All-solid-waste-based cementing material for inducing chlorine salt in waste incineration fly ash by using active magnesium oxide and preparation method of all-solid-waste-based cementing material

Abstract

The invention discloses an all-solid-waste-based cementing material for inducing chlorine salt in waste incineration fly ash by using active magnesium oxide and a preparation method of the all-solid-waste-based cementing material. According to the invention, active magnesium oxide is utilized to induce in-situ conversion of the chlorine salt in the waste incineration fly ash into the cementing material, so that the problems of unstable curing system and potential secondary environmental pollution caused by harmful impurity chlorine salt are effectively improved, and the reaction degree and strength development of the cementing system are promoted under the action of co-processing the copper-containing electroplating sludge; and meanwhile, it is guaranteed that the heavy metal leaching concentration of the system meets the GB / T 16889-2008 national safety landfill standard. The cementing material prepared by the invention is expected to be used as building materials for roadbeds, land leveling, pit backfilling and the like, effectively widens the value-added utilization mode of solid wastes, realizes efficient toxicity reduction of the waste incineration fly ash, has positive influence on the environment, society and economy, and has wide application prospects. And an innovative sustainable development mode is provided for resource utilization of solid wastes and green transformation of the building industry.

Description

Technical Field

[0001] The present invention relates to the field of safe disposal and resource utilization of solid waste, and particularly relates to an all-solid waste-based cementitious material for inducing chlorides in municipal solid waste incineration fly ash by using active magnesium oxide and a preparation method thereof. Background Art

[0002] Municipal solid waste incineration power generation technology is currently the main means of disposing of municipal solid waste, with the characteristics of reduction, harmlessness, and energy utilization. However, a large amount of incineration fly ash, incinerator slag, and toxic flue gas will inevitably be generated during the treatment process. Municipal solid waste incineration fly ash refers to the capture residue of the flue gas purification system of incineration equipment, which contains high-concentration chlorides, heavy metals, and trace organic pollutants and is classified as hazardous waste. According to statistics, the output of municipal solid waste incineration fly ash continues to increase and has exceeded 10 million tons. Improper disposal will seriously threaten the ecological environment and human health. Therefore, promoting the harmless disposal and resource utilization of fly ash has become a research focus in the energy and environmental fields. At present, the solidification and stabilization technology has become the mainstream disposal method for municipal solid waste incineration fly ash worldwide due to its advantages such as simple operation, high economic efficiency, and wide application range. Ordinary Portland cement is the most mature binder and is widely used for the solidification and stabilization of hazardous waste. However, the chloride component in municipal solid waste incineration fly ash will damage the cement matrix structure through effects such as expansive salting out, and the heavy metal component will inhibit the cement hydration process through effects such as ion exchange, resulting in a significant decline in the compatibility and durability of the solidification system and unable to exert its due stabilization effect. Although washing pretreatment can remove more than 80% of the soluble chlorides and some heavy metals in municipal solid waste incineration fly ash, the large amount of waste liquid generated therefrom needs to be treated by high-energy-consuming processes such as evaporation crystallization, increasing the recycling cost and causing waste of chloride resources. Therefore, it is urgent to develop a low-carbon new binder suitable for the characteristics of municipal solid waste incineration fly ash.

[0003] Magnesium oxychloride cement is a new type of cementitious material generated by the reaction of active magnesium oxide and chloride salts. Compared with ordinary silicate cement, it has superior characteristics such as energy saving and low carbon, short setting time and high compressive strength. In recent years, it has shown unique application value in the field of hazardous waste solidification and stabilization. Studies have shown that magnesium oxychloride cement will form a needle-shaped 5Mg(OH)2•MgCl2•8H2O crystal interlaced network structure during the hydration process. The dense structure can fix pollutant particles through physical coating. At the same time, the crystal surface has abundant active sites, which can convert heavy metals into stable forms through coordination, complexation and ion exchange. The dual mechanism can achieve efficient solidification and stabilization of pollutants. In addition, the moderately alkaline environment of magnesium oxychloride cement gives it high compatibility with heavy metals, which can effectively avoid the risk of re-dissolution of amphoteric metals such as lead and zinc caused by the strong alkaline environment, and maintain sufficient alkalinity to inhibit the leaching of acidic pollutants. Based on the high chloride characteristics of waste incineration fly ash (20-30%), active magnesium oxide, a by-product of lithium extraction from brine, is used as an inducing activator. Through scientific composition design, it is expected to use impure chloride salts as a beneficial resource to in situ synthesize new low-carbon cementitious materials that can meet the needs of safe landfill and even low-end building materials applications.

