High-corrosion-resistance environment-friendly ceramic and preparation method thereof

Abstract

The invention relates to the technical field of ceramic materials, in particular to high-corrosion-resistance environment-friendly ceramic and a preparation method of the high-corrosion-resistance environment-friendly ceramic. 20 to 22 percent of Al2O3; 4 to 6 percent of Fe2O3; 2.0 to 3.5 percent of CaO; 0.5 to 1.0 percent of MgO; 0.8% to 1.2% of K2O and Na2O; sO3: less than or equal to 0.03%; pb + Cd + Cr < 6 + >: < = 2 ppm; the balance is impurities. According to the scheme, the craft ceramic can be prepared from the tailings, meanwhile, residues such as the heavy metal content are strictly controlled, components are controlled to be stable, and therefore unification of high corrosion resistance and environmental friendliness is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and particularly relates to a highly corrosion-resistant environmental protection ceramic and a preparation method thereof. Background Art

[0002] Ceramics are prone to irreversible destructive changes in physical structure or chemical composition in specific chemical environments (such as acid, alkali, salt solutions, molten salts, high-temperature gases or water vapor, etc.), resulting in significant degradation or even failure of key properties such as strength, hardness, and insulation, that is, the ceramic corrosion phenomenon. Specifically, it is manifested as surface erosion and dissolution becoming rough and porous, preferential corrosion at grain boundaries leading to grain shedding and a sharp drop in strength, phase transformation or decomposition of material components (such as hydration expansion cracking), and stress corrosion cracking under the combined action of stress and corrosive media. This is closely related to the ceramic composition and process. Using tailings as raw materials for handicraft ceramics not only meets the environmental protection requirements but also reduces production costs, but the corrosion resistance drops sharply.

[0003] CN117124451B discloses a daily-use ceramic production line and its process. By separately drying the interior and exterior of the clay blank, the possibility of the clay blank cracking, thermally cracking, and deforming is reduced, thereby reducing the defective rate. However, this technical solution mainly focuses on the drying uniformity problem in the ceramic production process and does not involve the optimization of the durability of ceramic materials in corrosive environments such as acids and alkalis. In addition, this solution does not mention the technical path for preparing ceramics using environmental protection raw materials such as tailings, so there are obvious deficiencies in terms of environmental protection and resource recycling. CN110981414B discloses a manufacturing process for a ceramic cup. By reasonably proportioning raw materials such as kaolin, SiO2, Na2O, K2O, Al2O3, and CaCO3, the manufactured ceramic cup still has high thermal stability with a relatively thin wall thickness. However, this technical solution mainly focuses on the thermal stability of the ceramic cup and does not deeply explore its durability in corrosive environments such as acids and alkalis. At the same time, this solution does not involve the use of tailings or industrial waste, cannot effectively solve the shortcoming of traditional ceramic materials in terms of environmental protection, and also fails to overcome problems such as the decomposition of sulfides in tailings ceramics to produce SO2, the migration and enrichment of heavy metal ions, and the fluctuation of alkali metal content affecting corrosion resistance.

[0004] The above problems indicate that the existing handicraft ceramics still have significant deficiencies in terms of corrosion resistance and environmental protection performance, especially lacking effective solutions in terms of long-term stability and resource recycling in the face of complex chemical environments. Summary of the Invention

[0005] To solve the above problems, the present invention provides a highly corrosion-resistant environmental protection ceramic and its preparation method, which can not only use tailings to prepare technical ceramics, but also strictly control the residues such as heavy metal content, control the composition stability, so as to realize the unity of high corrosion resistance and environmental protection.

[0006] A highly corrosion-resistant environmental protection ceramic, the chemical composition of which meets the following requirements in terms of mass percentage of oxides: SiO2: 68 - 72%; Al2O3: 20 - 22%; Fe2O3: 4 - 6%; CaO: 2.0 - 3.5%; MgO: 0.5 - 1.0%; K2O + Na2O: 0.8 - 1.2%; SO3: ≤0.03%; Pb + Cd + Cr 6+ : ≤2 ppm; The rest are impurities.

[0007] This ceramic takes the silicon-aluminum system dominated by kaolin (SiO2 + Al2O3 ≥ 88%) as the core framework, inhibits the corrosion of the glass phase by strictly limiting the alkali metal content (K2O + Na2O ≤ 1.2%), and regulates the iron and calcium components (Fe2O3 4 - 6% + CaO 2.0 - 3.5%) to form calcium iron garnet phase to seal the grain boundary pores during sintering. At the same time, the environmental protection control elements of sulfur and heavy metals (SO3 ≤ 0.03%, Pb + Cd + Cr 6+ ≤2 ppm) are reduced to the limit. The risk of corrosion induction is reduced from the source of the composition, and a fully dense corrosion-resistant network with interwoven acicular mullite as the matrix is constructed.

[0008] A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke in a mass ratio of 10 - 15:1, introduce an inert mixed gas with an oxygen content of 5 - 8% by volume, roast at 730 - 770 °C for 1 - 2 h, coarsely crush, perform magnetic separation, and further crush to D 90 ≤60 μm to obtain magnetic concentrate; Step (2) Ball milling leaching - purification: Add magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling according to a mass ratio of 95 - 105:22 - 28:7 - 9, add a leaching reagent 6 - 8 times the total mass of magnetic separation concentrate, red mud and porous carbon, adjust the pH to 2.5 - 3.5, ball mill for 3 - 5 h, unload, stir with gas and then precipitate and dehydrate, then make into slurry, ball mill for 20 - 30 min, unload, dehydrate, calcine in a weak reducing atmosphere, and crush to obtain pre-calcined active material; The leaching reagent is an aqueous solution mixture of citric acid with a mass fraction of 4-6wt%, oxalic acid with a mass fraction of 1.0-1.5wt%, and sodium hexametaphosphate with a mass fraction of 0.08-0.12wt%. Step (3) Shaping and calcining: After mixing the pre-calcined active material and kaolin in a mass ratio of 1:9-10, it is refined to a particle size D 90 ≤2.0μm, then shaped, sintered under the condition that the volume fraction of oxygen is 0.5-1.5%, and a highly corrosion-resistant environmental protection ceramic is obtained after cooling.

