Method and device for recycling silicon dioxide from alkaline waste liquid containing sodium silicate

Abstract

The invention relates to a method and device for recycling silicon dioxide from sodium silicate-containing alkaline waste liquid, and the method comprises the following steps: carrying out first solid-liquid separation on the sodium silicate-containing alkaline waste liquid to obtain first feed liquid; adding an acid solution into the first feed liquid to a first pH value, and carrying out an acidification reaction to obtain a second feed liquid; alkali liquor is added into the second feed liquid to adjust the pH value back to a second pH value, and third feed liquid is obtained; sequentially carrying out curing reaction and second solid-liquid separation on the third feed liquid to obtain gel; and sequentially carrying out acid pickling, third solid-liquid separation, water washing, fourth solid-liquid separation, drying and calcining on the gel to obtain a silicon dioxide product. The method provided by the invention is simple in process, the silicon dioxide product with good purity and dispersity can be obtained, and resource recycling of the sodium silicate-containing alkaline waste liquid can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment, in particular to a method and device for recycling silicon dioxide from sodium silicate-containing alkaline waste liquid. BACKGROUND

[0002] In the production and manufacturing process of the semiconductor industry, the cleaning link is an important link. At present, a mixed solution of sodium hydroxide (NaOH) solution and hydrogen peroxide (H2O2) is often used to clean glass or silicon wafers in the existing process, and the main purpose is to remove the nanoscale surface layer, so that the cleaned surface remains flat, thereby achieving the purpose of cleaning surface contaminants (such as organic residues, particles, metal ions, etc.). In this cleaning process, a large amount of alkaline waste liquid containing 0.1-10% sodium silicate (Na2SiO3) is produced.

[0003] At present, the main treatment method for sodium silicate-containing alkaline waste liquid is neutralization and discharge, that is, by adding an acidic substance to adjust the pH value of the waste liquid to neutral, so that it meets the environmental discharge standard and is discharged. However, silicon is an important resource, and the above method results in waste of silicon resources. The silicon element in sodium silicate exists in a dissolved state in the waste liquid, and if it can be effectively recovered, it will have important economic value. In addition, the neutralization process requires a large amount of acidic neutralizing agent, increasing the processing cost of enterprises, and a large amount of solid suspended sludge is produced after neutralization, increasing the load of solid-liquid separation, and increasing the links of sludge transportation and landfill, resulting in additional costs and environmental pressure.

[0004] CN119639464A discloses a silicon alkali etching liquid for the semiconductor industry and an etching method thereof. The alkali etching liquid comprises the following components by mass fraction: 40-50 parts of alkali, 2-3 parts of surfactant, 1-2 parts of sodium dodecyl polyoxyethylene ether sulfate, 0.1-0.4 parts of active additive, and 70-80 parts of pure water. The method has high efficiency and quality in the etching process, but does not provide an effective resource recycling method for the generated alkaline waste liquid.

[0005] CN103570167A discloses a recovery and treatment method and system for silicon wafer alkali etching waste liquid, which combines electrolysis technology with ion exchange membrane technology to realize the recycling of silicon wafer alkali etching waste liquid. However, the recovery and treatment technology used in this method is complex and requires professional equipment, increasing the investment and operating costs.

[0006] Therefore, for the sodium silicate-containing alkaline waste liquid generated in the semiconductor industry, it is necessary to provide a resource recycling method and device, which is a technical problem to be solved in the present field. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application aims to provide a method and device for recycling silicon dioxide from sodium silicate-containing alkaline waste liquid, which has a simple process and can obtain silicon dioxide products with good purity and dispersity, and realizes recycling of the sodium silicate-containing alkaline waste liquid.

