Method for recovering palladium from radioactive waste liquid by using sulfur-containing extraction agent

Abstract

The invention relates to a method for recovering palladium from radioactive waste liquid by using a sulfur-containing extraction agent. The method comprises the following steps: extracting the radioactive waste liquid by using the sulfur-containing extraction agent; washing the extracted organic phase with a detergent; the washed organic phase is subjected to reverse extraction through a reverse extraction agent, and product liquid of palladium is obtained; the sulfur-containing extracting agent is selected from one or more of dihexyl sulfide, dibutyl sulfide, dioctyl sulfide, dodecyl sulfide, dibutyl sulfoxide and dioctyl sulfoxide. Compared with the prior art, palladium can be recycled from the radioactive waste liquid in a high-selectivity mode.

Description

Technical Field

[0001] The present invention belongs to the technical field of spent fuel reprocessing, and relates to a method for recovering palladium from radioactive waste liquid by using a sulfur-containing extractant. Background Art

[0002] Palladium (Pd) is an important precious metal with unique physical and chemical properties, such as excellent hydrogen absorption performance, ultra-high electrical conductivity, and superior catalytic performance. Spent fuel contains a considerable amount of palladium, which is an important fission product element. Therefore, spent fuel can be regarded as an artificial resource library of palladium. Each ton of spent fuel from a reactor with a burnup of 33000 MWd / t contains approximately 1 kg of palladium. Most of the palladium in spent fuel is stable isotopes, and only one isotope 107 Pd is radioactive with a half-life of 6.5 million years, but the intensity of its β-ray is only 35 keV. If it can be recovered, it is expected to be applied in the industrial field. With the booming development of the nuclear power industry, the palladium resources in spent fuel will increase day by day. If the recovery process can be mastered, it will truly turn waste into treasure and generate additional economic benefits.

[0003] On the other hand, the influence of platinum group metals on the vitrification of high-level radioactive waste liquid is an inevitable problem in the joule heating ceramic melter technology. Previously, problems such as the operation of the melter caused by the deposition of platinum group metals have occurred in the joule heating ceramic melter. Therefore, actively carrying out research on the palladium recovery process from high-level radioactive waste liquid can, on the one hand, broaden the secondary resource scope of platinum group metals and create conditions for the wide application of platinum group metals in the future; on the other hand, it can ensure the smooth operation of the glass solidification plant and eliminate the adverse effects of platinum group metals on the melting process from the source, which has important significance.

[0004] Patent CN105002359A discloses a method for extracting palladium from an aqueous phase, using a diazine hydrazone pyridine derivative to selectively separate palladium from the aqueous phase, especially from alkali metals and alkaline earth metals. However, this patent does not involve the extraction of palladium from high-level radioactive waste liquid in reprocessing.

[0005] Patent CN115522052A discloses a method for recovering rare precious metals from high-level radioactive waste liquid in spent fuel reprocessing. In this method, N,N'-diethyl-N,N'-dicyclohexyl malonamide (DEDCHMA) is used as an extractant to extract palladium ions. The organic phase is back-extracted, and the back-extraction liquid is concentrated to obtain palladium salts. The extraction time is 0 - 30 min, the nitric acid concentration is 0.05 - 5 mol / L, the type of diluent is one of dichloromethane, n-dodecane, and cyclohexane, the nitric acid concentration is 0.05 - 5 mol / L, the extractant concentration is 0.02 - 0.5 mol / L, the extraction temperature is 10 - 50 °C, the mixing ratio of the aqueous phase to the organic phase is 1:10 - 10:1, and the type of back-extractant is one of secondary water, dilute nitric acid, thiourea, or oxalic acid. However, the extractant selected in this patent has a relatively complex structure, is relatively difficult to synthesize, and does not consider extraction selectivity.

