Method for separating and recovering iron, aluminum and titanium from red mud based on multistage vertical electrophoresis acid-base regeneration technology

Abstract

The invention discloses a method for separating and recycling iron, aluminum and titanium in red mud based on multistage vertical electrophoresis acid-base regeneration. According to the method, red mud recycling and a flue gas desulfurization process are coupled, and online controllable regeneration of an acid-base reagent and gradient selective extraction of elements are realized. The method is characterized in that regeneration of acid liquor and alkali liquor of the multi-stage vertical electrophoretic separation unit is combined with gradient leaching-selective precipitation, so that cyclic utilization of sulfuric acid / alkali is realized, consumption of additional reagents is reduced, and high-selectivity recovery of aluminum, iron and titanium is realized; the method is high in process closed-loop degree, prominent in concept of treating waste with waste and remarkable in resource utilization and environmental governance synergistic benefit. The method is suitable for large-scale red mud treatment and flue gas desulfurization co-production, and has good engineering popularization value.

Description

Technical Field

[0001] This invention belongs to the field of separation and purification technology in the resource utilization of solid waste, and relates to a method for separating and recovering iron, aluminum and titanium from red mud based on multi-stage vertical electrophoresis acid-base regeneration technology. Background Technology

[0002] Red mud is a highly alkaline solid waste generated during alumina production, rich in various metallic elements. With soaring global demand for aluminum alloys, annual red mud production has reached approximately 180 million tons, with accumulated stockpiles exceeding 4 billion tons. However, the current recycling rate of red mud is less than 4%, with the vast majority still disposed of through open-air dumping or landfilling, posing a long-term and severe pollution threat to soil, water bodies, and the ecological environment. Although red mud is considered waste, its rich metallic resources (valuable metals such as iron, aluminum, and titanium account for 40%–80% of the total) make it an important associated mineral source, potentially alleviating the pressure on increasingly depleted natural mineral resources. For its occurrence form, acid leaching is an effective method for extracting these metals, characterized by its simple process and high recovery rate, enabling high-value metal recovery while reducing environmental risks. However, this method still faces a core bottleneck in industrial-scale applications: the enormous consumption of inorganic acids leads to high costs and secondary pollution, significantly restricting the resource recovery benefits of red mud.

[0003] To overcome the bottleneck of acid and alkali consumption and achieve recycling, vertical electrophoresis technology has shown revolutionary potential. Following green chemistry principles, this technology effectively suppresses ion diffusion by filling the separation channel with a fine supporting medium to form a porous network structure, using electromigration as the core driving force to achieve highly efficient separation. Under the action of an applied electric field, anions and cations in the solution migrate in opposite directions and accumulate near the electrodes, thereby achieving in-situ one-step regeneration of acid and alkali, constructing a green and efficient acid-alkali recycling system. Compared with traditional membrane separation technologies (such as membrane electrodialysis and bipolar membrane electrodialysis), vertical electrophoresis does not require ion exchange membranes, fundamentally avoiding long-standing industry problems such as membrane fouling, scaling, and concentration polarization, significantly reducing operating and maintenance costs. It is particularly suitable for high-salt systems, demonstrating excellent stability and economy. This technology has excellent process compatibility and can be coupled with flue gas desulfurization and acid leaching of metals. By introducing desulfurization wastewater into the vertical electrophoresis system, acid can be efficiently regenerated and reused for leaching desulfurization slag or metal-containing solids, thus constructing a self-circulating acid-alkali pathway within the system. This innovative coupling model can not only significantly reduce acid and alkali consumption during the red mud resource utilization process, but also provide a new technical approach for the efficient separation and recycling of polymetals. Summary of the Invention

