A method for repairing contaminated soil using kitchen waste
Through the preparation and modification of modified biochar, the problem of insufficient adsorption and fixation ability of biochar in heavy metal contaminated soil is solved, efficient adsorption of heavy metals and soil repair is achieved, and healthy wheat growth is promoted.
Patent Information
- Application Number
- CN202210925892.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-03
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2042-08-03
AI Technical Summary
In the prior art, when dealing with heavy metal contaminated soil, the adsorption and fixation capacity of biochar is limited, especially the fixation effect of anionic pollutants is poor, and the commonly used ball milling method is inefficient and easy to produce dust.
By preparing modified biochar with kitchen waste, the pore structure and surface area are enhanced by hydrothermal treatment and ultrasound, polar functional groups and zinc chloride are introduced on the surface, and coordinated modification is carried out by combining aspartic acid and polyisocyanate. Improve the adsorption performance of heavy metals.
It significantly improves the heavy metal adsorption capacity of biochar and forms an efficient soil repair agent, which can effectively reduce the bioavailability of heavy metals in the soil, improve the soil environment, and promote wheat growth.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of kitchen waste resource treatment, and in particular to a method for repairing contaminated soil by utilizing kitchen waste. Background Art
[0002] Kitchen waste is food waste generated by people's daily life activities. With the improvement of the quality of life of Chinese residents and the development of the catering industry, the amount of kitchen waste is showing a clear upward trend. my country's kitchen waste has the characteristics of high water content, high organic matter, high salt content, high oil content and easy to rot. If it is not handled in time, it is easy to produce bad odor, breed pathogens and microorganisms, and cause environmental pollution problems.
[0003] At present, the main methods for kitchen waste treatment include anaerobic digestion, landfill and incineration. Among them, landfill is the most widely used, but this technology takes up a lot of land. At the same time, landfill will also produce a lot of methane gas. As a greenhouse gas, the specific warming potential of methane is much higher than that of carbon dioxide. Therefore, it is necessary to find new ways to treat kitchen waste. Since kitchen waste is rich in organic matter, making it into biochar with good adsorption capacity can realize the resource utilization of kitchen waste. Biochar is highly stable in the soil and has a good "carbon sequestration" effect. It is a good way to fix carbon.
[0004] Nowadays, land pollution and damage is a major problem that hinders the social and economic development of my country. The situation of land pollution and damage in my country is serious, among which the problem of heavy metal soil pollution caused by industrial and mining industries is particularly prominent. Heavy metal pollutants are difficult to degrade after entering the soil. They are hidden, irreversible, and cumulative. Then they are enriched through the food chain, which poses a great threat to the survival of animals and plants, human health and social development.
[0005] At present, the remediation technology for heavy metal contaminated soil mainly adopts chemical remediation methods, but the large amount of chemical agents used in the remediation process can easily cause secondary pollution of the soil. Biochar has good adsorption performance, stable chemical properties, can reduce the biological effectiveness of heavy metals in the soil, and can increase crop yields at the same time, and the raw materials are extensive and low in cost, so that it has obvious advantages and application value in the treatment of heavy metal contaminated soil. However, in the process of treating heavy metal pollution, the adsorption and fixation capacity of biochar on heavy metals is very limited, especially for the fixation of some anionic pollutants, there are some limitations, so that it cannot achieve the expected passivation and repair effect. At present, the modification method is often used to improve the adsorption and fixation capacity of biochar on heavy metals, among which ball milling is a commonly used biochar modification technology. However, the ball milling method has problems such as low efficiency and easy generation of dust during the grinding modification process. To this end, the present invention provides a heavy metal soil remediation agent using kitchen waste to prepare modified biochar as a solid matrix, solves the adsorption problem of biochar, and provides an effective way for the repair of heavy metal contaminated soil. Summary of the invention
[0006] In view of this, the purpose of the present invention is to provide a method for repairing contaminated soil by using kitchen waste, and a method for treating heavy metal contaminated soil by using modified biochar prepared from kitchen waste.
