Lateritic nodules

Oxides and hydroxides Bauxite laterites copper oxide ores uranium ores zinc ores and calcines manganese ores and nodules... 

Nevertheless, manganese nodules can, at best, be considered to be similar to land-based nickel laterites, and consequently most of the processing techniques that have been tried are similar to those used on lateritic ores. Reduction roasting followed by ammonia leaching, as in the Nicaro process, and high-temperature sulfuric acid leaching, as in the Moa Bay operation, have been extensively tried to process nodules. 

More than 90% of the world s nickel is obtained from pentlandite ((FeNi)9S8), a nickel-sulfitic mineral, mined underground in Canada and the former Soviet Union (Sevin 1980 IARC 1976 WHO 1991). One of the largest sulfitic nickel deposits is in Sudbury, Ontario (USPHS 1993). Nickeliferous sulfide deposits are also found in Manitoba, South Africa, the former Soviet Union, Finland, western Australia, and Minnesota (Norseth and Piscator 1979 USPHS 1993). Most of the rest of the nickel obtained is from nickel minerals such as laterite, a nickel oxide ore mined by open pit techniques in Australia, Cuba, Indonesia, New Caledonia, and the former Soviet Union (Sevin 1980). Lateritic ores are less well defined than sulfitic ores, although the nickel content (1 to 3%) of both ores is similar (USPHS 1993). Important deposits of laterite are located in New Caledonia, Indonesia, Guatemala, the Dominican Republic, the Philippines, Brazil, and especially Cuba, which holds 35% of the known reserves (USPHS 1993). Nickel-rich nodules are found on the ocean floor, and nickel is also present in fossil fuels (Sevin 1980). 

Muller, J. Joubert, J.C. (1974) Synthese en milieu hydrothermal et caracterisation de Voxyhydroxyde de vanadium V OOH et d une nouvelle variete allotropic du dioxide VO2. J. Solid State Chem. 11 79—87 Muller, J.P. Bocquier, G. (1986) Dissolution of kaolinites and accumulation of iron oxides in lateritic-ferruginous nodules Mineralogical and microstructural transformations. Geoderma 37 113-136... 

Muller, J.P. Bocquier, G. (1987) Textural and mineralogical relationships between ferruginous nodules and surrounding clayey matrices in a laterite from Cameroon. In Schultz, L.G. et al. (eds.) Proc. Int. Clay Conf. Denver, 1985, Clay Min. Soc., Bloomington, 186-194... 

Figure 3.13 Schematic illustration of the formation and evolution of successive laterite facies. (A) Mottled clay layer with ferruginised nodules and bleached zones. (B) Secondary fillings of kaolinite in bleaching zones. (C) Ferruginisation of kaolinite and the formation of pseudo-conglomeratic iron crust. (D) Evolution of haematite nodules into pisolites with the formation of pisolitic crust (after Nahon, 1986 Thomas, 1994).

Cobalt and Nickel Recovery. Cobalt and nickel are relatively valuable metals often found in complex ores such as laterites or deep sea nodules. The metals can only be extracted from these ores by hydrometallurgy. A proposed recovery scheme based on coupled transport is shown in Figure 9.29. The first membrane contains LIX 54, which produces a nickel and copper concentrate and a cobalt raffinate stream. The concentrate stream is then passed to a second Kelex 100 membrane, which produces a copper and nickel stream. The cobalt III raffinate stream is neutralized and reduced to cobalt II, which can then be concentrated by a LIX 51 membrane. 

Important deposits of laterite are located in New Caledonia, Indonesia, Guatemala, the Dominican Republic, the Philippines, Brazil, and especially Cuba which holds 35% of the known reserves. Nickel-rich nodules are found on the ocean floor, and nickel is also present in fossil fuels. 

Ferruginous and aiuminous clay soils are frequent products of weathering in tropical latitudes. They are characterized by the presence of iron and aluminium oxides and hydroxides. These compounds, especially those of iron, are responsible for the red, brown and yellow colours of the soils. The soils may be fine grained, or they may contain nodules or concretions. Concretions occur in the matrix where there are higher concentrations of oxides in the soil. More extensive accumulations of oxides give rise to laterite. 

Other sources of nickel, especially in deep-ocean polymetallic nodules (see Manganese) lying on the Pacific Ocean floor, will probably have an important economic role in the future. As a general rule, to be mineable, a nickel ore deposit must be able to produce annually at least 40,000 tonnes of nickel, that is, 800,000 tonnes for a period of 20 years. Annual world nickel production is 925,000 tonnes (2003), of which 70% is consumed for stainless steels. The world s largest nickel-producing countries are Russia, Canada, New Caledonia, and Australia. In 2005, the major nickel projects were the laterite deposit of Goro (New Caledonia, France) and the sulfide ore deposit of Voise/s Bay (Newfoundland, Canada). 

Cobalt reserves (known ore bodies that may be worked) in the world are estimated to 3.2 milKon tonnes (cobalt content) [30.4]. An estimate of the reserve base (known ore bodies that may be worked at some future time) gave 10 million tonnes, of which the DRC accounts for 25%. Most of this large reserve base is in nickel-bearing laterite deposits and in sedimentary copper deposits of DRC and Zambia. In addition millions of tonnes of speculative cobalt resources exist in manganese nodules on the ocean floor. 

---