Laterites Leaching

Other apphcations include dewatering extremely fine (0.1 llm) laterite leach tailings (91). These pelletizing processes should be compared in flocculant consumption and operating and capital costs with belt-filter presses. 

Cheng, C. Y. Purification of synthetic laterite leach solution by solvent extraction using D2EHPA. Hydrometallurgy 2000, 56, 369-386. 

In 2005, the British Geological Survey published data that indicated that 45% of the world primary cobalt originated from the Shaba province, in the DRC (3). Moreover, no primary cobalt production exists in the USA, which is completely dependent on foreign imports for their cobalt usages. The announced additional supply of cobalt from the HPAL laterite leaching plants has not yet met with expectations. To minimize the risks of supply due to world competition and political instability, it is therefore essential to maximize the recycling of cobalt... 

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. 

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. 

J.H. Kyle, Jarosite / Alunite in Nickel Laterite Leaching - Friend or Foe , ALTA 2003 Nickel / Cobalt - 9, ALTA Metallurgical Services, Castlemaine, Victoria, Australia, 2003. 28pp... 

D.T White, Commercial Development of the Magnesia Mixed Hydroxide Process for Recovery of Nickel and Cobalt from Laterite Leach Solutions, Hydrometallurgy of Nickel and Cobalt 2009, J.J. Budac, R. Fraser, I. Mihaylov, V. G. Papangelakis and D.J. Robinson, Eds., CIM, Montreal, Quebec, Canada, 2009, 351-367. 

Keywords Base Metals, Laterite, Leaching, Solvent Extraction, Mixed Chloride... 

FIGURE 5.12 Bulong flow sheet for purification of nickel and cobalt from laterite leach liquor. (From Sole, K. C. and Cole, P. M. 2001. In Ion exchange and solvent extraction, vol. 15, New York Marcel Dekker. With permission.)... 

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. 

High alumina minerals are found where intense weathering and leaching has dissolved the siHca. It is generally befleved that a very humid, subtropical climate is required for this (lateritic) stage of weathering. 

Pressure-acid leaching was used to extract cobalt from Blackbird mine ores before its closing in 1974. The result was a very fine cobalt powder which was subjected to a seeding process to produce cobalt granules. Leaching methods are also used in the refinement of lateritic ores. 

Lateritic Ores. The process used at the Nicaro plant in Cuba requires that the dried ore be roasted in a reducing atmosphere of carbon monoxide at 760°C for 90 minutes. The reduced ore is cooled and discharged into an ammoniacal leaching solution. Nickel and cobalt are held in solution until the soflds are precipitated. The solution is then thickened, filtered, and steam heated to eliminate the ammonia. Nickel and cobalt are precipitated from solution as carbonates and sulfates. This method (8) has several disadvantages (/) a relatively high reduction temperature and a long reaction time (2) formation of nickel oxides (J) a low recovery of nickel and the contamination of nickel with cobalt and (4) low cobalt recovery. Modifications to this process have been proposed but all include the undesirable high 760°C reduction temperature (9). 

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). 

Laterite Reduction roasting 2 NiO + C —> 2 Ni + C02 Ammonia-ammonium carbonate leaching in the presence of oxygen... 

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. 

Swamy KM, Sukla LB, Narayana KL, Kar KN, Panchanadikar VV (1995) Use of ultrasound in microbial leaching of nickel from laterites. Ultrason Sonochem 2(1) S5-S9... 

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. 

Chalkley, M. E. Toirac, I. L. The acid pressure leach process for nickel and cobalt laterite. Part I review of operations at Moa. Hydrometallurgy and Refining of Nickel and Cohalt, Annual Hydrometallurgy Meeting of CIM, 27th, Sudbury, Ont., Aug. 17-20, 1997, 341-353. 

Georgiou, D. Papangelakis, V. G. Sulfuric acid pressure leaching of alimonitic laterite chemistry and kinetics. Hydrometallurgy 1998, 49, 23 16. 

Papangelakis, V. G. Georgiou, D. Rubisov, D. H. Control of iron during the sulfuric acid pressure leaching of limonitic laterites. Iron Control and Disposal, Proceedings of the International Symposium on Iron Control in Hydro-metallurgy, 2nd, Ottawa, Oct. 20-23, 1996, 263-274. 

Rubisov, D. H. Papangelakis, V. G. Sulfuric acid pressure leaching of laterites—prediction of metal solubilities and speciation analysis at temperature. EPD Congress 1999, Proceedings of Sessions and Symposia held at the TMS Annual Meeting, San Diego, Feb. 28-Mar. 4, 1999, 535-546. 

Rubisov, D. H. Krowinkel, J. M. Papangelakis, V. G. Sulphuric acid pressure leaching of laterites—universal kinetics of nickel dissolution for limonites and limonitic/saprolitic blends. Hydrometallurgy 2000, 58, 1-11. 

Kyle, J. H. Pressure acid leaching of Australian nickel/cobalt laterites. Publ. Australas. Inst. Min. and Metall. 1996, 6/ 96, 245-250. 

Virnig, M. J. Mackenzie, J. M. W. Wolfe, G. A. Boley, B. D. Nickel laterite processing Recovery of nickel from ammoniacal leach liquors. Miner. Metall. Process. 2001, 18, 18-24. 

Rice, N. M. Gibson, R. W. Solvent extraction with Cyanex 301 and 302 for the upgrading of chloride leach liquors from lateritic nickel ores. Value Adding through Solvent Extraction, [Papers presented at ISEC 96], Melbourne, Mar. 19-23, 1996, 1, 715-720. 

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. 

The dissolution of goethite in acidic media and the reprecipitation of the Fe as hematite, is a crucial process in the high-temperature leaching of nickel laterite ores. At 250 °C the rate of transformation increased as the Eh of the system was lowered... 

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... 

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