A method for preventing silica gel from being produced in red mud leachate

Abstract

The present invention relates to a method for preventing the generation of silica gel in red mud leachate. The red mud is dried, crushed, ground, and sieved. The powdered red mud is dissolved in water to produce a slurry, which is allowed to stand and delaminated to obtain a lower layer of dealkalized red mud concentrated slurry. The concentrated red mud slurry is then reselected to obtain red mud concentrate and red mud tailings. The red mud concentrate is further treated by bioflocculation and precipitation to obtain a desiliconized red mud concentrate. The desiliconized red mud concentrate is then subjected to chemical leaching or bioleaching. An H2O2 solution is added to the leaching system. After leaching, the leached liquid is allowed to stand or be filtered to recover valuable metal elements in the filtrate. The trace silicon remaining in the desiliconized red mud concentrate dissolves and then forms a secondary mineralization to form a crystalline quartz precipitate. The present invention effectively removes silicon-containing minerals from the red mud before leaching, removing silicon at the source. During the leaching process, the silicon remaining in the red mud dissolves and then forms a secondary mineralization to form a synchronous crystalline quartz precipitate, thereby maximally suppressing or eliminating the negative impact of silica gel on red mud leaching.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy of red mud, and particularly relates to a method for preventing the generation of silica gel in red mud leachate. Background Art

[0002] Red mud is a solid or semi-solid silty waste discharged during the alumina production process. Due to its high salinity and alkali content, strong corrosiveness, and certain radioactivity, its comprehensive utilization efficiency is low, and it is mostly stored in dams. The output of red mud varies depending on the ore grade, production process, and technological level. For every ton of alumina produced, 0.8 to 2 tons of red mud are emitted. Currently, the total global red mud stockpile is approximately 5 billion tons, while my country's cumulative red mud stockpile has exceeded 3 billion tons and is increasing at a rate of 120 million tons per year. When stored, red mud poses serious ecological risks to the surrounding groundwater, surface water, soil, and atmospheric environment. Therefore, it is urgently needed to dispose of red mud harmlessly and as a resource.

[0003] Red mud is rich in rare earth elements such as Sc, Y, La, and Ce. Extracting these valuable metals from red mud has become one of the important ways to comprehensively utilize red mud as a resource. Currently, the mainstream methods for leaching valuable metals from red mud are acid leaching and bioleaching. However, since most of my country's bauxite resources are high-silicon, low-iron diaspore, with a silica content exceeding 10% and an aluminum-silicon ratio generally below 8.0, and diaspore is mostly cryptocrystalline or microcrystalline aggregates, tightly embedded with silicate minerals. As a result, the alkaline red mud waste discharged during alumina smelting has a high silicon content, with a mass ratio of aluminum oxide to silicon oxide as high as 1.1 to 1.2. When chemical acid leaching of red mud is performed using inorganic acids such as hydrochloric acid and sulfuric acid, or when bioleaching of red mud is performed using thiobacillus and fungi, the high content of silica in the red mud will enter the leachate along with the rare earth elements in the form of silicic acid (H4SiO4). Under low pH conditions (approximately 1.7 to 2.2), silicic acid forms an amorphous silicic acid sol or gel due to the hydrolysis of anions and the coordination and polycondensation of oxygen on hydroxyl groups. If the concentration of SiO2 dissolved from the red mud is too high (over 2.0 g / L), it may even gel into a semi-solid hydrogel during storage, causing the leachate to lose fluidity.

[0004] During the hydrometallurgical process, the silica gel formed will seriously affect the leaching and subsequent recovery efficiency of valuable metal elements in red mud, mainly manifested as follows: (1) silica gel will wrap and block the red mud mineral particles, hinder the deep leaching of valuable metal ions, and reduce the leaching rate of metal ions; (2) silica gel will adhere to the surface of industrial filter cloth, reducing the filtration efficiency of the leachate; (3) silica gel will make it difficult for the organic phase of the leachate to separate and generate a large amount of emulsion, reducing the extraction efficiency of the leachate.

