Process for the separation of silicate from magnesium in black mica

Abstract

The application provides a method for separating silicon and magnesium in black talc. The method comprises the following steps: mixing black talc powder with alkali materials and calcining, adding into water for leaching, solid-liquid separation, to obtain filtrate and residue; introducing carbon dioxide into the filtrate for reaction, solid-liquid separation, to obtain silicic acid and sodium carbonate solution, the silicic acid is calcined to obtain silicon dioxide powder, and the sodium carbonate solution is evaporated to obtain sodium carbonate solid; the residue is added with water to prepare a slurry, carbon dioxide is introduced into the slurry for reaction, solid-liquid separation, to obtain silicic acid residue and magnesium bicarbonate solution, the silicic acid residue is washed with acid to obtain pure polysilicic acid (hydrated white carbon black) and acid washing solution; the above-mentioned magnesium bicarbonate solution is pyrolyzed to obtain sodium bicarbonate solution and magnesium carbonate, and the magnesium carbonate is dried and calcined to obtain magnesium oxide. The method for separating and extracting silicon and magnesium in black talc by alkali fusion-calcination breaks the stable T-O-T structure of black talc, realizes efficient separation of silicon and magnesium resources, and cooperates with a suitable preparation route to obtain silicon dioxide and magnesium oxide products.

Description

Technical Field

[0001] This invention relates to the field of black talc separation applications, and more particularly to methods for separating silicon and magnesium from black talc and their comprehensive applications. Background Technology

[0002] Currently, research has been conducted on separating and extracting silicon and magnesium from talc to prepare a series of chemical products. The extraction and utilization technology for magnesium mainly involves: acid leaching of talc powder with sulfuric acid; soluble substances such as magnesium oxide enter the acid solution; the magnesium-containing solution undergoes alkali treatment, reaction, filtration, washing, drying, and calcination to obtain magnesium oxide, which is further reduced to metallic magnesium through an in-situ high-temperature carbon reduction reaction. The separation process for silicon mainly involves: acid leaching of talc powder followed by filtration; the resulting filter cake is then washed, alkali-hydrolyzed, reacted, filtered, washed, and dried to prepare silica. However, these utilization technologies suffer from the problem of producing only one product and failing to achieve simultaneous comprehensive utilization of silicon and magnesium, resulting in low utilization rates of the effective components. Summary of the Invention

[0003] The main objective of this invention is to provide a method for separating silicon and magnesium from black talc, in order to solve the technical problem that the existing technology produces only one product, which cannot achieve the comprehensive utilization of silicon and magnesium at the same time, resulting in low utilization rate of effective components.

[0004] To achieve the above objectives, the present invention provides a method for separating magnesium silicate from black talc, comprising the following steps: Black talc is mixed with an alkaline substance and calcined at 250~380℃, then leached in water for the first solid-liquid separation to obtain filtrate and filter residue; wherein the mass ratio of black talc powder to alkaline substance is (1:0.5)~(1:2). Carbon dioxide gas is introduced into the filtrate to carry out a reaction, and a second solid-liquid separation is performed to obtain the solid, which is silicic acid; the silicic acid is then calcined to obtain silicon dioxide powder. The filter residue is slurried with water and then reacted with carbon dioxide gas to carry out a third solid-liquid separation, yielding silica residue and magnesium bicarbonate solution. The silica residue is then acid-washed to obtain polysilicic acid. The magnesium bicarbonate solution is pyrolyzed to obtain sodium bicarbonate solution and magnesium carbonate, and the magnesium carbonate is dried and calcined to obtain magnesium oxide.

[0005] According to an embodiment of this application, the black talc and the alkaline substance react in a rotary kiln, and the rotation speed of the rotary kiln is 1~5 r / min. The rotary kiln is equipped with a stirring rod, and the mixture of black talc and alkaline substances is located within the stirring range of the stirring rod.

[0006] According to an embodiment of this application, the step of introducing carbon dioxide gas into the filtrate to carry out the reaction includes: The filtrate flows from the open container into the mixing tube, and after being sprayed and mixed with carbon dioxide gas, it returns from the mixing tube to the open container. The reaction time is 30 min to 2 h.

[0007] According to an embodiment of this application, the filtrate is sprayed out after flowing at a rate of 300-700 mL / min, and the carbon dioxide is introduced into the mixing tube at a rate of 10-100 mL / min.

