A method for synchronous high-temperature solidification and materialization of high-iron red mud and electromagnetic wave absorbing powder functional material

Abstract

The present invention discloses a method for simultaneously producing high-iron red mud with high-temperature solid alkali and materialization, as well as an electromagnetic wave absorbing powder functional material. A mixture comprising high-iron red mud, magnetite, high-titanium slag, purified cobalt-manganese slag, alumina, and quartz is ball-milled and activated, and then preheated, calcined, cooled, and finely ground to obtain the electromagnetic wave absorbing powder functional material. This method not only stabilizes the structured alkali and free alkali in the high-iron red mud, but also produces an electromagnetic wave absorbing powder functional material with excellent wave absorption properties. This material can be used as a high-quality raw material for preparing large quantities of electromagnetic wave shielding building materials. The method is characterized by low cost and high yield, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to an electromagnetic wave absorbing powder functional material, in particular to an electromagnetic wave absorbing powder functional material containing components such as zinc-cobalt-manganese-iron composite ferrite and orthotitanate. The present invention also relates to a method for utilizing aluminum oxide and silicon oxide to regulate the state of soluble free alkali in red mud at high temperature, while simultaneously adding mineral raw materials to realize the functional material conversion of components such as iron, titanium, and rare earth in high-iron red mud. The method belongs to the technical field of harmless treatment and material utilization of non-ferrous metal metallurgical solid waste. Background Art

[0002] As a major global aluminum producer, China accounted for 24% of global bauxite production and 80% of global bauxite imports in 2020. It also produced 55% of global red mud, approximately 100 million tons. Historical red mud stockpiles have exceeded 1 billion tons, and the environmental risks they pose are a persistent concern for the industry. Large-scale accumulations of red mud not only consume land resources but, if improperly managed, can also pose risks such as dam failures and soil and water pollution. Large-scale, low-cost disposal of red mud remains a global challenge, and achieving its reduction and resource utilization remains a key concern for the industry.

[0003] The high alkali content of red mud is a limiting factor in the large-scale utilization of bulk red mud. Red mud's high alkali content can easily lead to problems such as product efflorescence, alkali-aggregate reaction, and steel corrosion when used in various applications. Research has shown that harmful alkalis are soluble alkalis, not all alkalis in red mud. Bayer process red mud contains two main types of alkali-containing substances: residual NaOH, sodium aluminate, and other solutions from bauxite leaching, and hydrated sodium aluminosilicates formed by the reaction of sodium aluminate solutions with SiO2.

[0004] (1) Insoluble alkali. The Bayer process is to mix bauxite with a high A / S ratio with a NaOH solution. Under high temperature and high pressure, the aluminum oxide in the bauxite reacts with NaOH to form a sodium aluminate solution. The silicon minerals in the bauxite are decomposed by NaOH to form sodium silicate, which enters the solution and reacts with the sodium aluminate solution to form hydrated sodium aluminosilicate (sodium silicate slag). The sodium silicate slag and the iron, titanium and excess silicon minerals in the bauxite are discharged in the form of precipitation, and after repeated washing, they are sent to the yard to form red mud. From the above process, it can be seen that the insoluble alkali in the red mud is hydrated sodium aluminosilicate. Under different reaction conditions, the composition and structure of the generated sodium silicate slag are also different. This is because there are Al(OH)4 and aluminosilicate ions in the sodium aluminate solution. Under different production conditions, the above ions will transform into each other and undergo condensation reactions to form small structural units, and gradually form crystal nuclei. As the crystal nuclei grow, different types of sodium silicate slag are formed. Common sodium silicate slags produced during the alumina production process include cancrinite, sodalite, type A zeolite, drenoite, and amorphous sodium hydrous aluminosilicate. Under suitable conditions, different types of sodium silicate slags can undergo transformations. Sodium silicate slags generated at lower temperatures can transform into cancrinite at higher temperatures.

