Method for hydrothermally synthesizing zeolite molecular sieve from multi-element solid waste, zeolite molecular sieve and application of zeolite molecular sieve

Abstract

The invention provides a method for hydrothermally synthesizing a zeolite molecular sieve from multiple solid wastes, the zeolite molecular sieve and application, and belongs to the technical field of environmental protection-resource recycling. The synthesis method comprises the following steps: pretreating fly ash and steel slag or silica fume to obtain a treated product; adding a sodium hydroxide solution into the treated product, and carrying out hydrothermal reaction to obtain a zeolite product; when the treatment product is a calcined product of fly ash and steel slag, the zeolite product is a Y-type zeolite molecular sieve; when the treatment product is a geopolymer, the zeolite product is an analcime molecular sieve. According to the present invention, fly ash, steel slag and steel slag multi-element solid waste are adopted as cheap raw materials, and an alkali fusion hydrothermal synthesis method and a geopolymer in-situ conversion method are adopted to prepare the efficient, low-cost and environment-friendly zeolite molecular sieve, such that the low-cost prepared zeolite molecular sieve is obtained while the heavy metal wastewater is treated at the low cost; the efficient comprehensive utilization of the fly ash, the steel slag and the silica fume is realized.

Description

Methods for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste, and applications of zeolite molecular sieves. Technical Field

[0001] This disclosure belongs to the field of environmental protection and resource recycling technology, specifically relating to a method for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste, as well as the zeolite molecular sieves and their applications. Background Technology

[0002] With the rapid development of industries such as chemicals, cables, and batteries, large amounts of lead-containing waste are being discharged into waterways without treatment. Lead is one of the most common heavy metal pollutants with high solubility and strong mobility, accumulating through the food chain and causing enormous harm to organisms and humans. Currently, lead pollution remediation technologies mainly aim to change the form in which lead exists, making it stable and reducing its mobility and bioavailability. Among these, adsorption methods have advantages such as low cost, simple operation, low energy consumption, and high efficiency, making them one of the most promising technologies for heavy metal wastewater removal. In recent years, domestic and international research has found that nanomaterials, industrial solid waste, modified chitosan, and biochar materials can all serve as good adsorbents for the treatment of lead pollution.

[0003] Industrial solid waste refers to various waste residues, dust, and other solid wastes generated during industrial production processes. Industrial solid waste includes slag, metakaolin, red mud, fly ash, coal gangue, phosphorus slag, and silica fume, among others.

[0004] In addition, the minerals currently used to synthesize zeolite molecular sieves are mainly aluminosilicate minerals, which have high raw material costs. Currently, molecular sieves are also prepared using monolithic solid waste. However, this method cannot achieve the synergistic treatment of multiple solid wastes and requires the addition of other silicon or aluminum source raw materials as well as some other hazardous organic substances. Furthermore, the synthesis time is long, the process of extracting aluminum or silicon sources is complex, and multiple high-temperature calcination and heating dissolution processes are required, resulting in high energy consumption. Summary of the Invention

[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a method for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste, as well as the zeolite molecular sieves and their applications.

[0006] One aspect of this disclosure provides a method for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste, the method comprising:

[0007] Fly ash and steel slag or silica fume are pretreated to obtain the treated product;

[0008] Sodium hydroxide solution is added to the processed product, and a hydrothermal reaction is carried out to obtain a zeolite product;

[0009] When the processed product is a calcined product of fly ash and steel slag, the zeolite product is a Y-type zeolite molecular sieve; when the processed product is a geopolymer, the zeolite product is analcime molecular sieve.

[0010] Optionally, when the processed product is a calcined product of fly ash and steel slag, the fly ash and steel slag are pretreated to obtain the processed product, which includes:

[0011] Fly ash is dissolved in sodium hydroxide solution and calcined to obtain calcined fly ash product;

[0012] Steel slag is dissolved in aluminum hydroxide solution and calcined to obtain the calcined steel slag product.

[0013] Optionally, the temperature for calcining fly ash dissolved in sodium hydroxide solution is 750-850℃, and the time is 0.5-1.5h.

[0014] The steel slag is dissolved in aluminum hydroxide solution and calcined at a temperature of 450-550℃ for 1.5-2.5 hours.

[0015] Optionally, when the processed product is a calcined product of fly ash and steel slag, sodium hydroxide solution is added to the processed product, and a hydrothermal reaction is carried out to obtain a zeolite product, comprising:

[0016] The calcined steel slag product and the calcined fly ash product were weighed according to a Si / Ai ratio of 3.0, and sodium hydroxide solution was added to the weighed calcined fly ash product and calcined steel slag product, followed by aging treatment.

[0017] The aged samples were subjected to a hydrothermal reaction.

[0018] The sample after hydrothermal synthesis reaction was centrifuged, filtered, washed, dried, ground, and sieved to obtain Y-type zeolite molecular sieve.

[0019] Optionally, the aging treatment is carried out at a temperature of 35-45°C for 2-4 hours; and / or,

[0020] The hydrothermal reaction temperature is 80-100℃, the time is 22-26h, and the stirring speed is 10-20r / min; and / or,

[0021] The drying process is carried out at a temperature of 35-45℃.

[0022] Optionally, when the processed product is a geopolymer, fly ash and silica fume are pretreated to obtain the processed product, which includes:

[0023] Fly ash and silica fume were mixed in a mass ratio of (2-4):1 as cement raw materials, and sodium dodecyl sulfonate, anhydrous sodium silicate, water, and hydrogen peroxide were added sequentially to the cement raw materials to obtain a mixed slurry.

[0024] The mixed slurry is placed in a mold, vibrated and sealed, and the sealed mold is cured at room temperature to obtain a block sample. The block sample is then cured at high temperature and at room temperature in sequence to obtain a geopolymer.

[0025] Optionally, when the processed product is a geopolymer, a sodium hydroxide solution is added to the processed product, and a hydrothermal reaction is carried out to obtain a zeolite product, comprising:

[0026] Sodium hydroxide solution was added to the geopolymer, followed by hydrothermal treatment. The product after hydrothermal treatment was washed until the pH of the filtrate was 8.0, and then dried to obtain analcime molecular sieve.

[0027] Optionally, the hydrothermal treatment is performed at a temperature of 210-230°C for a time of 15-17 hours; and / or,

[0028] The drying temperature is 100-110℃.

[0029] In another aspect of this disclosure, a multi-component solid waste-based hydrothermal synthesis method for zeolite molecular sieves is proposed, wherein the zeolite molecular sieve is synthesized using the method described above.

[0030] Another aspect of this disclosure proposes an application of a multi-component solid waste-based hydrothermal synthetic zeolite molecular sieve, which uses the multi-component solid waste-based hydrothermal synthetic zeolite molecular sieve described above for the removal of heavy metal ions from wastewater.

[0031] This disclosure presents a method for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste, as well as the zeolite molecular sieves and their applications. The method includes: pretreating fly ash and steel slag or silica fume to obtain a treated product; adding sodium hydroxide solution to the treated product and reacting it hydrothermally to obtain a zeolite product; when the treated product is a calcined product of fly ash and steel slag, the zeolite product is a Y-type zeolite molecular sieve; when the treated product is a geopolymer, the zeolite product is analcime molecular sieve. This disclosure uses fly ash, steel slag, and multi-component solid waste of steel slag as inexpensive raw materials, and prepares efficient, low-cost, and environmentally friendly zeolite molecular sieves through alkaline fusion hydrothermal synthesis and in-situ conversion of geopolymers. This low-cost zeolite molecular sieve synthesis achieves efficient comprehensive utilization of fly ash, steel slag, and silica fume while treating heavy metal wastewater at low cost. Attached Figure Description

[0032] Figure 1 is a flowchart of a method for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste according to a specific embodiment of this disclosure.

[0033] Figure 2 is the XRD pattern of the zeolite molecular sieve of Embodiment 1 of this disclosure;

[0034] Figure 3 is a SEM image of the zeolite molecular sieve of Embodiment 1 of this disclosure;

[0035] Figure 4 is the XRD pattern of the zeolite molecular sieve of Embodiment 2 of this disclosure;

[0036] Figure 5 is a SEM image of the zeolite molecular sieve of Embodiment 2 of this disclosure. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0038] As shown in Figure 1, one aspect of this disclosure provides a method S100 for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste, specifically including the following steps S110 to S120:

[0039] S110. Pre-treat fly ash and steel slag or silica fume to obtain the treated product.

