Method for recovering zirconium from red mud
By using alkaline substances in red mud to react with carbon dioxide to generate soluble complexes, the problem of low zirconium recovery rate in red mud is solved, an efficient, low-cost and environmentally friendly zirconium recovery process is achieved, and resource utilization efficiency is improved.
Patent Information
- Application Number
- CN202510865866.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-26
- Publication Date
- 2025-09-26
AI Technical Summary
The existing technology for recovering zirconium from red mud has problems such as low leaching rate, complex treatment methods and high costs, making it difficult to achieve economically feasible recovery of rare earth elements.
Alkaline substances (XOH, XHCO3, X2CO3) and carbon dioxide are used to react with red mud under high pressure and high temperature conditions to generate soluble complexes. Through solid-liquid separation and circulating liquid reuse design, the zirconium leaching rate and resource utilization efficiency are improved.
The zirconium leaching rate was significantly increased to 85% to 98%, reagent costs and energy consumption were reduced, and full quantitative utilization and environmentally friendly treatment of red mud were achieved.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of comprehensive recovery and utilization of red mud, and in particular to a method for recovering zirconium from red mud. Background Art
[0002] Red mud, a solid powdery waste generated during the alumina smelting process, has long been a focus of attention in both the industrial and environmental sectors. Red mud is not only produced in large quantities but also highly alkaline. Depending on the production process, it is primarily categorized as Bayer process red mud, sintering process red mud, and combined process red mud. Since the widespread adoption of the Bayer process for alumina production, global red mud stockpiles have exceeded 4.5 billion tons and continue to grow at a rate of 100-150 million tons annually. This large-scale accumulation of red mud not only consumes significant land resources but also poses a significant risk to the surrounding environment. Therefore, comprehensive utilization and reduction of red mud are crucial. Red mud has a complex chemical composition, containing key elements such as iron, silicon, calcium, aluminum, titanium, sodium, and potassium. It is also rich in rare earth elements such as vanadium, gallium, zirconium, and scandium. These rare earth elements, particularly zirconium, have unique physical and chemical properties, offering broad application prospects in the nuclear, aerospace, and electronics industries. However, due to the relatively low content of rare earth elements in red mud and their dispersion in various phases in an isomorphous form, their extraction and recycling face many challenges.
[0003] Currently, researchers and industry have explored various processes for extracting rare earth elements from red mud, primarily hydrometallurgical processes and combined pyrometallurgical-hydrometallurgical processes. Hydrometallurgical processes typically utilize leaching agents such as acids, alkalis, or organic solvents to dissolve the rare earth elements in the red mud into a solution through chemical reactions. These elements are then separated from the solution through precipitation, extraction, and electrolysis. The combined pyrometallurgical-hydrometallurgical process, on the other hand, first uses high-temperature treatment to alter the red mud's physical structure, making the rare earth elements more readily leached. Hydrometallurgical processes are then used for extraction.
[0004] While these processes have achieved some success in extracting rare earth elements from red mud, numerous challenges remain. For example, while organic acid leaching can improve zirconium leaching rates, its high processing costs make it unsuitable for industrial application. Alkali-acid leaching, on the other hand, suffers from complex processing, low zirconium leaching rates, high costs, and poor economic viability. Therefore, there is an urgent need to develop a method for recovering zirconium from red mud that offers high leaching efficiency, low reagent consumption, simple processing, and is economically viable. Summary of the Invention
[0005] The present application provides a method for recovering zirconium from red mud to solve the following technical problem: how to recover zirconium from red mud at a low cost.
[0006] The present invention provides a method for recovering zirconium from red mud, the method comprising:
[0007] mixing red mud, alkali and solvent in proportion to obtain a mixed material;
[0008] introducing carbon dioxide gas into the mixture to carry out a chemical reaction under set pressure and temperature conditions to obtain a reaction mixture;
[0009] performing solid-liquid separation on the reaction mixture to obtain a zirconium-containing leachate and red mud waste residue;
[0010] Wherein, the base is one or more of XOH, XHCO3, X2CO3, X represents Na + , K + or NH 4+ .
[0011] Optionally, in the mixed material, the mass ratio of the alkali, the dry basis of the red mud and the solvent is (0.1-0.2): (0.25-0.7):1.
[0012] Optionally, the set pressure is 0.1 MPa to 4.0 MPa.
