CA1184389A - Purification treatment of a uranium bearing concentrate - Google Patents

Abstract

Process for the purification of uranium concentrates containing impurities, in particular at least one of the zirconium and / or hafnium elements, comprising the treatment of said concentrates in an acidic and hot aqueous medium with hydrogen peroxide to cause the formation of peroxide uranium which is characterized in that in a first step, and in order to quantitatively precipitate the uranium and dissolve all or part of the impurities, the uranium concentrate is suspended in the aqueous medium, then acidifies said suspension slowly and in a controlled manner with an acid agent, the resulting acidified aqueous medium is treated with hydrogen peroxide, causing the formation of a precipitate containing essentially uranium and almost all of the zirconium and / or hafnium which is separated from the liquid phase charged with impurities, then in a second step the precipitate from the first step is treated with the medium n of an acid agent to cause the transformation and the solubilization of uranium into soluble uranyl ions and the liquid phase containing the uranyl ions is separated from the solid phase formed of a compound containing zirconium and / or hafnium . according to a variant of the process of the invention, in the first step, the acidified aqueous medium is treated using a source of fluoride ions.

Description

The invention relates to a purificatiorl method of uraniferous concentrates containing impurities, of which, in particular, zirconium and / or hafnium, which comprises, according to a new combination, in a first step, the treatment of uranium concentrates, first by an agent acid introduced in strictly controlled quantity, then by hydrogen peroxide in order to form peroxide impure uranium, and, in a second step, the treatment of the impure uraniferous solid phase resulting from the first step by means of an acid agent ensuring the obtaining of a purified uraniferous liquor.
It has long been known that uraniferous centers contain or are likely to con-hold many impurities whose presence is revealed annoying during the u] time purification of uranium.
The treatment of such uranium concentrates includes usually wears, first the solubilisate: uranium ion in the form of uranyl salts and impurities accompanying it pagnant, then the precipitation of uranium under an apparatus peroxide peroxide by use of hydrogen peroxide.
Specialized literature describes such -treatment-and describes the difficulties in obtaining a compound sufficiently pure from uranium due to the presence of impurities.
The most general process is applied to treatment of a uranium concentrate is described in The extractive Metallurgy oE Uranium)> by R. MERITT, edition 1971 - Colorado School of Mines Research Institute, pages 247 and 248l as well as in Proceeding of the International Conference on the Peaceful uses of ~ tomic ~ nergy>), United Nations, Vol. VIII, pp. 141 to 143 (1955) by EL ZIMMER
on Preparation and Separation of Uranium Peroxide, as a stage in the chemical purification of Crude Uraniferous Products. These articles state that if 1 ~ precipita-tion of uranium within the impure solution the con-theoretically, allows to maintain in solution the impurities present, the uranium precipitate obtained is retained non-negligible amounts of impurities when the separation of said precipitate takes place, despite a consequent and prolonged washing. So the precipitation and washing uranium peroxide makes it possible to remove impurities such as argen-t, arsenic, aluminum, boron, bismuth, calcium, ma ~ nesium, manganese, molybdenum, vanadium, sodium, nickel, antimony, tin and zinc, but do not provide a reasonably reasonable disposal of Eer, phosphorus and silicon, if other treatments are not previously practical.
When the uranium concentrate also contains other impurities such as zirconium and / or haEnium, these generally preclpitate simultaneously with the ura-nium, during treatment with hydrogen peroxide of aqueous solutions containing them, giving a peroxide of uranium which does not lead subsequently to obtaining uranium sufficiently pure for nuclear applications.
Based on this general method of processing uraniferous concentrates, the specialized literature described improved processes, making the same use of peroxide of hydrogen to precipitate uranium peroxide from aqueous solutions of uranium acids containing equal-ment of solubilized impurities, these processes are distinguished guarantor of each other by means proper to the elimination-tion of one or more specific impurities.
This is how in the Report of Investigations 7931 of US Bureau of Mines 1974, by M. SH ~ BBIR and KE
T ~ ME, dealing with the Precipitation of uranium by the hydrogen peroxide)>, is described a means of obtaining pure uranium peroxide which consists in treating, at temperature ambient, an acidic aqueous solution of uranium, enriched in impurity molybdenifere and vanadi.fère, by means of pero-hydrogen xyde by adjusting the pH of ladi-te solution a various values between 3 and 6, and this for a four hour time. According to this study, the authors specify that the pH of said solution must be maintained between 3.5 and 5 to obtain a precipitate of ura peroxide sufficiently purified nium.
Such a procedure, if it was applied to concentrates very impure uranium containing the particular impurities such as zirconium, and / or hafnium, could not lead to the obtaining of an impure uranium peroxide, since the said particular impurities would precite.
with uranium during the introduction of hydrogen peroxide.
Another process, more advanced with regard to impu-present, is described in the United States patent n 2.7.70.521. This process proposes the treatment of a solution tion of uranyl sulfate first comprising the prec: Lpi-tation impurities such as iron, copper, chromium, cobalt, nickel, manganese, molybdenum ~ by regulation the pH of the solution between 3 and ~ using carbona-te of calcium, then, after the separation of the impurity precipitate, the treatment of the impure-depleted uranium solution-using hydrogen peroxide introduced into said solution, to precipitate uranium peroxide, the medium of precipitation being kept at a maximum temperature equal to 65C and has a pH between 2.5 and 3.5.
The interest of such a process appears limited when the uranyl sulfate solution to be treated contains no only the usual impurities, but also those constituted by zirconium and / or hafnium. Because, this pro-cede practicing selective precipitation of impurities in means of calcium carbonate, is likely to lower the content of SO ~ ions in the uranium solution and consequently cause partial coprecipitation dlurani.um, zirconium and / or hafnium at the same time as impurities to be eliminated, resulting in a loss not neglected uranium. Much more, only a fraction zirconium and / or hafnium being precipitated with the impurities, the other fraction remaining in solution in li--that their uranium will be precipitated at the same time as the pero-uranium xyde.
Thus, the previous art offers the man of the art solutions that cannot fully satisfy it when a uranium liquor resulting from solubilization dlun concentrated by means of an agent aci.de, count to the number impurities present zirconium and / or hafnium, because the proposed treatments lead to precipitation of uranium and some of the specific impurities aforementioned specifics, requires further treatment to purify uranium peroxide in order to obtain purity required in nuclear applications.
Consequently, the recommended treatments cannot not meet user requirements, the Applicant, continuing his research, found and developed a purifying process: ion of uranium concentrates, ex-t early inconvenience and allowing you to obtain queur uranifere dlune purity very improved.
