Method for selectively separating and extracting gallium

Abstract

The invention discloses a method for selectively separating and extracting gallium, and belongs to the technical field of non-ferrous metallurgy. The invention discloses a method for selectively separating and extracting gallium, aiming at the problems of low separation and extraction efficiency of low-concentration gallium in an acidic complex system, insufficient selectivity of a traditional gallium adsorption material, limited adsorption capacity and the like. An amidoxime functionalized calixarene structural unit with precise cavity size and multiple coordination sites is designed and synthesized, and the three-dimensional covalent organic framework material with high crystallinity and porosity is constructed through dynamic covalent chemical regulation and control. The method has the advantages of strong selective coordination capability, high chemical stability and large specific surface area, and can realize efficient capture and enrichment recovery of low-concentration gallium in an acidic multi-metal coexistence environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-ferrous metal metallurgy, and particularly relates to a preparation method of a covalent organic framework material based on amidoxime-functionalized calix[4]arene and its application in selectively adsorbing and recovering gallium in an acidic medium. Background Art

[0002] As a critical metal, gallium has an irreplaceable position in modern high-tech industries and is one of the core raw materials promoting the development of semiconductors, new energy, communications, and national defense technologies. With its excellent semiconductor properties and low melting point characteristics, gallium plays a key role in the preparation of third-generation semiconductor materials (such as gallium nitride and gallium arsenide), which are widely used in fields such as 5G communications, high-speed electronic devices, photovoltaic power generation, and laser technology. In particular, gallium nitride (GaN)-based high-power devices have become the core materials for a new generation of power electronics and radio frequency devices due to their high efficiency, high temperature resistance, and high-frequency characteristics. In addition, gallium-based alloys (such as gallium-indium-tin alloys) have shown broad application prospects in flexible electronics, thermal interface materials, and intelligent sensing fields due to their unique liquid metal properties.

[0003] With the rapid development of high-tech industries, a large number of gallium-containing secondary resources (such as semiconductor waste, LED production waste, fly ash, etc.) have emerged. After leaching treatment, these resources usually form acidic or alkaline complex solution systems, in which the gallium concentration is low and often coexists with elements such as aluminum, zinc, and iron. The similar chemical properties make the separation difficult. Especially in an acidic environment, traditional extraction and precipitation methods have problems such as poor selectivity, low recovery rate, and high reagent consumption. Therefore, developing efficient and highly selective gallium adsorption materials to achieve precise separation and enrichment of gallium in complex systems is of great significance for resource recycling and metal security. Chinese Patent Application No. 202510182621.4 discloses the preparation of a hydroxamic acid-functionalized UiO-66-(COOH) 2 fiber membrane adsorbent and its application in adsorbing gallium, which has the characteristics of easy preparation, green and environmentally friendly preparation process, can adsorb gallium ions from trace gallium solutions under acidic conditions, high selective adsorption rate, fast adsorption rate, and easy recovery and recycling of powder materials. Chinese Patent Application No. 202411381795.5 discloses a structure of an amidoxime resin with characteristic functional groups of bis-amidoxime and imide dioxime, which has a large mass transfer contact area of resin particles and improves the adsorption performance of the resin for gallium. Chinese Patent Application No. 202411015949.9 provides a supercritical CO 2Preparation method of gallium-adsorbing porous chelating resin assisted by amidoximation, which solves the problem that the current process cannot improve the degree of amidoximation on the surface and inside the micropores of the porous chelating resin spheres in a feasible, operable and quantitative manner. Chinese Patent Application No. 202411058205.5 discloses a gallium adsorbent, which uses a nitrogen-containing organic substance to perform nitrogen doping on molybdenum oxide. The obtained nitrogen-doped molybdenum oxide-based nanowires achieve efficient selective adsorption of gallium ions in a coexisting system of impurity ions, and have excellent cyclic stability for the adsorption of gallium ions, solving the problems of low adsorption efficiency, poor selective adsorption and poor recycling performance of the existing technology for low-concentration rare-dispersed metal gallium. Chinese Patent Application No. 202410791402.1 discloses a method for synthesizing a gallium-targeting adsorption material and deeply extracting gallium, which overcomes the problem of poor structural stability of traditional extractants in an industrial highly acidic environment, effectively increases the solvent affinity of pyrrolyl pillar[5]arene functional groups in an acidic aqueous solution system, realizes efficient adsorption, and the stable aromatic ring silicon-based skeleton ensures its good cyclic service life under highly acidic conditions. Chinese Patent Application No. 202410301843.9 provides a preparation method of hydroxamic acid-functionalized gallium ion adsorption resin. The hydroxamic acid-functionalized gallium ion adsorption resin prepared by this method can effectively adsorb gallium ions, with high adsorption rate and adsorption capacity, and can efficiently and selectively recover gallium from a complex system. Chinese Patent Application No. 202311258889.9 provides a method for preparing a magnetic chitosan-based solid gallium ion adsorbent using ion imprinting technology. At pH = 4, the maximum adsorption capacity for gallium ions reaches 434 mg / g, far exceeding the existing gallium ion adsorbents. Through competitive experiments, it is proved that it has excellent selective adsorption for gallium ions. Summary of the Invention

