A method for in-situ preparation of MXene / biomass interfacial evaporation material

Abstract

The present application relates to a method for preparing MXene / biomass interfacial evaporation material in situ, and belongs to the technical field of interfacial evaporation. The present application uses in-situ etching method to complete MAX phase etching, biomass pretreatment and boron adsorption active component construction simultaneously, solving the problems of traditional preparation process of MXene and biomass material, such as complexity, strong corrosion, easy flocculation and single function. The method comprises the following steps: first, preparing a choline chloride-based deep eutectic solvent etching solution; second, using the etching solution to heat and react with the mixture of MAX phase, lignocellulose and magnesium chloride in situ, and then performing solid-liquid separation by centrifugation, so that the obtained solid phase is a mixture of magnesium chloride anchored multi-layer MXene and lignocellulose solid residue; third, adding deionized water and ultrasonic-assisted stripping of multi-layer MXene into single-layer MXene; fourth, washing and freeze-drying treatment to obtain interfacial evaporation composite material. The present application realizes the integration of efficient evaporation and synchronous boron adsorption, is suitable for seawater desalination and other fields, and has the advantages of environmental protection and easy scaling.

Description

Technical Field

[0001] This invention belongs to the field of interfacial evaporation material preparation, specifically relating to a method for in-situ preparation of MXene / biomass interfacial evaporation materials. Background Technology

[0002] With the increasingly severe global water shortage, water purification technologies such as seawater desalination and wastewater treatment have become research hotspots. Interfacial evaporation technology, with its advantages of low energy consumption and high evaporation efficiency, shows broad application prospects in the field of seawater desalination. MXene, as a novel two-dimensional transition metal carbide / nitride material, possesses ultra-high photothermal conversion efficiency, excellent hydrophilicity, large specific surface area, and stable physicochemical properties. It can rapidly convert light energy into heat energy, significantly improving the seawater interfacial evaporation rate, making it a preferred photothermal material for constructing efficient interfacial evaporation systems.

[0003] The preparation of MXenes mainly relies on fluorine-containing etching systems, represented by direct etching with hydrofluoric acid (HF) and in-situ etching with hydrochloric acid-lithium fluoride (HCl+LiF), with the latter being the most widely used. However, these methods involve highly corrosive etchants, resulting in serious environmental pollution, high operational safety risks, and cumbersome preparation processes. To overcome these shortcomings, researchers have developed fluorine-free etching strategies such as electrochemical etching, high-temperature alkaline treatment, molten salt synthesis, and eutectic solvent etching. Among these, green eutectic solvents can etch the MAX phase to prepare MXenes under mild conditions. For example, Chinese patent application CN202310298407.6 discloses a MAX phase etching method based on a novel metal salt eutectic solvent, which uses a metal salt eutectic solvent for fluorine-free etching and achieves surface modification of MXenes, but it does not involve synergistic pretreatment of biomass materials. Therefore, how to simultaneously achieve biomass pretreatment and modification during MXene etching to simplify the preparation process of composite materials is a technical problem that urgently needs to be solved in this field. Furthermore, in the field of interfacial evaporation applications, the MXene / biomass interfacial evaporation materials currently prepared based on the eutectic solvent system have a single function, only used for seawater desalination. They are difficult to simultaneously recover high-value elements such as boron, magnesium, and potassium from seawater, resulting in low resource utilization and failing to achieve the dual goals of freshwater production and resource recovery.

[0004] Therefore, developing a simple, environmentally friendly composite material preparation method that can simultaneously achieve MXene preparation, biomass modification, and functional component loading, while also possessing efficient interfacial evaporation and high-value element adsorption functions, has become an urgent technical problem to be solved. Summary of the Invention

[0005] To address the problems of complex traditional preparation processes, strong corrosiveness, easy flocculation of MXene aqueous dispersions and lignin pretreatment solutions, and limited material functionality in existing technologies, the present invention aims to provide a method for in-situ preparation of MXene / biomass interfacial evaporation materials. This method uses a choline chloride-based eutectic solvent as a green etching solution, and simultaneously completes MAX phase etching, biomass pretreatment, and boron-absorbing active component construction through a one-step in-situ reaction. This simplifies the preparation process, improves material performance, and achieves integrated high-efficiency evaporation and simultaneous boron absorption.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] (1) Mix choline chloride and cobalt chloride in proportion, place them in an oil bath, and react them at 500 rpm and 80~100 ℃ for 1~3 h to prepare a eutectic solvent etching solution;

[0008] (2) Mix the MAX phase with lignocellulose in proportion and stir at 500 rpm for 60 min until uniform. Then slowly add magnesium chloride and continue stirring for 30 min. Set aside.

