CN115254059A - Chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions in wastewater and preparation method thereof - Google Patents
Chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions in wastewater and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of waste water purification, and particularly relates to a chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions in waste water and a preparation method thereof.
Description
Technical Field
The invention belongs to the technical field of wastewater purification, and particularly relates to a chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions in wastewater and a preparation method thereof.
Background
Water is a source of life and one of the most important essential material resources on which human beings live and develop. However, with the rapid development of industry and agriculture, various heavy metals (such as Pb (II), hg (II), cu (II), zn (II), cr (VI) and Cd (II)) are discharged into the environment, and the global water resource safety is directly threatened. Chromium (Cr) is one of the most common and most toxic heavy metal contaminants. Cr is mainly present in the form of trivalent chromium (Cr (III)) and hexavalent chromium (Cr (VI)) in the natural environment. Cr (III) is slightly or even non-toxic, while Cr (VI) is widely regarded for its carcinogenicity, high toxicity, teratogenicity and bioaccumulation, and is one of the first toxic pollutants designated by the EPA in the United states. In 23.7.7.2019, hexavalent chromium and compounds thereof are listed in the first list of toxic and harmful water pollutants in China. The World Health Organization (WHO) set the maximum allowable concentrations of Cr (VI) in surface water and drinking water to 0.1mg/L and 0.05mg/L, respectively. High-concentration Cr (VI) wastewater is generated every year in polluting industries such as steel manufacturing, textile, electroplating, chromium plating and the like. Therefore, the chromium-containing wastewater needs to be treated to meet the requirement of discharge standard.
To date, a series of technologies for removing Cr (VI) from wastewater, such as chemical oxidation, solvent extraction, ion exchange, coprecipitation, electrocoagulation, biological treatment, membrane separation, etc., have been developed, and these methods have high energy consumption, large-scale instruments, high cost, etc., and greatly reduce practical applications. The adsorption method has the advantages of environmental friendliness, low cost, simplicity in operation, high efficiency and the like, is considered to be the most promising method, and has become a research and application hotspot in recent years. The adsorption efficiency is mainly related to the type of adsorbent. At present, various adsorbents such as biochar, montmorillonite, cellulose, zero-valent iron and the like are widely used for removing Cr (VI) in water. However, due to the disadvantages of low adsorption capacity, high cost, difficult regeneration, etc., they have limited further applications, such as the removal of Cr (VI) from water with glauconite at low cost by Naghipour D et al (Naghipour D, et al, al. Water and environmental Journal,2020,34 (1): 45-56), but the adsorption capacity of the adsorbent for Cr (VI) is only 12.21mg/g. XiangL et al (Xiang L, et, al.chemical Engineering Journal,2021, 408.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to prepare an environment-friendly adsorbing material with multiple adsorption sites and high adsorption capacity, and hexavalent chromium ions in wastewater can be removed through adsorption and reduction, namely the preparation method of the chitosan/EDTA/polypyrrole adsorbing material for efficiently removing the hexavalent chromium ions in the wastewater, chitosan is used as a framework of the adsorbing material, hydroxyl on the surface can be combined with pyrrole through hydrogen bond action, and amino on the surface can be crosslinked with ethylenediamine tetraacetic acid dianhydride to generate a polymer. The method comprises the following steps of (1) removing hexavalent chromium ions by using positively charged nitrogen atoms on pyrrole molecules through electrostatic attraction and reduction, removing the hexavalent chromium ions or reduced trivalent chromium ions by using ethylenediaminetetraacetic acid through chelation of carboxyl and amino, and removing the hexavalent chromium ions by using three materials, wherein the three materials are as follows:
s1: reacting chitosan with ethylenediamine tetraacetic dianhydride through amide to generate chitosan/EDTA polymer;
s2: the pyrrole monomer is attached to the surface of the chitosan/EDTA through hydrogen bond acting force, and then polypyrrole is formed through in-situ polymerization to be coated on the surface of the chitosan/EDTA, so that the chitosan/EDTA/polypyrrole composite adsorbing material is obtained.
Preferably, the preparation steps of the chitosan/EDTA polymer in S1 are as follows:
s11: dissolving chitosan in an acetic acid solution, adding methanol, uniformly stirring, adding ethylenediamine tetraacetic dianhydride into the chitosan solution, and stirring at room temperature until gel appears;
s12: after the reaction is finished, filtering the precipitate and washing the precipitate by using NaOH solution to remove unreacted ethylenediamine tetraacetic dianhydride;
s13: the product was washed with dilute hydrochloric acid, deionized water and ethanol and dried to obtain chitosan/EDTA polymer.
