A coal gasification slag-based supported NaA zeolite catalyst and its preparation method and application

Abstract

The present invention belongs to the fields of solid waste resource recovery and high-value utilization, as well as catalytic technology, and particularly relates to a method for preparing a coal gasification slag-based supported NaA zeolite catalyst and its application. The present invention successfully loads metal oxides or elemental metals onto the NaA zeolite through the adsorption of heavy metal ions combined with a calcination treatment. The introduction of the metal active component significantly enhances the catalyst's catalytic performance, demonstrating excellent activity in the catalytic reduction of p-nitrophenol.

Description

Technical Field

[0001] The present invention belongs to the field of solid waste resource and high-value utilization and catalysis technology, and particularly relates to a coal gasification slag-based supported NaA zeolite catalyst, a preparation method and an application thereof. Background Art

[0002] Coal gasification slag, a byproduct of the coal gasification process, primarily consists of silicon (Si) and carbon (C), and is a heterogeneous industrial solid waste. In recent years, researchers have focused on utilizing silicon, an active component in coal gasification slag, to prepare high-performance NaA zeolite adsorbent materials for heavy metal ion removal. Adsorption has become a preferred method for water treatment due to its high efficiency, ease of operation, and easy regeneration. However, traditional research often overlooks the risk of heavy metal ion release into the environment during adsorbent use. Consequently, the reuse of spent zeolite adsorbents has gradually attracted considerable attention. Zeolite adsorbents containing heavy metal ions are classified as hazardous solid waste and can cause significant secondary pollution. Currently, the main treatment methods for spent adsorbents include incineration of carbonaceous adsorbents or landfilling after solidification / stabilization. However, these methods consume large amounts of lime and cement and may further pollute the environment.

[0003] p-Nitrophenol is a highly toxic and difficult-to-degrade nitrophenol compound containing -NO2 and -OH groups on its benzene ring. Once it enters the water, p-nitrophenol will cause great harm to the survival, growth and reproduction of aquatic organisms. Therefore, catalytic degradation of p-nitrophenol into low-toxic compounds is of great significance. The present invention converts the silicon in the coal gasification slag into a NaA type zeolite adsorbent material with excellent adsorption performance through the phase transformation process, and selectively adsorbs heavy metal ions (such as Fe 3+ 、Co 2+ 、Ni² + 、Cu 2+ and Zn 2+ Waste NaA zeolite materials (such as those used in the AMO x -NAZ and AM0-NAZ (AM=Fe, Cu, Co, Zn, Ni, etc.) active functional materials to achieve resource recycling of discarded NaA type zeolite materials.

[0004] This method not only solves the secondary pollution problem of discarded zeolite adsorbents but also provides a new approach for the high-value utilization of coal gasification slag. By converting discarded adsorbents into catalytically active functional materials, this method not only reduces potential environmental hazards but also provides a highly effective solution for the catalytic degradation of toxic pollutants such as p-nitrophenol, with significant environmental and economic significance. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a coal gasification slag-based supported NaA zeolite catalyst and a preparation method and application thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for preparing a coal gasification slag-based supported NaA zeolite catalyst, comprising the following steps:

[0008] (1) Place the coal gasification slag in an oven to dry out the moisture, grind it in a ball mill, and sieve it. The sieved sample is dried and evenly dispersed in a 1 mol / L dilute hydrochloric acid solution by ultrasonication. Then, magnetic stirring is performed in a water bath to separate the solid and liquid. The purpose of this step is to dissolve the metal oxides (such as iron oxide) and impurities in the coal gasification slag, remove impurities, and improve the purity of silicon and aluminum.

[0009] (2) The solid residue after solid-liquid separation in step (1) is added to a 2.5 mol / L sodium hydroxide solution, magnetically stirred at room temperature, and then centrifuged to obtain a pure silicon liquid. The purpose of this step is to convert the silicon and aluminum in the solid residue into soluble sodium silicate and sodium metaaluminate. The purpose is to extract the silicon liquid and provide a silicon source for the subsequent synthesis of NaA zeolite.

[0010] (3) The silicon liquid in step (2) and sodium aluminate are mixed and stirred at room temperature, and after being evenly mixed, they are transferred to a stainless steel hydrothermal kettle for hydrothermal reaction to finally obtain a pure phase NaA type zeolite, named NAZ; the purpose of this step is to react the silicon liquid (mainly sodium silicate) with sodium aluminate under hydrothermal conditions to form the crystal structure of NaA type zeolite through condensation and rearrangement.

