Environmentally friendly method for producing low-carbon silicon dioxide

Abstract

To solve such a problem that a method for manufacturing silicon dioxide at a current time involves a large amount of energy consumption, and further, is not environment-friendly.SOLUTION: An environment-friendly low-carbon silicon oxide manufacturing method comprises: a step (a) of drying waste silicon slurry; a step (b) of crushing and sorting the dried waste silicon slurry to obtain silicon oxide (SiOx, x=0, 1 or 2) with a weight percentage (wt%) of 40 to 95, in which metallic silicon (SiOx, x=0) accounts for 5wt% to 40wt% of silicon oxide content; a step (c) of mixing the silicon oxide in the process (b) and an alkali metal aqueous solution to cause reaction therebetween, and controlling a reaction temperature between 100°C and 150°C, thereby obtaining a sodium silicate aqueous solution; and a step (d) of mixing the sodium silicate aqueous solution in the process (c) and sulfuric acid to cause reaction therebetween, and further, performing solid-liquid separation them and drying them, as to obtain silicon dioxide thereafter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a manufacturing method, and more particularly to an environmentally friendly method for producing low carbon silicon dioxide. [Background technology]

[0002] Semiconductors are deeply involved in the operation of modern electrical devices, with their performance constantly improving, their designs becoming increasingly complex and sophisticated, and their applications expanding. Semiconductors enable us to use laptops, mobile phones, and tablet PCs, promote the development of automotive electronics, avionics, and medical equipment, and significantly improve the energy efficiency of large and small household appliances and lighting fixtures. While semiconductors are an important foundation of modern science and technology, they also produce a large amount of waste. Semiconductor waste contains many heavy metals, including lead and cadmium, which can cause neurological disorders if ingested by the human body, and hexavalent chromium and arsenic, which are carcinogenic. Semiconductor waste also often contains strong acids and alkalis, which, in extreme cases, can pose immediate danger to the human body if they come into contact with the body.

[0003] Waste silicon slurry generated in semiconductor manufacturing processes occurs during the polishing and thinning processes of silicon wafers, when silicon wafers or other substrate materials are planarized using chemical corrosion or machinery. Currently, most of the waste silicon slurry generated during the cutting and polishing processes is separated into solids and liquids through wastewater treatment, concentrated into solids, and collected, and then landfilled by a waste disposal company. However, landfilling waste silicon slurry is prone to environmental pollution, and because waste silicon slurry contains large amounts of silicon dioxide and silicon metal, it is a waste to directly landfill reusable resources.

[0004] Currently, the raw material required to produce silicon dioxide by the precipitation method is sodium silicate, and the conventional method for producing sodium silicate involves converting silica sand and sodium carbonate extracted from mines into solid sodium silicate at high temperatures of 1000°C to 1300°C, and then acidifying the solid sodium silicate to produce silicon dioxide. However, this production method requires a large amount of external heat source for heating, which is not only energy-intensive but also environmentally unfriendly.

[0005] Therefore, in an era where economic circulation and green energy are becoming mainstream, one of the key challenges facing the industry is to convert waste generated in the semiconductor manufacturing process into reusable silicon dioxide products while also meeting the requirements of energy conservation, low carbon emissions, and a green environment. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention solves the problem that the production of silicon dioxide by converting silica sand and sodium carbonate into solid sodium silicate at high temperatures of 1000 to 1300°C and then acidifying it consumes a large amount of energy and is not environmentally friendly. [Means for solving the problem]

[0007] In view of the above, the present invention provides an environmentally friendly method for producing low-carbon silicon dioxide, which not only achieves energy-saving and low-carbon effects but also meets the requirements for a green environment.

[0008] To achieve the above objectives, the present invention provides an environmentally friendly method for producing low-carbon silicon dioxide, which includes steps (a), (b), (c), and (d): step (a) involves drying waste silicon slurry; step (b) involves crushing and screening the dried waste silicon slurry to obtain silicon oxide (SiOx, x=0, 1, or 2) with a weight percentage (wt%) of 40 to 95, of which metallic silicon (SiOx, x=0) accounts for 5 to 40 wt% of the silicon oxide content; step (c) involves mixing and reacting the silicon oxide from step (b) with an aqueous alkali metal solution, controlling the reaction temperature between 100 and 150°C to obtain an aqueous sodium silicate solution; step (d) involves mixing and reacting the aqueous sodium silicate solution from step (c) with sulfuric acid, followed by solid-liquid separation and drying to obtain silicon dioxide.