[0008] According to an embodiment of this application, the process of adding water to the filter residue to form a slurry and then introducing carbon dioxide gas for reaction includes: The filter residue is mixed with water to form a filter slurry. The filter slurry flows from the open container into the mixing pipe and is mixed with carbon dioxide gas in a spray manner before returning from the mixing pipe to the open container.

[0009] According to the embodiments of this application, in the step of calcining the black talc with an alkaline substance at 250~380°C, then adding water for leaching and performing the first solid-liquid separation: The solid-liquid ratio for water immersion is 1:1-1:8 g / mL. The first solid-liquid separation is performed by low-speed centrifugation at 500-3000 rpm.

[0010] According to an embodiment of this application, the silica slag is acid-washed with dilute acid, wherein the dilute acid is at least one of hydrochloric acid and sulfuric acid, and the concentration is 0.1-1 mol / L.

[0011] According to the embodiments of this application, the calcination temperature of the silica is 50-200°C.

[0012] According to an embodiment of this application, the pyrolysis temperature of the magnesium bicarbonate solution is 50-100°C.

[0013] According to the embodiments of this application, the drying temperature of the magnesium carbonate is 80-120℃, the calcination temperature is 400-700℃, and the calcination time is 1-4h.

[0014] In the above-described method for separating silica and magnesium from black talc, black talc reacts with an alkaline substance to break down its structure through alkali fusion and remove its blackening component, carbon. In subsequent processes, a suitable preparation route is selected, with silica and magnesium oxide as the main products. This method simultaneously yields both silica and magnesium oxide, making it valuable for industrial application. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a process flow diagram of a method for separating silicon and magnesium from black talc according to one embodiment of this application.

[0017] Figure 2 This is a schematic diagram of the gas-liquid enhancement device according to one embodiment of this application.

[0018] Figure 3 This is a SEM image of the silica product of Embodiment 10 of this application.

[0019] Figure 4 This is an XRD analysis spectrum of the filter residue according to one embodiment of this application.

[0020] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0023] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0024] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0025] This invention provides a method for separating magnesium silicate from black talc, comprising the following steps: S100: Black talc is mixed with an alkaline substance and calcined at 250~380℃, then leached in water for the first solid-liquid separation to obtain filtrate and filter residue. The mass ratio of black talc powder to alkaline substance is (1:0.5)~(1:2).

[0026] In this step, since black talc is a triclinic crystal system, its structure belongs to the 2:1 type (TOT type) layered mineral. Each unit cell is formed by two layers of silicon-oxygen tetrahedra sandwiching a layer of magnesium hydroxide octahedral plates, and each unit cell is also interspersed with a single or multiple layers of organic matter, resulting in a compact and stable structure.

[0027] Theoretically, the interlayer spacing of black talc is 2.875 Å, which is very small, close to the length of a chemical bond (approximately 2.5 Å). Therefore, its small interlayer spacing makes it difficult for other guest ions to insert. Furthermore, the relatively small interlaminar spacing leads to relatively strong interlayer interactions, making Mg-Si separation difficult. In black talc, Si and O are connected by covalent bonds, and Si and Mg share an oxygen atom, which also contributes to the difficulty in separating Mg-Si. Due to the 2:1 (TOT) structure of black talc, it is even more difficult to separate Mg and Si compared to layered silicate compounds like serpentine.

[0028] In some related technologies, Mg and Si elements are selectively leached using mixed acids. However, this method requires high acid corrosion resistance of the reaction vessel, thus limiting its application. Therefore, this application adopts a different design approach, using alkali fusion to break down the black talc structure.

[0029] Black talc is mixed with alkaline substances and calcined at 250~380℃, and the mass ratio of black talc powder to alkaline substances is (1:0.5)~(1:2).

[0030] Extensive experiments have determined that alkali dissolution is achieved using a relatively mild calcination temperature and a relatively small amount of alkaline substances. The calcination is conventional, which, compared to microwave alkali fusion, is more suitable for large-scale industrial production. Furthermore, the relatively low temperature results in less alkali consumption, making it suitable for widespread industrial application.

