CN115403042A - Hierarchical porous carbon material for efficiently capturing iodine and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of environmental pollution treatment, and provides a graded porous carbon material for efficiently capturing iodine and a preparation method and application thereof, aniline, phytic acid and an oxidant are mixed in proportion, polymerization reaction is carried out for 0.5-24 h at 25-80 ℃, and a product is dried to obtain an intermediate 1; carbonizing the intermediate 1 at 300-900 ℃ for 0.5-10h to obtain an intermediate 2; soaking the intermediate 2 in 0.1-10M alkaline solution, drying, and activating at 800 ℃ in a non-oxidizing atmosphere to obtain a graded porous carbon material for efficiently capturing iodine; according to the invention, the phytic acid is used for carrying out in-situ doping on polyaniline, and the porous carbon material formed after carbonization and activation has the characteristics of high specific surface area and hierarchical porosity, is high in iodine capture efficiency, and shows extremely high adsorption activity and wide application range of the porous carbon material. The application range is wide and the using steps are simple; the preparation method has simple and easy operation process, low process cost and wide application range, and can realize industrial production.

Description

A hierarchical porous carbon material for efficiently capturing iodine and its preparation method and application

technical field

The invention belongs to the technical field of environmental pollution control, and in particular relates to a hierarchical porous carbon material for efficiently capturing iodine, a preparation method and application thereof.

Background technique

As one of the most common radionuclides, radioactive iodine has attracted much attention due to its persistent damage from its radioactive nature and its availability from spent fuel reprocessing and nuclear leaks. The untold suffering of the Chernobyl and Fukushima disasters still hurts thousands of people today. In addition, many chemical companies and pharmaceutical companies are facing the problem of iodine wastewater treatment. Therefore, exploring effective iodine capture materials has important theoretical significance and practical value.

Among the existing iodine capture materials, silver-exchanged zeolites, silver-loaded aerogels, and metal-organic frameworks are favored for their good iodine capture effects. However, the cost of silver-based capture materials is high, and metal-organic framework materials cannot Unstable, which limits their application to some extent. Recently, porous organic polymers such as porous aromatic frameworks, porous organic frameworks, porous hydrophenazine frameworks, conjugated microporous polymers, covalent organic frameworks, covalent triazine frameworks, and hypercrosslinked polymers have been widely used to capture radioactivity. However, the preparation of these porous organic polymers requires complex and expensive precursors, tedious preparation steps, and toxic organic solvents.

Porous carbon material is a traditional adsorption material. Due to its large surface area, large capacity, and good thermal stability, it is not only frequently used in the treatment of organic wastewater and heavy metal wastewater, but also increasingly used in the treatment of iodine-containing wastewater. Porous carbon materials can be produced by pyrolysis or carbonization of various biomasses and porous polymers. However, these porous materials have limited ability to trap iodine in aqueous solution. Therefore, it is of great scientific significance and application value to explore the preparation of green porous carbon materials that are environmentally friendly and have excellent effects.

Contents of the invention

The present invention aims at the above-mentioned technical problems, and aims to provide a hierarchical porous carbon material for efficiently capturing iodine and its preparation method and application. The hierarchical porous carbon material prepared by the method has high iodine capture efficiency, a wide range of applications and simple steps of use; at the same time The preparation method has simple and easy operation process, low process cost, wide application range and can realize industrialized production.

In order to achieve the above object, the technical scheme adopted in the present invention is: a preparation method of a hierarchical porous carbon material that efficiently captures iodine, mixing aniline, phytic acid and an oxidizing agent in proportion, and performing a polymerization reaction. The polymerization reaction temperature is 25-80°C. The polymerization reaction time is 0.5-24 h, and the product is dried to obtain intermediate 1; intermediate 1 is carbonized at a high temperature of 300-900 ° C for 0.5-10 h to obtain intermediate 2; intermediate 2 is soaked in alkaline solution and dried, Then activate under a non-oxidizing atmosphere to obtain a hierarchical porous carbon material that efficiently captures iodine; wherein: the molar ratio of oxidant to aniline is 0.01:1-4:1, and the molar ratio of phytic acid to aniline is 0.01:1-1:1, The concentration of the alkaline solution is 0.1-10M; the soaking time of the intermediate 2 in the alkaline solution is ≤24 h, the activation temperature is 300-1000° C., and the activation time is 0.5-10 h.

