CN114768773A - Heavy metal adsorption material for edible liquid and preparation method and application thereof - Google Patents
Heavy metal adsorption material for edible liquid and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a heavy metal adsorption material for edible liquid, and a preparation method and application thereof. The invention takes natural polymer chitosan and cyclodextrin which meet the use standard of national food additives and are widely applied as adsorbing materials, the chitosan and the cyclodextrin are grafted to polyvinylidene fluoride to obtain the polyvinylidene fluoride material containing amino and hydroxyl and grafted chitosan-cyclodextrin, and the hydroxyl on the cyclodextrin and the amino on the chitosan play a synergistic effect, so that the adsorbing material has good adsorption effect on heavy metal ions such as copper, cadmium, lead and the like.
Description
Technical Field
The invention relates to the technical field of food processing materials, in particular to a heavy metal adsorption material for edible liquid and a preparation method and application thereof.
Background
Heavy metal means a density of 4.5g/cm3The above metal elements, heavy metals, are toxic, non-biodegradable, and exist in the environment in different oxidation states for a long time. Heavy gold in the environmentThe method belongs to industrial production activities mainly derived from human beings, such as coal-fired power generation, mining, heavy metal mining, leather electroplating, production of heavy metal-containing products and the like, and heavy metal impurities released by the activities can pollute the atmosphere, soil and water bodies. Heavy metals easily enter a human body through a food chain, are accumulated and enriched in the human body, and finally cause serious damage to the human body, for example, heavy metal pollution in directly drinkable liquid such as drinking water, tea water, traditional Chinese medicine decoction and the like is closely related to the physical health of consumers, so that the efficient removal of the heavy metal residues in the liquid before drinking the liquid is very important.
In the prior art, polyvinylidene fluoride micro-filtration membranes and separation membranes are generally adopted to remove heavy metals in water, for example, patent CN106621842A discloses a preparation method, a regeneration method and an application of a chelating micro-filtration membrane, in which a micromolecular chelating agent melamine is grafted onto a PVDF membrane to prepare the chelating micro-filtration membrane capable of adsorbing heavy metals. Patent CN106582335A discloses a preparation method of modified PVDF for heavy metal ion adsorption type separation membrane, in which polyamide-amine is grafted onto a PVDF membrane to prepare a separation membrane capable of adsorbing heavy metals. The adsorbing material has strong adsorption capacity on heavy metals, but the adsorbing material is grafted with a melamine micromolecule chelating agent and polyamide-amine, and obviously cannot be directly used for edible liquid.
Patent CN109999765A discloses a preparation method of a beta-cyclodextrin polymer grafted polyvinylidene fluoride adsorption material, hydroxyl is introduced through double bond nucleophilic addition reaction, then acrylic acid is connected through hydroxyl esterification, and finally polymerization reaction is carried out on double bonds in the acrylic acid on a polyvinylidene fluoride acrylic acid material and double bonds in GMA-beta-cyclodextrin polymer, so that the beta-cyclodextrin polymer is grafted to the polyvinylidene fluoride material. In addition, the beta-cyclodextrin polymer grafted polyvinylidene fluoride adsorption material prepared by the patent has a good adsorption effect on lead, but has a poor effect on other common heavy metals such as copper, cadmium and the like, so that the use value of the beta-cyclodextrin polymer grafted polyvinylidene fluoride adsorption material is limited.
Disclosure of Invention
The invention aims to provide an adsorbing material which has a good adsorbing effect on various heavy metal ions, has good chemical stability and high safety and can be applied to edible liquid.
In order to solve the technical problems, the invention provides a heavy metal adsorption material for edible liquid, which is a polyvinylidene fluoride material grafted with chitosan-cyclodextrin, wherein the cyclodextrin is grafted on the polyvinylidene fluoride, and the chitosan is grafted on the cyclodextrin through a cross-linking agent.
Further, the grafting rate of the cyclodextrin and the chitosan on the polyvinylidene fluoride in the heavy metal adsorbing material is 30-60%. The grafting rate of the adsorbing material is high, and correspondingly, the adsorbing material has good heavy metal ion adsorption capacity.
