Gregorio Borge

Development of a Modified Bromley's Methodology (MBM) for the estimation of ionic media effects on solution equilibria Part 1. Calculation of the interaction parameters in the molar and molal scales at 25°C

Abstract The development of a methodology in order to study the medium effects on solution equilibria is presented in this series. This methodology uses Bromleys approach for the estimation of activity coefficients of species in solution. In this first part, the values of the interaction parameters obtained by means of the so-called Modified Bromleys Methodology (MBM) are given for more than 80 strong electrolytes for both the molar and the molal scales at 25°C. The parameters are calculated from the recommended values of the mean activity coefficients in the molal scale collected in the literature.

Development of a Modified Bromley's Methodology (MBM) for the estimation of ionic media effects on solution equilibria. Part 2. Correlation of the molar and molal interaction parameters with the charge and crystal radii of the ions

Abstract The interaction parameters of strong electrolytes obtained for both the molar and molal scales using the Modified Bromleys Methodology (MBM) have been correlated with the ionic charge and individual crystal radius of each ion. The correlation function for each ion with opposite counterions is a straight line centered in the water radius value (1.39 × 10−10m). These correlations allow the prediction of values of unknown interaction parameters of a cation with several anions even if only one interaction parameter of the cation with a given anion is known.

Development of a Modified Bromley's Methodology for the estimation of ionic media effects on solution equilibria: Part 3. Application to the construction of thermodynamic models

Abstract The development of the Modified Bromleys Methodology (MBM) is extended for the estimation of the activity coefficients of individual species in aqueous solution at 25°C in single and mixed ionic media. The estimation is compared with literature data of activity coefficients of mixtures of electrolytes in water and applied to (a) the prediction of the ionic product of water in aqueous solutions containing different salts which are commonly used as background electrolytes (NaCl, KNO3 and NaClO4) and (b) the equilibrium constants of the Cr(VI)–H2O system.

Optimisation of flow-injection-hydride generation inductively coupled plasma spectrometric determination of selenium in electrolytic manganese.

Flow-injection-hydride generation procedure for Se in electrolytic manganese was optimized by means of the experimental design approach. Instrumental variables like power supplied (P), sample (F) and argon (G) flow rates together with chemical variables like NaBH(4) and HCl concentrations were studied. In case of the chemical variables, it was concluded that sodium tetrahydridoborate concentrations higher than 1.0% extinguished the plasma while HCl concentration should always be higher than 0.6moldm(-3). The analysis of effects suggested that all the instrumental variables are significant factors, and the optimum conditions were P=1550W, F=4.75mLmin(-1) and G=0.6mLmin(-1). The influence of Mn was specially studied and it was concluded that the interferences were negligible if Mn is below 2.0gL(-1). In the same sense, the interferences of antimony(III), arsenic(V) and mercury(II) were also considered negligible. Finally, a detection limit of 0.0005% (w/w) was obtained (a repeatability R.S.D. <2.0% for all Se concentrations tried). Some manganese samples were also spiked with different concentrations of Se(IV) and the results demonstrated to be in good statistical agreement with expected values.

On the liquid junction potential for the determination of equilibrium constants by means of the potentiometric technique without constant ionic strength

Abstract A modified method for the calculation of liquid junction potentials based on the Henderson equation is proposed. The estimation of the activity coefficients and the conductivities is performed by means of the Modified Bromley Methodology [ G. Borge, R. Castano, M.P. Carril, M.S. Corbillon, J.M. Madariaga, Fluid Phase Equilibria 121 (1996) 85–98; G. Borge, N. Etxebarria, L.A. Fernandez, M.A. Olazabal, J.M. Madariaga, Fluid Phase Equilibria 121 (1996) 99–109. ] and the Extended Falkenhagen Equation [ A. De Diego, Conductivity of concentrated electrolytic solutions: study of the dependence with concentration and temperature, Ph.D. Thesis, University of the Basque Country, Bilbao, 1996. ]. The efficiency of the method has been tested in potentiometric titrations without constant ionic strength. Its applicability to potentiometric titrations with constant ionic strength is also discussed.

Determination of ion exchange equilibrium constants of strongly acidic resins with alkaline-earth metals by means of the potentiometric titrations technique.

A recently developed methodology for the determination of ion exchange equilibrium constants has been applied to ion exchange systems of 1:2 stoichiometry. Potentiometric titrations with variable ionic strength were carried out. Ionic medium titrations were performed for the estimation of the liquid junction potential. The modified Bromleys methodology and the Wilson model were used for the estimation of the activity coefficients of the species in the aqueous and resin phase, respectively. A modification of the Henderson equation is used for the estimation of liquid junction potentials in the mixtures including 1:2 electrolytes. Equilibrium constants for the H(+)/M(2+) (M=Mg, Ca, Sr and Ba) exchange systems in the strongly acidic resins Dowex CM-15 and Dowex C650 were studied.

Permeation of Mixtures of Four Phenols through a Supported Liquid Membrane in NaCl 1.0 mol·dm−3 Medium

The permeation of four phenols (phenol, 2-chlorophenol, 2-nitrophenol, and 2,4-dichlorophenol) through a supported liquid membrane has been studied in NaCl 1.0 mol·dm−3medium. The flux of each phenol was determined by measuring in real time the change of their concentration in the strip phase by making use of a fiber optic spectrophotometer and a multivariate calibration. The model for the permeation of phenol alone was first developed by making permeation experiments of a phenol, and then permeation studies of the mixture were carried out and the model was extended to those phenols. It was found that the permeation of a phenol is interfered with by the presence of other phenols.

Determination of equilibrium constants of strong acidic ion exchange resins by potentiometric titrations.

A new method for the determination of ion exchange equilibrium constants is developed. A technique based in the application of potentiometric titrations is used in the study of non selective strong acidic resins. Potentiometric titrations are carried out without constant ionic strength, so a mathematical treatment is developed in order to take into account the estimation of the activity coefficients and the liquid junction potentials. The ion exchange thermodynamic equilibrium constants for two resins, Dowex CM-15 and Dowex C650, between the proton form and the alkaline metals at 25 degrees C are given.

Comparison of thermodynamic models for ion exchange between strongly acidic resins and the metal transitions Ni(II) and Cu(II)

Abstract The ion-exchange equilibrium constants of the systems H + Ni(II) and H + Cu(II) for the strongly acidic cationic resins Dowex CM-15 and Dowex C650 have been determined. The results have been interpreted by means of three ion-exchange thermodynamic models currently used. Differences in the application of the models and necessary further developments for some of them are given.

Determination of thermodynamic equilibrium constants of H+–Zn(II), H+–Cd(II) and H+–Fe(III) exchanges on strongly acidic exchangers

Abstract The ion-exchange equilibrium constants of the H + –Zn(II), H + –Cd(II) and H + –Fe(III) systems for the strongly acidic cationic resins Dowex CM-15 and Dowex C650 have been determined. The results have been interpreted by means of the surface complex formation model, the three-parameter model and the Wilson model. A methodology for the prediction of the equilibrium constant values of the three-parameter and Wilson models from the values obtained using the surface complex formation model is given and discussed.