Method of extracting americium

FIELD: chemistry.

SUBSTANCE: invention relates to methods of extracting americium in form of americium dioxide from solutions. The invention can be used in the technology of extracting americium from production and radioactive wastes. The method involves concentrating nitric acid solution containing americium and impurities to americium content of not less than 100 mg/l by multi-step deposition of a precipitate containing americium, followed by dissolution thereof each time in a new portion of the starting solution. The precipitate containing americium is obtained from each portion of the solution by adding to 3.8-6.0 M nitric acid solution, which contains americium and impurities, ammonium hydroxide or an alkali metal hydroxide until achieving residual acidity of 0.1-0.2 M, oxalic acid to concentration of 10-50 g/l and adjusting acidity of the obtained reaction mixture to pH 0.6-2.3 if there are hydrolysable impurities in the starting solution and to pH 0.6-3.5 if not. The precipitate obtained by deposition from the americium-concentrated solution is then calcined and the calcined precipitate is then dissolved in nitric acid solution. Americium is then extracted from the obtained solution by a tributyl phosphate-based solid extractant, re-extracted, americium oxalate is deposited from the re-extract and then calcined to americium dioxide.

EFFECT: wider range of methods of extracting americium.

3 cl, 2 ex

 

The invention relates to a method of extraction of americium in the form of americium dioxide from solutions. The invention can be used in the technology of extraction of americium from the speed of production and radioactive waste. The americium dioxide is used, for example, ionizing radiation sources used in exploration (logging).

There is a method of extraction of americium in the form of americium dioxide from solution [U.S. patent No. 3781404, publ. 25.12.1973]. By this method from a solution containing americium and impurities precipitated oxalate americium introduction of oxalic acid, the precipitate is filtered and calcined him with the receipt of americium oxide.

There is a method of extraction of americium in the form of americium dioxide from solutions [RF patent №2335554, IPC C22B 60/02, C22B 3/20 (2006.01), publ. 10.10.2008]. The method includes the deposition of the nitric acid solution containing americium and impurities, sludge, containing americium, calcining the resulting sludge to oxides, dissolution in nitric acid to obtain a nitric acid solution, from which the extraction of americium using solid extractant based diisooctylphthalate, reextraction americium, deposition of one stripped off of reextract americium oxalate and its annealing to americium dioxide. The method chosen for the prototype.

Task izobreteniya expanding Arsenal of methods of extraction of americium.

Task is the fact that the method of extraction of americium in the form of americium dioxide from solutions, including operation of the deposition of the nitric acid solution containing americium and impurities, sludge, containing americium, calcining the resulting sludge to oxides, dissolution in nitric acid solution, the extraction of americium from the resulting nitric acid solution using solid extractant and the subsequent reextraction, deposition of reextract americium oxalate and its annealing to americium dioxide, carry out the concentration of nitric acid solution containing americium and impurities content of americium at least 100 mg/l by repeated deposition of sediment containing americium, its subsequent dissolution each time a new portion of the initial solution, while the precipitate containing americium is produced by the introduction of 3.8÷6.0 M nitric acid solution containing americium and impurities, ammonium hydroxide or alkali metal to a residual acidity of 0.1÷0.2 M oxalic acid to a concentration of 10÷50 g/l and adjusting the pH of the obtained reaction mixture to a pH of 0.6÷2,3 if the initial solution gidrolizuyushchie impurities or pH 0,6÷3,5 in their absence, the calcination to the oxides send the precipitate obtained by precipitation from concentrated on americium solution, and the extraction and ericia carried out using solid extractant on the basis of tributyl phosphate.

From the filtrate obtained after separation of the precipitate, containing americium, precipitated hydroxide of americium, which is dissolved in the original solution.

From the filtrate obtained after separation of the precipitate, containing americium, precipitated oxalate americium on the media-calcium oxalate, dissolved in nitric acid from nitric acid solution precipitated hydroxide of americium, which is dissolved in the original solution.

The method is as follows.

Example 1.

Recycle nitric acid solutions of radioactive waste with concentrations of americium to tens of mg/l; from impurities can be: iron, aluminum, magnesium, chromium, Nickel, silicon, calcium, etc. in concentrations up to several grams per liter.

3.8÷6.0 M nitric acid solution containing americium and other impurities that enter solution of ammonium hydroxide or hydroxide of an alkali metal (lithium, sodium, potassium) to a residual acidity of 0.1÷0.2 M, then 10÷50 g/l of oxalic acid, and adding ammonium hydroxide or alkali metal hydroxide adjust the acidity of the solution to a pH of 0.6÷2,3 if the initial solution gidrolizuyushchie impurities (iron, aluminium) or to pH 0,6÷3.5 in the absence of initial solution gidrolizuyushchie impurities. (At pH more than 2.3 compounds of iron, aluminum, fitting in the sediment, stronger contaminate the precipitate containing americium.

After stirring and aging the reaction mixture for a specified time get the precipitate containing americium; this precipitate, containing compounds of americium, ammonium or alkali metal, and impurities. The precipitate contains multicomponent oxalate complex. Apparently, americium contained in the Deposit in the form of oxalate. Studies have shown, the most complete deposition of americium from 3,8÷6,0 M solution and with a minimum amount of impurities contained in the initial solution is adding hydroxide to a residual acidity of 0.1÷0.2 M, 10÷50 g/l of oxalic acid and adjusting the pH of the solution to a pH of 0.6÷2,3 if the initial solution gidrolizuyushchie impurities (iron, aluminium) or to pH 0,6÷3.5 in the absence of initial solution gidrolizuyushchie impurities. These conditions result in a decrease in the concentration of americium in solution in a single deposition ≈27÷45 times.

