Method of treating rare-earth phosphate concentrate separated from apatite

FIELD: chemistry.

SUBSTANCE: invention relates to methods of separating deactivated rare-earth elements during nitric acid treatment of apatite concentrate from nitrate-phosphate solutions. The method of treating a rare-earth phosphate concentrate isolated from apatite involves decomposition of the rare-earth phosphate concentrate with nitric acid, treating the obtained solution with oxalic acid with precipitation of rare-earth oxalates in two steps, at the first step of precipitation of oxalates of thorium and rare-earth elements, 5-10% oxalic acid in stoichiometric amount is added to rare-earth elements present in the solution, and at the second step of precipitation of rare-earth oxalates, 110-115% oxalic acid in stoichiometric amount is added to rare-earth elements present in the initial solution, and the rare-earth oxalates are then calcined to rare-earth oxides.

EFFECT: invention provides high economic efficiency of the process, which is achieved by avoiding the need to process and bury the precipitate containing thorium.

3 cl, 2 ex

 

The invention relates to a method of allocating deactivated rare earth elements (REE) in nitric acid processing of Apatite concentrate from nitrogen and phosphate solutions obtained by dissolving the phosphate concentrate REE.

The Khibiny Apatite concentrate contains ≈1% REE oxides. The content of thorium 0,001-0,003%, which determines the specific activity of 0.004-0,12B/g, lower than the permissible limits for non-radioactive materials, in accordance with the Sanitary rules (JV 2.6.1.798-99)≤to 0.74 Bq/g due To the close chemical properties to the properties of the REE, selecting REE of Apatite concentrate thorium is concentrated in the final product - oxides REE content of 0.1-0.3%. The specific activity of rare earth product is 4.2 to 12.5 Bq/g, which, according to the Sanitary rules, it is not possible to attribute it to non-radioactive materials.

A method of refining rare earth phosphate concentrate, isolated from Apatite, including the decomposition of REE concentrate concentrated (10-12N) nitric or hydrochloric acid when heated, processing the obtained solution of oxalic acid when it is 200%excess over the stoichiometric quantity to REE with deposition of oxalates of the rare earths, Department of oxalate precipitate, washing and calcination to obtain the sum of the REE oxides containing 93-95% of the foundations of the CSOs substances, 5-7% of impurities, mainly calcium, iron, silicon, phosphorus. ("Complex of nitric acid processing of phosphate rock. Ed. Goldikova A.L. and Kopylova B.A. - L: Chemistry, 1982, s-159)

A method of refining rare earth phosphate concentrate, isolated from Apatite. /Patent RU No. 2148019, MKI CO1F 17/00, SW 3/06/. Decomposition of rare earth phosphate concentrate REE was carried out by simultaneous dissolution in nitric or hydrochloric acid in the presence of oxalic acid. The precipitate of oxalate is washed with water and made red-hot until the REE oxides. This method is adopted for the prototype.

The disadvantages of these methods is to obtain REE oxides with a thorium content of exceeding health standards (JV 2.6.1.798-99). The operation of separation of thorium these methods of processing of phosphate of rare earth concentrates to oxides of rare-earth elements is not provided.

There is also known a method of decontamination of the REE in the processing of loparite concentrate by allocations from the nitric acid solution REE relettering cake, which undergoes further processing and disposal. (Patent No. 2145980 "Method for processing of loparite concentrate", MKI SW 59/00, 34/12).

The disadvantage of this method is the need for additional processing of iron-thorium cake and organization of his burial.

Also known the way of extras is clonage separation of thorium from rare earth elements during their extraction with tributyl phosphate. (Zelikman. N.A. and other "metallurgy of rare earths, thorium and uranium". Of ferrous and nonferrous metallurgy. M, 1960).

The disadvantages of this method include its multi-stage, introduction organophosphorus compounds that fertilizer is not recommended, as the ingress of impurities organophosphorus compounds, which are prone to hydrolysis, can cause spontaneous decomposition of ammonium nitrate, which is included in the fertilizer. In addition, the allocation of concentrates of thorium from the organic solutions will require additional work on their recycling and landfill or storage of imported thorium products.

The technical result of this invention is to provide a decontaminated total rare earth concentrates in nitric-acid treatment of Apatite with the exception of discharges, increase the economic efficiency of the method due to its simplicity.

The technical result is achieved by the fact that nitrogen and phosphate solutions, obtained by the decomposition of rare earth phosphate concentrate nitric acid, is fractional (two-stage) precipitation of oxalates REE. At the first stage of deposition is introduced oxalic acid in the amount of 5-10% of stoichiometry on the REE present in the solution. Consumption of oxalic acid in the second stage of deposition of the Oxus is the ATA is 110-115% of stoichiometry on REE, contained source of nitrogen-phosphate solution. The thorium oxalate precipitates together with a part of oxalates REE. The precipitate of oxalate of thorium and REE is separated from the solution by filtration. Sediment washed from the filter with the flow of the filtrate obtained in the second stage of deposition is deactivated oxalates REE, then return in the manufacture of fertilizers.

The resulting suspension by dilution of sludge filtrate aradioactive and may be sent in the production of fertilizers. Thus, thorium, who was in Apatite concentrate and passed into the main product is fertilizer, returns again in their production.

