EP0005420A1 - A method of purifying a substance by the selective alkaline carbonate leaching of said substance to remove uranium therefrom - Google Patents

A method of purifying a substance by the selective alkaline carbonate leaching of said substance to remove uranium therefrom Download PDF

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Publication number
EP0005420A1
EP0005420A1 EP79850040A EP79850040A EP0005420A1 EP 0005420 A1 EP0005420 A1 EP 0005420A1 EP 79850040 A EP79850040 A EP 79850040A EP 79850040 A EP79850040 A EP 79850040A EP 0005420 A1 EP0005420 A1 EP 0005420A1
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Prior art keywords
leaching
substance
uranium
effected
substances
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EP79850040A
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German (de)
French (fr)
Inventor
Erik Gustav Bäck
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Boliden AB
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Boliden AB
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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
    • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
    • C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
    • C22B60/0221—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes by leaching
    • C22B60/0247—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes by leaching using basic solutions or liquors

Definitions

  • the present invention relates to a novel purifying process for separation uranium from a uranium-containing substance, by subjecting said substance to a selective, alkaline leaching process.
  • substances is herein meant primarily phosphorous - containing, carbon- containing and/or sulphur-containing substances having compounds of one or more of the metals aluminium, magnesium, calcium and iron.
  • Purification of the substance is effected by leaching a finely-divided slurry thereof in a leaching liquid containing 0.3-1.5 mole of carbonate ions per litre and having an oxidation potential of 0.3-1 V, said leaching process being effected so that the leaching liquid, subsequent to said leaching process, has a pH of 8.5 to 10.5.
  • the leaching process is carried out at a pressure of 0.2-2.0 MPa.
  • uranium has been found in building materials and radioactive substances have been found in fertilizers such as phosphates, phosphorites and apatites. When mining slates or shales containing kerogen, it would also seem necessary to separate the uranium present therein. Granite also contains uranium. Moreover, uranium is a valuable crude product for the manufacture of energy.
  • Uranium is present in the form of an impurity in many substances.
  • crude phosphate normally contains from 200 - 400 grams of uranium per ton;
  • phosphorite normally contains from 100 - 1000 grams of uranium per ton;
  • apatite normally contains 50 - 200 grams of uranium per ton;
  • granite normally contains 0 - 100 grams of uranium per ton;
  • slates and shales normally contain 50 - 1500 grams of uranium per ton.
  • the method according to the invention is suitably effected by wet grinding the substance, optionally whilst adding an oxidant to the leaching liquid, in a mill, such as a ball or rod mill.
  • the suspension obtained is then transferred to an autoclave, suitably a tube reactor vessel, by means of a pump.
  • the suspension is treated in the autoclave for a sufficient period of time in the presence of an oxidant, normally from 0.25 to 24 hours, at a pressure of 0.2-2.0 MPa, whereafter the leaching liquid is separated from the leaching residues.
  • the leaching residues can then be used as a purified crude material for different processes, such as the manufacture of fertilizers and the recovery of valuable products present in the substances.
  • the reactor is suitably cooled by lowering the pressure stepwise whilst, at the same time, utilizing the heat content of the suspension to heat the input material to the reactor.
  • the suspension is conveniently thickened by sedimentation or separation, and is finally filtered through a suitable filter, such as a drum filter, a disc filter or band filter.
  • a suitable filter such as a drum filter, a disc filter or band filter.
  • the leached uranium is then removed from the leaching liquid, for example by precipitating with an alkali in accordance with the formula:
  • Another method is to utilize the ion exchange reaction of, for example, a cation exchanger.
  • Hexavalent uranium, UO 3 forms in a carbonate ion environment the complex ions U0 2 (C0 3 )3 +.
  • the uranium precipitated out can then be used in a known manner.
  • the temperature should be between 120-180°C. This temperature is obtained by supplying heat to the reactor vessel, and the temperature is suitably regulated by maintaining a total pressure of 0.3-2.0 MPa in the autoclave. It is necessary that the pH of the suspension upon termination of the leaching process is in excess of 8.5, in order to obtain the necessary selective, and beneath about 10.5, to prevent the precipitation of uranates.
  • Tests were carried out to remove uranium from scales by selective, alkaline carbonate leaching.
  • An autoclave was charged with the dewatered material with a dry weight of 400 g. 1200 ml hot water and reagens were added. During heating of the charge from 0°C up to 150 0 C, oxygen with a partial pressure of 0.5 MPa was added.
  • Tests were carried out to remove uranium from phosphate rock by selective alkaline carbonate leaching.
  • the phosphate rock was crushed and comminuted to a grain size -- 1.0 mm and charged into a Parr Mini reactor together with an alkali solution. Oxygen was added, during heating up to 150°C, with a total pressure of 1.2 MPa.
  • the uranium yield was not sufficient,at least not for industrial application,but it can readily be improved by further comminuting of the rock and by optimizing the physical and chemical conditions of the method, e.g. by prolonging of the leaching time.

