Physical Chemistry Research
Volume:5 Issue: 1, Winter 2017

Kinetic Monte Carlo simulation was applied to investigation of kinetics and mechanism of oxalic acid degradation by direct and heterogeneous catalytic ozonation. La-containing perovskites including LaFeO3, LaNiO3, LaCoO3 and LaMnO3 was studied as catalyst for oxalic acid ozonation. The reaction kinetic mechanisms of each abovementioned catalytic systems has been achieved. The rate constants values for the each step of the reaction mechanisms were obtained as adjustable parameters by kinetic Monte Carlo simulation. Comparison of the direct and catalytic ozonation simulated results proves the lanthanum-based perovskites catalysts displays significant roles during oxalic acid ozonation by increasing reactivity of ozone and oxalic acid on the surface of catalyst. Also the effect of inlet ozone concentration and initial amount of LaMO3 (M= Fe, Ni, Co, Mn) on the rate of oxalic acid decomposition has been studied. The kinetic Monte Carlo simulation results of this research have satisfactorily agreement with the existing experimental data for the oxalic acid ozonation.

The density and viscosity values at T= (293.15 to 323.15) K for binary mixtures of nitromethane with 2-propanol, 2-butanol and 2-pentanol were measured over the entire composition range. From the experimental data, excess molar volumes, thermal expansion coefficients, excess thermal expansions, partial molar volumes at infinite dilution and deviations in viscosity were calculated. The results were discussed in terms of intermolecular interactions and structure of studied binary mixtures. Free-volume theory coupled with the Peng–Robinson–Stryjek–Vera equation of state has been applied for calculation of viscosities of pure compounds and the binary liquid mixtures. The Agreement between experimental data and theoretical values was satisfactory.

Surfactant molecules are used as interesting tools to study the structure, function and stability of proteins. Protonation states of amino acids may be changed in the presence of surfactants. In this work, using experimental observations and molecular dynamic simulation, the effects of sodium dodecyl sulfate on the acid dissociation constants of tryptophan was examined. The acid–base equilibrium of tryptophan molecules was examined in the aqueous solution and in the presence of different concentrations of SDS. Different concentrations of SDS have diverse effects on the values of pKa1. However, the effect of SDS on pKa2 is similar in all concentration ranges. Furthermore, the microconstants related to the same equilibria (k11, k22, k12, and k21) have different values in the presence and absence of SDS. These results show the different protonation states of tryptophan molecules in the presence and absence of surfactant. Molecular dynamics simulation showed that in the absence of SDS, tryptophan molecules form molecular aggregates similar to the result of stacking. But in the presence of SDS, stacking between tryptophan molecules is disrupted by hydrophobic and hydrogen bonding interactions of surfactant.

Using surface analysis, simultaneous effects of temperature (260-380ºC) and ethanol concentration (0-1%) on dimethyl ether (DME) selectivity, yields of hydrocarbon and DME, and methanol conversion were investigated in methanol dehydration reaction over γ-Al2O3 catalyst. Methanol conversion and yield of hydrocarbon/DME were found to be significantly affected by temperature and the temperature-ethanol concentration interactions. In addition, DME selectivity and yield of DME were found to be influenced by the process temperature, and ethanol concentration as well as their interactions. BET surface area measurement and scanning electron microscopy technique (SEM) confirmed that the catalyst deactivation was intensified at higher temperatures by increasing ethanol concentration. Using statistical regression, a mathematical model was developed, and then validated, to describe simultaneous effects of temperature and feedstock ethanol concentration on DME selectivity. Although the model was statistically significant, curvature was not significant. Therefore, a two-level full factorial design of experiment approach was followed as a promising strategy for DME selectivity modeling and interpretation of data in this work.

The influence of cation-π interactions on the strength and nature of intramolecular O...H hydrogen bond has been investigated by quantum chemical calculations in orthohydroxy benzaldehyde (HBA) compound. Ab initio calculations have been performed at MP2/6-311** level of theory. Vibrational frequencies and physical properties such as chemical potential and chemical hardness of these compounds have been systematically explored. The natural bond orbital (NBO) analysis and the Bader’s quantum theory of atoms in molecules (QTAIMs) have also been used to elucidate the interaction characteristics of these complexes. The intramolecular O...H hydrogen bond has been putted in the categories weak to medium in the investigated systems. The results obtained from calculations and the topological parameters derived from the Bader theory suggest that the strongest interaction and the highest electron density at BCP (bond critical point) are related to the Be2+HBA complex. The HOMO–LUMO energy has also been evaluated. Furthermore, numerous correlations between topological, geometrical and energetic parameters have been found.