[0008] To achieve the object, the present application adopts the following technical solutions:

[0009] In the first aspect, the present application provides a method for recycling silicon dioxide from sodium silicate-containing alkaline waste liquid, which comprises the following steps:

[0010] (1) performing first solid-liquid separation on the sodium silicate-containing alkaline waste liquid to obtain a first liquid;

[0011] (2) adding acid to the first liquid obtained in step (1) to a first pH value and performing acidification reaction to obtain a second liquid;

[0012] (3) adding alkali to the second liquid obtained in step (2) to adjust the pH value to a second pH value to obtain a third liquid;

[0013] (4) sequentially performing ripening reaction and second solid-liquid separation on the third liquid obtained in step (3) to obtain a gel;

[0014] (5) sequentially performing acid washing, third solid-liquid separation, water washing, fourth solid-liquid separation, drying and calcination on the gel obtained in step (4) to obtain a silicon dioxide product.

[0015] In the present application, first, the solid impurities (such as large particle glass slag) in the waste liquid are removed by first solid-liquid separation to obtain a relatively clear first liquid; acid is added to the first liquid to a first pH value to perform acidification reaction, so that sodium silicate is converted into hydrated silicon dioxide, and the conversion of sodium silicate is as complete as possible by controlling the first pH value to dissolve impurities; then, the pH value of the second liquid is adjusted to a second pH value by adding alkali to obtain a third liquid, which can provide a pH condition for promoting the polymerization of hydrated silicon dioxide to form a gel, thereby reducing the time required for subsequent ripening reaction; then, the third liquid is subjected to ripening reaction to fully polymerize the silicon dioxide to form a stable gel, which is convenient for subsequent separation and treatment; finally, the gel is sequentially subjected to acid washing, third solid-liquid separation, water washing, fourth solid-liquid separation, drying and calcination to obtain a silicon dioxide product with high purity and large specific surface area.

[0016] In the present application, the following reactions occur when acid is added to the first liquid:

[0017] ;

[0018] wherein: A represents a hydrogen ion (H + ); B represents an anion combined with the hydrogen ion, such as F - , Cl - , SO4 2- , NO3 - , etc.; and n represents the valence of the anion B.

[0019] Preferably, the sodium silicate-containing alkaline waste liquid in step (1) contains 0.1-10% of sodium silicate and 1-5% of hydroxyl ion in terms of mass percentage. The mass percentage of sodium silicate is 0.1-10%, for example, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%, but is not limited to the listed values, and other values not listed in the value range are also applicable. The mass percentage of hydroxyl ion is 1-5%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0020] Preferably, the first solid-liquid separation method in step (1) includes filtration.

[0021] In the present application, the first solid-liquid separation method can be filtration, and the second, third and fourth solid-liquid separation methods can be centrifugation.

[0022] Preferably, the filtration precision is 400-800 mesh, for example, it can be 400 mesh, 450 mesh, 500 mesh, 550 mesh, 600 mesh, 650 mesh, 700 mesh, 750 mesh or 800 mesh, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0023] Preferably, the acid solution in step (2) includes any one or a combination of at least two of sulfuric acid, hydrochloric acid or nitric acid.

[0024] Preferably, the mass concentration of the acid solution is 15-30%, for example, it can be 15%, 16%, 18%, 20%, 22%, 24%, 26%, 28% or 30%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0025] Preferably, the acid solution is added at a rate of 1-15 mL / min, for example, it can be 1 mL / min, 2 mL / min, 4 mL / min, 6 mL / min, 8 mL / min, 10 mL / min, 12 mL / min, 14 mL / min or 15 mL / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0026] Preferably, the first pH value is 5-6, for example, it can be 5, 5.2, 5.4, 5.6, 5.8 or 6, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0027] In the present application, by preferably controlling the range of the first pH value, the conversion of sodium silicate into silica hydrate can be promoted, and the cost of adding acid solution can be controlled. When the first pH value is too small, white silica precipitate is directly produced, but the cost of acid solution is greatly increased, and the subsequent wastewater treatment cost is also increased; when the pH value is too large, sodium silicate is not completely converted, which causes waste of resources, and easily leads to reduction of dispersibility and specific surface area.

[0028] Preferably, stirring is performed during the acidification reaction.

[0029] Preferably, the stirring rate in the acidification reaction is 50-200 rpm, for example, it can be 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm or 200 rpm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0030] Preferably, the temperature of the acidification reaction is 40-60℃, for example, it can be 40℃, 42℃, 44℃, 46℃, 48℃, 50℃, 52℃, 54℃, 56℃, 58℃ or 60℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0031] In the present application, by preferably controlling the temperature of the acidification reaction, the reaction rate of sodium silicate and acid can be accelerated, so that silica is formed faster, and the reaction time is shortened, and the production efficiency is improved. When the temperature of the acidification reaction is too low, the reaction rate is slow, and the reaction time is prolonged, which is not conducive to improving the production efficiency; when the temperature of the acidification reaction is too high, the ion activity is high, which leads to violent local reaction, increases the risk in the reaction process, and also easily causes carbonization of organic components contained in the waste liquid, affecting the purity of the silica product.

[0032] Preferably, the acidification reaction time is 15-45 min, for example, it can be 15 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min or 45 min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0033] In the present application, by preferably controlling the acidification reaction time, the sodium silicate can be ensured to fully react with the acid, so that more silicate ions in the sodium silicate are converted into silicic acid, the resource recovery rate is improved, and the formed silicic acid is more uniform and stable.

[0034] Preferably, the alkali solution in step (3) comprises potassium hydroxide and / or sodium hydroxide.

[0035] Preferably, the mass concentration of the alkali solution is 5-10%, for example, it can be 5%, 6%, 7%, 8%, 9% or 10%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0036] Preferably, the rate of adding the alkali solution is 5-15 L / min, for example, it can be 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 11 L / min, 12 L / min, 13 L / min, 14 L / min or 15 L / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0037] Preferably, stirring is performed during the pH value adjustment process.

[0038] Preferably, the stirring rate in the pH value adjustment process is 50-200 rpm, for example, it can be 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm or 200 rpm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0039] Preferably, the second pH value is 7.0-7.5, for example, it can be 7.0, 7.1, 7.2, 7.3, 7.4 or 7.5, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0040] In the present application, by preferably controlling the range of the second pH value, the silicic acid can more easily form a uniform gel structure during the ripening process, and can form silica with a larger specific surface area and good dispersibility during the subsequent drying and calcination processes.

[0041] Preferably, the temperature of the pH value back adjustment is 40-60℃, for example, it can be 40℃, 42℃, 44℃, 46℃, 48℃, 50℃, 52℃, 54℃, 56℃, 58℃ or 60℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0042] Preferably, the ripening reaction in step (4) comprises stirring the third feed solution in a constant temperature water bath.

[0043] Preferably, the temperature of the ripening reaction is 40-80℃, for example, it can be 40℃, 42℃, 44℃, 46℃, 48℃, 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃ or 80℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0044] Preferably, the stirring rate of the ripening reaction is 50-200rpm, for example, it can be 50rpm, 60rpm, 70rpm, 80rpm, 90rpm, 100rpm, 110rpm, 120rpm, 130rpm, 140rpm, 150rpm, 160rpm, 170rpm, 180rpm, 190rpm or 200rpm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0045] Preferably, the time of the ripening reaction is 3-6h, for example, it can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0046] In the present application, by preferably controlling the temperature and time of the ripening reaction, it can be ensured that the silicic acid particles are fully polymerized and stable, forming a uniform gel structure, so as to form a silica product with a larger specific surface area and high purity during the subsequent drying and calcination processes. When the temperature of the ripening reaction is too low, it is not conducive to the formation of the gel structure; when the temperature of the ripening reaction is too high, the gel structure forms too quickly, resulting in a decrease in the dispersibility and specific surface area of the product, and there is a risk of carbonization of the organic components, affecting the purity of the product.

[0047] Preferably, the acid used in the pickling in step (5) comprises hydrochloric acid and / or nitric acid.

