An iminodiacetic acid type chelating resin, its preparation method and application

Abstract

The application relates to an iminodiacetic acid type chelating resin and a preparation method and application thereof, and the preparation method comprises the following steps: (1) in the case that the stirring speed is 200-350 r / min, two dispersants are dissolved in water, then ethylbenzene, glycidyl methacrylate, trimethylolpropane trimethacrylate, isooctane and di-t-butyl peroxide are added, the raw materials are reacted after ultrasonic mixing, centrifugal separation is carried out after the reaction is completed, the filter cake is cleaned and dried, and resin microspheres are obtained; (2) in the stirring state, the resin microspheres obtained in the step (1) are added into water, then iminodiacetic acid is added, stirring is continued, then preliminary reaction is carried out by heating, NaOH is further added, reaction is carried out by heating, after the reaction is completed, filtration, cleaning and drying are carried out, and the iminodiacetic acid type chelating resin is obtained. The chelating resin particle size can be controlled, the particle size is relatively large, the specific surface area is large, the adsorption capacity is high, and the chelating resin can be used for adsorbing lead ions in heavy salt matrix.

Description

Technical Field

[0001] This invention relates to the field of packing technology for solid phase extraction columns, specifically to an iminodiacetic acid-type chelating resin and its preparation method and application. Background Technology

[0002] GB 5009.12-2023, the National Food Safety Standard for the Determination of Lead in Food, was officially released on September 6, 2023. The new standard adds a pretreatment method for high-salt samples to the "First Method: Graphite Furnace Atomic Absorption Spectrometry," applicable to matrices such as table salt, soy sauce, pickled foods, hot pot base, and instant noodle salt packets. The national standard recommends using iminodiacetic acid-type chelating resin for desalting and enrichment. This resin achieves the separation and enrichment of the target analyte through chelation of lead ions with iminodiacetic acid groups.

[0003] The existing patent (CN119708302A) discloses a preparation method that uses chloromethylated polystyrene resin as a matrix, and obtains the target resin through swelling, amination and substitution reactions. The product has a specific surface area of ​​20-55 m² / g, an average pore size of 45-55 nm, and a degree of crosslinking of 5-10%. However, this swelling method is complex, easily affected by environmental interference, has poor product stability, and is difficult to scale up for production, thus limiting its market application.

[0004] The adsorption mechanism of this resin is cation exchange, and its exchange capacity is significantly affected by pH: the exchange capacity is extremely low at pH < 2, and tends to saturate at pH > 4, with the optimal working pH being above 4. The resin is usually supplied in sodium form (capacity approximately 0.4 meq / mL), but potassium or ammonium forms can also be used. However, commercially available iminodiacetic acid (IDA) columns require the sample pH to be adjusted to around 7.5 to obtain ideal recovery rates. The national standard (GB5009.12-2023) specifies a pH ≈ 4.5~6.5. Under this loading environment, the lead recovery rate in high-salt matrices is only about 30%, indicating that the method adaptability of commercially available IDA columns needs improvement. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide an iminodiacetic acid-type chelating resin.

[0006] The purpose of this application is also to provide a method for preparing and applying the above-mentioned iminodiacetic acid type chelating resin.

[0007] To achieve the objectives of this invention, the following technical solutions are provided in this application.

[0008] In a first aspect, this application provides an iminodiacetic acid-type chelating resin, comprising a resin microsphere and iminodiacetic acid groups grafted onto the surface of the resin microsphere, wherein the resin microsphere is formed by copolymerization of glycidyl methacrylate and trimethylolpropane trimethacrylate. In this application, the resin microsphere is a three-dimensional cross-linked network formed by copolymerization of glycidyl methacrylate and trimethylolpropane trimethacrylate. The network porosity can be precisely controlled by adjusting the amount of TMPTMA, and the cross-linking density determines the micropore / mesopore distribution, thereby determining the adsorption and separation effect of the microsphere on the target analyte, while providing higher strength to prevent the microsphere from being easily broken. In complex matrices of heavy salts, vacuum pressurization is usually required in the pretreatment to allow the sample solution to pass through the column rapidly and fully, which also requires the packing material to have a certain rigidity to ensure the best adsorption effect. Furthermore, both monomers belong to the ester family and share similar properties such as density, solubility, surface tension, and polymerization reactivity. During polymerization, they readily form uniform, stable-sized droplets under stirring shear forces, resulting in regular spherical structures. Spherical structures offer high specific surface area utilization and large adsorption capacity, leading to better application results. However, if conventional divinylbenzene is used as a crosslinking agent, its poor compatibility with glycidyl methacrylate can cause stratification and result in poor spherical quality.

