FR2826667A1 - Treatment of rare earth mineral with high iron content for recuperation of rare earth metals as an aqueous solution involves reacting the mineral with sulfuric acid, firing, mixing the calcined material with aqueous solution, and separating - Google Patents

Abstract

Method for treatment of a rare earth mineral with a high iron content consists of: (a) making the mineral react with sulfuric acid; (b) firing the mixture obtained at a temperature of at least 780 deg C; (c) mixing the calcined material with an aqueous solution; and (d) separating the liquid and solid phases from the mixture to obtain a first aqueous phase containing the rare earths and a residue containing iron.

Description

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PROCESS FOR TREATING A RARE EARTH ORE IN
HIGH IRON CONTENT
The present invention relates to a method for processing a rare earth ore with a high iron content, for example of the monazite type.
Processes are known for the recovery of rare earths from concentrates of rare earth ores by acid or alkaline attack. However, in the case of certain ores, these known methods are not entirely satisfactory. They do not in fact allow an effective separation of the rare earths from the other elements and impurities, in particular iron, and their implementation is not simple.

 The object of the invention is the development of a process which makes it possible to obtain, from an iron-rich ore, rare earths of good purity, in particular with respect to iron.

 For this purpose, the process of the invention, for the treatment of a rare earth ore with a high iron content, is characterized in that it comprises the following stages: - the ore is reacted with acid sulfuric; - Cooking the mixture obtained at a temperature of at least 780 C; - The product from the cooking of the previous step is mixed with an aqueous solution; - The liquid phase is separated from the solid phase of this mixture, whereby a first aqueous phase containing rare earths is obtained.

 Other characteristics, details and advantages of the invention will appear even more completely on reading the description which follows, as well as a concrete but nonlimiting example intended to illustrate it.

 It is specified here that by rare earth is understood the elements of the group constituted by scandium, yttrium and the elements of the periodic classification with atomic number included inclusively between 57 and 71.

 The method of the invention is applicable to the treatment of any rare earth ore with a high iron content.

 By high iron content is meant an iron content of at least 10%, more particularly of at least 20%, this content being able to be at least 40%, or even at least 50% in the case of raw ores. This content is expressed here by mass of Fe 2 O 3 relative to the ore.

 More particularly, the method of the invention applies to the treatment of altered ores, that is to say ores in which the minerals are

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 scattered, thin and nested and for which physical separations are usually ineffective.

 As ores with a high iron content and capable of being treated by the process of the invention, mention may be made of certain monazites and altered or secondary monazites, ores in which the rare earths are present mainly in the form of more or less complex phosphates . We can thus mention rabophanite or florencite.

 Mention may also be made of mixed monazite-basnesite-iron ores.

 The invention also applies to the treatment of a concentrated ore, that is to say an ore whose content of rare earths has been increased and that of iron decreased by using known enrichment methods of the type flotation or gravimetry for example.

 The first step of the process of the invention consists in reacting the ore, raw or concentrated, with sulfuric acid. Prior to the sulfuric attack, the ore is ground, preferably at a particle size (mean particle diameter) of approximately 100 μm, more particularly at most 50 μm.

 A concentrated sulfuric acid, for example 95%, is preferably used. We work with an amount of acid which is between a minimum amount to attack the ore and a maximum amount so that the mixture obtained is in the form of a paste. Preferably, one works with an amount of acid such that the weight ratio of acid / weight of ore is between 1 and 2, more particularly between 1 and 1.5.

 It is advantageous, during the reaction with sulfuric acid, to heat the ore / acid mixture, for example to a temperature of at least 150 C.

 Mixing is done using any suitable device.

 The second step of the process of the invention consists in cooking the mixture obtained in the previous step. This cooking is done at a temperature of at least 780 C. This temperature can be for example between 7800C and 820 C. In this range of temperatures, the most effective separation of the rare earths from iron is obtained.

 The cooking time can vary for example between 1 and 3 hours, once the cooking temperature is reached.