[0011] (4) dissolving a heavy metal salt in deionized water to prepare a heavy metal salt solution, adding the NaA zeolite obtained in step (3) to the heavy metal salt solution, stirring, and then collecting the NaA zeolite material that has adsorbed heavy metal ions, and rinsing with deionized water for storage;

[0012] (5) The NaA type zeolite adsorbing heavy metal ions obtained in step (4) is placed in an alumina crucible, calcined and kept warm for a corresponding time, and the obtained sample is collected.

[0013] Furthermore, in step (1), 1 g of coal gasification slag corresponds to 20 mL of dilute hydrochloric acid solution; the temperature of the water bath is 85°C.

[0014] Water bath heating provides a uniform and stable temperature environment, preventing local overheating or uneven reactions. A temperature of 85°C effectively promotes the reaction of silicon, aluminum, and other components in the gasification slag with dilute hydrochloric acid, allowing them to fully dissolve or disperse. Excessively high temperatures can trigger side reactions.

[0015] Dilute hydrochloric acid dissolves metal oxides and other soluble components in coal gasification slag. A ratio of 20 mL of dilute hydrochloric acid per 1 gram of coal gasification slag ensures sufficient contact between the active ingredients in the slag and prevents incomplete reactions due to insufficient acid. Excessive acid can complicate subsequent processing. A moderate concentration of 1 mol / L dilute hydrochloric acid effectively dissolves metal oxides in coal gasification slag without causing excessive corrosion or excessive byproducts due to high acid concentrations.

[0016] Furthermore, in step (2), 40 mL of sodium hydroxide solution is used for every 2 g of the filter residue obtained in step (1). Adding too much sodium hydroxide solution will increase side reactions and affect the purity of the silicon solution; insufficient sodium hydroxide will result in insufficient dissolution of the silicon in the filter residue, reducing the silicon extraction efficiency and thus affecting the subsequent synthesis of NaA zeolite.

[0017] Furthermore, in step (3), the amount of sodium aluminate added is limited to 2 g of sodium aluminate per 40 mL of the silicon liquid obtained in step (2), the hydrothermal temperature is 90° C., and the hydrothermal time is 18 h.

[0018] The addition of sodium metaaluminate is limited to ensure a silicon-to-aluminum molar ratio close to the theoretical value for NaA zeolite (Si / Al ≈ 1), thereby avoiding the formation of impurities. The hydrothermal reaction is carried out at 90°C, providing an optimal temperature and pressure environment to promote the dissolution, rearrangement, and crystallization of the aluminosilicate, forming NaA zeolite. An 18-hour reaction time ensures the complete crystallization process, resulting in highly crystalline and pure NaA zeolite.

[0019] Furthermore, in step (4), the heavy metal salt is one of copper nitrate trihydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, iron nitrate nonahydrate and zinc nitrate hexahydrate, the heavy metal ion concentration is 40 mg / L, and the addition ratio of the NaA type zeolite material and the heavy metal salt solution is limited to 1 mg:1 mL.

[0020] Furthermore, the calcination atmosphere in step (5) is calcined in air atmosphere to obtain the NaA type zeolite loaded with metal oxides, the calcination temperature is 500-600°C, and the holding time is 4-8h.

[0021] Furthermore, the calcination atmosphere in step (5) is H2 / Ar (5 vol% H2) mixed atmosphere to obtain the metal-loaded NaA zeolite, the calcination temperature is 500-600°C, and the holding time is 4-8h.

[0022] The present invention also provides a coal gasification slag-based supported NaA zeolite catalyst prepared by the preparation method.

[0023] The present invention also provides application of the coal gasification slag-based supported NaA zeolite catalyst in the catalytic reduction of p-nitrophenol.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] (1) The present invention uses coal gasification slag as raw material and converts it into high-value-added NaA zeolite (NAZ) through acid treatment, alkali dissolution, hydrothermal synthesis and other steps. This not only realizes the high-value-added utilization of effective components of coal gasification slag, but also applies it to the adsorption and removal of heavy metal ions, thus realizing waste treatment and resource utilization of coal gasification slag, which is in line with the concepts of green chemistry and sustainable development.

[0026] (2) The present invention adopts conventional chemical treatment and hydrothermal synthesis methods, which have mild process conditions, simple operation, and are easy to industrialize. Using coal gasification slag as raw material significantly reduces the preparation cost of the zeolite catalyst and avoids the high cost of high-purity silicon and aluminum sources in traditional zeolite synthesis.

