A long-lasting phosphorus removal filler suitable for river, lake and reservoir systems

Abstract

This application relates to a long-lasting phosphorus removal functional packing material suitable for river, lake, and reservoir systems. The preparation method of the functional packing material includes: S100. Carbonization of biomass materials; S200. Preparation of composite powder; S300. Preparation of composite liquid; S400. Preparation of mixed slurry; S500. Casting and curing of the mixed slurry. The functional packing material of this application is prepared from biochar materials and by-products of the iron and steel smelting industry (slag and steel slag). Combined with active component screening, particle size distribution, and high-temperature reverse curing, the functional material achieves effective phosphorus removal under low-concentration pollution conditions. The functional packing material involved in this application has a wider phosphorus removal range and stronger performance, effectively reducing the land area required for constructed wetlands and constructing highly efficient phosphorus removal units.

Description

Technical Field

[0001] This article relates to the field of constructed wetland fillers, and in particular to a functional filler that can achieve deep phosphorus removal, its preparation method, and its application. Background Technology

[0002] According to my country's current surface water environmental quality standards, the total phosphorus concentration in river and lake systems is relatively low (the total phosphorus standards for Class V and Class III rivers are 0.4 and 0.2 mg / L, respectively, and for Class V and Class III lakes and reservoirs are 0.2 and 0.05 mg / L, respectively). When wastewater treatment plants receive wastewater with high concentrations of phosphorus pollution, and the total phosphorus concentration of the treated effluent is in the range of 0.3-0.5 mg / L, connecting it to an constructed wetland treatment system is currently the most economical, stable, and easy-to-maintain combination solution. The selection of the packing material in the constructed wetland system is often a key factor in its further removal of phosphorus pollution.

[0003] Traditional adsorption media typically undergo a rapid adsorption phase, relying on the high affinity of phosphorus to surface active sites driven by a concentration gradient. This is followed by a slow adsorption phase where the adsorption rate drops sharply due to internal diffusion resistance and site saturation. In this situation, after adsorbing a certain concentration of phosphorus, the number of active adsorption sites decreases, and the driving force of the concentration gradient at the solid-liquid interface weakens. As the phosphorus concentration in the initially low-concentration water further decreases, deep phosphorus removal is often impossible. This leads to adsorption media failure, hinders the improvement of functional wetland treatment effects, and fails to effectively prevent phosphorus from entering the natural wetland system, thus increasing the risk of eutrophication.

[0004] To further enhance the removal capacity of low-concentration phosphorus pollution, current methods mainly employ loading lanthanide metals to expand the adsorption threshold of materials, thereby achieving the removal of low-concentration phosphorus. However, the preparation process often requires high temperature and pressure, resulting in complex processes, high energy consumption, and high costs. Constructed wetland packing materials are highly sensitive to cost due to their large usage, high transportation costs, difficult maintenance, high replacement costs, high demand for long-term stability, and insufficient economic benefits inherent in the application scenarios. Therefore, the main bottleneck for their large-scale promotion and application lies in how to prepare more long-term stable packing materials within a lower cost framework. Summary of the Invention

[0005] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of this application.

[0006] To address the aforementioned issues, this invention provides a deep phosphorus removal functional material suitable for river, lake, and reservoir systems, along with its preparation method. This aims to resolve the failure and cost issues of traditional constructed wetland fillers in the removal of low-concentration phosphorus pollution.

[0007] The technical solution provided in this application is as follows: The first aspect of this application provides a method for preparing a functional filler, the method comprising: S100. carbonization of biomass materials; S200. preparation of composite powder; S300. preparation of composite liquid; S400. preparation of mixed slurry; S500. casting and curing of the mixed slurry; The order of steps S200 and S300 is not important.

[0008] In one exemplary embodiment, step S100 includes: carbonizing biomass material under a protective atmosphere or oxygen-deficient conditions to obtain biochar.

[0009] In an exemplary embodiment, in step S100, the biomass material is selected from one or more of rice husks, reeds, corn cobs, corn stalks, and peach shells; optionally, it is straw.

[0010] In one exemplary embodiment, in step S100, the carbonization temperature is 400-800°C and the carbonization time is 1.5-2.5 h; preferably, the carbonization temperature is 600°C and the carbonization time is 2 h.

[0011] In one exemplary embodiment, in step S100, the protective atmosphere is a nitrogen atmosphere.

[0012] In one exemplary embodiment, in step S100, the particle size of the biochar is 150-160 μm, or 75-80 μm, or 35-43 μm.

