NL8102236A - METHOD FOR REMOVING IRON (III) FROM A SOLUTION. - Google Patents

Description

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Method of removing iron (III) from a solution.

The invention relates to a method in the field of hydrometallurgy. More particularly, the invention relates to the recovery of metal from aqueous solutions by solvent extraction and subsequent stripping of the metal-loaded solvent with sulfuric acid.

The removal of iron from aqueous solutions is required in many industrial processes. For example, in the case of metal iron ore or concentrate leaching, iron is often dissolved together with the desired metals and must be removed from the resulting solution before the desired metal is recovered. In another example, alum (aluminum sulfate) solutions, prepared by the action of sulfuric acid on clay, typically contain iron, where the alum solution, if iron had been removed, could be used to prepare pure alumina for further use as a catalyst support material or in the preparation of aluminum metals.

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

In practice, iron is precipitated by chemical means, performing difficult solid-liquid separations and coprecipitations accompanied by loss of valuable components. Solvent extraction has been found to reduce these problems.

The extraction of iron (III) from acidic aqueous sulfate liquids using water immiscible organic solutions containing either bis (2-ethylhexyl) hydrogen phosphate, further referred to simply as BEHP, or tri-n-octyl phosphine oxide, further referred to simply as TOPO, is known. Long et al., British Patent 970,885; Roddy et al., J. Inorg.Nucl.Chem. 33, k3 1099-1118; Nagasubramanian et al U; S; patent k. 168,297; Sekine et al., T. Inorg.Nucl., Chem. 38, 7, 13-7-11350; and Diaz Nogueira et al., German Offenlegungsschrift 26, 5130 C.A.

87 26576 (k). However, when the organic solution loaded with iron (III) contains only BEHP, the iron cannot be completely stripped therefrom with sulfuric acid. When the extraction solvent contains only TOPO, only about 25% of the total amount of iron (III) is extracted from the aqueous solution into the organic phase. There is therefore a need for an extraction mixture which will extract the majority of the iron (III) in the organic phase and allow the majority of the iron (III) to be stripped therefrom with sulfuric acid.

The challenge provides a method of removing iron (III) from an aqueous iron (III) containing solution, contacting the solution with an extraction solvent comprising an extractant and optionally a water-immiscible organic diluent. wherein the extractant comprises a mixture of about 1-10 parts by volume. of a suitable organophosphoric acid, having at least 6 carbon atoms, and about 1 part by volume. of a tertiary (C 1 -C 12 q) phosphine oxide; the liquid mixture is allowed to separate into two phases; and separates the aqueous phase from the net iron (IIl) loaded organic phase.

The invention also provides a method as described above with the additional steps that the residual iron (HI) loaded organic solution is contacted with an aqueous sulfuric acid solution for the iron (III) in the aqueous acidic phase to strip; the aqueous acidic phase, containing water-soluble iron (III) salts, is separated; and the stripped organic phase 20 is recovered and then reused in the extraction of another iron (III) containing aqueous solution.

When carrying out the process of the invention, suitable extraction solvents and stripping solutions are prepared as follows: The extraction solvent may preferably be prepared by about 1-50 parts by volume. extractant with about 99-50 parts by volume. of a water-immiscible organic diluent, although pure extractant could be used. The extractant consists of a mixture of an organophosphoric acid with at least 30 6 carbon atoms and a tertiary C 1 -G 2 g) phosphine oxide.

Suitable organophosphoric acids are selected from the alkyl, cyeloalkyl, aryl, substituted aryl, and aralkylphosphoric acids. Representative examples include bis (n-hexyl) hydrogen phosphate, bis (n-heptyl) hydrogen phosphate, bis (n-octyl) hydrogen phosphate, bis (2-ethylhexyl) -35 hydrogen phosphate, bis (n-hexadecyl) hydrogen phosphate, bis (n -octadecyl) - hydrogen phosphate, nu-butyl (n-hexadecyl) hydrogen phosphate, methyl (n-hexyl) hydrogen or phosphate, n-butyl (2-ethylhexyl) hydrogen phosphate, n-octadecyl (2-ethylhexyl) hydrogen phosphate »diphenylhydrogen phosphate, 8

