METHODS FOR EXTRACTING AND RETRIEVING THE URANIUM PRESENT IN AN AQUEOUS SOLUTION INCLUDING PHOSPHORIC ACID
20180355457 ยท 2018-12-13
Inventors
- Laure DEHUYSER (Limoges, FR)
- Hamid MOKHTARI (Boisseuil, FR)
- Pascal NARDOUX (Panazol, FR)
- Philippe MOREL (Dinsac, FR)
- Yvon PREVOST (Bessines Sur Gartempe, FR)
- Christophe ROYE (Saint-Aignan, FR)
Cpc classification
International classification
Abstract
A method for extracting uranium (VI) from an aqueous solution including phosphoric acid, which includes placing the aqueous solution 5 in contact with an organic material, followed by separating the aqueous solution and the organic material. The organic material includes a solid polymer substrate impregnated with a compound having the following general formula (I):
##STR00001##
The invention also relates to a method for retrieving uranium (VI) from an aqueous solution including phosphoric acid.
Claims
1. Method for extracting uranium(VI) from an aqueous solution S comprising phosphoric acid, this method including placing the aqueous solution S in contact with an organic material, followed by separation of the aqueous solution and the organic material, characterized in that the organic material comprises a solid polymeric substrate impregnated with a compound meeting following general formula: ##STR00005## where: m is an integer of 0, 1 or 2; R.sup.1 and R.sup.2, the same or different, are a linear or branched, saturated or unsaturated hydrocarbon group having 6 to 12 carbon atoms; R.sup.3 is: a hydrogen atom; a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 12 carbon atoms and optionally one or more heteroatoms; a saturated or unsaturated hydrocarbon group comprising one or more rings of 3 to 8 carbon atoms, the ring(s) optionally comprising one or more heteroatoms; or an aryl group comprising one or more rings, the ring(s) optionally comprising one or more heteroatoms; or else R.sup.2 and R.sup.3 together form a group (CH.sub.2).sub.n where n is an integer ranging from 1 to 4; R.sup.4 is: a linear or branched, saturated or unsaturated hydrocarbon group having 2 to 8 carbon atoms; a saturated or unsaturated hydrocarbon group comprising one or more rings, the ring(s) optionally comprising one or more heteroatoms; or an aromatic group comprising one or more rings, the ring(s) optionally comprising one or more heteroatoms; and R.sup.5 is a hydrogen atom or a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 12 carbon atoms.
2. The extraction method according to claim 1, wherein the compound meets the following particular formula (I-a): ##STR00006## where: R.sup.1 and R.sup.2 are an alkyl group having 8 to 10 carbon atoms; one from among R.sup.3 and R.sup.5 is a hydrogen atom and the other from among R.sup.3 and R.sup.5 is an alkyl group having 4 to 10 carbon atoms; and R.sup.4 is an alkyl group having 4 to 6 carbon atoms.
3. The extraction method according to claim 1, wherein the compound is selected from among: ethyl 1-(N,N-diethylhexylcarbamoyl)ethylphosphonate, meeting the particular formula (I-a) where R.sup.1 and R.sup.2 are both a 2-ethylhexyl group, R.sup.4 is an ethyl group, one from among R.sup.3 and R.sup.5 is a hydrogen atom whilst the other from among R.sup.3 and R.sup.5 is a methyl group; ethyl 1-(N,N-diethylhexylcarbamoyl)nonylphosphonate, meeting the particular formula (I-a) where R.sup.1 and R.sup.2 are both a 2-ethylhexyl group, R.sup.4 is an ethyl group, one from among R.sup.3 and R.sup.5 is a hydrogen atom whilst the other from among R.sup.3 and R.sup.5 is an n-octyl group; butyl 1-(N,N-diethylhexylcarbamoyl)nonylphosphonate, meeting the particular formula (I-a) where R.sup.1 and R.sup.2 are both a 2-ethylhexyl group, R.sup.4 is an n-butyl group, one from among R.sup.3 and R.sup.5 is a hydrogen atom whilst the other from among R.sup.3 and R.sup.5 is an n-octyl group; butyl 1-(N,N-dioctylcarbamoyl)nonylphosphonate, meeting the particular formula (I-a) where R.sup.1 and R.sup.2 are both an n-octyl group, R.sup.4 is an n-butyl group, one from among R.sup.3 and R.sup.5 is a hydrogen atom whilst the other from among R.sup.3 and R.sup.5 is an n-octyl group; and isopropyl 1-(N,N-diethylhexylcarbamoyl)nonylphosphonate, denoted DEHCNPIP, meeting the particular formula (I-a) above where R.sup.1 and R.sup.2 are both a 2-ethylhexyl group, R.sup.4 is an isopropyl group, one from among R.sup.3 and R.sup.5 is a hydrogen atom whilst the other from among R.sup.3 and R.sup.5 is an n-octyl group, the compound preferably being butyl 1-(N,N-diethylhexylcarbamoyl)nonylphosphonate.