[0005] To avoid the negative impact of silica gel formation on red mud leaching efficiency, current research has used phosphoric acid to leach SiO2 from red mud and enrich rare earth elements in the red mud residue. Alternatively, high-temperature roasting and concentrated acid leaching are used to inhibit the coagulation and condensation reaction of monomeric silicic acid, retaining Si in the red mud residue. Alternatively, coagulation-silica gel seed flocculation-activated carbon adsorption is used to desiliconize the red mud acid leachate. These methods suffer from drawbacks such as high energy consumption due to strong acid, incomplete desiliconization, co-leaching of rare earth elements and SiO2 from the red mud, or loss of valuable metals during desiliconization of the acid leachate. Summary of the Invention

[0006] To address the above issues, the present invention provides a method for preventing the formation of silica gel in red mud leachate. This method not only effectively removes silicon-containing minerals in red mud before leaching, preventing silicon-containing minerals in red mud from dissolving in the leachate to form silica gel at the source, but also creates a strong oxidizing environment during the red mud leaching process by adding H2O2. This allows the silicon element remaining in the red mud concentrate and dissolved in the leachate during the leaching process to undergo secondary mineralization to form crystalline quartz, which is then simultaneously precipitated in the leachate. This maximizes the inhibition or elimination of silica gel formation in the leachate, avoiding or reducing the negative impact of silica gel on red mud leaching. Another advantage of this method is that it can enrich the red mud with Fe, Ti, and rare earth element minerals while removing silicon-containing minerals from the red mud.

[0007] The present invention is specifically achieved through the following technical solutions. According to the present invention, a method for preventing the generation of silica gel in red mud leachate includes red mud dealkalization, red mud concentrated slurry gravity separation, red mud concentrate desiliconization, and desiliconized red mud concentrate leaching, specifically comprising the following steps:

[0008] (1) Red mud dealkalization: After drying, the red mud is crushed and ground, and passed through a 150-mesh sieve to obtain powdered red mud. The powdered red mud is dissolved in water (the mass ratio of powdered red mud to water is 1:5), stirred to form a red mud slurry, and allowed to settle naturally for 5 to 10 minutes. The slurry is separated into layers. The upper layer is an alkaline solution rich in NaOH, which can be further used to recover caustic soda, and the lower layer is the concentrated red mud slurry after dealkalization;

[0009] (2) Gravity separation of red mud concentrate: The red mud concentrate obtained in step (1) is mixed with water to prepare a slurry, which is then passed through a spiral chute or a shaking table for gravity separation. The red mud concentrate with a higher density (density greater than 3.5 g / cm 3 ) and red mud tailings with lower density (density less than 3.0g / cm 3 ).

[0010] The red mud concentrate is mainly a mixture of the following minerals: hematite (density = 5.0g / cm 3 ), goethite (density = 4.2 g / cm 3 ), rutile (density = 4.0 g / cm3 ), anatase (density = 3.9 g / cm 3 ), perovskite (density = 4.4g / cm 3 ), monazite (density = 5.2g / cm 3 ), bastnaesite (density = 4.9 g / cm 3 ), xenotime (density = 4.7 g / cm 3 ).

[0011] The red mud tailings are mainly a mixture of the following minerals: quartz (density = 2.6g / cm 3 ), calcite (density = 2.7g / cm 3 ), aluminosilicate minerals (density ≤ 2.9 g / cm 3 ).

[0012] The red mud concentrate is rich in Fe, Ti and rare earth elements, and mainly contains the following types of minerals: hematite and goethite are iron-containing minerals; rutile, anatase and perovskite are titanium-containing minerals; monazite, fluorocarbon cerium ore and xenotime are rare earth element-containing minerals; rare earth elements are also present in isomorphous forms in titanium- and iron-containing minerals such as hematite, rutile and perovskite.

[0013] The red mud tailings are mainly silicon-containing minerals, which can be further made into products such as water glass and zeolite.

