Lanthanum hydroxide with carbon dioxide adsorption function and preparation method and application thereof

Abstract

The invention relates to the technical field of carbon dioxide adsorption, and discloses lanthanum hydroxide with a carbon dioxide adsorption function as well as a preparation method and application thereof, the lanthanum hydroxide has a rod-like structure, the length of the rod-like structure is 50-300nm, the diameter of the rod-like structure is 10-30nm, and the length-diameter ratio of the rod-like structure is 5-20. The invention discloses a method for preparing lanthanum hydroxide. The method comprises the following steps: (1) adding alkali liquor into an aqueous solution of lanthanum salt to adjust the pH value of the aqueous solution to be greater than 7; (2) performing three-frequency ultrasonic treatment on the material obtained in the step (1); and (3) drying a solid material obtained by separating the material subjected to the three-frequency ultrasonic treatment. The lanthanum hydroxide can effectively adsorb carbon dioxide, so that removal of carbon dioxide in reaction tail gas is realized, and the lanthanum hydroxide has relatively high carbon dioxide adsorption capacity and is particularly suitable for removing carbon dioxide in reaction tail gas of oxidative coupling of methane.

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide adsorption, and in particular to lanthanum hydroxide with carbon dioxide adsorption function and a preparation method and application thereof. Background Art

[0002] Carbon dioxide is one of the main gases causing the greenhouse effect, but most of the carbon dioxide emitted by industry is not fully recycled, which not only accelerates the pace of the greenhouse effect but also wastes a large amount of carbon dioxide resources. Therefore, the recycling and resource utilization of carbon dioxide has important scientific significance and application value.

[0003] Commonly used carbon dioxide adsorption materials in the prior art are ethanolamine and complex amine; these materials have the disadvantages of being easily degraded and having high regeneration energy consumption, and the problem of equipment corrosion needs to be further solved.

[0004] Rare earth elements have similar chemical properties to alkaline earth metal elements. Compared with other rare earth elements, lanthanum particles have higher conductivity due to their smaller particle radius. Lanthanum, alone or in combination with other elements, can be used as a highly efficient catalyst in glass, electronics, ceramics, and high-temperature reactions. Lanthanum hydroxide is usually used in the fields of environmental protection, optoelectronics, medicine, ceramics, and metals. There are no literature reports on the use of lanthanum hydroxide in the field of carbon dioxide adsorption. Summary of the invention

[0005] The purpose of the present invention is to provide a lanthanum hydroxide with carbon dioxide adsorption function and a preparation method and application thereof.

[0006] In order to achieve the above object, the first aspect of the present invention provides a lanthanum hydroxide with carbon dioxide adsorption function, wherein the lanthanum hydroxide has a rod-like structure, the length of the rod-like structure is 50-300nm, the diameter is 10-30nm, and the aspect ratio is 5-20.

[0007] The second aspect of the present invention provides a method for preparing lanthanum hydroxide having a carbon dioxide adsorption function, the method comprising:

[0008] (1) adding an alkali solution to an aqueous solution of a lanthanum salt to adjust the pH of the aqueous solution to be greater than 7;

[0009] (2) subjecting the material obtained in step (1) to triple-frequency ultrasonic treatment;

[0010] (3) Drying the solid material obtained after separation of the material after triple-frequency ultrasound.

[0011] The third aspect of the present invention provides lanthanum hydroxide with carbon dioxide adsorption function prepared by the method described above.

[0012] A fourth aspect of the present invention provides a method for adsorbing carbon dioxide, the method comprising contacting the lanthanum hydroxide having carbon dioxide adsorption function described above with a gas containing carbon dioxide, thereby achieving carbon dioxide adsorption;

[0013] Alternatively, lanthanum hydroxide with carbon dioxide adsorption function is prepared according to the above method, and then the lanthanum hydroxide is contacted with a gas containing carbon dioxide to achieve carbon dioxide adsorption.

[0014] Through the above technical solution, the present invention achieves the following beneficial effects:

[0015] (1) The present invention provides a lanthanum hydroxide having a rod-like structure, which can effectively adsorb carbon dioxide, thereby achieving the removal of carbon dioxide in the reaction tail gas, and has a high carbon dioxide adsorption capacity, and is particularly suitable for removing carbon dioxide in the reaction tail gas of methane oxidative coupling.

