Composite repairing material for soil cadmium pollution and preparation method of composite repairing material

Abstract

The invention discloses a composite remediation material for soil cadmium pollution and a preparation method thereof, and belongs to the technical field of soil pollution remediation. The preparation method comprises the following steps: mixing the protective bacterium-loaded biochar, the silicon-calcium powder and the adhesive, drying, and crushing. The used material has the characteristic of environmental friendliness, the cadmium in the soil is adsorbed through the specially-made protective bacterium-loaded biochar, the cadmium ions are enriched by utilizing the porous structure of the biochar, the cadmium is fixed by virtue of the biotransformation effect of the saccharomyces cerevisiae, and the content of the cadmium in an exchange state in the soil is reduced. By adding the silicon-calcium powder, cadmium in an exchange state in the soil can be converted into cadmium in a residue state, and absorption and enrichment of plants to the cadmium in the soil are reduced. According to the method, secondary pollution caused by chemical reagents is avoided on the premise that the soil cadmium pollution remediation effect is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil pollution remediation, and particularly relates to a composite remediation material for soil cadmium pollution and a preparation method thereof. Background Art

[0002] Soil is the basis of agricultural production. However, with the rapid development of the national economy, heavy metal-containing pollutants enter the soil through various channels, gradually forming soil heavy metal pollution. Soil heavy metal pollution has attracted worldwide attention due to its concealment, long-term nature, and irreversibility. It not only degrades soil fertility, reduces crop yield and quality, but also can cause agricultural product pollution and water resource pollution, and endanger human life and health through the food chain.

[0003] Patent CN110607248B discloses a Vogesella sp. strain A6 for repairing soil cadmium pollution and its uses. The Vogesella sp. strain A6 used in this invention is preserved in the China Center for Type Culture Collection, and the preservation number is CCTCC NO: M2018277. The strain of this invention is classified and named as Vogesella sp., and has the ability to remove cadmium in the soil. Through the screening and identification of cadmium-resistant strains, the cadmium removal ability of this strain under specific culture conditions, as well as the evaluation of the cadmium form conversion ability in cadmium-polluted soil and the remediation effect on soil cadmium pollution under laboratory conditions, are verified.

[0004] Although the above patent can reduce the content of exchangeable cadmium in the soil, it only relies on microbial fixation, and has poor and slow remediation effects on severely cadmium-polluted soil.

[0005] Patent CN105567249B discloses a chemical remediation agent for cadmium pollution in farmland soil, which is composed of 10 - 30 parts of humic acid, 10 - 30 parts of ammonium sulfate, 10 - 30 parts of potassium dihydrogen phosphate, 10 - 15 parts of citric acid, 5 - 15 parts of disodium dihydrogen pyrophosphate, 5 - 10 parts of biosurfactant, 5 - 10 parts of cadmium chemical detoxifying agent, and 5 - 10 parts of bentonite mixed. The remediation agent is evenly applied into the soil by plowing with the soil, and the application amount per mu is 40 - 50 kg, and then harrowed evenly and irrigated. The remediation agent of this invention makes the cadmium in the soil form a more stable chelated state that is not easily absorbed and utilized by plants through activation, chelation, and adsorption, changes from small molecules to macromolecules, realizes the passivation of cadmium in the soil, reduces its toxicity, and is suitable for the chemical remediation of cadmium pollution in calcareous farmland soil.

[0006] Although the above patent has a certain effect on reducing the content of exchangeable cadmium, a large amount of artificially synthesized chemicals are used therein, which greatly changes the soil components, and thus has potential adverse effects on the microbial ecology in the soil.

[0007] Therefore, it is of great significance to develop a composite remediation material for soil cadmium pollution that is friendly to nature and has remarkable effects. Summary of the Invention

[0008] In view of the deficiencies of the prior art, the materials used in the present invention have the characteristics of environmental friendliness. Cadmium in the soil is adsorbed by the specially prepared protected bacteria-carrying biochar, and its porous structure is used to enrich cadmium ions. With the help of the biological transformation of Saccharomyces cerevisiae, cadmium is fixed, and the content of exchangeable cadmium in the soil is reduced. By adding silicon-calcium powder, it can convert the exchangeable cadmium in the soil into residual cadmium, reducing the absorption and enrichment of cadmium by plants in the soil. The technical problems raised in the background art are solved. Specifically, the technical solution of the present invention includes the following:

[0009] A preparation method of a composite remediation material for soil cadmium pollution, the preparation method comprising the following steps:

[0010] The protected bacteria-carrying biochar, silicon-calcium powder and binder are mixed and then ventilated and dried at 35°C for 24 h, and then pulverized and passed through a 20-mesh sieve to obtain the composite remediation material.

