Super-hydrophilic-oleophobic composite surface foamed copper, preparation method thereof and application of the same in continuous steady-state demulsification of oil-in-water emulsion

Abstract

The application discloses super-hydrophilic-oleophobic composite surface foam copper and a preparation method and application of the super-hydrophilic-oleophobic composite surface foam copper in continuous and steady demulsification of oil-in-water emulsion. 2 The super-hydrophilic-oleophobic composite surface foam copper has a surface energy of 10-30 mJ / m 2 , a water contact angle in air of 0-5°, an oil contact angle in air of 95.2-131.0°, and an oil contact angle under water of 145.6-154.8°. The application utilizes the large pore advantage of the foam copper and the long permeation channel obtained by stacking to realize a high-flux and high-efficiency demulsification process, the composite surface greatly reduces the pollution of oil droplets to the surface of the foam copper, and the release of oil stains is strengthened, so that the obtained foam copper can realize high efficiency, high flux, and continuous demulsification of oil-in-water emulsion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil-water separation, in particular to a super-hydrophilic and oleophobic composite surface foam copper capable of continuously and stably demulsifying oil-in-water emulsion and a preparation method and application thereof. BACKGROUND

[0002] Modern industry produces a large amount of oil-containing wastewater every day, and how to efficiently, quickly and continuously treat oil-water mixture is still a challenging problem. Since 2004, when Jiang Lei et al. first published the research on oil-water separation based on special wetting stainless steel mesh, super-wetting materials have attracted attention due to their high efficiency, energy saving and environmental protection. Compared with immiscible oil-water mixture, emulsified oil-water mixture is difficult to be quickly separated by simple super-wetting materials due to small particle size of dispersed phase droplets, high stability, and the presence of surfactants in some emulsions. According to statistics, oil-in-water emulsion accounts for three-quarters of the complex industrial oil-water emulsion. In order to make super-wetting materials separate these oil-in-water emulsions, special demulsification driving force needs to be built on the material, such as micro-nano-porous materials based on size sieving effect, and charged surface materials based on charge shielding effect. However, the size sieving effect makes the material appear trade-off effect between demulsification flux and demulsification efficiency, and it is difficult to obtain a material with high efficiency and high flux. The introduction of rich charged groups on the surface of the material will increase the adsorption of surfactants and the adhesion of oil droplets, thereby greatly reducing the demulsification durability of the material and making it difficult to achieve stable and continuous demulsification.

[0003] In order to improve the demulsification flux, some studies propose to use a large-pore substrate for super-wetting modification, build a demulsification driving force on its surface, and prolong the action time of the surface and the emulsion by extending the permeation channel, thereby greatly improving the demulsification efficiency without sacrificing too much flux. The controllable wetting foam copper prepared in Chinese invention patent CN104264209B grows copper hydroxide nanoneedles on the surface by electrochemical oxidation in sodium hydroxide solution, which can achieve underwater super-oleophobicity and oil-underwater super-hydrophobicity. However, the foam copper has large pore size and short permeation channel, and can only be used to separate immiscible oil-water mixture, and does not have sufficient demulsification performance. Similarly, the super-hydrophilic and super-hydrophobic foam coppers prepared in Chinese invention patent application CN116966757A also cannot provide sufficient demulsification performance.

[0004] The super-hydrophilic and super-oleophobic cellulose sponge prepared by phase inversion solidification in Chinese invention patent CN105778158B has micrometer-sized pores on one side and nanometer-sized pores on the other side, and the demulsification efficiency for oil-in-water emulsion is more than 99.9%. However, the too small pore size fails to break the limitation of trade-off effect, and the flux is only 150 L·m -2 ·h -1CN116408054A prepared 3D Janus sponge, due to the controllable wettability and interconnected cage structure, ultra-high porosity and tortuous permeation channel, the demulsification efficiency of more than 99% and the demulsification flux of more than 11000L·m -2 ·h -1 of oil-in-water emulsion, but the demulsification durability is not shown. CN114733499A prepared Janus positive and negative charge type super-hydrophilic / underwater super-oleophobic foam copper group combines the super-wetting effect, surface charge effect and long permeation channel effect to realize more than 99% separation efficiency of oil-in-water emulsion, and further improves the flux to 30000L·m -2 ·h -1 , but the demulsification durability is still not shown.

[0005] CN116444853A prepared super-hydrophilic / oleophobic charged melamine sponge, doped with perfluorooctanoic acid on the surface to improve the oil pollution resistance of the material, under the premise of ensuring more than 97% demulsification efficiency and about 35000L·m -2 ·h -1 initial flux, about 20000L·m -2 ·h -1 flux can still be provided after separating 500mL oil-in-water emulsion. But the surface with rich charge is easy to attract surfactant, and the uniform surface adsorbed surfactant will inevitably change the wettability, so that the demulsification performance cannot reach a steady state to realize continuous demulsification process.

[0006] The above existing technologies are based on modification of three-dimensional substrates to improve the demulsification efficiency, flux and durability of oil-in-water emulsion. Although some technologies overcome the trade-off between efficiency and flux, it is still difficult to realize stable and long-acting continuous demulsification process under the premise of high flux and high efficiency, and to achieve all three. SUMMARY

[0007] The purpose of the present application is to provide a super-hydrophilic-oleophobic composite surface foam copper with long-acting and stable demulsification performance under the premise of high flux and high efficiency, and a preparation method thereof.

[0008] Another purpose of the present application is to provide the application of the super-hydrophilic-oleophobic composite surface foam copper to high-efficiency, rapid and continuous demulsification of oil-in-water emulsion.

[0009] To achieve the above-mentioned purposes of the application, the technical scheme adopted by the present application is as follows:

[0010] The application discloses super-hydrophilic and oleophobic composite surface foamed copper, which is obtained by simultaneously depositing amino-carbon nanotubes and fluorinated carbon nanotubes on the surface of foamed copper with copper hydroxide nanoneedles. 2 The water contact angle in air is 0-5°, the oil contact angle in air is 95.2-131.0°, and the oil contact angle under water is 145.6-154.8°.

[0011] The preparation method of the super-hydrophilic and oleophobic composite surface foamed copper comprises the following steps:

[0012] 1) after cleaning the initial foamed copper, the foamed copper is immersed in an oxidizing solution containing sodium hydroxide and ammonium persulfate for chemical oxidation, copper hydroxide nanoneedles are grown on the surface, and then the foamed copper is rinsed with deionized water and dried;

[0013] 2) the obtained foamed copper with copper hydroxide nanoneedles is fully immersed in a hydroxyethyl cellulose aqueous solution, and then the foamed copper is taken out, washed with deionized water to remove excess hydroxyethyl cellulose and dried;

[0014] 3) after mixing amino-carbon nanotubes and fluorinated carbon nanotubes, the mixture is configured into a uniform suspension solution by using an organic solvent, the foamed copper obtained in step 2) is fully immersed in the suspension solution, and then the foamed copper is taken out and dried to obtain the super-hydrophilic and oleophobic composite surface foamed copper.

[0015] To further achieve the object of the application, preferably, in step 1), the pore diameter of the initial foamed copper is 50-400 μm, and the thickness is 0.5-10 mm; the cleaning is ultrasonic cleaning with acetone, anhydrous ethanol and deionized water respectively for 5-20 min, and the foamed copper is dried at a temperature of 10-30 ℃ for 1-5 hours after cleaning.

[0016] Preferably, in step 1), in the oxidizing solution containing sodium hydroxide and ammonium persulfate, the concentration of sodium hydroxide is 1-10 mol / L, and the concentration of ammonium persulfate is 0.05-0.5 mol / L; the immersion oxidation time is 5-15 min, and the foamed copper is rinsed with deionized water after oxidation and then dried at a temperature of 10-30 ℃ for 1-5 hours.

[0017] Preferably, in step 2), the concentration of the hydroxyethyl cellulose solution is 0.5-5 g / L, the immersion time is 0.5-5 hours, and the foamed copper is dried at a temperature of 10-30 ℃ for 1-5 hours after immersion.

[0018] Preferably, the length of the amino-carbon nanotubes is 10-100 μm, the diameter is 20-500 nm, the purity is greater than 95.0 wt%, and the amino content is greater than 0.3 wt%.

[0019] Preferably, in step 3), the organic solvent is one or more of methanol, ethanol, acetone; the mass ratio of the amino-functionalized carbon nanotubes to the fluorinated carbon nanotubes is 20:80-80:20, and the total concentration of the prepared suspension solution is 0.5-5 g / L; the soaking time is 10-30 minutes, and the drying is performed at a temperature of 40-80 DEG C for 0.5-1 hour after the soaking.

[0020] Preferably, the fluorinated carbon nanotubes are prepared by the following steps:

[0021] 1) the amino-functionalized carbon nanotubes are dispersed in an alkane solvent to form a dispersion liquid with a concentration of 0.5-5 g / L, and magnetic stirring is performed at a speed of 200-1000 rpm; the alkane solvent is n-hexane or cyclohexane;

[0022] 2) perfluorooctanoyl chloride is added dropwise to the amino-functionalized carbon nanotube dispersion liquid obtained in step 1), the concentration of the perfluorooctanoyl chloride in the dispersion liquid is 1-10 g / L after the dropwise addition is completed, and the stirring is continuously performed for 5-30 minutes;

[0023] 3) the liquid obtained in step 2) is filtered, and the obtained solid is dried at a temperature of 40-80 DEG C for 1-5 hours;

[0024] 4) the dried solid is ground to obtain the fluorinated carbon nanotubes.

[0025] The application of the super-hydrophilic and oleophobic composite surface of the foam copper in continuous and steady demulsification of oil-in-water emulsion.

[0026] Preferably, 10-100 pieces of the super-hydrophilic and oleophobic composite surface of the foam copper are stacked into a columnar shape as a filter substrate, the foam copper is first wetted with water, then the oil-in-water emulsion is poured from the upper part of the foam copper filter substrate, the oil-in-water emulsion is quickly demulsified when passing through the super-hydrophilic and oleophobic composite surface of the foam copper column, and the demulsified oil-in-water emulsion flows out of the foam copper column to form a filtrate of immiscible oil-water mixture, the foam copper does not need to be cleaned during the continuous and steady demulsification process, the oil content in the obtained filtrate is equivalent to that in the feed emulsion, and the filtration flux reaches 5000-16000 L·m -2 ·h -1 .

[0027] Compared with the prior art, the application has the following characteristics and advantages:

[0028] 1) the super-hydrophilic and oleophobic composite surface of the foam copper for treating oil-in-water emulsion is prepared by simultaneously depositing amino-functionalized carbon nanotubes and fluorinated carbon nanotubes on the surface of the foam copper, and the obtained foam copper greatly reduces the surface energy without affecting the water permeability;

[0029] 2) The present application utilizes the advantage of large pore size of foam copper to obtain high demulsification flux, and super-hydrophilic-oil-repellent composite surfaces of foam copper are stacked in the vertical direction to extend the penetration channel on the basis of super-wetting demulsification mechanism to improve the demulsification performance, thereby overcoming the trade-off effect between efficiency and flux in the process of demulsification of oil-in-water emulsion, and realizing high flux and high efficiency demulsification process;

[0030] 3) The super-hydrophilic-oil-repellent composite surface in the present application provides stable oil pollution resistance, greatly improves the demulsification durability of the material, and enables the foam copper to maintain high flux and high efficiency for a long time during the demulsification process;

[0031] 4) The super-hydrophilic-oil-repellent composite surface foam copper has good oil pollution release capacity, and can gradually release free oil after demulsification after the demulsification process is stable, and the release amount is equivalent to the oil content in the emulsion, which can maintain the dynamic balance of oil accumulation in the material, keep the demulsification performance of the foam copper stable, and realize continuous demulsification process without cleaning. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The present application is a schematic diagram of the preparation process of the super-hydrophilic-oil-repellent composite surface foam copper in the present application;

[0033] Figure 2 The present application is a scanning electron microscope (SEM) image of the foam copper with a pore size of 100-200 mu m only cleaned in Example 1 of the present application;

[0034] Figure 3 The present application is a scanning electron microscope (SEM) image of the foam copper with a pore size of 100-200 mu m only cleaned in Example 1 of the present application;

[0035] Figure 4 The present application is a scanning electron microscope (SEM) image of the super-hydrophilic-oil-repellent composite surface foam copper prepared in Example 1 of the present application;

[0036] Figure 5 The present application is a scanning electron microscope (SEM) image of the super-hydrophilic-oil-repellent composite surface foam copper prepared in Example 1 of the present application;

[0037] Figure 6 The present application is a scanning electron microscope (SEM) image of the super-hydrophilic-oil-repellent composite surface foam copper prepared in Example 1 of the present application;

[0038] Figure 7 The present application is a scanning electron microscope (SEM) image of the super-hydrophilic-oil-repellent composite surface foam copper prepared in Example 1 of the present application;

[0039] Figure 8The photo of the contact angle of 1,2-dichloroethane on the super-hydrophilic-oleophobic composite surface of the foamed copper prepared in Example 1 of the present application in water;

[0040] Figure 9 The photo of the penetration process of the super-hydrophilic-oleophobic composite surface of the foamed copper prepared in Example 1 of the present application in air for deionized water;

[0041] Figure 10 The schematic diagram of the demulsification device of the super-hydrophilic-oleophobic composite surface of the foamed copper prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0042] In order to better understand the present application, the present application is further described below in combination with examples and drawings, but the scope of the present application claimed is not limited to the scope represented by the examples.

[0043] The super-hydrophilic-oleophobic composite surface of the foamed copper is prepared by the following steps:

[0044] 1) The initial foamed copper is cleaned and then immersed in an oxidizing solution containing sodium hydroxide and ammonium persulfate for chemical oxidation, so that copper hydroxide nanoneedles are grown on the surface, and then the foamed copper is washed with deionized water and dried;

[0045] 2) The foamed copper with the copper hydroxide nanoneedles is immersed in a hydroxyethyl cellulose aqueous solution, and then after being taken out, the excess hydroxyethyl cellulose is washed away with deionized water and dried;

[0046] 3) The amino-functionalized carbon nanotubes and fluorinated carbon nanotubes are mixed and then configured into a uniform suspension solution with ethanol, and then the foamed copper obtained in step 2) is immersed in the suspension solution, and then after being taken out and dried, the super-hydrophilic-oleophobic composite surface of the foamed copper is obtained.

