JPS58181728A - Method for recovering uranium from wet process phosphoric acid - Google Patents

Abstract

PURPOSE:To recover uranium inexpensively and simply from wet process phosphoric acid in a high yield by adding an alkaline earth metallic compound to the phosphoric acid, further adding gypsum dihydrate, and capturing uranium in a hemihydration stage. CONSTITUTION:An alkaline earth metallic compound is added to wet process phosphoric acid contg. uranium obtd. by treating phosphate ore so as to adjust the concn. of alkaline earth metallic ions in the phosphoric acid to >=0.1wt%. After further adding gypsum dihydrate, the phosphoric acid is heated and held at above the transition temp. of hemihydrate gypsum to cause transition from the gypsum dihydrate to hemihydrate gypsum and to capture uranium. All of the formed hemihydrate gypsum is separated from the phosphoric acid, dispersed in water, and hydrated to cause transition to gypsum dihydrate and to shift the uranium to the liq. phase. The mother liquor after the hydration is separated, and by adding a precipitant, the uranium is recovered as an insoluble precipitate. Said wet process phosphoric acid may be used after defluorination. The preferred alkaline earth metallic ions are Ca or Mg ions. Gypsum dihydrate separated after transition can be recycled.

Description

[Detailed Description of the Invention] The present invention is a method for recovering trace amounts of uranium contained in wet phosphoric acid obtained by decomposing phosphate rock with mineral acids such as sulfuric acid and phosphoric acid using gypsum as a medium. It is related to.

Natural phosphate rock generally contains 100 to 200 ppm of uranium, and most of it is transferred to the phosphoric acid solution during the so-called wet phosphoric acid manufacturing process, in which this is wet-decomposed with a mixed acid of phosphoric acid and sulfuric acid. do.

Although the concentration of uranium in the phosphoric acid solution is not very high,
Since the absolute amount of phosphoric acid solution produced is very large, attempts have been made to recover uranium from wet phosphoric acid.

As industrial methods for recovering uranium from wet phosphoric acid, solvent extraction methods, ion exchange methods, precipitation methods, adsorption methods, etc. are known. Although the swamp medium extraction method is currently being industrialized worldwide, it requires purification of phosphoric acid as a punishment to prevent sludge formation during the extraction process, and the equipment costs are higher. However, since the extraction solvent is expensive, complicated operations are required to avoid its loss. Furthermore, in addition to the necessity of pretreatment of phosphoric acid in the ion exchange method, the concentration of the diphosphoric acid solution supplied to the ion exchange column has not yet been widely put to practical use.

Precipitation and absorption methods require further improvement because the uranium recovery agent is expensive and its loss is a problem.

On the other hand, the present inventors have already developed a wet phosphoric acid production method in which phosphate rock is decomposed with sulfuric acid. Method for producing wet phosphoric acid with a high content (Japanese Patent Application Laid-Open No. 57-27911) Furthermore, hemihydrate wax and/or a compound that produces hemihydrate wax is added to the wet phosphoric acid, and all of it is converted to hemihydrate wax. , characterized in that wet phosphoric acid and hemihydrate wax are separated, the separated hemihydrate wax is hydrated, then the aquarium wax is separated, and a precipitant is added to the separated liquid to recover uranium as an insoluble precipitate. A method for recovering uranium from wet phosphoric acid (Japanese Patent Application No. 56-24242) and an industrial recovery method (related to improvement of the process of the latter invention)
(Japanese Patent Application No. 162077/1982) t-proposed.

The present invention relates to improvements in the steps of these methods for recovering uranium from wet phosphoric acid, and has achieved and completed a method that achieves a high recovery rate with simple operations. That is, a SiO□ source and an alkali source were added to phosphoric acid obtained by various wet phosphoric acid production methods (hereinafter referred to as wet phosphoric acid) or wet phosphoric acid, and fluorine in the wet phosphoric acid was removed as an alkali silicate fluoride. After adding an alkaline earth metal compound to phosphoric acid with a low fluorine content (hereinafter referred to as defluorinated phosphoric acid), adding dihydrate wax and maintaining the temperature above the transition temperature of hemihydrate wax, if necessary, adding at least an equivalent amount of sulfuric acid to the residual alkaline earth ions in the phosphoric acid to separate all the hemihydrate wax, hydrate the hemihydrate wax, and then separate it; This invention relates to an industrial method for recovering uranium from wet phosphoric acid or defluorophosphoric acid, which is characterized by adding a precipitant to the separated mother liquor and recovering uranium as an insoluble precipitate.