Described oxidizing agent is persulfate or peroxide, and persulfate is any one in ammonium persulfate, sodium persulfate, potassium persulfate, manganese persulfate, potassium hydrogen persulfate or potassium peroxymonosulfonate. The oxide is hydrogen peroxide or peracetic acid; the alkaline solution is any one of metal hydroxide solution, metal peroxide solution or metal carbonate solution.

Further, the persulfate is ammonium persulfate; the alkaline solution is potassium hydroxide solution.

The molar ratio of oxidant to aniline is 0.75:1; the molar ratio of phytic acid to aniline is 0.4:1; the concentration of alkaline solution is 1M.

Further, the carbonization temperature is 400° C.; the carbonization time is 4 hours; the soaking time of the intermediate 2 in alkali solution is 6 hours; the activation temperature is 800° C.; the activation time is 1 hour.

The carbonization atmosphere is any one of nitrogen atmosphere, hydrogen atmosphere, helium atmosphere or argon atmosphere. Preferably, the carbonization atmosphere is a nitrogen atmosphere.

A hierarchical porous carbon material capable of efficiently trapping iodine prepared by any one of the preparation methods.

Utilizing the application of the hierarchical porous carbon material for efficiently capturing iodine in removing iodine in wastewater, the wastewater is iodine-containing wastewater, the initial pH value is 3-9, and the concentration of molecular iodine in iodine-containing wastewater is 1-500 mg /L, graded porous carbon material is added during the treatment process, the usage amount of graded porous carbon material is 0.01-5 g/L, and the wastewater treatment time is 0.1-24 h.

The initial pH value of the iodine-containing wastewater is 3-7, the concentration of molecular iodine in the iodine-containing wastewater is 100-500 mg/L, and the usage amount of the hierarchical porous carbon material is 0.1-0.5 g/L; the wastewater treatment time is 0.5 -2 h.

Wastewater includes iodine-containing wastewater, organic wastewater, heavy metal wastewater, and other domestic and industrial wastewater suitable for activated carbon treatment.

Adding a hierarchical porous carbon material that efficiently captures iodine during the treatment process is very simple. The hierarchical porous carbon material that efficiently captures iodine prepared by the present invention has a very high removal effect on iodine-containing wastewater. Under the condition of initial pH = 7, 1 h The internal removal rate can reach more than 95%.

In the present invention, phytic acid is used as a dopant for polyaniline, a precursor of porous carbon. This is because in the synthesis of polyaniline, the pH value of the system must be acidic. Although hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid can be used to prepare polyaniline theoretically, the structure of polyaniline formed by these inorganic acids is relatively tight, and it is more compact than The surface area is very small, and the specific surface area, pore volume, and pore size distribution of the porous carbon formed after carbonization and activation are not ideal.

Phytic acid is a high molecular organic acid. Its aqueous solution can not only provide a lower pH value, but also act as a cross-linking agent to link aniline molecules to form polymer hydrogels. In the process of carbonization and alkali activation, most of the polyaniline skeleton and doped phytic acid are eroded to form a large number of pores. The specific surface area of this high molecular polymer after carbonization and activation exceeds 2300 m ² /g, and the pore size is distributed in a hierarchical porous manner. , containing a large number of micropores, mesopores and mesopores at the same time, so it has a good capture ability for elemental iodine in aqueous solution. This kind of polymer structure hydrogel is formed in the precursor stage, and the nitrogen-containing functional groups and phosphorus-containing functional groups on the polymer backbone are decomposed during carbonization and activation to generate a large number of hierarchical porous structures and apply it to the treatment of iodine-containing wastewater. It has certain innovation and application potential.