[0048] Preferably, the mass concentration of the acid solution used in the acid washing is 1-15%, for example, it can be 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14% or 15%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0049] Preferably, the temperature of the acid washing is 30-50℃, for example, it can be 30℃, 32℃, 34℃, 36℃, 38℃, 40℃, 42℃, 44℃, 46℃, 48℃ or 50℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0050] In the present application, by performing acid washing and preferably controlling the temperature of acid washing, impurities can be further effectively removed, thereby facilitating the improvement of the purity and dispersibility of the silicon dioxide.

[0051] Preferably, the temperature of the water washing in step (5) is 60-80℃, for example, it can be 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃ or 80℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0052] Preferably, the water washing mode includes countercurrent washing.

[0053] Preferably, the number of times of water washing is 2-6 times, for example, it can be 2 times, 3 times, 4 times, 5 times or 6 times.

[0054] In the present application, by performing water washing and controlling the temperature of water washing, residual soluble impurities such as sodium salts can be further removed, thereby obtaining a silicon dioxide product with higher purity.

[0055] Preferably, the temperature of the drying in step (5) is 80-200℃, for example, it can be 80℃, 90℃, 100℃, 120℃, 140℃, 160℃, 180℃ or 200℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0056] Preferably, the drying time is 2-4h, for example, it can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0057] Preferably, the calcination temperature is 200-600℃, for example, it can be 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃ or 600℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0058] Preferably, the calcination time is 2-4h, for example, it can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h, but not limited to the listed values, other values not listed in the range of values are also applicable.

[0059] In the present application, by removing free water through drying, the energy consumption in the calcination process is reduced, and the product is prevented from discoloration, by removing residual organic impurities through calcination, the silica product has higher purity and whiteness, and the specific surface area is increased.

[0060] Preferably, the specific surface area of the silica product is 150-250m 2 / g, for example, it can be 150m 2 / g, 160m 2 / g, 170m 2 / g, 180m 2 / g, 190m 2 / g, 200m 2 / g, 210m 2 / g, 220m 2 / g, 230m 2 / g, 240m 2 / g or 250m 2 / g, but not limited to the listed values, other values not listed in the range of values are also applicable.

[0061] In the second aspect, the present application provides a device for recycling silica from sodium silicate-containing alkaline waste liquid, which is used in the method for recycling silica from sodium silicate-containing alkaline waste liquid as described in the first aspect of the present application.

[0062] The device comprises, in sequence along the flow direction of the liquid, a waste liquid collection tank, a first solid-liquid separation device, a pH value adjustment tank, a maturation reaction tank and a second solid-liquid separation device.

[0063] The gel product outlet of the second solid-liquid separation device is connected with an acid washing tank, the acid washing tank, a third solid-liquid separation device, a water washing tank and a fourth solid-liquid separation device are connected in sequence along the moving direction of the gel phase, the gel product outlet of the fourth solid-liquid separation device is connected with a drying device, and the product outlet of the drying device is connected with a calcination device.

[0064] In the present application, the acidification reaction and the pH value adjustment are both carried out in the pH value adjustment tank.

[0065] In the present application, the waste liquid outlets of the second solid-liquid separation device, the third solid-liquid separation device and the fourth solid-liquid separation device are all connected with a wastewater station for treatment and discharge.

[0066] The device provided by the application is used in the method for recycling silicon dioxide from the sodium silicate-containing alkaline waste liquid, can realize efficient recovery of high-purity silicon dioxide from the sodium silicate-containing alkaline waste liquid, and has simple structure, low equipment investment and industrial application prospect.

[0067] Compared with the prior art, the application has the following beneficial effects:

[0068] (1) The method provided by the application can effectively recover the silicon resources in the waste liquid through acidification reaction, pH value adjustment and ripening reaction, etc., and at the same time, the obtained silicon dioxide product has high purity and dispersity, large specific surface area and high economic value.

