Surface characterization of untreated and hydro‐thermally pre‐treated Turkey oak woods after UV‐C irradiation

The aim of this study was to determine the effect of UV‐C irradiation on the Turkey oak wood surface (Quercus cerris L.). In order to compare the effect of irradiation, both untreated wood samples and those treated with steam and heat were analyzed. The steam treatments were carried out in an autoclave at 130 °C; samples were then heated in an oven for 2 h at 180 °C. The physical and chemical changes brought about in the untreated and treated wood samples by the UV‐C light were monitored by colorimetry (color changes), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) (chemical composition) and scanning electron microscopy (SEM) (microstructure and morphology). A detailed analysis of the results indicates that the UV‐C treatment caused irreversible changes in both the chemical composition and morphology of the wood samples via photooxidation and photodegradation processes. Depending on the type of pre‐treatment used, these processes affected the wood samples differently. Copyright © 2014 John Wiley & Sons, Ltd.     

Carbohydrate reactions during high-temperature steam treatment of aspen wood

Aspen wood was treated with steam at different time-temperature severity factors. Analysis of the amounts of acids released revealed a relationship between the acidity and the formation of furfural and hydroxymethyl furfural as degradation products from carbohydrates. It is suggested that two concurrent or consecutive mechanisms are responsible for the observed results: a homolytic cleavage and an acid hydrolysis of glucosidic linkages in the polysaccharides. By preimpregnating the wood with alkali, hydrolysis can be eliminated, resulting in a much cleaner depolymerization of the polysaccharides without any further acid-catalyzed degradation. The enzymatic digestibility of the steam-treated wood material for the formation of glucose was compared with that of steam-exploded wood. A more efficient route for glucose production from steam-exploded wood was found as long as the biomass-pretreated material was homogeneous and without shives.     

Design of electrospun polyacrylonitrile nanofiber–coated nonwoven structure for sound absorption

Acoustic felts are commonly used in white goods. Bearing that into mind, this paper aims to enhance sound absorption behavior of such felts, in particular, within the low and medium frequency ranges. In doing so, wool and jute felt samples were coated with electrospun polyacrylonitrile nanofibrous membrane. These nanocoated felts were studied in terms of their sound absorption performance, air permeability, and surface morphology. The results indicated that the air permeability of the felts could be drastically decreased by coating with nanofibers, which was required for better acoustic performance of felt‐like structures. Moreover, the samples having higher amount polyacrylonitrile nanofibers tended to demonstrate better sound absorbency.     

Steam pretreatment of douglas-fir wood chips

Douglas-fir sapwood and heartwood were impregnated with SO₂ and steam exploded at three severity levels, and the cellulose-rich, water-insoluble component was enzymatically hydrolyzed. The high-severity conditions resulted in near complete solubilization and some degradation of hemicelluloses and a significant improvement in the efficiency of enzymatic digestibility of the cell ulose component. At lower severity, some of the hemicellulose remained un hydrolyzed, and the cellulose present in the pretreated solids was not readily hydrolyzed. The medium-severity pretreatment conditions proved to be a good compromise because they improved the enzymatic hydrolyzability of the solids and resulted in the recovery of the majority of hemicellulose in a monomeric form within the water-soluble stream. Sapwood-derived wood chips exhibited a higher susceptibility to both pretreatment and hydrolysis and, on steam explosion, formed smaller particles as compared to heartwood-derived wood chips.

     

Determination of the thermal modification degree of beech wood using thermogravimetry

Thermal modification is one of the environmental friendly wood preservation technologies. During this process, changes of the main woody cell wall components occur, which lead to improved dimensional stability, lower hygroscopicity and improvement in biological durability. Several chemical reactions which occur during thermal treatment of wood caused changes in wood properties. During TG measurements, thermal decomposition reactions, which was not completed during previous thermal modification process, continued in wood samples, meaning that more thermally treated samples exhibited lower mass losses in a certain or whole temperature range up to 600 °C. Therefore, mass loss, obtained within selected temperature range, could be used as a marker of previous thermal treatment. The aim of the present work is to evaluate suitability of a thermogravimetric method (TG) for determination of a degree of thermal treatment of beech wood. On the basis of thermally untreated sample and those which were thermally modified at 180, 190, 200, 210, 215 and 220 °C in the absence of oxygen, respectively, and with known values of mass loss during the modification processes, several calibration curves were constructed. They represent mass loss in a certain temperature range during TG measurement versus mass loss during previous thermal modification. In a temperature range from 130 to 300 °C and from 130 to 320 °C under nitrogen atmosphere, a linear dependence was observed; correlation coefficients R ² were 0.87 and 0.91, respectively. In wider temperature range and under air atmosphere, lower correlation coefficients were obtained. High correlation coefficient, higher than 0.95, was observed in a temperature range from 25 to 130 °C under both atmospheres. In this region, dehydration due to rehydration of thermally modified samples occurs. The results of this work were compared with those obtained for Norway spruce.     