[0047] Figure 1 The preparation process of the super-hydrophilic-oleophobic composite surface of the foamed copper is shown. The reaction mechanism of the chemical oxidation is that the copper atoms are oxidized by ammonium persulfate to form copper ions, which combine with hydroxyl ions to form needle-shaped copper hydroxide precipitates, and the specific reaction equation is as follows:

[0048]

[0049] The carbon nanotube deposition onto the foam copper has the following features: the hydroxyethyl cellulose used for surface modification is a finished product prepared by alkali cellulose liquid phase method, and has a viscosity of 100-5000 mPa·s. After contacting with water, a large number of hydroxyl groups can be combined with water molecules stably to exhibit strong water retention. After the foam copper is soaked in the hydroxyethyl cellulose solution, the hydroxyethyl cellulose is crosslinked on the surface of the foam copper to form a network structure, and a large number of hydroxyl groups are provided. The amino-functionalized carbon nanotube used for deposition is a finished product prepared by a gas phase chemical deposition method, and has an amino content of about 0.45 wt%. In the fluorination modification process, the amino groups on the surface of the carbon nanotube are subjected to amidation reaction with the acyl halide groups of perfluorooctanoyl chloride to form amide groups, so that the fluorinated chain segment is stably grafted on the carbon nanotube to prepare fluorinated carbon nanotube. The oxidized foam copper is soaked in the carbon nanotube mixed dispersion liquid, the needle-shaped surface of the foam copper provides a point of attachment for the winding and locking of the clustered carbon nanotubes, and the amino groups on the amino-functionalized carbon nanotube and the amide groups on the fluorinated carbon nanotube form stable hydrogen bonds with the hydroxyl groups of the hydroxyethyl cellulose on the surface of the foam copper, further improving the firmness of the attachment.

[0050] The demulsification process of the foam copper with super-hydrophilic and oleophobic composite surface on the treatment of oil-in-water emulsion: when the oil-in-water emulsion contacts the foam copper, due to the super-hydrophilic property of the surface of the foam copper, the water phase rapidly penetrates into the penetration channel and passes through the entire foam copper filter core into the filtrate, and the good water permeability and the large pore size of the foam copper provide a high flux; the emulsified oil droplets are limited by the oleophobic property of the material and move downward in the penetration channel, and at the same time, the oil droplets are squeezed, collided, coalesced and completed the demulsification process, and due to the stable and long-acting oleophobic property of the material surface, the demulsified oil droplets further grow into free oil phase and are finally released into the filtrate from the penetration channel. When the released oil phase and the emulsified oil entering the penetration channel reach equilibrium, the oil accumulation in the material reaches a stable state, and the demulsification performance also tends to be stable; the surfactant falls off from the surface of the oil droplets, part of which is adsorbed by the van der Waals force of the foam copper surface, and part of which forms micelles and separates from the inside of the material.

[0051] The continuous demulsification mechanism of the super-hydrophilic-oleophobic composite surface of the foamed copper when treating oil-in-water emulsion is as follows: first, due to the super-hydrophilic property of the surface of the foamed copper, the water phase quickly penetrates through the foamed copper after contacting the foamed copper, and the large pores of the foamed copper and the super-hydrophilic surface jointly ensure low penetration resistance and high demulsification flux. At the same time, since the pore size of the foamed copper is larger than the particle size of most emulsified oil droplets, the emulsified oil droplets enter the penetration channel of the foamed copper together with the water phase. Due to the stable oleophobic property of the fluorocarbon nanotube micro area on the surface of the foamed copper, the emulsified oil droplets are continuously blocked, collided and repelled by the surface of the foamed copper in the tortuous penetration channel, which greatly reduces the passing speed, and a large number of emulsified oil droplets are gathered in the penetration channel, and the mutual collision and extrusion between the oil droplets gradually causes the emulsified oil droplets to coalesce, grow and demulsify into free oil. The stacked foamed copper greatly prolongs the length of the penetration channel to ensure that most of the emulsified oil droplets can complete the above demulsification process in the penetration channel, thereby completing the high-efficiency demulsification process.

[0052] Since the composite surface foamed copper has extremely low oil adhesion, the free oil after demulsification can be easily released from the penetration channel of the foamed copper into the filtrate with the flow, and forms an immiscible oil-water mixture with the water phase. After the demulsification process reaches a steady state, the amount of free oil released from the penetration channel is consistent with the amount of emulsified oil entering the penetration channel, and the amount of oil accumulated in the foamed copper can maintain a dynamic balance, thereby maintaining the stability of the material demulsification performance. For oil-in-water emulsion containing surfactant, the surfactant detached from the surface of the oil droplets during the demulsification process first adsorbs on the super-hydrophilic surface of the foamed copper, and when the critical micelle concentration is reached, free micelles are formed and enter the filtrate with the water flow. Due to the presence of the fluorocarbon nanotube oleophobic micro area, the foamed copper surface can still maintain good oil adhesion resistance and oil stain release performance after adsorbing the surfactant.

[0053] Example 1

[0054] The foamed copper with a pore size of 100-200 μm (size 1.6 cm x 1.6 cm x 2 mm) was sequentially cleaned with acetone, anhydrous ethanol and deionized water for 10 minutes each time; 50 ml of 5 mol / L sodium hydroxide solution and 50 ml of 0.2 mol / L ammonium persulfate solution were mixed uniformly, and the cleaned foamed copper was immersed in the mixed solution for 10 minutes, and the foamed copper was turned over every 30 seconds during the reaction; after the reaction was completed, the foamed copper was rinsed with deionized water and dried to obtain foamed copper with copper hydroxide nanoneedles. Figure 2 The scanning electron microscope (SEM) image of the foamed copper with a pore size of 100-200 μm only cleaned for this example is shown. Figure 2 The clear and smooth skeleton morphology of the unmodified foamed copper is shown, Figure 2 The interpolated image in the upper left corner shows that the foamed copper is composed of interconnected polygonal cage holes, with a pore size of about 100-300 microns.Figure 3 Scanning electron microscope (SEM) image of the copper foam with copper hydroxide nanoneedles prepared in Example 1. The nanoneedles uniformly cover the surface of the copper foam skeleton, with a length of about 5-10 microns, which provides an ideal roughness, helping the entanglement and fixation of carbon nanotubes, and at the same time enhances the superhydrophilic property of the material surface.

[0055] The copper foam is then soaked in 100 mL of a 1 g / L hydroxyethyl cellulose solution for 4 hours, and after being taken out, it is rinsed with deionized water and dried to obtain the hydroxyethyl cellulose modified copper foam.

[0056] The aminated carbon nanotubes are purchased from Xianfeng Nanometer Material Technology Co., Ltd., with a length of 50 μm, a diameter of 8-15 nm, a purity of > 97.0 wt%, an amino content of > 0.45 wt%, and a type of multi-walled carbon nanotubes.

[0057] Preparation of fluorinated carbon nanotubes:

[0058] The purchased aminated carbon nanotubes are dispersed in n-hexane to form a dispersion liquid of 1 g / L, and magnetic stirring is performed at a speed of 500 rpm; perfluorooctanoyl chloride is added dropwise to the obtained aminated carbon nanotube dispersion liquid, and after the dropwise addition is completed, the concentration of perfluorooctanoyl chloride in the dispersion liquid is 1 g / L, and stirring is continued for 5 minutes; the obtained solution is filtered, and the obtained solid is dried at a temperature of 60°C for 1 hour; the dried solid is ground to obtain fluorinated carbon nanotubes.

[0059] 0.4 g of aminated carbon nanotubes and 0.6 g of fluorinated carbon nanotubes are mixed and dispersed in 100 mL of ethanol to form a uniform carbon nanotube dispersion liquid, and the hydroxyethyl cellulose modified copper foam is soaked in the carbon nanotube dispersion liquid for 30 minutes, and after being taken out, it is dried at a temperature of 60°C for 1 hour to obtain a copper foam with a superhydrophilic-oleophobic composite surface.

