Method for improving organic carbon reservoir of soil of reclamation cultivated land by using waste red bricks of building

Abstract

According to the method, the main raw material of the red bricks is clay, the red bricks are rich in iron and aluminum oxides after being fired, the porosity of the red bricks is 20%-30%, and the red bricks have the potential of improving the organic carbon library of the soil. The construction waste red bricks are subjected to structure and particle surface modification, and the obtained iron-based modified material based on the construction waste red bricks mainly comprises Al2O3, Fe < 3 + > oxide, SiO2, MgO and the like, and has a strong mineral adsorption effect and a physical isolation effect on soil organic carbon; and after material modification, a relatively strong soil organic carbon improving effect is achieved on acidic and alkaline reclamation farmland soil, the farmland soil carbon library level is effectively improved, the quality of a new reclamation land is improved, the materials and the process adopted in the whole preparation process are environmentally friendly, new pollutants are not introduced, and the cultivation cost of the farmland is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation in reclaimed farmland, and in particular relates to a method for improving the organic carbon pool of soil in reclaimed farmland by utilizing waste red bricks from construction. Background Art

[0002] With the rapid development of the social economy, in order to effectively utilize rural land and accelerate rural revitalization, it is urgent to reclaim scattered, idle, abandoned or demolished homesteads and convert them into agricultural land. However, currently, reclaimed rural land generally faces multiple quality problems, the most important of which are: 1. Abandoned red bricks, as construction waste, have low economic value and low willingness to be recycled and reused, which easily leads to the residue of abandoned red bricks in cultivated land, and eventually the intrusion of reclaimed land exceeds the standard, seriously affecting the quality of cultivated land.

[0003] 2. Due to the complex sources of topsoil, the newly reclaimed farmland has an extremely low soil organic carbon content, often around 6%, which makes it difficult to form soil aggregates, has poor water and fertilizer retention capacity, and reduces the quality of the farmland.

[0004] Existing technologies for increasing the soil organic carbon pool in newly reclaimed farmland often involve adding organic fertilizers, returning straw to the fields, and using biochar. The technical idea behind these measures is to "increase the total amount of soil carbon," but they do not actually consider the soil's own protection of organic carbon and its mineralization and decomposition effects, such as invention patent CN118985250A.

[0005] Red bricks are primarily made of clay, which, after firing, is rich in iron and aluminum oxides. Their porosity ranges from 20% to 30%. Based on the soil mineral carbon pump theory, they have the potential to increase the soil organic carbon pool. To address these two major challenges of newly reclaimed land, waste red bricks from the reclamation process are being used to prepare soil organic carbon-enhancing materials. This not only addresses the challenge of managing intrusive materials in newly reclaimed land, but also increases the soil organic carbon content in the land, thereby improving the quality of the reclaimed land and reducing the cost of fertilizing the land. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems existing in the prior art and provide a method for improving the organic carbon pool in the soil of reclaimed farmland by utilizing waste red bricks from construction.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions: A method for preparing an iron-based modified material using waste red bricks from construction, the method comprising the following steps: Step S1: crushing and ball-milling discarded red bricks from buildings to obtain micron-sized red brick powder; Step S2: fully mixing the micron-sized red brick powder and montmorillonite to obtain a mixture of the micron-sized red brick powder and montmorillonite; Step S3: adding a soluble salt solution of trivalent iron to a mixture of micron-sized red brick powder and montmorillonite, adjusting the pH of the mixture to 7.5-8.5 or 5.5-6.5 according to the acidity and alkalinity of the reclaimed farmland soil, and drying the adjusted mixture to a moisture content of less than 3%, thereby obtaining an iron-based modified material based on the micron-sized red brick powder; Step S4: applying the iron-based modified material evenly to the soil surface before sowing, and performing rotary tillage to level the field.

