Ethylenediamine tetramethylenephosphonic acid modified starch as well as preparation method and application thereof

Abstract

The invention provides ethylenediamine tetramethylenephosphonic acid modified starch and a preparation method and application thereof.The preparation method includes the steps that a starch dispersion solution and an acid-catalyzed ethylenediamine tetramethylenephosphonic acid solution are mixed, ammonium persulfate is added, and a constant-temperature stirring reaction is conducted under nitrogen protection; after the reaction liquid is cooled, ethanol is added to precipitate a grafted product, and the ethylenediamine tetramethylenephosphonic acid modified starch is obtained. According to the ethylenediamine tetramethylenephosphonic acid modified starch, ethylenediamine tetramethylenephosphonic acid and natural polymer starch are grafted to form a polymer-based heavy metal trapping agent, synchronous and efficient removal of multiple metals in strongly acidic wastewater can be realized, and the pH value of the wastewater does not need to be pre-adjusted.

Description

Technical Field

[0001] This invention relates to the field of heavy metal capture agents, specifically to a starch modified with ethylenediaminetetramethylenephosphonic acid, its preparation method, and its applications. Background Technology

[0002] Existing polymeric heavy metal scavengers are mostly synthetic organic polymers, which suffer from drawbacks such as high monomer toxicity and difficulty in degradation. In contrast, natural polymeric scavengers offer advantages such as readily available raw materials, low cost, simple synthesis processes, and easily degradable products. Therefore, the research and development of modified natural polymeric scavengers is currently a focus of research and development both domestically and internationally. In the process of developing modified natural polymeric heavy metal scavengers, modified starch has been the most extensively studied because it is not only abundant in resources but also more water-soluble than other modified polymeric scavengers, making it more suitable for heavy metal scavenging.

[0003] Patent application CN115490288A discloses a modified starch heavy metal chelating agent and chelating material, its preparation method, and its application. Using starch as a matrix, the starch is cross-linked and activated using epoxy groups. Then, an imino compound containing one or more carboxyl groups is used to modify the cross-linked starch through an ammoniation reaction with the epoxy groups, resulting in modified starch with multiple carboxyl groups. Since both nitrogen atoms and oxygen atoms in the carboxyl groups have unbonded electrons, they can coordinate with the empty orbitals of metal ions to form coordinate bonds, thereby enhancing the chelation efficiency of heavy metal ions. By using porous media such as zeolite and activated carbon as adsorption carriers, the adsorption surface area is increased while shaping the chelating agent to prevent long-term agglomeration and reduced heavy metal ion chelation effect. This modified starch heavy metal chelating agent is inexpensive, easy to industrially produce, reusable, and has a good removal effect on heavy metal ions, demonstrating strong practicality and wide applicability. However, this modified starch heavy metal scavenger can only achieve a high heavy metal removal rate in neutral or alkaline environments, which requires additional adjustment of the pH in the wastewater during use, thus limiting its application. Summary of the Invention

[0004] To achieve simultaneous and efficient removal of multiple metals from highly acidic wastewater without pre-adjusting the wastewater's pH, this invention provides a method for preparing ethylenediaminetetramethylenephosphonic acid-modified starch, comprising the following steps:

[0005] The starch dispersion solution was mixed with the acid-catalyzed ethylenediaminetetramethylenephosphonic acid solution, and ammonium persulfate was added. The mixture was stirred at a constant temperature under nitrogen protection. After the reaction solution was cooled, ethanol was added to precipitate the grafted product, thus obtaining ethylenediaminetetramethylenephosphonic acid modified starch.

[0006] Based on the above, the starch dispersion solution is prepared by dispersing 0.5g to 2g of starch in 50mL of deionized water.

[0007] Based on the above, the ethylenediaminetetramethylenephosphonic acid solution is prepared by dissolving 0.5g to 2g of ethylenediaminetetramethylenephosphonic acid in 10mL of deionized water and adjusting the pH to 4.0 with dilute sulfuric acid.

[0008] Based on the above, when the starch dispersion solution and the ethylenediaminetetramethylenephosphonic acid solution are mixed, the mass ratio of the starch dispersion solution to the ethylenediaminetetramethylenephosphonic acid solution is 1:(0.5-2).

