Phytic acid-modified nanohydroxyapatite / chitosan composite chelating gel and method of making

Abstract

The present application relates to the technical field of composite gel material, and particularly relates to a phytic acid modified nano-hydroxyapatite / chitosan composite chelating gel and a preparation method thereof.The technical scheme is as follows: the composite chelating gel is prepared by sol blending and microwave in-situ solidification of chitosan, nano-hydroxyapatite and phytic acid;the particle size of the nano-hydroxyapatite is 20-60 nm;the degree of deacetylation of the chitosan is greater than or equal to 90%;one end of the phytic acid molecule is bonded to the calcium ion active site on the surface of the nano-hydroxyapatite, and the phosphoric acid group on the molecular chain of the phytic acid molecule and the amino group on the chitosan molecular chain form coordination crosslinking to form an organic-inorganic interpenetrating network structure.The present application solves the problems of nano-hydroxyapatite agglomeration, insufficient mechanical strength of chitosan and weak interfacial bonding force of the two phases by the double bridging action of phytic acid, and a composite chelating gel with excellent comprehensive performance of adsorption capacity, selectivity, structural stability and adsorption rate is obtained.

Description

Technical Field

[0001] This invention relates to the field of composite gel materials technology, and more particularly to phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel and its preparation method. Background Technology

[0002] Nuclear medicine technologies (such as PET-CT, iodine-131 treatment for thyroid cancer, hyperthyroidism treatment, thyroid function testing, and technetium-99m imaging) are widely used in clinical practice. The resulting radioactive waste is characterized by small volume, short half-lives of the radionuclides, low radioactivity, and limited treatment space. Currently, existing technologies for the adsorption and treatment of typical medical radionuclides such as iodine-131 and technetium-99m in nuclear medicine radioactive waste have the following main shortcomings:

[0003] Conventional adsorption materials such as activated carbon, zeolite, and ordinary ion exchange resins have low adsorption capacity and poor selectivity for radionuclides such as iodine-131 and technetium-99m, which exist in the form of anions, and cannot achieve efficient enrichment. Activated carbon mainly relies on physical adsorption and lacks recognition sites for specific nuclides; although zeolite and ordinary resins have some ion exchange capacity, they are not effective for I-131. - TcO4 - Due to insufficient affinity of anions, the removal rate is limited in complex waste liquid systems.

[0004] While chitosan-based adsorbents possess good biocompatibility and abundant amino functional groups, pure chitosan gels exhibit poor mechanical strength and are prone to swelling or even collapse in aqueous solutions, making long-term stable operation under dynamic column adsorption conditions difficult. Introducing nano-hydroxyapatite into the chitosan matrix can improve the structural stability of the material to some extent, but nano-hydroxyapatite itself is highly prone to aggregation, leading to a decrease in specific surface area, burying of active adsorption sites, and hindering the full realization of adsorption performance.

[0005] Existing composite gel materials are mostly prepared by room temperature cross-linking or freeze-drying. The resulting materials have a simple pore structure, high diffusion resistance of radioactive ions inside the gel, and long adsorption equilibrium time, which makes it difficult to meet the needs of hospitals for rapid disposal of large quantities of radioactive flushing waste liquid.

[0006] In summary, existing adsorption materials cannot simultaneously achieve high adsorption capacity, high selectivity, good aqueous phase structural stability, and rapid adsorption kinetics. There is an urgent need to develop a novel adsorption material that can comprehensively address these technical problems. Therefore, this application proposes a phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel and its preparation method. Summary of the Invention

[0007] The purpose of this invention is to address the technical shortcomings of existing adsorption materials for radioactive nuclides such as iodine-131 and technetium-99m, which have low adsorption capacity, poor selectivity, unstable aqueous phase structure, and slow adsorption rate. The invention proposes a phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel and its preparation method.

[0008] In a first aspect, this application provides a phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel, wherein the composite chelating gel is prepared by sol-coating and microwave in-situ curing of chitosan, nano-hydroxyapatite and phytic acid.

[0009] The nano-hydroxyapatite has a particle size of 20–60 nm, and the chitosan has a degree of deacetylation ≥90%.

[0010] One end of the phytic acid molecule is bonded to the calcium ion active site on the surface of nano-hydroxyapatite, and the phosphate groups on its molecular chain form coordination crosslinks with the amino groups on the chitosan molecular chain, forming an organic-inorganic interpenetrating network structure.