[0004] However, the new cementitious system faces the problem of low solubility of magnesium hydroxide, which leads to insufficient free magnesium ions in the pore solution of the system, making it difficult to react with soluble chloride ions to form hydration products, affecting the development of compressive strength of cementitious materials. Preliminary experiments have shown that by adding heavy metal cations to drive precipitation conversion reactions, the dissolution rate of magnesium ions can be significantly increased, the difficulty of crystallization can be reduced, and the nucleation growth of hydration products can be promoted. Based on the solubility product regulation mechanism, the synergistic treatment of copper-enriched electroplating sludge in low-carbon cementitious materials to produce all-solid waste-based cementitious materials can not only improve the performance of cementitious materials while absorbing large amounts of industrial solid waste, but also use hydration products to stabilize the potential toxic elements of raw materials, with both economic and environmental benefits, providing important support for the construction of waste-free cities, but there is currently a lack of relevant exploration and research. Therefore, it is urgent to find a method for the resource utilization of chloride salts from waste incineration fly ash and the simultaneous solidification and disposal of multi-source solid waste.

[0005] The present invention mainly aims at the following existing technical problems:

[0006] (1) Fly ash from waste incineration is highly toxic and has a huge output. Its resource utilization rate is relatively limited and it is difficult to dispose of on a large scale.

[0007] (2) Endogenous chloride salts in waste incineration fly ash cause multiple negative effects in traditional silicate cement-based binder systems.

[0008] (3) Solidified and stabilized products generally have poor mechanical properties and can only meet the requirements for safe landfill disposal, so their application is limited. Summary of the invention

[0009] The purpose of the present invention is to provide a fully solid waste-based cementitious material using active magnesium oxide to induce chloride salts from waste incineration fly ash and a preparation method thereof, and to utilize the component complementary mechanism of active magnesium oxide and chloride salts from waste incineration fly ash to simultaneously synergistically treat copper-containing electroplating sludge to solve the problem of low solubility of magnesium hydroxide. By adjusting the composition and optimizing the technical route, a good hydration reaction process is ensured and abundant hydration products are generated, and a new low-carbon fully solid waste-based cementitious material with both efficient fixation of pollutants and significantly improved mechanical properties is prepared, providing a feasible solution to the problems of harmless disposal and resource utilization of fly ash.

[0010] To achieve the above object, the present invention is implemented by the following technical solutions:

[0011] The invention discloses a fully solid waste-based cementitious material which utilizes active magnesium oxide to induce chloride salts from fly ash from garbage incineration. The fully solid waste-based cementitious material uses 5Mg(OH)2•MgCl2•8H2O and Mg(OH)2 crystal phase as main hydration reaction products. The raw material formula includes active magnesium oxide, fly ash from garbage incineration and copper-containing electroplating sludge, and an appropriate amount of additives are added to improve the performance of the cementitious material.

[0012] As a further improvement, the additive described in the present invention is any one of citric acid, potassium phosphate, copper chloride, etc., or a mixture of several of them.

[0013] As a further improvement, the compressive strength of the all-solid waste-based cementitious material described in the present invention is 6.46~10.98MPa.

[0014] The present invention also discloses a method for preparing a solid waste-based cementitious material using activated magnesium oxide to induce chloride salts from fly ash from garbage incineration. The specific operation includes the following steps:

[0015] S1: Active magnesium oxide, waste incineration fly ash, copper-containing electroplating sludge, and additives are uniformly mixed in a mass ratio of (52.5-67.5): (17.5-22.5): (10-30): (0.34-0.26) to obtain a mixed dry material; wherein the waste incineration fly ash and copper-containing electroplating sludge are dried to a constant weight before mixing;

[0016] S2: Mix deionized water and mixed dry materials in a mass ratio of (0.43-0.45):1.00 to obtain fresh slurry, stir thoroughly and pour into a mold for vibration molding, and perform heat curing under sealed conditions;

[0017] S3: After short-term heat curing, a solidified body with initial strength is obtained, which is demoulded and placed in a curing box for standard curing to obtain a solidified finished product.