[0013] In an exemplary embodiment, step S200 includes: mixing the biochar, industrial by-product, and calcium hydroxide to obtain a composite powder; wherein the particle size of the biochar is larger than the particle size of the industrial by-product.

[0014] In an exemplary embodiment, in step S200, the industrial by-product is two or more of slag, steel slag, red mud, fly ash, lithium slag, and gold slag; preferably, the industrial by-product is slag and steel slag.

[0015] In one exemplary embodiment, in step S200, the particle size of the industrial by-product is 150-160 μm, or 75-80 μm, or 35-43 μm.

[0016] In one exemplary embodiment, in step S200, the biochar has a particle size of 150-160 μm, and the industrial by-product has a particle size of 75-80 μm, or 35-43 μm; or The biochar has a particle size of 75-80 μm, and the industrial by-product has a particle size of 35-43 μm.

[0017] In an exemplary embodiment, in step S200, the composite powder contains, by weight percentage, 30%-50% biochar, 20%-50% slag, 1%-25% steel slag, and 10%-20% calcium hydroxide.

[0018] In one exemplary embodiment, in step S200, the composite powder comprises, by weight percentage, 40% biochar, 40% slag, 10% steel slag, and 10% calcium hydroxide; or Biochar 40%, slag 25%, steel slag 25%, calcium hydroxide 10%; or The composition is 40% biochar, 40% slag, 10% steel slag, and 20% calcium hydroxide.

[0019] In one exemplary embodiment, step S300 includes: mixing liquid hydrated sodium silicate and sodium hydroxide to obtain a composite liquid.

[0020] In one exemplary embodiment, in step S300, the composite liquid contains 70%-80% liquid hydrated sodium silicate and 20%-30% sodium hydroxide by weight percentage.

[0021] In one exemplary embodiment, in step S300, the composite liquid contains 80% liquid hydrated sodium silicate and 20% sodium hydroxide by weight percentage.

[0022] In one exemplary embodiment, step S300 further includes a heating step of the mixture; Optionally, the heating temperature is 50-70°C; preferably, it is 60°C.

[0023] In one exemplary embodiment, step S400 includes: mixing the composite powder and the composite liquid, stirring, to form a mixed slurry.

[0024] In one exemplary embodiment, in step S400, the composite powder comprises 55%-65% by weight and the composite liquid comprises 45%-35%.

[0025] In one exemplary embodiment, in step S400, the composite powder comprises 65% by weight and the composite liquid comprises 35%.

[0026] In one exemplary embodiment, in step S400, the stirring speed is 100-300 rpm and the stirring time is 5-7 minutes; preferably, the stirring speed is 100 rpm and the stirring time is 5 minutes.

[0027] In one exemplary embodiment, step S500 includes: after the mixed slurry is poured into a mold, cured, and demolded, it undergoes high-temperature reverse curing in air, and then cooled to room temperature for molding; specifically: The mixed slurry is injected into a mold and sealed. The mold is then transferred to a curing chamber for curing and demolding. After demolding, the mold is exposed to air and transferred to a forced-air drying oven for high-temperature reverse curing. After high-temperature reverse curing, the sample is cooled to room temperature and stored in a cool, dry, and sealed environment for later use.

[0028] In one exemplary embodiment, in step S500, the curing temperature is 60-80°C and the curing time is 2-4 hours; preferably, the curing temperature is 70°C and the curing time is 3 hours.

[0029] In one exemplary embodiment, in step S500, the temperature of the high-temperature reverse curing is 90-110°C, and the high-temperature reverse curing time is 1-2 hours; preferably, the temperature of the high-temperature reverse curing is 100°C, and the curing time is 1 or 2 hours.

[0030] In one exemplary embodiment, the method further includes a raw material pretreatment step, comprising grinding and sieving the biochar and the industrial by-product respectively before use; Optionally, the grinding device is a ball mill; Optionally, grinding media are also added during the grinding process; Optionally, the grinding media is a steel ball or zirconium oxide.

[0031] In one exemplary embodiment, in the pretreatment step, the amount of material loaded in the ball mill is 40%-70% of the grinding jar capacity.

[0032] In one exemplary embodiment, in the pretreatment step, the amount of grinding media is 20%-40% of the capacity of the grinding jar; In one exemplary embodiment, in the pretreatment step, the ball mill rotates at 200-300 rpm and grinds for 1.5-2.5 hours; preferably, the rotation speed is 300 rpm and the grinding time is 2 hours.

[0033] In one exemplary embodiment, the pretreatment step involves sieving through a multi-stage sieve, specifically: Particles with a diameter of 150-160 μm are screened using 100-mesh and 90-mesh sieves, particles with a diameter of 75-80 μm are screened using 180-mesh and 200-mesh sieves, and particles with a diameter of 35-43 μm are screened using 325-mesh and 400-mesh sieves.