* I

phenyl (2-ethylhexyl) hydrogen phosphate, n-dodecyl (p-tolyl) hydrogen phosphate, n-decyl (naphthyl) hydrogen or phosphate, 2-ethylhexyl (p-octylphenyl) hydrogen phosphate, bis (p-octylphenyl J hydrogen or phosphate) , his (hezyl) hydrogen or phosphate, benzyl (2-ethylhexyl) hydrogen phosphate, benzyl (octadeeyl) hydrogen phosphate, dicyclohexyl hydrogen phosphate, cyclohexyl (dodecyl) hydrogen phosphate, phenyl phosphate phenyl phosphate, phenyl phosphate, phenyl phosphate divaterophosphate, bis- (2-ethylhexyl) divaterophosphate diphosphate, octyl trisodium phosphate, etc. Generally, any organophosphorous acid having at least 6 carbon atoms in the hydrocarbon chain with a maximum molecular weight of about 600 is suitable in the preferred embodiment. Phosphoric acid is a dialkyl (C8 -C18 g) vessel of ester phosphate The most preferred organophosphoric acid is his (2-ethylhexyl) vessel of ester or phosphate (BEHP).

Suitable tertiary phosphine oxides are selected from the alkyl, alpha-hydroxycycloalkyl, cycloalkyl, aryl, substituted aryl, aralkyl, alpha-hydroxybenzyl and bridges containing phosphine oxides. Re-. presentative examples include tri-n-butylphosphine oxide, triisobutylphosphine oxide, tri-n-pentylphosphine oxide, tri-n-hexylphosphine oxide, tri-n-heptylphosphine oxide, tri-n-octylphosphine oxide, tri-n-decylphosphine-1 oxide n-dodecylphosphine oxide, tri-n-hexadecylphosphine oxide, tri-n-octadecylphosphine oxide, tri-n-eicosylphosphine oxide, di-n-octyl (methyl) phosphine oxide, di-n-octadecyl (ethyl) phosphine oxide (di-n-octyl) isobutyl) -phos fine oxide, diethyl (n-octadecyl) phosphine fine oxide, di-n-decyl (n-butyl) phosphine oxide, diisobutyl (n-hexyl) phosphine oxide, di-n-butyl (cyclohexyl) -> phosphine oxide, dicyclohexyl (n-octyl) phosphine oxide, dicyclohexyl (methyl) phosphine oxide, dicyclooctyl (ethyl) phosphine oxide, dicyclohexyl (benzyl) phosphine oxide, tricyclohexyl phosphine oxide, di-n-octyl (phenyl) phosphine) phosphine oxide, diphenyl (ethyl) phosphine oxide, triphenylphos fine oxide, triphthyl phosphine fine oxide, diphenyl (cyclohexyl) phosphine) fine oxide, dicyclopentyl (p-tolyl) phosphine oxide, tribenzylphosphine oxide, tris (p-tolyl) fo spine oxide, tris (p-ethylphenyl) phosphine oxide, tris (p-octylphenyl) phosphine oxide, tris (2,3-dimethylphenyl) phosphine oxide, tris (2, U-dimethylphenyl) phosphine oxide, tris (2,5-dimethyl If enyl ) phosphine oxide, tris (3, U-dimethylphenyl) phosphine oxide, bis (p-tolyl) n-octyl phosphine oxide, 5 di-n-hexyl (2-dimethylphenyl) phosphine oxide, tris (p-chlorophenyl) phosphine oxide, bis (p-bromophenyl) ) n-hexylphosphine oxide, tris (3,5-dimethylbenzyl) phosphine oxide, benzyl bis (alpha-hydroxybenzyl) phosphine fine oxide, di cyclohexyl- 8102236 it- -4- (alpha-hydroxybenzyl) phosphine oxide, cyelohexyl (1-hydroxycyclohexyl) - phenylphosphine oxide, cyclopentyl (1-hydroxycyclopentyl) phenylphosphine, benzyl (alpha-hydroxybenzyl) cyclohexylphosphine oxide, 1- (U-heptyl) -2,6-dihydroxy-1-phosphacyclohexane-1-oxide (U-heptylbis) bydroxybenzyl) -5 phosphine oxide n-octyl bis- (p-cfloorphenyl) phosphine oxide, 9-octyl-9-phospha-bicyclo 3,3-nonane-9-oxide, etc. Generally, any tertiary phosphine oxide with low water solubility is suitable . The preferred tertiary phosphine oxide is tri-n-octyl phosphine oxide (TOPO).

