Cationic polyacrylamide grafted chitosan modified magnetic carbon material, preparation method and application

Abstract

The invention discloses a cationic polyacrylamide grafted chitosan modified magnetic carbon material as well as a preparation method and application thereof. The grafted chitosan modified magnetic carbon material is prepared from the following main raw materials: peanut shells, a ferric chloride solution, chitosan, an ammonium ceric nitrate solution and polyacrylamide. The peanut shells are used for preparing a magnetic carbon material; the chitosan is used for preparing a chitosan modified carbon material, and the ceric ammonium nitrate solution and the polyacrylamide are used for preparing a grafted-modified magnetic carbon material; the scheme provided by the invention has the advantage that the algae can be efficiently removed in a relatively wide temperature range (25-45 DEG C) under the condition of simulating seawater salinity.

Description

Technical Field

[0001] The present application relates to the technical field of water treatment, and in particular to a cationic polyacrylamide grafted chitosan modified magnetic carbon (magnetic carbon) material, a preparation method and an application thereof. Background Art

[0002] Algae belong to the eukaryotic organisms in the kingdom of protists, some of which belong to prokaryotes, such as algae in the phylum Cyanobacteria. They mainly live in water, have no vascular structure, and can photosynthesize. With the rapid development of industry and agriculture, eutrophication of water bodies has become increasingly serious, resulting in frequent algal blooms in some areas, posing a threat to the safety of drinking water quality. The hazards caused by algae include clogging filters, releasing odorous substances and algal toxins, and increasing the concentration of disinfection by-products. Therefore, how to efficiently remove algal pollution in water and ensure safe water use has become an urgent problem to be solved. In the past two decades, due to agricultural activities, domestic sewage discharge and industrial wastewater pollution, the occurrence of eutrophic harmful algal blooms in lakes and drinking water reservoirs has increased worldwide. The presence and excessive growth of algae in water bodies pose significant challenges to the aquatic environment and aquatic organisms. For example, a large number of algae leads to a decrease in oxygen levels in the water, making it difficult for other organisms to maintain sufficient nutrition and survival, and promotes the production of a variety of cyanobacterial toxins associated with fatal diseases. The organic matter inside these algae cells, especially the toxins released when the algae cells rupture, poses a major threat to public health, tourism, fisheries and ecosystems. Therefore, algae pollution has become a global problem that cannot be ignored.

[0003] In the study of algae removal, adsorption stands out for its relative safety and low environmental impact. Carbon materials are widely used in the preparation of adsorbents due to their high specific surface area, high pore volume, strong adsorption capacity and excellent sustainability. The excellence of carbon materials also lies in their good chemical stability, which makes it an ideal choice to improve the efficiency of algae removal by modifying carbon materials. Under the current background of environmental protection, the method of using carbon materials for algae adsorption has shown good prospects in dealing with the problem of eutrophication of water bodies. Through further research and improvement, the adsorption performance of carbon materials can be optimized, and their efficiency in water treatment can be improved, providing a sustainable and effective solution for maintaining water quality, ecological balance and human health. At present, studies have shown that chitosan-modified magnetic carbon materials have a removal effect on microalgae, but the material only has a high removal efficiency under strong acid and strong alkali conditions, and microalgae reproduce in neutral or weakly alkaline water, so how to improve the microalgae removal efficiency at this pH is still worth exploring.

