A self-assembled modified composite material, its preparation method and application

Abstract

This disclosure provides a self-assembled modified composite material, its preparation method, and its applications. The self-assembled modified composite material includes modified desulfurization gypsum with fly ash as a carrier, and a lanthanum-based material that self-assembles and adsorbs onto the fly ash. This disclosure yields a self-assembled modified composite material with excellent phosphorus removal efficiency and low cost, achieving a phosphorus removal efficiency of up to 99.9%, while also exhibiting fluoride removal capabilities, with a fluoride ion removal rate of up to 98%. This disclosure combines desulfurization gypsum with fly ash, effectively integrating the adsorption properties of fly ash. Furthermore, this disclosure self-assembles the lanthanum-based material onto the modified desulfurization gypsum with fly ash as a carrier, forming a composite material with a uniform coordination structure and a large specific surface area, further enhancing the adsorption performance and application range of the composite material. This disclosure achieves the comprehensive resource utilization of industrial waste residue, providing a new direction for the resource utilization of solid waste.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of solid waste resource utilization, and particularly relates to a self-assembled modified composite material and a preparation method and application thereof. BACKGROUND

[0002] Phosphorus is one of the pollutants causing water eutrophication. With the rapid growth of production and consumption of phosphorus-containing detergents and the development of phosphating technology, the discharge of phosphorus-containing wastewater is rapidly increasing. Part of the phosphorus in wastewater comes from agricultural waste; at the same time, the large use of phosphorus-containing detergents in life also significantly increases the content of phosphorus in domestic wastewater. In addition, the wastewater discharged by the phosphorus chemical, chemical fertilizer, papermaking, rubber, dye and textile printing and dyeing, pesticide, coking, fermentation, pharmaceutical and other industries often contains phosphorus compounds. High-phosphorus industrial wastewater discharged into nature will make water eutrophication more and more serious. In order to protect the green mountains and clear water, enterprises have increased the investment in phosphorus-rich wastewater treatment. It is very important to select an economical, practical and efficient phosphorus removal agent according to the traditional process conditions.

[0003] At present, the main method for wastewater phosphorus removal is chemical precipitation. Chemical precipitation for phosphorus removal refers to adding a reagent to wastewater, which mixes with dissolved salts such as phosphate in wastewater to form particulate, non-dissolved substances. The reagents used are generally aluminum salts, iron salts (ferrous salts), lime, iron-aluminum polymers, etc. Chemical precipitation requires the addition of a large amount of flocculant, and the treatment cost is high.

[0004] Therefore, it is of great significance to prepare a low-cost and high-performance wastewater phosphorus removal material. SUMMARY

[0005] The following is a summary of the subject matter of the detailed description. This summary is not intended to limit the scope of the claims.

[0006] In view of the deficiencies of the prior art, the purpose of the present disclosure is to provide a self-assembled modified composite material and a preparation method and application thereof. The present disclosure prepares a self-assembled modified composite material with excellent phosphorus removal effect and low cost, and the phosphorus removal efficiency can reach 99.9%, and the composite material also has a fluorine removal effect, and the removal rate of fluorine ions can reach 98%. The present disclosure combines desulfurization gypsum with fly ash, effectively combining the adsorption performance of fly ash. When the composite material is applied to wastewater treatment, the precipitate generated by chemical reaction can efficiently adsorb pollutants in wastewater and accelerate its sedimentation, fully utilizing the advantages of various solid wastes. Moreover, the present disclosure self-assembles lanthanum-based materials on the modified desulfurization gypsum with fly ash as the carrier, forming a composite material with a uniform coordination structure, which has a large specific surface area, further enhancing the adsorption performance and application range of the composite material. The present disclosure realizes the comprehensive utilization of industrial waste residues, achieves the purpose of "waste treatment with waste", meets the environmental requirements, and provides a new direction for the resource utilization of solid waste.

[0007] To achieve this purpose, the present disclosure adopts the following technical solutions:

[0008] In a first aspect, the present disclosure provides a self-assembled modified composite material, which comprises modified desulfurization gypsum with fly ash as a carrier, and lanthanum-based materials self-assembled on the fly ash.

[0009] It should be noted that desulfurization gypsum is a solid waste generated simultaneously with flue gas desulfurization. Desulfurization gypsum is fine, with a particle size generally not exceeding 90 μm. Its main component is calcium sulfate dihydrate, with a content higher than 90%. Desulfurization gypsum also contains calcium carbonate, calcium sulfite, and soluble salts composed of sodium, potassium, and magnesium sulfates or chlorides, and other impurities.

[0010] It should be noted that fly ash is fine ash collected from flue gas after coal combustion, and is the main solid waste discharged by coal-fired power plants. Due to its large specific surface area, generally 1600-3500 cm 2 / g, it exhibits high adsorption performance.

[0011] It should be noted that desulfurization gypsum and fly ash are bulk solid wastes, and large-scale storage leads to occupation of a large amount of land resources, causing harm to the climate, soil, plants, and human health. By comprehensively considering their characteristics, it is possible to develop a new composite material by resource utilization of these solid wastes, and the composite material can be applied to wastewater treatment, achieving the purpose of waste treatment with waste, reducing wastewater treatment costs, and providing a new development direction for wastewater treatment.

[0012] Based on this, the self-assembled modified composite material with excellent phosphorus removal effect and low cost is prepared, and the phosphorus removal efficiency can reach 99.9%, and the fluorine removal effect is also achieved, and the fluorine ion removal rate can reach 98%. The desulfurization gypsum and fly ash are combined in the self-assembled modified composite material, and the adsorption performance of the fly ash is effectively combined. When the composite material is applied to wastewater treatment, the precipitate generated by chemical reaction can efficiently adsorb the pollutants in the wastewater and accelerate the sedimentation, and the advantages of various solid wastes are fully utilized. Moreover, the lanthanum-based material is self-assembled on the modified desulfurization gypsum with fly ash as the carrier to form a composite material with a uniform coordination structure, and the composite material has a large specific surface area, which further enhances the adsorption performance and application range of the composite material. The self-assembled modified composite material realizes the comprehensive utilization of industrial waste residues, achieves the purpose of "waste treatment with waste", meets the environmental requirements, and provides a new direction for the resource utilization of solid waste.

[0013] As an optional technical solution of the present disclosure, the self-assembled modified composite material is in a microspherical structure.

[0014] In the present disclosure, the self-assembled modified composite material in a microspherical structure helps to further improve its adsorption performance.

