JPH09203792A - Method for separating and recovering platinum group elements - Google Patents

Abstract

(57) [Abstract] [Problem] Platinum group element is a rare metal raw material that is industrially extremely valuable, but an effective method for separating and recovering the platinum group element contained in the waste liquid of the spent nuclear fuel reprocessing plant. However, there is a problem that the platinum group element is disturbed in the waste treatment and disposal process, and it is still difficult to stably secure the platinum group element which is a rare metal raw material. SOLUTION: An anion nitro complex formation step of forming an anion nitro complex of the platinum group element by adding nitrous acid or nitrite to a nitric acid solution containing a platinum group element, and bringing the nitric acid solution into contact with an anion exchange resin. And an elution recovery step of contacting the anion exchange resin with an aqueous solution containing a complexing agent to elute and recover the platinum group element in the solution. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention separates and recovers a platinum group element from a solution containing a platinum group element, such as a waste liquid generated at a reprocessing plant for spent nuclear fuel or a nitric acid solution of a dissolved residue of the spent nuclear fuel. The present invention relates to a method for separating and recovering platinum group elements.

[0002]

2. Description of the Related Art Ruthenium (Ru), Rhodium (R)
h), Platinum group elements such as palladium (Pd) are used not only in ornaments but also in the fields of electric appliances as electronic materials and electric materials, and in fields such as synthetic chemistry, petrochemistry and automobile industries as catalysts. It is a very important metal element. However, the natural mineral resources of platinum group elements are scarce, and their reserves and production are concentrated in extremely limited countries,
Therefore, the supply system of platinum group elements is extremely weak.
In particular, there are almost no platinum group element mines in Japan at present, all of which rely on imports from overseas, the prices are extremely high, and securing raw material supply is an important issue.

On the other hand, the spent nuclear fuel generated in a nuclear power plant contains a considerable amount of platinum group elements. For example, the amount of platinum group element contained per 1 t of spent fuel of a normal burnup in a light water reactor is about 1900 g of ruthenium, 320 g of rhodium, and 850 g of palladium. If all of these platinum group elements are recovered and their radioactivity is reduced to a usable level, the amount of chemical catalyst used in Japan is currently about 36% for palladium and about 60% for rhodium.
%, Ruthenium is almost 100% satisfied.

In the spent fuel reprocessing process called the purex method, which is currently used industrially, after dissolving the spent fuel with nitric acid, uranium (U) and plutonium (Pu) are extracted and separated by a solvent extraction method. And reused. Platinum group elements remain in the extraction residual liquid together with various other fission products, and are treated as radioactive waste liquid. This waste liquid becomes a high-level waste liquid through a nitric acid recovery process and an evaporative concentration process, and is finally planned to be stored and disposed in the deep strata in the form of a vitrified body.

In the reprocessing process, the platinum group element is not separated and recovered in any step. For this reason, colloidal precipitates of platinum group elements are deposited during storage of the high-level waste liquid and during the storage period, which makes it difficult to handle the waste liquid and form a uniform solidified body. In addition, in the vitrification process of high-level waste liquid, radioactive ruthenium oxide, which is easily volatilized, is generated, so there is a risk of volatilization and diffusion during high-temperature processing.To solve this, expensive and complicated ruthenium removal equipment is required. Needed.

A part of the platinum group element in the spent fuel becomes an insoluble residue in the dissolution process, but a considerable part thereof is dissolved in nitric acid and exists in the solution. The dissolved amount of these elements depends on the burnup of the fuel, the concentration of the nitric acid solution used, the melting temperature, etc.
It is said that about 60 to 90% of ruthenium is dissolved. Under normal dissolution conditions, most of rhodium remains undissolved and remains in the insoluble residue, but this residue is raised to a higher temperature, or a strong oxidizing agent (for example, hydrogen peroxide, IV
By adding valent cerium ions and II valent silver ions), almost all of them can be dissolved.

