Preparation method and application of water pollution ecological restoration material

Abstract

The present invention provides a preparation method and application of a water pollution ecological restoration material, comprising crushing arsenic-enriched scolopendra, impregnating it with Fe-Mn, washing, pyrolyzing, and refining to obtain scolopendra biochar, wherein the molar ratio of Fe to Mn in the impregnation solution used during the Fe-Mn impregnation is 1-3:5-10, and CaO powder is added during pyrolysis. The scolopendra biochar prepared in this way reduces arsenic volatilization pollution during the preparation process and enhances the adsorption capacity of the scolopendra biochar. The present invention provides a preparation method and application of a water pollution ecological restoration material, reducing arsenic pollution during the preparation of biochar from arsenic-enriched scolopendra, and enhancing the arsenic adsorption capacity of the biochar.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental pollution restoration, and in particular to a preparation method and application of a water pollution ecological restoration material. Background Art

[0002] With the development of China's industrialization, water pollution is becoming increasingly serious. Arsenic (As) is one of the main pollutants, which is highly toxic and carcinogenic. Centipede grass is an arsenic hyperaccumulator. He Zhenyan's research team at the Institute of Botany, Chinese Academy of Sciences, has revealed the molecular mechanism of centipede grass's efficient long-distance arsenic transport and explored the evolutionary mechanism of centipede grass's arsenic hyperaccumulation characteristics, providing core molecular elements for the construction of plants for arsenic pollution remediation engineering. Numerous scholars have also verified that centipede grass can successfully absorb arsenic from the soil during its growth. Currently, centipede grass has been used to enrich arsenic in contaminated soil. Arsenic-enriched centipede grass can be treated through landfilling and incineration pyrolysis.

[0003] However, after the arsenic-rich centipede grass is landfilled and decomposed by microorganisms for a long time, the arsenic enriched in its body will be decomposed and released into the landfill soil during the mineralization process of its branches and leaves, causing secondary pollution of the soil.

[0004] Arsenic-rich scolopendra pyrolysis produces biochar, a carbonaceous material characterized by a porous structure, high specific surface area, large pore volume, and abundant functional groups. Biochar is considered an ideal environmental remediation material. Therefore, pyrolysis of arsenic-rich scolopendra pyrolysis to produce biochar is used for the remediation of water pollutants. This method allows for the full utilization of arsenic-rich scolopendra pyrolysis to produce commercially valuable biochar, enabling energy and resource recovery.

[0005] The Chinese patent document with application number 2021103285188 and patent name "Method for preparing composite biochar for preventing and controlling heavy metal pollution" provides a method for preparing composite biochar for preventing and controlling heavy metal pollution. Specifically, centipede grass is used to enrich heavy metal arsenic and lead in the soil. After that, centipede grass is sintered with hydroxyapatite, sepiolite and chitosan, and compounded with microorganisms to prepare composite biochar. The heavy metal arsenic and lead are stably enriched or coated in the composite biochar, which significantly reduces the potential danger of heavy metal arsenic and lead to the environment, and also provides a new development idea for the treatment of heavy metal biomass.

[0006] However, in the patent scheme, high-temperature sintering is performed when preparing composite biochar. The arsenic enriched in centipede grass is often in the form of organic arsenic and sulfide-bound arsenic, which is extremely unstable at high temperatures. Therefore, it is easily decomposed or oxidized into gaseous arsenic compounds As2O3 and AsO during high-temperature pyrolysis, causing secondary pollution. In addition, the surface of the prepared composite biochar is usually negatively charged, and arsenic in polluted water is usually in the form of negatively charged arsenic oxide ions (AsO4 3- or AsO33- ) exists in the form of negatively charged arsenic oxide ions and biochar due to electrostatic repulsion, which will produce a certain repulsion effect, affecting the adsorption of biochar. Summary of the Invention

[0007] In view of this, the present invention provides a preparation method and application of a water pollution ecological restoration material, which reduces arsenic pollution in the process of preparing biochar from arsenic-enriched centipede grass and improves the adsorption capacity of arsenic in contaminated water.

[0008] To achieve the above object, the present invention provides a method for preparing a water pollution ecological restoration material, comprising the following steps:

[0009] Arsenic-enriched centipede grass particles are immersed in a Fe-Mn mixed solution, stirred, and ultrasonicated to obtain a biomass suspension;

[0010] The biomass suspension is filtered and washed to obtain centipede grass biomass particles;

[0011] CaO powder is added to the centipede grass biomass particles, pyrolyzed, and cooled to room temperature to obtain the water pollution ecological restoration material.

