Volume 14 Issue 1

Soybean residues were pretreated with 6% of HCl and NaOH, respectively, and then nanofibrillated cellulose (NFC) was prepared using the high pressure homogenization method. The effects of different pretreatment methods on the structure, properties, and NFC preparation of soybean residues were studied. Analysis of the X-ray diffraction, specific surface area, porosity, and thermal stability showed that pre-treatment of the soybean residues allowed the basic crystallinity to be maintained. Specific surface area, porosity, and thermal stability increased. Acid treatment led to the greatest increases. The soybean residues were treated with 6% hydrochloric acid at 80 °C for 1 h, and homogenized 15 times under a pressure of 60 MPa to obtain NFC.

Reactivity is an important parameter when considering the chemical modification or dissolution of cellulose. Different pretreatment methods affect cellulose reactivity by decreasing its degree of polymerization (DP) and crystallinity. In this study, the molar mass of cellulose was decreased via enzymatic pretreatment. Three commercial endoglucanase-rich products were tested. The target was to reduce the viscosity of the pulp to below 200 mL/g and, thus, increase the reactivity of the cellulose. For comparison, cellulose was also pretreated with ozone, and the effects of each pretreatment method on crystallinity and monosaccharide composition of the resulting pulps were investigated.  Both enzymatically treated and ozone-treated pulps were esterified using homogeneous and heterogeneous methods, and the degrees of substitution for these treated pulps were much higher than the esters when the untreated pulp was used. Cellulose esters from the pretreated pulps formed films with good mechanical properties by solvent casting.

The feasibility of separating small molecular organic compounds in the aqueous fraction of methyl bio-oils (AFMBO) using nanofiltration (NF) and reverse osmosis (RO) membranes was studied. Four kinds of commercially available NF and RO membranes were studied preliminarily by using model solutions (aqueous solution of methyl glycosides and glycerol). The membrane module was spiral wound, which is a more suitable format for industrialization than the flat-sheet format for dead-end filtration. The NF400-600 membrane exhibited the best separation performance; the permeate flux was 48.6 L/(m2·h), the methyl glucosides (MEG) rejection ratio was 95.4%, and the transmission of glycerol was 81.0% with an initial concentration of 10 g/L (0.4 MPa, 45 ºC). Compared with the model solution, the NF performance of AFMBO, which included permeate flux, rejection of MEG, transmission of glycerol, and separation of the other components in AFMBO, was investigated. The more complex constituents of AFMBO led to NF400-600 permeability and separating property decline compared with the model solution in the same operating conditions; meanwhile more serious and even irreversible membrane fouling occurred. This research provided a reference for membrane separation industrial feasibility and application of AFMBO.

Effects of acid, alkali, ionic liquid (IL), and microwave-alkali pretreatments on cellulosic water hyacinth (WH) were investigated based on the total reducing sugars (TRS) and ethanol production. For the first time, IL pretreatment with (1-Ethyl-3-methylimidazolium acetate ([EMIM][Ac]) was used for WH, and the efficiency was compared with the other methods. Cellulase and Saccharomyces cerevisiae were fermented together for 72 h. Based on the results, all pretreatment methods effectively increased the sugar content as well as the ethanol yield. Untreated WH had 25 ± 1.5 mg/g of TRS, which was increased to 157 ± 8.2 mg/g, 95 ± 3.1 mg/g, 51 ± 4.2 mg/g, and 45 ± 2.6 mg/g via alkali, microwave-alkali, acid, and IL pretreatments, respectively. The highest TRS level of 402 mg/g was obtained in 24 h and 6.2 ± 0.4 g/L of ethanol in 48 h of fermentation with the alkali-treated WH. The ethanol production was followed by other treatment methods of WH in the order of microwave-alkali, acid, and IL. The results indicated that the ethanol production from WH was related to the type of pretreatment as well as the TRS production.

Surface and dynamic viscoelastic properties of the reproduction cork from Quercus variabilis were studied in detail. There were 16 chemical elements in the Q. variabilis cork determined by the energy dispersive spectrometric (EDS) spectrum, and the contents of C and O were the highest. The mean colorimetric parameters L*, a*, and b* were 60.8, 14.0, and 30.6, respectively. The surface contact angles of Quercus variabilis cork were measured using an automatic contact angle meter. Three different types of liquid media (distilled water, formamide, and diiodomethane) were respectively dropped on the surface of corks using a microsyringe. The initial contact angles of water, formamide, and diiodomethane on the cork surface were 112.0°, 85.1°, and 75.2°, and the corresponding values decreased to 102.1°, 30.7°, and 72.1° when the liquids permeated the cork surface for 10 s. The moisture content values were 4.3%, 6.0%, and 9.0% when the dry cork samples were placed in the relative humidity conditions of 45%, 65%, and 85%, respectively, for 30 days. FT-IR spectra indicated the content of suberin in the sclereids and lenticels was much less than the content found in the pure corks. In the dynamic mechanical analysis (DMA) spectrum, three obvious relaxation processes could be observed in the tan δ curve.

