scholarly journals Surface Thermodynamics, Viscosity, Activation Energy of N-Methyldiethanolamine Aqueous Solutions Promoted by Tetramethylammonium Arginate

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1337
Author(s):  
Xiangfeng Tian ◽  
Lemeng Wang ◽  
Pan Zhang ◽  
Dong Fu
Keyword(s):  
Activation Energy ◽  
Surface Tension ◽  
Diffusion Coefficient ◽  
Aqueous Solutions ◽  
Quantitative Relationship ◽  
Viscosity Data ◽  
Surface Thermodynamics ◽  
Surface Entropy ◽  
Operation Conditions ◽  
Surface Enthalpy

The surface tension and viscosity values of N-methyldiethanolamine (MDEA) aqueous solutions promoted by tetramethylammonium arginate ([N1111][Arg]) were measured and modeled. The experimental temperatures were 303.2 to 323.2 K. The mass fractions of MDEA (wMDEA) and [N1111][Arg] (w[N1111][Arg]) were 0.300 to 0.500 and 0.025 to 0.075, respectively. The measured surface tension and viscosity values were satisfactorily fitted to thermodynamic models. With the aid of experimentally viscosity data, the activation energy (Ea) and H2S diffusion coefficient (DH2S) of MDEA-[N1111][Arg] aqueous solution were deduced. The surface entropy and surface enthalpy of the solutions were calculated using the fitted model of the surface tension. The quantitative relationship between the calculated values (surface tension, surface entropy, surface enthalpy, viscosity, activation energy, and H2S diffusion coefficient) and the operation conditions (mass fraction and temperature) was demonstrated.

scholarly journals Molecular Dynamics Simulation of the Surface Tension of Aqueous Sodium Chloride: from Dilute to Highly Supersaturated Solutions and Molten Salt

2017 ◽  
Author(s):  
Xiaoxiang Wang ◽  
Chuchu Chen ◽  
Kurt Binder ◽  
Uwe Kuhn ◽  
Ulrich Pöschl ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Sodium Chloride ◽  
Concentration Dependence ◽  
Inflection Point ◽  
Dynamics Simulation ◽  
Nacl Solution ◽  
Surface Entropy ◽  
Surface Enthalpy ◽  
Supersaturated Solutions

Abstract. Sodium chloride (NaCl) is one of the key components of atmospheric aerosols. The surface tension of aqueous NaCl solution (σNaCl,sol) and its concentration dependence are essential to determine the equilibrium water vapor pressure of aqueous NaCl droplets. Supersaturated NaCl solution droplets are observed in laboratory experiments and under atmospheric conditions, but the experimental data for σNaCl,sol are mostly limited up to sub-saturated solutions. In this study, the surface tension of aqueous NaCl is investigated by molecular dynamics (MD) simulations and pressure tensor method from dilute to highly supersaturated solutions. We show that the linear approximation of concentration dependence of σNaCl,sol at molality scale can be extended to the supersaturated NaCl solution until a molality of ~9.6 mol kg−1 (i.e., solute mass fraction (xNaCl) of ~0.36). Energetic analyses show that this monotonic increase of surface tension is driven by the increase of excessive surface enthalpy (∆H) as the solution becomes concentrated. After that, the simulated σNaCl,sol remains almost unchanged until xNaCl of ~0.47 (near the concentration upon efflorescence). The existence of the inflection point at xNaCl of ~0.36 and the stable surface tension of xNaCl between ~0.36 and ~0.47 can be attributed to a competitive growth of excessive surface entropy term (T · ∆S) and the excessive surface enthalpy term (∆H). After a second inflection point at xNaCl of ~0.47, the simulated σNaCl,sol gradually regains the growing momentum with a tendency to approach the surface tension of molten NaCl (~148.4 mN m−1 at 298.15 K, MD simulation based extrapolation). This fast increase of σNaCl,sol at xNaCl > 0.47 is primarily still an excessive surface enthalpy-driving process, although contribution from concurrent fluctuation of excessive surface entropy is expected but in a relatively smaller scale. Our results reveal different regimes of concentration dependence of the surface tension of aqueous NaCl at 298.15 K: a water-dominated regime (xNaCl from 0 to ~0.36), a transition regime (xNaCl from ~0.36 to ~0.47) and a molten NaCl-dominated regime (xNaCl from ~0.47 to 1).