[0014] (3) Desiliconization of red mud concentrate: In order to remove the quartz and aluminosilicate minerals that are not effectively separated in the gravity separation process in step (2) and remain in the red mud concentrate, the red mud concentrate is further treated by biological flocculation precipitation, specifically including:

[0015] (3.1) Inoculate Paenibacillus polymyxa into a sterilized activation culture medium and culture at 32-35°C with stirring or shaking for 3 days to obtain an activated Paenibacillus polymyxa seed solution;

[0016] The activation culture medium uses deionized water as a solvent, and its components include, by weight percentage: 2% glucose, 0.5% peptone, 0.3% yeast extract, 0.1% K2HPO4, 0.01% CaCl2, and 0.005% MgSO4;

[0017] (3.2) The activated Paenibacillus polymyxa seed solution obtained in step (3.1) was inoculated into the sterilized flocculation culture medium and cultured with stirring or shaking at 32-35°C. When the number of viable bacteria CFU in the flocculation culture medium exceeded 2.0×10 7When the polysaccharide content exceeds 1.2 g / L, the culture is terminated. The culture solution is centrifuged at 4000-5000 rpm for 3-5 minutes, and the supernatant is discarded. The remaining viscous liquid is the bioactive flocculant. The resulting bioactive flocculant can be freeze-dried and converted into a powder for long-term storage. It is then dissolved in deionized water for use. The preparation method of the bioactive flocculant powder includes: low-temperature evaporation and concentration of the resulting bioactive flocculant at a temperature of 50-60°C and a pressure of 0.01-0.1 MPa, followed by freeze-drying at a temperature of -30-40°C and a vacuum of 0.03 mbar to obtain a powder.

[0018] The inoculation volume of the Paenibacillus polymyxa seed solution in this step accounts for 2-5% of the volume of the flocculation culture solution. The flocculation culture solution uses deionized water as the solvent and contains, by weight, the following components: 15% glucose, 2.5% yeast extract, 0.1% K₂HPO₄, 0.01% CaCl₂, and 0.005% MgSO₄. The flocculation culture solution is sterilized at 121°C for 30 minutes.

[0019] (3.3) The red mud concentrate obtained in step (2) and the bioactive flocculant obtained in step (3.2) are added to water, and the pH value of the resulting flocculation system is adjusted to 5.6 to 5.8 using dilute hydrochloric acid (e.g., 0.1 to 1 mol / L hydrochloric acid solution). After slow stirring, the mixture is allowed to stand for 20 to 30 minutes, the supernatant is discarded, and the collected flocculated precipitate is rinsed with clean water to obtain a further desiliconized red mud concentrate.

[0020] In the flocculation system, the mass (g) of the red mud concentrate accounts for 5-10% of the combined volume (mL) of the bioactive flocculant and water, while the volume (mL) of the bioactive flocculant accounts for 14-16% of the combined volume (mL) of the bioactive flocculant and water. In this flocculation system, aluminosilicate minerals such as quartz, kaolinite, and illite are negatively charged due to their low isoelectric points (IEPs), and substances such as polysaccharides in the bioactive flocculant are negatively charged and hydrophobic. Therefore, the silicon-containing aluminosilicate minerals such as quartz, kaolinite, and illite are dispersed in the mud, while other Fe, Ti, and rare earth minerals are flocculated and precipitated by the bioactive flocculant, ultimately completing the desiliconization of the red mud concentrate.

[0021] (4) Desiliconized red mud concentrate leaching process: The leaching system used in this step can be a chemical leaching system composed of inorganic acid or a biological leaching system composed of acid-producing microorganisms;

[0022] The red mud concentrate after desiliconization in step (3) is put into a chemical leaching system containing an acid leaching solution composed of an inorganic acid. The acid leaching solution is formed by a certain concentration of one or two or three of phosphoric acid, nitric acid, and hydrochloric acid, and the pH of the acid leaching solution is less than 2.0. The mass of the added red mud concentrate after desiliconization accounts for 5-50% of the mass of the acid leaching solution in the chemical leaching system. After the pH value of the chemical leaching system is lower than 2.0, a H2O2 solution with a concentration of 0.9-1.5 mol / L is added. The volume (mL) of the H2O2 solution added to the chemical leaching system is 16-18% of the mass (g) of the added red mud concentrate after desiliconization (i.e., 16-18 mL of H2O2 solution is added for every 100 g of the desiliconized red mud concentrate). The reaction is then carried out on a shaking table (constant temperature oscillator) for 2-10 hours. After completion, the leaching solution is allowed to stand or filtered or extracted, and the filtrate is collected to recover valuable metal elements such as rare earth elements. The trace silicon elements remaining in the desiliconized red mud concentrate dissolve in the acid leaching solution and then form secondary mineralization to form crystalline quartz precipitation, which is discharged with the filter residue.