[0069] (2) The method provided by the application makes the pH value of the third liquid tend to be neutral, can reduce the reagent cost and sludge treatment cost required for adjusting the pH value in the waste water treatment process, avoids resource waste, has good economic benefit and environmental benefit, and has wide industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0070] Figure 1 is a structural schematic view of the device provided by the embodiment 1 of the application;

[0071] Among them, 1-waste liquid collection tank; 2-first solid-liquid separation device; 3-pH value adjustment tank; 4-ripening reaction tank; 5-second solid-liquid separation device; 6-acid washing tank; 7-third solid-liquid separation device; 8-water washing tank; 9-fourth solid-liquid separation device; 10-drying device; 11-calcining device; 12-waste water station. DETAILED DESCRIPTION

[0072] The technical solutions of the application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to understand the application and should not be regarded as specific limitation to the application.

[0073] In one specific embodiment, the method for recycling silicon dioxide from the sodium silicate-containing alkaline waste liquid provided by the application is carried out in a device, such as Figure 1As shown in the figure, the device comprises, in sequence along the flow direction of the material liquid, a waste liquid collection tank 1, a first solid-liquid separation device 2, a pH value adjusting tank 3, a maturation reaction tank 4, and a second solid-liquid separation device 5, the gel product outlet of the second solid-liquid separation device 5 being connected with an acid washing tank 6, the acid washing tank 6, a third solid-liquid separation device 7, a water washing tank 8, and a fourth solid-liquid separation device 9 being connected in sequence along the moving direction of the gel phase, the gel product outlet of the fourth solid-liquid separation device 9 being connected with a drying device 10, the product outlet of the drying device 10 being connected with a calcination device 11, and the waste liquid outlets of the second solid-liquid separation device 5, the third solid-liquid separation device 7, and the fourth solid-liquid separation device 9 being connected with a waste water station 12. The first solid-liquid separation device adopts a safety filter, and the second solid-liquid separation device, the third solid-liquid separation device, and the fourth solid-liquid separation device adopt high-speed centrifuges. The device has simple structure and low equipment investment, and can realize high-efficiency recovery of high-purity silicon dioxide from sodium silicate-containing alkaline waste liquid.

[0074] Example 1

[0075] The present embodiment provides a method and device for recycling silicon dioxide from sodium silicate-containing alkaline waste liquid. The structural schematic diagram of the device is shown in Figure 1 The method comprises the following steps:

[0076] (1) Store the sodium silicate-containing alkaline waste liquid (containing 1% of sodium silicate and 2% of sodium hydroxide in terms of mass percentage) in the waste liquid collection tank 1, and then filter in the first solid-liquid separation device 2, the filtering precision of the first solid-liquid separation device 2 being 500 meshes, so as to filter out glass slag large particles and obtain a first material liquid;

[0077] (2) Transport the first material liquid obtained in step (1) to the pH value adjusting tank 3, add 5 mL / min of 20% mass concentration sulfuric acid to obtain a first pH value of 5.5, and perform acidification reaction under the condition of a stirring rate of 100 rpm and a temperature of 50℃ for 30 min, to obtain a second material liquid;

[0078] (3) Add 10 L / min of 8% mass concentration sodium hydroxide to the second material liquid in the pH value adjusting tank 3 in step (2) to adjust the pH value to a second pH value of 7.2, the stirring rate in the pH value adjustment being 100 rpm and the temperature being 50℃, to obtain a third material liquid;

[0079] (4) Transport the third material liquid obtained in step (3) to the maturation reaction tank 4 and place it in a constant-temperature water bath for stirring to perform maturation reaction, the temperature of the maturation reaction being 60℃, the stirring rate being 100 rpm, and the time of the maturation reaction being 4 h, and then transport it to the second solid-liquid separation device 5 for centrifugation, to obtain a gel;

[0080] (5) The gel obtained in step (4) is transported to an acid washing tank 6, and is subjected to acid washing with 8% hydrochloric acid at a temperature of 40°C, and then is transported to a third solid-liquid separation device 7 to be centrifuged, the gel obtained by centrifugation is transported to a water washing tank 8, and is subjected to countercurrent water washing 4 times at a temperature of 70°C, and then is transported to a fourth solid-liquid separation device 9 to be centrifuged, the gel obtained by centrifugation is transported to a drying device 10 to be dried at 100°C for 3h, and then is transported to a calcining device 11 to be calcined at 400°C for 3h, thereby obtaining a silicon dioxide product.

