JPS59200998A - Method of processing liquid waste containing uranium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing or recovering silane from waste liquid from manufacturing processes that handle uranium fluoride.

For example, the process of producing uranium dioxide from uranium hexafluoride uses the following reaction.Uranium fluoride is an extremely reactive substance that reacts immediately when it comes into contact with water.

UF, + 2H20= UO2F2 +
4HF
(112UO2F2+ 8HF +14NH40H
= (NH4)2U20□10+2NH4F++ +10
(2) When uranium hexafluoride is heated and evaporated and the gaseous uranium hexafluoride is bathed in water (%T=), it is hydrolyzed as shown in equation (1) to form an aqueous solution of uranyl fluoride and water fluoride. ,
Next, when aqueous ammonia is added, the reaction occurs as shown in equation (2), and uranyl fluoride is converted to ammonium deuterate (AD).
It precipitates as U). This ADH slurry is filtered and shaped into a cake to be used as a raw material for uranium dioxide. This f
The liquid contains a small amount of uranium, and discharging it directly from the plant as waste liquid poses environmental conservation problems.
Processing methods to remove or recover uranium are desired.

Conventionally, the following methods have been considered for treating waste liquid containing uranium.

(1) Dilution method This method is a method in which waste liquid containing uranium is simply diluted with water. This method requires large amounts of water, depending on the uranium concentration in the solution, and therefore uranium recovery is not possible.

(2) Alkaline earth metal salt precipitation method In this method, an alkaline earth metal oxide such as lime and one or more than 2 lj of water are added to a solution containing uranium, ammonia, and fluorine. In this method, all the fluorine in the alkaline earth metal is precipitated as fluoride, and at the same time, uranium is also co-precipitated and removed. In this method, not only uranium but also fluorine can be removed at the same time, but a large amount of precipitate, which is difficult to filter, is generated in large quantities, and a large amount of labor is required to process the precipitate over t''.

! , most of the precipitate is alkaline earth total fluoride, so the uranium conversion in the precipitate is relatively low, making it extremely difficult to recover the uranium in the precipitate, and there is no choice but to discard it. (Special Publication No. 47-55199).

<3) Ion exchange method In this method, the uranium-containing waste liquid is brought into contact with a total ion exchange resin, and the uranium is adsorbed on the uranium total ion exchange resin, thereby removing uranium from the waste liquid. The uranium adsorbed by the ion-exchange hatsumode is recovered by ejecting it with a nitrate. This method is excellent for removing and recovering uranium, but if it is not necessary to recover all of the uranium, there are problems in processing the recycled waste liquid, and it is not economical in terms of deterioration of the ion exchanger. do not have.

(4) In contrast to the conventional methods described above, a method for removing and recovering uranium was proposed by adding water glass to waste liquid containing uranium in the coexistence of fluorine and ammonia (Special Publications Publication No. 4).
B-38320).

This method uses silicon divanide, which is generated from added water glass,
It is said that all the precipitates are generated by co-precipitation of ammonium fluoride and ADU, and the production rate is high, the filtration property is good, and the uranium removal rate is extremely high at over 99.7%.

Furthermore, since the amount of water glass added is small, the amount of precipitate produced is small, and the uranium concentration in the precipitate is relatively high, and the uranium can be easily recovered by nitric acid treatment. It is said that it can be recovered. However, the problem with this method is that in order to completely generate the precipitate, the amount of fluorine added must be more than 5%, and the amount of ammonia must be more than 1%.
Since it is necessary to add slightly more than the equivalent of 17, high concentrations of fluorine and ammonium remain in the liquid after the formed precipitate is separated by Δ1. What is the ammonium in the sap? Although it is possible to remove high-temperature fluorine from the liquid by distilling it into a highly alkaline solution, discharging high-temperature fluorine as waste from a plant without first treating it poses environmental conservation problems; processing is required.

That is, fluorine originating from uranium hexafluoride is expressed by the above formulas (1) to (
As is clear from 2), the amount is 6 mol per 1 mol of uranium hexafluoride, and it is dissolved in water.
If t/l were due only to uranium hexafluoride, only 55 mg/l (as F) of fluorine would be dissolved in water.

However, in the invention described in the above publication, fluorine must be added in the form of ammonium fluoride (as F), and even if water glass 1~29/L f is added to produce sodium silicofluoride. , attached sword 0L
This is because 7 in. fluorine remains dissolved in water at about 9'I/l (as F). To remove this fluorine, V
There are methods of <11 to (3) above, but it goes without saying that the dilution method is used, and the present amount is also often used. As mentioned above, it is unavoidable that a large amount of precipitate will be produced, equivalent to the amount of sediment that can be filtered per ton of uranium.In any case, the above invention is extremely effective in recovering uranium, but it is extremely disadvantageous in treating waste liquid after recovery. I can say that.

