CN107096393B - Thermally stable and super-hydrophobic ceramic-carbon nanotube composite membrane and membrane distilled water treatment application thereof - Google Patents

Thermally stable and super-hydrophobic ceramic-carbon nanotube composite membrane and membrane distilled water treatment application thereof Download PDF

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CN107096393B
CN107096393B CN201710217392.0A CN201710217392A CN107096393B CN 107096393 B CN107096393 B CN 107096393B CN 201710217392 A CN201710217392 A CN 201710217392A CN 107096393 B CN107096393 B CN 107096393B
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董应超
马丽宁
朱丽
司一然
杨凤林
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Dalian University of Technology
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Abstract

A thermal-stability and super-hydrophobic ceramic-carbon nanotube composite membrane and a membrane distilled water treatment application thereof belong to the technical field of inorganic membranes. The preparation of the composite membrane adopts a chemical vapor deposition method, takes the ceramic hollow fiber membrane as a carrier, and can obtain the ceramic-carbon nanotube hollow fiber composite membranes with different structures and performances by changing different preparation conditions such as catalyst loading capacity, reaction temperature and reaction time and controlling the structure, loading capacity and loading state of the carbon nanotube. The composite membrane with the structure of completely covering the carbon nano tube with thermal stability and super-hydrophobicity is obtained by regulating and optimizing the preparation conditions. The composite membrane can realize seawater desalination, zero discharge of high-salinity wastewater and high-efficiency treatment of other wastewater (such as electroplating heavy metal wastewater, printing and dyeing wastewater, antibiotic wastewater and the like) through membrane distillation, and has good membrane distillation performance.

Description

Thermally stable and super-hydrophobic ceramic-carbon nanotube composite membrane and membrane distilled water treatment application thereof
Technical Field
The invention relates to a thermally stable and super-hydrophobic ceramic-carbon nanotube composite membrane and a membrane distilled water treatment application thereof, belonging to the technical field of inorganic membranes.
Background
With the development of global economy and explosive growth of the population, the demand for water resources is increasing. The Chinese average fresh water amount is only 1/4 of the world and is listed in one of the 13 most water-poor countries of the world. The fresh water resource can only occupy seven ten-thousandth of the water resource of the earth ball,seawater accounts for 97.3 percent, so that seawater and brackish water desalination is an important choice for meeting the requirements of industrial and domestic water at present. The industrial high-salinity wastewater (wastewater with the total salt mass fraction of at least 1%) which is simultaneously derived from industrial processes such as chemical industry, metallurgy, electroplating, petroleum, natural gas and the like contains high-concentration inorganic salt (Cl)-、SO4 2-、Na+、Ca2+Etc.), if the wastewater is directly discharged, the ecological environment is endangered, water and salt resources are wasted, the concentration of the saline water in the conventional treatment method cannot be too high, and the zero discharge treatment technology of the high-salinity wastewater is urgently needed to be developed. Membrane-process seawater desalination is one of the main approaches for realizing the open source increment of fresh water resources. The existing membrane seawater desalination technologies mainly comprise Reverse Osmosis (RO), Electrodialysis (ED), Pervaporation (PV), multi-effect evaporation (MED), multi-stage flash evaporation (MFS), Mechanical Vapor Recompression (MVR) and the like. Although the reverse osmosis technology is the main seawater desalination technology (the concentration upper limit is 70-90 g/L) at present, the operation cost is low, the problems of operation pressure rise, membrane pollution and the like can be caused by salinity rise in the operation process, the produced concentrated water cannot reach the level of direct industrial utilization, and only can be directly discharged into the sea, otherwise, the environmental pollution can be caused, and the reverse osmosis technology is not suitable for desalination of high-salinity wastewater. Electrodialysis (ED) has insufficient desalination efficiency, and because seawater has high conductivity, current efficiency is low, and operating cost and energy consumption are high. In addition, electrodialysis easily causes electrochemical corrosion of electrolytic water and electrode plates, and the treatment of high-concentration salt-containing wastewater is difficult to achieve (the upper limit of concentration is 200 g/L). Pervaporation (PV) is a technology suitable for high-concentration seawater desalination, has an ideal treatment effect, is widely applied to middle east regions, but has higher operation temperature and larger energy consumption demand. Multi-effect evaporation (MED), multi-stage flash evaporation (MFS) and Mechanical Vapor Recompression (MVR) have the problems of high investment and operating costs and non-corrosion resistance of the device.
The Membrane Distillation (MD) is a membrane separation process combining membrane technology and distillation process, and takes a hydrophobic microporous membrane as a medium, and volatile components in feed liquid permeate through membrane pores in a vapor form under the action of vapor pressure difference on two sides of the membrane, so that the separation purpose is realized. Compared with other separation processes, the membrane distillation has the advantages of high separation efficiency, mild operation conditions, low requirements on the interaction between the membrane and raw material liquid and the mechanical properties of the membrane and the like. The membrane distillation technology is a membrane technology means which can realize seawater, high-concentration brine or sewage desalination by utilizing low-temperature waste heat or waste heat, and theoretically can achieve 100% recovery, thereby realizing zero emission of high-concentration brine. With the increasing attention paid to low-order waste heat, a solution is provided for the energy consumption problem of the membrane distillation technology, so that the membrane distillation has an increasingly wide application prospect in the fields of seawater desalination and high-salt water treatment. For membrane distillation, the nature of the separation membrane determines the effectiveness of desalination and high brine treatment as well as the equipment operating time and cost. Firstly, the distillation membrane needs to have good hydrophobicity (super-hydrophobicity is optimal), so that liquid can be prevented from entering a membrane pore channel, and a steam layer is formed on a solid-liquid interface; secondly, the distillation membrane needs to have high porosity and proper membrane aperture (100-300nm) to reduce membrane resistance so that water vapor can smoothly permeate the membrane body to enter the condensation side; finally, the distillation membrane also needs to have good physical and chemical stability, temperature resistance, wetting resistance and pollution resistance, and good desalination rate and membrane flux can be ensured in the processes of seawater desalination and high-salinity wastewater treatment. At present, distillation membranes in the market are mainly organic polymer membranes, such as polypropylene (PP), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE) and the like, and the membranes have the problems of insufficient thermal stability and chemical stability, membrane pollution and the like, so that the membrane structure and performance are attenuated to different degrees in long-term operation, and commercial organic polymer membranes are not designed according to membrane distillation operation conditions, and the membrane distillation performance of the commercial organic polymer membranes needs to be improved. Therefore, the development of a novel high-performance membrane material for seawater desalination and high-salinity wastewater membrane distillation is of great significance.
