A preparation method and application of zeolite ceramsite for advanced treatment of ammonia nitrogen wastewater

Abstract

The present invention discloses a zeolite ceramsite for deep treatment of ammonia nitrogen wastewater, its preparation method and application, which relate to the field of ammonia nitrogen wastewater treatment. The preparation method includes: (1) mixing acidified fly ash, phosphorus tailings and montmorillonite, and then adding a pore-forming agent to obtain a premixed powder; (2) performing wet mixing to obtain a highly dispersed premixed powder; (3) adding sodium aluminate and sodium hydroxide, mixing, pulverizing and grinding to obtain a fully mixed powder; (4) pressing and molding to obtain columnar green materials with a diameter of 5-8 mm and a length of 8-10 mm, drying and then roasting, and naturally cooling to room temperature to obtain activated ceramsite; (5) adding the activated ceramsite to deionized water for hydrothermal reaction, washing and drying to obtain the zeolite ceramsite for deep treatment of ammonia nitrogen wastewater. The zeolite ceramsite of the present invention has the characteristics of large specific surface area, developed pore structure and high compressive strength, and has advantages such as high selectivity for NH4+ in ammonia nitrogen wastewater and strong ability to resist interfering ions. The effect remains good after cyclic regeneration.

Description

Technical Field

[0001] The invention relates to the field of ammonia nitrogen wastewater treatment, and in particular to a zeolite ceramsite for deep treatment of ammonia nitrogen wastewater, and a preparation method and application thereof. Background Art

[0002] Ammonia is an important raw material in the phosphorus chemical industry. Some chemical reactions in the production process will generate ammonia nitrogen as a by-product and be discharged from the wastewater. Ammonia nitrogen (free NH3 and ionized NH4 + Ammonia nitrogen (NH3) is a common wastewater pollutant and a key monitoring indicator for industrial wastewater discharge in my country. Ammonia nitrogen in phosphorus chemical industry wastewater differs from ammonia nitrogen in domestic wastewater in that it exhibits high concentrations, poor biodegradability, and a high concentration of interfering ions. Improperly treated ammonia nitrogen wastewater poses serious risks to the ecological environment and human health.

[0003] Currently, the main methods for treating ammonia nitrogen wastewater are biological, chemical, and physicochemical methods. Biological methods have the advantages of large processing capacity, low cost, and stable reaction. However, they have high requirements for the biodegradability of wastewater, and microorganisms are sensitive to the environment, which limits the use of biological denitrification. Chemical methods have the advantages of wide application range, fast reaction speed, and high treatment effect. However, they have disadvantages such as secondary pollution, expensive chemical reagents, and high cost, which limit the application of chemical methods in treating ammonia nitrogen in wastewater. Physicochemical methods have the advantages of simple operation, low energy consumption, recyclability, and environmental friendliness, and are widely used in the treatment of ammonia nitrogen wastewater.

[0004] The ammonia nitrogen concentration of wastewater discharged from the phosphorus chemical industry is generally around 200 mg / L, which is a medium-low concentration. It also contains Ca 2+ Mg 2+ 、Fe 3+ 、SO4 2- PO4 3- In traditional treatment methods such as biological treatment, the ammonia nitrogen concentration in wastewater is too high, and the carbon-nitrogen ratio of wastewater is low, so additional carbon sources need to be added, which increases the cost of treatment. If chemical agents are added for treatment, the treatment cost will increase under ideal conditions without considering the generation of secondary pollutants, and it is difficult to treat the ammonia nitrogen concentration to below 30 mg / L at one time. If physical and chemical methods are used, with zeolite as a typical representative for treatment, there will still be some limitations. On the one hand, the upper limit of the concentration that zeolite can treat is not high, and on the other hand, many interfering ions will react with NH4 + Competition for reaction sites results in very limited removal efficiency.

[0005] Therefore, there is an urgent need to develop a zeolite preparation method with high selectivity for ammonia nitrogen in wastewater and strong anti-interference ability, aiming to provide a deep treatment method for ammonia nitrogen wastewater in the phosphorus chemical industry. Summary of the Invention

[0006] The object of the present invention is to solve the deficiencies of the above-mentioned background technology. Taking fly ash as the base material, supplemented with phosphorus tailings and montmorillonite as additives, a preparation method of zeolite ceramsite for deep treatment of ammonia-nitrogen wastewater is provided, which has high selectivity for ammonia-nitrogen in wastewater and strong anti-interference ability.

[0007] The technical solution of the present invention is as follows: A preparation method of zeolite ceramsite for deep treatment of ammonia-nitrogen wastewater, comprising the following steps:

[0008] A preparation method of zeolite ceramsite for deep treatment of ammonia-nitrogen wastewater, characterized by comprising the following steps:

[0009] (1) Mix acidified fly ash, phosphorus tailings, and montmorillonite in a mass ratio of (5~10):(1~5):1, and then add stearic acid as a pore-forming agent in an amount of 1%~5% of the total mass of acidified fly ash, phosphorus tailings, and montmorillonite to obtain a premixed powder.

