CS199535B2 - Process for the separation of metals - Google Patents

Abstract

1320375 Solvent extraction LE NICKEL 23 July 1970 [12 Aug 1969] 35684/70 Heading C1A Metal values are extracted from a neutral aqueous chloride solution containing at least 7 gm. equ. per litre Cl<SP>1</SP> ions by contact with an immiscible organic solution of a sulphonium salt. Preferably the salt is di-(C 7 to C 13 alkyl)-methyl sulphonium chloride. It may be used to remove Co and Fe from Ni chloride solutions having an initial Ni/Co wt. ratio of 6/1 to 1/2. The process may be carried out in several stages in countercurrent : between each stage the aqueous phase is evaporated to its initial Cl<SP>1</SP> concentration and the organic phase is stripped with water or di@. HCl for use in the next stage. The organic solution may contain 0À2-1 mole/l. of sulphonium salt, and the organic/aqueous volume ratio may be 1/2 to 10/1. The solvent may be butyl acetate, butyl oxide, methyl iso-propyl or -butyl ketone, diisobutyl ketone, CH 2 Cl- CH 2 Cl, CCl 2 =CHCl, CHCl 3 , CHBr 3 , or 1,2- dichlorobenzene.

Description

The invention relates to a process for the separation of metals contained in an aqueous solution in the form of chlorides, which are iron, nickel and cobalt. These metals are contained in - industrial chloride solutions, for example from nickel processing.

The separation of - iron and - cobalt, - which - are mainly contained in nickel chloride solutions, is carried out by known methods. - The oldest is the precipitation of iron and cobalt in the form of - trivalent - oxides after oxidation of chloride solutions with a -pH control. Other, later processes use - solid - ion exchangers, such as - resins or - liquid - ion exchangers, such as long-chain tertiary - amines or quaternized - amines. - In the case of liquid ion exchangers, again. a liquid / liquid extract occurs, wherein the active agent itself is diluted in a poorly miscible or immiscible solvent with water capable of absorbing the complex and retaining in a stable form. Also. It has been proposed to use mineral ion exchangers, such as titanium phosphates, the disadvantage of which is that they hydrolyze readily.

All these processes have - shortcomings which - make their industrial use - either laborious or uncertain. - At the earliest: - the process - the precipitation of iron - and - the cobalt oxi2 by means of - - - ozone, - - chlorine - - - or hypochlorites - encounters - considerable - difficulties, - which are - in · - ^; - - that - the hydroxides - ¹ precipitate mainly - in - the - colloidal - form, - and - the filtration of these - hydroxides is - - very - difficult - further - in that - from - These precipitated solutions carry a substantial amount. - adsorbed in said - precipitate.

In the case of materials which - act - as - ion exchangers, they are - anion exchange - resins - of the type - quaternary - - ammonium - - - derivatives - polystyrene, - or - - o- - - liquid - amines, - a - chlorinating agent, - - generally - free - - hydrochloric acid, - to form the - chloride complex anions; - which - leads to - - - considerable technological difficulties - in practical implementation - of this procedure. - In addition, - a - separate - solution - of - chloride - nickel - saturated with - hydrochloric acid - which - cannot - be virtually separated. In addition to the difficulty of transporting such acidic solutions, it is impossible to count upon the processing of nickel by the classical route; - such as - for example - by electrolysis - on - insoluble - accidents or reductions - - by hydrogen - under - - pressure ·. - However, it cannot be denied - that - without difficulty - resulting from the use of - free - hydrochloric acid - - separation - extraction - liquid / liquid - would have obvious - - - advantages; due to - ease of execution - and the - - possibility - to carry out cleaning operations in a continuous · - and - controllable manner. The complex elements capable of forming complex chlorides, such as cobalt, can be selectively extracted from the aqueous phase into the organic phase containing the complexing agent and then recovered by washing the organic phase with water. The resulting aqueous phase from this extraction contains nickel in the form of chloride without significantly changing its concentration due to the extraction operation.

Furthermore, it is known to use sulfonium salts as a complexing agent to separate metals in an aqueous solution. In this known process, the aqueous phase to be purified must form a strongly acidic environment. For example, to separate an aqueous solution of nickel chloride and cobalt, the aqueous phase must contain 200 to 400 g · free hydrochloric acid per liter of solution. Therefore, the solution to be separated cannot be substantially concentrated with nickel and cobalt salts.