[0027] (3) The present invention successfully loads metal oxides or metal elements onto NaA zeolite by adsorbing heavy metal ions and combining them with calcination. The introduction of metal active components significantly enhances the catalytic performance of the catalyst, particularly in the catalytic reduction of p-nitrophenol, where it exhibits excellent activity.

[0028] (4) The metal-loaded NaA zeolite catalyst has a high specific surface area, rich pore structure, and uniformly dispersed active sites, which can effectively adsorb reactants and provide sufficient catalytic active centers. In the catalytic reduction reaction of p-nitrophenol, the catalyst can efficiently reduce p-nitrophenol to p-aminophenol with a fast reaction rate and high conversion rate.

[0029] (5) By adjusting the calcination atmosphere (air or H2 / Ar mixture), NaA zeolite catalysts loaded with metal oxides or metal elements can be prepared. This flexibility allows the catalyst to adapt to different catalytic reaction requirements and expands its application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the X-ray diffraction pattern of the NaA type zeolite material powder obtained in step 3;

[0031] Figure 2 This is a scanning electron microscope image of the NaA zeolite material powder obtained in step 3;

[0032] Figure 3 The adsorbed metal ion Cu was calcined in a H2 / Ar (5 vol% H2) mixed atmosphere obtained in step 5. 2+ X-ray diffraction pattern of NaA type zeolite material powder;

[0033] Figure 4 This is the result diagram of the effect of the amount of catalyst added on the catalytic performance;

[0034] Figure 5 This is the result diagram of the effect of the concentration of p-nitrophenol solution on the catalytic performance;

[0035] Figure 6 This figure shows the effect of the quality of sodium borohydride on catalytic performance. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the examples, but the present invention is not limited to the following examples.

[0037] The coal gasification slag in the following examples was provided by a coal chemical enterprise in Shandong.

[0038] Table 1. Elemental analysis of coal gasification slag ad / %

[0039] C H N O 46.57 0.89 0.20 52.34

[0040] Table 2. Composition analysis of coal gasification slag. Content of each component ad / %

[0041] <![CDATA[K2O]]> <![CDATA[SiO2]]> <![CDATA[SO3]]> <![CDATA[Al2O3]]> CaO <![CDATA[Fe2O3]]> MgO <![CDATA[P2O5]]> <![CDATA[TiO2]]> <![CDATA[Na2O]]> 1.05 41.52 2.10 19.76 18.70 10.40 1.88 0.4 0.82 3.37

[0042] Example 1

[0043] (1) 8 g of coal gasification slag was placed in an oven at 100 ° C for 8 h to dry the moisture, and then ball milled for 1-2 h at a speed of 300-500 r / min. After ball milling, it was sieved through a 200-mesh sieve. 4 g of the sieved coal gasification slag was taken several times and added to 80 mL of 1 mol / L dilute hydrochloric acid solution for uniform ultrasonic dispersion. The mixture was magnetically stirred in a water bath at 85 ° C for 2 h, and then solid-liquid separation was performed to obtain the filter residue.

[0044] (2) 2 g of the filter residue obtained in step (1) was added to 40 mL of 2.5 mol / L sodium hydroxide solution and uniformly dispersed by ultrasonication, magnetically stirred at room temperature for 6 h, and then centrifuged to obtain a relatively pure silicon liquid;

[0045] (3) The silicon liquid (40 mL) obtained by centrifugation in step (2) was mixed with 2 g of sodium aluminate at room temperature and stirred. After the mixture was evenly mixed, it was transferred to a stainless steel hydrothermal kettle at 90°C and kept warm for 18 hours to finally obtain a pure phase NaA type zeolite "NAZ";

[0046] (4) Dissolve copper nitrate trihydrate in deionized water to prepare a corresponding heavy metal ion solution with a concentration of 40 mg / L. Add 60 mg of NaA zeolite obtained in step (3) to 60 mL of the heavy metal ion solution, stir at 25°C for 2 h, and then collect the adsorbed heavy metal ions Cu 2+ NaA zeolite "Cu2+ -NAZ", rinsed with deionized water and stored for subsequent experiments;

[0047] (5) The adsorbed heavy metal ions Cu obtained in step (4) 2+ NaA type zeolite material (Cu 2+ -NAZ) was placed in an alumina crucible and calcined at 550°C in a H2 / Ar (5 vol% H2) mixed atmosphere and kept warm for 6 h, and the related sample "Cu-NAZ" was collected at room temperature.