[0009] In this solution, iron ore tailings are subjected to low-oxygen reduction roasting at 730-770°C to convert hematite into magnetite for magnetic separation enrichment, and at the same time, part of the sulfur impurities are removed; in the ball milling stage, heavy metal ions are dissociated in an acidic complex system with a pH of 2.5-3.5 citric acid / oxalic acid, and are targeted adsorbed by porous carbon. During the process of aeration stirring and precipitation dehydration, most of the porous carbon is washed out; finally, the organic matter is completely decomposed by calcination, and trace heavy metals are sealed in the grossular lattice.

[0010] The pre-calcined active material and kaolin are compounded in a ratio of 1:9-10, greatly improving the nucleation density of mullite. During sintering, a low-oxygen atmosphere diluted with N2 is used to control the oxygen concentration. At a high temperature of 1250°C, in a low-oxygen atmosphere of 0.5-1.5%, part of Fe2O3 is converted into magnetite, and the two cooperate with CaO / SiO2 to react to form a highly dense grossular phase, while inhibiting the precipitation of harmful FeO phase. At the same time, the K2O-Al2O3-SiO2 ternary eutectic promotes the directional growth of acicular mullite, forming a super-stable structure with interlocking crystals, completely physically blocking the penetration channels of corrosive media.

[0011] Preferably, in step (1), the total iron content of the iron ore tailings is ≥28%, the sulfur content is ≤3%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is ≥55%.

[0012] To ensure the effect of low-oxygen reduction roasting, it is necessary to control the particle size of the iron ore tailings and sieve it with a sieve mesh above 50 meshes.

[0013] Preferably, the CaO content of the red mud is less than 15%, and the total content of Pb+Cd+Cr 6+ ≤100 ppm.

[0014] Preferably, in step (2), the solid content after pulping is 10-15%.

[0015] Preferably, in step (2), the specific surface area of the porous carbon is 550-650 m 2 / g.

[0016] Preferably, after aeration and stirring, precipitation and dehydration are carried out, and then pulping is carried out. EDTA is added until the concentration is 0.008 - 0.012 M, the pH is adjusted to 5.8 - 6.2, ball milling is carried out for 20 - 30 min, unloading is carried out, and calcination is carried out in a weak reducing atmosphere, and then crushing is carried out to obtain pre-calcined active material.

[0017] Adding 0.008 - 0.012 M of EDTA buffer solution with pH 5.8 - 6.2 can strongly chelate residual lead and cadmium, further reducing the residual toxicity in the solid phase.

[0018] Preferably, the weak reducing atmosphere described in step (2) is 0.8 - 1.2% O2, 1.0 - 1.4% CO, 2.8 - 3.2% CO2 by volume, and the rest is N2.

[0019] Citric acid, oxalic acid, and EDTA need to be cracked into CO2 / H2O under oxygen-deficient conditions. Therefore, the oxygen content needs to be controlled to prevent residual carbon from affecting subsequent ceramic sintering; trace amounts of Pb / Cd / Cr are wrapped by Fe2O3 to form solid solutions in a weak reducing atmosphere, such as Fe2O3 - PbO, or reduced to metallic elements and embedded in the lattice; avoiding excessive formation of FeO in strong reduction leads to agglomeration and inactivation of the pre-calcined material.

[0020] Preferably, the sintering process of calcination in the weak reducing atmosphere described in step (2) is: heating to 740 - 760 °C at a rate of 2 - 5 °C / min and holding for 2 - 3 h.

[0021] Preferably, in step (3), the sintering process under the condition that the volume fraction of oxygen is 0.5 - 1.5% is: heating to 1230 - 1280 °C at a rate of 2 - 5 °C / min and holding for 2 - 3 h.

[0022] Preferably, for the kaolin, SiO2 + Al2O3 ≥ 97% and K2O + Na2O ≤ 0.8%.

[0023] Compared with the prior art, the present invention has the following advantages: 1. The core advantage of this solution lies in innovatively achieving the precise unity of solid waste resource utilization and super corrosion-resistant structure. Through the synergistic compatibility of magnetic separation enrichment of iron ore tailings and red mud, the limit of heavy metal residual toxicity in the tailings is compressed to ≤ 0.1 ppm by a multi-stage purification process, ensuring environmental protection.

[0024] 2. By controlling the atmosphere in high-temperature processes such as calcination and sintering in this solution, the formation of FeO is inhibited, and magnetite / Fe2O3 is transformed into a calcium iron garnet phase grain boundary filler. At the same time, the iron and calcium components are precisely locked, and a calcium iron garnet phase closed grain boundary is formed directionally in low-oxygen sintering, blocking the penetration path of corrosive media from the source, and improving the strong acid and strong base resistance of the ceramic matrix compared with traditional ceramics. Detailed implementation mode

[0025] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention. Example 1

[0026] A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke in a mass ratio of 12:1, introduce a nitrogen mixed gas with 6% oxygen by volume, calcine at 750 °C for 1.5 h, coarsely crush, perform magnetic separation, and further crush to D 90 of 53 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO in the red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling leaching - purification: Add magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling according to a mass ratio of 100:25:8, add a leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 4 h, unload the material, stir while ventilating and then precipitate and dehydrate, then make a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload the material, and calcine in a weakly reducing atmosphere. The calcination process is to heat up to 750 °C at 4 °C / min, hold for 2.5 h, and crush to obtain pre-calcined active material; The leaching reagent is an aqueous mixed solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; The weakly reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin in a mass ratio of 1:9.5, refine to a particle size D 90 of 1.5 μm, then mold, and sinter under the condition that the oxygen volume fraction is 1.0%, and obtain a highly corrosion-resistant environmental protection ceramic after cooling; The SiO2 + Al2O3 in the kaolin is 97.5%, and the K2O + Na2O is 0.65%; The sintering process under the condition of 1.0% oxygen volume fraction is as follows: heating to 1250 °C at a rate of 3 °C / min and holding for 2.5 h. Example 2