Compared with the prior art, the beneficial effect of the present invention is reflected in that the hierarchical porous carbon material that efficiently traps iodine is used to replace silver-exchanged zeolite, silver-loaded airgel, and porous organic polymer, which reduces the cost of wastewater treatment and reduces the need for Secondary pollution of the environment; the preparation method is simple and easy for industrialized production; the method can be used for organic wastewater and heavy metal wastewater treatment, and has a wide range of applications; the reaction system can react at room temperature, the device is simple, low in cost and environmentally friendly, and has industrialization application prospects.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required in the embodiments of the present invention. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those skilled in the art can also obtain other drawings based on these drawings without any creative effort.

Figure 1 is the precursor (a-b) prepared in Example 1, the scanning electron microscope images (c-d) and the element distribution energy spectrum (e-h) of the hierarchical porous carbon material;

Figure 2 is the _N2 adsorption/desorption isotherm (a) and pore size distribution diagram (b) of the hierarchical porous carbon material prepared in Example 1 and commercially available activated carbon;

Figure 3 is the X-ray photoelectron spectrum (a) and high-resolution C 1 s spectrum (b) of the hierarchical porous carbon material and intermediates prepared in Example 1;

Fig. 4 is the Raman spectrogram of the hierarchical porous carbon material prepared in Example 1;

Figure 5 is the X-ray photoelectron spectrum (a) and the high-resolution I 3 d spectrum (b) of the hierarchical porous carbon material prepared in Example 1 before and after iodine adsorption;

Fig. 6 is the Raman spectrogram of the hierarchical porous carbon material prepared in Example 1 before and after iodine adsorption and after ethanol washing;

Fig. 7 is the effect diagram of the removal of iodine-containing wastewater by the hierarchical porous carbon material prepared in Example 1 and other inorganic porous materials;

Fig. 8 is the effect diagram of the removal of different concentrations of iodine-containing wastewater by the hierarchical porous carbon material prepared in Example 1;

Fig. 9 is the effect diagram of the removal of iodine-containing wastewater by hierarchical porous carbon materials prepared under different molar ratios of oxidant and aniline;

Fig. 10 is the effect diagram of the removal of iodine-containing wastewater by the hierarchical porous carbon material prepared by phytic acid and aniline under different molar ratios;

Fig. 11 is the removal effect diagram of iodine-containing wastewater by the iodine capture material prepared during different polymerization temperatures;

Fig. 12 is the removal effect diagram of iodine-containing wastewater by the iodine capture material prepared during different polymerization times;

Figure 13 shows the removal effect of iodine-containing wastewater by hierarchical porous carbon materials prepared under different carbonization temperatures;

Fig. 14 is the effect diagram of the removal of iodine-containing wastewater by hierarchical porous carbon materials prepared after activation by different alkali concentrations;

FIG. 15 is a graph showing the trapping effect of gaseous iodine by the hierarchical porous carbon material prepared in Example 1. FIG.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than All the embodiments; based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts all belong to the protection scope of 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 art to which this invention belongs, and the disclosures cited herein and the materials cited by them are hereby incorporated by reference.

Equivalents to the specific embodiments described which are recognized by those skilled in the art by routine experimentation are intended to be incorporated herein.

The experimental methods in the following examples are conventional methods unless otherwise specified. The instruments and equipment used in the following examples, unless otherwise specified, are routine laboratory instruments and equipment; the experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

1. Preparation of hierarchical porous carbon materials for efficient iodine capture: According to the data in Table 1, 0.916 mL of aniline (0.01 mol), 1.712 g of ammonium persulfate (0.0075 mol), 3.687 mL of 50% phytic acid (0.004 mol) and 6 mL of Ionized water was mixed quickly in an ice-water bath and allowed to stand at room temperature for polymerization. In order to remove excess acid and by-products, the product was washed in ultrapure water and then filtered and dried to obtain intermediate 1. The intermediate 1 was carbonized in a nitrogen atmosphere at 400° C. using a tube furnace to obtain an intermediate 2 . The intermediate 2 was soaked in 2 mL of 4 M KOH, dried and placed in a tube furnace for activation at 800°C in a nitrogen atmosphere for 1 hour. After cooling, the sample was washed repeatedly with deionized water until the pH value reached 7. After filtration and drying, a hierarchical porous carbon material with high efficiency for trapping iodine was obtained.