The composition of the extractant comprises about 1-10 parts by volume. of the organophosphoric acid, preferably about 1-3 parts by volume. per vol.dl. of the tertiary phosphine oxide.

In general, a wide variety of water-immiscible organic liquids can be used as the connecting agent. Preferably the diluent is an aliphatic or aromatic petroleum distillate. Most preferably, the diluent is kerosene. Suitable diluents include, but are not limited to benzene, toluene, xylene, kerosene, naphtha and the like.

In carrying out the process according to the invention, the iron (HI) containing aqueous solution is contacted batchwise, continuously in the same flow direction or continuously in the opposite flow direction, with the extraction solvent.

The ratio of aqueous to organic phases is preferably chosen so that the iron (III) is removed as efficiently as possible. It is believed that water to organic phase ratios of 1:20 to 20: 1 are effective, although other ratios may also prove effective depending on the specific separation. Phase contact is generally realized in devices called "mixer settlers", although many other types of devices are available and suitable. In the mixer, one phase is dispersed within the others by stirring or any other suitable form of agitation The extraction solvent then forms a complex with the iron (III) which joins the organic phase of the two-phase liquid mixture, the dispersion then flows to the settler (settling part) where the phases separate under quiescent conditions. generally, the extraction is carried out between 0 and 100 ° C, preferably between 20 and 70 ° C.

After the extraction, the aqueous solution is free from iron (III) 81 0 2 2 3 6 -5-> · 4 and ready for further treatment, e.g., alumina precipitation.

The extraction solvent loaded with iron (III) flows into the stripping cycle, where about 0.05-20.0 parts by volume. of a solution of a sulfuric acid, preferably 0.1-0.5 parts by volume. is brought into contact with a vol.dl. of the solvent. As a result, the iron (IIl) moves to the water phase in the form of a soluble salt of the sulfuric acid used. Phase contact can be realized with mixer settlers or other suitable devices. Various mixer-10 settlers, usually about 1-10 and most preferably about 1-6, which are connected in series are normally required to process the desired amount of iron (III) to be stripped. Stripping is generally performed between 0 and 100 ° C, most preferably between 20 and 70 ° C.

The stripped iron (III) -free solvent is recycled to the extraction cycle to treat incoming iron (III) containing aqueous solutions. From. sulfuric acid from the stripping cycle, containing the dissolved iron (III) salts, can be discarded or treated to remove iron therefrom, e.g. by electrolysis and recycled to the stripping cycle.

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

Applications where the method of the invention may be used include, but are not limited to, extractions from aqueous solutions of cobalt, nickel, rare earth, uranium, vana-25 diurn, copper, alum, zinc and silver to include only one number.

The invention is further illustrated by the following examples. These examples are for illustrative purposes only and not to limit the invention. All parts and percentages are by weight unless otherwise indicated.

Example I

An oxidized solution of alum containing iron (III) sulfate 3+ 3, equivalent to 1 ^ -70 micrograms Fe / cm was introduced at a rate of 1000 cm ^ / min. fed into an extraction cycle, which consisted of four stage mixer settlers. There, the solution was contacted in a continuous, countercurrent manner at 35H0 ° C with an extraction solvent containing U.5 vol. # BEHP, 3 vol. # Ρ0Ρ0 and 92.5 vol. # 3 kerosene in an amount of 500 cm per min was added to give a 2: 1 volume ratio water phase: organic phase 81 0 2 2 3 6 φ. ± '! ""; : "-! -6-. After not extracting four at this ratio, an aqueous alum solution containing about 5.0 micrograms of 3 + 3 · 3 Fe · cm was obtained at a rate of about 1000 cm per minute.

