A Janus silica fiber aerogel, its preparation method and application

Abstract

This invention relates to a Janus silica fiber aerogel, its preparation method, and its application. The method includes: mixing tetraethyl silicate with a mixed solution of anhydrous ethanol and hydrochloric acid, heating and evaporating to obtain a spinning solution, then electrospinning to obtain a silica fiber membrane; adding a hydrophobic silica fiber precursor dispersion obtained by different methods to a hydrophilic silica fiber dispersion; freezing at low temperature to obtain a Janus silica fiber dispersion; and finally freeze-drying the obtained Janus silica fiber dispersion to obtain a Janus silica fiber aerogel. The Janus silica fiber aerogel of this invention can simultaneously and efficiently separate light oil-water mixtures and heavy oil-water mixtures, effectively solving the problem that current hydrophilic and hydrophobic separation membranes only have single wettability and can only selectively allow water or oil permeation.

Description

Technical Field

[0001] This invention relates to the field of oil-water separation technology, and in particular to a Janus silica fiber aerogel, its preparation method, and its application. Background Technology

[0002] The indiscriminate discharge of oily wastewater is a huge waste of water resources and fossil raw materials. Therefore, developing new and efficient oil-water separation materials to reduce the environmental and human impact of oily wastewater and to promote energy conservation and environmental protection is of great significance.

[0003] Common separation methods include gravity separation, combustion separation, adsorption separation, and centrifugation. However, these methods generally suffer from drawbacks such as low separation efficiency, cumbersome operation, high equipment costs, and secondary pollution. Membrane separation, as a technology in the field of oil-water separation, has attracted much attention due to its advantages of high separation efficiency, low consumption, energy saving, and cost-effectiveness.

[0004] Based on their surface wettability, oil-water separation membranes can be broadly classified into hydrophilic membranes, hydrophobic membranes, and membranes with opposite wettability. Hydrophilic and hydrophobic membranes possess only a single wettability, allowing only selective water or oil permeation. In industrial separation processes, various types of mixtures often exist, such as (light oil) oil-water mixtures or (heavy oil) oil-water mixtures. For hydrophilic membranes, when the density of the oil being separated is greater than that of water, the oil settles on the membrane surface, preventing water contact and thus preventing separation. For hydrophobic membranes, when the density of the oil being separated is less than that of water, the water settles on the membrane surface, preventing oil contact and thus preventing separation. Therefore, there is an urgent need to develop a Janus separation membrane with opposite wettability that can simultaneously separate light and heavy oil-water mixtures.

[0005] Therefore, how to prepare a Janus separation material that can simultaneously and efficiently separate light and heavy oil-water mixtures is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a Janus silica fiber aerogel, its preparation method, and its application, in order to address the shortcomings of existing technologies and solve the technical problem that oil-water separation membranes in the prior art cannot simultaneously separate light oil and heavy oil and have low separation efficiency.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing Janus silica fiber aerogel, comprising the following steps:

[0009] (1) Mix tetraethyl silicate and solvent A, and heat to evaporate to obtain a spinning solution;

[0010] (2) Electrospinning the spinning solution to obtain a silica fiber membrane;

[0011] (3) The silica fiber membrane was dispersed in an aqueous solution of tert-butanol to obtain a silica fiber dispersion;

[0012] (4) After mixing a portion of the silica fiber dispersion with tetraethyl silicate and oxalic acid, a hydrophilic silica fiber precursor dispersion is obtained; the hydrophilic silica fiber precursor dispersion is frozen to obtain a hydrophilic silica fiber dispersion.

[0013] Another portion of the silica fiber dispersion was mixed with compound A and oxalic acid to obtain a hydrophobic silica fiber precursor dispersion.

[0014] (5) Mix the hydrophobic silica fiber precursor dispersion and the hydrophilic silica fiber dispersion and freeze them to obtain Janus silica fiber dispersion;

[0015] (6) The Janus silica fiber dispersion obtained in step (5) is freeze-dried to obtain Janus silica fiber aerogel;

[0016] The compound A is one or more of methyltrimethoxysilane, methyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, dimethoxymethylvinylsilane, methoxytrimethylsilane, ethoxytrimethylsilane, and ethyltriethoxysilane.