It is an object of the present invention to provide a process for the removal of uranium and fluorine that is more advantageous and easier to perform than conventional methods. Furthermore, it is an object of the present invention to process uranium waste without further adding ammonia and fluorine.
There are few mulberry products for toilet use, and there is good transmissibility.
? ! i. The present invention provides a method for removing and recovering uranium and fluorine, which produces less precipitate and which is both easy and economical to recover and dispose of.

In order to achieve the above object, the present inventors conducted various studies and found a satisfactory method as described below.

The purpose of the present invention is to completely generate a precipitate by adding water glass and an alkaline earth metal salt while heating or heating and concentrating a molten liquid (!) containing uranium.
By separating the precipitate from the solution, uranium is removed and recovered and fluorine is removed.

The present invention will be explained below using specific examples.

Specific Example I When recovering uranium (1) First, when a solution containing uranium is heated at about 80 to 100°C or water glass is added while heating and concentrating it, sodium deuterate (Na2U20y
) #Fluorine to sodium silicofluoride (Na25j, F
6) is produced, and Keishun soda is decomposed into water to produce KeiW (5i02).

Silicon rfl (SiO+) acts as a binder for the solids of the above-mentioned sodium deuterate and sodium silicofluoride, and has the function of firmly adhering the solids to each other. By heating or heating the rice, its effect is fully promoted, and the solid mud layer becomes 2
It becomes gelatinous when the concentration reaches about 5 l/l.

Water glass is J Engineering S standard sodium silicate No. 1-3 (Na2
0-ns102)t<Use. J I S g,'r
%Sodium silicate has products No. 1 to 3, but 5i02
/Na, the higher the molar ratio of 20, the better. This is because the gelation of (1K[7 (Si02)) is fast.

Addition number 4 of water glass is s relative to the amount of solids in the bath liquid.
Add 20 to 50% as ho. When storing the solution, either reduced pressure or normal pressure may be used, and δ4 is reduced until the size of the isomorphic substance in the solution is approximately 2 to 57 cm.

If the solution A already has a solid content of this level, it is only necessary to heat it at about 50 to 80° C. for about 1 to 2 hours after adding water glass.

(2) After sieving, the bath liquid is passed through once to separate solids and liquid. Fluorine remains in the liquid, and uranium is contained in the solid matter. This isomorphic material is used for uranium recovery.

In other words, in order to recover uranium from the nucleated solid, it is sufficient to elute it with lithogenic acid, as is well known. - (3) On the other hand, the P solution with residual fluorine is about 80~
When water glass and alkaline earth metal salt 'fc are added while heating or heating and concentrating at 100°C, a calcium fluoride precipitate is produced by the reaction as shown in the following formula.

Oa2+ + 2F'-→CaF2↓ This precipitate is extremely fine and has low permeability, but by heating or thermal condensation, it can be converted to By firmly adhering the beads and precipitate particles to each other, it has good filterability and becomes a dense precipitate.The addition of water glass J, 4- is performed by adding an alkaline earth metal salt to the liquid. The amount of the alkaline earth metal salt is about 1.0 to 2-θ times the equivalent weight of fluorine in the solution.

Alkaline earth metal salts include (3a(OH)2.CaO0
3゜Preferably a neutral salt, i.e. CaC'12 # OaB''
4r Ca("3) 21ca3(po4)2 is suitable. This is because the pH of the first liquid becomes alkaline due to water glass path ≦ addition.
This is because it is necessary to adjust the HMJ, and in order to reduce the amount of strings required at this time, alkaline earth metals are preferable. Mj (OH) instead of Oa salt
2.

MS'003, MfCt4, Mff304,
MS' (NO3)2, NO3(PO4)2
can also be used.

Similarly to (1) above, when thermally concentrating at the cutting edge, either reduced pressure or normal pressure may be used.
Until it becomes a degree? 0 flat. There is already this much solid in the bath liquid! If J29 degrees, it will be about 50-80℃ after adding water glass.
All you have to do is heat it for about 1 to 2 hours.

Thereafter, the entire solution is filtered to separate the solids and the first liquid, the solids containing fluorine are discarded as waste, and the liquid is discharged as wastewater after pH adjustment.

