Transition metal structure regulation inorganic adsorbent for separating cesium and strontium as well as preparation method and application of transition metal structure regulation inorganic adsorbent

Abstract

The invention relates to the technical field of radionuclide separation and adsorption, in particular to a transition metal structure regulation inorganic adsorbent for separating cesium and strontium as well as a preparation method and application of the transition metal structure regulation inorganic adsorbent. The preparation method comprises the following steps: (1) carrying out precipitation reaction on a salt solution of first transition metal ions and a heteropoly acid solution in a constant-temperature magnetic stirring water bath kettle under a heating condition; and (2) adding a salt solution of second ions into the system obtained in the step (1) to prepare the transition metal structure regulation and control inorganic adsorbent. The material is simple in preparation method, the inorganic material is controllable in morphology and structure and good in stability, has an excellent adsorption effect on nuclides of cesium and strontium, can reach adsorption equilibrium within 20 min, and is suitable for efficient treatment of industrial-scale wastewater containing radioactive cesium and strontium.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radionuclide separation adsorption, and particularly relates to a transition metal structure regulated inorganic adsorbent for separating cesium and strontium, a preparation method and application thereof. BACKGROUND

[0002] Energy is an important basis for the development of human society. Nuclear energy has become an important part of the energy structure in many countries due to its safety, high efficiency, economy and cleanliness. As the Fukushima nuclear accident has warned, further improving nuclear safety and the level of radioactive pollution prevention is an important measure to ensure environmental safety, public health and efficient and sustainable development of nuclear energy. Cesium ( 134 Cs, beta emitter; 137 Cs, beta and gamma emitter) and strontium ( 90 Sr, beta emitter) have the characteristics of strong radioactivity, relatively long half-life, high heat release and large proportion of radioactivity, and are the primary target nuclides to be removed in radioactive waste liquid.

[0003] For the nuclide Cs in radioactive wastewater, zeolites are mostly used for removal. However, zeolite inorganic adsorbents usually have slow adsorption speed, and it takes several days or even longer to reach adsorption equilibrium. Moreover, the adsorption of Sr is weak, and when a large amount of alkali metal ions coexist in the wastewater (such as Na ions in seawater), the adsorption performance of zeolite for Cs will be significantly reduced due to competitive adsorption. In order to reduce the content of radioactive Sr in nuclear pollution water, adsorption materials such as activated carbon, artificial minerals and chelating resins are often used. For example, the ALPS multi-nuclide removal and purification system of the Fukushima accident. However, the effective removal of nuclide Sr is still one of the difficulties in the treatment of radioactive wastewater. For the existing separation technology, different adsorption materials are mostly used to treat cesium and strontium elements respectively, so multiple treatment systems need to be used in actual application, which is complicated to operate, easy to cause large equipment area and increase the amount of secondary waste. If a high-efficiency separation material that can simultaneously remove high-heat-releasing nuclides Cs and Sr can be developed, it will greatly simplify the wastewater purification process, improve the decontamination efficiency and reduce the amount of secondary waste generated, which is of great significance for building an advanced wastewater treatment technology system.

[0004] Inorganic adsorbent material has become a research hotspot in recent years due to its high selectivity, stable physical and chemical properties, and easy solidification. Heteropoly acid salt inorganic adsorbent is considered to have very good application prospects in the field of nuclide Cs separation. CN105032341A discloses a preparation method of an inorganic material for treating wastewater containing cesium, strontium and cobalt: potassium pyrophosphate and sodium metavanadate are mixed, and zirconium oxychloride is added under strong acidity to generate a precipitate, the pH is adjusted, and drying is performed to obtain a phosphorus-containing heteropoly acid salt; the phosphorus-containing heteropoly acid salt is mixed with titanium sulfate or titanium tetrachloride aqueous solution, and an aqueous sodium carbonate solution is added dropwise for water bath to obtain a mixture solution, and the mixture solution is high-pressure baked, filtered, washed and dried to obtain an adsorbent composed of titanium oxide and inorganic heteropoly acid salt. However, the preparation process needs to adjust the pH value for multiple times and relies on high-pressure equipment, and the process is complex and has high energy consumption. In addition, the chemical stability of heteropoly acid salt material has always been a concern, which greatly limits the practical application of heteropoly acid salt inorganic adsorbent in the field of radioactive waste.

