CEC enhancer modified charcoal fungicide, preparation method and evaluation method

Abstract

The invention relates to a CEC enhancer modified biochar fungicide, a preparation method and an evaluation method, the CEC enhancer modified biochar fungicide comprises: a biochar carrier, which is prepared by pyrolyzing crop straw at 400-600 DEG C under a limited oxygen condition; preliminarily modifying the biochar, mixing and oscillating the biochar carrier and a potassium permanganate solution, performing ultrasonic treatment, filtering, cleaning with pure water, filtering and drying to obtain potassium permanganate modified biochar; the cellulose sulfate is obtained by mixing sulfuric acid and isopropanol at low temperature and then reacting cellulose at low temperature; the reinforcing agent modified biochar is obtained by mixing preliminarily modified biochar and cellulose sulfate in pure water, heating and stirring at 40-60 DEG C, and drying in a vacuum oven; the functional bacterial agent is prepared by the following steps: mixing the reinforcing agent modified biochar with an Rs-2 bacterial suspension, oscillating for 2 hours at the temperature of 30 DEG C and the speed of 170rpm, and carrying out suction filtration and natural air drying, so as to obtain the biochar bacterial agent.

Description

Technical Field

[0001] The present invention relates to the technical field of biochar agents, and in particular to a CEC enhancer-modified biochar agent, a preparation method and an evaluation method. Background Art

[0002] Soil salinization is a global problem affecting agriculture. About 1 billion hectares of land are affected by salinization. At this stage, it is mainly caused by the expansion of irrigated soil area, rising global temperatures, which have led to an increase in agricultural water use, coupled with incorrect soil irrigation methods. The evaporation of groundwater with high Na+ content and the infiltration of large amounts of sodium-containing irrigation water cause a large amount of Na+ to accumulate in the soil, giving the soil the characteristics of sodium saline-alkali soil. The Na+ in sodium saline-alkali soil replaces the Ca in soil colloids. 2+ Mg 2+ This causes soil particle dispersion, reduced permeability, and soil compaction, while also inhibiting microbial activity and disrupting nutrient cycling. Furthermore, high-salinity environments can also cause osmotic stress and ion toxicity in plant roots, inhibiting plant growth, exacerbating soil degradation, and affecting soil productivity, thereby reducing food production and disrupting the international agricultural structure. The main methods for remediating saline-alkali soils include physical, chemical, and biological measures. However, traditional methods are limited to some extent by climatic factors. Furthermore, due to the "salt follows water" characteristic of saline-alkali soils, it is difficult to inhibit the upward movement of salt-induced cations in the soil water and promote the downward movement of ions. Furthermore, repeated salt evaporation and infiltration exacerbate the irreversible process of soil degradation. Microbial improvement technology, with its advantages of being eco-friendly, low-cost, versatile, and having great potential for technological integration, is currently one of the most promising methods for saline-alkali land improvement. Shafi Ullah et al. inoculated different PGPRs in different saline soils and found that Azospirillum brasiliensis promoted the growth of sunflowers at different stages of their development, enhancing their salt tolerance and yield. Many research results show that rhizosphere growth-promoting bacteria interact with plants, improving plant growth, microbial metabolism, and increasing microbial diversity.

[0003] However, microbial remediation is plagued by issues such as inconsistent results, poor adaptability, limited functionality, and technical difficulties in storage. Research has shown that biochar's unique pore structure provides a suitable habitat for microorganisms, partially avoiding ion stress and competition from other microorganisms in high-salinity environments, thus enhancing its potential as a biotransporter. Biochar also has widespread application in saline-alkali soil remediation. As an excellent soil conditioner, biochar has excellent water retention and ion exchange capacity, while also significantly improving soil structure and controlling salt migration. Yuqi Qi et al. used Frankia F1 strains loaded with different biochars to treat ginseng continuous cropping soils, resulting in increases in soil nutrients by 9.1%-55.43%, enzyme activity by 16.8%-52.73%, and microbial abundance by 1.24%-9.81%. Kazem Ghassemi-Golezani et al. used biochar to load rhizosphere bacteria to alleviate salt stress in rapeseed. Potted experiments showed increases in rapeseed seed and oilseed yields by 83-109% and 69-115%, respectively. However, biochar's low density of natural surface functional groups results in weak cation exchange capacity, making it difficult to efficiently adsorb or release nutrients such as potassium and calcium from the soil, and limiting its microbial loading. Furthermore, its uneven pore structure can inhibit vertical water infiltration, resulting in insufficient regulation of downward water flow and hindering the coordinated transport of water and nutrients. Therefore, modifying biochar to improve cation exchange capacity, microbial loading, and water retention is a bottleneck in saline-alkali soil improvement. Yanru Wang et al. used HCl solution to immobilize Pseudomonas juncea CN-1 on biochar, achieving a 78.7% removal rate of the fungicide carbendazim in soil. The modified biochar immobilized >80% of the microbes. Our research group also modified saline-alkali soil by loading Enterobacter homae Wu-15 with Ca₃(PO₄)₂ and MgO. The modified biochar increased microbial adsorption by 10.37%-11.1%, reduced soil ESP and EC by 53.6% and 46.7%, and increased SOM and AP by 25.94% and 13.85-fold, respectively. In general, modified biochar can better adsorb excess Na in soil + and release Ca 2+ / Mg 2+ , reducing the sodium adsorption ratio and pH value.

[0004] Cellulose sulfate (CS) is rich in sulfate and carboxyl groups, which give it excellent cation exchange capacity. It also has advantages such as gelation and film-forming properties, and is used as a soil remediation and adsorbent. Wenqian Li et al. reacted CS with chitosan to load Fe3O4 to produce a new mesoporous microsphere adsorbent. When CHT:CS=1:6, the sulfate groups of CS and the amino groups of CHT increased its adsorption capacity for Congo red to 66%. According to the ion exchange mechanism, the new adsorbent is highly selective, and the removal rate follows the Zn 2+ >Cu 2+ >Cr 2+ >Pb2+>Cd2+, among which the rate of Zn 2+ The adsorption rate reached 96.6%. Komal et al. loaded sulfated cellulose onto GO, SGO, and CGO using toluene and pyridine as catalysts. They demonstrated that the carboxyl groups on CGO formed a hydrogen bond network with ECNF, improving adsorption performance. The adsorption of ciprofloxacin and ofloxacin reached 45.05 mg / L and 85.3 mg / L, respectively. Vanja Kokol et al. prepared microporous CNF-CA membranes with high fluidity and cation exchange properties by in situ covalent crosslinking (esterification) of cellulose with citric acid, a crosslinker and a carboxyl source. The electrostatic interaction of the negatively charged particles (carboxyl groups), membrane wetting / swelling, and high hydrophilicity improved membrane permeability (>87%), protein adsorption by 10%-20%, and desorption by >98%. Furthermore, the compressive elastic modulus of CNFs at different ratios increased to 20 kPa, influenced by the degree of esterification / crosslinking. Later, VanjaKokol added carboxymethyl fiber to the microporous CNF-CA membrane to prepare CMC-CNF-CA membrane. The carboxyl groups on CA, the esterification of CNF, and the CMC-enhanced membrane surface active sites further improved the cation exchange and loading capacity of the membrane. The static binding capacity (SBC) of CMC-CNF-CA for lysozyme within 3.3 hours was 370-1080 mg / g, the dynamic binding capacity (DBC) was 165-417 mg / g, the elution yield was 78-99%, and the recovery rate was >95%

[23] . Therefore, in order to solve the problems of weak cation exchange capacity and limited microbial load of biochar agents, it was proposed to modify biochar with CS to enhance the effect of biochar agents in improving sodium saline-alkali soil. Summary of the Invention

[0005] This application, based on the characteristics of sodium saline-alkali soil and long-term treatment goals, improves the cation exchange capacity and adsorption capacity of PGPR by modifying the biochar agent with CS, thereby enhancing the treatment effect of saline-alkali soil. At the same time, biochar is modified by means of chemical oxidation, mineral loading (such as calcium phosphate modification) or functional group introduction (such as potassium permanganate modification), which increases the water retention of biochar, provides more nutrients to the soil, further enhances its ion exchange capacity, etc., and significantly improves the improvement effect of biochar agent on saline-alkali soil. The effects of CS, calcium phosphate and potassium permanganate on the microstructure of biochar and the loading performance of biochar on microorganism Rs-2 are explored; the improvement effect of modified biochar agent on sodium saline-alkali soil and its salt-dissolving and growth-promoting performance on plants are explored through potted experiments; the improvement principle of biochar agent on sodium saline-alkali soil in the biochar-Rs-2-crop-salt-alkali soil system is explained. The use of CS modified biochar agent with strong cation exchange capacity provides a new technology for its treatment of saline-alkali land.

[0006] Its main technical solutions are as follows:

[0007] The present invention provides a CEC enhancer modified biochar agent, comprising:

[0008] Biochar carrier, produced by pyrolysis of crop straw at 400-600°C under oxygen-limited conditions;

[0009] The biochar was initially modified by mixing the biochar carrier with a potassium permanganate solution, shaking, ultrasonicating, filtering, washing with pure water, filtering, and drying to obtain a potassium permanganate-modified biochar;

[0010] Cellulose sulfate, obtained by mixing sulfuric acid and isopropyl alcohol at low temperature and then reacting cellulose at low temperature;

[0011] Enhancer modified biochar, which is obtained by mixing the preliminary modified biochar and cellulose sulfate in pure water, heating and stirring at 40-60°C, and drying in a vacuum oven;

[0012] Functional bacterial agent: the enhancer-modified biochar was mixed with the Rs-2 bacterial suspension, shaken at 170 rpm and 30 °C for 2 h, filtered, and naturally air-dried to obtain the biochar agent;

[0013] The CEC enhancer is loaded in the pores of biochar, the functional bacteria are embedded in the enhancer-biochar composite matrix, and the cellulose sulfate and Ca 2+ Generate electrostatic / electronic cross-linking to form a network structure.

[0014] Furthermore, the surface of the enhancer-modified biochar is composited with calcium phosphate and cellulose sulfate.

[0015] Further, cellulose sulfate and preliminary modified biochar are mixed in pure water at a ratio of 1:5, wherein the ratio of Ca3(PO4)2 to cellulose sulfate is not less than 1:0.25 and not more than 1:1.

[0016] The present invention also provides a method for preparing a CEC enhancer-modified biochar agent, which is used for preparing the above-mentioned CEC enhancer-modified biochar agent, comprising the following steps:

[0017] The biochar carrier is prepared by pyrolyzing crop straw at 400-600°C under oxygen-limited conditions;

[0018] The biochar carrier and the potassium permanganate solution are mixed, shaken, ultrasonicated, filtered, washed with pure water, filtered and dried to obtain potassium permanganate-modified biochar;

[0019] Sulfuric acid and isopropyl alcohol are mixed at low temperature and then reacted with cellulose at low temperature to obtain modified cellulose sulfate;

[0020] The preliminarily modified biochar and cellulose sulfate are mixed in pure water, heated and stirred at 40-60° C., and then dried in a vacuum oven to obtain the enhancer-modified biochar;

[0021] The enhancer-modified biochar was mixed with the Rs-2 bacterial suspension, shaken at 170 rpm and 30°C for 2 h, filtered, and naturally air-dried to obtain a biochar agent.

[0022] Furthermore, the biochar carrier is prepared according to the following method:

[0023] Place the crushed corn stalks in a forced air drying oven at 100°C to dry them to remove excess moisture, then crush them in a crusher and pass through an 80-mesh sieve;

[0024] 25 g of corn straw and a mixture of corn straw and Ca3(PO4)2 were added to 125 mL of deionized water and stirred at 350 rpm for 45 min to mix them completely to obtain a mixed solution 1;

[0025] The mixed solution was placed in an oven at 80°C for drying, and then crushed to pass through a 60-mesh sieve to obtain a processed sample;

[0026] The treated sample was transferred to a corundum ark reactor and placed in a tube furnace for pyrolysis. The heating rate was 10 °C min-1 under the condition of N2 flow rate of 150 mL min-1. -1 , raise the temperature to 500℃ and maintain it for 2h, then cool it down and take it out to obtain the biochar carrier.

[0027] Furthermore, the preparation method of the enhancer-modified biochar includes:

[0028] The biochar carrier and potassium permanganate solution were mixed in a ratio of 1:8, shaken, and ultrasonicated, and then filtered and washed with pure water until the pH reached a stable level, and then filtered and dried to obtain potassium permanganate-modified biochar;

[0029] Then, the cation exchange enhancer was modified to prepare cellulose sulfate. Sulfuric acid and isopropyl alcohol were mixed at a ratio of 1:1 at low temperature, and then 6.25% cellulose was added and reacted at low temperature for 1 hour. The mixture was washed with isopropyl alcohol and ethanol, and dried for later use to obtain cellulose sulfate.

[0030] The prepared cellulose sulfate and biochar carrier were mixed in pure water at a ratio of 1:5, then heated and stirred at 50°C for 3 hours, and dried in a vacuum oven for 48 hours to obtain preliminary modified biochar, in which the ratio of Ca3(PO4)2 to cellulose sulfate was not less than 1:0.25 and not higher than 1:1.

[0031] Furthermore, the Rs-2 bacterial suspension was prepared as follows:

[0032] Preparation of LB medium: Weigh 2 g of peptone, 2 g of sodium chloride, and 1 g of yeast extract powder into a 250 ml conical flask, add 200 ml of deionized water, pH 7.0-7.2, and sterilize the prepared LB medium in a high-temperature and high-pressure sterilizer at 121°C for 20 min. After cooling, remove from the oven and set aside.

[0033] Solid culture medium preparation steps: Weigh 2g of peptone, 2g of sodium chloride, 1g of yeast extract powder, and 4g of peptone into a 250ml conical flask, add 200ml of deionized water, and then sterilize the prepared solid culture medium in a high-temperature and high-pressure sterilizer at 121°C for 20 minutes. Pour the unsolidified liquid solid culture medium into a culture dish and wait for it to solidify before use;

[0034] Preparation of bacterial suspension: Inoculate 2% Rs-2 seed solution into a 250 ml conical flask containing 200 ml of LB medium on a clean bench. Incubate at 170 rpm and 30°C for 24 h. Centrifuge at 6500 rpm and 4°C for 8 min in a low-temperature high-speed centrifuge. Rinse twice with deionized water. Then add an equal amount of deionized water to prepare the Rs-2 bacterial suspension.

