阅读说明：本技术 油水分离氧化石墨烯/碳纳米管复合过滤膜的制备方法 (Preparation method of graphene oxide/carbon nano tube composite filtering membrane for oil-water separation ) 是由 陈文革 袁茹欣 栗雯绮 于 2021-07-07 设计创作，主要内容包括：本发明公开了油水分离氧化石墨烯/碳纳米管复合过滤膜的制备方法,利用碳纳米管具有优良的机械性能以及独特的孔道结构特点,与石墨烯共同使用形成在空间上具有三维结构的复合材料,不仅增加了填料与基体的接触面积,还可以发挥石墨烯和碳纳米管的协同效应,可以构建,改变和优化膜通道,提高渗透效果,所得的纳米复合材料具有比传统单种填料改性更优异的脱盐和防污性能。(The invention discloses a preparation method of an oil-water separation graphene oxide/carbon nano tube composite filtering membrane, which utilizes the characteristics of excellent mechanical property and unique pore structure of a carbon nano tube to be used together with graphene to form a composite material with a three-dimensional structure in space, not only increases the contact area of a filler and a matrix, but also can play a synergistic effect of the graphene and the carbon nano tube, can construct, change and optimize a membrane channel, and improve a permeation effect, and the obtained nano composite material has more excellent desalting and antifouling properties than the modification of the traditional single filler.)

1. The preparation method of the graphene oxide/carbon nano tube composite filtering membrane for oil-water separation is characterized by comprising the following specific operation steps of:

step 1, raw material selection

The graphene oxide nano tube membrane comprises lamellar graphene oxide, a carbon nano tube and a base membrane, wherein the base membrane is a cellulose microporous filtering membrane, the aperture of the cellulose microporous filtering membrane is 0.2-0.4 mu m, and the cellulose microporous filtering membrane with the aperture of 0.2-0.4 mu m is subjected to ultrasonic cleaning and drying for later use;

step 2, preparing graphene oxide dispersion liquid and carbon nano tube dispersion liquid

Respectively mixing the graphene oxide and the carbon nano tube in the step 1 with distilled water in a ratio of 1-2: mixing the components according to a mass ratio of 1000, magnetically stirring the components at a speed of 50-150 rpm for 1-3 hours at room temperature, and simultaneously carrying out dispersion regulation and control on the mixed solution with ultrasonic waves of 30-50 kHz to obtain a graphene oxide dispersion liquid and a multi-walled carbon nanotube dispersion liquid;

step 3, preparing a mixed solution of graphene oxide and multi-walled carbon nanotubes

Mixing the graphene oxide dispersion liquid prepared in the step 2 and the multi-walled carbon nanotube dispersion liquid according to the volume capacity of 1: 1-1: 3, and performing dispersion regulation and control on the mixed liquid for 30-60 minutes by using ultrasonic waves of 30-50 kHz to obtain a mixed liquid of graphene oxide and multi-walled carbon nanotubes;

step 4, designing a vacuum filtration device

The vacuum filtration device comprises a conical filter flask (6), an hourglass-shaped filtration connector (4) is sleeved above the mouth of the filter flask (6), a filter cup (2) is connected onto the filtration connector (4), a sand core disc (410) is arranged at the upper port of the filtration connector (4), a layer of sand core (411) is arranged on the sand core disc (410), and the lower end of the filter cup (2) is buckled on the sand core disc (410) and is connected with the filtration connector (4) in a clamping manner through a metal clamp (3);

the lower half part of the suction filtration connector (4) is divided into two layers, the inner layer is used for liquid to pass through, the outer layer is a cavity layer, and the cavity layer is connected with a vacuum pump (7) through a conduit (5);

step 5, preparing a graphene oxide/multi-walled carbon nanotube composite membrane

When the filter flask works, the filter flask needs to be taken down firstly, the basement membrane in the step 1 is placed in the middle of the sand core plate to cover the sand core, the bottom of the filter flask is used for pressing the circumferential edge of the basement membrane to enable the circumferential edge to be exactly aligned with the upper port of the filter flask, and the bottom of the filter flask and the upper port of the suction filtration connector are clamped by a metal clamp; pouring the mixed solution of the graphene oxide and the multi-walled carbon nanotubes prepared in the step (3) into a filter cup, opening a vacuum pump, carrying out suction filtration for 2-12 hours at the pressure of 0.07-0.12 MPa, and closing the vacuum pump when the mixed solution is gradually deposited to a thin film with a smooth plane and no wet layer bulge to obtain a uniform, flat and wet graphene oxide/multi-walled carbon nanotube composite film;

step 6, drying and packaging

Taking out the graphene oxide/multi-walled carbon nanotube composite membrane prepared in the step 5, and drying in a vacuum drying oven at 60-80 ℃ for 40-60 minutes, wherein the vacuum degree is controlled to be 1-10 Pa; then the bracket is taken out and is arranged on the bracket for standby.