[0013] Optionally, the temperature of the chemical reaction is 100° C. to 180° C., and the time of the chemical reaction is 4 h to 20 h.
[0014] Optionally, the temperature of the chemical reaction is 145° C. to 160° C., and the time of the chemical reaction is 8 h to 10 h.
[0015] Optionally, the mass fraction of water in the red mud is ≤20%.
[0016] Optionally, in the dry basis of the red mud, the mass fraction of Zr is 0.15% to 0.30%, and the mass fraction of Na2O is 6% to 8%.
[0017] Optionally, after obtaining the zirconium-containing leachate and red mud waste residue, the method further comprises:
[0018] Dezirconiumizing the zirconium-containing leachate to obtain a circulating liquid;
[0019] The circulating liquid is returned to the mixed material for recycling.
[0020] Optionally, the solid-liquid separation of the reaction mixture to obtain a zirconium-containing leachate and red mud waste residue comprises:
[0021] performing solid-liquid separation on the reaction mixture to obtain a first liquid phase and red mud residue;
[0022] Washing the red mud residue with hot water at 90° C. to 98° C. to obtain a second liquid phase and red mud waste residue;
[0023] The first liquid phase and the second liquid phase are mixed to obtain a zirconium-containing leachate.
[0024] Optionally, the mass of Zr in the zirconium-containing leachate is 85% to 98% of the mass of Zr in the red mud.
[0025] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:
[0026] The present invention provides a method for recovering zirconium from red mud, comprising: mixing red mud, an alkali, and a solvent in proportion to obtain a mixture; introducing carbon dioxide gas into the mixture to carry out a chemical reaction under set pressure and set temperature conditions to obtain a reaction mixture; performing solid-liquid separation on the reaction mixture to obtain a zirconium-containing leachate and red mud waste residue; wherein the alkali is one or more of XOH, XHCO3, and X2CO3, and X represents Na + , K + or NH 4+ Under high-pressure CO2, alkaline substances (XOH, X2CO3) react with CO2 to produce HCO3-. HCO3- forms a soluble complex with zirconium in red mud, significantly increasing its solubility. This complexation mechanism allows for efficient transfer of zirconium from the red mud solid phase to the liquid phase, thereby increasing the zirconium leaching rate. Furthermore, alkaline reagents such as NaHCO3 and K2CO3 are less expensive than other leaching agents and are widely available, helping to reduce the cost of the entire process. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.
[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.
[0029] Figure 1 A schematic flow chart of a method for recovering zirconium from red mud provided in an embodiment of the present application. DETAILED DESCRIPTION
[0030] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.
[0031] The range descriptions described in this article, such as numerical ranges, ratio ranges, etc., include all possible sub-ranges and single numerical values within the range. For example, the range description of "1 to 6" or "1~6" covers all sub-ranges from 1 to 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including", "comprising", etc. used in this article mean "including but not limited to"; relational terms such as "first" and "second" are only used to distinguish different entities or operations, and do not imply an actual sequence or association relationship; "and / or" means that multiple situations can exist alone or at the same time; expressions such as "at least one", "multiple", and "at least one" refer to any combination of corresponding objects, including a combination of single or multiple objects. The proportional relationships involved in the article, such as mass ratios, molar ratios, etc., should be understood as the corresponding relationship between the first and second terms of the proportional formula in the order of description. The raw materials, reagents, instruments and equipment used in this article can be purchased on the market or prepared by existing methods.
[0032] Figure 1 A schematic flow chart of a method for recovering zirconium from red mud provided in an embodiment of the present application.
[0033] See Figure 1 , the present application embodiment provides a method for recovering zirconium from red mud, the method comprising:
[0034] S1, mixing red mud, alkali and solvent in proportion to obtain a mixed material;
[0035] In some embodiments, the mass fraction of water in the red mud is ≤20%.
[0036] In the examples of the present application, the mass fraction of water in the provided red mud does not exceed 20%. Based on the water content in the red mud, the mass of water added subsequently can be adjusted accordingly to ensure that the solid-liquid ratio in the reaction system is within an appropriate range, thereby effectively improving the leaching efficiency.
[0037] In some embodiments, the mass fraction of Zr in the dry basis of the red mud is 0.15% to 0.30%, and the mass fraction of Na2O is 6% to 8%.