[0035] Furthermore, during the preparation of the biochar agent, the dried enhancer-modified biochar was mixed with the Rs-2 bacterial suspension at a ratio of 1:1 (m:V), shaken at 170 rpm and 30°C for 2 h, filtered, and naturally air-dried to obtain the biochar agent.

[0036] The present invention also provides an evaluation method for evaluating the CEC enhancer-modified biochar agent, wherein the evaluation method is used to evaluate the characterization of the biochar agent, wherein the characterization of the biochar agent includes: adsorption performance evaluation, compatibility evaluation of the biochar agent with the rhizosphere growth-promoting bacteria Rs-2, and water holding capacity evaluation of the modified biochar agent.

[0037] Furthermore, the adsorption performance assessment includes the following steps:

[0038] After culturing Rs-2 for 24 hours, the bacterial solution was centrifuged at 6500 rpm for 6 minutes to obtain Rs-2 cells, which were then washed three times with pH 7.0 buffer and resuspended in a 1:1 ratio to obtain an Rs-2 bacterial suspension.

[0039] 100 mg of modified biochar was placed in a 50 mL conical flask, and then 20 mL of Rs-2 bacterial suspension was added and placed in a shaker at a temperature of 28 ° C and a rotation rate of 170 rpm for 2 hours. The biochar adsorption equilibrium concentration was determined, and then 1 mL of the mixture of Rs-2 and biochar was drawn, and then centrifuged at 1500 rpm for 5 minutes. The supernatant was taken and the colony count of the bacterial suspension and the supernatant was determined by the plate count method to obtain the adsorption capacity of the modified biochar for Rs-2.

[0040] Furthermore, the compatibility assessment method of the biochar agent and the rhizosphere growth-promoting bacteria Rs-2 includes:

[0041] Take 100 mL of the culture medium of Rs-2 grown for 24 hours, centrifuge at 2000 rpm for 10 minutes, discard the supernatant, and add 50 mL of sterile water;

[0042] After heating the bacterial suspension in a 60°C water bath for 30 minutes, centrifuge at 8000 rpm for 10 minutes. The supernatant is filtered through a 0.22 μm filter to obtain a twice-concentrated EPS solution. Determination of polysaccharide content in EPS: The phenol-sulfuric acid method is used to determine polysaccharide content. To measure polysaccharides, 1 mL of sample or standard glucose solution of varying concentrations is added to 1 mL of each solution, followed by 5 mL of concentrated sulfuric acid and rapid shaking. After incubation at room temperature in the dark for 20 minutes, the absorbance is measured at 490 nm. A standard curve is plotted with the polysaccharide concentration on the horizontal axis and the absorbance on the vertical axis to calculate the polysaccharide concentration in the sample.

[0043] Determination of protein content in EPS: Use Coomassie Brilliant Blue G250 to determine the protein content. Take 5 mL of sample or standard protein solution of different concentrations and add 5 mL of Coomassie Brilliant Blue G-250. After shaking, react for 5 minutes and then measure the absorbance at 595 nm. The horizontal axis is the protein concentration and the vertical axis is the absorbance. Draw a standard curve and calculate the protein content in the sample based on the standard curve.

[0044] Furthermore, the water holding capacity evaluation method of the modified biochar agent includes:

[0045] 100.0 g of air-dried loam was passed through a 20-mesh sieve, mixed with the materials in proportion, and transferred to a plastic bottle with a diameter of 4.5 cm and a height of 15 cm. The mixture of soil and materials was weighed as m1, and then deionized water was slowly added to the bottle until the soil was saturated and weighed again as m2. The water holding capacity (WHR%) of the material was calculated using the following equation:

[0046]

[0047] Where WHR% represents the water holding rate of the material, m1 represents the weight of the container and material before absorbing water, and m2 represents the weight of the container and material after absorbing water;

[0048] The weighed plastic bottles m2 were incubated at 25°C for 30 days. The bottles were recorded at specified time intervals and recorded by m x The material is weighed and its water holding capacity (WR%) is calculated using the following equation:

[0049]

[0050] Where m1 represents the weight of the entire container before absorbing water, m x Indicates the weight of the container at each specified time interval.

[0051] In this study, corn straw was used as raw material and calcium phosphate was added to prepare biochar. Then, potassium permanganate and CS were used to modify and load the rhizosphere growth-promoting bacteria Rs-2 to obtain the biochar agent. At the same time, SEM, infrared, and contact angle characterization methods showed that the CS-modified biochar introduced a large number of hydrophilic functional groups, which increased its water retention capacity and adsorption capacity. 2+ Electrostatic / electronic cross-linking is generated to form a network structure, which increases the surface active sites and improves the adsorption capacity.

[0052] (2) The rhizosphere growth-promoting bacteria Rs-2 were loaded onto the modified biochar, and the two had good compatibility. The colony count adsorbed by Rs-2 reached 17.5◇109 CFU / mL, and the protein and polysaccharide produced by Rs-2 reached 1.15 mg / mL and 415.2 μg / mL.

[0053] (3) The introduction of CS increased the sulfate groups, -OR, -COOR, -PO4R, Ca2+, etc. on the surface of biochar, increasing the cation exchange capacity to 70 cmol / kg; at the same time, -OH, -COOH, and -PO4R improved the water retention capacity of the biochar agent, among which SD, WHR, and WR increased by 273.72%, 42.07%, and 19.09%, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0055] Figure 1 The distribution in the middle is SEM images of CS (a), KBC (b), CS-BC (c), 10CS-BC (d), 5CS-BC (e), 3CS-BC (f), and 2.5CS-BC (g) and EDS element distribution map of 5CS-BC (h);

[0056] Figure 2 X-ray photoelectron spectra of CS (a), KBC (b), CS-BC (c), 10CS-BC (d), 5CS-BC (e), 3CS-BC (f), and 2.5CS-BC (g);

[0057] Figure 3 FTIR spectra of CS, KBC, CS-BC, 10CS-BC, 5CS-BC, 3CS-BC, and 2.5CS-BC, respectively;

[0058] Figure 4 XRD patterns of CS, KBC, CS-BC, 10CS-BC, 5CS-BC, 3CS-BC, and 2.5CS-BC, respectively;

[0059] Figure 5 Contact angle reflection diagrams of CS (a), KBC (b), CS-BC (c), 10CS-BC (d), 5CS-BC (e), 3CS-BC (f), and 2.5CS-BC (g);

[0060] Figure 6 Physicochemical properties of biochar modified by pH (a) and EC (b) of KBC, CS-BC, 2.5CS-BC, 3CS-BC, 5CS-BC, and 10CS-BC, respectively;

[0061] Figure 7 These are the reflection diagrams of CEC of KBC, CS-BC, 2.5CS-BC, 3CS-BC, 5CS-BC, and 10CS-BC;

[0062] Figure 8Reflects the colony count (a) of KBC, CS-BC, 2.5CS-BC, 3CS-BC, 5CS-BC, and 10CS-BC loaded with microorganism Rs-2, as well as the protein (b) and polysaccharide (c) contents produced after loading with microorganism Rs-2;

[0063] Figure 9 It reflects the swelling degree SD (a), water holding rate WHR (b) and water holding capacity WR (c) of KBC-Rs-2, CS-BC-Rs-2, 2.5CS-BC-Rs-2, 3CS-BC-Rs-2, 5CS-BC-Rs-2 and 10CS-BC-Rs-2 at different times. DETAILED DESCRIPTION

[0064] To make the purpose, technical solutions and advantages of the present invention clearer, the following Figure 1-3 The embodiments of the present invention are described in further detail.

