Process for synchronously and efficiently recovering aluminum oxide and iron ore concentrate based on solid waste synergistic reduction of red mud

Abstract

The invention belongs to the technical field of industrial solid waste treatment and resource utilization, and discloses a process for synchronously and efficiently recycling aluminum oxide and iron ore concentrate based on solid waste synergistic reduction of red mud. The process comprises the following steps: mixing red mud, iron-containing carbon industrial dust, a sodium source additive and a solid carbonaceous reducing agent, and roasting to obtain a roasted product; the roasted product is subjected to wet grinding to obtain slurry, and the slurry is sequentially subjected to water leaching, cooling and filtering to obtain filtrate and filter residues; performing magnetic separation on the filter residues to obtain iron ore concentrate; introducing CO2 into the filtrate for carbonation decomposition to obtain aluminum hydroxide; and sequentially washing, drying and calcining the aluminum hydroxide to obtain the aluminum oxide. The recovery rate of the iron ore concentrate obtained through the technology is 98.7%, and the iron grade reaches up to 86.4%; the purity of the aluminum oxide is 98.91%. The process has good economic benefit potential while realizing efficient separation of iron and aluminum, and provides an important economic basis for industrial application.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste treatment and resource utilization technology, and in particular to a process for the simultaneous and efficient recovery of alumina and iron concentrate based on the synergistic reduction of red mud by solid waste. Background Technology

[0002] Red mud is a highly alkaline industrial solid waste generated during the production of alumina from bauxite. It exhibits various colors depending on its iron oxide content and is characterized by high water content and the presence of harmful components such as heavy metals. The large-scale accumulation of red mud has caused serious environmental problems and even endangers the survival of plants and animals; therefore, the comprehensive utilization of red mud has received considerable attention.

[0003] Currently, the main methods for disposing of red mud are relatively extensive and traditional, with drawbacks such as significant environmental impact, high energy consumption, and high disposal costs. These methods require specific qualifications and permits, and existing disposal models are no longer sufficient to meet the needs, necessitating the development of new disposal technologies. At present, my country's red mud disposal technology faces bottlenecks such as difficulties in efficient dealkali removal, low extraction efficiency of valuable elements, and low conversion rate of laboratory results. Core patents are monopolized by foreign companies, and the high cost of technology import hinders the development of comprehensive utilization of red mud.

[0004] Despite the significant importance of red mud resource utilization and the existence of numerous studies and practices, its large-scale, high-value, and full-chain resource utilization process still faces a series of severe challenges. First, red mud has a complex composition and phase structure, with valuable components existing primarily in the form of chemically stable compounds. These compounds are extremely fine in size and tightly interlocked, making extraction difficult, resulting in low separation efficiency and high costs. Second, existing resource utilization technologies generally suffer from high processing costs. Red mud itself has low value density, limiting the market value of the processed products and hindering economic feasibility, thus restricting the industrialization and promotion of these technologies. Third, the strong alkalinity and potentially harmful components of red mud pose a long-term environmental risk of soil and groundwater pollution during storage. Resource utilization technologies must address these environmental hazards, increasing process complexity and treatment costs. Secondary pollution could negate the environmental benefits. Fourth, current red mud treatment technologies are relatively isolated, focusing on single-component disposal or developing processes solely based on the properties of red mud itself. They fail to achieve complementary components and energy through co-processing with other bulk solid wastes, nor do they systematically achieve simultaneous and efficient recovery of multiple components, resulting in low overall resource utilization efficiency. Therefore, developing a green and low-carbon integrated technology that can work synergistically across waste systems and achieve multi-component synergistic recycling has become an urgent problem for those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of red mud, such as large stockpiles, low resource utilization rate, and high environmental risks.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a process for the simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste, comprising the following steps: S1. Red mud, iron-containing carbon industrial dust, sodium source additives and solid carbonaceous reducing agent are mixed and then roasted to obtain roasted products. S2. The roasted product is wet-ground to obtain a slurry. The slurry is then sequentially soaked in water, cooled, and filtered to obtain a filtrate and a filter residue. S3. Magnetic separation of the filter residue yields iron concentrate; CO2 is introduced into the filtrate for carbonation decomposition to obtain aluminum hydroxide. S4. Aluminum hydroxide is obtained by sequentially washing, drying and calcining aluminum hydroxide.

