CAx-KOH-coated PANI magnetic porous adsorbent as well as preparation method and application thereof

Abstract

The invention discloses a CAx-KOH-coated PANI magnetic porous adsorbent as well as a preparation method and application thereof, relates to the field of electric harmful gas treatment, and aims at solving the problem that an efficient, high-capacity and high-selectivity adsorbent is lacked for SF6 and decomposition products thereof. Comprising the following steps: step 1, weighing citric acid and potassium hydroxide, dissolving the citric acid and potassium hydroxide in deionized water, mixing, heating and evaporating to prepare gel, and calcining and carbonizing the gel to obtain a CAx-KOH carbon material; 2, citric acid is dissolved in water to prepare an acid solution, aniline is added into the acid solution to be dissolved, magnetic powder is added, finally ammonium persulfate is added for a polymerization reaction, a reaction product is washed, dried and ground, and magnetic PANI is obtained; 3, the waste composite insulator rubber is subjected to liquid nitrogen freezing, ground into powder and calcined, and insulator porous rubber powder is obtained; and step 4, dispersing the CAx-KOH carbon material, the magnetic PANI and the insulator porous rubber powder in deionized water, stirring and mixing, drying, calcining, and grinding to obtain the CAx-KOH-coated PANI magnetic porous adsorbent.

Description

Technical Field

[0001] This invention relates to the field of power industry hazardous gas treatment technology, and more specifically, to a CAx-KOH@PANI magnetic porous adsorbent, its preparation method, and its application. Background Technology

[0002] Sulfur hexafluoride (SF6) is widely used in high-voltage circuit breakers, GIS equipment, and semiconductor etching processes due to its excellent insulation and arc-quenching properties. However, SF6 has a strong greenhouse effect, with a global warming potential (GWP) 22,000-23,900 times that of CO2, and it can remain stable in the atmosphere for over 3,200 years. During the operation of power equipment, SF6 decomposes under the influence of electric arcs, producing highly toxic substances (such as SOF2, SO2F2, and HF). These decomposition products not only corrode equipment but also endanger personnel safety. Therefore, developing efficient adsorbents to achieve the recovery, purification, and control of SF6 decomposition products has become a major demand in the power environmental protection field.

[0003] Conventional adsorbents such as activated alumina, silica gel, activated carbon, and molecular sieves, while possessing certain adsorption capacities, suffer from weak adsorption of SF6 and its decomposition products, inactivation under high humidity, poor selectivity, and the need for frequent regeneration, making them unsuitable for the efficient recovery and separation of SF6 in practical industrial applications. Novel adsorbents, such as metal-modified molecular sieves, metal-organic frameworks, and porous aromatic frameworks, offer alternatives. Metal-modified molecular sieves exhibit some adsorption capacity for SF6, and the introduction of K... + Ca 2+ The use of isocations increased the SF6 adsorption capacity to 3.56 mmol / g, with an SF6 / N2 selectivity of 6002. However, its preparation process requires multiple ion exchanges and high-temperature activation, making it complex and costly. While metal-organic frameworks (MOFs) possess high specific surface areas, their poor hydrothermal stability makes them susceptible to structural damage upon contact with HF or water vapor, and their expensive raw materials hinder large-scale production. Porous aromatic frameworks (PAFs) resist HF corrosion through rigid C-C bonds and can capture SF6 at 10 bar, but their synthesis relies on precious metal catalysts, resulting in low mechanical strength and a significant increase in bed pressure drop after packing. Therefore, existing technologies require further improvement and enhancement. Summary of the Invention

[0004] The technical problem to be solved by this invention is:

[0005] Existing technologies lack highly efficient, high-capacity, and selective adsorbents for SF6 and its decomposition products.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] This invention provides a method for preparing a CAx-KOH@PANI magnetic porous adsorbent, comprising the following steps:

[0008] Step 1: Preparation of CAx-KOH carbon material: Weigh citric acid and potassium hydroxide according to the proportion and dissolve them in deionized water. Mix them, heat and evaporate to prepare CAx-KOH gel. Calcine and carbonize the CAx-KOH gel to obtain CAx-KOH carbon material.