[0065] The experimental instruments and corresponding experimental reagents used in this application are described as follows:

[0066] Table experimental instruments

[0067] Table Experimental apparatus

[0068]

[0069] Experimental reagents

[0070] Table of experimental reagents

[0071] Table Experimentalreagent

[0072]

[0073]

[0074] The preparation method for enhancer-modified biochar includes: purchasing crushed corn straw in a forced air drying oven at 100°C to remove excess moisture, then pulverizing it in a crusher and passing it through an 80-mesh sieve to obtain a finer powder. 25g of corn straw and a mixture of corn straw and Ca₃(PO₄)₂ were added to 125mL of deionized water and stirred at 350rpm for 45 minutes to thoroughly mix. The mixed solution was dried in an oven at 80°C and then pulverized until it passed through a 60-mesh sieve. Finally, the treated sample was transferred to a corundum Ark reactor and pyrolyzed in a tube furnace. Under an N₂ flow rate of 150mLmin⁻¹, the temperature was increased at a rate of 10°Cmin⁻¹ to 500°C and maintained for 2 hours. After cooling, the biochar (BC) sample was removed. The sample was mixed with potassium permanganate solution at a ratio of 1:8, shaken, and sonicated. The modified biochar was then filtered and washed with pure water until the pH reached a stable level. The resulting KBC was filtered and dried to obtain potassium permanganate-modified biochar (KBC). Cellulose sulfate was then prepared by mixing sulfuric acid and isopropanol at a ratio of 1:1 at low temperature. 6.25% cellulose was then added and reacted at low temperature for 1 hour. The mixture was then washed with isopropanol and then ethanol, and air-dried for later use. The resulting cellulose sulfate (CS) was then mixed with modified biochar in pure water at a ratio of 1:5, with the Ca₃(PO₄)₂ to CS ratios of 1:0.25, 1:0.3, 1:0.5, and 1:1. The mixture was heated and stirred at 50°C for 3 hours and dried in a vacuum oven for 48 hours. The dried samples were named CS-BC, 2.5CS-BC, 3CS-BC, 5CS-BC, and 10CS-BC, respectively.

[0075] The preparation method of Rs-2 bacterial suspension includes: LB culture medium: weigh 2g of peptone, 2g of sodium chloride, and 1g of yeast extract powder into a 250ml conical flask, add 200ml of deionized water, and the pH value is 7.0-7.2. Then, place the prepared LB culture medium in a high-temperature and high-pressure sterilizer at 121°C for 20 minutes, and take it out after cooling for use.

[0076] Solid culture medium: Weigh 2g of peptone, 2g of sodium chloride, 1g of yeast extract powder, and 4g of peptone into a 250ml conical flask, add 200ml of deionized water, and then place the prepared solid culture medium in a high-temperature and high-pressure sterilizer at 121℃ for 20min. Pour the unsolidified liquid solid culture medium into a culture dish and wait for it to solidify before use.

[0077] On a clean bench, 2% Rs-2 seed liquid was inoculated into a 250ml conical flask containing 200ml LB culture medium, cultured at 170rpm and 30℃ for 24h, then centrifuged at 4℃ and 6500rpm for 8min in a low-temperature high-speed centrifuge, washed twice with deionized water, and then an equal amount of deionized water was added to prepare an Rs-2 bacterial suspension.

[0078] The preparation method of biochar agent includes: taking a certain amount of dry biochar and mixing it with Rs-2 bacterial suspension in a ratio of 1:1 (m:V), shaking at 170 rpm and 30°C for 2 h, filtering, and air-drying to obtain biochar agents, which are recorded as KBC-Rs-2, CS-BC-Rs-2, 2.5CS-BC-Rs-2, 3CS-BC-Rs-2, 5CS-BC-Rs-2, and 10CS-BC-Rs-2.

[0079] Biochar characterization included analysis of the pore size distribution and internal network structure using a Hitachi JSM-6700F scanning electron microscope (SEM), and elemental composition analysis using EDS. X-ray photoelectron spectroscopy (XPS, Escalab 250xi, USA) with a resolution of less than 0.5 eV and XPS Peak Spectroscopy 4.1 software was used to analyze and visualize the C1s, Ca 2p, S2p, and P 2p peaks. Fourier transform infrared spectroscopy (FTIR, Nicolet Avatar 360, USA) was recorded between 4000 and 400 cm⁻¹ with a resolution of 4 cm⁻¹. X-ray diffraction results were recorded on an X-ray diffractometer (XRD, D8 Advance, Bruker, Germany) using Cu Kα (λ = 1.54056 Å) radiation at 40 kV and 40 mA. The contact angle was measured using a contact angle meter (OSA200 series) and the material was tableted using a tablet press. The measurement angle range was 10°-80°.

[0080] Adsorption experiment: The number of microbial colonies on modified biochar was determined to explore the adsorption behavior of biochar on Rs-2. After culturing Rs-2 for 24 hours, the bacterial solution was centrifuged at 6500 rpm for 6 minutes to obtain Rs-2 cells. The cells were then washed three times with PBS (pH = 7.0) buffer and resuspended in a 1:1 ratio to obtain an Rs-2 suspension. 100 mg of modified biochar CS-BC, 2.5 CS-BC, 3 CS-BC, 5 CS-BC, and 10 CS-BC were placed in a 50 mL conical flask, and 20 mL of Rs-2 suspension was added. The mixture was placed in a shaker for 2 hours (28°C, 170 rpm) to determine the equilibrium concentration of biochar adsorption. 1 mL of the Rs-2 and biochar mixture was then aspirated and centrifuged at 1500 rpm for 5 minutes. The supernatant was collected and the colony counts of the bacterial suspension and supernatant were determined by plate count to obtain the adsorption capacity of modified biochar on Rs-2.

[0081] Compatibility of biochar with the growth-promoting rhizobacterium Rs-2: Extraction of EPS from Wu-15: Take 100 mL of a 24-hour-old Rs-2 culture and centrifuge at 2000 rpm for 10 minutes. Discard the supernatant and add 50 mL of sterile water. To remove impurities from the culture medium, rinse twice: centrifuge at 2000 rpm for 3 minutes, discard the supernatant, and add 50 mL of sterile water. Finally, extract EPS: Heat the bacterial suspension in a 60°C waterbath for 30 minutes, then centrifuge at 8000 rpm for 10 minutes. Pass the supernatant through a 0.22 μm filter to obtain a twice-concentrated EPS solution.

[0082] Determination of polysaccharide content in EPS: Polysaccharides were determined using the phenol-sulfuric acid method. To each sample or standard glucose solution of varying concentrations, 1 mL of 6% phenol was added, followed by 5 mL of concentrated sulfuric acid and rapid shaking. The mixture was incubated in the dark for 20 minutes at room temperature, and the absorbance was measured at 490 nm. A standard curve (y = 0.0178x - 0.079, R² = 0.9992) was plotted with polysaccharide concentration on the abscissa and absorbance on the ordinate, to calculate the polysaccharide concentration in the sample. Each treatment was repeated three times.

