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Proton Effects on Quaternary Cation Exchange and Flocculation of Silver Hill Illite
Author(s) -
Thellier Catherine,
Sposito Garrison,
Holtzclaw Kenneth M.
Publication year - 1992
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/sssaj1992.03615995005600020014x
Subject(s) - chemistry , illite , flocculation , perchlorate , aqueous solution , inorganic chemistry , desorption , ion exchange , adsorption , nuclear chemistry , clay minerals , mineralogy , ion , organic chemistry
The investigation of quaternary cation exchange and flocculation in dilute suspensions of illite with mixed Na‐K‐Ca‐Mg perchlorate solutions was extended to consider the effect of aqueous protons. The exchange reactions and flocculation of Silver Hill illite at inial pH (pH i ) = 6 or 8, three total perchlorate concentrations (9, 5, or 2 mol c m −3 ), and varying initial Na/Ca or Na/Mg ratios in the aqueous solution phase were studied. It was found that pH i had little or no effect on exchangeable cation selectivity or total adsorbed metal charge. The degree of flocculation, as described by the percentage light transmission through the illite suspensions, was found to be highly pH i dependent. The effect of pH i was greatest in the 5 mol c m −3 perchlorate background, where, at an exchangeable bivalent charge fraction near 0.3, the suspension was almost completely flocculated at pH i = 6 but dispersed at pH i = 8. Overall, at a given exchangeable bivalent charge fraction, the illite suspensions became less flocculated, and showed greater sensitivity to exchangeable Ca vs. Mg, as pH i increased from 6 to 8. Changes in pH i thus produced colloidal effects just the inverse of changes in the total perchlorate concentration. Analysis of the pH dependence of the light‐transmission data suggested that the mechanism of illite flocculation was affected greatly by the adsorption‐desorption reactions of a small number of protons on the edge surfaces of suspended particles.