In addition, in order to achieve the optimum effect of the complexing agent, it is necessary to work with a relatively polar organic solvent. This kind of organic solvent is not always applicable to the organic extraction phase, especially not when it is desirable to treat the high density aqueous phase.

These disadvantages are overcome by the method of separating iron, nickel and cobalt metals in aqueous solution by selective liquid / liquid extraction between the aqueous phase containing the chlorides of these metals and the organic phase containing the sulfonium salt in the organic solution. a solvent which is poorly miscible with water, wherein at least one metal selectively passes from the aqueous phase to the organic phase according to the invention, characterized in that it is a neutral aqueous phase which contains the chlorides of said metals and has a total · Concentration of chloride ions at least equal to 7 grams / l · solution, acts · organic phase, the ratio of organic phase: aqueous phase being 1: 2 to 10: 1 and, organic · organic solvent is a light non-polar solvent from the group including esters such as acetates and butyl propionates. Such as butyl acetate, ethers, for example, dibutyl ether, and ketones, for example methylsopropyl ketone, methyl isobutyl ketone, and then the obtained organic phase containing, for example, cobalt chloride, is washed with another aqueous phase, formed water or acidified with hydrochloric acid. wherein the ratio of the organic phase to the second aqueous phase is 1: 1 to 1. 40: 1.

Furthermore, when the. According to the method of the metal separation process according to the invention, the organic phase recovered by the second water phase can be transferred to the next at least one extraction stage.

In the metal separation process according to the invention, the neutral aqueous phase, which comprises nickel chloride and cobalt chloride, can be treated with the organic phase in at least two separate stages and the separated organic phases obtained are regenerated successively with a single second aqueous phase. to a cobalt chloride concentration in the second aqueous phase of 130 g / l.

An advantage of the metal separation process according to the invention is that it is no longer necessary to supply the chloride ions in the form of hydrochloric acid to facilitate the transition of the chloro-cobalt trichloride or the chloro-ferric complex into the organic phase. '

Organic solvent. used in the separation of metals according to the invention is a solvent which is light, non-chlorinated and poorly miscible or immiscible with water, such as a low molecular weight ester, ether or ketone. The combined effect of an organic solvent of this kind and a suitable concentration of the complexing agent to form the extracting organic phase causes a significant reduction in the losses of the complexing agent during the extraction process.

According to the invention, it is thus possible to use nickel and cobalt chlorides in aqueous concentrated sulphonium salt solution practically in the absence of free hydrochloric acid and using an organic solvent capable of providing good separation between the aqueous and organic phases and a suitable extraction step with minimizing losses of the complexing agent.

The complexing agent is an alkylsulfonium chloride corresponding to the general formula:

Ri \ Rz — S + C /

R3 in which

R 1 represents methyl and

R 2 and R 3 represent each alkyl having a total number of carbon atoms of 7 to 13.

The complexing agent is preferably di-sec- (alkyl C 6 -C 10 methylsulfonium chloride), in particular di-sec-decylmethylsulfonium chloride.

The complexing agent is dissolved in an organic solvent of limited miscibility or immiscibility with water, preferably in the ester of the alcohol. . average molecular weight, such as, for example, in butyl, amyl and hexyl acetate acetates and propionates, or also in a ketone such as methylsopropyl ketone, methyl isobutyl ketone and di-isobutyl ketone, or also in an ether such as dibultylether, and / or finally in a mixture of other organic solvents with. with organic solvents. However, halogenated solvents such as 1,2-dichloroethane, chloroform, trichlorethylene, bromoform and dichlorobenzene are also suitable for this purpose.

The aqueous solutions to be treated according to the invention originate mainly from the refining treatment of nickel. These are, for example, concentrated solutions obtained by dissolving hydrochloric acid by-products resulting from the elimination of mainly cobalt from nickel solutions either. by oxidation or 'sulphuration' of the stone during the 'treatment of chlorination' water, which served to 'wash the nickel stone during the chlorination melting treatment'. It can naturally go as well. o. products derived from the action of chlorine or hydrochloric acid on any nickel - containing material, such as. for example, used catalysts and ores or alloys containing both nickel and cobalt.

