EP0100744A1 - Process for extracting uranium from phosphoric acids using alkylpyrophosphoric acids - Google Patents

Process for extracting uranium from phosphoric acids using alkylpyrophosphoric acids Download PDF

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EP0100744A1
EP0100744A1 EP83420127A EP83420127A EP0100744A1 EP 0100744 A1 EP0100744 A1 EP 0100744A1 EP 83420127 A EP83420127 A EP 83420127A EP 83420127 A EP83420127 A EP 83420127A EP 0100744 A1 EP0100744 A1 EP 0100744A1
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Prior art keywords
extraction
uranium
extracting
acid
alkylpyrophosphoric
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EP0100744B1 (en
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Antoine Floreancig
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Uranium Pechiney
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Uranium Pechiney
Pechiney Ugine Kuhlmann SA
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
    • C22B60/02—Obtaining thorium, uranium, or other actinides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
    • C22B60/02—Obtaining thorium, uranium, or other actinides
    • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
    • C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
    • C22B60/0252—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries
    • C22B60/026—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries liquid-liquid extraction with or without dissolution in organic solvents

Definitions

  • the invention relates to an improved method of extraction using an agent, consisting of alkylpyrophosphoric acids, of uranium present in phosphoric acid solutions, method which makes it possible to maintain the extraction power over said agent over time. by limiting its degradation.
  • alkylpyrophosphoric acids as uranium extraction agent, used in a form dissolved in an organic diluent, such as that petroleum cut, kerosene, etc .
  • the most commonly used extraction agent being alkylpyrophosphoric acid obtained by reaction of P 2 O 5 with octanol 2.
  • recovering the uranium contained in phosphoric acid at a rate of 90 to 200 milligrams of uranium oxide U 3 0 8 per liter consists first of all in contacting the solution of phosphoric acid with the extraction aqent most commonly constituted by octylpyrophosphoriqiie acid in solution in kerosene, the extraction of uranium being carried out against the current in a group of mixing and sedimentation tanks in cascade .
  • the phase organic containing in solution the octylpyrophosphorioue acid charged in uranium, separated from the solution of phosphoric acid is treated by contact by means of hydrofluoric acid giving the uranium fluoride (UF 4 ) and the deuraniated octylpyrophosphoric acid.
  • alkylpyrophosphoric acids as uranium extraction agent, and in particular octylpyrophosphoric acid, lies in the fact of their strong extracting power, even when they are used in organic solution very diluted, allowing them to extract, with a very good yield, the uranium present, even in very small quantity, in solutions of phosphoric acids.
  • French patent 2,423,545 describes a process for extracting uranium from phosphoric acid solutions whose extracting agent is a pyrophosphoric acid diester such as dicaproyl pyrophosphate or dioctyl pyrophosphate, a process according to which the hydrolysis of said extracting agent would be strongly dimine, while the re-extraction of uranium present in the organic phase is carried out by means of an alkaline solution and no longer by means of hydrofluoric acid.
  • a pyrophosphoric acid diester such as dicaproyl pyrophosphate or dioctyl pyrophosphate
  • the process according to the invention for the extraction of uranium contained in phosphoric acid solutions by means of an extraction agent consisting of an alkylpyrophosphoric acid, which consists in bringing the mineral phase of phosphoric acid and an organic phase containing the extraction agent by creating an emulsion is characterized in that, in an extraction unit comprising n cascade stages, for each extraction stage, the emulsion is produced during '' a first step by simultaneously subjecting the two phases for a time T1 to an intense mechanical shearing action corresponding to a shear coefficient of at least 5000 second-l in order to increase the contact surfaces between these two phases, then said emulsion during a second step is suddenly broken in a time T 2 , the total time required for the completion of the two steps being at most 20 minutes.
  • the extraction unit has a number of stages n of between 2 and 20.
  • the mineral and organic phases must be subjected to an intense mechanical shearing action corresponding to a very high shear coefficient.
  • this shear coefficient is chosen in the interval 5000 seconds to 50,000 seconds but preferably in the interval 10,000 seconds to 25,000 seconds.
  • the total time required to carry out the two stages according to the invention is preferably at most equal to 10 minutes for an extraction stage.
  • the times T 1 and T 2 of execution of the two stages can vary within wide limits, their ratio T 1 / T 2 can be chosen within the limits 1/100 to 5/1 and preferably within the limits 1 / 25 to 2/1.
  • the emulsion between the two organic and mineral phases is produced by any means known to those skilled in the art, making it possible to quickly and vigorously obtain the finest emulsion possible, in order to multiply the surfaces of contact and obtain a very high extraction yield.
  • the rapid separation of the organic and mineral phases can be obtained by physical means using any known means allowing rapid rupture of said emulsion.
  • the extracting agent, entrained by the desuranic phosphoric acid can be recovered by a physical separation of centrifugation for example and joined to the recycled extraction agent after re-extraction of the uranium .
  • the uranium extracting agent is chosen from the well-known group of alkylpyrophosphoric acids, the alkyl radical of which is a carbon chain corresponding to the C 7 to C 13 alcohols obtained by oxo synthesis, such as for example octanol 2, ethylhexanol, decanol.
  • the preparation of alkylpyrophosphoric acid can be carried out in a known manner by adding P 2 0 5 to the abovementioned alcohol, used alone or as a mixture with a hydrocarbon.
  • the preparation temperature of the alkylpyrophosphoric acid is generally between 30 ° C and 80 ° C, but preferably between 30 ° C and 40 ° C.
  • the uranium extraction agent is generally dissolved in an alphatic and / or aromatic hydrocarbon, such as kerosene for example.
  • the mixture thus formed constitutes the organic phase of extraction of uranium, which contains from 5 to 100 g / l but preferably from 20 to 50 g / l of alkylpyrophosphoric acid.
  • the phosphoric acid solutions resulting from the attack on phosphate ores generally contain from 30 to 200 milligrams of uranium per liter, this uranium being partly in the form U IV and for the other in the form U VI.
  • the uranium VI is then reduced to uranium IV by the treatment of the solutions of phosphoric acids by means of iron, which is in the form of powder when the reduction treatment is carried out in a reactor or also in the form of scrap metal when the reduction treatment is carried out in a column.
  • the phosphoric acid solutions containing suspended solids are subjected to a separation operation, before being brought into contact with the extraction agent in solution in an aliphatic and / or aromatic hydrocarbon.
  • the two mineral and organic phases to be extracted and extracting are then brought into intimate contact in the form of a fine emulsion which is quickly broken in order to separate the organic phase loaded with uranium from the mineral phase with deuranied acid.
  • the organic phase loaded with uranium is then treated with an aqueous hydrofluoric acid solution, this solution containing 10 ° or 20%, but preferably 14 to 18% by weight of free HF.
  • the temperature at which the uranium is re-extracted by hydrofluoric acid is between 0 ° C and 60 ° C but preferably between 10 ° C and 30 ° C, temperature at which the degradation of the alkylpyrophosphoric acid remains low (less than 2%).
  • the uranium then precipitates in the form of UF 4 , which is separated from the liquid medium by any means chosen from those known to those skilled in the art.
  • the desuranized alkylpyrophosphoric acid is then recycled directly to the extraction of the uranium contained in the phosphoric acid solutions after optional recharging with new alkylpyrophosphoric acid, while the desuranized phosphoric acid solutions are themselves subjected to centrifugation to recover the mechanically driven extractant.
  • This example illustrates the method of extracting uranium according to the invention, using alkylpyrophosphoric acids compared to the extraction method most commonly used in the processes belonging to the prior art.
  • This acid is reduced either by powdered iron in a stirred tank for tests 1 to 4, or in a column by plate iron for tests 5 and 6.
  • the reduced phosphoric acid contains Fe II and Fe III in an Fe II / Fe III ratio between 5 and 5.3.
  • the phosphoric acid is treated with the extracting agent in solution in kerosene at a rate of 30 g / l.
  • the reduced phosphoric acid flow rate was 200 l / h while that of the extractant solution was 20 l / h.
  • the desuranized solvent was recycled to extraction after adding a fraction of an hour of the extractant.
  • Test No. 1 which illustrates the prior art, was carried out in an industrial installation, the extraction unit of which consisted of a battery of 4 mixer-settlers - extraction unit in which the cumulative times T l and T 2 for 4 stages as defined in the method according to the invention, is equal to 14 hours.
  • Test No. 2 illustrating the invention was carried out in an industrial installation, the extraction unit of which consisted of a 4-stage multi-stage centrifugal extractor, rotating at the speed of 2800 revolutions per minute, a unit in which the cumulative residence times T 1 and T 2 for 4 floors was less than two minutes.
  • Test No. 3 illustrating the prior art, differs from Test No. 1 in the nature of the extractant which in this case was a solution of ethylhexylpyrophosphoric acid.
  • Test No. 4 illustrating the invention, differs from Test No. 2 in the nature of the extractant which was ethylhexylpyrophosphoric acid.
  • Test n ° 5 differs from test n ° 1 only in the mode of reduction of phosphoric acid (on platelets in column).
  • Test n ° 6 differs from test n ° 2 by the mode of reduction of phosphoric acid and by the constitution of the extraction unit which included four single stage centrifugal extractors in battery - unit in which the cumulative residence times T 1 and T 2 was less than two minutes.
  • This example illustrates the method of extracting uranium according to the invention, using alkylpyrophosphoric acids, compared to the extraction method most commonly used in methods belonging to the prior art.
  • the phosphoric acid treated had the following composition:
  • Test No. 8 which illustrates the invention, was carried out like test 2, but using a battery comprising 3 single-stage centrifugal extractors.

