Modified radix asparagi straw biomass charcoal as well as preparation method and application thereof

Abstract

The invention discloses modified radix asparagi straw biomass charcoal as well as a preparation method and application thereof, and relates to the technical field of environmental protection and biology. The preparation method comprises the following steps: carrying out modification treatment on radix asparagi straws by using a binary modifier containing a nitrogen element and a phosphorus element, and carrying out drying treatment, pyrolysis treatment and washing treatment on the modified radix asparagi straws to prepare the modified radix asparagi straw biomass charcoal. The raw materials adopted by the invention are special, and the modifier can introduce nitrogen-containing and phosphorus-containing groups into the radix asparagi straws at the same time, thereby having important significance for increasing adsorption active sites of the biomass charcoal of the radix asparagi straws. The modified radix asparagi straw biomass charcoal is used for solidifying phosphate mineralizing bacteria to synergistically treat cadmium-polluted soil, so that the absorption of soil cadmium by rice can be effectively prevented and controlled, the quality and yield of rice grains can be improved, a multi-effect circulating mode of treating pollution by waste-biological synergy is formed, and the soil cadmium can be effectively prevented and controlled. The method has important theoretical value and practical application prospect for promoting agricultural green low-carbon development and pollution treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the fields of environmental protection and biotechnology, and in particular, relates to a modified asparagus straw biomass charcoal as well as a preparation method and application thereof. BACKGROUND

[0002] Among the numerous agricultural wastes, crop straw is a kind of resource with large quantity and low utilization rate. Reasonably and efficiently developing its potential not only can alleviate agricultural non-point source pollution, but also is a key link to build a low-carbon agricultural ecosystem. In recent years, as a product of pyrolysis of straw resources, biochar has become an ideal material for improving soil quality and remediating soil pollution due to its porous structure, large specific surface area, rich functional groups, high carbon content and other advantages. Especially in the adsorption of heavy metals, biochar has attracted much attention due to its low cost, wide source and environmental friendliness. However, the biochar prepared by in-situ pyrolysis often has small specific surface area, uneven pore size distribution and poor adsorption selectivity, and its performance is still limited by its pore structure and surface functional group distribution.

[0003] Biochar prepared from traditional grain crop straw (such as corn, rice, wheat), rice hulls, wood chips, fruit shells and other agricultural or forestry wastes has been extensively studied, and the raw materials are highly homogeneous. However, special sources (such as waste from processing of medicinal plants with specific physicochemical properties) have not been adequately developed and utilized, and their unique value has not been fully explored.

[0004] Asparagus officinalis L. Asparagus cochinchinensis Asparagus officinalis L. is a typical medicinal and edible Chinese herbal medicine, and its roots are used as medicine. The straw is difficult to return to the field or be used as fertilizer due to its high degree of lignification and thorny surface, and is a "difficult-to-handle" waste. It has been abandoned as an agricultural byproduct for a long time due to the lack of effective high-value utilization methods. At the same time, the soil in the main producing area of Asparagus officinalis L. is generally contaminated with cadmium (Cd), which threatens the safety of agricultural products and ecological health.

[0005] Therefore, how to solve the realistic dilemma of coexistence of agricultural waste disposal and heavy metal pollution in the Asparagus officinalis L. producing area, and turn the Asparagus officinalis L. straw into treasure while considering environmental friendliness and efficient remediation, has important theoretical value and practical application prospect for promoting the development of green and low-carbon agriculture and pollution control.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] The present application relates to the fields of environmental protection and biotechnology, and in particular, relates to a modified asparagus straw biomass charcoal as well as a preparation method and application thereof.

[0008] The present application is implemented as follows: In a first aspect, an embodiment of the present application provides a preparation method of a modified asparagus straw biomass charcoal, comprising the following steps: The asparagus straw is modified by using a dual modifier, and the modified asparagus straw is treated by drying, pyrolysis and washing to obtain modified asparagus straw biomass charcoal. The mass ratio of the dual modifier to the asparagus straw is 1: (0.8-2), and the dual modifier comprises nitrogen and phosphorus elements.

[0009] In the second aspect, the embodiments of the present application provide a modified asparagus straw biomass charcoal prepared by the preparation method as described above.

[0010] In the third aspect, the embodiments of the present application provide the application of the modified asparagus straw biomass charcoal prepared by the preparation method as described above or the modified asparagus straw biomass charcoal as described above in the treatment of cadmium contaminated soil or water.

[0011] The present application has the following beneficial effects: The preparation method of the modified asparagus straw biomass charcoal provided by the embodiments of the present application uses asparagus lignified stems as the raw material of the biomass charcoal for the first time, converts them into high-performance adsorption materials, realizes the directional upgrading of agricultural waste, and breaks through the limitations of traditional straw. By introducing a dual modifier, one-step method is used to realize the simultaneous doping of nitrogen and phosphorus elements and the synergistic effect of functional groups. The preparation process is simple and environmentally friendly, avoiding complex multi-step modification processes. It realizes the new path of turning waste into treasure while considering environmental friendliness and efficient repair, which has important theoretical value and practical application prospect for promoting the development of agricultural green and low carbon and pollution control.

[0012] The prepared modified asparagus straw biomass charcoal has strong cadmium pollutant removal capacity, wide environmental adaptability, strong ion interference resistance, and long service life. The composite material prepared by combining urea phosphate modified asparagus straw biomass charcoal (PUBC) and phosphate mineralization bacteria can simultaneously solve the cadmium pollution problem in the main producing area, effectively reduce the cadmium content in rice, and improve the quality and yield of rice grains, forming a multi-effect circular mode of "waste pollution control to promote production". BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0014] Figure 1 The appearance of asparagus; Figure 2SEM test analysis results of BC of Comparative Example 1 (a), PBC of Comparative Example 2 (b), UBC of Comparative Example 3 (c) and PUBC of Example 1 (d); Figure 3 XRD test analysis results of products of Example 1 and Comparative Examples 1-3; Figure 4 FTIR test analysis results of products of Example 1 and Comparative Examples 1-3; Figure 5 XPS full spectrum test analysis results (a) and high-resolution energy spectrum analysis results of C 1s (b), O 1s (c), P 2p (d) and N 1s (e) of products of Example 1 and Comparative Examples 1-3; Figure 6 Cd 2+ removal rates in solutions with different concentrations of Cd: 10 mg / L (a), 20 mg / L (b), 40 mg / L (c), 80 mg / L (d) and 120 mg / L (e); Figure 7 Cd 2+ removal results of products of Example 1 and Comparative Examples 1-3 in solutions with different initial pH values and Cd concentrations of 20 mg / L; Figure 8 Cd + removal results of products of Example 1 and Comparative Examples 1-3 in environments with different ionic strengths: left graph for Na 2+ , right graph for Ca 2+ ; Figure 9 Reusability test results of products of Example 1 and Comparative Examples 1-3: removal rate (a) and recovery rate (b); Figure 10 Cd enrichment prevention results of different products on rice: appearance of phosphate mineralization bacteria PMB-5 (a); urea phosphate modified asparagus straw biochar (b); mineralization bacteria successfully loaded on biochar (c); rice pot experiment (d); Cd content in rice grains (e); yield of rice grains (f); wherein, CK is a control group; T1 is PUBC; T2 is phosphate mineralization bacteria; and T3 is a composite material. DETAILED DESCRIPTION