[0009] In one embodiment of the first aspect, the ion exchange capacity of the iminodiacetic acid group is 0.8~2 mmol / g.

[0010] In one embodiment of the first aspect, the resin microspheres have an average particle size of 100-150 μm, a specific surface area of ​​95-300 m² / g, and a pore size of 8-20 nm. After the solid-phase extraction column packing is prepared into a finished column, the flow rate and adsorption capacity of the column are investigated during the pretreatment process. To ensure a relatively fast flow rate and improve experimental efficiency, a particle size of 100-150 μm is selected in this invention. After the packing material in this particle size range is prepared into a column, the flow rate is fast, and the interaction between the target analyte and the packing material is not insufficient due to excessively high flow rate, thus avoiding a decrease in recovery rate. Specific surface area and pore size are related not only to the overall ratio of the filler but also to the selection of the porogen. The porogen of this invention, through the combination of good and bad solvents, prepared fillers with a surface area of ​​95~300 m² / g and a pore size of 8~20 nm. Within this range, the adsorption effect of the filler on the target analyte is appropriate, which can prevent the specific surface area of ​​the filler from being too large, making it difficult to elute the target analyte; it can also prevent the problem of the target analyte not being adsorbed due to the specific surface area being too small.

[0011] In a second aspect, this application also provides a method for preparing the iminodiacetic acid-type chelating resin as described above, the method comprising the following steps: (1) At a stirring rate of 200~350 r / min, the two dispersants are dissolved in water, and then ethylbenzene, glycidyl methacrylate, trimethylolpropane trimethacrylate, isooctane and di-tert-butyl peroxide are added. After ultrasonic mixing, the mixture is stirred and heated to allow the raw materials to react. After the reaction is completed, the mixture is centrifuged and the filter cake is washed and dried to obtain resin microspheres. In suspension polymerization, the stirring rate determines the size and size distribution of monomer droplets. Under the reaction ratio of the present invention, a stirring rate of 200~350 r / min can obtain polymer microspheres with relatively regular spherical shape, uniform pore structure and good dispersibility. If the stirring speed is too low, the microspheres are prone to sticking together and the particle size is too large. An excessively large particle size will cause a sharp decrease in the specific surface area, thus affecting the adsorption performance of the packing material. If the stirring speed is too high, the number of small spheres will increase significantly and the microsphere size will be too small. On the one hand, this will lead to an increase in specific surface area, resulting in excessive adsorption of the target substance and incomplete elution. On the other hand, if the particle size is too small, the column pressure will be too high. When preparing high-salt food matrices, the sample solution cannot pass through the column, and the experiment will fail. Therefore, the stirring speed needs to be controlled within a certain range to obtain the best application effect of this invention.

[0012] (2) Under stirring, the resin microspheres obtained in step (1) are added to water, then iminodiacetic acid is added, stirring is continued, and then the temperature is raised to carry out a preliminary reaction. NaOH is added, and the temperature is raised to carry out the reaction. After the reaction is completed, the resin is filtered, washed, and dried to obtain the iminodiacetic acid chelating resin.

[0013] In one embodiment of the second aspect, step (1) includes at least one of the following technical features: A) The dispersants include hydroxypropyl methylcellulose and sodium dodecyl sulfate. The compounding principle of HPMC + SDS is based on the synergistic mechanism of steric hindrance of polymers and electrostatic repulsion of small molecules. HPMC, as a long-chain polymer, adsorbs on the particle surface and can prevent the aggregation of large particles and stabilize the colloidal skeleton through steric hindrance, but its dispersibility for small particles is not strong. SDS, as an anionic surfactant, can adsorb on hydrophobic surfaces and disperse fine particles through electrostatic repulsion, but its stability for large particles is insufficient. The dual dispersant system achieves the uniformity of pore structure by controlling the uniformity of droplet size, ultimately improving the batch reproducibility and separation efficiency of SPE packing.

[0014] B) The mass ratio of hydroxypropyl methylcellulose, sodium dodecyl sulfate and water is (2~4):1:(200~300).

[0015] C) The mass ratio of ethylbenzene, isooctane, glycidyl methacrylate, trimethylolpropane trimethacrylate and di-tert-butyl peroxide is (25~40): (5~10): (50~80): (30~55): (2~5).

[0016] D) After ultrasonic mixing, stir at a speed of 200~350r / min for 0.5~1h and then start the heating reaction.

