Method for coal gasification ash reconstruction lattice solidification and synergistic adsorption of heavy metals

Abstract

This invention relates to the field of high-value-added utilization of coal-based solid waste and heavy metal pollution control technology, specifically a method for the reconstruction of lattice solidification and synergistic adsorption of heavy metals in coal gasification ash. Addressing the problem of easy secondary leaching of heavy metals from coal gasification ash, this invention proposes a "step-by-step in-situ solidification-synergistic self-purification" mechanism. Heavy metal-containing coal gasification ash is mixed with sodium hydroxide and calcium oxide, and pretreated with mechanical activation and high-temperature activation to obtain activated clinker, achieving initial solidification of endogenous heavy metals. Through water bath aging and hydrothermal crystallization reactions, the precursor is driven to reconstruct the tobermorite crystal phase, causing isomorphic substitution of heavy metal ions and achieving deep in-situ solidification of the lattice. The generated geopolymer-type tobermorite is used for closed-loop adsorption and purification of process wastewater, and can be extended to the synergistic adsorption of exogenous heavy metal wastewater. This invention effectively blocks the risk of secondary heavy metal leakage, achieving near-zero discharge of process wastewater and "waste-to-waste" treatment of hazardous solid waste.

Description

Technical Field

[0001] This invention relates to the field of high-value-added utilization of coal-based solid waste and prevention and control of heavy metal pollution, specifically a method for reconstructing and solidifying the crystal lattice of coal gasification ash and synergistic adsorption of heavy metals. Background Technology

[0002] Coal is my country's primary energy source, and the core of its clean and efficient utilization lies in coal gasification technology. However, the coal gasification process generates a large amount of solid waste. According to incomplete statistics, my country produces more than 50 million tons of coal gasification slag annually. Currently, this gasification slag is mainly disposed of through extensive stockpiling and landfilling, which not only significantly increases the disposal costs for enterprises and occupies a large amount of land resources, but also the heavy metals and other harmful components contained in the slag are highly susceptible to causing serious environmental pollution when leached by rainwater.

[0003] For the treatment of waste containing heavy metals, existing technologies mostly employ simple physical coating with traditional cement. This method is highly susceptible to re-leaching under long-term weathering or acid / alkali erosion. In recent years, geopolymers, due to their unique three-dimensional aluminosilicate network structure, have demonstrated excellent physical trapping and chemical bonding capabilities for heavy metals, becoming a research hotspot in the fields of solid waste resource utilization and heavy metal solidification. However, the long-term solidification stability of traditional amorphous geopolymers for certain highly toxic heavy metals remains limited, and heavy metal solidification and the synthesis of high-value environmentally friendly materials are often separate processes, making it difficult to maximize the economic benefits of "treating waste with waste."

[0004] Furthermore, in exploring ways to prepare environmentally friendly materials such as hydrated calcium silicate (CSH) or crystalline tobermorite with high adsorption capacity from coal gasification ash, existing single activation methods have limited efficiency. More importantly, the waste liquid generated after hydrothermal synthesis usually contains trace amounts of free heavy metal ions and residual alkali. Direct discharge would pose a significant secondary environmental hazard, and existing processes generally lack an effective closed-loop mechanism for recapturing and recycling heavy metals in the waste liquid.

[0005] Therefore, in view of the technical pain points of the existing solid waste treatment and high-value synthesis phase separation, and the high likelihood of generating secondary pollution waste liquid, there is an urgent need to develop a combined recycling treatment process based on the "step-by-step in-situ solidification-synergistic self-purification" mechanism. Summary of the Invention

[0006] To address the shortcomings of existing heavy metal ion solidification technologies, such as poor stability, susceptibility to secondary leaching, and the difficulty in achieving closed-loop source treatment of large quantities of coal gasification solid waste, this invention provides a method for reconstructing lattice solidification and synergistic adsorption of heavy metals from coal gasification ash.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for reconstructing and solidifying the crystal lattice of coal gasification ash and synergistically adsorbing heavy metals includes the following steps:

[0009] Step 1, Source Connection and Activation Pretreatment: Mix coal gasification ash containing heavy metals with sodium hydroxide and calcium oxide, and perform mechanical activation and high-temperature activation pretreatment to obtain activated clinker;

[0010] Step 2, Water bath aging: Add deionized water to the activated clinker and carry out water bath heating and stirring aging to obtain tobermorite precursor slurry;

[0011] Step 3, hydrothermal deep crystallization: The tobermorite precursor slurry is transferred to a reactor for hydrothermal crystallization reaction. After the reaction, the mixture is separated into solid and liquid, washed and dried to obtain geopolymer tobermorite material and process waste liquid.