[0017] Solvent A is a mixture of anhydrous ethanol and hydrochloric acid solution.

[0018] Preferably, in step (1), the mass ratio of tetraethyl silicate to solvent A is 1:0.5-1.1; the mass ratio of anhydrous ethanol to hydrochloric acid solution is 1.9-2.5:1.0; the volume concentration of hydrochloric acid solution is 0.15-0.6%; in step (1), the mixture is stirred at a speed of 350-1200 rpm; and the heating and evaporation temperature is 78-85℃ for 35-200 min.

[0019] Preferably, the instrument used for electrospinning in step (2) is a syringe, with an inner diameter of 0.39–0.43 mm and an outer diameter of 0.69–0.73 mm. The electrospinning temperature in step (2) is 20–30 °C, the relative humidity is 30–40%, the voltage is 18–28 kV, the injection speed of the syringe is 0.15–1.0 mm / min, the translation speed of the needle is 120–300 mm / min, the translation stroke is 400–580 mm, and the distance between the needle and the receiving roller is 12–25 cm. The rotational speed of the receiving roller is 30–150 rpm.

[0020] Preferably, in step (3), the mass ratio of silica fiber membrane to tert-butanol aqueous solution is 1:80-100; the mass ratio of tert-butanol to water in the tert-butanol aqueous solution is 1-2:4; and the dispersion process in step (3) is stirred at a rate of 2500-13000 rpm for 0.5-12 h.

[0021] Preferably, in step (4), the mass ratio of the silica fiber dispersion, tetraethyl silicate, and oxalic acid is 100:0.8-1.5:0.02-0.1.

[0022] Preferably, the freezing temperature in step (4) is -18 to -70°C and the freezing time is 12 to 24 hours.

[0023] Preferably, in step (4), the mass ratio of the other part of the silica fiber dispersion, compound A and oxalic acid is 100:0.8-1.5:0.02-0.1; in step (4), stirring is carried out during the mixing process, and the stirring rate is 200-1000 rpm and the stirring time is 30-500 min.

[0024] Preferably, in step (5), the mass ratio of the hydrophobic silica fiber precursor dispersion to the hydrophilic silica fiber dispersion is 0.1–4.0:4.0–20.0; in step (5), the freezing temperature is -18–-70°C and the time is 12–24 h; in step (6), the freeze-drying pressure is 2.0–5.0 Pa, the time is 24–48 h, and the temperature is -40–-70°C.

[0025] The present invention also provides a Janus silica fiber aerogel obtained by the preparation method described above.

[0026] The present invention also provides an application of the Janus silica fiber aerogel in oil-water separation;

[0027] The oil-water mixture is a light oil-water mixture or a heavy oil-water mixture; the light oil is one or more of gasoline, kerosene, diesel, engine oil, n-hexane, cyclohexane, petroleum ether, toluene, xylene, isooctane, n-decane, and liquid paraffin; the heavy oil is one or more of chloromethane, 1,2-dichloroethane, bromobenzene, carbon tetrachloride, and chloroform.

[0028] The beneficial effects of this invention are:

[0029] This invention prepares Janus silica fiber aerogel using a relatively simple process, and can separate various types of oil-water mixtures (light oil or heavy oil) under gravity-only conditions, maximizing the separation needs of industrial oily wastewater, solving the impact of oily wastewater on the ecological environment, and the entire preparation and separation process can be made green, harmless, and economical. Attached Figure Description

[0030] Figure 1 Scanning electron microscope image of Janus silica fiber aerogel prepared in Example 1.

[0031] Figure 2 Scanning electron microscope image of Janus silica fiber aerogel prepared in Example 2.

[0032] Figure 3 This is a digital photograph of the Janus silica fiber aerogel prepared in Example 1.

[0033] Figure 4 This is a digital photograph of the Janus silica fiber aerogel prepared in Example 2.

[0034] Figure 5 This is a diagram showing the effect of Janus silica fiber aerogel prepared in Example 1 in separating a mixture of petroleum ether and water.

