SiC nanowire modified porous carbon oil-water separation membrane and preparation method thereof

Abstract

The invention relates to the technical field of chemical separation, and discloses a SiC nanowire modified porous carbon oil-water separation membrane and a preparation method thereof.The preparation method comprises the following steps that a porous carbon material is subjected to vacuum impregnation in a metal catalyst solution and dried, and a porous carbon substrate for SiC nanowire growth is obtained; the preparation method comprises the following steps: weighing a carbon source and a silicon source according to a preset ratio, flatly laying the silicon source to the bottom of a crucible, uniformly laying the carbon source on the surface of the silicon source, placing a porous carbon substrate for SiC nanowire growth in the middle of the crucible in a suspended manner through a bracket, carrying out temperature programming reaction, and finally cooling to room temperature to obtain the SiC nanowire modified porous carbon oil-water separation membrane. The oil-water separation membrane realizes on-demand separation of oil-water pollutants, can be applied to extremely severe environments, and can be industrially produced.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical separation, and in particular to a SiC nanowire modified porous carbon oil-water separation membrane and a preparation method thereof. Background Art

[0002] Due to the rapid development of modern industry, frequent oil spill accidents and a large amount of industrial oily wastewater discharge have damaged the ecological system and seriously threatened natural resources and human health. At present, conventional water-oil separation technologies include gravity, centrifugation, adsorption, and chemical methods, etc. Compared with conventional technologies, membrane separation technology has the advantages of simple operation, high efficiency, environmental friendliness, etc., and selects a suitable membrane through the special wettability of the membrane surface to solve actual pollution problems.

[0003] According to the different special wettabilities of the membrane surface, oil-water separation membranes can be divided into "water removal" type membranes and "oil removal" type membranes. "Water removal" type membranes can separate light oil / water mixtures or water-in-oil emulsions, while "oil removal" type membranes can separate heavy oil / water mixtures or oil-in-water emulsions. Due to the complexity of the actual application system, separation membranes with a single wetting property cannot meet the actual separation requirements. Therefore, it is urgent to develop oil-water separation membranes with transformable wettability to achieve the on-demand separation of oil-water pollutants. At present, a series of new intelligent responsive materials such as photo-responsive, electro-responsive, pH-responsive, and temperature-responsive can change the wettability of the membrane surface through external stimulus conditions, thereby realizing the function of on-demand separation. However, in the preparation process of intelligent responsive membranes, polymers or macromolecular organic substances are usually introduced, which not only have high costs and cumbersome preparation processes, but also have a great dependence on environmental conditions and the performance of the separated wastewater during use, seriously restricting the practical application of intelligent responsive membrane materials. In addition, the stability of organically modified separation membranes is poor and they cannot be applied to harsh environments. The use of organic reagents will also cause secondary pollution of water resources. Therefore, it is necessary to prepare a separation membrane with a simple process, no need for organic reagents, simple operation, and transformable wettability to solve the problems in the use of the above-mentioned separation membranes. Summary of the Invention

[0004] Based on the above, the purpose of the present invention is to provide a SiC nanowire modified porous carbon oil-water separation membrane and a preparation method thereof, so that the wettability of the oil-water separation membrane can be transformed to achieve the on-demand separation of oil-water pollutants.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] As a preferred scheme of a preparation method of a SiC nanowire modified porous carbon oil-water separation membrane, it includes the following steps:

[0007] Vacuum impregnate the porous carbon material in a metal catalyst solution, and dry it to obtain a porous carbon substrate;

[0008] Weigh the carbon source and silicon source in a preset ratio. Spread the silicon source evenly on the bottom of the crucible, and then evenly spread the carbon source on the surface of the silicon source. Suspend the porous carbon substrate in the middle of the crucible through a bracket, carry out a programmed temperature rise reaction, and finally cool it to room temperature to obtain a SiC nanowire modified porous carbon oil-water separation membrane.

[0009] As a preferred embodiment of a method for preparing a SiC nanowire modified porous carbon oil-water separation membrane, the porous carbon material includes one or more of carbon fiber cloth, carbon fiber felt, carbon fiber braid, pitch-based foam carbon, resin-based foam carbon, biomass-based porous carbon, activated carbon fiber felt, and carbon paper.

[0010] As a preferred embodiment of a method for preparing a SiC nanowire modified porous carbon oil-water separation membrane, the density of the porous carbon material is 0.01 - 0.6 g / cm 3 。

[0011] As a preferred embodiment of a method for preparing a SiC nanowire modified porous carbon oil-water separation membrane, the concentration of the metal catalyst solution is 0.005 - 0.5 mol / L.

[0012] As a preferred embodiment of a method for preparing a SiC nanowire modified porous carbon oil-water separation membrane, the solute of the metal catalyst solution includes one or more of transition metal salts such as iron salts, cobalt salts, and nickel salts.

[0013] As a preferred embodiment of a method for preparing a SiC nanowire modified porous carbon oil-water separation membrane, during the vacuum impregnation process, the impregnation time is 0.5 - 1 h.

[0014] As a preferred embodiment of a method for preparing a SiC nanowire modified porous carbon oil-water separation membrane, the molar ratio of the carbon source to the silicon source is (0.1 - 1):1

[0015] As a preferred embodiment of a method for preparing a SiC nanowire modified porous carbon oil-water separation membrane, the silicon source is prepared by compounding silicon powder and silica powder, and the molar ratio of the silicon powder to the silica powder is 1:(0.25 - 4); the carbon source includes one of carbon black, graphite, carbon nanotubes, and activated carbon.

[0016] As a preferred embodiment of a method for preparing a SiC nanowire modified porous carbon oil-water separation membrane, during the programmed temperature rise reaction process, the vacuum degree is 10 - 2000 Pa, and it is heated to 1200 - 1600 °C at a rate of 10 - 20 °C / min and held for 20 min - 50 min.

[0017] A SiC nanowire modified porous carbon oil-water separation membrane is prepared by the preparation method described in any one of the above.

[0018] The beneficial effects of the present invention are as follows:

[0019] The present invention provides a SiC nanowire modified porous carbon oil-water separation membrane. Silicon carbide nanowires grow on both the surface and inside of the porous carbon. The nanowires and the porous structure cooperate to form a membrane material with a rough structure at the overall micro-nano scale, which can significantly increase the oil contact angle in water and the water contact angle in oil of the membrane. This oil-water separation membrane has excellent amphiphilicity. After being wetted by oil, it has oleophilic and hydrophobic properties, and after being wetted by water, it has hydrophilic and oleophobic properties. It has an excellent wettability conversion function and can effectively achieve separation on demand. The membrane material can be well infiltrated by both water and oily liquids. The wettability can be adjusted by pre-wetting, and at the same time, the separation of light oil / water mixtures, heavy oil / water mixtures, water-in-oil and oil-in-water emulsions, immiscible organic substances, and high-viscosity oil-water mixtures can be realized, and it has a wide range of applications.

[0020] The preparation process of this separation membrane is simple. It is prepared using silicon carbide nanowire inorganic materials, avoiding the introduction of organic reagents, and will not cause harm to the environment and human body, being environmentally friendly and safe. At the same time, this oil-water separation membrane can withstand strong acids, strong alkalis, and high-temperature aerobic environments, can be applied to extremely harsh conditions, and can be directly cleaned by high-temperature treatment after use, can be reused without being washed with detergents, avoiding secondary pollution, and can be mass-produced to meet the requirements of industrial applications. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for description in the embodiments of the present invention. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the content of the embodiments of the present invention and these drawings.

[0022] Figure 1 It is an optical picture of the SiC nanowire modified porous carbon oil-water separation membrane prepared in Example 1. Among them, (a) is a polypropylene-based carbon fiber membrane, and (b) is a SiC nanowire modified porous carbon oil-water separation membrane;

[0023] Figure 2 It is a SEM image of the SiC nanowire modified porous carbon oil-water separation membrane prepared in Example 1;

[0024] Figure 3 It is an XRD pattern of the SiC nanowire modified porous carbon oil-water separation membrane prepared in Example 1;

[0025] Figure 4 It is the contact angle of the SiC nanowire modified porous carbon oil-water separation membrane prepared in Example 1 with respect to water and oil in air;

[0026] Figure 5 The separation fluxes and separation efficiencies of SiC nanowire-modified porous carbon substrates for separating different types of light oil / water mixtures or heavy oil / water mixtures at different deposition times are shown. Among them, (a) and (b) are the separation fluxes and separation efficiencies of light oil / water mixtures, respectively, and (c) and (d) are the separation fluxes and separation efficiencies of heavy oil / water mixtures, respectively;

[0027] Figure 6 The separation fluxes and separation efficiencies of SiC nanowire-modified porous carbon substrates for separating emulsions at different deposition times are shown. Among them, (a) is the separation flux and (b) is the separation efficiency. Specific embodiments

[0028] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosed content of the present invention more thorough and comprehensive. Unless otherwise defined, all technical and scientific terms used in the present invention belong to the technical field of the present invention.

[0029] This embodiment provides a method for preparing a SiC nanowire-modified porous carbon oil-water separation membrane, which includes the following steps:

[0030] S100. Vacuum impregnate the porous carbon material in a metal catalyst solution and dry it to obtain a porous carbon substrate;

[0031] Specifically, the porous carbon substrate is used for the growth of SiC nanowires; the porous carbon material includes one or more of carbon fiber cloth, carbon fiber felt, carbon fiber braid, pitch-based foam carbon, resin-based foam carbon, biomass-based porous carbon, activated carbon fiber felt, carbon paper; the concentration of the metal catalyst solution is 0.005-0.5 mol / L, preferably 0.01-0.3 mol / L; the solute of the metal catalyst solution includes one or more transition metal salts such as iron salts, cobalt salts, nickel salts, etc., preferably nickel nitrate; during the vacuum impregnation process, the impregnation time is 0.5-1 h.

[0032] S200. Weigh a preset ratio of carbon source and silicon source, lay the silicon source flat on the bottom of the crucible, then evenly spread the carbon source on the surface of the silicon source, suspend the porous carbon substrate in the middle of the crucible through a bracket, carry out a programmed temperature reaction, and finally cool to room temperature to obtain a SiC nanowire-modified porous carbon oil-water separation membrane.

[0033] Specifically, the molar ratio of the carbon source to the silicon source is (0.1 - 1):1, preferably; the silicon source is prepared by compounding silicon powder and silica powder, and the molar ratio of the silicon powder to the silica powder is 1:(0.25 - 4); the carbon source includes one of carbon black, graphite, carbon nanotubes, and activated carbon, preferably carbon black; during the programmed temperature rise reaction process, the vacuum degree is 10 - 2000 Pa, and the temperature is raised to 1200 - 1600 °C at a rate of 10 - 20 °C / min and kept warm for 20 min - 50 min, preferably at a vacuum degree of 10 - 500 Pa and the temperature is raised to 1300 - 1500 °C.

[0034] More specifically, the growth method of SiC nanowires in this embodiment is the vacuum thermal evaporation method. In other embodiments, the growth methods of SiC nanowires also include the carbothermal reduction method, the chemical vapor deposition method, the electrophoretic deposition method, and the sol - gel method; the nanowires used in this embodiment are silicon carbide nanowires. In other embodiments, amphiphilic ceramic nanowires such as titanium carbide nanowires can also be selected as nanowires.

[0035] The following are the specific test methods for the separation of different types of oil - water mixtures:

[0036] Light oil / water performance test: The prepared SiC nanowire - modified separation membrane is wetted in deionized water and used as a "water - removing" type membrane to efficiently separate light oil / water mixtures, such as cyclohexane / water mixture, petroleum ether / water mixture, n - heptane / water mixture, toluene / water mixture, and the oil - water ratio is 1:5;

[0037] Heavy oil / water performance test: The prepared SiC nanowire - modified porous carbon oil - water separation membrane (SiCNWs separation membrane) is wetted in the corresponding heavy oil and used as an "oil - removing" type membrane to efficiently separate heavy oil / water mixtures, such as dichloromethane / water mixture, 1,2 - dichloroethane / water mixture, bromobenzene / water mixture, carbon tetrachloride / water mixture, and the oil - water ratio is 5:1;

[0038] Performance test of oil-water emulsion: The prepared SiCNWs membrane with wetting selectivity was assembled into a membrane module, and various oil-water emulsions were filtered under negative pressure to test the separation effect of the oil-water separation membrane on the oil-water emulsion. The oil-water emulsions include surfactant-stabilized oil-in-water emulsion (O / W) and surfactant-stabilized water-in-oil emulsion (W / O); the oil-in-water emulsion (O / W) was prepared by adding 1 m of oil (i.e., cyclohexane, petroleum ether) to 99 mL of deionized water containing 10 mg of sodium dodecyl sulfate surfactant, and mechanically stirring (at a speed of 1000 rpm) for 12 h to obtain various milky white oil-in-water emulsions; the surfactant-stabilized water-in-oil emulsion (W / O) was prepared by adding 1 mL of deionized water to 99 mL of various oils (dichloromethane, 1,2-dichloroethane) containing 0.01 g of span 80, and mechanically stirring (1000 rpm) for 12 hours; both of the above stable emulsions (O / W) and (W / O) can remain stable for at least 2 days or more.

[0039] Oil-water separation performance test: Separation was carried out by gravity, and the oil-water separation flux and efficiency were calculated using Formula 1 and Formula 2:

[0040] Flux=V / ST (1)

[0041] η=(1-c / c 0 )×100% (2)

[0042] In Formulas (1) and (2), Flux, V, S, T, η, c, c 0 , are the separation flux (L / (h·m 2 ²)), the volume of the filtrate (L), the effective filtration area (m 2 ²), the separation time (h), the separation efficiency (%), the content of the dispersed phase in the emulsion, and the content of the dispersed phase in the corresponding filtrate. For water-in-oil and oil-in-water emulsions, the water content and oil content in the emulsion were measured using a Karl Fischer titrator and a total organic carbon analyzer, respectively.

[0043] The selective separation of water-in-oil emulsion and oil-in-water emulsion by the separation membrane can be achieved by adjusting the preparation conditions of the separation membrane. The switching of wettability can be completed by cleaning and drying the membrane surface with ethanol for membrane regeneration; after regeneration, the membrane is infiltrated with the corresponding liquid (water / oil) before use, that is, hydrophilic and oleophobic after being infiltrated with water, and hydrophobic and oleophilic after being infiltrated with oil.

[0044] The present invention will be further described below with specific examples.

[0045] Example 1

[0046] A preparation method of an SiC nanowire modified porous carbon oil-water separation membrane includes the following steps:

[0047] Put nickel nitrate solid into a certain volume of absolute ethanol, stir well to obtain a mixed solution with a concentration of 0.05 - 0.1 mol / L. The density is 0.1 g / cm 3 After the carbon fiber cloth is vacuum impregnated for 10 min, it is placed in a vacuum drying oven at 80 °C for 4 h to dry;

[0048] Weigh silicon powder and silicon dioxide powder with a molar ratio of 1:0.25 and mix them evenly to obtain a silicon source. Use graphite powder as a carbon source. Then, weigh the carbon source and silicon source with a molar ratio of 0.1:1 respectively. Spread the silicon source evenly on the bottom of a graphite crucible, and then evenly spread the carbon source on the surface of the silicon source. Support the carbon fiber membrane with a graphite bracket and suspend it in the middle of the graphite crucible. Then transfer the graphite crucible to a high-temperature carbonization furnace. After replacing the atmosphere, under the condition of a vacuum degree of 10 - 50 Pa, heat it at a rate of 10 °C / min to 1200 - 1300 °C, and keep it warm for 20 min to deposit SiC. After the program ends, naturally cool it to room temperature, take out the crucible, and remove the unreacted substances in the crucible to obtain the SiC nanowire modified carbon fiber cloth oil-water separation membrane;

[0049] Place the obtained SiC nanowire modified carbon fiber cloth oil-water separation membrane in a beaker, add 10 mL of deionized water to wet the separation membrane, and then fix it on the oil-water separation device. Pour four types of light oil-water mixtures, namely cyclohexane / water, petroleum ether / water, n-heptane / water, and toluene / water, from top to bottom. Similarly, add 10 mL of heavy oil to wet the separation membrane, and then fix it on the oil-water separation device. Corresponding to this, pour four types of heavy oil-water mixtures, namely dichloromethane / water, 1,2-dichloromethane / water, bromobenzene / water, and carbon tetrachloride / water, respectively.

[0050] The separation fluxes of the four light oil-water mixtures of the SiC nanowire modified porous carbon oil-water separation membrane prepared in this example are 8093 (L / (h·m 2 ))、8143 (L / (h·m 2 ))、8320 (L / (h·m 2 ))、7864 L / (h·m 2 )),and the separation efficiency is above 98.9%. The separation fluxes of the four heavy oil-water mixtures are 13145 (L / (h·m 2 ))、11484.3 (L / (h·m 2 ))、11836.6 (L / (h·m 2 ))、9876.4 (L / (h·m 2 )),and the separation efficiency is above 98.4%. The separation flux of the immiscible organic substances ethylene glycol and cyclohexane is 645 (L / (h.m 2 )),and the separation efficiency reaches 98%.

[0051] Example 2

[0052] A preparation method of a SiC nanowire modified porous carbon oil-water separation membrane, comprising the following steps:

[0053] Take nickel nitrate solid and place it in a certain volume of absolute ethanol, stir well to obtain a mixed solution with a concentration of 0.1 - 0.2 mol / L. After vacuum impregnating the carbon fiber cloth with a density of 0.1 g / cm 3 for 10 min, place it in a vacuum drying oven at 80 °C for 4 h to dry;

[0054] Weigh silicon powder and silicon dioxide powder with a molar ratio of 1:1 and mix them evenly to obtain a silicon source. Use graphite powder as a carbon source. Then, weigh the carbon source and the silicon source with a molar ratio of 0.5:1 respectively. Spread the silicon source evenly on the bottom of a graphite crucible, and then evenly spread the carbon source on the surface of the silicon source. Support the carbon fiber membrane with a graphite bracket and suspend it in the middle of the graphite crucible. Then transfer the graphite crucible to a high-temperature carbonization furnace. After replacing the atmosphere, under the condition of a vacuum degree of 150 - 300 Pa, heat it at a rate of 15 °C / min to 1300 - 1400 °C, and keep it at this temperature for 30 min to deposit SiC. After the program ends, cool it naturally to room temperature, take out the crucible, and remove the unreacted substances in the crucible to obtain the SiC nanowire modified carbon fiber cloth oil-water separation membrane;

[0055] Place the obtained SiC nanowire oil-water separation membrane in a beaker, add 10 mL of deionized water to wet the separation membrane, and then fix it on the oil-water separation device. Pour four kinds of light oil-water mixtures of cyclohexane / water, petroleum ether / water, n-heptane / water, and toluene / water from top to bottom; similarly, add 10 mL of heavy oil to wet the separation membrane, and then fix it on the oil-water separation device, and pour four kinds of heavy oil-water mixtures of dichloromethane / water, 1,2-dichloromethane / water, bromobenzene / water, and carbon tetrachloride / water respectively.

[0056] The separation fluxes of the SiC nanowire modified carbon fiber cloth oil-water separation membrane prepared in this example for the four light oil-water mixtures are 6147.9 (L / (h·m 2 ))), 6220 (L / (h·m 2 ))), 6073 (L / (h·m 2 ))), 6178 (L / (h·m 2 ))), and the separation efficiencies can all reach more than 98%; the separation fluxes of the four heavy oil-water mixtures are 10026 (L / (h·m 2 ))), 9253 (L / (h·m 2 ))), 9678 (L / (h·m 2 ))), 7713 (L / (h·m 2 ))), and the separation fluxes can all reach more than 95%.

[0057] Example 3

[0058] A preparation method of a SiC nanowire modified porous carbon oil-water separation membrane includes the following steps:

[0059] Take nickel nitrate solid and place it in a certain volume of absolute ethanol, stir well to obtain a mixed solution with a concentration of 0.2 - 0.4 mol / L. After vacuum impregnating the carbon fiber cloth with a density of 0.1 g / cm 3 for 10 min, place it in a vacuum drying oven at 80 °C and dry for 4 h;

