Method for preparing molecular sieve from coal gangue in a mild and green manner

Abstract

The application discloses a kind of gangue mild, green preparation method of molecular sieve, comprising the following steps: supplementary aluminum source, activated gangue, alkali source, seed crystal, water and hydrochloric acid are mixed, so that the molar ratio of SiO2, Al2O3, Na2O, hydrochloric acid, seed crystal and water is 1:(0.1-5.0):(0.5-2.5):(1.0-5.5):(0-0.1):(0-100), then uniformly mixed, and crystallization reaction is carried out, to obtain molecular sieve.The present application uses coal gangue powder, sodium hydroxide and supplementary aluminum source as raw material, combined with low-temperature alkali liquid phase activation method and solvent-free synthesis method, different framework structure of coal gangue-based molecular sieve with excellent structural characteristics can be prepared, different silicon-aluminum ratio when raw material is different, the present application supplements different amount of silicon-aluminum source for different raw materials to achieve suitable matching ratioThe crystallinity of molecular sieve prepared in the present application is good, and the hydrothermal stability is good, and heavy metal ions in water body can be removed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of molecular sieve preparation, and particularly relates to a method for preparing molecular sieve from coal gangue in a mild and green manner. BACKGROUND

[0002] Coal gangue is the main solid waste formed in the process of coal mining, and is a kind of gray-black rock with low carbon content associated with coal seams in the process of coal formation.

[0003] At present, coal gangue is difficult to handle and utilize, and has problems such as large output, large increment, complex composition, and difficult conversion and activation. Therefore, the utilization of coal gangue is mainly low-value utilization, which is divided into passive type, such as spreading and conversion utilization, such as preparation of building materials, preparation of soil additives, and use as energy materials. These methods can alleviate the problem of coal gangue accumulation to a certain extent, but they all belong to low-value utilization. How to maximize the extraction of valuable components from coal gangue, continuously improve the comprehensive utilization level of coal gangue, promote the application of high value-added products, and develop high-value utilization technology of coal gangue is imminent.

[0004] The chemical composition of coal gangue is mainly inorganic matter and organic matter. The main elements of the organic matter in coal gangue are C, and also contain H, N, S, O and other elements. The inorganic matter is mainly SiO2(30% to 65%) and Al2O3(15% to 40%). The composition of coal gangue is similar to that of molecular sieve, which is a potential raw material for the preparation of molecular sieve.

[0005] At present, there are 251 kinds of determined molecular sieve framework structures. Molecular sieve materials have shape-selective catalytic properties, strong catalytic acidity, good hydrothermal stability and many other advantages. FAU zeolite can be used for CO2 adsorption and removal of heavy metals in water, SOD and CAN zeolites can be used for removal of heavy metals in water, and GIS zeolite can be used for n-heptane isomerization as a catalyst, preparation of flocculants, etc. At present, the global molecular sieve market capacity is about 7 billion US dollars. The synthesis of molecular sieve from coal gangue can greatly save raw material cost and improve the economic benefit of molecular sieve production. Once the technology of mild conversion of coal gangue to prepare molecular sieve is implemented, it can greatly promote the high value-added conversion and utilization of coal gangue, and has economic and social benefits.

[0006] Patent CN1254681 discloses a method for synthesizing X-type zeolite by high-temperature alkali fusion activation of raw materials, and then hydrothermal synthesis. The coal gangue raw material is mixed with an alkali flux, dried, and then reacted at a certain temperature. Then, the product is aged and crystallized. The characteristics are as follows: the coal gangue raw material is uniformly mixed with Na2O, and then the mixture is heated and calcined at 500-1000℃ for 0.5-10 hours. The product is added with water for aging, and then the aged product is put into a kettle for crystallization. The crystallized product is filtered, washed and dried to obtain the target molecular sieve.

[0007] The patent CN114988426 provides a coal gangue-based molecular sieve and an alkali fusion-hydrothermal preparation method thereof. The preparation method comprises the following steps: mixing and grinding coal gangue powder and sodium hydroxide, and then performing calcination to obtain alkali fusion coal gangue; mixing the alkali fusion coal gangue, sodium metaaluminate and water, and then uniformly stirring to obtain a molecular sieve crude product; and performing filtration, washing and drying on the molecular sieve crude product in sequence to obtain the coal gangue-based molecular sieve. The alkali fusion-hydrothermal preparation method of the coal gangue-based molecular sieve can obtain the coal gangue-based molecular sieve with excellent structural characteristics by using coal gangue powder, sodium hydroxide and sodium metaaluminate as raw materials, and combining the alkali fusion method and the hydrothermal method.

[0008] In the document (Lu X, Shi D, Chen J. Sorption of Cu 2+ and Co 2+ using zeolitesynthesized from coal gangue: isotherm and kinetic studies[J]. EnvironmentalEarth Sciences, 2017, 76: 1-10.), coal gangue was used as raw material, which was activated at 800℃ and alkali fusion activated at 600℃, then water was added at a ratio of 8mL / g for aging, and the aging product was crystallized at 110℃ for 12h. After filtration, washing and drying, NaX molecular sieve was obtained, and was used for liquid phase adsorption of Cu 2+ and Co 2+ . The adsorption capacity of Cu 2+ and Co 2+ was 45.05mg / L and 44.53mg / L respectively.