[0007] The present invention solves the above technical problems by the following technical means:
[0008] A method for repairing contaminated soil using kitchen waste, comprising preparing biochar from kitchen waste, modifying the biochar to obtain modified biochar, mixing the modified biochar with auxiliary materials and stirring evenly to obtain a soil repair agent, directly applying the soil repair agent to the contaminated soil, and performing soil repair after mixing evenly.
[0009] Furthermore, the mass ratio of the auxiliary material to the modified biochar is (63-102):(80-100), and the mass ratio of the soil remediation agent to the contaminated soil is (0.6-1):100.
[0010] Furthermore, the auxiliary materials include the following raw materials in parts by weight: 5-10 parts of humic acid, 15-20 parts of wood ash, 30-50 parts of diatomaceous earth, 5-12 parts of dipotassium hydrogen phosphate, and 8-10 parts of ammonium sulfate.
[0011] Furthermore, the method for preparing biochar comprises the following steps:
[0012] (1) separating the kitchen waste into solid and liquid to obtain solid kitchen waste and waste oil and water;
[0013] (2) crushing solid kitchen waste, mixing it with water in a mass ratio of 1:(1.5-2), stirring for 30-60 minutes to obtain a mixed raw material, and putting the mixed raw material into a reactor to react for 4-8 hours;
[0014] (3) After the reaction is completed, the reactants are cooled to room temperature and then subjected to solid-liquid separation to obtain solid biochar. After drying for 1-2 hours, biochar is obtained.
[0015] The present invention utilizes kitchen waste to prepare biochar, and during the hydrothermal treatment process, part of the organic matter in the biomass is hydrolyzed and dissolved, so that the biochar has a pore structure.
[0016] Furthermore, the amount of the mixed material input in step (2) is 1 / 3-2 / 3 of the volume of the reactor, and the reaction temperature in the reactor is 180°C.
[0017] Further, the prepared biochar is modified to obtain modified biochar, and the biochar is modified using the following raw materials in parts by mass:
[0018] 1-5 parts of dry biochar, 15-90 parts of 3wt% hydrogen peroxide, 3-10 parts of 2mol / L zinc chloride solution, 1-15 parts of phosphate powder, 100-800 parts of 20-80mg / L aspartic acid solution, and 10-100 parts of polyisocyanate.
[0019] Furthermore, the specific preparation method of the modified biochar is as follows:
[0020] (1) crushing the obtained dried biochar, mixing the crushed biochar, hydrogen peroxide and water for 1-10 hours, and filtering to obtain pretreated biochar;
[0021] (2) drying the obtained pretreated biochar at a constant temperature for 1-2 hours and then immersing it in liquid nitrogen, immersing it for 2-9 hours, taking it out, filtering it and drying it for 5-8 hours to obtain the primary modified biochar;
[0022] (3) Deionized water and the initially modified biochar are used to prepare a biochar suspension with a concentration of 0.5 mg / L-2 mg / L. After ultrasonic treatment for 2-4 h, potassium hydroxide solution is added dropwise to adjust the pH value of the suspension to 8-13. Phosphate powder and zinc chloride solution are then added. After stirring evenly, aspartic acid solution is added dropwise. The mixture is heated and stirred at 20-60 °C for 12-36 h. The temperature is then adjusted to 60 °C-70 °C, polyisocyanate is added, and the reaction is continued for 6 h-10 h. The product is then washed with acetone, centrifuged, and dried to constant weight to obtain modified biochar.
[0023] Furthermore, in the biochar modification step (1), the mixing ratio of biochar to water is 1:(15-60) by mass.
[0024] Furthermore, the kitchen waste includes discarded vegetable leaves, leftovers, leftover rice, fruit peels, egg shells, tea dregs, and bones.
