FR2481941A1 - SOLVENT EXTRACTION PROCESS FOR THE REMOVAL OF IRON (III) FROM AQUEOUS SOLUTIONS - Google Patents

Abstract

PROCESS FOR THE TREATMENT OF AQUEOUS SOLUTIONS CONTAINING IRON WITH AN EXTRACTION SOLVENT. IT IS CHARACTERIZED IN THAT THIS SOLVENT INCLUDES AN ORGANOPHOSPHORIC ACID, A TERTIARY PHOSPHINE OXIDE AND AN ORGANIC THINNER NOT MISCIBLE IN WATER TO SEPARATE IRON III FROM THE AQUEOUS SOLUTION. THE IRON LOADED EXTRACTION SOLVENT CAN THEN BE TREATED WITH SULFURIC ACID TO RECOVER IRON III IN THE FORM OF WATER SOLUBLE SALT.

Description

 The present invention relates to hydrometallurgy. It relates more particularly to the recovery of metals from aqueous solutions, by extraction with solvents, then purification of the solvent loaded with metal by sulfuric acid.

 Removal of iron from aqueous solutions is necessary in many industrial processes. For example, when leaching ores or metalliferous concentrates, iron is frequently dissolved at the same time as the desired metal and must be removed from the solution obtained before the recovery of the desired metal. In another example, solutions of alum (aluminum sulphate), prepared by the action of sulfuric acid on clays, generally contain iron, the elimination of which would allow the alum solution to be used to produce pure alumina for the purpose of its subsequent use as a catalyst support material or in the manufacture of metallic aluminum.

In another example, iron must be removed from certain waste streams to meet pollution reduction regulations.

The usual practice is to precipitate iron by chemical means comprising solid-liquid separations and difficult co-precipitation, with the losses of precious constituents which they entail. Solvent extraction has been found to reduce these problems
The extraction of iron (III) from acidic aqueous sulphate liquors with water-immiscible organic solutions containing either bis (2-ethylhexyl) hydrogen phosphate, hereinafter abbreviated as BEHP, or trin-octylphosphine oxide, hereinafter abbreviated as TOPO, is well known in the art (Long et al., British patent
N 970,885; Roddy et al., J. Inorg. Nucl. Chem. 33, 4, 1099-1118; Nagasubramanian et al; U.S. Patent No. 4,168,297; Sekine et al., J. Inorg. Nucl. Chem. 38, 7, 1347 1350; and Diaz Nogueira et al., German patent application NO 2 645 130, CA 87 26 576 (4). However, if the organic solution loaded with iron (III) contains only BEHP, the iron cannot be completely removed therefrom by sulfuric acid. If the extraction solvent contains only TOPO about 25% only of the total iron (III) in the aqueous solution is extracted in the organic phase.

There is therefore a need for an extraction mixture extracting most of the iron (III) in the organic phase and most of the iron (III) can be removed from the latter with sulfuric acid.

The present invention provides a process for removing iron (III) from an aqueous solution containing iron (III), comprising contacting this solution with an extraction solvent, said extraction solvent comprising an agent for extraction and If desired an organic water-immiscible diluent, this extraction agent comprising a mixture of about 1 to 10 parts by volume of a suitable organophosphoric acid, having at least 6 carbon atoms, and about part by volume of a tertiary phosphine oxide (C4-C20); allowing the two-phase liquid mixture to settle; and separating the aqueous phase from the organic phase loaded with iron (III).

 The present invention also provides a process as described above, comprising the additional operations of bringing the residual organic solution loaded with iron (III) into contact with an aqueous solution of sulfuric acid to pass the iron (III) through. the acidic aqueous phase; separating the acidic aqueous phase containing iron (III) salts soluble in water; and recovering the purified organic phase for subsequent reuse in the extraction of another aqueous solution containing iron (III).

In the process of the invention, the preparation of the extraction solvents and of the appropriate purification solutions is carried out as follows
The extraction solvent is preferably prepared by changing approximately 1 to 50 parts by volume of extracting agent with approximately 99 to 50 parts by volume of a water-immiscible organic diluent, although '' one can use the pure extracting agent This extracting agent consists of a mixture of an organophosphoric acid having at least 6 carbon atoms and a tertiary phosphine oxide (in
C4 to C20).

