Binding Energy Of Water Molecule Research Articles

Preparation and molecular simulation of an environmentally friendly dust-fixing agent based on chitosan-gelatin.

In order to solve the hazard of coal mine dust, a dust-fixing agent (GC-TG-JFC) was prepared with gelatin, chitosan, octadecanol polyoxyethylene ether, and glutamine transaminase. The experimental conditions and the formulation were optimized by response surface method. The ratio of gelatin, chitosan, octadecanol polyoxyethylene ether, and glutamine transaminase was 0.405:0.211:0.095:0.286 and the dilution ratio was 1:30. The results of product performance test showed that the dust fixation rate could reach 99.95% when the wind speed was 9 m/s. The viscosity of the diluted solution was 42.5 mPa·s. The Forcite module in Materials studio software was used to analyze and calculate the radial distribution concentration, diffusion coefficient, and binding energy of the solution. The results showed that GC-TG-JFC migrated more water molecules to the surface of coal through the action of van der Waals force and hydrogen bond. In addition, the binding energy of water molecules increased and the diffusion coefficient decreased, which improved the binding ability of water molecules with coal. It could be found that GC-TG-JFC had good dust fixation performance by combining experiment and molecular dynamics method.

Sorption and diffusion properties of untreated and thermally modified beech wood dust

Dynamic water vapor sorption experiments were carried out using beech wood dust (from untreated and thermally modified wood) of two-particle sizes, (< 25 and 80–250 µm), obtained from abrasive sanding. Sorption isotherms were parameterized with the GAB and GDW models. Dust from thermally modified wood had significantly lower equilibrium moisture content compared to dust from untreated material, due to the reduction in primary sorption sites in treated material. The observed changes were quantified by the coefficients of the GAB and GDW models. Thermal modification and size of wood dust particles had no influence on binding energy of water molecules being linked to the secondary sorption sites. Water diffusivity decreased significantly with increasing moisture content, but only for monolayer sorption. For higher moisture content values, water diffusivity was practically independent of moisture content. These results were found for untreated and thermally modified material as well as for both dust size fractions. The influence of thermal modification on water diffusivity was unclear, which is attributed to the diffusion model, which represents dust particles as spheres and assumes instant hygroscopic equilibrium. Overall, this study indicates that the effectiveness of filtration processes likely depends strongly on sorption and diffusion properties of wood dust only at low moisture contents within the hygroscopic range.

Development of Energy-resource-efficient Equipment and Technologies of Environmentally Safe Microwave Processing of Oil Sludges

&#x0D; &#x0D; &#x0D; the results of the analysis of scientific papers and patent elaboration of the existing methods and technologies for the separation of water-oil emulsions made it possible to implement energy-efficient processes of microwave exposure to hydrocarbon- containing media. Based on the analysis of existing mathematical models of the direct and reverse oil-water emulsions structure and evaluation of the behavior of oil-water emulsions in the microwave field, a mathematical model of the interaction of microwave energy with oil-water emulsions 1 has been developed. The use of this model allows for the identification of the most effective parameters of the microwave exposure for phase separation with different compositions and dielectric parameters of emulsions. Computational experiments have been carried out to identify the dependence of the binding energy of water molecules and different grades of oil on the physicochemical properties of the emulsion and the technological factors of the sludge processing. An experimental installation of microwave sludge processing has been developed and manufactured, which allows determining the adequacy of the developed model.&#x0D; Keywords: microwave processing, oil sludge, phase separation&#x0D; &#x0D; &#x0D;

Solution of Tasks of Energy Efficiency of the Process of Drying Raw Plant Materials by Methods of Mathematical Modeling

