Low-concentration ammonia-nitrogen adsorbing material, preparation method and application thereof

Abstract

The application belongs to the technical field of ammonia nitrogen adsorption materials, and discloses a low-concentration ammonia nitrogen adsorption material and a preparation method and application thereof. The preparation method is as follows: taking zeolite powder as a matrix, adding nanoscale rice husk silicon dioxide and bentonite into the zeolite powder and uniformly mixing to obtain mixed powder; adding a sodium hydroxymethyl cellulose aqueous solution into the mixed powder and uniformly mixing to obtain mixed slurry; performing pill-making treatment on the mixed slurry to obtain spherical zeolite; drying the spherical zeolite and then performing calcination treatment to obtain modified zeolite balls, and taking the modified zeolite balls as the low-concentration ammonia nitrogen adsorption material. In the application, nanoscale rice husk silicon dioxide is used as a modifier, which can not only increase the specific surface area of the whole zeolite ball, provide more active sites for ammonia nitrogen adsorption, and improve the physical strength of the adsorption material, but also has low preparation cost, can utilize agricultural waste resources, and meets the requirements of economic benefits and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ammonia nitrogen adsorption materials, in particular to a low-concentration ammonia nitrogen adsorption material and a preparation method and application thereof. BACKGROUND

[0002] Zeolite has excellent ammonia nitrogen adsorption and ion exchange performance. At low ammonia nitrogen concentration, zeolite adsorbs ammonia nitrogen to form an ammonia-rich microenvironment, which is conducive to the enrichment of nitrifying microorganisms. At high ammonia nitrogen concentration, zeolite can maintain the concentration of free ammonia, which plays a good buffering role against water inflow shock. At present, zeolite as a biological filler has been widely used in nitrification, denitrification, partial nitrification, and anaerobic ammonia oxidation and other biological denitrification processes. However, the adsorption capacity of natural zeolite is limited, and when treating high-ammonia-nitrogen wastewater, the adsorption saturation state is reached quickly, and some denitrification microorganisms sensitive to zeolite may be inhibited, thereby affecting the stability of the overall denitrification.

[0003] In order to solve the above technical problems, the person skilled in the art usually chooses to replace natural zeolite with artificially synthesized zeolite, and modifies the zeolite by acid-base modification, heating calcination, and organic modification, etc. to change the surface properties and pore structure of the zeolite, enhance its affinity for ammonia nitrogen, and thus improve the adsorption capacity. However, in actual modification of the zeolite, a large amount of energy is usually consumed, greatly increasing the processing cost, and easily causing secondary pollution, making it difficult to realize large-scale popularization and use. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a low-concentration ammonia nitrogen adsorption material and a preparation method and application thereof.

[0005] The low-concentration ammonia nitrogen adsorption material and the preparation method and application thereof of the present application are realized by the following technical solutions:

[0006] The first object of the present application is to provide a preparation method of a low-concentration ammonia nitrogen adsorption material, comprising the following steps:

[0007] Step 1, preparation of mixed powder:

[0008] Zeolite powder is used as the substrate, nanoscale rice husk silica is used as the modifier, and bentonite is used as the binder. The nanoscale rice husk silica and the binder are added to the zeolite powder and mixed to obtain the mixed powder.

[0009] Step 2, preparation of mixed slurry:

[0010] The mixed powder is added with a sodium hydroxymethyl cellulose aqueous solution and mixed to obtain the mixed slurry.

[0011] Step 3, calcination treatment after pill making:

[0012] The mixed slurry is subjected to pill-making treatment to obtain spherical zeolite; and the spherical zeolite is dried and subjected to calcination treatment to obtain modified zeolite spheres, which are used as low-concentration ammonia-nitrogen adsorption materials.

[0013] It should be noted that the present application preferably uses nanoscale rice husk silicon dioxide as a modifier, and by uniformly mixing the nanoscale rice husk silicon dioxide with zeolite powder, the modification of the zeolite spheres is realized in the process of preparing the spherical zeolite spheres. On the one hand, the zeolite spheres can have more negative charges on the surface, thereby enhancing the electrostatic attraction of ammonium ions; on the other hand, the surface hydroxyl groups of the silicon dioxide have strong electronegativity, and form hydrogen bonds with the nitrogen atoms in the ammonia-nitrogen molecules, thereby further improving the stability and strength of the ammonia-nitrogen adsorption. Meanwhile, the nanoscale rice husk silicon dioxide can increase the specific surface area of the zeolite spheres as a whole, thereby providing more active sites for ammonia-nitrogen adsorption, improving the physical strength of the adsorption material, and being low in preparation cost and capable of utilizing agricultural waste resources, thereby meeting the economic interests and environmental protection requirements.

[0014] In order to ensure that the added nanoscale rice husk silicon dioxide can fully modify the zeolite powder, in some preferred embodiments of the present application, the addition amount of the nanoscale rice husk silicon dioxide is 4% to 10% of the mass of the zeolite powder.