[0040] It should be noted that different processing methods for fly ash and steel slag or silica fume during step S110 will yield different processing products. For example, when modifying them, calcined products will be obtained, and when they are subjected to molding and oxidation synthesis processes, geopolymers will be obtained.

[0041] In some preferred embodiments, when the processed product is a calcined product of fly ash and steel slag, the fly ash and steel slag are pretreated to obtain the processed product, which includes:

[0042] Place 10-30 parts by weight of fly ash in a 100 mL porcelain crucible. Separately weigh 70-90 wt% sodium hydroxide and add 10-30 mL of deionized water to it. After complete dissolution, a sodium hydroxide solution is formed. Pour the sodium hydroxide solution into the porcelain crucible. Place the porcelain crucible in a muffle furnace for calcination at a calcination temperature of 750-850℃ and a heating rate of 10℃ / min for 0.5-1.5 h. Cool the crucible to room temperature in the furnace to obtain the calcined fly ash product. Grind the cooled modified raw material into powder, pass it through a 100-mesh sieve, and place it in a desiccator for later use.

[0043] In a 100mL porcelain crucible containing 10-30 parts by weight of steel slag, separately weigh 40-60wt% aluminum hydroxide and add 10-30mL of deionized water. After complete dissolution, pour the aluminum hydroxide solution into the crucible. Place the crucible in a muffle furnace and calcine for 1.5-2.5 hours at a calcination temperature of 450-550℃ and a heating rate of 10℃ / min. Cool to room temperature in the furnace to obtain the calcined steel slag product. Grind the cooled modified raw material into powder, pass it through a 100-mesh sieve, and store it in a desiccator for later use.

[0044] As a further preferred option, the content of fly ash and steel slag can be preferably 10 parts by mass, 20 parts by mass, 30 parts by mass, etc. Of course, other parts by mass can also be preferred, and there is no specific limitation on this.

[0045] As a further preferred option, the mass fraction of sodium hydroxide added to fly ash can preferably be 70wt%, 80wt%, or 90wt%, the calcination temperature can preferably be 750℃, 800℃, or 850℃, and the calcination time can preferably be 0.5h, 1h, or 1.5h.

[0046] The preferred mass fraction of aluminum hydroxide added to the steel slag is 40wt%, 50wt%, or 60wt%, the preferred calcination temperature is 450℃, 500℃, or 550℃, and the preferred calcination time is 1.5h, 2h, or 2.5h.

[0047] This embodiment, by controlling parameters such as component content and calcination temperature, enables the extraction of silicon and aluminum sources in a single calcination step, eliminating the need for the addition of other organic substances and complex processes such as multiple calcinations and heating dissolutions. Furthermore, the primary particles formed under the calcination conditions of this embodiment form a preliminary framework through physical bonding or layout sintering, providing a supporting foundation for the growth of zeolite crystals.

[0048] In some other preferred embodiments, when the processed product is a geopolymer, fly ash and silica fume are pretreated to obtain the processed product, which includes:

[0049] Mix fly ash and silica fume in a ball mill at a ratio of (2-4):1 for 8-12 minutes to obtain cement raw materials. Weigh a certain amount of cement raw materials and pour them into a cement paste mixer. Add 0.2-0.4% sodium dodecyl sulfonate and stir slowly for 1-3 minutes. Then add a solution of 25-30% anhydrous sodium silicate and 35-45% water, which has been mixed evenly and allowed to stand for 20-25 hours. Stir slowly for 1-3 minutes, then stir quickly for 1-3 minutes. Finally, add 0.5-1.5% hydrogen peroxide and stir slowly for 1-3 minutes to obtain a mixed slurry. Pour the mixed slurry into a pre-oiled mold (20mm×20mm×20mm), compact it for about 4-6 minutes, and then seal it. Place the sealed mold in a cement constant temperature and humidity standard curing chamber and cure for 20-25 hours at a temperature of 20℃ and a humidity of 93%. Remove the mold, disassemble the mold, seal the block specimen, and place it in a high-temperature curing chamber at 60-70℃ for 20-25 hours. Then, remove it and place it in a cement constant temperature and humidity standard curing chamber for sealed curing until the desired age of 20-25 hours to obtain the geopolymer.

