A method and system for staged deep detoxification of waste incineration fly ash
By using a stepwise water washing method with EDTA and acetic acid solutions, deep and efficient removal of heavy metals in different chemical forms from waste incineration fly ash was achieved, solving the problem of stable heavy metal residues in existing technologies and reducing reagent costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QINGDAO UNIV OF TECH
- Filing Date
- 2025-12-10
- Publication Date
- 2026-07-21
AI Technical Summary
Existing water washing technology is not thorough in removing heavy metals from fly ash from waste incineration, resulting in residual heavy metals being converted into a stable form, which makes it difficult to meet the requirements for harmlessness. In addition, it consumes a lot of reagents and is costly.
After primary water washing of fly ash with EDTA solution, BCR chemical speciation analysis determined that the residual heavy metals were mainly in the weak acid extractable state. Then, secondary water washing with acetic acid solution was performed to achieve targeted removal.
It significantly improves the removal rate of heavy metals such as Pb, Zn, Cu and Cd, reduces leaching toxicity, meets the standards for safe disposal and resource utilization, and reduces reagent costs.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of hazardous solid waste treatment technology, and relates to a method and system for cascade deep detoxification of fly ash from waste incineration. Background Technology
[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.
[0003] Waste incineration fly ash is typically rich in high concentrations of potentially toxic heavy metals (such as Pb, Zn, Cu, and Cr), posing a significant risk of leaching and migration, and is explicitly classified as hazardous waste. Existing water washing technologies generally suffer from incomplete removal, high reagent consumption, and high costs. Single water washing methods have limited efficiency in removing heavy metals and are insufficient to meet the requirements for harmless treatment.
[0004] While washing with added chemicals (such as inorganic acids like hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; organic acids like citric acid, oxalic acid, and acetic acid; salts like ammonium chloride and sodium bicarbonate; and chelating agents like dithiocarbamate and thiourea) can significantly improve the initial removal rate of various heavy metals, a certain amount of heavy metals generally remains in the fly ash residue after a single wash. Currently, this problem is usually attributed to the residual heavy metals transforming into more stable chemical forms, leading to a tendency to use stronger or larger doses of the same chemicals for repeated washing. However, this method not only easily leads to excessive chemical dosage but also results in poor removal of heavy metals. Therefore, developing a new, deep, efficient, and cost-effective targeted detoxification method has become a key technical challenge urgently needing to be solved in this field. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for deep detoxification of fly ash from waste incineration. The method provided by this invention achieves deep and efficient removal of heavy metals from fly ash, and the final product meets the standards for safe disposal or resource utilization.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows: Firstly, a method for staged deep detoxification of fly ash from waste incineration includes the following steps: The fly ash is pretreated by natural carbonation to stabilize its pH value to approximately neutral, thus obtaining pretreated fly ash. Pretreated fly ash was washed with EDTA solution for the first stage, and the solid-liquid separation was performed to obtain the first stage washed residue. The residual heavy metals in the first stage washed residue were mainly distributed in the weak acid extractable state. Acetic acid solution was used to perform secondary washing on the primary water washing residue.
[0007] Based on the problems raised in the background technology, the present invention uses the BCR method to analyze the chemical speciation of heavy metals. The study shows that when most current reagents are used to wash pretreated fly ash, the residual heavy metals do not remain in a single stable chemical form, but rather exist in multiple chemical forms. For further removal of residual heavy metals in multiple chemical forms, it is difficult to achieve deep removal using a single reagent. The washing process with different reagents and the degree of washing will affect the distribution of chemical speciation. Therefore, it is extremely difficult to formulate composite reagents for further washing of heavy metals in different chemical forms, and such methods are not universally applicable.