[0009] Step 2, Preparation of magnetic PANI: Weigh citric acid and dissolve it in water to prepare an acid solution; add aniline to the acid solution to dissolve, add magnetic powder, and finally add ammonium persulfate to carry out a polymerization reaction. Wash, dry, and grind the reaction product to obtain the magnetic PANI.

[0010] Step 3: Preparation of porous rubber powder for insulators: Waste composite insulator rubber is frozen with liquid nitrogen, the frozen insulator is ground into powder, and calcined to obtain the porous rubber powder for insulators;

[0011] Step 4: Preparation of CAx-KOH@PANI magnetic porous adsorbent: Disperse CAx-KOH carbon material, magnetic PANI and insulator porous rubber powder in deionized water, stir and mix thoroughly, dry, calcine, and grind to obtain the CAx-KOH@PANI magnetic porous adsorbent.

[0012] Furthermore, in step 1, x represents the mass ratio of CA to KOH, and the value of x is 1, 2 or 3.

[0013] Furthermore, in step 2, the mass ratio of aniline to magnetic powder is 4 to 6:2.

[0014] Furthermore, the calcination temperature in step 3 is 400–600°C.

[0015] Furthermore, the drying conditions in step 2 are drying at 60°C for 2 hours.

[0016] Furthermore, in step 4, the mass ratio of CAx-KOH, magnetic PANI, and porous insulator rubber is 3-5:3-5:7-9.

[0017] Furthermore, in step 4, the calcination temperature is no more than 400℃ and the calcination time is 4 hours.

[0018] The present invention also provides a CAx-KOH@PANI magnetic porous adsorbent prepared by any of the methods described in the above technical solutions.

[0019] The present invention also provides an application of the CAx-KOH@PANI magnetic porous adsorbent described in the above technical solution in the preparation of adsorbents for SF6 adsorption.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention creates a porous structure in the adsorbent by adding porous rubber powder to the insulator, which significantly increases the specific surface area of ​​the material and provides more adsorption sites. By doping with CAx-KOH and magnetic PANI, the π electron cloud of the benzene ring and the amine group (-NH-) can generate a dipole interaction with the fluorine atom of SF6, selectively capturing SF6 through the molecular sieve effect, which greatly improves the adsorption capacity and selectivity of the adsorbent.

[0022] The CAx-KOH@PANI magnetic porous adsorbent of this invention exhibits significant advantages in adsorption performance, stability, recyclability, and environmental friendliness. It also has a wide range of raw material sources, is inexpensive, can realize the resource utilization of waste composite insulator rubber, and has a simple and safe preparation method. Attached Figure Description

[0023] Figure 1 The infrared spectrum of the CAx-KOH@PANI magnetic porous adsorbent in the embodiments of the present invention is shown below.

[0024] Figure 2 Thermogravimetric curve of the CAx-KOH@PANI magnetic porous adsorbent in the embodiments of the present invention;

[0025] Figure 3 This is an adsorption-desorption curve of the CAx-KOH@PANI magnetic porous adsorbent in the embodiments of the present invention;

[0026] Figure 4 This is a microstructure diagram of the CAx-KOH@PANI magnetic porous adsorbent in an embodiment of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, exemplary embodiments or examples of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described embodiments or examples are merely some, not all, of the embodiments or examples of the present invention. All other embodiments or examples obtained by those skilled in the art based on the embodiments or examples of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0029] In a typical embodiment, the present invention provides a method for preparing a CAx-KOH@PANI magnetic porous adsorbent, comprising the following steps:

[0030] Step 1: Preparation of CAx-KOH carbon material: Weigh citric acid and potassium hydroxide according to the proportion and dissolve them in deionized water. Mix them, heat and evaporate to prepare CAx-KOH gel. Calcine and carbonize the CAx-KOH gel to obtain CAx-KOH carbon material.