[0004] The object of the present invention is to overcome the technical problem of low separation and extraction efficiency of low-concentration gallium in the current acidic complex system, and to overcome the defects of traditional gallium adsorption materials such as insufficient selectivity, limited adsorption capacity and poor acid stability. A preparation method of an amidoxime-based calixarene covalent organic framework adsorption material and its method for targeted recovery of gallium are provided. Based on the coordination chemical properties of gallium ions, an amidoxime-functionalized calixarene structural unit with precise cavity size and multiple coordination sites is designed and synthesized, and a three-dimensional covalent organic framework material with high crystallinity and porosity is constructed through dynamic covalent chemistry regulation. Through the synergistic effect of the amidoxime group and the calixarene, this material forms multiple recognition sites for gallium ions, and has the advantages of strong selective coordination ability, high chemical stability and large specific surface area, and can realize the efficient capture and enrichment recovery of low-concentration gallium in an acidic multi-metal coexisting environment.

[0005] To solve the above problems, the technical solutions adopted by the present invention are as follows: The present invention provides a method for selectively separating and extracting gallium, and the specific steps are as follows: (1) Calix[4]arene and hexamethylenetetramine are heated under reflux in a mixed solvent of methanesulfonic acid and dichloromethane. After cooling to room temperature, powdered NaHCO 3 or K 2 CO 3 is added until no more bubbles are generated. After extraction, concentration and recrystallization, tetraformylcalix[4]arene is obtained; (2) The ground tetraformylcalix[4]arene is mixed with 4,4-biphenylcarbonitrile in a mixed solvent of o-dichlorobenzene and n-butanol and subjected to ultrasonic treatment. After degassing, it is vacuum-sealed and reacted under microwave irradiation. After the reaction is completed, it is cooled, washed and dried to obtain calix[4]arene COF; (3) Calix[4]arene COF is refluxed with a hydroxylamine derivative in a solvent and washed to obtain amidoxime-based calix[4]arene COF; (4) The amidoxime-based calix[4]arene COF is added to a gallium-containing solution system, and the targeted adsorption separation and extraction of gallium are achieved through a constant-temperature reaction.

[0006] Preferably, in the above method for selectively separating and extracting gallium, the specific processes of extraction, concentration and recrystallization in step (1) are as follows: extracting with dichloromethane, performing rotary evaporation under reduced pressure on the organic phase to obtain a crude product, and recrystallizing with dichloromethane to obtain yellow solid tetraformylcalix[4]arene.

[0007] Preferably, in the above method for selectively separating and extracting gallium, the molar ratio of calix[4]arene to hexamethylenetetramine in step (1) is (1:1.2) - (1:4), the volume ratio of methanesulfonic acid to dichloromethane is (4:1) - (6:1), the reaction time is 12 - 24 h, and the stirring time after adding powdered NaHCO 3 or K 2 CO 3 is 0.5 - 2 h.