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  • Chemical & Material Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
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  • Manufacturing & Machinery (AREA)
  • Environmental & Geological Engineering (AREA)
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Abstract

Procédé d'extraction de l'uranium contenu dans les solutions d'acides phosphoriques au moyen d'un agent d'extraction constitué par un acide alkylpyrophosphorique, qu consiste à mettre en contact sous agitation la phase minérale d'acide phosphorique et une phase organique contenant l'agent d'extraction en créant une émulsion, qui se caractérise en ce que, dans une unité d'extraction comprenant n étages en cascade, pour chaque étage d'extraction, l'émulsion est produite lors d'une première étape en soumettant simutanément les deux phases pendant un temps T1 à une action mécanique de cisaillement intense, correspondant à un coefficient de cisaillement d'au moins 5 000 seconde<->¹ dans le but de multiplier les surfaces de contact entre ces deux phases, puis ladite émulsion lors d'une deuxième étape est brutalement cassée en un temps T2, le cumul des temps nécessaires à la réalisation des deux étapes étant au plus de 20 minutes.Process for the extraction of uranium contained in solutions of phosphoric acids by means of an extraction agent consisting of an alkylpyrophosphoric acid, which consists in bringing the mineral phase of phosphoric acid into contact with an organic phase containing the extraction agent by creating an emulsion, which is characterized in that, in an extraction unit comprising n cascade stages, for each extraction stage, the emulsion is produced during a first stage in simultaneously subjecting the two phases for a time T1 to an intense mechanical shearing action, corresponding to a shear coefficient of at least 5,000 seconds <-> ¹ in order to increase the contact surfaces between these two phases, then said emulsion during a second step is suddenly broken in a time T2, the total time required for the completion of the two steps being at most 20 minutes.

Description

L'invention concerne un procédé amélioré d'extraction au moyen d'un agent, constitué par les acides alkylpyrophosphoriques, de l'uranium présent dans les solutions d'acide phosphorique, procédé permettant de conserver dans le temps le pouvoir d'extraction audit agent en limitant sa dégradation.The invention relates to an improved method of extraction using an agent, consisting of alkylpyrophosphoric acids, of uranium present in phosphoric acid solutions, method which makes it possible to maintain the extraction power over said agent over time. by limiting its degradation.

Depuis longtemps déjà et comme l'atteste le grand nombre de publications dans ce domaine, de nombreuses recherches ont été effectuées pour trouver le procédé d'extraction de l'uranium présent dans les solutions d'acide phosphorique, qui soit le mieux adapté et le plus performant.For a long time now and as evidenced by the large number of publications in this field, much research has been carried out to find the method of extraction of uranium present in phosphoric acid solutions, which is the most suitable and the more efficient.

Dans le groupe des procédés d'extraction actuellement connu, l'homme de l'art a retenu celui qui fait usage des acides alkylpyrophosphoriques comme agent d'extraction de l'uranium, mis en oeuvre sous une forme solubilisée dans un diluant organique, tel que coupe pétrolière, kérosène, etc....., l'agent d'extraction le plus usité étant l'acide alkylpyrophosphoriques obtenu par réaction de P2O5 sur l'octanol 2.In the group of extraction processes currently known, those skilled in the art have chosen the one which uses alkylpyrophosphoric acids as uranium extraction agent, used in a form dissolved in an organic diluent, such as that petroleum cut, kerosene, etc ....., the most commonly used extraction agent being alkylpyrophosphoric acid obtained by reaction of P 2 O 5 with octanol 2.

