Preparation method and application of ion-type covalent organic framework material with high cadmium removal efficiency

Abstract

A method for preparing a highly efficient cadmium-removing ionic covalent organic framework material and its application belong to the field of high-value preparation technology for aquatic product processing by-products. The method involves dissolving a surfactant, a protic acid catalyst, an amino monomer, functionalized silica, and a sulfonic acid functionalizing reagent in an organic solvent / water mixture to obtain a suspension; dissolving the aldehyde monomer 2,4,6-tricarboxylic acid-1,3,5-benzenetricarboxylic acid in an organic solvent to obtain an aldehyde monomer solution; adding the aldehyde monomer solution to the suspension under mechanical stirring; and obtaining the ionic covalent organic framework through a solvothermal reaction. The covalent organic framework silica particles prepared by this invention have the characteristics of large specific surface area, good thermal stability, specific adsorption, strong enrichment ability, rapid separation, reusability, and convenient operation. Furthermore, this preparation method is more convenient and has a shorter reaction time than ordinary synthesis methods.

Description

Technical Field

[0001] This invention belongs to the field of high-value preparation technology of aquatic product processing by-products, and particularly relates to a method for preparing an efficient cadmium-removing ionic covalent organic framework material and its application. Background Technology

[0002] The inedible parts of squid account for approximately 20% of their total weight, including viscera, skin, cartilage, and eyes. Currently, these byproducts are mostly processed into fishmeal for use as animal feed and fishing bait, or buried or discarded directly. This not only wastes resources but also potentially pollutes the environment due to their decay. Developing high-value-added products to utilize these byproducts could not only improve resource utilization efficiency but also reduce environmental pollution and further promote the development of the squid processing industry.

[0003] Aquatic products exhibit a significant tendency to accumulate heavy metals. Different types of aquatic organisms, such as fish, shrimp, shellfish, and algae, show varying abilities to accumulate various heavy metals, leading to widespread public concern about heavy metal pollution in aquatic products. Among numerous aquatic animals, squid, which feed on plankton, have relatively high levels of arsenic and cadmium in their bodies. Although the squid's liver is rich in nutrients, accounting for approximately 15% of its body weight, the large amounts of harmful heavy metals accumulated in the squid's liver negatively impact human food safety and the use of animal feed.

[0004] Adsorption technology is widely recognized as an effective method for removing and enriching heavy metals in water and aquatic products, offering advantages such as high efficiency, low cost, and ease of operation. Based on these advantages, porous materials have attracted significant attention due to their ability to bind with heavy metals. Recently, researchers have designed and synthesized various porous adsorbents for extracting and enriching heavy metals in aquatic environments and aquatic products. However, the functions of these adsorbents are often not fully utilized due to their irregular pore structures and lack of specific functional groups.

[0005] Therefore, the key lies in developing a processing technology that is easy to operate, can quickly adsorb nutrients, and can efficiently convert the nutrients in squid viscera into valuable substances, in order to meet the above challenges. Summary of the Invention

[0006] The purpose of this invention is to address the problems of high cost of heavy metal detection, complex operation methods and unsatisfactory adsorption capacity, low heavy metal removal rate and high nutrient loss rate in squid processing. This invention provides a method for preparing an efficient cadmium-removing ionic covalent organic framework material and its application. This method is easy to operate and simple to synthesize. The prepared material has strong adsorption capacity and can effectively remove cadmium from squid and efficiently convert nutrients in the squid's viscera.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a highly efficient cadmium-removing ionic covalent organic framework material is disclosed. The method comprises: dissolving a surfactant, a protic acid catalyst, an amino monomer, functionalized silica, and a sulfonic acid functionalizing agent in a mixed solvent of organic solvent and water to obtain a suspension; dissolving an aldehyde monomer, 2,4,6-tricarboxylic acid-1,3,5-benzenetricarboxylic acid, in an organic solvent to obtain an aldehyde monomer solution; adding the aldehyde monomer solution to the suspension under mechanical stirring; and obtaining an ionic covalent organic framework COF@SO3H-SiO2 with a silica gel core through a solvothermal reaction. In the organic framework material synthesized by this invention, the sulfonic acid groups are negatively charged, which can enhance the electrostatic interaction with positively charged metal ions. Simultaneously, the synthesized covalent organic framework material can coordinate with metal ions. The aldehyde monomer used has three carboxylic acid groups, which can also coordinate with metal ions.

