AlFe-gypsum material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to an AlFe-gypsum material as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving an aluminum source and an iron source in water to obtain an Al-Fe mixed solution; the preparation method comprises the following steps: adding calcined gypsum into an Al-Fe mixed solution, uniformly stirring, standing, cooling and drying to obtain the AlFe-gypsum material, and when the AlFe-gypsum material is applied to a constructed wetland for treating sewage and / or a sewage treatment system comprising the constructed wetland, the problems that natural ore as a matrix is easy to saturate during adsorption and low in specific pollutant removal capacity can be solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and more specifically relates to an AlFe-gypsum material and a preparation method and application thereof. Background Art

[0002] In artificial wetland ecosystems, phosphorus exists primarily in the form of inorganic phosphates, polyphosphates, and organic phosphates. Polyphosphates and organic phosphates are easily decomposed and ultimately exist as inorganic phosphates. Chemical reactions have a greater advantage in removing inorganic salts.

[0003] Wetland matrix is ​​the most effective and easily controlled pathway for wetland phosphorus removal. The selection of different fillers can also enhance phosphorus removal efficiency. Typically, the matrix removes phosphorus from wastewater through a series of physical and chemical processes, including interception, precipitation, filtration, adsorption, and complexation. Therefore, the phosphorus adsorption process by constructed wetland matrix is ​​quite complex. The matrix surface carries an electrical charge, which attracts negatively charged phosphate ions from the environment. This phenomenon is known as non-specific phosphorus adsorption by the matrix. Under certain conditions, metal ions in the matrix may dissolve into the water and react with phosphate ions to form insoluble or slightly soluble phosphorus-containing precipitates. This mechanism not only improves phosphorus removal efficiency but also reduces the risk of phosphorus re-release into the water. Metal ions such as iron and aluminum in the matrix hydrolyze in water to form hydroxides or hydroxyl complexes. These products can combine with phosphate ions to form insoluble or slightly soluble phosphorus-containing precipitates. For example, iron and aluminum hydroxides can react with phosphate ions to form stable iron or aluminum phosphate precipitates, effectively removing phosphorus from water.

[0004] Currently, commonly used wetland matrix components include gravel, zeolite, sand, soil, or cinders. These matrix materials are widely available, relatively low-cost, and have certain adsorption properties and physical support functions, which can meet the basic construction requirements of artificial wetlands. However, due to the uneven pore size distribution of natural minerals, there are a large number of micropores and a small number of macropores. This may cause the adsorption sites of the matrix to be quickly saturated when treating highly contaminated water bodies, resulting in a decrease in removal efficiency. Secondly, the adsorption selectivity of natural mineral matrices for different pollutants is poor, making it difficult to effectively distinguish and remove specific pollutants.

[0005] In response to the above problems, existing technologies have proposed the use of artificial modification of natural substrates to increase the adsorption capacity of substrates. Current modification schemes include: magnetic modification, acid modification, layered double hydroxide (LDHs) coating modification, etc. In some schemes, the removal effect of water pollutants by commonly used wetland substrates after modification by different methods was studied. The results showed that the use of H +Acid modification by replacing the metal cations in the filler can increase the specific surface area of ​​the natural matrix, and the pore size modification process is simple and the removal effect is good, but it is time-consuming and easy to destroy the crystal structure of the filler, and waste gas and waste liquid are generated during the modification process, which has the risk of causing secondary pollution; LDHs coating modification can also increase the specific surface area of ​​the filler, improve the adsorption of the filler, and improve the filler's decontamination ability, especially the removal effect of heavy metal ions, but it has high requirements for the modification equipment; magnetic modification of the filler using magnetic materials can induce microbial enzyme synthesis, enhance enzyme activity, increase microbial degradation rate and filler recovery rate, but the filler specific surface area, total pore volume and micropore volume will decrease, reducing the physical adsorption capacity of the filler.

