Chitosan modified cyanobacteria biochar material as well as preparation method and application thereof

Abstract

The invention belongs to the field of pollutant control, and particularly relates to a chitosan modified cyanobacteria biochar material as well as a preparation method and application thereof. The preparation method of the chitosan modified cyanobacteria biochar material comprises the following steps: modifying cyanobacteria biochar in an organic solvent by using chitosan to increase-NH and-NH2 functional groups in the cyanobacteria biochar so as to obtain a mixed solution A; adding an aldehyde group-containing cross-linking agent into the mixed solution A, so that the aldehyde group in the cross-linking agent is combined with the amino group of the chitosan, and the surface of the blue-green algae biochar is negatively charged to obtain a mixed solution B; adjusting the pH value to 2.6-11 to obtain a mixed solution C, and drying and sieving the mixed solution C to obtain the chitosan modified cyanobacteria biochar material. The chitosan modified cyanobacteria biochar material disclosed by the invention has a relatively good adsorption effect and recoverability on heavy metal ions and antibiotics.

Description

Technical Field

[0001] The invention belongs to the field of pollutant prevention and control, and specifically relates to a chitosan-modified cyanobacteria biochar material and a preparation method and application thereof. Background Art

[0002] Blue algae live in nutrient-rich water bodies. They often reproduce in large numbers in the summer and form a layer of blue-green foam with a fishy smell on the water surface, which is called water bloom. When the blue algae reproduce further and their number increases further, a green tide is formed. Green tides can cause water quality to deteriorate. In severe cases, they will deplete oxygen in the water and cause the death of fish. In addition, some types of blue algae can also produce microcystins.

[0003] At present, there are three methods to deal with cyanobacteria: physical method, chemical method and biological method. The physical method is to remove cyanobacteria from water bodies through mechanical equipment or activated carbon, aeration and oxygenation, etc.; the chemical method is to use chemical reagents to inhibit or kill cyanobacteria; the biological method is to remove cyanobacteria by measures such as fast-growing aquatic plants, animals, and artificial biological floating islands. However, although the above methods can effectively remove cyanobacteria from water bodies, the cyanobacteria after removal are not effectively treated.

[0004] Prior art publication number CN103130297A discloses a method for treating mercury-containing wastewater with modified cyanobacteria, which is carried out by acidification treatment of cyanobacteria to obtain modified cyanobacteria for adsorbing mercury. Publication number CN116903112A discloses a method for preparing cross-linked modified cyanobacteria for purifying hexavalent chromium wastewater with cyanobacteria, which is also treated with acid to remove chloride ions to obtain modified inactive cyanobacteria powder, and then reacted with glutaraldehyde to obtain a cross-linked modified cyanobacteria powder, which can have a good adsorption effect on hexavalent chromium. It can be seen that the prior art modifies cyanobacteria by chemical methods, and the modified cyanobacteria obtained are mainly for single metal ion adsorption, but the heavy metals in the existing water body are multiple, and there are also some non-heavy metal organic pollutants. Therefore, it is necessary to further study the cyanobacteria modification method. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a chitosan-modified cyanobacteria biochar material and a preparation method and application thereof, which can be used to have a good adsorption effect on various heavy metals and organic pollutants in water bodies.

[0006] In order to solve the above technical problems, the technical solutions of the present invention are specifically as follows.

[0007] The first aspect of the present invention provides a preparation method of a chitosan-modified cyanobacteria biochar material, comprising the following steps: modifying cyanobacteria biochar with chitosan in an organic solvent to increase -NH and -NH2 functional groups in the cyanobacteria biochar to obtain a mixed solution A; adding an aldehyde-containing cross-linking agent to the mixed solution A to combine the aldehyde groups in the cross-linking agent with the amino groups of chitosan, so that the surface of the cyanobacteria biochar is negatively charged to obtain a mixed solution B; adjusting the pH to 2.6-11 to obtain a mixed solution C, drying and sieving the mixed solution to obtain the chitosan-modified cyanobacteria biochar material, wherein the mass ratio of cyanobacteria biochar, chitosan and cross-linking agent is 60-90:40-60:1-4; the modification temperature is 80°C-100°C, and the time is 30min-40min; the reaction time of the mixed solution A and the aldehyde-containing cross-linking agent is 30min-40min.

