A microbial modified biochar for synergistic remediation of cadmium - contaminated soil and carbon sequestration and emission reduction, and its preparation method and application

Abstract

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 its preparation method and application. This method 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 velezinoff, 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, and has important application value for the remediation of heavy metal cadmium contaminated soil. Moreover, the microbial modified biochar has simple ingredients and a simple production process, and has a good prospect for promotion and application.

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 sequestration and emission reduction, as well as a preparation method and application thereof. Background Art

[0002] Soil carbon dioxide emissions are a key pathway for carbon exchange between terrestrial ecosystems and the atmosphere. Their emission levels and spatial distribution have significant impacts on the global carbon cycle and climate change. A growing number of studies indicate that soil carbon dioxide emissions undermine global climate change efforts. As global climate change intensifies, enhancing soil carbon sequestration has become a key strategy for addressing climate change. Soil carbon sequestration not only reduces atmospheric carbon dioxide concentrations and mitigates climate change, but also improves soil fertility and promotes sustainable agricultural development. However, current soil carbon sequestration technologies have limitations, making it difficult to achieve optimal results in practical applications.

[0003] Soil CO2 emissions are primarily generated through the decomposition of organic matter by soil microorganisms, plant roots, and soil animals through respiration. The factors influencing soil CO2 emissions are complex. Studies have shown that heavy metal pollution can also significantly impact soil CO2 emissions. Heavy metal pollution alters the chemical and physical properties of the soil. Heavy metal accumulation can lead to imbalances in soil pH, affecting soil fertility and affecting soil microbial function and community structure. These factors are all fundamentally related to soil CO2 emissions. Due to the complexity of these influencing factors, the current development of soil carbon sequestration and emission reduction technologies has been relatively one-sided, lacking a mature theory. Furthermore, in the face of the even more complex issue of carbon sequestration and emission reduction in heavy metal-contaminated soils, the diverse ways heavy metals impact the soil ecosystem and the highly complex environment mean that current research on the mechanisms of this process remains controversial.

[0004] Biochar is a porous solid particulate material obtained by pyrolyzing biomass such as straw under high-temperature conditions in the absence of or anoxic conditions. As a material with excellent adsorption properties, it is widely used in soil remediation. It can improve the physical and chemical properties of the soil and effectively adsorb heavy metals such as cadmium in the soil, reducing their bioavailability in the soil and thus reducing their potential harm to plants and humans. However, in terms of carbon sequestration and emission reduction, the role of biochar is not strong, especially because the carbon sequestration and emission reduction effect of biochar is also affected by the type of raw material used in its preparation. Corn straw is an important and abundant raw material for making biochar, but studies have shown that biochar produced from corn straw has almost no carbon sequestration effect, making it difficult to use it to achieve carbon sequestration and emission reduction goals, which also limits the utilization of corn straw to a certain extent.

[0005] In addition, there are also reports on the use of microorganisms to repair heavy metal pollution and fix carbon. For example, various Bacillus species have been reported to have certain effects on repairing cadmium-contaminated soil, and photosynthetic bacteria such as Rhodopseudomonas palustris have carbon fixation. However, the effects of single biochar and single microbial bacteria are also limited, and the effects of different species 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. Chinese invention patent publication number CN117402626A discloses a rice straw biochar equipped with Bacillus cereus with carbon fixation ability. When applied to soil, it can increase the soil organic carbon content, but the biochar cannot treat heavy metal pollution; Chinese invention patent publication number CN112592240A discloses a biocarbon-based composite conditioner for repairing soil cadmium pollution. It uses Bacillus subtilis and Rhodopseudomonas palustris with cadmium fixation ability to reduce the bioavailability of cadmium and improve the heavy metal cadmium pollution in the soil. However, the composite conditioner has complex ingredients, a cumbersome production process, and no carbon fixation function.

