Modified mikania micrantha charcoal as well as preparation and application thereof in environmental improvement

Abstract

The invention discloses modified mikania micrantha charcoal as well as preparation and application thereof in environmental improvement. The invasive plant mikania micrantha is used as a raw material, and the modified mikania micrantha biochar is prepared through a multi-way modification method; the method is simple in process, low in cost and environment-friendly. The modified mikania micrantha biochar shows efficient adsorption performance on phosphate in a solution in a treatment adsorption experiment. In addition, the modified mikania micrantha charcoal also has an algal inhibition effect, so that a new thought is provided for controlling algal blooms. The invention also explores the potential of resource reutilization of the phosphorus-absorbing biochar as a fertilizer, which not only provides a new way for phosphorus pollution treatment, but also opens up a new field for resource utilization of invasive organisms. Through the research, we expect to provide an innovative biochar-based solution for the treatment of phosphorus-polluted water and provide a new idea for the management of invasive organisms. The method not only is beneficial to environmental protection, but also can promote sustainable development.

Description

Technical Field

[0001] The present invention belongs to the field of resource utilization of invasive plants to prepare biochar and its application, and specifically relates to multi-pathway modified invasive plant Mikania micrantha biochar and its preparation method and application in a method for synchronously absorbing phosphate and environmental improvement. Background Art

[0003] The resource utilization of invasive organisms has attracted attention because it can reduce the cost of prevention and control and achieve resource reuse. In particular, converting invasive organisms into biochar can not only effectively control biological invasions, but also play an important role in environmental governance. Biochar, a carbon-rich solid material obtained by pyrolysis of plant biomass, has been widely used in soil improvement, wastewater treatment, carbon sequestration and other fields.

[0004] Eutrophication not only leads to frequent algal blooms, but also seriously damages the ecological balance and water quality of freshwater systems. Therefore, the development of effective phosphorus pollution control technologies has become a hot topic in environmental science research. Among the many control technologies, adsorption is favored because of its high efficiency in removing water pollutants. As a new adsorption material, biochar shows great potential in water remediation. Nevertheless, there are still some problems in the adsorption and removal of pollutants by biochar, such as unstable adsorption performance and difficulty in recycling; single target for treating pollutants and strong selectivity. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the object of the present invention is to provide a modified Mikania micrantha biochar and its preparation and application in environmental improvement.

[0006] The present invention uses the invasive plant Mikania micrantha as a raw material and prepares modified Mikania micrantha biochar through a multi-path modification method. These modified Mikania micrantha biochars show efficient adsorption performance for phosphate in solution in treatment adsorption experiments, and can explain its mechanism of action. In addition, the modified Mikania micrantha biochar also has an algae-inhibiting effect, which provides a new idea for controlling algal blooms. Furthermore, the present invention also explores the potential for resource recycling of biochar as fertilizer after absorbing phosphorus, which not only provides a new way to control phosphorus pollution, but also opens up a new field for the resource utilization of invasive organisms. Through this research, we hope to provide an innovative biochar-based solution for the treatment of phosphorus-contaminated water bodies and provide new ideas for the management of invasive organisms. This not only helps environmental protection, but also promotes sustainable development.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The present invention provides a method for preparing modified micrantha biochar, comprising the following steps:

[0009] Step 1: Collect the invasive plant Mikania micrantha, cut it into pieces, air-dry it, crush it, and sieve it to obtain Mikania micrantha powder;

[0010] Step 2: preparing Mikania micrantha biochar by nitrogen pyrolysis of the Mikania micrantha powder obtained in step 1;

[0011] Step 3: immersing the Mikania micrantha biochar obtained in step 2 in a magnesium chloride solution, immersing under stirring conditions, washing the soaked Mikania micrantha biochar to neutrality, drying, and sieving to obtain magnesium chloride-modified Mikania micrantha biochar;

[0012] Step 4: immersing the Mikania micrantha biochar obtained in step 2 in a hydrochloric acid solution, immersing under stirring conditions, washing the soaked Mikania micrantha biochar to neutrality, drying, and sieving to obtain hydrochloric acid-modified Mikania micrantha biochar;

[0013] Step 5: subjecting the Mikania micrantha biochar obtained in step 2 to mechanical ball milling to obtain ball-milled modified Mikania micrantha biochar;

[0014] Step 6: Repeat step 5 with the magnesium chloride-modified Mikania micrantha biochar of step 3 to obtain composite modified Mikania micrantha biochar.

