An iron-based additive, its preparation method and use

Abstract

This invention belongs to the field of metallurgical solid waste resource utilization technology, specifically disclosing an iron-based additive, its preparation method, and its application. The preparation method includes: mixing red mud, sodium salt, and a reducing agent; subjecting the mixture to reduction roasting to obtain reduced clinker; grinding and separating the reduced clinker by magnetic separation to obtain iron concentrate, thus obtaining the iron-based additive. This invention uses red mud, sodium salt, and a reducing agent stored in alumina plants as raw materials. The sodium salt significantly lowers the reduction temperature of iron ore, and by controlling the temperature and the amount of reducing agent added, the hematite is partially or completely reduced. The resulting iron-based additive is returned to the Bayer process leaching, which can significantly improve the alumina leaching rate. Simultaneously, the titanium minerals in the obtained titanium-containing tailings exist in a specific phase or in the form of amorphous sodium titanate, exhibiting higher reactivity. This invention realizes the recycling and value-added utilization of solid wastes such as red mud, and has good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical solid waste resource utilization technology, specifically relating to an iron-based additive, its preparation method and application, and particularly to a method for preparing an iron-based additive for Bayer process leaching using red mud. Background Technology

[0002] Red mud is a major solid waste generated during alumina production, and traditional landfill and stockpiling disposal methods pose significant environmental risks. Globally, alumina production capacity based on high-iron trihydrate gibbsite continues to grow, leading to a significant increase in the proportion of high-iron red mud. In 2025, global high-iron bauxite production exceeded 250 million tons, with Guinea bauxite accounting for over 40% and showing an upward trend. The recovery of iron and titanium from high-iron, high-titanium red mud has attracted widespread research interest, and technological advancements mainly fall into two categories: hydrometallurgical and pyrometallurgical methods.

[0003] Hydrometallurgical methods involve leaching iron from red mud using acidic solutions such as hydrochloric acid, sulfuric acid, or oxalic acid. This method has low energy consumption and can achieve high metal recovery rates and grades. However, conditions favorable to iron dissolution can also promote the leaching of other elements, thus requiring complex and expensive pretreatment to remove interfering elements, which hinders its large-scale industrial application.

[0004] Pyrometallurgical processes typically use carbon-based reducing agents to obtain metallic iron or magnetite at high temperatures, making them suitable for the value-added utilization of high-iron red mud. Based on the reduction temperature, they can be divided into reduction smelting and solid-state reduction. The former melts the material into a liquid state at high temperatures, promoting mass transfer and facilitating iron polymerization. Solid-state reduction has a lower temperature than smelting (<1300℃), and after the reaction, grinding and beneficiation yield iron concentrate and tailings containing minerals such as titanium. Compared to hydrometallurgical processes, pyrometallurgical processes can obtain more valuable metallic iron, while enriching valuable elements such as titanium and aluminum in the tailings, reducing the difficulty of utilization and providing a direction for the large-scale disposal of high-iron red mud. However, high energy consumption is accompanied by high carbon emissions, and the titanium minerals in the tailings have low activity, requiring high-concentration acid leaching during the extraction process.

[0005] The non-lime Bayer process eliminates the addition of lime, reducing red mud at the source and significantly increasing the alumina leaching rate while simplifying the mineral composition of the red mud, resulting in red mud with an iron content approaching 55%. In addition to iron minerals, most red mud also contains 5-10% TiO2; achieving the separation and high-value utilization of iron and titanium compounds is of great significance for the sustainable development of the alumina industry. In the Bayer process's evaporation stage, the concentration of various salts in the solution continuously increases. When this concentration exceeds their solubility, crystallization occurs, and these sodium salt crystals are often discarded as waste.

[0006] The raw materials used in the production of reduced iron powder are iron ore powder and iron scale with high purity. A two-stage reduction process of carbothermal reduction + hydrogen reduction is often used to obtain iron powder with high metallization rate. The production cost is high, and when used as an additive for Bayer process leaching, it increases the production cost of alumina. Summary of the Invention

[0007] In view of at least one problem existing in the prior art, the present invention aims to provide an iron-based additive, its preparation method and application.