[0025] The present invention adopts low-concentration hydrogen peroxide to oxidize biochar, and introduces rich polar functional groups on the surface of biochar. After liquid nitrogen enters the biochar, it is evaporated and the liquid state becomes gaseous. The volume expansion expands the pore structure of the biochar, and increases the number of micropores and surface area that are beneficial to the adsorption of heavy metals. Zinc chloride will adhere to the surface of biochar, which can enhance the cation-π effect and provide more adsorption sites. Thereby improving the ability to adsorb heavy metals, adding aspartic acid, the amide group in aspartic acid makes it easier for zinc chloride to interact through intermolecular hydrogen bonds and dipole moments, making the zinc chloride more densely arranged and less likely to fall off. At the same time, polar groups such as the carboxyl group of aspartic acid are also grafted onto the biochar. After adding polyisocyanate, since the polyisocyanate molecular chain contains two or more isocyanate end groups, the isocyanate group at one end reacts with the amine and hydroxyl groups on the biochar, and the unreacted isocyanate groups retain their reaction activity, and the biochar is synergistically modified, so that the surface energy of the modified biochar and the number of groups that chelate and adsorb heavy metals are increased, further enhancing the adsorption performance of heavy metals.
[0026] Beneficial effects:
[0027] 1. The present invention uses kitchen waste as material, consumes a large amount of kitchen waste, realizes the recycling of biological waste resources, and is green and environmentally friendly.
[0028] 2. The present invention improves the pore structure and number of micropores of biochar and increases the specific surface area by oxidizing biochar prepared from kitchen waste. Aspartic acid, phosphate and zinc chloride are added to further modify the biochar. A large number of carboxyl groups are grafted on the surface of the biochar, which greatly increases the adsorption active sites of the biochar and improves the capacity of the biochar to adsorb heavy metals.
[0029] 3. The soil remediation agent prepared by mixing the modified biochar with humic acid, wood ash, diatomaceous earth, potassium dihydrogen phosphate and ammonium sulfate can effectively remediate heavy metal soil, thereby reducing soil pollution. DETAILED DESCRIPTION
[0030] The present invention will be described in detail below with reference to embodiments:
[0031] Example 1: Biochar preparation
[0032] The biochar used in the present invention can be prepared by the following steps:
[0033] (1) separating the kitchen waste into solid and liquid to obtain solid kitchen waste and waste oil and water;
[0034] (2) crushing solid kitchen waste, mixing it with water in a mass ratio of 1:1.5, stirring for 60 minutes to obtain a mixed raw material, and placing the mixed raw material into a reactor to react at 180° C. and 1.3 MPa for 4 hours;
[0035] (3) After the reaction is completed, the reactants are cooled to room temperature and then subjected to solid-liquid separation to obtain solid biochar, which is then dried in hot air at 50° C. for 2 h to obtain biochar.
[0036] Example 2: Preparation of soil remediation agent
[0037] This embodiment weighs the raw materials according to the following mass:
[0038] 5g biochar, 90g 3wt% hydrogen peroxide, 10g 2mol / L zinc chloride solution, 15g phosphate powder, 800g 20mg / L aspartic acid solution, 100g polyisocyanate.
[0039] The preparation steps are as follows:
[0040] (1) The dried biochar prepared in Example 1 was crushed and passed through a 50-mesh sieve, and the crushed biochar, water and hydrogen peroxide were mixed in a mass ratio of 1:15 for 10 hours, and the pretreated biochar was obtained by suction filtration;
[0041] (2) drying the obtained pretreated biochar at a constant temperature of 40° C. for 2 h and then immersing it in liquid nitrogen. After immersing it for 9 h, the pretreated biochar was taken out, filtered and dried for 8 h to obtain the primary modified biochar;
[0042] (3) Deionized water and the initially modified biochar were used to prepare a biochar suspension with a concentration of 2 mg / L. After ultrasonic treatment at 70 kHz and a power of 500 W for 4 h, potassium hydroxide solution was added dropwise to adjust the pH value of the suspension to 13. Phosphate powder and zinc chloride solution were then added. After stirring evenly, aspartic acid solution was added dropwise. The mixture was heated and stirred at 60 °C for 12 h. Subsequently, the temperature was maintained at 60 °C, polyisocyanate was added, and the reaction was continued for 10 h. The product was washed with acetone, centrifuged, and dried to constant weight to obtain modified biochar.