The process according to the invention, for purifying uraniferous concentrates containing impurities of which, in particular, one among the elements constituting the group in the form of zirconium and / or hafnium comprising the treatment of said concentrates in an acidic aqueous medium and hot with dlhydro ~ ene peroxide to cause ~ ormati.on of dluranium peroxide, is characterized in that, in a first step and, in order to precipitate quantitatively the uranium and to solubilize all or part impurities, the uraniferous concentrate is suspended in the aqueous medium, then acidify slowly and in a controlled manner said suspension by means of a acid agent, the aqueous medium is treated acidified resultan-t by means of hydrogen peroxide causing the formation a precipitate containing essentially uranium and almost all of the zirconium and / or hafnium that we separates the impure-charged liquid phase, then, in a second step ". We are dealing with the prec: ipite from the first e-tape using an acid agent to cause the transformation and solubilization of uranium into ions soluble uranyles, and separating the liquid phase containing uranyl ions of the solid phase formed from a compound containing zirconium and / or hafnium.
The solid uranium concentrates subject to the pro-cede according to the invention are those which come from hydrometallurgical elements of well-known uranium ores skilled in the art ~ They usually come in the appearance of a solid mixture, composed mainly uranium and, in minor part of impurities such as, by example, ary: nt, arsenic, aluminum, bismuth, calcium, magnesium, manganese, molybdenum, vanana-dium, sodium, nickel, antimony, tin and, in particular, at least one of the metals constituting the group formed by zirconium and / or hafnium.
Liquid uranium concentrates subject to pro-cede according to the invention contain the same i.rnpuretes c.lue those found in uran concentrates: iferes sol: i.dc-`s and, in particular, at least one of the metals constituting the group formed by zirconium and hafnium.
3U According to the first stage of treatment, when the uranium concentrate to be purified is soli.de, it is dispersed in an aqueous medium maintained under stirring, in cons constituting a suspension which is treated with an acid agent.
The acid agent is then slowly introduced into said suspension, in such a way as to dissolve not only uranium, but also most of the impurities present.
The time of slow introduction of the acid agent is generally between 5 and 200 minutes, but it is preferably chosen between 10 and 120 minutes.
The amount of acid agent to be introduced for preferentially solubilize the impurities is general-determined in equivalent 1-1 + compared to -contents in uranium and impurities present, excluding any-zirconium and hafnium. In practice, the quantity of acid agent to be introduced is determined by reference to alkaline and / or assimilated cations.
The quantity of acidic acid to be introduced into this first step of the process of the invention corresponds at least to the stoichiometry of said cations: it is preferen-between 1.1 and 2.5 times this stoechio-metrics.
In practice, the amount of acid agent to intro to dissolve is such that the concentration of free ~ 1 after acid dification is at least 0.01 N and, preferably, at least minus 0.1 N.
~ depending on the amount of acid agent introduced in the aqueous suspension of the uraniferous concentrate, the medium acidifies result-t remains as a suspension aqueous, or is presented under the appearance of a iqueur possibly offering low turbidity. In this last-deny this case, the liquor contains in solution all of uranium and the vast majority of impurities initially present in the uranium concentrate.
The temperature of the acidified medium results, does it look like a suspension or a solution, are you controlled and must be at most equal to 70C; but she is preferably kept within a temperature range between 30C and 40C.
In the event that the uraniferous concentrate occurs under the aspect of a solution, this solution undergoes the same acidification that the concentrate concentrates.
The resulting acidified aqueous medium, maintained at the desired temperature is then treated with peroxide of hydrogen introduced into said medium in an amount at least equal to twice the stoichiometry necessary to precipitation of uranium peroxide alone.
The amount of hydrogen peroxide is at least equal to 1.4 times the stoichiometric amount required to precipitation of perox ~ uranium and preferential-ment between two and three times the ladi-te stoichiometry, so that the uranium and the impurities formed by at least one of the elements belongs to the group formed by the zirconium and hafnium initially present in the container centered uranium, are transformed and maintained under a solid form.
Solid state transformation and maintenance uranium and at least one of the zirconium elements and hafnium takes place, as is well known to humans art, at a pH generally between 2.5 and 4.5 which is controlled by the introduction of an alkaline agent such as sodium, potassium or ammonium hydroxide.
After the introduction of hydrogen peroxide ~ e in the acidified medium, whose temperature and pH are main-held at the chosen values, the suspension resulting from said processing, is then subjected to a ripening operation, consisting in maintaining agitation in the field of temperatures initially chosen, for a time at most equal to 6 hours, and preferably between 2 hours and 4 hours.
At the end of this last mature operation ment, the suspension is subject to a separation operation liquid-solid which can possibly be realized in presence of a filter aid such as, for example Kieselgure, Diatomaceous earth, by a known means of those skilled in the art such as filtration, settling or centering fugation, and the solid phase from this separation is washed mo ~ in water or an aqueous solution of pero-0.2 x hydrogen xyde in a sufficient amount for entrain the impregnation liquor from the solid phase.
According to a variant which can be applied to during the first stage, in the bu-t to obtain a liqueur much more reproducible purity uranium, whatever either the uraniferous concentrate used, we treat the mid-aqueous place acidified by means of a source of fluoride ions, playing the role of complexing agent.
~ In the context of this variant, the temperature of the resulting medium, whether it is in the form of a suspension or solution, is controlled and must be at least equal at 70C; but, it is preferably maintained in an inter-temperature valle included entr. 90C and 100C.
The resulting acidified aqueous medium, maintained at desired temperature, is then treated by an ion source fluorides, this source being constituted, for example, by the compounds HF, NaF, KF, NH4F, Na2SiF6, making it possible to be the solubilization of almost all impurities present, used alone or as a mixture.
The complexing agent is introduced into the millet: ieu aqueous acidifies in an amount such that the ratio molar F / (Zr- ~ H ~) is at least equal to 1, and preferably, between ~ and 10.
While the agent is being introduced complexing, the temperature of the aqueous medium is maintained at least at 70C and preferably between 90 ~ C and 100C.
~ ready to introduce the complexing agent into the acidified medium whose temperature is maintained at the values chosen, the solution resulting from said treatment is often put into a ripening operation consis-tan-t by hand nir in agi-tation in the field of -initial temperatures-chosen for a time at most equal to 6 hours, and preferably between 1 hour and 4 hours.
At the end of the ripening operation, the acidified and complexed aqueous solution is then cooled at a temperature below 60C and, preferably, between 30C and 40C, plliS is treated with pero-xyde h ~ drogen in-product in said medium according to a quantity at least equal to the stoechioma-sort necessary for the precipitation of uranium peroxide alone and preferential-ment between 2 and lO times said s-toechiometry.
After the introduction of the hydrogen peroxide in the medium cooled, the suspension resulting from this treatment are you subject to a slow pH adjustment which is chosen between

