Hydrophilic-hydrophobic composite felt, and preparation method and application thereof

Abstract

This invention provides a hydrophilic-hydrophobic composite felt, its preparation method, and its application. The preparation method includes the following steps: mixing, spraying, and stacking fibers of different thicknesses, followed by sintering to obtain a metal fiber felt with a small inner pore size and a large outer pore size; etching and modifying the metal fiber felt to obtain a superhydrophilic metal fiber felt; and performing chemical vapor deposition on the surface of the superhydrophilic metal fiber felt to obtain a hydrophilic-hydrophobic composite felt. The hydrophilic-hydrophobic composite felt comprises a first hydrophobic outer layer, a hydrophilic inner layer, and a second hydrophobic outer layer, which are sequentially adjacent. It has a high processing throughput and good demulsification effect, and can be applied to emulsions of different properties. At the same time, the preparation method is simple to operate, low in cost, and easy to scale up for production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of petrochemical industry, environmental protection and water treatment, and particularly relates to a hydrophilic-hydrophobic composite felt and a preparation method and application thereof. BACKGROUND

[0002] Petroleum chemical industry, coal chemical industry, metallurgy, machinery manufacturing, textile printing and dyeing, leather and many other industries such as industrial production, shipping and maritime affairs will produce a large amount of oily wastewater. At least nearly ten million tons of oil substances enter the water body through various channels every year in the world, which not only causes resource waste but also causes great harm to the marine and river water environment and soil environment. Therefore, the treatment of oily wastewater has attracted widespread attention.

[0003] Oil pollution often exists in the form of suspension, emulsion and dissolution. The oil droplets of floating oil and dispersed oil are relatively large and easy to handle, and can be completely removed by gravity sedimentation, parallel plate or corrugated plate enhanced sedimentation, cyclone separation, conventional filler coalescence separation and other methods. For dissolved oil, it can be removed by adsorption and biological treatment. Because the content of dissolved oil in most wastewater is extremely low, it has little impact on the environment. The particle size of emulsified oil (0.1-10 μm) is very small, and there are often surfactants in the wastewater, which makes the emulsion tend to be in a stable state, so it is difficult to separate oil and water. Therefore, it has become the focus and difficulty of oily wastewater treatment. At the same time, with the increasingly stringent discharge requirements, resource shortage and deterioration of the ecological environment, the traditional process with the single goal of clean water cannot meet the requirements of resource recovery and environmental sustainable development.

[0004] The key to oil-water separation and resource recovery of emulsion wastewater is demulsification. The current demulsification methods mainly include flocculation air flotation, biological method, centrifugal separation, membrane separation, coalescence separation, electric field separation, ultrasonic separation and other methods. These methods each have their own scope of application and advantages and disadvantages. The flocculation air flotation method needs to add demulsifier and flocculant, and the disadvantages are large occupation area, high drug consumption and secondary pollution of sludge. The biological method has poor anti-fluctuation and high requirements for the quality of the influent, and needs pretreatment. The centrifugal separation has small treatment capacity, low efficiency and high equipment maintenance cost. The electric field, electrochemistry and ultrasonic separation devices have complex structure, high cost and high energy consumption, and are difficult to be applied on a large scale. The conventional coarse coalescence material in coalescence separation is easy to be cemented, and the separation performance is poor when the emulsification is serious. The membrane separation demulsification method can limit micron-sized oil droplets in a small space due to its small pore size and adjustable wettability, so that the oil droplets are easy to coalesce and demulsify, and thus it has become a research direction widely concerned. However, the demulsification membrane has problems such as complex manufacturing process, small flux and low demulsification efficiency, which limits its practical application.

[0005] Therefore, in order to realize the rapid demulsification of emulsion and form a continuous oil phase that can be recycled, it is urgent to develop a demulsification material with low cost, low energy consumption, good effect and large treatment flux in the field. SUMMARY

[0006] The purpose of this invention is to provide a hydrophilic-hydrophobic composite felt, its preparation method and application. The composite felt, which is prepared by overall hydrophilic modification and outer layer hydrophobic modification, has a hydrophilic inner layer and a hydrophobic outer layer. It has a large throughput and good demulsification effect, and can be used for emulsions of different properties. At the same time, the preparation method is simple and easy to operate, low in cost and easy to scale up.

[0007] To achieve this objective, the present invention employs the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a hydrophilic-hydrophobic composite felt, the method comprising the following steps:

[0009] (1) After mixing, spraying, and stacking fibers of different thicknesses, sintering is carried out to obtain a metal fiber felt with small inner pore size and large outer pore size.

[0010] (2) The metal fiber felt described in step (1) is etched and modified to obtain a superhydrophilic metal fiber felt.

[0011] (3) Chemical vapor deposition is performed on the surface of the superhydrophilic metal fiber felt described in step (2) to obtain a hydrophilic-hydrophobic composite felt.

[0012] In this invention, superhydrophilic means that the static contact angle of a water droplet on its surface is less than 5°, and hydrophobic means that the static contact angle of a water droplet on its surface is greater than 150°; the superhydrophilic metal fiber felt prepared by this invention can completely spread water droplets on it within 0.2-5s.

[0013] This invention uses fibers of different thicknesses to make metal fiber felt with small inner pore size and large outer pore size. Then, through overall hydrophilic modification and outer hydrophobic modification, a composite material with a hydrophilic inner layer and a hydrophobic outer layer is prepared. It has a large processing capacity and good demulsification effect, and can be applied to emulsions with different properties.

[0014] As a preferred technical solution of the present invention, the diameter of the fiber in step (1) is 0.5-30μm, for example, it can be 0.5μm, 1μm, 3μm, 5μm, 7μm, 10μm, 14μm, 18μm, 20μm, 24μm, 28μm or 30μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] Preferably, the sintering temperature in step (1) is 400-1000℃, for example, it can be 400℃, 500℃, 600℃, 700℃, 800℃, 900℃ or 90℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, the sintering time in step (1) is 10-90 min, for example, it can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Preferably, the pore size of the inner layer of the metal fiber felt in step (1) is 0.5-20μm, for example, it can be 0.5μm, 1μm, 3μm, 5μm, 7μm, 10μm, 14μm, 18μm or 20μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] Preferably, the pore size of the outer layer of the metal fiber felt in step (1) is 5-100μm, for example, it can be 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] It is worth noting that the pore size of the inner layer of the metal fiber felt in this invention is smaller than the pore size of the outer layer of the metal fiber felt. For example, when the pore size of the outer layer of the metal fiber felt is 5 μm, the pore size of the inner layer is < 5 μm.

[0020] Preferably, the metal fiber felt in step (1) is made of stainless steel and / or iron-chromium-aluminum.

[0021] As a preferred technical solution of the present invention, the etching modification in step (2) is carried out in an etching solution.

[0022] In this invention, before the metal fiber felt is etched and modified, it is ultrasonically cleaned in acetone, ethanol and deionized water for 10 minutes in sequence to thoroughly remove surface impurities, and then dried in a vacuum drying oven at 60°C.

[0023] Preferably, the etching solution is a mixed solution of FeCl3 and HCl.

[0024] Preferably, the etching solution contains 5%-40% FeCl3 by mass and 0.5-1.5 mol / L HCl by mass.

[0025] In this invention, the mass concentration of FeCl3 in the etching solution is 5%-40%, for example, it can be 5%, 7%, 10%, 15%, 20%, 25%, 30%, 35% or 40%, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] In this invention, the concentration of HCl in the etching solution is 0.5-1.5 mol / L, for example, it can be 0.5 mol / L, 0.7 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.3 mol / L or 1.5 mol / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the etching modification time in step (2) is 30-90s, for example, it can be 30s, 40s, 50s, 60s, 70s, 80s or 90s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] As a preferred technical solution of the present invention, the etching modification in step (2) further includes washing, oxidation treatment and drying in sequence.

[0029] Preferably, the oxidation treatment is carried out in an oxidizing solution.

[0030] Preferably, the oxidizing solution is a hydrogen peroxide solution with a mass fraction of 20%-40%, such as 20%, 24%, 28%, 30%, 34%, 38%, or 40%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] It is worth noting that after etching modification, oxidation treatment is performed. After oxidation, a passivation film is formed on the surface of the metal fiber felt, which is more stable and can further enhance the surface roughness of the metal fiber felt.