[0008] Furthermore, in step S1, during ball milling, the ball milling medium is zirconia balls, and the process includes adding water and a stabilizing dispersant, wherein the ball-to-material ratio is (3-10):1, the water-to-material ratio is (0.5-3):1, and the weight ratio of the stabilizing dispersant to water is 1:(5-40).

[0009] Furthermore, the stabilizing dispersant is a polycarboxylate water reducer, and the polycarboxylate water reducer includes tetrahydrofuran ether polyoxyethylene ether and isoprene polyoxyethylene ether.

[0010] Furthermore, during the ball milling, the speed is 300-400 r / min, the single milling time is 15-20 min, and the process is repeated 5 times.

[0011] Furthermore, in step S2, the average particle size of the micron-sized red brick powder is 2.5-3 μm, and the particle size of the montmorillonite is 0.2-1 μm. The micron-sized red brick powder and the montmorillonite are fully mixed in a mass ratio of (2-10):1.

[0012] Furthermore, in step S3, the mass volume ratio of the mixture to the soluble trivalent iron salt solution is 0.5 g:1 L, the soluble trivalent iron salt solution is ferric chloride or ferric nitrate, the concentration is 0.2~0.3 mol / L, the suspension is formed by ultrasonic treatment for 2 hours, and the suspension is allowed to stand at room temperature for 24 hours.

[0013] Furthermore, in step S3, when adjusting the pH of the mixture, when the target reclaimed farmland soil is acidic soil with a pH of less than 6.5, CaO is used to adjust the pH of the mixture to 7.5-8.5; when the reclaimed farmland is alkaline soil with a pH of more than 7.5, wood vinegar is used to adjust the pH of the mixture to 5.5-6.5.

[0014] Application of the iron-based modified material prepared by the method of the present invention in the process of improving the organic carbon pool in reclaimed farmland soil.

[0015] Furthermore, in the process of repairing and reclaiming cultivated land, it is mixed with organic fertilizer or compound fertilizer before planting crops, and the amount of fertilizer per 10,000 m 2 Apply 30-75kg of iron-based modified materials made of micron-sized waste red brick powder as a conditioning agent; if the soil organic carbon content is less than 6g / kg, the input amount is 75kg / hm22 , the input amount for soil organic carbon content of 6-12g / kg is 50kg / hm 2 , the input amount for soil organic carbon content>12g / kg is 30kg / hm 2 , and immediately carry out rotary tillage to break up the soil, with a tillage depth of 12~20cm. During the planting process, conditioners are added once every 5 years, and the addition is stopped when the soil organic carbon content reaches 20g / kg.

[0016] The beneficial effects of the present invention are: Based on the idea of increasing the total carbon supply in the soil, this invention, according to the "soil mineral carbon pump" theory, also incorporates the strategy of "protecting soil carbon". That is, by adding "iron-based modified materials of micron-level discarded red brick powder", not only the protective effect of clay minerals on soil organic carbon is utilized, but also the formation of iron-aluminum oxides on the mineral surface is enhanced through iron-based modification, further enhancing the adsorption of original carbon in the soil, and also enhancing the retention of soluble organic carbon, microbial carbon, etc. in the soil.

[0017] At the same time, the present invention recycles the abandoned red bricks and other construction waste generated during the reclamation process, which not only reduces the environmental risks of the abandoned red bricks, but also effectively improves the carbon pool level of farmland soil and improves the quality of the newly reclaimed land.