The invention takes natural polymer chitosan and cyclodextrin which meet the use standard of national food additives and are widely applied as adsorbing materials, the chitosan and the cyclodextrin are grafted to polyvinylidene fluoride to obtain the polyvinylidene fluoride material containing amino and hydroxyl grafted chitosan-cyclodextrin, and the hydroxyl on the cyclodextrin and the amino on the chitosan play a synergistic effect, so that the adsorbing material has good adsorbing effect on heavy metal ions such as copper, cadmium, lead and the like.
The second aspect of the invention provides a preparation method of the heavy metal adsorbing material for the edible liquid, which comprises the following steps:
s1, removing HF from polyvinylidene fluoride under the conditions of strong alkali and strong oxidizing property to generate a functional carbon-carbon double bond structure;
s2, under the action of a condensing agent, performing esterification reaction on cyclodextrin and acrylic acid, and introducing a functional carbon-carbon double bond structure on the cyclodextrin;
s3, under the initiation of an initiator, polymerizing a polyvinylidene fluoride material containing carbon-carbon double bonds and acrylated cyclodextrin containing carbon-carbon double bonds, and grafting cyclodextrin on polyvinylidene fluoride;
s4, under the action of a cross-linking agent glyoxal, performing cross-linking on the cyclodextrin and the chitosan to obtain the chitosan-cyclodextrin grafted polyvinylidene fluoride material.
Further, the step S1 specifically includes: and putting the polyvinylidene fluoride material into a mixed solution of an alkaline solution and a potassium permanganate solution, stirring for reaction, filtering after the reaction is finished, and washing residual reactants on the surface by using deionized water to obtain the polyvinylidene fluoride material with HF removed. In the step, HF of polyvinylidene fluoride is removed under the conditions of strong alkali and strong oxidizing property, and a functional carbon-carbon double bond structure is generated, so that a polyvinylidene fluoride material with good chemical stability can be modified.
Further, the step S2 specifically includes: adding cyclodextrin and a condensing agent into a dimethylformamide solution, adding acrylic acid, heating and stirring, filtering to remove generated precipitates, adding acetone into filtrate to precipitate a product, and washing a solid obtained after solid-liquid separation step by step with dilute acetic acid, a potassium bicarbonate solution and water to obtain an acrylic acid cyclodextrin polymer. The method for synthesizing the acrylated cyclodextrin by adopting the condensing agent has the advantages of mild reaction conditions, less generated by-products and easy purification of products, and is favorable for improving the grafting density and the chemical stability of the adsorbing material.
Further, the condensing agent used in step S2 is dicyclohexylcarbodiimide or 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide.
Further, the step S3 specifically includes: and (3) adding the polyvinylidene fluoride material subjected to HF removal and obtained in the step (S1) and the acrylic acid cyclodextrin polymer obtained in the step (S2) into a dimethylformamide solution, then adding a proper amount of initiator, stirring and reacting under the protection of inert gas, adding a methanol solution into a reaction solution after the reaction is finished, precipitating a product, filtering, washing and drying to obtain the polyvinylidene fluoride material grafted with cyclodextrin. The carbon-carbon double bond structure formed by removing HF from the polyvinylidene fluoride material and the carbon-carbon double bond in the acrylic acid esterified cyclodextrin polymer are subjected to polymerization reaction, so that high-density cyclodextrin is grafted on the polyvinylidene fluoride material, and the intermediate product has high chemical stability.
Further, the step S4 specifically includes: and (2) dissolving chitosan in an acidic aqueous solution, adding the cyclodextrin grafted polyvinylidene fluoride material obtained in the step (S3), heating and stirring, adding a cross-linking agent for reaction, adjusting the pH to 7-8 with an alkaline solution, continuing the reaction, cooling the solution, filtering, and washing the precipitate with deionized water to obtain the chitosan-cyclodextrin grafted polyvinylidene fluoride material. According to the step, cyclodextrin and chitosan are crosslinked under the action of a crosslinking agent, so that an amino group with a good adsorption effect on heavy metal ions is introduced, the amino-hydroxyl-containing grafted chitosan-cyclodextrin polyvinylidene fluoride material is finally obtained, and the hydroxyl and the amino have a synergistic effect, so that the adsorbing material has a good adsorption effect on heavy metal ions such as copper, cadmium, lead and the like.