[0009] In one embodiment, the waste silicon slurry of step (a) is generated in a semiconductor manufacturing process.

[0010] In one embodiment, the moisture content of the dried waste silicon slurry in step (a) is less than 10 wt %.

[0011] In one embodiment, the aqueous alkali metal solution in step (c) is an aqueous sodium hydroxide solution, and the concentration of the aqueous sodium hydroxide solution is 45 wt %.

[0012] In one embodiment, in step (c), the reaction temperature of the silicon oxide and the aqueous alkali metal solution is maintained between 100°C and 150°C by controlling the content of metallic silicon in the silicon oxide.

[0013] In one embodiment, the higher the silicon metal content, the closer the reaction temperature is to 150°C.

[0014] In one embodiment, in step (c), the reaction time is 2 hours or more.

[0015] In one embodiment, in step (c), besides obtaining a sodium silicate aqueous solution, hydrogen is also obtained after the mixing reaction.

[0016] In one embodiment, the sulfuric acid concentration in step (d) is between 30 wt% and 80 wt%.

[0017] In one embodiment, the sulfuric acid in step (d) is waste sulfuric acid generated in semiconductor manufacturing processes.

[0018] In one embodiment, in step (d), the reaction time is between 30 minutes and 2 hours.

[0019] In one embodiment, the purity of the silicon dioxide obtained in step (d) is greater than 94 wt%.

[0020] In the environmentally friendly method for producing low-carbon silicon dioxide of the present invention, a waste silicon slurry is used to produce sodium silicate by a self-exothermic reaction between the metallic silicon contained in the silicon oxide and an alkali metal aqueous solution, which reaches the required reaction temperature. The sodium silicate aqueous solution is then mixed with sulfuric acid to produce silicon dioxide. Compared to well-known current methods for producing silicon dioxide, the method of the present invention does not require a large amount of external heat source for the heating reaction, resulting in energy-saving and low-carbon effects. Furthermore, since the raw materials used, the waste silicon slurry and sulfuric acid, are process waste products generated in the semiconductor manufacturing process, the method of the present invention meets the requirements for a green environment. [Effects of the Invention]

[0021] The environmentally friendly method for producing low-carbon silicon dioxide provided by the present invention not only achieves the effects of energy saving and low carbon emissions, but also meets the requirements of a green environment. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a flow diagram of a method for producing silicon dioxide according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The preferred embodiment of the method for producing environmentally friendly low-carbon silicon dioxide of the present invention will be described below with reference to the accompanying drawings, in which like elements are denoted by like reference numerals.

[0024] Figure 1 is a flow chart of an embodiment of the method for producing environmentally friendly low-carbon silicon dioxide according to the present invention. As shown in Figure 1, the method for producing environmentally friendly low-carbon silicon dioxide according to the present invention includes steps (a) to (d). The technology of each step is described in detail below.

[0025] First, in step (a), waste silicon slurry is dried. Waste silicon slurry is generated during the semiconductor manufacturing process, and examples thereof include, but are not limited to, waste silicon wafers, silicon wafer cutting processes, silicon wafer polishing, and waste silicon slurry generated during packaging and package inspection processes. In step (a), the waste silicon slurry generated during the semiconductor manufacturing process is placed in a drying furnace and dried to remove moisture, resulting in a dried waste silicon slurry with a moisture content of less than 10 wt% (weight percentage).

[0026] Next, in step (b), the dried waste silicon slurry is crushed and separated to obtain silicon oxide (SiOx, x = 0, 1, or 2) with a weight percentage (wt%) of 40 to 95, of which metallic silicon (Si / SiOx, x = 0) accounts for 5 to 40 wt% of the silicon oxide content. Here, the waste silicon slurry is classified based on its metallic silicon content, and silicon oxide with a content of 40 to 95 wt% is separated from the waste silicon slurry, and metallic silicon (Si) accounts for 5 to 40 wt% of the silicon oxide content. The purpose of this is to control the reaction temperature in the subsequent mixing reaction in step (c); that is, by controlling the metallic silicon content, the chemical reaction in step (c) can reach the required temperature.