In this way, the method of the present invention separates the uranium recovery process and the phosphoric acid production process as completely separate processes, so it can be produced and recovered by any method, the precipitant is inexpensive, and The operation is also very simple compared to the bath medium extraction method.

The present invention will be explained in more detail below.

In carrying out the present invention, in the wet phosphoric acid production method in which phosphate rock is decomposed with a mixed acid of 100% and phosphoric acid, an oxidizing agent is coexisted in the reaction step to generate parrot wax, and the uranium in the solution is converted to hexavalent uranium. It is preferable to use wet phosphoric acid which has been oxidized and then released the produced gypsum (9') or defluorinated phosphoric acid which has further reduced the fluorine content in the wet phosphoric acid.

As an oxidizing agent, KCfi03, NaCQO3, H20□
Compared to uranium such as , KMnQl, HNO3, and hydrochloric acid, tetravalent uranium is easily incorporated into hemihydrate wax, so hexavalent uranium is reduced to tetravalent uranium by adding a reducing agent such as metallic iron or by electrolytic reduction. It is desirable to keep it. Next, an alkaline earth metal compound is added and dissolved in the raw phosphoric acid to increase the alkaline earth metal ion concentration in the phosphoric acid. The alkaline earth metal compound is not particularly limited, but O is easily available.
Phosphate, CaO1Ca(OH)2, C as a compound
aCO2, 0aCR2 or MgO as Mg compound
, Mg(OH)2, Mg, COs, MgcI12
Any one of the following may be added and dissolved. As for the amount added, the alkaline earth metal ion concentration in phosphoric acid is 0.1.
It is preferable to increase the content by % or more, and although the upper limit is not particularly limited, it is usually up to about 5%, and if it is more than that, there is no significant effect, but if it is less than 0.1%, the effect is small. The present invention is able to obtain a high uranium recovery rate simply by incorporating the simple process of adding and dissolving an alkaline earth metal compound to the raw material phosphoric acid.The fact that a high uranium recovery rate can be obtained by simply incorporating the simple process of adding and dissolving an alkaline earth metal compound to the raw material phosphoric acid is due to the fact that when large alkaline earth metal ions are present, uranium and calcium are substituted. This is thought to be because the reaction is accelerated.

Next, hydrite (dihydrate) is added to the phosphoric acid, and this dihydrate acts as a scavenger for uranium in the hemihydration process. Although it is preferable to reuse a part of the by-product dihydrate produced in the subsequent water utilization process, dihydrate produced from other processes is also effective.

The amount of painting is generally determined by the slurry concentration in the hemihydration process being 5.
Add so that the amount becomes ~40% by weight.

In the next hemihydration step, the slurry of phosphoric acid and hydrite is maintained at a temperature at which dihydrate is transformed into hemihydrate. The transition temperature is about 100 to 120°C, and if necessary, half-hydration can be carried out in an autoclave. The produced hemihydrate contains 10 ppm to 5000 ppm of uranium, but the mother liquor contains 0 alkaline earth metal ions.
．． Since 1% or more is dissolved, if necessary as a next step, it is the same as sulfur No. 56-24242).

That is, the hemihydrate that has captured uranium is dispersed and hydrated in water, and in the process of transferring the hemihydrate to the dihydrate, uranium is expelled from the solid phase to the liquid phase. This operation is also a feature of the present invention, and the advantage of using gypsum as a uranium recovery medium is that the process of extracting uranium from hemihydrate quartz can be carried out by simple water utilization operations. A trace amount of sulfuric acid, a water utilization promoter, or an oxidizing agent may be added to the hydration reaction to promote the reaction. The reaction can be carried out at room temperature. The dihydrate produced through irrigation contains almost no uranium, and the hydrated mother liquor from which uranium has been eluted (hereinafter referred to as the recovered liquid) may be mechanically recycled for separation to increase the uranium concentration in the recovered liquid. .

Through the above steps, uranium is separated from the phosphoric acid solution, and finally a recovered solution containing substantially no phosphoric acid is obtained in the form of a solution. The recovered liquid usually contains several tens of ppp of uranium (U).
Although uranium can be obtained in amounts ranging from m to several thousand ppm, uranium can be easily and economically recovered by applying a precipitation method. Caustic soda, ammonium compounds and the like are commonly used as precipitants, but divalent iron salts, organic chelating reagents and the like are also used. Since phosphoric acid liquid, which is the raw material for recovered uranium, is the main product, we cannot add additives that would reduce the value of the product, but the recovered liquid is now completely separated from the phosphoric acid manufacturing process. In addition to the above-mentioned precipitants, the liquid properties can be adjusted arbitrarily by adding additives such as flocculants, adsorbents, full coat agents, surfactants, and pH adjusters. It can be recycled in the chemical process, and the rest can be discharged as is and used for cement.
It can be said that this process is extremely advantageous industrially.