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  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

A method of purifying uranium-containing substances containing compounds of one or more of the metals aluminium, magnesium, calcium and iron by removing the uranium from said substances. The purification is effected by selective, alkaline carbonate leaching of the uranium. The substance is finely divided and slurried in an aqueous solution containing 0.3-1.5 moie/l of carbonate ions and having an oxidation potential of 0.3-1 V, and subsequent to the leaching process the leaching liquid has a pH of between 8.5 and 10.5 at a pressure of 0.2 to 2.0 MPa.
The substance may be finely-divided by wet-grinding, and the leaching solution used as the grinding liquid. The leaching is preferably effected in a tube reactor vessel in which the substance is slurried in leaching liquid at a temperature of 120-180° C and leached at a partial pressure of oxygen of 0.1-0.6 MPa.

Description

  • The present invention relates to a novel purifying process for separation uranium from a uranium-containing substance, by subjecting said substance to a selective, alkaline leaching process. By substances is herein meant primarily phosphorous - containing, carbon- containing and/or sulphur-containing substances having compounds of one or more of the metals aluminium, magnesium, calcium and iron. Purification of the substance is effected by leaching a finely-divided slurry thereof in a leaching liquid containing 0.3-1.5 mole of carbonate ions per litre and having an oxidation potential of 0.3-1 V, said leaching process being effected so that the leaching liquid, subsequent to said leaching process, has a pH of 8.5 to 10.5. The leaching process is carried out at a pressure of 0.2-2.0 MPa.
  • It has been discovered in recent times that radioactive material is abundently present in a highly undesirable manner in industrial products. Thus, uranium has been found in building materials and radioactive substances have been found in fertilizers such as phosphates, phosphorites and apatites. When mining slates or shales containing kerogen, it would also seem necessary to separate the uranium present therein. Granite also contains uranium. Moreover, uranium is a valuable crude product for the manufacture of energy.
  • Thus, the removal of radioactive components from a long list of materials is highly desirable, it being of particular interest to remove uranium, which is one of the most abundant radioactive materials in nature. It has now been found that such purification can be effected to advantage without removing aluminium, magnesium, calcium and iron from the substances at the same time. This enables the method to be used on a commercial scale, for purifying substances containing said metals in large quantities. The method can also be used to advantage on those substances which contain phosphorus, carbon and sulphur, and particularly kerogen-containing substances such as slates and shales.
  • Uranium is present in the form of an impurity in many substances. Thus, crude phosphate normally contains from 200 - 400 grams of uranium per ton;phosphorite normally contains from 100 - 1000 grams of uranium per ton; apatite normally contains 50 - 200 grams of uranium per ton; granite normally contains 0 - 100 grams of uranium per ton; and slates and shales normally contain 50 - 1500 grams of uranium per ton.
  • The pressure leaching of uranium ores for removing uranium therefrom with carbonate solutions is generally known. It has now been found possible to use this technique for the purpose of removing uranium from other materials, a surprisingly good and selective purifying result being obtained.
  • It has also surprisingly been found possible to effect the purifying of such substances by carbonate leaching processes with a considerably higher yield than that obtained when using acid leaching processes, which was not previously supposed. Purification of substances in accordance with the invention has been found to give a substantially better result during a 24 hours leaching time than a seven day leaching time using conventional sulphuric acid leaching processes. A sulphuric acid leaching process at the same temperature and pressure as with the present invention, provides a much poorer result.
  • It has previously been presumed that when leaching with an alkaline solution, the materials must be ground to a much higher degree of fineness, which would render the process much more expensive than an acid leaching process (Erzmetall 30 (1977) page 147). It has been found, however, that extremely good results are obtained with materials which are ground to a lesser degree of fineness than that previously considered necessary.