Beet pulp has a high feed value, but after pressing it has a sufficiently high humidity, which leads to rapid spoilage. One of the ways to stabilize the quality of beet pulp is drying with superheated steam of reduced pressure. Mathematical modeling of heat transfer during convective drying of beet pulp is proposed. A feature of the model is the description of the drying process, which ensures its high intensity due to high heat and mass transfer ratios and preserves the quality of the finished product as a result of the process at a reduced pressure of transfer medium. In the period of a constant drying speed, dehydration of macroscopic pores topologically related to the sample surface, which are characterized by a relatively low binding energy of water molecules with the liquid phase, is taken into account. According to experimental data, the proportion of water content in these pores is 60…70% of the total moisture content. In the final stage of this period, an increase in the binding energy occurs due to the removal of water from microcapillaries, which is explained by the formation of structured clusters in thin wetting films of water molecules. The change in steam temperature as a result of passing through the product layer was 8 … 10 K, and the relative temperature change was 5 … 10%. The parameters of the models were identified in the following range of parameters: superheated steam temperature 393 … 453 K; speed of superheated steam 3 … 5 m/s; the pressure inside the drying chamber is 40 … 100 kPa; the specific load of the product on the grate is 8 … 24 kg/m2. The interpretation of the simulation results is presented by the dependences of the temperature difference between beet pulp and heat carrier T on the temperature of superheated steam Ts at various pressures P: 1 - 100 kPa; 2 - 80 kPa; 3 - 60 kPa; 4 - 40 kPa; υ = 4 m/s; at various specific loads of beet pulp on the gas distribution grid qsp: 1 - 8 kg/m2; 2 - 16 kg/m2; 3 - 24 kg/m2; υ = 4 m/s; P = 60 kPa and various speeds of superheated steam υ: 1 - 5 m/s; 2 - 4 m/s; 3 - 3 m/s. A sufficient convergence of the results was ensured, in which the deviation of the calculated data from the experimental data did not exceed 12, 5% in absolute value. The obtained results of the simulation can be used in the operational control of the technological parameters of the process of drying beet pulp with superheated steam of reduced pressure with a restriction on the temperature mode due to the receipt of a high quality product.

ОБРАЗОВАНИЕ π-КОМПЛЕКСОВ АТОМОВ МЕДИ С АКРИЛОВОЙ, МАЛЕИНОВОЙ И ФУМАРОВОЙ КИСЛОТАМИ В ВОДНОЙ СРЕДЕ

Using the methods of quantum chemical modeling, the interaction of copper atoms with acrylic (HA), maleic (H2M), and fumaric (H2F) acids in the presence of water has been studied. It was established that water molecules, being electron-donor ligands, strengthen the (dπ-pπ)-interaction in π-complexes of Cu0 with unsaturated organic acids. Eight stable structures with molecular forms of ligands (two with HA, three with H2M and H2F) were revealed, among which the most stable complexes are [Cu0(H2O)(HA)], [Cu0(H2O)2(H2M) and [Cu0(H2O)2(H2F)]. Topological analysis of the electron density distribution at the node Cu(-C=C-) showed that only in one case ([Cu0(H2O)2(H2F)]) copper atoms form molecular orbitals with both carbon atoms. In all other complexes, one carbon atom is involved in the formation of a π-bond. In addition, a synergistic effect of π-ligands on the binding energy of water molecules by copper atoms was found.

Tracking the Structural Evolution of 4-Aminobenzoic Acid in the Transition from Solution to the Gas Phase.

Here, cryogenic ion mobility-mass spectrometry (cryo-IM-MS) is used to investigate intracluster proton transfer reactions of 4-aminobenzoic acid during the transition from solution to the gas phase. Previous studies have shown that protonation of the amine group of 4-aminobenzoic acid (4-ABAH+) is favored in solution (N-protomer), whereas protonation of the carboxylic acid group is favored in the gas phase (O-protomer). Results from cryo-IM-MS (80 K) studies of hydrated 4-ABAH+ ions, 4-ABAH+(H2O)n, are interpreted as evidence that the proton transfer reaction occurs through a water bridge at n = 6 connecting the -NH3+ and -COOH groups, that is, a Grotthuss mechanism. The weak binding energy of water molecules imposes limits for obtaining first-principles collisional cross sections (CCSs) of hydrated ions; consequently, candidate structures for 4-ABAH+(H2O)0-6 ions are derived by correlating experimental arrival-time distributions to theoretically determined CCSs. To our knowledge, these are the first first-principles determinations of CCS for hydrated ions. Apolar cosolvents, particularly acetonitrile, have been postulated to inhibit proton transfer by blocking the Grotthuss mechanism, but our data suggest that acetonitrile simply stabilizes the ammonium ion.

Thermoanalytical study of drying kinetics of lignocellulosic fuels

Lignocellulosic matter is usually hydrophilic, so its drying, in addition to the heat of the phase transition for water, also requires compensation of adsorption energy. In the present work experimental studies have been carried out to quantify the moisture adsorption energy, for wood sawdust, cellulose and lignin with varying moisture content. The experiments were performed on the basis of a thermal analysis complex STA449F1. The data were obtained for isothermal drying conditions at different temperatures. A mathematical model is proposed for the evaporation rate of various water energy forms in lignocellulosic fuel. A method is proposed for the experimental determination of the binding energy of water molecules with organic matter and its dependence on moisture content.