[0004] At present, there is almost no prior art on the use of magnetic carbon materials to remove algae. Several patent documents related to iron-related algae removal are as follows: 1. A method for treating raw water containing algae is disclosed in the publication number CN109110966A: first, Cl2 is added for chlorination treatment; polyferric chloride is added for treatment; coagulant and activated silicate are added for treatment; flocculation, precipitation, and filtration treatment. The method for treating raw water containing algae of the present invention is based on conventional water treatment, by pre-chlorination treatment of raw water containing algae, and then polyferric chloride, coagulant and activated silicate are added to treat raw water containing algae. The algae removal effect is good, and the algae removal rate reaches 98.5%. The algae removal effect is excellent, and cyanobacteria and other pollutants in the water body can be effectively removed; 2. A floating aerogel algae removal catalyst, a preparation method and a floating algae removal agent are disclosed in the publication number CN117772282A. The floating algae removal catalyst uses guar gum as a carrier matrix and is loaded with a single metal atom; a single metal atom is added to the carrier matrix. The metal atom includes one of copper, iron, cobalt and manganese atoms; the single metal atom can catalyze the decomposition of persulfate in the floating algaecide to form a large number of active oxygen free radicals, which then attack the surface morphology and internal organizational structure of the algae cells, resulting in the destruction of cell integrity and a significant decrease in cell activity, thereby achieving the algae removal effect; at the same time, the single metal atom can form a cross-linked network structure with guar gum through a coupling reaction to form an aerogel, so that the algaecide can stably float on the water surface, which can efficiently remove algae and is conducive to subsequent recycling and reuse. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present application provides a cationic polyacrylamide grafted chitosan modified magnetic carbon material that can effectively remove algae within a wide temperature range (25-45°C) and under simulated seawater salinity conditions.

[0006] In order to solve the above technical problems, the technical solution adopted in the present application is: a cationic polyacrylamide grafted chitosan modified magnetic carbon (magnetic carbon) material, the main raw materials for the preparation of the modified magnetic carbon include: peanut shells, ferric chloride solution, chitosan, ammonium cerium nitrate solution and polyacrylamide; the peanut shells are used to prepare the magnetic carbon material; the chitosan is used to prepare the chitosan modified carbon material, and the ammonium cerium nitrate solution and polyacrylamide are used to prepare the grafted-modified magnetic carbon material (cationic polyacrylamide grafted chitosan modified magnetic carbon material, CPAM-CTS@MBC).

[0007] Furthermore, the specific preparation process of the magnetic carbon material includes: under the protection of nitrogen, calcining peanut shells at 400-600°C for 0.5-3h, and then sieving with a 50-200 mesh sieve to obtain carbonized peanut shells; then adding the carbonized peanut shells to a sodium hydroxide solution, wherein the weight ratio of the carbonized peanut shells to the sodium hydroxide is 3-5:1, and stirring the reaction at 400-500rpm for 20-25h; then, adding an equal volume of 1-1.2mol / L ferric chloride solution to the reaction solution (the amount added here is related to the magnetism, and generally speaking, the greater the addition, the greater the magnetism of the subsequent synthesized product), stirring for 20-40min, and then centrifuging and washing with ultrapure water to a pH of 6.5-7.5 of the washing liquid, drying, and pyrolyzing at 500-600°C for 20-40min under nitrogen conditions to obtain a magnetic carbon material.

[0008] Furthermore, the preparation of the chitosan modified carbon material (CTS@MBC) includes the following specific preparation processes: dissolving chitosan in an acetic acid solution with a volume concentration of 1-3%, adding the prepared magnetic carbon material, wherein the mass ratio of chitosan to the magnetic carbon material is 1:4-6; then stirring at 30-50°C for 20-40 minutes, then adding a NaOH solution with a concentration of 1-3 mol / L to precipitate the black substance, and then washing with ultrapure water until the washing liquid is neutral; filtering, and drying the filtered solid in a vacuum oven to obtain chitosan modified magnetic biochar.

[0009] Furthermore, the preparation process of the grafted-modified magnetic carbon material includes: dispersing the chitosan-modified carbon material in ultrapure water, then adding it to a reaction vessel, and continuously introducing nitrogen into the reaction vessel to remove oxygen therein; then, adding ammonium cerium nitrate solution to the solution, stirring and then adding cationic polyacrylamide (CPAM) solution, wherein the weight ratio of polyacrylamide: ammonium cerium nitrate is 3-5:1, and the weight ratio of polyacrylamide: chitosan is 2-4:1; then heating in a water bath to 40-60°C and reacting for 2-4 hours; after the reaction is completed, using a magnet to separate the black flocculent substance, and repeatedly washing it with ethanol and water to a pH of 7, and then vacuum drying the substance to obtain a grafted-modified magnetic carbon material (cationic polyacrylamide grafted chitosan modified magnetic carbon material).

