ABSTRACT:

Polymetallic sea nodules are the potential sources of copper, nickel, cobalt and manganese. As the land based resources of these metals are depleting very fast, a considerable R&D effort have been made all over the world to extract the metals from the sea nodules during the past four decades. The paper summarises the processes developed by various R&D organisations and metallurgical consortia for the extraction of metal values from the sea nodules. Since the copper, nickel and cobalt in the sea nodules are in oxide forms and they associate in the lattices of iron and manganese minerals, for extraction of these metals the lattices are broken either by hydrometallurgical reduction or by reductive pyro-treatment. Based on this criteria, processing methods have been broadly divided into two categories:

  • pyrometallurgical treatment followed by hydrometallurgical processing and

  • purely hydrometallurgical processing.

Processes developed under these two categories have been discussed highlighting their merits and demerits. Pilot plant studies carried out by various metallurgical consOltia like Knnecott Copper Corporation, Deep Sea Ventures, Metallurgie Hoboken - Overpelt, International Nickel Company are also given. The R&D efforts made in India in the processing of sea nodules during last one decade and the future programme are also discussed.

INTRODUCTION

The manganese and iron concretions known as manganese nodules or polymetallic sea nodules contain many valuable metals like Cu, Ni and Co besides trace amounts of Zn, Mo, Pb, Y, Tl, Au, Pt, Ti, Zr, Ag, Cd etc., were first discovered by H.M.S. Challenger Expedition during 1872-76. As the land-based resources of nonferrous metals are rapidly depleting, interest in finding ways for recovering valuable metals from the sea nodules is increasing. A comparison between land based reserves and ocean reserves for Cu, Ni, Co and Mn is given in Table-l (Das, 1989).

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