[0007] Furthermore, in S1, the amount of iron-containing carbon industrial dust is 15-55% of the mass of red mud, and the iron-containing carbon industrial dust includes one or more of converter ash, electric furnace dust collector ash and blast furnace ash.

[0008] Furthermore, in S1, the amount of sodium source additive is 10-30% of the mass of red mud, and the sodium source additive includes one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and sodium sulfate.

[0009] Furthermore, in S1, the amount of solid carbonaceous reducing agent is 5-15% of the mass of red mud, and the solid carbonaceous reducing agent includes one or more of coke powder, petroleum coke, coal powder, carbon black, graphite and biochar.

[0010] Furthermore, in S1, the calcination temperature is 600~1350℃, and the calcination time is 15~100min.

[0011] Furthermore, in S2, the solid-liquid ratio of wet grinding is 1:3~7.

[0012] Furthermore, in step S2, the immersion time is 1-3 hours, the immersion temperature is 60-100℃, and the final cooling temperature is ≤40℃.

[0013] Furthermore, in step S3, the temperature of magnetic separation is 60~100℃.

[0014] Furthermore, in step S3, during carbonation decomposition, CO2 is stopped when pH=9.

[0015] Furthermore, in step S4, the drying temperature is 100~120℃; the calcination temperature is 800~1200℃, and the calcination time is 1~3h.

[0016] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: 1. Achieve collaborative disposal of solid waste and promote the development of a circular economy. This invention utilizes two types of industrial solid waste—red mud and iron-containing carbon industrial dust—as core raw materials, employing a co-roasting process to recycle them. On one hand, red mud, as a source of alumina and iron, fundamentally alleviates the problem of its storage. On the other hand, the fixed carbon in the iron-containing carbon industrial dust can act as a reducing agent, replacing traditional fossil fuels and reducing the additional input of reducing agents. This process not only disposes of large quantities of red mud and iron-containing carbon industrial dust, reducing the land resources occupied by solid waste storage, but also avoids environmental problems such as soil alkalization and groundwater pollution caused by solid waste storage, truly achieving the recycling of waste resources and aligning with the national circular economy development strategy.

[0017] 2. Simultaneous and efficient recycling of both high-value products significantly improves resource utilization. This invention achieves the simultaneous and efficient recovery of iron and aluminum, two valuable elements, from red mud through a process design of "roasting-wet grinding-water leaching-magnetic separation-carbonation". Under optimal process conditions, the recovery rate of iron concentrate can reach 98.7%, and the total iron grade is as high as 86.4%, meeting the quality requirements of iron concentrate for steel smelting; the purity of alumina is increased to 98.91%, reaching the grade of high-quality metallurgical grade alumina. Compared with traditional red mud single iron or aluminum extraction processes, this invention significantly improves the comprehensive utilization rate of resources, avoids the waste of valuable elements, and realizes the high-value utilization of red mud.

[0018] 3. The process design is scientific and reasonable, and the product quality is stable and controllable. This invention employs a process sequence that prioritizes water immersion over magnetic separation, effectively preventing the loss of soluble aluminum salts during magnetic separation and significantly improving the alumina recovery rate. Simultaneously, by performing multi-stage combined washing of aluminum hydroxide, the content of impurities such as sodium in the alumina product is significantly reduced, ensuring product purity. Furthermore, this invention clarifies the reasonable ranges for key process parameters such as the dosage of raw materials and additives, roasting temperature, and roasting time. The process conditions are highly controllable, easy to operate, and can stably produce high-quality iron concentrate and alumina products, providing reliable technical support for industrial production.

[0019] 4. It has significant economic and environmental benefits and broad prospects for industrialization. This invention offers a low-cost operating process, and under laboratory conditions, the treatment of red mud can generate substantial net profits, including revenue from the sale of iron concentrate and alumina, as well as income related to solid waste disposal. Compared to traditional red mud landfilling and incineration, this invention eliminates the need for high solid waste disposal costs and the cost of purchasing reducing agents, while also creating significant economic value through product conversion. In terms of environmental benefits, this invention avoids the environmental risks associated with red mud stockpiling at the source. Furthermore, the process uses non-fossil energy instead of traditional fossil fuels as a reducing agent, effectively reducing carbon emissions during production, which aligns perfectly with the national "dual carbon" target requirements and possesses significant potential for industrialization and promotion.