[0015] In some preferred embodiments of the present application, the binder is one or both of bentonite and kaolin. In the present application, it is considered that when a single kaolin is used as a binder, the mechanical strength of the zeolite spheres can be improved, but the porosity will decrease, and therefore the binder is more preferably bentonite.

[0016] In some more preferred embodiments of the present application, the addition amount of the bentonite is 15% to 20% of the mass of the zeolite powder, so that the added bentonite can bond the components into one body, which is beneficial to the subsequent process of making the spherical zeolite.

[0017] The present application also adds a cellulose derivative aqueous solution to the mixed powder, uses the cellulose derivative aqueous solution as an adhesive and thickening agent, realizes the increase of the viscosity of the system, and ensures the mechanical strength and integrity of the prepared zeolite spheres. In some preferred embodiments of the present application, the cellulose derivative in the cellulose derivative aqueous solution used is one or more of sodium hydroxymethyl cellulose, hydroxypropyl methyl cellulose and methyl cellulose. The cellulose derivative in the cellulose derivative aqueous solution is more preferably sodium hydroxymethyl cellulose.

[0018] In some more preferred embodiments of the present application, the mass concentration of the cellulose derivative in the cellulose derivative aqueous solution used is 2% to 3%, and 0.2 mL to 0.4 mL of the cellulose derivative aqueous solution is added per 1 g of the mixed powder, so as to ensure that the added cellulose derivative aqueous solution can realize the above-mentioned effects.

[0019] In some preferred embodiments of the present application, the calcination temperature of the calcination treatment is 550-650℃, and the calcination time is 0.5-2h, so that under the calcination conditions, the partial surface hydroxyl groups of the rice husk silica in the spherical zeolite change due to condensation reaction, exposing active sites that can form hydrogen bonds with ammonia nitrogen molecules and other interactions, to achieve modification of the zeolite spheres, obtaining modified zeolite spheres as low-concentration ammonia nitrogen adsorption materials.

[0020] In some preferred embodiments of the present application, the drying temperature when drying the spherical zeolite is 100-110℃, and the drying time is 2-4h.

[0021] In some preferred embodiments of the present application, the nanoscale rice husk silica used is prepared by the following steps:

[0022] 1) Grinding clean rice husks to obtain rice husk powder with a particle size of ≤200μm.

[0023] 2) Dispersing the rice husk powder in a citric acid solution, and performing acid immersion treatment at room temperature to remove metal impurities in the rice husk powder, and after the acid immersion treatment is completed, performing solid-liquid separation to obtain a solid phase component; washing and drying the solid phase component to obtain the rice husk powder after acid immersion treatment.

[0024] 3) Dispersing the rice husk powder after acid immersion treatment in a sodium hydroxide solution, and performing heating treatment at 85-95℃ to make the silicon dioxide in the rice husk powder after acid immersion treatment react with sodium hydroxide to form sodium silicate, and performing solid-liquid separation to obtain a liquid phase component.

[0025] 4) Adding hydrochloric acid solution dropwise to the liquid phase component to make the sodium silicate in the liquid phase component react with hydrochloric acid to form silicon dioxide gel, obtaining a gel material.

[0026] 5) Drying the gel material to obtain the nanoscale rice husk silica.

[0027] It should be noted that in some preferred embodiments of the present application, the concentration of citric acid in the citric acid solution is 18-20g / L; and 25-35g of the rice husk powder is added per 1L of the citric acid solution, to remove metal impurities in the rice husk powder by citric acid, thereby improving the purity and quality of the rice husk silica. In more preferred embodiments of the present application, the concentration of citric acid in the citric acid solution is 19.2g / L; and 30g of the rice husk powder is added per 1L of the citric acid solution.

[0028] In some preferred embodiments of the present application, the mass concentration of sodium hydroxide in the sodium hydroxide solution is 150g / L-200g / L; and 130g-170g of the rice husk powder treated by acid immersion is added to 1L of the sodium hydroxide solution, so as to separate silicon dioxide from the rice husk powder in the form of sodium silicate. In more preferred embodiments of the present application, the concentration of sodium hydroxide in the sodium hydroxide solution is 172.5g / L; and 150g of the rice husk powder treated by acid immersion is added to 1L of the sodium hydroxide solution, so as to separate silicon dioxide from the rice husk powder in the form of sodium silicate.

[0029] In some preferred embodiments of the present application, the treatment time of the acid immersion treatment is 60min-120min, so as to ensure that the contact time of citric acid in the citric acid solution with the rice husk powder is sufficient, thereby effectively removing the metal impurities in the rice husk powder.

[0030] In some preferred embodiments of the present application, the treatment time of the heating treatment is 60min-120min, so as to ensure that the rice husk powder treated by acid immersion can be fully contacted with the sodium hydroxide solution, thereby promoting the reaction of silicon dioxide in the rice husk powder treated by acid immersion with sodium hydroxide to generate sodium silicate.

