NO131082B - - Google Patents

Description

Procedure for the separation of nickel from cobalt.

The present invention relates to a method

to separate divalent nickel from trivalent cobalt present in an aqueous ammonia phase, by liquid-liquid extraction. The invention also relates to the nickel and cobalt which are obtained by means of the aforementioned method.

A method of separation, as discussed above,

has been disclosed in U.S. Patent No. 3,276,863, wherein the extractant employed1 was an aliphatic α-hydroxyketone oxime, such as 5,8-diethyl-7-hydroxy-6-dodecanone-

oxime. For the extraction of other metals, e.g. copper, vanadium and molybdenum, Norwegian patent no. 115065 recommends

using an acylated 2-hydroxybenzophenone oxime,

e.g. 5-dodecyl-2-hydroxybenzophenone oxime. The latter oximes are described as particularly effective for the extraction of copper, and the separation of copper from iron, in areas at low pH, the extraction being considerably improved at the low pH, e.g. a pH of

1.4 - 2.3, when a mixture of the two types of said oxime extractants was used. This is in contrast to the previously mentioned aliphatic α-hydroxyketone oximes, which are preferably used at a pH higher than 7. Analogous results were obtained according to Belgian Patent No. 751,804 in the separation of copper, when the alkylated 2 -hydroxybenzophenone oxime contained one or more electron-withdrawing substituents, such as a nitro group, on an aromatic core.

It has now surprisingly been found that the alkylated 2-hydroxybenzophenone oximes discussed above, and in particular mixtures of such an oxime with an aliphatic α-hydroxyketone oxime, give excellent results when used as extractants in the separation of Ni(II) from Co (III) by liquid-liquid extraction from aqueous ammonia media, i.e. in the area at a relatively high pH. The improvement, compared to the results obtained with the aliphatic oxime alone, consists in a higher loading capacity under similar conditions, while subsequent backwashing of the extracted Ni(II) with dilute sulfuric acid proved far more effective.

The present invention can be described as relating to a method for separating Ni(II) from Co(III) which is present in an aqueous ammonia phase, by liquid-liquid extraction, in which method the aqueous phase is brought into contact with an organic phase comprising an organic solvent, which is substantially miscible with water, and - as extractant - (A) a 2-hydroxybenzophenone oxime of the general formula

1 2

- where each of the symbols R and R individually means an aliphatic hydrocarbyl or hydrocarbyloxy group (hydrocarbyl = hydrocarbon radical) with 1 to 25 carbon

atoms, E''" means an electron-withdrawing substituent, and each of the subsymbols m, n, and p may be zero or an integer in the range from 1 to 4, provided that the 12 1 total number of carbon atoms in R m , R n and 3 E ptil together lie in the range from 3 to 25 - , alone or together with (B) an aliphatic α-hydroxyketone oxime of the general formula

- where each of the symbols R <3> and R 4 means a hydrocarbyl group, and R means a hydrocarbyl group or a hydrogen atom - , and/or (C) a 2-hydroxyphenyl-aliphatic-hydrocarbylketone oxime of the general formula - where the symbol R^ means an aliphatic hydrocarbyl or alkoxyl group of 1 to 25 carbon atoms, R 7 means an aliphatic group, E 2 means an electron-withdrawing substituent, and each of the subsymbols x and y can be zero or a integer in the range from 1 to 4, with the condition that it

6 7 2

total number of carbon atoms in R , R and E together lie

x y

in the range from 3 to 25 -, or alternatively a mixture of only the oximes B and C, so that it is possible for the organic phase to be loaded with nickel, after which the resulting organic phase is separated from the aqueous phase.

In the general formula (I) above, for example, the substituent (e) R"*" can mean alkyl, aralkyl, alkenyl, alkapolyenyl or alkoxyl groups, which groups can be branched or unbranched and can contain inert substituents and/or heteroatoms. The number of carbon atoms in said groups is preferably in the range from 5 to 20, especially from 7 to 14. Examples of suitable alkyl groups: methyl, ethyl, tert-butyl, sec-hexyl, sec-octyl, sec-decyl, sec- dodecyl and sec-hexadecyl. Suitable alkenyl groups preferably include those containing no more than one ethylenic double bond, such as pentenyl, octenyl, decenyl, dodecenyl and octadecenyl. Alkyl groups are preferred, especially those containing a branched carbon chain, e.g. secondary alkyl groups. The substituent R 2 can, for example, mean the hydrocarbyl groups listed above as examples for r\ Provided that the total number of substituents R^"

and/or R 2 present is greater than one (m + n> 1),

at least two such substituents may be the same or different from each other. Preferred are compounds that do not contain-1 2

hold more than one of each of the substituents R and R (m = n = 1) , especially those containing only one substituent B?" (m = 1,

n = zero), preferably in the 5-position.