[0008] Preferably, in the above method for selectively separating and extracting gallium, the specific processes of vacuum sealing after degassing, reacting under microwave irradiation, and cooling, washing and drying in step (2) are as follows: performing several freeze-pump-thaw cycles for degassing, pumping the pressure in the heat-resistant glass tube to 0.1 Pa and then vacuum-sealing, and placing it in a microwave reactor; heating to a specific temperature at a programmed rate and then maintaining the temperature for heating, performing microwave-assisted irradiation at a set power condition for 10 min, and repeating the irradiation operation at intervals of 60 min; after the reaction is completed, waiting for the system to cool to room temperature, filtering and washing the precipitate with DMF, water and absolute ethanol in sequence, and drying under vacuum at 60 °C for a period of time to obtain acetonitrile-calix[4]arene COF.

[0009] Preferably, in the above method for selectively separating and extracting gallium, in step (2), the molar ratio of tetramethoxylcalix[4]arene to linker 4,4-biphenylcarbonitrile is (1:1) to (3:2), the volume ratio of o-dichlorobenzene to n-butanol is (3:1) to (1:1), the ultrasonic time of the mixture is 20 to 30 min, the number of freeze-pump-thaw cycle degassing times is 3 to 4 times, the temperature is programmed to rise to 90 to 120 °C, the reaction time is 24 to 48 h, the microwave-assisted radiation power is 500 to 1000 W, and the vacuum drying time is 6 to 12 h.

[0010] Preferably, in the above method for selectively separating and extracting gallium, in step (3), the molar ratio of calix[4]arene COF, hydroxylamine hydrochloride and N,N-dimethylformamide is (1:6) to (1:10), and the volume ratio of ethanol to N,N-dimethylformamide is (1:40) to (1:60). The reaction temperature is 80 to 100 °C, and the reaction time is 24 to 36 h.

[0011] Preferably, in the above method for selectively separating and extracting gallium, in step (4), the hydrogen ion concentration of the gallium-containing solution system is 0.05 to 4 mol / L, the reaction temperature is 25 to 90 °C, and the reaction time is 0.5 to 5 h.

[0012] The present invention adopts the above method for selectively separating and extracting gallium, and obtains the following beneficial effects: (1) In the method for selectively separating and extracting gallium of the present invention, the formylation of calix[4]arene is one of the important methods for functionalizing and modifying such supramolecular hosts. The traditional hexamethylenetetramine formylation reaction (Duff reaction) uses trifluoroacetic acid as the reaction medium, which has strong corrosiveness, complex post-treatment, and may cause side reactions. Therefore, replacing it with a mixed solution system of methanesulfonic acid (MSA) and dichloromethane with stronger activity and lower corrosiveness can reduce the synthesis time and improve the yield of tetramethoxylcalix[4]arene. Secondly, in the synthesis process of nitrile-calix[4]arene COF, a general synthesis strategy is pioneered, and microwave-assisted radiation is used at intervals while heating. In this method, the ingenious addition of microwave conditions can promote the directional growth of crystals, improve the material properties, and significantly improve the reaction efficiency to prepare nitrile-calix[4]arene COF. In addition, replacing triethylamine with N,N-dimethylformamide with slightly weaker alkalinity can reduce the by-products generated due to the presence of strong bases and improve the purity of the product, and finally obtain amidoxime-calix[4]arene COF.

[0013] (2) A method for selectively separating and extracting gallium according to the present invention. The amidoxime moiety in the adsorbent material realizes highly selective recognition of gallium ions through the synergistic action of coordination and hydrogen bonding. This interaction has both strong binding force and dynamic tunability, which is the key to achieving high-capacity adsorption and desorption under mild conditions; the rigid cavity structure of the calixarene moiety can precisely match the coordination geometric requirements of gallium ions through the pre-organization effect, significantly improving the selectivity. The regular pore structure of the covalent organic framework can optimize the pore size and the spatial arrangement of functional moieties through monomer design and synthesis condition regulation, which not only strengthens the mass transfer kinetics of gallium ions in the pores, but also generates a "molecular recognition enhancement effect" through the synergistic action of the amidoxime-calixarene double sites. Description of the Drawings

[0014] Figure 1 It is a process diagram for the formation of amidoxime-calix[4]arene COF. Detailed Embodiments

