Rubidium and cesium ion selective adsorbent based on graphene composite material and application of rubidium and cesium ion selective adsorbent

Abstract

The invention belongs to the field of selective adsorbents, and particularly relates to a rubidium and cesium ion selective adsorbent based on a graphene composite material and application thereof.The rubidium and cesium ion selective adsorbent is prepared by conducting surface carboxyl activation and crown ether grafting on the surface of a three-dimensional cross-linked graphene skeleton to obtain a crown ether functionalized graphene composite material; and performing in-situ growth of copper ferrocyanide nanoclusters on the crown ether functionalized graphene composite material. The rubidium cesium ion selective adsorbent realizes efficient selective adsorption of Rb < + > and Cs < + >, reaches adsorption equilibrium within 30 min in simulated high-level liquid waste, has Cs < + > and Rb < + > saturated adsorption capacities of 185 mg / g and 142 mg / g respectively, and has excellent acid-base stability and electrochemical regeneration capacity.

Description

Technical Field

[0001] This invention relates to the field of selective adsorbent technology, specifically to a rubidium-cesium ion selective adsorbent based on graphene composite materials and its application. Background Technology

[0002] Rubidium and cesium, as typical alkali metal elements, occupy an irreplaceable strategic position in modern high-tech industries. Their high reactivity, low ionization energy, and unique photoelectric properties make them widely used in atomic clocks, magnetohydrodynamic power generation, special glasses, catalysts, and nuclear energy.

[0003] Ion adsorption has become one of the mainstream separation strategies due to its advantages such as simple operation, controllable cost, and ease of scaling up. The performance of the adsorbent material directly determines the technical limit of the entire process.

[0004] For a long time, inorganic ion exchange materials such as ferrocyanides, phosphates, and titanates have been used for the selective capture of cesium ions. Among them, Prussian blue analogs such as copper ferrocyanide and nickel ferrocyanide were once considered the most promising adsorption media due to their open lattice channels and excellent coordination affinity for cesium ions. These materials form size-matched stable complex structures with cesium ions through lattice voids or specific coordination sites, thereby achieving selective enrichment of cesium from complex matrices. In early wastewater treatment practices, these materials did indeed exhibit relatively good selectivity in highly competitive ion environments such as high sodium and high potassium, effectively addressing the technical requirements for the initial removal of cesium at that time. However, as wastewater composition becomes increasingly complex and the requirements for final disposal standards become increasingly stringent, traditional inorganic adsorbents have revealed a series of inherent defects that are difficult to overcome in deeper applications.

[0005] Ultimately, the limitations of these materials stem from inherent contradictions in their intrinsic physicochemical properties. On the one hand, to maintain high selectivity for cesium ions, the materials must rely on highly ordered and precisely sized lattice channels, which typically implies a low specific surface area and limited active site density. On the other hand, real-world waste liquid systems often exhibit complex conditions with high viscosity, high turbidity, and the coexistence of multiple valent ions, leading to significantly increased mass transfer resistance and slow adsorption kinetics. Furthermore, these inorganic materials generally have low mechanical strength and are prone to pulverization, easily causing increased pressure drop or even blockage in fixed-bed or column chromatography operations, severely affecting the stability of engineered operation. Crucially, their hydrothermal stability is insufficient; in strong acid and strong alkali environments, structural collapse or dissolution of active components can easily occur, not only reducing adsorption efficiency but also potentially introducing secondary pollution. Moreover, existing materials are almost unable to effectively distinguish rubidium ions from cesium, which have extremely similar chemical properties, yet both are valuable in some high-end applications (such as high-purity rubidium extraction). The lack of synergistic separation capabilities restricts the full-component recovery of resources. The aforementioned problems are not isolated, but rather coupled and exacerbate each other: increasing crystallinity to enhance selectivity often sacrifices kinetic performance, while introducing porous structures to improve mass transfer may disrupt the specificity of the coordination environment. This trade-off in performance constitutes a theoretical bottleneck that is difficult for existing technologies to overcome.

