Modified nano filter material for water pollution control and preparation method of modified nano filter material

Abstract

The invention relates to the technical field of water treatment materials, and discloses a modified nano filter material for water pollution control and a preparation method thereof.The filter material is solid powder composed of natural zeolite powder, natural rare earth mineral powder, a fluxing regulator, an embedded oxidizing agent and an ion exchange enhancer, the liquid phase bonding curing agent is composed of modified water glass and acid rare earth active liquid. Asynchronous double-nozzle granulation is adopted in the process, and an acid-base in-situ reaction is initiated to achieve curing; carrying out gradient drying, carrying out low-temperature eutectic sintering at 680-720 DEG C, and cleaning micropores in situ by utilizing an embedded oxidant; and finally, a communicating pore channel is constructed by dissolving out a reaction byproduct salt phase through water quenching. According to the filter material disclosed by the invention, the balance of high mechanical strength and high specific surface area is realized while the crystal lattice activity of the zeolite is retained, the rare earth component is cured in a skeleton in a chemical bonding form, and the filter material has the capability of synchronously removing ammonia nitrogen and total phosphorus and good environmental safety.

Description

Technical Field

[0001] This invention relates to the field of water treatment materials technology, specifically to a modified nanofilter material for water pollution control and its preparation method. Background Technology

[0002] With the increasing severity of eutrophication in water bodies, the deep removal of ammonia nitrogen and phosphate has become a crucial step in wastewater treatment. Natural zeolite, due to its unique skeletal structure and excellent cation exchange performance, is widely used for the adsorption and removal of ammonia nitrogen in water. However, natural zeolite typically exists in powder or irregular ore form, and its direct application in engineering filter columns can lead to excessive head loss or loss with the water flow. Therefore, it is necessary to prepare it into granular filter media with a specific particle size and mechanical strength.

[0003] In the granulation and sintering process of zeolite filter media, there is an irreconcilable contradiction between mechanical strength and adsorption activity. To obtain the wear resistance and water immersion resistance required for engineering applications, high sintering temperatures or the addition of large amounts of binders are usually necessary. However, natural zeolites (especially clinoptilolite) are quite sensitive to temperature. Excessively high sintering temperatures can cause their crystal structure to collapse, thereby losing their ion exchange activity. On the other hand, excessive inorganic binders can easily clog the micropores and mesopores of zeolite by forming a glassy phase at high temperatures, leading to a significant decrease in specific surface area and increased mass transfer resistance. Lowering the sintering temperature can preserve zeolite activity, but it often results in insufficient filter media strength, making it prone to breakage or pulverization during water backwashing.

[0004] Natural zeolite has extremely weak removal capacity for anionic pollutants (such as phosphate). To achieve simultaneous removal of ammonia nitrogen and total phosphorus, existing technologies often modify zeolite with rare earth elements (such as lanthanum and cerium). Currently, common modification methods are surface impregnation or coating after molding. This physical adhesion or weak chemical adsorption binding method is not strong. Under long-term water flow or changes in acidity and alkalinity, the loaded active components are easily detached and dissolved into the water. This not only reduces the service life of the filter media and phosphorus removal efficiency, but also causes secondary pollution due to the release of rare earth ions.

[0005] Existing modified filter media preparation processes still face the challenge of controlling pore structure. Conventional granulation processes often employ simple physical mixing, lacking precise design of the internal microstructure of the particles. During sintering and densification, the lack of effective pore-forming or internal cleaning mechanisms easily leads to the formation of closed pores within the filter media, resulting in low utilization of effective adsorption sites. Although some technologies have attempted to introduce organic pore-forming agents, the escape pathways of residual carbon or gases from organic combustion are often obstructed, frequently compromising the integrity of the overall particle structure. Therefore, developing a modified filter media that can achieve both low-temperature, high-strength bonding and stable loading of active components, while possessing a well-developed interconnected pore structure, is a pressing technical problem to be solved in the field of water treatment materials. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a modified nanofilter material for water pollution control and its preparation method, which solves the problems of existing zeolite filter materials where it is difficult to balance mechanical strength and adsorption activity during preparation, the weak binding force of functionalized modified components leading to easy loss and secondary pollution, and the blockage of micropores and impeded mass transfer caused by sintering densification.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a modified nanofilter material for water pollution treatment, which is prepared by granulation and sintering of raw materials containing solid powder raw materials and liquid phase binder and curing agent; The solid powder raw material comprises the following components in parts by weight: Natural zeolite powder: 58-75 parts; Natural rare earth mineral powder: 10-20 parts; Flux modifier: 2-5 parts; Embedded oxidant: 3-7 parts; Ion exchange enhancer: 4-8 parts; The liquid phase binder and curing agent comprises a modified water glass liquid phase binder and an acidic rare earth active liquid.

[0008] Preferably, the natural zeolite powder is natural clinoptilolite powder; The natural rare earth mineral powder is one or more of the following: natural basalt fluoride powder, monazite powder, or xenotime powder. The fluxing modifier is one or more of anhydrous sodium carbonate, potassium carbonate, or borax. The embedded oxidant is one or more of sodium persulfate, potassium persulfate, or ammonium persulfate; The ion exchange enhancer is ammonium chloride.

[0009] Preferably, the modified water glass liquid phase binder is prepared by: Dilute liquid sodium silicate with a modulus of 2.2-2.6 with deionized water to a Baume degree of 30-32Be', then add 0.3%-0.8% sodium dodecylbenzenesulfonate by mass of the diluted solution and stir until it becomes transparent.

[0010] Preferably, the preparation method of the acidic rare earth active liquid is as follows: The natural fluorocarbon cerium ore powder is mixed with industrial hydrochloric acid with a mass concentration of 20%-31% at a solid-liquid mass ratio of 1:(3-5), and reacted at 80-95℃ for 3-5 hours. The slag is removed by filtration, and the pH of the filtrate is adjusted to 0.5-1.5.

[0011] Secondly, the present invention provides a method for preparing modified nanofilter material for water pollution treatment, comprising the following steps: Weigh out the natural zeolite powder, natural rare earth mineral powder, fluxing modifier, embedded oxidant and ion exchange enhancer according to the weight parts, and mix them evenly to obtain a premixed dry powder. The premixed dry powder is added to the granulation equipment and sprayed through a dual-nozzle system. First, a modified water glass liquid phase binder is sprayed to nucleate the powder. After the mother ball is formed, an acidic rare earth active liquid is sprayed to solidify it, thus obtaining green granules. The green pellets are dried in stages to control the final moisture content; The dried green pellets are heated and sintered, the channels are cleaned with embedded oxidant, and a liquid phase eutectic is formed at 680-720°C with fluxing agent, followed by liquid phase welding. The sintered particles are cooled by water quenching and soaked in water to dissolve the internal salt phase by-products, and then dried to obtain the finished product.

[0012] Preferably, the nozzle for spraying the modified water glass liquid phase binder is located in the material discharge area of ​​the granulation equipment, and the nozzle for spraying the acidic rare earth active liquid is located in the pelletizing area of ​​the granulation equipment. The mass ratio of the injection flow rate of the modified water glass liquid phase binder to that of the acidic rare earth active liquid is (1.4-2.0):1; The total amount of the modified water glass liquid phase binder and the acidic rare earth active liquid is 35%-45% of the total mass of the premixed dry powder.

[0013] Preferably, the segmented drying includes: The first stage of drying is at a temperature of 65-75℃ and a drying time of 30-50 minutes; The second stage of drying is at a temperature of 105-115℃ and a drying time of 60-80 minutes. The final moisture content is controlled to be below 4.5%.

[0014] Preferably, the heating and sintering process includes: Heat to 380-420℃ at a rate of 5-10℃ / min and hold for 20-40 minutes, then continue heating to 680-720℃ and sinter at a constant temperature for 90-120 minutes.