Preferably, S2 includes the following steps:
s21: grinding and crushing dried chitosan/EDTA, adding the crushed chitosan/EDTA into a beaker filled with deionized water, uniformly stirring, and adding hydrochloric acid to adjust the pH value;
s22: adding pyrrole solution into the solution of S21 and stirring, and then adding FeCl into the solution 3 Continuously stirring the solution, and gradually changing the solution into dark green;
s23: sealing for a certain time at 4 ℃, then filtering the obtained product, washing the product with distilled water and ethanol until the filtrate is neutral, and drying and storing to obtain the chitosan/EDTA/polypyrrole adsorbing material.
Preferably, the solid-to-liquid ratio of the chitosan to the acetic acid solution in S11 is 1.
Preferably, the volume ratio of the acetic acid solution to the methanol in S11 is 1.
Preferably, the mass ratio of the chitosan to the ethylenediamine tetraacetic dianhydride in S11 is 1.05-1.
Preferably, the solid-liquid ratio of the chitosan/EDTA polymer to the added amount of the pyrrole in S22 is 1:4 to 3:1.
preferably, feCl in S22 3 The concentration of the solution is 0.4-2 mol/L.
Preferably, the sealing time in S23 is 8 to 36 hours.
A chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions in wastewater is prepared by adopting the preparation method.
Compared with the prior art, the invention has the beneficial effects that:
1. the raw materials used by the invention comprise chitosan, EDTA and polypyrrole, are all environment-friendly materials, and cannot generate secondary pollution to the environment.
2. The material has the advantages of simple preparation method, low price and great economic benefit when being used for removing hexavalent chromium ions in wastewater.
3. The three raw materials of the adsorbing material all participate in removing hexavalent chromium ions, and the removing mode comprises electrostatic attraction, reduction, chelation, ion exchange and the like, so that the material has larger adsorption capacity on the hexavalent chromium ions.
4. Interfering ion SO 4 2- 、NO 3 - Cu (II), zn (II) and the like have little influence on the removal of hexavalent chromium ions, so the material is suitable for removing the hexavalent chromium ions in a complex wastewater environment.
5. The material has good regenerability, and the removal rate of hexavalent chromium ions can still be kept above 80% after the adsorption and desorption are circulated for five times.
Drawings
FIG. 1 is an infrared spectrum of chitosan/EDTA/polypyrrole absorbent material and raw material monomer;
FIGS. 2-4 are scanning electron micrographs of polypyrrole, chitosan/EDTA, and chitosan/EDTA/polypyrrole adsorbent material;
FIG. 5 is a graphical representation of the effect of different adsorption times on the amount of hexavalent chromium ion adsorbed;
FIG. 6 is a graphical representation of the effect of hexavalent chromium ion concentration in the solution on the amount of adsorption at different temperatures;
FIG. 7 is a graphical representation of the effect of different pH on hexavalent chromium ion removal;
FIG. 8 is a graph showing the effect of coexisting ions on the adsorption amount of hexavalent chromium;
figure 9 is a graphical representation of the effect of five adsorption-desorption cycles on hexavalent chromium ion removal.
Detailed Description
The following describes embodiments of the present invention in detail. The following examples are illustrative only and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications.
Example one
S1: preparation of chitosan/EDTA Polymer:
s11: 1g of chitosan was dissolved in 20mL of 10% acetic acid solution, and then 80mL of methanol was added and stirred for 30 minutes. Adding ethylenediamine tetraacetic dianhydride (1 g dissolved in 10mL of methanol) into the solution, and stirring at room temperature for 24 hours until gel appears;
s12: after the reaction was completed, the precipitate was filtered and washed with a NaOH solution having a pH of 11 to remove unreacted ethylenediaminetetraacetic dianhydride.
S13: the precipitate was washed with 0.1mol/L hydrochloric acid, deionized water and ethanol. The final product was dried in an oven at 40 ℃ for 48 hours and stored in a desiccator.
S2: preparing a chitosan/EDTA/polypyrrole adsorbing material:
s21: grinding and crushing 0.25g of dried chitosan/EDTA polymer, adding the crushed material into a beaker filled with 100mL of deionized water, stirring for 5 minutes, then adding 1mL of concentrated hydrochloric acid, and continuing stirring for 30 minutes;
s22: 150 μ L of pyrrole was added to the solution of S21, and the mixture was continuously stirred for 3 hours, after which 6.5mL of FeCl having a concentration of 0.1mol/L was added 3 Continuing stirring the solution for 10 minutes;
s23: sealed at 4 ℃ for 24 hours. The resulting product was filtered and washed with distilled water and ethanol until the filtrate was neutral, dried in an oven at 40 ℃ for 48 hours, and stored in a desiccator.
