DE1034606B - Process for the separation of nuclear-pure ammonium urate - Google Patents

Description

Process for the separation of nuclear pure ammonium urate subject The invention is a method for the separation of the purest, easily filterable Ammonium uranium with the help of gaseous ammonia.

The use of gaseous ammonia, e.g. B. for the production of Fertilizers, belongs to the state of the art. Especially in mixed fertilizer production One has already used ammonium-air mixtures, which makes for this special Case show certain advantages. For example, the heat of reaction is better dissipated. However, such procedures are based on very specific tasks, and the one that has been found Solution is therefore limited to a relatively narrow range. Results that the Transfer of the known processes to other applications that are far removed from the application point of view Would suggest problems cannot be derived from them.

Ammonium uranium is quantitatively made from uranium (VI) salt solutions with ammonia deposited. This deposition usually takes place with an aqueous solution of ammonia and then leads to a precipitate that is difficult to filter and wash out, which can carry impurities out of the solution through adsorption. One such The method is therefore unsuitable. if a separation of uranium in a very pure form, for example after high purification by a liquid-liquid extraction process, should be made.

A proposal has already been made to overcome the disadvantages just described the deposition of uranium as ammonium uranium by boiling uranium salt solutions with the addition of urea in what is known as a homogeneous precipitation reaction. Here a product that is easy to filter is obtained, but the quality must be taken into account of urea, if uranium is to be deposited in a highly pure form, unusual and demands that are not easy to meet are made.

It has now been found that ammonium uranium from aqueous solutions of Uranium salts in an extremely pure and easily filterable form and in a very economical form Way by using gaseous ammonia mixed with air or a other inert gas is introduced into the solution to be precipitated, is deposited.

Gaseous ammonia is produced from neutral or acidic aqueous solutions eagerly received. If ammonia gas is passed undiluted into or directly onto the solution of a uranium salt to be precipitated, so is. even with the liveliest mixing, that Occurrence of local excesses in the solution and thus a precipitation of ammonium uranate unavoidable in a form that is difficult to filter. Only after dilution of the ammonia gas by an inert gas, e.g. B. air, the gas mixture can be introduced directly into the solution and the absorption of the ammonia then takes place with appropriate division the gas bubbles take place evenly in the entire solution space. With such an absorption of ammonia, the ammonium urate is precipitated in easily filterable, very pure form.

The most favorable degree of dilution of the ammonia gas depends on several factors Factors. For example, it is sufficient if mixed vigorously and at higher temperatures - above 70 ° C - is precipitated, a dilution of the ammonia gas with the equal volume of inert gas, while under otherwise identical conditions in the Near room temperature ammonia with about twice the volume or larger volumes should be diluted with inert gas.

It has also been found that the precipitation temperature also has an influence on the formation of the precipitate. As expected, very easily filterable precipitates are obtained when working in the heat, but such precipitates can also be obtained at moderate precipitation rates and somewhat greater dilution of the ammonia gas at medium to low temperatures. The precipitates obtained under the last-mentioned conditions are relatively fine-grained, but of uniform grain size, the individual grains being almost spherical. The shape of these grains is retained during the thermal decomposition of the ammonium uranate to uranium trioxy d (U0,) or uranium oxide (U.0.). B. under hydrogen to uranium dioxide (U02), with no sintering of the resulting products observed below 900 ° C. Since these properties are of essential technological importance in many cases, precipitation at low to medium temperatures generally not exceeding 70 ° C., of course only in combination with the use of dilute ammonia gas, is a preferred embodiment of the process of the invention.

Ammonium uranate deposited at high temperatures is, as before was found above, very easy to filter and also correspondingly pure, but consists of needle-shaped crystals or agglomerations of such crystals. Such a product has a lower bulk density than the above, with a stronger one Sintering also occurs more easily during annealing. Where such properties are desired precipitation at a higher temperature will be preferable.

Although the process of the invention because of the high purity of the then produced ammonium uranium especially for the separation of uranium is suitable for pure solutions, it is by no means limited in its application this limited. It is well known that the deposition of uranium is also carried out by ammonia done at different stages of uranium processing, especially during extraction of uranium from ores. This is very often done using the so-called soda process, in which VI-valent uranium is obtained as a complex, soluble carbonate. From such After acidification and expulsion of carbonic acid, uranium solutions can be deposited with ammonia the method of the invention differing from the usual method leads to an easily filterable product.

