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

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