[0009] Based on the above, the preparation method of the ethylenediaminetetramethylenephosphonic acid modified starch further includes centrifuging the grafted product, washing it sequentially with ethanol and deionized water to remove unreacted ethylenediaminetetramethylenephosphonic acid and ammonium persulfate, and vacuum drying it at 60°C for 12h to 48h to obtain the ethylenediaminetetramethylenephosphonic acid modified starch.

[0010] The present invention also provides an ethylenediaminetetramethylenephosphonic acid modified starch, which is prepared by the above-described preparation method.

[0011] Specifically, the reaction formula for the ethylenediaminetetramethylenephosphonic acid-modified starch is as follows:

[0012]

[0013] The present invention also provides an application of ethylenediaminetetramethylenephosphonic acid modified starch, which can be used as a heavy metal capture agent in industrial wastewater treatment.

[0014] This invention has outstanding substantive features and significant progress compared to the prior art. Specifically, the ethylenediaminetetramethylenephosphonic acid modified starch, its preparation method, and its application provided by this invention analyze the characteristics of starch and ethylenediaminetetramethylenephosphonic acid. Utilizing the characteristic that starch is composed of glucose units linked by α-1,4 and α-1,6 glycosidic bonds, and that each glucose unit contains three free hydroxyl groups at the C2, C3, and C6 positions, which can act as nucleophiles, this ensures that during the grafting reaction with ethylenediaminetetramethylenephosphonic acid, the hydroxyl groups (-OH) of starch attack the phosphorus atoms of the phosphonic acid groups, leading to dehydration condensation, forming phosphonate ester bonds (POC), and releasing water molecules. Ultimately, this yields a natural polymer-based metal scavenger capable of removing heavy metals from industrial wastewater.

[0015] Specifically, by pre-treating ethylenediaminetetramethylenephosphonic acid with H2SO4 or HCl, the four phosphonic acid groups (-PO3H2) in ethylenediaminetetramethylenephosphonic acid are protonated to -PO3H3. + The oxygen atom in the phosphonate group can still provide a lone pair of electrons, which can combine with heavy metal ions through coordinate bonds to form M.2+ The ←:O-PO3H2 structure enhances electrophilicity, ensuring the formation of a robust polymer structure during grafting with starch.

[0016] Simultaneously, the hydroxyl groups produced by starch hydrolysis can form an OH···O=P hydrogen bond network with phosphonic acid groups, exposing more coordination sites. Furthermore, the acidic environment promotes the cleavage of starch glycosidic bonds, disrupting the starch crystalline region and generating a large number of short-chain dextrin or glucose units, exposing internally grafted EDTMPs, increasing the accessibility of phosphonic acid groups, and producing more free hydroxyl groups, enhancing the hydrogen bond network and hydrophilicity, facilitating the diffusion of heavy metals to active sites. This achieves the goal of simultaneous and efficient removal of multiple metals in strongly acidic wastewater without the need for pre-adjusting the wastewater pH. Attached Figure Description

[0017] Figures 1 to 9 The present invention describes the removal rates of iron, zinc, nickel, and manganese by ethylenediaminetetramethylenephosphonic acid modified starch under different sulfuric acid concentrations and temperatures.

[0018] Figure 10 The infrared spectrum of ethylenediaminetetramethylenephosphonic acid-modified starch provided by this invention.

[0019] Figure 11 The NMR spectrum of starch modified with ethylenediaminetetramethylenephosphonic acid provided by this invention is shown. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0021] Example

[0022] This embodiment provides a method for preparing ethylenediaminetetramethylenephosphonic acid modified starch, the specific steps of which include:

[0023] Disperse 5g of starch in 50mL of deionized water; dissolve 3g of ethylenediaminetetramethylenephosphonic acid in 30mL of deionized water, and adjust the pH to 4.0 with dilute sulfuric acid to avoid hydrolysis of phosphonic acid groups.

