Modified fly ash environmental remediation material as well as preparation method and application thereof
By physically or chemically modifying fly ash to disrupt its glassy structure, increase its specific surface area, and add surface-active functional groups, modified fly ash with excellent adsorption and fixation properties for heavy metals Pb and Cd can be prepared. This solves the problem of limited modification effect of fly ash in existing technologies and achieves efficient and stable soil heavy metal remediation and environmentally friendly improvement effects.
Patent Information
- Application Number
- CN202511757021.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-27
- Publication Date
- 2026-01-30
AI Technical Summary
Existing fly ash modification methods are complex, costly, and have limited modification effects, making it difficult to meet the actual needs of soil heavy metal pollution remediation. Furthermore, there is a lack of systematic research on the remediation mechanism and long-term effectiveness of modified fly ash in actual soil environments.
By physically or chemically modifying fly ash to disrupt its glassy structure, increase its specific surface area and add surface-active functional groups, and then treating it with acid or alkali solutions, modified fly ash environmental remediation materials with excellent adsorption and fixation properties for heavy metals Pb and Cd can be prepared.
It significantly improves the adsorption and fixation capacity of fly ash for heavy metals, reduces production costs, achieves efficient and stable soil heavy metal remediation, and is also environmentally friendly, improving soil fertility.
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Figure CN121422909A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of industrial solid waste resource utilization and environmental pollution control, and particularly relates to a modified fly ash environmental remediation material and a preparation method and application thereof. BACKGROUND
[0002] Fly ash is a large amount of industrial solid waste produced by coal-fired power plants, industrial boilers and other coal-fired equipment, and the annual output is huge. The accumulation and storage of a large amount of fly ash not only occupies valuable land resources, but also easily causes secondary environmental risks such as dust pollution and heavy metal leaching of underground water. Harmless disposal and resource utilization of fly ash have become an urgent environmental problem to be solved.
[0003] The chemical composition of fly ash is mainly SiO2, Al2O3, Fe2O3 and CaO, which has natural compatibility with soil mineral components, and fly ash itself has a certain porous structure and specific surface area, and theoretically has adsorption potential for heavy metal ions. However, the glass structure of original fly ash is dense, the specific surface area is limited, and the number of surface active functional groups is small, which leads to low adsorption capacity of heavy metals and unstable passivation effect, and it is difficult to meet the actual needs of soil heavy metal pollution remediation, which limits its large-scale application in this field.
[0004] Soil heavy metal pollution (especially lead and cadmium pollution) has become a global environmental problem, which seriously threatens the quality and safety of agricultural products and human health. Chemical passivation technology has become one of the current mainstream soil remediation technologies due to its low cost, simple operation, high remediation efficiency and suitability for large-area contaminated soil treatment. The core of this technology is to add a passivation agent to the contaminated soil to change the existence form of heavy metals in the soil through adsorption, complexation, precipitation and ion exchange, thereby reducing the bioavailability and environmental mobility of heavy metals. Therefore, developing new types of passivation materials with high efficiency, low cost, environmental friendliness and wide sources is the key to promoting the industrial application of chemical passivation technology.
[0005] Using fly ash to prepare environmental remediation materials can not only realize "waste treatment with waste", reduce the cost of soil remediation, but also open up a new path for high-value resource utilization of fly ash, and has significant environmental, economic and social benefits. However, the modification methods of fly ash in the prior art often have problems such as complex process, high cost, limited modification effect, and lack of systematic research on the remediation mechanism and long-term effect of modified fly ash in actual soil environment.
[0006] Therefore, the present application provides a modified fly ash environmental remediation material with simple process, low cost and remarkable remediation effect, and a preparation method and application thereof. SUMMARY
[0007] The present application aims at overcoming the deficiencies of the prior art, and provides a modified fly ash environmental remediation material, which has excellent adsorption and fixation performance for heavy metals Pb and Cd.
[0008] Another object of the present application is to provide a preparation method of the modified fly ash environmental remediation material, which is simple in process and low in cost.
[0009] Still another object of the present application is to provide an application of the modified fly ash environmental remediation material in heavy metal passivation of soil.
[0010] To achieve the above objects, the present application adopts the following technical solutions.