[0012] The preparation method of the water pollution ecological restoration material provided by the present invention achieves the effect of synergistically enhancing the adsorption capacity of the ecological restoration material and reducing secondary pollution during arsenic pyrolysis by impregnating the material with an Fe-Mn mixed solution and adding CaO for pyrolysis.

[0013] Optionally, the Fe-Mn mixed solution is a solution prepared by mixing FeCl 3 • 6H 2 O and KMnO 4 .

[0014] Optionally, the molar ratio of Fe to Mn in the Fe-Mn mixed solution is 1-3:5-10.

[0015] Optionally, the mass of the CaO powder added during the pyrolysis is 5% to 25% of the mass of the centipede grass biomass particles.

[0016] Optionally, the purity of the CaO powder is 99.9%.

[0017] Optionally, the water pollution ecological restoration material is refined by washing, drying and sieving.

[0018] Optionally, the arsenic-enriched scutellaria baicalensis particles are sieved with a sieve opening of 5 to 10 meshes before being soaked, and the scutellaria baicalensis biochar is sieved with a sieve opening of 90 to 110 meshes during refining.

[0019] Optionally, the pyrolysis temperature is 450-650° C., the pyrolysis time is 1-3 h, and the heating rate is 13-15° C. / min.

[0020] Optionally, the ultrasound is performed using a constant temperature ultrasonic oscillator at a constant temperature of 30-50°C.

[0021] The present invention also provides an application of a water pollution ecological restoration material. The water pollution ecological restoration material is centipede grass biochar. The centipede grass biochar is used to adsorb arsenic in polluted water and reduce the toxicity of arsenic in the water.

[0022] The above technical solution of the present invention includes at least the following beneficial effects:

[0023] 1. The present invention provides a preparation method of a water pollution ecological restoration material, comprising the steps of: placing arsenic-enriched scutellaria baicalensis particles in an Fe-Mn mixed solution for immersion; first, the surface of the scutellaria baicalensis biochar generated after the immersion is modified to load Fe / Mn oxides, thereby enhancing the electronegativity of the surface of the scutellaria baicalensis biochar, thereby promoting its adsorption of negatively charged arsenic oxide ions in the polluted water body; secondly, the surface of the scutellaria baicalensis biochar generated after the immersion is loaded with iron and manganese, and these substances fix As through complexation, ion exchange and precipitation; the specific surface area of ​​the biochar generated after the pyrolysis of the immersed scutellaria baicalensis increases by 65 times, and the pore size decreases by 75%, which also increases the adsorption capacity for arsenic to a certain extent; in summary, compared with the prior art, the scutellaria baicalensis biochar of the present invention has greatly increased the adsorption capacity for arsenic. Furthermore, the Mn oxide loaded in the modified scutellaria biochar is generated as MnO2. MnO2 has strong oxidizing properties, promoting the redox reaction, namely the conversion of trivalent arsenic to pentavalent arsenic. Since pentavalent arsenic is less toxic than trivalent arsenic, it reduces the toxicity of arsenic in polluted water. The addition of CaO powder during the pyrolysis of the scutellaria biomass pellets of the present invention has been shown to significantly reduce the volatilization rate of arsenic. Compared to prior art methods that do not add CaO powder during pyrolysis, the volatilization rate of gaseous arsenic compounds As2O3 and AsO produced during the pyrolysis of arsenic-enriched scutellaria is significantly reduced. The addition of CaO during Fe-Mn impregnation and pyrolysis has a synergistic effect. Experiments have shown that the removal rate and adsorption capacity of arsenic in water by centipede grass biochar prepared by Fe-Mn impregnation and CaO addition during pyrolysis are not only significantly higher than the removal rate and adsorption capacity of arsenic in water by centipede grass biochar prepared by Fe-Mn impregnation or pyrolysis alone, but also significantly higher than the sum of the removal rates and adsorption capacities of arsenic in water by centipede grass biochar prepared by Fe-Mn impregnation alone and CaO addition during pyrolysis alone.

[0024] 2. The present invention provides a method for preparing a water pollution ecological restoration material. The prepared centipede grass biochar is loaded with Fe on its surface and has certain magnetism. After completing the adsorption of arsenic in the water body, the centipede grass biochar can be enriched at a fixed position in the water body through an external electric field, which is convenient for recycling and processing, and reduces the risk of secondary pollution to the water body.