[0015] Furthermore, in step 1, the pulverization is performed using a stainless steel high-speed pulverizer.

[0016] Furthermore, in step 1, the sieving is through a 90-110 mesh sieve, preferably through a 100 mesh sieve.

[0017] Furthermore, in step 2, the nitrogen pyrolysis method is carried out under nitrogen conditions, heating to 480-520°C (preferably 500°C) at a heating rate of 4-5°C / min (preferably 5°C / min), and then maintaining for 1.8-2.2h (preferably 2h) to obtain a pyrolysis product, which is then cooled to room temperature and sieved to obtain Mikania micrantha biochar.

[0018] Preferably, the sieving is through a 90-110 mesh sieve, preferably through a 100 mesh sieve.

[0019] It is further defined that in step 3, the concentration of the magnesium chloride solution is 1.8 to 2.2 mol / L, preferably 2 mol / L.

[0020] Furthermore, in step 3, the ratio of the Mikania micrantha biochar to the magnesium chloride solution is 0.8-1.2 g: 8-12 mL; preferably 1 g: 10 mL.

[0021] It is further defined that in step 4, the concentration of the hydrochloric acid solution is 0.8 to 1.2 mol / L, preferably 1 mol / L.

[0022] It is further defined that in step 4, the ratio of the Mikania micrantha biochar to the hydrochloric acid solution is 0.8-1.2 g: 8-12 mL; preferably 1 g: 10 mL.

[0023] Furthermore, in steps 3 and 4, the soaking under stirring conditions is room temperature and 150-230 r / min for 22-26 hours; preferably room temperature and 180 r / min for 24 hours.

[0024] Furthermore, in steps 3 and 4, the drying condition is 50-70° C. for 22-26 hours; preferably 60° C. for 24 hours.

[0025] Furthermore, in steps 3 and 4, the sieving is through a 90-110 mesh sieve, preferably through a 100 mesh sieve.

[0026] It is further defined that in step 5, the ratio of zirconium oxide balls used in the mechanical ball milling treatment to the Mikania micrantha biochar is 90-110 g:0.9-1.1 g; preferably 100 g:1 g.

[0027] It is further defined that in step 5, the rotation speed of the mechanical ball milling treatment is 280 to 320 r / min, preferably 300 r / min.

[0028] Furthermore, in step 5, the mechanical ball milling treatment time is 11 to 14 hours, preferably 12 hours.

[0029] Furthermore, in step 5, the rotation direction is changed every 2.5 to 4 hours (preferably 3 hours) during the ball milling process.

[0030] The present invention also provides magnesium chloride-modified Mikania micrantha biochar, hydrochloric acid-modified Mikania micrantha biochar, ball-milled modified Mikania micrantha biochar, and composite-modified Mikania micrantha biochar prepared by the above-mentioned preparation method.

[0031] The present invention also provides an application of the modified Mikania micrantha biochar, which is at least one of the applications (a) to (d):

[0032] (a) Used to adsorb phosphate in polluted environments.

[0033] (b) Used to control algal blooms.

[0034] (c) For soil improvement.

[0035] (d) For promoting plant growth.

[0036] Preferably, in (a), the polluted environment is at least one of polluted water and polluted soil.

[0037] Preferably, in (b), the bloom is controlled by inhibiting the growth of algae. Further, the algae include at least one of Chlorella vulgaris and Microcystis aeruginosa.

[0038] Preferably, in (d), the plant includes at least one of soybean and wheat.

[0039] Furthermore, the modified Mikania micrantha biochar obtained after adsorbing phosphate to equilibrium is used in promoting plant growth.

[0040] It is further defined that the modified Mikania micrantha biochar is added to the polluted water body, the original phosphate concentration in the polluted water body is 10 mg / L to 400 mg / L, the addition amount is 0.08 to 0.12 g / L, and stirring is performed at room temperature to complete the polluted water body treatment for phosphate adsorption.

[0041] Preferably, the dosage is 0.1 g / L.

[0042] It is further defined that the stirring condition is room temperature and 150-230 r / min for 22-26 h; preferably room temperature and 180 r / min for 24 h.

[0043] In the present invention, the room temperature is 10 to 35°C, further 15 to 35°C, and further 25°C.

