From 1989 to 1996, Metal Mining Agency of Japan (MMAJ) performed studies on the recovery of iron, manganese copper and nickel from manganese nodules under the commission of the Ministry of International Trade and Industry. After investigating existing processes and comparing their respective performance with the same manganese nodules, the MMAJ developed a smelling and chlorine reaching process. The processes is the combination of pyrometallurgical and hydrometallurgical treatments, which enabled the efficient recovery of manganese, nickel, copper and cobalt.
Since the discovery of manganese nodules in 19th century, people has regarded manganese nodules as an increasingly important source of valuable metals, including nickel, cobalt, copper and manganese. In Japan, the Ministry of International Trade and Industry (MITI) and private industry have been actively investigating manganese nodules and developing mining technology for the nodules for the last 25 years. From both technical and economical points of view, it is necessary for exploitation of the nodules to develop a suitable metallurgical processing. It is difficult to recover nickel, copper and cobalt contained in manganese nodules by any usual process, for such metals arc present as oxides and oxyhydroxides of the manganese and iron phases. For example, a French institute, IFREMER-GEMONOD estimated that the cost of processing would account for more than half of the total cost of the exploitation (Charles et al., 1990). Therefore, the MMAJ started a project in 1989, to study the recovery of iron, manganese, copper, cobalt and nickel from manganese nodules under the commission of the MITI.
The following five processes were chosen for the study:
reduction and ammoniacal leaching,
cuprion ammoniacal leaching,
high-temperature and high-pressure sulfuric acid leaching,
reduction and hydrochloric acid leaching, and
smelting and sulfuric acid leaching.