Volume 11 Issue 1

The objective of this study was to investigate the color and chemical changes of thermo-vacuum treated larch wood. Specimens were heat treated in a vacuum at various temperatures for 4 h. The color parameters of untreated and heat-treated samples were measured using the CIELab color system. Changes in the chemistry of larch wood were investigated using X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy, and UV-Vis spectroscopy. The results showed that the color of larch wood became darker at higher treatment temperatures. The O/C ratio decreased with an increase in treatment temperature. The C1 peaks showed that there was an elevated content of lignin and extractives on the wood surface after heat treatment. There were more free radicals for thermally treated wood samples, as demonstrated by the increase in the intensities of the ESR signals. Some groups of lignin that contribute to the darkness of the wood increased after thermo-vacuum treatment. Changes in surface chemistry may be the cause of discolorations that occurred during thermo-vacuum treatment.

For the controlled release of pesticides, a novel composite porous hydrogel (LBPAA) was prepared based on lignin and polyacrylic acid for use as the support frame of a pore structure for water delivery. The LBPAA was analyzed to determine its water-swelling and slow release properties. The controlled release properties of LBPAA were evaluated through experiments in relation to the cumulative release of pesticides, with particular emphasis on environmental effects and release models. The porous LBPAA hydrogel showed improved properties compared to polyacrylic acid, and could therefore be considered an efficient material for application in controlled release systems in agriculture.

Water hyacinth (Eichhornia crassipes) is an invasive floating plant that has caused many environmental problems in Asia. Efficiently removing and utilizing this biomass has become an urgent issue. In this work, the composition of water hyacinth biomass (WHB) was analyzed with the Van Soest method. The combined cellulose and hemicellulose content reached 58.6%, and the lignin content was very low compared with other biomass. An efficient alkali pretreatment technology for WHB was developed, and the enzymatic hydrolysis of WHB to reducing sugars was investigated. With favorable hydrolysis conditions for the alkali-pretreated WHB, the cellulose conversion rate reached almost 100%. Structural changes resulting from WHB pretreatment and hydrolysis were analyzed by Fourier-transform infrared spectrometry and scanning electron microscopy. This work demonstrates that WHB is an alternative cellulose source for bioenergy production.

The process of dehydration of glucose to 5-hydroxymethylfurfural (HMF), using caprolactam-lithium chloride (CPL/LiCl) as a solvent, was investigated. Dual-wavelength ultraviolet spectrophotometry provides a new approach for the determination of glucose conversion rate and yield of HMF. Experiments were performed to demonstrate the accuracy and precision of this method. Various reaction parameters, such as the ratio of ionic liquid, reaction temperature, reaction time, catalyst dosage, and solid absorbent, were investigated in detail for the dehydration of glucose. The optimal conditions were explored. Finally, a possible mechanism for the dehydration of fructose to HMF was proposed.

To test the hypothesis that wood coated with rutile TiO2 nanostructures can undergo degradation because of the photocatalytic activity of TiO2, three sets of wood specimens were aged at an accelerated rate. These three sets consisted of blank wood (BW), HDTMOS/MTMOS-coated wood (WHM), and TiO2/HDTMOS/MTMOS-coated wood (WTHM). After exposure to 155-h UV irradiation, the wettability of WTHM changed from hydrophobic to hydrophilic. This indicated that the initial low-surface free-energy materials underwent degradation because of the photocatalytic activity of TiO2. After exposure to 960 h of UV light irradiation and water spray, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) of WTHM showed that rutile TiO2 nanostructures had partially peeled off the wood surface. This suggested that the adjacent wood surface also suffered degradation because of the photocatalytic activity of TiO2. Although the rutile TiO2 coating noticeably enhanced the color stability during UV light aging, it made a relatively small contribution to the color stability of the wood during UV light and water spray weathering process. This study suggests that to derive the greatest benefit from modification of wood surfaces with rutile TiO2 nanostructures for weathering resistance, it is necessary to take measures to inhibit the photocatalytic activity of TiO2 or to fix the TiO2 coating on the wood surface.

Soaking aqueous ammonia (SAA) pretreatment of corn stover was carried out at three temperatures (30, 50, and 70 ºC) and three concentrations of ammonia solution (5, 15, and 25 wt.%). The delignification kinetic model, based on three first-order reactions, was applied to describe the kinetic behavior of lignin removal from corn stover during SAA pretreatment. The first, second, and third terms were based on the initial, bulk, and residual phases of delignification, respectively. The results showed that the model fitted well with the data obtained from the experiments. The activation energies for the delignification reactions were estimated as 61.05 and 59.46 kJ/mol in the bulk and residual phases, respectively. Delignification selectivity increased with increasing reaction temperature.

