Method for preparing active silicon-based material from red mud

Abstract

The invention aims to provide a method for preparing an active silicon-based material from red mud, which belongs to the technical field of resource utilization, and comprises the following steps: carrying out acid leaching on the red mud by using hydrochloric acid to remove alkaline components and soluble metal oxides in the red mud so as to obtain acid leaching residues mainly comprising SiO2; then, a small amount of alkaline red mud is mixed for neutralization washing, residual acidic substances are effectively removed, and the acid leaching residues are converted into neutral leaching residues. And calcining to promote the activation of a silicon phase, thereby finally preparing the active silicon-based material with large specific surface area and excellent chemical stability. The process is simple and convenient to operate, is suitable for large-scale production, and can effectively improve the additional value of the red mud.

Description

Technical Field

[0001] The invention belongs to the technical field of resource utilization, and specifically relates to a method for preparing active silicon-based materials from red mud. Background Art

[0002] Red mud is an alkaline solid waste produced during the production of alumina. Its main components include SiO 2 、Al 2 O 3 ,CaO,Fe 2 O 3 、Na 2 O, etc. Due to the rapid development of the alumina industry, the annual output of red mud in my country has reached more than 100 million tons, of which more than 90% has not been effectively utilized and is mainly disposed of in the form of stockpiling. Red mud is highly alkaline and corrosive. Long-term stockpiling not only occupies a large amount of land resources, but may also lead to the leaching of alkaline substances and heavy metals, pollute groundwater, and seriously threaten the surrounding ecological environment. Therefore, achieving harmless treatment and resource utilization of red mud has become an important issue that needs to be urgently solved in the field of comprehensive utilization of solid waste and environmental protection in my country.

[0003] In view of the high alkalinity of red mud, acid leaching has been widely studied to remove its alkaline components. 2 O 3 ,CaO,Fe 2 O 3 、Na 2 Soluble components such as O are selectively dissolved to obtain SiO 2 The acid leaching residue is mainly composed of the red mud, which realizes the dealkalization transformation of red mud. It is worth noting that during the acid leaching process, the physical structure of the red mud is reconstructed. 2 The acid leaching residue is then released and converted into active silicon dioxide. After calcination and activation, the acid leaching residue can be further transformed into an active silicon-based material with a large specific surface area and excellent chemical stability.

[0004] Active silicon-based materials have broad application prospects in many fields due to their excellent physical and chemical properties. For example, it can be used as a filler for polyvinyl chloride to improve the mechanical properties and heat resistance of the material; it can be used in the preparation of microcrystalline glass and ceramics to improve the structural strength and corrosion resistance of the product; in addition, it can also be used as a catalyst carrier to provide an efficient and stable support system in the catalytic reaction. Therefore, the preparation of active silicon-based materials based on red mud acid leaching residue can not only achieve the high-value utilization of red mud and increase its added value, but also effectively reduce the stockpile of red mud and alleviate the environmental pollution problems it brings, which has important environmental and economic significance.

