SE434123B - PROCEDURE FOR SELECTIVE EXTRACTION OF METAL IONS FROM A WATER SOLUTION - Google Patents

Description

It has surprisingly been found that a selective extraction of metal ions from an aqueous solution of the metal ions is possible if the extraction is carried out with an extractant based on an unsaturated fatty acid or a mixture of unsaturated fatty acids. This extraction is preferably carried out with one or more unsaturated aliphatic carboxylic acids. Advantageously, a mixture is used which consists of at least 50% of oleic acid and otherwise of, for example, linoleic and / or linolenic acid.

The fatty acid or fatty acid mixture may, in addition to the mentioned constituents, also contain a certain amount of saturated fatty acids, as is the case, for example, with oleic acid of technical quality. In a particular embodiment of the invention, a certain amount of oxime is also added to the above-mentioned extractant, for example a (cyclo) aliphatic oxime and in particular cyclohexanone oxime. The weight ratio between fatty acid and oxime is then preferably between 0.5 and 50.

The addition of an oxhine to the extractant has an effect on the "partition coefficients". In the following description, this term refers to the ionic concentration of a particular metal in the organic medium divided by the ionic concentration of the same metal in the aqueous phase after equilibration. selectivity, and furthermore, the separation between the organic phase and the aqueous phase after extraction is also improved.

For the extraction of metal ions from the aqueous solution, a pH in the range 4-9 is preferably used. In particular, Cu ions and Ni ions mostly pass into the organic medium at a pH between 5.5 and 9, while at a pH between 4 and 5.5 mainly Cu ions pass into the organic medium. In strongly acidic medium, i.e. at a pH below about 2, all the metal ions go back into the aqueous phase, so that the organic medium is then virtually completely free of metal ions.This circumstance is used in the practical implementation of the process according to the invention. the value of the extraction is not in itself critical and is largely determined by the extractant used and the metal ions to be extracted.The exact value can be determined experimentally only after the choice of extractant.With the fatty acid reactions, a pH above 8 is not The extraction process usually takes place at room temperature, although the temperature of the various liquids also plays a role. The minimum value is generally dependent on the viscosity of the various liquids. the organic medium, which must not be too high. On the other hand, the temperature must not rise too high in order to avoid one of the components evaporating too much. Of course, the choice of temperature also affects the kinetics of the extraction and the separation between the organic phase and the aqueous phase after the extraction.

The invention also relates to the extractants used in the process according to the invention. The extractants can be used as such or in the form of a solution. Suitable solvents are the usual, substantially apolar solvents, such as kerosene, hexane, isobutane, perchlorethylene, or special solvents developed for extractants. The use of less apolar solvents such as methyl isobutyl ketone and the like is also possible without having a particularly adverse effect on the extraction. The consumption of solvents increases in this case, as the solvents dissolve in the water. Advantageously, an extractant is used, which per liter consists of 5-40 g of cyclohexanone oxime, 20-250 g of fatty acid mixture, consisting essentially of oleic acid, and otherwise mainly of apolar solvents.

The weight ratio of fatty acid to oxime can be between 0.5 and 50. These values refer to extractants with such a proportion of oxime that the oxime has a clear effect on the selectivity of the extraction.

Admittedly, it is possible that in certain compositions of the extractants, in which case the starting point is mainly from fatty acids, the phase separation after the extraction proceeds less well. In such a case, this phase separation can be significantly improved by adding a small amount of oxime to the fatty acid. In this case, it may be a question of a weight ratio between fatty acid and oxime of the order of 50 to just over 500.

An advantage of the use of the extractants according to the invention is in particular the fact that simple, less expensive chemical compounds can be used, the toxicity of which is usually lower than for the known extractants. In addition, especially with nickel ions, the extraction rate is higher than with other known extraction agents, for which the extraction rate is generally low. The process according to the invention as well as the extractants according to the invention are particularly suitable for selective extraction of Cu and Ni ions from aqueous solutions, in which Cr and Zn ions are also present. In the following, the invention will be further described in connection with the accompanying drawing, in which Fig. 1 illustrates an embodiment of the method according to the invention for separating, for example, from a galvanic industry derived Fe-, Ni-, Zn- and Cu ions using fatty acids and oxime; Fig. 2 shows substantially the same embodiment, in which, however, a further concentration and concentration step for Ni ions is provided; and Fig. 3 is a diagram showing the relationship between the partition coefficients of Cu and Ni ions between the organic phase and the aqueous phase as a function of the pH value when using extractants according to the invention. It should be noted that the invention is not limited to the illustrated and described embodiments thereof.

Fig. 1 illustrates a process for separating Fe, Cu, Ni, Zn and Cr. A brief account provides the following schedule. You go out! thereby from a mixture of solid hydroxides of the said metals.