Adsorption performance: the adsorption reached equilibrium at 24 hours. The maximum adsorption capacity of the solution for hexavalent chromium ions is 401.25mg/g at 45 ℃ and pH of 2. After 5 times of cyclic adsorption and desorption, the adsorption capacity was maintained at 81.26%.
Example two
S1: preparation of chitosan/EDTA polymer:
s11: 1g of chitosan was dissolved in 20mL of 10% acetic acid solution, and then 80mL of methanol was added and stirred for 30 minutes. Ethylenediamine tetraacetic dianhydride (1.5 g in 10mL methanol) was added to the solution and stirred at room temperature for 24 hours until gel appeared;
s12: after the reaction is finished, filtering precipitates and washing the precipitates by using a NaOH solution with the pH value of 11 to remove unreacted ethylenediamine tetraacetic dianhydride;
s13: the precipitate was finally washed with 0.1mol/L hydrochloric acid, deionized water and ethanol and the final product was dried in an oven at 40 ℃ for 48 hours and stored in a desiccator.
S2: preparing a chitosan/EDTA/polypyrrole adsorbing material:
s21: grinding 0.25g of dried chitosan/EDTA polymer, adding into a beaker containing 100mL of deionized water, stirring for 5 minutes, then adding 1mL of concentrated hydrochloric acid, and continuing stirring for 30 minutes;
s22: 150 μ L of pyrrole was added to the solution of S21, and the mixture was continuously stirred for 3 hours, after which 6.5mL of FeCl having a concentration of 0.1mol/L was added 3 The solution was stirred for 10 minutes.
S23: the reaction mixture was sealed at 4 ℃ for 24 hours, the resulting product was filtered and washed with distilled water and ethanol until the filtrate was neutral, dried in an oven at 40 ℃ for 48 hours, and stored in a desiccator.
Adsorption performance: the adsorption reached equilibrium at 16 hours. The maximum adsorption capacity of the solution for hexavalent chromium ions is 375.49mg/g at 45 ℃ and pH of 2. After 5 times of cyclic adsorption and desorption, the adsorption capacity was maintained at 85.43%.
Example three
S1: preparation of chitosan/EDTA Polymer:
s11: 1g of chitosan was dissolved in 20mL of 10% acetic acid solution, and 80mL of methanol was added and stirred for 30 minutes. Ethylenediaminetetraacetic dianhydride (1.5 g in 10mL methanol) was added to the solution and stirred at room temperature for 24 hours until gel appeared;
s12: after the reaction is finished, filtering precipitates and washing the precipitates by using a NaOH solution with the pH value of 11 to remove unreacted ethylenediamine tetraacetic dianhydride;
s13: the precipitate was washed with 0.1mol/L hydrochloric acid, deionized water and ethanol. The final product was dried in an oven at 40 ℃ for 48 hours and stored in a desiccator.
S2: preparing a chitosan/EDTA/polypyrrole adsorbing material:
s21: grinding 0.25g of dried chitosan/EDTA polymer, adding into a beaker containing 100mL of deionized water, stirring for 5 minutes, then adding 1mL of concentrated hydrochloric acid, and continuing stirring for 30 minutes;
s22: to the solution of S21, 100. Mu.L of pyrrole was added, and the mixture was continuously stirred for 3 hours, after which 4mL of FeCl having a concentration of 0.1mol/L was added 3 Continuing stirring the solution for 10 minutes;
s23: sealed at 4 ℃ for 24 hours. The resulting product was filtered and washed with distilled water and ethanol until the filtrate was neutral, dried in an oven at 40 ℃ for 48 hours and stored in a desiccator.
Adsorption performance: the adsorption reached equilibrium at 28 hours. The maximum adsorption capacity for hexavalent chromium ions in the aqueous solution at 45 ℃ and a pH of 2 is 349.59mg/g. After 5 times of cyclic adsorption and desorption, the adsorption capacity was maintained at 84.39%.
On the basis of the above embodiment, the structure and morphology of the chitosan/EDTA/polypyrrole adsorbing material prepared by the invention are further analyzed and explained by infrared spectroscopy and a scanning electron microscope.