[0016] (2) Most of the carbon dioxide adsorbents in the prior art can only adsorb carbon dioxide at low temperatures, while the lanthanum hydroxide of the present invention can achieve carbon dioxide adsorption at a higher temperature, without the need to cool the reaction tail gas, thereby improving energy utilization efficiency.

[0017] (3) The lanthanum hydroxide of the present invention can adsorb carbon dioxide to form lanthanum carbonate, and the generated lanthanum carbonate can be used as a phosphorus-reducing drug and can also be used as an adsorbent for adsorbing phosphorus in wastewater. Therefore, the product of the lanthanum hydroxide provided by the present invention after adsorbing carbon dioxide has broad application prospects. The lanthanum hydroxide of the present invention can organically combine the treatment of methane oxidative coupling reaction tail gas with phosphorus-reducing drugs and adsorbents for adsorbing phosphorus, thereby increasing the added value of the byproducts of methane oxidative coupling.

[0018] (4) The present invention adjusts the pH of the lanthanum salt aqueous solution to be alkaline and combines it with triple-frequency ultrasonic treatment to prepare lanthanum hydroxide with a rod-like structure. Preferably, the lanthanum hydroxide prepared by the method of the present invention has a higher specific surface area. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the XRD pattern of lanthanum hydroxide prepared in Example 1. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0021] The first aspect of the present invention provides a lanthanum hydroxide having a carbon dioxide adsorption function, wherein the lanthanum hydroxide has a rod-like structure, the length of the rod-like structure is 50-300 nm, the diameter is 10-30 nm, and the aspect ratio is 5-20.

[0022] In the present invention, the testing method for the length, diameter and aspect ratio of the rod-like structure is as follows: 5-10 samples in the field of view are selected, and the length and diameter of the rod-like structure are measured using a measuring instrument provided in a scanning electron microscope, and then the average length and diameter of the rod-like structure of the 5-10 samples in the field of view are calculated as data of the length and diameter of the samples, and the aspect ratio is calculated based on the average length and average diameter of the samples.

[0023] In the present invention, the length of the rod-like structure can be 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 120nm, 130nm, 140nm, 150nm, 160nm, 180nm, 200nm, 250nm, 300nm, and a range consisting of any of the above point values, preferably 80-200nm.

[0024] In the present invention, the diameter of the rod-like structure can be 10nm, 12nm, 14nm, 15nm, 17nm, 19nm, 20nm, 24nm, 25nm, 28nm, 30nm, and a range consisting of any of the above point values, preferably 15-25nm.

[0025] In the present invention, the aspect ratio of the rod-like structure can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and a range consisting of any of the above points, preferably 5-15, and more preferably 5-10.

[0026] According to the present invention, preferably, the specific surface area of ​​the lanthanum hydroxide is 50-100m 2 / g, pore volume is 0.1-1cm 3 / g.

[0027] In the present invention, the specific surface area of ​​the lanthanum hydroxide can be 50m 2 / g, 60m 2 / g, 70m 2 / g, 75m 2 / g, 80m 2 / g, 85m 2 / g, 90m 2 / g, 95m 2 / g、100m 2 / g, and the range of the above arbitrary point values. The pore volume of the lanthanum hydroxide is 0.1cm 3 / g, 0.2cm3 / g, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, and ranges consisting of any of the above point values.

[0028] The second aspect of the present invention provides a method for preparing lanthanum hydroxide having a carbon dioxide adsorption function, the method comprising:

[0029] (1) adding an alkali solution to an aqueous solution of a lanthanum salt to adjust the pH of the aqueous solution to be greater than 7;

[0030] (2) subjecting the material obtained in step (1) to triple-frequency ultrasonic treatment;

[0031] (3) Drying the solid material obtained after separation of the material after triple-frequency ultrasound.

[0032] According to the present invention, the type of the lanthanum salt is not particularly limited and can be a commonly used water-soluble lanthanum salt. Preferably, the lanthanum salt includes at least one of lanthanum nitrate, lanthanum chloride and lanthanum acetate, and more preferably lanthanum nitrate and / or lanthanum chloride.

[0033] According to the present invention, preferably, the concentration of lanthanum in the aqueous solution of lanthanum salt is 0.1-5mol / L (for example, it can be 0.1mol / L, 0.5mol / L, 0.8mol / L, 0.9mol / L, 1mol / L, 1.5mol / L, 2mol / L, 2.5mol / L, 3mol / L, 3.5mol / L, 4mol / L, 4.5mol / L, 5mol / L, and the range composed of any of the above values), more preferably 0.1-3mol / L, further preferably 0.5-2mol / L, and further preferably 0.8-2mol / L. Limiting the concentration of lanthanum in the aqueous solution of lanthanum salt to the above range can further improve the adsorption performance of lanthanum hydroxide to carbon dioxide.

