A method for efficiently preparing silica gel and white carbon black by taking smelting slag as raw material

Abstract

The application discloses a method for efficiently preparing silica gel and white carbon black by taking smelting slag as raw material; the application relates to the fields of solid waste resource utilization, separation and purification and material preparation; the method is as follows: nickel-iron slag or copper smelting slag rich in SiO2 is dissolved under suitable acid leaching conditions, and after centrifugal separation, a supersaturated silicic acid solution is obtained; under normal temperature and in an open environment, stirring and surface activation are utilized to control the precipitation rate of the silicic acid gel system, to adjust the structure, morphology and size of the silica gel particles, to form a glue liquid mixture containing silica gel fine particles, and after glue liquid separation, wet silica gel is washed and dried to obtain dry silica gel, and after calcination, white carbon black with SiO2 content greater than 99 wt% is prepared; the method adopts an alkali-free preparation process taking smelting waste slag as raw material, and has the advantages of wide raw material adaptability, low energy consumption, low production cost, good product quality and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste resource utilization, separation and purification, and material preparation, and particularly relates to a method for efficiently preparing silica gel and white carbon black by using smelting slag as raw material. BACKGROUND

[0002] Silicon accounts for about 27.6% of the earth's crust, second only to oxygen. SiO2 is rich in many ores, tailings, beneficiation slag and smelting slag. In many cases, SiO2 is regarded as a gangue component and is discarded or used as a siliceous additive for cement, concrete, brick and other low-value building materials. For example, the main impurity of laterite nickel ore is SiO2, and the nickel-iron slag produced after nickel recovery usually contains 35-60% of SiO2; the copper smelting slag produced after copper recovery from copper sulfide ore usually contains 30-40% of SiO2; and the lithium slag powder produced after lithium recovery from spodumene usually contains 40-60% of SiO2. The common feature of these solid wastes is the high content of SiO2. SiO2 in water-quenched nickel-iron slag mainly exists in amorphous non-crystalline state, which has high activity and is easily dissolved in acid, so it is convenient to recover by acid method. Copper smelting slag mainly exists in crystalline Fe2SiO4 phase, although it is not as easy to dissolve in acid as non-crystalline SiO2, but under appropriate raw material particle size and acid leaching process parameters, most of the Fe2SiO4 phase can also be decomposed, and silicon and iron are released at the same time. However, for these solid wastes, the current research is still in the research stage, and the utilization rate is still very low, mainly in the form of stacking or landfill, which not only occupies a large amount of land, but also causes serious threat to the ecological environment. In order to reduce these solid wastes on a large scale and improve their resource utilization value, it is necessary to develop a universal high-value and efficient solid waste utilization method.

[0003] Silica gel, also known as hydrated silicon dioxide (SiO2·nH2O), is a kind of inorganic compound with porous structure, non-toxic and odorless, which has the characteristics of high temperature resistance, electrical and chemical stability, high insulation and other properties. Wet silica gel is jelly-like due to the high content of free water, and dry silica gel is the product of drying wet silica gel, which has very low water content. White carbon black is the product of high-temperature calcination of dry silica gel, which contains a small amount of crystal water. The purity of silica gel and white carbon black is usually measured by SiO2 content. Silica gel and white carbon black are widely used, dry silica gel is often used as a drying agent, an adsorbent and a molecular sieve, and white carbon black is often used as an additive for rubber, paint and plastic to improve the wear resistance of rubber, the uniform dispersibility of paint and the mechanical properties of plastic.

[0004] Traditional precipitation method is still the main method for industrial production of silica gel and white carbon black, which uses high-quality quartz sand as raw material, reacts with caustic soda to generate sodium silicate as intermediate product, then reacts sodium silicate with acid to generate silica gel, and finally prepares dry silica gel through washing, drying and other process steps, and obtains white carbon black after calcination. The present application develops a method for efficiently recovering SiO2 from nickel-iron slag or copper smelting slag to prepare silica gel and white carbon black with high economic value. Compared with the traditional precipitation method, the metallurgical slag can be selected as raw material, which not only can reduce the stock of solid waste on a large scale, but also does not need alkali solution and intermediate product of sodium silicate in the whole preparation process, so the process flow is short, thereby significantly reducing the cost of raw materials and solvents, reducing the process cost of silica gel, and having very important industrial popularization value.

