Composite phosphorus removal material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of water treatment agents, and particularly discloses a composite phosphorus removal material and a preparation method and application thereof. The method comprises the following steps: adding biomass, palygorskite, starch and a first cross-linking agent into water, and carrying out first reaction to obtain a first cross-linked body solution; adjusting the pH value of the first cross-linking body solution to be alkalescent, adding chitosan, a second cross-linking agent and an initiator, carrying out a second reaction, and freeze-drying the obtained solid to obtain a second cross-linking body; and adding the second crosslinking body and a surfactant into a mixed solution containing rare metal salt and inorganic metal salt, stirring and dipping to obtain the composite phosphorus removal material. Biomass, palygorskite and starch are used as main materials of an adsorption carrier, chitosan is grafted to improve the adsorption performance, rare metal salt and inorganic metal salt are used as active components, and the phosphorus removal effect is improved; in the preparation process, a pyrolysis process is not needed, reaction conditions are mild, and the method has the advantages of low carbon, environmental protection, low equipment requirement and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment agents, and in particular to a composite phosphorus removal material and a preparation method and application thereof. Background Art

[0002] At present, phosphide pollution has become one of the serious environmental problems in water bodies. As a common pollutant in wastewater, the presence of phosphide can lead to eutrophication of water bodies, algae outbreaks and water quality deterioration. Wastewater phosphorus removal technology is mainly divided into two categories: biological phosphorus removal and physicochemical phosphorus removal. Physicochemical phosphorus removal can be divided into chemical precipitation, electrocoagulation, crystallization, adsorption and the like. Among them, adsorption phosphorus removal technology has been widely used in phosphorus removal due to its large capacity, rich adsorbent active points, low energy consumption, low pollution, high efficiency, fast, easy operation, recyclable and low cost. Adsorption phosphorus removal technology uses certain porous or large specific surface area materials to achieve the phosphorus removal process of wastewater mainly through surface precipitation, ion exchange or attachment adsorption of phosphorus on the surface of the adsorbent. On the other hand, my country's phosphate resources are not sufficient. Due to the large application of phosphate fertilizers in agriculture, phosphate resources are relatively tight. Therefore, it is necessary to take an effective measure to recycle phosphorus while controlling the phosphorus element in wastewater.

[0003] At present, inorganic metal compounds are generally used as dephosphorization agents, such as the method of using calcium salts, iron salts and aluminum salts to generate insoluble phosphate precipitates with metal ions and phosphate to remove phosphorus from wastewater. Metal oxides, metal hydroxides and metal salts of metal elements such as iron, lanthanum and zirconium can also be used to adsorb and recover phosphorus through ligand exchange, hydrogen bonding, Lewis acid-base action and surface precipitation. However, the adsorption capacity and adsorption efficiency of existing dephosphorization adsorbents still need to be improved. Summary of the invention

[0004] In view of the above problems, the present invention provides a composite phosphorus removal material and a preparation method and application thereof. The present invention uses biomass, palygorskite and starch as the main materials of the adsorption carrier, and then grafts chitosan to improve the adsorption performance. Rare metal salts and inorganic metal salts are used as active components to improve the interaction with the phosphorus element, thereby further improving the phosphorus removal effect.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing a composite phosphorus removal material, comprising the following steps: S1, adding biomass, palygorskite, starch and a first cross-linking agent into water, and performing a first reaction at 65° C. to 85° C. to obtain a first cross-linked body solution; S2, adjusting the pH value of the first cross-linked body solution to be weakly alkaline, adding chitosan, a second cross-linking agent and an initiator, performing a second reaction at 70° C. to 90° C., and freeze-drying the obtained solid to obtain a second cross-linked body; S3, adding the second cross-linked body and the surfactant into a mixed solution containing rare metal salts and inorganic metal salts, stirring and impregnating, and obtaining a composite phosphorus removal material.

