A ternary geopolymer immobilizing heavy metal ions and a method for preparing the same

Abstract

The present application relates to the technical field of solid waste resource, and particularly relates to a ternary geopolymer capable of solidifying heavy metal ions and a preparation method thereof.The present application provides a preparation method of the ternary geopolymer capable of solidifying heavy metal ions, which comprises the following steps: mixing fly ash, pyrolysis residue, slag, standard sand and alkaline active agent to obtain a powder mixture, and mixing the powder mixture with water to solidify and obtain the ternary geopolymer.The ternary geopolymer prepared by the present application can achieve 99.90% solidification efficiency on Pb and Mn, and more than 90% reduction of Cl in the fly ash and more than 80% reduction of petroleum hydrocarbon in the pyrolysis residue.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to a ternary geopolymer capable of solidifying heavy metal ions and its preparation method. Background Technology

[0002] Crude oil is the lifeblood of modern industry. In 2023, global oil production reached 4.51 billion tons. However, the extraction and transportation of crude oil inevitably generate large amounts of oil-sludge (OS). Statistics show that every 1,000 tons of crude oil produced results in the emission of 5 tons of OS. Currently, China's OS inventory exceeds 140 million tons.

[0003] Due to its hazardous characteristics, organic waste (OS) has been classified as hazardous waste in many countries. Improper OS disposal can cause serious soil and groundwater pollution, and the emitted malodorous gases can enter the atmosphere, causing unpredictable damage to the ecological environment and human health. Currently, pyrolysis can simultaneously achieve the dual goals of harmless disposal and resource utilization of OS, and has become an important OS disposal technology. Under anaerobic or anoxic conditions, OS can be degraded into high-calorific-value pyrolysis gas and oil at 500–800℃; simultaneously, pyrolysis residue (PR) is discharged from the bottom of the furnace, and fly ash (FA) is collected by bag filters.

[0004] The obtained PR and FA contain small amounts of total petroleum hydrocarbons (TPHs) and heavy metals (HMs). Since the oil content of PR and FA is above 0.3 wt%, they cannot be directly used in agriculture. Therefore, the PR and FA produced by OS pyrolysis become unusable solid waste products. Summary of the Invention

[0005] This invention provides a ternary geopolymer capable of solidifying heavy metal ions and its preparation method. Pyrolysis residues and fly ash, the products of oil sludge pyrolysis, cannot be recycled or utilized due to their inherent oil content. This invention utilizes the presence of inorganic materials such as silicon dioxide, aluminum oxide, and calcium oxide in pyrolysis residues and fly ash, blending them with slag and standard sand. By reducing the amount of slag and standard sand used, the pyrolysis residues and fly ash are consumed. Simultaneously, a usable ternary geopolymer is obtained, achieving a solidification rate of over 99.90% for Pb and Mn in the pyrolysis residues and fly ash, a reduction rate of over 90% for Cl in fly ash, and a reduction rate of over 80% for petroleum hydrocarbons in the pyrolysis residues. This significantly reduces the environmental risk of pyrolysis residues and fly ash and achieves solid waste resource utilization.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a ternary geopolymer capable of solidifying heavy metal ions, comprising: mixing fly ash, pyrolysis residue, slag, standard sand and alkaline activator to obtain a powder mixture, and then solidifying the powder mixture with water to obtain a ternary geopolymer; wherein the fly ash and the pyrolysis residue are both pyrolysis products of oily sludge, and the oil content in the pyrolysis residue is 2-3 wt%;

[0008] The fly ash comprises, by weight, 48-50 parts CaO, 1-2 parts SiO2, 0.5-1 parts Al2O3, 1-1.5 parts Fe2O3, 1-1.5 parts MgO, 6-7 parts Na2O, 10-11 parts K2O, 8-9 parts SO3, 0.5-1 parts BaO, 0.1-0.2 parts PbO, 2-3 parts haloalkane compounds, 11-12 parts free chlorine, and 4-5 parts free fluorine.