[0011] A modified fly ash environmental remediation material, which is obtained by physical modification or chemical modification treatment of original fly ash; the modification treatment is to destroy the vitreous structure of the fly ash, increase its specific surface area, and increase the number of surface active functional groups, including hydroxyl groups.
[0012] Further, the chemical modification is a process of soaking, stirring, washing and drying the original fly ash with an acid solution or an alkali solution; wherein:
[0013] The acid solution is selected from one or more of hydrochloric acid, sulfuric acid and nitric acid, and has a concentration of 0.5-2 mol / L;
[0014] The alkali solution is selected from one or more of sodium hydroxide solution and potassium hydroxide solution, and has a concentration of 0.5-2 mol / L.
[0015] Further, the modified fly ash has a saturated adsorption capacity of Pb 2 + of not less than 15 mg / g, and a saturated adsorption capacity of Cd 2 + of not less than 5 mg / g, and the adsorption capacity is improved compared with that of the unmodified original fly ash.
[0016] A method for preparing a modified fly ash environmental remediation material, comprising the following steps:
[0017] a) raw material pretreatment: drying the original fly ash at 60-105 DEG C for 4-12 hours, grinding and then passing through an 80-100 mesh sieve to obtain pretreated fly ash;
[0018] b) modification reaction: mixing the pretreated fly ash with a modifier solution at a mass / volume ratio of 1:3-1:10 (g / mL), stirring at a speed of 200-400 r / min at 40-80 DEG C for 1-4 hours; the modifier solution is the acid solution or the alkali solution according to claim 2;
[0019] c) Solid-liquid separation and washing: After the reaction is complete, the solid and liquid are separated, the solid product is collected, and washed with deionized water until the pH of the washing solution is 6.5-7.5;
[0020] d) Drying and finished product: The washed solid product is dried at 60-105℃ for 8-24 hours, ground and passed through a 100-200 mesh sieve to obtain modified fly ash environmental remediation material.
[0021] Application of a modified fly ash environmental remediation material in passivating heavy metals in soil, reducing the bioavailability of heavy metals in soil, or remediating heavy metal-contaminated soil.
[0022] Furthermore, the heavy metals include at least lead (Pb) and cadmium (Cd).
[0023] Furthermore, the application method is as follows: the modified fly ash is mixed evenly with the contaminated soil at 1% to 5% of the dry weight of the contaminated soil, the soil moisture content is adjusted to 60% to 80% of the field capacity, and the soil is cured for 20 to 40 days; the application can increase the soil pH value by 0.5 to 2.0 units, promote the conversion of heavy metals from the ion exchange state to the residual state, and the conversion efficiency is not less than 40%.
[0024] The beneficial effects of this invention are as follows:
[0025] 1. Wide range of raw material sources and low cost: Using fly ash, a major industrial solid waste, as the core raw material, it not only solves the environmental problems caused by fly ash accumulation and realizes the high-value-added resource utilization of solid waste, but also significantly reduces the production cost of environmental remediation materials, which is in line with the green development concept of "treating waste with waste".
[0026] 2. Simple and efficient modification process: The physical or chemical modification method has fewer process steps, is easy to operate, has mild reaction conditions, low energy consumption, does not require complicated equipment, and is easy to realize large-scale industrial production;
[0027] 3. Excellent and stable repair performance: The modified fly ash exhibits a disrupted vitreous structure, significantly increased specific surface area, and a substantial increase in the number of surface-active functional groups, thus enhancing its ability to repair Pb. 2 + and Cd 2 The adsorption and fixation capacity of + is significantly improved; its remediation mechanism is clear. Through multiple mechanisms such as increasing soil pH, specific adsorption, complexation and co-precipitation, it transforms highly active heavy metals in the soil into low-activity and stable residual states, fundamentally reducing the migration and bioavailability of heavy metals, and the remediation effect is long-lasting and stable.
[0028] 4. Highly environmentally friendly: The chemical composition of modified fly ash is similar to that of soil minerals, so it will not damage the physical and chemical properties of the soil or introduce new pollutants. At the same time, it can replenish the soil with beneficial elements such as available silicon, improve soil fertility, and achieve the dual effect of pollution remediation and soil improvement. Attached Figure Description
[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0030] Figure 1 To investigate the solidification mechanism of heavy metal Pb in modified fly ash;
[0031] Figure 2 To investigate the solidification mechanism of heavy metal Cu in modified fly ash;
[0032] Figure 3 To investigate the solidification mechanism of heavy metal Cd in modified fly ash;
[0033] Figure 4 XRD analysis diagrams of fly ash before and after modification;
[0034] Figure 5 The images show the FTIR analysis results of fly ash before and after modification.