 After cooking and in a third step of the process, the product thus obtained is mixed with an aqueous solution or water. There is thus obtained a medium comprising a liquid phase which contains the solubilized rare earths and a solid phase consisting of insoluble impurities, in particular iron. The separation of the phases is done by any means

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 known and thus makes it possible to obtain, at the end of the process of the invention, the rare earths in the aqueous phase.

 It is possible, according to a variant of the invention, to add a base to the above-mentioned aqueous phase containing rare earths and which was obtained at the end of the process as described above. This addition of base can be in the form of an aqueous solution, the base being more particularly ammonia. This addition is generally carried out with an amount of base such that the medium obtained has a pH of between approximately 3 and approximately 4 and it causes precipitation of residual impurities. The liquid phase is separated from the solid phase of the mixture thus obtained, whereby a second aqueous phase is obtained containing rare earths whose purity is increased.

 The aqueous phases containing the rare earths (first or second phase mentioned above) which have been obtained in the manner described above can then undergo different types of treatment to recover the rare earths in specific forms.

 Thus, it is possible to add to the above aqueous phases an anion, carbonate for example to obtain a precipitate of rare earth carbonate.

 It is also possible to subject these aqueous phases to a liquid-liquid extraction in order to extract the rare earths therefrom.

 An example will now be given.

EXAMPLE
We start from a monazite ore with the following mass composition:
Rare earth oxides (TR203): 19% Fe203: 49.2% SiOz 4.3% Art203: 4.1%
P205: 9.3%
S04: 0.7%
60g of this ore are mixed with 95g of 95% sulfuric acid. The mixing is done in 15 minutes by heating to 1800C so as to obtain a solid.

 The mixture is then calcined in a crucible for 2 hours at 800 C. After calcination, 59g of calcined product are recovered and this product is mixed 1 hour with 0.41 of water. We filter. 41 g of dry residue and 0.361 of filtrate are obtained.

 The residue has the following mass composition:

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TR203: 6% (2.46g)
Fe203: 59% Si02: 8% Ah03: 6%
P205: 12%
S04: 6%
This residue is washed. The washing water of this residue contains 0.428 g of TR203.

TR203 : 21, 4g/l (7, 70g) Fe203 : 0, 00g/1 P205 : O, 02gl1
S04 : 27, 5g/1
Le taux de terres rares solubilisées et obtenues à partir du minerai de départ est de 80%.The filtrate has the following composition:

TR203: 21.4g / l (7.70g) Fe203: 0.00g / 1 P205: O, 02gl1
S04: 27.5g / 1
The rate of rare earth solubilized and obtained from the starting ore is 80%.

Claims (8)

 CLAIMS 1-Process for treating a rare earth ore with a high iron content, characterized in that it comprises the following stages: - the ore is reacted with sulfuric acid; - Cooking the mixture obtained at a temperature of at least 780 C; - The product from the cooking of the previous step is mixed with an aqueous solution; - The liquid phase is separated from the solid phase of this mixture, whereby a first aqueous phase containing rare earths is obtained. 2-A method according to claim 1, characterized in that the ore is an ore having an iron content of at least 10%, in particular at least 20%.  3-A method according to claim 1 or 2, characterized in that the ore is a raw ore having an iron content of at least 40%.  4-Method according to one of the preceding claims, characterized in that the ore is a monazite type ore. 5-Process according to one of claims 1 to 4, characterized in that a base is added to the first above-mentioned aqueous phase containing rare earths and then the liquid phase is separated from the solid phase of the mixture thus obtained, whereby obtains a second aqueous phase containing rare earths. 6-Process according to one of the preceding claims, characterized in that a carbonate anion is added to the first or to the second aqueous phase containing rare earths, whereby a precipitate of rare earth carbonate is obtained.  7 - Method according to one of the preceding claims, characterized in that during the reaction of the ore with sulfuric acid, the ore / acid mixture is heated. <Desc / Clms Page number 6>  8-A method according to one of the preceding claims, characterized in that the first or the second aqueous phase containing rare earths is subjected to a liquid-liquid extraction to extract the rare earths.