Specific example (1) When uranium is not recovered (1) First, a solution containing uranium is heated and evaporated at about 80 to 100° C. and mixed with water glass and alkaline earth gold salt. The uranium in the solution is sodium diuranate (Na2U207). A mixture of sodium silicofluoride (Na25iF6) and calcium fluoride (caF2) is produced from xfluorine. Sodium silicate is hydrolyzed to produce silicon m (5i02), which has the effect of firmly fixing the above-mentioned precipitates together. The effect is promoted by heating or heat concentration, and the solid concentration becomes 59 /
When it becomes 1 or more, it becomes a gel. As the water glass, the JIS standard sodium silicate described in Example I is used. The amount of water glass added is 1 to 20% as Si'02 based on the amount of solids in the solution, including the addition of the alkaline earth metal salt 711]i described below. The alkaline earth metal salt is added in an amount of about 1.0 to 2.0 times the fluorine equivalent of the uranium-containing solution. The metal salts are the same as in Example 1. After that, the concentration of solids in the solution is about 2~s
Heat and concentrate y7 until it reaches a certain level, but if the solid concentration in the solution is already about 2 to 50 to 80
All you have to do is heat it at ℃ for about 1 to 2 hours.

(2) After filtering, the bath liquid is filtered through 7J4 to completely separate the solids and the f-liquid. Uranium and fluorine are contained in the solid matter and are not included in the f-liquid.

(3) Solids are treated as waste and P liquids are treated as wastewater.
Discharge after adjusting H.

Example 1 While calorothermically concentrating 7 tons of 95 m of uranium and 1 t of uranyl nitrate/sodium fluoride solution containing 50 mg/lf of fluorine, 0.49 ml of water glass (JKS silica soda No. 6) was added to bring the volume of flf to about A Reduced to. After washing, the precipitate wJ generated was separated by η1. Water glass (same as above) and calcium chloride C are added while further heating and concentrating approximately 200 kg of each liquid.
! a0t2 (z 0,3g each.

0.6 g was added, the volume was reduced to about A, and the formed precipitate +r was separated. The uranium content in the P solution is 0.2 mW
/ The uranium removal rate is 998% or less, and the fluorine content is [1+ my/ or less, the fluorine removal rate ii:
It was more than 99.8'Xi.

The total amount of precipitate produced was about 1 g and 1 piece.

Comparative test (method described in Japanese Patent Publication No. 48-38320) Ammonium fluoride (109/l as F) and ammonium chloride (NH3) were added to the solution containing uranium 2 and fluorine.
20 t/l) f and further water glass I f/
lf was added and stirred, and the generated precipitate +P was separated. The uranium content in the P liquid was less than 0.2 mf/l, the uranium removal rate was 998 mf/l or more, and the fluorine-containing fluorine was hardly removed at 97 mf/l. Add calcium oxide 20f171 to this stream) 1 and precipitate? After generating +, P was separated, and the fluorine content in the P solution was less than 11 mW/l, and the fluorine removal rate was almost 100%, but the total amount of generated precipitate was about 22 r.

Example 2 Uranium 95tn/l and fluorine 50n as in Example 1
While fully heating L mL of uranyl nitrate/sodium fluoride bath solution containing 1 g/lk, add water glass (J Engineering S Silicic Acid 7-Ta 5
M ) 0.4f, calcium chloride 0aCt, f
[Add 169 calories and the volume is about 8%! Reduced and generated sinking! 1/l was separated by P. Approximately 125 m7 of swamp liquid! The uranium content was less than 0.2 mf/, and the uranium removal rate was 99.8% or more, and the fluorine content was less than 0.2 mf/, and the fluorine removal rate was 99.8% or more. The total amount of precipitate produced was about 1.1 g.

As is clear from what has been described above, the present invention is a method for treating waste liquid containing uranium that is advantageous over conventional methods in the following points.

+1+ Fluorine can be easily removed along with uranium removal and recovery.

(2) Since there is no need to add ammonia and fluorine, the amount of alkaline earth metal salt required to remove added fluorine can be smaller than in the conventional method.

(3) By heating or heating and concentrating, the amount of water glass added can be reduced compared to the conventional method.

(4) Since the precipitate produced is not only highly permeable but also dense, it is difficult to use the conventional alkaline earth metal salt precipitation method (and the method described in Japanese Patent Publication No. 48-38320, which uses this method for fluorine removal). The amount of sludge generated is small compared to other methods.

(5) (2!, (3), (4+) The uranium content in the precipitate is relatively high.

(6) In both the case of recovering uranium and the case of recovering uranium and disposing of it as a solid substance containing uranium, the treatment of uranium and feces can be carried out easily and advantageously because there is little sludge produced.

Among the agents: 1) Akira Sub-agent Ryo Hagi Hara -

Claims (1)

[Claims] In a method for removing and recovering uranium from a solution containing uranium, water glass and alkaline earth metal salts are added to the solution containing uranium while heating or heating the solution to form a precipitate, and the precipitate is separated from the solution. A waste liquid treatment method characterized by: