CN114835257B - A fast adsorption type iron-doped porous constructed wetland filler and its preparation method and application - Google Patents

Abstract

The invention discloses a rapid adsorption type iron-doped porous constructed wetland filler and a preparation method and application thereof, and belongs to the technical field of environmental engineering water treatment. The packing is formed by bonding a plurality of small particles containing multiple components, and at least 1 groove and a fine pore canal among the particles are formed on the packing. The filler provided by the invention can rapidly adsorb nitrogen, and the filler component strengthens the microbial nitrogen removal effect, so that the filler can effectively intercept and biodegrade nitrogen pollutants. Compared with the existing filler, the filler provided by the invention has the advantages of good water permeability, large specific surface area, easiness in adhesion of microorganisms and formed biological film thickness and stability; the adsorption to ammonia nitrogen is rapid, the adsorption quantity is large, and the combined action of the modified mineral substance and the iron element strengthens the adsorption effect; the iron element is coupled with the removal of nitrogen element, and the enhancement of electron transfer by doped graphene and humus further improves the nitrogen removal effect.

Description

A fast adsorption type iron-doped porous constructed wetland filler and its preparation method and application

Technical field

The invention belongs to the technical field of environmental engineering water treatment, and specifically relates to a fast adsorption type iron-doped porous artificial wetland filler and its preparation method and application.

Background technique

The constructed wetland system is an ecological engineering system and can be used for advanced sewage treatment, water purification, non-point source pollution control, etc. Among them, biological filler is an important part of the constructed wetland system and is responsible for providing carriers for organisms. The nature and treatment of the filler The effect is closely related.

The fillers widely used in existing constructed wetland projects are mainly natural minerals, such as limestone, wollastonite or pyrite, and industrial products such as slag or iron slag. Due to the closed internal pores, such fillers have a small specific surface area and cannot effectively increase The overall biomass and nitrogen removal effect inside the constructed wetland; in the existing technology, artificial wetland fillers are generally prepared through physical mixing and filling or roasting and molding. The main problem is that the internal pores are not connected, which is not conducive to the attachment and internal attachment of microorganisms. Increase the contact area with polluted water; the existing constructed wetland fillers still have the problem of low nitrogen adsorption capacity, and the ammonia nitrogen treatment effect is not ideal when the hydraulic load is large; the electron transfer properties of the existing constructed wetland fillers are not good enough, which affects the filler The extracellular electron transfer of microorganisms is not conducive to the oxidation and reduction process of nitrogen-containing compounds in the water; there is a general lack of scientific usage methods when using constructed wetland fillers.

Contents of the invention

In order to solve the deficiencies of the existing technology, the present invention provides a fast adsorption type iron-doped porous constructed wetland filler, a preparation method thereof, and an application method in nitrogen removal. Through the three-dimensional structure of the internal particles of the filler, the specific surface area of the filler is increased. , enhance the rapid adsorption performance of ammonia nitrogen, the biological transformation process of nitrogen and the extracellular electron transfer process of microorganisms, optimize the use of artificial wetland fillers, and achieve the efficient removal of nitrogen compounds in polluted water by artificial wetlands.

The present invention adopts the following solutions to achieve:

A fast adsorption iron-doped porous constructed wetland filler. The constructed wetland filler is made up of a plurality of small particles bonded together. Fine pore channels are formed between the mutually bonded small particles. The pore channels are formed in the constructed wetland filler. Internally connected; there is at least one groove on the artificial wetland filler.

Further, the shape of the constructed wetland filler is a spherical shape with grooves, the diameter of the constructed wetland filler is 8-60 mm, and the volume of the grooves accounts for 15-40% of the volume of the constructed wetland filler. Groove shapes include circles, polygons or irregular shapes.

Further, the number of pore channels is at least 30.

Further, the small particles are made from a mixture of multiple inorganic minerals; the mixture of inorganic minerals includes the following components by weight: 13-16% modified activated carbon powder, 20-25% modified zeolite powder, 12 ~15% reduced iron powder, 12~15% attapulgite powder, 23~27% bentonite, 1~3% graphite, 0.5~1.0% pore former, 5~7% quartz powder and 0.03~0.05% graphene.

The reduced iron powder can form iron oxides to promote the adsorption capacity of ammonia nitrogen; the reduced iron powder and its oxides can be used as electron donors to promote autotrophic denitrification and denitrification, which can solve the problem of insufficient carbon sources. problem and improve the denitrification effect.

Further, the modified activated carbon powder is original activated carbon pretreated by oxidation/acidification, and then can be loaded with sodium ions or iron ions by impregnation.

Further, the modified zeolite powder includes sodium chloride modified zeolite powder.

Further, the graphene is single-layer, few-layer or multi-layer graphene prepared by physical method or chemical method.

Furthermore, the pore-forming agent includes ammonium bicarbonate, which can form a porous structure inside the prepared filler, which is easy for microorganisms to adhere to, increases the specific surface area of the filler, increases the contact points between the filler and sewage, and makes the filler and pollutants full contact reaction.

Using sodium bentonite as a binder can avoid the problem of secondary pollution of water quality caused by organic binders. It can be bonded to materials such as iron filings. After roasting, it can ensure the nitrogen removal efficiency of the iron powder while ensuring that the various components of the filler can be combined with each other. ; At the same time, it can fully contact each component to improve the bonding effect; and using 25% to 30% can improve the strength of the filler particles and resist external loads.

A preparation method of artificial wetland filler, including the following steps:

(1) Mix modified activated carbon powder, modified zeolite powder, reduced iron powder, attapulgite powder, bentonite, pore-forming agent, quartz powder and graphene evenly to form a mixture, and add 28 to 32% by weight of water to the mixture , stir evenly again and then extrude to form strip-shaped wet filler. After drying, strip-shaped dry filler is obtained. Place it in a high-temperature furnace isolated from air and sinter at 550-600°C for 55-65 minutes, and then sinter at 900-950°C for 55-55 minutes. After 65 minutes, the modified strip-shaped dry filler was obtained.

In the above process, the sintering temperature gradually rises to 550-600°C, and the internal porous structure of the filler is formed under the action of the pore-forming agent. The sintering temperature is continued at 550-600°C for 55-65 minutes, which can fully remove the organic matter covering the surface. Sintering at 900-950°C for 55-65 minutes can form filler with considerable strength to meet the load strength requirements for constructed wetland construction and long-term operation.

(2) Crush the obtained strip-shaped dry filler and sieve to obtain irregular particles with a particle size of 7 to 28 mesh, which are small particles;

(3) Mix the small particles with walnut powder whose weight is 6 to 8% of the small particles, spray an appropriate amount of binder and an appropriate amount of water on the surface of the mixture, and constantly stir the mixture. Stop spraying and stirring when it is ready for shaping. The artificial wetland filler is obtained through mold pressing and drying.

Further, the size of the modified activated carbon powder, modified zeolite powder, reduced iron powder, attapulgite powder, bentonite, and quartz powder in step (1) is 200 to 400 mesh, preferably 200 mesh; the walnuts in step (3) The size of the powder is 200-300 mesh, preferably 200 mesh; the cross-sectional diameters of the strip-shaped wet filler and strip-shaped dry filler described in step (1) are both 10-50mm, preferably 5mm-20mm; The length of the strip-shaped wet filler and strip-shaped dry filler is 10-30 mm; the drying method includes placing it in the air or drying at a temperature of 50-75°C.

Application of constructed wetland filler in removing nitrogen compounds from sewage.

Further, the applications include rapid adsorption of ammonia nitrogen, biotransformation of nitrogen and applications in microbial extracellular electron transfer.

Furthermore, in order to achieve better results, the method for removing nitrogen compounds in sewage by artificial wetland filler is: after hanging the film, it is located in the artificial wetland anaerobically (dissolved oxygen is less than 0.2mg/L) or After the filler in the hypoxic (dissolved oxygen 0.2 ~ 2.0 mg/L) area continuously purifies the contaminated water for 24-48 hours, the filler needs to be exposed to the air for at least 0.5 ~ 1.0 hours before continuing to use; or after being coated with film, it should be within the range of dissolved oxygen. Use under changing conditions from anaerobic/anoxic to aerobic (greater than 2.0mg/L).

Beneficial effects of the present invention:

Irregular tiny particles are used to form the filler body. The tiny particles are bonded with a binder. There are pores between the irregular particles. Three-dimensional connected pores are formed inside the filler. The entire filler contains at least 30 pore channels. There are also other holes on the filler body. The grooves further increase the specific surface area, can accommodate more microorganisms, and increase the contact area with the water body.

The small particles that make up the filler body contain components with strong adsorption capacity for ammonia nitrogen, including modified zeolite, modified activated carbon, and iron oxide. These components can quickly adsorb ammonia nitrogen, and the reaction of microorganisms occurs more quickly than that of microorganisms, which can compensate for the microbial reaction. Insufficient reaction, further conversion and degradation by microorganisms after adsorption, can reduce the hydraulic retention time and increase the amount of water treated.

The iron contained in the small particles that make up the filler body can undergo an iron-nitrogen coupling reaction with nitrate nitrogen in the water body. Under the changing conditions of anaerobic/anoxic/aerobic conditions, it can further promote the microbial reduction process of nitrate nitrogen.

The small particles that make up the filler body contain graphene, whose good electrical conductivity improves the extracellular electron transfer between the filler and microorganisms, and improves the nitrogen conversion of microorganisms.

The invention provides a filler that can quickly adsorb nitrogen, and the filler components strengthen the nitrogen removal effect of microorganisms, and the filler can effectively intercept and biodegrade nitrogen pollutants. Compared with existing fillers, the filler of the present invention has good water permeability, large specific surface area, easy attachment of microorganisms, thick and stable biofilm formed, rapid adsorption of ammonia nitrogen, large adsorption capacity, combined effect of modified minerals and iron elements The adsorption effect is strengthened; the iron element couples the removal of nitrogen, while the doped graphene and humus strengthen the electron transfer, further improving the nitrogen removal effect.

Description of the drawings

Figure 1 is an appearance design diagram of the filler of the present invention.

Figure 2 is a structural diagram of the artificial wetland filler according to the present invention, in which (a) is a plan view; (b) is a cross-sectional view.

Figure 3 is an electron microscope image of the constructed wetland filler prepared in Example 1, where (a) is before the filler is used; (b) is after the filler is used.

Figure 4 is an XRD pattern of the constructed wetland filler prepared in Example 1, where (a) is before the filler is used; (b) is after the filler is used.

Figure 5 is an EDS diagram of the constructed wetland filler prepared in Example 1, where (a) is before use of the filler; (b) after use of the filler.

Figure 6 is the ammonia nitrogen adsorption rate curve of the constructed wetland filler described in Example 2.

Detailed ways

Through the local connection of the internal particles of the constructed wetland filler, a three-dimensional channel structure inside the filler is constructed to increase the specific surface area of the filler, enhance the rapid adsorption performance of ammonia nitrogen, the biological transformation process of nitrogen and the extracellular electron transfer process of microorganisms, and optimize the use of constructed wetland fillers. , realize the efficient removal of nitrogen compounds in polluted water by artificial wetlands; the artificial wetland filler is made of a plurality of small particles bonded together, and there is at least one groove on the filler and pores between the particles; the small particles are made of a variety of inorganic minerals Made of a mixture; the shape of the constructed wetland filler is a spherical shape with grooves, with a diameter of 8-60mm, and the groove volume accounts for 15-40% of the filler volume. The grooves can be round, polygonal or irregularly shaped to form a filler There are at least 30 pore channels between the small particles (Fig. 1, Fig. 2); according to the properties of the filler of the present invention, a method of using the filler of the present invention is proposed.

The present invention will be further described below in conjunction with the accompanying drawings and specific examples. These descriptions are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conventional conditions or manufacturing methods will be used. It is carried out under the conditions recommended by the manufacturer. The reagents or instruments used are conventional products that can be purchased commercially if the manufacturer is not indicated.

Specific examples are given below.

Example 1

Commercially available activated carbon powder (200 mesh) is pretreated with oxidation/acidification to pretreat the original activated carbon, and then loaded with sodium ions for modification using an impregnation method to obtain modified activated carbon powder (200 mesh). The preparation method of the modified activated carbon powder can be referred to: Zhu Minjun. Study on the preparation of pomelo peel activated carbon and its ammonia adsorption performance (D). Xiangtan University. 2020.

