Temperature-sensitive chitosan and nano magnetite composite material as well as preparation method and application thereof

Abstract

The invention discloses a temperature-sensitive chitosan and nano magnetite composite material as well as a preparation method and application thereof, and belongs to the technical field of photocatalytic materials. The method comprises the following steps: S1, dissolving a chitosan material in an organic solvent I, and adding 2-bromoisobutyryl bromide for reaction in a protective gas atmosphere to obtain brominated chitosan; adding brominated chitosan and a temperature-sensitive monomer into an organic solvent II, adding a transition metal catalyst, and reacting to obtain temperature-sensitive chitosan; s2, adding a trivalent iron salt and a divalent iron salt into an acetic acid solution to obtain an iron salt solution, and then adding temperature-sensitive chitosan and glycerol to obtain a mixed solution; and S3, dropwise adding the mixed solution obtained in the step S2 into an ethanol water solution of sodium hydroxide to obtain the temperature-sensitive chitosan and nano magnetite composite material. The composite material prepared by the invention has high catalytic degradation rate on methyl orange and rhodamine, and can realize the effect of efficiently catalyzing and degrading organic pollutants in wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials, and in particular relates to a temperature-sensitive chitosan and nano-magnetite composite material and a preparation method and application thereof. Background Art

[0002] Printing and dyeing wastewater is becoming a serious environmental problem due to its high toxicity, high chemical oxygen demand, high biochemical oxygen demand, high content of organic pollutants, and resistance to chemical, photochemical and biodegradation. Its acute toxicity, stability and difficulty in decomposition in the environment have attracted great attention from the global community. Direct discharge into the water system will cause great harm to fish, aquatic microorganisms and mammals. Highly toxic dyes will also reduce the light transmittance of water, thereby reducing the quality and transparency of water, affecting the photosynthetic activity of aquatic plants, causing hypoxia in aquatic ecosystems, and thus causing damage to aquatic ecosystems; at the same time, printing and dyeing wastewater is also extremely harmful to humans, and can cause allergic problems such as contact dermatitis, respiratory diseases, eye and respiratory tract irritation, and may even lead to kidney cancer, bladder cancer, etc. Therefore, treating printing and dyeing wastewater is of extremely important practical and economic significance for alleviating the water resource crisis, protecting the ecological environment, and promoting the sustainable development of the printing and dyeing industry. At present, physical, chemical and biological treatment technologies can be used to treat printing and dyeing wastewater. Although these technical methods are relatively mature, they still have many problems such as high cost, low efficiency, instability, and easy to cause secondary pollution. Photocatalytic oxidation technology has become an important method for degrading printing and dyeing and other high-concentration organic wastewaters because of its advantages such as simple operation, high efficiency, non-toxicity, high efficiency, no secondary pollution, and repeated use of materials. The core problem of photocatalytic technology lies in photocatalytic materials, so the development of a green, low-cost catalytic material with excellent dye degradation effect is the current research focus.

[0003] In the field of photocatalysis, TiO 2 , ZnO, Fe 2 O 3 , Fe 3 O 4 Semiconductors such as , CdS, etc. have significant photocatalytic properties and are gradually being used in the field of wastewater treatment. 3 O 4 ) has the advantages of low toxicity, simple preparation, easy separation, absorption of the full spectrum of light in the solar spectrum, and recycling. As a photocatalytic material, it has a wide range of application prospects and has attracted extensive attention from researchers. For example, Chinese patent CN113087023A discloses a magnetic nanoparticle ferroferric oxide and its preparation method and application. The invention uses a coprecipitation method to prepare a magnetic nanoparticle Fe 3 O 4The particle size is uniform and not easy to agglomerate. It has excellent visible light photocatalytic and adsorption properties. It can adsorb and degrade Congo red and methyl blue dyes, and catalytically degrade rhodamine B dye under visible light. However, the effect of the magnetic nanoparticles in catalyzing the degradation of rhodamine B is limited.

[0004] Chitosan is produced by the non-acetylation of chitin, the main component of crustacean shells and fungal biomass, and it is easily obtained from seafood processing waste. Due to the large number of amino and hydroxyl groups in its structure, its amino group can be protonated, has good adsorption capacity for a variety of heavy metal ions, and complexes with amine groups, it has been widely used as a biosorbent for removing various metal ions and dyes from wastewater. However, from the perspective of practical applications, chitosan still has limitations such as unsatisfactory mechanical properties and deformation after drying. More importantly, chitosan is highly pH-sensitive and can only be dissolved under acidic conditions. It is difficult to dissolve in water and has poor hydrophilicity, resulting in a small contact area with organic dyes in water and a low degradation rate of organic pollutants.

[0005] Therefore, it is of great significance to provide a photocatalytic material that has good degradation effect on organic pollutants and strong self-stability. Summary of the invention

[0006] In view of the above shortcomings of the prior art, one of the objects of the present invention is to provide a method for preparing a thermosensitive chitosan and nano-magnetite composite material. The prepared composite material is used as a catalyst for degrading organic pollutants, has a high catalytic degradation rate for methyl orange and rhodamine, and can achieve the effect of efficient catalytic degradation of organic pollutants in wastewater.

[0007] The above object of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a temperature-sensitive chitosan and nano-magnetite composite material comprises the following steps:

[0009] S1, dissolving chitosan material in an organic solvent 1, adding 2-bromoisobutyryl bromide to react in a protective gas atmosphere to obtain brominated chitosan; then adding brominated chitosan and a thermosensitive monomer to an organic solvent 2, adding a transition metal catalyst to react to obtain thermosensitive chitosan;

[0010] S2, adding trivalent iron salt and divalent iron salt to acetic acid solution to obtain iron salt solution, and then adding temperature-sensitive chitosan and glycerol to obtain a mixed solution;

[0011] S3, adding the mixed solution obtained in step S2 dropwise into an ethanol aqueous solution of sodium hydroxide to obtain a thermosensitive chitosan and nano-magnetite composite material.

[0012] The present invention uses chitosan material and thermosensitive monomer as reaction raw materials, and adopts atom transfer radical polymerization (ATRP) to prepare thermosensitive chitosan. By performing thermosensitive modification on chitosan, the hydrophilicity of chitosan can be improved, and the contact effect of chitosan in water can be enhanced, so as to facilitate the degradation of organic pollutants in water by composite microspheres, and improve the degradation effect of composite microspheres on organic pollutants. In addition, compared with directly mixing chitosan solution with thermosensitive material, the material prepared by ATRP method in the present invention is more solid, and the material prepared by chemical bond method is more stable and has better catalytic effect. Subsequently, the thermosensitive chitosan is mixed with trivalent iron salt and divalent iron salt, so that the thermosensitive chitosan and nano-magnetite are composited to form a composite material with higher photocatalytic efficiency. The obtained composite material is used as a catalytic material for degrading organic dyes, and has high catalytic activity, which greatly improves the degradation effect on organic pollutants; at the same time, the material also has the characteristics of strong stability and low preparation cost.

[0013] Preferably, in step S1, the concentration of the chitosan material in the organic solvent 1 is 0.5 g / (100-200) mL.

[0014] Preferably, in step S1, the mass volume ratio of the chitosan material to 2-bromoisobutyryl bromide is 0.5:(1-10) g / mL; the mass ratio of the brominated chitosan to the thermosensitive monomer is 1:(5-20).

[0015] Preferably, in step S1, the temperature-sensitive monomer is N-isopropylacrylamide.

[0016] Preferably, in step S1, the transition metal catalyst includes at least one of cuprous chloride, ferrous bromide, cuprous bromide, cupric bromide or ferrous chloride.

[0017] Preferably, in step S2, the total molar concentration of the divalent iron salt and the trivalent iron salt in the iron salt solution is 0.1-0.5 mol / L.

[0018] Preferably, in step S2, the molar ratio of the divalent iron salt to the trivalent iron salt is (1-3):(1-2).

[0019] Preferably, in step S2, the ratio of the total mass of the divalent iron salt and the trivalent iron salt to the mass of the thermosensitive chitosan is 1:(1-2).

[0020] Preferably, in step S2, the ratio of the total mass of the divalent iron salt and the trivalent iron salt to the mass of glycerol is (1-10):0.2.

[0021] Preferably, in step S3, the mass volume ratio (m:v:v) of sodium hydroxide, anhydrous ethanol and water in the ethanol aqueous solution of sodium hydroxide is (10-14): (55-65): (35-45) g / mL / mL.

[0022] Preferably, the preparation method further comprises the following steps: preparing chitosan into chitosan microcapsules before use, specifically, the chitosan is dissolved in acetic acid solution to obtain chitosan acetic acid solution, the chitosan acetic acid solution is added dropwise to the oil phase solution, stirred evenly to obtain an oil-in-water emulsion, and the chitosan microcapsules are obtained after washing and drying.

[0023] The present invention prepares chitosan microcapsules through chitosan, which can form a larger specific surface area, improve the subsequent reaction efficiency with 2-bromoisobutyryl bromide, enhance the effect of temperature-sensitive modification, and further enhance the catalytic degradation effect of the composite microspheres on organic pollutants.

[0024] More preferably, the oil phase solution is prepared by dissolving terephthalaldehyde and polyglycerol polyricinoleate in a mixed solvent of benzyl benzoate and cyclohexane to obtain the oil phase solution.

[0025] More preferably, the concentration of terephthalaldehyde in the oil phase solution is 0.5wt%~2wt%, and the concentration of polyglycerol ricinoleate is 2wt%~6wt%.

[0026] Another object of the present invention is to provide a temperature-sensitive chitosan and nano-magnetite composite material prepared by the preparation method.

[0027] Another object of the present invention is to provide an application of the thermosensitive chitosan and nano-magnetite composite material prepared by the preparation method in catalytic degradation of methyl orange or rhodamine.

[0028] Preferably, the method for applying the thermosensitive chitosan and nano-magnetite composite material in the catalytic degradation of methyl orange comprises the following steps: adding the thermosensitive chitosan and nano-magnetite composite material to a methyl orange solution, ultrasonically treating it for 5 to 40 minutes under light-proof conditions, and then treating it under natural light for 30 to 60 minutes to complete the photocatalytic degradation.

[0029] Preferably, the application method of the thermosensitive chitosan and nano-magnetite composite material in the catalytic degradation of rhodamine comprises the following steps: adding the thermosensitive chitosan and nano-magnetite composite material to a rhodamine solution, mixing, then adding 0.1-0.3 mmol / L PMS solution, and performing a catalytic degradation reaction under natural light conditions.

[0030] Compared with the prior art, the present invention is beneficial in that:

[0031] (1) The present invention uses chitosan material and thermosensitive monomer as reaction raw materials to prepare thermosensitive chitosan. By performing thermosensitive modification on chitosan, the hydrophilicity of chitosan can be improved, and the contact effect of chitosan in water can be enhanced, thereby facilitating the degradation of organic pollutants in water by composite microspheres and improving the degradation effect of composite microspheres on organic pollutants.

[0032] (2) Compared with directly mixing the chitosan solution with the thermosensitive material, the material prepared by the ATRP method in the present invention is more solid, and the material prepared by the chemical bond method is more stable and has a better catalytic effect.

[0033] (3) The thermosensitive chitosan and nano-magnetite composite material prepared by the present invention is a new type of catalytic material. The catalytic activity of the catalytic material is high, and the degradation rate of the organic pollutant methyl orange is as high as 81%, and the degradation rate of rhodamine is as high as 86%, which greatly improves the degradation effect. In addition, the composite material prepared by the present invention has good chemical stability and thermal stability, and has potential applications in pollutant adsorption and removal and gas adsorption separation.

[0034] (4) The present invention uses chitosan to prepare chitosan microcapsules, which can form a larger specific surface area, improve the subsequent reaction efficiency with 2-bromoisobutyryl bromide, enhance the effect of temperature-sensitive modification, and further enhance the catalytic degradation effect of the composite microspheres on organic pollutants. The degradation rate of the organic pollutant methyl orange is as high as 98%, and the degradation rate of rhodamine is as high as 99%.

[0035] (5) The catalytic material of the present invention can be reused and easily recycled without causing secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a physical picture of the thermosensitive chitosan and nano-magnetite composite material obtained in Example 1;

[0037] Figure 2 This is the infrared spectrum of the thermosensitive chitosan and nano-magnetite composite material obtained in Example 1;

[0038] Figure 3 This is a diagram showing the degradation effect of the catalytic material of Example 1 on methyl orange. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The embodiment of the present invention provides a method for preparing a temperature-sensitive chitosan and nano-magnetite composite material, comprising the following steps:

[0041] S1, dissolving chitosan material in an organic solvent 1, adding 2-bromoisobutyryl bromide to react in a protective gas atmosphere to obtain brominated chitosan; then adding brominated chitosan and a thermosensitive monomer to an organic solvent 2, adding a transition metal catalyst to react to obtain thermosensitive chitosan;

[0042] S2, adding trivalent iron salt and divalent iron salt to acetic acid solution to obtain iron salt solution, and then adding temperature-sensitive chitosan and glycerol to obtain a mixed solution;

[0043] S3, adding the mixed solution obtained in step S2 dropwise into an ethanol aqueous solution of sodium hydroxide to obtain a thermosensitive chitosan and nano-magnetite composite material.

[0044] In some embodiments, the organic solvent 1 is a mixed solvent of triethylamine and dichloromethane, and the organic solvent 2 is methanol and water. The concentration of the chitosan material in the organic solvent 1 is 0.5 g / (100-200) mL; for example, the concentration of the chitosan material in the organic solvent 1 is 0.5 g / 100 mL, 0.5 g / 160 mL, 0.5 g / 200 mL, etc.

[0045] In some embodiments, in step S1, the mass volume ratio of the chitosan material to 2-bromoisobutyryl bromide is 0.5:(1~10) g / mL; the mass ratio of the brominated chitosan to the thermosensitive monomer is 1:(5~20); and the thermosensitive monomer is N-isopropylacrylamide.

[0046] In some embodiments, the transition metal catalyst includes at least one of cuprous chloride, ferrous bromide, cuprous bromide, cupric bromide, or ferrous chloride.

[0047] In some embodiments, in step S2, the total molar concentration of the ferrous iron salt and the ferric iron salt in the ferric salt solution is 0.1-0.5 mol / L, for example, the total molar concentration of the ferrous iron salt and the ferric iron salt in the ferric salt solution is 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc. The molar ratio of the ferrous iron salt to the ferric iron salt is (1-3): (1-2), for example, the molar ratio of the ferrous iron salt to the ferric iron salt is 1:1, 1:2, 3:1, etc.

[0048] The total mass ratio of the divalent iron salt and the trivalent iron salt to the mass ratio of the thermosensitive chitosan is 1:(1-2). The total mass ratio of the divalent iron salt and the trivalent iron salt to the mass ratio of glycerol is (1-10):0.2.

[0049] The mass volume ratio (m:v:v) of sodium hydroxide, anhydrous ethanol and water in the ethanol aqueous solution of sodium hydroxide is (10~14):(55~65):(35~45) g / mL / mL.

[0050] In some embodiments, the preparation method further includes the following steps: chitosan is made into chitosan microcapsules before use, and the specific operation is as follows: chitosan is dissolved in acetic acid solution to obtain chitosan acetic acid solution, the chitosan acetic acid solution is added dropwise to the oil phase solution, stirred evenly to obtain an oil-in-water emulsion, and chitosan microcapsules are obtained after washing and drying.

[0051] Among them, the preparation method of the oil phase solution is: dissolving terephthalaldehyde and polyglycerol ricinoleate in a mixed solvent of benzyl benzoate and cyclohexane to obtain the oil phase solution; the concentration of terephthalaldehyde in the oil phase solution can be 0.5wt%~2wt%, and the concentration of polyglycerol ricinoleate can be 2wt%~6wt%; for example, the concentration of terephthalaldehyde in the oil phase solution can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, etc., and the concentration of polyglycerol ricinoleate in the oil phase solution can be 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 6wt%, etc.

[0052] In the following examples and comparative examples, the deacetylation degree of chitosan is ≥95%, the viscosity is 100-200 mPa.s; and the volume concentration of the acetic acid solution is 1%-5%.

[0053] Example 1

[0054] This embodiment provides a method for preparing a temperature-sensitive chitosan and nano-magnetite composite material, comprising the following steps:

[0055] S1, dissolving chitosan in an acetic acid solution with a volume concentration of 2% to obtain a chitosan acetic acid solution with a chitosan concentration of 2wt%, dissolving terephthalaldehyde and polyglycerol ricinoleate in a mixed solvent of benzyl benzoate and cyclohexane (the volume ratio of benzyl benzoate to cyclohexane is 1:1) to obtain a mixed oil phase solution, wherein the concentration of terephthalaldehyde in the mixed oil phase solution is 1wt%, and the concentration of polyglycerol ricinoleate is 4wt%; then, adding 10mL of the chitosan acetic acid solution dropwise to 100mL of the mixed oil phase solution, stirring at 700 rpm to form a uniform water-in-oil emulsion, washing to remove unreacted reagents, and drying to obtain chitosan microcapsules;

[0056] S2, 0.5 g chitosan microcapsules, 97 mL dichloromethane and 3 mL triethylamine were mixed in a reactor and gently stirred in an ice water bath at 2°C; then, 2 mL 2-bromoisobutyryl bromide was slowly added dropwise to the solution under nitrogen. After 8 h, the reacted chitosan microcapsules were washed with ethanol and dried at 50°C to obtain brominated chitosan; 0.1 g brominated chitosan and 0.5 g N-isopropylacrylamide were added to a mixed solvent of 20 mL methanol and 30 mL water, and then 0.03 g CuBr and 0.1 g CuBr were added. 2 The catalyst composed of the above ingredients and 0.1 mL of pentamethyl diethylene triamine were reacted under nitrogen for 24 h to obtain thermosensitive chitosan.

[0057] S3, add 3g of ferric chloride hexahydrate and 1.54g of ferrous sulfate heptahydrate to 83mL of 1% acetic acid solution (Fe 2+ :Fe 3+ =1:2), forming an iron salt solution; then adding 4.54g of temperature-sensitive chitosan and 0.2g of glycerol, stirring for 30min to obtain a mixed solution;

[0058] S4. Take 60 mL of anhydrous ethanol, 40 mL of distilled water and 12 g of sodium hydroxide and put them into a 250 mL beaker. Add a magnet and stir for 2.5 h until the solution becomes colorless and transparent to obtain an ethanol aqueous solution of sodium hydroxide. Then use a 5 mL syringe to drop the mixed solution obtained in step S3 into the ethanol aqueous solution of sodium hydroxide at a rate of 2 mL / min. Wash the product three times with ethanol and distilled water in turn. Dry it at 50°C for 3 h to obtain a thermosensitive chitosan and nano-magnetite composite material.

[0059] The actual picture of the composite material prepared in Example 1 is as follows Figure 1 As shown in the figure, it can be seen that the temperature-sensitive chitosan composite nano-magnetite material can form a spherical material with regular morphology, good spherical effect, and a large specific surface area. The infrared spectrum of the composite material prepared in Example 1 is shown in Figure 2 As shown in the figure, it can be seen that the infrared spectrum contains 1650cm -1 The left and right sides belong to the characteristic peaks of the amide bonds of the thermosensitive material, and also include the characteristic peaks of chitosan, proving that the material was successfully prepared.

[0060] Example 2

[0061] This embodiment provides a method for preparing a temperature-sensitive chitosan and nano-magnetite composite material, comprising the following steps:

[0062] S1, dissolving chitosan in an acetic acid solution with a volume concentration of 2% to obtain a chitosan acetic acid solution with a chitosan concentration of 2wt%, dissolving terephthalaldehyde and polyglycerol ricinoleate in a mixed solvent of benzyl benzoate and cyclohexane (the volume ratio of benzyl benzoate to cyclohexane is 1:1) to obtain a mixed oil phase solution, wherein the concentration of terephthalaldehyde in the mixed oil phase solution is 0.5wt%, and the concentration of polyglycerol ricinoleate is 4.5wt%; then, 10mL of the chitosan acetic acid solution is added dropwise to 100mL of the mixed oil phase solution, while stirring at 700 rpm to form a uniform water-in-oil emulsion, washing to remove unreacted reagents, and drying to obtain chitosan microcapsules;

[0063] S2, 0.5 g chitosan microcapsules, 97 mL dichloromethane and 3 mL triethylamine were mixed in a reactor and gently stirred in an ice water bath at 2°C; then, 1 mL 2-bromoisobutyryl bromide was slowly added dropwise to the solution under nitrogen. After 8 h, the reacted chitosan microcapsules were washed with ethanol and dried at 50°C to obtain brominated chitosan; 0.1 g brominated chitosan and 1 g N-isopropylacrylamide were added to a mixed solvent of 20 mL methanol and 30 mL water, and then 0.03 g CuBr and 0.1 g CuBr were added. 2 The catalyst composed of the above ingredients and 0.1 mL of pentamethyl diethylene triamine were reacted under nitrogen for 24 h to obtain thermosensitive chitosan.

[0064] S3, add 1.497g of ferric chloride hexahydrate and 1.54g of ferrous sulfate heptahydrate to 83mL of 1% acetic acid solution (Fe 2+ :Fe 3+ =1:1), forming an iron salt solution; then, 6.074 g of temperature-sensitive chitosan and 0.6 g of glycerol were added, and the mixture was stirred for 30 min to obtain a mixed solution.

[0065] S4. Take 60 mL of anhydrous ethanol, 40 mL of distilled water and 12 g of sodium hydroxide and put them into a 250 mL beaker. Add a magnet and stir for 2.5 h until the solution becomes colorless and transparent to obtain an ethanol aqueous solution of sodium hydroxide. Then use a 5 mL syringe to drop the mixed solution obtained in step S3 into the ethanol aqueous solution of sodium hydroxide at a rate of 1 mL / min. Wash the product three times with ethanol and distilled water in turn. Dry it at 50°C for 6 h to obtain a thermosensitive chitosan and nano-magnetite composite material.

[0066] Example 3

[0067] This embodiment provides a method for preparing a temperature-sensitive chitosan and nano-magnetite composite material, comprising the following steps:

[0068] S1, dissolving chitosan in an acetic acid solution with a volume concentration of 2% to obtain a chitosan acetic acid solution with a chitosan concentration of 2wt%, dissolving terephthalaldehyde and polyglycerol ricinoleate in a mixed solvent of benzyl benzoate and cyclohexane (the volume ratio of benzyl benzoate to cyclohexane is 1:1) to obtain a mixed oil phase solution, wherein the concentration of terephthalaldehyde in the mixed oil phase solution is 2wt%, and the concentration of polyglycerol ricinoleate is 3wt%; then, 10mL of the chitosan acetic acid solution is added dropwise to 100mL of the mixed oil phase solution, while stirring at 700 rpm to form a uniform water-in-oil emulsion, washing to remove unreacted reagents, and drying to obtain chitosan microcapsules;

[0069] S2, 0.5 g chitosan microcapsules, 97 mL dichloromethane and 3 mL triethylamine were mixed in a reactor and gently stirred in an ice water bath at 2°C; then, 10 mL 2-bromoisobutyryl bromide was slowly added dropwise to the solution under nitrogen. After 8 h, the reacted chitosan microcapsules were washed with ethanol and dried at 50°C to obtain brominated chitosan; 0.1 g brominated chitosan and 2 g N-isopropylacrylamide were added to a mixed solvent of 20 mL methanol and 30 mL water, and then 0.03 g CuBr and 0.1 g CuBr were added. 2 The catalyst composed of the above ingredients and 0.1 mL of pentamethyl diethylene triamine were reacted under nitrogen for 24 h to obtain thermosensitive chitosan.

[0070] S3, add 1.497g of ferric chloride hexahydrate and 4.62g of ferrous sulfate heptahydrate to 83mL of 1% acetic acid solution (Fe 2+ :Fe 3+ =3:1), forming an iron salt solution; then adding 6.117g of temperature-sensitive chitosan and 0.12g of glycerol, stirring for 30min to obtain a mixed solution;

[0071] S4. Take 60 mL of anhydrous ethanol, 40 mL of distilled water and 12 g of sodium hydroxide and put them into a 250 mL beaker. Add a magnet and stir for 2.5 h until the solution becomes colorless and transparent to obtain an ethanol aqueous solution of sodium hydroxide. Then use a 5 mL syringe to drop the mixed solution obtained in step S3 into the ethanol aqueous solution of sodium hydroxide at a rate of 3 mL / min. Wash the product three times with ethanol and distilled water in turn. Dry it at 50°C for 3 h to obtain a thermosensitive chitosan and nano-magnetite composite material.

[0072] Example 4

[0073] The preparation method of the thermosensitive chitosan and nano-magnetite composite material of this embodiment comprises the following steps:

[0074] S1. 0.5 g chitosan, 97 mL dichloromethane and 3 mL triethylamine were mixed in a reactor and gently stirred in an ice-water bath at 2°C. Then, 2 mL 2-bromoisobutyryl bromide was slowly added dropwise to the solution under nitrogen. After 8 h, the reacted chitosan was washed with ethanol and dried at 50°C to obtain brominated chitosan. 0.1 g brominated chitosan and 0.5 g N-isopropylacrylamide were added to a mixed solvent of 20 mL methanol and 30 mL water, and then 0.03 g CuBr and 0.1 g CuBr were added. 2 The catalyst composed of the above ingredients and 0.1 mL of pentamethyl diethylene triamine were reacted under nitrogen for 24 h to obtain thermosensitive chitosan.

[0075] S2, add 3g of ferric chloride hexahydrate and 1.54g of ferrous sulfate heptahydrate to 83mL of 1% acetic acid solution (Fe 2+ :Fe 3+ =1:2), forming an iron salt solution; then adding 4.54g of temperature-sensitive chitosan and 0.2g of glycerol, stirring for 30min to obtain a mixed solution;

[0076] S3, take 60 mL of anhydrous ethanol, 40 mL of distilled water and 12 g of sodium hydroxide and add them to a 250 mL beaker, add a magnet, stir for 2.5 h until it becomes colorless and transparent, and obtain an ethanol aqueous solution of sodium hydroxide; then use a 5 mL syringe to drop the mixed solution obtained in step S3 into the ethanol aqueous solution of sodium hydroxide at a rate of 2 mL / min, wash the product with ethanol and distilled water three times in turn, and dry it at 50°C for 3 h to obtain a thermosensitive chitosan and nano-magnetite composite material;

[0077] That is, compared with Example 1, the step of preparing chitosan into microcapsules is omitted in this example.

[0078] Comparative Example 1

[0079] The preparation method of the thermosensitive chitosan and nano-magnetite composite material of this comparative example is basically the same as that of Example 1, except that step S4 is as follows: the mixed solution obtained in step S3 is directly dried and ground to obtain a composite material with a powdery morphology.

[0080] Comparative Example 2

[0081] The preparation method of the thermosensitive chitosan and nano-magnetite composite material of this comparative example is basically the same as that of Example 1, except that step S2 is as follows:

[0082] 0.5 g chitosan microcapsules were dissolved in 50 mL of 1% acetic acid solution, stirred evenly, and then a thermosensitive material poly N-isopropylacrylamide solution (0.1 g of the thermosensitive material was dissolved in 10 mL of distilled water) was added, and then stirred evenly to obtain thermosensitive chitosan;

[0083] That is, compared with Example 1, the ATRP polymerization step is omitted in this comparative example, and chitosan and the temperature-sensitive material are directly mixed.

[0084] Comparative Example 3

[0085] The preparation method of the thermosensitive chitosan and nano-magnetite composite material of this comparative example comprises the following steps:

[0086] S1. Add 3 g of ferric chloride hexahydrate and 1.54 g of ferrous sulfate heptahydrate to 83 mL of 1% acetic acid solution (Fe 2+ :Fe 3+ =1:2), forming an iron salt solution; then adding 4.54g chitosan and 0.2g glycerol, stirring for 30min to obtain a mixed solution;

[0087] S2, take 60 mL of anhydrous ethanol, 40 mL of distilled water and 12 g of sodium hydroxide and add them to a 250 mL beaker, add a magnet, stir for 2.5 h until it becomes colorless and transparent, and obtain an ethanol aqueous solution of sodium hydroxide; then use a 5 mL syringe to drop the mixed solution obtained in step S3 into the ethanol aqueous solution of sodium hydroxide at a rate of 2 mL / min, wash the product with ethanol and distilled water three times in turn, and dry it at 50°C for 3 h to obtain a thermosensitive chitosan and nano-magnetite composite material;

[0088] That is, compared with Example 1, this comparative example omits the step of preparing chitosan into microcapsules, and does not perform temperature-sensitive modification on chitosan, but directly prepares chitosan and nano-magnetite into microspheres.

[0089] Application Example 1

[0090] The composite materials prepared in the examples and comparative examples were applied to the catalytic degradation of methyl orange, and the specific steps were as follows:

[0091] Accurately prepare a 20 mg / L methyl orange solution (made from 0.0205 g methyl orange and 1 L distilled water), weigh 10 mg of the above-mentioned catalytic material and add it to 100 mL of methyl orange solution (20 mg / L), and use an ultrasonic cleaner to ultrasonically treat it for 5 min under light-proof conditions to allow the methyl orange to be completely pre-adsorbed on the surface of the catalytic material.

[0092] The above solution was placed under natural light for illumination, and after reacting for 1 hour, it was taken out and centrifuged at 40×100 r for 10 minutes to obtain the supernatant.

[0093] The UV-visible spectrophotometer was used to detect 20 mg / L methyl orange in the full band of 300 nm to 600 nm, and the best detection (around 464 nm) was selected. The absorbance of the above clear solution was measured at the best detection wavelength, and the degradation rate was calculated. The calculation formula of the degradation rate is as follows:

[0094] Degradation rate = (A 降解前 -A 降解后 ) / A 降解前 ×100%

[0095] Among them, A 降解前 A represents the absorbance corresponding to the peak at 464 nm measured before the methyl orange solution is mixed with the material; 降解后 It represents the absorbance corresponding to the peak at 464 nm measured after the methyl orange solution and the material are mixed and stirred under light;

[0096] in, Figure 3 This is a diagram showing the degradation effect of the catalytic material of Example 1 on methyl orange. The degradation rate is calculated to be 98%. The degradation rate results of each embodiment and comparative example are shown in Table 1.

[0097] Table 1 Catalytic degradation effect of photocatalytic materials on methyl orange

[0098]

[0099] From the results in Table 1, it can be seen that the degradation rate of the thermosensitive chitosan and nano-magnetite composite material of the present invention on the organic dye methyl orange is as high as 98%, and the catalytic effect is good. Compared with Example 1, Example 4 omits the step of preparing chitosan into microcapsules, and the degradation rate of methyl orange is reduced to 81%, indicating that preparing chitosan into microcapsules can improve the effect of thermosensitive modification.

[0100] Compared with Example 1, in Comparative Example 1, the material is not made into microspheres, but directly dried to obtain a powder material, and the degradation rate of methyl orange is reduced to 48%, mainly because the morphology of the microsphere material can significantly increase the contact area between the material and the organic dye methyl orange, thereby significantly improving the catalytic effect; in Comparative Example 2, the ATRP polymerization step is omitted, and chitosan and the thermosensitive material are directly mixed, and the degradation rate of methyl orange is reduced to 75%, indicating that compared with directly mixing the chitosan solution with the thermosensitive material, the catalytic effect of the composite material can be improved by performing temperature-sensitive modification of chitosan by ATRP; in Comparative Example 3, the step of preparing chitosan into microcapsules is omitted, and chitosan is not subjected to temperature-sensitive modification, and chitosan and magnetite are directly prepared into microspheres, and the degradation rate of methyl orange is reduced to 36%, indicating that the degradation effect of the composite material on methyl orange can be improved by performing temperature-sensitive modification of chitosan by the method of the present invention.

[0101] Application Example 2

[0102] The application method of this application example is different from that of Application Example 1. The catalytic degradation object of this application example is rhodamine, and the application process is as follows: prepare a 5 mg / L RhB solution and measure 50 mL of RhB solution in a 100 ml conical flask. Weigh about 5 mg of photocatalytic material and add it to the conical flask and mix it. Add 0.2 mmol / L PMS solution, shake well and stir magnetically. Under natural light conditions, take out 1 mL of sample at regular intervals. Filter the reaction with a 0.22 µL membrane and add 100 µL of anhydrous ethanol to terminate the reaction. Then use a UV spectrophotometer to measure the remaining RhB content in the solution to determine the degradation rate at each time point.

[0103] The degradation rates of rhodamine by the catalytic materials of the embodiments and comparative examples in this application example at 30 min are shown in Table 2 below.

[0104] Table 2 Catalytic degradation effect of photocatalytic materials on rhodamine

[0105]

[0106] As shown in Table 2, the degradation rate of the thermosensitive chitosan and nano-magnetite composite material for the organic dye rhodamine is as high as 99% at 30 minutes, and the catalytic effect is good. Compared with Example 1, Example 4 omits the step of preparing chitosan into microcapsules, and the degradation rate of rhodamine is reduced to 86%, indicating that preparing chitosan into microcapsules can improve the effect of thermosensitive modification.

[0107] Compared with Example 1, in Comparative Example 1, the material is not made into microspheres, but directly dried to obtain a powder material. The degradation rate of methyl orange is reduced to 58%, and the catalytic effect is deteriorated, indicating that the microsphere morphology has a better degradation effect on rhodamine; in Comparative Example 2, the ATRP polymerization step is omitted, and chitosan and the thermosensitive material are directly mixed, and the degradation rate of rhodamine is reduced to 65%, indicating that compared with directly mixing the chitosan solution with the thermosensitive material, the ATRP method is used to perform temperature-sensitive modification of chitosan to improve the catalytic effect of the composite material; in Comparative Example 3, the step of preparing chitosan into microcapsules is omitted, and chitosan is not temperature-sensitively modified. Chitosan and magnetite are directly prepared into microspheres, and the degradation rate of rhodamine is reduced to 39%, indicating that the method of the present invention is used to perform temperature-sensitive modification of chitosan to improve the degradation effect of the composite material on rhodamine.

[0108] Application Example 3

[0109] Based on the test results of the above application example 1, this application example examines the reusability of the composite material prepared in Example 1. The material is reused after centrifugation, washing, and drying. The specific steps are as follows:

[0110] Weigh 10 mg of the recovered catalytic material and add it to 100 mL of methyl orange solution (20 mg / L). Use an ultrasonic cleaner to ultrasonically treat it for 5 min under light-proof conditions to completely pre-adsorb methyl orange on the surface of the catalytic material. Put the above solution under natural light, react for 1 hour, take it out, centrifuge it at 40×100 r for 10 min, and take the supernatant. Measure the absorbance of the above supernatant at the optimal detection wavelength, calculate the degradation rate, and the degradation results of the recovered catalytic material are shown in Table 3 below.

[0111] Table 3 Catalytic degradation effect of recycled catalytic materials on methyl orange

[0112]

[0113] From the results in Table 3, it can be seen that the recycled catalytic material still maintains a good catalytic effect. After being reused for 5 times, the degradation rate of methyl orange is still maintained at 93%.

[0114] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a thermosensitive chitosan and nano-magnetite composite material, characterized in that: The following steps are involved: S1, dissolving chitosan material in an organic solvent 1, adding 2-bromoisobutyryl bromide to react in a protective gas atmosphere to obtain brominated chitosan; then adding brominated chitosan and a thermosensitive monomer to an organic solvent 2, adding a transition metal catalyst to react to obtain thermosensitive chitosan; S2, adding trivalent iron salt and divalent iron salt to acetic acid solution to obtain iron salt solution, and then adding temperature-sensitive chitosan and glycerol to obtain a mixed solution; S3, adding the mixed solution obtained in step S2 dropwise into an ethanol aqueous solution of sodium hydroxide to obtain a thermosensitive chitosan and nano-magnetite composite material.

2. The method for preparing a thermosensitive chitosan and nano-magnetite composite material according to claim 1, characterized in that: In step S1, the mass volume ratio of the chitosan material to 2-bromoisobutyryl bromide is 0.5:(1-10) g / mL; the mass ratio of the brominated chitosan to the temperature-sensitive monomer is 1:(5-20); and / or the temperature-sensitive monomer is N-isopropylacrylamide.

3. The method for preparing a thermosensitive chitosan and nano-magnetite composite material according to claim 1, characterized in that: The ratio of the total mass of the divalent iron salt and the trivalent iron salt to the mass of the thermosensitive chitosan is 1:(1-2).

4. The method for preparing a thermosensitive chitosan and nano-magnetite composite material according to claim 1, characterized in that: The ratio of the total mass of the divalent iron salt and the trivalent iron salt to the mass of glycerol is (1-10):0.

2.

5. The method for preparing a thermosensitive chitosan and nano-magnetite composite material according to claim 1, characterized in that: The preparation method also includes the following steps: before use, chitosan is made into chitosan microcapsules, and the specific operation is as follows: chitosan is dissolved in acetic acid solution to obtain chitosan acetic acid solution, the chitosan acetic acid solution is added dropwise to the oil phase solution, stirred evenly to obtain oil-in-water emulsion, and chitosan microcapsules are obtained after washing and drying.

6. The method for preparing a thermosensitive chitosan and nano-magnetite composite material according to claim 5, characterized in that: The preparation method of the oil phase solution is as follows: dissolving terephthalaldehyde and polyglycerol ricinoleate in a mixed solvent of benzyl benzoate and cyclohexane to obtain the oil phase solution.

7. The thermosensitive chitosan and nano-magnetite composite material prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the thermosensitive chitosan and nano-magnetite composite material prepared by the preparation method according to any one of claims 1 to 6 in catalytic degradation of methyl orange or rhodamine.

9. The use according to claim 8, characterized in that: The application method of the thermosensitive chitosan and nano-magnetite composite material in catalytic degradation of methyl orange has the following steps: adding the thermosensitive chitosan and nano-magnetite composite material to a methyl orange solution, ultrasonically treating for 5 to 40 minutes under light-proof conditions, and then treating under natural light for 30 to 60 minutes to complete the catalytic degradation.

10. The use according to claim 8, characterized in that: The application method of the thermosensitive chitosan and nano-magnetite composite material in catalytic degradation of rhodamine comprises the following steps: adding the thermosensitive chitosan and nano-magnetite composite material to a rhodamine solution, mixing, then adding 0.1-0.3 mmol / L PMS solution, and performing a catalytic degradation reaction under natural light conditions.

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