[0043] (4) Weigh 100 g of the prepared modified biochar, mix it with 10 g of humic acid, 20 g of wood ash, 50 g of diatomaceous earth, 12 g of dipotassium hydrogen phosphate, and 10 g of ammonium sulfate, stir and mix at room temperature for 8 h, and prepare a soil remediation agent after mixing evenly.
[0044] Example 3: Preparation of soil remediation agent 2
[0045] This embodiment weighs the raw materials according to the following mass:
[0046] 1 g of biochar, 15 g of 3 wt% hydrogen peroxide, 3 g of 2 mol / L zinc chloride solution, 1 g of phosphate powder, 100 g of 80 mg / L aspartic acid solution, and 10 g of polyisocyanate.
[0047] The preparation steps are as follows:
[0048] (1) The dried biochar prepared in Example 1 was crushed and passed through a 50-mesh sieve, and the crushed biochar and water were mixed with hydrogen peroxide in a mass ratio of 1:60 for 1 hour, and then filtered to obtain pretreated biochar;
[0049] (2) drying the obtained pretreated biochar at a constant temperature of 40° C. for 1 h and then immersing it in liquid nitrogen. After immersing it for 2 h, the pretreated biochar was taken out, filtered and dried for 5 h to obtain the primary modified biochar;
[0050] (3) Deionized water and the initially modified biochar were used to prepare a biochar suspension with a concentration of 0.5 mg / L. After ultrasonic treatment at 100 kHz and 700 W for 2 h, potassium hydroxide solution was added dropwise to adjust the pH value of the suspension to 8. Phosphate powder and zinc chloride solution were then added. After stirring evenly, aspartic acid solution was added dropwise. The mixture was heated and stirred at 20 °C for 36 h. The temperature was then adjusted to 70 °C, polyisocyanate was added, and the reaction was continued for 6 h. The product was washed with acetone, centrifuged, and dried to constant weight to obtain modified biochar.
[0051] (4) Weigh 80 g of the prepared modified biochar, 5 g of humic acid, 15 g of wood ash, 30 g of diatomaceous earth, 5 g of dipotassium hydrogen phosphate, and 8 g of ammonium sulfate, and stir and mix them at room temperature for 8 h. After mixing evenly, a soil remediation agent was obtained.
[0052] Example 4: Preparation of soil remediation agent 3
[0053] This embodiment weighs the raw materials according to the following mass:
[0054] 3 g of biochar, 53 g of 3 wt% hydrogen peroxide, 6 g of 2 mol / L zinc chloride solution, 8 g of phosphate powder, 400 g of 50 mg / L aspartic acid solution, and 55 g of polyisocyanate.
[0055] The preparation steps are as follows:
[0056] (1) The dried biochar prepared in Example 1 was crushed and passed through a 50-mesh sieve, and the crushed biochar and water were mixed with hydrogen peroxide in a mass ratio of 1:47 for 6 hours, and the pretreated biochar was obtained by suction filtration;
[0057] (2) drying the obtained pretreated biochar at a constant temperature of 40° C. for 1.5 h and then immersing it in liquid nitrogen. After immersing it for 5 h, the pretreated biochar was taken out, filtered and dried for 7 h to obtain the primary modified biochar;
[0058] (3) Deionized water and the initially modified biochar were used to prepare a biochar suspension with a concentration of 1 mg / L. After ultrasonic treatment at 40 kHz and 300 W for 3 h, potassium hydroxide solution was added dropwise to adjust the pH value of the suspension to 11. Phosphate powder and zinc chloride solution were then added. After stirring evenly, aspartic acid solution was added dropwise. The mixture was heated and stirred at 40 °C for 24 h. The temperature was then adjusted to 65 °C, polyisocyanate was added, and the reaction was continued for 8 h. The product was washed with acetone, centrifuged, and dried to constant weight to obtain modified biochar.
[0059] (4) Weigh 90 g of the prepared modified biochar, 8 g of humic acid, 17 g of wood ash, 40 g of diatomaceous earth, 9 g of dipotassium hydrogen phosphate, and 9 g of ammonium sulfate, and stir and mix them at room temperature for 8 h. After mixing evenly, a soil remediation agent was obtained.
