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Papers by Alberto E Regazzoni

Croatica Chemica Acta, 2007

TiO 2 surface complexation by bidentate organic ligands is analysed in terms of the ligand Bronst... more TiO 2 surface complexation by bidentate organic ligands is analysed in terms of the ligand Bronstead and Lewis basicities. The complexation and basicity constants comply with linear Gibbs Energy relationships (LGERs). For dicarboxylic acids, the surface chelate bond makes an approximately constant contribution to the stability. The proton transfer to the surface modulates the pH dependence of stability. A correlation exists between the surface complexation constant of the neutral acid H 2 L and the ligand first acidity constant. On the other hand, the surface complexation constants of dianions L 2- of cathecols and aminophenols are positively correlated with the ligand second acidity constant. Apparent stability is determined by the competition of H + and surface metal ions for the ligand. Stability trends are strongly influenced by the Bronstead acid base reaction between the acid ligands H 2 L and the surface, whereas the stability of the surface chelate contributes to the overall...

Journal of colloid and interface science, 2017

Chemisorption of Eu(3+) and Tb(3+) on SBA-15 functionalized with succinic groups has been studied... more Chemisorption of Eu(3+) and Tb(3+) on SBA-15 functionalized with succinic groups has been studied by in situ steady-state fluorescence measurements. The enhancement of the emission sensitive bands indicates that both ions adsorb forming inner-sphere surface complexes. Adsorption is a fast process that attains equilibrium in about 5min. The variation of the peaks maxima (I592 and I616, for europium, and I490 and I545, for terbium) with the total ion concentration is accounted for by the sum of the contributions due to the adsorbed and free ions. The former contribution is langmuirian. At pH 4.5, the respective adsorption constants are 5×10(5) and 3×10(5)M(-1), and the maximum adsorption capacities are 5.10×10(-4) and 5.23×10(-4)molg(-1). The mismatch between the latter values and the number of attached carboxylic groups is discussed. Comparison with other functionalized mesoporous silicas indicates that the anchored succinic groups are very efficient for removing lanthanide ions from...

The Journal of Physical Chemistry B, 2005

FTIR spectra of hexacyanoferrate(III)-exchanged hydrotalcites (A) and ratio of the absorbance due... more FTIR spectra of hexacyanoferrate(III)-exchanged hydrotalcites (A) and ratio of the absorbance due to interlamellar ferricyanide and carbonate ions (B). The broad band centered at ca. 3440 cm −1 is due to the ν O−H stretching vibration of hydrogen-bonded geminal OH groups and water molecules, and that at 1636 cm −1 corresponds to the bending of water. Bands at 2117 and 2034 cm −1 are due to the ν C≡N vibration of the intercalated complex, and that at 1365 cm −1 corresponds to interlamellar free carbonate. 1 The linear dependence of the ratio (A 2117 + A 2034)/A 1365 with x (i.e., the mole fraction of HT(Fe(CN) 6) 1/3) confirms that Fe(CN) 6 3− ions do not replace CO 3 2− anions.

Journal of colloid and …, 1989

... conditions. Stationary state dissolution according to Scheme [ 13 ] yields RI = k~httkehKa, {... more ... conditions. Stationary state dissolution according to Scheme [ 13 ] yields RI = k~httkehKa, { >Fen'} [ FeY2-] exp ( azeAlPo / kT) { k-et, [ FeY-] }, [151 + k~htl exp ( azeA~bo / kT) - 1 Journal of Colloid and Interface Science, Vol. 130, No. ...

Journal of Colloid and Interface Science, 1984

... Adsorption of EDTA and IronEDTA Complexes on Magnetite and the Mechanism of Dissolution of Ma... more ... Adsorption of EDTA and IronEDTA Complexes on Magnetite and the Mechanism of Dissolution of Magnetite by EDTA MIGUEL A. BLESA, ELENA ... 1. The data fit well into Langmuir isotherms; from these, areas per adsorbed molecule at saturation coverage and Gibbs energies of ...

Journal of Materials Science, 1996

ABSTRACT The dissolution of YBa2Cu3O6.8 in acidic aqueous solutions was studied at 298 K as a fun... more ABSTRACT The dissolution of YBa2Cu3O6.8 in acidic aqueous solutions was studied at 298 K as a function of pH, nature and concentration of present anions and time, t. In the range 2.0 less than or equal to pH less than or equal to 4.0, dissolution is congruent and proceeds to completion; dissolution profiles are deceleratory and comply with a contracting volume rate law up to t(0.5). The rate of dissolution, which is limited by slow surface reactions, decreases with increasing pH; the kinetic order on proton concentration is a fractional and variable number. At higher pH values, dissolution is arrested at intermediate conversion values. In these cases, congruent dissolution is followed by the precipitation of less soluble solid phases which form a passive layer. The nature of this passive layer depends on pH and on the nature and concentration of present anions, which also define the extent of conversion attained at passivation. The dissolution behaviour of YBa2Cu3O6.8 is described in terms of two consecutive surface reactions: fast equilibrated protonation of surface metal ions is followed by the slow release of cations. Barium surface ions are identified as the more reactive sites. The effect of the fast initial leaching of barium ions on the reactivity of yttrium and copper sites is discussed. The influence of the formal Cu(III) oxidation state is also stressed.