[0011] The composite chelating gel has a multi-level porous structure formed during microwave curing.

[0012] Optionally, the mass ratio of chitosan, nano-hydroxyapatite, and phytic acid is: 1.0–2.5 parts chitosan, 0.6–1.8 parts nano-hydroxyapatite, and 0.3–1.2 parts phytic acid.

[0013] Optionally, the composite chelating gel is a block or granular hydrogel that has been microwave-cured in situ.

[0014] Secondly, this application provides a method for preparing phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel as described in the first aspect, comprising the following steps:

[0015] S1. Preparation of chitosan sol: Add chitosan to an aqueous solution of acetic acid with a mass concentration of 1% to 3%, and stir at a constant temperature until completely dissolved to obtain chitosan sol.

[0016] S2. Nano hydroxyapatite dispersion: Nano hydroxyapatite is added to deionized water and ultrasonically dispersed to obtain a nano hydroxyapatite dispersion.

[0017] S3. Phytic acid surface modification: Phytic acid is added to the nano-hydroxyapatite dispersion obtained in step S2, the pH of the system is adjusted to 4.5-6.0, and the reaction is stirred at room temperature to allow phytic acid to be grafted onto the surface of the nano-hydroxyapatite, thus obtaining a phytic acid-modified nano-hydroxyapatite suspension.

[0018] S4. Sol-gel crosslinking: The phytic acid-modified nano-hydroxyapatite suspension obtained in step S3 is added dropwise to the chitosan sol obtained in step S1, and the two phases are stirred to fully mix and carry out the crosslinking reaction.

[0019] S5. Microwave in-situ curing: Transfer the mixed sol obtained in step S4 to a molding mold, place it in a microwave curing device, and treat it under microwave power of 280-400W for 8-16 minutes to cure in-situ and obtain a composite hydrogel.

[0020] S6. Washing and activating: The composite hydrogel obtained in step S5 is repeatedly washed with deionized water to remove unreacted free phytic acid and residual acetic acid, and to activate the adsorption active sites, thereby obtaining the phytic acid modified nano-hydroxyapatite / chitosan composite chelating gel.

[0021] Optionally, in step S4, the mass ratio of nano-hydroxyapatite to chitosan is 0.6–1.8:1.0–2.5, and the amount of phytic acid added is 20%–70% of the mass of nano-hydroxyapatite.

[0022] Optionally, the microwave power in step S5 is 320-360W, and the processing time is 10-14min.

[0023] Optionally, the washing in step S6 may be repeated 3 to 5 times with deionized water.

[0024] Thirdly, this application also provides the application of the phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel described in the first aspect in the preparation of radionuclide adsorption materials.

[0025] Optionally, the radionuclide is iodine-131 and / or technetium-99m.

[0026] Compared with the prior art, this application includes at least one of the following beneficial technical effects:

[0027] One end of the phytic acid molecule is bonded to the calcium ion active site on the surface of nano-hydroxyapatite, which can effectively destroy the aggregation between nano-hydroxyapatite particles, so that the nano-hydroxyapatite is distributed in a dispersed state in the gel system, exposing more calcium phosphate adsorption active sites and avoiding the decrease in adsorption capacity caused by aggregation.

[0028] Phosphate groups on phytic acid molecular chains coordinate with amino groups on chitosan molecular chains to form an organic-inorganic interpenetrating network structure, which enhances the overall mechanical strength of the gel, improves its anti-swelling performance in the aqueous phase, and enables it to maintain structural integrity and prevent disintegration under dynamic column adsorption conditions.

[0029] Phytic acid provides phosphate functional groups that offer exclusive chelation sites for anion-containing radionuclides such as I⁻ and TcO⁴⁻, giving the composite chelating gel the ability to selectively adsorb anions of typical radionuclides in nuclear medicine such as iodine-131 and technetium-99m. This enables the selective removal of target radionuclides in complex waste liquid systems where competing anions coexist.

[0030] Phytic acid simultaneously modifies the surface of nano-hydroxyapatite and crosslinks chitosan, enabling the adsorption function of nano-hydroxyapatite and the matrix framework function of chitosan to form an organic combination through phytic acid molecules. A chelating synergistic effect is generated between the organic and inorganic phases, and the overall adsorption performance of the composite gel is better than the simple sum of the performance of each individual component.