[0015] Aiming at the problems of low separation and extraction efficiency of low-concentration gallium in acidic complex systems, insufficient selectivity and limited adsorption capacity of traditional gallium adsorbents, based on the coordination chemical properties of gallium ions, an amidoxime-functionalized calixarene structural unit with precise cavity size and multiple coordination sites is designed and synthesized, and a three-dimensional covalent organic framework material with high crystallinity and porosity is constructed through dynamic covalent chemistry regulation. Multiple recognition sites for gallium ions are formed, which have the advantages of strong selective coordination ability, high chemical stability and large specific surface area, and can realize the efficient capture, enrichment and recovery of low-concentration gallium in an acidic multi-metal coexisting environment. As Figure 1 shown, the treatment process of the present invention specifically includes the following steps: The preparation of the gallium adsorbent amidoxime-calix[4]arene COF (CX[4]-AO-COF) first requires the synthesis of tetrakis(formyl)calix[4]arene (CX[4]-CHO), and the synthesis of nitrile-calix[4]arene COF (CX[4]-BPCN-COF) with 4,4'-biphenylcarbonitrile (BPCN), and finally the amidoxime-calix[4]arene COF (CX[4]-AO-COF) is prepared through a post-modification strategy. The specific synthesis scheme is as follows: (1) Synthesis of tetrakis(formyl)calix[4]arene (CX[4]-CHO): Dissolve calix[4]arene (CX[4]) and hexamethylenetetramine in a mixed solvent of methanesulfonic acid (MSA) / dichloromethane (V:V=(4:1)~(6:1)) according to a molar ratio of (1:1.2)~(1:4) and heat under reflux for 12~24 h. After the reaction is completed, wait for the system to cool to room temperature, and add powdered NaHCO 3 or K 2 CO 3, until no more bubbles are generated. After stirring for 0.5 - 2 h, extract with dichloromethane, and rotary evaporate the organic phase under reduced pressure to obtain the crude product. Recrystallize from dichloromethane to obtain the yellow solid tetrakis(formyl)calix[4]arene.

[0016] (2)Synthesis of nitrile-calix[4]arene COF (CX[4]-BPCN-COF): Add the ground tetrakis(formyl)calix[4]arene and the linker 4,4'-biphenylcarbonitrile in a molar ratio of (1:1) - (3:2) into a 20 mL Pyrex tube. Subsequently, add a mixed solvent of o-dichlorobenzene and n-butanol (6 ml, V:V = (3:1) - (1:1)) to the tube. Ultrasonic the mixture for 20 - 30 min, degas through 3 - 4 freeze-pump-thaw cycles, and evacuate the pressure in the Pyrex tube to 0.1 Pa and then seal it under vacuum. Place it in a microwave reactor. Heat under a programmed temperature of 90 - 120 °C for 24 - 48 h, and perform microwave-assisted radiation at 500 - 1000 W for 10 min, repeating the radiation operation at intervals of 60 min. After the reaction is completed, wait for the system to cool to room temperature, and filter and wash the precipitate successively with DMF, water, and absolute ethanol. Dry it under vacuum at 60 °C for 6 - 12 h to obtain acetonitrile-calix[4]arene COF.

[0017] (3)Synthesis of amidoxime-calix[4]arene COF (CX[4]-AO-COF): Dissolve calix[4]arene COF, hydroxylamine hydrochloride, and N,N-dimethylformamide in an ethanol solution (the molar ratio of acetonitrile-calix[4]arene COF to hydroxylamine hydrochloride is 1:6 - 1:10, and the volume ratio of ethanol to N,N-dimethylformamide is 1:40 - 1:60). Stir the mixture under reflux at 80 - 100 °C for 24 - 36 h, and wash the precipitate successively with H 2 O and absolute ethanol to finally obtain amidoxime-based calix[4]arene COF.

[0018] (4)Adsorption experiment of amidoxime-calix[4]arene COF (CX[4]-AO-COF) for gallium: Add the synthesized amidoxime-based calix[4]arene covalent organic framework adsorbent into a gallium-containing solution system with a hydrogen ion concentration of 0.05 - 4 mol / L, and react at a temperature of 25 - 90 °C for 0.5 - 5 h to achieve the targeted adsorption separation and extraction of gallium.

