A fully solid waste-based gelling material using activated magnesium oxide to induce chloride salts from waste incineration fly ash and its preparation method

Abstract

The present invention discloses a fully solid waste-based cementitious material using activated magnesium oxide to induce chloride salts from waste incineration fly ash and a preparation method thereof. The present invention uses activated magnesium oxide to induce the in-situ conversion of chloride salts from waste incineration fly ash into a cementitious material, effectively improving the instability of the solidification system and the potential secondary environmental pollution problems caused by the harmful impurity chloride salts, promoting the reaction degree and strength development of the cementitious system under the action of the coordinated disposal of copper-containing electroplating sludge, and ensuring that the heavy metal leaching concentration of the system complies with the national safe landfill standard GB / T 16889-2008. The cementitious material prepared by the present invention is expected to be used as a construction material such as roadbed, land leveling, and mine backfill, effectively broadening the way of value-added utilization of solid waste, while achieving efficient detoxification of 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.

Description

Technical Field

[0001] The present invention relates to the field of safe disposal and resource utilization of solid waste, and in particular to a fully solid waste-based gelling material utilizing activated magnesium oxide to induce chloride salts from fly ash from garbage incineration, and a preparation method thereof. Background Art

[0002] Waste incineration power generation technology is currently the main means of disposing of urban domestic waste. It has the characteristics of volume reduction, harmlessness and energy utilization, but the treatment process will inevitably produce a large amount of incineration fly ash, incineration slag and toxic flue gas. Waste incineration fly ash refers to the captured residue of the flue gas purification system of the incineration equipment. It contains high concentrations of chloride salts, heavy metals and trace organic pollutants and is classified as hazardous waste. According to statistics, the output of 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 is a research focus in the field of energy and environment. At present, solidification and stabilization technology has become the mainstream disposal method for waste incineration fly ash worldwide due to its advantages such as simple operation, cost-effectiveness and wide applicability. Ordinary Portland cement is the most mature binder, widely used for the solidification and stabilization of hazardous waste. However, the chloride content of waste incineration fly ash can destroy the cement matrix structure through processes such as expansion and salting out, while heavy metal components can inhibit the cement hydration process through processes such as ion exchange, resulting in a significant decrease in the compatibility and durability of the solidification system, making it unable to achieve its expected stabilization effect. Although water washing pretreatment can remove more than 80% of the soluble chloride salts and some heavy metals in waste incineration fly ash, the large amount of waste liquid generated requires high-energy treatment such as evaporation and crystallization, increasing recycling costs and wasting chloride resources. Therefore, there is an urgent need to develop new low-carbon binders that are suitable for the characteristics of waste incineration fly ash.

[0003] Magnesium oxychloride cement is a novel cementitious material formed by the reaction of activated magnesium oxide and chloride salts. Compared to ordinary Portland cement, it offers advantages such as energy conservation and low carbon emissions, a short setting time, and high compressive strength. In recent years, it has demonstrated unique application value in the solidification and stabilization of hazardous waste. Research has shown that during the hydration process, magnesium oxychloride cement forms a network of interlaced needle-shaped 5Mg(OH)2•MgCl2•8H2O crystals. This dense structure can physically immobilize pollutant particles. The crystal surface also possesses abundant active sites, which can convert heavy metals into stable forms through coordination, complexation, and ion exchange. This dual mechanism enables efficient solidification and stabilization of pollutants. Furthermore, the moderately alkaline environment of magnesium oxychloride cement imparts high compatibility with heavy metals, effectively preventing the risk of re-dissolution of amphoteric metals such as lead and zinc caused by a strongly alkaline environment while maintaining 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 induction activator. After scientific composition design, it is expected that impure chloride salts can be used as beneficial resources 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 the compressive strength of the cementitious material. Preliminary experiments have shown that by adding heavy metal cations to drive the precipitation conversion reaction, the dissolution rate of magnesium ions can be significantly increased, the difficulty of crystallization can be reduced, and the nucleation and 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, there is an urgent need 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 addresses the following technical problems:

[0006] (1) Fly ash from waste incineration is highly toxic and has a huge output. Its resource utilization rate is relatively limited, making it 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 applications are limited. Summary of the Invention

[0009] The purpose of the present invention is to provide a fully solid waste-based cementitious material that utilizes activated magnesium oxide to induce chloride salts from waste incineration fly ash, and a preparation method thereof. The component complementarity mechanism of activated magnesium oxide and chloride salts from waste incineration fly ash is utilized to simultaneously and 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. A new low-carbon fully solid waste-based cementitious material with both efficient pollutant fixation 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 through the following technical solutions:

[0011] The present invention discloses a fully solid waste-based cementitious material which utilizes active magnesium oxide to induce chloride salts from waste incineration fly ash. 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, waste incineration fly ash 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 of 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 gelling material using activated magnesium oxide to induce chloride salts from fly ash from garbage incineration. The specific operation comprises the following steps:

[0015] S1: Activated 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 a fresh slurry, stir thoroughly, pour into a mold, vibrate, and perform heat curing under sealed conditions;

[0017] S3: After a short period of 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 waste incineration fly ash in step S1 of the present invention is detoxified fly ash obtained by low-temperature pyrolysis of dioxins, which provides a chlorine source in the gelling system.

[0019] As a further improvement, the active magnesium oxide in step S1 of the present invention 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.

[0020] As a further improvement, the copper-containing electroplating sludge particle size in step S1 of the present invention 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 precipitated replacement ions in the gelling system.

[0021] As a further improvement, the heat curing conditions 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 standard curing conditions in step S3 of the present invention are a temperature of 20±2°C, a relative humidity ≥95%, and a time of at least 25 days.

[0023] The present invention provides a new approach for the harmless disposal and resource utilization of waste incineration fly ash. Activated magnesium oxide is used to effectively stimulate the in-situ conversion of endogenous chloride salts in waste incineration fly ash into low-carbon cementitious materials. The solubility product regulation mechanism of copper-containing electroplating sludge is coupled to release magnesium ions to improve system performance, thereby preparing a new low-carbon, all-solid waste-based cementitious material with good mechanical properties and extremely low pollutant leaching.

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

[0025] (1) The present invention innovatively proposes a raw material ratio scheme, namely, activated magnesium oxide: waste incineration fly ash: copper-containing electroplating sludge: additive = (52.5-67.5): (17.5-22.5): (10-30): (0.26-0.34), which directly converts the harmful impurity chloride salt component of waste incineration fly ash into a beneficial resource required for the preparation of cementitious materials, thereby realizing the high-content recovery and resource utilization of waste incineration fly ash, and avoiding the problem of difficult treatment of a large amount of high-salt waste liquid caused by the water washing and dechlorination process. Compared with traditional silicate cement solidification products, the energy consumption and the risk of pollutant re-dissolution are lower, the overall preparation process is simpler and more efficient, and the carbon emissions of the disposal process are lower.

[0026] (2) The present invention innovatively proposes the coordinated disposal of copper-containing electroplating sludge, promoting the release of free magnesium ions into the pore solution through precipitation equilibrium reaction, effectively alleviating the problem of limited hydration process caused by the low solubility of magnesium hydroxide, ensuring the strength development of the cementitious system, and inducing the formation of a dense matrix filled with needle-like 5Mg(OH)2•MgCl2•8H2O phase and fine lamellar Mg(OH)2 phase stacking, so that the new solidified product has mechanical properties that meet the needs of the building materials field, and has broader application prospects than traditional silicate cement solidified products.

[0027] (3) The present invention prepares low-carbon all-solid waste-based cementitious materials by adding modifiers and heat curing. By adding additives such as citric acid, potassium phosphate, and copper chloride and selecting a suitable curing temperature (40-60°C), the hydration reaction process is ensured while generating abundant hydration products that provide strength, thereby improving the mechanical properties and long-term durability of the product.

