WO2023070930A1 - Two-dimensional chalcogen compound, and preparation method therefor and application thereof - Google Patents

Abstract

Disclosed in the present invention is a two-dimensional chalcogen compound. The two-dimensional chalcogen compound is a crystalline material and has the chemical formula of (NH₄)₂[Sn₃S₇]; unit cell parameters are formula I and formula II, i.e., α=β=90°, and γ=120°; and a space group is formula III. Further disclosed in the present invention are a preparation method for a two-dimensional chalcogen compound and an application of the two-dimensional chalcogen compound in iodine vapor adsorption. The two-dimensional chalcogen compound disclosed in the present invention can remove iodine vapor under different iodine vapor concentrations (as low as 400 ppm) and within a relatively wide temperature range (25°C-75°C), and has no iodine desorption phenomenon caused by long-time standing.

Description

Two-dimensional chalcogen compound and its preparation method and application technical field

The invention relates to the technical field of adsorption materials, in particular to a two-dimensional chalcogen compound and its preparation method and application.

Background technique

Nuclear energy is one of the most promising clean energy sources for the future of mankind. However, with the continuous development of nuclear power, the reserves of spent fuel are also increasing. Spent fuel contains unfissioned uranium-235, which needs to be recovered and reused, and a large amount of gaseous radioactive iodine is produced in this process (ie spent fuel reprocessing). Compared with solid radioactive waste, gaseous radioactive iodine has the characteristics of high mobility and easy migration with airflow, which leads to a larger pollution area and is more likely to cause serious harm to the ecological environment and human health. Research on nuclear accidents such as Chernobyl and Fukushima has shown that radioactive iodine is a type of radioactive nuclide that spreads quickly and is highly harmful. Therefore, the adsorption and treatment of gaseous iodine in waste gas from reprocessing plants has become an important research direction for radioactive waste gas treatment. At present, people mainly use methods such as dry dust removal, liquid absorption and solid phase adsorption to remove radioactive iodine in gas. Dry dedusting has low treatment efficiency for radioactive gases and is mainly used for the disposal of radioactive aerosols. The liquid absorption method mainly includes mercury washing, pickling and alkali washing. Although this method has a high absorption efficiency, it will use a large amount of toxic mercuric nitrate or strong acid and alkali such as nitric acid and sodium hydroxide. The operation and maintenance costs of the equipment are high, and it is easy to generate a large amount of radioactive waste liquid. Solid phase adsorption is one of the important iodine removal methods, and the most commonly used method is silver-containing zeolite. Although silver-based zeolites have high removal efficiency for iodine, the large use of silver leads to high cost of adsorption materials and brings certain environmental pollution problems.

The current industrial solid-phase adsorption method for capturing radioactive iodine mainly relies on the use of active silver (Ag) loaded on various solid supports as the adsorbent. Active silver (silver nanoparticles/silver nanoclusters/silver ions) can convert radioactive iodine into solid AgI, thereby removing iodine. The biggest limitation of this adsorbent in practical application is the instability of the Ag-I bond (the bond energy between Ag-I is usually 66 kJ/mol). When the iodine-loaded silver-based adsorbent is further processed, the unstable Ag-I bond is prone to breakage under the influence of external conditions such as light and temperature, which will lead to the re-release of radioactive iodine and cause radioactive pollution.

Furthermore, the traditional industrial method for handling and trapping iodine compounds is to impregnate activated carbon with organic amines, such as triethylenediamine and potassium iodide. Triethylenediamine is the most common impregnant used in activated carbon sorbents to capture radioactive iodine species. Compared with other adsorbents, triethylenediamine-impregnated activated carbon has excellent adsorption capacity and high purification efficiency, and the process of capturing iodine is relatively simple; however, its disadvantages are also obvious: (1) The capacity of the adsorbent increases with (2) The sublimation of organic amines is easy to occur, resulting in a significant decrease in the iodine absorption efficiency of impregnated carbon materials; (3) Iodine adsorption is an exothermic process, and organic amines reduce the ignition point of impregnated carbons. exacerbated potential safety hazards.

Metal-organic framework materials and covalent organic framework materials are a new class of crystalline porous materials. Due to the diversity of their metal centers and ligands, they have variable chemical properties, and this type of material is widely used in radioactive iodine. remove. However, the expensive price of its organic ligands limits its practical application.

Contents of the invention

In order to solve the above technical problems, the present invention synthesizes a novel two-dimensional layered sulfide material, which can achieve efficient removal of iodine vapor.

The present invention provides the technical scheme as follows:

The present invention provides a two-dimensional chalcogen compound, the two-dimensional chalcogen compound is a crystalline material, the chemical formula is (NH ₄ ) ₂ [Sn ₃ S ₇ ], and the unit cell parameters are:

α=β=90°, γ=120°, the space group is

The present invention also provides the preparation method of the two-dimensional chalcogen compound, comprising the following steps: reacting the tin source and the sulfur element in diethylenetriamine at 150°C to 180°C to obtain the two-dimensional chalcogen compound Chalcogen compounds; wherein, the molar ratio of the tin source to the sulfur element is 1:1-5.

