Volume 9 Issue 3

, industrial alkaline lignin/poly (vinyl alcohol) (PVOH) cross-linked films, industrial alkaline lignin/poly (vinyl alcohol) blend films, and neat poly (vinyl alcohol) films were prepared by casting. The films were investigated by Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry analysis (TGA), and dynamic mechanical analysis (DMA). The water contact angles for the three kinds of films were studied as well. The crosslinking reaction between alkaline lignin and PVOH was strong, which was attributed to the high hydrolysis degree of PVOH and the high reactivity of formaldehyde. Compared with the neat PVOH film, the crystallinity of the cross-linked film decreased slightly; the thermal stability of the cross-linked film was higher; DMA analysis showed that the Tg and the tanδ magnitude of the alkaline lignin/PVOH reaction film both decreased slightly. Lignin and the cross-linking reaction both improved the water resistance of films. Therefore, this research has provided a detailed analysis of the characterization of the films while exploring the potential of direct usage of industrial alkaline lignin in polymer materials.

An effective strategy for sugar production from corn stover was established through a combination of green liquor pretreatment (8% total titratable alkali charge, 40% sulfidity, 140 °C, and 1 h) and enzymatic hydrolysis with a specialized enzyme cocktail. Green liquor pretreatment was demonstrated as an effective first step for sugar production due to the selective removal of lignin (39.70%), high carbohydrate recovery yield (81.53%), and obvious enhancement of enzymatic hydrolysis after pretreatment. When a specialized enzyme cocktail (cellulase, β-glucosidase, and xylanase at a ratio of 1:1.88:6.61, supplemented with 0.05 g of PEG 6000 per g of glucan) was applied, near-theoretical hydrolysis yield was achieved (glucan hydrolysis yield of 93.53% and xylan hydrolysis yield of 86.00%). A total fermentable sugar production of 50.14 g was obtained per 100 g of dry corn stover, including 36.08 g of glucose and 14.06 g of xylose.

A simple, rapid, accurate, and practical headspace gas chromatographic method is proposed for the determination of hydrogen peroxide residues in bleaching effluent. of hydrogen peroxide with ceric sulfate, under acidic conditions, where hydrogen peroxide is converted to oxygen, which is then measured using headspace gas chromatography (HS-GC) coupled with a thermal conductivity detector (TCD). The results show that a complete conversion of hydrogen peroxide to oxygen can be achieved within 3 min at a temperature of 70 °C and a H2SO4 concentration of 0.2 M. Under optimized conditions, the method has an excellent measurement precision (relative standard deviation = 0.78%) and good recovery (100.2 ± 2.6%). does not require the use of organic reagents.

Paper sheets were dipped in maleic anhydride-acylated chitosan (MAAC) to enhance their wet strength and antibacterial performance. The wet strength of paper sheets treated with MAAC or chitosan solutions and cured at 90 and 170 °C was investigated. Escherichia coli was used to evaluate the antibacterial performance of the treated paper sheets. The antibacterial performance was determined by measuring the absorbance at 610 nm based on the turbidity of the bacterial suspension on the surface of the treated paper sheets. The MAAC performed better than chitosan in improving wet strength, especially in the case of permanent wet strength. Paper sheets treated with MAAC under certain conditions resulted in 23 to 33% improvements in the permanent wet strength. As a result of the surface treatment, a reduction of at least 80% in E. coli growth was observed. The MAAC was more efficient in inhibiting the growth of E. coli than chitosan.

Treatment of bleaching effluents from pulp and paper mills using oil palm empty fruit bunch (EFB) fibers as an adsorbent was conducted to remove color and organic pollutants. Empty fruit bunch fibers were chemically modified with polyethylenimine to enhance the adsorption capacity toward anionic species in the effluents. Effluents from the primary clarifier and aerated treatment pond were treated, and the performance of the adsorbent was investigated in terms of decolorization, total organic carbon, and oxygen demand level. Increasing adsorbent dosage and lower pH resulted in greater adsorption performance. The highest decolorization and reduction of total organic carbon of the effluents were 95.0% and 58.2%, respectively. The adsorption equilibrium can be achieved after 4 h of the adsorption process.

With the sustained growth of dissolving pulp demand all over the world, the search for alternative bamboo materials has come into focus in China due to the shortage of wood and the abundance of bamboo resources. In this study, to obtain updated information concerning green bamboo growing in southeastern China and to develop its processing technologies for dissolving pulp, the fiber morphology, chemical composition, elemental composition, degree of polymerization (DP) of cellulose, and crystallinity index (CrI) of cellulose were investigated. The experimental results show that green bamboo has potential for use as dissolving pulp because it has a lower Runkel ratio and fines content than moso bamboo, and a much lower lignin content and similar α-cellulose and hemicellulose contents compared to softwoods and hardwoods. Compared to the cortex and culm, the node had the shortest fibers and more than 30% of fines, the highest content of extractives and lignin, and the lowest α-cellulose content. As a result, a de-knotting operation prior to cooking can contribute to the production of high-grade dissolving pulp. The DP and CrI of cellulose from the node were much lower than that of cellulose from the culm and cortex. Moreover, green bamboo had the high content of ash, primarily distributed in the cortex. The concentration of Si was 4487 ppm in the cortex, nearly five times higher than that in the culm and node.

