CA1174859A - Process for recovering uranium as a peroxyde from an uranium ore treatment sulfuric solution - Google Patents

Abstract

The invention relates to a method for recovering uranium from an attack solution of a uranium-bearing ore with sulfuric acid in which the uranium is precipitated in the form of uranium peroxide by the addition of peroxide. hydrogen, characterized in that an alkaline agent is added, before the precipitation of the uranium peroxide, at a pH equal to or slightly higher than the precipitation pH of the uranium peroxide. The present invention therefore provides a process allowing, from attack solutions of uranium ores, the quantitative recovery of uranium in the form of a peroxide of purity in accordance with the commercial specifications of uranium concentrates, without requiring any prior treatment. concentration and purification of uranium by solvent or resin.

Description

~ ~ 7 ~ 85 ~
The invention relates to a method for recover uranium from a solution resulting from the attack of a uranium ore by a sulfuric acid solution (hereinafter called liquor or sulfuric attack solution) which consists of precipitating uranium in the form of peroxy-by adding hydrogen peroxide after removing the impurities likely to co-precipitate with peroxide uranium.
The precipitation of uranium by the addition of water oxygenation is a well known operation. She is described in U.S. Patent No. 2,770,521. She is not applied industrially only to solutions rich in uranium or relatively concentrated solutions pro-from the elution of uranium from a resin or a uranium extraction solvent, i.e.
solutions containing at least about 10 g / l of uranium.
Problems arise when you want directly apply this uranium recovery method to attack solutions of uranium ores, the principal 1 20 cipal being the obtaining of an impure precipitate contaminated by ; impurities in the solution and co-precipitating with uranium at the precipitation pH of ura peroxide nium (2.5 - 4), another being the need to employ relatively high amounts of hydrogen peroxide, ¦ much greater than the stoichiometric quantity (l mole ! of H202 per gram atom of uranium).
The object of the present invention is to provide a method making it possible, from attack solutions to ! uranium ores, quantitative recovery of u ranium in the form of a purity peroxide in accordance with commercial specifications of uranium concentrates, ¦ without requiring any prior processing of * ~

,, ~ 17485 ~
concentration and purification of ura ~ ium by solvent or resin.
The procedure of the invention is based on the observation that claimant that if we add to the liquor sulfuric attack on uranium ores, previously - the addition of hydrogen peroxide ~ ne, an alkaline agent to a pH equal to or slightly higher than the precipitation pH
uranium peroxide, the uranium remains in solution while that sulfates and certain impurities precipitate.
Said alkaline agent is calcium hydroxide, calcium carbonate, their mixture, or a mixture sodium hydroxide with a soluble calcium salt.
The process for recovering uranium from a solution resulting from attack with sulfuric acid of a uranium ore according to the present invention slste to add to said solution an alkaline agent and to separate the formed pr ~ cipity which contains the sulfates and impurities in the initial solution and to treat the so-remaining lution, containing most of the uranium, '' By hydrogen peroxide at a pH equal or slightly i lnférleur to that of the additive step of said alkaline agent and separating the precipitate of uranium peroxide formed.
¦ The alkaline agent used for precipitation j sulphates and impurities in the attack solution Ran uranlfère is calcium hydroxide or carbonate of ! calclum or a mixture of both. Calcium hydroxide can be used solid or as a lime milk ! containing 50 ~ 400 g / l calcium hydroxide.
! The alkaline agent can also be a soluble salt calclum and sodlum hydroxide.
The precipitation pH of sulfates and im-purities depends on the impurities contained in the liquor

- 2 -:

~ 1 ~ 4859 attack. It is, in general, rule between 2 and 4, but preferably between 2.5 and 3.5. This pH is chosen from so that the quantity of uranium entrained by the preci-pity remains within acceptable limits.
The precipitate of gypsum and impurities obtained pre-can be discarded after filtration and washing when it contains little uranium, but it is better to recycle it at the uranium ore attack workshop ! to recover the uranium.
The precipitation of gypsum and impurities can be done at the temperature of the uranium-bearing ulcer from from the attack, that is to say between 20 and 80C.
But it is not excluded that this precipitation is carried out killed at temperatures other than the above range (between 5 and 100 C).
It may be necessary when the liquor of atta-that uranium mineral contains Fe2 + ions, to oxidize beforehand these in the ferric state Fe3 ~ by an oxy-dant appropriate. Oxygenated water can advantageously be used for this oxidation.
Precipitation of uranium in the form of pure peroxide is carried out as indicated previously at a pH slightly lower than or equal to the precipitation pH
sulfates and impurities from the previous step.
The peroxide preciplatlon pH is understood between 2 and 4, but preferably between 2.5 and 3.5.
The precipitation of the peroxide is carried out at a temperature between 0 and 60 C, preferably between 20 and 40 C.
In order to improve uranium depletion of the solution, the precipitation of uranium is carried out in the presence of recycled uranium peroxide or from

