Short-chain molecular brush modified activated carbon, preparation method and application thereof

Abstract

This invention provides a short-chain molecular brush modified activated carbon, its preparation method, and its application. The preparation method includes the following steps: mixing activated carbon and an acid solution, followed by sequential standing, solid-liquid separation, and activation to obtain acid-modified activated carbon; mixing a silane coupling agent, a solvent, and the acid-modified activated carbon, adjusting the pH, and then performing a first reaction to obtain an intermediate product; mixing a short-chain molecular brush, an initiator, a solvent, and the intermediate product, and then performing a second reaction to obtain the short-chain molecular brush modified activated carbon. The prepared short-chain molecular brush modified activated carbon can not only efficiently separate and recover rare earth elements, but its adsorption environment pH is also compatible with actual low-concentration rare earth element industrial wastewater, and it has good stability, can be recycled, and is economically viable.

Description

Technical Field

[0001] This invention belongs to the field of rare earth element recovery, and relates to a short-chain molecular brush material, particularly to a short-chain molecular brush modified activated carbon and its preparation method and application. Background Technology

[0002] Rare earth elements are an important class of strategic mineral resources, widely used in high-tech fields such as electronics, instruments, optics, and magnetic materials. Their unique electronic structure endows rare earth elements with special chemical and physical properties, making them irreplaceable in materials science and engineering. The presence of rare earth ions in the aquatic environment mainly originates from the mining and smelting processes of rare earth ores. Due to their toxicity and bioavailability, the release of rare earth ions poses a threat to water quality. Therefore, the recovery of rare earth ions is of great significance for protecting the aquatic environment and achieving sustainable development. Currently, various technologies and methods, such as chemical precipitation, ion exchange, electrochemical methods, and adsorption materials, are used for the recovery of rare earth ions.

[0003] CN108893625A discloses a process for preparing high-purity lanthanum by extraction. The process uses 3N industrial-grade lanthanum chloride aqueous solution as feed, P204-TBP as a composite extractant, and consists of five steps: fractional extraction to separate NaMgCaBaPbZn / La, fractional extraction to separate La / CePrNdAlSmFe, and back-extraction section 1 and back-extraction section 2. By implementing the above process, the separation of lanthanum from metal elements such as cerium, praseodymium, neodymium, samarium, iron, aluminum, zinc, lead, barium, calcium, magnesium, and sodium can be successfully achieved. The high-purity lanthanum chloride solution has a relatively high purity, but the extraction process is complex and costly.

[0004] CN105861831A discloses a method for precipitating and recovering rare earth elements from a rare earth salt solution. The method includes the following steps: adding a precipitant containing calcium and / or magnesium basic compounds and an ammonium-containing solution to the rare earth salt solution for a mixed precipitation reaction. The amount of precipitant used is 101-130% of the theoretical amount of rare earth elements in the solution, and the precipitant can be a solid or an aqueous slurry. After the rare earth precipitation, solid-liquid separation is performed to obtain rare earth precipitate and mother liquor. The rare earth precipitate is then calcined to obtain rare earth oxides. This method uses inexpensive and readily available calcium and / or magnesium basic compound precipitants, the preparation process is simple and controllable, and it significantly reduces the amount of ammonium compounds used, thus reducing ammonia nitrogen pollution. However, the above method uses a chemical reaction to precipitate and enrich rare earth elements, inevitably introducing chemical substances and generating precipitation waste liquid.

[0005] CN114807601A discloses a method for adsorbing rare earth element lanthanum using phosphoric acid-modified kaolin. The method includes mixing kaolin raw materials and a modifier, ball milling, washing and drying in sequence to obtain the phosphoric acid-modified kaolin. The material is then desorbed and recycled. However, the material has obvious structural instability under high salt and high acid conditions, resulting in poor practical application.

[0006] In existing technologies, there is a lack of research on efficient extraction processes for rare earth elements. Furthermore, in real-world wastewater solutions with high salinity and acidity, the adsorption effect of conventional materials on low concentrations of rare earth elements is significantly reduced due to the influence of coexisting ions.