[0027] A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix the iron ore tailings and coke at a mass ratio of 15:1, introduce an inert mixed gas with 8% oxygen by volume, roast at 750 °C for 1.5 h, coarsely crush, perform magnetic separation, and further crush to D 90 of 54 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO content of the red mud is 10%, and the total content of Pb+Cd+Cr 6+ is 85 ppm; Step (2) Ball milling leaching - purification: Add the magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling at a mass ratio of 103:26:8, add a leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 4 h, unload the material, stir with gas and then precipitate and dehydrate, then make a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload the material, and calcine in a weak reducing atmosphere. The calcination process is heating to 750 °C at a rate of 5 °C / min and holding for 3 h, and then crushing to obtain pre-calcined active material; The leaching reagent is an aqueous mixed solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin at a mass ratio of 1:10, refine the particle size to D 90 of 1.5 μm, then mold, sinter under the condition of 1.0% oxygen volume fraction, and obtain a highly corrosion-resistant environmental protection ceramic after cooling; The SiO2+Al2O3 of the kaolin is 97.8%, and the K2O+Na2O is 0.62%; The sintering process under the condition of 1.0% oxygen volume fraction is as follows: heating to 1250 °C at a rate of 4 °C / min and holding for 2 - 3 h. Example 3

[0028] A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix the iron ore tailings and coke in a mass ratio of 10:1, introduce an inert mixed gas with 5% oxygen by volume, calcine at 740 °C for 2 h, coarsely crush, perform magnetic separation, and further crush to D 90 of 55 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO content of the red mud is 12%, and the total content of Pb+Cd+Cr 6+ is 90 ppm; Step (2) Ball milling leaching - purification: Add the magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling in a mass ratio of 95:22:7, add a leaching reagent 7 times the total mass of the magnetic separation concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 5 h, unload the material, stir with gas and then precipitate and dehydrate, then make a slurry, add EDTA until the concentration is 0.012 M, adjust the pH to 6.2, ball mill for 25 min, unload the material, and calcine in a weakly reducing atmosphere. The calcination process is to heat up to 760 °C at 3 °C / min and hold for 2 h, and then crush to obtain pre-calcined active material; The leaching reagent is an aqueous mixed solution of 4 wt% citric acid, 1.0 wt% oxalic acid and 0.08 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 580 m 2 / g; The weakly reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (3) Molding and calcination: Mix the pre-calcined active material and kaolin in a mass ratio of 1:10, and then refine to a particle size D 90 of 1.6 μm, then mold, and sinter under the condition that the oxygen volume fraction is 1.3%, and obtain a highly corrosion-resistant environmental protection ceramic after cooling; The SiO2+Al2O3 of the kaolin is 98.1%, and the K2O+Na2O is 0.71%; The sintering process under the condition that the oxygen volume fraction is 0.8% is: heat up to 1260 °C at 3 °C / min and hold for 3 h. Example 4

[0029] A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix the iron ore tailings and coke in a mass ratio of 14:1, introduce an inert mixed gas with 7% oxygen by volume, calcine at 760 °C for 1.5 h, coarsely crush, perform magnetic separation, and further crush to D 90 of 50 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO content of the red mud is 11.6%, and the total content of Pb+Cd+Cr 6+ is 78 ppm; Step (2) Ball milling leaching - purification: Add magnetic concentrate, red mud and porous carbon to a zirconia ball mill for ball milling according to a mass ratio of 101:25:8, add a leaching reagent 8 times the total mass of magnetic concentrate, red mud and porous carbon, adjust the pH to 3.2, ball mill for 4.5 h, unload the material, precipitate and dehydrate after aeration and stirring, then make a slurry, add EDTA until the concentration is 0.008 M, adjust the pH to 5.8, ball mill for 30 min, unload the material, calcine in a weakly reducing atmosphere, the calcination process is to heat up to 760 °C at 4 °C / min, keep warm for 2 h, and crush to obtain pre-calcined active material; The leaching reagent is an aqueous solution mixture of 4.6 wt% citric acid, 1.2 wt% oxalic acid and 0.09 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 620 m 2 / g; The weakly reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin according to a mass ratio of 1:9, refine it to a particle size D 90 of 1.8 μm, then mold it, sinter it under the condition that the volume fraction of oxygen is 1.2%, and obtain a highly corrosion-resistant environmental protection ceramic after cooling; The SiO2+Al2O3 of the kaolin is 98.2%, and the K2O+Na2O is 0.71%; The sintering process under the condition that the volume fraction of oxygen is 0.9% is: heat up to 1250 °C at 3 °C / min and keep warm for 2.5 h. Example 5

[0030] A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix the iron ore tailings and coke according to a mass ratio of 12:1, introduce an inert mixed gas with 6% oxygen by volume, roast at 740 °C for 1.5 h, coarsely crush, perform magnetic separation, and further crush to D 90 of 56 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO content of the red mud is 13%, and the total content of Pb+Cd+Cr 6+ is 68 ppm; Step (2) Ball milling leaching - purification: Add the magnetic separation concentrate, red mud and porous carbon into a zirconia ball mill for ball milling according to the mass ratio of 97:23:9. Add leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon. Adjust the pH to 3, ball mill for 4 h, unload the material, precipitate and dehydrate after aeration and stirring, then make it into pulp, add EDTA until the concentration is 0.011 M, adjust the pH to 6, ball mill for 30 min, unload the material, and calcine in a weakly reducing atmosphere. The calcination process is to heat up to 760 °C at a rate of 2 °C / min, hold for 2 h, and crush to obtain the pre - calcined active material; The leaching reagent is an aqueous solution mixture of 6 wt% citric acid, 1.3 wt% oxalic acid and 0.11 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 620 m 2 / g; The weakly reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (3) Molding and calcination: After mixing the pre - calcined active material and kaolin according to the mass ratio of 1:9, refine it to a particle size D 90 of 1.7 μm, then mold it, and sinter it under the condition that the volume fraction of oxygen is 0.9%. After cooling, a highly corrosion - resistant environmental - protection ceramic is obtained; The SiO2 + Al2O3 of kaolin is 97.9%, and K2O + Na2O is 0.68%; The sintering process under the condition that the volume fraction of oxygen is 1.1% is: heat up to 1250 °C at a rate of 3 °C / min and hold for 2 h. Example 6

