Preparation method of a complex of high-efficiency chelated metal ions and application thereof

Abstract

The application belongs to the technical field of complex preparation, and discloses a preparation method and application of a complex for efficiently chelating metal ions, which comprises the following steps: S1, weighing each raw material; S2, preparing a polyvinyl alcohol solution, and adding all raw materials except an initiator into the polyvinyl alcohol solution to prepare a mixed solution by stirring and mixing; S3, adding the initiator into the mixed solution after cooling to prepare an intermediate solution by stirring; and S4, performing a dialysis on the intermediate solution to obtain a complex PVA-g-EDDS. The application modifies polyvinyl alcohol by modifying ethylenediamine disuccinic acid on the surface of a film, so as to obtain PVA-g-EDDS. The PVA-g-EDDS has multiple strong chelating sites on a molecular chain, can treat metal ion wastewater with high concentration, and is also effective in chelating metal ions for low-concentration wastewater. After chelation, the molecular weight is increased, so that the metal chelate is intercepted by the film, and the wastewater treatment efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of complex preparation, and particularly relates to a preparation method of a complex for efficiently chelating metal ions and application of the complex. BACKGROUND

[0002] The pollution and damage of heavy metals to the natural environment are quite serious, and a large amount of waste liquid and waste residue generated in industry contains a large amount of heavy metal ions. If not properly treated, the heavy metal ions cannot be eliminated from the environment, and even secondary pollution to the environment will be caused. For example, in the production of batteries, electroplating and nuclear industry, waste liquid and waste residue containing high-radioactive metal ions need to explore an effective green purification treatment technology.

[0003] At present, industrial waste containing heavy metals is treated by simple landfill method or ordinary chemical precipitation method, i.e. treated by EDTA, DTPA, NTA and other chelating agents and then precipitated. Although the ground pollution source can be temporarily eliminated, the traditional chelating agents have poor biodegradability and certain toxicity, and the damage to underground water sources or underground microbial environment is irreversible. Membrane treatment is a very promising method, which has the advantages of high efficiency, low composition and recyclability, but also has the limitations of selectivity and the polymers must have chemical stability, high affinity to target metal cations and low affinity to ultrafiltration membranes. Therefore, developing new and affordable chelating agents to enhance the "high efficiency and green" characteristics of the chelating extraction of metal ions in the membrane treatment process is a hot issue in this field. However, the cellulose filter membrane widely used in the market has very low treatment efficiency for high or low concentration of heavy metal wastewater. For high concentration of heavy metal wastewater, multi-stage membrane treatment is needed to make the effluent meet the standard, otherwise it is easy to cause the accumulation of metal hydroxide, greatly reducing the service life. And for low concentration of heavy metal wastewater, due to the concentration difference effect and small metal ion particle size, the low concentration of metal ions easily penetrates the filter membrane, resulting in failure of heavy metal interception. SUMMARY

[0004] In order to solve the problems in the prior art, the present application discloses a preparation method of a complex for efficiently chelating metal ions and application of the complex.

[0005] The application discloses a preparation method of a complex for efficiently chelating metal ions, which comprises the following steps of S1: taking ethylenediamine disuccinic acid as a reference substance, polyvinyl alcohol, ethylenediamine disuccinic acid, a catalyst and a reaction medium have different molar ratios with the ethylenediamine disuccinic acid respectively, a certain amount of ethylenediamine disuccinic acid is weighed, polyvinyl alcohol solutions are configured according to the molar ratios with the ethylenediamine disuccinic acid respectively, and the ethylenediamine disuccinic acid, the catalyst and the reaction medium are weighed S2: the weighed ethylenediamine disuccinic acid, the catalyst and the reaction medium are added into the polyvinyl alcohol solution to be stirred and mixed at a certain temperature, so that a mixed solution is obtained S3: after the mixed solution is naturally cooled to a certain temperature, the temperature is kept, a certain amount of an initiator is gradually added into the mixed solution to be stirred in a certain reaction time, so that an intermediate solution is obtained S4: the intermediate solution is dialyzed for a period of time, so that the complex PVA-g-EDDS is obtained.

[0006] Further, the catalyst in S2 is triphenylphosphine, and the reaction medium is dimethyl sulfoxide.