[0010] (2) Using an ethanol aqueous solution as a dispersant, place the premixed powder obtained in step (1) in the dispersant, stir at a constant temperature of 60~75 °C in a water bath for 1~4 h, and then obtain a highly dispersed premixed powder through centrifugation and drying.

[0011] (3) Add sodium aluminate to the highly dispersed premixed powder obtained in step (2) to adjust the silicon-aluminum ratio to 1:(1~1.5), then add solid sodium hydroxide, and mix and grind thoroughly to less than 200 mesh to obtain a fully mixed powder.

[0012] (4) Press the fully mixed powder obtained in step (3) into a columnar green body with a diameter of 5~8 mm and a length of 8~10 mm, dry it, and then put it into a muffle furnace for roasting, and naturally cool it to room temperature to obtain activated ceramsite.

[0013] (5) Add the activated ceramsite obtained in step (4) to deionized water, carry out hydrothermal reaction at 75~95 °C for 4~12 h, wash and dry after the reaction is completed to obtain zeolite ceramsite for deep treatment of ammonia-nitrogen wastewater.

[0014] Preferably, in step (1), the acidified fly ash is prepared by the following method: Place fly ash in dilute hydrochloric acid with a mass concentration of 5%~10%, the mass ratio of fly ash to dilute hydrochloric acid is 1:(10~20), stir in a water bath at 65~85 °C for 2~4 h, and then obtain acidified fly ash through suction filtration, washing, and drying. Fly ash usually contains a certain amount of iron substances, including Fe2O3 (or hematite, siderite, limonite, etc.) that is easily soluble in acid and magnetic iron compounds that are difficult to dissolve in acid. However, iron is an inert agent for synthesizing zeolite and will also cause the zeolite product to be light green or brick yellow. By reacting hydrochloric acid with soluble iron and entering the solution, the purpose of partial iron removal is achieved.

[0015] In step (2) of the present invention, wet dispersion is adopted. Stearic acid is melted into a liquid phase at 60-65 °C and dispersed in an aqueous solution of ethanol. The pore-forming agent stearic acid is uniformly dispersed in the solid powder through stirring. Compared with ordinary direct mixing, the pore-forming agent can be mixed more gently and uniformly.

[0016] Preferably, in step (2), the volume fraction of the ethanol aqueous solution is 10%-20%, and the mass ratio of the premixed powder to the dispersant is 1: (5-10).

[0017] Preferably, in step (3), the mass ratio of sodium hydroxide to acidified fly ash is 1:1. Further, in step (3), the silicon-aluminum ratio n(Si / Al) = 1:1.

[0018] Preferably, in step (4), the drying is carried out at 95-105 °C for 1-2 h. The roasting includes first heating to 400-500 °C at a heating rate of 5-8 °C / min for preheating for 30-60 minutes, and then heating to 550-750 °C at a heating rate of 10-12 °C / min for heat preservation for 1-4 h.

[0019] Preferably, in step (5), the mass ratio of activated ceramsite to deionized water is 1:3-10.

[0020] Preferably, in step (5), the hydrothermal reaction is carried out at 75-85 °C for 6 h.

[0021] Preferably, in step (5), the cleaning and drying include: washing with deionized water until the pH of the washing liquid is 7-10, and then drying at 95-105 °C for 1-2 h.

[0022] In the raw materials used in the present invention: the content range of SiO2 in acidified fly ash is 60%-70%, the content range of Al2O3 is 15%-20%, and the rest is MgO+CaO and impurities; the content range of SiO2 in phosphorus tailings is 4%-10%, the content range of Al2O3 is 0.15%-1.5%, and the rest is MgO+CaO and impurities; the content range of SiO2 in montmorillonite is 50%-60%, the content range of Al2O3 is 20%-25%, and the rest is MgO+CaO and impurities (the above percentages are all mass percentages).

[0023] The content of SiO2 in acidified fly ash, phosphorus tailings, and montmorillonite is higher than that of Al2O3. Therefore, sodium aluminate needs to be added to adjust the silicon-aluminum ratio n(Si / Al), that is, the molar ratio of element silicon to element aluminum in the raw materials.

[0024] The present invention provides a zeolite ceramsite for deep treatment of ammonia-nitrogen wastewater prepared according to the above preparation method.

[0025] The present invention also provides an application of zeolite ceramsite for deep treatment of low-concentration ammonia nitrogen wastewater.

[0026] Preferably, the ammonia nitrogen concentration in the wastewater is 50 mg / L to 200 mg / L, and the dosage of zeolite ceramsite in the wastewater is 40 to 120 g / L.