In the metal separation process according to the invention, the aqueous phase consisting of an aqueous metal chloride solution is contacted by mechanical stirring with an organic phase containing a complexing agent and an organic solvent, preferably butyl acetate, for a period not exceeding 5 minutes and at a volume ratio. an organic phase to an aqueous phase of 1: 2 to 10: 1, preferably 1: 1 to 3: 1. The mixture is then left to stand after decantation, the two phases are separated. The organic phase containing cobalt chloride is washed with a second aqueous phase containing water, optionally with slightly acidified hydrochloric acid, in a volume ratio of organic phase to second aqueous phase of 1: 1 to 40: 1, which operation gives a regenerated organic phase. stage. and an aqueous phase containing cobalt and thereby a higher concentration of cobalt chloride, the ratio of the volumes of the organic phase to water during the wash. The organic phase recovered in this way can be reused for further extraction. The cobalt-containing aqueous phase can also be used to further wash the organic phase up to a cobalt chloride concentration of 130 g cobalt chloride per liter. These operations are preferably carried out at 'room temperature', but also higher or lower temperatures can be used in the present case. .

The process of the invention is the simplest method of separating metals according to the invention, and it is, of course, possible, without departing from the scope of the invention, to apply modified methods such as countercurrent extraction in extruders of the type of packed columns, rotary disc columns, 'Pulse columns, centrifugal multilayer'. extractors or multiple hydrocyclones.

Preferably, the process of the invention is applied to the treatment of chloride solutions derived from nickel processing, wherein the solutions contain nickel and cobalt in a ratio of 6: 1 to 1: 2 relative to each other, but this technique can be advantageously used in cleaning nickel chloride solutions with much

5 lower concentrations of cobalt containing, for example, 40 parts by weight of nickel per part by weight of cobalt.

The concentration of the complexing agent in the organic phase may be between 0.2 and 1 mol / liter, preferably between 0.3 and 0.5 moles per liter, bearing in mind that at low concentrations the selectivity to the chloride complex is 'higher but' there is a significant loss of complexing agent, while at higher concentrations the selectivity is lower, however, losses of the complexing agent are also lower.

Process for separating metals according to the invention. is explained through below. These examples are given by way of illustration only and are not intended to limit the scope of the invention in any way.

Example 1

Effect of solvent.

A substantially neutral chloride solution containing 152 g / l of nickel and 25.2 g / l of cobalt, i.e. having a chloride ion concentration of 6 equivalents / liter and a Ni / Co weight ratio of about 6, was obtained by acid dissolution. 'Hydrochloric' sludge, resulting from the selective oxidation of cobalt with sodium hypochlorite, during the treatment of an impure nickel sulphate solution resulting from the treatment of cobalt-rich nickel-containing sulfuric waste. '

During a series of comparative experiments, 500 ml of this solution were each contacted in a separating funnel with 1 liter of organic phase, i.e. a solution containing 0.3 moles of di-sec-decylmethylphonium chloride in one of the organic solvents of the group consisting of 1,2- dichloroethane, trichlorethylene, bromoform, 1,2-dichlorobenzene, butyl acetate, and a mixture of 75% trichlorephylene and 25% bromoform. After mechanical stirring for 1 minute, the mixture was allowed to decant. Oasy 'decanting and clarifying both phases. se ·. the phases are separated. The organic phase is washed with a second aqueous phase, i.e. 500 ml of water slightly acidified with hydrochloric acid, and the degree of separation is determined by analyzing the aqueous phase obtained after this last operation. Losses of 'active' 'material' due to entrainment into the aqueous' phases are evaluated by determining the percentage of sulfonium compound prior to the 'extraction operation'. 'after her.

Obtained results . 'are summarized' in Tab. In which the extraction capacity of the sulfonium compound is expressed in grams of cobalt based on 1 kg of crude active mass delivered at a concentration of 2 equivalents per kg.

199585

Table I

Solvent

Phase decantation time (min)

Selectivity Extr. Action Metal loss liquid (kg active to organic (g cobalt.on the material.kg kg kg of active extracted / weight γ material) cobalt) cobalt | . weight / 'nickel'

1,2-dichloroethane 10 > 1000 48 3.0 trlchlorethylene 7 8 40 2,0 broinoform 3 > 1000 37 2.5 1,2-dlchlorobenzene 12 12 48 1.0 trichlorethylene plus bromoform (75:25 by volume) 3 > 1000 40 1.5 butyl acetate ‘3 3 38 0.1

As shown in Table I, the nature of the organic solvent affects not only selectivity but also complexing agent losses and decantation times. From the table, it is apparent that butyl acetate, while not guaranteeing excellent cobalt selectivity, on the other hand, makes it possible to reduce the loss of active material in a significant way, the phase separation being particularly fast and efficient.