[0025] 3. The present invention also provides an application of water pollution ecological restoration materials, in which arsenic-enriched centipede grass is prepared into centipede grass biochar, which not only reduces the potential danger of heavy metal arsenic to the environment, but also allows the modified centipede biochar to be used again for the adsorption of arsenic in polluted water bodies. While adsorbing arsenic in the polluted water bodies, it can also reduce the toxicity of arsenic in the polluted water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The comparison chart of the removal rate of arsenic in water by biochar prepared in Example 1 of the present invention and Comparative Examples 1, 2, and 3 (the removal rate of arsenic in water by biochar prepared from different materials is shown in Figure 2). Figure 1 shown);

[0027] Figure 2 The adsorption capacity of arsenic in water by biochar prepared in Example 1 of the present invention and Comparative Examples 1, 2, and 3 is compared (the adsorption capacity of arsenic in water by biochar prepared from different materials is shown in Figure 1). Figure 2 shown);

[0028] Figure 3 The scanning electron microscope images of the biochar prepared in Example 1 and Comparative Examples 1, 2, and 3 of the present invention (the scanning electron microscope images of the biochar prepared from different materials are as follows Figure 3 shown);

[0029] Figure 4 The X-ray diffraction patterns of Example 1 and Comparative Example 3 of the present invention (the X-ray diffraction patterns of BC and Ca-FMBC are as follows Figure 4 shown).

[0030] Figure 5 The comparison chart of the oxidation rate of trivalent arsenic in water by biochar prepared in Example 1 of the present invention and Comparative Examples 1, 2, and 3 (the oxidation rate of trivalent arsenic in water by biochar prepared from different materials is shown in Figure 1). Figure 5 shown);

[0031] Figure 6 The volatilization rate of As in the pyrolysis process of Example 1 of the present invention and Comparative Examples 1, 2, and 3 is compared (the volatilization rate of As in the pyrolysis process of different materials is shown in FIG. Figure 6 shown);

[0032] In the figure: Ca-BC represents comparative example 1; FMBC represents comparative example 2; BC represents comparative example 3; Ca-FMBC represents embodiment 1; A represents the scanning electron microscope image of BC, B represents the scanning electron microscope image of Ca-FMBC, and C represents the scanning electron microscope image of Ca-FMBC after arsenic absorption. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the following will be combined with the appended drawings of the embodiments of the present invention. Figure 1-6, clearly and completely describing the technical solutions of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments derived by ordinary technicians in this field fall within the scope of protection of the present invention.

[0034] The arsenic content of the arsenic-enriched scutellaria plants used in the examples of the present invention and the comparative examples was the same, at 0.05%, meaning approximately 0.5g of arsenic was present in 1kg of the plants. The water pollution ecological restoration material prepared in the examples of the present invention is referred to as scutellaria biochar.

[0035] Example 1

[0036] S1 Crushing: The centipede grass after cleaning the dust is naturally air-dried, crushed to increase the contact area with the impregnation solution to facilitate impregnation modification, and sieved through a 10-mesh sieve to obtain centipede grass crushed particles.

[0037] S2 Fe-Mn impregnation: Weigh 200g of centipede grass crushed particles and place them in 700mL of a mixed solution of 0.2mol / L FeCl3•6H2O and 1mol / L KMnO4 for immersion, with a molar ratio of Fe to Mn of 1:5. Stir in a fixed direction for 5mins, then place the Fe-Mn mixed solution in a constant temperature ultrasonic oscillator at 40℃ for 2h to allow the centipede grass crushed particles to be fully soaked in the Fe-Mn solution to obtain a biomass suspension.

[0038] S3 washing: The biomass suspension was filtered with a suction filter, and the retained solid was washed three times with ultrapure water and then dried in an oven at 80° C. to obtain the impregnated centipede grass biomass particles.

[0039] S4 pyrolysis: add 20g of CaO powder with a purity of 99.9% to 200g of soaked centipede grass biomass particles to obtain a mixture; after uniformly mixing the mixture, place it in a muffle furnace at 500℃ under oxygen-free conditions for pyrolysis for 2h, and the heating rate of the muffle furnace is 10℃ / min. After cooling to room temperature, take out the centipede grass biochar from the muffle furnace to obtain centipede grass biochar.

[0040] S5 refining: The centipede grass biochar was rinsed with deionized water, filtered, dried at 105°C and passed through a 100-mesh sieve to finally produce centipede grass biochar with low volatile As and high As adsorption efficiency.

[0041] Example 2

[0042] S1 Crushing: The centipede grass after cleaning the dust is naturally air-dried, crushed to increase the contact area with the impregnation solution to facilitate impregnation modification, and sieved through a 5-mesh sieve to obtain centipede grass crushed particles.