[0034] In one exemplary embodiment, the pretreatment step of the biochar includes: loading the biochar into a ball mill, with the loading amount being 50%-70% of the grinding jar capacity; adding steel balls as grinding media, the steel balls having a diameter of 10 mm and the steel ball loading amount being 30% of the grinding jar capacity; and sieving after grinding.

[0035] In one exemplary embodiment, the pretreatment step of the industrial by-product includes: loading the industrial by-product into a ball mill, with the loading amount being 40% of the grinding jar capacity; adding 10 mm diameter zirconium oxide as grinding media, with the zirconium oxide loading amount being 25% of the grinding jar capacity; and sieving after grinding.

[0036] The second aspect of this application provides a functional filler prepared by the above method.

[0037] In one exemplary embodiment, the mechanical strength of the functional filler is 38-45 MPa.

[0038] The third aspect of this application provides the use of the above-mentioned functional packing material as a packing material for achieving low-concentration phosphorus removal in river, lake and reservoir systems.

[0039] In one exemplary embodiment, the initial total phosphorus concentration in the river, lake, and reservoir system is ≤0.4 mg / L (preferably 0.2-0.4 mg / L); after phosphorus removal using the functional packing material, the total phosphorus concentration in the river, lake, and reservoir system is ≤0.05 mg / L, and the total phosphorus removal rate is 100%.

[0040] Compared with existing related technologies, the beneficial effects of this application are as follows: (1) The deep phosphorus removal functional packing material applicable to river, lake and reservoir systems involved in this application can purify Class V (total phosphorus concentration = 0.2 mg / L) lakes and reservoirs to Class III (total phosphorus concentration = 0.05 mg / L) under low concentration phosphorus pollution conditions, thereby further achieving deep purification of water bodies and reducing the diffusion of phosphorus into river, lake and reservoir systems.

[0041] (2) The phosphorus removal packing material of this application utilizes a stable inorganic composite gel structure to ensure the loading of excessive calcium-based active phosphorus removal function, ensuring the long-term effectiveness of the material and preventing rapid release in the short term. This can significantly reduce the replacement cycle of wetland packing material and avoid increased operation and maintenance costs and disturbance of effluent water quality caused by packing material replacement. (3) It mainly uses low-cost industrial by-products that are rich in iron and calcium, combined with the addition of relatively inexpensive calcium-based and iron-based components, to achieve effective removal of phosphorus. Compared with loading lanthanide metals, it greatly reduces the preparation cost and reduces the risk of lanthanide metals migrating into the natural environment. As a wetland filler, it can be more accepted by users. (4) In the preparation and application process, the functional filler involved in this application utilizes the gradation combination between biochar material and industrial by-product material to enhance the phosphorus removal function of the material. The stability of the molding structure is controlled by the particle size difference, which not only ensures the full contact between calcium-based and iron-based active components and phosphorus pollution in water, but also ensures that the material has good mechanical stability.

[0042] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application may be realized and obtained by means of the methods described in the description. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0044] This application provides a method for preparing a functional filler, the method comprising: S100. carbonization of biomass materials; S200. preparation of composite powder; S300. preparation of composite liquid; S400. preparation of mixed slurry; S500. curing and molding of mixed slurry; The order of steps S200 and S300 is not important.

[0045] In this embodiment of the application, step S100 includes: carbonizing the biomass material under a protective atmosphere to obtain biochar.

[0046] In this embodiment of the application, in step S100, the biomass material is selected from one or more of rice husks, reeds, corn cobs, corn stalks, and peach shells; optionally, it is straw.

[0047] In the embodiments of this application, in step S100, the carbonization temperature is 400-800℃ and the carbonization time is 1.5-2.5h. For example, the carbonization temperature is 400℃, 500℃, 600℃, 700℃, 800℃ and the carbonization time is 1.5 hours, 2 hours, 2.5 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable. Preferably, the carbonization temperature is 600℃ and the carbonization time is 2 hours.

[0048] In this embodiment of the application, in step S100, the protective atmosphere is a nitrogen atmosphere.

[0049] In this embodiment of the application, in step S100, the particle size of the biochar is 150-160 μm, or 75-80 μm, or 35-43 μm.

[0050] In this embodiment, step S200 includes: mixing the biochar, industrial by-product, and calcium hydroxide to obtain a composite powder; wherein the particle size of the biochar is larger than that of the industrial by-product. By controlling the particle size distribution of the biochar material and the industrial by-product, the final porosity of the material is controlled through particle size distribution, providing a structural basis for its deep phosphorus removal function and ensuring the stability of the material in terms of mechanical strength.