[0031] Step 2, Preparation of magnetic PANI: Weigh citric acid and dissolve it in water to prepare an acid solution; add aniline to the acid solution to dissolve, add magnetic powder, and finally add ammonium persulfate to carry out a polymerization reaction. Wash, dry, and grind the reaction product to obtain the magnetic PANI.

[0032] Step 3: Preparation of porous rubber powder for insulators: Waste composite insulator rubber is frozen with liquid nitrogen, the frozen insulator is ground into powder, and calcined to obtain the porous rubber powder for insulators;

[0033] Step 4: Preparation of CAx-KOH@PANI magnetic porous adsorbent: Disperse CAx-KOH carbon material, magnetic PANI and insulator porous rubber powder in deionized water, stir and mix thoroughly, dry, calcine, and grind to obtain the CAx-KOH@PANI magnetic porous adsorbent.

[0034] In a typical embodiment, preferably, in step 1, x represents the mass ratio of CA to KOH, and the value of x is 1, 2, or 3. A three-dimensional network structure is formed. In step 1, the solvent is evaporated by heating, and a porous gel with a three-dimensional network structure is prepared from CAx-KOH. The introduction of KOH provides an alkaline environment and affects the cross-linking process of the gel. + Ions exist as charge-balancing ions in the organic framework, and multiple factors work together to form a structure with abundant micropores.

[0035] In a typical embodiment, preferably, the mass ratio of aniline to magnetic powder in step 2 is 4-6:2. In step 2, an organic acid provides a protonated environment, ammonium persulfate acts as an oxidant to initiate aniline polymerization, and the magnetic powder (Fe3O4) binds to the polyaniline (PANI) chains through coordination bonds, forming a core-shell structure by being coated by PANI, which imparts superparamagnetism to the material, thereby achieving efficient recovery of the adsorbent after use.

[0036] In a typical embodiment, preferably, the calcination temperature in step 3 is 400–600°C. The method of this invention employs a green, solvent-free physical approach, using cryogenic liquid nitrogen pulverization technology to pretreat waste insulator rubber into fine powder. The powder undergoes high-temperature pyrolysis under a controlled atmosphere, where the organic components carbonize to form a porous carbon framework, while the inorganic silicon-oxygen chains are transformed into SiO2 nanoparticles. Together, they construct a composite material with a high specific surface area. The porous structure significantly increases the adsorption sites, making it a potential adsorbent, while simultaneously achieving high-value resource utilization of waste.

[0037] In a typical embodiment, preferably, the drying conditions in step 2 are drying at 60°C for 2 hours.

[0038] In a typical embodiment, preferably, the mass ratio of CAx-KOH, magnetic PANI, and porous insulator rubber in step 4 is 3-5:3-5:7-9.

[0039] In a typical embodiment, preferably, the calcination temperature in step 4 is no more than 400°C, and the calcination time is 4 hours. In step 4, the CAx-KOH precursor, insulator carbon powder, and polyaniline (PANI) are co-impregnated and dispersed, achieving preliminary mixing and self-assembly through intermolecular forces. Subsequently, high-temperature calcination causes thermal transformation of each component: citrate decomposes to generate gas, etching out abundant mesopores; PANI carbonizes to form a nitrogen-doped carbon layer, firmly combining each component together. Finally, together with the original structure of CAx-KOH and insulator carbon, a nitrogen-doped composite material with multi-level pores is formed.

[0040] The beneficial effects of the present invention will be described below with reference to specific embodiments.