These dissolved platinum group elements are neptunium (Np) and americium (A) in addition to nuclear fuel substances such as uranium and plutonium existing in the fuel solution.
m), minor actinide elements such as curium (Cm), alkali metal elements such as cesium (Cs), alkaline earth metal elements such as barium (Ba) and strontium (Sr), neodymium (Nd), cerium (Ce), etc. Rare earth metal elements, molybdenum (Mo), zirconium (Z
r) and tellurium (Te) coexist with various fission products.

The platinum group element in the fuel solution is finally transferred to the high-level radioactive liquid waste through the reprocessing step. This effluent contains small amounts of uranium, plutonium extraction residues, and platinum group elements dissolved in nitric acid and almost all of the fission products. In addition to their complicated composition and diverse chemical properties, these solutions have strong radioactivity, and as a result, effective methods have not yet been established for the separation and recovery of valuable elements in them. is there.

[0009]

As described above, the platinum group element is a rare metal raw material that has an extremely high utility value industrially but cannot be supplied domestically, and is a waste liquid generated in a reprocessing plant for spent nuclear fuel. If the platinum group element is separated and recovered from the above, it is possible to secure a stable supply of rare metal raw materials, improve the processing performance of the reprocessing plant waste, and contribute greatly to the reduction of the radioactivity level of the waste liquid. Despite this, conventionally, an effective method for separating and recovering platinum group elements from the waste liquid of the spent nuclear fuel reprocessing plant has not been established, and interference with platinum group elements occurs in the waste treatment and disposal process, In addition, there is a problem that it is still difficult to stably secure the platinum group element, which is a rare metal raw material.

The present invention has been made to solve the above problems, and contains a platinum group element such as a waste liquid generated at a reprocessing plant for spent nuclear fuel and a nitric acid solution of the dissolved residue of the spent nuclear fuel. It is an object of the present invention to provide a method for separating and recovering a platinum group element capable of separating and recovering a platinum group element with high yield and high purity from a solution.

[0011]

A method for separating and recovering a platinum group element according to the present invention is a nitric acid solution containing a platinum group element such as ruthenium, rhodium or palladium.
Anion nitro complex formation step of adding nitrous acid or nitrite to form an anion nitro complex of the platinum group element, and the nitric acid solution that has undergone the anion nitro complex formation step is contacted with an anion exchange resin, And an adsorption step of selectively adsorbing the platinum group element on the anion exchange resin.

In the method for separating and recovering a platinum group element according to a second aspect of the present invention, the anion exchange resin having the platinum group element adsorbed in the adsorption step is contacted with an aqueous solution containing a complexing agent such as thiourea or ammonia. Then, an elution recovery step of elution recovery of the platinum group element adsorbed on the anion exchange resin is provided after the adsorption step.

In the method for separating and recovering platinum group elements according to the third aspect of the present invention, the concentration of nitric acid ion in the nitric acid solution is 2 mol / l or less before adding nitrous acid or nitrite in the anion nitro complex forming step. It is provided with an ion concentration adjusting step of adjusting the hydrogen ion concentration within the range of 0.01 to 2 mol / l.

In the method for separating and recovering platinum group elements according to the present invention, the waste liquid generated in the reprocessing step of the spent nuclear fuel or the nitric acid solution of the dissolved residue of the spent nuclear fuel contains the platinum group elements. Claim 1 as a nitric acid solution
Therefore, the invention according to any one of claims 3 to 4 is applied.

The inventors of the present invention first describe nitric acid solutions containing platinum group elements such as waste liquid generated in the reprocessing step of spent nuclear fuel and nitric acid dissolved liquid of the dissolved residue of spent nuclear fuel (these solutions are referred to as " (Also referred to as "treatment liquid"), a typical anion for ruthenium, rhodium, palladium in an aqueous solution containing nitric acid and nitrite ions and various other metal elements contained in the treatment liquid in order to separate and recover platinum group elements. We have investigated the adsorption properties of exchange resins.