[0019] The present invention will be further described below in conjunction with specific embodiments.

[0020] Example 1 A method for selective separation and extraction of gallium in this example specifically includes the following steps: (1) Dissolve calix[4]arene (CX[4]) and hexamethylenetetramine in a mixed solvent of methanesulfonic acid (MSA) / dichloromethane (V:V = 4:1) at a molar ratio of 1:1.2 and heat under reflux for 12 h. After the reaction is completed, wait for the system to cool to room temperature, and add powdered NaHCO 3 or K 2 CO 3 , until no more bubbles are generated. After stirring for 0.5 h, extract with dichloromethane, and rotary evaporate the organic phase under reduced pressure to obtain a crude product. Recrystallize from dichloromethane to obtain yellow solid tetraformyl calix[4]arene.

[0021] (2) Add the ground tetraformyl calix[4]arene and linker 4,4-biphenylcarbonitrile to a 20 mL Pyrex tube at a molar ratio of 1:1. Subsequently, add a mixed solvent of o-dichlorobenzene and n-butanol (6 ml, V:V = 3:1) to the tube. Ultrasonic the mixture for 20 min, degas through 3 freeze-pump-thaw cycles, and evacuate the pressure in the Pyrex tube to 0.1 Pa and then vacuum seal it. Place it in a microwave reactor. Program the temperature to 90 °C and heat for 24 h, and perform microwave-assisted radiation at 500 W for 10 min, repeating the radiation operation at intervals of 60 min. After the reaction is completed, wait for the system to cool to room temperature, and filter and wash the precipitate with DMF, water, and absolute ethanol in sequence. Dry under vacuum at 60 °C for 60 h to obtain acetonitrile-calix[4]arene COF.

[0022] (3) Dissolve calix[4]arene COF, hydroxylamine hydrochloride, and N,N-dimethylformamide in an ethanol solution (the molar ratio of acetonitrile-calix[4]arene COF to hydroxylamine hydrochloride is 1:6, and the volume ratio of ethanol to N,N-dimethylformamide is 1:40). Stir the mixture under reflux at 80 °C for 24 h, and wash the precipitate with H 2 O and absolute ethanol in sequence to finally obtain amidoxime-calix[4]arene COF.

[0023] (4) Add the synthesized amidoxime-calix[4]arene covalent organic framework adsorbent material to a gallium-containing solution system with a hydrogen ion concentration of 0.05 mol / L, and react at 25 °C for 0.5 h to achieve the targeted adsorption separation and extraction of gallium, and the adsorption rate of gallium is 99.24%.

[0024] Example 2 A method for selectively separating and extracting gallium in this example specifically includes the following steps: (1) Dissolve calix[4]arene (CX[4]) and hexamethylenetetramine in a mixed solvent of methanesulfonic acid (MSA) / dichloromethane (V:V = 6:1) at a molar ratio of 1:4 and heat under reflux for 24 h. After the reaction is completed, wait for the system to cool to room temperature, and add powdered NaHCO 3 or K 2 CO 3 , until no more bubbles are generated. After stirring for 2 h, extract with dichloromethane, and rotary evaporate the organic phase under reduced pressure to obtain a crude product. Recrystallize from dichloromethane to obtain yellow solid tetraformylcalix[4]arene.

[0025] (2) Add the ground tetraformylcalix[4]arene and linker 4,4-biphenylcarbonitrile to a 20 mL Pyrex tube at a molar ratio of 3:2. Subsequently, add a mixed solvent of o-dichlorobenzene and n-butanol (6 ml, V:V = 1:1) to the tube. Ultrasonic the mixture for 30 min, degas it three times through 4 freeze-pump-thaw cycles, and evacuate the pressure in the Pyrex tube to 0.1 Pa and then seal it under vacuum. Place it in a microwave reactor. Heat it at a programmed temperature of 120 °C for 48 h, and irradiate it under microwave assistance at 1000 W for 10 min, and repeat the irradiation operation at intervals of 60 min. After the reaction is completed, wait for the system to cool to room temperature, and filter and wash the precipitate with DMF, water, and absolute ethanol in sequence. Dry it under vacuum at 60 °C for 12 h to obtain acetonitrile-calix[4]arene COF.