If electron-withdrawing substituents E"<*>" are present

present in the 2-hydroxyphenyl group, such a substituent should preferably occupy the 3-position therein. But compounds having no more than one substituent E^" (p = zero or 1) are preferred. Examples of electron-withdrawing substituents E"*" are the halogen atoms, especially chlorine, bromine and iodine, nitro-

groups, the cyano group, and an alkoxycarbonyl group, such as the methoxy or ethoxycarbonyl group. Chlorine becomes common-

show preferred. Although the presence of a substituent E"<*>" may be useful in certain cases, excellent results can be obtained

tater in the absence of this (p = 0).

The total number of carbon atoms in R"*", R"*" and E''" to

m n p

together is preferably in the range from 5 to 20, and in particular

1 2

from 7 to 14. If R and R are both absent (m = n = zero), the substituent(s) E1 must of course provide the required number of carbon atoms, e.g. in the form of one or more alkoxycarbonyl groups.

The following are examples of useful 2-hydroxybenzophenone oximes of the general formula I: 5-sec-octyl-2-hydroxybenzophenone oxime, 5-sec-nonyl-2-hydroxybenzophenone oxime, 5-sec-dodecyl-2-hydroxybenzophenone- oxime, 4-dodecyloxy-2-hydroxybenzophenone oxime, 5-sec-pentyl-4'-tert-butyl- and 5-sec-octyl-2',4',5'-trimethyl-2-hydroxybenzophenone oxime.

In particular, outstanding results have been achieved

with 5-sec-nonyl-2-hydroxybenzophenone-oxime (I; m= 1, n=p=

zero). Suitable compounds as defined above, and progress-

ways of their production are also disclosed in Dutch Patent Application No. 6,614,688 and in Belgian Patent Document No. 751,804.

Preferably, a mixture of one or more of the 2-hydroxybenzophenone oximes of the general formula I with one or more aliphatic α-hydroxyketone oximes of the general formula II is used. The hydrocarbyl groups denoted by R 3 and R 4 are, for example, aliphatic or alkaryl groups, preferably unsaturated hydrocarbyl or branched alkyl groups containing from 6 to 20 carbon atoms. The following are examples of suitable groups: alkenyl groups, such as heptenyl, octenyl, decenyl and octadecenyl, and - especially - sec. lower alkyl groups, such as 1-ethylpentyl, 1-ethylhexyl, 1-ethyl-6-methyloctyl, 1-butyldecyl, 1-butylhexadecyl and 1-butyl-11-methyltridecyl. Such compounds are preferred

3 4 5

where the groups R and R are the same, while R can, for example, denote the hydrocarbyl groups listed above as examples for R 3 and R 4 , but R 5 preferably means a hydrogen atom. It is advantageous that the total number of carbon atoms in R 3 , R 4 and R 5 together lies in the range from 12 to 40, and preferably from 12 to 20. Suitable compounds are, for example, 19-hydroxy-hexatriaconta-9,27- dien-18-one oxime, and especially 6,9-diethyl-8-hydroxy-7-tetradecanone oxime and 5,8-diethyl-7-hydroxy-6-dodecanone oxime. The latter is particularly preferred. A mixture comprising this compound together with 5-sec-nonyl-2-hydroxybenzophenone oxime has given particularly advantageous results when it was used as an extractant according to the method of the present invention.

The extractant may consist of a mixture comprising at least one of each of components A and C or, more preferably, B and C.