 Suitable organophosphoric acids are chosen from alkyl-cycloalkyl, -aryl, (substituted aryl) and aralkylphosphoric acids. Examples of these include the hydrogen phosphates of bis (n-hexyl), bis (n @ hepty-), bis (n-octyl), bis (2-ethylhexyl), bis (n- hexadecyl), bis (n-octadecyl), n-butyl (n-hexadecyl), methyl (n-hexyl), n-butyl (2-ethylhexyl), n-octadecyl (2-ethylhexyl), diphenyl, phenyl (2-ethylhexyl), n-dodecyl (p-tolyl), n-decyl (naphthyl), 2-ethylhexyl (p-octylphenyl), bis (poctylphenyl), bis (benzyl), benzyl (2-ethylhexyl), benzyl (octadecyl), dicyclohexyl, cyclohexyl (dodecyl), n-octyl, phenyl, benzyl dihydrogen phosphates, (p-chlorophenyl), bis (2-ethylhexyl) , octyl trihydrogen phosphate, etc. In general, any organophosphoric acid having at least 6 carbon atoms in the hydrocarbon chain can be used, and an average molecular weight of approximately 600. In the preferred embodiment, the organophosphoric acid is a C 6 to dialkyl hydrogen phosphate Cl8. The preferred organophosphoric acid is bis (2-ethylhexyl) hydrogen phosphate (BEHP).

 Suitable tertiary phosphine oxides are chosen from alkyl oxides, α -hydroxycycloalkyl-, cycloalkyl-, aryl, (substituted aryl) -, aralkyl, α -hydroxybenzyl- phosphines and bridged phosphine oxides. Examples of these are the oxides of tri-n-butylphosphine, triisobutylphosphine, tri-n-pentylphosphine, tri-n-hexylphosphine, tri-n-heptylphosphine, tri-n-octylphosphine, tri - n-decylphosphine , tri-n-dodecylphosphine, tri-n-hexadecylphosphine, tri-n-octadecylphosphine, tri-n-eicosylphosphine, di-n-octyl (methyl) phosphine, di-n-octadecyl (ethyl) phosphine, di-n-octyl (isobutyl) phosphine, diethyl (n-octadecyl) phosphine, di-n-decyl (n-butyl) phosphine, diisobutyl (n-hexyl) phosphine, di-n-butyl (cyclohexyl) phosphine, dicyclohexyl (n-octyl) phosphine , dicyclohexyl (methyl) phosphine, dicyclooctyl (ethyl) phosphine, dicyclohexyl (benzyl) phosphine, tricyclohexylphosphine, dicyclohexyl-benzyl) phosphine, tricyclohexylphosphine, di-n-octyl (phenyl) phosphine, di-n-hexyl (p-tolyl) , diphenyl (ethyl) phosphine, triphenylphosphine, trinaphthylphosphine, diphenyl (cyclohexyl) phosphine, dicyclopentyl (ptolyl) phosphine, tribenzylphosphine, tris (p-tolyl) phosphine, tris (p-ethylphenyl) phosphine, tris (p-octylphenyl) phosphine, tris (2,3-dimethylphenyl) phosphine, tris (2,4-dimethylphenyl) phosphine, tris (2,5-dimethylphenyl) phosphine, tris (3,4-dimethylphenyl) phosphine, bis ( p-tolyl) n-octylphosphine, di-n-hexyl (2,4-dimethylphenyl) phosphine, tris (p-chlorophenyl) phosphine, bis (p-bromophenyl) n-hexylphosphine, tris (3,5-dimethylbenzyl) phosphine, benzyl bis (Çq-hydroxybenzyl) phosphine, dicyclohexyl (α -hydroxybenzyl) phosphine, cylclohexyl (1-hydroxycyclohexyl) phenylphosphine, cyclopentyl (1-hydroxycyclopentyl) phenylphosphine, benzyl (α -hydroxybenzyl) cyclohexylphosphine, 1- (4-heptyl) -2,6-dihydroxy oxide -phos- phacyclohexane, 4-heptylbis (Di-hydroxylbenzyl) phosphine oxide, n-octylbis (p-chlorophenyl) phosphine oxide, 9-octyl-9-phosphabicyclo- 3,3-oxide. nonane, etc ...

In general, any tertiary phosphine oxide having low solubility in batten can be used. The preferred tertiary phosphine oxide is tri-n-octylphosphine oxide. Holiday tertiary phosphine oxide is tri-n-octylphosphine oxide (TOPO).