[0004] This invention proposes a method for separating and recovering iron, aluminum, and titanium from red mud based on multi-stage vertical electrophoresis acid-base regeneration technology. This method combines wet desulfurization of red mud with an acid-base regeneration-stepwise acid leaching-alkali extraction process. Multi-stage vertical electrophoresis drives the directional electromigration of sodium and sulfate ions in a sodium sulfate solution, regenerating sulfuric acid and sodium hydroxide. Furthermore, the system's internal material circulation creates a self-sustaining acid-base supply system, significantly reducing the consumption of external acid and alkali reagents. By adjusting the operating voltage and number of stages of the vertical electrophoresis system, the concentrations of the regenerated acid and alkali can be flexibly controlled to meet the different acidity requirements for the stepwise leaching of valuable metals from red mud, creating conditions for subsequent pH-controlled precipitation to obtain high-purity single-metal products. Overall, this method constructs a technological path of "treating waste with waste and turning waste into treasure," transforming red mud from an environmental burden into a high-value resource, enhancing the economic benefits of resource recovery while strengthening the ecological sustainability of the process.

[0005] The technical solution of this invention: A method for separating and recovering iron, aluminum, and titanium from red mud based on multi-stage vertical electrophoresis acid-base regeneration technology includes the following steps: (1) Flue gas desulfurization: Red mud is prepared into a slurry and reacted with sulfur-containing industrial flue gas in a wet desulfurization reaction to fix sulfur dioxide in the flue gas; after the wet desulfurization reaction, solid-liquid separation is performed to obtain desulfurization liquid mainly composed of sodium sulfate and desulfurization tailings rich in iron, aluminum, and titanium; (2) Acid-base regeneration: The desulfurization liquid obtained in step (1) is continuously fed into the first-stage vertical electrophoresis separation unit of the multi-stage vertical electrophoresis system, and under the action of an external electric field perpendicular to the direction of liquid flow, the desulfurization liquid is regenerated. Sodium ions in the sulfur solution migrate towards the cathode and accumulate on the cathode side, causing sulfate ions to migrate towards the anode and accumulate on the anode side. Simultaneously, hydroxide ions and hydrogen ions generated by the electrode reaction form sodium hydroxide solution on the cathode side and sulfuric acid solution on the anode side, respectively, thus achieving in-situ salt conversion in the desulfurization solution and simultaneous regeneration of acid and alkali solutions. The regenerated alkali solution from the first-stage vertical electrophoretic separation unit enters the next-stage vertical electrophoretic separation unit in the alkali branch, and the regenerated acid solution from the first-stage vertical electrophoretic separation unit enters the next-stage vertical electrophoretic separation unit in the acid branch; subsequent stages... Vertical electrophoretic separation units operate in cascades in the same manner, causing the regenerated alkali solution to be concentrated stage by stage along the alkali branch and the regenerated acid solution to be concentrated stage by stage along the acid branch. When the acid concentration produced by a certain stage of vertical electrophoretic separation unit in the acid branch does not reach the set value, the cathode-side product stream of that stage of vertical electrophoretic separation unit flows back to the inlet of the same stage of vertical electrophoretic separation unit, mixes with the feed from the previous stage of vertical electrophoretic separation unit in the acid branch, and then re-enters the same stage of vertical electrophoretic separation unit for separation, while the anode-side product stream is sent to the next stage of vertical electrophoretic separation unit in the acid branch for further concentration; when a certain stage of vertical electrophoretic separation unit in the alkali branch... When the concentration of the alkaline solution produced by the vertical electrophoresis separation unit does not reach the set value, the product stream on the anode side of the vertical electrophoresis separation unit is returned to the inlet end of the vertical electrophoresis separation unit, mixed with the feed from the previous vertical electrophoresis separation unit in the alkali branch, and then re-enters the vertical electrophoresis separation unit for separation. Meanwhile, the product stream on the cathode side is sent to the next vertical electrophoresis separation unit in the alkali branch for further concentration until a regenerated acid solution and a regenerated alkaline solution with a concentration that meets the requirements of the subsequent stepwise acid leaching and stepwise precipitation processes are obtained; (3) Stepwise acid leaching: First, the concentration obtained in step (2) is 1~1.5 The desulfurized tailings obtained in step (1) were leached with a regenerated acid solution of mol / L at room temperature to selectively extract aluminum and obtain an aluminum-rich leachate. The remaining solid after leaching was then leached with a regenerated sulfuric acid solution of not less than 4 mol / L at 100~120 ℃ to obtain a leachate rich in iron and titanium. (4) Stepwise precipitation: a) The pH of the aluminum-rich leachate was adjusted to 4~4.5 by adding a regenerated alkali solution. After the impurities were removed by precipitation, the pH was adjusted to 5~6 to obtain aluminum hydroxide. b) The leachate rich in iron and titanium was leached with an equimolar amount of EDTA to adjust the pH to 1.5~2 and react at 80~100 ℃ for 2 hours to precipitate metatitanic acid; then adjust the pH to 3~3.5 at room temperature to remove impurities, and continue to adjust the pH to ≥ 12 to precipitate iron hydroxide; (5) Material reflux: the regenerated sulfuric acid obtained in step (2) is reused in the stepwise acid leaching in step (3), and the regenerated alkali solution obtained in step (2) is reused in the stepwise pH adjustment precipitation in step (4); the remaining mother liquor, mainly sodium sulfate, after aluminum precipitation is refluxed to the first-stage vertical electrophoresis separation unit of the multi-stage vertical electrophoresis system and used as feed for acid and alkali regeneration; the remaining solution containing free EDTA and residual alkali after iron and titanium precipitation is reused in the iron and titanium precipitation in step (4). Precipitation process; Sodium sulfate crystals precipitated due to the recycling of EDTA and the enrichment of salt in the system are dissolved or prepared and then returned to the multi-stage vertical electrophoresis separation unit for regeneration; thus forming a closed-loop cycle process of "desulfurization liquid / sodium sulfate solution - multi-stage vertical electrophoresis regeneration acid and alkali - regenerated acid for leaching - regenerated alkali for precipitation - mother liquor reflux regeneration"; (6) Product calcination: The aluminum hydroxide, iron hydroxide and metatitanic acid precipitates obtained in step (4) are calcined to obtain alumina, iron oxide and titanium oxide products.