[0035] Figure 6 The image shows the effect of Janus silica fiber aerogel prepared in Example 1 in separating a mixture of carbon tetrachloride and water. Detailed Implementation

[0036] This invention provides a method for preparing Janus silica fiber aerogel, comprising the following steps:

[0037] (1) Mix tetraethyl silicate and solvent A, and heat to evaporate to obtain a spinning solution;

[0038] (2) Electrospinning the spinning solution to obtain a silica fiber membrane;

[0039] (3) The silica fiber membrane was dispersed in an aqueous solution of tert-butanol to obtain a silica fiber dispersion;

[0040] (4) After mixing a portion of the silica fiber dispersion with tetraethyl silicate and oxalic acid, a hydrophilic silica fiber precursor dispersion is obtained; the hydrophilic silica fiber precursor dispersion is frozen to obtain a hydrophilic silica fiber dispersion.

[0041] Another portion of the silica fiber dispersion was mixed with compound A and oxalic acid to obtain a hydrophobic silica fiber precursor dispersion.

[0042] (5) Mix the hydrophobic silica fiber precursor dispersion and the hydrophilic silica fiber dispersion and freeze them to obtain Janus silica fiber dispersion;

[0043] (6) The Janus silica fiber dispersion obtained in step (5) is freeze-dried to obtain Janus silica fiber aerogel;

[0044] The compound A is one or more of methyltrimethoxysilane, methyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, dimethoxymethylvinylsilane, methoxytrimethylsilane, ethoxytrimethylsilane, and ethyltriethoxysilane.

[0045] Solvent A is a mixture of anhydrous ethanol and hydrochloric acid solution.

[0046] In this invention, the mass ratio of tetraethyl silicate to solvent A in step (1) is 1:0.5 to 1.1, preferably 1:0.6 to 1.0, and more preferably 1:0.7 to 0.9.

[0047] In this invention, the mass ratio of anhydrous ethanol to hydrochloric acid solution is 1.9–2.5:1.0, preferably 2.0–2.3:1.0, and more preferably 2.1–2.2:1.0.

[0048] In this invention, the volume concentration of the hydrochloric acid solution is 0.15-0.6%, preferably 0.16-0.5%, and more preferably 0.17-0.4%.

[0049] In this invention, after mixing in step (1), the mixture is stirred at a speed of 350-1200 rpm, preferably 400-1100 rpm, and more preferably 500-1000 rpm.

[0050] In this invention, the heating and evaporation temperature is 78-85°C, preferably 79-83°C, and more preferably 80-82°C; the heating and evaporation time is 35-200 min, preferably 40-150 min, and more preferably 45-100 min.

[0051] In this invention, the instrument used for electrospinning in step (2) is a syringe, the inner diameter of the syringe needle is 0.39-0.43 mm, and the outer diameter of the needle is 0.69-0.73 mm; the temperature of electrospinning in step (2) is 20-30℃, the relative humidity is 30-40%, the voltage is 18-28 kV, the injection speed of the syringe is 0.15-1.0 mm / min, the translation speed of the needle is 120-300 mm / min, the translation stroke is 400-580 mm, and the distance between the needle and the receiving roller is 12-25 cm; the rotational speed of the receiving roller is 30-150 rpm.

[0052] In this invention, the inner diameter of the syringe needle in step (2) is preferably 0.40-0.42 mm, more preferably 0.41 mm, and the outer diameter of the needle is preferably 0.70-0.72 mm, more preferably 0.71 mm.

[0053] In this invention, the electrospinning temperature in step (2) is preferably 21-29°C, more preferably 22-28°C; the relative humidity of electrospinning is preferably 31-39%, more preferably 32-38%.

[0054] In this invention, the voltage for electrospinning is preferably 19-27 kV, and more preferably 20-25 kV.

[0055] In this invention, the injection speed of the syringe is preferably 0.16-0.90 mm / min, more preferably 0.20-0.80 mm / min; the needle translation speed of electrospinning is preferably 130-270 mm / min, more preferably 140-260 mm / min; and the translation stroke of electrospinning is preferably 420-570 mm, more preferably 450-550 mm.

[0056] In this invention, the distance between the needle and the receiving roller is preferably 15-23 cm, and more preferably 16-21 cm.