[0026] (3) Dissolve calix[4]arene COF, hydroxylamine hydrochloride, and N,N-dimethylformamide in an ethanol solution (the molar ratio of acetonitrile-calix[4]arene COF to hydroxylamine hydrochloride is 1:10, and the volume ratio of ethanol to N,N-dimethylformamide is 1:60). Stir the mixture under reflux at 100 °C for 36 h, and wash the precipitate with H 2 O and absolute ethanol in sequence to finally obtain amidoxime-calix[4]arene COF.

[0027] (4) Add the synthesized amidoxime-calix[4]arene covalent organic framework adsorbent material to a gallium-containing solution system with a hydrogen ion concentration of 4 mol / L, and react at 90 °C for 5 h to achieve targeted adsorption separation and extraction of gallium, and the adsorption rate of gallium is 99.69%.

[0028] Example 3 A method for selective separation and extraction of gallium in this example specifically includes the following steps: (1) Dissolve calix[4]arene (CX[4]) and hexamethylenetetramine in methanesulfonic acid (MSA) / dichloromethane (V:V = 4.5:1) at a molar ratio of 1:2 and reflux for 16 h. After the reaction is completed, wait for the system to cool to room temperature, and add powdered NaHCO 3 or K 2 CO 3 , until no more bubbles are generated. After stirring for 1 h, extract with dichloromethane, and rotary evaporate the organic phase under reduced pressure to obtain the crude product. Recrystallize from dichloromethane to obtain yellow solid tetramethoxycarbonyl calix[4]arene.

[0029] (2) Add the ground tetramethoxycarbonyl calix[4]arene and linker 4,4-biphenylcarbonitrile to a 20 mL Pyrex tube at a molar ratio of 6:5. Subsequently, add a mixed solvent of o-dichlorobenzene and n-butanol (6 mL, volume ratio = 2:1) to the tube. Ultrasonic the mixture for 25 min, degas it through 3 freeze-pump-thaw cycles, and evacuate the pressure in the Pyrex tube to 0.1 Pa and then seal it under vacuum. Place it in a microwave reactor. Heat it at a programmed temperature of 100 °C for 28 h, and irradiate it under microwave assistance at 600 W for 10 min, and repeat the irradiation operation at intervals of 60 min. After the reaction is completed, wait for the system to cool to room temperature, and filter and wash the precipitate with DMF, water, and absolute ethanol in sequence. Dry it under vacuum at 60 °C for 8 h to obtain acetonitrile-calix[4]arene COF.

[0030] (3) Dissolve calix[4]arene COF, hydroxylamine hydrochloride, and N,N-dimethylformamide in an ethanol solution (the molar ratio of acetonitrile-calix[4]arene COF to hydroxylamine hydrochloride is 1:7, and the volume ratio of ethanol to N,N-dimethylformamide is 1:45). Stir the mixture under reflux at 85 °C for 28 h, and wash the precipitate with H 2 O and absolute ethanol in sequence to finally obtain amidoxime-calix[4]arene COF.

[0031] (4) Add the synthesized amidoxime-calix[4]arene covalent organic framework adsorbent to a gallium-containing solution system with a hydrogen ion concentration of 1 mol / L, react at 45 °C for 1 h, realize the targeted adsorption separation and extraction of gallium, and the adsorption rate of gallium is 99.38%.

[0032] Example 4 A method for selectively separating and extracting gallium in this example specifically includes the following steps: (1) Dissolve calix[4]arene (CX[4]) and hexamethylenetetramine in a mixed solvent of methanesulfonic acid (MSA) / dichloromethane (V:V = 5:1) at a molar ratio of 1:3 and reflux for 18 h. After the reaction is completed, wait for the system to cool to room temperature, and add powdered NaHCO3 or K 2 CO 3 , until no more bubbles are generated. After stirring for 1.5 h, extract with dichloromethane, and rotary evaporate the organic phase under reduced pressure to obtain the crude product. Recrystallize from dichloromethane to obtain the yellow solid tetrakis(formyl)calix[4]arene.

