A quaternary ammonium salt / magnetic biochar composite material, its preparation method and application

Abstract

This invention discloses a quaternary ammonium salt / magnetic biochar composite material, its preparation method, and its application. Rice husk-based biochar is prepared using agricultural waste as raw material. Magnetic iron-based biochar is synthesized through an alkaline chemical co-precipitation method. Then, it is combined with quaternary ammonium salt compounds via ion exchange to form a quaternary ammonium salt / magnetic biochar composite material. The obtained composite material exhibits significant bactericidal effects and superior slow-release quaternary ammonium salt performance. Furthermore, the used quaternary ammonium salt / magnetic biochar composite material can be used to prepare a regenerated quaternary ammonium salt / magnetic biochar composite material, with better bactericidal effects than the initial use, achieving the recycling and reuse of the composite material. The preparation method of this invention uses widely available and inexpensive raw materials. The obtained composite material adsorbs free bacteria through high-density charge adsorption, avoiding the development of drug resistance and secondary environmental pollution. It can be applied to wastewater treatment, providing a new material and method for solving the problem of pathogenic bacteria pollution in water bodies.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically relating to a quaternary ammonium salt / magnetic biochar composite material, its preparation method, and its application. Background Technology

[0002] With the rapid development of society and economy, water scarcity has affected human activities and constrained social development. Wastewater reuse is an effective way to alleviate water scarcity and reduce water pollution. However, there are many problems in the actual reuse of reclaimed water. Studies have shown that various pathogenic microorganisms, such as Shigella, Salmonella, Campylobacter, Escherichia coli, and enteroviruses, still remain in the initial water after conventional sewage treatment. These may lead to outbreaks of diseases such as acute gastroenteritis and typhoid fever. Therefore, efficient sterilization treatment of reclaimed water is essential to ensure water quality safety.

[0003] Quaternary ammonium compounds (QACs) are a class of cationic surfactants and antibacterial agents with broad-spectrum bactericidal activity, widely used in food processing, wastewater treatment, and other industries. As water-soluble chemical bactericides, QACs have drawbacks when used alone, including uncontrollable release rates, short antibacterial activity cycles, easy induction of bacterial resistance, and environmental pollution due to residual toxicity. Conventional wastewater treatment technologies cannot remove QACs; large amounts of QACs are absorbed by activated sludge or discharged into the environment with effluent, polluting surface water and rivers, thus limiting their use as antibacterial agents. By chemically bonding QACs to the surface of porous materials to create QAC-modified materials, the problems of rapid diffusion and biocidal activity of QACs can be overcome, and the materials can maintain long-term antibacterial activity, effectively achieving high efficiency, low toxicity, and slow-release properties of the antibacterial agent.

[0004] Commonly used carriers for existing antibacterial agents include clay minerals, diatomaceous earth, metal-organic frameworks, graphene oxide, and inorganic microporous materials. Studies have found that graphene oxide exhibits superior bactericidal effects when used as a carrier, but its high production cost makes large-scale production and application in practical applications difficult. Composite materials made using widely available and inexpensive carriers, such as PTQ (chlorinated natural rubber-quaternary ammonium salt) and HNTs-CS@Ag (chitosan-silver nanocomposite material), generally have moderate bactericidal effects and require larger dosages. Furthermore, composite bactericidal materials supported by even cheaper carriers such as diatomaceous earth and clay minerals, while reducing production costs, increase the likelihood of pipe and equipment blockages, and these materials are difficult to recycle. CN105284812A discloses a broad-spectrum antibacterial amphiphilic biochar material, its preparation method, and its uses. Through covalent coupling and distillation-precipitation polymerization, a broad-spectrum antibacterial agent, quaternary ammonium salt, is uniformly fixed on the surface of the amphiphilic biochar material. The resulting broad-spectrum antibacterial amphiphilic biochar material possesses advantages such as broad-spectrum antibacterial activity, long-lasting antibacterial stability, and reusability. However, the preparation method is complex and lacks recyclability. CN107398256A discloses a magnetic straw quaternary ammonium salt / attapulgite composite material, its preparation method, and its applications. Using rice straw, attapulgite, and 3-chloro-2-hydroxypropyltrimethylammonium chloride as raw materials, a magnetic straw quaternary ammonium salt / attapulgite composite material is prepared via a liquid-phase method. This solves the problem of flocculent matter often remaining in water treated with straw quaternary ammonium salt flocculants. However, the attapulgite, acting as a natural clay, may increase the burden on pipelines, and its bactericidal and recyclability effects are limited.

