Microbial modified biomass charcoal for cadmium-contaminated soil remediation and carbon sequestration and emission reduction and preparation method and application thereof

Abstract

The invention belongs to the technical field of heavy metal contaminated soil improvement agents, and particularly relates to microorganism modified biomass charcoal for cadmium contaminated soil remediation and carbon sequestration and emission reduction and a preparation method and application thereof. According to the method, a biomass charcoal material and a microbial remediation technology are coupled, mixed bacteria of bacillus subtilis, bacillus velezensis and rhodopseudomonas palustris are adsorbed and fixed by biomass charcoal prepared by taking corn straw as a raw material, and the prepared microbial modified biomass charcoal can be used for treating the heavy metal cadmium polluted soil, so that the heavy metal cadmium polluted soil can be effectively remediated. The dual functions of cadmium fixation and carbon fixation and emission reduction are efficiently achieved in a short time, and the method has important application value in remediation of heavy metal cadmium contaminated soil. Moreover, the microorganism modified biomass charcoal is simple in component and simple and convenient in preparation process, and has a very good popularization and application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy metal contaminated soil conditioners, and specifically relates to a microbial modified biochar for cadmium contaminated soil remediation and coordinated carbon fixation and emission reduction, as well as a preparation method and application thereof. Background Art

[0002] Soil carbon dioxide emissions are an important way for terrestrial ecosystems to exchange carbon with the atmosphere. Their emissions and spatial distribution have an important impact on the global carbon cycle and climate change. More and more studies have shown that soil carbon dioxide emissions will weaken global climate efforts. As the problem of global climate change intensifies, improving the carbon sequestration capacity of soil has become an important strategy for addressing climate change. Soil carbon sequestration can not only reduce the concentration of carbon dioxide in the atmosphere and alleviate climate change, but also improve soil fertility and promote sustainable agricultural development. However, current soil carbon sequestration technology has certain limitations and it is difficult to achieve ideal results in practical applications.

[0003] Carbon dioxide emissions from soil are mainly produced by the decomposition of organic matter through the respiration of soil microorganisms, plant roots and soil animals. The factors affecting soil carbon dioxide emissions are relatively complex. Studies have shown that heavy metal pollution can also have a significant impact on soil carbon dioxide emissions. Heavy metal pollution can change the chemical and physical properties of the soil. Heavy metal accumulation can lead to soil pH imbalance, affect soil fertility, and affect soil microbial functions and community structure; and these factors are basically related to soil carbon dioxide emissions. Due to the complexity of influencing factors, the current development of soil carbon sequestration and emission reduction technology has always been relatively one-sided, and there is no mature theory; in the face of more complex carbon sequestration and emission reduction in heavy metal-contaminated soils, due to the diversity of heavy metals' impact on the soil ecological environment and the high complexity of the environment, the current research on the impact mechanism of this process is still controversial.

[0004] At the same time, the problem of heavy metal pollution in my country's cultivated land soil is becoming increasingly serious, with the rate of exceeding the standard reaching 19.4%. In particular, the rate of cadmium (Cd) in the soil points is the highest, reaching 7.0%. Cadmium is a highly toxic, highly mobile and persistent heavy metal. 2+ Cadmium is widely present in the earth's crust in the form of organic and inorganic complexes. Cadmium is easy to migrate and transform in the soil, making it easier to accumulate along the food chain and ultimately endanger human health. Therefore, in the face of the severe situation of cadmium pollution, repairing contaminated soil, reducing carbon dioxide emissions from cadmium-contaminated soil, and restoring soil ecological functions have become urgent issues to be addressed.

[0005] Biochar is a porous solid granular material obtained by pyrolysis of biomass such as straw under high temperature conditions with or without oxygen. As a material with good adsorption properties, it is widely used in soil remediation. It can improve the physical and chemical properties of soil, effectively adsorb heavy metals in soil, such as cadmium, and reduce their bioavailability in soil, thereby reducing their potential harm to plants and humans. In terms of carbon sequestration and emission reduction, the role of biochar is not strong, especially the carbon sequestration and emission reduction effect of biochar is also affected by the type of raw materials. Corn straw is an important raw material for making biochar, but studies have shown that biochar produced from corn straw has almost no carbon sequestration effect, and it is difficult to use it to achieve the purpose of carbon sequestration and emission reduction, which also limits the use of corn straw to a certain extent.