At present, because ceramic membranes have the advantages of good chemical stability, pollution resistance, high temperature resistance, high separation efficiency, easy regeneration, long service life and the like, researches on hydrophobic modification and membrane distillation application of ceramic membranes have been advanced to a certain extent, most of hydrophobic modification modes are grafted Fluorosilane (FAS), but the technical bottleneck of the application is the poor thermal stability of FAS, and FAS is generally connected with ceramic through covalent bondsThe bonding of the membrane surface leads FAS molecules to fall off due to bond breakage in the long-term membrane distillation process, so that the hydrophobicity of the ceramic membrane is reduced, and the problem of membrane infiltration is caused. The international authoritative Journal AIChE Journal in the chemical field newly reports that SiNCO inorganic nano-particle modified porous Si3N4The ceramic membrane is used for membrane distillation desalination, has similar hydrophobicity (water contact angle 142 degrees) and higher thermal stability compared with the traditional fluorosilane modification, but the membrane distillation performance of the ceramic membrane is far lower than that of a commercial polymer membrane, and the preparation condition is relatively harsh (NH)3Atmosphere, 600 ℃ firing). In the method, aiming at water treatment applications such as seawater desalination, zero discharge of high-salinity wastewater and the like, the carbon nanotube-modified porous ceramic membrane has higher hydrophobicity (super-hydrophobicity, water contact angle of 170 degrees) and good thermal stability, and the water treatment application is realized through a membrane distillation process.
The carbon nano tube has good thermal stability and super-hydrophobicity, resists strong acid and strong base, and is not oxidized basically at the temperature of 600 ℃, and the characteristics enable the carbon nano tube to become an excellent membrane making material or membrane modifier for applications such as seawater desalination, high-salt water membrane distillation and the like. For existing carbon nanotube-based separation membranes for membrane distillation, such as carbon nanotube polymer composite membranes and bucky paper membranes. On one hand, in the process of preparing the carbon nanotube polymer film, the carbon nanotubes need to be oxidized firstly to improve the uniform dispersion degree of the carbon nanotubes in the polymer film, so that the hydrophobicity of the carbon nanotubes is reduced, and therefore, the prepared polymer-carbon nanotube film does not give full play to the hydrophobic property of the carbon nanotubes and the film distillation performance is not ideal. For the bucky paper membrane, although the carbon nanotubes are staggered with each other to form a developed high-porosity structure, the carbon nanotubes are loaded on the carrier in a filtering manner, so that the carbon nanotubes are not firmly combined with the carrier, and are easy to fall off in the application process, thereby causing the problems of membrane structure and membrane performance attenuation, secondary pollution and the like. In view of the above, the carbon nanotube composite membrane material which has good support property and high bonding strength between the carbon nanotube and the carrier, can fully exert the advantages of the carbon nanotube such as super-hydrophobicity, thermal stability and electrical conductivity, and is easy to prepare on a large scale is provided, and the applications of seawater desalination, high-salt water zero emission, other water treatment and the like are realized, so that the carbon nanotube composite membrane material has important significance.
The composite film material with good carbon nanotube and carrier bonding performance can be prepared in situ by using a Chemical Vapor Deposition (CVD) method, the inherent characteristics of the carbon nanotube can be effectively ensured, and the structure, the loading capacity and the loading state of the carbon nanotube are easy to regulate and control through preparation parameters. The method is carried out under the conditions of high temperature (600 ℃ C.) -800 ℃ and atmosphere (carbon source gas, carrier gas), so that the film carrier needs to have high temperature resistance and heat stability of the atmosphere. Compared with the traditional organic polymer membrane, the hollow fiber ceramic membrane prepared by one-step molding through the phase inversion-sintering technology has the advantages of high filling density, effective membrane area per unit volume, asymmetric membrane structure prepared by one-step molding and the like, has the characteristics of high temperature resistance, high thermal stability, high chemical stability and the like, and is a very suitable membrane carrier for high-temperature in-situ loaded carbon nano tubes. Meanwhile, the ceramic hollow fiber membrane has large finger-shaped holes and a high-porosity structure, so that the gas mass transfer resistance in the CVD process can be effectively reduced, and sufficient nucleation and growth spaces are provided for the carbon nano tubes. Under different CVD preparation conditions, ceramic-carbon nanotube hollow fiber composite membranes with different structures and properties can be obtained, particularly the structures, the loading amounts and the loading states of the carbon nanotubes, the hydrophobicity, the water and gas flux, the pore diameters and the like of the composite membranes. Therefore, it is necessary to perform a series of characterization of composite membranes prepared under different conditions in order to select the composite membrane with the best structure and properties, resulting in the best membrane distillation performance.
Seawater and high-salinity wastewater often contain hydrophilic humic acid, glycerol, natural organic matters and other substances, the adhesion and accumulation of the substances on the surface of a membrane often cause organic pollution of the membrane, and the reduction of the hydrophobicity of the surface of the membrane is an important factor for causing membrane infiltration and the reduction of the membrane distillation performance. In view of this, because the carbon nanotube has good conductivity, the membrane pollution of the composite membrane completely covered by the carbon nanotube can be reduced by an electrochemical auxiliary method, and the membrane distillation performance of the composite membrane is ensured. This is because, under the electrochemical assistance, electrostatic force exists between the contaminants and the separation membrane, and other possible mechanisms of action are added, so that the adhesion and accumulation of the contaminants on the membrane surface can be suppressed, and membrane contamination can be reduced.
Furthermore, the structure and property design of the ceramic-carbon nanotube hollow fiber composite membrane oriented to the water treatment application process can be carried out, different water treatment applications can be carried out according to different membrane properties and performances, and the ceramic-carbon nanotube hollow fiber composite membrane can be expanded to other water treatment applications such as electroplating heavy metal wastewater, printing and dyeing wastewater, antibiotic wastewater and the like.
Disclosure of Invention
The invention aims to provide a high-performance carbon nanotube ceramic-carbon nanotube composite membrane with good thermal stability and super hydrophobicity, which realizes seawater desalination, zero discharge of high-salinity wastewater and other water treatment processes through a membrane distillation process.