[0083] Determination of protein content in EPS: Protein content was determined using Coomassie Brilliant Blue G-250. Add 5 mL of sample or standard protein solution of varying concentrations to 5 mL of Coomassie Brilliant Blue G-250, shake well, and react for 5 minutes. The absorbance was then measured at 595 nm. The abscissa represents protein concentration, and the ordinate represents absorbance. A standard curve (y = 7.2051x + 0.0967, R² = 0.9955) was plotted and used to calculate the protein content of the sample. Each treatment was repeated three times.

[0084] Water retention properties of modified biochar: (1) Water absorption rate:

[0085] 0.1 g of material (mo) was added to a 1000 mL beaker containing 1000 mL of deionized water and soaked at 25°C for 24 hours. The swollen hydrogel (m1) was filtered through a 200-mesh filter bag to remove excess water. The swelling degree (SD) of the product was calculated using the following equation:

[0086]

[0087] Where SD represents the water absorption performance of each material, mo represents the mass of the material before water absorption, and m1 represents the mass of the material after water absorption.

[0088] (2) Water holding capacity of modified biochar agent:

[0089] A total of 100.0 g of air-dried loam was passed through a 20-mesh sieve, mixed with the materials in the appropriate proportions, and transferred to a plastic bottle with a diameter of 4.5 cm and a height of 15 cm. The soil and material mixture (m1) was weighed, and deionized water was slowly added to the bottle until the soil was saturated. The mixture (m2) was weighed again. Experimental groups were designed with various material ratios, as well as a control group without material addition. The water retention rate (WHR%) of the materials was calculated using the following equation.

[0090]

[0091] Where WHR% represents the water holding rate of the material, m1 represents the weight of the container and material before absorbing water, and m2 represents the weight of the container and material after absorbing water.

[0092] The weighed plastic bottles m2 were incubated at 25°C for 30 days. The bottles were recorded at designated time intervals (1, 3, 5, 7, 10, 15 days) and the weight of the bottles was recorded as m2. x The water holding capacity (WR%) of the material was calculated using the following equation.

[0093]

[0094] Where m1 represents the weight of the entire container before absorbing water, m x Indicates the weight of the container at each specified time interval.

[0095] Statistics: Microsoft Excel, Origin, and SPSS were used for data processing and one-way ANOVA was used to analyze the data statistically, and p < 0.05 was used as the standard to determine the significant differences among the treatments.

[0096] Results and Analysis:

[0097] Results and physicochemical properties of modified biochar gel (other characterizations of gel):

[0098] Refer to the attached Figure 1, scanning electron microscopy (SEM) analysis, EDS;

[0099] Figure 1 SEM images of CS (a), KBC (b), CS-BC (c), 10CS-BC (d), 5CS-BC (e), 3CS-BC (f), and 2.5CS-BC (g), and EDS element distribution map of 5CS-BC (h)

[0100] As shown in Figure 1(ag), scanning electron micrographs (a) show that the esterification reaction disrupts the original regular arrangement and hydrogen bond network between cellulose molecular chains, resulting in disordered arrangement. This results in a rough surface of the resulting cellulose sulfate (CS), with minor undulations, wrinkles, and depressions, indicating a certain cation exchange capacity. Scanning electron micrographs (bg) show that the surface of the potassium permanganate-modified biochar is highly porous, exhibiting varying degrees of regular arrangement and collapse depending on the addition ratio of calcium phosphate to cellulose sulfate. This is likely due to the strong oxidizing properties of potassium permanganate, which alters the biochar structure. Furthermore, the presence of calcium phosphate and cellulose sulfate on the biochar surface clearly indicates that the biochar has increased active sites, facilitating the adsorption of nutrients and microorganisms, while also increasing hydrophilicity, producing gel-like properties, and cation exchange capacity. However, the KBC particles may be metal oxides or minerals produced by the reaction of potassium permanganate as a strong oxidant. The element image (h) of 5CS-BC shows that the surface of the modified biochar is rich in C, P, O, Ca, and S, which further indicates that calcium phosphate and cellulose sulfate are successfully compounded on the surface of the biochar. These elements can provide additional nutrients for the loaded rhizosphere growth-promoting bacteria Rs-2, improve bacterial activity and compatibility, and at the same time increase the cation exchange capacity of the modified biochar under the action of cellulose sulfate. Calcium phosphate provides a large amount of Ca 2+ , improve its Na + The replacement of Na+ improves soil quality, and rhizospheric growth-promoting bacteria reduce the stress of Na+ on plants, thereby promoting plant growth.

[0101] X-ray photoelectron spectroscopy (XPS) analysis:

[0102] Figure 2 X-ray photoelectron spectra of CS (a), KBC (b), CS-BC (c), 10CS-BC (d), 5CS-BC (e), 3CS-BC (f), and 2.5CS-BC (g); Figure 2The XPS spectrum in further shows the surface element composition and valence states of C, Ca, P, and S on the biochar surface. It can be seen that after potassium permanganate modification of biochar, the functional groups on the biochar surface are oxidized, resulting in a significant increase in oxygen content, which indicates that there are more oxygen-containing functional groups (such as ester groups and hydroxyl groups) on the modified biochar. The high-resolution C1s XPS spectrum shows two peaks at 284.8 and 286 eV, which are divided into C=C / C–C and COC. In the high-resolution scan of Ca 2p, 347.5 eV and 351 eV respectively indicate that they belong to Ca2p. 3 / 2 and Ca2p 1 / 2 orbitals, corresponding to the trivalent and divalent states of Ca.

[0103] At the same time, the relative phosphorus content on the surface of the modified biochar was significantly increased, with 5CS-BC and 2.5CS-BC having the highest content, indicating that calcium phosphate was successfully composited onto the biochar. In the high-resolution scanning image of P 2p, after adding calcium phosphate and cellulose sulfate, the P 2p near 133.5eV increased significantly. 3 / 2 The peak is PO / P=O, and it can be clearly seen that the atomic ratio and content have increased significantly. This may be due to the oxidizing ability of potassium permanganate, which produces H2PO4, HPO4 2- PO4 3- and other metal phosphates, while the P2p of CS-BC 3 / 2 The peak enhancement may be due to the fact that potassium permanganate oxidation produces a certain catalytic ability on the surface of biochar, and some active sites on its surface may promote the reaction of phosphorus compounds in the environment with cellulose sulfate or biochar to generate new phosphorus-containing substances. 1 / 2 The peak indicates that phosphorus may have combined with oxygen-containing functional groups on the biochar surface to form new phosphorus-containing functional groups (such as CO-PO3). This is likely due to the oxidative effect of potassium permanganate, oxygen during the reaction, temperature, crystal deformation, and other factors that break the chemical bond between biochar and metal phosphate. Therefore, the modification of biochar with cellulose sulfate and calcium phosphate combined with potassium permanganate can change the oxygen- and phosphorus-containing functional groups on the biochar surface, increase the cation exchange capacity, nutrient content, and adsorption capacity of the modified biochar, and improve the effect of saline-alkali land improvement.