[0007] Therefore, developing a material for the efficient recovery of rare earth elements and its preparation method is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a short-chain molecular brush modified activated carbon, its preparation method and application. The prepared short-chain molecular brush modified activated carbon can not only efficiently recover rare earth elements, but also effectively selectively adsorb low concentrations of rare earth elements in high-salt and high-acid solutions, and the adsorption material can be reused.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing short-chain molecular brush modified activated carbon, the preparation method comprising the following steps:

[0011] (1) Mix activated carbon and acid solution, and then perform static standing, solid-liquid separation and activation in sequence to obtain acid-modified activated carbon;

[0012] (2) Mix the silane coupling agent, solvent and acid-modified activated carbon described in step (1), then adjust the pH, and then carry out the first reaction to obtain the intermediate product;

[0013] (3) Mix the short-chain molecular brush, initiator, solvent and the intermediate product of step (2), and then carry out a second reaction to obtain the short-chain molecular brush modified activated carbon.

[0014] This invention provides a preparation method that uses activated carbon activated by acid solution as a substrate, and utilizes the vinyl groups of silane coupling agent as polymerization grafting sites for grafted short-chain molecular brushes to graft phosphate molecular brushes onto the surface of activated carbon. The phosphate groups are used to coordinate and complex rare earth ions, which can not only achieve highly selective adsorption of rare earth elements, but also maintain excellent adsorption effect in high salt and high acid environments. The preparation method is simple, uses mature chemical products as raw materials, and is easy to industrialize.

[0015] As a preferred technical solution of the present invention, the acid solution in step (1) includes any one or at least two of nitric acid, hydrochloric acid or sulfuric acid. Typical but not limited combinations include: a combination of nitric acid and hydrochloric acid, a combination of hydrochloric acid and sulfuric acid, or a combination of nitric acid, hydrochloric acid and sulfuric acid, etc.

[0016] Preferably, the volume ratio of activated carbon to acid solution in step (1) is (0.2-1):1, for example, it can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] As a preferred technical solution of the present invention, the settling time in step (1) is 6-48h, for example, it can be 6h, 10h, 12h, 15h, 18h, 20h, 24h, 30h, 36h, 40h, 42h or 48h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the activation temperature in step (1) is 500-1000℃, for example, it can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 500-700℃.

[0019] Preferably, after the solid-liquid separation in step (1) and before activation, the process further includes washing and drying in sequence.

[0020] As a preferred technical solution of the present invention, the silane coupling agent in step (2) includes a vinyl silane coupling agent.

[0021] Preferably, in step (2), the amount of silane coupling agent added is 0.5%-15% of the solvent volume, for example, it can be 0.5%, 1%, 3%, 5%, 6%, 8%, 10%, 12%, 14% or 15%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, in step (2), the volume ratio of the acid-modified activated carbon to the solvent is (0.05-1):1, for example, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] As a preferred technical solution of the present invention, the mixing method in step (2) is as follows: acid-modified activated carbon is added to a solvent and then dispersed, and then a silane coupling agent is added to it.

[0024] In this invention, the solvent in step (2) includes any one or a combination of at least two of ethanol, toluene, or deionized water, preferably a combination of ethanol and deionized water. The volume ratio of ethanol to deionized water is (1-9):1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0025] Preferably, the dispersion method includes ultrasound.

[0026] Preferably, the dispersion time is 1-20 min, for example, it can be 1 min, 3 min, 5 min, 7 min, 10 min, 12 min, 15 min, 18 min or 20 min, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the pH adjustment to 3-6 in step (2) can be, for example, 3, 3.2, 3.5, 3.7, 4, 4.2, 4.5, 4.7, 5, 5.2, 5.5, 5.7 or 6, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 3-5.

[0028] In this invention, the reagent used to adjust the pH in step (2) includes any one or a combination of at least two of sodium carbonate, hydrochloric acid, or sodium hydroxide.

[0029] Preferably, the temperature of the first reaction in step (2) is 25-85℃, for example, it can be 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃ or 85℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the reaction time in step (2) is 1-14h, for example, it can be 2h, 4h, 5h, 6h, 8h, 10h, 11h, 12h, 13h or 14h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, step (2) further includes washing and drying after the first reaction.