[0034] According to the present invention, preferably, the alkali in the alkali solution is a compound of Group IA metal, preferably sodium hydroxide and / or potassium hydroxide.

[0035] According to the present invention, the concentration of the alkali solution is not particularly limited, as long as the pH of the aqueous solution of the lanthanum salt can meet the requirements. Preferably, the concentration of the alkali solution is 1-3 mol / L.

[0036] According to the present invention, the temperature for adding the alkali solution is not particularly limited, and for example, it can be carried out at room temperature (15-40° C.).

[0037] According to the present invention, the method of adding the alkali solution is not particularly limited, and the alkali solution can be added dropwise, in a flowing manner, or intermittently. Those skilled in the art can make a selection according to actual needs.

[0038] According to the present invention, preferably, the aqueous solution of the lanthanum salt is placed in a stirring state, and then the alkali solution is added to the aqueous solution of the lanthanum salt. More preferably, the stirring speed is above 800 rpm (preferably 800-1500 rpm). The stirring time (which can be understood as the time for adding the alkali solution) can be 10-60 min.

[0039] According to the present invention, in order to further improve the adsorption rate of lanthanum hydroxide to carbon dioxide; preferably, in step (1), the pH of the aqueous solution is adjusted to 11-13.

[0040] According to the present invention, preferably, the conditions of the triple-frequency ultrasonic treatment include: ultrasonic treatment at 35-45KHz for 30-60min, then adjusting the ultrasonic frequency to 75-80KHz for 30-60min, and then adjusting the ultrasonic frequency to 95-100KHz for 30-120min. Limiting the conditions of the triple-frequency ultrasonic treatment to the above range can promote the conversion of lanthanum salt into lanthanum hydroxide having a rod-like structure, while increasing the amount of carbon dioxide adsorbed by lanthanum hydroxide.

[0041] According to the present invention, preferably, the drying conditions include: a temperature of 80-120°C (for example, 80°C, 90°C, 100°C, 110°C, 120°C, and a range consisting of the values ​​of any of the above points), and a time of 12-100h (for example, 12h, 20h, 30h, 40h, 50h, 60h, 70h, 80h, 90h, 100h, and a range consisting of the values ​​of any of the above points).

[0042] In the present invention, the drying atmosphere is not particularly limited and may be an air atmosphere or a nitrogen atmosphere.

[0043] According to the present invention, preferably, the method further comprises: before drying, washing the solid material with water and alcohol; more preferably, the alcohol used in the alcohol washing is a low-carbon alcohol (such as a C1-C4 monohydric alcohol), more preferably ethanol.

[0044] The third aspect of the present invention provides lanthanum hydroxide with carbon dioxide adsorption function prepared by the method described above.

[0045] A fourth aspect of the present invention provides a method for adsorbing carbon dioxide, the method comprising contacting the lanthanum hydroxide having carbon dioxide adsorption function described above with a gas containing carbon dioxide, thereby achieving carbon dioxide adsorption;

[0046] Alternatively, lanthanum hydroxide with carbon dioxide adsorption function is prepared according to the above method, and then the lanthanum hydroxide is contacted with a gas containing carbon dioxide to achieve carbon dioxide adsorption.

[0047] In the present invention, lanthanum hydroxide can generate lanthanum carbonate after absorbing carbon dioxide. Lanthanum carbonate can be used as a phosphorus-reducing drug and can also be used as an adsorbent for adsorbing phosphorus in wastewater.

[0048] According to the present invention, the contact temperature can be selected according to actual needs, but the inventors of the present invention have found that the lanthanum hydroxide of the present invention can adsorb carbon dioxide at a higher temperature and has a higher carbon dioxide adsorption capacity at a higher temperature. Preferably, the contact temperature is 450-650°C (for example, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, and the range composed of the above arbitrary point values).

[0049] According to the present invention, the lanthanum hydroxide of the present invention can absorb carbon dioxide at a relatively high temperature, so the lanthanum hydroxide of the present invention can be directly used for the adsorption of carbon dioxide in high-temperature reaction tail gas. Preferably, the carbon dioxide-containing gas includes at least one of methane oxidative coupling reaction tail gas, automobile tail gas and refinery tail gas, preferably methane oxidative coupling reaction tail gas.