[0031] In some preferred embodiments of the present application, the drying temperature of the gel material is 55℃-65℃, and the drying time is 2h-6h.

[0032] The second object of the present application is to provide a low-concentration ammonia-nitrogen adsorption material prepared by the preparation method.

[0033] The third object of the present application is to provide an application of the low-concentration ammonia-nitrogen adsorption material in adsorbing low-concentration ammonia-nitrogen.

[0034] In some preferred embodiments of the present application, the low-concentration ammonia-nitrogen refers to the ammonia-nitrogen concentration in a water body to be treated being ≤50mg / L.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] In the process of synthesizing zeolite balls, the present application uses nanoscale rice husk silicon dioxide to modify the product. On the one hand, the zeolite ball surface can have more negative charges, enhancing the electrostatic attraction of ammonium ions. On the other hand, the hydroxyl groups on the surface of silicon dioxide have strong electronegativity, forming hydrogen bonds with nitrogen atoms in ammonia-nitrogen molecules, further improving the stability and strength of ammonia-nitrogen adsorption. At the same time, nanoscale rice husk silicon dioxide can increase the specific surface area of the zeolite ball as a whole, providing more active sites for ammonia-nitrogen adsorption, and improving the physical strength of the adsorption material. The present application has low preparation cost and can utilize agricultural waste resources, meeting the requirements of economic benefits and environmental protection.

[0037] The application uses nanoscale rice hull silica as a modifier, which is widely available, low in cost and renewable, realizes effective utilization of resources and meets the requirements of sustainable development. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 A scanning electron microscope image of the rice hull powder prepared in Example 1.

[0039] Figure 2 A scanning electron microscope image of the nanoscale rice hull silica prepared in Example 1.

[0040] Figure 3 A scanning electron microscope image of the low-concentration ammonia nitrogen adsorption material prepared in Example 1.

[0041] Figure 4 A comparison diagram of the ammonia nitrogen adsorption capacity of the low-concentration ammonia nitrogen adsorption materials of Example 1 and Comparative Example 1.

[0042] Figure 5 A diagram of the change of the ammonia nitrogen adsorption effect of the low-concentration ammonia nitrogen adsorption material of Example 1 with time before and after coating with a biofilm. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the application will be described in detail below.

[0044] Example 1

[0045] This embodiment provides a low-concentration ammonia nitrogen adsorption material, which is prepared by the following steps:

[0046] Step 1, preparation of mixed powder:

[0047] 1.1) Preparation of nanoscale rice hull silica:

[0048] 1.1.1) Grind clean rice hulls to obtain rice hull powder with a particle size of ≤200 μm.

[0049] 1.1.2) Disperse the rice hull powder obtained above in an acid leaching solution with a concentration of 19.2 g / L of citric acid solution, according to the dosage ratio of 30 g of rice hull powder per 1 L of citric acid solution, and perform acid leaching treatment at room temperature for 90 min to remove metal impurities in the rice hull powder. After acid leaching treatment, filter to obtain a solid phase component; wash the solid phase component and dry it at 60°C for 4 h to obtain the acid leached rice hull powder.

[0050] 1.1.3) The acid leached rice husk powder is dispersed in a sodium hydroxide solution as the alkali treating agent with a concentration of 172.5 g / L at a ratio of 150 g of the acid leached rice husk powder per 1 L of the sodium hydroxide solution, and heated at 90 °C for 90 min to react the silicon dioxide in the acid leached rice husk powder with the sodium hydroxide to form sodium silicate, and filtered to obtain a liquid phase component.

[0051] 1.1.4) The liquid phase component obtained above is added with a 1 mol / L hydrochloric acid solution dropwise to react the sodium silicate in the liquid phase component with the hydrochloric acid to form a silicon dioxide gel, and a gel material is obtained.

[0052] 1.1.5) The gel material obtained above is washed until the washing liquid is neutral, and then dried at 60 °C for 4 h to obtain the nano-sized rice husk silicon dioxide.

[0053] 1.2) Mixing zeolite powder, nano-sized rice husk silicon dioxide and bentonite:

[0054] The zeolite powder is mixed with the nano-sized rice husk silicon dioxide and the bentonite at a ratio of 5% of the nano-sized rice husk silicon dioxide based on the mass of the zeolite powder and 18% of the bentonite based on the mass of the zeolite powder to obtain a mixed powder.

[0055] Step 2, preparing a mixed slurry:

[0056] The mixed powder obtained above is mixed with a corresponding volume of a 2.5% by mass hydroxymethyl cellulose sodium aqueous solution to obtain a mixed slurry.

[0057] Step 3, calcination after pill making:

[0058] 3.1) The mixed slurry obtained above is placed in a pill making machine to make pills to obtain spherical zeolite.

[0059] 3.2) The spherical zeolite obtained above is dried at 105 °C for 3 h, and then transferred into a muffle furnace to be calcined at 600 °C for 1 h to obtain modified zeolite spheres, which are used as low concentration ammonia nitrogen adsorption materials.

