Preparation method and application of highly renewable ultrathin two-dimensional adsorbent

Abstract

The application belongs to the technical field of functional adsorption materials, and particularly discloses a preparation method of highly renewable ultrathin two-dimensional adsorbents and application thereof, wherein the preparation method comprises the following steps: slowly adding a Na3VO4 solution into an InCl3 solution, and stirring to obtain a uniformly mixed brownish soil solution; adjusting the pH of the obtained brownish soil solution to 1-3 by using a nitric acid solution, ensuring that the solution finally presents a transparent bright yellow color, and then transferring the solution into a polytetrafluoroethylene-lined high-pressure reaction kettle for a hydrothermal synthesis reaction; after the reaction is completed, the high-pressure reaction kettle is naturally cooled to room temperature, the obtained reaction product is centrifugally separated, and then is sequentially cleaned multiple times by using deionized water and ethanol, and finally is treated by ultrasonic waves to obtain an ultrathin two-dimensional InVO4 nanometer adsorbent with strong negative charges on the surface. The preparation method is simple, the adsorption reaction is mild and rapid, and can realize the enrichment of ppb-level ultra-low concentration rare earth ions by nearly 100 times.

Description

Technical Field

[0001] This invention belongs to the field of functional adsorption materials technology, specifically relating to a method for preparing a highly renewable ultrathin two-dimensional adsorbent and its application. Background Technology

[0002] Rare earth elements play a crucial role in many high-tech products due to their unique chemical and physical properties, such as permanent magnet materials, catalysts, and optical and electronic devices. While widely distributed in nature, rare earth elements are present in low concentrations, and their extraction often results in significant environmental damage, including soil erosion, water pollution, and ecosystem disruption. Furthermore, numerous industrial activities, such as electronics manufacturing, mining, and chemical processes, generate wastewater containing rare earth elements. Direct discharge of this wastewater without treatment not only pollutes the environment but also wastes valuable resources. Recovering rare earth elements from wastewater can reduce the direct extraction of these valuable resources, thereby mitigating negative environmental impacts and promoting resource recycling and sustainable development. The application of adsorption materials in wastewater treatment has become an important environmental protection technology. These materials can effectively remove and recover various pollutants in water, including heavy metal ions, organic pollutants, and other harmful substances. Due to their high efficiency, economy, and ease of operation, adsorption technology has been widely used in the purification of industrial wastewater and domestic sewage.

[0003] Traditional adsorbents such as zeolites, silica gel, and activated carbon have been reported to have unsatisfactory efficiencies in the extraction and separation of rare earth element (REE) ions from aqueous solutions. In addition, emerging organic and inorganic adsorbents, including metal-organic frameworks (MOFs), carbon-based adsorbents, polymer adsorbents, adsorbents derived from natural organics, and metal oxide nanomaterials, have been developed to pursue higher REE recovery efficiencies. Since REE ions are electron-accepting trivalent cations, most adsorbents possess negatively charged functional groups (such as amino, phosphonic, and carbonyl groups) or surfaces that act as electron donors to achieve efficient coordination or attraction of REE ions. Despite acceptable adsorption capacities, the most frequently reported adsorption mechanisms are precipitation and complexation. Low reversibility and harsh desorption conditions often lead to permanent damage to active adsorption sites, posing a significant challenge to the sustainability of adsorbents.

[0004] In the development of highly efficient adsorbents, ultrathin two-dimensional materials have demonstrated unique advantages. These materials, with their high specific surface area and strong surface energy, can specifically and efficiently adsorb specific pollutants in water. For example, materials with a strongly negatively charged surface exhibit excellent enrichment effects on heavy metal ions and certain positively charged organic molecules. Their ultrathin nature also promotes rapid adsorption kinetics, making the treatment process faster and more efficient. Furthermore, these materials typically possess good chemical stability and renewability, allowing for reuse through a simple elution process, further reducing wastewater treatment costs. Therefore, these ultrathin two-dimensional materials show great potential and application value in improving wastewater treatment efficiency and environmental friendliness. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a highly renewable ultrathin two-dimensional adsorbent and its application. This method achieves efficient adsorption of rare earth ions through electrostatic interactions based on a physical adsorption process, constructing ultrathin two-dimensional InVO4 nanoribbons (NB) with a strong negative charge to achieve super-strong adsorption and enrichment of rare earth ions in water. Benefiting from its ultrathin few-layer structure, the surface of this InVO4 adsorbent possesses abundant lone electron pairs, which are rich in a large net negative charge (-28.7 meV). This adsorbent can be used at room temperature and pressure to rapidly extract and enrich various rare earth element ions (Ce) from water. 3+ Eu 3+ Er 3+ Tm 3+ and Yb 3+ Based on a quasi-cation exchange strategy, rapid and efficient multiple adsorption can be achieved using NaCl solution under mild conditions.

