RU2742330C1 - Method for processing eudialyte concentrate - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to processing of eudialyte concentrate and can be used for production of pure compounds of zirconium, hafnium and rare-earth elements. Eudialyte concentrate is decomposed by nitric acid to obtain gel, drying gel, water leaching gel with conversion of rare-earth elements into solution, and in insoluble residue of zirconium compound, as well as separation of solution from precipitate, followed by separation of zirconium compounds. Drying of gel is carried out at temperature from 180 to 200°C. In order to extract zirconium compounds, the residue after aqueous washing is subjected to nitrogen leaching in the presence of fluorine-containing compounds in amount of 4.0 to 4.5 mol of fluorine per 1 mol of zirconium. Obtained pulp is filtered and the precipitate is washed on the filter. Combined solution after nitric leaching and washing of the residue is neutralized in two steps at first to pH = 5-6 to separate the zirconium compounds precipitate, and then to pH = 9-11 to separate manganese hydroxide. Precipitate of zirconium compounds is dissolved in nitric acid and directed into a cycle for extraction separation of zirconium and hafnium using a solution of tributyl phosphate in a hydrocarbon diluent to obtain highly pure compounds of zirconium and hafnium.

EFFECT: method provides both high degree of recovery of REE and zirconium in form suitable for obtaining especially pure compounds of zirconium and hafnium.

1 cl, 2 ex

Description

The invention relates to methods for processing eudialyte concentrate and can be used to obtain rare earth elements (hereinafter referred to as REE) and highly pure compounds of zirconium, hafnium.

A known method of processing eudialyte concentrate, including the decomposition of the concentrate with sulfuric acid at a temperature of 80-120 ° C, filtering the pulp, followed by two-stage water washing of the insoluble sediment. Zirconium is isolated from the sulfuric acid solution by extraction with a mixture of trioctylamine, octanol and kerosene, or crystallization with preliminary evaporation (RU No. 2649606, C 22 B 34/14, 59/00, 3/08, С01B 33/12 2018).

The disadvantages of this method is the low degree of extraction of REE from eudialyte concentrate - no more than 60%.

A known method for increasing the filterability of pulps during sulfuric acid processing of eudialyte concentrate, including sulfuric acid processing of eudialyte concentrate with the addition of sodium fluoride, subsequent filtration of the pulp, washing the precipitate and separating REE and zirconium by the extraction method (RU No. 2626121, C 22 B 34/14, 59/00, 3/08, 2017).

The disadvantage of this method is the need for the separation of zirconium and REE extraction from corrosive sulphate-fluoride media, with low distribution coefficients of the target components.

There is a known method of processing eudialyte concentrate, which consists in opening the concentrate with sulfuric acid, diluting the pulp with a solution of sodium sulfate, separating the insoluble residue by filtration, processing the filtrate by sequential precipitation of aluminum alum, zirconium, iron and manganese hydroxides and isolating REE from the insoluble residue of opening the sulfate concentrate by converting REE into nitrates or chlorides (RU No. 2183225, C 22 B 34/14, 59/00, 3/08, 2002).

The disadvantages of this method are the low degree of extraction of both zirconium from 68 to 76% and REE from 47 to 52%.

A known method of processing eudialyte concentrate, which consists in the decomposition of the concentrate with hydrochloric acid, drying the resulting gel at a temperature of 130-170 ° C, water treatment of the gel with transfer to a solution of REE and acid leaching of zirconium from the gel after water treatment (RU No. 2040568, C 22 B 34 / 14, 59/00, 1995).

The disadvantages of this method are the use of a corrosive hydrochloric acid concentrate, as well as the lack of a description of the extraction of zirconium from the gel after water washing.

The closest in technical essence to the claimed is a method of processing eudialyte concentrate by decomposing the concentrate with nitric or hydrochloric acid, followed by simultaneous thermal treatment of the gel, regeneration of the acid and aqueous leaching of the gel with transfer into a solution of rare earth elements in an autoclave at a temperature of 175-250 ° C, separation of the insoluble residue from the REE solution and the separation of zirconium from the insoluble residue by wet gravity separation (RU No. 2522074, C 22 B 34/14, 59/00, 3/06, 2014).

One of the disadvantages of the known method is the impossibility of providing a high degree of extraction (more than 90%), as zirconium, hafnium, and REE. In addition, the use of an autoclave in the process of water leaching leads to the oxolation of bonds in the structure of zirconium hydroxide, which significantly complicates its processing, which is a necessary stage in obtaining highly pure zirconium and hafnium compounds.

