Search Results (28)

The interaction between clay minerals and electrolyte solutions critically affects waterflooding efficiency in enhanced oil recovery (EOR). This study systematically investigated the adsorption and thermodynamic properties of montmorillonite, illite, and kaolinite in different cationic solutions (K⁺, Na⁺, Ca²⁺, Mg²⁺), integrating adsorption isotherm analysis with immersion calorimetry for the first time. Montmorillonite showed the highest adsorption capacity, with the cation affinity following K⁺ > Na⁺ > Ca²⁺ > Mg²⁺. The highest immersion enthalpy was observed in KCl solution, indicating the dominant roles of ionic radius and solvation energy. Cation adsorption induced deformation of clay lamellae and modification of Si-O and Al-OH groups. These findings suggest that optimizing injected ion composition can enhance reservoir stability and waterflood performance, providing thermodynamic insights for EOR process optimization. Full article

The long-term conservation of Prunus persica (peach), a crop of significant agronomic and genetic value, remains challenging due to its recalcitrance to conventional cryopreservation methods. Low tolerance to dehydration and cryoprotectant toxicity often results in poor survival and regrowth, thereby limiting the reliability of germplasm storage. This study evaluated whether combining an alginate hydrogel matrix with Pluronic F-68 improves vitrification efficiency and post-thaw regeneration of peach shoot tips by enhancing dehydration dynamics and reducing cryo-injury. Shoot tips were immobilized in thin sodium alginate layers on aluminum foil strips, with the hydrogel providing mechanical stabilization and moderating water loss during exposure to PVS3 and subsequent liquid nitrogen immersion. To further mitigate cryoinjury, Pluronic F-68, a non-ionic surfactant with membrane-stabilizing properties, was incorporated into the system. Differential scanning calorimetry revealed that the hydrogel reached complete vitrification after 120 min in PVS3, whereas encapsulated shoot tips required 150 min for full suppression of crystallization. The optimized system achieved 71% post-cryopreservation survival and 40% regrowth, compared with 25% and 9% in non-encapsulated controls. PF-68 accelerated vitrification kinetics, lowered crystallization enthalpies, and improved post-thaw viability. These findings demonstrate that engineered hydrogel–surfactant matrices can stabilize the microenvironment during vitrification and offer a promising approach for the long-term cryopreservation of peach germplasm. Full article

Traditional taco preparation methods, such as oil immersion and steaming, can significantly affect the nutritional and metabolic characteristics of the final product. This study evaluated tacos made with five commercial nixtamalized maize flours and four common fillings (chicharron, beef skirt, potato, and refried beans), processed using three different methods: Plain, Full-Fat, and Patted-Dry. We assessed their chemical composition, starch digestibility, and thermal properties, and measured satiety-related hormone responses in mice. Fillings had a stronger influence on protein, fat, and moisture content than tortilla type. Full-fat tacos exhibited increased amylose–lipid complex formation and a lower gelatinization enthalpy, whereas plain tacos retained more retrograded starch and a crystalline structure. In vitro digestion revealed that Plain tacos, especially those with plant-based fillings, had the highest resistant starch content and the lowest predicted glycemic index. Hierarchical clustering showed that resistant starch, moisture, and gelatinization onset temperature were closely linked in the Plain samples, whereas lipid-driven variables dominated in the Full-Fat tacos. In mice, tacos with a higher resistant starch content led to greater GLP-1 levels, lower ghrelin levels, and reduced insulin responses, suggesting improved satiety and glycemic control. Patted-Dry tacos showed intermediate hormonal effects, supporting their potential as a balanced, health-conscious alternative. These findings demonstrate how traditional preparation techniques can be leveraged to enhance the nutritional profile of culturally relevant foods, such as tacos. Full article