[0031] A preparation method of a highly corrosion - resistant environmental - protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix the iron ore tailings and coke according to the mass ratio of 14:1, introduce an inert mixed gas with 6% oxygen by volume, roast at 760 °C for 1.5 h, coarsely crush, magnetically separate, and further crush to D 90 of 54 μm to obtain the magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50 - mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO content of the red mud is 14%, and the total content of Pb + Cd + Cr 6+ is 69 ppm; Step (2) Ball milling leaching - purification: The magnetic separation concentrate, red mud and porous carbon are added to a zirconium ball mill for ball milling according to a mass ratio of 103:26:8. An leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon is added, the pH is adjusted to 3, ball milling is carried out for 4 h, the material is unloaded, after aeration stirring, precipitation and dehydration are carried out, and then pulping is carried out. Ball milling is carried out for 30 min, the material is unloaded, and calcination is carried out in a weakly reducing atmosphere. The calcination process is to heat up to 760 °C at 4 °C / min, keep the temperature for 2.5 h, and pulverize to obtain a pre-calcined active material; The leaching reagent is an aqueous mixed solution of 5 wt% citric acid, 1.1 wt% oxalic acid and 0.10 wt% sodium hexametaphosphate by mass fraction; The specific surface area of the porous carbon is 630 m 2 / g; The weakly reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume ratio; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin according to a mass ratio of 1:10, it is refined to a particle size D 90 of 1.6 μm, and then molded and sintered under the condition that the volume fraction of oxygen is 1.3%. After cooling, a highly corrosion-resistant environmental protection ceramic is obtained; The SiO2+Al2O3 of kaolin is 98.2%, and K2O+Na2O is 0.67%; The sintering process under the condition that the volume fraction of oxygen is 0.8% is: heating up to 1250 °C at 4 °C / min and keeping the temperature for 2.5 h.

[0032] Comparative Example 1 The difference from Example 1 is that in step (1), a nitrogen mixture gas containing 10% oxygen by volume is introduced: A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix the iron ore tailings and coke according to a mass ratio of 12:1, introduce a nitrogen mixture gas containing 10% oxygen by volume, roast at 750 °C for 1.5 h, coarsely pulverize, carry out magnetic separation, and further pulverize to D 90 of 53 μm to obtain a magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO of the red mud is 10%, and the total content of Pb+Cd+Cr 6+ is 88 ppm; Step (2) Ball milling leaching-purification: Add magnetic separation concentrate, red mud and porous carbon to a zirconium ball mill for ball milling according to a mass ratio of 100:25:8. Add a leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon. Adjust the pH to 3, ball mill for 4 h, unload the material, precipitate and dehydrate after aeration and stirring, then make it into a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload the material, and calcine in a weakly reducing atmosphere. The calcination process is to heat up to 750 °C at a rate of 4 °C / min, hold for 2.5 h, and pulverize to obtain a pre-calcined active material; The leaching reagent is an aqueous solution mixture of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate by mass fraction; The specific surface area of the porous carbon is 600 m 2 / g; The weakly reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume ratio; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin according to a mass ratio of 1:9.5, refine it to a particle size D 90 of 1.5 μm, then mold it, and sinter it under the condition that the volume fraction of oxygen is 1.0%, and obtain a highly corrosion-resistant environmental protection ceramic after cooling; The SiO2 + Al2O3 of kaolin is 97.5%, and the K2O + Na2O is 0.65%; The sintering process under the condition that the volume fraction of oxygen is 1.0% is: heat up to 1250 °C at a rate of 3 °C / min and hold for 2.5 h.

[0033] Comparative Example 2 The difference from Example 1 is that magnetic separation is not carried out: A preparation method of a highly corrosion-resistant environmental protection ceramic, including: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke according to a mass ratio of 12:1, introduce a nitrogen mixture with 6% oxygen by volume, roast at 750 °C for 1.5 h, coarsely pulverize, and further pulverize to D 90 of 53 μm to obtain ore powder; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the ore powder is 34%; The CaO of the red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling leaching - purification: The magnetic separation concentrate, red mud, and porous carbon are added to a zirconium ball mill for ball milling at a mass ratio of 100:25:8. Leaching reagent eight times the total mass of the magnetic separation concentrate, red mud, and porous carbon is added, the pH is adjusted to 3, ball milling is carried out for 4 h, the material is unloaded, aerated and stirred, then precipitated and dehydrated, and then slurried. EDTA is added until the concentration reaches 0.01 M, the pH is adjusted to 6, ball milling is carried out for 30 min, the material is unloaded, and calcination is carried out in a weakly reducing atmosphere. The calcination process is to heat up to 750 °C at 4 °C / min and hold for 2.5 h, and then pulverize to obtain the pre-calcined active material; The leaching reagent is an aqueous mixed solution of 5 wt% citric acid, 1.3 wt% oxalic acid, and 0.1 wt% sodium hexametaphosphate by mass fraction; The specific surface area of the porous carbon is 600 m 2 / g; The weakly reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume ratio; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin at a mass ratio of 1:9.5, it is refined to a particle size D 90 of 1.5 μm, then molded, and sintered under the condition that the volume fraction of oxygen is 1.0%, and a highly corrosion-resistant environmental protection ceramic is obtained after cooling; The SiO2 + Al2O3 of kaolin is 97.5%, and the K2O + Na2O is 0.65%; The sintering process under the condition that the volume fraction of oxygen is 1.0% is: heating up to 1250 °C at 3 °C / min and holding for 2.5 h.