[0031] During microwave in-situ curing, the moisture inside the mixed sol rapidly and uniformly vaporizes and escapes under microwave irradiation, forming a multi-level interconnected pore structure inside the gel. This provides a transport channel for the diffusion of radioactive ions within the gel phase, shortening the time required for adsorption equilibrium.

[0032] In the composite chelating gel, nano-hydroxyapatite and chitosan are chemically bonded through phytic acid crosslinking, making it difficult for the active adsorbent components to detach from the gel matrix. No powder is precipitated during aqueous operation, and it can still maintain a high adsorption capacity retention rate after multiple adsorption-desorption regeneration cycles.

[0033] In summary, this invention solves the problems of agglomeration of nano-hydroxyapatite, insufficient mechanical strength of chitosan, and weak interfacial bonding between the two phases by utilizing the dual bridging effect of phytic acid, thus obtaining a composite chelating gel with excellent comprehensive performance in terms of adsorption capacity, selectivity, structural stability, and adsorption rate. Attached Figure Description

[0034] Figure 1 A flowchart for the preparation of phytic acid-modified nano-hydroxyapatite / chitosan composite chelate gel; Detailed Implementation

[0035] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0036] Example 1

[0037] like Figure 1This embodiment provides a method for preparing phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel, including the following steps:

[0038] S1. Preparation of chitosan sol: Weigh 2.0g of chitosan with a degree of deacetylation ≥90%, add it to 100mL of 2% acetic acid aqueous solution, and stir at room temperature until completely dissolved to obtain chitosan sol.

[0039] S2. Dispersion of nano-hydroxyapatite: Weigh 1.2g of nano-hydroxyapatite (particle size 30-50nm), add it to 50mL of deionized water, and ultrasonically disperse it for 15min to obtain a nano-hydroxyapatite dispersion.

[0040] S3. Phytic acid surface modification: Add 0.8g of phytic acid to the nano-hydroxyapatite dispersion obtained in step S2, adjust the pH of the system to 5.0 with dilute ammonia, stir at room temperature for 2h to graft phytic acid onto the surface of nano-hydroxyapatite, and obtain phytic acid modified nano-hydroxyapatite suspension.

[0041] S4. Sol-linking: The phytic acid-modified nano-hydroxyapatite suspension obtained in step S3 is slowly added dropwise to the chitosan sol obtained in step S1, and the mixture is stirred continuously for 30 minutes to ensure that the two phases are fully mixed and crosslinking reaction occurs.

[0042] S5. Microwave in-situ curing: The mixed sol obtained in step S4 is transferred to a molding mold, placed in a microwave curing device, and treated at a microwave power of 340W for 12 minutes to cure in-situ and obtain a composite hydrogel.

[0043] S6. Washing and Activation: The composite hydrogel obtained in step S5 is washed four times with deionized water to remove unreacted free phytic acid and residual acetic acid, and to activate the adsorption active sites, thus obtaining phytic acid modified nano-hydroxyapatite / chitosan composite chelating gel.

[0044] Example 2

[0045] This embodiment provides a method for preparing phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel, including the following steps:

[0046] S1. Preparation of chitosan sol: Weigh 1.0g of chitosan with a degree of deacetylation ≥90%, add it to 50mL of 1% acetic acid aqueous solution, and stir at room temperature until completely dissolved to obtain chitosan sol.

[0047] S2. Dispersion of nano-hydroxyapatite: Weigh 0.6g of nano-hydroxyapatite (particle size 20-40nm), add it to 30mL of deionized water, and ultrasonically disperse it for 10min to obtain a nano-hydroxyapatite dispersion.

[0048] S3. Phytic acid surface modification: Add 0.3g of phytic acid to the nano-hydroxyapatite dispersion obtained in step S2, adjust the pH of the system to 4.5 with dilute ammonia, stir the reaction at room temperature for 1.5h, so that phytic acid is grafted onto the surface of nano-hydroxyapatite to obtain phytic acid modified nano-hydroxyapatite suspension.

[0049] S4. Sol-linking: The phytic acid-modified nano-hydroxyapatite suspension obtained in step S3 is slowly added dropwise to the chitosan sol obtained in step S1, and the mixture is stirred continuously for 20 minutes to ensure that the two phases are fully mixed and crosslinking reaction occurs.

