Method for separating iron from an organic phase containing uranium and method for extracting uranium from an aqueous solution of mineral acid containing uranium and iron

Abstract

The application relates to a method for separating iron from an initial liquid organic phase containing uranium and iron, wherein the initial liquid organic phase is contacted with an aqueous solution referred to as aqueous de-ironing solution, whereby the iron passes into the aqueous solution to form a final liquid aqueous phase, and uranium remains in the initial liquid organic phase to form a final liquid organic phase referred to as de-ironed organic phase. The method is characterised in that the aqueous de-ironing solution contains an inorganic acid and uranium, and does not contain iron. The application also relates to a method for extracting uranium from an aqueous solution of an inorganic acid containing uranium and iron.

What is claimed is: 
     
         1 . Method for separating iron from an initial liquid organic phase containing uranium and iron, wherein the initial liquid organic phase is contacted with an aqueous solution referred to as aqueous de-ironing solution, whereby the iron passes into the aqueous solution to form a final liquid aqueous phase, and uranium remains in the initial liquid organic phase to form a final liquid organic phase referred to as de-ironed organic phase; said method being characterised in that the aqueous de-ironing solution contains an inorganic acid and uranium, and does not contain iron. 
     
     
         2 . Method according to  claim 1 , wherein the initial liquid organic phase comprises an organic extraction system comprising an organic extractant or a mixture of organic extractant(s), diluted in an organic diluent, non-reactive and non-miscible with water. 
     
     
         3 . Method according to  claim 2 , wherein the organic extraction system comprises an extractant selected from organophosphorous compounds and mixtures thereof. 
     
     
         4 . Method according to  claim 3 , wherein the organic extraction system comprises an extractant selected from acid organophosphorous compounds such as dialkylphosphoric acids, bifunctional organophosphorous compounds, neutral phosphine oxides such as trialkylphosphine oxides, and mixtures thereof. 
     
     
         5 . Method according to  claim 4 , wherein the extraction system comprises the mixture of an acid organophosphorous compound and of a neutral phosphine oxide. 
     
     
         6 . Method according to  claim 2 , wherein, the extractant system comprises as extractant a compound which corresponds to the following general formula (I): 
       
         
           
           
               
               
           
         
         wherein: 
         m is a whole number equal to 0, 1 or 2; 
         R 1  and R 2 , identical or different, are a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; 
         R 3  is:
 a hydrogen atom; 
 a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms and optionally one or more heteroatoms; 
 a monocyclic hydrocarbon group, saturated or unsaturated, comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms; or 
 a monocyclic aryl or heteroaryl group; 
 
         or instead R 1  and R 3  together form a —(CH 2 ) n — group wherein n is a whole number ranging from 1 to 4; 
         R 4  is a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 2 to 8 carbon atoms, or a monocyclic aromatic group; whereas 
         R 5  is a hydrogen atom or a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms. 
       
     
     
         7 . Method according to  claim 6 , wherein the compound of formula (I) corresponds to the following specific formula (I-a): 
       
         
           
           
               
               
           
         
         wherein: 
         m, R 4  and R 5  are as defined in  claim 6 ; 
         R 2  is a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; whereas 
         R 3  is:
 a hydrogen atom; 
 a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms and optionally one or more heteroatoms; 
 a monocyclic hydrocarbon group, saturated or unsaturated, comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms; or 
 a monocyclic aryl or heteroaryl group. 
 
       
     
     
         8 . Method according to  claim 6 , wherein the compound of formula (I) corresponds to the specific formula (I-b): 
       
         
           
           
               
               
           
         
         wherein m, n, R 4  and R 5  are such as defined in  claim 6 . 
       
     
     
         9 . Method according to  claim 1 , wherein the initial organic phase contains from 0.5 g/L to 10 g/L of uranium and from 0.1 to 10 g/L of iron. 
     
     
         10 . Method according to  claim 1 , wherein the inorganic acid of the aqueous de-ironing solution is selected from sulphuric acid, nitric acid, hydrochloric acid, phosphoric acid, and mixtures thereof. 
     
     
         11 . Method according to  claim 10 , wherein the inorganic acid of the aqueous de-ironing solution is sulphuric acid. 
     
     
         12 . Method according to  claim 1 , wherein the quantity of uranium provided by the aqueous de-ironing solution is such that the concentration of uranium in the organic phase is at least equal to 50%, preferably at least equal to 60%, further preferably at least equal to 70%, of the concentration of uranium corresponding to saturation of the organic phase with uranium. 
     
     
         13 . Method according to  claim 1 , wherein the concentration of uranium, expressed in [U], of the aqueous de-ironing solution is from 0.10 to 800 g/L, preferably from 30 to 50 g/L, for example 40 g/L. 
     
