Hugo Bianchi - Profile on Academia.edu (original) (raw)

Papers by Hugo Bianchi

The (water+acetonitrile) mixture revisited: A new approach for calculating partial molar volumes

The Journal of Chemical Thermodynamics, 2006

Density and viscosity of (water+acetonitrile) mixtures were measured over the whole composition r... more Density and viscosity of (water+acetonitrile) mixtures were measured over the whole composition range at the temperatures: (298.15, 303.15, 308.15, 313.15, and 318.15)K. A new mathematical approach was developed which allows the calculation of the derivatives of density with respect to composition avoiding the appearance of local discontinuities. Thus, reliable partial molar volumes and thermal expansion coefficients were obtained.

The Journal of Physical Chemistry B, 2007

Refractive indices n and salt concentrations ms of coexisting phases of the ternary system 1,4-di... more Refractive indices n and salt concentrations ms of coexisting phases of the ternary system 1,4-dioxane + water + potassium chloride were measured along the liquid-liquid-solid coexistence curve near the liquid-liquid critical end point. Refractive index measurements were carried out in the range 0.689 x 10-3 < t = (T - Tc)/Tc < 0.118 while salt concentrations were determined for the temperature range 1.84 x 10-3 < t < 8.07 x 10-2. From these experimental results, compositions fD (mass fraction of dioxane on a salt-free basis) and densities rho of coexisting phases were obtained. The shape of the coexistence curve was analyzed using alternatively n, ms, fD, and rho as order parameters. In all cases, the obtained coexistence curve displays, asymptotically, Ising behavior. Outside the asymptotic critical domain, n, ms, and rho show significant deviations of the effective critical exponent from its Ising value, while the concentration variable fD requires no corrections to simple scaling. On the basis of the present results, we conclude that this system shows no indication of multicritical behavior.

The Journal of Chemical Thermodynamics, 2005

Ionic association between Cu 2+ (aq) and SO 2À 4 ðaqÞ has been studied in the temperature range (... more Ionic association between Cu 2+ (aq) and SO 2À 4 ðaqÞ has been studied in the temperature range (298 to 473) K using a spectrophotometric technique. Experiments were designed to minimize the contribution of other protolytic equilibria in solution. The values of the ionic association equilibrium constant at different temperatures and pressures were fitted to an appropiate equation that allows the calculation of the thermodynamic quantities for states close to the saturation line. Using BjerrumÕs model for ionic association evidence for two ion pair populations was obtained. The process of ion pairing is discussed and a possibility to reconcile the continuum model (Bjerrum) with molecular simulation results is suggested.

Excess molar volumes and densities of (methanol+water) at temperatures between 323 K and 573 K and pressures of 7.0 MPa and 13.5 MPa

The Journal of Chemical Thermodynamics, 1997

ABSTRACT Densities of {xCH3OH+(1−x)H2O} relative to water were measured in a vibrating-tube densi... more ABSTRACT Densities of {xCH3OH+(1−x)H2O} relative to water were measured in a vibrating-tube densimeter at the temperatures (323,373,423,473,523, and 573) K and at pressures of 7.0 MPa and 13.5 MPa. Excess molar volumesVmEfor {xCH3OH+(1−x)H2O} were calculated from the experimental densities for the mixtures, using accurate equations of state for water and methanol. The data were treated with a modified corresponding-state model based on the properties of pure water. An empirical function was used to fit small differences between the compression factors of {xCH3OH+(1−x)H2O} and the compression factor of H2O at the same reduced temperature and the same reduced pressure. The corresponding-states treatment reproduces the measured densities to within the experimental uncertainty of 0.4 kg·m−3at all of the temperatures and pressures studied, except atT=573 K andp=13.5 MPa. The densities, excess molar volumes, partial molar volumes, isothermal compressions, and cubic expansion coefficients from the model are consistent with the limited literature data available. The behaviour ofVmEatT=573.6 K andp=13.7 MPa indicates either a very narrow region of (vapour+liquid) phase separation, or near-critical behaviour atx≈0.44 with the critical pressurepc≤13.5 MPa.

Journal of Solution Chemistry, 1995

A Picker flow microcalorimeter and a flow densimeter were used to obtain apparent molar heat capa... more A Picker flow microcalorimeter and a flow densimeter were used to obtain apparent molar heat capacities and apparent molar volumes of aqueous solutions of Na3P04 and mixtures of Na,zHP04 and NaH2P04. Identical measurements were also made on solutions of tetramethylammonium salts to evaluate the importance of anion.cation interactions. The experimental apparent molar properties were analyzed in terms of a simple extended Debye-H~lckel model and the Pitzer ion-interaction model, both with a suitable treatment for the effect of chemical relaxation on heat capacities, to derive the partial molar properties of H2PO~(aq), HPO~(aq) and PO~(aq) at infinite dilution. The volume and heat capacity changes for the second and third ionization of H3PO4(aq) have been determined from the experimental data. The importance of ionic complexation with sodium is discussed.