[0006] In addition, there are also reports on the use of microorganisms to repair heavy metal pollution and fix carbon. For example, a variety of Bacillus has been reported to have a certain role in repairing cadmium-contaminated soil, and photosynthetic bacteria such as Rhodopseudomonas palustris have a carbon fixation effect. However, the effects of single biochar and single microbial bacteria are also limited, and the effects of different types vary greatly. Therefore, the actual application effect is still insufficient and cannot fully meet the needs of heavy metal pollution repair and soil carbon fixation. The Chinese invention patent with publication number CN117402626A discloses a rice straw biochar equipped with Bacillus cereus with carbon fixation ability, which can be applied to the soil to increase the organic carbon content of the soil, but the biochar cannot handle heavy metal pollution; the Chinese invention patent with publication number CN112592240A discloses a biocarbon-based composite conditioner for repairing soil cadmium pollution, using Bacillus subtilis and Rhodopseudomonas palustris with cadmium fixation ability to reduce the biological effectiveness of cadmium and improve the heavy metal cadmium pollution in the soil, but the composite conditioner has complex ingredients, cumbersome production process, and no carbon fixation function.

[0007] Therefore, in the case that there is a close relationship between heavy metal pollution in soil and carbon dioxide emissions, but the mutual influence and mechanism are unclear, facing the dual needs of remediation of heavy metal contaminated soil and carbon sequestration and emission reduction, it is of great significance to strengthen relevant research and develop technologies for remediation of heavy metal contaminated soil and coordinated carbon sequestration and emission reduction. Summary of the invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing dual technologies of heavy metal, especially cadmium-contaminated soil remediation and carbon fixation and emission reduction, and provide a preparation method of microbial modified biochar material that can quickly and efficiently remediate cadmium-contaminated soil and simultaneously improve the soil's carbon fixation capacity. This method couples biochar material with microbial remediation technology, and has the dual functions of quickly and efficiently achieving cadmium fixation and carbon fixation and emission reduction in heavy metal cadmium-contaminated soil, and has important application value for the remediation of heavy metal cadmium-contaminated soil.

[0009] The purpose of the present invention is to provide a method for preparing microbial modified biochar for synergistic carbon fixation and emission reduction in cadmium-contaminated soil remediation.

[0010] Another object of the present invention is to provide microbial modified biochar prepared by the above method for cadmium contaminated soil remediation and synergistic carbon fixation and emission reduction.

[0011] Another object of the present invention is to provide the application of the above-mentioned microbial modified biochar in the restoration of cadmium-contaminated soil and coordinated carbon fixation and emission reduction.

[0012] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0013] The present invention couples biochar materials with microbial remediation technology, and uses biochar made from corn stalks as raw materials to adsorb and fix a mixed bacteria of Bacillus subtilis, Bacillus velez and Rhodopseudomonas palustris. The prepared microbial modified biochar has both cadmium contaminated soil remediation and soil carbon fixation functions, and can achieve the dual functions of cadmium fixation and carbon fixation and emission reduction in heavy metal cadmium contaminated soil in a short time and with high efficiency, and has important application value for the remediation of heavy metal cadmium contaminated soil.

[0014] Specifically, the present invention provides a method for preparing microbial modified biochar for synergistic carbon fixation and emission reduction in cadmium-contaminated soil remediation, the method using biochar to adsorb and fix mixed bacteria to obtain microbial modified biochar; the biochar is made from corn stalks as raw materials; the mixed bacteria is a mixed bacteria of Bacillus subtilis, Bacillus velezii and Rhodopseudomonas palustris.

[0015] Preferably, the method for preparing the biochar is: pyrolyzing corn stalk powder under anaerobic or anoxic conditions at 300-600° C. for 1-3 h (more preferably pyrolyzing at 450° C. for 2 h) to obtain the biochar.

[0016] More preferably, the particle size of the corn stalk powder is less than or equal to 2 mm.

[0017] Optionally, the anaerobic or anoxic condition may be an anaerobic or anoxic condition formed by using nitrogen at a flow rate of 400-800 mL / min (preferably 600 mL / min) as a protective gas.