[0031] During the calcination process, the main calcination reactions that occur in black talc are: 3MgO·4SiO2·H2O + 8NaOH → 4Na2SiO3+ 3Mg(OH)2+_2H2O In addition, carbon in black talc will also produce carbon dioxide gas during the calcination process. Thus, the calcined black talc will also form a large number of pores, increasing the surface area, which is beneficial for the subsequent reaction of filter residue with carbon dioxide.

[0032] XRD analysis was performed on the filter residue; the results are shown in [link to XRD analysis]. Figure 4 The elemental composition of the filter residue is as follows: Si 50.24%, Mg 99.88%, Na 24.57%.

[0033] Black talc has a powder structure, which increases its contact area with alkaline substances. In some embodiments, the black talc powder has a particle size of 1000-1250 mesh. The alkaline substance is sodium hydroxide.

[0034] In some embodiments, the mass ratio of black talc powder to alkali is 1:1 to 1:1.5. Under these conditions, the alkali-fusion reaction is more complete and the effect is better.

[0035] In some embodiments, the calcination temperature is 280-330°C. Under these conditions, the alkali-fusion reaction is more complete, resulting in a higher conversion rate.

[0036] After the alkali fusion reaction, the reactants are added to water for leaching, performing the first solid-liquid separation to obtain filtrate and filter residue. The method of the first solid-liquid separation is not specifically limited, such as filtration or centrifugation. In some embodiments, the solid-liquid separation method is low-speed centrifugation at 500-3000 rpm. For example, the centrifugation speed is 1500-2500 rpm.

[0037] S200: Carbon dioxide gas is introduced into the filtrate to carry out a reaction, and a second solid-liquid separation is performed to obtain the solid, silicic acid. The silicic acid is then calcined to obtain silicon dioxide powder.

[0038] The introduction of carbon dioxide gas into the filtrate constitutes a carbonization reaction. The carbonization reaction is as follows: Na2SiO3+CO2+ nH2O→Na2CO3+SiO2·nH2O The second solid-liquid separation method can be the same as the first solid-liquid separation method, and will not be described again. The liquid in the second solid-liquid separation is a sodium carbonate solution. In some embodiments, the sodium carbonate solution is evaporated to obtain sodium carbonate.

[0039] S300: The filter residue is mixed with water to form a slurry, and carbon dioxide gas is introduced to react and perform a third solid-liquid separation to obtain silica slag and magnesium bicarbonate solution. The silica slag is then acid-washed to obtain polysilicic acid.

[0040] The filter residue is mixed with water to obtain a filter slurry. Passing carbon dioxide gas into the filter slurry also constitutes a carbonization reaction. The carbonization reaction is as follows: Na2SiO3+CO2+ nH2O→Na2CO3+SiO2·nH2O Mg(OH)₂ + 2CO₂ → Mg(HCO₃)₂ A small amount of Mg(OH)2 is converted into MgCO3.

[0041] The method for the third solid-liquid separation can be the same as that for the first solid-liquid separation, and will not be repeated here.

[0042] S400: The magnesium bicarbonate solution is pyrolyzed to obtain sodium bicarbonate solution and magnesium carbonate, and the magnesium carbonate is dried and calcined to obtain magnesium oxide.

[0043] In the above-described method for separating silica and magnesium from black talc, black talc reacts with an alkaline substance to break down its structure through alkali fusion and remove its blackening component, carbon. In subsequent processes, a suitable preparation route is selected, with silica and magnesium oxide as the main products. This method simultaneously yields both silica and magnesium oxide, making it valuable for industrial application.

[0044] In some embodiments, the black talc and the alkaline substance react in a rotary kiln at a rotation speed of 1-5 r / min. A stirring rod is placed in the rotary kiln, and the mixture of black talc and the alkaline substance is located within the stirring range of the stirring rod.

[0045] The rotary kiln rotates at a speed of 1-5 r / min. Under these conditions, the rotation of the kiln ensures thorough mixing of the talc and alkaline substances, resulting in a more efficient alkali-fusion reaction. Furthermore, the reactants tend to solidify during the alkali-fusion reaction. Therefore, a stirring rod is placed inside the rotary kiln. During rotation, the stirring rod breaks up the solidified surfaces, promoting thorough mixing of the talc and alkaline substances as the kiln rotates.

[0046] In some embodiments, the step of introducing carbon dioxide gas into the filtrate to carry out the reaction includes: The filtrate flows from the open container into the mixing tube, and after being sprayed and mixed with carbon dioxide gas, it returns from the mixing tube to the open container. The reaction time is 30 min to 2 h.