- 3 -~ 174859 of a pxecedente operation. Addition of peroxide already precipitate accéL ~ xe la ~ itesse de precision: pitation de l'uxa ~
nium and allows to precipitate ~ uantitat ~ Yement ur ~ nium of the solution even when the amount of oxygenated water in ~
troduite is weak.
The alkaline agent used to ~ eutralize the H + ions released during the precipitation of ura peroxide ~
nium is an alkaline solution.
This alkaline solution is preferably, ~
sodium hydroxide, but can be a solution, hy ~
potassium hydroxide or ammonia solution.
Precipitation, peroxide can be done batch or continuous in one or more reactors serial.
Continuous precipitation in the presence of peroxy-uranium already pr ~ precipitate allows to obtain a product "better filterable.
The hydrogen peroxide content of ~ a solution of im ~
pregenation of the peroxide precipitate must be sufficient, at least equal to 100 mg / l. If this ten, them in oxygenated water is too ~ weak, the precipitation, one of ~ 'uxanium is not total, there may even be resolubili ~ ation of uranium.
Loss by degradation of oxy ~ enee water during of the precipitation reaction of uranium peroxide can be lowered by the use of well-known stabilizers from hydrogen peroxide in an acid medium, as for example between other dipicolinic acid or acid ét ~ ylènediamine ~
¦ tetraacetic.
When the pH of precipitation of pure peroxide is not high enough to completely precipitate I ~ uranium ~ l ~ uranium residual from the solution obtained ¦ after separation and recovery of the peroxide pxecipite ~ 17 ~ 859 uranium can be precipitated at a pH higher than that of pH of precipitation of pure peroxide by addition of hydro-sodium or ammonium or calcium xyde and eventual-oxygenated water. The impure precipitate obtained during of this exhaustion is recycled in the attack liqueur before precipitation of impurities and gypsum.
Partially oxygenated water can be introduced in the form of sodium peroxide.
The precipitate according to the recovery invention uranium in the form of pure peroxide applies to all the sulfuric attack processes of ura- ores nifers, that they are carried out in a usual way (solid ratio between 0.5 and 2) or by pasting liquid solid ratio ~ 0.5), by heap leaching or by a very dilute sulfuric solution (0.5 to 5 g / l) in pre ~
sence of an oxidant strong enough to cause oxidation of uranium and iron (case of leaching "in situ" in the ground for example).

The invention will now be illustrated with reference to , shown in Figure 1 attached schematically ¦ an embodiment of the present invention.
I According to Figure 1, the ground uranium ore M
¦ has an appropriate dimension is introduced into the reactor attack (A) with the sulfuric attack liquor, pre-Ence presence of an oxidizing agent. The boilie obtained after j attack is conducted in (B) where the s ~ paratlon takes place of an attack residue Sl constituted by the mixture of the ma-unaffected materials and calcium sulfate precipitate from recycling area from the washing area (G), and of a sulfuric liquor Ll resulting from the attack, I
!

.

~ 1 ~ 48Sg containing e ~ solution uranium a ~ so that the fraction of iron and impurities dissolved during the attack.
The Sl cake impregnating mother liquors are then extracted in (C) using ~ 'an adequate quantity of water and the resulting liquor L2 is mixed with liquor L1 to form the liquor h3.
The S2 cake containing the attacking materials, recycled calcium sulphate and unresolved impurities lubricated during the attack operation is isolated and rejected.
- The L3 liquor obtained after attacking the ore is then introduced in D where the introduction takes place a neutralizing agent such as sodium hydroxide clum to set the pH to the desired value pHl.
At the exit of D ~ a suspension is collected constituted by a solid phase containing sulphate calcium and insoluble lmpuretes at pHl, and a phase liquid containing the uranlum in so ~ ution, which one realizes separation at E into a solid fraction S4 rich in impurities and calcium sulphate and an L4 iiqueur.
The precipitate S4 is then introduced into (G) jo ~ is washed with an adequate amount of water.
One thus obtains a precipitate ~ S5 rich in iron, , impregnation liquor and a liquid fraction L5 j to give L6.
I The residue S5 rich in impurities can be removed.
! mined at the exit of (G). But in the event that a co-precipitation of uranium and impurities, it it is better to recycle this precipitate in the reactor attack (A), where the co-precipitated uranium redissolves and where impurities are removed from the cycle at the same time than unassigned materials.