[0005] Therefore, there are few reports on bactericidal materials that can simultaneously remove pathogens from reclaimed water during wastewater reuse. In addition, there are shortcomings in existing composite materials and insufficient preparation technology. There is an urgent need to develop a new type of composite material that is low in cost, has a good long-lasting bactericidal effect, and can be repeatedly recycled and reused. This is of great significance for realizing the safe reuse of wastewater. Summary of the Invention

[0006] To address the above problems, this invention provides a quaternary ammonium salt / magnetic biochar composite material, its preparation method, and its application. Rice husk-based biochar is prepared using agricultural waste as raw material. Magnetic iron-based biochar is synthesized via alkaline chemical co-precipitation. Then, it is combined with quaternary ammonium salt compounds via ion exchange to form a quaternary ammonium salt / magnetic biochar composite material. The resulting composite material exhibits superior slow-release quaternary ammonium salt properties and a long-lasting and significant bactericidal effect. Furthermore, the used quaternary ammonium salt / magnetic biochar composite material can be used to prepare a regenerated quaternary ammonium salt / magnetic biochar composite material, achieving recycling and reuse of the composite material. The bactericidal effect is superior to that of the initially prepared composite material. This biochar composite material can be applied to wastewater treatment, laying the foundation for the efficient removal of microorganisms from wastewater.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] On the one hand, the present invention provides a method for preparing a quaternary ammonium salt / magnetic biochar composite material, characterized in that magnetic iron-based biochar is synthesized using rice husk-based biochar as a carrier via an alkaline chemical coprecipitation method, and then quaternary ammonium salt compounds are exchanged via an ion exchange method to prepare a quaternary ammonium salt / magnetic biochar composite material.

[0009] The above preparation method includes the following steps:

[0010] (1) Preparation of rice husk-based biochar:

[0011] ① The carbonized product obtained by washing and drying rice husks to constant weight and then carbonizing them at high temperature;

[0012] ②The carbonized product obtained in step ① is washed, dried, ground and sieved to obtain rice husk-based biochar;

[0013] (2) Preparation of magnetic iron-based biochar:

[0014] ① Place the rice husk-based biochar obtained in step (1) in deionized water and ultrasonically vibrate to obtain a biochar suspension;

[0015] ② Dissolve FeSO4·7H2O and FeCl3·6H2O in dilute hydrochloric acid solution and stir under N2 environment. Adjust the pH with ammonia water to obtain a magnetic iron-based solution.

[0016] ③ Under water bath conditions, the biochar suspension prepared in step ① is added to the magnetic iron-based solution obtained in step ② while stirring. After cooling to room temperature, the product is separated by a permanent magnet. The magnetic product is washed, dried and sieved to obtain magnetic iron-based biochar.

[0017] (3) Preparation of quaternary ammonium salt / magnetic biochar composite material: After adding the magnetic iron-based biochar obtained in step (2) to deionized water, quaternary ammonium salt compounds were added for full impregnation. After hydrothermal reaction, the product was cooled and separated with a permanent magnet. Then, the product was washed, vacuum dried, ground and sieved to obtain quaternary ammonium salt / magnetic biochar composite material.

[0018] Furthermore, the rice husks in step (1) are washed 2-3 times; the drying temperature is 60-70℃ and the time is 10-15h; the high-temperature carbonization method is as follows: the rice husks are placed in a tube furnace, N2 is introduced at a constant rate of 3-5L / h, the temperature is raised to 500-600℃ at a rate of 10-20℃ / min, the N2 is introduced and then the carbonization is stopped after 1-3h, and CO2 with a concentration of 15-20% is introduced to react for 1-2h, and then cooled to room temperature in a N2 protective atmosphere.

[0019] Furthermore, in step (1), the carbonized product is washed 3-5 times until the pH of the washing solution is neutral; the drying temperature is 60-70℃ and the time is 20-30h; the filter sieve aperture range is 90-110 mesh; and the particle size of the rice husk-based biochar is 0.9-1.2mm.

