Amount Of Water In Solution Research Articles

Experimental Constraints on Deliquescence of Calcium Perchlorate Mixed with a Mars Regolith Analog

Hygroscopic salts within the Martian regolith may actively participate in the near-surface water cycle by exchanging water vapor via solid-state salt hydration and deliquescence. To elucidate this process, experimental work has constrained the phase diagram of Mars-relevant salts and the stability of the resultant brines. However, salt interactions with a Mars-like regolith, which itself can exchange water vapor with the atmosphere via adsorption, has not yet been well explored. Here, to better understand water exchange with a salty Mars-like regolith and, particularly, the potential to form brines, we have conducted a series of experiments using JSC Mars-1 regolith simulant mixed with calcium perchlorate in a Mars simulation chamber at a temperature <5°C and a relative humidity <20%. During the experiments, we measured the sample mass, as well as the temperature and relative humidity of the sample and the chamber. We found that the water uptake of a salty Mars-like regolith is about twice as fast as that of a salt-free regolith. Furthermore, we found evidence to suggest that deliquescence occurred; however, not all the salt within the sample may have entered solution. The amount of water in solution was small and did not lead to regolith darkening. Our results suggest that, under the tested experimental conditions, salt deliquescence and regolith adsorption can occur simultaneously.

Effects of Synthetic Parameters on the Structure and Catalytic Performance of Cu−Cr Catalysts Prepared by a Non-Alkoxide Sol−Gel Route

The surface areas of Cu−Cr xerogels prepared by an epoxide assisted route are highly dependent on synthetic conditions like gelation temperature, amount of water in the solvent, and gel aging time. Gelation temperature affects the relative rates of hydrolysis and condensation, the amount of water in solution adjusts the solution pH, and the aging process influences the microstructural properties of the xerogels. These factors affect the stability of the sol particles in solution and the final structure of the gel. Thermogravimetric and differential thermogravimetric analysis, specific surface area measurement through nitrogen adsorption, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy are employed to determine particle size distribution and morphology of the different particulate products (i.e., gels, powders) obtained via different synthesis conditions, both before and after thermal treatments. The xerogel surface area can reach up to 230 m2/g by adjusting the operating parameters. Moreover, the results show that the Cu−Cr catalysts with CuCr2O4 and Cr2O3 phases obtained by calcining the as-prepared xerogels in 20% O2 in Ar have better activity for glycerol catalytic conversion than catalysts with Cu and Cr2O3 phases that were obtained by calcination in Ar. In addition, the activity of catalysts increased with the surface areas of xerogels. It is noteworthy that the catalysts have significant selectivity to 1,2-propanediol (54%) and 1-propanol (36%) at 32% conversion of glycerol at 210 °C and 4.1 MPa H2 pressure.

Electrosorption of tri(n)octylphosphine oxide from methanol and water-methanolic solutions on a polarized mercury electrode

The adsorption of tri(n)octylphosphine oxide on the mercury electrode in methanolic and water-methanolic solutions of LiCl has been examined from electrocapillary measurements. In methanolic solutions this substance shows the typical characteristic features of an organic adsorbate. The isotherms are congruent only with respect to potential on the negative side of the electrocapillary maximum and in this region a Frumkin isotherm is obeyed with an interaction parameter equal to α = 0.3 corresponding to intermolecular attraction. On the positive side the isotherms are non congruent with respect to both the electrical variables, while the system may be described by a Frumkin isotherm either with constant Γ s = 1.03 × 10 −10 mole cm −2 and α decreasing with the increase of the positive charges on the electrode or with constant α = 0.3 and decreasing Γ s . In water-methanolic solutions the adsorption of tri(n)octylphosphine oxide increases, due mainly to the decrease of its solubility. In parallel a clear dependence of Γ s on the amount of water in solutions is detected. Γ s is seen to increase with the water content of the solutions probably due to a partial overlap of the hydrocarbon chains of this substance.

Hydrogen evolution from KHF 2, melts at platinum electrodes

Overvoltage measurements at bright platinum electrodes have been carried out, by the galvanostatic method, in order to investigate the hydrogen evolution reaction from molten KHF 2 baths containing different amounts of water in solution. The equations (α) e − + HF → 1 2 H 2 + F − (β) e − + H 3O + → 1 2 H 2 + H 2O are attributed to the observed electrode reactions. In the region of current density corresponding to the transition from reaction (α) to (β), the electrode is treated as a bi-electrode.