[0006] Patent CN110592391A discloses a method for purifying crude gold powder. In this method, the platinum and palladium-containing filter residue is calcined at high temperature under an inert atmosphere. The material obtained by calcination is added with hydrochloric acid to dissolve, obtaining a palladium and platinum-containing filtrate. After extraction with an extractant and back-extraction of the extraction organic phase, hydrazine hydrate is added to the obtained palladium-containing back-extraction liquid for reduction to obtain palladium powder. The extractant is a mixture of diisopentyl sulfide and di-n-octyl sulfide, and the volume ratio of diisopentyl sulfide to di-n-octyl sulfide is (2 - 3):1. The diluent is n-dodecane, and the phase regulator is an organic compound of ketoxime type. The diluent and the phase regulator are 3 - 4 times and 0.1 - 0.2 times the volume of the extractant respectively. The number of countercurrent extraction stages is 4 - 8, so that the content of palladium in the raffinate is less than 30 ppm. Countercurrent washing is carried out with 0.01 - 0.2 mol / L dilute hydrochloric acid, and the number of countercurrent washing stages is 2 - 3, so that the content of platinum in the washed organic phase is less than 1 ppm. Back-extraction is carried out with ammonia water in a countercurrent manner, and the number of countercurrent back-extraction stages is 2 - 4, so that the content of palladium in the back-extracted organic phase is less than 0.5 ppm. The concentration of the ammonia water is 1 - 2 mol / L, and the washing liquid for countercurrent washing is returned to enter the extraction section for extraction together with the palladium and platinum-containing filtrate. However, this patent only involves the separation of platinum and palladium in crude gold and does not involve the recovery of palladium from high-level radioactive waste liquid in reprocessing. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for recovering palladium from radioactive waste liquid by using a sulfur-containing extractant, which can highly selectively recover palladium from radioactive waste liquid and overcome at least one defect of the above-mentioned existing technologies.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] One of the technical solutions of the present invention is to provide a method for recovering palladium from radioactive waste liquid by using a sulfur-containing extractant, which includes the following steps:

[0010] S1. Extract the radioactive waste liquid with a sulfur-containing extractant;

[0011] S2. Wash the extracted organic phase with a detergent to remove the impurity ions entrained in the organic phase;

[0012] S3. Back-extract the washed organic phase with a stripping agent to obtain a product solution of palladium;

[0013] In step S1, the sulfur-containing extractant is selected from one or more of dihexyl sulfide, dibutyl sulfide, dioctyl sulfide, dodecyl sulfide, dibutyl sulfoxide, and dioctyl sulfoxide.

[0014] Further, in step S1, the concentration of the sulfur-containing extractant is 0.04 - 0.5 mol / L.

[0015] Further, in step S1, the sulfur-containing extractant is dissolved in a diluent, and the diluent is selected from one or more of dodecane, toluene, xylene, mesitylene, kerosene, dichloromethane, dichloroethane, n-octanol, and acetonitrile. The volume ratio of the extractant and the diluent to the radioactive waste liquid is 1:(0.5 - 3).

[0016] As a preferred technical solution, in step S1, the volume ratio of the extractant and the diluent to the radioactive waste liquid is 1:(1 - 2).

[0017] Further, in step S1, the extraction time is 5 - 20 min.

[0018] As a preferred technical solution, in step S2, the impurities are selected from one or more of cesium (Cs), strontium (Sr), barium (Ba), zirconium (Zr), molybdenum (Mo), rhenium (Re), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), yttrium (Y), ruthenium (Ru), and rhodium (Rh).

[0019] Further, in step S2, the detergent is selected from one or more of nitric acid (HNO3), hydrochloric acid (HCl), and sulfuric acid (H2SO4), and the concentration of the detergent is 0.1 - 3 mol / L.

[0020] As a preferred technical solution, in step S2, the concentration of the washing is 0.1 - 1 mol / L.

[0021] Further, in step S2, the detergent is dissolved in water, and the volume ratio of the extracted organic phase to the detergent and water is (0.5 - 3):1.

[0022] As a preferred technical solution, in step S2, the volume ratio of the extracted organic phase to the detergent and water is (1 - 2):1.

[0023] Further, in step S2, the washing time is 5 - 20 min.

[0024] As a preferred technical solution, the number of washing times in step S2 is one to three times.

[0025] Furthermore, in step S3, thiourea is used as the stripping agent, and the concentration of the stripping agent is 0.1 - 0.5 mol / L.

[0026] Furthermore, in step S3, the stripping agent is dissolved in water, and the volume ratio of the washed organic phase to the stripping agent and water is (0.5 - 3):1.

[0027] As a preferred technical solution, in step S3, the volume ratio of the washed organic phase to the stripping agent and water is (1 - 2):1.

