CCMSSC 00322, CCMSSC 00406, and CCMSSC 00336, respectively, when the induction media contained alkali lignin, inorganic salt, and vitamin B1. In general, induction media containing alkali lignin with or without glucose were favorable for laccase secretion. The results revealed that the type of induction material and the nature of the fungus play important roles in the expression of ligninolytic enzymes. These findings would be helpful for selection of the appropriate type of strain and for optimization of integrated industrial ligninolytic enzyme production.

Composite films with different Kappaphycus alvarezii seaweed and corn starch concentrations were developed, and the effect of these concentrations on the films’ optical, mechanical, and water vapor barrier properties were investigated. The chemical interactions between the two components in the film were verified by chemical composition and Fourier transform infrared (FTIR) spectroscopy investigations. The results showed that the mechanical properties and opacity of the composite films were enhanced with the addition of seaweed. Among the compositions, a composite film with 3% seaweed and 1% starch exhibited the highest tensile strength and elongation at break. The water vapor permeability (WVP) of the composite films linearly increased with the increments of starch and seaweed concentrations. The FTIR analysis also revealed intermolecular interactions between the two components, consistent with the good miscibility of seaweed and starch in the blend. Therefore, different concentrations of the blend of seaweed and starch could be used to tailor a film with certain desired functional properties.

Effects of various surface modifications were evaluated relative to the mechanical properties of sugar palm fiber/glass fiber (SPF/GF) reinforced thermoplastic polyurethane (TPU) hybrid composites. The 6 wt.% alkaline, 2 wt.% silane, and combined 6 wt.% alkaline-2 wt.% silane treatment of SPF were carried out for 3 h to improve the fiber/matrix interaction of SPF/GF with TPU. The SPF and GF were fixed at 30 wt.% and 10 wt.% fiber loading, respectively, and were fabricated using the melt compounding method followed by hot compression in a moulding machine. Mechanical properties, such as tensile, flexural, and impact strength, were evaluated using a universal testing machine and an Izod impact tester. The untreated and treated hybrid composites were characterized by FTIR spectroscopy. The tensile, flexural, and impact strength of the combined 6 wt. % alkaline-2 wt. % silane treatment was improved 16%, 39%, and 18%, respectively, as compared to the untreated SPF/GF reinforced TPU hybrid composites. Moreover, the scanning electron microscopy (SEM) showed a good fiber and matrix interfacial bonding in the hybrid composites. Thus, this treated hybrid composites could be suitable for fabricating automotive parts.

5-Hydroxymethyl furfural (5-HMF) was prepared using microcrystalline cellulose as the raw material, an ionic liquid as the solvent, and ethyl butyrate as the co-solvent. The decomposition of microcrystalline cellulose to 5-HMF in an ionic liquid/organic solvent (ethyl butyrate) biphasic system was investigated. The optimum conditions were an ionic liquid:organic solvent ratio of 1:4, reaction temperature of 130 °C, and reaction time of 3 h, which resulted in yields of 5-HMF and reducing sugar of 40.95% and 41.7%, respectively. The ionic liquid was re-utilized. The re-utilization process of the biphasic system was also studied. The solvent [BMIM]Cl could be reused twice. The primary recovery rate of [BMIM]Cl was 75.6%, and the yield of 5-HMF was 32.6%. The second recovery rate of [BMIM]Cl was 46.8%, and the yield of 5-HMF was 17.6%.

Solid fuel for heating is an important product, and for sustainability reasons, it is important to replace nonrenewable fuels with renewable resources. This entails that the raw material base for pellet production has to increase. A broader spectrum of materials for pelleting involves variation in biomass substances. This variation, due to lack of knowledge, limits the possibilities to increase the pellet production using new raw materials. In this study, pellets were produced with a single pellet press from 16 different pure biomass substances representing cellulose, hemicellulose, other polysaccharides, protein, lignin, and extractives, and five different wood species, representing softwoods and hardwoods. All pellets were analyzed for the work required for compression and friction, maximum force needed to overcome the backpressure, pellet hardness, solid density, and moisture uptake. The results showed that the hardest pellets were produced from the group of celluloses, followed by rice xylan and larch arbinogalactan. The weakest pellets were from the group of mannans. Conclusions are that the flexible polysaccharides have a greater impact on the pelletizing process than previously known, and that the differences between xylan and glucomannan may explain the difference in the behavior of pelletizing softwoods and hardwoods.

Kraft lignin (KL) was valorized by introducing phenolic hydroxyl groups and adjusting the molecular weight by oxidative depolymerization. Hydrogen peroxide with copper sulfate as a catalyst was employed in this process. The depolymerized lignin (DL) was characterized with differential ultraviolet spectrum (UV), Fourier transform infrared (FT-IR) spectrometry, gel permeation chromatography (GPC), and heteronuclear single quantum correlation (HSQC) spectra. Both the molecular weight (Mw and Mn) and the polydispersity of the depolymerized lignin decreased compared with default kraft lignin. The content of phenolic hydroxyl groups increased from 1.55 to 2.66 mmol/g. The depolymerized lignin was used in the synthesis of lignin-phenol-formaldehyde (LPF) resin as a substitution of phenol. The physical properties including viscosity, bonding strength, and free formaldehyde content of the adhesive met the GB/T 14704-2006 standard with the substitution of 50% phenol with DL.