Thus, all known methods of processing eudialyte concentrate do not provide a simultaneous high degree of extraction (more than 90%) of zirconium, hafnium and REE. In addition, the extracted zirconium from the eudialyte concentrate by the known methods is a technical product, the issue of deep purification of zirconium from impurities, including hafnium, is not considered.

The problem to be solved by the invention is to provide a simultaneous high degree of extraction (more than 90%) from the eudialyte concentrate not only REE, but also zirconium in a form suitable for obtaining highly pure compounds of zirconium and hafnium.

To achieve the technical result in the proposed method, including the decomposition of the concentrate with nitric acid to obtain a gel, drying the gel, water leaching of the gel with the transfer of rare earth elements into the solution, and into the insoluble precipitate of the zirconium compound, the separation of the solution from the sediment followed by the isolation of zirconium compounds, the drying of the gel is carried out at a temperature from 180 to 200 ° C, to isolate zirconium compounds, the precipitate after water washing is subjected to nitric acid leaching in the presence of fluorine-containing compounds in an amount of 4.0 to 4.5 mol of fluorine per 1 mol of zirconium, the pulp is filtered, the precipitate is washed on a filter, and the combined solution after nitric acid leaching and washing of the precipitate is neutralized in two stages, first to pH = 5-6, separating the zirconium-containing precipitate, and then to pH = 9-11 to separate manganese hydroxide, after which the precipitate of zirconium compounds is dissolved in nitric acid and sent to the cycle extraction separation of zirconium and hafnium using We use a solution of tributyl phosphate in a hydrocarbon diluent to obtain highly pure zirconium and hafnium compounds.

Drying the gel at temperatures below 180 ° C leads to the formation of a less compact dry gel, which increases the capture of the aqueous phase during the separation of the insoluble sediment after aqueous and acidic treatment of the dry gel.

The addition of fluorine-containing compounds at the stage of nitric acid leaching of the gel at a molar ratio of fluorine in an amount of 4.0 to 4.5 to 1 mole of zirconium provides a quantitative transfer of zirconium into a nitric acid solution. When the molar ratio of fluorine to zirconium is less than 4.0: 1, the degree of transfer of zirconium to nitric acid solution decreases, the addition of fluorine-containing compounds to the system at the stage of nitric acid leaching of the gel in a molar ratio of fluorine to zirconium in an amount of more than 4.5: 1 is impractical, since it is not accompanied by an improvement. qualitative characteristics of the zirconium leaching process.

As the fluorine-containing compounds, one or a mixture of several of the following salts can be used: sodium fluoride, potassium fluoride or potassium fluorosilicate.

The solutions after aqueous and nitric acid leaching of the gel can be reused for, respectively, aqueous and nitric acid leaching of the next portion of the dry gel. In the case of nitric acid solution of zirconium, the solution is adjusted for the concentration of nitric acid (re-strengthened) before reuse. It is advisable to return the solutions to the cycle after aqueous and nitric acid leaching up to four times, which allows increasing the concentration of REE and zirconium in aqueous and nitric acid solutions, respectively, and reducing the amount of reagents used.

The rasters after nitric acid leaching of zirconium also contain a significant amount of manganese. With an increase in the pH of the solution to 8 or more, manganese precipitates in the form of manganese (II) hydroxide, which upon contact with air, as well as upon dissolution of the precipitate in nitric acid, transforms into an inactive, poorly filterable manganese (IV) hydroxide, which complicates further processing of such a solution. Therefore, the pH of the solution is neutralized in two stages: after nitric acid leaching, first to pH = 5-6, the precipitate of zirconium compounds is separated, while manganese remains in the filtrate. Then the filtrate is neutralized to pH = 9-11 and the manganese hydroxide precipitate is separated.

The precipitate of zirconium compounds is dissolved in nitric acid and sent to the cycle of extraction purification and separation of zirconium and hafnium with a solution of tributyl phosphate in a hydrocarbon diluent. The cycle of extraction separation of zirconium and hafnium is carried out in a cascade of centrifugal extractors.

The proposed method is implemented by the following examples:

Example 1

A sample of eudialyte concentrate weighing 50 g, containing 6.4% zirconium and 1.09% REE was treated with 100 cm ^{3 of a} 30% nitric acid solution, the resulting gel was dried at a temperature of 200 ° C, and 56 g of dry gel was obtained. The dry gel was treated with 200 cm ^{3 of} distilled water, the insoluble precipitate was filtered off and washed on the filter with distilled water. 5.5 g of potassium fluorosilicate was added to the washed precipitate and treated with 250 cm ^{3 of a} 30% nitric acid solution, the pulp was filtered, the precipitate was washed on the filter with distilled water. The combined solution after nitric acid leaching and washing of the precipitate was neutralized with ammonia solution to pH = 5, after filtration of the pulp, 30.5 g of precipitate were obtained. Then the filtrate was neutralized with ammonia solution to pH = 9.5, the manganese hydroxide precipitate was filtered off.