[0027] The preparation principle of the zeolite ceramsite of the present invention is as follows:

[0028] In terms of raw materials, fly ash is used as the silicon-aluminum source skeleton material, phosphate tailings are used as the flux, montmorillonite is used as the binder, and solid stearic acid is introduced as the pore-forming agent; sodium aluminate is used as the aluminum source supplement to adjust the silicon-aluminum ratio; sodium hydroxide is added as the alkali flux to promote the dissolution of the vitreous body in the raw materials during high-temperature calcination, effectively destroying the crystal structures of inert substances (quartz and mullite), and at the same time decomposing the silicon-aluminum active substances therein into the aluminosilicate colloid required for synthesizing zeolite, significantly improving the overall activation level of the raw materials and providing an alkaline environment for subsequent hydrothermal treatment.

[0029] In step (4), high-temperature calcination forms the ceramsite matrix. High-temperature calcination can also destroy the crystal phase structures of inert components such as mullite and quartz to release amorphous SiO2 and Al2O3, significantly improving the activity of raw materials such as fly ash and phosphate tailings, thus facilitating crystallization in subsequent hydrothermal reactions.

[0030] The purpose of step (5) for hydrothermal reaction is to crystallize to form zeolite. Finally, the prepared zeolite ceramsite has a good adsorption effect on ammonium-form ammonia nitrogen in ammonia nitrogen wastewater. The zeolite ceramsite has high physical strength and can be reused repeatedly after regeneration, avoiding secondary pollution.

[0031] The beneficial effects of the present invention are as follows:

[0032] (1) The present invention provides a way for resource utilization of solid waste. Using industrial solid wastes - fly ash and phosphate tailings as the main base materials, A-type zeolite ceramsite is prepared by the method of alkali melting-hydrothermal treatment. Its rich microporous structure endows it with excellent adsorption performance. The cylindrical zeolite ceramsite has a strength as high as 12.3 MPa, a long service life and is convenient for recycling.

[0033] (2) The present invention uses phosphate tailings rich in calcium and magnesium as raw materials to replace part of the fly ash to prepare A-type zeolite ceramsite. On the one hand, a large amount of CO2 will escape during the high-temperature calcination of dolomite in the phosphate tailings to form a rich pore structure, expanding the pore size range of the zeolite ceramsite from mesopores to micropores; on the other hand, CaO and MgO generated during the high-temperature calcination process act as fluxes, which can reduce the melting point of the system and promote the progress of the reaction.

[0034] (3) The high-temperature roasting of the present invention has a good promoting effect on the subsequent hydrothermal synthesis. Specifically, during high-temperature roasting, CaO and MgO react with the sodium silicate in the raw materials, causing the Na in the sodium silicate to + be freed from its compound; during hydrothermal synthesis, in addition to the Na contained in the raw material sodium hydroxide + , the free Na + ions can supplement it and react with the silicate (SiO4 4- ) and aluminate (AlO4 5- ) ions in the system together to form zeolite crystals faster and more efficiently.

[0035] (4) The zeolite ceramsite provided by the present invention has a high selectivity for NH in wastewater 4+ and shows strong anti-interference ability when there are interfering ions such as Ca 2+ , Mg 2+ , SO4 2- , HPO4 2- , H2PO4 - , PO4 3- . This is mainly because a large amount of Ca 2+ , Mg 2+ introduced by the phosphorus tailings are solidified on the surface of the zeolite ceramsite, which has a same-sex repulsion effect on Ca 2+ , Mg 2+ in the wastewater; secondly, the pores formed by the escape of CO2 during the high-temperature calcination of the phosphorus tailings belong to the micropore size, which has a shielding effect on large-diameter ion groups such as SO4 2- , HPO4 2- , H2PO4 - , PO4 3- .

[0036] (4) The zeolite ceramsite provided by the present invention is suitable for the treatment of medium and low-concentration wastewater containing ammonia nitrogen of 50-200 mg / L. After 8 hours of reaction, the ammonia nitrogen removal efficiency in the wastewater can reach more than 95%, and the deep treatment effect is remarkable. Moreover, it can be recycled, and the ammonia nitrogen removal rate of the desorbed and regenerated zeolite ceramsite still reaches more than 90%.