In particular, as a result of intensive studies focusing on the effect of addition of nitrite ion on the adsorption of these metal elements in a nitric acid solution, the platinum group elements of ruthenium, rhodium and palladium were found to exist in the presence of nitrite ion. It was found that the adsorptivity of the above to the anion exchange resin is remarkably increased.

An example of the results of the measurement of the effect of the addition of nitrite ion on the adsorption of each platinum group element of ruthenium, rhodium and palladium on the anion exchange resin is shown.
FIG. 1 is a graph showing the nitrite ion concentration dependence of the adsorption partition coefficient of these platinum group elements in a 0.1 mol / l nitric acid aqueous solution using a commonly used quaternary ammonium group anion exchange resin. The concentration of nitrite ion in the solution was adjusted by adding sodium nitrite (NaNO ₂ ). The adsorption partition coefficient is defined as (metal concentration in resin / metal concentration in solution) at adsorption equilibrium.

From FIG. 1, the adsorption partition coefficient for each element of ruthenium, rhodium and palladium is remarkably increased by the addition of NaNO ₂ , and in the presence of 0.1 to 1.0 mol / l of nitrite ion, the platinum content of these platinum elements is increased. It can be seen that the adsorption distribution coefficient of the group element increases several hundred times and shows a large value of several hundreds to several thousands. That is, under such conditions of nitrite ion concentration, these platinum group elements in the solution are strongly adsorbed by the anion exchange resin and migrate from the solution side to the resin side.

The effect of promoting adsorption of each platinum group element of ruthenium, rhodium and palladium to the anion exchange resin in the presence of nitrite ion is almost independent of the type and structure of the exchange group of the anion exchange resin. When the present inventors measured using anion exchange resins having a primary to tertiary amine group, a pyridine group, a dipyrrolyl group, a benzimidazole group, and an ammonium group as an exchange group, respectively, the results were almost the same as in FIG. was gotten. That is, almost all of the anion exchange resins based on high molecular weight polymers which are commercially available have the similar adsorbing effect.

Each of the platinum group elements of ruthenium, rhodium and palladium is the second transition metal element of Group VIII in the periodic table, and Ru ³⁺ , Rh ³⁺ and Pd ²⁺ which are these metal ions.
Forms a stable complex with a nitrite ion (NO ₂ ⁻ ) containing a nitrogen atom having a strong coordination bond. Therefore, in a solution in the presence of nitrite ions, the coordination number of NO ₂ ⁻ that binds to these metal ions increases as the NO ₂ ⁻ ion concentration increases, and these metals become negatively charged. The nitro complex becomes strongly adsorbable to the anion exchange resin.

On the other hand, metal elements other than these platinum group elements in the nitric acid solution, especially alkali such as Cs contained in the nitric acid solution of the waste solution of the spent nuclear fuel reprocessing plant or the dissolved residue of the spent nuclear fuel. Metal element, B
Alkali earth metal elements such as a and Sr, rare earth metal elements such as Y, Nd and Ce, fission product elements such as Mo, Zr and Te, and coexisting elements such as actinide elements such as U, Pu, Np, Am and Cm. The adsorptivity of to the anion exchange resin is
It was observed that the addition of nitrite or nitrite hardly changed.

Further, Cs, Ba, Sr, Y, Nd, C
The coexisting elements such as e, Am, Cm, Mo, and Zr do not form an anion nitrato complex in the nitric acid solution and all exist in the form of cation, and are not adsorbed to the anion exchange resin at all. U, Pu, and Np form an anion nitrato complex in a relatively concentrated nitric acid solution having a nitrate ion concentration of 2 mol / l or more, and thus are well adsorbed on an anion exchange resin. Particularly, at 1.5 mol / l or less, since an anion complex is not formed, U, Pu and Np are hardly adsorbed.

Therefore, the concentration of nitrate ion in the treatment liquid is about 2
After adjusting to less than mol / l, nitrite or nitrite is added to form an anion nitro complex of platinum group elements of ruthenium, rhodium and palladium, and then only these platinum group elements are selectively applied to the anion exchange resin. It is possible to adsorb and separate from other elements that coexist in the solution.

Further, the inventors of the present invention have made further intensive studies to elute and recover the platinum group elements adsorbed on the anion exchange resin, and as a result, have found the following method. That is,
The ion exchange resin after adsorbing platinum group elements such as ruthenium, rhodium, and palladium from the treatment liquid,
Thiourea (SC (NH ₂ ) ₂ ) or ammonia (NH
₃ ) Contact with the containing aqueous solution to elute and recover the platinum group element adsorbed on the ion exchange resin.

The present invention will be described in more detail below by dividing it into (1) ion concentration adjusting step, (2) anion nitro complex forming step, (3) adsorption step, and (4) elution recovery step.

(1) Ion Concentration Adjusting Step In the present invention, first, a nitric acid solution containing a platinum group element such as a waste liquid generated in a reprocessing step of a spent nuclear fuel and a nitric acid solution of a dissolved residue of the spent nuclear fuel (hereinafter referred to as “ The concentration of nitric acid in "treatment liquid") is adjusted in the range of 0.01 to 2 mol / l, preferably 0.1 to 1.5 mol / l.

The nitrate ion concentration in these solutions is 2 mo.
When it becomes 1 / l or more, U ⁴⁺ , U coexisting in the solution
Metal ions such as O ₂ ²⁺ , Pu ⁴⁺ , and Np ⁴⁺ form an anion complex with NO ₃ ⁻ ions existing in a large amount in the solution. Since these anion complexes have strong adsorptivity to anion exchangers, it is difficult to separate them from platinum group elements.

The hydrogen ion concentration in the solution is 2 mol.
Above 1 / l, a large amount of H ⁺ in the solution combines with NO ₂ ⁻ ions to be added later to generate nitrite molecules. This nitrous acid is easily decomposed by heat, light, etc., and the nitric oxide gas generated by the decomposition interferes with the column operation when performing column-type adsorption in the next adsorption step.

The hydrogen ion concentration in the solution is 0.01
At mol / l or less, ions of various metal elements including platinum group elements in the solution form hydroxides by the hydrolysis reaction and precipitate, and the adsorptivity to the ion exchanger decreases in the subsequent adsorption step. Resulting in. For the above reasons, in the present invention, the nitric acid concentration in the treatment liquid is adjusted to the range of 0.01 to 2 mol / l. The nitric acid concentration in the solution can be easily adjusted by adding nitric acid or pure water, and in some cases, known chemical denitration method or electrolytic denitration method can be used.

[0030] (2) an anion nitro complexation step above treatment solution after nitric acid concentration adjustment, NO ₂ ^- was added ion-containing reagents to produce a nitro complexes of platinum group ions in solution. As a matter of course, the addition amount of the NO ₂ ⁻ ion-containing reagent needs to correspond to the existing amounts of ruthenium, rhodium, and palladium in the treatment liquid. In the nitric acid solution having the above concentration, the oxidation states of these metals are Ru (III) and Rh (III
) And Pd (II), and at least a 4-fold molar amount for ruthenium and rhodium and a 3-fold molar amount for palladium are required to form the respective anion nitro complexes. The maximum coordination number of these metal nitro complexes is 6 for ruthenium and rhodium, and 4 for palladium.

According to the results of the experiments conducted by the inventors of the present invention, the stoichiometric amount of NO required to form the maximum coordination number nitro complex is 1 to 4 times the NO amount with respect to the existing amount of these metals in the solution. By adding ₂ ^- ions, the maximum value of the adsorption partition coefficient can be obtained. If more NO ₂ ⁻ ions are added, excess NO ₂ ⁻ ions in the solution will be competitively adsorbed on the anion exchange resin, and the adsorption distribution coefficient will be reduced. Figure 1 is NO adsorption distribution coefficient in solution as described above ₂ ^-
It shows the relationship with the ion concentration. Further, in the presence of excess NO ₂ ⁻ ions, as described above, the generation of nitric oxide gas also interferes with the adsorption operation.

