Full Citation & Abstract

PUBLICATION NUMBER   AAT 9540542 TITLE   DISSOLUTION KINETICS OF LUNAR SIMULANTS AND THE SORPTION OF OXYANIONS AND NICKEL ON SECONDARY WEATHERING PRODUCTS (GLASS, MINERAL BASALT) AUTHOR   EICK, MATTHEW JOSEPH DEGREE   PHD SCHOOL   UNIVERSITY OF DELAWARE DATE   1995 PAGES   223 ADVISER   SPARKS, DONALD L. SOURCE   DAI-B 56/08, p. 4196, Feb 1996 SUBJECT   GEOCHEMISTRY (0996); PHYSICS, ASTRONOMY AND ASTROPHYSICS (0606) The dissolution kinetics of two lunar simulants (mineral basalt and glass) were investigated at pH values of 3, 5, and 7 and in the presence of naturally occurring organic acids. For both lunar simulants reductions in pH and the presence of the organic acids accelerated the dissolution rate. The dissolution of the glass simulant proceeded via a diffusion mechanism. In contrast, the dissolution of the basalt simulant proceeded by a surface controlled reaction. The sorption kinetics and mechanisms for trace elements contained in the lunar soils were investigated using goethite and kaolinite. A pressure-jump relaxation technique in conjunction with X-ray absorption fine structure spectroscopy (XAFS) was used to examine arsenate and chromate adsorption on goethite. It was determined that both oxyanions formed a mixture of mono- and bidentate surface complexes depending on the loading rate. The bidentate surface complex predominated at higher loading rates. Nickel sorption on kaolinite was examined using XAFS and transmission electron microscopy (TEM). Based on XAFS results and crystallographic considerations it was determined that Ni formed a bidenate binuclear complex on kaolinite followed by nucleation and the precipitation of a Ni(OH)$/sb2$ solid phase. TEM revealed that the solid phase was distributed in isolated clusters or islands on the kaolinite surface.