[0005] At present, in addition to the traditional precipitation method and the gas phase method for preparing silica gel and white carbon black, the recovery of SiO2 from solid waste to prepare silica gel and white carbon black has gradually become a research hotspot, and there have been some reports on the preparation of silica gel or white carbon black from solid waste. However, in addition to the difference in raw materials, the process method has no essential difference from the traditional method. However, the present application has significant differences from the traditional production raw materials and methods in terms of raw materials and process methods. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provides a method for efficiently preparing silica gel and white carbon black from smelting slag. The method is as follows: the nickel-iron slag or copper smelting slag is dissolved under suitable acid leaching conditions, and after centrifugal separation, a supersaturated silicic acid solution is obtained. In an open environment at room temperature, stirring and surface activation are used to control the precipitation rate of the silicic acid gel system, adjust the particle structure, morphology and size of the silica gel, and form a gel-liquid mixture containing fine silica gel particles. After separation of the gel-liquid, the wet silica gel is washed and dried to obtain dry silica gel, and white carbon black with SiO2 content greater than 99 wt% is prepared after calcination. The method uses an alkali-free preparation process using smelting slag as raw material, which has the advantages of wide raw material adaptability, low energy consumption, low production cost, good product quality and the like.

[0007] To achieve the above technical effects, the following technical solutions are adopted:

[0008] A method for efficiently preparing silica gel and white carbon black from smelting slag, the specific steps are as follows:

[0009] Step S1: Pretreatment of silica-containing material

[0010] The smelting slag is dried at 100-120℃ for 4-8h, then placed in a ball mill at 200-500 rpm for 0.5-6h, then passed through a 200 mesh or higher mesh screen to obtain a powder with suitable particle size, which is weighed and used as the solute for the next step of acid leaching;

[0011] Step S2: acid leaching

[0012] The powder of suitable particle size obtained in step S1 is leached with an acid solution, and the leaching process is carried out under stirring, so that the silicon minerals in the smelting slag are dissolved into the solution, while the gangue components remain in the slag, obtaining a slag-liquid mixture;

[0013] Step S3: slag-liquid separation

[0014] The slag-liquid mixture obtained in step S2 is separated to obtain a supersaturated silicic acid solution with suitable stability and a leaching slag mainly composed of gangue components;

[0015] Step S4: gelation

[0016] The supersaturated silicic acid solution with suitable stability obtained in step S3 is stirred, so that the supersaturated silicic acid in the solution gradually precipitates, and after nucleation, growth and agglomeration, silica gel particles are formed and suspended in the solution, obtaining a suspension containing silica gel particles; the stirring rate is 200-800 rpm, and the stirring time is 6-14 h;

[0017] Step S5: gel-liquid separation

[0018] The suspension containing silica gel particles obtained in step S4 is vacuum filtered to obtain a wet silica gel in the form of jelly containing impurities and a mixed solution of acid and salt containing impurities;

[0019] Step S6: washing and drying

[0020] The wet silica gel in the form of jelly containing impurities obtained in step S5 is washed with pure water at a liquid-solid ratio of 4:1-6:1 through 5-7 stages, and then dried at 100-120°C for 6-12 h to obtain dry silica gel;

[0021] Step S7: the dry silica gel prepared in step S6 is calcined at 480-580°C for 2-6 h, so that the silica gel is decomposed to form white carbon black with a SiO2 content of more than 99 wt%;

[0022] In step S4, the supersaturated silicic acid solution is stirred while a surfactant is added to slow down the nucleation and growth rate of the silica gel and adjust the microstructure of the white carbon black;

[0023] The surfactant is a polyethylene glycol (PEG) solution, and the PEG addition amount is 0.5%-3.5% of the mass of the silicon-containing material.

[0024] Further, the smelting slag in step S1 is a nickel-iron slag, a copper smelting slag and a silicon-containing material, which is rich in SiO2 components; when SiO2 in these smelting slags exists in an amorphous non-crystalline state, the recycling effect of silicon is best.

[0025] Further, the acid solution in step S2 is sulfuric acid or hydrochloric acid solution. The leaching process conditions selected are related to the solute type, mineral type, solute crystallization degree, solvent type, concentration, and economic and technical indicators of recovery. For easy dissolution, lower acid concentration is generally used, while for difficult dissolution, higher acid concentration is generally used.

[0026] Further, the residue liquid separation in step S3 uses centrifugal filtration, vacuum filtration or pressure filtration. The specific filtration method used is mainly determined by the type of raw material. When the stability of the supersaturated silicic acid solution formed by leaching is low, and even a small amount of silicic acid sol is precipitated from the solution, centrifugal separation must be used. When the amount of silicic acid sol generated in the solution is small and filtration is not difficult, vacuum filtration can be used. In the case between the two, pressure filtration can be used.

[0027] Further, the purity of the dry silica gel in step S6 is more than 99 wt%.