[0005] (2) Soluble alkali. In the Bayer process of extracting alumina, a high-concentration NaOH solution is used to leach aluminum from bauxite. NaOH reacts with aluminum-containing substances in the bauxite to produce soluble substances such as sodium aluminate and sodium silicate. A portion of NaOH does not participate in the reaction and remains. This portion of NaOH and soluble sodium aluminate solutions are discharged with the red mud. In addition, NaOH reacts with CO2 in the air to produce Na2CO3 during storage. The longer the storage time, the greater the Na2CO3 content. Therefore, the soluble alkali in red mud is mainly NaOH, Na2CO3, sodium aluminate, etc. Due to the characteristics of its production process, red mud contains a high pH value and alkali content. The pH value of red mud is generally 10-13, and the pH value of the leachate can even reach 12-14, far exceeding the national emission standard GB5058-85 "Non-ferrous Metal Industry Solid Waste Pollution Control Standard". The content of alkaline substances (Na2O, K2O) is also high, with sintered red mud containing 2% to 5% and Bayer red mud containing 4% to 13%. These highly alkaline attached liquids easily seep into groundwater, damaging the ecological environment and severely limiting the utilization of red mud. Free alkali is the main form of alkalinity in red mud, existing in the red mud liquid phase and on the surface of the mineral phase. It easily migrates to the red mud surface due to dissolution reactions and evaporation, resulting in the "frosting" phenomenon on the red mud surface.

[0006] From an elemental perspective, red mud is rich in CaO, SiO2, Al2O3, and Fe2O3. These are the same oxides required to make Portland cement clinker and can partially replace the raw materials for Portland cement clinker. Studies have shown that adding 1% by mass of Bayer red mud to the preparation of Portland cement does not change the mineral composition of the resulting cement, nor does it affect the cement's hydration and strength development, demonstrating the feasibility of using Bayer red mud to make Portland cement. However, the industrial requirement for an alkali content in cement is less than 0.8% (based on 100% by mass of oven-dried solids), which is the main reason why red mud has not been used in large quantities to make cement. Therefore, exploring simple and inexpensive methods for dealkalization of red mud is particularly meaningful.

[0007] Domestic and international scholars have conducted extensive research on red mud dealkalization, aiming to effectively reduce its alkali content and achieve resource utilization. Currently, the main dealkalization processes include water washing, acid leaching, suspended carbonization, and calcium ion exchange. Large-scale application of red mud dealkalization technology requires identifying dealkalization targets, clarifying the degree of dealkalization, improving dealkalization efficiency, and reducing costs based on comprehensive utilization. This is a global challenge that urgently needs to be addressed, and its core is to overcome the primary contradiction between dealkalization technology and treatment costs. The environmental safety issues posed by red mud remain unresolved, and large amounts of red mud are still stored in dams.

[0008] Multi-metal composite ferrites and their loaded functional components possess excellent electromagnetic properties, making them a class of high-performance composite absorbing materials. Existing bulk high-speed iron red mud is just the right material. It contains the iron, titanium, rare earth oxides, and other components required for the preparation and strengthening of composite absorbing ferrites. Furthermore, the aluminum-silicon-calcium components it contains are highly similar to concrete. Therefore, by transforming high-speed iron red mud into a functional absorbing material through a short-process solid-phase reaction method, organically coupled with the existing functional building materials industry, which has an annual industrial demand of tens of millions of tons, it can effectively achieve large-scale and low-cost disposal of red mud solid waste. Summary of the Invention

[0009] In response to the problems of high alkali content and high cost of existing dealkalization technology in the existing technology, the first purpose of the present invention is to provide a method for simultaneous high-temperature solid alkali and materialization of high-iron red mud. This method uses high-iron red mud as the main raw material and adds mineral auxiliary raw materials such as alumina, silicon oxide and magnetite. Through a one-step high-temperature reaction, it can not only regulate the state of soluble free alkali in the red mud to form a stable silicate molten phase, but also convert components such as iron, titanium, and rare earth into a multi-metal composite ferrite phase and manganese titanate phase with excellent wave absorbing function, thereby obtaining high-quality electromagnetic wave absorbing functional materials, providing new technical ideas for the value-added utilization and large-scale disposal of high-iron red mud.

[0010] The second object of the present invention is to provide an electromagnetic wave absorbing powder functional material with excellent wave absorbing performance, which can be used as a high-quality raw material for preparing large quantities of electromagnetic wave shielding building materials.

[0011] In order to achieve the above technical objectives, the present invention provides a method for simultaneous high-temperature solid alkali and materialization of high-iron red mud. The method is to activate a mixture of high-iron red mud, magnetite, high-titanium slag, purified cobalt-manganese slag, alumina and quartz through ball milling, and then preheat, roast, cool and finely grind in sequence to obtain an electromagnetic wave absorbing powder functional material.