2. The preparation method of the graphene oxide/carbon nanotube composite filtering membrane for oil-water separation according to claim 1, wherein a suction filtration adapter (402) is further disposed on the suction filtration connector (4), and the suction filtration adapter (402) is connected to the conduit (5).

3. The preparation method of the graphene oxide/carbon nanotube composite filter membrane for oil-water separation according to claim 1, wherein the thickness of the graphene sheet oxide in step 1 is 0.5-1.2 nm, and the particle size is 0.5-5 μm.

4. The preparation method of the graphene oxide/carbon nanotube composite filter membrane for oil-water separation according to claim 2, wherein the carbon nanotubes in step 1 are COOH-functional multi-wall carbon nanotubes, and have a diameter of 10-200 nm and a length of 10-30 μm.

5. The preparation method of the graphene oxide/carbon nanotube composite filtering membrane for oil-water separation according to claim 2, wherein the thickness of the cellulose microporous filtering membrane in the step 1 is 0.6-2 μm, and the size diameter is 40-50 mm.

6. The preparation method of the graphene oxide/carbon nanotube composite filtering membrane for oil-water separation according to claim 2, wherein a filter cup cover (1) is further disposed on the filter cup (2).

Technical Field

The invention belongs to the technical field of oil-water separation, and particularly relates to a preparation method of an oil-water separation graphene oxide/carbon nano tube composite filtering membrane.

Background

In recent years, the development of strong economy is accelerated, so that serious industrial pollution discharge and frequent marine oil leakage events are caused, people pay more and more attention to the problem of water pollution of domestic water and rivers, and the sewage problem becomes the environmental pollution problem which needs to be solved urgently by national laws and regulations. The membrane separation technology for solving the problem of oil-water separation in sewage is one of the current common technologies due to the characteristics of simple filtration, high efficiency, energy conservation, environmental protection, easy control and the like, and the membrane separation material is the key of the membrane separation technology and determines the main performance index of the membrane technology. The lamellar microporous structure of graphene has an interception characteristic on particulate matters, and is widely used for research on a membrane structure, but cannot be applied on a large scale due to the defects of low dispersion performance and the like, and graphene oxide, which is a derivative material of graphene, has excellent characteristics such as large specific surface area, good bacteriostatic ability and hydrophilicity, compared with the conventional graphene separation membrane, is less prone to aggregation compared with graphene, and the interlayer spacing of GO is more advantageous than that of graphene due to the rich oxygen-containing functional groups (such as epoxy groups, hydroxyl groups, carboxyl groups and the like) on the surface, and the characteristics attract researchers to make extensive research on sewage treatment.

However, the conventional GO membrane process has the disadvantages that need to be further overcome, for example, when the GO filtration membrane is operated for a long time, due to the fact that the membrane surface and the inside are easily scaled by pressure driving, in the later use process, the separation efficiency and the reuse efficiency are reduced, and the reason is that the distance between GO layers is gradually reduced in the use process, so that the membrane flux is reduced, the maintenance cost is increased, the service life is shortened, and the GO filtration membrane process becomes a major disadvantage of the membrane filtration technology. Therefore, the separation membrane with excellent mechanical strength and flexibility is prepared, high-density sub-nanometer micropores with uniform pore size distribution are introduced into the membrane, and the interlayer distance of GO is increased, so that the rapid permeation of water molecules and the effective interception of salt ions/organic molecules become research targets for improving the membrane flux.