[0032] Incidentally, NO ₂ ^- is not particularly necessary to limit as ion-containing reagent, can be preferably used alkali metal is inexpensive without adsorption onto anion exchanger, ammonium, nitrite of an alkaline earth metal . Also,
It is also possible to directly generate NO ₂ ⁻ ions by adding a suitable reducing agent to the treatment liquid or performing a technique such as electrolytic reduction.

(3) Adsorption step By contacting the solution obtained in the treatment solution adjusting step with an anion exchange resin, ruthenium, rhodium,
Only palladium is adsorbed by the resin, moves from the solution phase to the resin phase, and is separated from other elements in the solution. Note that ruthenium is mainly exchanged and adsorbed on the resin in the form of anion complex of nitrosyl / nitro, and rhodium and palladium are in the form of anion nitro complex.

Known column type and batch type can be preferably utilized for the adsorption operation. That is, in the column type, the ion exchange resin is packed in a column, the treatment solution is passed through, and ruthenium, rhodium, and palladium in the solution are adsorbed on the resin. In the batch system, the treatment liquid and the ion exchange resin are put in a container and stirred or shaken to adsorb ruthenium, rhodium and palladium in the solution onto the resin. The shape of the ion exchange resin to be used is not particularly limited, and it is preferable to use spherical resin particles of macropore type, gel type or carrier-supporting type having a particle size of about several tens to several hundreds of microns which is usually used industrially. You can Also, the adsorption temperature is not particularly limited, and may be in the range of room temperature to 80 ° C. which is usually industrially easily realized. It is possible to accelerate the adsorption rate to some extent by raising the temperature.

(4) Elution recovery step In order to elute and recover ruthenium, rhodium and palladium adsorbed on the anion exchange resin through the adsorption step,
The present inventors diligently studied various eluents and elution conditions, and as a result, thiourea (SC (NH ₂ ) ₂ ) and ammonia (NH ₃ ) are extremely excellent eluents for these platinum group elements. I found a thing.

These reagents have a strong complex-forming ability with the above platinum group ion through a coordinate bond of a nitrogen atom, MX _n ²⁺ ,
MX _n ³⁺ (M = Ru, Rh, Pd, X = SC (NH ₂ ) ₂
Alternatively, a stable cation complex such as NH ₃ , n = 1 to 6) is formed. Therefore, the platinum group nitro complex adsorbed on the anion exchange resin is eluted from the resin by a ligand substitution reaction with these eluents. The thiourea reagent is water-soluble and can be dissolved in water or dilute nitric acid solution to
It is preferably used as a several mol / l thiourea solution.
On the other hand, as the NH ₃ eluent, commercially available aqueous ammonia is used as 0.1
It may be used by diluting to about several mol / l. The concentrations of these reagents as the eluent are not particularly limited. On the other hand, as a matter of course, the amount of the eluent used needs to correspond to the amount of the platinum group element adsorbed, and according to the results of the study conducted by the present inventors, it is at least twice the molar amount of the platinum group element adsorbed. The adsorbed platinum group ion can be completely eluted by using a 4-fold molar amount or more.

The above-mentioned elution operation can be carried out in the same manner as in the column type and batch type described in the adsorption step. By contacting the resin with an eluent solution, ruthenium, rhodium, Palladium Each metal ion is eluted and transferred from the resin phase to the solution phase for separation and recovery. The temperature of the elution operation may be in the range of room temperature to about 80 ° C. which is industrially easily realized as in the adsorption step.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1. In the following embodiment, an example of performing a separation and recovery test by applying the method for separating and recovering a platinum group element according to the present invention to a treatment liquid simulating a reprocessing waste liquid of a spent nuclear fuel will be shown according to a test procedure. .

