Method for avoiding generation of silica gel in red mud leachate

Abstract

The invention relates to a method for avoiding generation of silica gel in red mud leachate, which comprises the following steps: drying red mud, crushing, grinding and sieving, dissolving powdery red mud in water to prepare slurry, and standing and layering to obtain red mud concentrated slurry with a dealkalized lower layer; the method comprises the following steps: reselecting red mud concentrated slurry to obtain red mud concentrate and red mud tailings, further treating the red mud concentrate by adopting biological flocculation precipitation to obtain desiliconized red mud concentrate, carrying out chemical leaching or biological leaching on the desiliconized red mud concentrate, adding an H2O2 solution into a leaching system, standing or filtering a leaching solution after leaching is completed, and recycling the red mud concentrate and the red mud tailings. Valuable metal elements in the filtrate are recovered; and dissolving trace silicon remained in the desiliconized red mud concentrate, and performing secondary mineralization to form crystalline quartz precipitate. According to the method, silicon-containing minerals in the red mud are effectively removed before leaching of the red mud, silicon is removed from the source, silicon elements remaining in the red mud in the leaching process are dissolved and then secondarily mineralized into crystalline quartz to synchronously precipitate, and the negative influence of silica gel on leaching of the red mud can be inhibited or eliminated to the maximum extent.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy of red mud, and in particular relates to a method for preventing silica gel from being produced in red mud leaching liquid. Background Art

[0002] Red mud is a solid or semi-solid powdery mud waste discharged during the production of alumina. Due to the high salt and alkali content, strong corrosiveness, and certain radioactivity of red mud, its comprehensive utilization efficiency is low, and it is mainly stored in dams. The output of red mud varies depending on the ore grade, production process, and technical level. For every 1.0 ton of alumina produced, 0.8 to 2.0 tons of red mud will be discharged. At present, the total stockpile of red mud in the world is about 5 billion tons, and the cumulative stockpile of red mud in my country has exceeded 3 billion tons, and is increasing at a rate of 120 million tons per year. When red mud is stored, it will cause serious ecological risks to the surrounding groundwater, surface water, soil, and atmospheric environment. Therefore, it is urgent 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 metal elements from red mud has become one of the important ways to comprehensively utilize red mud resources. At present, the mainstream methods for leaching valuable metal elements from red mud are acid leaching and bioleaching. However, since most of my country's bauxite resources are high-silicon and low-iron diaspore, the silica content exceeds 10%, the aluminum-silicon ratio is generally lower than 8.0, and diaspore is mostly cryptocrystalline or microcrystalline aggregates, which are closely embedded with silicate minerals. As a result, the silicon content in the alkaline red mud waste discharged during alumina smelting is very high, and the mass ratio of alumina to silicon oxide is as high as 1.1 to 1.2. When chemical acid leaching of red mud is carried out using inorganic acids such as hydrochloric acid and sulfuric acid, or when biological leaching of red mud is carried out using thiobacillus and fungi, the high content of silicon dioxide 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 (about 1.7-2.2), silicic acid forms an amorphous silica 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 red mud is too high (more than 2.0g / 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 in the following ways: (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 emulsions, reducing the extraction efficiency of the leachate.

[0005] In order to avoid the negative impact of silica gel on the leaching efficiency of red mud, studies have been conducted to use phosphoric acid to leach SiO2 from red mud and enrich rare earth elements in the red mud residue, or to use high temperature roasting and concentrated acid leaching to inhibit the condensation reaction of monomeric silicic acid to retain Si in the red mud residue, or to use condensation-silica gel seed flocculation-activated carbon adsorption to desiliconize the acid leaching solution of red mud. The above methods have the disadvantages of high energy consumption of strong acid, incomplete desiliconization, co-leaching of rare earth elements and SiO2 from red mud, or loss of valuable metals during desiliconization of the acid leaching solution. Summary of the invention