[0057] In this invention, the rotational speed of the receiving roller is preferably 35-140 rpm, and more preferably 40-130 rpm.

[0058] In this invention, in step (3), the silica fiber membrane is first cut into squares of 0.5cm*0.5cm to 3.0cm*3.0cm, and then dispersed in a tert-butanol aqueous solution, preferably 1.0cm*1.0cm to 2.0cm*2.0cm, and more preferably 1.0cm*1.0cm.

[0059] In this invention, the mass ratio of silica fiber membrane to tert-butanol aqueous solution in step (3) is 1:80-100, preferably 1:85-95, and more preferably 1:83-93.

[0060] In this invention, the mass ratio of tert-butanol to water in the tert-butanol aqueous solution is 1 to 2:4, preferably 1.2 to 1.8:4, and more preferably 1.3 to 1.7:4.

[0061] In this invention, during the dispersion process in step (3), stirring is carried out at a speed of 2500-13000 rpm, preferably 2700-12000 rpm, and more preferably 3000-11000 rpm; the stirring time is 0.5-12 h, preferably 1-11 h, and more preferably 2-8 h.

[0062] In this invention, the mass ratio of a portion of the silica fiber dispersion, tetraethyl silicate, and oxalic acid in step (4) is 100:0.8-1.5:0.02-0.1, preferably 100:0.9-1.4:0.03-0.09, and more preferably 100:1.0-1.3:0.04-0.08.

[0063] In this invention, the freezing temperature in step (4) is -18 to -70°C, preferably -20 to -65°C, and more preferably -30 to -55°C; the freezing time is 12 to 24 hours, preferably 13 to 21 hours, and more preferably 15 to 20 hours.

[0064] In this invention, the mass ratio of another part of the silica fiber dispersion, compound A and oxalic acid in step (4) is 100:0.8-1.5:0.02-0.1, preferably 100:0.9-1.4:0.03-0.09, and more preferably 100:1.0-1.3:0.04-0.08.

[0065] In this invention, during the mixing process in step (4), stirring is performed. The stirring rate is 200-1000 rpm, preferably 300-700 rpm, and more preferably 400-600 rpm. The stirring time is 30-500 min, preferably 40-300 min, and more preferably 50-200 min.

[0066] In this invention, the mass ratio of the hydrophobic silica fiber precursor dispersion to the hydrophilic silica fiber dispersion in step (5) is 0.1-4.0:4.0-20.0, preferably 0.5-3.5:5.0-19.0, and more preferably 0.8-3.0:5.5-18.0.

[0067] In this invention, the freezing temperature in step (5) is -18 to -70°C, preferably -19 to -65°C, and more preferably -20 to -55°C; the freezing time is 12 to 24 hours, preferably 15 to 22 hours, and more preferably 16 to 20 hours.

[0068] In this invention, the freeze-drying pressure in step (6) is 2.0 to 5.0 Pa, the time is 24 to 48 hours, and the temperature is -40 to -70°C.

[0069] In this invention, the freeze-drying pressure in step (6) is preferably 2.0 to 3.5 Pa, more preferably 2.0 to 2.5 Pa; the freeze-drying time is preferably 28 to 45 h, more preferably 30 to 40 h; and the freeze-drying temperature is preferably -40 to -70 °C, more preferably -50 to -60 °C.

[0070] The present invention also provides a Janus silica fiber aerogel obtained by the preparation method described above.

[0071] The present invention also provides an application of the Janus silica fiber aerogel in oil-water separation;

[0072] The oil-water mixture is a light oil-water mixture or a heavy oil-water mixture; the light oil is one or more of gasoline, kerosene, diesel, engine oil, n-hexane, cyclohexane, petroleum ether, toluene, xylene, isooctane, n-decane, and liquid paraffin; the heavy oil is one or more of chloromethane, 1,2-dichloroethane, bromobenzene, carbon tetrachloride, and chloroform.

[0073] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0074] Example 1

[0075] Weigh 20g of tetraethyl silicate, 8g of anhydrous ethanol and 4g of 0.2% hydrochloric acid solution and mix them. Stir at 500rpm and heat at 80℃ for 45min to evaporate. Then cool to room temperature to obtain the spinning solution.