[0006] Therefore, how to construct a novel adsorbent that combines high specific surface area, fast mass transfer channels, excellent structural stability, and dual high selectivity for rubidium and cesium ions, and break through the inherent constraints between selectivity, kinetics, and stability of traditional inorganic materials, has become a key challenge and an urgent technical problem for those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a rubidium-cesium ion selective adsorbent based on graphene composite materials and its application, in order to solve the above-mentioned problems.

[0008] The purpose of this invention is to provide a rubidium-cesium ion selective adsorbent based on graphene composite materials and its application, which can be achieved through the following technical solutions: In a first aspect, a rubidium-cesium ion selective adsorbent based on graphene composite material is obtained by surface carboxyl activation and crown ether grafting on the surface of a three-dimensional cross-linked graphene framework to obtain a crown ether-functionalized graphene composite material, and then in-situ growing copper ferrocyanide nanocrystal clusters on the crown ether-functionalized graphene composite material to obtain the rubidium-cesium ion selective adsorbent based on graphene composite material.

[0009] Furthermore, the three-dimensional cross-linked graphene framework is prepared by hydrothermal self-assembly of graphene oxide and curing with boric acid as a cross-linking agent.

[0010] Furthermore, the graphene oxide underwent a hydrothermal self-assembly reaction at 180±3℃ for at least 6 hours.

[0011] Furthermore, the three-dimensional cross-linked graphene framework is doped with 5 at.% nitrogen atoms, which coexist in the form of pyridine nitrogen and graphitic nitrogen, wherein the proportion of pyridine nitrogen is not less than 60%.

[0012] Furthermore, the crown ether used for crown ether grafting is a dibenzo-18-crown-6-amino derivative, and the grafting process includes: After activating the three-dimensional cross-linked graphene framework in 2-(N-morpholino)ethanesulfonic acid buffer solution, the carboxyl groups were activated by the N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide system, and then the amide condensation was completed by reacting with dibenzo-18-crown-6-amino derivatives.

[0013] Furthermore, the dibenzo-18-crown-6-amino derivative is 4'-aminobenzo-18-crown-6.

[0014] Furthermore, the crown ether used for crown ether grafting is carboxydicyclohexyl-18-crown-6, and the grafting process includes: Three-dimensional cross-linked graphene frameworks were dispersed in N,N-dimethylformamide and then subjected to esterification or amidation by heating under a catalytic system of N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine.

[0015] Furthermore, the method for in-situ growth of copper ferrocyanide nanocrystal clusters on crown ether-functionalized graphene composites includes the following steps: Crown-ether-functionalized graphene composites were dispersed in water, and copper nitrate and potassium ferrocyanide were added sequentially under nitrogen protection to react, controlling the Cu²⁺ content. + With [Fe(CN)6] 4- The molar ratio of the two components was 2~2.5:1, and the reaction was carried out at 40℃ for 4 hours. The product obtained from the reaction was obtained by centrifugation, washing, and vacuum drying.

[0016] Secondly, the rubidium-cesium ion selective adsorbent based on graphene composite material is used in the adsorption treatment of waste liquid containing rubidium-cesium ions or in resource recovery.

[0017] Furthermore, the rubidium-cesium ion selective adsorbent based on graphene composite material is packed into a fixed-bed adsorption column to adsorb waste liquid containing rubidium and cesium ions. After adsorption saturation, ammonium nitrate solution is used for elution to recover rubidium and cesium salts.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention constructs a novel rubidium-cesium ion selective adsorbent that combines rapid mass transfer, dual ion selectivity, and stability in extreme environments. This rubidium-cesium ion selective adsorbent simultaneously achieves high adsorption capacity, high selectivity, and high cycling stability, completely resolving the inherent contradiction between selectivity, kinetics, and stability in traditional inorganic adsorbents, and providing a reliable technical path for the safe and efficient separation of rubidium and cesium ions from high-level radioactive waste liquids. Detailed Implementation

[0019] The present invention will be further described in detail below through specific embodiments.