Commercially available zeolite powder (200 mesh) was modified with sodium chloride solution to obtain modified zeolite powder (200 mesh). The preparation method of the modified zeolite powder can refer to: Fu Jinxiang, Zhang Yanping, Li Sen, You Kun, Fan Donghan, Li Xin. Preparation of modified zeolite ammonia nitrogen adsorbent and its application in domestic sewage treatment (J). Silicon Bulletin of Salts, 2021, 40(5): 1728-1734.

Mix the mass percentage of 15% modified activated carbon powder (200 mesh), 20% modified zeolite powder (200 mesh), 13.2% iron powder (200 mesh), 12% attapulgite powder (200 mesh), 25% bentonite (200 mesh) ), 3% graphite (200 mesh), 0.5% pore-forming agent (ammonium bicarbonate), 6.6% quartz powder (200 mesh) and 0.05% graphene (physical method few layers), mix evenly, then add 30% of the weight of these mixtures % of tap water, stir evenly to make a slurry, mechanically extrud into strip-shaped wet fillers of 10 to 50 mm, place them in the air to naturally air-dry to obtain strip-shaped dry fillers, and place them in an air-isolated muffle furnace for 600 ℃ for 1 hour, and then sintered at 900℃ for 1 hour to obtain the modified strip dry filler. Crush the obtained modified strip dry filler and sieve to obtain irregular particles with a particle size of 7 to 28 mesh, and then Mix the small particles with walnut powder (200 mesh) whose weight is 6 to 8% of the small particle material, and then spray an appropriate amount of binder and an appropriate amount of water on the surface of the two mixtures, while constantly stirring the mixture until it can be molded. Stop spraying and stirring, press and shape through the mold, and obtain the artificial wetland filler after drying (the appearance of the artificial wetland filler is shown in Figure 1).

Figure 2 is a structural diagram of the filler prepared in this embodiment (Figure 2a is a plan view; Figure 2b is a cross-sectional view); it can be seen from Figure 2 that the three-dimensional connected pores of the filler increase the specific surface area, and the groove structure provides more accommodation for microorganisms.

Furthermore, the electron microscope image of the filler (Figure 3) shows that the surface of the filler (Figure 3a) before use is rough, with dense and abundant voids. The filler surface has a large specific surface area, which is conducive to the growth of microorganisms on the biofilm. The microbial biofilm can grow on the filler. The outer surface and inner pores are formed. These special surface morphological characteristics also indicate that the filler is suitable as a water treatment filter material; after the test (Figure 3b), it can be observed that the filler surface is rich in microbial biofilms secreting mucus-like exopolymer substances. At the same time, the micron-sized pores in the filler are covered by many crystalline precipitates.

Furthermore, the XRD pattern of the filler surface (Figure 4a is before the filler is used; Figure 4b is after the filler is used) shows that the filler before use is mainly composed of ferric oxide (Fe ₂ O ₃ ), and the iron minerals in the filler after use are (Figure 3b), in addition to the original Fe ₂ O ₃ , there are other peaks, ferrous oxide (FeO), ferric oxide (Fe ₃ O ₄ ) and tetragonal lepidocrocite (Fe+3O(OH) ), morphological and valence transformations occurred.

Furthermore, the EDS diagram of the filler surface (Figure 5a is before the filler is used; Figure 5b is after the filler is used) shows that the mass fraction of iron in the used filler is reduced from 8.97% to 3.34%, while the mass fraction of oxygen is reduced from 8.97% to 3.34%. 44.76% increased to 53.3%, and more iron oxides were generated; it can be seen that these characteristics of the filler surface will be beneficial to the biological transformation process of nitrogen and the extracellular electron transfer process of microorganisms.

Example 2

In this example, an ammonia nitrogen adsorption experiment was performed. NH ₄ Cl was dissolved in distilled water to obtain a solution with an ammonia nitrogen concentration of 10 mg/L. Then, 5 g of the filler prepared in Example 1 was weighed and added to a group of equipment with an ammonia nitrogen concentration of 10 mg/L. In a 250ml Erlenmeyer flask that has been prepared with the solution, shake the Erlenmeyer flask at a constant temperature and low speed (60r·min ^-1 ) at 20°C to fully react with the solution. , 13.3min, and 20min respectively, test the ammonia nitrogen concentration of the solution, and calculate the change of ammonia nitrogen adsorption rate with time; from Figure 6, it can be seen that the ammonia nitrogen adsorption amount increases with time, 0-10min is the process of rapid adsorption of ammonia nitrogen by the filler, and 10g of filler within 10s It can adsorb 1.15±0.05mg/g ammonia nitrogen. After 10 minutes, the adsorption capacity of the filler increases slowly and basically reaches the adsorption equilibrium stage. The maximum equilibrium adsorption capacity is 3.2±0.21mg/g. The filler has a very rapid adsorption capacity for ammonia nitrogen.