[0033] (2) Add the ground tetrakis(formyl)calix[4]arene and the linker 4,4'-biphenylcarbonitrile into a 20 mL Pyrex tube according to a molar ratio of 7:5. Subsequently, add a mixed solvent of o-dichlorobenzene and n-butanol (6 ml, V:V = 1.5:1) to the tube. Ultrasonic the mixture for 25 min, degas it three times through 4 freeze-pump-thaw cycles, and evacuate the pressure in the Pyrex tube to 0.1 Pa and then seal it under vacuum. Place it in a microwave reactor. Heat it under a programmed temperature rise to 110 °C for 32 h, perform microwave-assisted radiation at 700 W for 10 min, and repeat the radiation operation at intervals of 60 min. After the reaction is completed, wait for the system to cool to room temperature, and filter and wash the precipitate with DMF, water, and absolute ethanol in sequence. Dry it under vacuum at 60 °C for 10 h to obtain acetonitrile-calix[4]arene COF.

[0034] (3) Dissolve calix[4]arene COF, hydroxylamine hydrochloride, and N,N-dimethylformamide in an ethanol solution (the molar ratio of acetonitrile-calix[4]arene COF to hydroxylamine hydrochloride is 1:8, and the volume ratio of ethanol to N,N-dimethylformamide is 1:50). Stir the mixture under reflux at 90 °C for 30 h, and wash the precipitate with H 2 O and absolute ethanol in sequence to finally obtain amidoxime-based calix[4]arene COF.

[0035] (4) Add the synthesized amidoxime-based calix[4]arene covalent organic framework adsorbent into a gallium-containing solution system with a hydrogen ion concentration of 2 mol / L, react at 60 °C for 2 h, realize the targeted adsorption separation and extraction of gallium, and the adsorption rate of gallium is 99.49%.

[0036] Example 5 A method for selectively separating and extracting gallium in this example specifically includes the following steps: (1) Dissolve calix[4]arene (CX[4]) and hexamethylenetetramine in a mixed solvent of methanesulfonic acid (MSA) / dichloromethane (V:V = 5.5:1) according to a molar ratio of 1:3.5 and heat under reflux for 20 h. After the reaction is completed, wait for the system to cool to room temperature, and add powdered NaHCO 3 or K 2 CO 3, until no more bubbles are generated. After stirring for 1.8 h, extract with dichloromethane, and perform rotary evaporation under reduced pressure on the organic phase to obtain the crude product. Recrystallize from dichloromethane to obtain the yellow solid tetraformylcalix[4]arene.

[0037] (2) Add the ground tetraformylcalix[4]arene and the linker 4,4'-biphenylcarbonitrile into a 20 mL Pyrex tube according to the molar ratio (4:3). Subsequently, add the mixed solvent of o-dichlorobenzene and n-butanol (6 mL, volume ratio = 2:1) into the tube. Ultrasonic the mixture for 25 min, degas it three times through 4 freeze-pump-thaw cycles, and evacuate the pressure in the Pyrex tube to 0.1 Pa and then seal it under vacuum. Place it in a microwave reactor. Heat it under the condition of programmed temperature rise to 115 °C for 40 h, perform microwave-assisted radiation at 800 W for 10 min, and repeat the radiation operation at intervals of 60 min. After the reaction is completed, wait for the system to cool to room temperature, and filter and wash the precipitate with DMF, water, and absolute ethanol in sequence. Dry it under vacuum at 60 °C for 11 h to obtain acetonitrile-calix[4]arene COF.

[0038] (3) Dissolve calix[4]arene COF, hydroxylamine hydrochloride, and N,N-dimethylformamide in an ethanol solution (the molar ratio of acetonitrile-calix[4]arene COF to hydroxylamine hydrochloride is 1:9, and the volume ratio of ethanol to N,N-dimethylformamide is 1:55). Stir the mixture under reflux at 95 °C for 32 h, and wash the precipitate with H 2 O and absolute ethanol in sequence to finally obtain amidoxime-based calix[4]arene COF.

