A method for extracting palladium from radioactive waste solutions

Abstract

The present application relates to a kind of methods for extracting palladium from radioactive waste liquid, and the radioactive waste liquid is mixed with the organic phase containing pyridine derivative for extraction, the pyridine derivative is one or more of Ph-BTP, Ph-BTBP or Ph-BTPhen, respectively, as shown in the following structure: compared with prior art, the palladium extraction method of the present application is simple and feasible, easy to industrial production, by adjusting the concentration of extractant, phase ratio etc. can make the single-stage extraction rate of palladium greater than 99%, and the extraction equilibrium time is short, can meet the demand of palladium recovery, and the application prospect in the field of palladium recovery and high-level radioactive waste disposal is widely.

Description

Technical Field

[0001] This invention relates to the field of radioactive waste treatment and disposal technology, and in particular to a method for extracting palladium from radioactive waste liquid. Background Technology

[0002] High-level radioactive waste contains precious metals such as ruthenium, rhodium, and palladium. The palladium content is closely related to the reactor type and fuel burnup depth. For example, a standard commercial pressurized water reactor with an average burnup depth of 33 GWd / t has a Pd content >1 kg Pd / tU. The total palladium resources contained in high-level radioactive waste are enormous, and with the booming development of the nuclear power industry, the amount of palladium resources generated will continue to increase. On the other hand, recovering and utilizing palladium (Pd) from high-level radioactive waste can fundamentally eliminate its adverse effects on the glass solidification and melting process.

[0003] Solvent extraction is the mainstream method for separating and extracting palladium. Since the 1960s, extensive research has been conducted both domestically and internationally on palladium extraction processes and extractant development. Patent CN101020964 A discloses a method for extracting and separating palladium using solid-phase extraction. It uses polymer microspheres bonded with palladium extractants as the stationary phase and a hydrochloric acid solution containing noble and base metals as the mobile phase. Palladium can be extracted and separated from noble metal catalysts, platinum group metal concentrates, or precious metal concentrates obtained from secondary resources through hydrochloric acid elution, thiourea, or ammonia elution. However, the stationary phase has a short lifespan and poor recycling performance under radioactive conditions, generating large amounts of radioactive solid waste. Furthermore, solid-phase extraction is not suitable for treating large quantities of industrial waste liquids.

[0004] Patent CN 105002359 A discloses a method for extracting palladium from an aqueous phase, using a diazepine pyridine derivative as the extractant and employing solvent extraction to obtain an extract phase containing palladium. The extractant achieves its maximum palladium distribution ratio (approximately 47) at a 2M HNO3 nitric acid concentration. The preferred extraction time is 120 min, and the extraction equilibrium time is long.

[0005] Patent CN 101713026 A discloses a method for extracting palladium from high-level radioactive waste liquid. The method uses triisobutylphosphine sulfide (TiBPS) as the extractant and employs a solvent extraction method, extracting palladium from simulated high-level radioactive waste liquid through steps such as extraction, washing, and back-extraction. TiBPS contains sulfur and phosphorus, which does not conform to the principles of green and sustainable development.

[0006] Currently reported palladium extraction methods have drawbacks such as low extraction partition ratios of extractants (e.g., tributyl phosphate, trialkyl phosphate oxide, partition ratio less than 10), long extraction equilibrium times (e.g., dialkyl sulfides, equilibrium time 8-10 hours), and non-compliance with green and sustainable development principles. As a result, they cannot efficiently separate and recover palladium. Furthermore, extraction processes such as solid-phase extraction and ion exchange are not suitable for the treatment of large quantities of industrial waste liquids. Summary of the Invention

[0007] The purpose of this invention is to provide a method for extracting palladium from radioactive waste liquid, and to efficiently separate and recover palladium.