[0034] Comparative Example 3 The difference from Example 1 is that the total iron content of the iron ore tailings is 28%; A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix the iron ore tailings and coke at a mass ratio of 12:1, introduce a nitrogen mixed gas containing 6% oxygen by volume, roast at 750 °C for 1.5 h, coarsely pulverize, magnetic separate, and further pulverize to D 90 of 53 μm to obtain the magnetic concentrate; The total iron content of the iron ore tailings is 28%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 53%; The CaO of the red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling, leaching and purification: The magnetic separation concentrate, red mud and porous carbon are added to a zirconium ball mill for ball milling according to a mass ratio of 100:25:8. An leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon is added. The pH is adjusted to 3, and ball milling is carried out for 4 h. Then, discharging is performed. After aeration stirring, precipitation and dehydration are carried out. Subsequently, pulping is carried out, and EDTA is added until the concentration reaches 0.01 M. The pH is adjusted to 6, and ball milling is carried out for 30 min. Then, discharging is performed, and calcination is carried out under a weak reducing atmosphere. The calcination process is to heat up to 750 °C at a rate of 4 °C / min and hold for 2.5 h, and then pulverize to obtain a pre-calcined active material; The leaching reagent is an aqueous solution mixture of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin according to a mass ratio of 1:9.5, it is refined to a particle size D 90 of 1.5 μm, and then molded. Sintering is carried out under the condition that the volume fraction of oxygen is 1.0%. After cooling, a highly corrosion-resistant environmental protection ceramic is obtained; The SiO2 + Al2O3 of kaolin is 97.5%, and K2O + Na2O is 0.65%; The sintering process under the condition that the volume fraction of oxygen is 1.0% is: heating up to 1250 °C at a rate of 3 °C / min and holding for 2.5 h.

[0035] Comparative Example 4 The difference from Example 1 is that the iron ore tailings are not subjected to magnetic separation enrichment treatment: A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Ball milling leaching - purification: The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; The CaO of the red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; The magnetic separation concentrate, red mud and porous carbon are added to a zirconium ball mill for ball milling according to a mass ratio of 100:25:8. An leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon is added. The pH is adjusted to 3, and ball milling is carried out for 4 h. Then, discharging is performed. After aeration stirring, precipitation and dehydration are carried out. Subsequently, pulping is carried out, and EDTA is added until the concentration reaches 0.01 M. The pH is adjusted to 6, and ball milling is carried out for 30 min. Then, discharging is performed, and calcination is carried out under a weak reducing atmosphere. The calcination process is to heat up to 750 °C at a rate of 4 °C / min and hold for 2.5 h, and then pulverize to obtain a pre-calcined active material; The leaching reagent is an aqueous solution mixture of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (2) Forming and calcining: After mixing the pre-calcined active material and kaolin in a mass ratio of 1:9.5, it is refined to a particle size D 90 of 1.5 μm, then formed, sintered under the condition that the volume fraction of oxygen is 1.0%, and a highly corrosion-resistant environmental protection ceramic is obtained after cooling; The SiO2 + Al2O3 of kaolin is 97.5%, and K2O + Na2O is 0.65%; The sintering process under the condition that the volume fraction of oxygen is 1.0% is: heating to 1250 °C at 3 °C / min and holding for 2.5 h.

[0036] Comparative Example 5 The difference from Example 1 is that the calcium content of the red mud is 25%: A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix the iron ore tailings and coke in a mass ratio of 12:1, introduce a nitrogen mixed gas with 6% oxygen by volume, roast at 750 °C for 1.5 h, coarsely crush, magnetic separate, and further crush to D 90 of 53 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO of the red mud is 25%, and the total content of Pb + Cd + Cr 6+ is 98 ppm; Step (2) Ball milling leaching - purification: Add the magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling in a mass ratio of 100:25:8, add a leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 4 h, unload, aerate and stir, then precipitate and dehydrate, then make a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload, and calcine in a weak reducing atmosphere. The calcination process is heating to 750 °C at 4 °C / min and holding for 2.5 h, and then pulverize to obtain the pre-calcined active material; The leaching reagent is an aqueous solution mixture of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume; Step (3) Forming and calcining: After mixing the pre-burned active material and kaolin in a mass ratio of 1:9.5, it is refined to a particle size D 90 of 1.5 μm, then formed, sintered under the condition that the volume fraction of oxygen is 1.0%, and a highly corrosion-resistant environmental protection ceramic is obtained after cooling; The SiO2 + Al2O3 of kaolin is 97.5%, and the K2O + Na2O is 0.65%; The sintering process under the condition that the volume fraction of oxygen is 1.0% is: heating to 1250 °C at 3 °C / min and holding for 2.5 h.

[0037] Comparative Example 6 The difference from Example 1 is that no leaching reagent was added in step (2): A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke in a mass ratio of 12:1, introduce a nitrogen mixture containing 6% oxygen by volume, roast at 750 °C for 1.5 h, coarsely crush, magnetically separate, and further crush to D 90 of 53 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO of the red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling leaching - purification: Add magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling in a mass ratio of 100:25:8, add 8 times the total mass of magnetic separation concentrate, red mud and porous carbon of water, adjust the pH to 3, ball mill for 4 h, discharge, stir with gas and then precipitate and dehydrate, then make a slurry, adjust the pH to 6, ball mill for 30 min, discharge, and calcine in a weak reducing atmosphere. The calcination process is heating to 750 °C at 4 °C / min and holding for 2.5 h, and then crushing to obtain the pre-burned active material; The specific surface area of the porous carbon is 600 m 2 / g; The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume; Step (3) Forming and calcining: After mixing the pre-burned active material and kaolin in a mass ratio of 1:9.5, it is refined to a particle size D 90It is 1.5 μm, and then molded. It is sintered under the condition that the oxygen volume fraction is 1.0%, and a highly corrosion-resistant environmental protection ceramic is obtained after cooling; The SiO2 + Al2O3 of kaolin is 97.5%, and the K2O + Na2O is 0.65%; The sintering process under the condition that the oxygen volume fraction is 1.0% is as follows: heating to 1250 °C at 3 °C / min and holding for 2.5 h.