[0050] As a further preferred option, the ratio of fly ash to silica fume can be preferably 2:1, 3:1, 4:1, etc.

[0051] As a further preferred option, the temperature for high-temperature curing can be 60℃, 65℃, 70℃, etc., and the time can be 20h, 22h, 24h, 25h, etc.

[0052] This embodiment improves material dispersibility and surface properties by adding reagents such as sodium dodecyl sulfonate, anhydrous sodium silicate solution, and hydrogen peroxide, thereby enhancing the performance of the mixed slurry and cement products, optimizing the geopolymer's properties, and influencing its microstructure and physicochemical properties. Secondly, by subjecting the mixed slurry to multi-stage curing after molding, the geopolymer is fully hydrated and hardened, acquiring sufficient strength and stability to facilitate subsequent hydrothermal reactions and other operations. Sodium dodecyl sulfonate improves material dispersibility, reduces agglomeration, and ensures uniform distribution of silica and alumina species in the mixed slurry, promoting homogeneity in subsequent reactions and preventing structural damage caused by localized stress concentration. Microbubbles generated by hydrogen peroxide decomposition form a porous structure in the mixed slurry, optimizing the material's porosity and specific surface area. The geopolymer curing process promotes hydration reactions and crystal growth through temperature gradients, forming a dense matrix. The high-temperature curing stage (60-70℃) accelerates the condensation reaction of aluminosilicates, improving the material's early strength and providing stable support for subsequent hydrothermal reactions.

[0053] This embodiment achieves the formation of geopolymers under relatively mild conditions by controlling parameters such as the content of each component, the mixing order, and the processing time, without the need for high-speed stirring or high-temperature calcination. The geopolymer itself is a three-dimensional network structure cementitious material with ceramic-like mechanical strength. Its structure contains silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra connected by covalent bonds, forming a stable framework that provides a self-supporting matrix for subsequent hydrothermal conversion into zeolite.

[0054] S120. Sodium hydroxide solution is added to the processed product, and a hydrothermal reaction is carried out to obtain a zeolite product.

[0055] It should be noted that when the processed product of step S120 is different, the corresponding hydrothermal reaction will also be different, thus obtaining different zeolite products. For example, when the processed product is the calcination product of fly ash and steel slag, the zeolite product is Y-type zeolite molecular sieve; when the processed product is geopolymer, the zeolite product is analcime molecular sieve.

[0056] In some preferred embodiments, when the processed product is a calcined product of fly ash and steel slag, sodium hydroxide solution is added to the processed product, and a hydrothermal reaction is carried out to obtain a zeolite product, comprising:

[0057] Weigh out 8-12 parts by mass of the calcined steel slag and fly ash products according to a Si / Al ratio of 3.0. Pour these into an Erlenmeyer flask, add 70-90 mL of 2-4 mol / L sodium hydroxide solution, and stir rapidly until homogeneous. Then, age the mixture at 35-45℃ for 2-4 hours. After aging, place the sample in a water bath for hydrothermal reaction, controlling the hydrothermal temperature at 80-100℃ and the hydrothermal time at 22-26 hours, with a low stirring speed (10-20 r / min). After the hydrothermal synthesis reaction is complete, remove the sample, centrifuge and filter, repeatedly wash the filter residue with anhydrous ethanol or distilled water, dry in a 35-45℃ oven, grind, and pass through an 180-mesh sieve to obtain Y-type zeolite molecular sieve.

[0058] As a further preferred option, the temperature of the hydrothermal reaction can be preferably 80℃, 85℃, 90℃, 95℃, 100℃, etc., and the time can be preferably 22h, 23h, 24h, 25h, 26h, etc.

