Cellulose cross-linked carbon sponge / MXene composite material and preparation method and application thereof

Abstract

The application discloses a cellulose cross-linked carbon sponge / MXene composite material and a preparation method and application thereof, and belongs to the technical field of noble metal resource recovery and functional adsorption materials. x MXene nanosheets are used as a functional component, and cellulose nanofilaments are introduced as an interface cross-linking agent. The composite material utilizes the synergistic effect of nitrogen coordination sites in the CMS and low-valence titanium active sites in the MXene, realizes efficient adsorption and in-situ reduction of Au(III), exhibits good selectivity for Au(III) in a complex multi-ion system, and is suitable for the recovery of noble metal ions in a complex system such as electronic waste leaching liquid.

Description

Technical Field

[0001] This invention relates to the field of functional composite materials and precious metal resource recycling technology, specifically to a cellulose cross-linked carbon sponge / MXene composite material, its preparation method, and its application. Background Technology

[0002] The rapid development of the electronics and information industry has led to the continuous generation of large amounts of electronic waste. Among these, printed circuit boards (PCBs), central processing units (CPUs), connectors, and integrated circuits contain abundant precious metal resources such as gold, silver, and palladium. Compared with natural ores, electronic waste typically has a higher content of precious metals and thus possesses significant resource utilization value. Therefore, developing efficient and green precious metal recycling technologies has become an important research direction in the field of resource recycling.

[0003] Currently, precious metal recycling mainly includes pyrometallurgy, hydrometallurgy, and adsorption separation methods. Pyrometallurgy suffers from high energy consumption and severe pollution; while hydrometallurgy, although possessing high leaching efficiency, typically requires large amounts of acids, alkalis, and organic extractants, resulting in complex processes, secondary pollution, and high operating costs. In contrast, adsorption methods, due to their simple process, good selectivity, ease of regeneration, and environmental friendliness, are gradually becoming an important development direction for precious metal resource recycling from electronic waste. The development of high-performance adsorption materials is key to achieving efficient recycling.

[0004] Three-dimensional carbon sponges (CMS) possess a continuous three-dimensional porous network structure, a large specific surface area, good mass transfer performance, and ease of functionalization, leading to their widespread application in adsorption and separation in recent years. Through nitrogen doping or surface functional group modulation, CMS can provide abundant coordination sites for noble metal ions, exhibiting excellent adsorption capacity for noble metal ions such as Au(III). However, when relying solely on CMS for adsorption, the number of active sites remains limited, and there is still room for further improvement in the selectivity and adsorption efficiency of noble metal ions in complex multi-component systems.

[0005] Two-dimensional transition metal carbides (nitrides), especially Ti3C2Tx MXene, possess layered structures, high specific surface areas, excellent electrical conductivity, and abundant surface functional groups (-OH, -O, -F, etc.), providing a large number of active sites and exhibiting high adsorption and in-situ reduction capabilities for noble metal ions such as Au(III). Therefore, combining MXene with three-dimensional porous carbon materials to fully leverage their synergistic advantages has become an important direction in adsorption material research.

[0006] However, current technologies for combining MXene with three-dimensional carbon framework materials often employ simple impregnation, physical loading, or electrostatic adsorption methods. MXene primarily adheres to the matrix surface through weak interfacial interactions, resulting in limited interfacial bonding. During adsorption, elution, and recycling, MXene sheets are prone to detachment, recombination, or agglomeration, leading to a reduction in effective active sites and decreased structural stability and recyclability of the composite material, thus limiting its practical application in complex precious metal recycling systems.

[0007] Furthermore, existing research focuses more on improving the adsorption capacity or adsorption rate of composite materials, while relatively little research is conducted on the construction of the interfacial stability between MXene and the three-dimensional carbon framework and its impact on the long-term stability, recyclability, and Au(III) selective adsorption performance in complex coexisting ion systems. This is especially true for materials containing Zn. 2+ Fe 3+ Cu 2+ Ni 2+ In complex leaching systems with competing ions, how to improve the selective adsorption capacity of materials for Au(III) while ensuring stable MXene loading remains a technical problem that urgently needs to be solved in this field.

