397. The extent of dissociation of salts in water. Part VIII. An equation for the mean ionic activity coefficient of an electrolyte in water, and a revision of the dissociation constants of some sulphates

Precise conductance measurements are reported on dilute aqueous solutions of the sodium and potassium salts of orthophosphoric acid at 25 • C. Conductance measurements on solutions of electrolytes such as these phosphate salts that exist in solution as complicated mixtures of ions have previously proved difficult to interpret. To overcome this, a mathematical method has been developed to calculate the concentrations of all the species in the aqueous system M 3 PO 4 /M 2 HPO 4 /M 2 HPO 4 /H 3 PO 4 (M = Na or K) over a continuous range of stoichiometries. The Lee-Wheaton conductance equation has been used to interpret the conductance of these multicomponent solutions in terms of the limiting ionic conductances and concentrations of all the ions in the solution. The limiting molar conductances of the ions H 2 PO − 4 and HPO 2− 4 and the ion-pair formation constants of these ions with sodium and potassium ions were determined. This work has enabled the accurate determination of solution parameters for the important hydrogenphosphate ions in water and provides an excellent example of the use of an advanced conductance theory in the analysis of the conductance of multicomponent electrolyte systems.

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“…In this work the Davies equation was used to calculate values of y 1 , y 2 , and y 3 . This equation has the form (3) at 25…”

Section: Speciation Calculationsmentioning

confidence: 99%

Precise Conductance Measurements on Dilute Aqueous Solutions of Sodium and Potassium Hydrogenphosphate and Dihydrogenphosphate

2006

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“…Para o modelo RFPQ, isso pode ter ocorrido devido ao fato deos modelos deatividade para eletrólito possuíremfai-xas de concentração para serem utilizados, e para forças iônicas abaixo de 0,1 molal, modelos como o de Bromleysão pouco sensíveisa mudanças de concentração (Davies, 1938), ou seja, as atividades possuem uma variação insignificantepara mudanças de concentrações entre 1mEq L -1 e5 mEq L -1 , e dessa forma não conseguemrepresentar as três concentrações utilizadas com apenas um parâmetro ajustável.O mesmo vale para o modelo RSPQ, pois como o modelo emprega a concentração total apenas no cálculo do equilíbrioas mudanças de concentração-são menos significantes em comparação aos modelos RFC e RFPQ.…”

Section: Resultados E Discus-sõesunclassified

ESTUDO CINÉTICO DA TROCA IÔNICA DO SISTEMA BINÁRIO Cu2+-Na+ UTILIZANDO A RESINA AMBERLITE IR-120

Reinehr

Gallo²,

Raizer³

et al. 2013

Engevista

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Resumo: A presença de metais pesados em águas residuais industriais é uma relevante forma de poluição. O conhecimento das características cinéticas dos processos de transferência de massa é fundamental para o desenvolvimento de processos de trocaiônica utilizados na remoção destes metais. Neste trabalho, foram testados quatro modelos cinético para descrever a troca iônica do sistema binário Cu +2 -Na + sobre a resina Amberlite IR-120. Os modelos se distinguem pelaetapa limitante da transferência de massa considerada do processo (resistência no filme externo e resistência intrapartícula) e pela força motriz para a transferência de massa utilizada (gradiente de concentração e gradiente de potencial quími-co). Os experimentos foram realizados na temperatura de 25 o C e pH inicial 4. O modelo de resistência intrapartícula e força motriz em termos dogradiente de concentração foi o mais efetivo na representação dos dados experimentais, indicando que, possivelmente, a resistência intrapartícula é a etapa limitante do processo de transferência de massa. O valor encontrado para o coeficiente de transferência de massa foi de 3,698x10 -2 min -1 . Palavras-chave:Troca iônica, Cobre, Potencial químico.Abstract:The presence of heavy metals in wastewaters is a relevant kind of pollution.The knowledge of the kinetic characteristics of the mass transfer processes is fundamental to development of ionexchange processes used to removal of these metals. In this study, four kinetic models were tested to describe the ion exchange of the binary system Cu +2 -Na + using the resin Amberlite IR-120. These modelsdifferentiate themselves in the limiting step of the process (external filmresistance and intraparticular resistance) and in the mass transfer driving force (concentration gradient and chemical potential gradient). Experiments were carried at a temperature of 25 o C and starting pH of 4. The intraparticular resistance and driving force by concentration gradient model was the most effective representing the experimental data, indicating that, possibly, the intraparticular resistance is the limiting step of the mass transfer process. The value found for the mass transfer coefficient was 3.698x10 -2 min -1 .

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“…The activity coefficients may be estimated by using the Davies equation (Davies, 1938(Davies, , 1967 -…”

Section: Methodsologymentioning

confidence: 99%

An interfacial equilibria model for the electrokinetic properties of a fat emulsion. Part II: Magnesium, zinc and proton interactions with the interface

Gaskin

Hall

Williams

1993

Chemical Speciation & Bioavailability

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The semi-empirical thermodynamic model reported in an earlier paper (Hallet a/., 1991) is further developed to describe the zeta potential behaviour of an intravenous fat emulsion in the presence of magnesium and zinc cations. The effect of interfacial protonation is also explored. We have now established that a previously reported formation constant for the calcium interaction is actually a conditional value and together with the new data for zinc and magnesium, overall formation constants are calculated.

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397. The extent of dissociation of salts in water. Part VIII. An equation for the mean ionic activity coefficient of an electrolyte in water, and a revision of the dissociation constants of some sulphates

Cited by 510 publications

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Precise Conductance Measurements on Dilute Aqueous Solutions of Sodium and Potassium Hydrogenphosphate and Dihydrogenphosphate

Precise Conductance Measurements on Dilute Aqueous Solutions of Sodium and Potassium Hydrogenphosphate and Dihydrogenphosphate

ESTUDO CINÉTICO DA TROCA IÔNICA DO SISTEMA BINÁRIO Cu2+-Na+ UTILIZANDO A RESINA AMBERLITE IR-120

An interfacial equilibria model for the electrokinetic properties of a fat emulsion. Part II: Magnesium, zinc and proton interactions with the interface

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