  • As a result of the selectivity of the method when leaching uranium from uranium-containing substances, important advantages are gained in the form of low reagent consumption and a lowering in the percentage of metals lost. An acid leaching process is not selective in this respect.
  • The method according to the invention is suitably effected by wet grinding the substance, optionally whilst adding an oxidant to the leaching liquid, in a mill, such as a ball or rod mill. The suspension obtained is then transferred to an autoclave, suitably a tube reactor vessel, by means of a pump. The suspension is treated in the autoclave for a sufficient period of time in the presence of an oxidant, normally from 0.25 to 24 hours, at a pressure of 0.2-2.0 MPa, whereafter the leaching liquid is separated from the leaching residues. The leaching residues can then be used as a purified crude material for different processes, such as the manufacture of fertilizers and the recovery of valuable products present in the substances. When using a tube reactor vessel, the reactor is suitably cooled by lowering the pressure stepwise whilst, at the same time, utilizing the heat content of the suspension to heat the input material to the reactor.
  • The suspension is conveniently thickened by sedimentation or separation, and is finally filtered through a suitable filter, such as a drum filter, a disc filter or band filter. The leached uranium is then removed from the leaching liquid, for example by precipitating with an alkali in accordance with the formula:
    Figure imgb0001
  • Another method is to utilize the ion exchange reaction of, for example, a cation exchanger. Hexavalent uranium, UO3, forms in a carbonate ion environment the complex ions U02(C03)3+. The uranium precipitated out can then be used in a known manner.
  • Further, it is necessary to maintain an oxidation potential of 0.3-1 V, which as previously mentioned is conveniently effected by supplying oxygen under pressure so as to obtain a partial pressure of oxygen of 0.1-0.6 MPa. It is also possible to add other oxidants, such as peroxides and the like.
  • In order to obtain a satisfactory leaching yield in respect of uranium, the temperature should be between 120-180°C. This temperature is obtained by supplying heat to the reactor vessel, and the temperature is suitably regulated by maintaining a total pressure of 0.3-2.0 MPa in the autoclave. It is necessary that the pH of the suspension upon termination of the leaching process is in excess of 8.5, in order to obtain the necessary selective, and beneath about 10.5, to prevent the precipitation of uranates.
  • The advantages afforded by the method of the present invention will now be illustrated with reference to two examples.
    • Example 1
  • Tests were carried out to remove uranium from scales by selective, alkaline carbonate leaching.
  • The crushed scale was comminuted to K80 = 30 µm in a wet grinding rod mill with 50% solids. An autoclave was charged with the dewatered material with a dry weight of 400 g. 1200 ml hot water and reagens were added. During heating of the charge from 0°C up to 1500C, oxygen with a partial pressure of 0.5 MPa was added.
  • The test results and the metal yields obtained are shown in tables 1 and 2.
    Figure imgb0002
    Figure imgb0003
  • It appears from the tables that it is possible to recover uranium from scales with a high yield (87%) and without any substantial dissolution of other metals.Compared to other leach treatments (A, B, D, E, F) the alkaline carbonate leaching (C) is extremely selective.
    • Example 2
  • Tests were carried out to remove uranium from phosphate rock by selective alkaline carbonate leaching.
  • The phosphate rock was crushed and comminuted to a grain size -- 1.0 mm and charged into a Parr Mini reactor together with an alkali solution. Oxygen was added, during heating up to 150°C, with a total pressure of 1.2 MPa.
  • The test results and the metal yields obtained are shown in tables 1 and 2.
    Figure imgb0004
    Figure imgb0005
    It appears from the tables that the method makes it possible to dissolve uranium from phosphate rock with only minor dissolution of other elements.
  • The uranium yield was not sufficient,at least not for industrial application,but it can readily be improved by further comminuting of the rock and by optimizing the physical and chemical conditions of the method, e.g. by prolonging of the leaching time.

