A method for synthesizing zirconium-modified A-type molecular sieve by one-pot method using fly ash as raw material

Abstract

The application discloses a method for synthesizing zirconium modified A type molecular sieve by using fly ash as raw material, and belongs to the technical field of resource comprehensive utilization. The preparation steps comprise one-pot synthesis of zirconium metal molecular sieve through raw material mixing, alkali fusion activation, direct addition of zirconium solution, stirring and aging, crystallization, suction filtration and washing and drying. The method does not need to introduce zirconium through post-processing mode, and reduces the generation of waste liquid in the ion exchange or isomorphous substitution process. Meanwhile, since no template agent is used in the preparation process, the molecular sieve does not need to be calcined to remove the template agent, the zirconium content of the synthesized molecular sieve is as high as 10.83wt%, the adsorbent has high adsorption capacity for As(V) in a solution, the maximum adsorption capacity can reach 104.63mg / g, and the adsorbent can be recycled for multiple times. The synthesis method is simple, effectively reduces the generation of pollutants and energy consumption in the synthesis process, the zirconium content of the synthesized molecular sieve is high, and the molecular sieve has high adsorption capacity for As(V).

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resource comprehensive utilization, and particularly relates to a method for synthesizing zirconium modified A-type molecular sieve by one-pot method from fly ash. BACKGROUND

[0002] Fly ash is the main solid waste discharged by coal-fired power plants. Every ton of coal consumed will produce 50-200 kg of fly ash. At present, China mainly relies on thermal power generation, and more than 700 million tons of fly ash are produced annually, and the comprehensive utilization rate has been hovering between 66% and 70%. The unused fly ash is mainly disposed by landfill and stacking, which not only occupies land resources but also brings serious environmental risks.

[0003] The main chemical elements of fly ash are silicon and aluminum, which can be used as raw materials for preparing silicoaluminate molecular sieves. At present, the process for synthesizing molecular sieves from fly ash is relatively mature. However, the adsorption capacity of molecular sieves for As(V) existing in the form of anion in water is weak. In order to improve the adsorption capacity of molecular sieves for As(V), the molecular sieves need to be modified by metals. The existing modification methods mainly include the addition of template agent hydrothermal method and post-treatment method. The addition of template agent hydrothermal method mainly adds the compound generated by the metal ion and the template agent into the raw material, which can introduce the metal ion into the molecular sieve structure during the synthesis process to prepare the metal modified molecular sieve. However, this method needs calcination to remove the template agent to obtain the product in the later stage, which not only increases the energy consumption but also produces air pollutants. The post-treatment method mainly includes ion exchange method and isomorphous substitution method. The ion exchange method exchanges the metal ion in the metal salt aqueous solution with the counter cation outside the molecular sieve framework to introduce the metal ion into the site of the original counter ion in the molecular sieve to generate the metal modified molecular sieve. The isomorphous substitution method is to immerse the molecular sieve in the metal solution to make the framework elements of the molecular sieve and the metal ions undergo solid-liquid phase replacement reaction, so as to introduce the metal ions into the framework to obtain the metal molecular sieve. However, the post-treatment method needs to immerse the synthesized molecular sieve, so a large amount of waste liquid will be generated, and the process is complex and time-consuming.

[0004] Therefore, the one-pot hydrothermal synthesis of zirconium modified A-type molecular sieve from fly ash without using template agent not only successfully introduces a large amount of Zr ions into the structure of A-type molecular sieve, effectively improves the removal capacity of the molecular sieve for As(V) in water, but also has a simple synthesis process and does not need to remove the template agent by calcination in the later stage, so that no metal waste liquid is generated. SUMMARY

[0005] The purpose of the present application is to provide a preparation method for synthesizing zirconium modified A-type molecular sieve by one-pot method from fly ash, which solves the problems of complex process and high energy consumption in the modification process of molecular sieve.