     
         14 . Method according to  claim 1 , wherein, during the contacting the initial organic phase is mixed with the aqueous de-ironing solution then said mixture is decanted, wherein the contacting is carried out in a battery of 1 to 5 mixers-decanters, counter-current supplied with the initial organic phase and with the aqueous de-ironing solution. 
     
     
         15 . Method according to  claim 1 , wherein the final aqueous phase contains more than 90% of the weight of iron contained in the initial organic phase, and less than 1% of the weight of uranium contained in the initial organic phase, and the de-ironed organic phase contains at least 90% of the weight of uranium contained in the initial organic phase, and less than 10% of the weight of iron contained in the initial organic phase. 
     
     
         16 . Method for extracting uranium from a first aqueous solution of an inorganic acid containing uranium and iron, wherein at least the following successive steps are carried out:
 a) the first aqueous solution of inorganic acid is contacted with a first liquid organic phase; whereby are obtained, on the one hand, a second liquid organic phase containing a majority by weight of the quantity of uranium contained in the first aqueous solution of inorganic acid, and a minority by weight of the quantity of iron contained in the first aqueous solution of inorganic acid and, on the other hand, a second desuraniated aqueous phase containing the inorganic acid, a minority by weight of the quantity of uranium contained in the aqueous solution of inorganic acid, and a majority by weight of the quantity of iron contained in the aqueous solution of inorganic acid;   b) the iron is separated from the second liquid organic phase containing uranium and iron, by contacting the second liquid organic phase with a third aqueous solution referred to as aqueous de-ironing solution, whereby the iron passes into the aqueous de-ironing solution to form a final liquid aqueous phase, and uranium remains in the second liquid organic phase to form a final liquid organic phase referred to as de-ironed organic phase;   
       said method being characterised in that the aqueous de-ironing solution contains an inorganic acid and uranium, and does not contain iron. 
     
     
         17 . Method according to  claim 16 , wherein the inorganic acid of the first aqueous solution of inorganic acid of step a) is a solution of phosphoric acid, sulphuric acid or nitric acid. 
     
     
         18 . Method according to  claim 16 , wherein the first aqueous solution of inorganic acid of step a) contains from 0.1 to 10 g/L of iron, and from 0.05 to 10 g/L of uranium. 
     
     
         19 . Method according to  claim 16 , wherein the first aqueous solution of inorganic acid is an aqueous uranium bearing solution of phosphoric acid, such as industrial phosphoric acid, coming from the lixiviation, attack, of a natural phosphate ore, generally based on apatite, by sulphuric acid, or an aqueous uranium bearing solution of sulphuric acid or nitric acid coming from the lixiviation, attack, of a non-phosphate uranium bearing ore, for example non-apatite based, respectively by sulphuric acid or nitric acid. 
     
     
         20 . Method according to  claim 16 , wherein, in step a), the second organic phase obtained contains at least 90% by weight, for example from 95 to 100% by weight, of the quantity of uranium contained in the first aqueous solution of inorganic acid (starting solution), and from 0.1 to 50% by weight of the quantity of iron contained in the first aqueous solution of inorganic acid; and the second desuraniated aqueous phase obtained contains the inorganic acid, from 0 to 10% by weight of the quantity of uranium, and from 50 to 99.9%, for example from 80% to 90% by weight of the quantity of iron contained in the first aqueous solution of inorganic acid (starting solution). 
     
     
         21 . Method according to  claim 16 , wherein the second organic phase obtained at the end of step a) contains from 0.5 to 10 g/L of uranium and from 0.1 to 10 g/L of iron, and the second aqueous phase obtained at the end of step a) contains from 0 to 100 mg/L of uranium and from 0.1 to 6 g/L of iron. 
     
     
         22 . Method according to  claim 16 , which further comprises a step c) wherein the iron-removed organic phase obtained in step b) is contacted with an aqueous solution of a complexing base; whereby are obtained, on the one hand, an aqueous phase loaded with uranium and, on the other hand, an organic phase free of uranium, and further containing said complexing base. 
     
     
         23 . Method according to  claim 22 , which further comprises a step d) wherein the organic phase free of uranium, further containing the complexing base obtained in step c), is contacted with the aqueous phase coming from step b) and neutralised, whereby are obtained, on the one hand, an organic phase consisting of the organic solvent which is sent back to step a) and, on the other hand, an aqueous phase. 
     
     
         24 . Method according to  claim 22 , which further comprises a step e) wherein the aqueous phase loaded with uranium obtained in step c), is contacted with a base such as sodium hydroxide, whereby an uranate precipitate, such as sodium uranate precipitate, which is separated, and an aqueous solution which is sent to step c) after addition of a complexing base, are obtained. 
     
     
         25 . Method according to  claim 24 , wherein all or part of the uranate precipitate, such as sodium uranate, obtained in step e), is dissolved in an inorganic acid such as sulphuric acid, and the aqueous solution obtained containing an inorganic acid and uranium is sent to step b) after having optionally adjusted the concentration of inorganic acid.