A general framework of classical non-local density functional theory (NLDFT) is presented, in order to consider the adsorption of spherical molecules in porous materials of any geometry. Fluid-fluid ...interactions and fluid-solid interactions can be repulsive or attractive. Some techniques that have been developed for the computation of weighted densities of hard-spheres are extended to attractive ones, in order to deal with an arbitrary pore geometry. This way, the computation method introduced in this work is validated by a comparison with analytical results for simple cases, and is directly applied to more complex systems. Density distributions depending on multi-dimensional effects are presented, and some radial distribution functions are recovered from NLDFT computations. Finally, the case of attractive continuous curved walls is detailed, which represents a large variety of real systems (e.g. micro and mesoporous silica, zeolites, carbonaceous nanoporous materials, etc.). With the new way of computation proposed, a general solution is presented, valid for any shape of continuous pore surface, by considering mathematical properties of discrete geometry due to the discretisation of the computational space with FFT computations.
A theoretical molecular simulation study of the encapsulation of gaseous SO2 at different temperature conditions in a type II porous liquid is presented here. The system is composed of cage ...cryptophane-111 molecules that are dispersed in dichloromethane, and it is described using an atomistic modelling of molecular dynamics. Gaseous SO2 tended to almost fully occupy cryptophane-111 cavities throughout the simulation. Calculations were performed at 300 K and 283 K, and some insights into the different adsorption found in each case were obtained. Simulations with different system sizes were also studied. An experimental-like approach was also employed by inserting a SO2 bubble in the simulation box. Finally, an evaluation of the radial distribution function of cryptophane-111 and gaseous SO2 was also performed. From the results obtained, the feasibility of a renewable separation and storage method for SO2 using porous liquids is mentioned.
Sequestration of acid gas in geological formations is a disposal method with potential economic and environmental benefits. The process is governed by variables such as gas–water interfacial tension, ...wetting transition, and gas adsorption into water, among other things. However, the influence of the pressure and temperature on these parameters is poorly understood. This study investigates these parameters using coarse-grained molecular dynamics (CG-MD) simulations and density gradient theory (DGT). Simulations were carried out at 313.15 K and a pressure range of 0–15 MPa. A comparison was made against H2S–water systems to clarify the effects of adsorption on interfacial tension due to vapor–liquid–liquid equilibrium. The predicted H2S–water interfacial tension and phase densities by CG-MD and DGT matched the experimental values well. The adsorption can be quantified via the Gibbs Adsorption function Γ12, which correlated well with the three-phase transition. On the one hand, pressure increments below the three-phase transition revealed a significant adsorption of H2S. On the other hand, above the three-phase transition, the Gibbs Adsorption capacity remained constant, which indicated a saturation of H2S at the water surface due to liquid–liquid equilibrium. Finally, H2S behaves markedly differently in wetting transition, rather than the involved for CO2 to different molecular layers beneath the surface of aqueous solutions. In this respect, H2S is represented by a first-order wetting transition while CO2 presents a critical wetting. Finally, it has also been found that the preferential adsorption of H2S over the H2O interface is greater if compared to that of CO2, due to its strong interaction with water. In fact, we have also demonstrated that CO2 under triphasic conditions strongly influences the wetting of the ternary system.
Rising trends in fish filleting are increasing the amount of processing by-products, such as skins of turbot, a flatfish of high commercial value. In line with circular economy principles, we propose ...the valorization of turbot skins through a two-step process: initial gelatin extraction described for the first time in turbot, followed by hydrolysis of the remaining solids to produce collagen hydrolysates. We assayed several methods for gelatin extraction, finding differences in gelatin properties depending on chemical treatment and temperature. Of all methods, the application of NaOH, sulfuric, and citric acids at 22 °C results in the highest gel strength (177 g), storage and loss moduli, and gel stability. We found no relation between mechanical properties and content of pyrrolidine amino acids, but the best performing gelatin displays higher structural integrity, with less than 30% of the material below 100 kDa. Collagen hydrolysis was more efficient with papain than alcalase, leading to a greater reduction in Mw of the hydrolysates, which contain a higher proportion of essential amino acids than gelatin and show high in vitro anti-hypertensive activity. These results highlight the suitability of turbot skin by-products as a source of gelatin and the potential of collagen hydrolysates as a functional food and feed ingredient.
Fluorinated ionic liquids (FILs) have received increasing attention due to their physicochemical properties. They allow us to enlarge the tuneability power of traditional ionic liquids. With the aim ...to understand the thermodynamic behavior of these compounds, a study of solid–fluid transitions using differential scanning calorimetry, thermogravimetric analysis, rheology, and molecular dynamics simulation has been performed. A comparison between different cations, anions, and hydrogenated alkyl chains was carried out using ionic liquids with fluorinated alkyl chain lengths equal to or longer than four carbon atoms. In this work, we provide evidence of the fluorinated domain influence on the thermodynamic behavior of these compounds. Moreover, the results suggest that the nanosegregation of the fluorous domains might be an interesting structural feature that modifies and/or enhances the rich phase behavior of the FILs, increasing the probability of these compounds to adopt different conformations. This information is crucial to design the best FIL and can increase their potential on a wide range of applications.