2.5 and -4.5 by the introduction of an alkaline agent such as Sodium, potassium or ammonium hydroxide.
The suspension coming out of the pH adjustment is in turn subjected to a consi-tant ripening operation to keep it agitated in the field of -temperatures lower than 60C for a time at most equal to 6 hours, and preferably between 2 and 4 hours.
At the end of the first stage, the solid phase separated and washed is formed with the precipitate containing the pero-uranium oxide and at least one of the zirconium compounds and / or hafniurn, while the liquid phase contains virtually all other impurities.
According to the second stage of treatment, the phase Solid 3C, mainly uranium, from the first step, is stirred and then treated with a acidic agent, either in the pasty state under which it is present, either after being suspended in a aqueous medium constituted by water or by a liquor of recycling.
The amount of acid agent introduced into this second e-tape within the solid uranium phase, in the state or in aqueous suspension, corresponds to the only solubilization of uranium present in said phase.
The solid uranium phase, before being subjected to the action of the acid agent, in the state, or after formation of an aqueous suspension, can be brought to a temperature between 60 and 100C, and, first: Eerence between 85 and 95C, however, it may be desirable that the elevation of the temperature is done after the introduction of the acid agent:
in the latter case, the temperature rise takes place in a slow way to be able to control the clearance gas resulting from the dissolution of uranium.
The uranium dissolution operation is com-completed by a ripening operation of the acidified medium at the temperature selected in the above interval, which generally requires a time of at least one hour, and, preferably between 3 and 5 hours.
20 `The suspension resulting from the treatment of dissolu-tion and ripening is usually cooled to a temperature at most equal to 40C in order to reduce the solubility of the zirconium and / or hafnium compound in the aqueous phase. Then, said suspension is subject to a separation operation to collect a liquor purified rich in uranium, and to isolate a solid phase holding the impurities constituted by the compounds of zirco-nium and / or hafnium.
The acid agent used in both e-tapes of the process according to the invention can be chosen from the group consists of nitric acid, sulfuric acid, acid hydrochloric and hydrofluoric acid. This acidic agent may be the same in both stages, but it may be desirable that it be different and that it even be constituted ..... ..

by the mixture of at least two of these acids ~
Thus ~ the method according to the invention is distinguished of the prior art by solubilization and elimination of the main impurities in the first step, while that the second stage is characterized by the sole dlssolu-tion impure uranium from step one and removing it nation of the last impurities under a solid elm.
In practice, the purification process of concen-very uraniferes according to the invention, which can be implemented in a continuous or discontinuous manner, includes the sequences following:
a) suspension of the uraniferous concentrate to be purified, in an aqueous medium maintained in a state of agitation, or intro duction of the uranium liquor to be treated, -15 b) introduction of an acid agent in a controlled amount and in a slow manner, the agitated medium being hand-held at an adequate temperature, c) introduction of hydrogen peroxide into the aqueous medium resulting from sequence b) in an amount at least equal at twice the stoichiometry required for the single precipitation of uranium peroxide, the pH of the medium aqueous being maintained in the range 2.5 to 4.5, d ~ ripening of the suspension from sequence c) by being kept under agitation for at most 6 hours, under the chosen temperature and pH conditions sies in sequences b) and c), e) separation of a liquor charged with solubilized impurities and a solid phase containing mainly uranium in the peroxidized form, f) washing the solid phase originating from sequence e), g) suspending the uraniferous solid phase in a aqueous medium, consisting of water or a liquor recycling, h) dissolution of uranium by means of a quantity at most stoichiometric compared to the uranium present of a acid agent in the uranium suspension from the sequence g), heated before or during acidification, i) ripening of the suspension from sequence h) by keeping it stirred for at least one hour and at a chosen temperature, j) cooling of the suspension from the sequence i) at a temperature at plus ~ equal to 40C, k) separation of a liquor rich in purified uranium and of a solid phase contains one among the impurities constituted by a compound of zirconium and / or hafnium.
According to the variant, the sequences b, c, d, are carried out as follows:
b) introduction of an acid agent according to a controlled quantity and in a slow manner, the agitated medium being maintained at an adequate temperature;
bl) .complexation of impurities by means of an agent plexant, constituted by a source of fluoride ions /
in a controlled amount and in a slow manner, the medium being maintained at an adequate temperature, b2) ripening of the medium from sequence b by keeping it stirred for at most 6 hours, under the chosen temperature conditions in sequences a) and b), b3) cooling of the medium from the sequence b2 at a temperature below 60C;
c) introduction of hydrogen peroxide into the medium aqueous resulting from sequence b3 in an amount at less equal to the stoichiometry necessary for the sole precipitation of uranium peroxide, cl) slow adjustment of the medium pl from the sequence c) up to a pll between ~ 2, S and ~, 5;
d) ripening of the suspension from sequence c by being kept under agitation for at most 6 hours, under temperature and pll conditions chosen in the sequences b3 and cl.
The invention will be better understood from the reading which will follow preferred embodiments of the invention made with reference to the following drawings:
- Figure 1 represents a diagram illustrating the two steps of the method according to the invention; and - Figure 2 shows a diagram illustrating a variant of the process of figure 1.
According to Figure 1, the uraniferous concentrate Sl is suspended in A in an aqueous medium maintained under agitation and constitutes by mixing the liqueurs of recycling L13 and L15.
The suspension Ll thus obtained is then treated in B by the slow introduction of the acid agent L20 for dissolve all or part of the impurities-your initially pre-feels in the uraniferous concentrate, while the tempera-ture of the medium, controlled, is at most equal to 80C.
The acidified suspension L2 t maintained at the time aforementioned perature and with stirring, is treated in C, at temperature and pH controls, by an aqueous solution of hydrogen peroxide, of which the active quantity is at least 1.4 times the stoichiometric amount needed to the formation of uranium peroxide.
L3 suspension of uranium hydroxide: ium from of C is subjected to a ripening operation in D, con-trying to keep it stirred in the area of temperatures initially chosen and for a time at more equal to 6 hours.
At the end of this ripening operation, the resulting suspension L ~ is subject to separation liquid-solid by giving an L5 liquor, charged with impurity retes and an S5 cake containing almost all of the uranium initially present in the uraniferous concentrate,

3 ~ 3 ~

accompanies impurities of zirconium and / or hafnium.
The S5 cake is then washed at F using a aqueous solution L23 giving a liquor L6 resulting the impure liquor impregnating the cake S5, and a cake S6.
The mixed L5 and L6 liquors constitute a liquor L14, part of which L15 is recycled to A, while that the other part L16 is extracted from the processing cycle.
The S6 cake is suspended in ~ in a aqueous recycling liquor L18, then suspenslon L7 resulting is acidified to H by an acid liquor L24, whose amount of acid corresponds to the solubili.sa- scule tion of the uranium, then said suspension is brought to a -temperature at most equal to 100C.
lS The resulting suspension L8 is subjected to a ripening operation in I has a temperature identical to that practiced in H and for a time of at least one hour.
~ the outcome of the ripening operation, the above resulting pension Lg is subject to a sepa-ration by giving a purified L1o liqueur, rich in uranium, and a precipitate S10, mainly forms of zirconium and / or hafnium.
The precipitate S10 is then washed in K with a aqueous liquor L25, gives an L ~ l liqueur and a cake Sl1, practically free of uranium.
The uraniferous liquors Llo and Lll are mixed by donating liquor L17, part of which L18 is recycled in G, while the other part Llg corresponds to the liquor uranium production.
The cake Sll is subjected in M to an operation of plump using an L26 aqueous liquor, giving an L12 suspension which is subject to a separation operation liquid-solid ration in N.