[0008] To achieve the objectives of this invention, the specific technical solution is as follows: A method for preparing an iron-based additive includes the following steps: Red mud, sodium salt, and reducing agent are mixed to obtain a mixture; The mixture is subjected to reduction roasting to obtain reduced clinker; The reduced clinker was subjected to magnetic separation to obtain an iron-based additive.

[0009] Preferably, the Fe2O3 content in the red mud is greater than 30%. More preferably, the red mud is one or more of low-temperature leaching, medium-temperature leaching, and high-temperature leaching red mud. More preferably, the red mud is high-iron red mud.

[0010] Preferably, the sodium salt is sodium salt crystallization residue precipitated during the Bayer process evaporation, and the sodium salt crystallization residue contains more than 40% Na2O (calculated as Na2O), and includes one or more of sodium carbonate, sodium sulfate, sodium oxalate, sodium fluoride, and sodium oxide.

[0011] Preferably, the reducing agent includes one or more of lignite, bituminous coal, graphite powder, and activated carbon.

[0012] Preferably, the mixture is obtained by ball milling.

[0013] Preferably, the amount of sodium salt added is 5 wt.% to 50 wt.% of the weight of the red mud.

[0014] Preferably, the amount of reducing agent added is 5 wt.% to 50 wt.% of the weight of the red mud.

[0015] Preferably, the reduction calcination temperature is 800°C to 1200°C, and the time is 20 minutes to 200 minutes.

[0016] Preferably, the magnetic separation adopts wet weak magnetic separation with a magnetic field strength of 0.03Tesla to 0.80Tesla.

[0017] Preferably, the reduction roasting is carried out in a rotary kiln, muffle furnace, or tunnel kiln.

[0018] Preferably, before the magnetic separation, the reduced clinker is crushed and ground until more than 70% passes through a 300-mesh sieve.

[0019] An iron-based additive, prepared by the above method, comprises one or more of metallic iron, Fe3O4 and FeO.

[0020] Preferably, the iron-based additive is added to the Bayer process leaching system; the amount of the iron-based additive added is 0.3 wt.% to 5.0 wt.% of the weight of bauxite, based on the total iron content.

[0021] Preferably, the Bayer dissolution temperature is between 200°C and 280°C.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses red mud, sodium salt (crystallization slag) and reducing agent stored in alumina plants as raw materials. The sodium salt significantly reduces the reduction temperature of iron minerals, and iron-based additives for Bayer process leaching can be produced at lower temperatures and energy consumption.

[0023] (2) The iron-based additive of the present invention is composed of one or more of Fe, FeO and Fe3O4. By controlling the activation effect of sodium salt and the temperature and the amount of reducing agent added, the phase composition of the iron-based additive can be regulated, so that it exhibits high efficiency and slow release characteristics in the Bayer process, which is conducive to the full dissolution of alumina.

[0024] (3) The sodium salt of this invention reacts with titanium minerals to generate highly active sodium titanate, which reacts with water during wet magnetic separation to form Na+. + / H + Ion exchange is used to recover the alkali, and the titanium-containing components after water immersion are further activated and can be used for subsequent extraction of titanium components.

[0025] (4) The red mud and sodium salt (crystallized slag) of this invention can both be derived from solid waste from alumina production, realizing their high-value utilization and further reducing production costs. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0027] A method for preparing an iron-based additive includes the following steps: Red mud, sodium salt, and reducing agent are mixed to obtain a mixture; The mixture is subjected to reduction roasting to obtain reduced clinker; The reduced clinker is subjected to magnetic separation to obtain iron concentrate.

[0028] In a specific embodiment, the Fe2O3 content in the red mud is greater than 30%, and it can be various red muds produced during the alumina production process, including but not limited to one or more of low-temperature leaching, medium-temperature leaching, and high-temperature leaching red muds. Preferably, high-iron red mud is used, which has a high iron content to facilitate the subsequent recovery and utilization of iron resources.

