NL8000832A - PROCESS FOR THE EXTRACTION OF URANIUM FROM WET PROCESS PHOSPHORIC ACID. - Google Patents

Description

STAMICARBON B.V. '

Inventors: Cornells A.M. WETERINGS in Stein Johannes A. JANSSEN in Schinveld 1 3158

, PROCESS FOR THE EXTRACTION OF URANIUM FROM WET PROCESS PHOSPHORIC ACID

The invention relates to a process for the recovery of uranium from wet-process phosphoric acid by liquid-liquid extraction with organic phosphoric acid esters.

Such a method is known from Ind. and Eng. Chem 49 5 (1957) No. 4, p. 628-638, wherein alkyl phosphates and alkyl pyrophosphates are mentioned as extractants, Ind. Spooky. Chem. 3 (1972) No. 1, p. 122-128 and JL3 (1974) No. 3, p. 286-291, wherein as extractants mixtures of alkyl phosphates and trialkyl phosphine oxides, respectively. mixtures of alkyl phenyl phosphates dissolved in an aliphatic hydrocarbon, such as kerosene.

A drawback of this known method is that only a part of the uranium present in the phosphoric acid is extracted, so that several extraction steps are required. In this extraction treatment, part of the extractant is lost with the phosphoric acid solution, which, in view of the very high price of the extractants, considerably increases the cost of the process.

The invention now provides a method in which it is equal to extract uranium from wet-process phosphoric acid with a considerably smaller amount of extractant than in the known method and in which the losses of extractant are also considerably lower.

This is achieved according to the invention by adjusting the sulfate content of the phosphoric acid to be extracted to a value of less than 2% by weight, calculated relative to the weight of PgO. in the phosphoric acid, by adding a divalent metal compound which reacts with sulfate ions to form a phosphoric acid insoluble sulfate, and separating the metal sulfate precipitate formed.

Preferably, the sulfate content of the phosphoric acid to be extracted is adjusted to a value of less than 0.6% by weight, calculated relative to the weight amount of P0 in the phosphoric acid.

Λ 5

Examples of suitable metal compounds are oxides, hydroxides, and salts, such as carbonates, sulfides, nitrates, phosphates 8000832 2 and chlorides, of calcium, magnesium and barium. Mixtures of such compounds can also be used.

A calcium and / or barium compound is preferably used as the metal compound. Particularly suitable calcium and / or barium compounds are carbonates and sulfides, because when these are used the anions do not remain in the phosphoric acid.

The amount of metal compound to be added is not critical, it should only be sufficient to react with so much sulfate in the phosphoric acid that the residual sulfate content is calculated below 10 2 wt%, preferably below 0.6 wt%, relative to the weight amount of PgO,., K®. Preferably an amount of metal compound is used which is at least equivalent to the amount of sulfate in the phosphoric acid to be extracted. If a metal compound is used which also reacts with other components present in the phosphoric acid, the amount of metal compound to be added must of course be adjusted.

The metal sulfate precipitate formed after the addition of the metal compound can be separated from the phosphoric acid in various ways, for example by filtration, centrifugation, decantation.

In addition to the insoluble metal sulfate formed, the precipitate contains part of the fluorine compounds and metal impurities present in the wet-process phosphoric acid. The amount of these impurities in the precipitate is determined, inter alia, by the nature and amount of the metal compound used and the type of wet-process phosphoric acid used. The precipitate can be worked up in various ways, optionally with recovery of the original metal sulfate-reactive metal compound.

The method according to the invention can be used in combination with various known extraction agents for uranium, such as a mixture of di (2-ethylhexyl) phosphoric acid and trioctyl phosphine oxide in kerosene, or a mixture of mono and dioctylphenyl phosphoric acids. in kerosene. The uranium can also be recovered from the extraction medium in a known manner, for example by precipitation with the aid of ammonium carbonate.

The method according to the invention can in principle be applied to various types of wet-process phosphoric acid. However, since it has been found that the uranium extraction efficiency decreases with increasing PoO content of the phosphoric acid, dilute 8000832 if 3 phosphoric acid is used, for example, with a PgO content of 30% by weight or less. It has further been found that the uranium extraction efficiency is adversely affected by soluble fluorine compounds in the phosphoric acid. In the process according to the invention, a part of these fluorine compounds is separated from the phosphoric acid with the metal sulphate precipitate, so that further fluorine removal is usually not necessary. When starting from a wet process phosphoric acid with a high fluorine content, the fluorine content can be reduced by adding an excess of reactive metal compound relative to the sulphate to be removed and / or by adding silicon compounds, optionally mixed with alkali compounds. Preferably, the fluorine content of the phosphoric acid to be extracted is set at a value of less than 0.7% by weight, calculated with respect to the weight by weight of PgOg phosphoric acid.

The invention is further illustrated in the following previews.

Example 1 Test no, 1

In a beaker, 100 grams of wet process phosphoric acid, with a ^ 2 ^ 5 content of wt%, an SO 2 content of 1.5 wt%, a fluorine stop at 1.2 % by weight and a uranium content of 120 ppm. Then, with stirring, a 1 wt.% Solution of a flocculant was added in an amount of 4 ml of flocculane / liter of phosphoric acid. The clear top layer was then separated from the precipitate formed, which contained most of the organic impurities and inert components contained in the phosphoric acid.

To the liquid thus separated, an amount of solid BaCO was added with stirring in a 40% by weight excess relative to

O

sulfate. This practically immediately produced a precipitate, which was then filtered off. Solid potassium chlorate was added to the filtrate in an amount of 100 mg / 100 grams of H 2 PO 4, after which the mixture was stirred O * x for about 5 minutes so as to convert the tetravalent uranium to the hexavalent state. To the resulting liquid, an extractant was added in a volume ratio to the phosphoric acid of 1-2, consisting of a solution of 0.5 mole of di (2-ethylhexyl) phosphoric acid and 0.125 mole of trioctylphosphine oxide in 1 liter of kerosene. The resulting mixture was stirred intensively at a temperature of 45 ° C for 10 minutes.