[0008] Furthermore, this invention found that while primary washing of raw fly ash with EDTA solution has a certain removal effect on various heavy metals such as Pb, Zn, Cu, and Cd, the leaching concentration of heavy metals such as Pb in the primary washing residue still exceeds the limits specified in the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial)" (HJ 1134-2020), indicating that EDTA washing alone cannot achieve complete detoxification of fly ash. To improve the detoxification effect, this invention attempted natural carbonation pretreatment of fly ash, but found that after pretreatment, the leaching of Pb, Zn, Cu, and Cd in the residue was even more excessive after EDTA washing under the same conditions. This phenomenon indicates that conventionally combining existing pretreatment and washing technologies cannot solve the problem of deep detoxification and may even introduce new environmental risks.
[0009] This invention utilizes EDTA solution to analyze the chemical speciation of heavy metals in the primary washed residue of naturally carbonated pretreated fly ash. The analysis revealed that residual heavy metals (such as Pb, Zn, Cu, and Cd) in this residue do not exist in a stable residual state, but are highly enriched in the least stable weakly acid-extractable state. This key finding indicates that residual heavy metals theoretically still pose a high risk of environmental migration, but also means that they can be effectively removed by mild acidic reagents. Based on this finding, this invention further designed a secondary targeted washing step. Since the extractant corresponding to the weakly acid-extractable state is acetic acid solution, this invention uses acetic acid solution for the secondary washing of the primary washed residue. Experimental results confirm that this secondary washing can efficiently and accurately remove the weakly acid-extractable heavy metals enriched in the residue. After this treatment, the total amount and leaching concentration of various heavy metals in the obtained fly ash product are significantly reduced, consistently below the limits required by HJ 1134-2020, successfully achieving the goal of deep detoxification and harmlessness of waste incineration fly ash.
[0010] Secondly, a fly ash washing residue is obtained by the waste incineration fly ash cascade deep detoxification method described in the first aspect of the present invention.
[0011] Thirdly, an application of the fly ash washing residue described in the second aspect of the present invention in the field of building materials.
[0012] Fourthly, a cascaded deep detoxification system for waste incineration fly ash, used in the cascaded deep detoxification method for waste incineration fly ash described in the first aspect of this invention, comprising: A pretreatment device is used to pretreat fly ash by natural carbonation. A primary water washing unit is used to mix pretreated fly ash from the pretreatment unit with EDTA solution and then wash it with water. EDTA solution source, used to supply EDTA solution to the primary water washing unit; The first solid-liquid separation device is used to separate the solid and liquid components from the material from the primary washing device; The BCR chemical speciation analyzer is used to detect the heavy metal chemical speciation of the primary water washing residue from the first solid-liquid separation unit. A secondary water washing device is used to mix the primary water washing residue from the first solid-liquid separation device with an acetic acid solution and then perform agitation and water washing. Acetic acid solution source, used to provide acetic acid solution to the secondary water washing unit.
[0013] The second solid-liquid separation device is used to separate the solid and liquid components from the material from the secondary washing device.
[0014] The beneficial effects of this invention are as follows: (1) This invention overcomes the limitations of a single washing agent in removing heavy metals of various forms by using a step-by-step process of “EDTA water washing + acetic acid water washing”, thereby achieving deep and thorough removal of heavy metals from fly ash.
[0015] (2) Compared with EDTA water washing alone, the present invention significantly improves the removal rate of heavy metals such as Pb, Zn, Cu and Cd, and significantly reduces the total amount of heavy metals and leaching toxicity in the final product, meeting the HJ1134-2020 standard, laying the foundation for its safe resource utilization.
[0016] (3) This invention uses BCR chemical speciation analysis as the key basis for reagent selection. Based on the specific occurrence form of heavy metals in the residue after primary water washing (mainly weak acid extraction form), acetic acid solution is accurately selected as the secondary water washing agent, realizing the transformation from "conventional treatment" to "targeted removal", and improving the targeting and removal efficiency of the agent.