[0017] E) The reaction temperature and time are as follows: first react at 55~60℃ for 3~5 hours, then raise the temperature to 70~75℃ and react for 10~16 hours. Using staged heating can prevent explosive polymerization caused by excessively rapid temperature increases, resulting in more regular sphericity and more stable performance of the product.

[0018] F) The cleaning process involves sequentially using tetrahydrofuran and ethanol, with each cleaning performed at least twice.

[0019] The drying temperature described in G) is 60~80℃.

[0020] In one embodiment of the second aspect, in step F), the temperature of the tetrahydrofuran used for cleaning is 50-60°C, and the temperature of the ethanol used for cleaning is room temperature. Post-treatment with heated tetrahydrofuran effectively removes residual monomers and oligomers; room temperature methanol washing rapidly replaces THF, resulting in faster drying; to prevent microsphere breakage due to prolonged high-temperature drying, a hot-cold dual-solvent washing combined with gradient centrifugation is used to improve the surface cleanliness of the microspheres and maintain their morphological integrity.

[0021] In one embodiment of the second aspect, step (2) includes at least one of the following technical features: 1) The stirring rate is 200~300 r / min.

[0022] 2) The mass ratio of iminodiacetic acid, resin microspheres and NaOH is (1.2~1.5):1:(0.6~0.8).

[0023] 3) After adding iminodiacetic acid, continue stirring for 0.5~1h.

[0024] 4) The initial reaction temperature is 50~55℃, and the reaction time is 1~3h.

[0025] 5) The reaction conditions after adding NaOH are to react at 55~65℃ for 1~3h first, and then at 70~75℃ for 10~16h.

[0026] 6) The cleaning process involves rinsing with deionized water at least twice, followed by rinsing with ethanol at least once.

[0027] 7) The drying temperature is 60~80℃.

[0028] In a third aspect, this application also provides an application of the iminodiacetic acid-type chelating resin as described above, said iminodiacetic acid-type chelating resin being used as a solid-phase extraction column packing for the adsorption and separation of heavy metal ions.

[0029] In one embodiment of the third aspect, the pH of the adsorption is 6-7.5. Appendix B of GB5009.12-2023 "Determination of Lead in Food" describes "the pH after volume adjustment as 4.5-6.5". Pretreatment of seasoning packets according to this national standard revealed that when the pH is between 4.5 and 6.5, the recovery rate of commercial IDA columns is between 30% and 60%. Only when the pH is adjusted to 7.5 can the recovery rate of commercial IDA columns reach over 85%. The imino column prepared by this invention can achieve a high lead recovery rate in a heavy salt matrix within the pH range described in the national standard, and maintains a high recovery rate even when the pH is adjusted to 7.5, thus having a wider range of applications.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The specific surface area and particle size of the matrix spheres of the present invention can be controlled, therefore the specific surface area and particle size of the fillers prepared from the matrix spheres can also be controlled. Using TRIM to replace the traditional DVB and EGDMA crosslinking system can provide more crosslinking networks, which is beneficial to improving the specific surface area.

[0031] (2) The solid phase extraction packing material prepared by the present invention has a large particle size of 100~150 μm, which can be used for short-time loading of high-salt matrix samples and can ensure a fast flow rate.

[0032] (3) The present invention uses HPMC and SDS dual dispersants in synergy to solve the problem of wide pore size distribution of monodispersants; (4) The present invention uses heated tetrahydrofuran post-treatment to effectively remove residual monomers and oligomers; room temperature methanol washing can quickly replace THF and dry faster; to prevent microsphere breakage caused by long-term high temperature drying, hot-cold dual solvent washing combined with gradient centrifugation separation technology is used to improve the surface cleanliness of microspheres and maintain their morphological integrity.

[0033] (5) In the preparation of the base spheres, segmented heating is adopted to prevent the system from bursting due to excessive temperature rise, resulting in more regular sphericity and more stable performance of the product. Attached Figure Description

[0034] Figure 1 This is a particle size distribution diagram of the base spheres prepared in Example 1 of the present invention.

[0035] Figure 2 This is a SEM image of the packing material prepared in Example 1 of the present invention.

[0036] Figure 3 The nitrogen adsorption-desorption BET curve of the packing material prepared in Example 1 of the present invention.

[0037] Figure 4This is a BJH pore size distribution diagram of the packing material prepared in Example 1 of the present invention. Detailed Implementation

[0038] Unless otherwise stated, implied from the context, or as is customary in the art, all parts and percentages in this application are based on weight, and all testing and characterization methods used are concurrent with the filing date of this application. Where applicable, any patent, patent application, or disclosure relating to this application is incorporated herein by reference in its entirety, and its equivalent patent families are also incorporated herein by reference, particularly the definitions disclosed in these documents concerning synthetic techniques, product and processing design, polymers, comonomers, initiators, or catalysts in the art. If any definition of a specific term disclosed in the prior art is inconsistent with any definition provided in this application, the definition provided in this application shall prevail.