4. The extraction method according to claim 1, wherein the solid polymeric substrate is formed of a polymer comprising at least one repeat unit selected from among an olefin unit, benzene unit, acrylic ester unit and mixtures of these units, this polymer advantageously being a divinylbenzene/styrene copolymer or an acrylic ester polymer.
5. The extraction method according to claim 1, wherein the solid polymeric substrate has a specific surface area, determined by the BET method, of between 300 m.sup.2/g and 1000 m.sup.2/g.
6. The extraction method according to claim 1, wherein the solid polymeric substrate is in the form of beads of which at least 90% by number advantageously have a mean bead size d.sub.90 of between 200 m and 900 m.
7. The extraction method according to claim 1, wherein the organic material comprises at least 2.5 wt. %, advantageously from 10 wt. % to 70 wt. % and, preferably, from 20 wt. % to 60 wt. % of compound.
8. The extraction method according to claim 1, wherein the contacting of the aqueous solution S with the solid organic material comprises at least one circulation of a mobile phase formed by the aqueous solution S, on a stationary phase formed by the organic material.
9. Method for recovering uranium(VI) from an aqueous solution S comprising phosphoric acid, said method comprises: (a) extracting uranium(VI) from the aqueous solution S with an extraction method according to claim 1; and (b) placing the organic material obtained after step (a) in contact with a basic aqueous solution, followed by separation of the organic material and the basic aqueous solution after which uranium(VI) is recovered in the basic aqueous solution.
10. The recovery method according to claim 9, wherein the placing in contact of the organic material obtained after step (a) with the basic aqueous solution comprises the eluting, with a mobile phase formed by the basic aqueous solution, of a stationary phase formed by the organic material.
11. The recovery method according to claim 9, wherein the basic aqueous solution has a pH of 8 or higher, advantageously of between 8.5 and 12 and, preferably, of between 9 and 11.
12. The recovery method according to claim 9, wherein the basic aqueous solution is an aqueous solution of an alkaline metal salt or ammonium salt, the salt being advantageously selected from among a carbonate and the metal being advantageously selected from among sodium and potassium.
13. The recovery method according to claim 9, further comprising regeneration of the organic material, the regeneration comprising, after step (b): (c) placing the organic material obtained after step (b) in contact with an acid aqueous solution, followed by separation of the organic material and the acid aqueous solution after which the organic material is regenerated.
14. The recovery method according to claim 14, further comprising, between steps (b) and (c): (b) washing with water of the organic material separated at step (b).
15. The recovery method according to claim 13, wherein the contacting of the organic material separated at step (b), and optionally washed at step (b), with the acid aqueous solution comprises at least one washing with a mobile phase formed by the acid aqueous solution, on a stationary phase formed by the organic material.
16. The recovery method according to claim 13, wherein the aqueous acid solution has a concentration of if ions of 20 mol/L or less, advantageously between 0.1 mol/L and 10 mol/L and, preferably, between 1 mol/L and 7 mol/L.