[0012] Step 4, Closed-loop purification of process wastewater: At least a portion of the tobermorite material obtained in step 3 is added to the process wastewater for adsorption and purification.

[0013] Step 5, Co-adsorption of exogenous wastewater: The tobermorite material obtained in step 3 is added to exogenous heavy metal wastewater for adsorption and purification.

[0014] As a further aspect of the present invention: the coal gasification ash includes coarse coal gasification ash and / or fine coal gasification ash.

[0015] As a further embodiment of the present invention: the coal gasification ash residue comprises, by mass percentage: 45.0%-60.0% silicon dioxide, 10.0%-20.0% aluminum oxide, 5.0%-15.0% calcium oxide, 5.0%-12.0% iron oxide, 1.0%-5.0% sulfur trioxide, 1.0%-4.0% potassium oxide, 0.5%-3.0% phosphorus pentoxide, and 0.5%-3.0% magnesium oxide.

[0016] As a further aspect of the present invention: in step 1, the amount of sodium hydroxide added is calculated based on the liquid-solid ratio of the hydrothermal crystallization reaction in the subsequent step 3, so that the initial concentration of sodium hydroxide in the liquid phase of the hydrothermal crystallization reaction is controlled at 1.8-2.2 mol / L.

[0017] As a further aspect of the present invention: in step 1, the amount of calcium oxide added is such that the molar ratio of calcium to silicon in the reaction system is 0.8-1.2.

[0018] As a further aspect of the present invention: in step 1, the mechanical activation is ball milling, with a ball milling speed of 450-550 r / min and a ball milling time of 20-40 min; the high-temperature activation is calcination at 800-900℃ under a nitrogen atmosphere at a heating rate of 5-20℃ / min and holding at that temperature for 0.5-1.5 h.

[0019] As a further aspect of the present invention: in step 2, the solid-liquid ratio of deionized water added is 1:10-1:30 g / ml, the water bath heating temperature is 80-90℃, and the aging and stirring time is 30-60 minutes.

[0020] As a further aspect of the present invention: in step 3, the temperature of the hydrothermal crystallization reaction is 130-180℃, and the reaction time is 12-24 hours.

[0021] As a further aspect of the present invention: in steps 4 and 5, the dosage of the tobermorite material is 0.05-0.15 g / L, and the adsorption contact time is 8-24 h.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] (1) The present invention adopts mechanical cell disruption and alkali-calcium synergistic thermal activation process to reduce the reaction activation energy and reduce the roasting temperature to 800-900℃, effectively breaking the inert network of fine slag, while avoiding the volatilization critical point of low boiling point heavy metals such as As and Pb, thus eliminating the risk of heavy metal gasification escape from the source.

[0024] (2) This invention induces the amorphous gel to reconstruct crystalline tobermorite, and uses isomorphous substitution to embed heavy metal ions into the lattice, realizing the transformation from physical embedding to chemical solid solution, which significantly improves the curing stability. The comprehensive curing rates of As, Se and Mn can reach 64.8%, 69.5% and 71.8%, respectively.

[0025] (3) The tobermorite prepared by this invention has a porous layered structure and a retention rate of over 87% for residual heavy metal ions in process wastewater, achieving near-zero wastewater discharge; it also has excellent purification capabilities for exogenous wastewater, particularly for Zn. 2+ and Cr 6+ The adsorption capacities are 98.9 mg / g and 27.2 mg / g, respectively.

[0026] (4) The raw material of this invention is bulk solid waste, the process is simple, no expensive inducing agent is required, the energy consumption is low, and the resource utilization of hazardous solid waste and "waste treatment" are realized, which has good application prospects. Attached Figure Description

[0027] Figure 1 This is a general technical roadmap of the method of the present invention.

[0028] Figure 2 This is an industrial process diagram of the method of the present invention.

