Method for separating iron powder through Bayer process red mud pretreatment

Abstract

The method for separating the iron powder through Bayer process red mud pretreatment comprises the steps that Bayer process red mud slurry and a liquid medium are mixed, and mixed slurry is formed; adding a pretreatment aid into the mixed slurry, and pretreating the mixed slurry to modify the surface property of the red mud iron powder in the mixed slurry or improve the rheological property of the mixed slurry; the pretreated mixed slurry is subjected to rotational flow separation, the red mud iron powder is enriched in a solid enrichment phase obtained through rotational flow separation, and the solid enrichment phase containing the red mud iron powder and a liquid dispersion phase are obtained; separating the solid enriched phase containing the red mud iron powder to obtain iron oxide powder; and recycling the liquid dispersion phase as a liquid medium mixed with the Bayer process red mud slurry. According to the embodiment of the invention, through the synergistic effect of mixing, pretreatment and cyclone separation, the separation efficiency and grade of the red mud iron powder are effectively improved from multiple aspects of physical property adjustment, surface property modification and the like.

Description

Technical Field

[0001] The present application relates to the technical field of light metal metallurgy, and in particular to a method for pre-treating and separating iron powder from red mud in the Bayer process. Background Art

[0002] Red mud, a waste product generated during alumina production, gets its name from its reddish-red, slurry-like appearance. With the continuous development of the aluminum industry, red mud production has increased annually, becoming the largest source of pollution in alumina production. The storage of red mud not only occupies significant land and incurs significant construction and maintenance costs, but can also cause environmental problems such as groundwater contamination and dust generation. Furthermore, red mud's high viscosity and moisture content make it difficult to dry and utilize, limiting its resource utilization.

[0003] Currently, the comprehensive utilization of red mud primarily focuses on extracting valuable metals and using it as a general mineral raw material. While existing technologies for separating iron powder from red mud suffer from low yields, high costs, and low grades, the use of methods such as high-gradient magnetic separation and coal-based direct reduction processes can significantly improve the grade and recovery of iron concentrate while reducing yield and costs. For example, while widely used, magnetic separation and gravity separation methods suffer from high equipment investment, high operating costs, and low recovery rates. Summary of the Invention

[0004] The present application provides a method for pre-treating and sorting iron powder from red mud by the Bayer process, in order to solve the following technical problem: how to improve the sorting efficiency and grade of red mud iron powder.

[0005] The present invention provides a method for pre-treating and separating iron powder from red mud by the Bayer process, comprising:

[0006] mixing the Bayer process red mud slurry with a liquid medium to form a mixed slurry;

[0007] adding a pretreatment aid to the mixed slurry and pretreating the mixed slurry to modify the surface properties of the red mud iron powder in the mixed slurry or improve the rheological properties of the mixed slurry;

[0008] The pretreated mixed slurry is subjected to cyclone separation to enrich the red mud iron powder in the solid enriched phase of the cyclone separation, thereby obtaining a solid enriched phase containing red mud iron powder and a liquid dispersed phase;

[0009] Separating iron oxide powder from the solid-rich phase containing red mud iron powder;

[0010] The liquid dispersed phase is recycled and used as a liquid medium for mixing with the Bayer process red mud slurry.

[0011] Optionally, the liquid medium includes at least one of the following: water, red mud filtrate, and the mass concentration of the mixed slurry is 50-500 g / L.

[0012] Optionally, a dispersant is added to the liquid medium, and the mass of the dispersant is 0.01-0.5% of the mass of the red mud slurry; and / or,

[0013] A pH regulator is added to the liquid medium, and the mass of the pH regulator is 0.01-0.5% of the mass of the red mud slurry.

[0014] Optionally, the functional groups of the pretreatment aid include at least one of the following: carboxyl, hydroxyl, amino, and sulfonic acid groups, and the mass of the pretreatment aid is 0.05-5% of the mass of the red mud slurry.

[0015] Optionally, the pretreatment temperature is 30-120° C., and the pretreatment time is 0.05-2 hours.

[0016] Optionally, the parameters of the cyclone separation include: a feed pressure of 0.05-0.25 MPa, and a bottom flow port diameter of 10-50 mm.

[0017] Optionally, the pretreatment aid is an organic compound or an inorganic compound with surface activity, and the pretreatment aid can undergo chemical adsorption or physical adsorption with the surface of the red mud iron powder.

[0018] Optionally, the pretreatment aid includes at least one of the following: acrylic acid and its derivatives, polyacrylic acid and its derivatives, polyacrylamide and its derivatives, polyacrylate and its derivatives, oxalic acid and its derivatives, polyvinyl alcohol and its derivatives.

[0019] Optionally, the pretreatment aid further comprises nanomaterials, which can form a stable composite structure with the surface of the red mud iron powder, and the mass of the nanomaterials is 0.01-1% of the mass of the red mud slurry.

[0020] Optionally, the method further includes:

[0021] The liquid dispersed phase is subjected to evaporation and concentration treatment to recover useful components; the temperature of the evaporation and concentration treatment is 60-100° C., and the time of the evaporation and concentration treatment is 0.5-3 hours.

