Research Articles

A study to assess the efficiency of coconut husks (CHs) in removing methylene blue (MB) dye from wastewaters in Malaysia was carried out. A fixed bed column adsorber was set up using flow rates of 40 and 80 mL/min, and the adsorbent (CH) was prepared using the base treatment method with NaOH as activating agent. Three different column bed depths (10, 20, and 25 cm) and unit weights of adsorbent (103, 213, and 260 g) were used. Two models, the bed depth service time (BDST) and Thomas models, were used to validate the adsorption capacity results and breakthrough curve. Changing the bed depth from 20 to 25 cm did not result in a significant change in adsorption capacity, therefore a 20-cm bed depth is recommended as the most efficient. Similarly, adsorption capacity increased as flow rates increased from 40 to 80 mL/min, indicating that a flow rate of 80 mL/min yielded optimum efficiency. The two models also provided predictions with good fits of the bed depth effect, the adsorption capacity, and the breakthrough curve of CH for MB removal.

The created surface irregularities, namely roughness profile Ra, after the sawing of spruce, beech, and oak wood on a sliding mitre saw with manual saw blade feeding were studied. The created surface roughness was monitored at a cut height, e, of 50 mm using three basic modes of solid wood transversal sawing (flatwise cross-cutting at φ2=90°, flatwise edge-mitre cross-cutting, and flatwise mitre cross-cutting at φ2=45°). The monitored surface was made using a sliding mitre saw with the gradual application of saw blades with 24, 40, or 60 teeth, and special saw blade with 24 teeth and a chip limiter (CL), respectively. The saw blades used had identical angle geometries. Three levels of feed force, Fp, of 15, 20, and 25 N corresponding to a range of feed forces used by different operators were used in the experiment. The roughness of sawn surfaces was significantly influenced by cutting model, wood species, type of saw blade, and feed force. The created surface roughness values were very close to the plane milling values.

Rice husks (RH) are a potential biomass source for bio-energy production in China, such as bio-gas production by gasification technology. In this paper, a bench-scale downdraft fixed bed gasifier (DFBG) and a tar sampling system were designed. The effect of equivalence ratio (ER) on gasification performance in terms of the temperature in the gasifier, the composition distribution of the producer gas, and the tar content in the producer gas was studied. The maximum lower heating value of 4.44 MJ/Nm³, minimum tar content of 1.34 g/Nm³, and maximum cold gas efficiency of 50.85% were obtained at ER of 0.211. In addition, the characteristics of gasification byproducts, namely bio-char and bio-tar, were analyzed. The proximate and ultimate analysis (especially of the alkali metal), the surface morphology, the surface area, and the pore size distribution of the rice husk char (RHC) were obtained by the use of X-ray fluorescence (XRF) and scanning electron microscopy (SEM), as well as by using the Brunauer-Emmett-Teller (BET) method. The components of light tar and heavy tar were obtained by using gas chromatography-mass spectrometry (GC-MS).

Ultra-low-density fiberboards (ULDFs) were prepared by a liquid frothing technique using plant fibers as the matrix and Si-Al compounds as the filler to be used as a versatile bio-based composite. Si-Al compounds played an important role in the fire properties of ULDFs. Fire intensity and the amount of volatiles were significantly restrained because of the Si-Al compounds. To determine the combustion mechanism of ULDFs treated by Si-Al compounds, the microstructure of burned specimens was tested by chemical analysis, X-ray diffractometer (XRD), and infrared spectrometer (IR). According to the results from gas chromatography, glucose, xylose, and mannose disappeared in the bottom ashes. After combustion, the XRD profiles of the two ashes became weaker and broader; the sharpest peaks at 18.6° (2q) that represented Si-Al compounds remained; the obvious peaks at 22° (2q) from cellulose were gone. The results from IR suggested the characteristic functional groups OH, CH, and C=O from carbohydrate also disappeared, and absorbance at 1200 to 400 cm^-1, which attributed to the vibration of Si-O, Al-O, and Si-O-Si bonds, increased. In conclusion, fibers are almost completely pyrolyzed at 780 °C. The crystalline structure of Si-Al compounds is rearranged and more amorphous silicon oxide and aluminum oxide are generated.

The effect of degumming pretreatment on whole cotton stalk alkaline peroxide mechanical pulp (APMP) was researched. Degumming pretreatment was used as the first stage of an APMP pulping process, replacing conventional hot water pretreatment. Two degumming agents of sodium hydroxide (NaOH) and sodium oxalate (Na₂C₂O₄) were researched separately. The efficiency of hot water pretreatment, NaOH pretreatment, and Na₂C₂O₄ pretreatment on pectin and metal ions removal was compared. After pretreatment of hot water, NaOH, and Na₂C₂O₄, pectin content was reduced to 4.0%, 2.1%, 1.6%, respectively, compared to original material (4.3%), at removal rates of 7%, 51%, and 64%, respectively. For metal ions, especially transition metal ions, the removal rate was up to 20% after degumming pretreatment. The brightness of the handsheets was 64% ISO, 68% ISO, and 73% ISO, respectively. The dirt count was 2674 mm²·m^-2, 533 mm²·m^-2, and 132 mm²·m^-2, respectively. After Na2C2O4 pretreatment, the tension index and tear index were increased to 40.5 N·m·g^-1 and 4.5 mN·m²·g^-1, respectively. Through degumming pretreatment, pectin, metal ions, and dirt count were reduced efficiently, and the brightness and physical strength were improved significantly.

