A chitosan-porphyrin supramolecular polymer network dye adsorbent and a preparation method and application thereof

Abstract

The application belongs to the technical field of new functional materials for environmental adsorption, and provides a chitosan-porphyrin supramolecular polymer network dye adsorbent, a preparation method and application thereof. The chitosan-porphyrin supramolecular polymer network dye adsorbent is abbreviated as CSH-THPPNa, and the preparation method is as follows: porphyrin sodium is dissolved in a buffer solution with pH = 4.0, the molar ratio of chitosan to porphyrin sodium is controlled to be 1:57.2-1:400, chitosan is mixed with the prepared porphyrin sodium solution, ultrasonic treatment is carried out for 15 min, stirring is carried out for 12 h, filtration is carried out, the green solid powder obtained by filtration is vacuum dried, and the CSH-THPPNa is obtained. Raw materials are cheap and easy to obtain, the process is simple, easy and convenient to operate, and is beneficial to industrial production; the chitosan-porphyrin supramolecular polymer network dye adsorbent has the advantages of low cost, high adsorption capacity, fast adsorption rate, good adsorption selectivity, easy recycling and the like, has excellent adsorption performance on dyes in wastewater, and has a good application prospect. The chitosan-porphyrin supramolecular polymer network dye adsorbent can efficiently adsorb anionic dyes, and can also effectively separate anionic and cationic dyes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new functional materials for environmental adsorption, and particularly relates to a chitosan-porphyrin supramolecular polymer network dye adsorbent, a preparation method and application thereof, and particularly relates to the application in dye adsorption. BACKGROUND

[0002] Organic dyes are a class of pollutants in industrial wastewater, which are difficult to treat due to their physical and chemical, thermal stability and optical stability. Therefore, the removal of dyes in wastewater has attracted widespread attention, and various technologies have been studied. Among various wastewater treatment methods such as ion exchange method, biological separation method, microbial degradation method, adsorption method, chemical precipitation method, membrane separation method and electrochemical method, the adsorption method is one of the most suitable technologies due to its easy accessibility, simple operation and high removal efficiency. However, traditional materials such as activated carbon, zeolite and ion exchange resin always expose the shortcomings of low adsorption capacity / selectivity, poor chemical modifiability and non-recyclability. It is of great significance to prepare adsorbents with high efficiency, renewability, low cost, high adsorption capacity and high selectivity. Supramolecular polymer networks have the following advantages: 1) Supramolecular polymer networks can be constructed from molecules through various non-covalent interactions, avoiding tedious organic synthesis; 2) The adsorption performance of polymer networks of polymerized functional monomers is superior to that of single monomers, achieving the effect of overall amplification; 3) Supramolecular polymer networks are degradable under external stimuli, which are environmentally friendly and recyclable.

[0003] As an adsorbent, the preparation of supramolecular polymer networks should adopt an economic, green and simple method. Therefore, cross-linking of inexpensive, commercial and environmentally friendly polymers through non-covalent interactions is a feasible way. Chitosan (CS) is a natural polysaccharide, which has no toxicity, biocompatibility, biodegradability, hydrophilicity, antibacterial activity and adsorption performance. Chitosan has potential coulombic interactions, hydrogen bonds and van der Waals forces for the adsorption of dyes and metal ions due to its large number of amino and hydroxyl functional groups, and is a potential adsorbent.

[0004] Porphyrin is a class of water-soluble nitrogen-containing biological pigments (cytochrome pigments), which is undoubtedly the best ligand in biology. Incorporating porphyrin molecules into chitosan to prepare supramolecular polymer networks will bring special properties to the network system. First, porphyrin is fluorescent, which will endow the obtained supramolecular network polymer with fluorescence. Second, due to the inherent properties of porphyrin, the supramolecular polymer network system will have antibacterial properties. SUMMARY

[0005] The present application provides a chitosan-porphyrin supramolecular polymer network dye adsorbent, a preparation method and application thereof, which can efficiently adsorb anionic dyes and selectively separate cationic and anionic dyes as an adsorbent.