[0006] In order to solve the above problems, the technical scheme adopted by the present application is as follows:

[0007] A method for synthesizing zirconium-modified A-type molecular sieve by one-pot method using fly ash as raw material, characterized in that solid waste fly ash generated by a coal-fired power plant is used as the main raw material, and zirconium-modified A-type molecular sieve is synthesized by one-pot method under the condition of not using a template agent; the preparation steps include raw material mixing, alkali fusion activation, direct addition of zirconium solution, stirring and aging, crystallization, suction filtration and washing, and drying.

[0008] Further, the molecular sieve is synthesized by one-pot hydrothermal crystallization method using fly ash, diatomite, sodium hydroxide, and sodium carbonate after alkali fusion activation, and zirconium solution under the condition of not adding a template agent.

[0009] The method for synthesizing zirconium-modified A-type molecular sieve by one-pot method using fly ash as raw material as described above specifically includes the following steps,

[0010] (1) Raw material mixing: mix and grind fly ash, diatomite, sodium hydroxide, and sodium carbonate according to a specific ratio, wherein the fly ash is passed through a 100-mesh sieve;

[0011] (2) Alkali fusion activation: calcine the mixed solid in step (1) at a certain temperature, grind thoroughly after cooling, and obtain an activated product;

[0012] (3) Adjust the concentration of zirconium solution: dissolve zirconium oxychloride octahydrate in deionized water and stir to dissolve thoroughly;

[0013] (4) Stirring and aging: mix the activated product in step (2) and the zirconium-containing solution in step (3) thoroughly, stir, and then age;

[0014] (5) Crystallization: place the mixed gel liquid in step (4) in a hydrothermal reaction kettle, and place the reaction kettle in a constant-temperature drying box for heat preservation;

[0015] (6) Suction filtration and washing: cool the gel liquid obtained in step (5) to room temperature, suction filter to obtain a solid residue, and wash the residue with deionized water for 3-4 times;

[0016] (7) Take out the product obtained in step (6), dry in a constant-temperature drying box for a period of time, and obtain the zirconium-modified A-type molecular sieve.

[0017] Further, the mass ratio of fly ash, diatomite, NaOH, and Na2CO3 in step (1) is m(FA):m(DE):m(NaOH):m(Na2CO3)=9.1:0.9:16:1.

[0018] Further, the calcination temperature of the raw material mixture in step (2) is 490-510℃, and the time is 1.5-2.5h.

[0019] Further, the step (3) zirconium solution concentration is 0.1-0.2 mol / L.

[0020] Further, the step (4) is introduced into the stirring aging process of the A type molecular sieve by dissolving zirconium into deionized water, the solid-liquid ratio is 1:5, the stirring time is 1.5-2h, and the aging time is 3.5-4.5h.

[0021] Further, the step (5) zirconium directly participates in the crystallization process of the A type molecular sieve, and does not need to be introduced by post-treatment, the crystallization temperature is 85-95℃, and the crystallization time is 3.5-4.5h.

[0022] Further, the drying temperature of step (7) is 60-70℃, and the drying time is 20-24h.

[0023] Compared with the prior art, the beneficial technical effects of the present application: the present application is prepared by one-pot hydrothermal crystallization of solid waste fly ash generated by coal-fired power plants and zirconium-containing solution without adding template agent, compared with the post-treatment method and the direct synthesis method using template agent, the method does not need to carry out secondary synthesis or calcination to remove the template agent for the prepared molecular sieve, simplifies the synthesis steps, and reduces the energy consumption. The best synthesis conditions of the fly ash one-pot synthesis zirconium modified A type molecular sieve are that the zirconium-containing solution concentration is 0.15 mol / L, the solid-liquid ratio is 1:5, the crystallization temperature is 90℃, and the crystallization time is 4h, and the zirconium content of the synthesized zirconium modified A type molecular sieve is 10.83wt%. The method uses a one-pot hydrothermal synthesis method without template agent, and synthesizes an A type molecular sieve with high zirconium content, the molecular sieve has high adsorption capacity for As(V), and can realize solid waste resourceization, low energy consumption and high efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is the flow process chart of embodiment 2 of the present application. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present application are described in detail below, so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the protection scope of the present application is more clearly and explicitly defined.