[0006] The multi-stage vertical electrophoresis system is composed of two or more cascaded vertical electrophoresis separation units, preferably as follows: Figure 4 The cascaded structure shown; wherein each stage of vertical electrophoretic separation unit can adopt, as shown in the figure Figure 2 and Figure 3 The structure shown includes a power supply section, a vertical electrophoresis separation chamber, a sample input section, a sample collection section, and a gas collection section. The first-stage vertical electrophoresis separation unit is used to initially separate the desulfurization liquid, which is mainly composed of sodium sulfate, into regenerated acid and regenerated alkali. Starting from the second-stage vertical electrophoresis separation unit, it is divided into acid and alkali branches that operate independently but in coordination. The vertical electrophoresis separation units at each stage of the acid branch are connected in series according to the product flow direction on the anode side, and the vertical electrophoresis separation units at each stage of the alkali branch are connected in series according to the product flow direction on the cathode side. The acid or alkali output from the previous stage is used as the feed for the corresponding branch of the next stage, so as to achieve the separate-path progressive enrichment and concentration of acid and alkali. The power supply section includes a regulated DC power supply 1, whose positive and negative terminals are respectively connected to the anode plate 2 and the cathode plate 3, and is used to provide a stable electric field perpendicular to the liquid flow direction for the vertical electrophoresis separation chamber 4. The vertical electrophoresis separation chamber 4 is a rectangular cavity structure with two evenly distributed water outlets 5 at the bottom and a sample inlet 6 at the top. Gas collection ports 7 are respectively located near the anode and cathode. Baffles 8 are installed between the two water outlets 5 and the sample inlet 6 and the gas collection port 7. The vertical electrophoretic separation chamber 4 is filled with quartz sand with a particle size of 0.01 to 3 mm as a support medium 9; The vertical electrophoresis separation chamber 4 has condensation chambers 10 attached to its front and rear sides respectively, forming a sandwich structure. The condensation chamber 10 is provided with a condensation chamber inlet 11 and a condensation chamber outlet 12 for circulating cooling medium to maintain temperature stability during the separation process. In addition, the vertical electrophoresis separation chamber 4 is provided with supports 13 at both ends to facilitate the placement and fixation of the equipment. The sample input section includes a sample solution storage container 14 and a single-channel peristaltic pump 15. The sample solution is transported to the inlet 6 at the top of the vertical electrophoresis separation chamber 4 via the single-channel peristaltic pump 15. The sample collection section includes an outlet water collection container 16 and a multi-channel peristaltic pump 17. The solutions from each outlet are collected by the multi-channel peristaltic pump 17 at the same flow rate. The total outlet water flow rate is equal to the sample inlet flow rate to maintain the stability of the liquid level in the separation chamber. The gas collection section includes a gas collection bag 18 and a gas transmission pipe 19. The gas transmission pipe 19 is connected to the gas collection port 7 and the gas collection bag 18 respectively. During operation, the liquid level in the separation chamber is lower than the interface of the gas transmission pipe.

