Modifications to the Freundlich equation to describe anion sorption over a large range and to describe competition between pairs of ions

N. J. Barrow, P. Cartes, M. L. Mora

    Research output: Contribution to journalArticle

    36 Citations (Scopus)

    Abstract

    We measured sorption of selenite and phosphate, both separately and in competition, in a Chilean Andisol. We also used previously published data for competitive sorption of arsenate and phosphate by a clay subsoil. We wrote computer programs that allowed us to compare the fits of differing versions of equations to describe individual sorption and competitive sorption. For the selenite-phosphate data, the index term of the Freundlich equation decreased as concentration increased. This was described using the Sibbesen modification of the Freundlich equation. This modification was then included in competition equations. For both the selenite-phosphate and the arsenate-phosphate data, competition was not 'symmetrical', that is, the competition terms were not reciprocals of each other. We think this occurred because competition between ions is not only competition for adsorption sites but also involves electrical effects that follow penetration of the surface.

    Original languageEnglish
    Pages (from-to)601-606
    Number of pages6
    JournalEuropean Journal of Soil Science
    Volume56
    Issue number5
    DOIs
    Publication statusPublished - 1 Oct 2005

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