[0006] Because the physical and chemical properties of natural ores also present numerous challenges after modification, new synthetic wetland substrates have been extensively researched. Artificially composited wetland substrates can precisely control their physical and chemical properties to meet specific wastewater treatment requirements, thereby increasing their adsorption capacity. Common examples include activated carbon and water plant excess sludge composites. In some technical solutions, novel non-combustible fillers have been prepared using gypsum, diatomaceous earth, water treatment sludge, and aluminum slag as raw materials. These artificial wetland substrates achieve phosphorus removal rates exceeding 90%, but aluminum is toxic to plants, which can negatively impact plant growth. While there are numerous approaches to creating artificial composite wetland substrates, the high cost of preparing them using methods like high temperature and electrolysis makes them relatively difficult to implement in practice. Furthermore, some metal elements in the substrates are toxic to wetland plants, inhibiting their growth and reducing the pollutant removal capacity of the wetland system, thereby impacting the wetland's ecological benefits and landscape value. Therefore, finding an artificial wetland substrate material that is simple to prepare, improves pollutant removal capacity, and promotes wetland plant growth remains an urgent challenge. Summary of the Invention

[0007] The purpose of the present invention is to provide an AlFe-gypsum material and a preparation method and application thereof, so as to solve the problem that natural ores are easily saturated in adsorption and have low removal capacity for specific pollutants.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] One of the technical solutions of the present invention is to provide a method for preparing an AlFe-gypsum material, comprising the following steps:

[0010] dissolving an aluminum source and an iron source in water to obtain an Al-Fe mixed solution;

[0011] Adding gypsum to the Al-Fe mixed solution, stirring evenly, standing and cooling, and then drying to obtain the AlFe-gypsum material.

[0012] Furthermore, the aluminum source includes AlCl3 and / or Al2(SO4)3.

[0013] Furthermore, the iron source includes FeCl3 and / or Fe2(SO4)3.

[0014] Furthermore, the usage ratio of the aluminum source, the iron source and water is 13.33-26.66 g:16.22-32.44 g:1000 mL.

[0015] Furthermore, the mass ratio of the Al-Fe mixed solution to plaster of Paris is 0.5-1:0.8-1.2.

[0016] Furthermore, the cooling time is 10 minutes.

[0017] Furthermore, the drying temperature is 65° C. and the drying time is 3-5 hours.

[0018] The second technical solution of the present invention: provides an AlFe-gypsum material, which is prepared by the above-mentioned preparation method.

[0019] The contents of Ca, Al and Fe in the AlFe-gypsum material provided by the present invention are 131.15-146.24 mg / g, 1.37-2.77 mg / g and 21.01-39.98 mg / g, respectively.

[0020] The third technical solution of the present invention is to provide an application of the above-mentioned AlFe-gypsum material in sewage treatment.

[0021] Furthermore, the sewage treatment includes preparing an artificial wetland for treating sewage and / or a sewage treatment system including an artificial wetland.

[0022] The fourth technical solution of the present invention: provides an artificial wetland for treating sewage, wherein the matrix of the artificial wetland for treating sewage comprises the above-mentioned AlFe-gypsum material.

[0023] Furthermore, the particle size of the AlFe-gypsum material is between 1.0-2.0 cm.

[0024] The fifth technical solution of the present invention: provides a sewage treatment system comprising an artificial wetland, wherein the matrix of the artificial wetland in the sewage treatment system comprises the above-mentioned AlFe-gypsum material.

[0025] Furthermore, the particle size of the AlFe-gypsum material is between 1.0-2.0 cm.

[0026] Technical solution six of the present invention: provides a method for treating sewage using an artificial wetland, wherein the matrix material of the artificial wetland in the method includes the above-mentioned AlFe-gypsum material.

[0027] Technical solution seven of the present invention: provides a method for improving the phosphorus removal effect of artificial wetland treatment of sewage, wherein the matrix material of the artificial wetland in the method includes the above-mentioned AlFe-gypsum material.

[0028] The bimetallic mixed solution in the present invention increases the metal ion content in the matrix material, thereby improving the phosphorus removal effect of the wetland matrix. Under long-term water stagnation conditions of plants, Fe ions can form a film on the roots, absorb Al ions, and reduce the toxic effect of Al on plants. This can improve the phosphorus removal capacity of the wetland while ensuring the ecological effect and landscape value of the artificial wetland.