scholarly journals Molecular dynamics simulation of the surface tension of aqueous sodium chloride: from dilute to highly supersaturated solutions and molten salt

2018 ◽  
Vol 18 (23) ◽  
pp. 17077-17086 ◽  
Author(s):  
Xiaoxiang Wang ◽  
Chuchu Chen ◽  
Kurt Binder ◽  
Uwe Kuhn ◽  
Ulrich Pöschl ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Sodium Chloride ◽  
Concentration Dependence ◽  
Inflection Point ◽  
Nacl Solution ◽  
Surface Entropy ◽  
Excess Surface ◽  
Surface Enthalpy ◽  
Supersaturated Solutions

Abstract. Sodium chloride (NaCl) is one of the key components of atmospheric aerosols. The surface tension of aqueous NaCl solution (σNaCl,sol) and its concentration dependence are essential to determine the equilibrium water vapor pressure of aqueous NaCl droplets. Supersaturated NaCl solution droplets are observed in laboratory experiments and under atmospheric conditions, but the experimental data for σNaCl,sol are mostly limited up to subsaturated solutions. In this study, the surface tension of aqueous NaCl is investigated by molecular dynamics (MD) simulations and the pressure tensor method from dilute to highly supersaturated solutions. We show that the linear approximation of concentration dependence of σNaCl,sol at molality scale can be extended to the supersaturated NaCl solution until a molality of ∼10.7 mol kg−1 (i.e., solute mass fraction (xNaCl) of ∼0.39). Energetic analyses show that this monotonic increase in surface tension is driven by the increase in excess surface enthalpy (ΔH) as the solution becomes concentrated. After that, the simulated σNaCl,sol remains almost unchanged until xNaCl of ∼0.47 (near the concentration upon efflorescence). The existence of the “inflection point” at xNaCl of ∼0.39 and the stable surface tension of xNaCl between ∼0.39 and ∼0.47 can be attributed to the nearly unchanged excess surface entropy term (T⋅ΔS) and the excess surface enthalpy term (ΔH). After a “second inflection point” at xNaCl of ∼0.47, the simulated σNaCl,sol gradually regains the growing momentum with a tendency to approach the surface tension of molten NaCl (∼175.58 mN m−1 at 298.15 K, MD simulation-based extrapolation). This fast increase in σNaCl,sol at xNaCl>0.47 is a process driven by excess surface enthalpy and excess surface entropy. Our results reveal different regimes of concentration dependence of the surface tension of aqueous NaCl at 298.15 K: a water-dominated regime (xNaCl from 0 to ∼0.39), a transition regime (xNaCl from ∼0.39 to ∼0.47) and a molten NaCl-dominated regime (xNaCl from ∼0.47 to 1).

scholarly journals Spray adjuvant characteristics affecting agricultural spraying drift

2015 ◽  
Vol 35 (1) ◽  
pp. 109-116 ◽  
Author(s):  
RONE B. DE OLIVEIRA ◽  
ULISSES R. ANTUNIASSI ◽  
MARCO A. GANDOLFO
Keyword(s):  
Surface Tension ◽  
Wind Tunnel ◽  
Aqueous Solutions ◽  
Formation Process ◽  
Droplet Diameter ◽  
Brilliant Blue ◽  
Medium Size ◽  
Blue Dye ◽  
Methods Of Evaluation ◽  
Spray Adjuvants

This study defined the main adjuvant characteristics that may influence or help to understand drift formation process in the agricultural spraying. It was evaluated 33 aqueous solutions from combinations of various adjuvants and concentrations. Then, drifting was quantified by means of wind tunnel; and variables such as percentage of droplets smaller than 50 μm (V50), 100 μm (V100), diameter of mean volume (DMV), droplet diameter composing 10% of the sprayed volume (DV0.1), viscosity, density and surface tension. Assays were performed in triplicate, using Teejet XR8003 flat fan nozzles at 200 kPa (medium size droplets). Spray solutions were stained with Brilliant Blue Dye at 0.6% (m/ v). DMV, V100, viscosity cause most influence on drift hazardous. Adjuvant characteristics and respective methods of evaluation have applicability in drift risk by agricultural spray adjuvants.