[0022] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0023] The embodiment of the present application provides a method for pre-treating and sorting iron powder from Bayer red mud. First, a mixed slurry suitable for sorting is prepared by mixing Bayer red mud slurry with a liquid medium. This process adjusts the physical properties of the red mud slurry, reduces its viscosity and improves its fluidity, providing a good basic condition for subsequent sorting operations. Good fluidity enables the red mud iron powder to be more evenly distributed during the cyclone separation process, thereby improving the sorting efficiency. Secondly, the addition of pretreatment additives is a key link in this technical solution. The role of pretreatment additives is mainly reflected in two aspects: one is to modify the surface properties of the red mud iron powder. Adjusting the surface charge, hydrophilicity and other properties of the red mud iron powder can enhance its separation efficiency during the cyclone separation process. For example, making the surface of the red mud iron powder more hydrophobic, so that it is more inclined to be enriched in the solid-enriched phase during the cyclone separation process, thereby improving the grade of the iron powder; the second is to improve the rheological properties of the mixed slurry. Pretreatment aids can reduce the viscosity of the mixed slurry, promote its smooth flow during cyclone separation, reduce energy consumption, and improve separation efficiency. Finally, the pretreated mixed slurry is separated through a cyclone separation process. Cyclone separation uses the action of centrifugal force to enrich the red mud iron powder with a higher density into the solid enrichment phase, thereby achieving effective separation of the red mud iron powder from other components. Since the previous mixing and pretreatment steps have created favorable conditions for sorting, this process can efficiently achieve the enrichment of red mud iron powder and improve its grade. In addition, the recycling of the liquid dispersed phase as a mixing medium not only saves resources, but also optimizes the separation efficiency and reduces costs. In summary, the embodiments of the present application effectively improve the separation efficiency and grade of red mud iron powder by the synergistic effect of mixing, pretreatment and cyclone separation, starting from multiple aspects such as physical property adjustment and surface property modification. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following summarizes the drawings necessary for the embodiments or the description of the prior art. Obviously, for professionals in this field, other relevant drawings can be derived based on these drawings without creative efforts.

[0026] Figure 1 This is a flow chart of a method for pre-treating and separating iron powder from Bayer red mud provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] To more clearly illustrate the purpose, technical solutions, and advantages of the embodiments of the present application, the technical solutions of the embodiments are described in detail below with reference to the accompanying drawings. Please note that the embodiments described herein are merely illustrative and do not represent all possible implementation paths. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present application without creative effort are within the scope of protection of this application.

[0028] 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.

[0029] Figure 1 This is a flow chart of a method for pre-treating and separating iron powder from Bayer red mud provided in an embodiment of the present application.

[0030] See Figure 1 The present invention provides a method for pre-treating and separating iron powder from red mud by the Bayer process, comprising:

[0031] S1. Mixing the Bayer process red mud slurry with a liquid medium to form a mixed slurry;

[0032] S2. adding a pretreatment aid to the mixed slurry and pretreating the mixed slurry to modify the surface properties of the red mud iron powder in the mixed slurry or improve the rheological properties of the mixed slurry;

[0033] S3, subjecting the pretreated mixed slurry to cyclone separation, so that the red mud iron powder is enriched in the solid enriched phase of the cyclone separation, to obtain a solid enriched phase containing red mud iron powder and a liquid dispersed phase;

[0034] S4. Separating iron oxide powder from the solid-rich phase containing red mud iron powder; and recycling the liquid dispersed phase as a liquid medium for mixing with the Bayer process red mud slurry.

[0035] Bayer process red mud slurry: A slurry formed by red mud and water produced during the Bayer process for alumina production. Its main components include iron oxide, aluminum oxide, silicon oxide, etc., of which red mud iron powder is an important component with recycling value. Liquid medium: A liquid used to dilute and adjust the properties of red mud slurry, usually water or red mud filtrate. Pretreatment additive: A chemical substance that can change the surface properties of red mud iron powder or improve the rheological properties of the mixed slurry. Cyclone separation: A process that uses a centrifugal field to separate solid particles. By adjusting the feed pressure and cyclone structural parameters, the separation of particles of different densities can be achieved.

[0036] Mixing Bayer red mud slurry with a liquid medium reduces its viscosity and improves its fluidity, facilitating subsequent separation. Pretreatment additives, through chemical or physical adsorption, alter the surface charge distribution or hydrophilicity / hydrophobicity of the red mud iron powder, making it easier to separate from other components during cyclone separation. Pretreatment additives reduce the viscosity of the mixed slurry, improving its fluidity, reducing energy loss, and increasing separation efficiency. Cyclone separation utilizes a centrifugal field to concentrate the denser red mud iron powder into a solid-enriched phase, separating it from other components. Recycling the liquid dispersed phase conserves resources and reduces costs. This method is widely used in the resource utilization of Bayer red mud, particularly for the efficient recovery of iron powder from red mud, improving resource utilization and reducing environmental pollution. By optimizing pretreatment additives and cyclone separation parameters, the grade and recovery rate of iron powder can be further improved.

[0037] In some embodiments, the liquid medium includes at least one of the following: water, red mud filtrate, and the mass concentration of the mixed slurry is 50-500 g / L.

[0038] Red mud filtrate: The liquid obtained after filtering the Bayer red mud contains a certain amount of soluble components and can be recycled as a liquid medium.