[0060] Comparative Example 1:
[0061] This comparative example is in contrast to Example 2. The main difference is that no hydrogen peroxide is added to treat the biochar during the preparation process of step (1) when preparing the modified biochar. The remaining raw material ratios and steps are the same as those of Example 2. The specific preparation steps are as follows:
[0062] (1) crushing the dried biochar prepared in Example 1 and passing it through a 50-mesh sieve to obtain pretreated biochar;
[0063] (2) drying the obtained pretreated biochar at a constant temperature of 40° C. for 2 h and then immersing it in liquid nitrogen. After immersing it for 9 h, the pretreated biochar was taken out, filtered and dried for 8 h to obtain the primary modified biochar;
[0064] (3) Deionized water and the initially modified biochar were used to prepare a biochar suspension with a concentration of 2 mg / L. After ultrasonic treatment at 70 kHz and a power of 500 W for 4 h, potassium hydroxide solution was added dropwise to adjust the pH value of the suspension to 13. Phosphate powder and zinc chloride solution were then added. After stirring evenly, aspartic acid solution was added dropwise. The mixture was heated and stirred at 60 °C for 12 h. Subsequently, the temperature was maintained at 60 °C, polyisocyanate was added, and the reaction was continued for 10 h. The product was washed with acetone, centrifuged, and dried to constant weight to obtain modified biochar.
[0065] (4) Weigh 100 g of the prepared modified biochar, mix it with 10 g of humic acid, 20 g of wood ash, 50 g of diatomaceous earth, 12 g of dipotassium hydrogen phosphate, and 10 g of ammonium sulfate, stir and mix at room temperature for 8 h, and prepare a soil remediation agent after mixing evenly.
[0066] Comparative Example 2:
[0067] This comparative example is in contrast to Example 2. The main difference is that no polyisocyanate is added to treat the biochar during the preparation of step (3) when preparing the modified biochar. The remaining raw material ratios and steps are the same as those of Example 2. The specific preparation steps are as follows:
[0068] (1) The dried biochar prepared in Example 1 was crushed and passed through a 50-mesh sieve, and the crushed biochar and water were mixed with hydrogen peroxide in a mass ratio of 1:15 for 10 hours, and the pretreated biochar was obtained by suction filtration;
[0069] (2) drying the obtained pretreated biochar at a constant temperature of 40° C. for 2 h and then immersing it in liquid nitrogen. After immersing it for 9 h, the pretreated biochar was taken out, filtered and dried for 8 h to obtain the primary modified biochar;
[0070] (3) Deionized water and the initially modified biochar were used to prepare a biochar suspension with a concentration of 2 mg / L. After ultrasonic treatment at 70 kHz and a power of 500 W for 4 h, potassium hydroxide solution was added dropwise to adjust the pH value of the suspension to 13. Subsequently, phosphate ester powder and zinc chloride solution were added, stirred evenly, and aspartic acid solution was added dropwise. The mixture was heated and stirred at 60 °C for 12 h, and the modified biochar was obtained by filtration.
[0071] (4) Weigh 100 g of the prepared modified biochar, mix it with 10 g of humic acid, 20 g of wood ash, 50 g of diatomaceous earth, 12 g of dipotassium hydrogen phosphate, and 10 g of ammonium sulfate, stir and mix at room temperature for 8 h, and prepare a soil remediation agent after mixing evenly.
