Method for preparing FAU type zeolite from fine coal gasification slag and application of FAU type zeolite

Abstract

The invention aims to provide a method for preparing FAU type zeolite from fine coal gasification slag and application of the FAU type zeolite, and belongs to the technical field of solid waste treatment and resource utilization. Efficient conversion of an inert silicon-aluminum phase in the fine slag is achieved by conducting pretreatment, alkali fusion-hydrothermal synergistic activation and crystallization control on the fine coal gasification slag; and the FAU type zeolite product with high crystallinity and high purity is prepared. The coal gasification fine slag is used as the raw material, the source is wide, the cost is low, the preparation period is short, no pollution by-product is generated in the synthesis process, the adsorption effect is excellent, the purpose of treating waste with waste is achieved, and the method has ideal application prospects in the aspect of industrial wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment and resource utilization technology, specifically relating to a method for preparing FAU-type zeolite using coal gasification fine slag and its application. Background Technology

[0002] Resource utilization of coal gasification slag is a significant practical need in the fields of environmental protection and resource recycling. As a solid waste generated during coal gasification, coal gasification slag mainly contains unreacted residual carbon components and ash components such as inorganic minerals from coal. Improper disposal of coal gasification slag can lead to pollution of soil, water bodies, and the atmosphere. Resource utilization can effectively reduce its volume and mitigate negative environmental impacts. Furthermore, coal gasification slag contains valuable components; resource utilization can recover these valuable resources, simultaneously achieving both volume reduction and resource recovery of large-scale industrial waste.

[0003] Heavy metal pollution is characterized by its difficulty in treatment, high toxicity, and significant harm. With rapid industrial development, the problem of heavy metal pollution is becoming increasingly serious. Cadmium (Cd) is one of the most toxic heavy metal pollutants in water, and Cd in the environment enters water sources from wastewater discharged from mining, electroplating, and metallurgical activities. As a carcinogen, Cd increases the risk of lung and prostate cancer, and may also cause skeletal deformities and kidney damage. Therefore, the treatment of Cd pollution has become a key research issue for scholars today.

[0004] Currently, the main remediation technologies for cadmium pollution control at home and abroad include coagulation and sedimentation, chemical precipitation, membrane separation, ion exchange, and adsorption. Among them, adsorption is widely used to treat heavy metal pollution due to its high efficiency, low cost, and strong recyclability.

[0005] FAU-type zeolites are a class of aluminosilicate molecular sieve materials with a three-dimensional macroporous structure. Due to their large pore size, high specific surface area, and excellent ion exchange and adsorption properties, they are widely used in petroleum catalytic cracking, gas separation, environmental purification, and fine chemical industries.

[0006] In recent years, research on FAU-type zeolites has begun to attract the attention of some scholars. CN202311322197.6 provides a method for preparing and applying a FAU-Y type zeolite-supported multi-component transition metal catalyst, which introduces the generation of FAU-Y type zeolite-supported multi-component transition metal catalyst by adding aluminum powder to support heavy metal ions; CN202211470592.4 provides a method for preparing a honeycomb-shaped FAU-type zeolite molecular sieve, which introduces the preparation of a directing agent solution and the use of aluminum source, alkali source and silicon source as raw materials to finally obtain a honeycomb-shaped FAU-type zeolite molecular sieve; CN202210222004.9 provides an iron-based FAU-type zeolite composite material, its preparation method and application, which introduces the preparation of a zeolite precursor by mixing red soil, inorganic alkali and added cobalt source and heating to activate it, followed by hydrothermal crystallization to obtain an iron-based FAU-type zeolite composite material.

[0007] Data from recent years shows that FAU-type zeolites are typically prepared using high-purity silicon and aluminum sources, such as sodium silicate, sodium aluminate, or aluminum salts, via an alkaline hydrothermal crystallization process. While this synthetic route can yield FAU-type zeolites with high crystallinity, it is highly dependent on the purity of the raw materials, which mainly rely on chemical products, resulting in high production costs. Furthermore, the synthesis process usually requires the addition of organic template agents or large amounts of alkaline auxiliaries, which can lead to increased energy consumption, complex post-processing steps, and a heavier environmental burden.

[0008] Compared to traditional high-purity silicon and aluminum sources, coal gasification fine slag offers stable and low-cost sources. Furthermore, its utilization process simultaneously achieves solid waste reduction and resource recovery, demonstrating significant advantages in raw material availability and environmental impact. In addition, as a widely sourced industrial byproduct, the composition of coal gasification fine slag fluctuates within a certain range. However, through pretreatment and controlled synthesis conditions, the activity and crystallization behavior of silicon and aluminum can be effectively controlled, enabling its efficient conversion into FAU-type zeolite. This allows for meeting material performance requirements while simultaneously achieving cost control and environmental friendliness. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing FAU-type zeolite using coal gasification fine slag and its application. This method uses coal gasification fine slag as raw material and achieves deep activation of the inert silicon-aluminum phase in the coal gasification fine slag without introducing expensive external silicon-aluminum sources, and can controllably synthesize FAU-type zeolite with high crystallinity and high phase purity.

