High-performance ceramsite, its preparation method and application

Abstract

The application provides a preparation method of high-performance ceramsite, comprising the following steps: improving and pretreating red mud by using desulfurization gypsum to obtain improved red mud; mixing and sufficiently homogenizing the improved red mud, zeolite, nut shell, binder and waste glass powder according to a certain ratio to obtain raw material; adding inorganic polymer flocculant solution to the raw material to form dry thick paste; granulating, drying and shaping the dry thick paste, and then roasting, so as to obtain the high-performance ceramsite. The preparation method is economic, efficient and environmentally friendly, the required raw materials are simple and easy to obtain, and the waste resources are fully utilized. The obtained ceramsite contains conventional large pore structure and mesopore structure, and has high compressive strength, good adsorption performance, good nitrogen and phosphorus removal effect, no back-alkali and frosting phenomenon, and the content of heavy metals and leaching toxicity are not over standard, and the ceramsite is safe and stable.

Description

Technical Field

[0001] This application belongs to the fields of comprehensive water environment management (preparation technology of water purification filler) and solid waste resource utilization technology. Specifically, it relates to a method for preparing adsorption filler for sewage treatment facilities or landscape construction such as constructed wetlands, biological filters, sewage treatment plant deep treatment ponds, and in-situ ecological restoration of rivers, and its application. Background Technology

[0002] Red mud, a major solid waste that has long been difficult for the alumina production industry to dispose of, has seen a series of measures implemented in recent years aimed at promoting its harmless and resource-oriented treatment, and addressing key issues such as red mud modification, graded utilization, and low-cost dealkalization. Red mud is rich in active metals such as Fe, Al, Ca, and Mg, which can form precipitates with phosphates; its structural characteristics and mineral composition make it a phosphorus-adsorbing matrix. However, red mud recovered from stockpiles is often in powder form, with limited phosphorus adsorption capacity and difficulty in secondary recycling; at the same time, its loose structure and high salinity and alkalinity place high demands on its rational disposal and comprehensive resource utilization.

[0003] Expanded clay aggregates are classified into calcined expanded clay aggregates and non-calcined expanded clay aggregates based on their manufacturing process. They consist of two parts: a ceramic matrix (structural material) and additives. Generally, the preparation method for red mud expanded clay aggregates involves granulation followed by dealkali removal, or dealkali removal followed by granulation. Currently, the main methods for controlling alkali in the red mud granulation process are granulation followed by acid leaching for dealkali removal, or water washing / acid leaching / neutralization with acidic gas for dealkali removal followed by granulation. However, these techniques are not economically viable, have high costs, and can cause secondary pollution problems.

[0004] Zeolite is an abundant aluminosilicate mineral with the general chemical formula M. x / n (AlO2) x (SiO2) y Zeolite, with its high content of active silicon and active aluminum, exhibits excellent ion exchange performance and a large internal specific surface area. Therefore, its surface readily combines with alkali metal or alkaline earth metal cations, making it a consistently effective adsorbent for ammonia nitrogen, organic pollutants, and heavy metal ions. However, the removal of ammonia nitrogen by natural zeolite is limited. Modified zeolite (acid-, alkali-, salt-, and thermal) is more commonly used, but requires specific technologies and equipment, increasing production costs, resulting in poor economic efficiency and cumbersome procedures. Summary of the Invention

[0005] Faced with the challenges of low utilization rate and high requirements for reduction and harmlessness in the disposal of bulk solid waste red mud, the unresolved issues of nitrogen and phosphorus pollution and eutrophication in water bodies, and the difficulties in achieving both adsorption effect and strength in red mud ceramsite, developing a high-performance ceramsite with a reasonable raw material structure and controllable cost to achieve solid waste disposal and deep treatment / recycling of nitrogen and phosphorus has significant economic value and environmental benefits.

[0006] In view of the above-mentioned technical problems, the purpose of this application is to provide a method for preparing high-performance ceramsite.

[0007] To achieve the above objectives, this application proposes the following solution:

[0008] In a first aspect, a method for preparing high-performance ceramsite is provided, comprising:

[0009] S1. Red mud is pretreated with desulfurized gypsum to obtain improved red mud;

[0010] S2. Mix and homogenize the modified red mud with zeolite, nut shells, binder, and waste glass powder to obtain raw material; wherein, the modified red mud is 40-120 parts, the zeolite powder mixture is 40-120 parts, the nut shells are 10-40 parts, the binder is 10-40 parts, and the waste glass powder is 2-5 parts.

[0011] S3. Add an inorganic polymer flocculant solution to the raw material to form a dry, thick paste;

[0012] S4. After granulating, drying and shaping the dry thick paste, calcining it to obtain high-performance ceramic particles.

[0013] Preferably, in step S1, the amount of desulfurized gypsum used is 2-20%; the improvement pretreatment time is 7-20 days; the improvement pretreatment specifically includes: mixing desulfurized gypsum into red mud, fully wetting it, and spraying water at regular intervals.

[0014] Preferably, the zeolite is a mixture of zeolite powder and granules; the mixture includes zeolite powder and zeolite granules; the mass ratio of zeolite powder to zeolite granules is 1~3:1.

[0015] Preferably, the zeolite is any one or more of natural zeolites; the zeolite powder passes through a 70-100 mesh sieve; and the zeolite particles have a particle size of 0.3-1 mm.