Hydroxides of Fe, Cr, Cu, Ni, Zn solution in acid (pH 2-3) solid Fe- + Cr-hydroxidej Cu, Ni, Zn, Cr aqueous solution extraction (pH: 5.5-8) Cu, Ni (organic phase) Cr, Zn extraction (pH: -2 - +1) cr (oH) 3 zn-jgner iw aqueous solution Cu, Ni (aqueous phase) extraction (pH: 4-5.5) Cu (Org_) Ni (aqueous solution) extraction (pH: -2 - + 1 'Cu (aqueous solution fl 10 15 20 25 30 35 40 7802594-7 Fig. 1 shows a device which essentially consists of a solution vessel A and 4 "mixer-settler" units B, C, D and E. For a description of such a combination of mixing and sedimentation vessels, reference is made to the journal "Chemical Engineer" 1976-01-i9, pages 96 and 97. However, other apparatus suitable for extraction purposes may also be used, such as a pulsation column.

A description of this type of extraction columns can be found in Dutch patent specification 123 177.

Into the vessel A is introduced through the line 1 an amount of solid material, which consists of a mixture of Fe, Cr, Zn, Ni and Cu hydroxides.

Through line 2, so much acid, for example sulfuric acid, is added that the pH adjusts to a value between 2 and 3, whereby the Cu, Ni and Zn ions together with a part of the Cr ions change into dissolved form. The remaining solid material, essentially Fe hydroxide, is taken out for further processing through line 3.

The resulting acidic, Cu, Zn, Cr and Ni ions containing the solution are passed through line 4 to the mixing part of unit B.

The line 5 is supplied with an organic phase coming from unit C, which consists of a solution of cyclohexanone oxide and a mixture of fatty acids. This fatty acid is commercially available under the name "technical oleic acid". Through the line so much lye is added that the pH is adjusted to a value between 5.5 and 8. This absorbs the Cu and Ni ions in the organic phase. On the other hand, the Cr ions remain in the aqueous phase, while Cr (III) hydroxide precipitates when the very low solubility product is precipitated, and in a further working step the Cr and Zn ions can be separated from each other.

The organic phase is then passed through line 8 into the mixing part of unit C. Through line 9 so much acid is added that the pH is now adjusted to a value between -2 and +1, whereby both Cu- and Ni- the ions are taken up in the aqueous phase. A large part of this aqueous phase is returned through the line 10 from the sedimentation vessel of unit C to the mixing part. An advantage is that Cu and Ni sulphate crystallize out. The crystals formed can be separated continuously or discontinuously and transferred through the line II to the unit D. This builds up an additional purification step into the process. Namely, the crystallization avoids that any co-extracted impurities, such as Fions, interfere with the further process or even may contaminate the end product. Since the water phase in unit D does not need to be neutralized, the consumption of lye is reduced to a minimum. Through line 12, an organic extractant is supplied from the unit E, which consists essentially of the same hexane-dissolved fatty acid mixture, as mentioned above. In order to achieve a good separation of the two phases, it may be necessary to add a small amount of oxime to the fatty acid mixture.

Through the line 13 so much lye is added that the pH value of the solution is between 4 and 5.5. Due to this change in the pH value, all Cu ions migrate to the organic phase. The aqueous phase then contains only Ni ions, which "can be separated in a known manner. In line 14 the organic phase is transferred to the mixing part of unit E, which mixture part through line 15 is also supplied with an amount of acid Due to the strong acidification of the liquid, the Cu ions migrate to the aqueous phases. ions, possibly after crystallization of CuSO4 by recycling the aqueous phase.

Fig. 2 illustrates the same procedure as in Fig. 1, the same symbols having the same meaning. However, in the method illustrated in Fig. 2, two additional "mixer-settler" units F and G have been added.

The solution of Ni ions emanating from unit D is passed through line 22 to unit F together with an organic phase coming from unit G, which is essentially composed of the above-mentioned fatty acid mixture and of cyclohexanone oxime dissolved in hexane. Lye is added through line 17, so that the pH of the solution adjusts to a value between 5.5 and 8. This absorbs the Ni ions in the organic phase, after which this organic phase is transferred through line 18 to unit G. This unit is supplied by line 19 so much acid, that the pH set at a value between -2 and + 1.

This frees the organic phase from Ni ions. Thereafter, this phase is recycled through the line 21 to the unit F. A part of the aqueous phase is recycled from the sedimentation part to the mixing part in the unit G, whereby the concentration of Ni ions in the unit G is increased. If the solubility of the Ni salt is exceeded, crystals of the salt can be taken out through the line 20. In the above-described embodiments of the process according to the invention, it has been assumed that no losses of organic medium will occur. . In practice, however, a small part of the organic medium will always dissolve in the aqueous phase, so an addition of organic medium is required as before.

In the diagram in Fig. 3, the ratio between the partition coefficients in the aqueous phase and the organic phase is plotted as a function of the pH value for Cu ions and Ni ions. In the experiments illustrated by curve a, the organic phase consisted of 90% by weight of hexane and 10% by weight of an oleic acid mixture (70% by weight of oleic acid, 10% by weight of hexane and 20% by weight of saturated fatty acids such as pentadecanecarboxylic acid, tridecanecarboxylic acid and undecanecarboxylic acid ). In the experiments illustrated by curve b, the organic phase consisted of 90% by weight of hexane, 9% by weight of oleic acid mixture, and 1% by weight of cyclohexanone oxime. It is clear from the diagram that the extractant according to the invention is excellently suitable for a selective extraction of Cu ions and Ni ions.