[0028] Further, the leaching conditions in step S2 are as follows: acid concentration 0.5-3 mol / L, liquid-solid ratio 3-15:1, leaching temperature 20-80°C, leaching time 10-120 min, and stirring rate 300-800 rpm.

[0029] Further, the centrifugal filtration separation conditions are as follows: rotation speed control at 500-3000 rpm, and centrifugal separation time for 5-10 min.

[0030] In step S4, the supersaturated silicic acid solution is stirred, and the surface active agent is added to slow down the nucleation and growth rate of silica gel, adjust the microstructure of white carbon black, and make the white carbon black particles more refined, with larger pore size and specific surface area. The addition of the surface active agent has little effect on the purity of the silica gel and white carbon black. For example, adding polyethylene glycol (PEG) solution as a surface active agent, the PEG addition amount is 0.5%-3.5% of the mass of the silicon-containing material, which can improve the subsequent gel liquid separation effect and increase the pore size and specific surface area of the white carbon black.

[0031] This method for preparing silica gel does not need alkali dissolution, does not need to form sodium silicate, and directly reacts with acid to form silicic acid sol, with the significant characteristics of short process, high efficiency, and low production cost.

[0032] The impurities in step S5 can be Mg, Fe, Ni, Co, Li, Cr, Ca, K, Na and the like. If the concentration of these elements is high in the leaching solution, they can be comprehensively recovered as valuable elements to improve economic benefits. For example, taking nickel-iron slag as raw material and sulfuric acid as solvent, the solution obtained by gelatinization and liquid separation is mainly magnesium sulfate crude solution, which can be further used to comprehensively recover Mg to prepare magnesium sulfate. For another example, taking copper smelting slag as raw material and sulfuric acid as solvent, the solution obtained by gelatinization and liquid separation is mainly ferrous sulfate solution, which can be considered to comprehensively recover Fe to prepare ferrous sulfate or iron hydroxide and the like.

[0033] The beneficial effects of the present application are:

[0034] 1. The raw material has wide adaptability and can process different types of silicon-containing materials. On the one hand, by the technical method of the present application, when processing water-quenched nickel-iron slag with high amorphous SiO2 content, the recovery rate of silicon can be more than 90%, the recovery rate of magnesium can be more than 85%, and silicon gel and white carbon black with purity more than 99 wt% can be produced. On the other hand, when processing copper smelting slag mainly containing fayalite crystal phase, the recovery rate of silicon is about 70%, and the purity of white carbon black can reach more than 99.5 wt%. It can also be used to process amorphous and crystalline mixed silicon-containing materials, such as air-cooled nickel-iron slag.

[0035] 2. The product has great flexibility, and the purity of silicon product can be controlled by reducing the process flow. Silicon gel can be prepared without calcination, and white carbon black can be prepared after calcination. If only the purity of silicon gel and white carbon black is concerned, no surfactant is needed in the gelation process, which can further reduce the production cost. When the product is required to have large pore size and specific surface area, a small amount of surfactant needs to be added in the gelation process, although the production cost increases, but the microstructure of the product is improved.

[0036] 3. When processing different silicon-containing materials, the slag rate (the mass ratio of the leaching residue in the preparation process to the mass of the nickel-iron slag raw material) is different. When processing water-quenched electric furnace nickel-iron slag, the slag rate is about 20%, and when processing copper smelting slag, the slag rate is about 50%. The slag rate reflects the utilization rate of the raw material. For solid waste raw materials, the smaller the slag rate, the stronger the solid waste reduction ability.

[0037] 4. When processing solid waste containing amorphous SiO2, the present application can comprehensively recover other valuable elements in the solid waste. For example, when taking nickel-iron slag as raw material, silicon can be recovered at the same time, and magnesium can be recovered to prepare magnesium products such as magnesium sulfate, magnesium nitrate, magnesium hydroxide, magnesium oxide and the like, and the MgO content in the residue is significantly reduced, which is more suitable for some building materials with strict requirements on MgO content. Thus, while improving economic benefits, it is possible to realize the resource utilization of solid waste.