[0015] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. If specific conditions are not specified in the embodiments, conventional conditions or manufacturer recommended conditions are used. If the used reagents or instruments are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0016] The existing biochar raw materials are seriously homogeneous, and common agricultural or forestry wastes such as crop straw (such as rice straw, wheat straw, and corn straw), rice husk, wood chips, and fruit shells are often used; and special sources (such as waste generated during processing of medicinal plants and having specific physicochemical properties) are not paid enough attention to, and their unique value is not fully tapped. For waste such as the woody and thorny stems of asparagus racemosus, which is difficult to handle, there is a lack of effective high-value utilization approaches, and it cannot be composted or used for feed.

[0017] The present application develops a technical path for converting the woody and thorny stems of asparagus racemosus into high-performance adsorption materials, taking into account the characteristics of the stems, such as being woody, thorny, and difficult to be commonly recycled, and realizes a new path of turning waste into treasure while considering environmental friendliness and efficient remediation. The present application has important theoretical value and practical application prospects for promoting the development of green and low-carbon agriculture and pollution control. The specific implementation is as follows: In a first aspect, an embodiment of the present application provides a preparation method of modified asparagus racemosus straw biomass charcoal, comprising the following steps: The asparagus racemosus straw is modified by a dual modifier, and the modified asparagus racemosus straw is subjected to drying treatment, pyrolysis treatment, and washing treatment to obtain modified asparagus racemosus straw biomass charcoal. The mass ratio of the dual modifier to the asparagus racemosus straw is 1: (0.8-2), and the dual modifier comprises nitrogen and phosphorus elements.

[0018] It should be noted that the present application first uses the woody stems of asparagus racemosus as a biochar raw material, filling the technical gap in the preparation of biochar from medicinal plant residues. In view of the characteristics of the stems of asparagus racemosus, such as being woody, thorny, and difficult to be commonly recycled, a technical path for converting the stems into high-performance adsorption materials is developed, and waste is turned into treasure. The special organic components (lignin and cellulose structure) contained in the medicinal plant residues are fully utilized, so that a more optimal porous structure and rich surface active sites are formed after pyrolysis, laying a foundation for high performance.

[0019] In an optional embodiment, the mass ratio of the dual modifier to the asparagus racemosus straw is 1:1. Preferably, the dual modifier is selected from at least one of urea phosphate, guanidine phosphate, monoammonium phosphate, and diammonium phosphate. Preferably, the dual modifier comprises urea phosphate (CO(NH2)2·H3PO4).

[0020] It should be noted that the prior art commonly uses a single modifier (such as phosphoric acid, potassium hydroxide, zinc chloride, etc. for activation, or urea alone for nitrogen doping) or a multi-step process (such as acid washing followed by alkali modification, step-by-step doping of nitrogen and phosphorus, etc.) to modify biochar; among them, a single modifier can only introduce a single type of functional group (such as phosphate or amino), has limited functionality, is difficult to achieve synergistic effect, and usually requires a complex process flow, multiple modification processes, a complex process flow, a long time-consuming, high cost, and may generate more waste liquid, poor environmental friendliness; nitrogen and phosphorus co-doping is difficult, and effective and simultaneous doping of two key elements of nitrogen (N) and phosphorus (P) is difficult.

[0021] The dual modifier contains nitrogen and phosphorus elements, and the synergistic doping one-step method can achieve modification treatment; the dual modifier simultaneously introduces high-activity amine groups (-NH2) and phosphoric acid groups (-PO4) and other multiple functional groups, realizes efficient co-doping of nitrogen and phosphorus elements, overcomes the limitations of single modification and the complexity of multi-step modification, and has an extremely simple, efficient and environmentally friendly process.

[0022] Urea phosphate, as a dual modifier containing nitrogen and phosphorus elements, has advantages such as low cost, easy availability, and environmental friendliness, but its use in modifying biochar is still rarely reported. By modifying asparagus straw with urea phosphate, phosphorus and nitrogen elements can be introduced simultaneously, generating a large number of cadmium-philic functional groups, greatly improving the complexation, precipitation and exchange capacity of biochar for Cd 2+ , and achieving dual optimization of structure and performance and chemical reaction activity.

[0023] In an optional embodiment, the temperature of the modification treatment is room temperature, and the time is 20h-26h; And / or, the temperature of the drying treatment is 75℃-85℃; And / or, the temperature of the pyrolysis treatment is 480℃-520℃, and the treatment is carried out under a protective atmosphere for 1.8h-2.3h; preferably, the protective atmosphere is nitrogen or helium; And / or, the washing treatment includes cleaning to a constant pH of the washing liquid.

[0024] It should be noted that during the modification treatment, a one-step immersion treatment is carried out, and the immersion solvent is water. From the perspective of economic and benefit balance, the dual modifier and the asparagus straw are soaked in a ratio of 1:1. In order to make the soaking treatment more thorough, the immersion treatment is assisted by an oscillator at room temperature. The speed of the oscillator and the time of the immersion treatment can be reasonably adjusted according to the actual amount of material being treated.

[0025] The time of the drying treatment can be reasonably adjusted according to the actual amount of material being treated, and the material is dried to a constant weight state, i.e. the mass measured at least three times is within the allowable error range.

[0026] The equipment for pyrolysis treatment is not particularly limited, and in the embodiments of the present application, a tube furnace (OTF-1200X-S, China) is used, and in other embodiments of the present application, reasonable adjustment can be made according to actual conditions.

[0027] The flow rate of the protective atmosphere during pyrolysis treatment is 90 mL / min-110 mL / min, and specific adjustment can be made according to actual conditions. Exemplarily, any one of 90 mL / min, 95 mL / min, 100 mL / min and 110 mL / min, or other values within the range of 90 mL / min-110 mL / min. As a medicinal plant residue, asparagus straw is rich in special organic components (such as lignin, cellulose structure), and after pyrolysis, a more optimal porous structure and rich surface active sites are formed, which improves the adsorption potential and lays the foundation for high performance.

[0028] In the washing treatment, deionized water is used to clean the asparagus straw after pyrolysis treatment, and the cleaning is continued until the pH of the washing liquid is constant.