[0009] (3) Add the mixture obtained in step (2) to the etching solution obtained in step (1), react at a reaction temperature of 160~180 ℃ and a stirring speed of 500 rpm for 1~3 h, and centrifuge to separate the solid and liquid phases. The resulting solid phase is a mixture of magnesium chloride-anchored multilayer MXene and lignocellulose solid residue.

[0010] (4) Add deionized water to the solid phase obtained in step (3) and sonicate to peel off the multilayer MXene into a single layer MXene;

[0011] (5) Wash the product obtained in step (4) and pre-freeze the solid obtained after washing into a three-dimensional block. After freeze-drying, the MXene / biomass interface evaporation composite material is obtained.

[0012] Preferably, the molar ratio of choline chloride to cobalt chloride in step (1) is 1:2.

[0013] Preferably, the MAX phase in step (2) is Ti3AlC2.

[0014] Preferably, the amounts of the MAX phase, lignocellulose and magnesium chloride added in step (2) are 400 g, 100 g and 50 g, respectively.

[0015] Preferably, the solid-liquid ratio of the mixed raw material to the etching solution in step (3) is 1:20 g / mL.

[0016] Preferably, the ultrasonic power in step (4) is 400 W, with a single session lasting 10 minutes and repeated 5 to 7 times.

[0017] Preferably, the washing in step (5) is washing with deionized water until the pH is 6; the pre-freezing temperature is -40 ℃ and the freeze-drying time is 48 h.

[0018] Step (1) Choline chloride acts as a hydrogen bond acceptor, and cobalt chloride acts as a hydrogen bond donor. Through hydrogen bonding, they form a eutectic solvent (DES), which significantly lowers the melting point of the system, giving it good fluidity and reactivity. Simultaneously, the Co in cobalt chloride... 2+ It provides Lewis acid active sites, which can selectively attack the Al layer in the MAX phase, laying the foundation for subsequent efficient etching. Compared with traditional strong acid and strong base etchants, this DES system does not produce any highly corrosive or toxic substances throughout the process, and has good environmental friendliness.

[0019] Step (2) Magnesium chloride is uniformly distributed on the surface of the MAX phase particles and lignocellulose fibers through electrostatic adsorption and surface loading. The core lies in the magnesium source (Mg... 2+ The MAX phase is pre-dispersed in the reaction raw material system. Utilizing the abundant polar functional groups such as hydroxyl groups in lignocellulose, the adhesion stability of magnesium chloride on the solid surface is enhanced through ion-dipole interactions. Simultaneously, the layered structure surface of the MAX phase is also Mg... 2+ It provides physical adsorption sites, laying the material foundation for the in-situ anchoring of Mg²⁺ in the subsequent high-temperature reaction stage, ensuring the uniform loading of magnesium components in the MXene interlayer and lignocellulose skeleton, and avoiding uneven material properties caused by local enrichment or absence.

[0020] Step (3) Co in DES 2+ As a Lewis acid, it selectively etches the Al layer in the MAX phase, releasing Al atoms from the interlayer through coordination and transforming them into multilayered MXene. Simultaneously, the lignocellulose undergoes structural loosening and the dissolution and removal of some components (hemicellulose, lignin), forming a porous lignocellulose framework in situ. Magnesium chloride pre-loaded on the surface of the mixture, during etching, utilizes electrostatic adsorption, chemical coordination, and spatial confinement effects to bind Mg... 2+ It is in situ anchored between the newly formed multilayered MXene layers and on the surface of the lignocellulose skeleton. After centrifugation and solid-liquid separation, the resulting solid phase is a mixture of multilayered MXene anchored by magnesium chloride and porous lignocellulose skeleton.

[0021] Step (4) The cavitation effect and mechanical vibration generated by ultrasound act on the multilayer MXene, overcoming the interlayer van der Waals forces, causing the magnesium chloride-anchored multilayer MXene to further peel off into single layers. Mg pre-anchored between the MXene layers 2+ On the one hand, hydration increases the interlayer spacing, reducing the energy required for peeling; on the other hand, positively charged Mg...2+ The electrostatic repulsion between the MXene and the negatively charged groups on the MXene surface effectively inhibits the recombination of monolayer MXene after peeling, thereby obtaining a stable monolayer MXene dispersion system.