[0009] In the document (Zhou J, Zheng F, Li H, et al. Optimization of post-treatment variables to produce hierarchical porous zeolites from coal gangue to enhance adsorption performance [J]. Chemical Engineering Journal, 2020, 381: 122698.) activated coal gangue is used as raw material, calcined at 650℃ to obtain activated coal gangue, they mix the activated coal gangue powder with deionized water, sodium aluminate and sodium hydroxide, then 25℃ aging for 12 hours, then hydrothermal crystallization at 90℃ to obtain A type molecular sieve, and the dried molecular sieve powder is treated with alkali and ultrasonic treatment, finally the A type molecular sieve with hierarchical pore structure is prepared, and the removal efficiency of Cu 2+ and Rh-B (Rhodamine B) is increased to 83.5% and 95.1%

[0010] At present, the activation methods for coal gangue are thermal activation and alkali fusion activation method, which generally need to calcine the coal gangue sample at 800℃ to remove the carbon in the coal gangue, and then perform alkali fusion activation, and the activation temperature is generally 600-800℃. The synthesis method of molecular sieve is mainly hydrothermal synthesis method, which has harsh pretreatment conditions, complicated operation, huge energy consumption and poor technical and economic properties due to the consumption of solvent to produce organic waste liquid. SUMMARY

[0011] In order to overcome the technical problems of high energy consumption and high cost in the prior art, the present application provides a method for preparing molecular sieve from coal gangue in a mild and green manner, which combines low-temperature alkali liquid-phase activation method with solvent-free synthesis method, has mild pretreatment conditions, low energy consumption, simple operation, high preparation efficiency, clean conversion, and does not consume solvent to produce organic waste liquid, greatly improves the synthesis environment, reduces economic cost, improves economic benefit, and efficiently and highly values the industrial waste solid coal gangue, also significantly improves the problems of high yield and large stock of coal gangue.

[0012] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0013] A method for preparing molecular sieve from coal gangue in a mild and green manner, comprising the following steps:

[0014] The supplementary aluminum source, the activated coal gangue, the alkali source, the seed crystal, water and hydrochloric acid are mixed so that the molar ratio of SiO2, Al2O3, Na2O, hydrochloric acid and the seed crystal is 1:(0.1-5.0):(0.5-2.5):(1.0-5.5):(0-0.1), and then the mixture is uniformly ground, and a crystallization reaction is performed to obtain the SOD molecular sieve.

[0015] Further, the activated coal gangue is prepared by the following process: the coal gangue, sodium hydroxide and deionized water are uniformly mixed according to the mass ratio of 1:(1.0-2.0):(5.0-10.0), and then heated at 100-300℃ for 1-10h to obtain the activated coal gangue.

[0016] Further, the alkali source is NaOH, KOH or Na2CO3.

[0017] Further, the supplementary aluminum source is one of boehmite, aluminum chloride, aluminum hydroxide and aluminum isopropoxide.

[0018] Further, the mass concentration of the hydrochloric acid is 36.5%.

[0019] Further, the temperature of the crystallization reaction is 70-120℃, and the time is 12-36h.

[0020] Further, the supplementary aluminum source, the activated coal gangue, the alkali source, the seed crystal, water and hydrochloric acid are mixed so that the molar ratio of SiO2, Al2O3, Na2O, hydrochloric acid and the seed crystal is 1:(0.1-5.0):(0.5-2.5):(1.0-5.5):(0-0.1), and then the mixture is uniformly ground, and a crystallization reaction is performed to obtain the SOD molecular sieve.

[0021] Further, the supplementary aluminum source, the activated coal gangue and the hydrochloric acid are mixed so that the molar ratio of SiO2, Al2O3, Na2O, hydrochloric acid and the seed crystal is 1:(0.1-5.0):(0.5-2.5):(1.0-5.5):(0-0.1), and then the mixture is uniformly ground, and then a crystallization reaction is performed at 70-120℃ for 12-36h to obtain the SOD molecular sieve.

[0022] Further, the supplementary aluminum source and the activated coal gangue are mixed so that the molar ratio of SiO2, Al2O3, Na2O and the seed crystal is 1:(0.1-5.0):(0.5-2.5):(0-0.1), and then the mixture is uniformly ground, and a crystallization reaction is performed to obtain the CAN molecular sieve.

[0023] Further, the supplementary aluminum source, activated coal gangue and water are mixed to make the molar ratio of SiO2, Al2O3, Na2O, crystal seed and water 1:(0.1-5.0):(0.5-2.5):(0-0.1):(0-100), mixed under stirring for 2-8h, and then crystallized at 70-120 DEG C for 12-36h to obtain the GIS molecular sieve.

[0024] Compared with the prior art, the present application has the beneficial effects of:

[0025] The present application can prepare coal gangue-based molecular sieves with excellent structural characteristics and different framework structures by combining alkali activation method and solvent-free synthesis method, and the raw materials have different silicon-aluminum ratios. The present application supplements different amounts of silicon-aluminum sources for different raw materials to achieve a suitable ratio, i.e. 1:(0.1-5.0):(0.5-2.5):(1.0-5.5):(0-0.1):(0-100). The molecular sieves prepared in the present application have good crystallinity and good hydrothermal stability, and the removal efficiency of heavy metal ions in water is greater than 90%, among which the removal efficiency of Pb 2+ ions is as high as 99.82%.