17. The recovery method according to claim 13, wherein the aqueous acid solution comprises at least one inorganic acid selected from the group formed by sulfuric acid, nitric acid, phosphoric acid and hydrochloric acid, this inorganic acid being advantageously sulfuric acid.
18. The extraction method according to claim 1, wherein the aqueous solution S comprises at least 0.1 mol/L, advantageously from 1 mol/L to 10 mol/L, preferably from 2 mol/L to 9 mol/L and, more preferably, from 3 mol/L to 7 mol/L of phosphoric acid.
19. The extraction or recovery method according to claim 18, characterized in that the aqueous solution S is a solution resulting from attack of a natural phosphate by sulfuric acid.
20. The recovery method according to claim 9, wherein the aqueous solution S comprises at least 0.1 mol/L, advantageously from 1 mol/L to 10 mol/L, preferably from 2 mol/L to 9 mol/L and, more preferably, from 3 mol/L to 7 mol/L of phosphoric acid.
21. The extraction or recovery method according to claim 20, characterized in that the aqueous solution S is a solution resulting from attack of a natural phosphate by sulfuric acid.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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[0164]
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[0166]
[0167]
DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS
Example 1: Preparation of a Material According to the Invention
[0168] The preparation of the organic material, comprising a solid polymeric substrate and a compound meeting formula (I) detailed above, was carried out starting with the following compounds: [0169] the solid polymeric substrate, hereafter called resin: Amberlite XAD-7 trade mark resin marketed by the Dow Chemical Company. This resin, formed of an acrylic ester polymer, is in the form of beads having a particle size of between 250 m and 840 m, a specific surface area of 450 m.sup.2/g (BET method) and a pore diameter of 300 ; and [0170] the compound: butyl 1-(N,N-diethylhexylcarbamoyl)-nonylphosphonate, denoted DEHCNPB. This compound was synthesized in accordance with the teaching of document [2], by implementing steps A, B, C and E of the reaction scheme shown in FIG. 1 of this document [2].
[0171] Impregnation of the solid polymeric substrate with DEHCNPB was obtained by wet process.
[0172] For this process, the DEHCNPB was first dissolved in a volatile solvent. The mixture obtained was then placed in contact with the Amberlite XAD-7 resin for impregnation thereof with DEHCNPB.
[0173] The solvent was then evaporated in vacuo so that the resulting organic material was in the form of dry beads of impregnated resin, the weight proportion of DEHCNPB in the impregnated resin, or organic material, being 50 wt. %.
[0174] In the remainder of the present description, for ease of authoring, the expressions organic material and impregnated resin, which have the same meaning, are used.
Example 2: Properties of an Organic Material of the Invention to Extract and to Recover Uranium(VI) from Synthetic Aqueous Phosphoric Acid Solutions
[0175] 2.1 Evaluation of U(VI) Extraction Capacity by Contact Tests
[0176] The capacity of the organic material in Example 1 to extract uranium(VI) from aqueous phosphoric acid solutions was determined by contact tests conducted in accordance with the following protocol: [0177] 250 mg of impregnated resin such as obtained in Example 1 were mixed with 10 mL of an aqueous phosphoric acid solution formed by a synthetic aqueous phosphoric acid solution comprising 1 mol/L of phosphoric acid and varying concentrations of uranium(VI), and optionally iron(III); the redox potential of this synthetic aqueous phosphoric acid solution was 550 mV (in relation to the Ag/AgCl reference electrode); [0178] the mixture obtained was left under agitation for 23 h, at ambient temperature, using an incubator agitator; after which the solid and liquid phases forming this mixture were separated by filtration.
[0179] The concentrations of uranium(VI), determined by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), were measured: [0180] in the initial synthetic aqueous phosphoric acid solution, before contacting thereof with the organic material formed by the dry beads of impregnated resin; and [0181] in the liquid phase after contacting with the resin, or filtrate.
[0182] The difference found between the concentration of uranium(VI) in the initial synthetic solution and in the filtrate corresponds to the amount of uranium(VI) extracted by the organic material.