[0024] The starch dispersion was mixed with the ethylenediaminetetramethylenephosphonic acid solution catalyzed by dilute sulfuric acid at a mass ratio of 1:1. Ammonium persulfate was added as an initiator, and the mixture was stirred at a constant temperature of 70°C for 6 hours under nitrogen protection, while maintaining the pH at 7.0.

[0025] After the reaction solution was cooled, ethanol was added to precipitate the grafted product. The product was centrifuged at 8000 rpm for 15 min. Finally, it was washed three times with ethanol and deionized water to remove unreacted ethylenediaminetetramethylenephosphonic acid and ammonium persulfate. The product was then vacuum dried at 60 °C for 24 h to obtain a white granular product, which is ethylenediaminetetramethylenephosphonic acid modified starch.

[0026] This embodiment also provides an ethylenediaminetetramethylenephosphonic acid-modified starch prepared by this method, with the following reaction formula:

[0027]

[0028] Specifically, such as Figure 9 and Figure 10 The images shown are the infrared spectrum and nuclear magnetic resonance spectrum of starch modified with ethylenediaminetetramethylenephosphonic acid, respectively. Figure 9 The meanings of the characteristic peaks are as follows: 898: Symmetric stretching vibration of PO in the phosphonic acid group. 1001: Asymmetric vibration of PO. 1209: P=O stretching vibration. 2989: CH vibration from ethylene (-CH2-). 1623: Amide I band (C=O stretching vibration), C=O stretching vibration of acetaminophen (-NHCOCH3). 1540: Amide II band (NH bending + CN stretching), coupled peak of NH bending and CN stretching vibrations of acetaminophen. 1460: CN stretching vibration (amino group), CN stretching vibration of amino group (-NH2), the higher the degree of deacetylation, the more significant this peak. 1151: COC stretching vibration (glycoring skeleton), COC asymmetric stretching vibration of β-(1→4) glycosidic bonds in the sugar ring, a characteristic peak of the chitosan skeleton.

[0029] At the same time, from Figure 10 The 4ppm represents another group of CH2 protons in the piperazine ring. The 5ppm represents the CH2 protons adjacent to the dithiocarboxylic acid group in the piperazine ring.

[0030] That is, from Figure 9 and Figure 10 It can be concluded that acid-catalyzed ethylenediaminetetramethylenephosphonic acid did indeed undergo a grafting reaction with starch, which corroborates the aforementioned reaction process.

[0031] This embodiment also provides an application of ethylenediaminetetramethylenephosphonic acid modified starch, which can be used as a heavy metal capture agent in industrial wastewater treatment to achieve simultaneous and efficient removal of multiple metals in strongly acidic wastewater without the need to pre-adjust the pH value of the wastewater.

[0032] Heavy metal removal test and comparative test

[0033] Heavy metal removal test 1

[0034] To prepare 10% sulfuric acid: First, add approximately 150 mL of deionized water to a beaker. Accurately measure approximately 11.8 mL of 98% concentrated sulfuric acid using a graduated cylinder. Slowly pour the concentrated sulfuric acid into the water along a glass rod, stirring constantly.

[0035] Take 50 mg of ferrous sulfate heptahydrate, 49.54 mg of zinc sulfate heptahydrate, 44.76 mg of nickel sulfate hexahydrate, 30.78 mg of manganese sulfate monohydrate, and 58.27 mg of chromium sulfate hydrate respectively into the prepared sulfuric acid (the mother liquor contains 50 mg / L of iron, 100 mg / L of zinc, 50 mg / L of nickel, and 50 mg / L of manganese).

[0036] Pour the prepared mother liquor into a flask, add the ethylenediaminetetramethylenephosphonic acid modified starch provided in this embodiment as a metal scavenging agent, place it in a water bath and set the temperature to 25°C, stir quickly for 5 minutes and then stir slowly for 10 minutes.

[0037] After the reaction is complete, let it stand for 30 minutes, and take the supernatant to detect the concentration of iron, nickel, chromium, manganese and zinc metals in the solution.

[0038] The results are as follows Figure 1 As shown, the removal rates of each metal were finally calculated as follows: iron: 94%, nickel: 93%, chromium: 94%, manganese: 90%, zinc: 95%.

