A highly corrosion-resistant environmentally friendly ceramic and its preparation method

Abstract

The present invention relates to the technical field of ceramic materials, and in particular to a highly corrosion-resistant environmentally friendly ceramic and a preparation method thereof. The chemical composition, calculated by oxide mass percentage, satisfies the following requirements: 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+ : ≤2ppm; the rest are impurities. This solution not only allows the use of tailings to produce process ceramics, but also strictly controls the content of heavy metals and other residuals, ensuring stable composition, thus achieving a combination of high corrosion resistance and environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a highly corrosion-resistant environmentally friendly ceramic and a preparation method thereof. Background Art

[0002] Ceramics are susceptible to irreversible destructive changes in their physical structure or chemical composition in specific chemical environments (such as acids, alkalis, salt solutions, molten salts, high-temperature gases or water vapor), resulting in a significant decline in key properties such as strength, hardness, and insulation, or even failure. This phenomenon is known as ceramic corrosion. This phenomenon manifests itself in surface erosion and dissolution, making the surface rough and porous; preferential corrosion of grain boundaries, leading to grain shedding and a sudden drop in strength; phase transitions or decomposition of material components (such as hydration expansion cracking); and stress corrosion cracking under the combined action of stress and corrosive media. This phenomenon is closely related to the ceramic composition and process. Using tailings as a raw material for handicraft ceramics, while meeting environmental protection requirements and reducing production costs, also results in a sharp decline in corrosion resistance.

[0003] CN117124451B discloses a daily-use ceramic production line and its process, which reduces the possibility of cracking, thermal cracking and deformation of the clay blank by drying the inside and outside of the clay blank separately, thereby reducing the defective rate. However, this technical solution mainly focuses on the problem of drying uniformity 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, the solution does not mention the technical path of using environmentally friendly raw materials such as tailings to prepare ceramics, so there are obvious deficiencies in environmental protection and resource recycling. CN110981414B discloses a production process for ceramic cups, which makes the ceramic cups produced have high thermal stability even with thinner wall thickness by rationally proportioning raw materials such as kaolin, SiO2, Na2O, K2O, Al2O3 and CaCO3. However, this technical solution mainly focuses on the thermal stability of the ceramic cup, and does not make an in-depth discussion on its durability in corrosive environments such as acids and alkalis. At the same time, this plan does not involve the utilization of tailings or industrial waste, and cannot effectively solve the shortcomings of traditional ceramic materials in terms of environmental protection. It also fails to overcome the common problems of tailings ceramics such as sulfide decomposition to produce SO2, migration and enrichment of heavy metal ions, and fluctuations in alkali metal content affecting corrosion resistance.

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

[0005] To solve the above problems, the present invention provides a highly corrosion-resistant environmentally friendly ceramic and a preparation method thereof, which can not only utilize tailings to prepare process ceramics, but also strictly control the residual heavy metal content and other residues, and control the stability of the composition, thereby achieving the unity of high corrosion resistance and environmental protection.

[0006] A highly corrosion-resistant environmentally friendly ceramic, whose chemical composition, calculated as oxide mass percentage, satisfies:

[0007] SiO2: 68-72%;

[0008] Al2O3: 20-22%;

[0009] Fe2O3: 4-6%;

[0010] CaO: 2.0-3.5%;

[0011] MgO: 0.5-1.0%;

[0012] K2O+Na2O: 0.8-1.2%;

[0013] SO3: ≤0.03%;

[0014] Pb+Cd+Cr 6+ :≤2ppm;

[0015] The rest are impurities.

[0016] This ceramic uses a kaolin-dominated silicon-aluminum system (SiO2+Al2O3≥88%) as its core skeleton. By strictly limiting the alkali metal content (K2O+Na2O≤1.2%), the glass phase dissolution is inhibited, and the iron-calcium composition (Fe2O34-6%+CaO2.0-3.5%) is regulated to form an astronomical garnet phase to seal the grain boundary pores during sintering. At the same time, sulfur and heavy metal environmental control elements (SO3≤0.03%, Pb+Cd+Cr 6+ ≤2ppm) to the limit. The risk of corrosion induction is reduced from the source of the ingredients, and a fully dense corrosion-resistant network based on interwoven acicular mullite is constructed.

