STUDIES ON INDIAN-OCEAN MANGANESE NODULES .1. PHYSICOCHEMICAL CHARACTERISTICS AND CATALYTIC ACTIVITY OF FERROMANGANESE NODULES

The detailed physicochemical characterization of manganese nodules from seven stations of the central Indian Ocean has been carried out on the basis of chemical analyses, TG-DTA, XRD, surface oxygen, surface hydroxyl groups, surface acidity, nitrogen adsorption-desorption isotherms, and electrical conductivity, Analysis for the bulk oxidation;state indicates that more than 98% of the Mn is present as Mn(IV). The surface acidity, determined on the basis of irreversible adsorption of noninteracting amines, increases with increased number of surface hydroxyl groups. The surface area of samples dried at 110 degrees C ranges from 97 to 130 m(2)/g, while the average pore diameter and cumulative pore volume range from 35 to 143 Angstrom and from 0.10 to 0.33 cm(3)/g, respectively. The various physicochemical characteristics have been correlated with catalytic activity for CO oxidation and H2O2 decomposition. (C) 1995 Academic Press, Inc