[0008] Therefore, there is an urgent need to provide a composite adsorbent material and its preparation method that has stable interfacial bonding, strong MXene loading, good cycling stability, and can achieve efficient and selective recovery of Au(III), so as to meet the application requirements of green and efficient recovery of precious metal resources in electronic waste. Summary of the Invention

[0009] In view of this, and in response to the problems of insufficient interfacial bonding, easy detachment of MXene sheets, poor stability during recycling, and limited selective adsorption capacity of Au(III) in complex coexisting ion systems that are common in existing MXene-three-dimensional carbon skeleton composite materials, this invention provides a cellulose cross-linked carbon sponge / MXene composite adsorbent material and its preparation method.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A cellulose cross-linked carbon sponge / MXene composite material, wherein the cellulose cross-linked carbon sponge / MXene composite material comprises a three-dimensional carbon sponge skeleton (CMS) and Ti3C2T x Composed of MXene nanosheets and cellulose nanofibers (CNF); Among them, the Ti3C2T x MXene nanosheets are connected to a three-dimensional carbon sponge framework via cellulose nanofibers, and the Ti3C2T xMXene nanosheets are loaded on the surface and inner walls of the pores of the three-dimensional carbon sponge framework.

[0012] The cellulose nanofibers form a carbonaceous interface connection structure during the carbonization process, enabling Ti3C2T x MXene nanosheets are stably fixed on the surface of a three-dimensional carbon sponge skeleton to construct a three-dimensional-two-dimensional hierarchical composite structure with a stable interface, thereby improving the interfacial stability and recycling stability of the composite material.

[0013] In the above-mentioned cellulose crosslinked carbon sponge / MXene composite material of the present invention, with a dry weight of 0.130 g for the three-dimensional carbon sponge skeleton, Ti3C2T was added. x The amount of MXene nanosheets is 20-100 mg, and the amount of cellulose nanofibers is 0.1-2.0 g / 100 mL of water.

[0014] This invention utilizes cellulose nanofibers (CNF) as an interfacial crosslinking agent. CNF relies on its abundant hydroxyl groups to crosslink with Ti3C2T. x The oxygen-containing functional groups on the MXene surface form an interface, which further transforms into a continuous carbonaceous connecting layer during carbonization, thereby enhancing the interfacial bonding between CMS and MXene and achieving stable fixation of MXene nanosheets on a three-dimensional carbon sponge framework. While maintaining the rapid mass transfer advantage of the three-dimensional porous structure, this invention improves the interfacial stability and recyclability of the composite material, and further enhances its efficient and selective adsorption and recovery capacity of Au(III) in complex electronic waste leaching systems. Compared with traditional CMS / MXene physical composite materials, this invention achieves a transformation from weak physical adsorption to stable interfacial bonding through the continuous carbonaceous interface layer formed by CNF carbonization, fundamentally improving the fixation capacity of MXene in a three-dimensional carbon framework.

[0015] In this invention, CNF achieves stable fixation of MXene nanosheets on the CMS framework through interfacial bonding and carbonization to form a carbon-based linkage structure, thereby improving the interfacial bonding stability and recycling stability of the composite material, and applying it to the efficient selective adsorption and recovery of noble metal ions such as Au(III).

[0016] Furthermore, the mass fraction of cellulose nanofibers in the cellulose crosslinked carbon sponge / MXene composite material is 0.1-2 wt%.

[0017] This invention also provides a method for preparing the above-mentioned cellulose crosslinked carbon sponge / MXene composite material, comprising the following steps: (1) Forming Ti3C2T by etching Ti3AlC2MAX phase material x MXene nanosheet dispersion; (2) Disperse cellulose nanofibers in water to form a cellulose nanofiber dispersion; (3) Ti3C2T x MXene nanosheet dispersion and cellulose nanofiber dispersion are mixed to form a uniform composite dispersion system under the action of CNF; (4) The three-dimensional carbon sponge is placed in a composite dispersion system for impregnation treatment, so that Ti3C2T x MXene nanosheets and cellulose nanofibers are loaded onto a three-dimensional carbon sponge; (5) The impregnated three-dimensional carbon sponge was quick-frozen and then freeze-dried to fix its internal structure. After freeze-drying, it was carbonized to obtain cellulose cross-linked carbon sponge / MXene composite material.