[0009] The pyrolysis residue comprises, by weight, 12-13 parts CaO, 25-28 parts SiO2, 7-9 parts Al2O3, 6-7 parts Fe2O3, 2-3 parts MgO, 1-2 parts Na2O, 1-1.5 parts K2O, 14-15 parts SO3, 14-15 parts BaO, 0.2-0.3 parts TiO2, 0.01-0.05 parts PbO, 0.1-0.2 parts MnO, 9-10 parts haloalkane compounds, and 0.2-0.4 parts free chlorine;

[0010] The slag composition is as follows: by weight, it includes 30-35 parts CaO, 28-33 parts SiO2, 16-18 parts Al2O3, 0.2-0.4 parts Fe2O3, 10-11 parts MgO, 0.5-0.7 parts Na2O, 0.3-0.4 parts K2O, 2-3 parts SO3, 0.8-0.9 parts TiO2, 0.2-0.3 parts MnO, 2-3 parts haloalkane compounds, and 0.05-0.07 parts free chlorine.

[0011] Fly ash has a smaller particle size and a composition similar to slag, making it a suitable substitute for slag. Pyrolysis residue, on the other hand, has a larger particle size and can replace standard sand as aggregate. Furthermore, both fly ash and pyrolysis residue possess a hierarchical porous structure, facilitating the adsorption and locking of free ions. The pyrolysis residue and fly ash used in this invention are products of oil sludge pyrolysis, thus containing a small amount of oil. The organic matter in this oil may adsorb moisture, altering the distribution of moisture during the hydration process, leading to weaker localized hydration reactions and insufficient strength in certain areas. Additionally, the saturated light hydrocarbons in the oil readily volatilize during the hydration stage, forming pores and microcracks, significantly reducing the material's strength.

[0012] Furthermore, considering that under normal circumstances, the overall strength of geopolymers will decline significantly after the introduction of solid wastes such as fly ash, small-particle fly ash is added to replace part of the slag, and large-particle pyrolysis residue is used to replace part of the standard sand to construct a richer particle size distribution and slow down the drastic strength decline after the addition of fly ash and pyrolysis residue.

[0013] Solid waste composed of fly ash and pyrolysis residue, along with slag and standard sand, can serve as ternary Si-Al-Ca precursors. Upon addition of an alkaline activator, the Si-Al-Ca precursors further form a dense network and gel. During alkaline activation, heavy metals Pb and Mn in the fly ash and pyrolysis residue are solidified within the gel network structure. Free chlorine and free fluorine are adsorbed within the porous structure of the fly ash and pyrolysis residue and onto the surface of inorganic particles in the gel network. Halogenated alkane compounds can be adsorbed into the three-dimensional network structure and fixed in the ternary geopolymer through physical adsorption or by chemical bonding with the active aluminosilicate component. Therefore, while obtaining ternary geopolymers, the problems of heavy metal leaching, chlorine leaching, and halogenated alkane compound pollution can be solved, achieving environmental protection.

[0014] Preferably, the mass ratio of fly ash to slag is 1:2 to 1:9, the mass ratio of pyrolysis residue to standard sand is 1:2 to 1:9, and the mass ratio of slag to standard sand is 1:3.

[0015] More preferably, the mass ratio of fly ash to slag is 1:3 to 1:5, the mass ratio of pyrolysis residue to standard sand is 1:3 to 1:5, and the mass ratio of slag to standard sand is 1:3.

[0016] More preferably, the mass ratio of fly ash to slag is 1:3.5 to 1:4.6, the mass ratio of pyrolysis residue to standard sand is 1:3.5 to 1:4.6, and the mass ratio of slag to standard sand is 1:3.

[0017] More preferably, the mass ratio of fly ash to slag is 1:4, the mass ratio of pyrolysis residue to standard sand is 1:4, and the mass ratio of slag to standard sand is 1:3.