[0009] Further, the surfactant is one of sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB), or polyvinyl alcohol (PVP), preferably sodium dodecyl sulfate (SDS); the protic acid catalyst is p-toluenesulfonic acid or trifluoroacetic acid; the amino monomer is one of 2,2'-dihydroxy-4,4'-biphenyldiamine (BHBD), 2,6-diaminoanthraquinone (DAAQ), or 2-hydroxy-1,3-propanediamine (DAHP); the functionalized silica is aminated SiO2 or aldehyde-modified SiO2, preferably aminated silica; the sulfonic acid functionalizing agent is one of p-aminobenzenesulfonic acid, amino-isophenylenesulfonic acid, aminonaphthalenesulfonic acid, or sodium p-aminobenzenesulfonate; and the organic solvent is one of tetrahydrofuran, ethanol, or acetonitrile.

[0010] Further, the molar ratio of the surfactant to 2,4,6-tricarboxylic acid is 0.5–1.5:1; the molar ratio of the protic acid catalyst to 2,4,6-tricarboxylic acid is 0–5:1; the molar ratio of the amino monomer to 2,4,6-tricarboxylic acid is 1–2:1; the mass ratio of the functionalized silica to 2,4,6-tricarboxylic acid is 50–150:100; and the molar ratio of the sulfonic acid functionalizing reagent to 2,4,6-tricarboxylic acid is 0–5:1.

[0011] Furthermore, the concentration of amino-modified functionalized silica in the suspension is preferably 1.5–2 g / L.

[0012] Furthermore, in the mixed solvent, the volume ratio of organic solvent to water is 1 to 2:1.

[0013] Furthermore, the temperature of the solvothermal reaction is 100–150°C, and the time is 0.5–10 h.

[0014] Furthermore, the method also includes the following operations: after the reaction is complete, the sample is collected under centrifugation conditions, then washed three times each with acetonitrile and water, and subsequently freeze-dried under vacuum.

[0015] Furthermore, the centrifugation temperature is 4-20℃, preferably 4℃; the centrifugation speed is 5000-11000rpm, preferably 10000rpm; and the freezing temperature is -40℃.

[0016] An application of the ionic covalent organic framework material prepared by the above method, wherein the application is:

[0017] Step 1: High-speed pulverize squid viscera concentrate, add water and stir until homogenized, preheat to 30-50℃ and maintain for 10 minutes, adjust the pH of the homogenate to the optimal conditions, add compound enzyme, and mix the compound enzyme system evenly into the squid viscera homogenate. Hydrolyze and inactivate under the optimal conditions to convert the heavy metal cadmium in the squid viscera concentrate from the bound state to the free state, fully release it, and centrifuge to obtain squid viscera high-protein hydrolysate.

[0018] Step 2: Using ionized covalent organic framework silica particles COF@SO3H-SiO2 as an efficient enrichment packing for separating heavy metal cadmium, the high-protein hydrolysate of squid viscera from Step 1 is passed through the enrichment packing (the enrichment packing is used to fill the column, and the hydrolysate passes through the column) to obtain a high-protein hydrolysate of squid viscera with significantly reduced cadmium content. After freeze-drying, the high-protein hydrolysate of squid viscera is obtained.

[0019] Further, in step one, the squid is a marine cephalopod, including but not limited to one or more of squid, cuttlefish, and calamari; the complex enzyme is two or more of flavor protease, pepsin, papain, trypsin, alkaline protease, and animal protease, preferably trypsin and alkaline protease; the mass ratio of the complex enzyme to trypsin and alkaline protease is 1:0.1-1, preferably 1:0.3.

[0020] Further, in step one, the mass ratio of the squid viscera concentrate to water is 1:3-10, preferably 1:5; the mass ratio of the compound enzyme to the squid viscera concentrate is 0.1-1:100.