[0038] 5. The present application can solve the hydrometallurgical problems caused by the soluble SiO2 minerals to a great extent, and convert the harmful substances (silicic acid) in the conventional metallurgical process into high value-added silicon products, providing a new way to expand the application range of hydrometallurgical technology and the comprehensive utilization range of minerals. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. The drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0040] Figure 1 XRD pattern of the water-quenched nickel-iron slag used in the present application Embodiment 1 to Embodiment 5;

[0041] Figure 2 XRD pattern of the silica gel prepared in the present application Embodiment 1;

[0042] Figure 3 XRD pattern of the white carbon black prepared in the present application Embodiment 1;

[0043] Figure 4 Visible-infrared absorption spectrum of the silica gel prepared in the present application Embodiment 1;

[0044] Figure 5 Visible-infrared absorption spectrum of the white carbon black prepared in the present application Embodiment 1;

[0045] Figure 6 SEM pattern of the silica gel prepared in the present application Embodiment 1;

[0046] Figure 7 SEM pattern of the white carbon black prepared in the present application Embodiment 1;

[0047] Figure 8 XRD pattern of the crystalline and amorphous mixed nickel-iron slag used in the present application Embodiment 7;

[0048] Figure 9 XRD pattern of the raw copper smelting slag used in the present application Embodiment 7 and Embodiment 8;

[0049] Figure 10 Full process flow chart of the silica gel and white carbon black prepared in the present application. DETAILED DESCRIPTION

[0050] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0051] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0052] It should be noted that the terms used herein are only intended to describe specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a presence of the features, steps, operations and / or combinations thereof.

[0053] In the following examples, all reagents and consumables were purchased from conventional reagent manufacturers in the art unless otherwise specified; and the experimental methods and technical means used were conventional methods and means in the art unless otherwise specified.

[0054] The method for efficiently preparing silica gel and white carbon black from smelting slag provided by the present application will be described below with reference to the examples, and the protection scope of the present application is not limited by the following examples.

[0055] Example 1

[0056] The method for efficiently preparing silica gel and white carbon black from smelting slag provided by the present application is provided in this embodiment, and the specific steps are as follows:

[0057] The XRD of the water-quenched nickel-iron slag as the raw material is as shown in Figure 1The chemical composition of the slag is shown in Table 1. In combination with the chemical composition analysis of the slag in Table 1, the figure shows that the SiO2 in the slag mainly exists in an amorphous non-crystalline state, and only a small amount of crystalline magnesium-iron olivine phase (Mg, Fe)2SiO4 exists in the slag. The SiO2 content in the slag is 39.6 wt%. The nickel-iron slag is dried at 120°C for 4h, and then placed in a corundum ball mill tank and ball milled in a ball mill at a speed of 500 rpm for 0.5h. After ball milling, the material is sieved through a 200 mesh sieve to obtain a fine powder of the nickel-iron slag. 20 g of the fine powder of the nickel-iron slag is taken as the solute for acid leaching. A sulfuric acid solution is used as the solvent, and the solute is leached at room temperature while stirring to obtain a solid-liquid mixture. The leaching conditions are: the concentration of sulfuric acid is 2.5 mol / L, the liquid-solid ratio is controlled at 10:1 (L / Kg), the stirring rate is 500 rpm, the leaching time is 10 min, and the leaching is carried out at room temperature. The solid-liquid mixture obtained by leaching is centrifuged at 1500 rpm for 5 min to obtain a leaching residue and a leaching solution. The leaching solution mainly contains supersaturated silicic acid, magnesium sulfate and Fe 3+ , Ca 2+ , Al 3+ and other impurity ions. 0.2 g of PEG is dissolved in 20 ml of pure water to form a PEG solution, which is added dropwise to the leaching solution while using a shear-type stirring paddle to mechanically stir at a speed of 600 rpm at room temperature for 12 h. The supersaturated silicic acid in the solution gradually precipitates from the liquid phase, coagulates into a colloid, and forms a gel-liquid mixture composed of colloidal fragments and the leaching solution. After vacuum filtration of the gel-liquid mixture, a semi-solid colloid and a magnesium sulfate solution containing Fe 3+ , Ca 2+ , Al 3+ and other impurities are obtained. The semi-solid colloid is washed with pure water for 6 times until the solution is neutral, and then dehydrated to obtain a jelly-like wet silica gel. The liquid-solid ratio used for each washing is equal to 5:1 (L / Kg). The wet silica gel is dried in a drying box at 120°C for 10 h to obtain dry silica gel with a SiO2 content of more than 99 wt%. The dry silica gel is calcined in a muffle furnace at 550°C for 6 h to obtain white carbon black with a SiO2 content of more than 99 wt%.

[0058] The magnesium sulfate solution containing impurities obtained after separation of the above gel-liquid can be used as a raw material for comprehensive magnesium recovery, which is not specifically discussed in the present application.

[0059] Table 1 Chemical composition of the nickel-iron slag used in the present application (wt%)

[0060]

[0061] Note: The symbol indicates that the unit of content is g / t.