[0018] The materials and processes used in the entire preparation process of the present invention are environmentally friendly, do not introduce new pollutants, and reduce the cost of arable land cultivation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of the method for improving the soil organic carbon pool of reclaimed farmland using waste red bricks from construction; Figure 2 is the isothermal adsorption curve of glucose by the iron-based modified red brick powder of the present invention; Figure 3 is the fitting curve of soil organic carbon content in alkaline reclaimed land in Example 1 of the present invention; Figure 4 This is the fitting curve of soil organic carbon content in acidic reclaimed land in Example 2 of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0021] A method for preparing an iron-based modified material using waste red bricks from construction, the method comprising the following steps: Step S1: crushing and ball-milling discarded red bricks from buildings to obtain micron-sized red brick powder; Step S2: fully mixing the micron-sized red brick powder and montmorillonite to obtain a mixture of the micron-sized red brick powder and montmorillonite; Step S3: adding a soluble salt solution of trivalent iron to a mixture of micron-sized red brick powder and montmorillonite, adjusting the pH of the mixture to 7.5-8.5 or 5.5-6.5 according to the acidity and alkalinity of the reclaimed farmland soil, and drying the adjusted mixture at a drying temperature of 40-60° C. until the moisture content is less than 3%, thereby obtaining an iron-based modified material based on micron-sized red brick powder; Step S4: applying the iron-based modified material evenly to the soil surface before sowing, and performing rotary tillage to level the field.

[0022] In the step S1, during ball milling, the ball milling medium is zirconia balls, and the step of adding water and a stabilizing dispersant is included, wherein: the ball-to-material ratio is (3-10):1, the water-to-material ratio is (0.5-3):1, and the weight ratio of the stabilizing dispersant to water is 1:(5-40).

[0023] The stabilizing dispersant is a polycarboxylate water-reducing agent made from renewable raw materials. The stabilizing dispersant inhibits the agglomeration of brick powder particles through electrostatic repulsion, increases the specific surface area, increases the ligand exchange and cationic bridge effect of the product, improves the adsorption and isolation of soil organic carbon, and reduces the mineralization of soil organic carbon. Therefore, the stabilizing dispersant added during the ball milling process can further improve the dispersibility of the particles. This micron-sized red brick powder (2.5~3μm) has a large specific surface area and can effectively adsorb soil particles, helping the soil to form stable aggregates, improve the physical structure of the soil, improve the soil porosity, and enhance the air permeability and water retention. In this embodiment, the polycarboxylate water-reducing agent includes tetrahydrofuran ether polyoxyethylene ether and isoprene polyoxyethylene ether.

[0024] During the ball milling, the speed is 300-400 r / min, the single milling time is 15-20 min, and the process is repeated 5 times.

[0025] In step S2, the average particle size of the micron-sized red brick powder is 2.5-3 μm, and the particle size of the montmorillonite is 0.2-1 μm. The micron-sized red brick powder and the montmorillonite are fully mixed in a mass ratio of (2-10):1.

[0026] In step S3, the mass volume ratio of the mixture to the soluble trivalent iron salt solution is 0.5g:1L, the soluble trivalent iron salt solution is ferric chloride FeCl3 or ferric nitrate Fe(NO3)3, with a concentration of 0.2~0.3mol / L, ultrasonic treatment for 2h to form a suspension, and then standing at room temperature for 24h.

[0027] Fe 3+ The addition of can further generate hydrated iron oxide (Fe(OH)3) on the surface of the material through hydrolysis, and through the hydroxyl bridging effect between clay layers, the material has higher organic carbon adsorption capacity and adsorption sites than the raw materials, and finally Fe 3+Combines with soil organic matter to form a stable organic-inorganic complex, reduces the mineralization and decomposition of organic matter, increases soil organic carbon content and soil carbon sink capacity, and reduces soil carbon loss.

[0028] In step S3, when adjusting the pH of the mixture, when the target reclaimed farmland soil is acidic soil with a pH of less than 6.5, CaO is used to adjust the pH of the mixture to 7.5-8.5; when the reclaimed farmland soil is alkaline soil with a pH of more than 7.5, wood vinegar is used to adjust the pH of the mixture to 5.5-6.5.

[0029] Waste red bricks are rich in clay minerals such as iron and aluminum. The present invention modifies the structure and particle surface of waste red bricks to obtain an iron-based modified material based on micron-sized waste red brick powder. The main components are Al2O3, Fe 3+ Oxides, SiO2 and MgO, etc., have strong carbon fixation capabilities and can repair both acidic and alkaline reclaimed land.