[0006] Compared with the prior art, the preparation method of the composite phosphorus removal material provided by the present invention adopts a first cross-linking agent to cross-link biomass, palygorskite and starch at a specific temperature. In the first reaction process, the biomass, palygorskite and starch are continuously interlaced and cross-linked to form an adsorption carrier material similar to a three-dimensional network, and the specific surface area is increased to form an organic whole; in addition, in the first reaction process, starch (including starch in biomass) is gelatinized under the action of hot water, and absorbs a large amount of water, gradually expands, and forms a large pore-forming filling body; then, under weak alkali and specific temperature conditions, the biomass and starch on the first cross-linked body undergo a graft cross-linking reaction with chitosan, and the specific surface area is further increased, and the rich amino functional groups provide adsorption sites for adsorbing phosphorus in water, which is combined with cellulose. The hydrogen bonding effect of the hydroxyl groups on the upper cross-linked body and the alcoholic hydroxyl groups on the starch further improves the binding ability and adsorption effect with the phosphorus element; while removing the moisture in the obtained solid by freeze-drying, the gelatinization effect of the starch disappears, its volume is greatly reduced, and a large number of narrow internal pores are formed, which improves the adsorption performance of the composite phosphorus removal material; finally, the second cross-linked body is immersed in a mixed solution containing active components (rare metal salts and inorganic metal salts). Under the action of surfactants, the rare metal salts and inorganic metal salts are uniformly absorbed into the second cross-linked body. The rare metal salts and inorganic metal salts can adsorb and recover the phosphorus element in the wastewater through ligand exchange, hydrogen bonding, Lewis acid-base action and surface precipitation, which further improves the adsorption efficiency of the composite phosphorus removal material and improves the phosphorus removal effect.

[0007] The present invention uses biomass, palygorskite and starch as the main materials of the adsorption carrier, and then grafts chitosan to improve the adsorption performance. Rare metal salts and inorganic metal salts are used as active components to improve the interaction with phosphorus elements and further improve the phosphorus removal effect. Biomass is a renewable and low-pollution resource with diverse components, mainly including organic polymer substances such as cellulose, lignin, hemicellulose, starch, oil, sugar, aldehydes, etc., which has the characteristics of being renewable and biodegradable. Its products can enter the natural cycle again and are an important renewable resource; palygorskite itself has a large specific surface area and adsorption capacity, and has certain rheological properties and catalytic properties; starch can adsorb many organic compounds and inorganic compounds, and starch is also biodegradable. In addition, starch also has the performance of heating gelatinization. The present invention uses starch as a pore-forming agent, and through heating gelatinization and freeze drying, the internal voids of the composite phosphorus removal material are expanded, and the specific surface area and adsorption capacity are further improved. Chitosan is biodegradable, and the reaction activity of the amino group in its molecular structure is strong, and chemical modification reactions can be carried out to increase the active sites of the adsorption carrier.

[0008] The preparation method of the composite phosphorus removal material provided by the present invention does not require a pyrolysis process during the preparation process, has mild reaction conditions, has the advantages of being low-carbon and environmentally friendly, having low equipment requirements and low cost, and has high market application value.

[0009] Preferably, in S1, the biomass is selected from plant straw, branches, waste wood or flowers and plants.

[0010] For example, in S1, the biomass needs to be acid-leached first to remove impurities such as ash and organic matter on the surface and inside of the biomass, and further improve the purity of the biomass. The present invention does not limit the specific conditions of acid leaching, and conventional operations in the art can be used.

[0011] Preferably, in S1, the starch is selected from at least one of corn starch, tapioca starch or wheat starch.

[0012] The preferred starch of the present invention contains both straight-chain starch and branched-chain starch, which have different adsorption properties and can form crystalline complexes with phosphorus in wastewater to precipitate, thus producing a certain adsorption and removal effect.

[0013] Preferably, in S1, the first cross-linking agent is N,N'-methylenebisacrylamide.

[0014] Preferably, in S1, the mass volume ratio of the biomass, the palygorskite, the starch, the first cross-linking agent and the water is (65~75)g:(10~15)g:(15~20)g:(18~25)g:(0.8~1.2)L.

[0015] By limiting the amount of each substance in S1, the present invention can better control the morphology of the obtained first cross-linked body and the subsequent second cross-linked body, and maximize the cross-linking effect and specific surface area. The present invention uses starch as a pore-forming agent, and can obtain a high porosity with a relatively low amount of pore-forming agent starch added, and the internal voids are relatively narrow, which greatly increases the specific surface area of ​​the composite phosphorus removal material.

[0016] Preferably, in S1, the time of the first reaction is 5 h to 6 h.

[0017] Preferably, in S2, ammonia water is used to adjust the pH value of the first cross-linked body solution to 8-9.

[0018] The present invention performs the second reaction under specific weakly alkaline conditions (pH=8-9), which is conducive to cross-linking of chitosan and the first cross-linker.

[0019] Preferably, in S2, the second cross-linking agent is a silane coupling agent, and the initiator is ammonium sulfite.