[0038] The lower limit of Zr mass fraction (0.15%) on the dry basis of red mud ensures that the zirconium concentration in the red mud reaches the threshold for economic recovery, ensuring the economic feasibility of zirconium recovery and avoiding the disproportionate energy and reagent consumption caused by low grade, thereby ensuring the economic benefits of the recovery process. The upper limit of Zr mass fraction (0.30%) can limit the crystallinity of zirconium minerals (such as zircon or perovskite) in high-grade red mud. Excessive crystallinity may lead to an overly dense mineral structure, requiring higher reaction intensity (such as temperature or pressure) to effectively leach zirconium. By controlling the upper limit of Zr mass fraction, it is possible to maintain a high zirconium content while avoiding overly harsh reaction conditions, reducing energy consumption and equipment requirements. For example, in the dry basis of red mud, the mass fraction of Zr can be 0.15%, 0.18%, 0.21%, 0.24%, 0.27%, 0.30%, etc.; the mass fraction of Na2O can be 6%, 6.4%, 6.8%, 7.2%, 7.6%, 8%, etc.
[0039] In some embodiments, the base is one or more of XOH, XHCO3, X2CO3, where X represents Na + , K + or NH 4 + .
[0040] Under the pressure of 0.1MPa to 4.0MPa, XOH and X2CO3 can continuously react with CO2 (such as XOH+CO2→XHCO3) to generate HCO3 - ,HCO3 - It can form a soluble complex with Zr, significantly improving the solubility of zirconium. This complexation mechanism enables the efficient transfer of zirconium from the solid phase of red mud to the liquid phase, thereby increasing the leaching rate of zirconium. - The concentration of Na in the alkali is maintained continuously, promoting the transfer of zirconium from the solid phase to the liquid phase. + , K + The mineral structure of zirconium in red mud can be destroyed by ion exchange (such as replacing Ca in perovskite). 2+ ), releasing the encapsulated zirconium element. The thermal decomposition characteristics of ammonium salts make NH4 + Decomposition at high temperature produces NH3, which further adjusts the pH gradient of the reaction system and enhances the leaching kinetics.
[0041] In some embodiments, in the mixed material, the mass ratio of the alkali, the red mud on a dry basis, and the solvent is (0.1-0.2):(0.25-0.7):1.
[0042] In the embodiment of the present application, the solvent can be water. The mass ratio of the alkali, the dry basis of the red mud and the solvent is (0.1-0.2): (0.25-0.7): 1. By controlling the alkali concentration, sufficient bicarbonate (HCO3 - ) or carbonate (CO3 2- ) concentration, promoting the complexation reaction of zirconium and HCO3-. The red mud dry basis ratio limits the solid content of the material to avoid excessive solids leading to increased mass transfer resistance in the reactor, while maintaining sufficient red mud processing capacity. The high proportion of solvent (base is 1) provides sufficient liquid phase volume to support the effective dissolution and diffusion of CO2, reduce the viscosity of the high-pressure reaction system, and improve the mass transfer efficiency. The lower limit of the ratio (alkali 0.1, red mud 0.25) can reduce reagent consumption and equipment load; the upper limit (alkali 0.2, red mud 0.7) accelerates the leaching reaction by increasing the solid-liquid contact area. Illustratively, the mass ratio of the alkali, the red mud on a dry basis, and the solvent may be 0.1:0.25:1, 0.1:0.35:1, 0.1:0.45:1, 0.1:0.55:1, 0.1:0.65:1, 0.2:0.25:1, 0.2:0.35:1, 0.2:0.45:1, 0.2:0.55:1, and the like.
[0043] S2. introducing carbon dioxide gas into the mixture to carry out a chemical reaction under set pressure and set temperature conditions to obtain a reaction mixture;
[0044] Carbon dioxide dissolves in water to form HCO₃⁻, which forms a soluble complex with zirconium in red mud, significantly increasing its solubility. This complexation allows zirconium to transfer from the solid phase of red mud to the liquid phase, with a leaching rate of 85% to 98%.
[0045] In some embodiments, the set pressure is 0.1 MPa to 4.0 MPa.