[0006] This invention is achieved by the following technical solution: a chitosan-porphyrin supramolecular polymer network dye adsorbent, wherein the chitosan-porphyrin supramolecular polymer network dye adsorbent is abbreviated as CSH-THPPNa, and the structural formulas of chitosan and porphyrin are shown below:

[0007] ;

[0008] The preparation method of CSH-THPPNa is as follows: sodium porphyrin is dissolved in a buffer solution with pH = 4.0 to prepare sodium porphyrin with a concentration of 2.58 × 10⁻⁶. -5 In a solution of M, the molar ratio of chitosan to sodium porphyrin is controlled to be 1:57.2-1:400. Chitosan is mixed with the prepared sodium porphyrin solution, then sonicated for 15 min, stirred for 12 h, filtered, and finally the green solid powder obtained by filtration is vacuum dried for 12 h to obtain the chitosan-porphyrin supramolecular polymer network dye adsorbent.

[0009] The preparation method of sodium porphyrin is as follows: 1.00g of 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin and 0.4g of sodium ethoxide are added to 250mL of methanol and stirred at room temperature for 2h. After the reaction is complete, the solvent is evaporated to dryness to obtain sodium porphyrin.

[0010] The buffer solution is a 20 mL 0.1 M citrate-sodium citrate buffer solution.

[0011] Furthermore, the molar ratio of sodium porphyrin to chitosan is 1:286.

[0012] The present invention also provides the application of the chitosan-porphyrin supramolecular polymer network dye adsorbent in dye adsorption, wherein the dye is at least one of anionic eosin B, orange-yellow G, and sodium acid fuchsin.

[0013] The specific method for further adsorbing dyes is as follows: disperse the chitosan-porphyrin supramolecular polymer network dye adsorbent in the dye-containing wastewater to be treated at an addition amount of 1 g / L; stir continuously, take samples of the solution once at regular intervals, and test the ultraviolet spectrum of the sample, that is, adsorb and remove anionic dyes from the water; the specific method for regenerating the adsorbent after adsorption is as follows: filter after adsorption, ultrasonically vibrate the adsorbent with 0.4-0.6 M sodium hydroxide solution, then wash with deionized water, centrifuge, and reprecipitate in sodium porphyrin buffer solution, thus completing the regeneration.

[0014] The concentration of dye in the wastewater to be treated is 50 mg / L.

[0015] The chitosan-porphyrin supramolecular polymer network dye adsorbent exhibits selective adsorption of dyes; when cationic and anionic dyes are mixed, only anionic dyes are adsorbed.

[0016] The specific method for selective adsorption is as follows: Chitosan-porphyrin supramolecular polymer network dye adsorbent is dispersed in the wastewater to be treated, which contains both anionic and cationic dyes. The amount of adsorbent added is 1 g / L. The mixture is stirred continuously, and the solution is sampled at regular intervals. The ultraviolet spectrum of the sample is then tested. This means that the anionic dyes in the water are adsorbed and removed, leaving only cationic dyes in the solution.

[0017] The wastewater to be treated contains either a mixture of anionic eosin B and cationic malachite green hydrochloride, or a mixture of anionic orange yellow G and cationic malachite green hydrochloride, with a concentration of 5 mg / L for each mixture.

[0018] The preparation principle of the chitosan-porphyrin supramolecular polymer network dye adsorbent is that under acidic conditions, protonated chitosan and sodium porphyrin have electrostatic interactions, which are then crosslinked by sodium porphyrin to form a chitosan-porphyrin supramolecular polymer network.

[0019] Compared with existing technologies, the chitosan-porphyrin supramolecular polymer network described in this invention is simple and convenient to prepare, consumes little energy, uses inexpensive and readily available raw materials with low toxicity, and can efficiently adsorb anionic dyes and be recycled. In particular, it can also effectively separate anionic and ionic dye ions, making it a green and environmentally friendly multifunctional dye adsorbent.

[0020] Using supramolecular polymer networks as materials opens up an effective and economical way to adsorb and separate materials, which will promote further research on the construction of novel polymer materials based on intermolecular non-covalent interactions, thereby improving the selective adsorption and separation capabilities of organic dyes in aqueous solutions. Attached Figure Description

[0021] Figure 1 The chitosan-porphyrin supramolecular polymer network dye adsorbent (CSH-THPPNa) prepared in Example 1 1 H NMR spectrum;

[0022] Figure 2 The XRD pattern of the chitosan-porphyrin supramolecular polymer network dye adsorbent (CSH-THPPNa) prepared in Example 1 is shown below.

[0023] Figure 3 The solid-state fluorescence spectrum of the chitosan-porphyrin supramolecular polymer network dye adsorbent (CSH-THPPNa) prepared in Example 1 is shown.

[0024] Figure 4The images show scanning electron microscope (SEM) images of the chitosan-porphyrin supramolecular polymer network dye adsorbent (CSH-THPPNa) prepared in Example 1. In the images: (a) is a solid-state SEM image of chitosan, (b) is a solid-state SEM image of protonated chitosan, (c) is a solid-state SEM image of sodium porphyrin, and (d) is a solid-state SEM image of the chitosan-porphyrin supramolecular polymer network.

[0025] Figure 5 The image shows the adsorption of dye solution (50 mg / L) by the chitosan-porphyrin supramolecular polymer network dye adsorbent (CSH-THPPNa) prepared in Example 1. In the image: (a)-(c) are the UV-Vis absorption spectra of the dye absorption intensity as a function of time during the adsorption of three dyes, Eosin B (EB), Orange G (OG), and Acid Fuchs Red Sodium Salt (FS), by CSH-THPPNa; (d)-(f) are the adsorption efficiencies of CSH-THPPNa during the adsorption of the three dyes, EB, OG, and FS.

[0026] Figure 6 The adsorption diagram shows the regeneration of the dye solution (50 mg / L) after five consecutive adsorption-desorption cycles by the chitosan-porphyrin supramolecular polymer network dye adsorbent (CSH-THPPNa) prepared in Example 1.

[0027] Figure 7 The selective adsorption of the chitosan-porphyrin supramolecular polymer network dye adsorbent CSH-THPPNa prepared in Example 1 on a mixed dye solution (5 mg / L) of anionic eosin B (EB) and cationic malachite green hydrochloride (MG) and anionic orange yellow G (OG) and cationic malachite green hydrochloride (MG): (a) UV-Vis absorption spectra of the solution before and after adsorption of the mixed solution of anionic EB and cationic MG by CSH-THPPNa; (b) UV-Vis absorption spectra of the solution before and after adsorption of the mixed solution of anionic OG and cationic MG by CSH-THPPNa. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise defined, 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 pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0030] Equivalent technologies of the specific embodiments described herein that are readily apparent to those skilled in the art through routine experimentation are included in this application.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the instruments and equipment used in the following examples are all standard laboratory instruments and equipment; unless otherwise specified, the experimental materials used in the following examples were all purchased from regular biochemical reagent stores.

[0032] Example 1: A method for preparing a chitosan-porphyrin supramolecular polymer network dye adsorbent abbreviated as CSH-THPPNa, specifically including the following steps: First, 1.00 g of 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin (Adamas Reagents) and 0.4 g of sodium ethoxide were added to 250 mL of methanol and stirred at room temperature for 2 h. After the reaction was complete, the solvent was evaporated to dryness to obtain sodium porphyrin (THPPNa).

[0033] THPPNa was dissolved in a buffer solution at pH 4.0 to prepare THPPNa with a concentration of 2.58 × 10⁻⁶. -5 In the solution of M, 25 mg of chitosan (CS) (degree of deacetylation ≥95%, viscosity 100-200 mpa.s, Adamas Reagent Company) was added and mixed with the prepared sodium porphyrin solution. The mixture was then sonicated for 15 min, stirred for 12 h, filtered, and finally the green solid powder obtained by filtration was vacuum dried for 12 h to obtain the chitosan-porphyrin supramolecular polymer network dye adsorbent CSH-THPPNa.

[0034] The prepared chitosan-porphyrin supramolecular polymer network 1 H NMR such as Figure 1 As shown, after the addition of THPPNa, the peaks on CSH associated with H2-H6 protons shifted to the lower field, indicating that there is an electrostatic interaction between CSH and THPPNa, forming a chitosan-porphyrin supramolecular polymer network.

[0035] The XRD pattern of the prepared chitosan-porphyrin supramolecular polymer network is as follows: Figure 2As shown, the CS sample (green line) exhibits a broad diffraction peak at 2θ = 20.0°, which is a characteristic diffraction peak of all typical CS materials. After protonation, the characteristic diffraction peak of CS shifts from 20.0° to 18.2°, accompanied by a narrowing of the full width at half maximum (FWHM) (blue line). According to Bragg's law (2dsinθ = nλ), the distance between CSH samples increases due to the repulsion of like charges. THPPNa shows broad characteristic diffraction peaks at 2θ = 8.19°, 22.1°, 30.3°, and 31.8° (red lines). In the CSH-THPPNa (black line) diagram, the diffraction peaks belonging to THPPNa become broader and weaker, indicating a decrease in crystallinity and the formation of an amorphous chitosan-porphyrin supramolecular polymer network.

[0036] Solid-state fluorescence spectroscopy, such as Figure 3 As shown, the maximum fluorescence emission peak of CS is located at 410 nm. The fluorescence intensity of CSH is significantly enhanced. THPPNa exhibits weak emission at 450 nm. Compared with CSH, the emission band of the chitosan-porphyrin supramolecular polymer network shows a blue shift (from 413 nm to 401 nm), and the characteristic emission peak of THPPNa is significantly enhanced at 450 nm. This is because the presence of CSH disperses THPPNa into a supramolecular polymer network, inhibiting the aggregation of THPPNa in the solid state, leading to enhanced emission of THPPNa.

[0037] Scanning electron microscope images such as Figure 4 As shown, Figure 4 (a) is a solid-state scanning electron microscope image of chitosan. Figure 4 (b) is a solid-state scanning electron microscope image of protonated chitosan. Figure 4 (c) is a solid-state scanning electron microscope image of sodium porphyrin. Figure 4 (d) is a solid-state scanning electron microscope image of the chitosan-porphyrin supramolecular polymer network. From Figure 4 In (a), it can be observed that the surface of chitosan is relatively smooth, while the surface of protonated chitosan is rougher. This is because under acidic conditions, there is electrostatic repulsion after protonation of chitosan, which promotes the uneven fragmentation of protonated chitosan. Figure 4 In (c), it can be observed that sodium porphyrin has an irregular rod-like structure. Figure 5 In (d), it can be observed that the chitosan-porphyrin supramolecular polymer has a network structure.

[0038] The UV-Vis spectrum of dye adsorption for the chitosan-porphyrin supramolecular polymer network dye adsorbent is shown below. Figure 6As shown in the figure. This experiment explored the dye adsorption capacity of chitosan-porphyrin supramolecular polymer network dye adsorbent in aqueous solution. 20 mg of chitosan-porphyrin supramolecular polymer network dye adsorbent was added to 20 mL of a 50 mg / L aqueous solution of eosin B (EB), orange G (OG), and sodium fuchsin (FS). The solution was continuously stirred at room temperature, and samples were taken at regular intervals for a total of 5 samples. The UV spectra of the samples were then measured. The UV spectra show that the UV absorption peak intensities of EB, OG, and FS continuously decrease over time. Within 10 minutes of adsorption, the EB absorption intensity decreased from 0.888 to 0.0113; within 20 minutes, the OG absorption intensity decreased from 1.37 to 0.0670; and within 30 minutes, the FS absorption intensity decreased from 1.64 to 0.0209. This indicates that the chitosan-porphyrin supramolecular polymer network CSH-THPPNa has the ability to adsorb dyes EB, OG, and FS.

[0039] The recycling and regeneration of chitosan-porphyrin supramolecular polymer network dye adsorbent CSH-THPPNa, such as Figure 7 As shown, the filtered chitosan-porphyrin supramolecular polymer network CSH-THPPNa was ultrasonically vibrated in a 0.4-0.6 M sodium hydroxide solution, then washed with deionized water, centrifuged, and re-precipitated in a sodium porphyrin buffer solution to complete regeneration. After adsorbing dye under the same conditions, it was filtered out, and its adsorption efficiency could still reach over 95%.

[0040] Comparative Example 1: Adsorption was performed under the same conditions as in Example 1, except that protonated chitosan (CSH) was used as the adsorbent.

[0041] Comparative Example 2: Adsorption was carried out under the same conditions as in Example 1, except that chitosan CS was used as the adsorbent.

[0042] The dye adsorption efficiencies of the chitosan-porphyrin supramolecular polymer network adsorbent CSH-THPPNa are shown in Table 1. The supramolecular network adsorbent CSH-THPPNa achieved a 99.70% removal rate for EB within 10 minutes, 94.60% for OG within 20 minutes, and 99.30% for FS within 30 minutes. When CSH was used as the adsorbent, the removal rates for EB were 95.1% within 60 minutes, OG 82.5% within 60 minutes, and FS 97.7% within 70 minutes. When CS was used as the adsorbent, the removal rates for EB were only 56.2% within 630 minutes, OG 56.1% within 630 minutes, and FS 75.8% within 630 minutes. These results indicate that CSH-THPPNa significantly improves pollutant removal efficiency compared to CS and CSH. This enhanced adsorption capacity can be attributed to the formation of the cross-linked supramolecular polymer network CSH-THPPNa through the addition of THPPNa to CS.

[0043] Table 1: Adsorption comparison results of the chitosan-porphyrin supramolecular polymer network dye adsorbent (CSH-THPPNa) prepared in Example 1 and the control adsorbents (protonated chitosan (CSH) and chitosan (CS)) on dye solution (50 mg / L).

[0044]

[0045] Selective adsorption of dyes by chitosan-porphyrin supramolecular polymer network dye adsorbents, such as Figure 7 As shown, CSH-THPPNa was placed in a pipette secured with absorbent cotton. Two dyes with opposite charges, EB and malachite green oxalate (MG), were mixed in a 1:1 mass ratio. A purple solution of red EB and blue MG was added dropwise to the pipette. The red EB was absorbed by CSH-THPPNa (CSH-THPPNa changed from light green to red), while the blue MG passed through rapidly. Figure 7 Figure (a) shows the UV spectral changes of the mixed dye solution (EB+MG) before and after adsorption with CSH-THPPNa: the purple solution turns blue, and two characteristic absorption bands at 519 nm (EB) and 617 nm (MG) are observed in the mixture of EB and MG solutions. However, the absorbance of EB at 519 nm decreases significantly, while the absorbance of MG at 617 nm remains unchanged after adsorption. These results are very consistent with the changes in visible color after adsorption. This indicates that only EB can be adsorbed, while MG cannot be adsorbed by CSH-THPPNa. This property makes CSH-THPPNa a potential absorbent for separating cationic and anionic dyes. Furthermore, OG is also one of the most commonly used anionic dyes.

[0046] The same selectivity experiments were conducted between OG and MG, such as​ As shown in (b), when a green solution of yellow OG and blue MG is added to a pipette, the color of SPN changes from light green to yellow, and the blue MG passes through rapidly, causing the mixed solution to change from green to blue. For the mixture of OG and MG solutions, three characteristic absorption bands can be observed at 425 nm (MG), 479 nm (OG), and 617 nm (MG). However, the absorbance of OG at 479 nm decreases significantly, while the absorbance of MG at 425 and 617 nm remains unchanged after adsorption, indicating that most OG molecules have been selectively captured from the OG / MG solution by SPN. Therefore, from the above comparative study, it can be concluded that CSH-THPPNa is a satisfactory anionic dye selective separation absorbent.

[0047] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A chitosan-porphyrin supramolecular polymer network dye adsorbent, characterized in that: The chitosan-porphyrin supramolecular polymer network dye adsorbent is abbreviated as CSH-THPPNa, wherein the structural formulas of chitosan and porphyrin are shown below: ； The preparation method of CSH-THPPNa is as follows: sodium porphyrin is dissolved in a buffer solution with pH = 4.0 to prepare sodium porphyrin with a concentration of 2.58 × 10⁻⁶. -5 The solution of M is prepared by controlling the molar ratio of chitosan to sodium porphyrin to be 1:57.2-1:

400. The chitosan is mixed with the prepared sodium porphyrin solution, then sonicated for 15 min, stirred for 12 h, filtered, and finally the green solid powder obtained by filtration is vacuum dried for 12 h to obtain the chitosan-porphyrin supramolecular polymer network dye adsorbent. The preparation method of sodium porphyrin is as follows: 1.00g of 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin and 0.4g of sodium ethoxide are added to 250mL of methanol and stirred at room temperature for 2h. After the reaction is complete, the solvent is evaporated to dryness to obtain sodium porphyrin.

2. The chitosan-porphyrin supramolecular polymer network dye adsorbent according to claim 1, characterized in that: The buffer solution is a 20 mL 0.1 M citrate-sodium citrate buffer solution.

3. The chitosan-porphyrin supramolecular polymer network dye adsorbent according to claim 1, characterized in that: The molar ratio of sodium porphyrin to chitosan is 1:

286.

4. The application of the chitosan-porphyrin supramolecular polymer network dye adsorbent according to claim 1 in dye adsorption, characterized in that: The dye is at least one of anionic eosin B, orange-yellow G, and sodium acid fuchsin.

5. The application according to claim 4, characterized in that: The specific method is as follows: disperse the chitosan-porphyrin supramolecular polymer network dye adsorbent in the wastewater containing dye, with an addition amount of 1 g / L; stir continuously, take a sample of the solution once at regular intervals, and test the ultraviolet spectrum of the sample, which indicates the adsorption and removal of anionic dyes in the water; after adsorption, the specific method for adsorbent regeneration is as follows: after adsorption, filter, ultrasonically vibrate the adsorbent with 0.4-0.6 M sodium hydroxide solution, wash with deionized water, centrifuge, and reprecipitate in sodium porphyrin buffer solution, which completes the regeneration.

6. The application according to claim 5, characterized in that: The concentration of dye in the wastewater to be treated is 50 mg / L.

7. The application of the chitosan-porphyrin supramolecular polymer network dye adsorbent according to claim 1 in dye screening and adsorption, characterized in that: When cationic and anionic dyes are mixed, this chitosan-porphyrin supramolecular polymer network dye adsorbent only adsorbs anionic dyes.

8. The application according to claim 7, characterized in that: The specific method of selective adsorption is as follows: Chitosan-porphyrin supramolecular polymer network dye adsorbent is dispersed in the wastewater to be treated, which contains both anionic and cationic dyes. The amount of adsorbent added is 1 g / L. The mixture is stirred continuously, and the solution is sampled at regular intervals. The ultraviolet spectrum of the sample is then tested. This means that the anionic dyes in the water are adsorbed and removed, leaving only cationic dyes in the solution.

9. The application according to claim 8, characterized in that: The wastewater to be treated contains either a mixture of anionic eosin B and cationic malachite green hydrochloride, or a mixture of anionic orange yellow G and cationic malachite green hydrochloride, with a concentration of 5 mg / L for each mixture.

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