Further, the cross-linking agent used in the step S4 is glyoxal or glutaraldehyde.
The preparation method disclosed by the invention is mild and controllable in reaction conditions, less in generated impurities, easy to purify the product, capable of preparing the high-density grafted chitosan-cyclodextrin polyvinylidene fluoride material, good in adsorption effect on various heavy metal ions, good in chemical stability and high in safety, and capable of being applied to edible liquid.
In a third aspect of the invention, the heavy metal adsorbing material for the edible liquid is prepared into a film, a plate, a particle or a coating form and is applied to a container.
The heavy metal adsorption material disclosed by the invention is good in chemical stability, high in safety and strong in adsorption effect, can effectively adsorb heavy metals in edible liquid, ensures the dietary health of people, can be directly applied to containers such as cups, bowls and kettles in various forms, and has a good market application prospect.
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FIG. 1 is a synthesis process of a heavy metal adsorbing material for edible liquid in the embodiment of the invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in the present disclosure, it is understood that each intervening value, to the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.
The embodiment of the invention provides a heavy metal adsorption material for edible liquid and a preparation method thereof. The grafting rate of cyclodextrin and chitosan on polyvinylidene fluoride is 30-60%.
The preparation method of the heavy metal adsorption material for the edible liquid comprises the following steps:
s1, removing HF from polyvinylidene fluoride (PVCD) under the conditions of strong alkali and strong oxidizing property to generate a functional carbon-carbon double bond structure. The method comprises the following specific steps: placing the polyvinylidene fluoride material into a mixed solution of an alkaline solution and a potassium permanganate solution at the temperature of 30-50 ℃, and stirring for reaction, wherein the alkaline solution is one selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium carbonate and sodium carbonate, the stirring speed is 200-800 rmp, and the reaction time is 1-3 h; and filtering after the reaction is finished, and washing the residual reactant on the surface by using deionized water to obtain the polyvinylidene fluoride material with HF removed.
S2, under the action of a condensing agent, the cyclodextrin (beta-CD) and Acrylic Acid (AA) are subjected to esterification reaction, and a functional carbon-carbon double bond structure is introduced into the cyclodextrin. The method comprises the following specific steps: adding cyclodextrin and a condensing agent into a dimethylformamide solution (DMF), wherein the condensing agent is Dicyclohexylcarbodiimide (DCC) or 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide; adding acrylic acid, heating and stirring, wherein the adding temperature is 30-50 ℃, the stirring speed is 200-800 rmp, and the reaction time is 16-32 h; then filtering to remove the generated precipitate, adding acetone into the filtrate to precipitate the product, after solid-liquid separation, washing the obtained solid step by step with dilute acetic acid, potassium bicarbonate solution and water to obtain the acrylic acid cyclodextrin polymer, and drying for later use.
And S3, polymerizing the polyvinylidene fluoride material containing the carbon-carbon double bond and the acrylic acid esterified cyclodextrin containing the carbon-carbon double bond under the initiation of an initiator, and grafting cyclodextrin on the polyvinylidene fluoride. The method comprises the following specific steps: and (2) adding the polyvinylidene fluoride material without HF obtained in the step (S1) and the acrylic acid cyclodextrin polymer obtained in the step (S2) into a dimethylformamide solution, and then adding a proper amount of initiator, wherein the mass ratio of the polyvinylidene fluoride material to the acrylic acid cyclodextrin polymer is 1-10: 1, the mass ratio of the polyvinylidene fluoride material to the initiator is 30-60: 1, and the initiator is benzoyl oxide or Azobisisobutyronitrile (AIBN). Stirring and reacting under the protection of inert gas, wherein the inert gas is nitrogen or argon, the reaction temperature is 60-80 ℃, the stirring speed is 200-800 rmp, and the constant temperature reaction is carried out for 6-12 hours; and (3) adding an anhydrous methanol solution into the reaction solution after the reaction is finished, precipitating and separating out the product, filtering, washing, removing residues on the surface of the product to obtain the polyvinylidene fluoride material grafted with cyclodextrin, and drying for later use.