Table 1 Preparation test parameters of hierarchical porous carbon materials

2. Characterization of Hierarchical Porous Carbon Materials for Efficient Iodine Capture:

1. Surface morphology of hierarchical porous carbon materials with high efficiency of iodine capture: The hierarchical porous carbon materials with high efficiency of iodine capture are obtained by carbonization and activation of polyaniline precursor doped with phytic acid. From the scanning electron microscope (SEM) photos of the precursor obtained in the preparation process of Example 1, it can be seen that the newly prepared precursor is in the shape of nanorods with a length of about 150 nm, and there are no obvious micropores in the rods (Figure 1 a-b) . After carbonization and activation processes, the resulting hierarchical porous carbon exhibits a loose nanostructure (Fig. 1c). In addition to the formation of a large number of large pores in the interstices of the porous carbon, many small pores were also generated on the rod-like framework due to the erosion of the polymer network (Fig. 1d). Further, through the energy spectrum distribution diagram of the hierarchical porous carbon material with high efficiency of iodine capture, it can also be observed that the nitrogen (N) and phosphorus (P) elements on the precursor disappear after being prepared into porous carbon (Fig. 1 e-h), which not only The successful synthesis of inorganic porous carbon materials was demonstrated, and the functional groups of N and P on the precursor polymer were reacted during the preparation of porous carbon to form a 3D porous network.

2. Pore structure of the hierarchical porous carbon material for efficiently capturing iodine: the surface area and pore structure of the hierarchical porous carbon material for efficiently capturing iodine prepared in Example 1 were obtained by nitrogen adsorption-desorption. As shown in Fig. 2a, the hierarchically porous carbon material with high efficiency for iodine capture exhibits sharp nitrogen uptake at low relative pressure, indicating the presence of a microporous structure, which is similar to that of commercially available activated carbons. However, the isotherm of the hierarchical porous carbon material with high efficiency for iodine capture continues to rise after a gentle process at the relative pressure P / P ₀ = 0.8-1.0, and forms a hysteresis loop with the shape of H1, which is similar to that of the commercially available activated carbon different, showing the presence of mesopores and macropores in porous carbons. Further calculated according to the adsorption isotherm with P / P ₀ close to 1.00, the BET surface area of the hierarchical porous carbon material with high efficiency for iodine capture is 2303 m ² /g, and the total pore volume is 1.35 cm ³ /g, which is 1635 m ² higher than that of the commercially available activated carbon /g surface area and 0.89 cm ³ /g pore volume. On the other hand, the pore size distribution confirms that the pore sizes of hierarchic porous carbon materials with high efficiency for iodine capture span the three dimensions of micropores, mesopores and macropores (Fig. 2b), and account for 28.9%, 45.2% and 25.9%, respectively, Only microporous structure.

3. Chemical composition of the hierarchical porous carbon material for efficiently capturing iodine: the chemical composition of the hierarchical porous carbon material for efficiently capturing iodine prepared in Example 1 was identified by X-ray photoelectron spectroscopy (XPS). Through XPS full-spectrum analysis, it was found that in addition to the peaks of C 1 s and O 1 s , the peaks of N 1 s and P 2 p on the precursor intermediate 1 almost completely disappeared (Fig. 3a), which is consistent with the hierarchical porous The results of the energy spectrum surface distribution of elements on the carbon material are consistent, indicating that the N-containing groups on the precursor polyaniline skeleton and the P-containing groups on the phytic acid are corroded during the preparation of porous carbon. Further, through the C 1 s high-resolution spectrum of the hierarchical porous carbon material that efficiently captures iodine, it is found that it does not present a symmetrical peak shape. in CC, CO and C=O structures (Fig. 3b).