[0072] Comparative Example 3:
[0073] This comparative example is in contrast to Example 2. The main difference is that no aspartic acid is added to treat the biochar when preparing the modified biochar. The remaining raw material ratios and steps are the same as those in Example 2. The specific preparation steps are as follows:
[0074] (1) The dried biochar prepared in Example 1 was crushed and passed through a 50-mesh sieve, and the crushed biochar, water and hydrogen peroxide were mixed in a mass ratio of 1:15 for 10 hours, and the pretreated biochar was obtained by suction filtration;
[0075] (2) drying the obtained pretreated biochar at a constant temperature of 40° C. for 2 h and then immersing it in liquid nitrogen. After immersing it for 9 h, the pretreated biochar was taken out, filtered and dried for 8 h to obtain the primary modified biochar;
[0076] (3) Deionized water and the initially modified biochar were used to prepare a biochar suspension with a concentration of 2 mg / L. After ultrasonic treatment at 70 kHz and a power of 500 W for 4 h, potassium hydroxide solution was added dropwise to adjust the pH value of the suspension to 13. Phosphate ester powder and zinc chloride solution were then added. After stirring evenly, the mixture was heated and stirred at 60 °C for 12 h. Subsequently, the temperature was maintained at 60 °C, polyisocyanate was added, and after reacting for 10 h, the product was washed with acetone, centrifuged, and dried to constant weight to obtain modified biochar.
[0077] (4) Weigh 100 g of the prepared modified biochar, mix it with 10 g of humic acid, 20 g of wood ash, 50 g of diatomaceous earth, 12 g of dipotassium hydrogen phosphate, and 10 g of ammonium sulfate, stir and mix at room temperature for 8 h, and prepare a soil remediation agent after mixing evenly.
[0078] Comparative Example 4:
[0079] This comparative example is in contrast to Example 2, the main difference being that the biochar was not modified, and the soil remediation agent used was weighed according to the following mass:
[0080] 100g biochar, 10g humic acid, 20g wood ash, 50g diatomaceous earth, 12g dipotassium hydrogen phosphate, and 10g ammonium sulfate.
[0081] The preparation steps are as follows:
[0082] The biochar, humic acid, wood ash, diatomaceous earth, potassium dihydrogen phosphate and ammonium sulfate prepared in Example 1 were stirred and mixed for 8 hours to prepare a soil remediation agent.
[0083] Comparative Example 5:
[0084] This comparative example is in contrast to Example 2, the main difference being that modified biochar is not used, and ordinary activated carbon is used. The soil remediation agent used is weighed according to the following raw materials:
[0085] Activated carbon 100g, humic acid 10g, wood ash 20g, diatomaceous earth 50g, dipotassium hydrogen phosphate 12g, ammonium sulfate 10g.
[0086] The preparation steps are as follows:
[0087] The activated carbon, humic acid, wood ash, diatomaceous earth, potassium dihydrogen phosphate and ammonium sulfate were stirred and mixed for 8 hours to prepare a soil remediation agent.
[0088] Experiment 1: Heavy metal soil remediation experiment
[0089] The soil remediation agents prepared in Example 2 and Comparative Examples 1-5 were used to remediate heavy metal contaminated soil. Normal soil was used to prepare the heavy metal contaminated soil in the laboratory. Cd solution, Cr solution, Pb solution, and Hg solution with standard solution concentrations were added to the normal soil. The heavy metal contaminated soil was obtained after stirring and standing for 2 days, wherein the initial content of Cd was 59.28 mg / kg, the initial content of Cr was 2043 mg / kg, the Pb was 1159 mg / kg, the Hg was 1403 mg / kg, and the soil pH was 5.22.
[0090] The heavy metal-contaminated soil was evenly placed in 7 flower pots of the same size for testing, with 1 kg of soil in each pot. Six flower pots were taken to repair the heavy metal soil using the soil remediation agents prepared in Example 2 and Comparative Examples 1-5, respectively. The mass ratio of the added soil remediation agent to the soil was 8 g:1 kg. The soil was fully mixed and a blank control was added. No soil remediation agent was added to the flower pot. Pure water was then added to the 7 flower pots to keep the soil moisture content at 28%. The heavy metal content in the soil was detected after 30 days. The test was repeated three times. The test results are shown in Table 1:
[0091] Table 1
[0092]
[0093]
[0094] Experiment 2: Wheat growth test
[0095] The soils of Example 1, Comparative Examples 1-5 and the blank control group after completing Experiment 1 were used in the wheat growth experiment, which was carried out on the second day after the heavy metal content in the soil was detected.