Chemical Physics Letters, Dec 1, 2006

Sorption of toluene and nitrobenzene by dodecyl sulfate intercalated-hydrotalcite was studied as ... more Sorption of toluene and nitrobenzene by dodecyl sulfate intercalated-hydrotalcite was studied as a function of solute concentration. The correlation between the derived partition coefficients and the solubilities of the aromatic solutes in water indicates that the main sorption mechanism is partitioning. The partition behavior of nitrobenzene is Henry ideal, whereas the isotherm for toluene is convex, i.e., type III. These unlike behaviors are accounted for by casting the activity coefficients of the solutes solubilized within the hydrophobic interlamellar space of the hybrid-hydrotalcite in terms of the Flory-Huggins theory, the value of the mixing parameter determining the isotherm shape.

Catal Today, 2002

The use of ATR–FTIR to probe the adsorption of oxalic and salicylic acids, and of mixtures of bot... more The use of ATR–FTIR to probe the adsorption of oxalic and salicylic acids, and of mixtures of both, onto TiO2 (Degussa P-25) demonstrates the potential of the technique to characterise the evolution of the catalyst with time, including surface poisoning. Under equilibrium dark conditions, three surface species are formed by oxalate, and two by salicylate. Their stabilities, described by conditional Langmuir-type equilibria involving the dissociative, electroneutral adsorption of the acids H2L, are at pH 3.7, 2.4×106, 3.0×104 and 3.0×103 mol−1 dm3 for oxalic acid, and 2.9×105 and 9.1×103 mol−1 dm3 for salicylic acid. The nature of the species is discussed in terms of their spectral features. The displacement of each acid from the surface by addition of the other one was followed also by ATR–FTIR. The results demonstrate that oxalate displaces totally chemisorbed salicylate, whereas salicylate displaces oxalate only partially. These results are explained by assuming competitive chemisorption onto two different surface sites, plus oxalate adsorption onto a site that exhibits negligible affinity for salicylate. Irreversible adsorption by partially oxidised products in the course of photocatalytic processes can therefore be assessed by ATR–FTIR.

Colloids and Surfaces, 1983

ABSTRACT

The Journal of Physical Chemistry B, 2005

The intercalation of hexacyanoferrate(III) in chloride-hydrotalcite was studied as a function of ... more The intercalation of hexacyanoferrate(III) in chloride-hydrotalcite was studied as a function of the composition of the equilibrated aqueous phase, the relevant solution variable being the ratio (C Fe(CN) 6 3-) 1/3 /C Cl -. The isotherm shows that the exchange is markedly nonideal and reveals the segregation of two solid phases of fixed compositions at (C Fe(CN) 6 3-) 1/3 /C Cl -) 17.1 M -2/3 . This is the first case of solid phase segregation during anion exchange in hydrotalcite systems diagnosed from thermodynamic measurements. In agreement, PXRD patterns of the partially exchanged solids indicate that these phases, with distinct basal spacings, coexist in the range 0.21 e x e 0.86. The observed behavior is accounted for by classical thermodynamic formalisms of ion exchange. The limitations of other representations commonly used to describe anion exchange in layered double hydroxide systems are stressed. A rationale of the structural changes accompanying the exchange is also offered.

The Journal of Physical Chemistry B, 2005

A structural study of the thermal evolution of Ni 0.69 Cr 0.31 (OH) 2 (CO 3 ) 0.155 ‚nH 2 O into ... more A structural study of the thermal evolution of Ni 0.69 Cr 0.31 (OH) 2 (CO 3 ) 0.155 ‚nH 2 O into NiO and tetragonal NiCr 2 O 4 is reported. The characteristic structural parameters of the two coexisting crystalline phases, as well as their relative abundance, were determined by Rietveld refinement of powder x-ray diffraction (PXRD) patterns. The results of the simulations allowed us to elucidate the mechanism of the demixing process of the oxides. It is demonstrated that nucleation of a metastable nickel chromite within the common oxygen framework of the parent Cr III -doped bunsenite is the initial step of the cationic redistribution. The role that trivalent cations play in the segregation of crystalline spinels is also discussed.