The extractant comprises about 1 to 10 parts by volume of the organophosphoric acid, preferably about 1 to 3 parts by volume, per part by volume of the tertiary phosphine oxide.

 In general, a variety of water-immiscible organic liquids can be used as diluent. The diluent is preferably an aliphatic or aromatic petroleum distillate, preferably kerosene. As suitable diluents, non-limiting examples include benzene, toluene, xylene, kerosene, naphtha, etc.

 To carry out the process of the invention, the aqueous solution containing iron (III) is brought into contact, batchwise or continuously parallel or continuously countercurrently, with the extraction solvent. The ratio of the aqueous phase to the organic phase must be chosen so as to eliminate iron (III) in the most efficient way.

It is believed that ratios of the aqueous phase to the organic phase of 1:20 to 20: 1 are effective, although other ratios may prove to be effective, depending on the particular separation carried out. The phase contact is usually made in "mixer-settlers", although there are many other types of devices that are suitable. In the mixer, one of the phases is dispersed in the other by stirring with an agitator or by any other suitable means. The extraction solvent then forms a complex with the iron (III) which passes into the organic phase of the two-phase liquid mixture. The dispersion then flows into the decanter where the separation of the phases takes place, at rest. In general, the extraction is carried out between 0 and 100 ° C., preferably between 20 and 70 C.

After extraction the aqueous solution is free of iron (III) and ready for further processing, for example for the precipitation of alumina. The extraction solvent loaded with iron (III) flows in the purification circuit in which approximately 0.05 to 20.0 parts by volume, preferably 0.1 to 0.5 parts by volume of a sulfuric acid solution are brought into contact with part by volume of solvent. This operation has the effect that the iron (III) passes into the aqueous phase in the form of a soluble salt of the sulfuric acid used. The phases can be contacted with mixer-settlers or other suitable devices. Several mixer-settlers, usually about 1 to 10, preferably about 1 to 6, connected in series, are normally necessary to carry out the desired degree of iron (III) removal. The elimination is generally carried out between 0 and 100 OC, preferably between 20 and 70 OC,
The purified iron-free solvent (III) is recycled in the extraction circuit for the treatment of aqueous solutions containing iron (III) entering the installation.

The sulfuric acid coming from the purification circuit, containing the iron (III) salts in solution can either be discarded, or treated for the elimination of iron, for example by electrolysis, and recycled in the purification circuit.

The preferred sulfuric acid contains at least 100 g of sulfuric acid per liter, preferably about 150 to 500 grams per liter.

As non-limiting applications of the process of the invention, mention will be made of the extraction of cobalt, nickel, rare earths, uranium, vanadium, copper, aluminum, zinc and silver, etc. .. from aqueous solutions.

The following nonlimiting examples are given by way of illustration of the invention. Unless otherwise indicated, the parts and percentages are all by weight.

EXAMPLE 1
An oxidized alum solution containing ferric sulfate is introduced in an amount equivalent to 1470 micrograms of Fe3 + / ml, at a rate of 1000 ml / min., In an extraction circuit consisting of 4 stages of mixer-settlers.

There, it is brought into contact, at 40 ° C., continuously, countercurrent, with an extraction solvent containing 4.5% by volume of BEHP, 3% by volume of TOPO and 92.5% by volume. of kerosene, which is added at the rate of 500 ml / min to give a volume ratio of the aqueous phase to the organic phase of 2: 1. After the four extraction stages at this ratio, an aqueous solution of alum is obtained containing approximately 5.0 micrograms of Fe3 + / ml at a rate of approximately 1000 ml per minute.

EXAMPLE 2
The organic extraction solvent loaded with iron from the ex
Example 1, containing approximately 2955 micrograms of Fe3 + / ml, leaves the extraction circuit at approximately 500 ml / min and it is introduced into a purification circuit. In this circuit, it is brought into continuous contact at 40 ° C., in three stages of counter-current mixer-settlers, with a purification current consisting of an aqueous solution of sulfuric acid. containing 200 g of sulfuric acid per liter of solutions is introduced with a flow rate of 100 ml / minute, so as to obtain a volume ratio of the aqueous phase to the organic phase of 0.2 after the three stages of purification at this report, an acidic purification liquor is obtained containing 14,650 micrograms of Fe3 + / ml with a flow rate of approximately 100 ml / minute.

