Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/25/2001
Publication Date: 10/25/2001
Citation: LAIRD, D.A. POLARITY INFLUENCES ON SORPTION MECHANISMS OF ORGANIC MOLECULES ON HYDRATED SMECTITIES. AGRONOMY ABSTRACTS. 2001. CD-ROM. MADISON, WI. ASA-CSSA-SSSA.
Technical Abstract: Sorption of organic molecules on smectite surfaces from aqueous systems is governed by net system free energy changes for water-clay, adsorbate-clay, water-water, and water-adsorbate interactions. Sorption of polar organic molecules is largely controlled by the difference between the strength of the water-clay and adsorbate-clay interactions. Pyridine, for example, is not sorbed on smectites in a molecular form from aqueous systems because it is not polar enough to compete with water for solvation of the adsorbed inorganic cations but it is too polar (lacks a nonpolar moiety) to interact with hydrophobic nanosites on the smectite surfaces. By contrast, weakly polar molecules such as atrazine and 3-butylpyridine are sorbed as molecular species because they have both polar and nonpolar moieties and are capable of simultaneously interacting with both the hydrophobic nanosites and water molecules solvating the adsorbed cations. Sorption of nonpolar organic molecules is driven by the large difference in strength of the water-water and water-adsorbate interactions.