[0016] Preferably, the waste glass powder has a particle size that passes through a 50-100 mesh sieve;

[0017] The binder is one or more of sodium silicate, cement, bentonite, starch, cellulose, resin, and gelatin;

[0018] Red mud is one or more of the following: Bayer process red mud, sintering process red mud, or mixed process red mud.

[0019] Preferably, the concentration of the inorganic polymeric flocculant solution is 20~30g / L; the inorganic polymeric flocculant is polyaluminum chloride, polyferric chloride, polyferric sulfate or polyaluminum sulfate.

[0020] Preferably, the particle size of the nut shell is 0.4~0.8mm; the nut shell is any one or more of the following: walnut shell, macadamia nut shell, pine nut shell, pistachio shell, hazelnut shell, almond shell, cashew shell.

[0021] Preferably, the particle size of the high-performance ceramsite is 0.5~2cm.

[0022] Preferably, the roasting temperature is 650~1200℃; the roasting time is 4~10h; the drying and shaping temperature is 45~65℃; and the drying and shaping time is 4~8h.

[0023] Secondly, a high-performance ceramsite is provided, which is prepared using the aforementioned preparation method.

[0024] Thirdly, it provides applications of high-performance ceramsite in the treatment of any type of wastewater, including nitrogen-containing wastewater, phosphorus-containing wastewater, and wastewater containing both nitrogen and phosphorus.

[0025] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0026] 1. Using desulfurized gypsum-modified red mud, zeolite, nut shells, binders, and waste glass powder as raw materials, and adding an inorganic polymer flocculant solution, a dry, thick paste is prepared. After granulation, drying, shaping, and calcination, the resulting ceramsite contains both conventional macroporous and mesoporous structures. While ensuring high compressive strength, it also exhibits good adsorption performance and effective removal of nitrogen and phosphorus. Furthermore, the prepared ceramsite shows no signs of alkali return or blooming, and the heavy metal content and leaching toxicity do not exceed standards. It is economical, efficient, safe, and stable.

[0027] 2. The method for preparing ceramsite not only requires simple and readily available raw materials, but also overcomes the harsh conditions of preparing red mud ceramsite, consumes a variety of solid wastes, solves the problem of needing complicated auxiliary materials to reduce alkalinity and plasticization costs, and can also alleviate the problem of zeolite powder waste generated during the mining of natural zeolite.

[0028] 3. The prepared ceramsite significantly reduces treatment costs by treating waste with waste, and achieves simultaneous removal of nitrogen and phosphorus anions and cations, as well as the harmless utilization of resources. The maximum adsorption capacity of the prepared ceramsite in a nitrogen-phosphorus single system reaches 20.4951 mg / g and 8.7404 mg / g, respectively. In a nitrogen-phosphorus mixed system, the phosphorus removal rate can approach 100%, and the cylinder compressive strength can reach as high as 4.9632 MPa. After further optimization, it can be widely used in constructed wetlands, biological filters, advanced wastewater treatment ponds, aquatic ecological landscape construction, and in-situ ecological restoration of rivers. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 is a picture of red mud zeolite ceramsite with a particle size of 1.5 cm prepared in Example 4.

[0031] Figure 2 shows the adsorption effect of ceramsite on nitrogen and phosphorus in a single system in Experiment Example 1. (a) shows the trend of ammonia nitrogen adsorption over time, (b) shows the trend of total phosphorus adsorption over time, (c) shows the trend of ammonia nitrogen equilibrium adsorption over time with the concentration of the adsorption equilibrium solution, and (d) shows the trend of total phosphorus equilibrium adsorption over time with the concentration of the adsorption equilibrium solution.

[0032] Figure 3 shows the fitting curves of Langmuir, Freundlich, and Radke-Prausnitz isothermal adsorption models of ceramsite in a single system in Experiment Example 1. Among them, (a) is the fitting curve of Langmuir isothermal adsorption model, (b) is the fitting curve of Freundlich isothermal adsorption model, and (c) is the fitting curve of Radke-Prausnitz isothermal adsorption model.

[0033] Figure 4 shows the adsorption effect of ceramsite on nitrogen and phosphorus in the mixed system of Experiment Example 2. (a) shows the trend of ammonia nitrogen adsorption over time, (b) shows the trend of total phosphorus adsorption over time, (c) shows the trend of ammonia nitrogen equilibrium adsorption over time with the concentration of the adsorption equilibrium solution, and (d) shows the trend of total phosphorus equilibrium adsorption over time with the concentration of the adsorption equilibrium solution. Detailed Implementation

[0034] Some embodiments provide a method for preparing high-performance ceramsite, including:

[0035] S1. Red mud is pretreated with desulfurized gypsum to obtain improved red mud;

[0036] S2. Mix and homogenize the modified red mud with zeolite, nut shells, binder, and waste glass powder to obtain raw material; wherein, the modified red mud is 40-120 parts, the zeolite powder mixture is 40-120 parts, the nut shells are 10-40 parts, the binder is 10-40 parts, and the waste glass powder is 2-5 parts.

[0037] S3. Add an inorganic polymer flocculant solution to the raw material to form a dry, thick paste;

[0038] S4. After granulating, drying and shaping the dry thick paste, calcining it to obtain high-performance ceramic particles.