[0035] Figure 6 This is a diagram showing the changes in the microstructure of fly ash before modification.
[0036] Figure 7 This is a diagram showing the changes in the microstructure of modified fly ash.
[0037] Figure 8 The diagram shows the kinetic adsorption of Pb by fly ash before and after modification.
[0038] Figure 9 The diagram shows the kinetic adsorption of Cd by fly ash before and after modification.
[0039] Figure 10 This is a diagram showing the speciation of heavy metal Pb.
[0040] Figure 11 This is a diagram showing the morphological classification of the heavy metal Cu.
[0041] Figure 12 This is a diagram showing the morphological changes of the heavy metal Cd.
[0042] Figure 13 The diagram shows the morphological changes of four metals before and after stabilization. Detailed Implementation
[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0044] A modified fly ash environmental remediation material is obtained by physical or chemical modification of raw fly ash. The core of the modification process is to destroy the dense glassy structure of fly ash, increase its specific surface area, and increase the number of surface-active functional groups (such as hydroxyl and carboxyl groups), thereby significantly improving its adsorption and fixation capacity for heavy metal ions.
[0045] Chemical modification is a process of soaking, stirring, washing and drying the original fly ash with an acid solution or an alkaline solution; wherein the acid solution is selected from one or more mixed solutions of hydrochloric acid, sulfuric acid and nitric acid, with a concentration of 0.5 to 2 mol / L; the alkaline solution is selected from one or more mixed solutions of sodium hydroxide solution and potassium hydroxide solution, with a concentration of 0.5 to 2 mol / L.
[0046] Modified fly ash for heavy metal Pb 2 + and Cd 2 The saturated adsorption capacities of + are no less than 15 mg / g and 5 mg / g, respectively, which is more than 50% higher than the adsorption capacity of unmodified original fly ash.
[0047] The preparation method of the above-mentioned modified fly ash environmental remediation material includes the following steps:
[0048] 1. Raw material pretreatment: Place the raw fly ash in an oven at 60-105℃ and dry for 4-12 hours to remove moisture, then grind it through an 80-100 mesh sieve to obtain pretreated fly ash for later use;
[0049] 2. Modification reaction: The pretreated fly ash and the modifier solution are mixed at a mass-to-volume ratio of 1:3 to 1:10 (g / mL), placed in a constant temperature stirring device, and stirred continuously at 200 to 400 r / min for 1 to 4 hours at 40 to 80℃; the modifier solution is the above-mentioned acid solution or alkaline solution.
[0050] 3. Solid-liquid separation and washing: After the reaction is completed, solid-liquid separation is performed by vacuum filtration or centrifugation to collect the solid product; the solid product is repeatedly washed with deionized water until the washing liquid is neutral (pH = 6.5-7.5);
[0051] 4. Drying and finished product: Place the washed solid product in an oven at 60-105℃ and dry for 8-24 hours. After taking it out, grind it through a 100-200 mesh sieve to obtain modified fly ash environmental remediation material. Store it in a sealed, light-proof container for later use.
[0052] Applications of the modified fly ash environmental remediation materials: Modified fly ash environmental remediation materials are used to passivate heavy metals in soil, reduce the bioavailability of heavy metals in soil, or remediate soil contaminated with heavy metals; among which, heavy metals include at least lead (Pb) and cadmium (Cd).
[0053] The specific application method is as follows: the modified fly ash environmental remediation material is mixed evenly with the contaminated soil at a ratio of 1% to 5% of the dry weight of the contaminated soil, the soil moisture content is adjusted to 60% to 80% of the field water holding capacity, and the soil is cured for 20 to 40 days to achieve the passivation and remediation of heavy metals in the soil.
[0054] After modified fly ash environmental remediation materials are applied to the soil, the soil pH value can be increased by 0.5 to 2.0 units, and the conversion of ion-exchangeable lead and cadmium in the soil into stable residual states can be promoted with a conversion efficiency of not less than 40%. The bioavailability of heavy metals in the soil is reduced by more than 30%.