[0023] Alternatively, the red mud concentrate after desiliconization in step (3) is fed into a bioleaching system composed of acid-producing microorganisms. The acid-producing microorganisms used in the bioleaching system are acid-producing fungi such as Aspergillus niger and Penicillium, or heterotrophic bacteria such as Acetobacter and Lactobacillus, or autotrophic bacteria such as Thiobacillus thiooxidans. After bacterial cell culture, the cells are separated from the acidic fermentation broth, and the acidic fermentation broth produced by the acid-producing microorganisms is used to leach the red mud. The acidic fermentation broth has a pH of less than 3.0. The acidic fermentation broth is generally one or more of oxalic acid, citric acid, gluconic acid, fumaric acid, succinic acid, and sulfuric acid. The mass of desiliconized red mud concentrate added accounts for 5-20% of the mass of the acidic fermentation broth in the bioleaching system. After the pH value of the bioleaching system falls below 2.0, a 0.9-1.5 mol / L H2O2 solution is added. The volume (mL) of H2O2 added to the bioleaching system is 8-9% of the mass (g) of the desiliconized red mud concentrate added (i.e., 8-9 mL of H2O2 solution is added for every 100 g of desiliconized red mud concentrate). The bioleaching process is then shaken on a shaker (constant temperature oscillator) for 8-72 hours. After completion, the bioleaching solution is allowed to stand or undergo filtration or extraction treatment. The filtrate is collected and valuable metal elements such as rare earth elements are recovered. The trace silicon remaining in the desiliconized red mud concentrate dissolves in the acidic fermentation broth and then undergoes secondary mineralization to form a crystalline quartz precipitate, which is discharged with the filter residue.

[0024] In the chemical leaching system or biological leaching system, the valuable metal elements Fe, Ti and rare earth elements in hematite, goethite, rutile, anatase, perovskite, monazite, fluorocarbon cerium and xenotime in the red mud concentrate are attacked by hydrogen ions and acid radicals, undergoing acidolysis and complexation reactions, dissolving from the ore body and entering the acid leaching solution or acid fermentation solution (leachate) in a soluble form. After the trace silicon element remaining in the red mud concentrate is dissolved in the acid leaching solution or acid fermentation solution (leachate), it is re-mineralized to form crystalline quartz precipitation (i.e., converted from soluble ion form to insoluble crystalline form) due to the strong oxidizing environment created by H2O2, thereby preventing the formation of silica gel in the leaching solution.

[0025] Compared with the prior art, the present invention has obvious advantages and beneficial effects. By means of the above technical solution, the present invention can achieve considerable technological advancement and practicality, and has a wide range of utilization value. It has at least the following advantages:

[0026] (1) The present invention removes silicon-containing minerals such as quartz and aluminosilicate from the red mud by physical gravity separation and biological flocculation before leaching the valuable metal elements in the red mud. The silicon-containing minerals in the red mud are effectively removed before the red mud is leached, thereby preventing the silicon-containing minerals in the red mud from dissolving in the leaching liquid to form silica gel at the source. Moreover, in the process of leaching the valuable metal elements in the red mud, a strong oxidizing environment is created by adding H2O2, so that the silicon elements remaining in the red mud concentrate and dissolved in the leaching liquid during the leaching process are secondary mineralized to form crystalline quartz, thereby being synchronously precipitated in the leaching liquid, thereby maximizing the inhibition or elimination of the formation of silica gel in the leaching liquid, avoiding or reducing the negative impact on the red mud leaching, and achieving the purpose of avoiding the formation of silica gel in the whole process and in all directions.

[0027] (2) The present invention enriches minerals containing Fe, Ti and rare earth elements in red mud concentrate through a gravity separation process, which not only improves the leaching efficiency of valuable metal elements, but also reduces the amount of inorganic acid and organic acid used in chemical leaching of red mud concentrate, and shortens the fermentation liquid culture time and reduces the amount of energy substances required for microorganisms in biological leaching of red mud concentrate, ultimately achieving the goal of reducing energy consumption and controlling costs.

[0028] (3) Adding a pre-dealkali step before red mud gravity separation can reduce the acid consumption of the leaching process while recovering caustic soda from the red mud.