[0060] Example 2

[0061] The present example provides a low concentration ammonia nitrogen adsorption material, which is prepared by the following steps:

[0062] Step 1, preparing a mixed powder:

[0063] 1.1) Preparing nano-sized rice husk silicon dioxide:

[0064] 1.1.1) The clean rice husks are ground to obtain rice husk powder with a particle size of ≤200 μm.

[0065] 1.1.2) The rice husk powder obtained above is dispersed in a citric acid solution with a concentration of 18 g / L as the acid leaching solution, according to the dosage ratio of 25 g of rice husk powder per 1 L of citric acid solution, and is subjected to acid leaching treatment at room temperature for 60 min to remove metal impurities in the rice husk powder. After the acid leaching treatment, the solid phase component is obtained by filtration. The solid phase component is washed and dried at 55°C for 6 h to obtain the rice husk powder after acid leaching treatment.

[0066] 1.1.3) The rice husk powder after acid leaching treatment is dispersed in a sodium hydroxide solution with a concentration of 150 g / L as the alkali treatment agent, according to the dosage ratio of 130 g of the rice husk powder after acid leaching treatment per 1 L of sodium hydroxide solution, and is subjected to heating treatment at 85°C for 60 min to make the silicon dioxide in the rice husk powder after acid leaching treatment react with sodium hydroxide to form sodium silicate. The liquid phase component is obtained by filtration.

[0067] 1.1.4) The liquid phase component obtained above is added dropwise with a 1 mol / L hydrochloric acid solution to make the sodium silicate in the liquid phase component react with the hydrochloric acid to form a silicon dioxide gel, thereby obtaining a gel material.

[0068] 1.1.5) The gel material obtained above is washed until the washing liquid is neutral, and then is dried at 55°C for 6 h to obtain the nano-sized rice husk silicon dioxide.

[0069] 1.2) Mixing zeolite powder, nano-sized rice husk silicon dioxide and bentonite:

[0070] The zeolite powder is used as a matrix, and the nano-sized rice husk silicon dioxide and the bentonite are added to the zeolite powder according to the dosage ratio of 4% of the nano-sized rice husk silicon dioxide and 15% of the bentonite based on the mass of the zeolite powder, and are uniformly mixed to obtain a mixed powder.

[0071] Step 2, preparation of a mixed slurry:

[0072] The mixed powder obtained above is added with a corresponding volume of a 2% mass concentration hydroxymethyl cellulose sodium aqueous solution according to the dosage ratio of 0.2 mL of the 2% mass concentration hydroxymethyl cellulose sodium aqueous solution per 1 g of the mixed powder, and is uniformly mixed to obtain a mixed slurry.

[0073] Step 3, calcination treatment after pill making:

[0074] 3.1) The mixed slurry obtained above is placed in a pill making machine for pill making treatment to obtain spherical zeolite.

[0075] 3.2) After drying the above obtained spherical zeolite at 100°C for 4h, it is transferred into a muffle furnace and calcined at 550°C for 2h to obtain modified zeolite spheres, which are used as low-concentration ammonia-nitrogen adsorption materials.

[0076] Example 3

[0077] This example provides a low-concentration ammonia-nitrogen adsorption material, which is prepared by the following steps:

[0078] Step 1, preparation of mixed powder:

[0079] 1.1) Preparation of nano-sized rice husk silica:

[0080] 1.1.1) The clean rice husk is ground to obtain a rice husk powder with a particle size of ≤200μm.

[0081] 1.1.2) The above obtained rice husk powder is dispersed in an acid leaching solution with a concentration of 20g / L of citric acid solution, according to the dosage ratio of 35g of rice husk powder per 1L of citric acid solution, and is subjected to acid leaching treatment at room temperature for 120min to remove metal impurities in the rice husk powder. After acid leaching treatment, the solid phase component is obtained by filtration. After washing the solid phase component, it is dried at 65°C for 2h to obtain the acid leached rice husk powder.

[0082] 1.1.3) The above acid leached rice husk powder is dispersed in an alkali treatment agent with a concentration of 200g / L of sodium hydroxide solution, according to the dosage ratio of 170g of the acid leached rice husk powder per 1L of sodium hydroxide solution, and is subjected to heating treatment at 95°C for 120min to react the silica in the acid leached rice husk powder with sodium hydroxide to form sodium silicate. The liquid phase component is obtained by filtration.

[0083] 1.1.4) 1mol / L hydrochloric acid solution is added dropwise to the above obtained liquid phase component to react the sodium silicate in the liquid phase component with hydrochloric acid to form silica gel, thereby obtaining a gel material.

[0084] 1.1.5) The gel material is washed until the washing liquid is neutral, and then dried at 65°C for 2h to obtain the nano-sized rice husk silica.

[0085] 1.2) Mixing of zeolite powder, nano-sized rice husk silica and bentonite:

[0086] The zeolite powder is used as a base, and the nano-sized rice hull silica is added to the zeolite powder in an amount of 10% of the mass of the zeolite powder, and the bentonite is added to the zeolite powder in an amount of 20% of the mass of the zeolite powder, and then the nano-sized rice hull silica and the bentonite are mixed uniformly in the zeolite powder to obtain a mixed powder.