[0017] (4) In the deep washing stage, the present invention uses inexpensive, readily available and environmentally friendly acetic acid, which effectively reduces the overall reagent cost while ensuring efficient removal of heavy metals extracted by weak acid, and avoids the problem of fly ash matrix damage that may be caused by the use of strong acid. Attached Figure Description
[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0019] Figure 1 This is a flowchart of the waste incineration fly ash cascade deep detoxification method in an embodiment of the present invention. Detailed Implementation
[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0022] Given that single water washing technology is difficult to achieve deep removal of heavy metals, and existing enhanced water washing processes generally lack specificity for the occurrence forms of residual heavy metals, thus restricting the efficiency and economy of deep detoxification of fly ash, this invention proposes a method and system for tiered deep detoxification of fly ash from waste incineration.
[0023] A typical embodiment of the present invention provides a method for cascaded deep detoxification of fly ash from waste incineration, comprising the following steps: The fly ash is pretreated by natural carbonation to stabilize its pH value to approximately neutral, thus obtaining pretreated fly ash. Pretreated fly ash was washed with EDTA solution for the first stage, and the solid-liquid separation was performed to obtain the first stage washed residue. The residual heavy metals in the first stage washed residue were mainly distributed in the weak acid extractable state. Acetic acid solution was used to perform secondary washing on the primary water washing residue.
[0024] The term "approximately neutral" as used in this invention refers to a pH value of 6.8 to 7.2.
[0025] In some embodiments, during the primary water washing process, the liquid-to-solid ratio of EDTA solution to pretreated fly ash is 5–20 mL / g, and the concentration of EDTA solution is 0.5–8 g / L. Under these conditions, residual heavy metals in the primary water washing residue are mainly distributed in a weakly acidic extractable state. Specifically, the liquid-to-solid ratio of EDTA solution to pretreated fly ash is 8–12 mL / g, and the concentration of EDTA solution is 1–6 g / L.
[0026] In some embodiments, the primary water washing time is 10–80 min. Under these conditions, the residual heavy metals in the primary water washing residue are mainly distributed in the weakly acid-extractable state. Specifically, the primary water washing time is 20–60 min.
[0027] By controlling the liquid-solid ratio of EDTA solution to pretreated fly ash, the concentration of EDTA solution, and the washing time, it is beneficial to achieve efficient and synergistic removal of multiple heavy metals.
[0028] In some embodiments, during the secondary washing process, the liquid-to-solid ratio of the acetic acid solution to the primary washing residue is 5-20 mL / g, and the concentration of the acetic acid solution is 0.01-0.10 mol / L. Specifically, the liquid-to-solid ratio is 8-12 mL / g, and the concentration of the acetic acid solution is 0.02-0.08 mol / L.
[0029] In some embodiments, the secondary water wash time is 5 to 60 minutes. Specifically, the secondary water wash time is 10 to 50 minutes.
[0030] Studies have shown that by controlling the liquid-solid ratio of acetic acid solution to primary water washing residue, the concentration of acetic acid solution, and the water washing time, the acetic acid solution can be used to target and remove heavy metals enriched in the weak acid extraction state.
[0031] Another embodiment of the present invention provides a fly ash washing residue, which is obtained by the above-mentioned waste incineration fly ash cascade deep detoxification method.
[0032] A third embodiment of the present invention provides an application of the above-mentioned fly ash washing residue in the field of building materials.
[0033] A fourth embodiment of the present invention provides a cascaded deep detoxification system for waste incineration fly ash, used to implement the above-mentioned cascaded deep detoxification method for waste incineration fly ash, comprising: A pretreatment device is used to pretreat fly ash by natural carbonation. The primary water washing device is used to mix the pretreated fly ash from the pretreatment device with EDTA solution and perform agitation and water washing. EDTA solution source, used to supply EDTA solution to the primary water washing unit; The first solid-liquid separation device is used to separate the solid and liquid components from the material from the primary washing device; The BCR chemical speciation analyzer is used to detect the heavy metal chemical speciation of the primary water washing residue from the first solid-liquid separation unit. A secondary water washing device is used to mix the primary water washing residue from the first solid-liquid separation device with an acetic acid solution and then perform agitation and water washing. Acetic acid solution source, used to provide acetic acid solution to the secondary water washing unit.