[0041] Example 1

[0042] A low-temperature liquid nitrogen-pulverized insulator rubber-doped CAx-KOH@PANI magnetic porous adsorbent and its preparation method include the following steps:

[0043] Step 1: Preparation of CA-KOH carbon material: Weigh 2g of citric acid (CA, C6H8O7) and 2g of potassium hydroxide (KOH) and dissolve them in 100mL of deionized water. Stir magnetically for 20min to obtain a mixed solution. Place the mixed solution in an 80℃ water bath and heat to evaporate for 12h to obtain CA-KOH gel. Place the CA-KOH gel in an atmospheric tube furnace and carbonize it at 600℃ for 1.5h to obtain CA-KOH carbon material.

[0044] Step 2, Preparation of Magnetic PANI: Weigh 10g of organic acid and add it to the reaction vessel. Stir with a stirrer until the acid is completely dissolved. Add 4g of aniline and stir until it is completely dissolved in the acid solution. Then add 2g of magnetic powder and stir thoroughly. Finally, add 142mL of ammonium persulfate aqueous solution (containing 20g of ammonium persulfate) and carry out the polymerization reaction for 25min. After the reaction is completed, filter the reaction product and wash it three times alternately with ethanol and deionized water. Place the washed filter cake in an oven to dry and grind it to obtain magnetic PANI.

[0045] Step 3: Preparation of insulator powder: Take composite insulator rubber, add liquid nitrogen to freeze it, take out the frozen insulator sheet and grind it into powder, then put it into a muffle furnace and fire it at 400℃ for 2 hours. After taking it out, cool it to room temperature to obtain insulator powder.

[0046] Step 4: Preparation of CAx-KOH@PANI magnetic porous adsorbent: Weigh 4g CAx-KOH, 4g magnetic PANI, and 8g insulator powder into a beaker, add an appropriate amount of deionized water to disperse them, and stir at 30℃ for 4 hours. Dry the stirred sample at 100℃ for 2 hours. After drying, perform preliminary grinding, place in a crucible, and calcine using a muffle furnace. Grind the calcined sample again and sieve using a 200-mesh sieve to obtain the CAx-KOH@PANI magnetic porous adsorbent.

[0047] Example 2

[0048] The difference between this embodiment and Embodiment 1 is that in step 2, the preparation of magnetic PANI: 10g of organic acid is weighed and added to the reaction vessel, and stirred with a stirrer to completely dissolve the acid; 5g of aniline is added and stirred until completely dissolved in the acid solution, then 2g of magnetic powder is added and stirred thoroughly, and finally 142mL of ammonium persulfate aqueous solution (containing 20g of ammonium persulfate) is added to carry out the polymerization reaction for 25min. After the reaction is completed, the reaction product is filtered and washed three times alternately with ethanol and deionized water. The washed filter cake is placed in an oven to dry and then ground to obtain magnetic PANI.

[0049] Example 3

[0050] The difference between this embodiment and Example 1 is that in step 2, 10g of organic acid is weighed and added to the reaction vessel, and stirred with a stirrer to completely dissolve the acid; 6g of aniline is added and stirred until completely dissolved in the acid solution; then 2g of magnetic powder is added and stirred thoroughly; finally, 142mL of ammonium persulfate aqueous solution (containing 20g of ammonium persulfate) is added to carry out the polymerization reaction for 25min. After the reaction is completed, the reaction product is filtered and washed three times alternately with ethanol and deionized water. The washed filter cake is placed in an oven to dry and then ground to obtain magnetic PANI.

[0051] Example 4

[0052] The difference between this embodiment and Embodiment 1 is that in step 1, 4g of citric acid (CA, C6H8O7) and 2g of potassium hydroxide (KOH) are weighed and dissolved in 100mL of deionized water, and the mixture is magnetically stirred for 20min to obtain a mixed solution; the mixed solution is placed in a water bath at 80℃ and heated to evaporate for 12h to obtain CA2-KOH gel; the CA2-KOH gel is placed in an atmospheric tube furnace and carbonized at 600℃ for 1.5h to obtain CA2-KOH carbon material.