[0096] Complete, healthy, and full wheat seeds were selected, 50 seeds were sown in each pot, the sowing depth was 2 cm, and water was irrigated every other day to maintain the soil moisture content at 70-72%. After one week of growth, the seedlings were thinned out, and 15 best-growing seedlings were kept in each pot. After 8 days of cultivation, the effect of soil on wheat growth was observed, and the sprout length and root length of wheat were recorded. The experiment was repeated three times, and the results are shown in Table 2.
[0097] Table 2
[0098] Experimental Group Survival rate / % Bud length / cm Root length Example 2 94 6.67 5.72 Comparative Example 1 82 5.99 4.73 Comparative Example 2 73 4.39 4.07 Comparative Example 3 77 4.58 4.32 Comparative Example 4 66 3.74 3.58 Comparative Example 5 62 2.96 3.11 Blank control group 56 1.66 2.69
[0099] Data Analysis:
[0100] 1. According to the data in Table 1, the heavy metal content of the soil after repair by the soil repair agent prepared in Example 2 and Comparative Examples 1-5 has decreased. After the addition of the soil repair agent prepared in Example 2 of the present invention, the heavy metal content of the soil has decreased most significantly compared with the blank control group, with Cd decreased by 47.13 mg / kg, Cr decreased by 1853 mg / kg, Pb content decreased by 1027 mg / kg, and Hg decreased by 1275 mg / kg. At the same time, the survival rate of wheat increased by 38% compared with the blank control group, and the bud height and root length were also significantly higher than those of the blank control group, indicating that the soil repair agent prepared according to the raw material ratio and method disclosed in the present invention has good heavy metal adsorption capacity, and the repaired soil is more suitable for the growth of wheat.
[0101] 2. After adding the soil remediation agent prepared in Comparative Example 1, compared with Example 2, the content of Cd is 9.79 mg / kg more, the content of Cr is 373 mg / kg more, the content of Pb is 217 mg / kg more, and the content of Hg is 279 mg / kg more. Comparative Example 1 does not pretreat the biochar, and the data of each group are worse than those of Group 1. It can also be seen in Table 2 that the survival rate of wheat in Comparative Example 1 is 12% worse than that in Example 1, the bud length is 0.68 cm shorter, and the root length is 0.99 cm shorter, indicating that the use of hydrogen peroxide to modify biochar in the present invention increases the ability of biochar to adsorb heavy metals, improves the survival rate of wheat, and makes wheat grow healthier
[0102] 3. After adding the soil remediation agent prepared in Comparative Example 2, compared with Example 1, the Cd content is 24.67 mg / kg more, the Cr content is 1028 mg / kg more, the Pb content is 550 mg / kg more, and the Hg content is 794 mg / kg more; after adding the soil remediation agent prepared in Comparative Example 3, the Cd content is 11.6 mg / kg more than the Cd content of Example 1, the Cr content is 886 mg / kg more than the Cr content of Example 1, the Pb content is 515 mg / kg more, and the Hg content is 704 mg / kg more; Comparative Examples 2 and 3 did not add polyisocyanate or aspartic acid, and the ability to adsorb heavy metals in the soil was also reduced. In the wheat growth test, compared with Example 1, the survival rates of Comparative Examples 1 and Comparative Example 2 were 21% and 17% lower than that of Example 1, the bud lengths were 2.31 cm and 2.09 cm shorter, respectively, and the root lengths were 1.65 cm and 1.4 cm shorter. Comparative Examples 2 and 3 illustrate that the phosphate ester and aspartic acid, zinc chloride, and polyisocyanate in the present invention act synergistically on biochar to modify the biochar, and adding it to heavy metal soil can effectively reduce the biological effectiveness of heavy metals in the soil and reduce the inhibitory effect of heavy metal pollution on wheat growth.
[0103] 4. After adding the soil remediation agent prepared in Comparative Example 4, Cd decreased by 13.85 mg / kg, Cr decreased by 590 mg / kg, Pb content decreased by 399 mg / kg, Hg decreased by 411 mg / kg, the survival rate of wheat was only 66%, the buds did not grow high, and the root length grew slowly, indicating that the growth of wheat was greatly affected. Comparative Example 4 did not modify the biochar, and the effect of adsorbing heavy metals was not obvious. Comparative Example 5 used common activated carbon, which had a weaker ability to adsorb and fix heavy metals than the biochar prepared by the present invention.