[0015] Preferably, the water quenching cooling process is as follows: The sintered particles are directly introduced from a high temperature state into circulating water at a temperature of 20-40℃. The soaking and cleaning time is 20-50 minutes, until the reaction byproduct salt phase inside the filter material dissolves.

[0016] Preferably, the drying step to obtain the finished product includes: After soaking and washing, the particles are subjected to solid-liquid separation and sieving, and then dried at 100-115℃ to constant weight.

[0017] This invention provides a modified nanofilter material for water pollution treatment and its preparation method. It has the following beneficial effects: 1. This invention employs low-temperature eutectic sintering technology. By introducing a fluxing agent and utilizing the byproduct salt generated from the acid-base reaction to construct a low-melting-point eutectic system, the sintering temperature is reduced to 680-720℃. This temperature range is lower than the lattice collapse temperature of natural clinoptilolite, effectively avoiding pore closure and loss of active sites caused by high-temperature sintering. While ensuring the filter material possesses the mechanical strength required for engineering applications, it retains the ion exchange performance of the zeolite framework.

[0018] 2. This invention utilizes an asynchronous dual-nozzle granulation process, employing an in-situ solidification reaction between acidic rare-earth active liquid and modified water glass within the particles to construct a chemically bonded three-dimensional rare-earth silicate framework. This structure endows the filter media with the ability to simultaneously remove ammonia nitrogen and phosphate. The zeolite framework is responsible for ion exchange removal of ammonia nitrogen, while the solidified rare-earth components are responsible for chemical adsorption removal of total phosphorus. Furthermore, the rare-earth elements exist in stable silicate or oxide forms, reducing the loss rate of active components under water flow scouring, thus ensuring the long-term effectiveness and environmental safety of the material.

[0019] 3. This invention combines embedded oxidation cleaning with a salt template pore-forming mechanism. During the heat treatment stage, an embedded oxidant decomposes and removes impurities from the zeolite micropores. Furthermore, the dissolution characteristics of the reaction byproduct salt phase during the water quenching cleaning stage are utilized to construct interconnected pore structures within the particles. This synergistic effect increases the specific surface area and apparent porosity of the filter media, reduces mass transfer resistance, solves the micropore clogging problem caused by sintering densification in traditional ceramic granule filter media, and improves adsorption efficiency. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, examples, comparative examples, and test examples. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Preparation Examples 1-6: Preparation Example 1: This preparation example provides a method for preparing a modified water glass liquid phase binder (denoted as component A-1), including the following steps: Take 100 parts of liquid sodium silicate (modulus 2.4, initial Baume degree 40 Be') and place it in a mixing jar. Add an appropriate amount of deionized water for dilution, and check the solution density while stirring until the Baume degree is adjusted to 31 Be'. Then, add 0.5% (by mass) of sodium dodecylbenzenesulfonate to the diluted water glass solution and stir at high speed for 15 minutes until the solution is homogeneous, transparent, and free of air bubbles. This yields modified water glass liquid phase binder component A-1. In this example, the anionic surfactant sodium dodecylbenzenesulfonate is used to ensure its chemical stability in the alkaline silicate system.

[0022] Preparation Example 2: This preparation example provides a method for preparing a modified water glass liquid phase binder (denoted as component A-2), including the following steps: Take 100 parts of liquid sodium silicate (modulus 2.6, initial Baume degree 42Be') and place it in a stirred tank. Add deionized water for dilution, and control the stirring speed to adjust the Baume degree of the solution to 32Be'. Then add 0.8% of sodium dodecylbenzenesulfonate by mass of the diluted solution and continue stirring for 20 minutes to ensure complete dissolution and dispersion, thus obtaining modified water glass liquid phase binder component A-2. This component has high viscosity and silicon content, making it suitable for the preparation of high-strength particles.

[0023] Preparation Example 3: This preparation example provides a method for preparing a modified water glass liquid phase binder (denoted as component A-3), including the following steps: Take 100 parts of liquid sodium silicate (modulus 2.2, initial Baume degree 38Be') and place it in a mixing tank. Add deionized water to dilute it and adjust the Baume degree of the solution to 30Be'. Then add 0.3% sodium dodecylbenzenesulfonate by mass of the diluted solution and stir for 10 minutes to obtain modified water glass liquid phase binder component A-3. This component has good flowability and permeability.

[0024] Preparation Example 4: This preparation example provides a method for preparing an acidic rare earth active liquid (denoted as component B-1), including the following steps: Weigh 50 parts of natural fluorocarbon cerium ore powder (TREO≥45%, particle size 300 mesh) and put it into a rubber-lined reactor. Add 200 parts of industrial hydrochloric acid with a mass concentration of 25% (solid-liquid mass ratio 1:4). Turn on the steam heating to raise the temperature to 90℃, maintain the constant temperature and stir and leach for 4 hours at a speed of 150r / min. After the reaction is completed, perform plate and frame filter press while hot to filter out insoluble slag, collect the filtrate and cool it to room temperature. Detect the pH value of the filtrate, add an appropriate amount of water or hydrochloric acid to adjust the pH value to 1.0, and obtain acidic rare earth active liquid component B-1.

[0025] Preparation Example 5: This preparation example provides a method for preparing an acidic rare earth active liquid (denoted as component B-2), including the following steps: Weigh 50 parts of natural fluorocarbon cerium ore powder (TREO≥45%, particle size 300 mesh) and add it to a reactor. Add 150 parts of industrial hydrochloric acid with a mass concentration of 31% (solid-liquid mass ratio 1:3). Heat to 95℃ and leach with constant temperature stirring for 5 hours to maximize the rare earth ion leaching rate. Filter while hot to remove slag and collect the filtrate. Detect and adjust the pH of the filtrate to 0.5 to obtain high-concentration acidic rare earth active liquid component B-2. This component has high acidity and strong reactivity, making it suitable for rapid curing processes.

[0026] Preparation Example 6: This preparation example provides a method for preparing an acidic rare earth active liquid (denoted as component B-3), including the following steps: Weigh 50 parts of natural fluorocarbon cerium ore powder (TREO≥45%, particle size 300 mesh) and add them to a reactor. Add 250 parts of industrial hydrochloric acid with a mass concentration of 20% (solid-liquid mass ratio 1:5). Heat to 80℃ and leach with stirring at a constant temperature for 3 hours. Filter while hot to remove slag and collect the filtrate. Detect and adjust the pH of the filtrate to 1.5 to obtain acidic rare earth active liquid component B-3. This component has a relatively mild acidity and a slow reaction rate.

[0027] Examples 1-5: Example 1

[0028] This embodiment provides a modified nanofilter material for water pollution treatment and its preparation method, including the following steps: (1) Powder functionalization premixing: Weigh out 60 parts of natural clinoptilolite powder, 10 parts of natural bastnaesite powder (as a framework reinforcement and slow-release source), 3 parts of anhydrous sodium carbonate (flux modifier), 4 parts of sodium persulfate (intercalated oxidant), and 6 parts of ammonium chloride (ion exchange enhancer). Put the above raw materials into a plow mixer and dry mix at 50 r / min for 15 minutes. After mixing evenly, discharge the material for later use (total powder weight 83 parts).

[0029] (2) Asynchronous dual-nozzle granulation: The premixed dry powder obtained in step (1) is added to an inclined disc granulator (disc inclination angle 50°, rotation speed 20 r / min). The granulator is equipped with a dual-fluid spray system, with nozzle A located upstream of the disc rolling trajectory (material drop zone) and nozzle B located downstream (pelletizing zone).

[0030] Nucleation stage: First, open nozzle A and spray the modified water glass liquid phase binder (component A-1) prepared in Example 1 at a spray pressure of 0.3 MPa to initially agglomerate the powder into mother spheres of 1-2 mm.

[0031] Solidification stage: After the mother ball is formed, keep nozzle A open and open nozzle B at the same time to spray the acidic rare earth active liquid (component B-1) prepared in Example 4.

