Preparation method of amino acid metal cation adsorption material and application thereof

Abstract

This invention discloses a method for preparing an amino acid-based metal cation adsorbent and its application. This invention belongs to the technical field of radioactive waste gas treatment and functional adsorbent materials. The amino acid-based metal cation adsorbent prepared by this invention is a composite material in which an amino acid-based metal cation ionic liquid is mounted on a three-dimensional porous substrate. Through the synergistic mechanism of mass transfer from the three-dimensional porous substrate and chemical complexation and physical dissolution of the ionic liquid, it achieves efficient capture and irreversible fixation of elemental iodine (I2) and iodine aerosol in nuclear medical waste gas. The material is prepared under mild conditions, without the need for high temperature and high pressure, has stable chemical properties, and the production process is green, pollution-free, and easy to control. It exhibits excellent application effects in the fields of nuclear medical iodine waste gas and iodine aerosol purification, providing an efficient, low-cost, and easily industrialized solution for the treatment of radioactive iodine waste gas in nuclear medical settings.

Description

Technical Field

[0001] This invention belongs to the technical field of radioactive waste gas treatment and functional adsorption materials. More specifically, this invention relates to a method for preparing an amino acid-based metal cation adsorption material and its application. Background Technology

[0002] In the field of nuclear medicine, radioactive iodine isotopes (mainly...) 131 I) Due to its high affinity for human thyroid tissue, radioactive iodine is widely used in the diagnosis and treatment of diseases such as hyperthyroidism and thyroid cancer, and is also used in medical research such as radiopharmaceutical labeling. In the clinical administration, production and synthesis, waste reagent disposal, and cleaning and disinfection of diagnostic and treatment equipment, volatile iodine-containing waste gas is inevitably released. Its core pollutant is molecular iodine (I2), which also carries radioactive isotopes. 131 I. 131 Iodine (I-) has a half-life of approximately 8 days, is highly volatile, and has high radioactivity. It can enter the human body through respiration and specifically accumulate in the thyroid gland, significantly increasing the risk of thyroid cancer and posing a serious threat to medical staff, patients, and the surrounding environment. According to the emission standards for waste gas in the nuclear medical industry, iodine waste gas must be efficiently purified to ensure that the radioactivity in the emitted gas meets safety standards. Therefore, developing iodine waste gas adsorption technology suitable for nuclear medical scenarios has become a key aspect of nuclear medical safety control.

[0003] The current challenge in removing iodine from waste gas from nuclear medical procedures lies in: 1. The iodine content is very low; it is generally found in the exhaust gas of nuclear medicine departments. 131 The activity concentration of I is approximately 103 Bq / m3, and its mass concentration is as low as 0.17×10-3 ppt based on the activity, which is in the ultra-trace level. This requires the material to still have extremely strong adsorption driving force and deep capture capability at extremely low concentrations. 2. Iodine in nuclear medical waste gas has a high humidity, meaning it exhibits a large number of competing H2O molecules that compete for adsorption. Therefore, the material needs to be... 131 The I2 formed by I has high selectivity and is resistant to water interference; 3. The purification process for nuclear medical waste gas needs to avoid secondary desorption, because the material itself, after adsorption, will become a new adsorbent. 131 Since it is a radioactive source, the iodine adsorbed there cannot undergo secondary desorption, as this would cause secondary hazards.

[0004] Existing adsorption technologies can be categorized into four types: carbon-based iodine adsorption technology uses porous carbon materials such as activated carbon, activated carbon fiber, and activated carbon cloth as the matrix, relying on the physical adsorption of porous carbon to capture iodine gas; silver-based inorganic porous iodine adsorption technology uses inorganic porous materials such as molecular sieves, silica gel, porous alumina, and porous glass / ceramics as carriers, loading nano-silver or silver oxide active components into the carrier pores through processes such as ion exchange and impregnation loading, relying on the redox reaction of silver and iodine to generate silver iodide, thus achieving chemical capture of iodine gas; metal-organic framework / covalent organic framework (MOF / COF) iodine adsorption technology uses crystalline porous materials of metal-organic frameworks (MOF) and covalent organic frameworks (COF) as the adsorbent body, relying on the tunable pore structure and ultra-high specific surface area of ​​the material, through the physical confinement of the pores, and the complexation and charge transfer effects of functional groups such as amino, thioether, carboxyl, and open metal sites grafted on the material framework with iodine to achieve iodine gas capture; metal sulfides / The iodine adsorption technology based on bismuth-based inorganic functional materials uses layered metal sulfides, bismuth / lead-based oxides, and other inorganic functional materials as the main adsorbents. It achieves iodine capture through interlayer intercalation of materials and the redox reaction between metal active sites and iodine to generate metal iodides.

[0005] Chinese patent CN121318739A discloses a method for preparing and applying a metal sulfide adsorbent for adsorbing iodine and methyl iodine. While these materials exhibit some adsorption capacity for both iodine and methyl iodine, with diethylenetriamine-guided adsorption showing superior results, their preparation requires a hydrothermal reaction at 110-220℃ for 2-9 days. The reaction conditions are harsh and time-consuming. Furthermore, the adsorption is triggered entirely by the mass transfer gradient formed by the high concentration of iodine. Faced with ultra-trace amounts of iodine at sub-ppt levels in nuclear medicine, they cannot form an effective adsorption driving force, making it difficult for iodine molecules to reach the active sites between the material layers, resulting in a complete lack of deep trapping capability. Simultaneously, the metal sulfide framework and amino active sites of the material are both strongly polar and hydrophilic. In near-saturated, high-humidity waste gas from nuclear medicine, water molecules will preemptively occupy all adsorption sites and form a water film barrier between the layers, completely shielding the material's ability to adsorb iodine molecules. More importantly, its iodine fixation relies solely on physical intercalation and weak complexation, without forming stable chemical bonds. The adsorption process itself is reversible; once the ambient temperature and humidity fluctuate or the gas phase iodine concentration decreases, the adsorbed iodine will continuously desorb and be released, completely failing to meet the safety standard of zero secondary pollution in nuclear medicine.

