Interaction of gases with lunar materials (12001): Textural changes induced by sorbed water

• Published in: Journal of colloid and interface science Vol. 55; no. 2; pp. 358 - 369
• Main Author: Fuller, E.L
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.1976
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/0021-9797(76)90043-6

The details of the mechanism by which water is sorbed on lunar soils has been further elucidated with a somewhat more detailed examination of an Apollo 12 sample (12001). The generality of the reactions is shown to extend to this sample. The inherent external surface accepts sorbed vapors in a rather classical manner commensurate with the existence of 0.34 m 2/g. In addition, the water vapor penetrates beyond this surface into inner regions, where an additional 0.63 m 2/g is generated, whereupon additional water vapor adsorbs. Both the inner and outer area chemisorb water on which additional physisorption occurs. Nitrogen sorption serves as a nonspecific sorbate as an aid in evaluating the geometric changes induced by thermal and/or water reactions. The inner surfaces adsorb nitrogen only when the chemisorbed water is removed. These restricted avenues are envisioned as laminar hydrous alumino-silicate (induced by water vapor incorporation) and/or “ink bottles” formed by water vapor attack along “ion spike” radiation damage tracks. It is relatively certain that the sorbed water has allowed atomic reorganization of the disordered surface regions by one of these mechanisms. The laminar structure, akin to terrestrial clays, seems to be the predominant state for this sample, wherein lies the 2.7-fold increase in sorption capacity. The surface also shows an appreciable affinity for carbon dioxide. This appears to be cooperative phenomena to form a surface bicarbonate specie, involving prechemisorbed water.