[0059] In this embodiment, under the aforementioned low-temperature hydrothermal conditions, the silicon and aluminum species in the calcined fly ash and steel slag products redissolve and directionally crystallize to form Y-type zeolite. Simultaneously, the low stirring speed (10-20 r / min) reduces crystal breakage, promotes crystal growth along a specific direction, and encourages interweaving to form a continuous three-dimensional network structure. Furthermore, the concentration of the NaOH solution (2-4 mol / L) and the aging time (2-4 h) optimize the silicon-to-aluminum ratio (Si / Al = 3.0), resulting in a more stable zeolite molecular sieve crystal structure.

[0060] In some preferred embodiments, when the processed product is a geopolymer, sodium hydroxide solution is added to the processed product, and a hydrothermal reaction is carried out to obtain a zeolite product, including: in-situ conversion using a hydrothermal synthesis method, placing fly ash-silica-based geopolymer blocks into a polytetrachloroethylene hydrothermal reactor, adding 20-40 mL of a 3-4 mol / L sodium hydroxide solution, sealing, and hydrothermally crystallizing at 210-230°C for 15-17 h. After hydrothermal completion, the hydrothermal product is repeatedly washed until the pH of the filtrate is close to 8.0, and then dried at 100-110°C to obtain analcime molecular sieve.

[0061] As a further preferred option, the temperature of the hydrothermal reaction can be preferably 210℃, 220℃, 230℃, etc., and the time can be preferably 15h, 16h, 17h, etc.

[0062] In this embodiment, the geopolymer mass undergoes in-situ transformation under high-temperature hydrothermal conditions (210-230℃, 15-17h), during which its original network structure gradually depolymerizes and reorganizes into analcime crystals. Since the geopolymer itself already possesses a certain strength, the crystals preferentially grow within the matrix during the transformation process, forming a reinforcing phase that complements the original structure, thereby retaining its self-supporting properties.

[0063] This embodiment uses industrial solid wastes such as fly ash, steel slag, and silica fume as raw materials to synthesize zeolite molecular sieves. The synthesis and preparation conditions are simple, and zeolite molecular sieves are synthesized using inexpensive raw materials, which can turn waste into treasure, reduce costs, and eliminate the need to add other silicon sources, aluminum sources, or other organic matter, as well as additional template agents. This avoids the high cost and resource consumption of the current method of preparing zeolite molecular sieves using chemically synthesized powders and kaolin mineral resources.

[0064] In another aspect of this disclosure, a zeolite molecular sieve is proposed, which is prepared by the hydrothermal synthesis method described above. For example, using fly ash, steel slag and steel slag multi-element solid waste as inexpensive raw materials, a high-efficiency, low-cost, environmentally friendly zeolite molecular sieve is prepared by alkaline fusion hydrothermal synthesis and geopolymer in-situ conversion method. The specific process is described above and will not be repeated here.

[0065] The zeolite molecular sieves of this embodiment include Y-type zeolite and anticline zeolite. Y-type zeolite has a supercage structure, where crystals interact through hydrogen bonds and van der Waals forces to form closely packed aggregates, thus exhibiting high compressive strength. In the three-dimensional framework structure of anticline zeolite, the silicon-aluminum tetrahedra are connected by oxygen bridges, forming stable cubic crystals with tight inter-crystal bonding, making them resistant to collapse.

[0066] In another aspect, this disclosure proposes an application of a zeolite molecular sieve for the removal of heavy metal ions from water, such as Pb. 2+ The removal rate can reach 99.04%.

[0067] The zeolite molecular sieve of this embodiment has a low synthesis cost. The zeolite molecular sieve can be powder particles or block materials with a certain strength. It can effectively remove heavy metal ions from water and has great advantages and application prospects in adsorption, separation and catalysis. It can achieve low-cost treatment of heavy metal wastewater, and also realize the efficient comprehensive utilization of fly ash, steel slag and silica fume.

[0068] The method for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste will be further illustrated below with specific embodiments:

[0069] Example 1

[0070] This example demonstrates a method for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste, comprising the following steps:

[0071] Phase 1: Modification process of zeolite molecular sieve raw materials:

[0072] S1. Weigh 20.0g of fly ash raw material and place it in a 100mL porcelain crucible. Separately, weigh 80wt% sodium hydroxide in a drying beaker and pour 20mL of deionized water into the beaker. After complete dissolution, pour the sodium hydroxide solution into the porcelain crucible. Calcinate the crucible in a muffle furnace at a calcination temperature of 800℃ and a heating rate of 10℃ / min for 1 hour, then cool it to room temperature in the furnace. Grind the cooled modified raw material into powder, pass it through a 100-mesh sieve, and place it in a desiccator for later use.