Molecular dynamics simulation of hydrocarbon molecule adsorption on kaolinite (0 0 1) surface

Molecular dynamics simulation method was used to systematically study the adsorption configuration, density distribution and adsorption energy of H2O, CO2, CH4, N2, C8H18 and fluorocarbon molecules C3F8 and C5F12 on kaolinite (0 0 1) surface. The enrichment characteristics of fluid molecules and the stability of adsorption configuration under reservoir temperature and pressure conditions are analyzed and discussed. The study shows that under the condition of reservoir temperature and pressure, the fluid molecules exhibit stratified adsorption characteristics on kaolinite (0 0 1) surface, in which the first adsorption layer has a higher regional density and the adsorption molecules are arrested by a higher free energy potential well, and the temperature and pressure have no significant influence on the potential barrier, meaning a adsorption phase state with ordered structure and stable configuration. In second and third adsorption layers, it was found that the free energy potentials well are lower, and the fluid is in a transition phase state with lower stability. The adsorption energy and free energy calculation results of the adsorption system show that the seven kinds of fluids are adsorbed on the kaolinite (0 0 1) surface in the order of H2O > C3F8 > C5F12 > C8H18 > CO2 > CH4 > N2. The water and fluorocarbon molecules, which have a much larger binding energy than the C8H18 and CH4 molecules, can displace oil and gas molecules in kaolinite reservoirs, while carbon dioxide can only displace methane molecules adsorbed on the kaolinite surface. It has been shown that as the increase of temperature and pressure, the binding energy of water molecules and C3F8 decreases significantly, but the binding energy of C5F12, C8H18, CO2 and methane molecules increases by 20%, 36%, 50% and 90% respectively, indicating that water flooding and C5F12 surfactant flooding can enhance oil recovery under high temperature and pressure conditions.

Emission of dimers from a free surface of heated water

The emission rate of water dimers from a free surface and a wetted solid surface in various cases was calculated by a simplified Monte Carlo method with the use of the binding energy of water molecules. The binding energy of water molecules obtained numerically assuming equilibrium between the free surface of water and vapor in the temperature range of 298–438 K corresponds to the coordination number for liquid water equal to 4.956 and is close to the reference value. The calculation results show that as the water temperature increases, the free surface of water and the wetted solid surface become sources of free water dimers. At a temperature of 438 K, the proportion of dimers in the total flow of water molecules on its surface reaches 1%. It is found that in the film boiling mode, the emission rate of dimers decreases with decreasing saturation vapor. Two mechanisms of the emission are described.

Water and other tetrahedral liquids: order, anomalies and solvation

In order to understand the common features of tetrahedral liquids with water-like anomalies, the relationship between local order and anomalies has been studied using molecular dynamics simulations for three categories of such liquids: (a) atomistic rigid-body models for water (TIP4P, TIP4P/2005, mTIP3P, SPC/E), (b) ionic melts, BeF2 (TRIM model) and SiO2 (BKS potential) and (c) Stillinger–Weber liquids parametrized to model water (mW) and silicon. Rigid-body, atomistic models for water and the Stillinger–Weber liquids show a strong correlation between tetrahedral and pair correlation order and the temperature for the onset of the density anomaly is close to the melting temperature. In contrast, the ionic melts show weaker and more variable degrees of correlation between tetrahedral and pair correlation metrics, and the onset temperature for the density anomaly is more than twice the melting temperature. In the case of water, the relationship between water-like anomalies and solvation is studied by examining the hydration of spherical solutes (Na+, Cl−, Ar) in water models with different temperature regimes of anomalies (SPC/E, TIP4P and mTIP3P). For both ionic and nonpolar solutes, the local structure and energy of water molecules is essentially the same as in bulk water beyond the second-neighbour shell. The local order and binding energy of water molecules are not perturbed by the presence of a hydrophobic solute. In the case of ionic solutes, the perturbation is largely localized within the first hydration shell. The binding energies for the ions are strongly dependent on the water models and clearly indicate that the geometry of the partial charge distributions, and the associated multipole moments, play an important role. However the anomalous behaviour of the water network has been found to be unimportant for polar solvation.

