Volume 9 Issue 3

Autohydrolysis pre-treatments were performed for the production of hemicellulose-rich autohydrolysates from silver birch (Betula pendula) chips prior to chemical pulping. Pre-treatment conditions were varied with respect to time (from 30 to 120 min) and temperature (130 and 150 °C), covering a P-factor range from 10 to 238. Hydrolysates were analyzed in terms of carbohydrates, lignin, volatile organic acids, and furanoic compounds. The analytical data were subjected to various chemometric techniques to establish the relationships between dissolved organic components, hardwood and softwood used in the experiments, and applied pre-treatment conditions. Using this method, differences between the wood species could be clearly seen, and a relatively accurate model for the autohydrolysis of birch chips was developed.

A crosslinked chitosan membrane (I) and a hydroxymethylated lignin-chitosan crosslinked membrane (II) were prepared using glutaraldehyde as the crosslinking agent. Fourier transform infrared spectroscopy (FTIR) was used to identify the chemical structures of the crosslinked membranes and the presence of an absorption peak at 1515 cm^-1 indicated the presence of lignin. Scanning electron microscope (SEM) images revealed that membrane (I) possessed a smooth surface, while membrane (II) exhibited a homogeneous embossed surface without any agglomeration. The Cu(II) ion adsorption properties of both membranes were analyzed. The results indicated that the static adsorption capacities of membranes (I) and (II) were 195 mg Cu(II)/cm² and 275 mg Cu(II)/cm², respectively, and their dynamic chelation capacities were 2.89 mg Cu(II)/cm² and 4.59 mg Cu(II)/cm², respectively. Membrane (I) was suitable only for use in aqueous solutions with pH values of 3.5 to 9.0, while membrane (II) maintained its shape even in concentrated hydrochloric acid or 1 M NaOH solution. The Cu(II) ion absorption properties and resistance to acid and alkali of membrane (II) were superior to those of membrane (I), indicating that hydroxymethylation of the lignin-chitosan crosslinked membrane is worthy of further investigation.

Peanut shell char (PSC) was converted into active carbon monoliths (ACMs) by adding a binder that was easy to make. The conversion process involved adding the PSC into H3PO4-loaded sawdust, extruding the mixture, and finally heating the resulting monoliths for different times. The properties of the resulting ACMs were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared analysis, nitrogen adsorption-desorption, X-ray diffraction, and thermogravimetric analysis. The H3PO4-loaded sawdust could be used as a binder for converting powdered PSC into well-shaped ACMs without visual cracks. The resulting ACMs maintained their monolithic shape, even in water. The ACMs showed a much higher specific surface area (SSA, 850 to 915 m²/g) than the PSC (105 m²/g). The largest SSA (915 m²/g) was achieved by activation for 50 min. Increasing the activation time decreased the SSA and apparent density, but only slightly impacted the carbon structure. This research might lead to value-added conversion of bio-chars.

A comprehensive process was developed to make full use of the solid and liquid products during the production of activated carbon. Almond shell waste was modified with phosphoric acid and thermally treated to give activated carbon. Wood vinegar was generated and collected within the temperature range of 90 to 500 °C, and the maximum amount of the wood vinegar was in the range of 170 to 370 °C, which also gave the strongest anti-pathogens activities with the lowest pH and the highest organic acid content. The remaining residue after wood vinegar generation was further calcined in inert atmosphere to obtain high surface area activated carbon. The pre-treatment of almond shell with H3PO4 leads to the higher surface area, but H3PO4 solution with concentration more than 40% does not increase the surface area further. The impregnation of H3PO4 helps the formation of pores in the almond shell during the calcination, and gives higher iodine number and methylene blue sorption capacity of the resultant activated carbon materials.

This study investigated the morphology, electrochemical modification with respect to the wood fiber direction, and mechanical properties of wood modified by in situ polymerization with polyaniline (PANI). This polymerization formed a composite material with applications as an anti-static, electromagnetic, anti-corrosion, and heavy metal purifying materials. The polymer was found throughout the entire structure of the wood and was quantified within the wood cell wall and middle lamella by SEM-EDX. The presence of PANI affected the conductivity of the composite specimens, which was found to be higher in the fiber direction, indicating a more intact percolation pathway of connected PANI particles in this direction. The PANI modification resulted in a small reduction of the storage modulus, the maximum strength, and the ductility of the wood, with decreases in the properties of specimens conditioned in an environment above 66% relative humidity. The in situ-polymerized PANI strongly interacted with the lignin component of the veneers, according to the decrease in the lignin glass transition temperature (Tg) noted in DMA studies.