[0029] The present invention discloses the following technical effects:

[0030] The preparation method of the AlFe-gypsum material provided by the present invention is simple, the reaction environment is easy to achieve, the step of mixing the bimetallic solutions can be carried out in the same reaction tank, the operation is simple, and time and labor are saved. The AlFe-gypsum material has a rich pore structure, a small pore size distribution range, a large number of micropores and mesopores, a large contribution to the total pore volume, and a higher specific surface area, thereby providing more adsorption sites and a larger adsorption capacity for pollutants in sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 Schematic diagram of the preparation process flow of AlFe-gypsum material.

[0033] Figure 2 The BET test result fitting curves of the AlFe-gypsum ball material and natural limestone prepared in Example 1, wherein a is the pore volume and pore size differential distribution relationship of the AlFe-gypsum ball material, b is the BET isothermal adsorption curve of the AlFe-gypsum ball material, c is the pore volume and pore size differential distribution relationship of the natural limestone, and d is the BET isothermal adsorption curve of the natural limestone.

[0034] Figure 3 These are the experimental results of the adsorption kinetics of phosphorus by AlFe-gypsum balls of Examples 1-3, where a is Example 1, b is Example 2, and c is Example 3.

[0035] Figure 4 Schematic diagram of artificial wetland device.

[0036] Figure 5 is the purification capacity of natural limestone for pollutants, where a is the removal rate of COD and b is the removal rate of TP.

[0037] Figure 6 is the purification capacity of AlFe-gypsum matrix material for pollutants, where a is the removal rate of COD and b is the removal rate of TP. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0040] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0041] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0042] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0043] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0044] The raw materials and reagents used in the specific embodiments of the present invention are all commercially available products.

[0045] The particle size of the natural limestone used in the specific embodiment of the present invention is between 0.6-1.0 cm.

[0046] The room temperature and normal temperature involved in the specific embodiments of the present invention both refer to 20-30°C.

[0047] Figure 1 Schematic diagram of the preparation process flow of AlFe-gypsum material.

[0048] Example 1

[0049] The preparation steps of AlFe-gypsum material include (AlFe-gypsum ball material):

[0050] S1. Weigh 13.33 g of dried anhydrous AlCl3 powder and 32.44 g of anhydrous FeCl3 powder, place them in a beaker and store them in a fume hood. Use a dried graduated cylinder to measure 1 L of pure water, slowly add a small amount to the mixed powder several times, and use a stirrer to completely mix the solution to obtain an Al-Fe mixed solution. To prevent the solution from splashing due to a violent reaction, wait for the reaction to stabilize after each addition. After the solution cools to room temperature, place it in a refrigerator and store it under refrigeration at 5°C.

[0051] S2, the dried gypsum powder was added to the Al-Fe mixed solution prepared in step S1, and the mixture was mixed and stirred at a ratio of 1g gypsum powder: 0.7g Al-Fe mixed solution to prepare an AlFe-gypsum solution;

[0052] S3. Slowly pour the AlFe-gypsum solution prepared in step S2 into a spherical mold with a diameter of 1 cm. After cooling at room temperature for about 10 minutes, place it in an oven at 65°C and dry it for 3 hours. Then take out the mold, cool it to room temperature and demould it to obtain a new wetland matrix AlFe-gypsum ball material.

[0053] Figure 2 The BET test result fitting curves of the AlFe-gypsum ball material and natural limestone prepared in Example 1, wherein a is the differential distribution relationship of the pore volume and pore size of the AlFe-gypsum ball material, b is the BET isothermal adsorption curve of the AlFe-gypsum ball material, c is the differential distribution relationship of the pore volume and pore size of the natural limestone, and d is the BET isothermal adsorption curve of the natural limestone. As can be seen from the figure, in a, the differential distribution of pore volume and pore size in the AlFe-gypsum ball material gradually decreases with the increase of pore size, indicating that there are fewer macropores in the material; in the small pore size range (0-20nm), the pore volume / pore size differential distribution is higher, indicating that there are more micropores and mesopores, which helps to increase the adsorption capacity of the material. In B, the nitrogen adsorption capacity of the AlFe-gypsum ball material increases with the increase of relative pressure (P / P0), and reaches a maximum value of about 47.0cm when the relative pressure is close to 1.0. 3 / g, which indicates that the material has a large pore volume; and the IV type adsorption isotherm and H3 type hysteresis loop appear, which indicates that the material has a layered structure, a complex pore structure, and the presence of micropores, mesopores, etc. In c, the pore size distribution range of natural limestone is relatively wide, between 0-150nm, and the pore distribution is dense in the range of 0-20nm, which indicates that limestone is a complex pore structure material with micropores, mesopores and macropores. In D, the trend of the limestone adsorption and desorption curve is similar to that of the AlFe-gypsum matrix material, and the IV type adsorption isotherm and H3 type hysteresis loop also appear, but the maximum adsorption capacity of nitrogen is 3.5cm 3 / g. In summary, the content of micropores and mesopores in AlFe-gypsum ball material is higher than that in natural limestone, and the adsorption capacity is greater than that in natural limestone.