[0104] In the high-resolution scan of S2p, S2p near 166.5ev, 169ev and 170ev 3 / 2 and S2p 1 / 2Peaks were identified, indicating sulfur-containing oxidation states or organic sulfides. This is likely due to potassium permanganate oxidation of the biochar, which enhances its interactions with other molecules and provides more binding sites for subsequent loading. The sulfur groups on cellulose sulfate react with the binding sites on the biochar, resulting in the formation of sulfonyl groups and small amounts of metal sulfates on the biochar surface. Therefore, the modified biochar possesses a certain acidity, which can reduce the alkalinity of saline-alkali soils. The loading of cellulose sulfate can also increase the water retention properties of the biochar.

[0105] Fourier transform infrared spectroscopy (FTIR) analysis:

[0106] Figure 3 These are the FTIR spectra of CS, KBC, CS-BC, 10CS-BC, 5CS-BC, 3CS-BC, and 2.5CS-BC respectively; the cation exchange capacity of biochar materials is related to the oxygen-containing functional groups on the biochar, such as hydroxyl (-OH), carboxyl (-COOH), and phenol (-OH). The presence of phosphorus-containing functional groups such as P=O and PO in biochar also shows that the biochar material has good nutrients. At the same time, cellulose sulfate contains -SO3H, which has a certain cation exchange capacity. Figure 2-3 The FTIR spectrum in the figure shows the changes in the functional groups on the surface of biochar. -1 The stretching vibration of phenolic hydroxyl group (-OH) was observed at 1700-1750cm -1 The stretching vibration of C=O and 1600-1400cm -1 The stretching vibration of CO further proves the existence of carboxyl group (-COOH), which is mainly caused by potassium permanganate oxidizing the biochar surface and increasing the oxygen-containing functional groups on the biochar surface.

[0107] 1200-1100cm -1 The stretching vibration of -SO3H and OS at 1000cm -1 The increase in the peak intensity may be due to the loading of a large amount of cellulose sulfate on the modified biochar, or the interaction between the active sites on the biochar surface and the cellulose sulfate to form new hydrogen bonds, etc. At the same time, the peak intensity of 1400-1600 cm -1 The peak at is usually SO4 2- and SO3 2- The stretching vibration of S=O in the matrix further proves that cellulose sulfate is successfully composited onto biochar.

[0108] -OH, P=O groups at 3600-3200 cm -1 、1583-1625cm -1The peak at is enhanced, which may be due to the stretching of PO-C, the distribution of hydrogen bond PO groups, etc., indicating that after the addition of calcium phosphate, phosphoric acid, (hydrogen) phosphate, phosphorus-containing oxides, etc. appear under the multiple effects of potassium permanganate and cellulose sulfate.

[0109] Figure 4 XRD patterns of CS, KBC, CS-BC, 10CS-BC, 5CS-BC, 3CS-BC, and 2.5CS-BC, respectively; Figure 4 Figure 2 shows the XRD patterns of the prepared CS and different biochars. KBC (KBC) shows that corn straw, which contains small amounts of elements such as K and Ca, is modified with potassium permanganate and CS to form CaCO₃ (2θ = 29.4°), K₂C₂O₆ (2θ = 68°), and C₃SO₃ (2θ = 50.5°). After calcium phosphate modification, the main diffraction peaks in KBC-2Ca-CS, KBC-4Ca-CS, KBC-6Ca-CS, and KBC-8Ca-CS are attributed to C₄H₆CaO₃S₆₃H₂O (2θ = 25.7°, 26.5°, and 32.8°), Ca₂(CO₃)SO₄₄H₂O (2θ = 29.3°, 49.5°, and 64°), and C₂H₆CaO₆S₂ (2θ = 31.7° and 39.6°). Figure 4 It can be seen that CS and calcium phosphate were successfully loaded onto biochar, and CS reacted with the calcium-containing functional groups on biochar, improving the physical and chemical properties of biochar to a certain extent.

[0110] Figure 5 Contact angles of CS (a), KBC (b), CS-BC (c), 10CS-BC (d), 5CS-BC (e), 3CS-BC (f), and 2.5CS-BC (g); Water drop test (WDT) was performed on biochar, biochar with CS and calcium phosphate added to analyze the contact angles of microdroplets on the sample surface, such as Figure 2-5 (a) and (b), the contact angles of CS and KBC are 45.2° and 40.4° respectively, and the kinship is poor, but Figure 2-5 The contact angle of CS-BC in (c) is 24.1°, indicating that the addition of CS changes the functional groups (-OH, -COOH) on the surface of biochar, weakening the hydrophobicity of the ester group and enhancing the hydrophilicity of the sulfonic acid group, thus changing the hydrophilicity of the modified biochar. At the same time, the addition of calcium phosphate further enhances the hydrophilicity of the modified biochar. Figure 2-5 (d), (e), (f), (g), the contact angles of 10CS-BC, 5CS-BC, 3CS-BC, and 2.5CS-BC are 39.5°, 37.6°, 30.2°, and 37.9°, respectively. The addition of calcium phosphate increases the content of phosphorus-containing functional groups, especially phosphate groups, in the modified biochar, which is consistent with the Figure 2-4The FTIR spectra of the modified biochar were consistent with those of the control group, indicating that the phosphorus-containing functional groups increased the hydrophilicity of the modified biochar.

[0111] Figure 6 Physicochemical properties of biochar modified with KBC, CS-BC, 2.5CS-BC, 3CS-BC, 5CS-BC, and 10CS-BC, respectively, are shown in Figures (a) and (b). Because saline-alkali soils inherently have high pH and alkalinity, the addition of soil amendments such as biochar may exacerbate soil alkalinity due to their inherent alkalinity. Furthermore, the high temperatures experienced during the pyrolysis process may further increase the alkalinity of some biochars, leading to the production of hazardous substances (such as polycyclic aromatic hydrocarbons), potentially negatively impacting soil ecosystems. Figure 2-6 As shown in the figure, it can be seen that after biochar is modified with CS, its pH value is significantly reduced and its EC is greatly increased. The pH value of 5CS-BC is 7.05 and the EC is 173.1μs / cm. This may be because the acidity and complexing solubility of CS change the physical and chemical properties of the modified biochar, resulting in a decrease in pH value; and the increase in EC may be due to the ionization of sulfur-containing groups on CS and the release of H by CS acidic ionization. + The addition of CS enhanced the surface charge of the modified biochar. Therefore, the changes in the physical and chemical properties of modified biochar can, to a certain extent, increase the ion exchange capacity of the soil, reduce the soil ion content, and change enzyme activity and microbial community structure.