[0018] Furthermore, the Ti3C2T mentioned in step (1) x The preparation method of MXene nanosheet dispersion is as follows: Ti3AlC2 was added to an etching system containing 12 M HCl, followed by the slow addition of LiF. The mixture was stirred to form a homogeneous etching system, and then hydrothermally reacted at 150 °C for 72 h. The Al layer was selectively etched away to form a few-layer Ti3C2T. x After the reaction of MXene material was completed, the resulting product was centrifuged, washed, and dried to obtain Ti3C2T. x MXene nanosheets, and finally Ti3C2T x MXene nanosheets were dispersed in water to obtain Ti3C2T x MXene nanosheet dispersion.

[0019] Furthermore, the mass concentration of the cellulose nanofiber dispersion in step (2) is 0.1-2 wt%.

[0020] Furthermore, the preparation method of the three-dimensional carbon sponge in step (4) is as follows: melamine sponge is carbonized under an inert atmosphere to obtain a three-dimensional carbon sponge.

[0021] Furthermore, the quick-freezing described in step (5) is performed using liquid nitrogen for rapid freezing.

[0022] Furthermore, the carbonization temperature in step (5) is 600-900℃.

[0023] During the carbonization process, the CNF forms a continuous carbonaceous connecting layer, enabling MXene nanosheets to form a stable interface connection with the carbon sponge skeleton, reducing MXene sheet shedding and improving the cycle stability of the composite material.

[0024] This invention also provides the application of the above-mentioned cellulose crosslinked carbon sponge / MXene composite material in the recovery of precious metal ions.

[0025] Furthermore, the noble metal ion is Au(III).

[0026] Furthermore, Au(III) is recovered from the leachate of electronic waste CPUs in the application, the leachate containing Cu 2 + Ni 2+ Fe 3+ Competing ions.

[0027] The composite material of this invention is suitable for complex systems such as multi-ion systems and electronic waste leachates, enabling efficient and selective enrichment of Au(III) and exhibiting good recyclability. By constructing a stable interfacial connection structure through CNF, the immobilization stability of MXene in the composite material is improved while maintaining the three-dimensional porous mass transfer advantages of CMS, providing a structural basis for the recycling of the material and the selective adsorption of Au(III) in complex systems.

[0028] The composite material of the present invention still maintains a removal rate of over 95% for Au(III) after at least 5 adsorption-desorption cycles.

[0029] The beneficial effects of this invention are as follows: 1. This invention uses CNF as an interfacial crosslinking agent, utilizing the abundant hydroxyl groups on the CNF surface to interact with Ti3C2T x The interaction between functional groups on the MXene surface, combined with subsequent carbonization treatment to form a stable carbonaceous connecting layer, enables uniform and stable loading of MXene nanosheets on the surface of the CMS three-dimensional framework. Compared with traditional physical impregnation or simple loading methods, this invention enhances the interfacial bonding between CMS and MXene, reduces the possibility of MXene sheet detachment and agglomeration during recycling, improves the overall structural stability of the composite material, and provides a reliable structural basis for the long-term recycling of the material.

[0030] 2. The composite material prepared by this invention has excellent recyclability. The results of the cyclic adsorption experiment show that after 5 adsorption-desorption cycles, the removal rate of Au(III) remains above 95%, and the removal efficiency is maintained at 98% to 100% in the first 4 cycles. This indicates that the stable interface constructed by CNF can effectively reduce MXene sheet shedding and improve the long-term stability of the composite material.

[0031] 3. The composite material of this invention exhibits excellent selectivity for Au(III). In Zn-containing... 2+ Fe 3+ Cu 2+ Ni 2+In the simulated system of competing ions, the removal rate of Au(III) is close to 100%, while the removal rates of other metal ions remain at a low level. This indicates that the material of the present invention has excellent Au(III) specific recognition and selective adsorption capabilities, which can meet the requirements of precious metal recovery in complex systems.

[0032] 4. This invention is applied to the CPU leaching solution system of electronic waste. The material of this invention achieves a recovery rate of 97.83% for Au(III), while the removal rate of coexisting ions such as Ni and Cu does not exceed 3.6%. This indicates that the composite material can preferentially identify and enrich Au(III) in a multi-ion competitive environment, and has excellent Au(III) selective adsorption performance, which can meet the application requirements of complex precious metal recycling systems.