[0008] The present invention utilizes chitosan to modify the cyanobacteria biochar, and adds -NH and -NH2 functional groups, which have good complexation with various heavy metals. The aldehyde groups provided by the crosslinking agent react with the amino groups of chitosan to form covalent bonds, so that the surface of the cyanobacteria biochar is negatively charged, and the electrostatic adsorption with positively charged heavy metal ions is promoted, thereby achieving the effect of adsorption of various metal ions. In addition, chitosan belongs to aminopolysaccharide polymers, which are rich in C and N elements. Using chitosan to modify the cyanobacteria biochar will increase the C and N content, and reduce the O and H content, so that the chitosan-modified cyanobacteria biochar material has higher aromaticity and more binding sites; and the aldehyde groups provided by the crosslinking agent can react with the amino groups of chitosan to form covalent bonds, thereby enhancing the stability of the structure of the chitosan-modified cyanobacteria biochar material, so that it is not easy to deform or degrade during the adsorption process.

[0009] In another preferred embodiment, the organic solvent is an acetic acid solution, the mass volume ratio of the chitosan to the acetic acid solution is 5g-6g:1L; the mass percentage concentration of the acetic acid solution is 1.9%-2.4%; and the deacetylation degree of the chitosan is 80%-95%.

[0010] The deacetylation degree of chitosan refers to the ratio of the number of monomers without acetyl groups in the homologous mixture of chitosan to the total monomer amount. Since the acetyl group in chitin is difficult to be completely removed, chitosan contains some acetylglucosamine residues. The biological activity of chitosan is closely related to the amino group on its sugar ring. The higher the deacetylation degree, the better the biological activity. Therefore, the present invention selects chitosan with a deacetylation degree of 80% to 95%.

[0011] In another preferred embodiment, the particle sizes of the cyanobacteria biochar and the chitosan-modified cyanobacteria biochar material are both 100 mesh to 120 mesh.

[0012] In another preferred embodiment, the specific preparation process of the cyanobacteria biochar is as follows: The cyanobacteria powder is carbonized at 300°C to 600°C for 2h to 5h to reduce carbonization byproducts, and then crushed to obtain cyanobacteria biochar.

[0013] In another preferred embodiment, the crosslinking agent is a glutaraldehyde solution, and the mass percentage concentration of the glutaraldehyde solution is 1% to 2%. Glutaraldehyde as a crosslinking agent can not only maintain the stability of the chitosan morphology, but also effectively improve the mechanical properties of chitosan and provide effective aldehyde positions.

[0014] The second aspect of the present invention provides the chitosan-modified cyanobacteria biochar material.

[0015] The third aspect of the present invention provides the use of the chitosan-modified cyanobacteria biochar material in the preparation of a heavy metal adsorbent.

[0016] In another preferred embodiment, the heavy metals are Cu, Pb and Cd.

[0017] The third aspect of the present invention provides the use of the chitosan-modified cyanobacteria biochar material in the preparation of an organic pollutant adsorbent, wherein the organic pollutant is an antibiotic; and the antibiotic is a fluorine-containing organic drug.

[0018] In another preferred embodiment, the fluorine-containing organic drugs are ciprofloxacin and ofloxacin.

[0019] Compared with the prior art, the present invention has the following beneficial effects.

[0020] (1) The present invention uses cyanobacteria biochar, chitosan and a cross-linking agent in a mass ratio of 60-90:40-60:1-4 as reaction raw materials, uses chitosan to modify the cyanobacteria biochar, reacts at 80°C-100°C for 30min-40min to increase the -NH and -NH2 functional groups in the cyanobacteria biochar, and complexes with various heavy metals through -NH and -NH2. Then, an aldehyde-containing cross-linking agent is added to react for 30min-40min, and the aldehyde group of the cross-linking agent reacts with the amino group of chitosan to form a covalent bond, so that the surface of the cyanobacteria biochar is negatively charged, and the electrostatic adsorption with positively charged heavy metal ions is promoted, thereby achieving the effect of adsorbing various metal ions.