[0043] S2 Fe-Mn impregnation: Weigh 200g of centipede grass crushed particles and place them in 700mL of a mixed solution of FeCl3•6H2O and KMnO4 for immersion, with a molar ratio of Fe to Mn of 1:10, and stir in a fixed direction for 5 minutes. Then, place the Fe-Mn mixed solution in a constant temperature ultrasonic oscillator at 30℃ and ultrasonicate for 2 hours to allow the centipede grass crushed particles to be fully soaked in the Fe-Mn solution to obtain a biomass suspension.

[0044] S3 washing: The biomass suspension was filtered with a suction filter, and the retained solid was washed three times with ultrapure water and then dried in an oven at 80° C. to obtain the impregnated centipede grass biomass particles.

[0045] S4 pyrolysis: add 10g of CaO powder with a purity of 99.9% to 200g of soaked centipede grass biomass particles to obtain a mixture; after uniformly mixing the mixture, place it in a muffle furnace at 450℃ under oxygen-free conditions for pyrolysis for 1h with a heating rate of 13℃ / min. After cooling to room temperature, take out the centipede grass biochar from the muffle furnace to obtain centipede grass biochar.

[0046] S5 refining: The centipede grass biochar was rinsed with deionized water, filtered, dried at 105°C and passed through a 90-mesh sieve to finally produce centipede grass biochar with low volatile As and high As adsorption efficiency.

[0047] Example 3

[0048] S1 Crushing: The centipede grass after cleaning the dust is naturally air-dried, crushed to increase the contact area with the impregnation solution to facilitate impregnation modification, and sieved through a 10-mesh sieve to obtain centipede grass crushed particles.

[0049] S2 Fe-Mn impregnation: Weigh 200g of centipede grass crushed particles and place them in 700mL of a mixed solution of FeCl3•6H2O and KMnO4 for immersion, with a molar ratio of Fe to Mn of 3:10. Stir in a fixed direction for 5 minutes, then place the Fe-Mn mixed solution in a 50℃ constant temperature ultrasonic oscillator for 3 hours to allow the centipede grass crushed particles to be fully soaked in the Fe-Mn solution to obtain a biomass suspension.

[0050] S3 washing: The biomass suspension was filtered with a suction filter, and the retained solid was washed three times with ultrapure water and then dried in an oven at 80° C. to obtain the impregnated centipede grass biomass particles.

[0051] S4 pyrolysis: add 50g of CaO powder with a purity of 99.9% to 200g of soaked centipede grass biomass particles to obtain a mixture; after uniformly mixing the mixture, place it in a muffle furnace at 650℃ under oxygen-free conditions for pyrolysis for 3h with a heating rate of 15℃ / min. After cooling to room temperature, take out the centipede grass biochar from the muffle furnace to obtain centipede grass biochar.

[0052] S5 refining: The centipede grass biochar was rinsed with deionized water, filtered, dried at 105 °C and passed through a 110-mesh sieve to finally produce centipede grass biochar with low volatile As and high As adsorption efficiency.

[0053] Example 4

[0054] S1 Crushing: The centipede grass after cleaning the dust is naturally air-dried, crushed to increase the contact area with the impregnation solution to facilitate impregnation modification, and sieved through an 8-mesh sieve to obtain centipede grass crushed particles.

[0055] S2 Fe-Mn impregnation: Weigh 200g of centipede grass crushed particles and place them in 700mL of a mixed solution of FeCl3•6H2O and KMnO4 for immersion, with a molar ratio of Fe to Mn of 3:5. Stir in a fixed direction for 5 minutes, then place the Fe-Mn mixed solution in a constant temperature ultrasonic oscillator at 40℃ for 3 hours to allow the centipede grass crushed particles to be fully soaked in the Fe-Mn solution to obtain a biomass suspension.

[0056] S3 washing: The biomass suspension was filtered with a suction filter, and the retained solid was washed three times with ultrapure water and then dried in an oven at 80° C. to obtain the impregnated centipede grass biomass particles.

[0057] S4 pyrolysis: add 20g of CaO powder with a purity of 99.9% to 200g of soaked centipede grass biomass particles to obtain a mixture; after uniformly mixing the mixture, place it in a muffle furnace at 650℃ under oxygen-free conditions for pyrolysis for 2h with a heating rate of 15℃ / min. After cooling to room temperature, take out the centipede grass biochar from the muffle furnace to obtain centipede grass biochar.

[0058] S5 refining: The centipede grass biochar was rinsed with deionized water, filtered, dried at 105°C and passed through a 100-mesh sieve to finally produce centipede grass biochar with low volatile As and high As adsorption efficiency.

[0059] Comparative Example 1

[0060] Compared with Example 1, only the Fe-Mn impregnation step was not performed.