scholarly journals Unexpected Role of Electronic Coupling between Host Redox Centers in Transport Kinetics of Lithium Ions in Olivine Phosphate Materials

2021 ◽  
Author(s):  
Yu Gao ◽  
Jun Huang ◽  
Yuwen Liu ◽  
Shengli Chen
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Lithium Ion ◽  
Transport Kinetics ◽  
Electronic Coupling ◽  
Lithium Ions ◽  
Kinetics Of ◽  
Olivine Phosphate ◽  
Redox Centers

The discrepancy between the trend in the diffusion coefficient of lithium ion (DLi+) and that in the activation energy of ion hopping signals hidden factors determining ion transport kinetics in...

scholarly journals Drying Kinetics of Noni Seeds

2019 ◽  
Vol 11 (5) ◽  
pp. 250 ◽  
Author(s):  
Wellytton Darci Quequeto ◽  
Osvaldo Resende ◽  
Patrícia Cardoso Silva ◽  
Fábio Adriano Santos e Silva ◽  
Lígia Campos de Moura Silva
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Diffusion Coefficient ◽  
Moisture Content ◽  
Mathematical Models ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Information Criterion ◽  
Drying Kinetics ◽  
Kinetics Of

Noni seeds have been used for years as an important medicinal source, with wide use in the pharmaceutical and food industry. Drying is a fundamental process in the post-harvest stages, where it enables the safe storage of the product. Therefore, the present study aimed to fit different mathematical models to experimental data of drying kinetics of noni seeds, determine the effective diffusion coefficient and obtain the activation energy for the process during drying under different conditions of air temperature. The experiment used noni seeds with initial moisture content of 0.46 (decimal, d.b.) and dehydrated up to equilibrium moisture content. Drying was conducted under different controlled conditions of temperature, 40; 50; 60; 70 and 80 ºC and relative humidity, 24.4; 16.0; 9.9; 5.7 and 3.3%, respectively. Eleven mathematical models were fitted to the experimental data. The parameters to evaluate the fitting of the mathematical models were mean relative error (P), mean estimated error (SE), coefficient of determination (R2), Chi-square test (c2), Akaike Information Criterion (AIC) and Schwarz’s Bayesian Information Criterion (BIC). Considering the fitting criteria, the model Two Terms was selected to describe the drying kinetics of noni seeds. Effective diffusion coefficient ranged from 8.70 to 23.71 × 10-10 m2 s-1 and its relationship with drying temperature can be described by the Arrhenius equation. The activation energy for noni seeds drying was 24.20 kJ mol-1 for the studied temperature range.

scholarly journals Ultrasonic irradiation of chemical compounds in aqueous solutions

1992 ◽  
Author(s):  
Αναστασία Κοτρωναρου
Keyword(s):  
Aqueous Solutions ◽  
Ultrasonic Irradiation ◽  
Energy Utilization ◽  
Oxidation Products ◽  
Utilization Efficiency ◽  
Interfacial Region ◽  
Reaction Products ◽  
Operation Conditions ◽  
Cavitation Bubbles ◽  
Ph Range