[0046] Within the pressure range of 0.1 MPa to 4.0 MPa, the solubility of CO₂ significantly increases, causing the reaction system to approach or reach a supercritical state. At this point, the gas-liquid interfacial tension approaches zero, allowing CO₂ molecules to rapidly diffuse into the liquid phase in the form of nanobubbles, fully contacting the red mud particles. This enhances mass transfer efficiency at the gas-liquid interface, ensuring that CO₂ fully dissolves in water to form HCO₃⁻, which then forms a soluble complex with zirconium, increasing its solubility. The pressure range of 0.1 MPa to 4.0 MPa helps maintain the HCO₃⁻ concentration, which is crucial for the complexation reaction between zirconium and HCO₃⁻. Dynamically introducing CO₂ maintains this concentration, promoting efficient transfer of zirconium from the red mud solid phase to the liquid phase. The lower pressure limit of 0.1 MPa reduces the pressure resistance requirements for the equipment, allowing standard pressure reactors to meet the requirements, thereby reducing equipment investment costs. Furthermore, the upper pressure limit of 4.0 MPa achieves a balance between energy consumption and efficiency by shortening the reaction time, avoiding the additional energy consumption associated with excessive pressure. Within the pressure range of 0.1 MPa to 4.0 MPa, the CO2 partial pressure and temperature synergistically form a pH gradient, which facilitates the selective dissolution of zirconium and the suppression of impurities. The initial high pressure promotes bicarbonate formation. As the reaction proceeds, the pressure decreases and the system pH increases, further optimizing the zirconium extraction efficiency. Exemplary pressure settings include 0.1 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, and 4.0 MPa.
[0047] In the embodiment of the present application, the reactor can be placed in an oil bath at a certain temperature for leaching reaction. The oil bath provides a uniform and stable temperature field through heat conduction, ensuring that the temperature inside the reactor remains constant within the set range. This precise temperature control is crucial for the complexation reaction kinetics of zirconium: high temperature (100℃~180℃) can accelerate the dissociation of zirconium minerals (such as perovskite) in red mud, while avoiding the decomposition and failure of bicarbonate (HCO3-) due to temperature fluctuations.
[0048] Compared with air heating, the thermal conductivity of the oil bath is higher (the thermal conductivity of mineral oil is about 0.15W / m·K), which can quickly transfer heat to the reaction materials and shorten the time it takes for the reaction to reach a steady state. The homogeneous heat transfer characteristics of the oil bath can avoid the appearance of local high-temperature areas in the reactor, thereby reducing the coking phenomenon caused by local overheating of silicates or iron oxides in the red mud, ensuring the fluidity of the leachate and the subsequent solid-liquid separation efficiency. The combination of the oil bath system and the pressure-resistant reactor can safely achieve a high-pressure leaching environment of 0.1MPa to 4.0MPa. The thermal insulation performance of the oil bath reduces heat loss and can reduce energy consumption compared to direct electric heating. At the same time, the stable temperature environment extends the service life of the reactor seals.
[0049] In some embodiments, the temperature of the chemical reaction is 100° C. to 180° C., and the time of the chemical reaction is 4 h to 20 h.
[0050] High temperatures (100°C to 180°C) significantly enhance the dissolution kinetics of zirconium, causing the dissociation of silicate / titanate-encapsulated zirconium minerals (such as perovskite) in red mud. The lower temperature limit (100°C) reduces the energy consumption of the high-pressure reactor while compensating for the reaction rate by increasing the reaction time, optimizing both cost and efficiency. Within the temperature range of 100°C to 180°C, bicarbonate (HCO3-) can remain stable and participate in the complexation reaction of zirconium, preventing the decomposition of bicarbonate due to excessively high temperatures. This ensures the continuous complexation of zirconium with HCO3- and increases the solubility of zirconium. Furthermore, the temperature range of 100°C to 180°C prevents the increased corrosion of the reactor materials caused by excessively high temperatures, thereby extending the service life of the reactor and its seals and reducing equipment maintenance costs. The preferred temperature range is 145°C to 160°C. Illustratively, the temperature of the chemical reaction may be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, etc.
[0051] There are differences in the composition and crystallinity of zirconium minerals in red mud, and the flexible setting of the chemical reaction time (4h to 20h) can adapt to such differences. For zirconium minerals with high crystallinity or difficult to leach, a longer chemical reaction time (such as close to 20h) can ensure that the zirconium element is fully dissolved; while for zirconium forms that are easy to leach, a shorter chemical reaction time (such as close to 4h) can improve processing efficiency and reduce energy consumption. In addition, the gradient time design of 4h to 20h also allows for flexible adjustment of the reaction process according to the type and quality of the added alkali to ensure efficient leaching of the zirconium element. The chemical reaction time is preferably 8h to 10h. Exemplarily, the chemical reaction time can be 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, etc.