[0061] Comparative Example 2

[0062] Compared with Example 1, only no CaO powder was added during pyrolysis.

[0063] Comparative Example 3

[0064] Compared to Example 1, the Fe-Mn impregnation step was not performed, and no CaO powder was added during pyrolysis.

[0065] test

[0066] 1. Determination of indicators of centipede grass biochar

[0067] The BET method (specific surface area measurement) uses the principle of gas adsorption to calculate and record the specific surface area, pore volume, and pore diameter of the biochar by measuring the amount and pressure of the adsorbed gas. The specific surface area, total pore volume, and pore diameter of the biochars from Example 1 and Comparative Examples 1, 2, and 3 were calculated and recorded using a 3H-2000PS Surface Area and Pore Structure Analyzer (Beijing Bester Technology Co., Ltd.). Table 1 shows the specific surface area, total pore volume, and pore diameter of the biochars from Example 1 and Comparative Examples 1, 2, and 3.

[0068] The X'Pert Pro X-ray diffractometer (XRD) produced by PANalytical of the Netherlands was used to analyze the crystal structure of the material. The S4800 field emission scanning electron microscope produced by Hitachi of Japan was used to observe the appearance of the sample. Figure 3 、 Figure 4 .

[0069] Table 1 Related indicators of different biochars

[0070]

[0071] According to Table 1, the specific surface area of ​​the centipede grass biochar prepared in Example 1 is increased by about 65.5 times compared with that in Comparative Example 1, and the average pore diameter is about 10 / 67 of that in Comparative Example 1, and the total pore volume of the centipede grass biochar prepared in Example 1 is increased and the pore diameter is smaller. The only difference between the two is that there is Fe-Mn impregnation in Example 1, and there is no Fe-Mn impregnation in Comparative Example 1. The specific surface area of ​​the centipede grass biochar prepared in Comparative Example 2 is increased by about 65.8 times compared with that in Comparative Example 3, and the average pore diameter is about 10 / 74 of that in Comparative Example 3, and the total pore volume of the centipede grass biochar prepared in Comparative Example 2 is increased and the pore diameter is smaller. The only difference between the two is that there is Fe-Mn impregnation in Comparative Example 2, and there is no Fe-Mn impregnation in Comparative Example 3. It can be seen that the pores of the centipede grass biochar prepared by Fe-Mn impregnation are small and dense, and the specific surface area is increased.

[0072] Since the specific surface area and pore size of biochar are important structural parameters that affect the capacity to adsorb pollutants, the higher the specific surface area, the larger the contact area between pollutants and biochar, and the greater the amount of pollutants adsorbed. The small pore size is also inversely proportional to the adsorption capacity of biochar to a certain extent. Biochar with small and dense pores and a large specific surface area has a strong adsorption and fixation effect on pollutants.

[0073] According to the analysis in Table 1, Fe-Mn impregnation can also enhance the adsorption capacity of Scolopendra biochar for arsenic in water by increasing the specific surface area of ​​Scolopendra biochar and reducing the pores.

[0074] Attachment Figure 3A shows that the surface of the centipede grass biochar prepared in comparative example 3 is relatively smooth. Figure 3 B shows that the surface of the centipede grass biochar prepared in Example 1 has a large number of densely packed small particles. Figure 3 Figure C shows a large number of large protruding particles on the surface of the centipede grass biochar. This indicates that the centipede grass biochar prepared after Fe-Mn impregnation and CaO addition during pyrolysis forms loaded particles on its surface. When adsorbed in polluted water, it is more likely to adsorb pollutants in the water, forming composite particles.

[0075] Attachment Figure 4 X-ray diffraction analysis of the centipede grass biochar prepared in Example 1 and Comparative Example 3 shows that the surface of the centipede grass biochar prepared in Comparative Example 3 is mainly CaCO3, and the particulate matter loaded on the surface of the centipede grass biochar prepared in Example 1 is MnO2 and iron oxides. The loaded particulate matter has a certain affinity for arsenic. In addition, it can enhance the electronegativity of the biochar surface and serve as an adsorption site for arsenic in water, promoting the electrostatic adsorption of arsenic and these oxides, thereby promoting the adsorption of arsenic in water.

[0076] According to the attached Figure 3 、 4 Analysis shows that Fe-Mn impregnation is achieved by modifying the surface of centipede grass biochar by loading particles, enhancing the electronegativity of the biochar surface to enhance the electrostatic adsorption effect, and thus enhancing the adsorption capacity of centipede grass biochar for arsenic in water.