[0006] To achieve the above objectives, one of the technical solutions of the present invention is: a method for preparing a highly renewable ultrathin two-dimensional adsorbent, comprising the following steps:

[0007] (1) Add Na3VO4 solution to InCl3 solution and stir to obtain a uniform brownish-brown solution;

[0008] (2) Use nitric acid solution to adjust the pH of the brownish-yellow solution obtained in step (1) to 1-3 to ensure that the solution eventually appears as a transparent bright yellow. Then transfer it to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal synthesis reaction.

[0009] (3) The high-pressure reactor in step (2) is naturally cooled to room temperature. The obtained reaction product is centrifuged and then washed with deionized water and ethanol several times in sequence. Finally, after ultrasonic treatment, an ultrathin two-dimensional InVO4 nano-adsorbent with a strong negative charge on the surface is obtained.

[0010] In a preferred embodiment of the present invention, the concentration ratio of Na3VO4 solution to InCl3 solution in step (1) is 1:1.5-2.5, and the concentration of Na3VO4 solution is 0.03-0.08 M / L.

[0011] In a preferred embodiment of the present invention, the volume ratio of Na3VO4 solution to InCl3 solution in step (1) is 1:0.8-1.2.

[0012] In a preferred embodiment of the present invention, the filling rate of the reactor in step (2) is 40-50 vol%.

[0013] In a preferred embodiment of the present invention, the concentration of the nitric acid solution in step (2) is 15-25 vol%.

[0014] In a preferred embodiment of the present invention, the temperature of the hydrothermal synthesis reaction in step (3) is 150-200°C and the time is 15-20h.

[0015] To achieve the above objectives, the second technical solution of the present invention is: a highly renewable ultrathin two-dimensional adsorbent prepared by a method for preparing a highly renewable ultrathin two-dimensional adsorbent.

[0016] To achieve the above objectives, the third technical solution of the present invention is: the application of a highly renewable ultrathin two-dimensional adsorbent in the adsorption and recovery of rare earth ions in wastewater.

[0017] In a preferred embodiment of the present invention, the method of application includes adding the adsorbent to the recovery wastewater containing rare earth ions at a concentration of 0.1-0.3 g / L and stirring for 40-80 min.

[0018] More preferably, the concentration of rare earth ions in the recovered wastewater containing rare earth ions is 10-150 ppm, and the rare earth ions include Ce. 3+ Eu 3+ Er 3+ Tm 3+ Yb 3+ At least one of them.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention achieves precise control over the morphology of InVO4 nanoribbons through a simple, single-step hydrothermal method, and successfully introduces a high density of negative charges. This is crucial for improving the performance of materials in various applications, such as catalysts, energy storage, and environmental remediation. A significant advantage of this method is its simplicity and efficiency; the synthesis of ultrathin nanoribbons can be achieved simply by adjusting the concentration and pH of the reactants, without the need for complex equipment or expensive chemical reagents.

[0021] 2. This invention utilizes a hydrothermal method to synthesize InVO4 at relatively low temperatures, which helps maintain the structural stability of InVO4 while reducing production costs;

[0022] 3. The adsorbent of the present invention has a super negative charge on its surface, which can significantly increase the active sites on the material surface, thereby improving its performance in pollutant adsorption, heavy metal ion capture and as an electrochemical active material; especially in applications such as the recovery of rare earth ions from wastewater, this material shows great potential due to its excellent adsorption performance. Attached Figure Description

[0023] Figure 1 SEM and TEM images of the ultrathin two-dimensional InVO4 nano-adsorbent prepared in Example 1;

[0024] Figure 2 XRD patterns of the ultrathin two-dimensional InVO4 nano-adsorbent prepared in Example 1 and the corresponding standard card;

[0025] Figure 3 The surface charge of the ultrathin two-dimensional InVO4 nano-adsorbent prepared in Example 1 and the effect of solution pH on its surface charge;

[0026] Figure 4 The image shows the adsorption effect of the ultrathin two-dimensional InVO4 nano-adsorbent prepared in Example 1 on different concentrations and types of rare earth ions.