[0006] Therefore, there is a close relationship between heavy metal pollution in soil and carbon dioxide emissions, but the mutual influence and mechanism are unclear. Faced with 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

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing dual technologies for the remediation of heavy metal, especially cadmium-contaminated soil and carbon sequestration and emission reduction, and provide a preparation method for microbial-modified biochar materials that can quickly and efficiently remediate cadmium-contaminated soil and simultaneously improve the soil's carbon sequestration capacity. This method couples biochar materials with microbial remediation technology, and has the dual functions of quickly and efficiently achieving cadmium fixation and carbon sequestration and emission reduction in heavy metal cadmium-contaminated soil, and has important application value for the remediation of heavy metal cadmium-contaminated soil.

[0008] The purpose of the present invention is to provide a method for preparing microbial modified biochar for cadmium-contaminated soil remediation and coordinated carbon sequestration and emission reduction.

[0009] 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.

[0010] Another object of the present invention is to provide the application of the above-mentioned microbial modified biochar in the remediation of cadmium-contaminated soil and the coordinated carbon sequestration and emission reduction.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0012] The present invention couples biochar materials with microbial remediation technology, and uses biochar made from corn straw as raw material to adsorb and fix a mixed bacteria of Bacillus subtilis, Bacillus Velez and Rhodopseudomonas palustris. The prepared microbial modified biochar has both the functions of repairing cadmium-contaminated soil and soil carbon fixation. It 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 repair of heavy metal cadmium-contaminated soil.

[0013] Specifically, the present invention provides a method for preparing microbial-modified biochar for cadmium-contaminated soil remediation and synergistic carbon fixation and emission reduction. The method uses biochar to adsorb and fix mixed bacteria to obtain microbial-modified biochar; the biochar is made from corn straw as raw material; the mixed bacteria is a mixture of Bacillus subtilis, Bacillus velezii and Rhodopseudomonas palustris.

[0014] Preferably, the biochar is prepared by pyrolyzing corn straw powder at 300-600° C. for 1-3 h (more preferably at 450° C. for 2 h) under anaerobic or anoxic conditions to obtain the biochar.

[0015] More preferably, the particle size of the corn straw powder is less than or equal to 2 mm.

[0016] Optionally, the anaerobic or anoxic condition can be formed by using nitrogen at a flow rate of 400-800 mL / min (preferably 600 mL / min) as a protective gas.

[0017] Preferably, the Bacillus subtilis, Bacillus velezensis 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.

[0018] Preferably, the mass ratio of the biochar to the mixed bacterial liquid is 1:(5-15), more preferably 1:10.

[0019] In the preparation method, the method of using biochar to adsorb and immobilize the mixed bacteria is to mix the biochar with the mixed bacteria solution and then culture it for 12-48 hours, preferably with shaking at 100-200 rpm and 25-35°C for 12-48 hours.

[0020] The resulting microbial-modified biochar material is then dried. Preferably, the drying method is freeze-drying. Compared to conventional drying, freeze-drying does not damage the loaded bacteria due to excessively high temperatures.

[0021] Specifically, the method for preparing microbial modified biochar provided by the present invention comprises the following steps:

[0022] S1. Cultivation of bacterial species: Bacillus subtilis, Bacillus velezensis, and Rhodopseudomonas palustris were cultured separately to obtain three bacterial suspensions;

[0023] 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 co-cultured for 12-48 hours to obtain a mixed bacterial solution;

[0024] S3. Preparation of biochar material: corn straw powder with a particle size of less than or equal to 2 mm was pyrolyzed at 300-600 ° C for 1-3 h under anaerobic or anoxic conditions to obtain biochar, and the obtained biochar was dried and passed through a 60-100 mesh sieve to obtain biochar powder;

[0025] S4. Preparation of microbial-modified biochar material: The mixed bacterial solution obtained in step S2 is mixed with the biochar powder obtained in step S3 in a mass ratio of (5-15):1, and then cultured at 100-200 rpm and 25-35°C for 12-48 hours to allow the mixed bacteria to be evenly adsorbed and fixed on the surface of the biochar. The adsorbed and fixed biochar is collected and freeze-dried to obtain microbial-modified biochar.

[0026] Preferably, the OD600 of the bacterial suspensions of Bacillus subtilis, Bacillus velezensis and Rhodopseudomonas palustris in step S1 are all 0.5-1.5. More preferably, OD600=1.0

[0027] Preferably, in step S1, the culture conditions for Bacillus subtilis, Bacillus velezensis and Rhodopseudomonas palustris are all 30° C. and 180 rpm with shaking, more preferably 30° C. and 180 rpm.