[0077] In summary, Fe-Mn impregnation enhances the adsorption capacity of Scolopendra biochar on arsenic in water by enhancing the electrostatic adsorption on the biochar surface and changing the specific surface area of ​​Scolopendra biochar itself.

[0078] 2. Detection and testing of arsenic in solution

[0079] 2.1 Determination of the removal efficiency and adsorption capacity of arsenic in solution by Scutellaria baicalensis biochar

[0080] Arsenic adsorption experimental method from arsenic-contaminated solution: Source of arsenic in the arsenic-contaminated solution: Na₃AsO₃ solution, arsenic content: 50 mg / L, arsenic valence: +3. Add 1 g / L of arsenic-contaminated biochar to the arsenic-contaminated solution. For example, weigh 0.02 g of arsenic-contaminated biochar to 20 mL of the arsenic-contaminated solution and then shake in a shaker for 24 hours to complete adsorption.

[0081] Arsenic concentration in solution is determined using atomic fluorescence spectrometry. An arsenic solution is mixed with potassium borohydride. Under acidic conditions, hydride gas is generated and released from the solution. After mixing with argon and hydrogen, it enters an atomizer and is ignited. The hydride decomposes at high temperatures and transforms into ground-state atomic vapor. Once these free atoms become gaseous ground-state atoms, they absorb radiation energy of a certain frequency from an external light source and transition to a high-energy state. Simultaneously, they emit radiation of the same or different wavelength as the original excitation radiation. By measuring the intensity of this radiation, the arsenic content in the water and the concentration of the solution can be determined. The arsenic concentration in the solution is determined using an AF-610A atomic fluorescence spectrometer (Beijing Rayleigh Analytical Instrument Co., Ltd.).

[0082] According to the above experimental method, the removal rate and adsorption amount of arsenic in the solution by the centipede grass biochar in Example 1, Comparative Examples 1, 2, and 3 were determined. Figure 1 、 Figure 2 .

[0083] Removal rate (%) = (initial concentration - As concentration of the solution after adsorption) / initial concentration.

[0084] Adsorption amount (mg / g) = (initial concentration - As concentration of the solution after adsorption) / volume of the adsorption solution.

[0085] According to the attached Figure 1 、 2 It can be seen that the removal rate and adsorption amount of arsenic in water by the centipede grass biochar prepared in Example 1 are significantly increased compared with the centipede grass biochar prepared in Comparative Example 1. The only difference between the two is that there is Fe-Mn impregnation in Example 1 and there is no Fe-Mn impregnation in Comparative Example 1.

[0086] The centipede grass biochar prepared in Comparative Example 2 showed significantly higher arsenic removal rates and adsorption capacity compared to the centipede grass biochar prepared in Comparative Example 3. The only difference between the two is that Comparative Example 2 included Fe-Mn impregnation, while Comparative Example 3 did not. This suggests that Fe-Mn impregnation enhances the centipede grass biochar's ability to adsorb arsenic from water.

[0087] According to the attached Figure 1 、 2 It can be seen that the centipede grass biochar prepared in Comparative Example 3 not only fails to absorb arsenic from the water during water adsorption, but actually releases arsenic into the water. Compared to the centipede grass biochar prepared in Comparative Example 1, the centipede grass biochar prepared in Comparative Example 3 has a higher arsenic removal rate and adsorption capacity. The only difference between Comparative Example 1 and Comparative Example 3 is that CaO powder was added during pyrolysis in Comparative Example 1, while no CaO powder was added during pyrolysis in Comparative Example 3.

[0088] The centipede grass biochar prepared in Example 1 has a higher removal rate and adsorption capacity for arsenic in water than the centipede grass biochar prepared in Comparative Example 2. The only difference between the two is that CaO powder is added during pyrolysis in Example 1, while no CaO powder is added during pyrolysis in Comparative Example 2. It can be seen that the addition of CaO during pyrolysis enhances the adsorption capacity of centipede grass biochar for arsenic in water.

[0089] According to the attached Figure 1 、 2 It can be seen that the removal rate and adsorption amount of arsenic in water by the centipede grass biochar prepared in Example 1 are significantly higher than the removal rate and adsorption amount of arsenic in water by the centipede grass biochar prepared in Comparative Example 1, and are also significantly higher than the removal rate and adsorption amount of arsenic in water by the centipede grass biochar prepared in Comparative Example 2, and are also significantly higher than the sum of the removal rate and adsorption amount of arsenic in water by the centipede grass biochar prepared in Comparative Example 1 and Comparative Example 2.