[0087] Step 2, preparation of a mixed slurry:

[0088] According to the ratio of 0.4 mL of a 3% mass concentration sodium hydroxymethyl cellulose aqueous solution per 1 g of the mixed powder, the corresponding volume of the 3% mass concentration sodium hydroxymethyl cellulose aqueous solution is added to the mixed powder obtained above, and then the mixed slurry is obtained after mixing.

[0089] Step 3, calcination treatment after pill making:

[0090] 3.1) The mixed slurry obtained above is placed in a pill making machine for pill making treatment, and then the spherical zeolite is obtained.

[0091] 3.2) The spherical zeolite obtained above is dried at 110°C for 2 h, and then is transferred into a muffle furnace for calcination treatment at 650°C for 0.5 h, and then the modified zeolite ball is obtained, which is used as a low-concentration ammonia nitrogen adsorption material.

[0092] Example 4

[0093] The present embodiment provides a low-concentration ammonia nitrogen adsorption material, and the low-concentration ammonia nitrogen adsorption material is prepared by the following steps:

[0094] Step 1, preparation of a mixed powder:

[0095] 1.1) Preparation of nano-sized rice hull silica:

[0096] 1.1.1) The clean rice hull is ground to obtain a rice hull powder with a particle size of ≤200 μm.

[0097] 1.1.2) The rice hull powder obtained above is dispersed in an acid leaching solution with a concentration of 19.2 g / L of citric acid solution in an amount of 30 g of the rice hull powder per 1 L of the citric acid solution, and then is subjected to acid leaching treatment at room temperature for 90 min to remove metal impurities in the rice hull powder, and then is filtered after the acid leaching treatment to obtain a solid phase component; the solid phase component is washed and dried at 60°C for 4 h to obtain the rice hull powder after acid leaching treatment.

[0098] 1.1.3) The acid-processed rice hull powder is dispersed in a sodium hydroxide solution as the alkali treatment agent with a concentration of 172.5 g / L, at a ratio of 150 g of the acid-processed rice hull powder per 1 L of the sodium hydroxide solution, and heated at 90°C for 90 min to allow the silicon dioxide in the acid-processed rice hull powder to react with the sodium hydroxide to form sodium silicate, and then filtered to obtain a liquid phase component.

[0099] 1.1.4) The liquid phase component obtained above is added dropwise with a 1 mol / L hydrochloric acid solution to allow the sodium silicate in the liquid phase component to react with the hydrochloric acid to form a silicon dioxide gel, and a gel material is obtained.

[0100] 1.1.5) The gel material obtained above is washed until the washing liquid is neutral, and then dried at 60°C for 4 h to obtain the nano-sized rice hull silicon dioxide.

[0101] 1.2) Mixing zeolite powder, nano-sized rice hull silicon dioxide, and kaolin:

[0102] The zeolite powder is used as the matrix, and the nano-sized rice hull silicon dioxide is added to the zeolite powder at a ratio of 5% of the mass of the zeolite powder, and the kaolin is added to the zeolite powder at a ratio of 18% of the mass of the zeolite powder, and then mixed to obtain a mixed powder.

[0103] Step 2, preparing a mixed slurry:

[0104] The mixed powder obtained above is added with a corresponding volume of a 2.5% mass concentration hydroxymethyl cellulose sodium aqueous solution at a ratio of 0.3 mL of the 2.5% mass concentration hydroxymethyl cellulose sodium aqueous solution per 1 g of the mixed powder, and then mixed to obtain a mixed slurry.

[0105] Step 3, pill-making and calcination:

[0106] 3.1) The mixed slurry obtained above is placed in a pill-making machine for pill-making treatment to obtain spherical zeolite.

[0107] 3.2) The spherical zeolite obtained above is dried at 105°C for 3 h, and then transferred into a muffle furnace for calcination treatment at 600°C for 1 h to obtain modified zeolite spheres, which are used as low-concentration ammonia-nitrogen adsorption materials.

[0108] The only difference between this comparative example and Example 1 is that:

[0109] In this example, kaolin is used as the binder.

[0110] Example 5

[0111] The embodiment provides a low-concentration ammonia nitrogen adsorption material, and the low-concentration ammonia nitrogen adsorption material is prepared through the following steps.

[0112] Step 1, preparing a mixed powder:

[0113] 1.1) preparing nanoscale rice hull silica:

[0114] 1.1.1) grinding clean rice hulls to obtain rice hull powder with a particle size of less than or equal to 200 μm.

[0115] 1.1.2) dispersing the obtained rice hull powder in an acid leaching solution with a concentration of 19.2 g / L of citric acid solution, according to the dosage ratio of 30 g of rice hull powder per 1 L of citric acid solution, and performing acid leaching treatment at room temperature for 90 min, so as to remove metal impurities in the rice hull powder; after the acid leaching treatment is completed, filtering to obtain a solid phase component; washing the solid phase component and drying at 60 DEG C for 4 h to obtain acid leaching treated rice hull powder.