[0020] The following detailed description of embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] Example 1 First, a three-dimensional cross-linked graphene framework was prepared. 5.0 g of graphene oxide (GO) powder was dispersed in 500 mL of deionized water and sonicated for 30 min to form a uniform and stable brownish-yellow colloidal suspension with a solid content of 1.0 wt%. Subsequently, 0.42 g of boric acid (H3BO3) was added as a cross-linking agent and stirred thoroughly until completely dissolved. The resulting mixture was transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reactor and subjected to a hydrothermal reaction at 180 °C for 6 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The gel-like product was then removed and washed three times each with deionized water and anhydrous ethanol to remove unreacted substances and byproducts. Finally, it was placed in a freeze dryer and dried at -50 °C and 10 Pa for 24 h to obtain the three-dimensional cross-linked graphene framework. The three-dimensional cross-linked graphene framework is black, lightweight, and has a macroscopic continuous network structure. Its BET specific surface area is 472 m² / g, as determined by nitrogen adsorption-desorption isotherm. The pore size distribution exhibits a bimodal characteristic: the diameter of macropore channels is concentrated in the range of 50~200 nm, and the mesoporous region is concentrated in the range of 2~10 nm. Its conductivity is 128 S / m as measured by the four-probe method.

[0022] In a preferred embodiment of the present invention, 1.2 g of urea was added as a nitrogen source to the above hydrothermal reaction system, while other conditions remained unchanged. X-ray photoelectron spectroscopy (XPS) analysis of the resulting nitrogen-doped three-dimensional graphene framework showed a nitrogen content of 5.1 at.%, of which approximately 62% was pyridine nitrogen, approximately 38% was graphitic nitrogen, and the remainder was a small amount of pyrrole nitrogen. This doped structure not only enhanced the density of Lewis basic sites on the material surface but also significantly improved its structural stability under strong radiation conditions.

[0023] Next, the surface carboxyl groups of the above-mentioned three-dimensional cross-linked graphene framework were activated and grafted with crown ethers. 1.0 g of the dried three-dimensional cross-linked graphene framework was immersed in 100 mL of 2-(N-morpholino)ethanesulfonic acid (MES) buffer solution at pH 4.5 and activated by shaking at room temperature for 30 min to fully expose the surface carboxyl groups. Then, 0.115 g of N-hydroxysuccinimide (NHS) and 0.192 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) were added, and the mixture was reacted at 25 °C in the dark for 2 h to complete the activation of the carboxyl groups as an O-acyl isourea intermediate. After separation by filtration, the solid product was transferred to a deionized water / ethanol mixed solvent (volume ratio 1:1, total volume 100 mL) containing 0.35 g of a dibenzo-18-crown-6-amino derivative (DB18C6-NH2; for example, 4'-aminobenzo-18-crown-6, CAS No.: 60835-71-8), and the reaction was continued at 37 °C for 12 h. After the reaction was completed, the product was collected by centrifugation and washed three times each with deionized water, ethanol, and acetone to thoroughly remove unreacted small molecules. Finally, it was vacuum dried at 60 °C for 12 h to obtain the crown ether-functionalized graphene composite material.

[0024] XPS quantitative analysis revealed that the surface nitrogen atomic percentage of the obtained crown ether-functionalized graphene composite material was 1.92%. The cavity diameter of this crown ether structure was approximately 2.6–3.2 Å, similar to that of Rb. + The ionic radii (1.52 Å) are highly matched, forming a stable 1:1 complex with a stability constant log K of 4.35 determined by UV-Vis titration.

[0025] In another preferred embodiment of the present invention, when the pH of the target waste liquid system is <2, dicyclohexyl-18-crown-6 (DCH18C6; CAS number 17455-23-1) is used instead of DB18C6. The grafting reaction is then carried out in anhydrous N,N-dimethylformamide (DMF): 1.0 g of the three-dimensional cross-linked graphene backbone is dispersed in 100 mL of DMF, and 0.38 g of DCH18C6-COOH (carboxylated dicyclohexyl-18-crown-6, CAS: 125139-87-1), 0.23 g of N,N'-dicyclohexylcarbodiimide (DCC), and 0.03 g of 4-dimethylaminopyridine (DMAP) are added. The reaction is carried out at 60°C for 8 h under a nitrogen atmosphere. After the reaction, the generated dicyclohexylurea precipitate is removed by filtration, and the product is washed sequentially with DMF, ethanol, and diethyl ether, and then dried under vacuum at 60°C.

