Nickel extraction laterite processing

It has been mentioned in an earlier chapter that nickel deposits are basically of two types sulfidic and lateritic (oxide). The scenario of nickel extraction from nickel sulfide concentrates and nickeliferrous pyrrho tite (these two are the two products of physical beneficiation of nickel sulfide ores), and from limonitics and gamieritics (these are the common lateritic ores) has been presented in Figure 5.6. It can be seen that nickel is extracted from its various sources by pyro, pyro-hydro and hydroprocessing. The account given here pertains to the latter two processes applied to the various nickel sources. 

PAL II [Pressure Acid Leach] A process for extracting nickel from laterite ores. Operated in Australia. 

There are three classes of SX reagents, viz. acidic, basic and solvating. Acidic extractants exchange for metal ions, basic extractants are positively charged and extract anionic metal complexes and solvating extractants solubilize neutral metal complexes or ion pairs in the organic phase. For Ni/Co extraction and separation in nickel laterite processing, only acidic and... 

Nickel Laterite Processing A Variety of Solvent Extraction... 

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). 

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). 

Caron A process for extracting nickel and cobalt from lateritic ores by reductive roasting, followed by leaching with ammoniacal ammonium carbonate solution in the presence of oxygen. Developed by M. H. Caron at The Hague in the 1920s and used in Cuba (where the location of the mine is named Nicaro, after the metal and the inventor) and in Australia. 

Cobalt is produced as a coproduct of nickel or copper refining. Copper-cobalt sulfide concentrates can be processed by the RLE process. Mixed cobalt-nickel sulfides can be precipitated from ammoniacal leach solutions and as mixed nickel-cobalt hydroxide or carbonate from acid sulfate leach processes. From chloride leach solutions, cobalt can be separated by solvent extraction. Most cobalt production is associated with nickel production from sulfide and laterite ores. Pressure leaching, solvent extraction followed by the electrowinning of... 

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

The Goro process (Figure 5.14) developed by INCO (now CVRD-lnco) for the treatment of a nickel laterite deposit in New Caledonia (Bacon and Mihaylov 2002 Mihaylov et al. 2000 Mihaylov et al. 1995) also treats the laterite leach liquor directly but uses a completely different approach. The flow sheet involves the coextraction of nickel and cobalt by SX with the sulfnr-snbstitnted organophosphinic acid, CYANEX 301, followed by their separation in chloride medinm by SX using an amine extract. 

In the oxide-silicate ores nickel is so disseminated within the laterite that conventional ore-dressing methods do not work. The ore is often treated directly in py-rometallurgical processes, high-temperature reduction with carbon. This process yields ferronickd. Laterite ores are also leached with sulfuric acid in a high-tem-perature, high-pressure process. Nickel and cobalt are separated from purified solutions by solvent extraction. 

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