[0030] In the process of repairing and reclaiming cultivated land, mix it with organic fertilizer or compound fertilizer before planting crops, and use 10,000m 2 Apply 30-75kg of iron-based modified materials made of micron-sized waste red brick powder as a conditioning agent; if the soil organic carbon content is less than 6g / kg, the input amount is 75kg / hm2 2 , the input amount for soil organic carbon content of 6-12g / kg is 50kg / hm 2 , the input amount for soil organic carbon content>12g / kg is 30kg / hm 2 , and immediately carry out rotary tillage to break up the soil, with a tillage depth of 12~20cm. During the planting process, conditioners are added once every 5 years, and the addition is stopped when the soil organic carbon content reaches 20g / kg.

[0031] In addition, the iron-based modified material prepared by the method of the present invention should be applied to paddy fields as far as possible to avoid reducing the efficiency of iron-aluminum oxides.

[0032] The present invention is respectively provided for acidic soil and alkaline soil, comprising the following steps: The waste red bricks were sequentially placed into a hammer crusher and crushed to less than 5 mm, and then ball-milled using a planetary ball mill. Water and a stabilizing dispersant were added during the ball milling. The ball-milling medium was zirconia balls with a diameter of 2.0 mm. The ball-to-material ratio was 3:1, the water-to-material ratio was 3:1, the weight ratio of the stabilizing dispersant to water was 1:10, and the stabilizing dispersant was tetrahydrofuran ether polyoxyethylene ether. The ball milling speed was 300 r / min, the single grinding time was 15 min, and the process was repeated 5 times. After ball milling, micron-sized red brick powder with an average particle size of 2.55±0.32 μm was obtained. The micron-sized waste red brick powder and montmorillonite with a particle size of 0.2-1 μm are mixed in a mass ratio of 10:1 to prepare a mixture of micron-sized red brick powder and montmorillonite; A 0.2 mol / L FeCl3 solution was mixed with a mixture of micron-sized red brick powder and montmorillonite, and the mass volume ratio of the mixture of micron-sized red brick powder and montmorillonite to a soluble salt solution of trivalent iron was 0.5 g:1 L, and the mixture was maintained for 12 hours to obtain a mixture. The pH of the mixture was adjusted to 7.5-8.5 and 5.5-6.5 for acidic and alkaline soils, respectively. The mixture was dried at 40°C until the moisture content was less than 3%, thereby obtaining an iron-based modified material of micron-sized waste red brick powder; The obtained iron-based modified materials of micron-sized waste red brick powder with different pH values were evaluated in the laboratory. The method used was isothermal adsorption method. The adsorbed organic carbon was glucose. 0.2 g of iron-based modified materials of micron-sized waste red brick powder was added to 50 mL of glucose solution. The solution was shaken at 150 rpm for 24 h at 25 ° C. After filtering with a 0.45 μm filter membrane, the glucose content in the solution was determined by high performance liquid chromatography. The results were fitted using the Freundlich model, as shown in the following figure. Figure 2 The fitting parameters are shown in Table 1: The adsorption of glucose by the iron-based modified material of micron-sized waste red brick powder at pH 5.5-6.5 is higher than that at pH 7.5-8.5.

[0033] In order to further accurately evaluate the usage of iron-based modified materials of micron-sized waste red brick powder in acidic and alkaline newly reclaimed farmland, the following examples are further illustrated. It should be pointed out that the matters not described in detail in the present invention are all conventional operating methods in this field and are not the focus of the present invention.

[0034] Example 1 alkaline soil Newly reclaimed cultivated land soil was selected for potted plantation experiments. The surface soil of the reclaimed land came from subway excavation soil. The pH of the 0-20 cm surface soil was 8.55, the soil organic carbon content was 5.61 g / kg, the soil total nitrogen content was 0.68%, the soil total phosphorus content was 0.51%, the soil alkaline nitrogen content was 16.2 mg / kg, the available phosphorus content was 12.8 mg / kg, and the available potassium content was 112.5 mg / kg.