[0011] Further, the preparation method of the protected bacteria-carrying biochar includes the following steps:

[0012] Corn straw, peanut shells and wheat straw are mixed in a mass ratio of 4:2:4 to obtain composite straw;

[0013] The composite straw is dried by baking at 80°C for 1 h, and then pulverized to a size that can pass through a 60-mesh sieve to obtain composite powder;

[0014] The composite powder and sodium metasilicate nonahydrate are mixed in a mass ratio of 3:1 to obtain a composite substrate;

[0015] The composite substrate is pyrolyzed at 550°C to 600°C for 2 h, and then pulverized to a size that can pass through a 60-mesh sieve to obtain modified biochar;

[0016] The modified biochar and the Saccharomyces cerevisiae suspension are mixed and then ventilated and dried at 35°C for 24 h to obtain bacteria-carrying biochar;

[0017] Gelatin, hydroxypropyl methylcellulose and sterile water are mixed in a mass ratio of 2:1:50 to obtain a protective solution;

[0018] The protective solution is evenly sprayed on the surface of the bacteria-carrying biochar and then ventilated and dried at 35°C for 6 h to obtain the protected bacteria-carrying biochar;

[0019] The functions of using corn straw, peanut shells and wheat straw are as follows: the porous structure formed after their pyrolysis is beneficial to the adsorption of cadmium, and can provide a part of carbon source for Saccharomyces cerevisiae, and has no adverse effects on the soil;

[0020] The function of using sodium metasilicate nonahydrate is as follows: Sodium metasilicate nonahydrate can modify the biochar-based material, improve the stabilization effect of biochar-based material on cadmium in soil, and has resistance to abiotic stress and biotic stress;

[0021] The function of using gelatin and hydroxypropyl methylcellulose is as follows: The protection system composed of the two can block the pores on the surface of the biochar carrying bacteria, further prevent the direct contact between alkaline substances and Saccharomyces cerevisiae during the storage of the composite material, improve the use activity of Saccharomyces cerevisiae, and can decompose after contacting the soil without affecting the efficacy of the biochar carrying bacteria.

[0022] Furthermore, the preparation method of the Saccharomyces cerevisiae suspension includes the following steps:

[0023] Inoculate Saccharomyces cerevisiae into 500 mL of YPD liquid medium, and cultivate it at 30 °C with shaking at 200 r / min for 120 h to obtain a Saccharomyces cerevisiae solution;

[0024] Centrifuge the Saccharomyces cerevisiae solution at 3000 r / min for 5 min, remove the supernatant, and wash it with 1000 mL of sterile normal saline to obtain activated Saccharomyces cerevisiae;

[0025] Mix D(+)-anhydrous trehalose, potassium dihydrogen phosphate, dipotassium hydrogen phosphate and sterile water according to a mass ratio of 50:68:87:1000 to obtain a buffer solution;

[0026] After mixing the activated Saccharomyces cerevisiae and the buffer solution, count through a hemocytometer, and measure the density of Saccharomyces cerevisiae to be 1×10 7 CFU / mL to 1×10 8 CFU / mL to obtain a Saccharomyces cerevisiae suspension;

[0027] The function of using D(+)-anhydrous trehalose, potassium dihydrogen phosphate and dipotassium hydrogen phosphate is as follows: The pH buffer system composed of the three can improve the resistance of Saccharomyces cerevisiae to alkaline environment;

[0028] Furthermore, the preparation method of the YPD liquid medium includes the following steps:

[0029] Mix yeast extract, peptone, glucose and sterile water, sterilize it at 121 °C for 30 min, and let it cool to room temperature to obtain YPD liquid medium.

[0030] Furthermore, the mass ratio of yeast extract:peptone:glucose:sterile water is 1:2:2:100.

[0031] Further, the mass ratio of the modified biochar to the suspension of Saccharomyces cerevisiae is 2:1. The functions of using the modified biochar and the suspension of Saccharomyces cerevisiae are as follows: during the reproduction and metabolism of Saccharomyces cerevisiae, the biotransformation effect can reduce the content of exchangeable cadmium in the soil. By wrapping Saccharomyces cerevisiae with the modified biochar, the direct contact area between Saccharomyces cerevisiae and alkaline substances can be reduced, thereby improving the resistance of Saccharomyces cerevisiae to the alkaline environment.

[0032] Further, the mass ratio of the protective liquid to the biochar carrying bacteria is 1:25.