[0060] Figure 4 Scanning electron microscope (SEM) image of the copper foam with a superhydrophilic-oleophobic composite surface prepared in Example 1. Figure 4 It can be seen that the skeleton of the composite surface copper foam prepared in Example 1 is completely covered by carbon nanotube clusters, with a cluster diameter of 0.1-1 microns, in which the aminated carbon nanotube clusters constitute the superhydrophilic region of the surface, and the fluorinated carbon nanotube clusters constitute the oleophobic microregion of the surface, and the two types of carbon nanotubes together constitute the composite surface of the copper foam.

[0061] Figure 5 The attenuated total reflection-Fourier transform infrared spectrum (ATR-FTIR) of the copper foam with a superhydrophilic-oleophobic composite surface prepared in Example 1 is shown in the following figure, and in the analysis, the peaks at 1240 cm -1 and 3449 cm -1The peaks at 1 1 1 1 and 1 1 1 2 cm"1 respectively show the stretching vibration of C-F and -NH2, indicating the existence of fluorinated carbon nanotubes and aminated carbon nanotubes.

[0062] Figure 6 The XPS surface element analysis chart of the super-hydrophilic-oleophobic composite surface foamed copper prepared in this example 1, which contains C, N, O, F, Cu five main elements, F and N elements mainly come from fluorinated carbon nanotubes and aminated carbon nanotubes.

[0063] Figure 7 and Figure 8 The contact angle photos of 1,2-dichloroethane on the super-hydrophilic-oleophobic composite surface foamed copper prepared in this example 1 in air and in water, respectively, from the figure, it can be seen that the contact angle of 1,2-dichloroethane on the super-hydrophilic-oleophobic composite surface foamed copper in air is 119°, and the contact angle of 1,2-dichloroethane on the super-hydrophilic-oleophobic composite surface foamed copper under water is 153°, indicating that the super-hydrophilic-oleophobic composite surface foamed copper has the characteristics of oleophobic in air and super-oleophobic under water.

[0064] Figure 9 The photo of the penetration process of deionized water on the super-hydrophilic-oleophobic composite surface foamed copper prepared in this example 1 in air, from the figure, it can be seen that within 1 1.64 seconds after the water droplet contacts the surface, the water droplet gradually spreads and penetrates into the material, indicating that the super-hydrophilic-oleophobic composite surface foamed copper has the characteristics of super-hydrophilic in air.

[0065] Oil-in-water emulsion demulsification test. The prepared foamed copper is cut into a circular piece with a diameter of 1.5 cm, and then 40 pieces are stacked in the vertical direction to obtain a super-hydrophilic-oleophobic composite surface foamed copper filter core. The super-hydrophilic-oleophobic composite surface foamed copper filter core is loaded in the upper glass tube (inner diameter of 1.5 cm) of the glass filtration device, and the circular piece of foamed copper can be tightly inserted in the glass tube, clamped and sealed, the lower end of the clamp is a beaker containing filtrate, and the upper part is a separatory funnel for containing emulsion, and the whole device is vertically placed, as shown in Figure 10 The volume ratio of water to toluene emulsion is 1:50, and 0.3 g / L of sodium dodecyl sulfate is added as a surfactant.

[0066] Example 2

[0067] The foam copper with pore size of 100-200 μm (size 1.6 cm x 1.6 cm x 2 mm) is cleaned with acetone, anhydrous ethanol and deionized water in sequence for 10 minutes respectively by ultrasonic cleaning; 50 ml of 5 mol / L sodium hydroxide solution is mixed with 50 ml of 0.2 mol / L ammonium persulfate solution uniformly, and the cleaned foam copper is immersed in the mixed solution for reaction for 10 minutes, and the foam copper is turned over every 30 seconds during the reaction; after the reaction, the foam copper is rinsed with deionized water and dried to obtain the foam copper with copper hydroxide nanoneedles

[0068] Then the foam copper is immersed in 100 ml of 1 g / L hydroxyethyl cellulose solution for reaction for 4 hours, and after being taken out, it is rinsed with deionized water and dried to obtain the foam copper modified by hydroxyethyl cellulose.

[0069] The aminated carbon nanotube is purchased from Xianfeng Nanometer Material Technology Co., Ltd., with the number XFM62 (similar related models can also be used, which has little effect on the final performance, and the model is used in the example based on cost and convenience consideration, and the same model is selected in the following examples), the length is 50 μm, the diameter is 8-15 nm, the purity is > 97.0 wt%, the amino content is > 0.45 wt%, and the type is multi-walled carbon nanotube.

[0070] Preparation of fluorinated carbon nanotube:

[0071] The purchased aminated carbon nanotube is dispersed in n-hexane to form a dispersion liquid of 2 g / L, and magnetic stirring is carried out at a speed of 800 rpm; perfluorooctanoyl chloride is added dropwise to the obtained aminated carbon nanotube dispersion liquid, and after the dropwise addition is completed, the concentration of perfluorooctanoyl chloride in the dispersion liquid is 2 g / L, and the stirring is continued for 10 minutes; the obtained solution is filtered, and the obtained solid is dried at a temperature of 60°C for 2 hours; the dried solid is ground to obtain fluorinated carbon nanotube.

[0072] 0.4 g of aminated carbon nanotube is mixed with 0.6 g of fluorinated carbon nanotube, and dispersed in 100 ml of ethanol to form a uniform carbon nanotube dispersion liquid, and the foam copper modified by hydroxyethyl cellulose is immersed in the carbon nanotube dispersion liquid for reaction for 30 minutes, and after being taken out, it is dried at a temperature of 60°C for 1 hour to obtain the foam copper with super-hydrophilic-oil-repellent composite surface.

[0073] Oil-in-water emulsion demulsification test. The prepared foam copper was cut into a circular piece with a diameter of 1.5 cm, and then 10 pieces were stacked in the vertical direction to obtain a foam copper filter core with a super-hydrophilic-oil-repellent composite surface. The foam copper filter core with a super-hydrophilic-oil-repellent composite surface was loaded into the upper glass tube (with an inner diameter of 1.5 cm) of a glass filtration device. The circular piece of foam copper could be tightly inserted into the glass tube, and was tightly sealed by clamps. The lower end of the clamps was a beaker containing filtrate, and the upper end was a separatory funnel containing emulsion. The entire device was placed vertically. The demulsification test was performed using a water-in-1,2-dichloroethane emulsion with a volume ratio of 1:200. No additional surfactant was added to the emulsion.

[0074] Example 3

[0075] The foam copper with a pore size of 100-200 μm (size 1.6 cm x 1.6 cm x 2 mm) was sequentially ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 10 minutes each. 50 ml of a 5 mol / L sodium hydroxide solution was mixed with 50 mL of a 0.2 mol / L ammonium persulfate solution, and the cleaned foam copper was immersed in the mixed solution for 10 minutes, with the foam copper being turned over every 30 seconds during the reaction. After the reaction, the foam copper was rinsed with deionized water and air-dried to obtain foam copper with copper hydroxide nanoneedles.

[0076] The foam copper was then immersed in 100 mL of a 1 g / L hydroxyethyl cellulose solution for 4 hours, and was then removed, rinsed with deionized water, and air-dried to obtain foam copper modified with hydroxyethyl cellulose.

[0077] The amino-functionalized carbon nanotubes were purchased from Xianfeng Nanometer Material Technology Co., Ltd. with the product number XFM62, a length of 50 μm, a diameter of 8-15 nm, a purity of >97.0 wt%, an amino content of >0.45 wt%, and a type of multi-walled carbon nanotubes.