The above SEM and XPS results show that the hierarchical porous carbon material that efficiently captures iodine is made to form an inorganic porous carbon material with carbon as the main element. The structure of the hierarchical porous carbon material with high efficiency of iodine capture prepared in Example 1 was further characterized by Raman technique, and two very strong absorption bands were found (Fig. 4). The absorption band located at 1590 cm ⁻¹ belongs to the G band, representing sp ^carbon structures such as graphite. Another absorption band located at 1345 cm ⁻¹ belongs to the D band, corresponding to the disordered or defect-structured graphite. It can be seen that the intensity ratio of the D band to the G band can indicate the defects of the carbon material, and the hierarchical porous carbon material prepared in Example 1 with high efficiency for trapping iodine is calculated to be 0.91, indicating that the porous carbon has disordered graphite characteristics.

4. Treatment mechanism of iodine-containing wastewater: Since molecular iodine (I ₂ ) and iodide ions (I ⁻ ) coexist in the water phase, the iodine in iodine-containing wastewater may be captured as multiple iodine ions (I ₃ ⁻ and I ₅ ⁻ ) form exists. The hierarchical porous carbon after iodine capture was characterized by XPS, and obvious double bands of I 3 d structure were found on the spectrum, representing I 3 d _3/2 and I 3 d _5/2 respectively (Fig. 5a). Analyzing the high-resolution spectra of these two bands, it is found that they can be divided into two doublets, of which the doublets at 630.2 eV and 618.8 eV are completely consistent with I ₂ , while the other doublet is located at a higher The position of the binding energy (Fig. 5b), which is not consistent with I ₃ ⁻ and I ₅ ⁻ that should be located at the lower binding energy position, indicating that the trapped iodine does not exist in the form of I ₃ ⁻ and I ₅ ⁻ , but It mainly exists in the form of I ₂ , and due to the strong chemical adsorption between I ₂ and the functional groups on the hierarchical porous carbon material with high efficiency for trapping iodine, the I 3 d binding energy position of part of I ₂ moves to a higher direction. The hierarchical porous carbon Raman spectrum of highly efficient iodine capture after iodine capture supports this judgment, because in addition to the D peak at 1345 cm ⁻¹ and the G peak at 1590 cm ⁻¹ in the Raman spectrum, the No characteristic peaks belonging to I ₃ ⁻ and I ₅ ⁻ were observed at ⁻¹ and 164 cm ⁻¹ (Fig. 6). It can further be seen from the Raman spectrum that after washing the iodine captured on the hierarchical porous carbon material with high efficiency of iodine capture with ethanol, the shape of the spectrum does not change significantly. The capture of iodine is mainly an adsorption process, and the captured iodine is mainly in the form of I ₂ .

Since the specific surface area of adsorption-based inorganic porous materials has a crucial impact on the adsorption performance, the role of phytic acid in the formation of hierarchically porous carbon materials for efficient iodine capture was investigated. In the traditional synthesis of polyaniline, the pH of the system must be acidic, so in theory hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid can all be used to prepare polyaniline. However, the polyaniline formed by these inorganic acids has a relatively compact structure and a small specific surface area. Phytic acid is a high molecular organic acid. Its aqueous solution can not only provide a lower pH value, but also act as a cross-linking agent to link aniline molecules to form polymer hydrogels. During carbonization and alkali activation, the polyaniline skeleton and doped phytic acid were mostly eroded to form a large number of pores, which decreased from 12.25% and 9.16% of N and P elements on the precursor to 2.30% and 0.79% on the porous carbon, respectively. % can be seen. Therefore, the specific surface area of the high molecular polymer precursor after carbonization and activation exceeds 2300 m ² /g. Such a large specific surface area even exceeds that of commercially available activated carbons with high specific surface areas, and thus has better iodine capture ability than commercially available activated carbons.

The average pore diameter of the hierarchically porous carbon material that efficiently captures iodine prepared in Example 1 is 2.3 nm, which is close to the 2.2 nm average pore diameter of commercially available activated carbon. Since the two materials have similar average pore diameters, they are both suitable for the adsorption of iodine molecules.