[0029] Figure 3 The image shows the XRD pattern of the geopolymer-type tobermorite prepared in this invention. Detailed Implementation

[0030] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0031] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0032] Figure 1 This is a general technical roadmap of the method of the present invention. Figure 2 This is an industrial process diagram of the method of the present invention. Figure 1 and Figure 2 As shown, this invention innovatively integrates the source ash discharge of coal chemical industry with downstream high-value treatment, constructing a co-production and recycling system of "cascade solidification-synergistic purification". This system directly connects to the bottom ash discharge of the coal gasification production unit, directly introducing the separated ash rich in heavy metals into the system. Firstly, the inert network of the fine ash is deconstructed through mechanical grinding and chemical activation steps, achieving the removal of inherent Mn in the system. 2+ As 3+ Preliminary pre-curing via plasma; then, through precise control of the Ca / Si molar ratio of the system, in-situ synthesis of geopolymer-type tobermorite via aging and high-pressure hydrothermal reaction, driving phase transformation and reconstruction of the amorphous precursor, utilizing its unique lattice channel structure to promote Al 3+ Pb 2+ The synthesis of tobermorite-based composite materials not only utilizes the isomorphous substitution of heavy metal ions to achieve closed-loop purification of the residual liquid from this synthesis process, enabling near-zero discharge and internal recycling of process water, but also has wide applications in the treatment of exogenous Zn-containing wastewater. 2+ Cr 6+ The co-treatment of heavy metal wastewater ultimately produces environmentally friendly, non-fired brick aggregates and other building materials.

[0033]

Example 1

[0034] A method for reconstructing adsorption and closed-loop in-situ solidification of heavy metals in coal gasification ash residue. The raw material used in this embodiment is fine coal gasification ash residue with excessive heavy metals, and its specific chemical composition is shown in the table below:

[0035] Table 1 Chemical composition of coal gasification ash

[0036]

[0037] Step 1: The above-mentioned coal gasification fine slag is dried and weighed. Calcium oxide powder is added at a target calcium-silicon molar ratio (Ca / Si) of 0.8, and sodium hydroxide solid is added at an initial concentration of 2 mol / L based on the subsequent water addition. The mixture is then thoroughly mixed. The mixture is placed in a ball mill and mechanically ball-milled at 500 rpm for 30 minutes. Subsequently, the ball-milled material is transferred to a tube furnace with a nitrogen atmosphere and heated to 850°C, then calcined at this temperature for 1 hour. Under the combined action of mechanical stress and alkali-calcium synergistic thermal activation, the original inert aluminosilicate glass network of the fine slag is deconstructed, allowing free heavy metal ions to be initially immobilized in situ within the amorphous aluminosilicate framework. After cooling, the activated clinker is obtained.

[0038] Step 2: Add deionized water to the activated clinker prepared in Step 1 at a solid-liquid ratio of 1:20 g / mL, place in a constant temperature water bath, and age with continuous mechanical stirring at 90℃ for 40 min. This allows the active silica dissolved in the clinker to fully hydrate with the pre-embedded calcium source to form calcium silicate hydrate (CSH) gel, thus obtaining tobermorite precursor slurry.

[0039] Step 3: Transfer the tobermorite precursor slurry obtained in Step 2 to a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner, seal it, and place it in the stainless steel reactor for constant temperature hydrothermal crystallization reaction at 150℃ for 12 hours.

[0040] Step 4: The product is filtered to achieve solid-liquid separation, dried, ground and sieved to obtain tobermorite with adsorption properties.

[0041]

Example 2

[0042] XRD analysis was performed on the tobermorite obtained in Example 1, and the resulting spectrum is shown below. Figure 3 As shown, compared with the standard card, it was identified as Tobermori stone.

[0043]

Example 3

[0044] This embodiment aims to verify the preliminary in-situ consolidation effect of heavy metal ions in coal gasification fine slag after synergistic activation by mechanical and high-temperature thermochemical methods as described in Example 1. The leaching test process was strictly carried out in accordance with the provisions of the national environmental protection standard "Solid Waste Leaching Toxicity Leaching Method - Water Leaching Method" (HJ557-2010).

[0045] Step 1: Weigh 3g of the activated calcined material obtained after cooling in Example 1 and place it in an extraction bottle. Add 30mL of deionized water as a leaching agent to the extraction bottle at a liquid-to-solid ratio of 10:1 (L / kg).

[0046] Step 2: Tightly cap the extraction bottle and fix it on the horizontal oscillation device. Adjust the frequency of the horizontal oscillation device to 110 r / min and continue horizontal oscillation for 8 hours at room temperature.

[0047] Step 3: After shaking, remove the extraction bottle and let it stand at room temperature for 16 hours. After standing, take the supernatant and filter it using a microporous membrane with a pore size of 0.45 μm to collect the leachate.

