Preparation method and application of adsorbent for removing nitrophenol in nitrobenzene

Abstract

This invention provides a method for preparing an adsorbent for removing nitrophenol from nitrobenzene and its application. The preparation method includes the following steps: 1) subjecting a mixture including a precipitant, a metal salt, and a solvent to a hydrothermal reaction to obtain a reaction solution; 2) subjecting the reaction solution to a first drying treatment and a calcination treatment sequentially to obtain a metal compound; 3) subjecting a mixture including graphene oxide, a reducing agent, and a polyamine to a first reduction reaction to obtain a dilute sol of graphene oxide material; 4) adding the metal compound to the dilute sol of graphene oxide material to a second reduction reaction, followed by a second drying treatment to obtain the adsorbent. The above method is simple to use and can effectively remove nitrophenol from nitrobenzene without generating excessive waste liquid discharge during the adsorption process.

Description

Technical Field

[0001] This invention relates to the field of chemistry, and more particularly to a method for preparing and applying an adsorbent for removing nitrophenol from nitrobenzene. Background Technology

[0002] Nitrobenzene is an important industrial raw material with wide applications in polyurethane materials, dyes, pesticides, pharmaceuticals, and explosives. However, during the production of nitrobenzene, incomplete nitration and side reactions often result in byproducts such as nitrophenol. These impurities not only affect the purity of nitrobenzene but may also adversely impact subsequent processing.

[0003] Currently, the primary method for removing nitrophenol from crude nitrobenzene is washing, which mainly utilizes multi-stage washing processes such as acid washing, alkaline washing, and neutral washing to remove acids and nitrophenol byproducts entrained in the crude nitrobenzene. However, washing removes nitrophenol from crude nitrobenzene, resulting in the discharge of large amounts of wastewater. Furthermore, due to the high biochemical toxicity of nitrophenols, this wastewater requires further treatment. Adsorption can effectively solve these wastewater treatment problems. The basic principle of adsorption is to utilize the porous structure of the adsorbent to adsorb impurity molecules such as nitrophenol onto the adsorbent surface through physical or chemical action, thereby purifying nitrobenzene. However, traditional powder adsorbent materials suffer from limited separation efficiency and, in practical applications, are limited by high bed pressure drop and high energy consumption. Current adsorbent preparation methods are complex, and the resulting adsorbents have low adsorption efficiency, making it difficult to effectively remove nitrophenol from nitrobenzene.

[0004] Therefore, there is an urgent need for a method to prepare an adsorbent that is simple to prepare, can effectively remove nitrophenol from nitrobenzene, has low industrial cost and does not cause a large amount of waste liquid discharge. Summary of the Invention

[0005] This invention provides a method for preparing an adsorbent. The method is simple, and the prepared adsorbent can effectively remove nitrophenol from nitrobenzene without generating excessive waste liquid discharge.

[0006] This invention provides an adsorbent that can effectively remove nitrophenol from nitrobenzene. It is simple to use during the adsorption process and does not generate excessive waste liquid discharge.

[0007] This invention provides a method for removing nitrophenol from nitrobenzene. The method uses the above-mentioned adsorbent to remove nitrophenol from nitrobenzene, and has the characteristics of high efficiency in removing nitrophenol and low waste liquid generation.

[0008] The first aspect of this invention provides a method for preparing an adsorbent, comprising the following steps:

[0009] 1) A reaction solution is obtained by hydrothermal reaction of a mixture including a precipitant, a metal salt, and a solvent;

[0010] 2) The reaction solution is subjected to a first drying treatment and a calcination treatment in sequence to obtain a metal compound;

[0011] 3) A mixed system including graphene oxide, a reducing agent, and polyamines is subjected to a first reduction reaction to obtain a dilute sol of graphene oxide material;

[0012] 4) The metal compound is added to the graphene oxide sol containing amino groups to carry out a second reduction reaction, and after a second drying treatment, the adsorbent is obtained.