[0026] Subsequently, copper ferrocyanide nanocrystals were grown in situ on the crown-ether-functionalized graphene composite material. 0.5 g of the crown-ether-functionalized graphene composite material was ultrasonically dispersed in 200 mL of deionized water to form a uniform suspension. Under nitrogen protection, 0.146 g (0.6 mmol) of copper nitrate (Cu(NO3)2·3H2O) was added first, and after stirring for 30 min, 0.098 g (0.24 mmol) of potassium ferrocyanide (K4[Fe(CN)6]·3H2O) was slowly added dropwise, controlling the Cu²⁺ content. + With [Fe(CN)6] 4- The molar ratio was 2.5:1 (slightly in excess to ensure complete copper precipitation). The reaction system was maintained at 40℃ and stirred continuously for 4 hours. After the reaction was complete, the product was collected by high-speed centrifugation (10000 rpm, 10 min) and repeatedly washed with deionized water until the filtrate was free of potassium. + (Detected by flame photometry), and then vacuum dried at 60℃ for 12h to obtain the final rubidium-cesium ion selective adsorbent based on graphene composite material.

[0027] The stability of the adsorbent in extreme chemical environments was verified by the following tests: the samples were immersed in 1 mol / L HNO3 and 2 mol / L NaOH solutions, respectively, and analyzed after 72 h. ICP-MS results showed that the Cu dissolution was 0.07 mg / L and 0.09 mg / L, and the Fe dissolution was 0.06 mg / L and 0.08 mg / L, respectively, all below 0.1 mg / L, proving that it is structurally stable under strong acid and strong alkali conditions.

[0028] Adsorption performance tests were conducted in a simulated high-level radioactive waste liquid system. The simulated solution was prepared with the following composition: NaNO3 1.0 mol / L, KNO3 0.5 mol / L, Ca(NO3)2 0.1 mol / L, Sr(NO3)2 0.05 mol / L, CsNO3 1.0 × 10⁻⁶ -4 mol / L, RbNO3 1.0×10 -5 The concentration of Cs was adjusted to mol / L, and the pH was adjusted to 6.0 using HNO3 or NaOH. 0.050 g of adsorbent was added to 50 mL of the above simulated solution and incubated at 25°C with constant shaking. Samples were taken periodically, filtered through a 0.22 μm filter membrane, and the residual Cs were determined by atomic absorption spectrometry (AAS). + With Rb + Concentration. Kinetic data show that Cs + The adsorption rate reaches over 90% within 15 minutes and equilibrium is reached within 30 minutes; Rb + The equilibration time is slightly longer, reaching 90% in about 25 minutes and complete equilibration in 30 minutes. Based on the Langmuir isotherm model fitting, Cs... +The saturated adsorption capacity is 185 mg / g, Rb + It is 142 mg / g.

[0029] The selectivity coefficient was calculated using the partition coefficient Kd (mL / g) and the separation factor α. Kd = [(C0 C e ) / C e ] × (V / m), where C0 and C e The initial and equilibrium concentrations are given by , V is the solution volume (mL), and m is the adsorbent mass (g). In a 1 mol / L NaNO3 medium, Cs + The Kd value is 1.32 × 10 4 mL / g, Rb + The Kd value is 9.8 × 10³ mL / g. The separation factor α(Cs / Na) = Kd(Cs) / Kd(Na), and Kd(Na) was determined to be 15.5 mL / g, therefore α(Cs / Na) = 852; similarly, Kd(K) = 15.8 mL / g, α(Rb / K) = 620.

[0030] To verify the engineering applicability, a fixed-bed column experiment was conducted. A 316L stainless steel column with an inner diameter of 10 mm and a bed height of 200 mm was used, loaded with 15.7 g of adsorbent (bed volume BV = 15.7 mL). Simulated high-level radioactive waste was continuously fed at a flow rate of 2 BV / h (i.e., 31.4 mL / h), and the temperature was maintained at 25°C. Cs samples were taken from the effluent at regular intervals for analysis. + Concentration. The breakthrough point is defined as the effluent Cs. + The concentration reaches 5% of the feed concentration (i.e., 5 × 10). -6 The treatment volume was determined at mol / L. Experimental results showed that the breakthrough point was not reached even when the breakthrough volume reached 1200 BV (i.e., 18.8 L), indicating that the adsorbent has extremely high dynamic adsorption capacity and excellent bed utilization efficiency.

