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Percent of Copper Diffusing in the Adsorbed and Electrolyte‐Solution Phases in Kaolinite and Montmorillonite
Author(s) -
Phillips R. E.,
Barnhisel R. I.,
Ellis J. H.
Publication year - 1972
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/sssaj1972.03615995003600010007x
Subject(s) - kaolinite , chemistry , electrolyte , montmorillonite , diffusion , analytical chemistry (journal) , phase (matter) , adsorption , cation exchange capacity , dissolution , inorganic chemistry , mineralogy , thermodynamics , soil water , chromatography , electrode , physics , environmental science , organic chemistry , soil science
The apparent diffusion coefficient, D e , of a cation diffusing in soil was proposed to be D e m = [ D s m (dC s /dC sa } + 1 D a m ( dC a /dC sa )] / [1 + dC p /dC sa ] where D s m and 1 D a m are the diffusion coefficients of the cation in the electrolyte‐solution phase and in the adsorbed phase (exchangeable cations), respectively, and where the frame of reference in each case is with respect to the entire soil mass. The symbols C s , C a and C p are concentrations of electrolyte‐solution cations, adsorbed cations, and precipitated or immobilized cations, respectively; C sa is defined to be the sum of C s and C a . The concentrations are expressed with respect to the total volumetric water content of the system. The quantities, dC s /dC sa , dC a /dC sa , and dC p /dC sa were evaluated in experiments independent of the measurement of D e m . The relative contributions of D s m and 1 D a m to D e m were evaluated over a large range of C sa values for Cu 2+ diffusing in water‐saturated kaolinite and montmorillonite. In kaolinite clay with a cation exchange capacity (CEC) of 0.065 meq g ‐1 , the percent of total diffusion due to diffusion in the adsorbed phase was 100, 52, 34, 22, 18, 9, and 7 at C sa concentrations of 0.015, 0.02, 0.03, 0.04, 0.05, 0.06, and 0.08 meq g ‐1 , respectively. In montmorillonite clay with a CEC of 0.70 meq g ‐1 , the percent of total diffusion due to diffusion in an adsorbed phase was 100, 57, 42, 34, 28, 20, and 13 at C sa concentrations of 0.03, 0.05, 0.10, 0.15, 0.20, 0.40, and 0.70 meq g ‐1 , respectively.