[0029] In an optional embodiment, the washing treatment further includes a drying treatment, and the temperature of the drying treatment is 55℃-65℃. After drying to a constant weight, the modified asparagus straw biomass charcoal is prepared.

[0030] In an optional embodiment, the preparation method further includes raw material pretreatment: the asparagus straw is dried by sun drying, ground by a pulverizer, and sieved by a 100-mesh sieve to obtain straw raw material.

[0031] In a second aspect, embodiments of the present application provide a modified asparagus straw biomass charcoal prepared by the preparation method as described above.

[0032] In a third aspect, embodiments of the present application provide a modified asparagus straw biomass charcoal prepared by the preparation method as described above or the application of the modified asparagus straw biomass charcoal as described above in the treatment of cadmium-contaminated soil or water.

[0033] The existing modified biochar has the following limitations: (1) limited adsorption capacity: the maximum adsorption capacity for target pollutants (such as Cd) may not be high enough or the improvement range is limited. (2) high pH sensitivity: the adsorption performance fluctuates greatly and the stability is poor in a wide pH range, especially under acidic or alkaline conditions. (3) weak resistance to ion interference: in actual water bodies, coexisting cations (such as Na + , Ca 2+ ) will significantly compete for adsorption sites, resulting in a significant decrease in removal rate. (4) poor cycle stability: after regeneration for several times, the adsorption capacity and material structure retention rate are low.

[0034] This invention improves the structure and chemical properties of asparagus straw through urea phosphate chemical modification, and for the first time combines modified asparagus straw biochar with phosphate mineralizing strains for the remediation of cadmium pollution in soil. This approach is beneficial for improving the adsorption capacity for cadmium, has a wide pH applicability, enhances resistance to ion interference, and strengthens cycle stability.

[0035] This method not only solves the practical dilemma of coexistence between agricultural waste disposal and heavy metal pollution in asparagus producing areas, but also proposes a new path that takes into account both environmental friendliness and efficient remediation. It has important theoretical value and practical application prospects for promoting green and low-carbon agricultural development and pollution control.

[0036] It should be noted that the embodiments of the present invention apply modified asparagus straw biochar to the treatment of cadmium-contaminated soil, realizing a dual-effect recycling model of "treating pollution with waste," as detailed below: This invention innovatively proposes and implements a dual-effect recycling model of "waste-to-pollution" with strong regional relevance, simultaneously addressing two key environmental issues in the main production area (medicinal plant cultivation and processing zone): first, the challenge of waste disposal by efficiently and resourcefully treating locally difficult-to-manage medicinal plant waste (asparagus stems); second, the challenge of environmental pollution by utilizing high-performance adsorbent materials derived from this waste to address potential cadmium pollution in the area (such as farmland soil remediation or water purification). This recycling model forms a closed loop, organically combining waste resource utilization with pollution control, resulting in significant environmental and economic benefits.

[0037] In an optional embodiment, when treating cadmium-contaminated soil, the modified asparagus straw biochar is solidified with mineralizing bacteria to obtain a composite material. During the solidification process, the ratio of mineralizing bacteria to modified asparagus straw biochar is 1g:2.5mL-1g:20mL; preferably 1g:7.5mL-1g:12.5mL. Preferably, the mineralizing bacteria are phosphate mineralizing bacteria, selected from at least one of Burkholderia, Bacillus, and Enterobacter.

[0038] Furthermore, the Enterobacter was selected from PMB-5 with accession number CGMCC NO.28795; its taxonomic name is Enterobacter. Enterobacter sp.; deposited on October 27, 2023; identification result: viable; deposit address: Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

[0039] It should be noted that the current heavy metal remediation technology mainly focuses on physical adsorption or chemical passivation means, such as using a single adsorbent (biochar, activated carbon, zeolite, etc.) to treat heavy metal pollution, emphasizing the capture ability of the material to heavy metals. Single material adsorption is difficult to achieve long-term stable passivation of heavy metals, and is greatly affected by soil pH, coexisting ions, etc. Such methods are often limited to surface adsorption or ion exchange mechanisms, and have limited stability improvement for high mobility elements such as cadmium in soil.

[0040] Although the biological passivation method (such as mineralization bacteria) has developed, it lacks systematic integration with functional materials (such as modified biochar). Although biological mineralization can generate insoluble heavy metal phosphate minerals, the process is slow and lacks a supporting carrier. There is almost no technology to integrate "high-performance adsorbent + biological mineralization" in a coordinated manner to improve overall remediation effect.

[0041] The embodiment of the present application carries out mineralization on phosphate mineralization bacteria to construct a "modified thymus australis straw biomass charcoal + mineralization bacteria synergistic application" soil cadmium pollution passivation system. The biomass charcoal can effectively load microorganisms and help the microorganisms to colonize in the rhizosphere. At the same time, the biomass charcoal can quickly capture Cd 2+ by physical adsorption, surface complexation, ion exchange and other mechanisms. The phosphate mineralization bacteria induce Cd 2+ to react with phosphate to form insoluble Cd3(PO4)2 and other minerals, forming a synergistic path of "adsorption-mineralization", which greatly enhances the long-term stability of heavy metals.

[0042] In addition, the mineralization of phosphate mineralization bacteria plays a key role in the cadmium passivation mechanism. Some phosphate mineralization bacteria strains (such as some Bacillus) can secrete phosphate substances to induce cadmium to form low-solubility cadmium phosphate minerals, achieving the stabilization of cadmium. Compared with the single material adsorption method, the synergistic application of phosphate mineralization bacteria strains and modified biochar can produce "physical and chemical passivation + biological mineralization" double mechanism, significantly improving the fixation rate and stability of soil Cd, and has good application prospect.

[0043] In an optional embodiment, before the solidification treatment, the phosphate mineralization bacteria are further subjected to expansion culture; The temperature of the expansion culture is 28-32°C, and the phosphate mineralization bacteria are collected after the logarithmic growth phase of the phosphate mineralization bacteria to prepare a bacterial suspension; after adjusting the OD 600 value of the bacterial suspension to 0.6-0.8, the solidification treatment is performed; wherein the culture medium for expansion culture includes NaCl, protein peptone, yeast extract powder and solvent in a mass ratio of 1:1:0.5:10; Preferably, sterile normal saline or PBS buffer is added to the collected phosphate mineralization bacteria to prepare a bacterial suspension.

[0044] It should be noted that, in the process of culturing the phosphate mineralization bacteria to the logarithmic growth phase, in order to ensure the growth environment and growth efficiency of the phosphate mineralization bacteria, the shaking treatment is carried out during the culture process, and the rate of the shaking treatment can be reasonably adjusted according to actual needs. In the embodiment of the present application, the rate of the shaking treatment is 150 rpm.

