AVS 46th International Symposium
    Surface Science Division Monday Sessions
       Session SS1+EM-MoM

Invited Paper SS1+EM-MoM3
Spectroscopic Studies of Sorption Processes at Metal Oxide-Aqueous Solutions Interfaces

Monday, October 25, 1999, 9:00 am, Room 606

Session: Chemistry on Oxides
Presenter: G.E. Brown, Jr., Stanford U.
Authors: G.E. Brown, Jr., Stanford U.
T. Kendelewicz, Stanford U.
P. Liu, LBNL
J.R. Bargar, Stanford Synchrotron Radiation Lab.
J.P. Fitts, Stanford U.
A.L. Foster, Stanford U.
J.D. Ostergren, Stanford U.
G.A. Parks, Stanford U.
A.H. Templeton, Stanford U.
H.A. Thompson, LANL
S.N. Towle, Intel Corp.
T.P. Trainor, Stanford U.
P. Eng, Adv. Photon Source
S. Sutton, Adv. Photon Source
Correspondent: Click to Email
Chemical interactions at metal oxide-aqueous solution interfaces are of great significance in atmospheric and environmental chemistry. They help control many important processes including dissolution and crystal growth of natural solids and the sorption a nd desorption of aqueous metal ions, which can sequester or release heavy metal contaminants in atmospheric and aquatic environments. Metal oxide-water interfaces in natural systems are extremely complex when viewed at the molecular level because of the many variable that must be accounted for and the difficulty in observing the products of interfacial reactions under in-situ conditions (i.e., with bulk water present). To make this problem more tractable, we have employed a reductionist approach in which interfacial reaction products are examined in simplified model systems under carefully controlled conditions using a combination of classical surface chemistry methods, synchrotron radiation-based surface science methods, and other spectroscopic and scanning force microscopy methods. The resulting information at macroscopic and atomic/molecular scales allows sorption behavior to be correlated with chemical species information, including the structure, composition, and mode of sorption of adsorbates, and, in selected cases, the types of reactive sites on adsorbent surfaces and the effect of aging time. In parallel model system studies, we have also examined the effects of common inorganic ligands, organic ligands, and biofilms on the sorption of metal ions at mineral-water interfaces, and we have used the results as a basis for studies of As and Pb speciation in contaminated soils and mine tailings. These studies have revealed the structure and composition of adsorbates, and for single-crystal adsorbents, have allowed us to place constraints on the stoichiometry of sorption reactions, including the types of reactive sites to which the adsorbate binds. Selected examples of these studies will be presented.