Yadollah Maham

Densities, excess molar volumes, and partial molar volumes for binary mixtures of water with monoethanolamine, diethanolamine, and triethanolamine from 25 to 80°C

We have measured densities of binary mixtures of water with monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) over the full range of compositions and over the temperature range from 25 to 80°C. Results of these measurements have been used in calculating excess molar volumes and partial molar volumes. Knowledge of the volumetric properties of these mixtures is useful in connection with industrial treatment of acidic gases; derived excess molar volumes and partial molar volumes can be used as a basis for understanding some of the molecular interactions in water-organic mixtures.

Sorption of phenol by selected biopolymers : isotherms, energetics, and polarity

The behavior of phenol in the terrestrial environment is strongly regulated by its reaction with soil components. We report here on the uptake of phenol by soil minerals (goethite, kaolinite, and montmorillonite) and by organics that may occur naturally in or be added to soil (two lignins, chitin, cellulose, collagen, and activated carbon). Our objectives were to determine the energetics and capacity for their uptake of phenol using batch equilibration, calorimetry, and CPMAS 13 C NMR and to evaluate the relation of organic carbon referenced sorption coefficient (K oc ) with the polarity of biopolymers. The biopolymers sorbed 2-45-fold more phenol than did the minerals

Viscosities and excess properties of aqueous solutions of ethanolamines from 25 to 80° C

Viscosities of aqueous solutions of monoethanolamine and triethanolamine have been measured from 25 to 80°C over the entire range of concentrations. The excess Gibbs energies for viscous flow have been calculated for aqueous solutions of monoethanolamine, triethanolamine, and also for diethanolamine and methyldiethanolamine from our earlier work [J. Chem. Eng. Data39, 290 (1994)]. The entropy of viscous flow was obtained by using the temperature dependence of the excess Gibbs energy for viscous flow. The structural effects on the viscosity, excess Gibbs energy, and entropy for viscous flow are discussed.

MOLAR HEAT CAPACITIES OF ALKANOLAMINES FROM 299.1 TO 397.8 K: GROUP ADDITIVITY AND MOLECULAR CONNECTIVITY ANALYSES

The molar heat capacities of 14 alkanolamine compounds have been measured at five separate temperatures in the range 299.1 to 397.8 K. These compounds were monoethanolamine (MEA), monomethylethanolamine (MMEA), dimethylethanolamine (DMEA), monoethylethanolamine (MEEA), diethylethanolamine (DEEA), n-propylethanolamine (n-PEA), diisopropylethanolamine (di-PEA), diethanolamine (DEA), methyldiethanolamine (MDEA), ethyldiethanolamine (EDEA), n-butyldiethanolamine(n-BDEA), tert-butyldiethanolamine (tert-BDEA), triethanolamine (TEA) and 2-amino-2-methylpropan-1-ol (AMP). Molar heat capacities of these compounds show a structural dependence, where the molar heat capacity of one molecule may be considered as the sum of various group contributions. Hence, the reported molar heat capacity data have been used as input to a group additivity analysis that yields estimates of CH 2 , OH, NH and N group contributions to molar heat capacities at each investigated temperature. The additivity principle has been explored in more detail by using molecular connectivity indexes to obtain a simple five-term equation that models the molar heat capacities of the investigated alkanolamines over the entire experimental temperature range.

The kinetics of thermal instability in nanocrystalline silver and the effect of heat treatment on the antibacterial activity of nanocrystalline silver dressings.

