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The use of rate equations for a quantitative description of K desorption from soils in an external electric field (electro‐ultrafiltration)
Author(s) -
Grimme H.
Publication year - 1979
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.19791420107
Subject(s) - desorption , chemistry , soil water , ultrafiltration (renal) , electrolyte , suspension (topology) , analytical chemistry (journal) , electrodialysis , reaction rate constant , electric field , chromatography , membrane , kinetics , adsorption , soil science , environmental science , electrode , mathematics , physics , quantum mechanics , homotopy , pure mathematics , biochemistry
Ions can be extracted from soils by applying an external electric field to a soil suspension. When a constant field strength is employed characteristic desorption parameters can be calculated from the results, such as maximum desorbable quantity, halftime, and rate constant. The method consists of a combination of electrodialysis and ultrafiltration and is called electro‐ultrafiltration (EUF). It was found that the K transfer from the central compartment A to the cathode compartment B follows a first order rate law, if compartment A contains only the solution of a strong electrolyte such as KCl. If a soil suspension is introduced into compartment A the bulk of K that is transferred to compartment B has first to be desorbed from the soil particles hence the designation as desorption for the transfer from a soil suspension. In this case a second order rate law is followed. The rate equations allow the calculation of the quantity of K involved in the desorption process and the rate with which it is released. It was found that invariably only the exchangeable K takes part in the desorption reaction. The desorption rate differs between soils and depends on clay content and the quantity of exchangeable K present in the soil. It is suggested that the desorption data may provide a means of describing the soil K status by kinetic parameters.