In the present work, a modified correlation is presented for the second virial coefficients of both polar and nonpolar fluids based on the corresponding states principle. The second virial coefficients of gaseous polar and non-polar compounds were calculated and compared with experimental data and with other correlations. Comparisons with the existing correlations show that the present work is more accurate and reliable for nonpolar and polar compounds. The results also show that the present work is nearly equivalent to the Meng et al. correlations for second virial coefficients of nonpolar fluids. The second virial coefficient of refrigerants, nonhydrogen bonding compounds and alcohols give a satisfactory result with respect to other correlations. The new correlations for the second coefficients need only the critical temperature, critical pressure, acentric factor and reduced dipole moment as parameters. According to the results, the root mean square deviation of second virial coefficients of the nonpolar compound, polar haloalkanes, and nonhydrogen bonding molecules, and alcohols are 10.58, 11.57 and 75.29 respectively.

This paper presents a systematic study of the surface chemistry, porous texture and adsorptive characteristics of prepared new activated carbon using Persian mesquite grain. Several techniques and methodologies such as, proximate analysis, N2 adsorption–desorption isotherms, scanning electron microscope (SEM), Fourier transform infrared spectroscopy(FT-IR), X-ray Diffraction (XRD), X-ray photoelectron spectroscopy(XPS), temperature programmed desorption (TPD), Thermo gravimetric analysis TGA/DTA, elemental analysis(CHNS), Boehm titration, and point of zero charge (pHpzc) have been used to determine physicochemical properties of raw material and activated carbon respectively. The prepared activated carbon has been also used to remove methyl orange (MO) and methylene blue(MB) as anionic and cationic azo dyes.

In this paper, at first we have formulated the lowest order constrained variational method for the relativistic case of an interacting fermion system at finite temperature. Then we have used this formalism to calculate some thermodynamic properties of liquid in the relativistic regime. The results show that the difference between total energies of relativistic and non-relativistic cases of liquid decreases by increasing the density. On the other hand, at densities smaller than , which is close to the theoretical saturation point of the system, this difference increases as the temperature increases. We have found that the relativistic calculations lead to the thermodynamic characteristics for liquid which are in a better agreement with the experimental data with respect to those of non-relativistic calculations.

Interaction of Ni complex(Salen= N, N´-ethylene bis(salicylideneimine)) with hen egg-white lysozyme (HEWL) was studied by absorption spectroscopy, competitive binding study and thermal denaturation study. The protein binding affinity of Ni complex was found to be (3.0×103M−1). The binding plot obtained from the absorption titration data gives a binding constant of 2.4 (± 0.3)×103 M-1. It was found that the charge transfer band of the metal complex was perturbed in the presence of (HEWL). Thermal denaturation study of HEWL with Ni complex revealed the ΔTm of 5±0.2 °C. The thermodynamic parameters (ΔHº > 0 and ΔSº > 0) showed that the hydrophobic interaction leads to the increasing entropy which is brought about by interaction with the complex. The negative ΔGº values for interaction of HEWL with the Ni complex indicate the spontaneity of the complexation.

The effect of magnetic field on the liquid-liquid equilibrium of two ternary systems (water acetic acid butyl acetate and water acetic acid dimethyl succinate) at 298.15 K under atmospheric pressure was investigated. The results obtained show that the strength of the magnetic field (0.02 T) affects the solubility of acetic acid in the used organic solvents. Distribution coefficients and separation factors were determined from the experimental LLE tie-line data for these systems. The comparisons indicated that the separation factor for the mixtures with dimethyl succinate is more effective than those with butyl acetate. The reliability of the tie-line data was ascertained through the Othmer-Tobias method. The tie-line data of studied ternary systems were also correlated using NRTL method and the values of the binary interaction parameters were obtained. It was concluded that the NRTL model accurately correlates the experimental data of the mentioned ternary systems.

Coordination of Cu ions adsorbed on plausible sites of a silicalite-2 lattice has been investigated computationally via hybrid density functional theory method at the B3LYP/6-311* and B3LYP/Def2-TZVP levels of theory using molecular models of the active site. The symmetrical coordination of Cu ions to almost five oxygen atoms of the all-silica framework in six-membered ring (6MR) sites of the main channels was the most stable configuration of Cu-silicalite-2 clusters. On the contrary, the metal cation was found to be most weakly bound in sites at the intersections where the metal ion was twofold coordinated. Implications on the catalytic chemistry for adsorption or activation of different molecules on the exchanged sites are discussed. The average binding energy was calculated to be ~46 kcal/mol for Cu/silicalite-2. Although chemisorbed, the relatively weak bindings of Cu supported some unusual reactivity of high-silica Cu-doped ZSM-11 catalysts in previous studies and evinced that this adsorbent can offer substantial capacities with respect to the guest molecules, e.g., in pollution abatement.

