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Electrolyte Concentration and Composition Effects on Sulfate Sorption by Two Spodosols
Author(s) -
Courchesne François
Publication year - 1991
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/sssaj1991.03615995005500060012x
Subject(s) - sorption , electrolyte , chemistry , ionic strength , inorganic chemistry , composition (language) , aqueous solution , adsorption , organic chemistry , linguistics , philosophy , electrode
Few reports exist on the influence of electrolyte concentration and composition on SO 4 retention, although sorption experiments have been conducted with a variety of supporting electrolytes. Sulfate sorption by the B horizon of two forest Spodosols from Quebec was measured as a function of supporting electrolyte concentration and cationic composition, solution pH, and reaction time. The solutions had an ionic strength ( I ) of ≈0 (deionized H 2 O), 0.001, 0.01, 0.1, and 1.0 M NaCl, 0.01 M KCl, and 0.01 M CaCl 2 . Increasing the ionic strength of the electrolyte (NaCl) always decreased SO 4 sorption at pH 4.25. It was proposed that increased Cl ‐ ion competition for sorption sites and the formation of NaSO ‐ 4 aqueous complexes (2.8, 14, and 55% of total SO 4 at 0.01, 0.1, and 1.0 M NaCl) contributed to the observed trend. Increasing electrolyte concentration also lowered SO 4 sorption by both horizons in the range of pH 3.0 to 5.2. Moreover, the influence of pH on sorption was more pronounced at low electrolyte concentration. At a constant I value, the cationic composition of the electrolyte also had an impact on SO 4 sorption. The presence of Ca 2+ and K + favored sorption, compared with Na + . A mechanism involving the formation of a surface complex between Ca 2+ or K + and SO 2‐ 4 is proposed to explain the experimental data. The results of this study support the hypothesis that the composition and concentration of the electrolyte influence SO 4 sorption by Spodosols and that both should be considered when comparing the SO 4 ‐sorption capacity of soil materials from distinct experiments or when projecting laboratory results to field conditions.