[0037] (5) The preparation process of the zeolite ceramsite of the present invention is simple and safe, suitable for industrial-scale production. Moreover, most of the raw materials of the present invention are solid wastes such as tailings and tailings residues, and the win-win goal of "treating waste with waste" can also be achieved. <> BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the N2 adsorption-desorption curve and pore size distribution diagram for preparing ZC-01 in Example 1;

[0039] Figure 2X-ray diffraction analysis spectrum (XRD) of ZC-01 prepared in Example 1

[0040] Figure 3 Scanning electron microscope image (SEM) and energy dispersive spectroscopy scan (EDS) of ZC-01 prepared in Example 1;

[0041] Figure 4 Treatment effects of ZC-01, ZC-02, ZC-03, ZC-04 prepared in Examples 1 - 4 and ZC-05, ZC-06 prepared in Comparative Examples 1 - 2 on actual ammonia nitrogen wastewater under different pH conditions;

[0042] Figure 5 Treatment effect of the regenerated ZC-01 used in Example 5 on ammonia nitrogen wastewater after desorption and regeneration;

[0043] Figure 6 Treatment effect of ZC-01 prepared in Example 1 on ammonia nitrogen wastewater containing interfering ions;

[0044] Figure 7 Physical picture of ZC-01 prepared in Example 1. Detailed implementation manners

[0045] The following specific examples further illustrate the present invention in detail. The drugs used in the examples are all commercially available products without special instructions, and the methods used are all conventional methods in the art without special instructions. The raw material dosages in Examples 1 - 4 are as shown in Table 1 below.

[0046] Table 1 Raw material dosages (g)

[0047]

[0048] The acidified fly ash used in the following examples is prepared according to the following steps:

[0049] The fly ash is sieved through a 200-mesh sieve. The sieved fly ash is placed in dilute hydrochloric acid with a mass concentration of 5%. The mass ratio of fly ash to dilute hydrochloric acid is 1:20. Stir at a constant temperature of 65 °C in a water bath for 2 h, then separate by suction filtration, wash the filter cake with distilled water multiple times until the pH value is close to 7, and then dry and grind the filter cake to obtain acidified fly ash.

[0050] Example 1

[0051] This example provides a preparation method of zeolite ceramsite for deep treatment of ammonia nitrogen wastewater, including the following steps:

[0052] (1) Mix 21 g of acidified fly ash (containing 69.35% SiO₂ and 17.52% Al₂O₃), 6 g of phosphorus tailings (containing 4.6% SiO₂ and 0.25% Al₂O₃), and 3 g of montmorillonite (containing 58.95% SiO₂ and 20.06% Al₂O₃), and add 1 g of stearic acid particles as a pore-forming agent to obtain a premixed powder.

[0053] (2) Use an ethanol aqueous solution with a volume fraction of 20% as a dispersant. Place the premixed powder in the dispersion liquid according to a mass ratio of the premixed powder to the dispersant of 1:10, stir in a constant temperature water bath at 65 °C for 1 h, and then obtain a highly dispersed premixed powder through centrifugation and drying.

[0054] (3) Then add 15.8 g of sodium aluminate to adjust the silicon-aluminum ratio of the powder n(Si / Al) = 1:1, and then add 21 g of solid sodium hydroxide, and mix and grind thoroughly to less than 200 mesh to obtain a fully mixed powder.

[0055] (4) Press the fully mixed powder into a mold to obtain columnar particles with a diameter of 5 - 8 mm and a length of 8 - 10 mm. After drying in an oven at 105 °C for 1 h, put it into a muffle furnace. First, heat it at a heating rate of 8 °C / min to 400 °C and preheat for 30 minutes, then heat it at a heating rate of 10 °C / min to 750 °C and hold for 1 h, and naturally cool to room temperature to obtain activated ceramsite.

[0056] (5) Add the activated ceramsite to deionized water. The mass ratio of the activated ceramsite to deionized water is 1:6. Perform a hydrothermal reaction at 85 °C for 6 h. After the reaction is completed, take it out and rinse it with ionized water until the pH of the washing liquid is 8 - 10, and dry it in an oven at 105 °C for 1 h to obtain zeolite ceramsite for the deep treatment of ammonia nitrogen wastewater, denoted as ZC - 01. The physical diagram is as Figure 7 shown.

[0057] Example 2

[0058] This example provides a preparation method for zeolite ceramsite for the deep treatment of ammonia nitrogen wastewater, including the following steps:

[0059] (1) Mix 24 g of acidified fly ash (containing 69.35% SiO₂ and 17.52% Al₂O₃), 3 g of phosphorus tailings (containing 4.6% SiO₂ and 0.25% Al₂O₃), and 3 g of montmorillonite (containing 58.95% SiO₂ and 20.06% Al₂O₃), and add 1 g of stearic acid particles as a pore-forming agent to obtain a premixed powder.

[0060] (2) Using an ethanol aqueous solution with a volume fraction of 20% as a dispersant, place the premixed powder in the dispersant according to the mass ratio of the premixed powder to the dispersant of 1:10, stir in a constant temperature water bath at 60 °C for 1 h, and then obtain the highly dispersed premixed powder through centrifugation, washing, and drying.

[0061] (3) Add 17.6 g of sodium aluminate to adjust the silicon-aluminum ratio n(Si / Al) = 1:1, and then add 24 g of solid sodium hydroxide, and fully mix and grind to below 200 mesh to obtain the fully mixed powder.