The ultrasonic irradiation of para-nitrophenol, S(-II), and parathion is studied in aqueous solutions at 20 kHz and ~ 75 W-cnT2. Para-nitrophenol was degraded primarily by denitration and secondarily by ΌΗ radical attack to yield N 02, NO3, benzoquinone, hydroquinone, 4-nitrocatechol, formate and oxalate. These reaction products and the kinetic observations are consistent with a model involving high-temperature reactions of p-nitrophenol in the interfa.cia.1 region of cavitation bubbles. The average effective temperature of the interfacial region surrounding the cavitation bubbles was estimated to be T ~ 800 K. Ultrasonic irradiation of S(-II) is studied in aqueous solutions over the pH range 7 - 12. The reaction of HS“ with OH is the principal pathway for theoxidation of S(-II) at pH > 10; the oxidation products are SO2“, SO2", and S20 Upon prolonged sonication, SO2" is the only observed product. At pH < 8.5, thermal decomposition of H2S within or near collapsing cavitation bubbles becomes the important pathway and elemental sulfur is found as an additional product of the sonolysis of S(-II). The sonolytic oxidation of H2S at pH > 10 was successfully modeled with an aqueous-phase free-radical chemistry mechanism and assumingcontinuous and uniform ΌΗ input into solution from the imploding cavitation bubbles. Parathion degradation occurred primarily by enhanced hydrolysis and secondarily by direct ΌΗ radical attack.The effect of various physical and chemical parameters on sonolytic yields is examined. The observed effects are in qualitative agreement with the sonolysis mechanisms proposed for the chemicals of interest and the existing hydrodynamic theories of acoustic cavitation. The formation of iodine upon ultrasonic irradiation of potassium iodide solutions and the sonolysis of S(-II) are used as probes to compare the sonochemical efficiency of different experimental set-ups. This work elucidates the mechanisms of the ultrasonic decomposition of typical organic and inorganic pollutants. It is shown that ultrasound has the potential to become a viable alternative for the destruction of chemical contaminants in water and wastewater. The current limitation of sonolysis is its low energy utilization efficiency, but there is room for improvement by optimizing reactor design and physical/chemical operation conditions. This work offers some recommendations and insight in that respect.

scholarly journals PECULARITIES OF MICELLE FORMATION OF PENTACYCLIC GLYCOSIDES IN AQUEOUS SOLUTIONS

2021 ◽  
Vol 64 (4) ◽  
pp. 26-33
Author(s):  
Natalia V. Mironenko ◽  
Irina V. Shkutina ◽  
Vladimir F. Selemenev
Keyword(s):  
Surface Tension ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Aqueous Solutions ◽  
Hydrodynamic Radius ◽  
Critical Concentration ◽  
Micelle Formation ◽  
Cylindrical Shape ◽  
Scattering Method ◽  
Dynamic Light Scattering Method

The regularities of changes in structural characteristics during the formation of associates in micellar aqueous solutions of triterpene saponins Quillaja Saponin and Sapindus Mukorossi are considered. The dependence of surface tension and adsorption on the concentration of an aqueous saponin solution is analyzed, and the values of surface activity and parameters of the adsorption layer are calculated. The average values of diffusion coefficients for spherical and cylindrical micelles are determined based on the measurement of the solution viscosity. The effect of the electrolyte solution on the surface tension and viscosity of glycoside solutions is studied: when the electrolyte is introduced into the saponin solution, the surface tension decreases, which leads to a shift in the critical concentration of micelle formation towards lower concentrations. The introduction of potassium chloride electrolyte reduces the degree of ionization and, as a result of suppressing the electroviscosity effect, leads to a decrease in the viscosity of the solution. The dynamic light scattering method is used to determine the size of glycoside aggregates. It is established that there are aggregates of several sizes in an aqueous solution of saponin. The size and shape of aggregates were calculated using the concepts of micelle packing parameters. In the region of very low concentrations of glycoside solutions, when approaching the critical concentration of micelle formation in the solution, there are spherical micelles. A further increase in the saponin concentration in the solution leads to a decrease in the content of structures with a hydrodynamic radius of 50-80 nm and the appearance of larger agglomerates with sizes greater than 100 nm. It was found that micelles acquire a less hydrated and more densely packed cylindrical shape in the concentration range of 1.7-2.6 mmol/dm3. Compaction of associates leads to an increase in the content of particles with a hydrodynamic radius of 150-250 nm and larger ones, and their presence predicts the appearance of larger agglomerates. Analyzing the data obtained using the dynamic light scattering method, it can be concluded that aggregates of several sizes co-exist in the volume of aqueous saponin solutions at certain concentrations.

Sign in / Sign up

Export Citation Format

Share Document