[0033] Further, the binder is obtained by mixing soy peptone and sterile water. The function of using soy peptone is that it has good viscosity after being mixed with water and can serve as a protein source for Saccharomyces cerevisiae.

[0034] Further, the mass ratio of the soy peptone to the sterile water is 1:20.

[0035] Further, the mass ratio of the protective biochar carrying bacteria, silicon-calcium powder, and the binder is 5:2:3.

[0036] A composite remediation material for soil cadmium pollution prepared by the preparation method of a composite remediation material.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The present invention first obtains a special protective biochar carrying bacteria through scientific proportioning and processing technology. By utilizing the porous structure and chemical adsorption sites of the modified biochar, cadmium in the soil is adsorbed into it, thereby reducing the total content of cadmium in the soil. At the same time, sodium metasilicate nonahydrate itself has resistance to abiotic and biotic stress, which can reduce the absorption and enrichment of cadmium by plants in the soil. Then, by using the biotransformation effect during the reproduction and metabolism of Saccharomyces cerevisiae, the content of exchangeable cadmium in the soil is continuously reduced. By adding silicon-calcium powder, the exchangeable cadmium in the soil can be quickly converted into residual cadmium, and the alkalinity of the silicon-calcium powder will continuously decrease during this process. Since the alkaline environment is not conducive to the survival of Saccharomyces cerevisiae, Saccharomyces cerevisiae needs to be added to a buffer solution and then wrapped with the modified biochar to form biochar carrying bacteria, and a protective liquid that can be slowly decomposed by the soil is sprayed on the biochar carrying bacteria to avoid Saccharomyces cerevisiae being directly exposed to a relatively high alkaline environment in the early stage of repairing soil cadmium pollution, thereby improving the biological activity of Saccharomyces cerevisiae. Finally, a composite remediation material that can effectively repair soil cadmium pollution without causing secondary pollution is obtained. Specific embodiments

[0039] The technical solutions of the present invention will be clearly and completely described below through embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0040] Unless otherwise specified, the raw materials and reagents used in the present invention below are all commercially available products or can be prepared by known methods.

[0041] Sodium metasilicate nonahydrate, D(+)-trehalose anhydrous, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, gelatin, hydroxypropyl methylcellulose and peptone from soybeans were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0042] The strain number of Saccharomyces cerevisiae is CICC 31362, which was purchased from the China Center for Industrial Culture Collection.

[0043] Preparation Example 1:

[0044] A preparation method of protected bacteria-carrying biochar specifically includes the following process:

[0045] Mix 4 parts by weight of corn straw, 2 parts by weight of peanut shells and 4 parts by weight of wheat straw, then put them into an oven and adjust the temperature to 80 °C for dry baking for 1 h. After dry baking, put them into a powder grinder for grinding until a composite powder that can pass through a 60-mesh sieve is obtained. Put 3 parts by weight of the composite powder and 1 part by weight of sodium metasilicate nonahydrate into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into a sealed dry baking furnace, adjust the temperature to 600 °C, pyrolyze for 2 h, take them out, let them cool to room temperature, and then put them into a powder grinder for grinding until a modified biochar that can pass through a 60-mesh sieve is obtained. Put 1 part by weight of yeast extract, 2 parts by weight of peptone, 2 parts by weight of glucose and 100 parts by weight of sterile water into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into an autoclave, adjust the temperature to 121 °C for sterilization for 30 min, take them out and let them cool to obtain YPD liquid medium. Inoculate a strain of Saccharomyces cerevisiae into a sterile culture flask containing 500 mL of YPD liquid medium, and put the sterile culture flask into an oscillating incubator, adjust the temperature to 30 °C, adjust the rotation speed to 200 r / min, and culture for 120 h to obtain a Saccharomyces cerevisiae solution. Put the Saccharomyces cerevisiae solution into a centrifuge, adjust the rotation speed to 3000 r / min, centrifuge for 5 min, filter to remove the supernatant, and wash the remaining material with 1000 mL of sterile normal saline to obtain activated Saccharomyces cerevisiae. Put 50 parts by weight of D(+)-trehalose anhydrous, 68 parts by weight of potassium dihydrogen phosphate, 87 parts by weight of dipotassium hydrogen phosphate and 1000 parts by weight of sterile water into a stirrer and stir at a speed of 300 r / min for 20 min to obtain a buffer solution. Continuously add activated Saccharomyces cerevisiae to the buffer solution until, by counting with a hemocytometer, the density of Saccharomyces cerevisiae is measured to be 1×10 8 CFU / mL to obtain a Saccharomyces cerevisiae suspension. Put 2 parts by weight of the modified biochar and 1 part by weight of the Saccharomyces cerevisiae suspension into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into a ventilated drying oven, adjust the temperature to 35 °C and dry for 24 h to obtain biochar loaded with bacteria. Put 2 parts by weight of gelatin, 1 part by weight of hydroxypropyl methylcellulose and 50 parts by weight of sterile water into a stirrer and stir at a speed of 100 r / min for 30 min to obtain a protective solution. Uniformly spray 1 part by weight of the protective solution on the surface of 25 parts by weight of the biochar loaded with bacteria, then put them into a ventilated drying oven, adjust the temperature to 35 °C and dry for 6 h to obtain a protected biochar loaded with bacteria.