[0018] Preferably, the Bacillus subtilis, Bacillus velez and Rhodopseudomonas palustris are mixed in a bacterial liquid volume ratio of (1-3):(1-3):(1-3), more preferably in a volume ratio of 2:2:3.

[0019] Preferably, the mass ratio of the biochar to the mixed bacterial liquid is 1:(5-15), and more preferably 1:10.

[0020] In the preparation method, the method of using biochar to adsorb and fix the mixed bacteria is to mix the biochar with the mixed bacterial solution and then culture it for 12-48 hours, preferably at 100-200 rpm and 25-35° C. for 12-48 hours.

[0021] Finally, the obtained microbial modified biomass carbon material is dried. Preferably, the drying method is freeze-drying. Compared with ordinary drying, freeze-drying will not cause damage to the loaded bacteria due to excessively high temperature.

[0022] Specifically, the method for preparing microbial modified biochar provided by the present invention comprises the following steps:

[0023] S1. Cultivation of bacterial species: Bacillus subtilis, Bacillus velez and Rhodopseudomonas palustris were cultured to obtain three bacterial suspensions;

[0024] S2. Co-culture of mixed bacteria: The three bacterial suspensions were mixed in a volume ratio of (1-3): (1-3): (1-3), and then the co-culture was continued for 12-48 hours to obtain a mixed bacterial solution;

[0025] S3. Preparation of biochar material: Pyrolyze corn stalk powder with a particle size of less than or equal to 2 mm under anaerobic or anoxic conditions at 300-600°C for 1-3h to obtain biochar, dry the obtained biochar, and sieve through a 60-100 mesh sieve to obtain biochar powder;

[0026] S4. Preparation of microbial modified biochar material: Mix the mixed bacterial solution obtained in step S2 with the biochar powder obtained in step S3 in a mass ratio of (5-15):1, and then culture at 100-200rpm and 25-35℃ for 12-48h to allow the mixed bacteria to be evenly adsorbed and fixed on the surface of the biochar, collect the adsorbed and fixed biochar, and freeze-dry to obtain microbial modified biochar.

[0027] Preferably, the OD600 of the bacterial suspensions of Bacillus subtilis, Bacillus velez and Rhodopseudomonas palustris in step S1 are all 0.5-1.5. More preferably, OD600=1.0

[0028] Preferably, in step S1, the culture conditions of Bacillus subtilis, Bacillus velez and Rhodopseudomonas palustris are all 30° C. and 180 rpm with shaking, more preferably 30° C. and 180 rpm.

[0029] Preferably, Bacillus subtilis is cultured for 12-48 h (more preferably 24 h).

[0030] Preferably, Bacillus velezensis is cultured for 24-60 h (more preferably 48 h).

[0031] Preferably, Rhodopseudomonas palustris is cultured for 6-8 days (more preferably 7 days).

[0032] In addition, preferably, the culture conditions of Rhodopseudomonas palustris require the addition of lighting conditions (preferably 10-100 watt tungsten filament lamp).

[0033] Optionally, the culture medium for Bacillus subtilis and Bacillus Velez is: 2.0-4.0 g beef extract, 8.0-12.0 g peptone, 4.0-6.0 g sodium chloride, distilled water to 1.0 L, pH 6.5-7.5.

[0034] Preferably, the culture medium for Bacillus subtilis and Bacillus velezii is: 3.0 g beef extract, 10.0 g peptone, 5.0 g sodium chloride, distilled water to 1.0 L, pH 7.0.

[0035] Optionally, the culture medium for Rhodopseudomonas palustris is: 0.8-1.2 g of dipotassium hydrogen phosphate, 0.4-0.6 g of magnesium sulfate, 8.0-12.0 g of yeast extract, distilled water to 1.0 L, and pH 6.5-7.5.

[0036] Preferably, the culture medium for Rhodopseudomonas palustris is: 1.0 g of dipotassium hydrogen phosphate, 0.5 g of magnesium sulfate, 10.0 g of yeast extract, and distilled water to make up to 1.0 L, with a pH of 7.0.

[0037] Preferably, the co-culture conditions in step S2 are shaking culture at 25-35° C. and 100-200 rpm for 12-48 h, more preferably at 30° C. and 180 rpm for 24 h.