[0026] Embodiment 1

[0027] A preparation method of fly ash one-pot synthesis zirconium modified A type molecular sieve, characterized in that, comprising the following steps,

[0028] (1) raw material mixing: mix and grind fly ash, diatomite, sodium hydroxide and sodium carbonate according to a specific ratio, wherein the fly ash is passed through a 100 mesh sieve;

[0029] (2) Alkali fusion activation: the mixed solid in step (1) is calcined at 500°C for 2h, and the activated product is obtained after grinding;

[0030] (3) Adjusting the concentration of zirconium solution: zirconium oxychloride octahydrate is dissolved in deionized water and stirred to fully dissolve, and the concentration of the zirconium-containing solution is adjusted to 0.1 mol / L.

[0031] (4) Stirring and aging: the activated product in step (2) is mixed with the zirconium solution in step (3) at a solid-liquid ratio of 1:5, stirred for 2h, and then aged for 4h;

[0032] (5) Crystallization: the mixed gel liquid in step (4) is placed in a hydrothermal reaction kettle, and the reaction kettle is placed in a 90°C constant temperature drying box for 4h;

[0033] (6) Filtration and washing: the gel liquid obtained in step (5) is cooled to room temperature, and the solid residue is obtained by filtration. The residue is washed with deionized water 4 times to obtain a zirconium-modified A-type molecular sieve;

[0034] (7) The product obtained in step (6) is taken out and dried in a 60°C constant temperature drying box for 24h to obtain a zirconium-modified A-type molecular sieve.

[0035] Example 2

[0036] (1) Raw material mixing: fly ash, diatomite, sodium hydroxide, and sodium carbonate are mixed and ground according to a specific ratio, and the fly ash is sieved through a 100 mesh screen;

[0037] (2) Alkali fusion activation: the mixed solid in step (1) is calcined at 500°C for 2h, and the activated product is obtained after grinding;

[0038] (3) Adjusting the concentration of zirconium solution: zirconium oxychloride octahydrate is dissolved in deionized water and stirred to fully dissolve, and the concentration of the zirconium-containing solution is adjusted to 0.1 mol / L.

[0039] (4) Stirring and aging: the activated product in step (2) is mixed with the zirconium solution in step (3) at a solid-liquid ratio of 1:5, stirred for 2h, and then aged for 4h;

[0040] (5) Crystallization: the mixed gel liquid in step (4) is placed in a hydrothermal reaction kettle, and the reaction kettle is placed in a 90°C constant temperature drying box for 4h;

[0041] (6) Filtration and washing: the gel liquid obtained in step (5) is cooled to room temperature, and the solid residue is obtained by filtration. The residue is washed with deionized water 4 times to obtain a zirconium-modified A-type molecular sieve;

[0042] (7) Take out the product obtained in step (6), and dry in a constant temperature drying box at 60°C for 24h to obtain the zirconium modified A-type molecular sieve.

[0043] Example 3

[0044] (1) Raw material mixing: mix and grind fly ash, diatomite, sodium hydroxide and sodium carbonate according to a specific ratio, wherein the fly ash passes through a 100 mesh sieve;

[0045] (2) Alkali fusion activation: calcine the mixed solid in step (1) at 500°C for 2h, and grind thoroughly after cooling to obtain an activated product;

[0046] (3) Adjusting the concentration of zirconium solution: dissolve zirconium oxychloride octahydrate in deionized water and stir to dissolve thoroughly, and adjust the concentration of the zirconium-containing solution to 0.2 mol / L.

[0047] (4) Stirring and aging: mix the activated product in step (2) and the zirconium solution in step (3) thoroughly at a solid-liquid ratio of 1:5, stir for 2h, and then age for 4h;

[0048] (5) Crystallization: place the mixed gel liquid in step (4) in a hydrothermal reaction kettle, and place the reaction kettle in a constant temperature drying box at 90°C for 4h;

[0049] (6) Filtration and washing: cool the gel liquid obtained in step (5) to room temperature, and obtain a solid residue by filtration, and wash the residue with deionized water 4 times to obtain a zirconium modified A-type molecular sieve;

[0050] (7) Take out the product obtained in step (6), and dry in a constant temperature drying box at 60°C for 24h to obtain the zirconium modified A-type molecular sieve.