In order to achieve the purpose, the invention provides a thermally stable and super-hydrophobic ceramic-carbon nanotube composite membrane, wherein the membrane structure is a composite membrane that carbon nanotubes completely cover the surface of a spinel hollow fiber ceramic membrane, namely the carbon nanotubes completely cover the composite membrane. The pure water contact angle is 160-170 degrees, the liquid infiltration pressure is 2-2.5bar, and the gas flux is 25-35m3·m-2·h-1。
The preparation method of the composite membrane completely covered by the carbon nano tube comprises the following steps:
(1) cleaning and soaking a spinel hollow fiber ceramic membrane used as a carrier in absolute ethyl alcohol for 10-20min, then washing with pure water, and drying at 60-70 ℃ for 1-2h to obtain a treated spinel hollow fiber ceramic membrane;
(2) mixing Ni (NO)3)2Preparing into 25-35% solution, and vacuum dip coating Ni (NO)3)2Coating the solution on the treated carrier, drying at 90-110 ℃ for 2-4h, and then placing the dried carrier in a muffle furnace for roasting at 500-600 ℃ for 2-4h to obtain the NiO catalyst-loaded spinel hollow fiber ceramic membrane;
(3) putting the NiO catalyst-loaded spinel hollow fiber ceramic membrane into a quartz reaction tube, and introducing N into the quartz reaction tube2And H2Reducing the catalyst at 500-550 ℃ for 1-3h, wherein N is2The flow rate of (A) is 10-30ml/min, H2The flow velocity of (2) is 10-30ml/min; then the temperature is raised to 650-680 ℃, and the gas flow is switched to 20-30ml/min CH4And reacting for 3-5h to obtain the composite membrane completely covered by the carbon nano tube.
Further, the pretreatment of the membrane carrier is to wash and soak the spinel hollow fiber ceramic membrane serving as the membrane carrier with absolute ethyl alcohol for 10min, then wash the membrane carrier with pure water, and dry the membrane carrier at 60 ℃ for 1h to obtain the well-treated membrane carrier. In the step of preparing the catalyst-supporting spinel hollow fiber membrane, Ni (NO)3)2The solution is a solution with a mass concentration of 30%. The concentration is too low, the loading amount of the catalyst is small, and the growth amount of the carbon nano tube is small; the concentration is too high, the size of nickel oxide particles obtained after roasting is not uniform, and the nickel oxide particles are not uniformly distributed on the surface of the fiber tube, so that the generated carbon nano tube is not uniformly grown.
The step of preparing the catalyst-supported spinel hollow fiber membrane is to coat Ni (NO) by vacuum impregnation3)2And coating the solution on the treated carrier, drying at 100 ℃ for 2h, and then placing the carrier in a muffle furnace to roast at 500 ℃ for 2h to obtain the spinel hollow fiber membrane loaded with the nickel oxide catalyst. In the CVD reaction step, N2、H2、CH4The flow rates of (A) and (B) were all 20 ml/min.
The CVD reaction is that the spinel hollow fiber membrane loaded with the nickel oxide catalyst is placed in a quartz reaction tube, and N is introduced into the quartz reaction tube2And H2Heating to 500 deg.C at 5 deg.C/min, reducing catalyst at 500 deg.C for 1h, heating to 650 deg.C at 5 deg.C/min, and switching gas flow to CH4Reacting for a certain time, and finally switching the gas flow to N2And naturally cooling to obtain the composite film completely covered by the carbon nano tube. Composite films completely covered by carbon nanotubes with different structures can be obtained in different reaction times, the reaction time is short, the growth amount of the carbon nanotubes is small, and the composite films partially covered by the carbon nanotubes are obtained; the reaction time is longer, the growth amount of the carbon nano tube is increased, and the composite film completely covered by the carbon nano tube is obtained.
The ceramic-carbon nanotube hollow fiber composite membranes with different structures and performances are obtained according to different preparation parameters, and have different properties including the loading capacity, loading state, hydrophobicity, water and gas flux, membrane pore diameter and the like of the carbon nanotubes.
Has a pure water contact angle of 160-170 degrees, a liquid immersion pressure of 2-2.5bar and a gas flux of 25-35m3·m-2·h-1The composite film completely covered by the carbon nano tube has stable thermal super-hydrophobicity. The composite membrane completely covered by the carbon nano tube utilizes various waste heat or waste heat and other cheap energy sources for seawater desalination, and enhances the anti-pollution performance of the membrane by means of electrochemical assistance. Various kinds of waste heat or waste heat and other cheap energy are used for zero emission treatment of high-salinity wastewater, and the anti-pollution performance of the membrane is enhanced by means of electrochemical assistance. The method utilizes various kinds of waste heat or waste heat and other cheap energy sources to be used in the concentration and purification treatment processes of other waste water (such as electroplating heavy metal waste water, printing and dyeing waste water, antibiotic waste water and the like).
1) Seawater desalination application of composite membrane completely covered by carbon nano tube
The composite membrane with the carbon nanotubes completely covered was fixed on the hot water side (35 g.L) of a direct contact membrane distillation apparatus-1NaCl solution) temperature was 80 deg.c and cold water side (deionized water) temperature was 20 deg.c. In the process of desalting seawater by direct contact membrane distillation, the permeation flux of the membrane is stabilized at 37 L.m-2·h-1On the other hand, the salt rejection rate exceeds 99%, and membrane wetting does not occur during membrane distillation.
2) High-salinity water zero-emission application of composite membrane completely covered by carbon nano tube
The composite membrane with the carbon nanotubes completely covered was fixed on the hot water side (70 g.L) of a direct contact membrane distillation apparatus-1NaCl of (r) temperature was 80 ℃ and cold water side (deionized water) temperature was 20 ℃. The permeation flux of the membrane is stabilized at 25 L.m in the direct contact membrane distillation process-2·h-1About, the salt rejection rate exceeds 99%. Therefore, the composite membrane completely covered by the carbon nano tube has good high saline water treatment capacity.
When the composite membrane completely covered by the carbon nano tube is used for desalting brine by membrane distillation, the concentration of the brine is more than or equal to 70g·L-1In this case, the salt retention rate can be more than 99%.
