Preparation method of lawn brick capable of solidifying and stabilizing lead-contaminated soil
By mixing carbonized sugarcane bagasse with severe lead-contaminated soil, construction waste and fly ash under NaOH and ultrasonic conditions, lawn tiles are formed, and the problem of insufficient acid resistance and erosion resistance of solidified bodies in the prior art is solved, and lead is achieved Stabilization and resource utilization of polluted soil.
Patent Information
- Application Number
- CN202310549570.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-16
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2043-05-16
AI Technical Summary
The existing curing and stabilization methods are difficult to effectively reduce the total amount of heavy metals in the soil, and the cured body has insufficient acid resistance and erosion resistance, which cannot meet the strength requirements of building materials, and has failed to achieve resource utilization of contaminated soil.
Carbonized sugar cane bagasse and potassium carbonate are ground and heated to mix it with severe lead-contaminated soil, construction waste and fly ash. The modulus and ultrasonic assistance are adjusted by NaOH to form lawn tiles to achieve stable and solidification of lead-contaminated soil.
The biologically active migration of lead is reduced, the stability of lead-contaminated soil is achieved, the compressive strength requirements of building materials are met, and the resource recycling is achieved.
Smart Images
Figure CN116514518B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of lead-contaminated soil solidification, and in particular to a method for preparing lawn bricks capable of solidifying and stabilizing lead-contaminated soil. Background Art
[0002] The remediation of heavy metal pollution in soil generally starts from two ideas: one is to reduce the total amount of heavy metals in the soil, and the other is to control the activity of heavy metals in the soil and reduce their migration to the food chain. However, most of the existing technical means are difficult to reduce the total amount of heavy metals in the soil economically and efficiently. In order to effectively control the impact of heavy metals on agricultural product safety and human health, inhibiting, reducing or shielding the biological activity (i.e. bioavailability) of heavy metals will be a very effective means. At present, the commonly used technologies for solidification and stabilization methods include cement solidification and stabilization, lime solidification and stabilization, pharmaceutical solidification and stabilization, plastic material solidification and stabilization, self-cementing solidification and stabilization, and geopolymer solidification and stabilization. The above methods have their own advantages and disadvantages. Among them, the leaching rate of cement and lime solidification bodies is high, the solidification body has a large volume increase, and the acid resistance and erosion resistance are poor. The plastic material solidification body has poor aging resistance, the operation is complicated, the cost is high, and the application of the self-cementing solidification method is narrow.
[0003] The current research only focuses on the solidification and stabilization effect of artificially added powdered heavy metal reagents or slag containing heavy metals using kaolin or fly ash as raw materials, and rarely involves the solidification and stabilization research of soil containing heavy metals. In addition, whether the solidified body is used for geological landfill or for building materials, it needs to have sufficient strength to withstand a certain pressure. Generally, solid waste landfill requires about 5 MPa, and building materials require more than 10 MPa. At present, most of the research results on the solidification and stabilization method only meet the solid waste landfill standards and cannot achieve further resource utilization of contaminated soil. Summary of the invention
[0004] The purpose of the present invention is to overcome the problems in the prior art and provide a method for preparing lawn bricks capable of solidifying and stabilizing lead-contaminated soil.
[0005] The present invention provides a method for preparing a lawn brick capable of curing and stabilizing lead-contaminated soil, comprising the following steps:
[0006] Prepare carbonized bagasse, grind the carbonized bagasse and potassium carbonate in a mortar, mix thoroughly, heat to 600-650°C for 2-3 hours; take out the carbonized bagasse, soak it with hydrochloric acid, then wash it with deionized water until the aqueous solution is neutral, and dry it for later use;
[0007] Severe lead-contaminated soil was crushed and passed through a 2-2.5 mm sieve; construction waste was crushed into particles of 0.2-2.5 mm in size;
[0008] Add NaOH to adjust the modulus of the sodium silicate solution to 0.5;
[0009] Fully mix the carbonized bagasse, heavily lead-contaminated soil, construction waste and fly ash; then add the treated sodium silicate solution, stir, and react under ultrasonic conditions;
[0010] The slurry is injected into a lawn brick mold. When the volume of the injected slurry is 1 / 3 of the volume of the lawn brick mold, it is vibrated and then the mold is filled with the slurry. The slurry is vibrated again to obtain a homogeneous brick embryo. After curing, lawn bricks that can solidify and stabilize lead-contaminated soil are obtained.
[0011] Preferably, the preparation method of the carbonized bagasse is as follows: the cleaned bagasse is placed in a drying oven at 105°C for 8 hours and is put into a crucible, and the crucible is then placed in a tubular atmosphere furnace, heated to 400°C at a heating rate of 15°C / min and then kept warm for 2 hours.