[0029] In a specific embodiment, the sodium salt is a sodium salt crystallization slag product precipitated during the Bayer process evaporation. The sodium salt crystallization slag contains more than 40% Na2O (calculated as Na2O) and includes one or more of sodium carbonate, sodium sulfate, sodium oxalate, sodium fluoride, and sodium oxide. The crystallization slag plays multiple roles in the reduction roasting process: on the one hand, the sodium salt in the crystallization slag can significantly reduce the reduction temperature of iron minerals and promote the reduction and migration of iron minerals; on the other hand, the sodium salt in the crystallization slag can react with titanium minerals in red mud, and by adjusting the proportion of sodium salt added, highly active titanates can be generated at a certain temperature; in addition, the organic matter in the crystallization slag decomposes during the reduction roasting process, and the Na2O can be returned to the Bayer process leaching process to achieve alkali recovery, while reducing the concentration of organic matter in the alumina system.

[0030] In a specific embodiment, the reducing agent includes one or more of lignite, bituminous coal, graphite powder, and activated carbon.

[0031] In a specific embodiment, a mixture is obtained by ball milling.

[0032] In a specific embodiment, the amount of sodium salt added is 5 wt.% to 50 wt.% of the weight of the red mud. When the amount of sodium salt added is too small, its effect on promoting the reduction and activation of titanium minerals is not obvious; when the amount of sodium salt added is too large, it may introduce too many impurities and affect the grade of iron concentrate.

[0033] In a specific embodiment, lignite, bituminous coal, graphite powder, and activated carbon serve as reducing agents to reduce iron minerals to Fe, Fe3O4, and FeO. Preferably, the amount of reducing agent added is 5 wt.% to 50 wt.% of the weight of the red mud. Insufficient reducing agent leads to incomplete reduction; excessive reducing agent wastes resources and may introduce excessive ash. A suitable amount of reducing agent ensures that Fe, Fe3O4, and FeO exist in a specific proportion in the reduced iron concentrate. Since the reduction of iron minerals proceeds from the outside in, the iron-based additive forms a multilayered product of metallic iron and low-valence oxides, maximizing the utilization rate of the additive.

[0034] In a specific embodiment, the reduction roasting temperature is preferably 800°C to 1200°C, and the time is preferably 20 minutes to 200 minutes. Under these conditions, iron minerals can be partially or completely reduced to metallic iron, while titanium minerals react with sodium salts to form highly reactive titanates.

[0035] In a specific embodiment, the magnetic separation preferably employs wet weak magnetic separation. Before magnetic separation, the reduced clinker is preferably crushed and ground to a fineness of over 70% to pass through a 300-mesh sieve. The magnetic field strength of the magnetic separator is preferably between 0.03 Tesla and 0.80 Tesla. Through magnetic separation, iron concentrate (i.e., iron-based additives) and titanium-rich tailings can be obtained.

[0036] This invention also provides an iron-based additive, prepared by the above method, whose phase comprises one or more of metallic iron, Fe3O4, and FeO. This iron-based additive, through activation of the crystallizing slag and control of temperature and lignite addition, can prepare a specific iron phase composition, exhibiting high efficiency and slow release characteristics during the Bayer process leaching.

[0037] In a specific embodiment, the present invention further provides the application of the above-mentioned iron-based additive in the Bayer process leaching. Adding the iron-based additive to the Bayer process leaching system can significantly improve the alumina leaching rate. The amount of the iron-based additive added, based on the total iron content, is preferably 0.3 wt.% to 5.0 wt.% of the weight of bauxite. The preferred temperature for the Bayer process leaching is 200°C to 280°C.

[0038] In a specific embodiment, the method of this invention returns the iron-based additive to the Bayer process leaching, achieving the same effect as secondary reduced iron powder, with leaching indicators even superior to those of secondary reduced powder. The iron-rich red mud obtained after leaching can then be used as raw material to further prepare iron-based additives and titanium-rich materials, realizing the recycling of red mud. Within the scope of this invention, only the consumption of the reducing agent needs to be considered; other raw materials are all derived from waste products of the Bayer process, and additional iron-based additives, alkali, and titanium-rich materials are also produced, thus demonstrating excellent application prospects.

[0039] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0040] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0041] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0042] like Figure 1 The diagram shows the process flow of the method of the present invention.