[0026] Further, the present application uses coal gangue as raw material, and prepares four kinds of high-crystallinity molecular sieves with different framework structures through green crystallization (without organic template and solvent) technology under mild conditions (low temperature and low consumption). The molecular sieves show excellent performance in removing Cu 2+ , Cd 2+ , Pb 2+ heavy metal ions in water, CO2 adsorption, catalyzing n-heptane isomerization reaction, and making flocculants.

[0027] Further, since different framework structures correspond to different crystallization windows, the present application can obtain molecular sieves with different framework structures by adjusting the ratio, temperature and time.

[0028] Further, different ratios, temperatures and times can also obtain different crystallinity samples of the same framework molecular sieve, so the highest crystallinity molecular sieve sample can be obtained by adjusting the corresponding conditions.

[0029] Further, the activated coal gangue is used as a solid form of synthesis raw material into the kettle, the kettle space occupation is small, the pressure is small, and the product is easy to separate. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The present application is a process flow chart for preparing molecular sieves.

[0031] Figure 2 X-ray diffraction patterns of coal gangue, activated coal gangue and synthesized molecular sieves.

[0032] Figure 3 The X-ray diffraction patterns are for Comparative Example 1 and Example 7.

[0033] Figure 4 The X-ray diffraction pattern is shown in Example 3.

[0034] Figure 5 The X-ray diffraction pattern is shown in Example 8.

[0035] Figure 6 This is a scanning electron microscope image of Comparative Example 1.

[0036] Figure 7 This is a scanning electron microscope image of Example 6.

[0037] Figure 8 Cu for Comparative Example 1 and Example 6 2+ Adsorption performance diagram.

[0038] Figure 9 Cd for Comparative Example 1 and Example 6 2+ Adsorption performance diagram.

[0039] Figure 10 For Comparative Example 1 and Example 6, Pb 2+ Adsorption performance diagram. Detailed Implementation

[0040] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0041] According to ICP-OES testing, the molar ratio of SiO2:Al2O3 in the coal gangue of this invention is 1.67.

[0042] See Figure 1 The present invention discloses a mild and green method for preparing molecular sieves from coal gangue, the preparation process of which is as follows:

[0043] 1) Raw materials: silicon-aluminum source (one of boehmite, aluminum chloride, aluminum hydroxide and aluminum isopropoxide and coal gangue), alkali source (NaOH, KOH or Na2CO3), seed crystal (FAU zeolite), deionized water and hydrochloric acid (mass concentration of 36.5%).

[0044] 2) Synthesis ratio

[0045] Molar ratio: 1 SiO2: (0.1-5.0) Al2O3: (0.5-2.5) Na2O: (1.0-5.5) hydrochloric acid: (0-0.1) seed crystal.

[0046] The amount of the silicon-aluminum source is calculated based on SiO2 and Al2O3, and the amount of the alkali source is calculated based on Na2O.

[0047] 3) Preparation step

[0048] Activation of coal gangue: uniformly mix coal gangue, solid sodium hydroxide and deionized water in a mass ratio of 1: (1.0-2.0): (5.0-10.0), and then heat at 100-300°C for 1-10h to obtain activated coal gangue.

[0049] Solvent-free synthesis of nanoscale FAU molecular sieve: add one of pseudoboehmite, aluminum chloride, aluminum hydroxide and aluminum isopropoxide, activated coal gangue, hydrochloric acid and seed crystal according to the synthesis ratio, and stir uniformly, then transfer to a mortar and grind for 5-20 minutes, then transfer to a stainless steel high-pressure reaction kettle, put the reaction kettle into a preheated 70-90°C oven, keep for 12-36h, then take out the sample, recover the sample by centrifugation, washing and drying to obtain the final product.

[0050] Solvent-free synthesis of SOD molecular sieve: add activated coal gangue, aluminum chloride / aluminum hydroxide / pseudoboehmite and hydrochloric acid according to the synthesis ratio and stir uniformly, then transfer the above mixture to a mortar and grind for 5-20 minutes, then transfer to a stainless steel high-pressure reaction kettle, put the reaction kettle into a preheated 70-90°C oven, keep for 12-36h, then take out the sample, recover the sample by centrifugation, washing and drying to obtain the final product.

[0051] Solvent-free synthesis of CAN molecular sieve: add activated coal gangue, aluminum chloride / aluminum hydroxide / pseudoboehmite according to the synthesis ratio and stir uniformly, then transfer the above mixture to a mortar and grind for 5-20 minutes, then transfer to a stainless steel high-pressure reaction kettle, put the reaction kettle into a preheated 70-120°C oven, keep for 12-36h, then take out the sample, recover the sample by centrifugation, washing and drying to obtain the final product.

[0052] Hydrothermal synthesis of GIS molecular sieve: add activated coal gangue, aluminum chloride / aluminum hydroxide / pseudoboehmite and deionized water according to the synthesis ratio and stir uniformly for 2-8h, then transfer to a stainless steel high-pressure reaction kettle, put the reaction kettle into a preheated 70-120°C oven, keep for 12-36h, then take out the sample, recover the sample by centrifugation, washing and drying to obtain the final product.

