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Salt Displacement of Acid‐Treated Trioctahedral Vermiculites
Author(s) -
Kaddah Malek T.,
Coleman N. T.
Publication year - 1967
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/sssaj1967.03615995003100030015x
Subject(s) - vermiculite , chemistry , salt (chemistry) , ion exchange , cation exchange capacity , inorganic chemistry , nuclear chemistry , clay minerals , titratable acid , ion , mineralogy , soil water , geology , organic chemistry , paleontology , soil science , biochemistry
Freshly prepared and 30‐day‐aged samples of HCl‐treated trioctahedral vermiculites from Libby, Montana (L) and northeastern Transvaal, South Africa (S) were leached with 1 N or more dilute solutions of NaCl, KCl, CaCl 2 , or MgCl 2 . The exchange acidity, exchangeable H 3 O, Al, and Mg, and the cation‐exchange capacity after acid‐salt treatment were determined. With both the L and S minerals, the sum of the salt‐displaceable ions after acid treatment corresponded to approximately 90% of the initial CEC. For freshly acidified materials, the exchange acidity (consisting of displaced H 3 O and Al ions) comprised the bulk of the exchangeable ions. After 30 days of aging in water at room temperature, exchange acidity had decreased by around one‐half, and equivalent amounts of exchangeable Mg had appeared. The most striking findings concerned: (i) differences between the two minerals with regard to the amounts of H 3 O and Al displaced by salts, and (ii) differences in displaced H 3 O and Al depending on the exchanging cation and the concentration of the displacing solution. The exchange acidity from fresh HCl‐treated S vermiculite consisted of about 60% H 3 O and 40% Al when 1 N NaCl, CaCl 2 , or MgCl 2 was the displacing salt. For L vermiculite, titratable acidity displaced by 1 N NaCl, CaCl 2 , or MgCl 2 was around three‐fourths Al. For both minerals, exchange acidity measured with 1 N or 0.05 N KCl, 0.05 N NaCl, or 0.02 N CaCl 2 or MgCl 2 was almost entirely H 3 O. X‐ray patterns of K‐saturated, acidified samples showed interlayer deposits and reduced collapsibility when the samples were leached with KCl. There were virtually no indications of interlayer material when the samples were leached with 1 N CaCl 2 before KCl.