[0078] Preparation of fluorinated carbon nanotubes:

[0079] The purchased amino-functionalized carbon nanotubes were dispersed in n-hexane to form a dispersion liquid with a concentration of 3 g / L, and were subjected to magnetic stirring at a speed of 1000 rpm. Perfluorooctanoyl chloride was added dropwise to the obtained dispersion liquid of amino-functionalized carbon nanotubes, and the concentration of perfluorooctanoyl chloride in the dispersion liquid was 3 g / L after the addition was completed. The stirring was continued for 20 minutes. The obtained solution was filtered, and the obtained solid was dried at a temperature of 70 °C for 3 hours. The dried solid was ground to obtain fluorinated carbon nanotubes.

[0080] 0.4 g of amino-functionalized carbon nanotubes and 0.6 g of fluorinated carbon nanotubes were mixed and dispersed in 100 mL of ethanol to form a uniform carbon nanotube dispersion liquid. The foam copper modified with hydroxyethyl cellulose was immersed in the carbon nanotube dispersion liquid for 30 minutes, and was then removed and dried at a temperature of 60 °C for 1 hour to obtain foam copper with a super-hydrophilic-oil-repellent composite surface.

[0081] Oil-in-water emulsion demulsification test. The prepared foam copper was cut into a circular piece with a diameter of 1.5 cm, and then 100 pieces were stacked in the vertical direction to obtain a foam copper filter core with a super-hydrophilic-oil-repellent composite surface. The foam copper filter core with a super-hydrophilic-oil-repellent composite surface was loaded into the upper glass tube (with an inner diameter of 1.5 cm) of a glass filtration device, and the circular piece of foam copper could be tightly inserted into the glass tube, tightly sealed by clamps, and the lower end of the clamp was a beaker containing filtrate, and the upper part was a separatory funnel for containing emulsion. The entire device was placed vertically. A volume ratio of 1:50 water-in-peanut oil emulsion was used for demulsification test, and 0.3 g / L sodium dodecyl sulfate was added as a surfactant.

[0082] Example 4

[0083] The foam copper with a pore size of 100-200 μm (size 1.6 cm x 1.6 cm x 2 mm) was sequentially ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 minutes; 50 ml of 5 mol / L sodium hydroxide solution was mixed uniformly with 50 ml of 0.2 mol / L ammonium persulfate solution, and the cleaned foam copper was immersed in the mixed solution for 10 minutes, and the foam copper was turned over every 30 seconds during the reaction; after the reaction was completed, the foam copper was rinsed with deionized water and dried to obtain foam copper with copper hydroxide nanoneedles

[0084] Then the foam copper was immersed in 100 mL of 1 g / L hydroxyethyl cellulose solution for 4 hours, and after being taken out, it was rinsed with deionized water and dried to obtain foam copper modified with hydroxyethyl cellulose.

[0085] Aminated carbon nanotubes were purchased from Xianfeng Nanometer Material Technology Co., Ltd., with a length of 50 μm, a diameter of 8-15 nm, a purity of > 97.0 wt%, an amino content of > 0.45 wt%, and a type of multi-walled carbon nanotubes.

[0086] Preparation of fluorinated carbon nanotubes:

[0087] The purchased aminated carbon nanotubes were dispersed in n-hexane to form a dispersion liquid of 4 g / L, and magnetic stirring was carried out at a speed of 1000 rpm; perfluorooctanoyl chloride was added dropwise to the obtained aminated carbon nanotube dispersion liquid, and after the addition was completed, the concentration of perfluorooctanoyl chloride in the dispersion liquid was 4 g / L, and the stirring was continued for 30 minutes; the obtained solution was filtered, and the obtained solid was dried at a temperature of 80°C for 4 hours; the dried solid was ground to obtain fluorinated carbon nanotubes.

[0088] Take 0.2 g of amino carbon nanotubes and 0.8 g of fluorinated carbon nanotubes, mix them in 100 mL of ethanol to form a uniform carbon nanotube dispersion, soak the hydroxyethyl cellulose modified foam copper in the carbon nanotube dispersion, react for 30 minutes, take it out and dry at a temperature of 60°C for 1 hour, to obtain foam copper with super-hydrophilic and oleophobic composite surface.

[0089] Oil-in-water emulsion demulsification test. The prepared foam copper is cut into a circular piece with a diameter of 1.5 cm, then 40 pieces are stacked vertically to obtain a foam copper filter core with super-hydrophilic and oleophobic composite surface. The foam copper filter core with super-hydrophilic and oleophobic composite surface is loaded into the upper glass tube (inner diameter of 1.5 cm) of a glass filtration device, the circular foam copper can be tightly inserted into the glass tube, clamped and sealed, the lower end of the clamp is a beaker containing filtrate, and the upper part is a separatory funnel for containing emulsion, and the whole device is vertically placed, as shown in Figure 10 The oil-in-water emulsion demulsification test is carried out with a volume ratio of 1:50 of water to diiodomethane emulsion, and 0.3 g / L of sodium dodecyl sulfate is added as a surfactant.

[0090] Example 5

[0091] The foam copper with a pore size of 100-200 μm (size 1.6 cm x 1.6 cm x 2 mm) is ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in turn for 10 minutes; 50 ml of 5 mol / L sodium hydroxide solution is mixed uniformly with 50 mL of 0.2 mol / L ammonium persulfate solution, and the cleaned foam copper is immersed in the mixed solution for 10 minutes, and the foam copper is turned over every 30 seconds during the reaction; after the reaction, the foam copper is rinsed with deionized water and dried to obtain foam copper with copper hydroxide nanoneedles

[0092] Then the foam copper is soaked in 100 mL of 1 g / L hydroxyethyl cellulose solution for 4 hours, taken out and rinsed with deionized water, and dried to obtain hydroxyethyl cellulose modified foam copper.

[0093] Amino carbon nanotubes are purchased from Xianfeng Nanometer Material Technology Co., Ltd., with the number XFM62, a length of 50 μm, a diameter of 8-15 nm, a purity of > 97.0 wt%, an amino content of > 0.45 wt%, and a type of multi-walled carbon nanotubes.

[0094] Preparation of fluorinated carbon nanotubes:

[0095] The purchased aminated carbon nanotubes were dispersed in n-hexane to form a dispersion liquid of 5 g / L, and magnetic stirring was carried out at a speed of 1000 rpm; full-fluorooctyl chloride was added dropwise to the obtained aminated carbon nanotube dispersion liquid, and after the dropwise addition was completed, the concentration of full-fluorooctyl chloride in the dispersion liquid was 5 g / L, and stirring was continued for 30 minutes; the obtained solution was filtered, and the obtained solid was dried at a temperature of 80°C for 5 hours; the dried solid was ground to obtain fluorinated carbon nanotubes.

[0096] 0.8 g of aminated carbon nanotubes and 0.2 g of fluorinated carbon nanotubes were mixed and dispersed in 100 mL of ethanol to form a uniform carbon nanotube dispersion liquid, and the hydroxyethyl cellulose modified foam copper was soaked in the carbon nanotube dispersion liquid, reacted for 30 minutes, and then taken out and dried at a temperature of 60°C for 1 hour to obtain foam copper with a super-hydrophilic-oil-repellent composite surface.