In order to further judge the effect of pore size on iodine adsorption, several inorganic porous materials with different pore sizes were used for experiments. The commercially available activated carbon is activated carbon for supercapacitors, produced by Nanjing Xianfeng Nano Material Technology Co., Ltd., item number: 100566, SSA: 1800 m ² /g, pore size: 2.0-2.2 nm; carbon nanotubes, produced by Nanjing Xianfeng Nano Material Technology Co., Ltd. Produced by the company, with a purity of 95%, among which the product number of the pore diameter is 10-20 nm: 100252, the product number of the pore diameter greater than 50 nm: 100288; 13X molecular sieve, produced by Nanjing Xianfeng Nano Material Technology Co., Ltd., the product number: 102491, the pore size: ~0.9 nm; ZSM-5, produced by Nanjing Xianfeng Nano Material Technology Co., Ltd., article number: 102272, pore size: ~0.58nm.

It can be seen from Figure 7 that, in addition to commercially available activated carbon, other porous materials with larger pore sizes such as carbon nanotubes (with pore sizes of 10-20 nm and >50 nm, respectively), and porous materials with smaller pore sizes such as 13X molecular sieves (0.9 nm) and ZSM-5 molecular sieve (0.58 nm) both have lower iodine capture. This indicates that if the pore size of the porous material is too close to the kinetic diameter (0.54nm) of the iodine molecule, it may be difficult for the iodine molecule to migrate in the pores, and the too large pore size cannot effectively adsorb the iodine molecule. The hierarchical porous carbon material that efficiently captures iodine prepared in Example 1 of the present invention has abundant micropores and appropriate mesopore and macropore structure, and its hierarchical porous structure is conducive to the adsorption and migration of iodine molecules in the pores, so that in aqueous solution A good iodine capture effect was obtained.

3. Performance test of hierarchical porous carbon materials that efficiently capture iodine in iodine-containing wastewater:

The catalytic degradation experiment was carried out in a 150 mL iodine flask. The typical reaction system contained 0.3 g/L of the hierarchical porous carbon material that efficiently captures iodine prepared in Example 1, the initial iodine concentration was 500 mg/L, the solution volume was 100 mL, and pH = 7 . After the reaction solution was sealed, it was placed in a constant temperature shaker, and the reaction was shaken at a speed of 160 rpm at 25°C. After a certain time interval, the supernatant was taken out and filtered through a 0.22 μm membrane to remove porous carbon, and the iodine element (I ₂ ) and iodide ion (I ⁻ ) concentrations in the filtrate were simultaneously measured with a UV-Vis spectrophotometer.

Example of iodine-containing wastewater treatment 1. Effects of different initial iodine concentrations: When the initial iodine concentration in wastewater increases from 100 mg/L to 500 mg/L, the removal rate can reach more than 82% (Figure 8). Especially when the concentration was between 200-500 mg/L, the removal rate reached more than 90%, and the removal curves almost completely overlapped. It can also be seen from Figure 8 that 89% of the removal can be completed within 5 minutes, indicating that the iodine removal proceeds at a very fast rate, which is very beneficial for the rapid completion of iodine capture.

Iodine-containing wastewater treatment example 2. The influence of oxidant concentration during precursor preparation: During the polymerization of aniline, the polymerization of each monomer is accompanied by the transfer of two electrons and two protons. This type of polymerization requires large amounts of oxidizing agents. The oxidant is consumed as each monomer combines with the other and reacts, so the molar concentration of the oxidant should be close to that of the monomer. It can be seen from Figure 9 that the molar ratio of oxidant to aniline in the range of 1:0.75-1:1.25 can achieve higher removal efficiency. But too high oxidant content can not increase the yield of polyaniline, it will only convert part of polyaniline from reduced state to oxidized state, however any form of polyaniline will be carbonized eventually, so too much oxidant has no enhanced effect on iodine removal .

Iodine-containing wastewater treatment example 3. The influence of phytic acid concentration during precursor preparation: Phytic acid is a high molecular organic acid. Its aqueous solution can not only provide a lower pH value, but also act as a cross-linking agent to connect aniline molecules to form polymer hydrogel. During carbonization and alkali activation, most of the polyaniline skeleton and doped phytic acid were eroded to form a large number of pores. Since phytic acid can only be doped at specific positions on polyaniline, when the molar ratio of phytic acid to aniline is lower than 0.4: 1, the amount of phytic acid is completely sufficient, too much phytic acid cannot increase the polymer network structure, and is harmful to the formation of polyaniline. Porous carbon was not beneficial and thus did not further improve iodine capture efficiency (Fig. 10).