The kinetics of nanocrystalline silver dressing heat treatment was investigated via isothermal heat treatments at 90 degrees C, 100 degrees C, and 110 degrees C lasting 2-50h. Bactericidal efficacy of the dressings was measured via log reductions, while bacteriostatic longevity was determined via plate-to-plate transfer corrected zones of inhibition. Morphological evolution of the dressing was studied by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy, while changes in heat flow were measured by differential scanning calorimetry. Increasing temperature increased the rate at which dressing bactericidal activity and bacteriostatic longevity decreased. Once changes in dressing properties began, they occurred nonlinearly with time. The earliest biological, chemical, and physical indicators of altered dressing properties were loss of bacteriostatic longevity, silver-oxygen bonds, and fine features, respectively. An early change in heat flow appeared to be responsible for these indicators, while a later change corresponded to rapid grain growth occurring after a critical crystallite size (approximately 30 nm) was reached. The grain growth exponent was determined to be 2.8 for temperatures of 100-110 degrees C, with an activation energy of 177 kJ/mol, suggesting that normal grain growth occurred, with volume and/or grain boundary diffusion as the dominant forms of diffusion. The thermal instability of nanocrystalline silver should be accounted for during production, storage, and use of dressings. The properties required for nanosilver antimicrobial efficacy demonstrated in this study, as well as its thermal instability, should be taken into consideration for the development of nanosilver products in the future.

Effect of solvent structure on electron reactivity: 2-propanol/water mixtures

The reactivity of solvated electrons with efficient (nitrobenzene, acetone) and inefficient (phenol, toluene) scavengers is affected greatly by the solvent composition in 2-propanol/water mixed solvents. 2-Propanol is the only secondary alcohol that is completely miscible with water. The variation of the nitrobenzene rate constant k2 with solvent composition displays four viscosity zones, as in primary and tertiary alcohol/water mixtures. In zone (c), where the Stokes–Smoluchowski equation applies, the nitrobenzene k2 values in the secondary alcohol/water mixtures are situated between those in the primary and tertiary alcohols, due to the relative values of the dielectric permittivity e. The charge–dipole attraction energy varies as e−1.The two water-rich zones (c) and (d) are characterized by a large change of viscosity η and a small change in solvation energy (trap depth) Er; here k2 for all the scavengers correlates with the inverse of the viscosity. In the two alcohol-rich zones (a) and (b) the change...

Volumetric Properties of Poly (Vinyl Alcohol, Vinyl Sulfate Ester Salt) Polyelectrolytes in Salt Free Aqueous Solutions

Abstract Sharp break points in the apparent molar volume and compressibility functions of poly (vinyl alcohol co‐vinyl sulfate sodium salt) copolymers were found in the 0.01–0.03 molal‐segment concentration range in aqueous solution. Both apparent molar volume and compressibility increase linearly with concentration below the break point, while they show saturation type characteristic above the break point. The position of break point is independent of the vinyl‐sulfate/(vinyl‐sulfate and vinyl‐alcohol) group‐ratio of the polyelectrolyte. An association process between the individual polyelectrolyte molecules is suggested for the interpretation of break points. The partial molar volumes at infinite dilution depend linearly on the vinyl sulfate sodium salt group content. The partial molar volume contribution of (vinyl sulfate sodium salt)‐group and (vinyl alcohol)‐group were determined from concentration ranges corresponding to both the associated and non‐associated state of the polyelectrolyte salt.

Understanding the Role of Surface Micro-Texture on the Delayed Freezing of Drops on Cold Surfaces

Freezing of drops on surfaces has many consequences in icing of various systems, e.g. micro-condensers. It is known that when a water drop is placed on a cold surface and the surface temperature is reduced, it will not necessarily freeze when the surface temperature has reached zero degrees Celsius. The delay in freezing of a drop on a cold surface is not well understood; especially the effect that micro- and nano-texture of a surface has this delay. In this study, freezing and melting points of water drops on various micro-textured surfaces, i.e. superhydrophilic, and superhydrophobic have been measured by differential scanning calorimetry (DSC). A comparison of the experimental results with smooth hydrophilic and hydrophobic surfaces allows us to understand the roles of surface chemistry and roughness in freezing of drops in contact with such surfaces. It is found that when the surface chemistry is hydrophobic, roughness will delay the freezing and a drop may not freeze until the surface temperature has been lower than −15 ° C. On the contrary, for hydrophilic surfaces, roughness will shorten the freezing delay and facilitate formation of ice on the surface. This can explain the benefit of the superhydrophobic surfaces (SHS) in preventing ice formation.Copyright