During sequential bleaching operations, pulp fiber properties are gradually changed due to mechanical and chemical treatments. In this study, the correlations between pulp or fiber properties such as kappa number, viscosity, total charge, fiber length, and zero-span tensile strength as well as Scott bond of elemental chlorine free (ECF) bleached softwood kraft pulps was investigated. The influence of zero-span tensile strength and Scott bond on tensile and tear strength was also discussed. The Scott bond and zero-span tensile strength showed a strong logarithmic correlation with pulp kappa number and pulp viscosity, while the regression coefficient for Scott bond was negative. An overall deterioration of paper tensile and tear strength from pulps whether beaten or not were observed along the multi-stage ECF bleaching operations. Changing contributions to sheet tensile or tear strength could be mostly attributed to changes in zero-span tensile strength rather than Scott bond during ECF bleaching.

The characteristics of gutta-percha (i.e., chemical compound and melting and glass transition temperatures) and the performance of laminated wood (i.e., moisture content, density, shear strength, and delamination ratio) prepared from sengon wood (Paraserianthes falcataria L. Nielsen) bonded with a gutta-percha-based adhesive were investigated. The gutta-percha-based adhesive was prepared by modification of gutta-percha with 5% maleic anhydride (MAH) and 0.75% benzoyl peroxide (BPO) at various gutta-percha to toluene ratios (w/w) (i.e.,15:85; 17.5:82.5; 20:80; and 22.5:77.5), followed by heating at 70 °C in a water bath for 10 min. Laminated wood was manufactured using both modified and unmodified gutta-percha-based adhesives at 250 gm-2 of glue spread and clamped for 24 h. Terpenes, especially 1,3 butadiene, 2-methyl (CAS)-isoprene (trans 1,4- isoprene) (polyterpene), were found to be the dominant chemical component of gutta-percha. The glass transition and melting temperatures of gutta-percha were -56.75 °C and 51.67 °C, respectively. The modification of gutta-percha with MAH and BPO as an initiator resulted in improved performance for the laminated wood. Infra-red spectrometry of the modified gutta-percha-based adhesive showed a new peak at 1720 cm-1, indicating the C=O bond of MAH.

This work reports on the exploitation of Beta vulgaris for biosurfactant production by Bacillus licheniformis STK 01 and its optimization using statistical modeling of response surface methodology (RSM). Three variables were investigated: agro-waste concentration, pH, and temperature. The response and contour plots of the RSM showed perfect interaction among the variables, with the highest surface tension reduction of the culture medium to 30 mN/m observed at 42 °C, a pH of 8, and a substrate concentration of 4% (w/v). The biosurfactant produced demonstrated a high tendency for hydrocarbon emulsification. Furthermore, by numerical optimization techniques, the optimum conditions were found to be as follows: a pH of 6.72, an agro-waste concentration of 4% (w/v), and a temperature of 44.5 °C. The experiment conducted to validate the optimum conditions obtained showed a biosurfactant with remarkable surface activity, lowering the surface tension of the broth to 30 mN/m, when the organism was grown on B. vulgaris, and to 23.5 mN/m, when grown in glucose medium – the later representing one of the highest surface tension reductions ever reported for a biosurfactant. This study revealed, among others, that the exclusive utilization of cheap solid agro-waste without supplementation with a refined nutrient source is feasible and could ensure the economic sustainability of biosurfactant production.

There is an urgent need for a biodegradable, hydrophobic material that can be used in developing packaging materials. In this preliminary study, epicuticular wax has been extracted from the leaves of Calotropis procera and Alstonia scholaris using various solvents (i.e., ethanol, methanol, benzene, and acetone). The highest wax amounts were found to be 0.54 µg/cm² and 0.13 µg/cm² from Alstonia scholaris and Calotropis procera, respectively. The highest hydrophobicity (29.57%) was found to be in paper discs coated with epicuticular wax extracted with benzene from the adaxial surface of Calotropis procera.

In this paper, the NaOH pretreatment of banana pseudo-stem fiber for biogas production was investigated using a statistically designed set of experiments. A central composite design was used to identify the optimum pretreatment condition for four factors, i.e., NaOH concentration, pretreatment temperature, pretreatment time, and fiber length, on biogas fermentation of banana pseudo-stem fiber. The best pretreatment condition was 7.8% NaOH, 0.2-cm fiber length, and a temperature of 48 °C for 3 days. NaOH pretreatment increased the biogas yield of banana pseudo-stem fiber. The highest biogas yield was 463.0 mL·g^-1VSadded, which was 89.2% higher than that of the control, at 244.7 mL·g^-1VSadded.