[0018] More preferably, the mass ratio of fly ash to slag is 1:4 to 1:9, the mass ratio of pyrolysis residue to standard sand is 1:4 to 1:9, and the mass ratio of slag to standard sand is 1:3.

[0019] More preferably, the mass ratio of fly ash to slag is 1:9, the mass ratio of pyrolysis residue to standard sand is 1:9, and the mass ratio of slag to standard sand is 1:3.

[0020] Preferably, the amount of alkaline activator is 28 to 32 parts, based on the sum of the weights of the fly ash and slag.

[0021] More preferably, the amount of alkaline activator is 30 parts, based on the sum of the weights of the fly ash and slag.

[0022] Preferably, the alkaline activator is sodium hydroxide and sodium silicate.

[0023] Preferably, the mass ratio of the powder mixture to the water is (5-8):1.

[0024] Preferably, the fly ash has a particle size of 5-10 μm, the pyrolysis residue has a particle size of 30-50 μm, the slag has a particle size of 5-10 μm, and the standard sand has a particle size of 0.08-2 mm.

[0025] Particles of different sizes can fill different voids, contributing to a denser microstructure; gradient particle size design also helps improve the flowability and workability of ternary geopolymers. Micron-sized particles of fly ash, slag, and pyrolysis residues can provide better mechanical properties on a macroscopic scale, while also contributing to the formation of a continuous three-dimensional network structure. Millimeter-sized particles of standard sand primarily serve as aggregates, increasing material stability, preventing shrinkage cracking, and improving compressive strength.

[0026] Preferably, the curing conditions are: curing at 20-25°C for 1-2 days; followed by curing at 20-25°C and 55-65% humidity for 7-28 days.

[0027] The present invention also provides a ternary geopolymer for solidifying heavy metal ions prepared by the above preparation method, which has a solidification rate of more than 99.90% for both Pb and Mn, a reduction rate of more than 90% for Cl in fly ash, and a reduction rate of more than 80% for petroleum hydrocarbons in pyrolysis residue.

[0028] Preferably, after 30 days of freeze-thaw cycles or 30 days of acid rain erosion, the compressive strength of the ternary geopolymer capable of curing heavy metal ions is more than 95% of the compressive strength of the ternary geopolymer capable of curing heavy metal ions after 28 days of curing.

[0029] Therefore, the present invention has the following beneficial effects:

[0030] (1) This invention uses fly ash to replace part of the slag and pyrolysis residue to replace part of the standard sand, thus solving the solid waste pollution problem of fly ash and pyrolysis residue and obtaining ternary geopolymer materials that meet the application standards.

[0031] (2) The present invention ensures the strength of ternary geopolymer by compounding the ratio of fly ash and slag, the ratio of pyrolysis residue and standard sand, and the gradient particle size of fly ash, pyrolysis residue, slag and standard sand. The obtained ternary geopolymer can still maintain high compressive strength under extreme environments such as extreme cold and acid rain.

[0032] (3) The ternary geopolymer preparation method provided by the present invention can achieve a solidification efficiency of 99.90% for Pb and Mn in pyrolysis residue and fly ash, and achieve a reduction of more than 90% for Cl in fly ash and a reduction of more than 80% for petroleum hydrocarbons in pyrolysis residue. Attached Figure Description

[0033] Figure 1 The images are PSD and SEM images of fly ash, pyrolysis residue and slag, where a to c are the PSD images of fly ash, pyrolysis residue and slag respectively, and d to f are the SEM images of fly ash, pyrolysis residue and slag respectively.

[0034] Figure 2 XRD patterns of fly ash, pyrolysis residue and slag;

[0035] Figure 3 The diagram shows the curing capacity of ternary geopolymers, where a represents the curing capacity of Pb, b represents the curing capacity of Mn, c represents the curing capacity of chloride ions, and d represents the curing capacity of TPHs.