[0005] In summary, there is an urgent need for an efficient and industrially promotable technology to remove the alkaline components in red mud by acid leaching and perform deacidification and calcination activation treatment on the leaching residue, so as to prepare an active silicon-based material with excellent performance and realize the resource utilization and environmentally friendly disposal of red mud. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing an active silicon-based material from red mud with a simple process and industrial applicability, so as to realize the high-value utilization of red mud resources and effectively reduce its environmental hazards.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention uses hydrochloric acid to leach red mud to remove the alkaline components and soluble metal oxides therein, and obtains an acid leaching residue mainly composed of SiO 2 Subsequently, by mixing a small amount of alkaline red mud for neutralization washing, the residual acidic substances are effectively removed, and the acid leaching residue is converted into a neutral leaching residue. Through calcination treatment, the activation of the silicon phase is promoted, and finally an active silicon-based material with a large specific surface area and excellent chemical stability is prepared. The specific steps are as follows: The first step, pulping: Load washing water and red mud into a pulping tank according to a ratio, and the stirring paddle stirs at a rate of 500 - 3000 r / min driven by a motor for 5 - 30 min to prepare the red mud into a slurry state; The second step, leaching: Pump the slurry-like red mud into a leaching reaction kettle, add concentrated hydrochloric acid, raise the temperature in the reaction kettle to 45 - 105 °C, stir evenly throughout the process, and leach for 30 - 240 min; The third step, after the leaching is completed, use an acid-resistant slurry pump to pump the slurry mixture of the leaching solution and the leaching residue to a plate and frame filter press, squeeze and filter to obtain an acidic leaching residue and a filtrate. The acidic leaching residue is washed once with washing water and then reserved. The washed filtrate and the filtrate obtained from the first filtration are combined into a leaching solution; The fourth step, neutralization washing: Mix red mud and the acidic leaching residue into a pulping tank, add fresh water again, and the stirring paddle beats at a rate of 500 - 3000 r / min. Monitor the pH of the aqueous solution in the pulping tank during beating, and increase the addition amount of alkaline red mud according to the pH value until the pH of the aqueous solution in the pulping tank is stabilized at 6.5 - 7.5, then the neutralization washing is completed; The fifth step, after neutralization washing, pump the mixed slurry to a plate and frame filter press, squeeze and filter to obtain a neutral leaching residue, and the washing water is recycled to the first step of pulping and the third step process; The sixth step, place the neutral leaching residue in a kiln for calcination to obtain an active silicon-based material after calcination.

[0008] Further, in the first step, the dosage ratio of the washing water to the red mud is 0.5 - 3 L: 1 kg.

[0009] Further, the dosage ratio of the red mud to the concentrated hydrochloric acid in the second step is 1 kg: 0.5 - 8 L, and the mass concentration of the concentrated hydrochloric acid is 20 - 37%.

[0010] Further, the dosage ratio of the washing water to the acid leaching residue in the third step is 1 - 6 L: 1 kg.

[0011] Further, the mass ratio of the red mud to the acid leaching residue in the fourth step is 0.1 - 1:1; the volume of the fresh water is denoted as V, the total mass of the red mud and the acid leaching residue is denoted as m, and V:m is 1 - 6 L: 1 kg.

[0012] Further, the calcination temperature in the sixth step is 400 - 1000 °C, and the calcination time is 10 - 180 min.

[0013] The beneficial effects of the present invention are as follows: The process of the present invention is simple to operate, suitable for large-scale production, can effectively improve the added value of red mud, and provides an efficient and feasible technical route for comprehensive utilization of red mud.

[0014] In the present invention, through acid leaching, soluble components such as Al 2 O 3 , CaO, Fe 2 O 3 , Na 2 O in the red mud are selectively dissolved, so as to obtain an acid leaching residue mainly composed of SiO 2 , realizing the de-alkalization conversion of red mud. During the acid leaching process, the phase structure of the red mud is reconstructed, and the originally bound SiO 2 is released and converted into active silica. Subsequently, through calcination activation treatment, the acid leaching residue can be further formed into an active silica-based material with a large specific surface area and excellent chemical stability.

[0015] The specific surface area range of the red mud is 64.09 - 186.9 m 2 / g. The red mud contains sodium hydroxide, is alkaline, and has unstable chemical properties. After washing, the acid leaching residue does not contain alkaline substances, the main component is SiO 2 , has stable chemical properties, and the specific surface area can reach 332.4 m 2 / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0018] Example 1 The process flow for preparing an active silicon-based material from red mud in this example is as Figure 1 shown, and the specific composition of the red mud used is shown in Table 1.

[0019] Table 1: Chemical composition of red mud used in Example 1 The data in Table 1 represent mass fractions, with the unit of %.

[0020] (1) Put 100 L of washing water and 100 kg of red mud into a pulping tank, and the stirring paddle is driven by a motor to stir at high speed. The high-speed pulping time is 10 minutes to prepare the red mud into a slurry state.

[0021] (2) Pump the slurry-like red mud obtained in the first step into a leaching reactor, add 200 L of concentrated hydrochloric acid with a mass fraction of 37%, the temperature in the reactor rises to 100 °C, and stir evenly throughout the process for 240 minutes of leaching.