Example II

The iron-loaded, organic extraction solvent from 3+ 3 Example I, containing about 2955 micrograms Fe / cm, exited the extraction cycle at an amount of about 500 cm per minute and was fed to a stripping cycle. Here, the coni-10 was now contacted in three countercurrent mixer settier stages at 50 ° C with a strip feed consisting of a solution of sulfuric acid in water. The sulfuric acid solution, containing 200 g of sulfuric acid per

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liters of solution were fed at a rate of 100 cm <7> 7 minutes to obtain a volume ratio of aqueous phase: organic phase of Q2. After the three stripping steps at this ratio, an acidic 3+ 3 stripping liquid was obtained, which contained 1 ^ .650 micrograms Fe / cm 3 at a rate of about 100 cm / minute.

3+ /

The stripped organic phase, containing about 25 micrograms Fe / 3cm, was recovered and recycled at a rate of about 500cm / min to the extraction cycle of Example I, where it was used for the next iron extraction from entering, iron-containing alum solution.

Examples III-V

Iron-loaded organic solutions, which provide about 3g 3+ each. ·.

Containing 25 Fe per liter were prepared by extracting sulfuric acid containing alum solutions with the following extraction solvents. Extraction solvent A: kt5% BEHP, 3 vol. # TQP0, 92.5 vol. # Kerosene, extraction solvent B: J, 5 vol. # BEHP, 92.5 vol. # Kerosene, extraction solvent C: U, 5 vol. # BEHP , 95.5 vol. # Kerosene.

The iron-loaded solutions were then stripped by contact with aqueous sulfuric acid (200 g / l) in an amount to give an aqueous to organic phase volume ratio of 0.2 at U0 ° C, for varying numbers of mixer set tiert rappen, and the iron (III) content of the stripped organic phase was measured. The results obtained are shown below.

81 0 2 2 3 6 -7-

Solvent Number of mixer settler- Fe (III) concentration of stripped organic stripped phase (µg / cm ^) _ A. 3 25 B 14. 700 C 6 120

The above results show that the presence of Ρ0 oplosmiddel0 in the iron-loaded solvent greatly facilitates stripping Tan iron (III) therefrom.

jq Example VI

An oxidized solution of alum containing iron (III) sulfate 3+ 3 in an amount equivalent to 523 micrograms Fe / s, which had a pH of 2.6 and contained 8.08 wt.% Aluminum enzyme, was heated at 2h ° C extracted using a Burrell wrist action shaker with an equal volume amount of an extraction solvent, which consisted of 5 vol. # TOPQ and 95 vol. # kerosene. The two-phase liquid mixture was allowed to settle when the water phase was separated. Analysis of the water phase showed that only 2J, h% of the 3+.

The organic phase was extracted.

Examples VII-XIV

The procedure of Example VI was followed, it being understood that the 5 vol. Extractant used consisted of a mixture of BEHP and 100%. The Ρ0Ρ0 content in the extractant was varied from 0 to 50 vol. The aqueous phase, obtained after separation of the organic 3+ phase, was analyzed for Fe and aluminum to obtain extraction coefficients (E0 ^) and to calculate separation factors (S ^). The results obtained, summarized in Table A below, show that the optimum extractant composition for minimizing the aluminum extraction, while maintaining a high iron (III) extraction, ranges from + 0 to 50 vol. # Τ0Ρ0 is located.

81 02 2 3 6 -8-

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Example XV

Following the procedure of Example I in every material detail except that the extraction solvent now contained phenyl dihydrogen or phosphate, tris (2-ethylhexyl) phosphine oxide and benzene, nearly the same results were obtained.

Example XVI

Following the procedure of Example I in every material detail except that the extraction solvent now contained octyl trihydrogen diphosphate, tricylohexylphosphine oxide and toluene, almost the same results were obtained.

Examples XVII-XIX “

According to the procedure of Example I in every material detail, except that instead of the sulfuric acid solution, solutions of resp. hydrochloric acid, hydrogen fluoride and nitric acid were used, almost the same results were obtained.

Example XX

An aqueous caustic liquor with a concentration of 35 g / 1 Cu * 2, 5 g / 1 Fe 3 *, 10 g / 1 HgSO 2, 11 g / 1 Al 3 * and 2 g / l Cl "and a pH of 1.5 was contacted with an extraction solvent in portions with water / organic phase (A / O) volume ratios of 5.2 and t at 2k ° C for 5 minutes. The separation was adjusted to the pH of the phase using HaOH. pH of 1.5 and the contact was repeated until a constant equilibrium pH of 1.5 was obtained Test data and results are shown in Table B.