[0020] 5. The final residue generated after extracting iron and aluminum elements in this invention can be fully utilized. This step is the core key to achieving the "near-zero emission" goal and maximizing economic benefits. This invention uses a combination of XRD phase identification, XRF / ICP component analysis, and national standard leaching toxicity testing to conduct a comprehensive characteristic analysis of the residue, accurately defining its solid waste properties and ensuring the compliance and controllability of subsequent disposal. Based on the test results, a diversified resource utilization path can be systematically explored for the residue as a building material raw material (e.g., for the production of cement, bricks, and ceramsite), roadbed filling material, and soil conditioner. This constructs a closed-loop disposal system for red mud, encompassing "extraction of valuable elements—efficient utilization of residue," eliminating the environmental burden of red mud at its source and realizing the full-chain value transformation of solid waste resources. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 The XRD pattern of the iron concentrate obtained in Example 1; Figure 2 SEM images of the iron concentrate obtained in Example 1 at different scales; Figure 3 The image shows the EDS spectrum of the iron concentrate obtained in Example 1, where Figure A is the elemental surface distribution diagram and Figure B is the energy spectrum diagram. Figure 4 The particle size distribution diagram of the iron concentrate obtained in Example 1 is shown. Figure 5 The images show the physical images of Al(OH)3 and Al2O3 obtained in Example 1, where (a) is Al(OH)3 and (b) is Al2O3. Figure 6 The images show the morphology of the calcined products obtained in Examples 1-5. Figure 7 The graphs show the effect of total iron grade and iron recovery rate of the iron concentrate obtained in Examples 1-5; Figure 8 The graph shows the effect of total iron grade and iron recovery rate of the iron concentrate obtained in Examples 1 and 6-9. Figure 9 The graphs show the effect of total iron grade and iron recovery rate of the iron concentrate obtained in Examples 1 and 10-13. Figure 10 The graph shows the effect of the total iron grade and iron recovery rate of the iron concentrate obtained in Examples 1 and 14-17. Detailed Implementation

[0022] This invention provides a process for the simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste, comprising the following steps: S1. Red mud, iron-containing carbon industrial dust, sodium source additives and solid carbonaceous reducing agent are mixed and then roasted to obtain roasted products. S2. The roasted product is wet-ground to obtain a slurry. The slurry is then sequentially soaked in water, cooled, and filtered to obtain a filtrate and a filter residue. S3. Magnetic separation of the filter residue yields iron concentrate; CO2 is introduced into the filtrate for carbonation decomposition to obtain aluminum hydroxide. S4. Aluminum hydroxide is obtained by sequentially washing, drying and calcining aluminum hydroxide.

[0023] In this invention, in step S1, the amount of iron-containing carbon industrial dust is 15-55% of the mass of red mud, preferably 25-45%, and more preferably 35%. The iron-containing carbon industrial dust includes one or more of converter ash, electric furnace dust collector ash, and blast furnace ash.

[0024] In this invention, in step S1, the amount of sodium source additive is 10-30% of the mass of red mud, preferably 15-25%, and the sodium source additive includes one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and sodium sulfate.

[0025] In this invention, in step S1, the amount of solid carbonaceous reducing agent is 5-15% of the mass of red mud, preferably 10%, and the solid carbonaceous reducing agent includes one or more of coke powder, petroleum coke, coal powder, carbon black, graphite and biochar.

[0026] In this invention, in step S1, the calcination temperature is 600~1350℃, preferably 800~1200℃; the calcination time is 15~100min, preferably 25~75min.

[0027] In this invention, in step S2, the solid-liquid ratio of wet grinding is 1:3 to 7, preferably 1:4.