[0034] The second solid-liquid separation device is used to separate the solid and liquid components from the material from the secondary washing device.
[0035] The solid-liquid separation device described in this invention can be a filter, filter press, centrifuge, etc.
[0036] The EDTA solution source can be an EDTA solution storage tank.
[0037] The acetic acid solution source can be an acetic acid solution storage tank.
[0038] The pretreatment device, primary water washing device, and secondary water washing device described in this invention can be a treatment tank, through which EDTA solution, acetic acid solution, etc., can be introduced as needed.
[0039] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.
[0040] The chemical composition of the fly ash used in the following examples is shown in Table 1.
[0041] Table 1 Chemical composition of raw fly ash
[0042] Example 1: A method for cascaded deep detoxification of fly ash from waste incineration, such as Figure 1 As shown, the steps are as follows: (1) The original fly ash was exposed to air for natural carbonation. When the pH of the fly ash stabilized at 7, pretreated fly ash was obtained and then dried.
[0043] (2) Weigh 10 g of pretreated fly ash and mix it with 2 g / L EDTA solution at a liquid-solid ratio of 10 mL / g. Place the mixture on a magnetic stirrer and stir at 400 r / min for 20 min at room temperature.
[0044] (3) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and primary water washing residue and primary water washing liquid are obtained. The primary water washing residue is dried and ground into powder for subsequent analysis and testing.
[0045] (4) The leachate was prepared according to the method of HJ 557-2010 and the leaching concentration of heavy metals was determined. It was found that the leaching concentrations of Pb, Zn, Cu and Cd exceeded the limits of HJ 1134-2020. The chemical speciation analysis of the obtained primary water washing residue by BCR was performed and it was found that more than 55% of Pb, more than 35% of Zn, more than 45% of Cu and more than 70% of Cd were present in the weak acid extractable state.
[0046] (5) Mix the above-mentioned primary water washing residue with 0.06 mol / L acetic acid solution at a liquid-solid ratio of 10 mL / g, place it on a magnetic stirrer, and stir at 400 r / min for 30 min at room temperature.
[0047] (6) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and secondary water washing residue and secondary water washing liquid are obtained.
[0048] (7) The heavy metal content of the secondary washing residue was determined by ICP-OES, and the removal rates of Pb, Zn, Cu, and Cd were calculated to be 82.5%, 66.8%, 61.7%, and 85.6%, respectively. The leachate was prepared according to the method of HJ 557-2010, and the leaching concentration of heavy metals was determined. It was found that the leaching concentrations of Pb, Zn, Cu, and Cd were all lower than the limits required by HJ 1134-2020. BCR chemical speciation analysis of the secondary washing residue showed that the proportion of weakly acid-extractable forms of each heavy metal had significantly decreased (e.g., the proportion of weakly acid-extractable forms of Cd decreased to 5%). Example 2 A method for cascaded deep detoxification of fly ash from waste incineration, such as Figure 1 As shown, the steps are as follows: (1) The original fly ash was exposed to air for natural carbonation. When the pH of the fly ash stabilized at 7, pretreated fly ash was obtained and then dried.
[0049] (2) Weigh 10 g of pretreated fly ash and mix it with 5 g / L EDTA solution at a liquid-solid ratio of 12 mL / g. Place the mixture on a magnetic stirrer and stir at 400 r / min for 30 min at room temperature.
[0050] (3) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and primary water washing residue and primary water washing liquid are obtained. The primary water washing residue is dried and ground into powder for subsequent analysis and testing.