[0039] The numerical ranges in this application are approximate values ​​and therefore may include values ​​outside the range unless otherwise stated. A numerical range includes all values ​​from the lower limit to the upper limit, increasing by one unit, provided there is an interval of at least two units between any lower and any higher value. For example, if a component, physical, or other property (such as molecular weight) is described as 100 to 1000, this means that all individual values, such as 100, 101, 102, etc., are explicitly listed, as well as all subranges, such as 100 to 166, 155 to 170, 198 to 200, etc. For ranges containing values ​​less than 1 or fractions greater than 1 (e.g., 1.1, 1.5, etc.), one unit is appropriately considered as 0.0001, 0.001, 0.01, or 0.1. For ranges containing single digits less than 10 (e.g., 1 to 5), one unit is generally considered as 0.1. These are merely specific examples of what is intended to be expressed, and all possible combinations of values ​​between the listed minimum and maximum values ​​are considered to be clearly stated in this application. It should also be noted that the terms "first," "second," etc., used herein are not intended to specify a particular order, but are merely used to distinguish substances with different structures.

[0040] When referring to chemical compounds, unless explicitly stated otherwise, the singular includes all isomers and vice versa (e.g., "hexane" includes all isomers of hexane, individually or collectively). Additionally, unless explicitly stated otherwise, nouns described with "an," "a," or "the" also include their plural forms.

[0041] The terms “comprising,” “including,” “having,” and their derivatives do not exclude the presence of any other components, steps, or processes, regardless of whether such other components, steps, or processes are disclosed in this application. To eliminate any doubt, unless expressly stated otherwise, all compositions using the terms “comprising,” “including,” or “having” in this application may contain any additional additives, excipients, or compounds. Conversely, except for those necessary for operational performance, the term “substantially constitutes…” excludes any other components, steps, or processes described below with respect to that term. The term “consisting of…” does not include any components, steps, or processes not specifically described or listed. Unless expressly stated otherwise, the term “or” refers to the individual members listed or any combination thereof. Example

[0042] The embodiments of the present invention will be described in detail below. These embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0043] Unless otherwise specified, the raw materials and materials used in the embodiments of the present invention were purchased through general commercial channels.

[0044] The source information of the raw materials, materials, and instruments involved in the following embodiments or comparative examples is as follows: Commercialized small columns: Commercially available IDA small columns; TRIM, sodium hydroxide, SDS and other reagents were purchased from Aladdin Reagent (Shanghai) Co., Ltd. AB23 laboratory pH meter (Ohaus Instruments, Inc., USA); Nano ZS type nanolaser particle size analyzer (Malvin Instruments Ltd., UK); ASAP 2460 physical adsorption analyzer (McMed Instruments, Inc., USA); Atomic absorption spectrometer: equipped with a graphite furnace atomizer and a lead hollow cathode lamp. (PerkinElmer Instruments, Inc., USA) Example 1

[0045] The preparation method of an iminodiacetic acid type chelating resin filler is as follows: (1) The rotation speed was controlled at 200 rpm. 2g of hydroxypropyl methylcellulose and 1g of sodium dodecyl sulfate (SDS) were added to 200mL of water and dispersed and dissolved. 25g of ethylbenzene, 50g of glycidyl methacrylate, 30g of trimethylolpropane trimethacrylate (TRIM), 5g of isooctane, and 2g of di-tert-butyl peroxide were mixed and sonicated until transparent. The mixture was then added to the reaction vessel. After stirring for half an hour, the temperature was raised to 60℃ for 3 hours, and then raised to 70℃ for 10 hours. After the reaction was completed, the mother liquor was centrifuged. The filter cake was washed twice with 600mL of heated tetrahydrofuran and 600mL of room temperature ethanol, and then dried at 60℃ to obtain porous polymer-based spheres.