[0033] 5. This invention utilizes a continuous three-dimensional porous network structure of CMS to construct a rapid mass transfer channel, while MXene nanosheets provide abundant surface active sites. The synergistic effect of these two components enables Au(III) to diffuse rapidly and fully contact the active sites. Kinetic experiments show that the composite material of this invention has a fast adsorption rate, achieving efficient removal of Au(III) in a short time, improving the recovery efficiency of precious metals, and making it more suitable for the rapid treatment of high-concentration precious metal waste liquids.

[0034] 6. This invention fully utilizes CMS and Ti3C2T x The synergistic effect between MXenes allows CMS to provide abundant nitrogen coordination adsorption sites, while MXenes provide low-valent titanium active centers, enabling simultaneous Au(III) adsorption and in-situ reduction. XRD and XPS analyses further confirm that Au(III) can be reduced to Au(0) and stably deposited on the surface of the composite material, thereby improving the Au(III) fixation capacity and recovery efficiency, and endowing the material with excellent precious metal recovery performance. Attached Figure Description

[0035] Figure 1 The present invention is CMS@Ti3C2T x Schematic diagram of the preparation process, interface construction and Au(III) selective adsorption process of the @CNF composite adsorbent material; Figure 2 In this embodiment, CMS and CMS@Ti3C2T are used. x @CNF composite material macroscopic appearance and flexible structure display; Figure 3 In this embodiment, CMS@Ti3C2T x @SEM microstructure of CNF composite material; Figure 4 In this embodiment, CMS and MS@Ti3C2T are used. x@CNF and CMS@Ti3C2T x @CNF's gold adsorption properties; Figure 5 This embodiment illustrates the effect of different CNF contents on CMS@Ti3C2T x Au(III) adsorption properties of CNF; Figure 6 In this embodiment, CMS@Ti3C2T x @CNF selective adsorption simulation test of Au(III); Figure 7 In this embodiment, CMS@Ti3C2T x @CNF Cyclic test for Au(III); Figure 8 In this embodiment, CMS and Ti3C2T are used. x CMS@Ti3C2T x @CNF adsorbed Au(III) CMS@Ti3C2T x @CNF composite materials; Figure 9 In this embodiment, CMS@Ti3C2T x XPS spectra of gold adsorption on the CNF composite material; Figure 10 In this embodiment, CMS@Ti3C2T x XPS spectra of elements before and after gold adsorption in the CNF composite material. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1 A cellulose crosslinked carbon sponge / MXene composite material: (1) Ti3C2T x MXene preparation 2 g of Ti3AlC2MAX phase powder was weighed and slowly added to a PTFE beaker containing 100 mL of 12 M hydrochloric acid. The mixture was stirred with a magnetic stirrer in a fume hood for 1 h to ensure complete dispersion of Ti3AlC2 in the hydrochloric acid etching system. Then, 2.626 g of LiF was weighed and slowly added to the mixture under stirring. After the LiF addition was complete, stirring continued for 1 h to ensure complete dissolution of LiF and formation of a homogeneous in-situ etching system with the hydrochloric acid. The resulting mixture was transferred to a PTFE-lined reactor and hydrothermally reacted at 150 °C for 72 h. The in-situ generated etching species selectively removed the Al layer from Ti3AlC2, forming Ti3C2T. x MXene.

[0038] After the hydrothermal reaction was completed, the reaction system was allowed to cool naturally to room temperature. The resulting etching product was transferred to a centrifuge tube and centrifuged at 3500 rpm for 1 h. The supernatant rich in few-layer Ti3C2T was collected. x Nanosheets. The resulting product was then repeatedly washed by centrifugation with deionized water until the pH of the supernatant was greater than 6, to remove residual hydrochloric acid, LiF, and reaction byproducts. The washed Ti3C2T... x The product was placed in a vacuum drying oven and dried under vacuum at 70 °C for 12 h to obtain Ti3C2T. x MXene powder.

[0039] The prepared Ti3C2T x MXene possesses a typical two-dimensional layered structure, with terminal functional groups such as -O, -OH, and -F on its surface, providing active sites for the adsorption and subsequent immobilization of Au(III). The obtained Ti3C2T x Ti3C2T was prepared by adding MXene powder to deionized water and dispersing it by stirring or ultrasonication. x MXene aqueous dispersion, for later use. (See...) Figure 1 ).