[0073] S2. Weigh 20.0g of steel slag raw material and place it in a 100mL porcelain crucible. Separately, weigh 50wt% aluminum hydroxide into a drying beaker and pour 20mL of deionized water into the beaker. After complete dissolution, pour the aluminum hydroxide solution into the porcelain crucible. Calcinate the crucible in a muffle furnace at a calcination temperature of 500℃ and a heating rate of 10℃ / min for 2 hours, then cool it to room temperature in the furnace. Grind the cooled modified raw material into powder, pass it through a 100-mesh sieve, and place it in a desiccator for later use.

[0074] Second stage: Hydrothermal synthesis process of molecular sieves:

[0075] S3. Prepare an alkaline melt by weighing 10g of calcined activated steel slag / fly ash product into an Erlenmeyer flask according to Si / Al=3.0. Then add 80mL of 3mol / L sodium hydroxide solution and stir the mixture rapidly until homogeneous. Then age it at 40℃ for 3h.

[0076] S4. Place the aged sample into a water bath, control the hydrothermal temperature at 90℃, and the hydrothermal time at 24h. Carry out the hydrothermal reaction at a low stirring speed (10r / min).

[0077] S5. After the hydrothermal synthesis reaction is complete, take out the sample, centrifuge and filter, wash the filter residue repeatedly with anhydrous ethanol or distilled water, put it in a 40℃ oven for drying, grind it, and pass it through a 180-mesh sieve to obtain the zeolite product, namely, ZK-14 type molecular sieve.

[0078] Furthermore, the phase composition analysis of the alkali-melt hydrothermal synthesis product in this embodiment is shown in Figure 2. In the figure, Z represents Zeolite ZK-14, S represents Silicon oxide, and M represents Mullite. It can be seen that the molecular sieve synthesized under optimal activation conditions mainly consists of zeolite, silicon dioxide, and some amorphous substances. At this point, the crystal purity is high, and the crystal structure is relatively complete. Comparison with the XRD pattern of fly ash raw material shows that the mullite phase in the fly ash disappears, and the quartz phase transforms into the silicon dioxide phase. This indicates that alkali-melt roasting activation played a role. Analysis shows that the molecular formula of the synthesized product ZK-14 molecular sieve is Na. 3.68 Al 3.6 Si 8.4 O 24 (H2O), with a silicon-to-aluminum ratio of 2.3, belongs to type Y zeolite (Si / Al = 1.5–3), and its calculated density is 1.92 g / cm³. 3 .

[0079] Furthermore, the microstructure analysis of the alkali-melted hydrothermal synthesis product in this embodiment is shown in Figure 3. The synthesized ZK-14 molecular sieve mainly consists of smooth-surfaced columnar particles. The length of the columnar particles is approximately 200–500 nm, and the height and width are approximately 100 nm. Under high-magnification electron microscopy, almost no silica crystals are visible, indicating that their content is very low. Therefore, the molecular sieve prepared in this embodiment has high purity.

[0080] Furthermore, this embodiment demonstrates the synthesis of molecular sieves in wastewater containing Pb. 2+ The adsorption performance was analyzed, and as shown in Table 1, after the molecular sieve treatment for heavy metal adsorption in water, the concentration of heavy metal ions in the water decreased by 0.1918 mg / L, and the adsorption capacity was 19.81 mg / g. For Pb... 2+The removal rate reached 99.04%.