[0028] In this invention, in step S2, the immersion time is 1-3 hours, preferably 1.5-2.5 hours, and more preferably 2 hours; the immersion temperature is 60-100°C, preferably 70-90°C, and more preferably 80°C; and the final cooling temperature is ≤40°C.

[0029] In this invention, the temperature of magnetic separation in step S3 is 60~100℃, preferably 70~90℃, and more preferably 80℃.

[0030] In this invention, during S3, when carbonation decomposition is carried out, CO2 is stopped when pH=9.

[0031] In this invention, in step S4, the drying temperature is 100~120℃, preferably 110℃; the calcination temperature is 800~1200℃, preferably 900~1100℃, and more preferably 1000℃; the calcination time is 1~3h, preferably 2h.

[0032] In this invention, step S4 involves four stages of washing: the first stage uses water at 60-80°C for immersion-filtration; the second stage uses dilute ammonia solution at 5-7% concentration for immersion-filtration; the third stage uses dilute acetic acid solution at 1-3% concentration for immersion-filtration; and the fourth stage uses water at 60-80°C for immersion-filtration. The first stage removes most of the soluble sodium salts; the second stage inhibits the dissolution of Al(OH)3 and converts residual NaAlO2 into Al(OH)3, while NH4+... + Replaceable Na + The third washing stage neutralizes and removes the ammonium ions (NH4+) remaining from the second stage. + The process involves several steps: first, converting the NH4+ into soluble ammonium acetate for removal; second, selectively dissolving trace amounts of amphoteric metal impurities (hydroxides) that may co-precipitate under weakly acidic conditions, thereby further improving the chemical purity of the Al(OH)3 product; and third, washing until the filtrate is neutral to completely remove NH4+. + CH3COO - And sodium salts.

[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1 Red mud, blast furnace ash (35% of the red mud mass), and Na2CO3 (25% of the red mud mass) were mixed evenly. Coal powder (10% of the red mud mass) was spread on the surface of the mixture, and then placed in a muffle furnace. The temperature was raised to 1200℃ at a rate of 10℃ / min and roasted for 75 minutes to obtain the roasted product.

[0035] After the roasted product is pulverized and wet-ground into a slurry, it is first soaked in water. The slurry is then soaked in water at 80℃ for 2.5 hours under magnetic stirring and heating at a solid-liquid ratio of 1:4. After cooling to 40℃, it is filtered to reduce SiO3. 2- The leaching of the red mud was investigated. During filtration, CaO (5% of the red mud mass) was added to remove silicon and titanium. The mixture was magnetically stirred for 40 min, allowed to stand, and then filtered to obtain filter residue and filtrate containing mainly NaAlO2 and a small amount of Na2SiO3.

[0036] Iron concentrate is extracted from the filter residue by magnetic separation (magnetic field strength 125 mT).

[0037] CO2 gas was slowly introduced into the filtrate under magnetic stirring at 80℃, with pH monitored in real time, until the pH reached 9 and gas introduction was stopped to obtain Al(OH)3. First, the filtrate was pre-washed with 80℃ hot deionized water using an immersion-filtration method to remove most of the soluble sodium salts. Then, it was washed twice with 6.25% dilute ammonia water in the same manner to inhibit the dissolution of Al(OH)3 and convert residual NaAlO2 into Al(OH)3, while NH4+ was also used. + Replaceable Na + Next, the solution is impregnated with 1% dilute acetic acid and filtered to further remove sodium ions. The acid neutralizes any residual ammonia or alkali, forming soluble salts that are easy to wash off. Finally, the solution is washed with 80°C hot water until the filtrate is neutral, thoroughly removing NH4. + CH3COO - And sodium salts.

[0038] Finally, the washed Al(OH)3 was dried at 120℃ and then calcined at 1000℃ (heating rate 5℃ / min) for 2 hours to obtain high-purity Al2O3 product.

[0039] The elemental contents of the iron concentrate obtained in this embodiment are shown in Table 1. Table 1 shows that the total iron (TFe) content is 86.4%, the SiO2 content is 2.84%, the Na2O content is 1.30%, the K2O content is 0.36%, and the S and P contents are 0.33% and 0.035%, respectively. Compared with the magnetite (C60) standard, the TFe content of this iron concentrate is higher than the standard range (60–63%), while the SiO2, S, and P contents are all within the allowable range of the standard.

