1,720,972 research outputs found
Polysaccharide-based aerogel production for biomedical applications: A comparative review
No full textA comparative analysis concerning bio-based gels production, to be used for tissue regeneration, has been performed in this review. These gels are generally applied as scaffolds in the biomedical field, thanks to their morphology, low cytotoxicity, and high biocompatibility. Focusing on the time interval 2015-2020, the production of 3D scaffolds of alginate, chitosan and agarose, for skin and bone regeneration, has mainly been investigated. Traditional techniques are critically reviewed to understand their limitations and how supercritical CO2-assisted processes could overcome these drawbacks. In particular, even if freeze-drying represents the most widespread drying technique used to produce polysaccharide-based cryogels, supercritical CO2-assisted drying effectively allows preservation of the nanoporous aerogel structure and removes the organic solvent used for gel preparation. These characteristics are essential for cell adhesion and proliferation
Agarose, Alginate and Chitosan Nanostructured Aerogels for Pharmaceutical Applications: A Short Review
No full textIn this short review, drug delivery systems, formed by polysaccharide-based (i.e., agarose, alginate, and chitosan) aerogels, are analyzed. In particular, the main papers, published in the period 2011–2020 in this research field, have been investigated and critically discussed, in order to highlight strengths and weaknesses of the traditional production techniques (e.g., freeze-drying and air evaporation) of bio-aerogels with respect to supercritical CO2 assisted drying. Supercritical CO2 assisted drying demonstrated to be a promising technique to produce nanostructured bio-aerogels that maintain the starting gel volume and shape, when the solvent removal occurs at negligible surface tension. This characteristic, coupled with the possibility of removing also cross-linking agent residues from the aerogels, makes these advanced devices safe and suitable as carriers for controlled drug delivery applications
Biomass Gasification: an Advanced Conceptual Model for Downdraft Reactor
No full textThere is an urgent need for research efforts aimed at developing technologies capable of efficiently gasifying sustainable biomasses composed of organic waste from various industrial processes. This work constitutes a crucial contribution to the field by addressing the pressing need for sustainable biofuels production. It introduces an innovative open-source mathematical model, implemented in Python, designed to simulate the complex process of gasifying advanced biomasses within a downdraft gasifier. Termed the “bi-equilibrium with tar cracking” model, it represents a significant advancement in the modelling of biomass gasification, offering a versatile and comprehensive tool for researchers and engineers in the field. The model’s multi-zone framework is particularly noteworthy, as it meticulously divides the downdraft gasifier into four distinct zones: the drying zone, where moisture content is reduced; the pyrolysis zone, where biomass undergoes thermal decomposition; the separation zone, where tar and other pyrolysis products are destined to different treatments; and the gasification zone, where syngas is produced. This granular approach enables a detailed analysis of each stage, facilitating a deeper understanding of the intricate gasification process. Furthermore, the model’s multi-scale nature incorporates parameters within the separation section, allowing for the simulation of molecular-level phenomena, such as the formation of preferential pathways. These pathways play a pivotal role in determining the composition of the resulting syngas, making the model exceptionally valuable for predicting and optimizing syngas quality
Different Drying Techniques Can Affect the Adsorption Properties of Agarose-Based Gels for Crystal Violet Removal