[0007] Furthermore, the operating voltage, influent flow rate, residence time, reflux ratio, and cooling intensity of each stage of the vertical electrophoretic separation unit can be adjusted according to the acid and alkali concentrations required for subsequent aluminum leaching, iron-titanium leaching, and stepwise precipitation, so as to achieve flexible control of the regenerated acid and alkali concentrations.

[0008] The beneficial effects of this invention are as follows: By introducing multi-stage vertical electrophoresis technology, a self-sustaining acid-base cycle system is constructed within the system, significantly reducing the consumption of external acid and base reagents; by adjusting the working voltage and operating stage of the electrophoresis system, the concentration of regenerated acid and base can be flexibly controlled to meet the differentiated acidity conditions required for the stepwise leaching of valuable metals such as iron, aluminum, and titanium in red mud, achieving efficient metal separation; combined with selective EDTA complexation and stepwise pH control of regenerated base, high-purity single metal products can be obtained, improving the quality and value of resource recovery; overall, a closed-loop process path of "treating waste with waste and turning waste into treasure" is formed, transforming red mud from an environmental burden into a high-value resource, enhancing the ecological sustainability of the entire process while improving economic benefits. Attached Figure Description

[0009] Figure 1 This is a process flow diagram of the separation and recovery of iron, aluminum, and titanium from red mud based on multi-stage vertical electrophoretic acid-base regeneration proposed in this invention.

[0010] Figure 2 This is a schematic diagram of the overall structure of the vertical electrophoresis system used in this invention.

[0011] Figure 3 This is a schematic diagram showing the overall structure and partial disassembly of the vertical electrophoresis separation chamber in this invention.

[0012] Figure 4 This is a schematic diagram of the operation mode and cascade configuration of the multi-stage vertical electrophoresis system in this invention.

[0013] In the diagram: 1-Regulated DC power supply; 2-Anode plate; 3-Cathode plate; 4-Vertical electrophoresis separation chamber; 5-Water outlet; 6-Sample inlet; 7-Gas collection port; 8-Baffle; 9-Support medium; 10-Condensation chamber; 11-Condensation chamber inlet; 12-Condensation chamber outlet; 13-Support; 14-Sample solution storage container; 15-Single-channel peristaltic pump; 16-Water collection container; 17-Multi-channel peristaltic pump; 18-Gas collection bag; 19-Gas transfer tube. Detailed Implementation

[0014] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0015] Example 1 Experimental investigation of the acid neutralization ability of red mud: Red mud from an alumina plant in Henan Province, China, was used as raw material to investigate its acid neutralization and sulfur fixation capabilities. The red mud was dried and crushed to below 1 mm, then reacted with 0.5 M H₂SO₄ at 60℃ and a liquid-to-solid ratio of 6 L / kg for 6 h to simulate an industrial flue gas desulfurization process. After the reaction, solid-liquid separation was performed, and the components of the filtrate and filter residue were analyzed and compared with the original red mud. The main ionic composition of the filtrate is shown in Table 1. The chemical composition comparison between the original red mud and the filter residue after reaction is shown in Table 2.