[0028] Preferably, Bacillus subtilis is cultured for 12-48 h (more preferably 24 h).

[0029] Preferably, Bacillus velezensis is cultured for 24-60 h (more preferably 48 h).

[0030] Preferably, Rhodopseudomonas palustris is cultured for 6-8 days (more preferably 7 days).

[0031] In addition, preferably, the culture conditions of Rhodopseudomonas palustris require additional lighting conditions (preferably 10-100 watt tungsten filament lamp).

[0032] Optionally, the culture medium for Bacillus subtilis and Bacillus velezii 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, and pH 6.5-7.5.

[0033] Preferably, the culture medium for Bacillus subtilis and Bacillus velez is: 3.0 g beef extract, 10.0 g peptone, 5.0 g sodium chloride, and distilled water to 1.0 L, with a pH of 7.0.

[0034] 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, and distilled water to a volume of 1.0 L, with a pH of 6.5-7.5.

[0035] 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 a volume of 1.0 L, with a pH of 7.0.

[0036] Preferably, the co-culture conditions in step S2 are shaking culture at 25-35° C. and 100-200 rpm for 12-48 hours, more preferably at 30° C. and 180 rpm for 24 hours.

[0037] Preferably, in step S2, the bacterial suspensions of Bacillus subtilis, Bacillus velezensis and Rhodopseudomonas palustris are mixed in a volume ratio of 2:2:3.

[0038] Preferably, in step S3, the pyrolysis is carried out at 450° C. for 2 h.

[0039] Optionally, the anaerobic or anoxic condition in step S3 can be formed by using nitrogen at a flow rate of 400-800 mL / min (preferably 600 mL / min) as the protective gas.

[0040] Preferably, the dried biochar in step S3 is sieved through a 60-mesh sieve to obtain biochar powder.

[0041] Preferably, the mass ratio of the mixed bacterial liquid to the biochar powder in step S4 is 10:1.

[0042] Preferably, the shaking culture conditions in step S4 are 120 rpm, 30° C., and 24 h.

[0043] Preferably, the drying method is freeze-drying. Compared with ordinary drying, freeze-drying will not damage the loaded bacteria due to excessively high temperature.

[0044] Preferably, the freeze-drying method is: first freezing at -80-20°C for 12-48 hours, and then freeze-drying for 24-60 hours.

[0045] 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.

[0046] The microbial-modified biochar material can achieve the dual functions of cadmium fixation and carbon sequestration 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 the remediation of cadmium-contaminated soil and carbon sequestration and emission reduction (reducing the emission of carbon dioxide from cadmium-contaminated soil) should also be within the scope of protection of the present invention.

[0047] The present invention has the following beneficial effects:

[0048] (1) The present invention couples biochar materials with microbial remediation technology, and uses biochar made from corn straw as raw material 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 sequestration 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 negative carbon dioxide emissions continue to appear thereafter), which has important application value for the remediation of heavy metal cadmium contaminated soil.

[0049] (2) The microbial modified biochar material of the present invention has simple components and a simple production process, and has a good prospect for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a graph showing the 24-hour cadmium adsorption of a solution containing 30 mg / kg cadmium by mixed bacteria of different types and proportions in Example 1 of the present invention (different letters on the columns indicate significant differences).

[0051] Figure 2 This is a SEM morphology of the mixed bacteria in Example 1 of the present invention.

[0052] Figure 3 This is the SEM morphology of the biochar in Example 2 of the present invention.

[0053] Figure 4 This is an SEM image of the microbial-modified biochar material in Example 2 of the present invention.

[0054] Figure 5 This is a graph showing 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).

[0055] Figure 6 This is a graph showing 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).