[0028] (4) The hydration reaction products of the gelling system can solidify and stabilize the endogenous heavy metals in the raw materials. The heavy metals and other pollutants enriched in electroplating sludge and waste incineration fly ash can be efficiently stabilized in the solid matrix through a variety of synergistic effects such as physical isolation and chemical bonding, thereby significantly reducing the risk of leaching and migration of heavy metals.

[0029] Overall, compared to traditional silicate cement solidification and stabilization methods, the present invention utilizes activated magnesium oxide to induce the in-situ conversion of chloride salts from waste incineration fly ash into a cementitious material. This effectively mitigates the instability of the solidification system and potential secondary environmental pollution caused by harmful chloride impurities. It also promotes the reaction and strength development of the cementitious system through the coordinated treatment of copper-containing electroplating sludge, while ensuring that the system's heavy metal leaching concentration complies with the national safe landfill standard GB / T 16889-2008. The cementitious material prepared by the present invention is expected to be used as a construction material for roadbeds, land leveling, and mine backfill, effectively expanding the value-added utilization of solid waste while achieving efficient detoxification of waste incineration fly ash. This has positive impacts on the environment, society, and economy, and provides an innovative and 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 The present invention is a schematic diagram of the process of preparing a fully solid waste-based cementitious material by using activated magnesium oxide to induce chloride salts from waste incineration fly ash. DETAILED DESCRIPTION

[0031] The present invention discloses a solid waste-based gelling material and a preparation method thereof using activated magnesium oxide to induce chloride salts from fly ash of garbage incineration. Figure 1In order to make the technical solution and practical effects of the present invention clear, the present invention is described in detail below. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] The present invention discloses a fully solid waste-based cementitious material which utilizes active magnesium oxide to induce chloride salts from waste incineration fly ash. 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, waste incineration fly ash 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, or a combination thereof. This additive is used to provide crystal nucleation sites, reduce water erosion, and improve the performance of the gel system. The additive is used in an amount of 0.5 wt% 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 gelling material using activated magnesium oxide to induce chloride salts from fly ash from garbage incineration. The specific operation comprises the following steps:

[0036] S1: Activated 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. 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. After fully stirring, pour it into a mold for vibration molding and perform heat curing under sealed conditions.

[0038] S3: After a short period of heat curing, a solidified body with initial strength is obtained. The solidified body is demoulded and placed in a curing chamber for standard curing to obtain the final product. Standard curing conditions are a temperature of 20±2°C, a relative humidity of ≥95%, and a duration of at least 25 days.

[0039] In some specific embodiments, waste incineration fly ash is detoxified fly ash obtained through low-temperature pyrolysis of dioxins, providing a chlorine source in the gelling system. Activated magnesium oxide is obtained by calcining a lithium byproduct from salt lake brine extraction or by directly wet-processing brine, providing a magnesium source in the gelling system. Copper-containing electroplating sludge, with a particle size requirement of 100% passing a 100-mesh sieve and no less than 85% passing a 200-mesh sieve, provides precipitated replacement ions in the gelling system. The mass ratio of activated magnesium oxide to waste incineration fly ash is maintained at 3:1.

[0040] In some specific embodiments, the raw materials need to be dried and pre-treated before mixing, and if necessary, ground and sieved to ensure that the raw materials are in a uniform powder state, in order to prevent the raw materials from getting damp and agglomerating, which may affect the reaction process.

[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 precipitation conversion reaction, thereby reacting with the dissolved chloride ions in the waste incineration fly ash to form magnesium chloride, promote the formation of hydration products, and ensure the strength development of the gelling system.

[0042] In some specific embodiments, the heat curing condition is a temperature of 40-60° C. for at least 3 days, in order to accelerate the dissolution of the reactants and promote the hydration reaction process.