[0015] In an embodiment, the particle size D50 of the self-assembled modified composite material is 10-100 μm, for example, it can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0016] In the present disclosure, the particle size D50 of the self-assembled modified composite material is within the range of 20-50 μm, which is more helpful for the dispersion adsorption of the microspherical composite material.

[0017] As an optional technical solution of the present disclosure, the mass fraction of the lanthanum-based material is 1%-10% based on the mass of the self-assembled modified composite material, for example, it can be 2.5%, 5%, 7.5% or 10%, etc.

[0018] In the present disclosure, if the mass fraction of the lanthanum-based material is too small, there are less fluorine removal effective substances in the composite material, and the performance is poor. If the mass fraction of the lanthanum-based material is too large, because of its low solubility, it cannot be effectively self-assembled on the modified desulfurization gypsum with fly ash as the carrier, the effective substance content of the composite material will not increase, the performance of the composite material is difficult to be effectively improved, and the lanthanum-based material is wasted instead.

[0019] In an embodiment, the lanthanum-based material includes any one or a combination of at least two of lanthanum sulfate, lanthanum nitrate or lanthanum chloride.

[0020] The present disclosure can utilize the principle that the lanthanum-based material generates lanthanum fluoride precipitate with fluorine ions to achieve the effect of removing fluorine.

[0021] As an optional technical solution of this disclosure, the modified desulfurization gypsum with fly ash as the carrier is used as the basis, and the mass fraction of the modified desulfurization gypsum is 10%-50%, for example, it can be 10%, 20%, 33% or 50%, etc.

[0022] In this disclosure, if the mass fraction of modified desulfurized gypsum is too small, the amount of calcium participating in the reaction to precipitate and remove fluoride will be less, resulting in a poor fluoride removal effect; if the mass fraction of modified desulfurized gypsum is too large, the proportion of other effective agents such as lanthanum and fly ash will decrease relatively, and the overall fluoride removal performance of the composite material will actually decrease.

[0023] In one embodiment, the fly ash has a porous structure, and the porosity of the fly ash is 50%-80%, for example, it can be 50%, 60%, 70% or 80%, etc.

[0024] In this disclosure, fly ash has a large specific surface area, resulting in high adsorption activity. Furthermore, the bead walls have a porous structure with a porosity of 50-80%, exhibiting strong water absorption. Additionally, the desulfurized gypsum and lanthanum-based materials self-assemble into the surface and pores of the fly ash, thus possessing specific wastewater treatment characteristics.

[0025] In a second aspect, this disclosure provides a method for preparing a self-assembled modified composite material as described in the first aspect, the method comprising the following steps:

[0026] Modified desulfurized gypsum with fly ash as a carrier and lanthanum-based aqueous solution were mixed and subjected to hydrothermal reaction, followed by calcination to obtain the assembled modified composite material.

[0027] The preparation method disclosed herein is simple in process and the main raw materials are solid waste (desulfurized gypsum and fly ash), which is inexpensive. It realizes the comprehensive utilization of industrial waste residue and achieves the goal of "treating waste with waste" while meeting environmental requirements, providing a new direction for the resource utilization of solid waste.

[0028] As an optional technical solution of this disclosure, the solid-liquid ratio of the modified desulfurization gypsum with fly ash as the carrier and the lanthanum-based aqueous solution is (0.8-1.2) mg:(2-6) mL, wherein the range of the modified desulfurization gypsum with fly ash as the carrier, “(0.8-1.2) mg”, can be, for example, 0.8 mg, 0.9 mg, 1 mg, 1.1 mg or 1.2 mg, etc., and the range of the lanthanum-based aqueous solution, “(2-6) mL”, can be, for example, 2 mL, 3 mL, 4 mL, 5 mL or 6 mL, etc.

[0029] In this disclosure, if the solid-liquid ratio of the modified desulfurization gypsum with fly ash as the carrier to the lanthanum-based aqueous solution is too large, that is, the content of the lanthanum-based aqueous solution is low, the defluorination effect is poor; if the solid-liquid ratio of the modified desulfurization gypsum with fly ash as the carrier to the lanthanum-based aqueous solution is too small, the adsorption capacity of the modified desulfurization gypsum with fly ash as the carrier is limited, and the content of lanthanum-based material cannot be increased after adsorption saturation, resulting in the inability to improve the performance of the composite material and a waste of lanthanum-based material.

[0030] In one embodiment, the solute in the lanthanum-based aqueous solution includes any one or a combination of at least two of lanthanum sulfate, lanthanum nitrate, or lanthanum chloride.

[0031] In one embodiment, the mass ratio of solute to solvent in the lanthanum-based aqueous solution is (1-2):(100-200), wherein the range of solute selection in the lanthanum-based aqueous solution "1-2" can be, for example, 1, 1.2, 1.4, 1.6, 1.8 or 2, and the range of solvent selection in the lanthanum-based aqueous solution "100-200" can be, for example, 100, 120, 140, 160, 180 or 200.

[0032] In this disclosure, while ensuring complete solute dissolution, the mass ratio of the solute is increased as much as possible, thereby increasing the content of effective substances. This helps to increase the content of lanthanum-based materials that self-assemble onto modified desulfurization gypsum with fly ash as a carrier, thus enhancing the wastewater defluorination capacity of the composite material.

[0033] In one embodiment, the temperature of the hydrothermal reaction is 35-65°C, for example, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C or 65°C, and the time is 1-2 hours, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours.

[0034] In this disclosure, the hydrothermal reaction is carried out at 35-65℃ for 1-2 hours. The lower the temperature, the higher the solubility of lanthanum sulfate. The higher the temperature, the faster its self-assembly and adsorption onto the modified desulfurized gypsum with fly ash as the carrier can be increased. However, the temperature should not be too low or too high.

[0035] In one embodiment, the calcination temperature is 200-400℃, for example, 200℃, 250℃, 300℃, 350℃ or 400℃, and the time is 20-60min, for example, 20min, 30min, 40min, 50min or 60min.

[0036] In this disclosure, if the calcination temperature is too low, the composite material cannot be effectively sphericalized, and the substances cannot be effectively combined together; if the calcination temperature is too high, the effective substances in the relevant raw materials may decompose, resulting in a significant reduction in the performance of the composite material.

[0037] In one embodiment, the heating rate of the calcination is 2-3℃ / min, for example, it can be 2℃ / min, 2.2℃ / min, 2.4℃ / min, 2.6℃ / min, 2.8℃ / min or 3℃ / min, etc.