[0054] The surface area, pore volume and average pore diameter of AlFe-gypsum ball materials are: 21.99m 2 ·g -1 , 0.07cm 3 ·g -1 and 11.33nm; the surface area, pore volume and average pore diameter of natural limestone are: 1.10m 2 ·g -1 , 0.01cm 3 ·g -1 and 29.57 nm. Comparative analysis shows that the AlFe-gypsum ball material has a larger specific surface area and pore volume, which further explains the reason for the larger adsorption capacity.

[0055] ICP-MS tests were performed on the AlFe-gypsum ball material and natural limestone obtained in Example 1. The results showed that the Ca, Al, and Fe contents in the AlFe-gypsum ball material were 137.86 mg / g, 1.37 mg / g, and 39.98 mg / g, respectively, and the Ca, Al, and Fe contents in the natural limestone were 165.25 mg / g, 2.84 mg / g, and 2.02 mg / g, respectively. Comparative analysis shows that the Ca content of the AlFe-gypsum ball material is close to that of the natural limestone, the Al content of the former is 1.47 mg / g lower than that of the former, but the Fe content is nearly 20 times that of the latter. 3+ It will hydrolyze in water to form hydrated iron oxide, the rich hydroxyl groups on its surface can react with PO4 in the solution 3- Ligand exchange reaction occurs to form a stable inner layer complex, which is one of the strongest phosphorus adsorption mechanisms. It is firmly adsorbed and not easy to desorb. The enriched high concentration of Fe provides highly active Fe hydroxyl sites for the AlFe-gypsum balls, which has stronger chemical phosphorus removal ability. At the same time, the solubility and porous structure of gypsum are used to synergistically improve the phosphorus fixation effect. Limestone mainly relies on slow Ca-P precipitation. Its low iron and aluminum content and dense structure severely limit the adsorption efficiency, so it has a higher chemical adsorption capacity for phosphorus in water.

[0056] Example 2

[0057] The preparation steps of AlFe-gypsum material include (AlFe-gypsum ball material):

[0058] S1. Weigh 26.66 g of dried anhydrous AlCl3 powder and 16.22 g of anhydrous FeCl3 powder into a beaker and store in a fume hood. Use a dried graduated cylinder to measure 1 L of pure water, slowly add a small amount to the mixed powder several times, and use a stirrer to completely mix the solution to obtain an Al-Fe mixed solution. To prevent the solution from splashing due to a violent reaction, wait for the reaction to stabilize after each addition. After the solution cools to room temperature, place it in a refrigerator and store it under refrigeration at 5°C.

[0059] S2, the dried gypsum powder was added to the Al-Fe mixed solution prepared in step S1, and the mixture was mixed and stirred at a ratio of 1g gypsum powder: 0.7g Al-Fe mixed solution to prepare an AlFe-gypsum solution;

[0060] S3. Slowly pour the AlFe-gypsum solution prepared in step S2 into a spherical mold with a diameter of 1 cm. After cooling at room temperature for about 10 minutes, place it in an oven at 65°C and dry it for 3 hours. Then take out the mold, cool it to room temperature and demould it to obtain a new wetland matrix AlFe-gypsum ball material.

[0061] Example 3

[0062] The preparation steps of AlFe-gypsum material include (AlFe-gypsum ball material):

[0063] S1. Weigh 13.33 g of dried anhydrous AlCl3 powder and 16.22 g of anhydrous FeCl3 powder, place them in a beaker and store them in a fume hood. Use a dried graduated cylinder to measure 1 L of pure water, slowly add a small amount to the mixed powder several times, and use a stirrer to completely mix the solution to obtain an Al-Fe mixed solution. To prevent the solution from splashing due to a violent reaction, wait for the reaction to stabilize after each addition. After the solution cools to room temperature, place it in a refrigerator and store it under refrigeration at 5°C.