[0020] For example, in S2, the silane coupling agent is KH-550‌.

[0021] Preferably, in S2, the mass volume ratio of the first cross-linked body solution, the chitosan, the second cross-linking agent and the initiator is (0.8~1.2)L:(30~40)g:(3~5)g:(2~4)g.

[0022] Preferably, in S2, the time of the second reaction is 1 h to 2 h.

[0023] For example, in S2, crushing is required after freeze drying.

[0024] The present invention can better graft a specific amount of chitosan onto the first cross-linked body by limiting the conditions of the second reaction. At the same time, since the first reaction time is short, under specific temperature conditions, biomass, palygorskite, starch, chitosan and cross-linking agent (including the first cross-linking agent and the second cross-linking agent that have not reacted completely) can continue to undergo the second reaction on the basis of the first cross-linked body, further optimizing the structural morphology of the obtained cross-linked body, which is beneficial to improving the specific surface area and porosity of the second cross-linked body after subsequent freeze-drying, and increasing the number of active sites of the second cross-linked body, thereby further improving the adsorption capacity and phosphorus removal effect of the composite phosphorus removal material.

[0025] Preferably, in S3, the rare metal salt is selected from at least one of yttrium salts, lanthanum salts, cerium salts, neodymium salts, titanium salts, zirconium salts or vanadium salts.

[0026] Preferably, in S3, the inorganic metal salt is selected from at least one of aluminum salt, calcium salt or iron salt.

[0027] Further preferably, in S3, the aluminum salt is selected from at least one of aluminum sulfate, aluminum chloride, aluminum silicate or alum.

[0028] Further preferably, in S3, the calcium salt includes at least one of calcium chloride, calcium sulfate, calcium carbonate, calcium hydroxide or calcium oxalate.

[0029] Further preferably, in S3, the iron salt includes at least one of ferric chloride, ferric sulfate or ferric nitrate.

[0030] Preferably, in S3, the surfactant is stearic acid.

[0031] The preferred surfactant in the present invention can increase the surface tension of the system and optimize the distribution state of the rare metal salt and the inorganic metal salt on the second cross-linked body, thereby improving the adsorption effect of the composite phosphorus removal material on phosphorus, and is also beneficial to the subsequent application as a slow-release phosphate fertilizer.

[0032] Preferably, in S3, the mass volume ratio of the second cross-linked body, the surfactant and the mixed solution is 100g:(3~5)g:(1~1.2)L.

[0033] Preferably, in S3, the concentration of the rare metal salt in the mixed solution is 1.25 mol / L to 1.35 mol / L, and the concentration of the inorganic metal salt is 0.6 mol / L to 0.8 mol / L.

[0034] It should be noted that, in the present invention, the concentration of the rare metal salt refers to the concentration of the rare metal ions, and the concentration of the inorganic metal salt refers to the concentration of the inorganic metal ions.

[0035] Preferably, in S3, the temperature of the stirring and immersing is 10° C. to 40° C., and the time is 2 h to 3 h.

[0036] In step S3 of the present invention, high concentrations of rare metal ions and inorganic metal ions are incorporated into the second cross-linked body with a high specific surface area through stirring and impregnation, which is beneficial to the improvement of the subsequent phosphorus removal effect.

[0037] In a second aspect, the present invention provides a composite phosphorus removal material prepared by the composite phosphorus removal material preparation method.

[0038] The composite phosphorus removal material provided by the present invention uses almost all pollution-free raw materials, and the product after phosphorus removal can store phosphorus. The biodegradable properties of cellulose, starch and chitosan can be used as a slow-release phosphate fertilizer to fully utilize the phosphorus in wastewater. In addition, the composite phosphorus removal material also contains certain rare metal salts and inorganic metal salts. The rare metal salts can promote the rooting of crops and improve the emergence rate. The inorganic metal salts can also be used as base fertilizers for crops. The two can jointly promote the nutrient absorption of crops and improve the quality of crops.

[0039] Preferably, the porosity of the composite phosphorus removal material is 70% to 95%.

[0040] In a third aspect, the present invention provides a composite phosphorus removal material prepared by the method for preparing the composite phosphorus removal material or the use of the composite phosphorus removal material in removing phosphorus and fluorine from wastewater or preparing crop fertilizers.