[0018] As a further improvement, the fly ash from waste incineration in step S1 of the present invention is dioxin detoxified fly ash by low-temperature pyrolysis, which provides a chlorine source in the gelling system.

[0019] As a further improvement, the reactive magnesium oxide in step S1 of the present invention is obtained by calcining the by-products of lithium extraction from salt lake brine or directly by wet method from brine, which provides a magnesium source in the gelling system.

[0020] As a further improvement, the particle size requirement of the copper-containing electroplating sludge in step S1 of the present invention is that the passing rate through a 100-mesh sieve reaches 100%, and the passing rate through a 200-mesh sieve is not less than 85%, which provides precipitation replacement ions in the gelling system.

[0021] As a further improvement, the conditions for heat curing in step S2 of the present invention are a temperature of 40-60°C and a time of at least 3 days.

[0022] As a further improvement, the conditions for standard curing in step S3 of the present invention are a temperature of 20±2°C, a relative humidity of ≥95%, and a time of at least 25 days.

[0023] The present invention provides a new way for the harmless treatment and resource utilization of fly ash from waste incineration. By effectively activating the endogenous chloride salts in fly ash from waste incineration with reactive magnesium oxide to in-situ transform them into low-carbon gelling materials, coupling with the solubility product regulation mechanism of copper-containing electroplating sludge, releasing magnesium ions to improve the system performance, a new type of low-carbon all-solid waste-based gelling material with good mechanical properties and extremely low pollutant leaching is prepared.

[0024] Compared with the prior art, the features and beneficial effects of the present invention are as follows:

[0025] (1) The present invention innovatively proposes a raw material ratio scheme, that is, reactive magnesium oxide: fly ash from waste incineration: copper-containing electroplating sludge: additive = (52.5-67.5):(17.5-22.5):(10-30):(0.26-0.34). It directly transforms the harmful impurity chloride salt component in fly ash from waste incineration into a beneficial resource necessary for preparing gelling materials, not only realizing the high-ratio recovery and resource utilization of fly ash from waste incineration, but also avoiding the problem of difficult treatment of a large amount of high-salt waste liquid caused by the water washing and dechlorination link. Compared with traditional Portland cement solidified products, it has lower energy consumption and lower risk of pollutant re-dissolution, the overall preparation process is simpler and more efficient, and the carbon emission during the disposal process is lower.

[0026] (2) The present invention innovatively proposes to co - dispose of copper - containing electroplating sludge. By means of precipitation equilibrium reaction, it promotes the release of free magnesium ions into the pore solution, effectively alleviating the problem of limited hydration process caused by the low solubility of magnesium hydroxide, ensuring the strength development of the gelling system, and inducing the formation of a dense matrix filled with needle - rod - shaped 5Mg(OH)2•MgCl2•8H2O phase and fine lamellar Mg(OH)2 phase stacking. This enables the new solidified product to possess mechanical properties meeting the requirements of the building materials field and has a broader application prospect compared with traditional Portland cement solidified products.

[0027] (3) The present invention prepares a low - carbon all - solid - waste - based gelling material by adding modifiers and heat - curing methods. By incorporating additives such as citric acid, potassium phosphate, copper chloride, etc. and selecting an appropriate curing temperature (40 - 60 °C), it ensures the progress of the hydration reaction while generating abundant strength - providing hydration products, improving the mechanical properties and long - term durability of the product.

[0028] (4) The hydration reaction products of the gelling system achieve the solidification and stabilization of endogenous heavy metals in raw materials. Pollutants such as heavy metals enriched in electroplating sludge and municipal solid waste incineration fly ash can be efficiently stabilized in the solid matrix through various synergistic effects such as physical encapsulation and chemical bonding, thus significantly reducing the leaching and migration risk of heavy metals.