[0183] The uranium(VI) loading capacity of this impregnated resin corresponds to the amount of uranium(VI) extracted by this impregnated resin. This loading capacity, denoted C.sub.U and expressed in mg of uranium/g of impregnated resin (denoted mg U/g), was determined with the following formula:
where: [0184] C.sub.ini: concentration of uranium(VI) in the initial synthetic aqueous solution of phosphoric acid (in mg/L) [0185] C.sub.end: concentration of uranium(VI) in the filtrate (in mg/L) [0186] V.sub.solution: volume of initial synthetic aqueous solution of phosphoric acid contacted with the impregnated resin for 23 h (in L) [0187] m.sub.resin: weight of impregnated resin (in g)
[0188] The coefficient of distribution for uranium, denoted K.sub.d, was determined with the following formula:
where C.sub.U and C.sub.end have the same meaning as previously.
[0189] Table 1 below gives the results obtained with four initial synthetic aqueous solutions of phosphoric acid, denoted S1 to S4, having varying initial concentrations of uranium(VI) and optionally of iron(III).
TABLE-US-00001 TABLE 1 C.sub.ini of Fe(III) C.sub.ini of U(VI) C.sub.end of U(VI) C.sub.U Solution (g/L) (mg/L) (mg/L) (mg U/g) K.sub.d S1 245 1 9.7 9.7 S2 493 6 19.0 2.8 S3 3 225 5 8.6 1.7 S4 3 477 21 18.6 0.9
[0190] The results in Table 1 show that, for a same ratio of liquid phase to solid phase, denoted Liquid/Solid below, the impregnated resin allows the extraction of 9.7 g and 19.0 g of uranium(VI) per kg of impregnated resin from solutions S1 and S2 only comprising uranium(VI) in respective initial concentrations in the order of 250 mg/L and 500 mg/L.
[0191] It is to be noted that such results are much higher than those observed with a hybrid organic-inorganic material such as described in document [6]. In particular, with reference to the results in Table 1 on page 24 of this document [6], uranium(VI) loading capacities of 6.96 g and 9.72 g per kg of organic-inorganic hybrid material are respectively obtained with the same Liquid/Solid ratio, for initial synthetic aqueous phosphoric acid solutions comprising 1 mol/L of phosphoric acid and with concentrations of uranium(VI) slightly higher than those of solutions S1 and S2.
[0192] The results in Table 1 above also show that the impregnated resin allows selective extraction of uranium(VI) over iron(III). Indeed, with the above-cited Liquid/Solid ratios, loading capacities C.sub.U of 8.6 g and 18.6 g of uranium(VI) per kg of impregnated resin were obtained with solutions S3 and S4 comprising both uranium(VI) and iron(III). Such values, although slightly lower than those obtained with solutions S1 and S2, remain high.
[0193] By comparison, there is a loading capacity of 7.44 g of uranium(VI) per kg of hybrid organic-inorganic material described in Table 1 of document [6] with an initial synthetic aqueous solution of phosphoric acid comprising 1 mol/L of phosphoric acid and concentrations of 3295 mg/L of iron(III) and 374 mg/L of uranium(VI). With the same Liquid/Solid ratio and a lower concentration of uranium(VI) in solution S3, the loading capacity observed with the impregnated resin remains higher.
[0194] 2.2 Evaluation of U(VI) Extraction and Recovery Capacity by Column Tests
[0195] The capacity of the organic material in Example 1 to extract and then to recover the uranium(VI) contained in an aqueous phosphoric acid solution was also determined by column tests conducted following the protocol described below.
[0196] The loading capacity, denoted C.sub.U and expressed in g of uranium/L of impregnated resin (denoted g U/L), was calculated with the formula given below:
where: [0197] C.sub.ini: concentration of uranium(VI) in the initial synthetic aqueous solution of phosphoric acid (in g/L) [0198] C.sub.end: concentration of uranium(VI) in the samples collected at the sampler outlet (in g/L) [0199] V.sub.solution: volume of initial synthetic aqueous solution of phosphoric acid placed in contact with the impregnated resin (in L) [0200] V.sub.resin: volume of packed bed of impregnated resin (in L)
[0201] The impregnated resin such as obtained in Example 1 was hydrated with demineralised water to allow the sampling of 15 mL of a packed volume of impregnated resin. These 15 mL of hydrated and impregnated resin were placed in a column having a diameter of 2 cm, the height reached by the bed of impregnated resin being close to 40 mm (ratio between bed height and column diameter in the order of 2).