4 - ~, F, ~
The L6 liquor obtained after elimination of the impurities purities of the L3 liquor and constituted by the mixture of liquors L4 and L5 is then introduced into reactor F
where the introduction of oxygenated water, primers of uranium peroxide from recycling the separation zone H, and an alkaline agent such as sodium hydroxide to adjust the pH to the desired value pH2, with PH2 less than or equal to pH1.
At the exit of F, a suspension is collected consisting of a solid phase of uranium peroxide and a desuraniated or highly depleted liquid phase in uranium, which separates into H in a fraction solid S7 rich in uranium, and an L7 liquor.
The precipitate S7 is then introduced at I where wash with an adequate amount of water or a solutlon very diluted in hydrogen peroxide. We obtain thus a pure precipitate of uranium peroxide, the impurity content is below specification and an L8 liquor.
Lqueurs L7 and L8 are combined to form the Lg liquor which is either rejected when its content uranium is considered to be low enough to be treated a second time in J to recover traces of ura-nium.
The Lg liquor constituted by the mixture of li-queurs L7 and L8 is in this case introduced in J o ~ effect kills the introduction of an alkaline agent to bring the pH up of solution with a pH3 value higher than pHl, primers precipitate from recycling separation zone K, and optionally hydrogen peroxide.
- At the end of J, we get a suspension consisting of a depleted Llo liquor which is isolated and 1 1 ~ 4859 discarded or recycled at the ore attack shop for use its oxidizing potential due to residual oxygenated water the.
The solid S10 is partially recycled into ~, the other part rich in uranium but too impure to be commercial is attached to L3.
The following examples illustrate the invention.

The uranium scourer used has for composition:

U Fe SO4 Al Mo 1.3 g / l 3.8 g / l 16.8 g / l 5 g / l 10 mg / l In a first experiment A, this solution is brought to pHl of 3.0 by addition of a lime milk then the precipitate obtained is filtered and washed.
The uranium contained in the liquor obtained pre-immediately is then precipitated by oxygenated water and the pH is adjusted to PH2 = 3.3 by addition of a hydroxide sodium. The amount of hydrogen peroxide is 1 kg per kg of treated uranium. Under these conditions, the precipitation uranium is almost total. The uranium content of the solution is less than 2 mg / l, and the peroxide obtained has for composition that indicated in the table below After.
In a second experiment, we subject with uranium liquor the same treatments as those indicated prec ~ demment, but both pH are set to Hl 3.5 and PH2 3 ~ 3-~ Under these conditions, the precipitation of the ura-! 30 nium by hydrogen peroxide is also almost total. He stays in the filtrate less than 2 mg / l. ~ a composition of the peroxide is given in the table below.

1 17485g .
Precipitated ~ t ~ Qn of prec; ~ p ~ atiQ ~ of uranium peroxide sulfa ~ tes ...
Experience P 1 U. PH2 Coprecipitate Compos ~ tion of peroxide in % _ _ ...

% ~ ~%% 4 ~%
_. _ A 3.0 0.6 3.3 59 0.16 0.05 0.010 0.5 0.26: `
_ _ _.
B 3.5 2.9 3, 163. 0.03 0.05 0.002 0.1 0.02 The peroxide obtained in B is very pure and can be processed without penalty by uranium converters.
Uranium coprecipitated at pHl is recovered during recycling from the precipitate to the attack on the ore.

This example shows that by operating according to the invention tion (Experiment B) a very pure peroxide is obtained which can . be marketed as is.

¦ EXAMPLE 2 The solution used for testing is a etching solution of the ore whose impurities have been previously removed by lime precipitation.
The table below gives the evolution of the uranium and hydrogen peroxide content of the filtered solution _ g _ !

~ 1 ~ 485 ~
which is obtained during the precipitation of u ranium at PH2 depending on whether this precipitation is carried out whether or not primers are present. ;

XmDrces PH2 test d ~ Duration of precipitation in minutes r 1 0 3.5 U mg / l 775 704 524 417 46 18 H22 mg / l 1150865 815 760 200 20 __ 2100 3.5 U mg / l 7753.6 2.8 1 1.2 22 mg / l 575 204 200 170 140 _.
3 0 3.2 U mg / l 775 550 330 75 45 44 . _ 2 2 g / l 1150 410 360 240 100 20 4100 3.2 ~ ~ g / l 77518 14 8 3 1 . N ~ 2 ~ g / l 1150 750 700 sao 480 350.

These tests show that the addition of primers I reduces the consumption of oxygenated water while ¦ accelerating the precipitation of uranium.

A uraniferous ore having the following composition:
. U 0.35%
! Fe 2.1%
Al 6.5%
MB - 0.001%
- 10.-". ''"'''.