[0045] In the embodiment of the present application, the centrifugal treatment is used to collect the phosphate mineralization bacteria, and the speed and time of the centrifugal treatment can be reasonably adjusted according to actual needs. In the embodiment of the present application, the speed of the centrifugal treatment is 5000 rpm, and the time is 10 min.

[0046] In the optimal embodiment, the OD value of the bacterial suspension is adjusted to 0.8, that is, the phosphate mineralization bacteria in the bacterial suspension is 3.3×10 600 CFU / mL. 8 CFU / mL.

[0047] It should be noted that the culture medium in the embodiment of the present application is an LB bacterial culture medium, and the solvent is ultrapure water; in other embodiments, the solvent can also be selected from deionized water, pure water, distilled water and the like.

[0048] In the optimal embodiment, the culture medium includes 10.00 g of NaCl, 10.00 g of proteose peptone, 5.00 g of yeast extract powder, 1 L of ultrapure water, and the pH of the culture medium is 7.0.

[0049] In the optional embodiment, the degree of cadmium pollution of the soil is 2.8 mg / kg-3.2 mg / kg; In the treatment of cadmium contaminated soil, it also includes: adding 0.9%-1.2% of the modified asparagus straw biomass charcoal, 0.9%-1.2% of the composite material and 0.9%-1.2% of the bacterial suspension to the cadmium contaminated soil; The composite material is equal to the number of viable bacteria in the bacterial suspension, and both are 4.5×10 10 CFU-4.6×10 10 CFU. 600 The OD value of the bacterial suspension is 0.8.

[0050] The features and properties of the present application are further described in detail in combination with the following examples.

[0051] Example 1 The present embodiment provides a preparation method of modified asparagus straw biomass charcoal, which includes the following steps: (1) Raw material pretreatment The asparagus straw is ground by a pulverizer after being dried by sunlight, and is sieved by a 100-mesh screen to obtain raw asparagus straw, which is used as a raw material.

[0052] (2) Modification treatment The raw asparagus straw in step (1) is mixed with urea phosphate as a modifier at a mass ratio of 1:1, and then is soaked for 24 h at room temperature with the aid of an oscillator (at a speed of 250 rpm), which is used as a raw material.

[0053] (3) Drying treatment The asparagus straw after the modification treatment in step (2) is subjected to drying treatment at a temperature of 80°C until the mass is within the allowable error range in three measurements, which is used as a raw material.

[0054] (4) Pyrolysis treatment The asparagus straw after the drying treatment in step (3) is subjected to pyrolysis treatment at a temperature of 500°C for 2 h under a nitrogen atmosphere with a nitrogen flow rate of 100 mL / min, which is used as a raw material.

[0055] The pyrolysis equipment is a tube furnace (OTF-1200X-S, China).

[0056] (5) Washing treatment and drying treatment The asparagus straw after the pyrolysis treatment in step (4) is washed with deionized water until the pH of the washing liquid is stable, and then is dried at 60°C until the weight is constant to obtain modified asparagus straw biochar, which is denoted as PUBC.

[0057] Comparative Example 1 The comparative example provides a preparation method of asparagus straw biochar, which is different from example 1 only in that the modification treatment in step (2) is omitted.

[0058] The prepared unmodified asparagus straw biochar is denoted as BC.

[0059] Comparative Example 2 The comparative example provides a preparation method of modified asparagus straw biochar, which is the same as example 1, and is different only in that: (2) Modification treatment The modifier is phosphoric acid (H3PO4).

[0060] The finally prepared modified asparagus straw biochar is denoted as PBC.

[0061] Comparative Example 3 The comparative example provides a preparation method of modified asparagus straw biochar, which is the same as example 1, and is different only in that: (2) Modification treatment The modifier is urea (CO(NH2)2).

[0062] The finally prepared modified asparagus straw biomass charcoal is denoted as PUBC.

[0063] Test Example 1 In this test example, the appearance of the raw material asparagus is photographed, and the relevant pictures are shown in Figure 1 From the right picture in Figure 1 , it can be clearly seen that there are many thorns on the asparagus stem.

[0064] Test Example 2 In this test example, the products of Example 1 and Comparative Examples 1-3 are respectively subjected to SEM test analysis to observe the influence of the modifier on the formation of porous biomass charcoal of asparagus straw, and the relevant results are shown in Figure 2 : BC of Comparative Example 1 (a), PBC of Comparative Example 2 (b), UBC of Comparative Example 3 (c) and PUBC of Example 1 (d).

[0065] From the test results in Figure 2 , it can be seen that the introduction of phosphorus doping, nitrogen doping and phosphorus-nitrogen co-doping leads to significant changes in the structure of asparagus straw biomass charcoal. Specifically, the following is: The asparagus straw biomass charcoal modified by urea phosphate in Example 1 (PUBC, d) presents a more uniform and ordered pore structure with the least fragmentation, which is due to the co-doping effect of phosphorus (P) and nitrogen (N), which promotes the formation of pores during pyrolysis. The unmodified asparagus straw biomass charcoal (BC, a) of Comparative Example 1 presents a complete but highly fragmented pore structure. The asparagus straw biomass charcoal modified by phosphoric acid in Comparative Example 2 (PBC, b) has a lower fragmentation degree than BC because the H3PO4 treatment stabilizes part of the biomass charcoal structure, but its pore structure is still incomplete. The surface of the asparagus straw biomass charcoal modified by urea in Comparative Example 3 (UBC) is rougher and granular than that of PUBC in Example 1.

[0066] The above situation is due to the difference in the pyrolysis process of urea (CO(NH2)2) and urea phosphate (CO(NH2)2·H3PO4) doping on the surface of biomass charcoal: urea doping can form a granular compound, while urea phosphate doping promotes the distribution of phosphorus (P) and nitrogen (N) on the surface of biomass charcoal to be more uniform.

[0067] Test Example 3 In this test example, the products of Example 1 and Comparative Examples 1-3 are respectively subjected to XRD test analysis, and the test results are shown in Figure 3 .

[0068] From the test results in Figure 3The XRD results of BC, PBC, UBC and PUBC showed that the main structure of all the biochars were typical amorphous carbon configuration. The characteristic diffraction peaks of KCl (KCL PDF #41-1476), CaCO3 (PDF #81-2027) and quartz (PDF #27-2096) were detected in BC and UBC, while only the peak of quartz was detected in PBC. This indicated that the crystal materials were formed in-situ during the treatment of asparagus straw with urea, while the treatment with phosphoric acid and urea-phosphate converted the biochar into amorphous carbon structure, which was helpful for the formation of biochar structure. The introduction of modifiers during the pyrolysis of biomass would affect the types of functional groups of biochar.

[0069] Test Example 4 The products of Example 1 and Comparative Examples 1-3 were respectively subjected to FTIR test analysis, and the test results are shown in Table 2. Figure 4 .