[0046] (2) Add 200 mL of deionized water to the reactor, and slowly add 50 g of porous spheres at 200 rpm. After stirring for 10 minutes, add 60 g of iminodiacetic acid and continue stirring for 1 hour. Increase the temperature to 55°C and react for 3 hours. Then add 30 g of NaOH, increase the temperature to 65°C and react for 1 hour. Increase the temperature to 75°C and react for 16 hours to end the reaction. Wash the product three times with 600 mL of deionized water and once with 600 mL of room temperature ethanol. Dry at 60°C to obtain iminodiacetic acid type chelating resin filler. Example 2

[0047] The preparation method of an iminodiacetic acid type chelating resin filler is as follows: (1) The rotation speed was controlled at 200 rpm. 4 g of hydroxypropyl methylcellulose and 1 g of sodium dodecyl sulfate (SDS) were added to 200 mL of water and dispersed and dissolved. 40 g of ethylbenzene, 80 g of glycidyl methacrylate, 55 g of trimethylolpropane trimethacrylate (TRIM), 10 g of isooctane, and 5 g of di-tert-butyl peroxide were mixed and sonicated until transparent. The mixture was then added to the reaction vessel. After stirring for 1 hour, the temperature was raised to 55 °C and reacted for 5 hours. The temperature was then raised to 75 °C and reacted for 10 hours. After the reaction was completed, the mother liquor was centrifuged. The filter cake was washed twice with 600 mL of heated tetrahydrofuran and 600 mL of room temperature ethanol, and then dried at 70 °C to obtain porous polymer-based spheres.

[0048] (2) Add 200 mL of deionized water to the reactor, and slowly add 50 g of porous spheres at 250 rpm. After stirring for 10 minutes, add 75 g of iminodiacetic acid and continue stirring for 1 hour. Heat to 50°C and react for 3 hours. Then add 40 g of NaOH, heat to 65°C and react for 1 hour. Heat to 75°C and react for 10 hours to end the reaction. Wash the product three times with 600 mL of deionized water and once with 600 mL of room temperature ethanol. Dry at 70°C to obtain iminodiacetic acid type chelating resin filler. Example 3

[0049] The preparation method of an iminodiacetic acid type chelating resin filler is as follows: (1) The rotation speed was controlled at 350 rpm. 3g of hydroxypropyl methylcellulose and 1g of sodium dodecyl sulfate (SDS) were added to 200mL of water and dispersed and dissolved. 32.5g of ethylbenzene, 65g of glycidyl methacrylate, 42.5g of trimethylolpropane trimethacrylate (TRIM), 7.5g of isooctane, and 3.5g of di-tert-butyl peroxide were mixed and sonicated until transparent. The mixture was then added to the reaction vessel. After stirring for half an hour, the temperature was raised to 60℃ for 5 hours, and then raised to 70℃ for 16 hours. After the reaction was completed, the mother liquor was centrifuged. The filter cake was washed twice with 600mL of heated tetrahydrofuran and 600mL of room temperature ethanol, and then dried at 80℃ to obtain porous polymer-based spheres.

[0050] (2) Add 200 mL of deionized water to the reactor, and slowly add 50 g of porous spheres at 300 rpm. After stirring for 10 minutes, add 67.5 g of iminodiacetic acid and continue stirring for 0.5 h. Heat to 55 °C and react for 3 hours. Then add 35 g of NaOH and heat to 55 °C for 3 hours. Finally, heat to 70 °C and react for 16 hours to end the reaction. Wash the product three times with 600 mL of deionized water and once with 600 mL of room temperature ethanol. Dry at 80 °C to obtain iminodiacetic acid chelating resin.

[0051] Comparative Example 1 The preparation method of an iminodiacetic acid type chelating resin filler is as follows: (1) The rotation speed was controlled at 200 rpm. 2g of hydroxypropyl methylcellulose was added to 200mL of water and dispersed and dissolved. 25g of ethylbenzene, 50g of glycidyl methacrylate, 30g of trimethylolpropane trimethacrylate (TRIM), 5g of isooctane, and 2g of di-tert-butyl peroxide were mixed and sonicated until transparent. The mixture was then added to the reaction vessel. After stirring for half an hour, the temperature was raised to 70℃ and reacted for 10-16 hours. After centrifuging the mother liquor, the filter cake was washed twice with 600mL of heated tetrahydrofuran and 600mL of room temperature ethanol, and then dried at 60℃ to obtain porous polymer-based spheres.

[0052] (2) Add 200 mL of deionized water to the reactor, and slowly add 50 g of porous spheres at 200 rpm. After stirring for 10 minutes, add 60 g of iminodiacetic acid and continue stirring for 1 hour. Heat to 55°C and react for 1-3 hours. Then add 30 g of NaOH, heat to 65°C and react for 3 hours. Finally, heat to 75°C and react for 16 hours to end the reaction. Wash the product three times with 600 mL of deionized water and once with 600 mL of room temperature ethanol. Dry at 60°C to obtain iminodiacetic acid chelating resin.