[0010] Furthermore, the present application also provides a method for preparing the above-mentioned cationic polyacrylamide grafted chitosan modified magnetic carbon material, and the specific preparation steps of the method include:

[0011] (1) Preparation of magnetic biochar: Under the protection of nitrogen, peanut shells are calcined at 400-600°C for 0.5-3h, and then sieved with a 50-200 mesh screen to obtain carbonized peanut shells; then the carbonized peanut shells are added to a sodium hydroxide solution, wherein the weight ratio of the carbonized peanut shells to the sodium hydroxide is 3-5:1, and stirred at 400-500 rpm for 20-25h; then, an equal volume of 1-1.2 mol / L ferric chloride solution is added to the reaction solution (the amount added here is related to the magnetic properties, and generally speaking, the greater the addition, the greater the magnetic properties of the subsequent synthesized product), stirred for 20-40min, and then centrifuged and washed with ultrapure water to a pH of 6.5-7.5, and after drying, pyrolyzed at 500-600°C for 20-40min under nitrogen conditions to obtain a magnetic carbon material (MBC);

[0012] (2) Preparation of chitosan modified carbon material (CTS@MBC): Chitosan was dissolved in an acetic acid solution with a volume concentration of 1-3%, and the prepared magnetic carbon material was added, wherein the mass ratio of chitosan to magnetic carbon material was 1:4-6; then stirred at 30-50°C for 20-40 minutes, and then a NaOH solution with a concentration of 1-3 mol / L was added to precipitate the black substance, and then washed with ultrapure water until the washing liquid was neutral; filtered, and the filtered solid was placed in a vacuum oven for drying to obtain chitosan modified magnetic biochar;

[0013] (3) Preparation of grafted-modified magnetic carbon material: The chitosan-modified carbon material is dispersed in ultrapure water and then added to a reaction vessel, and nitrogen is continuously introduced into the reaction vessel to remove oxygen therein; then, ammonium cerium nitrate solution is added to the solution, and after stirring, a cationic polyacrylamide (CPAM) solution is added, wherein the weight ratio of polyacrylamide: ammonium cerium nitrate is 3-5:1, and the weight ratio of polyacrylamide: chitosan is 2-4:1; then, the mixture is heated to 40-60°C in a water bath and reacted for 2-4 hours; after the reaction is completed, the black flocculent material is separated by a magnet, and repeatedly washed with ethanol and water until the pH is 7, and then the material is vacuum dried to obtain a grafted-modified magnetic carbon material (cationic polyacrylamide grafted chitosan modified magnetic carbon material, CPAM-CTS@MBC).

[0014] Furthermore, the vacuum drying mentioned above in the present application specifically involves placing the material in a vacuum oven and drying it at 75-85° C. for 10-15 hours.

[0015] The present application also provides an application of the above-mentioned cationic polyacrylamide grafted chitosan modified magnetic carbon material, which is specifically used for the adsorption and separation of Chlorella in a water environment.

[0016] Furthermore, the water environment is a simulated seawater environment.

[0017] Furthermore, the salinity range of the simulated seawater is a NaCl concentration of 10-50 g / L.

[0018] Furthermore, the temperature of the water environment is 25-45°C.