[0051] (4) The leachate was prepared according to the method of HJ 557-2010 and the leaching concentration of heavy metals was determined. It was found that the leaching concentrations of Pb, Zn, Cu and Cd exceeded the limits of HJ 1134-2020. The chemical speciation analysis of the obtained primary water washing residue by BCR was performed and it was found that more than 52% of Pb, more than 32% of Zn, more than 42% of Cu and more than 65% of Cd were present in the weak acid extractable state.
[0052] (5) Mix the above-mentioned primary water washing residue with 0.04 mol / L acetic acid solution at a liquid-solid ratio of 10 mL / g, place it on a magnetic stirrer, and stir at 400 r / min for 20 min at room temperature.
[0053] (6) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and secondary water washing residue and secondary water washing liquid are obtained.
[0054] (7) The heavy metal content of the secondary washing residue was determined by ICP-OES, and the removal rates of Pb, Zn, Cu, and Cd were calculated to be 77.3%, 62.1%, 56.6%, and 79.2%, respectively. The leachate was prepared according to the method of HJ 557-2010, and the leaching concentration of heavy metals was determined. It was found that the leaching concentrations of Pb, Zn, Cu, and Cd were all lower than the limits required by HJ 1134-2020. BCR chemical speciation analysis of the secondary washing residue showed that the proportion of weakly acid-extractable forms of each heavy metal had significantly decreased (e.g., the proportion of weakly acid-extractable forms of Cd decreased to 7%). Example 3 A method for cascaded deep detoxification of fly ash from waste incineration, such as Figure 1 As shown, the steps are as follows: (1) The original fly ash was exposed to air for natural carbonation. When the pH of the fly ash stabilized at 7, pretreated fly ash was obtained and then dried.
[0055] (2) Weigh 10 g of pretreated fly ash and mix it with 2 g / L EDTA solution at a liquid-solid ratio of 8 mL / g. Place the mixture on a magnetic stirrer and stir at 400 r / min for 20 min at room temperature.
[0056] (3) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and primary water washing residue and primary water washing liquid are obtained. The primary water washing residue is dried and ground into powder for subsequent analysis and testing.
[0057] (4) The leachate was prepared according to the method of HJ 557-2010 and the leaching concentration of heavy metals was determined. It was found that the leaching concentrations of Pb, Zn, Cu and Cd exceeded the limits of HJ 1134-2020. The chemical speciation analysis of the obtained primary water washing residue by BCR was performed and it was found that more than 50% of Pb, more than 32% of Zn, more than 40% of Cu and more than 62% of Cd were present in the weak acid extractable state.
[0058] (5) Mix the above-mentioned primary water washing residue with 0.02 mol / L acetic acid solution at a liquid-solid ratio of 10 mL / g, place it on a magnetic stirrer, and stir at 400 r / min for 10 min at room temperature.
[0059] (6) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and secondary water washing residue and secondary water washing liquid are obtained.
[0060] (7) The heavy metal content of the secondary washing residue was determined by ICP-OES, and the removal rates of Pb, Zn, Cu, and Cd were calculated to be 75.8%, 63.5%, 54.5%, and 77.1%, respectively. The leachate was prepared according to the method of HJ 557-2010, and the leaching concentration of heavy metals was determined. It was found that the leaching concentrations of Pb, Zn, Cu, and Cd were all lower than the limits required by HJ 1134-2020. BCR chemical speciation analysis of the secondary washing residue showed that the proportion of weakly acid-extractable forms of each heavy metal had significantly decreased (e.g., the proportion of weakly acid-extractable forms of Cd decreased to 11%). Comparative Example 1 A method for detoxifying fly ash from waste incineration, comprising the following steps: (1) The original fly ash was exposed to air for natural carbonation. When the pH of the fly ash stabilized at 7, pretreated fly ash was obtained and then dried.
[0061] (2) Weigh 10 g of pretreated fly ash and mix it with 4 g / L EDTA solution at a liquid-solid ratio of 10 mL / g. Place the mixture on a magnetic stirrer and stir at 400 r / min for 30 min at room temperature.
