Geopolymer / sludge extract-based high-salinity fly ash solidification agent and solidification method
Through the synergistic hydration reaction of geopolymer/sludge extract-based solidifier, a dense gel structure is formed, which solves the problem of easy salt precipitation in high-salt incineration fly ash during landfilling and achieves efficient and low-cost solidification effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGJIANG SURVEY PLANNING DESIGN & RES CO LTD
- Filing Date
- 2023-11-17
- Publication Date
- 2026-07-07
Smart Images
Figure CN117645423B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a geopolymer / sludge extract-based high-salt fly ash curing agent and curing method, belonging to the technical field of industrial waste resource utilization and hazardous waste curing. Background Technology
[0002] Incineration has become the dominant process for industrial solid waste treatment due to its ability to significantly reduce volume, render waste harmless, and recover resources. However, industrial waste has a complex composition, and most of it is high-salt waste. As a result, fly ash, the most important secondary byproduct of incineration, is enriched with large amounts of heavy metals and salts, making it a typical hazardous waste. It must be rendered harmless before it can be safely landfilled.
[0003] Solidification / stabilization technology is currently the most widely used fly ash treatment process due to its advantages such as simple process, low treatment cost, and high efficiency in treating heavy metals. Among them, silicate cement is the most commonly used solidification material. It can undergo a hydration reaction to form a solidified body with good mechanical properties. Through encapsulation, precipitation, and adsorption, it can solidify heavy metals within the solidified body, reducing the leaching of pollutants.
[0004] However, with increasingly stringent standards for hazardous waste landfill in my country, particularly the control of total water-soluble salt content, has become a critical issue for safe landfilling. Traditional cementitious solidifiers primarily target heavy metal solidification and cannot effectively encapsulate all salts, resulting in high total salt precipitation. Therefore, it is necessary to develop low-cost, high-efficiency solidifiers to address the practical needs of safe landfilling of high-salt incineration fly ash.
[0005] The main difficulty in solidifying total salt content lies in the rapid hydration process of ordinary silicate cement. The different formation rates of hydration products such as calcium silicate hydrate (CSH) and ettringite (AFT) result in a loose structure of the solidified body, making it easy for salts to leach out.
[0006] Geopolymer materials have advantages such as dense structure and controllable hydration reaction. When used in curing materials, they can quickly form a dense curing structure, effectively contain salt ions, and prevent them from leaching out in large quantities.
[0007] In addition, a large amount of residual sludge is generated during the sewage treatment process. The main direction of this invention is to comprehensively utilize geopolymer materials and domestic sewage sludge to achieve both effective solidification of total salt and waste utilization of geopolymer materials and domestic sewage sludge. Summary of the Invention
[0008] To address the problems existing in related high-salt fly ash solidification technologies, this invention provides a method for solidifying salt and heavy metals in fly ash using a geopolymer / sludge extract-based solidifier, enabling its safe landfill.
[0009] The strategy adopted in this invention is to utilize the synergistic hydration reaction between geopolymer waste and cement to form more cementitious hydration products, which promotes a more compact microstructure of the solidified body, fixes heavy metals, and reduces salt leaching.
[0010] In addition, a large amount of residual sludge is generated as a major byproduct during the treatment of domestic sewage. By extracting acidic polysaccharides (such as alginate and galacturonic acid) and other gel polymers from it as a solidification binder, the efficiency of adsorption / solidification of salt ions and heavy metal ions in the solidification process can be further improved, which can solve the solidification and stabilization problem of high-salt fly ash to a certain extent.
[0011] The technical solution adopted in this invention is:
[0012] A geopolymer / sludge extract-based high-salt fly ash solidifier comprises the following components by weight: 2-3 parts cement; 0.2-1 parts blast furnace slag; 0.2-0.5 parts fly ash; and 0.1-0.2 parts sludge extract, which can effectively solidify soluble salts in high-salt waste incineration fly ash.
[0013] The above-mentioned geopolymer / sludge extract-based high-salt fly ash solidifying agent, wherein the high-salt waste incineration fly ash contains Na + K + Ca 2+ Mg 2+ Cl - SO4 2- One or more of the inorganic salt ions, with a total salt content of not less than 20%.