The Carbon Nano Tube (CNT) is used as an ideal inorganic additive of the filter membrane, so that the aim is possible, the carbon nano tube has excellent mechanical property and unique pore channel structure characteristic, and the oxidized carbon nano tube increases rich oxygen-containing groups, so that the carbon nano tube has good hydrophilicity, stable chemical property, high specific surface area and good adsorption property, and can provide a good support carrier and a filter medium for the GO membrane. The one-dimensional carbon nano tube and the two-dimensional graphene are used together, so that the composite material with a three-dimensional structure in space can be formed, the contact area of the filler and the matrix is increased, the synergistic effect of the graphene and the carbon nano tube can be exerted, the membrane channel can be constructed, changed and optimized, the permeation effect is improved, and the obtained nano composite material has more excellent desalting and antifouling performance than the single traditional filler modification.

Disclosure of Invention

The invention aims to provide a preparation method of an oil-water separation graphene oxide/carbon nano tube composite filtering membrane, which solves the problems of low flux, complex preparation and high cost existing in the operation of the current oil-water separation membrane.

The technical scheme adopted by the invention is as follows: the preparation method of the graphene oxide/carbon nano tube composite filtering membrane for oil-water separation comprises the following specific operation steps:

step 1, raw material selection

The graphene oxide nano tube membrane comprises lamellar graphene oxide, a carbon nano tube and a base membrane, wherein the base membrane is a cellulose microporous filtering membrane, the aperture of the cellulose microporous filtering membrane is 0.2-0.4 mu m, and the cellulose microporous filtering membrane with the aperture of 0.2-0.4 mu m is subjected to ultrasonic cleaning and drying for later use;

step 2, preparing graphene oxide dispersion liquid and carbon nano tube dispersion liquid

Respectively mixing the graphene oxide and the carbon nano tube in the step 1 with distilled water in a ratio of 1-2: mixing the components according to a mass ratio of 1000, magnetically stirring the components at a speed of 50-150 rpm for 1-3 hours at room temperature, and simultaneously carrying out dispersion regulation and control on the mixed solution with ultrasonic waves of 30-50 kHz to obtain a graphene oxide dispersion liquid and a multi-walled carbon nanotube dispersion liquid;

step 3, preparing a mixed solution of graphene oxide and multi-walled carbon nanotubes

Mixing the graphene oxide dispersion liquid prepared in the step 2 and the multi-walled carbon nanotube dispersion liquid according to the volume capacity of 1: 1-1: 3, and performing dispersion regulation and control on the mixed liquid for 30-60 minutes by using ultrasonic waves of 30-50 kHz to obtain a mixed liquid of graphene oxide and multi-walled carbon nanotubes;

step 4, designing a vacuum filtration device

The vacuum filtration device comprises a conical filter flask, a hourglass-shaped filtration connector is sleeved above the mouth of the filter flask, a filter cup is connected onto the filtration connector, a sand core disc is arranged at the upper port of the filtration connector, a layer of sand core is arranged on the sand core disc, and the lower end of the filter cup is buckled on the sand core disc and is clamped and connected with the filtration connector through a metal clamp;

the lower half part of the suction filtration connector is divided into two layers, the inner layer is used for liquid to pass through, the outer layer is a cavity layer, and the cavity layer is connected with a vacuum pump through a conduit;

step 5, preparing a graphene oxide/multi-walled carbon nanotube composite membrane

When the filter flask works, the filter cup is required to be taken down firstly, the basement membrane in the step 1 is placed in the middle of the sand core plate to cover the sand core, the bottom of the filter cup is used for pressing the circumferential edge of the basement membrane to enable the circumferential edge to be exactly aligned with the upper port of the filter flask, and the bottom of the filter cup and the upper port of the suction filtration connector are clamped by the metal clamp; pouring the mixed solution of the graphene oxide and the multi-walled carbon nanotubes prepared in the step (3) into a filter cup, opening a vacuum pump, carrying out suction filtration for 2-12 hours at the pressure of 0.07-0.12 MPa, and closing the vacuum pump when the mixed solution is gradually deposited to a thin film with a smooth plane and no wet layer bulge to obtain a uniform, flat and wet graphene oxide/multi-walled carbon nanotube composite film;

step 6, drying and packaging

Taking out the graphene oxide/multi-walled carbon nanotube composite membrane prepared in the step 5, and drying in a vacuum drying oven at 60-80 ℃ for 40-60 minutes, wherein the vacuum degree is controlled to be 1-10 Pa; then the bracket is taken out and is arranged on the bracket for standby.