[0053] Comparative Example 2 The preparation method of an iminodiacetic acid type chelating resin filler is as follows: (1) The rotation speed was controlled at 200 rpm. 2g of hydroxypropyl methylcellulose and 1g of sodium dodecyl sulfate (SDS) were added to 200mL of water and dispersed and dissolved. 25g of ethylbenzene, 50g of glycidyl methacrylate, 30g of divinylbenzene, and 2g of di-tert-butyl peroxide were mixed and sonicated until transparent. The mixture was then added to the reaction vessel. After stirring for half an hour, the temperature was raised to 70℃ and reacted for 10-16 hours. After centrifuging the mother liquor, the filter cake was washed twice with 600mL of heated tetrahydrofuran and 600mL of room temperature ethanol, and then dried at 60℃ to obtain porous polymer-based spheres.

[0054] (2) Add 200 mL of deionized water to the reactor, and slowly add 50 g of porous spheres at 200 rpm. After stirring for 10 minutes, add 60 g of iminodiacetic acid and continue stirring for 1 hour. Heat to 55°C and react for 1-3 hours. Then add 30 g of NaOH and heat to 65°C and react for 1-3 hours. Finally, heat to 75°C and react for 10-16 hours to end the reaction. Wash the product three times with 600 mL of deionized water and once with 600 mL of room temperature ethanol. Dry at 60°C to obtain iminodiacetic acid chelating resin.

[0055] Comparative Example 3 The preparation method of an iminodiacetic acid type chelating resin filler is as follows: (1) The rotation speed was controlled at 500 rpm. 2g of hydroxypropyl methylcellulose and 1g of sodium dodecyl sulfate (SDS) were added to 200mL of water and dispersed and dissolved. 25g of ethylbenzene, 50g of glycidyl methacrylate, 30g of trimethylolpropane trimethacrylate (TRIM), 5g of isooctane, and 2g of di-tert-butyl peroxide were mixed and sonicated until transparent. The mixture was then added to the reaction vessel. After stirring for half an hour, the temperature was raised to 70℃ and reacted for 10-16 hours. After centrifuging the mother liquor, the filter cake was washed twice with 600mL of heated tetrahydrofuran and 600mL of room temperature ethanol, and then dried at 60℃ to obtain porous polymer-based spheres.

[0056] (2) Add 200 mL of deionized water to the reactor, and slowly add 50 g of porous spheres at 200 rpm. After stirring for 10 minutes, add 60 g of iminodiacetic acid and continue stirring for 1 hour. Heat to 55°C and react for 1-3 hours. Then add 30 g of NaOH and heat to 65°C and react for 1-3 hours. Finally, heat to 75°C and react for 10-16 hours to end the reaction. Wash the product three times with 600 mL of deionized water and once with 600 mL of room temperature ethanol. Dry at 60°C to obtain iminodiacetic acid chelating resin. Test Implementation Examples

[0057] The seed pellets prepared in Example 1 were dispersed in ethanol, and the particle size of the microspheres was measured using a nanolaser particle size analyzer. The measurement was performed three times, and the data closest to the average value was taken. The results are shown below. Figure 1 .

[0058] from Figure 1 It can be seen that the seed pellets of Example 1 have good uniformity in size, with a single-peak distribution and D(50) of about 131 micrometers.

[0059] The surface morphology of the iminodiacetic acid filler prepared in Example 1 was characterized using a Hitachi S-4800 field emission scanning electron microscope with an accelerating voltage of 25 kV. The results are shown in the figure. Figure 2 .

[0060] from Figure 2 It can be seen that the prepared filler particles are relatively uniform.

[0061] N2 adsorption-desorption experiments were performed on a Micromertics ASAP 2460 physical adsorption instrument. The sample (the substrate spheres prepared in Example 1) was activated under vacuum at 373 K for 3 h, and then nitrogen adsorption experiments were conducted at 77 K. The results are shown below. Figure 3 , Figure 4 .

[0062] Combination Figure 3 , Figure 4 As can be seen, the adsorption-desorption curves of Example 1 show that the substrate spheres are mainly mesoporous, with mesopores of 10-14 nm as the main component, very few micropores, and a small number of macropores. The adsorption capacity is low in the low P / P0 region and rises sharply in the high P / P0 region, which belongs to the H3 type hysteresis loop (desorption line is on top, with a large opening).

[0063] The specific surface area of ​​the finished products from Examples 1-3 and Comparative Examples 1-3 was calculated using the BET method, and the pore size distribution was calculated using the BJH method. The results are shown in Table 1.

