Cobalt solvent extraction

A mineral ore contains cobalt and small amounts of nickel. In order to determine the nickel concentration it must be separated from cobalt. Solvent extraction using 0.01 M 8-hydroxyquinoline in CHCI3 is chosen. Which metal should be extracted from the other, and at what pH Consider Figure 9.3 and connected text. 

With the use of appropriate additives (anti-pitting agents), pitting in the cobalt round can be suppressed without interfering with phase disengagement in cobalt solvent extraction. Cobalt deposit stress decreased with increasing temperature and current density. 

The new process would include the pressure leaching of the nickel sulphide, cobalt solvent-extraction plant for separation of the nickel, solution purification and neutralizing plants, and nickel electro winning tankhouse. Cobalt can be shipped out as cobalt salt solution fi om solvent extraction solution or optionally as cobalt cathodes from cobalt electrowinning plant. The expansion is designed to be build and commissioned in modular stages. 

Pregnant leach solution containing copper, cobalt and nickel, is pumped from the PLS storage tank through heat exchangers to the extraction trains. The PLS minimum temperature is 15 °C and maximum 50 °C when entering into solvent extraction. The extraction train contains DOP unit, spirok unit and mixer-settlers. After the last mixer settler, the aqueous phase is directed to raffinate after settler. From the after settler the solution is pumped to raffinate filter and to cobalt solvent extraction. 

The state of the art of nickel and cobalt solvent extraction in the nickel laterite industry is assessed, covering the reagents in commercial use (organophosphorus reagents, carboxylic acids, chelating oximes and amines), research developments and chemical fundamentals that result in the different approach taken with each of the reagent types. 

In addition, solvent extraction is appHed to the processing of other metals for the nuclear industry and to the reprocessing of spent fuels (see Nuclearreactors). It is commercially used for the cobalt—nickel separation prior to electrowinning in chloride electrolyte. Both extraction columns and mixer-settlers are in use. 

The mixture can be separated by distillation. The primary phosphine is recycled for use ia the subsequent autoclave batch, the secondary phosphine is further derivatized to the corresponding phosphinic acid which is widely employed ia the iadustry for the separation of cobalt from nickel by solvent extraction. With even more hindered olefins, such as cyclohexene [110-83-8] the formation of tertiary phosphines is almost nondetectable. 

Solvent Extraction Reagents. Solvent extraction is a solution purification process that is used extensively in the metallurgical and chemical industries. Both inorganic (34,35) and organic (36) solutes are recovered. The large commercial uses of phosphine derivatives in this area involve the separation of cobalt [7440-48-4] from nickel [7440-02-0] and the recovery of acetic acid [61-19-7] and uranium [7440-61-1]. 

Metal Extraction. As with other carboxyhc acids, neodecanoic acid can be used in the solvent extraction of metal ions from aqueous solutions. Recent appHcations include the extraction of zinc from river water for deterrnination by atomic absorption spectrophotometry (105), the coextraction of metals such as nickel, cobalt, and copper with iron (106), and the recovery of copper from ammoniacal leaching solutions (107). 

The liquid-liquid extraction (solvent extraction) process was developed about 50 years ago and has found wide application in the hydrometallurgy of rare refractory and rare earth metals. Liquid-liquid extraction is used successfully for the separation of problematic pairs of metals such as niobium and tantalum, zirconium and hafnium, cobalt and nickel etc. Moreover, liquid-liquid extraction is the only method available for the separation of rare earth group elements to obtain individual metals. 

Theory. Conventional anion and cation exchange resins appear to be of limited use for concentrating trace metals from saline solutions such as sea water. The introduction of chelating resins, particularly those based on iminodiacetic acid, makes it possible to concentrate trace metals from brine solutions and separate them from the major components of the solution. Thus the elements cadmium, copper, cobalt, nickel and zinc are selectively retained by the resin Chelex-100 and can be recovered subsequently for determination by atomic absorption spectrophotometry.45 To enhance the sensitivity of the AAS procedure the eluate is evaporated to dryness and the residue dissolved in 90 per cent aqueous acetone. The use of the chelating resin offers the advantage over concentration by solvent extraction that, in principle, there is no limit to the volume of sample which can be used. 

The given structure shows two molecules of TTA to have reacted with a cobalt ion to form the cobalt-TTA complex, in which the cobalt atom forms a valence bond solid lines) with one, and a coordinate bond (broken lines) with the other, oxygen atom of each TTA molecule. Thus, in the cobalt-TTA complex there is a six-membered ring formed by each TTA molecule with the cobalt atom. Metal chelate complexes of this type have good stability, they are nonpolar and soluble in the organic phase. The usefulness of the chelating extractants in solvent extraction is therefore obvious. 

Solvent extraction is often applied to separate two chemically similar metals such as nickel/ cobalt, adjacent rare earths, niobium/tantalum, zirconium/hafnium, etc. For the purpose of elaboration, the example of the separation of two chemically similar elements such as zirconium and hafnium from their nitrate solution, using TBP as an extractant is considered. The solvent extraction process in this case is chemically constant (K) is given by ... 

Jayachandran, J. Dhadke, P. M. Solvent extraction separation of cobalt(II) with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A). Chem. Anal. 1999, 44, 157-165. 

Preston, J. S. Solvent extraction of cobalt and nickel by organophosphorus acids. I. Comparison of phosphoric, phosphonic, and phosphinic acid systems. Hydrometallurgy 1982, 9, 115-133. 

Xun, F. Golding, J. A. Solvent extraction of cobalt and nickel in bis(2,4,4-tri-methylpentyl)phosphinic acid, Cyanex-272. Solvent Extr. Ion Exch. 1987, 5, 205-226. 

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. 

Nogueira, C. A. Delmas, F. New flowsheet for the recovery of cadmium, cobalt and nickel from spent Ni-Cd batteries by solvent extraction. Hydrometallurgy 1999, 52, 267-287. 

Cole, P. M. The introduction of solvent-extraction steps during upgrading of a cobalt refinery. Hydrometallurgy 2002, 64, 69-77. 

Feather, A. M. Cole, P. M. The separation of cobalt from nickel ammonium sulfate solution by solvent extraction. Value Adding through Solvent Extraction, [Papers presented at ISEC 96], Melbourne, Mar. 19-23, 1996, 1, 511-516. 

Gandhi, M. N. Deorkar, N. V. Khopkar, S. M. Solvent extraction separation of cobalt(II) from nickel and other metals with Cyanex-272. Talanta 1993, 40, 1535-1539. 

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. 

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