Timber is used extensively in construction. Therefore, it is important to characterize the response of wood when exposed to elevated temperatures for a sustained period of time. In fire-resistant designs for timber structures, the main goal is to assess in-fire and post-fire structural integrity. The objectives of this study were to study the immediate effect and the residual effect of temperature on bending properties for Chinese larch (Larix gmelinii). A total of 72 specimens were subjected to a static 3-point bending test at various temperatures. The results indicated that both the bending strength (BS) and modulus of elasticity (MOE) decreased nonlinearly as the temperature was increased from 20 to 225 °C for the immediate effect test. For the residual effect test, both the BS and MOE first increased non-linearly and then decreased with increasing temperature. There were significant differences between the immediate effect test and the residual effect test for both BS and MOE. The bending properties in the residual effect test were larger than those in the immediate effect test.

Ternary blend membranes were prepared with polysulfone (PSf), sulfonated polysulfone (SPSf), and cellulose nanofibers (CNF) by a Loeb-Sourirajan (L-S) phase inversion process. The cross-section and bottom surface morphology of the membranes were analyzed by scanning electron microscopy (SEM), and the performance of the membranes was evaluated in terms of pure water flux, bovine serum albumin (BSA) rejection, contact angle, tensile strength, and breaking elongation. The morphology of the cellulose nanofibers (CNF) was detected by transmission electron microscopy (TEM). Results showed that within a certain range, the addition of SPSf improved compatibility between PSf and CNF, and the addition of CNF could improve the hydrophilicity of the membranes. The maximum value of pure water flux reached 137.6 L/m2h, and the minimum value of BSA rejection reached 95.8% when CNF content was 0.3 wt% in casting solution. Also, a certain addition of CNF could enhance the mechanical properties of the membranes.

Biodegradable and environmentally friendly biocomposites produced by a combination of biodegradable thermoplastics and natural fiber have gained increasing interest in recent years. In this work, eco-friendly biocomposites made from poly(butylene succinate) (PBS) and different weight percentages (10, 30, 50, and 70 wt%) of oil palm mesocarp fiber (OPMF) were fabricated via a melt blending process followed by hot-press molding. The biocomposites showed an improvement in storage and loss moduli with increasing fiber content, as indicated by dynamic mechanical analysis. Also, the water uptake and thickness swelling of the biocomposites increased with fiber content. The presence of fiber improved the biodegradability of the PBS, as evidenced from soil decomposition and scanning electron microscopy studies. Conversely, the presence of fiber lowered the melting and crystallization temperature as well as the thermal stability of neat PBS. The biocomposites from PBS and OPMF could be promising biocomposite materials because of their improved mechanical properties and biodegradability compared to neat PBS.

Intrinsically conductive bamboo products were polymerized by the impregnation of an aniline monomer solution into a bamboo substrate and the in situ polymerization of PANI to obtain a semi-conducting material; the bamboo products thus obtained combined characteristics of conductivity of the PANI polymer and the strength of natural bamboo. Light microscopy and scanning electronic microscopy images showed that PANI was uniformly dispersed within the cell lumen and cell wall of the bamboo substrate. The weight percent gain and volume bulk increase of the modified bamboo were 5.18 and 14.9%, respectively. Equilibrium uptake studies showed that the modified bamboo was less hydrophilic, caused by the addition of hydrophobic PANI. The electrical conductivity of the bamboo/PANI composite ranged from 3 × 10^-4 to 1 × 10^–3 S cm^-1, which was tuned by changing the phosphate acid concentration. Fourier transform infrared spectra revealed that PANI was closely polymerized onto the cell wall, allowed by the accessibility of the amine groups of the aniline monomer to the hydroxyl groups of the bamboo matrix. Furthermore, X-ray diffraction analysis indicated that after the in situ polymerization of PANI, the bamboo cellulose maintained a classic cellulose structure, while its degree of crystallinity was decreased.

The aim of this work was to make biodegradable plastics from renewable resources. Paper-based biodegradable plastics were produced via a sol-gel process by using zinc chloride solution. The optimum conditions were a zinc chloride concentration of 65%, reaction temperature of 70 °C, reaction time of 5 s, aging time of 3 h, and glycerol concentration of 10%. Fourier transform infrared spectroscopy (FT-IR) and wide-angle X-ray diffraction (XRD) revealed that no chemical reaction occurred and the crystal form of the cellulose remained cellulose I, but the degree of crystallinity decreased. Compared to other biodegradable plastics, these paper-based biodegradable plastics had better mechanical properties and greater biodegradability.