[0020] Furthermore, in step (2), the weight ratio of rice husk-based biochar to deionized water is 1:8-12; the frequency of ultrasonic oscillation is 20-80kHz, and the duration is 3-5h.

[0021] Furthermore, in step (2), the weight ratio of FeSO4·7H2O, FeCl3·6H2O, and dilute hydrochloric acid solution is 1:2-

[0022] 4:10-15, the concentration of dilute hydrochloric acid is 0.3-0.5 mol / L; the concentration of ammonia water is 20-30%, and the pH of the magnetic iron-based solution is 9.5-10.5.

[0023] Furthermore, in step (2), the magnetic iron-based solution and the biochar suspension are in a volume ratio of 1:3-5; the water bath...

[0024] The temperature is 65-75℃, and the stirring time is 1.5-3h; the washing method is: first wash with anhydrous ethanol, then wash with deionized water, the number of washings is 1-3 times and 3-5 times respectively, until the pH value of the washing solution is neutral; the drying temperature is 65-80℃, and the time is 24-48h; the filter sieve aperture range is 90-110 mesh.

[0025] Furthermore, the quaternary ammonium salt compound in step (3) is one or two of tetradecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, and hexadecyltrimethylammonium chloride.

[0026] Furthermore, the weight ratio of the magnetic iron-based biochar, quaternary ammonium compounds, and deionized water in step (3) is as follows:

[0027] The ratio of deionized water to dilute water is 1:10-50:100-400, and the amount of deionized water added is sufficient for thorough soaking. The soaking time is 12-20 hours.

[0028] Furthermore, in step (3), the hydrothermal reaction temperature is 60-70℃ and the time is 3-5h; the washing is performed 3-5 times until the pH of the washing liquid is neutral; the vacuum drying temperature is 65-75℃ and the time is 24-48h; and the filter sieve aperture range is 90-110 mesh.

[0029] On the other hand, recycled quaternary ammonium salt / magnetic biochar composite materials can be prepared using the used quaternary ammonium salt / magnetic biochar composite materials as raw materials.

[0030] A method for preparing a recycled quaternary ammonium salt / magnetic biochar composite material is characterized in that the used quaternary ammonium salt / magnetic biochar composite material is washed, dried and sieved, and then ion-exchanged with a quaternary ammonium salt compound to prepare a recycled quaternary ammonium salt / magnetic biochar composite material.

[0031] The above preparation method includes the following steps:

[0032] (1) The above-mentioned quaternary ammonium salt / magnetic biochar composite material after use is separated and recovered by a permanent magnet, washed with deionized water 3-5 times until the washing liquid is neutral; dried at 65-80℃ for 24-48h, and ground through a 90-110 mesh sieve to obtain the recovered material.

[0033] (2) After adding the recycled material obtained in step (1) to deionized water, add quaternary ammonium salt compounds to fully impregnate the material, carry out hydrothermal reaction and then cool it. Separate the product with a permanent magnet, and then wash, vacuum dry, grind and sieve to obtain the regenerated quaternary ammonium salt / magnetic biochar composite material.

[0034] Furthermore, the quaternary ammonium salt compound in step (2) is one or two of tetradecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, and hexadecyltrimethylammonium chloride.

[0035] Furthermore, in step (2), the weight ratio of the recycled material, quaternary ammonium salt compound, and deionized water is 1:10-

[0036] The ratio of 50:100-400 is used to ensure sufficient immersion, and the immersion time is 12-20 hours.

[0037] Furthermore, in step (2), the hydrothermal reaction temperature is 60-70℃ and the time is 3-5h; the washing is performed 3-5 times until the pH of the washing liquid is neutral; the vacuum drying temperature is 65-75℃ and the time is 24-48h; and the filter sieve aperture range is 90-110 mesh.

[0038] The present invention also provides an application of quaternary ammonium salt / magnetic biochar composite material or recycled quaternary ammonium salt / magnetic biochar composite material in wastewater treatment.

[0039] The specific method for the above application is as follows: add the quaternary ammonium salt / magnetic biochar composite material or the recycled quaternary ammonium salt / magnetic biochar composite material to the wastewater at a dosage of 20-50 mg / L.