[0202] 2.2.1 Evaluation of Capacity to Extract U(VI) Contained in a Solution S5
[0203] An initial synthetic aqueous solution of phosphoric acid, denoted S5, having a redox potential of 550 mV (relative to the Ag/AgCl reference electrode), and comprising 1 mol/L of phosphoric acid and a concentration of uranium(VI) of 160 mg/L, was prepared and injected at 10 BV/h (BV meaning bed volume or volume of bed of impregnated resin) into the column comprising the impregnated resin.
[0204] A sampler was positioned at the outlet of the column to recover samples of the aqueous solution after contacting of the solution S5 with the impregnated resin. This aqueous solution was depleted of U(VI) since it had been extracted by the resin. The amount of uranium(VI) contained in each of the fractions of aqueous solution collected from the column was determined by ICP-AES and therefore corresponded to the amount of uranium(VI) that had not been extracted by the impregnated resin.
[0205] The amount of extracted uranium(VI) was inferred from the difference.
[0206] Appended
[0209] With reference to the breakthrough curve of uranium(VI) in this
[0210] The impregnated resin has a uranium(VI) loading capacity of 19.2 g of uranium/L, therefore indicating that 288 mg of uranium(VI) were extracted with this impregnated resin.
[0211] 2.2.2 Evaluation of the Capacity to Recover the U(VI) Extracted by the Impregnated Resin
[0212] After the extraction phase described in Chapter 2.2.1 above, the column was washed with demineralised water at 4 BV/h, to remove residual traces of phosphoric acid remaining on the impregnated resin.
[0213] The impregnated resin was then eluted with an aqueous 1.5 mol/L solution of sodium carbonate injected at 1 BV/h.
[0214] Fractions of eluate were collected at the column outlet to determine the volume thereof and the amount of U(VI) contained therein. These fractions recovered at regular intervals (every 2 h) and their characteristics are given in Table 2 below. Table 2 also gives the number of BVs of aqueous sodium carbonate solution used at these time intervals for the recovery of U(VI).
TABLE-US-00002 TABLE 2 Elapsed time (h) 2 4 6 8 10 12 14 Volume (ml) 24.8 26.4 27.1 25.7 25.2 25.7 35.1 Cumulative volume 24.8 51.2 78.3 104.0 129.2 154.9 190.0 (ml) BV 1.7 1.9 1.8 1.7 1.7 1.7 2.3 Cumulative BV 1.7 3.4 5.2 6.9 8.6 10.3 12.7 Quantity of eluted 173.7 94.8 8.0 3.9 2.7 2.1 2.2 U(VI), (mg) Cumulative quantity 173.7 268.5 276.5 280.4 283.1 285.2 287.4 of eluted U(VI), (mg) Cumulative elution 60.2 93.1 95.9 97.3 98.2 98.9 99.7 yield (%)
[0215] It follows from Table 2 above that the elution of uranium(VI) by the aqueous sodium carbonate solution is quantitative: more than 95% of the uranium(VI) initially extracted by the impregnated resin were eluted in 6 BVs.
[0216] After an elution time of 14 h, 99.7% of the uranium(VI) extracted by the resin had been recovered.
[0217] 2.2.3 Evaluation of the Capacity to Extract U(VI) Contained in Solution S6
[0218] An initial synthetic aqueous solution of phosphoric acid, denoted S6, having a redox potential of 500 mV (relative to the Ag/AgCl reference electrode) and comprising 1 mol/L of phosphoric acid, a concentration of uranium(VI) of 160 mg/L and a concentration of iron(III) of 2.9 g/L was prepared and injected into the column comprising the impregnated resin at 10 BV/h.