[0064] S2, the dried gypsum powder was added to the Al-Fe mixed solution prepared in step S1, and the mixture was mixed and stirred at a ratio of 1g gypsum powder: 0.7g Al-Fe mixed solution to prepare an AlFe-gypsum solution;

[0065] S3. Slowly pour the AlFe-gypsum solution prepared in step S2 into a spherical mold with a diameter of 1 cm. After cooling at room temperature for about 10 minutes, place it in an oven at 65°C and dry it for 3 hours. Then take out the mold, cool it to room temperature and demould it to obtain a new wetland matrix AlFe-gypsum ball material.

[0066] Comparative Example 1

[0067] The preparation steps of AlFe-gypsum material include (AlFe-gypsum ball material):

[0068] S1. Weigh 13.33 g of dried anhydrous AlCl3 powder and 32.44 g of anhydrous FeCl3 powder, place them in a beaker and store them in a fume hood. Use a dried graduated cylinder to measure 1 L of pure water, slowly add a small amount to the mixed powder several times, and use a stirrer to completely mix the solution to obtain an Al-Fe mixed solution. To prevent the solution from splashing due to a violent reaction, wait for the reaction to stabilize after each addition. After the solution cools to room temperature, place it in a refrigerator and store it under refrigeration at 5°C.

[0069] S2, the dried gypsum powder was added to the Al-Fe mixed solution prepared in step S1, and the mixture was mixed and stirred at a ratio of 1g gypsum powder: 0.4g Al-Fe mixed solution to prepare an AlFe-gypsum solution;

[0070] S3. Slowly pour the AlFe-gypsum solution prepared in step S2 into a spherical mold with a diameter of 1 cm. After cooling at room temperature for about 10 minutes, place it in an oven at 65°C and dry it for 3 hours. Then take out the mold, cool it to room temperature and demould it to obtain a new wetland matrix AlFe-gypsum ball material.

[0071] The resulting material shows drying shrinkage and cracking phenomenon, which is caused by insufficient water, uneven mixing, and drying cracking. This phenomenon will lead to the degradation of pore structure and Al 3+ It accelerates dissolution, thus reducing the service life of the material and increasing the accumulation of Al in the roots of plants, inhibiting plant growth and indirectly weakening the phosphorus removal capacity of artificial wetlands.

[0072] Comparative Example 2

[0073] The preparation steps of AlFe-gypsum material include (AlFe-gypsum ball material):

[0074] S1. Weigh 13.33 g of dried anhydrous AlCl3 powder and 32.44 g of anhydrous FeCl3 powder, place them in a beaker and store them in a fume hood. Use a dried graduated cylinder to measure 1 L of pure water, slowly add a small amount to the mixed powder several times, and use a stirrer to completely mix the solution to obtain an Al-Fe mixed solution. To prevent the solution from splashing due to a violent reaction, wait for the reaction to stabilize after each addition. After the solution cools to room temperature, place it in a refrigerator and store it under refrigeration at 5°C.

[0075] S2, the dried gypsum powder was added to the Al-Fe mixed solution prepared in step S1, and the mixture was mixed and stirred at a ratio of 1g gypsum powder: 1.3g Al-Fe mixed solution to prepare an AlFe-gypsum solution;

[0076] S3. Slowly pour the AlFe-gypsum solution prepared in step S2 into a spherical mold with a diameter of 1 cm. After cooling at room temperature for about 10 minutes, place it in an oven at 65°C and dry it for 3 hours. Then take out the mold, cool it to room temperature and demould it to obtain a new wetland matrix AlFe-gypsum ball material.

[0077] The resulting material is loose and easily broken because excess moisture prolongs the drying process, reducing its density and strength. This phenomenon causes the material to become brittle when exposed to water, resulting in insufficient support and subsequent breakage. This can lead to problems such as reduced phosphorus removal capacity and pipe blockage in constructed wetlands.