Determination of Cu, Pb, Fe, and Zn in plant component polymers of a hyperaccumulating plant.

Phytoremediation is an innovative technology that utilizes the natural properties of plants to remediate hazardous waste sites. For more cost-effective phytoremediation, it is important to utilize a hyperaccumulating plant after phytoremediation, i.e. the recovery of valuable metals and the production of useful materials. In this work, the determination of metals in plant component polymers in a fern, Athyrium yokoscense, as a hyper-accumulating plant was established using steam explosion, Wayman's extraction method, and ICP emission spectrometry. After A. yokoscense plants were treated by steam explosion, the steam-exploded A. yokoscense were separated into four plant component polymers, ie. water-soluble material fraction, holocellulose fraction, methanol-soluble lignin fraction, and residual lignin fraction. The concentrations of Cu, Pb, Fe, and Zn in these plant component polymers and the dry weights of plant component polymers were measured. These analytical process determining metals in the plants will contribute to not only the evaluation and the efforts of phytoremediation using a hyperaccumulating plant, but also to the development of more effective phytoremediation.     

Comparison of Different Pretreatment Strategies for Enzymatic Hydrolysis of Wheat and Barley Straw

In biomass-to-ethanol processes a physico-chemical pretreatment of the lignocellulosic biomass is a critical requirement for enhancing the accessibility of the cellulose substrate to enzymatic attack. This report evaluates the efficacy on barley and wheat straw of three different pretreatment procedures: acid or water impregnation followed by steam explosion versus hot water extraction. The pretreatments were compared after enzyme treatment using a cellulase enzyme system, Celluclast 1.5 L from Trichoderma reesei, and a beta-glucosidase, Novozyme 188 from Aspergillus niger. Barley straw generally produced higher glucose concentrations after enzymatic hydrolysis than wheat straw. Acid or water impregnation followed by steam explosion of barley straw was the best pretreatment in terms of resulting glucose concentration in the liquid hydrolysate after enzymatic hydrolysis. When the glucose concentrations obtained after enzymatic hydrolyses were related to the potential glucose present in the pretreated residues, the highest yield, approximately 48% (g g-1), was obtained with hot water extraction pretreatment of barley straw; this pretreatment also produced highest yields for wheat straw, producing a glucose yield of approximately 39% (g g-1). Addition of extra enzyme (Celluclast 1.5 L+Novozyme 188) during enzymatic hydrolysis resulted in the highest total glucose concentrations from barley straw, 32-39 g L-1, but the relative increases in glucose yields were higher on wheat straw than on barley straw. Maldi-TOF MS analyses of supernatants of pretreated barley and wheat straw samples subjected to acid and water impregnation, respectively, and steam explosion, revealed that the water impregnated + steam-exploded samples gave a wider range of pentose oligomers than the corresponding acid-impregnated samples.     

Pretreatments of wheat straw for possibility use in maintenance-free compressed green roof substrates

Green roofs are a key measure used to alleviate the urban heat island effect and reduce stagnant water from urban runoff. However, the expensive substrate material and high construction cost restrict the large-scale application of green roofs. Wheat straw (WS) contains abundant nutrients needed for plant growth; however, burning this straw waste causes severe environmental pollution. In this study, six pretreatment methods, including mixed, soaked, hydrothermal, ultrasonic, microwave, and steam explosion, and three liquid media, including deionized water, acetic acid, and wood vinegar, were used to treat WS to improve its properties and decrease its environmental pollution effects. The results showed that, compared to other treatments, physical methods (microwave, ultrasonic) used in conjunction with wood vinegar could effectively break down the particle structure of WS and increase porosity. Most of the crystallinities were reduced by 1.45–6.66% compared to WS when using these methods, and the absolute values of the surface zeta potential were reduced by 4.224.67 mV. Additionally, the contents of macromolecular lignocellulose, which is difficult to decompose, were reduced by 3.6613.75%. Compared with the use of deionized water or acetic acid, wood vinegar reduced the compressive force of the WS substrates and the energy consumption of compression. Hydrophilic groups such as hydroxyl were introduced into the WS to increase the water absorption rate. Overall, the microwave-assisted wood vinegar pretreatment was an effective method for improving the WS properties for use as a potential alternative substrate material in green roof construction.