[0012] In the existing technology, high-iron red mud not only contains a large amount of alkali, but also contains useful metal elements such as iron, titanium, and rare earths. The alkali in high-iron red mud mainly includes three types, namely molten alkali, structural alkali, and free alkali. The molecular formula of molten alkali is Na2O·nSiO2 (n>4), which exists in a glassy state, has a stable structure, is difficult to dissolve in water, and is not harmful; structural alkali is Na2O·nSiO2 (1≤n<3.5), which is combined with silicon and aluminum in a simple form, has strong alkalinity, and has certain harmfulness; free alkali is Na2CO3, NaHCO3, sodium aluminate, etc. attached to the surface of other minerals, is easily soluble in water, has strong alkalinity, and is highly harmful. Therefore, stabilizing the structural alkali and free alkali in high-iron red mud is the key to realizing the resource utilization of useful metals in high-iron red mud. The technical solution of the present invention, by introducing alumina and quartz, can convert the structural alkali and soluble alkali in red mud into a stable silicate molten phase during a high-temperature solid-phase reaction. At the same time, magnetite, high-titanium slag, purified cobalt-manganese slag, etc. are used to react with useful metal elements such as iron, titanium, and rare earth in red mud to form a multi-metal composite ferrite phase and a manganese titanate phase, both of which have excellent electromagnetic wave absorption properties, thereby obtaining an electromagnetic wave absorbing powder functional material with excellent wave absorption performance, which can be used to prepare high-quality raw materials for large-scale electromagnetic wave shielding building materials.

[0013] As a preferred solution, the mixing ratios of high-iron red mud, magnetite, high-titanium slag, purified cobalt-manganese slag, alumina and quartz in the mixture satisfy the following requirements: the mass ratio of (Zn+Co+Mn) / Fe is between 0.45 and 0.75; the mass ratio of Ti / Mn is between 0.55 and 0.85; the molar ratio of SiO2 / Na2O is between 4 and 8; the molar ratio of Al2O3 / (Al2O3+Na2O+SiO2) is between 0.05 and 0.2; the mass ratio of (Zn+Co) / Mn is between 0.05 and 0.15, and the total iron content is not less than 25%. The technical solution of the present invention controls the molar ratio of SiO2 / Na2O and the molar ratio of Al2O3 / (Al2O3+Na2O+SiO2) within an appropriate range, and can regulate the conversion of structural alkali and soluble alkali in high-iron red mud into stable molten silicate during high-temperature roasting. The technology of direct solid alkali treatment of high-iron red mud can improve the utilization rate of red mud and reduce the cost of dealkalization. At the same time, the technical solution of the present invention controls the formation of multi-metal composite ferrite phase and manganese titanate phase during roasting by strictly controlling the mass ratio of (Zn+Co+Mn) / Fe, the mass ratio of Ti / Mn, the mass ratio of (Zn+Co) / Mn and the total iron content. Under the preferred composition ratio, the mineral phase in the high-iron red mud is reconstructed during the high-temperature solid-phase reaction and directionally converted into multi-metal composite ferrite phase, manganese titanate phase and stable silicate molten phase. In particular, a large number of studies have shown that in an oxidizing atmosphere (such as air atmosphere), elements such as Mg, Zn, Na, and K in high-iron red mud easily enter the ferrite lattice and occupy tetrahedral voids (A position); Al elements easily occupy octahedral voids (B position); while elements such as Si and P will not enter the ferrite structure. Elements such as Ca, Mg, Na, K, and Al that easily enter the lattice gap have a greater impact on the wave absorption energy of ferrite products. The technical solution of the present invention can migrate the impurity elements occupying the A and B positions of the ferrite structure out of the spinel structure through the chemical driving force generated by reacting with them to form corresponding stable molten silicates, thereby effectively improving the wave absorption performance of the ferrite product; at the same time, SiO2 reacts with impurity elements such as sodium and aluminum to generate a stable molten liquid phase, which can realize solid alkali while converting multi-metal ferrite.

[0014] As a preferred solution, the iron content of the high-iron red mud is not less than 25% by weight, and the sodium oxide content is not more than 15% by weight.

[0015] As a preferred solution, the iron content of the magnetite concentrate is not less than 68% by mass.

[0016] As a preferred solution, the purified cobalt-manganese slag is smelting slag from a hydrometallurgical zinc smelting system, wherein the mass percentage content of the three elements cobalt, manganese and zinc is not less than 90%, and the mass percentage content of the two elements cobalt and manganese is not less than 85%.