[0047] Since the mass transfer rate of the gas-liquid two-phase reaction is also a challenge of this process, at least one of the filtrate and filter residue slurry carbonization can be carried out using a gas-liquid enhancement device (i.e., a mixing tube), which can reach the reaction endpoint in a shorter time.

[0048] See Figure 2An open container is connected to the external atmospheric pressure. The open container contains a reaction system of filtrate and carbon dioxide gas. The open container has multiple openings, such as a three-necked flask. One opening allows a portion of the filtrate to be drawn into a mixing tube via a filtrate line. Exemplarily, the mixing tube has a first branch, a second branch, and a third branch, all extending into the inner cavity of the mixing tube. The first branch is connected to the filtrate line, with its end furthest from the filtrate line being constricted, thus creating a spray of filtrate. The second branch is connected to the carbon dioxide line, with its end furthest from the carbon dioxide line pointing towards the constricted end of the first branch, ensuring thorough contact and mixing of the sprayed filtrate with the carbon dioxide, and then entering the filtrate within the open container through the third branch. Under these conditions, the mass transfer rate of the gas-liquid two-phase reaction is significantly increased, the reaction time is shortened to 30 min–2 h, and the reaction efficiency is greatly improved.

[0049] In some embodiments, the reaction time is 40 min to 1 h. Under these conditions, the reaction time is shortened and the reaction rate is faster.

[0050] In some embodiments, the filtrate is sprayed out after flowing at a rate of 300-700 mL / min, and the carbon dioxide is introduced into the mixing tube at a rate of 10-100 mL / min.

[0051] In some embodiments, the reaction of adding water to the filter residue to form a slurry and then introducing carbon dioxide gas includes: The filter residue is mixed with water to form a filter slurry. The filter slurry flows from the open container into the mixing pipe and is mixed with carbon dioxide gas in a spray manner before returning from the mixing pipe to the open container.

[0052] For specific reaction conditions and principles, please refer to the relevant descriptions of the reaction when carbon dioxide gas is passed through the filtrate, which will not be repeated here.

[0053] In some embodiments, in the step of calcining the black talc with an alkaline substance at 250-380°C, then adding water for leaching to perform the first solid-liquid separation: The solid-liquid ratio for water immersion is 1:1-1:8 g / mL. The first solid-liquid separation is performed by low-speed centrifugation at 500-3000 rpm.

[0054] In some embodiments, the silica slag is acid-washed with dilute acid, wherein the dilute acid is at least one of hydrochloric acid and sulfuric acid, and the concentration is 0.1-1 mol / L.

[0055] In some embodiments, the calcination temperature of the silica is 50-200°C.

[0056] The calcination of silicic acid is a dehydration reaction, and its specific reaction principle is as follows: SiO2·nH2O→SiO2+nH2O In some specific embodiments, the calcination temperature of silica is 80-150°C. Under these conditions, the calcination temperature is relatively mild, and the reaction efficiency is relatively high.

[0057] In some embodiments, the pyrolysis temperature of the magnesium bicarbonate solution is 50-100°C.

[0058] In some embodiments, the magnesium carbonate is dried at a temperature of 80-120°C, calcined at a temperature of 400-700°C, and calcined for 1-4 hours.

[0059] This invention achieves deep separation of silicon and magnesium in black talc ore. Using black talc ore as raw material, it prepares nano-silica and high-purity magnesium products, solving the problems of low resource utilization and low-value, single-product diversification of black talc. The separation process uses simple reagents, has low energy consumption and low cost, produces very little waste gas, and allows for wastewater recycling. The process is simple and easily industrialized. Compared with the acid method, the alkali fusion-carbonation technology not only achieves carbon dioxide fixation and reduces greenhouse gas emissions, but also recovers sodium carbonate byproducts during production, which is a raw material for the production of water glass.

[0060] The technical solution of this application will be described below with reference to specific embodiments.

[0061] Example 1 This embodiment provides a method for separating magnesium silicate from black talc, including the following steps: S100: Take 240 g of black talc powder and 216 g of alkali (sodium hydroxide, with a mass ratio of 1:0.9), ball mill and mix them evenly, and calcine at 300 ℃ for 2 h. Weigh 500 g of the calcined material, add 500 mL of water and stir at room temperature for 1.5 h, filter to obtain filtrate and filter residue, determine the element content in the filtrate by ICP-OES, and calculate the leaching rate as shown in Table 1.