[0007] Further, the molar ratio between the polyvinyl alcohol and the ethylenediamine disuccinic acid ranges from 2 to 1, the molar ratio between the triphenylphosphine and the ethylenediamine disuccinic acid ranges from 0.1 to 1.1, and the molar ratio between the diethyl azodicarboxylate and the ethylenediamine disuccinic acid ranges from 0.5 to 2.5.

[0008] Further, the mixing temperature in S2 is 80-140 DEG C, the temperature in S3 is reduced to 20-60 DEG C, and the reaction time is 2-12h.

[0009] Further, the temperature in S3 is reduced to 30-40 DEG C, and the reaction time is 2-4h.

[0010] Further, the prepared PVA-g-EDDS is dialyzed by using a dialysis membrane, the molecular weight cut-off of the dialysis membrane is 500-2000 Da, and the dialysis time is 1-3 days.

[0011] The application discloses the application of the complex for efficiently chelating metal ions, and the application of any one of the prepared PVA-g-EDDS comprises the following steps of:

[0012] The PVA-g-EDDS is applied to membrane filtration of cobalt ions, nickel ions, copper ions, zinc ions, lead ions, zinc ions, calcium ions and manganese ions in wastewater.

[0013] Further, the PVA-g-EDDS is applied to treatment of wastewater by combining an ultrafiltration membrane, and the transmembrane pressure is set to be 0.1-2.0 bar.

[0014] The application has the following beneficial effects:

[0015] The present application is based on the principle of coordination chemistry, and the biocompatibility and non-toxic polyvinyl alcohol is chemically modified by modifying the surface of the membrane with ethylenediamine disuccinic acid, thereby obtaining a new water-soluble polymer, which is called PVA-g-EDDS. The present application improves the retention of metal ions by adding PVA-g-EDDS in wastewater. The high molecular chelating agent has multiple strong chelating sites on a molecular chain, and can treat wastewater with high concentration of metal ions. At the same time, for low concentration wastewater, it is also effective to chelate metal ions, and after chelation, the molecular weight is increased, so that the metal chelate is retained by the membrane, greatly improving the wastewater treatment efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The flow chart of the preparation method of the complex for efficiently chelating metal ions in the embodiments of the present application. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the present application, the technical solutions in the specific embodiments of the present application will be clearly and completely described below.

[0018] The application discloses a preparation method of a complex of high-efficiency metal ion chelation, which comprises the following steps: S1, taking ethylenediamine disuccinic acid as a reference, polyvinyl alcohol, ethylenediamine disuccinic acid, a catalyst and a reaction medium have different molar ratios with ethylenediamine disuccinic acid respectively, a certain amount of ethylenediamine disuccinic acid is weighed, polyvinyl alcohol solution is configured according to the molar ratio with ethylenediamine disuccinic acid respectively, and ethylenediamine disuccinic acid, the catalyst and the reaction medium are weighed; S2, the weighed ethylenediamine disuccinic acid, the catalyst and the reaction medium are added into the polyvinyl alcohol solution to be stirred and mixed at a certain temperature, so that a mixed solution is obtained; S3, after the mixed solution is naturally cooled to a certain temperature, the temperature is kept, a certain amount of an initiator is gradually added into the mixed solution to be stirred in a certain reaction time, so that an intermediate solution is obtained; and S4, the intermediate solution is dialyzed for a period of time, so that the complex PVA-g-EDDS is obtained. According to the coordination chemistry principle, the polyvinyl alcohol with biocompatibility and non-toxicity is chemically modified by being modified on the membrane surface with ethylenediamine disuccinic acid, so that a new water-soluble polymer, namely PVA-g-EDDS, is obtained. The PVA-g-EDDS is added into wastewater to improve the interception of metal ions. The high-molecular chelating agent has multiple strong chelating sites on a molecular chain, and can treat wastewater with high-concentration metal ions. Meanwhile, the high-molecular chelating agent is also effective in chelating metal ions in wastewater with low concentration, and the chelation increases the molecular weight, so that the metal chelate is intercepted by a membrane, and the wastewater treatment efficiency is greatly improved. Compared with a traditional EDTA chelating agent, the EDDS can be decomposed more environmentally friendly, and there is no environmental pollution problem, and the EDDS is easier to combine with metal ions, so that the chelating capacity of the oligomeric PVA is greatly improved. Meanwhile, the EDDS has the recyclable property, and is more economic and environmentally friendly.