[0006] Chinese patent CN121537614A relates to a porous aromatic ionic framework material, its preparation method, and its application in iodine adsorption. This material is prepared via Friedel-Crafts alkylation, requiring no post-modification steps. It exhibits high adsorption capacity for both vapor and solution-based elemental iodine, excellent stability, and recyclability. However, its performance advantage is limited to high-capacity adsorption under saturated iodine vapor conditions. In nuclear medicine settings with extremely low abundances of trace iodine, it lacks sufficient concentration gradient to drive iodine molecules into the microporous structure and cannot achieve targeted capture of extremely low concentrations of iodine molecules, resulting in virtually zero deep purification capability. Although the aromatic framework possesses certain hydrophobic properties, the core unit responsible for iodine adsorption is a strongly hydrophilic ionic group. In high-humidity environments, water molecules preferentially bind to these ionic sites, directly rendering the core functional unit of iodine adsorption ineffective, thus completely lacking iodine selectivity against water interference.

[0007] Chinese patent CN112672809A relates to a particulate porous inorganic material that exhibits a strong ability to adsorb gaseous iodine upon contact. Once loaded with iodine, it can be transformed into a dense glass or glass-ceramic matrix with iodine confined within it through simple heat treatment. This material has a strong adsorption capacity for gaseous iodine, and after adsorption, the dense matrix formed through heat treatment can achieve iodine sequestration, making it suitable for long-term storage of radioactive iodine in nuclear fuel processing. However, its silver-based active sites require a sufficient concentration of iodine molecules to trigger an effective chemical reaction, and it only functions in high-concentration iodine environments. Faced with ultra-trace amounts of iodine at sub-ppt levels in nuclear medicine, the silver sites cannot be effectively activated, and the capture efficiency for extremely low concentrations of iodine is negligible. Furthermore, the only way to permanently fix iodine is through subsequent high-temperature heat treatment for vitrification. However, such high-temperature operations are impossible to perform on radioactive adsorbent materials in nuclear medicine settings. Before heat treatment, the adsorbed iodine not only faces the risk of physical desorption, but the generated silver iodide can also dissolve in high-humidity environments.

[0008] Chinese patent CN119186524A discloses a ZIF-8@Cu-BTCMOF composite material, its preparation method, and its applications. This MOF composite material improves water stability and iodine adsorption capacity, solving the problem of poor water stability in traditional MOF materials. However, it still does not overcome the inherent defects of MOF materials: its so-called water stability only ensures that the material will not collapse under high humidity, but it does not solve the problem of strong competitive adsorption of iodine molecules by water molecules. The open metal sites of the MOF framework and core adsorption are strongly hydrophilic. Under high humidity, water molecules will preferentially occupy all active sites, directly rendering the iodine adsorption function ineffective. At the same time, its iodine fixation relies only on microporous physical confinement and weak metal complexation, without forming irreversible chemical bonds. The adsorption process is completely reversible. Once environmental conditions change, the adsorbed iodine will continue to desorb and be released, which completely fails to meet the standard of permanent fixation and zero secondary risk required for nuclear medicine.

[0009] Chinese patent CN121496740A discloses a melamine-modified collagen fiber iodine adsorbent. This material uses collagen fibers from animal hides such as cowhide and pigskin as a matrix. After alkali activation to fully expose active functional groups, melamine is covalently grafted onto the collagen fibers via a Schiff base reaction using dialdehydes such as glutaraldehyde as crosslinking agents. The core of the material relies on the carboxyl groups, hydroxyl groups, and benzene ring π bonds of the collagen fibers, as well as the high-density nitrogen-rich lone pair electron sites introduced by melamine, to achieve iodine capture through hydrogen bonding, electrostatic interactions, and Lewis acid-base electron transfer complexation. Its core advantages are: it uses natural bio-based raw materials and mild aqueous solution preparation process, the reaction temperature does not exceed 50℃ throughout the process, it does not require high temperature and high pressure equipment, organic solvents and precious metal raw materials, the preparation steps are simple, low cost and green and environmentally friendly, and it has the potential for large-scale preparation; however, all performance verification of this material was completed in a high concentration of iodine environment, without hierarchical pore mass transfer structure, when facing ppt-level ultra-trace iodine, the mass transfer resistance of iodine molecules is large, the active sites cannot be activated, and there is no effective capture effect; it is completely deactivated under high humidity environment, the material as a whole is a strongly hydrophilic system, and no anti-water interference design was made. Under near-saturated high humidity conditions at room temperature, water molecules will preferentially occupy all active sites, form a water film to block iodine contact, the adsorption performance decreases by more than 90%, and the iodine selectivity is completely lost.

[0010] In recent years, ionic liquid-based composite adsorbent materials have become a research hotspot in the field of iodine adsorption due to their excellent chemical complexation properties. However, their application in the purification of iodine waste gas in nuclear medicine is still in the exploratory stage. Most existing ionic liquid composite adsorbent materials are designed for the high temperature and high humidity iodine waste gas scenarios in the nuclear industry, which do not meet the core requirements of nuclear medicine for room temperature and high humidity, trace iodine, and prevention of secondary desorption. In addition, the ionic liquid loading process of some materials is complicated and difficult to achieve large-scale production.