[0017] As a preferred solution, the mass percentage content of titanium dioxide in the high-titanium slag is not less than 85%.

[0018] As a preferred embodiment, the fineness of the mixed material satisfies the requirement that the mass percentage of the -325 mesh particle size is not less than 95%. The mixed powder of the present invention can be prepared by finely grinding solid raw materials such as high-iron red mud, magnetite, high-titanium slag, purified cobalt-manganese slag, alumina, and quartz and then compounding them in proportion, or by first compounding the solid powders in proportion and then compounding them. By controlling the mixed powder to be within an appropriate particle size range, high-temperature solid-phase reaction is facilitated.

[0019] As a preferred embodiment, the ball milling activation conditions are: a rotation speed of 20-50 rpm, a ball-to-material mass ratio of 5:1-10:1, and an activation time of 3-5 hours. The ball mill jar is filled with 30-40% steel balls by volume. The ball milling activation process, in which the hard balls vigorously impact, grind, and agitate the raw materials through the mill's rotation or vibration, significantly reduces reaction activation energy, refines grain size, enhances powder activity, improves sintering ability, and induces low-temperature chemical reactions. The high-titanium slag in the mixed raw materials is a titanium dioxide-rich concentrate obtained by melting titanium ore in an electric furnace, separating the titanium dioxide and iron in the ore. However, titanium oxide has a high melting point and poor activity, requiring the ball milling process and repeated collisions and crushing to produce a series of surface bond breaks and lattice defects in the high-titanium slag. These defects then expand, promoting rapid solid-phase reactions during calcination.

[0020] As a preferred embodiment, the preheating conditions are: in an air atmosphere, at a temperature of 800°C to 950°C, for 30 to 90 minutes. The preferred preheating temperature conditions can decompose the metal salts or high-valent metal oxides in the raw materials into highly active metal oxides, which is beneficial for the subsequent high-temperature solid-phase reaction.

[0021] As a preferred embodiment, the calcination conditions are: calcination in an air atmosphere at a temperature of 1050°C to 1150°C for 45 to 180 minutes. During the calcination process, the liquid phase content in the reaction system is controlled to be 15% to 25% by weight. At the preferred calcination temperature, the formation of composite ferrite and orthotitanate can be promoted. If the calcination temperature is too high, the liquid phase volume of the system will exceed 50% during the calcination process, causing excessive dissolution of valuable metals such as iron, titanium, manganese, cobalt, and zinc into the liquid phase, resulting in a decrease in the production of the target product. If the calcination temperature is too low, the solid-phase reaction will be difficult to complete.

[0022] As a preferred solution, the cooling conditions include rapid cooling to room temperature using water cooling. During the roasting process, sodium oxide reacts with oxides such as silicon and aluminum to form an appropriate amount of liquid phase. The rapid cooling process using water cooling prevents the high-temperature molten alkali from cooling quickly enough to transform into a well-crystalline structured alkali, thereby reducing the alkali leaching rate of the product to zero. Excessively slow cooling increases the water solubility of the sodium oxide in the product, which is detrimental to solid alkali.

[0023] As a preferred solution, the fine grinding satisfies the requirement that the mass percentage of the -200 mesh particle size is 100%.

[0024] The alumina and quartz used in the present invention are conventional commercially available raw materials and are analytically pure reagents.

[0025] The present invention also provides an electromagnetic wave absorbing powder functional material obtained by the method. The electromagnetic wave absorbing powder functional material of the present invention has good wave absorbing performance and does not contain free alkali.

[0026] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0027] 1) The technical solution of the present invention uses high-iron red mud, magnetite, high-titanium slag, purified cobalt-manganese slag, aluminum oxide and silicon oxide as raw materials through high-temperature solid-phase reaction, which can not only achieve the control of the generation and amount of molten alkali liquid phase during the roasting process to reduce the entry of impurities into the composite ferrite structure and avoid the influence of impurities on the electromagnetic wave absorption performance of the generated ferrite, but also can convert free alkali and structured alkali into stable molten alkali. At the same time, the iron, titanium, manganese, cobalt, rare earth and other raw materials are used to generate composite ferrite and orthotitanate with excellent electromagnetic wave absorption performance through high-temperature solid-phase reaction, thereby achieving the purpose of simultaneous solid alkali and material conversion.