[0051] In this embodiment of the application, in step S200, the industrial by-product is two or more of the following: slag, steel slag, red mud, fly ash, lithium slag, and gold slag; preferably, the industrial by-product is slag and steel slag.

[0052] In this embodiment of the application, in step S200, the particle size of the industrial by-product is 150-160 μm, or 75-80 μm, or 35-43 μm.

[0053] In this embodiment of the application, in step S200, the particle size of the biochar is 150-160 μm, and the particle size of the industrial by-product is 75-80 μm, or 35-43 μm; or The biochar has a particle size of 75-80 μm, and the industrial by-product has a particle size of 35-43 μm.

[0054] In this embodiment of the application, in step S200, the composite powder contains, by weight percentage, 30%-50% biochar, 20%-50% slag, 1%-25% steel slag, and 10%-20% calcium hydroxide; for example, 30%, 40%, 50% biochar, 20%, 30%, 40%, 50% slag, 1%, 5%, 10%, 15%, 20%, 25% steel slag, and 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% calcium hydroxide, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0055] In this embodiment of the application, in step S200, the composite powder comprises, by weight percentage, 40% biochar, 40% slag, 10% steel slag, and 10% calcium hydroxide; or Biochar 40%, slag 25%, steel slag 25%, calcium hydroxide 10%; or The composition is 40% biochar, 40% slag, 10% steel slag, and 20% calcium hydroxide.

[0056] In this embodiment of the application, step S300 includes: mixing liquid hydrated sodium silicate and sodium hydroxide to obtain a composite liquid.

[0057] In this embodiment of the application, in step S300, the composite liquid contains, by weight percentage, 70%-80% liquid hydrated sodium silicate and 20%-30% sodium hydroxide; for example, the liquid hydrated sodium silicate is 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, and the sodium hydroxide is 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0058] In this embodiment of the application, in step S300, the composite liquid contains 80% liquid hydrated sodium silicate and 20% sodium hydroxide by weight percentage.

[0059] In this embodiment of the application, step S300 further includes heating the mixture to accelerate the dissolution of sodium hydroxide using a heat-assisted method. The heating temperature is 50-70°C, for example, it can be 50°C, 55°C, 60°C, 65°C, or 70°C, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable; preferably, it is 60°C.

[0060] In this embodiment of the application, step S400 includes: mixing the composite powder and the composite liquid, stirring, and forming a mixed slurry.

[0061] In the embodiments of this application, in step S400, the composite powder is 55%-65% by weight percentage, and the composite liquid is 45%-35%; for example, the composite powder is 55%, 60%, 65%, and the composite liquid is 35%, 40%, 45%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0062] In this embodiment of the application, in step S400, the composite powder is 65% and the composite liquid is 35% by weight percentage.

[0063] In this embodiment of the application, in step S400, the stirring speed is 100-300 rpm and the stirring time is 5-7 minutes; for example, the stirring speed is 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm and the stirring time is 5 minutes, 6 minutes, 7 minutes, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable. Preferably, the stirring speed is 100 rpm and the stirring time is 5 minutes.

[0064] In this embodiment of the application, step S500 includes: after the mixed slurry is poured into the mold, cured, and demolded, it undergoes high-temperature reverse curing in air, and then cooled to room temperature for molding; specifically: The mixed slurry is injected into a mold and sealed. The mold is then transferred to a curing chamber for curing and demolding. After demolding, the mold is exposed to air and then transferred to a forced-air drying oven for high-temperature reverse curing to reduce the moisture content in the structure, interrupt the reaction process, and expose more active sites. After the high-temperature reverse curing, the sample is cooled to room temperature and stored in a cool, dry, and sealed environment for later use.

[0065] In this embodiment of the application, in step S500, the curing temperature is 60-80℃ and the curing time is 2-4 hours; for example, the curing temperature is 60℃, 65℃, 70℃, 75℃, 80℃ and the curing time is 2 hours, 3 hours, 4 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable. Preferably, the curing temperature is 70℃ and the curing time is 3 hours.

[0066] In this embodiment of the application, in step S500, the temperature of high-temperature reverse curing is 90-110℃ and the high-temperature reverse curing time is 1-2 hours; for example, the temperature of high-temperature reverse curing is 90℃, 100℃, 110℃, and the high-temperature reverse curing time is 1 hour, 1.5 hours, or 2 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable. Preferably, the temperature for high-temperature reverse curing is 100℃, and the curing time is 1 or 2 hours.