[0021] (2) The chitosan in the present invention effectively increases the content of C and N elements in cyanobacteria biochar, making it more aromatic and having more binding sites. The aldehyde groups in the cross-linking agent react with the amino groups in the chitosan to form covalent bonds, thereby enhancing the stability of the structure of the chitosan-modified cyanobacteria biochar material, making it less likely to degrade during the adsorption process, thereby improving the degradation efficiency.

[0022] (3) The chitosan-modified cyanobacteria biochar material in the present invention has -OH and -COOH groups. Both -OH and -COOH groups are π electron donors, which can form a p-π conjugated system with adjacent π bonds. Therefore, they can bind to ciprofloxacin and ofloxacin, thereby achieving the adsorption of antibiotic drugs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The process flow chart of the preparation method of chitosan modified cyanobacteria biochar material.

[0024] Figure 2 This is a picture of cyanobacteria mud.

[0025] Figure 3 This is a picture of chitosan modified cyanobacteria biochar material.

[0026] Figure 4 This is an electron micrograph of unmodified cyanobacteria biochar.

[0027] Figure 5 This is an electron micrograph of chitosan-modified cyanobacteria biochar.

[0028] Figure 6 These are infrared spectra of three types of cyanobacteria biochar. In the figure, 1 is CBC, 2 is KBC, and 3 is BC. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Unless otherwise specified, the experimental methods described in the following examples are all conventional methods; the reagents and materials described are all commercially available unless otherwise specified.

[0031] Chitosan is a naturally derived polysaccharide with a wide range of applications. It is present in the cell walls of some species of fungi; while commercial chitosan can be prepared from chitin, the incorporation of chitosan promotes adsorption interactions due to the introduction of a variety of functional groups. In addition, chitosan has the characteristics of large dosage, non-toxicity, good biodegradability, natural antibacterial, and no secondary pollution. The presence of a large number of functional groups and their high chemical reactivity are the reasons why chitosan has excellent adsorption properties. However, the poor solubility of chitosan in neutral aqueous solutions and low mechanical strength further limit its application in aqueous solution treatment.

[0032] The present invention utilizes chitosan to modify the cyanobacteria biochar, thereby increasing -NH and -NH2 functional groups, and the -NH and -NH2 functional groups have good complexation with various heavy metals. The aldehyde group provided by the cross-linking agent can react with the amino group of the chitosan to form a covalent bond, so that the surface of the cyanobacteria biochar is negatively charged, and the electrostatic adsorption with the positively charged heavy metal ions is promoted, thereby achieving the effect of adsorption of various metal ions. In addition, the cyanobacteria biochar is modified by chitosan, and the C and N elements in the chitosan-modified cyanobacteria biochar material are effectively improved, so that it has higher aromaticity and more binding sites, and then the aldehyde group in the cross-linking agent reacts with the amino group in the chitosan to form a covalent bond, thereby enhancing the stability of the chitosan-modified cyanobacteria biochar material structure, thereby further improving the adsorption effect.

[0033] The blue algae in the present invention are Chaohu blue algae. The blue algae are first surrounded by a net to the vicinity of a fixed algae suction port to facilitate the collection of algae-rich water. Pumping devices are dispersed around the separation station. After the algae-rich water is collected by the pumping device, it is sent to the algae-water separation device. The blue algae in the algae-rich water are floated on the water surface by pressurized flotation to achieve algae-water separation. After that, the algae residue initially separated enters the algae residue regulating tank for deep mechanical dehydration. The blue algae mud obtained after dehydration is as follows: Figure 2 As shown, subsequent modification experiments were performed.

[0034] The following is a detailed description of a chitosan-modified cyanobacteria biochar material and its preparation method and application.

[0035] Example 1: A method for preparing chitosan-modified cyanobacteria biochar material, such as Figure 1 As shown, the following steps are included.