[0011] Chinese patent CN120361874A discloses a method for preparing ionic liquid-modified MOF-808 for adsorbing radioactive iodine and its application. This material uses an in-situ impregnation method to load ionic liquid into the pores of MOF-808, combining the porous structure of MOF with the heteroatom adsorption sites of the ionic liquid, thus improving the radioactive iodine removal performance. Furthermore, the hydrophobic ionic liquid modification improves adsorption performance under high humidity conditions, solving some of the problems of traditional MOF failure under high humidity. However, it still suffers from drawbacks such as a multi-step synthesis process, high requirements for reaction conditions, difficulty in controlling batch stability, low efficiency in large-scale production, and high cost.

[0012] Chinese patent CN118416857A discloses a method for modifying amine compounds such as triethylenediamine and hexamethylenetetramine, which have methyl iodine adsorption functions, into functionalized amine ionic liquids by quaternization reaction with haloalkyl compounds. This liquid is mainly used as an impregnating agent for porous carriers such as activated carbon and activated carbon fibers for radioactive iodine protection in the ventilation system of nuclear power plants. While retaining the excellent iodine removal performance of amine compounds, the material significantly reduces the volatility of raw materials and has significantly improved thermal stability compared to TEDA. However, this material is designed entirely for high-concentration iodine and low-humidity conditions in nuclear power plants, and it fundamentally fails to meet the three rigid constraints of iodine removal from nuclear medical waste gas: First, it lacks the ability to deeply purify ultra-trace iodine. All performance verifications were completed in ppm-level high-concentration iodine environments. Effective complexation adsorption can only be triggered under high-concentration iodine conditions, and there is a serious risk of secondary desorption. Iodine fixation is mainly based on reversible amine complexation, without forming strong irreversible chemical bonds. When the ambient temperature and humidity fluctuate and the gas phase iodine concentration drops to ultra-trace levels, the adsorption equilibrium shifts rapidly in the reverse direction, and the adsorbed iodine will continue to desorb and be released, which completely fails to meet the safety requirements of zero secondary pollution in nuclear medical treatment.

[0013] Chinese patent CN117946332A discloses a method for synthesizing a PCN-333(Fe) metal-organic framework (MOF) matrix with a macroporous structure via a solvothermal reaction. Then, an imidazole-based ionic liquid with a strong attraction to iodine is introduced in situ into the pores, ultimately yielding an IL@MOF composite adsorbent. The material leverages the MOF's macroporous structure to achieve rapid mass transfer of iodine molecules, and captures iodine through the strong electrostatic complexation between the ionic liquid and iodine molecules within the pores. The physical confinement effect of the MOF pores further enhances the adsorption effect. Its core advantages are: inexpensive and readily available precursor raw materials, a relatively simple synthesis route, excellent thermal stability, and a capacity retention rate exceeding 99% after 5 adsorption cycles. It also exhibits excellent adsorption capacity and regeneration performance in high-temperature, high-concentration iodine vapor treatment scenarios involving nuclear waste. However, all performance verifications of this material demonstrate its effective adsorption capacity under high concentrations of iodine (mg / m³ and above). When faced with ultra-trace amounts of iodine (ppt level) in nuclear medicine, it lacks an in-situ enrichment mechanism, resulting in insufficient mass transfer driving force for iodine molecules. This prevents effective contact between iodine molecules and the active sites of the ionic liquid within the pores, rendering it ineffective at capturing extremely low concentrations of iodine. Furthermore, all tests were conducted under high-temperature and dry conditions, completely avoiding the competitive adsorption problem of water molecules. The open metal sites and active groups of the MOF are both strongly hydrophilic. Under near-saturated high-humidity conditions in nuclear medicine, water molecules preferentially condense within the pores, occupying all active sites and completely blocking the adsorption pathway of iodine molecules, leading to a decrease in iodine adsorption performance of over 90%.

[0014] In summary, existing iodine adsorption technologies generally suffer from at least one of the following drawbacks when dealing with the high-humidity, room-temperature waste gas environment containing trace iodine aerosols in nuclear medicine: (1) low adsorption efficiency for trace iodine, with significant performance degradation under high humidity conditions; (2) primarily physical adsorption, with iodine easily desorbed secondary, posing a risk of secondary pollution; (3) insufficient mechanical strength of the materials, resulting in poor reusability; and (4) complex preparation processes or high raw material costs, making it difficult to adapt to the industrialization and usage needs of nuclear medicine facilities. Therefore, it is crucial to develop a novel iodine adsorption material that is suitable for nuclear medicine scenarios, highly efficient in preventing desorption, low-cost, and easily scalable.

