Iron laterites, nickel from

The Cawse plant in Western Anstralia also recovered lateritic nickel from an anuno-niacal liqnor by SX (Bnrvill 1999 Kyle and Furfaro 1997). The flow sheet includes PAL, iron oxidation and removal, and precipitation of cobalt/nickel hydroxide. Today, the processing stops here and the mixed hydroxide precipitate is shipped to Scandinavia for refining. However, for several years, this intermediate product was subjected to an ammonia re-leach, followed by SX to prodnce a pure nickel sulfate for nickel EW while cobalt was precipitated as the sulfide. 

The treatments used to recover nickel from its sulfide and lateritic ores differ considerably because of the differing physical characteristics of the two ore types. The sulfide ores, in which the nickel, iron, and copper occur in a physical mixture as distinct minerals, are amenable to initial concentration by mechanical methods, eg, flotation (qv) and magnetic separation (see SEPARATION,MAGNETIC). The lateritic ores are not susceptible to these physical processes of beneficiation, and chemical means must be used to extract the nickel. The nickel concentration processes that have been developed are not as effective for the lateritic ores as for the sulfide ores (see also Metallurgy, extractive Minerals recovery and processing). 

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... 

R.A. Bergman, Nickel production from low-iron laterite ores process descriptions, QM Bull. 2003, 96( 1072), June-july, 127-138. 

Valuable mineral deposits which form by residual concentration pertain to iron, manganese, aluminum, nickel, clays, tin and gold. Aluminum comes almost exclusively from residual concentrations of bauxite, which result from the laterihsation of alumina rich igneous rocks like syenites under tropical and subtropical climatic conditions. Laterites also contribute nearly 80% of the world s reserves of nickel at grades better than 1% Ni. They form by residual concentrations as a result of weathering of mafic and ultramafic igneous rocks, which are relatively enriched in nickel. 

The lateritic hydrous nickel silicate ores are formed by the weathering of rocks rich in iron and magnesium in humid tropical areas. The repeated processes of dissolution and precipitation lead to a uniform dispersal of the nickel that is not amenable to concentration by physical means therefore, these ores are concentrated by chemical means such as leaching. Fateritic ores are less well defined than sulfide ores. The nickel content of lateritic ores is similar to that of sulfide ore and typically ranges from 1% to 3% nickel. Important lateritic deposits of nickel are located in Cuba, New Caledonia, Indonesia, Guatemala, the Dominican Republic, the Philippines, and Brazil. Fossil nickeliferous laterite... 

World nickel metal production in 2002 was 678000 tons [39]. Hydrometallurgy has typically been applied to the treatment of nickel-copper mattes, anode nickel, and reduced laterite ore. The sulfide concentrates are usually oxidized by roasting and then smelted to copper-iron-nickel sulfide matte (75-80% Cu-Ni), which is refined or used directly to make M onel metal. Cathode nickel can be produced from a variety of electrolytes, including chloride, sulfate, or a mixed chloride-sulfate. The former two are acid systems used in leaching and electrowinning. Mixed chloride-sulfate electrolytes are used for electrorefining the nickel sulfide matte from the traditional matte-smelting operations. 

Development of the Jarosite process in the zinc industry in the 1960s led to an understanding that iron could be precipitated from nickel laterite atmospheric leach solutions, at moderate acid levels, by the addition of an alkali such as potassium, sodium, or ammonia, whilst maintaining a temperature in excess of 90°C [4]. 

Researchers at the National Technical University of Athens published a number of papers in the 1980s and early 1990s, where jarosite precipitation of iron from nickel laterite acid leach solutions was considered [9, 10, 11, 12]. 

EXTRACTION OF NICKEL, COBALT AND IRON FROM LATERITE ORES BY MIXED CHLORIDE LEACH PROCESS... 

Nickel laterite is nickel mineral changed by weathering, etching, enrichment, and then it turns loose clay-like, composed of iron, aluminum, silicon, and some hydrous oxides. The element and moisture content are rich in this kind of ore. The elemental composition and content (Table 1) can be obtained by XRF elemental analysis and chemical analysis.XRD demonstrated that host minerals of the iron-enriched and magnesium-depleted version of laterites are mainly ferric iron oxides, typically goethite, FeO(OH), and nickel embedded in the mineral is mainly as the pattern of NiO (Figure 1). All of the samples came from Baosteel. 

Nickel, with a relative abundance in the Earth s crust of 70 mg/kg, is twice as abundant as copper, and the Earth s inner core is supposedly made of a Ni-Fe alloy (see Section 13.2). Nickel never occurs free in nature but only as an alloy with iron in certain meteorites. However, due to its chalcophile geochemical character, like copper, most nickel occurs primarily as minerals in combination with arsenic, antimony, and sulfur. Nickel is mined from two types of ore deposits primary nickel-bearing sulfide orebodies and secondary nickel-bearing laterite deposits. 

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