[0039] Heavy metal removal test 2

[0040] Experiment 2 followed a similar procedure to Experiment 1, except that the prepared mother liquor was poured into a flask, placed in a water bath at 35°C, and stirred rapidly for 5 minutes followed by slow stirring for 20 minutes. After the reaction was complete, the mixture was allowed to stand for 30 minutes, and the supernatant was collected to determine the concentrations of iron, nickel, chromium, manganese, and zinc in the solution.

[0041] The results are as follows Figure 2 As shown, the removal rates of each metal were finally calculated as follows: iron: 96%, nickel: 94%, chromium: 95%, manganese: 91%, zinc: 95%.

[0042] Heavy metal removal test three

[0043] Experiment 3 follows roughly the same steps as Experiment 1, except that in Experiment 3, 20% sulfuric acid is prepared: First, add approximately 150 mL of deionized water to a beaker. Accurately measure approximately 25 mL of 98% concentrated sulfuric acid using a graduated cylinder. Slowly pour the concentrated sulfuric acid along a glass rod into the water while stirring.

[0044] After the reaction is complete, let it stand for 30 minutes, and take the supernatant to detect the concentration of iron, nickel, chromium, manganese and zinc metals in the solution.

[0045] The results are as follows Figure 3As shown, the removal rates of each metal were finally calculated as follows: iron: 91%, nickel: 85%, chromium: 87%, manganese: 85%, zinc: 88%.

[0046] Heavy metal removal test four

[0047] Experiment 4 followed a similar procedure to Experiment 1, the difference being that the heavy metal concentrations in the mother liquor were as follows: iron: 100 mg / L, zinc: 50 mg / L, nickel: 100 mg / L, and manganese: 150 mg / L. After the reaction was complete, the solution was allowed to stand for 30 minutes, and the supernatant was collected to determine the concentrations of iron, nickel, chromium, manganese, and zinc. The results are as follows: Figure 4 As shown.

[0048] Heavy metal removal test five

[0049] Experiment 5 followed largely the same steps as Experiment 2, the difference being that the heavy metal concentrations in the mother liquor in Experiment 5 were: iron: 100 mg / L, zinc: 50 mg / L, nickel: 100 mg / L, and manganese: 150 mg / L. After the reaction was complete, the solution was allowed to stand for 30 minutes, and the supernatant was collected to determine the concentrations of iron, nickel, chromium, manganese, and zinc. The results are as follows: Figure 5 As shown.

[0050] Heavy metal removal test six

[0051] Experiment 6 followed largely the same steps as Experiment 3, the difference being that the heavy metal concentrations in the mother liquor in Experiment 5 were: iron: 100 mg / L, zinc: 50 mg / L, nickel: 100 mg / L, and manganese: 150 mg / L. After the reaction was complete, the solution was allowed to stand for 30 minutes, and the supernatant was collected to determine the concentrations of iron, nickel, chromium, manganese, and zinc. The results are as follows: Figure 6 As shown.

[0052] Heavy metal removal test seven

[0053] Experiment 7 followed a similar procedure to Experiment 1, except that the heavy metal concentrations in the mother liquor in Experiment 4 were: 150 mg / L for zinc, 150 mg / L for nickel, and 50 mg / L for manganese. After the reaction was complete, the solution was allowed to stand for 30 minutes, and the supernatant was collected to determine the concentrations of iron, nickel, chromium, manganese, and zinc. The results are as follows: Figure 7 As shown.

[0054] Heavy metal removal test eight

[0055] Experiment 8 followed largely the same steps as Experiment 2, the difference being that the heavy metal concentrations in the mother liquor in Experiment 5 were: 150 mg / L for zinc, 150 mg / L for nickel, and 50 mg / L for manganese. After the reaction was complete, the solution was allowed to stand for 30 minutes, and the supernatant was collected to determine the concentrations of iron, nickel, chromium, manganese, and zinc. The results are as follows: Figure 8 As shown.