[0036] S1. Put the wet cyanobacteria with a moisture content of 70% into an oven, set the temperature to 80°C, leave it for 12 hours, take it out and grind it into powder, pass it through a 100-mesh sieve to obtain cyanobacteria powder; compact the cyanobacteria powder and fill it in a crucible and place it in a muffle furnace, set the furnace temperature to a heating rate of 20°C / min, use a nitrogen-filled muffle furnace to set the required preheating temperature to start preheating, open the nitrogen valve during the preheating process, and introduce nitrogen into the furnace to form an inert atmosphere. The nitrogen pressure is 0.5 gauge pressure. After reaching the preheating temperature and the nitrogen atmosphere is stable, put the cyanobacteria powder into the furnace, adjust the temperature of the muffle furnace, heat it to 600°C and heat it for 2 hours, and obtain cyanobacteria biochar after cooling to room temperature, grind it through a 100-mesh sieve to obtain cyanobacteria biochar with a moisture content of 5%.

[0037] S2. Dissolve 6 g of chitosan with a deacetylation degree of 95% in 1 L of 1.9% acetic acid solution, heat and stir until completely dissolved, add 9 g of cyanobacteria biochar, heat in a water bath at 80° C. for 30 min to obtain a mixed solution A; add 100 mL of 1% glutaraldehyde solution at a mass percentage concentration of 1% to the mixed solution A, stir and react at 80° C. for 30 min to obtain a mixed solution B; adjust the pH of the mixed solution B to 11 with 1 mol / L NaOH solution, continue heating for 60 min, and obtain a mixed solution C.

[0038] S3, the mixed solution C was washed three times with deionized water, placed in an oven at 80°C for 12 h, and ground through a 100-mesh sieve to obtain chitosan-modified cyanobacteria biochar, such as Figure 3 shown.

[0039] Example 2: A method for preparing chitosan-modified cyanobacteria biochar material, comprising the following steps.

[0040] S1. Put the wet cyanobacteria with a moisture content of 80% into an oven, set the temperature to 90°C, leave it for 12 hours, take it out and grind it into powder, pass it through a 100-mesh sieve to obtain cyanobacteria powder; compact the cyanobacteria powder and fill it in a crucible and place it in a muffle furnace, set the furnace temperature to a heating rate of 20°C / min, use a nitrogen-filled muffle furnace to set the required preheating temperature to start preheating, open the nitrogen valve during the preheating process, and introduce nitrogen into the furnace to form an inert atmosphere. The nitrogen pressure should be 0.6 gauge pressure. After reaching the preheating temperature and the nitrogen atmosphere is stable, put the cyanobacteria powder into the furnace, adjust the temperature of the muffle furnace to 500°C and heat it for 3 hours, and obtain cyanobacteria biochar after cooling to room temperature, grind it through a 100-mesh sieve to obtain cyanobacteria biochar with a moisture content of 10%.

[0041] S2. Dissolve 6 g of chitosan with a deacetylation degree of 80% in 1 L of acetic acid solution with a mass percentage concentration of 2%, heat and stir until completely dissolved, add 9 g of cyanobacteria biochar, heat in a water bath at 90° C. for 35 min, and obtain a mixed solution A; add 100 mL of a glutaraldehyde solution with a mass percentage concentration of 1.5% to the mixed solution A, stir and react at 90° C. for 35 min, and obtain a mixed solution B; adjust the pH of the mixed solution B to 11 with a 1 mol / L NaOH solution, continue heating for 60 min, and obtain a mixed solution C.

[0042] S3. The mixed solution C was washed three times with deionized water, dried in an oven at 80°C, and ground through a 100-mesh sieve to obtain chitosan-modified cyanobacteria biochar.

[0043] Example 3: A method for preparing chitosan-modified cyanobacteria biochar material, comprising the following steps.

