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Parameter Estimation of an Adsorption Model for Describing Ion‐Pair Adsorption
Author(s) -
Cichota Rogerio,
Vogeler Iris,
Bolan Nanthi S.,
Clothier Brent E.
Publication year - 2009
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2008.0129
Subject(s) - adsorption , biological system , set (abstract data type) , chemistry , soil water , mathematics , computer science , soil science , environmental science , programming language , biology
The simultaneous retention of both cations and anions due to ion‐pair adsorption (IPA) has been identified in several soils. The mechanism controlling IPA is not yet understood, however, and the mathematical description of this phenomenon is only incipient. In this study, a parameterization analysis was performed using a recently proposed adsorption model that considers the occurrence of IPA. The model, which has two alternative approaches to describe IPA, has been shown in a previous study to describe experimental data reasonably well. That analysis was incomplete, however, as the parameter uncertainties were not estimated. In this study, with the parameterization procedure using the maximum‐likelihood method, a robust estimation of the model parameters, including the analysis of their uncertainties, was developed. The model was fitted to a data set obtained in batch experiments using the variable‐charge Egmont soil, from New Zealand, and a comprehensive combination of SO 4 and Ca concentrations. This procedure allowed the analysis of some of the underlying model characteristics and also some inferences about the IPA phenomenon. Overall, it was shown that the proposed adsorption model is a useful tool for the modeling of solutes in soils where IPA occurs.