[0010] The present invention adopts the following technical solution: A method for preparing FAU-type zeolite using coal gasification fine slag includes the following steps: S1. After grinding and sieving the fine coal gasification slag, dry it and then acid wash the powder after grinding and sieving to remove impurities to obtain pretreated fine coal gasification slag. S2. The pretreated coal gasification fine slag is mixed with sodium hydroxide in a certain proportion and activated at high temperature to realize the chemical restructuring of silicon and aluminum in the coal gasification fine slag, and the alkaline fusion roasting product is obtained. Then, deionized water is added to the alkaline fusion roasting product and stirred thoroughly. After stirring is stopped, the product is allowed to stand for aging. S3. The aged aqueous solution is subjected to hydrothermal crystallization, and the resulting sample is washed and dried to finally obtain FAU type zeolite.

[0011] Furthermore, in S1, the mesh size of the fine coal gasification slag after grinding and sieving is less than or equal to 150 μm.

[0012] Furthermore, in S1, the pickling uses a hydrochloric acid solution with a concentration of 2 mol / L, and the solid-liquid ratio of the hydrochloric acid solution to the powder after grinding and sieving is 1:7 g / mL.

[0013] Furthermore, in S2, the mass ratio of the pretreated coal gasification fine slag to sodium hydroxide is 1:1.0-1.4.

[0014] Furthermore, in S2, the high-temperature activation temperature is 650°C, and the activation time is 1.5-2 hours.

[0015] Furthermore, in S2, the mass ratio of the alkali-melted roasting product to deionized water is 1:5, and the stirring time is 2 hours.

[0016] Furthermore, in S2, the settling and aging time is 18-24 hours.

[0017] Furthermore, in S3, the hydrothermal crystallization temperature is 90-105℃ and the time is 12-18h.

[0018] The FAU-type zeolite prepared using coal gasification slag is applied to the adsorption treatment of heavy metals.

[0019] The principle of this invention is as follows: This invention is based on the amorphous or weakly crystalline silicon and aluminum components in coal gasification slag. After alkaline activation, active silicon and aluminum species are dissolved out. By controlling the silicon-aluminum ratio and sodium-silicon ratio, a suitable precursor is formed. During the aging process, silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra rearrange to generate crystal nuclei. Subsequently, crystal growth is achieved through hydrothermal crystallization, and finally, the framework structure of FAU-type zeolite is constructed.

[0020] The beneficial effects of this invention are as follows: 1. The raw materials of this invention are widely available, with coal gasification fine slag, which is polluting to the environment, as the main source of silicon and aluminum. There is no need to introduce additional industrial-grade silicon and aluminum reagents, which not only significantly reduces production costs, but also realizes the high added value utilization of coal gasification fine slag, with good environmental and economic benefits.

[0021] 2. This invention achieves deep activation of the inert silica-alumina phase through mixed grinding, high-temperature alkali fusion, and aging-hydrothermal synergy, thereby improving the crystallinity and phase purity of FAU-type zeolite.

[0022] 3. The process of this invention is stable, has a wide parameter window, and is well adaptable to fine slag from coal gasification of different sources. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the preparation method of the present invention; Figure 2 The FAU-type zeolite prepared in Example 1 of this invention is a Cd-type zeolite. 2+ Adsorption performance diagram; Figure 3 The FAU-type zeolite prepared in Example 2 of this invention is a Cd-type zeolite. 2+ Adsorption performance diagram; Figure 4 The FAU-type zeolite prepared in Example 2 of this invention reacts with different concentrations of Cd. 2+ Comparison chart of adsorption performance differences; Figure 5 The adsorption kinetics of different metals on the FAU-type zeolite prepared in Example 2 of this invention are shown. Figure 6 This is a scanning electron microscope image of the FAU-type zeolite prepared in Example 2 of the present invention; Figure 7 The image shows the XRD pattern of the FAU-type zeolite prepared in Example 2 of this invention.

[0024] Figure 8 The FAU-type zeolite prepared in Example 3 of this invention is a Cd-type zeolite. 2+ Adsorption performance diagram; Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In this invention, the coal gasification slag is preferably fine coal gasification slag. The composition of the coal gasification slag in this invention was analyzed using X-ray fluorescence spectrometry (XRF): SiO2: 31.280%, Fe2O3: 28.148%, Al2O3: 15.841%, CaO: 13.654%, SO3: 4.036%, K2O: 1.732%, P2O5: 1.062%, TiO2: 1.730%, Na2O: 0.865%, MgO: 0.586%, Cl: 0.584%, ZrO2: 0.180%, SrO: 0.137%, MnO: 0.086%, ZnO: 0.064%, Rb2O: 0.014%, and the balance being impurities. In this embodiment of the invention, the coal gasification slag is preferably sourced from the Jinzhong Coal Mine in Shanxi Province.