[0032] Parameter control: The flow rate mass ratio of nozzle A to nozzle B is controlled to be approximately 1.8:1. During this process, the total consumption of component A is 21 parts, and the total consumption of component B is 11.5 parts (liquid-to-solid mass ratio approximately 39%). The particles undergo an acid-base coupling reaction and solidify during the rolling process until they grow to a particle size of 3-5 mm, at which point they are thrown out of the disc by centrifugal force.

[0033] (3) Gradient low-temperature drying: The green pellets are fed into a mesh belt dryer. The first stage drying temperature is set at 70℃ for 40 minutes; the second stage drying temperature is set at 110℃ for 70 minutes. The moisture content of the dried pellets is controlled below 4.5%.

[0034] (4) Low-temperature eutectic sintering and in-situ oxidation: The dried granules are fed into a rotary kiln. First, the temperature is increased to 400°C at a rate of 8°C / min and held for 30 minutes to clean the pores using free radicals generated from the decomposition of sodium persulfate. Then, the temperature is further increased to 700°C and sintered at this constant temperature for 100 minutes. At this temperature, sodium carbonate, the reaction byproduct sodium chloride, and the sodium silicate surface layer form a liquid-phase eutectic, enabling liquid-phase welding.

[0035] (5) Quenching and dissolution and finished product packaging: The high-temperature particles (approximately 600°C) exiting the kiln are directly dropped into a 30°C circulating water tank for water quenching and soaked in water for 30 minutes to dissolve the solidified eutectic salt phase. The cleaned particles are then classified by a vibrating screen and dried at 105°C to obtain the finished product. Example 2

[0036] This embodiment provides a modified nanofilter material for water pollution treatment and its preparation method, including the following steps: (1) Powder functionalization premixing: Weigh out 70 parts of natural clinoptilolite powder, 10 parts of natural bastnaesite powder, 4 parts of anhydrous sodium carbonate, 4 parts of sodium persulfate, and 6 parts of ammonium chloride. The mixing process is the same as in Example 1.

[0037] (2) Asynchronous dual-nozzle granulation: The operating steps are the same as in Example 1, except that the liquid phase binder is component A-3 (high fluidity) prepared in Preparation Example 3, and the acidic rare earth active liquid is component B-1 prepared in Preparation Example 4. The flow rate mass ratio of component A to component B is controlled at 2:1, the total amount of component A is 22 parts, and the total amount of component B is 11 parts.

[0038] (3) Gradient low temperature drying: Same as in Example 1.

[0039] (4) Low-temperature eutectic sintering and in-situ oxidation: The dried granules were fed into a rotary kiln. The preheating process was the same as in Example 1; the sintering temperature was set at 680°C, and sintering was carried out at a constant temperature for 120 minutes. Due to the increased amount of flux sodium carbonate, the eutectic point of the system was lowered, thus achieving effective liquid-phase sintering strength at 680°C and preserving the zeolite framework activity to the maximum extent.

[0040] (5) Quenching and dissolution and finished product packaging: Same as in Example 1. Example 3

[0041] This embodiment provides a modified nanofilter material for water pollution treatment and its preparation method, including the following steps: (1) Powder functionalization premixing: Weigh out 64 parts of natural clinoptilolite powder, 10 parts of natural bastnaesite powder, 2 parts of anhydrous sodium carbonate, 4 parts of sodium persulfate, and 5 parts of ammonium chloride. The mixing process is the same as in Example 1.

[0042] (2) Asynchronous dual-nozzle granulation: The operating steps are the same as in Example 1, except that the liquid phase binder is component A-2 (high viscosity) prepared in Preparation Example 2, and the acidic rare earth active liquid is component B-3 (mild acidity) prepared in Preparation Example 6. The flow rate mass ratio of component A to component B is controlled at 1.6:1, the total amount of component A is 20 parts, and the total amount of component B is 12.5 parts.

[0043] (3) Gradient low temperature drying: Same as in Example 1.

[0044] (4) Low-temperature eutectic sintering and in-situ oxidation: The dried granules were fed into a rotary kiln. The preheating process was the same as in Example 1; the sintering temperature was set at 720°C and sintered at a constant temperature for 90 minutes. Due to the reduction in flux usage, the temperature was appropriately increased to ensure the amount of liquid phase generated, while 720°C was still below the lattice collapse critical temperature of clinoptilolite.

[0045] (5) Quenching and dissolution and finished product packaging: Same as in Example 1. Example 4

[0046] This embodiment provides a modified nanofilter material for water pollution treatment and its preparation method, including the following steps: (1) Powder functionalization premixing: Weigh out 68 parts of natural clinoptilolite powder, 10 parts of natural bastnaesite powder, 3 parts of anhydrous sodium carbonate, 5 parts of sodium persulfate, and 7 parts of ammonium chloride. The mixing process is the same as in Example 1.

[0047] (2) Asynchronous dual-nozzle granulation: The operation steps are the same as in Example 1, except that the liquid phase binder is component A-1 prepared in Preparation Example 1, and the acidic rare earth active liquid is component B-2 (high concentration, high acidity) prepared in Preparation Example 5.

[0048] The flow rate mass ratio of component A to component B was controlled at 1.5:1, with a total dosage of 21 parts of component A and 14 parts of component B. High concentrations of rare earth ions were used to form a denser rare earth silicate framework within the particles, providing more phosphate adsorption sites.

[0049] (3) Gradient low temperature drying: Same as in Example 1.

[0050] (4) Low-temperature eutectic sintering and in-situ oxidation: The process parameters are the same as in Example 1.

[0051] (5) Quenching and dissolution and finished product packaging: Same as in Example 1. Example 5

[0052] This embodiment provides a modified nanofilter material for water pollution treatment and its preparation method, including the following steps: (1) Powder functionalization premix: Same as Example 1.

[0053] (2) Asynchronous dual-nozzle granulation: The operating steps are the same as in Example 1, except that the liquid phase binder used is Component A-1 prepared in Preparation Example 1, and the acidic rare earth active liquid used is Component B-1 prepared in Preparation Example 4. The spray parameters were adjusted: the flow rate-to-mass ratio of Component A to Component B was controlled at 1.4:1 (i.e., the proportion of acidic rare earth liquid was relatively increased). The total amount of Component A was 19.6 parts, and the total amount of Component B was 14 parts. A higher proportion of acidic liquid is beneficial for more thorough neutralization of alkaline silicates and for creating a slightly acidic environment locally, promoting deep penetration of rare earth ions.

[0054] (3) Gradient low temperature drying: Same as in Example 1.

[0055] (4) Low-temperature eutectic sintering and in-situ oxidation: The process parameters are the same as in Example 1.

[0056] (5) Quenching and dissolution and finished product packaging: Same as in Example 1.

[0057] Comparative Examples 1-6: Comparative Example 1: Compared with Example 1, the difference is that anhydrous sodium carbonate (flux modifier) ​​is not added to the raw material formula, and the sintering temperature in step (4) is set to 850℃ (simulating the traditional high-temperature sintering process). The other steps and parameters are the same.

[0058] Comparative Example 2: Compared with Example 1, the difference is that the granulation method in step (2) is different. Instead of using asynchronous dual-nozzle spraying, component A and component B are pre-mixed outside the machine and then sprayed into the granulator through a single nozzle. The remaining steps and parameters are the same.

[0059] Comparative Example 3: Compared with Example 1, the difference is that sodium persulfate (embedded oxidant) is not added to the raw material formula, while the other steps and parameters are the same.

[0060] Comparative Example 4: Compared with Example 1, the difference is that anhydrous sodium carbonate is not added to the raw material formula, and the sintering temperature in step (4) remains unchanged at 700°C. The other steps and parameters are the same.