Sorption isotherm of corn distillers dried grains with solubles (DDGS) and its prediction using chemical composition

Corn distillers dried grains with solubles (DDGS) has high feed value due to its nutritive contents. The ratio of wet distillers grains (WDG) and condensed distillers solubles (CDS) added during the production process determines the chemical composition of DDGS. Effect of changing this ratio on water sorption behaviour of DDGS, at different temperature, was studied. Five mathematical models were evaluated to explain the sorption behaviour of DDGS. Prediction of sorption isotherm from chemical composition using a four-component model was also investigated. DDGS followed a BET Type III isotherm with higher equilibrium moisture content at increasing relative humidity. Difference in the sorption isotherm curves of DDGS samples reduced as equilibrium relative humidity increased. Equilibrium moisture content of DDGS samples reduced with lowering of CDS quantity added during production process. Modified Halsey equation was found suitable for mathematically explaining the sorption behaviour of DDGS. Binding energy of water molecule with DDGS increased with lowering of CDS level. Sorption behaviour of DDGS can be predicted from the chemical composition of protein, sugar, minerals, starch, fibre and glycerol. Increase in CDS level increased the percent relative deviation of predicted values calculated using the modified four-component model and might be due to the interaction between the chemical compounds present in the samples.

Photodissociation Dynamics of 4-Aminobenzonitrile+(Water)nClusters

The photodissociation dynamics of 4-aminobenzonitrile+(water)n (4ABN +Wn) (n = 1-18) clusters was investigated using a home-built linear-tandem time-of-flight (TOF) mass spectrometer consisting of two stages. Massselected cluster cations (n = 8-18) were irradiated by photons with energies ranging from 2.15 to 2.95 eV in the field-free region at the second stage. The average numbers of ejected water molecules were obtained at various photon energies from the photofragmentation mass spectra, from which the average binding energies of water molecules were estimated. Also, the optimum structures of the clusters and binding energies of the water molecules were suggested via theoretical calculations. The local excitation (LE) band observed in the photodissociation spectra of the 4ABN+Wn (n = 1-3) clusters and 4ABN2 + shifted to blue with increase in the number of solvated water molecules.

Liquid water in the domain of cubic crystalline ice Ic.

Vapor-deposited amorphous water ice when warmed above the glass transition temperature (120-140 K), is a viscous liquid which exhibits a viscosity vs temperature relationship different from that of liquid water at room temperature. New studies of thin water ice films now demonstrate that viscous liquid water persists in the temperature range 140-210 K. where it coexists with cubic crystalline ice. The liquid character of amorphous water above the glass transition is demonstrated by (1) changes in the morphology of water ice films on a nonwetting surface observed in transmission electron microscopy (TEM) at around 175 K during slow warming, (2) changes in the binding energy of water molecules measured in temperature programmed desorption (TPD) studies, and (3) changes in the shape of the 3.07 micrometers absorption band observed in grazing angle reflection-absorption infrared spectroscopy (RAIRS) during annealing at high temperature. whereby the decreased roughness of the water surface is thought to cause changes in the selection rules for the excitation of O-H stretch vibrations. Because it is present over such a wide range of temperatures, we propose that this form of liquid water is a common material in nature. where it is expected to exist in the subsurface layers of comets and on the surfaces of some planets and satellites.

IR spectroscopic estimation of the binding energies of water molecules adsorbed on dispersed systems. Part 3. γ-Al2O3

There are three modes of interaction between water molecules and centers in γ-Al2O3, which arise from marked differences in hydrogen-bond energy.

Transition state model for water exchange in the first solvation shell of hydrated cations according to quantum chemical calculations

Based on the theoretically calculated m.o. values for the binding energy of water molecules in the first and second solvation sphere of cations, the relation between bonding energies and experimentally observed hydration energies is discussed. Furthermore, the experimental values for the activation energy of water exchange in the first solvation layer are related to the binding energies of these water molecules, leading to strong support for an exchange mechanism involving the second hydration shell and a higher coordinated transition state.

An Interpretation of the “Molecular Space” on the Basis of Quantum Chemical Calculations of Hydrated Ions

Abstract Quantum chemical calculation has been made for the sizes of the hydration shells of the metal ions as well as for the binding energies of water molecules in the hydration shells. The results of the both calculations give the basis of the size of the molecular space. Although the experimental value of the molecular space, (20±5A)3, does not exactly agree with the calculated value, we assume that the quantum chemically obtained hydration sphere refers to the molecular space.