[0044] S1. Put the wet cyanobacteria with a moisture content of 80% into an oven, set the temperature to 100°C, and take it out after leaving it for 12 hours, grind it into powder, and pass it through a 100-mesh sieve to obtain cyanobacteria powder; compact the cyanobacteria powder and fill it in a crucible and place it in a muffle furnace, set the furnace temperature to a heating rate of 20°C / min, use a nitrogen-filled muffle furnace to set the required preheating temperature to start preheating, open the nitrogen valve during the preheating process, and introduce nitrogen into the furnace to form an inert atmosphere. The nitrogen pressure should be 0.5 gauge pressure. After reaching the preheating temperature and the nitrogen atmosphere is stable, put the sample into the furnace. According to the experimental requirements, adjust the temperature of the muffle furnace to 300°C and heat it for 5 hours. After cooling to room temperature, obtain cyanobacteria biochar, grind it through a 100-mesh sieve to obtain cyanobacteria biochar with a moisture content of 10%.

[0045] S2. Dissolve 5 g of chitosan with a deacetylation degree of 95% in 1 L of acetic acid solution with a mass percentage concentration of 2.4%, add 8 g of cyanobacteria biochar, and heat in a water bath at 100° C. for 40 min to obtain a mixed solution A; add 100 mL of a 2% mass percentage glutaraldehyde solution to the mixed solution A, stir and react at 100° C. for 40 min to obtain a mixed solution B; adjust the pH of the mixed solution B to 11 with a 1 mol / L NaOH solution, continue heating for 60 min, and obtain a mixed solution C.

[0046] S3. The mixed solution C was washed three times with deionized water, dried in an oven at 80°C, and ground through a 100-mesh sieve to obtain chitosan-modified cyanobacteria biochar.

[0047] KOH is a commonly used activated carbon modifier with obvious improvement effect. In order to illustrate that chitosan has better modification effect, KOH is used to modify cyanobacteria biochar as a comparative example.

[0048] Comparative Example 1: A method for preparing cyanobacteria biochar material, comprising the following steps.

[0049] S1. Put the wet cyanobacteria with a moisture content of 70% into an oven and set the temperature to 80°C. After leaving it for 12 hours, take it out and grind it into powder, pass it through a 100-mesh sieve to obtain cyanobacteria powder; compact the cyanobacteria powder and fill it in a crucible and place it in a muffle furnace. Set the furnace temperature to a heating rate of 20°C / min, use a nitrogen-filled muffle furnace to set the required preheating temperature and start preheating. During the preheating process, open the nitrogen valve and introduce nitrogen into the furnace to form an inert atmosphere. The nitrogen pressure should be 0.5 gauge pressure. After reaching the preheating temperature and the nitrogen atmosphere is stable, put the sample into the furnace. According to the experimental requirements, adjust the temperature of the muffle furnace to 400°C and heat it for 2 hours. After cooling to room temperature, obtain cyanobacteria biochar, grind it through a 100-mesh sieve to obtain cyanobacteria biochar with a moisture content of 5%.

[0050] S2. Take 9 g of cyanobacteria biochar and add it to 200 mL of 0.4 mol / L KOH solution. Stir the mixture on a magnetic stirrer for 2 h, dry it in an oven at 80 °C for 12 h, then wash it three times with deionized water, and dry it in an oven at 80 °C for 12 h to obtain KOH-modified cyanobacteria biochar.

[0051] Examples 1 to 3 all obtained a chitosan-modified cyanobacteria biochar material, and the effects were comparable. The chitosan-modified cyanobacteria biochar material in Example 1 is used as an example for description.

[0052] 1. Heavy metal adsorption effect of cyanobacteria biochar obtained by different treatment methods in water bodies.

[0053] The cyanobacteria biochar prepared in Example 1 is marked as BC, the chitosan-modified cyanobacteria biochar is marked as CBC, and the KOH-modified cyanobacteria biochar obtained in Comparative Example 1 is marked as KBC.

[0054] Scanning electron microscope was performed on BC and CBC, and the results were as follows Figure 4 and Figure 5 As shown in the figure, it can be seen that the CBC obtained after the cyanobacteria biochar BC is modified by chitosan has a higher porosity and specific surface area, and can provide more adsorption sites and adsorption space during the adsorption process, so that the adsorption capacity is significantly improved.