[0044] Compared with the prior art, the present invention has the following advantages and effects:

[0045] (1) The present invention first prepares the invasive plant Mikania micrantha into biochar, and then performs a variety of modification methods on the Mikania micrantha biochar to prepare a modified Mikania micrantha biochar material, which is used for the efficient and stable adsorption of phosphate in polluted water bodies, thereby solving the pollution of eutrophication of water bodies and the prevention and control and utilization of the invasive plant Mikania micrantha; it also has the application of inhibiting algae growth and in soil improvement and promoting plant growth.

[0046] (2) The present invention uniformly covers the surface of biochar (Mikania micrantha) with metal ions "Mg" to obtain stable and uniform biochar, which is then ball-milled to increase the specific surface area of ​​the biochar. Chemical and physical modifications can improve the adsorption properties and thus be used to adsorb phosphates in polluted water.

[0047] (3) Using the invasive plant Mikania micrantha as the raw material for biochar has a simple process, low cost and is environmentally friendly. Using the invasive plant Mikania micrantha to synthesize a phosphate adsorbent in water effectively improves the adsorption effect of phosphate in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the effect of different modified Mikania micrantha biochar dosages on the phosphorus removal efficiency and adsorption capacity of biochar;

[0049] Figure 2 This is a diagram showing the adsorption kinetics of different modified Mikania micrantha biochars;

[0050] Figure 3 It is the adsorption isotherm effect diagram of different modified Mikania micrantha biochar;

[0051] Figure 4 is a scanning electron microscope image of the unmodified Mikania micrantha biochar in Example 1;

[0052] Figure 5 These are scanning electron microscope images of modified Mikania micrantha biochar obtained by various modification methods in Example 1; wherein, a: MMBC; b: HMBC; c: QMBC; d: FMBC. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The materials used in the embodiments are all commercially available samples unless otherwise specified, and the methods used are all conventional methods in the art unless otherwise specified. The phosphate described in the embodiments is potassium dihydrogen phosphate (KH2PO4).

[0054] Example 1

[0055] This embodiment provides a method for preparing biochar of the invasive plant Mikania micrantha by multiple pathways, which specifically comprises the following steps:

[0056] S1, cutting the collected invasive plant Mikania micrantha into pieces, drying them in the sun, crushing them using a stainless steel high-speed grinder, and passing them through a 100-mesh sieve to obtain Mikania micrantha powder;

[0057] S2. Put the Mikania micrantha powder obtained in step S1 into a crucible to fill the entire crucible, cover and seal it, place it in a muffle furnace, aerate nitrogen (99%) for about 10 minutes before heating to isolate the oxygen in the muffle furnace, then set the muffle furnace to heat to 500°C, the heating rate is about 5°C / min, and keep it for 2 hours to obtain the pyrolysis product. After cooling to room temperature, weigh the biochar, sieve it with a 100-mesh sieve, and obtain Mikania micrantha biochar; record it as MBC; the scanning electron microscope image is as follows Figure 4 shown.

[0058] S3, immerse the 500℃ Mikania micrantha biochar in a 2mol / L MgCl2 solution with a material-liquid ratio of 1 / 10 (w / v), shake it in a constant temperature oscillator (25℃, 180r / min) for 24 hours, vacuum filter it, wash it with distilled water until it is neutral, dry it at 60℃ for 24h, and pass it through a 100-mesh sieve to obtain magnesium chloride modified Mikania micrantha biochar; record it as MMBC; the scanning electron microscope picture is as follows Figure 5As shown in a in .

[0059] S4, immerse the 500℃ Mikania micrantha biochar in a 1mol / L HCl solution with a material-liquid ratio of 1 / 10 (w / v), shake it in a constant temperature oscillator (25℃, 180r / min) for 24 hours, vacuum filter, wash with distilled water until neutral, dry at 60℃ for 24h, pass through a 100-mesh sieve, and obtain hydrochloric acid-modified Mikania micrantha biochar; record it as HMBC; the scanning electron microscope image is as follows Figure 5 As shown in b.

[0060] S5. Use a planetary ball mill (QM-3SP2, Nanjing Nanda Instrument Co., Ltd.) to prepare ball-milled Mikania micrantha biochar. Put 100g of zirconia balls and 1g of Mikania micrantha biochar (500℃) into a ball mill for mechanical ball milling, with a ball-to-carbon ratio of 100:1 (100g:1g). The speed of the planetary ball mill was set to 300r / min, and the ball milling time was 12h. During the ball milling process, the rotation direction was changed every 3h, and after the ball milling was completed, the ball-milled modified Mikania micrantha biochar was obtained; it was denoted as QMBC; the scanning electron microscope image is as follows Figure 5 As shown in c.