[0013] The adsorbent preparation method described above,

[0014] In step 1), the metal salt includes cobalt salt and vanadium salt, and the molar concentration of the metal salt in the mixed solution is 0.1~0.3 mol / L; and / or,

[0015] The precipitant includes at least one of ammonia, sodium hydroxide, and urea, and the molar amount of the precipitant is 1 to 1.2 times the molar amount of the metal salt; and / or,

[0016] In step 3), the mass concentration of graphene oxide in the mixed system is 1–10 mg / mL; and / or,

[0017] The mass of the polyamine is 0.5 to 8 times the mass of the graphene oxide; and / or,

[0018] The mass of the reducing agent is 0.5 to 2 times the mass of the graphene oxide; and / or,

[0019] In step 4), the mass of the metal compound is 0.1 to 0.4 times the mass of the graphene oxide.

[0020] In the preparation method of the adsorbent as described above, in step 2), the metal compound includes a metal element, which includes cobalt and vanadium, wherein the mass percentage of cobalt in the metal element is 20-80%; and / or,

[0021] The vanadium element has a mass percentage content of 20-80% in the metallic elements.

[0022] In the above-described method for preparing the adsorbent, the hydrothermal reaction in step 1) is carried out at a temperature of 90–180°C for 12–24 h.

[0023] The adsorbent preparation method described above,

[0024] In step 2), the first drying treatment is carried out at a temperature of 60–100°C for 10–15 hours; and / or,

[0025] The calcination treatment is carried out at a temperature of 300–500°C for 4–6 hours.

[0026] The adsorbent preparation method described above,

[0027] In step 3), the reaction temperature of the first reduction reaction is 20~60℃, and the reaction time is 2~4h; and / or,

[0028] In step 4), the reaction temperature of the second reduction reaction is 60–180°C, and the reaction time is 6–18 h; and / or,

[0029] The second drying process is performed at a temperature of -30 to -100°C for 36 to 60 hours.

[0030] A second aspect of the present invention provides an adsorbent comprising a support and a metal element supported on the support;

[0031] The carrier includes graphene oxide material, which contains amino groups.

[0032] The adsorbent described above has a porosity of 85-99%; and / or,

[0033] The metal element in the adsorbent has a mass percentage content of 2-12%; and / or,

[0034] The graphene oxide material in the adsorbent has a mass percentage of 65-95%.

[0035] The adsorbent described above is prepared by a method comprising the following steps:

[0036] A mixture comprising a metal salt and a precipitant is subjected to a hydrothermal reaction, followed by a first drying treatment and a calcination treatment to obtain a metal compound containing the metal element; then the metal compound is mixed with graphene oxide material, and subjected to a reduction reaction and a second drying treatment to obtain the adsorbent.

[0037] A third aspect of the present invention provides a method for removing nitrophenol from nitrobenzene, comprising the following steps: removing nitrophenol from nitrobenzene using an adsorbent as described above or an adsorbent prepared by the method described above.

[0038] The method for preparing the adsorbent provided by this invention involves modifying graphene oxide with polyamines and loading metal elements to obtain a porous layered adsorbent containing amino groups and loaded with metal elements. This preparation method is simple, and the resulting adsorbent can effectively remove nitrophenol from nitrobenzene without using harsh reaction conditions, while not generating excessive wastewater. It has high industrial economic efficiency while protecting the environment. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] Currently, in the preparation of nitrobenzene, incomplete nitration and side reactions often result in the formation of byproducts such as nitrophenol. The generation of nitrophenol not only poses challenges to subsequent separation and purification processes but also potentially harms the environment and equipment. Washing methods for removing nitrophenol from nitrobenzene generate large amounts of waste liquid, causing environmental pollution. Adsorption methods can effectively address this environmental pollution problem; however, some traditional adsorbents have limited adsorption efficiency, and the preparation of adsorbents is complex, leading to increased industrial costs.

[0041] Therefore, there is an urgent need for a simple preparation process that produces an adsorbent that can efficiently remove nitrobenzene from nitrobenzene.

[0042] Based on this, the first aspect of the present invention provides a method for preparing an adsorbent, comprising the following steps:

[0043] 1) A reaction solution is obtained by hydrothermal reaction of a mixture including a precipitant, a metal salt, and a solvent;

[0044] 2) The reaction solution was subjected to a first drying treatment and a calcination treatment in sequence to obtain a metal compound;

[0045] 3) A mixed system including graphene oxide, a reducing agent, and polyamines is subjected to a first reduction reaction to obtain a dilute sol of graphene oxide material;

[0046] 4) The metal compound is added to the dilute sol of graphene oxide material to carry out a second reduction reaction, and after a second drying treatment, the adsorbent is obtained.