Treatment of poplar wood using glyoxal as a non-formaldehyde cross-linking reagent was investigated. Cross-linking occurred with glyoxal in the presence of the catalysts aluminum sulfate, magnesium chloride, zinc nitrate, maleic anhydride, ammonium dihydrogen phosphate, ammonium persulfate. Ammonium persulfate was found to be the most effective single catalyst, which may be due to the synergistic catalytic effect of NH4+ and S2O82-, Further, catalyst combinations produced higher overall performance in comparison with the single one, and the optimal combination was maleic anhydride and ammonium persulfate. An increase in ammonium persulfate improved wood dimensional stability and anti-leaching properties, but weakened the hydrophobicity and deepened the colour of the modified wood. Considering the balance between anti-swelling efficiency, leachability, and water uptake, the optimum catalyst concentration was 2%. Although the addition of sodium hydroxide into a glyoxal solution can reduce wood discoloration, it may also reduce the modification efficiency.

Effects of heat treatment on some physical properties of Scots pine (Pinus sylvestris L.) wood densified using a thermo-mechanical method were determined. Samples were densified in the radial direction with a specially designed hydraulic press machine with target compression ratios of 20% and 40%, and at 110 °C and 150 °C. Then, heat treatment was applied to the samples during 2 h at three different temperatures (190 °C, 200 °C, and 210 °C). In order to determine the changes occurring in physical properties, tests of actual compression ratio, spring-back, compression ratio recovery effect, swelling (TS 4084) in compression direction (radial), and density (TS 2472) were conducted. According to results of the research, at the same target compression ratio (20% or 40%), higher actual compression ratio and density increase were observed in the samples densified at 110 ºC in comparison to those densified at 150 ºC. While an increase of 42% in density was being obtained, small rates of decreases up to 4% were observed after heat treatment. Application of heat treatment and increase of treatment temperature significantly influenced dimensional stability of densified Scots pine. Furthermore in comparison to samples without heat treatment, effects of compression ratio recovery were reduced by 80%.

As a furan derivative from 5-hydroxymethylfurfural (HMF) or other biomass-based carbohydrates, 2,5-diformylfuran (DFF) is one of the most important platform molecules in the organic chemicals industry. Although it has many potential applications in the future, the production of DFF on a large scale is currently a challenge. As an alternative to the production of DFF from HMF, the target product DFF could be obtained from biomass-derived glucose with a complex catalytic system (AlCl3·6H2O/NaBr and a vanadium compound assisted with molecular oxygen) carried out in N,N-dimethylformamide (DMF). In this research, reactions were conducted in reactors with different capacities. The results showed that DFF yields based on glucose could reach 35 to 48% with almost complete transformation of glucose. This one-pot two-step reaction is characterized by the abundance and low cost of the starting materials and by the elimination of the separation and purification of HMF. This has great potential for applications in the future production of DFF on a large scale after further advancements and optimizations.

Furfural residues (FRs) were pretreated with laccase or a laccase-mediator (1-hydroxybenzotriazole, HBT) system to produce fermentable sugar for bioethanol production. Compared to laccase-only pretreatment, laccase-mediator pretreatment dissolved more lignin. Approximately 10.5% of the initially present lignin was removed when FRs were treated with a laccase loading of 100 U/g of dry substrate in 1% (w/w) HBT at 48 °C for 24 h in an acetate buffer (pH 4.8). The enzymatic saccharification process was carried out by a combined laccase or laccase-mediator pretreatment without washing of the treated solids. The results showed that active laccase had a negative effect on the rate and yield of enzymatic hydrolysis. Laccase-oxidized HBT seriously reduced glucose yield. However, non-oxidized HBT increased glucose yield when laccase was deactivated at 121 °C for 20 min prior to enzymatic hydrolysis. The highest glucose yield, 80.9%, was obtained from the substrate pretreated with 100 U/g of dry substrate laccase and 1% (w/w) HBT at 48 °C for 24 h in an acetate buffer (pH 4.8). Furthermore, the structures of FRs before and after laccase-mediator pretreatment were characterized by scanning electron microscopy (SEM) and Fourier Transform Infrared spectroscopy (FT-IR).