[0015] The amino acid-based metal cation composite material of this invention achieves the iodine removal requirements of nuclear medical waste gas through an innovative synergistic mechanism of "three-dimensional porous channel mass transfer enrichment - amino acid ionic liquid complexation and dissolution". On the one hand, in response to the deep purification requirements of ultra-trace iodine in nuclear medical waste gas, the material relies on a three-dimensional through-porous framework to achieve low-resistance and rapid mass transfer of ppt-level ultra-trace iodine molecules. Then, iodine is pre-enriched in situ by amino acid ionic liquid, which greatly increases the local iodine concentration. Finally, chemical capture is achieved through the high-density amino and carboxyl active sites in the ionic liquid, completing the efficient and deep purification of ultra-trace iodine. On the other hand, in response to the problem of strong competitive adsorption of water molecules in high humidity environments, the material captures iodine with strong chemical complexation and exclusive dissolution as the core. Its binding energy is much higher than that of the physical adsorption of water molecules and active sites. At the same time, the coordinated and anchored active sites do not hydrolyze and deactivate in high humidity environments, and the hydrophobic three-dimensional framework does not absorb water, swell, or block pores. It can still maintain high selectivity and stable adsorption performance for iodine under near-saturated high humidity conditions. Simultaneously, the material utilizes strong chemical complexation to form thermodynamically stable irreversible complexes of adsorbed iodine, coupled with a three-dimensional porous structure providing physical adsorption sites. Iodine molecules are captured within the cavities through van der Waals forces. The abundant nitrogen-active sites on the material surface possess strong electrostatic attraction, capable of adsorbing polarized iodine species and preventing secondary contamination risks from secondary desorption of radioactive iodine. Furthermore, the material exhibits full-process aqueous solution processability, requiring no high-temperature, high-pressure equipment, organic solvents, or precious metal catalysts throughout the preparation process. The process is mild and controllable, with simple parameters, excellent batch stability, and a short single-batch preparation cycle, completely resolving the industry pain point of the difficulty in large-scale preparation using existing technologies. Moreover, the core functional raw materials utilize green bio-based amino acids and inexpensive, readily available general-purpose metal hydroxides, containing no precious metal components. This results in low raw material costs and a green, pollution-free production process, combining extreme cost advantages with environmental benefits, making it suitable for low-cost use in nuclear medical civilian applications. Summary of the Invention

[0016] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0017] To achieve these objectives and other advantages of the present invention, an amino acid-based metal cation adsorbent material is provided, wherein the adsorbent material is a composite material in which an amino acid-based metal cation ionic liquid is mounted on a three-dimensional porous substrate; wherein the amino acid-based metal cation ionic liquid is prepared by an acid-base neutralization reaction between amino acids and metal hydroxides.

[0018] Preferably, the amino acid is one or a combination of cystine, lysine, arginine, and glycine; the metal cation of the metal hydroxide is one or a combination of sodium, lithium, potassium, magnesium, calcium, iron, copper, cobalt, lutetium, and aluminum; and the three-dimensional porous substrate is one or a combination of polyacrylamide, polypropylene, polyvinyl alcohol, low-density polyether, multi-walled carbon nanotubes, single-walled carbon nanotubes, melamine-formaldehyde resin, lignocellulose, and nylon.

[0019] Preferably, a method for preparing an amino acid-based metal cation adsorbent material as described above includes the following steps: Step 1: Add amino acids and metal hydroxides to water, stir to obtain a mixed solution, and sonicate the mixed solution to obtain an amino acid metal cation salt solution; Step 2: The amino acid metal cation salt solution is subjected to rotary evaporation to obtain an amino acid-based metal cation ionic liquid; Step 3: After ultrasonic cleaning and drying of the three-dimensional porous structure substrate, a pretreated substrate is obtained; Step 4: Mix the amino acid-based metal cation ionic liquid with water, then immerse the pretreated substrate in the mixture, ultrasonically vibrate it, remove the immersed three-dimensional porous structure substrate and place it in an oven for reaction. During the reaction, rotate the substrate up and down periodically to obtain the amino acid-based metal cation adsorbent material.

[0020] Preferably, in step one, the molar concentration ratio of amino acids to metal hydroxide is 1:1~2, the water is deionized water, the mass ratio of metal hydroxide to deionized water is 1:15~70, the ultrasonic oscillation time is 5~15 min, and the rotation speed of the oscillator is 250~300 r / min.

[0021] Preferably, in step two, the rotary evaporation temperature is 45~55℃ and the rotary evaporation time is 1~3h.

[0022] Preferably, in step three, the three-dimensional porous structure substrate is cut into a cuboid with dimensions of 25-30 mm in length, 10-15 mm in width, and 3-10 mm in thickness. The three-dimensional porous structure substrate is cleaned by ultrasonic oscillation with anhydrous ethanol for 20-30 minutes, with the oscillator speed at 250-300 r / min. The cleaning is repeated 2-3 times. The drying temperature is 30-40℃, and the drying time is 5-10 minutes.

[0023] Preferably, in step four, the water is deionized water, the mass ratio of deionized water to amino acid-based metal cation ionic liquid is 1:4 to 1:32, the mass-to-volume ratio of amino acid-based metal cation ionic liquid to three-dimensional porous substrate is 0.02g:10mL to 0.03g:10mL, the ultrasonic oscillation time is 5 to 20 min, the oscillator speed is 250 to 300 r / min, the oven reaction temperature is 65 to 75℃, the reaction time is 2 to 3 h, and the turning interval is 3 to 5 min.

[0024] Preferably, the amino acid-based metal cation adsorbent material is used to capture radioactive iodine and iodine aerosols in nuclear medical waste gas.

[0025] Preferably, the amino acid-based metal cation adsorbent material is used to purify iodine-containing waste gas under normal temperature and high humidity conditions in a nuclear medical setting.

[0026] The present invention includes at least the following beneficial effects: 1. Comparison of core mechanism and adaptability to multiple forms of iodine: Existing mainstream iodine adsorption technologies all adopt a single action mechanism, which cannot meet the treatment requirements of multiple forms of iodine in nuclear medical waste gas. Among them, carbon-based / activated carbon materials rely only on single physical adsorption and are only effective in capturing high concentrations of molecular iodine, with extremely poor adaptability to trace iodine and organic iodine; silver-based materials rely on a single Ag-I chemical bond as the core, which can only play a role in molecular iodine, and the bond is easily broken in high humidity environments; MOF / COF materials are mostly based on a single complexation or physical confinement mechanism, and have no effective capture ability for iodine aerosols, with only some materials being adaptable to methyl iodine; ordinary ionic liquid materials adopt a single complexation action, and the complexation efficiency will decrease significantly under low concentration trace iodine conditions.