[0047] Specifically, in step 1), the precipitant can adjust the pH of the solution, promoting the hydrolysis and precipitation of the metal salt to form a metal compound. Hydrothermal conditions can accelerate the reaction rate and improve the yield and purity of the metal compound. Simultaneously, the hydrothermal reaction can form nanomaterials with specific morphologies and structures. These materials possess a large specific surface area and abundant surface active sites, which are beneficial for improving the adsorption performance and catalytic activity of the adsorbent.

[0048] This invention does not impose any particular limitation on the mixing method of the precipitant and the metal salt. The precipitant and the metal salt can be dissolved separately in a solvent before mixing, or they can be dissolved together in a solvent before mixing. This invention also does not impose any particular limitation on the solvent, as long as it can dissolve both the precipitant and the metal salt. In one specific embodiment, the solvent is deionized water. The reaction solution obtained after the hydrothermal reaction is an aqueous solution containing the metal compound.

[0049] It is understandable that, due to the strong alkalinity of the aforementioned metal compounds, containers with corrosion-resistant properties can be used for their preparation. For example, the metal compounds can be prepared in a stainless steel reactor lined with polytetrafluoroethylene (PTFE).

[0050] In step 2), the above reaction solution is subjected to a first drying treatment and a calcination treatment in sequence to obtain a metal compound. It is understood that, prior to the first drying treatment, in order to obtain a metal compound of higher purity, filtration and washing treatments are also included. This invention does not impose any particular limitations on the filtration and washing treatments, as long as a relatively pure metal compound can be obtained.

[0051] It should be clarified that if the temperature is too high during calcination, the metal compound will be completely converted into a metal oxide. In order to utilize the high alkalinity of the metal compound to remove nitrophenol, the present invention will convert most of the metal compound into metal hydroxide and a small part into metal oxide during the calcination process.

[0052] In step 3), the role of the polyamine in the mixed system is to amination of graphene oxide, and the role of the reducing agent is to reduce part of the graphene oxide. Before reduction, the graphene oxide is in a solution state. After the action of the reducing agent and the polyamine, the graphene oxide solution becomes a dilute sol of graphene oxide material. The dilute sol state of the graphene oxide material allows the solute to be highly dispersed, avoiding particle agglomeration, which is conducive to the formation of an adsorbent with a large specific surface area and improves its adsorption efficiency.

[0053] This invention does not specifically limit the polyamines, as long as they can aminate graphene oxide. For example, polyamines include, but are not limited to, at least one of ethylenediamine, hexamethylenediamine, diethylenetriamine, hydroxylamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0054] The present invention does not impose any special limitation on the reducing agent, as long as it can reduce graphene oxide. For example, the reducing agent includes, but is not limited to, at least one of ascorbic acid, sodium thiosulfate, hydroiodic acid, hydrogen, hydrazine, and sodium borohydride.

[0055] In step 3), approximately one-third of the reducing agent participates in the first reduction reaction. The remaining two-thirds of the reducing agent participates in the second reduction reaction in step 4, where the metal compound is added to the dilute sol of the graphene oxide material. Compared to the first reduction reaction, most of the oxygen atoms in the graphene oxide material are reduced in the second reduction reaction, and the metal compound has adhered to the graphene oxide material. After a second drying process, the adsorbent is obtained.

[0056] Through the above method, this invention prepares an adsorbent with high nitrophenol efficiency. When using this adsorbent to remove nitrophenol from nitrobenzene, no waste liquid is generated, which is beneficial to environmental protection. Furthermore, the adsorbent prepared by the above method has good chemical stability and mechanical properties, which helps to reduce bed pressure drop and energy consumption, thereby improving industrial economics.

[0057] As mentioned above, in the preparation method of the adsorbent, the metal salt includes cobalt salt and vanadium salt. Cobalt hydroxide and vanadium hydroxide have high alkalinity and can effectively neutralize nitrophenol through acid-base neutralization reaction. This invention further limits the molar concentration of the metal salt in the mixed solution to 0.1~0.3 mol / L. For example, the molar concentration of the metal salt in the mixed solution includes, but is not limited to, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, or any combination thereof. By limiting the concentration of the metal salt within the above range, sufficient dispersion of the metal salt in the solvent can be ensured, which is beneficial for preparing a more uniform metal compound. A uniform metal compound has a larger specific surface area, thereby improving the adsorption performance of the adsorbent.