[0048] Step 4: The concentration of target heavy metals in the collected leachate was detected and analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Simultaneously, the untreated raw coal gasification fine slag was subjected to leaching tests under the same conditions as a control group. Specific detection results are shown in Table 2 below. After the "mechanical-high temperature" activation pretreatment, the primary leaching of each target heavy metal was significantly inhibited. The leaching concentrations of As, Se, and Mn decreased significantly by 7.5 μg / L, 25.9 μg / L, and 2.7 μg / L respectively compared to the original slag. The solidification rates of the aforementioned endogenous heavy metals through "mechanical-high temperature activation" were 8.6%, 30.2%, and 5.7%, respectively. From the solidification mechanism perspective, this is because under the synergistic excitation of mechanical stress and alkali-calcium flux, the original inert silica-alumina glass network of the fine slag was effectively deconstructed, causing the free heavy metal ions to be initially embedded and in-situ sealed within the newly formed amorphous aluminosilicate network framework, thereby weakening their migration and leaching ability in the aqueous environment.

[0049]

Example 4

[0050] This embodiment aims to verify the deep lattice locking effect of the geopolymer-type tobermorite obtained in Example 1 on heavy metals, highlighting the core advantages of the hydrothermal reconstruction process of this invention. The leaching test process was also strictly carried out in accordance with the provisions of the national environmental protection standard "Solid Waste Leaching Toxicity Leaching Method - Water Leaching Method" (HJ557-2010).

[0051] Take the hydrothermal solidified sample 3 obtained after drying, grinding and sieving in Example 1 and place it in an extraction bottle. Add 30 ml of deionized water as the leaching agent at a liquid-to-solid ratio of 10:1 (L / kg). After sealing the extraction bottle, fix it on a horizontal shaking device and continuously shake it horizontally at a speed of 110 r / min for 8 h. After shaking, remove the extraction bottle and let it stand for 16 h. Then, filter it through a 0.45 μm microporous membrane to collect the final leachate.

[0052] Step 4: Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to analyze the leachate from the hydrothermal waste liquid and the tobermorite solidified body, and the data were compared with the leaching data of the untreated raw fine slag. Since the hydrothermal reaction occurs in a liquid phase system, some heavy metals, besides being locked inside and outside the solid crystal lattice, also dissolve directly into the hydrothermal waste liquid. Therefore, when evaluating the actual solidification effect, it is not sufficient to only consider the leaching amount of the solid phase; the "free amount in the hydrothermal waste liquid" and the "amount detached from the tobermorite leaching test" must be added together to obtain the total unsolidified free amount in the system for comparison. Specific detection results are shown in Table 2.

[0053] Table 2. Test results of heavy metal curing rate during the activated pre-curing and hydrothermal deep crystallization stages.

[0054]

[0055] The results showed that the initial concentrations of As, Se, and Mn in the hydrothermal waste liquid were 20.8 μg / L, 24.3 μg / L, and 12.1 μg / L, respectively; while the tobermorite solidified body exhibited extremely high stability, with very low secondary leaching concentrations of only 10.0 μg / L, 1.86 μg / L, and 1.2 μg / L, respectively. After adding the amounts of these two unsolidified portions and comparing them with the leaching amount of the original residue, it was calculated that after the hydrothermal deep crystallization treatment of this invention, the final comprehensive solidification rates of As, Se, and Mn reached 64.8%, 69.5%, and 71.8%, respectively.

[0056]

Example 5

[0057] This embodiment aims to verify the effect of the geopolymer-type tobermorite finally synthesized in Example 1 on the closed-loop in-situ adsorption and purification of the process wastewater generated by the hydrothermal and washing processes of this invention.

[0058] Step 1: Collect the mixed waste liquid rich in trace heavy metal ions and residual alkali generated in the filtration and washing process of Example 1.

[0059] Step 2: Weigh 0.1g of the tobermorite sample prepared in Example 1 into an Erlenmeyer flask as an adsorbent, and add 100ml of the waste liquid from Step 1.