[0038] As an optional technical solution of this disclosure, the preparation method of the modified desulfurized gypsum includes:

[0039] The desulfurized gypsum raw material is washed with water, and then the washed desulfurized gypsum is mixed with sulfuric acid aqueous solution and subjected to water bath heating reaction to obtain the modified desulfurized gypsum.

[0040] In this disclosure, the purpose of washing the desulfurized gypsum raw material with water is to remove impurities. Then, the washed desulfurized gypsum is mixed with an aqueous sulfuric acid solution for a hydrothermal reaction, which can further remove salts or impurities.

[0041] In one embodiment, the mass ratio of the desulfurized gypsum after water washing to the sulfuric acid aqueous solution is 1:(20-50), for example, it can be 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 or 1:50, etc.

[0042] In this disclosure, the desulfurized gypsum washed with water and sulfuric acid aqueous solution are mixed at a mass ratio of 1:(20-50) to remove salt or impurities and further purify the desulfurized gypsum.

[0043] In one embodiment, the sulfuric acid aqueous solution comprises 98% sulfuric acid and water, wherein the mass ratio of the 98% sulfuric acid to water is (2-5):(20-50), for example, it can be 2:20, 2:50, 2:35, 3.5:35, 5:20 or 5:50, etc.

[0044] In one embodiment, the temperature of the water bath heating reaction is 80-90°C, for example, 80°C, 82°C, 84°C, 86°C, 88°C, or 90°C, and the time is 1-2 hours, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, or 2 hours.

[0045] In this disclosure, a water bath heating reaction at 80-90℃ for 1-2 hours can remove insoluble impurities and allow lanthanum-based materials to self-assemble onto modified desulfurized gypsum with fly ash as a carrier.

[0046] As an optional technical solution of this disclosure, the method for preparing modified desulfurization gypsum with fly ash as a carrier includes:

[0047] The modified desulfurization gypsum and fly ash are mixed to obtain the modified desulfurization gypsum with fly ash as the carrier.

[0048] In this disclosure, modified desulfurization gypsum and fly ash can be mixed to obtain modified desulfurization gypsum with fly ash as the carrier, which effectively combines the adsorption properties of fly ash. When applied to wastewater treatment, the precipitate produced by the chemical reaction can efficiently adsorb pollutants in the solution and accelerate their sedimentation, giving full play to the advantages of various solid wastes.

[0049] In one embodiment, the mass ratio of the modified desulfurized gypsum to fly ash is (10-60):(60-100), wherein the range of the modified desulfurized gypsum selection "10-60" can be, for example, 10, 20, 30, 40, 50 or 60, and the range of the fly ash selection "60-100" can be, for example, 60, 70, 80, 90 or 100.

[0050] In this disclosure, the mass ratio of modified desulfurized gypsum to fly ash is (10-60):(60-100), which can effectively combine the wastewater treatment capacity of desulfurized gypsum with the adsorption capacity of fly ash.

[0051] In one embodiment, the fly ash is first washed with water before being mixed with the modified desulfurization gypsum.

[0052] In this disclosure, the purpose of first washing the fly ash with water is to remove impurities.

[0053] As an optional technical solution of this disclosure, the preparation method includes the following steps:

[0054] (1) Dry the desulfurized gypsum raw material at 100-120℃ (e.g., 100℃, 105℃, 110℃, 115℃ or 120℃, etc.), then grind it to a mesh size of 100-200 mesh (e.g., 100 mesh, 150 mesh or 200 mesh), then mix the ground desulfurized gypsum raw material and water at a mass ratio of 1:(3-5) (e.g., 1:3, 1:4 or 1:5, etc.) to make a slurry, and stir and wash it at 70-90℃ for 20-40 minutes, then filter to obtain filter residue, and then dry and crush and sieve the filter residue at 100-120℃ (e.g., 100℃, 105℃, 110℃, 115℃ or 120℃, etc.) to obtain water-washed desulfurized gypsum;

[0055] (2) The desulfurized gypsum washed with water and sulfuric acid aqueous solution are mixed at a mass ratio of 1:(20-50), and the mixture is heated in a water bath at 80-90℃ for 1-2 hours under stirring. The mixture is then filtered to obtain filter residue. The filter residue is then dried and crushed and sieved at 100-120℃ (e.g., 100℃, 105℃, 110℃, 115℃ or 120℃, etc.) to obtain modified desulfurized gypsum.

[0056] (3) Dry the fly ash at 100-120℃ (e.g., 100℃, 105℃, 110℃, 115℃ or 120℃, etc.), then grind it to a mesh size of 100-200 mesh (e.g., 100 mesh, 150 mesh or 200 mesh), then mix the ground fly ash and water at a mass ratio of 1:(3-5) (e.g., 1:3, 1:4 or 1:5, etc.) to make a slurry, and stir and wash it at 45-55℃ for 30-50 minutes, then filter to obtain filter residue, and then dry and crush and sieve the filter residue at 100-120℃ (e.g., 100℃, 105℃, 110℃, 115℃ or 120℃, etc.) to obtain water-washed fly ash;

[0057] (4) The modified desulfurized gypsum and the washed fly ash are mixed in a mass ratio of (10-60):(60-100) to obtain modified desulfurized gypsum with fly ash as carrier.

[0058] (5) Lanthanum sulfate and water are mixed at a mass ratio of (1-2):(100-200) to obtain a lanthanum-based aqueous solution. Then, the modified desulfurization gypsum with fly ash as the carrier and the lanthanum-based aqueous solution are mixed at a solid-liquid ratio of (0.8-1.2) mg:(2-6) mL and subjected to a hydrothermal reaction at 35-65℃ for 1-2 h. Then, the mixture is soaked for 24-48 h (e.g., 24 h, 30 h, 36 h, 42 h, or 48 h, etc.). The filter residue is obtained by filtration and then transferred to an oven at 100-120℃ (e.g., 100℃, 105℃, 110℃, 115℃, or 120℃) for drying for 2-4 hours (e.g., 2 hours, 3 hours, or 4 hours). Then, it is calcined at a constant temperature in a muffle furnace at 200-400℃ for 20-60 minutes, with a heating rate of 2-3℃ / min. After calcination, it is cooled and ground to obtain the self-assembled modified composite material.