[0061] Comparative Example 5: Compared with Example 1, the differences are as follows: Raw material formulation adjustment: natural fluorocarbon cerium ore powder is not added in step (1), and the amount of natural clinoptilolite powder is adjusted to 70 kg; the B component (acidic activator) used in step (2) is replaced with ordinary industrial hydrochloric acid solution without rare earth ions (pH value adjusted to 1.0). The remaining steps and parameters are the same.

[0062] Comparative Example 6: Compared with Example 1, the differences are as follows: Raw material formulation adjustment: natural fluorocarbon cerium ore powder is not added in step (1), and the amount of natural clinoptilolite powder is adjusted to 70 kg; component B in step (2) is replaced with ordinary industrial hydrochloric acid; after sintering in step (4), a rare earth post-impregnation process is added, that is, the sintered particles are immersed in a 5% lanthanum chloride solution for 2 hours, and then dried to obtain the finished product (simulating traditional surface loading modification). The remaining steps and parameters are the same.

[0063] Test Examples 1-6: Test Example 1: Verification of the protective effect of low-temperature eutectic sintering on the lattice activity of zeolites: This test case aims to quantitatively assess the degree of damage to the zeolite crystal structure caused by different sintering processes by measuring the cation exchange capacity (CEC) of the material. Cation exchange capacity is the most critical characteristic indicator of zeolite materials, directly reflecting the integrity of the tetrahedral structure in its aluminosilicate framework. When zeolite undergoes high temperatures that cause lattice collapse or a glassy transition, its ion exchange sites are permanently lost.

[0064] Experimental steps: (1) The finished particles prepared in Examples 1, 2, and 3, Comparative Example 1 (high temperature sintering), and Comparative Example 4 (without flux), as well as untreated natural clinoptilolite ore, were used as test samples. Each group of samples was placed in an oven and dried at 105 degrees Celsius for 2 hours to remove adsorbed water. Then, they were ground in a mortar and passed through a 100-mesh standard sieve. The powder that passed through the sieve was collected for later use.

[0065] (2) Accurately weigh 2.000 g of each powder sample and place it in a 250 mL Erlenmeyer flask. Add 100 mL of a neutral ammonium acetate solution with a concentration of 1 mol / L. Place the Erlenmeyer flask in a constant temperature shaker and shake at 150 rpm for 2 hours at 25 degrees Celsius to allow the ammonium ions in the solution to fully exchange with the cations in the zeolite channels.

[0066] (3) Centrifuge the exchanged suspension and discard the supernatant. Add fresh ammonium acetate solution to the precipitate and repeat the above exchange step 3 times to ensure that the exchangeable cations in the zeolite lattice are completely replaced by ammonium ions. After the exchange is completed, wash the precipitate 5 times with 95% ethanol solution until no acetate ions are detected in the washing solution to remove residual physically adsorbed ammonium salts.

[0067] (4) Transfer the washed sample to the distillation tube of the Kjeldahl nitrogen analyzer, add excess magnesium oxide powder and distilled water, and perform distillation. Since the ammonium ions exchanged in the sample will be converted into ammonia gas and released under alkaline conditions, the released ammonia gas is absorbed by boric acid solution. Finally, the boric acid absorption solution is titrated with a standard hydrochloric acid solution with a concentration of 0.05 mol / L, and the cation exchange capacity of each sample is calculated based on the volume of hydrochloric acid consumed.

[0068] Experimental data Table 1. Results of cation exchange capacity (CEC) determination for each group of samples under different heat treatment conditions. Sample number Brief description of processing conditions Sampling mass (g) Hydrochloric acid titration volume (mL) Cation exchange capacity (mmol / 100g) Relative ore retention rate (%) Natural raw ore Unprocessed reference sample 2.000 58.45 146.12 100.00 Example 1 700℃, containing flux 2.000 51.32 128.30 87.80 Example 2 680℃, high flux 2.000 52.88 132.20 90.47 Example 3 720℃, low flux 2.000 49.95 124.87 85.45 Comparative Example 1 850℃, without flux 2.000 11.04 27.60 18.88 Comparative Example 4 700℃, without flux 2.000 53.02 132.55 90.71 (Note: Although Comparative Example 4 has a high retention rate, subsequent cylinder compressive strength tests showed that its structure was loose and no effective sintering was formed. It is only used here as a comparison of lattice thermal stability.) Results Analysis and Conclusions: Based on the data analysis in Table 1, the cation exchange capacity of natural clinoptilolite ore is 146.12 mmol / 100g, which is the benchmark value for assessing whether subsequent processes will damage lattice activity.

[0069] Comparative Example 1, using the traditional ceramic sintering temperature of 850°C, showed a sharp decrease in cation exchange capacity to 27.60 mmol / 100g, with a relative retention rate of only 18.88%. This data indicates that at the high temperature of 850°C, the microporous channels inside the zeolite underwent severe collapse, with most of the aluminosilicate lattice transforming into an amorphous glassy state or a dense feldspar phase. This resulted in the closure or destruction of the originally active ion exchange sites, causing the material to lose its core function as a water treatment adsorbent.

[0070] In contrast, the cation exchange capacities of Examples 1, 2, and 3 remained above 124 mmol / 100g, with relative retention rates consistently between 85% and 90%. Data fluctuations were mainly influenced by fine-tuning of the sintering temperature and the amount of outer silica gel coating, but overall remained at a high level. This confirms the effectiveness of the low-temperature eutectic sintering mechanism proposed in this invention: by introducing sodium carbonate as a fluxing agent and generating sodium chloride in situ within the system, a surface liquid phase based on sodium silicate was successfully induced to form in the range of 680 to 720 degrees Celsius. This temperature range is entirely within the thermal stability range of natural clinoptilolite (typically less than 750 degrees Celsius).

[0071] It is worth noting that Comparative Example 4 also maintained a high CEC value (132.55 mmol / 100g) at 700 degrees Celsius, indicating that 700 degrees Celsius itself did not destroy the zeolite structure. However, combined with the physical state observations during the actual preparation process, Comparative Example 4, due to the lack of sodium carbonate flux, failed to generate sufficient liquid phase for interparticle welding at this temperature, resulting in extremely low strength of the finished product, which could not meet the requirements of engineering applications.

[0072] The technical solution of this invention successfully resolves the contradiction between sintering strength and lattice activity. By utilizing the low-temperature eutectic effect, the original framework structure and ion exchange performance of zeolite are preserved to the greatest extent while ensuring the mechanical strength of the particles.

[0073] Test Example 2: Verification of dissolution and pore-forming efficiency of in-situ salt templates: This test aims to verify the technical mechanism of the salt phase, a reaction byproduct, as a sacrificial template for pore formation proposed in this invention by quantitatively detecting the changes in chloride ion content and corresponding porosity evolution in the sample before and after the cleaning process. The test focuses on whether the eutectic salt phase inside the sintered body can be effectively removed under mild water washing conditions, and the contribution of this removal process to the final pore structure of the filter media.

[0074] Experimental steps: (1) Examples 1, 4 (high rare earth / high salt concentration), Comparative Example 1 (high temperature sintering), and Comparative Example 4 (low temperature without flux) were selected as test objects. For Examples 1 and 4, samples were taken at two points: before water quenching after rotary kiln sintering (referred to as the sintered state) and at the final product (referred to as the cleaned state). For the comparative example samples, the final product was taken directly. All samples were dried at 105 degrees Celsius to constant weight.

[0075] (2) Determination of chloride ion content (salt residue): Accurately weigh 10.00 g of the ground powder sample, place it in a beaker, add 100 mL of deionized water, heat to boiling for 15 minutes and sonicate for 10 minutes to extract residual soluble chloride from the sample. Filter to separate the solid and liquid, add potassium chromate indicator to the filtrate, and titrate with standard silver nitrate solution to calculate the mass percentage of water-soluble chloride ions in the sample.