[0052] The CO2 partial pressure and temperature work synergistically to form a pH gradient: the initial high pressure promotes the formation of bicarbonate, and as the reaction proceeds, the pressure decreases and the pH of the system increases, which can achieve the selective dissolution of zirconium and the suppression of impurity elements.
[0053] S3. Performing solid-liquid separation on the reaction mixture to obtain a zirconium-containing leachate and red mud waste residue.
[0054] Through solid-liquid separation means such as centrifugation or filter pressing, the soluble zirconium complex is enriched in the liquid phase, so that the zirconium leaching rate is increased to 85% to 98%.
[0055] In some embodiments, the solid-liquid separation of the reaction mixture to obtain a zirconium-containing leachate and red mud waste residue comprises:
[0056] performing solid-liquid separation on the reaction mixture to obtain a first liquid phase and red mud residue;
[0057] Washing the red mud residue with hot water at 90° C. to 98° C. to obtain a second liquid phase and red mud waste residue;
[0058] The first liquid phase and the second liquid phase are mixed to obtain a zirconium-containing leachate.
[0059] Solid-liquid separation by centrifugation or filter press can effectively enrich soluble zirconium complexes in the liquid phase, preliminarily separating zirconium from solid waste residues and laying the foundation for subsequent zirconium extraction. Washing the red mud residue with hot water at 90°C to 98°C can further remove the zirconium-containing solution remaining in the red mud residue, thereby increasing the amount of zirconium recovered and improving the overall recovery rate. Mixing the first liquid phase (the zirconium-containing solution obtained by the initial solid-liquid separation) with the second liquid phase (the zirconium-containing solution obtained by washing the red mud residue) can achieve homogenization of the zirconium concentration, eliminate the risk of crystallization caused by local oversaturation, optimize the quality of the leachate, and facilitate the subsequent zirconium extraction and purification process. The hot water washing process not only recovers the zirconium remaining in the red mud residue, but also washes away some impurities, such as residual alkali and other soluble salts, thereby reducing the impurity content in the leachate and improving the purity of the zirconium product. After washing, the alkalinity of the red mud waste is significantly reduced (the pH value is stabilized at 7.5-8.5), and the Na2O content is also reduced to a low level (1.00%-2.00%). This allows the waste to be directly used in the preparation of cement roadbed materials and other building materials, realizing the harmless disposal and resource utilization of solid waste.
[0060] In some embodiments, after obtaining the zirconium-containing leachate and red mud waste, the method further comprises:
[0061] Dezirconiumizing the zirconium-containing leachate to obtain a circulating liquid;
[0062] The circulating liquid is returned to the mixed material for recycling.
[0063] The circulating fluid contains residual HCO3- and CO3 2 - and other alkaline ions, which can act as alkaline media to repeatedly participate in the complexation reaction of zirconium, thereby reducing the amount of fresh alkali (such as NaHCO3, K2CO3, etc.) added and significantly reducing the consumption of reagents. Through the closed-loop reuse design of the circulating liquid, the discharge of salt-containing wastewater can be reduced, and high-concentration Na + , K +Plasma pollution to water bodies meets environmental protection requirements. Reusing circulating fluid not only reduces reagent costs but also wastewater treatment expenses, thereby improving overall economic benefits. It also reduces the demand for fresh water resources, facilitating water conservation and utilization. Finally, recycling circulating fluid achieves resource recycling, reduces waste generation and emissions, and aligns with the concept of sustainable development. By continuously optimizing the recycling process, we can further improve resource utilization efficiency and reduce environmental impact.
[0064] The closed-loop recycling design of the circulating fluid reduces the discharge of saline wastewater and prevents water pollution from high-concentration Na+ and K+ ions. Furthermore, the treated red mud waste reduces the Na2O content to 1.00% to 2.00%, and the pH value stabilizes at 7.5 to 8.5, meeting the environmental requirements for building material utilization.
[0065] In some embodiments, the mass of Zr in the zirconium-containing leachate is 85% to 98% of the mass of Zr in the red mud.