[0039] The selection of an appropriate liquid medium has a decisive influence on the solid and liquid properties of the mixed slurry, and thus significantly affects its sorting effect. Water is the most commonly used liquid medium, which is low-cost and easy to obtain. Red mud filtrate contains a certain amount of soluble components, which can provide a certain chemical environment, help the pretreatment additives to play their role, and realize the recycling of resources. This method is applicable to Bayer red mud from different sources. By selecting a suitable liquid medium, the sorting process can be optimized according to the specific composition and properties of the red mud. For example, for red mud containing more soluble salts, using red mud filtrate as a liquid medium can better adjust the chemical environment of the mixed slurry. Example:

[0040] Pure water was used as the liquid medium, and the mass concentration of the mixed slurry was 100 g / L for cyclone separation.

[0041] Red mud filtrate was used as the liquid medium, the mixed slurry concentration was 300 g / L, and cyclone separation was performed after adding pretreatment additives.

[0042] A mixture of water and red mud filtrate was added to the mixed slurry at a mass concentration of 200 g / L for cyclone separation.

[0043] Water was used as the liquid medium, the mass concentration of the mixed slurry was 50 g / L, and the cyclone separation parameters were optimized to improve the iron powder recovery rate.

[0044] Red mud filtrate was used as the liquid medium, the mixed slurry concentration was 500 g / L, nanomaterials were added as pretreatment aids, and cyclone separation was performed.

[0045] A mixture of water and red mud filtrate was added to the mixed slurry at a mass concentration of 150 g / L, and cyclone separation was performed to recover iron powder in the red mud.

[0046] In some embodiments, a dispersant is added to the liquid medium, and the mass of the dispersant is 0.01-0.5% of the mass of the red mud slurry; and / or,

[0047] A pH regulator is added to the liquid medium, and the mass of the pH regulator is 0.01-0.5% of the mass of the red mud slurry.

[0048] Dispersant: A chemical substance that prevents particle aggregation and improves particle dispersion, typically used to improve the stability of the mixed slurry. pH adjuster: A chemical substance used to adjust the pH of the mixed slurry, which can affect the effectiveness of pretreatment additives and the surface properties of red mud iron powder.

[0049] Dispersants can prevent red mud particles from agglomerating, improve the stability of the mixed slurry, and make the red mud iron powder more evenly distributed during the cyclone separation process, thereby improving the separation efficiency. pH regulators can change the pH of the mixed slurry, thereby affecting the surface charge distribution of the red mud iron powder, optimizing the effect of pretreatment additives, and further improving the separation efficiency and iron powder grade. After adding dispersants and pH regulators, the composition and characteristics of various types of red mud slurries can be finely adjusted, thereby significantly improving the adaptability and operating efficiency of the separation process. For example, when processing high-silicon red mud, iron powder can be better separated by adjusting the pH value. Example:

[0050] 0.1% sodium polyacrylate was added to the mixed slurry as a dispersant and cyclone separation was performed.

[0051] Sodium hydroxide was used as a pH regulator to adjust the pH value of the mixed slurry to 8, and cyclone separation was performed.

[0052] 0.05% dispersant and 0.05% pH regulator were added to the mixed slurry to optimize the cyclone separation parameters.

[0053] Citric acid was used as a pH regulator to adjust the pH value of the mixed slurry to 6, and cyclone separation was performed.

[0054] Add 0.5% dispersant to the mixed slurry and perform cyclone separation to improve the iron powder recovery rate.

[0055] Hydrochloric acid is used as a pH regulator to adjust the pH value of the mixed slurry to 4, and cyclone separation is performed to recover iron powder in the red mud.

[0056] In some embodiments, the functional group of the pretreatment aid includes at least one of the following: carboxyl, hydroxyl, amino, and sulfonic acid groups, and the mass of the pretreatment aid is 0.05-5% of the mass of the red mud slurry.

[0057] Functional groups refer to atomic groups with specific chemical properties in organic compounds, such as carboxyl (-COOH), hydroxyl (-OH), amino (-NH2), and sulfonic acid (-SO3H). These functional groups can undergo chemical or physical adsorption on the surface of red mud iron powder.

[0058] Pretreatment additives, with their functional groups, can produce chemical or physical adsorption on the surface of red mud iron powder, thereby changing the surface properties of the red mud iron powder and making it easier to separate from other components during cyclone separation. For example, carboxyl and sulfonic acid groups can be adsorbed on the surface of red mud iron powder through ion exchange, increasing its surface charge and thus improving separation efficiency. By selecting pretreatment additives with specific functional groups, the separation process can be optimized according to the specific composition and properties of the red mud. For example, when processing red mud with a high alumina content, the use of pretreatment additives containing amino groups can more effectively achieve the separation of iron powder. Example:

[0059] Polyacrylic acid (containing carboxyl groups) is used as a pretreatment auxiliary agent, with a mass of 1% of the mass of the red mud slurry, for cyclone separation.

[0060] Polyacrylic acid amine (containing amino groups) is added to the mixed slurry as a pretreatment auxiliary agent, with a mass of 0.5% of the mass of the red mud slurry, and cyclone separation is performed.

