Eucalyptus bleached kraft pulp-ionic liquid inks for 3D printing of ionogels and hydrogels.

3D printing has been recently recognized as one of the most promising technologies due to the multiple options to fabricate cost-effective and customizable objects. However, the necessity to substitute fossil fuels as raw materials is increasing the research on bio-based inks with recyclable and eco-friendly properties. In this work, we formulated inks for the 3D printing of ionogels and hydrogels with bleached kraft pulp dissolved in [Emim][DMP] at different concentrations (1-4 wt%). We explored each ink's rheological properties and printability and compared the printability parameters with a commercial ink. The rheological results showed that the 3 % and 4 % cellulose-ionic liquid inks exhibited the best properties. Both had values of damping factor between 0.4 and 0.7 and values of yield stress between 1900 and 2500 Pa. Analyzing the printability, the 4 wt% ink was selected as the most promising because the printed ionogels and the hydrogels had the best print resolution and fidelity, similar to the reference ink. After printing, ionogels and hydrogels had values of the elastic modulus (G') between 103 and 104 Pa, and the ionogels are recyclables. Altogether, these 3D printed cellulose ionogels and hydrogels may have an opportunity in the electrochemical and medical fields, respectively.

Effect of autohydrolysis and ionosolv treatments on eucalyptus fractionation and recovered lignin properties.

Wood fractionation is key for the integral valorization of its three main components. In this sense, recovering the hemicellulosic fraction after the ionosolv treatment of lignocellulosic materials is one of the main drawbacks of this process. Thus, the incorporation of a previous autohydrolyisis step to recover the hemicellulosic sugars before the ionosolv treatment is an interesting approach. The influence of both treatments, autohydrolysis and ionosolv, on the biomass fractions recovery yields was studied by a central composite design of experiments, varying the autohydrolysis temperature in a 175-195 °C range and ionosolv time between 1-5 h. Lignin recovery and cellulose purity were maximized at 184 °C and 3.5 h of autohydrolysis temperature and ionosolv time, respectively. In addition, lignin properties were incorporated to the statistical model, revealing lignin recondensation at severe conditions and a higher influence of the ionosolv treatment on lignin characteristics. These results remarked the importance of studying the effect of both treatments in the whole fractionation process and not each process separately and enhanced the understanding of the treatments combination in a complete fractionation biorefinery approach.

Organosolv and ionosolv processes for autohydrolyzed poplar fractionation: Lignin recovery and characterization.

Biomass fractionation plays a major role in the search for competitive biorefineries, where the isolation and recovery of the three woody fractions is key. In this sense, we have used autohydrolyzed hemicellulose-free poplar as feedstock to compare two fractionation processes, organosolv and ionosolv, oriented to lignin recovery. The recovered lignins were then characterize by different techniques (NMR, GPC, TGA). Both treatments were tested at different temperatures to analyze temperature influence on lignin recovery and properties. The highest lignin recovery was obtained with the ionosolv process at 135 °C, reaching a solid yield of ~70%. Lignin characterization showed differences between both treatments. Lignins enriched in C-O linkages and G units were recovered with the organosolv process, where increasing temperature led to highly depolymerized lignins. However, lignins with higher C-C linkages and S units contents were obtained with the ionosolv process, producing more thermically stable lignins. In addition, increasing temperature caused lignin repolymerization when employing ionic liquids as solvents. Therefore, this work outlines the most important differences between ionosolv and organosolv processes for biomass fractionation, focusing on lignin recovery and its properties, which is the first step in order to valorize all biomass fractions.

Cellulose ionogels, a perspective of the last decade: A review.

Cellulose ionogels have been extensively studied due to the variability of their properties and applications. The capability of trapping an ionic liquid in a biodegradable solid matrix without losing its properties makes this type of material a promising substitute for fossil fuel-derived materials. The possibility to formulate ionogels chemically or physically, to choose between different ionic liquids, cellulose types, and the possibility to add a wide range of additives, make these ionogels an adaptable material that can be modified for each target application in many fields such as medicine, energy storage, electrochemistry, etc. The aim of this review is to show its versatility and to provide a summary picture of the advances in the field of cellulose ionogels formulation (chemical or physical methods), as well as their potential applications, so this review will serve as a stimulus for research on these materials in the future.

Acidic depolymerization vs ionic liquid solubilization in lignin extraction from eucalyptus wood using the protic ionic liquid 1-methylimidazolium chloride.

Protic ionic liquids have been proposed as effective solvents for the selective extraction of lignin from wood. In this work, the protic ionic liquid 1-methylimidazolium chloride has been used to extract lignin at different biomass loadings, temperatures, and times to understand the influence of treatment severity on the lignin dissolution mechanism. The maximum lignin recovery (82.35 g lignin/100 g biomass lignin) was achieved at 10% (w/w) biomass loading, 135 °C, and 6 h. An increase in treatment severity leads to an acid cleavage of ether linkages, which increases the average molecular weight and thermal stability of lignins due to C-C repolymerization. HSQC-NMR analysis showed the effect of operating conditions on the predominant mechanism of lignin depolymerization. At mild conditions, there is a preferential degradation of G units (the typical depolymerization mechanism of ionic liquid treatments); but at the most severe conditions, S units are predominantly removed, as usually occurs in acidic treatments. This work contributes to better understanding the different lignin extraction mechanisms occurring with a protic ionic liquid depending on different operating conditions.

Chitosan-reinforced cellulosic bionogels: Viscoelastic and antibacterial properties.