[0056] Figure 7This is a graph of the carbon dioxide emission rate of soil after the biochar material and the microbially modified biochar material in Example 3 of the present invention are added to cadmium-contaminated soil. DETAILED DESCRIPTION

[0057] The present invention will be further described below with reference to the accompanying drawings and specific examples, but the examples do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0058] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0059] In the following embodiments:

[0060] The selected Bacillus subtilis is Bacillus subtilis B1 strain, which comes from Beina Bio-Henan Industrial Microbiology Engineering Technology Research Center (https: / / www.bncc.com / ), with the preservation number BNCC188159 and the preservation time of September 27, 2021.

[0061] The selected Bacillus Velez subtilis was the Bacillus Velez subtilis strain B2, which was obtained from the Guangdong Provincial 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.

[0062] The Rhodopseudomonas palustris strain R was obtained from Guangdong Provincial 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.

[0063] The culture medium used was:

[0064] The culture medium for Bacillus subtilis and Bacillus velezii was: 3.0 g beef extract, 10.0 g peptone, 5.0 g sodium chloride, and distilled water to 1.0 L, with a pH of 7.0.

[0065] The culture medium for Rhodopseudomonas palustris was as follows: 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.

[0066] Example 1 Study on the adsorption effect of cadmium by mixed bacteria in different proportions

[0067] 1. Preparation of single bacterial suspension and mixed bacterial solution

[0068] (1) Enrichment culture of bacterial strains

[0069] Inoculate 10% by volume of Bacillus subtilis B1 into the culture medium, and culture in a conditioned incubator at 30°C and 180 rpm for 24 hours to obtain a Bacillus subtilis B1 suspension;

[0070] The culture medium was inoculated with 10% of the volume ratio of Bacillus Velez B2, and the culture was shaken in a conditioned incubator at 30°C and 180 rpm for 48 hours to obtain a suspension of Bacillus Velez B2;

[0071] Rhodopseudomonas palustris R was inoculated into the culture medium at a transfer rate of 10% by volume, and cultured in an incubator at 30° C., 180 rpm, and 40-watt tungsten light for 7 days to obtain a Rhodopseudomonas palustris R bacterial suspension.

[0072] (2) Culture of mixed bacteria

[0073] Select the Bacillus subtilis B1 suspension, Bacillus velezensis B2 suspension and Rhodopseudomonas palustris R suspension cultured in step (1) with OD600=1.0, and use a volume ratio of 3 3 Orthogonal experiments were performed to construct mixed strains, and 9 different ratios were obtained from MB1 to MB9. 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.

[0074] Table 1 Bacteria mixed in different proportions

[0075]

[0076] 2. Experiment on the adsorption of cadmium by single bacterial suspension and mixed bacterial suspension

[0077] 5 ml of each mixed bacterial solution and each single bacterial suspension were mixed with 50 ml of CdCl2 solution (cadmium concentration of 30 mg / kg) and shaken at 30°C and 180 rpm. After 24 hours, the supernatant was collected and filtered through a 0.22 μm filter membrane. The cadmium content of the supernatant was determined using an inductively coupled plasma optical emission spectrometer.

[0078] 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 them, the mixed bacteria MB5 with 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 the adsorption capacity of a single bacterium.

[0079] Example 2 Preparation of microbial modified biochar material

[0080] 1. According to the same method as 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 cultured at 30°C and 180 rpm for 24 h to obtain a mixed bacterial solution.

[0081] 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 velezini both belong to the genus Bacillus and have a straight rod shape.

[0082] 2. Preparation of biochar materials

[0083] The crushed corn stalks were air-dried at room temperature, then ground and 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, and the flow rate of nitrogen protective gas was adjusted to 600 mL / min. The crucible was subjected to oxygen-free carbonization 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.

[0084] like Figure 3 As shown, the prepared biochar exhibited a porous structure, indicating that it was a suitable carrier for bacterial loading.

[0085] 3. Preparation of microbial modified biochar materials

[0086] 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 h, and shaken to allow the mixed bacteria to be evenly adsorbed and fixed on the surface of the biochar. The adsorbed and fixed biochar was collected, frozen in a -80°C refrigerator for 24 h, and then freeze-dried in a freeze dryer for 48 h to obtain a microbial modified biochar material.

[0087] 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.