[0036] Figure 4 The strength of the ternary geopolymer is given by , where a is the compressive strength at 7d and 28d, and b is the ratio of the compressive strength at 7d / 28d.

[0037] Figure 5 The results represent the mass loss due to freeze-thaw cycles and acid rain corrosion, where a is the mass loss of the ternary geopolymer after 30 freeze-thaw cycles, c is the loss rate of the ternary geopolymer after 30 freeze-thaw cycles, b is the mass loss of the ternary geopolymer after 30 days of acid rain corrosion, and d is the loss rate of the ternary geopolymer after 30 days of acid rain corrosion.

[0038] Figure 6 The results of the environmental risk assessment of the geopolymer after a 30-day durability test are shown, where a is the Pb leaching concentration, b is the Mn leaching concentration, c is the Cl content, and d is the TPH content.

[0039] Figure 7 The results show the compressive strength of the ternary geopolymer, where a is the compressive strength of the ternary geopolymer after 30 days of durability testing, and b is the ratio of the compressive strength of the ternary geopolymer after 30 days of durability testing to that after 28 days.

[0040] Figure 8 The images show fragments of the F00P00 sample, where a represents 28 days of curing, b represents 30 days of freeze-thaw cycles, and c represents 30 days of acid rain corrosion.

[0041] Figure 9 Comparative analysis of the hydration characteristics of F00P00 under different conditions is presented, where a is the XRD diffraction pattern, b is the FTIR spectrum, c is the TG curve, d is the DTG curve, e1 is the SEM image after freeze-thaw cycle, and e2 is the SEM image after acid rain corrosion. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0043]

Example

[0044] The slag in this section was purchased from Longze Water Purification Materials Co., Ltd. in Gongyi City, Henan Province, with a particle size of 5-10μm; the standard sand was purchased from Xiamen Aisiou Standard Sand Co., Ltd., which is a legal benchmark material equivalent to the international standard ISO679 for testing cement strength, with a particle size of 0.08-2mm; sodium hydroxide (NaOH), with a purity of 95%, was purchased from Mairuier; sodium silicate (Na2O·2SiO2), with a purity of 98%, was purchased from Mairuier.

[0045] In this section, fly ash and pyrolysis residue are products obtained from the pyrolysis of oily sludge. The specific components of fly ash, pyrolysis residue, and slag are shown in Tables 1 and 2, and the specific composition of oily sludge is shown in Tables 3 and 4.

[0046] Table 1 Chemical Composition Table 1

[0047]

[0048] Table 2 Chemical Composition Table 2

[0049]

[0050] Table 3. Elemental composition of oily sludge (wt.%)

[0051]

[0052] Table 4. Industrial Analysis of Oily Sludge (wt.%)

[0053]

[0054] Example 1

[0055] Weigh fly ash, pyrolysis residue, slag, standard sand, and alkaline activator according to the proportions in Table 5, and mix for 120 seconds. Then add water and mix for another 120 seconds to obtain a homogeneous mortar. Pour the mortar into a mold, cure at room temperature for 1 day, then demold. Subsequently, cure in a constant temperature and humidity environment (20℃, 60%) for 7 or 28 days. The alkaline activator, prepared by mixing sodium hydroxide and sodium silicate, has a modulus of 1.5.

[0056] Except for the specific formulations as shown in Table 5, the preparation methods of the other examples and comparative examples are exactly the same as those in Example 1.

[0057] Table 5. Proportions of ternary geopolymers

[0058]

[0059]

[0060] [Performance Testing]

[0061] 1. Performance evaluation of fly ash and pyrolysis residue

[0062] Toxicity evaluation and heavy metal leaching experiments were conducted on fly ash and pyrolysis residue, and the results are shown in Tables 6 and 7.

[0063] Table 6 Toxicity evaluation of fly ash and pyrolysis residue

[0064]

[0065] Table 7. Heavy metal leaching results (mg / L) from fly ash and pyrolysis residue.