[0005] In summary, the prior art is difficult to achieve efficient and simultaneous removal of cesium and strontium due to insufficient adsorption selectivity, poor material stability, or complex preparation process. It is of great significance to develop an inorganic adsorbent material which is simple to prepare, has excellent chemical stability and can quickly adsorb cesium and strontium, to simplify the radioactive wastewater treatment process, improve the decontamination efficiency and reduce secondary waste. SUMMARY

[0006] In view of the above technical difficulties, the purpose of the present application is to provide a transition metal structure regulated inorganic adsorbent for separating cesium and strontium, and a preparation method and application thereof. Based on the coprecipitation method, the adsorbent is synthesized by embedding and anti-embedding. The preparation method of the present application is simple, and the obtained adsorbent has the characteristics of controllable morphology and structure, good chemical stability, fast adsorption speed for cesium and strontium, and high treatment efficiency.

[0007] To achieve the above purpose, the first technical solution adopted by the present application is:

[0008] A preparation method of a transition metal structure regulated inorganic adsorbent for separating cesium and strontium, comprising the following steps:

[0009] (1) A salt solution of a first transition metal ion and a heteropoly acid solution are subjected to a precipitation reaction in a constant-temperature magnetic stirring water bath under heating conditions;

[0010] (2) A salt solution of a second ion is added to the system obtained in step (1) to obtain the transition metal structure regulated inorganic adsorbent.

[0011] In an optional embodiment, the first transition metal ion is selected from Ti 2+ , Zr 2+ , Fe 2+ , Ni 2+ , Cu2+ Co 2+ Mn 2+ Fe 3+ at least one of them.

[0012] In an alternative embodiment, the heteropoly acid is selected from at least one of phosphomolybdic acid, phosphosilicic acid, phosphotungstic acid, phosphovanadic acid, phosphomolybdovanadic acid, phosphotungstovanadic acid, phosphosilicovanadic acid, phosphomolybdosilicic acid, phosphotungstomolybdic acid and phosphosilicotungstic acid.

[0013] In an alternative embodiment, the second ion is selected from at least two of Ti 4+ Ce 4+ Zr 4+ Sn 4+ Fe 3+ Ce 3+ Ga 3+ Y 3+ Al 3+ Cr 3+ Cd 2+ Sn 2+ K + Na + and NH4 + .

[0014] In a specific embodiment, the first transition metal ion is Co 2+ , the second ion is Fe 3+ and NH4 + .

[0015] In another specific embodiment, the first transition metal ion is Fe 3+ , the second ion is Ce 3+ Sn 4+ and NH4 + .

[0016] In yet another specific embodiment, the first transition metal ion is Fe 3+ , the second ion is Sn 4+ Sn 2+ and NH4 + .

[0017] The way of adding the salt solution of the second ion can be to add multiple metal ions at the same time (for example: mixing multiple metal ions in advance, and then adding the mixture), or to add multiple metal ions one by one in sequence.

[0018] In an alternative embodiment, in step (1), the molar ratio of the first transition metal salt to the heteropoly acid is 1: (1-20), and the concentration of the heteropoly acid is 0.005-0.1 mol / L.

[0019] In an optional embodiment, the step of the first transition metal ion reacting with the heteropolyacid to undergo a precipitation reaction includes:

[0020] Stir at 50–90℃ for 5–30 min; the stirring speed is 100–500 r / min.

[0021] In an optional embodiment, the salt solution of the first transition metal ion is an oxalate solution, a chloride solution, a nitrate solution, or a sulfate solution.

[0022] In an optional implementation, step (2) includes:

[0023] Add the salt solution of the second ion to the system obtained in step (1), and stir the reaction at 50-90℃ for 30-120 min; the stirring speed is 100-500 r / min;

[0024] After the reaction is completed, allow the mixture to stand for at least 12 hours; preferably, the standing time is 24 hours.

[0025] In an optional embodiment, the salt solution of the second ion is an oxalate solution, a chloride solution, a nitrate solution, or a sulfate solution.