[0040] (2) Preparation of CNF dispersion 0.5 wt% cellulose nanofibers (CNF) were added to deionized water, and a uniform and stable CNF dispersion system was obtained by ultrasonic dispersion and mechanical stirring for 1 h. The abundant hydroxyl groups on the CNF surface can react with Ti3C2T x The functional groups on the surface of MXene form an interface and transform into a carbonaceous connection structure during the subsequent carbonization process, thereby enhancing the interfacial bonding stability between MXene and the CMS framework.

[0041] (3) CMS@Ti3C2T x @CNF composite material preparation The Ti3C2T prepared above x MXene powder was added to a 0.5 wt% CNF aqueous dispersion, in which Ti3C2T x The amount of MXene added was 20-100 mg, adjusted according to the required loading. Ultrasonic dispersion was performed in an ice-water bath for 1 h, followed by mechanical stirring for 20 min to allow Ti3C2T to disperse. x MXene nanosheets were uniformly dispersed in a CNF aqueous dispersion system to obtain a homogeneous and stable Ti3C2T. x MXene / CNF composite dispersion.

[0042] The pretreated and dried melamine sponge (MS) was placed in the above Ti3C2T x In the MXene / CNF composite dispersion, the sponge was repeatedly squeezed with tweezers to ensure the composite dispersion fully penetrated the sponge until the entire sponge turned black and the color distribution was uniform. The impregnated MS was then immersed in the composite dispersion and allowed to stand for 1 hour to allow the Ti3C2T... x MXene and CNF were fully infiltrated and loaded into the MS 3D framework. The impregnated MS samples were then removed and instantaneously frozen in liquid nitrogen to form a stable ice crystal template structure inside. The frozen samples were then freeze-dried in a freeze dryer for 48 h to obtain MS@Ti3C2T. x @CNF composite precursor. Finally, the obtained MS@Ti3C2T x The CNF composite precursor was carbonized at 600 °C for 2 h under N2 with a flow rate of 200 sccm according to the above CMS carbonization conditions. After cooling to room temperature, CMS@Ti3C2T was obtained. x @CNF composite materials.

[0043] The results showed that the composite material obtained in Example 1 still maintained a complete three-dimensional porous structure and exhibited good flexibility and structural integrity (see Example 1). Figure 2 SEM observations showed that Ti3C2T x MXene nanosheets are uniformly loaded onto the surface of the CMS fiber framework, and CNF forms an interfacial network, which improves the stability of the composite structure (see [link]). Figure 3 ).

[0044] In Example 1, the CMS (Carbonized Melamine Sponge) is a three-dimensional carbon sponge material obtained by high-temperature carbonization of commercial melamine sponge (MS). The original MS possesses a continuous three-dimensional porous network structure and good flexibility. After carbonization, the polymer framework undergoes pyrolytic transformation, forming a CMS three-dimensional carbon framework with conductivity, abundant pore structure, and nitrogen-doped active sites. The resulting CMS maintains its overall three-dimensional structure while exhibiting good mechanical integrity and flexibility, and can serve as a support matrix for loading and stabilizing MXene nanosheets (e.g., ...). Figure 1 (As shown).

[0045] Comparative Example 1 The technical solution is basically the same as that in Example 1, except that the commercial melamine sponge was not pre-carbonized, and the resulting material is denoted as MS@Ti3C2T. x @CNF.

[0046] Experimental Example 1: Au(III) Adsorption Experiment Weigh out 10 mg CMS and 10 mg MS@Ti3C2T respectively. x @CNF and 10 mg CMS@Ti3C2T x The CMS@Ti3C2T composite material was placed in 50 mL Erlenmeyer flasks, and 20 mL of an initial concentration of 20 mg / L (20 ppm) Au(III) aqueous solution was added. The flasks were then shaken in a constant-temperature shaker at room temperature (25 ℃) for 12 h to allow adsorption equilibrium to be reached. After adsorption, approximately 5 mL of the supernatant was collected and filtered through a 0.22 μm aqueous disposable needle filter. The concentration of Au(III) in the post-adsorption solution was determined using ICP-OES, and the Au(III) removal rate and adsorption capacity were calculated based on the change in Au(III) concentration before and after adsorption. The results show that, compared with CMS alone and other comparative materials, CMS@Ti3C2T… x The @CNF composite material exhibits higher Au(III) adsorption efficiency, indicating that the CMS three-dimensional mass transfer structure is compatible with Ti3C2T. x There is a clear synergistic effect among active sites (see...) Figure 4 ).