[0040] Beneficial effects:

[0041] (1) The quaternary ammonium salt / magnetic biochar composite material prepared by this invention uses biochar as the original loading material and agricultural waste as the raw material for calcination, realizing the resource utilization of solid waste and biochar materials, which is conducive to further promotion and application.

[0042] (2) The quaternary ammonium salt / magnetic biochar composite material prepared by this invention combines biochar with magnetic particles to prepare magnetic iron-based biochar. The composite material can be separated from water by a permanent magnet to achieve solid-liquid separation.

[0043] The reuse of materials has advantages such as environmental protection, energy saving, and low cost, which is conducive to its promotion and application.

[0044] (3) The quaternary ammonium salt / magnetic biochar composite material prepared by the present invention has bactericide quaternary ammonium salt compounds loaded on the surface of magnetic biochar. The composite material has good bactericidal performance and slow release function, which can effectively solve the problems of difficult release rate, short antibacterial activity cycle, inability to be reused, and secondary pollution of water caused by the residue of disinfectant when water-soluble bactericide quaternary ammonium salt is used alone.

[0045] (4) In the process of loading quaternary ammonium salt, the magnetic iron-based biochar is fully impregnated with quaternary ammonium salt compound and then subjected to hydrothermal reaction, which can maximize the activation and enhancement of the combination of quaternary ammonium salt and magnetic biochar, thereby increasing the loading of quaternary ammonium salt on the surface of magnetic biochar and effectively enhancing the bactericidal performance of composite material; secondly, quaternary ammonium salt is fixed on the surface of magnetic biochar through chemical bonds to form quaternary ammonium salt modified material, so that composite material can maintain long-term antibacterial activity.

[0046] (5) The quaternary ammonium salt / magnetic biochar composite material obtained by the present invention is a quaternary ammonium salt polymer material. By adsorbing free bacteria and other substances through the high-density charge on the surface of the material, it can avoid the generation of drug resistance and secondary environmental pollution to a certain extent.

[0047] (6) The quaternary ammonium salt / magnetic biochar composite material prepared by the present invention can be recycled, and the bactericidal effect of the recycled composite material is better than that of the first-prepared composite material, which meets the current requirements of green and sustainable industry development. Attached Figure Description

[0048] Figure 1 Scanning electron microscope image of magnetic iron-based biochar;

[0049] Figure 2 A schematic diagram of the quaternary ammonium salt / magnetic biochar composite material after loading with quaternary ammonium salt;

[0050] Figure 3 This is a slow-release curve of quaternary ammonium salt in the quaternary ammonium salt / magnetic biochar composite material. Detailed Implementation

[0051] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Example 1: Preparation of Magnetic Iron-Based Biochar

[0053] A method for preparing magnetic iron-based biochar, the specific steps of which are as follows:

[0054] (1) Preparation of rice husk-based biochar:

[0055] ① After washing the rice husks twice with deionized water, dry them in a drying oven at 60℃ for 12 hours until constant weight and collect them; place the obtained rice husks in a tube furnace and introduce N2 at a constant rate of 4L / h, heat to 550℃ at a rate of 15℃ / min, carbonize for 2 hours, then stop the N2 introduction and introduce CO2 with a concentration of 20% to react for 1.5 hours. After cooling to room temperature in a N2 protective atmosphere, the carbonized product is obtained.

[0056] ②The carbonized product obtained in step ① is washed 4 times until the pH of the washing solution is neutral. It is then dried in a drying oven at 60℃ for 24 hours. The dried material is then ground through a 100-mesh sieve to obtain rice husk-based biochar with a particle size of 0.9-1.2 mm.

[0057] (2) Preparation of magnetic iron-based biochar

[0058] ① Mix rice husk-based biochar and deionized water at a weight ratio of 1:10, and ultrasonically vibrate at a frequency of 40kHz for 4 hours to obtain a fully mixed and homogeneous biochar suspension.

[0059] ② Dissolve 3.0g FeSO4·7H2O and 8.5g FeCl3·6H2O in 38mL of 0.4mol / L dilute hydrochloric acid solution. Stir rapidly in N2 environment, and add 25% ammonia water dropwise while stirring to adjust the pH of the solution to 10, thus obtaining a magnetic iron-based solution.