[0039] The above technical solution combines the advantages of the physicochemical properties of red mud and zeolite. On the one hand, it introduces the abundant micropores of zeolite, enriching its adsorption sites, improving the hydraulic conductivity, and supporting the compressive strength of the ceramsite. At the same time, it can fully absorb solid waste red mud and adjust the silicon / aluminum / iron ratio in the ceramsite. On the other hand, it works synergistically with nut shells, waste glass solid waste, binders, and inorganic polymer flocculants to achieve synergistic effects. Moreover, each material is burned to partial melting and solidified into hard aggregate particles after cooling, which synergistically establishes effective mechanical strength, resulting in higher strength, lower water absorption, better thermal insulation performance, and longer service life, thereby achieving the effect of treating waste with waste and simultaneous denitrification and phosphorus removal.

[0040] The addition of nut shells enhances porosity and hardness, while also providing a slow-release carbon source when used as a water treatment filler. It also offers stable performance and avoids secondary pollution. However, excessive nut shells can degrade the strength and stability of the expanded clay aggregate, making it loose and difficult to shape. Conversely, insufficient nut shells reduce the lightweight nature of the expanded clay aggregate and impair its adsorption and water purification effects.

[0041] In some preferred embodiments, the mixture comprises 80-120 parts of modified red mud, 60-80 parts of zeolite powder, 10-30 parts of nut shells, 10-30 parts of binder, and 2-5 parts of waste glass.

[0042] In some embodiments, the desulfurized gypsum is a byproduct generated during coal-fired power generation (the main components are CaSO4·2H2O and CaSO3), and its origin is not limited.

[0043] In some preferred embodiments, in step S1, the amount of desulfurized gypsum used is 2-20%, more preferably 2-5%; the improvement pretreatment time is 7-20 days; the improvement pretreatment specifically includes: mixing desulfurized gypsum into red mud, fully wetting it, and spraying water at regular intervals. It should be explained that the purpose of spraying water at regular intervals is to maintain a moist state, usually spraying water once every 1-2 days.

[0044] In some embodiments, the red mud is one or more of Bayer process red mud, sintering process red mud, or mixed process red mud, and its place of origin is not limited.

[0045] In some preferred embodiments, the zeolite is a mixture of zeolite powder and particles. Using a mixture of zeolite powder and particles can ensure the hardness and structure of the ceramsite while ensuring a high number of enrichment and adsorption sites. The mixture of zeolite powder and particles includes zeolite powder and zeolite particles. The mass ratio of zeolite powder to zeolite particles is 1~3:1.

[0046] In some preferred embodiments, the zeolite is any one or more of natural zeolites, such as clinoptilolite, mordenite, flaky zeolite, chalcogenite, and tufted zeolite.

[0047] In some preferred embodiments, the zeolite powder passes through a 70-100 mesh sieve and is light red; the zeolite particles have a particle size of 0.3-1 mm and are light green.

[0048] In some preferred embodiments, the particle size of the nut shell is 0.4~0.8mm; the nut shell is any one or more of the following: walnut shell, macadamia nut shell, pine nut shell, pistachio shell, hazelnut shell, almond shell, and cashew shell. If the nut shell particle size is too large, it can easily lead to an uneven pore structure inside the ceramsite, which directly affects the adsorption, heat preservation, thermal insulation, and sound absorption properties of the ceramsite. Furthermore, it can degrade the lightweight properties and strength of the ceramsite. If the particle size is too small, it will burn or decompose too quickly during the firing process, resulting in insufficient expansion performance of the ceramsite, and a small particle size is also unfavorable for pore formation.

[0049] In some preferred embodiments, the particle size of the waste glass powder passes through a 50-100 mesh sieve; specifically, the waste glass is collected broken glass products, which are washed, dried, and then fully crushed into powder, ground, and then passed through a 50-100 mesh sieve.

[0050] In some embodiments, the binder is one or more of sodium silicate, cement, bentonite, starch, cellulose, resin, gelatin, etc., and is more preferably sodium silicate.

[0051] In some preferred embodiments, the concentration of the inorganic polymeric flocculant solution is 20-30 g / L; the inorganic polymeric flocculant is polyaluminum chloride, polyferric chloride, polyferric sulfate, or polyaluminum sulfate.

[0052] In some embodiments, in step S4, the granulation can be carried out manually, by mold, or by machine. The granulation method includes, but is not limited to, hand-rolling, extrusion molding, granulation machine, or other methods, as long as the granulation is not loose.

[0053] In some preferred embodiments, the particle size of the high-performance ceramic particles is 0.5~2cm.

[0054] In some preferred embodiments, the calcination temperature is 650~1200℃; the calcination time is 4~10h.

[0055] In some preferred embodiments, the drying and shaping temperature is 45~65℃; the drying and shaping time is 4~8h.

[0056] One embodiment provides a high-performance ceramsite, prepared using the aforementioned preparation method.

[0057] Some embodiments also provide the application of the high-performance ceramsite prepared in conjunction with the red mud zeolite as an adsorbent in the field of wastewater treatment.

[0058] Specifically, it can be applied to the treatment of any type of wastewater, including nitrogen-containing wastewater, phosphorus-containing wastewater, and wastewater containing both nitrogen and phosphorus.