[0116] 1.1.3) dispersing the acid leaching treated rice hull powder in an alkali treatment agent with a concentration of 172.5 g / L of sodium hydroxide solution, according to the dosage ratio of 150 g of the acid leaching treated rice hull powder per 1 L of sodium hydroxide solution, and performing heating treatment at 90 DEG C for 90 min, so that the silica in the acid leaching treated rice hull powder reacts with sodium hydroxide to generate sodium silicate; filtering to obtain a liquid phase component.

[0117] 1.1.4) adding 1 mol / L hydrochloric acid solution dropwise into the obtained liquid phase component, so that the sodium silicate in the liquid phase component reacts with the hydrochloric acid to form a silica gel, and a gel material is obtained.

[0118] 1.1.5) washing the gel material until the washing liquid is neutral, and then drying at 60 DEG C for 4 h to obtain the nanoscale rice hull silica.

[0119] 1.2) mixing zeolite powder, nanoscale rice hull silica and bentonite:

[0120] Taking the zeolite powder as a matrix, according to the dosage ratio of 5% of the nanoscale rice hull silica to the mass of the zeolite powder and 18% of the bentonite to the mass of the zeolite powder, nanoscale rice hull silica and bentonite are added into the zeolite powder and uniformly mixed to obtain a mixed powder.

[0121] Step 2, preparing a mixed slurry:

[0122] According to the ratio of adding 0.3 mL of 2.5% mass concentration hydroxypropyl methyl cellulose aqueous solution per 1 g of the mixed powder, the corresponding volume of 2.5% mass concentration hydroxypropyl methyl cellulose aqueous solution was added to the mixed powder obtained above, and mixed uniformly to obtain a mixed slurry.

[0123] Step 3, calcination treatment after pill making:

[0124] 3.1) The mixed slurry obtained above was placed in a pill making machine for pill making treatment to obtain spherical zeolite.

[0125] 3.2) The spherical zeolite obtained above was dried at 105°C for 3 h and then transferred to a muffle furnace for calcination treatment at 600°C for 1 h to obtain modified zeolite spheres, which were used as low concentration ammonia nitrogen adsorption material.

[0126] The difference between this comparative example and Example 1 is only that:

[0127] In this example, hydroxypropyl methyl cellulose aqueous solution was used instead of sodium hydroxymethyl cellulose aqueous solution in Example 1.

[0128] Example 6

[0129] This example provides a low concentration ammonia nitrogen adsorption material, which is prepared by the following steps:

[0130] Step 1, preparation of mixed powder:

[0131] 1.1) Preparation of nano-sized rice husk silica:

[0132] 1.1.1) Clean rice husk was ground to obtain rice husk powder with a particle size of ≤200 μm.

[0133] 1.1.2) A 19.2 g / L citric acid solution was used as the acid leaching solution, and the rice husk powder obtained above was dispersed in the acid leaching solution according to the dosage ratio of adding 30 g of rice husk powder per 1 L of citric acid solution, and was subjected to acid leaching treatment at room temperature for 90 min to remove metal impurities in the rice husk powder. After acid leaching treatment, the solid phase component was obtained by filtration. The solid phase component was washed and dried at 60°C for 4 h to obtain acid leached rice husk powder.

[0134] 1.1.3) A 172.5 g / L sodium hydroxide solution was used as the alkali treatment agent, and the acid leached rice husk powder was dispersed in the alkali treatment agent according to the dosage ratio of adding 150 g of the acid leached rice husk powder per 1 L of sodium hydroxide solution, and was subjected to heating treatment at 90°C for 90 min to react the silica in the acid leached rice husk powder with sodium hydroxide to form sodium silicate. Filtration was performed to obtain a liquid phase component.

[0135] 1.1.4) To the above obtained liquid phase component, 1 mol / L hydrochloric acid solution was added dropwise to react sodium silicate in the liquid phase component with hydrochloric acid to form silica gel, and a gel material was obtained.

[0136] 1.1.5) The above gel material was washed until the washing liquid was neutral, and then dried at 60°C for 4h to obtain the nano-sized rice husk silica.

[0137] 1.2) Mixing zeolite powder, nano-sized rice husk silica and bentonite:

[0138] With the zeolite powder as the matrix, the nano-sized rice husk silica was added in an amount of 5% of the mass of the zeolite powder, and the bentonite was added in an amount of 18% of the mass of the zeolite powder, and the nano-sized rice husk silica and the bentonite were added to the zeolite powder and mixed to obtain a mixed powder.

[0139] Step 2, preparation of a mixed slurry:

[0140] According to the ratio of adding 0.3 mL of 2.5% mass concentration methyl cellulose aqueous solution per 1 g of the mixed powder, the corresponding volume of 2.5% mass concentration methyl cellulose aqueous solution was added to the above obtained mixed powder and mixed to obtain a mixed slurry.