[0081] The waste liquid discharged from the second solid-liquid separation device 5, the third solid-liquid separation device 7 and the fourth solid-liquid separation device 9 is transported to a waste water station 12, and is discharged after harmless treatment.

[0082] Example 2

[0083] The present embodiment provides a method and device for recycling silicon dioxide from sodium silicate-containing alkaline waste liquid, wherein the device is the same as that in Example 1, and the method comprises the following steps:

[0084] (1) The sodium silicate-containing alkaline waste liquid (having the same composition as in Example 1) is stored in a waste liquid collection tank, and then is filtered in a first solid-liquid separation device, wherein the filtering precision of the first solid-liquid separation device is 400 mesh, and the glass slag large particles are filtered out, thereby obtaining a first feed liquid;

[0085] (2) The first feed liquid obtained in step (1) is transported to a pH value adjusting tank, 30% sulfuric acid is added at a rate of 3mL / min to obtain a first pH value of 5, and the acidification reaction is carried out at a stirring rate of 200rpm and a temperature of 40°C for 45min, thereby obtaining a second feed liquid;

[0086] (3) The second feed liquid in the pH value adjusting tank in step (2) is added with 10% sodium hydroxide at a rate of 9L / min to adjust the pH value to a second pH value of 7, wherein the stirring rate in the pH value adjustment is 200rpm, and the temperature is 40°C, thereby obtaining a third feed liquid;

[0087] (4) The third feed liquid obtained in step (3) is transported to a ripening reaction tank and is placed in a constant temperature water bath to be stirred for ripening reaction, wherein the ripening reaction temperature is 80°C, the stirring rate is 50rpm, and the ripening reaction time is 3h, and then is transported to a second solid-liquid separation device to be centrifuged, thereby obtaining a gel;

[0088] (5) The gel obtained in step (4) is transported to an acid washing tank, and acid washing is performed using 2% hydrochloric acid, the temperature of the acid washing is 50°C, then transported to a third solid-liquid separation device for centrifugation, the gel obtained by centrifugation is transported to a water washing tank, and countercurrent water washing is performed 4 times at a temperature of 60°C, then transported to a fourth solid-liquid separation device for centrifugation, the gel obtained by centrifugation is transported to a drying device for drying at 80°C for 4h, then transported to a calcining device for calcining at 200°C for 4h, and a silicon dioxide product is obtained.

[0089] Example 3

[0090] The present embodiment provides a method and device for recycling silicon dioxide from sodium silicate-containing alkaline waste liquid, the device is the same as that of example 1, and the method comprises the following steps:

[0091] (1) The sodium silicate-containing alkaline waste liquid (the composition is the same as that of example 1) is stored in a waste liquid collection tank, then filtered in a first solid-liquid separation device, the filtering precision of the first solid-liquid separation device is 800 meshes, and glass slag large particles are filtered out to obtain a first feed liquid;

[0092] (2) The first feed liquid obtained in step (1) is transported to a pH value adjusting tank, 15% sulfuric acid is added at a rate of 4mL / min to obtain a first pH value of 6, and acidification reaction is performed at a stirring rate of 50rpm and a temperature of 60°C for 15min to obtain a second feed liquid;

[0093] (3) The second feed liquid in the pH value adjusting tank in step (2) is added with 5% sodium hydroxide at a rate of 8L / min to adjust the pH value to a second pH value of 7.5, the stirring rate in the pH value adjustment is 50rpm, the temperature is 60°C, and a third feed liquid is obtained;