[0006] In view of the above problems, the present invention provides a method for avoiding the generation of silica gel in red mud leachate, which can not only effectively remove silicon-containing minerals in red mud before leaching, but also prevent silicon-containing minerals in red mud from dissolving in the leaching liquid to form silica gel from the source, and at the same time, create a strong oxidizing environment by adding H2O2 during the red mud leaching process, so that the silicon element remaining in the red mud concentrate and dissolved in the leaching liquid during the leaching process is secondary mineralized to form crystalline quartz, thereby precipitating synchronously in the leaching liquid, thereby maximizing the inhibition or elimination of the formation of silica gel in the leaching liquid, and avoiding or reducing the negative impact of silica gel on red mud leaching. Another advantage of this method is that it can enrich the Fe, Ti and rare earth element minerals in the red mud while removing the silicon-containing minerals in the red mud.

[0007] The present invention is specifically implemented by the following technical scheme. According to the method proposed by the present invention, a method for avoiding the generation of silica gel in red mud leaching liquid includes red mud dealkalization, red mud concentrated mud gravity separation, red mud concentrate desiliconization, and desiliconized red mud concentrate leaching, which specifically includes the following steps:

[0008] (1) Red mud dealkalization: After the red mud is dried, it 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), and stirred to form red mud slurry. The slurry is allowed to stand and naturally settle for 5 to 10 minutes. The slurry is separated into layers. The upper layer is an alkali solution rich in NaOH, from which caustic soda can be further recovered, and the lower layer is the concentrated red mud slurry after dealkalization;

[0009] (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 into 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 = 5.0 g / 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 = 2.6 g / cm 3 ), calcite (density = 2.7g / cm 3 ), aluminosilicate minerals (density ≤ 2.9g / 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, bastnaesite and xenotime are rare earth element-containing minerals; rare earth elements are also present in isomorphous forms in hematite, rutile, perovskite and other titanium- and iron-containing minerals.

[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 of 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) inoculating Paenibacillus polymyxa into a sterilized activation culture medium, stirring or shaking and culturing at 32 to 35° C. for 3 days to obtain an activated Paenibacillus polymyxa seed solution;

[0016] The activation culture medium uses deionized water as 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) inoculating the activated Bacillus polymyxa seed solution obtained in step (3.1) into the sterilized flocculation culture solution, stirring or shaking the culture solution at 32 to 35°C; when the CFU of live bacteria in the flocculation culture solution exceeds 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, the supernatant is discarded, and the remaining viscous liquid is the bioactive flocculant; the obtained bioactive flocculant can 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 50-60°C and a pressure of 0.01-0.1 MPa, and then freeze-dried at a temperature of -30--40°C and a vacuum degree of 0.03 mbar, and finally made into powder.

[0018] The inoculation volume of the polymyxa bacillus 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 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 condition of the flocculation culture solution is 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 into water, and the pH value of the obtained 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), and the mixture is slowly stirred and 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 red mud concentrate after further desiliconization.

[0020] The mass (g) of red mud concentrate in the flocculation system accounts for 5-10% of the sum of the volumes (mL) of the bioactive flocculant and water, and the volume (mL) of the bioactive flocculant accounts for 14-16% of the sum of the volumes (mL) of the bioactive flocculant and water. In the flocculation system, aluminosilicate minerals such as quartz, kaolinite, and illite are negatively charged due to their lower isoelectric points (IEP), and polysaccharides and other substances in the bioactive flocculant are negatively charged and hydrophobic, so silicon-containing quartz, kaolinite, illite, and other aluminosilicate minerals are dispersed in the mud, while other Fe, Ti, and rare earth minerals are flocculated and precipitated by the bioactive flocculant, and finally further desiliconization of the red mud concentrate is completed.