[0066] The mass of Zr in the zirconium-containing leachate is 85% to 98% of the mass of Zr in the red mud. This demonstrates that the transfer efficiency of zirconium from the solid phase to the liquid phase of the red mud is extremely high, allowing for the full recovery of rare earth metal resources present in the red mud. This not only addresses the core issues of low leaching efficiency and high costs in existing technologies, but also achieves both economic and environmental benefits in red mud treatment through closed-loop recycling and waste residue resource utilization, providing a scalable technical path for the efficient recovery of rare earth elements.
[0067] In summary, the technical solutions of the embodiments of the present application mainly solve the problems of low leaching rate, complex treatment methods, and high energy consumption in the recovery process of zirconium from red mud. The specific solutions are as follows:
[0068] Mixture preparation: red mud, alkali (XOH, XHCO3, X2CO3, where X represents Na + , K + or NH4 + ) and water in proportion to obtain a mixture. This step provides a suitable alkaline environment for subsequent reactions by controlling the type and proportion of the base.
[0069] High-pressure CO2 reaction: The mixed material is placed in a reactor and carbon dioxide gas is introduced until the reactor reaches a set pressure (0.1Mpa to 4.0Mpa). In this high-pressure CO2 environment, alkaline substances react with CO2 to produce HCO3-, which can form a soluble complex with zirconium in red mud, significantly increasing its solubility.
[0070] Heating leaching: The reactor is heated to leach the mixture at a set temperature (100°C to 180°C). The high temperature accelerates the dissociation of zirconium minerals in the red mud, further improving the leaching efficiency of zirconium.
[0071] Solid-liquid separation and washing: The mixed material after leaching is subjected to solid-liquid separation, and then the red mud residue is washed with hot water to recover the zirconium remaining in the residue, further improving the recovery rate.
[0072] Recycling of circulating liquid: The circulating liquid obtained after the zirconium-containing leachate is dezirconized can be returned to the mixed material as a supplementary source of alkali and / or water, realizing the recycling of resources and reducing reagent consumption and wastewater treatment costs.
[0073] Through the above method, the leaching rate of Zr in red mud can reach 85% to 98%, significantly improving the recovery efficiency of zirconium; the use of cheap alkaline reagents such as NaHCO3 and K2CO3, combined with the recycling liquid reuse design, reduces reagent costs and energy consumption; the Na2O content of the treated red mud waste residue is reduced to 1.00% to 2.00%, and the pH value is stabilized at 7.5 to 8.5, which can be directly used in building materials production, realizing the full quantitative utilization and environmentally friendly treatment of red mud.
[0074] Therefore, the technical solution of the embodiment of the present application effectively solves the problem of zirconium recovery in red mud by optimizing reaction conditions, utilizing the synergistic effect of high-pressure CO2 environment and alkaline reagents, and designing a circulating liquid reuse, thereby realizing an efficient, low-cost, and environmentally friendly zirconium recovery process.
[0075] The present application is further described below with reference to specific examples. Experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with national / industry standards. If there are no corresponding national / industry standards, the methods are carried out in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.
[0076] Example 1
[0077] 50g of red mud, 20g of NaHCO₃, and 90ml of water were mixed and added to a reactor, stirring evenly. The red mud contained 20% water, 6% Na₂O, and 0.26% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 0.5 MPa. The leaching temperature was 150°C for 10 hours. After leaching, the solid-liquid separation of the red mud residue was washed with 98°C hot water, resulting in a pH of 8.0, a Na₂O content of 1.00%, and a Zr leaching rate of 98.18%.
[0078] Example 2
[0079] 35g of red mud, 5.0g of NH4CO3 and 10g of NaHCO3, and 96.5ml of water were mixed and added to a reactor, stirring evenly. The red mud contained 10% water, 7.2% Na2O, and 0.24% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 1.0 MPa. The leaching temperature was 120°C for 20 hours. After leaching, the solid-liquid separation of the red mud residue was washed with 90°C hot water, resulting in a pH of 7.5, a Na2O content of 1.76%, and a Zr leaching rate of 95.73%.