[0050] S5. Microwave in-situ curing: The mixed sol obtained in step S4 is transferred to a molding mold, placed in a microwave curing device, and treated at a microwave power of 280W for 16 minutes to cure in-situ and obtain a composite hydrogel.

[0051] S6. Washing and Activation: The composite hydrogel obtained in step S5 is washed three times with deionized water to remove unreacted free phytic acid and residual acetic acid, and to activate the adsorption active sites, thus obtaining phytic acid modified nano-hydroxyapatite / chitosan composite chelating gel.

[0052] Example 3

[0053] This embodiment provides a method for preparing phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel, including the following steps:

[0054] S1. Preparation of chitosan sol: Weigh 2.5g of chitosan with a degree of deacetylation ≥90%, add it to 120mL of 3% acetic acid aqueous solution, and stir at room temperature until completely dissolved to obtain chitosan sol.

[0055] S2. Dispersion of nano-hydroxyapatite: Weigh 1.8g of nano-hydroxyapatite (particle size 40-60nm), add it to 60mL of deionized water, and ultrasonically disperse it for 20min to obtain a nano-hydroxyapatite dispersion.

[0056] S3. Phytic acid surface modification: Add 1.2g of phytic acid to the nano-hydroxyapatite dispersion obtained in step S2, adjust the pH of the system to 6.0 with dilute ammonia, stir at room temperature for 3h to graft phytic acid onto the surface of nano-hydroxyapatite, and obtain phytic acid modified nano-hydroxyapatite suspension.

[0057] S4. Sol-linking: The phytic acid-modified nano-hydroxyapatite suspension obtained in step S3 is slowly added dropwise to the chitosan sol obtained in step S1, and the mixture is stirred continuously for 40 minutes to ensure that the two phases are fully mixed and crosslinking reaction occurs.

[0058] S5. Microwave in-situ curing: Transfer the mixed sol obtained in step S4 to the molding mold, place it in the microwave curing equipment, and treat it under microwave power of 400W for 8 minutes to cure in-situ and obtain the composite hydrogel.

[0059] S6. Washing and Activation: The composite hydrogel obtained in step S5 is washed 5 times with deionized water to remove unreacted free phytic acid and residual acetic acid, and to activate the adsorption active sites, thus obtaining phytic acid modified nano-hydroxyapatite / chitosan composite chelating gel.

[0060] Example 4

[0061] This embodiment provides a method for preparing phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel, including the following steps:

[0062] S1. Preparation of chitosan sol: Weigh 1.5g of chitosan with a degree of deacetylation ≥90%, add it to 75mL of acetic acid aqueous solution with a mass concentration of 2.5%, and stir at room temperature until completely dissolved to obtain chitosan sol.

[0063] S2. Dispersion of nano-hydroxyapatite: Weigh 1.0 g of nano-hydroxyapatite (particle size 25-45 nm), add it to 40 mL of deionized water, and ultrasonically disperse it for 12 min to obtain a nano-hydroxyapatite dispersion.

[0064] S3. Phytic acid surface modification: Add 0.5g of phytic acid to the nano-hydroxyapatite dispersion obtained in step S2, adjust the pH of the system to 5.5 with dilute ammonia, stir the reaction at room temperature for 2.5h, so that phytic acid is grafted onto the surface of nano-hydroxyapatite to obtain phytic acid modified nano-hydroxyapatite suspension.

[0065] S4. Sol-linking: The phytic acid-modified nano-hydroxyapatite suspension obtained in step S3 is slowly added dropwise to the chitosan sol obtained in step S1, and the mixture is stirred continuously for 25 minutes to ensure that the two phases are fully mixed and crosslinking reaction occurs.

[0066] S5. Microwave in-situ curing: The mixed sol obtained in step S4 is transferred to a molding mold, placed in a microwave curing device, and treated at a microwave power of 320W for 14 minutes to cure in-situ and obtain a composite hydrogel.

[0067] S6. Washing and Activation: The composite hydrogel obtained in step S5 is washed four times with deionized water to remove unreacted free phytic acid and residual acetic acid, and to activate the adsorption active sites, thus obtaining phytic acid modified nano-hydroxyapatite / chitosan composite chelating gel.