[0019] As an implementation form, the catalyst in S2 is triphenylphosphine, the reaction medium is dimethyl sulfoxide, and the initiator in S3 is diethyl azodicarboxylate. The triphenylphosphine can effectively activate the initiator diethyl azodicarboxylate, so as to promote the generation of free radicals, improve the reaction activity, achieve a good reaction rate at a lower temperature, reduce energy consumption and reduce the possibility of side reactions. The dimethyl sulfoxide is a polar aprotic solvent, has good dissolving performance, can well dissolve diethyl azodicarboxylate, triphenylphosphine and other reaction components, and ensures that the reaction substances are fully contacted and uniformly mixed. The diethyl azodicarboxylate can be decomposed to generate two free radicals under the condition of heating. By controlling the temperature and the adding rate, the generation speed of the free radicals can be effectively managed, so as to finely control the reaction process.

[0020] As an implementation form, the molar ratio between the polyvinyl alcohol and the ethylenediamine disuccinic acid ranges from 2 to 1, the molar ratio between the triphenylphosphine and the ethylenediamine disuccinic acid ranges from 0.1 to 1.1, and the molar ratio between the diethyl azodicarboxylate and the ethylenediamine disuccinic acid ranges from 0.5 to 2.5.

[0021] By adjusting the molar ratio between polyvinyl alcohol and ethylenediamine disuccinic acid, an appropriate amount of ethylenediamine disuccinic acid groups can be introduced onto the polyvinyl alcohol chains, thereby improving the grafting efficiency. If the molar ratio is too low, close to 1:1, there are not enough grafting sites on the polyvinyl alcohol chains to accommodate enough EDDS. If the molar ratio is too high, close to 2:1, it will lead to excessive polyvinyl alcohol competing with ethylenediamine disuccinic acid, affecting the grafting effect. The amount of triphenylphosphine as catalyst directly affects the activity of the reaction. The appropriate molar ratio can ensure that the reaction is neither too violent nor too slow, thereby better controlling the reaction rate. If the amount of triphenylphosphine is too small, it cannot effectively activate the initiator, leading to incomplete reaction, and if the amount of triphenylphosphine is too large, it will initiate unnecessary side reactions. Therefore, selecting the appropriate molar ratio can maximize the reduction of byproduct generation. The ratio of azobisdimethylvaleronitrile to ethylenediamine disuccinic acid helps to balance the kinetics of the reaction, avoiding reaction runaway due to too high or too low radical concentration. Too high radical concentration leads to polyvinyl alcohol chain breakage, while too low concentration makes the reaction progress slowly.

[0022] As an embodiment, the mixing temperature in S2 is 80-140℃, and the temperature is reduced to 20-60℃ in S3, and the reaction time is 2-12h. Preferably, the temperature is reduced to 30-40℃ in S3, and the reaction time is 2-4h. Higher temperature can accelerate the diffusion between reactants, promote the interaction between polyvinyl alcohol and ethylenediamine disuccinic acid, and thus speed up the grafting reaction. This means that more chemical reactions can be completed in a shorter time, improving production efficiency. Heating can increase the kinetic energy of molecules, making it easier for reactant molecules to collide and react, thereby increasing the overall reaction activity. This is particularly important for chemical reactions that require higher energy to start. Reducing the temperature in S3 can better control the reaction rate, avoiding side reactions or over-reactions due to excessive temperature. By gradually adding the initiator and reacting at a lower temperature, it can ensure that the reaction is carried out in a more gentle environment. Lower temperature helps to reduce the generation of byproducts, thereby improving the purity of the product. In addition, appropriate temperature can prevent excessive crosslinking or breakage of polyvinyl alcohol chains, ensuring that the product has good structural stability and expected performance. Compared with high-temperature reactions, low-temperature reactions generally require less energy input, which can save energy consumption and reduce production costs. Longer reaction time can ensure that reactants have enough time to interact, thereby achieving higher conversion rate. This helps to improve the yield of the product, ensuring that most of the raw materials are fully utilized. However, too long reaction time will lead to unnecessary energy consumption and increased production costs. A reaction time of 2-4 hours can balance the sufficiency of the reaction and production efficiency, ensuring high-quality products in a shorter time.