[0060] Weigh silicon powder and silicon dioxide powder with a molar ratio of 1:2 and mix them evenly to obtain a silicon source. Use graphite powder as the carbon source. Then, weigh the carbon source and the silicon source with a molar ratio of 0.75:1 respectively. Spread the silicon source on the bottom of a graphite crucible, and then evenly spread the carbon source on the surface of the silicon source. Support the carbon fiber membrane with a graphite bracket and suspend it in the middle of the graphite crucible. Then transfer the graphite crucible to a high-temperature carbonization furnace. After replacing the atmosphere, under the condition of a vacuum degree of 300 - 500 Pa, heat it at a rate of 10 °C / min to 1400 - 1500 °C, keep it warm for 40 min to deposit SiC. After the program ends, naturally cool it to room temperature, take out the crucible, and remove the unreacted substances in the crucible to obtain the SiC nanowire modified carbon fiber cloth oil-water separation membrane;

[0061] Place the obtained SiC nanowire modified carbon fiber cloth oil-water separation membrane in a beaker, add 10 mL of deionized water to moisten the separation membrane, and then fix it on an oil-water separation device. Pour four types of light oil-water mixtures, namely cyclohexane / water, petroleum ether / water, n-heptane / water, and toluene / water, from top to bottom. Similarly, add 10 mL of heavy oil to moisten the separation membrane, and then fix it on the oil-water separation device. Pour four types of heavy oil-water mixtures, namely dichloromethane / water, 1,2-dichloromethane / water, bromobenzene / water, and carbon tetrachloride / water, correspondingly.

[0062] The separation fluxes of the SiC nanowire modified carbon fiber cloth oil-water separation membrane for the four light oil-water mixtures are 3356 (L / (h·m 2 ))), 3618 (L / (h·m 2 ))), 3239 (L / (h·m 2 ))), and 3418 (L / (h·m 2 ))), respectively, and the separation efficiency exceeds 99%. For the four heavy oil-water mixtures, the separation fluxes are 8329.14 (L / (h·m 2 ))), 7215.6 (L / (h·m 2 ))), 7618.3 (L / (h·m 2 ))), and 6514.3 (L / (h·m2 ), and the separation efficiency reaches over 99% in both cases. In addition, under negative pressure drive, the membrane can effectively separate oil-in-water emulsions and water-in-oil emulsions simultaneously. The separated oil-in-water emulsions and water-in-oil emulsions respectively exhibit a clear and transparent liquid state, and under observation with a polarized light microscope, both show a homogeneous phase structure.

[0063] Example 4

[0064] A preparation method of a SiC nanowire modified porous carbon oil-water separation membrane includes the following steps:

[0065] Take nickel nitrate solid and place it in a certain volume of absolute ethanol, stir well to obtain a mixed solution with a concentration of 0.4 - 0.5 mol / L. Immerse the carbon fiber cloth with a density of 0.1 g / cm 3 in vacuum for 10 min, and then place it in a vacuum drying oven at 80 °C for 4 h to dry;

[0066] Weigh silicon powder and silicon dioxide powder with a molar ratio of 1:4 and mix them evenly to obtain a silicon source. Use graphite powder as the carbon source. Then, weigh the carbon source and the silicon source with a molar ratio of 1:1 respectively. Spread the silicon source at the bottom of a graphite crucible, and then evenly spread the carbon source on the surface of the silicon source. Support the carbon fiber membrane with a graphite bracket and suspend it in the middle of the graphite crucible. Then transfer the graphite crucible to a high-temperature carbonization furnace. After replacing the atmosphere, under the condition of a vacuum degree of 300 - 500 Pa, heat it at a rate of 20 °C / min to 1500 - 1600 °C, and keep it warm for 50 min to deposit SiC. After the program ends, naturally cool it to room temperature, take out the crucible, and remove the unreacted substances in the crucible to obtain the SiC nanowire modified carbon fiber cloth oil-water separation membrane;

[0067] Place the obtained SiC nanowire modified carbon fiber cloth oil-water separation membrane in a beaker, add 10 mL of deionized water to wet the separation membrane, and then fix it on an oil-water separation device. Pour four types of light oil-water mixtures, namely cyclohexane / water, petroleum ether / water, n-heptane / water, and toluene / water, from top to bottom. Similarly, add 10 mL of heavy oil to wet the separation membrane, and then fix it on the oil-water separation device. Pour four types of heavy oil-water mixtures, namely dichloromethane / water, 1,2-dichloromethane / water, bromobenzene / water, and carbon tetrachloride / water, correspondingly.