[0058] Furthermore, the present invention does not impose any special limitation on the type of salt ions of the metal salt. For example, the metal salt includes at least one of nitrate metal salt, sulfate metal salt, and metal chloride, which can be selected according to actual needs.

[0059] In another specific embodiment, the precipitant includes at least one of ammonia, sodium hydroxide, and urea. By using the above-mentioned precipitant, the pH value of the hydrothermal reaction can be effectively adjusted, allowing the metal compound to be effectively generated and crystallized. To achieve a higher precipitation efficiency of the metal compound, the present invention further controls the molar amount of the precipitant in step 1) to be 1 to 1.2 times the molar amount of the metal salt, which can result in a higher conversion rate when the metal ions in the hydrothermal reaction system react to form metal compounds.

[0060] In another specific embodiment, the mass concentration of graphene oxide in the mixing system in step 3) is 1–10 mg / mL. For example, the mass concentration of graphene oxide in the mixing system includes, but is not limited to, a range of 1 mg / mL, 3 mg / mL, 5 mg / mL, 7 mg / mL, 9 mg / mL, 10 mg / mL, or any combination thereof. This invention further limits the concentration of graphene oxide within the above range, which can effectively control the sheet size and thickness of graphene oxide, forming fine and uniform graphene oxide particles. Fine graphene oxide particles have a higher specific surface area and more active sites, which can improve the adsorption performance of the adsorbent.

[0061] In another specific embodiment, the present invention further specifies that the mass of the polyamine in step 3) is 0.5 to 8 times the mass of graphene oxide, which can ensure that there is enough polyamine to react with graphene oxide, while reducing the occurrence of side reactions, which is beneficial to the formation of aminated graphene oxide material.

[0062] In another specific embodiment, the mass of the reducing agent in step 3) is 0.5 to 2 times the mass of graphene oxide. By controlling the mass ratio of the reducing agent to graphene oxide, it is beneficial to make the graphene oxide undergo a more complete reduction reaction, which can reduce the defects and oxygen-containing functional groups on the surface of graphene oxide, improve its chemical stability, and thus improve the chemical stability of the adsorbent.

[0063] In another specific embodiment, in order to prepare an adsorbent with a large specific surface area, the present invention further controls the mass of the metal compound in step 4) to be 0.1 to 0.4 times the mass of graphene oxide. By controlling the mass ratio of the metal compound and graphene oxide within the above range, it is beneficial to improve the adsorption efficiency of the adsorbent.

[0064] As mentioned above, the metal compound prepared in step 2) includes the metal elements cobalt and vanadium.

[0065] The mass percentage of cobalt in the metal is 20% to 80%. For example, the mass percentage of cobalt in the metal includes, but is not limited to, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or any combination thereof.

[0066] In another specific embodiment, the vanadium element has a mass percentage content of 20% to 80% in the metal element. For example, the mass percentage content of vanadium element in the metal element includes, but is not limited to, a range of 20%, 30%, 40%, 50%, 60%, 70%, 80%, or any combination thereof.

[0067] Specifically, the mass percentage of cobalt and vanadium in the metallic elements can be determined by calcination-digestion-inductively coupled plasma atomic emission spectrometry (ICP-AES). The specific testing method is as follows: First, weigh 0.2 g of the above adsorbent into a crucible using a balance, and calcine it in a muffle furnace at 700 °C for 2 h (heating rate 2 °C / min); then, after cooling to room temperature, place the crucible on a stirrer, add 10 ml of aqua regia, and stir at 80 °C until the solid is completely dissolved and the system is clear. Dilute with 10 ml of distilled water; finally, determine the cobalt and vanadium metal contents separately using ICP-AES. The testing instrument is an Agilent 720 / 725 ICP-AES atomic emission spectrometer, with a plasma gas flow rate of 10 L / min, an auxiliary gas flow rate of 1 L / min, and an nebulizer gas flow rate of 1 L / min.