[0067] In this embodiment of the application, the method further includes a raw material pretreatment step, comprising: grinding and sieving the biochar and the industrial by-product respectively before use; Optionally, the grinding device is a ball mill; Optionally, grinding media are also added during the grinding process; Optionally, the grinding media is a steel ball or zirconium oxide.

[0068] In this embodiment of the application, in the pretreatment step, the loading amount in the ball mill is 40%-70% of the grinding jar capacity to ensure the grinding effect; for example, it can be 40%, 50%, 60%, or 70%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0069] In the embodiments of this application, in the pretreatment step, the amount of grinding media is 20%-40% of the capacity of the grinding tank; for example, it can be 20%, 30%, or 40%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0070] In the embodiments of this application, in the pretreatment step, the ball mill rotates at a speed of 200-300 rpm and grinds for 1.5-2.5 hours; for example, the rotation speed is 200 rpm, 250 rpm, 300 rpm, and the grinding time is 1.5 hours, 2 hours, 2.5 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable. Preferably, the rotation speed is 300 rpm and the grinding time is 2 hours.

[0071] In this embodiment of the application, the pretreatment step involves screening through a multi-stage sieve, specifically: Particles with a diameter of 150-160 μm are screened using 100-mesh and 90-mesh sieves, particles with a diameter of 75-80 μm are screened using 180-mesh and 200-mesh sieves, and particles with a diameter of 35-43 μm are screened using 325-mesh and 400-mesh sieves.

[0072] In this embodiment of the application, the pretreatment step of the biochar includes: loading the biochar into a ball mill, with the loading amount being 50%-70% of the grinding jar capacity; adding steel balls as grinding media, the diameter of the steel balls being 10 mm, and the steel ball loading amount being 30% of the grinding jar capacity; and sieving after grinding.

[0073] In this embodiment of the application, the pretreatment step of the industrial by-product includes: loading the industrial by-product into a ball mill, with the loading amount being 40% of the grinding jar capacity; adding 10 mm diameter zirconium oxide as grinding media, with the zirconium oxide loading amount being 25% of the grinding jar capacity; and sieving after grinding.

[0074] This application also provides a functional filler prepared by the above method.

[0075] In the embodiments of this application, the mechanical strength of the functional filler is 38-45 MPa.

[0076] This application also provides a method for using the above-mentioned functional packing material as a packing material to achieve the removal of low-concentration phosphorus in river, lake and reservoir systems.

[0077] In this embodiment of the application, the initial total phosphorus concentration in the river, lake and reservoir system is ≤0.4 mg / L; preferably, it is 0.2-0.4 mg / L; after phosphorus removal using the functional packing material, the total phosphorus concentration in the system is ≤0.05 mg / L, and the total phosphorus removal rate is 100%.

[0078] The present application will be further described in detail below with reference to specific embodiments, but these embodiments should not be construed as limiting the present application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this invention.

[0079] The raw materials used in this application are all conventional products on the market.

[0080] Unless otherwise specified, all materials and reagents used in the embodiments of this application are commercially available.

[0081] Experimental methods not specified in the examples are generally performed under standard conditions or as recommended by the manufacturer.

[0082] Example 1 This application provides a method for preparing a functional filler, comprising the following steps: Step (1) Carbonization of biomass materials: Collect straw raw materials, remove impurities and soil, and crush the straw into small pieces with a size of less than 2 cm to increase the contact area with heat and ensure uniform carbonization in the subsequent process. Use a dryer to reduce the moisture content of the straw to below 15% to avoid high moisture content from reducing the pyrolysis carbonization efficiency. Send the pretreated straw into a muffle furnace and heat it at high temperature under oxygen-deficient conditions. The temperature is designed to be 600℃ and the carbonization time is 2 hours. After carbonization is completed, lower the temperature to room temperature and take out the straw carbon particles. At the same time, there is no need to remove the ash, which is retained in the material. Step (2) Biochar Grinding and Sieving: Evenly load the straw charcoal into the ball mill, ensuring the loading amount is controlled to within 50% of the grinding jar capacity to guarantee grinding efficiency. Add an appropriate amount of steel balls as grinding media; the steel balls should have a diameter of 10 mm and the loading amount should be 30% of the grinding jar capacity. Set the ball mill speed to 300 rpm and the grinding time to 2 hours. After grinding, use 100-mesh and 90-mesh sieves to collect straw charcoal particles with a particle size of 150-160 μm. Store the ground and sieved straw charcoal in a dry, sealed container for later use.