[0066]

[0067] The heavy metal leaching results of fly ash and pyrolysis residue obtained in Table 7 are compared with the standards proposed by the U.S. Environmental Protection Agency, GB5085.3-2007 "Standard for Identification of Hazardous Waste - Leaching Toxicity Identification", GB16889-2008 "Standard for Pollution Control of Municipal Solid Waste Landfills", and GB18598-2019 "Standard for Pollution Control of Hazardous Waste Landfills". The heavy metal leaching amounts all meet the emission standards. However, the leaching amounts of Pb in fly ash and Mn in pyrolysis residue are relatively large, which may pose environmental safety problems for production and application.

[0068] 2. Morphological evaluation of fly ash, pyrolysis residue and slag

[0069] PSD tests were performed on fly ash, pyrolysis residue, and slag, and the results are as follows: Figure 1 a~ Figure 1As shown in c, observations show that fly ash and pyrolysis residue have a hierarchical porous structure. The average particle size of fly ash is 6.2 μm, and the average particle size of slag is 6.3 μm. Based on particle size and composition, fly ash can be used as a replacement material for slag. The pyrolysis residue has a larger particle size, with an average particle size of 37.9 μm.

[0070] SEM analysis was performed on fly ash, pyrolysis residue, and slag, and the results are as follows: Figure 1 d~ Figure 1 As shown in f, observations show that fly ash, pyrolysis residue, and slag are irregular particles of different sizes, and their particle size ranges are consistent with the results of PSD.

[0071] XRD tests were performed on fly ash, pyrolysis residue, and slag, and the results are as follows: Figure 2 As shown in the figure, it can be observed that the peaks corresponding to the important components appearing in Tables 1 and 2 can all be detected by XRD.

[0072] 3. Performance evaluation of ternary geopolymers

[0073] ① Curing ability of heavy metals / Cl / TPHs

[0074] The curing ability of the ternary geopolymers or geopolymers prepared in Examples 1-3 and Comparative Examples 1-7 was tested, and the curing ability for Pb, Mn, chloride ions and TPHs was tested respectively. The results are as follows: Figure 3 As shown.

[0075] observe Figure 3 a and Figure 3 b shows that, observing the data from the three sets of F10P00, F20P00, and F30P00, it can be seen that as the amount of fly ash added increases, its inherent Pb content is high, thus the Pb curing ability of the corresponding ternary geopolymer decreases, while the Mn curing ability of the corresponding ternary geopolymer increases. The ternary geopolymers or geopolymers prepared in Examples 1-3 and Comparative Examples 1-7 all have Pb and Mn curing abilities of over 98%, and the ternary geopolymers prepared in Examples 1-3 have Pb and Mn curing abilities of over 99.90%.

[0076] In addition, the ternary geopolymers prepared in Examples 1 to 3 also have good chloride ion curing efficiency, reaching over 87%; the curing efficiency for TPHs is over 63%, which can fix most of the petroleum hydrocarbons and solve the problem that oil in fly ash and pyrolysis residues hinders their resource utilization.

[0077] ②Intensity

[0078] The compressive strength of the ternary geopolymers or geopolymers prepared in Examples 1-3 and Comparative Examples 1-7 was tested, and the results are as follows: Figure 4 As shown.

[0079] observe Figure 4 As can be seen from point a, the compressive strength of the ternary geopolymer decreases significantly with the addition of fly ash and pyrolysis residue. It is noteworthy that observation... Figure 4 As shown in b, the compressive strength of the geopolymers under the three formulations F10P00, F20P00, and F20P60 after 7 days of curing is higher than that after 28 days of curing. The strength ratios of F10P00 and F20P00 are slightly higher than 100%, while the strength ratio of F20P60 reaches 105%.