1. Infrared (FT-IR) analysis
The structure of the adsorbing material is characterized by adopting a Siemens fly Nicolet6700 type infrared spectrometer (FT-IR), and the wave number is 400-4000 cm -1 . FIG. 1 shows the IR spectra of the feed and adsorbent. The major signal in chitosan is the sugar ring signal (1034 cm) -1 、1165cm -1 ) Amide I (1653 cm) -1 ) And amide II (1594 cm) -1 ) The vibration of (2). 1623cm in chitosan/EDTA spectrum -1 And 1725cm -1 The two new vibrational peaks at (a) can be attributed to the carbonyl group of the amide and the carbonyl group of the carboxyl group, respectively. Furthermore, chitosan/EDTA/polypyrrole was found to be 1540cm in comparison to chitosan/EDTA -1 、1455cm -1 、1033cm -1 And 897cm -1 There is a new peak due to pyrrole ring symmetry vibration, C-N being stretching, C-H stretching and C-H bending vibration, respectively.
2. Scanning Electron Microscope (SEM) analysis
The morphology of the adsorbing material was observed by using a scanning electron microscope of SU8010 model from Hitach corporation of Japan. FIGS. 2 to 4 are scanning electron micrographs at 10000 times magnification. From fig. 2, it can be seen that polypyrrole is an agglomerate formed by agglomeration of spherical particles, the surface of chitosan/EDTA in fig. 3 is relatively smooth, and the surface of chitosan/EDTA/polypyrrole in fig. 4 is obviously roughened due to coverage of polypyrrole.
3. Absorption performance of chitosan/EDTA/polypyrrole absorption material on hexavalent chromium ions in water
3.1. Kinetics of adsorption
Weighing 6mg of chitosan/EDTA/polypyrrole adsorbing material, adding the chitosan/EDTA/polypyrrole adsorbing material into a scintillation bottle containing 18mL of 100mg/L hexavalent chromium solution, taking out 0.2mL of solution at intervals, filtering the solution by using a 0.45-micron polypropylene film, adding 1, 5-dibenzoyl dihydrazide solution for dyeing, and finally measuring the concentration of hexavalent chromium in the solution at the wavelength of 540nm by using an ultraviolet-visible spectrophotometer. The adsorption capacity of the adsorption material to hexavalent chromium ions can be calculated according to the following formula:
in the formula C 0 、C t Respectively is the initial concentration of hexavalent chromium ions in the solution, the concentration at the time t, and mg/L; v is the volume of the solution, mL; m is the mass of the adsorbent, mg; q. q.s t The adsorption amount of the adsorption material to hexavalent chromium ions at the time t is mg/g.
FIG. 5 is a time-varying relation of the adsorption amount of the hexavalent chromium ions by the adsorbing material, the chitosan/EDTA/polypyrrole can remove 85% of the hexavalent chromium ions in the solution within 8 hours, and the equilibrium adsorption capacity is 279.63mg/g. By contrast, the chitosan/EDTA can only remove 24% of hexavalent chromium ions in the solution within 8 hours, and the equilibrium adsorption capacity is 98.66mg/g, which indicates that the chitosan/EDTA/polypyrrole adsorbing material has higher adsorption capacity for the hexavalent chromium ions.
3.2. Adsorption isotherm
FIG. 6 is an isothermal adsorption curve of hexavalent chromium ions at different temperatures by the chitosan/EDTA/polypyrrole adsorbent material, and it can be seen that, as the temperature increases, the maximum adsorption amount of hexavalent chromium ions by the chitosan/EDTA/polypyrrole adsorbent material increases from 330.75mg/g (25 ℃) to 401.25mg/g (45 ℃), which indicates that the adsorption of hexavalent chromium ions by the material is an endothermic process, and in addition, the adsorption process conforms to the Langmuir adsorption model, which indicates that the adsorption process of hexavalent chromium ions by the material is mainly single-layer adsorption.
3.3 influence of pH on adsorption Performance
FIG. 7 shows the removal rate of hexavalent chromium ions by the chitosan/EDTA/polypyrrole absorbent material at different pH values. It was found that the removal rate of Cr (VI) was at most 93.1% at pH 2. The removal rate of hexavalent chromium ions gradually decreased with an increase in pH, and the removal rate was 71.9% at pH 6. Then, the removal rate of hexavalent chromium ions rapidly decreases with the increase of the pH value, and at a pH of 8, the removal rate of hexavalent chromium ions is only 35.3%. This is because at a lower pH, the protonation degree of the nitrogen atom in the chitosan/EDTA/polypyrrole absorbent material is high, and the surface potential of the chitosan/EDTA/polypyrrole absorbent material is increased, so that more hexavalent chromium ions can be removed by the electrostatic attraction.
