Laterite containing nickel

A similar process has been devised by the U.S. Bureau of Mines (8) for extraction of nickel and cobalt from United States laterites. The reduction temperature is lowered to 525°C and the hoi ding time for the reaction is 15 minutes. An ammoniacal leach is also employed, but oxidation is controlled, resulting in high extraction of nickel and cobalt into solution. Mixers and settlers are added to separate and concentrate the metals in solution. Organic strippers are used to selectively remove the metals from the solution. The metals are then removed from the strippers. In the case of cobalt, spent cobalt electrolyte is used to separate the metal-containing solution and the stripper. MetaUic cobalt is then recovered by electrolysis from the solution. Using this method, 92.7 wt % nickel and 91.4 wt % cobalt have been economically extracted from domestic laterites containing 0.73 wt % nickel and 0.2 wt % cobalt (8). 

Jarosite containing nickel laterite leach residues are chemically stable if kept in contact with alkali (sodium) containing liquors. Jarosite breakdown remains manageable, even in the absence of the stabilizing alkali ions, particularly where excess acid neutralizing reagent has been added, as occurs when processing via the mixed hydroxide process route. 

The success of the carbonaceous reduction of iron oxide has opened doors for the beneficiation of other minerals that coexist with oxides of iron also known as mineral sands. Examples of these ores are ilmenite, containing titanium dioxide and laterite ore, containing nickel oxide. Titanium dioxide (Ti02) is one of the most important inorganic materials used as a pigment for paper, plastics, paints, textile, and so on. 

In contrast to the sulfide ores, the lateritic ores were formed over long periods of time as a result of weathering of exposed nickel-containing rocks. The lateritic weathering process resulted in nickel solutions that were redeposited elsewhere in the form of oxides or siUcates. One type of laterite is nickeliferous limonitic iron laterite (Ee, Ni)O(OH) which consists primarily of hydrated iron oxide in which the nickel is dispersed in soHd solution. 

The laterites can be divided into three general classifications (/) iron nickeliferrous limonite which contains approximately 0.8—1.5 wt % nickel. The nickel to cobalt ratios for these ores are typically 10 1 (2) high siUcon serpentinous ores that contain more than 1.5 wt % nickel and (J) a transition ore between type 1 and type 2 containing about 0.7—0.2 wt % nickel and a nickel to cobalt ratio of approximately 50 1. Laterites found in the United States (8) contain 0.5—1.2 wt % nickel and the nickel occurs as the mineral goethite. Cobalt occurs in the lateritic ore with manganese oxide at an estimated wt % of 0.06 to 0.25 (9). 

Societe Le Nickel (SLN) employ similar chemistry at their operations to treat mattes obtained from the pyrometallurgical treatment of Ni-bearing oxidic laterite ores.104 It has demonstrated at laboratory scale that Ni-containing lateritic ores may be directly leached into HC1 acid solution without pyrometallurgical pre-concentration at atmospheric pressure and relatively low temperature (ca. 70 °C).105... 

More than 90% of the nickel and cobalt in laterite ores (1.0-1.6% nickel) can readily be leached by sulfuric acid at >240 °C, typically producing large volumes of relatively dilute leach solution containing 3-6 gL-1 of nickel and around 40 gL-1 H2S04.98 In addition to nickel and cobalt these leach solutions contain Al, Cr, Ca, Cu, Fe, Mg, Mn, Na, Si, and Zn.89 The design of reagents and protocols for the separation and concentration of metal values in these streams has depended heavily on differences in the coordination chemistry of the components. 

In metallurgy, hydrogen sulfide is used to precipitate copper sulfide from nickel—copper-containing ore leach solutions in Alberta, Canada, or to precipitate nickel and cobalt sulfides from sulfuric acid leaching of laterite ores in Moa Bay, Cuba (120) (see Metallurgy, extractive metallurgy). 

In the early 1800s, the principal sources of nickel were in Germany and Scandinavia, Very large deposits of lateritic (oxide or silicate) nickel ore were discovered in New Caledonia in 1865. The sulfide ore deposits were discovered in Sudbury, Ontario in 1883 and, since 1905, have been the major source of the element, The most common ore is pentlandite, (FeNi Sg, which contains about 34% nickel. Pent-landite usually occurs with pyrrhotite, an iron-sulfide ore, and chalcopyrite. CuPeS2. See also Chalcopyrite Pentlandite and Pyrrhotite, The greatest known reserves of nickel are in Canada and Russia, although significant reserves also occur in Australia, Finland, the Republic of South Africa, and Zimbabwe. 

The extraction of nickel from Cuban lateritic ores on a commercial scale has been described by Baragwanath and Chatelain (B4). The Nicaro nickel project was operated for almost two years during the Second World War and produced 2,600,000 Ib/month of nickel oxide. The laterite ores, containing 1.5% nickel, were dried to reduce the moisture content of the ore from 28 to 2.5%, ground to 90% —100 mesh, roasted in a reducing... 

Iwasaki et al. (17) reported a segregation process in which nickel is recovered from iron laterites and oxidized nickel ores. Halide salts such as sodium or calcium chloride, and a solid reductant such as metallurgical coke were mixed with the ore prior to roasting. The amount of halide salts was varied from 5 to 16% and the coke containing 85% fixed carbon... 

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. 

Calcium in the form of calcium carbonate contained in limestone is added in the neutralization processes after nickel laterite leaching. Calcium sulfate solids in the form of gypsum (and possibly hemihydrate and anhydrite) precipitate and have the potential to form scale on equipment and piping surfaces. 

Smelting to ferronickel is essentially the same as matte smelting, except that no sulfur is added. It is often applied to laterite ores. The resulting iron-nickel alloy contains 20-50% nickel [46]. 

Nickel-cobalt-containing laterite l ores are available in Cuba, New Caledonia, Papua New Guinea and the Philippines. 

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