In the general formula III for 2-hydroxyphenyl-1-aliphatic-hydrocarbylketone-oxime (C) the substituent R or - if x is greater than 1 - each of them can mean an alkyl, aralkyl, alkenyl, alkapolyenyl or alkyl group , which group may be branched or unbranched, and if desired may contain inert substituents and/or heteroatoms. The number of carbon atoms in such groups R can lie in the range from 1 to 25, preferably from 5 to 20, and especially three. ? ti... 14. The following are examples of suitable alkyl groups: methyl, ethyl, tert-butyl, sec-hexyl, sec-heptyl, sec-o":Lvi, 1,1,3,3-tetramethylbutyl, sec- nonyl, sec-undecyl and sec-pentadecyl. Suitable alkenyl groups preferably include those containing no more than one ethylenic double bond, such as pentenyl, octenyl, decenyl, dodecenyl and octadecenyl. Alkyl groups are preferred, especially secondary or tertiary alkyl groups Preferred compounds are those containing no more than one substituent R (x = 1), which is preferably present in the 5-position.

7

The aliphatic group R can for example be an alkyl, alkenyl or alkapolyenyl group. Said groups can either be branched or unbranched and they can, if desired, contain inert substituents and/or heteroatoms.

An unbranched group has usually proved very advantageous. The number of carbon atoms in the group R 1 can for example be from 1 to 20, preferably from 1 to 11. An alkyl group is usually preferred. The following are examples of suitable alkyl groups: methyl, ethyl, n-pentyl, n-heptyl, n-octyl, n-nonyl, n-undecyl, n-tridecyl and n-heptadecyl. The number of carbon atoms 6 7

in the substituents R and R are preferably substantially the same.

If desired, one or more electron-withdrawing substituents E 2 can be present in the 2-hydroxyphenyl group, and then such a substituent should preferably occupy the 3-position there. But compounds containing no more than one substituent

E 2 (y = zero or 1) is preferred. Examples of ° electron-withdrawing substituents E 2 are the halogen atoms, especially chlorine, bromine and iodine, the nitro group, and an alkoxycarbonyl group, such as the methoxy or ethoxycarbonyl group. Chlorine is usually preferred. Although the presence of a substituent E 2 may be useful in certain cases, excellent results have been obtained in the absence of such a substituent (y = 0).

It should be understood that the total number of carbon atoms in 6 7 2 o Rx' ^ °^ Ey together ranges from 3 to 25, preferably from 10 to 25, while a total number of from about 14 to 18 carbon atoms has been found to be particularly suitable. If R is not present (x = zero), the substituent(s) may

E 2 if necessary contribute to the required number of carbon atoms, for

for example in the form of one or more alkoxycarbonyl groups.

The following are examples of very suitable 2-hydroxyphenyl-aliphatic-hydrocarbylketone-oximes (C): (5-sec-heptyl-2-hydroxyphenyl)-n-heptylketone-oxime, (5-sec-octyl-2-hydroxyphenyl)- n-octyl-ketone-oxime, (5-sec-nony1-2-hydroxyphenyl)-n-nonyl-ketone-oxime, (5-sec-heptyl-2-hydroxyphenyl)-n-nonyl-ketone-oxime and (5 -sec-octyl-2-hydroxyphenyl)-methyl-ketone-oxime.

The following are further examples: (5-methyl-2-hydroxyphenyl)-n-tridecyl-ketone-oxime, (5-sec-heptyl-2-hydroxyphenyl)-methyl-ketone-oxime, (5-sec-dodecyl-2 -hydroxyphenyl)-ethyl-ketone-oxime, (5-sec-undecyl-2-hydroxyphenyl)-n-pentyl-ketone-oxime, (5-sec-hexyl-2-hydroxyphenyl)-n-undecyl-ketone-oxime, (5-sec-pentadecy1-2-hydroxyphenyl)-n-heptyl-ketone-oxime, (5-sec-octyl-2-hydroxyphenyl)-n-undecyl-ketone-oxime, (5-sec-octyl-2-hydroxyphenyl )-n-heptadecyl-ketone-oxime and the corresponding compounds which have a chlorine atom in the 3-position of the phenyl group, such as (5-sec-octyl-3-chloro-2-hydroxyphenyl)-n-nonyl-ketone- oxime.

When mixtures of two or more different types of extractants are used, their relative amounts can vary within wide limits. Suitable molar ratios between the different types of components can, for example, range from 10:1 to 1:10. For the preferred mixtures, which comprise at least one of each of components A and B, the suitable mole ratios between A and B are usually in the range from 10:1 to 1:4, preferably from 5:1 to 1:1, and especially from 4:1 to 2:1. Similar mole ratios are suitable, for example, for mixtures comprising C and B components.