[0068] To verify the technical effect of the composite chelating gel of the present invention, the following control group materials were set up:

[0069] Control group 1: pure chitosan gel, prepared according to the method of Example 1 but without the addition of nano-hydroxyapatite and phytic acid;

[0070] Control group 2: Chitosan-nano hydroxyapatite binary composite gel without phytic acid modification, prepared according to the method in Example 1 but without the addition of phytic acid;

[0071] Control group 3: Phytic acid modified pure chitosan gel, prepared according to the method of Example 1 but without the addition of nano-hydroxyapatite;

[0072] Control group 4: Commercial inorganic molecular sieve radioactive adsorption packing material;

[0073] Control group 5: Granular activated carbon adsorption material.

[0074] Experiment 1: Saturated Adsorption Capacity Test. Simulated radioactive waste liquid containing iodine-131 and technetium-99m was prepared and statically adsorbed at room temperature until adsorption equilibrium was reached. The saturated adsorption capacity of each group of materials was then measured. The results are shown in Table 1.

[0075] Table 1. Test results of saturated adsorption capacity of each group of materials.

[0076] Example 1: Composite Chelating Gel <![CDATA[4.72×10 6 ]]> <![CDATA[3.96×10 6 ]]> Control group 1: Pure chitosan gel <![CDATA[1.14×10 6 ]]> <![CDATA[0.87×10 6 ]]> Control group 2 binary composite gel <![CDATA[2.35×10 6 ]]> <![CDATA[1.91×10 6 ]]> Control group 3: Phytic acid-modified chitosan <![CDATA[2.81×10 6 ]]> <![CDATA[2.43×10 6 ]]> Control group 4 commercial molecular sieve <![CDATA[1.53×10 6 ]]> <![CDATA[1.26×10 6 ]]> Control group: 5 granular activated carbon <![CDATA[0.98×10 6 ]]> <![CDATA[0.74×10 6 ]]>

[0077] As shown in Table 1, the saturated adsorption capacity of the composite chelating gel in Example 1 of this invention for iodine-131 and technetium-99m is significantly higher than that of all control group materials.

[0078] Experiment 2: Adsorption selectivity test under complex coexisting ion environment. A solution containing a high concentration of Cl- was prepared. - NO3 - SO4 2- Na + Ca 2+ The adsorption was performed on simulated hospital wastewater, with impurity ion concentrations mimicking the complex water quality conditions of clinical nuclear medicine flushing wastewater. The removal rate of the target nuclide was measured after adsorption. The results are shown in Table 2.

[0079] Table 2. Nuclide Removal Rate of Each Group of Materials under Complex Coexisting Ions Environment

[0080] Example 1: Composite Chelating Gel 96.4% 94.1% Control group 1: Pure chitosan gel 57.2% 51.8% Control group 2 binary composite gel 73.5% 69.3% Control group 3: Phytic acid-modified chitosan 81.7% 78.5%

[0081] As shown in Table 2, under conditions of coexistence of a large number of competing anions, the removal rates of iodine-131 and technetium-99m by the composite chelating gel of the present invention still reach 96.4% and 94.1%, respectively.

[0082] Experiment 3: Adsorption kinetics test. The time required for each group of materials to reach equilibrium for nuclide adsorption was recorded. The adsorption equilibrium time of the composite chelating gel in Example 1 of this invention was 35 min; the equilibrium time of the binary chitosan-hydroxyapatite gel in control group 2 was 115 min; and the equilibrium time of the phytic acid-modified chitosan gel in control group 3 was 78 min.

[0083] Experiment 4: Structural stability and regeneration performance test. The composite chelating gel of Example 1 of this invention was immersed in simulated radioactive waste liquid, and the changes in gel morphology were observed. The results showed that no powder was shed from the gel, and the structure remained intact. After 5 adsorption-desorption regeneration cycles, the adsorption capacity retention rate was still higher than 86%. The pure chitosan gel of Control Group 1 and the binary composite gel of Control Group 2 showed breakage and loss after 2-3 cycles.