[0038] Preferably, in step S2, the bacterial suspensions of Bacillus subtilis, Bacillus velezensii and Rhodopseudomonas palustris are mixed in a volume ratio of 2:2:3.

[0039] Preferably, in step S3, pyrolysis is performed at 450° C. for 2 h.

[0040] Optionally, the anaerobic or anoxic condition in step S3 may be an anaerobic or anoxic condition formed by using nitrogen at a flow rate of 400-800 mL / min (preferably 600 mL / min) as a protective gas.

[0041] Preferably, the biochar dried in step S3 is sieved through a 60-mesh sieve to obtain biochar powder.

[0042] Preferably, in step S4, the mass ratio of the mixed bacterial liquid to the biochar powder is 10:1.

[0043] Preferably, the shaking culture conditions in step S4 are 120 rpm, 30° C., and 24 h.

[0044] Preferably, the drying method is freeze-drying. Compared with ordinary drying, freeze-drying will not cause damage to the loaded bacteria due to excessively high temperature.

[0045] Preferably, the freeze-drying method is: first freezing at -80-20°C for 12-48 hours, and then freeze-drying for 24-60 hours.

[0046] More preferably, the freeze-drying method is: first freezing at -80°C for 24 hours, and then freeze-drying for 48 hours to obtain the microbial modified biochar material.

[0047] The microbial modified biochar material can achieve the dual functions of cadmium fixation and carbon fixation and emission reduction in heavy metal cadmium contaminated soil in a short time and with high efficiency. Therefore, the microbial modified biochar material and its application in cadmium contaminated soil remediation and carbon fixation and emission reduction (reducing the emission of carbon dioxide in cadmium contaminated soil) should also be within the protection scope of the present invention.

[0048] The present invention has the following beneficial effects:

[0049] (1) The present invention couples biochar materials with microbial remediation technology, and uses biochar made from corn stalks as raw materials to adsorb and fix a mixed bacteria of Bacillus subtilis, Bacillus velezensis and Rhodopseudomonas palustris. The prepared microbial modified biochar can achieve the dual functions of cadmium fixation and carbon fixation and emission reduction in a short time and with high efficiency for heavy metal cadmium contaminated soil (negative carbon dioxide emissions appear after about 20 days of treatment, and continue to show negative carbon dioxide emissions thereafter), which has important application value for the remediation of heavy metal cadmium contaminated soil.

[0050] (2) The microbial modified biochar material of the present invention has simple components, a simple production process, and has a good prospect for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a graph showing the 24-hour cadmium adsorption of mixed bacteria of different types and proportions on a solution with a cadmium content of 30 mg / kg in Example 1 of the present invention (different letters on the columns indicate significant differences).

[0052] Figure 2 This is a SEM morphology of the mixed bacteria in Example 1 of the present invention.

[0053] Figure 3 This is the SEM morphology of the biochar in Example 2 of the present invention.

[0054] Figure 4 This is a SEM image of the microbial modified biochar material in Example 2 of the present invention.

[0055] Figure 5This is a graph of the effective cadmium content in soil before and after the remediation of cadmium-contaminated soil by the biochar material and the microbially modified biochar material in Example 2 of the present invention (different letters on the columns indicate significant differences).

[0056] Figure 6 This is a graph of the content of various forms of cadmium in soil before and after the remediation of cadmium-contaminated soil by the biochar material and the microbially modified biochar material in Example 2 of the present invention (different letters on the columns indicate significant differences).

[0057] Figure 7 This is a graph of carbon dioxide emission rates from soil after the biochar material and microbially modified biochar material in Example 3 of the present invention are added to cadmium-contaminated soil. DETAILED DESCRIPTION

[0058] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0059] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0060] In the following embodiments:

[0061] The selected Bacillus subtilis is Bacillus subtilis B1 strain, which comes from Beina Bio-Henan Industrial Microbiological Strain Engineering Technology Research Center (https: / / www.bncc.com / ), with the deposit number BNCC188159 and the deposit time of September 27, 2021.

[0062] The selected Bacillus Velez subtilis strain was Bacillus Velez subtilis strain B2, which was from Guangdong Microbial Culture Collection Center (https: / / www.gdmcc.net / # / swzysjk), with a collection number of GDMCC NO.: 1.1375 and a collection date of July 2, 2018.