[0012] Preferably, the ultrasonic condition is achieved by inserting an ultrasonic vibrator with a power of 200-400w, and reacting for 30-35min under the action of ultrasound.
[0013] Preferably, the slurry injected into the lawn brick mold includes the following raw materials in parts by weight: 3 parts of carbonized bagasse, 30-35 parts of heavily lead-contaminated soil, 5-10 parts of construction waste, 54-60 parts of fly ash, and 50-55 parts of sodium silicate.
[0014] Preferably, the weight ratio of the carbonized bagasse to potassium carbonate is 1:1.
[0015] Preferably, the washed carbonized bagasse is dried in a drying oven at 105°C for 8 h.
[0016] Preferably, the mold filled with the slurry and compacted is sealed with a polyethylene film, placed in a constant temperature curing box preheated to 40° C., and cured for 24-48 hours;
[0017] When the bricks in the above mold will not be deformed when touched, demold them and take them out. Cover them with a wet cloth on an open space with a temperature greater than 15°C and continue to cure for 20 days. Spray room temperature water on the wet cloth evenly every day to keep it moist. If the temperature is less than 15°C, place it in a curing box or take other insulation measures.
[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: the preparation method of the lawn brick of the solidifiable stabilized lead-contaminated soil of the present invention uses bagasse as a raw material, which is mixed with pre-treated heavily Pb-contaminated soil, construction waste and fly ash after carbonization, and is formed into lawn bricks through further maintenance measures under the action of alkali excitation and ultrasound assistance, so that Pb (II) in the Pb-contaminated soil no longer migrates and transforms, thereby reducing its negative environmental effects to a minimum, and at the same time can realize resource recycling, which is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a scanning electron microscope (SEM) photograph of the lawn brick prepared in this example.
[0020] Figure 2 This is the energy spectrum (SEM-EDS) of the lawn brick prepared in this example. DETAILED DESCRIPTION
[0021] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0022] Embodiment 1:
[0023] Put 3 parts of bagasse that have been washed and dried in a drying oven at 105℃ for 8h into a crucible, and then place the crucible in a tubular atmosphere furnace, heat it to 400℃ at a heating rate of 15℃ / min, and then keep it warm for 2h. Take out the crucible and grind the carbonized bagasse and 3 parts of potassium carbonate in a mortar for 10 min, mix them thoroughly, and continue to put the crucible into a tubular atmosphere furnace, heat to 600℃ and continue for 2h. Take out the carbonized bagasse and soak it in 1 mol / L hydrochloric acid for 30 min, then wash it with ionized water until the aqueous solution is neutral, and finally dry it in a drying oven at 105℃ for 8h;
[0024] 30 parts of heavily lead-contaminated soil were crushed using a continuous crusher and passed through a 2 mm sieve; 10 parts of construction waste (clay bricks, cement blocks, etc.) were crushed using a hammer crusher with a particle size of approximately 0.2~2.5 mm.
[0025] Add appropriate amount of NaOH to adjust the modulus of the sodium silicate solution to 0.5;
[0026] Put the treated carbonized bagasse, heavily lead-contaminated soil, construction waste and 54 parts of fly ash into a mixer and stir for 3-8 minutes to fully mix them. Then add 50 parts of the treated sodium silicate solution in step 3 and continue stirring for 15 minutes. At the same time, insert an ultrasonic vibrator and set the power to about 300 W. React under ultrasound for 30 minutes.
[0027] Transfer the above slurry to the lawn brick mold. When it is transferred to 1 / 3 of the mold volume, fix it on a vibration table and vibrate it for 20 minutes to remove the bubbles in the lower layer. Then fill the mold with the slurry and continue to fix it on the vibration table and vibrate it for 30 minutes. In this way, a homogeneous brick embryo can be obtained.
[0028] The mold containing the slurry was sealed with a polyethylene film and placed in a constant temperature curing box preheated to 40°C for 24-48 hours.
[0029] When the bricks in the mold are not deformed when touched, remove them from the mold and cover them with a wet cloth on an open space with a temperature greater than 15°C for 20 days. Spray room temperature water on the wet cloth evenly every day to keep it moist. If the temperature is less than 15°C, it is recommended to place it in a curing box or take other insulation measures.
[0030] The result is a lawn brick that can solidify and stabilize lead-contaminated soil.
[0031] The compressive strength of the lawn bricks prepared in this embodiment was also tested, which was 21.32 Mpa. The total lead concentration of the leachate measured by the leaching toxicity test was 194.4 μg / L, which is much lower than the Pb concentration limit of 5 mg / L specified in the "Hazardous Waste Identification Standard - Leaching Toxicity Identification" (GB5085.3-2007).