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

[0044] Table 1 Heavy metal leaching concentrations from waste incineration fly ash and copper-containing electroplating sludge

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

[0046] The following is an explanation of the method for preparing a low-carbon, green, all-solid waste-based cementitious material derived from garbage incineration fly ash chloride salts activated by activated magnesium oxide proposed in the present invention through specific examples:

[0047] Example 1

[0048] A method for preparing a fully solid waste-based cementitious material by using activated magnesium oxide to induce chloride salts from waste incineration fly ash, the specific steps of which are as follows:

[0049] (1) The waste incineration fly ash and copper-containing electroplating sludge were placed in a 105°C forced air drying oven and dried to constant weight;

[0050] (2) Activated magnesium oxide, waste incineration fly ash, copper-containing electroplating sludge, and additives were weighed in a mass ratio of 67.5:22.5:10:0.34 and uniformly mixed using a stirrer (speed 200 r / min, time 2 min) to obtain a mixed dry material;

[0051] (3) Deionized water and the mixed dry materials were weighed in a mass ratio of 0.43:1.00, and mixed evenly using a stirrer (speed 500 r / min, time 5 min) to obtain a fresh slurry;

[0052] (4) Inject the prepared fresh slurry into a 50×50×50mm 3 Vibration molding in a square mold (vibration amplitude ≤ 5 mm, vibration frequency 18-24 times / min, vibration time 10-15 s), followed by heat curing at 60 °C under sealed conditions for 3 days;

[0053] (5) After a short period of curing, a solidified body with initial strength is obtained, which is demoulded and transferred to a standard curing box for standard curing for at least 25 days (temperature is 20±2°C, relative humidity ≥ 95%) to obtain a cured product.

[0054] (6) After the curing period, the performance of the solidified product was tested. The data showed that the compressive strength of the low-carbon cementitious material derived from waste incineration fly ash reached 6.46 MPa, which met the strength requirements for national safe landfill in GB / T 16889-2008.

[0055] (7) After the curing period, the solidified product was tested for heavy metal leaching concentration according to GB 5085.3-2007 “Identification Standard for Hazardous Waste – Identification of Leaching Toxicity”. The test results are shown in Table 2:

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

[0057] Heavy metals (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 fully solid waste-based cementitious material by using activated magnesium oxide to induce chloride salts from waste incineration fly ash, the specific steps of which are as follows:

[0060] (1) The waste incineration fly ash and copper-containing electroplating sludge were placed in a 105°C forced air drying oven and dried to constant weight;

[0061] (2) Activated magnesium oxide, waste incineration fly ash, copper-containing electroplating sludge, and additives were weighed in a mass ratio of 60:20:20:0.3 and uniformly mixed using a stirrer (speed 200 r / min, time 2 min) to obtain a mixed dry material;

[0062] (3) Deionized water and the mixed dry materials were weighed in a mass ratio of 0.44:1.00, and mixed evenly using a stirrer (speed 500 r / min, time 5 min) to obtain a fresh slurry;

[0063] (4) Inject the prepared fresh slurry into a 50×50×50 mm 3 Vibration molding in a square mold (vibration amplitude ≤ 5 mm, vibration frequency 18-24 times / min, vibration time 10-15 s), followed by heat curing at 60°C under sealed conditions for 3 days;

[0064] (5) After a short period of curing, a solidified body with initial strength is obtained, which is demoulded and transferred to a standard curing box for standard curing for at least 25 days (temperature is 20±2°C, relative humidity ≥ 95%) to obtain a cured product.

[0065] (6) After the curing period, the performance of the solidified product was tested. The data showed that the compressive strength of the low-carbon cementitious material derived from waste incineration fly ash reached 8.34 MPa, which met the strength requirements for national safe landfill in GB / T 16889-2008.

