Relative stabilities of metal complexes of 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol

Ohyoshi, Emiko

doi:10.1016/s0277-5387(00)81387-x

Cited by 20 publications

(15 citation statements)

References 12 publications

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“…This new bond formation decreases the randomness and configurational vibration of the system, resulting in large negative entropy contribution (Table 7) and suggests a weak interaction of metal ions with water molecules as compared to the adsorbent. [1] In the adsorption process, three PAR molecules interact with central metal to neutralize its charge. The reported complexes of rare earths with b-diketones such as 2-thenoyltrifluoroacetylacetone (HTTA) are of the type M(TTA) 3 Á2S in solvent extraction system, where S is the donor ligand to satisfy the coordination number of central metal atom.…”

Section: Thermodynamic Studiesmentioning

confidence: 99%

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Kinetics, Thermodynamics, and Sorption Profile of Eu(III) and Tm(III) on 4‐(2‐Pyridylazo) Resorcinol (PAR) Imbedded Polyurethane Foam

Saeed

Ahmed

Chaudary

et al. 2003

Solvent Extraction and Ion Exchange

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The adsorption studies of Eu(III) and Tm(III) was investigated on 4-(2pyridylazo) resorcinol (PAR) loaded polyurethane foam (PUF). The sorption conditions were optimized with respect to pH, shaking time, and loading capacity. Kinetic of sorption of Eu(III) and Tm(III) were evaluated at different intervals of time. The diffusion coefficient of Eu(III) and Tm(III) are found to be 4.48 Â 10 À5 cm 2 sec À1 and 7.81 Â 10 À5 cm 2 sec À1 . The Freundlich constant (1=n) are estimated to be 0.56 and 0.47 for Eu(III) and Tm(III), respectively, reflects a surface heterogeneity of the PUF. Langmuir isotherm gives a saturated capacity of 1.95 Â 10 À5 mol g À1 for Eu(III) and 1.01 Â 10 À4 mol g À1 for Tm(III), suggest a monolayer coverage of the surface. The Dubinin-Radushkevich (D-R) isotherm is applied and the sorption mean free energy (E) was calculated and was in the range 11-12 kJ mol À1 suggesting chemisorption involving chemical bonding is responsible for the adsorption process. The thermodynamics parameters such as enthalpy (DH), entropy (DS) and Gibbs free energy (DG) were calculated and interpreted. The large negative values of DH indicates that the adsorption of metal ions on PAR-loaded PUF is an exothermic process. A possible explanation of this exothermicity related to bonding has been given. The sorption is greatly affected in the presence of oxalate, citrate, tartrate, and phosphate.

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Section: Thermodynamic Studiesmentioning

confidence: 99%

“…[1][2][3][4][5][6] Polyurethane foam (PUF) has been widely used for the separation and preconcentration of trace metal ions. This reagent is a dibasic and simultaneously forms the protonated and normal type of complexes with metal ions.…”

Section: Introductionmentioning

confidence: 99%

Kinetics, Thermodynamics, and Sorption Profile of Eu(III) and Tm(III) on 4‐(2‐Pyridylazo) Resorcinol (PAR) Imbedded Polyurethane Foam

Saeed

Ahmed

Chaudary

et al. 2003

Solvent Extraction and Ion Exchange

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“…For example in metal rich ratios the species like ML and/or MHL are predominant and in ligand rich ratios the ML 2 and MHL 2 are main species. With attention to previous published data 22,23 about the system under study ones has a trivial task to choose more useful metal to ligand ratios. In this Figure 1.…”

Section: Resultsmentioning

confidence: 99%

“…The entire absorption spectra-pH data were analyzed globally and the results of the global analysis for complexation of Ni-PAR system summarized in Table 2. The previous reported values [21][22][23] of the system on Ni-PAR in the same conditions, with respect to ionic strength and temperature, are also inserted in Table 2 for simplicity of the comparison.…”

Section: Resultsmentioning

confidence: 99%

Spectrophotometric studies on the protonation and nickel complexation equilibria of 4-(2-pyridylazo) resorcinol using global analysis in aqueous solution