[0021] (4) Desiliconized red mud concentrate leaching process: The leaching system used in this step can be a chemical leaching system composed of inorganic acids 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 with an acid leaching solution composed of inorganic acid, wherein the acid leaching solution is formed by a certain concentration of phosphoric acid, nitric acid, and hydrochloric acid, or a mixture of two or three, and the pH of the acid leaching solution is less than 2.0. The added mass of the 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, and the added volume (mL) of the H2O2 solution in the chemical leaching system is 16-18% of the added mass (g) of the red mud concentrate after desiliconization (i.e., 16-18 mL of H2O2 solution is added for every 100 g of the red mud concentrate after desiliconization); then, the reaction is oscillated on a shaking table (constant temperature oscillator) for 2-10 hours, and after completion, the leaching solution is left to stand or filtered or extracted, and the filtrate is collected to recover the valuable metal elements such as rare earth elements therein. The trace silicon elements remaining in the desiliconized red mud concentrate are dissolved in the acid leaching solution and then secondary mineralized to form crystalline quartz precipitation, which is discharged with the filter residue.

[0023] Alternatively, the red mud concentrate after desiliconization in step (3) is put into a bioleaching system composed of acid-producing microorganisms, and 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 the bacterial cells are cultured, they are separated from the acidic fermentation liquid, and the acidic fermentation liquid produced by the acid-producing microorganisms is used to leach the red mud, and the pH of the acidic fermentation liquid is lower than 3.0. The acidic fermentation liquid is usually one or more of oxalic acid, citric acid, gluconic acid, fumaric acid, succinic acid, and sulfuric acid. The added mass of the desiliconized red mud concentrate accounts for 5-20% of the mass of the acidic fermentation liquid in the bioleaching system. After the pH value of the bioleaching system is lower than 2.0, a H2O2 solution with a concentration of 0.9-1.5 mol / L is added. The added volume (mL) of H2O2 in the bioleaching system is 8-9% of the added mass (g) of the desiliconized red mud concentrate (i.e., 8-9 mL of H2O2 solution is added for every 100 g of desiliconized red mud concentrate); then the reaction is oscillated on a shaking table (constant temperature oscillator) for 8-72 hours. After completion, the bioleaching liquid is left to stand or filtered or extracted, and the filtrate is collected to recover the rare earth elements and other valuable metal elements therein. The trace silicon element remaining in the desiliconized red mud concentrate is dissolved in the acidic fermentation liquid and then secondary mineralized 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, and acidolysis and complexation reactions occur to dissolve from the ore body and enter the acid leaching solution or acid fermentation solution (leaching solution) 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 (leaching solution), 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 technical progress and practicality, and has a wide range of utilization value, and has at least the following advantages:

[0026] (1) The present invention removes silicon-containing minerals such as quartz and aluminosilicate in red mud by physical gravity separation and biological flocculation process before leaching the valuable metal elements in red mud, and effectively removes the silicon-containing minerals in red mud before leaching, thereby preventing the silicon-containing minerals in red mud from dissolving in the leaching liquid to form silica gel from the source. In addition, in the process of leaching the valuable metal elements in red mud, H2O2 is added to create a strong oxidizing environment, 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 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 can not only improve the leaching efficiency of valuable metal elements, but also reduce the amount of inorganic acid and organic acid used in chemical leaching of red mud concentrate, and shorten the fermentation liquid culture time and reduce 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) A pre-dealkali treatment step is added before the red mud gravity separation, which can reduce the acid consumption of the leaching process while recovering the caustic soda in 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] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In the following examples, if no specific conditions are specified, all are carried out under conventional conditions or conditions recommended by the manufacturer. Raw materials and reagents used without indicating the manufacturer are all conventional products that can be purchased commercially. The polymyxa bacillus used was purchased from the mall Beina Chuanglian Biotechnology Co., Ltd., item 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 400g of the powdered red mud and place it in a 10L polyethylene bottle, add 2L of deionized water (the mass of deionized water is 2000g), stir it with a magnetic stirrer for 30 minutes to make red mud slurry, let it stand and settle naturally for 10 minutes, the slurry is separated, and the upper supernatant without red mud particles is poured out, leaving the dealkalized red mud concentrated slurry.