[0061] Oxalic acid (containing carboxyl group) was used as a pretreatment auxiliary agent, with a mass of 0.1% of the mass of the red mud slurry, for cyclone separation.

[0062] Polyvinyl alcohol (containing hydroxyl groups) is added to the mixed slurry as a pretreatment auxiliary agent, with a mass of 2% of the mass of the red mud slurry, and cyclone separation is performed.

[0063] Polyacrylate (containing carboxyl groups) was used as a pretreatment aid, with a mass of 3% of the mass of the red mud slurry, for cyclone separation.

[0064] Sulfonated polystyrene (containing sulfonic acid groups) is added to the mixed slurry as a pretreatment auxiliary agent, with a mass of 0.05% of the mass of the red mud slurry, and cyclone separation is performed.

[0065] In some embodiments, the pretreatment temperature is 30-120° C., and the pretreatment time is 0.05-2 hours.

[0066] During the pretreatment process, temperature is crucial to the interaction between the pretreatment agent and the surface of the red mud iron powder. As the temperature increases, the physical and chemical characteristics of the red mud surface change, such as the increase in specific surface area and the decomposition and transformation of chemical components, which helps to accelerate chemical reactions and physical adsorption processes. For example, the functional groups in the pretreatment agent (such as carboxyl, hydroxyl, amino, etc.) can bind to the active sites on the surface of the red mud iron powder more quickly. This binding can be achieved through the formation of chemical bonds (chemical adsorption) or weak interactions such as van der Waals forces (physical adsorption). For example, when using a pretreatment agent containing carboxyl groups (such as polyacrylic acid), high temperature can promote the interaction between carboxyl groups and metal ions (such as Fe 3+) undergoes an ion exchange reaction, thereby forming a uniform adsorption layer on the surface of the red mud iron powder. The formation of this adsorption layer can effectively adjust the surface charge layout of the red mud iron powder, making it easier to separate from other components during the cyclone separation process. In addition, an increase in temperature can also reduce the viscosity of the mixed slurry and further improve its rheological properties. Lower viscosity helps the pretreatment additive to be more evenly dispersed in the mixed slurry, thereby increasing its chance of contact with the red mud iron powder and enhancing the pretreatment effect. However, too high a temperature may cause the pretreatment additive to decompose or fail. Therefore, it is necessary to select a suitable temperature range (30-120°C) based on the chemical properties of the pretreatment additive and the specific composition of the red mud. The length of the pretreatment time directly determines whether the interaction between the pretreatment additive and the red mud iron powder surface can reach a sufficient state. If the time is too short, the pretreatment additive may not be fully adsorbed on the surface of the red mud iron powder, thereby weakening the separation effect. Too long a time may waste energy and may even lead to excessive adsorption of the pretreatment additive, forming an overly stable adsorption layer, which is not conducive to subsequent cyclone separation. Therefore, the pretreatment time needs to be optimized according to the type of pretreatment additive and the properties of the red mud, usually between 0.05-2 hours. The length of the pretreatment time is also related to the concentration and temperature of the pretreatment additive. At higher temperatures, the adsorption rate of the pretreatment additive is accelerated, so the pretreatment time can be appropriately shortened; conversely, at lower temperatures, the treatment time needs to be extended to ensure that the additive can fully play its role. In addition, the higher the concentration of the pretreatment additive, the more opportunities it has to contact the surface of the red mud iron powder, but too high a concentration may lead to increased costs, so a balance needs to be found between the pretreatment time and the additive concentration. Example:

[0067] The pretreatment was carried out at 60°C for 0.5 hours, and then cyclone separation was performed.

[0068] The pretreatment was carried out at 100°C for 1 hour, and then cyclone separation was performed.

[0069] The pretreatment was carried out at 30°C for 2 hours, and then cyclone separation was performed.

[0070] The pretreatment was carried out at 80°C for 1.5 hours, and then cyclone separation was performed.

[0071] The pretreatment was carried out at 120°C for 0.5 hours, and then cyclone separation was performed.

[0072] The pretreatment was carried out at 90°C for 1 hour, and then cyclone separation was performed to recover the iron powder in the red mud.

[0073] In some embodiments, the parameters of the cyclone separation include: a feed pressure of 0.05-0.25 MPa, and a bottom flow port diameter of 10-50 mm.

[0074] During cyclone separation, feed pressure is a key factor influencing the strength of the centrifugal field. Higher feed pressure generates stronger centrifugal forces, allowing denser red mud iron fines to be flung toward the outer wall of the cyclone, where they are concentrated in the solid-rich phase. Feed pressure directly impacts the efficiency and separation performance of cyclone separation. If the feed pressure is too low, the centrifugal force is insufficient, and the red mud iron fines may not be fully separated. Excessive feed pressure, on the other hand, can lead to increased equipment wear and energy consumption. The selection of feed pressure requires a comprehensive consideration of the properties of the red mud slurry, the structural parameters of the cyclone, and the effectiveness of pretreatment additives. For example, pretreated red mud slurry, due to its improved surface properties, can achieve better separation results at lower feed pressures. Typically, feed pressures range from 0.05 to 0.25 MPa. The underflow diameter is a key structural parameter of the cyclone, determining the discharge rate of the solid-rich phase and the separation performance. The larger the underflow port diameter, the faster the solid-rich phase is discharged, but it may cause some insufficiently separated particles to enter the underflow, thereby reducing the sorting accuracy; the smaller the underflow port diameter, although it can improve the sorting accuracy, it may cause the underflow discharge speed to be too slow, or even block the underflow port. Optimizing the underflow port diameter requires comprehensive consideration of the particle distribution and density differences of the red mud slurry and other key structural parameters of the cyclone. For example, when processing red mud with finer particles, the underflow port diameter can be appropriately reduced to improve the sorting accuracy; when processing red mud with coarser particles, the underflow port diameter can be appropriately increased to ensure smooth discharge of the underflow. Typically, the underflow port diameter of the cyclone is in the range of 10-50mm, which is suitable for process flows with smaller processing volumes. Example:

[0075] The cyclone with a feed pressure of 0.1 MPa and a bottom flow port diameter of 20 mm was used for separation.

[0076] The cyclone with a feed pressure of 0.2 MPa and a bottom flow port diameter of 30 mm was used for separation.

[0077] The separation was carried out using a cyclone with a feed pressure of 0.05 MPa and a bottom flow port diameter of 10 mm.

[0078] The cyclone with a feed pressure of 0.15 MPa and a bottom flow port diameter of 40 mm was used for separation.

[0079] The cyclone with a feed pressure of 0.25 MPa and a bottom flow port diameter of 50 mm was used for separation.

[0080] A cyclone with a feed pressure of 0.12 MPa and a bottom flow port diameter of 25 mm was used for separation to recover iron powder from red mud.

[0081] In some embodiments, the pretreatment aid is an organic compound or an inorganic compound with surface activity, and the pretreatment aid can undergo chemical adsorption or physical adsorption with the surface of the red mud iron powder.

[0082] Chemical adsorption refers to the process in which the functional groups of the pretreatment agent bind to the active sites on the surface of the red mud iron powder through chemical bonds. This binding is usually irreversible, and the adsorption layer formed is stable and strong. For example, when a pretreatment agent containing carboxyl groups (such as polyacrylic acid) is used, the carboxyl groups can bind to the metal ions (such as Fe 3+ ) forms a stable chemical bond through ion exchange reaction. The formation of this chemical bond can significantly change the surface charge distribution of red mud iron powder and increase its surface negative charge, making it easier to separate from other components during cyclone separation. Physical adsorption refers to the process in which the functional groups of the pretreatment additives are combined with the surface of red mud iron powder through weak interactions such as van der Waals forces. This adsorption is usually reversible, and the adsorption layer formed is relatively weak. Physical adsorption can mainly improve the surface properties of red mud iron powder and optimize the rheological properties of the mixed slurry. For example, when a pretreatment additive containing hydroxyl groups (such as polyvinyl alcohol) is used, the hydroxyl groups are combined with the hydroxyl groups or other functional groups on the surface of the red mud iron powder by means of hydrogen bonds, and then a layer of adsorption layer is evenly covered on the surface of the red mud iron powder. This adsorption layer can change the surface hydrophilicity of the red mud iron powder, making it easier to disperse in the mixed slurry.

[0083] In some embodiments, the pretreatment aid includes at least one of the following: acrylic acid and its derivatives, polyacrylic acid and its derivatives, polyacrylamide and its derivatives, polyacrylate and its derivatives, oxalic acid and its derivatives, polyvinyl alcohol and its derivatives.

[0084] Acrylic acid and its derivatives (such as polyacrylic acid, polyacrylamide, polyacrylate, etc.) contain functional groups such as carboxyl and amino groups, and have good surface activity and adsorption properties. Oxalic acid and its derivatives contain two carboxyl groups and have strong chemical adsorption capacity. The two carboxyl groups of oxalic acid can combine with metal ions on the surface of red mud iron powder through ion exchange reaction to form a stable bidentate coordination structure. Polyvinyl alcohol and its derivatives are rich in hydroxyl groups and show excellent surface activity and strong adsorption capacity. By optimizing the type, functional group, concentration of pretreatment additives, and adjusting the temperature and time of pretreatment, personalized adjustments can be made to red mud slurries with different compositions and properties, thereby improving the efficiency of the sorting process and improving the grade of iron powder. Example:

[0085] Polyacrylic acid is used as a pretreatment additive, with a mass of 1% of the mass of the red mud slurry, for cyclone separation.

[0086] Polyacrylamide is added as a pretreatment aid to the mixed slurry, with a mass of 0.5% of the mass of the red mud slurry, and cyclone separation is performed.

[0087] Oxalic acid was used as a pretreatment aid, with a mass of 0.1% of the mass of the red mud slurry, for cyclone separation.

[0088] Polyvinyl alcohol is added as a pretreatment aid to the mixed slurry, with a mass of 2% of the mass of the red mud slurry, and cyclone separation is performed.

[0089] Polyacrylate was used as a pretreatment aid, with a mass of 3% of the mass of the red mud slurry, for cyclone separation.

[0090] Sulfonated polystyrene is added to the mixed slurry as a pretreatment auxiliary agent, the mass of which is 0.05% of the mass of the red mud slurry, and cyclone separation is performed.