Ghasemi¹,

Ниази²,

Maeder³

2007

J. Braz. Chem. Soc.

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A protonação e complexação de Ni(II) por 4-(2-piridilazo) resorcinol (PAR) em força iônica 0,1 mol L-1 KNO 3 a 25 °C, foram estudadas por análise global. Em titulações espectrofotométricas, a dependência linear ou quase linear da concentração e a existência de espécies em menores concentrações podem causar dificuldades na avaliação dos dados. Espectros de absorção e as correspondentes constantes de equilíbrio calculadas ou são desconhecidos ou mal estabelecidos. Dessa forma, torna-se difícil ajustar um modelo confiável aos dados. Na análise global de segunda ordem, titulações espectrofotométricas com diferentes concentrações iniciais são simultaneamente analisadas. Assim, condições para a formação signifitiva de todas as espécies podem ser obtidas e, conseqüentemente, a matriz de concentração é completada. EQUISPEC é um programa computacional que usa matriz gerada em ambiente MATLAB para análise global de segunda ordem de dados espectrofotométricos. As titulações espectrofotométricas foram efetuadas, no mínimo, para quatro diferentes valores da razão metal-ligante. The protonation and Ni(II) complexation of 4-(2-pyridylazo) resorcinol (PAR) in ionic strength 0.1 mol L-1 KNO 3 at 25 °C has been studied by global analysis. In spectrophotometric titrations, linear or near-linear dependence of concentration profiles and the existence of minor species can cause difficulties in the evaluation of the data. Both calculated absorption spectra and the corresponding equilibrium constants are not or only poorly defined. The result is the inability to reliably fit a reasonable model to the data. In second order global analysis, a number of spectrophotometric titrations with different initial concentrations are simultaneously analyzed. In this way, conditions for the significant formation of all species can be obtained and consequently the concentration matrix is augmented to full rank. EQUISPEC is a computer program using the matrix based MATLAB environment for second order global analysis of spectrophotometric equilibrium data. The spectrophotometric titrations were carried out at least in four different metal to ligand ratios.

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“…chelate effect between UO 2 2+ -PAN-PUF system with lower number of reactant molecules as compared to the water molecules set free from the ordered hydration structure of central metal atom in sorption process [33,34]. Moreover, the inner sphere complexes have unfavorable enthalpy and favorable entropy terms because the hydration zone is disrupted to a greater extent that result in a net endothermic enthalpy term [35]. The very large values of enthalpy and entropy indicate the strong forces between the ions and the ligands [34].…”

Section: Mechanism Of Sorptionmentioning

confidence: 99%

Adsorption modeling and thermodynamic characteristics of uranium(VI) ions onto 1-(2-pyridylazo)-2-naphthol (PAN) supported polyurethane foam

Saeed¹,

Ahmad²

2005

Radiochimica Acta

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The sorption of uranium(VI) ions onto PAN loaded PUF has been investigated. Quantitative sorption of uranium(VI) onto PAN loaded PUF was achieved after 30 minutes equilibration time from pH 7 buffer solution. The sorption data followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. Langmuir parameters Q = 45.3 ± 0.2 µmol g −1 and b = (76.2 ± 0.2) × 10 3 dm 3 mol −1 , Freundlich constants 1/n = 0.21 ± 0.01 and K F = 229 ± 21 µmol g −1 and D-R parameters β= − 0.0015 ± 0.00005 kJ 2 mol −2 , X m = 72.23 ± 3.11 µmol g −1 and E = 18.3 ± 0.3 kJ mol −1 have been evaluated. The variation of sorption data with temperature gives ∆H = 176 ± 5 kJ mol −1 , ∆S = 626 ± 17 J mol −1 K −1 and ∆G = −10.6 ± 0.7 kJ mol −1 at 298 K. The positive value of enthalpy (∆H) and negative value of free energy (∆G) show endothermic and spontaneous nature of sorption respectively. A number of solvents were tested to elute the uranium-PAN complex from the PAN loaded PUF, only amine solvents and cyclohexanone have the capability to desorb the complex. The sorption mechanism has been discussed.

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Relative stabilities of metal complexes of 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol

Cited by 20 publications

References 12 publications

Kinetics, Thermodynamics, and Sorption Profile of Eu(III) and Tm(III) on 4‐(2‐Pyridylazo) Resorcinol (PAR) Imbedded Polyurethane Foam

Kinetics, Thermodynamics, and Sorption Profile of Eu(III) and Tm(III) on 4‐(2‐Pyridylazo) Resorcinol (PAR) Imbedded Polyurethane Foam

Spectrophotometric studies on the protonation and nickel complexation equilibria of 4-(2-pyridylazo) resorcinol using global analysis in aqueous solution

Adsorption modeling and thermodynamic characteristics of uranium(VI) ions onto 1-(2-pyridylazo)-2-naphthol (PAN) supported polyurethane foam

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