[0053] Solvent-free synthesis did not obtain GIS molecular sieve.

[0054] Comparative Example 1 (thermal activation + base fusion activation + hydrothermal synthesis of FAU)

[0055] (1) 10 g of coal gangue was calcined at 800°C for 3 h to obtain thermally activated coal gangue;

[0056] (2) 2 g of the thermally activated coal gangue obtained in step (1) was mixed with 2.4 g of sodium hydroxide and calcined at 600°C for 3 h to obtain base fusion activated coal gangue;

[0057] (3) The base fusion activated coal gangue obtained in step (2) was mixed with deionized water at a liquid to solid ratio of 8:1 and stirred for 6 h for aging;

[0058] (4) The solution obtained in step (3) was placed in a polytetrafluoroethylene liner of a stainless steel autoclave, and then the autoclave was sealed. The autoclave was transferred to an oven preheated to 110°C and kept for 8 h. The autoclave was quenched with tap water, and the sample was recovered by centrifugation, washing, and drying to obtain the final product.

[0059] Example 1

[0060] (1) 10 g of coal gangue, 10 g of sodium hydroxide, and 75 mL of water were mixed and stirred uniformly, and then transferred to a preheated oven at 150°C. After 1 h, the activated coal gangue was obtained;

[0061] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with 0.1864 g of pseudoboehmite, 2.1712 g of hydrochloric acid, and 0.05 g of FAU seeds. After mixing uniformly, the mixture was ground for 10 minutes to obtain a mixture;

[0062] (3) The mixture obtained in step (2) was placed in a polytetrafluoroethylene liner of a stainless steel autoclave, and then the autoclave was sealed. The autoclave was transferred to an oven preheated to 60°C and kept for 12 h. The autoclave was quenched with tap water, and the sample was recovered by centrifugation, washing, and drying to obtain the final product.

[0063] Example 2

[0064] (1) 10 g of coal gangue, 15 g of sodium hydroxide, and 75 mL of water were mixed and stirred uniformly, and then transferred to a preheated oven at 150°C. After 1 h, the activated coal gangue was obtained;

[0065] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with 0.1864 g of pseudoboehmite, 2.1712 g of hydrochloric acid, and 0.05 g of FAU seeds. After mixing uniformly, the mixture was ground for 10 minutes to obtain a mixture;

[0066] (3) The mixture obtained in step (2) was placed in the polytetrafluoroethylene lining of a stainless steel autoclave, and then the autoclave was sealed. The autoclave was transferred to an oven preheated to 60°C, and was kept for 12 h. Then, the autoclave was quenched with tap water. The sample was recovered by centrifugation, washing and drying to obtain the final product.

[0067] Example 3

[0068] (1) 10 g of coal gangue, 15 g of sodium hydroxide and 75 mL of water were uniformly mixed and stirred, and then were transferred to an oven preheated to 200°C. After being kept for 2 h, the activated coal gangue was obtained;

[0069] (2) The activated coal gangue obtained in step (1) was mixed with deionized water at a liquid-solid ratio of 8:1 and was aged by stirring for 6 h;

[0070] (3) The solution obtained in step (2) was placed in the polytetrafluoroethylene lining of a stainless steel autoclave, and then the autoclave was sealed. The autoclave was transferred to an oven preheated to 110°C, and was kept for 12 h. Then, the autoclave was quenched with tap water. The sample was recovered by centrifugation, washing and drying to obtain the final product.

[0071] Figure 4 The XRD pattern of Example 3 is shown in the figure. The XRD pattern has characteristic peaks corresponding to the GIS framework, indicating that the sample is a GIS molecular sieve.

[0072] Example 4

[0073] (1) 10 g of coal gangue, 15 g of sodium hydroxide and 75 mL of water were uniformly mixed and stirred, and then were transferred to an oven preheated to 250°C. After being kept for 1 h, the activated coal gangue was obtained;

[0074] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with 0.1864 g of pseudoboehmite, 1.0856 g of hydrochloric acid and 0.05 g of FAU seeds to obtain a mixture. The mixture was ground for 10 min;

[0075] (3) The mixture obtained in step (2) was placed in the polytetrafluoroethylene lining of a stainless steel autoclave, and then the autoclave was sealed. The autoclave was transferred to an oven preheated to 60°C, and was kept for 12 h. Then, the autoclave was quenched with tap water. The sample was recovered by centrifugation, washing and drying to obtain the final product.

[0076] Example 5

[0077] (1) 10 g of coal gangue, 20 g of sodium hydroxide and 75 mL of water were uniformly mixed and stirred, and then were transferred to an oven preheated to 250°C. After being kept for 1 h, the activated coal gangue was obtained;

[0078] (2) Take 1 g of the activated coal gangue obtained in step (1) and add 0.1864 g of pseudoboehmite, 1.0856 g of hydrochloric acid and 0.05 g of FAU seeds to mix evenly, and then grind for 10 minutes to obtain a mixture;

[0079] (3) Put the mixture obtained in step (2) into the polytetrafluoroethylene lining of a stainless steel autoclave, then seal the autoclave, transfer the autoclave to an oven preheated to 60°C, and keep for 12 h, then quench the autoclave with tap water, recover the sample by centrifugation, washing and drying, and obtain the final product.