[0219] As previously, a sampler was positioned at the column outlet to determine by ICP-AES analysis the amount of uranium(VI) contained in each of the fractions of aqueous solution collected from the column, and via the difference, the amount of extracted uranium(VI).
[0220] The curves reflecting the changes in concentration of uranium(VI) found in the fractions of aqueous solution collected at the column outlet (denoted [U].sub.S6 and expressed in mg/L) and the trend in uranium(VI) loading capacity of the impregnated resin (denoted C.sub.U(S6) and expressed in g of uranium(VI)/L) as a function of the number of BVs are given in
[0221] It is observed that the loading capacity C.sub.U of the impregnated resin decreases slightly in the presence of iron (III) to tend towards a value of 15.5 g U(VI)/L (curve C.sub.U(S6)), compared with 19.2 g U(VI)/L in the presence of uranium alone (curve C.sub.U(S5)). The competition between the two elements U(VI) and Fe(III) is reflected by a breakthrough curve [U].sub.S6 whose plateau is reached more rapidly (at about 300 BVs) compared with 370 BVs for the solution S5 (curve [U].sub.S5).
[0222] It is specified that the amount of iron(III) extracted by the impregnated resin was not determined directly via the fractions of aqueous solution collected at the outlet of the sampler; the amount of iron extracted by the resin in each of the fractions remains too slight, compared with the 2.9 g Fe/L initially contained in solution S6; the delta for iron extracted in each of the fractions cannot therefore be measured.
[0223] Failing this, mineralisation of the resin was carried out to place its iron(III) content in solution. For this mineralisation, the resin is placed in solution to assay the amounts of uranium(VI) and iron(III). To do so, the resin is first calcined and then dissolved in nitric acid.
[0224] This mineralisation allowed the determination that the amount of iron(III) present on the impregnated resin was 21 mg, a value which corresponds to an iron(III) loading capacity of the impregnated resin, denoted C.sub.Fe, of 1.4 g iron(III)/L.
[0225] Therefore, out of the 370 BV flows, only 0.13% of iron(III) was extracted from solution S6, which proves to be very low.
2.2.4 Evaluation of the Capacity to Recover Iron(III) Present on the Impregnated Resin, after Elution of U(VI)
[0226] After the extraction phase described in Chapter 2.2.3 above, and as previously described in Chapter 2.2.2, the resin column was washed with water at 4 BV/h, followed by elution of the uranium(VI) present on the impregnated resin with an aqueous 1.5 mol/L solution of sodium carbonate injected at 1 BV/h.
[0227] After this elution with the aqueous sodium carbonate solution, uranium(VI) was recovered quantitatively in the eluate, but not iron(III). Indeed, in the presence of sodium carbonate, iron(III) is precipitated on the resin in the form of iron hydroxide Fe(OH).sub.3. In addition, as seen in Chapter 2.2.3 above, by means of the selectivity of the compound meeting general formula (I), there is practically no extraction of iron (III) by the impregnated resin. The amount of iron(III) hydroxide precipitate on the resin is therefore small and does not perturb the flow of the aqueous solutions of sodium carbonate or of sulfuric acid in the resin column.
[0228] After eluting the U(VI), the column was washed a second time with demineralised water at 4 BV/h, followed by elution of the resin column using an aqueous 3.5 mol/L solution of sulfuric acid at 1 BV/h to recover iron(III).
[0229] This elution allows the impregnated resin to be depleted of the iron present in the form of Fe(OH).sub.3 and allows regeneration of the DEHCNPB extractant of the impregnated resin. The phosphonic acid function of the extractant, that was deprotonated at the elution step with the aqueous sodium carbonate solution, is reprotonated when eluting with the aqueous sulfuric acid solution.
[0230] The impregnated resin is then ready for a new extraction/stripping cycle.
[0231] To support of these facts, monitoring of iron(III) was carried out.