[0062] The XRD of the silica gel and white carbon black prepared from this example is shown in Figure 2 and Figure 3 The product is composed of only amorphous silica without any crystal phase; the visible-infrared absorption spectrum of the prepared silica gel and white carbon black is shown in Figure 4 , Figure 5 The characteristic peaks of the absorption spectrum correspond to the characteristic peaks of white carbon black, and combined with the XRD analysis results of Figure 2 and Figure 3 , it is proved that the prepared product is silica gel and white carbon black. The SEM of the prepared silica gel and white carbon black is shown in Figure 6 , Figure 7 The prepared white carbon black is a collection of micro-porous structures formed by the agglomeration of a large number of fine flaky particles, which is consistent with the porous micro-morphology characteristics of white carbon black. From the figure, it can be seen that the generated silica gel is a sub-micron particle-like aggregate. Since the internal pore size of the silica gel and white carbon black is generally in the nanometer level (see the BET test results in Table 5), it is difficult to directly observe the sub-micron particle internal pore size at this magnification.

[0063] Example 2:

[0064] The method provided in this example is a high-efficiency method for preparing silica gel and white carbon black from smelting slag. The raw material is the same as that of Example 1, and the process method is similar to that of Example 1, but there are some differences in the process parameters, which are as follows:

[0065] The nickel-iron slag was dried at 100°C for 8 h, then placed in a maroon ball mill tank and put into a ball mill at a speed of 200 rpm for 6 h. After ball milling, the material was sieved through a 200-mesh sieve to obtain a fine powder of the nickel-iron slag. 20 g of the fine powder of the nickel-iron slag was weighed as the solute for acid leaching. Sulfuric acid solution was used as the solvent, and the solute was leached at room temperature while stirring to obtain a solid-liquid mixture. The leaching conditions were as follows: the concentration of sulfuric acid was 0.5 mol / L, the liquid-solid ratio was controlled at 15:1 (L / Kg), the stirring rate was 300 rpm, the leaching temperature was 80°C, and the leaching time was 120 min. The solid-liquid mixture obtained by leaching was centrifuged at 500 rpm for 10 min to obtain a leaching residue and a leaching solution. The leaching solution mainly contained supersaturated silicic acid, magnesium sulfate, and impurity ions such as Fe 3+ , Ca 2+ , Al 3+ , etc. 0.1 g of PEG was dissolved in 20 ml of pure water to form a PEG solution, which was added dropwise to the leaching solution while a shear-type stirring paddle was used for mechanical stirring at a speed of 200 rpm at room temperature. The stirring time was 14 h, so that the supersaturated silicic acid in the solution gradually precipitated and coagulated into a colloid, forming a colloidal solution mixture composed of colloidal fragments and the leaching solution. After vacuum filtration of the colloidal solution mixture, a semi-solid colloid and a magnesium sulfate solution were obtained, and the solution contained Fe3+ , Ca 2+ , Al 3+ and other impurities. After the semi-solid gel is washed with pure water for 5 times until the solution is neutral, wet silica gel is obtained. The liquid-solid ratio used in each washing is equal to 6 (L / Kg). The washed wet silica gel is placed in a drying oven at 100°C for 12 h to obtain dry silica gel with SiO2 content of more than 99 wt%. The dry silica gel is calcined in a muffle furnace at 480°C for 6 h to obtain white carbon black with SiO2 content of more than 99 wt%.

[0066] Example 3:

[0067] The method provided in the embodiment uses smelting slag as raw material to efficiently prepare silica gel and white carbon black. The raw material is the same as that in Example 1, and the process method is similar to that in Example 1, but there are some differences in process parameters, which are as follows.