[0022] Step (5) Washing removes residual solvent and soluble byproducts; pre-freezing crystallizes water molecules into ice, fixing the mixture into a three-dimensional block shape; during freeze-drying, the ice crystals sublimate under vacuum, leaving a porous network structure that is interconnected. This three-dimensional porous structure not only provides unobstructed channels for water transport and vapor escape, but also uniformly loads the monolayer MXene anchored by magnesium chloride onto the surface of the lignocellulose porous framework, ultimately obtaining a three-dimensional block MXene / biomass interfacial evaporation composite material that combines efficient photothermal interfacial evaporation performance with boron ion adsorption function.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. It uses widely available biomass raw materials and replaces the traditional strong acid and strong base etching of MAX phase with choline chloride-based eutectic solvent, which has the advantages of low cost and green environmental protection.

[0025] 2. The MAX phase etching, biomass pretreatment and boron-absorbing component loading are completed simultaneously through a one-step in-situ reaction. The overall process is simple, easy to operate, and has low energy consumption, making it easy to achieve industrial-scale production.

[0026] 3. The prepared composite material has both photothermal evaporation and boron adsorption properties, and can simultaneously remove boron in seawater desalination, achieving synergistic effects of energy utilization and water purification. Attached Figure Description

[0027] Figure 1 For the preparation process flow diagram Detailed Implementation

[0028] The following detailed description of an in-situ preparation method for MXene / biomass interface evaporation materials provided by the present invention, with reference to specific embodiments, is provided in detail below. However, the following content should not be construed as limiting the scope of protection of the present invention.

[0029] Example 1

[0030] MXene / biomass composites were prepared using a traditional stepwise process. First, 100 g of Ti3AlC2 was slowly added to an etching solution consisting of 100 g of LiF and 2 L of 9 M HCl, and the mixture was reacted at 35 °C and 300 rpm for 24 h with stirring. After the reaction, the precipitate was washed six times with deionized water at 3500 rpm for 5 min each time, until the pH of the supernatant reached 6, yielding a multilayer MXene precipitate. Subsequently, deionized water was added, and the mixture was ultrasonically exfoliated at 200 W for 1 h, followed by centrifugation at 3500 rpm for 1 h. The supernatant was collected to obtain a monolayer MXene aqueous dispersion with a concentration of 5 mg / mL. Meanwhile, 69.81 g of choline chloride (0.5 mol) and 129.8 g of cobalt chloride (1.0 mol) were weighed and reacted at 90 °C and 500 rpm for 2 h to prepare a eutectic solvent. 5 g of poplar wood powder was added to 100 mL of the eutectic solvent and pretreated at 120 °C and 500 rpm for 3 h. After the reaction, the mixture was centrifuged and the lignocellulose was washed with deionized water until the supernatant was colorless, yielding pretreated lignocellulose. Finally, 400 mL of MXene aqueous dispersion was taken, and 0.5 g of lignocellulose and 0.25 g of magnesium chloride were added and mixed evenly in deionized water. The mixture was stirred at 500 rpm for 2 h. Severe flocculation occurred immediately during the mixing process. The flocculated mixture was transferred to a mold and pre-frozen at -40 °C to form a three-dimensional block. After freeze-drying for 48 h, a three-dimensional blocky MXene / biomass interfacial evaporation composite material was obtained. Under one solar radiation intensity, the evaporation rate of this material was 1.30 kg / m³. 2 The adsorption capacity for boron ions in seawater is 11 mg / m³. 2 .

[0031] Example 2

[0032] 69.81 g of choline chloride (0.5 mol) and 129.8 g of cobalt chloride (1.0 mol) were weighed and placed in an oil bath. The mixture was reacted at 500 rpm and 90 °C for 2 h to prepare a eutectic solvent etching solution. 400 g of Ti3AlC2 and 100 g of poplar powder were mixed and stirred at 500 rpm for 60 min until homogeneous. Then, 50 g of magnesium chloride was slowly added, and stirring was continued for 30 min to obtain a mixed raw material. The obtained mixed raw material was added to 11 L of the above etching solution (solid-liquid ratio 1:20 g / mL), and the mixture was reacted at 170 °C and 500 rpm for 2 h. After centrifugation to separate the solid and liquid phases, the obtained solid phase was a mixture of magnesium chloride-anchored multilayer MXene and lignocellulose solid residue. Deionized water was added to the obtained solid phase, and ultrasonication was performed at a power of 400 W for 10 min at a time, repeated 5-7 times, to peel off the multilayer MXene into a single layer of MXene. The obtained product was washed to pH 6, and the resulting solid was pre-frozen at -40 °C into a three-dimensional block. After freeze-drying for 48 h, a three-dimensional blocky MXene / biomass interfacial evaporation composite material was obtained.

[0033] Example 3

[0034] The process is basically the same as in Example 2, except that 69.81 g of choline chloride (0.5 mol) and 97.38 g of cobalt chloride (0.75 mol) were weighed and placed in an oil bath, and reacted at 500 rpm and 80 °C for 3 h to prepare a eutectic solvent etching solution.