[0081] Table 1. Molecular sieves in Example 1 for their effect on heavy metal ions Pb in water. 2+ Exchange volume

[0082]

[0083] In this embodiment, fly ash is used as the aluminum source and steel slag as the silicon source. Alkali melting disrupts the aluminosilicate structure in both the aluminum and silicon sources, breaking chemical bonds and transforming the crystal structure into highly reactive amorphous or partially crystalline substances. This allows silicon and aluminum to dissolve and react more readily. The silicon and aluminum species in the raw materials react with alkalis (such as sodium hydroxide or aluminum hydroxide) to form intermediate products such as aluminosilicate complexes. These intermediate products, in subsequent hydrothermal reactions, can arrange themselves in an orderly manner and undergo condensation reactions according to the crystal structure rules of the molecular sieve, recombining to form molecular sieve crystals with specific pore structures and chemical compositions. This achieves efficient resource utilization, solves waste disposal problems, reduces the cost of molecular sieve preparation, eliminates the need for template agents and other reagents required in traditional hydrothermal methods, effectively simplifying the preparation process. Furthermore, the synthesized zeolite molecular sieve exhibits high crystallinity.

[0084] Example 2

[0085] This example demonstrates a method for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste, comprising the following steps:

[0086] Phase 1: Geopolymer Preparation Process

[0087] S1. Mix fly ash and silica fume in a 3:1 ratio in a ball mill for 10 minutes to obtain cement raw materials. Weigh a certain amount of cement raw materials and pour them into a cement paste mixer. Add 0.25% sodium dodecyl sulfonate and stir slowly for 2 minutes. Then add a solution of 28% anhydrous sodium silicate and 40% water, which has been mixed evenly and allowed to stand for 24 hours. Stir slowly for 2 minutes, then stir quickly for 2 minutes. Finally, add 1% hydrogen peroxide and stir slowly for 2 minutes to obtain a mixed slurry. Pour the mixed slurry into a pre-oiled mold (20mm×20mm×20mm), compact it for about 5 minutes, and then seal it. Place the sealed mold in a cement constant temperature and humidity standard curing chamber and cure for 24 hours at a temperature of 20℃ and a humidity of 93%. Remove the mold, disassemble the mold, seal the block specimen, and place it in a high-temperature curing chamber at 65℃ for 24 hours. Then, remove it and place it in a cement constant temperature and humidity standard curing chamber for sealed curing until the desired age of 24 hours to obtain the geopolymer.

[0088] Second stage: Synthesis of geopolymer hydrothermal in-situ conversion products:

[0089] S2. In-situ conversion using hydrothermal synthesis: Fly ash-silica-based polymer blocks were added to a polytetrachloroethylene hydrothermal reactor, along with 30 ml of a 3.5 mol / L sodium hydroxide solution. The reactor was sealed and hydrothermally crystallized at 220°C for 16 hours. After hydrothermal treatment, the hydrothermal product was repeatedly washed until the pH of the filtrate approached 8.0, and then dried at 105°C to obtain the zeolite product, i.e., analcime.

[0090] Furthermore, the phase composition analysis of the zeolite product synthesized by hydrothermal in-situ conversion of fly ash and silica fume geopolymer in this embodiment is shown in Figure 4. The zeolite product of hydrothermal in-situ conversion of geopolymer is analcime, and its overlap with PDF#01-070-157 is relatively high, indicating that the synthesized analcime is relatively pure and has few impurities.

[0091] Furthermore, the microstructure analysis of the zeolite product synthesized by hydrothermal in-situ conversion of fly ash-silica geopolymer in this embodiment is shown in Figure 5. The crystallization effect of analcime is good, and the crystallized product has a 24-sided structure with an average grain size between 10 μm and 15 μm. There are many analcime crystals with distinct edges and corners. The smaller the grain size, the larger its specific surface area and the better its adsorption performance.

[0092] Furthermore, this embodiment also demonstrates the Pb content of the synthesized molecular sieve in wastewater. 2+ Pb in wastewater 2+ The adsorption performance of the geopolymer at a concentration of 200 mg / L and a pH of 6.25 was analyzed, as shown in Table 2. The compressive strength of the geopolymer block after 7 days was 116 MPa, indicating its effectiveness against Pb. 2+ The removal rate was 96.56%.

[0093] For Pb 2+ The removal rate reached 96.56%.