For the selective extraction of Ni(II) from Co(III) according to the invention, the extractant, which should be substantially insoluble in water, is usually used in a diluted form in a water-immiscible organic solvent. The concentration of the extractant, or the mixture of its components, can vary widely and is usually in the range from 2 to 50% by weight, preferably from 5

to 15% by weight, based on the organic phase. It is recommended that the water-immiscible solvent be chosen so that the organic phase does not dissolve in the aqueous medium, or vice versa, or only to a small extent. The re-

lateral miscibility of the phases should preferably not exceed

exceed 5% by volume, and should preferably be lower than 1% by volume. Suitable solvents are, for example, halogenated solvents, such as chloroform, 1,2-dichloroethane, 1,2-dichloropropane and di(2-chloroethyl)ether, and especially hydrocarbons, such as kerosene, toluene and xylenes.

The organic phase can also contain, if desired

other materials, such as a conditioning agent, which is usually a long-chain aliphatic alcohol, to prevent the formation of emulsions which in certain cases may form during the extraction of the aqueous medium.

The method according to the invention is special

useful for separating nickel and cobalt from leach liquors,

which can for example be obtained by leaching suitable ores with ammonia (e.g. under pressure) after the raw ore has been brought into a suitable form, e.g. by crushing, grinding and sieving. When cobalt is present in a lower oxidation state than Co(III),

e.g. as Co(II) is usually the case, it must first be oxidized to a trivalent state, e.g. by exposing the aqueous medium to the action of an oxidizing agent before it is "brought into contact with the organic phase. The resulting aqueous medium then comprises Ni (II) and Co(III). Suitable oxidizing agents are, for example, hydrogen peroxide, or more preferably oxygen or an oxygen-containing gas,

especially air. If a leaching liquid is used as starting material, the oxidation can also be carried out during the leaching process. The aqueous medium, which is usually a solution, may also comprise one or more ammonium compounds, such as the carbonate or bicarbonate, sulphate, chloride, nitrate or hydroxide. The concentration of the metal in the aqueous ammonia medium can vary within wide limits, and it is usually between 0.01 and 1 mol/l, preferably between 0.05 and 0.5 mol/l.

The selective extraction of Ni(II) according to the invention is carried out by bringing the aqueous medium into contact with the organic phase containing the extractant or agents, and it is recommended to promote the contact between the phases with vigorous stirring. Ni(II) is then selectively transferred to the organic phase, while Co(III) essentially remains in the aqueous phase. Stirring is preferably continued until equilibrium has been established between the phases, which is usually the case after about 10 seconds to 3 minutes. An advantageous volume ratio between the organic phase and the aqueous phase has been found to be 1:3 to 3:1.

But other conditions can also be used. As a rule takes place

the extraction smooth at ambient temperature. But higher or lower temperatures are not excluded.

After the separation of the phases, the extra-

harden Ni (II) be recovered from the charged organic phase,

in which it is usually present in the form of a solution of one or more complexes with the extractant or agents, by removal with an aqueous solution of a strong acid, such as nitric or sulfuric acid. The latter is particularly preferred. The removal from the organic phase can also be carried out by alternately bringing said phase into contact with an aqueous solution containing an acid and with water.

Ni (II) is then transferred to the aqueous removal medium which

the corresponding nicke1 salts, e.g. as NiSO^, and can then be recovered from there by conventional techniques, for example as salts by evaporation of the water and/or crystallization,

or - preferably - as the metal by direct electrolysis,

while the organic phase containing the released extractant is advantageously used again in subsequent extractions. But in some cases it may be desirable to use a base

such as ammonia to the removal process, in which case nickel is precipitated by evaporation of ammonia, preferably as the hydroxide. It is also possible to recover nickel directly as metal from the charged organic phase, by hydration of the latter, which often enables nickel to be obtained in the form of a powder.

A similar technique to the one mentioned above for the recovery of nickel can of course also; used for re-

recovery of cobalt from the aqueous raff Li at phase. Before re-

the recovery of cobalt from this aqueous phase, the latter can be fed back repeatedly to the extraction unit, e.g.

when it is desired to obtain a concentrated solution, and a separating stream may be removed therefrom to recover cobalt.