Parmi les nombreuses recherches en ce domaine, il est possible de citer les travaux de R.S. Long, matérialisés par le compte rendu des Conférences de Genève du 8 au 20 août 1955, volume VIII , page 524, sur la "récupération de l'uranium des phosphates par extraction au moyen de solvants", et le brevet américain 2 866 680 concernant un procédé d'extraction de l'uranium en solution acide au moyen d'un solvant constitué par un acide alkylpyrophosphorique.Among the many researches in this field, it is possible to cite the work of RS Long, materialized by the report of the Geneva Conferences from August 8 to 20, 1955, volume VIII, page 524, on the "recovery of uranium from phosphates by extraction using solvents ", and US Pat. No. 2,866,680 concerning a process for the extraction of uranium in acid solution using a solvent constituted by an alkylpyrophosphoric acid.

Selon les travaux de R.S. Long, la récupération de l'uranium contenu dans l'acide phosphorique à raison de 90 à 200 milligrammes d'oxyde d'uranium U308 par litre, consiste tout d'abord à mettre en contact la solution d'acide phosphorique avec l'aqent d'extraction constitué le plus couramment par l'acide octylpyrophosphoriqiie en solution dans du kérosène, l'extraction de l'uranium se faisant à contre courant dans un groupe de cuves de mélange et de sédimentation en cascade. Puis, dès la sortie de la dernière cuve de sédimentation, la phase organique contenant en solution l'acide octylpyrophosphorioue chargé en uranium, séparée de la solùtion d'acide phosphorique, est traitée par contact au moyen d'acide fluorhydrique en donnant le fluorure d'uranium (U F4) et l'acide octylpyrophosphorique désuranié.According to the work of RS Long, recovering the uranium contained in phosphoric acid at a rate of 90 to 200 milligrams of uranium oxide U 3 0 8 per liter, consists first of all in contacting the solution of phosphoric acid with the extraction aqent most commonly constituted by octylpyrophosphoriqiie acid in solution in kerosene, the extraction of uranium being carried out against the current in a group of mixing and sedimentation tanks in cascade . Then, right out of the last sedimentation tank, the phase organic containing in solution the octylpyrophosphorioue acid charged in uranium, separated from the solution of phosphoric acid, is treated by contact by means of hydrofluoric acid giving the uranium fluoride (UF 4 ) and the deuraniated octylpyrophosphoric acid.

Il est de notoriété que l'intérêt d'utiliser les acides alkylpyrophosphoriques comme agent d'extraction de l'uranium, et en particulier l'acide octylpyrophosphorique,réside dans le fait de leur fort pouvoir extractant, même quand ils sont utilisés en solution organique très diluée, leur permettant d'extraire, avec un très bon rendement, l'uranium présent, même en très faible quantité, dans les solutions d'acides phosphoriques.It is well known that the advantage of using alkylpyrophosphoric acids as uranium extraction agent, and in particular octylpyrophosphoric acid, lies in the fact of their strong extracting power, even when they are used in organic solution very diluted, allowing them to extract, with a very good yield, the uranium present, even in very small quantity, in solutions of phosphoric acids.

Cependant, lorsque l'extraction de l'uranium des solutions d'acides phosphoriques est réalisée à l'échelle industrielle au moyen de l'acide octylpyrophosphorique par exemple, il est connu que l'agent d'extraction de l'uranium, dès lors qu'il a été débarrassé de l'uranium et qu'il est recyclé à l'extraction, ne possède plus le pouvoir d'extraction initial, c'est-à-dire que le coefficient d'extraction dudit agent est abaissé comparativement à sa valeur d'origine. Et il devient alors nécessaire, soit de faire l'appoint en acide alkylpyrophosphorique pour ramener à un niveau raisonnable le coefficient d'extraction, soit même de remplacer la totalité de l'agent d'extraction usagé par un agent neuf.However, when the extraction of uranium from phosphoric acid solutions is carried out on an industrial scale by means of octylpyrophosphoric acid for example, it is known that the uranium extracting agent, therefore that it has been freed from uranium and that it is recycled for extraction, no longer has the initial extraction power, that is to say that the extraction coefficient of said agent is lowered compared to its original value. And it then becomes necessary, either to add alkylpyrophosphoric acid to bring the extraction coefficient to a reasonable level, or even to replace all of the used extraction agent with a new agent.

De nombreuses tentatives ont alors été faites pour conserver aux acides alkylpyrophosphoriques et en particulier à l'acide octylpyrophosphorique leur coefficient d'extraction initial, lorsqu'ils sont mis en oeuvre pour extraire l'uranium des solutions d'acides phosphoriques. Parmi les moyens proposés pour sauvegarder le pouvoir extractant dudit agent, il a été suggéré de pratiquer la réextraction de l'uranium contenu dans l'acide alkylphosphorique utilisé, non plus au moyen de l'acide fluorhydrique mais par une solution alcaline, puisqu'il était admis que l'acide alkylpyrophosphorique chargé en uranium subissait une hydrolyse de la part de l'acide fluorhydrique, agent de réextraction habituel, en donnant des esters d'acide phosphorique. fiais il a également été proposé d'autres moyens tel celui qui consiste en l'ajout d'un tiers corps, par exemple l'octanol 2 ou le tibutylphos- phate, à l'agent d'extraction constitué par un acide alkylpyrophosphorique ou encore d'employer comme agent d'extraction de l'uranium, d'autres acides alkylpyrophosphoriques, offrant une sensibilité amoindrie à l'hydrolyse acide, ou bien à abaisser la température d'extraction, etc....C'est dans cet esprit que le brevet français 2 423 545, décrit un procédé d'extraction de l'uranium de solutions d'acide phosphorique dont l'agent d'extraction est un diester de l'acide pyrophosphorique tel que le pyrophosphate de dicaproyle ou encore le pyrophosphate de dioctyle, procédé selon lequel l'hydrolyse dudit agent d'extraction serait fortement diminée, tandis que la réextraction de l'uranium présent dans la phase organique s'effectue au moyen d'une solution alcaline et non plus par l'intermédiaire de l'acide fluorhydrique.Numerous attempts have then been made to preserve the initial extraction coefficient for alkylpyrophosphoric acids and in particular for octylpyrophosphoric acid, when they are used to extract uranium from phosphoric acid solutions. Among the means proposed to safeguard the extracting power of said agent, it has been suggested to practice the re-extraction of the uranium contained in the alkylphosphoric acid used, no longer by means of hydrofluoric acid but by an alkaline solution, since it was admitted that the alkylpyrophosphoric acid loaded with uranium underwent a hydrolysis on the part of hydrofluoric acid, usual agent of re-extraction, by giving esters of phosphoric acid. have also been proposed other means such as that which consists of the addition of a third body, for example octanol 2 or tibutylphosphate, to the extracting agent constituted by an alkylpyrophosphoric acid or else to employ as uranium extracting agent, other alkylpyrophosphoric acids, offering a reduced sensitivity to acid hydrolysis, or to lowering the extraction temperature, etc. It is in this spirit that French patent 2,423,545 describes a process for extracting uranium from phosphoric acid solutions whose extracting agent is a pyrophosphoric acid diester such as dicaproyl pyrophosphate or dioctyl pyrophosphate, a process according to which the hydrolysis of said extracting agent would be strongly dimine, while the re-extraction of uranium present in the organic phase is carried out by means of an alkaline solution and no longer by means of hydrofluoric acid.