[0028] Furthermore, the stripping time in step S3 is 5 - 20 min.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention utilizes the "hard and soft acid-base theory". Based on palladium being a soft acid, a suitable soft-base sulfur-containing extractant is selected to establish an efficient extraction model, realizing the highly selective recovery of palladium. The primary extraction rate of palladium is > 99%, the distribution ratio D Pd > 250, and it has specific selectivity for palladium, and the separation factor SF for impurity ions > 4900;

[0031] (2) The present invention has simple operation and is easy to industrialize, and it is a promising method for recovering palladium from high-level radioactive waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a comparison chart of the extraction rates for recovering palladium and separating other metal ions from radioactive waste liquid in the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The present invention will be described in detail below with reference to specific embodiments. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0034] Unless otherwise specified, the equipment used in the following embodiments is all conventional equipment in the art; unless otherwise specified, the reagents used are all commercially available products or prepared by conventional methods in the art. Those not described in detail in the following embodiments can all be achieved by conventional experimental means in the art.

[0035] The simulated radioactive waste liquid feed solution contains 17 common fission products, namely yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), cesium (Cs), strontium (Sr), barium (Ba), zirconium (Zr), molybdenum (Mo), rhenium (Re), ruthenium (Ru), rhodium (Rh), and palladium (Pd), and the solvent is 3 mol / L nitric acid (HNO₃).

[0036] Example 1:

[0037] A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant, the specific steps are as follows:

[0038] S1. Extraction of palladium: Add a dodecane solution of 0.05 mol / L dihexyl sulfide to the simulated radioactive waste liquid feed solution according to a volume ratio of organic phase to aqueous phase (simulated radioactive waste liquid feed solution) of 1:1, extract for 10 min, and let it stand for phase separation;

[0039] S2. Washing of the organic phase: Transfer the extracted organic phase, add an aqueous solution of 0.1 mol / L nitric acid according to a volume ratio of organic phase to aqueous phase of 1:1, wash for 10 min, let it stand for phase separation, and wash once to remove the impurity ions entrained in the organic phase;

[0040] S3. Stripping of palladium: Transfer the washed organic phase, add an aqueous solution of 0.1 mol / L thiourea according to a volume ratio of organic phase to aqueous phase of 1:1, strip for 10 min, let it stand for phase separation, transfer the aqueous phase, and obtain the product solution of palladium.

[0041] The distribution ratio and separation factor in the palladium extraction process in Example 1 are shown in Table 1.

[0042] Table 1 Distribution ratio and separation factor in the palladium extraction process in Example 1

[0043] Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Cs 0.036 8227 Pr 0.025 11847 Sr 0.023 12877 Nd 0.035 8462 Ba 0.034 8711 Sm 0.058 5106 Mo 0.017 17422 Eu 0.047 6301 Zr 0.043 6888 Gd 0.040 7404 Re 0.026 11391 Y 0.026 11391 La 0.029 10213 Ru 0.023 12877 Ce 0.025 11847 Rh 0.020 14809 Pd 296.17 /

[0044] As Figure 1 shown in Table 1, the distribution ratio of palladium is as high as 296, while the distribution ratios of other metal ions are only 10 -2 , which can prove that the extraction separation process has good selectivity for palladium, and the primary extraction rate of palladium > 99%. Through the method of this example, palladium in radioactive waste liquid can be effectively and selectively recovered.

[0045] Example 2:

[0046] A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant, the specific steps are as follows:

[0047] S1. Extraction of palladium: Add a 0.5 mol / L solution of dihexyl sulfide in dodecane to the simulated radioactive waste liquid feedstock at a volume ratio of organic phase to aqueous phase (simulated radioactive waste liquid feedstock) of 1:1, extract for 10 min, and let it stand for phase separation.

[0048] S2. Washing of the organic phase: Transfer the extracted organic phase, add an aqueous solution of 1 mol / L nitric acid at a volume ratio of organic phase to aqueous phase of 1:1, wash for 10 min, let it stand for phase separation, and wash twice to remove the impurity ions entrained in the organic phase.

[0049] S3. Stripping of palladium: Transfer the washed organic phase, add an aqueous solution of 0.5 mol / L thiourea at a volume ratio of organic phase to aqueous phase of 1:1, strip for 10 min, let it stand for phase separation, transfer the aqueous phase, and obtain the product solution of palladium.

[0050] The distribution ratio and separation factor in the palladium extraction process in Example 2 are shown in Table 2.

