RU2638719C1 - Method of processing hydroxide cake produced at alkaline dissection of monazite concentrate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used to process a cake containing rare-earth and radioactive elements produced by dissection of monazite concentrate by an alkaline method. The method includes the preparation of rare-earth and radioactive chlorides through a solid-phase sintering step of hydroxide cake with ammonium chloride. The sintering process is carried out at a temperature of 300°C followed by removal of excess ammonium chloride by sublimation at a temperature of 350°C.

EFFECT: producing rare-earth chlorides and radioactive elements without the use of liquid-phase methods, resulting in a reduction of flow solutions of acids or carbonates due to replacing them with ammonium chloride, an excess of which can be easily regenerated.

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Description

The invention relates to the technology of rare and radioactive elements and can be used for processing cake containing rare earth and radioactive elements obtained by opening the monazite concentrate by the alkaline method.

Existing methods for the separation and purification of dephosphored rare-earth cake are carried out using resource-intensive liquid-phase opening processes in hydrochloric or nitric acid, as well as in solutions of ammonium carbonates or alkali metals.

A known method is when the obtained cake is cleaned of impurities in a mixture of ammonium carbonate / bicarbonate using an autoclave opening. In this case, only thorium and uranium pass into the solution (Aly M. Abdel-Rehim // Hydrometallurgy. 2002. V. 67. P. 9-17). This liquid-phase method has common disadvantages associated with the high consumption of ammonium carbonates and the formation of a large volume of processed solutions.

The known method [RU, patent No. 2323989. A method of processing monazite, published on November 27, 2006], when a cake of hydroxides of rare-earth and radioactive elements is treated with a solution of nitric acid at a pH of 3.5-4.5. The disadvantages of this liquid-phase method is the large volume of processed solutions.

A known method of processing hydroxides of rare earth and radioactive elements [Alekseev S.V., Zaitsev V.A. Thorium in nuclear power. M .: Technosphere, 2014 - 288 p.] By dissolving in concentrated hydrochloric acid at a temperature of 80 ° C for 1 hour. The disadvantage of this liquid-phase method is the high consumption of hydrochloric acid.

The prototype of the present invention is a method of processing rare earth oxides (prototype) [RU 2014134929 application for the invention of 08.28.2014] obtained after the interaction of monazite concentrate with soda ash at a temperature of 750-850 ° C, chlorination using ammonium chloride in a reactor without access of oxygen at a temperature of 200-300 ° C to obtain water-soluble rare earth chlorides.

To obtain water-soluble rare earth chlorides using ammonium chloride, in addition to rare-earth oxides, their hydroxides can be used.

The present invention is aimed at solving the problem of reducing the consumption of reagents and reducing the volume of processed solutions by transferring a hydroxide cake containing hydroxides of rare-earth and radioactive elements obtained by alkaline opening of monazite concentrate into water-soluble chlorides of rare-earth and radioactive elements by the solid-phase method.

The objective is achieved by the fact that the opening of hydroxides of rare earth and radioactive elements is carried out using solid-phase sintering with ammonium chloride, taken in a mass ratio of hydroxide cake: ammonium chloride 1: 3. The process is carried out at a temperature of 300 ° C for 60 minutes.

The process proceeds with the formation of solid chlorides of rare earth and radioactive elements, gaseous ammonia and water. Process gases containing ammonia and water are cleaned from dust and trapped by known methods.

The resulting chloride cake is heated to 350 ° C to transfer to a gaseous state and remove excess ammonium chloride from the system. The gas phase is sent to desublimation to regenerate ammonium chloride.

The specimen chloride of rare earths and radioactive elements is the final product and can be used for subsequent separation into individual components by known methods.

Example 1

A portion of hydroxide cake containing as its main components: rare earth elements 66.72%, thorium 5.56%, uranium 0.44%, iron 0.78%, not opened during alkaline opening, 4.4% monazite with a total weight of 8 g, according to the mass ratio of 1: 3 (hydroxide cake: ammonium chloride) is mixed with 24 g of ammonium chloride and kept at 280 ° C for 60 minutes. The resulting chloride cake is heated to 350 ° C and maintained at this temperature until the separation of excess ammonium chloride ceases. The result of a solid-phase autopsy is a 12.6 g chloride chloride cake containing chlorides of rare-earth and radioactive elements, as well as impurities - an unchlorinated residue and monazite that did not open during an alkaline autopsy. The degree of chlorination of rare earth elements is 91.98%, thorium - 66.23%, uranium - 36.17%, iron - 77.15%.

Example 2

A portion of hydroxide cake weighing 8 g of elemental composition according to example 1 according to the mass ratio of hydroxide cake: ammonium chloride - 1: 3 is mixed with 24 g of ammonium chloride and kept at 300 ° C for 60 minutes. The resulting product is heated to 350 ° C and maintained at this temperature until the separation of excess ammonium chloride ceases.

The result of a solid-phase autopsy is a specimen of chlorides in an amount of 12.8 g, containing chlorides of rare-earth and radioactive elements, as well as impurities - an unchlorinated residue and monazite not opened during an alkaline autopsy. The degree of chlorination of rare earths is 98.85%, thorium is 72.15%, uranium is 52.87%, and iron is 85.26%.

Example 3

A portion of hydroxide cake weighing 8 g of elemental composition according to example 1 according to the stoichiometric ratio of hydroxide cake: ammonium chloride - 1: 2 is mixed with 16 g of ammonium chloride and kept at 240 ° C for 60 minutes. The resulting product is heated to 350 ° C and maintained at this temperature until the separation of excess ammonium chloride ceases.

The result of solid-state autopsy is a 10.4 g chloride chloride cake containing chlorides of rare-earth and radioactive elements, as well as impurities - an unchlorinated residue and monazite that did not open during an alkaline autopsy. The degree of chlorination of rare earths is 75.68%, thorium is 31.44%, uranium is 12.68%, and iron is 55.59%.

Thus, from the above examples it follows that the proposed method provides the production of rare earth and radioactive chloride without the use of liquid phase methods and reduces the consumption of acid or carbonate solutions by replacing them with ammonium chloride, the excess of which can be easily regenerated.

Claims (1)

 A method of processing hydroxide cake obtained by alkaline opening of monazite concentrate, including the production of rare earth and radioactive element chlorides, characterized in that the production of chloride of these elements is carried out by solid phase sintering with ammonium chloride in a weight ratio of cake: ammonium chloride 1: 3 at a temperature of 300 ° C for 60 minutes, followed by removal of excess ammonium chloride at a temperature of 350 ° C.