It goes without saying that if the extraction is carried out in a countercurrent manner over several floors, an improved selectivity is achieved.

In addition, as is evident from the following examples, the conditions of this exemplary embodiment are not optimal in terms of selectivity.

Example 2

The effect of the concentration of the complexing agent in the organic phase is the volume of a neutral chloride solution containing 137 g / l nickel and 70 g cobalt, i.e. the Ni / S podíl mass fraction is substantially 2 and the concentration is 7 equivalents of C * / liter. contact in a separatory funnel with two volumes of an organic solution of the same sulfonic acid compound dissolved in butyl acetate at concentrations of 0.3 to 0.4 and 0.5 moles per liter. The mixture was stirred for 1 minute and then allowed to decant. The two phases are separated and analyzed, with the extraction results shown in Table II.

Table II

Concentration of the sulfonium derivative: in butyl acetate

Selectivity of metal to organic phase transition _____ cobalt mass \ nickel weight /

Capacity / g Co per kg of active material ·

0.3 M 40 52 0.4 M 12 48 0,5 M 7 32

It can be seen from Table II that when the concentration of the complexing agent in the organic phase increases, the selectivity of the sulfonic compound to cobalt decreases at the same time. The same is true of the absorption capacity, expressed as the weight of cobalt retained by 1 kg of active matter.

Example 1 a d 3

Effect of concentration of the solution to be cleaned

Examples 1 and 2 show that the optimum concentration of the complexing agent dissolved in butyl ethane is 0.3 mol / ltr. For this concentration of 0.3 M of the same sulfonium derivative, in this embodiment, the concentration of the solution intended for purification, consisting of a mixture of nickel chloride and cobalt chloride in a weight ratio of Ni: Co = 1.7 and a concentration of ions Cl * 5.5 to 9.5 equivalents / liter. During extraction, the volume ratio of organic phase:: aqueous phase is equal to 3. Table III below summarizes the extraction results.

189535 · ; Table III 10 Concentration of processed Metals passed Capacity aqueous solution. into the organic phase / g What per kg active (Cl / L equivalents) ( cobalt mass> weight of nickel J | mass 5.5 1.6 20 May 6.3 2 28 7.3 15 Dec . 45 7.9 > 1000 · 53 8.8 ^z .... > 1000 56 9.5 - > 1000 62

. It is apparent from the above table that the concentration of salts expressed by Cl ions is a determining factor. Selectivity. as this concentration increases, it increases very rapidly and becomes excellent under the conditions of Example 3 at a Cl ion content of greater than 7 equivalents / liter.

Example 4

Importance of N: Co weight ratio for extraction selectivity

Use a solution of the same sulfonium derivative in. Butyl acetate, 0,3 mol / liter, v / v. ratio of organic phase to. Under the above conditions, the weight ratio of N: Co in saline varies. solution, a mixture of cobalt chloride and chloride. nickel having. constant ion concentration. Cl equals 7 equivalents / liter.

Table IV summarizes the extraction results.

N: Co weight ratio in the treated aqueous solution

Table IV.

Metals passed into the organic phase weight of cobalt weight of nickel

Capacity / g Co per kg of active mass

0> 1000

0.5> 1000

240

From Table IV. It is clear that the selectivity decreases as the Ni: Co weight ratio in the treated solution increases. Threshold. the reversal of the cobalt selectivity is between 2: 6 Ni:: Co weight ratios.

Ex. k 1 and d 5

Influence of the weight ratio of organic phase to aqueous phase

Use. A solution of Example 3 having a N: Co weight ratio of 1.7 and a Cl ion concentration of 7 equivalents / liter. The volume ratio between the organic and aqueous phases is varied, while the concentration of the complexing agent in the organic phase is maintained. to 0.3 mol / liter. The volume ratios between the two phases were studied for values between 2 and 8. Table V summarizes the extraction results.