[0017] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0018] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0019] The iron ore tailings and coke are mixed in a mass ratio of 10-15:1, and an inert mixed gas containing 5-8% oxygen by volume is introduced. The mixture is roasted at 730-770℃ for 1-2h, coarsely crushed, magnetically separated, and further crushed to D 90 ≤60μm, magnetic concentrate is obtained;

[0020] Step (2) ball milling leaching-purification:

[0021] The magnetic concentrate, red mud and porous carbon are added to a zirconium ball mill in a mass ratio of 95-105:22-28:7-9, and a leaching agent is added in an amount of 6-8 times the total mass of the magnetic concentrate, red mud and porous carbon. The pH is adjusted to 2.5-3.5, and the mixture is ball-milled for 3-5 hours. The mixture is unloaded, aerated and stirred, and then precipitated and dehydrated. The mixture is then slurried, ball-milled for 20-30 minutes, unloaded, dehydrated, calcined in a weak reducing atmosphere, and pulverized to obtain a pre-calcined active material.

[0022] The leaching agent is a mixed aqueous solution of 4-6 wt% citric acid, 1.0-1.5 wt% oxalic acid and 0.08-0.12 wt% sodium hexametaphosphate;

[0023] Step (3) forming and calcining:

[0024] Mix the pre-burned active material with kaolin in a mass ratio of 1:9-10 and refine to a particle size of D 90 ≤2.0μm, then formed, sintered under the condition of oxygen volume fraction of 0.5-1.5%, and obtained highly corrosion-resistant environmentally friendly ceramics after cooling.

[0025] This scheme converts hematite into magnetite through low-oxygen reduction roasting of iron ore tailings at 730-770°C for magnetic separation and enrichment, while simultaneously removing some sulfur impurities. During the ball milling stage, heavy metal ions are dissociated in an acidic complexing system (pH 2.5-3.5) of citric acid / oxalic acid, and targetedly adsorbed by porous carbon. Most of the porous carbon is washed out during the precipitation and dehydration process after ventilation and stirring. Finally, organic matter is completely decomposed through calcination, and trace heavy metals are sealed in the calcium-iron garnet lattice.

[0026] The pre-calcined active material is compounded with kaolin at a ratio of 1:9-10, significantly increasing the nucleation density of mullite. During sintering, a low-oxygen atmosphere diluted with N2 is used to control the oxygen concentration. At 1250°C and in a 0.5-1.5% low-oxygen atmosphere, Fe2O3 is partially converted to ferroferric oxide. These two react synergistically with CaO / SiO2 to form a highly dense andradite phase, while suppressing the precipitation of the harmful FeO phase. Furthermore, the K2O-Al2O3-SiO2 ternary eutectic promotes the directional growth of acicular mullite, forming an ultra-stable interlocking crystal structure that completely physically blocks the permeation pathways of corrosive media.

[0027] Preferably, the 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; and the total iron content of the magnetic concentrate is ≥55%.

[0028] In order to ensure the effect of low-oxygen reduction roasting, it is necessary to control the particle size of the iron ore tailings and sieve them with a sieve of 50 mesh or above.

[0029] Preferably, the CaO content of the red mud is less than 15%, and the Pb+Cd+Cr 6+Total content ≤100ppm.

[0030] Preferably, the solid content after slurrying in step (2) is 10-15%.

[0031] Preferably, the porous carbon in step (2) has a specific surface area of ​​550-650m 2 / g.

[0032] Preferably, the mixture is precipitated and dehydrated after ventilation and stirring, and then slurried, EDTA is added until the concentration is 0.008-0.012M, the pH is adjusted to 5.8-6.2, ball milled for 20-30 minutes, unloaded, calcined in a weak reducing atmosphere, and pulverized to obtain the pre-burned active material.

[0033] Adding 0.008-0.012M EDTA buffer, pH 5.8-6.2, can strongly chelate residual lead and cadmium, further reducing solid-phase residual toxicity.

[0034] Preferably, the weak reducing atmosphere in step (2) is 0.8-1.2% by volume of O2, 1.0-1.4% by volume of CO, 2.8-3.2% by volume of CO2, and the remainder being N2.

[0035] Citric acid, oxalic acid, and EDTA need to be decomposed 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 encapsulated by Fe2O3 in a weakly reducing atmosphere to form a solid solution, such as Fe2O3-PbO, or reduced to a metal element and embedded in the crystal lattice. Avoid strong reduction to generate excessive FeO, which may lead to agglomeration and deactivation of the pre-fired material.

[0036] Preferably, the sintering process of the weak reducing atmosphere calcination in step (2) is: heating to 740-760°C at 2-5°C / min and keeping the temperature for 2-3h.

[0037] Preferably, in step (3), the sintering process under the condition of oxygen volume fraction of 0.5-1.5% is: heating to 1230-1280°C at 2-5°C / min and keeping warm for 2-3h.