The present invention is also characterized in that,

the suction filtration connector is also provided with a suction filtration adapter nozzle, and the suction filtration adapter nozzle is connected with the guide pipe.

In the step 1, the thickness of the lamellar graphene oxide is 0.5-1.2 nm, and the particle size is 0.5-5 μm.

The carbon nano tube in the step 1 is a COOH functional group multi-wall carbon nano tube, the diameter size is 10-200 nm, and the length is 10-30 mu m.

In the step 1, the thickness range of the cellulose microporous filter membrane is 0.6-2 mu m, and the size diameter is 40-50 mm.

The filter bowl is also provided with a filter bowl cover.

The invention has the beneficial effects that: the preparation method of the oil-water separation graphene oxide/carbon nano tube composite filtering membrane further improves the problems that in the prior art, an oil-water separation membrane in a staggered stack of graphene oxide layers is low in separation efficiency, easy to scale, complex to prepare and difficult to reuse. The carbon nano tubes are used for expanding the spacing between the flaky graphene, the structural stability of the membrane is enhanced, the porosity is improved, the water flow channel is improved, the permeation effect is improved, and the hydrophilicity of the graphene oxide membrane is also greatly improved. The composite membrane prepared by the vacuum filtration technology has uniform pore distribution, high surface flatness and long service life (more cycle times).

Drawings

FIG. 1 is a diagram of a homemade vacuum filtration device of the present invention;

FIG. 2 is a view of a sand core tray apparatus of the present invention;

FIG. 3 is a schematic view of a suction filtration connector of the present invention;

FIG. 4 is a Scanning Electron Microscope (SEM) image of graphene oxide/carbon nanotubes of examples 1-3 of the present invention;

fig. 5 is a water contact angle test chart of graphene oxide/carbon nanotubes according to embodiments 1 to 3 of the present invention;

FIG. 6 is a graph of pure water flux and toluene emulsion rejection for GO/CNTs composite membranes of examples 1-3 of the present invention;

FIG. 7 is a graph of the cycle efficiency of GO/CNTs composite membranes of the present invention;

in the figure, 1, a filter cup cover, 2, a filter cup, 3, a metal clamp, 4, a suction filter connector, 5, a guide pipe, 6, a filter flask, 7, a vacuum pump, 410, a sand core disc, 411, a sand core and 402, a suction filter adapter nozzle.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

All the embodiments of the invention adopt the vacuum filtration device shown in figure 1 for filtration, and the specific structure is as follows: the vacuum filtration device comprises a conical filter flask 6, an hourglass-shaped filtration connector 4 is sleeved above the opening of the filter flask 6, a filter cup 2 is connected onto the filtration connector 4, a sand core disc 410 is arranged at the upper port of the filtration connector 4, a layer of sand core 411 is arranged on the sand core disc 410, and the lower end of the filter cup 2 is buckled on the sand core disc 410 and is connected with the filtration connector 4 in a clamping manner through a metal clamp 3;

the lower half part of the suction filtration connector 4 is divided into two layers, the inner layer is used for liquid to pass through, the outer layer is a cavity layer, and the cavity layer is connected with a vacuum pump 7 through a conduit 5;

the filter bowl 2 is also provided with a filter bowl cover 1.

The suction filtration connector is also provided with a suction filtration adapter 402, and the suction filtration adapter 402 is connected with the conduit 5.

Example 1

The target is as follows: preparing a composite membrane with the volume-volume ratio of graphene oxide to carbon nanotube dispersion liquid being 1:1, comprising the following steps:

step 1, selecting specifications of raw materials, and selecting graphene oxide with the thickness of 0.5nm and the particle size of 0.5 mu m. Carbon nanotubes having a diameter of 10nm and a length of 10 μm. A porous membrane of a base cellulose having a pore diameter of 0.2 μm, a thickness of 0.6 μm and a diameter of 40 mm.

Step 2, preparing graphene oxide dispersion liquid and carbon nanotube dispersion liquid, and mixing the graphene oxide and the carbon nanotubes in the step 1 with distilled water in a ratio of 2: the graphene oxide dispersion liquid and the carbon nanotube dispersion liquid are mixed according to the mass ratio of 1000 mL for standby, and the mixture is magnetically stirred at the speed of 100 revolutions per minute for 1.5 hours at room temperature, and meanwhile, the dispersion of the mixture is regulated and controlled by ultrasonic waves of 45 kHz.