[0043] To demonstrate the applicability of this invention to red mud produced by different processes, two types of red mud were selected for experiments in the following examples: (1) red mud produced by a low-temperature leaching process of an alumina plant, with a total iron content (TFe) of 45.58% and (2) high-iron red mud produced by a non-lime Bayer process high-temperature leaching process of an alumina plant, with a total iron content (TFe) of 54.98%. The chemical composition of the two types of red mud is shown in Table 1. The sodium salt was produced by the Bayer process evaporation slag, whose main components were a mixture of sodium carbonate (60.70%), sodium sulfate (12.20%) and sodium oxalate (5.46%). The reducing agent was a commercially available product.

[0044] Table 1. Main chemical composition (%) of the red mud samples used in the experiment Example 1 100g of red mud (Red Mud No. 2, TFe=54.98%), 20g of crystallizing slag, and 20g of lignite were wet-milled in a planetary ball mill for 30min (400r / min, ball-to-material ratio 20:1). The obtained raw material was granulated and then reduced in a small rotary kiln at 1100℃ for 40min to obtain reduced clinker. The clinker was first crushed to 70% through a disc mill and passed through 300 mesh, and then subjected to wet magnetic separation under a magnetic field strength of 0.08 Tesla to obtain iron concentrate and tailings.

[0045] The obtained iron concentrate has an iron grade of 91.20% and an iron recovery rate of 93.20%; the tailings TiO2 grade is 21.90% and the tailings TiO2 recovery rate is 80.45%.

[0046] Take 30g of bauxite (Al2O3=43.10%, SiO2=2.15%, Fe2O3=26.40%, TiO2=2.05%), add the above iron concentrate (the amount added is 1wt.% of the weight of the bauxite based on the total iron content), and 220g / L Na2O k (α) k A sodium aluminate solution (3.0 g / L) was mixed and dissolved at 260°C for 60 min. The relative dissolution rate of alumina was 98.70%, and the yielded red mud contained 52.10% TFe.

[0047] Comparative Example 1 Take 100g of red mud (Red Mud 2#, TFe=54.98%) and 20g of lignite, without adding crystallizing slag, and other conditions are the same as in Example 1. The iron grade of the iron concentrate obtained by separation is 78.20%, and the iron recovery rate is 87.33%; the TiO2 grade of the tailings is 13.50%, and the TiO2 recovery rate of the tailings is 40.35%.

[0048] Take 30g of bauxite (Al2O3=43.10%, SiO2=2.15%, Fe2O3=26.40%, TiO2=2.05%), add the above iron concentrate (the amount added is 1wt.% of the weight of the bauxite based on the total iron content), and 220g / L Na2O k (α) k A sodium aluminate solution of 3.0 g / L was mixed and dissolved at 260°C for 60 min. The relative dissolution rate of alumina was 92.70%, and the yield of red mud was 48.70% TFe.

[0049] Example 2 Take 100g of red mud (red mud 2#, TFe=54.98%), 30g of crystallization slag and 20g of lignite, and carry out reduction roasting (reduction temperature 950℃, reduction time 200min) and magnetic separation in the same way as in Example 1.

[0050] The iron concentrate obtained had an iron grade of 85.20% and an iron recovery rate of 88.20%; the tailings had a TiO2 grade of 16.90% and a TiO2 recovery rate of 75.40%.

[0051] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 1.5 wt.% of the weight of the bauxite based on the total iron content), and 220g / L Na2O. k (α) k A sodium aluminate solution (3.0 g / L) was mixed and dissolved at 260°C for 60 min. The relative dissolution rate of alumina was 99.10%, and the yield of red mud (TFe=52.50%) was achieved.

[0052] Example 3 Take 100g of red mud (red mud 2#, TFe=54.98%), 15g of crystallization slag and 10g of lignite, and carry out reduction roasting in the same way as in Example 1 (reduction temperature 850℃, reduction time 180min), with a magnetic separation magnetic field strength of 0.30Tesla.

[0053] The obtained iron concentrate has an iron grade of 75.20% and an iron recovery rate of 83.60%; the tailings TiO2 grade is 15.40% and the tailings TiO2 recovery rate is 70.45%.

[0054] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 2wt.% of the weight of the bauxite based on the total iron content), and 210g / L Na2O. k (α) k A sodium aluminate solution (3.0 g / L) was mixed and dissolved at 260°C for 40 min. The relative dissolution rate of alumina was 96.90%, and the yield of red mud contained 49.10% TFe.