[0029] Generally speaking, compared with the traditional Portland cement solidification and stabilization disposal method, the present invention uses active magnesium oxide to induce the in - situ conversion of chlorides in municipal solid waste incineration fly ash into gelling materials, effectively improving the instability of the solidification system and potential environmental secondary pollution problems caused by harmful impurity chlorides. Under the action of co - disposing of copper - containing electroplating sludge, it promotes the reaction degree and strength development of the gelling system, and at the same time ensures that the heavy metal leaching concentration in the system meets the national safety landfill standard of GB / T 16889 - 2008. The gelling material prepared by the present invention is expected to be used as building materials such as roadbeds, land leveling, and mine backfilling, effectively broadening the ways of value - added utilization of solid waste, while achieving the efficient detoxification of municipal solid waste incineration fly ash, having a positive impact on the environment, society and economy, and providing an innovative sustainable development model for the resource utilization of solid waste and the green transformation of the construction industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic flow chart of the present invention for preparing an all - solid - waste - based gelling material by using active magnesium oxide to induce chlorides in municipal solid waste incineration fly ash. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention discloses an all - solid - waste - based gelling material using active magnesium oxide to induce chlorides in municipal solid waste incineration fly ash and its preparation method. For the specific operation steps, refer to Figure 1In order to make the technical solution and practical effect of the present invention clear, the present invention is described in detail below. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0032] The invention discloses a fully solid waste-based cementitious material which utilizes active magnesium oxide to induce chloride salts from fly ash from garbage incineration. The fully solid waste-based cementitious material uses 5Mg(OH)2•MgCl2•8H2O and Mg(OH)2 crystal phase as main hydration reaction products. The raw material formula includes active magnesium oxide, fly ash from garbage incineration and copper-containing electroplating sludge, and an appropriate amount of additives are added to improve the performance of the cementitious material.

[0033] In some specific embodiments, the additive is any one of citric acid, potassium phosphate, copper chloride, etc. or a mixture of several thereof. The purpose is to provide crystal nucleation sites and reduce the influence of water erosion, thereby improving the performance of the gelling system. The amount of the additive is 0.5wt% of the mass of the active magnesium oxide.

[0034] In some specific embodiments, the compressive strength of the all-solid waste-based cementitious material is 6.46~10.98 MPa, and the heavy metal leaching amount meets the national safe landfill requirements of GB / T 16889-2008, among which Zn≤100 mg / L, Pb≤0.25 mg / L, Cr≤4.5 mg / L, Cd≤0.15 mg / L, As≤0.3 mg / L, and Cu≤40 mg / L.

[0035] The present invention also discloses a method for preparing a solid waste-based cementitious material using activated magnesium oxide to induce chloride salts from fly ash from garbage incineration. The specific operation includes the following steps:

[0036] S1: Active magnesium oxide, waste incineration fly ash, copper-containing electroplating sludge, and additives are uniformly mixed in a mass ratio of (52.5-67.5): (17.5-22.5): (10-30): (0.34-0.26) to obtain a mixed dry material, wherein the waste incineration fly ash and copper-containing electroplating sludge are dried to a constant weight before mixing.

[0037] S2: Mix deionized water and mixed dry materials in a mass ratio of (0.43-0.45):1.00 to obtain fresh slurry, stir thoroughly and pour into a mold for vibration molding, and perform heat curing under sealed conditions.

[0038] S3: After short-term heat curing, a solidified body with initial strength is obtained, which is demoulded and placed in a curing box for standard curing to obtain a solidified finished product. The standard curing conditions are a temperature of 20±2 °C, a relative humidity of ≥95%, and a time of at least 25 days.

[0039] In some specific embodiments, the fly ash from waste incineration is the detoxified fly ash with dioxins pyrolyzed at low temperature, providing a chlorine source in the cementitious system; the active magnesium oxide is obtained by calcining the by-products of lithium extraction from salt lake brine or directly by wet method from brine, providing a magnesium source in the cementitious system; the particle size of the copper-containing electroplating sludge requires that the passing rate through a 100-mesh sieve reaches 100%, and the passing rate through a 200-mesh sieve is not less than 85%, providing precipitation replacement ions in the cementitious system. The mass ratio of the active magnesium oxide to the fly ash from waste incineration is maintained at 3:1.

[0040] In some specific embodiments, it is necessary to perform a drying pretreatment on the raw materials before mixing, and if necessary, perform a grinding and screening treatment on the raw materials to ensure that the raw materials are in a uniform powder state, aiming to avoid the influence on the reaction process caused by the raw materials getting damp and caking.