[0032] As a preferred technical solution of the present invention, the short-chain molecular brush in step (3) includes vinyl phosphate and / or cis-propenyl phosphate.

[0033] Preferably, the initiator in step (3) includes benzoyl peroxide.

[0034] Preferably, the mass-to-volume ratio of the intermediate product and the short-chain molecular brush in step (3) is (0.2-1):1 g / mL, for example, it can be 0.2:1 g / mL, 0.3:1 g / mL, 0.4:1 g / mL, 0.5:1 g / mL, 0.6:1 g / mL, 0.7:1 g / mL, 0.8:1 g / mL, 0.9:1 g / mL or 1:1 g / mL, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably (0.3-1):1 g / mL.

[0035] Preferably, the mass ratio of the intermediate product to the initiator in step (3) is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably (1-4):1.

[0036] Preferably, the solvent includes any one or a combination of at least two of ethanol, toluene, or deionized water.

[0037] As a preferred technical solution of the present invention, the mixing method in step (3) is as follows: the intermediate product is added to the solvent, and then a short-chain molecular brush and an initiator are added to it in sequence.

[0038] Preferably, the initiator is added 0-30 minutes after the addition of the short-chain molecular brush, for example, it can be 0 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the mixing temperature in step (3) is 45-95℃, for example, it can be 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ or 90℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the temperature of the second reaction in step (3) is 45-95℃, for example, it can be 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ or 90℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 85-95℃.

[0041] Preferably, the reaction time in step (3) is 6-24h, for example, it can be 6h, 9h, 10h, 12h, 15h, 18h, 20h, 21h or 24h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] Preferably, step (3) further includes washing and drying after the second reaction.

[0043] It should be noted that the present invention does not impose specific requirements or special limitations on the characteristics of the washing solution, temperature, and number of washes. The role of washing in the present invention is to remove excess material and avoid affecting the purity of the product. Therefore, it is understood that other washing solutions that can achieve this function can be used in the present invention. Those skilled in the art can make adaptive adjustments to the washing solution, temperature, and number of washes according to the usage scenario and testing conditions.

[0044] It should be noted that the present invention does not impose specific requirements or special limitations on the drying device, temperature, and time. The role of drying in the present invention is to dry the material. Those skilled in the art can make adaptive adjustments to the drying device, temperature, and time according to the usage scenario and testing conditions.

[0045] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0046] (1) Mix activated carbon and acid solution in a volume ratio of (0.2-1):1, then let stand for 6-48 hours, separate solid and liquid, wash and dry in sequence, and then activate at a temperature of 500-1000℃ to obtain acid-modified activated carbon.

[0047] The acid solution includes any one or a combination of at least two of nitric acid, hydrochloric acid, or sulfuric acid.

[0048] (2) Add the acid-modified activated carbon described in step (1) into a solvent and disperse it for 1-20 min. Then add a silane coupling agent and adjust the pH to 3-6. Carry out the first reaction at a temperature of 25-85℃ for 1-14 h. Then wash and dry to obtain the intermediate product.

[0049] The volume ratio of the acid-modified activated carbon to the solvent is (0.05-1):1;

[0050] The silane coupling agent includes a vinyl silane coupling agent; the amount of the silane coupling agent added is 0.5%-15% of the solvent volume;

[0051] (3) Add the intermediate product to the solvent, then add the short-chain molecular brush and the initiator in sequence, and then carry out the second reaction at a temperature of 45-95℃ for 6-24h. After washing and drying, the short-chain molecular brush modified activated carbon is obtained.

[0052] The short-chain molecular brush comprises vinyl phosphate and / or cis-propenyl phosphate; the mass-to-volume ratio of the intermediate product to the short-chain molecular brush is (0.2-1):1 g / mL;

[0053] The initiator includes benzoyl peroxide; the mass ratio of the intermediate product to the initiator is (1-10):1;

[0054] The initiator is added 0-30 minutes after the addition of the short-chain molecular brush.

[0055] Secondly, the present invention provides a short-chain molecular brush modified activated carbon, wherein the short-chain molecular brush modified activated carbon is prepared by the preparation method described in the first aspect.