[0029] (4) The present invention does not use high-temperature roasting, concentrated acid pressurization and other methods to control the formation of silica gel, nor does it introduce insoluble adsorption materials to cause the loss of mineral particles and soluble valuable metal elements. It has the advantages of mild reaction conditions, green and environmental protection, easy operation, and convenient industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1This is a SEM image (magnified 30,000 times) of the crystalline quartz precipitate formed by secondary mineralization after the trace silicon element remaining in the desiliconized red mud concentrate of Example 1 was dissolved in the acid leaching solution. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] Unless otherwise specified, all experiments were conducted under conventional conditions or manufacturer recommendations. Raw materials and reagents not identified by manufacturer are commercially available. Paenibacillus polymyxa was purchased from Beina Chuanglian Biotechnology Co., Ltd., catalog number BNCC138393.

[0033] Example 1

[0034] (1) Red mud dealkalization: Take sintered red mud, the total content of quartz and aluminosilicate minerals in the red mud is 42.7%. Place the sintered red mud in a drying oven at 80°C and dry for 48 hours. Grind it and pass it through a 150-mesh sieve to obtain powdered red mud with a particle size of less than 0.106 mm. Take 400 g of the powdered red mud and place it in a 10 L polyethylene bottle. Add 2 L of deionized water (the mass of deionized water is 2000 g). Use a magnetic stirrer to stir for 30 minutes to make a red mud slurry. Let it stand and settle naturally for 10 minutes. The slurry is separated into layers. The upper supernatant without red mud particles is poured out to leave the dealkalized red mud concentrated slurry.

[0035] (2) Gravity separation of red mud concentrated slurry: The red mud concentrated slurry was mixed with water in a volume ratio of 1:9 to obtain a slurry (the volume percentage of the red mud concentrated slurry in the slurry was 10%). The slurry was passed into a small spiral chute at a flow rate of 5.0 L / min for gravity separation. The inner edge ore zone was the red mud tailings, and the outer edge ore zone was the red mud concentrate. The red mud concentrate was collected, and the total content of quartz and aluminosilicate minerals in the red mud concentrate was reduced to 9.8%.

[0036] (3) Desiliconization of red mud concentrate: In order to remove the quartz and aluminosilicate minerals that are not effectively separated in the gravity separation process in step (2) and remain in the red mud concentrate, the red mud concentrate is further treated by biological flocculation precipitation, specifically including:

[0037] (3.1) Take a loopful of Paenibacillus polymyxa stored on a solid LB plate and inoculate it into sterilized activation medium. Incubate the culture on a constant temperature shaker at 120 rpm and 35°C for 72 h to obtain an activated Paenibacillus polymyxa seed solution.

[0038] The activation culture medium uses deionized water as a solvent, and its components include, by weight percentage: 2% glucose, 0.5% peptone, 0.3% yeast extract, 0.1% K2HPO4, 0.01% CaCl2, and 0.005% MgSO4;

[0039] (3.2) Take 20 mL of the activated Bacillus polymyxa seed solution from step (3.1) and inoculate it into 1000 mL of sterilized flocculation culture medium. Incubate the culture on a constant temperature shaker at 120 rpm and 35°C for 56 h. At this time, the CFU of viable bacteria is 2.6 × 10 7 , the polysaccharide content is 1.41 g / L. The cultured flocculation culture fluid is centrifuged at 5000 rpm for 5 minutes in a centrifuge, the supernatant is discarded, and the remaining viscous liquid is the bioactive flocculant. The bioactive flocculant can also be freeze-dried and made into powder for long-term storage, and dissolved in deionized water when used. The preparation method of the bioactive flocculant powder includes: low-temperature evaporation and concentration of the obtained bioactive flocculant at a temperature of 50 to 60°C and a pressure of 0.01 to 0.1 MPa, and then freeze-drying at a temperature of -30 to -40°C and a vacuum degree of 0.03 mbar to finally make it into powder.

[0040] The flocculation culture solution uses deionized water as a solvent and comprises, by weight, 15% glucose, 2.5% yeast extract, 0.1% K2HPO4, 0.01% CaCl2, and 0.005% MgSO4. The flocculation culture solution is sterilized at 121°C for 30 minutes.