[0023] As an embodiment, the finally prepared PVA-g-EDDS is dialyzed using a dialysis membrane with a molecular weight cut-off of 500-2000 Da for 1-3 days. Preferably, the dialysis membrane has a molecular weight cut-off of 800-1200 Da and the dialysis time is 2 days. The dialysis membrane can selectively allow small molecules to pass through according to its molecular weight cut-off, while preventing large molecules from passing through. Therefore, by dialysis, small molecular by-products generated during synthesis can be effectively removed, improving the purity of the product. A molecular weight cut-off of 500-2000 Da can ensure that the large molecular structure of PVA-g-EDDS is not damaged, while removing unnecessary small molecules, thereby protecting the integrity and functionality of the product. The dialysis time is 1-3 days, which can be adjusted according to actual conditions to ensure that small molecular impurities are completely removed, while avoiding resource waste caused by excessive dialysis. Longer dialysis time can further improve the purity of the product. Selecting a molecular weight cut-off of 800-1200 Da can more accurately remove unnecessary small molecular impurities, while ensuring that the large molecular structure of PVA-g-EDDS is not affected. This selectivity helps to improve the purity and quality of the product.

[0024] The present application discloses the application of a complex that efficiently chelates metal ions, using any of the PVA-g-EDDS prepared as described above, which includes: PVA-g-EDDS is used for membrane filtration of cobalt ions, nickel ions, copper ions, zinc ions, lead ions, zinc ions, calcium ions and manganese ions in wastewater.

[0025] As an embodiment, PVA-g-EDDS is used in combination with ultrafiltration membrane to treat wastewater, and the transmembrane pressure is set to 0.1-2.0 bar. Preferably, the transmembrane pressure is set to 0.5-0.8 bar.

[0026] Example:

[0027] Example 1

[0028] First, weigh 3.65 g of ethylenediamine disuccinic acid, according to the molar ratio range of polyvinyl alcohol to ethylenediamine disuccinic acid of 2-1, the molar ratio range of triphenylphosphine to ethylenediamine disuccinic acid of 0.1-1.1, the molar ratio range of azobisdimethylvaleric acid diethyl ester to ethylenediamine disuccinic acid of 0.5-2.5, weigh 3.28 g of triphenylphosphine, 4.35 g of azobisdimethylvaleric acid diethyl ester and prepare a polyvinyl alcohol solution with DMSO as the solvent.

[0029] A solution of polyvinyl alcohol (500 mg, 10 mL DMSO, 11.4 mmol, 1 eq) was added to a mixture containing triphenylphosphine (3.28 g, 12.5 mmol, 1.1 eq), ethylenediamine disuccinic acid (3.65 g, 12.5 mmol, 1.1 eq) and 50 mL of dimethyl sulfoxide (DMSO) at 120 °C. Diethyl azodicarboxylate (4.35 g, 25 mmol, 2.2 eq) was added gradually over 2 hours at 30 °C. The resulting solution was then stirred overnight at room temperature. The reaction medium was transferred to a dialysis tube (MWCO ~ 1000 Da) and dialyzed against DMSO for two days to remove all the organic components except the functionalized polymer. Finally, dialysis was performed against water to remove all the DMSO and the yield of PVA-g-EDDS was 90%.

[0030] First, a solid sample was prepared: a weighed amount of metal ions (Co2+, Ni2+, Cs+) was taken and the chelating agent was weighed according to a 1 :4 molar ratio between metal cations and EDDS.

[0031] The weighed chelating agent was dissolved in water and the metal cation solution was added. The mixture was stirred at room temperature for three hours and then filtered using a ceramic membrane (Aldrich, MWCO = 20 kDa) at a transmembrane pressure of 0.5 bar. Filtration was stopped when the permeate represented 15% of the total solution. The filtrate was analyzed by ICP-MS. The results showed a complexation adsorption rate of 96% for Ni(II) and 86% for Co(II).