The precipitate is filtered off, the major part of the impurities contained in the original solution remains in the filtrate.

The precipitate is dissolved in a fresh portion of the original solution. To the solution add ammonium hydroxide or an alkali metal, oxalic acid and adjust the pH (in the above values). Precipitating sludge containing americium, and dissolving the precipitate each time a new portion of the original solution, concentrate Rast is the PR for the americium content of americium in solution of not less than 100 mg/l (typically 100÷500 mg/l).

From the concentrated solution, are precipitated sludge containing americium, under the above conditions, or from a concentrated solution of precipitated hydroxide of americium by adding sodium hydroxide to a pH of 6.0÷7,0.

The precipitate is dried and calcined at a predetermined temperature to oxides which dissolve in the nitric acid solution, the solution is directed to the extraction.

Extraction of americium in the form of americium nitrate is performed with the use of solid extractant on the basis of tributyl phosphate (tax-TBP). Impurities practically not extracted, remain in aqueous solution. The extraction is carried out in a static mode by contact with the extractant, placed in a container, 0.1 M solution containing americium, within a specified time, after which the extractant is washed with water and extravert americium in the form of americium nitrate water.

In the received reextract add the specified amount of crystalline ammonium oxalate to precipitate the oxalate of americium. The precipitate is filtered off, dried and calcined to americium dioxide. When the processing solution containing americium in the amount of 50 mg/l, received americium dioxide in the number of 56.5 mg, the content of impurities therein 0.1 wt.%.

Example 2.

The filtrate remaining after separation by filtration of the precipitate, containing americium, contains 0.1 mg/l of americium, the principal amount of impurities, has a pH of 1.5. The filtrate is sent to the additional extraction of americium.

To do this, to the filtrate was added sodium hydroxide to pH=7,0, with sediment build-up, including americium hydroxide contaminated by impurities, which were separated from the mother liquor and dissolved in the original solution sent for recycling. The mother solution with the concentration of americium 0.01 mg/l, containing impurities, have sent conditioning and disposal.

Example 3.

The filtrate remaining after separation by filtration of the precipitate, containing americium, contains 0.1 mg/l of americium, the main impurities, has a pH of 1.5. The filtrate is sent to the additional extraction of americium.

To do this, to the filtrate was added a given amount of oxalic acid and chetyrehletnego calcium nitrate. Acidity was maintained at pH=1.0 to 2.0. The resulting reaction mixture was stirred for a given time. Got the precipitate of calcium oxalate with zoosadism with him americium oxalate. The precipitate was filtered and dissolved in a small volume of concentrated nitric acid. In this solution was dissolved precipitates obtained in the same way in the processing of other parties to the filtrate until the concentration of americium in the solution is not reached 10 mg/l

The Queen cells from the co-precipitation of calcium oxalate and oxalate americium containing impurities, have sent kondicionirovanie burial.

From the resulting nitrate solution was besieged americium hydroxide by adding sodium hydroxide to pH 7, and keeping the reaction mixture for a specified time, then the precipitation is separated from the mother liquor by filtration. The precipitate of hydroxide americium containing impurities dissolved in the original solution of the momentum production sent for recycling; from the mother liquor from the precipitation of hydroxide americium besieged calcium hydroxide, which is sent for processing, and the mother liquor from the precipitation of calcium hydroxide containing impurities, have sent conditioning and disposal.

1. The method of extraction of americium in the form of americium dioxide from solutions, including deposition of nitric acid solution containing americium and impurities, to obtain a precipitate containing americium, calcining the resulting sludge to oxides, dissolution in nitric acid solution, the extraction of americium from the resulting nitric acid solution using solid extractant and the subsequent reextraction, deposition of reextract americium oxalate and its annealing to americium dioxide, characterized in that carry out the initial concentration of nitric acid solution containing americium and impurities content of americium at least 100 mg/l by repeated deposition of sediment, containing the his americium, with its subsequent dissolution each time a new portion of the original solution, and the precipitate containing americium obtained from each portion of the solution by introducing 3.8÷6.0 M nitric acid solution containing americium and impurities, ammonium hydroxide or alkali metal to a residual acidity of 0.1÷0.2 M oxalic acid to a concentration of 10÷50 g/l and adjusting the pH of the obtained reaction mixture to a pH of 0.6÷2,3 if the initial solution gidrolizuyushchie impurities or to a pH of 0.6÷3,5 in their absence, with the calcination to the oxides send the precipitate obtained by deposition from the concentrated on americium solution, and extraction of americium carried out using solid extractant on the basis of tributyl phosphate.

2. The method according to claim 1, characterized in that the filtrate remaining after separation by filtration of the precipitate, containing americium, precipitated hydroxide of americium, which is dissolved in the original solution.

3. The method according to claim 1, characterized in that the filtrate remaining after separation by filtration of the precipitate, containing americium, precipitated oxalate americium on the media-calcium oxalate, dissolved in nitric acid from nitric acid solution precipitated hydroxide of americium, which is dissolved in the original solution.



 

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