[0059] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0060] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0061] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0062] A method for preparing high-performance ceramsite using red mud zeolite in synergistic preparation, the specific steps of which are as follows:

[0063] (1) Add 2%~20% desulfurized gypsum to the red mud for pretreatment. The improvement time is 7~20 days until the reaction is complete before putting it into use.

[0064] (2) The mixture of red mud modified by desulfurized gypsum and zeolite powder, nut shells, binder and waste glass are fully homogenized into raw material. The mass parts of each raw material are: 40-120 parts of modified red mud, 40-120 parts of zeolite powder mixture, 10-40 parts of nut shells, 10-40 parts of sodium silicate, and 2-5 parts of waste glass.

[0065] (3) Add an appropriate amount of inorganic polymer flocculant solution to the fully homogenized raw material to bind it into a dry, thick paste that is easy to form. Then, shape it using hand-kneading, extrusion molding, granulation, or other methods.

[0066] (4) The product is prepared by baking at 45~65℃ for 4~8h and then roasting. The preheating time for roasting is 30~60min, and the roasting temperature and time are 650~1200℃ and 4~10h, respectively.

[0067] The prepared shaped ceramic particles have a particle size between 0.5 and 2 cm.

[0068] It should be noted that the desulfurization gypsum selected in step ① comes from an aluminum plant in Zhengzhou (the main components are CaSO4·2H2O and CaSO3).

[0069] It should be noted that in each embodiment and comparative example, the red mud selected in step ① is sourced from Bayer process red mud of Pingguo Aluminum Industry in Guangxi, and the proportion of constant components in its composition is shown in Table 1.

[0070] Table 1. Proportion of constant components in red mud

[0071]

[0072] It should be noted that in each embodiment and comparative example, the specific steps of the improvement in step (1) are as follows: 2~20% desulfurized gypsum is added to the red mud for pretreatment, fully wetted, sprayed with water at regular intervals, and observed for 7~20 days.

[0073] It should be noted that in each embodiment and comparative example, the zeolite powder-particle mixture in step (2) is clinoptilolite, composed of zeolite powder and zeolite particles, wherein the mass ratio of zeolite powder to zeolite particles is 1~3:1. The zeolite powder passes through a 70~100 mesh sieve and is light red, while the zeolite particles have a particle size of 0.3~1mm and are light green. However, the zeolite powder-particle mixture is not limited to clinoptilolite; other natural zeolites can also be used, such as mordenite, flaky zeolite, chalcogenite, and caloite.

[0074] It should be noted that in each embodiment and comparative example, the nut shells in step (2) are walnut shells with a particle size of 0.4~0.8mm. As agricultural solid waste, walnut shells can act as pore-forming agents in ceramsite to improve porosity, hardness, and service life. As a type of solid waste biomass, it can slowly release carbon when used as a water treatment filler, providing a carbon source for nitrogen and phosphorus removal on the one hand, and being relatively stable and not causing secondary pollution on the other; it also has higher strength, lower water absorption, and better heat insulation performance. Of course, in addition to walnut shells, other nut shells such as macadamia nut shells, pine nut shells, pistachio shells, hazelnut shells, almond shells, and cashew shells can also be used as substitutes.

[0075] It should be noted that in each embodiment and comparative example, the binder used in step (2) is sodium silicate.

[0076] It should be noted that in each embodiment and comparative example, the waste glass in step (2) is collected broken high borosilicate glass products, which are washed, dried and fully crushed into powder, ground and sieved through a 50-100 mesh, and the strength of the ceramic particles can be effectively improved through the high-temperature melting process.

[0077] It should be noted that in each embodiment and comparative example, the inorganic polymeric flocculant in step (3) is selected as PAC solid particles, with the chemical formula [Al2(OH)]. n Cl 6-n ] mThe product content is 25-40%, and it is pale yellow. The concentration of the prepared PAC solution is 20-30 g / L. At high temperatures, it generates binding materials, increasing the hardness of the ceramsite; at the same time, it produces hydrogen chloride gas, which increases the porosity.

[0078] It should be noted that the high-temperature calcination in step (4) means that the ceramsite material is calcined to partial melting to increase the liquid phase content. At the same time, the foaming agent reacts and foams, generating a large number of millimeter-sized pores in the melt. In the subsequent cooling process, the melt cools and solidifies into a glass body, and the generated pores remain in the glass body to form ceramsite. In addition, the hardness of the ceramsite particles gradually increases during the high-temperature sintering process.

[0079] It should be noted that the ceramsite prepared in this invention uses modified red mud and natural zeolite as the ceramic matrix, with other materials serving as additives. The various raw materials (red mud modified with desulfurized gypsum, natural zeolite, nut shells, waste glass, binder, and inorganic polymer flocculant) in the ceramsite, in specific proportions and particle sizes, are interconnected in terms of alkali control, structure, and adsorption performance, exhibiting synergistic effects as follows:

[0080] In the desulfurized gypsum modified with Ca 2+ It preferentially precipitates with alkaline carbonates in red mud, and then undergoes calcium-sodium replacement with chemically bound alkalis. It can also precipitate with free hydroxide, carbonate, and aluminate ions in the liquid phase of red mud, producing calcium hydroxide, calcium carbonate, tricalcium aluminate, and hydrated calcium aluminate, etc. Pretreatment with desulfurized gypsum can significantly reduce the pH, EC, and Na and Al content of red mud. It can both solidify the structure and enhance the ion adsorption capacity of ceramsite, making it economical and efficient.