[0050] According to the present invention, preferably, the contact method comprises: mixing lanthanum hydroxide and water to obtain a suspension, and then introducing a gas containing carbon dioxide; preferably, the weight ratio of the lanthanum hydroxide to water is 0.01-5:1, more preferably 0.1-1:1.

[0051] According to the present invention, preferably, the contacting method comprises: loading lanthanum hydroxide into a fixed bed, a fluidized bed or a moving bed, and then introducing a gas containing carbon dioxide.

[0052] According to the present invention, preferably, the amount of carbon dioxide adsorbed by every 1000 g of lanthanum hydroxide is 110-120 g.

[0053] According to a particularly preferred embodiment of the present invention, the method for preparing lanthanum hydroxide with carbon dioxide adsorption function includes: lanthanum chloride is dissolved in water (relative to each mole of lanthanum chloride, the amount of water is 0.5-0.6L), stirred to completely dissolve, 1.5-2mol / L potassium hydroxide solution is added dropwise, the pH value is adjusted to 11.2-11.5, the stirring speed is maintained at 1300-1200rpm during the addition, and the time of the addition is 15-20min. After the addition is completed, the reaction solution is subjected to triple-frequency ultrasonic treatment, ultrasonicated at 40-45KHz for 55-60min, and then the ultrasonic frequency is adjusted to 70-75KHz for 55-60min, and then the ultrasonic frequency is adjusted to 90-95KHz for 115-120min. Then centrifugation is performed, and the obtained solid material is washed with water and alcohol (ethanol) and placed in an oven, and dried at 90-95°C for 95-100h in an air atmosphere to obtain lanthanum hydroxide.

[0054] The present invention will be described in detail below by way of examples. In the following examples,

[0055] The manufacturer of the three-frequency ultrasonic device is Kunshan Ultrasonic Instrument Co., Ltd., and the model is KQ-400VDE;

[0056] All raw materials are commercially available.

[0057] Example 1

[0058] Accurately weigh 1 mol of lanthanum nitrate hexahydrate and dissolve it in 1L of deionized water, stir to completely dissolve it, add 3 mol / L potassium hydroxide solution, adjust the pH value to 12.5, maintain the stirring speed at 1100 rpm during the addition, and add for 10 minutes. After the addition is completed, the reaction solution is subjected to triple-frequency ultrasonic treatment, ultrasonic at 40KHz for 30 minutes, then the ultrasonic frequency is adjusted to 80KHz for 40 minutes, and then the ultrasonic frequency is adjusted to 100KHz for 60 minutes. Then centrifugal separation is performed, and the obtained solid material is washed with water and alcohol (ethanol) and placed in an oven, and dried at 80°C for 100 hours to obtain lanthanum hydroxide.

[0059] Figure 1 is the XRD pattern of lanthanum hydroxide prepared in Example 1, Figure 1 It can be seen that the XRD pattern of lanthanum hydroxide prepared in Example 1 (above) is almost identical to the standard pattern of lanthanum hydroxide (below), indicating that the product prepared in the present invention is lanthanum hydroxide.

[0060] Example 2

[0061] Accurately weigh 3 mol of lanthanum nitrate hexahydrate and dissolve it in 1L deionized water, stir to completely dissolve it, add 3 mol / L sodium hydroxide solution, adjust the pH value to 13, maintain the stirring speed at 1500 rpm during the addition, and add for 10 minutes. After the addition is completed, the reaction solution is subjected to triple-frequency ultrasonic treatment, ultrasonic at 35KHz for 40 minutes, ultrasonic at 75KHz for 60 minutes, and ultrasonic at 95KHz for 80 minutes. Then centrifuge, wash the obtained solid material with water and alcohol (ethanol), and place it in an oven, dry it at 110°C for 48 hours in an air atmosphere to obtain lanthanum hydroxide.

[0062] Example 3

[0063] Accurately weigh 3 mol of lanthanum acetate and dissolve it in 1L of deionized water, stir to completely dissolve it, add 2 mol / L potassium hydroxide solution, adjust the pH value to 11, maintain the stirring speed at 1400rpm during the addition, and add for 20 minutes. After the addition is completed, the reaction solution is subjected to triple-frequency ultrasonic treatment, ultrasonic at 45KHz for 50 minutes, then the ultrasonic frequency is adjusted to 80KHz for 50 minutes, and then the ultrasonic frequency is adjusted to 100KHz for 100 minutes. Then centrifugal separation is performed, and the obtained solid material is washed with water and alcohol (ethanol) and placed in an oven, and dried at 100°C for 60 hours in an air atmosphere to obtain lanthanum hydroxide.