[0090] While Example 1 includes both Fe-Mn impregnation and the addition of CaO during pyrolysis, Comparative Example 1 lacks Fe-Mn impregnation compared to Example 1, and Comparative Example 2 lacks the addition of CaO during pyrolysis compared to Example 1. Therefore, the removal rate and adsorption capacity of arsenic in water by the centipede grass biochar prepared by simultaneously including Fe-Mn impregnation and the addition of CaO during pyrolysis are not only significantly higher than the removal rate and adsorption capacity of arsenic in water by the centipede grass biochar prepared by either Fe-Mn impregnation or the addition of CaO during pyrolysis, but also significantly higher than the sum of the removal rates and adsorption capacities of arsenic in water by the centipede grass biochar prepared by either Fe-Mn impregnation or the addition of CaO during pyrolysis. This shows that the addition of CaO during Fe-Mn impregnation and pyrolysis has a synergistic effect.

[0091] 2.2 Determination of trivalent arsenic oxidation rate in solution

[0092] Arsenic adsorption experimental method from arsenic-contaminated solution: Source of arsenic in the arsenic-contaminated solution: Na₃AsO₃ solution, arsenic content: 50 mg / L, arsenic valence: +3. Add 1 g / L of arsenic-contaminated biochar to the arsenic-contaminated solution. For example, weigh 0.02 g of arsenic-contaminated biochar to 20 mL of the arsenic-contaminated solution and then shake in a shaker for 24 hours to complete adsorption.

[0093] Desorption of arsenic from the solution: Under acidic pH and 96°C water bath conditions, a mixed solution of ammonium oxalate and ascorbic acid was used to desorb the trivalent arsenic and pentavalent arsenic adsorbed on the biochar into the solution.

[0094] Reduction of pentavalent arsenic in solution: The national standard borohydride reduction colorimetric method is used, that is, after the sample is digested, potassium iodide-thiourea is added and heated to reduce pentavalent arsenic to trivalent arsenic.

[0095] Arsenic concentration in solution is determined using atomic fluorescence spectrometry. An arsenic solution is mixed with potassium borohydride. Under acidic conditions, hydride gas is generated and released from the solution. After mixing with argon and hydrogen, it enters an atomizer and is ignited. The hydride decomposes at high temperatures and transforms into ground-state atomic vapor. Once these free atoms become gaseous ground-state atoms, they absorb radiation energy of a certain frequency from an external light source and transition to a high-energy state. Simultaneously, they emit radiation of the same or different wavelength as the original excitation radiation. By measuring the intensity of this radiation, the arsenic content in the water and the concentration of the solution can be determined. The arsenic concentration in the solution is determined using an AF-610A atomic fluorescence spectrometer (Beijing Rayleigh Analytical Instrument Co., Ltd.).

[0096] Two identical centipede grass biochars were prepared using the methods of Example 1, Comparative Examples 1, 2, and 3, for a total of 8 portions. The 8 portions of centipede grass biochar were divided into two groups, each group including the centipede grass biochar prepared in Example 1, Comparative Examples 1, 2, and 3, and were placed in 8 identical arsenic-contaminated solutions for adsorption, followed by desorption. After desorption, 8 solutions containing trivalent arsenic and pentavalent arsenic were obtained, which were filtered. One group performed a reduction of pentavalent arsenic and then measured the concentration of trivalent arsenic, while the other group directly measured the trivalent arsenic in the solution. The concentration of pentavalent arsenic in the solution was the difference between the concentration of trivalent arsenic in the corresponding reduced solution and the concentration of trivalent arsenic in the unreduced solution, as shown in Table 2 and Table 3. Figure 5 .

[0097] The oxidation rate of trivalent arsenic in water = the concentration of pentavalent arsenic in the solution / the concentration of trivalent arsenic in the unreduced solution.

[0098] Table 2 Oxidation rate of trivalent arsenic in water by biochar prepared from different materials

[0099]

[0100] According to Table 2 and Figure 5 It can be seen that the centipede grass biochar prepared in Example 1 significantly increased the oxidation rate of trivalent arsenic in water compared to the centipede grass biochar prepared in Comparative Example 1. The only difference between the two is that Example 1 is impregnated with Fe-Mn, while Comparative Example 1 is not. The centipede grass biochar prepared in Comparative Example 2 also significantly increased the oxidation rate of trivalent arsenic in water compared to the centipede grass biochar prepared in Comparative Example 3. The only difference between the two is that Comparative Example 2 is impregnated with Fe-Mn, while Comparative Example 3 is not. This shows that Fe-Mn impregnation can improve the oxidation rate of trivalent arsenic in water by centipede grass biochar.