[0059] The present disclosure utilizes the above-described preparation method to enable lanthanum-based materials to self-assemble onto modified desulfurized gypsum supported by fly ash, forming a microspherical composite material with a uniformly coordinated structure and a large specific surface area, with a BET value of 4-10 m. 2 / g, further enhancing the adsorption performance and application range of the material. Furthermore, the preparation method is simple, and the main raw material is solid waste, resulting in low cost. This achieves the comprehensive resource utilization of industrial waste residue, realizing the goal of "treating waste with waste," while meeting environmental requirements and providing a new direction for the resource utilization of solid waste.

[0060] Thirdly, this disclosure provides an application of the self-assembled modified composite material as described in the first aspect in the field of water treatment technology.

[0061] In this disclosure, the self-assembled modified composite material can be widely used in wastewater treatment to effectively remove phosphorus from wastewater. For wastewater with a phosphorus content of 2200 mg / L, the addition of this composite material can reduce the total phosphorus to below 0.5 mg / L, with a phosphorus removal efficiency of up to 99.9%. The composite material also has a good effect on fluoride removal, and under optimal conditions, the fluoride ion removal rate can reach 98%.

[0062] The numerical range described in this disclosure includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this disclosure will not exhaustively list the specific point values ​​included in the range.

[0063] Compared with the prior art, this disclosure has the following beneficial effects:

[0064] (1) This disclosure presents a self-assembled modified composite material with excellent phosphorus removal effect and low cost, achieving a phosphorus removal efficiency of up to 99.9% and also exhibiting fluoride removal effect, with a fluoride ion removal rate of up to 98%. This disclosure combines desulfurized gypsum with fly ash, effectively combining the adsorption properties of fly ash. When this composite material is applied to wastewater treatment, the precipitate generated by the chemical reaction can efficiently adsorb pollutants in the wastewater and accelerate their sedimentation, fully utilizing the advantages of various solid wastes. Furthermore, this disclosure self-assembles lanthanum-based materials onto modified desulfurized gypsum with fly ash as the carrier, forming a composite material with a uniform coordination structure and a large specific surface area, which further enhances the adsorption performance and application range of the composite material.

[0065] (2) The self-assembled modified composite material prepared in this disclosure can be widely used in wastewater treatment. For wastewater with a phosphorus content of about 2200 mg / L, the addition of this composite material can reduce the total phosphorus to below 0.5 mg / L, and the phosphorus removal efficiency can reach 99.9%.

[0066] (3) The preparation method provided in this disclosure is simple and low in cost, realizes the comprehensive utilization of industrial waste residue, achieves the purpose of "treating waste with waste", and meets environmental requirements, providing a new direction for the resource utilization of solid waste.

[0067] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0068] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0069] Figure 1 This is a SEM image of the self-assembled modified composite material prepared in Example 5 of this disclosure. Detailed Implementation

[0070] The technical solutions of this disclosure will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this disclosure and should not be construed as specific limitations thereof.

[0071] Example 1

[0072] This embodiment provides a self-assembly modified composite material, which includes modified desulfurized gypsum with fly ash as a carrier, and lanthanum-based material that self-assembles and adsorbs onto the fly ash.

[0073] The self-assembled modified composite material has a microspherical structure and a particle size D50 of 10 μm.

[0074] Based on the mass of the self-assembled modified composite material, the mass fraction of the lanthanum-based material is 2.5%, and the lanthanum-based material is lanthanum sulfate;

[0075] Based on the mass of the modified desulfurization gypsum with fly ash as the carrier, the mass fraction of the modified desulfurization gypsum is 20%, the fly ash has a porous structure, and the porosity of the fly ash is 65%.

[0076] This embodiment also provides a method for preparing the above-mentioned self-assembled modified composite material, the method comprising the following steps:

[0077] (1) Dry the desulfurized gypsum raw material at 105°C, then grind it to 100 mesh. Then mix the ground desulfurized gypsum raw material and pure water at a mass ratio of 1:3 to make a slurry. Heat the slurry in a water bath to 80°C and stir and wash for 30 minutes. Then filter to obtain filter residue. Then dry and crush and grind the filter residue at 105°C. Screen it with a 100 mesh sieve. Discard the material on the sieve and take the material under the sieve to obtain the desulfurized gypsum after water washing.

[0078] (2) The desulfurized gypsum washed with water was mixed with 98% sulfuric acid and water at a mass ratio of 1:4:40. The mixture was stirred and kept at a constant temperature for 2 hours under the condition of heating to 85°C in a water bath. Then the filter residue was obtained by suction filtration. Subsequently, the filter residue was dried and crushed and ground at 105°C. It was then sieved with a 100-mesh sieve. The material on the sieve was discarded, and the material under the sieve was taken to obtain the modified desulfurized gypsum.

[0079] (3) Dry the fly ash at 105°C, then grind it to 100 mesh. Then mix the ground fly ash and pure water at a mass ratio of 1:3 to make a slurry. Heat the slurry in a water bath to 50°C and stir and wash for 30 minutes. Then filter to obtain filter residue. Then dry and crush and grind the filter residue at 105°C. Screen it with a 100 mesh screen. Discard the material on the screen and take the material under the screen to obtain the washed fly ash.

[0080] (4) The modified desulfurized gypsum and the washed fly ash were mixed at a mass ratio of 20:80 to obtain modified desulfurized gypsum with fly ash as the carrier.

[0081] (5) Lanthanum sulfate and pure water were mixed at a mass ratio of 1:150 to obtain a lanthanum-based aqueous solution. Then, the modified desulfurized gypsum with fly ash as the carrier and the lanthanum-based aqueous solution were mixed at a solid-liquid ratio of 1 mg:2.5 mL. The mixture was stirred and kept at a constant temperature for 1 h under water bath heating to 50 °C. Then, it was soaked for 24 h and filtered to obtain filter residue. The filter residue was transferred to an oven at 105 °C and dried for 2 h. Then, it was calcined at a constant temperature in a muffle furnace at 250 °C for 60 min. The calcination heating rate was 2 °C / min. After calcination, it was placed in a desiccator and cooled naturally before grinding to obtain the self-assembled modified composite material.

[0082] Example 2

[0083] This embodiment provides a self-assembly modified composite material, which includes modified desulfurized gypsum with fly ash as a carrier, and lanthanum-based material that self-assembles and adsorbs onto the fly ash.

[0084] The self-assembled modified composite material has a microspherical structure and a particle size D50 of 10 μm.