[0027] This invention innovatively adopts a dual synergistic mechanism of "porous channel mass transfer - ionic liquid complexation and dissolution", which can simultaneously achieve physical interception of iodine aerosol and irreversible chemical complexation of trace molecular iodine and organic iodine, perfectly meeting the treatment needs of various forms of iodine waste gas in nuclear medical treatment.

[0028] 2. Comparison of Trace Iodine Adsorption Efficiency under Normal Temperature and High Humidity: Normal temperature (25℃) and relative humidity (RH) of 90% are the core operating conditions for treating iodine-containing waste gas in nuclear medicine. Existing technologies exhibit significant shortcomings in trace iodine adsorption performance under these conditions. The adsorption efficiency of commercial carbon-based / activated carbon materials is ≤45%; the adsorption efficiency of biomass-based materials is 60-70%, with efficiency fluctuations reaching 15-20%; silver-based materials experience performance degradation ≥40% under these conditions, with an effective adsorption efficiency ≤50%; the adsorption efficiency of ordinary ionic liquid-supported materials is ≤38.7%; and the performance degradation of conventional MOF materials is 42%, with an effective adsorption efficiency ≤58%.

[0029] Under this core operating condition, the present invention achieves a trace iodine adsorption efficiency of ≥98%, and the performance degradation during long-term operation is <2%, completely solving the problems of low adsorption efficiency and large performance fluctuations of existing technologies under normal temperature and high humidity conditions.

[0030] 3. Comparison of Iodine Aerosol Capture Efficiency: Efficient capture of iodine aerosol is a crucial step in the purification of waste gas from nuclear medical treatment, but current technologies are severely inadequate in this regard. Powdered / granular carbon-based, silver-based, and MOF / COF materials achieve only 50-60% capture efficiency for iodine aerosol, as the aerosol easily penetrates the bed. Ordinary bulk carbon materials achieve 60-70% capture efficiency, but the pores are prone to blockage, leading to a rapid decline in capture efficiency.

[0031] This invention achieves a capture efficiency of ≥99% for iodine aerosols, with no pore blockage in the material and an efficiency decay of <1% during long-term operation, effectively solving the industry pain points of iodine aerosol penetration and pore blockage.

[0032] 4. Comparison of iodine desorption rates: Under the actual operating conditions of nuclear medicine at room temperature, high humidity, and with airflow scouring, existing iodine adsorption materials generally suffer from high desorption rates, posing a serious risk of secondary pollution. Carbon-based / biomass materials, based on physical adsorption, have a reversible adsorption process and an iodine desorption rate >30%; silver-based materials, under high humidity conditions, experience Ag-I bond hydrolysis, resulting in an iodine desorption rate ≥15%; conventional MOF / ionic liquid materials have an iodine desorption rate of 5-10%.

[0033] This invention achieves iodine fixation through irreversible chemical complexation, with an iodine desorption rate of <0.01%, which is negligible, thus eliminating secondary pollution from radioactive iodine at the source.

[0034] 5. Comparison of Material Morphology and Engineering Applicability: The morphological characteristics of existing iodine adsorbent materials make it difficult to match their engineering applicability with the application requirements of nuclear medical sites. Powder / granular form is the mainstream form of existing materials. These materials are easily lost with airflow, resulting in a large pressure drop in the bed and requiring additional molding and processing before use. Existing bulk materials require the addition of 20-30wt% binder, and their compressive strength is only 0.2-0.5MPa, making them extremely fragile. Although the bed pressure is reduced, the pores are prone to blockage.

[0035] This invention is a three-dimensional porous block material that requires no binder, has excellent mechanical strength, can be directly cut into any size to fit nuclear medical equipment, and reduces bed pressure. There is no material loss or pore blockage during use, realizing the design of "material as filter element", which is perfectly adapted to the installation and airflow conditions of nuclear medical equipment.

[0036] 6. Comparison of Preparation Processes and Costs: Existing iodine adsorbent materials have complex preparation processes and high costs, making large-scale promotion difficult. Silver-based materials require multiple reaction steps and rely on the precious metal silver, with raw material costs accounting for over 60%. MOF / COF materials require hydrothermal / solvothermal synthesis at 120-180℃ followed by multiple modification steps, requiring the use of organic solvents and a preparation cycle of >72 hours. Ordinary ionic liquid materials require multiple alkylation and impregnation processes, also requiring organic solvents, with a preparation cycle of 48-72 hours. Although carbon-based materials have simple preparation processes, they require high-temperature activation at 300-500℃.

[0037] This invention employs a one-step aqueous solution processing technology, which can complete the reaction at room temperature or medium-low temperature conditions. It does not require high-temperature and high-pressure equipment, organic solvents, or catalysts. The raw materials are inexpensive amino acids and metal hydroxides. The preparation process is green, environmentally friendly, and extremely low in cost.