[0094] Table 2. Molecular sieves for heavy metal ions Pb in water in Example 2 2+ Exchange volume

[0095]

[0096] This embodiment uses fly ash as the aluminum source and silica fume as the silicon source to synthesize self-supporting zeolite molecular sieves through in-situ conversion of geopolymers. This avoids complex post-processing steps and simplifies the preparation process. The synthesized zeolite molecular sieves have a self-supporting structure and can be independently molded without additional binders. This avoids the blockage of the molecular sieve pore structure or the adverse effects of binders on its adsorption performance. In practical applications, it can better maintain structural stability and has good adsorption performance.

[0097] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for hydrothermal synthesis of zeolite molecular sieves based on multi-component solid waste, characterized in that, The method includes: pretreating fly ash and steel slag or silica fume to obtain a treated product; adding sodium hydroxide solution to the treated product and reacting it hydrothermally to obtain a zeolite product; when the treated product is a calcined product of fly ash and steel slag, the zeolite product is a Y-type zeolite molecular sieve; when the treated product is a geopolymer, the zeolite product is analcime molecular sieve.

2. The method according to claim 1, characterized in that, When the processed product is a calcined product of fly ash and steel slag, the fly ash and steel slag are pretreated to obtain the processed product, including: dissolving fly ash in sodium hydroxide solution and calcining it to obtain a calcined fly ash product; and dissolving steel slag in aluminum hydroxide solution and calcining it to obtain a calcined steel slag product.

3. The method according to claim 2, characterized in that, The temperature for calcining fly ash dissolved in sodium hydroxide solution is 750-850℃, and the time is 0.5-1.5h; the temperature for calcining steel slag dissolved in aluminum hydroxide solution is 450-550℃, and the time is 1.5-2.5h.

4. The method according to any one of claims 1 to 3, characterized in that, When the processed product is a calcined product of fly ash and steel slag, sodium hydroxide solution is added to the processed product, and a hydrothermal reaction is carried out to obtain a zeolite product, including: weighing the calcined product of steel slag and the calcined product of fly ash according to a Si / Ai ratio of 3.0, adding sodium hydroxide solution to the weighed calcined product of fly ash and the calcined product of steel slag, and aging the product; subjecting the aged sample to a hydrothermal reaction; and centrifuging, filtering, washing, drying, grinding, and sieving the sample after the hydrothermal reaction to obtain a Y-type zeolite molecular sieve.

5. The method according to claim 4, characterized in that, The aging treatment is carried out at a temperature of 35-45℃ for 2-4 hours; and / or the hydrothermal reaction is carried out at a temperature of 80-100℃ for 22-26 hours with a stirring speed of 10-20 r / min; and / or the drying treatment is carried out at a temperature of 35-45℃.

6. The method according to claim 1, characterized in that, When the processed product is a geopolymer, fly ash and silica fume are pretreated to obtain the processed product, which includes: mixing fly ash and silica fume at a mass ratio of (2-4):1 as cement raw materials, and sequentially adding sodium dodecyl sulfonate, anhydrous sodium silicate, water, and hydrogen peroxide to the cement raw materials to obtain a mixed slurry; placing the mixed slurry in a mold, vibrating it, sealing it, and then curing the sealed mold at room temperature to obtain a block sample; then sequentially curing the block sample at high temperature and at room temperature to obtain the geopolymer.

7. The method according to claim 6, characterized in that, When the processed product is a geopolymer, sodium hydroxide solution is added to the processed product, and a hydrothermal reaction is carried out to obtain a zeolite product, including: adding sodium hydroxide solution to the geopolymer, carrying out hydrothermal treatment, washing the product after hydrothermal treatment until the pH of the filtrate is 8.0, and drying the product to obtain analcime molecular sieve.

8. The method according to claim 7, characterized in that, The hydrothermal treatment is performed at a temperature of 210-230℃ for 15-17 hours; and / or the drying treatment is performed at a temperature of 100-110℃.

9. A multi-component solid waste-based hydrothermal synthesis zeolite molecular sieve, characterized in that, The zeolite molecular sieve is synthesized using the method described in any one of claims 1-8.

10. An application of a multi-component solid waste-based hydrothermal synthesis of zeolite molecular sieves, characterized in that, The multi-component solid waste-based hydrothermal synthesis zeolite molecular sieve described in claim 9 is used to remove heavy metal ions from wastewater.

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