[0056] The short-chain molecular brush modified activated carbon prepared by this invention is a novel material for the efficient recovery of rare earth ions. It possesses advantages such as simple structure, convenient modification, stability, and strong adsorption capacity, and can maintain good performance even in high-salt and high-acid environments. The short-chain molecular brush modified activated carbon material exhibits higher affinity and selectivity, enabling efficient recovery of rare earth ions from the aquatic environment. Furthermore, it is reusable and cost-effective.

[0057] Thirdly, the present invention provides an application of short-chain molecular brush modified activated carbon as described in the second aspect, wherein the short-chain molecular brush modified activated carbon is used to adsorb and recover rare earth elements.

[0058] In this invention, the short-chain molecular brush modified activated carbon is used to adsorb and recover rare earth elements from high-salt, high-acid solutions. The high-salt, high-acid solution is a solution with a salt ion content ≥3g / L and a pH ≤2.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] The preparation method of short-chain molecular brush modified activated carbon provided by this invention is simple, uses mature chemical products as raw materials, and is easy to scale up. The prepared short-chain molecular brush modified activated carbon can not only efficiently separate and recover rare earth elements, but also has an adsorption environment pH that matches the actual low-concentration rare earth element industrial wastewater. It can selectively adsorb rare earth elements in industrial wastewater containing 3%-10% rare earth elements and maintain a high adsorption capacity. It can also maintain excellent adsorption effect in high-salt and high-acid environments with salt ion content ≥3g / L and pH≤2, and has good stability. It can be recycled and is economical. Attached Figure Description

[0061] Figure 1 The image shows the SEM image of the acid-modified activated carbon in step (1) of Example 1.

[0062] Figure 2 The image shows the SEM image of the intermediate product in step (2) of Example 1.

[0063] Figure 3 This is a SEM image of the short-chain molecular brush modified activated carbon obtained in Example 1;

[0064] Figure 4 The nitrogen adsorption-desorption curves of activated carbon, acid-modified activated carbon, intermediate products, short-chain molecular brush modified activated carbon, and materials after adsorbing rare earth elements in Example 1 are shown.

[0065] Figure 5 The BJH pore size distribution curves of the acid-modified activated carbon, intermediate product, short-chain molecular brush modified activated carbon, and the material after adsorbing rare earth elements in Example 1 are shown.

[0066] Among them, AC is activated carbon, AC' is acid-modified activated carbon, AC'-V is an intermediate product, AC'-V-VPA is short-chain molecular brush modified activated carbon, and AC'-V-VPA@REE is short-chain molecular brush modified activated carbon after adsorbing rare earth elements. Detailed Implementation

[0067] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0068] The silane coupling agents used in the following examples and comparative examples are all commercially available vinyltriethoxysilanes.

[0069] Example 1

[0070] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon, the preparation method comprising the following steps:

[0071] (1) Mix 20 mL of activated carbon and 20 mL of nitric acid, let stand for 48 h, filter the nitric acid, then wash with deionized water and dry, and then activate at 600 °C for 6 h to obtain acid-modified activated carbon.

[0072] (2) The acid-modified activated carbon described in step (1) was added to the first solvent at a volume ratio of 0.5:1 and ultrasonically dispersed for 10 min. Then, a silane coupling agent was added to it. After that, the pH was adjusted to 3.5 with hydrochloric acid. After standing for 1 h, the pH did not change. Then, the first reaction was carried out at a temperature of 80℃ for 6 h. Then, the first solvent was filtered off. The liquid was repeatedly washed with deionized water and ethanol until no precipitate was formed when the washed liquid was added to silver sulfate solution. Then, it was placed in a vacuum drying oven and dried at a temperature of 40℃ for 12 h to obtain the intermediate product.

[0073] The first solvent is a mixed solution of ethanol and deionized water in a volume ratio of 3:1;

[0074] The amount of the silane coupling agent added is 2% of the volume of the first solvent;

[0075] (3) Disperse 1g of intermediate product in toluene, then heat in an oil bath at 90°C for 30min, then add 3mL of vinyl phosphoric acid and 0.5g of benzoyl peroxide, and then carry out a second reaction at 90°C for 24h. After filtering to remove toluene, wash repeatedly with deionized water and ethanol, and then place in a vacuum drying oven at 40°C for 12h to obtain the short-chain molecular brush modified activated carbon.