[0084] It is worth noting that this invention modifies the surface of nano-hydroxyapatite using phytic acid. One end of the phytic acid molecule bonds to the calcium ion active sites on the surface of the nano-hydroxyapatite, disrupting the aggregation between nano-hydroxyapatite particles and dispersing them in a dispersed state within the gel system, thus exposing more calcium phosphate adsorption active sites. The phosphate groups on the phytic acid molecular chain form coordination crosslinks with the amino groups on the chitosan molecular chain, constituting an organic-inorganic interpenetrating network structure. This gives the gel anti-swelling properties in the aqueous phase and maintains structural integrity without disintegration under dynamic column adsorption conditions. The phosphate functional group provided by phytic acid is I. - TcO4 - The presence of anionic anion-type radionuclides provides exclusive chelation sites, enabling the composite chelating gel to selectively remove iodine-131 and technetium-99m in complex wastewater systems with competing anions. During microwave in-situ curing, moisture within the mixed sol rapidly and uniformly vaporizes under microwave irradiation, forming multi-level interconnected pores within the gel. This provides transport channels for the diffusion of radioactive ions within the gel phase, shortening the time required for adsorption equilibrium. Nano-hydroxyapatite and chitosan form chemical bonds through phytic acid crosslinking, preventing the active adsorbent components from detaching from the gel matrix. No powder precipitation occurs during aqueous phase operation, and a high adsorption capacity retention rate is maintained even after multiple adsorption-desorption regeneration cycles.

[0085] Example 5 provides an integrated rapid solidification device for treating nuclear medical waste liquid. The phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel described in any of Examples 1-4 is used as the filling material for the adsorption module. The device has an integrated cabinet structure and occupies less than 1m² of floor space. 2 It includes a pretreatment module, an adsorption module, a microwave rapid solidification module, an online radiation monitoring module, and an intelligent control module.

[0086] The pretreatment module is used for pH adjustment and flocculation sedimentation pretreatment of radioactive waste liquid from nuclear medical treatment. It consists of a waste liquid collection tank, an automatic pH adjustment tank, and a flocculation sedimentation unit connected in sequence. The waste liquid collection tank has a waste liquid inlet at the top and a drain outlet at the bottom, which is connected to the inlet of the automatic pH adjustment tank via a pipeline. The automatic pH adjustment tank is equipped with a pH sensor and an acid / base dosing pump to adjust the pH of the waste liquid to 6-8. The flocculation sedimentation unit is connected to the outlet of the automatic pH adjustment tank and is equipped with a stirring device and a flocculant dosing device. The flocculation sedimentation unit has a sludge discharge outlet at the bottom and a clear liquid outlet at the top to remove suspended solids and some impurities from the waste liquid.

[0087] The adsorption module is connected to the pretreatment module and is filled with the phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel described in any of Examples 1-4, used for selective adsorption of radionuclides in waste liquid. The adsorption module consists of one or more detachable vertical adsorption columns. The inlet of the adsorption column is connected to the clear liquid outlet of the flocculation and sedimentation unit via a pipeline, and the outlet of the adsorption column is connected to the online radiation monitoring module via a pipeline. The adsorption column is equipped with a water distributor and a water collector. The height of the composite chelating gel is 70%–90% of the effective height of the adsorption column. The waste liquid flows through the adsorption column from top to bottom at a flow rate of 0.5–3.0 BV / h.

[0088] The microwave rapid setting and curing module is connected to the adsorption module and includes a sealed microwave curing oven and a cement-based curing silo. The microwave curing oven is equipped with a microwave generator and a temperature sensor, with a microwave frequency of 2.45 GHz and an output power of 280–400 W. A curing mold is installed inside the oven cavity. The cement-based curing silo is connected to the inlet of the microwave curing oven via a screw conveyor and is used to quantitatively add cement-based raw materials to the adsorbed saturated gel. The cement-based raw material is ordinary Portland cement or composite Portland cement, and the cement addition amount is 20%–50% of the gel mass.

[0089] An online radiation monitoring module is installed at the treatment inlet and / or outlet of the device to detect the radioactivity of the waste liquid in real time. The online radiation monitoring module includes a first radioactivity detector installed at the inlet of the adsorption column and a second radioactivity detector installed at the outlet of the adsorption column. The detectors are NaI(Tl) scintillator detectors or semiconductor detectors, with a detection limit of 10 Bq / L.

[0090] The intelligent control module is electrically connected to the pretreatment module, adsorption module, microwave rapid coagulation and solidification module, and online radiation monitoring module, respectively, for automatic control of the entire treatment process. The intelligent control module includes a PLC controller and a touch screen. The PLC controller is connected via signal lines to a pH sensor, acid / alkali dosing pump, stirring device, flocculant dosing device, microwave generator, temperature sensor, first radioactivity detector, and second radioactivity detector. The touch screen is used to display various operating parameters and receive user commands.