[0038] Comparative Example 7 The difference from Example 1 is that in step (2), the proportion of red mud is too high: A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke at a mass ratio of 12:1, introduce a nitrogen mixture containing 6% oxygen by volume, roast at 750 °C for 1.5 h, coarsely crush, perform magnetic separation, and further crush to D 90 It is 53 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO of the red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling leaching - purification: Add magnetic concentrate, red mud and porous carbon to a zirconia ball mill for ball milling at a mass ratio of 100:35:8, add a leaching reagent 8 times the total mass of magnetic concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 4 h, unload the material, stir with air and then precipitate and dehydrate, then make a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload the material, and calcine in a weak reducing atmosphere. The calcination process is heating to 750 °C at 4 °C / min and holding for 2.5 h, and then crushing to obtain pre-calcined active material; The leaching reagent is an aqueous mixed solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin at a mass ratio of 1:9.5, refine to a particle size D 90 It is 1.5 μm, and then molded. It is sintered under the condition that the oxygen volume fraction is 1.0%, and a highly corrosion-resistant environmental protection ceramic is obtained after cooling; The SiO2 + Al2O3 of kaolin is 97.5%, and the K2O + Na2O is 0.65%. The sintering process under the condition that the volume fraction of oxygen gas is 1.0% is as follows: heating up to 1250 °C at 3 °C / min and holding for 2.5 h.

[0039] Comparative Example 8 The difference from Example 1 is that step (2) is in an air atmosphere: A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke at a mass ratio of 12:1, introduce a nitrogen mixed gas with an oxygen content of 6% by volume, roast at 750 °C for 1.5 h, coarsely crush, perform magnetic separation, and further crush to D 90 of 53 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO of red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling leaching - purification: Add magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling according to a mass ratio of 100:25:8, add a leaching reagent 8 times the total mass of magnetic separation concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 4 h, unload the material, stir with air and then precipitate and dehydrate, then make a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload the material, and calcine in an air atmosphere. The calcination process is to heat up to 750 °C at 4 °C / min and hold for 2.5 h, and then crush to obtain pre-calcined active material; The leaching reagent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin at a mass ratio of 1:9.5, refine to a particle size D 90 of 1.5 μm, then mold, sinter under the condition that the volume fraction of oxygen gas is 1.0%, and obtain a highly corrosion-resistant environmental protection ceramic after cooling; The SiO2 + Al2O3 of kaolin is 97.5%, and the K2O + Na2O is 0.65%. The sintering process under the condition that the volume fraction of oxygen gas is 1.0% is as follows: heating up to 1250 °C at 3 °C / min and holding for 2.5 h.

[0040] Comparative Example 9 The difference from Example 1 is that the heat preservation time during the calcination process is too long: A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke at a mass ratio of 12:1, introduce a nitrogen mixed gas with 6% oxygen by volume, roast at 750 °C for 1.5 h, coarsely crush, perform magnetic separation, and further crush to D 90 to 53 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO of the red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling leaching - purification: Add magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling at a mass ratio of 100:25:8, add a leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 4 h, unload, stir with gas and then precipitate and dehydrate, then make a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload, and calcine in a weak reducing atmosphere. The calcination process is to heat up to 750 °C at 4 °C / min, keep warm for 4 h, and crush to obtain pre-calcined active material; The leaching reagent is an aqueous mixed solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin at a mass ratio of 1:9.5, refine to a particle size D 90 of 1.5 μm, then mold, and sinter under the condition that the oxygen volume fraction is 1.0%, and a highly corrosion-resistant environmental protection ceramic is obtained after cooling; The SiO2 + Al2O3 of the kaolin is 97.5%, and the K2O + Na2O is 0.65%; The sintering process under the condition that the oxygen volume fraction is 1.0% is: heat up to 1250 °C at 3 °C / min and keep warm for 2.5 h.

[0041] Comparative Example 10 The difference from Example 1 is that in step (3), the proportion of kaolin is too small: A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke in a mass ratio of 12:1, introduce a nitrogen mixture gas with 6% oxygen by volume, roast at 750 °C for 1.5 h, coarsely crush, and perform magnetic separation, and further crush to D 90 to 53 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%; The CaO in the red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling leaching - purification: Add magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling in a mass ratio of 100:25:8, add a leaching reagent 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 4 h, unload the material, stir with gas and then precipitate and dehydrate, then make a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload the material, and calcine in a weak reducing atmosphere. The calcination process is to heat up to 750 °C at 4 °C / min and hold for 2.5 h, and then crush to obtain pre-calcined active material; The leaching reagent is an aqueous mixed solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume ratio; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin in a mass ratio of 1:8, refine to a particle size D 90 to 1.5 μm, then mold, and sinter under the condition that the oxygen volume fraction is 1.0%, and obtain a highly corrosion-resistant environmental protection ceramic after cooling; The SiO2 + Al2O3 in the kaolin is 97.5%, and the K2O + Na2O is 0.65%; The sintering process under the condition that the oxygen volume fraction is 1.0% is: heat up to 1250 °C at 3 °C / min and hold for 2.5 h.

[0042] Comparative Example 11 The difference from Example 1 is that during the sintering process in step (3), the oxygen concentration is too high: A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke in a mass ratio of 12:1, introduce a nitrogen mixture gas with 6% oxygen by volume, roast at 750 °C for 1.5 h, coarsely crush, and perform magnetic separation, and further crush to D90 It is 53 μm to obtain magnetic concentrate; The total iron content of iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of magnetic concentrate is 65%; The CaO of red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling leaching - purification: Add magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling according to a mass ratio of 100:25:8, add a leaching reagent 8 times the total mass of magnetic separation concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 4 h, unload the material, precipitate and dehydrate after aeration and stirring, then make a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload the material, and calcine in a weakly reducing atmosphere. The calcination process is to heat up to 750 °C at 4 °C / min and keep it warm for 2.5 h, and then pulverize to obtain pre-calcined active material; The leaching reagent is an aqueous mixed solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of porous carbon is 600 m 2 / g; The weakly reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, 94.8% N2 by volume; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin according to a mass ratio of 1:9.5, refine it to a particle size D 90 of 1.5 μm, then mold it, and sinter it under the condition that the volume fraction of oxygen is 5.0%. After cooling, a highly corrosion-resistant environmental protection ceramic is obtained; The SiO2 + Al2O3 of kaolin is 97.5%, and the K2O + Na2O is 0.65%; The sintering process under the condition that the volume fraction of oxygen is 5.0% is: heat up to 1250 °C at 3 °C / min and keep it warm for 2.5 h.