No full textAgarose-based gels were produced either by freeze-drying or by supercritical drying for crystal violet (CV) removal from aqueous solutions. The microporosity features of these structures highly affected the final adsorption properties. In particular, agarose cryogels were characterized by a macroporous and irregular morphology, with a low value of specific surface area (11 ± 6 m2/g) with respect to the nanoporous agarose aerogels (154 ± 12 m2/g). To test the efficacy of CV removal, two different types of adsorption test were performed, i.e., batch-mode and multi-step mode. Operating in the multi-step mode, the adsorption performance was larger both for cryogels and aerogels, since this adsorption method allowed a more effective contact between CV and agarose adsorbent. In particular, using 300 mg of cryogels, a removal efficiency of 74% was achieved; using the same quantity of aerogels, 96% of removal efficiency was reached after eight steps of adsorption. Desorption of CV from aerogels was realized using ascorbic acid and, after regeneration, 93% of removal efficiency was preserved, even after three cycles in multi-step filtration mode
Supercritical-CO2 Assisted Electrospray to Produce Cellulose Acetate+Rutin Micro-Carriers
No full textSupercritical-CO2 assisted electrospray is a new process used to produce polymeric micro- and nanoparticles characterized by tunable and regular morphologies. The major innovation consists of the addition of supercritical CO2 to the polymeric solution, obtaining a gas expanded liquid having reduced values of viscosity and surface tension. Due to its biodegradability and biocompatibility, cellulose acetate (CA) was selected as polymeric carrier for microparticles production, that can be used for drug delivery applications. Indeed, CA solutions were loaded with a poorly-water soluble compound, rutin (RUT), to improve its bioavailability. The experiments were performed at different CA concentrations (0.5 and 1 wt%) and different RUT concentration, that was varied from 2.5 to 7.5 wt% with respect to CA; the applied voltage was set at 30 kV. CA/RUT microparticles were successfully produced; working at 140 bar and 30 kV, particles characterized by an average diameter of 980±120 nm and networked fibers were obtained, processing 1 wt% CA solution and using a RUT concentration of 7.5 wt% with respect to CA. IR spectroscopy revealed the physical dispersion of RUT into CA particles
Supercritical Phase Inversion to Produce Photocatalytic Active PVDF-coHFP_TiO2 Composites for the Degradation of Sudan Blue II Dye
No full textTiO2-loaded poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-coHFP) membranes were produced by supercritical CO2-assisted phase inversion. Three different TiO2 loadings were tested: 10, 20, and 30 wt% with respect to the polymer. Increasing the TiO2 amount from 10 wt% to 20 wt% in the starting solution, the transition from leafy-like to leafy-cellular morphology was observed in the section of the membrane. When 30 wt% TiO2 was used, the entire membrane section showed agglomerates of TiO2 nanoparticles. These polymeric membranes were tested to remove Sudan Blue II (SB) dye from aqueous solutions. The adsorption/photocatalytic processes revealed that membrane morphology and TiO2 cluster size were the parameters that mainly affected the dye removal efficiency. Moreover, after five cycles of exposure of these membranes to UV light, SB removal was higher than 85%
Production of Photocatalytic Membranes by Supercritical Phase Inversion for the Removal of Antibiotics from Waste-Water
No full textIn recent years, scientific research has faced the numerous problems deriving from the presence of active ingredients in surface and groundwater. Traditional removal methods, such as adsorption and bioremediation, have several disadvantages; thus, in this work, membranes based on cellulose acetate loaded with Fe-N-TiO2, were tested for the photocatalytic degradation of Ceftriaxone Sodium from aqueous solution. The immobilization of the photocatalyst allows to overcome the limits of the photocatalytic process in suspension, which requires expensive and time-consuming post-treatments. Membranes were obtained by supercritical CO2 phase inversion process and were subjected to characterizations such as EDX, TGA, FT-IR, Raman spectroscopy and, subsequently, tested in adsorption tests in the dark and in the presence of visible light, to evaluate their photocatalytic activity. The variations in the concentration of the antibiotic, during the tests conducted, were monitored by HPLC chromatographic analysis. Samples with 10% and 30% by weight of Fe-N-TiO2 demonstrated relatively low adsorption efficiencies of the target contaminant, respectively equal to 22% and 18% in 180 minutes, for reasons related both to the morphology of the samples products, which changes from cellular to finger-like as the photocatalyst load increases, and to the quality of the dispersion. The membrane loaded with 20% by weight of Fe-N-TiO2 allowed a degradation of the model pollutant of 35% in 180 minutes; moreover, the reusability of the membranes was verified. The photocatalytic tests showed that the photocatalytic efficiency was highly correlated to the dispersion of the photocatalyst nanoparticles and to its loading in the polymeric membranes