[0062] (4) Press the fully mixed powder into a mold to obtain columnar particles with a diameter of 5 - 8 mm and a length of 8 - 10 mm. After drying in an oven at 105 °C for 1 h, put it into a muffle furnace. First, heat it at a heating rate of 8 °C / min to 400 °C and preheat for 30 minutes, then heat it at a heating rate of 10 °C / min to 750 °C and calcine for 1 h, and naturally cool to room temperature to obtain activated ceramsite.

[0063] (3) Add the activated ceramsite to deionized water, with the mass ratio of the activated ceramsite to deionized water being 1:6, carry out a hydrothermal reaction at 75 °C for 6 h. After the reaction is completed, take it out and rinse it with ionized water until the pH of the washing solution is 8 - 10, and dry it in an oven at 105 °C for 1 h to obtain zeolite ceramsite for the deep treatment of ammonia-nitrogen wastewater, denoted as ZC-02. Example 3

[0064] This example provides a preparation method for zeolite ceramsite for the deep treatment of ammonia-nitrogen wastewater, including the following steps:

[0065] (1) Mix 21 g of acidified fly ash (containing 69.35% SiO2, 17.52% Al2O3), 14 g of phosphorus tailings (containing 4.6% SiO2, 0.25% Al2O3), and 3 g of montmorillonite (containing 58.95% SiO2, 20.06% Al2O3), and add 1 g of stearic acid particles as a pore-forming agent to obtain the premixed powder.

[0066] (2) Using an ethanol aqueous solution with a volume fraction of 10% as a dispersant, place the premixed powder in the dispersant according to the mass ratio of the mixed powder to the dispersant of 1:10, stir in a constant temperature water bath at 65 °C for 1 h, and then obtain the highly dispersed premixed powder through centrifugation, washing, and drying.

[0067] (3) Add 16.3 g of sodium aluminate to adjust the silicon-aluminum ratio n(Si / Al) = 1:1, and then add 21 g of solid sodium hydroxide, and fully mix and grind to below 200 mesh to obtain the fully mixed powder.

[0068] (4) The whole mixed powder was pressed into shape using a mold to obtain cylindrical particles with a diameter of 5-8 mm and a length of 8-10 mm. The particles were dried in a drying oven at 105 °C for 1 h and then calcined in a muffle furnace. The temperature was first increased to 400 °C at a heating rate of 8 °C / min and preheated for 30 min. The temperature was then increased to 750 °C at a heating rate of 10 °C / min and calcined for 1 h. The particles were naturally cooled to room temperature to obtain activated particles.

[0069] (5) The activated particles were added into deionized water with a mass ratio of activated ceramsite to deionized water of 1:6. The particles were subjected to hydrothermal reaction at 75 °C for 6 h. After the reaction was completed, the particles were taken out and rinsed with deionized water until the pH of the washing solution was 8-10. The particles were dried in a drying oven at 105 °C for 1 h to obtain zeolite ceramsite for deep treatment of ammonia nitrogen wastewater, which was recorded as ZC-03.

[0070] Example 4

[0071] This embodiment provides a method for preparing zeolite ceramsite for deep treatment of ammonia nitrogen wastewater, comprising the following steps:

[0072] (1) 21 g of acidified fly ash (containing SiO2 69.35%, Al2O3 17.52%), 6 g of phosphate tailings (containing SiO2 4.6%, Al2O3 0.25%), 3 g of montmorillonite (containing SiO2 58.95%, Al2O3 20.06%), and 1 g of stearic acid particles as a pore-forming agent were added to obtain a premixed powder.

[0073] (2) Using 10% ethanol aqueous solution as the dispersant, the premixed powder was placed in the dispersant at a mass ratio of 1:10, stirred in a constant temperature water bath at 60 °C for 0.5 h, and then centrifuged, washed, and dried to obtain a highly dispersed premixed powder.

[0074] (3) Add 16.0 g of sodium aluminate to adjust the silicon-aluminum ratio n(Si / Al) to 1:1, then add 21 g of sodium hydroxide solid, mix thoroughly and grind to below 200 mesh to obtain a complete mixed powder.

[0075] (4) The whole mixed powder was pressed into shape using a mold to obtain cylindrical particles with a diameter of 5-8 mm and a length of 8-10 mm. The particles were dried in a drying oven at 105 °C for 1 h and then placed in a muffle furnace. The mixture was first heated to 400 °C at a heating rate of 8 °C / min and preheated for 30 min. The mixture was then heated to 750 °C at a heating rate of 10 °C / min and calcined for 1 h to obtain activated particles.