[0091] In some embodiments, the pretreatment aid further comprises a nanomaterial, which can form a stable composite structure with the surface of the red mud iron powder, and the mass of the nanomaterial is 0.01-1% of the mass of the red mud slurry.

[0092] Nanomaterials refer to materials with a size between 1 nanometer and 100 nanometers, which have special physical and chemical properties. These properties include high specific surface area, quantum size effect, surface effect and interface effect. The high specific surface area of ​​nanomaterials means that they have more active sites, which enables them to interact more effectively with the surface of red mud iron powder, thereby improving the overall performance. The quantum size effect, that is, when the size of nanomaterials is reduced to the quantum size of atoms or molecules, the behavior and properties of their carriers such as electrons, photons and phonons will change significantly, which may lead to changes in the optical, electrical and magnetic properties of nanomaterials. For example, band structure modulation, optical property changes, electronic structure modulation and carrier confinement effects, etc., these changes in turn affect the adsorption and separation properties of the material. Interaction between nanomaterials and red mud iron powder: The main role of nanomaterials in the pretreatment process is to form a stable composite structure with the surface of red mud iron powder through their special physical and chemical properties, thereby changing the surface properties of red mud iron powder. Example:

[0093] Nano-silicon dioxide is added to the mixed slurry as a pretreatment aid, with a mass of 0.1% of the mass of the red mud slurry, and cyclone separation is performed.

[0094] Nano-alumina is used as a pretreatment aid, with a mass of 0.5% of the mass of the red mud slurry, for cyclone separation.

[0095] Nano calcium carbonate is added to the mixed slurry as a pretreatment aid, with a mass of 0.05% of the mass of the red mud slurry, and cyclone separation is performed.

[0096] Nano-iron oxide is used as a pretreatment aid, with a mass of 0.2% of the mass of the red mud slurry, for cyclone separation.

[0097] Nano zinc oxide is added to the mixed slurry as a pretreatment auxiliary agent, with a mass of 0.3% of the mass of the red mud slurry, and cyclone separation is performed.

[0098] Nano-titanium oxide is used as a pretreatment aid, with a mass of 0.1% of the mass of the red mud slurry, to perform cyclone separation and recover iron powder in the red mud.

[0099] In some embodiments, the method further comprises:

[0100] The liquid dispersed phase is subjected to evaporation and concentration treatment to recover useful components; the temperature of the evaporation and concentration treatment is 60-100° C., and the time of the evaporation and concentration treatment is 0.5-3 hours.

[0101] The liquid dispersion typically contains a variety of soluble components, such as sodium aluminate, sodium silicate, and sodium carbonate. These components are of high economic value, and evaporation concentration can be used to concentrate them to a certain concentration for subsequent recycling. Direct discharge of bulk liquid chemicals can pollute the atmosphere, particularly due to the 10% pipe leaks common during loading and unloading at docks. Evaporation concentration can reduce the volume of the liquid dispersion and alleviate the burden of wastewater treatment. Evaporation concentration is performed within a temperature range of 60 to 100°C to achieve a balance between evaporation efficiency and energy consumption. Higher temperatures accelerate evaporation but also increase energy consumption. This temperature range ensures efficient evaporation while avoiding energy waste caused by overheating. The evaporation concentration process should be performed within a time range of 0.5 to 3 hours to ensure sufficient concentration of the soluble components in the solution. A shorter time may result in incomplete concentration, while a longer time increases energy consumption and equipment operating costs.

[0102] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0103] Example 1

[0104] Preparation of mixed slurry: Bayer process red mud slurry is mixed with water to form a mixed slurry with a mass concentration of 150 g / L.

[0105] Pretreatment: polyacrylic acid in an amount of 0.5% by mass of the red mud slurry was added to the mixed slurry as a pretreatment aid, the pretreatment temperature was controlled at 60° C., and the pretreatment time was 0.5 hour.

[0106] Cyclone separation: The pretreated mixed slurry is subjected to cyclone separation, and the feed pressure is controlled to be 0.1MPa and the bottom flow port diameter is 20mm.

[0107] Separation and recovery: Iron oxide powder is separated from the solid enriched phase of cyclone separation, and the liquid dispersed phase is recycled.

[0108] Example 2

[0109] Preparation of mixed slurry: Bayer process red mud slurry and red mud filtrate were mixed to form a mixed slurry with a mass concentration of 200 g / L.

[0110] Pretreatment: add oxalic acid in an amount of 1% by mass of the red mud slurry as a pretreatment aid to the mixed slurry, control the pretreatment temperature to 80° C., and the pretreatment time to 1 hour.

[0111] Cyclone separation: The pretreated mixed slurry is subjected to cyclone separation, and the feed pressure is controlled to be 0.15MPa and the bottom flow port diameter is 25mm.

[0112] Separation and recovery: Iron oxide powder is separated from the solid enriched phase of cyclone separation, and the liquid dispersed phase is recycled.

[0113] Example 3

[0114] Preparation of mixed slurry: Bayer process red mud slurry is mixed with water to form a mixed slurry with a mass concentration of 250 g / L.

[0115] Pretreatment: Add polyacrylic acid amine as a pretreatment aid in an amount of 1.5% by mass of the red mud slurry to the mixed slurry, control the pretreatment temperature to 70° C., and the pretreatment time to 0.8 hour.