The solicde S13, constitutes practically only impurities zirconium and / or hafnium, is eliminated from the cycle of treatment, while the L13 liquor is recycled to A.
According to FIG. 2, illustrating the variant, the concentrated uraniferous Sl is suspended at A in a aqueous medium maintained under stirring and constitutes by the mixture of recycling liquors L13 and L15.
Ia suspension Ll thus o ~ held is then treated in B by the introduction of the L20 acid agent for dissolve all or part of the impurities-your initially pre-sentes da.ns concentrates uraniferous, while the temperature middle, controlled, is at least equal to 70C.
The acidified suspension L2, maintained at room temperature above-mentioned stripping and with stirring, is treated in BA at by means of a complexing agent constituted by a source of ions fluorides, introdu.it according to L45 in controlled quantity and dune slow way.
The aqueous medium L41, originating from the complexation, is then subjected to a BB ripening operation, trying to keep it stirred in the area of temperatures initially chosen and for a time at more equal to 6 hours.
At the end of this ripening operation, the suspens.ion L42 is subject to cooling in BC
up to a temperature below 60C.
The L43 suspension maintained at the pre-mentioned and with stirring, is treated in C at temperature controlled by an aqueous solution of hydrogen peroxide L21r whose active quantity is at least equal to the quan-stoichiometric tite necessary for the formation of uranium pero ~ yded.
The uranium peroxide suspension L3 from Provence of C is subjected in CA to an adjustment of pH until a value between 2.5 and 4.5 by introducing the solution L22.
L44 suspension of uranium peroxide from of CA is then subjected to a ripening operation in D, consisting in keeping it stirred in the domai.ne initially chosen pH and temperatures, and for a time at most equal to 6 hours.
At the end of this ripening operation, the resulting suspension L4 is subject to separation li.quide-solid, possibly in the presence of an agent S46 promoting separation, by giving a charyee L5 liquor in impurities and an S5 cake comprising almost all uranium originally present in the uranium concentrate fère, accompanies impurities of zirconium and / or hainium.
I, e cake S5 is then washed in F by means of a aqueous solution L23 giving an entraining L6 liquor impure impregnation liquor from cake S5 and a cake S
The mixed L5 and L6 liquors constitute a liquor Ll ~, part of which L15 is recycled to A while that the other part L16 is extracted from the processing cycle.
The S6 cake is suspended in G in a aqueous liquor for recycling Ll ~, then the suspension L7 resulting is acidi ~ iee en ~ by an acid liquor L2 ~, whose amount of acid corresponds to the sole solubilisa--tion of uranium then, said suspension is brought to a temperature at most equal to 100C.
The resulting suspension L ~ is subjected to a ripening operation in I at an identical temperature to that practiced in H and for a time of at least one hour.
~ the outcome of the ripening operation, the above resulting pension Lg is subject to a sepa-ration, possibly in the presence of a favorite S47 ac3en-t.
separation, giving a purified, rich Llo liquor 3 ~

uranium, and an S10 precipitate mainly forms composed of zirconium and / or hafnium.
The precipitate S10 is then washed in K with a L25 aqueous liquor gives an Lll liqueur and a cake It will be practically free of uranium.
The uranium liquors L1o and Lll are mixed by giving liquor L17, part of which L18 is recycled in G, while the other part Llg corresponds to the liquor of production of urani.um.
The cake Sll is subjected in M to an operation of plump using an L26 aqueous liquor giving a L12 suspension which is subject to a sepa.ration operation liquid-solid in N.
The solid S13 is practically the only impurities zirconium and / or hafnium, is eliminated from the cycle of treatment, while the L13 liquor is recycled to A.
. The invention will be better understood thanks to the examples which illustrate its scope.
EXAMPLE 1:
This example pursues the goal of illustrating the importance of turing of the ripening operation in D, during the first step, the acidic aqueous suspension after in production of hydrogen peroxide on the yield of precipitation of uranium in a peroxide form.
To do this, 200 g of a concentrated ammonium uranate in 200 g of water.
The ammonium uranate concentrate has the composition following in percent by weight:
V: 61.16%
MB: 0.3 ~%
Zr: 1.33 ~
N ~ I4 ~: 4.78%
Miscellaneous: 32.34%
We added, in 20 minutes, to the suspensi.on thus formed .

30 g of 100% HNO3, then 57 g of H2O2 at 100 ~, the pH of medium being so controlled over the value 3, while the time perature of said suspension was maintained at 35 ~ C.
The influence of the ripening time is perceived ble by observing the results mentioned in the Table I below, which have been established as a function of time devotes to the actual operation called ripening, after separation and washing of the cake.
Six tests have been carried out for varying times from 0 to 4 hours, 30 minutes, after introduction of the peroxycle of hydrogen in the acid suspension.

E 'ILTRATGATEAU
TIME TRIAL ~.
h, mnUmg / l Momg / lll2O% Mo / sec Zr / sec _ in ppm in ppm . B 0.3011 1 150 32 509 13 070 C 1.30 ~ 10 1 150 30 360 13 106 D 2.30 <10 1 100 30 389 11 357 E 3.30 <10 1 350 32 416 13 600

4.30 <10 1,450 31,489 The table reveals that the ripening time must be at least one hour for ~ ue uranium solubilized or completely precipitated.
EXAMPLE 2:
This example illustrates the influence of ~ quantity of the acid agent in-product, during the second stage, to effect the total dissolution of uranium contained in uranium peroxide, obtained during the first stage.
Two tests were carried out by varying the quantity of the acid agent introduced. The influence of amount of said aci ~ e agent is demonstrated by the results mentioned in table II.
For this, we implemented the first step of the process using the uraniferous concentrate defined in Example I, which led to obtaining a wet cake S6, subjected to the second step of the method according to the invention.
For each test, 200 g of cake S6 were used, form of impure uranium peroxide.
TABLE II

U, Mo, Zr and M + content in the liquor resulting from the dissolution and ripening precipitate from first stage _ HNO U Mo Zr Acidity g (100%) mg / 1 ~ free 39.65 430.8 150 200 0.1 N

