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.

Description

TECHNICAL FIELD[0001]The invention relates to a method for separating iron, from a liquid organic phase containing uranium and iron.[0002]More precisely, the invention relates to a method for separating iron, from a liquid organic phase containing uranium and iron.[0003]The invention applies to the separation of iron from a uranium (uranium bearing, “uranifère”) liquid organic phase, containing an organic extraction system comprising an organic extractant diluted in an organic diluent.[0004]This organic phase may be notably an organic phase resulting from the extraction of uranium by a solvent from an aqueous uranium bearing solution of mineral, inorganic acid, such as phosphoric acid, nitric acid or sulphuric acid.[0005]The invention thus further relates to a method for extracting uranium from an aqueous solution of mineral acid, containing uranium and iron.[0006]This aqueous solution of mineral acid may equally well be an aqueous uranium bearing solution of phosphoric acid, such a...

AI Technical Summary

Benefits of technology

The patent text explains a method for removing iron from uranium-containing organic phases using a specific aqueous solution. The method is economical and selectively eliminates iron without losing uranium or causing precipitation of iron. It also reduces the number of unitary operations and eliminates impurities that can be detrimental to the process. Overall, the method improves the purity of the uranium-containing phase.

Problems solved by technology

Yet, this uranium bearing organic phase also contains the impurities listed above, and mainly iron which is extremely bothersome and does not make it possible to obtain, during the following step of back extraction (“désextraction”), uranium having the required purity with a view to its later use.

As an example, iron precipitates in the form of iron hydroxide during the step of re-extraction (“réextraction”) of uranium, which requires additional filtration operations and poses problems with regard to carrying out the method.

A co-extraction of impurities such as iron and phosphates is disadvantageous because it makes it difficult to comply with the ASTM specifications on uranium bearing concentrates.

Although promising, this method has several major drawbacks:the novel synergistic extractant mixture used increases the partition coefficients of uranium and iron compared to conventional solvents, but uranium / iron selectivity is less good;the operating expenses turn out to be higher whatever the acid chosen for selective de-ironing of the solvent, notably on account of industrial phosphoric acid losses, of the impact of potential recycling at the step of lixiviation of the ore, and of losses of reagent.

More exactly, if industrial de-ironed phosphoric acid is used, then it is necessary to add mixer-decanter stages to de-iron the acid (to remove iron from the acid, to deferrize the acid); if a mixture of phosphoric acid and sulphuric acid is used, this has an impact on the step of lixiviation of the ore, and a contamination of industrial phosphoric acid takes place; and if oxalic acid is used, the cost of this reagent is high, and the reagent regeneration yield is insufficient.

Yet, the appearance of a third phase is totally unacceptable for a method intended to be implemented at an industrial scale.

Furthermore, the presence within the spacer group of a P—O or P—S bond, which is easily hydrolysable, makes these compounds extremely sensitive to hydrolysis.

Although these novel extractant molecules make it possible to do without a synergistic mixture of extractants and although they are more efficient in terms of uranium extraction, they are however not sufficiently selective to enable the elimination of the step of de-ironing of the solvent in a method for beneficiating uranium contained in uranium bearing phosphate ores.

Yet, this uranium bearing organic phase, just like the organic phase derived from an aqueous uranium bearing solution of phosphoric acid, also contains the impurities listed above, and mainly iron, and this is extremely bothersome and does not make it possible to obtain, during the following step of back extraction, uranium having the required purity in view of its later use.

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