Supercritical assisted electrospray/spinning to produce PVP+quercetin microparticles and microfibers
No full textThe addition of supercritical CO2 to a polymeric solution allows to achieve an expanded liquid, characterized by reduced viscosity and surface tension. Thanks to this peculiarity, polyvinylpyrrolidone (PVP) microparticles and microfibers loaded with quercetin (QT) were produced, using a supercritical CO2 assisted electrohydrodynamic process. The experiments were performed at different pressure, applied voltage, and polymer concentration; whereas, QT/PVP ratio was maintained constant at 3.5% w/w in all tested solutions. At 3% w/w PVP, particles with an average diameter of 0.77±0.24 μm were produced. At 15% w/w PVP, fibers were instead obtained, with an average diameter of 2.81±1.38 μm. The transition from electrospray to electrospinning occurred as a consequence of the polymer concentration that determined an increase in the solution viscosity. IR spectroscopy demonstrated the physical dispersion of QT into PVP fibers, and DSC showed that this drug was amorphous after processing. QT bioavailability was improved in the loaded fibers; it was released up to 30 times faster than from the unprocessed powder, and more than 90% of its native antioxidant activity was preserved
Towards strengthening resilience of organizations by risk management tools: A scientometric perspective on COVID-19 experience in a healthcare and industrial setting
No full textDuring the COVID-19 pandemic, the healthcare system and the global supply chain were exposed to an unpredicted event, which increased awareness about the need of more effective strategies to support decision-making process and to empower safety barriers. In this work, a combined scientometric and systematic review was performed to analyze tools and methodologies able to combine resilience with more traditional risk assessment, learning from the experience posed by the COVID-19 crisis. Bibliometric and literature content analyses were carried out focusing on resilience management upon the incoming of an unexpected event. The systematic analysis of the methods and models developed on the basis of different pandemic waves provides a natural guide for future research development
Blending recycled poly(lactic acid) (PLA) with elastane recovered from textile fibers: A sustainable valorization approach
No full textThe recycling of elastane from textile waste and its reintegration into polymeric matrices represents a possible pathway towards the achievement of a real circular economy in the textile industry. This study investigates the dissolution and recovery of elastane using environmentally friendly solvents and its subsequent blending with recycled poly(lactic acid) (PLA). Among tested solvents, dimethyl sulfoxide (DMSO) was the most effective, dissolving elastane at 120 °C with a solubility limit of 40.77 mg EL/g DMSO at 160 °C. Recovery via non-solvent induced phase separation (NIPS) allowed for 75–80 % solvent recovery, with residual DMSO reduced down to 5–6 % after drying. Blends of recycled PLA with recovered elastane (5–15 wt.%) were produced via melt extrusion and evaluated for mechanical and thermal properties. Tensile tests revealed that adding elastane reduced the elastic modulus (from 3.52 GPa for PLA to 3.14 GPa for PLA+15) while increasing elongation at break. However, tensile strength declined due to poor interfacial adhesion between PLA and elastane. Dynamic mechanical thermal analysis (DMTA) confirmed elastane's limited compatibility with PLA, showing separate glass transition temperatures at ∼60 °C (PLA) and ∼10 °C (elastane). Differential scanning calorimetry (DSC) indicated an increase in PLA crystallinity (from 19.5 % for PLA to 24.9 % for PLA+5), followed by stabilization around 20.7 % at higher elastane content. Scanning electron microscopy (SEM) revealed elastane dispersion within the PLA matrix, with droplet coalescence at higher elastane concentrations. Despite its limited compatibility, this study highlights the potential for elastane to have a second life and demonstrates the feasibility of incorporating it into recycled PLA. It lays the foundation for future research on compatibilization strategies to improve mechanical performance
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