[0056] Heavy metal removal test nine

[0057] Experiment Nine followed a similar procedure to Experiment Three, the main difference being that in Experiment Five, the heavy metal concentrations in the mother liquor were: 150 mg / L for zinc, 150 mg / L for nickel, and 50 mg / L for manganese. After the reaction was complete, the solution was allowed to stand for 30 minutes, and the supernatant was collected to determine the concentrations of iron, nickel, chromium, manganese, and zinc. The results are as follows: Figure 9 As shown.

[0058] Comparative Experiment 1

[0059] The procedures for Comparative Experiment 1 and Heavy Metal Removal Experiment 1 were largely the same, except that starch was used as the heavy metal scavenging agent in Comparative Experiment 1. After the reaction was completed, the mixture was allowed to stand for 30 minutes, and the supernatant was taken to detect the concentrations of iron, nickel, chromium, manganese, and zinc in the solution. Finally, the removal rates of each metal were calculated: iron: 69%, nickel: 57%, chromium: 35%, manganese: 60%, and zinc: 25%.

[0060] Comparative Experiment 2

[0061] The procedures for Comparative Experiment 2 and Comparative Experiment 1 were largely the same, except that Comparative Experiment 1 used ethylenediaminetetramethylenephosphonic acid (EDTA) as the heavy metal scavenging agent. After the reaction was completed, the mixture was allowed to stand for 30 minutes, and the supernatant was collected to determine the concentrations of iron, nickel, chromium, manganese, and zinc in the solution. The removal rates for each metal were calculated as follows: iron: 20%, nickel: 20%, chromium: 38%, manganese: 25%, and zinc: 18%.

[0062] Therefore, the ethylenediaminetetramethylenephosphonic acid-modified starch provided by this invention achieves simultaneous and efficient removal of multiple metals from strongly acidic wastewater without the need for pre-adjustment of the wastewater pH. Compared with ungrafted ethylenediaminetetramethylenephosphonic acid and ungrafted starch, it significantly improves the removal rate of various heavy metals.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for preparing ethylenediaminetetramethylenephosphonic acid modified starch, comprising the following steps: The starch dispersion solution was mixed with the acid-catalyzed ethylenediaminetetramethylenephosphonic acid solution, and ammonium persulfate was added. The mixture was then stirred at a constant temperature under nitrogen protection. After the reaction solution was cooled, ethanol was added to precipitate the grafted product, yielding ethylenediaminetetramethylenephosphonic acid modified starch.

2. The method for preparing ethylenediaminetetramethylenephosphonic acid modified starch according to claim 1, characterized in that: The starch dispersion solution was prepared by dispersing 0.5g to 2g of starch in 50 mL of deionized water.

3. The method for preparing ethylenediaminetetramethylenephosphonic acid modified starch according to claim 2, characterized in that: The ethylenediaminetetramethylenephosphonic acid solution was prepared by dissolving 0.5g to 2g of ethylenediaminetetramethylenephosphonic acid in 10 mL of deionized water and adjusting the pH to 4.0 with dilute sulfuric acid.

4. The method for preparing ethylenediaminetetramethylenephosphonic acid modified starch according to claim 3, characterized in that: When the starch dispersion solution is mixed with the ethylenediaminetetramethylenephosphonic acid solution, the mass ratio of the starch dispersion solution to the ethylenediaminetetramethylenephosphonic acid solution is 1:(0.5-2).

5. The method for preparing ethylenediaminetetramethylenephosphonic acid modified starch according to claim 4, characterized in that: The process also includes centrifuging the grafted product, washing it sequentially with ethanol and deionized water to remove unreacted ethylenediaminetetramethylenephosphonic acid and ammonium persulfate, and then vacuum drying it at 60°C for 12-48 hours to obtain the ethylenediaminetetramethylenephosphonic acid modified starch.

6. A starch modified with ethylenediaminetetramethylenephosphonic acid, characterized in that: The ethylenediaminetetramethylenephosphonic acid modified starch is prepared by the preparation method described in any one of claims 1 to 5.

7. An application of the ethylenediaminetetramethylenephosphonic acid modified starch according to claim 6, characterized in that: This ethylenediaminetetramethylenephosphonic acid-modified starch can be used as a heavy metal capture agent in industrial wastewater treatment.

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