[0080] Example 3
[0081] Mix 30g red mud, 5.0g NH4HCO3 + 5.0g Na2CO3, and 97ml water, add them into the reactor, and stir evenly;
[0082] Red mud contains 10% water, 7.2% Na2O, and 0.24% Zr. Carbon dioxide was introduced into the reactor, and the pressure was controlled at 2.5 MPa. The leaching temperature was set at 180°C for 4 hours. After leaching, the solid-liquid separated red mud residue was washed with 90°C hot water. The pH value was 7.8, the Na2O content of the red mud waste residue was 1.63%, and the Zr leaching rate was 91.29%.
[0083] Example 4
[0084] 40g of red mud, 10g of NH4CO3, 5g of K2CO3, and 98ml of water were mixed and added to a reactor, stirring evenly. The red mud contained 5% water, 8% Na2O, and 0.15% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 3.0 MPa. The leaching temperature was 180°C for 15 hours. After leaching, the solid-liquid separation of the red mud residue was washed with 95°C hot water, resulting in a pH of 8.0, a Na2O content of 2.00%, and a Zr leaching rate of 86.55%.
[0085] Example 5
[0086] 70g of red mud, 5.0g of NH4CO3, 15g of KHCO3, and 100ml of water were mixed and added to a reactor, stirring evenly. The red mud contained 0% water, 6% Na2O, and 0.20% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 3.5 MPa. The leaching temperature was 150°C for 8 hours. After leaching, the solid-liquid separation of the red mud residue was washed with 94°C hot water, resulting in a pH of 8.2, a Na2O content of 1.50%, and a Zr leaching rate of 85.34%.
[0087] Example 6
[0088] 25g of red mud, 5.0g of NaOH + 5.0g of KOH, and 100ml of water were mixed and added to a reactor and stirred evenly. The red mud contained 0% water, 6% Na2O, and 0.20% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 4.0 MPa. The leaching temperature was 100°C for 12 hours. After leaching, the solid-liquid separation of the red mud residue was washed with 90°C hot water. The pH was 8.5, the Na2O content of the red mud waste residue was 1.60%, and the Zr leaching rate was 86.48%.
[0089] Example 7
[0090] 60g of red mud, 13.0g of KHCO3 + 2.0g of KOH, and 100ml of water were mixed and added to a reactor and stirred evenly. The red mud contained 0% water, 6% Na2O, and 0.21% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 4.0 MPa. The leaching temperature was 150°C for 10 hours. After leaching, the solid-liquid separated red mud residue was washed with 90°C hot water. The pH was 8.5, the Na2O content of the red mud waste residue was 1.70%, and the Zr leaching rate was 89.46%.
[0091] Comparative Example 1
[0092] 50g of red mud, 20g of NaHCO₃, and 90ml of water were mixed and added to a reactor, stirring evenly. The red mud contained 20% water, 6% Na₂O, and 0.26% Zr. The leaching temperature was 150°C for 10 hours. After leaching, the solid-liquid separation of the red mud residue was washed with 98°C hot water. The pH was 10.1, the Na₂O content of the red mud waste residue was 1.00%, and the Zr leaching rate was 55.43%.
[0093] Comparative Example 2
[0094] 40g of red mud, 2g of NH4CO3 + 3g of K2CO3, and 98ml of water were mixed and added to a reactor, stirring evenly. The red mud contained 5% water, 8% Na2O, and 0.15% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 3.0 MPa. The leaching temperature was 180°C, and the leaching time was 15 hours. After leaching, the solid-liquid separation of the red mud residue was washed with 95°C hot water, resulting in a pH of 7.9, a Na2O content of 1.70%, and a Zr leaching rate of 18.12%.
[0095] Comparative Example 3
[0096] 70g of red mud, 5.0g of NH4CO3 + 15g of KHCO3, and 100ml of water were mixed and added to a reactor, stirring evenly. The red mud contained 0% water, 6% Na2O, and 0.20% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 3.5 MPa. The leaching temperature was maintained at 40°C for 8 hours. After leaching, the solid-liquid separation of the red mud residue was washed with 94°C hot water, resulting in a pH of 8.9, a Na2O content of 2.6%, and a Zr leaching rate of 25.15%.
[0097] Comparative Example 4
[0098] 80g of red mud, 5.0g of NaOH + 5.0g of KOH, and 100ml of water were mixed and added to a reactor and stirred evenly. The red mud contained 0% water, 6% Na2O, and 0.20% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 4.0 MPa. The leaching temperature was 100°C for 12 hours. After leaching, the solid-liquid separated red mud residue was washed with 90°C hot water. The pH value was 8.5, the Na2O content of the red mud waste residue was 1.60%, and the Zr leaching rate was 55.23%.