[0068] The nickel-iron slag is dried at 120°C for 4 h, and then placed in a corundum ball mill tank and ball milled in a ball mill at a speed of 500 rpm for 0.5 h. After ball milling, the material is sieved through a 200-mesh sieve to obtain nickel-iron slag powder, and 20 g of the powder is taken as the solute for acid leaching. Sulfuric acid solution is used as the solvent, and the solute is leached at room temperature while stirring to obtain a solid-liquid mixture. The leaching conditions are as follows: the concentration of sulfuric acid is 3 mol / L, the liquid-solid ratio is controlled at 3:1 (L / Kg), the stirring rate is 800 rpm, the leaching time is 10 min, and the leaching is carried out at room temperature without heating. The solid-liquid mixture obtained by leaching is centrifuged at 3000 rpm for 5 min to obtain leaching residue and leaching solution, and the leaching solution mainly contains supersaturated silicic acid, magnesium sulfate and Fe 3+ , Ca 2+ , Al 3+ and other impurity ions. 0.7 g of PEG is dissolved in 20 ml of pure water to form a PEG solution, which is added dropwise to the leaching solution while a shear-type stirring paddle is used for mechanical stirring at a speed of 800 rpm at room temperature for 6 h. In this way, the supersaturated silicic acid in the solution is gradually precipitated and coagulated into a gel from the liquid phase, forming a gel-liquid mixture composed of gel fragments and leaching solution. After vacuum filtration of the gel-liquid mixture, a semi-solid gel and a magnesium sulfate solution are obtained, and the solution contains Fe 3+ , Ca 2+ , Al 3+ and other impurities. After the semi-solid gel is washed with pure water for 7 times until the solution is neutral, wet silica gel containing a small amount of surfactant is obtained. The liquid-solid ratio used in each washing is equal to 4:1 (L / Kg). The washed wet silica gel is placed in a drying oven at 120°C for 6 h to obtain dry silica gel with SiO2 content of more than 99 wt%. The dry silica gel is calcined in a muffle furnace at 580°C for 2 h to obtain white carbon black with SiO2 content of more than 99 wt%.

[0069] Example 4:

[0070] The method for efficiently preparing silica gel and white carbon black from smelting slag provided in this embodiment has the same raw material as in Example 1 and a similar process to that in Example 1, but there are some differences in the process parameters, which are as follows:

[0071] The nickel-iron slag was dried at 110°C for 6 h, then placed in a corundum ball mill tank and ball milled in a ball mill at a speed of 400 rpm for 3 h. After ball milling, the material was sieved through a 200-mesh sieve to obtain a fine powder of the nickel-iron slag, 20 g of which was used as the solute for acid leaching. Sulfuric acid solution was used as the solvent, and the solute was leached at room temperature while stirring to obtain a solid-liquid mixture. The leaching conditions were as follows: the concentration of sulfuric acid was 2 mol / L, the liquid-to-solid ratio was controlled at 10:1 (L / Kg), the stirring rate was 500 rpm, the leaching time was 30 min, and the leaching was carried out at room temperature without heating. The solid-liquid mixture obtained by leaching was centrifuged at 1500 rpm for 7 min to obtain a leaching residue and a leaching solution, and the leaching solution mainly contained supersaturated silicic acid, magnesium sulfate, and Fe 3+ , Ca 2+ , Al 3+ , and other impurity ions. 0.4 g of PEG was dissolved in 20 ml of pure water to form a PEG solution, which was added dropwise to the leaching solution while using a shear-type stirring paddle to mechanically stir at a speed of 500 rpm at room temperature for 8 h. This caused the supersaturated silicic acid in the solution to gradually precipitate and coagulate into a colloid, forming a colloidal solution mixture composed of colloidal fragments and the leaching solution. After vacuum filtration of the colloidal solution mixture, a semi-solid colloid and a magnesium sulfate solution were obtained, and the solution contained Fe 3+ , Ca 2+ , Al 3+ , and other impurities. After the semi-solid colloid was washed with pure water for 7 times until the solution was neutral, wet silica gel containing a small amount of surfactant was obtained. The liquid-to-solid ratio used for each washing was equal to 5:1 (L / Kg). The washed wet silica gel was dried in a drying oven at 110°C for 4 h to obtain dry silica gel with a SiO2 content of more than 99 wt%. The dry silica gel was calcined in a muffle furnace at 520°C for 4 h to obtain white carbon black with a SiO2 content of more than 99 wt%.

[0072] Example 5:

[0073] The method for efficiently preparing silica gel and white carbon black from smelting slag provided in this embodiment has similar preparation steps to those in Example 4, but the only difference is that no surfactant is added during the colloidal formation process. The purity of the silica gel and white carbon black prepared using this method is not significantly different from that in Example 1. However, the pore size and specific surface area of the silica gel and white carbon black prepared using this method are relatively small.

[0074] Example 6

[0075] The method provided in this example is a method for efficiently preparing silica gel and white carbon black using smelting slag as raw material. The process is the same as that of Example 1, but the solvent used is different. In Example 1, sulfuric acid solution is used, while in this example, hydrochloric acid solution is used. Although the process of this example is the same as that of Example 1, there are differences in the composition of the leaching solution, the composition of the liquid phase after separation of the gel solution, and the recovery rate of silicon and slag rate. After leaching, the leaching solution obtained in this example contains supersaturated silicon acid, FeCl2, and impurity ions such as Ca 2+ , Al 3+ , Mg 2+ . After separation of the gel solution, the liquid phase is mainly ferrous chloride solution, which contains Ca 2+ , Al 3+ , Mg 2+ impurities. In the future, comprehensive recovery of Fe to prepare ferrous chloride, iron hydroxide, and other substances can be considered.

