A new generalized Henry-Setschenow equation for predicting the solubility of air gases (oxygen, nitrogen and argon) in seawater and saline solutions

Competitive Electrohydrodynamic and Electrosolutal Advection Arrests Evaporation Kinetics of Droplets

This article reports the hitherto unreported phenomenon of arrested evaporation dynamics in pendant droplets because of electric field stimulus. The evaporation kinetics of pendant droplets of electrically conducting saline solutions in the presence of a transverse, alternating electric field is investigated experimentally. While the increase of field strength reduces the evaporation rate, increment in field frequency has the opposite effect. The same has been explained on the solvation kinetics of ions in polar water. Theoretical analysis reveals that change in surface tension and the diffusion-driven evaporation model cannot predict the decelerated evaporation. With the aid of particle image velocimetry, suppression of internal circulation velocity within the droplet is observed under electric field stimulus, which directly affects the evaporation rate. A mathematical scaling model is proposed to quantify the effects of electrohydrodynamic circulation and electrothermal and electrosolutal advection on the evaporation kinetics. The analysis encompasses major governing parameters, namely, the thermal and solutal Marangoni numbers, the electrohydrodynamic number, the electro-Prandtl and electro-Schmidt numbers, and their respective contributions. It has been shown that the electrothermal Marangoni effect is suppressed by the electric field, leading to deteriorated evaporation rates. Additionally, the electrosolutal Marangoni effect further suppresses the internal advection, further reducing the evaporation rate by a larger proportion. Stability analysis reveals that the electric body force retards the stable internal advection. The stability mapping also illustrates that if the field strength is high enough for the electrosolutal advection to overshadow the solutal Marangoni effect completely, it can lead to improvement in evaporation rates.

Production and application of O2 enriched air produced by fresh and salt water desorption in chemical plants

Oxygen enriched air intensifies oxidation processes since smaller reactors reach the same conversion of typical unit operations that employ simple air as reactant. However, the cost to produce pure oxygen or oxygen enriched air with traditional methods, i.e. cryogenic separation or membrane technologies, may be unaffordable. Here, we propose a new continuous technology for gas mixture separation, focusing on the production of oxygen enriched air as a case study. This operation is an absorption-desorption process that takes advantage of the higher oxygen solubility in water compared to nitrogen. In a pressurized solubilisation tank, water absorbs air. Subsequently, reducing pressure desorbs oxygen enriched air. PRO/II 9.3 (Simsci-Scheider Electrics) simulated, optimized, and calculated the capital and operative expenses of this technology. Moreover, we tested for the first time salt water instead of distilled water as appealing possibility for chemical plant near sea and ocean. We varied the inlet water flowrate between 5 and 15 m³/h. The optimum operative absortion unit pressure is 15-35 barg. After degassing, water may be recycled. With salt water, the extracted quantity of enriched air decreases compared with the desorption from fresh water (20% less), while the concentration of oxygen is independent from the salt concentration. The cost of enriched air at the optimum condition is 2-3.35 EUR/Nm³.

Oxygen Reduction by Homogeneous Molecular Catalysts and Electrocatalysts

The oxygen reduction reaction (ORR) is a key component of biological processes and energy technologies. This Review provides a comprehensive report of soluble molecular catalysts and electrocatalysts for the ORR. The precise synthetic control and relative ease of mechanistic study for homogeneous molecular catalysts, as compared to heterogeneous materials or surface-adsorbed species, enables a detailed understanding of the individual steps of ORR catalysis. Thus, the Review places particular emphasis on ORR mechanism and thermodynamics. First, the thermochemistry of oxygen reduction and the factors influencing ORR efficiency are described to contextualize the discussion of catalytic studies that follows. Reports of ORR catalysis are presented in terms of their mechanism, with separate sections for catalysis proceeding via initial outer- and inner-sphere electron transfer to O₂. The rates and selectivities (for production of H₂O₂ vs H₂O) of these catalysts are provided, along with suggested methods for accurately comparing catalysts of different metals and ligand scaffolds that were examined under different experimental conditions.