[0061] S6. Add 2 mol / L MgCl2 solution to the Mikania micrantha biochar (500℃) at a ratio of 1:10, shake on a constant temperature oscillator (25℃, 180r / min) for 24 hours, vacuum filter, wash with distilled water until neutral, and dry at 60℃ for 24 hours to obtain magnesium chloride-modified Mikania micrantha biochar; put 100g of zirconium oxide balls and 1g of magnesium chloride-modified Mikania micrantha biochar into a ball mill for mechanical ball milling, with a ball-to-carbon ratio of 100:1 (100g:1g). The speed of the planetary ball mill was set to 300r / min, and the ball milling time was 12h. During the ball milling process, the rotation direction was changed every 1h, and after the ball milling was completed, the composite modified Mikania micrantha biochar was obtained; it was denoted as FMBC; the scanning electron microscope image was as follows Figure 5 As shown in d.

[0062] from Figure 4-Figure 5 It can be seen that the microstructure of Mikania micrantha biochar changed significantly after different modification treatments. Figure 4 The surface morphology of the unmodified Mikania micrantha biochar is shown. The biochar exhibits a certain pore structure, but the surface is relatively rough and the pore distribution is uneven. Figure 5 a in Figure 4 It was found that the surface of the micrantha biochar modified with magnesium chloride showed a smoother feature and the pore structure became clearer. This phenomenon indicates that magnesium chloride modification may have a positive effect on improving the porosity and surface properties of biochar. Figure 5Figure b is the SEM image of HMBC. Compared with the original biochar, the surface of the biochar modified with hydrochloric acid appears cleaner and the pore structure is also increased. This shows that hydrochloric acid modification can effectively remove impurities on the surface of biochar, thereby increasing its specific surface area. Figure 5 Figure c shows the effect of ball milling on the morphology of biochar. Ball milling modification leads to the breakage and refinement of biochar particles, converting larger particles into smaller fragments and increasing the specific surface area of ​​biochar. Finally, Figure 5 The d in the Figure 5 a and Figure 5 The results showed that this composite modification method not only retained the pore structure of biochar, but also further refined the particles through ball milling, which may further improve the adsorption performance of biochar.

[0063] Overall, SEM showed that different chemical and physical modifications can significantly change the microstructure of biochar, which in turn may have an impact on its performance in environmental applications. The physical properties of original and modified biochar are shown in Table 1.

[0064] Table 1 Physical properties of original Mikania micrantha biochar and modified Mikania micrantha biochar

[0065]

[0066] Table 1 lists in detail the physical properties of the original biochar and various modified biochars. Specific surface area is a key indicator for evaluating the performance of adsorption materials, and its size is directly related to the adsorption potential and efficiency of the material. Generally speaking, a larger specific surface area indicates that the material has more adsorption active sites, and may thus exhibit better adsorption efficiency. Combined with Table 1, it can be found that the modified biochar samples generally show an increase in specific surface area, especially the composite modified biochar (FMBC), whose specific surface area is significantly increased to 334.3591m 2 / g, far exceeding other types of biochar. This significant increase can be attributed to the synergistic effect of various modifications, as follows:

[0067] Synergistic effects of modification:

[0068] The preparation of composite modified biochar (FMBC) combines multiple technologies such as chemical modification and physical modification. These modification methods may have complementary effects on the microstructure and surface chemical properties of the material, thereby promoting a significant increase in the specific surface area. For example, chemical modification may enhance the hydrophilicity of the material by introducing additional functional groups; while physical modification, such as ball milling, may destroy the original structure of biochar and induce more pores and edge sites. These changes all help to increase the specific surface area.

[0069] Co-optimization of structure and chemical properties:

[0070] The modification process not only changes the chemical composition of biochar, but also may optimize its microstructure. The functional groups introduced by chemical modification may promote the formation and expansion of pore structure during physical modification. This synergistic optimization of structure and chemical properties is the key factor leading to a significant increase in specific surface area.