[0032] Preferably, the oxidation treatment time is 30-90 min, for example, it can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the drying temperature is 50-70°C, for example, it can be 50°C, 54°C, 58°C, 60°C, 64°C, 68°C or 70°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the drying time is 1-3 hours, for example, it can be 1 hour, 1.4 hours, 1.8 hours, 2 hours, 2.4 hours, 2.8 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] As a preferred technical solution of the present invention, the deposition materials in the chemical vapor deposition in step (3) include polydimethylsiloxane (PDMS) and ammonium bicarbonate.

[0036] In this invention, the ammonium bicarbonate can decompose into gas at a lower temperature to assist PDMS deposition. A very thin layer of PDMS is deposited on the outer fibers of the metal fiber felt, but the pore size of the outer layer of the metal fiber felt is not changed after the PDMS is deposited.

[0037] Preferably, the polydimethylsiloxane is prepared by mixing a prepolymer and a curing agent.

[0038] Preferably, the prepolymer is Dow Corning 184 silicone rubber component A.

[0039] Preferably, the curing agent is Dow Corning 184 silicone rubber component B.

[0040] Preferably, the mass ratio of the prepolymer to the curing agent is (10-15):1, for example, it can be 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Preferably, the mass ratio of polydimethylsiloxane to ammonium bicarbonate is (0.4-0.6):1, for example, it can be 0.4:1, 0.44:1, 0.48:1, 0.5:1, 0.54:1, 0.58:1 or 0.6:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] As a preferred technical solution of the present invention, the temperature of chemical vapor deposition in step (3) is 70-90℃, for example, it can be 70℃, 74℃, 78℃, 80℃, 84℃, 88℃ or 90℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the chemical vapor deposition time in step (2) is 30-90 min, for example, it can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the chemical vapor deposition in step (2) is followed by washing and drying.

[0045] Preferably, the drying temperature is 70-90℃, for example, it can be 70℃, 74℃, 78℃, 80℃, 84℃, 88℃ or 90℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the drying time is 1-3 hours, for example, it can be 1 hour, 1.4 hours, 1.8 hours, 2 hours, 2.4 hours, 2.8 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0048] (1) After mixing, spraying and stacking fibers of different thicknesses, sintering them at 400-1000℃ for 10-90 minutes to obtain metal fiber felt with small inner pore size and large outer pore size.

[0049] The diameter of the fiber is 0.5-30 μm;

[0050] (2) Immerse the metal fiber felt described in step (1) in the etching solution for 30-90s, wash it, and then oxidize it in a hydrogen peroxide solution with a mass fraction of 20%-40% for 30-90min. After that, dry it at 50-70℃ for 1-3h to obtain a superhydrophilic metal fiber felt.

[0051] The etching solution is a mixed solution of FeCl3 and HCl;

[0052] (3) The superhydrophilic metal fiber felt and the deposition material described in step (2) are subjected to chemical vapor deposition at 70-90℃ for 30-90 min, washed and dried at 70-90℃ for 1-3 h to obtain a hydrophilic-hydrophobic composite felt.

[0053] The deposition material comprises a mixture of polydimethylsiloxane and ammonium bicarbonate.

[0054] Secondly, the present invention provides a hydrophilic-hydrophobic composite felt, which is prepared by the preparation method described in the first aspect.

[0055] The hydrophilic-hydrophobic composite felt comprises a first hydrophobic outer layer, a hydrophilic inner layer, and a second hydrophobic outer layer that are sequentially adjacent to each other.

[0056] In this invention, the first hydrophobic fiber outer layer and the second hydrophobic fiber outer layer are thin layers composed of several fibers after PDMS deposition.

[0057] It is worth noting that when the hydrophilic-hydrophobic composite felt is used as a demulsification medium, the emulsified oil droplets first aggregate into larger oil droplets on the hydrophobic fiber layer in a wetting and coalescing manner. The small oil droplets that have not been demulsified are further demulsified on the hydrophilic fiber layer by compression and coalescing, thereby improving the demulsification efficiency. At the same time, the structure of the outer hydrophobic layer and the inner hydrophilic layer significantly improves the processing throughput.