S4, under the action of a cross-linking agent glyoxal, performing cross-linking on the cyclodextrin and the chitosan to obtain the chitosan-cyclodextrin grafted polyvinylidene fluoride material. The method comprises the following specific steps: dissolving chitosan in an acidic aqueous solution, wherein the acidic aqueous solution is a hydrochloric acid aqueous solution or an acetic acid aqueous solution; then adding the polyvinylidene fluoride material grafted with cyclodextrin obtained in the step S3, wherein the mass ratio of the polyvinylidene fluoride material grafted with cyclodextrin to chitosan is 2-10: 1; heating to 60-80 ℃, adding a cross-linking agent under stirring for reaction, wherein the cross-linking agent is glyoxal or glutaraldehyde, and reacting for 1-2 h; adjusting the pH value to 7-8 by using an alkaline solution, and continuously reacting for 0.5-1 h; and (3) filtering after the solution is cooled, and washing the precipitate with deionized water to obtain the polyvinylidene fluoride material grafted with chitosan-cyclodextrin.
According to the embodiment of the invention, natural polymer chitosan and cyclodextrin which meet the use standards of national food additives and are widely applied are used as adsorbing materials, the chitosan and cyclodextrin are grafted to polyvinylidene fluoride to obtain a polyvinylidene fluoride material containing amino and hydroxyl grafted chitosan-cyclodextrin, and the synthesis process is shown in figure 1.
The heavy metal adsorption material has good chemical stability and high safety, and the hydroxyl on the cyclodextrin and the amino on the chitosan have a synergistic effect, so that the adsorption material has a good adsorption effect on heavy metal ions such as copper, cadmium and lead, can effectively adsorb heavy metals in edible liquid, and ensures the diet health of people. And the heavy metal adsorption material can be prepared into the forms of films, plates, particles, coatings and the like, can be directly applied to containers such as cups, bowls, kettles and the like, and has good market application prospect.
The present invention will be described in detail below by way of specific examples.
Example 1
S1, at 40 ℃, putting 10g of polyvinylidene fluoride material into a mixed solution of potassium hydroxide with the mass fraction of 20% and potassium permanganate with the mass fraction of 4%, and stirring for 2 hours at 500 rmp; and filtering after the reaction is finished, and washing the residual reactant on the surface by using deionized water to obtain the polyvinylidene fluoride material without HF.
S2, adding 3g of beta-cyclodextrin and 5.5g of dicyclohexylcarbodiimide into 100ml of dimethylformamide solution, then adding 1.82ml of acrylic acid, wherein the molar ratio of beta-CD, DCC and AA is 1:10:10, and stirring at 30 ℃ for 24 hours at 500 rmp; filtering to remove the generated precipitate, adding 100ml acetone into the filtrate to precipitate the product, filtering again, washing the precipitated precipitate with dilute acetic acid, potassium bicarbonate solution and water for 3 times, removing the residue on the surface of the product to obtain the acrylic acid cyclodextrin polymer, and drying the obtained product at 60 ℃ for later use.
S3, adding 5g of HF-removed polyvinylidene fluoride material and 2g of acrylic acid cyclodextrin polymer B into 100ml of dimethylformamide solution, then adding 0.1g of azobisisobutyronitrile, wherein the mass ratio of the polyvinylidene fluoride material to AIBN is 50:1, and stirring and reacting at a constant temperature of 70 ℃ and a constant temperature of 500rmp for 8 hours under the protection of nitrogen; after the reaction is finished, the reaction solution is precipitated by 100ml of anhydrous methanol, filtered, and the precipitate is washed for 3 times by deionized water to remove residues on the surface of a product, thus obtaining the polyvinylidene fluoride material grafted with cyclodextrin, and the polyvinylidene fluoride material is dried at 60 ℃ for standby.