[0076] (5) The activated particles were added to deionized water at a mass ratio of 1:6. The activated ceramsite was subjected to a hydrothermal reaction at 75°C for 6 h. After the reaction was completed, the particles were taken out and rinsed with deionized water. They were then dried in a drying oven at 105°C for 1 h to obtain zeolite ceramsite for deep treatment of ammonia nitrogen wastewater. This was designated as ZC-04. Comparative Example 1

[0077] This comparative example provides a method for preparing mesoporous ceramsite, including the following steps:

[0078] (1) Mix 21 g of acidified fly ash (containing 69.35% SiO₂ and 17.52% Al₂O₃), 3 g of phosphorus tailings (containing 4.6% SiO₂ and 0.25% Al₂O₃), and 3 g of montmorillonite (containing 58.95% SiO₂ and 20.06% Al₂O₃) to obtain a premixed powder. )]]

[0079] (2) Use an ethanol aqueous solution with a volume fraction of 20% as a dispersant. Place the premixed powder in the dispersant according to the mass ratio of the premixed powder to the dispersion liquid of 1:10. Stir in a constant temperature water bath at 60 °C for 1 h, and then obtain a highly dispersed premixed powder through centrifugation, washing, and drying.

[0080] (3) Add 15.8 g of sodium aluminate to adjust the silicon-aluminum ratio n(Si / Al) = 1:1, and then add 21 g of solid sodium hydroxide. Mix and grind thoroughly to less than 200 mesh to obtain a fully mixed powder.

[0081] (4) Press the fully mixed powder into pellets using a mold to obtain columnar particles with a diameter of 5 - 8 mm and a length of 8 - 10 mm. Dry in an oven at 105 °C for 1 h, then put it into a muffle furnace. First, heat it at a heating rate of 8 °C / min to 400 °C and preheat for 30 minutes, and then heat it at a heating rate of 10 °C / min to 750 °C and calcine for 1 h. Naturally cool to room temperature to obtain activated ceramsite.

[0082] (3) Add the activated ceramsite to deionized water. The mass ratio of the activated ceramsite to deionized water is 1:6. Perform a hydrothermal reaction at 75 °C for 6 h. After the reaction is completed, take it out and rinse with ionized water. Dry in an oven at 105 °C for 1 h to obtain zeolite ceramsite for deep treatment of ammonia nitrogen wastewater, denoted as ZC - 05.

[0083] Comparative Example 2

[0084] This comparative example provides a method for preparing mesoporous ceramsite, including the following steps:

[0085] (1) Mix 21 g of acidified fly ash (containing 69.35% SiO₂ and 17.52% Al₂O₃) and 3 g of montmorillonite (containing 58.95% SiO₂ and

[0085] 20.06% Al₂O₃), and add 1 g of stearic acid particles as a pore-forming agent to obtain a premixed powder.

[0086] (2) Use an ethanol aqueous solution with a volume fraction of 20% as a dispersant. Place the premixed powder in the dispersant according to the mass ratio of the premixed powder to the dispersion liquid of 1:10. Stir in a constant temperature water bath at 60 °C for

[0086] 1 h, and then obtain a highly dispersed premixed powder through centrifugation, washing, and drying.

[0087] (3) 15.4 g of sodium aluminate was added to adjust the silicon-aluminum ratio n(Si / Al) = 1:1, and then 21 g of solid sodium hydroxide was added. The mixture was fully mixed and ground to less than 200 mesh to obtain a fully mixed powder.

[0088] (4) The fully mixed powder was pressed into pellets using a mold to obtain cylindrical pellets with a diameter of 5 - 8 mm and a length of 8 - 10 mm. After drying in an oven at 105 °C for 1 h, it was placed in a muffle furnace. First, it was heated to 400 °C at a heating rate of 8 °C / min and preheated for 30 minutes, and then heated to 750 °C at a heating rate of 10 °C / min and calcined for 1 h. It was naturally cooled to room temperature to obtain activated ceramsite.

[0089] (3) The activated ceramsite was added to deionized water. The mass ratio of the activated ceramsite to deionized water was 1:6. It was hydrothermally reacted at 75 °C for 6 h. After the reaction was completed, it was taken out and rinsed with ionized water, and then dried in an oven at 105 °C for 1 h to obtain zeolite ceramsite for the deep treatment of ammonia-nitrogen wastewater, denoted as ZC-06.