[0014] The above-mentioned high-salt fly ash curing agent based on a geopolymer / sludge extract is made of PO 42.5 grade ordinary Portland cement.
[0015] The above-mentioned high-salt fly ash solidifying agent based on a geopolymer / sludge extract, wherein the sludge extract extraction steps are as follows: adding CO3 to domestic sewage sludge. 2- After shaking and centrifugation, solid and liquid are separated. The supernatant is discarded, and acid solution is added to adjust the pH. After standing, the gel-like solid precipitate is collected by centrifugation and freeze-dried to obtain the sludge extract.
[0016] The above-mentioned high-salt fly ash solidifying agent based on a geopolymer / sludge extract, wherein the CO3 2- Derived from one or both of sodium carbonate and potassium carbonate, CO3 2- The dosage is 5-20% of the dry weight of the sludge.
[0017] The above-mentioned geopolymer / sludge extract-based high-salt fly ash solidifying agent has a pH adjustment range of 1.8 to 2.4.
[0018] The above-mentioned geopolymer / sludge extract-based high-salt fly ash curing agent has a standing time of 30 min to 4 h.
[0019] The preparation method of the geopolymer / sludge extract-based high-salt fly ash solidifying agent described in any of the above claims.
[0020] S1: Add CO3 to sewage sludge 2- After shaking and centrifugation, solid and liquid separation was achieved. The supernatant was discarded, and acid solution was added to adjust the pH. After standing, the gel-like solid precipitate was collected by centrifugation at 8000 rpm to 12000 rpm and then freeze-dried to obtain the sludge extract.
[0021] S2: By weight, mix 2-3 parts of cement, 0.2-1 parts of blast furnace slag, 0.2-0.5 parts of fly ash, and 0.1-0.2 parts of sludge extract evenly and grind them into fine powder. This is the geopolymer / sludge extract-based high-salt fly ash curing agent.
[0022] The method for solidifying high-salinity waste incineration fly ash using the solidifying agent described in any of the above-mentioned methods includes the following steps:
[0023] S1: By weight, mix 2-3 parts cement, 0.2-1 parts blast furnace slag, 0.2-0.5 parts fly ash, and 0.1-0.2 parts sludge extract evenly, and grind into fine powder for later use;
[0024] S2: After adding the solidifying agent from step S1 to the high-salt waste incineration fly ash to be treated, add water and stir until uniform to obtain a mixture;
[0025] S3: Transfer the mixture to a mold for molding, and cure for 5-10 days to fully solidify and obtain the cured body.
[0026] In the above-mentioned method for curing high-salt waste incineration fly ash with a curing agent, the mass of water in step S2 is 20-55% of the total mass of the mixture of high-salt waste incineration fly ash and curing agent.
[0027] In the sludge extract preparation step, the gel-like solid precipitate is collected by centrifugation at 8000 rpm to 12000 rpm and then freeze-dried. Preferably, the centrifugation speed is 10000 rpm.
[0028] In the above-mentioned method for curing high-salt waste incineration fly ash with a curing agent, the salt content of the high-salt waste incineration fly ash to the mass ratio of the curing agent in step S2 is 1:0.2 to 0.5.
[0029] Among the above conditions, the preferred ratio of the total soluble salt content of high-salt waste incineration fly ash to the mass of the solidifying agent is 1:0.3. The selection principle is as follows: the solidifying agent undergoes a hydration reaction to form a cementitious structure that encapsulates the high-salt fly ash. If the relative proportion of the solidifying agent is too low, the solidification effect will be insignificant, and salt and heavy metals will easily precipitate. If the relative proportion of the solidifying agent is too high, excessive cement hydration will cause the alkalinity of the system to rise rapidly, resulting in the metadecomposition and precipitation of hydration products, which may promote the dissolution of salt ions in the system.