[0048] Figure 1 This is the X-ray diffraction pattern of the NaA type zeolite material powder obtained in step 3. It can be seen that the diffraction peaks 2θ = 7.3°, 10.3°, 12.5°, 16.1°, 21.8°, 24.1°, 26.2°, 27.1°, 29.9° and 34.4° correspond to the (200), (220), (222), (420), (600), (622), (640), (642), (820) and (664) crystal planes of NaA type zeolite, respectively (JCPDS card number 89-5423).

[0049] Figure 2 This is a scanning electron microscope image of the NaA zeolite material powder obtained in step 3. It can be seen that the NaA zeolite is in a uniform prismatic block shape with a size of about 1.5 μm.

[0050] Figure 3 The adsorbed metal ion Cu was calcined in a H2 / Ar (5 vol% H2) mixed atmosphere obtained in step 5. 2+ X-ray diffraction pattern of NaA type zeolite material powder; the pattern shows the characteristic diffraction peaks of Cu (JCPDS card No. 89-2838) phase, 2θ = 43.5°, 50.5°, 74.2° corresponding to the (111), (200) and (220) crystal planes of Cu, respectively.

[0051] Example 2

[0052] The difference between Example 2 and Example 1 is that the calcination temperature is 500°C and the holding time is 6h.

[0053] Example 3

[0054] The difference between Example 3 and Example 1 is that the calcination temperature is 600°C and the holding time is 6h.

[0055] Example 4

[0056] The difference between Example 4 and Example 1 is that the calcination atmosphere in step (5) is calcined at 550°C in an air atmosphere and kept warm for 6 hours, and the obtained sample "CuO-NAZ" is collected.

[0057] Example 5

[0058] The difference between Example 5 and Example 4 is that the calcination atmosphere in step (5) is calcination at 500°C in an air atmosphere and keeping warm for 6 hours, and the obtained sample "CuO-NAZ" is collected.

[0059] Example 6

[0060] The difference between Example 6 and Example 4 is that the calcination atmosphere in step (5) is calcination at 600°C in an air atmosphere and keeping warm for 6 hours, and the obtained sample "CuO-NAZ" is collected.

[0061] Example 7

[0062] The difference between Example 7 and Example 1 is that the calcination holding time is 4 hours, and the other conditions are exactly the same.

[0063] Example 8

[0064] The difference between Example 8 and Example 1 is that the calcination holding time is 8 hours, and the other conditions are exactly the same.

[0065] Example 9

[0066] The difference between Example 9 and Example 1 is that the metal salt is cobalt nitrate hexahydrate, and the other conditions are exactly the same.

[0067] Example 10

[0068] The difference between Example 10 and Example 1 is that the metal salt is nickel nitrate hexahydrate, and the other conditions are exactly the same.

[0069] Example 11

[0070] The difference between Example 11 and Example 1 is that the metal salt is ferric nitrate nonahydrate, and the other conditions are exactly the same.

[0071] Example 12

[0072] The difference between Example 12 and Example 1 is that the metal salt is zinc nitrate hexahydrate, and the other conditions are exactly the same.

[0073] Comparative Example 1

[0074] The difference between Comparative Example 1 and Example 1 is that the calcination temperature is 400°C and the holding time is 6h.

[0075] Comparative Example 2

[0076] The difference between Comparative Example 2 and Example 1 is that the calcination temperature is 700°C and the holding time is 6h.

[0077] Comparative Example 3

[0078] Comparative Example 3 is the adsorption of heavy metal ions Cu without calcination 2+ NaA type zeolite.

[0079] Comparative Example 4

[0080] The difference between Comparative Example 4 and Example 4 is that the calcination atmosphere in step (5) is calcined at 400°C in an air atmosphere and kept warm for 6 hours, and the obtained sample "CuO-NAZ" is collected.

[0081] Comparative Example 5

[0082] The difference between Comparative Example 5 and Example 4 is that the calcination atmosphere in step (5) is calcined at 700°C in an air atmosphere and kept warm for 6 hours, and the obtained sample "CuO-NAZ" is collected.

[0083] Comparative Example 6

[0084] The difference between Comparative Example 6 and Example 1 is that the calcination holding time is 10 hours, and the other conditions are exactly the same.

[0085] Comparative Example 7

[0086] The difference between Comparative Example 7 and Example 1 is that the calcination holding time is 2 hours, and the other conditions are exactly the same.