[0046] Preparation Example 2:

[0047] A preparation method of silicon-calcium powder specifically includes the following process:

[0048] Put 10 parts by weight of tobermorite into a powder grinder for grinding until a silicon-calcium powder that can pass through a 40-mesh sieve is obtained.

[0049] Preparation Example 3:

[0050] Preparation method of the adhesive, specifically including the following process:

[0051] Put 1 part by weight of soy peptone and 20 parts by weight of sterile water into a stirrer and stir at a speed of 60 r / min for 10 min to obtain the adhesive.

[0052] Preparation Example 4:

[0053] Preparation method of the protected bacteria-carrying biochar, specifically including the following process:

[0054] Mix 4 parts by weight of corn straw, 2 parts by weight of peanut shells and 4 parts by weight of wheat straw, then put them into a baking oven, adjust the temperature to 80 °C and dry-bake for 1 h. After dry-baking, put them into a pulverizer and pulverize until it can pass through a 60-mesh sieve to obtain a composite powder. Put 3 parts by weight of the composite powder and 1 part by weight of sodium metasilicate nonahydrate into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into a sealed dry-baking furnace, adjust the temperature to 600 °C and pyrolyze for 2 h, take them out, let them cool to room temperature and then put them into a pulverizer and pulverize until it can pass through a 60-mesh sieve to obtain modified biochar. Put 1 part by weight of yeast extract, 2 parts by weight of peptone, 2 parts by weight of glucose and 100 parts by weight of sterile water into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into an autoclave, adjust the temperature to 121 °C and sterilize for 30 min, take them out and let them cool to obtain YPD liquid medium. Inoculate a Saccharomyces cerevisiae into a sterile culture flask containing 500 mL of YPD liquid medium, and put the sterile culture flask into an oscillating incubator, adjust the temperature to 30 °C and the rotation speed to 200 r / min, and culture for 120 h to obtain a Saccharomyces cerevisiae solution. Put the Saccharomyces cerevisiae solution into a centrifuge, adjust the rotation speed to 3000 r / min, centrifuge for 5 min, filter to remove the supernatant, and rinse the remaining material with 1000 mL of sterile normal saline to obtain activated Saccharomyces cerevisiae. Put 50 parts by weight of D(+)-anhydrous trehalose, 68 parts by weight of potassium dihydrogen phosphate, 87 parts by weight of dipotassium hydrogen phosphate and 1000 parts by weight of sterile water into a stirrer and stir at a speed of 300 r / min for 20 min to obtain a buffer solution. Continuously add activated Saccharomyces cerevisiae to the buffer solution until, through counting with a hemocytometer, the density of Saccharomyces cerevisiae is measured to be 1×10 7 CFU / mL to obtain a Saccharomyces cerevisiae suspension. Put 2 parts by weight of the modified biochar and 1 part by weight of the Saccharomyces cerevisiae suspension into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into a ventilated drying oven, adjust the temperature to 35 °C and dry for 24 h to obtain bacteria-carrying biochar. Put 2 parts by weight of gelatin, 1 part by weight of hydroxypropyl methylcellulose and 50 parts by weight of sterile water into a stirrer and stir at a speed of 100 r / min for 30 min to obtain a protective solution. Uniformly spray 1 part by weight of the protective solution on the surface of 25 parts by weight of the bacteria-carrying biochar, then put it into a ventilated drying oven, adjust the temperature to 35 °C and dry for 6 h to obtain the protected bacteria-carrying biochar.

