Evaporation-triggered microdroplet nucleation and the four life phases of an evaporating Ouzo drop

Evaporating liquid droplets are omnipresent in nature and technology, such as in inkjet printing, coating, deposition of materials, medical diagnostics, agriculture, food industry, cosmetics, or spills of liquids. While the evaporation of pure liquids, liquids with dispersed particles, or even liquid mixtures has intensively been studied over the last two decades, the evaporation of ternary mixtures of liquids with different volatilities and mutual solubilities has not yet been explored. Here we show that the evaporation of such ternary mixtures can trigger a phase transition and the nucleation of microdroplets of one of the components of the mixture. As model system we pick a sessile Ouzo droplet (as known from daily life - a transparent mixture of water, ethanol, and anise oil) and reveal and theoretically explain its four life phases: In phase I, the spherical cap-shaped droplet remains transparent, while the more volatile ethanol is evaporating, preferentially at the rim of the drop due to the singularity there. This leads to a local ethanol concentration reduction and correspondingly to oil droplet nucleation there. This is the beginning of phase II, in which oil microdroplets quickly nucleate in the whole drop, leading to its milky color which typifies the so-called 'Ouzo-effect'. Once all ethanol has evaporated, the drop, which now has a characteristic non-spherical-cap shape, has become clear again, with a water drop sitting on an oil-ring (phase III), finalizing the phase inversion. Finally, in phase IV, also all water has evaporated, leaving behind a tiny spherical cap-shaped oil drop.Comment: 40 pages, 12 figure

A General Correlation between the Temperature-Dependent Solubility and Solute and Solvent Molar Masses in Binary n-Alkane Mixtures

An increasingly popular solution in the oil-industry is long-distance sub-sea transportation of unprocessed well-streams. This will commonly expose the oil to temperatures significantly below the reservoir temperature, and possibly below the wax appearance temperature, resulting in precipitation and depostion of solids. Being able to predict the temperature dependent solubility of paraffinic components in oil may thus be crucial for developing the oil-fields of the future. In this paper, published data for binary normal-alkane mixtures is reviewed. A total of 43 unique solute-solvent data-sets, obtained from a total of 24 papers, are revisited, and based on thermodynamic considerations and the experimental data it is demonstrated that there is a log-linear relationship between the solubility and the temperature. Linear regression is employed to 1) obtain data-set-specific solubility-temperature best-fit parameters and 2) obtain a general correlation between the solubility and the solvent and solute molar masses and the temperature. Finally, it is demonstrated that the developed correlation carries predictive power even for multi-component mixtures by utilizing solvent and solute average molar masses.Comment: Sumbitted to Fuel (Elsevier) in Oct. 2012 - Rejected. 27 pages, 6 figures (Fig. 6 contains 43 subfigures). Published data for binary normal-alkane mixtures reviewed. 43 solute-solvent data-sets, from 24 references are revisited. Linear regression used to establish a general correlation between solubility, solvent/solute molar masses and temperatur

Thermodynamic Properties of Partially Miscible Systems: Part II- Binary Systems of Cyclohexane with Acetic Anhydride & Furfural

231-23

Imidazolium Magnetic Ionic Liquid Solubilities in Water

Magnetic ionic liquids (MILs) are room temperature ionic liquids that exhibit paramagnetic behavior. These liquids have tunable physiochemical properties with proposed applications in separations and drug delivery. It is, therefore, useful to know the solubility and micellar behavior of MILs in aqueous environments. Our group synthesized MILs with a FeCl4 anion and 1-alkyl-3-methylimidazolium cations and investigated aqueous solubility vs alkyl size (C2 through C10). We measured water solubility (MIL content in water saturated with the MIL) using UV-Vis spectroscopy, total organic carbon (TOC) analysis, and Total Nitrogen (TN) analysis. After observing micellar behavior for C(n)mim[FeCl4], where n > 6, we investigated the critical micelle concentration (CMC) of these MILs. Finally, we used Linear Free Energy Relationship (LFER) semi-empirical models to correlate the MIL water solubility to the MIL’s molecular volume. In the future, this LFER can predict the solubility of a MIL in water before the MIL is synthesized

Solubility of CO2 in Ionic Liquids with Additional Water and Methanol: Modeling with PC-SAFT Equation of State

The superior properties of specific ionic liquids (ILs), such as negligible volatility, high thermal stability, flexible designability, and their affinity to capture CO2, make them an attractive alternative to chemical and physical solvents that are currently used in CO2 capture processes. However, a limitation to use ILs for industrial CO2 capture is their high viscosity compared to conventional solvents, which leads to a lower CO2 capture rate and higher pumping cost. The viscosity of ILs can be reduced by adding a co-solvent, such as water or methanol. In this work, solubility, vapor–liquid equilibria (VLE), and liquid–liquid equilibria (LLE) for binary and ternary mixtures involving CO2, ILs, water, and methanol have been systematically investigated by employing perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state with two different strategies. ILs were considered as self-associating chain molecules with two association sites in the first strategy. As a comparison, they were regarded as strong electrolytes that dissociate into anions and cations in the second strategy. It was found that both strategies provide accurate correlations in modeling CO2 solubilities in ILs and LLE of binary ILs/water systems. Four ternary systems were selected to verify the predictive capability of the two strategies. For water-containing systems, both strategies performed excellently when binary interaction parameters (BIPs) can be obtained by fitting to experimental data, while they performed poorly for system with few experimental data. For cases where methanol acted as a co-solvent, accurate predictions were obtained with both strategies, even without any BIPs. PC-SAFT was found to be a potential practical tool to develop CO2 capture processes with new alternative solvents when there are sufficient experimental data for binary mixtures