Table V Volume ratio Values of metals passed Capacity organic phase into the organic phase / g 'cobalt per kg active aqueous phase (weight of cobalt> I mass \ nickel weight> 2 800 55 3 10 43 4 6 39 5 3 31 8 1.4 22nd

/

198995

From Table V it is apparent that the selectivity to cobalt decreases with increasing value of the volume ratio of organic phase to aqueous phase. : · .. ·? 1 and d 6

Operation flow for the separation of cobalt and nickel in a typical chloride solution of industrial processing

The sludges resulting from the treatment of the nickel salt solution during purification by the precipitation of mainly cobalt were completely dissolved in concentrated hydrochloric acid. The neutral solution obtained at about 60 ° C contained 178 g / l of nickel and 101 g / l of cobalt, i.e. the concentration of Cl ions was 9.5 equivalents / liter.

In view of the results of the preceding examples, this neutral aqueous solution is processed in several extraction steps as shown in Table 3 below. VI. Between each extraction step, the concentration of the aqueous phase is adjusted by evaporation to the original chloride ion concentration, the concentration being checked by density measurement; the organic phase was washed with a second aqueous phase, i.e. water slightly acidified with hydrochloric acid, resulting both in the release of cobalt in the form of an aqueous chloride solution and in the recovery of the active substance contained in butyl acetate. The organic phase was further used in the next extraction step.

Table VI below illustrates the efficiency of the metal separation process of the present invention, which allows to reduce the Co: Ni ratio in the nickel treated solution from 0.57 to 0.0095 in six extraction stages, with 98.3% cobalt being extracted in the form of % of an aqueous solution containing 0.57% nickel by weight, calculated with respect to the cobalt content. The seventh extraction stage makes it possible to further reduce the cobalt content of the nickel solution, since the Co: Ni weight ratio in the final solution is 0.000625; however, this last result was obtained at the expense of the purity of the cobalt solution corresponding to this seventh extraction stage.

However, this is not a problem as the organic phase containing cobalt contaminated with nickel can be recycled without difficulty to the level of the first extraction stage. During this step, nickel is replaced by cobalt contained in the original crude solution to be purified.

Table VI

Extraction degree Volume ratio <organic phase \ 1 aqueous phase / initial state Content Extracted cobalt (%) aqueous phase organic phase nickel 213 cobalt 121 nickel cobalt 1. 3 213 88.49 0.00 32.51 26.9 2. 3 212.75 58.35 0.25 30.14 24.9 3. 2 212.75 39.38 0.00 18.97 15.7 4. 2 212.65 23.02 0.10 16.36 13.5 5. 2 212.37 8.39 0.28 14.36 12.1 6. 1 212.32 2.02 0.05 6.37 5.2 Subtotal 0.68 118.98 98.3 7. 1 207.86 0.13 4.46 1.89 1.6 Summary 5.14 120.87 99.9

The content of di-sec- (alkyl C 10) methylsulfonium chloride was determined in the regenerated organic phase and its loss by entrainment into aqueous solutions and degradation was found to be very low, less than 0.05 kg per kg of extracted cobalt.

The process is suitable for countercurrent liquid / liquid extraction processes which allow equivalent results to be obtained for a limited number of extraction steps.

Claims (3)

A method of separating nickel and cobalt iron metals in an aqueous solution by selective liquid / liquid extraction between an aqueous phase containing the chlorides of these metals and an organic phase containing the sulfonyl salt in an organic solvent solution that is poorly miscible with water, wherein at least one The metal is selectively transferred from the aqueous phase to the organic phase, characterized in that the neutral aqueous phase, which contains the chlorides of said metals and has a total chloride ion concentration of at least 7 grams / liter of solution, is treated with an organic phase. phase is equal to 1: 2 to 10: 1 and the organic solvent in the organic phase is a light non-polar solvent selected from the group consisting of esters such as butyl and amyl acetate acetates and propionates such as butyl acetate, ethers such as dibutyl ether and ketones such as methylisopropyl ketone whereupon the organic phase obtained, e.g. containing cobalt chloride, is washed with an additional aqueous phase consisting of water or water acidified with hydrochloric acid, the ratio of this organic phase to the second aqueous phase being 1: 1 to 40: 1. 2. A process according to claim 1, wherein the organic phase recovered by the second aqueous phase is continuously transferred to the next at least one extraction stage. 3. A process according to claim 1 or 2, wherein the neutral aqueous phase comprising nickel chloride and cobalt chloride is treated with the organic phase in at least two separate stages and the separated organic phases obtained are regenerated successively with a single second aqueous phase up to a cobalt chloride concentration of 130 g / liter in the second aqueous phase.