[0030] The beneficial effects of this invention are as follows: Compared with related technologies, this invention proposes a simple and low-cost method for preparing a solidifying agent for incineration fly ash. Firstly, based on the reaction mechanism of geopolymers, it fully utilizes geopolymer additives from industrial solid waste (fly ash and blast furnace slag) to modify the ash composition of the solidifying agent. By using materials to slow down the hydration rate of CSH, the gel structure continuously polymerizes to form a denser aluminosilicate (C-(A)-SH) structure, effectively improving the hydration process of silicate cement, forming more hydration products, improving the porosity of the solidified body, making the microstructure more compact, and effectively containing salt ions to prevent their excessive leaching. Furthermore, the specific gel-like structures in sludge extracts penetrate and effectively cover the pore surface, further improving the density of the solidified body. The above components can synergistically fix salt ions and heavy metals in fly ash, meeting safe landfill requirements. This is a novel environmentally friendly technology for the synergistic treatment of high-salinity incineration fly ash and industrial solid waste. This method comprehensively utilizes various industrial solid wastes, is low-cost, has high solidification efficiency, and has broad application prospects. Attached Figure Description
[0031] Figure 1 This is a graph showing the total amount of soluble salts after sample 1 has been cured.
[0032] Figure 2 This is a graph showing the total amount of soluble salts after sample 2 has been cured. Detailed Implementation
[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings.
[0034] Comparative Example 1
[0035] Sample 1 of fly ash from the incineration of the waste to be treated was taken. The leaching concentration of Pb ions in the fly ash was 16.08 mg / L, the leaching concentration of Zn ions was 357.8 mg / L, the leaching concentration of Cr ions was 30.43 mg / L, the total soluble salt content was 28.5%, and the remaining pollution indicators met the control limits of GB 18598-2019.
[0036] 100g of fly ash sample 1 was added to a 250mL open beaker, followed by 10g of conventional silicate cement (the amount of curing agent added was approximately 30% of the salt content of the fly ash) to obtain a mixed powder. Water was added at a solid-liquid mass ratio of 1:0.4, and the mixture was stirred evenly with a stirrer. The mixture was then transferred to a mold and compacted. After standing at room temperature for 2 days, a cured body was obtained. The leaching concentrations of Pb, Cr, and Zn and the total amount of soluble salts in the cured body were determined according to HJ 766, HJ687, HJ766 and NY / T 1121.16.
[0037] Comparative Example 2
[0038] Two samples of fly ash from the incineration of the waste to be treated were taken. The leaching concentration of Cd ions in the fly ash was 6.75 mg / L, the leaching concentration of Zn ions was 845.4 mg / L, the leaching concentration of Pb ions was 9.58 mg / L, and the total soluble salt content was 47.5%. The remaining pollution indicators met the control limits of GB 18598-2019.
[0039] 100g of fly ash sample 2 was added to a 250mL open beaker, followed by 15g of conventional silicate cement (the ratio of curing agent mass to fly ash salt content was approximately 30%) to obtain a mixed powder. Water was added at a solid-liquid mass ratio of 1:0.4, and the mixture was stirred evenly. The mixture was then transferred to a mold and compacted. After standing at room temperature for 2 days, a solidified body was obtained. The leaching concentrations of Cd, Zn, and Pb in the solidified body were determined using HJ 766, and the total soluble salt content in the solidified body was determined using NY / T 1121.16.
[0040] Comparative Example 3
[0041] The treatment process was the same as in Comparative Example 1, except that silicate cement was replaced with an equal amount of fly ash curing agent (without sludge extract) for curing. In this example, the curing agent components were 2 parts cement, 0.5 parts blast furnace slag, and 0.3 parts fly ash. The mixture was left to stand under the same conditions, and relevant indicators were measured.
[0042] Comparative Example 4
[0043] The treatment process was the same as in Comparative Example 2, except that silicate cement was replaced with an equal amount of fly ash curing agent (without sludge extract) for curing. In this example, the curing agent components were 2 parts cement, 0.5 parts blast furnace slag, and 0.3 parts fly ash. The mixture was left to stand under the same conditions, and relevant indicators were measured.
[0044] Comparative Example 5
[0045] The treatment process was the same as in Comparative Example 1, except that silicate cement was replaced with an equal amount of fly ash solidifying agent (total sludge) for solidification. In this example, the solidifying agent components were 2 parts cement, 0.5 parts blast furnace slag, 0.3 parts fly ash, and 0.2 parts total sludge. The mixture was allowed to stand under the same conditions, and relevant indicators were measured.