[0097] Oil-in-water emulsion demulsification test. The prepared foam copper was cut into a circular piece with a diameter of 1.5 cm, and then 40 pieces were stacked in the vertical direction to obtain a foam copper filter core with a super-hydrophilic-oil-repellent composite surface. The foam copper filter core with a super-hydrophilic-oil-repellent composite surface was loaded into the upper glass tube (with an inner diameter of 1.5 cm) of a glass filtration device, and the circular piece-shaped foam copper could be tightly inserted into the glass tube. The glass tube was tightly sealed by clamps, and the lower end of the clamp was a beaker containing filtrate, and the upper end was a separatory funnel containing emulsion. The entire device was placed vertically, as shown in Figure 10 The oil-in-water emulsion demulsification test was carried out using water-in-olive oil emulsion with a volume ratio of 1:50, and 0.3 g / L of sodium dodecyl sulfate was added as a surfactant.

[0098] Comparative Example 1

[0099] The foam copper with a pore size of 100-200 μm (size 1.6 cm x 1.6 cm x 2 mm) was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in sequence for 10 minutes; 50 ml of 5 mol / L sodium hydroxide solution was mixed uniformly with 50 mL of 0.2 mol / L ammonium persulfate solution, and the cleaned foam copper was immersed in the mixed solution for 10 minutes, and the foam copper was turned over every 30 seconds during the reaction; after the reaction was completed, the foam copper was rinsed with deionized water and air-dried to obtain foam copper with copper hydroxide nanoneedles

[0100] Then the foam copper was soaked in 100 mL of 1 g / L hydroxyethyl cellulose solution for 4 hours, and then taken out and rinsed with deionized water and air-dried to obtain hydroxyethyl cellulose modified foam copper.

[0101] The aminated carbon nanotubes were purchased from Xianfeng Nanometer Material Technology Co., Ltd., with a code of XFM62, a length of 50 μm, a diameter of 8-15 nm, a purity of >97.0 wt%, an amino content of >0.45 wt%, and a type of multi-walled carbon nanotubes.

[0102] Preparation of fluorinated carbon nanotubes:

[0103] The purchased aminated carbon nanotubes were dispersed in n-hexane to form a dispersion of 1 g / L, and magnetic stirring was carried out at a speed of 500 rpm; to the obtained aminated carbon nanotube dispersion, perfluorooctanoyl chloride was added dropwise, and after the dropwise addition was completed, the concentration of perfluorooctanoyl chloride in the dispersion was 1 g / L, and stirring was continued for 5 minutes; the obtained solution was filtered, and the obtained solid was dried at a temperature of 60°C for 1 hour; the dried solid was ground to obtain fluorinated carbon nanotubes.

[0104] 1 g of aminated carbon nanotubes were taken and dispersed in 100 mL of ethanol to form a uniform carbon nanotube dispersion, and the hydroxyethyl cellulose modified foam copper was soaked in the carbon nanotube dispersion and reacted for 30 minutes. After taking out, it was dried at a temperature of 60°C for 1 hour to obtain foam copper with a strong charged super-hydrophilic and underwater super-oleophobic uniform surface.

[0105] Oil-in-water emulsion demulsification test. The prepared foam copper was cut into a circular piece with a diameter of 1.5 cm, and then 40 pieces were stacked in the vertical direction to obtain a foam copper filter core with a super-hydrophilic and oleophobic composite surface. The foam copper filter core with a super-hydrophilic and oleophobic composite surface was loaded into the upper glass tube (inner diameter of 1.5 cm) of a glass filtration device, and the circular piece of foam copper could be tightly inserted into the glass tube. The clamp was tightly sealed, and the lower end of the clamp was a beaker containing filtrate, and the upper end was a separatory funnel for containing emulsion. The entire device was placed vertically, as shown in Figure 10 The oil-in-toluene emulsion with a volume ratio of 1:50 was used for demulsification test, and 0.3 g / L of sodium dodecyl sulfate was added as a surfactant.

[0106] Comparative Example 2

[0107] The foam copper with a pore size of 100-200 μm (size 1.6 cm x 1.6 cm x 2 mm) was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in turn for 10 minutes; 50 ml of 5 mol / L sodium hydroxide solution was mixed uniformly with 50 mL of 0.2 mol / L ammonium persulfate solution, and the cleaned foam copper was immersed in the mixed solution and reacted for 10 minutes, and the foam copper was turned over every 30 seconds during the reaction; after the reaction was completed, the foam copper was rinsed with deionized water and air dried to obtain foam copper with copper hydroxide nanoneedles

[0108] Then the foam copper was soaked in 100 mL of 1 g / L hydroxyethyl cellulose solution for 4 hours, and after taking out, it was rinsed with deionized water and air dried to obtain hydroxyethyl cellulose modified foam copper.

[0109] Aminated carbon nanotubes were purchased from XFNANO Technology Co. Ltd. with the number XFM62, length of 50 μm, diameter of 8-15 nm, purity of >97.0 wt%, amino content of >0.45 wt%, and type of multi-walled carbon nanotubes.

[0110] Preparation of fluorinated carbon nanotubes:

[0111] The purchased aminated carbon nanotubes were dispersed in n-hexane to form a dispersion of 1 g / L, and magnetic stirring was carried out at a speed of 500 rpm; perfluorooctanoyl chloride was added dropwise to the obtained aminated carbon nanotube dispersion, and after the dropwise addition was completed, the concentration of perfluorooctanoyl chloride in the dispersion was 1 g / L, and stirring was continued for 5 minutes; the obtained solution was filtered, and the obtained solid was dried at a temperature of 60°C for 1 hour; the dried solid was ground to obtain fluorinated carbon nanotubes.

[0112] 1 g of fluorinated carbon nanotubes was taken and dispersed in 100 mL of ethanol to form a uniform carbon nanotube dispersion, and the hydroxyethyl cellulose modified foam copper was soaked in the carbon nanotube dispersion for 30 minutes, and then taken out and dried at a temperature of 60°C for 1 hour to obtain foam copper with a super-hydrophilic-oil-repellent uniform surface.

[0113] Oil-in-water emulsion demulsification test. The prepared foam copper was cut into a circular piece with a diameter of 1.5 cm, and then 40 pieces were stacked in a vertical direction to obtain a foam copper filter core with a super-hydrophilic-oil-repellent composite surface. The foam copper filter core with a super-hydrophilic-oil-repellent composite surface was loaded into the upper glass tube (with an inner diameter of 1.5 cm) of a glass filtration device, and the circular piece-shaped foam copper could be tightly inserted into the glass tube, and was tightly sealed by clamps. The lower end of the clamp was a beaker containing filtrate, and the upper end was a separatory funnel for containing emulsion. The entire device was placed vertically, as shown in Figure 10 The oil-in-water emulsion demulsification test was carried out using a water-in-toluene emulsion with a volume ratio of 1:50, and 0.3 g / L of sodium dodecyl sulfate was added as a surfactant.

[0114] Contact angle test

[0115] The contact angle of the super-hydrophilic-oil-repellent composite surface foam copper prepared in Examples 1-5, and the aminated carbon nanotube covered foam copper and fluorinated carbon nanotube covered foam copper prepared in Comparative Examples 1 and 2 was measured at room temperature using a JC2000C1 contact angle measuring instrument from Shanghai Zhongchen Digital Technology Equipment Co., Ltd. The contact angle of oil in air (1,2-dichloroethane), the contact angle of oil under water (1,2-dichloroethane), the initial contact angle of water in air, the final contact angle, and the water wetting time were measured, and the specific results are shown in Table 1.