[0021] Furthermore, in step one, the pH is 2 to 10, which can be adjusted appropriately according to the selected complex enzyme. For example, alkaline proteases (such as pepsin) are usually more active in a lower pH range, with the optimal pH being about 2-4; neutral proteases (such as trypsin) are usually most active in the neutral range, about between pH 6 and 8; and acidic proteases (such as papain) are more active under higher pH conditions, with the optimal pH being about 4-6.

[0022] Further, in step one, the hydrolysis temperature is 30-60℃, preferably 40℃, the magnetic stirring speed is 100-800rpm, preferably 500rpm, and the time is 2-6h, preferably 3h; the inactivation temperature is 100℃, and the time is 15-60min, preferably 30min.

[0023] Furthermore, in step one, the centrifugation speed is 5000-11000 rpm, preferably 10000 rpm, and the time is 10-30 min, preferably 15 min.

[0024] Further, in step two, the mass ratio of the ionized covalent organic framework silica particles COF@SO3H-SiO2 to the concentrated squid viscera extract is 0.005-0.01:100, preferably 0.05:100, and the adsorption time is 20-60 min, preferably 25 min.

[0025] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0026] 1. This invention provides an ionized functionalized covalent organic framework silica particles COF@SO3H-SiO2 as an adsorbent material. This material has both the ordered nanoporous structure of the covalent organic framework and can achieve rapid separation under external action to prevent secondary pollution, and has a high adsorption capacity for the heavy metal cadmium.

[0027] 2. This invention provides a method for preparing ionized functionalized covalent organic frameworks. The prepared covalent organic framework silica particles COF@SO3H-SiO2 have the characteristics of large specific surface area, good thermal stability, specific adsorption, strong enrichment ability, rapid separation, reusability, and convenient operation. At the same time, this preparation method is more convenient to operate and has a shorter reaction time than ordinary synthesis methods.

[0028] 3. This invention provides a process and application for converting cadmium-removed protein into high-value protein powder. It can effectively convert squid viscera concentrate, aquatic product waste, into high-value nutrient squid viscera hydrolyzed protein. The heavy metal cadmium is effectively removed by covalent organic framework silica particles COF@SO3H-SiO2, and the protein loss rate during the removal process is extremely low, less than 1%.

[0029] 4. This invention can be used to remove and efficiently enrich heavy metal cadmium ions from squid viscera high-protein hydrolysate, significantly reducing the cadmium content in squid viscera concentrate by more than 90% and the protein content loss in squid viscera high-protein hydrolysate by less than 1%. It can effectively solve the problem of excessive heavy metal cadmium content in squid viscera concentrate, laying the foundation for the high-value utilization of squid viscera concentrate. Attached Figure Description

[0030] Figure 1 Scanning electron microscope (SEM) image of covalent organic framework silica particles COF@SO3H-SiO2 provided in an embodiment of the present invention;

[0031] Figure 2 The Fourier transform infrared spectrum of the covalent organic framework silica particles COF@SO3H-SiO2 provided in the embodiment of the present invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be described in detail and accurately below. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. The numerical ranges in the following embodiments of the present invention should be understood as specifically disclosing each intermediate numerical range between the upper and lower limits of the reactant addition amount range of the invention. The upper and lower limits of these numerical ranges can be independently included or excluded from the range. The terms "comprising," "including," "having," and "containing" used in this specification are all open-ended terms, meaning to include but not limited to. Based on the embodiments of the present invention, all other embodiments obtained by any person skilled in the art without explicit inventive effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a method for preparing an ionic covalent organic framework material and a high-value cadmium-removing protein powder for efficiently removing cadmium from squid viscera concentrate. The specific steps are as follows:

[0035] Take 100g of squid viscera concentrate, add 500g of water and homogenize, adjust the pH to 8, add 0.3% trypsin and alkaline protease (trypsin:alkaline protease = 3:1) by mass of homogenate, heat the squid viscera protein hydrolysate to 40℃, hydrolyze for 3 hours, inactivate at 100℃ for 30 minutes, centrifuge at 4℃, centrifuge at 10000rpm for 20 minutes, and collect the supernatant for later use.