[0068] This invention further limits the mass ratio of cobalt and vanadium in the metal elements, which helps to improve the alkalinity of the metal compound and thus improve its adsorption efficiency of nitrophenol.

[0069] In the above preparation method, the present invention further limits the hydrothermal reaction temperature in step 1) to 90~180℃ and the hydrothermal reaction time to 12~24h, which is conducive to the more complete generation of metal compounds.

[0070] Furthermore, in the above preparation method, the temperature of the first drying treatment is 60–100°C, and the treatment time is 10–15 h. For example, the temperature of the first drying treatment includes, but is not limited to, 60°C, 70°C, 80°C, 90°C, 100°C, or any combination thereof; the treatment time of the first drying treatment includes, but is not limited to, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, or any combination thereof. By controlling the temperature and time of the drying treatment, it is beneficial to remove the solvent from the reaction solution and obtain a solid metal compound.

[0071] In another specific embodiment, the calcination treatment in step 2) is carried out at a temperature of 300–500°C for 4–6 hours. For example, the temperature of the first drying treatment includes, but is not limited to, 300°C, 350°C, 400°C, 450°C, 500°C, or any combination thereof; the drying time includes, but is not limited to, 4 hours, 5 hours, 6 hours, or any combination thereof. By limiting the calcination temperature and time, the metal compound can maintain its hydroxide state and exert its effect in the adsorbent as a metal compound, which is beneficial to improving the efficiency of the adsorbent in removing nitrophenol.

[0072] As mentioned above, in step 3), the reaction temperature of the first reduction reaction is 20~60℃ and the reaction time is 2~4h.

[0073] In step 4), the reaction temperature of the second reduction reaction is 60–180°C, and the reaction time is 6–18 h.

[0074] This invention, by controlling the reaction temperature and reaction time of the first and second reduction reactions, facilitates a more thorough reduction reaction of graphene oxide, improves the chemical stability of graphene oxide, and thus improves the chemical stability of the adsorbent.

[0075] In another specific embodiment, the processing temperature of the second drying treatment is -30 to -100°C, and the processing time is 36 to 60 hours. For example, the processing temperature of the second drying treatment includes, but is not limited to, a range of -30°C, -40°C, -50°C, -60°C, -70°C, -80°C, -90°C, -100°C, or any combination thereof; the processing time of the second drying treatment includes, but is not limited to, 36 hours, 48 ​​hours, 60 hours, or any combination thereof. By controlling the processing temperature and processing time of the second drying treatment, this invention facilitates the preparation of adsorbents with a large specific surface area and improves their adsorption efficiency.

[0076] A second aspect of the present invention provides an adsorbent comprising a support and a metal element supported on the support;

[0077] The carrier includes graphene oxide material, which contains amino groups.

[0078] This invention modifies graphene oxide with amino groups to obtain graphene oxide materials containing amino groups, resulting in adsorbents with excellent removal efficiency of nitrophenol from nitrobenzene. The inventors speculate that this is because amino groups can adsorb weakly acidic phenolic substances through electrostatic and hydrogen bonding interactions, significantly improving the chemisorption performance of the loaded adsorbent. The introduction of amino groups also gives the adsorbent a better specific surface area, providing numerous adsorption sites and significantly increasing adsorption capacity. Using graphene oxide containing amino groups also gives the adsorbent good chemical stability, maintaining its structure and performance during the adsorption of nitrophenol from nitrobenzene. Furthermore, the sheet-like structure and porous nature of graphene oxide containing amino groups results in a lower bed pressure drop when forming the adsorption bed, reducing operating pressure and energy consumption, thus saving industrial costs. It should be noted that the graphene oxide material in the adsorbent of this invention can be either entirely modified with amino groups, or it can be a graphene oxide material comprising a small portion of unmodified graphene oxide and most of the modified graphene oxide.