[0094] (4) The third feed liquid obtained in step (3) is transported to a ripening reaction tank and placed in a constant temperature water bath for stirring to perform ripening reaction, the temperature of the ripening reaction is 40°C, the stirring rate is 200rpm, the time of the ripening reaction is 6h, then transported to a second solid-liquid separation device for centrifugation, and a gel is obtained;

[0095] (5) The gel obtained in step (4) is transported to an acid washing tank, and acid washing is performed using 2% hydrochloric acid, the temperature of the acid washing is 50°C, then transported to a third solid-liquid separation device for centrifugation, the gel obtained by centrifugation is transported to a water washing tank, and countercurrent water washing is performed 4 times at a temperature of 60°C, then transported to a fourth solid-liquid separation device for centrifugation, the gel obtained by centrifugation is transported to a drying device for drying at 80°C for 4h, then transported to a calcining device for calcining at 200°C for 4h, and a silicon dioxide product is obtained.

[0096] Example 4

[0097] The embodiment provides a method for recycling silica from sodium silicate-containing alkaline waste liquid, and the difference from the embodiment 1 is that the temperature of the acidification reaction in the step (2) is 30°C.

[0098] Example 5

[0099] The embodiment provides a method for recycling silica from sodium silicate-containing alkaline waste liquid, and the difference from the embodiment 1 is that the temperature of the acidification reaction in the step (2) is 30°C.

[0100] Example 6

[0101] The embodiment provides a method for recycling silica from sodium silicate-containing alkaline waste liquid, and the difference from the embodiment 1 is that the temperature of the acidification reaction in the step (2) is 30°C.

[0102] Example 7

[0103] The embodiment provides a method for recycling silica from sodium silicate-containing alkaline waste liquid, and the difference from the embodiment 1 is that the temperature of the acidification reaction in the step (2) is 30°C.

[0104] Example 8

[0105] The embodiment provides a method for recycling silica from sodium silicate-containing alkaline waste liquid, and the difference from the embodiment 1 is that the temperature of the acidification reaction in the step (2) is 30°C.

[0106] The silica products prepared in the embodiments 1-8 are determined, and the results are shown in Table 1.

[0107] The purity of the obtained silica product is determined by the ignition weight loss method.

[0108] For the subsequent application of the obtained silica product in rubber, if the dispersibility of the obtained silica product is good, the subsequent application in rubber can also achieve good dispersibility. The silica product is applied to the preparation of silicone rubber, and the dispersion grade is tested according to GB / T6030-2006 “Rapid Comparison Method for Evaluation of Carbon Black and Carbon Black / Silica Dispersion in Rubber”.

[0109] The specific surface area of the silica product is determined by the BET method (instrument F-Sorb 2400).

[0110] Table 1

[0111]

[0112] From Table 1, the following points can be seen:

[0113] (1) From the data of examples 1-3, it can be seen that the method provided by the present application can make the specific surface area of the silica product reach 195 m 2 / g or more, the dispersion grade reach 8.8 or more, and the purity reach 98.58% or more under the optimal conditions.

[0114] (2) By comparing examples 1 and 4-5, it can be seen that the present application can further increase the specific surface area and dispersion of the silica product by preferably controlling the range of the first pH value and the acidification reaction temperature.

[0115] (3) By comparing examples 1 and 6, it can be seen that the present application can further increase the specific surface area and dispersion of the silica product by preferably controlling the range of the second pH value.

[0116] (4) By comparing examples 1 and 7-8, it can be seen that the present application can further increase the specific surface area and dispersion of the silica product by preferably controlling the temperature of the ripening reaction.

[0117] In summary, the method provided by the present application is simple, and can obtain a silica product with good purity and dispersion, and can realize the recycling and utilization of the sodium silicate-containing alkaline waste liquid.