[0026] In an optional embodiment, after the reaction of the salt solution containing the second ion is complete in step (2), the process further includes:

[0027] The reaction products were washed and dried.

[0028] Preferably, the cleaning method is washing with deionized water; more preferably, the number of washing cycles is 3 to 6.

[0029] Preferably, the drying method involves drying the washed product at 50–90°C for 12–24 hours.

[0030] The second technical solution adopted in this invention is:

[0031] A transition metal structure-regulated inorganic adsorbent for separating cesium and strontium is provided, which is prepared by any of the preparation methods provided in the above embodiments.

[0032] The third technical solution adopted in this invention is:

[0033] The application of the aforementioned transition metal structure-regulated inorganic adsorbent in the adsorption and separation of cesium and strontium involves contacting the aforementioned transition metal structure-regulated inorganic adsorbent with an aqueous solution containing cesium and strontium ions for a period of time, thereby achieving the adsorption of cesium and strontium by the inorganic adsorbent.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) The transition metal structure regulated inorganic adsorbent prepared by the method can realize the co-adsorption of cesium and strontium ions in wastewater;

[0036] (2) The transition metal structure regulated inorganic adsorbent is synthesized by using a coprecipitation conversion mechanism, and is regulated by embedding and anti-embedding, and the micro-regulation and the improvement of chemical stability are realized according to the changes of pores, surface charges and M-O-M bond forces;

[0037] (3) The preparation method of the transition metal structure regulated inorganic adsorbent is simple, does not need the pH adjustment process and the intermediate sample processing process in CN105032341A, is strong in operability, is low in raw material cost, and can be completed in a general device (without high-pressure equipment) under normal pressure, and has good economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 An electron microscope graph of the inorganic adsorbent prepared for Example 1;

[0039] Figure 2 An electron microscope graph of the inorganic adsorbent prepared for Example 2;

[0040] Figure 3 An adsorption rate graph of the inorganic adsorbent prepared for Example 1 on cesium;

[0041] Figure 4 An adsorption isotherm graph of the inorganic adsorbent prepared for Example 1 on cesium at 25 DEG C;

[0042] Figure 5 An adsorption rate graph of the inorganic adsorbent prepared for Example 1 on strontium;

[0043] Figure 6 An adsorption isotherm graph of the inorganic adsorbent prepared for Example 1 on strontium at 25 DEG C;

[0044] Figure 7 A chemical stability graph of the inorganic adsorbent prepared for Example 5. DETAILED DESCRIPTION

[0045] The application will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. In addition, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content of the application, and these equivalent forms also fall within the scope of the appended claims of the application.

[0046] Example 1

[0047] A 200 mL phosphotungstic acid solution with a concentration of 0.05 mol / L is prepared in a beaker, and then the beaker is placed in a water bath at 60°C. After heating and stirring, 5 mL of 0.25 mol / L cobalt chloride solution is added dropwise into the beaker, and stirring is performed at a rate of 300 r / min for 5 min. Then, 10 mL of 0.5 mol / L ammonium chloride solution and 3.5 mL of 0.5 mol / L iron chloride solution are sequentially added into the beaker, and stirring is continuously performed for 30 min. After that, the beaker is taken out and left to stand at room temperature for aging for 12 h. Then, the aged mixture is subjected to solid-liquid separation by using a water flow air extractor and a sand core funnel, and then is washed with deionized water for 3 times and filtered. Subsequently, the mixture is placed in a 90°C constant-temperature vacuum drying oven for drying for 12 h. Finally, after cooling, a spherical transition metal structure regulated inorganic adsorbent ( Figure 1 ) is obtained.

