| dc.description.abstract |
For the extraction of metal values from poly-metallic nodule several alternative techniques have been used. Out of these, the most promising ones are based on selctive reduction of metal oxides / hydroxides in aqueous slurry. The present work on metallurgical process development in India, Japan, Korea, as well as the earlier work in France, Russia, and USA are based on such techniques. The main advantages of reductive leaching technique are: (i) use of nodule in the form of a slurry, and therfore removal of naturally occuring moisture is not necessary, (ii) use of chemical reagent selecively for Cu, Ni, Co, and Mn, and (iii) use of moderate temperature during leaching, and therefore ease of reactor design and proces control. The aqueous reduction processes use different types of reductants e.g. Fe(II), Mn(II), SO2, CO, thiosulphate, glucose, and carbon in acidic as well as in ammoniacal media. Some of these reductants, such as CO, operate through a Cu(I)- Cu(II) couple to reduce the oxides, while reductants like Fe(II), and Mn(II) can operate directly, or through Cu(I)-Cu(II) couple. For almost a decade,the authors and their colleagues are involved in studying different aspects reductive leaching of polymetallic nodule, and currently involved in pilot testing of a SO2 based process. The paper gives a brief over-view of the processes using aqueous reduction technique. It particularly compares different processes developed using aqueous reduction technique. |
|