3) High-salinity wastewater zero-discharge application of composite membrane completely covered by carbon nano tube under electrochemical auxiliary condition
The composite membrane completely covered by the carbon nano tube is fixed on a direct contact membrane distillation device, and the direct current power supply provides electrochemical assistance and applies 2V voltage. Carrying out membrane distillation on the composite membrane under the condition of applying negative bias voltage, namely taking the composite membrane as a working electrode and connecting the working electrode with the negative electrode of a direct current power supply; the titanium net is used as a counter electrode and is connected with the anode of a direct current power supply. Hot water side of membrane distillation (70 g.L)-1NaCl and 30mg/L humic acid HA) at 80 ℃ and a cold water side (deionized water) at 20 ℃. Under the condition of electrochemical assistance (negative bias), the permeation flux of the membrane is stabilized at 25 L.m-2·h-1On the other hand, the retention rate of the salt exceeds 99 percent, which shows that the electrochemical assistance can reduce the pollution of the membrane and keep more stable membrane distillation performance. Therefore, the composite membrane completely covered by the electrochemical-assisted carbon nano tube has good high-salinity wastewater treatment capacity, and can effectively prevent organic matters such as humic acid and the like from polluting the composite membrane under the assistance of electrochemistry.
The beneficial effect of this application: the carrier of the composite membrane completely covered by the carbon nano tube is a spinel porous ceramic hollow fiber membrane, and the carbon nano tube is grown in situ by adopting a CVD method to form the composite membrane completely covered by the carbon nano tube. The pure water contact angle is 160-170 degrees, the liquid infiltration pressure is 2-2.5bar, and the gas flux is 25-35m3·m-2·h-1. The composite membrane has super-hydrophobicity and good thermal stability, and can realize seawater desalination, high-salinity wastewater zero discharge and other wastewater treatment through the membrane distillation process. The ceramic hollow fiber membrane is used as a carrier, and the large through finger hole structure not only can ensure the low resistance transmission of various gases in the chemical vapor deposition method, but also can provide sufficient space for the growth of the carbon nano tube. Meanwhile, the inherent advantages of high temperature resistance, chemical corrosion resistance, high mechanical strength and the like are also the basic requirements of preparing the carbon nano tube composite membrane directly by a chemical vapor deposition method, thereby ensuring the combination between the carbon nano tube and the carrier and preventing the carbon nano tube from being appliedThe falling off occurs in the process, which causes the problems of membrane structure damage, performance attenuation, secondary pollution and the like.
The composite membrane completely covered by the carbon nano tube has a developed mutually-communicated pore structure, high porosity, uniform pore size distribution and excellent thermal stability and super-hydrophobicity, so that seawater desalination, zero discharge of high-salinity wastewater and other wastewater treatment processes can be realized through membrane distillation, and the composite membrane has high membrane distillation flux and salt rejection rate of over 99%. Meanwhile, the composite membrane completely covered by the carbon nano tubes has higher pollution resistance when used for treating seawater and high-salinity wastewater through electrochemical assistance, and higher and stable membrane distillation flux and salt rejection rate are obtained. Therefore, the ceramic-carbon nanotube hollow fiber composite membranes with different structures and different properties can be prepared by a chemical vapor deposition method, and the difference of the properties such as pore size distribution, hydrophobicity, nitrogen flux and the like of the two different composite membrane structures is determined, so that different composite membrane structures can be designed according to a specific water treatment application process, and the application field of the inorganic membrane is expanded.
The hydrophobicity and the thermal stability of the composite film completely covered by the carbon nano tube are superior to those of other ceramic film modifiers, such as fluorosilane and SiNCO. Therefore, the membrane distillation performance is good, the interconnected network structure with high porosity is provided, the carbon nano tube has frictionless transmission performance to water vapor, the low resistance transmission of the water vapor in the membrane distillation process is ensured, high permeation flux is obtained, and meanwhile, the good super-hydrophobicity, thermal stability and electrical conductivity of the carbon nano tube are fully utilized, so that the carbon nano tube has good long-term anti-wetting property and anti-pollution capability in the membrane distillation process, and therefore, in the long-term membrane distillation operation process, the salt rejection rate of over 99 percent and the stable membrane distillation performance are obtained.
The structure, the loading capacity and the loading state of the carbon nano tube are easy to control by adopting a chemical vapor deposition method, composite membrane materials with different structures and different characteristics can be obtained through different operating conditions, and different composite membrane materials can be applied to different water treatment processes. The composite membrane partially covered by the carbon nano tube s has low hydrophobicity, so that membrane wetting is easily generated in the membrane distillation process, and the membrane distillation application is not facilitated. The carbon nano tube has a mutually communicated network structure and high porosity, and simultaneously, the carbon nano tube has good electrochemical property, so that the oil-water emulsion can be filtered by an electric auxiliary method, the membrane pollution is greatly reduced, and the flux of the membrane and the entrapment rate of oil are improved.
Drawings
FIG. 1 is a schematic diagram of a spinel hollow fiber membrane support.
FIG. 2 is a scanning electron micrograph of a cross section of a spinel hollow fiber membrane support.
Fig. 3 is a photograph of a pure water contact angle of a spinel hollow fiber membrane support.
FIG. 4 is a scanning electron micrograph of the surface of the composite film partially covered with carbon nanotubes in example 1.
FIG. 5 is a scanning electron micrograph of the surface of the composite film partially covered with carbon nanotubes in example 2.
FIG. 6 is a photograph showing the contact angle of pure water in the composite film partially covered with carbon nanotubes in example 2.
FIG. 7 is a scanning electron micrograph of the surface of the composite film completely covered with carbon nanotubes in example 3.
FIG. 8 is a scanning electron micrograph of the surface of the composite film completely covered with carbon nanotubes of example 4.
Fig. 9 is a photograph showing a contact angle of pure water of the composite film completely covered with carbon nanotubes in example 4.
FIG. 10 is a graph showing the membrane distillation performance of the composite membrane of example 4 on seawater.
FIG. 11 is a graph showing the membrane distillation performance for high brine using the composite membrane of example 4.
FIG. 12 is the membrane distillation performance of high salinity wastewater under electrochemically assisted conditions using the composite membrane of example 4.
FIG. 13 shows the membrane fouling of the high salinity wastewater (open circuit, negatively biased, and positively biased, respectively, from left to right) with the electrochemical assistance of the composite membrane of example 4.
Detailed Description
Example 1 preparation of partially carbon nanotube-capped composite films
A spinel hollow fiber membrane is used as a carrier to prepare a composite membrane partially covered by a carbon nano tube, and the method comprises the following steps:
firstly, cleaning and soaking a spinel hollow fiber ceramic membrane (shown in figure 1) serving as a carrier with absolute ethyl alcohol for 10min, then washing with pure water, and drying at 60 ℃ for 1h to obtain a treated carrier;
second, Ni (NO)3)2Preparing into 30% solution, and vacuum dip coating Ni (NO)3)2The solution is coated on the treated carrier, dried for 2h at 100 ℃ and then placed in a muffle furnace for roasting for 2h at 500 ℃. Conclusion by X-ray diffractometer (XRD) analysis: the spinel hollow fiber membrane loaded with NiO catalyst is obtained by the step.