[0038] In summary, the beneficial effects of this invention are as follows: excellent performance and adaptability to the core working conditions of nuclear medicine: under the normal temperature and high humidity working conditions of nuclear medicine, the adsorption efficiency for trace iodine is ≥98%, the interception effect of iodine aerosol is excellent, and the iodine is fixed through irreversible chemical complexation, the desorption rate is negligible, and the risk of secondary pollution is completely avoided. Mechanism innovation addresses industry pain points: The proposed "porous channel mass transfer - ionic liquid complexation and dissolution" synergistic mechanism is precisely designed to address the core pain points of trace iodine in nuclear medical waste gas, room temperature and high humidity, and prevention of secondary desorption, providing a brand-new material design concept for the purification of iodine waste gas in nuclear medical applications. The process is green and efficient, and easy to scale up: the entire process uses aqueous solution processing, and the reaction conditions are room temperature / medium and low temperature. It does not require high temperature and high pressure, organic solvents, catalysts, etc. The process steps are simple, energy and material consumption is low, and batch stability is good, making it easy to scale up and industrialize. Significant cost advantages, suitable for nuclear medicine use: The raw materials are inexpensive and readily available amino acids and metal hydroxides, without precious metal components. The calculated iodine capture cost is far lower than that of traditional metal-based and modified carbon-based adsorbent materials. At the same time, the material is a three-dimensional porous block with good mechanical strength. It can be cut and reused, which greatly reduces the use and maintenance costs of nuclear medicine sites. It has great potential for engineering applications: the material is a three-dimensional block structure that can be used directly, with low pressure and easy installation. The size can be flexibly cut according to the waste gas treatment needs of nuclear medical sites, and it can be adapted to various nuclear medical iodine waste gas treatment equipment, providing a practical solution for the treatment of radioactive iodine waste gas in nuclear medical scenarios.

[0039] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0040] Figure 1 This is a diagram illustrating the material flexibility of the Cys-Na@MF adsorbent material prepared in Example 1 of this invention; Figure 2 This is a scanning electron microscope image of the Cys-Na@MF adsorbent material prepared in Example 1 of the present invention; Figure 3 This is a scanning electron microscope image of the Cys-Mg@MF adsorbent material prepared in Example 2 of the present invention; Figure 4 This is a scanning electron microscope image of the Cys-Na@nylon adsorbent material prepared in Example 3 of the present invention; Figure 5 This is an adsorption capacity diagram of the Cys-Na@MF adsorbent material for adsorbing iodine gas in Application Example 1 of the present invention; Figure 6 This is a stability diagram of the Cys-Na@MF adsorbent material in Application Example 1 of this invention; Figure 7 This is an adsorption capacity diagram of iodine gas adsorbed by the Cys-Mg@MF adsorbent material in Application Example 2 of the present invention; Figure 8 This is a comparison chart showing the adsorption capacity of melamine-formaldehyde resin (MF) and Cys-Mg@MF adsorbent materials for iodine gas under high humidity conditions in Comparative Example 1 and Application Example 3 of the present invention. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0042] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0043] Example 1: Preparation of Cys-Na@MF adsorbent material Step 1: Dissolve 6.0194g of cystine and 2.0667g of sodium hydroxide in 40ml of deionized water, stir for 45min until completely dissolved to obtain a mixed solution, and sonicate at 250r / min for 10min to allow the cystine and sodium hydroxide to fully undergo an acid-base neutralization reaction to obtain a sodium cystine solution. Step 2: Place the sodium cystine solution obtained in Step 1 into a rotary evaporator and evaporate it at 50°C for 90 minutes to evaporate excess water, thereby obtaining a viscous sodium cystine ionic liquid. Step 3: Cut the melamine-formaldehyde resin (MF) sponge matrix into 25×10×3mm cuboids. Place the cut MF sponge in anhydrous ethanol and ultrasonically vibrate at 250r / min for 25min. Repeat the cleaning 3 times to remove impurities. After cleaning, put the sponge into a 35℃ oven and dry for 10min to obtain the pretreated MF substrate. Step 4: Take 20mg, 40mg, 80mg, 120mg, and 160mg of the sodium cystine ionic liquid obtained in Step 2 and mix them with 5mL of deionized water. Immerse the pretreated MF substrate in the mixed solution and use ultrasonic vibration at 250r / min for 15min to remove air bubbles inside the substrate, ensuring that the ionic liquid mixed solution fully wets the substrate. Then, place the composite material in an oven and react at 75℃, turning it over every 5min to ensure that the ionic liquid and sponge are tightly bonded. Finally, dry for 2h to obtain Cys-Na@MF adsorbent materials with different loading amounts.

[0044] Figure 2 The image shows a scanning electron microscope (SEM) image of the Cys-Na@MF adsorbent material prepared in Example 1 of this invention. The obtained material was characterized by SEM, which showed that the three-dimensional network structure of MF was intact and Cys-Na particles were attached to the surface.

[0045] Example 2: Preparation of Cys-Mg@MF adsorbent material Step 1: Dissolve 6.0194g of cystine and 1.5227g of magnesium hydroxide in 100ml of deionized water, stir for 45min until completely dissolved to obtain a mixed solution, and sonicate at 250r / min for 10min to allow the cystine and magnesium hydroxide to fully undergo an acid-base neutralization reaction to obtain a magnesium cystine solution. Step 2: Place the magnesium cystine solution obtained in Step 1 into a rotary evaporator and evaporate it at 50°C for 90 minutes to evaporate excess water, thereby obtaining a viscous magnesium cystine ionic liquid. Step 3: Cut the melamine-formaldehyde resin (MF) sponge matrix into 25×10×3mm cuboids. Place the cut MF sponge in anhydrous ethanol and ultrasonically vibrate at 250r / min for 25min. Repeat the cleaning 3 times to remove impurities. After cleaning, put the sponge into a 35℃ oven and dry for 10min to obtain the pretreated MF substrate. Step 4: Take 20 mg, 40 mg, 80 mg, 120 mg, and 160 mg of the cystine magnesium ion liquid from Step 2, respectively, and mix it with 5 mL of the cystine magnesium ion liquid obtained in Step 2 and 5 mL of deionized water. Immerse the pretreated MF substrate in this mixed solution and ultrasonically vibrate it at 250 r / min for 15 min to remove air bubbles inside the substrate and ensure that the ion liquid mixed solution fully wets the substrate. Then, place the composite material in an oven and react it at 75°C. Turn it over every 5 min to ensure that the ion liquid and sponge are tightly bonded. Finally, dry it for 3 h to obtain Cys-Mg@MF adsorbent materials with different loading amounts.