[0047] By adjusting the CNF content, CMS@Ti3C2T with different CNF contents were obtained. x The adsorption performance of the CNF composite material was optimized. Results showed that the material exhibited the best Au(III) adsorption performance when the CNF content was 0.5 wt%. Appropriate CNF can enhance the interfacial bonding between MXene and CMS, while excessive CNF may affect pore openness, thereby reducing mass transfer efficiency (see [link to relevant documentation]). Figure 5 ).

[0048] Experimental Example 2: Selective Adsorption Performance in Complex Ionic Systems To evaluate the application potential of the material in a real-world electronic waste leaching system, a simulated electronic waste liquid system containing multiple competing ions was constructed. The experimental system included Zn... 2+ Fe 3+ Cu 2+ Mg 2+ Ni 2+ And Al 3+ Coexisting ions were selected, and Au(III) was added for selective adsorption testing. The initial concentration of each competing ion was approximately 100 ppm (mg / L); 20 ppm (mg / L) of Au(III) was added simultaneously. The results showed that CMS@Ti3C2T... x The @CNF composite material exhibits near 100% removal of Au(III) while maintaining low adsorption rates for other competing ions, demonstrating excellent selective Au(III) capture capability (see [link to CNF composite material]). Figure 6 ).

[0049] Experiment Example 3 Cyclic Stability Test To evaluate the long-term performance of the composite material, CMS@Ti3C2T was tested. x @CNF was subjected to multiple adsorption-desorption cycle experiments. First, 10 mg of CMS@Ti3C2T was weighed. x The CMS@Ti3C2T composite material was added to 50 mL of Au(III) solution with an initial concentration of 20 mg / L and incubated at room temperature with shaking for 1 h. After adsorption, the adsorbed CMS@Ti3C2T composite material was collected by filtration. x @CNF composite material was washed with deionized water. Then, the washed composite material was added to 50 mL of a thiourea-hydrochloric acid mixed desorption solution, where the concentration of thiourea was 1 mol / L and the concentration of hydrochloric acid was 1 mol / L, with a volume ratio of thiourea solution to hydrochloric acid solution of 1:1. The solution was shaken at room temperature for 2 h to desorb Au(III) adsorbed on the material into the solution. After desorption, the composite material was recovered by filtration, washed with ethanol, and then dried in a vacuum drying oven at 70 ℃ for 12 h to obtain the regenerated CMS@Ti3C2T. x@CNF composite material. The regenerated material was added back to a 20 mg / L Au(III) solution for the next round of adsorption experiments, and the above adsorption-desorption process was repeated for a total of 5 cycles. The results showed that after 5 cycles, the material still maintained a high Au(III) removal efficiency, indicating that the interfacial bonding structure constructed by CNF can effectively reduce MXene sheet shedding and improve the stability of the composite material for recycling (see [link to CNF composite material]). Figure 7 ).

[0050] Experimental Example 4: Structural and Adsorption Mechanism Analysis XRD analysis of CMS and Ti3C2T x MXene, CMS@Ti3C2T x Structural analysis was performed on the @CNF and the composite material after Au(III) adsorption. The results showed that the composite material maintained a stable structure during adsorption, and Au-related characteristic peaks appeared after adsorption, proving that Au species were successfully loaded onto the material surface (see [link to article]). Figure 8 ).

[0051] XPS analysis was further used to analyze the surface chemical state of the composite material after Au(III) adsorption. Full-spectrum analysis showed the presence of the characteristic Au 4f peak after adsorption, confirming the successful introduction of Au. High-resolution Au 4f spectra further indicated that Au(III) underwent a reduction transformation during adsorption, forming Au4f. 0 Species (see Figure 9 ).

[0052] Comparison of XPS spectra of C, N, O, and Ti before and after adsorption revealed that Ti active sites and nitrogen-doped structures participated in the Au(III) adsorption and reduction process. Simultaneously, the overall structure of the composite material remained stable, further demonstrating that CNF interfacial crosslinking improved the material's stability (see [link to CNF interface]). Figure 10 ).