[0019] Advantages and beneficial effects of this application:

[0020] 1. This application uses peanut shells as raw materials for the first time to prepare a cationic polyacrylamide grafted chitosan modified magnetic carbon material (CPAM-CTS@MBC), which can effectively adsorb Chlorella; the adsorption of algae mainly relies on the net flocculation and electrostatic adsorption of this material for removal. In this process, temperature has a certain promoting effect on adsorption, and the maximum saturated adsorption capacity increases with the increase of temperature (the maximum adsorption capacity of CPAM-CTS@MBC obtained by adsorption isotherm experiment is 133.94 mg / g (25°C), 136.09 mg / g (30°C), 141.89 mg / g (35°C), 158.24 mg / g (40°C) and 159.2 mg / g (45°C)); at the same time, under the conditions of simulated seawater salinity, the removal rate of algae can also reach more than 80%, which is because when algae burst in the ocean, This will cause harmful algal blooms, which are harmful to the marine environment and human health. Therefore, this application studies the effect of Cl- on the algae removal efficiency of the optimal grafted-modified magnetic material. Under different Cl- concentrations (10g / L, 35g / L, 50g / L NaCl), CPAM-CTS@MBC can maintain a good removal efficiency. When the Cl- concentration is 35g / L of simulated seawater, the removal efficiency reaches more than 80%, but compared with the case without Cl- interference, the removal efficiency of CPAM-CTS@MBC for microalgae is reduced; through analysis, Cl- has little effect on the microalgae removal efficiency of CPAM-CTS@MBC, but when the Cl- concentration is high, Cl- will occupy some adsorption sites on CPAM-CTS@MBC, resulting in a decrease in the removal efficiency of CPAM-CTS@MBC for microalgae.

[0021] 2. The cationic polyacrylamide grafted chitosan modified magnetic carbon material of the present application, wherein the cationic polyacrylamide grafted on the material is hydrolyzed in water to capture flocculation and bridge microalgae, and then the microalgae floccules are adsorbed by electrostatic adsorption; and the saturation magnetization intensity of CPAM-CTS@MBC does not change before and after adsorption, and the material after adsorbing algae can be easily separated from the water using a magnet.

[0022] 3. The cationic polyacrylamide grafted chitosan modified magnetic carbon material of the present application can successfully adsorb Chlorella, and the microalgae floccules are successfully adsorbed into the pore structure of CPAM-CTS@MBC; from this, it can be analyzed that the mechanism of CPAM-CTS@MBC adsorbing microalgae includes net capture flocculation, electrostatic neutralization, and may be accompanied by bridging and other effects, thus achieving an ideal adsorption effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Comparison of the effects of different adsorbents on Chlorella before and after adsorption.

[0024] Figure 2 Effect of different pH on the adsorption and removal of Chlorella by materials.

[0025] Figure 3 Effects of different temperatures on the adsorption and removal of Chlorella by materials

[0026] Figure 4 Effect of different salinities on the adsorption and removal of Chlorella by materials.

[0027] Figure 5 SEM of the grafted-modified magnetic carbon material prepared in the examples of the present application.

[0028] Figure 6 SEM image of the grafted-modified magnetic carbon material prepared in the example of the present application after adsorbing Chlorella. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments and drawings to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only preferred embodiments, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] (1) Preparation of magnetic carbon material: Under the protection of nitrogen, peanut shell powder is used as raw material. The raw material is placed in a muffle furnace and calcined at 450-500°C for 3 hours to obtain peanut shell charcoal (BC), which is then sieved through a 200-mesh sieve; the sieved BC is then dispersed in an aqueous sodium hydroxide solution (the mass ratio of BC to sodium hydroxide is 4:1), and placed on a stirrer and stirred at 450 rpm for 24 hours. Subsequently, an equal volume of 1.2 mol / L ferric chloride aqueous solution is added to the reaction solution and stirred for another 30 minutes; the stirred mixture is centrifuged, and the obtained solid is washed with ultrapure water until the pH of the washing liquid is about 7, and then placed in a vacuum oven at 80°C for 12 hours. The obtained solid is placed in a tubular furnace for pyrolysis to obtain a black shiny substance as a magnetic carbon material (MBC);