[0035] Example 4

[0036] The process is basically the same as in Example 2, except that 69.81 g of choline chloride (0.5 mol) and 162.30 g of cobalt chloride (1.25 mol) were weighed and placed in an oil bath, and reacted at 500 rpm and 100 °C for 1 h to prepare a eutectic solvent etching solution.

[0037] Example 5

[0038] The process is basically the same as in Example 2, except that 450 g of Ti3AlC2 and 50 g of poplar powder are mixed and stirred at 500 rpm for 60 min until homogeneous. Then, 50 g of magnesium chloride is slowly added and the mixture is stirred for another 30 min to obtain the mixed raw materials.

[0039] Example 6

[0040] The reaction was basically the same as in Example 2, except that the mixed raw materials were added to 5.5 L of the above etching solution (solid-liquid ratio 1:10 g / mL), and reacted for 2 h at a reaction temperature of 170 °C and a stirring speed of 500 rpm. After centrifugation to separate the solid and liquid phases, the resulting solid phase was a mixture of magnesium chloride-anchored multilayer MXene and lignocellulose solid residue.

[0041] The interfacial evaporation composite materials prepared in Examples 2-6 exhibit an interfacial evaporation rate of 2.03 kg / m² under irradiation with one solar intensity. 2 The efficiency of the interfacial evaporation material was increased by 56.15% (1.30 kg / m³) compared to Example 1. 2 In addition, the adsorption capacity of boron ions in seawater can reach 23 mg / m³. 2 Compared to the interfacial evaporation material in Example 1, the efficiency was increased by 109.09% (11 mg / m³). 2 Furthermore, the material's performance did not significantly decline after being recycled 10 times.

[0042] As can be seen from the above embodiments, the preparation method of the present invention is green and environmentally friendly, and the process is simple. The prepared composite material has both high-efficiency interfacial evaporation and boron absorption properties, effectively solving many defects of the prior art and is suitable for industrial production and practical application.

[0043] The above embodiments are only some implementations of the present invention and do not constitute a limitation on the scope of protection of the present invention. Other technical solutions that can be obtained without creative effort based on the disclosure of these embodiments are all within the scope of protection of the present invention.

Claims

1. A method for in-situ preparation of MXene / biomass interfacial evaporation materials, characterized in that, Includes the following steps: (1) Mix choline chloride and cobalt chloride in proportion, place them in an oil bath, and react them at 500 rpm and 80~100 ℃ for 1~3 h to prepare a eutectic solvent etching solution; (2) Mix the MAX phase with lignocellulose in proportion and stir at 500 rpm for 60 min until uniform. Then slowly add magnesium chloride and continue stirring for 30 min. Set aside. (3) Add the mixture obtained in step (2) to the etching solution obtained in step (1), react at a reaction temperature of 160~180 ℃ and a stirring speed of 500 rpm for 1~3 h, and centrifuge to separate the solid and liquid phases. The resulting solid phase is a mixture of magnesium chloride-anchored multilayer MXene and lignocellulose solid residue. (4) Add deionized water to the solid phase obtained in step (3) and sonicate to peel off the multilayer MXene into a single layer MXene; (5) Wash the product obtained in step (4) and pre-freeze the solid obtained after washing into a three-dimensional block. After freeze-drying, the MXene / biomass interface evaporation composite material is obtained.

2. The method for in-situ preparation of MXene / biomass interfacial evaporation materials according to claim 1, characterized in that, The molar ratio of choline chloride to cobalt chloride in step (1) is 1:1.5 to 1:2.

5.

3. The method for in-situ preparation of MXene / biomass interfacial evaporation materials according to claim 1, characterized in that, The MAX phase mentioned in step (2) is Ti3AlC2.

4. The method for in-situ preparation of MXene / biomass interfacial evaporation materials according to claim 1, characterized in that, The amounts of MAX phase, lignocellulose and magnesium chloride added in step (2) are 350~500 g, 50~150 g and 50 g, respectively.

5. The method for in-situ preparation of MXene / biomass interfacial evaporation materials according to claim 1, characterized in that, In step (3), the mixture is added to the etching solution with a solid-liquid ratio of 1:10 to 1:30 g / mL.

6. The method for in-situ preparation of MXene / biomass interfacial evaporation materials according to claim 1, characterized in that, The ultrasonic power in step (4) is 200~400 W, 10 min per session, repeated 5~7 times.

7. The method for in-situ preparation of MXene / biomass interfacial evaporation materials according to claim 1, characterized in that, The washing in step (5) is to wash with deionized water until the pH is 5~6; the pre-freezing temperature is -20~-80 ℃, and the freeze-drying time is 24~48 h.

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