[0041] In some specific embodiments, the purpose of the copper-containing electroplating sludge is to provide copper ions in the reaction system, promote the release of free magnesium ions through a precipitation conversion reaction, and thus generate magnesium chloride through an ionic reaction with the dissolved chloride ions in the fly ash from waste incineration, promoting the formation of hydration products and ensuring the strength development of the cementitious system.

[0042] In some specific embodiments, the conditions for heat curing are a temperature of 40 - 60 °C and a time of at least 3 days. The purpose is to accelerate the dissolution of reaction substances and promote the hydration reaction process.

[0043] The fly ash from waste incineration and the raw materials of copper-containing electroplating sludge used in the following examples and comparative examples were tested for heavy metal leaching according to GB5085.3 - 2007 "Identification Standard for Hazardous Wastes - Identification of Leaching Toxicity", and the results are shown in Table 1.

[0044] Table 1 Heavy Metal Leaching Concentrations of Fly Ash from Waste Incineration and Copper-containing Electroplating Sludge

[0045] Heavy metal (mg / L) Zn Pb Mn Cr Cd As Ni Cu MSWI fly ash 1.626 12.150 0.002 0.032 0.023 0.011 0.002 0.037 Copper-containing electroplating sludge 24.086 2.102 5.006 0.033 0.268 3.826 0.223 52.669

[0046] The preparation method of the low-carbon green all-solid waste-based cementitious material derived from the activation of fly ash from waste incineration by active magnesium oxide chloride proposed by the present invention is explained below through specific examples:

[0047] Example 1

[0048] A method for preparing an all-solid waste-based cementitious material by using active magnesium oxide to induce fly ash chloride from waste incineration, the specific steps are as follows:

[0049] (1) Place the fly ash from waste incineration and the copper-containing electroplating sludge in a blast drying oven at 105 °C and dry to constant weight respectively;

[0050] (2)Weigh the reactive magnesium oxide, municipal solid waste incineration fly ash, copper-containing electroplating sludge, and additive according to the mass ratio of 67.5:22.5:10:0.34, and use a stirrer to mix them evenly (rotation speed 200 r / min, time 2 min) to obtain the mixed dry material;

[0051] (3)Weigh deionized water and the mixed dry material according to the mass ratio of 0.43:1.00, and use a stirrer to mix them evenly (rotation speed 500 r / min, time 5 min) to obtain the fresh slurry;

[0052] (4)Inject the prepared fresh slurry into a 50×50×50mm 3 square mold and vibrate it to form (vibration amplitude ≤ 5mm, vibration frequency 18 - 24 times / min, vibration time 10 - 15 s), then place it in a sealed condition at 60 °C for heat curing for 3 days;

[0053] (5)After short-term curing, obtain the solidified body with initial strength, demold it and transfer it to a standard curing box for standard curing for at least 25 days (temperature 20±2°C, relative humidity ≥ 95%), then the solidified finished product can be obtained.

[0054] (6)After the curing period, conduct performance tests on the solidified product. The data shows that the compressive strength value of the low-carbon cementitious material derived from municipal solid waste incineration fly ash reaches 6.46 MPa, meeting the strength requirements for national safe landfill in GB / T 16889-2008.

[0055] (7)After the curing period, conduct heavy metal leaching concentration tests on the solidified product according to GB 5085.3-2007 "Identification Standard for Hazardous Wastes - Identification for Leaching Toxicity". The test results are shown in Table 2:

[0056] Table 2 Heavy metal leaching concentration of the cementitious material in Example 1

[0057] Heavy metal (mg / L) Zn Pb Mn Cr Cd As Ni Cu Example 1 0.005 0.034 0.001 0.003 0.000 0.001 0.000 0.071

[0058] Example 2

[0059] A method for preparing a solid waste-based cementitious material by using reactive magnesium oxide to induce the chlorides in municipal solid waste incineration fly ash, the specific steps are as follows:

[0060] (1)Place the municipal solid waste incineration fly ash and copper-containing electroplating sludge in a blast drying oven at 105 °C and dry them to constant weight;

[0061] (2)Weigh the reactive magnesium oxide, municipal solid waste incineration fly ash, copper-containing electroplating sludge, and additive according to the mass ratio of 60:20:20:0.3, and use a stirrer to mix them evenly (rotation speed 200 r / min, time 2 min) to obtain the mixed dry material;