[0083] Step (3) Grinding and screening of by-products from iron and steel smelting: The collected slag and steel slag are coarsely crushed using a crusher to break large pieces of slag and steel slag down to a particle size of less than 25 mm. The coarsely crushed particles are then loaded into a ball mill at 40% of the grinding jar capacity. Zirconia with a diameter of 10 mm is added as grinding media at 25% of the jar capacity. The ball mill rotates at 300 rpm for 2 hours. After grinding, slag and steel slag particles with a particle size of 35-43 μm are screened using 325-mesh and 400-mesh screens. The ground and screened slag and steel slag particles are stored in a dry, sealed container for later use.

[0084] Step (4) Preparation of composite powder: The particle size distribution of biochar material and slag / steel slag is controlled to regulate the final porosity of the material, providing a structural basis for its long-term phosphorus removal function and ensuring the stability of the material in terms of mechanical strength. Biochar, slag, steel slag, and calcium hydroxide are composed of the following raw materials by weight percentage: biochar: 40%, slag: 40%, steel slag: 10%, calcium hydroxide: 10%.

[0085] Step (5) Preparation of composite liquid: Combine liquid hydrated sodium silicate and sodium hydroxide, and use a heat-assisted method to accelerate the dissolution of sodium hydroxide. The heating temperature is 60℃. The liquid hydrated sodium silicate and sodium hydroxide are composed of the following raw materials by weight percentage: liquid hydrated sodium silicate: 80%, sodium hydroxide: 20%.

[0086] Step (6) Preparation and casting of the mixed slurry: The composite powder and composite liquid are mixed in a reactor. The composite powder and composite liquid are composed of the following raw materials by weight percentage: 65% composite powder and 35% composite liquid. The stirring speed is 100 rpm and the stirring time is 5 minutes to form a mixed slurry. The mixed slurry is injected into a silicone mold and the mold is sealed by plastic sealing.

[0087] Step (7) Curing of the mixed slurry: Transfer the sealed mold to a curing chamber, cure at 70°C for 3 hours. After curing, demold the sample and expose it to the air. Transfer it to a forced-air drying oven for high-temperature reverse curing to reduce the moisture content in the structure, interrupt the reaction process, and expose more active sites. During the high-temperature reverse curing stage, the curing temperature is 100°C and the curing time is 1 hour, while maintaining forced-air ventilation in the forced-air drying oven.

[0088] Step (8) Preservation of molding materials: After the sample is cooled to room temperature after high temperature reverse curing, it is stored in a cool, dry, sealed environment for later use.

[0089] According to the Class V total phosphorus standard for lakes and reservoirs in the "Surface Water Environmental Quality Standard" (GB 3838-2002), simulated wastewater with a total phosphorus concentration of 0.2 mg / L was prepared. The molding material in this embodiment was placed in a fixed bed system with a solid-liquid ratio of 1 (g): 20 (ml), the bed height was 10 cm, and the fixed bed diameter was 5 cm. Simulated wastewater was continuously pumped in. After continuous water intake for 28 days, the effluent from the fixed bed was taken and filtered using a 0.22 μm filter membrane.

[0090] The mechanical strength of the molded sample in this embodiment was determined according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999).

[0091] The final total phosphorus concentration in water was determined according to the "Ammonium Molybdate Spectrophotometric Method" (GB 11893-89).

[0092] The mechanical strength and phosphorus removal of Example 1 are shown in Table 1.

[0093] Example 2 In this embodiment, step (1) is the same as step (1) in embodiment 1.

[0094] In step (2), straw charcoal particles with a particle size of 75-80 μm are sieved using 180-mesh and 200-mesh sieves. Other steps are the same as step (2) in Example 1.

[0095] Steps (3)-(8) are the same as steps (3)-(8) in Example 1.

[0096] The mechanical strength and phosphorus removal in Example 2 are shown in Table 1.

[0097] Example 3 In this embodiment, steps (1)-(3) are the same as steps (1)-(3) in embodiment 1.

[0098] Step (4) The composite powder preparation process, the biochar, slag, steel slag and calcium hydroxide are composed of the following raw materials by weight percentage: biochar: 40%, slag: 25%, steel slag: 25%, calcium hydroxide 10%. Other steps are the same as step (4) in Example 1.

[0099] Steps (5)-(8) are the same as steps (5)-(8) in Example 1.

[0100] The mechanical strength and phosphorus removal of Example 3 are shown in Table 1.

[0101] Example 4 In this embodiment, steps (1)-(3) are the same as steps (1)-(3) in embodiment 1.

