Estimation of surface ionization constants from electrokinetic data

Sprycha, Ryszard; Szczypa, J.

doi:10.1016/0021-9797(84)90221-2

Cited by 43 publications

(16 citation statements)

References 12 publications

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“…One possible method of distinguishing the relative contribution would be to directly measure electrolyte sorption as a function of changing electrolyte concentration and pH. This has been attempted by Smit and coworkers (27,32,33) and Sprycha and Szczypka (29,34,35). Their results indicate that electrolyte sorption may be somewhat greater than estimates based on the extrapolation techniques.…”

Section: Model Parameter Estimationmentioning

confidence: 57%

Surface complexation models: An evaluation of model parameter estimation using FITEQL and oxide mineral titration data

Hayes

Redden

Ela

et al. 1991

Journal of Colloid and Interface Science

394

266

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The ability of surface complexation models (SCMs) to fit sets of titration data as a function of changes in model parameters was evaluated using FITEQL and acid-base titration data of a-FeOOH, a-AlzO3, and TiO2. Three SCMs were evaluated: the triple-layer model (TLM), the constant capacitance model (CCM), and the diffuse-layer model (DLM). For all models evaluated, increasing the model input value for the total number of surface sites caused a decrease in the best-fit Log K values of the surface protolysis constants. In the case of the CCM, the best-fit surface protolysis constants were relatively insensitive to changes in the value of the capacitance fitting parameter, G, particularly for values of C1 greater than 1.2 F/m 2. Similarly, the best-fit values of TLM surface electrolyte binding constants were less influenced by changes in the value of C~ when C~ was greater than 1.2 F/m 2. For a given C1 value, the best-fit TLM values of the electrolyte binding constants were sensitive to changes in ApK, up to ApKa values of 3. For ApKa values above 3, no changes in the best-fit electrolyte binding constants were observed. Effects of the quality and extent of titration data on the best-fit values for surface constants are discussed for each model. A method is suggested for choosing a unique set of parameter values for each of the models.

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Section: Model Parameter Estimationmentioning

confidence: 57%

Surface complexation models: An evaluation of model parameter estimation using FITEQL and oxide mineral titration data

Hayes

Redden

Ela

et al. 1991

Journal of Colloid and Interface Science

394

266

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“…Due to experimental difficulties and uncertainity regarding its aqueous chemistry [20], the only measurable parameter for oleic acid emulsion is zeta potential. The application of zeta potential data for the estimation of K~a' was proposed by Sprycha and Szczypa [19]; however, in this paper another extrapolation method to determine the intrinsic dissociation constant was used.…”

Section: Naci Solutionsmentioning

confidence: 99%

“…The separation of charge in the SBM permits the use of a conventional molecular capacitator model to relate charge to potential gradients: In a typical application of SBM for the calculation of the parameters of the edl, the Oo or oa vs. pH values are utilized to estimate the Ki~' and Kic~ttio~ by means of socalled double extrapolations [11,18,19]. The remaining parameters of the edl are then calculated using values of K1 and K2, either arbjtrarly chosen [11,18], or estimated from background electrolyte adsorption data [14].…”

Section: Naci Solutionsmentioning

confidence: 99%

An estimation of the surface ionization constant of oleic acid in aqueous sodium chloride solution

Drzymala

1987

Colloid & Polymer Sci

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Abstract:The zeta potential (r measurements and the site binding theory were utilized for calculations of the parameters of the electrical double layer (edl), ionization, and complexation constants for oleic acid-aqueous sodium chloride solution interface. Assuming that ~ is equal to the diffuse layer potential (~a) of the edl, the charge of the diffuse part of the edl was calculated from the Gouy-Chapman equation. The intrinsic ionizaiton constant was then determined by an extrapolation method to be pK int = 4.4. Subsequently, the surface potential (~o) was calculated, and it was found that ~r changes by 50 mV per pH unit (50 mV/pH) or 42.5 mWpH for 10 -3 and 10 -2 M NaCI, respectively. For further calculations, the integral capacity of the outer zone of the compact part of the edl was F assumed to be K2 = 30 ~ for both ionic strengths. It was established that the intrinsic complexation constant for the binding of Na + ions with the surface of oleic acid is pK~ta = 2.9 _+ 0.5 if the integral capacity of the inner zone of the compact edl (K1) is 80 ~ for 10 -3 M NaC1, but 280 ~ for 10 -2 M NaC1. The use of the same K1 value for both ionic strengths gives a different pK~ for different NaC1 concentrations, and also provides unrealistic surface charge (0o) values greater for 10-3 M NaC1 than for 10-2 M NaC1, at the same pH of the solution.

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“…In fact, in James and Healy's original model, the solvation energy dominated the total free energy of adsorption one (DG chem ) in the original model. The value of DpK is a measurable quantity (although not accurately so (30)(31)) and was so high for the /2 species that the overall free energy for this species was positive. With the much smaller and in principle can be measured independently.…”

Section: Introductionmentioning

confidence: 97%

“…[5] where The coulombic contribution of species i is given as is the diffuse layer charge according to the Gouy-Chapman of the difficulty in measuring this value ( 30,31 and the surface charge is shows the variation of surface potential as a function of surface site density; lower site density produces lower potential and higher site density gives high potentials.…”

Section: Introductionmentioning

confidence: 99%