ENVR 61 |
| The charging behavior of α-alumina (0001)/water interfaces at different bulk pH values and salt concentrations has been studied by surface-specific sum-frequency vibrational spectroscopy. The results indicate that the crystalline substrate has a point of zero charge (PZC) around pH 6.0, which is about three pH units lower than powder alumina samples reported before. The different bonding geometry of (Aln)OH (n=1-3) groups at surfaces of crystalline and powder samples is likely responsible for the difference. We have also investigated the net polar orientation of water molecules at alumina/water interfaces with a phase-sensitive detection method. When the pH was changed from above to below the PZC, interfacial water molecules have their net polar orientation flipped following switching of the sign of the surface field. These findings should be relevant to our search of deeper understanding of molecular adsorption processes in water purification when the ionic adsorbents are involved. This work was supported by the NSF Science and Technology Center of Advanced Materials for Purification of Water with Systems (Water CAMPWS; CTS-0120978). |
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Advances in Adsorption Processes for Drinking Water Treatment and Sourcewater Protection
8:30 AM-9:35 AM, Monday, April 7, 2008 Morial Convention Center -- Rm. 236, Oral
Division of Environmental Chemistry |