[0064] Table 1. Particle size and BET data of the filler Table 1 shows that polymer microspheres with particle sizes in the range of 100-150 μm were prepared in Examples 1, 2, and 3. Adjusting the type of dispersant and pore-forming agent in step S1 can change the particle size and specific surface area of ​​the prepared seed spheres. Generally, the larger the microsphere particle size, the faster the flow rate of the pretreatment column during solvent percolation. However, if the microsphere particle size is too large, the corresponding specific surface area and adsorption performance will decrease, affecting the recovery rate of the packing material. Therefore, it is necessary to strictly limit the proportion of each reactant monomer within the preferred range. Comparative Example 1 used a single type of dispersant, resulting in seed pellets with a larger particle size than the preferred range of 100-150 μm. Comparative Example 2 removed the isooctane porogen and replaced the crosslinking agent TRIM with divinylbenzene, reducing the overall specific surface area of ​​the packing material. Comparative Example 3 increased the rotation speed, reducing the microsphere particle size to 58 μm. At this point, the specific surface area was too large, exceeding the preferred range, and the overall adsorption performance of the packing material was too strong, leading to a decrease in recovery rate and difficulty in eluting the target analyte. In addition, the small particle size of the microspheres made them prone to clogging during pretreatment of complex matrices, requiring negative pressure to achieve the column flow rates of Examples 1-3, which severely reduced pretreatment efficiency. Application Examples

[0065] The solid-phase extraction (SPE) column packing materials prepared in Examples 1-3 and Comparative Examples 1-3 were packed into columns with a capacity of 6 mL. Each column contained 500 mg of packing material, and the matrix was instant noodle seasoning packets. A commercially available IDA column was also selected for comparison, as shown in Table 3.

[0066] Microwave digestion: Weigh 0.5 g (accurate to 0.001 g) of the sample into a microwave digestion vessel, add 10 mL of nitric acid, and digest the sample according to the parameters in Table 2. Remove the acid to near dryness on a hot plate at 140 °C. After cooling, wash the digestion vessel 2-3 times with sodium acetate solution (2 mol / L), combine the washings in a 25 mL volumetric flask, and dilute to the mark with sodium acetate solution (2 mol / L). Mix well and set aside. Adjust the pH to 6 and 7.5 with 10 mol / L sodium hydroxide solution.

[0067] Table 2 Microwave Digestion Heating Program step Set temperature ℃ heating time (min) isothermal time (min) 1 120 5 5 2 160 5 10 3 180 5 10 The specific steps are as follows: Lead standard solution (10 μg / L): Pipette 100 μL of lead standard working solution (1.00 mg / L) into a 10 mL volumetric flask, add nitric acid solution (1+99) to the mark and mix well. The mass concentration of the lead standard solution used in the test chamber is 10 μg / L.

[0068] Spiked sample solution: Pipette 100 μL of lead standard working solution (1.00 mg / L) into 25 mL of sodium acetate solution (2 mol / L) and mix well. Blank is 25 mL of sodium acetate solution (2 mol / L).

[0069] Step 1, Activation Equilibrium: Pass 10 mL of nitric acid solution (1+99) through the column at a flow rate of 5 mL / min, then pass 5 mL of water and 5 mL of ammonium acetate solution (1 mol / L) through the column at a flow rate of 5 mL / min respectively. Step 2, Sample loading: Pipe 25 mL of reagent blank solution and spiked sample solution respectively and pass them through the column at a flow rate of 5 mL / min; Step 3, rinsing: Then wash the column with 5 mL of ammonium acetate solution (1 mol / L), and then wash off the ammonium acetate solution (1 mol / L) twice with 10 mL of water; Step 4, Elution: Finally, elute with 10 mL of nitric acid (1+99), collect the eluent, and prepare for analysis.

[0070] Instrument reference conditions: Atomic absorption spectrometer: equipped with graphite furnace atomizer and lead hollow cathode lamp.

[0071] Instrumentation and Method: Atomic absorption spectrometer detection conditions settings (Element: Lead; Wavelength (nm): 283.3; Slit width (nm): 0.5; Lamp current (mA): 10; Drying (℃ / s): 110 / 30; Ashing (℃ / s): 850 / 20; Atomization (℃ / s): 2450 / 3).

[0072] The test results are shown in Table 3.

