DE2424822C3 - Process for the mutual separation of cobalt (II) and nickel (II) by liquid-liquid extraction - Google Patents

Description

The present invention relates to a method / for selective deposition (separation) of cobalt (II) and nickel (II) from aqueous solutions containing these metal ions.

Extraction-based processes for separating cobalt and nickel on an industrial scale are available so far only very few known. Probably the best known methods are based on the ability of the Cobalts to form chloride complexes, then the cobalt with the help of extraction reagents of the anion exchanger type - e.g. B. with the help of amines - selectively extracted from the concentrated chloride solution can be. Since nickel does not form corresponding chloride complexes, there is a very sharp Ni-Co separation achieved; however, the deficiency of these methods is that of the concentrated chloride solutions Corrosion problems and the need to change the sulphate solution environment in most cases to name chloride solution.

Another group of extraction processes is based on the exploitation of ammonia complexes (e.g. U.S. Patent Nos. 32 76 863, 33 80 801 and 34 38 768, and Finnish Patent [Pat. No. 203/71]). In some of these processes, the cobalt is oxidized to its trivalent form while in the remaining processes, the two metals are present in bivalent form during separation (deposition).

In contrast, there is only a great deal about the selective deposition of nickel and cobalt from acidic solutions little known. In US Pat. No. 3,336,133 the extraction of nickel from solution containing cobalt using acidic thiosulphates and in the Finnish patent specification (Pat. Appl. No. 1892/72) is an extraction method using a Extraction agent mixture described. In US Pat. No. 3,399,055 there is a method of extracting deposited by cobalt from nickel-containing solution with the help of organic phosphoric acid.

The present invention aims to improve the mutual separation of nickel and Cobalt increases in the deposition of these metals from solutions containing these two metals achieve. In the method according to the invention, no special conditions are imposed on the nature of the anion of the solution; rather, the deposition can, for. B. from sulfate, carbonate or nitrate solution respectively.

The main features of the present invention emerge from claim 1.

The present invention is based on the observation that e.g. B. when working with organic Phosphoric acid as an extractant in the pH range from 4 to 7 due to the presence of magnesium Selectivity when separating Ni and Co experiences a decisive improvement. This improvement the selectivity is due to the fact that in the pH range mentioned, the magnesium in terms of its Extraction properties lies between cobalt and nickel and thus a weakening of the nickel extraction causes. The magnesium present during the extraction acts in the same way in the washing phase Simplifies the process, since magnesium leaves the organic phase after the nickel and washing can therefore also be carried out properly with a weakly concentrated acid solution. Continue washing can also be done with either cobalt or nickel solution. The extraction of the cobalt from the organic phase can by one of the generally known methods - for example by treatment with mineral acid solution of preferably 1 to 3 N -.

It is essential in the extraction according to the invention that the pH value during the extraction process is kept in the range 4 to 7, but preferably 5 to 6, since the best possible in this range Separation is to be achieved. The washing phase is also provided, provided it is made using a cobalt or magnesium solution is best done in the same pH range.

In the method according to the invention serves as Ex-

traction means
formula

organic phosphoric acid from the

R ₂ -O-P = O
OH

where R ₁ and R _{2 are} alkyl, aryl or alkylaryl radicals, but one of the two can also be hydrogen. This extractant is dissolved in an organic solvent; The solvents used are generally hydrocarbons or hydrocarbon mixtures, in particular kerosene. Next, this organic solution can also property-improving additives, such as. B. alcohols or tributyl phosphate. The extractant content of the solution is generally 5 to 30 percent by volume.

The aqueous solution to which the extraction according to the invention is applied contains 0.1 to 50 g C o / l and 0.1 to 100 g Ni / l and at least 5 g Mg 1. From the aqueous solution are prior to the invention Extraction to remove all metals that are extracted at pH lower than cobalt. Such metals are mainly iron, zinc and copper. The deposition of these metals can be done by either be carried out separately or by another known method.

The extractant content of the extraction solution and the volume ratio of organic matter

Table 1

and aqueous solution are selected based on the composition of the aqueous solution. The extraction temperature is 20 to 80 ^° C., but preferably 50 to 60 ^° C.

The invention is described in more detail below by means of examples.

example 1

ίο To the effect of the magnesium content on the To clarify the nickel-cobalt separation, a series of tests was carried out in the form of batch tests. The starting solution contained 10 g Co / 1, 9 g Ni / 1 and 11 g Na / 1 and 0 to 17 g Mg / 1. The extraction

took place with 20% (volume percent) di- (2-ethylhexyl) phosphoric acid at a volume ratio Vor _S / V _aq of 1: 1; Contact time 10 minutes, room temperature. During the extraction, the pH was adjusted by adding ammonia water

ίο held the desired value. After the phases had separated after the extraction, both phases were analyzed for their metal contents. From the results compiled in Table 1, the decisive importance of a magnesium

»5 addition with regard to the improvement of the Ni-Co selectivity clearly visible: the nickel extraction percentage (E _Nj ) then drops sharply. With the help of the separation factor Sco. In terms of Ni, a separation value of 56 was achieved in the most favorable case.