[0064] Example 4

[0065] 2 mol of lanthanum chloride was accurately weighed and dissolved in 1 L of deionized water, stirred to completely dissolve, and 2 mol / L potassium hydroxide solution was added dropwise, and the pH value was adjusted to 11. The stirring speed was maintained at 1200 rpm during the addition process, and the addition time was 20 min. After the addition was completed, the reaction solution was subjected to triple-frequency ultrasonic treatment, ultrasonicated at 45 KHz for 60 min, then the ultrasonic frequency was adjusted to 75 KHz for 60 min, and then the ultrasonic frequency was adjusted to 95 KHz for 120 min. Then centrifugation was performed, and the obtained solid material was washed with water and alcohol (ethanol) and placed in an oven, and dried at 90 ° C for 100 h in an air atmosphere to obtain lanthanum hydroxide.

[0066] Example 5

[0067] The method of Example 1 was followed, except that the pH value was adjusted to 8.

[0068] Example 6

[0069] The method of Example 1 was followed, except that the amount of lanthanum nitrate hexahydrate used was 5 mol.

[0070] Comparative Example 1

[0071] The method of Example 1 was followed, except that the triple-frequency ultrasonic treatment was replaced by a single-frequency ultrasonic treatment, that is, the reaction solution was ultrasonicated at 100 KHz for 130 min.

[0072] Comparative Example 2

[0073] The lanthanum hydroxide in Example 1 was replaced with commercially available lanthanum hydroxide (powder, without a rod-like structure).

[0074] Test Example 1

[0075] The specific surface area, pore volume, average pore diameter and average particle size of the lanthanum hydroxide prepared in the above examples and comparative examples, as well as the length, diameter and aspect ratio of the rod-like structure were tested. The test results are shown in Table 1.

[0076] The test methods for specific surface area (BET), pore volume (BJH), and average pore size (BJH) are as follows: the test is performed using the fully automatic physical adsorption instrument ASAP2420 of the American Micromeritics Instrument Company, a certain mass of sample is weighed and placed in a sample tube, the sample tube is placed in the instrument degassing station for degassing, the degassing condition is 350 degrees for 4 hours, and after natural cooling to room temperature, the sample tube is placed in the instrument analysis station for analysis, and the nitrogen adsorption and desorption isotherm is fully analyzed at liquid nitrogen temperature. The specific surface area of ​​the sample is calculated by the BET (Brunauer, Emmett, Teller) method, and the pore volume and average pore size of the sample are calculated by the BJH (Barret, Joyner, Halenda) method according to the desorption (adsorption) branch.

[0077] The testing method for the length, diameter and aspect ratio of the rod-like structure is: select 5-10 samples in the field of view, use the measuring instrument provided with the scanning electron microscope to measure the length and diameter of the rod-like structure, and then calculate the average length and average diameter of the rod-like structure of the 5-10 samples in the field of view as the data of the length and diameter of the samples, and calculate the aspect ratio based on the average length and average diameter of the samples.

[0078] Table 1

[0079]

[0080] Test Example 2

[0081] The carbon dioxide adsorption performance of the lanthanum hydroxide prepared in the above examples and comparative examples was tested.

[0082] (1) 10 g of lanthanum hydroxide is suspended in 100 g of deionized water, and the tail gas of the methane oxidative coupling reaction is passed through the suspension to adsorb carbon dioxide in the tail gas.

[0083] (2) 10 g of lanthanum hydroxide that has been crushed and sieved after tableting is placed on a fixed bed, and the tail gas of the methane oxidative coupling reaction passes through the bed layer to adsorb carbon dioxide in the tail gas of the reaction.

[0084] Examples 2, 3, and 4 use the method of step (2) to adsorb carbon dioxide, and the rest use the method of step (1) to adsorb carbon dioxide. The volume content of carbon dioxide in the reaction tail gas before adsorption in steps (1) and (2) is 3 volume %.

[0085] After each embodiment and comparative example was in contact with the reaction tail gas for the same time, the amount of carbon dioxide finally adsorbed by the suspension or fixed bed was calculated by weighing and recorded as the carbon dioxide adsorption amount.