[0058] As a preferred technical solution of the present invention, the thickness of the hydrophilic fiber inner layer is 100-400μm, for example, it can be 100μm, 150μm, 200μm, 250μm, 300μm, 350μm or 400μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] Preferably, the pore size of the hydrophilic fiber inner layer is smaller than that of the first hydrophobic fiber outer layer and the second hydrophobic fiber outer layer.

[0060] Preferably, the pore size of the hydrophilic fiber inner layer is 0.5-20μm, for example, it can be 0.5μm, 1μm, 3μm, 5μm, 7μm, 10μm, 14μm, 18μm or 20μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0061] Preferably, the thickness of the first hydrophobic fiber outer layer and the second hydrophobic fiber outer layer is 5-200 μm, for example, it can be 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 140 μm, 180 μm or 200 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0062] Preferably, the pore size of the first hydrophobic fiber outer layer and the second hydrophobic fiber outer layer is 20-100μm, excluding 20μm. For example, it can be 25μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] In this invention, the flux of the hydrophilic-hydrophobic composite felt is ≥6000 L·m -2 ·h -1 For example, it could be 6000 L·m -2 ·h -1 8000L·m -2 ·h -1 10000L·m -2 ·h -1 15000L·m -2 ·h -1 20000L·m -2 ·h -1 25000L·m -2 ·h -1 27000L·m -2 ·h -1 Or 30000 L·m -2 ·h -1This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0064] Preferably, the hydrophilic-hydrophobic composite felt has a demulsification efficiency of ≥98% for the emulsion, such as 98%, 98.2%, 98.4%, 98.6%, 98.8%, 99%, 99.4%, 99.5%, or 99.7%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0065] Thirdly, the present invention provides an application of the hydrophilic-hydrophobic composite felt described in the second aspect, wherein the hydrophilic-hydrophobic composite felt is used in the field of oil-water separation of emulsions.

[0066] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

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

[0068] (1) The hydrophilic-hydrophobic composite felt of the present invention is made of metal fiber felt with small inner pore size and large outer pore size by fibers of different thicknesses, and then prepared by overall hydrophilic modification and outer hydrophobic modification. The preparation method is simple and easy to operate, low cost and easy to scale up production.

[0069] (2) The hydrophilic-hydrophobic composite felt prepared by the present invention has a hydrophilic inner layer and a hydrophobic outer layer, which can handle a large throughput and has a good demulsification effect, and can be applied to emulsions of different properties. Attached Figure Description

[0070] Figure 1 This is a front view of the hydrophilic-hydrophobic composite felt prepared in Example 1;

[0071] Figure 2 This is a SEM side view of the hydrophilic-hydrophobic composite felt prepared in Example 1;

[0072] Figure 3 This is a schematic diagram of the demulsification oil-water separation device provided by the present invention;

[0073] Figure 4 Comparison of emulsified wastewater before and after filtration using the hydrophilic-hydrophobic composite felt prepared in Example 1;

[0074] Figure 5 The graph shows the changes in treatment flux and demulsification efficiency of the hydrophilic-hydrophobic composite felt prepared in Example 1 during the treatment of emulsified wastewater.

[0075] Wherein: 1-liquid inlet, 2-original liquid chamber, 3-hydrophilic-hydrophobic composite felt, 4-liquid outlet, 5-liquid outlet chamber. Detailed Implementation

[0076] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0077] Example 1

[0078] This embodiment provides a hydrophilic-hydrophobic composite felt and its preparation method, the preparation method including the following steps:

[0079] (1) After mixing, spraying and stacking fibers of different thicknesses, sintering at 800℃ for 40 min, a stainless steel fiber felt with an inner pore size of 2μm and an outer pore size of 30μm is obtained.

[0080] The diameter of the fiber is 0.5-30 μm;

[0081] (2) The stainless steel fiber felt from step (1) was ultrasonically cleaned in acetone, ethanol and deionized water for 10 min in sequence, dried at 60°C, then immersed in etching solution for 60 s, washed away excess etching solution with deionized water, oxidized in 30% hydrogen peroxide solution for 60 min, and then dried at 60°C for 2 h to obtain superhydrophilic stainless steel fiber felt.

[0082] The etching solution is a mixed solution of 40% FeCl3 and 1 mol / L HCl.