The present invention will be illustrated by the following examples.

Examples 1 to 5 Wet phosphoric acid (p
2o, concentration = 30%, F# degree = 1.5%, U concentration -1
00ppm) was placed in an autoclave equipped with a stirrer and heated to 87°C. As a pretreatment for reducing uranium in phosphoric acid to tetravalence, 0.2 g of iron powder was added with stirring. Each of the alkaline earth metal compounds shown in Table 1 was added and dissolved in the pretreated phosphoric acid. Add 50 g of hydrite wax to each of these phosphoric acids (Ul 1 degree = 2 p
pm)], adjust the slurry temperature to 110°C, and
The time was tailored. The entire amount of hydrated stone wax is transferred to hemihydrate stone wax.
After confirming that this was the case, phosphoric acid was obtained by filtration, and the uranium content and uranium yield in the hemihydration process are shown in Table 1.

Table - ■ Phosphate rock: P2o, 33%, CaO48.8%
, U 1100pp Then, after dispersing and hydrating 40 g of the hemihydrate wax A with 50 Ill of water,
After filtration, the washing water and mother liquor were combined to obtain 53 ml of recovered liquid. The uranium concentration in the recovered liquid was 551 ppm, and therefore the uranium yield in the Mizukiguchi operation was 98%. Further pHH
The overall uranium yield in I3 is 96% (Q, 98X0,9
8×0,999). Similar hydration operation
.

As a result of conducting the tests on hemihydrate waxes ■ and ■, the overall uranium yields were bottom ■-93%, A■-95%, &■, respectively.
■=96%.

Example 6 So-called defluorinated phosphoric acid obtained by defluorinating wet phosphoric acid (PzOs concentration = 30 degrees, F degree -0.5 degrees, Ui 11 degrees = too
ppm) 300 g was subjected to the same operations as in Examples 1 to 5. The mixture was placed in an autoclave equipped with a stirrer, and 0.2 g of iron powder was added for reduction treatment.

18.2 g of phosphate rock was added to the phosphoric acid and dissolved.

Next, 50 g of hydrated stone wax (U quality = 2 ppm) was added, the slurry temperature was adjusted to 110°C, and the mixture was reacted for 2 hours. After confirming that the entire amount of water stone wax has been transferred to hemiwater stone wax, it is filtered, P, 0.29.4%, T52 ppm
325 g of phosphoric acid was obtained. The hemihydrate wax cake was washed first with hot water and then with acetone to obtain 53 ml of recovered liquid. The uranium concentration in the recovered liquid was 552 ppm s, so the uranium yield in the irrigation operation was 98%. Further p
When the recovered residue with H4=1 was neutralized to 6 in I) H with ammonia water, 0.158 g of precipitate such as ammonium uranate containing 18.5% (as U) of uranium was obtained. The uranium yield of this operation was 99.9%. Therefore, the overall uranium yield was 96% (0.98XQ, 98XO0999).

Comparative Example 1 300 g of wet phosphoric acid as in Examples 1 to 5 was mixed with 0.0 g of phosphate rock.
43g was dissolved (the increased Ca io/concentration was 0).
, corresponds to 05%. ) As a result of performing exactly the same operations as in Examples 1 to 5, the uranium yield in the hemihydration step was 93%, the hydration step was 98%, and the precipitation step was 99.9%.Total uranium yield The yield was 91 inches (0.91X0.98X0.
999) i was there.

Claims (4)

[Claims] (1) Add an alkaline earth metal compound to wet phosphoric acid to bring the alkaline earth metal ion concentration in the wet phosphoric acid to 0.
1 weight or more, add dihydrate, maintain the temperature above the transition temperature of hemihydrate to transform it into hemihydrate, separate the produced hemihydrate, and hydrate the hemihydrate. 1. A method for recovering uranium from wet phosphoric acid, which comprises separating dihydrate sulfur obtained from the process and adding a precipitant to the separated mother liquor to recover uranium as an insoluble precipitate. (2) The method according to claim (1) using defluorinated phosphoric acid as wet phosphoric acid (3) Alkaline earth metal ion is Oa or Mg
The method according to claims (1) and (2). (4) The method according to claim 0), in which a part of the separated dihydrate is returned to phosphoric acid as a uranium recovery agent and used for circulation.