[0063] The selected Rhodopseudomonas palustris strain was Rhodopseudomonas palustris R, which was obtained from Guangdong Microbial Culture Collection Center (https: / / www.gdmcc.net / # / swzysjk), with a collection number of GDMCC NO.: 1.167 and a collection date of January 1, 2004.

[0064] The culture medium used was:

[0065] The culture medium for Bacillus subtilis and Bacillus Velezii is: 3.0 g beef extract, 10.0 g peptone, 5.0 g sodium chloride, distilled water to 1.0 L, pH 7.0.

[0066] The culture medium for Rhodopseudomonas palustris was: 1.0 g of dipotassium hydrogen phosphate, 0.5 g of magnesium sulfate, 10.0 g of yeast extract, and distilled water to 1.0 L, with a pH of 7.0.

[0067] Example 1 Study on the adsorption effect of mixed bacteria in different proportions on cadmium

[0068] 1. Preparation of single bacterial suspension and mixed bacterial suspension

[0069] (1) Enrichment culture of bacterial strains

[0070] Inoculate Bacillus subtilis B1 in a culture medium at a volume ratio of 10%, and culture in a culture incubator at 30°C and 180 rpm for 24 hours to obtain a Bacillus subtilis B1 bacterial suspension;

[0071] Inoculate the culture medium with a transfer amount of 10% by volume of Bacillus Velez B2, and culture in a conditioned incubator at 30° C. and 180 rpm for 48 hours to obtain a suspension of Bacillus Velez B2;

[0072] The palustris Rhodopseudomonas R was inoculated into the culture medium at a transfer rate of 10% by volume, and cultured in an incubator under shaking conditions of 30° C., 180 rpm, and 40 W tungsten light for 7 days to obtain a palustris R bacterial suspension.

[0073] (2) Cultivation of mixed bacteria

[0074] The Bacillus subtilis B1 suspension, the Bacillus Velez B2 suspension and the Rhodopseudomonas palustris R suspension cultured in step (1) with OD600=1.0 were selected, and the volume ratio of the bacterial suspension was 3 3 Orthogonal experiments were performed to construct mixed strains, and 9 different ratios from MB1 to MB9 were obtained. The specific mixing conditions are shown in Table 1. The mixed strains MB1 to MB9 were mixed and shaken and cultured at 30°C and 180 rpm for 24 h to obtain a mixed bacterial solution.

[0075] Table 1 Bacteria mixed in different proportions

[0076]

[0077] 2. Experiment on the adsorption of cadmium by single bacterial suspension and mixed bacterial suspension

[0078] 5 ml of the mixed bacterial solution with different ratios and each single bacterial suspension were taken respectively, mixed with 50 ml of CdCl2 solution (cadmium concentration was 30 mg / kg), shaken at 30 ° C and 180 rpm, and the supernatant was collected after 24 hours, filtered through a 0.22 μm filter membrane, and the cadmium content of the supernatant was determined using an inductively coupled plasma emission spectrometer;

[0079] The results are as follows Figure 1 As shown in the figure, the 24h adsorption capacity of cadmium in 30mg / kg CdCl2 solution by all mixed bacteria exceeded that of a single bacterium, among which the mixed bacteria MB5 of Bacillus subtilis B1, Bacillus Velez B2 and Rhodopseudomonas palustris R in a ratio of 2:2:3 had the largest adsorption capacity of 30mg / kg cadmium in 24h, about 16.79mg / kg, and the adsorption efficiency reached 55.97%, which was 2.5 to 3.6 times that of a single bacterium.

[0080] Example 2 Preparation of microbial modified biochar material

[0081] 1. According to the same method as in Example 1, a Bacillus subtilis B1 bacterial suspension, a Bacillus Velez B2 bacterial suspension and a Rhodopseudomonas palustris R bacterial suspension with an OD600 of 1.0 were cultured, and then mixed in a volume ratio of 2:2:3, and mixed and shaken and cultured at 30°C and 180rpm for 24h to obtain a mixed bacterial solution.

[0082] like Figure 2 As shown, the morphologies of the three bacteria in the mixed bacterial solution can be clearly seen, among which Rhodopseudomonas palustris has a rod-shaped to oval morphology and has flagella, while Bacillus subtilis and Bacillus velezine both belong to the genus Bacillus and are straight rod-shaped.