[0102] Step (4) The composite powder preparation process, the biochar, slag, steel slag and calcium hydroxide are composed of the following raw materials by weight percentage: biochar: 40%, slag: 40%, steel slag: 10%, calcium hydroxide: 20%. Other steps are the same as step (4) in Example 1.

[0103] Steps (5)-(8) are the same as steps (5)-(8) in Example 1.

[0104] The mechanical strength and phosphorus removal of Example 4 are shown in Table 1.

[0105] Example 5 In this embodiment, steps (1)-(6) are the same as steps (1)-(6) in embodiment 1.

[0106] Step (7) Mixed slurry curing process, high temperature reverse curing stage, curing temperature 100℃, curing time 2 hours, and keep the blower in the drying oven ventilated. Other steps are the same as step (8) in Example 1.

[0107] Step (8) is the same as step (8) in Example 1.

[0108] The mechanical strength and phosphorus removal of Example 5 are shown in Table 1.

[0109] Example 6 In this embodiment, steps (1)-(8) are the same as steps (1)-(8) in embodiment 1.

[0110] Step (8) Prepare simulated wastewater with a total phosphorus concentration of 0.4 mg / L according to the Class V total phosphorus standard in the "Surface Water Environmental Quality Standard" (GB 3838-2002), rather than the lake and reservoir standard. Other steps are the same as step (8) in Example 1.

[0111] The mechanical strength and phosphorus removal of Example 6 are shown in Table 1.

[0112] Example 7 In this embodiment, steps (1)-(8) are the same as steps (1)-(8) in embodiment 1.

[0113] Step (8) Prepare simulated wastewater with a total phosphorus concentration of 0.8 mg / L. Other steps are the same as step (8) in Example 1.

[0114] The mechanical strength and phosphorus removal in Example 7 are shown in Table 1.

[0115] Comparative Example 1 In this method: step (1) is the same as step (1) in Example 1.

[0116] In step (2), straw charcoal particles with a particle size of 150-160 μm are sieved using 100-mesh and 90-mesh sieves. Other steps are the same as step (2) in Example 1.

[0117] In step (3), slag and steel slag particles with a particle size of 150-160 μm are screened using 100-mesh and 90-mesh sieves. Other steps are the same as step (3) in Example 1.

[0118] Steps (4)-(8) are the same as steps (4)-(8) in Example 1.

[0119] The mechanical strength and phosphorus removal of Comparative Example 1 are shown in Table 1.

[0120] Comparative Example 2 In this method: step (1) is the same as step (1) in Example 1.

[0121] In step (2), straw charcoal particles with a particle size of 75-80 μm are sieved using 180-mesh and 200-mesh sieves. Other steps are the same as step (2) in Example 1.

[0122] In step (3), slag and steel slag particles with a particle size of 75-80 μm are screened using 180-mesh and 200-mesh sieves. Other steps are the same as step (3) in Example 1.

[0123] Steps (4)-(8) are the same as steps (4)-(8) in Example 1.

[0124] The mechanical strength and phosphorus removal of Comparative Example 2 are shown in Table 1.

[0125] Comparative Example 3 In this method: step (1) is the same as step (1) in Example 1.

[0126] In step (2), straw charcoal particles with a particle size of 35-43 μm are sieved using 325-mesh and 400-mesh sieves. Other steps are the same as step (2) in Example 1.

[0127] In step (3), slag and steel slag particles with a particle size of 35-43 μm are screened using 325 mesh and 400 mesh screens. Other steps are the same as step (3) in Example 1.

[0128] Steps (4)-(8) are the same as steps (4)-(8) in Example 1.

[0129] The mechanical strength and phosphorus removal of Comparative Example 3 are shown in Table 1.

[0130] Comparative Example 4 In this method: steps (1)-(3) are the same as steps (1)-(3) in Example 1.

[0131] Step (4) The composite powder preparation process, the biochar, slag, steel slag and calcium hydroxide are composed of the following raw materials by weight percentage: biochar: 40%, slag: 50%, steel slag: 0%, calcium hydroxide 10%. Other steps are the same as step (4) in Example 1.

[0132] Steps (5)-(8) are the same as steps (5)-(8) in Example 1.

[0133] The mechanical strength and phosphorus removal of Comparative Example 4 are shown in Table 1.

[0134] Comparative Example 5 In this method: steps (1)-(3) are the same as steps (1)-(3) in Example 1.

[0135] Step (4) The composite powder preparation process, the biochar, slag, steel slag and calcium hydroxide are composed of the following raw materials by weight percentage: biochar: 40%, slag: 45%, steel slag: 15%, calcium hydroxide 0%. Other steps are the same as step (4) in Example 1.

[0136] Steps (5)-(8) are the same as steps (5)-(8) in Example 1.