[0008] The objective of this invention can be achieved through the following technical solution: a method for extracting palladium from radioactive waste liquid, wherein the radioactive waste liquid is mixed with an organic phase O1 containing a palladium extractant pyridine derivative for extraction, wherein the pyridine derivative is one or more of Ph-BTP, Ph-BTBP, or Ph-BTPhen, and has the following structures respectively:

[0009]

[0010] Preferably, the method for preparing the pyridine derivative includes the following steps:

[0011] S1. Synthesis of amide hydrazone via nucleophilic addition reaction: Add hydrated or anhydrous hydrazine to a dimethyl nitrile solution, perform a nucleophilic addition reaction, and then separate the solid and liquid phases to obtain amide hydrazone;

[0012] S2. Synthesis of pyridine derivatives via condensation cyclization reaction: The ground amide hydrazone and diphenyl ethylene glycol are dispersed or dissolved in a solvent, and after condensation cyclization reaction, the pyridine derivatives are obtained by solid-liquid separation.

[0013] The diformonitrile has the following structure:

[0014]

[0015] The amide hydrazone has the following structure:

[0016]

[0017] More preferably, in step S1, dimethylnitrile is added to the reaction vessel, and then a solvent is added to dissolve or disperse it. When the temperature inside the reaction vessel is controlled at -2℃ to 2℃, hydrazine hydrate or anhydrous hydrazine is added dropwise. After the dropwise addition is completed, the temperature is raised to 15 to 50℃, and the reaction is stirred for 6 to 24 hours. After the reaction is completed, the mixture is separated into solid and liquid components. The filter cake is washed several times and then dried in a drying device to obtain amide hydrazone.

[0018] More preferably, in step S2, the ground amide hydrazone and diphenylethylene glycol are dispersed or dissolved in a solvent and reacted at 40–110°C for 3–72 h. After the reaction is completed, the mixture is separated into solid and liquid components, the filter cake is washed several times, and then dried in a drying device to obtain the pyridine derivative.

[0019] Preferably, the concentration of the pyridine derivative in the organic phase O1 is 0.1-500 mmol / L.

[0020] More preferably, the concentration of the pyridine derivative in the organic phase O1 is 2-100 mmol / L.

[0021] Preferably, the concentration of palladium in the radioactive waste liquid is in the range of 0.01-4.5 g / L.

[0022] Preferably, the concentration of HNO3 in the radioactive waste liquid is 1-5M.

[0023] Preferably, the diluent for the organic phase O1 is one or more of the following: dichloromethane, chloroform, dichloroethane, 1,1-difluoro-1,2-dichloroethane, trichloroethane, tetrachloroethane, furan, dioxane, acetonitrile, DMSO, hydrogenated kerosene, sulfonated kerosene, petroleum ether, ethyl acetate, benzene, toluene, xylene, pentane, and n-dodecane.

[0024] Different organic phases have different solubilities in the extractant, which affects the extraction results. Furthermore, different extractants have different extraction effects on palladium. Therefore, based on the equipment conditions and the palladium concentration in the waste liquid, and on the premise of meeting the palladium extraction requirements, the extractant and diluent of the organic phase O1 can be selected according to the equipment's corrosion resistance, solvent cost, extractant cost, or any other chemical or physical properties. At the same time, the process parameters should be adjusted accordingly.

[0025] Preferably, the ratio of the radioactive waste liquid to the organic phase O1 is 3:1 to 1:3 (V / V).

[0026] More preferably, the ratio of the radioactive waste liquid to the organic phase O1 is 3:2 to 2:3 (V / V).

[0027] Preferably, the mixing time between the radioactive waste liquid and the organic phase is 2-120 min, and the operating temperature is 15-60℃.

[0028] The extraction equilibrium times of Ph-BTP, Ph-BTBP, and Ph-BTPhen extractants differ, with Ph-BTP reaching equilibrium in as little as 5 minutes. The solvent extraction of palladium achieves a single-stage palladium extraction rate greater than 99%.

[0029] Preferably, the extraction is followed by washing and back-extraction.

[0030] More preferably, the washing process involves washing the extracted organic phase with a detergent.

[0031] More preferably, the back-extraction process involves mixing the extracting organic phase with an aqueous phase containing a back-extraction agent for back-extraction.

[0032] Preferably, the organic phase is pre-equilibrated before extraction.

[0033] Preferably, the method for extracting palladium from radioactive waste liquid is a solvent extraction method, which includes four steps: organic phase O1 pre-equilibration, solvent extraction, washing, and back-extraction.