[0116] Table 1

[0117]

[0118] From Table 1, it can be seen that the air oil contact angle of the super-hydrophilic-oil-repellent composite surface foam copper prepared by the present application for separating emulsified water-in-oil is between 95-125°, and the underwater oil contact angle is between 146-154°, which fully proves that the super-hydrophilic-oil-repellent composite surface foam copper has good oil-repellent performance in air and underwater. The initial water contact angle of the super-hydrophilic-oil-repellent composite surface foam copper in air is between 101-138°, and the water penetration time is between 0.86-56.50s, which shows that the introduction of the oil-repellent micro area of the composite surface prolongs the time of water first wetting the material to a certain extent, but ultimately does not affect the penetration of water to the material. The foam copper in Comparative Example 1 only deposits amino carbon nanotubes, lacks oil-repellent micro areas, and cannot provide oil-repellent performance in air. The foam copper in Comparative Example 2 only deposits fluorinated carbon nanotubes, and the uniform oil-repellent area greatly prolongs the water penetration time.

[0119] Surface oil repellency test

[0120] The surface energy, oil (diiodomethane) adhesion work and oil (diiodomethane) adhesion force of the super-hydrophilic-oil-repellent composite surface foam copper prepared in Examples 1-5 and the foam copper covered with amino carbon nanotubes and the foam copper covered with fluorinated carbon nanotubes prepared in Comparative Examples 1 and 2 were tested at room temperature by using a Germany Kruss K100 type contact angle measuring instrument, and the results are shown in Table 2.

[0121] Table 2

[0122]

[0123] From Table 2, it can be seen that the surface energy of the super-hydrophilic-oil-repellent composite surface foam copper prepared by the present application is between 12.92-20.19 mJ·m -2 , mainly with non-polar component surface energy, the adhesion work of diiodomethane on the surface is between 19.80-30.54 mJ·m -2 , and the adhesion force is between 7.8-26.1 μN, which shows that the adhesion between the super-hydrophilic-oil-repellent composite surface foam copper and the oil droplets is very weak, and has very strong oil pollution resistance. The super-hydrophilic uniform surface foam copper in Comparative Example 1 cannot be tested for effective surface energy, adhesion work and adhesion force because it cannot resist the penetration of oil droplets. In Comparative Example 2, even if the surface is uniformly covered with fluorinated carbon nanotubes, the surface energy, adhesion work and adhesion force are not significantly reduced compared with the composite surface.

[0124] Surfactant-stabilized water-in-oil emulsion demulsification test

[0125] When using the foam copper with super-hydrophilic-oleophobic composite surface to test the demulsification of oil-in-water emulsion, first, the foam copper is pre-wetted with deionized water, then the emulsion is added to the separatory funnel, and the emulsion is adjusted to enter the filter device and maintain a liquid column height of 1-2 cm above the foam copper. At this time, the water phase quickly passes through the foam copper, while the emulsified oil droplets in the water are repelled by the oleophobic surface in the penetration channel, and gradually complete demulsification through the processes of collision, extrusion and coalescence. The demulsified oil droplets continue to grow in the penetration channel and eventually become free oil phase. Benefiting from the low oil adhesion of the foam copper surface, the oil phase is finally discharged from the foam copper into the filtrate. 4000 mL of emulsion is continuously treated, and the penetration flux is measured every 500 mL. The water phase liquid in the beaker is tested for demulsification efficiency, and the oil phase liquid is measured for oil recovery. The demulsification efficiency is the ratio of the difference between the oil content in the emulsion before treatment and the oil content in the water phase after demulsification treatment to the oil content in the emulsion. The penetration flux is the volume of filtrate passing through per unit area per unit time. The specific results of separation efficiency, separation flux and oil recovery are shown in Table 3.

[0126] Table 3

[0127]

[0128]

[0129]

[0130] From Table 3, it can be seen that Example 1 can achieve relatively stable demulsification performance after treating 1500 mL of emulsion, and can stably provide a flux of 7734.09-8101.06 L·m -2 ·h -1 and a demulsification efficiency of 97.56%-98.19%. The oil recovery of each 500 mL emulsion treatment is very close to the oil content in the emulsion (10 mL / 500 mL). As can be seen from Examples 1-5, increasing the proportion of fluorinated carbon nanotubes from 20% to 80% can effectively improve the flux and demulsification efficiency after the demulsification stable state is stabilized.

[0131] Microscopically, this is mainly because the addition of oleophobic microzones on the super surface can prevent oil droplets from contacting the super-hydrophilic substrate. The more dense the oleophobic microzones, the less likely it is for oil droplets to bypass the oleophobic microzones to contact the super-hydrophilic substrate. During the high-flux demulsification process, the adhesion of oil droplets penetrating the hydration layer of the super-hydrophilic surface to the substrate is the main source of oil pollution. Therefore, the introduction of oleophobic microzones effectively reduces oil pollution, thereby achieving higher demulsification flux.

[0132] Macroscopically, the addition of the oleophobic fluorinated carbon nanotubes reduced the surface energy of the foam copper, and increased the energy barrier that the oil droplets needed to cross the superhydrophilic-oleophobic composite region to contact the superhydrophilic substrate, thus effectively reducing the possibility of oil droplets adhering to the material and the ground. However, when the ratio of fluorinated carbon nanotubes to aminated carbon nanotubes exceeded 60:40, further increasing the proportion of fluorinated carbon nanotubes did not significantly improve the effective flux. This was mainly because when the spacing of the oleophobic microzones was lower than the particle size of most oil droplets, most oil droplets could no longer contact the superhydrophilic region, and further increasing the density of the oleophobic microzones had little effect on reducing oil pollution. The introduction of the oleophobic microzones also strengthened the speed of free oil release from the foam copper, allowing the free oil phase to be smoothly released from the material and maintaining an oil content close to (with an error of less than 15%) that in the emulsion, which helped to maintain a dynamic balance of the accumulated oil in the foam copper and stable demulsification performance. In Examples 1-5, different water-in-oil emulsions with different proportions, different oil types, and whether or not a surfactant was added were tested, and although there were some performance differences, stable and long-term continuous demulsification was achieved.

[0133] As can be seen by comparing Comparative Example 1, a uniform strongly charged superhydrophilic surface is difficult to resist oil pollution for a long time, and the flux rapidly decreases to 100 L·m -2 ·h -1 during demulsification, and will even continue to decrease to complete blockage, with the demulsification efficiency decreasing to about 60%, and the oil accumulated in the material being difficult to remove. This is mainly because the charged surface quickly adsorbs the surfactant during demulsification, causing a change in surface wettability, and in this process, the lack of oleophobic microzones weakens the oil adhesion resistance performance.

[0134] As compared with Comparative Example 2, a uniform superhydrophilic-oleophobic surface also exhibits certain oil adhesion resistance and oil pollution release characteristics, but the flux and demulsification efficiency after stabilization are much lower than those of the foam copper with a composite surface. The accumulation of 40 pieces of foam copper with a uniform oleophobic surface in the filter core can only provide a flux of about 1000 L·m -2 ·h -1 and a demulsification efficiency of about 95% after performance stabilization, which is much lower than the worst demulsification performance of a filter core with 40 pieces of foam copper with a composite surface (a flux of about 2500 L·m -2 ·h -1 and a demulsification efficiency of 97% after stabilization), and even lower than the demulsification flux of about 1800 L·m -2 ·h -1 after stabilization of a filter core with 100 pieces of foam copper with a composite surface. This is mainly because the lack of hydrophilic regions greatly slows down the water permeability, and the hydration layer that can be provided is more unstable than that of the composite surface, so the relative pollution is more serious.