[0076] Example 7

[0077] The method provided in this example is a method for efficiently preparing silica gel and white carbon black using smelting slag as raw material. The preparation process is similar to that of Example 2, with the difference being that the sulfuric acid concentration used in the sulfuric acid leaching is 3 mol / L, and the stirring rate is 600 rpm. The difference also lies in the different crystallization degree of the raw material nickel-iron slag used. The type of nickel-iron slag is still electric furnace type nickel-iron slag, which comes from the same manufacturer as the nickel-iron slag of Example 1, but the production year is different, and it is an air-cooled product, which has a higher degree of crystallization. The XRD of this nickel-iron slag is shown in Figure 8 , and the chemical composition is shown in Table 2. The crystalline material is (Mg, Fe)2SiO4 phase, and the amorphous material is amorphous SiO2.

[0078] Table 2 Chemical composition of crystalline and amorphous mixed nickel-iron slag used in this example (wt%)

[0079]

[0080] Example 8

[0081] The method provided in this example is a method for efficiently preparing silica gel and white carbon black using smelting slag as raw material. The process is the same as that of Example 1, but the raw material used is different. In Example 1, the raw material is nickel-iron slag, while in this example, the raw material used is copper smelting slag. The composition of the copper smelting slag is shown in Table 3, and its XRD is shown in Figure 9The main phase structure of the slag is fayalite Fe2SiO4. The process of this example is the same as that of Example 1, but there are differences in the composition of the leaching solution, the composition of the liquid phase after separation of the gel, the recovery rate of silicon, the slag rate, and the like. The leaching solution obtained after leaching in this example contains supersaturated silicic acid, ferrous sulfate, and impurity ions such as Ca 2+ , Al 3+ , Zn 2+ , Mg 2+ , Na + , and the like. The main impurity in the liquid phase after separation of the gel is ferrous sulfate solution, which contains Ca 2+ , Al 3+ , Zn 2+ , Mg 2+ , Na + impurities. In the future, comprehensive recovery of Fe to prepare ferrous sulfate or iron hydroxide can be considered.

[0082] Table 3 Chemical composition of copper smelting slag (wt%)

[0083]

[0084] Example 9:

[0085] This example provides a method for efficiently preparing silica gel and white carbon black from smelting slag. The process is the same as that of Example 5, but the raw material used is different. The raw material used in Example 5 is nickel-iron slag, while the raw material used in this example is copper smelting slag.

[0086] The chemical composition of the silica gel and white carbon black prepared in the above examples is shown in Table 4:

[0087] Table 4 Chemical composition of silica gel and white carbon black prepared using the technology of the present application (mg / kg)

[0088]

[0089] Note: The symbol “ ” indicates that the unit of content is wt%. The symbol “-” indicates that it is below the detection limit of the instrument and has not been detected.

[0090] The specific surface area (m 2 / g), average pore size (nm), and pore volume (cm 3 / g) of the white carbon black prepared in the above examples are shown in Table 5:

[0091] Table 5 Specific surface area, average pore size, and pore volume of the prepared white carbon black

[0092]

[0093] Comparative Example 1:

[0094] The process method and process parameters of the present example are completely same as those of Example 4, only the raw material is different. The raw material used in the present example is zinc leaching residue, and its chemical composition is shown in Table 6.

[0095] Table 6 Chemical composition of zinc leaching residue produced by wet zinc smelting (wt%)

[0096]

[0097] Note: The remaining components are mainly O elements.

[0098] In the leaching process of the present example, most of the SiO2 is not leached, and the leaching solution is very unstable during the leaching process, and a large amount of silicic acid sol is generated, which inhibits the further dissolution of the reactants. After centrifugal separation, the precipitated silicic acid sol is mixed with the leaching residue, which is difficult to further separate. The Si leaching rate is only 12.5%. The obtained leaching solution has low silicon acid supersaturation, and no silica gel is precipitated after stirring for 8 h.

[0099] Example 2:

[0100] The process method and process parameters of the present example are completely same as those of Example 4, only the raw material is different. The raw material used in the present example is red mud, a metallurgical waste residue produced in the process of producing alumina, and its chemical composition is shown in Table 7.

[0101] Table 7 Chemical composition of the red mud used (wt%)

[0102]

[0103] Note: The remaining components are mainly crystal water.