[0032] Example 2

[0033] The PVA-g-EDDS of Example 1 was used as chelating agent;

[0034] First, a solid sample was prepared: a weighed amount of metal ions (Co2+, Ni2+, Cs+) was taken and the chelating agent was weighed according to a 1 :4 molar ratio between metal cations and EDDS.

[0035] The weighed chelating agent was dissolved in water and the metal cation solution was added. The mixture was stirred at room temperature for three hours and then filtered using a ceramic membrane (Aldrich, MWCO = 20 kDa) at a transmembrane pressure of 0.5 bar. Filtration was stopped when the permeate represented 15% of the total solution. The filtrate was analyzed by ICP-MS. The results showed a complexation adsorption rate of 96% for Ni(II) and 86% for Co(II).

[0036] Example 3

[0037] The PVA-g-EDDS of Example 1 was used as chelating agent;

[0038] Firstly, solid samples were prepared: firstly, a quantitative amount of metal ions (Co2+, Ni2+) was weighed, and then the chelating agent was weighed according to the molar ratio of metal cations to EDDS of 1:1.

[0039] The weighed chelating agent was dissolved in water, and then the metal cations were added. The mixture was stirred at room temperature for three hours, and finally filtered using a ceramic membrane (Aldrich, MWCO = 20 kDa) with a transmembrane pressure of 0.5 bar. The filtration was stopped when the permeate accounted for 15% of the total solution. The filtrate was analyzed by ICP-MS. The test results showed that the complex adsorption rate of Ni(II) was 50%, and that of Co(II) was 35%.

[0040] Example 4

[0041] The PVA-g-EDDS of Example 1 was used as the chelating agent.

[0042] Firstly, solid samples were prepared: firstly, a quantitative amount of metal ions (Pb(II), Cu(II), Cd(II), Zn(II)) was weighed, and then the chelating agent was weighed according to the molar ratio of metal cations to EDDS of 1:4.

[0043] The weighed chelating agent was dissolved in water, and then the metal cations were added. The mixture was stirred at room temperature for three hours, and finally filtered using a ceramic membrane (Aldrich, MWCO = 20 kDa) with a transmembrane pressure of 0.5 bar. The filtration was stopped when the permeate accounted for 15% of the total solution. The filtrate was analyzed by ICP-MS. The test results showed that the complex adsorption rate was greater than 97%.

[0044] Example 5

[0045] The PVA-g-EDDS of Example 1 was used as the chelating agent.

[0046] Firstly, solid samples were prepared: firstly, a quantitative amount of metal ions (Pb(II), Cu(II), Cd(II), Zn(II)) was weighed, and then the chelating agent was weighed according to the molar ratio of metal cations to EDDS of 1:2.

[0047] The weighed chelating agent was dissolved in water, and then the metal cations were added. The mixture was stirred at room temperature for three hours, and finally filtered using a ceramic membrane (Aldrich, MWCO = 20 kDa) with a transmembrane pressure of 0.5 bar. The filtration was stopped when the permeate accounted for 15% of the total solution. The filtrate was analyzed by ICP-MS. The test results showed that the complex adsorption rate was greater than 97%.

[0048] Example 6

[0049] The PVA-g-EDDS of Example 1 was used as the chelating agent.

[0050] Firstly, solid samples were prepared: firstly, a quantitative amount of metal ions (Pb(II), Cu(II), Cd(II), Zn(II)) was weighed, and then the chelating agent was weighed according to the molar ratio of metal cations to EDDS of 1 : 1.

[0051] The weighed chelating agent was dissolved in water, and then the metal cations were added. The mixture was stirred at room temperature for one hour, and finally filtration was performed using a ceramic membrane (Aldrich, MWCO = 20 kDa) at a transmembrane pressure of 0.5 bar. Filtration was stopped when the permeate accounted for 15% of the total solution. The filtrate was analyzed by ICP-MS. The results of the detection showed that the complex adsorption rates of Cd(II) were 0%, Zn(II) were 0%, Pb(II) were 50%, and Cu(II) were 96%.

[0052] Example 7

[0053] PVA-g-EDDS of Example 1 was used as the chelating agent;

[0054] Firstly, solid samples were prepared: firstly, a quantitative amount of metal ions (Pb(II), Cu(II), Ca(II), Mn(II) was weighed, and then the chelating agent was weighed according to the molar ratio of metal cations to EDDS of 1 : 1.

