Method for preparing industrial high modulus water glass by using microsilica

Abstract

The present application relates to a kind of method for preparing industrial high modulus water glass with micro silicon powder, select industrial ferrosilicon and by-product in the process of silicon production as raw material, through chemical treatment, the method for preparing water glass.The specific steps are as follows:1) first, the required micro silicon powder is calcined;2) acid leaching with hydrochloric acid, after reaction, centrifugal, water washing to obtain acid leaching residue;3) the micro silicon powder after acidification is mixed with sodium hydroxide solution according to proportion, and reacts in reactor, after the liquid of reaction is centrifuged, to obtain water glass.The method is mild, reaction temperature is low, and energy consumption is less.

Description

Technical Field

[0001] This invention belongs to the field of value-added utilization technology of mineral resource waste, specifically relating to a method for efficiently preparing water glass using industrial waste microsilica powder. Background Technology

[0002] Microsilica powder is an industrial byproduct generated during the production of industrial ferrosilicon and silicon. my country is a major producer of industrial ferrosilicon and silicon, producing hundreds of thousands of tons of microsilica powder annually. This microsilica powder is of high purity and has potential application value. The main component of microsilica powder is silicon dioxide (SiO2 content exceeding 96%), and it also contains other oxides such as aluminum, iron, and calcium. Impurities can affect product quality; for example, the presence of iron can give water glass a pale yellow color.

[0003] Water glass, also known as sodium silicate, is a widely used inorganic chemical raw material in various industries. It can be used as a raw material for products such as silica, zeolite molecular sieves, refractory materials, soil stabilizers, quick-drying cement, detergents, and adhesives. There are two methods for producing water glass: the dry method and the wet method. The dry method involves melting quartz sand with soda ash, sodium chloride, or mirabilite at around 1400℃ to produce molten sodium silicate, which then reacts with water under high temperature and pressure to form liquid water glass. The wet method involves mixing sodium hydroxide solution with silica sand in a specific ratio, followed by heating, stirring, filtration, and concentration to obtain the finished water glass (generally at 80-200℃). Both methods still have room for improvement. The dry method has wider applicability of raw materials but requires high-temperature, high-pressure equipment and has high energy consumption, generating waste gas that pollutes the environment. The wet method has lower energy consumption, but the water glass modulus is lower (below 2.5), which cannot meet market demand. Exploring low-energy, simple, and efficient production methods remains urgent.

[0004] In summary, based on the original water glass production method, the inventors have prepared high-modulus water glass through calcination, acid leaching activation, and low-temperature sealing, which can meet the performance requirements of various industries for water glass. Summary of the Invention

[0005] In order to make full use of resources and reduce production costs, the present invention aims to provide a method for preparing high-modulus water glass from industrial ferrosilicon and microsilica powder discarded during silicon production.

[0006] To achieve the above objectives, the present invention relates to a method for preparing industrial high-modulus water glass using a wet process with microsilica powder, comprising the following steps:

[0007] 1) Calcination: The microsilica powder is calcined at 600-900℃ to remove carbon impurities;

[0008] 2) Acid leaching activation: Microsilica powder is mixed with 37.5 wt.% hydrochloric acid solution and reacted at 35-90℃ for 0.5-1h. After the reaction, the mixture is centrifuged and washed with water to obtain acid leaching residue. The liquid-solid ratio of hydrochloric acid solution to microsilica powder is 9:1-5:1. Acid leaching activation can remove iron from microsilica powder, so that the iron content in water glass is below 50 ppm.

[0009] 3) Preparation of water glass: The acid leaching residue obtained in step 2) is mixed with sodium hydroxide solution and reacted in a reactor at 90-100℃ for 1-2 h. After centrifugation, water glass is obtained. The liquid-solid ratio of sodium hydroxide solution to silica powder is 2.05 mL / g, and the concentration of sodium hydroxide solution is 4-4.5 mol / L.

[0010] The water glass has the following properties: Na₂O ≥ 8.2%, SiO₂ ≥ 26.0%, Na₂O + SiO₂ ≥ 35%, modulus 3.2-3.5, iron ≤ 50 ppm, and density 1.30-1.39 g / cm³. 3 The dissolution rate is 93%-96%.

[0011] Specifically, the water glass has the following properties: Na₂O content 8.6%-9.28%, SiO₂ content 26.85%-28.98%, Na₂O+SiO₂ content 35.23%-38.26%, modulus 3.22-3.38, iron ≤50 ppm, and density 1.30-1.39 g / cm³. 3 The dissolution rate is 93%-96%.

[0012] Preferably, the reaction temperature in step 2) is 35°C.

[0013] Preferably, the reaction temperature in step 3) is 90°C.

[0014] In this invention, the microsilica powder undergoes acid leaching to remove metal oxides, and then reacts with caustic soda to dissolve in the form of sodium silicate. During the alkali leaching process, the high concentration of alkali ensures a high dissolution rate of SiO2.