The extraction of REE into the combined aqueous leaching solution and the solution after washing the insoluble precipitate of aqueous leaching was 95.8%, the extraction of zirconium was 0.015%. The extraction of zirconium into the zirconium hydroxide precipitate was 97.5%. The precipitate of zirconium compounds was dissolved in nitric acid and treated with a solution of tributyl phosphate in a hydrocarbon diluent; 99.3% of the sum of zirconium and hafnium present in the precipitate was transferred to the organic phase.

Example 2

A sample of eudialyte concentrate weighing 100 g, containing 6.4% zirconium and 1.09% REE was treated with a 30% solution of nitric acid in a volume of 200 cm ³ , the resulting gel was dried at 180 ° C, obtaining 113 g of dry gel. The dry gel was divided into two portions, the first portion was treated with distilled water in a volume of 200 cm ³ , the insoluble precipitate was filtered off and washed on a filter with distilled water. The second portion of the dry gel was treated with a solution after aqueous leaching of the first portion, before it was further strengthened with a washing solution to a volume of 200 cm ³ , the insoluble precipitate was filtered off and washed on a filter with distilled water.

To the first portion of the washed precipitate was added 6 g of sodium fluoride and treated with a 30% solution of nitric acid in a volume of 250 cm ³ , the pulp was filtered, the precipitate was washed on the filter with distilled water. The second portion of the washed precipitate was treated with an acidic filtrate obtained after nitric acid leaching of the first portion, previously adjusted to a volume of 250 cm ³ and a nitric acid concentration of 30%, then the precipitate was filtered off and washed on the filter with distilled water.

The combined solution after nitric acid leaching and washing the precipitate was neutralized with ammonia solution to pH = 5.5, after filtration of the pulp, 73 g of precipitate were obtained. Then the filtrate was neutralized with ammonia solution to pH = 10, the manganese hydroxide precipitate was filtered off.

The extraction of REE into the combined solution of aqueous leaching and solutions after washing two portions of insoluble sediments of aqueous leaching was 95.1%, the extraction of zirconium was 0.02%. The extraction of zirconium into the zirconium hydroxide precipitate was 98.3%. The precipitate of zirconium compounds was dissolved in nitric acid and treated with a solution of tributyl phosphate in a hydrocarbon diluent; 99.5% of the sum of zirconium and hafnium present in the precipitate was transferred to the organic phase.

Claims (5)

1. A method for processing eudialyte concentrate, including its decomposition with nitric acid to obtain a gel, drying the gel, water leaching of the gel with the transfer of rare earth elements into a solution, and into an insoluble precipitate of zirconium compounds, separation of the solution from the sediment, followed by the release of zirconium compounds, characterized in that drying of the gel is carried out at a temperature of 180 to 200 ° C, to isolate zirconium compounds, the precipitate after water washing is subjected to nitric acid leaching in the presence of fluorine-containing compounds in an amount of 4.0 to 4.5 mol of fluorine per 1 mol of zirconium, after which the pulp is filtered, the precipitate washed on a filter, and the combined solution after nitric acid leaching and washing the precipitate is neutralized in two stages, first to pH = 5-6 to separate the precipitate of zirconium compounds, and then to pH = 9-11 to separate manganese hydroxide, after which the precipitate of zirconium compounds is dissolved in nitric acid and sent to the cycle of extraction separation of zirconium and hafn using a solution of tributyl phosphate in a hydrocarbon diluent to obtain highly pure zirconium and hafnium compounds. 2. A method according to claim 1, wherein the solution after aqueous leaching of the gel can be reused for aqueous leaching of the next portion of the dry gel. 3. The method according to claim 1, characterized in that the solution after nitric acid leaching of the insoluble residue of aqueous leaching after adjusting the concentration of nitric acid can be reused for nitric acid leaching of the next portion of the dry gel. 4. The method according to claim 1, characterized in that at least one of the following salts can be used as fluorine-containing compounds: sodium fluoride, potassium fluoride, potassium fluorosilicate. 5. The method according to claim 1, characterized in that the cycle of extraction separation of zirconium and hafnium is carried out in a cascade of centrifugal extractors.