Toutefois, malgré les nombreuses solutions proposées, force est de constater que l'extraction en continu de l'uranium de valence IV, à l'échelle industrielle , au moyen d'un acide àlkylpyrophosphorique recyclé après la réextraction de l'uranium, exige à chaque cycle, un appoint important en acide alkylpyrophosphorique neuf, cet appoint pouvant atteindre souvent plus de la moitié de l'agent extractant utilisé pour un cycle.However, despite the many solutions proposed, it is clear that the continuous extraction of valence IV uranium, on an industrial scale, using an alkyl pyrophosphoric acid recycled after the re-extraction of uranium, requires each cycle, a significant addition of new alkylpyrophosphoric acid, this makeup often reaching more than half of the extractant used for a cycle.

Devant la quasi impossibilité sinon de maintenir, tout au moins de limiter la perte du pouvoir extractant des acides alkylpyrophosphoriques au contact des solutions d'acides phosphoriques contenant l'uranium, ilamême été proposé dans le brevet américain 4 293 529 de dégrader complétement par chauffage l'agent extractant à chaque cycle, puis, après oxydation de UIV en UV,, de réextraire l'uranium par une solution d'acide phosphorique.In front of the quasi impossibility if not to maintain, at least to limit the loss of the extracting power of alkylpyrophosphoric acids in contact with the solutions of phosphoric acids containing uranium, it was even proposed in the American patent 4 293 529 to degrade completely by heating l extracting agent at each cycle, then, after oxidation of UIV to U V , to re-extract the uranium with a solution of phosphoric acid.

Poursuivant ses recherches en ce domaine, en vue d'améliorer le procédé d'extraction de l'uranium à partir des solutions d'acides phosphoriques au moyen d'acides alkylpyrsphosphoriques, la demanderesse a pu observer que les pertes en agent d'extraction étaient la conséquence non seulement de l'action de l'acide fluorhydrique lors de la réextraction de l'uranium, mais aussi de l'action de l'acide phosphorique (et de ses impuretés) lors de son contact avec l'agent d'extraction, et ce d'une manière d'autant plus importante et critique que le temps de contact est plus long.Continuing her research in this field, with a view to improving the process for extracting uranium from solutions of phosphoric acids using alkylpyrsphosphoric acids, the applicant was able to observe that the losses of extracting agent were the consequence not only of the action of hydrofluoric acid during the re-extraction of uranium, but also of the action of phosphoric acid (and its impurities) during its contact with the extraction agent, and this all the more important and critical the longer the contact time.

Dès lors, forte des inconvénients précités et des phénomènes qu'elle a pu étudier, la demanderesse grâce à ses recherches, a trouvé et mis au point un procédé amélioré d'extraction de l'uranium contenu dans les solutions d'acides phosphoriques, au moyen d'un agent d'extraction choisi dans le groupe des acides alkylpyrophosphoriques qui permet d'éviter leur dégradation par hydrolyse acide, tout en leur conservant leur pouvoir extractant.Therefore, with the aforementioned drawbacks and the phenomena it has been able to study, the plaintiff, thanks to its research, has found and developed an improved process for extracting the uranium contained in solutions of phosphoric acids, means of an extraction agent chosen from the group of alkylpyrophosphoric acids which makes it possible to avoid their degradation by acid hydrolysis, while retaining their extracting power.

Le procédé selon l'invention de l'extraction de l'uranium contenu dans les solutions d'acides phosphoriques au moyen d'un agent d'extraction constitué par un acide alkylpyrophosphorique, qui consiste à mettre en contact sous agitation la phase minérale d'acide phosphorique et une phase organique contenant l'agent d'extraction en créant une émulsion, se caractérise en ce que, dans une unité d'extraction comprenant n étages en cascade, pour chaque étage d'extraction, l'émulsion est produite lors d'une première étape en soumettant simultanément les deux phases pendant un temps T1 à une action mécanique de cisaillement intense correspondant à un coefficient de cisaillement d'au moins 5000 seconde-l dans le but de multiplier les surfaces de contact entre ces deux phases, puis ladite émulsion lors d'une deuxième étape est brutalement cassée en un temps T2, le cumul des temps nécessaires à la réalisation des deux étapes étant au plus de 20 minutes.The process according to the invention for the extraction of uranium contained in phosphoric acid solutions by means of an extraction agent consisting of an alkylpyrophosphoric acid, which consists in bringing the mineral phase of phosphoric acid and an organic phase containing the extraction agent by creating an emulsion, is characterized in that, in an extraction unit comprising n cascade stages, for each extraction stage, the emulsion is produced during '' a first step by simultaneously subjecting the two phases for a time T1 to an intense mechanical shearing action corresponding to a shear coefficient of at least 5000 second-l in order to increase the contact surfaces between these two phases, then said emulsion during a second step is suddenly broken in a time T 2 , the total time required for the completion of the two steps being at most 20 minutes.