[0032] (2) Preparation of chitosan-modified carbon material: 0.3 g of chitosan was dissolved in 50 mL of acetic acid aqueous solution (1%, v / v), and 1.5 g of MBC was dispersed in the solution; after heating to 40°C in a water bath, the solution was stirred for 30 min, and 50 mL of 1 mol / L sodium hydroxide aqueous solution was added to the solution to precipitate a black substance; the precipitate was filtered, and washed with ultrapure water until the pH of the washing solution was 7, and then placed in a vacuum oven at 80°C for drying to obtain a chitosan-modified carbon material (CTS@MBC);

[0033] (3) Preparation of grafted-modified magnetic carbon material: CTS@MBC was dispersed in ultrapure water to obtain a mixed solution, and then the mixed solution was added to a three-necked flask, and nitrogen was continuously introduced into the flask to remove oxygen therein; then, an aqueous solution of ammonium cerium nitrate was added to the reaction solution, and after stirring, an aqueous solution of cationic polyacrylamide (CPAM) was added, wherein the weight ratio of polyacrylamide: ammonium cerium nitrate was 4:1, and the weight ratio of polyacrylamide: chitosan was 3:1, and then the mixture was heated to 50°C in a water bath and reacted for 3 hours; after the reaction was completed, a black flocculent substance was obtained, which was separated by a magnet and repeatedly washed with ethanol and water until the pH of the washing solution was 7, and then the substance was placed in a vacuum oven and dried at 60°C to obtain a grafted-modified magnetic carbon material (CPAM-CTS@MBC).

[0034] The grafted-modified magnetic carbon material (CPAM-CTS@MBC) prepared in Example 1 was applied to the adsorption of Chlorella:

[0035] (1) Chlorella adsorption experiment under fresh water conditions at a temperature of 25°C, the initial concentration of Chlorella was 250 mg / L, 2.5 g / L of grafted-modified magnetic material was added, and the mixture was oscillated at an oscillation intensity of 150 rpm for 10 min. After standing for 5 min, the flocculants were adsorbed to the bottom of the solution with a magnet, and the absorbance of the supernatant in the remaining solution was measured. The removal rate of microalgae was 98.60%;

[0036] (2) The adsorption experiment of Chlorella was carried out at 25°C in simulated seawater (NaCl concentration was 35 g / L). The initial concentration of Chlorella was 250 mg / L. 2.5 g / L of grafted-modified magnetic material was added to the microalgae solution. The solution was oscillated at an oscillation intensity of 150 rpm for 10 min. After standing for 5 min, the flocculants were adsorbed to the bottom of the solution with a magnet, and the absorbance of the supernatant in the remaining solution was measured. The removal rate of microalgae was 82%.

[0037] Figure 1As shown, it is a comparison diagram of the grafted-modified magnetic carbon material (CPAM-CTS@MBC) prepared in Example 1 and other adsorption materials (from left to right, respectively, the microalgae stock solution without adsorption treatment, the effect diagram of the adsorption of microalgae by the chitosan-modified magnetic carbon material, and the effect diagram of the adsorption of microalgae by the grafted-modified magnetic carbon material prepared in the present application). It can be seen from the figure that the adsorption effect of Chlorella is most ideal when the material of the present application is added, while the chitosan-modified magnetic carbon material (the material prepared in the first two steps of the present application) does not have a significant effect on the adsorption of Chlorella, which fully proves that the material of the present application is more suitable for the adsorption of Chlorella.

[0038] Figure 2 As shown in the figure, the effect of the grafted-modified magnetic carbon material (CPAM-CTS@MBC) prepared in this embodiment on the adsorption and removal of Chlorella under different pH conditions. The figure shows that when the pH is low or high, the degree of hydrolysis of polyacrylamide is poor. This is because when the pH is low or high, polyacrylamide cannot make the microalgae form flocs and thus be adsorbed by the material. At the same time, the surface of CPAM-CTS@MBC particles carries a negative charge due to the deprotonation of -NH2 under strong alkaline conditions, and the microalgae cells also carry negative charges. Therefore, under strong acid or strong algae conditions, the removal efficiency of microalgae is low; at the same time, analysis found that cationic polyacrylamide has a higher degree of hydrolysis under neutral and weak acid or weak alkaline conditions, which is the same as the optimal experimental pH of CPAM-CTS@MBC.