[0104] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention. The techniques, shapes, and structural parts not described in detail in the present invention are all known technologies.
Claims
1. A method for remediating contaminated soil using kitchen waste, characterized in that: The kitchen waste is prepared into biochar, the biochar is modified to obtain modified biochar, the modified biochar is mixed with auxiliary materials and stirred evenly to obtain a soil remediation agent, the soil remediation agent is directly applied to the contaminated soil, and the soil is remediated after being mixed evenly; The method for preparing biochar comprises the following steps: (1) separating the kitchen waste into solid and liquid to obtain solid kitchen waste and waste oil and water; (2) crushing solid kitchen waste, mixing it with water in a mass ratio of 1:(1.5-2), stirring for 30-60 minutes to obtain a mixed raw material, and putting the mixed raw material into a reactor to react for 4-8 hours; (3) After the reaction is completed, the reactants are cooled to room temperature and then solid-liquid separation is performed to obtain solid biochar. After drying for 1-2 hours, biochar is obtained; The specific preparation method of the modified biochar is as follows: (1) crushing the obtained dried biochar, mixing the crushed biochar, hydrogen peroxide and water for 1-10 hours, and filtering to obtain pretreated biochar; (2) drying the obtained pretreated biochar at a constant temperature for 1-2 hours and then immersing it in liquid nitrogen. After immersing it for 2-9 hours, the pretreated biochar was taken out, filtered and dried for 5-8 hours to obtain the primary modified biochar; (3) Use deionized water and the initially modified biochar to prepare a biochar suspension with a concentration of 0.5 mg / L-2 mg / L. After ultrasonic treatment for 2-4 h, potassium hydroxide solution is added dropwise to adjust the pH value of the suspension to 8-13. Then, phosphate powder and zinc chloride solution are added. After stirring evenly, aspartic acid solution is added dropwise. Heat and stir at 20-60 °C for 12-36 h. Then, the temperature is adjusted to 60 °C-70 °C, polyisocyanate is added, and the product is reacted for 6 h-10 h. Then, the product is washed with acetone, centrifuged, and dried to constant weight to obtain modified biochar.
2. A method for remediating contaminated soil using kitchen waste according to claim 1, characterized in that: The mass ratio of the auxiliary material to the modified biochar is (63-102): (80-100), and the mass ratio of the soil remediation agent to the contaminated soil is (0.6-1):
100.
3. The method for remediating contaminated soil using kitchen waste according to claim 1, characterized in that: The auxiliary materials include the following raw materials in parts by weight: 5-10 parts of humic acid, 15-20 parts of wood ash, 30-50 parts of diatomaceous earth, 5-12 parts of dipotassium hydrogen phosphate, and 8-10 parts of ammonium sulfate.
4. The method for remediating contaminated soil using kitchen waste according to claim 3, characterized in that: In step (2), the amount of the mixed material added is 1 / 3-2 / 3 of the volume of the reactor, and the reaction temperature in the reactor is 180°C.
5. The method for remediating contaminated soil using kitchen waste according to claim 4, characterized in that: The prepared biochar is modified to obtain modified biochar, and the biochar is modified using the following raw materials in parts by mass: 1-5 parts of dry biochar, 15-90 parts of 3wt% hydrogen peroxide, 3-10 parts of 2mol / L zinc chloride solution, 1-15 parts of phosphate powder, 100-800 parts of 20-80mg / L aspartic acid solution, and 10-100 parts of polyisocyanate.
6. The method for remediating contaminated soil using kitchen waste according to claim 5, characterized in that: In the biochar modification step (1), the mixing ratio of biochar and water is 1:(15-60) by mass.
7. A method for remediating contaminated soil using kitchen waste according to any one of claims 1 to 6, characterized in that: The kitchen waste includes discarded vegetable leaves, leftovers, leftover rice, fruit peels, egg shells, tea dregs, and bones.