H 55.81 409 230 8 236 2 N
According to this table, it appears that going from one free acidity 0.1 N to 2 N, the content of impurities Zr increased lie about ~ 0 times, thus showing the need for tightly control the amount of in-product acid for dissolve the uxaniferous precipitate from t the first step.
_ EMPLE 3:
This example reveals the importance that must be granted to the duration of the ripening operation I in the second e-tape, which follows the solu-tlon operation uranium from the precipitate resulting from the first step.
For this, we carried out five successive tests, using the same quantities of materials to be processed (200g) and processing (39.65g 100% HNO3) than in test G of example 2.
For each test, the acid suspension was hand-held.
a temperature of 90 ~ C, with stirring, for a time variable.
The results expressing the Zr contents in the phase aqueous, collected apxes ripening and separation, are collated in Table III.
TABLE III

IJKLM TEST
Time to ripening 1 2 3 4 5 in hours Zr soluble 365 260 220 200 190 Mo soluble _ _ _ _ 150 in mg / l _ ..
Soluble U _ _ _ 430.8 The table reveals the need to practice a ripening time of at least 2 hours and, more pre ~ eren-in the order of 4 hours, time for which the Zr and Mo impurity contents are acceptable.
_ EMPLE 4 (according to ~ igure 1):
In this example, the Applicant i.llustrates the method of the invention comprising the two stages of processing seriously.
According to the process, and in the first step of treatment, a zonc A of suspension was introduced, 200 parts by weight of a uranium-containing concentrate having the following composition expressed in% by dry weight:
U: 61.16%

MB: 0.3 ~ ~
Zr: 1.33%
NH4 +: 4 ~ 7 ~%
miscellaneous -i H2O: 32.34%
In this same zone A, 200 parts were introduced by weight of water, then we acted for the necessary time to the realization of a homogeneous suspensi.on.
To this suspension, the equivalent was added in 20 minutes 30 parts of 100% HNO3 (~ one B).
Then, to the acid suspension thus obtained, we added (zone C), 57.0 g of H2O2 (100%) (L21) in 20 minutes, at pH
control 3, by adding sodium hydroxide (L22).
The L3 suspension leaving zone C was subjected to a D-ripening operation, consisting in maintaining said suspension with stirring at a temperature of 35C
for 2:30 minutes.
The suspension L ~ l from D was then subjected to a separation operation at E, giving an LS liquor and a solid phase S5.
The solid phase S5 was then subjected to an operation in F by means of 200 parts by weight of water, gives a liquor L6 resulting from washing and a solid phase S6.
The liquors L5 and L6 were mixed giving a li-queur L1 ~ of which a fraction l, l5 was recycled in A at the suspension of the uranium concentrate, while the fraction L16 had left the cycle to avoid accumulation tion of impurities in the first stage.
The liquor Ll ~ represented 323 parts by weight, and had the following composition by weight:
~ o: 0.35%
U: 2 ppm H2O2: 5.0%
N ~ I ~ NO3: 12.9%
NaNO3: 1.7 H2O - ~ miscellaneous: 80.05 ~
Thus, 90/0% of the molybdenum initially present in the concentrated urani ~ era were eli.mines by means of liquor Ll4.
The S6 cake coming out of washing F represented 349 parts by weight of a wet cake. What is there after drying at 60 ~ C, had the following composition in percent in weight:
U: 65.4%
Mo: 0.05%
Zr: 1.34%
NH4: 0.4%
various + H2O: 32, ~ 1%
In the second stage of treatment according to the vention, the S6 cake from] a first milking stage-was treated in H with 65 parts of 100% HNO3. This acid was introduced slowly over 20 minutes, the suspension thus o ~ held L8, being brought to 90C in I and maintained at this temperature for 4 hours.
The Lg suspension leaving zone I was often put in a separation in J by giving an Llo liquor and a cake S10, which was washed in K using 22 parts by weight of water L25 giving a cake Sll and a liquor Lll.
The liquors Llo and Lll were mixed and constituted an L17 liquor which represented 450 parts by weight. This liqueur L17 had the following composition:
U: 27.2%
Mo: 0.016%
Zr: 0.005%
H2O + NO3 ~ miscellaneous: 72,779 ~
A fraction of the purified L17 liquor was recycled to G at the suspension of the cake S6 resulting from the pxe-first step while the Llo fraction constituted the liquor uranium production.
The cake Sll after drying at 60C represented a mass of S, 6 parts by weight. This cake contained practically 99.1% of the zirconium initially present in the concentrate uranium, and its uranium content was such that it represented a loss of 0.4% compared to uranium initially present in the concentrate which, as part of the continuous process, was it resuspended at M in a weakly acidic L26 liquor, to be recycled to A according to L13 liquor after filtration in N.
EXAMPLE 5:
In this example, the Applicant compared the process making use of the alternative to the process according to the vention not using said variant.
Test N illustrates the method according to the invention does not do not use of the variant, illustrated by FIG. 1.
Test 0 illustrates the object of the invention, according to the variant it: chandelier in Figure 2.
ji According to test N and, in the first step of treatment, we introduced into suspension zone A, 150 parts by weight of a commercial uranium concentrate from Niger, having the following composition expressed in% by weight on dry:
~: 68.2%
MB: 0.13%
zr: 2.44%
Na: 9.0%
miscellaneous - ~ ~ l2O: 20.23%
In this same area ~, i.ntroduced 123 parts by weight of water, then stirred for the necessary time to the production of a hornogenic suspension. To this suspended sion, we added in 20 minutes the equivalent of 39 parts of HNO3 at 100 ~ (zone ~). Then, at the suspension thus obtained naked, we added (zone C ~ 29.0 g of H2O2 (100 ~) (L21) in 20 - 23 ~