[0073] Table 3 Spike recovery rate of instant noodle seasoning packets packing name Lead recovery rate % (pH=6) Lead recovery rate % (pH=7.5) Example 1 85.4% 95.4% Example 2 94.6% 96.1% Example 3 91.7% 93.8% Comparative Example 1 45.6% 43.2% Comparative Example 2 33.9% 40.1% Comparative Example 3 20.0% 25.4% Commercial IDA small column 58.4% 94.7% Table 3 shows that the recovery rates of Examples 1-3, under the sample loading condition of pH=7.5, are comparable to those of commercial IDA columns. However, under the pretreatment sample loading condition of pH=6 in the national standard method "GB 5009.12-2023 National Food Safety Standard - Determination of Lead in Food", the lead recovery rate of the commercial columns is lower than that of Examples 1-3 of this invention. This indicates that the method of this invention has a wider range of applications and better performance. The lead recovery rates of Comparative Examples 1-3 are low and do not meet the application requirements.

[0074] The above description of the embodiments is intended to enable those skilled in the art to understand and apply this application. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, this application is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. An iminodiacetic acid type chelating resin, characterized in that, The iminodiacetic chelating resin comprises a resin microsphere and iminodiacetic acid groups grafted onto the surface of the resin microsphere, wherein the resin microsphere is formed by copolymerization of glycidyl methacrylate and trimethylolpropane trimethacrylate.

2. The iminodiacetic acid type chelating resin as described in claim 1, characterized in that, The ion exchange capacity of the iminodiacetic acid group is 0.8~2 mmol / g; The resin microspheres have an average particle size of 100-150 μm, a specific surface area of ​​95-300 m² / g, and a pore size of 8-20 nm.

3. A method for preparing an iminodiacetic acid-type chelating resin as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) At a stirring rate of 200~350r / min, the two dispersants were dissolved in water, and then ethylbenzene, glycidyl methacrylate, trimethylolpropane trimethacrylate, isooctane and di-tert-butyl peroxide were added. After ultrasonic mixing, the mixture was stirred and heated to allow the raw materials to react. After the reaction was completed, the mixture was centrifuged and the filter cake was washed and dried to obtain resin microspheres. (2) Under stirring, the resin microspheres obtained in step (1) are added to water, then iminodiacetic acid is added, stirring is continued, and then the temperature is raised to carry out a preliminary reaction. NaOH is added, and the temperature is raised to carry out the reaction. After the reaction is completed, the resin is filtered, washed, and dried to obtain the iminodiacetic acid chelating resin.

4. The method for preparing the iminodiacetic acid-type chelating resin as described in claim 3, characterized in that, Step (1) includes at least one of the following technical features: A) The dispersant comprises hydroxypropyl methylcellulose and sodium dodecyl sulfate; B) The mass ratio of hydroxypropyl methylcellulose, sodium dodecyl sulfate and water is (2~4):1:(200~300); C) The mass ratio of ethylbenzene, isooctane, glycidyl methacrylate, trimethylolpropane trimethacrylate, and di-tert-butyl peroxide is (25~40):(5~10):(50~80):(30~55):(2~5); D) After ultrasonic mixing, stir at a speed of 200~350r / min for 0.5~1h and then start heating to react; E) The reaction temperature and time are as follows: first react at 55~60℃ for 3~5h, then raise the temperature to 70~75℃ and react for 10~16h. F) The cleaning process involves tetrahydrofuran and ethanol, with each step performed at least twice. The drying temperature described in G) is 60~80℃.

5. The method for preparing the iminodiacetic acid-type chelating resin as described in claim 4, characterized in that, In F), the temperature of the tetrahydrofuran used for cleaning is 50~60℃, and the temperature of the ethanol used for cleaning is room temperature.

6. The method for preparing the iminodiacetic acid-type chelating resin as described in claim 3, characterized in that, Step (2) includes at least one of the following technical features: 1) The stirring rate is 200~300 r / min; 2) The mass ratio of iminodiacetic acid, resin microspheres, and NaOH is (1.2~1.5):1:(0.6~0.8); 3) After adding iminodiacetic acid, continue stirring for 0.5~1h; 4) The initial reaction temperature is 50~55℃, and the reaction time is 1~3h; 5) The reaction conditions after adding NaOH are to react at 55~65℃ for 1~3h first, and then at 70~75℃ for 10~16h. 6) The cleaning process involves rinsing with deionized water at least twice, followed by rinsing with ethanol at least once. 7) The drying temperature is 60~80℃.

7. The application of an iminodiacetic acid-type chelating resin as described in claim 1 or 2, characterized in that, The iminodiacetic acid-type chelating resin is used as a solid-phase extraction column packing material for the adsorption and separation of heavy metal ions in a heavy salt matrix.

8. The application of the iminodiacetic acid-type chelating resin as described in claim 7, characterized in that, The pH of the adsorption is 6-7.5.

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