[0048] Example 2

[0049] A 200 mL phosphotungstic acid solution with a concentration of 0.05 mol / L is prepared in a beaker, and then the beaker is placed in a water bath at 80°C. After heating and stirring, 5 mL of 0.25 mol / L iron trichloride solution is added dropwise into the beaker, and stirring is performed at a rate of 300 r / min for 20 min. Then, 5 mL of 0.25 mol / L cerium trichloride solution, 5 mL of 0.25 mol / L tin tetrachloride solution and 3.5 mL of 0.5 mol / L ammonium chloride solution are sequentially added into the beaker, and stirring is continuously performed for 1 h. After that, the beaker is taken out and left to stand at room temperature for aging for 24 h. Then, the aged mixture is subjected to solid-liquid separation by using a water flow air extractor and a sand core funnel, and then is washed with deionized water for 5 times and filtered. Subsequently, the mixture is placed in a 90°C constant-temperature vacuum drying oven for drying for 24 h. Finally, after cooling, a cubic transition metal structure regulated inorganic adsorbent ( Figure 2 ) is obtained.

[0050] Example 3

[0051] The adsorption rate and adsorption isotherm of the inorganic adsorbent prepared in Example 1 to cesium are shown in Figure 3 and Figure 4 . The adsorption rate of the adsorbent material of the present application to cesium is fast, and 96% of the adsorption equilibrium capacity can be reached in about 10 min, and the maximum adsorption capacity can reach 54.5 mg / g. The adsorption rate and adsorption isotherm of the material to strontium are shown in Figure 5 and Figure 6 . The adsorption rate of the material to strontium is slower than that to cesium before 20 min, but the adsorption equilibrium can also be basically reached in about 20 min, and the maximum adsorption capacity to strontium can reach 12.7 mg / g.

[0052] The adsorbent material 50mg was put into a solution with cesium and strontium concentration of 20mg / L, pH value was 6, and adsorbed for 1 hour, and the concentration of cesium and strontium ions before and after the reaction was measured. It was calculated that the adsorption rate of cesium could reach 100%, and the adsorption rate of strontium was 84.8%. Further investigation of the influence of sodium ion (Na + ) coexistence, the experiment was repeated in 0.1mol / L Na + solution (the initial concentration of cesium and strontium was kept at 20mg / L, and other conditions were consistent), and the adsorption rate of cesium was 98.9%, and the adsorption rate of strontium + was 79.0%.

[0053] Example 4

[0054] The adsorbent material prepared in Example 2 was put into a wastewater with cesium and strontium concentration of 20mg / L, pH value was 7, and adsorbed for 1 hour, and then solid-liquid separation was carried out, and the concentration of cesium and strontium ions before and after the reaction was measured. It was calculated that the adsorption rate of cesium was 100%, and the adsorption rate of strontium was 73.3%. Further investigation of the influence of sodium ion (Na + ) coexistence, the experiment was repeated in 0.1mol / L Na + solution (the initial concentration of cesium and strontium was kept at 20mg / L, and other conditions were consistent), and the adsorption rate of cesium was 98.4%, and the adsorption rate of strontium was 70.6%.

[0055] Example 5

[0056] A phosphomolybdic acid solution with a concentration of 0.05mol / L was prepared in a beaker, and then the beaker was placed in a water bath at 80℃, and after heating and stirring, 3mL of 0.25mol / L ferric chloride solution was added dropwise, and stirred at a rate of 300r / min for 20min; then 5mL of 0.25mol / L tin tetrachloride solution, 5mL of 0.25mol / L tin dichloride solution and 10mL of 0.5mol / L ammonium chloride solution were added into the beaker in turn, and stirred for 1h; then the beaker was taken out and placed at room temperature for 24h; then the mixture was separated by water flow air pump and sand core funnel, and then washed with deionized water for 5 times and filtered, and then placed in a 90℃ constant temperature vacuum drying oven for drying for 24h, and finally cooled to obtain a metal structure regulated inorganic adsorbent.

[0057] Example 6

[0058] In order to investigate the chemical stability of the metal structure regulated inorganic adsorbent prepared in Example 5, 50 mg of the metal structure regulated inorganic adsorbent and the heteropoly acid salt adsorbent without structure regulation were respectively placed in 10 ml transparent glass bottles, and 5 ml of deionized water was respectively added to the glass bottles. After sealing, the glass bottles were placed in a water bath temperature control shaker, the temperature was set to 25 DEG C, the oscillation rate was 120 rpm, and the oscillation time was set to 24 h and 72 h respectively. Finally, the molybdenum ion concentration in the solution was tested, and the chemical stability of the two adsorbents was analyzed. The results are shown in Table 6. Figure 7 As shown in Table 6, under different oscillation contact times, the percentage of molybdenum ions dissolved into the solution by the metal structure regulated inorganic adsorbent is less than that of the heteropoly acid salt adsorbent without structure regulation. It is proved that the adsorbent has good chemical stability.