[0038] Preferably, the kaolin has SiO2+Al2O3≥97%, and K2O+Na2O≤0.8%.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] 1. The core advantage of this solution lies in its innovative and precise integration of solid waste resource utilization and ultra-corrosion-resistant structures. Through the synergistic combination of magnetic separation and enrichment of iron ore tailings and red mud, a multi-stage purification process reduces the residual heavy metal toxicity in the tailings to ≤ 0.1ppm, ensuring environmental friendliness.

[0041] 2. This solution suppresses FeO formation by controlling the atmosphere during high-temperature processes such as calcination and sintering, converting ferroferric oxide / Fe2O3 into an andradite-phase grain boundary filler. Simultaneously, it precisely locks the iron-calcium components and directionally generates andradite-phase closed grain boundaries during low-oxygen sintering, blocking the penetration path of corrosive media at the source and improving the ceramic matrix's resistance to strong acids and alkalis compared to traditional ceramics. DETAILED DESCRIPTION

[0042] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention. Example 1

[0043] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0044] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0045] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0046] The 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%;

[0047] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0048] Step (2) ball milling leaching-purification:

[0049] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, unloaded, and precipitated and dehydrated after ventilation and stirring. The mixture was then slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, unloaded, and calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min, and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0050] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0051] Porous carbon specific surface area 600m 2 / g;

[0052] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0053] Step (3) forming and calcining:

[0054] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0055] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0056] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h. Example 2

[0057] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0058] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0059] The iron ore tailings and coke were mixed in a mass ratio of 15:1, and an inert mixed gas containing 8% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 54 μm, and magnetic concentrate is obtained;

[0060] The 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%;

[0061] The CaO content of red mud is 10%, Pb+Cd+Cr 6+ The total content is 85ppm;

[0062] Step (2) ball milling leaching-purification:

[0063] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 103:26:8, and a leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, the pH was adjusted to 3, ball milled for 4 hours, unloaded, ventilated and stirred, and then precipitated and dehydrated. Then, slurry was made, EDTA was added to a concentration of 0.01M, the pH was adjusted to 6, ball milled for 30 minutes, unloaded, and calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 5°C / min, kept warm for 3 hours, and crushed to obtain a pre-burned active material.

[0064] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0065] Porous carbon specific surface area 600m 2 / g;

[0066] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0067] Step (3) forming and calcining:

[0068] Mix the pre-burned active material with kaolin in a mass ratio of 1:10 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0069] Kaolin's SiO2+Al2O3 is 97.8%, and K2O+Na2O is 0.62%;

[0070] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 4℃ / min and keeping warm for 2-3h. Example 3

[0071] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0072] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0073] The iron ore tailings were mixed with coke in a mass ratio of 10:1, and an inert mixed gas containing 5% oxygen by volume was introduced. The mixture was roasted at 740 ° C for 2 h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 55 μm, and magnetic concentrate is obtained;

[0074] The 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%;

[0075] The CaO content of red mud is 12%, Pb+Cd+Cr 6+ The total content is 90ppm;

[0076] Step (2) ball milling leaching-purification:

[0077] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 95:22:7, and a leaching agent of 7 times the total mass of the magnetic concentrate, red mud and porous carbon was added, the pH was adjusted to 3, and the ball milling was carried out for 5 hours. The material was unloaded, and the material was ventilated and stirred before precipitation and dehydration. The material was then slurried, and EDTA was added to a concentration of 0.012M. The pH was adjusted to 6.2, and the material was ball milled for 25 minutes. The material was unloaded and calcined in a weak reducing atmosphere. The calcination process was heated to 760°C at 3°C / min and kept at this temperature for 2 hours. The material was then crushed to obtain a pre-calcined active material.

[0078] The leaching agent is a mixed aqueous solution of 4 wt% citric acid, 1.0 wt% oxalic acid and 0.08 wt% sodium hexametaphosphate;

[0079] Porous carbon specific surface area 580m 2 / g;

[0080] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0081] Step (3) forming and calcining:

[0082] Mix the pre-burned active material with kaolin in a mass ratio of 1:10 and refine to a particle size of D 90 The particle size is 1.6 μm, and then it is formed and sintered under the condition of 1.3% oxygen volume fraction. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0083] Kaolin's SiO2+Al2O3 is 98.1%, and K2O+Na2O is 0.71%;

[0084] The sintering process under the condition of oxygen volume fraction of 0.8% is: heating to 1260℃ at 3℃ / min and keeping warm for 3h. Example 4

[0085] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0086] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0087] The iron ore tailings were mixed with coke in a mass ratio of 14:1, and an inert mixed gas containing 7% oxygen by volume was introduced. The mixture was roasted at 760°C for 1.5 hours, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 50 μm, and magnetic concentrate is obtained;