Thirdly, placing the spinel hollow fiber membrane loaded with NiO catalyst into a quartz reaction tube, and introducing N into the quartz reaction tube2And H2The NiO catalyst-loaded spinel hollow fiber membrane is subjected to catalyst reduction at 500 ℃ for 1h (the flow rates are both 20ml/min), then the temperature is raised to 650 ℃, and the gas flow is switched to 20ml/min CH4And reacting for 15min to obtain the composite film partially covered by the carbon nano tube.
As a result: FIG. 2 is a scanning electron micrograph of a cross section of a spinel hollow fiber ceramic membrane, wherein the hollow fiber membrane has an asymmetric Sanming' diamond structure, finger-shaped pore structures are arranged on the inner surface and the outer surface of the hollow fiber membrane, and a sponge layer structure is arranged in the middle of the hollow fiber membrane, so that the hollow fiber membrane has high porosity, small effective membrane thickness, small mass transfer resistance and good gas permeation flux and mechanical strength, and is favorable for transferring a carbon-containing gas source between carrier membrane layers and improving the yield of carbon nano tubes; fig. 3 is a photograph showing a pure water contact angle of the spinel hollow fiber ceramic membrane, and it can be seen that the pure water contact angle is 17 °, and thus the spinel hollow fiber ceramic membrane has excellent hydrophilicity. FIG. 4 is a scanning electron micrograph of the surface of the composite film partially covered with carbon nanotubes. It can be seen that with a reaction time of only 15min, there is a large amount of ceramic support surface not covered by carbon nanotubes.
Example 2 preparation of partially carbon nanotube-capped composite films
A spinel hollow fiber membrane is used as a carrier, CVD reaction time is changed, and a composite membrane partially covered by a carbon nano tube is prepared, and the method comprises the following steps:
firstly, cleaning and soaking a spinel hollow fiber ceramic membrane serving as a carrier with absolute ethyl alcohol for 10min, then washing with pure water, and drying at 60 ℃ for 1h to obtain a treated carrier;
second, Ni (NO)3)2Preparing 35% solution, and vacuum dip coating Ni (NO)3)2The solution is coated on the treated carrier, dried for 2h at 100 ℃ and then placed in a muffle furnace for roasting for 2h at 500 ℃.
Thirdly, placing the spinel hollow fiber membrane loaded with NiO catalyst into a quartz reaction tube, and introducing N into the quartz reaction tube2And H2(the flow rates are all 25 ml/min.) for the NiO catalyst-loaded spinel hollow fiber membrane, the catalyst is reduced for 1h at 500 ℃, then the temperature is raised to 650 ℃, and the gas flow is switched to 20ml/min CH4And reacting for 45min to obtain the ceramic-carbon nanotube hollow fiber composite membrane. As can be seen from fig. 5: the surface of the ceramic film is partially covered with a carbon nanotube structure.
As a result: FIG. 5 is a scanning electron micrograph of the surface of a composite film partially covered with carbon nanotubes. It can be seen that, since the reaction time was extended to 45min, most of the carbon nanotubes covered the surface of the ceramic support, and there was also a portion of the ceramic support that was not covered with carbon nanotubes. Fig. 6 is a photograph showing the contact angle of pure water in the composite film partially covered with carbon nanotubes. Because the carbon nano tube has hydrophobicity and the ceramic carrier has hydrophilicity, the composite membrane partially covered by the carbon nano tube has lower hydrophobicity, the contact angle of pure water is 102 degrees, the infiltration pressure of liquid is 0.6bar, and the gas flux is 56 m3·m-2·h-1It is not suitable for membrane distillation applications.
Example 3 preparation of a composite film with complete coverage of carbon nanotubes
A spinel hollow fiber membrane is used as a carrier to prepare a composite membrane completely covered by carbon nano tubes, and the method comprises the following steps:
firstly, cleaning and soaking a spinel hollow fiber ceramic membrane serving as a carrier with absolute ethyl alcohol for 10min, then washing with pure water, and drying at 60 ℃ for 1h to obtain a treated carrier;
second, Ni (NO)3)2Preparing into 30% solution, and vacuum dip coating Ni (NO)3)2The solution is coated on the treated carrier, dried for 2h at 100 ℃ and then placed in a muffle furnace for roasting for 2h at 550 ℃.
Thirdly, placing the spinel hollow fiber membrane loaded with NiO catalyst into a quartz reaction tube, and introducing N into the quartz reaction tube2And H2The NiO catalyst-loaded spinel hollow fiber membrane is subjected to catalyst reduction at 500 ℃ for 1h (the flow rates are both 20ml/min), then the temperature is raised to 650 ℃, and the gas flow is switched to 20ml/min CH4And reacting for 2 hours to obtain the ceramic-carbon nanotube hollow fiber composite membrane.
As a result: FIG. 7 is a scanning electron micrograph of the surface of the composite film completely covered with carbon nanotubes. It can be seen that when the reaction time is 2h, the ceramic surface is completely covered by the interpenetrating carbon nanotube network structure, and the carbon nanotube film layer shows a developed interpenetrating pore structure and porosity.
Example 4 preparation of composite film with complete coverage of carbon nanotubes
A spinel hollow fiber membrane is used as a carrier, the reaction time of CVD is changed, and a composite membrane completely covered by carbon nano tubes is prepared, which comprises the following steps:
firstly, cleaning and soaking a spinel hollow fiber ceramic membrane serving as a carrier with absolute ethyl alcohol for 10min, then washing with pure water, and drying at 60 ℃ for 1h to obtain a treated carrier;
second, Ni (NO)3)2Preparing into 30% solution, and vacuum dip coating Ni (NO)3)2The solution is coated on the treated carrier, dried for 2h at 100 ℃ and then placed in a muffle furnace for roasting for 2h at 500 ℃.
Thirdly, placing the spinel hollow fiber membrane loaded with NiO catalyst into a quartz reaction tube, and introducing N into the quartz reaction tube2And H2The NiO catalyst-loaded spinel hollow fiber membrane is subjected to catalyst reduction at 500 ℃ for 1h (the flow rates are both 20ml/min), then the temperature is raised to 650 ℃, and the gas flow is switched to 20ml/min CH4And reacting for 3h to obtain the composite membrane completely covered by the carbon nano tube. As can be seen in fig. 8: the surface of the ceramic film is completely covered with the carbon nano tube network structure.