[0068] The separation flux of the SiC nanowire modified carbon fiber cloth separation membrane prepared in this example for the four light oil-water mixtures is 2551 (L / (h·m 2 ))、2501 (L / (h·m 2 ))、2418 (L / (h·m 2 ))、2779 (L / (h·m 2)) and the separation efficiency can reach over 99%. The separation fluxes of the four heavy oils are 5318.4 (L / (h·m 2 ))、4496.2 (L / (h·m 2 ))、4598.3 (L / (h·m 2 ))、4035.8 (L / (h·m 2 )) respectively, and the separation efficiency can reach over 98%. At the same time, this separation membrane can also separate emulsions. The separated liquid is observed as a homogeneous phase under a polarized light microscope, and the separation efficiency reaches over 98%.

[0069] Example 5

[0070] A preparation method of a SiC nanowire modified porous carbon oil-water separation membrane includes the following steps:

[0071] Take nickel nitrate solid and place it in a certain volume of absolute ethanol, stir well to obtain a mixed solution with a concentration of 0.01 mol / L. After vacuum impregnating the foam graphite with a density of 0.1 - 0.5 g / cm 3 for 10 min, place it in a vacuum drying oven at 80 °C for 4 h to dry.

[0072] Weigh silicon powder and silica powder with a molar ratio of 1:0.25 and mix them evenly to obtain a silicon source. Use graphite powder as the carbon source. Then weigh the carbon source and the silicon source with a molar ratio of 0.1:1 respectively. Spread the silicon source evenly on the bottom of a graphite crucible, and then evenly spread the carbon source on the surface of the silicon source. Support the foam graphite with a graphite bracket and suspend it in the middle of the graphite crucible. Then transfer the graphite crucible to a high-temperature carbonization furnace. After replacing the atmosphere, under the condition of a vacuum degree of 150 - 300 Pa, heat it at a rate of 10 °C / min to 1200 - 1400 °C, and keep it at this temperature for 20 min to deposit SiC. After the program ends, naturally cool it to room temperature, take out the crucible, and remove the unreacted substances in the crucible to obtain the SiC nanowire modified foam carbon oil-water separation membrane;

[0073] Place the obtained SiC nanowire modified foam carbon oil-water separation membrane in a beaker, add 10 mL of deionized water to wet the separation membrane, and then fix it on an oil-water separation device. Pour light oil-water mixtures such as cyclohexane / water, petroleum ether / water, and n-heptane / water from top to bottom.

[0074] The separation fluxes of the light oil-water mixtures separated by the separation membrane prepared in this example are 26726 L / (h·m 2 ), 24729 L / (h·m 2 ), 25983 L / (h·m 2 ) respectively, and the separation fluxes are all over 98%, indicating that using foam graphite as a porous carbon material can also prepare the required separation membrane, which has excellent separation performance for light oil-water mixtures.

[0075] Figure 1 This is an optical picture of the SiC nanowire-modified porous carbon oil-water separation membrane prepared in Example 1 of the present invention. In the figure, after the carbon fiber cloth is modified by SiC nanowires, it changes from black to white, from which it is speculated that new substances are formed on the surface of the carbon fiber; Figure 2 This is an SEM image of the SiC nanowire-modified porous carbon oil-water separation membrane prepared in Example 1. As can be seen from the figure, the surface of the carbon fiber is wrapped by nanowires, and the gaps between the carbon fibers are completely filled, forming a nanowire-modified separation membrane with a rough surface; Figure 3 This is an XRD pattern of the SiC nanowire-modified porous carbon oil-water separation membrane prepared in Example 1. As can be seen from the figure, in addition to the diffraction peaks of carbon fibers, diffraction peaks corresponding to the (111), (220), and (311) crystal planes of β-SiC are also observed near 2θ = 36°, 60°, and 72°, indicating that the nanowires grown on the surface of the carbon fiber are SiC nanowires; Figure 4 This is the contact angle of the SiC nanowire-modified porous carbon oil-water separation membrane prepared in Example 1 with water (Water) and oil (DCM) in air. As can be seen from the figure, the contact angles of the SiC nanowire membrane with water and oil in air are both 0°, indicating that the membrane has good wettability to both water and oily liquids, and the wettability can be converted by pre-wetting. It is applicable to separate light oil / water mixtures, heavy oil / water mixtures, water-in-oil and oil-in-water emulsions, and immiscible organic substances and high-viscosity oil-water mixtures, broadening its application range.