Sugar palm fibers (SPF) reinforced vinyl ester (VE) composites were prepared in this study. The SPFs were obtained from three different geographical locations: Kuala Jempol (Peninsular Malaysia), Tawau (West Malaysia), and Tasik Malaya (Indonesia). The SPFs were utilized as reinforcement material with a fixed loading of 10 wt.%. The reinforced VE composites were prepared using a wet lay-up compression moulding method. The physical properties examined were water absorption, thickness swelling, and moisture content. To determine the strength of the SPF composites, tests on the tensile, flexural, and impact strength related to mechanical properties were completed. A thermogravimetric analysis (TGA) was completed to observe the thermal properties. This study confirmed that the properties of the composites were affected by the strength of the fiber. The SPF/VE composites obtained from Kuala Jempol had the highest tensile, flexural, and impact strength compared to the SPF/VE composites from Indonesia and Tawua. In addition, SPF Jempol/VE also recorded the highest percentage of water absorption, thickness swelling, and moisture content. A comparison of thermal properties showed that SPF Tawau/VE had highest percentage of mass loss between fibers from the three geographic locations.

Alkali-oxygen pulping has received increasing attention as an environmentally compatible pulping process; however, the resulting pulp has low yield and properties due to carbohydrate degradation. In this work, the effect of regulating superoxide anion radicals (O2-•) on delignification selectivity in alkali-oxygen pulping was investigated. The pulp was characterized by Brunauer-Emmett-Teller (BET) analysis, scanning electron microscope (SEM), and X-ray diffraction (XRD). Lignin removal was improved by the regulation of O2-• in the 1,2,3-trihydroxybenzene auto-oxidation system with addition of sodium 2-anthraquinonesulfonate, especially for the pulp from cooking time 120 min. The degree and selectivity of delignification were improved with alkali-oxygen pulping when sodium 2-anthraquinonesulfonate was added to facilitate the generation of superoxide anion radicals. The results showed that the increased fiber liberation was beneficial for the accessibility of O2-• to lignin, which would improve the removal of lignin with negligible damage on cellulose, especially with regards to crystal area.

Diverse cell wall compositions were subjected to pretreatment and saccharification to produce bioethanol from 20 Erianthus arundinaceus accessions. Using four typical pairs of biomass samples, various physical and chemical pretreatments were employed to extract cell wall polymers. Mild chemical pretreatment (2% NaOH and 50 °C) yielded complete biomass saccharification, whereas the liquid hot water pretreatment achieved the highest bioethanol yield with a full sugar-ethanol conversion rate. Notably, the extraction of the lignin p-coumaryl alcohol (H) monomer greatly enhanced biomass saccharification, which may be attributed either to the improved accessibility of cellulose to enzymes after effective removal of lignin or to the maintained native cellulose microfibrils from the relatively less co-extraction of hemicellulose. Hence, the results suggested that the H-monomer-rich lignin may slightly associate with cell wall networks for greatly enhanced lignocellulose enzymatic hydrolysis after mild pretreatments. The present findings provide a strategy for both cost-effective biomass process technology and precise lignocellulose modification for bioenergy.

Effects of material, tool, and technological parameters were assessed during planar milling of thermally modified spruce (Picea abies L.) and oak (Quercus cerris L.) wood relative to the energy intensity of machining. The milling took place under the following conditions: cutting speeds of 20 m/s, 30 m/s, and 40 m/s; feed rates of 4 m/min, 8 m/min, and 11 m/min; and rake angles of 15 °, 20 °, and 25 °. Another change factor was the temperature of the thermal modification (20 °C – reference; 160 °C; 180 °C, and 210 °C). Each factor (cutting speed, rake angle, temperature, and feed rate) was found to have a statistically significant effect. The change in cutting speed had the greatest effect. The lowest power consumption was achieved with a cutting speed of 20 m/s, feed rate of 4 m/min, and rake angle of 25 °. In terms of thermal modification, thermally modified wood was machined with a lower power input. This result can be explained by the chemical processes in the wood and the reduced density in comparison with untreated wood. In comparison with density, the influence of changes in wood chemical composition did not have as great an impact on power input.

One-step pyrolysis is a promising thermal degradation process that has a fast reaction rate and high energy efficiency. In this study, high performance bamboo activated carbon was successfully prepared by one-step pyrolysis with different pyrolysis times (2.5 h, 5 h, and 10 h). Using a high pyrolysis temperature of 1050 °C, the specific surface area was remarkably increased to 2348 m²/g, which was substantially higher than the findings reported previously by other studies. The mesopore ratio was increased to 77.4%, which indicated that the bamboo activated carbon mainly contained microporous carbon and the mesoporosity was considerably developed. The activated carbon was then applied successfully to remove Methylene Blue from aqueous solutions. The adsorption equilibrium data was fit best to the Langmuir model. The maximum adsorption capacity ranged from 495 mg/g to 1667 mg/g.