[0040] Table 1 Chemical composition of iron concentrate

[0041] The XRD pattern of the iron concentrate obtained in this embodiment is as follows: Figure 1As shown, only diffraction peaks of the Fe phase appeared in the spectrum, and no peaks of the iron oxide phase were detected. The positions of each Fe peak perfectly matched those of the standard card PDF#06-0696, indicating that the iron in the iron concentrate exists primarily in the form of elemental iron (Fe). The results indicate that the high-temperature roasting and magnetic separation process can effectively enrich iron and improve the grade of iron concentrate.

[0042] The SEM images of the iron concentrate at different scales obtained in this embodiment are as follows: Figure 2 As shown, the refined iron ore is generally massive with a smooth surface and clear boundaries. At 2 μm, it can be clearly seen that the refined iron ore particles are composed of smaller nanoparticles, with clear particle edges, many structural layers, and significant adhesion between particles.

[0043] The EDS spectrum of the iron concentrate obtained in this embodiment is as follows: Figure 3 As shown in the figure, Figure A is the elemental distribution diagram and Figure B is the energy spectrum diagram. The iron content in the refined iron ore has increased compared with that before roasting, indicating that high-temperature roasting and magnetic separation can improve the total iron grade of the product and achieve the effect of enriching iron elements.

[0044] The particle size distribution diagram of the iron concentrate obtained in this embodiment is as follows: Figure 4 As shown, the iron concentrate exhibits a good normal distribution in terms of particle size, mainly concentrated in the range of 200–500 nm. The calculated average particle size is 325 nm. Comparing the test results with the particle size technical standard for magnetite C60, it was found that the particle size of this batch of iron concentrate meets the standard requirements (magnetite C60 particle size requirement <-0.075 mm).

[0045] The Al(OH)3 and Al2O3 obtained in this embodiment are as follows: Figure 5 As shown in the figure, (a) is Al(OH)3 and (b) is Al2O3. The chemical composition of Al2O3 is shown in Table 2. From Table 2, it can be seen that the purity of Al2O3 is above 97%, and can reach up to 98.91%, while the Na2O content is below 0.18%.

[0046] Table 2 Chemical composition of Al2O3

[0047] Example 2 Same as Example 1, except that the calcination temperature is 600°C.

[0048] Example 3 Same as Example 1, except that the calcination temperature is 800°C.

[0049] Example 4 Same as Example 1, except that the calcination temperature is 1000°C.

[0050] Example 5 Same as Example 1, except that the calcination temperature is 1350°C.

[0051] Figure 6 The images show the morphology of the calcined products obtained in Examples 1-5. Figure 7 The graphs show the effect of total iron grade and iron recovery rate of the iron concentrate obtained in Examples 1-5. Figure 6 and 7 It can be seen that the roasting temperature systematically affects the occurrence and selectivity of iron in red mud by regulating the reduction reaction process and the microstructure of the product. At 1200℃, the reaction completeness and product porosity are optimally matched, achieving simultaneous optimization of iron recovery rate (98.7%) and concentrate grade (86.4%).

[0052] Example 6 Same as Example 1, except that the roasting time is 15 min.

[0053] Example 7 Same as Example 1, except that the roasting time is 25 min.

[0054] Example 8 Same as Example 1, except that the roasting time is 50 min.

[0055] Example 9 Same as Example 1, except that the roasting time is 100 min.

[0056] Figure 8 This is a graph showing the effect of total iron grade and iron recovery rate of the iron concentrate obtained in Examples 1 and 6-9. Figure 8 As can be seen, the iron recovery rate remained at a high level (91.2%~99.8%) throughout the entire roasting time range. Even under the shorter condition of 15 min, the recovery rate reached 98.2%, indicating that the roasting-magnetic separation method adopted in this invention can quickly and efficiently convert iron minerals in red mud into a magnetic phase and achieve effective recovery. As the time was extended to 25 min, the recovery rate further increased to a peak of 99.8%, indicating that appropriately extending the time is beneficial to the complete mineral conversion and enhanced magnetism. It is worth noting that the recovery rate slightly decreased to 91.2% at 50 min, which is related to the crystal transformation of some iron minerals or the brief formation of a weakly magnetic intermediate phase at this time point; while as the time was further extended to 75 and 100 min, the recovery rate remained stable at a high level of 98.7%, showing that the process has good recovery stability over a longer period of time.