1. Preparation of treatment liquid Ruthenium (R
u), rhodium (Rh) and palladium (Pd) nitrates, and strontium (Sr) and neodymium (Nd) nitrates as representative elements of fission products,
It is dissolved in a mol / l nitric acid aqueous solution, and this is used as a simulated reprocessing waste liquid of spent nuclear fuel as a treatment liquid for a separation test. Sodium nitrite as a nitrite is added to this treatment liquid to determine the composition of the treatment liquid. The procedure was as follows (ion concentration adjusting step, anion nitro complex forming step). Ru 985.6mg / l Sr 783.4mg / l Rh 249.6mg / l Nd 1327.6mg / l Pd 796.1mg / l NO 3 - about _{0.2mol / l NaNO 2 1.0mol / l} H + about 0 0.2 mol / l The total amount of the treatment liquid introduced into the column in the following separation test was 30 ml.

2. Column preparation Adsorption, elution and recovery of platinum group elements were performed by a column method. A glass column having an inner diameter of 1 cm and a length of 30 cm was used as a column, and a quartz-supporting benzimidazole group anion exchange resin having an exchange capacity of 3.4 meq / g-resin was used as an anion exchange resin in the column with a height of 25 cm.
And the whole column was kept at a constant temperature of 60 ° C.

3. Adsorption The treatment liquid was supplied from the upper end of the column by a liquid feed pump at a flow rate of 5 ml / min to adsorb the platinum group element on the anion exchange resin (adsorption step).

4. Column Washing Subsequently, 50 ml of a nitric acid aqueous solution having a concentration of 0.1 mol / l was passed through the column in the same manner as above to wash the gap between the anion exchange resin and the inner wall of the column.

5. Elution and recovery Next, 0.1 mol containing 0.5 mol / l thiourea
50 ml of a 1 / l nitric acid solution was supplied to the column by the same operation as above (elution recovery step).

6. Sampling / Analysis The solution flowing out from the lower end of the column during the period of passing through the column was collected by a fraction collector by 10 ml, and the metal concentration in each fraction collected liquid was measured by ICP.
(Inductively coupled high frequency plasma) Quantitative analysis was performed by emission analysis to determine the relationship between the amount of effluent and the concentration of each metal in the effluent. The result is shown in FIG.

As shown in FIG. 2, strontium and neodymium in the treatment liquid are not adsorbed by the anion exchange resin and flow out together with the supplied treatment liquid and the subsequent cleaning liquid, while ruthenium, rhodium, and palladium are discharged. The platinum group element was strongly adsorbed on the anion exchange resin in the adsorption step, and was effectively eluted by the thiourea eluent supplied in the elution / recovery step, and was well separated from strontium and neodymium.

According to the above method for separating and recovering platinum group elements,
The recovery rates of platinum group elements from the simulated reprocessing waste liquid were ruthenium 99.2%, rhodium 98.1%, and palladium 99.%.
It was 6%.

As described above, according to the first embodiment, the platinum group element can be separated and recovered in a high yield and a high purity from the solution containing the platinum group element such as the spent reprocessing waste liquid of the spent nuclear fuel. By using such a method, it is possible to recycle the rare platinum group elements and secure a stable supply, and at the same time, improve the processing and disposal process performance of the reprocessing plant waste, It is possible to reduce the radioactivity level of the waste liquid.

[0048]

As described above, according to the invention of claim 1, the nitric acid solution or the nitrite salt is added to the nitric acid solution containing the platinum group element such as ruthenium, rhodium and palladium, and the platinum group element is added. Of the platinum group element in the solution by contacting the nitric acid solution with the anion exchange resin to selectively adsorb the platinum group element in the solution. It becomes possible to separate and collect the platinum group element from the solution in the form of anion by adsorbing it on the anion exchange resin,
There is an effect that the platinum group element, which is a rare metal raw material, can be recycled to secure a stable supply.