[0080] Example 6

[0081] (1) Mix 10 g of coal gangue, 15 g of sodium hydroxide and 75 mL of water uniformly, then transfer to a preheated 200°C oven, keep for 2 h, and then take out to obtain activated coal gangue;

[0082] (2) Take 1 g of the activated coal gangue obtained in step (1) and add 0.0932 g of pseudoboehmite, 1.0856 g of hydrochloric acid and 0.05 g of FAU seeds to mix evenly, and then grind for 10 minutes to obtain a mixture;

[0083] (3) Put the mixture obtained in step (2) into the polytetrafluoroethylene lining of a stainless steel autoclave, then seal the autoclave, transfer the autoclave to an oven preheated to 80°C, and keep for 24 h, then quench the autoclave with tap water, recover the sample by centrifugation, washing and drying, and obtain the final product.

[0084] Figure 2 The XRD patterns of coal gangue, activated coal gangue and synthetic molecular sieve can be seen from which it can be seen that the activated coal gangue generates active silicate species and successfully synthesizes a molecular sieve with a corresponding structure.

[0085] Figure 3 The XRD patterns of Comparative Example 1 and Example 6 are shown in the XRD patterns, which have characteristic peaks corresponding to the FAU framework, indicating that the sample is an FAU molecular sieve.

[0086] Figure 7 and Figure 8 are the scanning electron microscope pictures of Comparative Example 1 and Example 6, respectively, from which it can be seen that Comparative Example 1 ( Figure 7 ) and Example 6 ( Figure 8 ) have similar morphologies, and their crystals are all regular octahedral structure particles. The particle size of Comparative Example 1 is about 3-4 microns, while the particle size of Example 6 is about 500-600 nanometers, which shows that Example 6 is a nanoscale FAU molecular sieve.

[0087] Example 7

[0088] (1) 10 g of coal gangue, 15 g of sodium hydroxide, and 75 mL of water were mixed and stirred uniformly, and then transferred to a preheated 200°C oven, kept for 2 h, and then taken out to obtain activated coal gangue;

[0089] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with 0.0932 g of aluminum hydroxide, 1.0856 g of hydrochloric acid, and 0.05 g of FAU seeds to obtain a mixture, which was ground for 10 minutes;

[0090] (3) The mixture obtained in step (2) was placed in a polytetrafluoroethylene liner of a stainless steel autoclave, and then the autoclave was sealed and transferred to a preheated 80°C oven, kept for 24 h, and then quenched with tap water. The sample was recovered by centrifugation, washing, and drying to obtain the final product.

[0091] Example 8

[0092] (1) 10 g of coal gangue, 15 g of sodium hydroxide, and 75 mL of water were mixed and stirred uniformly, and then transferred to a preheated 200°C oven, kept for 2 h, and then taken out to obtain activated coal gangue;

[0093] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with 0.0932 g of aluminum hydroxide, 1.0856 g of hydrochloric acid, and 0.05 g of FAU seeds to obtain a mixture, which was ground for 10 minutes;

[0094] (3) The mixture obtained in step (2) was placed in a polytetrafluoroethylene liner of a stainless steel autoclave, and then the autoclave was sealed and transferred to a preheated 80°C oven, kept for 24 h, and then quenched with tap water. The sample was recovered by centrifugation, washing, and drying to obtain the final product.

[0095] Figure 6 The XRD pattern of Example 8 is shown in the figure, and the XRD pattern has characteristic peaks corresponding to the SOD framework, indicating that the sample is an SOD molecular sieve.

[0096] Example 9

[0097] (1) 10 g of coal gangue, 15 g of sodium hydroxide, and 75 mL of water were mixed and stirred uniformly, and then transferred to a preheated 200°C oven, kept for 2 h, and then taken out to obtain activated coal gangue;

[0098] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with 0.0932 g of aluminum hydroxide, 1.0856 g of hydrochloric acid, and 0.05 g of FAU seeds to obtain a mixture, which was ground for 10 minutes;

[0099] (3) Put the mixture obtained in step (2) into the polytetrafluoroethylene lining of a stainless steel autoclave, then seal the autoclave, transfer the autoclave to an oven preheated to 80°C, keep for 24 h, then quench the autoclave with tap water, recover the sample by centrifugation, washing and drying to obtain the final product.

[0100] Example 10

[0101] (1) Mix 10 g of coal gangue, 15 g of sodium hydroxide and 75 mL of water uniformly, then transfer to a preheated 200°C oven, keep for 2 h, then take out to obtain activated coal gangue;

[0102] (2) Mix 1 g of the activated coal gangue obtained in step (1) with 0.0932 g of pseudoboehmite, 0.5428 g of hydrochloric acid and 0.05 g of FAU seed crystals uniformly, then grind for 10 min to obtain a mixture;

[0103] (3) Put the mixture obtained in step (2) into the polytetrafluoroethylene lining of a stainless steel autoclave, then seal the autoclave, transfer the autoclave to an oven preheated to 60°C, keep for 24 h, then quench the autoclave with tap water, recover the sample by centrifugation, washing and drying to obtain the final product.