[0076] (3) Determination of physical structural parameters: Following the standard method of "Artificial Ceramic Filter Media for Water Treatment" (CJ / T 299-2008), the particle density (apparent density) and bulk density of each group of particle samples were determined using the Leigh flask method and the graduated cylinder method, respectively. The apparent porosity (i.e., open porosity) of each sample was calculated based on the density data. Apparent porosity is a key indicator for measuring the effective contact area between the filter media and the water body.

[0077] Experimental data: Table 2. Monitoring Table of Chloride Ion Content and Pore Structure Parameters of Each Group of Samples at Different Process Stages Sample number Process status Chloride ion content (%) <![CDATA[Particle density (g / cm 3 )]]> <![CDATA[Bulk density (g / cm 3 )]]> Apparent porosity (%) Example 1 Sintered state (unwashed) 3.42 1.98 1.15 28.4 Example 1 Cleaned state (finished product) 0.08 1.45 0.83 42.1 Example 4 Sintered state (unwashed) 4.15 2.05 1.21 24.6 Example 4 Cleaned state (finished product) 0.11 1.41 0.79 45.3 Comparative Example 1 Finished product (850℃) 0.04 2.35 1.48 14.2 Comparative Example 4 Finished product (without flux) 2.89 1.92 1.09 31.5 Results Analysis and Conclusions: According to the data in Table 2, Example 1, sintered in a rotary kiln but not washed with water, showed a chloride ion content as high as 3.42%. This confirms that the ammonium chloride added during the preparation process, as well as byproducts such as sodium chloride generated by the acid-base reaction, did not completely volatilize after water evaporation, but remained inside the particles as solid salts or eutectic salts. At this time, the apparent porosity of the sample was only 28.4%, and the particle density was relatively high (1.98 g / cm³). 3 This indicates that the salt phase filled the voids inside the particles at this point.

[0078] After soaking and leaching in deionized water, the chloride ion content of the cleaned product in Example 1 dropped sharply to 0.08%, with a removal rate exceeding 97%. Along with the removal of salt, its apparent porosity increased from 28.4% to 42.1%, while the particle density decreased to 1.45 g / cm³. 3 The dramatic change in this data quantitatively confirms the existence of the in-situ salt template mechanism: during sintering, the molten salt phase acts as a liquid-phase binder; after cooling, the salt phase recrystallizes and occupies space; during the water washing stage, the salt phase dissolves, leaving interconnected channels. Example 4, due to the use of a higher concentration of acidic rare earth activating solution (introducing more chloride ions) and a higher liquid-phase ratio, had a higher sintered salt content (4.15%) and a higher final porosity after dissolution (45.3%), further supporting the positive correlation between salt content and final porosity.

[0079] In contrast, Comparative Example 1, sintered at 850 degrees Celsius, had an extremely low chloride ion content (0.04%), primarily due to chloride volatilization caused by the high temperature. More importantly, its apparent porosity was only 14.2%, and its particle density was as high as 2.35 g / cm³. 3 This indicates that in the absence of low-temperature eutectic protection, high temperatures cause severe volume shrinkage and vitrification of the zeolite, and the original pores are blocked by molten silicate, failing to form effective filtration pores.

[0080] Comparative Example 4, sintered at low temperature without the addition of sodium carbonate flux, showed a high residual chloride ion content (2.89%) in its finished product. This is because the lack of a low-melting-point liquid phase system formed by sodium carbonate meant that pure sodium chloride (melting point 801°C) did not melt and flow at 700°C, but instead remained physically encapsulated in discrete crystals within the particles. Furthermore, due to its loose structure and blocked pores, subsequent water washing was inefficient, making it difficult to remove the internal salts. This demonstrates that the ternary eutectic system of sodium carbonate, sodium chloride, and sodium silicate constructed in this invention is crucial for achieving effective melt distribution of the salt template and subsequent efficient dissolution.

[0081] Test Example 3: Verification of Strength Formation During Asynchronous Gel Curing: This test case aims to examine the differences in particle forming strength and final mechanical strength between asynchronous dual-nozzle granulation and traditional mixed granulation methods. The test focuses on the green strength generated during the granulation stage (which determines whether continuous industrial production is possible without breakage) and the compressive strength of the finished product after sintering (which determines the wear resistance and hydraulic shear resistance of the filter media in water treatment reactors).

[0082] Experimental steps: (1) Green pellets and final products from the preparation processes of Example 1 (standard asynchronous spray), Example 5 (adjusted flow ratio), Comparative Example 2 (premixed single nozzle), and Comparative Example 5 (rare earth free common acid) were selected as test samples. To ensure the statistical significance of the data, 50 green pellets were randomly selected from each group for drop strength testing, and another 500 grams of final product pellets were selected for cylinder compression strength testing.

[0083] (2) Green pellet drop strength test: Wet green pellets, freshly rolled from the granulation disc, are dropped freely from a height of 0.5 meters onto a flat steel plate. Observe whether the pellets crack or break, and record the number of drops in which the pellets remain intact until they break. Calculate the average number of drops that each group of 50 samples can withstand. This index directly reflects the instantaneous curing ability of the liquid phase binder after a chemical reaction on the powder surface.

[0084] (3) Finished Product Cylinder Compressive Strength Test: The test was conducted according to the standard "Artificial Ceramic Abrasive Filter Media for Water Treatment" (CJ / T 299-2008). The dried finished granules were filled into a steel cylinder with an inner diameter of 50 mm and compacted to the marked height. A universal testing machine was used to apply downward pressure at a uniform speed, and the maximum pressure value at which the filler layer produced the specified compressive deformation was recorded. This value was then converted to cylinder compressive strength (MPa) through the force-bearing area.

[0085] (4) Wear rate and breakage rate test: Take 100 grams of finished particles and place them in an abrasion tester. Stir and grind them in pure water for 1 hour. After drying, sieve and weigh them. Calculate the mass ratio of powder generated by friction and impact to evaluate the density of the material structure surface.

[0086] Experimental data: Table 3. Comparison of Green Strength and Finished Mechanical Properties of Filter Media under Different Granulation Processes Sample number Brief description of process characteristics Green body drop strength (times / 0.5m) Finished cylinder compressive strength (MPa) Wear rate + breakage rate (%) Example 1 Asynchronous spraying, rare earth elements involved 6.8 6.42 1.15 Example 5 Asynchronous spraying, high acid ratio 7.2 6.18 1.28 Comparative Example 2 Premixed spray 1.4 2.05 4.86 Comparative Example 5 Asynchronous spraying, no rare earth elements 4.3 4.95 2.12 Results Analysis and Conclusions: According to the data in Table 3, the green body drop strength of Example 1 reached an average of 6.8 drops, the finished product cylinder compressive strength was 6.42 MPa, and the wear rate was only 1.15%. This indicates that through the asynchronous dual-nozzle process, alkaline modified water glass first wets the surface of the zeolite powder, and then the injected acidic rare earth active liquid initiates an in-situ acid-base reaction on the wetted layer. This in-situ reaction rapidly generates a tough silica gel and rare earth silicate composite shell on the particle surface, giving the green body high structural strength before drying, enabling it to withstand the drop during industrial production.

[0087] In contrast, the green compact of Comparative Example 2 had a drop strength of only 1.4 cycles, a significantly reduced finished product cylinder compressive strength of 2.05 MPa, and a wear rate as high as 4.86%. This is because when component A and component B are premixed, they undergo a violent gelation reaction in the mixing tank or pipeline before entering the granulator, generating gel clumps that have lost their binding activity. At this point, the sprayed liquid is essentially a mixture of water and gel fragments, which cannot form continuous chemical bonds on the surface of the zeolite powder. It only maintains its shape through the physical tension of water, resulting in a loose structure after drying, i.e., so-called pseudo-granules, which cannot meet the basic strength requirements of water treatment filter media.