[0112] Figure 7 The CEC reflection diagrams are KBC, CS-BC, 2.5CS-BC, 3CS-BC, 5CS-BC, and 10CS-BC respectively; the ion exchange capacity of biochar reflects the ability to maintain soil fertility. Biochar with stronger ion exchange capacity is better at adsorbing Na+ and replacing Ca 2+ , reducing the stress of sodium ions in sodium saline-alkali soil on plants has many great effects. Figure 2-7It can be seen that the modified biochar prepared by adding CS, biomass and calcium phosphate in a ratio of 1:0.4 has the best ion exchange capacity, reaching 70 coml / kg. However, compared with KBC, the ion exchange capacity of CS-BC is not much different. This may be because: (1) Potassium permanganate significantly oxidatively modifies the surface of biochar, introducing a large number of carboxyl functional groups, lactone group conjugates, aromatic compounds, etc. on the surface of biochar, thereby improving the adsorption of sodium ions in saline-alkali soil by biochar; (2) The addition of calcium phosphate and cellulose sulfate to a certain extent introduces sulfur functional groups, changes the surface charge, reduces the pH of biochar, promotes sodium-calcium exchange, and achieves a synchronous synergistic effect of adsorption-exchange; (3) However, if the calcium phosphate content is too low, the effective active sites will be reduced / , and when its content is increased, it may block the pores or aggregate the cellulose sulfate / , resulting in a decrease in ion exchange capacity. The interaction between calcium phosphate and cellulose sulfate affects the surface charge distribution and pore structure of the modified biochar, thereby affecting the ion exchange capacity. Kharel et al. increased the O / C of biochar and introduced a large number of oxygen-containing functional groups by surface ozone oxidation of biochar, which reduced the pH of biochar and increased the cation exchange capacity by 10 times, providing a basis for the application of high cation exchange capacity biochar in soil.

[0113] Adsorption compatibility of modified biochar with rhizospheric growth-promoting bacteria Rs-2. Figure 8 Reflects the colony count (a) of KBC, CS-BC, 2.5CS-BC, 3CS-BC, 5CS-BC, and 10CS-BC loaded with microorganism Rs-2, as well as the protein (b) and polysaccharide (c) contents produced after loading with microorganism Rs-2.

[0114] The unique structure and physical and chemical properties of biochar can provide a suitable living environment and nutrients for microorganisms to a certain extent. However, harmful substances will be produced during the burning process of biochar. Harmful substances and electrical conductivity will affect the metabolism of microorganisms and make them unsuitable for survival. Figure 8The colony count of microorganism Rs-2 loaded with biochar initially increased and then decreased. The protein content produced by microorganism Rs-2 in the biochar inoculum decreased after the addition of CS, while the polysaccharide content increased and then decreased. The protein and polysaccharide contents of KBC-Rs-2 and 5CS-BC-Rs-2 were 1.61 mg / ml and 1.15 mg / ml, respectively, and 143.300 μg / ml and 415.200 μg / ml, respectively. This may be because when potassium permanganate alone is used to modify biochar, no other carbon source is added to the biochar. Therefore, the microorganisms consume their own organic matter for metabolism and secrete substances such as protein. When CS is added to biochar, the biochar provides an external carbon source, encouraging the microorganisms to grow and reproduce, resulting in an increase in polysaccharide content and a decrease in protein content. Furthermore, the negative surface charge of CS may repel the adsorption of negatively charged proteins. After calcium phosphate-CS synergistically modified biochar, calcium phosphate provided nutrients for the growth and reproduction of microorganisms, promoted the growth and reproduction of Rs-2, and increased the content of protein and polysaccharides produced. However, when the calcium phosphate content was too high, it would cause the pores on the biochar surface to be blocked and the active sites to decrease, so the loading capacity, protein, and polysaccharide content decreased.

[0115] Figure 9 It reflects the swelling degree SD (a), water holding rate WHR (b) and water holding capacity WR (c) of KBC-Rs-2, CS-BC-Rs-2, 2.5CS-BC-Rs-2, 3CS-BC-Rs-2, 5CS-BC-Rs-2 and 10CS-BC-Rs-2 at different times.

[0116] Figure 9 The swelling degree, water holding rate, and water holding capacity of the biochar inoculants were measured. As shown in the figure, after potassium permanganate modification and the addition of CS and calcium phosphate, the swelling degree and water holding rate of the biochar inoculants first increased and then decreased. The SD and WHR of 5CS-BC-Rs-2 reached 273.72% and 42.065% respectively. However, comparing the water holding capacity of the biochar inoculants, KBC and CS-BC-Rs-2 showed the highest water holding capacity during the first seven days. It can be seen that the water holding capacity of the biochar inoculants decreased after the addition of CS and calcium phosphate. However, after the seventh day, the water holding capacity of 5CS-BC-Rs-2 reached the highest, reaching 19.09%. The water holding capacity of the biochar inoculants also showed an initial increase followed by a decrease over the same period. This may be due to the gelling properties of CS, which increased the swelling degree and water holding rate of the biochar inoculants. However, the addition of calcium phosphate, while Ca2+ reacted with CS to optimize the pore structure of the biochar inoculants, reduced the structural stability of CS, resulting in a low water holding capacity in the early stages. After the 7th day, the increase in water holding capacity may be due to the production of stable cell membranes by microorganisms colonizing in the soil and the slow-release properties of calcium phosphate-modified biochar.

Claims

1. A CEC enhancer modified biochar agent, characterized in that: include: Biochar carrier, produced by pyrolysis of crop straw at 400-600°C under oxygen-limited conditions; The biochar was initially modified by mixing the biochar carrier with a potassium permanganate solution, shaking, ultrasonicating, filtering, washing with pure water, filtering, and drying to obtain a potassium permanganate-modified biochar; Cellulose sulfate, obtained by mixing sulfuric acid and isopropyl alcohol at low temperature and then reacting cellulose at low temperature; Enhancer modified biochar, which is obtained by mixing the preliminary modified biochar and cellulose sulfate in pure water, heating and stirring at 40-60°C, and drying in a vacuum oven; Functional bacterial agent: the enhancer-modified biochar was mixed with the Rs-2 bacterial suspension, shaken at 170 rpm and 30 °C for 2 h, filtered, and naturally air-dried to obtain the biochar agent; The CEC enhancer is loaded in the pores of biochar, the functional bacteria are embedded in the enhancer-biochar composite matrix, and the cellulose sulfate and Ca 2+ Generate electrostatic / electronic cross-linking to form a network structure.

2. The CEC enhancer modified biochar agent according to claim 1, characterized in that: The surface of the enhancer-modified biochar is composited with calcium phosphate and cellulose sulfate.

3. The CEC enhancer modified biochar agent according to claim 1, characterized in that: Cellulose sulfate and preliminary modified biochar are mixed in pure water at a ratio of 1:5, wherein the ratio of Ca3(PO4)2 to cellulose sulfate is not less than 1:0.25 and not more than 1:

1.

4. A method for preparing a CEC enhancer-modified biochar agent, used for preparing the CEC enhancer-modified biochar agent according to any one of claims 1 to 3, characterized in that: The steps include: The biochar carrier is prepared by pyrolyzing crop straw at 400-600°C under oxygen-limited conditions; The biochar carrier and the potassium permanganate solution are mixed, shaken, ultrasonicated, filtered, washed with pure water, filtered and dried to obtain potassium permanganate-modified biochar; Sulfuric acid and isopropyl alcohol are mixed at low temperature and then reacted with cellulose at low temperature to obtain modified cellulose sulfate; The preliminarily modified biochar and cellulose sulfate are mixed in pure water, heated and stirred at 40-60° C., and then dried in a vacuum oven to obtain the enhancer-modified biochar; The enhancer-modified biochar was mixed with the Rs-2 bacterial suspension, shaken at 170 rpm and 30°C for 2 h, filtered, and naturally air-dried to obtain a biochar agent.