[0039] Figure 3 As shown in the figure, it is the effect of the grafted-modified magnetic carbon material (CPAM-CTS@MBC) prepared in this embodiment on the adsorption and removal of Chlorella at different temperatures; the algae adsorption mainly relies on the net flocculation and electrostatic adsorption of the material for removal. In this process, the temperature has a certain promoting effect on the adsorption, and the maximum saturated adsorption capacity increases with the increase of temperature (the maximum adsorption capacity of CPAM-CTS@MBC obtained by adsorption isotherm experiment is 133.94 mg / g (25°C), 136.09 mg / g (30°C), 141.89 mg / g (35°C), 158.24 mg / g (40°C) and 159.2 mg / g (45°C)).

[0040] Figure 4As shown, the effect of the grafted-modified magnetic carbon material (CPAM-CTS@MBC) prepared in this embodiment on the removal of Chlorella under different salinity conditions; under different Cl- concentration conditions (10g / L, 35g / L, 50g / L NaCl), CPAM-CTS@MBC can maintain a good removal efficiency. Under the condition of 35g / L Cl- concentration in simulated seawater, the removal efficiency reaches more than 80%, but compared with the case without Cl- interference, the removal efficiency of CPAM-CTS@MBC for microalgae is reduced. Through analysis, Cl- has little effect on the microalgae removal efficiency of CPAM-CTS@MBC, but when the Cl- concentration is high, Cl- will occupy some adsorption sites on CPAM-CTS@MBC, resulting in a decrease in the removal efficiency of CPAM-CTS@MBC for microalgae.

[0041] Figure 5 As shown, it is the SEM of the grafted-modified magnetic carbon material (CPAM-CTS@MBC) prepared in this embodiment. Through the SEM images (a and b are SEM images at different magnifications), it can be found that the surface of the CPAM-CTS@MBC material without adsorbing Chlorella has many gaps, the surface is rough and irregular, and fine fibers can be seen. Through observation, it can be found that the surface is covered with a layer of material. Through FTIR analysis, it is known that this is cationic polyacrylamide grafted chitosan coated on the surface of the magnetic carbon material.

[0042] Figure 6 As shown, the SEM image of the grafted-modified magnetic carbon material (CPAM-CTS@MBC) prepared in this embodiment after adsorbing Chlorella (a and b are SEM images at different magnifications). The SEM after adsorbing Chlorella shows that the microalgae flocs are successfully adsorbed by CPAM-CTS@MBC, and the microalgae flocs are successfully adsorbed into the pore structure of CPAM-CTS@MBC. From this, it can be analyzed that the mechanism of CPAM-CTS@MBC adsorbing microalgae includes net capture flocculation, electrostatic neutralization, and possibly accompanied by bridging and other effects, and multiple effects effectively improve the adsorption efficiency.

[0043] Example 2

[0044] (1) Preparation of magnetic carbon material: peanut shell powder was used as raw material and calcined in a muffle furnace under the protection of nitrogen to obtain peanut shell charcoal (BC); BC was then dispersed in a sodium hydroxide solution (the mass ratio of BC to sodium hydroxide was 3.5:1) and placed on a stirrer for stirring at 4800 rpm for 25 h, then an equal volume of 1.0 mol / L ferric chloride aqueous solution was added to the reaction solution and stirred for another 35 min; the stirred mixture was centrifuged, the obtained solid was washed with ultrapure water until the pH of the washing liquid was about 7, and then dried in a vacuum oven at 80°C for 12 h, and the obtained solid was placed in a tube furnace for pyrolysis to obtain a black shiny substance as a magnetic carbon material (MBC);