[0055] The weighed chelating agent was dissolved in water, and then the metal cations were added. The mixture was stirred at room temperature for three hours, and finally filtration was performed using a ceramic membrane (Aldrich, MWCO = 20 kDa) at a transmembrane pressure of 0.5 bar. Filtration was stopped when the permeate accounted for 15% of the total solution. The filtrate was analyzed by ICP-MS. The results of the detection showed that the complex adsorption rates of Cu(II) were 96%, and Pb(II) were 50%.

[0056] Comparative Example 1

[0057] EDTA with a concentration of 1% was used as the chelating agent;

[0058] Firstly, solid samples were prepared: firstly, a quantitative amount of metal ions (Co2+2+) was weighed, and then the chelating agent was weighed according to the molar ratio of metal cations to EDTA of 1 : 4.

[0059] The weighed chelating agent was dissolved in water, and then the metal cation solution was added. The mixture was stirred at room temperature for three hours, and finally filtration was performed using a ceramic membrane (Aldrich, MWCO = 20 kDa) at a transmembrane pressure of 0.5 bar. Filtration was stopped when the permeate accounted for 15% of the total solution. The filtrate was analyzed by ICP-MS. The results of the detection showed that the complex adsorption rate of Co(II) was 72%.

[0060] Comparative Example 2

[0061] EDTA with a concentration of 1% was used as the chelating agent;

[0062] First, prepare a solid sample: First, weigh out a certain amount of metal ions (Co2+, Ni). 2 +、Cs+), and then weigh the chelating agent according to the molar ratio of metal cations to EDTA of 1:4; dissolve the weighed chelating agent in water, and then add the metal cation solution. The mixture is stirred at room temperature for three hours. Finally, filter using a ceramic membrane (Aldrich, MWCO = 20 kDa) with a transmembrane pressure of 0.5 bar; stop filtration when the permeate accounts for 15% of the total solution, and analyze the filtrate by ICP-MS; the results show that the complexation adsorption rate of Ni(II) is 82% and that of Co(II) is 71%.

[0063] Comparative Example 3:

[0064] Use 1% DTPA as a chelating agent;

[0065] First, prepare a solid sample: First, weigh out a certain amount of metal ions (Co2+, Ni2+), and then weigh out the chelating agent according to the molar ratio of metal cations to DTPA of 1:1.

[0066] The weighed chelating agent was dissolved in water, and then metal cations were added. The mixture was stirred at room temperature for three hours. Finally, filtration was performed using a ceramic membrane (Aldrich, MWCO = 20 kDa) at a transmembrane pressure of 0.5 bar. Filtration was stopped when the permeate accounted for 15% of the total solution. The filtrate was analyzed by ICP-MS. The results showed that the complexation adsorption rate of Ni(II) was 37%, and that of Co(II) was 31%.

[0067] Comparative Example 4:

[0068] Use 0.5% NTA as a chelating agent;

[0069] First, prepare a solid sample: First, weigh out a certain amount of metal ions (Pb(II), Cu(II), Cd(II), Zn(II)), and then weigh out the chelating agent according to the molar ratio of metal cation to NTA of 1:4.

[0070] The weighed chelating agent was dissolved in water, and then metal cations were added. The mixture was stirred at room temperature for three hours. Finally, filtration was performed using a ceramic membrane (Aldrich, MWCO = 20 kDa) at a transmembrane pressure of 0.5 bar. Filtration was stopped when the permeate accounted for 15% of the total solution. The filtrate was analyzed by ICP-MS. The results showed that the complexation adsorption rate was greater than 72%.

[0071] Results analysis:

[0072] From Examples 1-7, it can be seen that PVA-g-EDDS can treat wastewater with high concentration of metal ions, and effectively chelate metal ions, increase molecular weight, and make the metal chelate membrane retained. In the treatment of wastewater with high concentration of metal ions, PVA-g-EDDS shows high metal ion retention efficiency. Even in the treatment of low concentration wastewater, PVA-g-EDDS can still effectively chelate metal ions and increase the molecular weight of metal chelates to be retained by membrane.