[0088] Furthermore, comparing Example 1 with Comparative Example 5 (without rare earth elements, using only hydrochloric acid), although Comparative Example 5 also employed an asynchronous spraying process, its green strength (4.3 times) and finished product strength (4.95 MPa) were superior to Comparative Example 2, but still significantly lower than Example 1. This data difference confirms the dual role of rare earth elements in the curing process: they not only serve as active sites for subsequent phosphorus removal but also participate in framework construction as crosslinking agents. The rare earth silicate precipitates formed by rare earth ions (such as lanthanum and cerium) and silicate ions have higher hardness and chemical stability than ordinary silica gels, thereby further improving the overall mechanical properties of the filter material. Example 5 further improved the green strength (7.2 times) by increasing the acid ratio, indicating that sufficient acid supply helps the gel reaction to proceed thoroughly. However, excessive acid can cause a slightly loose microstructure during subsequent sintering, resulting in a slight decrease in the finished product strength (6.18 MPa), but it is still within the excellent range.

[0089] Test Example 4: Comprehensive Comparison of Physical Structural Performance This test case aims to comprehensively evaluate the ability of different preparation processes to balance and control the microstructure and macroscopic mechanical properties of filter media through multi-dimensional physical parameter characterization. The test focuses on examining whether the synergistic mechanism of low-temperature eutectic sintering and embedded oxidation cleaning proposed in this invention can maximize the maintenance and development of the effective specific surface area and pore volume of zeolite while ensuring the mechanical strength required for engineering applications.

[0090] Experimental steps: (1) Sample preparation: Finished filter media prepared by Examples 1 to 5, and Comparative Examples 1 (high temperature sintering), 3 (without embedded oxidant), and 4 (without flux) were selected respectively. The particle samples were placed in a vacuum drying oven and degassed at 120 degrees Celsius for 4 hours to remove the moisture and impurity gases adsorbed in the pores.

[0091] (2) Specific surface area and pore structure determination: The specific surface area and pore size were measured using a fully automated specific surface area and pore size analyzer. Approximately 0.5 g of the degassed sample was weighed and nitrogen adsorption and desorption isotherms were measured at liquid nitrogen temperature (77 K). The specific surface area of ​​the sample was calculated based on the multi-point Brunauer-Emmett-Teller equation; the total pore volume and average mesopore size distribution were calculated using the Barrett-Joyner-Halenda model and desorption branch data.

[0092] (3) Macroscopic mechanical strength verification: In order to establish a correspondence with the microstructural parameters, the above batch of samples were subjected to cylinder compressive strength test again. The test method refers to "Artificial Ceramsite Filter Media for Water Treatment" (CJ / T 299-2008), and the stress value at the time of crushing was recorded.

[0093] (4) Bulk density determination: The natural bulk density of the sample was determined by measuring cylinder method. This index reflects the filling performance and internal density of the particles.

[0094] Experimental data: Table 4. Comprehensive test results of physical structure parameters and mechanical properties of finished filter media for each group Sample number Brief description of process characteristics <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Total pore volume (cm 3 / g)]]> Average pore size (nm) Cylinder compressive strength (MPa) <![CDATA[Bulk density (g / cm 3 )]]> Example 1 700℃, standard eutectic 38.45 0.214 8.24 6.42 0.83 Example 2 680℃, high flux 36.12 0.208 7.95 5.89 0.85 Example 3 720℃, low flux 35.88 0.198 8.56 6.75 0.88 Example 4 High rare earth content, high acidity 41.20 0.225 9.12 6.55 0.79 Example 5 High acid ratio 39.05 0.218 8.84 6.18 0.81 Comparative Example 1 850℃, high-temperature hard burning 4.12 0.035 18.50 12.45 1.48 Comparative Example 3 No embedded oxidant 18.56 0.112 6.45 6.30 0.95 Comparative Example 4 700℃, without flux 42.15 0.231 8.15 1.15 0.76 (Note: The larger average pore size in Comparative Example 1 is due to micropore collapse, leaving only a small number of macropores or cracks, rather than an effective mesoporous structure.) Results Analysis and Conclusions: Based on the data analysis in Table 4, the embodiments of the present invention have achieved a significant balance between microporous structure and macroscopic mechanical properties, confirming the synergistic effect of multiple modification mechanisms.

[0095] First, compared with Example 1 (specific surface area 38.45 m²), 2 / g) and Comparative Example 3 (specific surface area 18.56m²) 2 The processes for both examples ( / g) were identical except for the presence or absence of sodium persulfate. Data showed that Comparative Example 3, lacking an embedded oxidant, had only about half the specific surface area and total pore volume of Example 1. This indicates that organic impurities and adsorbed water inherent in the natural zeolite minerals occupied a large number of pores. The Example 1, by introducing sodium persulfate, decomposed and released oxygen free radicals in situ during the preheating stage, effectively cleaning and unblocking these micropores from the inside out, thus increasing the effective specific surface area of ​​the material.

[0096] Secondly, comparing Example 1 and Comparative Example 1 (high-temperature sintering), the specific surface area of ​​Comparative Example 1 decreased sharply to 4.12 m². 2 / g, the total pore volume is almost negligible (0.035cm³). 3 Although its compressive strength reached 12.45 MPa, it had completely lost its structural basis as a porous adsorbent material. This confirms that a high temperature of 850 degrees Celsius leads to severe lattice collapse and liquid-phase closure of the zeolite framework. In contrast, Example 1, using sodium carbonate-assisted low-temperature eutectic technology, achieved an engineering strength of 6.42 MPa at 700 degrees Celsius while retaining nearly 10 times the specific surface area of ​​the high-temperature sample.

[0097] Furthermore, comparing Example 1 and Comparative Example 4 (without flux), Comparative Example 4, although possessing the highest specific surface area (42.15 m²), 2 / g (because no liquid phase filling occurred), but its cylinder compressive strength is only 1.15MPa, far below the general standard for water treatment filter media (usually requiring greater than 4MPa), making it extremely easy to break and be lost under the scouring of water flow. This, in turn, proves the necessity of low-temperature liquid phase welding in this invention: an appropriate amount of liquid phase sacrifices a very small amount of porosity (slightly lower in Example 1 than in Comparative Example 4), but in return, it achieves a multiple increase in strength.

[0098] Furthermore, data from Examples 4 and 5 show that by increasing the concentration or proportion of the acidic rare earth active liquid, the specific surface area (41.20 m²) can be increased. 2 Both the per-g and average pore size (9.12 nm) showed slight improvements. This is attributed to the slight etching effect produced by the acidic solution during its reaction with the alkaline matrix, as well as the pore-expanding effect caused by the reaction gas (such as trace amounts of hydrogen chloride or water vapor), which further optimized the pore size distribution, making it more conducive to the diffusion and transport of macromolecular pollutants.

[0099] This invention solves the strength problem through low-temperature eutectic sintering, solves the pore blockage problem through embedded oxidation, and optimizes the pore structure through salt template leaching. The combination of these three methods achieves the optimal physical properties of the filter material.

[0100] Test Example 5: Simultaneous Removal Performance Test of Ammonia Nitrogen and Total Phosphorus: This test aims to quantitatively examine the simultaneous removal capacity of the modified filter media prepared in this invention for ammonia nitrogen and phosphate in water through a static adsorption equilibrium experiment. This test is the core basis for evaluating whether the material has achieved its design goal of combining the ion exchange function of zeolite with the chemical phosphorus removal function of rare earth elements, and focuses on comparing the differences in adsorption capacity of the two target pollutants under different process conditions.

[0101] Experimental steps: (1) Preparation of simulated pollutant solution: Ammonium chloride and potassium dihydrogen phosphate were dissolved in deionized water to prepare a high-concentration adsorbate solution with an ammonia nitrogen concentration of 100 mg / L and a total phosphorus concentration of 20 mg / L. The pH of the simulated solution was adjusted to 7.0 ± 0.2 using a trace amount of sodium hydroxide solution or hydrochloric acid solution to eliminate the interference of pH on the adsorption process.