[0051] Table 2 Distribution ratio and separation factor in the palladium extraction process in Example 2

[0052] Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Cs 0.038 8425 Pr 0.028 11434 Sr 0.025 12806 Nd 0.042 7623 Ba 0.040 8004 Sm 0.060 5336 Mo 0.019 16850 Eu 0.048 6670 Zr 0.048 6670 Gd 0.042 7623 Re 0.028 11434 Y 0.032 10005 La 0.032 10005 Ru 0.025 12806 Ce 0.028 11434 Rh 0.022 14552 Pd 320.15 /

[0053] As shown in Table 2, the distribution ratio of palladium is as high as 320, while the distribution ratio of other metal ions is only 10 -2 , which can prove that the extraction and separation process has good selectivity for palladium, and the primary extraction rate of palladium > 99%. The method of this example can effectively and selectively recover palladium from radioactive waste liquid.

[0054] Example 3:

[0055] A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant, the specific steps are as follows:

[0056] S1. Extraction of palladium: Add a 0.05 mol / L solution of dihexyl sulfide in dodecane to the simulated radioactive waste liquid feedstock at a volume ratio of organic phase to aqueous phase (simulated radioactive waste liquid feedstock) of 1:2, extract for 10 min, and let it stand for phase separation.

[0057] S2. Washing of the organic phase: Transfer the extracted organic phase, add an aqueous solution of 0.1 mol / L nitric acid at a volume ratio of organic phase to aqueous phase of 2:1, wash for 10 min, let it stand for phase separation, and wash three times to remove the impurity ions entrained in the organic phase.

[0058] S3. Stripping of palladium: Transfer the washed organic phase, add an aqueous solution of 0.1 mol / L thiourea at a volume ratio of organic phase to aqueous phase of 2:1, strip for 10 min, let it stand for phase separation, transfer the aqueous phase, and obtain the product solution of palladium.

[0059] In Example 3, the distribution ratio and separation factor in the palladium extraction process are shown in Table 3.

[0060] Table 3 Distribution Ratio and Separation Factor in the Palladium Extraction Process of Example 3

[0061] Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Cs 0.032 9318 Pr 0.023 12963 Sr 0.022 13553 Nd 0.034 8769 Ba 0.031 9618 Sm 0.060 4969 Mo 0.018 16564 Eu 0.045 6626 Zr 0.042 7099 Gd 0.042 7099 Re 0.025 11926 Y 0.025 11926 La 0.028 10649 Ru 0.022 13553 Ce 0.025 11926 Rh 0.018 16564 Pd 298.16 /

[0062] As shown in Table 3, the distribution ratio of palladium is as high as 298, while the distribution ratios of other metal ions are only 10 -2 , which can prove that the extraction separation process has good selectivity for palladium, and the primary extraction rate of palladium > 99%. Through the method of this example, palladium in the radioactive waste liquid can be effectively and selectively recovered.

[0063] Example 4:

[0064] A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant, the specific steps are as follows:

[0065] S1. Extraction of palladium: Add a dodecane solution of 0.05 mol / L dibutyl sulfoxide to the simulated radioactive waste liquid feedstock according to the volume ratio of the organic phase to the aqueous phase (simulated radioactive waste liquid feedstock) of 1:1, extract for 10 min, and let it stand for phase separation.

[0066] S2. Washing of the organic phase: Transfer the extracted organic phase, add an aqueous solution of 0.5 mol / L nitric acid according to the volume ratio of the organic phase to the aqueous phase of 1:1, wash for 10 min, let it stand for phase separation, and wash three times to remove the impurity ions entrained in the organic phase.

[0067] S3. Stripping of palladium: Transfer the washed organic phase, add an aqueous solution of 0.5 mol / L thiourea according to the volume ratio of the organic phase to the aqueous phase of 1:1, strip for 10 min, let it stand for phase separation, and transfer the aqueous phase to obtain the product liquid of palladium.

[0068] In Example 4, the distribution ratio and separation factor in the palladium extraction process are shown in Table 4.

[0069] Table 4 Distribution Ratio and Separation Factor in the Palladium Extraction Process of Example 4

[0070] Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Cs 0.028 8936 Pr 0.019 13169 Sr 0.020 12511 Nd 0.032 7819 Ba 0.030 8341 Sm 0.051 4906 Mo 0.018 13901 Eu 0.045 5560 Zr 0.041 6103 Gd 0.035 7149 Re 0.023 10879 Y 0.022 11374 La 0.025 10009 Ru 0.018 13901 Ce 0.021 11915 Rh 0.016 15638 Pd 250.22 /

[0071] As shown in Table 4, the distribution ratio of palladium is as high as 250, while the distribution ratios of other metal ions are only 10 -2 , which can prove that the extraction separation process has good selectivity for palladium, and the primary extraction rate of palladium > 99%. Through the method of this example, palladium in the radioactive waste liquid can be effectively and selectively recovered.