[0232] Fractions of aqueous solution were collected at the column outlet at regular intervals (every 2 h) when eluting with this aqueous solution of sulfuric acid, and then analysed.
[0233] The characteristics of these fractions (volume or amount of eluted iron(III)) are given in Table 3 below. This Table 3 also indicates the number of BVs used over these time intervals.
[0234] It is recalled that, when eluting uranium(VI) with the sodium carbonate solution, only 1.5 mg of iron(III) was previously eluted.
TABLE-US-00003 TABLE 3 Elapsed time (h) 2 4 6 8 10 12 14 Volume (ml) 26.5 28.8 29.8 28.0 28.2 27.8 20.2 Cumulative volume 26.5 55.3 85.0 113.0 141.2 169 189.2 (ml) BV 1.8 1.9 2.0 1.9 1.9 1.8 1.3 Cumulative BV 1.8 3.7 5.7 7.5 9.4 11.3 12.6 Quantity. of collected 4.1 6.2 4.4 1.8 0.9 0.5 0.0 Fe(III) (mg) Cumulative quantity. 4.1 10.3 14.7 16.5 17.4 17.9 17.9 of collected Fe(III) (mg) Consumed H.sup.+ (eq/L) 3.8 6.7 7.0 7.3 7.3 7.2 7.3 Concentration of 1.9 3.3 3.5 3.6 3.6 3.6 3.6 H.sub.2SO.sub.4 (mol/L)
[0235] After elution with the 3.5 mol/L aqueous sulfuric acid solution, the impregnated resin was mineralised after which it was shown that this resin only contained 112 mg of Fe(III)/L. This iron(III) loading capacity of the impregnated resin, denoted C.sub.Fe, is particularly low since it only represents 1.6 mg Fe, i.e. 7% of the complexed iron initially on the resin.
[0236] This elution with 3.5 mol/L aqueous solution of sulfuric acid allowed good removal of iron (yield of 85%) and regeneration of the impregnated resin. This regeneration can be demonstrated by assay, using sodium hydroxide, of the acidity of each of the fractions of aqueous acid solution collected after elution. The results obtained are also given in Table 3 above.
[0237] It is observed that for the first two collected fractions, 45% and 5% of the sulfuric acid of the initial 3.5 mol/L aqueous solution of sulfuric acid used for this elution were indeed consumed to regenerate the resin extractant and simultaneously carry out iron removal.
[0238] 2.2.5 Comparison Between Capacities to Extract U(VI) Contained in a Solution S7 and to Recover this U(VI) and Fe(III) Extracted by the Resin
[0239] An initial synthetic aqueous solution of phosphoric acid, denoted S7, comprising 1 mol/L of phosphoric acid, a concentration of uranium(VI) of 151 mg/L and a concentration of iron(III) of 2.9 g/L was prepared and injected, at 10 BV/h, into three columns of the type described above in Chapter 2.2 but respectively comprising: [0240] 15 mL of impregnated resin, or organic material, conforming to the invention, denoted Ri, [0241] 15 mL of a resin, denoted R1, formed by a styrene/divinylbenzene copolymer and phosphonic groups in sodium form, marketed under the trade name Lewatit TP 260; and [0242] 15 mL of a resin, denoted R2, formed by a crosslinked polystyrene and di-(2-ethylhexyl) phosphoric acid groups (D.sub.2EHPA), marketed under the trade name Lewatit VP OC 1026.
[0243] It is specified that these resins R1 and R2, both marketed by the Lanxess Company, are known for the extraction and recovery of uranium(VI) contained in aqueous phosphoric acid solutions. In particular, resin R1 is one of the resins potentially used in document [5].
[0244] With reference to
[0245] For each of the solid polymeric substrates, the U(VI) loading capacity was determined by measuring the uranium concentrations in all the fractions collected at the column outlet. After extraction and stripping of uranium(VI), each of these resins was mineralised to determine the amounts of iron(III) extracted by each of these resins Ri, R1 and R2.
[0246] The corresponding results, and the calculated values allowing determination of the selectivity of extraction of uranium(VI) over iron(III), are given in Table 4 below.
