Theoretical study on the atmospheric formation of sulfur trioxide as the primary agent for acid rain

The reaction mechanism of SO₂ with O₃ on the singlet potential energy surface has been investigated theoretically at the G3MP2B3//B3LYP/6-311+G(3df) level of theory. The reactants are initially associated with adducts IN1(O₂S–OOO) and IN2(OS-cyclic O₄) in a barrier-less process. Subsequently, these adducts undergo isomerization and dissociation processes to produce cis-OSOO + ³O₂, SO₃(C _s ) + ³O₂ and SO₃(D _3h ) + ³O₂ products. The SO₃(D _3h ) + ³O₂ is major product and the cis-OSOO + ³O₂ and SO₃(C _s ) + ³O₂ are minor products. No stable pathway has been found for the formation of trans-OSOO and cyclic-SOOO isomers in the reaction of SO₂ + O₃. For major product, the rate constant of SO₂ + O₃ reaction is 2.30 × 10⁻²³ cm³ molecule⁻¹ s⁻¹, at room temperature and atmospheric pressure.     

Fabrication of a novel electrospun molecularly imprinted nanomembrane coupled with high‐performance liquid chromatography for the selective separation and determination of acesulfame

A novel in situ molecularly imprinted sol–gel nanomembrane using nylon 6 as backbone was prepared by the electrospinning technique and coupled on‐line with high‐performance liquid chromatography. The prepared electrospun membrane exhibited extensive selectivity toward acesulfame in the presence of some selected sweeteners in a beverage sample, while the porosity and mechanical stability remained. The prepared electrospun membrane could be applied for 35 consequence extractions without a significant change in extraction recovery, swelling, and flooding. To achieve the best condition and efficiency for on‐line extraction, the effect of influential parameters was investigated. The limit of detection (signal/noise = 3:1) and limit of quantification (signal/noise = 10:1) were 0.6 and 2.0 ng/mL for acesulfame in the beverage samples, respectively. The linearity for the acesulfame was in the range of 2.0–250 ng/mL in beverage samples. The coefficients of determination values were ≥0.997 for all runs. The extraction recoveries of acesulfame in the beverage samples were between 80 and 85%.     

Theoretical study of reaction mechanism for Se + O<Subscript>3</Subscript>

The reaction mechanism of Se + O₃ on the singlet potential energy has been investigated at CCSD(T)/6-311++G(2df,2pd) level of theory based on the geometric parameters optimized at the B3LYP/6-311++G(3df,3pd) level of theory. The calculated results show that the reactants are firstly associated into the adduct Se–O₃ with any intrinsic barrier. Subsequently, through a variety of transformations of isomer Se–O₃, two kinds of products P₁(SeO₃(D_3h)) and P₂(SeO + ³O₂) are obtained. The breakage and formation of the chemical bonds in the reaction have been studied by the topological analysis of electronic density. The topological analysis results show that the ring transitional structure region does not only occur in cis-OSeOO → SeO₃(C_s) process but also occur in SeO₃(C_s) → SeO₃(D_3h).     

Mechanistic Investigation on Dynamic Interfacial Tension Between Crude Oil and Ionic Liquid Using Mass Transfer Concept

Ionic liquids (ILs) are a new kind of solvents that have recently gained an upsurge in attention in light of their unique potential for different applications. With respect to this, in the present study, applicability of an IL called 1-octadecyl-3-methylimidazolium chloride ([C18mim] [Cl]) as a new class of surfactant was investigated. Different interfacial tension (IFT) measurements were performed to find the effect of IL concentration and temperature on the IFT of water/crude oil system. The observed trend was explained based on mass transfer mechanisms including diffusion and convective mass transfer. In addition, the effect of rotational speed, ranging between 3000 and 9000 rpm, on the IFT was examined with the hypothesis that it can modify the convective mass transfer. Finally, since it has been reported that the Marangoni effect enhances the mass transfer flux in the surfactant solutions, two different methods of IFT measurements including the spinning drop and pendant drop methods were applied to investigate the effects of convective mass transfer on the equilibrium IFT.     