As a result: FIG. 8 is a scanning electron micrograph of the surface of the composite film completely covered with carbon nanotubes. Fig. 9 is a photograph showing a contact angle of pure water in the composite film completely covered with the carbon nanotubes. It can be seen that when the reaction time is 3h, the composite membrane completely covered by the carbon nanotubes has higher superhydrophobicity, the contact angle of pure water is 170 degrees, the liquid infiltration pressure is 2bar, and the gas flux is 30m3·m-2·h-1. Therefore, the controllable growth of the ceramic-carbon nanotube hollow fiber composite membrane can be realized through different preparation conditions, and the composite membranes with different structures and different properties can be obtained.
Example 5 application of composite Membrane completely covered with carbon nanotubes in Membrane distillation for seawater desalination
The seawater desalination application of the composite membrane completely covered by the carbon nano tube is carried out by direct contact membrane distillation, and the steps are as follows:
the first step is as follows: weighing a certain mass of NaCl, adding into pure water to prepare the NaCl with the concentration of 35 g.L-1The NaCl solution of (a) was used as simulated seawater.
The second step is that: the composite membrane with the carbon nanotubes completely covered was fixed on the hot water side (35 g.L) of a direct contact membrane distillation apparatus-1NaCl solution) temperature was 80 deg.c and cold water side (deionized water) temperature was 20 deg.c. The permeate flux of the membrane was calculated by periodically detecting the change in mass on the cold water side. The conductivity of the permeate was measured using a conductivity meter and the salt rejection was calculated. And after the composite membrane runs for 9 hours, carrying out hot water cleaning once.
The results show that: in the process of desalting seawater by direct contact membrane distillation, the permeation flux of the membrane is stabilized at 37 L.m-2·h-1On the other hand, the salt retention rate exceeds 99%, and the stabilization time exceeds 18 h. Therefore, the ceramic-carbon nanotube hollow fiber composite membraneHas stable membrane distillation seawater desalination performance, and the membrane can not be wetted in the membrane distillation process. Fig. 10 is a graph of membrane distillation performance of the composite membrane completely covered with carbon nanotubes on seawater.
Example 6 high-salt water zero-emission application of composite membranes with complete coverage of carbon nanotubes
The first step is as follows: weighing a certain mass of NaCl, adding into pure water to prepare the NaCl with the concentration of 70 g.L-1The NaCl solution was used as high salt water.
The second step is that: the composite membrane with the carbon nanotubes completely covered was fixed on the hot water side (70 g.L) of a direct contact membrane distillation apparatus-1NaCl of (r) temperature was 80 ℃ and cold water side (deionized water) temperature was 20 ℃. The permeate flux of the membrane was calculated by periodically detecting the change in mass on the cold water side. The conductivity of the permeate was measured using a conductivity meter and the salt rejection was calculated. And after the composite membrane runs for 6 hours, carrying out hot water cleaning once.
The results show that: the permeation flux of the membrane is stabilized at 25 L.m in the direct contact membrane distillation process-2·h-1About, the salt rejection rate exceeds 99%. Therefore, the ceramic-carbon nanotube hollow fiber composite membrane has good high brine treatment capacity and is expected to realize zero discharge of high brine. Fig. 11 is a graph of membrane distillation performance of a composite membrane completely covered with carbon nanotubes on high salt water.
Example 7 high-salt water zero-emission application of composite membranes with complete coverage of carbon nanotubes
The first step is as follows: weighing a certain mass of NaCl, adding into pure water to prepare into the NaCl with the concentration of 150 g.L-1The NaCl solution was used as high salt water.
The second step is that: the composite membrane with the carbon nanotubes completely covered was fixed on the hot water side (150 g. L) of a direct contact membrane distillation apparatus-1NaCl of (r) temperature was 80 ℃ and cold water side (deionized water) temperature was 20 ℃. The permeate flux of the membrane was calculated by periodically detecting the change in mass on the cold water side. The conductivity of the permeate was measured using a conductivity meter and the salt rejection was calculated. And after the composite membrane runs for 6 hours, carrying out hot water cleaning once.
The results show that: the permeation flux of the membrane is stable in the direct contact membrane distillation processAt 7.5 L.m-2·h-1About, the salt rejection rate exceeds 99%. Therefore, the ceramic-carbon nanotube hollow fiber composite membrane has good high brine treatment capacity and is expected to realize zero discharge of high brine.
Example 8 high-salinity wastewater zero-discharge application of composite membrane completely covered with carbon nanotubes under electrochemical-assisted conditions
The first step is as follows: weighing a certain mass of NaCl, adding into 30mg/L Humic Acid (HA) solution to prepare into a solution with the concentration of 70 g.L-1A mixed solution of NaCl and 30mg/L of HA was used as the high-salinity wastewater.
The second step is that: the composite membrane completely covered by the carbon nano tube is fixed on a direct contact membrane distillation device, and the direct current power supply provides electrochemical assistance and applies 2V voltage. The membrane distillation performance of the composite membrane was compared under three different conditions. One is membrane distillation of the composite membrane under open circuit conditions (no voltage applied). The second is that the composite membrane carries on the membrane distillation under exerting the negative bias condition, namely the composite membrane is regarded as the working electrode, connect the negative pole of the direct-current power; the titanium net is used as a counter electrode and is connected with the anode of a direct current power supply. Thirdly, the composite membrane is subjected to membrane distillation under the condition of applying positive bias, namely the composite membrane is used as a working electrode and is connected with the anode of a direct current power supply; the titanium net is used as a counter electrode and is connected with the negative electrode of a direct current power supply. Hot water side of membrane distillation (70 g.L)-1NaCl and 30mg/L HA) temperature was 80 ℃ and the cold side (deionized water) temperature was 20 ℃. The permeate flux of the membrane was calculated by periodically detecting the change in mass on the cold water side. The conductivity of the permeate was measured using a conductivity meter and the salt rejection was calculated. And after the composite membrane runs for 6 hours, carrying out hot water cleaning once.