[0035] (2) Gravity separation of red mud concentrated slurry: The red mud concentrated slurry was mixed with water at 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 of 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 loop of Paenibacillus polymyxa stored on the LB solid plate, inoculate it into the sterilized activation medium, and culture it on a constant temperature shaker at a speed of 120 rpm and 35° C. for 72 hours to obtain an activated Paenibacillus polymyxa seed solution;

[0038] The activation culture medium uses deionized water as 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 in step (3.1) and inoculate it into 1000 mL of sterilized flocculation culture medium. Incubate it 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 1.41g / L. The cultured flocculation culture fluid is centrifuged at 5000rpm for 5min 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 0.1MPa, and then freeze-drying at a temperature of -30 to -40°C and a vacuum degree of 0.03mbar, and finally making it into powder.

[0040] The flocculation culture solution uses deionized water as 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 condition of the flocculation culture solution is 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) are added to a 5 L glass beaker, and then 850 mL of deionized water is added to the glass beaker, and the pH value of the flocculation system is adjusted to 5.8 with dilute hydrochloric acid. After magnetic stirring for 5 minutes, the mixture is allowed to stand for 30 minutes, and the supernatant is poured out. 5 L of deionized water is added, and the mixture is stirred again for 1 minute, and then allowed to stand for 30 minutes. The supernatant is poured out, and the precipitate at the bottom of the beaker is collected to obtain a further desiliconized red mud concentrate, in which the total content of quartz and aluminosilicate minerals is 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 into a beaker containing 500 mL of sulfuric acid leaching solution (the concentration of the 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, and then allowed to stand for 30 min. 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 into a beaker containing 500 mL of sulfuric acid leaching solution (the concentration of sulfuric acid leaching solution was 2.0 mol / L), shaken on a shaker for 3 h, then allowed to stand for 30 min, and 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, while gel adhered to the filter paper when the supernatant of the control example was filtered. 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 with the control example, the method of Example 1 increased 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 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 is dissolved in the acid leaching solution. The dissolved silicon ions form regular hexahedral and oblique hexahedral crystalline quartz precipitates.

[0046] Example 2

[0047] In step (3.2), 50 mL of the activated Bacillus polymyxa seed solution in step (3.1) was inoculated into 1000 mL of sterilized flocculation culture solution, and cultured on a constant temperature 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) are added to a 5 L glass beaker, and then 840 mL of deionized water is added to the glass beaker, and the pH value of the flocculation system is adjusted to 5.8 with dilute hydrochloric acid. After magnetic stirring for 7 minutes, the mixture is allowed to stand for 30 minutes, the supernatant is poured out, and 5 L of deionized water is added and stirred again for 1 minute, and then the mixture is allowed to stand for 30 minutes. The supernatant is poured out, and the precipitate at the bottom of the beaker is collected to obtain a further desiliconized red mud concentrate, in which the total content of quartz and aluminosilicate minerals is 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 leaching solution (the concentration of the hydrochloric acid leaching solution 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 those in Example 1.