[0034] More preferably, the organic phase O1 pre-equilibration involves preparing an aqueous phase W1 with the same acidity as the radioactive waste liquid, fully contacting W1 with the organic phase O1, mixing them evenly, and then separating the organic phase for use in the extraction step. Pre-equilibration eliminates the influence of acidity changes during phase contact on the extraction results, ensuring the reproducibility of the experiment.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The palladium extraction method of the present invention is simple and feasible, and easy to industrialize. By adjusting the concentration of the extractant and the phase ratio, the single-stage extraction rate of palladium can be greater than 99%.

[0037] 2. The present invention has a short extraction equilibrium time, which can meet the requirements of palladium recovery and has broad application prospects in the fields of palladium recovery and high-level radioactive waste liquid treatment.

[0038] 3. This invention mitigates the impact of high-melting-point palladium on the glass solidification of high-electroactive waste liquid.

[0039] 3. The extractants of this invention are nitrogen-containing ligands, which are more in line with the principles of green and sustainable development because they contain only carbon, hydrogen, oxygen and nitrogen (CHON), and can be completely incinerated.

[0040] 4. Compared with existing palladium extractants, the palladium extractant disclosed in this invention is a highly efficient extractant. The extractant can be synthesized independently, the raw material cost is low, and it is widely available in the market. Attached Figure Description

[0041] Figure 1 The molecular structural formula of the extractant pyridine derivative;

[0042] Figure 2 The image shows the 1H NMR spectrum of the extractant Ph-BTP. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc., used can be purchased from chemical companies or prepared by existing methods.

[0044] Example 1

[0045] Synthesis of Ph-BTP:

[0046] Nucleophilic addition: 0.77 kg of diformonium I (2,6-pyridinediformonium), 8 L of anhydrous ethanol, and 2 L of tetrahydrofuran were added to a jacketed reactor. The cryogenic cooling liquid circulation pump was started, and when the temperature inside the reactor reached approximately 0 °C, 3 L of hydrazine hydrate was added dropwise. After the addition of hydrazine hydrate was completed, the temperature inside the reactor was maintained at 30 °C, and the mixture was stirred for 12 hours. After the reaction was completed, solid-liquid separation was performed using a filter press. The product was washed with pretreated ethanol and finally dried in a drying oven to obtain the target product, amide hydrazone I.

[0047] Condensation cyclization: 2.2 kg of phenylethylene glycol and 70 L of tetrahydrofuran were added to a jacketed reactor equipped with a reflux condenser. Then, 1.0 kg of powdered amide hydrazone I was added while stirring. The reaction was carried out at 70 °C for 5 hours with stirring. After the reaction was completed and cooled to room temperature, the product was separated and dried according to the method described in the nucleophilic addition step above, finally yielding the target product Ph-BTP. The 1H NMR spectrum of the target product Ph-BTP is shown below. Figure 2 .

[0048] Example 2

[0049] Synthesis of Ph-BTBP:

[0050] Nucleophilic addition: 0.8 kg of dicarboxynitrile II (2,2′-bipyridine-6,6′-dicarboxynitrile) and 50 L of anhydrous ethanol were added to a jacketed reactor. The cryogenic cooling liquid circulation pump was started, and when the temperature inside the reactor was around 0 °C, 6 L of hydrazine hydrate was added. After the hydrazine hydrate was added dropwise, the temperature inside the reactor was maintained at 40 °C, and the mixture was stirred for 10 hours. After the reaction was completed, the product, amide hydrazone II, was obtained by filtration, washing, and drying.

[0051] Condensation cyclization: 0.78 kg of phenylethylene glycol, 1.5 L of dimethyl sulfoxide, and 68.5 L of tetrahydrofuran were added to a jacketed reactor equipped with a reflux condenser. Then, 0.5 kg of powdered amide hydrazone II was added while stirring, and the mixture was stirred at 70 °C for 5 hours. After the reaction was completed and cooled to room temperature, the product was separated and dried according to the method described in the nucleophilic addition step above, finally yielding the target product Ph-BTBP.

[0052] Example 3

[0053] High-level radioactive waste liquid (US6843921B2) was separated to obtain a radioactive nitrate solution containing lanthanides, fragmented metal ions, and other metal ions. A radioactive waste liquid simulant without minor actinides was prepared and subjected to palladium single-stage extraction experiments. The elemental composition of the radioactive waste liquid simulant was La, Ce, Pr, Nd, Sm, Eu, Gd, Sr, Cs, Ba, Fe, Mo, Y, Pd, Re, K, Na, etc., with a total metal ion concentration of 5.2 × 10⁻⁶. -2 M.