Iodine-containing wastewater treatment example 4. Effect of polymerization temperature: Hierarchical porous carbon is carbonized and activated by the precursor phytic acid doped polyaniline. Aniline undergoes oxidative polymerization under the action of an oxidant, and aniline monomer molecules are connected to each other in the solution to form polymerization. Therefore, the degree of this chemical reaction and the polymer properties are closely related to the polymerization temperature. When the polymerization temperature rises from room temperature (25°C) to 60°C or even 80°C, the iodine capture efficiency of the obtained hierarchical porous carbon does not change much (Fig. It can be polymerized and does not require a higher polymerization temperature. From the perspective of saving energy, it is more appropriate to choose room temperature as the precursor polymer preparation temperature of hierarchical porous carbon.

Example 5 of the treatment of iodine-containing wastewater, the influence of polymerization time: when the hierarchical porous carbon precursor phytic acid doped polyaniline is polymerized, the aniline monomer molecules are connected to each other in the solution to form a polymer, and the phytic acid molecules are formed at the amino site. Doping eventually forms a hydrogel polymer, which requires a certain amount of polymerization time. In order to ensure that the polymerization reaction is complete, the formed polymer is completely shaped and aged, and the reaction start time is preset to 2 h. Further prolonging the reaction time, the trapping efficiency of iodine by the hierarchical porous carbon formed by carbonization and activation of the obtained polymer increased, and when the polymerization reaction time exceeded 6 h, the trapping of iodine by the obtained polymer no longer increased significantly (Figure 12) . This shows that too long polymerization time does not significantly change the structure of the polymer, and the formed polymer has no significant impact on the subsequent carbonization and activation processes.

Example 6 of iodine-containing wastewater treatment. Effect of carbonization temperature: As the carbonization temperature increases from 300°C to 900°C, the amount of iodine captured first increases and then gradually decreases (Figure 13). This is because a lower carbonization temperature helps to maintain the integrity of the polymer network structure, contributes to the formation of a graphitized carbon structure, and facilitates iodine capture, while a high temperature leads to the complete destruction of phytic acid and graphitic carbon lattice. Therefore, 400°C is the most suitable carbonization temperature.

Example 7 of the treatment of iodine-containing wastewater. The effect of alkali concentration on activation: In the absence of alkali activation, the obtained sample only obtained 36.3% iodine capture (Fig. 14), which indicates that the carbonized sample alone did not generate enough pores, and compared with Surface area and pore volume are very small. When activated with 0.1 M and 0.5 M alkali, the iodine capture rates reached 49.4% and 78.1%, respectively, indicating that the alkali began to play a porogenic role. Further, as the alkali concentration increased from 1 M to 7 M, the iodine capture continued to increase, but the magnitude of the increase gradually decreased, and the quality of the final samples was also gradually reduced, which means that too much alkali will completely destroy the carbonized polyaniline. structure, the carbon material skeleton is severely eroded, which is not conducive to the capture of iodine.

4. Performance test of hierarchical porous carbon materials with high efficiency of iodine capture in iodine-containing vapor: Since some iodine usually exists in gaseous form after the leakage of radioactive iodine, the capture experiment of gaseous iodine was carried out. The capture experiment was carried out at 80 °C and ambient pressure. Specifically, the porous carbon material (0.03 g) and solid iodine (1 g) were placed in a 20 mL weighing bottle, and then placed in a blast drying oven with the cap closed. The air drying oven is heated up to 80°C, and the weighing bottle is taken out of the air blast drying oven at regular intervals, and the bottle cap is opened after it cools down, and the porous carbon material is taken out for weighing, and then put back into the air blast drying oven to continue Experiment so that the amount of iodine captured can be obtained by weight increments.