Croatica Chemica Acta, 2007

TiO 2 surface complexation by bidentate organic ligands is analysed in terms of the ligand Bronst... more TiO 2 surface complexation by bidentate organic ligands is analysed in terms of the ligand Bronstead and Lewis basicities. The complexation and basicity constants comply with linear Gibbs Energy relationships (LGERs). For dicarboxylic acids, the surface chelate bond makes an approximately constant contribution to the stability. The proton transfer to the surface modulates the pH dependence of stability. A correlation exists between the surface complexation constant of the neutral acid H 2 L and the ligand first acidity constant. On the other hand, the surface complexation constants of dianions L 2- of cathecols and aminophenols are positively correlated with the ligand second acidity constant. Apparent stability is determined by the competition of H + and surface metal ions for the ligand. Stability trends are strongly influenced by the Bronstead acid base reaction between the acid ligands H 2 L and the surface, whereas the stability of the surface chelate contributes to the overall...

Journal of colloid and interface science, 2017

Chemisorption of Eu(3+) and Tb(3+) on SBA-15 functionalized with succinic groups has been studied... more Chemisorption of Eu(3+) and Tb(3+) on SBA-15 functionalized with succinic groups has been studied by in situ steady-state fluorescence measurements. The enhancement of the emission sensitive bands indicates that both ions adsorb forming inner-sphere surface complexes. Adsorption is a fast process that attains equilibrium in about 5min. The variation of the peaks maxima (I592 and I616, for europium, and I490 and I545, for terbium) with the total ion concentration is accounted for by the sum of the contributions due to the adsorbed and free ions. The former contribution is langmuirian. At pH 4.5, the respective adsorption constants are 5×10(5) and 3×10(5)M(-1), and the maximum adsorption capacities are 5.10×10(-4) and 5.23×10(-4)molg(-1). The mismatch between the latter values and the number of attached carboxylic groups is discussed. Comparison with other functionalized mesoporous silicas indicates that the anchored succinic groups are very efficient for removing lanthanide ions from...

The Journal of Physical Chemistry B, 2005

FTIR spectra of hexacyanoferrate(III)-exchanged hydrotalcites (A) and ratio of the absorbance due... more FTIR spectra of hexacyanoferrate(III)-exchanged hydrotalcites (A) and ratio of the absorbance due to interlamellar ferricyanide and carbonate ions (B). The broad band centered at ca. 3440 cm −1 is due to the ν O−H stretching vibration of hydrogen-bonded geminal OH groups and water molecules, and that at 1636 cm −1 corresponds to the bending of water. Bands at 2117 and 2034 cm −1 are due to the ν C≡N vibration of the intercalated complex, and that at 1365 cm −1 corresponds to interlamellar free carbonate. 1 The linear dependence of the ratio (A 2117 + A 2034)/A 1365 with x (i.e., the mole fraction of HT(Fe(CN) 6) 1/3) confirms that Fe(CN) 6 3− ions do not replace CO 3 2− anions.

Journal of colloid and …, 1989

... conditions. Stationary state dissolution according to Scheme [ 13 ] yields RI = k~httkehKa, {... more ... conditions. Stationary state dissolution according to Scheme [ 13 ] yields RI = k~httkehKa, { >Fen'} [ FeY2-] exp ( azeAlPo / kT) { k-et, [ FeY-] }, [151 + k~htl exp ( azeA~bo / kT) - 1 Journal of Colloid and Interface Science, Vol. 130, No. ...

Journal of Colloid and Interface Science, 1984

... Adsorption of EDTA and IronEDTA Complexes on Magnetite and the Mechanism of Dissolution of Ma... more ... Adsorption of EDTA and IronEDTA Complexes on Magnetite and the Mechanism of Dissolution of Magnetite by EDTA MIGUEL A. BLESA, ELENA ... 1. The data fit well into Langmuir isotherms; from these, areas per adsorbed molecule at saturation coverage and Gibbs energies of ...

Journal of Materials Science, 1996

ABSTRACT The dissolution of YBa2Cu3O6.8 in acidic aqueous solutions was studied at 298 K as a fun... more ABSTRACT The dissolution of YBa2Cu3O6.8 in acidic aqueous solutions was studied at 298 K as a function of pH, nature and concentration of present anions and time, t. In the range 2.0 less than or equal to pH less than or equal to 4.0, dissolution is congruent and proceeds to completion; dissolution profiles are deceleratory and comply with a contracting volume rate law up to t(0.5). The rate of dissolution, which is limited by slow surface reactions, decreases with increasing pH; the kinetic order on proton concentration is a fractional and variable number. At higher pH values, dissolution is arrested at intermediate conversion values. In these cases, congruent dissolution is followed by the precipitation of less soluble solid phases which form a passive layer. The nature of this passive layer depends on pH and on the nature and concentration of present anions, which also define the extent of conversion attained at passivation. The dissolution behaviour of YBa2Cu3O6.8 is described in terms of two consecutive surface reactions: fast equilibrated protonation of surface metal ions is followed by the slow release of cations. Barium surface ions are identified as the more reactive sites. The effect of the fast initial leaching of barium ions on the reactivity of yttrium and copper sites is discussed. The influence of the formal Cu(III) oxidation state is also stressed.