[0091] The method for treating radioactive waste liquid from nuclear medicine using the apparatus described in Example 5 includes the following steps:

[0092] (1) Pretreatment: Radioactive waste liquid from nuclear medical treatment enters the waste liquid collection tank through the waste liquid inlet for temporary storage, and then is transported to the pH automatic adjustment tank through the drain outlet. The pH sensor monitors the pH value of the waste liquid in real time. The PLC controller controls the acid and alkali dosing pump to add acid or alkali to the waste liquid according to the monitoring signal to adjust the pH of the waste liquid to 6-8. After pH adjustment, the waste liquid enters the flocculation and sedimentation unit. The PLC controller controls the flocculant dosing device to add polyaluminum chloride or polyacrylamide flocculant to the waste liquid. The stirring device stirs at a speed of 60-120 r / min for 5-15 min to flocculate and precipitate the suspended solids and some impurities in the waste liquid. The supernatant is discharged through the clear liquid outlet, and the precipitate is discharged through the sludge discharge outlet.

[0093] (2) Chelation Adsorption: The pretreated waste liquid enters the vertical adsorption column of the adsorption module at a flow rate of 0.5–3.0 BV / h. The waste liquid flows from top to bottom through the phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel layer. The composite chelating gel selectively adsorbs iodine-131 and technetium-99m radionuclides in the waste liquid. The purified water after adsorption treatment is discharged from the outlet of the adsorption column. When the radioactivity detection values ​​at the inlet and outlet of the adsorption column tend to be close, it indicates that the composite chelating gel is saturated. The PLC controller issues an alarm signal and stops the liquid feeding.

[0094] (3) Online monitoring: During the adsorption process, the first radioactivity detector detects the radioactivity of the waste liquid at the inlet of the adsorption column in real time, and the second radioactivity detector detects the radioactivity of the waste liquid at the outlet of the adsorption column in real time. The detection signal is fed back to the PLC controller. The PLC controller calculates the real-time removal rate based on the difference between the inlet activity and the outlet activity. When the removal rate is lower than the preset threshold or the outlet activity exceeds the emission standard, the PLC controller issues an early warning signal.

[0095] (4) Microwave rapid solidification: When the composite chelate gel in the adsorption module is saturated, the PLC controller controls the screw conveyor to quantitatively transport the cement-based raw material in the cement-based solidification silo to the molding mold of the microwave curing oven, and mix it evenly with the saturated gel. The amount of cement added is 20% to 50% of the gel mass. Close the microwave curing oven door, start the microwave generator, and irradiate it at a microwave power of 280 to 400W for 8 to 16 minutes to rapidly solidify the gel and cement-based raw material into a solidified body.

[0096] (5) Compliance with emission standards: After the radioactivity of the treated waste liquid is confirmed to meet the national emission standards by the online radiation monitoring module, the purified water will be discharged or reused. The solidified body will be removed from the microwave curing oven and transferred to a radioactive waste temporary storage container for further disposal.

[0097] This embodiment provides a method for operating an integrated rapid curing device with optimized operating parameters, including the following steps:

[0098] (1) Pretreatment: After the radioactive waste liquid from nuclear medical treatment is temporarily stored in the waste liquid collection tank, it is transported to the pH automatic adjustment tank at a flow rate of 2.0L / min. The pH automatic adjustment tank adjusts the pH of the waste liquid to 7.0±0.2. The adjusted waste liquid enters the flocculation and sedimentation unit. Polyaluminum chloride flocculant is added to the waste liquid at a dosage of 5-15mg / L. The stirring device is stirred at a speed of 90r / min for 10min. After settling for 30min, the supernatant enters the adsorption module.

[0099] (2) Chelation adsorption: The pretreated waste liquid enters the vertical adsorption column filled with the composite chelating gel of Example 1 at a flow rate of 1.5 BV / h. The effective filling height of the adsorption column is 1.2 m, the inner diameter is 0.15 m, the temperature of the waste liquid is 15-35℃, and the adsorption time is 40 min.