[0104] Example 11

[0105] (1) Mix 10 g of coal gangue, 15 g of sodium hydroxide and 75 mL of water uniformly, then transfer to a preheated 200°C oven, keep for 2 h, then take out to obtain activated coal gangue;

[0106] (2) Mix 1 g of the activated coal gangue obtained in step (1) with 0.0932 g of pseudoboehmite, 0.5428 g of hydrochloric acid and 0.05 g of FAU seed crystals uniformly, then grind for 10 min to obtain a mixture;

[0107] (3) Put the mixture obtained in step (2) into the polytetrafluoroethylene lining of a stainless steel autoclave, then seal the autoclave, transfer the autoclave to an oven preheated to 90°C, keep for 24 h, then quench the autoclave with tap water, recover the sample by centrifugation, washing and drying to obtain the final product.

[0108] Example 12

[0109] (1) Mix 10 g of coal gangue, 15 g of sodium hydroxide and 75 mL of water uniformly, then transfer to a preheated 200°C oven, keep for 2 h, then take out to obtain activated coal gangue;

[0110] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with 0.0932 g of pseudoboehmite, 0.5428 g of hydrochloric acid and 0.05 g of FAU crystal seeds, and then ground for 10 minutes to obtain a mixture;

[0111] (3) The mixture obtained in step (2) was placed in a polytetrafluoroethylene liner of a stainless steel autoclave, and then the autoclave was sealed. The autoclave was transferred to an oven preheated to 60°C, and kept for 12 h. Then, the autoclave was quenched with tap water. The sample was recovered by centrifugation, washing and drying to obtain the final product.

[0112] Example 13

[0113] (1) 10 g of coal gangue, 15 g of sodium hydroxide and 75 mL of water were mixed and stirred uniformly, and then transferred to an oven preheated to 200°C. After being kept for 2 h, the activated coal gangue was obtained;

[0114] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with 0.0932 g of pseudoboehmite, 0.5428 g of hydrochloric acid and 0.05 g of FAU crystal seeds, and then ground for 10 minutes to obtain a mixture;

[0115] (3) The mixture obtained in step (2) was placed in a polytetrafluoroethylene liner of a stainless steel autoclave, and then the autoclave was sealed. The autoclave was transferred to an oven preheated to 60°C, and kept for 12 h. Then, the autoclave was quenched with tap water. The sample was recovered by centrifugation, washing and drying to obtain the final product.

[0116] Example 14

[0117] (1) 10 g of coal gangue, 15 g of sodium hydroxide and 75 mL of water were mixed and stirred uniformly, and then transferred to an oven preheated to 200°C. After being kept for 2 h, the activated coal gangue was obtained;

[0118] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with 0.0932 g of pseudoboehmite, 0.5428 g of hydrochloric acid and 0.05 g of FAU crystal seeds, and then ground for 10 minutes to obtain a mixture;

[0119] (3) The mixture obtained in step (2) was placed in a polytetrafluoroethylene liner of a stainless steel autoclave, and then the autoclave was sealed. The autoclave was transferred to an oven preheated to 60°C, and kept for 12 h. Then, the autoclave was quenched with tap water. The sample was recovered by centrifugation, washing and drying to obtain the final product.

[0120] Example 15

[0121] (1) 10 g of coal gangue, 17 g of sodium hydroxide, and 100 mL of water were mixed and stirred uniformly, and then transferred to a preheated 300°C oven. After 1 h, the activated coal gangue was obtained;

[0122] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with aluminum isopropoxide, hydrochloric acid, and FAU seeds to obtain a mixture. The molar ratio of SiO2, Al2O3, Na2O, hydrochloric acid, and seeds was 1:2:2.5:1:0.05. The mixture was ground for 20 minutes;

[0123] (3) The mixture obtained in step (2) was placed in a polytetrafluoroethylene liner in a stainless steel high-pressure reaction kettle, and then the high-pressure reaction kettle was sealed. The high-pressure reaction kettle was transferred to a preheated 90°C oven and kept for 12 h. The high-pressure reaction kettle was quenched with tap water, and the sample was recovered by centrifugation, washing, and drying to obtain the final product.

[0124] Example 16

[0125] (1) 10 g of coal gangue, 13 g of sodium hydroxide, and 50 mL of water were mixed and stirred uniformly, and then transferred to a preheated 100°C oven. After 10 h, the activated coal gangue was obtained;

[0126] (2) 1 g of the activated coal gangue obtained in step (1) was mixed with aluminum chloride, hydrochloric acid, and FAU seeds to obtain a mixture. The molar ratio of SiO2, Al2O3, Na2O, hydrochloric acid, and seeds was 1:5:1.5:5.5:0.01. The mixture was ground for 15 minutes;

[0127] (3) The mixture obtained in step (2) was placed in a polytetrafluoroethylene liner in a stainless steel high-pressure reaction kettle, and then the high-pressure reaction kettle was sealed. The high-pressure reaction kettle was transferred to a preheated 85°C oven and kept for 20 h. The high-pressure reaction kettle was quenched with tap water, and the sample was recovered by centrifugation, washing, and drying to obtain the final product.