[0041] (3.3) 70 g of the red mud concentrate obtained in step (2) and 150 mL of the bioactive flocculant obtained in step (3.2) were added to a 5 L glass beaker, and 850 mL of deionized water was added to the glass beaker. The pH value of the flocculation system was adjusted to 5.8 with dilute hydrochloric acid. After magnetic stirring for 5 minutes, the mixture was allowed to stand for 30 minutes, and the supernatant was poured out. 5 L of deionized water was added, and the mixture was stirred again for 1 minute and allowed to stand for 30 minutes. The supernatant was poured out, and the precipitate at the bottom of the beaker was collected to obtain a further desiliconized red mud concentrate, in which the total content of quartz and aluminosilicate minerals was reduced to 1.4%.

[0042] (4) Leaching of desiliconized red mud concentrate: 50 g of the desiliconized red mud concentrate prepared in step (3.3) was added to a beaker containing 500 mL of sulfuric acid leaching solution (the concentration of sulfuric acid leaching solution was 2.0 mol / L), and 8.5 mL of 1.0 mol / L H2O2 was added. The mixture was shaken on a shaker for 3 h, then allowed to stand for 30 min, and the supernatant and leached residue were taken for analysis.

[0043] Comparative example: 50 g of the red mud concentrate collected in step (2) was added to a beaker containing 500 mL of sulfuric acid leachate (the concentration of the sulfuric acid leachate was 2.0 mol / L), shaken on a shaker for 3 h, and then allowed to stand for 30 min. The supernatant and leached residue were taken for analysis.

[0044] When the supernatant of Example 1 was filtered using filter paper, no gel adhered to the filter paper, and no silica gel was detected in the supernatant. However, when the supernatant of the control example was filtered, gel adhered to the filter paper. The leaching efficiencies of Ti, Fe, Sc, Y, La, and Ce in Example 1 were 63.1%, 37.1%, 42.8%, 46.4%, 35.0%, and 43.9%, respectively. The leaching efficiencies of Ti, Fe, Sc, Y, La, and Ce in the control example were 57.7%, 34.9%, 37.3%, 44.0%, 33.8%, and 41.0%, respectively. Compared to the control example, the method of Example 1 improved the leaching efficiency of Ti, Fe, Sc, Y, La, and Ce by 9.4%, 6.3%, 14.7%, 5.5%, 3.5%, and 7.1%, respectively.

[0045] Figure 1 This is an SEM image (magnified 30,000 times) of the crystalline quartz precipitate formed by secondary mineralization after the trace silicon elements remaining in the desiliconized red mud concentrate of Example 1 are dissolved in the acid leaching solution. The dissolved silicon ions form regular hexahedral and rhombohedral crystalline quartz precipitates.

[0046] Example 2

[0047] In step (3.2), 50 mL of the activated Paenibacillus polymyxa seed solution in step (3.1) was inoculated into 1000 mL of sterilized flocculation culture medium, and cultured on a thermostatic shaker at 130 rpm and 32° C. for 65 h.

[0048] In step (3.3), 90 g of red mud concentrate and 160 mL of the bioactive flocculant obtained in step (3.2) were added to a 5 L glass beaker, and 840 mL of deionized water was added to the glass beaker. The pH value of the flocculation system was adjusted to 5.8 with dilute hydrochloric acid. After magnetic stirring for 7 minutes, the mixture was allowed to stand for 30 minutes, the supernatant was poured out, and 5 L of deionized water was added and stirred again for 1 minute, and then allowed to stand for 30 minutes. The supernatant was poured out and the precipitate at the bottom of the beaker was collected to obtain a further desiliconized red mud concentrate, in which the total content of quartz and aluminosilicate minerals in the red mud concentrate was reduced to 1.5%.

[0049] In step (4), 70 g of the desiliconized red mud concentrate prepared in step (3.3) was added to a beaker containing 500 mL of hydrochloric acid leachate (the concentration of the hydrochloric acid leachate was 4.0 mol / L), 12 mL of 1.5 mol / L H2O2 was added, and the mixture was shaken on a shaker for 3 h, then allowed to stand for 30 min, and the supernatant and leached residue were taken for analysis.