[0090] Example 5

[0091] Weigh 5 g of each of ZC-01, ZC-02, ZC-03, ZC-04, ZC-05, and ZC-06, and treat 100 ml of actual phosphate chemical wastewater (containing interfering ions Ca 2+ 、Mg 2+ 、Al 3+ 、SO4 2- 、PO4 3- ) at pH values of 5, 7, and 9 respectively. The ammonia-nitrogen concentration is 200 mg / L, the treatment duration is 8 hours, and the shaking intensity of the shaker is 120 rpm. The determination of the ammonia-nitrogen concentration in the wastewater refers to the standard "Determination of Ammonia-Nitrogen in Water - Nessler Reagent Spectrophotometry" (HJ 535 2009). The results are as Figure 4 shown. It can be seen from Figure 4 that the ammonia-nitrogen removal rates of the zeolite ceramsite prepared in Examples 1 - 4 are significantly higher than those of the zeolite ceramsite prepared in Comparative Examples 1 - 2. Among them, the zeolite ceramsite prepared in Examples 1 - 4 has the best effect under neutral conditions (pH = 7). When pH = 7 and the reaction lasts for 8 hours, the ammonia-nitrogen removal rates of the zeolite ceramsite prepared in Examples 1 - 4 all reach over 95%; while under the same conditions, the ammonia-nitrogen removal rates of the zeolite ceramsite prepared in Comparative Examples 1 - 2 are only about 85%.

[0092] Example 6

[0093] The used ZC-01 in Example 5 was recovered and immersed in 100 ml of 1.5 mol / L NaCl solution for 2 h for desorption regeneration (Na +NH4 in ZC-01 + (ion exchange), and after drying, it was used again to treat the actual wastewater with an ammonia nitrogen concentration of 200 mg / L under the condition of pH 7 for 8 hours, and the shaking intensity of the shaker was 120 rpm. The results are as Figure 5 shown. From Figure 5 it can be seen that the ammonia nitrogen removal rate of ZC-01 after desorption regeneration still reached more than 90%.

[0094] Example 7

[0095] Weigh 5 g of ZC-01 prepared in Example 1 respectively, and conduct anti-interference ion tests in simulated ammonia nitrogen wastewater containing interfering ions Ca 2+ , Mg 2+ , Al 3+ . The ammonia nitrogen concentration in the simulated wastewater is 100 mg / L, the volume of the simulated wastewater is 100 ml, and the concentrations of Ca 2+ , Mg 2+ , Al 3+ in the simulated wastewater are 0.1 mol / L, 0.2 mol / L, and 0.5 mol / L respectively. The treatment duration is 8 hours, and the shaking intensity of the shaker is 120 rpm. The results are as Figure 6 shown. From Figure 6 it can be seen that the interfering ions have little effect on the adsorption effect of ZC-01. Under the condition of adding various interfering ions, the ammonia nitrogen removal efficiency of ZC-01 still reaches more than 90%, further testifying to the strong anti-interference ability of ZC-01 zeolite ceramsite.

[0096] Performance Test

[0097] (1) The chemical composition analysis (%) of ZC-01 prepared in Example 1 was carried out by using an X-ray fluorescence spectrometer (XRF), and the results are shown in Table 2 below.

[0098] Table 2 Chemical Composition Analysis (%) of ZC-01

[0099]

[0100] It can be seen from the data in Table 2 that the main components of ZC-01 are SiO2, Al2O3 and Na2O, and the chemical composition content is similar to that of the standard Na-A type zeolite.

[0101] (2) The pore structure parameters and compressive strength of ZC-01, ZC-02, ZC-03, ZC-04 prepared in Examples 1-4 and ZC-05, ZC-06 prepared in Comparative Examples 1-2 were tested by using a BET instrument respectively.

[0102] Table 3 Pore Structure Parameters and Compressive Strength of ZC-01

[0103]

[0104] As can be seen from the data in Table 3, the zeolite ceramsites of Examples 1-4 and Comparative Examples 1-2 have large single pore volumes and large total pore volumes, with average pore diameters ranging from 7.0568 nm to 16.627 nm, all falling within the mesopore range. However, it should be noted that Comparative Example 1, which is zeolite ceramsite without the addition of stearic acid (pore-forming agent), has an average pore diameter significantly smaller than that of Examples 1-4, demonstrating that the pore size formed by the release of CO2 during the high-temperature calcination of phosphate tailings is within the micropore size range (less than 2 nm). Comparative Example 2, which is zeolite ceramsite without the addition of phosphate tailings, has an average pore diameter slightly larger than that of Examples 1-4, again demonstrating that the pores formed during the high-temperature calcination of stearic acid (pore-forming agent) are within the mesopore size range (2-50 nm).

[0105] The N2 adsorption-desorption curve and pore size distribution diagram of ZC-01 prepared in Example 1 were plotted separately ( Figure 1 ),from Figure 1 The curve for ZC-01 is close to a Type II adsorption isotherm. Initially, the isotherm is convex, with an inflection point, indicating that monolayer adsorption reaches equilibrium. As pressure increases, multilayer adsorption gradually forms. The presence of an H3-type hysteresis loop indicates that the pores of the zeolite ceramsite are narrow pores formed by the accumulation of ribbon-like particles, providing more adsorption sites during the adsorption process. The pore size distribution of ZC-01 is concentrated in two size ranges: micropores of 1.88 nm and mesopores of 14.12 nm.