[0083] (3) The superhydrophilic metal fiber felt and the deposition material from step (2) were subjected to chemical vapor deposition at 80°C for 60 min, ultrasonically cleaned with deionized water for 10 min, and then dried at 80°C for 2 h to obtain the hydrophilic-hydrophobic composite felt.

[0084] The deposition material is polydimethylsiloxane (prepared by mixing Dow Corning 184 silicone rubber component A and Dow Corning 184 silicone rubber component B at a mass ratio of 10:1) and ammonium bicarbonate at a mass ratio of 0.5:1.

[0085] The SEM front view and side view of the hydrophilic-phobic composite felt prepared in this embodiment are shown below. Figures 1-2 As shown, by Figures 1-2 It is known that the hydrophilic-hydrophobic composite felt prepared by the present invention has a smaller inner pore size and a larger outer pore size; the prepared hydrophilic-hydrophobic composite felt includes a first hydrophobic fiber outer layer with a thickness of 100 μm, a hydrophilic fiber inner layer with a thickness of 300 μm, and a second hydrophobic fiber outer layer with a thickness of 100 μm that are sequentially adjacent.

[0086] Figure 4The images show a comparison of the emulsified wastewater before and after filtration using the hydrophilic-hydrophobic composite felt prepared in Example 1. Figure 5 This graph shows the changes in treatment flux and demulsification efficiency of the hydrophilic-hydrophobic composite felt prepared in Example 1 during the treatment of emulsified wastewater. The treatment flux of the hydrophilic-hydrophobic composite felt prepared in this example is 20787 L·m. -2 ·h -1 .

[0087] Example 2

[0088] This embodiment provides a hydrophilic-hydrophobic composite felt and its preparation method, the preparation method including the following steps:

[0089] (1) After mixing, spraying and stacking fibers of different thicknesses, sintering at 800℃ for 60 min, a stainless steel fiber felt with an inner pore size of 10μm and an outer pore size of 40μm is obtained.

[0090] The diameter of the fiber is 0.5-30 μm;

[0091] (2) The stainless steel fiber felt from step (1) was ultrasonically cleaned in acetone, ethanol and deionized water for 10 min in sequence, dried at 60°C, then immersed in etching solution for 70 s, washed away excess etching solution with deionized water, oxidized in 40% hydrogen peroxide solution for 50 min, and then dried at 60°C for 2 h to obtain superhydrophilic stainless steel fiber felt.

[0092] The etching solution is a mixed solution of 30% FeCl3 and 1.2 mol / L HCl.

[0093] (3) The superhydrophilic metal fiber felt and the deposition material from step (2) were subjected to chemical vapor deposition at 90°C for 50 min, ultrasonically cleaned with deionized water for 10 min, and then dried at 80°C for 2 h to obtain the hydrophilic-hydrophobic composite felt.

[0094] The deposition material is polydimethylsiloxane (prepared by mixing Dow Corning 184 silicone rubber component A and Dow Corning 184 silicone rubber component B at a mass ratio of 10:1) and ammonium bicarbonate at a mass ratio of 0.4:1.

[0095] The hydrophilic-hydrophobic composite felt prepared in this embodiment includes a first hydrophobic fiber outer layer with a thickness of 140 μm, a hydrophilic fiber inner layer with a thickness of 220 μm, and a second hydrophobic fiber outer layer with a thickness of 140 μm, which are sequentially adjacent.

[0096] The hydrophilic-hydrophobic composite felt prepared in this embodiment has a processing flux of 19096 L·m. -2 ·h -1 .

[0097] Example 3

[0098] This embodiment provides a method for preparing a hydrophilic-hydrophobic composite felt. Except for the different amounts of the inner and outer layer fibers in step (1), which make the thickness of the first and second hydrophobic fiber outer layers 3 μm, all other conditions are the same as in Example 1.

[0099] Example 4

[0100] This embodiment provides a method for preparing a hydrophilic-hydrophobic composite felt. Except for the different amounts of the inner and outer layer fibers in step (1), which make the thickness of the first and second hydrophobic fiber outer layers 240 μm, all other conditions are the same as in Example 1.

[0101] Example 5

[0102] This embodiment provides a method for preparing a hydrophilic-hydrophobic composite felt. Except for the etching time of 10s in step (2), all other conditions are the same as in Example 1.