The study and improvement of the corrosion resistance of materials used in concentrated solar power plants is a permanent field of research. This involves determining their chemical stability when in contact with heat transfer fluids, such as molten nitrate salts. Various studies indicate an improvement in the corrosion resistance of iron-based alloys with the incorporation of elements that show high reactivity and solubility in molten nitrate salts, such as Cr and Mo. This study analyzes the kinetic and thermodynamic aspects of the beginning of the corrosion process of ferritic steels immersed in Solar Salt at 400, 500, and 600 °C. The analysis of the kinetic data using the Arrhenius equation and the Transition State Theory shows that an increase in the Cr/Mo ratio reduces the activation energy, the standard formation enthalpy, and the standard formation entropy. This indicates that its incorporation favors the degradation of steel; however, the results show a reduction in the corrosion rate. This effect is possible due to a synergistic effect by the formation of insoluble Fe-oxide layers that favor the formation of a Cr oxide layer at the Fe-oxide-metal interface, which limits the subsequent oxidation of Fe. Full article

This study aims to evaluate the adsorptive, adhesive, and wetting energetic properties of five commercially available cleansers in contact with model dental polymer (PMMA). It was assumed that the selected parameters allow for determining the optimal concentration and place of key component accumulation for antibacterial activity in the bulk liquid phase and prevention of oral plaque formation at the prosthetic material surface. The adsorptive (Gibbs’ excesses Γ_LV, critical micellar concentration) and thermal (entropy and enthalpy) surface characteristics originated from surface tension γ_LV(T) and γ_LV(C) dependences. The surface wetting properties were quantified upon the contact angle hysteresis formalism on the advancing Θ_A, receding Θ_R contact angles, and γ_LV as the input data, which yield a set of wettability parameters: 2D adsorptive film pressure, surface free energy with its dispersive and polar components, work of adhesion, and adhesional tension, considered as interfacial interaction indicators. In particular, molecular partitioning K_p and Γ_LV are indicators of the efficiency of particular active substance accumulation in the volume phase, while γ_SV, a = Γ_SL/Γ_LV, and W_A point to the degree of its accumulation at the immersed polymer surface. Finally, the liquid penetration coefficient PC and the Marangoni temperature gradient-driven liquid flow speed were estimated. Full article

To understand why hematite of different genesis behave diversely in flotation systems, this study assesses the flotation response at pH 5 of bulk (morphology, texture, Crystal Preferential Orientation (CPO)) plus interfacial (surface area, zeta potential, immersion enthalpy, contact angle, induction time) characteristics of species formed under distinct metamorphic conditions: low-strain deformation (Hematite-1) versus high-strain deformation (Hematite-2). Hematite-2 (predominantly composed of specular and lamellar morphologies) shows (001) CPO and exhibits fewer Fe sites on its surface that undergo doubly coordinated Fe-OH when exposed to moisture. This results in a less reactive surface associated with a less ordered adsorbed water layer than Hematite-1, which is predominantly composed of granular and sinuous hematite. Those characteristics lead to a naturally hydrophobic behavior characterized by the exothermic energy below the Critical Immersion Enthalpy ($-{∆\mathrm{H}}_{\mathrm{i}\mathrm{m}\mathrm{m}}$ < 200 mJ/m²), lower values of zeta potential due to attenuated dissociation of Fe-OH_(surf), lower induction time (47 ms vs. 128 ms), higher contact angle (39° vs. 13°), and higher flotation recovery (21% vs. 12%) than Hematite-1. Full article

Various drying temperatures impact the texture of pasta and cause different drying defects. These by-products could reflect techno-functional characteristics which are suitable for cereal products. This research addresses the influence of low (LT) and high (HT) drying pasta defects with two granulations on the theoretical and functional characteristics of hard dough biscuits. By shifting from a LT to HT drying temperature, a higher onset and peak temperature was found due to the higher mobility of starch molecules with increasing crystalline stability. The lowest transition enthalpy of biscuit formulation was also observed for higher incorporation of fine HT pasta regrinds. The algebraic model of dough with consistography determined the poor-extensible gluten and a high resistance with a greater value of P/L and P indices for LT regrinds. Scanning electron microscopy revealed a heavy and dense texture with immersed starch granules for additional fine regrinds while coarse samples caused swell granules with greater diameter. Moreover, fine HT regrinds reflected the lowest L* value for biscuit due to heat gradient tension with the hard milling process which leads to protein denaturation with decreasing nitrogenous. Full article