[0076] In this embodiment, Figure 1-3 The images show SEM images of acid-modified activated carbon (denoted as AC'), modified activated carbon grafted with the intermediate product obtained in step (2) - silane coupling agent (denoted as AC'-V), and the obtained short-chain molecular brush modified activated carbon (denoted as AC'-V-VPA), respectively; Figure 1-3 It can be seen that there are no indistinguishable changes on the surfaces of the three materials, indicating the stability of the material surfaces.

[0077] In this embodiment, Figure 4-5 Table 1 shows the nitrogen adsorption-desorption curves and BJH pore size distribution curves for acid-modified activated carbon, intermediate products, short-chain molecular brush modified activated carbon, and materials after adsorbing rare earth elements. The pore size data shows that the pore size changes of the three materials are very small, indicating good material stability and minimal impact of the synthesis process on the physical properties. Table 2 shows the changes in elemental content. It can be seen that the phosphorus content of the AC'-V-VPA material increases significantly, indicating that the prepared short-chain molecular brush modified activated carbon material successfully grafts phosphate groups onto the activated carbon surface.

[0078] Table 1

[0079]

[0080] Table 2

[0081] O element content / % C element content / % P element content / % Si element content / % AC 12.95 86.19 0.39 0.47 AC' 14.38 85.15 0.13 0.48 AC'-V 13.56 84.77 0.56 1.02 AC'-V-VPA 12.57 83.79 2.49 1.15

[0082] Example 2

[0083] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon, the preparation method comprising the following steps:

[0084] (1) Mix 30 mL of activated carbon and 30 mL of nitric acid, let stand for 24 h, filter the nitric acid, then wash with deionized water and dry, and then activate at 650 °C for 12 h to obtain acid-modified activated carbon.

[0085] (2) The acid-modified activated carbon described in step (1) was added to the first solvent at a volume ratio of 0.2:1 and ultrasonically dispersed for 5 min. Then, a silane coupling agent was added to it. After that, the pH was adjusted to 5 with hydrochloric acid. After standing for 1 h, the pH did not change. Then, the first reaction was carried out at a temperature of 70°C for 10 h. Then, the first solvent was filtered off. The liquid was repeatedly washed with deionized water and ethanol until no precipitate was formed when the washed liquid was added to silver sulfate solution. Then, it was placed in a vacuum drying oven and dried at a temperature of 60°C for 8 h to obtain the intermediate product.

[0086] The first solvent is a mixed solution of ethanol and deionized water in a volume ratio of 1:1;

[0087] The amount of the silane coupling agent added is 2% of the volume of the first solvent;

[0088] (3) Disperse 1g of intermediate product in toluene, then heat in an oil bath at 80°C for 10 min, then add 3mL of vinyl phosphoric acid, and after 1 min add 0.4g of benzoyl peroxide. Then carry out the second reaction at 80°C for 10 h, then filter to remove toluene, wash repeatedly with deionized water and ethanol, and then place in a vacuum drying oven at 60°C for 8 h to obtain the short-chain molecular brush modified activated carbon.

[0089] Example 3

[0090] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon, the preparation method comprising the following steps:

[0091] (1) Mix 40 mL of activated carbon and 40 mL of nitric acid, let stand for 10 h, filter the nitric acid, then wash with deionized water and dry, and then activate at 700℃ for 15 h to obtain acid-modified activated carbon.

[0092] (2) The acid-modified activated carbon described in step (1) was added to the first solvent at a volume ratio of 1:1 and ultrasonically dispersed for 1 min. Then, a silane coupling agent was added to it. After that, the pH was adjusted to 6 with hydrochloric acid. After standing for 1 h, the pH did not change. Then, the first reaction was carried out at a temperature of 75°C for 3 h. Then, the first solvent was filtered off. The liquid was repeatedly washed with deionized water and ethanol until no precipitate was formed when the washed liquid was added to silver sulfate solution. Then, it was placed in a vacuum drying oven and dried at a temperature of 45°C for 6 h to obtain the intermediate product.

