Iranian Journal of Chemical Engineering (IJChE)

Abstract This study employs classical molecular dynamics simulations using the OPLS-AA force field to systematically investigate the influence of the length of alkyl chain on the structural, thermodynamic, and dynamical properties of a homologous series of pyridinium-based ionic liquids (methyl- to pentyl-pyridinium bromide). The main objective is to elucidate how the gradual elongation of the alkyl chain affects intermolecular interactions and ion transport behavior at the molecular level. The model demonstrates good agreement with available experimental density data, confirming its reliability for predicting physicochemical trends in these systems. The results indicate that increasing the length of the alkyl chain weakens electrostatic interactions and enhances free volume, leading to a systematic reduction in density and cohesive energy density. The structural analysis reveals well-defined cation–anion coordination shells, reflecting strong local ionic organization across all systems. The dynamical analysis shows a consistent decrease in the ionic mobility with the elongationof chains, due to stronger van der Waals interactions and steric effects, which in turn reduce diffusion and ionic conductivity. Importantly, the ionic transference numbers calculated from ion mobilities clearly demonstrate that cations contribute more to charge transport than anions in all investigated systems. This cation-dominated transport behavior provides a direct molecular-level explanation for the observed decrease in ionic conductivity by increasing the length of chains.

Abstract In this study, nanoporous silica aerogel and silica aerogel-activated carbon composites have been synthesized using a water glass precursor by cost effective ambient pressure drying method. Equilibrium and kinetics of benzene and ethyl benzene adsorption on silica aerogel and its composites have been measured in a batch mode at tree weights of adsorbent. For the first time, the experimental data have been fitted with intra-particle diffusion model for determining of diffusion coefficients. The saturation adsorption capacity of benzene and ethyl benzene vapours was 2033 mg.g-1 and 458 mg.g-1 respectively. The components uptake curves have been described by mathematical models of pseudo first order and pseudo second order models. It has been found that the pseudo first order model fits the experimental data better than the pseudo second order model. Also, the pseudo-second order model could be used for modeling of benzene adsorption over silica aerogel and silica aerogel-2% wt. activated carbon composite at the beginning of adsorption process. The diffusion coefficients of benzene and ethyl benzene within the silica aerogel were in the range of 〖2.16×10〗^(-14) - 〖6.66×10〗^(-13) m2.s-1 and 〖3.65×10〗^(-13) - 〖1.95×10〗^(-12) m2.s-1, respectively.

Abstract Migration of styrene monomer from polystyrene (PS) dishes was conducted during this research at temperatures of 5, 20, and 40 °C. According to the Food and Drug Administration (FDA) regulations, these experiments were performed in contact with 10%ethanol as a food simulant for the oil in water (o/w) emulsions. The dishes were filled in each of the defined temperatures and stored for 35 days. In relatively close intervals (1, 7, 15, 24, and 35 days) the amount of migration which occurred was determined by means of Head Space Gas Chromatography Mass Spectrometry (HS-GC-MS). By increasing storage time and temperature, the amount of migration was increased and in all times and temperatures styrene monomer was detected. In addition, a mathematical model based on the Fick’s second law was validated to predict migration from packaging material into the 10% ethanol. The resulted diffusion coefficients were 3.6×10-18, 4.9×10 -18, and 6×10 -18 (m2/s) in 5 ,20 and 40 °C respectively.

Abstract In this study some properties ofthe methanol-water mixture such as diffusivity, density, viscosity, and hydrogen bonding were calculated at different temperatures and atmospheric pressure using molecular dynamics simulations (MDS). The results were compared with the available experimental data as well as some theoretical models; overall indicating a good agreement. This shows the useful and effective application of MDS for determination ofphysical properties.