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Selective Dissolution Effects on Cation‐Exchange Capacity and Specific Surface of Some Tropical Soil Clays
Author(s) -
Reneau R. B.,
Fiskell J. G. A.
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/sssaj1970.03615995003400050038x
Subject(s) - cation exchange capacity , chemistry , bentonite , dithionite , dissolution , reagent , nuclear chemistry , saturation (graph theory) , mineralogy , inorganic chemistry , soil water , geology , organic chemistry , soil science , paleontology , mathematics , combinatorics , enzyme
Soil clays from eastern Panama and Wyoming bentonite changed in CEC and specific surface after sequential selective dissolution treatments. Dithionite‐citrate treatment of the clays resulted in a small increase in CEC at both pH 4.8 and 8.2 and a decrease in ethylene glycol retention. Free Fe 2 O 3 ranged from 2% to 9% of the clay weight and substantial Al 2 O 3 and SiO 2 were also removed. Further treatment with hot 0.5 N NaOH for 2 minutes again followed by citrate‐dithionite resulted in 20% to 40% loss in clay weight as SiO 2 and lesser amounts of Al 2 O 3 and Fe 2 O 3 . This treatment resulted in an increase of 7 meq in CEC at both pH ranges of soil clays and 20 meq for the bentonite. This was attributed to removal of interlayer material blocking exchange sites but there was a mean decrease in specific surface after this treatment. Clays treated with acid NH 4 F‐NH 4 Cl reagent for 10 minutes decreased sharply in specific surface and loss in clay weight was from 9% to 17% with SiO 2 > Al 2 O 3 > Fe 2 O 3 . After Na saturation and careful washing, Na replacement by 1 N NH 4 OAc at pH 4.8 also removed high amounts of F and Al making CEC estimation impractical because NaF and/or Na 3 AlF 6 was occluded in the process of Na saturation.