[0054] (1) Prepare a palladium-containing nitric acid solution with a palladium concentration of 12.5 mg / L and a nitric acid concentration of 3.2 mol / L.

[0055] (2) Prepare a Ph-BTP-dichloromethane solution with a Ph-BTP concentration of 5 mmol / L. Pre-equilibrate the organic phase using a 3.2 mol / L nitric acid aqueous solution.

[0056] (3) Mix the palladium-containing simulated waste liquid and Ph-BTP-dichloromethane organic phase at a ratio of 1:1, place them in a constant temperature water bath shaker, operate at room temperature, at a frequency of 200 rpm, and extract for 3 min.

[0057] (4) Separate the aqueous phase from the organic phase and determine the palladium concentration in the aqueous phase.

[0058] (5) Wash and extract the organic phase.

[0059] (6) Add the stripping agent palladium to the organic phase of extraction.

[0060] Results of steps (1) to (4): The single-stage extraction rate of palladium was 99.1%, and the extraction partition ratio was 110. The extraction partition ratios of some representative elements are shown in Table 1.

[0061] Table 1. Distribution ratio of some representative elements in the simulated material.

[0062]

[0063]

[0064] Example 4

[0065] The high-level radioactive waste liquid was separated to obtain actinide elements (US6843921B2), yielding a radioactive nitrate solution containing lanthanide elements, fragmented metal ions, and other metal ions. A radioactive waste liquid simulant without actinide elements was prepared and subjected to palladium single-stage extraction experiments. The elemental composition of the radioactive waste liquid simulant was the same as in Example 1.

[0066] (1) Prepare a palladium-containing nitric acid solution with a palladium concentration of 50 mg / L and a nitric acid concentration of 3.2 mol / L.

[0067] (2) Prepare a Ph-BTP-chloroform solution with a Ph-BTP concentration of 20 mmol / L. Pre-equilibrate the organic phase using a 3.2 mol / L nitric acid aqueous solution.

[0068] (3) The palladium-containing simulated waste liquid and Ph-BTP-chloroform solution with a ratio of 1:1.2 were mixed and placed in a constant temperature water bath shaker. The operating temperature was 35℃, the frequency was 200rpm, and the extraction time was 30min.

[0069] (4) Separate the aqueous phase from the organic phase and determine the palladium concentration in the aqueous phase.

[0070] Experimental results: The single-stage extraction rate of palladium was 99.8%.

[0071] Example 5

[0072] The high-level radioactive waste liquid was separated to obtain actinide elements (US6843921B2), yielding a radioactive nitrate solution containing lanthanide elements, fragmented metal ions, and other metal ions. A radioactive waste liquid simulant without actinide elements was prepared and subjected to palladium single-stage extraction experiments. The elemental composition of the radioactive waste liquid simulant was the same as in Example 1.

[0073] (1) Prepare a palladium-containing nitric acid solution with a palladium concentration of 300 mg / L and a nitric acid concentration of 5 mol / L.

[0074] (2) Prepare a Ph-BTP-dichloromethane solution with a Ph-BTP concentration of 200 mmol / L.

[0075] (3) Mix the palladium-containing simulated waste liquid and the pre-equilibrated Ph-BTP-dichloromethane solution at a ratio of 1:1, place them in a constant temperature water bath shaker, operate at room temperature, at a frequency of 200 rpm, and extract for 20 min.

[0076] (4) Separate the aqueous phase from the organic phase and determine the palladium concentration in the aqueous phase.

[0077] Experimental results: The single-stage extraction rate of palladium was 99.5%.

[0078] Example 6

[0079] A single-component palladium solution was prepared, and a palladium single-stage extraction experiment was conducted.

[0080] (1) Prepare a palladium-containing nitric acid solution with a palladium concentration of 1200 mg / L and a nitric acid concentration of 1.5 mol / L.

[0081] (2) Prepare a Ph-BTP-chloroform solution with a Ph-BTP concentration of 50 mmol / L.