TABLE-US-00004 TABLE 4 U(VI) loading Fe(III) loading Fe(III)/U(VI) ratio Resin capacity (g U(VI)/L) capacity (g Fe(III)/L) (%) Ri 15.5 1.4 9.0 R1 2.7 24.5 918 R2 1.7 3.3 191
[0247] It follows from the data in Table 4 above that the impregnated resin Ri used in the method of the invention allows values to be reached for uranium(VI) loading capacity, and hence for extraction, that are distinctly higher than those obtained with the commercial resins R1 and R2 commonly used to extract uranium (VI) from aqueous phosphoric acid solutions. In addition, the impregnated resin Ri also allows the extraction of this uranium(VI) with selectivity over iron(III) that is undeniably greater than that imparted by these resins R1 and R2.
Example 3: Properties of the Material of the Invention for the Extraction and Recovery of Uranium(VI) from Aqueous Phosphoric Acid Solutions
[0248] The three resins Ri, R1 and R2 used in Chapter 2.2.5 above were evaluated for their performance in extracting uranium(VI) contained in an aqueous phosphoric acid solution formed no longer by a synthetic solution but by an industrial solution.
[0249] This industrial solution, denoted SI, initially comprised 5 mol/L of phosphoric acid, 130 mg/L of uranium(VI) and 2.8 g/L of iron(III) with a redox potential of 490 mV (relative to the Ag/AgCl reference electrode).
[0250] As previously, 15 mL of each of the resins Ri, R1 and R2 were placed in a column having a diameter of 2 cm until a bed height of 40 mm was reached, to obtain a ratio of 2 between bed height and column diameter.
[0251] The industrial solution SI was injected into each of the columns at a rate of 10 BV/h for a time of 26 h.
[0252] The breakthrough curves, reflecting the changes in the concentration of uranium(VI) found in the fractions of aqueous solution collected at the column outlet, as a function of number of BVs, are given in
[0253] This
[0254] With reference to
[0255] The decrease in loading capacity of uranium(VI) that is here observed compared with that of 15.5 g U(VI)/L measured in Chapter 2.2.3 (curve C.sub.U(S6)) can be explained by the concentration of phosphoric acid in the aqueous solution SI from which it is desired to extract uranium(VI). Indeed, at a concentration of 5 mol/L of phosphoric acid, and no longer of only 1 mol/L, uranium(VI) is more strongly complexed in this aqueous solution S1 and is therefore more difficult to extract.
[0256] For each of the solid polymeric substrates, the U(VI) loading capacity was determined by measuring the uranium(VI) concentrations in all the fractions collected at the outlet of the column. After extraction followed by stripping of uranium(VI), the organic materials were mineralised on each of the three columns to determine the amounts of iron(III) extracted by each of the resins Ri, R1 and R2.
[0257] The corresponding results, and the calculated values allowing determination of the selectivity of extraction of uranium(VI) over iron(III), are given in Table 5 below.
TABLE-US-00005 TABLE 5 U(VI) loading Fe(III) loading Fe(III)/U(VI) ratio Resin capacity (g U(VI)/L) capacity (g Fe(III)/L) (%) Ri 6.9 0.74 11 R1 1.0 16.2 1620 R2 0.1 0.46 460
[0258] Table 5 confirms the decrease in loading capacity of uranium(VI) but also of iron (III) with the increased molar concentration of phosphoric acid in the aqueous solution from which it is desired to extract uranium.
[0259] However, it is undeniable that the impregnated resin used in the extraction and recovery methods conforming to the invention by far is the best compromise for the extraction of uranium(VI), and in a manner that is particularly selective with regard to iron(III).
BIBLIOGRAPHY
[0260] [1] U.S. Pat. No. 3,711,591
[2] WO 2013/167516 A1
[0261] [3] U.S. Pat. No. 4,599,221
[4] U.S. Pat. No. 4,402,917
[5] WO 2014/018422 A1
[6] WO 2014/127860 A1