[0055] Example 4 Take 100g of red mud (red mud 2#, TFe=54.98%), 25g of crystallization slag and 15g of lignite, and carry out reduction roasting in the same way as in Example 1 (reduction temperature 1000℃, reduction time 20min), with a magnetic separation magnetic field strength of 0.10Tesla.

[0056] The iron concentrate obtained had an iron grade of 89.20% and an iron recovery rate of 94.20%; the tailings TiO2 grade was 18.90% and the tailings TiO2 recovery rate was 75.45%.

[0057] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 1 wt.% of the weight of the bauxite based on the total iron content), and 230g / L Na2O. k (α) k A sodium aluminate solution (3.0 g / L) was mixed and dissolved at 255°C for 60 min. The relative dissolution rate of alumina was 98.80%, and the yield of red mud was 51.75% TFe.

[0058] Example 5 100g of red mud (Red Mud No. 2, TFe=54.98%), 5g of crystallizing slag, and 20g of lignite were wet-milled in a planetary ball mill for 30min (400r / min, ball-to-material ratio 20:1). The obtained raw material was granulated and then reduced in a small rotary kiln at 1200℃ for 40min to obtain reduced clinker. The clinker was first crushed to 70% through a disc mill until it passed through 300 mesh, and then subjected to wet magnetic separation under a magnetic field strength of 0.08 Tesla to obtain iron concentrate and tailings.

[0059] The obtained iron concentrate has an iron grade of 90.10% and an iron recovery rate of 93.21%; the tailings have a TiO2 grade of 23.12% and a TiO2 recovery rate of 83.40%.

[0060] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 1 wt.% of the weight of the bauxite based on the total iron content), and 220g / L Na2O. k (α) k A sodium aluminate solution (3.0 g / L) was mixed and dissolved at 260°C for 60 min. The relative dissolution rate of alumina was 97.80%, and the yield of red mud was 51.45% TFe.

[0061] Example 6 100g of red mud (Red Mud No. 2, TFe=54.98%), 50g of crystallizing slag, and 20g of lignite were wet-milled in a planetary ball mill for 30min (400r / min, ball-to-material ratio 20:1). The obtained raw material was granulated and then reduced in a small rotary kiln at 1000℃ for 40min to obtain reduced clinker. The clinker was first crushed to 70% through a disc mill and passed through 300 mesh, and then subjected to wet magnetic separation under a magnetic field strength of 0.08 Tesla to obtain iron concentrate and tailings.

[0062] The iron concentrate obtained had an iron grade of 89.30% and an iron recovery rate of 90.28%; the tailings had a TiO2 grade of 16.30% and a TiO2 recovery rate of 77.25%.

[0063] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 1 wt.% of the weight of the bauxite based on the total iron content), and 220g / L Na2O. k (α) k A sodium aluminate solution of 3.0 g / L was mixed and dissolved at 260°C for 60 min. The relative dissolution rate of alumina was 92.35%, and the yield of red mud was 48.40% TFe.

[0064] Example 7 Take 100g of red mud (red mud 1#, TFe=45.58%), 30g of crystallization slag and 25g of lignite, and carry out reduction roasting in the same way as in Example 1 (reduction temperature 1200℃, reduction time 40min), with a magnetic separation magnetic field strength of 0.10Tesla.

[0065] The iron concentrate obtained had an iron grade of 92.25% and an iron recovery rate of 94.50%; the tailings had a TiO2 grade of 14.90% and a TiO2 recovery rate of 84.45%.

[0066] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 2wt.% of the weight of the bauxite based on the total iron content), and 230g / L Na2O. k (α) k A sodium aluminate solution (3.0 g / L) was mixed and dissolved at 255°C for 60 min. The relative dissolution rate of alumina was 98.60%, and the yield of red mud (TFe=52.80%) was achieved.

[0067] Example 8 Take 100g of red mud (red mud 1#, TFe=45.58%), 10g of crystallization slag and 30g of lignite, and carry out reduction roasting in the same way as in Example 1 (reduction temperature 1000℃, reduction time 60min), with a magnetic separation magnetic field strength of 0.80Tesla.

[0068] The obtained iron concentrate has an iron grade of 87.25% and an iron recovery rate of 99.30%; the tailings have a TiO2 grade of 15.20% and a TiO2 recovery rate of 62.31%.