[0028] 2) The technical solution of the present invention uses high-risk solid waste high-iron red mud as raw material to directly convert the valuable components in the high-iron red mud into high-value complex phase absorbing materials through a one-step high-temperature solid-phase reaction, thereby realizing the resource utilization of its useful metals. At the same time, conventional roasting can be used to stabilize the alkali in the high-iron red mud to obtain an absorbing material without free alkali, avoiding the costly dealkalization and solid alkali processes. The method is simple to operate, low in cost, high in added value, and is conducive to industrial production.

[0029] 3) The electromagnetic wave absorbing powder functional material of the present invention has good wave absorbing performance and does not contain free alkali, and can be widely used as a high-quality raw material for preparing large quantities of electromagnetic wave shielding building materials. DETAILED DESCRIPTION

[0030] The following examples are intended to further illustrate the present invention in detail, but are not intended to limit the scope of protection of the claims of the present invention.

[0031] Example 1

[0032] The raw materials used include: high-iron red mud containing 30% TFe, 8.5% TiO2, and 12% Na2O; magnetite concentrate containing 68% Fe; purified cobalt-manganese slag containing 90% by weight of cobalt, manganese, and zinc, and 85% by weight of cobalt and manganese; high-titanium slag containing 85% TiO2; and commercially available analytical grade aluminum oxide and silicon dioxide. The high-magnetite, high-titanium slag, purified cobalt-manganese slag, aluminum oxide, and quartz are each finely ground to a -325 mesh particle size of 95% by weight to obtain a mixed material. The chemical composition of the mixture met the following requirements: a (Zn+Co+Mn) / Fe mass ratio of 0.75; a Ti / Mn mass ratio of 0.85; a SiO2 / Na2O molar ratio of 8; a Al2O3 / (Al2O3+Na2O+SiO2) molar ratio of 0.05; and a (Zn+Co) / Mn mass ratio of 0.05. The total iron content of the mixture was 25%. The mixture was mechanically activated in a ball mill with a 35% steel ball loading, a rotation speed of 30 rpm, an 8:1 ball-to-metal ratio, and an activation time of 3 hours. The mixture was preheated to 800°C and calcined at 1150°C for 90 minutes and 45 minutes, respectively. Both the preheating and calcining atmospheres were air. The calcined sample was rapidly cooled to room temperature using water. The cooled, calcined sample was ground to a particle size of -200 mesh, representing 100% of the total particle size, to yield a functional magnetic powder with microwave-absorbing properties and free of free alkali. After soaking the resulting powder in water for seven days, the free alkali content in the solution was determined to be zero. Furthermore, the powder exhibited an electromagnetic wave reflectivity of -20 dB within the 2-18 GHz frequency range, demonstrating excellent microwave-absorbing properties and suitable for use as a microwave-absorbing material in construction.

[0033] Example 2

[0034] The raw materials used include: high-iron red mud containing 32% TFe, 7.4% TiO2, and 11% Na2O; magnetite concentrate containing 69% Fe; purified cobalt-manganese slag containing 91% by weight of cobalt, manganese, and zinc, and 87% by weight of cobalt and manganese; high-titanium slag containing 87% TiO2; and commercially available analytical grade aluminum oxide and silicon dioxide. The high-magnetite, high-titanium slag, purified cobalt-manganese slag, aluminum oxide, and quartz are each finely ground to a -325 mesh particle size of 100% by weight to obtain a mixed material. The chemical composition of the mixture met the following requirements: a (Zn+Co+Mn) / Fe mass ratio of 0.45; a Ti / Mn mass ratio of 0.55; a SiO2 / Na2O molar ratio of 8; an Al2O3 / (Al2O3+Na2O+SiO2) molar ratio of 0.2; and a (Zn+Co) / Mn mass ratio of 0.15. The total iron content of the mixture was 26.5%. The mixture was mechanically activated in a ball mill with a 35% steel ball loading, a rotation speed of 30 rpm, an 8:1 ball-to-metal ratio, and an activation time of 5 hours. The mixture was preheated to 950°C and calcined at 1050°C for 30 minutes and 180 minutes, respectively. Both the preheating and calcining atmospheres were air. The calcined sample was rapidly cooled to room temperature using water. The cooled, calcined sample was ground to a particle size of -200 mesh, resulting in a functional magnetic powder with microwave-absorbing properties and no free alkali. After soaking the resulting powder in water for seven days, the free alkali content in the solution was measured to be zero. Furthermore, the powder exhibited an electromagnetic wave reflectivity of -19.5 dB within the 2-18 GHz frequency range, demonstrating excellent microwave-absorbing properties and suitable for use as a microwave-absorbing material in construction.

