Sorption of 2,4-dichlorophenoxyacetic acid by model particles simulating naturally occurring soil colloids

Binary and ternary model particles containing montmorillonite, ferrihydrite, and humic acid (HA) were used to determine the changes in the sorption behavior of the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid) upon the interassociation of these three major soil constituents. On single sorbents, 2,4-D sorption was high with S-type isotherms on ferrihydrite, moderate with L-type isotherms on HA, and zero on montmorillonite. In binary sorbents, ferrihydrite and humic acid coatings on montmorillonite provided sorption sites for 2,4-D, although the exclusion of the anionic form from highly charged clay surfaces partially obscured the role of Fe and HA as sorbents of 2,4D. Sorption of 2,4-D on ferrihydrite-HA binary particles was not very different from that on pure ferrihydrite because most of the ferrihydrite surface area was from micropores being not accessible to large humic macromolecules and hence remained available for herbicide sorption. In ternary sorbents HA coatings reduced the sorption of 2,4-D by the montmorillonite-ferrihydrite binary complex, indicating that HA blocked many of the sorption sites provided by the Fe coatings. This work shows that the amount and nature of the surface that remains available after the interassociation of single soil constituents is a critical parameter in determining the sorptive behavior of the resultant aggregate for ionizable contaminants such as 2,4D. Thus, the use of calculated sorption parameters such as K(oc), K(ow), K(minera), or K(Fe), for modeling contaminant behavior. In aquatic or soil environments may result in serious deviation from the reality. | Binary and ternary model particles containing montmorillonite, ferrihydrite, and humic acid (HA) were used to determine the changes in the sorption behavior of the herbicide 2,4-D (2,4-dicholorophenoxyacetic acid) upon the interassociation of these three major soil constituents. The results showed that the amount and nature of the surface that remains available after the interassociation of single oil constituents is a critical parameter in determining the sorptive behavior of the resultant aggregate for ionizable contaminants such as 2,4-D.

Bibliographic Details

Main Authors:	Celis, R., Hermosín, M.C., Cox, L., Cornejo, J.
Format:	artículo biblioteca
Language:	English
Published:	American Chemical Society 1999
Online Access:	http://hdl.handle.net/10261/61056
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