[0102] (2) Sample pretreatment: The finished filter media of Examples 1 to 5, and Comparative Examples 1 (high temperature sintering), 5 (rare earth-free), and 6 (surface impregnation) were selected. Each group of samples was ground and sieved, and particles with a particle size of 0.5 to 1.0 mm were selected for testing. The samples were washed three times with deionized water to remove surface dust, and then dried to constant weight in an oven at 105 degrees Celsius.

[0103] (3) Static adsorption experiment: Accurately weigh 0.200 g of each group of dried samples and place them in 250 ml stoppered conical flasks. Accurately add 100 ml of the simulated wastewater prepared above to each flask. Place the conical flasks in a constant temperature water bath shaker, set the temperature to 25 degrees Celsius, the rotation speed to 150 rpm, and shake in the dark for 24 hours to ensure that the adsorption reaches equilibrium.

[0104] (4) Concentration Detection and Calculation: After adsorption, the solution was allowed to stand and separate into layers. The supernatant was then filtered through a 0.45-micron filter membrane. The concentration of residual ammonia nitrogen in the filtrate was determined according to Nessler's reagent spectrophotometric method for the determination of ammonia nitrogen in water (HJ 535-2009); the concentration of residual total phosphorus in the filtrate was determined according to ammonium molybdate spectrophotometric method for the determination of total phosphorus in water (GB 11893-89). The unit adsorption capacity of each sample group was calculated based on the concentration difference before and after adsorption, the solution volume, and the mass of the adsorbent.

[0105] Experimental data: Table 5: Results of simultaneous adsorption capacity determination of ammonia nitrogen and total phosphorus for each group of filter media Sample number Brief description of process characteristics Ammonia nitrogen equilibrium adsorption capacity (mg / g) Total phosphorus equilibrium adsorption capacity (mg / g) Ammonia nitrogen removal rate (%) Total phosphorus removal rate (%) Example 1 700℃, standard eutectic 14.85 5.92 29.7 59.2 Example 2 680℃, high flux 15.12 5.68 30.2 56.8 Example 3 720℃, low flux 14.23 5.88 28.5 58.8 Example 4 High rare earth content, high acidity 13.78 8.45 27.6 84.5 Example 5 High acid ratio 14.92 6.15 29.8 61.5 Comparative Example 1 850℃, high-temperature hard burning 2.15 0.82 4.3 8.2 Comparative Example 5 No rare earth elements, only acid activation. 15.65 0.15 31.3 1.5 Comparative Example 6 Surface impregnation with rare earth 14.55 3.25 29.1 32.5 (Note: The removal rate is calculated based on the dosage of 2g / L set in this experiment and is only used for horizontal comparison. It does not represent the actual maximum removal rate in engineering.) Results Analysis and Conclusions: Based on the data analysis in Table 5, the modified filter material prepared in this invention successfully achieved simultaneous and efficient removal of ammonia nitrogen and phosphate, verifying the synergistic working mechanism of different active sites within the material.

[0106] First, regarding ammonia nitrogen adsorption performance: the ammonia nitrogen adsorption capacity of Examples 1 to 5 remained in the high range of 13.78 to 15.12 mg / g, which was almost the same as that of Comparative Example 5 (15.65 mg / g), which only underwent acid activation but did not add rare earth elements. Comparative Example 5 had the highest ammonia nitrogen adsorption value because its pores were not occupied by rare earth precipitates, fully exposing the original ion exchange sites of the zeolite. The data from the example group show that although the rare earth silicate framework occupied some space, the microporous channels of the zeolite were effectively unblocked due to the salt template pore-forming and embedded oxidation cleaning technology used in this invention, allowing most of the ion exchange sites to still be accessible to ammonium chloride. In contrast, Comparative Example 1, due to sintering at 850 degrees Celsius, experienced lattice collapse, and its ammonia nitrogen adsorption capacity plummeted to 2.15 mg / g, almost losing its processing capacity.

[0107] Secondly, regarding the total phosphorus adsorption performance: Example 1 achieved a total phosphorus adsorption capacity of 5.92 mg / g, which is superior to Comparative Example 5 (0.15 mg / g). This significant difference confirms that zeolite itself has almost no chemical adsorption capacity for phosphate, and the phosphorus removal function is entirely derived from the introduced acidic rare earth active liquid. When rare earth ions react with the silicate framework, rare earth hydrated oxides or lanthanum silicate microcrystals with positive charge characteristics are formed inside the pores and on the surface. These sites specifically capture phosphate in the water through a ligand exchange mechanism.

[0108] Of particular note is the comparison between Example 4 and Comparative Example 6. Example 4 (high rare earth formulation) exhibited the highest total phosphorus adsorption capacity of 8.45 mg / g, the highest among all groups. In contrast, Comparative Example 6, using a traditional surface impregnation process after sintering, achieved a total phosphorus adsorption capacity of only 3.25 mg / g. This demonstrates that surface impregnation only adheres a limited layer of active material to the outer surface of the particles, which is easily saturated and prone to detachment. In contrast, the in-situ doping and asynchronous granulation process of this invention deeply embeds the rare earth active components into the three-dimensional framework within the particles. Combined with the high porosity demonstrated in Test Example 2, water flow can penetrate the particles and utilize the deep rare earth sites for adsorption, thereby significantly increasing the saturated adsorption capacity per unit mass of filter media.

[0109] The technical solution of this invention protects the background function of zeolite in removing ammonia nitrogen through low-temperature eutectic and endows it with the additional function of removing total phosphorus through in-situ framework construction. The two types of active sites do not interfere with each other, coexist and complement each other, achieving the technical effect of multiple uses of one material.

[0110] Test Example 6: Material Stability and Safety Test (Long-Term Effectiveness): This test case aims to evaluate the chemical stability and environmental safety of modified filter media in long-term water treatment applications. The focus is on investigating whether there is a risk of release of the active rare earth components loaded in the filter media into the water body (rare earth leaching rate), and the filter media's resistance to corrosion under different pH conditions (acid and alkali loss rate). These are key indicators of whether a material can serve for a long time in complex real-world aquatic environments without causing secondary pollution.

[0111] Experimental steps: (1) Rare Earth Leaching Safety Test: Finished filter media prepared in Example 1 (standard eutectic), Example 4 (high rare earth content), and Comparative Example 6 (traditional surface impregnation modification) were selected. 50.0 g of each sample was weighed and placed in a polyethylene wide-mouth bottle. 1000 mL of deionized water (solid-liquid ratio 1:20) was added, and the pH was adjusted to 7.0. The sample bottles were placed in a constant-temperature shaker to simulate a water flow environment (100 rpm) and continuously shaken for 30 days. Samples were taken every 5 days, but the final equilibrium concentration on day 30 was used as the criterion. After filtration through a 0.22 μm filter membrane, the total concentration of rare earth elements such as lanthanum and cerium in the water was determined using inductively coupled plasma mass spectrometry.

[0112] (2) Chemical stability test for acid and alkali resistance: The chemical stability test method was improved according to the "Artificial Ceramsite Filter Media for Water Treatment" (CJ / T 299-2008).

[0113] Acid resistance test: Accurately weigh 100g of each group of dried filter media samples, place them in a 500ml beaker, add a 20% (w / w) industrial hydrochloric acid solution to soak them, and let them stand at room temperature for 24 hours with occasional stirring. After soaking, wash with deionized water until neutral, dry to constant weight, and calculate the mass loss rate.

[0114] Alkali resistance test: Take another 100g sample and immerse it in a 20% sodium hydroxide solution. Repeat the above steps. This test aims to simulate the destructive effect of extreme pH fluctuations on the filter media skeleton.