[0022] (3) After the leaching is completed, use an acid-resistant slurry pump to pump the slurry mixture of the leaching solution and the leaching residue to a plate and frame filter press for extrusion filtration to obtain 33.6 kg (mass without water) of acidic leaching residue. The acidic leaching residue is washed once with washing water and reserved for use. The volume of washing water used is 130 L, and the filtrate after washing is combined with the filtrate obtained from the first filtration to form the leaching solution.

[0023] (4) Mix the red mud and the acidic leaching residue and put them into a pulping tank. The mass ratio of red mud to acidic leaching residue is 0.1:1, and then add fresh water. The ratio of the volume of fresh water to the solid mass is 4 L:1 kg. Pulping is carried out under the high-speed stirring of the stirring paddle. During pulping, monitor the pH of the aqueous solution in the pulping tank, and increase the addition amount of alkaline red mud according to the pH value until the pH of the aqueous solution in the pulping tank is stabilized at 7 to complete neutralization washing.

[0024] (5) After neutralization washing, pump the mixed slurry to a plate and frame filter press for extrusion filtration to obtain about 37.8 kg (mass without water) of neutral leaching residue. The washing water is recycled to the first-step pulping and the third-step process.

[0025] (6) Place the neutral leaching residue in a kiln for calcination. The calcination temperature is 750 °C, and the calcination time is 90 minutes. After calcination, about 37 kg of active silicon-based material is obtained.

[0026] Example 2 The technological process for preparing active silicon-based materials from red mud in this example is as Figure 1 shown, and the specific composition of the red mud used is shown in Table 2.

[0027] Table 2: Chemical composition of red mud used in Example 2 The data in Table 2 represent mass fractions, with the unit of %.

[0028] (1) Load 60 L of washing water and 100 kg of red mud into a pulping tank, and the stirring paddle stirs at high speed driven by a motor. The high-speed pulping time is 10 minutes to prepare the red mud into a slurry state.

[0029] (2) Pump the slurry-like red mud obtained in the first step into a leaching reactor, add 240 L of concentrated hydrochloric acid with a mass fraction of 35%, the temperature in the reactor rises to 100 °C, and stir evenly throughout the process for 180 minutes of leaching.

[0030] (3) After the leaching is completed, use an acid-resistant slurry pump to pump the slurry mixture of the leaching solution and the leaching residue to a plate and frame filter press for extrusion filtration to obtain 39.1 kg of acidic leaching residue (excluding the mass of water). The acidic leaching residue is washed once with washing water and then reserved. The volume of washing water used is 160 L, and the filtrate after washing is combined with the filtrate obtained from the first filtration as the leaching solution.

[0031] (4) Mix and load the red mud and the acidic leaching residue into a pulping tank. The mass ratio of the red mud to the acidic leaching residue is 0.15:1, and then add fresh water. The ratio of the volume of fresh water to the solid mass is 3 L:1 kg. Pulping is carried out under the high-speed stirring of the stirring paddle. During pulping, monitor the pH of the aqueous solution in the pulping tank, and increase the addition amount of alkaline red mud according to the pH value until the pH of the aqueous solution in the pulping tank is stabilized at 7 - 7.5, and then the neutralization washing is completed.

[0032] (5) After neutralization washing, pump the mixed slurry to a plate and frame filter press for extrusion filtration to obtain about 44.6 kg of neutral leaching residue (excluding the mass of water). The washing water is recycled to the first pulping and the third step process.

[0033] (6) Place the neutral leaching residue in a kiln for calcination. The calcination temperature is 900 °C, and the calcination time is 60 minutes. After calcination, about 44 kg of active silicon-based materials are obtained.

[0034] The active silica-based material has a high specific surface area and a porous structure, which can form a good interfacial bond with the polyvinyl chloride matrix, thereby improving the mechanical properties of the composite material, such as tensile strength and hardness. At the same time, its addition can also enhance the thermal stability of polyvinyl chloride, improve the heat resistance, and improve the melt fluidity, thus optimizing the processing performance. In addition, the relatively high hardness of the active silica-based material enables it to enhance the wear resistance of polyvinyl chloride and extend the service life of the product.