[0055] Preparation Example 5:

[0056] A method for preparing protected bacteria-carrying biochar, specifically including the following process:

[0057] Mix 4 parts by weight of corn straw, 2 parts by weight of peanut shells and 4 parts by weight of wheat straw, then put them into an oven and adjust the temperature to 80 °C for dry baking for 1 h. After dry baking, put them into a pulverizer for pulverization until it can pass through a 60-mesh sieve to obtain a composite powder. Put 3 parts by weight of the composite powder and 1 part by weight of sodium metasilicate nonahydrate into a stirrer and stir at a speed of 30 r / min for 5 min, then put it into a sealed dry baking furnace, adjust the temperature to 550 °C, pyrolyze for 2 h, take it out, let it cool to room temperature, and then put it into a pulverizer for pulverization until it can pass through a 60-mesh sieve to obtain modified biochar. Put 1 part by weight of yeast extract, 2 parts by weight of peptone, 2 parts by weight of glucose and 100 parts by weight of sterile water into a stirrer and stir at a speed of 30 r / min for 5 min, then put it into an autoclave, adjust the temperature to 121 °C for sterilization for 30 min, take it out and let it cool to obtain YPD liquid medium. Inoculate a Saccharomyces cerevisiae into a sterile culture bottle containing 500 mL of YPD liquid medium, and put the sterile culture bottle into an oscillation incubator, adjust the temperature to 30 °C, adjust the rotation speed to 200 r / min, and culture for 120 h to obtain a Saccharomyces cerevisiae solution. Put the Saccharomyces cerevisiae solution into a centrifuge, adjust the rotation speed to 3000 r / min, centrifuge for 5 min, filter to remove the supernatant, and wash the remaining substance with 1000 mL of sterile physiological saline to obtain activated Saccharomyces cerevisiae. Put 50 parts by weight of D(+)-trehalose anhydrous, 68 parts by weight of potassium dihydrogen phosphate, 87 parts by weight of dipotassium hydrogen phosphate and 1000 parts by weight of sterile water into a stirrer and stir at a speed of 300 r / min for 20 min to obtain a buffer solution. Continuously add activated Saccharomyces cerevisiae to the buffer solution until, through counting with a hemocytometer, the density of Saccharomyces cerevisiae is measured to be 1×10 8 CFU / mL to obtain a Saccharomyces cerevisiae suspension. Put 2 parts by weight of the modified biochar and 1 part by weight of the Saccharomyces cerevisiae suspension into a stirrer and stir at a speed of 30 r / min for 5 min, then put it into a ventilated drying oven, adjust the temperature to 35 °C and dry for 24 h to obtain bacteria-carrying biochar. Put 2 parts by weight of gelatin, 1 part by weight of hydroxypropyl methylcellulose and 50 parts by weight of sterile water into a stirrer and stir at a speed of 100 r / min for 30 min to obtain a protective solution. Uniformly spray 1 part by weight of the protective solution on the surface of 25 parts by weight of the bacteria-carrying biochar, and then put it into a ventilated drying oven, adjust the temperature to 35 °C and dry for 6 h to obtain protected bacteria-carrying biochar.

[0058] Preparation Example 6:

[0059] A method for preparing protected bacteria-carrying biochar, specifically including the following process:

[0060] Mix 4 parts by weight of corn straw, 2 parts by weight of peanut shells and 4 parts by weight of wheat straw, and then put them into an oven and adjust the temperature to 80 °C for dry baking for 1 h. After dry baking, put them into a pulverizer for pulverization until the compound powder can pass through a 60-mesh sieve. Put 3 parts by weight of the compound powder and 1 part by weight of sodium metasilicate nonahydrate into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into a sealed dry baking furnace, adjust the temperature to 550 °C, pyrolyze for 2 h, take them out, and after cooling to room temperature, put them into a pulverizer for pulverization until the modified biochar can pass through a 60-mesh sieve. Put 1 part by weight of yeast extract, 2 parts by weight of peptone, 2 parts by weight of glucose and 100 parts by weight of sterile water into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into an autoclave, adjust the temperature to 121 °C for sterilization for 30 min, take them out and let them cool to obtain YPD liquid medium. Inoculate a strain of Saccharomyces cerevisiae into a sterile culture flask containing 500 mL of YPD liquid medium, and put the sterile culture flask into an oscillating incubator, adjust the temperature to 30 °C, adjust the rotation speed to 200 r / min, and culture for 120 h to obtain Saccharomyces cerevisiae liquid. Put the Saccharomyces cerevisiae liquid into a centrifuge, adjust the rotation speed to 3000 r / min, centrifuge for 5 min, filter to remove the supernatant, and rinse the remaining material with 1000 mL of sterile physiological saline to obtain activated Saccharomyces cerevisiae. Put 50 parts by weight of D(+)-anhydrous trehalose, 68 parts by weight of potassium dihydrogen phosphate, 87 parts by weight of dipotassium hydrogen phosphate and 1000 parts by weight of sterile water into a stirrer and stir at a speed of 300 r / min for 20 min to obtain a buffer solution. Continuously add activated Saccharomyces cerevisiae to the buffer solution until the density of Saccharomyces cerevisiae is measured to be 1×10 7 CFU / mL by counting with a hemocytometer to obtain a Saccharomyces cerevisiae suspension. Put 2 parts by weight of the modified biochar and 1 part by weight of the Saccharomyces cerevisiae suspension into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into a ventilated drying oven, adjust the temperature to 35 °C and dry for 24 h to obtain biochar loaded with bacteria. Put 2 parts by weight of gelatin, 1 part by weight of hydroxypropyl methylcellulose and 50 parts by weight of sterile water into a stirrer and stir at a speed of 100 r / min for 30 min to obtain a protective solution. Uniformly spray 1 part by weight of the protective solution on the surface of 25 parts by weight of the biochar loaded with bacteria, and then put it into a ventilated drying oven, adjust the temperature to 35 °C and dry for 6 h to obtain a protected biochar loaded with bacteria.