[0053] Example 5

[0054] The difference between this embodiment and Embodiment 1 is that in step 1, 6g of citric acid (CA, C6H8O7) and 2g of potassium hydroxide (KOH) are weighed and dissolved in 100mL of deionized water, and the mixture is magnetically stirred for 20min to obtain a mixed solution; the mixed solution is placed in a water bath at 80℃ and heated to evaporate for 12h to obtain CA3-KOH gel; the CA3-KOH gel is placed in an atmospheric tube furnace and carbonized at 600℃ for 1.5h to obtain CA3-KOH carbon material.

[0055] Example 6

[0056] The difference between this embodiment and embodiment 5 is that in step 3, 8g of composite insulator rubber is taken, added to liquid nitrogen for freezing, the frozen insulator sheet is taken out and ground into powder, and then placed in a muffle furnace and fired at 500°C for 2 hours. After being taken out and cooled to room temperature, insulator powder is obtained.

[0057] Example 7

[0058] The difference between this embodiment and embodiment 5 is that in step 3, 8g of composite insulator rubber is taken, added to liquid nitrogen for freezing, the frozen insulator sheet is taken out and ground into powder, and then placed in a muffle furnace and fired at 600°C for 2 hours. After being taken out and cooled to room temperature, insulator powder is obtained.

[0059] Infrared spectroscopy was performed on the CA-KOH@PANI magnetic porous adsorbent of Example 1, and the results are as follows: Figure 1 As shown, the adsorbent at 3626 cm⁻¹ -1 There is a distinct absorption peak at 1559 cm⁻¹, corresponding to the stretching vibration of -OH. -1 and 1445cm -1 An absorption peak is observed at 1127 cm⁻¹, corresponding to the stretching vibration of -NO₂. -1 There is an absorption peak at 1559 cm⁻¹, corresponding to the stretching vibration of CO. The silicone rubber / CA adsorbent shows an absorption peak at 1559 cm⁻¹. -1 and 1445cm -1 An absorption peak is observed at 1127 cm⁻¹, corresponding to the stretching vibration of -NO₂. -1There is an absorption peak at 1000 cm⁻¹, corresponding to the stretching vibration of CO. -1 The following shows multiple absorption peaks, corresponding to the stretching vibration of the methylene group (CH2). The silicone rubber adsorbent shows absorption peaks at 3000 cm⁻¹. -1 There is an absorption peak below, corresponding to the stretching vibration of the CH bond. At 1000 cm⁻¹ -1 The following absorption peaks correspond to the stretching vibrations of the Si-O bond.

[0060] Thermogravimetric analysis was performed on the CA-KOH@PANI magnetic porous adsorbent of Example 1, such as... Figure 2 As shown, with increasing temperature, the adsorbent mass changes little between 0°C and approximately 100°C, consisting mainly of evaporation of surface-adsorbed water or other low-boiling-point components. Between 100°C and 600°C, the adsorbent mass continuously decreases, indicating a complex chemical decomposition process in the sample, including the thermal decomposition of organic matter; at 600°C, the silicone rubber / CA@PANI adsorbent mass decreases to approximately 96%.

[0061] The CA-KOH@PANI magnetic porous adsorbent of Example 1 was subjected to BET testing, and the results are as follows: Figure 3 As shown, at low relative pressures (P / P0 < 0.1), the adsorption capacity of the silicone rubber / CA@PANI adsorbent increases slowly. With increasing relative pressure, the adsorption capacity gradually increases, especially when the relative pressure approaches 1, where it increases sharply, indicating a large pore structure. The desorption curve largely coincides with the adsorption curve in the low relative pressure region, but a significant hysteresis phenomenon begins to appear in the high relative pressure region (P / P0 > 0.4). The presence of the hysteresis loop indicates inhomogeneity of the pore structure or connectivity issues between pores. The hysteresis loop appears between relative pressures of approximately 0.4 and 0.9, indicating the presence of mesopores and micropores (pore sizes between 2 and 50 nm) in the adsorbent. The sharp increase in adsorption capacity at higher relative pressures suggests a large specific surface area and pore volume.