[0088] The 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%;

[0089] The CaO content of red mud is 11.6%, Pb+Cd+Cr 6+ The total content is 78ppm;

[0090] Step (2) ball milling leaching-purification:

[0091] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 101:25:8, and a leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, the pH was adjusted to 3.2, and the mixture was ball-milled for 4.5 hours. The mixture was unloaded, and the mixture was precipitated and dehydrated after aeration and stirring. The mixture was then slurried, and EDTA was added to a concentration of 0.008M. The pH was adjusted to 5.8, and the mixture was ball-milled for 30 minutes. The mixture was unloaded and calcined in a weak reducing atmosphere. The calcination process was heated to 760°C at 4°C / min, and the temperature was kept at this temperature for 2 hours. The calcined active material was then crushed to obtain the calcined active material.

[0092] The leaching agent is a mixed aqueous solution of 4.6 wt% citric acid, 1.2 wt% oxalic acid and 0.09 wt% sodium hexametaphosphate;

[0093] Porous carbon specific surface area 620m 2 / g;

[0094] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0095] Step (3) forming and calcining:

[0096] Mix the pre-burned active material with kaolin in a mass ratio of 1:9 and refine to a particle size of D 90 The particle size is 1.8 μm, and then it is formed and sintered under the condition of 1.2% oxygen volume fraction. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0097] Kaolin's SiO2+Al2O3 is 98.2%, and K2O+Na2O is 0.71%;

[0098] The sintering process under the condition of oxygen volume fraction of 0.9% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h. Example 5

[0099] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0100] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0101] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and an inert mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 740℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 56 μm, and magnetic concentrate is obtained;

[0102] The 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%;

[0103] The CaO content of red mud is 13%, Pb+Cd+Cr 6+ The total content is 68ppm;

[0104] Step (2) ball milling leaching-purification:

[0105] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 97:23:9, and a leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added. The pH was adjusted to 3, and the ball milling was carried out for 4 hours. The material was unloaded, and the material was ventilated and stirred before precipitation and dehydration. The material was then slurried, and EDTA was added to a concentration of 0.011M. The pH was adjusted to 6, and the ball milling was carried out for 30 minutes. The material was unloaded and calcined in a weak reducing atmosphere. The calcination process was heated to 760°C at 2°C / min, and the temperature was kept at this temperature for 2 hours. The material was then pulverized to obtain a pre-burned active material.

[0106] The leaching agent is a mixed aqueous solution of 6 wt% citric acid, 1.3 wt% oxalic acid and 0.11 wt% sodium hexametaphosphate;

[0107] Porous carbon specific surface area 620m 2 / g;

[0108] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0109] Step (3) forming and calcining:

[0110] Mix the pre-burned active material with kaolin in a mass ratio of 1:9 and refine to a particle size of D 90 The particle size is 1.7 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 0.9%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0111] Kaolin's SiO2+Al2O3 is 97.9%, and K2O+Na2O is 0.68%;

[0112] The sintering process under the condition of oxygen volume fraction of 1.1% is: heating to 1250℃ at 3℃ / min and keeping warm for 2h. Example 6

[0113] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0114] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0115] The iron ore tailings were mixed with coke in a mass ratio of 14:1, and an inert mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 760°C for 1.5 hours, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 54 μm, and magnetic concentrate is obtained;

[0116] The 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%;

[0117] The CaO content of red mud is 14%, Pb+Cd+Cr 6+ The total content is 69ppm;

[0118] Step (2) ball milling leaching-purification:

[0119] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 103:26:8, and a leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added. The pH was adjusted to 3, and the mixture was ball-milled for 4 hours. The mixture was unloaded, aerated and stirred, and then precipitated and dehydrated. The mixture was then slurried, ball-milled for 30 minutes, unloaded, and calcined in a weak reducing atmosphere. The calcination process was heated to 760°C at 4°C / min, and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0120] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.1 wt% oxalic acid and 0.10 wt% sodium hexametaphosphate;

[0121] Porous carbon specific surface area 630m 2 / g;

[0122] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0123] Step (3) forming and calcining:

[0124] Mix the pre-burned active material with kaolin in a mass ratio of 1:10 and refine to a particle size of D 90 The particle size is 1.6 μm, and then it is formed and sintered under the condition of 1.3% oxygen volume fraction. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0125] Kaolin's SiO2+Al2O3 is 98.2%, and K2O+Na2O is 0.67%;

[0126] The sintering process under the condition of oxygen volume fraction of 0.8% is: heating to 1250℃ at 4℃ / min and keeping warm for 2.5h.