Il est apparu en effet à la demanderesse, et ses travaux de recherche l'ont confirmé, qu'il est possible de réaliser l'extraction de l'uranium IV contenu dans les solutions d'acides phosphoriques au moyen d'un acide alkylpyrophosphorique avec un rendement d'au moins 98 S, tout en conservant à l'agent d'extraction recyclé toute son efficacité, avec un appoint d'agent d'extraction neuf de 5 à 10 fois plus faible que dans les procédés selon l'art antérieur, à condition que l'on forme énergiquement une émulsion entre les deux phases minérale et organique dont la dimension des particules est généralement inférieure à 45 microns puis que l'on sépare rapidement ces deux phases en cassant l'équilibre de l'émulsion.It has indeed appeared to the plaintiff, and his research work has confirmed it, that it is possible to carry out the extraction of uranium IV contained in the solutions of phosphoric acids by means of an alkylpyrophosphoric acid with a yield of at least 98%, while retaining all the effectiveness of the recycled extractant, with a supply of new extractant 5 to 10 times lower than in the processes according to the prior art , provided that an emulsion is vigorously formed between the two mineral and organic phases, the particle size of which is generally less than 45 microns, then that these two phases are rapidly separated by breaking the equilibrium of the emulsion.

En général, l'unité d'extraction comporte un nombre d'étages n compris entre 2 et 20. Mais selon une variante, l'unité d'extraction peut être composée d'un seul étage et dans ce cas n = 1.In general, the extraction unit has a number of stages n of between 2 and 20. However, according to a variant, the extraction unit can be composed of a single stage and in this case n = 1.

Pour aboutir à l'obtention d'une suspension dont les particules ont une dimension en générale inférieure à 45 microns, les phases minérale et organique doivent être soumises à une action mécanique de cisaillement intense correspondant à un coefficient de cisaillement très élevé. En général, ce coefficient de cisaillement est choisi dans l'intervalle 5000 seconde à 50000 seconde mais de préférence dans l'intervalle 10 000 seconde à 25 000 seconde.To obtain a suspension whose particles generally have a size of less than 45 microns, the mineral and organic phases must be subjected to an intense mechanical shearing action corresponding to a very high shear coefficient. In general, this shear coefficient is chosen in the interval 5000 seconds to 50,000 seconds but preferably in the interval 10,000 seconds to 25,000 seconds.

Le cumul des temps nécessaires à la réalisation des deux étapes selon l'invention est préférentiellement au plus égal à 10 minutes pour un étage d'extraction.The total time required to carry out the two stages according to the invention is preferably at most equal to 10 minutes for an extraction stage.

En outre, les temps T1 et T2 d'exécution des deux étapes peuvent varier dans de larges limites, leur rapport T1/T2 pouvant être choisi dans les limites 1/100 à 5/1 et de préférence dans les limites 1/25 à 2/1.In addition, the times T 1 and T 2 of execution of the two stages can vary within wide limits, their ratio T 1 / T 2 can be chosen within the limits 1/100 to 5/1 and preferably within the limits 1 / 25 to 2/1.

L'émulsion entre les deux phases organique et minérale est réalisée par tout moyen connu de l'homme de l'art, permettant d'obtenir d'une manière rapide et énergique l'émulsion la plus fine possible, afin de multiplier les surfaces de contact et d'obtenir un très fort rendement d'extraction.The emulsion between the two organic and mineral phases is produced by any means known to those skilled in the art, making it possible to quickly and vigorously obtain the finest emulsion possible, in order to multiply the surfaces of contact and obtain a very high extraction yield.

En général, la séparation rapide des phases organique et minérale peut être obtenue par voie physique en utilisant tout moyen connu permettant une rupture rapide de ladite émulsion.In general, the rapid separation of the organic and mineral phases can be obtained by physical means using any known means allowing rapid rupture of said emulsion.

Parmi les moyens physiques permettant de produire puis de détruire l'émulsion très fine des phases organiques et minérale, et de séparer très rapidement lesdites phases, il est possible d'utiliser des hydrocyclones aménagés, des extracteurs centrifuges à multiétages ou encore des extracteurs centrifuges monoétage, organisés en batterie.Among the physical means making it possible to produce and then destroy the very fine emulsion of the organic and mineral phases, and to very quickly separate said phases, it is possible to use fitted hydrocyclones, multi-stage centrifugal extractors or else single-stage centrifugal extractors , organized in battery.

De même, et pour diminuer les pertes, l'agent d'extraction, entraîné par l'acide phosphorique désuranié peut être récupéré par une séparation physique de centrifugation par exemple et joint à l'agent d'extraction recyclé après réextraction de l'uranium.Likewise, and in order to reduce losses, the extracting agent, entrained by the desuranic phosphoric acid can be recovered by a physical separation of centrifugation for example and joined to the recycled extraction agent after re-extraction of the uranium .

Comme cela a été dit, l'agent d'extraction de l'uranium est choisi dans le groupe bien connu des acides alkylpyrophosphoriques, dont le radical alkyl est une chaîne carbonée correspondant aux alcool en C7 à C13 obtenus par synthèse oxo, tels que par exemple l'octanol 2, l'éthylhéxanol, le décanol. La préparation de l'acide alkylpyrophosphorique peut s'effectuer d'une manière connue par addition de P205 à l'alcool précité, utilisé seul ou en mélange avec un hydrocarbure.As has been said, the uranium extracting agent is chosen from the well-known group of alkylpyrophosphoric acids, the alkyl radical of which is a carbon chain corresponding to the C 7 to C 13 alcohols obtained by oxo synthesis, such as for example octanol 2, ethylhexanol, decanol. The preparation of alkylpyrophosphoric acid can be carried out in a known manner by adding P 2 0 5 to the abovementioned alcohol, used alone or as a mixture with a hydrocarbon.

La température de préparation de l'acide alkylpyrophosphorique est généralement comprise entre 30° C et 80° C, mais de préférence entre 30° C et 40° C.The preparation temperature of the alkylpyrophosphoric acid is generally between 30 ° C and 80 ° C, but preferably between 30 ° C and 40 ° C.

L'agent d'extraction de l'uranium est généralement mis en solution dans un hydrocarbure alphatique et/ou aromatique, tel que les kérosènes par exemple. Le mélange ainsi formé constitue la phase organique d'extraction de l'uranium, qui contient de 5 à 100 g/1 mais de préférence de 20 à 50 g/1 d'acide alkylpyrophosphorique.The uranium extraction agent is generally dissolved in an alphatic and / or aromatic hydrocarbon, such as kerosene for example. The mixture thus formed constitutes the organic phase of extraction of uranium, which contains from 5 to 100 g / l but preferably from 20 to 50 g / l of alkylpyrophosphoric acid.