As can be seen from Figure 15, the hierarchical porous carbon material with high efficiency of iodine capture prepared in Example 1 has a good trapping effect on vapor iodine within 2 hours, and the trapping rate and trapping amount all exceed commercially available activated carbon, indicating that the example 1 The prepared hierarchical porous carbon material with high efficiency for iodine capture is a very promising gaseous iodine capture material. From the above performance test research, it can be seen that the hierarchic porous carbon material with high efficiency for capturing iodine involved in the present invention has a good capturing effect on both iodine and vapor iodine in aqueous solution, which proves that the technology involved in the present invention has a relatively wide application range.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (9)

1. A preparation method of a hierarchical porous carbon material for efficiently capturing iodine is characterized by comprising the following steps: mixing aniline, phytic acid and an oxidant in proportion, carrying out polymerization reaction at the temperature of 25-80 ℃ for 0.5-24 h, and drying the product to obtain an intermediate 1; carbonizing the intermediate 1 at 300-900 ℃ for 0.5-10h to obtain an intermediate 2; soaking and drying the intermediate 2 in an alkaline solution, and then activating in a non-oxidizing atmosphere to obtain a hierarchical porous carbon material; wherein: the molar ratio of the oxidant to the aniline is 0.01-4, the molar ratio of the phytic acid to the aniline is 0.01-1; the intermediate 2 is soaked in alkaline solution for 24 h or less, the activation temperature is 300-1000 ℃, and the activation time is 0.5-10h.

2. The method according to claim 1, wherein the step of preparing the graded porous carbon material for capturing iodine with high efficiency comprises: the oxidant is persulfate or peroxide, the persulfate is any one of ammonium persulfate, sodium persulfate, potassium persulfate, manganese persulfate, potassium hydrogen persulfate or potassium peroxymonosulfonate, and the peroxide is hydrogen peroxide or peroxyacetic acid; the alkaline solution is any one of a metal hydroxide solution, a metal peroxide solution or a metal carbonate solution; the carbonization atmosphere is any one of nitrogen atmosphere, hydrogen atmosphere, helium atmosphere or argon atmosphere.

3. The method according to claim 2, wherein the step of preparing the graded porous carbon material for capturing iodine with high efficiency comprises: the persulfate is ammonium persulfate; the alkaline solution is a potassium hydroxide solution; the carbonization atmosphere is a nitrogen atmosphere.

4. The method according to claim 1, wherein the step of preparing the graded porous carbon material for capturing iodine with high efficiency comprises: the molar ratio of oxidant to aniline is 0.75; the molar ratio of the phytic acid to the aniline is 0.4; the concentration of the alkaline solution was 1M.

5. The method according to claim 1, wherein the step of preparing the graded porous carbon material for capturing iodine with high efficiency comprises: the carbonization temperature is 400 ℃; the carbonization time is 4h; the intermediate 2 is soaked in alkali liquor for 6 hours; the activation temperature is 800 ℃; the activation time was 1 h.

6. The hierarchical porous carbon material for capturing iodine with high efficiency, which is prepared by the preparation method according to any one of claims 1 to 5.

7. The use of the hierarchical porous carbon material for efficiently capturing iodine according to claim 6 for removing iodine in wastewater, characterized in that: the initial pH value of the wastewater is 3-9, the concentration of molecular iodine in the wastewater is 1-500 mg/L, a graded porous carbon material is added in the treatment process, the using amount of the graded porous carbon material is 0.01-5 g/L, and the wastewater treatment time is 0.1-24 h.

8. Use according to claim 7, characterized in that: the initial pH value of the iodine-containing wastewater is 3-7, the concentration of molecular iodine in the iodine-containing wastewater is 100-500 mg/L, and the using amount of the hierarchical porous carbon material is 0.1-0.5 g/L; the time for wastewater treatment is 0.5-2 h; the wastewater comprises iodine-containing wastewater, organic wastewater, heavy metal wastewater and other domestic wastewater and industrial wastewater suitable for activated carbon treatment.

9. Use of the hierarchical porous carbon material for efficiently capturing iodine according to claim 6 for removing iodine from iodine-containing vapor.

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