[0041] The phosphorus removal product formed after the composite phosphorus removal material of the present invention absorbs phosphorus can be used as a slow-release phosphorus fertilizer and can be directly put into farmland to achieve controlled slow release of phosphorus. At the same time, it also has a certain repair effect on the soil and has resource recovery and utilization value. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] Example 1 This embodiment provides a method for preparing a composite phosphorus removal material, comprising the following steps: Sa, add the crushed plant straw into an acid solution with a pH of 2 to 4, soak it at room temperature for 8 hours, filter it, wash the solid with water until it is neutral, and obtain biomass.

[0044] Sb, 70g of biomass, 13g of palygorskite, 17g of corn starch and 21g of N,N'-methylenebisacrylamide were added to 1L of water, and a first reaction was carried out at 75°C and kept warm for 5.5h to obtain a first cross-linked body solution.

[0045] Sc, adjust the pH of the first cross-linked body solution to 8.5 with ammonia water, add 35g chitosan, 4g KH-550 and 3g ammonium sulfite, carry out the second reaction at 80°C, keep warm for 1.5h, separate the solid and liquid, freeze-dry the obtained solid, and crush it to obtain the second cross-linked body.

[0046] Sd, take 100g of the second cross-linked body and 4g of stearic acid and add them into 1L of a mixed solution containing 0.7mol / L lanthanum trichloride, 0.6mol / L cerium chloride and 0.7mol / L aluminum chloride, stir and immerse for 2.5h at room temperature to obtain a composite phosphorus removal material.

[0047] According to the test, the porosity of the composite phosphorus removal material in this embodiment is 88%.

[0048] Example 2 This embodiment provides a method for preparing a composite phosphorus removal material, comprising the following steps: Sa, add the crushed branches into an acid solution with a pH of 2 to 4, soak at room temperature for 8 hours, filter, wash the solid with water until it is neutral, and obtain biomass.

[0049] Sb, 72g of biomass, 12g of palygorskite, 18g of corn starch and 22g of N,N'-methylenebisacrylamide were added to 1.1L of water, and a first reaction was carried out at 80°C and kept warm for 5h to obtain a first cross-linked body solution.

[0050] Sc, adjust the pH of the first cross-linked body solution to 9 with ammonia water, add 38g chitosan, 3.5g KH-550 and 2.5g ammonium sulfite, carry out the second reaction at 75°C, keep warm for 2h, separate the solid and liquid, freeze-dry the obtained solid, and crush it to obtain the second cross-linked body.

[0051] Sd, take 100g of the second cross-linked body and 4.5g of stearic acid and add them into 1.2L of a mixed solution containing 0.5mol / L titanium tetrachloride, 0.8mol / L cerium chloride, 0.3mol / L calcium chloride and 0.4mol / L aluminum chloride, stir and immerse for 2.5h at room temperature to obtain a composite phosphorus removal material.

[0052] According to the test, the porosity of the composite phosphorus removal material in this embodiment is 85%.

[0053] Example 3 This embodiment provides a method for preparing a composite phosphorus removal material, comprising the following steps: Sa, add the crushed waste wood into an acid solution with a pH of 2 to 4, soak it at room temperature for 8 hours, filter it, wash the solid with water until it is neutral, and obtain biomass.

[0054] Sb, 75g of biomass, 10g of palygorskite, 20g of cassava starch and 25g of N,N'-methylenebisacrylamide were added to 1.2L of water, and a first reaction was carried out at 85°C and kept warm for 5h to obtain a first cross-linked body solution.

[0055] Sc, adjust the pH of the first cross-linked body solution to 9 with ammonia water, add 40g chitosan, 5g KH-550 and 4g ammonium sulfite, carry out the second reaction at 90°C, keep warm for 1.5h, separate the solid and liquid, freeze-dry the obtained solid, and crush it to obtain the second cross-linked body.

[0056] Sd, take 100g of the second cross-linked body and 5g of stearic acid and add them into 1.2L of a mixed solution containing 0.65mol / L lanthanum trichloride, 0.7mol / L cerium chloride, 0.2mol / L aluminum sulfate and 0.2mol / L ferric sulfate, stir and immerse for 3h at room temperature to obtain a composite phosphorus removal material.

[0057] According to the test, the porosity of the composite phosphorus removal material in this embodiment is 78%.

[0058] Example 4 This embodiment provides a method for preparing a composite phosphorus removal material, comprising the following steps: Sa, add crushed plant straws and flowers with a mass ratio of 2:1 into an acid solution with a pH of 2-4, soak for 8 hours at room temperature, filter, wash the solid with water until it is neutral, and obtain biomass.