[0061] Preparation Example 7:

[0062] A method for preparing biochar loaded with bacteria, specifically including the following process:

[0063] Mix 4 parts by weight of corn straw, 2 parts by weight of peanut shells and 4 parts by weight of wheat straw, then put them into an oven, adjust the temperature to 80 °C and dry-bake for 1 h. After dry-baking, put them into a pulverizer for pulverization until the size can pass through a 60-mesh sieve to obtain a composite powder. Put 3 parts by weight of the composite powder and 1 part by weight of sodium metasilicate nonahydrate into a stirrer, stir at a speed of 30 r / min for 5 min, then put them into a sealed dry-baking furnace, adjust the temperature to 600 °C, pyrolyze for 2 h, take them out, and after cooling to room temperature, put them into a pulverizer for pulverization until the size can pass through a 60-mesh sieve to obtain modified biochar. Put 1 part by weight of yeast extract, 2 parts by weight of peptone, 2 parts by weight of glucose and 100 parts by weight of sterile water into a stirrer, stir at a speed of 30 r / min for 5 min, then put them into an autoclave, adjust the temperature to 121 °C and sterilize for 30 min. Take them out and let them cool to obtain YPD liquid medium. Inoculate a strain of Saccharomyces cerevisiae into a sterile culture flask containing 500 mL of YPD liquid medium, and put the sterile culture flask into an oscillating incubator, adjust the temperature to 30 °C, adjust the rotation speed to 200 r / min, and culture for 120 h to obtain Saccharomyces cerevisiae liquid. Put the Saccharomyces cerevisiae liquid into a centrifuge, adjust the rotation speed to 3000 r / min, centrifuge for 5 min, filter to remove the supernatant, and wash the remaining substances with 1000 mL of sterile normal saline to obtain activated Saccharomyces cerevisiae. Put 50 parts by weight of D(+)-trehalose anhydrous, 68 parts by weight of potassium dihydrogen phosphate, 87 parts by weight of dipotassium hydrogen phosphate and 1000 parts by weight of sterile water into a stirrer, stir at a speed of 300 r / min for 20 min to obtain a buffer solution. Continuously add activated Saccharomyces cerevisiae to the buffer solution until the density of Saccharomyces cerevisiae is measured to be 1×10 8 CFU / mL by counting with a hemocytometer to obtain a Saccharomyces cerevisiae suspension. Put 2 parts by weight of the modified biochar and 1 part by weight of the Saccharomyces cerevisiae suspension into a stirrer, stir at a speed of 30 r / min for 5 min, then put them into a ventilated drying oven, adjust the temperature to 35 °C and dry for 24 h to obtain biochar loaded with bacteria.

[0064] Preparation Example 8:

[0065] A method for preparing protective biochar, specifically including the following process:

[0066] Mix 4 parts by weight of corn straw, 2 parts by weight of peanut shells and 4 parts by weight of wheat straw, then put them into an oven and adjust the temperature to 80 °C for dry baking for 1 h. After dry baking, put them into a pulverizer for pulverization until the resulting powder can pass through a 60-mesh sieve to obtain a composite powder. Put 3 parts by weight of the composite powder and 1 part by weight of sodium metasilicate nonahydrate into a stirrer and stir at a speed of 30 r / min for 5 min, then put them into a sealed dry baking furnace, adjust the temperature to 600 °C, pyrolyze for 2 h, take them out, let them cool to room temperature, and then put them into a pulverizer for pulverization until the resulting powder can pass through a 60-mesh sieve to obtain modified biochar. Put 2 parts by weight of gelatin, 1 part by weight of hydroxypropyl methylcellulose and 50 parts by weight of sterile water into a stirrer and stir at a speed of 100 r / min for 30 min to obtain a protective liquid. Uniformly spray 1 part by weight of the protective liquid on the surface of 25 parts by weight of bacteria-carrying biochar, then put it into a ventilated drying oven, adjust the temperature to 35 °C and dry for 6 h to obtain protective biochar.