[0073] From the comparison of Examples 1-4 and Comparative Examples 1-4, it can be seen that traditional chelating agents such as EDTA, DTPA and NTA are used. These traditional chelating agents usually have only one chelating site, and have limited ability to treat high concentration and low concentration wastewater. In the treatment of high concentration metal ion wastewater, traditional chelating agents cannot completely chelate all metal ions, resulting in low treatment efficiency. In the treatment of low concentration wastewater, the efficiency of traditional chelating agents is also limited, and they cannot effectively increase the molecular weight of metal chelates to be retained by membrane. PVA-g-EDDS shows high metal ion retention efficiency in the treatment of high concentration wastewater, because it has multiple chelating sites and can effectively chelate a large amount of metal ions. Traditional chelating agents cannot completely chelate all metal ions in the treatment of high concentration wastewater, resulting in lower efficiency than PVA-g-EDDS. PVA-g-EDDS shows high metal ion retention efficiency in the treatment of high concentration and low concentration wastewater, which is mainly due to its multiple strong chelating sites on the molecular chain, which can effectively chelate metal ions and increase the molecular weight of metal chelates to be retained by membrane. The efficiency of traditional chelating agents such as EDTA, DTPA and NTA in the treatment of high concentration and low concentration wastewater is relatively low, especially in the treatment of low concentration wastewater, traditional chelating agents cannot effectively increase the molecular weight of metal chelates to be retained by membrane. Therefore, PVA-g-EDDS as a high molecular chelating agent has significant advantages in wastewater treatment, which can significantly improve the retention efficiency of metal ions, especially in the treatment of high concentration and low concentration wastewater.

[0074] It should be understood that for those skilled in the art, modifications or changes can be made according to the above description, and all these modifications and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A method for preparing a complex that efficiently chelates metal ions, characterized in that, include: S1: Weigh out ethylenediamine disuccinic acid, polyvinyl alcohol, catalyst and reaction medium; S2: At a certain temperature, the weighed ethylenediamine disuccinic acid, catalyst and reaction medium are added to the polyvinyl alcohol solution and stirred to obtain a mixed solution; S3: After the mixed solution is cooled to a certain temperature, the temperature is maintained, and the initiator is gradually added to the mixed solution while stirring for a certain reaction time to obtain an intermediate solution; S4: Dialyze the intermediate solution for a period of time to obtain the complex PVA-g-EDDS.

2. The method for preparing a highly efficient chelating metal ion complex according to claim 1, characterized in that, include: The catalyst in S2 is triphenylphosphine, and the reaction medium is dimethyl sulfoxide; The S3 initiator is diethyl azodicarboxylate.

3. The method for preparing a highly efficient chelating metal ion complex according to claim 2, characterized in that, include: The molar ratio between polyvinyl alcohol and ethylenediamine disuccinic acid is in the range of 2-1; The molar ratio between triphenylphosphine and ethylenediamine disuccinic acid ranges from 0.1 to 1.

1. The molar ratio between diethyl azodicarboxylate and ethylenediaminedisuccinic acid ranges from 0.5 to 2.

5.

4. The method for preparing a highly efficient chelating metal ion complex according to claim 1, characterized in that, include: The mixing temperature in S2 is 80-140℃; In S3, the temperature is lowered to 20-60℃, and the reaction time is 2-12h.

5. The method for preparing a highly efficient chelating metal ion complex according to claim 4, characterized in that, include: In S3, the temperature is lowered to 30-40℃, and the reaction time is 2-4 hours.

6. The method for preparing a highly efficient chelating metal ion complex according to claim 1, characterized in that, include: The final PVA-g-EDDS were dialyzed using a dialysis membrane with a molecular weight cutoff of 500-2000 Da and a dialysis time of 1-3 days.

7. The application of a highly efficient metal ion chelating complex, wherein the PVA-g-EDDS prepared by any of the methods described in claims 1-6 is characterized in that, include: PVA-g-EDDS is used for membrane filtration of cobalt, nickel, copper, zinc, lead, calcium, and manganese ions in wastewater.

8. The application of the highly efficient chelating metal ion complex according to claim 7, characterized in that: PVA-g-EDDS is used in conjunction with ultrafiltration membranes to treat wastewater, with the transmembrane pressure set at 0.1-2.0 bar.

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