[0060] ③ Under 70℃ water bath conditions, 160ml of the biochar suspension prepared in step ① was added to the magnetic iron-based solution obtained in step ② while stirring. The mixture was stirred for 2 hours and then cooled to room temperature. The product was separated using a permanent magnet. The obtained product was first washed twice with anhydrous ethanol and then four times with deionized water until the pH of the washing solution was neutral. The product was then dried at 70℃ for 30 hours, ground, and passed through a 100-mesh sieve to obtain magnetic iron-based biochar.

[0061] The magnetic iron-based biochar obtained above was examined using a scanning electron microscope to observe the loading of magnetic iron particles, such as... Figure 1 As shown, a large number of magnetic iron particles are loaded on the surface of rice husk biochar.

[0062] Example 2: Preparation of Quaternary Ammonium Salt / Magnetic Biochar Composite Material

[0063] A method for preparing a quaternary ammonium salt / magnetic biochar composite material, the specific steps of which are as follows:

[0064] 1.0 g of the magnetic iron-based biochar prepared in Example 1 was added to 100 ml of deionized water, and 10.0 g of tetradecyltrimethylammonium chloride was added. The mixture was stirred continuously at room temperature for 15 h to fully impregnate the biochar. The mixture was then reacted in a water bath at 65 °C for 4 h. After cooling to room temperature, the product was magnetically separated using a permanent magnet to obtain the magnetically separated product. The product was washed repeatedly with deionized water 4 times until the pH of the washing solution was neutral. The washed product was then dried in a vacuum drying oven at 70 °C for 30 h and ground through a 100-mesh sieve to obtain a quaternary ammonium salt / magnetic biochar composite material with a magnetic biochar to quaternary ammonium salt mass ratio of 1:10.

[0065] Thermogravimetric analysis showed that 5.71% of the quaternary ammonium salt / magnetic biochar composite material obtained by using magnetic biochar to quaternary ammonium salt at a mass ratio of 1:10 was loaded onto the magnetic iron-based biochar. A schematic diagram of the loaded quaternary ammonium salt / magnetic biochar is shown below. Figure 2 As shown.

[0066] Example 3: Preparation of Quaternary Ammonium Salt / Magnetic Biochar Composite Material

[0067] A method for preparing a quaternary ammonium salt / magnetic biochar composite material, the specific steps of which are as follows:

[0068] 1.0 g of the magnetic iron-based biochar prepared in Example 1 was added to 300 ml of deionized water, and 30.0 g of quaternary ammonium salt compound was added. After thorough impregnation by continuous stirring at room temperature for 15 h, the mixture was reacted in a water bath at 65 °C for 4 h. After cooling to room temperature, the product was magnetically separated using a permanent magnet to obtain the magnetically separated product. The product was washed repeatedly with deionized water 4 times until the pH of the washing solution was neutral. The washed product was placed in a vacuum drying oven at 70 °C and dried for 30 h. After grinding through a 100-mesh sieve, a quaternary ammonium salt / magnetic biochar composite material with a magnetic biochar to quaternary ammonium salt mass ratio of 1:30 was obtained.

[0069] Thermogravimetric analysis showed that 11.39% of the quaternary ammonium salt compounds were loaded onto the magnetic iron-based biochar in the quaternary ammonium salt / magnetic biochar composite material obtained by using magnetic biochar and quaternary ammonium salt in a mass ratio of 1:30.

[0070] Example 4: Preparation of Quaternary Ammonium Salt / Magnetic Biochar Composite Material

[0071] A method for preparing a quaternary ammonium salt / magnetic biochar composite material, the specific steps of which are as follows:

[0072] 1.0 g of the magnetic iron-based biochar prepared in Example 1 was added to 400 ml of deionized water, and 50.0 g of quaternary ammonium salt compound was added. After thorough impregnation by continuous stirring at room temperature for 15 h, the mixture was reacted in a water bath at 65 °C for 4 h. After cooling to room temperature, the product was magnetically separated using a permanent magnet to obtain the magnetically separated product. The product was washed repeatedly with deionized water 4 times until the pH of the washing solution was neutral. The washed product was dried in a vacuum drying oven at 70 °C for 30 h and ground through a 100-mesh sieve to obtain a quaternary ammonium salt / magnetic biochar composite material with a magnetic biochar to quaternary ammonium salt mass ratio of 1:50.