[0076] Figure 5 This is the separation flux and separation efficiency of the SiC nanowire-modified porous carbon substrate for separating different types of light oil / water mixtures or heavy oil / water mixtures at different deposition times, Figure 6 This is the separation flux and separation efficiency of the SiC nanowire-modified porous carbon substrate for separating emulsions at different deposition times. From Figure 5 and Figure 6 it can be obtained that the SiC thermal deposition times in Examples 1-4 are 20 min, 30 min, 40 min, and 50 min in sequence, achieving different contents of SiC attached to the material. The separation fluxes and separation efficiencies are different for the materials with different SiC contents. Among them, Examples 1 and 2 can only separate light oil and heavy oil / water mixtures, and the separation efficiency of emulsions is very low. Examples 3 and 4 can separate both light oil and heavy oil emulsions and can achieve various types of separation. The separation flux and separation efficiency of Example 3 are better. Since the SiC content in Example 4 is too high, it also leads to a narrow fluid channel of the membrane, and the permeation flux data is weaker than that of Example 3.

[0077] The above are only the preferred embodiments of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, it can also include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing a SiC nanowire-modified porous carbon oil-water separation membrane, characterized in that: The following steps are involved: The porous carbon material is vacuum impregnated in a metal catalyst solution and dried to obtain a porous carbon substrate; The carbon source and silicon source in a preset ratio are weighed, the silicon source is spread flat on the bottom of the crucible, and then the carbon source is evenly spread on the surface of the silicon source. The porous carbon substrate is suspended in the middle of the crucible through a bracket, and a programmed temperature is raised to react. Finally, it is cooled to room temperature to obtain a SiC nanowire-modified porous carbon oil-water separation membrane.

2. The method for preparing the SiC nanowire-modified porous carbon oil-water separation membrane according to claim 1, characterized in that: The porous carbon material includes one or more of carbon fiber cloth, carbon fiber felt, carbon fiber braid, asphalt-based foamed carbon, resin-based foamed carbon, biomass-based porous carbon, activated carbon fiber felt, and carbon paper.

3. The method for preparing the SiC nanowire modified porous carbon oil-water separation membrane according to claim 1, characterized in that: The density of the porous carbon material is 0.01 to 0.6 g / cm 3 .

4. The method for preparing the SiC nanowire modified porous carbon oil-water separation membrane according to claim 1, characterized in that: The concentration of the metal catalyst solution is 0.005-0.5 mol / L.

5. The method for preparing the SiC nanowire modified porous carbon oil-water separation membrane according to claim 1, characterized in that: The solute of the metal catalyst solution includes one or more transition metal salts such as iron salt, cobalt salt, nickel salt, etc.

6. The method for preparing the SiC nanowire modified porous carbon oil-water separation membrane according to claim 1, characterized in that: During the vacuum impregnation process, the impregnation time is 0.5 to 1 hour.

7. The method for preparing the SiC nanowire modified porous carbon oil-water separation membrane according to claim 1, characterized in that: The molar ratio of the carbon source to the silicon source is (0.1-1):

1.

8. The method for preparing the SiC nanowire modified porous carbon oil-water separation membrane according to claim 1, characterized in that: The silicon source is prepared by compounding silicon powder and silicon dioxide powder, and the molar ratio of the silicon powder to the silicon dioxide powder is 1:(0.25-4); the carbon source includes one of carbon black, graphite, carbon nanotubes and activated carbon.

9. The method for preparing the SiC nanowire modified porous carbon oil-water separation membrane according to claim 1, characterized in that: During the programmed temperature reaction, the vacuum degree is 10-2000 Pa, the temperature is increased to 1200-1600° C. at a rate of 10-20° C. / min, and the temperature is kept for 20-50 minutes.

10. A SiC nanowire-modified porous carbon oil-water separation membrane prepared by the preparation method according to any one of claims 1 to 9.

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