Comparative study on the stabilities and properties of heterodimers containing the intermolecular interactions of CF2Cl2 with the isoelectronic and isostructure species of N2O and CO2

The computational investigations are carried out on the heterodimers containing CF₂Cl₂ with isoelectronic and isostructure (linear triatomics) species of N₂O and CO₂ through MP2/aug-cc-pV(D+d)Z, MP2/aug-cc-pV(T+d)Z//MP2/aug-cc-pV(D+d)Z, and CCSD(T)/aug-cc-pV(D+d)Z//MP2/aug-cc-pV(D+d)Z levels. Five and twelve heterodimers are located on the potential energy surface of CF₂Cl₂–CO₂ and CF₂Cl₂–N₂O systems, respectively. Binding energies of heterodimers in the CF₂Cl₂–CO₂ and CF₂Cl₂–N₂O systems corrected with BSSE are in the ranges of 1.30–5.79 and 1.30–6.85 kJ/mol at the MP2/aug-cc-pV(T+d)Z//MP2/aug-cc-pV(D+d)Z level, respectively. The calculated results reveal that the five most stable heterodimers among all heterodimers obtained for the CF₂Cl₂–CO₂ and CF₂Cl₂–N₂O systems belong to CF₂Cl₂–N₂O system. Therefore, CF₂Cl₂–N₂O system has more key role than CF₂Cl₂–CO₂ one in the atmosphere.     

Reflection of waves in a waveguide from a boundary with nonlinear stiffness: application to axial and flexural vibrations

Nonlinear Dynamics - The reflection of time-harmonic waves in a waveguide with a nonlinear boundary stiffness is considered with applications to rods and beams. Incident waves at frequencies that...     

Energy,Exergy, Exergoeconomic and Exergoenvironmental Impact Analyses and Optimization of Various Geothermal Power Cycle Configurations

Energy, exergy, and exergoeconomic evaluations of various geothermal configurations are reported. The main operational and economic parameters of the cycles are evaluated and compared. Multi-objective optimization of the cycles is conducted using the artificial bee colony algorithm. A sensitivity assessment is carried out on the effect of production well temperature variation on system performance from energy and economic perspectives. The results show that the flash-binary cycle has the highest thermal and exergy efficiencies, at 15.6% and 64.3%, respectively. The highest generated power cost and pay-back period are attributable to the simple organic Rankine cycle (ORC). Raising the well-temperature can increase the exergy destruction rate in all configurations. However, the electricity cost and pay-back period decrease. Based on the results, in all cases, the exergoenvironmental impact improvement factor decreases, and the temperature rises. The exergy destruction ratio and efficiency of all components for each configuration are calculated and compared. It is found that, at the optimum state, the exergy efficiencies of the simple organic Rankine cycle, single flash, double flash, and flash-binary cycles respectively are 14.7%, 14.4%, 12.6%, and 14.1% higher than their relevant base cases, while the pay-back periods are 10.6%, 1.5% 1.4%, and 0.6% lower than the base cases.     

Investigation of the formation of acid rain based on the sulfur tetroxide (SO4 (C2v)) and OH radical reaction

Structural Chemistry - The reaction pathways of sulfur tetroxide (SO4 (C2v)) with OH radical have been investigated at the MP2/6-31++G(d,p) and G3MP2B3 levels. The mechanism I (Transfer of O-atom...     

Synthesis and Characterization of Carbon-Stabilized Magnesium Nanoparticles

Magnesium nanopowder has attracted many interests in the recent years, which has a very difficult and costly synthesis process because of its high activity. In this work, magnesium nanoparticles stabilized with amorphous carbon (Mg–C nanoparticles) were synthesized by submerged arc discharge technique in kerosene. The arc discharge was generated between two electrodes of magnesium at the arc current of 1 A and arc voltage of 50 V. Mg–C nanoparticles were characterized by various techniques. Dynamic light scattering result indicated that size of magnesium nanoparticles is about 35 nm. X-ray diffraction showed that the produced sample consisted of hexagonal magnesium and amorphous carbon and there was no presence of magnesium oxides in the pattern. Field emission scanning electron microscopy and transmission electron microscopy results illustrated that the sample has morphology of agglomerated nanospheres. Energy dispersive X-ray spectroscopy demonstrated formation of 57 percent magnesium and 43 percent carbon. Differential scanning calorimetry analysis showed that the amorphous carbon increased ignition temperature of nanoparticles by 180 °C compared to pure magnesium micron-sized powder. Therefore, Mg–C nanoparticles can have many applications in different fields similar to magnesium nanopowders. However, by producing Mg–C nanoparticles, there is no need for vacuum chamber or inert gases during production and after that, since amorphous carbon protects magnesium nanoparticles from oxidation.