[0103] Example 6

[0104] This embodiment provides a method for preparing a hydrophilic-hydrophobic composite felt. Except for the etching time of 5 min in step (2), all other conditions are the same as in Example 1.

[0105] Example 7

[0106] This embodiment provides a method for preparing a hydrophilic-hydrophobic composite felt. Except for the chemical vapor deposition time of 10 min in step (3), all other conditions are the same as in Example 1.

[0107] Example 8

[0108] This embodiment provides a method for preparing a hydrophilic-hydrophobic composite felt. Except for the chemical vapor deposition time of 120 min in step (3), all other conditions are the same as in Example 1.

[0109] Comparative Example 1

[0110] This comparative example provides a method for preparing a hydrophilic-hydrophobic composite felt. Except for step (1), which uses only fibers of the same diameter to prepare stainless steel fiber felt with pore sizes of 30 μm for both inner and outer layers, all other conditions are the same as in Example 1.

[0111] Comparative Example 2

[0112] This comparative example provides a method for preparing a hydrophilic-hydrophobic composite felt. Except for step (3) chemical vapor deposition, all other conditions are the same as in Example 1.

[0113] The hydrophilic-hydrophobic composite felts prepared in the above embodiments and comparative examples were used to treat emulsion wastewater. The hydrophilic-hydrophobic composite felt 3 was placed in a demulsification oil-water separation device (its structural schematic diagram is shown below). Figure 3 As shown, the demulsifying oil-water separation device includes an inlet 1, a raw liquid chamber 2, an outlet 4, and an outlet chamber 5.

[0114] The specific process of treating emulsion wastewater with hydrophilic-hydrophobic composite felt is as follows: When the demulsification oil-water separation device is running, the original liquid chamber 2 and the outlet chamber 5 are separated by hydrophilic-hydrophobic composite felt 3. 1% emulsion wastewater (with an average oil droplet diameter of less than 10 μm) is continuously introduced through inlet 1, with the inlet pressure set to 30 kPa. The emulsion oil droplets coalesce in the hydrophilic-hydrophobic composite felt 3, and the demulsified and unstable mixture enters the outlet chamber 5, ultimately forming immiscible oil and water phases, which are then discharged through outlet 4. The demulsification efficiency of the prepared hydrophilic-hydrophobic composite felt for emulsions is shown in Table 1.

[0115] Table 1

[0116] Demulsification efficiency Example 1 98.3％ Example 2 99.0％ Example 3 86％ Example 4 94％ Example 5 70％ Example 6 82％ Example 7 92％ Example 8 98.1％ Comparative Example 1 65％ Comparative Example 2 76％

[0117] The following points can be drawn from Table 1:

[0118] (1) The preparation method provided in Examples 1-2 of this invention produces a hydrophilic-hydrophobic composite felt with a processing flux as high as 20700 L·m. -2 ·h -1 The demulsification efficiency is as high as 98% or more;

[0119] (2) Comparison of Examples 1 and 3-4 shows that when the hydrophobic fiber outer layer of the hydrophilic-hydrophobic composite felt is too thick, the demulsification effect is worse because the hydrophilic inner layer is too thin. When the hydrophobic fiber outer layer of the prepared hydrophilic-hydrophobic composite felt is too thin, the initial aggregation effect of the hydrophobic outer layer is small, and the undemulsified oil droplets directly enter the hydrophilic inner layer and block the pores, resulting in a decrease in processing throughput and a worse demulsification effect.

[0120] (3) Comparing Example 1 and Example 5-6, it can be seen that when the etching modification time is too short, the surface roughness is insufficient, resulting in insufficient wettability modification of the hydrophilic-hydrophobic composite felt; when the etching modification time is too long, the finer fibers inside the metal felt are corroded and broken, resulting in changes in the internal pore size of the hydrophilic-hydrophobic composite felt.

[0121] (4) Comparing Examples 1 and 7-8, it can be seen that when the chemical vapor deposition time is too short, too little PDMS is deposited, resulting in insufficient hydrophobicity of the metal fiber felt hydrophobic layer; when the chemical vapor deposition time is too long, too much PDMS is deposited, the demulsification efficiency does not decrease, but the deposited material is wasted and the cost increases.