[0035] During the potting simulation, the soil to be remediated was moved into the pot with a depth of 35 cm, a diameter of 50 cm at the top, and a diameter of 25 cm at the bottom. Rice and wheat were used as the crop rotation. Before wheat was planted, the iron-based modified material of micron-grade waste red brick powder was mixed with commercial organic fertilizer, with the application rate of commercial organic fertilizer being 15 t / hm2. 2, evenly mix 75kg / hm2 of the above organic fertilizer 2 An iron-based modified material containing micron-scale waste red brick dust was used. Immediately after fertilization, simulated soil tillage was performed at a depth of 20 cm. A control treatment without the addition of the iron-based modified material containing micron-scale waste red brick dust was also established. Subsequent management followed conventional farmer practices.

[0036] After normal crop planting, soil organic carbon content was observed every 6 months for 6 consecutive times. The results showed that after adding iron-based modified materials of micron-sized waste red brick powder with different pH values, the soil organic carbon content showed an exponential growth trend. After 2.5 years, the final soil organic carbon content of the iron-based modified materials of micron-sized waste red brick powder with pH 5.5, pH 6.0 and pH 6.5 was 11.00 g / kg, 10.80 g / kg and 9.68 g / kg, respectively, which were 1.93, 1.90 and 1.70 times the initial soil organic carbon, respectively. Figure 3 As shown. The control treatment without the iron-based modified material of micron-sized waste red brick powder had a soil organic carbon content of 7.89 g / kg after 2.5 years, which was much lower than that of the iron-based modified material with micron-sized waste red brick powder. It was only 71%, 73% and 82% of the iron-based modified material treatments with micron-sized waste red brick powder at pH 5.5, pH 6.0 and pH 6.5. The soil organic carbon growth equation is shown in Table 2: Example 2 acidic soil Newly reclaimed cultivated land soil was selected for potted plantation experiments. The surface soil of the reclaimed land came from the original soil at a depth of 1.2 meters. The soil pH was 5.65, the soil organic carbon content was 6.71 g / kg, the soil total nitrogen content was 0.49%, the soil total phosphorus content was 0.47%, the soil alkaline nitrogen content was 25.4 mg / kg, the available phosphorus content was 6.4 mg / kg, and the available potassium content was 92.3 mg / kg.

[0037] During the potting simulation, the soil to be remediated was moved into the pot with a depth of 35 cm, a diameter of 50 cm at the top, and a diameter of 25 cm at the bottom. Rice and wheat were used as the crop rotation. Before wheat was planted, the iron-based modified material of micron-grade waste red brick powder was mixed with commercial organic fertilizer, with the application rate of commercial organic fertilizer being 15 t / hm2. 2 50 kg / hm² of iron-based modified micron-grade waste red brick dust was evenly mixed into the organic fertilizer. Immediately after fertilization, simulated soil tillage was performed at a depth of 20 cm. A control treatment without the iron-based modified micron-grade waste red brick dust was also established. Subsequent management followed conventional farmer practices.