[0116] Cyclone separation: The pretreated mixed slurry is subjected to cyclone separation, and the feed pressure is controlled to be 0.12MPa and the bottom flow port diameter is 30mm.

[0117] Separation and recovery: Iron oxide powder is separated from the solid enriched phase of cyclone separation, and the liquid dispersed phase is recycled.

[0118] Example 4

[0119] Preparation of mixed slurry: Bayer process red mud slurry and red mud filtrate were mixed to form a mixed slurry with a mass concentration of 300 g / L.

[0120] Pretreatment: Add polyvinyl alcohol (2% by weight of the red mud slurry) as a pretreatment aid to the mixed slurry, control the pretreatment temperature at 90° C., and the pretreatment time at 1 hour.

[0121] Cyclone separation: The pretreated mixed slurry is subjected to cyclone separation, and the feed pressure is controlled to be 0.2MPa and the bottom flow port diameter is 35mm.

[0122] Separation and recovery: Iron oxide powder is separated from the solid enriched phase of cyclone separation, and the liquid dispersed phase is recycled.

[0123] Example 5

[0124] Preparation of mixed slurry: Bayer process red mud slurry is mixed with water to form a mixed slurry with a mass concentration of 180 g / L.

[0125] Pretreatment: polyacrylate in an amount of 1% by mass of the red mud slurry was added to the mixed slurry as a pretreatment aid, the pretreatment temperature was controlled at 75° C., and the pretreatment time was 0.6 hours.

[0126] Cyclone separation: The pretreated mixed slurry is subjected to cyclone separation, and the feed pressure is controlled to be 0.18MPa and the bottom flow port diameter is 28mm.

[0127] Separation and recovery: Iron oxide powder is separated from the solid enriched phase of cyclone separation, and the liquid dispersed phase is recycled.

[0128] Example 6

[0129] Preparation of mixed slurry: Bayer process red mud slurry and red mud filtrate were mixed to form a mixed slurry with a mass concentration of 220 g / L.

[0130] Pretreatment: 0.8% of the mass of red mud slurry of oxalic acid was added to the mixed slurry as a pretreatment aid, the pretreatment temperature was controlled at 85° C., and the pretreatment time was 0.7 hours.

[0131] Cyclone separation: The pretreated mixed slurry is subjected to cyclone separation, and the feed pressure is controlled to be 0.14MPa and the bottom flow port diameter is 32mm.

[0132] Separation and recovery: Iron oxide powder is separated from the solid enriched phase of cyclone separation, and the liquid dispersed phase is recycled.

[0133] Comparative Example 1

[0134] Preparation of mixed slurry: Bayer process red mud slurry is mixed with water to form a mixed slurry with a mass concentration of 150 g / L.

[0135] Pretreatment: No pretreatment additives were added, and cyclone separation was performed directly.

[0136] Cyclone separation: control the feed pressure to 0.1MPa and the bottom flow port diameter to 20mm.

[0137] Separation and recovery: Iron oxide powder is separated from the solid enriched phase of cyclone separation, and the liquid dispersed phase is recycled.

[0138] Comparative Example 2

[0139] Preparation of mixed slurry: Bayer process red mud slurry is mixed with water to form a mixed slurry with a mass concentration of 200 g / L.

[0140] Pretreatment: polyacrylic acid in an amount of 1% by mass of the red mud slurry was added to the mixed slurry as a pretreatment aid, but no pretreatment reaction was performed and cyclone separation was directly performed.

[0141] Cyclone separation: control the feed pressure to 0.15MPa and the bottom flow port diameter to 25mm.

[0142] Separation and recovery: Iron oxide powder is separated from the solid enriched phase of cyclone separation, and the liquid dispersed phase is recycled.

[0143] Comparative Example 3

[0144] Preparation of mixed slurry: Bayer process red mud slurry is mixed with water to form a mixed slurry with a mass concentration of 250 g / L.

[0145] Pretreatment: Add polyacrylic acid amine as a pretreatment aid in an amount of 1.5% by mass of the red mud slurry to the mixed slurry, control the pretreatment temperature to 70° C., and the pretreatment time to 0.8 hour.

[0146] Cyclone separation: No cyclone separation optimization was performed, the feed pressure was controlled at 0.05 MPa, and the bottom flow port diameter was 40 mm.

[0147] Separation and recovery: Iron oxide powder is separated from the solid enriched phase of cyclone separation, and the liquid dispersed phase is recycled.

[0148] Effect data: The effect data of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1.

[0149] Experimental methods for effect data:

[0150] 1. Determination of iron oxide powder grade

[0151] Sample collection: Iron oxide powder samples were collected from the solid enriched phase after cyclone separation.

[0152] Chemical analysis: X-ray fluorescence spectroscopy (XRF) was used to analyze the iron content in the iron oxide powder and calculate the grade of the iron oxide powder (expressed as the mass fraction of Fe2O3).

[0153] Repeated determination: Each sample was measured three times, and the average value was taken as the final result.

[0154] 2. Calculation of iron oxide powder recovery rate

[0155] Raw material analysis: Determine the initial iron content (expressed as the mass fraction of Fe2O3) in the Bayer process red mud slurry.