Chemical Physics Letters, Dec 1, 2006

Sorption of toluene and nitrobenzene by dodecyl sulfate intercalated-hydrotalcite was studied as ... more Sorption of toluene and nitrobenzene by dodecyl sulfate intercalated-hydrotalcite was studied as a function of solute concentration. The correlation between the derived partition coefficients and the solubilities of the aromatic solutes in water indicates that the main sorption mechanism is partitioning. The partition behavior of nitrobenzene is Henry ideal, whereas the isotherm for toluene is convex, i.e., type III. These unlike behaviors are accounted for by casting the activity coefficients of the solutes solubilized within the hydrophobic interlamellar space of the hybrid-hydrotalcite in terms of the Flory-Huggins theory, the value of the mixing parameter determining the isotherm shape.

Catal Today, 2002

The use of ATR–FTIR to probe the adsorption of oxalic and salicylic acids, and of mixtures of bot... more The use of ATR–FTIR to probe the adsorption of oxalic and salicylic acids, and of mixtures of both, onto TiO2 (Degussa P-25) demonstrates the potential of the technique to characterise the evolution of the catalyst with time, including surface poisoning. Under equilibrium dark conditions, three surface species are formed by oxalate, and two by salicylate. Their stabilities, described by conditional Langmuir-type equilibria involving the dissociative, electroneutral adsorption of the acids H2L, are at pH 3.7, 2.4×106, 3.0×104 and 3.0×103 mol−1 dm3 for oxalic acid, and 2.9×105 and 9.1×103 mol−1 dm3 for salicylic acid. The nature of the species is discussed in terms of their spectral features. The displacement of each acid from the surface by addition of the other one was followed also by ATR–FTIR. The results demonstrate that oxalate displaces totally chemisorbed salicylate, whereas salicylate displaces oxalate only partially. These results are explained by assuming competitive chemisorption onto two different surface sites, plus oxalate adsorption onto a site that exhibits negligible affinity for salicylate. Irreversible adsorption by partially oxidised products in the course of photocatalytic processes can therefore be assessed by ATR–FTIR.

Colloids and Surfaces, 1983

ABSTRACT

The Journal of Physical Chemistry B, 2005

The intercalation of hexacyanoferrate(III) in chloride-hydrotalcite was studied as a function of ... more The intercalation of hexacyanoferrate(III) in chloride-hydrotalcite was studied as a function of the composition of the equilibrated aqueous phase, the relevant solution variable being the ratio (C Fe(CN) 6 3-) 1/3 /C Cl -. The isotherm shows that the exchange is markedly nonideal and reveals the segregation of two solid phases of fixed compositions at (C Fe(CN) 6 3-) 1/3 /C Cl -) 17.1 M -2/3 . This is the first case of solid phase segregation during anion exchange in hydrotalcite systems diagnosed from thermodynamic measurements. In agreement, PXRD patterns of the partially exchanged solids indicate that these phases, with distinct basal spacings, coexist in the range 0.21 e x e 0.86. The observed behavior is accounted for by classical thermodynamic formalisms of ion exchange. The limitations of other representations commonly used to describe anion exchange in layered double hydroxide systems are stressed. A rationale of the structural changes accompanying the exchange is also offered.

The Journal of Physical Chemistry B, 2005

A structural study of the thermal evolution of Ni 0.69 Cr 0.31 (OH) 2 (CO 3 ) 0.155 ‚nH 2 O into ... more A structural study of the thermal evolution of Ni 0.69 Cr 0.31 (OH) 2 (CO 3 ) 0.155 ‚nH 2 O into NiO and tetragonal NiCr 2 O 4 is reported. The characteristic structural parameters of the two coexisting crystalline phases, as well as their relative abundance, were determined by Rietveld refinement of powder x-ray diffraction (PXRD) patterns. The results of the simulations allowed us to elucidate the mechanism of the demixing process of the oxides. It is demonstrated that nucleation of a metastable nickel chromite within the common oxygen framework of the parent Cr III -doped bunsenite is the initial step of the cationic redistribution. The role that trivalent cations play in the segregation of crystalline spinels is also discussed.