And 3, preparing a multi-walled carbon nanotube/graphene oxide mixed dispersion liquid, mixing the graphene oxide dispersion liquid prepared in the step 2 and the multi-walled carbon nanotube dispersion liquid according to the volume capacity of 1:1 to obtain a 50mL mixed liquid, and performing dispersion regulation on the mixed liquid for 40 minutes by using 35kHz ultrasonic waves.

Step 4, preparing a graphene oxide/multi-walled carbon nanotube composite membrane, firstly taking down a filter cup, placing the basement membrane obtained in the step 1 in the middle of a sand core disc to cover a sand core, pressing the circumferential edge of the basement membrane at the bottom of the filter cup to enable the circumferential edge of the basement membrane to be exactly aligned with the upper port of a filter bottle, and clamping the bottom of the filter cup and the upper port of a suction filtration connector by using a metal clamp; and (3) pouring the mixed solution of the graphene oxide and the multi-walled carbon nanotubes prepared in the step (3) into a filter cup, opening a vacuum pump, carrying out suction filtration for 2 hours at the pressure of 0.08Mpa, and closing the vacuum pump when the dispersion liquid is gradually deposited to a thin film with a smooth plane and no wet layer bulge, so as to obtain the uniform, flat and wet graphene oxide/multi-walled carbon nanotube composite film.

And 5, drying, packaging and sealing, taking the graphene oxide/multi-walled carbon nanotube composite membrane prepared in the step 4 and the base membrane out of the vacuum suction filter, and drying in a vacuum drying oven at 65 ℃ for 45 minutes with the vacuum degree controlled at 5 Pa. Then the stent is taken out and arranged on a special stent for standby.

Example 2

The target is as follows: preparing a composite membrane with the volume-volume ratio of graphene oxide to carbon nanotube dispersion liquid being 1:2, comprising the following steps:

step 1, selecting specifications of raw materials, and selecting graphene oxide with the thickness of 1.2nm and the particle size of 5 microns. Carbon nanotubes having a diameter of 200nm and a length of 30 μm. A base cellulose porous membrane having a pore diameter of 0.4 μm, a thickness of 2 μm and a diameter of 50 mm.

Step 2, preparing graphene oxide dispersion liquid and carbon nanotube dispersion liquid, and mixing the graphene oxide and the carbon nanotubes in the step 1 with distilled water in a ratio of 2: the graphene oxide dispersion liquid and the carbon nanotube dispersion liquid are mixed according to the mass ratio of 1000 mL for standby, and the mixture is magnetically stirred at the speed of 120 r/min for 2.5 hours at room temperature and simultaneously subjected to dispersion regulation and control by ultrasonic waves of 40 kHz.

And 3, preparing a multi-walled carbon nanotube/graphene oxide mixed dispersion liquid, mixing the graphene oxide dispersion liquid prepared in the step 2 and the multi-walled carbon nanotube dispersion liquid according to the volume capacity of 1:2 to form a 50mL mixed liquid, and performing dispersion regulation and control on the mixed liquid for 45 minutes by using 40kHz ultrasonic waves.

Step 4, preparing a graphene oxide/multi-walled carbon nanotube composite membrane, firstly taking down a filter cup, placing the basement membrane obtained in the step 1 in the middle of a sand core disc to cover a sand core, pressing the circumferential edge of the basement membrane at the bottom of the filter cup to enable the circumferential edge of the basement membrane to be exactly aligned with the upper port of a filter bottle, and clamping the bottom of the filter cup and the upper port of a suction filtration connector by using a metal clamp; and (3) pouring the mixed solution of the graphene oxide and the multi-walled carbon nanotubes prepared in the step (3) into a filter cup, opening a vacuum pump, carrying out suction filtration for 12 hours at the pressure of 0.09Mpa, and closing the vacuum pump when the dispersion liquid is gradually deposited to a film with a smooth plane and no wet layer bulge, so as to obtain the uniform, flat and wet graphene oxide/multi-walled carbon nanotube composite film.

And 5, drying, packaging and sealing, taking the graphene oxide/multi-walled carbon nanotube composite membrane prepared in the step 4 and the basement membrane out of a vacuum suction filter, and drying in a vacuum drying oven at 70 ℃ for 50 minutes with the vacuum degree controlled at 8 Pa. Then the stent is taken out and arranged on a special stent for standby.

