Volume 14 Issue 2

A highly selective cellulose-based adsorbent for mercury [(Hg)II] ion was prepared and characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectrometry, elemental analysis, and scanning electron microscopy. The results showed that functional thiosemicarbazide-grafted cellulose achieved equilibrium adsorption in 120 min, and the adsorbents had a Hg(II) ion removal rate of approximately 98.5% at a pH of 5.0. The adsorption kinetics fit the pseudo-second-order model, which indicated that the adsorption was a chemical process. Additionally, the adsorption isotherm data showed a best fit with the Langmuir isotherm model, with a maximum Hg(II) ion adsorption capacity of 331.1 mg/g. This adsorbent had a good selectivity for Hg(II) during competitive adsorption.

Catalytic pyrolysis may serve as an alternative production strategy to petroleum-derived fuels and chemicals. Furthermore, red mud, a toxic industrial bauxite byproduct, could serve as a sustainable catalyst and overcome the need for more robust catalysts. To test this, in situ catalytic pyrolysis was run on a semi-pilot scale reactor with various ratios of red mud and switchgrass (Panicum virgatum). Authors hypothesized that the coking process would render red mud environmentally friendly, improve soil quality, and yield for bioenergy crop production, like biochar. Therefore, this work investigated red mud’s capability to enhance bio-oil quality, as well as, how the modified biochar produced from in situ pyrolysis affected switchgrass seedling vigor, and root/shoot mass. The results indicated that red mud was effective at increasing soil pH and biochar and bio-oil yields, while reducing the total acid number in bio-oil. While a high loading of reacted red mud had a negative impact on plant yield, the addition of uncatalyzed biochar to pure red mud considerably improved the seedling yield in marginal soils. These results suggest that this technology has potential for valorizing a waste stream and creating a soil amendment from red mud that closes nutrient and bioenergy production cycles while potentially reducing soil pollution.

This study aimed to evaluate the tensile properties and the failure mechanisms of bamboo slivers that were subjected to different methods of laser-cutting with changing parameters. The failure of the sample was observed through in situ tensile testing combined with scanning electron microscopy. The results indicated that laser-cutting could achieve high efficiency and minimal size variation in machining; however, the calculated sample size needed modification. When the laser power, cutting rate, and sample size were equal to 40 W, 5 mm x s-1, and 2 mm, respectively, the achieved tensile strength was 328.8 MPa, and the tensile modulus was 25.2 GPa. During testing, the surface of the laser-cut sample exhibited brittle fractures (with its interior typically damaged between the basic tissue and the fiber interface), fiber breakage, and fiber extraction.

There is increasing interest in the application of ionic liquids for the pretreatment and fractionation of lignocelluloses. In this study, a series of functional acidic ionic liquids (ILs) with various heterocyclic organic cations were synthesized. Corn stalks were successfully fractionated into lignin, hemicelluloses, and cellulose when ultrasonically pretreated with ILs at 70 °C for 3 h, and subsequently treated with alkaline extraction. High yields of IL-isolated lignin (18.3% to 19.6%) and (8.3% to 14.6%) were obtained using ILs in the absence and presence of water, respectively. The yield of cellulose ranged from 40.0 to 77.0% from IL treatments, whereas the yield of hemicelluloses ranged from 1.1% to 17.3%. Enzymatic hydrolysis of the isolated cellulose residual produced 89.2% to 94.9% reducing sugar with 77.8% to 86.1% glucose, which corresponded to 80.5% to 91.4% enzymatic conversion of cellulose. Syringol and vanillin were found as the main lignin degradation products.

Pine wood is mainly composed of extractives, lignin, cellulose, and hemicelluloses (which include pentosans and hexosans). In the scope of biorefineries, the utilization of pine wood entails the selective separation of its major components. A sequence of aqueous and delignification treatments enables the selective separation of hemicelluloses (as soluble products from the aqueous fractionation step), lignin (as soluble products from the delignification stage), and cellulose (accumulated in the solid phase leaving the delignification stage). Delignification was done in media containing acetic acid or the ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate. Both the soluble hemicellulose-derived saccharides and the cellulose-containing solids were found to be suitable substrates for 5-hydroxymethylfurfural production in reaction media containing the ionic liquid 1-butyl-3-methylimidazolium chloride in the presence of Brønsted and/or Lewis acidic catalysts. The processing schemes considered in this work allowed an efficient utilization of the feedstock using environmentally friendly technologies.