[0027] Figure 5 The diagram shows the cyclic effect of rare earth ion adsorption, desorption and regeneration using the ultrathin two-dimensional InVO4 nano-adsorbent prepared in Example 1 with 1 mol / L NaCl solution as the desorbent.

[0028] Figure 6 This image shows the enrichment effect of the ultrathin two-dimensional InVO4 nano-adsorbent prepared in Example 1 on ultra-low concentration rare earth ions (0.1 ppm). Detailed Implementation

[0029] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0030] A method for preparing a highly renewable ultrathin two-dimensional adsorbent includes the following steps:

[0031] (1) Add Na3VO4 solution to InCl3 solution and stir to obtain a uniform brownish-brown solution;

[0032] (2) Use nitric acid solution to adjust the pH of the brownish-yellow solution obtained in step (1) to 1-3 to ensure that the solution eventually appears as a transparent bright yellow. Then transfer it to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal synthesis reaction.

[0033] (3) The high-pressure reactor in step (2) is naturally cooled to room temperature. The obtained reaction product is centrifuged and then washed with deionized water and ethanol several times in sequence. Finally, after ultrasonic treatment, an ultrathin two-dimensional InVO4 nano-adsorbent with a strong negative charge on the surface is obtained.

[0034] In step (1), the concentration ratio of Na3VO4 solution to InCl3 solution is 1:1.5-2.5, and the concentration of Na3VO4 solution is 0.03-0.08 M / L.

[0035] In step (1), the volume ratio of Na3VO4 solution to InCl3 solution is 1:0.8-1.2.

[0036] In step (2), the filling rate of the reactor is 40-50 vol%.

[0037] In step (2), the concentration of the nitric acid solution is 15-25 vol%.

[0038] The temperature of the hydrothermal synthesis reaction in step (3) is 150-200℃ and the time is 15-20h.

[0039] A method for preparing a highly renewable ultrathin two-dimensional adsorbent.

[0040] Application of a highly renewable ultrathin two-dimensional adsorbent in the adsorption and recovery of rare earth ions in wastewater.

[0041] The application method includes adding the adsorbent at a concentration of 0.1-0.3 g / L to the recovered wastewater containing rare earth ions and stirring for 40-80 minutes.

[0042] The rare earth ion concentration in the recovered wastewater containing rare earth ions is 10-150 ppm, and the rare earth ions include Ce. 3+Eu 3+ Er 3+ Tm 3+ Yb 3+ At least one of them.

[0043] In the following rare earth ion adsorption experiments, the concentrations of the relevant metal ions were measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0044] Example 1

[0045] An ultrathin two-dimensional renewable InVO4 adsorbent was prepared by the following method:

[0046] (a) Under continuous magnetic stirring, 10 ml of 0.05 mol / L Na3VO4 solution and 10 ml of 0.1 mol / L InCl3 solution were thoroughly mixed. Then, 0.02 ml of 20 vol% concentrated nitric acid was used to adjust the pH value to 2 to ensure that the mixed solution eventually presents a transparent bright yellow state.

[0047] (b) The inner liner of the polytetrafluoroethylene-lined stainless steel autoclave is 45 mL. The above mixed solution is transferred into the autoclave and hydrothermal synthesis reaction is carried out at 180°C for 18 hours.

[0048] (c) After centrifuging the obtained reaction product, the solid product was washed three times with 25 mL of deionized water and ethanol respectively, then treated with strong ultrasonic waves for 30 minutes, and finally freeze-dried to obtain ultrathin two-dimensional InVO4 nano-adsorbent.

[0049] Figure 1 The following are the observation results of the ultrathin two-dimensional InVO4 nanoparticles prepared in this embodiment under SEM and TEM. Figure 1 As can be seen, in the stacked state, the prepared InVO4 nanoribbons exhibit an overall undulating, cloud-like appearance, with thin layers of InVO4 nanofiber structure visible at the edges, thus preliminarily confirming their two-dimensional structure. However, under TEM imaging, the prepared InVO4 nanoribbons display an ultrathin two-dimensional few-layer structure, with a thickness even below 10 nm. This ultrathin two-dimensional structure may result in higher surface energy and other unique surface properties, thus easily leading to stacking and aggregation, as shown in the SEM images.

