Volume 9 Issue 1

The objective of this study was to investigate some mechanical and physical properties of three-layer particleboards with the core layer made from various willow (Salix viminalis) and industrial pine wood particle mixtures. Increasing willow content slightly worsened the modulus of elasticity and modulus of rupture but improved internal bond, screw holding, water absorption, and thickness swelling. The effects of resin content in the core layer and the density of particleboards were also studied. Mechanical properties, especially modulus of elasticity and internal bond, of particleboards with willow particles met the requirements of EN 312 standard for boards of type P2. The willow (Salix viminalis) can be considered as a substitute for pine wood for the manufacturing of the core layer of three-layer particleboards.

Characterizing the variance of material properties of natural fibers is of growing concern due to a wide range of new engineering applications when utilizing these natural fibers. The aim of this study was to evaluate the variance of the Young’s modulus of sunflower bark by (i) determining its statistical probability distribution, (ii) investigating its relationship with relative humidity, and (iii) characterizing its relationship with the specimen extraction location. To this end, specimens were extracted at three different locations along the stems. They were also preconditioned in three different rel­ative humidity environments. The c2-test was used for hypothesis testing with normal, Weibull, and log-normal distributions. Results show that the Young’s modulus follows a normal distribution. Two-sample t-test results reveal that the Young’s modulus of sunflower stem bark strongly depends on the conditioning’s relative humidity and the specimen’s extraction location; it significantly decreased as the relative humidity increased and significantly increased from the bottom to the top of the stem. The correlation coefficients between the Young’s modulus of different relative humid­ity values and of specimen extraction locations were determined. The calculation of correlation coefficients shows a linear relation between the Young’s modulus and the relative humidity for a given location.

Investigating the mechanical behaviour of silica bodies in oil palm empty fruit bunches (OPEFB) is important to improve the process of silica body removal. This study will assist in providing an understanding of the role of OPEFB as a bioresource material for the bioconversion process. The microstructure of silica bodies/protrusions on the OPEFB fibre surface was modelled using the finite element method, based on the information obtained from scanning electron microscopy (SEM). The effects of silica body geometry, possible anisotropy/orthotropy, and debonding between the interface of the silica body and OPEFB fibre were investigated. Agreements were observed between the results using both circular and spiked silica body models with different geometries and volume fractions. In addition, the cohesive debonding modelling results showed that once critical stress was activated, the stress-strain curve deviated from the no-debond model. The results also suggested that the value of cohesive energy should be between 0.5 kN/m and 4 kN/m.

The presence of dissolved organic matter, scientifically known as humic substances, gives an undesirable color and taste to water. In addition, they are the precursors of carcinogenic disinfection by-products upon disinfection treatment. Adsorption provides a potential means of removal of humic substances, and lignocellulosic biomass serves as a promising candidate. In this paper, we report the application of modified coconut copra residues for adsorption of humic substances from peat swamp runoff. The FTIR spectra suggest that coconut copra residues are genuinely rich with carboxyl groups with long alkyl chains; this renders the material a natural biosorbent, attaining an average of 50% removal under the conditions of testing. Upon treatment, dissolution of lignin and hemicellulose with the enhancement of effective carboxyl groups occurs, improving the adsorption efficiency to 96%; the treated water is visibly clear. The relative band abundance and band shifts further confirm the involvement of the surface functional groups in the adsorption process. The modified coconut copra residue is an attractive biosorbent option for removal of humic substances. The operating conditions are mild, involving non-toxic chemicals, and no pH adjustment is necessary to allow adsorption.

Nitrogen-enriched activated carbons prepared from bamboo residues were characterized by means of BET, XPS, and elemental analysis. Then adsorption experiments were carried out to study the effects of various physicochemical parameters such as contact time, temperature, pH, and initial concentration. Adsorption equilibrium was achieved within 120 min at a phenol concentration of 250 mg/L. When the pH was 4 and 0.1 g of the carbon absorbent and 100 mL of phenol solution at 250 mg/L were used, the phenol adsorption of the ACs with melamine and urea modifications were 219.09 mg/g and 214.45 mg/g, respectively. Both were greater than the capacity of unmodified AC, which was 163.82 mg/g. The Langmuir isotherm adsorption equation well described the experimental adsorption isotherms. The adsorption kinetics was well explained by pseudo-second-order kinetics rather than the pseudo-first-order. In conclusion, the nitrogen-enriched activated carbon proposed as adsorbents of the phenol wastewater were shown to be effective, which also means that bamboo residues have promise as activated carbon precursors for liquid phase adsorbents for environmental protection.