[0127] Comparative Example 1

[0128] The difference from Example 1 is that in step (1), a nitrogen mixed gas containing 10% by volume of oxygen is introduced:

[0129] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0130] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0131] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 10% oxygen by volume was introduced, and roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0132] The 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%;

[0133] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0134] Step (2) ball milling leaching-purification:

[0135] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, unloaded, and precipitated and dehydrated after ventilation and stirring. The mixture was then slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, unloaded, and calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min, and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0136] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0137] Porous carbon specific surface area 600m 2 / g;

[0138] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0139] Step (3) forming and calcining:

[0140] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0141] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0142] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0143] Comparative Example 2

[0144] The difference from Example 1 is that without magnetic separation:

[0145] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0146] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0147] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced, and roasted at 750℃ for 1.5h, coarsely crushed, and further crushed to D 90 The particle size is 53 μm, and the mineral powder is obtained;

[0148] The 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%;

[0149] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0150] Step (2) ball milling leaching-purification:

[0151] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, unloaded, and precipitated and dehydrated after ventilation and stirring. The mixture was then slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, unloaded, and calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min, and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0152] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0153] Porous carbon specific surface area 600m 2 / g;

[0154] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0155] Step (3) forming and calcining:

[0156] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0157] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0158] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0159] Comparative Example 3

[0160] The difference from Example 1 is that the total iron content of the iron ore tailings is 28%:

[0161] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0162] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0163] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0164] The 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%;

[0165] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0166] Step (2) ball milling leaching-purification:

[0167] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, unloaded, and precipitated and dehydrated after ventilation and stirring. The mixture was then slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, unloaded, and calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min, and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0168] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0169] Porous carbon specific surface area 600m 2 / g;

[0170] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0171] Step (3) forming and calcining:

[0172] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0173] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0174] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0175] Comparative Example 4

[0176] The difference from Example 1 is that the iron ore tailings are not subjected to magnetic separation and enrichment treatment:

[0177] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0178] Step (1) ball milling leaching-purification:

[0179] The iron ore tailings have a total iron content of 31% and a sulfur content of 2.8%, passing a 50-mesh sieve;

[0180] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0181] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, unloaded, and precipitated and dehydrated after ventilation and stirring. The mixture was then slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, unloaded, and calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min, and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0182] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0183] Porous carbon specific surface area 600m 2 / g;

[0184] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0185] Step (2) forming and calcining:

[0186] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0187] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0188] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0189] Comparative Example 5

[0190] The difference from Example 1 is that the red mud calcium content is 25%:

[0191] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0192] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0193] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0194] The 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%;

[0195] Red mud contains 25% CaO, Pb+Cd+Cr 6+ The total content is 98ppm;

[0196] Step (2) ball milling leaching-purification:

[0197] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, unloaded, and precipitated and dehydrated after ventilation and stirring. The mixture was then slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, unloaded, and calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min, and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0198] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0199] Porous carbon specific surface area 600m 2 / g;

[0200] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0201] Step (3) forming and calcining:

[0202] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0203] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0204] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0205] Comparative Example 6

[0206] The difference from Example 1 is that no leaching reagent is added in step (2):

[0207] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0208] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0209] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0210] The 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%;

[0211] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0212] Step (2) ball milling leaching-purification:

[0213] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and water 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, and the mixture was unloaded. After aeration and stirring, the mixture was precipitated and dehydrated. The mixture was then slurried, and the pH was adjusted to 6. The mixture was ball-milled for 30 minutes, and the mixture was unloaded. The mixture was calcined in a weak reducing atmosphere. The calcination process was to increase the temperature to 750°C at 4°C / min, and the temperature was kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0214] Porous carbon specific surface area 600m 2 / g;

[0215] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0216] Step (3) forming and calcining:

[0217] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0218] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0219] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0220] Comparative Example 7

[0221] The difference from Example 1 is that in step (2), the red mud ratio is too high:

[0222] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0223] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0224] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0225] The 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%;

[0226] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0227] Step (2) ball milling leaching-purification:

[0228] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:35:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, unloaded, and precipitated and dehydrated after ventilation and stirring. The mixture was then slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, unloaded, and calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min, and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0229] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0230] Porous carbon specific surface area 600m 2 / g;

[0231] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0232] Step (3) forming and calcining:

[0233] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0234] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0235] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0236] Comparative Example 8

[0237] The difference from Example 1 is that step (2) is in air atmosphere:

[0238] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0239] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0240] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0241] The 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%;

[0242] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0243] Step (2) ball milling leaching-purification:

[0244] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, unloaded, and precipitated and dehydrated after ventilation and stirring. The mixture was then slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, unloaded, and calcined in an air atmosphere. The calcination process was a temperature increase of 4°C / min to 750°C, and the temperature was kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0245] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0246] Porous carbon specific surface area 600m 2 / g;

[0247] Step (3) forming and calcining:

[0248] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0249] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0250] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0251] Comparative Example 9

[0252] The difference from Example 1 is that the holding time during the calcination process is too long:

[0253] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0254] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0255] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0256] The 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%;

[0257] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0258] Step (2) ball milling leaching-purification:

[0259] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, the pH was adjusted to 3, and the ball milling was carried out for 4 hours. The material was unloaded, and the material was ventilated and stirred before precipitation and dehydration. The material was then slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6, and the material was ball milled for 30 minutes. The material was unloaded, and the material was calcined in a weak reducing atmosphere. The calcination process was to increase the temperature to 750°C at 4°C / min, and the temperature was kept at this temperature for 4 hours. The material was then pulverized to obtain a pre-burned active material.

[0260] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0261] Porous carbon specific surface area 600m 2 / g;

[0262] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0263] Step (3) forming and calcining:

[0264] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0265] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0266] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0267] Comparative Example 10

[0268] The difference from Example 1 is that in step (3), the proportion of kaolin is too small:

[0269] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0270] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0271] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0272] The 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%;

[0273] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0274] Step (2) ball milling leaching-purification:

[0275] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, and then the mixture was discharged. After aeration and stirring, the mixture was precipitated and dehydrated. Subsequently, the mixture was slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, and then the mixture was discharged. The mixture was calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0276] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0277] Porous carbon specific surface area 600m 2 / g;

[0278] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0279] Step (3) forming and calcining:

[0280] Mix the pre-burned active material with kaolin in a mass ratio of 1:8 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0281] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0282] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0283] Comparative Example 11

[0284] The difference from Example 1 is that during the sintering process in step (3), the oxygen concentration is too high:

[0285] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0286] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0287] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0288] The 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%;

[0289] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0290] Step (2) ball milling leaching-purification:

[0291] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, and then the mixture was discharged. After aeration and stirring, the mixture was precipitated and dehydrated. Subsequently, the mixture was slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, and then the mixture was discharged. The mixture was calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0292] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0293] Porous carbon specific surface area 600m 2 / g;

[0294] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0295] Step (3) forming and calcining:

[0296] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 1.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 5.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0297] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0298] The sintering process under the condition of oxygen volume fraction of 5.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0299] Comparative Example 12

[0300] The difference from Example 1 is that in step (3), the particles are refined to a particle size of D 90 2.5μm:

[0301] A method for preparing highly corrosion-resistant environmentally friendly ceramics, comprising:

[0302] Step (1) Magnetic separation and enrichment of iron ore tailings:

[0303] The iron ore tailings and coke were mixed in a mass ratio of 12:1, and nitrogen mixed gas containing 6% oxygen by volume was introduced. The mixture was roasted at 750℃ for 1.5h, coarsely crushed, magnetically separated, and further crushed to D 90 The particle size is 53 μm, and magnetic concentrate is obtained;

[0304] The 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%;

[0305] Red mud contains 10% CaO, Pb+Cd+Cr 6+ The total content is 88ppm;

[0306] Step (2) ball milling leaching-purification:

[0307] The magnetic concentrate, red mud and porous carbon were added to a zirconium ball mill in a mass ratio of 100:25:8, and then milled. A leaching agent of 8 times the total mass of the magnetic concentrate, red mud and porous carbon was added, and the pH was adjusted to 3. The mixture was ball-milled for 4 hours, and then the mixture was discharged. After aeration and stirring, the mixture was precipitated and dehydrated. Subsequently, the mixture was slurried, and EDTA was added to a concentration of 0.01M. The pH was adjusted to 6. The mixture was ball-milled for 30 minutes, and then the mixture was discharged. The mixture was calcined in a weak reducing atmosphere. The calcination process was heated to 750°C at 4°C / min and kept at this temperature for 2.5 hours. The calcined active material was then crushed to obtain the calcined active material.

[0308] The leaching agent is a mixed aqueous solution of 5 wt% citric acid, 1.3 wt% oxalic acid and 0.1 wt% sodium hexametaphosphate;

[0309] Porous carbon specific surface area 600m 2 / g;

[0310] The weak reducing atmosphere is 1.0% O2, 1.2% CO, 3.0% CO2, and 94.8% N2 by volume;

[0311] Step (3) forming and calcining:

[0312] Mix the pre-burned active material with kaolin in a mass ratio of 1:9.5 and refine to a particle size of D 90 The particle size is 2.5 μm, and then it is formed and sintered under the condition of oxygen volume fraction of 1.0%. After cooling, a highly corrosion-resistant and environmentally friendly ceramic is obtained;

[0313] Kaolin's SiO2+Al2O3 is 97.5%, and K2O+Na2O is 0.65%;

[0314] The sintering process under the condition of oxygen volume fraction of 1.0% is: heating to 1250℃ at 3℃ / min and keeping warm for 2.5h.