Example 3

The target is as follows: preparing a composite membrane with the volume-volume ratio of graphene oxide to carbon nanotube dispersion liquid being 1:3, comprising the following steps:

step 1, selecting specifications of raw materials, and selecting graphene oxide with the thickness of 0.8nm and the particle size of 2 microns. Carbon nanotubes having a diameter of 100nm and a length of 25 μm. A porous membrane of a base cellulose having a pore diameter of 0.3 μm, a thickness of 1 μm and a diameter of 45 mm.

Step 2, preparing graphene oxide dispersion liquid and carbon nanotube dispersion liquid, and mixing the graphene oxide and the carbon nanotubes in the step 1 with distilled water in a ratio of 2: the graphene oxide dispersion liquid and the carbon nanotube dispersion liquid are mixed according to the mass ratio of 1000 mL for standby, and the mixture is magnetically stirred at the speed of 130 r/min for 2.5 hours at room temperature and simultaneously subjected to dispersion regulation and control by ultrasonic waves of 45 kHz.

And 3, preparing a multi-walled carbon nanotube/graphene oxide mixed dispersion liquid, mixing the graphene oxide dispersion liquid prepared in the step 2 and the multi-walled carbon nanotube dispersion liquid into a 50mL mixed liquid according to the volume capacity of 1:3, and performing dispersion regulation on the mixed liquid for 55 minutes by using 50kHz ultrasonic waves.

Step 4, preparing a graphene oxide/multi-walled carbon nanotube composite membrane, firstly taking down a cover of a filter cup, placing the base membrane obtained in the step 1 in the middle of a sand core disc to cover a sand core, pressing the circumferential edge of the base membrane at the bottom of the filter cup to enable the circumferential edge of the base membrane to be exactly aligned with the upper port of a filter bottle, and clamping the bottom of the filter cup and the upper port of a suction filtration connector by using a metal clamp; and (3) pouring the mixed solution of the graphene oxide and the multi-walled carbon nanotubes prepared in the step (3) into a filter cup, opening a vacuum pump, carrying out suction filtration for 6 hours under the pressure of 0.1Mpa, and closing the vacuum pump when the dispersion liquid is gradually deposited to a film with a smooth plane and no wet layer bulge, so as to obtain the uniform, flat and wet graphene oxide/multi-walled carbon nanotube composite film.

And 5, drying, packaging and sealing, taking the graphene oxide/multi-walled carbon nanotube composite membrane prepared in the step 4 and the base membrane out of the vacuum suction filter, and drying in a vacuum drying oven at 75 ℃ for 55 minutes with the vacuum degree controlled at 9 Pa. Then the stent is taken out and arranged on a special stent for standby.

The interlayer distance test results of the GO/CNTs composite membrane in the three examples are shown in Table 1, and it can be seen that the interlayer distance of the graphene oxide composite membrane is increased from 0.83nm to 0.96nm along with the increase of the addition amount of the carbon nano tubes.

Table 1 shows the comparison of the interlayer spacing between GO/CNTs composite membranes of examples 1-3

The test results of the surface roughness of the GO/CNTs composite membrane in the three examples are shown in Table 2, the roughness of the GO/CNTs composite membrane is increased, the average roughness (Ra) is increased from 6.556nm to 9.004nm, the surface of the membrane is rougher, the hydrophilicity is stronger, but the organic pollution resistance is weakened.

TABLE 2 roughness of GO/CNTs composite membranes at different content ratios

As can be seen from fig. 4, the sheets of the carbon nanotube intercalated graphene oxide are distributed in a staggered manner between the layers, so that the sheet distance is expanded, and the water flux is increased.

As can be seen from FIG. 5, as the addition amount of the carbon nanotubes is gradually increased, the contact angle of the GO/CNTs composite membrane is reduced from 71.17 degrees to 19.62 degrees, and the hydrophilicity of the membrane surface is further improved.

As can be seen from FIG. 6, the rejection rate of the GO/CNTs separation membrane reaches over 99%, and the highest rejection rate can reach 99.9%.

As can be seen from FIG. 7, after 6 cycles of separation filtration, the GO/CNTs composite membrane still can maintain 99.6% of rejection rate although the separation flux is reduced.