[0081] Red mud is rich in active metals such as Fe, Al, Ca, and Mg, which can form precipitates with phosphates, but its structure is loose. Zeolite, an aluminosilicate mineral, can help regulate the framework structure of red mud. Its surface easily combines with alkali metal or alkaline earth metal cations, and it has good adsorption effects on ammonia nitrogen and organic pollutants. It has good ion exchange performance, large internal specific surface area, and many adsorption sites. It also has ion exchange properties, adsorption and separation properties, catalytic properties, stability, chemical reactivity, reversible dehydration properties, and electrical conductivity, which can effectively inhibit the precipitation of alkali ions in red mud through pores.

[0082] The combined use of zeolite powder and granules can enrich adsorption sites, maintain the hardness structure of the ceramsite, and control alkalinity, thus making the mixture of red mud and zeolite powder and granules more stable and better at achieving simultaneous and efficient removal of anionic and cationic pollutants such as nitrogen and phosphorus.

[0083] The main function of waste glass is to adjust the Si / Al ratio in ceramsite, ensuring that the product has good sintering properties and stability. An appropriate amount of waste glass is crucial to the structure, performance, and lifespan of ceramsite.

[0084] Nut shells can act as pore-forming agents and expanding agents to increase porosity, exhibiting excellent adsorption capacity for organic matter and heavy metals, improving the hardness of ceramsite, and slow-releasing carbon sources. A certain proportion of nut shells with suitable particle size can significantly improve the physical structure, adsorption performance, and durability of ceramsite.

[0085] Inorganic polymer flocculants are beneficial for improving plasticity, strength and porosity. They also enhance adhesion by reacting with other materials such as binders, and can reduce water absorption while solidifying the structure.

[0086] During calcination, the components are tightly bound together through a melting and reforming process, increasing the hardness of the ceramsite. The fusion reaction between different components increases the liquid phase content, thereby improving the hardness of the ceramsite in terms of performance. The sintering process of ceramsite can effectively activate the raw materials, generate pores to enhance adsorption performance, solidify alkali metals, prevent the leaching of heavy metals and other harmful substances, and also avoid increasing the color of water when used in water treatment.

[0087] Example 1

[0088] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0089] ① The improved red mud obtained by adding 2% desulfurized gypsum and treating it for 20 days was selected.

[0090] ② The modified red mud and zeolite powder mixture (zeolite powder: zeolite particles = 1:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass proportions of each raw material are: 60 parts modified red mud, 60 parts zeolite powder mixture, 10 parts walnut shells, 10 parts sodium silicate, and 2 parts waste borosilicate glass powder.

[0091] ③ Add an appropriate amount of PAC solution (20g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude the paste into molds with a particle size of 0.75cm, bake at 45℃ for 4 hours to set the shape, and then calcine at 650℃ for 4 hours to obtain the final product.

[0092] Example 2

[0093] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0094] ① The improved red mud obtained by adding 2% desulfurized gypsum and treating it for 20 days was selected.

[0095] ② The modified red mud and zeolite powder mixture (zeolite powder: zeolite particles = 3:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass proportions of each raw material are: 60 parts modified red mud, 60 parts zeolite powder mixture, 10 parts walnut shells, 10 parts sodium silicate, and 2 parts waste borosilicate glass powder.

[0096] ③ Add an appropriate amount of PAC solution (20g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude the paste into molds with a particle size of 0.75cm, bake at 45℃ for 4 hours to set the shape, and then calcine at 650℃ for 4 hours to obtain the final product.

[0097] Example 3

[0098] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0099] ① The improved red mud obtained by adding 2% desulfurized gypsum and treating it for 20 days was selected.

[0100] ② The modified red mud and zeolite powder mixture (zeolite powder: zeolite particles = 2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass proportions of each raw material are: 60 parts modified red mud, 60 parts zeolite powder mixture, 10 parts walnut shells, 10 parts sodium silicate, and 2 parts waste borosilicate glass powder.

[0101] ③ Add an appropriate amount of PAC solution (20g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude the paste into molds with a particle size of 0.75cm, bake at 45℃ for 4 hours to set the shape, and then calcine at 650℃ for 4 hours to obtain the final product.

[0102] Example 4

[0103] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0104] ① The improved red mud obtained by adding 2% desulfurized gypsum and treating it for 20 days was selected.

[0105] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass proportions of each raw material are: 60 parts modified red mud, 60 parts zeolite powder mixture, 40 parts walnut shells, 10 parts sodium silicate, and 2 parts waste borosilicate glass powder.

[0106] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the ceramsite. Figure 1 As shown.

[0107] Example 5

[0108] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0109] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0110] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass proportions of each raw material are: 60 parts modified red mud, 60 parts zeolite powder mixture, 40 parts walnut shells, 10 parts sodium silicate, and 2 parts waste borosilicate glass powder.

[0111] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the final product.

[0112] Example 6

[0113] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0114] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0115] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass proportions of each raw material are: 60 parts modified red mud, 60 parts zeolite powder mixture, 40 parts walnut shells, 10 parts sodium silicate, and 5 parts waste borosilicate glass powder.