[0036] 0.5 g sodium dodecyl sulfate, 0.8 g 2,6-diaminoanthraquinone (DAAQ), 1 g aminated silica, and 0.9 g p-aminobenzenesulfonic acid were dissolved in tetrahydrofuran / water (200 mL / 300 mL) and sonicated for 5 minutes to obtain a suspension. 0.6 g of a tetrahydrofuran (400 mL) solution of 2,4,6-tricarboxylic acid-1,3,5-benzenetricarboxylic acid was added under mechanical stirring. The system was refluxed at 120 °C for 4 hours. After the reaction was complete, the suspension was collected and washed three times each with dimethylformamide and water. After washing, the suspension was freeze-dried under vacuum to obtain the functionalized covalent organic framework COF@SO3H-SiO2.

[0037] The supernatant of the hydrolyzed squid viscera was injected into a functionalized covalent organic framework COF@SO3H-SiO2 packed column for adsorption and enrichment of heavy metal cadmium. The filtrate was centrifuged and then freeze-dried to obtain hydrolyzed squid viscera protein powder.

[0038] The adsorption capacity of the functionalized covalent organic framework COF@SO3H-SiO2 for the heavy metal cadmium is shown in Table 1.

[0039] like Figure 2 As shown, the functional groups of the obtained magnetically functionalized covalent organic framework COF@SO3H-SiO2 were analyzed by Fourier transform infrared spectroscopy. First, at 1118 cm⁻¹... -1 Typical Si-O bands, with 3447 cm⁻¹ -1 The disappearance of the NH absorption peak, and the appearance of the 1617 C=O peak, 1568 exocyclic C=C peak, 1458 aromatic C=C peak, and 1260 C-N peak, indicate that the aldehyde group of 2,4,6-tricarboxylic acid underwent a Schiff base reaction with the amino group of 2,6-diaminoanthraquinone, resulting in an enol-ketone tautomerism. All these characteristic absorption peaks confirm the successful synthesis of COF@SO3H-SiO2.

[0040] As shown in Table 2, the reusability of the obtained magnetic functionalized covalent organic framework COF@SO3H-SiO2 was analyzed by ICP-MS. The results are shown in Table 2. COF@SO3H-SiO2 has good reusability. After 6 adsorption-desorption cycles, its reusability rate still reaches more than 80% of the initial state, which proves that it has good reusability.

[0041] Example 2

[0042] This embodiment provides a method for preparing an ionic covalent organic framework material and a high-value cadmium-removing protein powder for efficiently removing cadmium from squid viscera concentrate. Specifically:

[0043] Take 100g of squid viscera concentrate, add 600g of water and homogenize, adjust the pH to 8.5, add 0.1% trypsin and alkaline protease (trypsin:alkaline protease = 2:1) by weight of homogenate, heat the squid viscera protein hydrolysate to 40℃, hydrolyze for 6 hours, inactivate at 100℃ for 40 minutes, centrifuge at 4℃, centrifuge at 8000rpm for 20 minutes, and collect the supernatant for later use.

[0044] 0.6 g sodium dodecyl sulfate, 0.8 g p-toluenesulfonic acid, 0.9 g 2,6-diaminoanthraquinone (DAAQ), 1.2 g aminated silica, and 0.8 g p-aminobenzenesulfonic acid were dissolved in tetrahydrofuran / water (150 mL / 300 mL) and sonicated for 5 minutes to obtain a suspension. A tetrahydrofuran (450 mL) solution of 2,4,6-tricarboxylic acid-1,3,5-benzenetricarboxylic acid was added under mechanical stirring. The system was refluxed at 110 °C for 5 hours. After the reaction was complete, the suspension was collected and washed three times each with dimethylformamide and water. After washing, the suspension was freeze-dried under vacuum to obtain the functionalized covalent organic framework COF@SO3H-SiO2.

[0045] The supernatant of the hydrolyzed squid viscera was injected into a functionalized covalent organic framework COF@SO3H-SiO2 packed column for adsorption and enrichment of heavy metal cadmium. The filtrate was centrifuged and then freeze-dried to obtain hydrolyzed squid viscera protein powder.