[0032] Embodiment 2:
[0033] Put 3 parts of bagasse that have been washed and dried in a drying oven at 105℃ for 8h into a crucible, and then place the crucible in a tubular atmosphere furnace, heat it to 400℃ at a heating rate of 15℃ / min, and then keep it warm for 2h. Take out the crucible and grind the carbonized bagasse and 3 parts of potassium carbonate in a mortar for 10 min, mix them thoroughly, and continue to put the crucible into a tubular atmosphere furnace, heat to 600℃ and continue for 2h. Take out the carbonized bagasse and soak it in 1 mol / L hydrochloric acid for 30 min, then wash it with ionized water until the aqueous solution is neutral, and finally dry it in a drying oven at 105℃ for 8h;
[0034] 35 parts of heavily lead-contaminated soil were crushed using a continuous crusher and passed through a 2.5 mm sieve; 5 parts of construction waste (clay bricks, cement blocks, etc.) were crushed using a hammer crusher with a particle size of approximately 0.2~2.5 mm.
[0035] Add appropriate amount of NaOH to adjust the modulus of the sodium silicate solution to 0.5;
[0036] Put the treated bagasse, heavily lead-contaminated soil, construction waste and 54 parts of fly ash into a blender and stir for 3-8 minutes to fully mix them. Then add 55 parts of the treated sodium silicate solution in step 3 and continue stirring for 45 minutes. At the same time, insert an ultrasonic vibrator and set the power to about 300w. React under ultrasound for 30 minutes.
[0037] Transfer the above slurry to the lawn brick mold. When it is transferred to 1 / 3 of the mold volume, fix it on a vibration table and vibrate it for 20 minutes to remove the bubbles in the lower layer. Then fill the mold with the slurry and continue to fix it on the vibration table and vibrate it for 30 minutes. In this way, a homogeneous brick embryo can be obtained.
[0038] The mold containing the slurry was sealed with a polyethylene film and placed in a constant temperature curing box preheated to 40°C for 24-48 hours.
[0039] When the bricks in the mold are not deformed when touched, remove them from the mold and cover them with a wet cloth on an open space with a temperature greater than 15°C for 20 days. Spray room temperature water on the wet cloth evenly every day to keep it moist. If the temperature is less than 15°C, it is recommended to place it in a curing box or take other insulation measures.
[0040] The result is a lawn brick that can solidify and stabilize lead-contaminated soil.
[0041] The compressive strength of the lawn bricks prepared in this embodiment was also tested, which was 19.95 MPa. The total lead concentration of the leachate was measured by leaching toxicity test to be 301.8 μg / L, which is much lower than the Pb concentration limit of 5 mg / L specified in the "Hazardous Waste Identification Standard - Leaching Toxicity Identification" (GB5085.3-2007).
[0042] Embodiment three:
[0043] Put 3 parts of bagasse that have been washed and dried in a drying oven at 105℃ for 8h into a crucible, and then place the crucible in a tubular atmosphere furnace, heat it to 400℃ at a heating rate of 15℃ / min, and then keep it warm for 2h. Take out the crucible and grind the carbonized bagasse and 3 parts of potassium carbonate in a mortar for 10 min, mix them thoroughly, and continue to put the crucible into a tubular atmosphere furnace, heat to 600℃ and continue for 2h. Take out the carbonized bagasse and soak it in 1 mol / L hydrochloric acid for 30 min, then wash it with ionized water until the aqueous solution is neutral, and finally dry it in a drying oven at 105℃ for 8h;
[0044] 30 parts of heavily lead-contaminated soil were crushed using a continuous crusher and passed through a 2.5 mm sieve; 10 parts of construction waste (clay bricks, cement blocks, etc.) were crushed using a hammer crusher with a particle size of approximately 0.2~2.5 mm.
[0045] Add appropriate amount of NaOH to adjust the modulus of the sodium silicate solution to 0.5;
[0046] Put the treated carbonized bagasse, treated heavily lead-contaminated soil and construction waste and 60 parts of fly ash into a blender and stir for 3-8 minutes to fully mix them. Then add 50 parts of the treated sodium silicate solution in step 3 and continue stirring for 45 minutes. At the same time, insert an ultrasonic vibrator and set the power to 350 W. React under ultrasonic action for 30 minutes.
[0047] Transfer the above slurry to the lawn brick mold. When it is transferred to 1 / 3 of the mold volume, fix it on a vibration table and vibrate it for 20 minutes to remove the bubbles in the lower layer. Then fill the mold with the slurry and continue to fix it on the vibration table and vibrate it for 30 minutes. In this way, a homogeneous brick embryo can be obtained.
[0048] The mold containing the slurry was sealed with a polyethylene film and placed in a constant temperature curing box preheated to 40°C for 24-48 hours.
[0049] When the bricks in the mold are not deformed when touched, remove them from the mold and cover them with a wet cloth on an open space with a temperature greater than 15°C for 20 days. Spray room temperature water on the wet cloth evenly every day to keep it moist. If the temperature is less than 15°C, it is recommended to place it in a curing box or take other insulation measures.