[0079] Furthermore, this invention further enhances the performance of the adsorbent in removing nitrophenol from nitrobenzene by using a carrier loaded with metal elements. Specifically, the metal elements in this invention exist mostly as metal hydroxides and a small portion as metal oxides in the adsorbent. The inventors speculate that this is because, firstly, the metal hydroxide form of the metal elements gives the adsorbent high alkalinity, enabling it to effectively neutralize nitrophenol through acid-base neutralization reactions. Since nitrophenol is a weak acid, when it comes into contact with metal hydroxides, a neutralization reaction occurs, generating the corresponding salt and water, thereby preventing damage to the equipment from nitrophenol. Secondly, the aforementioned metal hydroxides have a large specific surface area and abundant surface active sites, which can physically adsorb nitrophenol molecules. This physical adsorption is achieved through weak interactions such as van der Waals forces and hydrogen bonds, effectively reducing the concentration of nitrophenol in the solution. In addition, the metal oxides give the adsorbent strong mechanical properties, which helps stabilize the structure of the adsorbent.

[0080] This invention utilizes an adsorbent comprising graphene oxide containing amino groups and a metal compound supported on the graphene oxide material to effectively remove nitrophenol from nitrobenzene through multiple mechanisms. Specifically, the adsorbent prepared by this invention has a large specific surface area and a uniform three-dimensional network structure with pores of varying sizes distributed between the layers. This suitable pore structure facilitates solution passage. The synergistic effect between the metal element and the amino-group-containing graphene oxide further increases the specific surface area and adsorption sites, significantly improving adsorption efficiency and selectivity. Furthermore, the adsorbent provided by this invention uses amino-group-containing graphene oxide as the material framework, with the metal element supported on it. The entire adsorbent has a monolithic structure, exhibiting excellent physical strength, chemical stability, and mechanical strength. It is easy to separate, recycle, and reuse, effectively avoiding the problems of easy aggregation, difficult separation, and large bed pressure drop encountered by powder adsorbents during liquid-phase adsorption. Using the above adsorbent for nitrophenol removal does not generate large amounts of waste liquid, which is beneficial to environmental protection.

[0081] In the adsorbent, the porosity is 85-99%, for example, including but not limited to 85%, 90%, 95%, 99%, or any combination thereof. The adsorbent in this invention has a high porosity, allowing more internal space for adsorbing nitrophenol, thereby increasing the total adsorption capacity of the adsorbent. This enables the adsorbent to adsorb more nitrophenol from nitrobenzene in a shorter time, improving the efficiency of nitrophenol removal.

[0082] In another specific embodiment, the mass percentage of the metal element in the adsorbent is 2% to 12%. For example, the mass percentage of the metal element in the adsorbent includes, but is not limited to, 2%, 4%, 6%, 8%, 10%, 12%, or any combination thereof. By further limiting the mass percentage of the metal element in the adsorbent, this invention ensures that the metal element has sufficient active sites in the adsorbent, while also helping to reduce bed pressure drop and energy consumption.

[0083] In another specific embodiment, the mass percentage of graphene oxide in the adsorbent is 65% to 95%. For example, the mass percentage of graphene oxide in the adsorbent includes, but is not limited to, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any combination thereof. By further limiting the mass percentage of graphene oxide in the adsorbent, this invention can increase the specific surface area of ​​the adsorbent, thereby improving the adsorption efficiency of nitrophenol. Furthermore, when the mass percentage of graphene oxide in the adsorbent is within the above range, the adsorbent exhibits high chemical stability and mechanical strength, is easy to separate, recycle, and reuse, and improves the practicality of the adsorbent.

[0084] The third aspect of the present invention provides a method for removing nitrophenol from nitrobenzene, specifically by using the adsorbent described above or the adsorbent prepared by the above method to remove nitrophenol from nitrobenzene, achieving a high nitrophenol removal rate, and having low industrial cost without causing a large amount of waste liquid discharge.

[0085] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0086] Example 1

[0087] The method for preparing the adsorbent in this embodiment includes the following steps:

[0088] (1) Dissolve 1.455g of cobalt nitrate hexahydrate, 0.785g of vanadium chloride and 0.6g of urea in 50mL of deionized water, stir at room temperature for 2h to fully dissolve and mix evenly, transfer the reaction solution to a stainless steel reactor lined with polytetrafluoroethylene, and carry out hydrothermal reaction at 140℃ for 18h to obtain the reaction solution.

[0089] (2) After cooling the reaction solution in step (1) to room temperature, filter the precipitate and wash it three times with ethanol and water until pH=7. Then, dry it in an oven at 80°C for 12 hours and finally calcine it in a muffle furnace at 500°C for 5 hours (heating rate 2°C / min) to obtain a metal compound containing metal elements.