[0026] Example 1 according to Figure 1 The flowchart is prepared using the following specific steps: The fine slag from coal gasification is ground to ensure that the particle size after grinding is ≤150μm.

[0027] The ground coal gasification slag was added to a 2 mol / L hydrochloric acid solution at a solid-liquid ratio of 1:7 g / mL and acid-washed at room temperature for 3 hours. After filtration, it was washed with deionized water until neutral and dried to obtain the pretreated slag.

[0028] A certain mass of coal gasification fine slag was weighed and mixed with sodium hydroxide at a mass ratio of 1:1.0. The mixed solution was placed in a tube furnace and calcined at 650℃ for 1.5 h to obtain the alkali-fused calcined product.

[0029] Take the roasted product and 5 times its mass of deionized water and stir at room temperature for 2 h to mix it evenly, then let it stand at 50℃ for 18 h to age.

[0030] The aged slurry was transferred to a hydrothermal reactor and subjected to hydrothermal crystallization at 100°C for 18 hours. After the reaction, the solid-liquid mixture was separated, repeatedly washed with water until neutral, and dried to obtain the FAU type zeolite product.

[0031] The FAU-type zeolite prepared in Example 1 was subjected to Cd... 2+ Ion adsorption performance test.

[0032] Figure 2 For Cd 2+ Under the conditions of an initial ion concentration of 100 mg / L, a volume of 0.1 L, and a FAU-type zeolite dosage of 1.5 g / L, the FAU-type zeolite prepared in Example 1 was used for adsorption treatment. After adsorption for 180 min, the adsorption of Cd was reduced. 2+ The ion removal rate reached 45%, indicating that the alkali content was too low and the release of active sites or mass transfer conditions were limited.

[0033] Example 2 The pretreated coal gasification slag from Example 1 was mixed with sodium hydroxide at a mass ratio of 1:1.2, and the remaining steps were the same to obtain an FAU type zeolite structure.

[0034] The FAU-type zeolite prepared in Example 2 was subjected to Cd treatment. 2+ Ion adsorption performance test.

[0035] Figure 3 For Cd 2+ Under the conditions of an initial ion concentration of 100 mg / L, a volume of 0.1 L, and a FAU-type zeolite dosage of 1.5 g / L, the FAU-type zeolite prepared in Example 2 was used for adsorption treatment. After adsorption for 180 min, the adsorption of Cd was reduced. 2+ The ion removal rate reached 55%, indicating that the active sites were fully utilized and the pore structure and mass transfer conditions were well coordinated under this ratio.

[0036] The adsorption performance of FAU-type zeolite (selected for optimal adsorption) prepared in Example 2 was compared for different cadmium ion concentrations. The dosage of FAU-type zeolite was 1.5 g / L, and the Cd concentration was measured. 2+ The solutions had concentrations of 100 mg / L and 200 mg / L, with a volume of 0.1 L, yielding Cd. 2+ Changes in concentration and removal rate during the adsorption process.

[0037] Figure 4 FAU-type zeolite at concentrations of 100 mg / L and 200 mg / L, respectively, showed its effect on Cd. 2+ Adsorption rate graph of the solution. At 100 mg / L, FAU-type zeolite maintained a high adsorption efficiency throughout 180 min, Cd 2+ The removal rate can reach 85%. After stirring is stopped after 180 minutes and the solution is allowed to stand for 2 days, the Cd content in the solution is... 2+ The concentration was further reduced to 4 mg / L, corresponding to a removal rate increase of 96%, indicating that FAU-type zeolite effectively removes low concentrations of Cd. 2+ It exhibits excellent adsorption performance and good long-term stability. At 200 mg / L, the adsorption effect of FAU-type zeolite significantly decreased within 180 min, with a removal rate of approximately 50%. After stopping stirring and allowing it to stand for 2 days, the Cd concentration in the solution decreased. 2+ When the concentration was reduced to 64 mg / L, the removal rate increased to about 68%, showing that FAU-type zeolite still has a certain adsorption capacity under high concentration conditions, but the overall efficiency is reduced.

[0038] from Figure 4 In the comparison, we found that at high concentrations of Cd 2+In solution, the adsorption effect did not reach the ideal level, possibly because the number of adsorption sites is limited.