[0087] Examples 1-3 and Comparative Examples 1-3 investigated the effect of calcination temperature on the catalytic performance of the materials. 60 mg of the zeolite materials obtained in Examples 1-3 and Comparative Examples 1-3 were added to 60 mL of a 20 mg / L p-nitrophenol solution containing 10 mg of sodium borohydride for catalytic reduction. The results are shown in Table 3.

[0088] Table 3. Comparison of catalytic performance of materials in Examples 1-3 and Comparative Examples 1-3

[0089] Calcination temperature Reduction rate (%) 550 (Example 1) 93 500 (Example 2) 75 600 (Example 3) 94 700 (Comparative Example 1) 93 400 (Comparative Example 2) 56 0 (Comparative Example 3) 0.5

[0090] Here are the reasons:

[0091] When the calcination temperature is lower than 550 degrees in Example 1, the heavy metal Cu loaded on the NaA zeolite 2+ The ions cannot be completely converted into elemental Cu, so the calcination temperature is set above 550 degrees. The lower the calcination temperature, the lower the elemental Cu conversion rate, and thus the reduction rate of p-nitrophenol is greatly reduced.

[0092] Examples 4-6 and Comparative Examples 4 and 5 investigated the effect of calcination temperature on catalytic performance during calcination in air atmosphere. The results are shown in Table 4.

[0093] Table 4. Comparison of catalytic performance of materials in Examples 4-6 and Comparative Examples 4 and 5

[0094] Atmosphere / temperature Reduction rate (%) Air 550 (Example 4) 90 Air 500 (Example 5) 82 Air 600 (Example 6) 90 Air 400 (Comparative Example 4) 73 Air 700 (Comparative Example 5) 89

[0095] Here are the reasons:

[0096] Calcination of Cu supported on NaA zeolite in air atmosphere 2+ ions, because of the participation of oxygen in the air, CuO, Cu 2+ The calcination temperature for the in-situ complete conversion of ions into CuO also needs to be higher than 550 degrees, but the electron transfer ability of CuO obtained in an air atmosphere is lower than that of elemental Cu, so the catalytic activity is reduced.

[0097] Example 1, Examples 7-8, and Comparative Examples 6-7 investigated the effect of holding time on the catalytic performance of the materials. 60 mg of the zeolite material obtained in Examples 1, 7-8, and Comparative Examples 6-7 was added to 60 mL of a 20 mg / L p-nitrophenol solution containing 10 mg of sodium borohydride for catalytic reduction. The results are shown in Table 5.

[0098] Table 5. Comparison of catalytic performance of materials in Examples 1, 7-8, and Comparative Examples 6-7

[0099] Holding time (h) Removal rate (%) 6 (Example 1) 93 4 (Example 7) 92 8 (Example 8) 90 10 (Comparative Example 6) 85 2 (Comparative Example 7) 80

[0100] Here are the reasons:

[0101] When the holding time is set in the range of 4-8h, the size distribution of elemental Cu is mainly concentrated in the range of 5-10nm. Such particle size ensures that elemental Cu has a large specific surface area and high catalytic reduction activity. When the holding time is extended to 10h, the size of the elemental Cu particles grows, the specific surface area decreases, and the risk of oxidation increases, resulting in low catalytic activity. However, if the holding time is too short, such as 2h, the Cu particles do not grow to the appropriate size. The small size causes a large amount of aggregation, which reduces the catalytic activity.

[0102] Examples 1 and 9-12 explored the effects of different metal salts. 60 mg of the zeolite material obtained in Examples 1 and 9-12 was added to 60 mL of a 20 mg / L p-nitrophenol solution containing 10 mg of sodium borohydride for catalytic reduction. The results are shown in Table 6.

[0103] Table 6. Comparison of catalytic performance of materials in Examples 1, 9-12

[0104] Metal Type Removal rate (%) Cu (Example 1) 93 Co (Example 9) 95 Ni (Example 10) 95 Fe (Example 11) 75 Zn (Example 12) 78

[0105] Here are the reasons:

[0106] Compared with metals Fe and Zn, the precious metal elements Co, Ni and Cu have higher electron transfer efficiency and accelerate the conversion of p-nitrophenol to p-aminophenol. For the elements Co, Ni and Cu with high catalytic efficiency, the lower-cost element Cu is used as a suitable catalyst.

[0107] Based on the above analysis, we further explored the effects of the amount of catalyst added, the concentration of p-nitrophenol solution and the quality of sodium borohydride on the catalytic performance.