[0066] (7) After the curing period, the solidified product was tested for heavy metal leaching concentration according to GB 5085.3-2007 “Identification Standard for Hazardous Waste – Identification of Leaching Toxicity”. The test results are shown in Table 3:

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

[0068] Heavy metals (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 fully solid waste-based cementitious material by using activated magnesium oxide to induce chloride salts from waste incineration fly ash, the specific steps of which are as follows:

[0071] (1) Place the waste incineration fly ash and copper-containing electroplating sludge in a 105°C forced air drying oven and dry them to constant weight;

[0072] (2) Activated magnesium oxide, waste incineration fly ash, copper-containing electroplating sludge, and additives were weighed in a mass ratio of 52.5:17.5:30:0.26 and uniformly mixed using a stirrer (speed 200 r / min, time 2 min) to obtain a mixed dry material;

[0073] (3) Deionized water and the mixed dry materials were weighed in a mass ratio of 0.45:1.00, and mixed evenly using a stirrer (speed 500 r / min, time 5 min) to obtain a fresh slurry;

[0074] (4) Inject the prepared fresh slurry into a 50×50×50mm 3 Vibration molding in a square mold (vibration amplitude ≤ 5 mm, vibration frequency 18-24 times / min, vibration time 10-15 s), followed by heat curing at 60 °C under sealed conditions for 3 days;

[0075] (5) After a short period of curing, a solidified body with initial strength is obtained, which is demoulded and transferred to a standard curing box for standard curing for at least 25 days (temperature is 20±2°C, relative humidity ≥ 95%) to obtain a cured product.

[0076] (6) After the curing period, the performance of the solidified product was tested. The data showed that the compressive strength of the low-carbon cementitious material derived from waste incineration fly ash reached 10.98 MPa, which met the strength requirements for national safe landfill in GB / T 16889-2008.

[0077] (7) After the curing period, the solidified product was tested for heavy metal leaching concentration according to GB 5085.3-2007 “Identification Standard for Hazardous Waste – Identification of Leaching Toxicity”. The test results are shown in Table 4:

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

[0079] Heavy metals (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 operating process of this comparative example is different from that of Example 1 in that no waste incineration fly ash is added in this comparative example, and the compressive strength of the solidified product reaches 0.78 MPa, meeting the strength requirements of GB / T 16889-2008 for national safe landfill.

[0082] The solidified product of this comparative example was 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 of Comparative Example 1

[0084] Heavy metals (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 operating process of this comparative example is different from that of Example 1 in that copper-containing electroplating sludge is no longer added in this comparative example, and the compressive strength of the solidified product reaches 3.58 MPa, meeting the strength requirements of GB / T 16889-2008 for national safe landfill.

[0087] The solidified product of this comparative example was 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:

[0088] Table 6 Heavy metal leaching concentration of the cementitious material of Comparative Example 2

[0089] Heavy metals (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 operating process of this comparative example is different from that of Example 1 in that the amount of additive in this comparative example accounts for 2wt% of the mass of the active magnesium oxide, and the compressive strength of the cured product reaches 4.11 MPa, meeting the strength requirements of GB / T 16889-2008 for national safe landfill.

[0092] The solidified product of this comparative example was 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:

[0093] Table 7 Heavy metal leaching concentration of the cementitious material of Comparative Example 3

[0094] Heavy metals (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] A comparative analysis of Comparative Example 1 and Example 1 reveals that the matrix space in Comparative Example 1 is primarily filled with stacked, fine lamellar Mg(OH)2 crystals and unhydrated particles. Consequently, the system exhibits poor bonding and poor solidification and stabilization effects on electroplating sludge, demonstrating the feasibility of using activated magnesium oxide to induce chloride salts in waste incineration fly ash. Preliminary experiments simulated the solubility product regulation process for copper ions and magnesium hydroxide, verifying the mechanism of action of the ion exchange reaction on the crystallization behavior and material strength enhancement of the hydration product under conditions that eliminate interference from solid waste impurities. This provides theoretical support for the synergistic effect of multi-source solid waste in the examples.