[0050] When the supernatant of Example 2 was filtered using filter paper, no gel adhered to the filter paper, and no silica gel was detected in the supernatant. The leaching efficiencies of Ti, Fe, Sc, Y, La, and Ce were 64.8%, 39.2%, 43.6%, 49.1%, 34.2%, and 45.7%, respectively.

[0051] The remaining steps are the same as in Example 1.

[0052] Example 3

[0053] Steps (1) to (3) are the same as in Example 1.

[0054] Step (4) uses a bioleaching system to leach the desiliconized red mud concentrate. The preparation method of the bioleaching system is as follows: a ring of mature Aspergillus niger spores on a solid PDA plate is inoculated into 1000 mL of sterilized sucrose culture medium (sucrose culture medium uses deionized water as a solvent and is composed of: 100 g / L sucrose, 0.5 g / L KNO3, 0.5 g / L KH2PO4, 2.0 g / L yeast extract, and 2.0 g / L peptone) and cultured on a thermostatic shaker at 30°C and 120 rpm for 72 hours. After the culture is completed, the Aspergillus niger mycelium is separated from the acidic fermentation broth by centrifugal filtration. 500 mL of the acidic fermentation broth was added to 50 g of the desiliconized red mud concentrate prepared in step (3.3), followed by 4 mL of a 1.0 mol / L H₂O₂ solution. The mixture was shaken on a shaker for 24 h and then allowed to stand for 30 min. The supernatant and leached residue were analyzed. When the supernatant was filtered using filter paper, no gel adhered to the filter paper, and no silica gel was detected in the supernatant. The leaching efficiencies for Ti, Fe, Sc, Y, La, and Ce were 72.0%, 41.5%, 44.8%, 49.6%, 33.1%, and 46.7%, respectively.

[0055] The above description is merely an embodiment of the present invention and does not constitute any form of limitation to the present invention. The present invention may also have other forms of embodiments based on the above structures and functions, which are not listed here one by one. Therefore, any simple modification, equivalent changes, and modifications made to the above embodiments by any person skilled in the art in accordance with the technical essence of the present invention without departing from the scope of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preventing the production of silica gel in red mud leachate, characterized in that The process includes red mud dealkalization, red mud concentrated slurry gravity separation, red mud concentrate desiliconization, and desiliconized red mud concentrate leaching, specifically including the following steps: (1) Red mud dealkalization: After drying the red mud, crush it, grind it, and sieve it to obtain powdered red mud. The powdered red mud is dissolved in water and stirred to form red mud slurry. The slurry is allowed to settle naturally and the slurry is separated into layers. The upper layer is an alkali solution rich in NaOH, and the lower layer is the concentrated red mud slurry after dealkalization. (2) Gravity separation of red mud concentrated slurry: The red mud concentrated slurry obtained in step (1) is mixed with water to prepare a slurry, which is then passed through a spiral chute or a shaking table for gravity separation. The red mud concentrate with a larger density and the red mud tailings with a smaller density are separated by gravity separation. The density of the red mud concentrate is greater than 3.5 g / cm 3 The density of red mud tailings is less than 3.0 g / cm 3 The red mud concentrate is mainly a mixture of hematite, goethite, rutile, anatase, perovskite, monazite, fluorocarbon cerium, and xenotime, and the red mud tailings are mainly a mixture of quartz, calcite, and aluminosilicate minerals; (3) Desiliconization of red mud concentrate: The red mud concentrate is further treated by biological flocculation and sedimentation, specifically including: (3.1) Inoculate Paenibacillus polymyxa into sterilized activation culture medium and culture at 32–35°C with stirring or shaking for 3 days to obtain an activated Paenibacillus polymyxa seed solution. (3.2) The activated Paenibacillus polymyxa seed solution obtained in step (3.1) was inoculated into the sterilized flocculation culture medium and cultured with stirring or shaking at 32-35°C. When the number of viable bacteria in the flocculation culture medium exceeded 2.0×10 7 When the CFU and polysaccharide content exceed 1.2 g / L, the culture is terminated, the culture medium is centrifuged, and the supernatant is discarded. The remaining viscous liquid is the bioactive flocculant; The flocculation culture medium uses deionized water as a solvent, and its components include, by weight percentage: 15% glucose, 2.5% yeast extract, 0.1% K2HPO4, 0.01% CaCl2, and 0.005% MgSO4. The sterilization conditions of the flocculation culture medium are 121°C for 30 minutes. (3.3) adding the red mud concentrate obtained in step (2) and the bioactive flocculant obtained in step (3.2) into water, adjusting the pH value of the resulting flocculation system to 5.6 to 5.8 with dilute hydrochloric acid, slowly stirring and then allowing to stand, discarding the supernatant, and rinsing the collected flocculated precipitate with clean water to obtain a further desiliconized red mud concentrate; (4) Leaching of desiliconized red mud concentrate: the red mud concentrate desiliconized in step (3) is put into a chemical leaching system containing an acid leaching solution composed of inorganic acid for chemical leaching, or the red mud concentrate desiliconized in step (3) is put into a biological leaching system composed of acid-producing microorganisms for biological leaching; an H2O2 solution with a concentration of 0.9 to 1.5 mol / L is added to the chemical leaching system or the biological leaching system, and after the chemical leaching or biological leaching is completed, the leaching solution is allowed to stand or filtered or subjected to extraction treatment, the filtrate is collected, and the valuable metal elements therein are recovered; the trace silicon element remaining in the desiliconized red mud concentrate is dissolved in the leaching solution and then secondary mineralized to form crystalline quartz precipitate, which is discharged with the filter residue.

