GEOC 174 |
| John S. Loring and Per Persson. Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden |
| An in situ method is presented for the simultaneous potentiometric and infrared spectroscopic titration of mineral suspensions. First, a mineral overlayer is deposited onto the surface of an internal-reflection element of a flow-through ATR cell. Next, a potentiometric titration of a suspension of the mineral is performed, and this solution is continuously pumped through the ATR cell and over the mineral overlayer. With each addition of titrant, both the solution pH and the infrared spectrum at the aqueous-mineral interface are recorded. Finally, the accumulated data are evaluated using a factor analysis in which the spectra are fit according to a model comprised of the equilibrium, mass-balance, and surface-charge relations that describe the reactions in solution and at the mineral surface. The spectra of the surface complexes are isolated, and their stoichiometries and formation constants are determined. The results of the application of this method to various geochemical systems are discussed. |
|
Vibrational Spectroscopy in the Earth and Environmental Sciences
8:00 AM-11:40 AM, Thursday, April 1, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |