Magnetic foaming freeze-dried modified chitosan material as well as preparation method and application thereof

Abstract

The invention discloses a magnetic foaming freeze-dried modified chitosan material as well as a preparation method and application thereof, and belongs to the field of underground water treatment in coal mine areas. The magnetic foaming freeze-drying modified chitosan material is obtained by combining ferroferric oxide modification, sodium dodecyl sulfate foaming modification and instant freezing modification, and the magnetic foaming freeze-drying modified chitosan material is of a modified chitosan microsphere structure suitable for adsorption of mine water pollutants. And the adsorbent can stably exist in neutral, alkaline and high-salt mine water solutions, and has relatively good removal capability on metal ions such as iron, manganese and calcium in the mine water.

Description

Technical Field

[0001] The invention belongs to the field of underground water treatment in coal mine areas, and specifically relates to a magnetic foaming freeze-dried modified chitosan material and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Mine water contains a large amount of heavy metal harmful elements, which causes water pollution problems in the process of coal mining and utilization. At present, the blocking of groundwater pollution in coal mining areas mainly relies on the means of "combining blocking and treatment". Among them, the "blocking" method is to use anti-seepage materials to achieve the sealing of groundwater bodies in mining areas to prevent the spread of sewage; the "treatment" means are mainly divided into physical adsorption, chemical method, thermal method and membrane separation method. The physical adsorption method is to achieve the purpose of reducing pollutants by adsorbing heavy metal ions in sewage through adsorbents such as zeolite, activated alumina, activated carbon, and resin. However, these adsorbents have low adsorption capacity, few raw material sources, high prices, and high carbon emissions, making it difficult to effectively remove pollutants. The chemical method removes salt from mine water by chemically reacting with ions in the mine water. The overall cost is high, and it is very expensive to remove highly mineralized mine water. The thermal method uses distillation to separate salt from water in mine water, thereby achieving the purpose of desalination. However, the evaporation device of this method is extremely prone to scaling, and the initial investment and energy consumption costs are high. It is only suitable for areas with sufficient thermal energy conditions. The membrane separation method is to pressurize the sewage and remove inorganic salt ions in the water through a separation membrane. This method is difficult to work for open underground mine sewage.

[0004] As a physical adsorption material with significant effects, chitosan, which has many advantages such as non-toxicity, high efficiency and biodegradability, has attracted widespread attention. Common types of chitosan on the market include chitosan, carboxymethyl chitosan, hydroxymethyl chitosan, water-soluble chitosan, etc. At present, the research direction of common chitosan materials is mainly to replace the surface groups of chitosan or add composite substances in the chemical modification of chitosan. There are few studies on the functional hybrid modification of chitosan, and most of them are focused on the preparation of modified chitosan membrane structure. The idea is relatively single, resulting in chitosan failing to give full play to its own adsorption performance and application potential. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a magnetic foaming freeze-dried modified chitosan material and its preparation method and application. The magnetic foaming freeze-dried modified chitosan material is prepared by freeze-drying and modification using ferroferric oxide, sodium dodecyl sulfate and chitosan as raw materials, and can stably exist in neutral, alkaline and high-salt mine water solutions, and has a good removal ability for metal ions such as iron, manganese and calcium in mine water. The material is a modified chitosan microsphere that can be used for the adsorption of mine water pollutants.

[0006] In order to achieve the above object, the technical solution of the present invention is: In a first aspect, the present invention provides a magnetic foaming freeze-dried modified chitosan material, wherein the magnetic foaming freeze-dried modified chitosan material is a porous microsphere structure, wherein ferrosoferric oxide particles are uniformly distributed on the porous microsphere structure; In terms of weight, the magnetic foaming freeze-dried modified chitosan material comprises: 0.1-1 parts of ferrosoferric oxide, 1.2-2 parts of chitosan, and 0.01-0.05 parts of sodium dodecyl sulfate.

[0007] Furthermore, in terms of weight, 0.1-0.5 parts of ferrosoferric oxide, 1.4-1.6 parts of chitosan, and 0.01-0.02 parts of sodium dodecyl sulfate are used.

[0008] The particle size of the microspheres is 2-2.5 mm, and the average particle size of the pores is 100-200 μm.

[0009] The principle of magnetic foaming freeze-dried modified chitosan material to adsorb heavy metal pollutants is that its macromolecules contain a large number of amino and hydroxyl groups. The lone pair of electrons on the nitrogen atom can be invested in the empty orbit of the metal ion to form a coordination bond, so that the amino and hydroxyl groups form a stable cyclic chelate with the heavy metal ions, thereby solidifying the heavy metal pollution source and achieving the purpose of reducing the amount of pollutants in mine water.

[0010] In a second aspect, the present invention provides a method for preparing a magnetic foaming freeze-dried modified chitosan material, comprising the following steps: S1: dissolving ferroferric oxide, chitosan and sodium dodecyl sulfate in an acid solution to prepare a magnetic foaming chitosan acid solution; S2: dripping the magnetic foamed chitosan acid solution into an alkaline coagulation liquid to obtain a coagulated magnetic foamed chitosan hydrogel, and then subjecting the hydrogel to aging, washing, cross-linking polymerization, and freeze-drying.

[0011] Sodium dodecyl sulfate is used as a foam stabilizer. A foam stabilizer is a surfactant that increases the surface tension of the liquid, thereby prolonging and stabilizing the foam to maintain long-term performance.

[0012] In one or more embodiments, ferroferric oxide is a nano ferroferric oxide powder, and its particle size is 100~500nm, preferably 100~200nm. Because chitosan itself has the ability of complexing and adsorbing iron ions, if the iron source is a substance such as ferrous chloride, new impurities will be introduced, resulting in a decrease in the ability of the product to adsorb iron ions. In addition, if ferroferric oxide is simply added, ferroferric oxide and chitosan are mixed, and dense chitosan-ferroferric oxide spheres will be obtained after drying, in which ferroferric oxide gathers into balls, greatly reducing the adsorption effect. In the present invention, ferroferric oxide exists in the form of microspheres, and the microspheres do not dissolve in chitosan.

[0013] In one or more embodiments, the chitosan is a 2-2.5 mm dark grey lightweight sphere.

[0014] In one or more embodiments, the acid is acetic acid, and the mass concentration of the acid solution is 2-3 wt.%, preferably 2.5 wt.%. Chitosan is a polymer compound, insoluble in water, alkali, and organic solution, but because it contains amino groups, it can form salts with acid solutions.

[0015] In one or more embodiments, in parts by weight, 0.1-1 parts of ferrosoferric oxide, 1.2-2 parts of chitosan, 0.01-0.05 parts of sodium dodecyl sulfate, and 40-60 parts of acid solution are used, preferably 0.1-0.5 parts of ferrosoferric oxide, 1.4-1.6 parts of chitosan, 0.01-0.02 parts of sodium dodecyl sulfate, and 40-50 parts of acid solution.

[0016] In one or more embodiments, in step S1, stirring is performed at 50-70° C. until all the components are dissolved.

[0017] In one or more embodiments, in step S2, the alkaline coagulation liquid is a mixture of alkali and water, and the alkali is a strong alkali, such as sodium hydroxide. Weak alkali is not conducive to coagulation. The mass ratio of alkali to water is (2-6): (40-60).

[0018] In one or more embodiments, in step S2, the preparation method of the alkaline coagulation liquid is: dissolving alkali in water to obtain an alkaline aqueous solution, stirring the aqueous solution until there is no alkaline solid, and waiting for coagulation at room temperature.

[0019] In one or more embodiments, in step S2, the dripping method is an injection dripping method, specifically: fix the syringe that sucks the magnetic foamed chitosan acid solution on the triple micro-injection pump, cover the dispensing plastic injection needle on the syringe head, adjust the height of the test bench below the micro-injection pump until the center of the syringe needle is 5~20 cm away from the liquid level, push the syringe at a propulsion speed of 1~3 μL / min, and drip the solution into the configured alkaline coagulation solution.

[0020] In one or more embodiments, in step S2, small amounts of dripping are used multiple times.

[0021] In one or more embodiments, the aging is to place the solidified magnetic foamed chitosan hydrogel in an alkaline coagulation solution for aging, and the aging time is 1 to 5 hours.

[0022] In one or more embodiments, the cleaning is performed multiple times with water after the aging is completed to wash away excess sodium hydroxide liquid and absorb surface moisture.

[0023] In one or more embodiments, the cross-linking polymerization is carried out using a cross-linking agent. The cross-linking agent is 2-5% glutaraldehyde, and the cross-linking time is 12-24 hours, preferably 20-24 hours.

[0024] In one or more embodiments, the freeze drying is to freeze the magnetic foamed chitosan hydrogel at -90~-70°C for 3~6h, and then place it in a vacuum for 12~24h. The obtained magnetic foamed chitosan hydrogel is instantaneously frozen at low temperature to achieve the effect of maintaining the original morphology of the material. If air drying is used, the material will become shrunken after drying, which greatly affects the adsorption effect of the material as an adsorbent.

[0025] In a third aspect, the present invention provides the use of the magnetic foamed freeze-dried modified chitosan material in the adsorption of pollutants in mine water.

[0026] The mine water pollutants include metal ions such as iron, manganese and calcium.

[0027] In a fourth aspect, the present invention provides a method for adsorbing pollutants in mine water, comprising: adding the above-mentioned magnetic foaming freeze-dried modified chitosan material as an adsorbent into the mine water.

[0028] When the heavy metal ions in the mine water pollutants are calcium ions and the calcium ion concentration is 200~220 mg / L, the ratio of adsorbent to mine water is (0.1~5g):(150~250mL).

[0029] When the heavy metal ions in the mine water pollutants are manganese ions and the manganese ion concentration is 30-40 mg / L, the ratio of the adsorbent to the mine water is (0.1-3 g):(150-250 mL), preferably (2-3 g):(150-250 mL).

[0030] When the heavy metal ions in the mine water pollutants are iron ions and the iron ion concentration is 35-45 mg / L, the ratio of the adsorbent to the mine water is (0.1-3 g):(150-250 mL), preferably (0.8-1.5 g):(150-250 mL).

[0031] One or some of the above technical solutions have the following advantages or beneficial effects: (1) The present invention provides a magnetic foaming freeze-dried modified chitosan material by combining ferroferric oxide modification, sodium dodecyl sulfate foaming modification and instant freezing modification. The chitosan material has a microsphere porous structure and can exist stably in neutral, alkaline and high-salt mine water solutions. It has a good removal ability for metal ions such as iron ions, manganese and calcium in mine water.

[0032] (2) The magnetic foaming freeze-dried modified chitosan material provided by the present invention introduces ferroferric oxide, and the formed ferroferric oxide nano-microspheres are magnetic and insoluble in the solution. In the subsequent adsorption test, the adsorption effect of iron ions in mine water can be significantly improved; if FeCl3·6H2O is introduced, the iron element of the material will exist in the mine water in an ionic state, and ionic iron is one of the characteristic pollutants in mine water. Not only can it not achieve the adsorption of common heavy metal ions in mine water, but it will also introduce new pollutants, which is not suitable for the treatment of mine water pollutants. Therefore, the iron source must be specifically selected as ferroferric oxide.

[0033] (3) The present invention provides a method for preparing modified chitosan microspheres suitable for adsorbing mine water pollutants, which has simple process, convenient operation and control, stable quality, high production efficiency and low production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0035] Figure 1 The SEM images and energy spectrum images of the magnetic foamed freeze-dried modified chitosan material prepared in Example 1 of the present invention; wherein (a) is a 35X magnified appearance morphology image, (b) is a 25X magnified cross-sectional image, and (c) is a 35X magnified energy spectrum image; Figure 2 The SEM energy spectrum diagram of the material prepared in Comparative Example 2 of the present invention; wherein (a) is a 50X magnified appearance morphology diagram, (b) is a 50X magnified cross-sectional diagram, and (c) is an 80X magnified cross-sectional energy spectrum diagram; Figure 3 The morphology of the material prepared in Comparative Example 1 of the present invention; wherein (a) and (c) are surface morphology of the shell of the air-dried chitosan material at different magnifications, and (b) is the cross-sectional microscopic morphology; Figure 4 The materials prepared in Example 1 and Comparative Examples 1-3 of the present invention are Ca 2+ Adsorption effect diagram; Figure 5The materials prepared in Example 1 and Comparative Examples 1-3 of the present invention have a certain Mn content. 2+ Adsorption effect diagram; Figure 6 The materials prepared in Example 1 and Comparative Examples 1-3 of the present invention are Fe 2+ Adsorption effect diagram. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0037] Generally, iron and manganese ions will not exist in one type of mine water, and a replacement reaction will occur. Therefore, two types of mine water with different properties are selected in the embodiment, high-salt mine water containing iron ions and a high-salt mine water rich in calcium and manganese ions.

[0038] The idea of ​​comparing the adsorption effects in the present invention is to add the same mass of air-dried chitosan (Comparative Example 1) and the new material of the present invention (Example 1) under full adsorption conditions (40 minutes) to statistically analyze the residual amount of metal ions in mine water, which is more in line with actual engineering conditions.

[0039] Example 1 1. Preparation of magnetic foaming freeze-dried modified chitosan material: A method for preparing a magnetic foaming freeze-dried modified chitosan material suitable for adsorbing mine water pollutants comprises the following steps: (1) Preparation of magnetic foamed chitosan acetic acid solution: Prepare a 2.5% by mass acetic acid diluted solution, take 1.75g ​​of 100nm ferroferric oxide powder and mix it with 15.75g chitosan powder, add the acetic acid diluted solution to 500g, then add 0.15g of sodium dodecyl sulfate powder, and stir at 60℃ water bath temperature until it is completely dissolved. (2) Prepare sodium hydroxide coagulation solution: Take 40 g of sodium hydroxide powder, add ultrapure water to 500 g, place the sodium hydroxide solution on a magnetic stirrer and stir until there is no sodium hydroxide solid at the bottom of the beaker. After leaving it at room temperature, divide it into small beakers and wait for the coagulation process.

[0040] (3) Solidification of magnetic foamed chitosan hydrogel: During the test, magnetic foamed chitosan acetic acid solution was aspirated in small amounts and multiple times, and the remaining magnetic foamed chitosan acetic acid solution was placed in a constant temperature water bath and stirred until the next liquid was taken. The syringe that sucked the magnetic foamed chitosan acetic acid solution was fixed on the triple micro-injection pump, and the 18G dispensing plastic injection needle was put on the syringe head. The height of the test bench under the micro-injection pump was adjusted until the center of the syringe needle was 10 cm above the liquid level. The syringe was pushed at a speed of 1.32 μL / min, and the solution was dripped into the prepared sodium hydroxide solidification solution.

[0041] (4) Hydrogel aging: The solidified magnetic foamed chitosan hydrogel is placed in a sodium hydroxide solidification solution for aging for more than 1 hour to solidify the unsolidified magnetic foamed chitosan. After the aging is completed, it is washed three times with ultrapure water to wash away the excess sodium hydroxide liquid and absorb the surface moisture.

[0042] (5) Cross-linking polymerization of magnetic foamed chitosan: Prepare a 3% glutaraldehyde solution, place the magnetic foamed chitosan hydrogel spheres in the glutaraldehyde cross-linking agent for 20-24 hours, and after the cross-linking is completed, wash them twice with anhydrous ethanol and three times with ultrapure water.

[0043] (6) Preparation of magnetic foamed chitosan aerogel: After absorbing the surface moisture of the magnetic foamed chitosan hydrogel balls, spread them flat on the freeze dryer tray, place the tray in a cold trap, tighten the air release valve, set the cold trap temperature to -80°C and freeze for 4 hours. After freezing, place the tray in a vacuum chamber, evacuate for 18 hours, turn off the vacuum pump, open the air release valve, take out the freeze-dried magnetic foamed chitosan after the air release is completed, thaw the freeze-dried magnetic foamed chitosan and let it dry naturally.

[0044] 2. Adsorption application of high-salt mine water containing calcium and manganese ions (1) Take high-salt mine water containing calcium and manganese ions into a volumetric flask and dilute to 2 L. Shake evenly and let it stand for 1 hour. Take 800 mL of the mine water after standing and divide it evenly into 4 beakers and wait for adsorption test.

[0045] (2) Take 0.5 g / 1.5 g / 2.5 g of the magnetic foamed and freeze-dried modified chitosan materials prepared in step 1 above, respectively, and put them in a gauze bag, soak them in deionized water for 30 min, and move the gauze onto a dust-free paper to absorb excess water on the surface.

[0046] (3) The gauze bags wrapped with magnetic foamed and freeze-dried modified chitosan materials were suspended in the mine water in three beakers respectively, and the mine water in the remaining beaker was used as a comparative example. The adsorption was carried out for 40 minutes at a simulated underground temperature of 30°C, and the gauze bags were removed after the adsorption was completed.

[0047] (4) After the solution was allowed to stand for 20 minutes, the supernatant was aspirated and filtered through a 22-micron organic filter membrane. The residual concentrations of calcium ions and manganese ions were measured using an inductively coupled plasma emission spectrometer.

[0048] 3. Adsorption application of high-salt mine water containing iron ions (1) Take high-salt mine water containing iron ions into a volumetric flask and dilute to 2 L. Shake evenly and let it stand for 1 hour. Take 1400 mL of the mine water after standing and divide it evenly into 7 beakers and wait for adsorption test.

[0049] (2) Take 0.5 g / 1.0 g / 1.5 g / 2.0 g / 2.5 g of the magnetic foamed and freeze-dried modified chitosan materials prepared in step 1 above, respectively, and put them in a gauze bag, soak them in deionized water for 30 min, and move the gauze onto dust-free paper to absorb excess moisture on the surface.

[0050] (3) The gauze bags wrapped with magnetic foamed and freeze-dried modified chitosan materials were suspended in the mine water in 6 beakers respectively, and the mine water in the remaining beaker was used as a comparative example. The adsorption was carried out for 40 minutes at a simulated underground temperature of 30°C, and the gauze bags were removed after the adsorption was completed.

[0051] (4) After the solution was allowed to stand for 20 minutes, the supernatant was aspirated and filtered through a 22-micron organic filter membrane. The residual iron ion concentration of the filtered solution was measured using an inductively coupled plasma emission spectrometer.

[0052] Comparative Example 1 1. Preparation of air-dried chitosan material: (1) Prepare a 2.5% by mass acetic acid dilution solution, take 17.5 g of chitosan powder and mix it, add the acetic acid dilution solution to 500 g, and stir in a water bath at 60°C until it is completely dissolved.

[0053] (2) Prepare sodium hydroxide coagulation solution: Take 40 g of sodium hydroxide powder, add ultrapure water to 500 g, place the sodium hydroxide solution on a magnetic stirrer and stir until the sodium hydroxide solid at the bottom of the beaker is completely dissolved. After leaving it at room temperature, divide it into small beakers and wait for the coagulation process.

[0054] (3) During the test, the chitosan acetic acid solution was aspirated in small amounts and multiple times, and the remaining chitosan acetic acid solution was placed in a constant temperature water bath and stirred until the next liquid was taken. The syringe that sucked the chitosan acetic acid solution was fixed on the triple micro-injection pump, and the 18G dispensing plastic injection needle was put on the syringe head. The height of the test bench below the micro-injection pump was adjusted until the center of the syringe needle was 10 cm above the liquid level. The syringe was pushed at a speed of 1.32 μL / min, and the solution was dripped into the prepared sodium hydroxide coagulation solution.

[0055] (4) The solidified chitosan hydrogel is placed in a sodium hydroxide solidification solution for aging for more than one hour to solidify the unsolidified chitosan. After the aging is completed, it is washed three times with ultrapure water to wash away the excess sodium hydroxide liquid and absorb the surface moisture.

[0056] (5) Prepare a 3% glutaraldehyde solution and place the chitosan hydrogel spheres in the glutaraldehyde crosslinker for 20-24 hours. After the crosslinking is completed, wash them twice with anhydrous ethanol and three times with ultrapure water.

[0057] (6) After absorbing the moisture on the surface of the chitosan hydrogel balls, place them in a cool and ventilated place and air-dry them until they are completely dry before taking them out.

[0058] 2. Adsorption application of high-salt mine water rich in calcium and manganese ions (1) Take a high-salt mine water rich in calcium and manganese ions into a volumetric flask and dilute to 2 L. Shake evenly and let it stand for 1 hour. Take 800 mL of the mine water after standing and divide it evenly into 4 beakers and wait for adsorption test.

[0059] (2) Take 0.5g / 1.5g / 2.5g of chitosan material respectively and put it in a gauze bag, soak it in deionized water for 30min, and move the gauze onto dust-free paper to absorb excess water on the surface.

[0060] (3) The gauze bags wrapped with chitosan material were suspended in the mine water in three beakers respectively, and the mine water in the remaining beaker was used as a comparative example. The adsorption was carried out for 40 minutes at a simulated underground temperature of 30°C, and the gauze bags were removed after the adsorption was completed.

[0061] (4) After the solution was allowed to stand for 20 minutes, the supernatant was aspirated and filtered through a 22-micron organic filter membrane. The residual concentrations of calcium ions and manganese ions were measured using an inductively coupled plasma emission spectrometer.

[0062] 3. Adsorption application of high-salt mine water containing iron ions (1) Take high-salt mine water containing iron ions into a volumetric flask and dilute to 2 L. Shake evenly and let it stand for 1 hour. Take 1400 mL of the mine water after standing and divide it evenly into 7 beakers and wait for adsorption test.

[0063] (2) Take 0.5g / 1.0g / 1.5g / 2.0g / 2.5g / 3.0g of air-dried chitosan material respectively and put it in a gauze bag, soak it in deionized water for 30min, and move the gauze onto dust-free paper to absorb excess water on the surface.

[0064] (3) The gauze bags wrapped with air-dried chitosan material were suspended in the mine water in 6 beakers respectively, and the mine water in the remaining beaker was used as a comparative example. The adsorption was carried out for 40 minutes at a simulated underground temperature of 30°C, and the gauze bags were removed after the adsorption was completed.

[0065] (4) After the solution was allowed to stand for 20 minutes, the supernatant was aspirated and filtered through a 22-micron organic filter membrane. The residual iron ion concentration of the filtered solution was measured using an inductively coupled plasma emission spectrometer.

[0066] Comparative Example 2 The difference from Example 1 is that sodium dodecyl sulfate powder is not added in step (1), air drying is performed in step (6) instead of freeze drying, and the other conditions are the same. If sodium dodecyl sulfate is not added, freeze drying is not required because there are no large pores inside.

[0067] Comparative Example 3 The difference from Example 1 is that step (6) is air-dried instead of freeze-dried, and the other conditions are the same.

[0068] Depend on Figure 1 It can be seen that the magnetic foamed freeze-dried modified chitosan material prepared by the present invention is a porous microsphere structure. Nano-ferroferric oxide particles are evenly distributed on the porous microsphere structure, and the particle size of the microsphere is 2-2.5 mm and the pore size is 100-200 μm.

[0069] Without adding sodium dodecyl sulfate powder or without flash freezing, the chitosan spheres will shrink into solid spheres, and the microscopic bubbles and cavities will disappear. Figure 1 (c) and Figure 2 From the green dots of iron in (c), it can be seen that without the addition of sodium dodecyl sulfate, iron will aggregate and there will be no bubble structure inside. Therefore, the addition of sodium dodecyl sulfate will produce a bubble structure and facilitate the dispersion of iron; and after freeze-drying, the bubble structure can exist stably for a long time without shrinkage.

[0070] Depend on Figure 4-5 It can be seen that under the same dosage conditions, the magnetic foaming freeze-dried modified chitosan material prepared by the present invention has a higher removal rate of calcium and manganese ions in mine water than air-dried chitosan. When 2.5g is added, the removal rates of the two materials differ by 32% and 35% for calcium and manganese ions, respectively. It can be considered that the magnetic foaming freeze-dried modified chitosan material prepared by the present invention has an adsorption capacity of calcium and manganese in mine water that is enhanced by about 32% and 35% compared with ordinary air-dried chitosan materials.

[0071] Depend on Figure 6It can be seen that under the same dosage conditions, the magnetic foaming freeze-dried modified chitosan material prepared by the present invention has a higher iron ion removal rate in mine water than air-dried chitosan. When 1g is added, the removal rates of the two differ by about 45%. Therefore, for mine water containing iron ions, the magnetic foaming freeze-dried modified chitosan material prepared by the present invention has an adsorption capacity enhanced by about 45% compared with ordinary air-dried chitosan material.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnetic foaming freeze-dried modified chitosan material, characterized in that: The magnetic foaming freeze-dried modified chitosan material is a porous microsphere structure, wherein the ferroferric oxide particles are evenly distributed on the porous microsphere structure; In terms of weight, the magnetic foaming freeze-dried modified chitosan material comprises: 0.1-1 parts of ferrosoferric oxide, 1.2-2 parts of chitosan, and 0.01-0.05 parts of sodium dodecyl sulfate.

2. The magnetic foaming freeze-dried modified chitosan material according to claim 1, characterized in that: 0.1-0.5 parts of ferrosoferric oxide, 1.4-1.6 parts of chitosan, and 0.01-0.02 parts of sodium dodecyl sulfate; The particle size of the microspheres is 2~2.5mm, and the average particle size of the pores is 100~200μm.

3. A method for preparing the magnetic foaming freeze-dried modified chitosan material according to claim 1 or 2, characterized in that: The following steps are involved: S1: dissolving ferroferric oxide, chitosan and sodium dodecyl sulfate in an acid solution to prepare a magnetic foaming chitosan acid solution; S2: dripping the magnetic foamed chitosan acid solution into an alkaline coagulation liquid to obtain a coagulated magnetic foamed chitosan hydrogel, and then subjecting the hydrogel to aging, washing, cross-linking polymerization, and freeze-drying.

4. The method according to claim 3, characterized in that Ferroferric oxide is nano-ferroferric oxide powder with a particle size of 100~500nm; The acid is acetic acid, and the mass concentration of the acid solution is 2-3wt.%; In step S1, according to weight parts, 0.1-1 parts of ferrosoferric oxide, 1.2-2 parts of chitosan, 0.01-0.05 parts of sodium dodecyl sulfate, and 40-60 parts of acid solution; In step S1, stirring is performed at 50-70°C until all the components are dissolved.

5. The method according to claim 3, characterized in that: In step S2, the alkaline coagulation liquid is a mixture of alkali and water, the alkali is a strong alkali, and the mass ratio of the alkali to water is (2-6):(40-60); In step S2, the preparation method of the alkali coagulation liquid is: dissolving alkali in water to obtain an alkali aqueous solution, stirring the aqueous solution until there is no alkali solid, and waiting for coagulation at room temperature.

6. The method according to claim 3, characterized in that In step S2, the dripping method is to use an injection dripping method, specifically: fix the syringe that absorbs the magnetic foamed chitosan acid solution on the triple micro-injection pump, cover the dispensing plastic injection needle on the syringe head, adjust the height of the test bench below the micro-injection pump until the center of the syringe needle is 5-20 cm above the liquid level, push the syringe at a propulsion speed of 1-3 μL / min, and drip the solution into the prepared alkaline coagulation solution; In step S2, small amounts of water are added repeatedly.

7. The method according to claim 3, characterized in that In step S2, the aging is to place the solidified magnetic foamed chitosan hydrogel in an alkaline coagulation solution for aging, and the aging time is 1 to 5 hours; The cross-linking polymerization is carried out by using a cross-linking agent; the cross-linking agent is 2-5% glutaraldehyde, and the cross-linking time is 12-24 hours; The freeze drying is to freeze the magnetic foamed chitosan hydrogel at -90 to -70°C for 3 to 6 hours, and then place it in a vacuum for 12 to 24 hours.

8. Use of the magnetic foaming freeze-dried modified chitosan material according to claim 1 or 2 or the magnetic foaming freeze-dried modified chitosan material prepared by the method according to any one of claims 3 to 7 in the adsorption of pollutants in mine water.

9. The use according to claim 8, characterized in that: The mine water contaminants include iron, manganese and calcium metal ions.

10. A method for adsorbing pollutants in mine water, characterized in that: The method comprises the following steps: adding the magnetic foaming freeze-dried modified chitosan material according to claim 1 or 2 as an adsorbent into mine water.

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