[0090] (3) Dissolve 0.5g of graphene oxide (GO) powder, 1g of ethylenediamine and 0.5g of ascorbic acid in 50mL of deionized water, and sonicate for 2h to carry out the first reduction reaction to obtain a uniform graphene oxide material dilute sol.

[0091] (4) Grind the metal compound obtained in step (2) into powder, take 0.1g and add it to the dilute sol of graphene oxide material in step (3), mix it evenly by ultrasonication and pour it into a glass bottle, then heat it at 95℃ for 8h to carry out the second reduction reaction, and then put it into a freeze dryer to carry out the second drying treatment at -60℃ for 24h to obtain the adsorbent.

[0092] The mass percentage of metal elements in the adsorbent, the mass ratio of cobalt and vanadium among the metal elements, and the mass percentage of graphene oxide material in the adsorbent are shown in Table 1.

[0093] Example 2

[0094] This embodiment is basically the same as Embodiment 1, except that 0.7275g of cobalt nitrate hexahydrate and 1.1775g of vanadium chloride were added in step 1) of this embodiment.

[0095] Example 3

[0096] This embodiment is basically the same as embodiment 1, except that 2.1825g of cobalt nitrate hexahydrate and 0.3925g of vanadium chloride were added in step 1) of this embodiment.

[0097] Example 4

[0098] This embodiment is basically the same as Embodiment 1, except that 0.5g of ethylenediamine was added in step 3) of this embodiment.

[0099] Example 5

[0100] This embodiment is basically the same as that of embodiment 1, except that 2g of ethylenediamine is added in step 3) of this embodiment.

[0101] Example 6

[0102] This embodiment is basically the same as embodiment 1, except that 0.05g of metal compound is added in step 4) of this embodiment.

[0103] Example 7

[0104] This embodiment is basically the same as embodiment 1, except that 0.2g of metal compound is added in step 4) of this embodiment.

[0105] Example 8

[0106] This embodiment is basically the same as embodiment 1, except that calcination is not performed in step 2) of this embodiment.

[0107] Example 9

[0108] This embodiment is basically the same as embodiment 1, except that a secondary drying process is not performed in step 4) of this embodiment.

[0109] Example 10

[0110] This embodiment is basically the same as Embodiment 1, except that urea is not added in step 1) of this comparative example.

[0111] Comparative Example 1

[0112] This comparative example is basically the same as Example 1, except that ethylenediamine is not added in step 3) of this comparative example.

[0113] Comparative Example 2

[0114] This comparative example is basically the same as the embodiment, except that this comparative example only performs steps 1) and 2) of embodiment 1.

[0115] Comparative Example 3

[0116] This comparative example is basically the same as the example, except that no metal compound is added in step 4) of this comparative example.

[0117] Test case

[0118] Porosity was determined using the mass-volume method. The specific testing method is as follows: First, the volume (V) of the regularly shaped aerogel sample was calculated. The mass (W1) of the dried aerogel sample was then weighed using an analytical balance. Next, the aerogel was immersed in anhydrous ethanol until adsorption reached saturation. The sample was removed, and the residual ethanol on the surface was removed and weighed (W2). The porosity of the aerogel was calculated using the above data. To ensure the accuracy of the results, each group of test samples underwent three parallel experiments. The porosity experimental results are expressed as the average of the parallel experiments, and the results are shown in Table 1.

[0119] Porosity P (%) is defined as:

[0120] P = (W2 - W1) / (ρV) × 100

[0121] Where ρ is the density of anhydrous ethanol (0.79 g / cm³). 3 ).

[0122] The nitrobenzene in this invention is obtained by adiabatic nitration of benzene and nitric acid, followed by acid washing to remove entrained acid, resulting in a mixture with a main composition of 93% nitrobenzene, 6% benzene, and 2000 pm of nitrophenol.

[0123] The adsorption experiment method for removing nitrophenol from nitrobenzene using an adsorbent in this invention is as follows: 100 ml of the adsorbent prepared in the examples and comparative examples is packed into a glass column, and 500 g of crude nitrobenzene is continuously fed at a rate of 100 g / h. After 5 h, a sample is taken for liquid chromatography analysis.