Solid–liquid interfacial phenomena play an essential role in our everyday lives and are often regarded as the outcome of interactions at the solid–liquid interface. However, the intricately intrinsic mechanism underlying interfacial interactions renders in situ simulations and direct measurements challenging. As an effective analytic method for studying solid–liquid interfacial interactions, microcalorimetry can provide the most basic thermodynamic information (including changes in enthalpy, entropy, and Gibbs free energy during solid–liquid binding/separation processes), which is extremely crucial for understanding interaction directionality and limitation. This review is dedicated to highlighting the pivotal role of microcalorimetry in studying solid–liquid immersion and adsorption processes. Specifically, we provide an overview of the commonly employed microcalorimetric methods, including differential scanning calorimetry (DSC), isothermal titration calorimetry (ITC), and immersion microcalorimetry (IM), and delve into the influence factors of enthalpy change, and finally discuss the specific applications of microcalorimetry in studying various solid–liquid binding processes. There remains a vast expanse of thermodynamic information regarding solid–liquid interactions that await exploration via calorimetry. Full article

In Peru, there are more than four thousand plants with medicinal properties, including muña, which helps digestion and improves health. The way to preserve these plants is drying up. The objective of this research was to investigate the coefficient of diffusion, enthalpy, and Gibbs free energy in the drying kinetics of muña leaves. Different pretreatments were carried out on the samples (without pretreatment, as well as treated by immersion in 1% ascorbic acid and bleaching at 60 °C for 30 s), and they were dehydrated at three temperatures (40, 50, and 60 °C). The drying kinetics were modeled using eight mathematical models to represent the drying curve. The water content was reduced by the drying process. The logarithmic model was selected, as it showed the best fit to represent the drying kinetics of the muña. Activation energy values were similar between treatments (p > 0.05). The increase in temperature decreases the enthalpy and entropy and increases the Gibbs free energy with the effective diffusion coefficient. The drying kinetics allows one to determine the drying time for the storage of the product and the thermodynamic properties for the design of the equipment. Full article

Three activated carbons with different physicochemical characteristics are prepared and their N₂ isotherms at 77 K and CO₂ isotherms at 273 K are determined. The energetic interaction between three activated carbons with different physicochemical properties, and two hydrocarbons as pure liquids and as binary mixtures at different concentrations, was characterized by determining the enthalpy of immersion, in order to evaluate the effect of adsorbents and adsorbates, as well as that of the addition of another adsorbate to the system. For the pure solvents, the enthalpy of immersion (ΔH_i) is higher for the aromatic compound (−94.98 to −128.80 J g⁻¹) than for the aliphatic compound (−16.36 to −53.35 J g⁻¹); for the mixtures, the values are between −36.39 and −98.37 J g⁻¹, where the interaction increases with the solid that was subjected to thermal treatment and presented the lowest content of surface oxygenated groups, while the energetic parameter decreases with the solid that presents chemical modification with nitric acid, behavior that is evident in the pure solvents and in the mixtures. Activated carbons have a CO₂ adsorption between 3.43 and 3.79 mmol g⁻¹. Full article

The study evaluates the performance of laboratory, single-layered particleboards made out of fructose-hydroxymethylfurfural-bishexamethylenetriamine (SusB) adhesive as a sustainable alternative. Several production parameters such as mat moisture content (MMC), adhesive amount and press time were varied and their effect on the bonding efficiency investigated. The internal bond strength (IB) and thickness swelling after 24 h of water immersion (TS) were taken as evaluation criteria for the bonding efficiency. pMDI-bonded particleboards were produced as fossil-based, formaldehyde-free reference. Particleboard testing was complemented by tensile shear strength measurements and thermal analysis. It was found that the MMC has the highest impact on the internal bond strength of SusB-bonded particleboards. In the presence of water, the reaction enthalpy of the main curing reaction (occurring at 117.7 °C) drops from 371.9 J/mol to 270.5 J/mol, leading to side reactions. By reducing the MMC from 8.7%, the IB increases to 0.61 N/mm², thus surpassing P2 requirements of the European standard EN312. At a press factor of 10 s/mm, SusB-bonded particleboards have a similar IB strength as pMDI-bonded ones, with 0.59 ± 0.12 N/mm² compared to 0.59 ± 0.09 N/mm². Further research on the improvement of the dimensional stabilization of SusB-bonded PBs is needed, as the TS ranges from 30–40%. Full article