[0043] Comparative Example 12 The difference from Example 1 is that in step (3), it is refined to a particle size D 90 of 2.5 μm: A preparation method of a highly corrosion-resistant environmental protection ceramic, comprising: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke according to a mass ratio of 12:1, introduce a nitrogen mixed gas with 6% oxygen by volume, roast at 750 °C for 1.5 h, coarsely pulverize, perform magnetic separation, and further pulverize to D 90 of 53 μm to obtain magnetic concentrate; The total iron content of the iron ore tailings is 31%, the sulfur content is 2.8%, and it passes through a 50-mesh sieve; the total iron content of the magnetic concentrate is 65%. The CaO in the red mud is 10%, and the total content of Pb + Cd + Cr 6+ is 88 ppm; Step (2) Ball milling leaching - purification: Add magnetic concentrate, red mud and porous carbon to a zirconia ball mill for ball milling according to a mass ratio of 100:25:8, add a leaching reagent 8 times the total mass of magnetic concentrate, red mud and porous carbon, adjust the pH to 3, ball mill for 4 h, unload the material, precipitate and dehydrate after aeration and stirring, then make a slurry, add EDTA until the concentration is 0.01 M, adjust the pH to 6, ball mill for 30 min, unload the material, and calcine in a weakly reducing atmosphere. The calcination process is to heat up to 750 °C at 4 °C / min and keep it for 2.5 h, and then crush to obtain the pre-calcined active material; The leaching reagent is an aqueous solution mixture of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate; The specific surface area of the porous carbon is 600 m 2 / g; The weakly reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume; Step (3) Molding and calcination: After mixing the pre-calcined active material and kaolin according to a mass ratio of 1:9.5, refine it to a particle size D 90 of 2.5 μm, then mold it, and sinter it under the condition that the volume fraction of oxygen is 1.0%. After cooling, a highly corrosion-resistant environmental protection ceramic is obtained; The SiO2 + Al2O3 in the kaolin is 97.5%, and the K2O + Na2O is 0.65%; The sintering process under the condition that the volume fraction of oxygen is 1.0% is: heat up to 1250 °C at 3 °C / min and keep it for 2.5 h.

[0044] The main element oxide compositions of Examples 1 - 6 and Comparative Examples 1 - 12 of the present invention are shown in Table 1 (the contents of other impurities are not listed in the table), and the performance detection methods and results of Examples 1 - 6 and Comparative Examples 1 - 12 of the present invention are shown in Table 2.

[0045] Table 1 Main element oxide compositions of Examples 1 - 6 and Comparative Examples 1 - 12

[0046] Table 2 Performance detection methods and results of Examples 1 - 6 and Comparative Examples 1 - 12

[0047] Examples 1-6 have better corrosion resistance compared to Comparative Examples 1-12, which benefits from the joint control of components and processes. As can be seen from Example 6, although EDTA is not added, it can still meet the target of Pb+Cd+Cr 6+ ≤2 ppm, and also has good corrosion resistance, indicating that EDTA is a supplementary reagent, mainly to further ensure the removal of target ions.

[0048] The difference between Comparative Example 1 and Example 1 is that the roasting oxygen concentration is 10%. A higher oxygen concentration may reduce the conversion efficiency of hematite to magnetite, and there is a downward trend in the magnetic separation recovery rate. This may lead to a decrease in the iron content in the pre-roasted active material, relatively insufficient formation of calcium iron garnet phase during sintering, weakened grain boundary sealing effect, and a decline in corrosion resistance.

[0049] The difference between Comparative Example 2 and Example 1 is that there is no magnetic separation treatment, mainly because the impurity content exceeds the standard, which has an adverse effect on acid corrosion resistance.

[0050] The difference between Comparative Example 3 and Example 1 is that the total iron content of the tailings is 28%, resulting in the iron content in the magnetic separation concentrate exceeding the lower limit of the process. The reduction in iron source supply may affect the full formation of the calcium iron garnet phase, the degree of grain boundary pore closure decreases, and the mechanical strength and alkali resistance of the material show a downward trend.

[0051] The difference between Comparative Example 4 and Example 1 is that the tailings are directly used, and non-magnetic separation may allow heavy metal minerals to directly enter the system. In the absence of selective separation, the adsorption efficiency of porous carbon for encapsulated heavy metals may be limited, and there is a risk of high heavy metal residues in the final product. At the same time, sulfide residues may exacerbate corrosion sensitivity.

[0052] The difference between Comparative Example 5 and Example 1 is that the CaO content in the red mud is 25%. High-calcium red mud may exceed the calcium dissolution capacity range of acid leaching. Excessive calcium is prone to form a calcium feldspar phase with a higher expansion coefficient during sintering, resulting in a decrease in the thermal expansion matching with the mullite matrix and a reduction in stability, leading to the generation of microcracks and ultimately affecting the corrosion resistance.

[0053] The difference between Comparative Example 6 and Example 1 is that the absence of leaching reagent reduces the heavy metal dissociation efficiency, and at the same time, the removal effect of soluble alkali metals in the red mud may be weakened. This may lead to a decrease in the stability of the glass phase and an increased tendency of the material to dissolve in an alkaline environment.

[0054] The difference between Comparative Example 7 and Example 1 is that excessive red mud may dilute the proportion of the silicon-aluminum matrix, making the Al2O3 content close to or lower than the lower limit value of 20%. This may affect the integrity of the mullite skeleton and lead to a downward trend in the load-bearing capacity of the material.

[0055] The difference between Comparative Example 8 and Example 1 is that in step (2), the atmosphere is air, which may not be conducive to the complete decomposition of organic matter, and there is a risk of increased carbon residue. At the same time, the lack of a weak reduction environment may reduce the encapsulation efficiency of heavy metals in iron oxides, potentially affecting the acid resistance of the material.