The density and polarization profiles of the dipolar hard ellipsoids confined between hard walls are studied using the density functional theory (DFT). The Hyper-Netted Chain (HNC) approximation is used to write excess grand potential of the system with respect to the bulk value. The number density is expanded up to zero and first order in polarization to find the results. For the zero order in polarization, the coupled integral equations for the directional densities are obtained. Then for the first order in polarization the coupled integral equations for the directional densities and polarization profiles are obtained. To simplify the calculations we use restricted orientation model (ROM) for the orientation of ellipsoids to find the density and polarization profiles. We also apply an electric field and write an expression for the excess grand potential of the system and obtain the coupled integral equations for the density and polarization profiles again. Finally we calculate the density and polarization profiles for different cases and compare the obtained results.

The monitoring and controlling of environmental pollutions are very important in biological and industrial processes, and a great interest is growing with the development of suitable gas–sensitive materials and hazardous chemical removal devices. In this work, the highly parameterized, empirical exchange–correlation functional M06–2X were employed to investigate the electronic sensitivity of perfect (PS) and Stone−Wales defective (SW) BNNTs toward NO molecule. A detailed analysis of the structural and electronic properties, reactivity and electron density of the states of various NO–BNNT complexes was performed. Our results reveal that the NO adsorption on the outer and inner surface sites of both PS and SW nanotubes is energetically favorable and unfavorable, respectively. The electronic property analysis indicates that the formation of Stone−Wales defect reduces the energy gap of BNNT and increases its electrical conductivity. In addition, adsorption of NO on the both PS− and SW−BNNTs reduces the energy gap of the nanotubes and increases their electrical conductance, which could serve as a signal for gas sensor. In addition, adsorption of NO radical on both BNNTs decreased the work function and so increases the field electron emission from the BNNT surfaces. The present results can provide useful guidance to develop modified BNNTs as a NO sensor.

Hydrogels, due to their unique potentials such as high-water content and hydrophilicity are interest for the controlled release of drug molecules. The present study aims to create a controlled-release system through the preparation and characterization of hydrogels based on pH-sensitive polymers such as poly (acrylic acid). Poly (acrylic acid), p(AA), hydrogel has been synthesized by radical polymerization in solution of AA as monomer, N,N'-Methylene bis acryl amide, (MBA), as cross linking agents and ammonium persulfate (APS) as initiator and N,N,Nʹ,Nʹ-tetramethylmethylenediamine (TEMED) as accelerator. The investigated hydrogel was characterized by FT-IR spectroscopy and the porosity of hydrogels was determined by Scanning Electron Microscope (SEM). The effect of pH on the swelling behavior of the hydrogel was studied in two different media (pH=1.1 and pH=7.4). The release percent of vitamin B12 has been investigated by UV-vis spectrophotometer. In addition, release of B12 was investigated in the presence of folic acid (B9). In same pH, in the presence of different amount of folic acid (B9), results showed that the samples involving the low release of vitamin B12 were arranged as follows: folic acid (25%) > folic acid (50%) > folic acid (75%).

An efficient method was employed for the ash and pyrite sulphur removal from bitumen using column flotation process. The bitumen samples containing 9.6% sulphur (6.81% in the pyrite sulphur form) and 26.4% ash were successfully showed up to 75.20% of pyrite sulphur (e.g.; 51.66% of total sulphur) and 70.81% of ash removal. The Box-Behnken Design (BBD) was employed to design the experiments, to optimize and evaluate the individual and interactive effects of six effective independent factors: the amounts of collector and frother agents, solid weight percentage in the pulp, particle size, wash water rate and feed rate. In order to investigate system a laboratory scale rig was built. In all experiments, pine oil and kerosene were considered as frother and collector agents, respectively. The best result for column flotation process were amount of collector (1.5 kg/tbitumen), amount of frother (0.3 ppm), pulp content (10% of solid), particle size (100 mesh), wash water rate (0.4 L/min), feed rate (1.5 L/min) and flotation time (10 min). The coefficient of determination, R2, showed that the RSM model can specify the variations with the accuracy of 0.924 and 0.938 for the percentage of ash and pyrite sulphur removal from bitumen, respectively.