[0055] BC, CBC and KBC were tested by infrared respectively, and the results are shown in Figure 6. Figure 6 It can be seen that the three cyanobacteria biochars have -1 The absorption peak may correspond to the stretching vibration of C=O, CBC at 3382cm -1 There is a broad absorption peak around the peak at , which may represent the stretching vibration of -OH. -1 When the absorption peak is about 1.5, there is a very obvious absorption peak, which may be the result of C=C stretching vibration. This shows that CBC contains more functional groups such as -OH and C=C, and therefore has more sites that can react with heavy metals.

[0056] Weigh 20 mg, 40 mg, 60 mg, 100 mg, 150 mg and 250 mg of BC, CBC and KBC respectively, place them in a 100 mL beaker, add 50 mL of water sample with a cadmium ion concentration of 100 mg / L, and heat at 25 °C and 200 r·min. -1 The mixture was shaken under the conditions of , and adsorption equilibrium was maintained for 2 h. The supernatant was filtered through a 0.45 μm filter membrane, and the heavy metal concentration of each liquid sample was determined by inductively coupled plasma mass spectrometry. The experiment was repeated 3 times.

[0057] The chromium ion concentrations in the cadmium ion solutions after BC adsorption were 80.68 mg / L, 80.55 mg / L, 78.6 mg / L, 73.84 mg / L, 73.95 mg / L, and 74.06 mg / L, respectively; the cadmium ion concentrations in the cadmium ion solutions after KBC adsorption were 55.66 mg / L, 50.63 mg / L, 44.35 mg / L, 43.18 mg / L, 45.63 mg / L, and 45.85 mg / L, respectively; the cadmium ion concentrations in the cadmium ion solutions after CBC adsorption were 16.33 mg / L, 15.9 mg / L, 15.86 mg / L, 15.25 mg / L, 16.45 mg / L, and 16.87 mg / L, respectively. It can be seen from the above results that CBC has the best adsorption of cadmium ions, and the adsorption amount can reach 423.8 mg / g. Taking the treatment effect and economic cost into consideration, the adsorption experiment of 100 mg / L cadmium ion solution was carried out and the dosage of cyanobacteria biochar obtained by different treatment methods was 100 mg.

[0058] Weigh 0.1g of BC, CBC, and KBC respectively and place them in 100mL beakers. Add 50mL of water sample with a cadmium ion concentration of 100mg / L. The concentration used is 0.1mol·L -1 NaOH and 0.1 mol·L -1 The pH of the solution was adjusted to 3, 4, 5, 6, 7, 8 and 9 at 25 °C and 200 r·min -1 The mixture was shaken under the conditions of , and samples were taken after 2 hours of adsorption equilibrium. After filtering through a 0.45 μm filter membrane, the heavy metal concentration of each liquid sample was determined by inductively coupled plasma mass spectrometry. The experiment was repeated 3 times.

[0059] The results showed that BC, CBC and KBC all achieved the best adsorption effect at pH 8. The cadmium ion concentrations in the cadmium ion solutions after adsorption by BC, KBC and CBC were 64.28 mg / L, 44.89 mg / L and 13.76 mg / L respectively. CBC had the best adsorption effect, and the adsorption amount could reach 431.2 mg / g.

[0060] Weigh 0.1g of BC, CBC, and KBC respectively and place them in 100mL beakers, add 50mL of water sample with a cadmium ion concentration of 100mg / L, and mix them at a temperature gradient of 25℃, 35℃, 45℃, 55℃, 65℃, and 75℃ at a speed of 200r·min. -1 The mixture was shaken under the conditions of , and samples were taken after 2 hours of adsorption equilibrium. After filtering through a 0.45 μm filter membrane, the heavy metal concentration of each liquid sample was determined by inductively coupled plasma mass spectrometry. The experiment was repeated 3 times.

[0061] The results showed that BC, CBC and KBC all achieved the best adsorption effect at a temperature of 25°C. The cadmium ion concentrations in the cadmium ion solutions after adsorption by BC, KBC and CBC were 75.46 mg / L, 53.21 mg / L and 26.78 mg / L respectively. CBC had the best adsorption effect, and the adsorption amount could reach 366.1 mg / g.

[0062] 2. Experiment on the removal effect of antibiotics.