[0039] (4) Add the synthesized amidoxime-based calix[4]arene covalent organic framework adsorbent into a gallium-containing solution system with a hydrogen ion concentration of 3 mol / L, react at 70 °C for 3 h to achieve the targeted adsorption separation and extraction of gallium, and the adsorption rate of gallium is 99.51%.

Claims

1. A method for selectively separating and extracting gallium, characterized in that: The specific steps are as follows: (1) Releasing calix[4]arene and hexamethylenetetramine in a mixed solvent of methanesulfonic acid and dichloromethane under reflux for reaction, cooling to room temperature, adding powdered NaHCO3 or K2CO3 until bubbles are no longer generated, extracting, concentrating and recrystallizing to obtain tetracarboxaldehyde-based calix[4]arene; (2) mixing the ground tetracarboxaldehyde calix[4]arene with a mixed solvent of 4,4-biphenylcarbonitrile, o-dichlorobenzene and n-butanol, subjecting the mixture to ultrasonic treatment, degassing and vacuum sealing, reacting the mixture under microwave radiation, cooling, washing and drying after the reaction, and obtaining calix[4]arene COF; (3) reflux reaction of calix[4]arene COF with a hydroxylamine derivative in a solvent, and washing to obtain amidoxime-calix[4]arene COF; (4) Adding the amidoxime-calix[4]arene COF into a gallium-containing solution system, and achieving targeted adsorption, separation and extraction of gallium through a constant temperature reaction.

2. The method for selectively separating and extracting gallium according to claim 1, characterized in that: The specific process of extraction, concentration and recrystallization in step (1) is as follows: extraction with dichloromethane, and vacuum rotary evaporation of the organic phase to obtain a crude product, and recrystallization from dichloromethane to obtain a yellow solid tetracarboxaldehyde calix[4]arene.

3. A method for selectively separating and extracting gallium according to claim 2, characterized in that: In the step (1), the molar ratio of calix[4]arene to hexamethylenetetramine is (1:1.2) to (1:4), the volume ratio of methanesulfonic acid to dichloromethane is (4:1) to (6:1), the reaction time is 12 to 24 hours, and the stirring time after adding powdered NaHCO3 or K2CO3 is 0.5 to 2 hours.

4. The method for selectively separating and extracting gallium according to claim 1, characterized in that: The specific process of degassing, vacuum sealing, reacting under microwave irradiation, and cooling, washing and drying in step (2) is as follows: degassing after several freeze-pump-thaw cycles, and vacuum sealing after the pressure in the heat-resistant glass tube is evacuated to 0.1 Pa, and placed in a microwave reactor; program heating to 90-120° C. and then constant temperature heating, microwave-assisted irradiation for 10 minutes under set power conditions, and repeating the irradiation operation at intervals of 60 minutes; after the reaction is completed, wait for the system to cool to room temperature, filter and wash the precipitate with DMF, water and anhydrous ethanol in turn, and vacuum dry at 60° C. to obtain acetonitrile-calix[4]arene COF.

5. The method for selectively separating and extracting gallium according to claim 4, characterized in that: In the step (2), the molar ratio of tetracarboxaldehyde calix[4]arene to the linker 4,4-biphenylcarbonitrile is (1:1) to (3:2), the volume ratio of o-dichlorobenzene to n-butanol is (3:1) to (1:1), the ultrasonic time of the mixture is 20 to 30 minutes, the number of freeze-pump-thaw cycle degassing is 3 to 4 times, the reaction time is 24 to 48 hours, the microwave-assisted radiation power is 500 to 1000 W, and the vacuum drying time is 6 to 12 hours.

6. The method for selectively separating and extracting gallium according to claim 1, characterized in that: In the step (3), the molar ratio of calix[4]arene COF, hydroxylamine hydrochloride and N,N-dimethylformamide is (1:6) to (1:10), the volume ratio of ethanol to N,N-dimethylformamide is (1:40) to (1:60), the reaction temperature is 80 to 100° C., and the reaction time is 24 to 36 hours.

7. The method for selectively separating and extracting gallium according to claim 1, characterized in that: In the step (4), the hydrogen ion concentration of the gallium-containing solution system is 0.05 to 4 mol / L, the reaction temperature is 25 to 90° C., and the reaction time is 0.5 to 5 h.

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