[0062] Example 2 The only difference from Example 1 is that the calcination time in S100 is 4 hours. Everything else is the same as in Example 1. The elemental content in the filtrate was determined, and the leaching rate was calculated as shown in Table 1.

[0063] Example 3 The only difference from Example 1 is that the amount of alkali added in S100 is changed so that the mass ratio of black talc powder to alkali is 1:1. Everything else is the same as in Example 1. The elemental content in the filtrate was measured, and the leaching rate was calculated as shown in Table 1.

[0064] Example 4 The only difference from Example 1 is that the amount of alkali added in S100 is changed so that the mass ratio of black talc powder to alkali is 1:1, and the calcination temperature is 350°C and the calcination time is 4 hours. Everything else is the same as in Example 1. The elemental content in the filtrate was measured, and the leaching rate was calculated as shown in Table 1.

[0065] Example 5 The only difference from Example 1 is that the amount of alkali added in S100 was changed so that the mass ratio of black talc powder to alkali was 1:1.1, and the calcination time was 4 hours. Everything else was the same as in Example 1. The elemental content in the filtrate was measured, and the leaching rate was calculated as shown in Table 1.

[0066] Example 6 The only difference from Example 1 is that the amount of alkali added in S100 is changed so that the mass ratio of black talc powder to alkali is 1:1.2. Everything else is the same as in Example 1. The elemental content in the filtrate was measured, and the leaching rate was calculated as shown in Table 1.

[0067] Example 7 The only difference from Example 1 is that the amount of alkali added in S100 was changed so that the mass ratio of black talc powder to alkali was 1:1.35, and the calcination time was 4 hours. Everything else was the same as in Example 1. The elemental content in the filtrate was determined, and the leaching rate was calculated as shown in Table 1.

[0068] Example 8 The only difference from Example 1 is that the amount of alkali added in S100 is changed so that the mass ratio of black talc powder to alkali is 1:1.5, and the calcination time is 4 hours. Everything else is the same as in Example 1. The elemental content in the filtrate was determined, and the leaching rate was calculated as shown in Table 1.

[0069] Example 9 The only difference from Example 1 is that the amount of alkali added in S100 is changed so that the mass ratio of black talc powder to alkali is 1:2, and the calcination time is 4 hours. Everything else is the same as in Example 1. The elemental content in the filtrate was measured, and the leaching rate was calculated as shown in Table 1.

[0070] Comparative Example 1 The only difference from Example 6 is that the calcination temperature in S100 is 400°C and the calcination time is 4 hours. Everything else is the same as in Example 6. The elemental content in the filtrate was determined, and the leaching rate was calculated as shown in Table 1.

[0071] Comparative Example 2 The only difference from Example 6 is that the calcination temperature in S100 is 550°C and the calcination time is 4 hours. Everything else is the same as in Example 6. The elemental content in the filtrate was determined, and the leaching rate was calculated as shown in Table 1.

[0072] Example 10 S200: Carbon dioxide was introduced into the filtrate obtained in Example 1, and a carbonization reaction was carried out using a gas-liquid enhancement device. The filtrate was circulated and sprayed out at 300 mL / min, and carbon dioxide gas was introduced at 50 mL / min. The reaction time was 40 min. Solid-liquid separation yielded silicic acid and sodium carbonate solution. The silicic acid was dehydrated at 80°C to obtain silicon dioxide with a purity greater than 99%.

[0073] S300: Take a certain amount of filter residue obtained in Example 1, add a certain volume of pure water (solid-liquid ratio of 1:15 g / mL), and carry out a carbonization reaction using a gas-liquid enhancement device. The slurry is circulated and sprayed out at 300 mL / min, and carbon dioxide gas is introduced at 50 mL / min. The reaction time is 60 min. Solid-liquid separation yields silica slag and magnesium bicarbonate solution, and the leaching rates of silicon and magnesium elements in the magnesium bicarbonate solution are calculated. The calculation method is as follows: The silicon and magnesium content in the solution before and after carbonization is determined by ICP. The leaching rate of each element = (element content before carbonization - element content after carbonization) / element content before carbonization.