 The purified organic phase, containing approximately 25 micrograms of Fe3 + / ml is recovered and recycled at a flow rate of approximately 500 ml / minute in the extraction circuit of example 1, where it is used for the subsequent extraction of iron from the alum solution containing iron, which enters the installation.

EXAMPLES 3-5
Organic solutions loaded with iron are prepared, each containing approximately 3 g of Fe3 + per liter, by extracting alum solutions containing sulfuric acid with the following extraction solvents:
Solvent Ex solvent composition
tensile extraction (% by volume)
4.5 1 from BEHP, 3 53 from TOPO,
92.5% kerosene
B 7.5% BEHP, 92.5% kerogen
C 4.5 53 from BEHP, 95.5 53 from
kerosene
The iron-loaded solutions are then purified by contact with aqueous sulfuric acid (200 g / l) in a proportion giving a ratio of the aqueous phase to the organic phase of 0.2 to 40 OC, for various numbers of mixer-settler stages, and the iron (III) content of the purified organic phase is measured. The results obtained are as follows
Solvent Number of stages Conc. in Fe (III) in the
of mixers - purified organic phase decanters (g / ml
A 3 25
B 14 700
C 6 120
The above results show that the presence of
TOPO in the iron-loaded solvent greatly facilitates the extraction of iron (III) from it.

EXAMPLE 6
An oxidized alum solution containing an amount of ferric sulfate equivalent to 523 micrograms of Fe / ml, which has a pH of 2.6 and contains 8.48 53 by weight of aluminum oxide, is extracted at 24 ° C. using a Burrell stirrer, with an equal volume of an extraction solvent consisting of 5% by volume of TOPO and 95% by volume of kerosene. The two-phase mixture is allowed to settle and the aqueous phase is separated. Analysis of the aqueous phase shows that only 27.4% of the Fe3 + is extracted by the organic phase.

EXAMPLES 7 to 14
The procedure of Example 6 is followed, except that 5% by volume of the extracting agent used is a mixture of BEHP and TOPO. In extracting agent from 0% to 50% by volume. In the aqueous phase obtained after separation of the organic phase, Fe3 + and aluminum are assayed to obtain extraction coefficients (E @@), and to calculate separation factors (Sf). The results obtained in Table I below indicate that the optimal composition of the extractant to minimize the extraction of aluminum, while maintaining a high extraction of iron (III), is in the range of 40 to 50% TOPO by volume.

TABLE I
Composition of (I) the extracting agent% EA extracts
Example (% by volume)
BEHP TOPO Fe3 + Al Fe3 + Al (Sf (2) 7 100 0 94.3 2.00 16.55 0.020 828 8 90 10 93.5 2.15 14.63 0.022 665 9 80 20 92.1 1.63 11, 76 0.017 692 10 75 25 91.4 1.11 10.70 0.011 973 11 70 30 91.4 1.11 10.68 0.011 971 12 65 35 92.6 1.11 13.61 0.011 1,146 13 60 40 93, 1 1.04 13.79 0.010 1379 14 50 50 92.9 1.04 12.99 0.010 1299 (1) EA = / metal / organic phase / metal / aqueous phase (2) Separation factor = EA (Fe3 +)
EA Al
EXAMPLE 15
By following the procedure of Example 1 in all its material details, except that the extraction solvent now contains phenyl dihydrogen phosphate, tris (2-ethylhexyl) phosphine oxide and benzene, practically identical results.

EXAMPLE 16
By following the procedure of Example 1 in all its material details, except that the extraction solvent this time contains octyl trihydrogen diphosphate, tricyclohexylphosphine oxide and toluene, practically identical results are obtained.

EXAMPLES 17-19
By following the procedure of Example 1 in all its material details, except that the sulfuric acid solution is replaced by hydrochloric, hydrofluoric and nitric acid solutions, respectively, almost identical results are obtained. EXAMPLE 20
An aqueous leach liquor containing 35 g / l of Cu + 2.5 g / l of Fe + 3.15 g / l of contact is brought into contact.
H2SO4, 11 g / l of Al + 3 and 2 g / l of Cl- and having a pH of 1.5, with an extraction solvent at 24 C, for 5 minutes, in aliquots with aqueous phase ratios / organic phase (A / O) of 5, 2 and 1 by volume. After separation, the pH of the aqueous phase is adjusted to 1.5 with NaCH and the contact is repeated until an equilibrium pH of 1.5 is reached. The data and test results are shown in Table II.