[0067] Example 1:

[0068] A preparation method of a composite remediation material for soil cadmium pollution specifically includes the following process:

[0069] Put 5 parts by weight of the protective bacteria-carrying biochar prepared in Preparation Example 1, 2 parts by weight of the silicon-calcium powder prepared in Preparation Example 2 and 3 parts by weight of the binder prepared in Preparation Example 3 into a stirrer and stir at a speed of 30 r / min for 20 min, then spread them evenly on a stainless steel plate with a thickness not exceeding 50 mm, put them into a ventilated drying oven, adjust the temperature to 35 °C and dry for 24 h, and then put them into a pulverizer for pulverization until the resulting powder can pass through a 20-mesh sieve to obtain a composite remediation material.

[0070] Example 2:

[0071] A preparation method of a composite remediation material for soil cadmium pollution specifically includes the following process:

[0072] Replace the protective bacteria-carrying biochar prepared in Preparation Example 1 in Example 1 with the protective bacteria-carrying biochar prepared in Preparation Example 4, and keep the other conditions the same as those in Example 1.

[0073] Example 3:

[0074] A preparation method of a composite remediation material for soil cadmium pollution specifically includes the following process:

[0075] Replace the protective bacteria-carrying biochar prepared in Preparation Example 1 in Example 1 with the protective bacteria-carrying biochar prepared in Preparation Example 5, and keep the other conditions the same as those in Example 1.

[0076] Example 4:

[0077] A preparation method of a composite remediation material for soil cadmium pollution specifically includes the following process:

[0078] Replace the protected bacteria-carrying biochar of Preparation Example 1 in Example 1 with the protected bacteria-carrying biochar of Preparation Example 6, and keep the other conditions the same as those in Example 1.

[0079] Comparative Example 1:

[0080] A preparation method of a composite remediation material for soil cadmium pollution specifically includes the following process:

[0081] Replace the protected bacteria-carrying biochar of Preparation Example 1 in Example 1 with the bacteria-carrying biochar of Preparation Example 7, and keep the other conditions the same as those in Example 1.

[0082] Comparative Example 2:

[0083] A preparation method of a composite remediation material for soil cadmium pollution specifically includes the following process:

[0084] Replace the protected bacteria-carrying biochar of Preparation Example 1 in Example 1 with the protected biochar of Preparation Example 8, and keep the other conditions the same as those in Example 1.

[0085] Comparative Example 3:

[0086] A preparation method of a composite remediation material for soil cadmium pollution specifically includes the following process:

[0087] Put 5 parts by weight of the protected bacteria-carrying biochar of Preparation Example 1 and 3 parts by weight of the binder of Preparation Example 3 into a stirrer and stir at a speed of 30 r / min for 20 min, then spread them evenly on a stainless steel plate with a thickness not exceeding 50 mm. Place them in a ventilated drying oven, adjust the temperature to 35 °C and dry for 24 h, then put them into a pulverizer for pulverization until they can pass through a 20-mesh sieve to obtain a composite remediation material.

[0088] Take cadmium-polluted soil from a certain place. The total cadmium content is measured to be 8.47 mg / kg by graphite furnace atomic absorption spectrophotometry, and the proportion of cadmium in the residual state is measured to be 16.6% by the "Tessier method". Divide 7000 g of this soil into 7 equal parts, and sprinkle 20 g of the composite remediation materials obtained in Examples 1-4 and Comparative Examples 1-3 respectively. Keep the soil moisture content at about 20%. Measure the proportion of cadmium in the residual state in the soil by the "Tessier method" on the 10th day, 30th day, 60th day and 120th day respectively. The results are shown in Table 1 below.

[0089] Table 1 Percentage content of cadmium in the residual state

[0090]

[0091] It can be seen from the data in the above table that:

[0092] (1) The composite remediation materials of Examples 1-4 can effectively increase the proportion of cadmium in the residual state in the soil.

[0093] (2) It can be seen from Comparative Example 1 that the buffer solution and the modified biochar can, to a certain extent, help Saccharomyces cerevisiae resist the alkaline environment, but the effect will gradually decrease. The absence of the protective solution will accelerate this process, resulting in a continuous decrease in the number of Saccharomyces cerevisiae and ultimately affecting the overall repair performance.