Example XXI

Following the procedure of Example XX in every material detail, except that a different extraction solvent was used, test data and results were obtained as shown in Table B.

TABLE B

30 Iron extraction isotherms (2 ^ ° C) 3+ equilibrium Fe Concentration (g / 1)

Example XX: 10% BEHP + %% Τ0Ρ0 in kerosene.

A / 0 Organic Aqueous% Cu extracted 5 7.75 2.60 1.5 2 5.72 1.29 3.6 1 3.93 0.22 0 81 0223 6 Ϋ ** f · * "ϊ1" “1 —1 1 «-„ - -1 —11 —1 τι (-10-

Example XXI: 10 $ ΒΕΚΡ + 6.7 $ ΤΟΡΟ in kerosene.

Α / Ο Organic Aqueous $ Cu extracted 5 8.25 2, k> 0 2 6.3b 0.88 1.6 5 1 3.88 0.17 0

Example XII

An aqueous caustic liquor with a concentration of 15.2 g / 1 Fe3 +, 22 g / 1 Cu2 +, 3 g / 1 Ag1 +, 20 g / 1 HgSO 2 and a pH of 1.5 was contacted at 50 ° C for 10 minutes charged with an extraction solvent in portions of organic phase / aqueous phase (0 / A) volume ratios of 6, k and 2. Ha the separation, the pH of the aqueous phase was adjusted using a 50% HaOH solution to a pH of 1.5 and the contact was repeated until a constant equilibrium pH was reached. Test data and results are shown in Table C.

15 TABLE C

10 $ BEHP + 6.7 $ Τ0Ρ0 in kerosene $ Extraction separation factors 0 / A Fe Ag Cu Fe / Ag Fe / Cu 2 92.8 2.8 0.1 U57 6.387 20 k 98.0 7.2 0.1 629 11,912 6 99.0 17.2 0.1 kJ9 16.660

Example XXIII

An aqueous lye liquid with a concentration of 2 g / 1

Fe3 +, 2 g / 1 Cu2 +, 2 g / l Zn2 +, 2 g / 1 Co2 +, 2 g / 1 ITi2 +, 2 g / 1 VU +, 3+ 25 2 g / 1 Eu with a pH adjusted to 1.0 using of H 2 SO 4, was contacted at 50 ° C for 10 minutes with an extraction solvent in portions with aqueous phase / organic phase (A / O) volume ratios of 4.2, 1. Test data and results are shown in Table D.

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: Example XXIV

An aqueous caustic liquor at a concentration of 2 g / l Fe ^ +, 2 g / l V * + with a pH with H ^ SO ^ adjusted to 1.0. was contacted with an extraction solvent 5 at 50 ° C for 10 minutes in portions with aqueous phase / organic phase (A / 0) volume ratios of U, 2 and 1. Test data and results are shown in Table E.

TABLE · E

7.5 $ BEHP + 5.1 $ TOPO in kerosene $ Extraction Separation Factors

10 A / 0 Fe V Fe / V

b 57.3 6.1 21 2 80.1 12.6 28 1 9b, k 22.2 58

Example XXV

15 Sen aqueous caustic liquid with a concentration of 2 g / l 3+ 2 ^, 2+

Fe, 2 g / l Co, and 2 g / l Ni and a pH of 1.5, adjusted with HgSO 4, were contacted at 50 ° C for 10 minutes with an extraction solvent in volume ratio aqueous phase / organic phase proportions. (A / 0) of 2 and 1. Test data and results 20 are shown in Table F.

TABLE F

7.5 $ BEHP + 5.1 $ Τ0Ρ0 in kerosene $ Extraction Separation Factors A / 0 Fe Co Ni Fe / Co 'Fé / Ni 25k 70.6 0 0 00 2 90.3 1.0 1.0 2k7 2k6 1 100.0 1.0 1.0 ^> 0

Example XXVI -

An aqueous caustic liquor with a concentration of 2 g / l 3+ 2+ 30 Fe, 2 g / l Zn and a pH adjusted to 0.8 with H 2 SO 4 was contacted at 50 ° C for 10 minutes charged with an extraction solvent, in portions with aqueous / organic phase (A / 0) volume ratios of U, 2 and 1. Test data and results are shown in Table G.