[0035] Comparative Example 1

[0036] In this comparative example, the (Zn+Co+Mn) / Fe quality is relatively low:

[0037] The raw materials used include: high-iron red mud containing 32% TFe, 7.4% TiO2, and 11% Na2O; magnetite concentrate containing 69% Fe; purified cobalt-manganese slag containing 91% by weight of cobalt, manganese, and zinc, and 87% by weight of cobalt and manganese; high-titanium slag containing 87% TiO2; and commercially available analytical grade aluminum oxide and silicon dioxide. The high-magnetite, high-titanium slag, purified cobalt-manganese slag, aluminum oxide, and quartz are each finely ground to a -325 mesh particle size of 100% by weight to obtain a mixed material. The chemical composition of the mixture met the following requirements: a (Zn+Co+Mn) / Fe mass ratio of 0.25; a Ti / Mn mass ratio of 0.55; a SiO2 / Na2O molar ratio of 8; an Al2O3 / (Al2O3+Na2O+SiO2) molar ratio of 0.2; and a (Zn+Co) / Mn mass ratio of 0.15. The total iron content of the mixture was 26.5%. The mixture was mechanically activated in a ball mill with a 35% steel ball loading, a rotation speed of 30 rpm, an 8:1 ball-to-material mass ratio, and an activation time of 5 hours. The mixture was preheated to 950°C and calcined at 1050°C for 30 minutes and 180 minutes, respectively. Both the preheating and calcining atmospheres were air. The calcined sample was rapidly cooled to room temperature using water cooling. The cooled, calcined sample was ground to a -200 mesh particle size, resulting in a functional magnetic powder with microwave-absorbing properties and no free alkali. After soaking the resulting powder in water for seven days, the free alkali content in the solution was measured to be zero. Furthermore, the powder exhibited a reflectivity of only -9.5 dB for electromagnetic waves within the 2-18 GHz frequency range, indicating poor microwave absorption.

[0038] Comparative Example 2

[0039] The molar ratio of SiO2 / Na2O and the molar ratio of Al2O3 / (Al2O3+Na2O+SiO2) in this comparative example are relatively low.

[0040] The raw materials used include: high-iron red mud containing 30% TFe, 8.5% TiO2, and 12% Na2O; magnetite concentrate containing 68% Fe; purified cobalt-manganese slag containing 90% by weight of cobalt, manganese, and zinc, and 85% by weight of cobalt and manganese; high-titanium slag containing 85% TiO2; and commercially available analytical grade aluminum oxide and silicon dioxide. The high-magnetite, high-titanium slag, purified cobalt-manganese slag, aluminum oxide, and quartz are each finely ground to a -325 mesh particle size of 95% by weight to obtain a mixed material. The chemical composition of the mixture met the following requirements: a (Zn+Co+Mn) / Fe mass ratio of 0.75; a Ti / Mn mass ratio of 0.85; a SiO2 / Na2O molar ratio of 3; an Al2O3 / (Al2O3+Na2O+SiO2) molar ratio of 0.02; a (Zn+Co) / Mn mass ratio of 0.05; and a total iron content of 25%. The mixture was mechanically activated in a ball mill with a 35% steel ball loading, a rotation speed of 30 rpm, an 8:1 ball-to-metal ratio, and an activation time of 3 hours. The mixture was preheated to 800°C and calcined at 1150°C for 90 minutes and 45 minutes, respectively. Both preheating and calcining were performed in air. The calcined sample was rapidly cooled to room temperature using water. The cooled, calcined sample was ground to a particle size of -200 mesh, representing 100% of the total particle size, to obtain a functional magnetic powder with microwave-absorbing properties and free of free alkali. After soaking the resulting powder in water for seven days, the free alkali content in the solution was determined to be zero. Furthermore, the powder exhibited a reflectivity of -8.8 dB for electromagnetic waves within the 2-18 GHz frequency range, indicating poor microwave-absorbing properties.

[0041] Comparative Example 3

[0042] The calcination temperature in this comparative example is relatively high.