[0085] Based on the mass of the self-assembled modified composite material, the mass fraction of the lanthanum-based material is 5%, and the lanthanum-based material is lanthanum sulfate;

[0086] Based on the mass of the modified desulfurization gypsum with fly ash as the carrier, the mass fraction of the modified desulfurization gypsum is 33%, the fly ash has a porous structure, and the porosity of the fly ash is 65%.

[0087] This embodiment also provides a method for preparing the above-mentioned self-assembled modified composite material, the method comprising the following steps:

[0088] (1) Dry the desulfurized gypsum raw material at 105°C, then grind it to 100 mesh. Then mix the ground desulfurized gypsum raw material and pure water at a mass ratio of 1:3 to make a slurry. Heat the slurry in a water bath to 80°C and stir and wash for 30 minutes. Then filter to obtain filter residue. Then dry and crush and grind the filter residue at 105°C. Screen it with a 100 mesh sieve. Discard the material on the sieve and take the material under the sieve to obtain the desulfurized gypsum after water washing.

[0089] (2) The desulfurized gypsum washed with water was mixed with 98% sulfuric acid and water at a mass ratio of 1:3:30. The mixture was stirred and kept at a constant temperature for 2 hours under the condition of heating to 85°C in a water bath. Then the filter residue was obtained by suction filtration. Subsequently, the filter residue was dried and crushed and ground at 105°C. It was then sieved with a 100-mesh sieve. The material on the sieve was discarded, and the material under the sieve was taken to obtain the modified desulfurized gypsum.

[0090] (3) Dry the fly ash at 105°C, then grind it to 100 mesh. Then mix the ground fly ash and pure water at a mass ratio of 1:3 to make a slurry. Heat the slurry in a water bath to 50°C and stir and wash for 30 minutes. Then filter to obtain filter residue. Then dry and crush and grind the filter residue at 105°C. Screen it with a 100 mesh screen. Discard the material on the screen and take the material under the screen to obtain the washed fly ash.

[0091] (4) The modified desulfurized gypsum and the washed fly ash were mixed at a mass ratio of 40:80 to obtain modified desulfurized gypsum with fly ash as the carrier.

[0092] (5) Lanthanum sulfate and pure water were mixed at a mass ratio of 1:150 to obtain a lanthanum-based aqueous solution. Then, the modified desulfurized gypsum with fly ash as the carrier and the lanthanum-based aqueous solution were mixed at a solid-liquid ratio of 1 mg:4 mL. The mixture was stirred and kept at a constant temperature for 1 h under water bath heating to 50 °C. Then, it was soaked for 24 h and filtered to obtain filter residue. The filter residue was transferred to an oven at 105 °C and dried for 2 h. Then, it was calcined at a constant temperature in a muffle furnace at 350 °C for 60 min. The calcination heating rate was 3 °C / min. After calcination, it was placed in a desiccator and allowed to cool naturally before grinding to obtain the self-assembled modified composite material.

[0093] Example 3

[0094] This embodiment provides a self-assembly modified composite material, which includes modified desulfurized gypsum with fly ash as a carrier, and lanthanum-based material that self-assembles and adsorbs onto the fly ash.

[0095] The self-assembled modified composite material has a microspherical structure and a particle size D50 of 40 μm.

[0096] Based on the mass of the self-assembled modified composite material, the mass fraction of the lanthanum-based material is 10%, and the lanthanum-based material is lanthanum sulfate;

[0097] Based on the mass of the modified desulfurization gypsum with fly ash as the carrier, the mass fraction of the modified desulfurization gypsum is 33%, the fly ash has a porous structure, and the porosity of the fly ash is 65%.

[0098] This embodiment also provides a method for preparing the above-mentioned self-assembled modified composite material, the method comprising the following steps:

[0099] (1) The desulfurized gypsum raw material is dried at 105°C and then ground to 100 mesh. The ground desulfurized gypsum raw material and pure water are mixed at a mass ratio of 1:4 to form a slurry. The slurry is heated to 80°C in a water bath and stirred and washed for 30 minutes. The slurry is then filtered to obtain filter residue. The filter residue is then dried and crushed at 105°C and sieved with a 100-mesh sieve. The material on the sieve is discarded, and the material under the sieve is taken to obtain the desulfurized gypsum after water washing.

[0100] (2) The desulfurized gypsum washed with water was mixed with 98% sulfuric acid and water at a mass ratio of 1:3:30. The mixture was stirred and kept at a constant temperature for 2 hours under the condition of heating to 85°C in a water bath. Then the filter residue was obtained by suction filtration. Subsequently, the filter residue was dried and crushed and ground at 105°C. It was then sieved with a 100-mesh sieve. The material on the sieve was discarded, and the material under the sieve was taken to obtain the modified desulfurized gypsum.

[0101] (3) Dry the fly ash at 105°C, then grind it to 100 mesh, then mix the ground fly ash and pure water at a mass ratio of 1:4 to make a slurry, and heat it in a water bath to 50°C and stir and wash it for 30 minutes. Then filter it to obtain filter residue, and then dry and crush and grind the filter residue at 105°C. Screen it with a 100 mesh sieve, discard the material on the sieve, and take the material under the sieve to obtain the washed fly ash.

[0102] (4) The modified desulfurized gypsum and the washed fly ash were mixed at a mass ratio of 40:80 to obtain modified desulfurized gypsum with fly ash as the carrier.

[0103] (5) Lanthanum sulfate and pure water were mixed at a mass ratio of 1:150 to obtain a lanthanum-based aqueous solution. Then, the modified desulfurized gypsum with fly ash as the carrier and the lanthanum-based aqueous solution were mixed at a solid-liquid ratio of 1 mg:3 mL. The mixture was stirred and reacted at a constant temperature for 1 h under water bath heating to 50 °C. Then, it was soaked for 24 h and filtered to obtain filter residue. The filter residue was transferred to an oven at 105 °C and dried for 2 h. Then, it was calcined at a constant temperature in a muffle furnace at 250 °C for 20 min. The calcination heating rate was 2 °C / min. After calcination, it was placed in a desiccator and allowed to cool naturally before grinding to obtain the self-assembled modified composite material.

[0104] Example 4

[0105] This embodiment provides a self-assembly modified composite material, which includes modified desulfurized gypsum with fly ash as a carrier, and lanthanum-based material that self-assembles and adsorbs onto the fly ash.

[0106] The self-assembled modified composite material has a microspherical structure and a particle size D50 of 30 μm.

