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Control of Nickel and Strontium Sorption by Free Metal Ion Activity
Author(s) -
Bowman R. S.,
O'Connor G. A.
Publication year - 1982
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/sssaj1982.03615995004600050010x
Subject(s) - sorption , strontium , nickel , chemistry , ionic strength , metal , ion exchange , inorganic chemistry , metal ions in aqueous solution , montmorillonite , ion , nuclear chemistry , adsorption , aqueous solution , organic chemistry
Formation of soluble complexes usually lowers sorption of metals by soils. The purpose of this study was to determine if changes in free Ni 2+ or Sr 2+ activity could explain differences in isotherms obtained in highly complexing SO 2‐ 4 systems vs. slightly complexing Cl ‐ systems. Sorption of Ni and Sr by homoionic montmorillonite and soil was studied using the batch isotherm technique. The Na + (0.1 N ) and Ca 2+ (0.02 N ) solutions of Cl ‐ and SO 2‐ 4 with Ni or Sr (10 −6 to 10 −4 M ) yielded systems in which up to 45% of soluble metal (M) was present as MSO 0 4 . Sorption was greater in the Cl ‐ vs. the SO 2‐ 4 systems at the same total M (Ni or Sr) concentration at equilibrium. Plotting data in terms of free M 2+ activity at equilibrium eliminated significant differences between corresponding isotherms. Sorption thus appeared to be controlled by M 2+ activity. The data supported the hypothesis that MSO 0 4 complexes were not sorbed and MCl + complexes sorbed only slightly if at all. Nickel sorption was greater than Sr sorption under similar conditions. The results illustrate the importance of correcting for ionic strength/ion pairing effects before making comparisons among isotherms.