[0043] The raw materials used include: high-iron red mud containing 32% TFe, 7.4% TiO2, and 11% Na2O; magnetite concentrate containing 69% Fe; purified cobalt-manganese slag containing 91% by weight of cobalt, manganese, and zinc, and 87% by weight of cobalt and manganese; high-titanium slag containing 87% TiO2; and commercially available analytical grade aluminum oxide and silicon dioxide. The high-magnetite, high-titanium slag, purified cobalt-manganese slag, aluminum oxide, and quartz are each finely ground to a -325 mesh particle size of 100% by weight to obtain a mixed material. The chemical composition of the mixture met the following requirements: a mass ratio of (Zn+Co+Mn) / Fe of 0.45; a mass ratio of Ti / Mn of 0.55; a molar ratio of SiO2 / Na2O of 8; a molar ratio of Al2O3 / (Al2O3+Na2O+SiO2) of 0.2; a mass ratio of (Zn+Co) / Mn of 0.15; and a total iron content of 26.5%. The mixture was mechanically activated in a ball mill with a 35% steel ball loading, a rotation speed of 30 rpm, an 8:1 ball-to-metal ratio, and an activation time of 5 hours. The mixture was preheated to 950°C and calcined at 1300°C for 30 minutes and 180 minutes, respectively. Both the preheating and calcining atmospheres were air. The calcined sample was rapidly cooled to room temperature using water. The cooled, calcined sample was ground to a particle size of -200 mesh, resulting in a functional magnetic powder with microwave-absorbing properties and free of free alkali. After soaking the resulting powder in water for seven days, the free alkali content in the solution was measured to be zero. Furthermore, the powder exhibited a reflectivity of only -10.5 dB for electromagnetic waves within the 2-18 GHz frequency range, indicating poor microwave absorption.

Claims

1. A method for simultaneous high-temperature solidification and materialization of high-iron red mud, characterized by: A mixture comprising high-iron red mud, magnetite, high-titanium slag, purified cobalt-manganese slag, alumina and quartz is subjected to ball milling activation, and then sequentially subjected to preheating, roasting, cooling and fine grinding to obtain an electromagnetic wave absorbing powder functional material; the mixing ratio of high-iron red mud, magnetite, high-titanium slag, purified cobalt-manganese slag, alumina and quartz in the mixture satisfies the following requirements: the mass ratio of (Zn+Co+Mn) / Fe is between 0.45 and 0.75; the mass ratio of Ti / Mn is between 0.55 and 0.85; the molar ratio of SiO2 / Na2O is between 4 and 8; the molar ratio of Al2O3 / (Al2O3+Na2O+SiO2) is between 0.05 and 0.2; the mass ratio of (Zn+Co) / Mn is between 0.05 and 0.15, and the total iron content is not less than 25%; The preheating conditions are: in an air atmosphere, at a temperature of 800°C to 950°C, for 30 to 90 minutes; The calcination conditions are: in an air atmosphere, at a temperature of 1050° C. to 1150° C., and for 45 to 180 minutes.

2. The method for simultaneous high-temperature solid alkali treatment and materialization of high-iron red mud according to claim 1, characterized in that: The high-iron red mud has an iron content of not less than 25% by mass and a sodium oxide content of not more than 15% by mass; The iron content of the magnetite concentrate is not less than 68% by mass; The purified cobalt-manganese slag is smelting slag from a hydrometallurgical zinc smelting system, wherein the mass percentage content of the three elements of cobalt, manganese and zinc is not less than 90%, and the mass percentage content of the two elements of cobalt and manganese is not less than 85%; The mass percentage content of titanium dioxide in the high-titanium slag is not less than 85%.

3. The method for simultaneous high-temperature solid alkali treatment and materialization of high-iron red mud according to claim 1, characterized in that: The fineness of the mixture satisfies that the mass percentage of -325 mesh particle size is not less than 95%.

4. The method for simultaneous high-temperature solidification and materialization of high-iron red mud according to claim 1, characterized in that: The conditions for ball milling activation are: a rotation speed of 20 to 50 rpm, a ball-to-material mass ratio of 5:1 to 10:1, and an activation time of 3 to 5 hours.

5. The method for simultaneous high-temperature solid alkali treatment and materialization of high-iron red mud according to claim 1, characterized in that: The cooling condition is: rapid cooling to room temperature by water cooling.

6. The method for simultaneous high-temperature solid alkali treatment and materialization of high-iron red mud according to claim 1, characterized in that: The mass percentage of the fine grinding to meet the -200 mesh particle size is 100%.

7. An electromagnetic wave absorbing powder functional material, characterized by: Obtained by the method according to any one of claims 1 to 6.