[0027] Then, in step (c), the silicon oxide of step (b) and the aqueous alkali metal solution are mixed and reacted, and the reaction temperature is controlled between 100 and 150°C to produce an aqueous sodium silicate solution (NaSiO 3(aq)) is obtained. In step (c), as described above, the reaction temperature during the reaction with the alkali metal aqueous solution is controlled by controlling the metallic silicon (Si) content in the silicon oxide, and the reaction temperature is maintained between 100°C and 150°C to obtain a sodium silicate aqueous solution. Furthermore, the higher the metallic silicon content in the silicon oxide, the higher the reaction temperature, approaching 150°C. Furthermore, in step (c), the reaction time during which the silicon oxide and the alkali metal aqueous solution are mixed and reacted is set to 2 hours or more, thereby allowing the silicon oxide and the alkali metal aqueous solution to react sufficiently.

[0028] In some embodiments, the aqueous alkali metal solution is aqueous sodium hydroxide (NaOH (aq) ) can be mentioned as an example, but is not limited to this. The concentration of the sodium hydroxide aqueous solution is, for example, 45 wt%. In some embodiments, the silicon oxide obtained in step (b) and a 45 wt% sodium hydroxide aqueous solution are added to a reaction vessel, and the metallic silicon content in the silicon oxide is controlled to be between 5 wt% and 40 wt%. By utilizing the self-exothermic reaction that occurs when silicon oxide (metallic silicon) reacts with sodium hydroxide, the reaction temperature is controlled to be between 100°C and 150°C. After two hours of reaction, solid-liquid separation is performed to obtain a residue that has not reacted with the sodium silicate aqueous solution.

[0029] The reaction scheme for step (c) is as follows: Si + 2H2O → SiO2 + 2H2 + heat (339 KJ / mole) ··· Reaction Equation (1) SiO2 + 2NaOH → Na2SiO3 + H2O + heat (85 KJ / mole) ··· Reaction equation (2).

[0030] It is worth noting that, as can be seen from reaction equation (1), hydrogen (H2) is obtained when silicon oxide and sodium hydroxide solution are mixed and reacted. In some applications, hydrogen can be used in fuel cells, for example. Fuel cells generate electricity and water through a chemical reaction between hydrogen and oxygen. This is not only completely pollution-free (the product is water), but also avoids the problem of long charging times for traditional batteries, making it the most promising new energy method available today. If it can be widely applied to vehicles and other highly polluting power generation devices, it can effectively reduce air pollution and the greenhouse effect.

[0031] Finally, in step (d), the sodium silicate solution from step (c) is mixed with sulfuric acid (H2SO4) to react, followed by solid-liquid separation and drying to obtain silicon dioxide (SiO2). The reaction time in step (d) is between 30 minutes and 2 hours. The reaction formula for step (d) is as follows: Na2SiO3+H2SO4→Na2SO4+SiO2+H2O···Reaction equation (3).

[0032] In step (d), the sulfuric acid concentration is between 30wt% and 80wt%, and the sulfuric acid can also be waste sulfuric acid generated in the semiconductor manufacturing process. For example, in silicon wafer factories, high-purity sulfuric acid is used to clean the surface of silicon wafers, mainly after removing the photoresist. The sulfuric acid used is added with hydrogen peroxide (H2O2), which acts as a strong oxidizing agent to oxidize the organic matter on the chips and break it down into CO2 and H2O, generating waste sulfuric acid. Applying this waste sulfuric acid to step (d) also achieves the goals of economic circulation and resource reuse.