[0060] Step 3: The mixture was placed in a constant temperature water bath shaker and continuously shaken for 24 hours at 25℃ and 180 rpm. After the adsorption reaction reached equilibrium, the system was filtered to achieve solid-liquid separation. The concentration of residual metal ions in the final filtrate was detected and analyzed using inductively coupled plasma mass spectrometry. The test results are shown in Table 3 below. As can be seen from Table 3, after this closed-loop adsorption treatment, trace amounts of free metal ions released from the waste liquid were effectively retained by the reconstructed porous lattice of tobermorite. Calculations showed that the unit adsorption capacity of tobermorite for As, Se, and Mn in this system reached 19.4 μg / g, 24.2 μg / g, and 14.0 μg / g, respectively, with removal rates of 93.5%, 99.4%, and 87%, respectively. This result fully demonstrates the excellent feasibility of this invention in purifying its own process waste liquid using its own synthetic product, perfectly realizing the internal circulation purification and extremely low discharge of wastewater in the entire heavy metal solidification process.

[0061] In the synthesis of geopolymer tobermorite, this invention achieves effective crystal phase reconstruction and heavy metal encapsulation within an initial calcium-silicon molar ratio (Ca / Si) ranging from 0.8 to 1.2. Since the overall heavy metal solidification effect is relatively good when the Ca / Si ratio is 0.8, samples under this ratio condition were specifically selected for solidification leaching tests in Examples 1-4 above.

[0062] Table 3 Test results of closed-loop in-situ adsorption purification of hydrothermal wastewater

[0063]

[0064]

Example 6

[0065] This embodiment aims to verify that tobermorite synthesized from different calcium-silicon molar ratios (Ca / Si = 0.8, 1.0, 1.2) can effectively utilize exogenous Zn-containing materials. 2+ Adsorption performance of heavy metal wastewater.

[0066] Step 1: Weigh 0.1g each of the tobermorite samples prepared in Example 1 (Ca / Si=0.8) and those prepared using the same process but with different initial calcium-silicon ratios (Ca / Si=1.0 and Ca / Si=1.2), and add them to a simulated Zn-containing solution with an initial concentration of 100mg / L and a volume of 100mL. 2+ In the conical flask containing the external wastewater, the pH of the system was adjusted to 6.

[0067] Step 2: Place the three conical flasks in a constant temperature water bath shaker, adjust the temperature to 25℃ and maintain a rotation speed of 180 rpm for continuous adsorption for 24 hours. After adsorption, separate each system by vacuum filtration, and determine the residual Zn in the filtrate using atomic absorption spectrometry. 2+Concentration. The test results are shown in Table 4 below. Tobermorite synthesized under three calcium-to-silicon ratios all exhibited excellent adsorption performance. Among them, when the Ca / Si ratio was 0.8, 1.0, and 1.2, the adsorption performance for Zn was the best. 2+ The equilibrium adsorption capacities reached 98.93 mg / g, 98.82 mg / g, and 97.71 mg / g, respectively. This extremely high unit adsorption capacity fully demonstrates that the tobermorite prepared in this invention can not only deeply and in-situ solidify endogenous heavy metals in fine slag, but also fully possesses the feasibility as a highly efficient and environmentally friendly adsorption material, which can be applied to the adsorption and purification of high concentrations of exogenous zinc (Zn). 2+ Heavy metal wastewater.

[0068] Table 4. Tobermorite synthesized with different calcium-to-silicon ratios and its effect on Zn 2+ Adsorption performance comparison

[0069]

[0070]

Example 7

[0071] This embodiment aims to verify that tobermorite synthesized from different calcium-silicon molar ratios (Ca / Si = 0.8, 1.0, 1.2) exhibits superior performance against exogenous Cr-containing... 6+ Adsorption performance of heavy metal wastewater.

[0072] Step 1: Weigh 0.05 g each of the tobermorite sample prepared in Example 1 (Ca / Si=0.8) and the sample prepared using the same process but with different initial calcium-silicon ratios (Ca / Si=1.0, Ca / Si=1.2), and add them to a 100 mL container of simulated Cr-containing solution with an initial concentration of 50 mg / L. 6+ In the conical flask containing the external wastewater, adjust the pH of the system to 2.

[0073] Step 2: Place the three conical flasks in a constant temperature water bath shaker, adjust the temperature to 25℃ and maintain a rotation speed of 180 rpm for continuous adsorption for 24 hours. After adsorption, separate each system by vacuum filtration, and determine the residual Cr in the filtrate using atomic absorption spectrometry. 6+ Concentration. The test results are shown in Table 5 below. Tobermorite synthesized under three different calcium-to-silicon ratios all exhibited good adsorption performance. Among them, when the Ca / Si ratio was 0.8, 1.0, and 1.2, the adsorption performance for Cr was particularly good. 6+ The equilibrium adsorption capacities reached 22.2 mg / g, 27.2 mg / g, and 17.4 mg / g, respectively. This stable unit adsorption capacity fully demonstrates that the tobermorite prepared in this invention can not only deeply and in-situ solidify endogenous heavy metals in fine slag, but also possesses the feasibility as an environmentally friendly adsorbent material, applicable to the adsorption and purification of high concentrations of exogenous zinc Cr. 6+ Heavy metal wastewater.