81 0 2 2 3 6 -13-

TABLE G

7.5 # BEEP + 5.1 # TOPO in kerosene% Extraction Separation Factors A / O Fe Zn Fe / Zn 5 b 29.6 1.8 23 2 55.1 1.8 66 1 82.1 1.8 366

Example XXVII

An aqueous lye liquor with a concentration of 15 g / l 10 Fe3 *, 22 g / l Cu2 +, 3 g / l Ag + and a pH of 0.76, adjusted with B ^ SO ^, was stirred at 50 ° C for 10 minutes contacted with an extraction solvent containing 10 # BEHP, 6.7 # TOPO in kerosene in portions with an organic / water phase (Ο / A) volume ratio of 2.

3Yes the separation, the solvent containing the extracted metals was then separated into portions. A portion of this 3+ loaded solvent was analyzed and found to contain 2.77 g / l Fe and 30.0 micrograms / cm3 Ag +. A second portion of the loaded solvent was contacted with 20 g / l sulfuric acid for 5 minutes at 50 ° C at an O / A ratio of 1. Test results showed that 95 # of the Ag and 0.2 # of the Fe were washed from the solvent.

81 02 23 6

Claims (15)

1. A method for removing iron (IH) from an aqueous iron (III) "containing solution, characterized in that the solution is contacted with an extraction solvent, an extractant and, optionally, a water-immiscible organic diluent. wherein the extractant comprises a mixture of about 1-10 parts by volume of an organophosphoric acid with at least 6 carbon atoms and about 1 part by volume of a tertiary (C 1 -C 6 q) phosphine oxide and the liquid mixture give the opportunity to separate into two phases and separate the aqueous phase from the extraction solvent loaded with iron (III). 2. Process according to claim 1, characterized in that the remaining iron (III) -loaded extraction solvent is additionally contacted with an aqueous solution of a sulfuric acid to strip the iron (III) into the aqueous phase. the iron (HI) containing water phase is separated; and the stripped extraction solvent is recovered for reuse in the extraction process. Process according to claim 1 or 2, characterized in that the organorphosphoric acid is a dialkyl (Cg-C 1 g) hydrogen phosphate. 20 i +. Process according to claim 3, characterized in that the dialkyl (C 8 -C 20 g) hydrogen phosphate bis (2-ethylhexyl) vessel is dust phosphate. Process according to claim 1 or 2, characterized in that the tertiary C 1 -C 2 Q phosphine oxide is tri-n-octyl phosphine oxide. 6. Process according to claim 1 or 2, characterized in that the water-immiscible organic diluent is an aliphatic or aromatic petroleum distillate. The process according to claim 1 or 2, characterized in that the extractant consists of about 50-75 vol. Bis (2-ethylhexyl) hydrogen phosphate and about 50-25 vol. Tri-n-octyl phosphine oxide. The process according to claim 2, characterized in that a volume part of the residual iron (III) loaded extraction solvent is contacted with about 0.05-20 parts by volume. of an aqueous sulfuric acid solution containing more than 100 g of sulfuric acid per liter of solution. 9. Process according to claim 1 or 2, characterized in that the starting aqueous iron (III) solution contains aluminum. Method according to claim 1 or 2, characterized in that 8102236 -15-. the starting aqueous solution of iron (III) contains copper. A method according to claim 1 or 2, characterized in that the starting aqueous iron (III) solution contains vanadium. A method according to claim 1 or 2, with the. characterized in that the starting aqueous iron (III) solution contains cobalt. Process according to claim 1 or 2, characterized in that the starting aqueous iron (III) solution contains rare earths. 10 1¾. Process according to claim 1 or 2, characterized in that the starting aqueous iron (III) solution contains silver, Process according to claim 1 or 2, characterized in that the starting aqueous iron (IIl) solution contains nickel. 16. A process according to claim 1 or 2, characterized in that the starting aqueous iron (HI) solution contains zinc. Process according to claim 1 or 2, characterized in that the starting aqueous iron (II) solution contains europium. 18. Process according to claim 1 or 2, characterized in that the starting aqueous iron (III) solution contains uranium. 8102236