[0074] The silica residue was washed with 0.1 mol / L hydrochloric acid and pure water. After drying the solid, hydrated silica (polysilicic acid) was obtained, and its SEM image is shown below. Figure 3 As shown.

[0075] S400: The above magnesium bicarbonate solution is pyrolyzed at 60°C to obtain sodium bicarbonate solution and magnesium carbonate. The magnesium carbonate is washed, dried, and then calcined to obtain magnesium oxide product with a purity greater than 98%.

[0076] Example 11 The only difference from Example 10 is that the amount of pure water added in S200 is changed so that the solid-liquid ratio of the filter residue to pure water is 1:20. The rest is the same as in Example 10. The leaching rates of silicon and magnesium in the magnesium bicarbonate solution are shown in Table 2.

[0077] Example 12 The only difference from Example 10 is that the amount of pure water added in S200 is changed so that the solid-liquid ratio of the filter residue to pure water is 1:25. The rest is the same as in Example 10. The leaching rates of silicon and magnesium in the magnesium bicarbonate solution are shown in Table 2.

[0078] Example 13 The only difference from Example 10 is that the amount of pure water added in S200 is changed so that the solid-liquid ratio of the filter residue to pure water is 1:32. The rest is the same as in Example 10. The leaching rates of silicon and magnesium in the magnesium bicarbonate solution are shown in Table 2.

[0079] Example 14 The only difference from Example 10 is that the amount of pure water added in S200 is changed so that the solid-liquid ratio of the filter residue to pure water is 1:37. The rest is the same as in Example 10. The leaching rates of silicon and magnesium in the magnesium bicarbonate solution are shown in Table 2.

[0080] Table 1. Reaction conditions and leaching rates of the examples and comparative examples Referring to Table 1, the data from Examples 1-9, Comparative Examples 1 and 2 show that within the range of a mass ratio of black talc to alkali material of 1:0.9 to 1:2, different calcination temperatures, calcination times, and alkali material ratios all affect the leaching rate of silicon (Si) and magnesium (Mg) in the water leaching reaction.

[0081] When the calcination temperature is 300℃, the silicon leaching rate generally shows a trend of initial fluctuation followed by a gradual increase as the alkali-to-material ratio increases (from 1:0.9 to 1:2). For example, in Example 1, with an alkali-to-material ratio of 1:0.9 and calcination for 2 hours, the silicon leaching rate is 40.21%; in Example 3, with the alkali-to-material ratio increased to 1:1 and calcination for 2 hours, the silicon leaching rate increases to 44.07%; in Example 8, with an alkali-to-material ratio of 1:1.5 and calcination for 4 hours, the silicon leaching rate further increases to 48.40%; and in Example 9, with an alkali-to-material ratio of 1:2 and calcination for 4 hours, the silicon leaching rate reaches 49.20%. Simultaneously, appropriately extending the calcination time also helps to improve the silicon leaching rate; for example, in Example 1 (calcination for 2 hours), the silicon leaching rate is 40.21%, and in Example 2 (same ratio as Example 1, calcination for 4 hours), the silicon leaching rate increases to 49.96%.

[0082] Regarding the magnesium leaching rate, it remained relatively low (1.00%-3.26%) in all examples, indicating that under these process conditions, magnesium mainly remained in the filter residue, achieving preliminary separation of silicon and magnesium and laying the foundation for subsequent magnesium extraction from the filter residue. However, comparing Example 6 with Comparative Examples 1 and 2 reveals that when the calcination temperature increased to 400℃ and 550℃, the silicon leaching rate decreased significantly. The silicon leaching rate in Comparative Example 1 (400℃) was only 26.92%, and in Comparative Example 2 (550℃) it was even lower at 14.50%. This indicates that excessively high calcination temperatures are not conducive to silicon leaching from black talc, and around 300℃ is a more suitable calcination temperature range.

[0083] Table 2 Conditions and leaching rates of carbonization reaction for each embodiment Referring to Table 2, the data from Examples 10-14 show that as the solid-liquid ratio of the filter residue slurry gradually increased from 1:15 g / mL to 1:37 g / mL, the leaching rates of silicon (Si) and magnesium (Mg) exhibited different trends during the carbonization reaction. Example 10 (1:15): The magnesium leaching rate was at a basic level, while the silicon leaching rate was low. Example 11 (1:20): The magnesium leaching rate slightly increased, while the silicon leaching rate increased significantly. Example 12 (1:25): The magnesium leaching rate increased significantly, while the silicon leaching rate increased slightly. Example 13 (1:32): The magnesium leaching rate reached its highest value, while the silicon leaching rate continued to increase. Example 14 (1:37): The magnesium leaching rate slightly decreased, while the silicon leaching rate continued to rise to its highest level.