[0050] Figure 2 The X-ray diffraction analysis of the ultrathin two-dimensional InVO4 adsorbent prepared in this embodiment, and its comparison with the standard PDF card (JCPDS No.: 48-0898), show that the obtained adsorbent basically conforms to the crystal form of orthorhombic InVO4. However, due to the special few-layer structure, crystal growth is disrupted, resulting in poor crystallinity. This is consistent with the basic characteristics of ultrathin two-dimensional materials.

[0051] Figure 3 This image shows the surface charge analysis of the ultrathin two-dimensional InVO4 nanoparticles prepared in this example. Zeta potential analysis revealed that the InVO4 adsorbent dispersed in deionized water exhibits a weakly acidic environment (pH approximately 5), at which point its surface is negatively charged with a charge of approximately -28.7 mV. Adjusting the pH of the suspension with HCl and NaOH showed little change in the surface charge of the prepared InVO4 adsorbent, indicating that this adsorbent can adsorb positively charged substances (organic matter, metal ions, etc.) over a wide pH range (3-10).

[0052] Example 2

[0053] The adsorption effect of the ultrathin two-dimensional InVO4 nanoparticles prepared in Example 1 on single rare earth ions was verified.

[0054] This embodiment uses different concentrations of single rare earth ion solutions to verify the adsorption capacity of the InVO4 adsorbent obtained in Example 1. The specific operation steps are as follows: Unless otherwise specified, all adsorption experiments in this embodiment are carried out under natural pH, room temperature and open system conditions. The pH of each rare earth ion solution under natural conditions is about 5.

[0055] This embodiment selected five rare earth ions (Ce). 3+ Eu 3+ Er 3+ Tm 3+ Yb 3+ Rare earth ions were used as the adsorbate, with corresponding 1 mol / L chloride solutions as stock solutions. During the adsorption experiments, the stock solutions were diluted with deionized water to the desired concentrations (10 ppm, 20 ppm, 50 ppm, 100 ppm, 150 ppm). The adsorption experiments were conducted as follows: 0.2 g / L InVO4 nanosheets were added to solutions containing different initial concentrations of rare earth ions. These solutions were placed in 20 mL glass bottles, and then magnetically stirred at 500 rpm. At specific time intervals (0 min, 5 min, 30 min, 60 min), 0.5 mL of the solution was collected to determine its adsorption performance. The remaining rare earth ion concentration in the solution was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0056] Adsorption performance is represented by comparing the amount of rare earth ions adsorbed by the adsorbent, and the calculation formula is as follows:

[0057]

[0058] Where, q t It is the adsorption capacity (mg / g), c0 and c tc represents the initial concentration and the remaining rare earth element concentration (ppm) at time t, respectively. a It is the concentration of adsorbent used in the adsorption process (0.2 g / L).

[0059] Figure 4 The graph shows the adsorption effect of ultrathin two-dimensional InVO4 nanoparticles on rare earth ions of different concentrations and types. It can be seen that due to the large amount of negative surface charge, the prepared adsorbent exhibits a strong affinity for all rare earth ions, especially for Yb, which has a large atomic weight and small ionic radius. 3+ The adsorption capacity can reach up to 317 mg / g. Therefore, it can be inferred that this adsorbent can be used for the efficient adsorption and recovery of various heavy metal ions.

[0060] Example 3

[0061] The adsorbent can be harmlessly regenerated using NaCl solution.

[0062] In this embodiment, NaCl is used as both a desorbent and a regenerator. It desorbs rare earth ions attached to the surface of the InVO4 adsorbent while simultaneously regenerating the adsorbent without damaging its surface. The specific steps are as follows: The desorption experiment uses a Tm solution with a concentration of 100 ppm. 3+ This was conducted as an example. First, following the steps in Example 2, an adsorbent that had already adsorbed rare earth ions was prepared. That is, at a concentration of 100 ppm Tm... 3+ 0.2 g / L of adsorbent was added to the solution and thoroughly mixed. After adsorption equilibrium was reached, the adsorption capacity was tested and calculated. The adsorbent, coated with rare earth ions, was then obtained by centrifugation and removal of the supernatant. 25 mL of 1 mol / L NaCl solution was then added to the adsorption flask. The mixture was then stirred for another 10 minutes to achieve complete desorption equilibrium. Samples were taken for ICP-OES testing to obtain the corresponding desorption rate. The formula for calculating the desorption rate is as follows:

[0063]

[0064] Where, q de It is the desorption rate (%), c f It is the desorbed Tm 3+ Concentration (mg / L), V is the volume of eluent used (L), m is the mass of adsorbent (g), q ad It is the adsorption capacity (mg / g).