[0128] Example 17

[0129] (1) 10 g of coal gangue, 15 g of sodium hydroxide, and 75 mL of water were mixed and stirred uniformly, and then transferred to a preheated 200°C oven. After 2 h, the activated coal gangue was obtained;

[0130] (2) The activated coal gangue obtained in step (1) was mixed with deionized water at a liquid-solid ratio of 8:1 and stirred for 2 h to age;

[0131] (3) The solution obtained in step (2) is placed in the polytetrafluoroethylene lining of a stainless steel high-pressure reaction kettle, then the high-pressure reaction kettle is sealed, the high-pressure reaction kettle is transferred to an oven preheated to 70 DEG C, and after being kept for 36h, the high-pressure reaction kettle is quenched with tap water, and the sample is recovered by centrifugation, washing and drying to obtain the final product.

[0132] Example 18

[0133] (1) 10g of coal gangue, 15g of sodium hydroxide and 75mL of water are uniformly mixed and stirred, and then transferred to a preheated 200 DEG C oven, kept for 2h, and then taken out to obtain activated coal gangue;

[0134] (2) The activated coal gangue obtained in step (1) is mixed with deionized water at a liquid-solid ratio of 8:1 and stirred for 8h to age;

[0135] (3) The solution obtained in step (2) is placed in the polytetrafluoroethylene lining of a stainless steel high-pressure reaction kettle, then the high-pressure reaction kettle is sealed, the high-pressure reaction kettle is transferred to an oven preheated to 120 DEG C, and after being kept for 12h, the high-pressure reaction kettle is quenched with tap water, and the sample is recovered by centrifugation, washing and drying to obtain the final product.

[0136] Example 19

[0137] (1) 10g of coal gangue, 15g of sodium hydroxide and 75mL of water are uniformly mixed and stirred, and then transferred to a preheated 200 DEG C oven, kept for 2h, and then taken out to obtain activated coal gangue;

[0138] (2) The activated coal gangue obtained in step (1) is mixed with deionized water at a liquid-solid ratio of 8:1 and stirred for 4h to age;

[0139] (3) The solution obtained in step (2) is placed in the polytetrafluoroethylene lining of a stainless steel high-pressure reaction kettle, then the high-pressure reaction kettle is sealed, the high-pressure reaction kettle is transferred to an oven preheated to 90 DEG C, and after being kept for 20h, the high-pressure reaction kettle is quenched with tap water, and the sample is recovered by centrifugation, washing and drying to obtain the final product.

[0140] The application of the FAU molecular sieve prepared by the solvent-free method in the present application in removing heavy metal ions in water bodies:

[0141] Molecular sieve materials have a wide range of applications. FAU molecular sieves are often used in CO2 adsorption, n-alkane cracking, and removal of heavy metals in water bodies (Thang H V, Grajciar L, Nachtigall P, et al. Adsorption of CO2 in FAU zeolites: Effect of zeolite composition[J]. Catalysis Today, 2014, 227: 50-56., Liu P, Zhang J, Peng S, et al. Thermodynamic Insight into Thermal Cracking of n-Hexane in the H-FAU Zeolite[J]. The Journal of Physical Chemistry C, 2022, 126(48): 20411-20422., Yurekli Y. Determination of adsorption characteristics of synthetic NaX nanoparticles[J]. Journal of hazardous materials, 2019, 378: 120743.); SOD molecular sieves are often used to remove heavy metal ions in water bodies (Wei E, Wang K, Muhammad Y, et al. Preparation and conversion mechanism of different geopolymer-based zeolite microspheres and their adsorption properties for Pb 2+[J]. Separation and Purification Technology, 2022, 282:119971.); CAN molecular sieves are often used to remove nitrogen, ammonia, and heavy metal ions from water bodies (Guo Tong, Zhu Junna, Guo Shujun, et al. Study on the preparation of magnetic calcium nepheline adsorbent from water plant iron sludge for the removal of ammonia nitrogen in water [J]. Journal of Northeast Normal University (Natural Science Edition), 2020, 52(04): 138-142., Hao Zhigang, Shi Peixiang, Lü Yongkang. Study on the preparation of calcium nepheline by rice husk ash solventless method and its mercury removal performance [J]. Nonmetallic Minerals, 2022, 45(05): 39-42.); GIS molecular sieves are often used to heptane isomerization, gas adsorption, etc. (Zhang Yang, Cui Yanhong, Ma Shoutao, et al. Preparation of rice husk-based high-purity NaP1 zeolite and its heptane isomerization performance evaluation [J]. Journal of Inorganic Chemistry, 2021, 37(09): 1613-1624. Lucero JM, Crawford JM, Wolden CA, et al. Tunability of ammonia adsorption over NaP zeolite[J]. Microporous and Mesoporous Materials, 2021, 324: 111288.). Among the synthesized products FAU, SOD, CAN, and GIS, FAU molecular sieves are widely used and represent a typical molecular sieve framework. Therefore, this invention selects FAU molecular sieves as a representative for the removal of heavy metal ions from water. Due to its unique pore structure, FAU molecular sieves have excellent adsorption and ion exchange performance and have great application potential. Its basic structural unit is a β-cage, which is connected by hexagonal prisms to form a supercage structure and a three-dimensional pore system. FAU molecular sieves have a uniform pore structure with a pore size of up to 10 Å. 2+ Cd 2+ and Pb 2+ These are common heavy metal ions in water, with hydration radii of 4.19 Å, 4.26 Å, and 4.01 Å, respectively. The pore size of FAU molecular sieve is larger than that of heavy metal ions, allowing them to easily enter the pores and be adsorbed.