[0080] ③Durability

[0081] The ternary geopolymers or geopolymers obtained in Examples 1-3 and Comparative Example 1 were subjected to 30-day freeze-thaw cycle tests and 30-day acid rain corrosion tests. The test methods are as follows, and the results are recorded in [the relevant section]. Figures 5-9 As shown.

[0082] Test method: The geopolymer sample was immersed in distilled water at 20±2℃ for 48 hours to saturate the water inside. The sample was then dried and allowed to stand for 30 minutes. Freeze-thaw cycle test: The geopolymer was frozen at -20±2℃ for 12 hours, then immersed in water at 20±2℃ for 12 hours, with the water level 20mm above the top of the sample. The performance of the sample was tested after 6, 12, 18, 24, and 30 freeze-thaw cycles. Acid rain corrosion test: Acid rain mainly consists of sulfuric acid and nitric acid. my country is a country with sulfuric acid-type acid rain because SO4... 2- Its contribution to acid rain acidity is far greater than that of NO3. - It has been reported that acid rain with a pH between 3.0 and 5.0 severely affects the mechanical properties and durability of concrete. In this study, sulfuric acid and nitric acid were used to simulate acid rain with a pH of 3.0, with a sulfuric acid to nitric acid molar ratio of 9:1. Weighed samples were immersed in the simulated acid rain solution, with the solution level 20 mm above the top of the specimen. The performance of the samples was tested after 6, 12, 18, 24, and 30 days.

[0083] 1) Results of quality loss

[0084] After 30 freeze-thaw cycles and 30 days of acid rain corrosion, the sample mass loss and loss rate are as follows: Figure 5 As shown. Overall, the samples exhibit good stability. Under the continuous action of freeze-thaw cycles, the sample structure was damaged, and the mass loss increased continuously. However, even after 30 tests, the mass loss remained below 1%. Figure 5 c). A possible reason is that during the freeze-thaw cycle, water may have further participated in the reaction and formed the bound water portion of the hydration products. At the same time, some water was absorbed and stored by the pores, both of which delayed the mass loss of the sample.

[0085] The mass change caused by 30 days of acid rain corrosion can be roughly divided into three stages. After 6 days of acid rain corrosion, the mass loss of the sample continuously increased and reached its maximum value (approximately 1-2%). During this process, particle detachment from the sample surface was observed. In H... + and SO4 2- Under the combined corrosion of acid rain and other factors, CaO and Al2O3 are eroded and dissolved, resulting in mass loss. During the 6–24 day corrosion process, the mass loss of the sample showed a continuous decreasing trend. This interesting phenomenon may stem from two aspects: firstly, during the immersion process, water continuously permeates through the pores on the block surface into the geopolymer matrix and participates in the hydration reaction; secondly, SO4 in the acid rain... 2- With some cations (e.g., Mg) 2+ Fe 2+ and Zn 2+ The aggregates combine to form crystals, which fill the pores and increase the density of the matrix. However, during the 24–30 day stage, mass loss began to increase in all samples. This indicates that acid rain corrosion once again became dominant, and the new hydration products could no longer compensate for the particle detachment caused by structural damage. The hydrated silicates on the corroded specimen surface transformed into CaSO4, reducing the adhesion between the aggregate and the gel, which directly led to the detachment of fine sand. From a longer-term perspective, the continuous mass loss of the samples after freeze-thaw cycles and acid rain corrosion is an inevitable trend, ultimately leading to the disintegration of the sample structure.