[0073] Thermogravimetric analysis showed that 19.25% of the quaternary ammonium salt compounds were loaded onto the magnetic biochar in the quaternary ammonium salt / magnetic biochar composite material obtained by using magnetic biochar to quaternary ammonium salt in a mass ratio of 1:50.

[0074] Example 5: Determination of sustained-release performance of quaternary ammonium salt / magnetic biochar composite material

[0075] The sustained-release performance of quaternary ammonium salt in the quaternary ammonium salt / magnetic biochar composite materials obtained in Examples 2-4 was determined. 10 mg of each of the quaternary ammonium salt / magnetic biochar composite materials prepared in Examples 2-4 was added to 10 mL of ultrapure water and placed in a shaker at 170 rpm for 72 h at room temperature. Samples were taken at 0, 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, and 72 h. After filtering the samples through a 0.45 μm filter membrane, the content of quaternary ammonium salt dissolved in the filtrate of the quaternary ammonium salt / magnetic biochar composite material was detected using the disulfiram method (refer to Tezel, U., Pierson, J.A., & Pavlostathis, SG (2006). Fate and effect of quaternary ammonium compounds on a mixed methanogenic culture. Water Research, 40(19), p. 3660-3668.).

[0076] like Figure 3 As shown, the test results indicate that the release of quaternary ammonium salts in the composite bactericidal materials gradually increases with prolonged impregnation time. After 72 hours of shaking incubation, the total release of quaternary ammonium salts in the three composite materials were 47.6, 89.5, and [missing data - likely related to quaternary ammonium salt release].

[0077] The concentrations were 134.8 mg / L, representing only 4.76%, 8.95%, and 13.48% of the initial amounts added, respectively. This demonstrates that the quaternary ammonium salt / magnetic biochar composite material prepared in this invention exhibits superior sustained-release quaternary ammonium salt properties, solving the problem of difficult-to-control quaternary ammonium salt release rate and extending the bactericidal action time.

[0078] Example 6: Determination of the antibacterial effect of quaternary ammonium salt / magnetic biochar composite material

[0079] Two common pathogenic strains in wastewater, Escherichia coli and Staphylococcus aureus, were selected to represent Gram-negative and Gram-positive bacteria, respectively. The bactericidal effect of the quaternary ammonium salt / magnetic biochar composite material obtained in Examples 2-4 at different dosages was determined according to GB / T14643.2-2009 "Detection Method of Bacteria and Algae in Industrial Circulating Cooling Water". The specific experimental setup and bactericidal effect are shown in Table 1.

[0080] As shown in Table 1, the quaternary ammonium salt / magnetic biochar composite material prepared in this invention exhibits good bactericidal properties against both *Escherichia coli* and *Staphylococcus aureus*. For the same type of quaternary ammonium salt / magnetic biochar composite material, the bactericidal effect gradually increases with increasing dosage. Furthermore, the bactericidal effect against *Escherichia coli* and *Staphylococcus aureus* increases with the increase of the quaternary ammonium salt loading rate in the quaternary ammonium salt / magnetic biochar composite material. This indicates that the quaternary ammonium salt / magnetic biochar composite material prepared in this invention has good bactericidal properties against both Gram-positive and Gram-negative bacteria.

[0081] Table 1 Comparison of bactericidal effects of composite materials with different loading ratios at different dosages.

[0082]

[0083] Example 7: Comparison of bactericidal effects between quaternary ammonium salt / magnetic biochar composite material and existing bactericidal materials.

[0084] GO-1227 is an organic bactericidal material provided by the Nanjing Institute of Soil Science, Chinese Academy of Sciences.

[0085] PS / Ag material is a disinfection material that is easy to prepare and was provided by the School of Environmental Science and Engineering, Harbin Institute of Technology.

[0086] PTQ material is a bactericidal material synthesized from natural rubber, provided by the School of Environmental Science and Engineering, Harbin Institute of Technology.