[0101] Arsenic in contaminated water is trivalent. The Fe-Mn impregnation step during the preparation of scutellaria biochar modifies the scutellaria biochar. This modified biochar is loaded with Mn, which forms MnO2 on the biochar surface. This highly oxidizing agent, now tetravalent, forms Mn. This MnO2 undergoes a redox reaction with the trivalent arsenic in the contaminated water, producing pentavalent arsenic, which reduces the Mn valence from tetravalent to divalent. Pentavalent arsenic is far less toxic than trivalent arsenic in water, so converting trivalent arsenic to pentavalent arsenic can reduce its toxicity.

[0102] In conclusion, Fe-Mn impregnation can enable S. truncatula biochar to reduce the toxicity of arsenic in contaminated water bodies.

[0103] 2.3 Determination of arsenic volatilization rate during pyrolysis

[0104] The methods of Example 1, Comparative Examples 1, 2, and 3 were used to prepare centipede grass biochar, and the mass before and after arsenic volatilization, i.e., the mass before calcination and the mass after calcination, were measured respectively. The mass difference was the mass of the volatilized arsenic, and the results were shown in Table 3. Figure 6 .

[0105] Arsenic volatilization rate = [M material arsenic (uncalcined) - M material arsenic (calcined)] / M material arsenic (uncalcined)

[0106] Table 3 Volatility of arsenic during pyrolysis (%)

[0107]

[0108] According to Table 3 and Figure 6 It can be seen that the volatilization rate of arsenic during pyrolysis of Comparative Example 3 is 38.2%, and the volatilization rate of arsenic during pyrolysis of Comparative Example 1 is 22.7%. The volatilization rate of arsenic during pyrolysis of Comparative Example 1 is reduced by 40.6% relative to that of Comparative Example 3. The only difference between the two is that CaO powder is added during pyrolysis of Comparative Example 1, while CaO powder is not added during pyrolysis of Comparative Example 3.

[0109] The volatilization rate of arsenic during pyrolysis of Comparative Example 2 was 38.1%, and the volatilization rate of arsenic during pyrolysis of Example 1 was 23.9%. The volatilization rate of arsenic during pyrolysis of Example 1 was reduced by 37.3% relative to that of Comparative Example 2. The only difference between the two was that CaO powder was added during pyrolysis of Example 1, while CaO powder was not added during pyrolysis of Comparative Example 2.

[0110] In summary, adding CaO during pyrolysis can significantly reduce the volatilization of arsenic.

[0111] In the present invention, unless otherwise clearly specified and limited, for example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be internal communication between two elements or an interaction relationship between two elements. Unless otherwise clearly specified and limited, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to specific circumstances.

[0112] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a water pollution ecological restoration material, characterized by: The following steps are involved: The arsenic-enriched centipede grass particles are immersed in an Fe-Mn mixed solution, stirred, and ultrasonicated to obtain a biomass suspension; the molar ratio of Fe to Mn in the Fe-Mn mixed solution is 1-3:5-10; The biomass suspension is filtered and the solid is washed to obtain centipede grass biomass particles; The centipede grass biomass particles are mixed with CaO powder, the mass of the CaO powder being 25% of the mass of the centipede grass biomass particles; pyrolysis is performed, the pyrolysis temperature is 450-650° C., the pyrolysis time is 1-3 hours, the heating rate is 13-15° C. / min, and the mixture is cooled to room temperature to obtain the water pollution ecological restoration material.

2. The method for preparing the water pollution ecological restoration material according to claim 1, characterized in that: The Fe-Mn mixed solution is a solution prepared by mixing FeCl3•6H2O and KMnO4.

3. The method for preparing the water pollution ecological restoration material according to claim 1, characterized in that: The purity of the CaO powder is 99.9%.

4. The method for preparing water pollution ecological restoration materials according to claim 1, characterized in that: The water pollution ecological restoration material is refined through washing, drying and sieving.

5. The method for preparing the water pollution ecological restoration material according to claim 4, characterized in that: The arsenic-enriched centipede grass particles are sieved before soaking, with a sieve opening of 5 to 10 meshes, and the water pollution ecological restoration material is sieved with a sieve opening of 90 to 110 meshes during refinement.

6. The method for preparing the water pollution ecological restoration material according to claim 1, characterized in that: The ultrasound was performed using a constant temperature ultrasonic oscillator at a constant temperature of 30-50°C.

7. An application of a water pollution ecological restoration material obtained by the preparation method of a water pollution ecological restoration material according to any one of claims 1 to 6, characterized in that: The water pollution ecological restoration material is used for adsorbing arsenic in polluted water bodies.

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