[0050] The result is a lawn brick that can solidify and stabilize lead-contaminated soil.
[0051] The compressive strength of the lawn bricks prepared in this embodiment was also tested, which was 19.44 MPa. The total lead concentration of the leachate was measured by leaching toxicity test to be 1248.4 μg / L, which is much lower than the Pb concentration limit of 5 mg / L specified in the "Hazardous Waste Identification Standard - Leaching Toxicity Identification" (GB5085.3-2007).
[0052] In this embodiment Figure 1 The scanning photos clearly show that heavy metal-contaminated loess and other materials such as fly ash undergo geopolymerization reaction to generate dense geopolymer gel (amorphous aluminosilicate gel), and its apparent morphology presents a non-completely uniform amorphous state with a dense structure.
[0053] In this embodiment Figure 2In the scanning photos, there are 37% Si, 17% Al, 14% Fe, 11% O, 7% Ca, 6% Na, 4% K, 3% Pb and 2% Mg, among which silicon-aluminum products and Pb are evenly distributed.
[0054] Before the reaction of this embodiment, the unstable state of Pb in the Pb-contaminated soil accounted for 96.24%. After the reaction process of this embodiment, it can be found that the unstable state of Pb in the soil is transformed into a stable state of organic matter binding state and residual state, the exchange state Pb is reduced by 32.48 percentage points, and the residual state Pb is increased by 37.05 percentage points. Combined with the changes in the form of Pb before and after the reaction, it can be concluded that after the solidification and stabilization reaction of this embodiment, Pb has been solidified and stabilized.
[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing lawn bricks capable of curing and stabilizing lead-contaminated soil, characterized in that: The following steps are involved: Prepare carbonized bagasse, grind the carbonized bagasse and potassium carbonate in a mortar, mix thoroughly, heat to 600-650°C for 2-3 hours; take out the carbonized bagasse, soak it with hydrochloric acid, then wash it with deionized water until the aqueous solution is neutral, and dry it for later use; Severe lead-contaminated soil was crushed and passed through a 2-2.5 mm sieve; construction waste was crushed into particles of 0.2-2.5 mm in size; Add NaOH to adjust the modulus of the sodium silicate solution to 0.5; Fully mix the carbonized bagasse, heavily lead-contaminated soil, construction waste and fly ash; then add the treated sodium silicate solution, stir, and react under ultrasonic conditions to obtain a slurry; The slurry is injected into a lawn brick mold, and when the volume of the injected slurry is 1 / 3 of the volume of the lawn brick mold, the slurry is vibrated, and then the mold is filled with the slurry, and the slurry is vibrated again to obtain a homogeneous brick embryo, and after curing, a lawn brick capable of curing and stabilizing lead-contaminated soil is obtained; The slurry injected into the lawn brick mold includes the following raw materials in parts by weight: 3 parts of carbonized bagasse, 30-35 parts of heavily lead-contaminated soil, 5-10 parts of construction waste, 54-60 parts of fly ash, and 50-55 parts of sodium silicate.
2. The method for preparing lawn bricks capable of curing and stabilizing lead-contaminated soil according to claim 1, characterized in that: The preparation method of the carbonized bagasse is as follows: the cleaned bagasse is placed in a drying box at 105°C for 8 hours and is put into a crucible, and then the crucible is placed in a tubular atmosphere furnace, heated to 400°C at a heating rate of 15°C / min and then kept warm for 2 hours.
3. The method for preparing lawn bricks capable of curing and stabilizing lead-contaminated soil according to claim 1, characterized in that: The ultrasonic condition is achieved by inserting an ultrasonic vibrator with a power of 200-400w, and reacting for 30-35min under the action of ultrasound.
4. The method for preparing lawn bricks capable of curing and stabilizing lead-contaminated soil according to claim 1, characterized in that: The weight ratio of the carbonized bagasse to potassium carbonate is 1:
1.
5. The method for preparing lawn bricks capable of curing and stabilizing lead-contaminated soil according to claim 1, characterized in that: The washed carbonized bagasse is dried in a drying oven at 105° C. for 8 h.
6. The method for preparing turf bricks capable of curing and stabilizing lead-contaminated soil according to claim 1, characterized in that: The mold filled with slurry and compacted is sealed with a polyethylene film and placed in a constant temperature curing box preheated to 40°C for 24-48 hours; When the bricks in the above mold will not be deformed when touched, demold them and take them out. Cover them with a wet cloth on an open space with a temperature greater than 15°C and continue to cure for 20 days. Spray room temperature water on the wet cloth evenly every day to keep it moist. If the temperature is less than 15°C, place it in a curing box or take other insulation measures.