[0088] Example 3 Remediation of Cadmium-Contaminated Soil by Microbial Modification of Biochar Materials

[0089] 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, respectively. 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), maintaining a moisture content of 30%. The soil was collected after 45 days, and the effective cadmium content and BCR-extractable cadmium content were determined using an inductively coupled plasma optical emission spectrometer.

[0090] The results are as follows Figure 5 As shown in the data, after 45 days of remediation, both biochar materials and microbial modified biochar materials significantly reduced the content of available cadmium in cadmium-contaminated soil. Compared with before remediation, the addition of 3g of microbial modified biochar material had the greatest effect on reducing the content of available 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, this 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, and the reason may be the limitation caused by the nature of the biochar itself.

[0091] 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.

[0092] Example 4 Study on the reduction of carbon dioxide emissions from cadmium-contaminated soil by microbial modified biochar materials

[0093] 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. The soil was then placed in a sealed gas collection bottle, the soil moisture content was adjusted to 30%, and the mixture was stirred evenly. The mixture was then placed at room temperature (15-35°C) and gas was collected on days 1, 4, 7, 14, 21, 30, and 40. The carbon dioxide content in the gas was measured using a greenhouse gas analyzer, and the carbon dioxide emission rate was calculated.

[0094] like Figure 7 The results shown indicate that:

[0095] (1) Only the group with microbial-modified biochar material showed negative carbon dioxide emissions, which showed the function of carbon sequestration and emission reduction.

[0096] 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 sequestration capacity.

[0097] (2) The treatment group with added biochar material showed a trend closer 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.

[0098] In summary, the microbial modified biochar material prepared by the present invention can effectively repair cadmium pollution in soil while reducing carbon dioxide emissions from cadmium-contaminated soil, showing good carbon sequestration ability.

[0099] 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 considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing microbial modified biochar for cadmium-contaminated soil remediation and synergistic carbon sequestration and emission reduction, characterized in that: Biochar is used to adsorb and immobilize mixed bacteria to obtain microbial modified biochar; the biochar is made from corn straw; the mixed bacteria is a mixed bacteria of Bacillus subtilis, Bacillus Velez and Rhodopseudomonas palustris; the Bacillus subtilis, Bacillus Velez and Rhodopseudomonas palustris are mixed in a bacterial liquid volume ratio of 2:2:3; the mass ratio of the biochar to the mixed bacteria is 1:(5-15).

2. 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 and the mixed bacteria and then culture them for 12-48 hours.

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

4. The method for preparing microbial modified biochar according to claim 3, characterized in that: The particle size of the corn straw powder is less than or equal to 2 mm.

5. The method for preparing microbial modified biochar according to claim 3, characterized in that: The obtained biochar is dried and passed through a 60-100 mesh sieve.

6. The method for preparing microbial modified biochar according to any one of claims 1 to 5, characterized in that: The steps include: S1. Cultivation of bacterial species: Bacillus subtilis, Bacillus velezensis, and Rhodopseudomonas palustris were cultured separately 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 co-cultured for 12-48 h to obtain a mixed bacterial solution; S3. Preparation of biochar material: corn straw powder with a particle size of less than or equal to 2 mm was pyrolyzed at 300-600 ° C for 1-3 h under anaerobic or anoxic conditions to obtain biochar, and the obtained biochar was dried and passed through a 60-100 mesh sieve to obtain biochar powder; S4. Preparation of microbial-modified biochar material: The mixed bacterial solution obtained in step S2 is mixed with the biochar powder obtained in step S3 in a mass ratio of (5-15):1, and then cultured at 100-200 rpm and 25-35°C for 12-48 hours to allow the mixed bacteria to be evenly adsorbed and fixed on the surface of the biochar. The biochar with adsorbed and fixed mixed bacteria is collected and freeze-dried to obtain microbial-modified biochar.

7. Microbial modified biochar prepared according to the method of any one of claims 1 to 6.

8. A method for remediating cadmium-contaminated soil and reducing carbon emissions, characterized in that: The soil is treated using the microbial-modified biochar according to claim 7, wherein the mass ratio of the microbial-modified biochar according to claim 7 to the cadmium-contaminated soil is 3:200; and the cadmium content in the cadmium-contaminated soil is 13 mg / kg.

Images