Further, since the reaction needs to be carried out under heating conditions, and the reaction time is relatively long, in order to avoid a large amount of volatilization of diethylenetriamine, it is preferable to carry out the reaction in a closed container.

In the present invention, diethylenetriamine acts as a solvent and a template in the reaction, and after the reaction is completed, ammonium ions are generated and exist in the pores of the two-dimensional chalcogen compound, which plays a role in balancing the interlayer charge . It is advisable to add diethylenetriamine in an amount to submerge the reactants, generally 1/5 to 3/5 of the volume of the reaction vessel.

Further, the tin source is tin element or tetravalent tin salt. The tin elemental substance includes but not limited to tin powder, tin particles, tin sticks, preferably tin powder. The tetravalent tin salt is preferably tin tetrachloride.

Further, the sulfur element is preferably sublimed sulfur.

Further, the reaction time is 3-7 days.

Further, the molar ratio of the tin source to the sulfur element is 3:7.

The present invention also provides the application of the two-dimensional chalcogen compound in the adsorption of iodine vapor.

In the two-dimensional chalcogen compound (NH ₄ ) ₂ [Sn ₃ S ₇ ] of the present invention, S ^2- in its molecular structure can reduce gaseous I ₂ to I ^- , and then react with I ^- through Sn ⁴⁺ Generate SnI ₄ , thereby realizing the adsorption of iodine vapor. Moreover, the generated SnI ₄ is stable in nature and will not desorb iodine due to standing for a long time.

Further, the iodine vapor is radioactive iodine vapor.

Further, at 25°C and an iodine vapor concentration of 400ppm, the two-dimensional chalcogenide has an iodine vapor adsorption capacity of 2.38g/g, and at 75°C and a 400ppm iodine vapor concentration, the iodine vapor The amount reached 2.35g/g.

Compared with prior art, the beneficial effect of the present invention is:

1. In view of the high cost of traditional silver-based zeolite materials and the limited amount of radioactive iodine adsorption in spent fuel exhaust, the present invention synthesized a new type of two-dimensional chalcogen compound (NH ₄ ) ₂ [Sn ₃ S ₇ ], Using S ^2- in the two-dimensional chalcogen compound to reduce I ₂ to I ^- , and then generate SnI ₄ through the reaction of Sn ⁴⁺ and I ^- , so as to realize the adsorption of radioactive iodine vapor.

2. The two-dimensional chalcogen compound of the present invention can realize the removal of iodine vapor under different iodine vapor concentrations (as low as 400ppm) and in a wider temperature range (25°C to 75°C), and will not The phenomenon of iodine desorption occurs after standing for a long time.

3. The two-dimensional chalcogen compound of the present invention is low in cost, and it is estimated that the material cost needed to absorb 1g of iodine vapor is only 0.4 yuan, which has the potential for industrial application.

Description of drawings

Figure 1 is a schematic structural diagram of (NH ₄ ) ₂ [Sn ₃ S ₇ ];

Figure 2 is a triangular node composed of Sn atoms and S atoms in the structure of (NH ₄ ) ₂ [Sn ₃ S ₇ ];

Fig. 3 is the thermogravimetric analysis diagram of (NH ₄ ) ₂ [Sn ₃ S ₇ ];

Figure 4(a) is a graph of the adsorption capacity of (NH ₄ ) ₂ [Sn ₃ S ₇ ] for high-concentration iodine vapor versus time at 75°C;

Figure 4(b) is a graph showing the change of adsorption amount of (NH ₄ ) ₂ [Sn ₃ S ₇ ] with iodine adsorbed after standing for a long time;

Fig. 5 is a graph showing the equilibrium adsorption capacity of (NH ₄ ) ₂ [Sn ₃ S ₇ ] for low-concentration iodine vapor at 25°C and 75°C.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terms used in the description of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The experimental methods used in the following examples are conventional methods unless otherwise specified, and the materials and reagents used can be obtained from commercial sources unless otherwise specified.

Example 1: Synthesis of two-dimensional chalcogenide (NH ₄ ) ₂ [Sn ₃ S ₇ ]

Add 3mmol of tin powder and 7mmol of sulfur powder into the reaction vessel, then add 4mL of diethylenetriamine, seal the reaction vessel, set the reaction temperature to 180°C, react for 4 days, and cool down to room temperature for 12 hours. After the reaction, the reaction product was washed with water to obtain yellow crystals, which were designated as SCU-SnS.

The obtained yellow crystals were subjected to X-ray single crystal diffraction test, and the crystallographic parameters are shown in Table 1.