The expansion of fish filleting, driven by the increasing demand for convenience food, concomitantly generates a rising amount of skinning by-products. Current trends point to a growing share of ...aquaculture in fish production, so we have chosen three established aquaculture species to study the properties of gelatin extracted from their skin: rainbow trout, commonly filleted; and seabass and seabream, marketed whole until very recently. In the first case, trout skin yields only 1.6% gelatin accompanied by the lowest gel strength (96 g bloom), while yield for the other two species exceeds 6%, and gel strength reaches 181 and 229 g bloom for seabass and seabream, respectively. These results are in line with the proportion of total imino acids analyzed in the gelatin samples. Molecular weight profiling shows similarities among gelatins, but seabass and seabream gelatins appear more structured, with higher proportion of β-chains and high molecular weight aggregates, which may influence the rheological properties observed. These results present skin by-products of seabream, and to a minor extent seabass, as suitable raw materials to produce gelatin through valorization processes.
This work contributes with experimental information of the properties of ethylene glycol-based Co3O4 nanofluids. Thermal conductivity, high-pressure density and rheological characterization were ...performed in the temperature range T=(283.15–323.15)K. Thermal conductivity and rheological behaviour were studied for nanofluid samples with concentrations of Co3O4 nanoparticles up to 25% in weight fraction whereas the densities of the nanofluid were analysed up to 5% at pressures up to 45MPa. Thermal conductivity showed in the range studied an increase with weight fraction and a decrease with temperature. A volumetric contractive behaviour was observed, and an increment in the nanoparticles concentration leads to a clear departure from ideal behaviour. The tests performed to analyse rheological properties showed that the viscosity of the nanofluids is nearly independent of the shear rate, thus evidencing the characteristic behaviour of a Newtonian fluid. Experimental viscosity and thermal conductivity were also compared with the estimations provided by several semiempirical equations proposed in the literature.
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•An experimental study of nanofluids stability was carried out.•The effects of Al2O3-SDBS over the thermos-physical properties were investigated.•The nanofluid with higher temporal ...stability was Al2O3 0.5 wt% and SDBS 0.32 wt%.•Surface tension increased as the concentration of the Al2O3 nanoparticles increased.•Newtonian behaviour and values close to those of water were found with SDBS.
Nanofluids are thermo-fluids engineered by dispersing nanosized particles in conventional base fluids used in heat transfer applications. In this experimental study, the temporal stability and thermophysical properties of water-based alumina nanofluids, such as thermal conductivity, surface tension and viscosity, were evaluated at three different concentrations (0.1 wt%, 0.5 wt%, and 1.0 wt%) using sodium dodecyl benzene sulfonate (SDBS) as dispersant agent. The results showed that the nanofluid prepared with 1.0 wt% exhibits thermal conductivity enhancements between 11% and 15% compared to deionized water. Additionally, a pseudoplastic behaviour was identified by means of a rheological study, which increased as the nanoparticle concentration increased. Nevertheless, the nanofluids with SDBS showed a Newtonian behaviour and viscosity values close to those of water, which is suitable to avoid frictional losses in pump processes. In turn, surface tension increases with the amount of DI-water in Al2O3 concentrations, but it decreases with the addition of SDBS, which has an important effect on the boiling applications of nanofluids. This work was carried out to highlight the importance of nanofluids stability in function of the surfactant added and the nanoparticle concentration, in the measurement of significant thermophysical properties such as surface tension, viscosity and thermal conductivity, which could be used to explain the nanofluids behaviour in different thermal devices.
The aim of this work is to study the evolution of the modern feed industry in Italy. Livestock feeding changed during the nineteenth century with the spread of oilseed cakes. In European countries ...with more advanced agriculture, traditional forages were gradually replaced by a new range of products made from tropical seeds and vegetable oils. Italy was among the European countries that created an industry for the manufacture of oilseed cakes during the nineteenth and twentieth centuries. In the 1930s, zootechnical feeding was modernized with the advent of compound feeds, which have been widely used since the mid-twentieth century. Italy became a European leader in feed manufacture, as the economic boom and increased purchasing power led to greater consumption of meat and dairy products. Though Italian and European production capacity remained high at the beginning of the twenty-first century, a new phase began with the emergence of other feed-producing countries and the impact of the international debate on the negative effects of intensive livestock farming on animal living conditions and ecological balances. The Italian case shows how the history of the feed industry constitutes an important chapter in the modernization of contemporary agriculture.
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