New chitosan-reinforced cellulosic bionogels were successfully formulated with different chitosan loadings (0.25, 0.5, 0.75, and 1 wt/wt. %). These materials were developed using cholinium lysinate, a bio-ionic liquid, being an ecological alternative to conventional ionogels. The rheological properties of these materials showed that all the studied viscoelastic properties were higher (elastic moduli, G'; loss moduli, G"; and complex viscosity, η*) as the chitosan loading increased. The reinforced bionogels were physical weak gels, and the proposed mechanism of formation was by hydrogen bonds. The bionogel with 1 wt/wt. % chitosan loading exhibited the highest viscoelastic properties (for 4 Hz, G': 552 kPa, G": 99 kPa, and η*: 22 kPa·s). Regarding the antibacterial properties, these gels showed a good inhibitory capacity to S. aureus and E. coli, especially against the latter bacterium. For these reasons, these novel ecofriendly gels are promising in the pharmaceutical/medical and biosensors sectors to develop new functional materials.

Viscoelastic properties of physical cellulosic bionogels of cholinium lysinate.

Novel ionogels with different cellulose contents, namely, 0.5, 1, 1.5 and 2 wt%, were formulated with cholinium lysinate (ChLys), and the rheological properties were evaluated at 3 and 7 days postgelation. Because of the biobased compounds contained in these ionogels, in this work, they are denoted as bionogels. These materials have great potential to yield functional biomaterials for use in the medical/pharmacological sector. Some knowledge of how cellulose is dissolved in ChLys was necessary to formulate the bionogels. The dissolution time was studied for each bionogel, with the dissolution times being 3, 4, 4.5, and 6.5 h for 0.5, 1, 1.5, and 2% cellulose, respectively. The bionogel with a 2% cellulose load had the highest rheological properties, i.e. elastic modulus (G'), loss modulus (G″) and complex viscosity (η*), on the studied postgelation days: G' (3 days): 0.7-50 kPa, G' (7 days): 1-100 kPa, G″ (3 days): 0.1-10 kPa, and G″ (7 days): 0.2-20 kPa, η* (3 days): 0.2-200 kPa s and η* (7 days): 0.4-300 kPa s. The postgelation time is an important parameter in the formulation of bionogels, since at 3 days postgelation, the networks continued to be constituted. Regarding classification, these bionogels were weak physical gels.

Tuning the rheological properties of cellulosic ionogels reinforced with chitosan: The role of the deacetylation degree.

The rheological and thermal properties of formulated cellulosic ionogels reinforced with chitosan with 54-84% deacetylation degrees (DDs) were studied. The ionogels were stable, and the linear viscoelastic regions (LVRs) were determined. The rheological spectra of the ionogels revealed strong physical gels. Moreover, the effect of the DD on the viscoelastic properties was significant. The ionogel reinforced with chitosan with a DD of 84% exhibited the greatest viscoelastic properties (G': ∼10.6 kPa, G": 20.6-1.7 kPa, and η*: 200-0.05 kPa s). The ionogels exhibited the same glass transition temperature, which was approximately -98 °C, and a melting temperature of 40 °C. In addition, these materials were shown to be thermoreversible. This study provided basic rheological and thermal evidence that could be used to design new ionogels reinforced with chitosan with a specific DD for use as scaffolds for wound management.

Effect of autohydrolysis on Pinus radiata wood for hemicellulose extraction.

The extraction of hemicellulose from pine wood was studied by applying autohydrolysis treatment. A central composite experimental design was carried out using different temperatures (150-190 °C) and times (30-90 min) to select the most favorable operating conditions for maximizing the extraction of hemicellulose and minimizing its degradation. This liquid phase was analyzed by HPLC to quantify oligosaccharides, monosaccharides and degradation products. The composition of the autohydrolyzed wood was determined and characterized, employing FTIR and TGA. Herein, 60% of the hemicelluloses were extracted under a temperature of 170 °C in 60 min, presenting primarily in an oligomeric form in the liquid phase, with the solid phase remaining enriched in cellulose and lignin.

Combining autohydrolysis and ionic liquid microwave treatment to enhance enzymatic hydrolysis of Eucalyptus globulus wood.

The combination of autohydrolysis and ionic liquid microwave treatments of eucalyptus wood have been studied to facilitate sugar production in a subsequent enzymatic hydrolysis step. Three autohydrolysis conditions (150 °C, 175 °C and 200 °C) in combination with two ionic liquid temperatures (80 °C and 120 °C) were compared in terms of chemical composition, enzymatic digestibility and sugar production. Morphology was measured (using SEM) and the biomass surface was visualized with confocal fluorescence microscopy. The synergistic cooperation of both treatments was demonstrated, enhancing cellulose accessibility. At intermediate autohydrolysis conditions (175 °C) and low ionic liquid temperature (80 °C), a glucan digestibility of 84.4% was obtained. Using SEM micrographs, fractal dimension (as a measure of biomass complexity) and lacunarity (as a measure of homogeneity) were calculated before and after pretreatment. High fractals dimensions and low lacunarities correspond to morphologically complex and homogeneous samples, that are better digested by enzyme cocktails.

Self-organizing maps and learning vector quantization networks as tools to identify vegetable oils.

Self-organizing map (SOM) and learning vector quantification network (LVQ) models have been explored for the identification of edible and vegetable oils and to detect adulteration of extra virgin olive oil (EVOO) using the most common chemicals in these oils, viz. saturated fatty (mainly palmitic and stearic acids), oleic and linoleic acids. The optimization and validation processes of the models have been carried out using bibliographical sources, that is, a database for developing learning process and internal validation, and six other different databases to perform their external validation. The model's performances were analyzed by the number of misclassifications. In the worst of the cases, the SOM and LVQ models are able to classify more than the 94% of samples and detect adulterations of EVOO with corn, soya, sunflower, and hazelnut oils when their oil concentrations are higher than 10, 5, 5, and 10%, respectively.