[0046] Comparative Example 6
[0047] The treatment process was the same as in Comparative Example 1, except that silicate cement was replaced with an equal amount of fly ash solidifying agent (total sludge) for solidification. In this example, the solidifying agent components were 2 parts cement, 0.5 parts blast furnace slag, 0.3 parts fly ash, and 0.2 parts total sludge. The mixture was allowed to stand under the same conditions, and relevant indicators were measured.
[0048] Example 1
[0049] The treatment process was the same as in Comparative Example 1, except that the silicate cement was replaced with an equal amount of high-salt fly ash curing agent for curing. In this example, the curing agent components were 2 parts cement, 0.5 parts blast furnace slag, 0.3 parts fly ash, and 0.2 parts sludge extract (the same applies below). The mixture was left to stand under the same conditions, and relevant indicators were measured.
[0050] Example 2
[0051] The treatment process was the same as that of Comparative Example 2, except that the silicate cement was replaced with an equal amount of high-salt fly ash curing agent for curing treatment, and the solidified materials were left to stand under the same conditions and the relevant indicators were measured.
[0052] Example 3: Scale-up Test
[0053] The treatment process was the same as in Example 1, except that 2 kg of fly ash sample 1 was taken, and 200 g of high-salt fly ash curing agent was added for curing treatment. The sample was then left to stand under the same conditions, and relevant indicators were measured. The results are as follows: Figure 1 As shown in Table 1.
[0054] Example 4: Scale-up Test
[0055] The treatment process was the same as in Example 2, except that 2 kg of fly ash sample 2 was taken, and 300 g of high-salt fly ash curing agent was added for curing treatment. The sample was then left to stand under the same conditions, and relevant indicators were measured. The results are as follows: Figure 2 As shown in Table 1.
[0056] Example 5
[0057] The treatment process is the same as in Example 1, except that, by weight, 3 parts of cement, 0.5 parts of blast furnace slag, 0.2 parts of fly ash, and 0.1 parts of sludge extract are added to a high-salt fly ash solidifying agent for solidification treatment. The ratio of the total soluble salt content of the high-salt waste incineration fly ash to the mass of the solidifying agent is 1:0.2.
[0058] Example 6
[0059] The treatment process is the same as in Example 2, except that, by weight, 3 parts of cement, 1 part of blast furnace slag, 0.2 parts of fly ash, and 0.1 parts of sludge extract are added to a high-salt fly ash solidifying agent for solidification treatment. The ratio of the total soluble salt content of the high-salt waste incineration fly ash to the mass of the solidifying agent is 1:0.4.
[0060] Example 7
[0061] The treatment process is the same as in Example 1, except that, by weight, 2.5 parts of cement, 0.3 parts of blast furnace slag, 0.5 parts of fly ash, and 0.15 parts of cement extract are added to a high-salt fly ash curing agent for curing treatment. The ratio of the total soluble salt content of the high-salt waste incineration fly ash to the mass of the curing agent is 1:0.5.
[0062] Example 8
[0063] The treatment process is the same as in Example 2, except that, by weight, 3 parts of cement, 0.2 parts of blast furnace slag, 0.2 parts of fly ash, and 0.1 parts of sludge extract are added to a high-salt fly ash solidifying agent for solidification treatment. The ratio of the total soluble salt content of the high-salt waste incineration fly ash to the mass of the solidifying agent is 1:0.2.
[0064] Table 1 shows the heavy metal leaching concentration results after curing in Comparative Examples 1-6 and Examples 1-4. The data in the table show that the concentration of Pb in fly ash sample 1 after curing with traditional silicate cement in Comparative Example 1 was 2.38 mg / L, and the concentration of Zn in fly ash sample 2 in Comparative Example 2 was 289.1 mg / L, both still exceeding the safe landfill threshold. In contrast, the heavy metal leaching concentration after curing with the fly ash curing agent provided by this invention was significantly reduced, both meeting the requirements for landfill entry according to the "Hazardous Waste Landfill Standard," and maintaining good curing effect even after scaling up the total curing volume.