EXAMPLE 21
By following the procedure of Example 20 in all its material details, except that a different extraction solvent is used, the data and results of
sai which appear in Table II.

TABLE II
Iron extraction isotherms (24 C)
Concentration of Fe3 + at equilibrium (g / l)
EXAMPLE 20: 10% BEHP + 8% TOPO in kerosene
A / O Phase Phase% of aqueous organic Cu extracted
5 7.75 2.60 1.5
2 5.72 1.29 3.6
1 3.93 0.22 O
EXAMPLE 21: 10% of BEHP + 6.7 53 of TOPO in kerosene
5 8.25 2.40 0
2 6.34 0.88 1.6
1 3.88 0.17 0
EXAMPLE 22
An aqueous leach liquor containing 15.2 g / l of Fe + 3, 22 g / l of Cu + 2 3 g / 1 of Ag +, 20 g / l of H2SO4 and having a pH of 1 is brought into contact. , 5, with an extraction solvent at 50 ° C. for 10 minutes in aliquots having volume ratios organic phase / aqueous phase (O / A) of 6.4 and 2. After separation, the pH of the 1.5 aqueous phase using a 50% solution of NaOH and the contact is repeated until an equilibrium pH is obtained. Data and results for sai are shown in Table III.

TABLE III
10% BEHP + 6.7% TOPO in kerosene
% extraction Separation factors
O / A Fe Ag Cu Fe / Ag Fe / Cu
2 92.8 2.8 0.1 457 6.387
4 98.0 7.2 0.1 629 11.912
6 99.0 17.2 0.1 479 16.660
EXAMPLE 23
An aqueous leach liquor containing 2 g / l of Fe + 3, 2 g / l of cu + 2, 2 g / l of +2 +2 +2 +4 is brought into contact.
Zn + 2, 2 g / l of Co + 2, 2 g / l of Ni +2, 2 g / l of V + 4, 2 g / l of
Eu 2, the pH of which is adjusted to 1.0 by H2SO4, with an extraction solvent at 50 ° C. for 10 minutes, in aliquots with aqueous phase / organic phase (A / O) ratios of 4.2.1. The test data and results are shown in Table IV.

TABLE IV 7.5% BEHP + 5.1% TOPO in kerosene
Extraction% Separation factor
A / O Fe Cu Zn Co Ni V Eu Fe / Cu Fe / Zn Fe / Co Fe / Ni Fe / V Fe / Eu 4 47.8 0 0.2 0 0 6.1 0 # 2,178 # # 14 # 2 70 , 4 0 0.2 0 0 7.2 0.8 # 2.833 # # 30 303 1 91.5 0 0.3 0 0 10.8 5.4 # 1.660 # # 90 191
EXAMPLE 24
An aqueous leach liquor containing 2 g / l of Fe + 3, 2 g / l of V + 4, the pH of which is adjusted to 1.0 by H2SO4, is brought into contact with an extraction solvent of 50 C for 10 minutes, in aliquots in which the volume ratios aqueous phase / organic phase
A / O are 4, 2 and 1. The data and test results are shown in Table V.

TABLE V
7.5% BEHP + 5.1% TOPO in kerosene
Extraction% Separation factor
A / O Fe V Fe / V
4 57.3 6.1 21
2 80.1- 12.6 28
1 94.4 22.2 58 EXAMPLE 25
An aqueous leach liquor containing 2 g / l of Fe + 3, 2 g / l of Co + 2 and 2 g / l of Ni + 2, the pH of which has been adjusted to 1.5, is brought into contact. H2SO4, with an extraction solvent at 50 ° C. for 10 minutes, in aliquot parts having volume ratios aqueous phase / organic phase (A / O) of 4, 2 and 1. The data and results of tests appear in the table VI.

TABLE VI
7.5% BEHP + 5.1% TOPO in kerosene
Extraction% Separation factor
A / O Fe Co Ni Fe / Co Fe / Ni
4 70.6 0 0 # #
2 90.3 1.0 1.0 247 246
1,100.0 1.0 1.0 # #
EXAMPLE 26
An aqueous leach liquor containing 2 g / l of Fe + 3, 2 g / l of Zn + 2 and whose pH has been adjusted to 0.8 by H2SO4 is brought into contact with an extraction solvent. at 50 OC, for 10 minutes, in aliquots having volume ratios aqueous phase / organic phase (A / O) of 4.2 and 1. The data and results of tests are indicated in table VII.