[0076] Using a 10mL syringe with an inner needle diameter of 0.41mm and an outer needle diameter of 0.71mm, electrospinning solution was drawn for electrospinning. The electrospinning voltage was controlled at 20kV, the injection speed at 0.40mm / min, and the receiving device consisted of aluminum foil wrapped around the receiving roller. The distance between the spinning needle and the receiving roller was 15cm, the rotation speed of the receiving roller was 100r / min, the translational speed of the electrospinning needle was 300mm / min, the translational stroke was 500mm, the spinning temperature was 25℃, and the relative humidity was 35%. A silica fiber membrane was obtained by electrospinning.

[0077] The 2g silica fiber membrane prepared by electrospinning was cut into 1.0cm*1.0cm squares and placed in a mixed solvent of 40g tert-butanol and 160g water. The mixture was stirred and dispersed at 10000rpm for 6h to obtain a silica fiber dispersion.

[0078] Take 100g of silica fiber dispersion, add 1g of tetraethyl silicate and 0.04g of oxalic acid, stir at 500rpm for 100min to obtain a hydrophilic silica fiber precursor dispersion; take 4g of the hydrophilic silica fiber precursor dispersion, add it to a freezing mold, place it in a low temperature freezer, and freeze at -70℃ for 12h to obtain a hydrophilic silica fiber dispersion;

[0079] Take another 100g of silica fiber dispersion, add 1g of methyltrimethoxysilane and 0.04g of oxalic acid, and stir at 500rpm for 100min to obtain a hydrophobic silica fiber precursor dispersion.

[0080] Add 0.2g of hydrophobic silica fiber precursor dispersion to the above hydrophilic silica fiber dispersion, and freeze again in a low temperature freezer at -70℃ for 12h to obtain Janus silica fiber dispersion.

[0081] The obtained Janus silica fiber dispersion was placed in a freeze dryer and freeze-dried for 24 hours at a pressure of 2.0 Pa and a temperature of -70 °C to obtain Janus silica fiber aerogel.

[0082] Electron microscopy was performed on the Janus silica fiber aerogel obtained in Example 1. The scanning results are as follows: Figure 1 As shown.

[0083] The Janus silica fiber aerogel obtained in Example 1 was photographed, and the digital photograph is shown below. Figure 3 As shown.

[0084] like Figure 5 As shown, the Janus silica fiber aerogel prepared in Example 1 was used to separate a mixture of petroleum ether and water with a separation efficiency of over 98%.

[0085] like Figure 6 As shown, the Janus silica fiber aerogel prepared in Example 1 was used to separate a mixture of carbon tetrachloride and water with a separation efficiency of over 99%.

[0086] Example 2

[0087] Weigh 100g of tetraethyl silicate, 50g of anhydrous ethanol and 20g of 0.5% hydrochloric acid solution and mix them. Stir at 800rpm and heat at 83℃ for 220min to evaporate. Then cool to room temperature to obtain the spinning solution.

[0088] Using a 10mL syringe with an inner needle diameter of 0.39mm and an outer needle diameter of 0.70mm, the spinning solution was drawn for electrospinning. The electrospinning voltage was controlled at 19kV, the injection speed at 0.60mm / min, and the receiving device consisted of aluminum foil wrapped around the receiving roller. The distance between the spinning needle and the receiving roller was 13cm, the rotation speed of the receiving roller was 150r / min, the translational speed of the electrospinning needle was 130mm / min, the translational stroke of the electrospinning was 570mm, the spinning temperature was 21℃, and the relative humidity was 33%. A silica fiber membrane was obtained by electrospinning.

[0089] 10g of silica fiber membrane prepared by electrospinning was cut into 2.0cm*2.0cm squares and placed in a mixed solvent of 200g tert-butanol and 700g water. The mixture was stirred and dispersed at 8000rpm for 12h to obtain silica fiber dispersion.

[0090] Take 500g of silica fiber dispersion, add 4g of tetraethyl silicate and 0.25g of oxalic acid, stir at 1000rpm for 200min to obtain a hydrophilic silica fiber precursor dispersion; take 10g of the hydrophilic silica fiber precursor dispersion, add it to a freezing mold, place it in a low temperature freezer, and freeze at -30℃ for 24h to obtain a hydrophilic silica fiber dispersion;

[0091] Take another 500g of silica fiber dispersion, add 4.5g of methyltrimethoxysilane and 0.25g of oxalic acid, and stir at 1000rpm for 200min to obtain a hydrophobic silica fiber precursor dispersion.