[0072] Example 5:

[0073] A method for recovering palladium from radioactive waste liquid by using a sulfur-containing extractant, the specific steps are as follows:

[0074] S1. Extraction of palladium: Add a dodecane solution of 0.05 mol / L dihexyl sulfide to the simulated radioactive waste liquid feedstock according to a volume ratio of the organic phase to the aqueous phase (simulated radioactive waste liquid feedstock) of 1:1, extract for 20 min, and let it stand for phase separation;

[0075] S2. Washing of the organic phase: Transfer the extracted organic phase, add an aqueous solution of 0.1 mol / L nitric acid according to a volume ratio of the organic phase to the aqueous phase of 1:1, wash for 20 min, let it stand for phase separation, and wash once to remove the impurity ions entrained in the organic phase;

[0076] S3. Stripping of palladium: Transfer the washed organic phase, add an aqueous solution of 0.1 mol / L thiourea according to a volume ratio of the organic phase to the aqueous phase of 1:1, strip for 20 min, let it stand for phase separation, transfer the aqueous phase, and obtain the product liquid of palladium.

[0077] The distribution ratio and separation factor in the palladium extraction process in Example 5 are shown in Table 5.

[0078] Table 5 Distribution ratio and separation factor in the palladium extraction process in Example 5

[0079] Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Metal ion Distribution ratio D <![CDATA[Separation factor SF Pd / M > Cs 0.038 8697 Pr 0.026 12712 Sr 0.026 12712 Nd 0.038 8697 Ba 0.035 9443 Sm 0.055 6009 Mo 0.019 17395 Eu 0.046 7185 Zr 0.045 7344 Gd 0.035 9443 Re 0.025 13220 Y 0.025 13220 La 0.030 11017 Ru 0.022 15023 Ce 0.026 12712 Rh 0.020 16525 Pd 330.50 /

[0080] As shown in Table 5, the distribution ratio of palladium is as high as 330, while the distribution ratios of other metal ions are only 10 -2 , which can prove that the extraction separation process has good selectivity for palladium, and the primary extraction rate of palladium > 99%. The method of this example can effectively and selectively recover palladium from radioactive waste liquid.

[0081] The above description of the embodiments is for those of ordinary skill in the art in this technical field to understand and use the invention. Those who are familiar with the technology in this field can obviously make various modifications to these embodiments easily, and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant, characterized in that: The method comprises the following steps: S1. extracting the radioactive waste liquid by a sulfur-containing extractant; S2, washing the extracted organic phase with a detergent; S3, stripping the washed organic phase with a stripping agent to obtain a palladium product solution; In step S1, the sulfur-containing extractant is selected from one or more of dihexyl sulfide, dibutyl sulfide, dioctyl sulfide, dodecyl sulfide, dibutyl sulfoxide, and dioctyl sulfoxide.

2. A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant according to claim 1, characterized in that: The concentration of the sulfur-containing extractant in step S1 is 0.04-0.5 mol / L.

3. A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant according to claim 1, characterized in that: In step S1, the sulfur-containing extractant is dissolved in a diluent, the diluent is selected from one or more of dodecane, toluene, xylene, trimethylbenzene, kerosene, dichloromethane, dichloroethane, n-octanol, and acetonitrile, and the volume ratio of the extractant to the diluent to the radioactive waste liquid is 1:(0.5-3).

4. A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant according to claim 1, characterized in that: The extraction time in step S1 is 5 to 20 minutes.

5. A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant according to claim 1, characterized in that: In step S2, the detergent is selected from one or more of nitric acid, hydrochloric acid and sulfuric acid, and the concentration of the detergent is 0.1-3 mol / L.

6. A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant according to claim 1, characterized in that: In step S2, the detergent is dissolved in water, and the volume ratio of the organic phase after extraction to the detergent and water is (0.5-3):

1.

7. A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant according to claim 1, characterized in that: The washing time in step S2 is 5 to 20 minutes.

8. A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant according to claim 1, characterized in that: In step S3, thiourea is used as the stripping agent, and the concentration of the stripping agent is 0.1-0.5 mol / L.

9. A method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant according to claim 1, characterized in that: In step S3, the stripping agent is dissolved in water, and the volume ratio of the washed organic phase to the stripping agent and water is (0.5-3):

1.

10. The method for recovering palladium from radioactive waste liquid using a sulfur-containing extractant according to claim 1, characterized in that: The stripping time in step S3 is 5 to 20 minutes.

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