[0070] From the FTIR results of Figure 4 , it can be seen that the FTIR spectra showed significant differences in functional groups (especially in the fingerprint region). The specific analysis is as follows: The main absorption bands in BC were located at 2397 cm -1 (ν(C≡N)), 2115 cm -1 (ν(C≡C)), 1567 cm -1 (ν(C=C)), 1425 cm -1 (ν(C=O / C=N)) and 568 cm -1 (δ(Si-O-Si)), in addition to 873 cm -1 and 744 cm -1 belonging to the vibration peaks of δ(CO3 2- ). After modification, the functional groups changed significantly: PBC modified by H3PO4 appeared new peaks at 1125 cm -1 (ν(C-O)), 960 cm -1 (ν(P-O-C)) and 482 cm -1 (ν(P-O-P)), confirming the successful introduction of phosphorus-containing groups; UBC modified by CO(NH2)2 mainly absorbed at 1031 cm -1 (ν(C-N)), 746 cm -1 (δ(C-H)) and 551 cm -1 (δ(Si-O)), reflecting the introduction of nitrogen functional groups; PUBC modified by CO(NH2)2·H3PO4 changed most significantly, at 3220 cm -1 and 3006 cm -1New peaks of ν(NH) and ν(CH) were observed at the fingerprint area, with a depth of 875 cm⁻¹. -1 (δ(POH)) and 482 cm -1 The strong absorption band of (ν(POP)) and 1168 cm⁻¹ -1 (ν(CO / P=O)) and 1070 cm -1 The weak peak of (ν(COP / POC)) indicates that CO(NH2)2·H3PO4 modification enhances the functional group diversity of biochar, forming a more complex chemical structure, which may improve its adsorption capacity.

[0071] Test Example 5 This test example performed XPS full-spectrum analysis (a) and high-resolution energy dispersive spectroscopy (EDS) analysis of C 1s (b), O 1s (c), P 2p (d), and N 1s (e) on the products of Example 1 and Comparative Examples 1-3, respectively. The test results are shown in [Figure number missing]. Figure 5 .

[0072] from Figure 5 XPS full-spectrum analysis of biochar showed that the modifier affected the content of P, O, and N elements in the biochar. Compared with BC, P content in PBC and PUBC increased significantly, while N content in UBC and PUBC increased, indicating that urea phosphate modification effectively increased the P and N content in biochar. XPS spectrum fitting analysis of the chemical forms of C, O, P, and N in the four biochars revealed that the CC / C=C bond ratio decreased after modification, while CP and CN bonds significantly increased. Figure 5 b).

[0073] O 1s ( Figure 5 c) The fitting results show that BC and UBC are mainly composed of C=O, CO, and Si-O, while PBC and PUBC mainly contain CO, C=O, PO, and P=O. Phosphorus modification may have promoted the oxidation reaction and increased the ratio of PO to P=O; CO(NH2)2 has little effect on oxygen-containing functional groups.

[0074] P 2p ( Figure 5 d) High-resolution spectral peak analysis results show that CP and PO bonds exist at 130.34 eV and 131.29 eV in BC; the binding energy of the modified sample is shifted upward, indicating that P=O / PO and POC bonds are generated.

[0075] N 1s ( Figure 5e) High-resolution XPS spectra show that nitrogen elements mainly exist in the form of pyridine nitrogen, quaternary nitrogen, pyrrole nitrogen, graphitic nitrogen and oxidized nitrogen. CO(NH2)2 modification (UBC) increases the proportion of oxidized nitrogen (27.28%) and introduces graphitic nitrogen (15.44%), while reducing pyrrole nitrogen to 8.61%; H3PO4 modification (PBC) increases pyrrole nitrogen (35.15%) and maintains a high proportion of pyridine nitrogen (48.62%); The pyridine nitrogen content of N, P co-modified (PUBC) is the highest (54.53%), the pyrrole nitrogen is significant (28.52%), but the proportion of graphitic nitrogen is the lowest (16.95%). This shows that urea phosphate modified biochar PUBC produces biochar with active and stable nitrogen types, suitable for catalysis, repair and other scenarios.

[0076] Experimental Example 1 This experimental example is used to study the modification effect of different urea phosphate contents on asparagus straw. In order to determine the optimal proportion of urea phosphate for modifying biochar, the mass ratio of asparagus straw to binary modifier urea phosphate is set to 0.5:1, 1:1, 1.5:1 and 2:1. After modification and calcination, the products of different mass ratios of asparagus straw and binary modifier urea phosphate are weighed and the yield is calculated, wherein the yield of modified asparagus straw biochar (%) = the mass of modified asparagus straw biochar after pyrolysis (g) / the total mass of the material before pyrolysis (g) x 100%.

[0077] The prepared products are used as adsorbents to study their removal effect on cadmium pollution in water. The test method is as follows: 2 g / L is added to a Cd 2+ solution with a concentration of 20 mg / L, and after 1200 min of vibration at 200 rpm, the supernatant is filtered with 0.45 μm, and the Cd 2+ concentration is determined by inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7900) to compare the effects of different proportions of urea phosphate modification. The relevant test results are shown in Table 1. Table 1 Yield and Cd removal rate of products prepared by different mass ratios of asparagus straw and binary modifier urea phosphate

[0078] As can be seen from Table 1, when the mass ratio of asparagus straw to dual-modifier urea phosphate is 0.5:1, the yield (38.85%) and the Cd removal rate (74.42%) are at a low level. This indicates that the amount of modifier is insufficient, and the modifier cannot fully act on the asparagus straw raw material, resulting in limited reaction efficiency and unsatisfactory modification effect. When the ratio is increased to 1:1, both indicators achieve the most significant leap. The yield is increased by 10.07 percentage points to 48.92%, and the Cd removal rate is increased by 5.46 percentage points to 79.88%. This leap indicates that, at this ratio, the reactants are reasonably matched, and the performance of the modifier is fully utilized. When the ratio is further increased to 1.5:1 and 2:1, the yield and the Cd removal rate continue to increase, but the increase is sharply narrowed. For example, from 1:1 to 1.5:1, the yield increases by only 2.15%, showing a typical marginal effect diminishing phenomenon. This means that the performance improvement brought by the continued increase of the amount of modifier is very limited, and the efficiency is reduced. Although the yield and the removal rate are optimal when the ratio of the modifier to the raw material is 2:1, the cost is doubled compared to the ratio of 1:1, which means double the cost in actual production. Therefore, the asparagus straw and the dual-modifier urea phosphate ratio of 1:1 is selected as the optimal ratio in the embodiment of the present application, which is a reasonable decision based on the comprehensive trade-off between performance and cost presented by the experimental data.