[0096] Through comparative analysis of Comparative Example 2 and Example 1, Example 2, and Example 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-shaped substances. At this time, the solubility of Mg(OH)2 is low and it is difficult to react with the chloride ions dissolved in the fly ash. With the increase of the amount of copper-containing electroplating sludge, the dissolution rate of magnesium ions in the pore solution of the embodiment is improved, and the matrix space is gradually filled with needle-shaped hydration products. The macroscopic strength development of the solidification system is significantly improved, from 3.58 MPa in Comparative Example 2 to 10.98 MPa in Example 3.

[0097] By comparing and analyzing Comparative Example 3 and Example 1, it can be found that the amount of additives needs to be in a suitable ratio to ensure the performance of the curing system. When the additive dosage is too high, the development of the compressive strength of the curing system will be affected. This is because the excessive additives trigger an ion competition effect, the components consume chloride ions and hydroxide ions in the solution, interfere with the nucleation growth of the main hydration products, and weaken the macro strength of the curing system, reducing it from 6.46 MPa in Example 1 to 4.11 MPa in Comparative Example 3.

[0098] The solidification system prepared by this invention meets the strength requirements for safe landfill in GB / T 16889-2008 and is expected to expand its application to non-load-bearing unit partition walls (>7 MPa). Compared to the raw materials of waste incineration fly ash and copper-containing electroplating sludge, the hydration products of the solidification product stabilize heavy metals through physical sequestration, ion exchange, and covalent bonding, resulting in a significant decrease in heavy metal leaching concentrations, meeting the requirements for safe landfill in GB / T 16889-2008. Overall, this invention innovatively utilizes activated magnesium oxide to induce endogenous chloride salts in waste incineration fly ash, establishing a new technology for solid waste pollutant stabilization and product recovery, contributing to the development of waste-free cities and the realization of a circular economy.

[0099] The above-described embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, utilize the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent changes. Therefore, any simple modifications 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 are still 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 chloride salts from fly ash from garbage incineration, characterized in that: The all-solid waste-based cementitious material uses 5Mg(OH)2•MgCl2•8H2O and Mg(OH)2 crystal phase as the main hydration reaction products. The raw material formula includes activated magnesium oxide, waste incineration fly ash and copper-containing electroplating sludge, plus an appropriate amount of additives to improve the performance of the cementitious material; the additive is any one of citric acid, potassium phosphate, and copper chloride or a mixture of several of them. The mass ratio of activated magnesium oxide: waste incineration fly ash: copper-containing electroplating sludge: additive is (52.5-67.5): (17.5-22.5): (10-30): (0.26-0.34).

2. The all-solid waste-based gelling material using activated magnesium oxide to induce chloride salts from 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.

3. A method for preparing a solid waste-based cementitious material using activated magnesium oxide to induce chloride salts from fly ash from garbage incineration as claimed in claim 1 or 2, characterized in that: The specific steps include: S1: uniformly mixing activated magnesium oxide, waste incineration fly ash, copper-containing electroplating sludge, and additives in a mass ratio of (52.5-67.5): (17.5-22.5): (10-30): (0.26-0.34) 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, vibrate, and perform heat curing under sealed conditions; S3: After a short period of 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.

4. The method for preparing a solid waste-based cementitious material using activated magnesium oxide to induce chloride salts from waste incineration fly ash according to claim 3, 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.

5. The method for preparing a solid waste-based cementitious material using activated magnesium oxide to induce chloride salts from waste incineration fly ash according to claim 3, 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.

6. The method for preparing a solid waste-based cementitious material using activated magnesium oxide to induce chloride salts from waste incineration fly ash according to claim 4 or 5, characterized in that: The copper-containing electroplating sludge in step S1 is required to have a particle size that passes 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.

7. The method for preparing a solid waste-based cementitious material using activated magnesium oxide to induce chloride salts from waste incineration fly ash according to claim 6, 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.

8. The method for preparing a solid waste-based cementitious material using activated magnesium oxide to induce chloride salts from fly ash from garbage incineration according to claim 4, 5 or 7, 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.

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