The invention will be further elucidated in the following by means of some examples.

Example 17 Cu ions were extracted at a concentration of 4.9 g / l by means of an extractant of varying composition at different pH values. The phase ratio was 1: 1. In Table 1 below, the partition coefficient (m) for Cu ions is previously given as a function of the pH value.

The extractant used was 10 ml of oleic acid mixture, of the kind mentioned above, and 90 ml of methyl butyl ketone, in which 1 g of cyclophene hexanone oxime was dissolved.

Table 1 Experiment No. pH ml 3.7 1.8 2 4.2 3.9 3 6.3 118.3 In the next experiments in which Cu ions with the same concentration were extracted, the partition coefficients of three different extractants with the same phase ratios were determined as in experiments' l-3. 78025911-7 8 - ~ - ._ .. ._.

»A = 10 ml oleic acid, 90 ml methyl isobutyl ketone with 1 g cyclohexanone oxime B = 25 ml oleic acid, 75 ml kerosene, 1 g cyclohexanone oxime C = 25 ml oleic acid, 75 ml kerosene Table 2 Experiment No. pH ABC 4 3.7 1.8 ~ 0 , 1 0.1 5 4.0 3.0 K 1.0 0.4 e 7 119 zo. 39 “The extraction of Ni ions at a concentration of 5.0 g / l is clearly illustrated by the following experiments. The extractant used was 90 ml of hexane with 10 ml of oleic acid in a phase ratio of 1: 1. * Experiment No. pH m 7 3.9 0 8 6.5 3.5 9 8 8 Example gel 2 9.6 g / l divalent Cu and 1.6 g / l divalent Co, were extracted with an extractant consisting of an aqueous solution containing 10% by weight of oleic acid (technical), 1% by weight of cyclohexanone-Coxime and 89% by weight of boiling point petrol. The ratio between organic phase and aqueous phase was 1: 1. In the table below, the partition coefficients for Cu and Co are given for some pH values.

Experiment No. pH mCu 'mCo 12 _ 4.6 2.24 0.024 13 5.7 17.3 0.03 14 6.6 114.14 0.07 Example gel 3 An aqueous solution containing 4.6 g of divalent Cu and 2 , 7 g of divalent Zn, was extracted with an extractant consisting of 10% by weight of oleic acid (technical) and 10% by weight of boiling point petrol.

The ratio of the organic phase to the aqueous phase was 1: 1.

The following results were obtained: 7802594-7 Experiment No. pH Cu n 15 5.6 171 0.8 Example gel 4, An aqueous solution containing 10 g / l divalent CO and 5 g / l divalent Ni was extracted on the described in Example 2 the method (experiment 16). Thereafter, the experiment was repeated without oxime (Experiment 17).

The results were: Experiment No. pH Cu Ni 16 5.7 400 0.09 17 5.7 230 0.2

Claims (12)

7802594-'7 to Patentkrav 1. l. Process for the selective extraction of metal ions belonging to groups IB, IIB, IIIB, IVB, VB, VIB, VIIB 0Ch VIII in the Periodic Table from an aqueous solution containing them by means of an organic medium, known as a of the attexification is carried out with an extractant containing at least one unsaturated fatty acid or a mixture of unsaturated fatty acids. Process according to Claim 1, characterized in that the fatty acid mixture consists of at least 50% oleic acid. Process according to Claim 1 or 2, characterized in that the fatty acid mixture also contains linoleic acid and / or linolenic acid. Process according to one of Claims 1 to 3, characterized in that the fatty acid mixture contains a certain amount of saturated fatty acids. ' Process according to one of Claims 1 to 4, characterized in that the extractant also contains a (cyclo) aliphatic oxime. Process according to Claim 5, characterized in that the extractant contains cyclohexanone oxime. Process according to Claim 5 or 6, characterized in that the weight ratio of fatty acid to oxime is between 0.5 and 500. Process according to Claim 7, characterized in that the weight ratio of fatty acid to oxime is between 0.5 and 50. Process according to Claims 1 and 5 for the selective extraction of Cu and Ni ions from an aqueous solution, characterized in that an extractant is used which contains one or more unsaturated fatty acids and a bylo) aliphatic oxime. 7802594-7 'H Process according to Claim 9, characterized in that Cu and Ni ions are extracted from an aqueous solution at a pH value between 5.5 and 9, that these Cu and Ni ions are taken up from the organic phase in the aqueous phase at a pH value between -2 and +1, that the Cu ions are then selectively removed from the aqueous phase at a pH value between 4.0 and 5.5 and then at a pH value between taken up from the organic phase in an aqueous phase. 11. A process according to claim 1, characterized in that after the separation of the Cu 2 and Ni ions from the organic phase carries out a further purification in the form of a crystallization of CuSO 4 and NiSO 4. Method according to one of Claims 1 to 11, characterized in that the extraction is carried out in a pulsation column.