[0057] Unlike the recovery rate, which exhibits a "high-level fluctuation and overall stability" characteristic, the TFe grade of iron concentrate shows a distinct trend of "rapid increase at first, then reaching a peak, and then slightly decreasing" with prolonged roasting time. When the roasting time increased from 15 min to 75 min, TFe significantly increased from 50.0% to 86.4%. This substantial increase indicates that a longer roasting time helps to more thoroughly separate iron minerals from gangue impurities such as aluminum and silicon, promoting the purification and enrichment of the iron phase. However, when the roasting time was extended to 100 min, TFe slightly decreased to 82.4%. This is because excessive heat caused a small amount of iron to recombine with impurity elements, or caused slight sintering and encapsulation of fine-grained iron phase, thus slightly reducing the concentrate grade.

[0058] Example 10 Similar to Example 1, except that the amount of blast furnace ash used is 15% of the mass of red mud.

[0059] Example 11 Similar to Example 1, except that the amount of blast furnace ash used is 25% of the mass of red mud.

[0060] Example 12 Similar to Example 1, except that the amount of blast furnace ash used is 45% of the mass of red mud.

[0061] Example 13 Similar to Example 1, except that the amount of blast furnace ash used is 55% of the mass of red mud.

[0062] Figure 9 This is a graph showing the effect of total iron grade and iron recovery rate of the iron concentrate obtained in Examples 1 and 10-13. Figure 9 It can be seen that the iron recovery rate increases monotonically with the increase of blast furnace ash content, continuously rising from 87.7% when the addition amount is 15% to 99.4% when it is 55%. This trend clearly shows that increasing the addition amount of blast furnace ash can effectively enhance the reducing atmosphere of the system. The fixed carbon and some combustibles rich in blast furnace ash provide more abundant and longer-lasting reducing gases (such as CO) during the roasting process, which promotes the full conversion of insoluble iron oxides (such as Fe2O3) in red mud into strongly magnetic iron phases (such as Fe3O4 or elemental iron) that are easier to recover by magnetic separation, thereby significantly improving the overall iron recovery efficiency.

[0063] The TFe grade of the concentrate exhibits a parabolic trend, first increasing and then decreasing, with the change in blast furnace ash content. When the addition amount increases from 15% to 35%, the TFe grade significantly increases from 74.0% to 86.4%, reaching its peak. At this stage, the appropriate reducing agent content not only promotes the efficient reduction and enrichment of iron, but may also facilitate the separation and purification of the iron phase from gangue minerals such as aluminosilicates by regulating melt properties or reaction pathways.

[0064] Example 14 Similar to Example 1, except that the amount of Na2CO3 used is 10% of the mass of the red mud.

[0065] Example 15 Similar to Example 1, except that the amount of Na2CO3 used is 15% of the mass of the red mud.

[0066] Example 16 Similar to Example 1, except that the amount of Na2CO3 used is 20% of the mass of the red mud.

[0067] Example 17 Similar to Example 1, except that the amount of Na2CO3 used is 30% of the mass of the red mud.

[0068] Sodium carbonate plays two main roles in the sintering process: First, as an alkaline flux, it can react with aluminum-containing minerals (such as aluminosilicates) to generate soluble sodium aluminate, creating favorable conditions for subsequent aluminum leaching; Second, sodium carbonate decomposes at high temperatures to produce Na2O, which can lower the melting point of the system, promote the reduction of iron oxides and the aggregation and growth of metallic iron, thereby improving the iron recovery rate and the grade of iron concentrate.