     

Effect of Double-Step Steam Explosion Pretreatment in Bioethanol Production from Softwood

The study investigated the production of bioethanol from softwood, in particular pine wood chip. The steam explosion pretreatment was largely investigated, evaluating also the potential use of a double-step process to increase ethanol production through the use of both solid and liquid fraction after the pretreatment. The pretreatment tests were carried out at different conditions, determining the composition of solid and liquid fraction and steam explosion efficiency. The enzymatic hydrolysis was carried out with Ctec2 enzyme while the fermentation was carried out using Saccharomyces Cerevisiae yeast “red ethanol”. It was found that the best experimental result was obtained for a single-step pretreated sample (10.6 g of ethanol/100 g of initial biomass dry basis) for a 4.53 severity. The best double-step overall performance was equal to 8.89 g ethanol/100 g of initial biomass dry basis for a 4.27 severity. The enzymatic hydrolysis strongly depended on the severity of the pretreatment while the fermentation efficiency was mainly influenced by the concentration of the inhibitors. The ethanol enhancing potential of a double-step steam explosion could slightly increase the ethanol production compared to single-step potential.     

Physical Pretreatment Methods for Improving Microalgae Anaerobic Biodegradability

Microalgae may be a potential feedstock for biogas production through anaerobic digestion. However, this process is limited by the hydrolytic stage, due to the complex and resistant microalgae cell wall components. This fact hinders biomass conversion into biogas, demanding the application of pretreatment techniques for inducing cell damage and/or lysis and organic matter solubilisation. In this study, sonication, thermal, ultrasound, homogeneizer, hydrothermal and steam explosion pretreatments were evaluated in different conditions for comparing their effects on anaerobic digestion performance in batch reactors. The results showed that the highest biomass solubilisation values were reached for steam explosion (65–73%) and ultrasound (33–57%). In fact, only applied energies higher than 220 W or temperatures higher than 80 °C induced cell wall lysis in C. sorokiniana. Nonetheless, the highest methane yields were not correlated to biogas production. Thermal hydrolysis and steam explosion showed lower methane yields in respect to non-pretreated biomass, suggesting the presence of toxic compounds that inhibited the biological process. Accordingly, these pretreatment techniques led to a negative energy balance. The best pretreatment method among the ones evaluated was thermal pretreatment, with four times more energy produced that demanded.     

Sound absorption properties of polyurethane foams derived from crude glycerol and liquefied coffee grounds polyol

The main objective of this study was to evaluate the sound absorption properties of rigid polyurethane foams (PUFs) produced from crude glycerol (CG) and/or liquefied coffee grounds derived polyol (POL). The lignin content of POL proved to have a major influence on the structure and mechanical properties of the foams. Indeed, the POL content increased the cell size of the foams and their stiffness, which subsequently influenced the sound absorption coefficients. The POL derived foam has slightly higher sound absorption coefficient values at lower frequencies, while the CG foam has higher sound absorption coefficient values at higher frequencies. In turn, the foam prepared using a 50/50 mixture of polyols presents slightly higher sound absorption coefficient values in the medium frequencies range due to a balance between the cell structure and the mechanical properties. The results obtained seem to suggest that the mechanisms involved in sound wave absorption depend on the formulation used to prepare the foams. Additionally higher POL contents improved the thermal stability of PUFs as well as their mechanical properties. From this work the suitability of CG and/or POL derived PUFs as sound absorbing materials has been proven.     

A technical and economic analysis of acid-catalyzed steam explosion and dilute sulfuric acid pretreatments using wheat straw or aspen wood chips

Lignocellulosic biomass is one of the most plentiful and potentially cheapest feedstocks for ethanol production. The cellulose component can be broken down into glucose by enzymes and then converted to ethanol by yeast. However, hydrolysis of cellulose to glucose is difficult, and some form of pretreatment is necessary to increase the susceptibility of cellulose to enzymatic attack. An analysis has been completed of two pretreatment options, dilute sulfuric acid hydrolysis and sulfur dioxide impregnated steam explosion, for two feedstocks, wheat straw and aspen wood chips. Detailed process flow sheets and material and energy balances were used to generate equipment cost information. A technical and economic analysis compared the two feedstocks for each of the two pretreatments. For the same pretreatment, sugars produced from aspen wood hydrolysis were cheaper because of the higher carbohydrate content of aspen, whereas dilute acid pretreatment is favored over acid-catalyzed steam explosion.     

