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Bivalent Ion Adsorption by an Oxisol
Author(s) -
Charlet Laurent,
Sposito Garrison
Publication year - 1989
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/sssaj1989.03615995005300030007x
Subject(s) - ionic strength , oxisol , chemistry , adsorption , bivalent (engine) , ion , point of zero charge , surface charge , inorganic chemistry , analytical chemistry (journal) , aqueous solution , chromatography , metal , soil water , organic chemistry , soil science , environmental science
Surface excesses of the bivalent ions Ca 2+ , Mg 2+ , and SO 2‐ 4 were measured on a Brazilian Oxisol suspended in Ca(ClO 4 ) 2 ), Mg(ClO4) 2 , or Li 2 SO 4 solution. The surface excess of Ca 2+ increased proportionally with pH in the range 2.5 to 6.0 and was independent of ionic strength in the range 26 to 67 mol m −3 . The surface excess of Mg 2+ as a function of pH, however, showed a significant dependence on ionic strength in the range from 34 to 176 mol m −3 . The surface excess of SO 2‐ 4 showed a dependence on ionic strength in the range 12 to 37 mol m −3 if pH was less than the point of zero net charge (PZNC = 4.2), but showed no dependence on ionic strength if pH was above the PZNC. All three bivalent ions showed significant adsorption above the PZNC of the soil. These trends were interpreted conceptually to suggest that, although the three bivalent ions may form both outer‐sphere and inner‐sphere surface complexes, the latter are more important for Ca 2+ than for Mg 2+ or SO 2‐ 4 .