When carrying out the method according to the invention, either the extraction or the removal or both processes can be carried out in batches, in a single step or in a number of consecutive steps, or preferably on

continuous way, for k ampel by applying is. rsd current

or counterflow technique.

EXAMPLE I

Extraction experiments were carried out in a specially designed separatory funnel consisting of c t graduated, straight-walled vessels with a capacity of 0.25 litres. At the bottom there was a £;top tap to provide timber out of the funnel. The top opening was used to introduce the double-bladed stirrer, and it also served as an infeed soap.

An aqueous ammonia feed solution containing

Ni (II) and Co(III) were prepared in the following manner. To a

stirred solution obtained by dissolving 40 g of "ammonium carbonate"

(Brocades) - essentially the double salt of ammonium-

bicarbonate and ammonium carbamate (NH^HCO^/ B^N-CO-ONH^) - in 200 ml of an aqueous solution containing 25% by weight NH^.

1.25 g of basic cobalt carbonate (CoC03, 2 Co(0H)2,

4 H2O) containing 0.6 g Co(II), and 21.00 g basic nickel-

carbonate (NiC03, 2 Ni(OH)2, 4 H20) containing 10.08 g Ni(II),

as the mentioned salts were added in portions in powder form.

The resulting solution was then made up to water

was 1 liter, and then heated for 3 hours at 80°C while air was bubbled through the solution to oxidize the Co(II)

to Co(III). The volume was then brought back to 1 litre.

The extraction solution was prepared by dissolving

0.096 mol of 5-sec-nonyl-2-hydroxybenzophenone oxime and 0.024 mol of 5,8-diethyl-7-hydroxy-6-dodecanone oxime in kerosene ("Shellsol K") and make 1 liter.

The aqueous and organic phases were brought into contact

with each other at a phase ratio of 1:10 (volume/volume) while stirring at a speed of 2200 r.p.m. The organic phase immediately turned dark-green, and the nod1 loading was full-

carried within 10 seconds. But the stirring continued in the 3rd

minutes. The layers were then given the opportunity to separate.

Analyzes of the aqueous layer showed that it contained

less than 0.1 wt% Ni(II) and more than 99 wt% Co (III),

based on the respective amounts originally present.

The removal from the organic layer was carried out with a

equal volume with 2-N H2S04 while stirring at a rate of 2200 r.p.m. Within 30 seconds, all Ni (II) was washed out.

Analysis of the aqueous layer after the separation of the phases showed that it contained 100% of the Ni(II) that was originally present in the organic extract phase, and only 0.1% by weight of the Co(III) that was originally present present in the aqueous starting solution.

EXAMPLE II

(a) An aqueous ammonia solution which was 0.01 M with respect to both Ni(II) and Co(II), and 0.2 M with respect to ammonium sulfate was prepared as follows. To a solution obtained by dissolving 2.38 g of NiCl,,.6 H2O,

2.38 g CoCl2.6 H20 and 26.3 g (NH^) in 800 ml of water, an aqueous solution containing 25% by weight of NH^ was added. Co(II), which were dissolved again by further addition of the aqueous ammonia. When a pH of 11 was reached, water was added to the solution up to 1 liter, after which the pH was readjusted to 11 by dropwise addition of aqueous ammonia. Air was then introduced into the solution for 1 hour at room temperature to oxidize Co(II) to Co(III).

The extraction solution was the same as that described in Example I.

The aqueous and organic phases were then brought into contact with each other by a phase ratio of 1:1 (volume/volume) while stirring at a speed of 2200 rpm. for 3 minutes, after which the layers were given the opportunity to separate from each other. Analysis of the organic phase showed that it contained Ni(II)

in a concentration of 0.01 mol/l, while d<;t no Co (III) could be detected.

The removal from the organic liquid was then carried out with an equal volume of 2-N H-jSO 4 by stirring at a speed of 2200 r.p.m. and the Ni(II) loading was completely erased within 30 seconds.

(b) On a tune analogous to that described under (a), the extraction was repeated - for comparison purposes only - using a solution containing 32.5 g of 5,8-diethyl-7-hydroxy- 6-dodecanone-oxime in one liter of kerosene, the solution being 0.12 M with act:/t material. Analysis of the charged organic phase showed that it contained Ni (II)

in a concentration of only 0.0062 mol/l.