Kraft mills have the potential to pre-extract hemicellulose from wood as another value added product. The impacts of pre-extracting xylan on pulp and handsheet properties, sodium and sulfur balances, and chemical make-ups in the kraft pulping process of Eucalyptus grandis were assessed. Xylan extractions using white liquor, green liquor, and NaOH were done under varying extraction times, temperatures, and alkaline concentrations; residues were subsequently pulped at 170 °C for 45 min. The highest xylan yield (15.15% w/w) was obtained with 2 M NaOH, at 120 °C for 90 min followed by white liquor (13.27% w/w), utilizing 20% AA at 140 °C for 90 min. Green liquor extraction with 2% total titratable alkali (TTA), at 160 °C and an H-factor of 800 produced the lowest yield (7.83% w/w). However, the green liquor extractions were the most practical for integration into the kraft process due to their limited effect on pulp yield and properties of handsheets produced from the pre-extracted woodchips and the sulfur and sodium make-up increase. White liquor extractions would favour high pulp yield with low kappa number and reduced chemical charge and cooking time. These results are important for technical-economic assessment of integrated kraft pulp biorefineries.

The pyrolysis of briquettes made from biomass is an available and economic technological route for the production of briquette charcoal, but by-products (tar and gas) cannot be brought into full utilization, leading to the waste of resources and the addition of environmental concerns. Temperature is the most important parameter that affects the distributions and properties of briquette charcoal. This work investigated the three kinds of products of the pyrolysis of sawdust briquette in a fixed bed across a wide temperature range (250 to 950 °C). The purpose of this experiment was to study the pyrolysis process and the properties of the resulting products (briquette charcoal, liquid, and gas) of sawdust briquettes and explore the optimum operating temperature to generate good quality briquette charcoal, liquid, and gaseous products simultaneously. According to the results, the optimum pyrolysis temperature range was 450 to 650 °C, for which the briquette charcoal produced within this range had the highest calorific value (2,9.14 to 30.21 MJ/kg). Meanwhile, the liquid product is considered to be useful for liquid fuels or valuable chemical materials, and the low heating value of the gaseous product was 11.79 to 14.85 MJ/Nm3 in this temperature range.

Direct dehydration of fructose and glucose to 5-hydroxymethylfurfural (5-HMF) was studied using ionic liquids (ILs) without adding any catalysts. Various ILs were screened, and the highest 5-HMF yield of 95.6% was obtained using 1-butyl-3-methylimidazolium tosylate ([BMIM][TSO]) at 353 K for 30 min. Proton nuclear magnetic resonance (1H NMR) spectra confirmed that the sulfonate hydrolysates of anions of [BMIM][TSO] acted as active sites for the dehydration of fructose to 5-HMF. The [BMIM][TSO] catalyzed dehydration reaction showed relatively low activation energy (Ea). A mixture of dimethyl sulfoxide and 1-sulfobutyl-3-methylimidazolium trifluoromethane sulfate (DMSO-[BSO3HMIM][OTF]) was used at 413 K for 50 min for the dehydration of glucose, which yielded 59.8% 5-HMF. The addition of t-butanol, as an isomerization promoter, to DMSO-[BSO3HMIM][OTF] led to a higher 5-HMF selectivity without sacrificing 5-HMF yield.

The kinetics of free cyanide biodegradation were investigated under simulated winter (5 °C) and optimum conditions (22 °C and pH of 11) using a Fusarium oxysporum isolate grown on Beta vulgaris waste as a sole carbon source in the presence of heavy metals, i.e. As, Fe, Cu, Pb, and Zn. The highest free cyanide degradation efficiency was 77% and 51% at 22 °C and 5 °C respectively, in cultures containing free cyanide concentration of 100 mg F-CN/L. When compared with the simulated winter conditions (5 °C), the specific population growth rate increased 4-fold, 5-fold, and 6-fold in 100, 200 and 300 mg F-CN/L, respectively, for cultures incubated at 22 °C in comparison to cultures at 5 °C; an indication that the Fusarium oxysporum cyanide degrading isolate prefers a higher temperature for growth and cyanide biodegradation purposes. The estimated energy of activation for cellular respiration during cyanide degradation was 44.9, 54, and 63.5 kJ/mol for 100, 200, and 300 mg F-CN/L cultures, respectively, for the change in temperature from 5 to 22 °C.