Separation factor S _CoNj = ^

whereby

'Mc

["Me] _aq

Mg g / l 0 E *, 3.5 <% l 8.5 E _n , 17.0 En, PH Eco <%) Ec " 2.5 E _c " (%) Ec " (%) (%) 8.5 (%> 11.8 1%) 1.9 1%) 1.9 3.0 21.8 21.2 9.0 20.7 6.0 5.1 5.2 3.6 4.0 40.4 34.9 35.1 26.8 25.5 5.9 24.3 3.2 4.5 53.7 46.4 48.9 35.7 39.8 3.9 33.1 1.8 5.0 62.3 53.0 62.3 33.7 57.1 4.5 45.2 1.5 5.5 64.8 56.6 62.6 5Q.7 4.6 45.4 2.9 6.0 67.0 70.2 60.5 8.7 46.1 4.5 6.5 62.2 12.2 45.9 7.6 7.0 Example! 2 63.6 served 47.0 hwefels
tr _ As a washing solution thinned Sc
1 r . 1 ··

With two different batches of organic phase, 65 sulfate solution or original extraction solution,

one of which contained 6.7 g Co / 1, 0.16 g Ni / 1 and 3.9 g which contained 12 g Co / 1, 9 g Ni / 1 and 9 g Mg / 1. All

Mg / 1 and the other 6.3 g Co / 1, 0.28 g Ni / 1 and 3.6 g of the aforementioned solutions were found in certain

Mb / 1, washing tests were carried out. Concentration ranges as useful. Too strong

While concentrated solutions do not prevent cobalt and nickel from separating, they do extensive cobalt circulation between the extraction and the "back extraction" phases. The results the washing tests are compiled in Tables 2 to 4. As can be seen in the table values leave, the sulfuric acid content of the washing solution should be between 5 and 15 g'l if possible. The appropriate concentration of the magnesium sulfate solution is around 10 g Mg / l, that of the cobalt sulfate solution is also around 10 g / l; these concentrations apply provided that the pH of the washing solution is approximately that of the extraction corresponds to the pH value. Too low a pH value leads to unnecessary back extraction of cobalt Consequence.

Table 2

As a washing solution, sulfuric acid in aqueous solution

H ₂ SO ₄

Co / Ni ratio of the
organic phase

Co *)

before the
To wash

after
To wash

l <- ° Jiot

22.5
22.5
22.5
22.5
42

in the washing phase.

119
105
104

74
114

89
71
40
7th
12th

Table 3

As a washing solution, magnesium sulfate solution

MeSOj pH v "," Co / Ni ratio of after , ( V au organic phase To wash Co before the 450 (g Mgil To wash 475 10 4.5 1 42 145 55 10 5.5 1 42 150 67 10 5.5 2 22.5 290 84 10 5.5 3 22.5 980 89 20th 5.5 1 42 35 12th 5.5 1 42 44

Table 4

As a washing solution, cobalt sulfate solution

ⁿ oSO, pH ν _{ΟΓ £} Co / Ni ratio of the after -, Co ^V T ₄ organic phase To wash before the 1710 To wash 1660 10 4.5 1 42 420 67 10 5.5 1 42 240 66 10 5.5 2 22.5 1080 83 10 5.5 3 22.5 980 90 15th 5.5 1 42 56 12 *) 5.5 1 42 44

*) As washing solution L-xlraklion-Spciselösung, 12 g Co 1.9 g Ni 9 g times.

Claims (6)

Patent claims: 1. Process for separating cobalt (II) and nickel (II) by liquid-liquid extraction, wherein aqueous solution containing these metal ions with an organic phosphoric acid containing solution Extraction agent is mixed, the phases are separated from one another after the extraction and the extractant is regenerated for the purpose of recovering the cobalt, characterized in that that the aqueous solution before the extraction a water-soluble magnesium compound is added. 2. The method according to claim 1, characterized in that the water-soluble magnesium compound in an amount of at least 5 g / l, but preferably in an amount of 10 to 20 g / l is added. 3. The method according to claim 1 or 2, characterized in that a magnesium (II) compound, z. B. magnesium sulfate, nitrate or carbonate is added. 4. The method according to any one of the preceding claims, characterized in that the extractant was washed with an aqueous magnesium solution containing about 5 to 50 g Mg / l is to avoid any nickel that may have passed into the extracted extractant to be washed out of the extractant prior to regeneration. 5. The method according to claim 4, characterized in that the washing in the pH range from 4.5 to 6 takes place. 6. The method according to any one of the preceding claims, characterized in that the temperature is kept in the range of 20 to 80 ^c C, but preferably in the range of 50 to 6OC.