[0079] Experimental Example 2 This experimental example is used to study the ratio of phosphate mineralization bacteria to modified asparagus straw biomass charcoal solidification treatment; in order to determine how many phosphate mineralization bacteria can be fixed per gram of urea phosphate modified asparagus straw biomass charcoal (PUBC), this experimental example gradually increases the dosage of bacterial suspension under the condition of fixing the mass of PUBC. The phosphate mineralization bacteria are enterobacter, which are selected from PMB-5 with the preservation number of CGMCC NO. 28795; the classification name is Enterobacter sp. Enterobacter The experimental method is as follows: PMB-5 bacteria are inoculated into LB culture medium for large-scale culture, wherein the LB culture medium is 10.00 g of NaCl, 10.00 g of peptone, 5.00 g of yeast extract powder, 1 L of pure water, and pH = 7.0; the culture conditions (temperature 30℃, shaking speed 150 rpm) are controlled, and the phosphate mineralization bacteria are cultured to the logarithmic growth phase. The phosphate mineralization bacteria precipitate is collected by centrifugal treatment (5000 rpm, 10 min); the collected phosphate mineralization bacteria precipitate is resuspended with sterile normal saline to prepare a bacterial suspension; The OD 600 value of the phosphate mineralization bacteria is adjusted to 0.8 (3.3 ×10 8 CFU mL -1) After resuspension, the bacterial suspension was mixed with urea phosphate modified asparagus straw biomass charcoal (PUBC) for immobilization treatment; the mixing ratio was PUBC mass: bacterial suspension volume of 1 g:2.5 mL, 1 g:5.0 mL, 1 g:7.5 mL, 1 g:10 mL, 1 g:12.5 mL, 1 g:15 mL and 1 g:20 mL; The mixed solution was placed in a constant temperature oscillator and oscillated for 24 hours at a suitable temperature (such as 25°C) to allow the phosphate mineralization bacteria to be fixed on the modified asparagus straw biomass charcoal. The modified asparagus straw biomass charcoal loaded with phosphate mineralization bacteria was separated by filtration and washed with sterile water to remove unbound free phosphate mineralization bacteria, and then naturally air-dried at room temperature to obtain a modified asparagus straw biomass charcoal composite material loaded with phosphate mineralization bacteria, denoted as composite material.

[0080] The OD 600 value of the supernatant after immobilization was determined to calculate the immobilization efficiency and loading amount of the modified asparagus straw biomass charcoal for phosphate mineralization bacteria. At the same time, the composite material was added to a 20 mg / L Cd 2+ solution at a dosage of 2 g / L to compare the removal rates of different proportion composite materials for cadmium, and finally the results of loading amount and Cd removal rate were comprehensively determined to determine the optimal proportion of phosphate mineralization bacteria and modified asparagus straw biomass charcoal. The relevant test results are shown in Table 2.

[0081] Table 2 Loading effect and Cd removal effect of different bacterial suspension and PUBC dosage ratio

[0082] As can be seen from the results in Table 2, with the increase of the dosage of bacterial suspension, the loading rate (immobilization efficiency) gradually decreases, but the absolute bacterial loading amount (CFU / g) of unit carrier material significantly increases and tends to saturation. At a ratio of 1:2.5 g / mL, although the PUBC loading rate is the highest, the loading amount is the lowest.

[0083] At a ratio of 1:10 g / mL, the PUBC loading rate of phosphate mineralization bacteria strain reaches 2.29×10 9 CFU / g, which is significantly increased compared with the previous groups (1-3); at this time, the Cd removal rate in the solution reaches 95.50%.

[0084] Continue to increase the dosage of bacterial suspension, although the loading capacity and removal rate can be slightly increased, but the utilization rate of bacterial suspension is sharply decreased, and the cost-effectiveness is significantly deteriorated, such as at the ratio of 1:20 g / mL, the input of bacterial suspension is doubled (from 10 mL to 20 mL), the loading capacity is only increased by 9.2%, and the Cd removal rate is only increased by 1.88%, which is a typical phenomenon of sharply decreasing marginal benefit; at this time, the loading rate is only 37.88%, which means that more than 60% of the bacterial suspension is wasted, which will cause unnecessary economic effect loss.

[0085] Therefore, when the ratio is 1:10 g / mL, the adsorption potential of the composite material has been fully tapped, which is the best balance point between loading capacity and functional performance. In consideration of the loading capacity, cost-effectiveness and heavy metal removal rate, the optimal loading ratio of PUBC and PMB-5 bacterial solution is determined to be 1 g:10 mL. The ratio can ensure that the adsorption sites of the carrier are used efficiently, and the ratio can prepare high-performance, low-cost heavy metal remediation composite materials.

[0086] Application Example 1 In this application example, the products of Example 1 and Comparative Examples 1-3 are used as adsorbents to study their removal effects on cadmium pollution in water.

[0087] The experimental method is as follows: 200 mg of the products of Example 1 and Comparative Examples 1-3 are weighed as adsorbents and added to 100 mL of Cd 2+ solution with different initial concentrations (10 mg / L, 20 mg / L, 40 mg / L, 80 mg / L, 120 mg / L) at 25°C for adsorption experiment, and the adsorbent dosage is kept at 2.00 g / L. The experiment is carried out in a constant temperature water bath oscillator, and the oscillation speed is 200 rpm to ensure uniform mixing of the solution. Sampling is carried out at different time points (15 min, 30 min, 60 min, 90 min, 120 min, 150 min, 200 min, 300 min, 600 min, 1200 min). The adsorption solution is filtered through a 0.45 μm filter membrane, and the Cd 2+ concentration is determined by inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7900). The related test results of cadmium removal rate in different concentrations of Cd 2+ solution are shown in Figure 6 : 10 mg / L (a), 20 mg / L (b), 40 mg / L (c), 80 mg / L (d), 120 mg / L (e).

[0088] From Figure 6The test results show that all biochar exhibits a characteristic adsorption trend: rapid initial absorption followed by a plateau, indicating saturation of adsorption sites. Different concentrations of Cd... 2+ In solution, at 1200 min, the cadmium removal rates ranged from 19.38% to 77.79% for BC, 23.33% to 77.04% for PBC, 32.35% to 91.71% for UBC, and 8.54% to 86.58% for PUBC. These results indicate that at different initial cadmium concentrations, the cadmium removal rate decreases with increasing cadmium concentration, while UBC and PUBC show significantly improved pollutant removal performance.

[0089] Application Example 2 This application example is used to study different initial pH values ​​and Cd values. 2+ In a 20 mg / L solution, the removal effects of the products from cadmium pollution in water in Examples 1 and Comparative Examples 1-3 were investigated. The experimental methods were the same as in Application Example 1, with the only difference being: Cd 2+ The solution concentration was a constant 20 mg / L, with different pH values ​​of 4, 5, 6, 7, 8, and 9. The test time was set at 1200 min after the reaction. Relevant test results are shown below. Figure 7 .