[0062] (3) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and primary water washing residue and primary water washing liquid are obtained. The primary water washing residue is dried and ground into powder for subsequent analysis and testing.
[0063] (4) The heavy metal content of the primary washing residue was determined by ICP-OES, and the removal rates of Pb, Zn, Cu and Cd were calculated to be 65.3%, 46.2%, 32.2% and 61.4%, respectively. The leachate was prepared according to the method of HJ 557-2010 and the heavy metal leaching concentration was determined. It was found that the leaching concentrations of Pb, Zn, Cu and Cd exceeded the limits of HJ 1134-2020.
[0064] Comparative Example 2 A method for staged deep detoxification of fly ash from waste incineration includes the following steps: (1) The original fly ash was exposed to air for natural carbonation. When the pH of the fly ash stabilized at 7, pretreated fly ash was obtained and then dried.
[0065] (2) Weigh 10 g of pretreated fly ash and mix it with 2 g / L EDTA solution at a liquid-solid ratio of 10 mL / g. Place the mixture on a magnetic stirrer and stir at 400 r / min for 20 min at room temperature.
[0066] (3) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and primary water washing residue and primary water washing liquid are obtained. The primary water washing residue is dried and ground into powder for subsequent analysis and testing.
[0067] (4) The leachate was prepared according to the method of HJ 557-2010 and the leaching concentration of heavy metals was determined. It was found that the leaching concentration of heavy metals such as Pb exceeded the limit of HJ 1134-2020. The chemical speciation analysis of the obtained primary water washing residue by BCR was performed and it was found that more than 55% of Pb, more than 35% of Zn, more than 45% of Cu, and more than 70% of Cd were present in the weak acid extractable state.
[0068] (5) Mix the above-mentioned primary water washing residue with 2 g / L EDTA solution at a liquid-solid ratio of 10 mL / g, place it on a magnetic stirrer, and stir at 400 r / min for 30 min at room temperature.
[0069] (6) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and secondary water washing residue and secondary water washing liquid are obtained.
[0070] (7) The heavy metal content of the secondary washing residue was determined by ICP-OES, and the removal rates of Pb, Zn, Cu, and Cd were calculated to be 67.2%, 58.4%, 33.9%, and 63.8%, respectively. The leachate was prepared according to the method of HJ 557-2010, and the leaching concentration of heavy metals was determined. It was found that the leaching concentrations of Pb, Zn, Cu, and Cd still exceeded the limit requirements of HJ 1134-2020. BCR chemical speciation analysis of the secondary washing residue showed that the proportion of weakly acid-extractable heavy metals did not decrease significantly.
[0071] Comparative Example 3 A method for staged deep detoxification of fly ash from waste incineration includes the following steps: (1) The original fly ash was exposed to air for natural carbonation. When the pH of the fly ash stabilized at 7, pretreated fly ash was obtained and then dried.
[0072] (2) Weigh 10 g of pretreated fly ash and mix it with 4 g / L citric acid solution at a liquid-solid ratio of 10 mL / g. Place the mixture on a magnetic stirrer and stir at 400 r / min for 20 min at room temperature.
[0073] (3) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and primary water washing residue and primary water washing liquid are obtained. The primary water washing residue is dried and ground into powder for subsequent analysis and testing.
[0074] (4) The leachate was prepared according to the method of HJ 557-2010 and the leaching concentration of heavy metals was determined. It was found that the leaching concentration of heavy metals such as Pb exceeded the limit of HJ 1134-2020. The chemical speciation analysis of the obtained primary water washing residue by BCR was performed and it was found that only 5% of Pb, 12% of Zn, 16% of Cu, and 20% of Cd were present in the weak acid extractable state.
[0075] (5) Mix the above-mentioned primary water washing residue with 0.06 mol / L acetic acid solution at a liquid-solid ratio of 10 mL / g, place it on a magnetic stirrer, and stir at 400 r / min for 30 min at room temperature.