[0035] As an additive in the preparation of glass-ceramics and ceramics, the active silica-based material has significant advantages. Its high specific surface area and active surface can enhance the mechanical strength and hardness of the material, while improving the heat resistance of the material and enhancing its stability in high-temperature environments. In addition, the active silica-based material helps to improve the rheological properties of the material, optimize the operability during the processing, and enhance the chemical corrosion resistance of the material through its chemical stability, thereby extending the service life.

[0036] The active silica-based material with a high specific surface area, as a catalyst support, has significant advantages. Its high specific surface area provides abundant active sites, effectively adsorbing and activating reactant molecules, thereby enhancing the activity of the catalyst. At the same time, the pore structure of the active silica-based material can be optimized by adjusting the preparation conditions, improving the mass transfer performance of the catalyst and enhancing the catalytic reaction efficiency. In addition, the active silica-based material has good electrical conductivity and is suitable for fields such as electrocatalysis and photocatalysis, further expanding its application scope as a catalyst support. Its excellent chemical stability enables the material to remain stable under various reaction conditions, thereby extending the service life of the catalyst.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing active silicon-based materials from red mud, characterized in that: The steps include: The first step is beating: washing water and red mud are put into a beating tank in proportion, and a stirring paddle is driven by a motor to stir at a rate of 500-3000r / min for 5-30min to prepare the red mud into a slurry state; The second step is leaching: the slurry red mud is pumped into the leaching reactor, concentrated hydrochloric acid is added, the temperature in the reactor is raised to 45-105°C, stirred at a constant speed throughout the process, and leaching is carried out for 30-240 minutes; The third step is to use an acid-resistant slurry pump to pump the slurry mixed with the leaching liquid and the leaching residue to a plate-frame filter press after the leaching is completed, and the acid leaching residue and the filtrate are obtained by extrusion filtration. The acid leaching residue is washed once with washing water and then reserved for use. The filtrate after washing is combined with the filtrate obtained by the first filtration to form the leaching liquid; Step 4: Neutralization and washing: Mix the red mud and the acidic leaching residue and put them into a pulping tank, then add new water, and use a stirring paddle to pulp at a rate of 500-3000r / min. During the pulping process, the pH of the aqueous solution in the pulping tank is monitored, and the amount of alkaline red mud added is increased according to the pH value. After the pH of the aqueous solution in the pulping tank is stabilized to 6.5-7.5, the neutralization and washing is completed; Step 5: After neutralization and washing, the mixed slurry is pumped to a plate and frame filter press for extrusion filtration to obtain neutral leaching residue, and the washing water is circulated to the first step of pulping and the third step; In the sixth step, the neutral leaching residue is placed in a kiln for calcination to obtain active silicon-based materials.

2. The method for preparing active silicon-based materials from red mud according to claim 1, characterized in that: In the first step, the ratio of washing water to red mud is 0.5-3L:1kg.

3. The method for preparing active silicon-based materials from red mud according to claim 1, characterized in that: In the second step, the usage ratio of the red mud to the concentrated hydrochloric acid is 1kg:0.5-8L, and the mass concentration of the concentrated hydrochloric acid is 20-37%.

4. The method for preparing active silicon-based materials from red mud according to claim 1, characterized in that: In the third step, the ratio of the washing water to the acidic leaching residue is 1-6L:1kg.

5. The method for preparing active silicon-based materials from red mud according to claim 1, characterized in that: In the fourth step, the mass ratio of red mud to acid leaching residue is 0.1-1:1; the volume of new water is recorded as V, the total mass of red mud and acid leaching residue is recorded as m, and V:m is 1-6L:1kg.

6. The method for preparing active silicon-based materials from red mud according to claim 1, characterized in that: The calcination temperature in the sixth step is 400-1000° C., and the calcination time is 10-180 min.

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