[0055] Example 1: Preparation of Alkali-Modified Fly Ash Environmental Remediation Materials
[0056] 1. Raw material pretreatment: Take 100g of raw fly ash, dry it in an oven at 105℃ for 12 hours to remove moisture, grind it with a high-speed pulverizer, and pass it through a 100-mesh sieve to obtain pretreated fly ash for later use.
[0057] 2. Modification reaction: Prepare 500 mL of 1 mol / L NaOH solution, add the pretreated fly ash and NaOH solution to the reaction vessel, place it on a constant temperature magnetic stirrer, and stir continuously at 300 r / min for 2 hours at 60℃.
[0058] 3. Solid-liquid separation and washing: After the reaction is completed, a vacuum filtration device is used to separate the solid and liquid, and the solid filter cake is collected. The solid filter cake is repeatedly washed with deionized water, and the pH value of the filtrate is measured after each washing until the pH value of the filtrate is about 7.0.
[0059] 4. Drying and finished product: The washed solid filter cake is placed in an oven at 105℃ and dried for 12 hours. After being taken out, it is ground and passed through a 100-mesh sieve to obtain alkali-modified fly ash environmental remediation material. It is then sealed and stored in a light-proof container for later use.
[0060] 5. Characterization of fly ash before and after modification:
[0061] The fly ash before and after modification was characterized by BET, SEM, and FTIR. The results showed that the modified fly ash particles were broken down and the specific surface area was significantly increased; the FTIR spectrum showed that the signals of functional groups such as -OH on the surface of the modified fly ash were enhanced.
[0062] Example 2: Preparation of acid-modified fly ash environmental remediation materials
[0063] 1. Raw material pretreatment: Same as the raw material pretreatment steps in Example 1;
[0064] 2. Modification reaction: Prepare 500 mL of 1 mol / L hydrochloric acid solution, add the pretreated fly ash and hydrochloric acid solution to the reaction vessel, place it on a constant temperature stirrer, and stir continuously at 250 r / min for 3 hours at 50℃.
[0065] 3. Solid-liquid separation and washing: After the reaction is completed, the solid product is collected by centrifugation (3000 r / min, 10 min) and washed repeatedly with deionized water until the washing solution is neutral.
[0066] 4. Drying and finished product: The washed solid product is placed in an 80℃ oven and dried for 16 hours. It is then ground through a 100-mesh sieve to obtain acid-modified fly ash environmental remediation material, which is then sealed and stored for later use.
[0067] Example 3: Adsorption performance test of modified fly ash for heavy metals in solution
[0068] A series of Pb(NO3)2 and Cd(NO3)2 solutions with different initial concentrations were prepared. Equal amounts of raw fly ash and modified fly ash prepared in Example 1 were weighed and placed in the above solutions for batch equilibrium adsorption experiments. The results are as follows: Figures 8-9 As shown, modified fly ash affects Pb 2+ and Cd 2+ The adsorption capacity is much higher than that of the original fly ash, and its adsorption process is more in line with the Langmuir model, indicating that it is mainly monolayer chemical adsorption.
[0069] Example 4: Application of modified fly ash in the remediation of Pb and Cd co-contaminated soil
[0070] 1. Test soil: Pb and Cd contaminated farmland soil was collected from the vicinity of a mining area. The soil pH was 5.2, the total Pb content was 850 mg / kg, and the total Cd content was 15.6 mg / kg. Among them, ion-exchangeable Pb accounted for 35% and ion-exchangeable Cd accounted for 42%.
[0071] 2. Experimental Design: Three treatment groups were set up, with three replicates in each group. Each pot contained 2 kg of soil (dry weight).
[0072] Control group (CK): No repair agents added;
[0073] Treatment group 1: Add alkali-modified fly ash prepared in Example 1 at a rate of 2% of the dry weight of the soil;
[0074] Treatment group 2: Add alkali-modified fly ash prepared in Example 1 at a rate of 4% of the dry weight of the soil;
[0075] 3. Experimental procedure: After thoroughly mixing the remediation agent with the soil, the soil moisture content was adjusted to 70% of the field capacity. The soil was then placed in an artificial climate chamber and kept at a constant temperature of 25°C and 60% humidity for 30 days. During this period, water was replenished regularly to maintain the moisture content.