[0106] (3) The ZC-01 prepared in Example 1 was tested using an X-ray diffraction analyzer (XRD) and compared with the diffraction file (PDF) card in the standard database, as shown in FIG. Figure 2 As shown. Figure 2 It can be seen that the diffraction characteristic peaks of the ZC-01 zeolite ceramsite prepared in Example 1 are highly consistent with the diffraction characteristic peaks of type A zeolite.

[0107] (4) The ZC-01 prepared in Example 1 was observed for microscopic morphology by field emission scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). Figure 3 The SEM images reveal a typical cubic structure of type A zeolite, with clear cubic morphology, distinct edges and corners, a smooth surface, and a complete crystal structure. EDS scanning reveals that the main elements Si, Al, Na, and O in the ZC-01 zeolite ceramsite are evenly distributed, with no over-enrichment of certain elements. This demonstrates that the ZC-01 prepared in Example 1 provides a uniform reaction space during the adsorption process.

Claims

1. A method for preparing zeolite ceramsite for deep treatment of ammonia nitrogen wastewater, characterized in that: The following steps are involved: (1) Acidified fly ash, phosphorus tailings, and montmorillonite are mixed in a mass ratio of (5-10):(1-5):1, and stearic acid is added as a pore-forming agent in an amount of 1%-5% of the total mass of the acidified fly ash, phosphorus tailings, and montmorillonite to obtain a premixed powder; (2) Using ethanol aqueous solution as a dispersant, the volume fraction of ethanol aqueous solution is 10%~20%, placing the premixed powder obtained in step (1) in the dispersant, the mass ratio of the premixed powder to the dispersion is 1: (5~10), stirring in a constant temperature water bath at 60~75℃ for 1~4 hours, and then centrifuging and drying to obtain a highly dispersed premixed powder; (3) adding sodium aluminate to the highly dispersed premixed powder obtained in step (2) to adjust the silicon-aluminum ratio to 1: (1-1.5), then adding sodium hydroxide solid, wherein the mass ratio of sodium hydroxide to fly ash is 1:1, and fully mixing and grinding to less than 200 mesh to obtain a fully mixed powder; (4) The fully mixed powder obtained in step (3) is pressed into shape to obtain a columnar raw material with a diameter of 5-8 mm and a length of 8-10 mm, which is then dried and placed in a muffle furnace for roasting. The roasting comprises first heating the material to 400-500°C at a heating rate of 5-8°C / min and preheating for 30-60 minutes, then heating the material to 550-750°C at a heating rate of 10-12°C / min and keeping the temperature for 1-4 hours, and then naturally cooling the material to room temperature to obtain activated ceramsite; (5) Add the activated ceramsite obtained in step (4) into deionized water and perform hydrothermal reaction at 75-95 °C for 4-12 h. After the reaction is completed, wash and dry the ceramsite to obtain zeolite ceramsite for deep treatment of ammonia nitrogen wastewater.

2. The method for preparing zeolite ceramsite for deep treatment of ammonia nitrogen wastewater according to claim 1, wherein In step (1), the acidified fly ash is prepared by a method comprising the following steps: placing fly ash in dilute hydrochloric acid with a mass concentration of 5-10%, with a mass ratio of fly ash to dilute hydrochloric acid of 1: (10-20), stirring in a constant temperature water bath at 65-85°C for 2-4h, and then filtering, washing, and drying to obtain acidified fly ash.

3. The method for preparing zeolite ceramsite for deep treatment of ammonia nitrogen wastewater according to claim 1, wherein In step (4), the drying is performed at 95-105°C for 1-2 hours.

4. The method for preparing zeolite ceramsite for deep treatment of ammonia nitrogen wastewater according to claim 1, wherein In step (5), the mass ratio of the activated ceramsite to deionized water is 1:3~10.

5. The method for preparing zeolite ceramsite for deep treatment of ammonia nitrogen wastewater according to claim 1, wherein In step (5), the hydrothermal reaction was carried out at 75 °C for 6 h.

6. The method for preparing zeolite ceramsite for deep treatment of ammonia nitrogen wastewater according to claim 1, wherein In step (5), the cleaning and drying comprises: washing with deionized water until the pH of the washing solution is 8-10, and then drying at 95-105°C for 1-2 hours.

7. A zeolite ceramsite for deep treatment of ammonia nitrogen wastewater, characterized in that: The invention is prepared by the preparation method of zeolite ceramsite for deep treatment of ammonia nitrogen wastewater according to any one of claims 1 to 6.

8. An application of zeolite ceramsite for deep treatment of ammonia nitrogen wastewater as claimed in claim 7, characterized in that: The ammonia nitrogen concentration in the wastewater is 50 mg / L~200 mg / L, and the dosage of zeolite ceramsite in the wastewater is 40~120 g / L.

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