[0046] Figure 3 The image shows a scanning electron microscope image of the Cys-Mg@MF adsorbent material prepared in Example 2 of this invention. The obtained material was characterized by SEM, which showed that the three-dimensional network structure of MF was intact and Cys-Mg particles were attached to the surface.

[0047] Example 3: Preparation of Cys-Na@Nylon Adsorbent Material Step 1: Dissolve 6.0194g of cystine and 2.0667g of sodium hydroxide in 40ml of deionized water, stir for 45min until completely dissolved to obtain a mixed solution, and sonicate at 250r / min for 10min to allow the cystine and sodium hydroxide to fully undergo an acid-base neutralization reaction to obtain a sodium cystine solution. Step 2: Place the sodium cystine solution obtained in Step 1 into a rotary evaporator and evaporate it at 50°C for 90 minutes to evaporate excess water, thereby obtaining a viscous sodium cystine ionic liquid. Step 3: Cut the nylon sponge substrate into cuboids of 25×10×3mm. Place the cut nylon sponge substrate in anhydrous ethanol and ultrasonically vibrate at 250r / min for 25min. Repeat the cleaning 3 times to remove impurities. After cleaning, place the nylon sponge substrate in a 35℃ oven and dry for 10min to obtain the pretreated nylon sponge substrate. Step 4: Take 120 mg of sodium cystine ionic liquid from Step 2 and mix it with 5 mL of deionized water. Immerse the nylon sponge matrix in the mixed solution and ultrasonically vibrate it at 250 r / min for 15 min to remove air bubbles inside the matrix and allow the ionic liquid to fully enter the matrix. Then, place the composite material in an oven and react it at 75°C. Turn it over every 5 min to ensure that the ionic liquid and sponge are tightly bonded. Finally, dry it for 2 h to obtain Cys-Na@nylon adsorbent material.

[0048] Figure 4 This is a scanning electron microscope image of the Cys-Na@nylon adsorbent material prepared in Example 3 of the present invention; The obtained material was characterized by SEM, which showed that the three-dimensional network structure of nylon was intact and that Cys-Na particles were attached to the surface.

[0049] Application Example 1: Application of Cys-Na@MF Static Adsorption S1: Cut the Cys-Na@MF adsorbent materials with different loading amounts obtained in Example 1 into cuboids with dimensions of 1cm×2.5cm×0.3cm, place them in a clean small beaker, weigh them accurately using an analytical balance, and record the initial mass (m0). S2: Transfer the small beaker containing the adsorbent material into a dry wide-mouth bottle. Place excess elemental iodine at the bottom of the wide-mouth bottle to ensure a saturated iodine vapor environment inside. Place the sealed wide-mouth bottle in a 75℃ constant temperature oven to conduct a static adsorption experiment. During adsorption, remove the wide-mouth bottle every 30 minutes, quickly transfer the small beaker containing the adsorbent material to a desiccator, cool to room temperature, and then accurately weigh it again (m). t ); S3: Repeat the above weighing operation until the mass is constant and adsorption reaches equilibrium. According to formula Q... t =(m t -m0) / m0 (where Q) t Calculate the adsorption capacity at different time points (where t is the adsorption capacity in g / g), plot the adsorption capacity-time curve, and determine the maximum adsorption capacity of the material for iodine vapor by curve fitting and data reading during the equilibrium stage; at the same time, put the adsorbed material into a storage bottle.

[0050] Adsorption capacity such as Figure 5 As shown, the maximum adsorption capacities corresponding to different loading amounts are 2.66 g / g, 4.41 g / g, 5.15 g / g, 5.88 g / g, and 6.71 g / g, and as... Figure 6 As shown, the material's mass percentage can still be maintained at 96.12% after one week.

[0051] Application Example 2: Application of Cys-Mg@MF Static Adsorption S1: Cut the Cys-Mg@MF adsorbent materials with different loading amounts obtained in Example 2 into cuboids with dimensions of 1cm×2.5cm×0.3cm, place them in a clean small beaker, weigh them accurately using an analytical balance, and record the initial mass (m0). S2: Transfer the small beaker containing the adsorbent material into a dry wide-mouth bottle. Place excess elemental iodine at the bottom of the wide-mouth bottle to ensure a saturated iodine vapor environment inside. Place the sealed wide-mouth bottle in a 75℃ constant temperature oven to conduct a static adsorption experiment. During adsorption, remove the wide-mouth bottle every 30 minutes, quickly transfer the small beaker containing the adsorbent material to a desiccator, cool to room temperature, and then accurately weigh it again (m). t); S3: Repeat the above weighing operation until the mass is constant and adsorption reaches equilibrium. According to formula Q... t =(m t -m0) / m0 (where Q) t Calculate the adsorption capacity at different time points (where t is the adsorption capacity in g / g), plot the adsorption capacity-time curve, and determine the maximum adsorption capacity of the material for iodine vapor by curve fitting and reading data during the equilibrium stage.