[0108] Investigate the effect of catalyst addition on catalytic performance

[0109] 50, 60, and 70 mg of the catalyst prepared in Example 1 were weighed and added to 60 mL of a 20 mg / L p-nitrophenol solution containing 10 mg of sodium borohydride for catalytic reduction. The results are shown in FIG. Figure 4 ,Depend on Figure 4 It can be seen that when the catalyst addition amount is 50 mg and the reduction time is 30 min, the reduction efficiency is 97.7%. With the increase of catalyst addition amount, the reduction efficiency of p-nitrophenol is inhibited. Due to the addition of excessive catalyst, the catalysts in the system agglomerate, so that the active surface is no longer excessively exposed, and the catalytic performance is greatly reduced.

[0110] Investigating the effect of the concentration of p-nitrophenol solution on catalytic performance

[0111] Weigh 3 portions of 60 mg of the catalyst prepared in Example 1 and add them to 60 mL of 5 mg / L, 10 mg / L and 20 mg / L p-nitrophenol solutions containing 10 mg of sodium borohydride for catalytic reduction. Figure 5 The results indicate that as the initial p-NP concentration increases, the catalytic reduction efficiency decreases to a certain extent, which may be due to the excessive occupation of active sites on the catalyst surface. When the initial p-NP concentration is 20 ppm (60 mg catalyst, 10 mg sodium borohydride, 60 mL solution volume), the reduction efficiency is 97.5%.

[0112] Investigating the effect of sodium borohydride quality on catalytic performance

[0113] Weigh 3 portions of 60 mg of the catalyst prepared in Example 1 and add them to 60 mL of 20 mg / L p-nitrophenol solution containing 10 mg, 30 mg, and 60 mg of sodium borohydride, respectively, for catalytic reduction. The results are shown in Table 1. Figure 6 The results show that with the increase of sodium borohydride usage, the reduction rate of p-nitrophenol continues to increase. The increase in the usage of sodium borohydride provides more hydrogen anions to the system, so the reduction efficiency is greatly improved.

Claims

1. Application of a coal gasification slag-based supported NaA zeolite catalyst in the catalytic reduction of p-nitrophenol, characterized in that: The preparation method of the coal gasification slag-based supported NaA zeolite catalyst comprises the following steps: (1) The coal gasification slag is dried to remove moisture, ground and sieved by a ball mill, and dried. The dried coal gasification slag is evenly dispersed by ultrasonic in a 1 mol / L dilute hydrochloric acid solution, and then magnetically stirred in a water bath for solid-liquid separation; (2) The solid residue after solid-liquid separation in step (1) is added to a sodium hydroxide solution with a concentration of 2.5 mol / L, magnetically stirred at room temperature, and then centrifuged to obtain a pure silicon liquid; (3) mixing the silicon liquid in step (2) with sodium aluminate at room temperature, stirring the mixture evenly, and performing a hydrothermal reaction to finally obtain a pure phase NaA type zeolite, named NAZ; (4) dissolving a heavy metal salt in deionized water to prepare a heavy metal salt solution, adding the NaA zeolite obtained in step (3) to the heavy metal salt solution, stirring, and then collecting the NaA zeolite material that has adsorbed heavy metal ions, and rinsing with deionized water for storage; (5) calcining the NaA zeolite adsorbing heavy metal ions obtained in step (4), keeping the temperature for a corresponding period of time, and collecting the obtained sample; In step (1), 1g of coal gasification slag corresponds to 20mL of dilute hydrochloric acid solution; the temperature of the water bath is 85°C; In step (2), every 2 g of the filter residue obtained in step (1) corresponds to 40 mL of sodium hydroxide solution; In step (3), the amount of sodium aluminate added is limited to 2 g of sodium aluminate per 40 mL of the silicon liquid obtained in step (2), the hydrothermal temperature is 90°C, and the hydrothermal time is 18 h; In step (4), the heavy metal salt is one of copper nitrate trihydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, iron nitrate nonahydrate and zinc nitrate hexahydrate, the heavy metal ion concentration is 40 mg / L, and the addition ratio of the NaA type zeolite material and the heavy metal salt solution is limited to 1 mg:1 mL; The calcination atmosphere in step (5) is to obtain the NaA type zeolite loaded with metal oxide by calcining in an air atmosphere, the calcination temperature is 500-600°C, and the holding time is 4-8h, or to obtain the NaA type zeolite loaded with metal element by calcining in a H2 / Ar mixed atmosphere, in which hydrogen accounts for 5% of the total volume and the remaining 95% is argon, the calcination temperature is 500-600°C, and the holding time is 4-8h.

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