[0083] 2. Preparation of biochar materials

[0084] The crushed corn stalks were air-dried at room temperature, then ground, passed through a 10-mesh stainless steel sieve to obtain corn stalk powder with a particle size of less than or equal to 2 mm, the corn stalk powder was placed in a corundum crucible, the flow rate of nitrogen protective gas was adjusted to 600 mL / min, and oxygen-free carbonization was performed in a muffle furnace at 450° C. for 2 h to obtain biochar, the obtained biochar was dried, and passed through a 60-mesh stainless steel sieve to obtain biochar powder;

[0085] like Figure 3 As shown, the prepared biochar exhibited a porous structure, indicating that it was a suitable carrier for bacterial loading.

[0086] 3. Preparation of microbial modified biochar materials

[0087] The mixed bacterial liquid cultured in step 1 and the biochar prepared in step 2 were mixed in a mass ratio of 10:1, placed in a shaker at 180 rpm and 30°C for 24 hours to allow the mixed bacteria to be evenly adsorbed and fixed on the surface of the biochar, and the adsorbed and fixed biochar was collected and frozen in a -80°C refrigerator for 24 hours, and then freeze-dried in a freeze dryer for 48 hours to obtain a microbial modified biochar material.

[0088] like Figure 4 As shown, a large number of bacteria are adsorbed and fixed on the surface of the prepared microbial modified biochar material, which also shows that the bacteria are successfully fixed on the surface of the biochar.

[0089] Example 3 Remediation of Cadmium-Contaminated Soil by Microbial Modification of Biomass Carbon Materials

[0090] 6g of the biochar material prepared in step 2 of Example 2, and 6g, 3g, and 1g of the microbial modified biochar material prepared in step 3 were added to 200g of cadmium-contaminated soil with a cadmium content of 13mg / kg. The soil was then placed in a culture pot, the soil moisture content was adjusted to 30%, stirred evenly, and then placed at room temperature (15-35°C), during which the moisture content was maintained at 30%. The soil was collected on day 45, and the effective cadmium content and BCR-extractable cadmium content were determined using an inductively coupled plasma emission spectrometer;

[0091] The results are as follows Figure 5 As shown, after 45 days of remediation, both biochar materials and microbial modified biochar materials significantly reduced the content of effective cadmium in cadmium-contaminated soil. Compared with before remediation, the addition of 3g of microbial modified biochar material had the largest decrease in the content of effective cadmium in cadmium-contaminated soil, which decreased by 55.65%. Compared with the microbial modified biochar treatment group with a lower addition amount of 1g, it shows that the greater the addition amount, the better the remediation effect on soil cadmium pollution. Comparing the microbial modified biochar treatment group with a larger addition amount of 6g and the biochar treatment group with 6g, it shows that the more the addition amount, the better the soil cadmium remediation effect. There may be a limit to the addition amount. The reason may be the limitation caused by the nature of the biochar itself.

[0092] like Figure 6 As shown, compared with before remediation, both biochar materials and microbial modified biochar materials significantly reduced the content of reducible and oxidizable cadmium, and increased the content of residual cadmium. Among them, the addition of 3g of microbial modified biochar materials had a greater increase in the content of residual cadmium in cadmium-contaminated soil, reaching 48.76%, while the content of reducible and oxidizable cadmium also decreased by 91.96% and 87.54%, respectively. The overall results also show that the remediation of cadmium pollution by microbial modified biochar materials is mainly to convert reducible and oxidizable cadmium into residual cadmium.

[0093] Example 4 Study on the reduction of carbon dioxide emissions from cadmium-contaminated soil by microbial modification of biochar materials

[0094] 1.5 ml of the mixed bacterial solution prepared in step 1 of Example 2, 1.5 g of the biochar prepared in step 2 of Example 2, and 1.5 g of the microbial modified biochar material prepared in step 3 of Example 2 were added to 50 g of cadmium-contaminated farmland soil with a cadmium content of 13 mg / kg, and a group of 50 g of cadmium-contaminated soil without addition was used as a control group. Then the soil was placed in a sealed gas collection bottle, the soil moisture content was adjusted to 30%, stirred evenly, and then placed at room temperature (15-35°C), and gas was collected on 1, 4, 7, 14, 21, 30, and 40 days, and the content of carbon dioxide in the gas was measured using a greenhouse gas analyzer to calculate the emission rate of carbon dioxide.