[0092] Add 0.1g of hydrophobic silica fiber precursor dispersion to the above hydrophilic silica fiber dispersion, and freeze again in a low temperature freezer at -32℃ for 23h to obtain Janus silica fiber dispersion.

[0093] The obtained Janus silica fiber dispersion was placed in a freeze dryer and freeze-dried for 30 h at a freeze-drying operating pressure of 4.5 Pa and a temperature of -55 °C to obtain Janus silica fiber aerogel.

[0094] Electron microscopy was performed on the Janus silica fiber aerogel obtained in Example 2. The scanning results are as follows: Figure 2 As shown.

[0095] The Janus silica fiber aerogel obtained in Example 2 was photographed, and the digital photograph is shown below. Figure 4 As shown.

[0096] The Janus silica fiber membrane prepared in this embodiment was used to separate a mixture of cyclohexane and water with a separation efficiency of over 98%.

[0097] The Janus silica fiber membrane prepared in this embodiment was used to separate a mixture of bromobenzene and water with a separation efficiency of over 98%.

[0098] Example 3

[0099] Weigh 200g of tetraethyl silicate, 110g of anhydrous ethanol and 50g of 0.3% hydrochloric acid solution and mix them. Stir at 1000rpm and heat at 78℃ for 500min to evaporate. Then cool to room temperature to obtain the spinning solution.

[0100] Using a 50mL syringe with an inner needle diameter of 0.42mm and an outer needle diameter of 0.72mm, the spinning solution was drawn for electrospinning. The electrospinning voltage was controlled at 25kV, the injection speed at 0.90mm / min, and the receiving device consisted of aluminum foil wrapped around the receiving roller. The distance between the spinning needle and the receiving roller was 22cm, the rotation speed of the receiving roller was 120r / min, the translational speed of the electrospinning needle was 200mm / min, the translational stroke of the electrospinning was 450mm, the spinning temperature was 27℃, and the relative humidity was 37%. A silica fiber membrane was obtained by electrospinning.

[0101] 20g of silica fiber membrane prepared by electrospinning was cut into 1.0cm*1.0cm squares and placed in a mixed solvent of 400g tert-butanol and 1200g water. The mixture was stirred and dispersed at 13000rpm for 12h to obtain silica fiber dispersion.

[0102] Take 1000g of silica fiber dispersion, add 13g of tetraethyl silicate and 0.9g of oxalic acid, stir at 1000rpm for 500min to obtain a hydrophilic silica fiber precursor dispersion; take 20g of the hydrophilic silica fiber precursor dispersion, add it to a freezing mold, place it in a low temperature freezer, and freeze at -50℃ for 20h to obtain a hydrophilic silica fiber dispersion;

[0103] Take another 1000g of silica fiber dispersion, add 12g of methyltrimethoxysilane and 0.8g of oxalic acid, stir at 1000rpm for 500min to obtain a hydrophobic silica fiber precursor dispersion;

[0104] Add 2g of hydrophobic silica fiber precursor dispersion to the above hydrophilic silica fiber dispersion, and freeze again in a low temperature freezer at -60℃ for 19h to obtain Janus silica fiber dispersion.

[0105] The obtained Janus silica fiber dispersion was placed in a freeze dryer and freeze-dried for 36 hours at a pressure of 3.5 Pa and a temperature of -60 °C to obtain Janus silica fiber aerogel.

[0106] The microstructure of the Janus silica fiber aerogel obtained in Example 3 is the same as that in Example 1.

[0107] The Janus silica fiber membrane prepared in this embodiment was used to separate a mixture of kerosene and water with a separation efficiency of over 98%.

[0108] The Janus silica fiber membrane prepared in this embodiment was used to separate a mixture of chloromethane and water with a separation efficiency of over 98%.