[0031] Regeneration performance was achieved via an electrochemical method. 0.1 g of the saturated adsorbent was placed in 50 mL of 0.5 mol / L NH4NO3 electrolyte. A graphite rod was used as the counter electrode, and Ag / AgCl (3M KCl) was used as the reference electrode. A constant potential of +1.2 V was applied for 15 min. The desorption solution was analyzed by AAS, and Cs... + With Rb + The desorption rates were 96.3% and 95.7%, respectively. The regenerated material was reused in the adsorption experiment, and this process was repeated for a total of 10 cycles. After the 10th cycle, Cs + The adsorption capacity was 170 mg / g, and the retention rate was 91.9%.

[0032] The application method of the adsorbent described in this invention is as follows: The adsorbent is packed into a fixed-bed adsorption column, the waste liquid flow rate is controlled at 1~5 BV / h, the operating temperature is 20~60℃, and the pH value is adjusted to 3~9 (if the waste liquid itself has a pH <2, then an adsorbent modified with DCH18C6 is used). After adsorption saturation, the feed is stopped, and the bed is rinsed with deionized water until the effluent is salt-free. Subsequently, 0.1~1.0 mol / L NH4NO3 solution is used as the eluent, the flow rate is 0.5~2 BV / h, and the elution volume is 2~5 BV. After the eluent is collected, it is evaporated, concentrated, and recrystallized to obtain high-purity RbNO3 and CsNO3 products, respectively. The entire process does not use organic solvents, and the secondary waste is mainly a low-concentration ammonium nitrate solution, which can be reused after simple treatment. The amount of waste generated is less than 1 / 10 of that of traditional solvent extraction processes.

[0033] Furthermore, this adsorbent is also suitable for resource recovery in non-nuclear fields. In an actual sample of brine from a salt lake (main ion concentration: Na...),... + 18.3 g / L, K + 12.5 g / L, Mg² + 4.2 g / L, Ca² + 1.1 g / L, Rb + 8.2 mg / L, Cs + 0.9 mg / L), add 0.1 g of adsorbent to 100 mL of brine, and shake at 25℃ for 2 h. After adsorption, Rb... + The concentration decreased to 0.18 mg / L, with an enrichment factor of 45.6 times; K + The concentration decreased from 12.5 g / L to 11.8 g / L, and the K / Rb separation factor α(K / Rb) = 382. The enriched solution can be directly used as feed for subsequent purification processes (such as ion exchange or crystallization), significantly reducing processing costs.

[0034] To evaluate the superiority of the technical solution of the present invention, the following comparative examples are provided: Comparative Example 1 Only a three-dimensional cross-linked graphene framework was used (without grafted crown ethers or loaded with ferrocyanide). In the same simulated waste liquid, Cs + With Rb + The Kd values ​​were 8.2 mL / g and 6.5 mL / g, respectively, indicating almost no selectivity.

[0035] Comparative Example 2 Only copper ferrocyanide was loaded onto the three-dimensional cross-linked graphene framework (without crown ether modification). Cs + Kd = 1.15×10 4 mL / g, but Rb + Kd is only 12.3 mL / g, which is less effective against Rb. +No ability to identify; and in the presence of high concentrations of K + In the system, Cs + The adsorption capacity decreased to 110 mg / g, indicating weak anti-interference ability.

[0036] Comparative Example 3 DB18C6 was grafted onto graphene only (without ferrocyanide). Rb + Kd = 8.9 × 10³ mL / g, but Cs + Kd is only 9.7 mL / g; in high Na+ environments... + In this context, Rb + The adsorption capacity decreased to 85 mg / g.

[0037] Comparative Example 4 Copper ferrocyanide was physically mixed with crown ether-functionalized graphene (non-in-situ intercalation). Although Cs + With Rb + All components were adsorbed, but the kinetics were significantly slower (equilibrium time > 2 h), and the capacity decreased by more than 30% after 5 cycles. SEM showed that the components underwent phase separation.