[0084] The above examples show that appropriately reducing the concentration of the filter residue slurry is beneficial for magnesium leaching, but an excessively high solid-liquid ratio will lead to a decrease in magnesium leaching efficiency; the silicon leaching rate increases continuously with the increase of the solid-liquid ratio, which may be related to the adequacy of carbon dioxide gas contact. The 1:32 solid-liquid ratio condition in Example 13 can better balance the efficient leaching of magnesium and the relatively low leaching of silicon, which is beneficial for subsequent purification of magnesium bicarbonate solution and preparation of high-purity magnesium products.

[0085] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for separating magnesium silicate from black talc, characterized in that, Includes the following steps: Black talc is mixed with an alkaline substance and calcined at 250~380℃, then leached in water for the first solid-liquid separation to obtain filtrate and filter residue; wherein the mass ratio of black talc powder to alkaline substance is (1:0.5)~(1:2). Carbon dioxide gas is introduced into the filtrate to carry out a reaction, and a second solid-liquid separation is performed to obtain the solid, which is silicic acid; the silicic acid is then calcined to obtain silicon dioxide powder. The filter residue is slurried with water and then reacted with carbon dioxide gas to carry out a third solid-liquid separation, yielding silica residue and magnesium bicarbonate solution. The silica residue is then acid-washed to obtain polysilicic acid. The magnesium bicarbonate solution is pyrolyzed to obtain sodium bicarbonate solution and magnesium carbonate, and the magnesium carbonate is dried and calcined to obtain magnesium oxide.

2. The method for separating silica and magnesium from black talc according to claim 1, characterized in that, The black talc and the alkaline substance react in a rotary kiln, the rotary kiln rotating at a speed of 1~5 r / min; The rotary kiln is equipped with a stirring rod, and the mixture of black talc and alkaline substances is located within the stirring range of the stirring rod.

3. The method for separating silica and magnesium from black talc according to claim 1, characterized in that, The step of introducing carbon dioxide gas into the filtrate to carry out the reaction includes: The filtrate flows from the open container into the mixing tube, and after being sprayed and mixed with carbon dioxide gas, it returns from the mixing tube to the open container. The reaction time is 30 min to 2 h.

4. The method for separating silica and magnesium from black talc according to claim 3, characterized in that, The filtrate is sprayed out after flowing at a rate of 300-700 mL / min, and the carbon dioxide is introduced into the mixing tube at a rate of 10-100 mL / min.

5. The method for separating silica and magnesium from black talc according to claim 1, characterized in that, The process of adding water to the filter residue to make a slurry and then introducing carbon dioxide gas for reaction includes: The filter residue is mixed with water to form a filter slurry. The filter slurry flows from the open container into the mixing pipe and is mixed with carbon dioxide gas in a spray manner before returning from the mixing pipe to the open container.

6. The method for separating magnesium silicate from black talc according to claim 1, characterized in that, In the step of calcining black talc with an alkaline substance at 250-380°C, followed by leaching in water for the first solid-liquid separation: The solid-liquid ratio for water immersion is 1:1-1:8 g / mL. The first solid-liquid separation is performed by low-speed centrifugation at 500-3000 rpm.

7. The method for separating silica and magnesium from black talc according to claim 1, characterized in that, The silica slag is acid-washed with dilute acid, wherein the dilute acid is at least one of hydrochloric acid and sulfuric acid, and the concentration is 0.1-1 mol / L.

8. The method for separating magnesium silicate from black talc according to claim 1, characterized in that, The calcination temperature of the silicic acid is 50-200℃.

9. The method for separating silica and magnesium from black talc according to claim 1, characterized in that, The pyrolysis temperature of the magnesium bicarbonate solution is 50-100℃.

10. The method for separating magnesium silicate from black talc according to any one of claims 1 to 9, characterized in that, The magnesium carbonate is dried at a temperature of 80-120℃, calcined at a temperature of 400-700℃, and calcined for 1-4 hours.

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