[0090] from Figure 7 The test results show that, with Cd 2+ As the pH of the solution increased from 4 to 9, BC exhibited a pattern of first decreasing and then increasing removal efficiency; at pH 7, the removal efficiency dropped to a low of 47.87%, and at pH 9, it reached a peak of 69.96%.

[0091] In contrast, the Cd removal rates of both PBC and UBC increased with increasing pH. At pH 9, the Cd removal rate of PBC reached 71.28%, and that of UBC reached 90.11%. PUBC showed the lowest sensitivity to pH changes, with removal efficiencies fluctuating between 77.98% and 83.40%.

[0092] The above results indicate that changes in pH value have the least impact on Cd removal rate, and with fewer operational constraints, Cd removal efficiency has consistently shown good performance.

[0093] Application Example 3 This application example studies the removal effect of the product from cadmium pollution in water in environments with different ionic strengths, specifically in Examples 1 and Comparative Examples 1-3, where the ion is Na+. + and Ca 2+, the concentrations of Na Figure 8 : left figure is Na + , right figure is Ca 2+ .

[0094] The experimental method is as follows: in a series of conical flasks containing 20 mL, 20 mg / L Ca 2+ solution, sodium chloride or calcium chloride solid is added respectively to obtain Na + or Ca 2+ solution system with concentrations of 0.00 M, 0.05 M, 0.10 M, 0.15 M and 0.20 M. After the initial pH value of all systems is uniformly adjusted to 7.0 using 0.1 M HCl or NaOH solution, the adsorbent (Example 1 or Comparative Examples 1-3) with a dosage of 2 g / L is accurately added. Subsequently, the conical flasks are sealed and oscillated at 25°C, 200 rpm for 1200 minutes. After the reaction is completed, the supernatant is taken and the cadmium content is determined using ICP-MS and the removal rate is calculated, and the related test results are shown in Figure 8 .

[0095] From the test results of Figure 8 , it can be seen that compared with the initial 0.00 M, the Cd removal rates of BC, PBC, UBC and PUBC are reduced by 16.84%, 6.54%, 6.43% and 3.16% respectively for 0.20 M Na + ; compared with the initial 0.00 M, the Cd removal rates of BC, PBC, UBC and PUBC are reduced by 29.39%, 19.39%, 5.32% and 6.15% respectively for 0.20 M Ca 2+ .

[0096] The above results show that PUBC has the strongest anti-ion interference ability, effectively reduces the influence of ion interference on cadmium removal, and has the most potential in practical application.

[0097] The specific analysis is as follows: PBC maintains a high removal efficiency at a lower ionic strength through the electrostatic and complexation interactions of the phosphate groups (C-O, P-O-C, P-O-P), while UBC effectively maintains its Cd removal performance through the stable complexation interactions promoted by the introduced amino and carbonyl groups. In particular, the outstanding performance of PUBC can be attributed to its more complex surface chemical properties, which further improve its resistance to ion competition and removal efficiency.

[0098] Application Example 4 This application example was used to study the reusability of the products from Example 1 and Comparative Examples 1-3, and adsorption-desorption experiments were conducted on each product for 10 cycles. The relevant test results are shown below. Figure 9 Cd removal rate (a), recovery rate (b).

[0099] The experimental method was as follows: Ca was initially prepared at a concentration of 20 mg / L. 2+ The adsorbent was added to the solution at a dosage of 2 g / L, and the mixture was shaken at 25 °C and 200 rpm for 1200 minutes to ensure sufficient adsorption equilibrium was reached. After adsorption, solid-liquid separation was performed on the sample; the Ca-loaded sample was then... 2+ The adsorbent was placed in 30 mL of 0.5 mol / L NaOH solution and shaken at 200 rpm for 3 hours at room temperature to study its desorption kinetics. After desorption, the adsorbent was washed with deionized water until neutral (pH ≈ 7.0) and dried before being used in subsequent adsorption-desorption cycle experiments to examine its reusability. The relevant test results are shown in […]. Figure 9 .

[0100] from Figure 9 The test results show that BC, PBC, UBC, and PUBC exhibited relatively stable Cd removal efficiencies over 10 consecutive cycles, ranging from 47.01% to 76.70%, 49.58% to 69.12%, 72.65% to 87.54%, and 69.50% to 77.97%, respectively. Figure 9 a).

[0101] from Figure 9 As can be seen from b, the recovery rate of BC showed a sharp decline after the 8th cycle, falling below 70% by the 10th cycle. PBC exhibited moderate performance, with the recovery rate falling below 80% after the 9th cycle. The recovery rate of UBC was 82.99% at the 10th cycle, while that of PUBC was 89.13% at the 10th cycle.

[0102] The above results indicate that urea phosphate-modified asparagus straw biochar has stronger durability and reusability, and can provide economic benefits.

[0103] Application Example 5 This application example is used to study the effects of different products on controlling cadmium accumulation in rice.

[0104] The experimental method is as follows: 1% PUBC (T1), PMB-5 bacterial suspension (T2), or 1% composite material (T3) were added to 2 kg of sieved farmland soil with a cadmium contamination level of 2.67 ± 0.24 mg / kg. The control group (CK) was used as the treatment group without any added materials. The viable bacteria count in the composite material and the bacterial suspension were equal, both being 4.58 × 10⁻⁶.10 CFU, OD of bacterial suspension 600 The value is 0.8, and each treatment sample is repeated 6 times. After adding the material for 7 days, two rice seedlings with basically the same growth are planted in each flowerpot. After the rice matures, the yield of the rice and the cadmium content in the rice grains are measured. The relevant test results are shown in Figure 10 : The morphology of phosphate mineralization bacteria PMB-5 (a); urea phosphate modified asparagus straw biochar (b); mineralization bacteria successfully loaded on biochar (c); rice pot experiment (d); cadmium content in rice grains (e); yield of rice grains (f); wherein, CK is the control group; T1 is PUBC; T2 is phosphate mineralization bacteria; T3 is the composite material.

[0105] The phosphate mineralization bacteria and PUBC are oscillated and loaded, and then scanning electron microscopy is performed. The results show that PMB-5 is successfully loaded in the pores of the biochar.