[0315] The compositions of the main element oxides of Examples 1-6 of the present invention and Comparative Examples 1-12 are shown in Table 1 (the contents of other impurities are not listed in the table). The performance test methods and results of Examples 1-6 of the present invention and Comparative Examples 1-12 are shown in Table 2.

[0316] Table 1 Composition of main element oxides of Examples 1-6 and Comparative Examples 1-12

[0317]

[0318] Table 2 Performance test methods and results of Examples 1-6 and Comparative Examples 1-12

[0319]

[0320] Compared with comparative examples 1-12, examples 1-6 have better corrosion resistance, which is due to the joint control of components and processes. As can be seen from example 6, although EDTA is not added, it can still meet the requirements of Pb+Cd+Cr 6+ ≤2ppm target, and also has good corrosion resistance, which shows that EDTA is a supplementary reagent, mainly to further ensure the removal of target ions.

[0321] Comparative Example 1 differs from Example 1 in that the roasting oxygen concentration was 10%. Higher oxygen concentrations may reduce the conversion efficiency of hematite to magnetite, leading to a downward trend in magnetic separation recovery. This may result in a reduction in the iron content of the pre-calcined active material, a relatively insufficient amount of andradite phase formed during sintering, a weakened grain boundary sealing effect, and a decrease in corrosion resistance.

[0322] The difference between Comparative Example 2 and Example 1 is that no magnetic separation treatment is performed, mainly because the impurity content exceeds the standard, which has an adverse effect on the acid corrosion resistance.

[0323] The difference between Comparative Example 3 and Example 1 is that the total iron content of the tailings is 28%, which causes the iron content of the magnetic concentrate to exceed the lower limit of the process. The reduced iron source supply may affect the full formation of the calcium iron garnet phase, the degree of closure of the grain boundary pores is reduced, and the mechanical strength and alkali resistance of the material show a downward trend.

[0324] Comparative Example 4 differs from Example 1 in that the tailings were used directly without magnetic separation, potentially allowing heavy metal minerals to enter the system. In the absence of selective separation, the porous carbon's adsorption efficiency for encapsulated heavy metals may be limited, leading to the risk of elevated heavy metal residues in the final product. Furthermore, residual sulfides may exacerbate corrosion sensitivity.

[0325] Comparative Example 5 differs from Example 1 in that the red mud contains 25% CaO. High-calcium red mud may exceed the calcium dissolution capacity of acid leaching. Excessive calcium can easily form anorthite, a phase with a high expansion coefficient, during sintering. This reduces thermal expansion compatibility with the mullite matrix, lowering stability and leading to microcracks, ultimately compromising corrosion resistance.

[0326] Comparative Example 6 differs from Example 1 in that the absence of a leaching agent reduces the efficiency of heavy metal dissociation and potentially weakens the removal of soluble alkali metals from red mud. This can lead to decreased glass phase stability and increased material corrosion in alkaline environments.

[0327] The difference between Comparative Example 7 and Example 1 is that excessive red mud may dilute the ratio of the silicon-aluminum matrix, causing the Al2O3 content to approach or fall below the lower limit of 20%. This may affect the integrity of the mullite skeleton and lead to a decrease in the material's load-bearing capacity.

[0328] The difference between Comparative Example 8 and Example 1 is that step (2) is performed in an air atmosphere, which may not be conducive to the complete decomposition of organic matter and may increase the risk of carbon residue. At the same time, the lack of a weakly reducing environment may reduce the efficiency of heavy metal sequestration in iron oxides, potentially affecting the acid resistance of the material.

[0329] The difference between Comparative Example 9 and Example 1 is that step (2) is kept warm for 4 hours. Prolonging the calcination time may cause excessive reduction of ferroferric oxide to FeO. The presence of FeO may trigger low-temperature eutectic phenomenon. In addition, the 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, making it impossible to carry out standard performance testing.

[0330] 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 density of the mullite network and a weakening of the penetration resistance of the corrosive medium.

[0331] 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 conversion of Fe2O3 to ferroferric oxide. The lack of ferroferric oxide may affect the efficiency of the formation of the calcium-iron garnet phase, and the increase in free Fe2O3 may have a potential impact on the brittleness of the material.

