Volume 7 Issue 1

The effect of mild acidic and alkaline pretreatments of various plant biomasses on their enzymatic hydrolysis has been studied. The yield of reducing sugars and utilization rate of the biomass were used as reliable characteristics of enzymatic digestibility of the biomasses. The experiments showed that alkaline pretreatment was more efficient than acidic pretreatment. As a result of alkaline pretreatment, a more efficient delignification of the biomasses and considerable improvement of the digestibility parameters were observed. It was found that residual lignin content in the biomass after alkaline pretreatment was related to initial lignin content in untreated biomass. Moreover, residual lignin showed an evident negative effect on enzymatic hydrolysis of pretreated biomass samples, and its removal contributed to higher enzymatic digestibility. It is more preferred to select a mild alkaline pretreatment for biomass that has low content of initial lignin. Such treatment yielded highly delignified biomass with increased percentage of cellulose fraction, which enhanced digestibility at low enzyme loading with a relatively short hydrolysis time.

In this study, an artificial neural network (ANN) approach was employed for modeling the moisture absorption (MA) and thickness swelling (TS) properties of oriented strand board (OSB) in various applications. A series of ANN models were developed for the analysis and prediction of correlations between processing parameters and MA and TS of OSB. An ANN model was found for modeling the effects of OSB treatment variables on the MA and TS. The required data for training and testing of the model were obtained from the experimental results of Salay (2010). In designing this model, the MA and TS of the OSB were determined using OSB treatment variables, including board layup type, resin type, application rate of resin, and wax content. When experimental data and results obtained from the ANN were compared by regression analysis using Matlab, it was determined that both groups of data (test and train) were consistent. It was demonstrated that the well-trained feed forward and back propagation multilayer ANN model is a powerful and sufficient tool for the prediction of MA and TS; therefore, by using ANN outputs, satisfactory results can be estimated, rather than measured and hence time and cost are reduced in all the required experimental activities.

The feasibility of the production of cellulose acetate (CA) from recycled paper dust from carton boxes was examined. Two pre-treatments were carried out on the carton box’s paper dust (CPD) to improve the pulp properties for better effect of synthesis. The results showed that the acid and oxygen-alkaline pretreatments were capable of increasing the alpha-cellulose content from 80.5 percent to 87.3 percent and 85.3 percent, respectively. Both pre-treatments also decreased the hemicellulose and ash contents by more than 50 percent. The degree of substitution (DS) of the resultant CA from pre-treated paper dust was improved from 1.94 to 2.13-2.16. The CA that was synthesized from the recycled paper dust showed comparable DS and had a similar trend of Fourier Transform Infrared (FTIR) spectra. Both pretreated pulps also showed an increment in the degree of crystallinity and had maximum degradation effect of temperature when compared to CPD CA. However, all the cellulose acetates produced showed a lower DS and thermal stability compared to commercial cellulose acetate (C CA). The degree of crystallinity of all the cellulose acetate was decreased in comparison to the original material.

The aim of this study was to investigate the effects of thermally compressed veneer laminating on some of the physical and mechanical properties of particleboard. Oriental beech (Fagus orientalis Lipsky)veneers were compressed under various press conditions. Commercially produced particleboard samples were laminated with such compressed veneer sheets. The density, 2-h and 24-h water absorption (WA) and thickness swelling (TS), bending strength (MOR), and modulus of elasticity (MOE) in the parallel and perpendicular directions to grain orientation were measured. The results showed that all of the particleboards laminated with compressed veneer had higher MOR and MOE values compared to unlaminated particleboard and particleboard laminated with non-compressed veneer. In the sandwiched panels, particleboards laminated with veneer sheets and compressed at a pressure of 4 MPa and a temperature of 150 oC had the highest MOR and MOE values. The MOR and MOE values decreased with increasing temperatures higher than 150 oC. The TS value for 2-h and 24-h immersion times decreased with increasing press temperature. The findings of this work could provide some insight in producing sandwich-type panels with improved properties. It appears that compressed veneer using different press temperatures and pressures could be considered as an alternative way of developing sandwich-type products with satisfactory structural properties.

The influence of three drying schedules on the selected mechanical properties of poplar wood (Populus alba L.) was evaluated in terms of suitability for structural applications. For this purpose, 70 mm-thick poplar lumber was conventionally dried by three different moisture content based schedules of T5-D2, T5-D4, and T5-D6. In these schedules, the wet bulb depression was changed as a means of increasing of the drying intensity. After drying, the mechanical properties of the lumber, including bending properties (MOE and MOR), toughness, shear strength parallel to grain, and tensile strength perpendicular to grain, were measured. Results revealed that the severe drying schedule (T5-D6) caused higher reductions in the mechanical properties of the dried boards, particularly the MOE and MOR. Furthermore, toughness and tensile strength perpendicular to grain were not affected by the increasing of the wet bulb depression. The influence of all the three adopted schedules on the mechanical properties was evaluated using the drying rate, final moisture content gradient, and qualitative characteristics of the dried boards.