En pratique, les solutions d'acides phosphoriques résultant de l'attaque de minerais phosphatés contiennert en général de 30 à 200 milligrammes d'uranium par litre, cet uranium étant pour une partie sous la forme U IV et pour l'autre sous la forme U VI.In practice, the phosphoric acid solutions resulting from the attack on phosphate ores generally contain from 30 to 200 milligrams of uranium per liter, this uranium being partly in the form U IV and for the other in the form U VI.

L'uranium VI est alors réduit en uranium IV par le traitement des solutions d'.acides phosphoriques au moyen de fer, se présentant sous forme de poudre quand le traitement de réduction s'effectue en réacteur ou encore sous forme de déchets de ferrailles quand le traitement de réduction s'effectue dans une colonne.The uranium VI is then reduced to uranium IV by the treatment of the solutions of phosphoric acids by means of iron, which is in the form of powder when the reduction treatment is carried out in a reactor or also in the form of scrap metal when the reduction treatment is carried out in a column.

Après que le traitement de réduction ait été effectué, les solutions d'acides phosphoriques contenant en suspension des matières solides, sont soumises à une opération de séparation, avant d'être mises en contact avec l'agent d'extraction en solution dans un hydrocarbure aliphatique et/ou aromatique.After the reduction treatment has been carried out, the phosphoric acid solutions containing suspended solids, are subjected to a separation operation, before being brought into contact with the extraction agent in solution in an aliphatic and / or aromatic hydrocarbon.

Les deux phases minérale et organique à extraire et extractante sont alors mises en contact intime sous la forme d'une fine émulsion qui est rapidement cassée afin de séparer la phase organique chargée en uranium de la phase minérale en acide désuraniée.The two mineral and organic phases to be extracted and extracting are then brought into intimate contact in the form of a fine emulsion which is quickly broken in order to separate the organic phase loaded with uranium from the mineral phase with deuranied acid.

Puis la phase organique chargée en uranium est alors traitée par une solution aqueuse d'acide fluorhydrique, cette solution contenant 10 °o à 20 % , mais de préférence de 14 à 18 % en poids de HF libre.The organic phase loaded with uranium is then treated with an aqueous hydrofluoric acid solution, this solution containing 10 ° or 20%, but preferably 14 to 18% by weight of free HF.

La température à laquelle s'effectue la réextraction de l'uranium par l'acide fluorhydrique est comprise entre 0° C et 60° C mais préférentiellement entre 10° C et 30° C, température à laquelle la dégradation de l'acide alkylpyrophosphorique reste faible (inférieure à 2%).The temperature at which the uranium is re-extracted by hydrofluoric acid is between 0 ° C and 60 ° C but preferably between 10 ° C and 30 ° C, temperature at which the degradation of the alkylpyrophosphoric acid remains low (less than 2%).

L'uranium précipite alors sous la forme d'UF4, qui est séparé du milieu liquide par un quelconque moyen choisi parmi ceux connus de l'homme de l'art.The uranium then precipitates in the form of UF 4 , which is separated from the liquid medium by any means chosen from those known to those skilled in the art.

L'acide alkylpyrophosphorique désuranié est alors recyclé directement à l'extraction de l'uranium contenu dans les solutions d'acides phosphoriques après recharge éventuelle en acide alkylpyrophosphorique neuf, tandis que les solutions d'acides phosphoriques désuraniées sont elles-mêmes soumises à centrifugation pour récupérer l'agent d'extraction mécaniquement entraîné.The desuranized alkylpyrophosphoric acid is then recycled directly to the extraction of the uranium contained in the phosphoric acid solutions after optional recharging with new alkylpyrophosphoric acid, while the desuranized phosphoric acid solutions are themselves subjected to centrifugation to recover the mechanically driven extractant.

L'invention sera mieux comprise grâce aux exemples illustratifs.The invention will be better understood thanks to the illustrative examples.

EXEMPLE 1EXAMPLE 1

Cet exemple illustre le procédé d'extraction de l'uranium selon l'invention, au moyen d'acides alkylpyrophosphoriques comparativement au procédé d'extraction le plus couramment employé dans les procédés appartenant à l'art antérieur.This example illustrates the method of extracting uranium according to the invention, using alkylpyrophosphoric acids compared to the extraction method most commonly used in the processes belonging to the prior art.

Pour ce faire, on a traité un acide phosphorique ex Togo-Maroc ayant la composition suivante :

Figure imgb0001
To do this, we treated a phosphoric acid ex Togo-Morocco having the following composition:
Figure imgb0001

Cet acide est réduit soit par du fer en poudre dans une cuve agitée pour les essais 1 à 4, soit dans une colonne par du fer en plaquette pour les essais 5 et 6.This acid is reduced either by powdered iron in a stirred tank for tests 1 to 4, or in a column by plate iron for tests 5 and 6.

L'acide phosphorique réduit contient du Fe II et du Fe III dans un rapport Fe II/Fe III compris entre 5 et 5,3.The reduced phosphoric acid contains Fe II and Fe III in an Fe II / Fe III ratio between 5 and 5.3.

L'acide phosphorique est traité par l'agent d'extraction en solution dans du kérosène à raison de 30 g/1. Le débit d'acide phosphorique réduit était de 200 1/h tandis que celui de la solution d'agent d'extraction était de 20 1/h.The phosphoric acid is treated with the extracting agent in solution in kerosene at a rate of 30 g / l. The reduced phosphoric acid flow rate was 200 l / h while that of the extractant solution was 20 l / h.

Le solvant chargé en uranium, après sa séparation d'avec l'acide phosphorique désuranié, était refroidi à 20° C puis traité par une solution de HF à 15 %, au débit de 2 1/h.The solvent loaded with uranium, after its separation from the deuraniated phosphoric acid, was cooled to 20 ° C. and then treated with a 15% HF solution, at a flow rate of 2 l / h.

Le solvant désuranié était recyclé à l'extraction après ajout d'une fraction heure de l'agent d'extraction.The desuranized solvent was recycled to extraction after adding a fraction of an hour of the extractant.