[0059] Sb, 65 g of biomass, 15 g of palygorskite, 15 g of wheat starch and 18 g of N,N'-methylenebisacrylamide were added to 0.8 L of water, and a first reaction was carried out at 65°C and kept warm for 6 hours to obtain a first cross-linked body solution.

[0060] Sc, adjust the pH of the first cross-linked body solution to 8 with ammonia water, add 30g chitosan, 3g KH-550 and 2g ammonium sulfite, carry out the second reaction at 70°C, keep warm for 1h, separate the solid and liquid, freeze-dry the obtained solid, and crush it to obtain the second cross-linked body.

[0061] Sd, take 100g of the second cross-linked body and 3g of stearic acid and add them into 1L of a mixed solution containing 1.25mol / L zirconium nitrate, 0.3mol / L ferric nitrate and 0.3mol / L calcium carbonate, stir and immerse for 2h at room temperature to obtain a composite phosphorus removal material.

[0062] According to the test, the porosity of the composite phosphorus removal material in this embodiment is 73%.

[0063] Comparative Example 1 This comparative example provides a preparation method of a composite phosphorus removal material, which is similar to Example 1, except that in Sb, palygorskite is replaced with biomass (plant straw) of equal mass. The remaining conditions are the same as those in Example 1 and will not be repeated. Finally, a composite phosphorus removal material with a porosity of 69% is obtained.

[0064] Comparative Example 2 This comparative example provides a preparation method of a composite phosphorus removal material, which is similar to Example 1, except that in Sb, starch is replaced with biomass (plant straw) of equal mass. The remaining conditions are the same as those in Example 1 and will not be described in detail. Finally, a composite phosphorus removal material with a porosity of 47% is obtained.

[0065] Comparative Example 3 This comparative example provides a preparation method of a composite dephosphorization material, which is similar to Example 1, except that the temperature of the first reaction in Sb is 50°C, and the temperature of the second reaction in Sc is 50°C. The remaining conditions are the same as those in Example 1 and will not be repeated. Finally, a composite dephosphorization material with a porosity of 54% is obtained.

[0066] Comparative Example 4 This comparative example provides a preparation method of a composite phosphorus removal material, which is similar to Example 1, except that: in Sc, hydrochloric acid is used to adjust the pH of the first cross-linked body solution to 6.5. The remaining conditions are the same as those in Example 1 and will not be repeated. Finally, a composite phosphorus removal material with a porosity of 62% is obtained.

[0067] Comparative Example 5 This comparative example provides a preparation method of a composite phosphorus removal material, which is similar to Example 1, except that chitosan and ammonium sulfite are omitted in Sc. The remaining conditions are the same as those in Example 1 and are not repeated here. Finally, a composite phosphorus removal material with a porosity of 60% is obtained.

[0068] Comparative Example 6 This comparative example provides a preparation method of a composite phosphorus removal material, which is similar to Example 1, except that: in Sc, KH-550 is replaced by chitosan of equal mass. The remaining conditions are the same as those in Example 1 and will not be repeated. Finally, a composite phosphorus removal material with a porosity of 65% is obtained.

[0069] Comparative Example 7 This comparative example provides a preparation method of a composite dephosphorization material, which is similar to Example 1, except that stearic acid is omitted in Sd. The remaining conditions are the same as those in Example 1 and are not described in detail. Finally, a composite dephosphorization material with a porosity of 85% is obtained.

[0070] Comparative Example 8 This comparative example provides a preparation method of a composite phosphorus removal material, which is similar to Example 1, except that the Sd step is omitted, and the second cross-linked body is the composite phosphorus removal material. The remaining conditions are the same as those in Example 1 and will not be repeated. Finally, a composite phosphorus removal material with a porosity of 86% is obtained.

[0071] Verification test In order to verify the phosphorus removal effect of the composite phosphorus removal materials provided in Examples 1 to 4 and Comparative Examples 1 to 8 on wastewater, the following test was conducted: high-grade pure potassium dihydrogen phosphate was dried at 110°C for 2h, cooled in a dryer, and 13 portions of phosphorus-containing wastewater (in terms of P) with a concentration of 100 mg / L were prepared, each 1L, as simulated wastewater; 0.5g of each composite phosphorus removal material of the embodiment and the comparative example was taken, and put into 13 portions of simulated wastewater respectively, and put into an oscillator, set the temperature to 25°C, the speed to 200rpm, and oscillate for 8h, then use membrane filtration, and use GB11893-89 ammonium molybdate spectrophotometry to determine the phosphorus content in the filtrate, and calculate the adsorption amount of the adsorbent. The specific results are shown in Table 1.