[0069] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 1.5 wt.% of the weight of the bauxite based on the total iron content), and 230g / L Na2O. k (α) k A sodium aluminate solution (3.0 g / L) was mixed and dissolved at 265°C for 60 min. The relative dissolution rate of alumina was 97.90%, and the yield of red mud (TFe=50.30%) was obtained.

[0070] Comparative Example 2 Take 100g of red mud (red mud 1#, TFe=45.58%) and 50g of lignite, without adding crystallizing slag, and carry out reduction roasting (reduction temperature 800℃) in the same way as in Example 1, with a magnetic separation magnetic field strength of 0.30Tesla.

[0071] The obtained iron concentrate has an iron grade of 65.15% and an iron recovery rate of 70.30%; the tailings have a TiO2 grade of 10.75% and a TiO2 recovery rate of 45.30%.

[0072] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 1 wt.% of the weight of the bauxite based on the total iron content), and 220g / L Na2O. k (α) k A sodium aluminate solution of 3.0 g / L was mixed and dissolved at 260°C for 60 min. The relative dissolution rate of alumina was 90.35%, and the yield of red mud was 47.25% TFe.

[0073] Comparative Example 3 100g of red mud (Red Mud No. 2, TFe=54.98%), 60g of crystallizing slag, and 20g of lignite were wet-milled in a planetary ball mill for 30min (400r / min, ball-to-material ratio 20:1). The obtained raw material was granulated and then reduced in a small rotary kiln at 900℃ for 60min to obtain reduced clinker. The clinker was first crushed to 70% through a disc mill until it passed through 300 mesh, and then subjected to wet magnetic separation under a magnetic field strength of 0.10 Tesla to obtain iron concentrate and tailings.

[0074] The iron concentrate obtained had an iron grade of 85.30% and an iron recovery rate of 79.28%; the tailings had a TiO2 grade of 13.25% and a TiO2 recovery rate of 50.10%.

[0075] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 1 wt.% of the weight of the bauxite based on the total iron content), and 220g / L Na2O.k (α) k A sodium aluminate solution (3.0 g / L) was mixed and dissolved at 260°C for 60 min. The relative dissolution rate of alumina was 89.25%, and the yielded red mud contained 47.10% TFe.

[0076] Example 9 Take 100g of red mud (TFe=52.10%) obtained from the dissolution in Example 1, mix it with 10g of crystallization slag and 30g of lignite, ball mill it, and carry out reduction roasting in the same way as in Example 1 (reduction temperature 1000℃, reduction time 40min), and the magnetic separation magnetic field strength is 0.08Tesla.

[0077] The obtained iron concentrate has an iron grade of 90.25% and an iron recovery rate of 92.40%; the tailings have a TiO2 grade of 22.20% and a TiO2 recovery rate of 83.50%.

[0078] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 1.0 wt.% of the weight of the bauxite based on the total iron content), and 220g / L Na2O. k (α) k A sodium aluminate solution (3.0 g / L) was mixed and dissolved at 260°C for 60 min. The relative dissolution rate of alumina was 98.90%, and the yield of red mud (TFe=52.70%) was obtained.

[0079] Example 10 Take 100g of red mud (TFe=50.30%) obtained from the dissolution in Example 8, mix it with 7.5g of crystallized slag and 30g of lignite, ball mill it, and carry out reduction roasting in the same way as in Example 1 (reduction temperature 1100℃, reduction time 30min), and the magnetic separation magnetic field strength is 0.08Tesla.

[0080] The obtained iron concentrate has an iron grade of 91.05% and an iron recovery rate of 90.40%; the tailings have a TiO2 grade of 20.85% and a TiO2 recovery rate of 85.30%.

[0081] Take 30g of bauxite as in Example 1, add the above-mentioned iron concentrate (the amount added is 1.5 wt.% of the weight of the bauxite based on the total iron content), and 210g / L Na2O. k (α) k A sodium aluminate solution (2.80 g / L) was mixed and dissolved at 265°C for 60 min. The relative dissolution rate of alumina was 98.40%, and the yield of red mud (TFe=51.90%) was achieved.