[0142] Application of FAU molecular sieves in the removal of heavy metal ions from water: using Cu 2+ Cd 2+ Pb 2+Target ions as molecular sieve adsorbents. 100 mg / L, 100 mg / L, and 300 mg / L adsorbate solutions were respectively prepared, 0.1 g of the FAU type molecular sieve was put into the adsorbate solution and stirred, and sampling was performed at 5 min, 7.5 min, 10 min, 15 min, 30 min, 45 min, 60 min, 80 min, 100 min, and 120 min when the adsorption was performed, and the collected solution was subjected to ICP test, so as to obtain the content change of the heavy metal ions before and after adsorption, and to determine the adsorption performance of the molecular sieve. The adsorption performance of the FAU molecular sieve is shown in Table 1 and Figure 8 、 Figure 9 and Figure 10 .

[0143] Table 1 Liquid phase adsorption performance of Comparative Example 1 and Example 6

[0144]

[0145] It can be seen from Table 1 and Figure 8 、 Figure 9 and Figure 10 that the removal rate of the molecular sieve prepared in Example 6 is higher than that of Comparative Example 1.

[0146] The main advantages of the present application are as follows:

[0147] The present application can activate coal gangue at low energy consumption and low time consumption, and obtain molecular sieves with various framework structures by taking coal gangue as raw material.

[0148] The present application combines the low-energy low-temperature alkali liquid phase activation method with the solvent-free synthesis, further optimizes the activation conditions, reduces the energy consumption and the generation of synthesis waste liquid compared with the traditional method, obtains the product under more mild, green and low-cost conditions, and meets the environmental protection concept.

[0149] In the preparation process of the present application, the treated coal gangue is taken as a synthetic raw material in a solid state into a kettle, the kettle occupies small space and has small pressure, the product is easy to separate, and the prepared molecular sieve material has excellent adsorption performance;

[0150] The above only describes the best embodiments of the present application, but cannot be understood as a limitation on the claims. The present application is not limited to the above embodiments, and the specific structure allows changes. Any changes made within the protection scope of the independent claims of the present application are within the protection scope of the present application.

[0151] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

Claims

1. A mild and green method for preparing molecular sieves from coal gangue, characterized in that, Includes the following steps: Supplementing the aluminum source, activated coal gangue, seed crystals, and hydrochloric acid, the molar ratio of SiO2, Al2O3, Na2O, hydrochloric acid, and seed crystals is 1:(0.1-5.0):(0.5-2.5):(1.0-5.5):(0-0.1). The mixture is then thoroughly mixed and subjected to a crystallization reaction to obtain a molecular sieve. Activated coal gangue is prepared by the following process: coal gangue, sodium hydroxide and deionized water are mixed evenly at a mass ratio of 1:(1.0-2.0):(5.0-10.0), and then heated in an oven at 100-300℃ for 1-10 hours to obtain activated coal gangue.

2. The method for preparing molecular sieves from coal gangue in a mild and green manner according to claim 1, characterized in that, The supplementary aluminum source is one of boehmite, aluminum chloride, aluminum hydroxide, and aluminum isopropoxide.

3. The method for preparing molecular sieves from coal gangue in a mild and green manner according to claim 1, characterized in that, The mass concentration of hydrochloric acid is 36.5%.

4. The method for preparing molecular sieves from coal gangue in a mild and green manner according to claim 1, characterized in that, The crystallization reaction takes place at a temperature of 70-120℃ for 12-36 hours.

5. The method for preparing molecular sieves from coal gangue in a mild and green manner according to claim 1, characterized in that, Supplementing aluminum source, activated coal gangue, seed crystals and hydrochloric acid are mixed to make the molar ratio of SiO2, Al2O3, Na2O, hydrochloric acid and seed crystals 1:(0.1-5.0):(0.5-2.5):(1.0-5.5):(0-0.1). Then, the mixture is ground evenly and crystallized to obtain nanoscale FAU molecular sieve.

6. The method for preparing molecular sieves from coal gangue in a mild and green manner according to claim 1, characterized in that, Supplementing the aluminum source, activating coal gangue, and hydrochloric acid, such that the molar ratio of SiO2, Al2O3, Na2O, hydrochloric acid, and seed crystals is 1:(0.1-5.0):(0.5-2.5):(1.0-5.5):(0-0.1), then grinding them evenly and carrying out a crystallization reaction, yields SOD molecular sieve.

7. The method for preparing molecular sieves from coal gangue in a mild and green manner according to claim 1, characterized in that, The supplementary aluminum source is mixed with activated coal gangue so that the molar ratio of SiO2, Al2O3, Na2O and seed crystals is 1:(0.1-5.0):(0.5-2.5):(0-0.1). The mixture is then ground evenly and crystallized at 70-120℃ for 12-36 hours to obtain CAN molecular sieve.

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