[0137] The mechanical strength and phosphorus removal of Comparative Example 5 are shown in Table 1.

[0138] Comparative Example 6 In this method: steps (1)-(6) are the same as steps (1)-(6) in Example 1.

[0139] Step (8) Mixing slurry curing process: Transfer the sealed mold to the curing box, the curing temperature is 70℃, the curing time is 3 hours. After curing, demold the sample and expose it to the air environment. Do not carry out the high temperature reverse curing stage. The sample directly enters step (8).

[0140] Step (8) is the same as step (8) in Example 1.

[0141] The mechanical strength and phosphorus removal of Comparative Example 6 are shown in Table 1.

[0142] Table 1. Strength of Examples and Comparative Examples and their Removal of Total Phosphorus from Water In summary, this application provides a functional packing material for deep phosphorus removal in river, lake, and reservoir systems, along with its preparation method and application. It aims to address the failure and cost issues of traditional constructed wetland packing materials in removing low-concentration phosphorus pollution. The composite packing material involved in this application is prepared from biochar materials and byproducts of the iron and steel smelting industry (slag and steel slag). Combined with active component screening, particle size distribution, and a high-temperature reverse curing process, the functional material achieves effective phosphorus removal under low-concentration pollution conditions while maintaining stable phosphorus removal performance. The packing material involved in this application has a wider phosphorus removal range and stronger performance, effectively reducing the land area required for constructed wetlands and constructing highly efficient phosphorus removal units.

[0143] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing a functional filler, the method comprising: S100. Carbonization of biomass materials: Biochar is obtained by carbonizing biomass materials under a protective atmosphere or oxygen-deficient conditions. S200. Preparation of composite powder: The biochar, industrial by-product, and calcium hydroxide are mixed to obtain a composite powder; wherein the particle size of the biochar is larger than the particle size of the industrial by-product. S300. Preparation of composite liquids: Liquid hydrated sodium silicate and sodium hydroxide are mixed to obtain a composite liquid; S400. Preparation of mixed slurry: The composite powder and composite liquid are mixed and stirred to form a mixed slurry; S500. Casting and curing of mixed slurry: After the mixed slurry is poured into the mold, cured, and demolded, it is subjected to high-temperature reverse curing in air and then cooled to room temperature to form the final product. The order of steps S200 and S300 is not important; the industrial by-products are selected from two or more of the following: slag, steel slag, red mud, fly ash, lithium slag, and gold slag.

2. The method according to claim 1, wherein, In step S100, the biomass material is selected from one or more of rice husks, reeds, corn cobs, corn stalks, and peach shells; and / or The carbonization temperature is 400-800℃, and the carbonization time is 1.5-2.5h; and / or The protective atmosphere is a nitrogen atmosphere; and / or The biochar has a particle size of 150-160 μm, or 75-80 μm, or 35-43 μm.

3. The method according to claim 1 or 2, wherein, The particle size of the industrial by-product is 150-160 μm, or 75-80 μm, or 35-43 μm; and / or The industrial by-products are slag and steel slag.

4. The method according to claim 3, wherein, In step S200, the composite powder comprises, by weight percentage, 30%-50% biochar, 20%-50% slag, 1%-25% steel slag, and 10%-20% calcium hydroxide; and / or The biochar has a particle size of 150-160 μm, and the industrial by-product has a particle size of 75-80 μm or 35-43 μm; and / or The biochar has a particle size of 75-80 μm, and the industrial by-product has a particle size of 35-43 μm.

5. The method according to claim 1 or 2, wherein, In step S300, the composite liquid contains 70%-80% liquid hydrated sodium silicate and 20%-30% sodium hydroxide by weight percentage.

6. The method according to claim 1 or 2, wherein, Step S300 also includes a heating step of the mixture; Optionally, the heating temperature is 50-70℃.

7. The method according to claim 1 or 2, wherein, In step S400, by weight percentage, the composite powder comprises 55%-65%, and the composite liquid comprises 45%-35%; and / or The stirring speed is 100-300 rpm, and the stirring time is 5-7 minutes.

8. The method according to claim 1 or 2, wherein, In step S500, the curing temperature is 60-80℃, and the curing time is 2-4 hours; and / or The temperature for high-temperature reverse curing is 90-110℃, and the high-temperature reverse curing time is 1-2 hours.

9. A functional filler prepared by any one of claims 1 to 8, wherein the mechanical strength of the functional filler is 38-45 MPa.

10. The use of the functional packing material according to claim 9 as a packing material for the removal of low-concentration phosphorus in river, lake and reservoir systems.

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