[0056] The difference between Comparative Example 9 and Example 1 is that in step (2), the heat preservation is for 4 h. Prolonging the calcination time may cause excessive reduction of magnetite to FeO. The presence of FeO may trigger a eutectic phenomenon at low temperatures, and the crystal grains are too large, resulting in a decrease in the sintering activity of the pre-sintered material and an increased risk of high-temperature deformation. During the experiment, the sample was severely deformed and damaged during the sintering stage, and standard performance tests could not be carried out.

[0057] The difference between Comparative Example 10 and Example 1 is that the proportion of kaolin is relatively low, which may lead to a decrease in the compactness of the mullite network and a weakened penetration resistance of the corrosion medium.

[0058] The difference between Comparative Example 11 and Example 1 is that during the sintering process in step (3), the oxygen concentration is too high, which may inhibit the transformation of Fe2O3 into magnetite. The shortage of magnetite may affect the formation efficiency of the andradite phase, and at the same time, the increase in free Fe2O3 may potentially affect the brittleness of the material.

[0059] The difference between Comparative Example 12 and Example 1 is that in step (3), it is refined to a particle size D 90 of 2.5 μm. Exceeding the upper limit of the process for the powder particle size may increase the porosity of particle packing, and the reaction activity and compactness are reduced. The existence of larger pores may accelerate the penetration of the medium, resulting in an increase in water absorption and a weakening of corrosion resistance.

[0060] In summary, based on the raw material principle and combined with process design, this solution applies iron ore tailings and red mud to the production of handicraft ceramics, and can obtain environmentally friendly ceramics with high corrosion resistance.

Claims

1. An environmentally friendly ceramic with high corrosion resistance, characterized in that, The chemical composition, calculated by mass percentage of oxides, satisfies the following: SiO2: 68 - 72%; Al2O3: 20 - 22%; Fe2O3: 4 - 6%; CaO: 2.0 - 3.5%; MgO: 0.5 - 1.0%; K2O + Na2O: 0.8 - 1.2%; SO3: ≤0.03%; Pb+Cd+Cr 6+ : ≤ 2 ppm; The rest are impurities.

2. A preparation method of the highly corrosion-resistant environmental protection ceramic as described in claim 1, characterized in that, It includes: Step (1) Magnetic separation enrichment of iron ore tailings: Mix iron ore tailings and coke at a mass ratio of 10 - 15:1, introduce an inert mixed gas with an oxygen content of 5 - 8% by volume, roast at 730 - 770 °C for 1 - 2 h, coarsely crush, perform magnetic separation, and further crush to D 90 ≤ 60 μm to obtain magnetic concentrate; Step (2) Ball milling leaching - purification: Add magnetic separation concentrate, red mud and porous carbon to a zirconia ball mill for ball milling according to a mass ratio of 95 - 105:22 - 28:7 - 9. Add a leaching reagent that is 6 - 8 times the total mass of the magnetic separation concentrate, red mud and porous carbon. Adjust the pH to 2.5 - 3.5, ball mill for 3 - 5 h, unload the material, precipitate and dehydrate after aeration stirring, then make it into pulp, ball mill for 20 - 30 min, unload the material, dehydrate, calcine in a weak reducing atmosphere, and crush to obtain pre - calcined active material; The leaching reagent is an aqueous solution mixture of citric acid with a mass fraction of 4 - 6 wt%, oxalic acid with a mass fraction of 1.0 - 1.5 wt% and sodium hexametaphosphate with a mass fraction of 0.08 - 0.12 wt%; Step (3) Shaping and calcining: After mixing the pre-fired active material and kaolin in a mass ratio of 1:9 - 10, it is refined to a particle size D 90 ≤2.0 μm, then formed, sintered under the condition that the volume fraction of oxygen gas is 0.5 - 1.5%, and a highly corrosion-resistant environmental protection ceramic is obtained after cooling.

3. The preparation method of the highly corrosion-resistant environmental protection ceramic according to claim 2, characterized in that, The total iron content of the iron ore tailings in step (1) is ≥28%, the sulfur content is ≤3%, and it passes through a 50 - mesh sieve; the total iron content of the magnetic concentrate is ≥55%.

4. The preparation method of the highly corrosion-resistant environmental protection ceramic according to claim 2, characterized in that, The CaO content of the red mud is less than 15%, and the total content of Pb + Cd + Cr 6+ ≤ 100 ppm; for the kaolin, SiO2 + Al2O3 ≥ 97% and K2O + Na2O ≤ 0.8%.

5. The preparation method of the highly corrosion-resistant environmental protection ceramic according to claim 2, characterized in that, The solid content after making into pulp in step (2) is 10 - 15%.

6. The preparation method of the highly corrosion-resistant environmental protection ceramic according to claim 2, characterized in that, The specific surface area of the porous carbon described in step (2) is 550 - 650 m 2 / g.

7. The preparation method of the highly corrosion-resistant environmental protection ceramic according to claim 2, characterized in that, After aeration stirring, precipitate and dehydrate, then make it into pulp, add EDTA until the concentration is 0.008 - 0.012 M, adjust the pH to 5.8 - 6.2, ball mill for 20 - 30 min, unload the material, calcine in a weak reducing atmosphere, and crush to obtain pre - calcined active material.

8. The preparation method of the highly corrosion-resistant environmental protection ceramic according to claim 2, characterized in that, The weak reducing atmosphere in step (2) is O2 with a volume ratio of 0.8 - 1.2%, CO with a volume ratio of 1.0 - 1.4%, CO2 with a volume ratio of 2.8 - 3.2%, and the rest is N2.

9. The preparation method of the highly corrosion-resistant environmental protection ceramic according to claim 2, characterized in that, The sintering process of calcining in the weak reducing atmosphere in step (2) is: heat up at 2 - 5 °C / min to 740 - 760 °C and hold for 2 - 3 h.

10. The preparation method of the highly corrosion-resistant environmental protection ceramic according to claim 2, characterized in that, In step (3), the sintering process under the condition that the volume fraction of oxygen is 0.5 - 1.5% is: heat up at 2 - 5 °C / min to 1230 - 1280 °C and hold for 2 - 3 h.

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