After removal. ra the organic phase with 2-N I^SO^, the resulting aqueous solution contained only 17.8% by weight of the Ni(II) originally present in the loaded organic solution. But c^n Ni(II) which was still in the organic phase could be easily removed from it in 30 seconds with the help of 2-N HN03-

Example II shows that a mixture of the 2 different component types used in experiment (a) had a superior loading capacity for Ni (II), compared to the extractant used alone in experiment (b), together early as the removal of Ni (II) with diluted B^f ^ was effected much faster. This is important for the recovery of metallic nickel from the resulting solution by electrolysis.

EXAMPLE III

The aqueous ammonia solution was the same as that extracted in Example II. The extraction solution was a 0.12 M solution of 5-sec-nonyl-2-hydroxybenzophenone oxime in "SHELLSOL K" (registered trademark for a kerosene fraction).

The aqueous solution and the extraction solution were brought into contact with each other in equal volumes while stirring at a speed of 2200 r.p.m. The loading of nickel was complete within 10 seconds. But the stirring was continued for 3 minutes, after which the layers were allowed to separate from each other. Co(III) could not be detected in the organic layer.

The removal from the organic layer was then carried out with an equal volume of 2-N I^SO^ by stirring at a speed of 2200 r.p.m. After 4 minutes of stirring, the resulting solution contained 73.3% of the nickel originally present in the organic layer. By comparing the removal result for this example with the result for example II under (a), it appears that from an extractant containing an oxime of type (A) together with an oxime of type (B), and an extractant containing an oxime of type (A) alone, the first extractant must be preferred.

Claims (6)

1. Process for separating Ni(II) from Co(III) present in an aqueous ammonia phase, by liquid-liquid extraction, by contacting the aqueous ammonia phase with an organic phase comprising an organic solvent which is essentially immiscible with water, and an extractant, characterized in that the extractant used is (A) a 2-hydroxybenzophenone oxime with the general formula - where each of the symbols R 1 and R 2 individually means an aliphatic hydrocarbyl- or hydrocarbyloxy group of 1 to 25 carbon atoms, E"*" means an electron-withdrawing substituent, and each of the subsymbols m, n and p may be zero or an integer in the range of 1 to 4, provided that the total Number carbon atoms in R 1, R 2 and E 1 together lie in the range from 3 to m n p 25 -, either alone or together with (B) an aliphatic α-hydroxyketone oxime of the general formula 3 4 - where each of the symbols R and R denotes a hydrocarbyl group, and R^ means a hydrocarbyl group or a hydrogen atom -, and/or (C) a 2-hydroxyphenyl-aliphatic-hydrjcarbylketone-oxime of the general formula - where the symbol R means an aliphatic hydrcarbyl or alkoxyl group of 1 to 25 carbon atoms, R <7> means an aliphatic group, E 2 means an electron-withdrawing substituent, and each of the subsymbols x and y can be zero or an integer t'll in the range 1 to 4, with the condition that c :t total number of carbon atoms in R 6 , R 7 and E together lies in the range from 3 to 25 -, or alternatively a mixture of are oximes 3 and C, whereby the organic phase is charged with nickel, hvcrel ter the resulting organic phase is separated from the aqueous phase which still contains the Co(III) values. 2. Process according to claim 1, characterized in that 5-sec-nonyl-2-hydroxybenzophenone-oxime is used as the oxyion with the general formula (I). 3. Process according to any one of the preceding claims, characterized in that 5,8-diethyl-7-hydroxy-6-dodecanone oxime is used as the oxime with the general formula (II). 4. Method according to any one of the preceding claims, characterized in that a mixture comprising 5-sec-nonyl-2-hydroxybenzophenone oxime and 5,8-diethyl-7-hydroxy-6-dodecanone oxime is used as extractant . 5. Process according to any of the preceding claims, characterized in that the oximes with the general formulas (I) and (II) are used with a molar ratio (I)/(II) in the range of from 5:1 to 1:1. 6. Method according to any one of the preceding claims, characterized in that the extractant is used with a concentration in the range from 5 to 15% by weight, based on the organic phase. (56) Listed publications: Norsk uti. document no. 115065 (40a-15/12) Generally available Norwegian application no. 1742/70