[0107] Based on the mass of the self-assembled modified composite material, the mass fraction of the lanthanum-based material is 5%, and the lanthanum-based material is lanthanum sulfate;

[0108] Based on the mass of the modified desulfurization gypsum with fly ash as the carrier, the mass fraction of the modified desulfurization gypsum is 33%, the fly ash has a porous structure, and the porosity of the fly ash is 65%.

[0109] This embodiment also provides a method for preparing the above-mentioned self-assembled modified composite material, the method comprising the following steps:

[0110] (1) Dry the desulfurized gypsum raw material at 105°C, then grind it to 100 mesh. Then mix the ground desulfurized gypsum raw material and pure water at a mass ratio of 1:3 to make a slurry. Heat the slurry in a water bath to 80°C and stir and wash for 30 minutes. Then filter to obtain filter residue. Then dry and crush and grind the filter residue at 105°C. Screen it with a 100 mesh sieve. Discard the material on the sieve and take the material under the sieve to obtain the desulfurized gypsum after water washing.

[0111] (2) The desulfurized gypsum washed with water was mixed with 98% sulfuric acid and water at a mass ratio of 1:2:18. The mixture was stirred and kept at a constant temperature for 2 hours under the condition of heating to 85°C in a water bath. Then the filter residue was obtained by suction filtration. Subsequently, the filter residue was dried and crushed and ground at 105°C. It was then sieved with a 100-mesh sieve. The material on the sieve was discarded, and the material under the sieve was taken to obtain the modified desulfurized gypsum.

[0112] (3) Dry the fly ash at 105°C, then grind it to 100 mesh. Then mix the ground fly ash and pure water at a mass ratio of 1:3 to make a slurry. Heat the slurry in a water bath to 55°C and stir and wash for 30 minutes. Then filter to obtain filter residue. Then dry and crush and grind the filter residue at 105°C. Screen it with a 100 mesh screen. Discard the material on the screen and take the material under the screen to obtain the washed fly ash.

[0113] (4) The modified desulfurized gypsum and the washed fly ash were mixed at a mass ratio of 10:100 to obtain modified desulfurized gypsum with fly ash as the carrier.

[0114] (5) Lanthanum sulfate and pure water were mixed at a mass ratio of 1:200 to obtain a lanthanum-based aqueous solution. Then, the modified desulfurized gypsum with fly ash as the carrier and the lanthanum-based aqueous solution were mixed at a solid-liquid ratio of 0.8 mg:6 mL. The mixture was stirred and kept at a constant temperature for 1 h under water bath heating to 50 °C. Then, it was soaked for 48 h and filtered to obtain filter residue. The filter residue was transferred to an oven at 105 °C and dried for 2 h. Then, it was calcined at a constant temperature in a muffle furnace at 250 °C for 40 min. The calcination heating rate was 2 °C / min. After calcination, it was placed in a desiccator and allowed to cool naturally before grinding to obtain the self-assembled modified composite material.

[0115] Example 5

[0116] This embodiment provides a self-assembly modified composite material, which includes modified desulfurized gypsum with fly ash as a carrier, and lanthanum-based material that self-assembles and adsorbs onto the fly ash.

[0117] The self-assembled modified composite material has a microspherical structure and a particle size D50 of 20 μm.

[0118] Based on the mass of the self-assembled modified composite material, the mass fraction of the lanthanum-based material is 10%, and the lanthanum-based material is lanthanum sulfate;

[0119] Based on the mass of the modified desulfurization gypsum with fly ash as the carrier, the mass fraction of the modified desulfurization gypsum is 33%, the fly ash has a porous structure, and the porosity of the fly ash is 65%.

[0120] This embodiment also provides a method for preparing the above-mentioned self-assembled modified composite material, the method comprising the following steps:

[0121] (1) The desulfurized gypsum raw material is dried at 105°C and then ground to 100 mesh. The ground desulfurized gypsum raw material and pure water are mixed at a mass ratio of 1:5 to form a slurry. The slurry is heated to 80°C in a water bath and stirred and washed for 30 minutes. The slurry is then filtered to obtain filter residue. The filter residue is then dried and crushed and ground at 105°C. The residue is sieved with a 100-mesh sieve. The material on the sieve is discarded, and the material under the sieve is taken to obtain the desulfurized gypsum after washing.

[0122] (2) The desulfurized gypsum washed with water was mixed with 98% sulfuric acid and water at a mass ratio of 1:5:45. The mixture was stirred and kept at a constant temperature for 2 hours under the condition of heating to 85°C in a water bath. Then the filter residue was obtained by suction filtration. Subsequently, the filter residue was dried and crushed and ground at 105°C. It was then sieved with a 100-mesh sieve. The material on the sieve was discarded, and the material under the sieve was taken to obtain the modified desulfurized gypsum.

[0123] (3) Dry the fly ash at 105°C, then grind it to 100 mesh. Then mix the ground fly ash and pure water at a mass ratio of 1:5 to make a slurry. Heat the slurry in a water bath to 50°C and stir and wash for 30 minutes. Then filter to obtain filter residue. Then dry and crush and grind the filter residue at 105°C. Screen it with a 100 mesh screen. Discard the material on the screen and take the material under the screen to obtain the washed fly ash.

[0124] (4) The modified desulfurized gypsum and the washed fly ash were mixed at a mass ratio of 60:60 to obtain modified desulfurized gypsum with fly ash as the carrier.

[0125] (5) Lanthanum sulfate and pure water were mixed at a mass ratio of 2:100 to obtain a lanthanum-based aqueous solution. Then, the modified desulfurized gypsum with fly ash as the carrier and the lanthanum-based aqueous solution were mixed at a solid-liquid ratio of 1.2 mg:2 mL. The mixture was stirred and kept at a constant temperature for 1 h under water bath heating to 50 °C. Then, it was soaked for 24 h and filtered to obtain filter residue. The filter residue was transferred to an oven at 105 °C and dried for 2 h. Then, it was calcined at a constant temperature in a muffle furnace at 250 °C for 40 min. The calcination heating rate was 2 °C / min. After calcination, it was placed in a desiccator and allowed to cool naturally before grinding to obtain the self-assembled modified composite material.

[0126] Figure 1 The SEM image of the self-assembled modified composite material prepared in this embodiment is shown. As can be seen from the figure, the particle size of the self-assembled modified composite material is 20 μm, and there are many small micropores on its surface. It can also be observed that particulate material is adsorbed on the surface of the microspheres, indicating that the lanthanum-based material is self-assembled and adsorbed onto the modified desulfurized gypsum with fly ash as the carrier.