[0082] (3) Mix the palladium-containing simulated waste liquid with a ratio of 1:1.5 and the pre-equilibrated Ph-BTP-chloroform solution, place them in a constant temperature water bath shaker, and operate at room temperature for 15 min.

[0083] (4) Separate the aqueous phase from the organic phase and determine the palladium concentration in the aqueous phase.

[0084] Experimental results: The single-stage extraction rate of palladium was 99.6%.

[0085] Example 7

[0086] The high-level radioactive waste liquid was separated to obtain actinide elements (US6843921B2), yielding a radioactive nitrate solution containing lanthanide elements, fragmented metal ions, and other metal ions. A radioactive waste liquid simulant without actinide elements was prepared and subjected to palladium single-stage extraction experiments. The elemental composition of the radioactive waste liquid simulant was the same as in Example 1.

[0087] (1) Prepare a palladium-containing nitric acid solution with a palladium concentration of 12.5 mg / L and a nitric acid concentration of 3.2 mol / L.

[0088] (2) Prepare a Ph-BTBP-chloroform solution with a Ph-BTBP concentration of 30 mmol / L.

[0089] (3) Mix the palladium-containing simulated waste liquid and the pre-equilibrated Ph-BTBP-chloroform solution at a ratio of 1:2, place them in a constant temperature water bath shaker, and operate at room temperature for 90 min.

[0090] (4) Separate the aqueous phase from the organic phase and determine the palladium concentration in the aqueous phase.

[0091] Experimental results: The single-stage extraction rate of palladium is approximately 99%.

[0092] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for extracting palladium from radioactive waste liquid, characterized in that, The radioactive waste liquid is mixed with an organic phase containing pyridine derivatives for extraction. The pyridine derivatives are one or both of Ph-BTP and Ph-BTBP, each having the following structures: ； The mixing time between the radioactive waste liquid and the organic phase is 2-120 min; The concentration of palladium in the radioactive waste liquid ranges from 0.01 to 4.5 g / L.

2. The method for extracting palladium from radioactive waste liquid according to claim 1, characterized in that, The preparation method of the pyridine derivative includes the following steps: S1. Synthesis of amide hydrazone via nucleophilic addition reaction: Add hydrated or anhydrous hydrazine to a dimethyl nitrile solution, perform a nucleophilic addition reaction, and then separate the solid and liquid phases to obtain amide hydrazone; S2. Synthesis of pyridine derivatives via condensation cyclization reaction: The ground amide hydrazone and diphenyl ethylene glycol are dispersed or dissolved in a solvent, and after condensation cyclization reaction, the pyridine derivatives are obtained by solid-liquid separation. The diformonitrile has the following structure: ； The amide hydrazone has the following structure: 。 3. The method for extracting palladium from radioactive waste liquid according to claim 1, characterized in that, The concentration of pyridine derivatives in the organic phase is 0.1-500 mmol / L.

4. The method for extracting palladium from radioactive waste liquid according to claim 3, characterized in that, The concentration of pyridine derivatives in the organic phase is 2-100 mmol / L.

5. The method for extracting palladium from radioactive waste liquid according to claim 1, characterized in that, The diluent for the organic phase is one or more of the following: dichloromethane, chloroform, dichloroethane, 1,1-difluoro-1,2-dichloroethane, trichloroethane, tetrachloroethane, furan, dioxane, acetonitrile, DMSO, hydrogenated kerosene, sulfonated kerosene, petroleum ether, ethyl acetate, benzene, toluene, xylene, pentane, and n-dodecane.

6. The method for extracting palladium from radioactive waste liquid according to claim 1, characterized in that, The ratio of the radioactive waste liquid to the organic phase is 3:1 to 1:

3.

7. The method for extracting palladium from radioactive waste liquid according to claim 1, characterized in that, The extraction process is carried out at a temperature of 15-60℃.

8. The method for extracting palladium from radioactive waste liquid according to claim 1, characterized in that, The organic phase was pre-equilibrated before extraction.

9. The method for extracting palladium from radioactive waste liquid according to claim 8, characterized in that, The pre-equilibration involves preparing an aqueous phase with the same acidity as the radioactive waste liquid, fully contacting the aqueous phase with the organic phase, mixing them evenly, and then separating the organic phase for extraction.

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