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The influence of ionic strength on the facilitated transport of cesium by kaolinite colloids
Author(s) -
Saiers James E.,
Hornberger George M.
Publication year - 1999
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/1999wr900055
Subject(s) - kaolinite , ionic strength , adsorption , colloid , partition coefficient , sorption , desorption , ionic bonding , chemistry , chemical engineering , inorganic chemistry , materials science , mineralogy , aqueous solution , chromatography , ion , organic chemistry , engineering
We report results of laboratory experiments on the co‐transport of 137 Cs by inorganic colloids composed of kaolinite. We find that under conditions of low pore water ionic strength, the kaolinite colloids significantly accelerate 137 Cs transport through columns packed with quartz sand, kaolinite mobility and the affinity of kaolinite for binding 137 Cs diminish with increasing ionic strength. As a result, kaolinite exerts a progressively smaller influence on 137 Cs transport as the ionic strength increases from 0.002 to 0.1 m. The 137 Cs breakthrough data are used to test a model that incorporates advection‐dispersion equations for the movement of kaolinite colloids, dissolved 137 Cs, and kaolinite‐associated 137 Cs and mass transfer equations for kaolinite deposition, 137 Cs adsorption by kaolinite, and 137 Cs adsorption by quartz sand; The partition coefficient for 137 Cs retention by kaolinite colloids and the first‐order rate coefficient for kaolinite deposition vary in a discernible fashion with changes in ionic strength. The adsorption rate coefficient and the sorption capacity term of the second‐order rate law taken to describe 137 Cs adsorption to the quartz sand are independent of ionic strength; however, the magnitude of the desorption coefficient varies logarithmically with ionic strength. This work indicates the need to account for enhanced movement of sorbing solutes by inorganic colloids and provides a basis for quantifying the response of colloid‐associated solute transport to changes in pore Water chemistry.