5. The method for preparing the CEC enhancer modified biochar agent according to claim 4, characterized in that: The biochar carrier is prepared according to the following method: Place the crushed corn stalks in a forced air drying oven at 100°C to dry them to remove excess moisture, then crush them in a crusher and pass through an 80-mesh sieve; 25 g of corn straw and a mixture of corn straw and Ca3(PO4)2 were added to 125 mL of deionized water and stirred at 350 rpm for 45 min to mix them completely to obtain a mixed solution 1; The mixed solution was placed in an oven at 80°C for drying, and then crushed to pass through a 60-mesh sieve to obtain a processed sample; The treated sample was transferred to a corundum ark reactor and placed in a tube furnace for pyrolysis. The heating rate was 10 °C min-1 under the condition of N2 flow rate of 150 mL min-1. -1 , raise the temperature to 500℃ and maintain it for 2h, then cool it down and take it out to obtain the biochar carrier.

6. The method for preparing the CEC enhancer modified biochar agent according to claim 4, characterized in that: The preparation method of the enhancer-modified biochar comprises: The biochar carrier and potassium permanganate solution were mixed in a ratio of 1:8, shaken, and ultrasonicated, and then filtered and washed with pure water until the pH reached a stable level, and then filtered and dried to obtain potassium permanganate-modified biochar; Then, the cation exchange enhancer was modified to prepare cellulose sulfate. Sulfuric acid and isopropyl alcohol were mixed at a ratio of 1:1 at low temperature, and then 6.25% cellulose was added and reacted at low temperature for 1 hour. The mixture was washed with isopropyl alcohol and ethanol, and dried for later use to obtain cellulose sulfate. The prepared cellulose sulfate and biochar carrier were mixed in pure water at a ratio of 1:5, then heated and stirred at 50°C for 3 hours, and dried in a vacuum oven for 48 hours to obtain preliminary modified biochar, in which the ratio of Ca3(PO4)2 to cellulose sulfate was not less than 1:0.25 and not higher than 1:

1.

7. The method for preparing the CEC enhancer-modified biochar agent according to claim 4, characterized in that: The Rs-2 bacterial suspension was prepared as follows: Preparation of LB medium: Weigh 2 g of peptone, 2 g of sodium chloride, and 1 g of yeast extract powder into a 250 ml conical flask, add 200 ml of deionized water, pH 7.0-7.2, and sterilize the prepared LB medium in a high-temperature and high-pressure sterilizer at 121°C for 20 min. After cooling, remove from the oven and set aside. Solid culture medium preparation steps: Weigh 2g of peptone, 2g of sodium chloride, 1g of yeast extract powder, and 4g of peptone into a 250ml conical flask, add 200ml of deionized water, and then sterilize the prepared solid culture medium in a high-temperature and high-pressure sterilizer at 121°C for 20 minutes. Pour the unsolidified liquid solid culture medium into a culture dish and wait for it to solidify before use; Preparation of bacterial suspension: Inoculate 2% Rs-2 seed solution into a 250 ml conical flask containing 200 ml of LB medium on a clean bench. Incubate at 170 rpm and 30°C for 24 h. Centrifuge at 6500 rpm and 4°C for 8 min in a low-temperature high-speed centrifuge. Rinse twice with deionized water. Then add an equal amount of deionized water to prepare the Rs-2 bacterial suspension.

8. The method for preparing the CEC enhancer-modified biochar agent according to claim 4, characterized in that: During the preparation of the biochar agent, the dried enhancer-modified biochar was mixed with the Rs-2 bacterial suspension at a ratio of 1:1 (m:V), shaken at 170 rpm and 30° C. for 2 h, filtered, and naturally air-dried to obtain the biochar agent.

9. An evaluation method for evaluating the CEC enhancer-modified biochar agent according to any one of claims 1 to 3, characterized in that: The evaluation method is used to evaluate the characterization of biochar agents, wherein the characterization of biochar agents includes: adsorption performance evaluation, compatibility evaluation of the biochar agent and the rhizosphere growth-promoting bacteria Rs-2, and water holding capacity evaluation of the modified biochar agent.

10. The evaluation method according to claim 9, characterized in that: The adsorption performance evaluation comprises the following steps: After culturing Rs-2 for 24 hours, the bacterial solution was centrifuged at 6500 rpm for 6 minutes to obtain Rs-2 cells, which were then washed three times with pH 7.0 buffer and resuspended in a 1:1 ratio to obtain an Rs-2 bacterial suspension. 100 mg of modified biochar was placed in a 50 mL conical flask, and then 20 mL of Rs-2 bacterial suspension was added and placed in a shaker at a temperature of 28 ° C and a rotation speed of 170 rpm for 2 hours. The biochar adsorption equilibrium concentration was determined, and then 1 mL of the mixed solution of Rs-2 and biochar was drawn, and then centrifuged at 1500 rpm for 5 minutes. The supernatant was taken and the colony counts of the bacterial suspension and the supernatant were determined by the plate count method to obtain the adsorption capacity of the modified biochar for Rs-2; The compatibility assessment methods for biochar agents and rhizosphere growth-promoting bacteria Rs-2 include: Take 100 mL of the culture medium of Rs-2 grown for 24 hours, centrifuge at 2000 rpm for 10 minutes, discard the supernatant, and add 50 mL of sterile water; After heating the bacterial suspension in a 60°C water bath for 30 minutes, centrifuge at 8000 rpm for 10 minutes. The supernatant is filtered through a 0.22 μm filter to obtain a twice-concentrated EPS solution. Determination of polysaccharide content in EPS: The phenol-sulfuric acid method is used to determine polysaccharide content. To measure polysaccharides, 1 mL of sample or standard glucose solution of varying concentrations is added to 1 mL of each solution, followed by 5 mL of concentrated sulfuric acid and rapid shaking. After incubation at room temperature in the dark for 20 minutes, the absorbance is measured at 490 nm. A standard curve is plotted with the polysaccharide concentration on the horizontal axis and the absorbance on the vertical axis to calculate the polysaccharide concentration in the sample. Determination of protein content in EPS: Use Coomassie Brilliant Blue G250 to determine the protein content. Take 5 mL of sample or standard protein solution of different concentrations and add 5 mL of Coomassie Brilliant Blue G-250. After shaking, react for 5 minutes and then measure the absorbance at 595 nm. The horizontal axis is protein concentration and the vertical axis is absorbance. Draw a standard curve and calculate the protein content in the sample based on the standard curve. Methods for evaluating the water holding capacity of modified biochar agents include: 100.0 g of air-dried loam was passed through a 20-mesh sieve, mixed with the materials in proportion, and transferred to a plastic bottle with a diameter of 4.5 cm and a height of 15 cm. The mixture of soil and materials was weighed as m1, and then deionized water was slowly added to the bottle until the soil was saturated and weighed again as m2. The water holding capacity (WHR%) of the material was calculated using the following equation: Where WHR% represents the water holding rate of the material, m1 represents the weight of the container and material before absorbing water, and m2 represents the weight of the container and material after absorbing water; The weighed plastic bottles m2 were incubated at 25°C for 30 days. The bottles were recorded at specified time intervals and recorded by m x The material is weighed and its water holding capacity (WR%) is calculated using the following equation: Where m1 represents the weight of the entire container before absorbing water, m x Indicates the weight of the container at each specified time interval.

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