[0062] (3) Weigh deionized water and the mixed dry materials in a mass ratio of 0.44:1.00, and use a stirrer to mix them evenly (rotation speed 500 r / min, time 5 min) to obtain fresh slurry;

[0063] (4) Inject the prepared fresh slurry into a 50×50×50 mm 3 square mold and vibrate it to form (vibration amplitude ≤ 5 mm, vibration frequency 18 - 24 times / min, vibration time 10 - 15 s), then place it under sealed conditions at 60°C for heat curing for 3 days;

[0064] (5) After short-term curing, obtain a solidified body with initial strength, demold it and transfer it to a standard curing box for standard curing for at least 25 days (temperature 20±2°C, relative humidity ≥ 95%), then the cured product can be obtained.

[0065] (6) After the curing period, perform performance tests on the cured product. The data shows that the compressive strength value of the low-carbon cementitious material derived from municipal solid waste incineration fly ash reaches 8.34 MPa, meeting the strength requirements for national security landfill in GB / T 16889-2008.

[0066] (7) After the curing period, test the heavy metal leaching concentration of the cured product according to GB 5085.3-2007 "Identification Standard for Hazardous Wastes - Identification for Leaching Toxicity". The test results are shown in Table 3:

[0067] Table 3 Heavy metal leaching concentration of the cementitious material in Example 2

[0068] Heavy metal (mg / L) Zn Pb Mn Cr Cd As Ni Cu Example 2 0.004 0.018 0.000 0.002 0.001 0.002 0.001 0.061

[0069] Example 3

[0070] A method for preparing a solid waste-based cementitious material by using active magnesium oxide to induce the chlorides in municipal solid waste incineration fly ash, the specific steps are as follows:

[0071] (1) Place the municipal solid waste incineration fly ash and copper electroplating sludge in a blast drying oven at 105°C and dry to constant weight;

[0072] (2) Weigh active magnesium oxide, municipal solid waste incineration fly ash, copper electroplating sludge, and additives in a mass ratio of 52.5:17.5:30:0.26, and use a stirrer to mix them evenly (rotation speed 200 r / min, time 2 min) to obtain mixed dry materials;

[0073] (3) Weigh deionized water and the mixed dry materials in a mass ratio of 0.45:1.00, and use a stirrer to mix them evenly (rotation speed 500 r / min, time 5 min) to obtain fresh slurry;

[0074] (4) Inject the freshly prepared slurry into a 50×50×50 mm 3 square mold and vibrate it into shape (vibration amplitude ≤ 5 mm, vibration frequency 18 - 24 times / min, vibration time 10 - 15 s), then place it under heat curing for 3 days under sealed conditions at 60 °C;

[0075] (5) After short - term curing, a solidified body with initial strength is obtained. Demold it and transfer it to a standard curing box for standard curing for at least 25 days (temperature 20±2 °C, relative humidity ≥ 95%), then the cured product can be obtained.

[0076] (6) After the curing period ends, perform performance tests on the cured product. The data shows that the compressive strength value of the low - carbon cementitious material derived from municipal solid waste incineration fly ash reaches 10.98 MPa, meeting the strength requirements for national safe landfill in GB / T 16889 - 2008.

[0077] (7) After the curing period ends, test the heavy metal leaching concentration of the cured product according to GB 5085.3 - 2007 "Identification Standard for Hazardous Wastes - Identification of Leaching Toxicity". The test results are shown in Table 4:

[0078] Table 4 Heavy metal leaching concentration of the cementitious material in Example 3

[0079] Heavy metal (mg / L) Zn Pb Mn Cr Cd As Ni Cu Example 3 0.006 0.029 0.002 0.003 0.001 0.002 0.000 0.145

[0080] Comparative Example 1

[0081] The difference in the operation process of this comparative example compared with Example 1 is that municipal solid waste incineration fly ash is no longer incorporated in this comparative example. The compressive strength value of the cured product reaches 0.78 MPa, meeting the strength requirements for national safe landfill in GB / T 16889 - 2008.