[0051] The zirconium modified A-type molecular sieve prepared in Example 2 is selected as an example for detection and analysis, and the maximum adsorption capacity of the prepared zirconium modified A-type molecular sieve for As(V) can reach 104.63 mg / g, the relative crystallinity calculated by Jade is 56.92%, and the zirconium content measured by ICP is 10.83%.

[0052] The above examples only describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for synthesizing zirconium-modified type A molecular sieves using fly ash as raw material, characterized in that... Using fly ash, a solid waste product from coal-fired power plants, as the main raw material, zirconium-modified type A molecular sieves are synthesized in one pot by introducing a zirconium-containing solution without the use of a template agent. The preparation steps include raw material mixing, alkali fusion activation, direct addition of zirconium solution, stirring and aging, crystallization, filtration and washing, and drying. The zirconium-modified type A molecular sieve is prepared by using fly ash, diatomaceous earth, sodium hydroxide and sodium carbonate to activate through high-temperature alkaline fusion, then adding a zirconium-containing solution during the stirring and aging process, and finally hydrothermal crystallization. Specifically, the steps include the following: (1) Raw material mixing: Fly ash, diatomaceous earth, sodium hydroxide and sodium carbonate are mixed and ground thoroughly in a certain proportion, wherein the fly ash passes through a 100-mesh sieve; wherein the mass ratio of fly ash, diatomaceous earth, NaOH and Na2CO3 is m(FA):m(DE):m(NaOH):m(Na2CO3)=9.1:0.9:16:1; (2) Alkali fusion activation: The solid mixed in step (1) is calcined at a certain temperature, cooled down and then ground thoroughly to obtain the activated product; (3) Adjust the zirconium solution concentration: Dissolve zirconium oxychloride octahydrate in deionized water and stir until fully dissolved; (4) Stirring and aging: The activated product in step (2) is thoroughly mixed with the zirconium-containing solution in step (3), stirred, and then aged. (5) Crystallization: Place the mixed gel solution from step (4) into a hydrothermal reactor and keep the reactor in a constant temperature drying oven. (6) Filtration and washing: Cool the gel obtained in step (5) to room temperature, filter to obtain solid residue, and wash the residue with deionized water 3-4 times; (7) Take out the product obtained in step (6) and dry it in a constant temperature drying oven for a period of time to obtain zirconium-modified type A molecular sieve.

2. The method for synthesizing zirconium-modified type A molecular sieves using fly ash as raw material according to claim 1, characterized in that, In step (2), the raw material mixture is roasted at a temperature of 490-510 ℃ for 1.5-2.5 h.

3. The method for synthesizing zirconium-modified type A molecular sieves using fly ash as raw material according to claim 1, characterized in that, In step (3), the zirconium solution concentration is 0.1-0.2 mol / L.

4. The method for synthesizing zirconium-modified type A molecular sieves using fly ash as raw material according to claim 1, characterized in that, The step (4) involves dissolving zirconium oxychloride octahydrate in deionized water and introducing it into the A-type molecular sieve through a stirring and aging process. This process involves mixing the activated product from step (2) with the zirconium-containing solution from step (3) at a certain solid-liquid ratio, stirring for a period of time, and then aging for a period of time. The solid-liquid ratio is 1:5, the stirring time is 1.5-2 hours, and the aging time is 3.5-4.5 hours.

5. The method for synthesizing zirconium-modified type A molecular sieves using fly ash as raw material according to claim 1, characterized in that, In step (5), zirconium ions directly participate in the crystallization process of type A molecular sieve without the need for post-treatment to introduce zirconium ions. The crystallization temperature is 85-95℃ and the crystallization time is 3.5-4.5h.

6. The method for synthesizing zirconium-modified type A molecular sieves using fly ash as raw material according to claim 1, characterized in that, The drying temperature in step (7) is 60-70℃ and the drying time is 20-24h.

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