The conductivity of dilute electrolyte solutions: Expanded lee and wheaton equation for symmetrical, unsymmetrical and mixed electrolytes

Journal of Solution Chemistry, 1993

The conductivity equation of Lee and Wheaton is expanded in a power series in the ionic strength ... more The conductivity equation of Lee and Wheaton is expanded in a power series in the ionic strength I. Different levels of approximation are analyzed and it is shown that for unsymmetrical electrolytes it is necessary to keep the terms I3/2lnI and I2 to maintain the performance of the full equation.

Journal of Solution Chemistry, 1989

As part of a cooperative study of the thermodynamic and transport properties of aqueous mixtures ... more As part of a cooperative study of the thermodynamic and transport properties of aqueous mixtures of NaCI and MgClz at 25~ we report values of the molar conductivities of the mixed electrolyte in the concentration range 0.5 to 3.6 molar. It was found that the conductivities in the mixtures differ from those calculated assuming additivity of the conductivities of the component binary solutions by 4.65 S-cm2-mol "1 at constant total molarity and 0.50 S-cm2-mol 1 at total ionic strength.

Journal of Solution Chemistry, 1992

The conductivities of dilute aqueous mixtures of NaCl-MgClz have been determined at various ionic... more The conductivities of dilute aqueous mixtures of NaCl-MgClz have been determined at various ionic compositions and at 25~ These results are used to assess the applicability of modern theories of electrolytic conductivity.

Journal of Solution Chemistry, 2000

A flow-through electrical conductance cell was assembled in order to measuremolar conductances of... more A flow-through electrical conductance cell was assembled in order to measuremolar conductances of dilute aqueous electrolytes with a high degree of accuracyat high temperatures and pressures. The design of the cell is based on the conceptdeveloped at the University of Delaware and built in 1995, with modificationsthat will allow the cell to operate at much higher temperatures (to 600°C) andpressures

Aerosol-Assisted Production of Mesoporous Titania Microspheres with Enhanced Photocatalytic Activity: The Basis of an Improved Process

ACS Applied Materials & Interfaces, 2010

An aerosol-based process was used to prepare mesoporous TiO(2) microspheres (MTM) with an average... more An aerosol-based process was used to prepare mesoporous TiO(2) microspheres (MTM) with an average diameter in the range of 0.5-1 microm. The structural characteristics and photocatalytic properties of the synthesized materials were determined. As-prepared MTM materials and those heated in air from 400 to 600 degrees C exhibited mesoporous texture with a narrow size distribution and an inorganic framework that consisted of 4-13 nm anatase crystallites. Pore volumes for the MTM materials were in the range of 0.17-0.34 cm(3) g(-1). Microspheres heated to 400 degrees C presented a locally ordered mesopore structure and possessed X-ray diffraction d spacings between 9.8 and 17.3 nm. Heating above 400 degrees C resulted in a loss of the mesoscopic order, a decrease of the surface area, retention of the porosity, and an increase of the anatase nanoparticle size to 13 nm. The accessibility of the pore volume was measured by monitoring the uptake of gallic acid (GA) using Fourier transform IR. The MTM materials made excellent catalysts for the photodegradation of GA, with the performance being higher than that of an equivalent sample of Degussa P25. The present MTM materials are advantageous in terms of their ease of separation from the aqueous phase, and hence a novel photocatalytic process is proposed based on separate adsorption and photocatalytic decomposition steps with an improved and more rational use of both catalyst and sunlight.

The Journal of Chemical Thermodynamics, 2003

The densities of aqueous solutions of 4-methylphenol and its mixtures with sodium hydroxide were ... more The densities of aqueous solutions of 4-methylphenol and its mixtures with sodium hydroxide were measured as a function of concentration at T ¼ 298 K at atmospheric pressure, and between the temperatures 373 K and 463 K at a pressure of 2 MPa. The partial molar volume at infinite dilution of 4-methylphenol (HCRES) and its sodium salt (NaCRES) were determined by the application of the Pitzer ion-interaction treatment to the solutions neglecting high order terms. The reported values of partial molar volume of 4-methylphenol are in good agreement with literature data.