[0016] Table 1 Ionic composition of the filtrate

[0017] Table 2 Comparison of the composition of raw red mud and filter residue

[0018] According to the data in Tables 1 and 2, the Na in the filtrate + With SO4 2- The high content and molar ratio (close to 1:2) indicate that sodium sulfate is the main component. Simultaneously, the significantly decreased Na₂O content and markedly increased SO₃ content in the filter residue confirm that the red mud achieved sodium dissolution and sulfur fixation during acid neutralization. Furthermore, valuable components such as Fe₂O₃, Al₂O₃, and TiO₂ were further enriched in the filter residue, providing a raw material basis for subsequent metal separation and extraction. These experimental results confirm the ability of red mud to fix sulfur and generate sodium sulfate solution under acidic conditions, indicating its suitability for desulfurization of sulfur-containing flue gas and providing a feasible basis for subsequent electrophoretic regeneration of acid and alkali and metal recovery processes.

[0019] Example 2 Acid-base regeneration performance evaluation of multi-stage vertical electrophoretic separation unit: A peristaltic pump was used to control the injection flow rate of the sodium sulfate filtrate, creating a vertically downward laminar flow and maintaining a flow rate of 0.2 mL / min at each outlet. A ruthenium-iridium electrode was connected to a DC regulated power supply, applying a stable electric field of 15 V perpendicular to the liquid flow direction. During operation, the separation temperature was maintained at 25–35 °C through condensate circulation. After 12 hours of operation, effluent samples were collected, and the regenerated acid solution near the anode area and the regenerated alkali solution near the cathode area were respectively guided to the next electrophoresis unit for further concentration; effluent that did not reach the target concentration was returned to the previous stage for reprocessing. This process was repeated four times, and the concentrations and purities of the acids and alkalis obtained after each stage are shown in Table 3.

[0020] Table 3. Acid-base concentration and purity of the effluent from each stage of treatment.

[0021] The results showed that vertical electrophoresis could effectively regenerate sodium sulfate filtrate into sulfuric acid and sodium hydroxide, and the concentration and purity of the regenerated acid and alkali significantly increased with the increase of the number of operating stages. After four stages of treatment, the sulfuric acid concentration reached 8.81 mol / L and the sodium hydroxide concentration reached 7.65 mol / L, with a purity exceeding 99.9%, fully meeting the different acidity requirements for the stepwise leaching of valuable metals from red mud.

[0022] Example 3 Stepwise extraction of metals from tailings after acid-base neutralization of red mud: The tailings leaching experiment was conducted in a 1000 mL three-necked flask equipped with a mechanical stirrer, constant temperature control (±0.5 ℃), and reflux condenser to prevent solvent loss during the reaction. The tailings of the red mud after acid-base neutralization were dried at 80℃, crushed, and sieved to a particle size ≤1 mm for stepwise acid leaching extraction.

[0023] First, aluminum was extracted: 600 mL of 1 mol / L H2SO4 was added to the reaction flask, along with 100 g of tailings at room temperature. The mixture was stirred at 300 r / min for 12 h. After the reaction, the residue was separated by vacuum filtration to obtain an aluminum-rich leachate. Then, iron and titanium were extracted: the solid residue after aluminum extraction was dried and crushed at 80 ℃, and 100 g of the residue was mixed with 600 mL of 4 mol / L H2SO4. The mixture was stirred at 110 ℃ for 12 h, and the residue was also filtered to obtain an iron- and titanium-rich leachate. The main metal components of the two leachates are shown in Table 4.

[0024] Table 4 Composition of aluminum-rich and iron-rich and titanium-rich leachates

[0025] The results showed that aluminum could be preferentially leached under low acid concentration (1 mol / L H2SO4) conditions, with an aluminum concentration of 16.85 g / L in the aluminum-rich leachate, while iron and titanium remained in the residue. Subsequently, high acid concentration (4 mol / L H2SO4) high-temperature leaching was used, and iron and titanium were effectively extracted, with iron concentration reaching 15.19 g / L and titanium concentration reaching 2.89 g / L. This achieved highly selective separation of aluminum from iron and titanium, providing an important foundation for subsequent precipitation and purification.