[0156] Product analysis: Determine the mass of iron oxide powder in the solid enriched phase after cyclone separation.

[0157] Recovery rate calculation: The recovery rate of iron oxide powder was calculated according to the following formula: Recovery rate (%) = (initial mass of Fe2O3 in red mud slurry ÷ mass of Fe2O3 in iron oxide powder) × 100

[0158] Repeat calculation: perform three repeated calculations on each embodiment and comparative example, and take the average value as the final result.

[0159] Table 1

[0160] Examples / Comparative Examples Iron oxide powder grade (%) Iron oxide powder recovery rate (%) Example 1 58 65 Example 2 60 70 Example 3 62 72 Example 4 65 75 Example 5 63 73 Example 6 64 74 Comparative Example 1 45 50 Comparative Example 2 48 55 Comparative Example 3 50 60

[0161] The above effect data table can intuitively compare the differences between different examples and comparative examples. The following conclusions can be drawn:

[0162] 1. Pretreatment additives:

[0163] Examples 1-6: Using different types of pretreatment additives (such as polyacrylic acid, oxalic acid, polyacrylamide, and polyvinyl alcohol), the grade and recovery rate of iron oxide powder were significantly improved, with grades ranging from 58% to 65% and recoveries ranging from 65% to 75%. Comparative Example 1: No pretreatment additive was added, and the grade of iron oxide powder was only 45%, and the recovery rate was only 50%. This demonstrates that pretreatment additives play a key role in improving iron powder grade and recovery.

[0164] 2. Pretreatment reaction:

[0165] Examples 1-6: All underwent pretreatment reactions, and the reaction conditions (temperature and time) were optimized, significantly improving the iron powder grade and recovery rate. Comparative Example 2: Although a pretreatment agent was added, no pretreatment reaction was performed. The iron oxide powder grade was 48% and the recovery rate was 55%. This demonstrates that the pretreatment reaction process is crucial for the agent to function effectively.

[0166] 3. Cyclone separation parameters:

[0167] Examples 1-6: By optimizing the feed pressure and underflow port diameter for cyclone separation, the iron powder grade and recovery rate were further improved. Comparative Example 3: Despite pretreatment, cyclone separation parameters were not optimized. The iron oxide powder grade was 50% and the recovery rate was 60%. This demonstrates that optimizing cyclone separation parameters significantly improves separation efficiency and iron powder grade.

[0168] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. 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 application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for pre-treating and separating iron powder from red mud by the Bayer process, comprising: mixing the Bayer process red mud slurry with a liquid medium to form a mixed slurry; adding a pretreatment aid to the mixed slurry and pretreating the mixed slurry to modify the surface properties of the red mud iron powder in the mixed slurry or improve the rheological properties of the mixed slurry; The pretreated mixed slurry is subjected to cyclone separation to enrich the red mud iron powder in the solid enriched phase of the cyclone separation, thereby obtaining a solid enriched phase containing red mud iron powder and a liquid dispersed phase; Separating iron oxide powder from the solid-rich phase containing red mud iron powder; The liquid dispersed phase is recycled and used as a liquid medium for mixing with the Bayer process red mud slurry.

2. The method according to claim 1, characterized in that The liquid medium includes at least one of the following: water and red mud filtrate, and the mass concentration of the mixed slurry is 50-500g / L.

3. The method according to claim 1 or 2, characterized in that A dispersant is added to the liquid medium, and the mass of the dispersant is 0.01-0.5% of the mass of the red mud slurry; and / or, A pH regulator is added to the liquid medium, and the mass of the pH regulator is 0.01-0.5% of the mass of the red mud slurry.

4. The method according to claim 1, wherein The functional groups of the pretreatment aid include at least one of the following: carboxyl, hydroxyl, amino, and sulfonic acid groups. The mass of the pretreatment aid is 0.05-5% of the mass of the red mud slurry.

5. The method according to claim 1, wherein The pretreatment temperature is 30-120° C., and the pretreatment time is 0.05-2 hours.

6. The method according to claim 1, wherein The parameters of the cyclone separation include: a feed pressure of 0.05-0.25 MPa, and a bottom flow port diameter of 10-50 mm.

7. The method according to claim 1, characterized in that The pretreatment aid is an organic compound or an inorganic compound with surface activity, and the pretreatment aid can undergo chemical adsorption or physical adsorption with the surface of the red mud iron powder.

8. The method according to claim 6, characterized in that The pretreatment auxiliary agent includes at least one of the following: acrylic acid and its derivatives, polyacrylic acid and its derivatives, polyacrylamide and its derivatives, polyacrylate and its derivatives, oxalic acid and its derivatives, polyvinyl alcohol and its derivatives.

9. The method according to claim 1, characterized in that The pretreatment aid further comprises nanomaterials, which can form a stable composite structure with the surface of the red mud iron powder. The mass of the nanomaterials is 0.01-1% of the mass of the red mud slurry.

10. The method according to claim 1, characterized in that The method further comprises: The liquid dispersed phase is subjected to evaporation and concentration treatment to recover useful components; the temperature of the evaporation and concentration treatment is 60-100° C., and the time of the evaporation and concentration treatment is 0.5-3 hours.

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