[0087] Common pathogenic bacteria in wastewater, Escherichia coli and Staphylococcus aureus, were selected. The bactericidal effects of the magnetic biochar / magnetic biochar composite material (1:10 mass ratio of magnetic biochar to quaternary ammonium salt), GO-1227, PS / Ag, and PTQ prepared in Example 2, were determined according to GB / T14643.2-2009, "Detection Method for Bacteria and Algae in Industrial Circulating Cooling Water". The optimal dosage of each existing bactericidal material was determined. Specific experimental setup and bactericidal effects are shown in Table 2.

[0088] As shown in Table 2, GO-1227, as an organic bactericide, requires a low dosage but has a high manufacturing cost, resulting in high operating costs in practical applications. PS / Ag, a disinfectant with a simple preparation method, has a moderate bactericidal effect but requires a large dosage. PTQ, a bactericide synthesized from natural rubber, is widely available and inexpensive to synthesize, but its bactericidal effect is also moderate, requiring a large dosage in practical applications. The comparative results show that the quaternary ammonium salt / magnetic biochar composite material prepared in this invention can achieve better bactericidal effects at a lower dosage, making it more practical than existing bactericides.

[0089] Table 2 Comparison of bactericidal effects between quaternary ammonium salt / magnetic biochar composite materials and existing bactericidal materials

[0090]

[0091] Example 8: Preparation of Regenerated Quaternary Ammonium Salt / Magnetic Biochar Composite Material

[0092] A method for preparing a recycled quaternary ammonium salt / magnetic biochar composite material, the specific steps of which are as follows:

[0093] (1) The used quaternary ammonium salt / magnetic biochar composite material was magnetically separated and recovered using a permanent magnet, washed with deionized water 4 times until the washing liquid was neutral; dried at 70℃ for 30h, and ground through a 100-mesh sieve to obtain the recovered material.

[0094] (2) According to the preparation method of Examples 2-4, replace “1.0g of magnetic iron-based biochar prepared in Example 1” in Examples 2-4 with “1.0g of recycled material obtained in step (1)”, and keep the other steps the same, and prepare recycled quaternary ammonium salt / magnetic biochar composite materials with a mass ratio of magnetic biochar to quaternary ammonium salt of 1:30, 1:40 and 1:50 respectively.

[0095] Example 9: Determination of the antibacterial effect of the regenerated quaternary ammonium salt / magnetic biochar composite material

[0096] Two common pathogenic bacteria strains in wastewater, Escherichia coli and Staphylococcus aureus, were selected to represent Gram-negative and Gram-positive bacteria, respectively. The bactericidal effects of different types of regenerated quaternary ammonium salt / magnetic biochar composite materials prepared in Example 8 at different dosages were determined according to GB / T14643.2-2009 "Detection Methods for Bacteria and Algae in Industrial Circulating Cooling Water". The specific experimental setup and bactericidal effects are shown in Table 3.

[0097] Table 3 Comparison of bactericidal effects between quaternary ammonium salt / magnetic biochar composite material and recycled quaternary ammonium salt / magnetic biochar composite material

[0098]

[0099] Table 3 shows that the bactericidal effect of the recycled quaternary ammonium salt / magnetic biochar composite material is higher than that of the initially prepared quaternary ammonium salt / magnetic biochar composite material. This is because the recycled material still retains quaternary ammonium salt groups, and the secondary preparation process increases the loading of quaternary ammonium salt on the surface of the magnetic biochar, thereby improving the bactericidal effect. The method for preparing the quaternary ammonium salt / magnetic biochar composite material of this invention not only realizes the recycling and reuse of the composite material, but also the recycled quaternary ammonium salt / magnetic biochar composite material prepared from the recycled material has a better bactericidal effect, giving full play to the advantages and characteristics of the material itself, and providing a new material and a new method for solving the problem of pathogenic bacteria pollution in water bodies.