[0026] Example 4 Fractional precipitation of metals in metal leaching solutions This example, based on the aluminum-rich leachate and iron- and titanium-rich leachate obtained in Example 3, demonstrates the high-purity separation and recovery of aluminum, iron, and titanium through stepwise precipitation experiments. All precipitation experiments were conducted in 100 mL three-necked flasks equipped with mechanical stirrers, temperature control devices (temperature control accuracy ±0.5 ℃), and reflux condensers to prevent solvent evaporation.

[0027] Take 50 mL of aluminum-rich leaching solution and place it in a three-necked flask. Slowly add the NaOH solution regenerated from Example 2 while stirring at room temperature to adjust the pH of the system to 4.0. Continue stirring for 1 hour to allow impurities to precipitate completely, and then filter to remove the impurities. Subsequently, continue to add NaOH solution dropwise to the filtrate to precisely adjust the pH to 5.0. After stirring for 2 hours, allow it to stand and age, and a white aluminum hydroxide precipitate will precipitate. After vacuum filtration and washing with deionized water, the precipitate is dried in a freeze dryer for 12 hours to obtain solid aluminum hydroxide.

[0028] Take 50 mL of iron- and titanium-rich leachate, add EDTA in an amount equal to the molar amount of iron in the leachate, and stir at 90 °C until completely dissolved. Adjust the pH of the system to 1.5 with regenerated NaOH solution, and continue the reaction at 90 °C for 1.5 hours. After the reaction is complete, cool to room temperature and filter to obtain a white metatitanic acid precipitate. Adjust the pH of the filtrate after titanium precipitation to 3.0 with NaOH solution at room temperature, stir for 1 hour to precipitate residual impurities, and remove by filtration. Subsequently, further adjust the pH of the filtrate to 12.0 to form a reddish-brown ferric hydroxide precipitate, which is then filtered and washed after stirring and aging. The resulting metatitanic acid and ferric hydroxide precipitates are washed with deionized water and then placed together with the aforementioned aluminum hydroxide precipitate in a freeze dryer for 12 hours.

[0029] The three dried precipitates were calcined in a muffle furnace: metatitanic acid was calcined at 500 °C for 2 hours to obtain titanium oxide; ferric hydroxide was calcined at 600 °C for 2 hours to obtain ferric oxide; and aluminum hydroxide was calcined at 1400 °C for 2 hours to obtain aluminum oxide. The composition of the three products obtained by ICP-MS analysis is shown in Table 5.

[0030] Table 5. Component percentages in iron, aluminum, and titanium precipitates

[0031] By employing a stepwise process of "preferential precipitation of aluminum through pH adjustment—selective precipitation of titanium through EDTA complexation—further pH adjustment for iron precipitation," combined with precise control of the regenerated alkali solution, high-purity alumina, iron oxide, and titanium oxide products were successfully separated and prepared from the mixed acid leaching solution. This process verifies the feasibility and superiority of the method of this invention in the separation and high-value utilization of valuable metals in red mud.