[0072] Table 1 Comparison of phosphorus removal effects of composite phosphorus removal materials on wastewater

[0073] Corn was used as the research object, and the application effect of the composite phosphorus removal material in the present invention as a crop fertilizer was observed by recording the germination and growth of corn seeds. The composite phosphorus removal material provided in Examples 1 to 4 was placed in industrial sewage containing excessive phosphorus, and phosphorus removal treatment was performed repeatedly until the phosphorus removal material reached a saturated state of phosphorus absorption. The phosphorus removal products in the saturated state of phosphorus absorption were then applied to the same soil as crop fertilizers, and fertilized on the same day after sowing. The blank control group was soil without adding the phosphorus removal product. Three soil samples were used in each group for parallel experiments. When other growth conditions remained consistent, the germination of corn seeds and the average number of subsequent fully expanded leaves were recorded at the same time every day, as shown in Table 2 below.

[0074] Table 2 Seedling and leaf expansion of corn seeds after fertilization

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite phosphorus removal material, characterized in that: The following steps are involved: S1, adding biomass, palygorskite, starch and a first cross-linking agent into water, and performing a first reaction at 65° C. to 85° C. to obtain a first cross-linked body solution; S2, adjusting the pH value of the first cross-linked body solution to be weakly alkaline, adding chitosan, a second cross-linking agent and an initiator, performing a second reaction at 70° C. to 90° C., and freeze-drying the obtained solid to obtain a second cross-linked body; S3, adding the second cross-linked body and the surfactant into a mixed solution containing rare metal salts and inorganic metal salts, stirring and impregnating, and obtaining a composite phosphorus removal material.

2. The method for preparing the composite phosphorus removal material according to claim 1, characterized in that: In S1, the biomass is selected from plant straw, branches, waste wood or flowers and plants; and / or In S1, the starch is selected from at least one of corn starch, tapioca starch or wheat starch; and / or In S1, the first cross-linking agent is N,N'-methylenebisacrylamide.

3. The method for preparing the composite phosphorus removal material according to claim 1, characterized in that: In S1, the mass volume ratio of the biomass, the palygorskite, the starch, the first cross-linking agent and the water is (65-75) g: (10-15) g: (15-20) g: (18-25) g: (0.8-1.2) L; and / or In S1, the time of the first reaction is 5h~6h.

4. The method for preparing the composite phosphorus removal material according to claim 1, characterized in that: In S2, the pH of the first cross-linked body solution is adjusted to 8-9 using aqueous ammonia; and / or In S2, the time of the second reaction is 1h~2h.

5. The method for preparing the composite phosphorus removal material according to claim 1, characterized in that: In S2, the second cross-linking agent is a silane coupling agent, and the initiator is ammonium sulfite; and / or In S2, the mass volume ratio of the first cross-linked solution, the chitosan, the second cross-linking agent and the initiator is (0.8~1.2)L:(30~40)g:(3~5)g:(2~4)g.

6. The method for preparing the composite phosphorus removal material according to claim 1, characterized in that: In S3, the rare metal salt is selected from at least one of yttrium salt, lanthanum salt, cerium salt, neodymium salt, titanium salt, zirconium salt or vanadium salt; and / or In S3, the inorganic metal salt is selected from at least one of aluminum salt, calcium salt or iron salt; and / or In S3, the surfactant is stearic acid.

7. The method for preparing the composite phosphorus removal material according to claim 1, characterized in that: In S3, the mass volume ratio of the second cross-linked body, the surfactant and the mixed solution is 100 g: (3-5) g: (1-1.2) L; and / or In S3, the concentration of the rare metal salt in the mixed solution is 1.25 mol / L to 1.35 mol / L, and the concentration of the inorganic metal salt is 0.6 mol / L to 0.8 mol / L.

8. The method for preparing the composite phosphorus removal material according to claim 1, characterized in that: In S3, the temperature of the stirring and immersing is 10°C to 40°C, and the time is 2h to 3h.

9. A composite phosphorus removal material, characterized in that: The composite phosphorus removal material is prepared by the preparation method of the composite phosphorus removal material according to any one of claims 1 to 8.

10. Use of the composite phosphorus removal material prepared by the preparation method of the composite phosphorus removal material according to any one of claims 1 to 8 or the composite phosphorus removal material according to claim 9 in removing phosphorus and fluorine from wastewater or preparing crop fertilizers.

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