RECENT DEVELOPMENTS IN PROCESSING OCEAN MANGANESE NODULES—A CRITICAL REVIEW

Abstract

This article reviews the state of the art in processing and extracting ocean manganese nodules. It briefly reviews the mining sites where abundant rich nodules occur and also describes the metal distribution in nodules. The physicochemical characteristics of the nodules, touching upon different facets such as mineralogy, geochemistry, moisture content, and textural properties of the nodules, are discussed in detail. In the extraction aspects of the nodules, is article reviews two different extraction routes often mentioned in the literature during the last two decades, namely hydrometallurgical and biohydrometallurgical treatments. The hydrometallurgical techniques include leaching by mineral acids, ammoniacal leaching, leaching at high temperature, and pressure and leaching with reducing agents. Reduction of manganese dioxide by organics and its probable application in leaching of nodules is described in a detailed manner. The biohydrometallurgy section extensively reviews the bioreduction phenomenon for manganese dioxide and suggests possible application in leaching of nodules. Projected future developments in the field, with an eye on commercialization, are also discussed.

Notes

Minerals shown in bold italics are the most common minerals found in nodules across the globe.

(Fuerstenau and Han 1977)

*Location of the nodule samples: DH-2 (21°50′N, 115°12′W; 3430 m); HRS-1 (22°N, 114°W; 3400 m) 2P-50 (13°53′S, 150°35′W; 3263 m) 2P-51 (9°52′S, 145°56′W, 4900 m) 2P-52 (9°57′N, 137°47′W, 4930 m) DWHD (16°29′S, 145°33′W, 1270 m)

*The text in the column denotes seven different locations of Central Indian Ocean from where the nodules were mined.