[0099] Comparative Example 5
[0100] 60g of red mud, 13.0g of KHCO₃ and 2.0g of KOH, and 100ml of water were mixed and added to a reactor and stirred evenly. The red mud contained 0% water, 6% Na₂O, and 0.21% Zr. Carbon dioxide was introduced into the reactor, and the pressure was maintained at 4.0 MPa. The leaching temperature was 150°C for 2 hours. After leaching, the solid-liquid separation of the red mud residue was washed with 90°C hot water. The pH was 8.9, the Na₂O content of the red mud waste residue was 2.70%, and the Zr leaching rate was 44.39%.
[0101] Comparing Comparative Example 1 with Example 1, the absence of carbon dioxide injection resulted in a decreased zirconium leaching rate. Comparing Comparative Example 2 with Example 4, lowering the leaching agent concentration resulted in a decreased leaching rate. Comparing Comparative Example 3 with Example 5, lowering the leaching temperature resulted in a decreased leaching rate. Comparing Comparative Example 4 with Example 6, increasing the red mud ratio resulted in a decreased leaching rate. Comparing Comparative Example 5 with Example 7, shortening the leaching time resulted in a decreased leaching rate.
[0102] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
[0103] The Na2O content of the red mud waste residue in the embodiment of the present invention is reduced to 1.00% to 2.00%, and the pH is stabilized at 7.5 to 8.5. The red mud waste residue can be directly used in the production of building materials, thereby achieving full quantitative utilization of the red mud and reducing storage pollution.
[0104] The embodiment of the present invention uses cheap alkaline reagents such as NaHCO3 and K2CO3, which reduces the reagent cost compared to the organic acid leaching method, and the closed-loop circulation design further reduces the total reagent consumption.
[0105] The foregoing is merely a detailed description of the present invention, intended to enable those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but rather is intended to conform to the broadest scope consistent with the principles and novel features claimed herein.
Claims
1. A method for recovering zirconium from red mud, the method comprising: mixing red mud, alkali and solvent in proportion to obtain a mixed material; introducing carbon dioxide gas into the mixture to carry out a chemical reaction under set pressure and temperature conditions to obtain a reaction mixture; performing solid-liquid separation on the reaction mixture to obtain a zirconium-containing leachate and red mud waste residue; Wherein, the base is one or more of XOH, XHCO3, X2CO3, X represents Na + , K + or NH4 + .
2. The method according to claim 1, characterized in that In the mixed material, the mass ratio of the alkali, the dry basis of the red mud and the solvent is (0.1-0.2):(0.25-0.7):
1.
3. The method according to claim 1, characterized in that The set pressure is 0.1Mpa to 4.0Mpa.
4. The method according to claim 1, wherein The temperature of the chemical reaction is 100° C. to 180° C., and the time of the chemical reaction is 4 hours to 20 hours.
5. The method according to claim 4, characterized in that The temperature of the chemical reaction is 145° C. to 160° C., and the time of the chemical reaction is 8 h to 10 h.
6. The method according to claim 1, wherein The mass fraction of water in the red mud is ≤20%.
7. The method according to claim 1, characterized in that In the dry basis of the red mud, the mass fraction of Zr is 0.15% to 0.30%, and the mass fraction of Na2O is 6% to 8%.
8. The method according to claim 1, characterized in that After obtaining the zirconium-containing leachate and red mud waste residue, the method further comprises: Dezirconiumizing the zirconium-containing leachate to obtain a circulating liquid; The circulating liquid is returned to the mixed material for recycling.
9. The method according to claim 1, characterized in that The solid-liquid separation of the reaction mixture to obtain a zirconium-containing leachate and red mud waste residue comprises: performing solid-liquid separation on the reaction mixture to obtain a first liquid phase and red mud residue; Washing the red mud residue with hot water at 90° C. to 98° C. to obtain a second liquid phase and red mud waste residue; The first liquid phase and the second liquid phase are mixed to obtain a zirconium-containing leachate.
10. The method according to claim 1, characterized in that The mass of Zr in the zirconium-containing leachate is 85% to 98% of the mass of Zr in the red mud.