[0063] Weigh 20 mg, 40 mg, 60 mg, 100 mg, 150 mg and 250 mg of CBC respectively and place them in 100 mL beakers. Set up two parallel experiments. Add 50 mL of water containing 10 μg / L ofloxacin and ciprofloxacin to each beaker and heat at 25 °C and 200 r·min. -1 The mixture was shaken under the conditions of , and adsorption equilibrium was maintained for 2 h. The supernatant was filtered through a 0.45 μm filter membrane, and the contents of ciprofloxacin and ofloxacin in each liquid sample were determined by high performance liquid chromatography-tandem triple quadrupole mass spectrometry. The experiment was repeated 3 times.

[0064] As the CBC dosage increased from 0.02g to 0.15g, the removal rate increased significantly, and the removal rates of ciprofloxacin increased from 35.04% and 40.45% to 78.1%, 94.03% and 96.83%, respectively. When the dosage increased to 0.25g, the removal rate of ciprofloxacin decreased to 95.38%, and the removal rate of ofloxacin increased from 36.34% and 42.56% to 76.5%, 93.48% and 96.9%, respectively. When the dosage increased to 250mg, the removal rate of ofloxacin decreased to 94.3%, so the optimal dosage of CBC was 150mg, at which time the adsorption performance of biochar was the best.

[0065] Weigh 0.15 g of CBC and place it in two 100 mL beakers. Add 50 mL of water sample with 10 μg / L concentration of ciprofloxacin and ofloxacin respectively. -1 NaOH and 0.1 mol·L -1 The pH of the two solutions was adjusted to 3, 4, 5, 6, 7, 8 and 9 by HCl at 25 °C and 200 r·min -1 The mixture was shaken under the conditions of , and samples were taken after 2 hours of adsorption equilibrium. After filtering through a 0.45 μm filter membrane, the contents of ciprofloxacin and ofloxacin in each liquid sample were determined by high performance liquid chromatography-tandem triple quadrupole mass spectrometry. The experiment was repeated 3 times.

[0066] With the increase of pH value, the adsorption of CBC on ciprofloxacin and ofloxacin first increased and then decreased; when the pH value was 6, the adsorption amount was the largest, and the adsorption rate of ciprofloxacin could reach 97.32%, and the adsorption rate of ofloxacin could reach 98.1%.

[0067] Weigh 0.15g of CBC and place it in two 100mL beakers. Add 50mL of water sample with 10μg / L concentration of ciprofloxacin and ofloxacin respectively. -1 The mixture was shaken under the conditions of , and samples were taken after 2 hours of adsorption equilibrium. After filtering through a 0.45μm filter membrane, the content of antibiotics in each liquid sample was determined by a high performance liquid chromatography-tandem triple quadrupole mass spectrometer. The experiment was repeated 3 times. The adsorption of antibiotics by CBC showed an upward trend, showing a positive effect of increasing temperature. The adsorption amount was the largest when the adsorption temperature was 35℃, and the adsorption rate of ciprofloxacin could reach 97.63%, and the adsorption rate of ofloxacin could reach 98.28%.

[0068] It can be seen from the above experimental results that the chitosan-modified cyanobacteria biochar material in the present invention has a good adsorption effect on Cu, Pb and Cd in water. According to the SEM, FTIR characterization methods and adsorption experimental parameters, the optimal process parameters are: the cyanobacteria biochar screening particle size is 100 mesh, the mass ratio of chitosan to cyanobacteria biochar is 6:9, and the prepared chitosan-modified cyanobacteria biochar material has good performance in adsorbing pollutants, heavy metals and antibiotics in water. Compared with the original cyanobacteria biochar, the addition of chitosan increases the surface adsorption sites of cyanobacteria biochar, and the adsorption capacity of the composite material is enhanced due to the introduction of various active functional groups.