[0071] In summary, the data in Table 1 clearly indicate that the specific surface area of ​​microchamomile biochar can be significantly increased by the comprehensive use of multiple modification technologies, which may enhance its adsorption performance. This synergistic effect is an important research direction and provides a scientific basis for optimizing material performance through modification.

[0072] Effect Experiment Example 1

[0073] 1. Experiment on phosphate adsorption by Mikania micrantha biochar

[0074] The orthogonal experiment was conducted with 4 factors and 3 levels, including the dosage of Mikania micrantha biochar (0.025-0.1 g / L), phosphate solution with different initial concentrations (10-50 mg / L), pH value (3-11), and oscillation temperature (15-35 ° C), and the samples were oscillated at 180 r / min for 24 h. The samples were filtered using a 0.45 mm filter, and the residual phosphate concentration was detected at 700 nm using a UV-visible spectrophotometer (P4UV). The experiments were conducted in quintuplicate. After the orthogonal experiment, the optimal conditions were 0.025 g / L of Mikania micrantha biochar, an initial concentration of 10 mg / L of phosphate solution, and oscillation at 180 r / min for 24 h at pH 7 at 25 ° C. The adsorption results under the optimal conditions are shown in Table 2.

[0075] 2. Experimental study on phosphate adsorption performance of modified Mikania micrantha biochar in various ways

[0076] The adsorption capacity of phosphate by different modified Mikania micrantha biochars under different conditions was studied. Potassium dihydrogen phosphate (KH2PO4) was dissolved in deionized water to prepare a 500 mg / L stock solution, which was diluted to the appropriate concentration as needed in the experiment. All batches of experiments were conducted in 50 mL centrifuge tubes.

[0077] In a phosphate solution with a concentration of 50 mg / L, different amounts of adsorbent (modified Mikania micrantha biochar) (0.025-0.8 g / L) were used to investigate the effect of biochar dosage on adsorption; the effects of different amounts of modified Mikania micrantha biochar on phosphorus removal efficiency and adsorption amount were as follows: Figure 1 As shown in Table 2. Figure 1The results in Table 2 show that when the adsorbent dosage increases, the adsorption efficiency usually shows a trend of first rising and then tending to a platform; when the adsorbent dosage is the same, the adsorption amount shows a trend of FMBC>QMBC>MMBC>HMBC. For the four modified biochars, MMBC, HMBC, QMBC and FMBC, the maximum values ​​of their adsorption efficiency are approximately 87.3%, 74.5%, 86.2% and 95.6%, respectively. This phenomenon reveals that different modification methods have significant differential effects on adsorption efficiency. This result shows that composite modification (FMBC) significantly enhances the adsorption performance of biochar. By comparing and analyzing the data in Table 2, the maximum value of MBC adsorption efficiency is about 66.5%. It can be observed that all modification methods have improved the adsorption performance of the original micro-chamomile biochar, among which the effect of composite modification is particularly significant.

[0078] In summary, the experimental results show that modified microchamomile biochar can significantly improve its adsorption efficiency and adsorption amount for specific target substances, and different modification methods have different effects on the improvement of adsorption performance. In this study, composite modification (FMBC) showed the best adsorption performance, which may be attributed to the synergistic effect of multiple modification technologies in this method, thereby significantly improving the adsorption capacity of biochar. Future research can further explore the interaction mechanism between different modification technologies and how they work together to improve the adsorption performance of biochar.

[0079] 0.1 g / L of different modified Mikania micrantha biochar was added to a 50 mg / L phosphate solution, and the adsorption kinetics was studied at different adsorption times (5 to 1880 min). The adsorption kinetics (Pseudo-first-order model and Pseudo-second-order model) of different modified Mikania micrantha biochars are shown in the figure below. Figure 2 As shown. Figure 2 It can be seen that the fastest adsorption rate can be observed in 0-60 minutes, and then the adsorption rate will slowly decrease. Finally, the adsorption equilibrium is reached almost at 3h.