[0076] (6) After the reaction is completed, vacuum filtration is performed to separate the solid and liquid, and secondary water washing residue and secondary water washing liquid are obtained.
[0077] (7) The heavy metal content of the secondary washing residue was determined by ICP-OES, and the removal rates of Pb, Zn, Cu and Cd were calculated to be 32.1%, 25.7%, 32.7% and 54.8%, respectively. The leachate was prepared according to the method of HJ 557-2010 and the heavy metal leaching concentration was determined. It was found that the leaching concentrations of Pb, Zn, Cu and Cd still exceeded the limit requirements of HJ 1134-2020.
[0078] The data obtained from the tests conducted on Examples 1-3 and Comparative Examples 1-3 are shown in Table 2.
[0079] Table 2. Experimental data of Examples 1-3 and Comparative Examples 1-3
[0080] Through the above embodiments and comparative examples, it is demonstrated that the method of the present invention achieves deep and efficient removal of heavy metals, and the final product meets the standards for safe disposal or resource utilization.
[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for staged deep detoxification of fly ash from waste incineration, characterized in that, Includes the following steps: The fly ash is pretreated by natural carbonation to stabilize its pH value to approximately neutral, thus obtaining pretreated fly ash. Pretreated fly ash was subjected to primary water washing with EDTA solution, and primary water washing residue was obtained after solid-liquid separation. The residual heavy metals in the primary water washing residue were mainly distributed in the weak acid extractable state. The chemical speciation of BCR in the obtained primary water washing residue was analyzed. The residue from the primary water washing process is subjected to secondary water washing using an acetic acid solution. The liquid-to-solid ratio of the EDTA solution to the pretreated fly ash is 5-20 mL / g, and the concentration of the EDTA solution is 0.5-8 g / L. In the secondary water washing process, the liquid-to-solid ratio of the acetic acid solution to the primary water washing residue is 5~20 mL / g, and the concentration of the acetic acid solution is 0.01~0.10 mol / L.
2. The method for deep detoxification of fly ash from waste incineration as described in claim 1, characterized in that, During the primary water washing process, the liquid-to-solid ratio of EDTA solution to pretreated fly ash is 8-12 mL / g, and the concentration of EDTA solution is 1-6 g / L.
3. The method for deep detoxification of fly ash from waste incineration as described in claim 1, characterized in that, The first-stage water wash time is 10-80 minutes.
4. The method for deep detoxification of fly ash from waste incineration as described in claim 1, characterized in that, The liquid-to-solid ratio is 8-12 mL / g, and the concentration of the acetic acid solution is 0.02-0.08 mol / L.
5. The method for deep detoxification of fly ash from waste incineration as described in claim 1, characterized in that, The secondary water wash time is 5-60 minutes.
6. A fly ash washing residue, obtained by the waste incineration fly ash staged deep detoxification method according to any one of claims 1 to 5.
7. The application of the fly ash washing residue as described in claim 6 in the field of building materials.
8. A cascaded deep detoxification system for fly ash from waste incineration, characterized in that, The method for implementing the staged deep detoxification method for fly ash from waste incineration as described in any one of claims 1 to 5 includes: A pretreatment device is used to pretreat fly ash by natural carbonation. The primary water washing device is used to mix the pretreated fly ash from the pretreatment device with EDTA solution and perform agitation and water washing. EDTA solution source, used to supply EDTA solution to the primary water washing unit; The first solid-liquid separation device is used to separate the solid and liquid components from the material from the primary washing device; The BCR chemical speciation analyzer is used to detect the heavy metal chemical speciation of the primary water washing residue from the first solid-liquid separation unit. A secondary water washing device is used to mix the primary water washing residue from the first solid-liquid separation device with an acetic acid solution and then perform agitation and water washing. Acetic acid solution source, used to provide acetic acid solution to the secondary water washing unit; The second solid-liquid separation device is used to separate the solid and liquid components from the material from the secondary washing device.