Processing Of Pacific Ocean Manganese Nodules

Abstract

ABSTRACT An acid leaching process of Pacific ocean nodules has been studied. Nodules were leached with 0.1-3.5 N sulfuric acid at 70-90°C for 2-30 hours. Kinetics of copper and nickel extraction was discussed. Nickel and cobalt were recovered from the leaching solutions with hydrogen sulfide or by the cementation under pH control using ferromanganese and iron. Nickel was successfully separated from cobalt by solvent extraction with LIX 64 N extracting system adding a small amount of sodium sulfite. INTRODUCTION In Japan, as well as in other advanced nations, Pacific ocean nodule development is an interesting subject. In Japan, consumption of copper, nickel and cobalt has a large share in the world, and depends almost on the foreign resources. In future, Pacific ocean nodules will be major resources of the metals for Japan. Since 1970, the basic and field experiments of the continuous line bucket mining system proposed by Masuda, have been made mainly in National Research Institute for Pollution and Resources of Japan (NRIPR). Japanese Manganese Nodule Develop Co. and Deep Ocean Mining Co. have been established for nodule mining in Japan. The Deep Ocean Mineral Association of Japan (DOMA) constructed the Hakurei Maru, a vessel for the cruise of nodule research. Japanese several company?s are joining in such international consortia of nodule development as Kennecott Joint Venture, Ocean Management Inc. and Ocean Mining Associates. The metallurgical research of Pacific ocean nodules, in Japan, has been conducted by Tohoku University, Fukushima Technical College, Yamaguchi University, NRIPR and so on. As far as the metallurgical processing of nodules, hydrometallurgical process is generally believed to be more profitable than pyrometallurgical process. However, each consortium has selected a different process. Kennecott Joint Venture proposed an ammonia leaching process (Cuprion process). l Ocean Mining Associates selected a hydrochloric acid leaching process. 2 Ocean Management Inc. preferred a pyrometallurgical process. 3 It is preferable, especially for Japan, that the metal concentrates or metal products are made from nodules in a floating plant (a process plant on floating structures) at the sea-area where they are being mined, or on a floating barge at an island's coast near the nodule area, mainly to save transportation cost. In the first step of nodule development, metal sulfide concentrates Or cemented metals should be commercially produced in the floating plant and fed into an operating smelter. Several hydrometallurgical processes for manganese nodules were evaluated by the present authors and reported in the Japanese literatures. 4–15 Processing at sea on a floating or sea-moored barge seems to provide several advantages, but a simple process is required for easy operation and maintenance. A sulfuric acid leaching process, operated at temperature below 100°C in 2-3 N acid concentration, may be well suited to these requirements.