minu-tes, a pl- ~ control 3,4, by means of an addition of hydroxycle sodium (L22).
Suspension L3, coming out of ~ zone C, was subjected to a ripening operation in D, consists in maintaining the ladi-te suspension with stirring at a temperature of 30C for 2 hours.
The L4 suspension, coming from D, was then subjected to an E separation operation, giving a liquor L5 and a solid phase S5.
The solid phase S5 was then subjected to an operation in F by means of 200 parts by weight of water, giving a liquor L6 resulting from washing and a solid phase of S6.
The liqueurs L5 and L6 were mixed in data an L14 liquor, an L15 fraction of which was recycled to A at the suspension of the uranium concentrate, while the fraction L16 was out of the cycle to avoid accumulation impurities in the first step.
The L14 liquor represented 300 parts by weight and contained 97 ~ 5% of the molybdenum initially present in the uranium concentrate, which were eliminated by means of said liquor.
The S6 cake, coming out of washing F, represented 260 parts by weight of a wet cake. This cake, after drying at 60C, had the following composition in percent in weight:
U: 68.0%
Mo: 0.02%
Zr: 2.44%
Na: 0.28%
Miscellaneous ~ H2O: 29.26%
In the second stage of processing, the cake S6 from the first stage of treatment, was treated in G per 260 parts of an L18 recycling liquor. Then suspension L7 was treated in H with 93.6 parts of ~ INO3 to 100%. This acid was introduced slowly over 20 minutes, the suspension obtained L8 being brought to 90C in I and main-held at this temperature for 2 hours.
The Lg suspension, leaving zone I, was subjected to a separation in J to give an Llo liquor and an S10 cake, which was washed in K using 17 parts by weight of water (L2S), giving a cake Sll and an L11 liqueur.
The liquors Llo and Lll were mixed and constituted a liquor L ~ 7 which represents 500 parts by weight.
This L17 liquor had the following composition:
U: 26.180%
MB: 0.007%
Zr: 0.050%
H2O ~ NO3 - ~ miscellaneous: 73.763%
A fraction of the purified L17 liquor was recycled to G has the suspension of the S6 cake resulting from the pre-first stage, while the Llg fraction constituted the uranium production liquor.
The cake Sll, after drying at 60C, represented a mass 9.5 parts by weight. This cake practically contained 94.7% of the zirconium initially present in the concentrate uranium, and its uranium content was such that it represented a loss of 0.4% compared to uranium initially present in the concentrate which, as part of the continuous process, was resuspended at M in a weakly acidic L26 liquor, to be rec ~ keyed in A according to liquor I, 13 after filtration in N.
According to test O, illustrating the method of the variant and, in the first step, we introduced into zone A
suspension, 500 parts by weight of the same uranium concentrate commercial than in test N.
In this same zone A, 500 parts in weight were introduced.
water then stirred for the time necessary ~ the 3 ~

creation of a homogeneous suspension. At this suspension, we added in 20 minutes the equivalent of 423 parts of 100% HNO3 (zone B). Then, the L2 suspension was intro-duite in BA, where a complexing treatment was carried out at 90C by 57.6 parts by weight of KF.
The resulting L41 aqueous medium was subjected to a ripening operation in Bs, consisting in maintaining said suspension with stirring at a temperature of 90C
for an hour.
The aqueous medium L42, leaving the zone Bs, was cooled in BC up to a temperature of 30C.
To the cooled L43 aqueous medium, 330.8 were added (zone C) parts of H2O2 (100%) (L21) in 25 minutes.
The L3 suspension, coming out of zone C, was subject to a slow pH adjustment to value 3.5 in CA by introduction of a liqurer L22 of hydroxide potassium.
Suspension L44, leaving the CA zone, was subjected to a ripening operation in D, consisting in maintaining said suspension with stirring at a temperature of 36C
for 45 minutes.
The suspension L ~ from D was then subjected to a separation operation at E, giving an L5 liquor and a solid phase S5.
The solid phase S5 was then subjected to an operation in F of washing by means of 200 parts by weight of water, giving an L6 liquor resulting from washing, and a sol phase: ide S6.
The L5 and L6 liquors were mixed giving a L14 liquor, one of which: Eraction L15 was recycled to A at the suspension of the uranium concentrate, while ~ ue the fraction L16 was out of the cycle to avoid accumulation The L14 liquor represented 4,700 parts and contained 97.6%.
molybdenum initially present in the uranium concentra fere, which were eliminated by means of said liquor.
The cake S6 coming out of washing F represented 1900 parts by weight of a wet cake. This cake, after drying, at 60 ~ C, had the following composition in for cen-t in weight:
U: 65.17%
MB: 0.003%
zr: 2 ~ 52 miscellaneous - ~ ~ 12O: 32.307%
In the second stage of processing, the S6 cake, from the first treatment e-tape, was treated in G by 57 ~ 3 parts of a recyc liqueur: Lage L18. Then the suspension L7 was treated in H by 172 parts of 100% HNO3. This acid was slowly introduced at 85C in 120 minutes, the suspension thus obtained L8 being hand-held at 85C in I
during 2 hours.
The Lg suspension, coming out of the 20ne I, was subjected to a separation in ~ giving an Llo liqueur and a cake S10, which was washed in K using 1100 parts by weight of water (L25) giving a cake Sll and a liquor Lll.
The liquors Llo and Lll were mixed and constituted an L17 liquor which represented 2850 parts in weight. This L17 liqueur head had the following composition:
U: 21.5%
MB: 0.001%
Zr: 0.010%
H2O - ~ NO3 + miscellaneous: 78.489%
A fraction of the purified L17 liquor was recycled to G to the suspension of the cake S6 results from the pre-first step - while the Eraction L19 was the - uranium production liquor.
The Sll cake, after drying at 60 ~ C, represents a mass 32.0 parts by weight. This cake practically contained 98.7% of the zirconium initially present in the concentrate uranium, and its uranium content was such that it represented a loss of 0.4 / Oo compared to uranium initially present in the concentre which, in the context of the continuous process, was resuspended at M in a weakly acidic L26 liquor to be recycled in ~ according to liquor L13 after filtration in N.
So the comparison of tests N and O reveals that the variant of the process according to the invention greatly improves sensibly the purity of the resulting uranium liquor Llg.

_ -In this example, the Applicant has applied the variant of the process according to 1.'inven-tion with three concentrates commercial uraniums from three industrial processes different, one of which, trial O, is described in the example

5.
The P trial treats a commercial uranium concentrate in the form of an impure magnesium uranate.
The Q test deals with a uranium-bearing commercial concentrate occurring in the form of an impure sodium uranate.
According to test P, illustrates the process according to variant and in the first stage, we entered the zone At suspension, 469 parts of the uranium concentrate salesperson with the following composition expressed in% in weight:
~: 70.6%
MB: 0.19%
Zr: 0.32%
PO4: 0.28%
N / A ~: 5.32 N114: 1.4 Na: 1.05 ~ i Mg: 0.3%
cau - ~ miscellaneous: 20.54 .,, 3 ~

In this same zone A, 500 parts by weight were introduced water then stirred for the time necessary to realization of a homogeneous suspension. At this suspension, we added in 20 minutes the equivalent of 423 parts of HNO3 at 100 ~ (zone B). Could the L2 suspension be intro-taken in BA, or did a complexing treatment at 90C by 7.84 parts by weight of KF.
The resulting L41 aqueous medium was subjected to BB ripening operation, consisting of maintaining ladi-te suspension with stirring at a temperature of 90C
for an hour.
I, aqueous medium L42, leaving zone BB was cooled in BC to a temperature of 30C.
To the cooled aqueous medium L43, we added (zone C), 321 parts of H2O2 (at 100%) (L21) in 25 minutes.
Suspension L3, leaving zone C, was subjected to a slow pH adjustment operation to the value 3.5 in CA by introduction of an L22 hydroxide liquor potassium.
The L44 suspension, coming out of the CA æone, was subject to a ripening operation in D, consists of keep said suspension under agitation at a temperature 36C for 45 minutes.
The L4 suspension, coming from D, was then subjected to an E separation operation, giving a liquor L5 and a solid phase S5.
The solid phase S5 was then subjected to an operation in F of washing by means of 200 parts by weight of water, giving an L6 liquor resulting from washing, and a solid phase S6.
The liqueurs L5 and L6 were mixed by giving a liquor I, 14 of which a fraction L15 was recycled to A at the suspension of the uraniEere concentrate, while the fraction L16 had left the cycle to avoid accumulation tion of impurities in the first stage.