3.4. Influence of interfering ions on adsorption Properties
The influence of coexisting ions (Cu (II), zn (II), SO) on the removal of hexavalent chromium ions was investigated at 25 deg.C 4 2- 、NO 3 - And SO 4 2- /NO 3 - ) And the concentration of hexavalent chromium ions are both 100mg/L. From fig. 8, it can be seen that when Cu (II) or Zn (II) is contained in the solution, the influence of the coexisting ions on the removal of hexavalent chromium ions in the solution is small because of the electrostatic repulsion between the positively charged chitosan/EDTA/polypyrrole absorbent material and the metal in the acidic environment. Anion SO 4 2- Or NO 3 - Is a low affinity ligand and has weak interaction with chitosan/EDTA/polypyrrole adsorbing materials.
3.5. Regeneration performance of adsorbent
The regeneration performance of the chitosan/EDTA/polypyrrole adsorbing material is researched through five continuous adsorption-desorption cycle experiments. Firstly, 30mg of chitosan/EDTA/polypyrrole adsorbing material is added into 90mL of hexavalent chromium solution with the concentration of 100mg/L for adsorption for 24 hours. The adsorbed material was then stirred in a 0.5mol/L NaOH solution for 2 hours to complete desorption. The adsorbent material was then added to a 1mol/L hydrochloric acid solution and stirred for 2 hours to regenerate the adsorption active sites. And finally, washing the adsorbing material to be neutral by using deionized water, and reusing the adsorbing material for the next adsorption test.
Fig. 9 is a schematic representation of five adsorption-desorption cycles. It can be found that the removal rates of the hexavalent chromium ions by the first three cycles are 91.3%, 88.1% and 85.6%, respectively, and the removal rates are not obviously reduced, which indicates that the adsorbent has good reusability. In the fourth and fifth cycles, the removal rate dropped to 82.81% and 81.26%, respectively, due to the fragmentation of the polypyrrole chains by repeated oxidation of hexavalent chromium ions. In addition, after five times of circulation, the chitosan/EDTA/polypyrrole adsorbing material can be directly separated from the aqueous solution, and the weight of the adsorbing material is not obviously lost, so that the practical application value of the chitosan/EDTA/polypyrrole adsorbing material is further explained.
In conclusion, the chitosan/EDTA/polypyrrole adsorbing material has more adsorption sites, for example, a nitrogen atom with positive charge on pyrrole can remove hexavalent chromium ions through electrostatic attraction and reduction, and carboxyl, hydroxyl and amino groups on the surfaces of chitosan and EDTA can chelate hexavalent chromium and trivalent chromium ions. All the three materials participate in removing hexavalent chromium ions in the solution, so that the chitosan/EDTA/polypyrrole adsorbing material has larger adsorption capacity on the hexavalent chromium ions. In addition, the material still has good regeneration and reutilization property after multiple adsorption-desorption cycles. Therefore, the chitosan/EDTA/polypyrrole is an excellent adsorbing material for removing hexavalent chromium ions from wastewater.
Therefore, the adsorbing material with the Cr (VI) adsorbing and reducing performances, which is prepared by the invention, adopts environment-friendly materials of chitosan, ethylenediamine tetraacetic dianhydride and pyrrole as raw materials. Chitosan (CS), a linear glucosamine polysaccharide produced by alkaline hydrolysis of shells of crustaceans such as shrimp, is widely used as a low-cost adsorbent for heavy metal removal due to reactivity of amine groups and stable chelation. Ethylenediaminetetraacetic acid (EDTA), an excellent metal ion chelating agent, has four carboxyl groups and two amino groups and is widely used as a cross-linking agent or modifier to improve the removal of heavy metal ions from water by adsorbents. Pyrrole has a positively charged nitrogen atom and can bind to Cr (VI) by electrostatic attraction while efficiently reducing Cr (VI) to Cr (III). Chitosan and ethylenediamine tetraacetic dianhydride react through amide to generate chitosan/EDTA polymer, and-NH-groups in pyrrole and abundant hydroxyl groups in chitosan form hydrogen bonds. In FeCl 3 Under the catalysis of the chitosan/EDTA/polypyrrole adsorbing material, pyrrole is polymerized in situ to generate polypyrrole which is coated on the surface of the chitosan/EDTA polymer to form the chitosan/EDTA/polypyrrole adsorbing material. Meanwhile, the agglomeration problem of polypyrrole can be solved by the existence of chitosan/EDTA. Experiments show that the maximum adsorption capacity of the adsorbing material for Cr (VI) is 401.25mg/g, and the adsorption capacity can still be maintained at more than 80% after the adsorbing and analyzing are cycled for 5 times.
Although the present invention has been described in detail with reference to the accompanying drawings, the present invention is not limited to the foregoing embodiments, and the above embodiments are only illustrative and not restrictive. It will be appreciated by those skilled in the art, given the benefit of this disclosure, that many variations of the pyridine complex chitosan/EDTA species in different ratios may be made without departing from the present invention and are intended to be within the scope of the present invention.
Claims (10)
1. A preparation method of chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions in wastewater is characterized by comprising the following steps:
s1: reacting chitosan with ethylenediamine tetraacetic dianhydride through amide to generate chitosan/EDTA polymer;
s2: the method comprises the steps of attaching pyrrole monomers to the surface of chitosan/EDTA through hydrogen bond acting force, and then forming polypyrrole to coat the surface of the chitosan/EDTA through in-situ polymerization to obtain the chitosan/EDTA/polypyrrole composite adsorbing material.
2. The preparation method of the chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions from wastewater according to claim 1, wherein the preparation steps of the chitosan/EDTA polymer in S1 are as follows:
s11: dissolving chitosan in an acetic acid solution, adding methanol, uniformly stirring, adding ethylenediamine tetraacetic dianhydride into the chitosan solution, and stirring at room temperature until gel appears;
s12: after the reaction is finished, filtering precipitates and washing the precipitates by using NaOH solution to remove unreacted ethylenediamine tetraacetic dianhydride;
s13: the product was washed with dilute hydrochloric acid, deionized water and ethanol and dried to obtain chitosan/EDTA polymer.
3. The method for preparing the chitosan/EDTA/polypyrrole absorbent material for removing the hexavalent chromium ions in the wastewater with high efficiency according to the claim 1, wherein the step of S2 comprises the following steps:
s21: grinding and crushing dried chitosan/EDTA, adding the crushed chitosan/EDTA into a beaker filled with deionized water, stirring, and adding hydrochloric acid to adjust the pH value;
s22: adding pyrrole solution into the solution of S21 and stirring, and then adding FeCl into the solution 3 Continuously stirring the solution, and gradually changing the solution into dark green;
s23: sealing for a certain time at 4 ℃, then filtering the obtained product, washing the product with distilled water and ethanol until the filtrate is neutral, and drying and storing to obtain the chitosan/EDTA/polypyrrole adsorbing material.
4. The preparation method of the chitosan/EDTA/polypyrrole absorbent material used for removing hexavalent chromium ions in wastewater with high efficiency according to claim 2, wherein the solid-to-liquid ratio of chitosan to acetic acid solution in S11 is 1 to 8 (g: mL) and 20 (g: mL), and the volume concentration of acetic acid solution is 8 to 20 percent.
5. The preparation method of the chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions from wastewater according to claim 2, wherein the volume ratio of the acetic acid solution to the methanol in S11 is 1 to 3-1.
6. The preparation method of the chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions in wastewater according to claim 2, wherein the mass ratio of the chitosan to the ethylenediamine tetraacetic dianhydride in S11 is 1.05-1, and the stirring time is 8-36 hours.
7. The method for preparing the chitosan/EDTA/polypyrrole absorbent material for removing the hexavalent chromium ions in the wastewater with high efficiency according to claim 2, wherein the solid-to-liquid ratio of the chitosan/EDTA polymer to the added amount of the pyrrole in S22 is 1 3 In a molar ratio of 1:4 to 3:1.
8. the chitosan/EDTA/polypyrazine for high efficiency removal of hexavalent chromium ions from wastewater according to claim 2The preparation method of the pyrrole adsorbing material is characterized in that FeCl in S22 3 The concentration of the solution is 0.4-2 mol/L.
9. The method for preparing the chitosan/EDTA/polypyrrole absorbent material for removing the hexavalent chromium ions in the wastewater with high efficiency according to the claim 2, wherein the sealing time in the S23 is 8 to 36 hours.
10. A chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions in wastewater, which is characterized by being prepared by the preparation method of the chitosan/EDTA/polypyrrole adsorbing material for efficiently removing hexavalent chromium ions in wastewater according to any one of claims 1 to 9.
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