TABLE VII
7.5% BEHP + 5.1% TOPO in kerosene
Extraction% Separation factor
A / O Fe Zn Fe / Zn
4 29.6 1.8 23
2 55.1 1.8 66
1 82.1 1.8 366
EXAMPLE 27
An aqueous leach liquor containing 15 g / l of Fe, 22 g / l of Cu, 3 g / l Ag + and of which the pH has been adjusted to 0.76 by H2SO4 is brought into contact with an extraction solvent containing 10% BEHP, 6.7% TOPO in kerosene at 50 C for 10 minutes, in aliquots having an organic phase / aqueous phase (O / A) volume ratio of 2.

After separation, the solvent containing the extracted metals is divided into aliquots. Analysis of an aliquot of this charged solvent shows that it contains 2.77 g / l Fe + 3 and 30.0 micrograms / mI Ag +. A second aliquot of the charged solvent is brought into contact with an O / A ratio of 1, with 5 g / l of sulfuric acid, for 5 minutes at 50 ° C. The test results show that 95% of the Ag and 0.2% of Fe + 3 are extracted from the solvent.

Claims (14)

 1 - Process for removing iron (III) from an aqueous solution containing iron (III), consisting in contacting this solution with an extraction solvent, this extraction solvent comprising an extraction agent and, if it is desires, an organic diluent immiscible with water, characterized in that this extracting agent comprises a mixture of approximately 1 to 10 parts by volume of an organophosphoric acid having at least 6 carbon atoms, and about 1 part by volume of a tertiary phosphine oxide at C4 to C20, in that the liquid is allowed to settle in two phases; and separating the aqueous phase from the extraction solvent loaded with iron (III). 2 - Method according to claim 1, characterized in that it comprises the additional operations of bringing the extraction solvent loaded with iron (III) residual with an aqueous solution of sulfuric acid to pass the iron (III ) in the aqueous phase, separating the aqueous phase containing iron (III); and recovering the purified extraction solvent for later re-use in the extraction process.  3 - Process according to any one of claims 1 and 2, characterized in that this organophosphoric acid is a di (C6 alkyl to  4 - Process according to claim 3, characterized in that this di hydrogen phosphate (C6 to C18 alkyl) is bis (2-ethylhexyl) hydrogen phosphate. 5 - Method according to any one of claims 1 and 2 ,. characterized in that this tertiary C4 to C20 phosphine oxide is tri-n-octylphosphine oxide.  6 a Method according to any one of claims 1 and 2s characterized in that this organic diluent not put target water is an aliphatic or aromatic petroleum distillate. 7 - Process according to any one of claims 1 and 2, characterized in that this extraction agent consists of approximately 50 to 75% by volume of bis (2-ethylhexyl) hydrogen phosphate and of approximately 50 a 25 So by volume of tri-n-octylphosphine oxide. 8 - Process according to claim 2, characterized in that one brings into contact a part by volume of the extraction solvent loaded with iron (III) residual with about 0.05 to 20 parts by volume of an aqueous solution of sulfuric acid containing more than 100 g of sulfuric acid per liter of solution. 9 - Process according to any one of claims 1 and 2, characterized in that the aqueous iron (III) starting solution contains aluminum. 10 - Process according to any one of claims 1 and 2, characterized in that the aqueous iron (III) starting solution contains copper.  ll - Process according to either of Claims 1 and 2, characterized in that the aqueous starting iron (III) solution contains vanadium. 12 - Process according to any one of claims 1 and 2, characterized in that the aqueous iron (III) starting solution contains cobalt.  13 - Process according to any one of claims 1 and 2, characterized in that the aqueous iron (III) starting solution contains rare earths. 14 - Method according to any one of claims 1 and 2, characterized in that the aqueous iron (III) starting solution contains silver. 15 - Process according to any one of claims 1 and 2, characterized in that the aqueous iron (III) starting solution contains nickel. 16 - Process according to any one of claims 1 or 2, characterized in that the aqueous iron (III) starting solution contains zinc 17 - Process according to any one of claims 1 and 2, characterized in that the aqueous iron (III) starting solution contains europium. 18 - Process according to any one of claims 1 and 2, characterized in that the aqueous iron (III) starting solution contains uranium.