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Cellulose nanocrystals (CNC) receive great attention for their physical and optical properties, high surface area, high tensile strength, rigidity (Young's modulus up to 140 GPa), and ease of surface modification. However, controlling the properties of CNC is still challenging, given the wide variety of pulp sources and the complexity of finding suitable processing conditions. In the present study, acid hydrolysis efficiently isolated CNC from wood Acacia mearnsii brown kraft pulp (AMKP). Initially, the AMKP was delignified by the treatment with acidified sodium chlorite. The Acacia mearnsii kraft pulp obtained was then subjected to acid hydrolysis with sulfuric acid at concentrations of 50 to 58% 45 °C for 60 min. The hydrolysate was sonicated in an ultrasonic processor for 30 min. The chemical composition was determined by Fourier transform infrared spectroscopy (FTIR), crystallinity by X-ray diffraction (XRD), zeta potential by Zetasizer ZS equipment, thermal stability by thermogravimetric analysis (TGA), and morphology by transmission electron microscopy (TEM) to verify the effect of acid concentration on the yield and properties of CNC. The optimization of the isolation process demonstrated that the maximum yield of 41.95% can be obtained when AMWP was hydrolyzed with sulfuric acid at a concentration of 54%. It was possible to isolate CNC with a crystallinity index between 71.66% and 81.76%, with the onset of thermal degradation at 240 °C; zeta potential of −47.87 to 57.23 mV; and rod-like morphology, with lengths and widths between 181.70 nm and 260.24 nm and 10.36 nm and 11.06 nm, respectively. Sulfuric acid concentration significantly affected the yield of acid hydrolysis, allowing the isolation of CNC with variable dimensions, high thermal stability, high crystallinity index, and great colloidal stability in aqueous medium. [ABSTRACT FROM AUTHOR]

Studies on plant-derived nanocellulose are mainly carried out with lignin-free materials. However, lignocellulosic materials can be used as an alternative raw material, mainly due to their low cost and low environmental impact. This work aimed to study and compare the influence of residual lignin on the nanofibrillation process, on the properties of the nanofibrils and the films formed from the cellulose nanofibrils of Acacia mearnsii De Wild. The cellulosic pulp was subjected to bleaching to remove the lignin and obtain the bleached pulp. Bleach and unbleached pulps were subjected to mechanical defibrillation to obtain cellulose nanofibrils. The effects of defibrillation and residual lignin content were analyzed by characterizing the suspensions and nanocellulose films formed from this material. In addition, an energetic study of the production process of different cellulose nanofibrils was carried out, considering the different levels of residual lignin present in the material. The results demonstrated that the residual lignin presence preserved the thermal properties and provided changes in the morphology of the films, the suspensions showed colloidal stability from pH 5.0 (between |25| and |30| kV), the increase of the lignin content in the pulp caused a slight expressive improvement in the antioxidant activity and a decrease in the suspension viscosities, which fitted the Herschel–Bulkley model well (R2 > 0.98). The mechanical properties of the films [127 MPa (NBR) and 75 MPa (N16)] and the energy consumption to produce nanofibrils [0.324 kWh (NBR) and 0.180 kWh (N16)] showed significant differences, pointing to the influence of residual lignin present in the materials. [ABSTRACT FROM AUTHOR]

Although wood is the main source for pulp and paper industry in Brazil, other renewable non-wood fibers could be key alternatives for papermaking. Thus, this study aimed to evaluate the properties of handsheets produced from a mixture of totora (Schoenoplectus californicus) (C.A. Mey.) and Eucalyptus spp. (eucalyptus) fibers. The pulps were refined in laboratory dybeater "PFI type," varying the number of revolutions, in order to obtain refining curves in the range of 15° to 60° SR. The optical, physical, and mechanical properties of the papers produced were evaluated. The addition of totora fibers influenced refining process and paper properties. Moreover, the handsheets produced with the highest content of totora fibers showed low mechanical resistance. Totora is not suitable to be used as a single source of fibers, especially when good mechanical performance is required. However, when the fibers were mixed with eucalyptus, the mixture achieved reasonable resistance. Furthermore, higher opacity was obtained by the addition of totora (≥97%), which is interesting for the printing and writing segment. [ABSTRACT FROM AUTHOR]

Maclura tinctoria is a tree species native from Brazil and rich in phenolic compounds. Since plant antibacterial activity is highly associated with phenolic compound concentration, we aim to evaluate the in vitro antimicrobial activity of different extracts against fish pathogenic bacteria. In addition, some phenolic compounds have central depressant effects and can be useful in aquaculture due to possible sedative and/or anesthetic effects. Four M. tinctoria extracts were extracted separately with ethanol; leaves (LE), bark (BE), heartwood (HE), and the sapwood (SE). In vitro antimicrobial activity was tested against Aeromonas strains at concentrations of 6400 to 3.125 μg/mL. The sedative effect was evaluated for 24 h with 30 and 100 mg/L concentrations. Chemical composition was analyzed by HPLC-DAD-MS. The HE extract had the best MIC (400 μg/mL) and MBC (800 μg/mL) compared to the LE, BE, and SE extracts. LE extract induced deep sedation and the BE, SE, and HE extracts induced light sedation. Additionally, BE, SE, and HE induced a normal behavior without side effects. Polyphenolic compounds with antimicrobial activity and sedative effects were identified mainly in HE. Thus, HE extract is safe and can be used as a sedative for silver catfish. [ABSTRACT FROM AUTHOR]