Claims

1. A method for separating and recovering iron, aluminum, and titanium from red mud based on multi-stage vertical electrophoretic acid-base regeneration technology, characterized in that, Includes the following steps: (1) Flue gas desulfurization: Red mud is prepared into a slurry and reacted with sulfur-containing industrial flue gas in a wet desulfurization reaction to fix sulfur dioxide in the flue gas; after the wet desulfurization reaction, solid-liquid separation is performed to obtain desulfurization liquid mainly composed of sodium sulfate and desulfurization tailings rich in iron, aluminum and titanium; (2) Acid-base regeneration: The desulfurization liquid obtained in step (1) is continuously fed into the first-stage vertical electrophoresis separation unit of a multi-stage vertical electrophoresis system. The first-stage vertical electrophoresis separation unit is used to initially separate the desulfurization liquid mainly composed of sodium sulfate into regenerated acid liquid and regenerated alkali liquid. Starting from the secondary vertical electrophoresis separation unit, it is divided into acid branch and alkali branch, which are independent but operate in coordination. The vertical electrophoresis separation units of each level in the acid branch are connected in series according to the product flow direction on the anode side, and the vertical electrophoresis separation units of each level in the alkali branch are connected in series according to the product flow direction on the cathode side. The acid or alkali solution output from the previous level is used as the feed for the corresponding branch of the next level, so as to realize the separate-path stepwise concentration of acid and alkali solution until the regenerated acid and alkali solution with the concentration required by the subsequent stepwise acid leaching and stepwise precipitation process are obtained. (3) Stepwise acid leaching: First, the regenerated acid solution with a concentration of 1~1.5 mol / L obtained in step (2) is used to leach the desulfurized tailings obtained in step (1) under normal temperature conditions to selectively extract aluminum and obtain aluminum-rich leachate; then, the remaining solid after leaching is leached with regenerated sulfuric acid with a concentration of not less than 4 mol / L at 100~120 ℃ to obtain leachate rich in iron and titanium; (4) Stepwise precipitation: a) Add regenerated alkali solution to the aluminum-rich leachate to adjust the pH to 4~4.5, and after removing impurities by precipitation, continue to adjust the pH to 5~6 to obtain aluminum hydroxide by precipitation; b) Add EDTA with an equimolar amount of iron to the leachate rich in iron and titanium, adjust the pH to 1.5~2 and react at 80~100 ℃ for 2 hours to obtain metatitanic acid by precipitation; Then, the pH was adjusted to 3-3.5 at room temperature to remove impurities, and then the pH was adjusted to ≥ 12 to precipitate ferric hydroxide; (5) Material return: The regenerated sulfuric acid obtained in step (2) was returned to the stepwise acid leaching in step (3), and the regenerated alkali solution obtained in step (2) was returned to the stepwise pH adjustment precipitation in step (4); the mother liquor remaining after aluminum precipitation, mainly composed of sodium sulfate, was returned to the first-stage vertical electrophoresis separation unit of the multi-stage vertical electrophoresis system and used as feed for acid and alkali regeneration; the solution containing free EDTA and residual alkali remaining after iron and titanium precipitation was returned to the iron and titanium in step (4). Precipitation process; Sodium sulfate crystals precipitated as EDTA is recycled and salts are enriched in the system are dissolved or prepared and then returned to the multi-stage vertical electrophoresis separation unit for regeneration; This forms a closed-loop cycle process of "desulfurization liquid / sodium sulfate solution - multi-stage vertical electrophoresis regeneration acid and alkali - regenerated acid for leaching - regenerated alkali for precipitation - mother liquor reflux regeneration"; (6) Product calcination: The aluminum hydroxide, iron hydroxide and metatitanic acid precipitates obtained in step (4) are calcined to obtain aluminum oxide, iron oxide and titanium oxide products.