The results show that: under the condition of open circuit, the permeation flux of the membrane is gradually reduced, and the salt retention rate is relatively stable. This is because HA adheres to the surface of the composite membrane, causing contamination of the membrane surface, and reducing the flux of the membrane. After cleaning, the flux of the membrane is recovered, which indicates that the adhesion of HA on the surface of the composite membrane is weak. Under the condition of electrochemical assistance (negative bias), the permeation flux of the membrane is stabilized at 25 L.m-2·h-1On the other hand, the salt rejection rate exceeds 99%, indicating that electrochemical assistance can be reducedLess membrane pollution and stable membrane distillation performance. This is because HA exhibits electronegativity in water, which means that there is mutual repulsion between HA and the negatively biased membrane, which action reduces HA accumulation on the membrane surface, reduces membrane fouling, and thus results in stable flux. However, under electrochemically assisted conditions (positive bias), the permeation flux of the membrane is significantly reduced, and after washing, the permeation flux of the membrane is not restored, and the salt rejection is also significantly reduced. This is because HA exhibits electronegativity in water, which means that there is an attraction between HA and the positively biased membrane, which enhances HA accumulation on the membrane surface, increasing membrane fouling, and thus the permeation flux and rejection rate of the membrane are decreasing. Therefore, the ceramic-carbon nanotube hollow fiber composite membrane has good high-salinity wastewater treatment capacity through electrochemical assistance, and is expected to realize zero discharge of high-salinity wastewater.
FIG. 12 shows membrane distillation performance of high-salinity wastewater under electrochemical assistance of a composite membrane completely covered with carbon nanotubes. FIG. 13 shows the membrane contamination of high salinity wastewater under the electrochemical-assisted condition of the composite membrane completely covered by carbon nanotubes.
Example 9 application of composite membrane completely covered with carbon nanotubes to heavy metal wastewater treatment
The application of the composite membrane for treating heavy metal wastewater by completely covering carbon nano tubes through direct contact membrane distillation comprises the following steps:
the first step is as follows: preparation of a catalyst containing Co2+、Cu2+、Ni2+And Mn2+The concentration of each heavy metal ion in the heavy metal wastewater solution is 5 mg.L-1。
The second step is that: the composite membrane completely covered by the carbon nano tube is fixed on a direct contact membrane distillation device, the temperature of a hot water side (heavy metal wastewater) is 80 ℃, and the temperature of a cold water side (deionized water) is 20 ℃. The permeate flux of the membrane was calculated by periodically detecting the change in mass on the cold water side. And measuring the concentration of each heavy metal ion in the penetrating fluid by utilizing ICP-MS (inductively coupled plasma-mass spectrometry) and calculating the retention rate. And after the composite membrane runs for 9 hours, carrying out hot water cleaning once.
The results show that: direct contact membrane distillation seawater desalination processThe permeation flux of the membrane is stabilized at 30 L.m-2·h-1About, the heavy metal retention rate exceeds 99%, and the stabilization time exceeds 18 h. Therefore, the composite membrane completely covered by the carbon nano tube has stable heavy metal wastewater treatment capacity.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.

Claims (4)

1. The application of the thermal-stable and super-hydrophobic ceramic-carbon nanotube composite membrane is characterized in that: the composite membrane takes a spinel hollow fiber ceramic membrane as a carrier and takes a composite structure that a carbon nano tube completely covers the carrier as a membrane structure; the pure water contact angle of the composite membrane is 160-170 degrees, the liquid infiltration pressure is 2-2.5bar, and the gas flux is 25-35m3·m-2·h-1(ii) a The preparation method of the composite membrane comprises the following steps:
(1) cleaning and soaking the spinel hollow fiber ceramic membrane used as a carrier in absolute ethyl alcohol for 10-20min, then washing with pure water, and drying at 60-70 ℃ for 1h to obtain a treated spinel hollow fiber ceramic membrane;
(2) mixing Ni (NO)3)2Preparing into 25-35% solution, and vacuum dip coating Ni (NO)3)2Coating the solution on the treated carrier, drying at 90-110 ℃ for 2h, and then placing the dried carrier in a muffle furnace for roasting at 500-600 ℃ for 2-4h to obtain a NiO catalyst-loaded spinel hollow fiber ceramic membrane;
(3) putting the NiO catalyst-loaded spinel hollow fiber ceramic membrane into a quartz reaction tube, and introducing N into the quartz reaction tube2And H2Reducing the catalyst for 1h at 500-550 ℃, wherein N is2The flow rate of (A) is 10-30ml/min, H2The flow rate of (A) is 10-30 ml/min; then the temperature is raised to 650-680 ℃, and the gas flow is switched to 20-30ml/min CH4After reaction for 3-5h, obtainingTo a composite film in which the carbon nanotubes are completely covered;
the composite membrane is applied to membrane distillation of seawater desalination, and specifically comprises the following steps:
the first step is as follows: weighing NaCl, adding into pure water to obtain a solution with a concentration of 35 g.L-1The NaCl solution of (a) is used as simulated seawater;
the second step is that: fixing the composite membrane completely covered with carbon nanotube on a direct contact membrane distillation device, wherein the hot water side solution is 35 g.L-1At a temperature of 80 deg.C; deionized water is adopted at the cold water side, and the temperature is 20 ℃; the change of the mass of the cold water side is periodically detected, and the permeation flux of the membrane is calculated.
2. The application of the thermal-stable and super-hydrophobic ceramic-carbon nanotube composite membrane is characterized in that: the composite membrane takes a spinel hollow fiber ceramic membrane as a carrier and takes a composite structure that a carbon nano tube completely covers the carrier as a membrane structure; the pure water contact angle of the composite membrane is 160-170 degrees, the liquid infiltration pressure is 2-2.5bar, and the gas flux is 25-35m3·m-2·h-1(ii) a The preparation method of the composite membrane comprises the following steps:
(1) cleaning and soaking the spinel hollow fiber ceramic membrane used as a carrier in absolute ethyl alcohol for 10-20min, then washing with pure water, and drying at 60-70 ℃ for 1h to obtain a treated spinel hollow fiber ceramic membrane;
(2) mixing Ni (NO)3)2Preparing into 25-35% solution, and vacuum dip coating Ni (NO)3)2Coating the solution on the treated carrier, drying at 90-110 ℃ for 2h, and then placing the dried carrier in a muffle furnace for roasting at 500-600 ℃ for 2-4h to obtain a NiO catalyst-loaded spinel hollow fiber ceramic membrane;
(3) putting the NiO catalyst-loaded spinel hollow fiber ceramic membrane into a quartz reaction tube, and introducing N into the quartz reaction tube2And H2Reducing the catalyst for 1h at 500-550 ℃, wherein N is2The flow rate of (A) is 10-30ml/min, H2The flow rate of (A) is 10-30 ml/min; then the temperature is raised to 650-680 ℃, and the gas flow is switched to 20-30ml/min CH4Reacting for 3-5h to obtain a composite film completely covered by the carbon nano tube;
the composite membrane is applied to membrane distillation with zero discharge of high-salinity wastewater, and specifically comprises the following steps:
the first step is as follows: weighing NaCl, adding into pure water to obtain a solution with a concentration of 70 g.L-1As high salt water;
the second step is that: fixing the composite membrane on a direct contact membrane distillation device, wherein 70 g.L is adopted on the hot water side-1At a temperature of 80 deg.C; the cold water side is deionized water, and the temperature is 20 ℃; the permeate flux of the membrane was calculated by periodically detecting the change in mass on the cold water side.