[0015] The chemical principles followed in this invention are as follows:

[0016] Alkali dissolution reaction: nSiO2 + 2NaOH = Na2O·nSiO2 + H2O

[0017] Specifically, in step 3), the reaction vessel is a polytetrafluoroethylene reaction vessel. Using a reaction vessel instead of traditional glass instruments, such as a three-necked flask, can prevent the generated water glass from adhering to the glass instruments.

[0018] The present invention has the following advantages:

[0019] (1) This invention obtains water glass with a modulus in the range of 3.2-3.5 through a one-step alkaline dissolution reaction. The method is simple and achieves the purpose of wet synthesis of high modulus industrial water glass; (2) Microsilica powder is an industrial by-product, so its value-added utilization is realized, realizing "turning waste into treasure" and reducing the production cost of water glass; (3) Through process adjustment, the dissolution rate of silica powder is achieved at more than 93% while ensuring that the modulus of water glass meets the conditions. Attached image description:

[0020] Figure 1 The image shows the XRD patterns of the raw materials, silica powder and water glass, used in Example 1.

[0021] Figure 2 The image shows the FT-IR spectra of the raw materials, silica powder and water glass, in Example 1.

[0022] Figure 3 The image shows scanning electron microscope (SEM) images of the raw materials, silica powder and water glass, used in Example 1. Specific Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] The composition of the microsilica powder used in the embodiments of the present invention is shown in the table below.

[0025] Table 1: Element Content Table

[0026]

[0027] Example 1

[0028] This embodiment relates to a method for preparing industrial high-modulus water glass using microsilica powder, comprising the following steps:

[0029] 1) Calcination: The microsilica powder is calcined at 900℃ to remove carbon impurities;

[0030] 2) Acid leaching activation: Microsilica powder is mixed with 37.5wt% hydrochloric acid solution and reacted at 35℃ for 0.5h. After the reaction is completed, the mixture is centrifuged and washed with water to obtain acid leaching residue, wherein the liquid-solid ratio of hydrochloric acid solution to microsilica powder is 9:1.

[0031] 3) Preparation of water glass: The acid leaching residue obtained in step 2) is mixed with 4 mol / L sodium hydroxide solution. The liquid-solid ratio of sodium hydroxide solution to silica powder is 2.05 mL / g. The mixture is heated at 100℃ for 2 h and centrifuged to obtain water glass.

[0032] Under the same conditions, the concentration of the sodium hydroxide solution in step 3) was changed to 3.8 mol / L, 4.2 mol / L, 4.4 mol / L, 4.5 mol / L, and 5 mol / L. Except for the 3.8 mol / L concentration, which was difficult to centrifuge to obtain water glass, water glass was obtained at the other concentrations. The following table shows the analysis of the silica dissolution rate in the microsilica powder, the modulus of the water glass, the SiO2 content in the water glass, the Na2O content, and the production cost.

[0033]

[0034] Figure 1 The image shows the XRD patterns of the raw material silica powder and water glass when the sodium hydroxide concentration was 4.4 mol / L in Example 1.

[0035] A broad peak at 2θ = 23° indicates the presence of amorphous silica. A broad peak near 2θ = 27°–32° corresponds to the (002) crystal plane of the silicate phase, indicating successful preparation of water glass.

[0036] Figure 2 The image shows the FT-IR spectra of the raw material silica powder and water glass when the sodium hydroxide concentration was 4.4 mol / L in Example 1.

[0037] Material: 479cm -1 The peak at 808 cm⁻¹ is a characteristic peak of Si-O. -1 The area near the characteristic peak of broadband absorption in Si-O is at 1119 cm⁻¹. -1 The prominent peak nearby indicates the formation of Si-O-Si, 1634 cm⁻¹. -1 The nearby characteristic absorption peaks are due to the H-OH bending vibration.

[0038] Water glass: at 611cm -1 The area represents the Na-O-Si vibrational zone of water glass, at 1003 cm⁻¹. -1 The area near the peak is a characteristic peak of Si-O asymmetric tensile vibration, at 1448 cm⁻¹. -1 The prominent peaks nearby indicate the formation of siloxane bonds (Si-O-Si), 1650 cm⁻¹. -1 The nearby characteristic absorption peak is due to the H-OH bending vibration, 3500 cm⁻¹ -1 The strong absorption band in the vicinity is due to the H-OH stretching vibration, indicating the successful preparation of water glass. Figure 3 The image shows scanning electron microscope (SEM) images of the raw materials, silica fume and water glass, when the sodium hydroxide concentration was 4.4 mol / L in Example 1. The SEM images show that the silica fume is agglomerated into spherical shapes, while the synthesized water glass is in irregular block form.