Claims (5)

1. A method of purifying uranium-containing substances containing compounds of one or more of the metals aluminium, magnesium, calcium and iron by removing the uranium from said substances, said purification being effected by selective, alkaline carbonate leaching of the uranium, wherein the substance is finely divided and slurried in an aqueous solution containing 0.3-1.5 mole/l of carbonate ions and having an oxidation potential of 0.3-1 V, and wherein, subsequent to the leaching process the leaching liquid has a pH of between 8.5 and 10.5 at a pressure of 0.2 to 2.0 MPa.
2. A method according to claim 1, wherein the substance is finely divided by wet-grinding, and wherein the leaching solution is used as the grinding liquid.
3. A method according to claim 1, wherein leaching is effected in a tube reactor vessel in which the substance is slurried in leaching liquid at a temperature of 120-180°C.
4. A method according to claim 1, wherein leaching is effected at a partial pressure of oxygen of 0.1-0.6 MPa.
5. A method according to claim 3, wherein the pressure in the tube reactor vessel is lowered stepwise during a heat exchange between the outgoing suspension and the suspension incoming to the tube reactor vessel.
EP79850040A 1978-05-08 1979-05-07 A method of purifying a substance by the selective alkaline carbonate leaching of said substance to remove uranium therefrom Withdrawn EP0005420A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE7805209A SE7805209L (en) 1978-05-08 1978-05-08 PROCEDURE FOR CLEANING A MINERAL THROUGH A SELECTIVE ALKALINE CARBON PAINTING FOR REMOVAL OF URANIUM
SE7805209 1978-05-08

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EP0005420A1 true EP0005420A1 (en) 1979-11-14

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ES (1) ES480302A1 (en)
FI (1) FI791454A (en)
MA (1) MA18420A1 (en)
SE (1) SE7805209L (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2545105A1 (en) * 1983-04-27 1984-11-02 Pechiney Uranium High-temperature pretreatment of uraniferous, vanadiferous or molybdeniferous ores containing clayey gangue by means of an alkaline aqueous solution
WO1984004333A1 (en) * 1983-04-27 1984-11-08 Pechiney Uranium High temperature pre-treatment by means of an aqueous alcolyne solution of clayish gangue ore containing at least one valuable element
FR2552108A1 (en) * 1983-09-21 1985-03-22 Pechiney Uranium High-temperature pretreatment by means of an alkaline aqueous solution of ores with a clayey gangue containing at least one upgradable element other than uranium, vanadium and molybdenum.

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB716597A (en) * 1952-01-11 1954-10-06 Ca Nat Research Council Leaching of uranium
FR1092946A (en) * 1949-11-29 1955-04-28 France Etat Processing of uranium ores
US3175878A (en) * 1960-02-24 1965-03-30 Phillips Petroleum Co Method of carbonate leaching uranium ores
DE2523933A1 (en) * 1975-05-30 1976-12-09 Helmut Dipl Ing Cronjaeger Uranium and vanadium extn from phosphates and basic ores - using leach contg. magnesium chloride, sodium carbonate and sodium bicarbonate

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1092946A (en) * 1949-11-29 1955-04-28 France Etat Processing of uranium ores
GB716597A (en) * 1952-01-11 1954-10-06 Ca Nat Research Council Leaching of uranium
US3175878A (en) * 1960-02-24 1965-03-30 Phillips Petroleum Co Method of carbonate leaching uranium ores
DE2523933A1 (en) * 1975-05-30 1976-12-09 Helmut Dipl Ing Cronjaeger Uranium and vanadium extn from phosphates and basic ores - using leach contg. magnesium chloride, sodium carbonate and sodium bicarbonate

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2545105A1 (en) * 1983-04-27 1984-11-02 Pechiney Uranium High-temperature pretreatment of uraniferous, vanadiferous or molybdeniferous ores containing clayey gangue by means of an alkaline aqueous solution
WO1984004333A1 (en) * 1983-04-27 1984-11-08 Pechiney Uranium High temperature pre-treatment by means of an aqueous alcolyne solution of clayish gangue ore containing at least one valuable element
FR2552108A1 (en) * 1983-09-21 1985-03-22 Pechiney Uranium High-temperature pretreatment by means of an alkaline aqueous solution of ores with a clayey gangue containing at least one upgradable element other than uranium, vanadium and molybdenum.

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Publication number Publication date
SE7805209L (en) 1979-11-09
FI791454A (en) 1979-11-09
ES480302A1 (en) 1980-03-01
MA18420A1 (en) 1979-12-31

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