[0093] The first solvent is a mixed solution of ethanol and deionized water in a volume ratio of 2:1;

[0094] The amount of the silane coupling agent added is 2% of the volume of the first solvent;

[0095] (3) Disperse 1g of intermediate product in toluene, then heat in an oil bath at 95°C for 18min, then add 1mL of vinyl phosphoric acid, and after 3min add 0.3g of benzoyl peroxide. Then carry out the second reaction at 95°C for 6h. Then filter to remove toluene, wash repeatedly with deionized water and ethanol, and then place in a vacuum drying oven at 45°C for 6h to obtain the short-chain molecular brush modified activated carbon.

[0096] Example 4

[0097] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the activation temperature of 750°C in step (1), all other conditions are the same as in Example 1.

[0098] Example 5

[0099] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for step (2), where the first solvent is a mixed solution of ethanol and deionized water with a volume ratio of 4:1, all other conditions are the same as in Example 1.

[0100] Example 6

[0101] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for step (2) where hydrochloric acid is used to adjust the pH to 2, all other conditions are the same as in Example 1.

[0102] Example 7

[0103] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for step (2) where hydrochloric acid is used to adjust the pH to 7, all other conditions are the same as in Example 1.

[0104] Example 8

[0105] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the temperature of the first reaction in step (2) being 85°C, all other conditions are the same as in Example 1.

[0106] Example 9

[0107] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the first reaction time of 10h in step (2), all other conditions are the same as in Example 1.

[0108] Example 10

[0109] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the oil bath heating in step (3) and the temperature of the second reaction being 85°C, all other conditions are the same as in Example 1.

[0110] Example 11

[0111] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the oil bath heating in step (3) and the temperature of the second reaction, which are both 105°C, the other conditions are the same as in Example 1.

[0112] Example 12

[0113] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the second reaction time of 15h in step (3), all other conditions are the same as in Example 1.

[0114] Example 13

[0115] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the addition of 4 mL of vinyl phosphate in step (3), all other conditions are the same as in Example 1.

[0116] Example 14

[0117] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the addition of 5 mL of vinyl phosphate in step (3), all other conditions are the same as in Example 1.

[0118] Example 15

[0119] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the addition of 0.2g of benzoyl peroxide in step (3), all other conditions are the same as in Example 1.

[0120] Example 16

[0121] This embodiment provides a method for preparing short-chain molecular brush modified activated carbon. Except for the addition of 0.1g benzoyl peroxide in step (3), all other conditions are the same as in Example 1.

[0122] Comparative Example 1

[0123] This comparative example provides a method for preparing short-chain molecular brush modified activated carbon. Except for step (1) where nitric acid was not added for modification, all other conditions are the same as in Example 1.

[0124] Comparative Example 2

[0125] This comparative example provides a method for preparing modified activated carbon. Except for replacing “vinylphosphoric acid” with “phosphoric acid” in step (3), all other conditions are the same as in Example 1.

[0126] The rare earth element adsorption effects of the materials prepared in the above examples and comparative examples were determined. The specific test method was as follows: the prepared short-chain molecular brush modified activated carbon was added to a rare earth mixed solution at a concentration of 1 g / L for adsorption for 10 h. The pH of the rare earth mixed solution was 5, and the rare earth mixed solution contained 10 mg / L of Dy, La, and Yb elements. The change in the rare earth element content in the rare earth mixed solution before and after adsorption was measured, and the adsorption rate was calculated. The adsorption results are shown in Table 3.

[0127] Table 3

[0128]

[0129]

[0130] As shown in Table 3:

[0131] (1) The preparation method provided by the present invention can efficiently separate and recover rare earth elements by preparing short-chain molecular brush modified activated carbon. Under preferred conditions, the recovery rate of Dy element is ≥80%, the recovery rate of La element is ≥40%, and the recovery rate of Yb element is ≥80%.