According to the second aspect of the present invention, the anion exchange resin having the platinum group element adsorbed thereon is brought into contact with an aqueous solution containing a complexing agent such as thiourea or ammonia and adsorbed on the anion exchange resin. Since the platinum group element is configured to be eluted and recovered, the platinum group element can be effectively eluted and recovered from the anion exchange resin having the platinum group element adsorbed, and particularly, thiourea or ammonia is used as a complexing agent. In such a case, the elution and recovery can be performed very effectively. Therefore, it becomes possible to separate and recover the platinum group element from the solution containing the platinum group element in a high yield, and it is possible to recycle the platinum group element which is a rare metal raw material and secure a stable supply. is there.

According to the invention of claim 3, before the addition of nitrous acid or nitrite in the step of forming an anion nitro complex, the concentration of nitrate ion in the nitric acid solution is set to 2 mol / mol.
Since it is configured to adjust the hydrogen ion concentration within the range of 0.01 to 2 mol / l, the anion nitro complex of the platinum group element is distinguished from the ions of other metal elements coexisting in the nitric acid solution. It is possible to selectively separate and collect platinum group elements by adsorbing on an anion exchange resin, and prevent column operation interference during column adsorption by nitric oxide gas generated by the generation and decomposition of nitrite molecules. In addition, it is possible to prevent the platinum group element in the nitric acid solution from deteriorating the adsorptivity to the anion exchange resin due to the formation and precipitation of the hydroxide due to the hydrolysis reaction. Rate and high purity can be separated and recovered, and the platinum group element, which is a rare metal raw material, can be recycled to ensure a stable supply.

According to the fourth aspect of the present invention, the waste liquid generated in the reprocessing step of the spent nuclear fuel or the nitric acid solution of the dissolved residue of the spent nuclear fuel is treated as a nitric acid solution containing a platinum group element, Since the invention according to any one of claims 1 to 3 is applied, a high yield of platinum group elements can be obtained from the waste liquid generated in the reprocessing step of the spent nuclear fuel and the dissolved residue of the spent nuclear fuel. Rate and high purity, it is possible to separate and recover, and it is possible to secure a stable supply of platinum group elements that are rare metal raw materials, improve the processing and disposal process performance of reprocessing plant waste, and radiate waste liquid. There is an effect that the performance level can be reduced.

[Brief description of drawings]

FIG. 1 Ruthenium, rhodium, and anion exchange resin
It is a graph which shows the measurement result of the nitrite ion concentration dependence of the adsorption distribution coefficient of each palladium platinum group element.

FIG. 2 is a graph showing a column separation test result of a simulated reprocessing waste liquid of spent nuclear fuel according to Embodiment 1 of the present invention.

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Claims (4)

[Claims] 1. An anion nitro complex producing step of producing an anion nitro complex of the platinum group element by adding nitrous acid or nitrite to a nitric acid solution containing a platinum group element such as ruthenium, rhodium or palladium, An adsorption step of bringing the nitric acid solution that has undergone the anion nitro complex formation step into contact with an anion exchange resin, and selectively adsorbing the platinum group element in the nitric acid solution onto the anion exchange resin. Method for separating and recovering elements. 2. The anion exchange resin having adsorbed the platinum group element in the adsorption step is brought into contact with an aqueous solution containing a complexing agent such as thiourea or ammonia to elute the platinum group element adsorbed on the anion exchange resin. An elution recovery step for recovery is provided after the adsorption step.
A method for separating and recovering the platinum group element described. 3. Before adding nitrous acid or nitrite in the step of forming an anion nitro complex, the nitric acid solution has a nitric acid concentration of 2 mol / l or less and a hydrogen ion concentration of 0.01 to 2 mol / l. The method for separating and recovering a platinum group element according to claim 1 or 2, further comprising an ion concentration adjusting step for adjusting. 4. A nitric acid solution containing a platinum group element is a waste liquid generated in a reprocessing step of a spent nuclear fuel or a nitric acid solution of a dissolved residue of the spent nuclear fuel. Item 4. A method for separating and recovering a platinum group element according to any one of Item 3.