The L14 liquor represented ~ 700 parts by weight and contained 98.9% of the molybdenum initially present in concentrates uranium, which were eliminated by means of said liquor.
The S6 cake, coming out of wash F, represented about 1900 parts by weight of a cake to moisten Ce cake, after drying at 60C, had the following composition in% by weight:
U: 66.3%
~ 0.003%
Zr: 0.39%
miscellaneous - ~ H2O: 33.307%
In the second stage of processing, the cake S6, from the first processing step, was processed in G by 578 parts of an L18 recycling liquor. Then, the L7 suspension was treated in H by 172 parts of HNO3 100%. This acid was slowly introduced at 85C in 120 minutes, the suspension thus obtained L8 being maintained at 85C in I for 2 hours.
The suspension Lg, leaving zone I, was subjected to a separation in J to give an Llo liqueur and an S10 cake, which was washed in K at average of 1100 parts by weight of water L25 giving a cake Sll and a liquor Lll.
The liquors Llo and Ll1 were mixed and constituted an L17 liquor which represented 2850 parts by weight ~ This li.queur L17 had the following compositioll:
U: 21.6%
MB: 0.001%
Zr: 0.010%
H2O + NO3 + miscellaneous: 78.389%
A fraction of the purified L17 liquor was recycled to G to the suspension of the S6 cake resulting from the first etapel while the Llg fraction constituted the liquor for the production of uranium.
Sll cake, after drying at 60C, represen-tait a mass of 5 parts by weight. This cake contained pra -tically 96.9% of the zirconium initially present in the concentrated uranium, and its uranium content was such that it represented a loss of 0.4 / Oo compared to the uranium initially present in the concentrate which, in as part of the continuous process, was it resuspended M in a weakly acidic L26 liquor, to be recycled in A according to liquor L13 after filtration in N.
According to test Q also illustrating the variant according to the invention, and in the first step, we introduced in suspension zone A, 255 parts by weight of the same commercial uranium concentrate as in test N, 15 having the following composition expressed in per cent by weight:
U: 64.9%
Zr: 1.1%
Na: 9.0%
SiO2: 2.7%
so4: 2.8%
F: 0.1%
water + miscellaneous: 22.2%
In this same zone A, 255 parts by weight were introduced of water, then we acted for the time necessary to homogeneous suspension. At this suspension, we added in 15 minutes the equivalent of 423 parts of 100% HNO3 (zone B). Then, the L2 suspension was intro-pick in BA, where a co ~ lplexation treatment was carried out at 75 ~ C per 14.3 parts by weight of KF.
The resulting L41 aqueous medium was subjected to a BB ripening operation, consisting in maintaining said suspension with stirring at a temperature of 90C
for 1 hour.
The aqueous medium L42, coming out of the zone BB, was 3i ~ 3 cooled in BC to a temperature of 30C.
In the cooled aqueous medium L ~ 3, we add (zone C), 160 parts of H2O2 (100%) (L21) in 25 minutes ~
The suspension L3, leaving zone C) was subject to a slow pH adjustment to value 3.5 in CA, by introduction of an L22 hydroxide liquor potassium.
The suspension L ~, leaving the zone CA, was there subject to a D ripening operation, consisting of maintain said suspension with stirring at a temperature 36C for 45 minutes.
The suspension L ~, coming from D, was then subjected to an E separation operation, giving a liquor L5 and a solid phase S5.
The solid phase S5 was then subjected to an operation of washing in F, using 200 parts by weight of water, don an L6 liquor resulting from washing, and a solid phase S6.
The L5 and L6 liquors were mixed giving an L ~ 4 liquor, of which an L15 fraction was recycled to A
to the suspension of the uranium concentrate, while the L16 fraction was out of the cycle to avoid accumulation the impurity in the first step.
The L14 liquor represented 2,500 parts by weight.
The S6 cake, coming out of wash F, represented 658 parts by weight of a wet cake. This cake, after drying at 60C, had the following composition in percent in polds:
U: 6 ~, ~%
Zr: 1.09 ~
miscellaneous - ~ H2O: 3 ~, 51%
In the second stage of processing, the S6 cake, from of the first stage of treatment, was treated in G by 1050 parts of an L18 recycling liquor. Then suspension L7 was treated in H with 87 parts of HNO3 a 100%. This acid was introduced slowly, at 85C in 120 minutes, the suspension thus obtained L8, being now naked at 85C in I for 2 hours.
The Lg suspension, leaving zone I, was - subjected to a separation in J by giving an L1o liquor and a S10 cake, which was subjected to washing in K at mo ~ en de 500 parts by weight of water L25, giving a cake Sll and a liquor Lll.
The liquors Llo and I, 11 were mixed and constituted an L17 liquor which represented 2540 parts in weight. This L17 liqueur had the following composition:
U: 24.9%
ær: 0.005%
H2O + NO3 - ~ miscellaneous: 70.595%
A fraction of the purified L17 liquor was recycled to G
when the S6 cake is suspended as a result of the pre-first stage, while the Llg fraction constituted the uranium production liquor.
The Sll cake, after drying at 60C, represented a mass of 9.3 parts by weight. This cake contained practically 98.9% of the zirconium initially present in the uranium concentrate, and its uranium content was such that it represented a loss of 2 / oo compared to the uranium initially present in the concentrate which, in part of the continuous process, was resuspended M in a weakly acidic L26 liquor, to be recycled in A according to liquor L ~ 3 after filtration in N.
Thus, the comparison of tests O, P and Q with test N shows that the variant improves the purity of uranium liqueùr resultan-te Llg, mal ~ re the diverse origins of uranium concentrates.

Claims (38)

The embodiments of the invention, concerning the-what an exclusive property right or lien is claimed, are defined as follows: 1. Purification process of uranium concentrates fathers containing impurities, in particular one at less zirconium and / or hafnium elements, comprising the treatment of said concentrates in an acidic aqueous medium and hot with hydrogen peroxide to cause the uranium peroxide formation, characterized in that in a first step, and in order to precipitate quantita-uranium and to dissolve all or part of the impurities, the uranium concentrate is suspended in the aqueous medium, then slowly acidified and controlled manner by means of an agent acid, the resulting acidified aqueous medium is treated with means of hydrogen peroxide by causing formation a precipitate containing essentially uranium and almost all of the zirconium and / or hafnium that is separates from the liquid phase laden with impurities, then in a second step, the precipitate from the first step using an acidic agent to cause transformation and solubilization of uranium into ions soluble uranyles and separating the liquid phase containing the uranyl ions of the solid phase formed of a compound containing zirconium and / or hafnium. 2. Purification process of uranium concentrates fères according to claim 1, characterized in that the time of introduction of the acid agent in the first step is between 5 and 200 minutes. 3. Purification process of uranium concentrates fères according to claim 1, characterized in that the time of introduction of the acid agent in the first step is between 10 and 120 minutes. 4. Purification process of uranium concentrates fères according to claim 1, characterized in that the amount of acid agent introduced in the first step is such as the concentration of free H + after acidification is at least 0.0lN. 5. Purification process of uranium concentrates fères according to claim 1, characterized in that the amount of acid agent introduced in the first step is such as the concentration of free H + after acidification is at least 0.1 lN. 6. Purification process of uranium concentrates fères according to claim 1, 2 or 4, characterized in that the acidified aqueous medium is a suspension or solution. 7. Purification process of uranium concentrates fères according to claim 1, characterized in that the treatment with hydrogen peroxide of the aqueous medium acidified takes place at a controlled temperature at most equal to 80 ° C. 8. Purification process of uranium concentrates fères according to claim 1, characterized in that the treatment with hydrogen peroxide of the aqueous medium acidified takes place at a controlled temperature included between 30 ° C and 40 ° C. 9. Purification process of uranium concentrates fères according to claim 1, characterized in that the amount of hydrogen peroxide introduced into the medium acidified aqueous is at least equal to 1 time the quantity stoichiometric necessary for the precipitation of peroxide uranium. 10. Purification process of uranium concentrates fères according to claim 1, characterized in that the amount of hydrogen peroxide introduced into the medium acidified aqueous is between 2 and 10 times the amount stoichiometric necessary for the precipitation of peroxide uranium. 11. Purification process of uranium concentrates fères according to claim 1, characterized in that one treats the acidified aqueous medium using a source fluoride ions. 12. Purification process of uranium concentrates fères according to claim 11, characterized in that the temperature of the acidified medium is at least equal to 70 ° C. 13. Process for the purification of uranium concentrates fères according to claim 11, characterized in that the temperature of the acidified medium is chosen in the interval 90 ° C to 100 ° C. 14. Purification process for uranium concentrates fères according to claim 11, characterized in that the source of fluoride ions is chosen from the group consisting of killed by the compounds HF, NaF, KF, NH4F and Na2SiF6, used alone or as a mixture. 15. Purification process for uranium concentrates fères according to claim 11, characterized in that the molar ratio F / (Zr + Hf) is at least equal to 1. 16. Purification process for uranium concentrates fères according to claim 11, characterized in that the molar ratio F / (Zr + Hf) is between 4 and 10. 17. Purification process of uranium concentrates fères according to claim 11, characterized in that, while the complexing agent is being introduced, the temperature aqueous medium is maintained at least 70 ° C. 18. Process for the purification of uranium concentrates fères according to claim 11, characterized in that, while the complexing agent is being introduced, the temperature of the aqueous medium is maintained at a value understood between 90 ° C and 100 ° C. l9. Process for the purification of uranium concentrates fères according to claim 11, characterized in that the acidified aqueous medium containing the complexing agent is maintained under stirring for a time at most equal to 6 hours. 20. Process for purifying uranium concentrates fères according to claim 11, characterized in that the acidified aqueous medium containing the complexing agent is kept stirring for a time between 1 and 4 hours. 21. Purification process of uranium concentrates fères according to claim 19, characterized in that the acidified aqueous medium containing the complexing agent is maintained at a temperature of at least 70 ° C. 22. Process for the purification of uranium concentrates fères according to claim 19, characterized in that the acidified aqueous medium containing the complexing agent is maintained at a temperature between 90 ° C and 100 ° C. 23. Purification process of uranium concentrates fères according to claim 11, characterized in that the complexed acid medium is cooled to a lower temperature lower than 60 ° C. 24. Process for the purification of uranium concentrates fères according to claim 11, characterized in that the complexed acid medium is cooled to a temperature taken between 30 ° C and 40 ° C. 25. Purification process of uranium concentrates fères according to claim 11, characterized in that the suspension from peroxidation is subjected to a slow adjustment of the pH, which is chosen between 2.5 and 4.5, by introduction of an alkaline agent. 26. Purification process of uranium concentrates fères according to claim 1, characterized in that the suspension resulting from treatment with hydro- peroxide gene is kept agitated for a time at most equal to 6 hours. 27. Purification process of uranium concentrates fères according to claim 1, characterized in that the suspension resulting from treatment with hydro- peroxide gene is kept stirring for a time included between 2 and 4 hours. 28. Purification process of uranium concentrates fères according to claim 1, characterized in that the suspension resulting from treatment with hydro- peroxide gene is maintained at a temperature at most equal to 80 ° C. 29. Process for the purification of uranium concentrates fères according to claim 1, characterized in that the suspension resulting from treatment with hydro- peroxide gene is maintained at a temperature between 30 ° C and 40 ° C. 30. Purification process for uranium concentrates fères according to claim 1, characterized in that the precipitate resulting from the first step is processed in the state by an acid agent. 31. Process for the purification of uranium concentrates fères according to claim 1, characterized in that the precipitate resulting from the first step is suspended sion in acidified water or in a recycling liquor acid clage. 32. Process for the purification of uranium concentrates fères according to claim 1, characterized in that the amount of acid agent required to process the preci-pity resulting from the first step is at most equal to the stoichiometric quantity corresponding to the uranium present. 33. Process for the purification of uranium concentrates fères according to claim 1, characterized in that the acid agent treatment of the precipitate resulting from the first step is carried out at a temperature between 60 ° C and 100 ° C. 34. Process for the purification of uranium concentrates fères according to claim 1, characterized in that the acid agent treatment of the precipitate resulting from the first step is carried out at a temperature between 85 ° C and 95 ° C. 35. Process for the purification of uranium concentrates fères according to claim 1, characterized in that the acid agent treatment of the precipitate resulting from the first step, takes at least 1 hour. 36. Process for the purification of uranium concentrates fères according to claim 1, characterized in that the acid agent treatment of the precipitate resulting from the first step, takes place in a time between 3 and 5 hours. 37. Process for the purification of uranium concentrates fères according to claim 1, characterized in that the suspension resulting from treatment with an acidic agent precipitate from the first stage is cooled to a temperature at most equal to 40 ° C. 38. Process for the purification of uranium concentrates fères according to claim 1, characterized in that the acid agent introduced in the first and second stage belongs to the group consisting of nitri-that, sulfuric and hydrochloric and the mixture of at least two of them.