[0080] 0.1 g / L of different modified Mikania micrantha biochar was added to different initial phosphate solutions (10-400 mg / L) to perform adsorption equilibrium measurements. The adsorption isotherms (Langmuir model and Freundlich model) of different modified Mikania micrantha biochars are shown in the figure below. Figure 3 As shown in Table 3. Figure 3 As shown in Table 3, both models can fit the adsorption of phosphate by biochar well. 2The Langmuir model can better describe the adsorption of phosphate by MMBC, HMBC and FMBC biochars, and the Freundlich model can better describe the adsorption of phosphate by QMBC. In addition, R L It is an important indicator for evaluating the adsorption performance of the Langmuir adsorption isotherm model. From the fitting results, the Langmuir adsorption isotherm model fitting parameter R L All of them are within the range of 0-1. According to the parameters of the Langmuir model fitting, the adsorption amount of phosphate by FMBC (Q m ) is the largest, which is 297.9 mg / g. m Indicates the maximum adsorption capacity.

[0081] Generally, all adsorption experiments in this example were performed on a shaker at 180 r / min for 24 hours, and then the samples were filtered using a 0.45 mm filter and the residual phosphate concentration was measured at 700 nm using a UV-visible spectrophotometer (P4UV). The experiments were performed in triplicate.

[0082] Table 2 Maximum adsorption rate of phosphate by Mikania micrantha biochar and different modified Mikania micrantha biochar

[0083] Adsorbent Maximum adsorption rate (%) MBC 66.5 MMBC 87.3 HMBC 74.5 QMBC 86.2 FMBC 95.6

[0084] Table 3 Fitting parameters of the isotherm model for phosphate adsorption by modified biochar

[0085]

[0086] 3. Algae inhibition experiment

[0087] The expanded cultured Chlorella vulgaris was added to the BG11 medium and divided into six experimental groups: 1 g / L of the Mikania micrantha biochar obtained in Example 1 and the modified Mikania micrantha biochar obtained by various modification methods were added;

[0088] Control group 1: no material was added to the culture medium;

[0089] Control group 2: adding 1 g / L of Mikania micrantha biochar obtained from S2 in Example 1;

[0090] Experimental group 1: adding 1 g / L of magnesium chloride to the Mikania micrantha biochar obtained in S3 of Example 1;

[0091] Experimental group 2: adding 1 g / L of hydrochloric acid-modified Mikania micrantha biochar obtained in S4 of Example 1;

[0092] Experimental group 3: adding 1 g / L of ball-milled modified Mikania micrantha biochar obtained in S5 of Example 1;

[0093] Experimental group 4: adding the composite modified Mikania micrantha biochar obtained by S6 in Example 1 at 1 g / L;

[0094] The initial density of each group of algae was set to 1×10 6 / mL, and then placed in a light constant temperature incubator for culture at a temperature of 25°C, and the culture bottle was shaken 3 times a day; according to the set time, samples were taken from each test group regularly to determine the number of algae; 5 replicates were set for each group, and the results are shown in Table 4.

[0095] The results of the experiment showed that the algae density of the control group 1 was 8.33×10 6 / mL; the algae density of control group 2 was 5.52×10 6 / mL; the algae density of experimental group 1 was 1.29×10 6 / mL, and the algae density of experimental group 2 was 3.55×10 6 / mL, and the algae density of experimental group 3 was 1.41×10 6 / mL, and the algae density of experimental group 4 was 1.52×10 5 The data of experimental groups 1-4 showed that the modified Mikania micrantha biochar may have a synergistic effect in inhibiting the growth of Chlorella. This synergistic effect may be due to the combination of different modification methods, which leads to the optimization of the structure and chemical properties of biochar, thereby enhancing its ability to inhibit algal growth.

[0096] Table 4 Algae density after 5 days of inhibition of Chlorella by modified Mikania micrantha biochar

[0097]

[0098] 4. Pot Plant Experiment

[0099] Soybean and wheat were used as pot test materials for seed germination and seedling growth, and were divided into four groups;

[0100] Control group: pure soil;

[0101] Experimental group A: adding Mikania micrantha biochar obtained in S2 of Example 1, with an addition amount of 1% w / w;

[0102] Experimental group B: the composite modified Mikania micrantha biochar obtained by S6 in Example 1 was added at a dosage of 1% w / w;

[0103] Experimental group C: Biochar obtained by adding the composite modified Mikania micrantha biochar of S6 in Example 1 to adsorb phosphate to equilibrium, with an addition amount of 1% w / w; all plants were grown at room temperature, and each pot of plants was watered once a day; on the 10th day, plants were selected for growth comparison; 5 replicates were set for each group. The results are shown in Tables 5-6.