1 17485 ~ `
Ca 0.17%
If 37.8 10 kg / h of this ore were treated in A with 10 l / h of an aqueous sulfuric liquor containing 40 g / l of H2SO4 and per 25 g / h of sodium chlorate, in the presence 1.1 kg / h of S5 wet recycling precipitate.
The porridge obtained after attack was transferred s ~ e in B o ~ the solid phases were separated Sl and Ll containing the solubilized uranium.
The cake Sl was then washed in C by 18 liters of water per hour, giving an inert residue S2 which was rejected and a residual liquor L2 which was attached with liqueur Ll.
The residue S2 expressed, in the dry state, was 10.3 kg per hour and contained only 0.007 ~ of ranium.
L3 scaler obtained by mixing liquors ; Ll and L2 had a flow rate of 24.5 l / h and had the composition next tion:
; 20 Uranium1.410 g / l Total Fe 3.8 g / l Fe2 ~ <0.02 g / l SiO20.13 g / l S0416.8 g / l Mo 0.001 g / l 0.24 g / l Al 3.8 g / l potential ~ 500 mV / DHW

This L3 liquor was introduced at D where it was treated with 0.98 l / h of a lime milk solution at 300 g / l in order to bring the pH of said solution included 1 17 ~ 85 ~
between 3.4 and 3.6. This caused precipitation dehydrated calcium sulfate and impurities like iron.
The suspension was then introduced in (E) where the L4 uranium liquor was separated representing a volume of 24.6 l / h and a solid S4 which was washed in G with 1 l / h of water to give 1.1 kg per hour of wet solid S5 containing 0.07% uranium and one liquor L5. The solid S5 was then recycled ~ the attack (A) ore.
L6 liquor obtained by combining liquors L4 and L5 had a flow rate of 25.6 l / h and contained 1.325 g / l uranium.
This solution was treated in F in 5 reac-cascades by 0.07 l / h of a solution of oxygenated water 300 g / l. In these reactors, arrived continuously 2 l / h of uranium peroxide pulp ~ 600 g / l from from separation H.
The pH was adjusted to 3.3 by controlled addition soda at 10 ~. We thus obtained a peroxide pulp of uranium which was treated in the separator H to give an S7 concentrated pulp, part of which was recycled into F, the other part was filtered and washed in I to give 0.058 kg / h of uranium peroxide expressed as dry. and an L8 liquor which was combined with L7 liquor to give the liqueur Lg. The uranium content of the Lg liquor was 2.5 mg / l, content low enough not to require site the solution depletion operation.
After drying, the solid S8 had the composition:

3 ~
U 70.1% Na 0.05 SO4 0.8% K 0.004%

~ 174859 Fe 0.09 ~ V 0.005%
Mo 0.005% If 0.05%
Ca 0.04% P 0.04%

Claims (7)

The embodiments of the invention, concerning the-what an exclusive property right or lien is claimed, are defined as follows: 1. Process for recovering uranium from from an attack solution of a uranium ore with sulfuric acid, said solution generally containing actually less than 10 g / l of solubilized uranium, said process comprising first the treatment of the solution resulting from attack by an alkaline agent for the purpose to partially remove the impurities by precipitation, then treatment of the partially purified uranium solution, using hydrogen peroxide to precipitate the peroxide uranium, finally the separation of the precipitate from the liquor mother, characterized in that, in order to decrease the consumption of hydrogen peroxide, and speed up the precipitation of uranium peroxide, it is recycled to the pre-precipitation of said peroxide a significant fraction of the above uranium peroxide pity obtained. 2. Method for recovering uranium according to claim 1, characterized in that the fraction of uranium peroxide recycled to precipitation is at least equal to 43 g / l. 3. Method for recovering uranium according to claim 1, characterized in that the precipitate constitutes titered by impurities is recycled to attack the ore. 4. Method for recovering uranium according to claim 1, 2 or 3, characterized in that, after the precipitation and washing of uranium peroxide, we treat the mixture of liquors resulting from precipitation and washing with an alkaline agent in order to precipitate residual impurities and uranium, said precipitate being recycled to attack. 5. Method according to claim 1, 2 or 3, characterized in that the uranium remaining in solution after precipitation of peroxide is recovered by precipitation by addition of hydrogen peroxide and / or alkaline element at a pH
greater than 3.5. 6. Method according to claim 1, character-laughed at in that the precipitation of pure peroxide is carried out at a temperature between 0 and 60 ° C. 7. Method according to claim 6, character-laughed at in that the precipitation of pure peroxide is carried out at a temperature between 20 and 40 ° C.