2. The method for preventing the generation of silica gel in red mud leachate according to claim 1, characterized in that In step (1), the red mud is ground and passed through a 150-mesh sieve, and the mass ratio of the powdered red mud to water is 1:

5.

3. The method for preventing the generation of silica gel in red mud leachate according to claim 1, characterized in that In step (3.1), the activation medium uses deionized water as a solvent, and its components include, by weight percentage, 2% glucose, 0.5% peptone, 0.3% yeast extract, 0.1% K2HPO4, 0.01% CaCl2, and 0.005% MgSO4.

4. The method for preventing the generation of silica gel in red mud leachate according to claim 1, wherein In step (3.2), the inoculation volume of the Bacillus polymyxa seed solution accounts for 2-5% of the volume of the flocculation culture solution.

5. The method for preventing the generation of silica gel in red mud leachate according to claim 1, characterized in that In step (3.2), the obtained bioactive flocculant is freeze-dried and then made into powder for long-term storage, and is dissolved in deionized water when used; The preparation method of the bioactive flocculant powder comprises: low-temperature evaporation and concentration of the obtained bioactive flocculant at a temperature of 50-60°C and a pressure of 0.01-0.1 MPa, and then freeze-drying at a temperature of -30--40°C and a vacuum degree of 0.03 mbar to prepare a powder.

6. The method for preventing the generation of silica gel in red mud leachate according to claim 1, characterized in that In step (3.3), the mass of the red mud concentrate in the flocculation system accounts for 5-10% of the sum of the volumes of the bioactive flocculant and water, and the volume of the bioactive flocculant accounts for 14-16% of the sum of the volumes of the bioactive flocculant and water. The mass unit of the red mud concentrate is g, and the volume units of the bioactive flocculant and the water are both mL.

7. The method for preventing the generation of silica gel in red mud leachate according to claim 1, characterized in that The acid leaching solution in the chemical leaching system described in step (4) is formed by one or a mixture of two or a mixture of three of phosphoric acid, nitric acid and hydrochloric acid, and the pH of the acid leaching solution is less than 2.0; the added mass of the desiliconized red mud concentrate accounts for 5 to 50% of the mass of the acid leaching solution in the chemical leaching system, and 16 to 18 mL of the H2O2 solution is added for every 100 g of the desiliconized red mud concentrate.

8. The method for preventing the generation of silica gel in red mud leachate according to claim 1, characterized in that The acid-producing microorganisms used in the bioleaching system described in step (4) are at least one of Aspergillus niger, Penicillium, Acetobacter, Lactobacillus, and Thiobacillus thiooxidans; the acid-producing microorganisms produce an acidic fermentation liquid, and the pH of the acidic fermentation liquid is lower than 3.0; the added mass of the desiliconized red mud concentrate accounts for 5 to 20% of the mass of the acidic fermentation liquid in the bioleaching system, and 8 to 9 mL of the H2O2 solution is added for every 100 g of the desiliconized red mud concentrate.

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