[0059] In summary, the transition metal structure regulated inorganic adsorbent can realize the adsorption and separation of high heat release radionuclides cesium and strontium, has fast adsorption speed, good adsorption kinetic performance, high adsorption capacity, good chemical stability, simple preparation method and strong operability, and is expected to play a great advantage in the treatment of wastewater containing radioactive cesium and strontium.

[0060] Although the preferred embodiments of the present application have been disclosed as above, they are not intended to limit the scope of the present application, and any person skilled in the art can make various modifications and improvements without departing from the main spirit and scope of the present application. Therefore, the protection scope of the present application should be subject to the actual claims of the patent application.

Claims

1. A method for preparing a transition metal structure-regulated inorganic adsorbent for separating cesium and strontium, characterized in that, Includes the following steps: (1) The salt solution of the first transition metal ion and the heteropolyacid solution were subjected to precipitation reaction under heating conditions in a constant temperature magnetically stirred water bath; (2) adding a salt solution of a second ion selected from at least two of Ti 4+ , Ce 4+ , Zr 4+ , Sn 4+ , Fe 3+ , Ce 3+ , Ga 3+ , Y 3+ , Al 3+ , Cr 3+ , Cd 2+ , Sn 2+ , K + , Na + , and NH4 + to the system obtained in step (1) to produce the transition metal structure-regulated inorganic adsorbent.

2. The production method according to claim 1, characterized by, the first transition metal ion is selected from the group consisting of Ti 2+ , Zr 2+ , Fe 2+ , Ni 2+ , Cu 2+ , Co 2+ , Mn 2+ , Fe 3+ .

3. The production method according to claim 1, characterized by, The heteropolyacid is selected from at least one of phosphomolybdic acid, phosphosilicate, phosphotungstic acid, phosphovanadic acid, phosphomolybdic vanadic acid, phosphotungstic vanadic acid, phosphosilicate vanadic acid, phosphomolybdic silicic acid, phosphotungstic acid, and phosphosilicate tungstic acid.

4. The method of claim 1, wherein, the first transition metal ion is Co 2+ , the second ion is Fe 3+ , and NH4 + ; or the first transition metal ion is Fe 3+ , the second ion is Ce 3+ , Sn 4+ , and NH4 + ; or the first transition metal ion is Fe 3+ , the second ion is Sn 4+ , Sn 2+ , and NH4 + .

5. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of the first transition metal salt to the heteropolyacid is 1:(1-20), and the concentration of the heteropolyacid is 0.005-0.1 mol / L.

6. The method of claim 1, wherein, The step of the precipitation reaction between the first transition metal ion and the heteropolyacid includes: Stir at 50–90℃ for 5–30 min; the stirring speed is 100–500 r / min.

7. The preparation method according to claim 1, characterized in that, Step (2) includes: Add the salt solution of the second ion to the system obtained in step (1), and stir the reaction at 50-90℃ for 30-120 min; the stirring speed is 100-500 r / min; After the reaction is complete, allow the mixture to stand and age for at least 12 hours.

8. The method of claim 1, wherein, In step (2), after the salt solution containing the second ion has reacted sufficiently, the process also includes: The reaction products were washed and dried. Preferably, the cleaning method is washing with deionized water; more preferably, the number of washing cycles is 3 to 6. Preferably, the drying method involves drying the washed product at 50–90°C for 12–24 hours.

9. A transition metal structure-regulated inorganic adsorbent for separating cesium and strontium, prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the transition metal structure-regulated inorganic adsorbent for separating cesium and strontium according to claim 9 in the adsorption and separation of cesium and strontium, wherein the transition metal structure-regulated inorganic adsorbent is contacted with an aqueous solution containing cesium and strontium ions for a period of time to achieve the adsorption of cesium and strontium by the inorganic adsorbent.

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