[0065] Figure 1 and Figure 2The figures show the total soluble salt content of samples 1 and 2 after solidification. As can be seen from the figures, the total soluble salt content in Comparative Example 1 was 19.6%, and in Comparative Example 2 it was 34.8%, indicating that conventional silicate cement has a poor solidification effect on salt ions. In Comparative Examples 3 and 4, the total soluble salt content decreased to 12.8% and 21.9%, respectively, indicating that the addition of geopolymer materials can improve the solidification effect. Comparative Examples 5 and 6 show the salt solidification results with the addition of whole sludge instead of sludge extract, indicating that the addition of raw sludge does not significantly improve the salt solidification efficiency. In Example 1, the total soluble salt content was 8.7%, in Example 2 it was 9.4%, in Example 3 it was 9.1%, and in Example 4 it was 10.2%, all significantly lower than the corresponding comparative examples. This shows that the solidified body formed after treatment with the fly ash solidifier of this invention has a denser microstructure, effectively fixing heavy metal ions and soluble salts, meeting the safety landfill limits.
[0066] Table 1. Results of solidified body metal leaching concentration (mg / L)
[0067]
Claims
1. A geopolymer / sludge extract-based high-salt fly ash curing agent, characterized in that, The product comprises the following components by weight: 2-3 parts cement; 0.2-1 parts blast furnace slag; 0.2-0.5 parts fly ash; and 0.1-0.2 parts sludge extract, which can effectively solidify soluble salts in high-salinity waste incineration fly ash; the sludge extract is acidic; and the high-salinity waste incineration fly ash contains Na. + K + Ca 2+ Mg 2+ Cl - SO4 2- The sludge extract contains one or more inorganic salt ions, with a total salt content of not less than 20%; the extraction steps of the sludge extract are as follows: adding CO3 to the domestic sewage sludge. 2- After shaking and centrifugation, solid and liquid separation is achieved. The supernatant is discarded, and acid solution is added to adjust the pH. After standing, the gel-like solid precipitate is collected by centrifugation at 8000 rpm to 12000 rpm. After freeze-drying, the sludge extract is obtained. The cement mentioned is PO 42.5 grade ordinary Portland cement.
2. The geopolymer / sludge extract-based high-salt fly ash curing agent according to claim 1, characterized in that, The CO3 2- Derived from one or both of sodium carbonate and potassium carbonate, CO3 2- The dosage is 5-20% of the dry weight of the sludge.
3. The geopolymer / sludge extract-based high-salt fly ash curing agent according to claim 1, characterized in that, The pH adjustment range is 1.8~2.4, and the standing time is 30min~4h.
4. A method for preparing a geopolymer / sludge extract-based high-salt fly ash solidifying agent according to any one of claims 1 to 3, characterized in that, S1: Add CO3 to sewage sludge 2- After shaking and centrifugation, solid and liquid separation was achieved. The supernatant was discarded, and acid solution was added to adjust the pH. After standing, the gel-like solid precipitate was collected by centrifugation at 8000 rpm to 12000 rpm and then freeze-dried to obtain the sludge extract. S2: By weight, mix 2-3 parts of cement, 0.2-1 parts of blast furnace slag, 0.2-0.5 parts of fly ash, and 0.1-0.2 parts of sludge extract evenly and grind them into fine powder. This is the geopolymer / sludge extract-based high-salt fly ash curing agent.
5. The method for curing high-salinity waste incineration fly ash with a curing agent according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1: By weight, mix 2-3 parts of cement, 0.2-1 parts of blast furnace slag, 0.2-0.5 parts of fly ash, and 0.1-0.2 parts of sludge extract evenly, and grind into fine powder. This is the geopolymer / sludge extract-based high-salt fly ash curing agent. S2: After adding the solidifying agent from step S1 to the high-salt waste incineration fly ash to be treated, add water and stir until uniform to obtain a mixture; S3: Transfer the mixture to a mold and shape it. Allow it to cure for 5-10 days to fully solidify and obtain the cured body.
6. The method for curing high-salinity waste incineration fly ash with a curing agent according to claim 5, characterized in that, In step S2, the total amount of soluble salts in the high-salt waste incineration fly ash and the mass ratio of the solidifying agent are 1:0.2~0.
5.
7. The method for curing high-salinity waste incineration fly ash with a curing agent according to claim 5, characterized in that, In step S2, the mass of water is 20-55% of the total mass of the mixture of high-salinity waste incineration fly ash and solidifying agent.