[0332] The difference between Comparative Example 12 and Example 1 is that in step (3), the particles are refined to a particle size of D 90The particle size of the powder exceeds the upper limit of the process, which may increase the porosity of the particle stacking, reduce the reaction activity, and reduce the density. The presence of larger pores may accelerate the penetration of the medium, resulting in increased water absorption and reduced corrosion resistance.

[0333] In summary, this plan is based on the raw material principle and combined with process design to apply iron ore tailings and red mud to the production of handicraft ceramics, which can obtain highly corrosion-resistant and environmentally friendly ceramics.

Claims

1. A method for preparing highly corrosion-resistant environmentally friendly ceramics, characterized in that: include: Step (1) Magnetic separation and enrichment of iron ore tailings: The iron ore tailings and coke are mixed in a mass ratio of 10-15:1, and an inert mixed gas containing 5-8% oxygen by volume is introduced. The mixture is roasted at 730-770℃ for 1-2h, coarsely crushed, magnetically separated, and further crushed to D 90 ≤60μm, magnetic separation concentrate is obtained; Step (2) ball milling leaching-purification: The magnetic concentrate, red mud and porous carbon are added to a zirconium ball mill in a mass ratio of 95-105:22-28:7-9, and a leaching agent is added in an amount of 6-8 times the total mass of the magnetic concentrate, red mud and porous carbon. The pH is adjusted to 2.5-3.5, and the mixture is ball-milled for 3-5 hours. The mixture is unloaded, aerated and stirred, and then precipitated and dehydrated. The mixture is then slurried, ball-milled for 20-30 minutes, unloaded, dehydrated, calcined in a weak reducing atmosphere, and pulverized to obtain a pre-calcined active material. The leaching agent is a mixed aqueous solution of 4-6 wt% citric acid, 1.0-1.5 wt% oxalic acid and 0.08-0.12 wt% sodium hexametaphosphate; Step (3) forming and calcining: Mix the pre-burned active material with kaolin in a mass ratio of 1:9-10 and refine to a particle size of D 90 ≤2.0μm, then formed, sintered under the condition of oxygen volume fraction of 0.5-1.5%, and cooled to obtain highly corrosion-resistant environmentally friendly ceramics; The chemical composition of highly corrosion-resistant environmentally friendly ceramics, calculated as a percentage of oxide mass, meets the following requirements: 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+ :≤2ppm; The rest are impurities.

2. The method for preparing highly corrosion-resistant environmentally friendly ceramics according to claim 1, wherein: The iron ore tailings in step (1) have a total iron content of ≥28%, a sulfur content of ≤3%, and pass through a 50-mesh sieve; the magnetic separation concentrate has a total iron content of ≥55%.

3. The method for preparing the highly corrosion-resistant environmentally friendly ceramic according to claim 1, wherein: The CaO content of the red mud is less than 15%, Pb+Cd+Cr 6+ The total content is ≤100ppm; the SiO2+Al2O3 of the kaolin is ≥97%, and the K2O+Na2O is ≤0.8%.

4. The method for preparing highly corrosion-resistant environmentally friendly ceramics according to claim 1, wherein: The solid content after slurrying in step (2) is 10-15%.

5. The method for preparing highly corrosion-resistant environmentally friendly ceramics according to claim 1, wherein: The porous carbon in step (2) has a specific surface area of ​​550-650m 2 / g.

6. The method for preparing highly corrosion-resistant environmentally friendly ceramics according to claim 1, wherein: After ventilation and stirring, the precipitate is dehydrated and then slurried. EDTA is added until the concentration is 0.008-0.012M, the pH is adjusted to 5.8-6.2, ball milled for 20-30 minutes, unloaded, calcined in a weak reducing atmosphere, and crushed to obtain the pre-burned active material.

7. The method for preparing highly corrosion-resistant environmentally friendly ceramics according to claim 1, wherein: The weak reducing atmosphere in step (2) is 0.8-1.2% by volume of O2, 1.0-1.4% by volume of CO, 2.8-3.2% by volume of CO2, and the remainder being N2.

8. The method for preparing highly corrosion-resistant environmentally friendly ceramics according to claim 1, wherein: The sintering process of the weak reducing atmosphere calcination in step (2) is: heating to 740-760°C at 2-5°C / min and keeping warm for 2-3h.

9. The method for preparing highly corrosion-resistant environmentally friendly ceramics according to claim 1, wherein: In step (3), the sintering process under the condition of oxygen volume fraction of 0.5-1.5% is: heating to 1230-1280°C at 2-5°C / min and keeping warm for 2-3h.

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