[0116] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the final product.

[0117] Example 7

[0118] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0119] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0120] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass proportions of each raw material are: 80 parts modified red mud, 60 parts zeolite powder mixture, 40 parts walnut shells, 30 parts sodium silicate, and 5 parts waste borosilicate glass powder.

[0121] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the final product.

[0122] Example 8

[0123] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0124] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0125] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass proportions of each raw material are: 80 parts modified red mud, 60 parts zeolite powder mixture, 10 parts walnut shells, 30 parts sodium silicate, and 5 parts waste borosilicate glass powder.

[0126] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the final product.

[0127] Example 9

[0128] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0129] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0130] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass proportions of each raw material are: 80 parts modified red mud, 60 parts zeolite powder mixture, 40 parts walnut shells, 30 parts sodium silicate, and 5 parts waste borosilicate glass powder.

[0131] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the final product.

[0132] Example 10

[0133] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0134] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0135] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass fractions of each raw material are: 120 parts modified red mud, 60 parts zeolite powder mixture, 30 parts walnut shells, 30 parts sodium silicate, and 5 parts waste borosilicate glass powder.

[0136] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the final product.

[0137] Example 11

[0138] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0139] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0140] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass fractions of each raw material are: 80 parts modified red mud, 60 parts zeolite powder mixture, 30 parts walnut shells, 30 parts sodium silicate, and 5 parts waste borosilicate glass powder.

[0141] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the final product.

[0142] Example 12

[0143] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0144] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0145] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass fractions of each raw material are: 80 parts modified red mud, 120 parts zeolite powder mixture, 30 parts walnut shells, 30 parts sodium silicate, and 5 parts waste borosilicate glass powder.

[0146] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the final product.

[0147] Example 13

[0148] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0149] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0150] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass fractions of each raw material are: 80 parts modified red mud, 80 parts zeolite powder mixture, 30 parts walnut shells, 30 parts sodium silicate, and 5 parts waste borosilicate glass powder.

[0151] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 6 hours to obtain the final product.

[0152] Example 14

[0153] This example provides a method for preparing high-performance ceramsite using red mud zeolite in synergy, as detailed below:

[0154] ① The improved red mud obtained by adding 5% desulfurized gypsum and treating it for 20 days was selected.

[0155] ② The modified red mud and zeolite powder mixture (2:1), walnut shells, sodium silicate, and waste borosilicate glass powder are thoroughly mixed to form raw material. The mass fractions of each raw material are: 80 parts modified red mud, 80 parts zeolite powder mixture, 30 parts walnut shells, 30 parts sodium silicate, and 5 parts waste borosilicate glass powder.

[0156] ③ Add an appropriate amount of PAC solution (30g / L) to the fully homogenized raw material to bind it into a dry, thick paste that is easy to shape. Extrude it into a mold with a particle size of 1.5cm, bake it at 60℃ for 8 hours to set it, and then calcine it at 800℃ for 8 hours to obtain the final product.

[0157] Comparative Example 1

[0158] Comparative Example 1 provides a type of ceramsite prepared by co-processing red mud and zeolite. The raw material selection and preparation method are the same as in Example 14. The difference is that the treatment time of red mud and desulfurized gypsum in Comparative Example 1 is only 1-2 hours.

[0159] Comparative Example 2

[0160] Comparative Example 2 provides a type of ceramsite prepared using red mud zeolite. The raw material selection and preparation method are the same as in Example 14. The difference is that in Comparative Example 2, the walnut shells are pre-fired into biochar before being used.

[0161] Comparative Example 3

[0162] Comparative Example 3 provides a type of ceramsite prepared using red mud zeolite. The raw material selection and preparation method are the same as in Example 14. The difference is that zeolite powder is used instead of zeolite powder-granule mixture in Comparative Example 3.

[0163] The adsorption effect, apparent density and cylinder compressive strength of the ceramsite prepared in Examples 1-14 and Comparative Examples 1-3 were measured, and the results are shown in Table 2.

[0164] Table 2. Equilibrium adsorption effect and cylinder compressive strength of ceramsite in single systems in Examples 1-14 and Comparative Examples 1-3.

[0165]

[0166] As can be seen from Table 2, a comparison of Examples 1-3 shows that increasing the proportion of zeolite powder to a certain extent increases the ammonia nitrogen removal rate, but the strength decreases; larger zeolite particles can provide better support for the hardness and strength of the ceramsite; the results show that the effect is better when the ratio of zeolite powder to zeolite particles is 2:1, which can maintain a certain strength while achieving high adsorption performance.

[0167] A comparison of Examples 4-5 shows that the strength and removal rate are better when the desulfurized gypsum addition ratio is 5%.

[0168] A comparison of Examples 5 and 6 shows that waste glass powder can improve the compressive strength of ceramsite.

[0169] A comparison of Examples 6 and 7 shows that increasing the binder content can significantly improve the strength; a comparison of Examples 8 and 9 shows that an excessively high binder content can affect the adsorption effect to some extent; considering Examples 6-9, the ratio of nut shell to binder is more suitable.