[0141] Step 3, calcination treatment after pill making:

[0142] 3.1) The above obtained mixed slurry was placed in a pill making machine for pill making treatment to obtain spherical zeolite.

[0143] 3.2) The above obtained spherical zeolite was dried at 105°C for 3h and then transferred to a muffle furnace for calcination treatment at 600°C for 1h to obtain modified zeolite spheres, which were used as low concentration ammonia nitrogen adsorption materials.

[0144] The difference between this comparative example and Example 1 is only that:

[0145] In this example, methyl cellulose aqueous solution was used instead of sodium hydroxymethyl cellulose aqueous solution in Example 1.

[0146] Comparative Example 1

[0147] This comparative example provides an ammonia nitrogen adsorption material, and the difference between this comparative example and Example 1 is only that:

[0148] In this comparative example, no nano-sized rice husk silica was added.

[0149] Experimental Part

[0150] The application is found by tests that the modified zeolite spheres prepared in Examples 1 to 6 have similar structures, and those skilled in the art should know that the structure determines the property, and the similar structures show that the low-concentration ammonia-nitrogen adsorption materials in Examples 1 to 6 have similar performances, so as to avoid redundancy, the structure and performance of the low-concentration ammonia-nitrogen adsorption material prepared in the application will be analyzed and described below by taking Example 1 as an example.

[0151] (I) Scanning electron microscope test

[0152] The rice hull powder, nanoscale rice hull silica and low-concentration ammonia-nitrogen adsorption material prepared in Example 1 are taken as examples, and the scanning electron microscope tests are respectively carried out, and the test results are respectively shown in Figures 1-3

[0153] Figure 1 The scanning electron microscope image of the rice hull powder prepared in Example 1 can be seen that the rice hull powder has a hierarchical porous structure, and the natural siliceous skeleton can be used as an ideal synthetic material of nanoscale silica.

[0154] Figure 2 The scanning electron microscope image of the nanoscale rice hull silica prepared in Example 1 can be seen that the prepared nanoscale silica has a high monodispersity, the particle size distribution range is 20nm to 50nm, there is no obvious agglomeration phenomenon, the particle surface presents a mesopore-micropore composite structure, which gives the material a high specific surface area of BET>500m 2 / g, which is suitable for high-load catalysis or adsorption application.

[0155] Figure 3 The scanning electron microscope image of the low-concentration ammonia-nitrogen zeolite adsorption material prepared in Example 1 can be seen that the prepared zeolite particle surface is uniformly coated with a nanoscale rice hull silica layer, forming a “core-shell” multi-level pore network, which significantly improves the adsorption kinetics and capacity of low-concentration ammonia-nitrogen.

[0156] (II) Adsorption performance test

[0157] The low-concentration ammonia-nitrogen adsorption materials in Example 1 and Comparative Example 1 are taken as examples, and the ammonia-nitrogen adsorption performance thereof is tested according to the following method, and the test results are shown in Figure 4 , and the test method is as follows:

[0158] (1) Uncoated biological membrane:

[0159] ​The initial ammonia nitrogen concentration of the simulated wastewater was 50 mg / L, 400 mL of the simulated wastewater was placed in a conical flask, 25 g of the zeolite ball adsorbent was added into the conical flask, and the conical flask was placed in a constant temperature shaker for 6 h, the rotation speed of the shaker was 150 rpm, and the temperature was 30°C; a small amount of supernatant was taken at intervals, and the ammonia nitrogen concentration of the supernatant was determined by using a standard method.

[0160] (2) Coated biofilm:

[0161] After the adsorbent of Example 1 and Comparative Example 1 was cultured in the sequencing batch fixed bed biofilm reactor for 1 week, the ammonia nitrogen adsorption capacity of the low-concentration ammonia nitrogen adsorbent after being coated with a biofilm was determined according to the process of step (1). In the sequencing batch fixed bed biofilm reactor, the low-concentration ammonia nitrogen adsorbent of Example 1 and Comparative Example 1 was used as the filler, respectively, the bottom was aerated to ensure that the dissolved oxygen concentration in the reactor was in the range of 3 mg / L to 5 mg / L, and the microorganisms adhered to the fixed filler to form a biofilm.

[0162] The ammonia nitrogen concentrations of the supernatants obtained by the above two tests were arranged as shown in Table 2. Figure 4 Figure 4 Table 2 is a comparison diagram of the ammonia nitrogen adsorption capacity of the low-concentration ammonia nitrogen adsorbent of Example 1 and Comparative Example 1, and it can be seen that, compared with Comparative Example 1, the ammonia nitrogen concentration of the supernatant after the treatment of Example 1 is significantly reduced in both the test of the biofilm without being coated with a biofilm and the test of the biofilm coated with a biofilm, which indicates that the low-concentration ammonia nitrogen adsorbent of Example 1 has a significantly improved ammonia nitrogen adsorption capacity due to the modification treatment of the rice husk silica. Figure 4 It can also be seen that, compared with Comparative Example 1, the low-concentration ammonia nitrogen adsorbent of Example 1 can also enhance the ability of the microorganisms in the biofilm to degrade ammonia nitrogen.