L'essai n° 1, qui illustre l'art antérieur, a été réalisé dans une installation industrielle dont l'unité d'extraction était constituée par une batterie de 4 mélangeurs-décanteurs - unité d'extraction dans laquelle le cumul des temps Tl et T2 pour 4 étages tels que définis dans le procédé selon l'invention, est égal à 14 heures.Test No. 1, which illustrates the prior art, was carried out in an industrial installation, the extraction unit of which consisted of a battery of 4 mixer-settlers - extraction unit in which the cumulative times T l and T 2 for 4 stages as defined in the method according to the invention, is equal to 14 hours.

L'essai n° 2 illustrant l'invention, a été réalisé dans une installation industrielle dont l'unité d'extraction était constituée par un extracteur centrifuge multiétages de 4 étages, tournant à la vitesse de 2800 tours par minute, unité dans laquelle le cumul des temps de séjour T1 et T2 pour 4 étages était inférieur à deux minutes.Test No. 2 illustrating the invention was carried out in an industrial installation, the extraction unit of which consisted of a 4-stage multi-stage centrifugal extractor, rotating at the speed of 2800 revolutions per minute, a unit in which the cumulative residence times T 1 and T 2 for 4 floors was less than two minutes.

L'essai n° 3, illustrant l'art antérieur, diffère de l'essai n° 1 par la nature de l'agent d'extraction qui était dans ce cas une solution d'acide éthylhexylpyrophosphorique.Test No. 3, illustrating the prior art, differs from Test No. 1 in the nature of the extractant which in this case was a solution of ethylhexylpyrophosphoric acid.

L'essai n° 4, illustrant l'invention, diffère de l'essai n° 2 par la nature de l'agent d'extraction qui était l'acide éthylhexylpyrophosphorique.Test No. 4, illustrating the invention, differs from Test No. 2 in the nature of the extractant which was ethylhexylpyrophosphoric acid.

L'essai n° 5, illustrant l'art antérieur, ne diffère de l'essai n° 1 que par le mode de réduction de l'acide phosphorique (sur plaquettes en colonne).Test n ° 5, illustrating the prior art, differs from test n ° 1 only in the mode of reduction of phosphoric acid (on platelets in column).

L'essai n° 6, illustrant l'invention, diffère de l'essai n° 2 par le mode de réduction de l'acide phosphorique et par la constitution de l'unité d'extraction qui comportait quatre extracteurs centrifuges monoétage en batterie - unité dans laquelle le cumul des temps de séjour T1 et T2 était inférieur à deux minutes.Test n ° 6, illustrating the invention, differs from test n ° 2 by the mode of reduction of phosphoric acid and by the constitution of the extraction unit which included four single stage centrifugal extractors in battery - unit in which the cumulative residence times T 1 and T 2 was less than two minutes.

Tous les résultats ont été consignés dans le tableau 1 ci-après :

Figure imgb0002
A travers les résultats ainsi rassemblés, il est possible de mesurer l'importance du procédé selon l'invention qui améliore le rendement d'extraction de l'uranium, mais réduit de 5 à 6 fois la consommation en agent d'extraction.All the results have been reported in Table 1 below:
Figure imgb0002
 Through the results thus collected, it is possible to measure the importance of the process according to the invention which improves the uranium extraction yield, but reduces the consumption of extractant by 5 to 6 times.

EXEMPLE 2EXAMPLE 2

Cet exemple illustre le procédé d'extraction de l'uranium selon l'invention, au moyen d'acides alkylpyrophosphoriques, comparativement au procédé d'extraction le plus couramment employé dans les procédés appartenant à l'art antérieur.This example illustrates the method of extracting uranium according to the invention, using alkylpyrophosphoric acids, compared to the extraction method most commonly used in methods belonging to the prior art.

Il concerne le traitement d'un acide phosphorique d'origine tunisienne à faible teneur en uranium.It concerns the treatment of a phosphoric acid of Tunisian origin with low uranium content.

L'acide phosphorique traité avait la composition suivante :

Figure imgb0003
The phosphoric acid treated had the following composition:
Figure imgb0003

L'essai n° 7, qui illustre l'art antérieur, a été conduit comme l'essai 1, dans une batterie de 4 mélangeurs-décanteurs.Test n ° 7, which illustrates the prior art, was carried out like test 1, in a battery of 4 mixer-settlers.

L'essai n° 8, qui illustre l'invention, a été réalisé comme l'essai 2, mais en faisant usage d'une batterie comportant 3 extracteurs-centrifuge monoétage.Test No. 8, which illustrates the invention, was carried out like test 2, but using a battery comprising 3 single-stage centrifugal extractors.

Les résultats ont été consignés dans le tableau 2 ci-après :

Figure imgb0004
The results are reported in Table 2 below:
Figure imgb0004

Ce deuxième tableau confirme les excellents résultats obtenus par l'exemple 1.This second table confirms the excellent results obtained by Example 1.

Claims (12)