S4, dissolving 0.5g of chitosan in 0.5mol/L hydrochloric acid aqueous solution, adding 3g of polyvinylidene fluoride material grafted with cyclodextrin, adding 1ml of cross-linking agent glyoxal under stirring at 80 ℃, reacting for 1.5h, adjusting the pH to 7-8 with 1mol/L NaOH solution, and continuing to react for 0.5 h; and (3) after the solution is cooled, filtering, washing and precipitating for 3 times by using deionized water to obtain the polyvinylidene fluoride material grafted with the chitosan-cyclodextrin polymer.
Example 2
S1, at 35 ℃, putting 10g of polyvinylidene fluoride material into a mixed solution of sodium hydroxide with the mass fraction of 20% and potassium permanganate with the mass fraction of 4%, and stirring for 1.5h at 800 rmp; and filtering after the reaction is finished, and washing the residual reactant on the surface by using deionized water to obtain the polyvinylidene fluoride material with HF removed.
S2, adding 3g of beta-cyclodextrin and 5g of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide into 100ml of dimethylformamide solution, then adding 2ml of acrylic acid, and stirring at 35 ℃ at 800rmp for 20 h; filtering to remove the generated precipitate, adding 100ml acetone into the filtrate to precipitate the product, filtering again, washing the precipitated precipitate with dilute acetic acid, potassium bicarbonate solution and water for 3 times, removing the residue on the surface of the product to obtain the acrylic acid cyclodextrin polymer, and drying the obtained product at 60 ℃ for later use.
S3, adding 5g of HF-removed polyvinylidene fluoride material and 2.5g of acrylic acid cyclodextrin polymer B into 100ml of dimethylformamide solution, then adding 0.1g of benzoyl oxide, and stirring and reacting at a constant temperature of 80 ℃ and 800rmp for 6 hours under the protection of argon; after the reaction is finished, the reaction solution is precipitated by 100ml of anhydrous methanol, filtered, and the precipitate is washed for 3 times by deionized water to remove residues on the surface of a product, so that the polyvinylidene fluoride material grafted with cyclodextrin is obtained and is dried at 60 ℃ for later use.
S4, dissolving 0.5g of chitosan in 0.5mol/L acetic acid aqueous solution, adding 3g of polyvinylidene fluoride material grafted with cyclodextrin, adding 1ml of cross-linking agent glutaraldehyde under stirring at 80 ℃, reacting for 2 hours, adjusting the pH to 8 by using 1mol/L NaOH solution, and continuing to react for 1 hour; and (3) after the solution is cooled, filtering, washing and precipitating for 3 times by using deionized water to obtain the polyvinylidene fluoride material grafted with the chitosan-cyclodextrin polymer.
Example 3
S1, placing 15g of polyvinylidene fluoride material into a mixed solution of 20 mass percent of calcium hydroxide and 4 mass percent of potassium permanganate at 40 ℃ and stirring for 2.5 hours at 600 rmp; and filtering after the reaction is finished, and washing the residual reactant on the surface by using deionized water to obtain the polyvinylidene fluoride material with HF removed.
S2, adding 5g of beta-cyclodextrin and 5g of dicyclohexylcarbodiimide into 150ml of dimethylformamide solution, then adding 2.5ml of acrylic acid, and stirring at 600rmp for 26h at 40 ℃; filtering to remove generated precipitate, adding 150ml acetone into the filtrate to precipitate the product, filtering again, washing the precipitated precipitate with dilute acetic acid, potassium bicarbonate solution and water for 3 times, removing residue on the surface of the product to obtain acrylic acid cyclodextrin polymer, and drying the obtained product at 60 deg.C for use.