[0127] Example 6

[0128] The difference between this embodiment and embodiment 5 is that the amount of lanthanum-based aqueous solution added in step (5) is adjusted so that the mass fraction of lanthanum-based material in the self-assembled modified composite material is 0.5%.

[0129] The remaining preparation methods and parameters are consistent with those in Example 5.

[0130] Example 7

[0131] The difference between this embodiment and embodiment 5 is that the amount of lanthanum-based aqueous solution added in step (5) is adjusted so that the mass fraction of lanthanum-based material in the self-assembled modified composite material is 20%.

[0132] The remaining preparation methods and parameters are consistent with those in Example 5.

[0133] Example 8

[0134] The difference between this embodiment and embodiment 5 is that the amount of modified desulfurized gypsum added in step (4) is adjusted so that the mass fraction of modified desulfurized gypsum in the fly ash-based modified desulfurized gypsum is 5%. The remaining preparation methods and parameters are the same as in embodiment 5.

[0135] Example 9

[0136] The difference between this embodiment and embodiment 5 is that the amount of modified desulfurized gypsum added in step (4) is adjusted so that the mass fraction of modified desulfurized gypsum in the modified desulfurized gypsum with fly ash as carrier is 75%.

[0137] The remaining preparation methods and parameters are consistent with those in Example 5.

[0138] Example 10

[0139] The difference between this embodiment and embodiment 5 is that the roasting temperature in step (5) is 150°C.

[0140] The remaining preparation methods and parameters are consistent with those in Example 5.

[0141] Example 11

[0142] The difference between this embodiment and embodiment 5 is that the roasting temperature in step (5) is 450°C.

[0143] The remaining preparation methods and parameters are consistent with those in Example 5.

[0144] Comparative Example 1

[0145] The difference between this comparative example and Example 5 is that a lanthanum-based aqueous solution is not prepared in step (5), that is, lanthanum sulfate is not self-assembled onto the modified desulfurized gypsum with fly ash as the carrier.

[0146] The remaining preparation methods and parameters are consistent with those in Example 5.

[0147] Comparative Example 2

[0148] The difference between this comparative example and Example 5 is that steps (1) and (2) are not performed, that is, modified desulfurized gypsum is not prepared, but fly ash and lanthanum-based aqueous solution are directly mixed.

[0149] The remaining preparation methods and parameters are consistent with those in Example 5.

[0150] Comparative Example 3

[0151] The difference between this comparative example and Example 5 is that step (3) is omitted, i.e., fly ash is not added, and instead the modified desulfurized gypsum and lanthanum-based aqueous solution are directly mixed.

[0152] The remaining preparation methods and parameters are consistent with those in Example 5.

[0153] Performance testing

[0154] Take 2g of the self-assembled composite material obtained in the above examples and the composite material obtained in the comparative example, and add them to 100mL of wastewater (TP concentration of 266.90mg / L and fluoride ion concentration of 258.6mg / L) to conduct defluorination and phosphorus removal effect experiments. The analysis and detection results of wastewater before and after treatment are shown in Table 1 below.

[0155] Table 1

[0156]

[0157]

[0158] analyze:

[0159] As shown in Table 1 above, the self-assembled modified composite material prepared in this disclosure can be widely used in wastewater treatment. With the addition of this composite material, the best phosphorus removal efficiency can reach 99.9%; at the same time, it also has a good defluorination effect.

[0160] As can be seen from Examples 5 and 6-7, if the mass fraction of lanthanum-based material in the self-assembled modified composite material is too small, the lanthanum salt content in the composite material will be low, which will lead to a decrease in the performance of the composite material. If the mass fraction of lanthanum-based material in the self-assembled modified composite material is too large, due to its low solubility, it still cannot be effectively self-assembled onto the modified desulfurized gypsum with fly ash as the carrier, which will result in no significant change or improvement in its material performance, and at the same time, it will cause a waste of lanthanum-based material.

[0161] As can be seen from Examples 5 and 8-9, if the mass fraction of modified desulfurized gypsum in the modified desulfurized gypsum with fly ash as the carrier is too small, the calcium content participating in the reaction precipitation for defluorination will be less, which will lead to a decrease in the performance of the composite material and a poor defluorination effect. If the mass fraction of modified desulfurized gypsum in the modified desulfurized gypsum with fly ash as the carrier is too large, the content of slightly soluble calcium sulfate will be too high, the defluorination reaction precipitation will be incomplete, and the adsorption performance of the composite material will be reduced.

[0162] As can be seen from Examples 5 and 10-11, if the calcination temperature is too low, the composite material cannot be effectively sphericalized, which will lead to a significant reduction in material performance; if the calcination temperature is too high, some substances in the composite material will decompose, which will also lead to a significant reduction in material performance.

[0163] As can be seen from Example 5 and Comparative Example 1, if lanthanum sulfate is not self-assembled onto the modified desulfurized gypsum with fly ash as a carrier, the effective material content will be low, which will lead to a decrease in the wastewater treatment performance of the composite material.

[0164] As can be seen from Example 5 and Comparative Example 2, if modified desulfurization gypsum is not prepared, and fly ash and lanthanum-based aqueous solution are directly mixed, the coagulation and sedimentation effect is poor, which will lead to a decrease in the wastewater treatment performance of the composite material.

[0165] As can be seen from Example 5 and Comparative Example 3, if fly ash is not added and the modified desulfurization gypsum and lanthanum-based aqueous solution are directly mixed, the adsorption performance will decrease, which will lead to a decrease in the wastewater treatment performance of the composite material.

[0166] In summary, the self-assembled composite material prepared in Example 5 showed good phosphorus and fluoride removal effects. Further, this composite material was prepared according to Example 5, and gradient experiments were conducted using materials of different masses. The material was added to 100 mL of wastewater (TP concentration of 266.90 mg / L and fluoride ion concentration of 258.6 mg / L) to conduct fluoride and phosphorus removal effect experiments. The analytical results before and after wastewater treatment are shown in Table 2 below.

[0167] Table 2

[0168]

[0169]

[0170] analyze:

[0171] As shown in Table 2 above, the self-assembled modified composite material prepared in this disclosure can be widely used in wastewater treatment. The wastewater treatment effect is better as the mass of the composite material increases. When 2g is added, the phosphorus removal efficiency is the highest, reaching 99.9%, and it also has a good defluorination effect.