[0082] The cured product of this comparative example is tested for heavy metal leaching concentration according to GB 5085.3 - 2007 "Identification Standard for Hazardous Wastes - Identification of Leaching Toxicity". The test results are shown in Table 5:

[0083] Table 5 Heavy metal leaching concentration of the cementitious material in Comparative Example 1

[0084] Heavy metal (mg / L) Zn Pb Mn Cr Cd As Ni Cu Comparative Example 1 1.683 0.052 0.095 0.021 0.036 0.123 0.004 4.782

[0085] Comparative Example 2

[0086] The difference in the operation process of this comparative example compared with Example 1 is that copper - containing electroplating sludge is no longer incorporated in this comparative example. The compressive strength value of the cured product reaches 3.58 MPa, meeting the strength requirements for national safe landfill in GB / T 16889 - 2008.

[0087] The solidified product of this comparative example was tested for the heavy metal leaching concentration in accordance with GB 5085.3-2007 Identification Standard for Hazardous Wastes - Identification for Extraction Toxicity. The test results are shown in Table 5:

[0088] Table 6 Heavy Metal Leaching Concentrations of the Cementitious Material in Comparative Example 2

[0089] Heavy metal (mg / L) Zn Pb Mn Cr Cd As Ni Cu Comparative Example 2 0.094 0.871 0.001 0.023 0.006 0.003 0.000 0.008

[0090] Comparative Example 3

[0091] The difference in the operation process of this comparative example compared with Example 1 is that the dosage of the additive in this comparative example accounts for 2 wt% of the mass of active magnesium oxide, and the compressive strength value of the solidified product reaches 4.11 MPa, meeting the strength requirements for national security landfilling in GB / T 16889-2008.

[0092] The solidified product of this comparative example was tested for the heavy metal leaching concentration in accordance with GB 5085.3-2007 Identification Standard for Hazardous Wastes - Identification for Extraction Toxicity. The test results are shown in Table 5:

[0093] Table 7 Heavy Metal Leaching Concentrations of the Cementitious Material in Comparative Example 3

[0094] Heavy metal (mg / L) Zn Pb Mn Cr Cd As Ni Cu Comparative Example 3 0.005 0.024 0.001 0.002 0.002 0.003 0.000 0.103

[0095] Through the comparative analysis of Comparative Example 1 and Example 1, it can be found that the matrix space of Comparative Example 1 is mainly filled by the stacking of fine lamellar Mg(OH)2 crystals and unhydrated particles. Therefore, the cementing effect of the system is poor, and the solidification and stabilization effect on electroplating sludge is not good, which proves the feasibility of using active magnesium oxide to induce the chlorides in municipal solid waste incineration fly ash. Through pre-experiments to simulate the solubility product regulation process of copper ions and magnesium hydroxide, the mechanism of the ion exchange reaction on the crystallization behavior of hydration products and the improvement of material strength was verified under the condition of excluding the interference of solid waste impurities, providing a theoretical support for the synergistic effect of multi-source solid wastes in the examples.

[0096] Through the comparative analysis of Comparative Example 2 and Examples 1, 2, and 3, it can be found that the main hydration products of Comparative Example 2 are Mg(OH)2 and a very small amount of needle-like substances. At this time, the solubility of Mg(OH)2 is relatively low, and it is difficult to react with the chloride ions leached from the fly ash. As the content of copper electroplating sludge increases, the dissolution rate of magnesium ions in the pore solution of the examples increases, and the matrix space is gradually filled by the interpenetration of needle-like hydration products. The macroscopic strength development of the solidification system is significantly improved, increasing from 3.58 MPa in Comparative Example 2 to 10.98 MPa in Example 3.

[0097] By comparing Comparative Example 3 and Example 1, it can be found that the dosage of the additive needs to be in an appropriate proportion to ensure the performance of the curing system. When the dosage of the additive is too high, it will affect the development of the compressive strength of the curing system. This is because the excessive additive triggers the ion competition effect, and the components consume chloride ions and hydroxide ions in the solution, interfering with the nucleation and growth of the main hydration products and weakening the macroscopic strength of the curing system, which decreases from 6.46 MPa in Example 1 to 4.11 MPa in Comparative Example 3.