[0053] Experimental results show that the CMS@Ti3C2T prepared in this invention... x @CNF composite adsorbent materials can be used in the treatment and recycling of waste liquids containing precious metals. Especially in complex systems such as CPU leachate from electronic waste, this material can achieve efficient and selective capture and recovery of Au(III) by utilizing the CMS three-dimensional mass transfer network, MXene active sites, and CNF stable interface structure.

[0054] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A cellulose crosslinked carbon sponge / MXene composite material, characterized in that, The cellulose crosslinked carbon sponge / MXene composite material consists of a three-dimensional carbon sponge skeleton and Ti3C2T. x Composed of MXene nanosheets and cellulose nanofibers; Among them, the Ti3C2T x MXene nanosheets are connected to a three-dimensional carbon sponge framework via cellulose nanofibers, and the Ti3C2T x MXene nanosheets are loaded on the surface and inner walls of the pores of the three-dimensional carbon sponge framework.

2. The cellulose crosslinked carbon sponge / MXene composite material according to claim 1, characterized in that, The mass concentration of the cellulose nanofiber dispersion in the cellulose crosslinked carbon sponge / MXene composite material is 0.1-2 wt%.

3. A method for preparing the cellulose crosslinked carbon sponge / MXene composite material according to claim 1 or 2, characterized in that, Includes the following steps: (1) Forming Ti3C2T by etching Ti3AlC2MAX phase material x MXene nanosheet dispersion; (2) Disperse cellulose nanofibers in water to prepare a cellulose nanofiber dispersion; (3) Ti3C2T x MXene nanosheet dispersion and cellulose nanofiber dispersion were mixed to obtain a composite dispersion system; (4) The three-dimensional carbon sponge is placed in a composite dispersion system for impregnation treatment, so that Ti3C2T x MXene nanosheets and cellulose nanofibers are loaded onto a three-dimensional carbon sponge; (5) The impregnated three-dimensional carbon sponge was left to stand for 1 h to allow the composite dispersion system to fully impregnate the three-dimensional pore structure. Then it was placed in liquid nitrogen for rapid freezing and vacuum freeze-drying for 48 h. The freeze-dried material was heated to 600 ℃ under nitrogen atmosphere protection at a heating rate of 5 ℃ / min for carbonization treatment. The nitrogen flow rate was 200 sccm to obtain cellulose cross-linked carbon sponge / MXene composite material.

4. The method for preparing a cellulose crosslinked carbon sponge / MXene composite material according to claim 3, characterized in that, The Ti3C2T mentioned in step (1) x The preparation method of MXene nanosheet dispersion is as follows: Ti3AlC2 was added to an etching system containing 12 M HCl, followed by the addition of LiF at a mass ratio of 2:2.

626. The mixture was stirred to form a homogeneous etching system, and then subjected to hydrothermal reaction at 150 °C for 72 h. The Al layer was selectively removed by etching to form a few-layer Ti3C2T. x After the reaction of MXene material was completed, the resulting product was centrifuged, washed, and dried to obtain Ti3C2T. x MXene nanosheets, and finally Ti3C2T x MXene nanosheets were dispersed in water to obtain Ti3C2T x MXene nanosheet dispersion.

5. The method for preparing a cellulose crosslinked carbon sponge / MXene composite material according to claim 3, characterized in that, The mass concentration of the cellulose nanofiber dispersion in step (2) is 0.1-2 wt%.

6. The method for preparing a cellulose crosslinked carbon sponge / MXene composite material according to claim 3, characterized in that, The preparation method of the three-dimensional carbon sponge in step (4) is as follows: melamine sponge is carbonized under an inert atmosphere to obtain a three-dimensional carbon sponge.

7. The method for preparing a cellulose crosslinked carbon sponge / MXene composite material according to claim 3, characterized in that, The quick-freezing described in step (5) is performed using liquid nitrogen.

8. The method for preparing a cellulose crosslinked carbon sponge / MXene composite material according to claim 3, characterized in that, The carbonization temperature in step (5) is 600–900℃.

9. The application of the cellulose crosslinked carbon sponge / MXene composite material according to claim 1 or 2 in the recovery of precious metal ions.

10. The application according to claim 8, characterized in that, The noble metal ion is Au(III).

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