Formaldehyde-free tannin-based furanic foams were prepared by applying infrared radiation (IR) as an alternative energy source. Up to now, tannin-based rigid foams have been produced via heat conduction or microwave radiation energy. The present innovative heating system allows for the production of extra-light products with low density (≤ 50 kg/m³). The IR-produced lightweight tannin foams (IR-TF) exhibited similar properties to those made by hot pressing (HP-TF), but IR-TF can be synthesized with much shorter production time. Although microwave-produced foams (MW-TF) can be obtained with even shorter production times, the IR-TFs are much more homogeneous. Therefore, the IR radiation-based process resulted in the most suitable compromise between foam properties and production time. Overall, IR-TF showed very competitive structural characteristics, such as high homogeneity, high porosity, and limited orthotropicity, which was similar to that shown by the hot press-produced foams. The mechanical properties and material costs are rather similar, but the production time for IR-TF is considerably shorter.

TEMPO/NaBr/NaClO-mediated surface oxidation of NCC, acid-extracted from aspen kraft pulp, was studied, and the properties of nanocellulose whiskers before and after oxidation were characterized by conductimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and atomic force microscopy. The resulting products with varied oxidation degrees were then applied in the deinked pulp to evaluate the improvements of fines retention and pulp drainage. It was found that TEMPO-oxidized NCC maintained its crystalline form of cellulose I, while it showed better dispersibility and smaller dimension due to the high level of carboxyl content and degree of oxidation. By adding NCC and TONCC to the deinked pulp, the retention was improved while the drainage rate was decreased to some extent. When TONCC samples were applied together with cationic polyacrylamide to constitute a microparticulate retention system, both fines retention and pulp drainage were apparently improved. Further study showed that the retention and drainage rate were significantly influenced by the degree of oxidation. TONCC sample with the highest DO (0.134) gave the highest retention and drainage rate, 89.6% and 9.41 mL/s, respectively.

Biohydrogen production from biomass is attracting many researchers in developing a renewable, clean and environmental friendly biofuel. The biohydrogen producer, Clostridium butyricum A1, was successfully isolated from landfill soil. This strain produced a biohydrogen yield of 1.90 mol H2/mol glucose with productivity of 170 mL/L/h using pure glucose as substrate. The highest cumulative biohydrogen collected after 24 h of fermentation was 2468 mL/L-medium. Biohydrogen fermentation using sago hampas hydrolysate produced higher biohydrogen yield (2.65 mol H2/mol glucose) than sago pith residue (SPR) hydrolysate that produced 2.23 mol H2/mol glucose. A higher biohydrogen productivity of 1757 mL/L/h was obtained when using sago hampas hydrolysate compared to when using pure glucose that has the productivity of 170 mL/L/h. A comparable biohydrogen production was also obtained by C. butyricum A1 when compared to C. butyricum EB6 that produced a biohydrogen yield of 2.50 mol H2/mol glucose using sago hampas hydrolysate as substrate. This study shows that the new isolate C. butyricum A1 together with the use of sago biomass as substrate is a promising technology for future biohydrogen production.

This research project deals with PVAc adhesives, their properties, and conditions of use. The primary objective of this study is to verify the dependence of the strength increase in a bonded joint on the curing time. The bonding process used the following PVAc adhesives: Kleiberit 303, Propellerleim 3W, 4B Plus, and Provotil, conforming to resistance classes D3 and D4 pursuant to ČSN EN 204. The test objects and processing of results were in accordance with ČSN EN 205. The readings were converted into charts demonstrating the strength increase in the bonded joints. The strength required in these adhesives by the standard is 10 MPa, and it is prescribed that the test should be performed over the 7 days following the assembly bonding (ČSN EN 204). The tested adhesives achieved this value in a time period of 75 min to 165 min, depending on the adhesive type. It also follows from the measurement that the results differ depending on the sort of adhesive. Comparison of the results with those of other authors (Košíček 1974; Eisner 1966; Eisner et al. 1983; Sedliačik 2005) indicates that the strength increase pattern is not changed with product development and that the differences are due to adhesive modifications by the manufacturers.

Ionic liquid treatment has been reported by several researchers as a possible step in the process of fractionating lignocellulosic biomass within the biorefinery concept. However, understanding how solvation can be achieved and how the feedstock biopolymers are affected is needed prior to a viable implementation. An effective two-component solvent system for the wood components cellulose and xylan has been developed. Furthermore, the solvation of these components in the system consisting of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate (EMIMAc) in a novel combination with the co-solvent 1-methylimidazole (MIM) is investigated. Focused beam reflectance measurement (FBRM) particle characterization in combination with microscopic analysis and molecular weight determinations (xylan) shows that cellulose and xylan can be most efficiently solvated using only 3 to 4% IL (n/n anhydro-glucose units and n/n anhydro-xylose units) and 9% IL, respectively, while still avoiding any significant polymer degradation. A model for a two-step process of cellulose solvation in the present system is proposed.