Premium
Aluminum in Soils: III. A Comparison of Extraction Methods in Soils and Clays
Author(s) -
McLean E. O.,
Heddleson M. R.,
Post G. J.
Publication year - 1959
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/sssaj1959.03615995002300040018x
Subject(s) - chemistry , soil water , triethanolamine , bentonite , salt (chemistry) , extraction (chemistry) , solubility , cation exchange capacity , illite , soil ph , nuclear chemistry , clay minerals , environmental chemistry , mineralogy , chromatography , geology , analytical chemistry (journal) , soil science , organic chemistry , paleontology
Samples of eight Ohio soils initially representing a wide range of extractable Al were moist‐equilibrated for 3 months with increasing increments of both H 2 SO 4 and Ca(OH) 2 . Al was then extracted, using five salt solutions. Previously dialyzed bentonite, Putnam, and illite clays were extracted of their accumulated (and added) Al by direct treatment with salt solutions and by removal with cation‐exchange resin (Dowex 50‐8X, 20 mesh). With low soil pH, NaCl, BaCl 2 , and NH 4 OAc at pH 4.8, all extracted comparable amounts of Al from the initialy more acid soils. However, soils less highly weathered initaly but made acid with H 2 SO 4 , released more Al to BaCl 2 than NH 4 OAc at pH 4.8. With soil pH values above 5, more Al was removed by NH 4 OAc at pH 4.8 than either NaCl or BaCl 2 . Relatively little Al was obtained by extracting with either NH 4 OAc at pH 7.0 or triethanolamine + BaCl 2 (Mehlich) solution regardless of soil pH. On the basis of extractability and solubility of Al and the possible effects on clay crystal stability, NH 4 OAc at pH 4.8 appeared to be superior as an extractant to the unbuffered neutral salts and to those buffered at pH 7.0 or above. The extractable Al appeared to be largely exchangeable, since the amounts removed did not exceed the CEC of the soils whether 0.4 to 1.2 symmetry (S) concentration of H 2 SO 4 was added, or 13 to 28 S of AlCl 3 were equilibrated with the soils. NH 4 OAc at pH 4.8, NaCl, and BaCl 2 all extracted comparable amounts of Al from the acid clays and the resin after contact with the clays. In clays without Al added, more Al was extracted from Putnam with salt solutions than from the other clays; but less was extracted from it with resin. In contrast, much more Al was removed with resin from illite than from the other clays, and much more than with salts. The contents of extractable Al in bentonite and Putnam clays prepared from H‐resin and Ca‐resin increased with time but continued essentially equal in value, whether it was an H‐ or Ca‐clay. The relative amounts of Al obtained from the resin by the various extractants depended upon the clay with which it had been equilibrated. Symmetry values for various cations showed the relative bonding of the cations by the resin was Al > Ca ≥ Ba > K > Na ≥ NH 4 > H.