[0104] In the leaching process of the present example, most of the SiO2 is not leached, and the Si leaching rate is only 10.1%. The obtained leaching solution has low silicon acid supersaturation, and no silica gel is precipitated after stirring for 8 h.

[0105] In summary, the present application discloses a method for efficiently preparing silica gel and white carbon black from smelting slag. The method is as follows: dissolving out the nickel-iron slag or copper smelting slag rich in SiO2 under suitable acid leaching conditions, obtaining a supersaturated silicic acid solution after centrifugal separation; controlling the silicic acid gel precipitation rate of the system, adjusting the silica gel particle structure, morphology and size, forming a gel-liquid mixture containing silica gel fine particles, and separating the gel-liquid to obtain dry silica gel after washing and drying, and then calcining to obtain white carbon black with SiO2 content greater than 99 wt%. The method uses an alkali-free preparation process using smelting waste slag as raw material, and has the advantages of wide raw material adaptability, low energy consumption, low production cost, good product quality, etc.

[0106] To the extent not already already described herein, it will be apparent from this detailed description of embodiments of the application, which can be made and used without departing from the spirit and scope of the application, many other embodiments of the application will be readily ascertainable to those skilled in the art and the inventor contemplates the use of only the preferred embodiments of the application in the following claims.

Claims

1. A method for efficiently preparing silica gel and precipitated silica from smelting slag, characterized in that, The specific steps of the method are as follows: Step S1: Pretreatment of silicon-containing materials The smelting slag is dried at 100-120℃ for 4-8 hours, then placed in a ball mill and ball-milled at 200-500 rpm for 0.5-6 hours. After passing through a sieve of 200 mesh or higher, powder of suitable particle size is obtained, weighed and used as the solute for the next acid leaching step. Step S2: Acid leaching The powder of suitable particle size obtained in step S1 is leached with an acid solution. The leaching process is stirred so that the silicon minerals in the smelting slag dissolve into the solution, while the gangue components remain in the slag, thus obtaining a slag-liquid mixture. Step S3: Separation of residue and liquid The residue-liquid mixture obtained in step S2 is separated to obtain a supersaturated silica solution with suitable stability and a leaching residue mainly composed of gangue. Step S4: Gel formation The supersaturated silica solution with suitable stability obtained in step S3 is stirred to allow the supersaturated silica to gradually precipitate out. After nucleation, growth, and aggregation, silica particles are formed and suspended in the solution to obtain a suspension containing silica particles. The stirring rate is 200–800 rpm and the stirring time is 6–14 h. Step S5: Separation of adhesive solution The suspension containing silica particles obtained in step S4 is vacuum filtered to obtain jelly-like wet silica gel containing impurities and a mixed solution of acid and salt containing impurities. Step S6: Wash and dry The jelly-like wet silica gel containing impurities obtained in step S5 is washed with pure water at a liquid-to-solid ratio of 4:1 to 6:1 for 5 to 7 stages, and then dried at 100 to 120°C for 6 to 12 hours to obtain dry silica gel. Step S7: The dry silica gel prepared in step S6 is calcined at 480-580℃ for 2-6 h to decompose the silica gel and generate white carbon black with a SiO2 content of more than 99 wt%. In step S4, the supersaturated silica solution is stirred, and a surfactant is added to slow down the nucleation and growth rate of silica gel and adjust the microstructure of silica. The surfactant is a polyethylene glycol solution, and the amount of polyethylene glycol solution added is 0.5% to 3.5% of the mass of the silicon-containing material. The smelting slag in step S1 is either nickel-iron slag or copper smelting slag containing silicon. In step S6, the purity of the dry silica gel exceeds 99 wt%.

2. The method for efficiently preparing silica gel and precipitated silica from smelting slag as described in claim 1, characterized in that, In step S2, the acid solution is either sulfuric acid or hydrochloric acid.

3. The method for efficiently preparing silica gel and precipitated silica from smelting slag as described in claim 1, characterized in that, In step S3, the sludge-liquid separation is achieved by centrifugal filtration, vacuum filtration, or pressure filtration.

4. The method for efficiently preparing silica gel and precipitated silica from smelting slag as described in claim 1, characterized in that, The leaching conditions in step S2 are as follows: acid concentration 0.5-3 mol / L, liquid-solid ratio 3-15:1, leaching temperature 20-80℃, leaching time 10-120 min, and stirring speed 300-800 rpm.

5. The method for efficiently preparing silica gel and precipitated silica from smelting slag as raw material as described in claim 3, characterized in that, The centrifugal filtration separation conditions are as follows: the rotation speed is controlled at 500-3000 rpm, and the centrifugation separation time is 5-10 min.

Images