[0170] A comparison of Examples 10-13 shows that increasing the proportion of zeolite powder mixture significantly improves nitrogen and phosphorus removal rates and ceramsite strength; however, the loose structure of red mud and excessive addition can lead to a decrease in strength. Example 13, with its balanced proportions of both, achieves a balance between strength and adsorption efficiency.

[0171] A comparison of Examples 13 and 14 shows that proper control of calcination conditions further enhances the adsorption and structural properties of the ceramsite.

[0172] In summary, the ceramsite prepared using the raw material ratio and particle size in Example 14 exhibits the best nitrogen and phosphorus removal effect, the highest cylinder compressive strength, and excellent overall performance.

[0173] Based on the data from Comparative Examples 1-3, the red mud in Comparative Example 1 was not subjected to long-term and effective prior modification, Biochar material was used to replace nut shells in Comparative Example 2, and Zeolite powder was used to replace the zeolite powder-granule mixture in Comparative Example 3. The purification efficiency and strength of the ceramsite prepared in these comparative examples were significantly reduced compared with the examples, and Comparative Example 1 showed alkali return in the later stage of use.

[0174] The application and environmental risk assessment of the high-performance ceramsite described in this invention in nitrogen and phosphorus adsorption are demonstrated in the following experimental examples:

[0175] Experimental Example 1

[0176] This experimental example specifically illustrates the adsorption performance of the ceramsite prepared in Example 14 above in nitrogen-phosphorus single-system solutions.

[0177] Adsorption kinetics experiments were conducted in solutions containing 10 mg / L ammonia nitrogen and 5 mg / L total phosphorus. Isothermal adsorption experiments were performed using solutions of different concentrations of ammonia nitrogen (0.5–1000 mg / L) and total phosphorus (0.3–1000 mg / L) to investigate the maximum adsorption capacity in a single system. The amount of ceramsite added in these steps was 2–5 g, and the solution volume was 40–80 mL.

[0178] In this experimental example, the adsorption effect of ceramsite on nitrogen and phosphorus in a single system is as follows: Figure 2 As shown, (a) represents the trend of ammonia nitrogen adsorption over time, (b) represents the trend of total phosphorus adsorption over time, (c) represents the trend of ammonia nitrogen equilibrium adsorption over time with the concentration of the adsorption equilibrium solution, and (d) represents the trend of total phosphorus equilibrium adsorption over time with the concentration of the adsorption equilibrium solution.

[0179] As shown in the figure, the time for the ceramsite to reach adsorption equilibrium in the ammonia nitrogen solution in this experimental example was 17 hours, at which point the removal rate reached 40-50%. According to the Langmuir isotherm adsorption model, the maximum adsorption capacity for ammonia nitrogen reached 20.4951 mg / g.

[0180] In this experimental example, the time for the ceramsite to reach adsorption equilibrium in the phosphorus solution was 36 hours, at which point the removal rate reached 60-70%.

[0181] The maximum adsorption capacity for phosphorus, fitted according to the Langmuir isotherm adsorption model, is 8.7404 mg / g.

[0182] In this test, the maximum adsorption capacity of ceramsite for ammonia nitrogen was 2.847 mg / g, compared to modified macroporous zeolite in other studies.

[0183] Compared with the red mud modified biochar (2.97 mg / g), the maximum adsorption capacity for phosphorus is nearly ten times higher, and the adsorption performance is significantly improved compared with other materials such as natural zeolite, tourmaline ceramsite, red mud ceramsite, and clay ceramsite (0.5~3 mg / g) in other studies.

[0184] The fitting curves of the Langmuir, Freundlich, and Radke-Prausnitz isotherm adsorption models of ceramsite in a single system in Experiment Example 1 are shown below. Figure 1 As shown in Figure 3, (a) is the fitting curve of the Langmuir isotherm adsorption model, (b) is the fitting curve of the Freundlich isotherm adsorption model, and (c) is the fitting curve of the Radke-Prausnitz isotherm adsorption model. The fitting results of ceramsite with the Langmuir, Freundlich, and Radke-Prausnitz models are shown in Figure 3.

[0185] Table 3 Fitting parameters for the isothermal adsorption model

[0186]

[0187] Experimental Example 2

[0188] This experimental example provides a detailed description of the adsorption performance of the ceramsite prepared in Example 14 above in a nitrogen-phosphorus mixed solution.

[0189] In this experimental example, the high-performance ceramsite prepared by ceramsite was investigated in a mixed solution of ammonia nitrogen and total phosphorus (NH4). + The adsorption capacity of ammonia nitrogen-total phosphorus mixed solutions (0.3-2000 mg / L) with ammonia nitrogen-total phosphorus concentrations (0.3-2000 mg / L) was analyzed over time to explore the adsorption threshold of the mixed system.

[0190] In this experimental example, the adsorption effect of ceramsite on nitrogen and phosphorus in the mixed system is as follows: Figure 4 As shown, (a) represents the trend of ammonia nitrogen adsorption over time, (b) represents the trend of total phosphorus adsorption over time, (c) represents the trend of ammonia nitrogen equilibrium adsorption over time with the concentration of the adsorption equilibrium solution, and (d) represents the trend of total phosphorus equilibrium adsorption over time with the concentration of the adsorption equilibrium solution.