[0076] 4. Effect detection: After the cultivation was completed, soil samples were collected, the soil pH value was measured, and the speciation of Pb and Cd in the soil was analyzed by BCR continuous extraction method. At the same time, the leaching amount of heavy metals was determined by TCLP (Toxicity Characteristic Leaching Procedure).
[0077] Test results:
[0078] Soil pH: The soil pH in treatment group 1 increased to 6.8, and the soil pH in treatment group 2 increased to 7.5, both significantly higher than the control group.
[0079] Heavy metal speciation: In treatment group 1, the proportion of ion-exchangeable Pb decreased to 18% and the proportion of ion-exchangeable Cd decreased to 22%; in treatment group 2, the proportion of ion-exchangeable Pb decreased to 12% and the proportion of ion-exchangeable Cd decreased to 15%; the proportions of residual Pb and Cd in both treatment groups increased significantly.
[0080] Leaching amount: In treatment group 1, the TCLP leaching amount of Pb decreased by 45% compared with the control group, and the TCLP leaching amount of Cd decreased by 52%; in treatment group 2, the TCLP leaching amount of Pb decreased by 62%, and the TCLP leaching amount of Cd decreased by 68%.
[0081] In summary, the modified fly ash prepared by this invention can significantly increase the pH value of contaminated soil, promote the transformation of highly active ion-exchangeable Pb and Cd in the soil into stable residual states, effectively reduce the bioavailability and leaching risk of heavy metals, and achieve significant remediation effects.
[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A modified fly ash environmental remediation material, characterized by: The material is obtained by physical modification or chemical modification treatment of raw fly ash; The modification treatment is to destroy the vitreous structure of fly ash, increase its specific surface area, and increase the number of surface active functional groups, including hydroxyl groups.
2. The modified fly ash environmental remediation material of claim 1, wherein, The chemical modification is a process of soaking, stirring, washing and drying of raw fly ash with acid solution or alkali solution; wherein: The acid solution is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, with a concentration of 0.5-2 mol / L; The alkali solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, with a concentration of 0.5-2 mol / L.
3. The modified fly ash environmental remediation material according to claim 1 or 2, characterized in that, The modified fly ash has a saturated adsorption capacity of not less than 15 mg / g for Pb 2+ and a saturated adsorption capacity of not less than 5 mg / g for Cd 2+ , and the adsorption capacity is improved compared with that of the unmodified original fly ash.
4. A method of preparing the modified fly ash environmental remediation material according to claim 1 or 2, characterized by, The method comprises the following steps: a) raw material pretreatment: dry the raw fly ash at 60-105℃ for 4-12 hours, grind and pass through an 80-100 mesh sieve to obtain pretreated fly ash; b) modification reaction: mix the pretreated fly ash with a modifier solution at a mass to volume ratio of 1:3-1:10 (g / mL), stir at a speed of 200-400 r / min at 40-80℃ for 1-4 hours; the modifier solution is the acid solution or alkali solution of claim 2; c) solid-liquid separation and washing: after the reaction is completed, separate the solid and liquid, collect the solid product, and wash with deionized water until the pH of the washing liquid is 6.5-7.5; d) drying and finished product: dry the washed solid product at 60-105℃ for 8-24 hours, grind and pass through a 100-200 mesh sieve to obtain the modified fly ash environmental remediation material.
5. Use of the modified fly ash environmental remediation material of any one of claims 1-3 in passivating soil heavy metals, reducing the bioavailability of heavy metals in soil, or remediating heavy metal contaminated soil.
6. Use according to claim 5, characterized in that, The heavy metals include at least lead Pb and cadmium Cd.
7. Use according to claim 5 or 6, characterized in that, The application mode is: mix the modified fly ash with the contaminated soil at 1%-5% of the dry weight of the contaminated soil, adjust the soil moisture content to 60%-80% of the field water holding capacity, and cure for 20-40 days; the application can increase the soil pH value by 0.5-2.0 units, promote the conversion of heavy metals from ion exchange state to residual state, and the conversion efficiency is not less than 40%.
Citation Information
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