[0118] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for the resource-based recovery of silica from sodium silicate-containing alkaline waste liquid, characterized in that, The method includes the following steps: (1) The alkaline waste liquid containing sodium silicate is subjected to a first solid-liquid separation to obtain a first liquid; (2) Add acid to the first liquid obtained in step (1) to the first pH value and carry out an acidification reaction to obtain the second liquid; (3) Add alkali solution to the second liquid obtained in step (2) to adjust the pH value back to the second pH value to obtain the third liquid; (4) The third liquid obtained in step (3) is subjected to a ripening reaction and a second solid-liquid separation to obtain a gel; (5) The gel obtained in step (4) is subjected to acid washing, third solid-liquid separation, water washing, fourth solid-liquid separation, drying and calcination in sequence to obtain silicon dioxide product.

2. The method according to claim 1, characterized in that, The sodium silicate alkaline waste liquid in step (1) contains 0.1-10% sodium silicate and 1-5% hydroxide ions by mass percentage.

3. The method according to claim 1 or 2, characterized in that, Step (1) The first solid-liquid separation method includes filtration; Preferably, the filtration precision is 400-800 mesh.

4. The method according to any one of claims 1-3, characterized in that, The acid solution in step (2) includes any one or a combination of at least two of sulfuric acid, hydrochloric acid, or nitric acid; Preferably, the mass concentration of the acid solution is 15-30%; Preferably, the acid solution is added at a rate of 1-15 mL / min; Preferably, the first pH value is 5-6; Preferably, stirring is performed during the acidification reaction; Preferably, the stirring rate during the acidification reaction is 50-200 rpm; Preferably, the acidification reaction is carried out at a temperature of 40-60°C; Preferably, the acidification reaction takes 15-45 minutes.

5. The method according to any one of claims 1-4, characterized in that, The alkaline solution in step (3) includes potassium hydroxide and / or sodium hydroxide; Preferably, the mass concentration of the alkaline solution is 5-10%; Preferably, the rate at which the alkali solution is added is 5-15 L / min; Preferably, stirring is performed during the pH adjustment process; Preferably, the stirring speed during the pH adjustment is 50-200 rpm; Preferably, the second pH value is 7.0-7.5; Preferably, the pH value is adjusted at a temperature of 40-60°C.

6. The method according to any one of claims 1-5, characterized in that, The ripening reaction in step (4) includes: placing the third liquid in a constant temperature water bath and stirring it; Preferably, the temperature of the ripening reaction is 40-80℃; Preferably, the stirring rate of the ripening reaction is 50-200 rpm; Preferably, the ripening reaction takes 3-6 hours.

7. The method according to any one of claims 1-6, characterized in that, The acid solution used in step (5) for pickling includes hydrochloric acid and / or nitric acid; Preferably, the mass concentration of the acid solution used for pickling is 1-15%; Preferably, the pickling temperature is 30-50°C.

8. The method according to any one of claims 1-7, characterized in that, The water temperature for washing in step (5) is 60-80℃; Preferably, the washing method includes countercurrent washing; Preferably, the number of water washes is 2-6.

9. The method according to any one of claims 1-8, characterized in that, The drying temperature in step (5) is 80-200℃; Preferably, the drying time is 2-4 hours; Preferably, the calcination temperature is 200-600℃; Preferably, the calcination time is 2-4 hours.

10. A device for the resource-based recovery of silica from sodium silicate-containing alkaline waste liquid, characterized in that, The apparatus is used in the method for resource recovery of silicon dioxide from sodium silicate alkaline waste liquid as described in any one of claims 1-9; The device includes a waste liquid collection tank, a first solid-liquid separation device, a pH adjustment tank, a maturation reaction tank, and a second solid-liquid separation device, which are connected in sequence along the direction of liquid flow. The gel product outlet of the second solid-liquid separation device is connected to the pickling tank. The pickling tank, the third solid-liquid separation device, the water washing tank, and the fourth solid-liquid separation device are connected in sequence along the direction of gel phase movement. The gel product outlet of the fourth solid-liquid separation device is connected to the drying device, and the product outlet of the drying device is connected to the calcination device.

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