[0052] Adsorption capacity such as Figure 7 As shown, the maximum adsorption capacity corresponding to different loading amounts is 2.24 g / g, 3.62 g / g, 4.72 g / g, 5.41 g / g, and 6.12 g / g.

[0053] Application Example 3: Application of Cys-Mg@MF in high humidity environment for iodine adsorption S1: Cut the Cys-Mg@MF adsorbent material with the maximum loading capacity obtained in Example 2 into a cuboid with dimensions of 1cm×2.5cm×0.3cm, place it in a clean small beaker, weigh it accurately using an analytical balance and record the initial mass (m0). S2: Transfer the small beaker containing the adsorbent material into a dry wide-mouth bottle. Place 1g of elemental iodine and 20ml of pure water at the bottom of the wide-mouth bottle to ensure a saturated iodine vapor environment inside. Place the sealed wide-mouth bottle in a 75℃ constant temperature oven to conduct a high-humidity adsorption experiment. During adsorption, remove the wide-mouth bottle every 30 minutes, quickly transfer the small beaker containing the adsorbent material to a desiccator, cool to room temperature, and then accurately weigh it again (m). t ); S3: Repeat the above weighing operation until the mass is constant and adsorption reaches equilibrium. Determine the maximum adsorption capacity of the material for iodine vapor.

[0054] Comparative Example 1: Iodine adsorption test in a high humidity environment using only a three-dimensional porous framework formed by melamine-formaldehyde resin (MF).

[0055] like Figure 8 As shown in Application Example 3 and Comparative Example 1, the adsorption capacity of MF for I2 at 75°C is 1.623 g / g, while the adsorption capacity of Cys-Mg@MF adsorbent material is 5.636 g / g.

[0056] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. An amino acid-based metal cation adsorbent material, characterized by, The adsorbent material is a composite material in which an amino acid-based metal cation ionic liquid is mounted on a three-dimensional porous substrate; the amino acid-based metal cation ionic liquid is prepared by acid-base neutralization reaction of amino acids and metal hydroxides.

2. The amino acid-based metal cation adsorbent material of claim 1, wherein, The amino acid is one or a combination of cystine, lysine, arginine, and glycine; the metal cation of the metal hydroxide is one or a combination of sodium, lithium, potassium, magnesium, calcium, iron, copper, cobalt, lutetium, and aluminum; and the three-dimensional porous substrate is one or a combination of polyacrylamide, polypropylene, polyvinyl alcohol, low-density polyether, multi-walled carbon nanotubes, single-walled carbon nanotubes, melamine-formaldehyde resin, lignocellulose, and nylon.

3. A method for producing the amino acid-based metal cation adsorbing material according to any one of claims 1 to 2, characterized by, Includes the following steps: Step 1: Add amino acids and metal hydroxides to water, stir to obtain a mixed solution, and sonicate the mixed solution to obtain an amino acid metal cation salt solution; Step 2: The amino acid metal cation salt solution is subjected to rotary evaporation to obtain an amino acid-based metal cation ionic liquid; Step 3: After ultrasonic cleaning and drying of the three-dimensional porous structure substrate, a pretreated substrate is obtained; Step 4: Mix the amino acid-based metal cation ionic liquid with water, then immerse the pretreated substrate in the mixture, ultrasonically vibrate it, remove the immersed three-dimensional porous structure substrate and place it in an oven for reaction. During the reaction, rotate the substrate up and down periodically to obtain the amino acid-based metal cation adsorbent material.

4. The method for producing an amino acid-based metal cation adsorbent material according to claim 3, wherein In step one, the molar ratio of amino acids to metal hydroxide is 1:1~2, the water is deionized water, the mass ratio of metal hydroxide to deionized water is 1:15~70, the ultrasonic oscillation time is 5~15 min, and the rotation speed of the oscillator is 250~300 r / min.

5. The preparation method of the amino acid-based metal cation adsorbent material as described in claim 3, characterized in that, In step two, the rotary evaporation temperature is 45~55℃ and the rotary evaporation time is 1~3h.

6. The method for preparing an amino acid-based metal cation adsorbing material according to claim 3, wherein In step three, the three-dimensional porous structure substrate is cut into a cuboid with dimensions of 25-30 mm in length, 10-15 mm in width, and 3-10 mm in thickness. The three-dimensional porous structure substrate is cleaned by ultrasonic oscillation with anhydrous ethanol for 20-30 minutes at a speed of 250-300 r / min. The cleaning is repeated 2-3 times. The drying temperature is 30-40℃ and the drying time is 5-10 minutes.

7. The preparation method of the amino acid-based metal cation adsorbent material according to claim 3, characterized in that, In step four, the water is deionized water, the mass ratio of deionized water to amino acid-based metal cation ionic liquid is 1:4 to 1:32, the mass-to-volume ratio of amino acid-based metal cation ionic liquid to three-dimensional porous substrate is 0.02g:10mL to 0.03g:10mL, the ultrasonic oscillation time is 5 to 20 min, the oscillator speed is 250 to 300 r / min, the oven reaction temperature is 65 to 75℃, the reaction time is 2 to 3 h, and the turning interval is 3 to 5 min.

8. The application of an amino acid-based metal cation adsorbent material as described in any one of claims 1 to 2, characterized in that, The aforementioned amino acid-based metal cation adsorbent material is used to capture radioactive iodine and iodine aerosols in nuclear medical waste gas.

9. The application of an amino acid-based metal cation adsorbent material as described in any one of claims 1 to 2, characterized in that, The aforementioned amino acid-based metal cation adsorbent material was used to purify iodine-containing waste gas under normal temperature and high humidity conditions in a nuclear medical setting.

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