[0135] In the prior art CN116444853A, the sponge surface has strong surface charge, and no composite surface structure is constructed, which is similar to Comparative Examples 1 and 2, and therefore it is difficult to realize the continuous oil-in-water emulsion demulsification process.

[0136] The present application prepares super-hydrophilic-oleophobic composite surface foam copper by simultaneously depositing amino-carbon nanotubes and fluorinated carbon nanotubes on the foam copper surface with copper hydroxide nanoneedles, stacks multiple pieces of foam copper to obtain a super-hydrophilic-oleophobic composite surface foam copper filter element, which has good oil pollution resistance in the process of treating oil-in-water emulsion, can continuously process a large amount of oil-in-water emulsion under the premise of maintaining high flux demulsification, and can release free oil after demulsification from the foam copper to maintain the stability of the demulsification performance of the foam copper.

[0137] 10-100 pieces of super-hydrophilic-oleophobic composite surface foam copper are stacked into a column as a filter substrate, which is first wetted with water, and then the oil-in-water emulsion is poured from the upper part of the foam copper filter substrate, and the emulsion can complete rapid demulsification when passing through the super-hydrophilic-oleophobic composite surface foam copper column, and then flows out from the foam copper column to form a filter liquid of immiscible oil-water mixture, and the foam copper does not need to be cleaned in the continuous and stable demulsification process, the oil content in the obtained filter liquid is equivalent to that in the feed emulsion, and the filtration flux can reach 5000-16000 L·m -2 ·h -1 ; the oil-in-water emulsion includes oil-in-water emulsion without surfactant and surfactant-stabilized oil-in-water emulsion.

[0138] The protection scope of the present application is not limited by the above-mentioned embodiments, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A foam copper of super-hydrophilic-oleophobic composite surface, characterized in that Preparation method of the super-hydrophilic-oleophobic composite surface of foam copper, comprising the following steps: 1) washing the initial foam copper and then immersing it in an oxidizing solution containing sodium hydroxide and ammonium persulfate for chemical oxidation, growing copper hydroxide nanoneedles on the surface, rinsing with deionized water and drying; 2) immersing the foam copper with copper hydroxide nanoneedles obtained in the hydroxyethyl cellulose aqueous solution, washing off the excess hydroxyethyl cellulose with deionized water after taking out, and drying; The surface energy of the super-hydrophilic-oleophobic composite surface of the foamed copper is 10-30 mJ / m 2 The water contact angle in air is 0-5°, the oil contact angle in air is 95.2-131.0°, and the oil contact angle under water is 145.6-154.8°.

2. The method for preparing a foamed copper of the super-hydrophilic-oleophobic composite surface according to claim 1, characterized in that 3) mixing the aminated carbon nanotubes and fluorinated carbon nanotubes, preparing a uniform suspension solution with an organic solvent, immersing the foam copper obtained in step 2) in the suspension solution, and drying after taking out to obtain the foam copper with a super-hydrophilic-oleophobic composite surface. Preparation method of the super-hydrophilic-oleophobic composite surface of foam copper, comprising the following steps: 1) washing the initial foam copper and then immersing it in an oxidizing solution containing sodium hydroxide and ammonium persulfate for chemical oxidation, growing copper hydroxide nanoneedles on the surface, rinsing with deionized water and drying; 2) immersing the foam copper with copper hydroxide nanoneedles obtained in the hydroxyethyl cellulose aqueous solution, washing off the excess hydroxyethyl cellulose with deionized water after taking out, and drying; 3. The method of claim 2, wherein the method further comprises: 3) mixing the aminated carbon nanotubes and fluorinated carbon nanotubes, preparing a uniform suspension solution with an organic solvent, immersing the foam copper obtained in step 2) in the suspension solution, and drying after taking out to obtain the foam copper with a super-hydrophilic-oleophobic composite surface.

4. The method of claim 2, wherein the method of claim 2 is characterized in that: In step 1), the pore size of the initial foam copper is 50-400 μm, and the thickness is 0.5-10 mm; the washing is ultrasonic cleaning with acetone, anhydrous ethanol and deionized water for 5-20 min, respectively, and the foam copper is dried at a temperature of 10-30 °C for 1-5 hours after washing.

5. The method of claim 2, wherein the method further comprises: In step 1), the concentration of sodium hydroxide in the oxidizing solution containing sodium hydroxide and ammonium persulfate is 1-10 mol / L, and the concentration of ammonium persulfate is 0.05-0.5 mol / L; the immersion oxidation time is 5-15 minutes, and the foam copper is rinsed with deionized water after oxidation and dried at a temperature of 10-30 °C for 1-5 hours.

6. The method of claim 2, wherein the method of claim 2 is characterized by: In step 2), the concentration of the hydroxyethyl cellulose aqueous solution is 0.5-5 g / L, the immersion time is 0.5-5 hours, and the foam copper is dried at a temperature of 10-30 °C for 1-5 hours after immersion.

7. The method of claim 2, wherein the method further comprises: 5 applying a copper layer on the superhydrophilic layer; and applying a copper layer on the superoleophobic layer. The length of the aminated carbon nanotube is 10-100 μm, the diameter is 20-500 nm, the purity is > 95.0 wt%, and the amino content is > 0.3 wt%.

8. The method of claim 2, wherein the method of preparing the foam copper of the super-hydrophilic-oleophobic composite surface is characterized by: In step 3), the organic solvent is one or more of methanol, ethanol and acetone; the mass ratio of the aminated carbon nanotube to the fluorinated carbon nanotube is 20:80-80:20, and the total concentration of the prepared suspension solution is 0.5-5 g / L; the immersion time is 10-30 minutes, and the foam copper is dried at a temperature of 40-80 °C for 0.5-1 hour after immersion. The fluorinated carbon nanotube is prepared by the following steps: 1) dispersing the aminated carbon nanotube in an alkane solvent to form a dispersion liquid with a concentration of 0.5-5 g / L, and performing magnetic stirring at a speed of 200-1000 rpm; the alkane solvent is n-hexane or cyclohexane; 2) drop full-fluorine octyl chloride into the amino-carbon nanotube dispersion obtained in step 1), the concentration of full-fluorine octyl chloride in the dispersion is 1-10 g / L after the dropping is completed, and the stirring is continued for 5-30 minutes; 3) filter the liquid obtained in step 2), and dry the obtained solid at a temperature of 40-80 ℃ for 1-5 hours; 4) grind the dried solid to obtain fluorinated carbon nanotubes.

9. The use of the super-hydrophilic-oleophobic composite surface of claim 1 for continuously and stably breaking the emulsion of oil-in-water emulsion.

10. Use of the super-hydrophilic-oleophobic composite surface of claim 9 for continuous steady-state demulsification of oil-in-water emulsions by foamed copper, characterized in that: 10-100 pieces of super-hydrophilic-oleophobic composite surface of foamed copper are stacked into a column as a filter base material, first wetted with water, and then an oil-in-water emulsion is poured from the upper part of the foamed copper filter base material, the oil-in-water emulsion is quickly demulsified when passing through the super-hydrophilic-oleophobic composite surface of the foamed copper column, and after demulsification, the oil-in-water emulsion flows out of the foamed copper column to form a filtrate of immiscible oil-water mixture, and during the continuous and stable demulsification process, the foamed copper does not need to be cleaned, the oil content in the obtained filtrate is equivalent to that in the feed emulsion, and the filtration flux reaches 5000-16000 L·m -2 ·h -1 .

Images