Example 3

In this example, a nitrogen removal experiment was performed. The packing prepared in Example 1 was packed into a column. The cross-sectional diameter of the column was 10cm, the height of the packing was 50cm, and the inlet water DO was controlled at 4 to 4.5 mg·L ^-1 and the temperature was at 30 ±1°C, inlet water pH 6.5, flow rate 2.7ml/min, use this packed column to treat nitrogen-containing wastewater with the inlet water quality shown in Table 1. After treatment with the packed column, the total organic carbon removal rate is 82.4 %, the ammonia nitrogen removal rate is 83.3%, the nitrate nitrogen removal rate is 91.4%, and the total nitrogen removal rate is 83.4% (Table 1); it can be seen that the filler has excellent nitrogen removal performance, especially the denitrification effect is good.

Table 1

The above-described embodiments are only preferred embodiments to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are within the protection scope of the present invention.

Claims (3)

1. The application of a fast adsorption type iron-doped porous constructed wetland filler, which is characterized by: application in removing nitrogen compounds in sewage; the application includes rapid adsorption of ammonia nitrogen, biological transformation of nitrogen and microbial extracellular electron transfer ; The artificial wetland filler is made up of a plurality of small particles bonded together, and pore channels are formed between the mutually bonded small particles. The pore channels are connected inside the artificial wetland filler; there are at least 1 pores on the surface of the artificial wetland filler. groove; The shape of the artificial wetland filler is a spherical shape with grooves. The diameter of the artificial wetland filler is 8~60mm. The volume of the grooves accounts for 15-40% of the volume of the artificial wetland fillers. Shapes include circles, polygons, or irregular figures; The small particles are made of a mixture of multiple inorganic minerals; the mixture of inorganic minerals includes the following components by weight: 13~16% modified activated carbon powder, 20~25% modified zeolite powder, 12~15% Reduced iron powder, 12~15% attapulgite powder, 23~27% bentonite, 1~3% graphite, 0.5~1.0% pore former, 5~7% quartz powder and 0.03~0.05% graphene; The pore-forming agent includes ammonium bicarbonate, and the graphene is single-layer, few-layer or multi-layer graphene prepared by physical or chemical methods; The modified activated carbon powder is obtained by pretreating activated carbon with oxidation/acidification, and then loading sodium ions or iron ions by impregnation for modification; the modified zeolite powder is sodium chloride modified zeolite powder; The preparation method of the artificial wetland filler includes the following steps: (1) Mix modified activated carbon powder, modified zeolite powder, reduced iron powder, attapulgite powder, bentonite, graphite, pore-forming agent, quartz powder and graphene evenly to form a mixture, add 28~32% by weight of the mixture of water, stir evenly again and squeeze to form strip-shaped wet filler. After drying, strip-shaped dry filler is obtained, which is placed in an air-isolated high-temperature furnace and sintered at 550-600°C for 55-65 minutes, and then sintered at 900-950°C. 55~65min, the modified strip dry filler is obtained; (2) Crush the obtained strip-shaped dry filler and sieve to obtain irregular particles with a particle size of 7 to 28 mesh, which are small particles; (3) Mix the small particles with walnut powder whose weight is 6~8% of the small particles, spray the binder and water on the surface of the mixture, and at the same time stir the resulting mixture until it is ready for shaping. Stop spraying and Stir, press and shape through a mold, and obtain artificial wetland filler after drying. 2. The application according to claim 1, characterized in that the number of the fine pore channels is at least 30. 3. The application according to claim 1, characterized in that: in step (1), the size of the modified activated carbon powder, modified zeolite powder, reduced iron powder, attapulgite powder, bentonite, and quartz powder is 200 to 400 mesh; The size of the walnut powder in step (3) is 200~300 mesh; the cross-sectional diameter of the strip wet filler and strip dry filler in step (1) is 10~50mm; the drying method includes drying in the air Place or dry at 50-75℃.