[0039] The adsorption kinetics of various metals for the FAU-type zeolite (selected with the best adsorption capacity) prepared in Example 2 are shown in the figure below. Figure 5 As shown, the adsorption kinetics results indicate that FAU-type zeolite has a high affinity for Pb. 2+ Cu 2+ and Cd 2+ All of them exhibited rapid and efficient adsorption performance.

[0040] The microscopic SEM image of the FAU-type zeolite (selected for optimal adsorption) prepared in Example 2 is shown below. Figure 6 As shown, the sample exhibits a multi-level particle structure, with large particles bearing fine crystals on their surfaces, demonstrating a hierarchical aggregation morphology. Microscopically, the sample consists of spherical or clustered particles formed by the self-assembly of numerous submicron-sized microcrystalline units, with rough surfaces and a distinct porous structure. This multi-level porous structure constructed from microcrystals not only helps to increase the specific surface area of ​​the material but also shortens the diffusion path of the adsorbate within the pores, thereby providing more effective active sites for the adsorption process.

[0041] The XRD pattern of the FAU-type zeolite (selected for optimal adsorption) prepared in Example 2 is shown below. Figure 7 As shown in the XRD pattern, no obvious impurity phase peaks were observed, indicating the successful synthesis of a relatively pure FAU-type zeolite structure with high crystallinity. The good crystallinity and complete three-dimensional channel structure of the FAU-type zeolite are characteristic of Cd... 2+ The diffusion and ion exchange of the ions are favorable. The supercage structure and large pore size help heavy metal ions enter the pores and interact with the negative potential points of the framework, thus exhibiting excellent adsorption performance.

[0042] Example 3 The pretreated coal gasification slag from Example 1 was mixed with sodium hydroxide at a mass ratio of 1:1.4, and the remaining steps were the same to obtain an FAU-type zeolite structure.

[0043] The FAU-type zeolite prepared in Example 3 was subjected to Cd treatment. 2+ Ion adsorption performance test.

[0044] Figure 8 For Cd 2+ Under the conditions of an initial ion concentration of 100 mg / L, a volume of 0.1 L, and a FAU-type zeolite dosage of 1.5 g / L, the FAU-type zeolite prepared in Example 3 was used for adsorption treatment. After adsorption for 180 min, the adsorption of Cd was reduced. 2+ The ion removal rate reached 50%, indicating that an excessively high ratio did not significantly improve effective adsorption, possibly due to excessive alkali or structural redundancy.

[0045] The above description only illustrates the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. A method for preparing FAU-type zeolite using coal gasification fine slag, characterized in that: Includes the following steps: S1. After grinding and sieving the fine coal gasification slag, dry it and then acid wash the powder after grinding and sieving to remove impurities to obtain pretreated fine coal gasification slag. S2. The pretreated coal gasification fine slag is mixed with sodium hydroxide in a certain proportion and activated at high temperature to realize the reformation of the silicon-aluminum chemical structure in the coal gasification fine slag, and the alkaline fusion roasting product is obtained. Then, deionized water is added to the alkaline fusion roasting product and stirred thoroughly. After stirring is stopped, the mixture is allowed to stand for aging. S3. The aged aqueous solution is subjected to hydrothermal crystallization, and the resulting sample is washed and dried to finally obtain FAU type zeolite.

2. The method for preparing FAU-type zeolite using coal gasification fine slag according to claim 1, characterized in that: In S1, the mesh size of the fine coal gasification slag after grinding and sieving is less than or equal to 150 μm.

3. The method for preparing FAU-type zeolite using coal gasification fine slag according to claim 1, characterized in that: In S1, the pickling uses a hydrochloric acid solution with a concentration of 2 mol / L, and the solid-liquid ratio of the hydrochloric acid solution to the powder after grinding and sieving is 1:7 g / mL.

4. The method for preparing FAU-type zeolite using coal gasification fine slag according to claim 1, characterized in that: In S2, the mass ratio of the pretreated coal gasification fine slag to sodium hydroxide is 1:1.0-1.

4.

5. The method for preparing FAU-type zeolite using coal gasification fine slag according to claim 1, characterized in that: In S2, the high-temperature activation temperature is 650℃, and the activation time is 1.5-2h.

6. The method for preparing FAU-type zeolite using coal gasification fine slag according to claim 1, characterized in that: In S2, the mass ratio of the alkali-melted roasting product to deionized water is 1:5, and the stirring time is 2 hours.

7. The method for preparing FAU-type zeolite using coal gasification fine slag according to claim 1, characterized in that: In S2, the settling and aging time is 18-24 hours.

8. The method for preparing FAU-type zeolite using coal gasification fine slag according to claim 1, characterized in that: In S3, the hydrothermal crystallization temperature is 90-105℃ and the time is 12-18h.

9. An FAU-type zeolite prepared by the method according to any one of claims 1-8, applied to the adsorption treatment of heavy metals.

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