[0100] (3) Online monitoring: The first radioactivity detector and the second radioactivity detector collect radioactivity data every 30 seconds. When the calculated removal rate is less than 95% for three consecutive times, the PLC controller determines that the adsorption column is close to saturation and stops the liquid feeding.

[0101] (4) Microwave rapid curing: After adsorption saturation, ordinary silicate cement accounting for 35% of the gel mass is added to the gel. After mixing evenly, it is placed in a microwave curing oven and irradiated for 12 minutes under microwave power of 350W. The compressive strength of the cured body reaches more than 15MPa.

[0102] (5) Solidified body performance test: The solidified body was subjected to leaching test according to GB / T 7023-2011 "Performance requirements for solidified bodies of low and intermediate level radioactive waste". The cumulative leaching fraction of iodine-131 and technetium-99m in the solidified body over 42 days was less than 1×10. - 4 cm 2 / d, meeting the solidification performance requirements for radioactive waste disposal.

[0103] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel, characterized in that, The composite chelating gel is prepared by sol-gel blending of chitosan, nano-hydroxyapatite and phytic acid and microwave in-situ curing. The nano-hydroxyapatite has a particle size of 20–60 nm, and the chitosan has a degree of deacetylation ≥90%. One end of the phytic acid molecule is bonded to the calcium ion active site on the surface of nano-hydroxyapatite, and the phosphate groups on its molecular chain form coordination crosslinks with the amino groups on the chitosan molecular chain, forming an organic-inorganic interpenetrating network structure. The composite chelating gel has a multi-level porous structure formed during microwave curing.

2. The phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel according to claim 1, characterized in that, The mass ratio of chitosan, nano-hydroxyapatite, and phytic acid is: chitosan 1.0–2.5 parts, nano-hydroxyapatite 0.6–1.8 parts, and phytic acid 0.3–1.2 parts.

3. The phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel according to claim 1, wherein the composite chelating gel is a block or granular hydrogel formed by microwave in-situ curing.

4. A method for preparing phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Preparation of chitosan sol: Add chitosan to an aqueous solution of acetic acid with a mass concentration of 1% to 3%, and stir at a constant temperature until completely dissolved to obtain chitosan sol. S2. Nano hydroxyapatite dispersion: Nano hydroxyapatite is added to deionized water and ultrasonically dispersed to obtain a nano hydroxyapatite dispersion. S3. Phytic acid surface modification: Phytic acid is added to the nano-hydroxyapatite dispersion obtained in step S2, the pH of the system is adjusted to 4.5-6.0, and the reaction is stirred at room temperature to allow phytic acid to be grafted onto the surface of the nano-hydroxyapatite, thus obtaining a phytic acid-modified nano-hydroxyapatite suspension. S4. Sol-gel crosslinking: The phytic acid-modified nano-hydroxyapatite suspension obtained in step S3 is added dropwise to the chitosan sol obtained in step S1, and the two phases are stirred to fully mix and carry out the crosslinking reaction. S5. Microwave in-situ curing: Transfer the mixed sol obtained in step S4 to a molding mold, place it in a microwave curing device, and treat it under microwave power of 280-400W for 8-16 minutes to cure in-situ and obtain a composite hydrogel. S6. Washing and activating: The composite hydrogel obtained in step S5 is repeatedly washed with deionized water to remove unreacted free phytic acid and residual acetic acid, and to activate the adsorption active sites, thereby obtaining the phytic acid modified nano-hydroxyapatite / chitosan composite chelating gel.

5. The method for preparing phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel according to claim 4, characterized in that, In step S4, the mass ratio of nano-hydroxyapatite to chitosan is 0.6-1.8:1.0-2.5, and the amount of phytic acid added is 20%-70% of the mass of nano-hydroxyapatite.

6. The method for preparing phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel according to claim 4, characterized in that, The microwave power in step S5 is 320-360W, and the processing time is 10-14 minutes.

7. The method for preparing phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel according to claim 3, characterized in that, The washing described in step S6 involves repeatedly washing with deionized water 3 to 5 times.

8. The application of the phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel according to claim 1 or 2 in the preparation of radionuclide adsorption materials.

9. The application of the phytic acid-modified nano-hydroxyapatite / chitosan composite chelating gel according to claim 8 in the preparation of radionuclide adsorption materials, characterized in that, The radionuclides are iodine-131 and / or technetium-99m.

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