[0065] Figure 5This embodiment demonstrates the effect of using NaCl as the eluent to elute rare earth ions from the prepared InVO4 adsorbent. It is evident that after adding NaCl, nearly 100% of the rare earth ions were eluted within 10 minutes, achieving an elution rate as high as 99%. Furthermore, the adsorbent prepared in this invention can be reused under the same conditions after elution. Multiple regeneration and reuse experiments demonstrate that the ultrathin two-dimensional InVO4 adsorbent prepared in this invention possesses extremely high stability, retaining approximately 88% of its adsorption capacity even after five reuses.

[0066] Example 4

[0067] The enrichment effect of the InVO4 adsorbent material prepared in Example 1 on ultra-low concentration rare earth ions (0.1 ppm) was verified.

[0068] In this embodiment, an ultra-low concentration (0.1 ppm) of Tm was used. 3+ For example, the enrichment effect of the synthesized ultrathin two-dimensional strongly negatively charged material on ultra-low concentration rare earth ions was verified. The specific steps are as follows:

[0069] In this embodiment, the enrichment experiment used a Tm-containing material containing 100 ppb. 3+ The adsorption was performed using 100 ml of solution and 0.2 g / L of adsorbent, with other procedures similar to those in Example 2. After the adsorption process reached equilibrium (30 minutes), centrifugation was performed to obtain adsorbent coated with rare earth ions. The adsorbent was then desorbed and regenerated using the procedures described in Example 3. The resulting NaCl solution was then diluted 5 times, and the Tm was measured by ICP-OES. 3+ The concentration was determined to yield the final recovered Tm. 3+ The amount.

[0070] Figure 6 This study investigated the enrichment effect of NaCl as the eluent on ultra-low concentration rare earth ions. The verification results showed that the adsorbent prepared in this invention could achieve a 78-fold enrichment of a rare earth ion solution with a concentration of only 100 ppb. The concentration of rare earth ions in the remaining solution was only 22 ppb, even lower than the standard for hexavalent chromium in Class V surface water in my country.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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 a highly renewable ultrathin two-dimensional adsorbent, characterized in that, Includes the following steps: (1) Add Na3VO4 solution to InCl3 solution and stir to obtain a uniform brownish-brown solution; (2) Use nitric acid solution to adjust the pH of the brownish-yellow solution obtained in step (1) to 1-3 to ensure that the solution eventually turns into a transparent bright yellow color. Then transfer it to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal synthesis reaction. (3) The high-pressure reactor in step (2) was naturally cooled to room temperature. The resulting reaction product was centrifuged and then washed with deionized water and ethanol several times. Finally, after ultrasonic treatment and freeze drying, an ultrathin two-dimensional InVO4 nano-adsorbent with a strong negative charge on the surface was obtained. In step (1), the concentration ratio of Na3VO4 solution to InCl3 solution is 1:1.5-2.5, the concentration of Na3VO4 solution is 0.03-0.08 M / L, and the volume ratio of Na3VO4 solution to InCl3 solution is 1:0.8-1.

2. In step (2), the concentration of the nitric acid solution is 15-25 vol%, and the filling rate of the reaction vessel is 40-50 vol%. The temperature of the hydrothermal synthesis reaction in step (3) is 150-200℃ and the time is 15-20 h.

2. A highly renewable ultrathin two-dimensional adsorbent prepared by the preparation method of the highly renewable ultrathin two-dimensional adsorbent as described in claim 1.

3. The application of a highly renewable ultrathin two-dimensional adsorbent as described in claim 2 in the adsorption and recovery of rare earth ions in wastewater.

4. The application of the highly renewable ultrathin two-dimensional adsorbent as described in claim 3 in the adsorption and recovery of rare earth ions in wastewater, characterized in that, The method of application includes adding the adsorbent to the recovery wastewater containing rare earth ions at a concentration of 0.1-0.3 g / L and stirring for 40-80 min.

5. The application of the highly renewable ultrathin two-dimensional adsorbent as described in claim 4 in the adsorption and recovery of rare earth ions in wastewater, characterized in that, The rare earth ion concentration in the recovered wastewater containing rare earth ions is 10-150 ppm, and the rare earth ions include Ce. 3+ Eu 3+ Er 3+ Tm 3+ Yb 3+ At least one of them.

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