[0191] In this experimental example, the time for the ceramsite to reach ammonia nitrogen adsorption equilibrium and phosphorus adsorption equilibrium in the solution was 16 hours, at which point the removal rates reached 30-40% and 98-100%, respectively. This is because phosphate, magnesium ions in the ceramsite, and ammonium ions in the solution react together to form struvite precipitate, resulting in a significant phosphorus adsorption effect in the mixed system, approaching 100%. Furthermore, the saturated adsorption capacity of the material for pollutants did not stabilize with increasing concentration but instead showed a continuous linear increase. With increasing ammonia nitrogen concentration, the removal rate stabilized between 70% and 80%.

[0192] Experimental Example 3

[0193] This experimental example provides a detailed description of the physicochemical properties and environmental risks of the ceramsite prepared in Example 14 above.

[0194] In this test, the compressive strength of the expanded clay aggregate was compared with that in "Lightweight Aggregates and Their Test Methods Part 1: Lightweight Aggregates" (GB / T17431.2-2010).

[0195] In this experimental example, the heavy metal content in the expanded clay aggregate was compared with the "Technical Guidelines for Pollution Prevention and Control in Solid Waste Recycling".

[0196] The heavy metal addition limits were identified according to the "Technical Specification for Environmental Protection of Co-processing Solid Waste in Cement Kilns" (HJ 662-2013) as specified in (HJ1091-2020). Leaching toxicity was determined according to the procedures outlined in "Leaching Methods for Solid Waste: Horizontal Oscillation Method" (HJ 557-2010), and the heavy metal content of the samples was detected using ICP (Inductively Coupled Plasma Emission Spectrometry).

[0197] The content of heavy metals in the leaching toxicity was determined by comparing it with the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" (GB5085.3—2007).

[0198] The physical properties of the expanded clay aggregates in this test example, such as compressive strength, mud content, apparent density, bulk density, and hydrochloric acid solubility, are shown in Table 4. The compressive strength meets the requirement of 1.5 MPa for industrial waste lightweight aggregates with a density grade of 1000 in "Lightweight Aggregates and Their Test Methods Part 1: Lightweight Aggregates" (GB / T 17431.2-2010).

[0199] Table 4 Physical Indicators

[0200]

[0201] The heavy metal content and leaching toxicity of the expanded clay in this test are shown in Table 5. They did not exceed the standard, and the environmental risk was acceptable.

[0202] Table 5 Comparison of Heavy Metal Content and Leaching Toxicity

[0203]

[0204] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-performance ceramsite, characterized in that, include: S1. Red mud is pretreated with desulfurized gypsum to obtain improved red mud; The improved pretreatment time is 7~20 days; The improved pretreatment specifically includes: mixing desulfurized gypsum into red mud, fully wetting it, and spraying water at regular intervals; S2. Mix and homogenize the modified red mud with zeolite, nut shells, binder, and waste glass powder to obtain raw material; wherein, the modified red mud is 40-120 parts, the zeolite powder mixture is 40-120 parts, the nut shells are 10-40 parts, the binder is 10-40 parts, and the waste glass powder is 2-5 parts. S3. Add an inorganic polymer flocculant solution to the raw material to form a dry, thick paste; S4. After granulating, drying and shaping the dry thick paste, calcining it to obtain high-performance ceramic particles.

2. The method for preparing high-performance ceramsite as described in claim 1, characterized in that, In step S1, the amount of desulfurized gypsum used is 2-20%.

3. The method for preparing high-performance ceramsite as described in claim 1, characterized in that, The zeolite is a mixture of zeolite powder and granules; the mixture includes zeolite powder and zeolite granules; the mass ratio of zeolite powder to zeolite granules is 1~3:1; the type of zeolite is any one or more of natural zeolites; the zeolite powder passes through a 70~100 mesh sieve; the particle size of the zeolite granules is 0.3~1mm.

4. The method for preparing high-performance ceramsite as described in any one of claims 1 to 3, characterized in that, The waste glass powder has a particle size that passes through a 50-100 mesh sieve; The binder is one or more of sodium silicate, cement, bentonite, starch, cellulose, resin, and gelatin; Red mud is one or more of the following: Bayer process red mud, sintering process red mud, or mixed process red mud.

5. The method for preparing high-performance ceramsite as described in any one of claims 1 to 3, characterized in that, The concentration of the inorganic polymeric flocculant solution is 20~30g / L; the inorganic polymeric flocculant is polyaluminum chloride, polyferric chloride, polyferric sulfate or polyaluminum sulfate.

6. The method for preparing high-performance ceramsite according to any one of claims 1 to 3, characterized in that, The particle size of the nut shell is 0.4~0.8mm; the nut shell is any one or more of the following: walnut shell, macadamia nut shell, pine nut shell, pistachio shell, hazelnut shell, almond shell, cashew shell.

7. The method for preparing high-performance ceramsite according to any one of claims 1 to 3, characterized in that, The particle size of the high-performance ceramic particles is 0.5~2cm.

8. The method for preparing high-performance ceramsite according to any one of claims 1 to 3, characterized in that, The roasting temperature is 650~1200℃; the roasting time is 4~10h; the drying and shaping temperature is 45~65℃; and the drying and shaping time is 4~8h.

9. A high-performance ceramsite, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the high-performance ceramsite as described in claim 9 in the treatment of any one of nitrogen-containing wastewater, phosphorus-containing wastewater, and wastewater containing both nitrogen and phosphorus.

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