Claims

1. A method for preparing a quaternary ammonium salt / magnetic biochar composite material, characterized in that, The method includes the following steps: (1) Preparation of rice husk-based biochar: ① The carbonized product obtained by washing and drying rice husks to constant weight and then carbonizing them at high temperature; ②The carbonized product obtained in step ① is washed, dried, ground and sieved to obtain rice husk-based biochar; (2) Preparation of magnetic iron-based biochar: ① Place the rice husk-based biochar obtained in step (1) in deionized water and ultrasonically vibrate to obtain a biochar suspension; ② Dissolve FeSO4·7H2O and FeCl3·6H2O in dilute hydrochloric acid solution, stir under N2 environment, adjust pH with ammonia water to obtain magnetic iron-based solution; ③ Under water bath conditions, the biochar suspension prepared in step ① is added to the magnetic iron-based solution obtained in step ② while stirring. After cooling to room temperature, the product is separated by a permanent magnet. The magnetic product is washed, dried and sieved to obtain magnetic iron-based biochar. (3) Preparation of quaternary ammonium salt / magnetic biochar composite material: After adding the magnetic iron-based biochar obtained in step (2) to deionized water, quaternary ammonium salt compounds were added for full impregnation. After hydrothermal reaction, the product was cooled and separated by a permanent magnet. Then, the product was washed, vacuum dried, ground and sieved to obtain quaternary ammonium salt / magnetic biochar composite material. The quaternary ammonium salt compound mentioned in step (3) is one or two of tetradecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, and hexadecyltrimethylammonium chloride.

2. The preparation method according to claim 1, characterized in that, The rice husks in step (1) are washed 2-3 times; the drying temperature is 60-70℃ and the time is 10-15 hours. The high-temperature carbonization method is as follows: rice husks are placed in a tube furnace, N2 is introduced at a constant rate of 3-5 L / h, the temperature is raised to 500-600℃ at a rate of 10-20℃ / min, carbonization is carried out for 1-3 hours, then the N2 introduction is stopped, CO2 with a concentration of 15-20% is introduced and reacted for 1-2 hours, and then cooled to room temperature in an N2 protective atmosphere. The carbonized product is washed 3-5 times until the pH of the washing solution is neutral; the drying temperature is 60-70℃ and the time is 20-30h; the sieve aperture range is 90-110 mesh; the particle size of the rice husk-based biochar is 0.9-1.2mm.

3. The preparation method according to claim 1, characterized in that, The weight ratio of rice husk-based biochar to deionized water in step (2) is 1:8-12; the frequency of ultrasonic oscillation is 20-80kHz, and the duration is 3-5h. The weight ratio of FeSO4·7H2O, FeCl3·6H2O, and dilute hydrochloric acid solution is 1:2-4:10-15, and the concentration of dilute hydrochloric acid is 0.3-0.5 mol / L; the concentration of ammonia water is 20-30%, and the pH of the magnetic iron-based solution is adjusted to 9.5-10.

5. The magnetic iron-based solution and biochar suspension are mixed at a volume ratio of 1:3-5; the water bath temperature is 65-75℃, and the stirring time is 1.5-3 hours; the washing method is as follows: first wash with anhydrous ethanol, then wash with deionized water, for 1-3 times and 3-5 times respectively, until the pH of the washing solution is neutral; the drying temperature is 65-80℃, and the drying time is 24-48 hours; the sieve aperture range is 90-110 mesh.

4. The preparation method according to claim 1, characterized in that, The weight ratio of the magnetic iron-based biochar, quaternary ammonium salt compound, and deionized water is 1:10-50:100-400, and the impregnation time is 12-20 hours; the hydrothermal reaction temperature is 60-70℃, and the time is 3-5 hours; the washing is performed 3-5 times until the pH of the washing solution is neutral; the vacuum drying temperature is 65-75℃, and the time is 24-48 hours; the sieve aperture range is 90-110 mesh.

5. The quaternary ammonium salt / magnetic biochar composite material prepared by the preparation method according to any one of claims 1-4.

6. A method for preparing a recycled quaternary ammonium salt / magnetic biochar composite material, characterized in that, After the used quaternary ammonium salt / magnetic biochar composite material of claim 1 is washed, dried, ground, and sieved, it is then ion-exchanged with quaternary ammonium salt compounds to produce a regenerated quaternary ammonium salt / magnetic biochar composite material.

7. The regenerated quaternary ammonium salt / magnetic biochar composite material prepared by the preparation method according to claim 6.

8. The application of the quaternary ammonium salt / magnetic biochar composite material according to claim 5 in wastewater treatment.

9. The application of the regenerated quaternary ammonium salt / magnetic biochar composite material according to claim 7 in wastewater treatment.

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