Interfacial tension of ethanol, water, and their mixtures in high pressure carbon dioxide: Measurements and modeling

Machine Learning-Based Interfacial Tension Equations for (H2 + CO2)-Water/Brine Systems over a Wide Range of Temperature and Pressure

Large-scale underground hydrogen storage (UHS) plays a vital role in energy transition. H2-brine interfacial tension (IFT) is a crucial parameter in structural trapping in underground geological locations and gas-water two-phase flow in subsurface porous media. On the other hand, cushion gas, such as CO2, is often co-injected with H2 to retain reservoir pressure. Therefore, it is imperative to accurately predict the (H2 + CO2)-water/brine IFT under UHS conditions. While there have been a number of experimental measurements on H2-water/brine and (H2 + CO2)-water/brine IFT, an accurate and efficient (H2 + CO2)-water/brine IFT model under UHS conditions is still lacking. In this work, we use molecular dynamics (MD) simulations to generate an extensive (H2 + CO2)-water/brine IFT databank (840 data points) over a wide range of temperature (from 298 to 373 K), pressure (from 50 to 400 bar), gas composition, and brine salinity (up to 3.15 mol/kg) for typical UHS conditions, which is used to develop an accurate and efficient machine learning (ML)-based IFT equation. Our ML-based IFT equation is validated by comparing to available experimental data and other IFT equations for various systems (H2-brine/water, CO2-brine/water, and (H2 + CO2)-brine/water), rendering generally good performance (with R2 = 0.902 against 601 experimental data points). The developed ML-based IFT equation can be readily applied and implemented in reservoir simulations and other UHS applications.

Contact angle of ethanol, water, and their mixtures on stainless steel surfaces in dense carbon dioxide

HYPOTHESIS

Contact angle can be a key parameter in chemical engineering. However, the development and the optimization of numerous processes using supercritical CO2, considered as environmentally friendly, require new measurements under dense CO2 atmosphere. Besides, the influence of the roughness or the wetting regime on the contact angle is known at ambient conditions but remains to be discussed for systems under high pressure.

EXPERIMENTAL

Contact angle measurements of ethanol, water, and their mixtures, with ethanol mass fractions ranging from 0.25 to 0.75, on two stainless steels in saturated CO2 at pressures ranging from 0.1 MPa to 15.1 MPa, and at313 K and 333 K were carried out in a set-up improving mass transfer between the studied liquid and the continuous fluid phase. Stainless steel surfaces have been characterized by atomic force and scanning electron microscopies allowing the application of the Wenzel equation.

FINDINGS

Ethanol wetted totally both stainless steels while contact angles of all other liquids were increased by the rise of pressure, with contact angles up to 128° for water at 15.1 MPa. Trapped bubbles were observed at the solid/liquid interface and the bubble formation is discussed. Furthermore, the potential influence of bubble presence on the wetting regime is prospected through the question: could the pressure rise modify the wetting regime?

Optimization of the Electrospray Process to Produce Lignin Nanoparticles for PLA-Based Food Packaging

The development of new processing methods is required in order to meet the continuous demand for thinner films with excellent barrier properties for food packaging and other applications. In this study, rice husk organosolv lignin nanoparticles were prepared using the electrospray method, which were applied to produce polylactic acid (PLA)-based films for food packaging. The effect of the following electrospray parameters has been investigated: lignin concentration (LC) ranging from 5-50 mg/mL, flow rate (FR) from 0.5-1 mL/min, applied voltage from 10-30 kV, and tip-to-collector distance (TCD) from 10-25 cm, on the morphology, size, polydispersity index (PDI), and Zeta potential (ZP) of lignin nanoparticles (LNPs). The response surface methodology with a Box-Behnken design was applied to optimize these parameters, while dynamic light scattering (DLS) and scanning electron microscopy (SEM) analyses were used to characterize the controlled LNPs. The results showed that the LNPs shape and sizes represent a balance between the solvent evaporation, LC, applied voltage, TCD and FR. The application of optimal electrospray conditions resulted in the production of LNPs with a spherical shape and a minimal size of 260 ± 10 nm, a PDI of 0.257 ± 0.02, and a ZP of -35.2 ± 4.1 mV. The optimal conditions were achieved at LC = 49.1 mg/mL and FR = 0.5 mL/h under an applied voltage of 25.4 kV and TCD = 22 cm. Then, the optimized LNPs were used to improve the properties of PLA-based films. Three types of PLA-lignin blend films were casted, namely lignin/PLA, LNPs/PLA and PLA-grafted LNPs. PLA-grafted LNPs exhibited a more uniform dispersion in PLA for lignin contents of up to 10% than other composite samples. Increasing the lignin content from 5% to 10% in PLA-grafted LNPs resulted in a significant increase in elongation at break (up to four times higher than neat PLA). The presence of PLA-grafted lignin led to a substantial reduction in optical transmittance in the UV range, dropping from 58.7 ± 3.0% to 1.10 ± 0.01%, while maintaining excellent transparency to visible light compared to blends containing lignin or LNPs. Although the antioxidant capacity of unmodified lignin is well-known, a substantial increase in antioxidant capacity was observed in LNPs and PLA-grafted LNP films, with values exceeding 10 times and 12 times that of neat PLA, respectively. These results confirm the significant potential of using studied films in food packaging applications.

Antioxidants from Hyeronima macrocarpa Berries Loaded on Nanocellulose: Thermal and Antioxidant Stability

This study investigated the effect of different storage temperatures (35-55 °C) on the bioactive substances and antioxidant properties of Hyeronima macrocarpa berries loaded on nanocellulose. NC was extracted from banana pseudo-stems and presented an interesting surface and porosity properties. The acidified ethanol extract showed better anthocyanin extraction (1317 mg C3G eq./100 g FW) and was used for the preparation of the powdered product, which presented an intense and uniform magenta color, with CIELAB parameters of L* = 59.16, a* = 35.61, and b* = 7.08. The powder exhibited significant stability at storage temperatures of 35 and 45 °C, in which there was no significant loss of anthocyanins or a decrease in antioxidant capacity. In addition, the color was stable for up to 4 months without adding any preservative agent. The anthocyanin-rich extract of H. macrocarpa reached an estimated shelf-life of 315 days (stored at 35 °C), as a result of the impregnation process between the extract and NC, with the ability to protect the bioactives from degradation, due to NC surface properties.