[0033] In some embodiments, the purity of the silicon dioxide obtained in step (d) may be greater than 94 wt%. In some applications, the silicon dioxide produced is widely used, for example, as a filler for rubber and plastic reinforcement, a matting agent for paints, and a carrier for food and medicines, or in a variety of commercial products, such as brick, glass, ceramics, plaster, granite, concrete, cleaning agents, skin care products, talc, and unshaped silicon dioxide is used as a food additive, food packaging material, toothpaste, and cosmetics, making it extremely versatile.

[0034] The following six examples demonstrate that the manufacturing method of the present invention can reliably produce environmentally friendly low-carbon silicon dioxide (see Table 1).

[0035] Example 1

[0036] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 50.52wt%, metallic silicon accounts for 9.36wt% of silicon oxide), add 3.9g of 45% liquid alkali (sodium hydroxide aqueous solution) and 20g of water, then stir evenly in a reactor, the reaction temperature will heat up to 103.8℃ due to exothermic reaction, after 2 hours solid-liquid separation will be performed and impurities will be removed. After that, the reacted sodium silicate and waste sulfuric acid will be obtained and mixed at 80℃ to precipitate, after which 3.25g of silicon dioxide (and 0.492L of hydrogen) will be obtained after filtering, washing and drying.

[0037] Example 2

[0038] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 58.07wt%, metallic silicon accounts for 12.74wt% of silicon oxide), add 3.9g of 45% liquid alkali and 20g of water, and then stir and react evenly in a reactor. The reaction temperature will naturally heat up to 119.6℃ due to the exothermic reaction, and after 2 hours of reaction, perform solid-liquid separation and remove impurities. Then, obtain the reacted sodium silicate and waste sulfuric acid, mix them together at 80℃, and precipitate. After filtering, washing and drying, 3.74g of silicon dioxide (and 0.670L of hydrogen) will be obtained.

[0039] Example 3

[0040] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 76.39wt%, metallic silicon accounts for 14.49wt% of silicon oxide), add 3.9g of 45% liquid alkali and 20g of water, and then stir and react evenly in a reactor. The reaction temperature will naturally heat up to 135℃ due to the exothermic reaction, and after 2 hours of reaction, perform solid-liquid separation and remove impurities. Then, obtain the reacted sodium silicate and waste sulfuric acid, mix them together and react at 80℃ to precipitate, filter, wash and dry, and obtain 4.92g of silicon dioxide (and 0.762L of hydrogen).

[0041] Example 4

[0042] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content 75.80wt%, metallic silicon accounts for 16.61wt% of silicon oxide), add 3.9g of 45% liquid alkali and 20g of water, then stir and react evenly in a reactor, the reaction temperature will heat up to 142℃ due to exothermic reaction, after 2 hours of reaction, solid-liquid separation will be performed and impurities will be removed. After that, the reacted sodium silicate and waste sulfuric acid will be obtained, mixed and reacted at 80℃, and precipitated, filtered, washed and dried, and 4.88g of silicon dioxide (and 0.874L of hydrogen) will be obtained.

[0043] Example 5

[0044] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content is 76.92wt%, metallic silicon accounts for 20.16wt% of silicon oxide), add 3.9g of 45% liquid alkali and 20g of water, and then stir and react evenly in a reactor. The reaction temperature will naturally heat up to 145℃ due to the exothermic reaction, and after 2 hours of reaction, perform solid-liquid separation and remove impurities. Then, obtain the reacted sodium silicate and waste sulfuric acid, mix them together at 80℃, and precipitate. After filtering, washing and drying, 4.95g of silicon dioxide (and 1.060L of hydrogen) will be obtained.

[0045] Example 6

[0046] Weigh out 3g of dried waste silicon slurry powder (silicon oxide content 82.16wt%, metallic silicon accounts for 32.60wt% of silicon oxide), add 3.9g of 45% liquid alkali and 20g of water, then stir and react evenly in a reactor, the reaction temperature will heat up to 149.5℃ due to exothermic reaction, after 2 hours of reaction, solid-liquid separation will be performed and impurities will be removed. After that, the reacted sodium silicate and waste sulfuric acid will be obtained, mixed and reacted at 80℃, and precipitated, filtered, washed and dried, and 6.34g of silicon dioxide (and 1.724L of hydrogen) will be obtained.

[0047] The six examples described above are summarized in Table 1.