[0172] Meanwhile, a self-assembled modified composite material was further prepared according to Example 5 and applied to high-concentration phosphorus and fluoride-containing wastewater. Gradient experiments were conducted using materials of different masses. The material was added to 100 mL of wastewater (TP concentration of 2266.00 mg / L and fluoride ion concentration of 2152.00 mg / L) to conduct experiments on the defluorination and phosphorus removal effects. The analysis and detection results before and after wastewater treatment are shown in Table 3 below.

[0173] Table 3

[0174]

[0175] analyze:

[0176] As shown in Table 3 above, for high-concentration wastewater with phosphorus and fluoride content of about 2200 mg / L, the addition of this composite material can reduce the total phosphorus to below 0.5 mg / L, and the phosphorus removal efficiency can reach 99.9%. At the same time, the composite material also has a good removal effect on fluoride, and under optimal conditions, the fluoride ion removal rate can reach 98%.

Claims

1. A self-assembled modified composite material, comprising a modified desulfurization gypsum with fly ash as a carrier, and a lanthanum-based material self-assembled and adsorbed on the fly ash; The preparation method of the modified desulfurization gypsum comprises: The desulfurization gypsum raw material is subjected to water washing treatment, and then the water-washed desulfurization gypsum and a sulfuric acid aqueous solution are mixed to perform a water bath heating reaction, so as to obtain the modified desulfurization gypsum.

2. The self-assembled modified composite material of claim 1, wherein, The self-assembled modified composite material is in a microspherical structure.

3. The self-assembled modified composite material of claim 1, wherein, The particle size D50 of the self-assembled modified composite material is 10-100 μm.

4. The self-assembled modified composite material of claim 1, wherein, The mass fraction of the lanthanum-based material is 1%-10% based on the mass of the self-assembled modified composite material.

5. The self-assembled modified composite material of claim 1, wherein, The lanthanum-based material comprises any one or a combination of at least two of lanthanum sulfate, lanthanum nitrate or lanthanum chloride.

6. The self-assembled modified composite material of claim 1, wherein, The mass fraction of the modified desulfurization gypsum with fly ash as a carrier is 10%-50% based on the mass of the modified desulfurization gypsum with fly ash as a carrier.

7. The self-assembled modified composite material of claim 1, wherein, The fly ash is in a porous structure, and the porosity of the fly ash is 50%-80%. 8.A preparation method of the self-assembled modified composite material according to any one of claims 1-7, comprising the following steps: The modified desulfurization gypsum with fly ash as a carrier and a lanthanum-based aqueous solution are mixed to perform a hydrothermal reaction, and the self-assembled modified composite material is obtained after calcination; The preparation method of the modified desulfurization gypsum comprises: The desulfurization gypsum raw material is subjected to water washing treatment, and then the water-washed desulfurization gypsum and a sulfuric acid aqueous solution are mixed to perform a water bath heating reaction, so as to obtain the modified desulfurization gypsum.

9. The production method according to claim 8, wherein The solid-liquid ratio of the modified desulfurization gypsum with fly ash as a carrier and the lanthanum-based aqueous solution is (0.8-1.2) mg:(2-6) mL.

10. The production method according to claim 8, wherein The mass ratio of solute and solvent in the lanthanum-based aqueous solution is (1-2):(100-200).

11. The production method according to claim 8, wherein The temperature of the hydrothermal reaction is 35-65 ℃, and the time is 1-2 h.

12. The method of making according to claim 8, wherein, The temperature of the calcination is 200-400 ℃, and the time is 20-60 min.

13. The method of making according to claim 8, wherein, The mass ratio of the water-washed desulfurization gypsum and the sulfuric acid aqueous solution is 1:(20-50).

14. The production method according to claim 8, wherein The temperature of the water bath heating reaction is 80-90 ℃, and the time is 1-2 h.

15. The method of making according to claim 8, wherein, The preparation method of the modified desulfurization gypsum with fly ash as a carrier comprises: The modified desulfurization gypsum and the fly ash are mixed to obtain the modified desulfurization gypsum with fly ash as a carrier.

16. The method of manufacturing according to claim 15, wherein, The mass ratio of the modified desulfurization gypsum and the fly ash is (10-60):(60-100).

17. The method of making according to claim 15, wherein, Before the fly ash is mixed with the modified desulfurization gypsum, the fly ash is subjected to water washing treatment.

18. The method of making according to claim 8, wherein, The preparation method comprises the following steps: (1) The desulfurization gypsum raw material is dried at 100-120 ℃, and then ground to a mesh number of 100-200 mesh. Then, the ground desulfurization gypsum raw material and water are mixed according to a mass ratio of 1:(3-5) to prepare a pulp, and stirred and washed at 70-90 ℃ for 20-40 min. Then, the filter residue is obtained by filtration. Subsequently, the filter residue is dried at 100-120 ℃ and crushed and sieved to obtain the water-washed desulfurization gypsum. (2) mixing the water-washed desulfurization gypsum and the aqueous solution of sulfuric acid according to a mass ratio of 1:(20-50), and carrying out water bath heating reaction at 80-90°C under stirring for 1-2h, then filtering to obtain filter residue, and then drying and crushing the filter residue at 100-120°C to obtain modified desulfurization gypsum; (3) drying fly ash at 100-120°C, grinding to a mesh number of 100-200, mixing the ground fly ash and water according to a mass ratio of 1:(3-5) to prepare slurry, and stirring and washing at 45-55°C for 30-50min, then filtering to obtain filter residue, and then drying and crushing the filter residue at 100-120°C to obtain water-washed fly ash; (4) mixing the modified desulfurization gypsum and the water-washed fly ash according to a mass ratio of (10-60):(60-100) to obtain modified desulfurization gypsum with fly ash as carrier; (5) mixing lanthanum sulfate and water according to a mass ratio of (1-2):(100-200) to obtain lanthanum-based aqueous solution, then mixing the modified desulfurization gypsum with fly ash as carrier and the lanthanum-based aqueous solution according to a solid-liquid ratio of (0.8-1.2)mg:(2-6)mL, and carrying out hydrothermal reaction at 35-65°C for 1-2h, then carrying out soaking treatment for 24-48h, filtering to obtain filter residue, transferring the filter residue to an oven at 100-120°C for drying for 2-4h, then constant-temperature calcining in a muffle furnace at 200-400°C for 20-60min, the heating rate of calcining is 2-3°C / min, after calcining, cooling and grinding to obtain the self-assembled modified composite material.

19. Application of the self-assembled modified composite material according to any one of claims 1-7 in the field of water treatment technology.

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