[0086] 2) Environmental risk assessment

[0087] In practical applications, solid waste-based building materials often expose greater environmental risks after long-term exposure to deteriorating environments. Therefore, it is necessary to conduct environmental risk assessments on samples after durability testing. It is not difficult to find that freeze-thaw cycles and acid rain corrosion did not significantly affect the ability of ternary geopolymers to solidify harmful substances. Figure 6 a and Figure 6 b shows the leaching and stabilization efficiency of typical heavy metals in ternary geopolymers F10P30, F20P60, and F30P90. The leaching concentrations of Pb and Mn in the samples were all below 0.01 mg / L, and the corresponding heavy metal stabilization efficiency remained above 99%. Figure 6 c and Figure 6 As shown in section d, the ternary geopolymer reduced the chloride ion and TPH content in solid waste by more than 90% and 60%, respectively, and the encapsulation effect of the geopolymer matrix on inorganic ions and organic matter was not weakened. In conclusion, after durability testing, the ternary geopolymer still exhibited low environmental risk characteristics.

[0088] 3) Compressive strength

[0089] Figure 7 The compressive strength results of the samples after 30 days of freeze-thaw cycles and acid rain corrosion are presented. Surprisingly, compared to samples cured under conventional conditions for 28 days, all durability test samples exhibited a strength retention rate of over 95%. More notably, the strength of most samples was even higher than that of the conventionally cured samples. After 30 days of acid rain corrosion, the compressive strength of sample F00P00 reached nearly 90 MPa, 1.15 times that under conventional conditions. This indicates that, regardless of whether it's freeze-thaw cycles or acid rain corrosion, prolonged immersion allows moisture to participate in the hydration reaction of the samples, increasing hydration products and thus forming a denser matrix. The compressive strength of the samples after freeze-thaw cycles is slightly lower than that of the acid rain-corroded samples. This is likely related to the experimental process, namely, that the freeze-thaw process of the samples was an intermittent immersion process, resulting in a lower overall degree of hydration gel development compared to samples subjected to continuous acid rain immersion.

[0090] 4) Hydration characteristics

[0091] Using sample F00P00 as a reference, the hydration characteristics of geopolymer samples under deteriorated conditions were further compared and analyzed. Figure 8 It is clearly observed that the interior of the 28-day cured specimens is grayish-white, and the overall structure is dry and brittle. In contrast, the specimens that underwent the 30-day durability test all exhibited a dark gray interior, with the matrix tightly bonded to the sand and gravel. This corresponds to the compressive strength results. Clearly, Figure 8 b and Figure 8 The sample in c absorbed more water, and the development of hydration products was more complete.

[0092] To gain a deeper understanding of the differences in the hydration characteristics of the samples under different environments, a series of characterization analyses were conducted. Figure 9 XRD diffraction patterns of F00P00 are shown. Significant differences in peak intensities are observed between quartz and calcite (or C-(A)-SH gel), primarily observed in the acid rain corrosion sample showing the strongest diffraction peak, followed by the freeze-thaw cycle sample, and the lowest in the conventionally cured sample. This again relates to the compressive strength of the sample ( Figure 7 Correspondingly. Furthermore, it can be seen from the FTIR spectrum that ( Figure 9 b) shows significant differences in wavebands representing (C,N)-ASH, Si-OT, and Si-O. The peak area of ​​the sample after durability testing is larger, indicating a change in the chemical environment of Si and the formation of a gel with a higher degree of polymerization. The TG curves show that the acid rain corrosion sample has slightly higher stability than the freeze-thaw cycle sample, and both are significantly higher than the 28-day sample. Figure 9c). The mass loss of F00P00 can be roughly divided into two stages. The first stage mainly involves the dehydration of hydration products between 30 and 200°C, while the second stage mainly represents the dehydration and decarbonization behavior of a small portion of other products and calcite between 200 and 750°C. Corresponding to the DTG curves, it can be found that the peak area of ​​the 28-day sample at 30–200°C is significantly higher than the other two. However, this does not necessarily mean a reduction in the content of hydration products. After undergoing a more complete hydration reaction, the degree of polymerization of the C-(A)-SH gel is enhanced, and the amount of bound water is reduced, which will ultimately promote the strength development of the sample. Meanwhile, the SEM microscopic images of the samples under different environments also show significant differences. The gel of the sample after freeze-thaw cycles is smoother and denser, with a small number of scattered gel particles distributed on the matrix. Figure 9 e1). And in Figure 9 e2 observations showed that the gel clusters and layered gels in the acid rain corrosion samples were interlinked and tightly adhered to the fine sand particles. Overall, after 30 days of durability testing, the simulated harsh environment did not cause significant damage to the samples; on the contrary, the hydration reaction was promoted, and the gel development was better, which confirms the high stability and strong resistance to degradation of the geopolymer.