[0069] In addition to some inorganic pollutants such as heavy metals, there are some other organic pollutants in the aqueous solution, such as some compounds with medicinal activity, which are widely used in human and animal husbandry. They are usually discharged with urine or feces, causing serious environmental pollution. In addition, excessive drug residues in aqueous solution or soil in the ecosystem may lead to the emergence of bacterial resistance, resulting in the existence of some uninhibited bacterial strains. The chitosan-modified cyanobacteria biochar material in the present invention can also remove fluorine-containing organic drugs such as ciprofloxacin and ofloxacin. After the above-mentioned conditions and corresponding results of the removal experiment of ciprofloxacin and ofloxacin, the final results show that the removal rate of ciprofloxacin and ofloxacin by the chitosan-modified cyanobacteria biochar material can reach 97.63% and 98.28%. The electron-withdrawing fluorine and nitrogen-containing aromatic heterocycles in the molecules of ciprofloxacin and ofloxacin are π electron acceptors, and the -OH and -COOH groups on the chitosan-modified cyanobacteria biochar materials are π electron donors, which can form a p-π conjugated system with adjacent π bonds, which helps the combination of these antibiotics with the chitosan-modified cyanobacteria biochar materials. At the same time, the chitosan-modified cyanobacteria biochar materials have good adsorption properties and recyclability for dye-contaminated water.

[0070] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing chitosan-modified cyanobacteria biochar material, characterized in that: The following steps are involved: The cyanobacteria biochar is modified by using chitosan in an organic solvent to increase the -NH and -NH2 functional groups in the cyanobacteria biochar to obtain a mixed solution A; Adding an aldehyde-containing crosslinking agent to the mixed solution A, the aldehyde group in the crosslinking agent combines with the amino group of chitosan to make the surface of the cyanobacteria biochar negatively charged, and obtaining a mixed solution B; adjusting the pH of the mixed solution B to 2.6-11 to obtain a mixed solution C, drying and sieving the mixed solution to obtain the chitosan-modified cyanobacteria biochar material; The mass ratio of cyanobacteria biochar, chitosan and cross-linking agent is 60~90:40~60:1~4; The modification temperature is 80° C. to 100° C., and the time is 30 min to 40 min. The reaction time of the mixed solution A and the aldehyde-containing cross-linking agent is 30 min to 40 min.

2. The method for preparing chitosan-modified cyanobacteria biochar material according to claim 1, characterized in that: The organic solvent is an acetic acid solution, and the mass volume ratio of the chitosan to the acetic acid solution is 5g-6g:1L; The mass percentage concentration of the acetic acid solution is 1.9% to 2.4%; the deacetylation degree of the chitosan is 80% to 95%.

3. The method for preparing chitosan-modified cyanobacteria biochar material according to claim 1, characterized in that: The particle sizes of the cyanobacteria biochar and the chitosan-modified cyanobacteria biochar material are both 100 meshes to 120 meshes.

4. The method for preparing chitosan-modified cyanobacteria biochar material according to claim 1, characterized in that: The specific preparation process of the cyanobacteria biochar is as follows: The cyanobacteria powder is carbonized at 300°C to 600°C for 2h to 5h and crushed to obtain cyanobacteria biochar.

5. The method for preparing chitosan-modified cyanobacteria biochar material according to claim 1, characterized in that: The cross-linking agent is a glutaraldehyde solution with a mass percentage concentration of 1% to 2%.

6. A chitosan-modified cyanobacteria biochar material prepared by the method for preparing a chitosan-modified cyanobacteria biochar material according to any one of claims 1 to 5.

7. Use of the chitosan-modified cyanobacteria biochar material according to claim 6 in preparing a heavy metal adsorbent.

8. The use of the chitosan-modified cyanobacteria biochar material in the preparation of a heavy metal adsorbent according to claim 7, characterized in that: The heavy metal is Cu, Pb and / or Cd.

9. A use of the chitosan-modified cyanobacteria biochar material according to claim 6 in preparing an organic pollutant adsorbent, characterized in that: The organic pollutant is an antibiotic; and the antibiotic is a fluorine-containing organic drug.

10. The use of chitosan-modified cyanobacteria biochar material in preparing an organic pollutant adsorbent according to claim 9, characterized in that: The fluorine-containing organic drug is ciprofloxacin and / or ofloxacin.

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