[0115] Experimental data: Table 6: Monitoring Results of Rare Earth Leaching Concentration and Acid / Alkali Mass Loss Rate of Filter Media in Each Group Sample number Brief description of process characteristics Rare earth leaching concentration after 30 days (mg / L) Acid resistance mass loss rate (%) Alkali resistance mass loss rate (%) Example 1 700℃, standard eutectic 0.012 1.24 1.85 Example 4 High rare earth content, high acidity 0.018 1.31 1.92 Comparative Example 6 Surface impregnation with rare earth 0.453 2.15 3.48 Comparative Example 1 850℃, high-temperature hard burning <0.001 0.45 0.62 National Standard / Reference Limit (Refer to surface water environmental quality standards or relevant toxicological safety thresholds) <0.100 <2.00 <2.00 (Note: Although Comparative Example 1 is extremely stable, the aforementioned tests have proven that it has no adsorption properties; the rare earth concentrations in the table represent the total amount of lanthanum and cerium ions.) Results Analysis and Conclusions: Based on the data analysis in Table 6, the modified filter material prepared by this invention exhibits excellent performance in terms of chemical stability and environmental safety, confirming the inherent advantages of skeleton solidification over surface loading.

[0116] Regarding environmental safety (rare earth leaching rate): After 30 days of long-term hydraulic shear immersion, the rare earth ion concentrations in the water in Examples 1 and 4 were only 0.012 mg / L and 0.018 mg / L, respectively. This value is far below the limit thresholds for heavy metals or specific trace elements in general surface water environmental quality standards and drinking water hygiene standards (typically reference values ​​are less than 0.1 mg / L). This directly confirms that the core mechanism of this invention is that rare earth elements are not simply physically adsorbed onto the particle surface, but rather form insoluble rare earth silicate precipitates with silicate ions through an acid-base coupled asynchronous gel reaction, and are further firmly locked in the lattice nodes of the three-dimensional aluminosilicate framework during low-temperature eutectic sintering. This chemical bonding reduces the mobility of rare earth ions.

[0117] In contrast, the rare earth leaching concentration in Comparative Example 6 (surface impregnation method) was as high as 0.453 mg / L, nearly 38 times that of Example 1. This is because the impregnation method only attaches the active components to the outermost layer of the filter media through physical adsorption or weak chemical bonds, resulting in weak binding forces. Under continuous water flow, desorption or peeling easily occurs. This not only leads to a rapid decline in the phosphorus removal performance of the filter media over time (short lifespan), but also brings the environmental risk of releasing rare earth pollutants into the water.

[0118] Regarding acid and alkali corrosion resistance: In 20% high-concentration hydrochloric acid and sodium hydroxide solutions, Example 1 showed mass loss rates of 1.24% and 1.85%, respectively, both meeting or exceeding the national standard requirements for artificial ceramic filter media (typically required to be less than 2%). Although its stability was slightly lower than that of the fully vitrified Comparative Example 1 (high-temperature sintering, loss rate <1%), considering that Comparative Example 1 had completely lost its adsorption activity, the slight loss in Example 1 is a minor cost necessary to obtain a high specific surface area and high active sites. The data from the examples show that the liquid-phase welded layer formed by low-temperature eutectic has good chemical corrosion resistance, protecting the internal zeolite skeleton from disintegration in acidic or alkaline wastewater fluctuations, thus ensuring a long service life of the filter media in industrial applications.

Claims

1. A modified nanofilter material for water pollution treatment, characterized in that, It is prepared by granulation and sintering of raw materials containing solid powder raw materials and liquid phase binder and curing agent; The solid powder raw material comprises the following components in parts by weight: Natural zeolite powder: 58-75 parts; Natural rare earth mineral powder: 10-20 parts; Flux modifier: 2-5 parts; Embedded oxidant: 3-7 parts; Ion exchange enhancer: 4-8 parts; The liquid phase binder and curing agent comprises a modified water glass liquid phase binder and an acidic rare earth active liquid.

2. The modified nanofilter material for water pollution treatment according to claim 1, characterized in that, The natural zeolite powder is natural clinoptilolite powder; The natural rare earth mineral powder is one or more of the following: natural basalt fluoride powder, monazite powder, or xenotime powder. The fluxing modifier is one or more of anhydrous sodium carbonate, potassium carbonate, or borax. The embedded oxidant is one or more of sodium persulfate, potassium persulfate, or ammonium persulfate; The ion exchange enhancer is ammonium chloride.

3. The modified nanofilter material for water pollution treatment according to claim 1, characterized in that, The preparation method of the modified water glass liquid phase binder is as follows: Dilute liquid sodium silicate with a modulus of 2.2-2.6 with deionized water to a Baume degree of 30-32Be', then add 0.3%-0.8% sodium dodecylbenzenesulfonate by mass of the diluted solution and stir until it becomes transparent.

4. The modified nanofilter material for water pollution treatment according to claim 1, characterized in that, The preparation method of the acidic rare earth active liquid is as follows: The natural fluorocarbon cerium ore powder is mixed with industrial hydrochloric acid with a mass concentration of 20%-31% at a solid-liquid mass ratio of 1:(3-5), and reacted at 80-95℃ for 3-5 hours. The slag is removed by filtration, and the pH of the filtrate is adjusted to 0.5-1.

5.

5. A method for preparing modified nanofilter material for water pollution treatment, characterized in that, The preparation of a modified nanofilter material for water pollution treatment according to any one of claims 1-4 includes the following steps: Weigh out the natural zeolite powder, natural rare earth mineral powder, fluxing modifier, embedded oxidant and ion exchange enhancer according to the weight parts, and mix them evenly to obtain a premixed dry powder. The premixed dry powder is added to the granulation equipment and sprayed through a dual-nozzle system. First, a modified water glass liquid phase binder is sprayed to nucleate the powder. After the mother ball is formed, an acidic rare earth active liquid is sprayed to solidify it, thus obtaining green granules. The green pellets are dried in stages to control the final moisture content; The dried green pellets are heated and sintered, the channels are cleaned with embedded oxidant, and a liquid phase eutectic is formed at 680-720°C with fluxing agent, followed by liquid phase welding. The sintered particles are cooled by water quenching and soaked in water to dissolve the internal salt phase by-products, and then dried to obtain the finished product.

6. The method for preparing modified nanofilter material for water pollution treatment according to claim 5, characterized in that, The nozzle for spraying the modified water glass liquid phase binder is located in the material discharge area of ​​the granulation equipment, and the nozzle for spraying the acidic rare earth active liquid is located in the pelletizing area of ​​the granulation equipment. The mass ratio of the injection flow rate of the modified water glass liquid phase binder to that of the acidic rare earth active liquid is (1.4-2.0):1; The total amount of the modified water glass liquid phase binder and the acidic rare earth active liquid is 35%-45% of the total mass of the premixed dry powder.

7. The method for preparing modified nanofilter material for water pollution treatment according to claim 5, characterized in that, The segmented drying includes: The first stage of drying is at a temperature of 65-75℃ and a drying time of 30-50 minutes; The second stage of drying is at a temperature of 105-115℃ and a drying time of 60-80 minutes. The final moisture content is controlled to be below 4.5%.

8. The method for preparing modified nanofilter material for water pollution treatment according to claim 5, characterized in that, The heating and sintering process includes: Heat to 380-420℃ at a rate of 5-10℃ / min and hold for 20-40 minutes, then continue heating to 680-720℃ and sinter at a constant temperature for 90-120 minutes.

9. A method for preparing modified nanofilter material for water pollution treatment according to claim 5, characterized in that, The water quenching cooling process is as follows: The sintered particles are directly introduced from a high temperature state into circulating water at a temperature of 20-40℃; The soaking and cleaning time is 20-50 minutes, until the reaction byproduct salt phase inside the filter material dissolves.

10. A method for preparing modified nanofilter material for water pollution treatment according to claim 5, characterized in that, The step of drying to obtain the finished product includes: After soaking and washing, the particles are subjected to solid-liquid separation and sieving, and then dried at 100-115℃ to constant weight.