[0124] The high-performance liquid chromatography (HPLC) method used in this invention was as follows: An Acquity UPLC I-Class plus ultra-high performance liquid chromatograph was used, with a Thermo Acquity UPLC BEH C18 column (50 mm × 2.1 mm, 1.7 μm). Gradient elution was performed using a 0.01 mol / L ammonium formate-formic acid aqueous solution (pH 4.0) as the mobile phase, at a flow rate of 0.4 mL / min, a column temperature of 30 °C, and an injection volume of 5 μL. The experimental results are shown in Table 2.

[0125] Table 1

[0126]

[0127] "-" indicates that no measurement is required.

[0128] Table 2

[0129]

[0130] As can be seen from the table, the adsorbents prepared in Examples 1-10 of the present invention have higher porosity than those in Comparative Examples 1-3, and have higher removal efficiency in removing nitrophenol from nitrobenzene.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an adsorbent, characterized in that, Includes the following steps: 1) A reaction solution is obtained by hydrothermal reaction of a mixture including a precipitant, a metal salt, and a solvent; 2) The reaction solution is subjected to a first drying treatment and a calcination treatment in sequence to obtain a metal compound; 3) A mixed system including graphene oxide, a reducing agent, and polyamines is subjected to a first reduction reaction to obtain a dilute sol of graphene oxide material; 4) The metal compound is added to the dilute sol of the graphene oxide material to carry out a second reduction reaction, and after a second drying treatment, the adsorbent is obtained.

2. The method for preparing the adsorbent according to claim 1, characterized in that, In step 1), the metal salt includes cobalt salt and vanadium salt, and the molar concentration of the metal salt in the mixture is 0.1~0.3 mol / L; and / or, The precipitant includes at least one of ammonia, sodium hydroxide, and urea, and the molar amount of the precipitant is 1 to 1.2 times the molar amount of the metal salt; and / or, In step 3), the mass concentration of graphene oxide in the mixed system is 1–10 mg / mL; and / or, The mass of the polyamine is 0.5 to 8 times the mass of the graphene oxide; and / or, The mass of the reducing agent is 0.5 to 2 times the mass of the graphene oxide; and / or, In step 4), the mass of the metal compound is 0.1 to 0.4 times the mass of the graphene oxide.

3. The method for preparing the adsorbent according to claim 1 or 2, characterized in that, In step 2), the metal compound comprises a metal element, which includes cobalt and vanadium, wherein the mass percentage of cobalt in the metal element is 20-80%; and / or, The vanadium element has a mass percentage content of 20-80% in the metallic elements.

4. The method for preparing the adsorbent according to any one of claims 1-3, characterized in that, The hydrothermal reaction described in step 1) has a reaction temperature of 90–180°C and a reaction time of 12–24 h.

5. The method for preparing the adsorbent according to any one of claims 1-4, characterized in that, In step 2), the first drying treatment is carried out at a temperature of 60–100°C for 10–15 hours; and / or, The calcination treatment is carried out at a temperature of 300–500°C for 4–6 hours.

6. The method for preparing the adsorbent according to any one of claims 1-5, characterized in that, In step 3), the reaction temperature of the first reduction reaction is 20~60℃, and the reaction time is 2~4h; and / or, In step 4), the reaction temperature of the second reduction reaction is 60–180°C, and the reaction time is 6–18 h; and / or, The second drying process is performed at a temperature of -30 to -100°C for 36 to 60 hours.

7. An adsorbent, characterized in that, The adsorbent is prepared according to any one of claims 1-6.

8. The adsorbent according to claim 7, characterized in that, The adsorbent includes a carrier and a metal element supported on the carrier; The carrier includes graphene oxide material, which contains amino groups.

9. The adsorbent according to claim 7 or 8, characterized in that, The porosity of the adsorbent is 85-99%; and / or, The metal element in the adsorbent has a mass percentage content of 2-12%; and / or, The graphene oxide material in the adsorbent has a mass percentage of 65-95%.

10. A method for removing nitrophenol from nitrobenzene, characterized in that, The method includes the following steps: removing nitrophenol from nitrobenzene using an adsorbent prepared by the method of any one of claims 1-4 or any one of claims 5-9.

Images