Author
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Laird, David |
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Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only Publication Acceptance Date: 9/11/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Mechanisms by which organic bases are adsorbed on hydrated smectite surfaces were investigated. Three Ca-saturated reference smectites (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 0.001 M HCl. After a 2 h equilibration, the amount of pyridine or 3-butylpyridine adsorbed 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 smectites indicating that pyridine was adsorbed as a protonated species by ion exchange. By contrast, 40 to 90% of added 3-butylpyridine was adsorbed on the smectites at neutral pHs while only small amounts of Ca were desorbed from the smectites. The results indicate that 3-butylpyridine is retained as a molecular species under neutral pH conditions and as an ionic species under acidic conditions. The results further indicate that hydrophobic interactions contribute substantially to the sorption of organic base on smectites with low surface charge density and high percentage of tetrahedral charge and are less important for smectites with high surface charge density and high percentage of octahedral charge. |