[0046] Example 3

[0047] This embodiment provides a method for preparing an ionic covalent organic framework material and a high-value cadmium-removing protein powder for efficiently removing cadmium from squid viscera concentrate. Specifically:

[0048] Take 100g of squid viscera concentrate, add 400g of water and homogenize, adjust the pH to 9, add 0.5% trypsin and alkaline protease (trypsin:alkaline protease = 5:1) by mass of homogenate, heat the squid viscera protein hydrolysate to 40℃, hydrolyze for 4 hours, inactivate at 100℃ for 20 minutes, centrifuge at 4℃, centrifuge at 9000rpm for 20 minutes, and collect the supernatant for later use.

[0049] 0.6 g sodium dodecyl sulfate, 0.8 g p-toluenesulfonic acid, 0.8 g 2,6-diaminoanthraquinone (DAAQ), 0.8 g aminated silica, and 0.8 g p-aminobenzenesulfonic acid were dissolved in tetrahydrofuran / water (200 mL / 300 mL) and sonicated for 5 minutes to obtain a suspension. A solution of 0.6 g 2,4,6-tricarboxylic acid in tetrahydrofuran (350 mL) was added under mechanical stirring. The system was refluxed at 110 °C for 4 hours. After the reaction was complete, the solution was collected and washed three times each with dimethylformamide and water. After washing, the solution was freeze-dried under vacuum to obtain the functionalized covalent organic framework COF@SO3H-SiO2.

[0050] The supernatant of the hydrolyzed squid viscera was injected into a functionalized covalent organic framework COF@SO3H-SiO2 packed column for adsorption and enrichment of heavy metal cadmium. The filtrate was centrifuged and then freeze-dried to obtain hydrolyzed squid viscera protein powder.

[0051] Comparative Examples 1-3

[0052] The adsorbent was prepared according to the method of Examples 1-3, except that the aldehyde monomer in Examples 1-3 was replaced with trialdehyde phloroglucinol.

[0053] Comparative Example 4

[0054] The adsorbent was prepared according to the method of Example 1, except that the p-aminobenzenesulfonic acid in Example 1 was removed.

[0055] Effect verification

[0056] 1. The high-protein hydrolysate of squid viscera was adsorbed using Examples 1-3, and the adsorption amount was determined. The specific operation was as follows: 5 mg of material was accurately weighed into a 10 mL centrifuge tube, and 5 mL of high-protein hydrolysate of squid viscera with a concentration of 2000 mg / L was added. After sonication for 1 min, the mixture was rotated and adsorbed in a long-axis rotary mixer at 25 °C in the dark for 2 h. The supernatant was then taken, and the peak area was determined by ICP-MS to calculate the adsorption amount.

[0057] Table 1 shows the adsorption capacity of covalent organic framework silica particles (COF@SO3H-SiO2) for the heavy metal cadmium.

[0058] Water contact angle (°) Maximum adsorption capacity (mg / g) Adsorption saturation time #1 (min) Adsorption saturation time #2 (min) Example 1 74 175.43 70 6 Example 2 63 169.72 84 9 Example 3 54 190.45 58 5 Comparative Example 1 125 172.32 108 14 Comparative Example 2 133 167.21 113 17 Comparative Example 3 116 180.66 90 10 Comparative Example 4 140 160.35 120 21

[0059] Note: Adsorption saturation time #1 indicates the time required to reach the maximum adsorption capacity; Adsorption saturation time #2 indicates the time required to reach 85% of the maximum adsorption capacity.

[0060] Table 2 shows the reusability of covalent organic framework silica particles COF@SO3H-SiO2.

[0061] Maximum adsorption capacity (mg / g) Adsorption saturation time #1 (min) Example 1 153.32 75 Example 2 144.26 88 Example 3 161.88 62

[0062] Note: Adsorption saturation time #1 indicates the time required to reach the maximum adsorption capacity.