[0132] (2) A comparison of Examples 1 and 6-7 shows that when the pH of the mixed solution of acid-modified activated carbon and silane coupling agent is adjusted to be too acidic, the silane coupling agent hydrolyzes too quickly, causing it to self-polymerize in the solution, resulting in a significant decrease in the recovery rate of rare earth elements; when the pH of the mixed solution of acid-modified activated carbon and silane coupling agent is adjusted to be neutral, the silane coupling agent hydrolyzes too slowly, resulting in a decrease in the grafting rate, which in turn leads to a decrease in the recovery rate of rare earth elements.

[0133] (3) Comparing Example 1 and Example 11, it can be seen that when the temperature of the second reaction is too high, the rapid decomposition of BPO makes it difficult for vinyl phosphoric acid to be grafted onto the material surface due to rapid polymerization in the solution, resulting in a decrease in the rare earth element recovery rate.

[0134] (4) A comparison of Examples 1 and 13-14 shows that when too much short-chain molecular brush-vinyl phosphate is added, the polymer blocks the carbon pores, reducing the number of phosphate groups exposed in the solution, which leads to a decrease in the rare earth element recovery rate. A comparison of Examples 1 and 15-16 shows that when too little initiator is added, the amount of grafted phosphate groups is too small, resulting in a decrease in the rare earth element recovery rate.

[0135] (5) Comparing Example 1 and Comparative Example 1, it can be seen that when activated carbon is not modified with acid solution, the rare earth element recovery rate decreases due to the small number of -OH on the surface. Comparing Example 1 and Comparative Example 2, it can be seen that when phosphoric acid is grafted onto the surface of activated carbon, the phosphoric acid cannot be grafted onto the material surface due to the lack of corresponding grafting sites, resulting in a decrease in the rare earth element recovery rate.

[0136] Based on the above test methods, the parameters of the rare earth mixed solution were changed, and the short-chain molecular brush modified activated carbon prepared in Example 1 was added to the rare earth mixed solution at a concentration of 1 g / L for adsorption for 10 h. The rare earth mixed solution contained 10 mg / L of Dy, La, and Yb elements. The parameters of the rare earth mixed solution and the adsorption results are shown in Table 4.

[0137] Table 4

[0138]

[0139]

[0140] As shown in Table 4, the short-chain molecular brush modified activated carbon prepared by this invention can maintain excellent adsorption effect in high-salt and high-acid environments of 3g / L or pH≤5.

[0141] The applicant declares that the detailed structural features of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components selected in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing short-chain molecular brush modified activated carbon, characterized in that, The preparation method includes the following steps: (1) Mix activated carbon and acid solution, and then perform static standing, solid-liquid separation and activation in sequence to obtain acid-modified activated carbon; (2) Mix the silane coupling agent, solvent and acid-modified activated carbon described in step (1), then adjust the pH, and then carry out the first reaction to obtain the intermediate product; (3) Mix the short-chain molecular brush, initiator, solvent and the intermediate product of step (2), and then carry out a second reaction to obtain the short-chain molecular brush modified activated carbon; The silane coupling agent in step (2) includes a vinylsilane coupling agent; The short-chain molecular brush in step (3) includes vinyl phosphate and / or cis-propenyl phosphate.

2. The preparation method according to claim 1, characterized in that, The acid solution in step (1) includes any one or a combination of at least two of nitric acid, hydrochloric acid, or sulfuric acid.

3. The preparation method according to claim 1, characterized in that, The volume ratio of activated carbon to acid solution in step (1) is (0.2-1):

1.

4. The preparation method according to claim 1, characterized in that, The settling time in step (1) is 6-48 hours.

5. The preparation method according to claim 1, characterized in that, The activation temperature in step (1) is 500-1000℃.

6. The preparation method according to claim 5, characterized in that, The activation temperature in step (1) is 500-700℃.

7. The preparation method according to claim 1, characterized in that, After solid-liquid separation in step (1) and before activation, washing and drying are performed sequentially.

8. The preparation method according to claim 1, characterized in that, In step (2), the amount of silane coupling agent added is 0.5%-15% of the solvent volume.

9. The preparation method according to claim 1, characterized in that, In step (2), the volume ratio of the acid-modified activated carbon to the solvent is (0.05-1):

1.

10. The preparation method according to claim 1, characterized in that, The mixing method in step (2) is as follows: acid-modified activated carbon is added to a solvent and then dispersed, followed by the addition of a silane coupling agent.