[0038] The performance data of the above embodiments and comparative examples are summarized in Table 1: Table 1

[0039] Data shows that only the three-layer synergistic structure described in this invention—namely, the three-dimensional cross-linked graphene framework providing a rapid mass transfer channel and the crown ether unit specifically recognizing Rb—is effective. + Precise capture of Cs by copper ferrocyanide crystal clusters + Only through spatial confinement and electronic coupling can functional integration be achieved, simultaneously realizing high selectivity, fast dynamics, and high stability.

[0040] In summary, the application scenarios of this invention cover multiple important fields such as waste liquid treatment and strategic metal resource recycling, and it has significant industrialization prospects and technological value.

[0041] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0042] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A rubidium and cesium ion-selective adsorbent based on a graphene composite material, characterized in that: The graphene composite material is obtained by grafting a crown ether on the surface of a three-dimensional cross-linked graphene framework through activation of the surface carboxyl group, and in-situ growth of copper ferrocyanide nanocrystal clusters on the graphene composite material functionalized with the crown ether.

2. The rubidium and cesium ion selective adsorbent based on graphene composite material according to claim 1, characterized in that: The three-dimensional cross-linked graphene framework is prepared by hydrothermal self-assembly of graphene oxide and solidification with boric acid as a cross-linking agent.

3. The rubidium and cesium ion-selective adsorbent based on graphene composite material according to claim 2, characterized in that: The graphene oxide is subjected to the hydrothermal self-assembly reaction at 180±3℃ for at least 6h.

4. The rubidium and cesium ion-selective adsorbent based on graphene composite material according to claim 1, characterized in that: The three-dimensional cross-linked graphene framework is doped with 5 at.% of nitrogen atoms, and the nitrogen atoms coexist in the form of pyridine-type nitrogen and graphite-type nitrogen, wherein the proportion of the pyridine-type nitrogen is not less than 60%.

5. The rubidium and cesium ion-selective adsorbent based on graphene composite material according to claim 1, characterized in that: The crown ether used for the crown ether grafting is a dibenzo-18-crown-6-amino derivative, and the grafting process comprises: After the three-dimensional cross-linked graphene framework is activated in a 2-(N-morpholino)ethanesulfonic acid buffer solution, the carboxyl group is activated by using an N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide system, and then reacted with the dibenzo-18-crown-6-amino derivative to complete the amide condensation.

6. The rubidium and cesium ion-selective adsorbent based on graphene composite material according to claim 5, characterized in that: The dibenzo-18-crown-6-amino derivative is 4'-aminobenzo-18-crown-6.

7. The rubidium and cesium ion-selective adsorbent based on graphene composite material according to claim 1, characterized in that: The crown ether used for the crown ether grafting is carboxylic dicyclohexyl-18-crown-6, and the grafting process comprises: The three-dimensional cross-linked graphene framework is dispersed in N,N-dimethylformamide, and heated to complete esterification or amide connection under the catalysis of an N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine catalysis system.

8. The rubidium and cesium ion-selective adsorbent based on graphene composite material according to claim 1, characterized in that: The method for in-situ growth of copper ferrocyanide nanocrystal clusters on the graphene composite material functionalized with the crown ether comprises the following steps: The crown ether functionalized graphene composite material is dispersed in water, and copper nitrate and potassium ferrocyanide are added in turn under nitrogen protection to react, the molar ratio of Cu² + and [Fe(CN)6] 4- is controlled to be 2-2.5:1, and the reaction is carried out at 40°C for 4h, and the product obtained by the reaction is centrifuged, washed and vacuum dried.

9. Use of a graphene composite material-based rubidium and cesium ion selective adsorbent according to any one of claims 1-8 in adsorption treatment of waste liquid containing rubidium and cesium ions.

10. Use according to claim 9, characterized in that: The graphene composite material-based rubidium and cesium ion selective adsorbent is packed in a fixed bed adsorption column to adsorb and treat waste liquid containing rubidium and cesium ions, and after adsorption saturation, ammonium nitrate solution is used for elution to recover rubidium salt and cesium salt.

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