TY - JOUR
T1 - Surface complexation models
T2 - An evaluation of model parameter estimation using FITEQL and oxide mineral titration data
AU - Hayes, Kim F.
AU - Redden, George
AU - Ela, Wendell
AU - Leckie, James O.
N1 - Funding Information:
This research was supported by Battalle Memorial Institute Pacific Northwestern Laboratories, Contract B-N-3975-A-E. The authors especially thank the project managers, Ken Krupka and JeffSernie, for their guidance and support of this research effort and their critical review of this manuscript. The critical review by Lynn Katz also greatly improved this manuscript.
PY - 1991/3/15
Y1 - 1991/3/15
N2 - 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 α-FeOOH, α-Al2O3, 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, C1, particularly for values of C1 greater than 1.2 F/m2. Similarly, the best-fit values of TLM surface electrolyte binding constants were less influenced by changes in the value of C1 when C1 was greater than 1.2 F/m2. For a given C1 value, the best-fit TLM values of the electrolyte binding constants were sensitive to changes in ΔpKa up to ΔpKa values of 3. For ΔpKa 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.
AB - 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 α-FeOOH, α-Al2O3, 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, C1, particularly for values of C1 greater than 1.2 F/m2. Similarly, the best-fit values of TLM surface electrolyte binding constants were less influenced by changes in the value of C1 when C1 was greater than 1.2 F/m2. For a given C1 value, the best-fit TLM values of the electrolyte binding constants were sensitive to changes in ΔpKa up to ΔpKa values of 3. For ΔpKa 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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U2 - 10.1016/0021-9797(91)90075-J
DO - 10.1016/0021-9797(91)90075-J
M3 - Article
AN - SCOPUS:0026124083
SN - 0021-9797
VL - 142
SP - 448
EP - 469
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
IS - 2
ER -