Chemical modification of Douglas fir bark and its subsequent utilization in adsorption of Pb(II) from aqueous solutions was investigated. The polysaccharidic moiety of barks was functionalized by periodate oxidation and derivatized after reductive amination in the presence of aminated oligo-carrageenans. Pb(II) adsorption isotherms of derivatized barks were then determined and compared to the capabilities of crude barks using the Langmuir adsorption model in terms of affinity (b) and maximum binding capacity (qmax). Compared to crude barks, the derivatization of barks by oligo-carrageenans resulted in significant enhancements of qmax and b by up to x8 and x4, respectively. The results obtained from crude barks on chemically grafted carboxylic and sulfated barks are discussed and interpreted through the Hard and Soft Acids and Bases (HSAB) theory.

Cassava residue from breweries is being generated in large amounts in Guangxi Province of China, and this has potential to cause serious environmental problems if disposed of improperly. Two-stage anaerobic fermentation is a promising method for the treatment of such residue. In this study, the effect of feed to microbes ratio (F/M ratio) on the anaerobic acidogenic fermentation of cassava residue was studied to determine the optimal F/M ratio and to maximize the performance in a subsequent methanogenic stage. The experiments were carried out at the F/M ratios of 0.2, 0.61, 1.02, 2.05, 3.07, and 4.09 g cassava-TS/g sludge-VSS in six laboratory-scale, completely stirred, tank reactors (CSTR) at mesophilic temperature (35°C). An F/M ratio of 1.02 g cassava-TS/g sludge-VSS resulted in the highest solid removal efficiency and VFA/COD ratio, while starch removal efficiency was still near 100 percent, and acidification was relatively high. As a further benefit, the VFA distribution was more suitable for the subsequent methanogenic fermentation stage.

Heat treatment often brings about some negative effects on mechanical properties of wood. Chinese fir is currently underutilized due to some inherent properties that limit its further applications. Using steam as a heating medium and a shielding gas, the heartwood and sapwood of Chinese fir were treated at a temperature ranging from 170ºC to 230ºC and time from 1 to 5 hours in an airtight chamber. Both the modulus of rupture (MOR) and modulus of elasticity (MOE) were increased for the sapwood specimens under the temperature less than 200ºC for short treatment times. The hardness was increased for both two kinds of specimens under the temperature less than or about 200ºC, compared to the untreated specimens. The temperature has a stronger effect on mechanical properties of wood than the time, and the temperature of 200 ºC is a critical point in modifying mechanical properties of wood.

In this study, several kraft pulps were produced by kraft pulping of fast-growing Eucalyptus with a wide range of cooking conditions. The dependences between pulp yields and some pulp properties, namely, kappa number, HexA contents, and cellulose viscosities, were well investigated. It was found that kraft pulp yields linearly decreased with the reduction of HexA-free kappa number in two different stages, respectively, in which a transition point of measured pulp yield of 48.7% was observed. A similar relationship between pulp yield and HexA was also found, in which the resulting transition point of HexA content was 67 μmol/g. Moreover, the logarithm of pulp viscosity was linearly proportional to the reduction of lignin-free pulp yields. Then, a novel empirical model was successfully developed based on these findings. The parameters in this empirical model were calculated by least-squares estimation using the experimental data from active alkali values of 13.2, 14.7 and 17.8. Another data set was used to verify the effectiveness of this model in predicting the pulp yields. Finally, a good agreement (a linear regression coefficient of 90.59%) between experimental and fitting data was obtained, which indicated that the kraft pulp yield of fast-growing Eucalyptus could be accurately predicted by this novel empirical model.

p–p stacking of the aromatic groups in SL. Results show that the charge-free aromatic groups of SL tend to form oriented p–p stacking with the spectroscopic characteristics of J–aggregates. The formation of J–aggregates in SL are recognized by a significant spectral red shift in fluorescent excitation spectra. The other effects that may cause spectral shift, such as the SL species, solvent effect, and the impurities, are investigated to confirm that the formation of J-aggregates is the only viable explanation for the significant spectral redshift of SL. causes molecular shrinkage of SL polyelectrolytes, but has no influence on J–aggregates of the aromatic groups as detected by lack of spectral shift, indicating that the aromatic groups are charge-free. This suggests that not all the aromatic groups but only the charge-free aromatic groups can form p–p stacking. This work demonstrates the presence of J–aggregation in aqueous SL solutions for the first time, which gives an insight in understanding the preferred orientation of the aromatic groups in lignin-based biopolymers.