[0078] Test example

[0079] Adsorption kinetics experiments were conducted on the AlFe-gypsum balls obtained in Examples 1 to 3 to determine the phosphorus adsorption capacity of different AlFe-gypsum ball materials. The steps are as follows:

[0080] 0.037 g of KH2PO4 powder was dissolved in 1 L of deionized water to prepare a KH2PO4 solution. 20 g of AlFe-gypsum balls were then added. Samples were taken at 120 rpm after the adsorption reaction had been carried out for 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, and 16 h. After being filtered through a 0.45 μm pinhole filter, the phosphorus concentration of the solution was measured by ammonium molybdate spectrophotometry. The pseudo-first-order kinetic model and pseudo-second-order kinetic model were used to simulate the adsorption process of phosphorus in water. The results are shown in Figure 2. Figure 3 shown.

[0081] Figure 3 Figure 1 shows the experimental results of phosphorus adsorption kinetics on AlFe-gypsum balls from Examples 1-3, where a represents Example 1, b represents Example 2, and c represents Example 3. As can be seen from the figure, phosphorus adsorption on the three materials is primarily due to surface and chemical reactions, with the material from Example 2 exhibiting the highest maximum phosphorus adsorption capacity of 0.33 mg / g.

[0082] The following experiment was conducted to explore the impact of natural limestone (particle size between 0.6-1 cm) and the AlFe-gypsum ball material obtained in Examples 1-2 of the present application on plant growth. The steps are as follows:

[0083] A quantity of the above three materials was spread flat on the bottom layer of three plastic boxes with dimensions of 23.2 cm × 13.4 cm × 9.4 cm, and filled with garden soil in a ratio of bottom substrate height: upper garden soil height = 1:2. Plant cultivation experiments were carried out at a temperature of 20-25°C, in ventilated and sunny conditions. In the plant cultivation experiment, calamus seedlings were selected as plants, and the number of plants planted was 6. The experimental water was prepared from a nutrient solution specially prepared for calamus, the main component of which was K fertilizer. The experimental water was replaced every 48 hours to ensure faster growth of calamus. On the 30th day, the plant roots were taken and the Na, Ca, Al, and Fe metal contents in the roots were determined by ICP-MS. The results are shown in Table 1.

[0084] Table 1 Effects of three matrix simulated wetlands on plant growth (unit: mg / g)

[0085]

[0086] It can be seen from the data in Table 1 that the Fe content of the plant roots in the simulated wetlands of the AlFe-gypsum ball materials obtained in Examples 1 and 2 is higher than that of natural limestone, and the Fe content in Implementation Case 1 is relatively the highest. Since when the Fe concentration in the water is high, a layer of Fe film will form on the surface of the plant roots under stagnant water conditions, which can adsorb Al ions. Therefore, the Al content of the plants in Implementation Case 1 is relatively the lowest. As Fe is an essential element in the growth process of plants, a rich Fe content is more conducive to plant growth. Al has a certain toxicity to plants, and a high concentration of Al inhibits plant growth. The Ca and Na contents of the plant roots in the simulated wetlands of Examples 1 and 2 are lower than those of natural limestone. This is because a high Al concentration is toxic to plants and will inhibit the plant's absorption of Ca 2+ 、Na + Plasma absorption, as well as Fe and Ca 2+ 、Na + There is a competitive relationship between metal ions during the absorption process of plant roots. High concentrations of Fe will occupy the absorption sites of plants, thereby reducing absorption.

[0087] The above-mentioned adsorption kinetics experiments and plant growth impact exploration experiments, based on the ecological effects and ecological landscape effects of wetlands, show that the maximum phosphorus adsorption capacity of the AlFe-gypsum ball material obtained in Example 1 is only 0.03 mg / g lower than that of Example 2. However, the results of the plant growth impact exploration experiment show that compared with Example 2, the Fe content of plant roots in the simulated wetland obtained in Example 1 increased by 3.75 mg / g and the Al content decreased by 8.09 mg / g, which is beneficial to wetland plant growth. Therefore, the AlFe-gypsum ball material obtained in Example 1 has higher overall value and is more suitable for practical applications.