Porous iron-based scaffolds were prepared by the simple replica method using polyurethane foam as a template and applying the sintering process in a tube furnace. Their surface morphology was characterized using scanning electron microscopy (SEM) and phase homogeneity was confirmed using X-ray diffraction (XRD). Corrosion behavior was determined using immersion and potentiodynamic polarization methods in phosphate buffered saline (PBS). The surface energy was calculated by studying the changes of enthalpy of calorimetric immersion. A preliminary biological test was also carried out and was done using the albumin adsorption procedure. Results of our work showed that in using the simple replica method it is possible to obtain iron biomaterial with morphology and mechanical properties almost identical to bones, and possessing adequate wettability, which gives the potential to use this material as biomaterial for scaffolds in orthopedics. Full article

Peroxide has been considered a chemical agent that can be used to tune the properties of polymeric materials. This research evaluated the influence of different concentrations of dialkyl peroxides on the mechanical, thermal, and morphological properties of linear low-density polyethylene (LLDPE) and ultra-high molecular weight polyethylene (UHMWPE). The neat polymer, as well as those with the addition of 1% and 2% by mass of dialkyl peroxides, were subjected to compression molding and immersion in water for 1 h, under controlled temperatures of 90 °C. The values of the gel content found in the samples indicated that the addition of peroxide to the LLDPE and to the UHMWPE promoted the formation of a reticulated network. The structure obtained by the crosslinking led to less reorganization of the chains during the crystallization process, resulting in the formation of imperfect crystals and, consequently, in the reduction in melting temperatures, crystallization and enthalpy. The mechanical properties were altered with the presence of the crosslinker. The polymers presented had predominant characteristics of a ductile material, with the occurrence of crazing with an increased peroxide content. Full article

The liquid-phase adsorption of toluene in cyclohexane and hexane solutions on modified activated carbons was evaluated; the energy involved in the interaction between these solutions and the solids was determined by immersion enthalpies of pure solvents and their mixtures, and the contribution of the system constituents was calculated by differential enthalpies. The thermal treatment generated modifications that favored adsorption and interaction with the evaluated solutions, since it increased the textural parameters and the basic character of the samples. Cyclohexane could create greater competition with the adsorption sites compared to hexane, but it favored the increase in adsorption capacities (0.416 to 1.026 mmol g⁻¹) and the interactions with the solid evaluated through the immersion enthalpies. The immersion enthalpies of pure solvents (−16.36 to −112.7 J g⁻¹) and mixtures (−25.65 to −104.34 J g⁻¹) had exothermic behaviors that were decreasing due to the possible displacement of solvent molecules when increasing the solute concentration in the mixtures. The differential enthalpies for toluene were negative (−18.63 to −2.14 J), mainly due to the π–π interaction with the solid, while those of the solvent–solid component tended to be positive values (−4.25 to 55.97 J) due to the displacement of the solvent molecules by those of toluene. Full article

The fabrication of form-stable phase change materials (FS-PCMs) usually involves four manufacturing processes: mixing, immersion, stabilization, and sintering. In each process, the operation parameters could affect the performance of the fabricated PCM composite. To gain an efficient and low-cost method for large-scale production of the molten salts/expanded graphite (EG) composite FS-PCMs, the effects of different operating parameters were investigated, including the stirring speed, evaporation temperature, melt-impregnation, cold-pressing pressure, and sintering temperature on the densification, microstructure, and thermophysical properties of the composite FS-PCMs. It was found that the microstructure, the morphology and durability, and the thermophysical properties such as thermal conductivity and specific heat enthalpy depended highly on the operating parameters. The following optimal operating parameters of the Ca(NO₃)₂–NaNO₃/EG composite FS-PCMs are suggested: the stirring speed of 20 rpm, the evaporation temperature of 98 °C, the melt-impregnation temperature of 280 °C, the cold-pressing pressure of 8 MPa, and the sintering temperature of 300 °C. The results of the present work can provide valuable insights for the large-scale production of the composite FS-PCMs. Full article