Nanocomposite-based lignocellulosic fibers 1. Thermal stability of modified fibers with clay-polyelectrolyte multilayers

The layer-by-layer (LbL) assembly process of creating highly structured thin films derived from layers of polyelectrolytes and nanoparticles was adopted in this study to modify the surface of lignocellulosic fibers. Aqueous dispersions of clay nanoplatelets were created with ultrasonication and characterized with dynamic light scattering and atomic force microscopy in which confirmed the presence of individual clay nanoplatelets. Film thickness of never-dried clay and poly(diallyldimethylammonium chloride) (PDDA) multilayers was studied with a quartz crystal microbalance with dissipation monitoring (QCM-D). Using identical LbL deposition parameters, a slurry of steam-exploded wood fibers was modified by alternate adsorption of PDDA and clay with multiple rinsing steps after each adsorption cycle. Zeta potential measurements were used to characterize the fiber surface charges after each adsorption step while SEM images revealed that the LbL film masked the cellulose microfibril structure. Using a thermogravimetric analyzer, LbL modified steam-exploded wood fibers were observed to attain increased thermal stability relative to the unmodified material tested in both air and nitrogen atmospheres. Significant char for the LbL clay coated steam-exploded wood suggests the multilayer film serves as a barrier creating an insulating layer to prevent further decomposition of the material. This nanotechnology may have a positive impact on the processing of lignocellulosic fibers in thermoplastic matrices, designing of paper-based overlays for building products, and modification of cellulosic fibers for textiles.     

Influence of steam explosion on the thermal stability of cellulose fibres

The aim of the present study was to compare the effect of different steam explosion treatments on the thermal degradation of a bleached cellulose. The intensity of a steam explosion treatment, which allows breakdown of the structural lignocellulosic material was determined by a correlation between time and temperature of the process.Results of this study showed that thermal degradation of cellulose fibres was limited when the severity factor applied was below 4.0. For higher intensities, determination of the degradation products in the water-soluble extract showed an important increase of the 5-hydroxymethyl-furfural concentration with the temperature. When the severity factor reached 5.2., TGA analysis showed that the increase of degradation products was coupled to an increase of the char level meaning a strong degradation of the cellulose. dTGA behaviour also showed that thermal stability of the steam explosion samples decreased with the intensity of the treatment. To conclude, a theoretical diagram predicting the degradation of the cellulose during the steam explosion treatment was established.     

Effects of structural design including cellular structure precision controlling and sharp holes introducing on sound absorption behavior of polyimide foam

This paper aims to effectively improve acoustic property of polyimide foam (PIF) by regulating cellular structure of PIF on a large scale and introducing sharp hole structure simultaneously, adopting a special mold with split structure in a closed-mold foaming route. In this work, PIF with same split structure but different pore cell sizes, density, and windows opening rate were produced in the first time. Due to the stepwise transition principle, the impedance of the air acoustic medium and the acoustic material was well matched. In addition, the characterization results showed the effectively effects of microporous structure and split structure characteristics of PIF on the acoustical absorption coefficient. For PIF-4, sound absorption coefficient kept around 0.9 from 900 to 6300 Hz. Especially, the resonance sound absorption characteristics was basically eliminated, which ensured the high efficiency sound absorption behavior of PIF in the broadband range from 600 to 6300 Hz region.     

Changes in cellulose supramolecular structure and molecular weight distribution during steam explosion of aspen wood

We have studied the cellulose supramolecular structure in pulps obtainedby steam explosion of aspen wood. The pulps were bleached with hydrogenperoxidein an OQP-sequence and characterised by size exclusion chromatography and¹³C cross polarisation magic angle spinning (CP/MAS)NMR-spectroscopy. With CP/MAS-NMR-spectroscopy and chemometrics we were able toseparate the supramolecular structural changes taking place during steamexplosion into two independent processes. One process was related to the extentof processing and showed degradation and dissolution of cellulose,hemicelluloseand lignin accompanied by an increase in cellulose content. The second processwas displayed by pulps having molecular weights below approximately 100000 andwas interpreted as showing the removal of dislocations and an increase incrystalline and/or paracrystalline cellulose in the cellulose fibrils.     