Claims

1. A method for preparing a highly efficient cadmium-removing ionic covalent organic framework material, characterized in that: The method is as follows: a surfactant, a protic acid catalyst, an amino monomer, functionalized silica, and a sulfonic acid functionalizing agent are dissolved in a mixed solvent of organic solvent and water to obtain a suspension; an aldehyde monomer 2,4,6-tricarboxyloyl-1,3,5-benzenetricarboxylic acid is dissolved in an organic solvent to obtain an aldehyde monomer solution; the aldehyde monomer solution is added to the suspension under mechanical stirring, and an ionic covalent organic framework COF@SO3H-SiO2 with silica gel as the core is obtained through a solvothermal reaction.

2. The method for preparing a highly efficient cadmium-removing ionic covalent organic framework material according to claim 1, characterized in that: The surfactant is one of sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB), or polyvinyl alcohol (PVP); the protic acid catalyst is p-toluenesulfonic acid or trifluoroacetic acid; the amino monomer is one of 2,2'-dihydroxy-4,4'-biphenyldiamine (BHBD), 2,6-diaminoanthraquinone (DAAQ), or 2-hydroxy-1,3-propanediamine (DAHP); the functionalized silica is aminated SiO2 or aldehyde-modified SiO2; the sulfonic acid functionalizing agent is one of p-aminobenzenesulfonic acid, amino-isophenylenesulfonic acid, aminonaphthalenesulfonic acid, or sodium p-aminobenzenesulfonate; and the organic solvent is one of tetrahydrofuran, ethanol, or acetonitrile.

3. The method for preparing a highly efficient cadmium-removing ionic covalent organic framework material according to claim 1, characterized in that: The molar ratio of the surfactant to 2,4,6-tricarboxylic acid is 0.5~1.5:1; the molar ratio of the protic acid catalyst to 2,4,6-tricarboxylic acid is 0~5:1; the molar ratio of the amino monomer to 2,4,6-tricarboxylic acid is 1~2:1; the mass ratio of the functionalized silica to 2,4,6-tricarboxylic acid is 50~150:100; and the molar ratio of the sulfonic acid functionalizing reagent to 2,4,6-tricarboxylic acid is 0~5:

1.

4. The method for preparing a highly efficient cadmium-removing ionic covalent organic framework material according to claim 1, characterized in that: The solvothermal reaction is carried out at a temperature of 100~150℃ for a time of 0.5~10 h.

5. The application of an ionic covalent organic framework material prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The application is as follows: Step 1: High-speed pulverize squid viscera concentrate, add water and stir evenly to form a homogenate, adjust the pH of the homogenate to 8-10, add compound enzyme, and mix the compound enzyme system evenly into the squid viscera homogenate. Hydrolyze and inactivate under optimal conditions to convert the heavy metal cadmium in the squid viscera concentrate from a bound state to a free state, fully release it, and centrifuge to obtain squid viscera high-protein hydrolysate. Step 2: Using ionic covalent organic framework COF@SO3H-SiO2 as an efficient enrichment packing for separating heavy metal cadmium, the squid viscera high-protein hydrolysate from Step 1 is passed through the enrichment packing to obtain a squid viscera high-protein hydrolysate with significantly reduced cadmium content. After freeze-drying, squid viscera high-protein hydrolysate powder is obtained.

6. The application of the ionic covalent organic framework material according to claim 5, characterized in that: In step one, the squid is one or more of cuttlefish, squid, and slug; the complex enzyme is two or more of flavor protease, pepsin, papain, trypsin, alkaline protease, and animal protease.

7. The application of the ionic covalent organic framework material according to claim 5, characterized in that: In step one, the mass ratio of the squid viscera concentrate to water is 1:3~10; the mass ratio of the compound enzyme to the squid viscera concentrate is 0.1~1:

100.

8. The application of the ionic covalent organic framework material according to claim 5, characterized in that: In step one, the hydrolysis temperature is 30~60℃, the magnetic stirring speed is 100~800 rpm, and the time is 2~6 h; the inactivation temperature is 100℃, and the time is 15~60 min.

9. The application of an ionic covalent organic framework material according to claim 5, characterized in that: In step two, the mass ratio of the ionic covalent organic framework COF@SO3H-SiO2 to the concentrated squid viscera extract is 0.005~0.01:100, and the adsorption time is 20~60 min.

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