[0062] Depend on Figure 4 As shown, the CA-KOH@PANI magnetic porous adsorbent of Example 1 exhibits an irregular blocky structure on its surface, with particles of varying sizes and shapes. The particle surfaces are rough and porous. Larger particles have diameters in the range of a few micrometers, while smaller particles and debris range in size from a few hundred nanometers to a few micrometers.

[0063] Example 8

[0064] Weigh a certain mass of CA-KOH@PANI magnetic porous adsorbent from Example 1, fix the adsorption column vertically, turn on the N2 / SF6 mixed gas, and purge the entire system at the experimental flow rate for at least 10-15 minutes to ensure that the air in the system is completely replaced. Record the experimental start time (t=0), and start continuously recording the change of the outlet SF6 concentration (Cout) with time (t) using the data acquisition system. Continue monitoring until the outlet concentration Cout reaches 95%-100% of the inlet concentration Cin, i.e., complete saturation. Record the gas breakthrough time and calculate the dynamic adsorption capacity. The results are shown in Table 1.

[0065] Table 1

[0066]

[0067] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a CAx-KOH@PANI magnetic porous adsorbent, characterized in that: Includes the following steps: Step 1: Preparation of CAx-KOH carbon material: Weigh citric acid and potassium hydroxide according to the proportion and dissolve them in deionized water. Mix them, heat and evaporate to prepare CAx-KOH gel. Calcine and carbonize the CAx-KOH gel to obtain CAx-KOH carbon material. Step 2, Preparation of magnetic PANI: Weigh citric acid and dissolve it in water to prepare an acid solution. Add aniline to the acid solution and dissolve it. Add magnetic powder and finally add ammonium persulfate to carry out a polymerization reaction. Wash, dry and grind the reaction product to obtain the magnetic PANI. Step 3: Preparation of porous rubber powder for insulators: Waste composite insulator rubber is frozen with liquid nitrogen, the frozen insulator is ground into powder, and calcined to obtain the porous rubber powder for insulators; Step 4: Preparation of CAx-KOH@PANI magnetic porous adsorbent: Disperse CAx-KOH carbon material, magnetic PANI and insulator porous rubber powder in deionized water, stir and mix thoroughly, dry, calcine, and grind to obtain the CAx-KOH@PANI magnetic porous adsorbent.

2. The preparation method of the CAx-KOH@PANI magnetic porous adsorbent according to claim 1, characterized in that: In step 1, x represents the mass ratio of CA to KOH, and the value of x can be 1, 2 or 3.

3. The preparation method of the CAx-KOH@PANI magnetic porous adsorbent according to claim 2, characterized in that: In step 2, the mass ratio of aniline to magnetic powder is 4-6:

2.

4. The preparation method of the CAx-KOH@PANI magnetic porous adsorbent according to claim 3, characterized in that: The calcination temperature in step 3 is 400–600℃.

5. The preparation method of the CAx-KOH@PANI magnetic porous adsorbent according to claim 4, characterized in that: The drying conditions in step 2 are drying at 60°C for 2 hours.

6. The method for preparing the CAx-KOH@PANI magnetic porous adsorbent according to claim 5, characterized in that: In step 4, the mass ratio of CAx-KOH, magnetic PANI, and porous insulator rubber is 3-5:3-5:7-9.

7. The method for preparing the CAx-KOH@PANI magnetic porous adsorbent according to claim 6, characterized in that: In step 4, the calcination temperature shall not exceed 400℃ and the calcination time shall be 4 hours.

8. A CAx-KOH@PANI magnetic porous adsorbent prepared by the method described in any one of claims 1 to 7.

9. The application of the CAx-KOH@PANI magnetic porous adsorbent of claim 8 in the preparation of an adsorbent for SF6 adsorption.

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