[0074] Table 5. Effects of tobermorite synthesized with different calcium-to-silicon ratios on Cr. 6+ Adsorption performance comparison

[0075]

[0076] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for reconstructing the crystal lattice, solidifying, and synergistically adsorbing heavy metals from coal gasification ash, characterized in that, Includes the following steps: Step 1, Source Connection and Activation Pretreatment: Mix coal gasification ash containing heavy metals with sodium hydroxide and calcium oxide, and perform mechanical activation and high-temperature activation pretreatment to obtain activated clinker; Step 2, Water bath aging: Add deionized water to the activated clinker and carry out water bath heating and stirring aging to obtain tobermorite precursor slurry; Step 3, hydrothermal deep crystallization: The tobermorite precursor slurry is transferred to a reactor for hydrothermal crystallization reaction. After the reaction, the mixture is separated into solid and liquid, washed and dried to obtain geopolymer tobermorite material and process waste liquid. Step 4, Closed-loop purification of process wastewater: At least a portion of the tobermorite material obtained in step 3 is added to the process wastewater for adsorption and purification. Step 5, Co-adsorption of exogenous wastewater: The tobermorite material obtained in step 3 is added to exogenous heavy metal wastewater for adsorption and purification.

2. The method for reconstructing the crystal lattice and synergistically adsorbing heavy metals from coal gasification ash slag according to claim 1, characterized in that, The coal gasification ash includes coarse coal gasification ash and / or fine coal gasification ash.

3. The method for reconstructing the crystal lattice and synergistically adsorbing heavy metals from coal gasification ash slag according to claim 2, characterized in that, The coal gasification ash residue comprises, by mass percentage: 45.0%-60.0% silicon dioxide, 10.0%-20.0% aluminum oxide, 5.0%-15.0% calcium oxide, 5.0%-12.0% iron oxide, 1.0%-5.0% sulfur trioxide, 1.0%-4.0% potassium oxide, 0.5%-3.0% phosphorus pentoxide, and 0.5%-3.0% magnesium oxide.

4. The method for reconstructing the crystal lattice and synergistically adsorbing heavy metals from coal gasification ash slag according to claim 1, characterized in that, In step 1, the amount of sodium hydroxide added is calculated based on the liquid-solid ratio of the hydrothermal crystallization reaction in the subsequent step 3, so that the initial concentration of sodium hydroxide in the liquid phase of the hydrothermal crystallization reaction is controlled at 1.8-2.2 mol / L.

5. The method for reconstructing the crystal lattice and synergistically adsorbing heavy metals from coal gasification ash slag according to claim 1, characterized in that, In step 1, the amount of calcium oxide added is such that the molar ratio of calcium to silicon in the reaction system is 0.8-1.

2.

6. The method for reconstructing the crystal lattice, solidifying, and synergistically adsorbing heavy metals from coal gasification ash slag according to claim 1, characterized in that, In step 1, the mechanical activation is ball milling, with a ball milling speed of 450-550 r / min and a ball milling time of 20-40 min; the high-temperature activation is calcination at 800-900℃ under a nitrogen atmosphere at a heating rate of 5-20℃ / min and holding at that temperature for 0.5-1.5 h.

7. The method for reconstructing the crystal lattice and synergistically adsorbing heavy metals from coal gasification ash slag according to claim 1, characterized in that, In step 2, the solid-liquid ratio of deionized water added is 1:10-1:30 g / ml, the water bath heating temperature is 80-90℃, and the aging stirring time is 30-60 minutes.

8. The method for reconstructing the crystal lattice, solidifying, and synergistically adsorbing heavy metals from coal gasification ash slag according to claim 1, characterized in that, In step 3, the temperature of the hydrothermal crystallization reaction is 130-180℃, and the reaction time is 12-24 hours.

9. The method for reconstructing the crystal lattice, solidifying, and synergistically adsorbing heavy metals from coal gasification ash slag according to claim 1, characterized in that, In steps 4 and 5, the dosage of the tobermorite material is 0.05-0.15 g / L, and the adsorption contact time is 8-24 h.

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