[0163] The present application also takes the low-concentration ammonia nitrogen adsorbent of Example 1 as an example to test the change of the ammonia nitrogen adsorption capacity of the low-concentration ammonia nitrogen adsorbent coated with a biofilm and the low-concentration ammonia nitrogen adsorbent without being coated with a biofilm with time according to the above method, and the test results are shown in Table 3. Figure 5

[0164] Figure 5 Table 3 is a diagram of the change of the ammonia nitrogen adsorption effect of the low-concentration ammonia nitrogen adsorbent of Example 1 with time before and after being coated with a biofilm, and it can be seen that the ammonia nitrogen adsorption situation at different times, for the zeolite material without a biofilm, the adsorption equilibrium time is about 50 min, and for the zeolite material with a biofilm, the adsorption equilibrium time is about 100 min, which indicates that the adsorption of ammonia nitrogen by the biofilm itself and the ion exchange of the zeolite form a two-stage adsorption, and a longer time is required to realize the synergistic saturation of the two, and the biofilm has a higher adsorption capacity and regeneration ability.

[0165] ​​Obviously, the above embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative labor shall fall within the protection scope of the present application.

Claims

1. A method for preparing a low-concentration ammonia nitrogen adsorption material, characterized in that: The following steps are involved: Using zeolite powder as a matrix and nano-rice husk silica as a modifier, adding nano-rice husk silica and a binder to the zeolite powder and mixing evenly to obtain a mixed powder; adding the cellulose derivative aqueous solution to the mixed powder and mixing evenly to obtain a mixed slurry; The mixed slurry is pelletized to obtain spherical zeolite; the spherical zeolite is dried and then calcined to obtain modified zeolite balls, and the modified zeolite balls are used as low-concentration ammonia nitrogen adsorption materials; The nano-scale rice husk silica is prepared by the following steps: Grinding the cleaned rice husk to ≤200 μm to obtain rice husk powder; Dispersing the rice husk powder in a citric acid solution, performing an acid leaching treatment at room temperature to remove metal impurities in the rice husk powder, and performing solid-liquid separation after the acid leaching treatment to obtain a solid phase component; washing and drying the solid phase component to obtain rice husk powder after acid leaching; Dispersing the acid-leached rice husk powder in a sodium hydroxide solution, heating it at 85° C. to 95° C. so that the silicon dioxide in the acid-leached rice husk powder reacts with the sodium hydroxide to form sodium silicate, and performing solid-liquid separation to obtain a liquid phase component; adding a hydrochloric acid solution dropwise to the liquid phase component to react the sodium silicate in the liquid phase component with the hydrochloric acid to form a silica gel, thereby obtaining a gel material; The gel material is dried to obtain the nano-scale rice husk silica.

2. The method for preparing a low-concentration ammonia nitrogen adsorption material according to claim 1, wherein: The addition amount of the nano-rice husk silica is 4% to 10% of the mass of the zeolite powder; The added amount of the binder is 15% to 20% of the mass of the zeolite powder.

3. The method for preparing a low-concentration ammonia nitrogen adsorption material according to claim 1, wherein: The binder is one or both of bentonite and kaolin.

4. The method for preparing a low-concentration ammonia nitrogen adsorption material according to claim 1, wherein: The cellulose derivative in the cellulose derivative aqueous solution is one or more of sodium hydroxymethyl cellulose, hydroxypropyl methyl cellulose and methyl cellulose; The mass concentration of the cellulose derivative in the cellulose derivative aqueous solution is 2% to 3%; And 0.2 mL to 0.4 mL of the cellulose derivative aqueous solution is added to every 1 g of the mixed powder.

5. The method for preparing a low-concentration ammonia nitrogen adsorption material according to claim 1, wherein: The calcination temperature of the calcination treatment is 550° C. to 650° C., and the calcination time is 0.5 h to 2 h.

6. The method for preparing a low-concentration ammonia nitrogen adsorption material according to claim 1, wherein: The concentration of citric acid in the citric acid solution is 18 g / L to 20 g / L; and 25 g to 35 g of the rice husk powder is added to every 1 L of the citric acid solution; The concentration of sodium hydroxide in the sodium hydroxide solution is 150 g / L to 200 g / L; and 130 g to 170 g of the rice husk powder after acid leaching is added to every 1 L of the sodium hydroxide solution.

7. The method for preparing a low-concentration ammonia nitrogen adsorption material according to claim 1, wherein: The acid leaching treatment time is 60min~120min; The heating treatment time is 60 min to 120 min.

8. A low-concentration ammonia nitrogen adsorption material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the low-concentration ammonia nitrogen adsorption material according to claim 8 in adsorbing low-concentration ammonia nitrogen.

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