Table 1 Crystallographic parameters of two-dimensional chalcogenides (NH ₄ ) ₂ [Sn ₃ S ₇ ]

Figure 1-2 is a schematic diagram of the structure of two-dimensional chalcogenides. It can be seen from the figure that Sn atoms and S atoms form a triangle-like node, and the nodes are connected to each other through S atoms to form a layered structure, and the layers are stacked to form a negatively charged frame structure. Ammonium ions exist in the pores of (NH ₄ ) ₂ [Sn ₃ S ₇ ], and play a role in balancing charges.

The obtained two-dimensional chalcogenides were subjected to a thermogravimetric test (TG). The TG test was carried out in a nitrogen atmosphere. The temperature range of the test was 30°C to 900°C, and the heating rate was 10°C/min. The results are shown in Figure 3.

It can be seen from Figure 3 that the 2D chalcogenides are stable at 200 °C under nitrogen atmosphere, which indicates that the material has good thermal stability. The mass reduction between 30°C and 100°C is mainly due to the volatilization of water molecules on the surface of SCU-SnS, and the structure collapses at around 200°C.

Example 2

At 75°C, the two-dimensional chalcogenide material was placed in a high-concentration iodine vapor (16000ppm) atmosphere, and the adsorption capacity of the material to iodine vapor was tested at intervals. The results are shown in Figure 4(a).

It can be seen from Figure 4(a) that as the reaction time continues to increase, the adsorption amount of iodine on the material first increases rapidly and then gradually becomes flat, and finally reaches an equilibrium value, and the adsorption amount reaches 6.8 g/g, which is The inorganic material with the highest adsorption capacity reported so far.

Example 3

The two-dimensional chalcogenide material adsorbed with iodine was left to stand, and the change of the adsorption amount of iodine on the material was tested at intervals, and the obtained results are shown in Fig. 4(b).

It can be seen from Figure 4(b) that the retention rate of iodine on the material is still close to 100% after standing for 6 days on the two-dimensional chalcogenide material adsorbed with iodine. This shows that the two-dimensional chalcogenide material will not desorb iodine due to standing for a long time, and has good adsorption stability.

Example 4

At 25°C and 75°C respectively, the two-dimensional chalcogenide material was placed in an atmosphere with a concentration of 400ppm iodine vapor (close to the concentration of iodine vapor in the process of spent fuel reprocessing), and the equilibrium adsorption capacity of the material to iodine vapor was tested, and the obtained The results are shown in Figure 5.

The results show that the material has an iodine vapor adsorption capacity of 2.38g/g at 25°C and a concentration of 400ppm iodine vapor. Under the vapor concentration, the adsorption capacity of iodine vapor reached 2.35g/g.

In summary, the novel two-dimensional chalcogen compound (NH ₄ ) ₂ [Sn ₃ S ₇ ] provided by the present invention has a good absorption effect on iodine vapor, and does not cause iodine desorption due to standing for a long time. It can be applied to the removal of radioactive iodine vapor in the process of spent fuel reprocessing.

The above-mentioned embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention shall be determined by the claims.

Claims (10)

1. The two-dimensional chalcogen compound is characterized in that the two-dimensional chalcogen compound is a crystalline material, the chemical formula is (NH ₄ ) ₂ [Sn ₃ S ₇ ], and the unit cell parameters are:

   

   α=β=90°, γ=120°, the space group is

   
2. The preparation method of the two-dimensional chalcogen compound according to claim 1 is characterized in that it comprises the following steps: at 150°C to 180°C, reacting the tin source and sulfur element in diethylenetriamine to obtain the obtained The two-dimensional chalcogen compound; wherein, the molar ratio of the tin source to the sulfur element is 1:1-5.
3. The method for preparing two-dimensional chalcogenides according to claim 2, wherein the reaction is carried out in a sealed environment.
4. The method for preparing two-dimensional chalcogenides according to claim 2, wherein the tin source is tin powder or tin tetrachloride.
5. The method for preparing two-dimensional chalcogenides according to claim 2, wherein the sulfur element is sublimed sulfur.
6. The method for preparing two-dimensional chalcogenides according to claim 2, wherein the molar ratio of the tin source to the sulfur element is 3:7.
7. The method for preparing two-dimensional chalcogenides according to claim 2, characterized in that the reaction time is 3-7 days.
8. The application of the two-dimensional chalcogen compound described in claim 1 in the adsorption of iodine vapor.
9. The application according to claim 8, characterized in that the iodine vapor is radioactive iodine vapor.
10. The application according to claim 8, characterized in that, at 25°C and 400ppm iodine vapor concentration, the two-dimensional chalcogen compound has an adsorption capacity of 2.38g/g for iodine vapor, and at 75°C and 400ppm Under the concentration of iodine vapor, the adsorption capacity of iodine vapor reached 2.35g/g.

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