estudo teve por objetivo determinar a composição química, densidade básica e parâmetros morfológicos dos traqueídeos da madeira de Cupressus lusitanica, visando verificar sua adequabilidade para produção de polpa celulósica. Foram utilizadas três árvores, com 16 anos, das quais extraíram-se discos que foram empregados na caracterização química, física e morfológica da madeira. A morfologia dos traqueídeos foi avaliada nos anéis correspondentes as idades 4, 7, 10, 13 e 16 anos. A partir dos parâmetros dos traqueídeos, calcularam-se os indicadores de qualidade da polpa. Foram observados baixos teores de cinzas e extrativos (0,27 e 2,13%, respectivamente), porém alto teor de lignina (32,52%). A densidade básica (0,375 g.cm-3) foi menor que de outras espécies de coníferas utilizadas para produção de celulose. Os traqueídeos apresentaram valores médios de 2,41 mm de comprimento; 31,40 µm de largura; 25,15 µm de diâmetro do lúmen e 3,12 µm de espessura de parede, que tenderam a uma elevação nos valores com o aumento da idade. De maneira geral, a madeira de C. lusitanica apresenta boas características tecnológicas para produção de celulose e papel, especialmente pelos índices morfológicos de qualidade observados. The objective of this study was to determine the chemical composition, basic density and tracheids morphological parameters of the wood of Cupressus lusitanica aiming to verify its suitability for cellulosic pulp production. Discs were collected from three 16-year-old trees to determine chemical, physical and morphological characteristics. The morphology of the tracheids was evaluated in the annual rings corresponding to the ages of 4, 7, 10, 13 and 16 years. The pulp quality parameters were calculated from the tracheid parameters. The chemical composition indicated low ash and extractive contents (0.27 and 2.13%, respectively), but high lignin content (32.52%). The basic density (0.375 g cm-3) was smaller than other species of softwood used for pulp production. The mean values of tracheids dimensions observed were 2.41 mm of length, 31.40 µm of width; 25.15 µm of lumen diameter and 3.12 µm of wall thickness, which tended to increase in values with increasing age. In general, C. lusitanica wood presents good technological characteristics for pulp and paper production, especially for the observed quality morphological index. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Wood Science / Revista Ciência da Madeira is the property of Brazilian Journal of Wood Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista de Gestão Ambiental e Sustentabilidade (GeAS) is the property of Revista de Gestao Ambiental e Sustentabilidade / UNINOVE and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A novel alternative was investigated for elevating the xylan content of eucalyptus pulp through xylan deposition in the course of the oxygen delignification stage. The pH in the range of 10-13 was the only variable evaluated, while the other variables were kept constant in a range similar to industrial practice. Xylans were obtained from unbleached and bleached eucalyptus pulps by cold caustic extraction (CCE), giving rise to brown xylan liquor (BXL) and white xylan liquor (WXL), respectively. The liquors were added to a commercial brown pulp during oxygen delignification. The xylan-enriched pulps were subsequently bleached to 90% ISO with the D(EP)D sequence, beaten in a PFI mill and evaluated for their physical and mechanical properties. Xylan deposition occurred at variable degrees depending upon the pH. Pulp bleachability was not impaired by WXL xylan deposition but was slightly negatively affected by BXL xylan. Pulp beatability was improved by both WXL and BXL xylan deposition. The deposited xylan was more stable across bleaching and beating with the WXL xylan than the BXL xylan deposits. At low energy consumption, the deposited xylan improved pulp physical and mechanical properties. Xylan extraction by CCE with subsequent deposition in the oxygen delignification is an interesting technique to manufacture eucalypt pulps of high xylan content. The potential for industrial application is high as no significant modification of current pulp mill installations is needed. [ABSTRACT FROM AUTHOR]

The effect of milling time on the structure of lignin was investigated by analyzing the quantity and molecular size distribution of thioacidolysis products obtained from wood and pulp of eucalypt ( Eucalyptus globulus). After milling, the ability of three solvent systems was determined to completely dissolve the wood or pulp meal. It was found that a mixture of DMSO and 50% aqueous tetrabutylammonium hydroxide was superior to either dimethylacetamide-LiCl or DMSO-tetrabutylammonium fluoride as solvent. By applying the minimum milling time required for complete dissolution, structurally unaltered wood or pulp could be further separated into lignin-carbohydrate fractions. These were analyzed by thioacidolysis. From eucalypt pulp, two different lignin-carbohydrate fractions were obtained, one glucan- and one xylan-enriched fraction, with the latter having more syringyl units in its lignin moieties. The developed solvent system seems to be universal because spruce and flax fibers and pulps could also be dissolved in it after milling. [ABSTRACT FROM AUTHOR]

Aerogels are 3-D nanostructures of non-fluid colloidal interconnected porous networks consisting of loosely packed bonded particles that are expanded throughout their volume by gas and exhibit ultra-low density and high specific surface area. Cellulose-based aerogels can be obtained from hydrogels through a drying process, replacing the solvent (water) with air and keeping the pristine three-dimensional arrangement. In this work, hybrid cellulose-based aerogels were produced and their potential for use as dressings was assessed. Nanofibrilated cellulose (NFC) hydrogels were produced by a co-grinding process in a stone micronizer using a kraft cellulosic pulp and a phenolic extract from Maclura tinctoria (Tajuva) heartwood. NFC-based aerogels were produced by freeze followed by lyophilization, in a way that the Tajuva extract acted as a functionalizing agent. The obtained aerogels showed high porosity (ranging from 97% to 99%) and low density (ranging from 0.025 to 0.040 g·cm−3), as well a typical network and sheet-like structure with 100 to 300 μm pores, which yielded compressive strengths ranging from 60 to 340 kPa. The reached antibacterial and antioxidant activities, percentage of inhibitions and water uptakes suggest that the aerogels can be used as fluid absorbers. Additionally, the immobilization of the Tajuva extract indicates the potential for dentistry applications. [ABSTRACT FROM AUTHOR]