[0038] After normal crop planting, soil organic carbon content was observed every 6 months for 6 consecutive times. The results showed that after adding iron-based modified materials of micron-sized waste red brick powder with different pH values, the soil organic carbon content showed an exponential growth trend. After 2.5 years, the final soil organic carbon content of the iron-based modified materials of micron-sized waste red brick powder with pH 7.5, pH 8.0 and pH 8.5 was 12.25g / kg, 12.01g / kg and 12.39g / kg, respectively, which were 1.83, 1.79 and 1.85 times the initial soil organic carbon, as shown in Figure 2. Figure 4 As shown. The control treatment without the iron-based modified material of micron-sized waste red brick powder had a soil organic carbon content of 9.86 g / kg after 2.5 years, which was much lower than that of the iron-based modified material with micron-sized waste red brick powder. It was only 80%, 82% and 80% of the treatments with the iron-based modified material of micron-sized waste red brick powder at pH 7.5, pH 8.0 and pH 8.5. The soil organic carbon growth equation is shown in Table 3: The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing iron-based modified materials using construction waste red bricks, characterized in that: The method comprises the following steps: Step S1: crushing and ball-milling discarded red bricks from buildings to obtain micron-sized red brick powder; Step S2: fully mixing the micron-sized red brick powder and montmorillonite to obtain a mixture of the micron-sized red brick powder and montmorillonite; Step S3: Add a soluble salt solution of trivalent iron to a mixture of micron-sized red brick powder and montmorillonite, and adjust the pH of the mixture to 7.5-8.5 or 5.5-6.5 according to the acidity and alkalinity of the reclaimed farmland soil, and dry the adjusted mixture to a moisture content of less than 3% to obtain an iron-based modified material based on micron-sized red brick powder.

2. The method for preparing iron-based modified materials using construction waste red bricks according to claim 1, characterized in that: In the step S1, during ball milling, the ball milling medium is zirconia balls, and the step of adding water and a stabilizing dispersant is included, wherein: the ball-to-material ratio is (3-10):1, the water-to-material ratio is (0.5-3):1, and the weight ratio of the stabilizing dispersant to water is 1:(5-40).

3. The method for preparing iron-based modified materials using construction waste red bricks according to claim 2, characterized in that: The stabilizing dispersant is a polycarboxylate water reducer, and the polycarboxylate water reducer includes tetrahydrofuran ether polyoxyethylene ether and isoprene polyoxyethylene ether.

4. The method for preparing iron-based modified materials using construction waste red bricks according to claim 2, characterized in that: During the ball milling, the speed is 300-400 r / min, the single milling time is 15-20 min, and the process is repeated 5 times.

5. The method for preparing iron-based modified materials using construction waste red bricks according to claim 1, characterized in that: In step S2, the average particle size of the micron-sized red brick powder is 2.5-3 μm, and the particle size of the montmorillonite is 0.2-1 μm. The micron-sized red brick powder and the montmorillonite are fully mixed in a mass ratio of (2-10):

1.

6. The method for preparing iron-based modified materials using construction waste red bricks according to claim 1, characterized in that: In step S3, the mass volume ratio of the mixture to the soluble trivalent iron salt solution is 0.5 g:1 L, the soluble trivalent iron salt solution is ferric chloride or ferric nitrate, and the concentration is 0.2-0.3 mol / L. The suspension is formed by ultrasonic treatment for 2 h and allowed to stand at room temperature for 24 h.

7. The method for preparing iron-based modified materials using construction waste red bricks according to claim 1, characterized in that: In step S3, when adjusting the pH of the mixture, when the target reclaimed farmland soil is acidic soil with a pH of less than 6.5, CaO is used to adjust the pH of the mixture to 7.5-8.5; when the reclaimed farmland soil is alkaline soil with a pH of more than 7.5, wood vinegar is used to adjust the pH of the mixture to 5.5-6.

5.

8. Use of an iron-based modified material prepared by the method according to any one of claims 1 to 7 in the process of increasing the organic carbon pool in reclaimed farmland soil.

9. The use according to claim 8, characterized in that In the process of repairing and reclaiming cultivated land, before planting crops, mix it with organic fertilizer or compound fertilizer, and apply 30-75 kg of iron-based modified materials of micron-grade waste red brick powder as a conditioning agent per hectare; among them, the input amount for soil organic carbon content below 6 g / kg is 75 kg / hm2. 2 , the input amount for soil organic carbon content of 6~12g / kg is 50kg / hm 2 , the input amount for soil organic carbon content>12g / kg is 30kg / hm 2 , and immediately carry out rotary tillage to break up the soil, with a tillage depth of 12~20cm. During the planting process, conditioners are added once every 5 years, and the addition is stopped when the soil organic carbon content reaches 20g / kg.

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