[0086] The calculation formula for the removal rate of carbon dioxide in the reaction tail gas is: (volume content of carbon dioxide in the reaction tail gas before adsorption-volume content of carbon dioxide in the reaction tail gas after adsorption) ÷ volume content of carbon dioxide in the reaction tail gas before adsorption × 100%.

[0087] Table 2

[0088]

[0089] It can be seen from Table 2 that compared with Comparative Examples 1-2, the lanthanum hydroxide prepared by the method of the present invention has a higher carbon dioxide adsorption capacity and a higher carbon dioxide removal rate. Preferably, the lanthanum hydroxide prepared in Example 2 and Example 4 has a higher carbon dioxide adsorption capacity and a carbon dioxide removal rate, and the carbon dioxide removal rate of Example 2 and Example 4 is close to 100%, which can meet the environment with extremely strict requirements on carbon dioxide content. More preferably, the lanthanum hydroxide of Example 4 can obtain a higher carbon dioxide adsorption capacity and a carbon dioxide removal rate at a higher temperature.

[0090] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A lanthanum hydroxide having a carbon dioxide adsorption function, characterized in that: The lanthanum hydroxide has a rod-like structure with a length of 50-300 nm, a diameter of 10-30 nm and an aspect ratio of 5-20.

2. The lanthanum hydroxide according to claim 1, wherein Specific surface area is 50-100m 2 / g, pore volume is 0.1-1cm 3 / g.

3. A method for preparing lanthanum hydroxide having carbon dioxide adsorption function, characterized in that: The method includes: (1) adding an alkali solution to an aqueous solution of a lanthanum salt to adjust the pH of the aqueous solution to be greater than 7; (2) subjecting the material obtained in step (1) to triple-frequency ultrasonic treatment; (3) Drying the solid material obtained after separation of the material after triple-frequency ultrasound.

4. The method according to claim 3, wherein: The lanthanum salt comprises at least one of lanthanum nitrate, lanthanum chloride and lanthanum acetate; and / or, the concentration of lanthanum in the aqueous solution of lanthanum salt is 0.1-3 mol / L, preferably 0.5-2 mol / L, more preferably 0.8-2 mol / L; and / or, the alkali in the alkali solution is a compound of a Group IA metal, preferably sodium hydroxide and / or potassium hydroxide; And / or, the concentration of the alkali solution is 1-3 mol / L; And / or, in step (1), the pH of the aqueous solution is adjusted to 11-13.

5. The method according to claim 3, wherein: The conditions of the triple-frequency ultrasonic treatment include: ultrasonic treatment at 35-45KHz for 30-60min, then adjusting the ultrasonic frequency to 75-80KHz for 30-60min, and then adjusting the ultrasonic frequency to 95-100KHz for 30-120min.

6. The method according to claim 3, wherein: The drying conditions include: temperature of 80-120° C. and time of 12-100 h.

7. The method according to claim 3, wherein: The method further comprises: before drying, washing the solid material with water and alcohol; Preferably, the alcohol used in the alcohol washing is a low-carbon alcohol, more preferably ethanol.

8. The lanthanum hydroxide with carbon dioxide adsorption function prepared by the method described in any one of claims 3 to 7.

9. A method for adsorbing carbon dioxide, characterized in that: The method comprises contacting the lanthanum hydroxide with carbon dioxide adsorption function described in any one of claims 1 to 2 and 8 with a gas containing carbon dioxide, thereby achieving carbon dioxide adsorption; Alternatively, lanthanum hydroxide with carbon dioxide adsorption function is prepared according to the method described in any one of claims 3 to 7, and then the lanthanum hydroxide is contacted with a gas containing carbon dioxide to achieve carbon dioxide adsorption.

10. The method according to claim 9, wherein: The contact temperature is 450-650°C; And / or, the carbon dioxide-containing gas comprises at least one of a reaction tail gas from methane oxidative coupling, automobile tail gas and refinery tail gas, preferably a reaction tail gas from methane oxidative coupling.

11. The method according to claim 9 or 10, wherein: The contact method comprises: mixing lanthanum hydroxide and water to obtain a suspension, and then introducing a gas containing carbon dioxide; preferably, the weight ratio of lanthanum hydroxide to water is 0.01-5:1, preferably 0.1-1:1; And / or, the contacting method comprises: loading lanthanum hydroxide into a fixed bed, a fluidized bed or a moving bed, and then introducing a gas containing carbon dioxide.

12. The method according to claim 9 or 10, wherein: The amount of carbon dioxide adsorbed by every 1000g of lanthanum hydroxide is 110-120g.

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