[0088] The AlFe-gypsum ball material (AlFe-gypsum matrix material) obtained in Example 1 and natural limestone (particle size between 0.6-1 cm) were used to prepare a vertical flow type artificial wetland. The artificial wetland device was as follows: Figure 4 As shown, the details are as follows:

[0089] The dimensions of the artificial wetland device are 1200mm×300mm×500mm, and the total effective volume of the reactor is 0.15m 3 , which is divided into three sections and consists of multiple upstream and downstream flows in series; the plants used in the experiment are calamus, with a planting density of 27.78 plants / m 2 , the temperature is maintained at 23-25℃, and light is provided regularly;

[0090] The control group used natural limestone as the wetland matrix; in the experimental group, the artificial wetland matrix was composed of AlFe-gypsum ball material and natural limestone (particle size 6-10 mm) mixed in a total height ratio of 1:2;

[0091] The influent pollutant concentration is prepared to exceed the national sewage discharge standards: COD concentration range is 58.25-66.12 mg / L, TP concentration range is 4.11-4.35 mg / L;

[0092] The artificial wetland adopts continuous water inlet mode, which is delivered by peristaltic pump with a flow rate of 1.0-1.3L / h and a hydraulic retention time of 48h. It runs for 30 days in total. The first sampling is taken on the 5th day of operation. The sampling is taken for 24 days in total. The effluent samples are tested for COD and TP with a chemical analyzer within 24 hours. The results are as follows Figure 5 and Figure 6 shown.

[0093] Figure 5 is the purification capacity of natural limestone for pollutants, where a is the removal rate of COD and b is the removal rate of TP.

[0094] Figure 6 is the purification capacity of AlFe-gypsum matrix material for pollutants, where a is the removal rate of COD and b is the removal rate of TP.

[0095] Depend on Figure 5 and Figure 6 It can be seen that the COD and TP removal rates of the artificial wetland with natural limestone matrix are stable at 43.48% and 48.62%, and the effluent concentrations are stable at 35.01 mg / L and 2.18 mg / L, respectively; when the AlFe-gypsum ball material prepared by the present invention is used as the artificial wetland matrix, the COD and TP removal rates are stable at 63.21% and 88.42%, and the effluent concentrations are stable at 22.88 mg / L and 0.47 mg / L, respectively. The effluent meets the emission limits specified in Table 1B of the "Shaanxi Province Yellow River Basin Wastewater Comprehensive Discharge Standard" (DB 61 / 224-2018).

[0096] The above experiments show that when the AlFe-gypsum ball material is used as a matrix for artificial wetlands, it can effectively improve the wetland system's ability to remove organic pollutants (COD) and total phosphorus (TP) in sewage.

[0097] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0098] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing AlFe-gypsum material, characterized in that the steps include: dissolving an aluminum source and an iron source in water to obtain an Al-Fe mixed solution; Adding gypsum to the Al-Fe mixed solution, stirring evenly, standing and cooling, and then drying to obtain the AlFe-gypsum material.

2. The preparation method according to claim 1, wherein The aluminum source includes AlCl3 and / or Al2(SO4)3; and / or, the iron source includes FeCl3 and / or Fe2(SO4)3; and / or, the usage ratio of the aluminum source, the iron source and water is 13.33-26.66g:16.22-32.44g:1000mL.

3. The preparation method according to claim 2, wherein The mass ratio of the Al-Fe mixed solution to plaster of Paris is 0.5-1:0.8-1.2; and / or the static cooling time is 10 minutes; and / or the drying temperature is 65° C. and the drying time is 3-5 hours.

4. An AlFe-gypsum material, characterized in that: The AlFe-gypsum material is prepared by the preparation method according to any one of claims 1 to 3.

5. Use of the AlFe-gypsum material according to claim 4 in sewage treatment.

6. The use according to claim 5, characterized in that The sewage treatment includes preparing an artificial wetland for treating sewage and / or a sewage treatment system including an artificial wetland.

7. An artificial wetland for treating sewage, characterized in that: The matrix of the artificial wetland for treating sewage comprises the AlFe-gypsum material according to claim 4.

8. A sewage treatment system comprising an artificial wetland, characterized in that: The matrix of the artificial wetland in the sewage treatment system comprises the AlFe-gypsum material according to claim 4.

9. A method for treating sewage using artificial wetlands, characterized in that: The matrix material of the artificial wetland in the method comprises the AlFe-gypsum material according to claim 4.

10. A method for improving phosphorus removal in wastewater treatment using artificial wetlands, characterized in that: The matrix material of the artificial wetland in the method comprises the AlFe-gypsum material according to claim 4.

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