[0106] The cadmium content of the rice grains treated in different ways is detected: the cadmium contents in CK, T1, T2 and T3 are 4.810 mg / kg, 2.763 mg / kg, 2.687 mg / kg and 1.901 mg / kg, respectively. Compared with no addition (CK), the addition of the composite material (T3) significantly reduces the cadmium content in the rice grains by 60.48%; compared with the PUBC treatment (T1) and the phosphate mineralization bacteria treatment (T2), it is reduced by 31.20% and 29.26%, respectively, indicating that the urea phosphate modified biochar and the mineralization bacteria Enterobacter sp. The composite application of PMB-5 can significantly enhance the control ability of cadmium migration from the soil to the rice grains, and has a synergistic effect. In addition, the weights of the grains in CK, T1, T2 and T3 are 38.695 g, 47.202 g, 51.315 g and 58.067 g, respectively. Compared with CK, the PUBC treatment (T1) and the phosphate mineralization bacteria treatment (T2), the weight of the grains in the composite treatment (T3) is further increased by 50.06%, 23.02% and 13.16%, respectively, indicating that the composite material has great potential in ensuring the safe production of crops and improving yield.

[0107] In summary, the modified asparagus straw biochar provided by the embodiment of the application and the preparation method and application thereof have the following characteristics: (1) Raw material innovation: high-value utilization of medicinal plant waste, filling the technical gap of preparing biochar from medicinal plant residues, and raw material selection has significant novelty and industrial application potential. For the first time, asparagus lignified stems are used as biochar raw materials, breaking through the limitations of traditional straw. Asparagus stems are difficult to be resourceized (composting / fertilizer) due to lignification and spiny characteristics. This technology converts them into high-performance adsorbent materials, realizing the directional upgrading of agricultural waste. Medicinal plant residues are rich in special organic components (such as lignin and cellulose structure), which form porous structures and surface active sites after pyrolysis, enhancing the adsorption potential.

[0108] (2) Simple modification process, urea phosphate as a dual modifier for N and P co-doping, realizing simultaneous doping of nitrogen-phosphorus elements and synergistic effect of functional groups. Urea phosphate has both urea (–NH2 source) and phosphoric acid (–PO4 source), which can introduce amine groups and phosphoric acid groups through one-step modification, overcoming the limitations of single modification. The process is simple and environmentally friendly, avoiding complex multi-step modification procedures.

[0109] (3) Phosphoric acid urea modified biochar has stronger removal capacity for cadmium pollutants: phosphoric acid urea modified asparagus straw biochar (PUBC) has a maximum adsorption capacity of 18.50 mg / g-28.22 mg / g at 25-45°C, while the original biochar without phosphoric acid urea modification has a maximum adsorption capacity of only 12.17 mg / g-23.48 mg / g. The removal rate of PUBC for Cd is 28.54%-86.58%, while the removal rate of unmodified biochar for Cd is 19.38%-77.79%.

[0110] (4) PUBC has wider environmental adaptability: PUBC maintains a stable Cd removal rate of 77.98%-83.40% at pH 4-9, with significantly better pH fluctuation resistance than unmodified biochar.

[0111] (5) PUBC has stronger anti-ion interference ability: PUBC shows better Cd removal performance than unmodified biochar.

[0112] (6) Modified biochar has longer service life: N-P co-doping improves structural stability and reduces active site loss. After 10 adsorption-desorption cycles, the PUBC regeneration rate is 89.13% (BC is only 61.29%).

[0113] (7) Synchronous solution of the main producing area cadmium pollution problem: the PUBC and phosphate mineralization bacteria joint preparation of composite material, compared with the control group (CK), single PUBC (T1) and single phosphate mineralization bacteria (T2), the composite material (T3) can effectively reduce the cadmium content in rice and improve the quality and yield of rice grains. Form a "waste pollution control to promote production" multi-effect cycle mode (waste resource + pollution control + crop yield improvement).

[0114] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing modified asparagus straw biochar, characterized in that, The method comprises the following steps: The asparagus straw is modified by a dual modifier, and the modified asparagus straw is dried, pyrolyzed and washed to obtain modified asparagus straw biochar. The mass ratio of the dual modifier to the asparagus straw is 1:(0.8-2), and the dual modifier comprises nitrogen and phosphorus.

2. The production method according to claim 1, characterized by, The mass ratio of the dual modifier to the asparagus straw is 1:

1. Preferably, the dual modifier is at least one selected from urea phosphate, guanidine phosphate, monoammonium phosphate and diammonium phosphate. Preferably, the dual modifier comprises urea phosphate.

3. The preparation method according to claim 1, characterized in that, The modification treatment is performed at room temperature for 20-26 hours. The drying treatment is performed at 75-85°C. The pyrolysis treatment is performed at 480-520°C under a protective atmosphere for 1.8-2.3 hours; preferably, the protective atmosphere is nitrogen or helium. The washing treatment comprises washing until the pH of the washing liquid is constant.

4. The method of claim 1, wherein, The washing treatment is followed by a drying treatment, which is performed at 55-65°C until the weight is constant, to obtain modified asparagus straw biochar.

5. A modified asparagus straw biochar, characterized by, The modified asparagus straw biochar is prepared by the preparation method of any one of claims 1-4.

6. Use of the modified asparagus straw biochar prepared by the preparation method of any one of claims 1-4 or the modified asparagus straw biochar of claim 5 in treating cadmium-contaminated soil or water.

7. Use according to claim 6, characterized in that, In the treatment of cadmium-contaminated soil, the modified asparagus straw biochar is solidified by mineralization bacteria to obtain a composite material. In the solidification treatment, the ratio of the mineralization bacteria to the modified asparagus straw biochar is 1g:2.5mL-1g:20mL; preferably, 1g:7.5mL-1g:12.5mL. Preferably, the mineralization bacteria are phosphate mineralization bacteria, which are at least one selected from Burkholderia, Bacillus and Enterobacter.

8. Use according to claim 7, characterized in that, Enterobacterium is selected from PMB-5 with the preservation number of CGMCC NO. 28795; the taxonomic name is Enterobacter cloacae Enterobacter sp.

9. Use according to claim 7, characterized in that, The solidification treatment is preceded by the expansion culture of the phosphate mineralization bacteria. The culture was carried out at a temperature of 28℃-32℃. After the bacteria reached the logarithmic growth phase, they were collected to prepare a bacterial suspension. The OD value of the bacterial suspension was then adjusted. 600 After the value reaches 0.6-0.8, a solidification treatment is performed; wherein, the culture medium for the expansion culture includes NaCl, peptone, yeast extract powder and solvent in a mass ratio of 1:1:0.5:10; Preferably, sterile normal saline or PBS buffer is added to the collected phosphate mineralization bacteria to obtain a bacterial suspension.

10. Use according to claim 7, characterized in that, The cadmium contamination degree of the soil is 2.4-3.0mg / kg. In the treatment of cadmium-contaminated soil, 0.9%-1.2% of the modified asparagus straw biochar, 0.9%-1.2% of the composite material and 0.9%-1.2% of the bacterial suspension are added to the cadmium-contaminated soil. The number of viable bacteria in the composite material and the bacterial suspension was equal, both being 4.5 × 10⁻⁶. 10 CFU-4.6×10 10 CFU, OD of bacterial suspension 600 The value is 0.8.

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