3. The application of the thermal-stable and super-hydrophobic ceramic-carbon nanotube composite membrane is characterized in that: the composite membrane takes a spinel hollow fiber ceramic membrane as a carrier and takes a composite structure that a carbon nano tube completely covers the carrier as a membrane structure; the pure water contact angle of the composite membrane is 160-170 degrees, the liquid infiltration pressure is 2-2.5bar, and the gas flux is 25-35m3·m-2·h-1(ii) a The preparation method of the composite membrane comprises the following steps:
(1) cleaning and soaking the spinel hollow fiber ceramic membrane used as a carrier in absolute ethyl alcohol for 10-20min, then washing with pure water, and drying at 60-70 ℃ for 1h to obtain a treated spinel hollow fiber ceramic membrane;
(2) mixing Ni (NO)3)2Preparing into 25-35% solution, and vacuum dip coating Ni (NO)3)2Coating the solution on the treated carrier, drying at 90-110 ℃ for 2h, and then placing the dried carrier in a muffle furnace for roasting at 500-600 ℃ for 2-4h to obtain a NiO catalyst-loaded spinel hollow fiber ceramic membrane;
(3) putting the NiO catalyst-loaded spinel hollow fiber ceramic membrane into a quartz reaction tube, and introducing N into the quartz reaction tube2And H2Reducing the catalyst for 1h at 500-550 ℃, wherein N is2The flow rate of (A) is 10-30ml/min, H2The flow rate of (A) is 10-30 ml/min; then the temperature is raised to 650-680 ℃, and the gas flow is switched to 20-30ml/min CH4Reaction 3-After 5h, obtaining a composite film completely covered by the carbon nano tube;
the composite membrane is applied to membrane distillation with zero discharge of high-salinity wastewater under electrochemical auxiliary conditions, and specifically comprises the following steps:
the first step is as follows: weighing NaCl, adding into 30mg/L humic acid solution to prepare 70 g.L-1The mixed solution of NaCl and 30mg/L humic acid is used as high-salinity wastewater;
the second step is that: fixing the composite membrane on a direct contact membrane distillation device, providing electrochemical assistance through a direct current power supply, and applying 2V voltage; the composite membrane is subjected to membrane distillation under the condition of applying negative bias, namely the composite membrane is used as a working electrode and is connected with the negative electrode of a direct current power supply; the titanium mesh is used as a counter electrode and is connected with the anode of a direct current power supply; or the composite membrane is subjected to membrane distillation under the condition of applying positive bias voltage, namely the composite membrane is used as a working electrode and is connected with the positive electrode of a direct current power supply; the titanium mesh is used as a counter electrode and is connected with the negative electrode of a direct current power supply; the hot water side of the membrane distillation adopts 70 g.L-1The temperature of the mixed solution of NaCl and 30mg/L humic acid is 80 ℃, the cold water side is deionized water, and the temperature is 20 ℃; the permeate flux of the membrane was calculated by periodically detecting the change in mass on the cold water side.
4. The application of the thermal-stable and super-hydrophobic ceramic-carbon nanotube composite membrane is characterized in that: the composite membrane takes a spinel hollow fiber ceramic membrane as a carrier and takes a composite structure that a carbon nano tube completely covers the carrier as a membrane structure; the pure water contact angle of the composite membrane is 160-170 degrees, the liquid infiltration pressure is 2-2.5bar, and the gas flux is 25-35m3·m-2·h-1(ii) a The preparation method of the composite membrane comprises the following steps:
(1) cleaning and soaking the spinel hollow fiber ceramic membrane used as a carrier in absolute ethyl alcohol for 10-20min, then washing with pure water, and drying at 60-70 ℃ for 1h to obtain a treated spinel hollow fiber ceramic membrane;
(2) mixing Ni (NO)3)2Preparing into 25-35% solution, and vacuum dip coating Ni (NO)3)2Solution coating of the treated supportDrying at 90-110 ℃ for 2h, and then placing the dried product in a muffle furnace to roast at 500-600 ℃ for 2-4h to obtain the NiO catalyst-loaded spinel hollow fiber ceramic membrane;
(3) putting the NiO catalyst-loaded spinel hollow fiber ceramic membrane into a quartz reaction tube, and introducing N into the quartz reaction tube2And H2Reducing the catalyst for 1h at 500-550 ℃, wherein N is2The flow rate of (A) is 10-30ml/min, H2The flow rate of (A) is 10-30 ml/min; then the temperature is raised to 650-680 ℃, and the gas flow is switched to 20-30ml/min CH4Reacting for 3-5h to obtain a composite film completely covered by the carbon nano tube;
the composite membrane is applied to membrane distillation of electroplating heavy metal wastewater, printing and dyeing wastewater or antibiotic wastewater;
the composite membrane is applied to treating electroplating heavy metal wastewater, and specifically comprises the following steps:
the first step is as follows: preparation of a catalyst containing Co2+、Cu2+、Ni2+And Mn2+The concentration of each heavy metal ion in the heavy metal wastewater solution is 5 mg.L-1；
The second step is that: fixing the composite membrane completely covered by the carbon nano tube on a direct contact membrane distillation device, wherein the hot water side adopts heavy metal wastewater solution, the temperature of the heavy metal wastewater solution is 80 ℃, the cold water side adopts deionized water, and the temperature of the deionized water is 20 ℃; the permeate flux of the membrane was calculated by periodically detecting the change in mass on the cold water side.
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CN105050696A (en) * 2013-03-05 2015-11-11 阿卜杜拉国王科技大学 Membrane for distillation including nanostructures, methods of making membranes, and methods of desalination and separation
CN104826503A (en) * 2015-05-27 2015-08-12 天津工业大学 Production formula and method of PVDF (polyvinylidene fluoride)/carbon nano-tube super-hydrophobic film

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