[0054] Step (4) uses a biological leaching system to leach the desiliconized red mud concentrate. The preparation method of the biological leaching system is as follows: a ring of mature Aspergillus niger spores on a solid PDA plate is inoculated into 1000 mL of sterilized (121° C., 103 kPa sterilization for 15 min) sucrose medium (the sucrose medium uses deionized water as a solvent, and its composition includes: sucrose 100 g / L, KNO3 0.5 g / L, KH2PO4 0.5 g / L, yeast extract 2.0 g / L, peptone 2.0 g / L), and cultured on a constant temperature shaker at 30° C. and 120 rpm for 72 hours. After the culture is completed, the Aspergillus niger hyphae and the acidic fermentation liquid are separated by centrifugal filtration. Take 500mL of acidic fermentation broth, add 50g of the desiliconized red mud concentrate prepared in step (3.3), add 4mL of 1.0mol / L H2O2 solution, shake on a shaker for 24h, then let stand for 30min, take the supernatant and leaching residue for analysis. When the supernatant was filtered with filter paper, no gel adhered to the filter paper, no silica gel was detected in the supernatant, and the leaching efficiencies of 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 is only an embodiment of the present invention, and does not limit the present invention in any form. The present invention can also have other forms of embodiments according to the above structures and functions, which are not listed one by one. Therefore, any simple modification, equivalent change and modification made by any technician familiar with the profession to the above embodiment according to the technical essence of the present invention without departing from the scope of the technical solution of the present invention still falls 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 leaching liquid, characterized in that It 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 the red mud is dried, it is crushed, ground, and sieved 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 stand and settle naturally. The slurry is separated into layers. The upper layer is an alkali solution rich in NaOH, and the lower layer is a 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, and then passed into a spiral chute or a shaking table for gravity separation, and the red mud concentrate with a larger density and the red mud tailings with a smaller density are separated by gravity separation; (3) Desiliconization of red mud concentrate: The red mud concentrate is further treated by biological flocculation and sedimentation, including: (3.1) inoculating Paenibacillus polymyxa into a sterilized activation culture medium, stirring or shaking and culturing at 32 to 35° C. for 3 days to obtain an activated Paenibacillus polymyxa seed solution; (3.2) inoculating the activated Bacillus polymyxa seed solution obtained in step (3.1) into the sterilized flocculation culture solution, stirring or shaking the culture solution at 32 to 35°C; when the CFU of live bacteria in the flocculation culture solution exceeds 2.0×10 7 When the polysaccharide content exceeds 1.2 g / L, the culture is terminated, the culture solution is centrifuged, the supernatant is discarded, and the remaining viscous liquid is the bioactive flocculant; The flocculation culture solution uses deionized water as 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 solution are sterilization at 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 obtained flocculation system to 5.6-5.8 with dilute hydrochloric acid, slowly stirring and then standing, pouring off the supernatant, and rinsing the collected flocculation precipitate with clean water to obtain a red mud concentrate after further desiliconization; (4) Leaching of desiliconized red mud concentrate: the desiliconized red mud concentrate in step (3) is placed in a chemical leaching system containing an acid leaching solution composed of an inorganic acid for chemical leaching, or the desiliconized red mud concentrate in step (3) is placed in a biological leaching system composed of acid-producing microorganisms for biological leaching; a 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 liquid 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 liquid and then secondary mineralized to form a crystalline quartz precipitate, which is discharged with the filter residue.

2. The method for preventing the generation of silica gel in red mud leaching liquid 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 leaching liquid according to claim 1, characterized in that In step (2), the density of the red mud concentrate is greater than 3.5 g / cm 3 The density of red mud tailings is less than 3.0g / cm 3 The red mud concentrate is mainly a mixture of hematite, goethite, rutile, anatase, perovskite, monazite, fluorocarbon cerium and xenotime; the red mud tailings are mainly a mixture of quartz, calcite and aluminosilicate minerals.

4. The method for preventing the generation of silica gel in red mud leaching liquid according to claim 1, characterized in that In step (3.1), the activation culture medium uses deionized water as 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.

5. The method for preventing the generation of silica gel in red mud leaching liquid according to claim 1, characterized in that 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; 6. The method for preventing the generation of silica gel in red mud leaching liquid according to claim 1, characterized in that In step (3.2), the obtained bioactive flocculant is freeze-dried and made into powder for long-term storage, and is dissolved in deionized water when used; The preparation method of 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 0.01-0.1MPa, and then freeze-drying at a temperature of -30--40°C and a vacuum degree of 0.03mbar to prepare powder.

7. The method for preventing the generation of silica gel in red mud leaching liquid according to claim 1, characterized in that In step (3.3), the mass (g) of red mud concentrate in the flocculation system accounts for 5-10% of the sum of the volumes (mL) 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.

8. The method for preventing the generation of silica gel in red mud leaching liquid 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.

9. The method for preventing the generation of silica gel in red mud leaching liquid 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 mass of the desiliconized red mud concentrate added accounts for 5-20% of the mass of the acidic fermentation liquid in the bioleaching system, and 8-9 mL of the H2O2 solution is added for every 100 g of the desiliconized red mud concentrate.

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