[0069] Figure 10 This is a graph showing the effect of total iron grade and iron recovery rate of the iron concentrate obtained in Examples 1 and 14-17. Figure 10 It can be seen that with the increase of sodium carbonate content, both iron recovery rate and iron concentrate grade (TFe%) show a trend of first increasing and then decreasing. Under the condition of sodium carbonate content of 25%, the alkalinity and reducing atmosphere of the system are optimally matched, iron oxides are almost completely reduced to metallic iron, and iron particles are fully aggregated and grown, forming loose magnetic agglomerates that are easy to dissociate. Under this condition, the iron recovery rate is as high as 98.7%, and the total iron grade also jumps to 86.4%, achieving simultaneous optimization of efficient iron recovery and high-grade enrichment.

[0070] In summary, this invention, with the resource utilization of red mud as its core, achieves the dual goals of reducing and rendering harmless solid waste, possessing both significant environmental and social value. 1. Reduction: Significantly reduce the amount of red mud stockpiles, gradually releasing the large amount of land resources occupied by stockpiles and enabling reuse; recover valuable elements such as iron and aluminum from red mud as secondary resources to replace primary mineral mining, reducing the consumption of natural resources and ecological damage to mines; promote the alumina industry to shift from a linear "resource-product-waste" model to a circular model, reduce resource input across the entire industrial chain, and contribute to the green transformation of the industry. Simultaneously, the project creates technical and management positions throughout the entire chain, optimizes the local employment structure, provides technical solutions and equipment, and enhances the industry's competitiveness.

[0071] 2. Harmlessness: Red mud is transformed from end-of-life waste into intermediate raw material, eliminating environmental risks such as alkaline leachate pollution, heavy metal migration, and dust caused by long-term stockpiling from the source. This completely resolves the pollution concerns of surrounding residents, mitigates NIMBY effects and community conflicts, and improves the harmonious relationship between enterprises and the local community. Through low-carbon process design and clean energy application, carbon emissions throughout the entire life cycle are reduced, contributing to the achievement of the "dual carbon" goals.

[0072] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste, characterized in that, Includes the following steps: S1. Red mud, iron-containing carbon industrial dust, sodium source additives and solid carbonaceous reducing agent are mixed and then roasted to obtain roasted products. S2. The roasted product is wet-ground to obtain a slurry. The slurry is then sequentially soaked in water, cooled, and filtered to obtain a filtrate and a filter residue. S3. Magnetic separation of the filter residue yields iron concentrate; CO2 is introduced into the filtrate for carbonation decomposition to obtain aluminum hydroxide. S4. Aluminum hydroxide is obtained by sequentially washing, drying and calcining aluminum hydroxide.

2. The process for simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste according to claim 1, characterized in that, In S1, the amount of iron-containing carbon industrial dust is 15-55% of the mass of red mud, and the iron-containing carbon industrial dust includes one or more of converter ash, electric furnace dust collector ash and blast furnace ash.

3. The process for simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste according to claim 2, characterized in that, The amount of sodium source additive in S1 is 10-30% of the mass of red mud, and the sodium source additive includes one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and sodium sulfate.

4. The process for simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste according to claim 3, characterized in that, In step S1, the amount of solid carbonaceous reducing agent is 5-15% of the mass of red mud, and the solid carbonaceous reducing agent includes one or more of coke powder, petroleum coke, coal powder, carbon black, graphite and biochar.

5. The process for simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste according to any one of claims 1 to 4, characterized in that, In step S1, the calcination temperature is 600~1350℃ and the calcination time is 15~100min.

6. The process for simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste according to claim 5, characterized in that, In S2, the solid-liquid ratio of wet grinding is 1:3~7.

7. The process for simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste, as described in claim 2 or 6, is characterized in that... In step S2, the immersion time is 1-3 hours, the immersion temperature is 60-100℃, and the final cooling temperature is ≤40℃.

8. The process for simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste, as described in claim 2, 3, or 6, is characterized in that... In step S3, the temperature of magnetic separation is 60~100℃.

9. The process for simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste according to claim 8, characterized in that, In step S3, during carbonation decomposition, CO2 is stopped when pH=9.

10. The process for simultaneous and efficient recovery of alumina and iron concentrate based on the co-reduction of red mud by solid waste according to claim 9, characterized in that, In step S4, the drying temperature is 100~120℃; the calcination temperature is 800~1200℃; and the calcination time is 1~3h.

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