[0095] like Figure 7 The results shown show that:

[0096] (1) Only the group with microbial-modified biochar material showed negative carbon dioxide emissions, which showed the function of carbon fixation and emission reduction.

[0097] After adding microbially modified biochar materials, the rate of carbon dioxide emission from cadmium-contaminated soil was faster than that of the non-added group (control group) at the beginning, but began to approach the emission rate of the non-added group after 10 days, and continued to decline. Negative carbon dioxide emissions began to appear 20 days after the addition, and continued to show negative carbon dioxide emissions thereafter, demonstrating carbon fixation ability.

[0098] (2) The treatment group with added biochar material showed a trend close to that of the group without addition, while the treatment group with added mixed bacteria showed a trend of high carbon dioxide emission. Although it began to decline over time, it was still higher than that of the group without addition.

[0099] In summary, the microbial modified biochar material prepared by the present invention can effectively repair soil cadmium pollution while reducing the carbon dioxide emissions from cadmium-contaminated soil, showing good carbon fixation ability.

[0100] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing microbial modified biochar for cadmium contaminated soil remediation and coordinated carbon fixation and emission reduction, characterized in that: Biochar is used to adsorb and fix mixed bacteria to obtain microbial modified biochar; the biochar is made from corn stalks as raw materials; the mixed bacteria is a mixed bacteria of Bacillus subtilis, Bacillus velezii and Rhodopseudomonas palustris.

2. The method for preparing microbial modified biochar according to claim 1, characterized in that: The Bacillus subtilis, Bacillus Velez and Rhodopseudomonas palustris are mixed according to a bacterial liquid volume ratio of (1-3):(1-3):(1-3).

3. The method for preparing microbial modified biochar according to claim 1 or 2, characterized in that: The mass ratio of the biomass charcoal to the mixed bacteria is 1:(5-15).

4. The method for preparing microbial modified biochar according to claim 1, characterized in that: The method of using biochar to adsorb and fix the mixed bacteria is to mix the biochar with the mixed bacteria and then culture them for 12-48 hours.

5. The method for preparing microbial modified biochar according to claim 1, characterized in that: The method for preparing the biomass charcoal comprises: pyrolyzing corn stalk powder at 300-600° C. for 1-3 hours under anaerobic or anoxic conditions to obtain the biomass charcoal.

6. The method for preparing microbial modified biochar according to claim 5, characterized in that: The particle size of the corn stalk powder is less than or equal to 2 mm.

7. The method for preparing microbial modified biochar according to claim 5, characterized in that: The obtained biochar is dried and passed through a 60-100 mesh sieve.

8. The method for preparing microbial modified biochar according to any one of claims 1 to 7, characterized in that: The steps include: S1. Cultivation of bacterial species: Bacillus subtilis, Bacillus velezinoff, and Rhodopseudomonas palustris were cultured to obtain three bacterial suspensions; S2. Co-culture of mixed bacteria: Bacillus subtilis, Bacillus Velez and Rhodopseudomonas palustris suspensions were mixed in a volume ratio of (1-3): (1-3): (1-3), and then the co-culture was continued for 12-48 hours to obtain a mixed bacterial solution; S3. Preparation of biochar material: Pyrolyze corn stalk powder with a particle size of less than or equal to 2 mm under anaerobic or anoxic conditions at 300-600°C for 1-3h to obtain biochar, dry the obtained biochar, and sieve through a 60-100 mesh sieve to obtain biochar powder; S4. Preparation of microbial modified biochar material: Mix the mixed bacterial solution obtained in step S2 with the biochar powder obtained in step S3 in a mass ratio of (5-15):1, and then culture at 100-200rpm and 25-35℃ for 12-48h to allow the mixed bacteria to be evenly adsorbed and fixed on the surface of the biochar, collect the biochar after the mixed bacteria are adsorbed and fixed, and freeze-dry to obtain microbial modified biochar.

9. Microbial modified biochar prepared according to any one of claims 1 to 8.

10. Application of the microbially modified biochar according to claim 9 in cadmium-contaminated soil remediation and carbon fixation and emission reduction.

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