Claims

1. A method for preparing a ternary geopolymer capable of solidifying heavy metal ions, characterized in that, include: Fly ash, pyrolysis residue, slag, standard sand, and alkaline surfactant are mixed to obtain a powder mixture. This powder mixture is then mixed with water and solidified to obtain a ternary geopolymer. Both the fly ash and the pyrolysis residue are pyrolysis products of oily sludge, with the pyrolysis residue containing 2-3 wt% oil. The fly ash comprises, by weight, 48-50 parts CaO, 1-2 parts SiO2, 0.5-1 parts Al2O3, 1-1.5 parts Fe2O3, 1-1.5 parts MgO, 6-7 parts Na2O, 10-11 parts K2O, 8-9 parts SO3, 0.5-1 parts BaO, 0.1-0.2 parts PbO, 2-3 parts haloalkane compounds, 11-12 parts free chlorine, and 4-5 parts free fluorine. The pyrolysis residue comprises, by weight, 12-13 parts CaO, 25-28 parts SiO2, 7-9 parts Al2O3, 6-7 parts Fe2O3, 2-3 parts MgO, 1-2 parts Na2O, 1-1.5 parts K2O, 14-15 parts SO3, 14-15 parts BaO, 0.2-0.3 parts TiO2, 0.01-0.05 parts PbO, 0.1-0.2 parts MnO, 9-10 parts haloalkane compounds, and 0.2-0.4 parts free chlorine; The slag composition is as follows: by weight, it includes 30-35 parts CaO, 28-33 parts SiO2, 16-18 parts Al2O3, 0.2-0.4 parts Fe2O3, 10-11 parts MgO, 0.5-0.7 parts Na2O, 0.3-0.4 parts K2O, 2-3 parts SO3, 0.8-0.9 parts TiO2, 0.2-0.3 parts MnO, 2-3 parts haloalkane compounds, and 0.05-0.07 parts free chlorine; The mass ratio of fly ash to slag is 1:4, the mass ratio of pyrolysis residue to standard sand is 1:4, and the mass ratio of slag to standard sand is 1:

3. The fly ash has a particle size of 5~10μm, the pyrolysis residue has a particle size of 30~50μm, the slag has a particle size of 5~10μm, and the standard sand has a particle size of 0.08~2mm. The curing conditions are as follows: at 20~25℃, curing for 1~2 days; then at 20~25℃ and 55~65% humidity, curing for 7~28 days.

2. The preparation method according to claim 1, characterized in that, With the total weight of the fly ash and slag being 100 parts, the weight of the alkaline activator is 30 parts.

3. The preparation method according to claim 1, characterized in that, The alkaline activator is sodium hydroxide and sodium silicate.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the powder mixture to the water is (5~8):

1.

5. The ternary geopolymer containing solidifiable heavy metal ions prepared by the preparation method according to any one of claims 1 to 4, characterized in that, The curing rates of Pb and Mn are both above 99.90%, the reduction rate of Cl in fly ash is above 90%, and the reduction rate of petroleum hydrocarbons in pyrolysis residue is above 80%.

6. The ternary geopolymer capable of solidifying heavy metal ions as described in claim 5, characterized in that, After 30 days of freeze-thaw cycles or 30 days of acid rain erosion, the compressive strength of the ternary geopolymer capable of curing heavy metal ions is more than 95% of the compressive strength of the ternary geopolymer capable of curing heavy metal ions after 28 days of curing.

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