S3, adding 6g of the polyvinylidene fluoride material subjected to HF removal and 4g of the acrylic acid cyclodextrin polymer B into 150ml of dimethylformamide solution, then adding 0.2g of azobisisobutyronitrile, and stirring and reacting at the constant temperature of 600rmp for 12 hours at the temperature of 60 ℃ under the protection of nitrogen; after the reaction is finished, the reaction solution is precipitated by 100ml of anhydrous methanol, filtered, and the precipitate is washed for 3 times by deionized water to remove residues on the surface of a product, thus obtaining the polyvinylidene fluoride material grafted with cyclodextrin, and the polyvinylidene fluoride material is dried at 60 ℃ for standby.
S4, dissolving 1g of chitosan in 0.5mol/L hydrochloric acid aqueous solution, adding 4g of polyvinylidene fluoride material grafted with cyclodextrin, adding 1.5ml of cross-linking agent glyoxal under stirring at 70 ℃, reacting for 1h, adjusting the pH to 7.5 by using 1mol/L potassium carbonate solution, and continuing to react for 0.5 h; and (3) after the solution is cooled, filtering, washing and precipitating for 3 times by using deionized water to obtain the polyvinylidene fluoride material grafted with the chitosan-cyclodextrin polymer.
Example 4
S1, at 50 ℃, putting 10g of polyvinylidene fluoride material into a mixed solution of 20 mass percent of sodium carbonate and 4 mass percent of potassium permanganate, and stirring for 3 hours at 300 rmp; and filtering after the reaction is finished, and washing the residual reactant on the surface by using deionized water to obtain the polyvinylidene fluoride material with HF removed.
S2, adding 3g of beta-cyclodextrin and 6g of dicyclohexylcarbodiimide into 100ml of dimethylformamide solution, then adding 1.67ml of acrylic acid, and stirring at 50 ℃ at 400rmp for 18 h; filtering to remove generated precipitate, adding 100ml acetone into the filtrate to precipitate the product, filtering again, washing the precipitated precipitate with dilute acetic acid, potassium bicarbonate solution and water for 3 times, removing residue on the surface of the product to obtain acrylic acid cyclodextrin polymer, and drying the obtained product at 60 deg.C for use.
S3, adding 5g of the polyvinylidene fluoride material without HF and 2g of the acrylic acid cyclodextrin polymer B into 100ml of dimethylformamide solution, then adding 0.1g of AIBN, and stirring and reacting at a constant temperature of 400rmp at 65 ℃ for 8 hours under the protection of argon; after the reaction is finished, the reaction solution is precipitated by 100ml of anhydrous methanol, filtered, and the precipitate is washed for 3 times by deionized water to remove residues on the surface of a product, thus obtaining the polyvinylidene fluoride material grafted with cyclodextrin, and the polyvinylidene fluoride material is dried at 60 ℃ for standby.
S4, dissolving 1g of chitosan in 0.5mol/L acetic acid aqueous solution, adding 5g of polyvinylidene fluoride material grafted with cyclodextrin, adding 2ml of cross-linking agent glutaraldehyde under stirring at 70 ℃, reacting for 1.5h, adjusting the pH to 7 by using 1mol/L NaOH solution, and continuing to react for 1 h; and (3) filtering after the solution is cooled, and washing and precipitating for 3 times by using deionized water to obtain the polyvinylidene fluoride material grafted with the chitosan-cyclodextrin polymer.
Comparative example 1
S1, at the temperature of 40 ℃, 10g of polyvinylidene fluoride material is put into a mixed solution of potassium hydroxide with the mass fraction of 20% and potassium permanganate with the mass fraction of 4% and stirred for 2 hours at 500 rmp; and filtering after the reaction is finished, and washing the residual reactant on the surface by using deionized water to obtain the polyvinylidene fluoride material with HF removed.