[0039] Example 2

[0040] This embodiment relates to a method for preparing industrial high-modulus water glass using microsilica powder, comprising the following steps:

[0041] 1) Calcination: The microsilica powder is calcined at 900℃ to remove carbon impurities;

[0042] 2) Acid leaching activation: Microsilica powder is mixed with 37.5wt% hydrochloric acid solution and reacted at 35℃ for 0.5h. After the reaction is completed, the mixture is centrifuged and washed with water to obtain acid leaching residue, wherein the liquid-solid ratio of hydrochloric acid solution to microsilica powder is 9:1.

[0043] 3) Preparation of water glass: The acid leaching residue obtained in step 2) is mixed with 4.5 mol / L sodium hydroxide solution. The liquid-solid ratio of sodium hydroxide solution to silica powder is 2.05 mL / g. The mixture is heated at 100℃ for 2 h and centrifuged to obtain water glass.

[0044] Under the same conditions, the temperature in step 3) was adjusted to 70℃, 80℃, 90℃, and 110℃, and the resulting water glass performance data are shown in the table below. It can be seen that when the temperature is below 90℃ or above 100℃, the SiO2 dissolution rate is too low.

[0045]

[0046] The silica dissolution rate is as follows: A certain mass of microsilica powder M1 from step 1) is weighed, centrifuged after reaction to obtain water glass. The water glass is washed with distilled water, dried at 80°C, and finally the residue M2 is weighed. The silica dissolution rate (M1-M2) / M1 is then calculated.

[0047] The silica content is calculated by titrating the modulus of the water glass and then calculating the volume of acid and alkali consumed, as well as the mass of water glass required for titration. The specific process is as follows:

[0048] Take about 1g of water glass in an Erlenmeyer flask, add 50mL of distilled water and 10 drops of methyl red indicator. Titrate with HCl standard solution until the color changes from yellow to slightly red, and record the volume of HCl consumed as V1. Add 3g of NaF, shake to dissolve, and the color changes from red to yellow. Titrate again with HCl until red, with an excess of 2mL, and record the volume of HCl consumed as V2. Let stand for 2 minutes, and titrate with NaOH standard solution until yellow, and record the volume of NaOH consumed as V3. At the same time, perform a blank experiment and record the volume of HCl consumed as V4.

[0049] Titration reaction equation: Na₂O·nSiO₂ + 2HCl + (n-1)H₂O = 2NaCl + nH₂SiO₃

[0050] H2SiO3+6NaF+H2O=Na2SiF6+4NaOH

[0051] Then n Na2O =0.5C HCl ·V1,n SiO2 =0.25C NaOH (V2-V3-V4)

[0052] m SiO2 % = n SiO2 ·M SiO2 / 1=60.1·n SiO2 m Na2O % = n Na2O ·M Na2O / 1=61.98·n Na2O

[0053]

[0054] The data above shows that this invention can meet the factory's requirements for water glass in a one-step process: Na₂O ≥ 8.2%, SiO₂ ≥ 26.0%, Na₂O + SiO₂ ≥ 35%, modulus 3.2-3.5, iron ≤ 50 ppm, and density 1.30-1.39 g / cm³. 3 .

Claims

1. A method for preparing industrial high-modulus water glass using a wet process with microsilica powder, characterized in that, Includes the following steps: 1) Calcination: The microsilica powder is calcined at 600-900℃ to remove carbon impurities; 2) Acid leaching activation: Microsilica powder is mixed with 37.5 wt.% hydrochloric acid solution and reacted at 35℃ for 0.5-1h. After the reaction, the mixture is centrifuged and washed with water to obtain acid leaching residue. The liquid-solid ratio of hydrochloric acid solution to microsilica powder is 9:1-5:

1. Acid leaching activation can remove iron from microsilica powder, so that the iron content in water glass is below 50 ppm. 3) Preparation of water glass: The acid leaching residue obtained in step 2) is mixed with sodium hydroxide solution and reacted in a reactor at 90-100 ℃ for 1-2 h. After centrifugation, water glass is obtained. The liquid-solid ratio of sodium hydroxide solution to silica powder is 2.05 mL / g, and the concentration of sodium hydroxide solution is 4-4.5 mol / L.

2. The method for preparing industrial high-modulus water glass using a wet process with microsilica powder according to claim 1, characterized in that, The reaction temperature in step 3) is 90℃.

3. The method for preparing industrial high-modulus water glass using a wet process with microsilica powder according to claim 1, characterized in that, The water glass has the following properties: Na₂O ≥ 8.2%, SiO₂ ≥ 26.0%, Na₂O + SiO₂ ≥ 35%, modulus 3.2-3.5, iron ≤ 50 ppm, and density 1.30-1.39 g / cm³. 3 The dissolution rate is 93%-96%.

4. The method for preparing industrial high-modulus water glass using a wet process with microsilica powder according to claim 1, characterized in that, The water glass has the following properties: Na₂O content 8.6%-9.28%, SiO₂ content 26.85%-28.98%, Na₂O + SiO₂ content 35.23%-38.26%, modulus 3.22-3.38, iron ≤50 ppm, and density 1.30-1.39 g / cm³. 3 The dissolution rate is 93%-96%.

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