[0104] Table 5 Growth status of soybean in different groups

[0105]

[0106] Table 6 Wheat growth status in different groups

[0107]

[0108] As shown in Tables 5-6, the growth conditions of soybeans and wheat in experimental group C were significantly better than those in other groups, indicating that the biochar obtained after the composite modified Mikania micrantha biochar adsorbed phosphate to equilibrium can be used as agricultural fertilizer to effectively promote plant growth; compared with experimental group B, experimental group C had a more prominent effect in promoting plant growth, indicating that the conditions in experimental group C are more favorable to plant growth.

[0109] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing modified Mikania micrantha biochar, characterized in that: The steps include: Step 1: Collect the invasive plant Mikania micrantha, cut it into pieces, air-dry it, crush it, and sieve it to obtain Mikania micrantha powder; Step 2: preparing Mikania micrantha biochar by nitrogen pyrolysis of the Mikania micrantha powder obtained in step 1; Step 3: immersing the Mikania micrantha biochar obtained in step 2 in a magnesium chloride solution, immersing under stirring conditions, washing the soaked Mikania micrantha biochar to neutrality, drying, and sieving to obtain magnesium chloride-modified Mikania micrantha biochar; Step 4: immersing the Mikania micrantha biochar obtained in step 2 in a hydrochloric acid solution, immersing under stirring conditions, washing the soaked Mikania micrantha biochar to neutrality, drying, and sieving to obtain hydrochloric acid-modified Mikania micrantha biochar; Step 5: subjecting the Mikania micrantha biochar obtained in step 2 to mechanical ball milling to obtain ball-milled modified Mikania micrantha biochar; Step 6: Repeat step 5 with the magnesium chloride-modified Mikania micrantha biochar of step 3 to obtain composite modified Mikania micrantha biochar.

2. The preparation method according to claim 1, characterized in that: In step 3, the concentration of the magnesium chloride solution is 1.8-2.2 mol / L; In step 3, the ratio of the Mikania micrantha biochar to the magnesium chloride solution is 0.8-1.2 g: 8-12 mL.

3. The preparation method according to claim 1, characterized in that: In step 4, the concentration of the hydrochloric acid solution is 0.8-1.2 mol / L; In step 4, the ratio of the Mikania micrantha biochar to the hydrochloric acid solution is 0.8-1.2 g: 8-12 mL.

4. The preparation method according to claim 1, characterized in that: In steps 3 and 4, the soaking conditions under stirring conditions are room temperature, 150-230 r / min, and soaking for 22-26 hours; In steps 3 and 4, the drying condition is 50-70° C. for 22-26 hours.

5. The preparation method according to claim 1, characterized in that: In step 5, the ratio of zirconium oxide balls used in the mechanical ball milling to micrantha biochar is 90-110 g:0.9-1.1 g; In step 5, the rotation speed of the mechanical ball milling treatment is 280-320 r / min; In step 5, the mechanical ball milling treatment time is 11 to 14 hours; In step 5, the rotation direction is changed every 2.5 to 4 hours during the ball milling process.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In step 1, the sieving is through a 90-110 mesh sieve; In step 2, the nitrogen pyrolysis method is carried out under nitrogen conditions, heating to 480-520° C. at a heating rate of 4-5° C. / min, and then maintaining for 1.8-2.2 hours to obtain a pyrolysis product, which is then cooled to room temperature and sieved to obtain Mikania micrantha biochar; In steps 3 and 4, the sieving is through a 90-110 mesh sieve.

7. Modified Mikania micrantha biochar, characterized by: The biochar is prepared by the preparation method according to any one of claims 1 to 6; the modified Mikania micrantha biochar is magnesium chloride modified Mikania micrantha biochar, hydrochloric acid modified Mikania micrantha biochar, ball milled modified Mikania micrantha biochar or composite modified Mikania micrantha biochar.

8. The use of the modified Mikania micrantha biochar according to claim 7, characterized in that: At least one of the following applies: (a) Used to adsorb phosphate in polluted environments; (b) for controlling algal blooms; (c) for soil improvement; (d) For promoting plant growth.

9. The use according to claim 8, characterized in that: In (a), the polluted environment is at least one of polluted water and polluted soil; (b), controlling algal blooms by inhibiting algal growth; In (d), the plant comprises at least one of soybean and wheat.

10. Use of the modified Mikania micrantha biochar obtained by adsorbing phosphate to equilibrium as described in claim 7 in promoting plant growth.

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