XPS characterization of wood chemical composition after heat‐treatment

XPS was used to characterize the chemical changes occurring after drying or applying a heat‐treatment to beech wood samples. Our results indicate that the surface of this air‐exposed material could be strongly affected either by the ambient atmosphere during storage or by the complex atmosphere in the oven during drying or heat‐treatment. However, the O/C ratio measured after removal of a thin slice of a few millimetres of an untreated sample is in reasonable agreement with that calculated from the well‐established chemical composition of beech. Through this methodology (equivalent to scraping for hard materials) it is expected to get a realistic characterization of the wood. The reliability and repeatability of the XPS measurements have been checked and the method applied to the study of the chemical changes of the beech samples subjected to heat‐treatment. Heating at 240 °C induces a significant decrease of the O/C ratio from 0.55 before to 0.44 after the treatment. Heat‐treatment induces also a decrease of the C₂ carbon contribution (carbon atom bound to a single non‐carbonyl oxygen) associated with an increase of the C₁ carbon contribution (carbon atoms bound only to carbon or hydrogen atoms), in agreement with chemical modifications reported previously in the literature. Thanks to the small analysed area of the equipment used in this study, different spots were analysed to demonstrate the presence or absence of a gradient of chemical composition due to thermal degradation or migration of extractives from within the wood structure to its surface. At the scale of our observations, the different wood samples investigated (dried or heat treated) appear to be homogeneous. Copyright © 2006 John Wiley & Sons, Ltd.     

Determination of naturally occurring formaldehyde levels in sap and wood tissue of maple trees using gas chromatgraphy/mass spectrometry

The occurrence of formaldehyde in sap and wood tissue of treated and untreated maple sugar trees was investigated using GC/MS. Samples were collected at different periods of the 2009 season and at different locations in Quebec, Canada. The natural concentration of formaldehyde found in untreated samples varied according to periods and locations and ranged from below the LOQ to 1.82 mg/kg for sap samples and from 2.39 to 8.92 mg/kg of fresh tissue for wood samples. Late season samples tended to have higher concentrations of formaldehyde. Samples of sap and wood tissue from tapholes treated with solutions of formaldehyde showed increased concentrations of formaldehyde for many days after treatment and were clearly distinct from untreated samples. These results will be useful to elaborate new inspection procedures for sugarbushes to control the illegal use of formaldehyde.     

汽爆技术促进中药资源高值化利用

汽爆技术在中药资源高值化利用中发挥的作用正在逐渐体现:汽爆处理打破中药植物细胞壁的屏障结构,有利于有效成分的分离提取;汽爆过程物料自体水解发生去糖苷化作用使天然植物中的苷元与糖基分离,提高苷类物质提取和分离效率;汽爆应用于中药炮制和中药脱毒有高效、快速和避免有效成分流失等优点;汽爆处理有利于中药非药用组分如纤维素、半纤维素等的有效分离和利用,联产乙醇、丁醇等能源和化工产品。本文对汽爆技术在中药资源高值化利用中的研究进展进行了综述。     

Probing crystallinity of never-dried wood cellulose with Raman spectroscopy

The structure of wood cell wall cellulose in its native state remains poorly understood, limiting the progress of research and development in numerous areas, including plant science, biofuels, and nanocellulose based materials. It is generally believed that cellulose in cell wall microfibrils has both crystalline and amorphous regions. However, there is evidence that appears to be contrary to this assumption. Here we show, using 1064-nm FT-Raman spectroscopy, that (1) compared to the crystalline state, cellulose in the never-dried native state is laterally aggregated but in a less-than crystalline state wherein internal chains are water-accessible, (2) hydroxymethyl groups (CH₂OH) in cellulose exist not only in the tg conformation but also in the gt rotamer form, and (3) in native-state fibrils, low-frequency Raman bands due to cellulose crystal domains are absent, indicating the lack of crystallinity. Further evidence of the absence of crystallinity of the fibrils was the failure of the normal 64 % H₂SO₄ hydrolysis procedure to produce nanocellulose crystals from untreated wood. X-ray diffraction data obtained on wood, treated-wood, and wood-cellulose samples were consistent with the new finding and indicated that full-width-at-half-height of the X-ray diffractograms and lateral disorder in samples as measured by Raman were correlated (R² = 0.95).