[0109] Example 4

[0110] Weigh out 40g of tetraethyl silicate, 16g of anhydrous ethanol and 8g of 0.2% hydrochloric acid solution, mix them, stir at 800rpm, heat and evaporate at 80℃ for 100min, and then cool to room temperature to obtain the spinning solution.

[0111] Using a 20mL syringe with an inner needle diameter of 0.41mm and an outer needle diameter of 0.71mm, the spinning solution was drawn for electrospinning. The electrospinning voltage was controlled at 20KV, the injection speed at 0.85mm / min, and the receiving device consisted of aluminum foil wrapped around the receiving roller. The distance between the spinning needle and the receiving roller was 15cm, the rotation speed of the receiving roller was 100r / min, the translational speed of the electrospinning needle was 300mm / min, the translational stroke was 500mm, the spinning temperature was 25℃, and the relative humidity was 35%. A silica fiber membrane was obtained by electrospinning.

[0112] 1g of silica fiber membrane prepared by electrospinning was cut into 1.0cm*1.0cm squares and placed in a mixed solvent of 30g tert-butanol and 70g water. The mixture was stirred and dispersed at 9000rpm for 6h to obtain silica fiber dispersion.

[0113] Take 100g of silica fiber dispersion, add 1.1g of tetraethyl silicate and 0.06g of oxalic acid, stir at 500rpm for 100min to obtain a hydrophilic silica fiber precursor dispersion; take 6g of the hydrophilic silica fiber precursor dispersion, add it to a freezing mold, place it in a low temperature freezer, and freeze at -70℃ for 11h to obtain a hydrophilic silica fiber dispersion;

[0114] Take another 100g of silica fiber dispersion, add 1.5g of methyltrimethoxysilane and 0.08g of oxalic acid, stir at 500rpm for 100min to obtain a hydrophobic silica fiber precursor dispersion;

[0115] Add 0.4 g of hydrophobic silica fiber precursor dispersion to the above hydrophilic silica fiber dispersion, and freeze again in a low temperature freezer at -69°C for 12 h to obtain Janus silica fiber dispersion.

[0116] The obtained Janus silica fiber dispersion was placed in a freeze dryer and freeze-dried for 24 hours at a freeze-drying operating pressure of 3.2 Pa and a temperature of -65 °C to obtain Janus silica fiber aerogel.

[0117] The microstructure of the Janus silica fiber aerogel obtained in Example 4 is the same as that in Example 1.

[0118] The Janus silica fiber membrane prepared in this embodiment was used to separate a mixture of isooctane and water with a separation efficiency of over 98%.

[0119] The Janus silica fiber membrane prepared in this embodiment was used to separate a mixture of chloroform and water with a separation efficiency of over 98%.

[0120] Performance testing: Table 1 below shows the experimental data on the separation rate of light oil by the Janus silica fiber membranes prepared in Examples 1-4. Table 2 shows the experimental data on the separation rate of heavy oil by the Janus silica fiber membranes prepared in Examples 1-4.

[0121] Table 1. Separation rates of light oil by Janus silica fiber membranes prepared in Examples 1-4

[0122]

[0123]

[0124] Table 2 shows the separation efficiency of heavy oil by Janus silica fiber membranes prepared in Examples 1-4.

[0125]

[0126]

[0127] As can be seen from the above embodiments, the present invention provides a Janus silica fiber aerogel, its preparation method, and its application. Experimental data shows that the Janus silica fiber aerogel prepared by the present invention achieves a separation rate of over 98% for light and heavy oils such as isooctane, petroleum ether, carbon tetrachloride, cyclohexane, bromobenzene, and kerosene. Therefore, the silica fiber aerogel prepared by the present invention exhibits excellent separation effects for both light oil-water mixtures and heavy oil-water mixtures.