[0048] [Table 1]

[0049] As can be seen from the above six examples, the present invention does not produce sodium silicate from conventional silica sand and sodium carbonate at high temperatures of 1000°C to 1300°C, but rather uses waste silicon slurry to achieve the required reaction temperature by controlling the metallic silicon content in the silicon oxide and the self-exothermic reaction caused by an alkali metal (sodium hydroxide) aqueous solution. Since no external heat source is required for the heating reaction, energy-saving and low-carbon effects are achieved. Furthermore, because the raw materials used, waste silicon slurry and waste sulfuric acid, are process waste generated in the semiconductor manufacturing process, the manufacturing method of the present invention meets the requirements of a green environment.

[0050] To summarize, in the environmentally friendly method for producing low-carbon silicon dioxide of the present invention, when using waste silicon slurry, the metallic silicon contained in the silicon oxide and an alkali metal aqueous solution undergo a self-exothermic reaction to reach the required reaction temperature to produce sodium silicate, and then the sodium silicate aqueous solution is mixed and reacted with sulfuric acid to produce silicon dioxide. Therefore, compared to well-known current methods for producing silicon dioxide, the production method of the present invention does not require a large amount of external heat source to carry out the heating reaction, thereby achieving energy-saving and low-carbon effects. Furthermore, since the raw materials used, the waste silicon slurry and sulfuric acid, are process waste generated in the semiconductor manufacturing process, the production method of the present invention meets the requirements of a green environment.

[0051] The above are only some of the embodiments of the present invention, and are not intended to limit the present invention. Any modifications or changes made without departing from the spirit and scope of the present invention should fall within the scope of the claims of the present invention. [Industrial Applicability]

[0052] The manufacturing method of the present invention uses waste silicon slurry, and the metallic silicon contained in the silicon oxide and the alkali metal aqueous solution undergo a self-exothermic reaction to reach the required reaction temperature to produce sodium silicate, and then the sodium silicate aqueous solution is mixed and reacted with sulfuric acid to produce silicon dioxide.Compared with the well-known current methods for manufacturing silicon dioxide, the present invention has the effects of energy saving and low carbon, and also meets the requirements of a green environment. [Explanation of symbols]

[0053] a, b, c, d process

Claims

1. (a) a step of drying the waste silicon slurry; (b) crushing and sorting the dried waste silicon slurry to obtain silicon oxide (SiOx, x=0, 1, or 2) with a weight percentage (wt%) of 40 to 95, of which metallic silicon (SiOx, x=0) accounts for 5 wt% to 40 wt% of the silicon oxide content; a step (c) of mixing and reacting the silicon oxide and the alkali metal aqueous solution of the step (b) and controlling the reaction temperature between 100°C and 150°C to obtain a sodium silicate aqueous solution; and step (d) of mixing and reacting the aqueous sodium silicate solution of step (c) with sulfuric acid, followed by solid-liquid separation and drying to obtain silicon dioxide.

2. 2. The method for producing environmentally friendly low-carbon silicon dioxide according to claim 1, wherein the waste silicon slurry in step (a) is generated in a semiconductor manufacturing process, and the moisture content of the dried waste silicon slurry is less than 10 wt %.

3. 2. The method for producing environmentally friendly low-carbon silicon dioxide according to claim 1, wherein in step (c), the reaction temperature of the silicon oxide and the alkali metal aqueous solution is maintained between 100°C and 150°C by controlling the content of metallic silicon in the silicon oxide.

4. 2. The method for producing environmentally friendly low-carbon silicon dioxide according to claim 1, wherein in step (c), in addition to obtaining a sodium silicate aqueous solution, hydrogen is also obtained after the mixing reaction.

5. 2. The method for producing environmentally friendly low-carbon silicon dioxide according to claim 1, wherein the sulfuric acid in step (d) is waste sulfuric acid generated in a semiconductor manufacturing process, and the sulfuric acid concentration is between 30 wt % and 80 wt %.

6. 2. The method for producing environmentally friendly low-carbon silicon dioxide according to claim 1, wherein in step (d), the reaction time is between 30 minutes and 2 hours.