2. The method for separating and recovering iron, aluminum, and titanium from red mud based on multi-stage vertical electrophoresis acid-base regeneration technology according to claim 1, characterized in that, The specific implementation process of acid-base regeneration in step (2) is as follows: The desulfurization liquid obtained in step (1) is continuously fed into the first-stage vertical electrophoresis separation unit of the multi-stage vertical electrophoresis system. Under the action of an external electric field perpendicular to the direction of liquid flow, sodium ions in the desulfurization liquid migrate towards the cathode and accumulate on the cathode side, while sulfate ions migrate towards the anode and accumulate on the anode side. Simultaneously, hydroxide ions and hydrogen ions generated by the electrode reaction form sodium hydroxide solution on the cathode side and sulfuric acid solution on the anode side, respectively, thereby realizing the in-situ conversion of salts in the desulfurization liquid and the synchronous regeneration of acid and alkali solutions. The regenerated alkali solution obtained from the first-stage vertical electrophoresis separation unit enters the next-stage vertical electrophoresis separation unit of the alkali branch, and the regenerated acid solution obtained from the first-stage vertical electrophoresis separation unit enters the next-stage vertical electrophoresis separation unit of the acid branch. Subsequent vertical electrophoresis separation units operate in cascade in the same manner, so that the regenerated alkali solution is concentrated step by step along the alkali branch, and the regenerated acid solution is concentrated step by step along the acid branch. When a certain acid branch When the concentration of the acid solution produced by the first-stage vertical electrophoresis separation unit does not reach the set value, the cathode-side product stream of this stage of vertical electrophoresis separation unit flows back to the inlet end of the same stage of vertical electrophoresis separation unit. After mixing with the feed from the previous stage of vertical electrophoresis separation unit in the acid branch, it re-enters the same stage of vertical electrophoresis separation unit for separation. Meanwhile, the anode-side product stream is sent to the next stage of vertical electrophoresis separation unit in the acid branch for further concentration. When the concentration of the alkali solution produced by a certain stage of vertical electrophoresis separation unit in the alkali branch does not reach the set value, the anode-side product stream of this stage of vertical electrophoresis separation unit flows back to the inlet end of the same stage of vertical electrophoresis separation unit. After mixing with the feed from the previous stage of vertical electrophoresis separation unit in the alkali branch, it re-enters the same stage of vertical electrophoresis separation unit for separation. Meanwhile, the cathode-side product stream is sent to the next stage of vertical electrophoresis separation unit in the alkali branch for further concentration, until regenerated acid solution and regenerated alkali solution with concentrations that meet the requirements of subsequent stepwise acid leaching and stepwise precipitation processes are obtained.

3. The method for separating and recovering iron, aluminum, and titanium from red mud based on multi-stage vertical electrophoretic acid-base regeneration technology according to claim 1, characterized in that, The multi-stage vertical electrophoresis system is composed of two or more cascaded vertical electrophoresis separation units. Each stage of the vertical electrophoresis separation unit includes a power supply section, a vertical electrophoresis separation chamber, a sample input section, a sample collection section, and a gas collection section.

4. The method for separating and recovering iron, aluminum, and titanium from red mud based on multi-stage vertical electrophoresis acid-base regeneration technology according to claim 1, characterized in that, The power supply section includes a regulated DC power supply, whose positive and negative terminals are connected to the anode plate and the cathode plate, respectively, to provide a stable electric field perpendicular to the liquid flow direction for the vertical electrophoresis separation chamber. The vertical electrophoresis separation chamber is a rectangular cavity structure with two evenly distributed water outlets at the bottom and a sample inlet at the top. Gas collection ports are located near the anode and cathode, respectively. Baffles are installed between the two water outlets, the sample inlet, and the gas collection ports. The vertical electrophoretic separation chamber is filled with quartz sand with a particle size of 0.01 to 3 mm as a support medium; The vertical electrophoresis separation chamber has condensation chambers attached to its front and rear sides to form a sandwich structure. The condensation chamber is equipped with a condensation chamber inlet and a condensation chamber outlet for circulating cooling medium to maintain temperature stability during the separation process. In addition, the vertical electrophoresis separation chamber is equipped with supports at both ends to facilitate the placement and fixation of the equipment; The sample input section includes a sample solution storage container and a single-channel peristaltic pump. The sample solution is delivered to the inlet at the top of the vertical electrophoresis separation chamber via the single-channel peristaltic pump. The sample collection section includes an outlet water collection container and a multi-channel peristaltic pump. The solutions from each outlet are collected by the multi-channel peristaltic pump at the same flow rate. The total outlet water flow rate is equal to the sample inlet flow rate to maintain the stability of the liquid level in the separation chamber. The gas collection section includes a gas collection bag and a gas transmission pipe. The gas transmission pipe is connected to the gas collection port 7 and the gas collection bag respectively. During operation, the liquid level in the separation chamber is lower than the interface of the gas transmission pipe.

Images