After the second stage of deposition receive oxalates REE with specific activity of 0.13-0.2 Bq/g that satisfy the health standards JV 2.6.1.798-99. For materials which are allowed to work without restrictions specific activity must be <to 0.74 Bq/g mother liquor of the second stage of deposition of REE also aradioactive.

The advantage of the proposed method lies in the fact that after calcination of the oxalate REE obtained in the second stage of deposition, the REE oxides of aradioactive and correspond to class 1 according to sanitary rules, allowing to work with them without restrictions. In addition, recycling of sludge containing thorium does not require additional costs for processing and disposal,which makes the process of allocating REE cost-effective.

Example 1. The experiments were conducted using nitrate-phosphate solutions obtained in the production of fertilizers JSC ACRON after allocation calcium nitrate. This solution was selected crematoria sodium. Received nitrate-phosphate solution had the composition, ppm,%:

RSA - 0,47; Th - 0,00047; P2O5- 22,5; Sa - 3,82; F - 0,2.

This solution was precipitated with gaseous ammonia phosphate of rare earth concentrate (FRSC) at pH of 1.4. Sediment FRSC separated from solution and was dissolved in 12N nitric acid. The obtained nitrogen-phosphate solution (PRA) composition, ppm,%:

RSA - 6,67; Th - 0,0067; P2O5of 6.31; Ca - 1,06; HNO3- UN; F - 0,001;

was heated to 90°C and then added to a solution of oxalic acid. Consumption of oxalic acid - 5% of the content of REE in Pras. Recovery of REE in terms of acidity 1,3N and small consumption of oxalic acid is 2% of the content in Pras. The resulting suspension was kept at 20-25°C for 20 hours. Then the precipitate was separated from the solution by filtration. Nitric-phosphoric acid solution after the precipitate was treated with oxalic acid at a temperature of 70-80°C for 1 hour. Consumption of oxalic acid - 115% from the content of REE in the original PRA. The resulting suspension was kept at 20-25°C for 2 hours. After that, the precipitate of oxalate REE were separated by filtration. The filtrate e.g. ulali flush first precipitate of oxalate of thorium and REE. The resultant slurry composition, ppm,%:

RSA - 0,1; Th - 0,004; P2O5and 4.4; Sa - 0,7; C2O-4 - 0,18; specific activity is 0.17 Bq/g; goes into the production of fertilizers on the stage of neutralization. Oxalates REE obtained in the second stage of the deposition, was dried and progulivali at 800°C for 6 hours. The composition of REE oxides, ppm,%:

RSA - 99; Th - 0,005; P2O5- 0,4; Sa - 0,3; specific activity of 0.2 Bq/g Extract REE 98% of the content in the original PRA.

Example 2. Experiments on the proposed method described in example 1, except that the nitrate-phosphate solution contained a greater quantity of thorium. The composition of the solution, ppm,%:

RSO to 0.5; Th Is 0.0015; P2O5- 23; Sa - 3,9; F - 0,18.

After deposition FRSC and dissolving it in nitric acid obtained nitrogen-phosphate solution composition, ppm,%:

RSA - 4,86; Th - 0,015; Ca - 0,73; F - 0,001; HNO3- 1,9N.

Consumption of oxalic acid in the first stage of deposition of oxalates thorium and REE was 10% of the content of REE in Pras. Consumption of oxalic acid in the second stage of the deposition of pure oxalate REE - 110% of the contents of REE in the original PRA. Recovery of REE in the first residue 5% of the content in the original PRA. Recovery of REE in the second precipitate of oxalate - 95%. Suspension after flushing the first precipitate of oxalate of thorium and REE with filter had composition, ppm,%:

RSA - 0,24; Th - 0,012; Ca - 0,52; C2O4--0,32; specific activity of 0.5 Bq/g

The composition of REE oxides obtained after calcination of the deactivated oxalates, ppm,%:

RSA - 99; Th - 0,003; P2O5to 0.3; Sa - 0,2; specific activity to 0.13 Bq/year

The positive effect of decontamination REE proposed method provides a two stage deposition process oxalates, where in the first stage is the separation of thorium from the base REE contained in the products of processing of Apatite with a view to their allocation. The economic efficiency of the process is achieved without the need for recycling and disposal of products containing thorium.

1. A method of processing rare earth phosphate concentrate, isolated from Apatite, including the decomposition of rare earth phosphate concentrate nitric acid, processing the obtained solution of oxalic acid precipitation of oxalates REE and their annealing to REE oxides, characterized in that the treatment with oxalic acid lead in two stages, with the first stage of deposition of oxalates thorium and REE serves 5-10% of oxalic acid from stoichiometry on the REE present in the solution, the second stage precipitation of oxalates REE - 110-115% of oxalic acid from stagione the AI on REE, present in the initial solution.

2. The method according to claim 1, characterized in that the precipitate of oxalate of thorium and REE, resulting in the first stage of deposition, wash off with the filter, the filtrate separated from the precipitate of oxalate of REE in the second stage of deposition, washout from the filter with a specific activity of 0.17 to 0.5 Bq/g return in the manufacture of fertilizers.

3. The method according to claim 1, characterized in that in the second stage sedimentation get oxalates REE, not containing thorium, after annealing gives the REE oxides with specific activity of 0.13-0.2 Bq/year



 

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