[0045] (2) Preparation of chitosan-modified carbon material: 0.4 g of chitosan was dissolved in 60 mL of acetic acid aqueous solution (1.2%, v / v), and 1.6 g of MBC was dispersed in the solution; after heating to 45°C in a water bath, the solution was stirred for 30 min, and 50 mL of 1 mol / L sodium hydroxide aqueous solution was added to the solution to precipitate a black substance; the precipitate was filtered and washed with ultrapure water until the pH of the washing solution was 7, and then dried in a vacuum oven at 80°C to obtain a chitosan-modified carbon material (CTS@MBC);

[0046] (3) Preparation of grafted-modified magnetic carbon material: CTS@MBC was dispersed in ultrapure water to obtain a mixed solution, and then the mixed solution was added to a three-necked flask, and nitrogen was continuously introduced into the flask to remove oxygen therein; then, ammonium cerium nitrate solution was added to the reaction solution, and after stirring, cationic polyacrylamide (CPAM) solution was added, wherein the weight ratio of polyacrylamide: ammonium cerium nitrate was 3.5:1, and the weight ratio of polyacrylamide: chitosan was 3.5:1, and then heated to 55°C in a water bath and reacted for 2.5h; after the reaction was completed, a black flocculent substance was obtained, which was separated by a magnet and repeatedly washed with ethanol and water until the pH of the washing solution was 7, and then the substance was placed in a vacuum oven and dried at 60°C to obtain a grafted-modified magnetic carbon material (CPAM-CTS@MBC).

[0047] It can be seen from the above examples that the cationic polyacrylamide grafted chitosan modified magnetic carbon material obtained by the present application using peanut shell powder as raw material can effectively adsorb and remove Chlorella in water environment (fresh water or sea water) in a wide range of temperature (25-45°C) and salinity (10-50g / L NaCl concentration); experimental results show that under optimal conditions, the removal efficiency of the magnetic carbon material for Chlorella is as high as 98.60%, and at 25°C, the maximum saturated adsorption capacity can reach 133.94mg / g. At the same time, the material has superparamagnetism, and the adsorbed Chlorella can be separated from the solution by a magnet; the scheme of the present application provides an efficient removal method for the removal of Chlorella in water environment.

Claims

1. A cationic polyacrylamide grafted chitosan modified magnetic carbon material, characterized in that: The main raw materials for preparing the grafted chitosan modified magnetic carbon material include: peanut shells, ferric chloride solution, chitosan, ammonium cerium nitrate solution and polyacrylamide; the peanut shells are used to prepare the magnetic carbon material; the chitosan is used to prepare the chitosan modified carbon material, and the ammonium cerium nitrate solution and polyacrylamide are used to prepare the grafted-modified magnetic carbon material.

2. The ionic polyacrylamide grafted chitosan modified magnetic carbon material according to claim 1, characterized in that: The magnetic carbon material has a specific preparation process comprising: calcining peanut shells at 400-600°C for 0.5-3h under the protection of nitrogen, and then sieving with a 50-200 mesh screen to obtain carbonized peanut shells; then adding the carbonized peanut shells to a sodium hydroxide solution, wherein the weight ratio of the carbonized peanut shells to the sodium hydroxide is 3-5:1, and stirring the reaction at 400-500rpm for 20-25h; subsequently, adding an equal volume of 1-1.2mol / L ferric chloride solution to the reaction solution, stirring for 20-40min, and then centrifuging and washing with ultrapure water to a pH value of 6.5-7.5 for the washing solution, and after drying, pyrolyzing at 500-600°C for 20-40min under nitrogen conditions to obtain the magnetic carbon material.

3. The ionic polyacrylamide grafted chitosan modified magnetic carbon material according to claim 1, characterized in that: The preparation of the chitosan modified carbon material specifically comprises the following steps: dissolving chitosan in an acetic acid solution with a volume concentration of 1-3%, adding the prepared magnetic carbon material, wherein the mass ratio of chitosan to the magnetic carbon material is 1:4-6; stirring at 30-50°C for 20-40 minutes, subsequently adding a NaOH solution with a concentration of 1-3 mol / L to precipitate a black substance, and then washing with ultrapure water until the washing liquid is neutral; filtering, and drying the filtered solid in a vacuum oven to obtain chitosan modified magnetic biochar.

