Skip to main content
ARS Home » Research » Publications at this Location » Publication #72508
Title: MECHANISMS FOR SORPTION OF WEAK ORGANIC BASES ON HYDRATED SMECTITE SURFACES

Author
item Laird, David
item Fleming, Pierce

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/8/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Mechanisms by which weak organic bases are sorbed on hydrated smectite surfaces were investigated. Three Ca-saturated reference bentonites (Otay, SPV, and Panther Creek) were dispersed in distilled water containing 5 micromoles of pyridine or 3-butylpyridine. The pH was adjusted between 7.5 and 3 using 0.01 M HCl. After a 2 hour equilibration, the amount of pyridine or 3-butylpyridine sorbed on the clay and the amount of Ca desorbed from the clay were determined. The results indicate negligible sorption of pyridine for neutral systems and nearly total sorption of pyridine for pHs less than the pKa of pyridine (5.2). Equivalent amounts of Ca were desorbed from the clays indicating that pyridine was sorbed as a protonated species by ion exchange. By contrast, 40 to > 90% of added 3-butylpyridine was sorbed on the clays at neutral pHs while only small amounts of Ca were desorbed. The results suggest that 3-butylpyridine is initially retained by hydrophobic bonding between the alkyl tail of the molecule and hydrophobic microsites located between the charge sites on smectite surfaces.