1°) Procédé d'extraction de l'uranium contenu dans les solutions d'acides phosphoriques au moyen d'un agent d'extraction constitué par un acide alkylpyrophosphorique consistant à mettre en contact sous agitation la phase minérale d'acide phosphorique et une phase organique contenant l'agent d'extraction en créant une émulsion, caractérisé en ce que, dans une unité d'extraction comprenant n étages en cascade, pour chaque étage d'extraction l'émulsion est produite lors d'une première étape en soumettant simultanément les deux phases contenant l'acide phosphorique et l'agent d'extraction pendant un temps T1 à une action mécanique de cisaillement intense correspondant à un coefficient de cisaillement d'au moins 5 000 seconde , dans le but de multiplier les surfaces de contact entre ces deux phases, puis ladite émulsion lors d'une deuxième étape est brutalement cassée en un temps T21 le cumul T1 + T2 des temps nécessaires à la réalisation des deux étapes étant au plus de 20 minutes.1) Method for extracting uranium contained in phosphoric acid solutions by means of an extraction agent consisting of an alkylpyrophosphoric acid consisting in bringing the mineral phase of phosphoric acid into contact with stirring organic containing the extraction agent by creating an emulsion, characterized in that, in an extraction unit comprising n cascade stages, for each extraction stage the emulsion is produced in a first step by simultaneously submitting the two phases containing phosphoric acid and the extracting agent for a time T 1 with an intense mechanical shearing action corresponding to a shear coefficient of at least 5,000 seconds, with the aim of increasing the contact surfaces between these two phases, then said emulsion during a second step is suddenly broken in a time T 21 the cumulative T 1 + T 2 of the times necessary for the completion of the two steps being at most 20 minutes. 2°) Procédé d'extraction de l'uranium selon la revendication 1, caractérisé en ce que l'unité d'extraction comporte un nombre d'étages n compris entre 2 et 20.2 °) A method of extracting uranium according to claim 1, characterized in that the extraction unit comprises a number of stages n between 2 and 20. 3°) Procédé d'extraction de l'uranium selon la revendication 1, caractérisé en ce que l'unité d'extraction comporte un seul étage.3 °) A method of extracting uranium according to claim 1, characterized in that the extraction unit comprises a single stage. 4°) Procédé d'extraction de l'uranium selon l'une quelconque des revendications 1 à 3, caractérisé en ce que le coefficient de cisaillement est choisi dans l'intervalle 5 000 seconde-1 à 50 000 seconde-1 et de préférence dans l'intervalle 10 000 seconde-1 à 25 000 seconde-1.4 °) A method of extracting uranium according to any one of claims 1 to 3, characterized in that the shear coefficient is chosen in the interval 5,000 seconds -1 to 50,000 seconds -1 and preferably in the interval 10,000 seconds -1 to 25,000 seconds -1 . 5°) Procédé d'extraction de l'uranium selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le cumul T1 + T2 des temps nécessaires à la réalisation des deux étapes est préférentiellement au plus égal à 10 minutes pour un étage d'extraction.5 °) A method of extracting uranium according to any one of claims 1 to 4, characterized in that the cumulative T 1 + T 2 of the times necessary for carrying out the two stages is preferably at most equal to 10 minutes for an extraction stage. 6°) Procédé d'extraction de l'uranium selon l'une quelconque des revendications 1 à 5, caractérisé en ce que le rapport T1/T2 des temps d'exécution des deux étapes pour un étage d'extraction est choisi dans les limites 1/100 à 5/1 et de préférence dans les limites 1/25 à 2/1.6 °) uranium extraction method according to any one of claims 1 to 5, characterized in that the ratio T 1 / T 2 of execution time of the two stages for an extraction stage is chosen within the limits 1/100 to 5/1 and preferably within the limits 1/25 to 2/1. 7°) Procédé d'extraction de l'uranium selon l'une quelconque des revendications 1 à 6, caractérisé en ce que l'agent d'extraction qui est un acide alkylpyrophosphorique, est obtenu par addition de P205 à un alcool,ayant une chaîne carbonée en C7 à C 13.7 °) A method of extracting uranium according to any one of claims 1 to 6, characterized in that the extraction agent which is an alkylpyrophosphoric acid, is obtained by addition of P 2 0 5 to an alcohol , having a C 7 to C 13 carbon chain. 8°) Procédé d'extraction de l'uranium selon la revendication 7, caractérisé en ce que la température d'obtention de l'acide alkylpyrophosphorique est compris entre 30° C et 80° C mais de préférence entre 30° C et 40° C.8 °) A method of extracting uranium according to claim 7, characterized in that the temperature for obtaining alkylpyrophosphoric acid is between 30 ° C and 80 ° C but preferably between 30 ° C and 40 ° vs. 9°) Procédé d'extraction de l'uranium selon l'une quelconque des revendications 1 à 8, caractérisé en ce que la phase organique chargée en uranium résultant de la deuxième étape, est traitée par une solution d'acide fluorhydrique pour réextraire l'uranium.9 °) uranium extraction process according to any one of claims 1 to 8, characterized in that the organic phase loaded with uranium resulting from the second step, is treated with a hydrofluoric acid solution to re-extract l 'uranium. 10°) Procédé d'extraction de l'uranium selon la revendication 9, caractérisé en ce que la solution d'acide fluorhydrique contient en poids de 10 à 20 %, mais de préférence de 13 à 18 % de HF.10 °) uranium extraction method according to claim 9, characterized in that the hydrofluoric acid solution contains by weight from 10 to 20%, but preferably from 13 to 18% of HF. 11°) Procédé d'extraction de l'uranium selon la revendication 9, caractérisé en ce que la température à laquelle s'effectue la réextraction de l'uranium par l'acide fluorhydrique est comprise entre 0° C et 60° C et de préférence entre 10° C et 30° C.11 °) A method of extracting uranium according to claim 9, characterized in that the temperature at which the re-extraction of uranium by hydrofluoric acid takes place is between 0 ° C and 60 ° C and preferably between 10 ° C and 30 ° C. 12°) Procédé d'extraction de l'uranium selon l'une quelconque des revendications 1 à 11, caractérisé en ce que l'on récupère par centrifugation l'agent d'extraction entraîné par l'acide phosphorique.12 °) A method of extracting uranium according to any one of claims 1 to 11, characterized in that the extraction agent is recovered by centrifugation entrained by phosphoric acid.
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FR2374931A1 (en) * 1976-12-27 1978-07-21 Exxon Research Engineering Co LIQUID MEMBRANES AND METHOD FOR RECOVERING URANIUM
FR2376688A1 (en) * 1977-01-10 1978-08-04 Anglian Water Authority Appts. for forming sewage treatment silicate prods. - includes mixing tube with static high shear device
FR2423545A1 (en) * 1977-08-25 1979-11-16 Minemet Rech Sa PROCESS FOR THE RECOVERY OF URANIUM CONTAINED IN PHOSPHATE SOLUTIONS
FR2449648A1 (en) * 1979-02-21 1980-09-19 Wyoming Mineral Corp PROCESS FOR THE PURIFICATION OF ACID SOLUTIONS CONTAINING METALS

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MA19852A1 (en) 1984-04-01
KR840005414A (en) 1984-11-12
BR8304067A (en) 1984-03-07
US4510122A (en) 1985-04-09
PH19136A (en) 1986-01-10
FI832749A0 (en) 1983-07-29
PT77136B (en) 1986-01-24
GR78860B (en) 1984-10-02
ES8404419A1 (en) 1984-05-01
EP0100744B1 (en) 1985-12-18
YU157783A (en) 1986-04-30
FI832749A (en) 1984-01-31
PT77136A (en) 1983-08-01
KR870002187B1 (en) 1987-12-28
JO1260B1 (en) 1985-04-20
OA07505A (en) 1985-03-31
FR2531102A1 (en) 1984-02-03
FR2531102B1 (en) 1986-08-14
CA1209808A (en) 1986-08-19
ES524587A0 (en) 1984-05-01
IL69342A (en) 1986-07-31

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