[0122] (5) Comparing Example 1 and Comparative Example 1, it can be seen that when metal fiber felt is made using only a single fiber, the resulting hydrophilic-hydrophobic composite felt is difficult to achieve both good demulsification effect and large throughput due to the uniform pore size. Comparing Example 1 and Comparative Example 2, it can be seen that when chemical vapor deposition modification is not performed, the metal fiber felt is a hydrophilic felt and does not have a composite hydrophilic-hydrophobic structure, resulting in a poor demulsification effect and a throughput far lower than that of the hydrophilic-hydrophobic composite felt.

[0123] The applicant declares that the detailed structural features of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components selected in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0124] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0125] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0126] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for producing a hydrophilic-hydrophobic composite felt, characterized by, The preparation method comprises the following steps: (1) mixing and spraying fibers with different thicknesses, and sintering at 400-1000 ℃ for 10-90 min to obtain a metal fiber felt with small inner layer pore size and large outer layer pore size; The diameter of the fiber is 0.5-30 μm; (2) immersing the metal fiber felt in step (1) in an etching solution for etching for 30-90 s, washing, and then oxidizing in a 20%-40% hydrogen peroxide solution for 30-90 min, and then drying at 50-70 ℃ for 1-3 h to obtain a super-hydrophilic metal fiber felt; The etching solution is a mixed solution of FeCl3 and HCl; In the etching solution, the mass concentration of FeCl3 is 5%-40%, and the concentration of HCl is 0.5-1.5 mol / L; (3) performing chemical vapor deposition on the super-hydrophilic metal fiber felt in step (2) and a deposition material at 70-90 ℃ for 30-90 min, washing, and then drying at 70-90 ℃ for 1-3 h to obtain a hydrophilic-hydrophobic composite felt; The deposition material comprises a mixture of polydimethylsiloxane and ammonium bicarbonate; The mass ratio of the polydimethylsiloxane and the ammonium bicarbonate is (0.4-0.6):

1.

2. The production method according to claim 1, characterized by, The pore size of the inner layer of the metal fiber felt in step (1) is 0.5-20 μm; The pore size of the outer layer of the metal fiber felt in step (1) is 5-100 μm.

3. The preparation method according to claim 1, characterized in that, The polydimethylsiloxane is prepared by mixing a prepolymer and a curing agent; The prepolymer is Dow Corning 184 silicone rubber component A; The curing agent is Dow Corning 184 silicone rubber component B; The mass ratio of the prepolymer and the curing agent is (10-15):

1.

4. A hydrophilic-hydrophobic composite felt, characterized by, The hydrophilic-hydrophobic composite felt is prepared by the preparation method in any one of claims 1-3; The hydrophilic-hydrophobic composite felt comprises sequentially adjacent first hydrophobic fiber outer layers, a hydrophilic fiber inner layer, and second hydrophobic fiber outer layers.

5. The hydrophilic-hydrophobic composite felt according to claim 4, wherein The thickness of the hydrophilic fiber inner layer is 100-400 μm.

6. The hydrophilic-hydrophobic composite felt according to claim 4, wherein The thickness of the first hydrophobic fiber outer layer and the second hydrophobic fiber outer layer is 20-200 μm.

7. The hydrophilic-hydrophobic composite felt according to claim 4, wherein The pore size of the hydrophilic fiber inner layer is smaller than that of the first hydrophobic fiber outer layer and the second hydrophobic fiber outer layer.

8. The hydrophilic-hydrophobic composite felt according to claim 4, wherein The pore size of the hydrophilic fiber inner layer is 0.5-20 μm.

9. The hydrophilic-hydrophobic composite mat according to claim 4, wherein, The pore size of the first hydrophobic fiber outer layer and the second hydrophobic fiber outer layer is 5-100 μm.

10. The hydrophilic-hydrophobic composite mat according to claim 4, wherein, The demulsification efficiency of the hydrophilic-hydrophobic composite felt on an emulsion is ≥98%.

11. Use of a hydrophilic-hydrophobic composite felt according to any one of claims 4-10, characterized in that, The hydrophilic-hydrophobic composite felt is used in the field of emulsion oil-water separation.

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