4. The ionic polyacrylamide grafted chitosan modified magnetic carbon material according to claim 1, characterized in that: The preparation process of the grafted-modified magnetic carbon material comprises: dispersing the chitosan-modified carbon material in ultrapure water, then adding the chitosan-modified carbon material into a reaction container, and continuously introducing nitrogen into the reaction container to remove oxygen therein; then, adding an ammonium cerium nitrate solution into the solution, stirring and then adding a cationic polyacrylamide solution, wherein the weight ratio of polyacrylamide: ammonium cerium nitrate is 3-5:1, and the weight ratio of polyacrylamide: chitosan is 2-4:1; then heating in a water bath to 40-60°C and reacting for 2-4h; after the reaction is completed, using a magnet to separate the black flocculent substance, and repeatedly washing with ethanol and water to a pH of 7, and then vacuum drying the substance to obtain the grafted-modified magnetic carbon material.

5. A method for preparing a cationic polyacrylamide grafted chitosan modified magnetic carbon material, characterized in that: The specific preparation steps of the method include: (1) Preparation of magnetic biochar: Under the protection of nitrogen, calcine peanut shells at 400-600°C for 0.5-3h, and then sieve through a 50-200 mesh screen to obtain carbonized peanut shells; then add the carbonized peanut shells to a sodium hydroxide solution, wherein the weight ratio of the carbonized peanut shells to the sodium hydroxide is 3-5:1, and stir at 400-500 rpm for 20-25h; then, add an equal volume of 1-1.2 mol / L ferric chloride solution to the reaction solution, stir for 20-40min, then centrifuge and wash with ultrapure water until the washing solution has a pH of 6.5-7.5, dry, and pyrolyze at 500-600°C for 20-40min under nitrogen conditions to obtain a magnetic carbon material; (2) Preparation of chitosan-modified carbon material: Dissolve chitosan in an acetic acid solution with a volume concentration of 1-3%, add the prepared magnetic carbon material, wherein the mass ratio of chitosan to the magnetic carbon material is 1:4-6; then stir at 30-50°C for 20-40 minutes, then add a NaOH solution with a concentration of 1-3 mol / L to precipitate the black substance, and then wash with ultrapure water until the washing liquid is neutral; filter, and put the filtered solid into a vacuum oven for drying to obtain chitosan-modified magnetic biochar; (3) Preparation of grafted-modified magnetic carbon material: The chitosan-modified carbon material is dispersed in ultrapure water and then added to a reaction vessel, and nitrogen is continuously introduced into the reaction vessel to remove oxygen therein; then, an ammonium cerium nitrate solution is added to the solution, and after stirring, a cationic polyacrylamide solution is added, wherein the weight ratio of polyacrylamide: ammonium cerium nitrate is 3-5:1, and the weight ratio of polyacrylamide: chitosan is 2-4:1; then, the mixture is heated to 40-60°C in a water bath and reacted for 2-4 hours; after the reaction is completed, the black flocculent material is separated by a magnet, and repeatedly washed with ethanol and water until the pH is 7, and then the material is vacuum dried to obtain the grafted-modified magnetic carbon material.

6. The method for preparing the cationic polyacrylamide grafted chitosan modified magnetic carbon material according to claim 5, characterized in that: The vacuum drying specifically involves placing the material in a vacuum oven and drying it at 75-85° C. for 10-15 hours.

7. An application of the cationic polyacrylamide grafted chitosan modified magnetic carbon material according to any one of claims 1 to 4, characterized in that: Used for adsorption separation of Chlorella in water environment.

8. The use of the cationic polyacrylamide grafted chitosan modified magnetic carbon material according to claim 7, characterized in that: The water environment is a simulated seawater environment, and the salinity range of the simulated seawater is a NaCl concentration of 10-50 g / L.

9. The use of the cationic polyacrylamide grafted chitosan modified magnetic carbon material according to claim 8, characterized in that: The temperature of the water environment is 25-45°C.

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