Nickel extraction Cobalt

Nickel and Cobalt. Often present with copper in sulfuric acid leach Hquors are nickel [7440-02-0] and cobalt [7440-48-4]. Extraction using an organophosphoric acid such as D2EHPA at a moderate (3 to 4) pH can readily take out the nickel and cobalt together, leaving the copper in the aqueous phase, but the cobalt—nickel separation is more difficult (274). In the case of chloride leach Hquors, separation of cobalt from nickel is inherently simpler because cobalt, unlike nickel, has a strong tendency to form anionic chloro-complexes. Thus cobalt can be separated by amine extractants, provided the chloride content of the aqueous phase is carefully controUed. A successhil example of this approach is the Falcon-bridge process developed in Norway (274). 

HydrometallurgicalProcesses. HydrometaHurgical refining also is used to extract nickel from sulfide ores. Sulfide concentrates can be leached with ammonia (qv) to dissolve the nickel, copper, and cobalt sulfides as amines. The solution is heated to precipitate copper, and the nickel and cobalt solution is oxidized to sulfate and reduced, using hydrogen at a high temperature and pressure to precipitate the nickel and cobalt. The nickel is deposited as a 99 wt % pure powder. 

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 oflaterite ores in Moa Bay, Cuba (120) (see Metallurgy, extractive metallurgy). 

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). 

It is worthwhile to point out that lithium extraction from inverse spinels V[LiM]04, such as V[LiNi]04 and V[LiCo]04 takes place at high voltage, typically between 4 and 5V [153]. Lithium is extracted from the octahedral 16d sites of these spinels with a concomitant oxidation of the divalent nickel or cobalt ions. From a structural point of view, this can be readily understood because lithium must be dislodged from the 16d octahedral sites, which are of low-energy, into neighboring energetically unfavorable 8b tetrahedra, which share all four faces with 16d sites that are occupied by nickel or cobalt and by lithium. Lithium extraction reactions... 

Partially extracted Raney cobalt is very active, but it is easily poisoned by sulfur and tends to lay down carbon more readily than Raney nickel (21). Cobalt is less active than nickel and much less selective to methane... 

Effective protocols have also been developed for the extraction of nickel and cobalt from chloride and ammoniacal process streams derived from leaching sulfidic ores or mattes.103 175 214 224 270-279 The greater thermodynamic stability of the Co11 chloroanionic complexes such as [CoCl4]2-over analogous Ni11 species has been exploited to effect the separation of nickel and cobalt via an... 

Duyvesteyn, W. P. C. Sabacky, B. J. Ammonia Leaching Process for Escondida Copper Concentrates (Reprinted from Extractive Metallurgy of Copper, Nickel, and Cobalt. Vol. 1, 1993). Trans. Inst. Min. Metall. Sect. C-Miner. Process. Extr. Metall. 1995, 104, C125-C140. 

Nagel, V. Gilmore, M. Scott, S. Bateman pulsed column pilot-plant campaign to extract cobalt from the nickel electrolyte stream at Anglo Platinum s base metal refinery. International Solvent Extraction Conference, Cape Town, South Africa, Mar. 17-21, 2002, pp 970-975. 

Martinez, R. V. Liranza, E. G. Barzaga, B. R. Daudinot, A. M. Cobalt recovery by solvent extraction from acid leach solutions of Caron s process mixed Ni/Co sulfide. Hydrometallurgy and Refining of Nickel and Cobalt, Annual Hydrometallurgy Meeting of CIM, 27th, Sudbury, Ont., Aug. 17-20, 1997, 293-304. 

Mercury was determined after suitable digestion by the cold vapour atomic absorption method [40]. Lead was determined after digestion by a stable isotope dilution technique [41-43]. Copper, lead, cadmium, nickel, and cobalt were determined by differential pulse polarography following concentration by Chelex 100 ion-exchange resin [44,45], and also by the Freon TF extraction technique [46]. Manganese was determined by flameless atomic absorption spectrometry (FAA). 

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. 

Sulfuric acid leach liquors, nickel and cobalt extraction from, 70 791 Sulfuric acid lithium recovery process, 75 125-126... 

For simple acidic extractants, such as carboxylic or sulfonic acids, the similarity in formation constants does not produce cobalt-nickel separation factors (Sn° 2) sufficiently large for commercial operation (Fig. 11.4). Data for pH versus extraction for some chelating acid extractants does seem to offer the possibility of separation [e.g., for the hydroxyoxime Acorga P50, the pHso for nickel(II) is 3.5 and for cobalt(II) 5.0]. Normally, this pH difference would be suitable for a separation process, but this particular system has hidden complications. The rate of nickel extraction is very slow compared with cobalt and, in addition, although cobalt is initially extracted... 

Earlier it was noted that nickel and cobalt could be extracted by carboxylic and sulfonic acids, with nickel being extracted at the lower pH. However, with alkylphosphorus acids, a selectivity reversal is observed, with cobalt being favored under acid conditions. The cobalt-nickel separation factor has been shown to depend upon metal concentration, reagent structure, diluent, temperature, and the presence of a diluent modifier. Thus, with increasing cobalt concentration the color of the extractant phase changes... 

The Sumitomo Metal Mining Co. in Japan uses a carboxylic acid extractant to recover nickel and cobalt from a solution obtained from the pressure leaching of metal sulfide concentrates with sulfuric acid.44 Iron, copper, zinc and manganese are removed from the leach liquor by conventional precipitation methods prior to the extraction of nickel and cobalt into a 40-60% solution... 

The ammonium sulfate contained in the raffinate is treated with lime to produce ammonia for recycle, and the extracted nickel and cobalt are transferred to a chloride medium (for subsequent separation by amine extractants, as described in Section 63.3.2.4) by stripping with 25% hydrochloric acid solution ... 

The Nippon Mining Co. refinery in Japan, which had previously used D2EHPA to extract cobalt from solutions obtained in the leaching of a mixed cobalt—nickel sulfide in sulfuric acid, changed in 1978 to the new extractant 2-ethylhexyl 2-ethylhexylphosphonate enabling a much-improved selectivity for cobalt over nickel to be obtained.8990 The process is carried out in three counter-current stages with an organic solution of phosphonic acid that has been converted to the ammonium salt by contact with aqueous ammonia ... 

Selectivities of potential hydrometallurgical interest that were demonstrated recently400 are the very good extractions of nickel and cobalt from acetonitrile, propylene carbonate, sulfolane or dimethylformamide by a cation exchanger copper, iron(II), iron(III) and zinc, present in the same solution, are either weakly extracted or are not extracted at all. It is also possible for copper to be extracted selectively from Fe3+ ions with an anion exchanger in dimethyl sulfoxide, dimethylformamide or dimethylacetamide.400... 

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