[0098] The curing system prepared by the present invention meets the strength requirements for national security landfilling in GB / T 16889-2008, and at the same time, it is expected to expand the application scope to non-load-bearing unit partition blocks (>7 MPa). Compared with the raw materials of municipal solid waste incineration fly ash and copper-containing electroplating sludge, the hydration products of the cured products play a role in physical encapsulation, ion exchange, covalent binding, etc. for the heavy metals, and the heavy metal leaching concentration shows a significant downward trend, all meeting the heavy metal leaching concentration requirements for national security landfilling in GB / T 16889-2008. Generally speaking, the present invention innovatively uses active magnesium oxide to induce endogenous chlorides in municipal solid waste incineration fly ash, establishing a new technical route for solid waste pollutant stabilization and product recycling, and making contributions to the construction of a waste-free city and the realization of circular economy.

[0099] The above-described embodiments are only illustrative of the present invention and are not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A solid waste-based cementitious material using activated magnesium oxide to induce chlorides in municipal solid waste incineration fly ash, characterized in that, The all-solid waste-based cementitious material has 5Mg(OH)2•MgCl2•8H2O and Mg(OH)2 crystal phase as main hydration reaction products, and the raw material formula includes activated magnesium oxide, waste incineration fly ash and copper-containing electroplating sludge, plus appropriate additives to improve the performance of the cementitious material.

2. The all-solid waste-based cementitious material using activated magnesium oxide to induce chlorides in municipal solid waste incineration fly ash according to claim 1, wherein, The additive is any one of citric acid, potassium phosphate, copper chloride, etc., or a mixture of several of them.

3. The all-solid waste-based cementitious material using activated magnesium oxide to induce chlorides in municipal solid waste incineration fly ash according to claim 1, characterized in that, The compressive strength of the all-solid waste-based cementitious material is 6.46~10.98 MPa.

4. A preparation method of a fully solid waste-based cementitious material using activated magnesium oxide to induce chlorides in municipal solid waste incineration fly ash as described in claim 1 or 2 or 3, characterized in that, The specific operation includes the following steps: S1: Active magnesium oxide, waste incineration fly ash, copper-containing electroplating sludge, and additives are uniformly mixed in a mass ratio of (52.5-67.5): (17.5-22.5): (10-30): (0.34-0.26) to obtain a mixed dry material; wherein the waste incineration fly ash and copper-containing electroplating sludge are dried to a constant weight before mixing; S2: Mix deionized water and the mixed dry material in a mass ratio of (0.43-0.45):1.00 to obtain a fresh slurry, stir thoroughly, pour into a mold for vibration molding, and perform heat curing under sealed conditions; S3: After short-term heat curing, a solidified body with initial strength is obtained, which is demoulded and placed in a curing box for standard curing to obtain a solidified finished product.

5. The preparation method of the all-solid waste-based cementitious material using activated magnesium oxide to induce chlorides in municipal solid waste incineration fly ash according to claim 4, characterized in that, The waste incineration fly ash in step S1 is detoxified fly ash obtained by low-temperature pyrolysis of dioxins, and provides a chlorine source in the gelling system.

6. The preparation method of the all-solid waste-based cementitious material using activated magnesium oxide to induce chlorides in municipal solid waste incineration fly ash according to claim 4, characterized in that, The active magnesium oxide in step S1 is obtained by calcining the byproduct of lithium extraction from salt lake brine or directly wet-processing the brine to provide a magnesium source in the gelling system.

7. The preparation method of the all-solid waste-based cementitious material using activated magnesium oxide to induce chlorides in municipal solid waste incineration fly ash according to claim 5 or 6, characterized in that, The copper-containing electroplating sludge particle size in step S1 is required to have a pass rate of 100% through a 100-mesh sieve and a pass rate of no less than 85% through a 200-mesh sieve, providing precipitation replacement ions in the gelling system.

8. The preparation method of the all-solid waste-based cementitious material using activated magnesium oxide to induce chlorides in municipal solid waste incineration fly ash according to claim 7, characterized in that, The heat curing conditions in step S2 are a temperature of 40-60° C. and a time of at least 3 days.

9. The preparation method of the all-solid waste-based cementitious material using activated magnesium oxide to induce chlorides in municipal solid waste incineration fly ash according to claim 5 or 6 or 8, characterized in that, The standard curing conditions in step S3 are a temperature of 20±2° C., a relative humidity of ≥95%, and a time of at least 25 days.

Images