S2, adding 3g of beta-cyclodextrin and 5.5g of dicyclohexylcarbodiimide into 100ml of dimethylformamide solution, then adding 1.82ml of acrylic acid, and stirring at 500rmp for 24h at 30 ℃; filtering to remove generated precipitate, adding 100ml acetone into the filtrate to precipitate the product, filtering again, washing the precipitated precipitate with dilute acetic acid, potassium bicarbonate solution and water for 3 times, removing residue on the surface of the product to obtain acrylic acid cyclodextrin polymer, and drying the obtained product at 60 deg.C for use.
S3, adding 5g of the polyvinylidene fluoride material subjected to HF removal and 2g of the acrylic acid cyclodextrin polymer B into 100ml of a dimethylformamide solution, then adding 0.1g of azobisisobutyronitrile, and stirring and reacting at a constant temperature of 70 ℃ of 500rmp for 8 hours under the protection of nitrogen; after the reaction is finished, the reaction solution is precipitated by 100ml of anhydrous methanol, filtered, and the precipitate is washed for 3 times by deionized water to remove residues on the surface of a product, thus obtaining the polyvinylidene fluoride material grafted with cyclodextrin, and the polyvinylidene fluoride material is dried at 60 ℃ for standby.
Comparative example 2
S1, at 35 ℃, putting 10g of polyvinylidene fluoride material into a mixed solution of 20 mass percent sodium hydroxide and 4 mass percent potassium permanganate, and stirring for 1.5h at 800 rmp; and filtering after the reaction is finished, and washing the residual reactant on the surface by using deionized water to obtain the polyvinylidene fluoride material with HF removed.
S2, adding 3g of beta-cyclodextrin and 5g of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide into 100ml of dimethylformamide solution, then adding 2ml of acrylic acid, and stirring at 35 ℃ at 800rmp for 20 h; filtering to remove the generated precipitate, adding 100ml acetone into the filtrate to precipitate the product, filtering again, washing the precipitated precipitate with dilute acetic acid, potassium bicarbonate solution and water for 3 times, removing the residue on the surface of the product to obtain the acrylic acid cyclodextrin polymer, and drying the obtained product at 60 ℃ for later use.
S3, adding 5g of HF-removed polyvinylidene fluoride material and 2.5g of acrylic acid cyclodextrin polymer B into 100ml of dimethylformamide solution, then adding 0.1g of benzoyl oxide, and stirring and reacting at a constant temperature of 80 ℃ and 800rmp for 6 hours under the protection of argon; after the reaction is finished, the reaction solution is precipitated by 100ml of anhydrous methanol, filtered, and the precipitate is washed for 3 times by deionized water to remove residues on the surface of a product, so that the polyvinylidene fluoride material grafted with cyclodextrin is obtained and is dried at 60 ℃ for later use.
Examples of the experiments
The polyvinylidene fluoride materials grafted with the chitosan-cyclodextrin polymer obtained in examples 1 to 4 and the polyvinylidene fluoride materials grafted with the cyclodextrin obtained in comparative examples 1 to 2 were sampled, and heavy metal ion static adsorption experiments were performed to perform Cu adsorption and Cu adsorption, respectively2 +、Pb2+、Cr3+Adsorption of (3).
Static adsorption experiment step: the solution to be treated contains Cu2+、Pb2+、Cr3+The solution to be treated is weighed into 18 parts by 500ml, and the 18 parts are poured into 18 conical flasks respectively, wherein the 18 conical flasks are divided into 6 groups, and 3 groups are used as parallel items. Next, 1g of each sample of the adsorbent prepared in examples 1 to 4 and comparative examples 1 to 2 was put into each group of erlenmeyer flasks, and then each group of erlenmeyer flasks was fixed in a constant temperature water bath oscillator at a temperature of 25 ℃ and sampled after shaking at a shaking frequency of 120r/min for 120 minutes. And (4) centrifuging the solution after adsorption treatment, and measuring the content of metal ions in the solution after adsorption by using atomic absorption spectroscopy. The results are shown in table 1 below:
TABLE 1 results of static adsorption experiments of heavy metal adsorbing materials obtained in examples 1 to 4 and comparative examples 1 to 2
According to experimental results, the polyvinylidene fluoride material grafted with the chitosan-cyclodextrin polymer prepared by the embodiment of the invention has uniform and good adsorption effect on heavy metal ions such as copper, cadmium, lead and the like, and the adsorption capacity is superior to that of the polyvinylidene fluoride material grafted with cyclodextrin.
Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and such changes and modifications will fall within the scope of the present invention.
Claims (10)
1. The heavy metal adsorption material for the edible liquid is characterized by being a polyvinylidene fluoride material grafted with chitosan-cyclodextrin, wherein the cyclodextrin is grafted on the polyvinylidene fluoride, and the chitosan is grafted on the cyclodextrin through a cross-linking agent.
2. The heavy metal adsorbing material for the edible liquid as claimed in claim 1, wherein the grafting ratio of the cyclodextrin and the chitosan on the polyvinylidene fluoride is 30-60%.
3. A method for preparing a heavy metal adsorbing material for edible liquid according to claim 1 or 2, comprising the following steps:
s1, removing HF from polyvinylidene fluoride under the conditions of strong alkali and strong oxidizing property to obtain a polyvinylidene fluoride material with HF removed;
s2, under the action of a condensing agent, carrying out esterification reaction on cyclodextrin and acrylic acid to obtain an acrylic acid cyclodextrin polymer;
s3, under the initiation of an initiator, polymerizing the polyvinylidene fluoride material containing carbon-carbon double bonds and the acrylic acid esterified cyclodextrin containing carbon-carbon double bonds to obtain the polyvinylidene fluoride material grafted with cyclodextrin;
s4, under the action of crosslinking agent glyoxal, crosslinking cyclodextrin and chitosan to obtain the polyvinylidene fluoride material grafted with chitosan-cyclodextrin.
4. The preparation method according to claim 3, wherein the step S1 specifically includes: and (3) putting the polyvinylidene fluoride material into a mixed solution of an alkaline solution and a potassium permanganate solution, stirring for reaction, filtering after the reaction is finished, and washing residual reactants on the surface by deionized water to obtain the polyvinylidene fluoride material with HF removed.
5. The preparation method according to claim 4, wherein the step S2 specifically includes: adding cyclodextrin and a condensing agent into a dimethylformamide solution, adding acrylic acid, heating and stirring, filtering to remove generated precipitates, adding acetone into filtrate to precipitate a product, and washing a solid obtained after solid-liquid separation step by step with dilute acetic acid, a potassium bicarbonate solution and water to obtain an acrylic acid cyclodextrin polymer.
6. The production method according to claim 5, wherein the condensing agent used in step S2 is dicyclohexylcarbodiimide or 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide.
7. The preparation method according to claim 4, wherein the step S3 specifically comprises: and (4) adding the polyvinylidene fluoride material subjected to HF removal and obtained in the step S1 and the acrylic acid cyclodextrin polymer obtained in the step S2 into a dimethylformamide solution, then adding a proper amount of initiator, stirring and reacting under the protection of inert gas, adding a methanol solution into a reaction solution after the reaction is finished, precipitating and separating out a product, and filtering, washing and drying to obtain the polyvinylidene fluoride material grafted with cyclodextrin.
8. The preparation method according to claim 4, wherein the step S4 specifically comprises: and (2) dissolving chitosan in an acidic aqueous solution, adding the polyvinylidene fluoride material grafted with cyclodextrin obtained in the step (S3), heating and stirring, adding a cross-linking agent for reaction, adjusting the pH to 7-8 with an alkaline solution, continuing the reaction, cooling the solution, filtering, and washing the precipitate with deionized water to obtain the polyvinylidene fluoride material grafted with chitosan-cyclodextrin.
9. The method according to claim 8, wherein the crosslinking agent used in step S4 is glyoxal or glutaraldehyde.
10. Use of a heavy metal adsorbing material for edible liquids according to claim 1 or 2, wherein the heavy metal adsorbing material is made into a film, a sheet, a granule, a coating and is applied to a container.
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