[0128] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of making a Janus silica fiber aerogel, characterized by, It comprises the following steps: (1) mixing tetraethyl orthosilicate and solvent A, heating and evaporating to obtain a spinning solution; (2) electrospinning the spinning solution to obtain a silica fiber membrane; (3) dispersing the silica fiber membrane into a tert-butyl alcohol aqueous solution to obtain a silica fiber dispersion liquid; (4) mixing part of the silica fiber dispersion liquid with tetraethyl orthosilicate and oxalic acid to obtain a hydrophilic silica fiber precursor dispersion liquid; freezing the hydrophilic silica fiber precursor dispersion liquid to obtain a hydrophilic silica fiber dispersion; mixing another part of the silica fiber dispersion liquid with compound A and oxalic acid to obtain a hydrophobic silica fiber precursor dispersion liquid; (5) mixing the hydrophobic silica fiber precursor dispersion liquid and the hydrophilic silica fiber dispersion liquid, and then freezing to obtain a Janus silica fiber dispersion; (6) freeze-drying the Janus silica fiber dispersion obtained in step (5) to obtain a Janus silica fiber aerogel; The compound A is one or more of methyltrimethoxysilane, methyltriethoxysilane, 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane, dimethoxymethylvinylsilane, methoxytrimethylsilane, ethoxytrimethylsilane and ethyltriethoxysilane; The solvent A is a mixture of anhydrous ethanol and a hydrochloric acid solution.

2. The production method according to claim 1, characterized by, The mass ratio of tetraethyl orthosilicate to solvent A in step (1) is 1:0.5-1.1; the mass ratio of anhydrous ethanol to hydrochloric acid solution is 1.9-2.5:1.0; the volume concentration of the hydrochloric acid solution is 0.15-0.6%; after mixing in step (1), stirring is performed at a rate of 350-1200 rpm; the temperature for heating and evaporating is 78-85℃, and the time is 35-200 min.

3. The preparation method according to claim 2, characterized in that, The apparatus used for electrospinning in step (2) is a syringe, the inner diameter of the needle of the syringe is 0.39-0.43 mm, and the outer diameter of the needle is 0.69-0.73 mm; the temperature for electrospinning in step (2) is 20-30℃, the relative humidity is 30-40%, the voltage is 18-28 kV, the injection speed of the syringe is 0.15-1.0 mm / min, the translation speed of the needle is 120-300 mm / min, the translation stroke is 400-580 mm, and the distance between the needle and the receiving drum is 12-25 cm; the rotation speed of the receiving drum is 30-150 rpm.

4. The production method according to claim 1, 2 or 3, characterized by, The mass ratio of the silica fiber membrane to the tert-butyl alcohol aqueous solution in step (3) is 1:80-100; the mass ratio of tert-butyl alcohol to water in the tert-butyl alcohol aqueous solution is 1-2:4; stirring is performed during the dispersion process in step (3) at a rate of 2500-13000 rpm for 0.5-12 h.

5. The preparation method according to claim 4, characterized in that, The mass ratio of part of the silica fiber dispersion liquid, tetraethyl orthosilicate and oxalic acid in step (4) is 100:0.8-1.5:0.02-0.

1.

6. The production method according to claim 5, wherein The freezing temperature in step (4) is -18--70℃, and the time is 12-24 h.

7. The production method according to claim 6, wherein The mass ratio of the other part of the silica fiber dispersion liquid, compound A and oxalic acid in the step (4) is 100:0.8-1.5:0.02-0.1; the mixing process in the step (4) is carried out with stirring, the stirring rate is independently 200-1000 rpm, and the stirring time is independently 30-500 min.

8. The production method according to claim 1, 5, 6 or 7, characterized by, The mass ratio of the hydrophobic silica fiber precursor dispersion liquid and the hydrophilic silica fiber dispersion in the step (5) is 0.1-4.0:4.0-20.0; the freezing temperature in the step (5) is-18--70℃, and the time is 12-24 h; the freeze-drying pressure in the step (6) is 2.0-5.0 Pa, the time is 24-48 h, and the temperature is-40--70℃.

9. The Janus silica fiber aerogel obtained by the preparation method in any one of claims 1-8.

10. Use of the Janus silica fiber aerogel of claim 9 in oil-water separation, characterized in that, The oil-water is a light oil-water mixture or a heavy oil-water mixture; the light oil is one or more of gasoline, kerosene, diesel, machine oil, n-hexane, cyclohexane, petroleum ether, toluene, xylene, isooctane, n-decane and liquid paraffin; and the heavy oil is one or more of 1,2-dichloroethane, bromobenzene, carbon tetrachloride and chloroform.

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