A green biocomposite of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) and cellulose aerogels was developed. Cellulose gel was prepared from NaOH/urea aqueous solution, and subsequent regenerating by Na2SO4 solution and freeze-drying resulted in porous cellulose aerogels. The P34HB/cellulose aerogel biocomposite was fabricated by immersion of porous cellulose in a polymer solution and hot-pressing. The morphology, crystallization, thermal, mechanical, and barrier properties (H2O) of biocomposite were investigated. The cellulose aerogels matrix exhibited a three-dimensional network structure with porosity and a wide pore size distribution, contributing to the change of the glass transition temperature and cold crystallization temperature of biocomposites. Compared with cellulose aerogels, the tensile strength and elongation at break of biocomposites were increased by as much as 48% and 25.1%, respectively. Moreover, biocomposites demonstrated an increased contact angle and water vapor permeability coefficient compared with the cellulose aerogel. The results revealed the potential of P34HB/cellulose aerogel biocomposites for practical application as packaging materials.

Wood processing is often performed at elevated temperatures under moisture-saturated conditions; therefore, it is important to understand the impact of the lignin content and lignin chemical structure on the thermo-mechanical properties of wood. In this study, genetically modified Populus trichocarpa wood specimens with down-regulated cinnamyl alcohol dehydrogenase, cinnamate 3-hydroxylase, and cinnamate 4-hydroxylase with altered lignin contents and/or lignin structures were utilized to probe the relationship between the lignin content, lignin monomer composition, and thermo-mechanical properties of solid wood. The thermo-mechanical properties of these unique samples were measured using dynamic mechanical analysis and the nuclear magnetic resonance (NMR) spin-spin relaxation time. The results showed that the transgenic P. trichocarpa samples had decreased storage and loss moduli compared with the wildtype. The solid-state NMR revealed increased lignin molecular mobility in the reduced-lignin transgenic lines. Also, noticeably reduced glass transition temperatures (Tg) were observed in the transgenic lines with reduced lignin contents and altered lignin monomer compositions compared with the wildtype. The increased lignin molecular mobility and reduced Tg in these samples can probably contribute to wood utilization and processing, such as lignin removal for pulp and paper and biofuels production, as well as particle consolidation during wood composite manufacturing.

Waste from the processing of hardwood and coniferous wood generated in the timber industries is difficult to dispose of and can cause considerable environmental impacts, such as soil and groundwater contamination. In this context, composites with varying concentrations of polypropylene, maleated polypropylene, and particulate Eucalyptus and Pinus waste were produced in a twin screw extruder and injection molded as test bodies for tensile and flexural tests. The morphology of the composites was investigated via scanning electron microscopy. The thermal properties were identified through differential scanning calorimetry. The tensile and flexural results for the two waste formulations indicated that the addition of vegetable fillers increased the modulus of elasticity and bending, and the compatibilizer provided increased resistance to stress and maximum deflection. The scanning electron micrographs illustrated the wetting of the cellulosic charge by the thermoplastic polymer with the compatibilizer, which corroborated the possible occurrence of an esterification reaction and hydrogen bonding interactions in the matrix-particle interface. The incorporation of waste in the composite resulted in the reduction of the degree of crystallinity of polypropylene, regardless of the use of the compatibilizer. This was explained by the barrier capacity of the charge, which prevented the growth of the crystals.

The compositions of the organic pollutants of chemi-mechanical pulping wastewater were studied using Fourier transform infrared spectra and gas chromatography-mass spectrometry. The chemical oxygen demand (COD) was approximately 18110 mg/L, and the ratio of biological oxygen demand to COD (BOD5/COD) was approximately 0.17, due to low biodegradability. In this study, Phanerochaete chrysosporium was selected and the changes in bacterial culture time required to transform pulping wastewater and the metabolites present before and after pretreatment in the wastewater were identified. A decline in the components of the pulping wastewater was observed. Initially, 43 kinds of organic compounds were detected in the raw water. After 3 days of treatment, only 21 organic compounds were detected. Then, 7 days later, the organic pollutants in the waste amounted to only 7 organic compounds. Through the analysis of analysis of P-RC APMP pulping wastewater and that treated by Phanerochaete chrysosporium using GC-MS, the relative content of organic acids was 12.4%, in which phenylpropionic acid had the highest concentration of 11.3%. So, in the culture medium, phenylpropionic acid as the single carbon source can be completely degraded within 96 h.

This work aimed to study the technical feasibility of using industrial gypsum, expanded polystyrene (EPS), and cellulose solid wastes in the production of acoustic insulation panels for buildings. Five traces of acrylic gypsum matrix were produced with variations in the proportions of cellulosic pulp and EPS and always maintaining the same proportion of recycled gypsum and water. The composites produced were tested according to the ISO 10534-2 (2015) standard for the determination of the coefficient of sound absorption and ABNT NBR 14715-2 (2010) for bending tests. The results didn’t show statistically significant differences in the coefficient of sound absorption with variations in the quantities of each material. However, the sonic frequency of the tests directly influenced the results, presenting a better performance at a low frequency (250 Hz). The results qualify the composite produced for use as acoustic insulation and can be used in plates for sound reflection in buildings in places where it doesn’t require resistance to great stresses.