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Diffusion of Iron in Montmorillonite as Determined by X‐ray Emission
Author(s) -
Ellis J. H.,
Phillips R. E.,
Barnhisel R. I.
Publication year - 1970
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/sssaj1970.03615995003400040016x
Subject(s) - montmorillonite , diffusion , analytical chemistry (journal) , ion , ionic bonding , chemistry , materials science , mineralogy , chromatography , thermodynamics , physics , organic chemistry
The experimental distribution of Fe 2+ and Fe 3+ diffusing in thin, water‐saturated montmorillonite clay films (43.5% H 2 O on oven dry basis) were obtained using a miniature‐probe attachment for an x‐ray emission spectrometer; the montmorillonite clay was initially Ca‐saturated. The ionic concentrations were measured in either 0.5‐ or 1.0‐mm intervals from the origin of the diffusing salt giving detailed, experimental distributions of the diffusing ions. The method is sensitive to slight changes of iron concentration resulting in precise determination of experimental distributions. The method should work equally well for diffusion studies involving other ions with atomic numbers greater than Na. The diffusion coefficient of Fe 3+ increased from 1.6 × 10 ‐7 cm 2 sec ‐1 at a concentration of 0.1 meq Fe 3+ per g clay to 4.35 × 10 ‐7 cm 2 sec ‐1 at a concentration of 1.6 meq Fe 3+ per g clay. Diffusion coefficients of Fe 2+ were measured at concentrations up to 0.6 meq per g clay. These values were two to five times larger than for Fe 3+ .