[0094] (3) It can be seen from Comparative Example 2 that the catalytic effect of the silicon-calcium powder and the adsorption effect of the modified biochar are both limited. Although the biotransformation effect of Saccharomyces cerevisiae is slow, it can continuously increase the proportion of cadmium in the residual state in the soil. If Saccharomyces cerevisiae is not added to the composite repair material, it will lead to a decrease in the overall repair performance, and it will become more obvious over time.

[0095] (4) It can be seen from Comparative Example 3 that the silicon-calcium powder has a significant and rapid catalytic effect on the conversion of exchangeable cadmium in the soil into residual cadmium. If the silicon-calcium powder is not added to the composite repair material, it will lead to a decrease in the early repair efficiency and the overall repair performance.

[0096] The above-described embodiments have elaborated in detail the technical solutions and beneficial effects of the present invention. It should be understood that the above is only a specific embodiment of the present invention and is not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A preparation method of a composite remediation material for soil cadmium pollution, characterized in that, The preparation method comprises the following steps: The protected bacteria-carrying biochar, silicon-calcium powder and binder are mixed and then ventilated and dried at 35°C for 24 h, and then pulverized and sieved through a 20-mesh sieve to obtain the composite repair material.

2. The preparation method of a composite remediation material for soil cadmium pollution according to claim 1, characterized in that, The preparation method of the protected bacteria-carrying biochar comprises the following steps: Corn straw, peanut shell and wheat straw are mixed according to a mass ratio of 4:2:4 to obtain composite straw; The composite straw is dried by roasting at 80°C for 1 h, and then pulverized to a size that can pass through a 60-mesh sieve to obtain composite powder; The composite powder and sodium metasilicate nonahydrate are mixed according to a mass ratio of 3:1 to obtain a composite substrate; The composite substrate is pyrolyzed at 550°C - 600°C for 2 h, and then pulverized to a size that can pass through a 60-mesh sieve to obtain modified biochar; The modified biochar and the suspension of Saccharomyces cerevisiae are mixed and then ventilated and dried at 35°C for 24 h to obtain bacteria-carrying biochar; Gelatin, hydroxypropyl methylcellulose and sterile water are mixed according to a mass ratio of 2:1:50 to obtain a protective solution; The protective solution is evenly sprayed on the surface of the bacteria-carrying biochar and then ventilated and dried at 35°C for 6 h to obtain the protected bacteria-carrying biochar.

3. The preparation method of a composite remediation material for soil cadmium pollution according to claim 2, characterized in that, The preparation method of the suspension of Saccharomyces cerevisiae comprises the following steps: Saccharomyces cerevisiae is inoculated into a 500 mL YPD liquid medium and cultured by shaking at 200 r / min at 30°C for 120 h to obtain a Saccharomyces cerevisiae solution; The Saccharomyces cerevisiae solution is centrifuged at 3000 r / min for 5 min, and then the supernatant is removed, and it is rinsed with 1000 mL of sterile physiological saline to obtain activated Saccharomyces cerevisiae; D(+)-anhydrous trehalose, potassium dihydrogen phosphate, dipotassium hydrogen phosphate and sterile water are mixed according to a mass ratio of 50:68:87:1000 to obtain a buffer solution; After the activated Saccharomyces cerevisiae and the buffer solution were mixed, the density of Saccharomyces cerevisiae was measured by counting with a hemocytometer to be 1×10 7 CFU / mL - 1×10 8 CFU / mL to obtain a Saccharomyces cerevisiae suspension.

4. The preparation method of a composite remediation material for soil cadmium pollution according to claim 2, characterized in that, The mass ratio of the modified biochar to the suspension of Saccharomyces cerevisiae is 2:

1.

5. The preparation method of a composite remediation material for soil cadmium pollution according to claim 2, characterized in that, The mass ratio of the protective solution to the bacteria-carrying biochar is 1:

25.

6. The preparation method of a composite remediation material for soil cadmium pollution according to claim 1, wherein, The binder is obtained by mixing soy peptone and sterile water.

7. The preparation method of a composite remediation material for soil cadmium pollution according to claim 6, characterized in that, The mass ratio of the soy peptone to the sterile water is 1:

20.

8. The preparation method of a composite remediation material for soil cadmium pollution according to claim 1, characterized in that, The mass ratio of the protected bacteria-carrying biochar, silicon-calcium powder and binder is 5:2:

3.

9. A composite repair material prepared by the preparation method of a composite repair material for soil cadmium pollution according to any one of claims 1 to 8.

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