[0082] The key data of the above embodiments and comparative examples are summarized in the table below: Table 3 The specific analysis is as follows: (1) In Comparative Example 1 without sodium salt, the iron concentrate grade was 78.20%, the iron recovery rate was 87.33%, the TiO2 recovery rate of tailings was 40.35%, and the alumina leaching rate was 92.70%. In Example 1, after adding 20g of sodium salt, the grades of all indicators increased to 91.20%, 93.20%, 80.45%, and 98.70%, respectively. In Comparative Example 2 without sodium salt, the iron concentrate grade was only 65.15%, while in Examples 7 and 8, after adding sodium salt, the grade all reached over 87%. This indicates that sodium salt can significantly promote the reduction of iron minerals and the activation of titanium minerals.

[0083] (2) In Examples 1-4, the sodium salt addition ranged from 15 to 30 g, and the alumina dissolution rate was above 96.9%, with the best effect observed at 20-30 g, significantly higher than the 92.70% of Comparative Example 1. In Examples 7-8, the sodium salt additions were 30 g and 10 g, respectively, and the alumina dissolution rates were 98.60% and 97.90%, respectively. This indicates that good results can be obtained with sodium salt additions ranging from 10 to 30 g.

[0084] (3) After adding sodium salt, the TiO2 grade of the tailings increased from 7.12% in the original ore to 15-22%, with a recovery rate of 62-85%, which effectively enriched titanium and facilitated subsequent extraction.

[0085] (4) In Examples 9 and 10, iron-based additives were prepared again using the red mud after dissolution in Examples 1 and 8 as raw materials. The iron concentrate grades were 90.25% and 91.05%, and the alumina dissolution rates were 98.90% and 98.40%, respectively. These results were comparable to the performance of the newly prepared additives, indicating that the red mud after dissolution can be reused as raw material, thus realizing the recycling of red mud.

[0086] (5) The examples covered reduction temperatures of 800~1200℃, reduction times of 20~200min, and magnetic field strengths of 0.08~0.80T, all of which achieved good separation and dissolution effects, indicating that the method of the present invention has a wide range of adaptability to process parameters.

[0087] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims

1. A method for preparing an iron-based additive, characterized in that, Includes the following steps: Red mud, sodium salt, and reducing agent are mixed to obtain a mixture; The mixture is subjected to reduction roasting to obtain reduced clinker; The reduced clinker was subjected to magnetic separation to obtain an iron-based additive.

2. The method according to claim 1, characterized in that, The sodium salt is sodium salt crystallization residue precipitated during the Bayer process evaporation. The sodium salt crystallization residue has a Na2O content greater than 40% and contains one or more of sodium carbonate, sodium sulfate, sodium oxalate, sodium fluoride, and sodium oxide. The reducing agent includes one or more of lignite, bituminous coal, graphite powder, and activated carbon; The red mud contains more than 30% Fe2O3 and is one or more of the following: low-temperature leaching, medium-temperature leaching, and high-temperature leaching red mud.

3. The method according to claim 1 or 2, characterized in that, The mixture was obtained by ball milling. The amount of sodium salt added is 5 wt.% to 50 wt.% of the weight of the red mud. The amount of reducing agent added is 5 wt.% to 50 wt.% of the weight of the red mud.

4. The method according to claim 1, characterized in that, The reduction calcination temperature is 800℃ to 1200℃, and the time is 20 minutes to 200 minutes.

5. The method according to claim 1, characterized in that, The magnetic separation employs wet weak magnetic separation with a magnetic field strength of 0.03Tesla to 0.80Tesla.

6. The method according to claim 1, characterized in that, Before the magnetic separation, the reduced clinker is crushed and ground until more than 70% passes through a 300-mesh sieve.

7. An iron-based additive, characterized in that, Prepared by the method of any one of claims 1 to 6, wherein the phase comprises one or more of metallic iron, Fe3O4 and FeO.

8. The application of the iron-based additive according to claim 7 in the Bayer process leaching, characterized in that, The iron-based additive is added to the Bayer process dissolution system.

9. The application according to claim 8, characterized in that, The amount of the iron-based additive added is from 0.3 wt.% to 5.0 wt.% of the total iron content of the bauxite.

10. The application according to claim 8, characterized in that, The Bayer process is used to dissolve substances at temperatures ranging from 200°C to 280°C.

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