11. The preparation method according to claim 10, characterized in that, The dispersion method includes ultrasound.

12. The preparation method according to claim 10, characterized in that, The dispersion time is 1-20 minutes.

13. The preparation method according to claim 1, characterized in that, Step (2) involves adjusting the pH to 3-6.

14. The preparation method according to claim 13, characterized in that, In step (2), the pH is adjusted to 3-5.

15. The preparation method according to claim 1, characterized in that, In step (2), the temperature of the first reaction is 25-85℃.

16. The preparation method according to claim 1, characterized in that, Step (2) The first reaction time is 1-14 hours.

17. The preparation method according to claim 1, characterized in that, Step (2) after the first reaction also includes washing and drying in sequence.

18. The preparation method according to claim 1, characterized in that, The initiator in step (3) includes benzoyl peroxide.

19. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of the intermediate product and the short-chain molecular brush in step (3) is (0.2-1):1 g / mL.

20. The preparation method according to claim 19, characterized in that, The mass-to-volume ratio of the intermediate product and the short-chain molecular brush in step (3) is (0.3-1):1 g / mL.

21. The preparation method according to claim 1, characterized in that, The mass ratio of the intermediate product to the initiator in step (3) is (1-10):

1.

22. The preparation method according to claim 21, characterized in that, The mass ratio of the intermediate product to the initiator in step (3) is (1-4):

1.

23. The preparation method according to claim 1, characterized in that, The solvent includes any one or a combination of at least two of ethanol, toluene, or deionized water.

24. The preparation method according to claim 1, characterized in that, The mixing method in step (3) is as follows: the intermediate product is added to the solvent, and then short-chain molecular brushes and initiators are added to it in sequence.

25. The preparation method according to claim 1, characterized in that, The initiator is added 0-30 minutes after the addition of the short-chain molecular brush.

26. The preparation method according to claim 1, characterized in that, The mixing temperature in step (3) is 45-95℃.

27. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the second reaction is 45-95℃.

28. The preparation method according to claim 27, characterized in that, In step (3), the temperature of the second reaction is 85-95℃.

29. The preparation method according to claim 1, characterized in that, The second reaction in step (3) takes 6-24 hours.

30. The preparation method according to claim 1, characterized in that, Step (3) after the second reaction also includes washing and drying in sequence.

31. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) Mix activated carbon and acid solution in a volume ratio of (0.2-1):1, then let stand for 6-48 hours, separate solid and liquid, wash and dry in sequence, and then activate at a temperature of 500-1000℃ to obtain acid-modified activated carbon. The acid solution includes any one or a combination of at least two of nitric acid, hydrochloric acid, or sulfuric acid. (2) Add the acid-modified activated carbon described in step (1) into a solvent and disperse it for 1-20 min. Then add a silane coupling agent and adjust the pH to 3-6. Carry out the first reaction at a temperature of 25-85℃ for 1-14 h. Then wash and dry to obtain the intermediate product. The volume ratio of the acid-modified activated carbon to the solvent is (0.05-1):1; The silane coupling agent includes a vinyl silane coupling agent; the amount of the silane coupling agent added is 0.5%-15% of the solvent volume; (3) Add the intermediate product to the solvent, then add the short-chain molecular brush and the initiator in sequence, and then carry out the second reaction at a temperature of 45-95℃ for 6-24h. After washing and drying, the short-chain molecular brush modified activated carbon is obtained. The short-chain molecular brush comprises vinyl phosphate and / or cis-propenyl phosphate; the mass-to-volume ratio of the intermediate product to the short-chain molecular brush is (0.2-1):1 g / mL; The initiator includes benzoyl peroxide; the mass ratio of the intermediate product to the initiator is (1-10):1; The initiator is added 0-30 minutes after the addition of the short-chain molecular brush.

32. A short-chain molecular brush modified activated carbon, characterized in that, The short-chain molecular brush modified activated carbon is prepared by the preparation method according to any one of claims 1-31.

33. An application of the short-chain molecular brush modified activated carbon as described in claim 32, characterized in that, The short-chain molecular brush modified activated carbon is used to adsorb and recover rare earth elements.

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