8000832>. 4

The mixture was then allowed to stand for 0.5 hours to form a two-layer system, then the aqueous H 2 PO 4 -containing bottom layer was tapped off.

By X-ray fluorescence analysis and liquid scintillation counting, the uranium content of both the drained H 2 PO 4 containing phase and the extractant phase was determined. The results are summarized in Table I.

Trial No. 2

The procedure of Test No. 1 was repeated except that an excess of 10 wt% BaCO2 over sulfate was used. The analysis results are also summarized in Table I.

Trial No. 3

The procedure of Experiment No. 1 was repeated except that an undersize of 30% by weight BaCOg relative to sulfate was used. The analysis results are also summarized in Table I.

15 Trial No. 4

The procedure of Run No. 1 was repeated without adding BaCOg. The analysis results are summarized in Table I.

Trial No. 5

The procedure of test no. 1 was repeated, whereby after separation of the sulphate and fluorine-containing precipitate, the concentration of sulphate in the solution was brought to 1.5 wt.%. The analysis results are summarized in Table I.

Table I.

after extraction_

25 wt.% SOj wt.% F ü content U-content D

in HgPOj-opl. in H ^ PO ^ -up. in H ^ PO ^ -up. in extr. _____ liquid ._

Test No. 1 0.1 0.2 25 ppm 305 ppm 12 "" 2 0.1 1.0 26 "300" 11.5 30 "" 3 0.5 1.1 29 "293" 10 "" 4 1 , 5 1.2 42 "251" 6 "" 5 1.5 0.1 38 "265" 7

D is here understood to mean: multitude of uranium in extraction liquid, wt. how many uranium in phosphoric acid after extraction

From the analysis results it can be clearly deduced (see test 1, 35 2, 3 compared to, blank test 4), that the SO 2 content of the liquid to be extracted has a very clear influence on the uranium extraction efficiency, 8000832 ^ -½ 5 and that the fluorine content (see test 5 compared to blank test 4) exerts a much smaller influence.

Example 2 Test No. 6 In the same manner as in Example 1, uranium was extracted from phosphoric acid. In this process, however, the uranium in the liquid after separation of the barium sulphate-containing precipitate was not oxidized with potassium chlorate, but reduced with iron curls (4 grams Fe / 100 grams H-PO), O 4, the solution was stirred for 15 minutes, and then the non- dissolved iron 10 with a magnet.

The analysis results are summarized in Table II.

Trial No. 7

The procedure of Run No. 6 was repeated with the proviso that only an excess of "10 wt% BaCO relative to sulfate was added

O

15 added. The analysis results are summarized in Table II.

Trial No. 8

The procedure of Run No. 6 was repeated, however, with an insufficient BaCOg addition. The analysis results are summarized in Table II.

Table II

20 after extraction_

wt.% SOj wt.% F U content ü content D

in HjjPOj opl. in H ^ PO ^ sol. in H ^ PO ^ sol. in extr. liquid test no. 6 0.1 0.2 85.5 ppm 111 ppm 1.3 25 "" 7 0.1 1 113 "23" 0.2 "-" 81 1 116 "12" 0.1

The analysis results show that although the extraction efficiency of the extractant on a reduced (U-containing) HPO-w 4 solution is quite low, the removal of sulphate and fluorine also in this case a considerable increase in uranium extraction efficiency. cause.

Example 3 Test No. 9

The procedure of Test No. 1 was repeated, however, without treatment of the solution with potassium chlorate.

The analysis results are summarized in Table III.

8000832 6

Trial No. 10

The procedure of Trial No. 9 was repeated, however, without BaCO-

O

addition.

The analysis results are summarized in Table III.

Table III

after extraction_

wt.% SO ^ wt.% F U content U content D

in HgPO ^ -opl. in H ^ PO ^ -up. in H ^ -PO ^ -opl. in extr.

Fluid Test No. 9 0.1 0.2 29 293 10 "10 1.5 1 74 148 2 8000832

Claims (7)

7 3158 Process for recovering uranium from wet-process phosphoric acid by liquid-liquid extraction with organic phosphoric acid esters, characterized in that the sulfate content of the phosphoric acid to be extracted is set at a value of less than 2% by weight, calculated with respect to the weight amount of P0 in the phosphoric acid, by adding a divalent metal compound which reacts with sulfate ions to form a phosphoric acid insoluble sulfate, and separating the metal sulfate precipitate formed. 2. Process according to claim 1, characterized in that the sulphate content of the phosphoric acid to be extracted is set to a value of less than 0.6% by weight, calculated with respect to the weight amount of PoO2 in the phosphoric acid. i Process according to either of Claims 1 and 2, characterized in that the sulfate content is reduced by adding a calcium and / or barium compound, and separating the formed calcium and / or barium sulfate. 4. Process according to any one of claims 1-3, characterized in that calcium and / or barium carbonate or sulfide are added to the phosphoric acid to be extracted. Process according to any one of claims 1 to 4, characterized in that the fluorine content of the phosphoric acid to be extracted is adjusted to a value of less than 0.7% by weight, calculated with respect to the weight amount of PgO 2, by adding of an excess of sulfur compound over a divalent metal and / or adding a silicon compound or mixture of alkali metal compound and silicon compound. A method according to claim 1, substantially as described in further elucidated in the examples. Uranium-containing extract obtained by using the method according to any one of claims 1-6, 8000832