Very favorable results are obtained when using the method of the invention is carried out continuously by e.g. B. a suitable, with mixing device and overflow provided precipitation vessel continuously supplied solution of VI-valent uranium and ammonia-inert gas mixture is introduced. Here, as a matter of course even in the case of discontinuous precipitation, is intended to ensure a quantitative The uranium deposition has a p $ value of 6.0 to 7.0. In combination the use of dilute ammonia gas results in this preferred mode of operation special regular results. It is useful for the ammonia to flow automatically to be regulated by an appropriate device so that the pli value of the solution is kept at about 6.5. In the case of continuous precipitation, a Product of coarser grain size than obtained with discontinuous precipitation. Examples 1. Into a container equipped with a heating jacket, propeller agitator and overflow stainless steel, content 600 l, 4001 one from a liquid-liquid extraction obtained aqueous uranyl nitrate solution containing weak nitric acid of the density 1.15 entered. The solution contained about 90 g uranium element / 1 and, based on the uranium metal content, 1-10 # -2% boron in the form of boric acid. After heating to 50 ° C, the agitator is running Ammonia gas at a rate of 401 / minute on the level of the solution passed, the introduction point close to the propeller circle of the agitator was laid. After the gas mixture had been introduced for about 5 hours, the pH became of 6.5 achieved. At this point, a uranyl nitrate solution became the same Composition as in the template added at a rate of 21 / minute, the introduction through a leading up to close to the bottom of the precipitation vessel Tube was made. The supply of ammonia gas was continued and thereby the temperature was kept at 50 ± 5 ° C and the pH at about 6.5. That from the container continuously running reaction mixture of solution and precipitate was a continuously acting drum filter fed and washed here continuously. The precipitate was slimy and difficult to filter. After drying it was the boron content is determined in such a way that the boron is in the form of trimethyl borate was distilled off and then measured photometrically with carmine, namely by comparison with a standard curve. The. Sensitivity of the boron determination was 0.05 ppm. It was found that the solid reaction product despite being more intense The washing still had a boron content of 5-10-4%, based on the uranium metal content, which makes the uranium compound completely unusable for nuclear physics purposes.

2. In the same vessel as used in Example 1, the same uranyl nitrate solution was again introduced with 1-10-2% boron in an amount of 4001. After heating to 50 ° C., a gas mixture of 1 part by volume of ammonia and 3 parts by volume of oil- and dust-free, carbonic acid-free air was introduced into the solution at a rate of 150 ] / minute, the vertically installed inlet pipe being bent at right angles about 50 cm above the bottom of the vessel, bringing the outlet end close to the propeller circle. In this way a fine distribution of the gas bubbles was achieved. After the gas mixture had been introduced for 5 hours, a pH of 6.5 had set in, with a faint ammonia odor. Then a uranyl nitrate solution was added at a rate of 21 / minute, which was introduced through a pipe reaching almost to the bottom of the precipitation vessel. The proportion of air in the gas mixture was reduced to 1: 2. The injection rate was about 150 liters per minute; at a temperature of 50 ± 5'C and a p11-`N'ert of about 6.5, the overflowing mixture of solution and precipitate was continuously drawn off and placed on a continuously operating drum filter, where it was thoroughly washed out. The precipitate turned out to be easily filterable and could be washed without difficulty. The boron in the dried ammonium urate was determined as described in Example 1. The result was a boron content of less than 1 - 10-5% and thus an ammonium uranate, which can be referred to as nuclear pure.

Claims (3)

PATENTA \ SPROGHE: 1. Process for the separation of nuclear pure, good filterable ammonium uranium from aqueous solutions of uranium (VI) salts with ammonia, characterized in that gaseous ammonia diluted by inert gases in the solutions is initiated. 2. The method according to claim 1, characterized in that that a pH of 6 to 7 is maintained in the solution during the precipitation. 3. Process according to Claims 1 and 2, characterized in that the temperature is kept below 70 ° C during the precipitation. Documents considered: German Patent No. 642 362; French patent specification No. 1 040 923.