CN110143645B - A solar thermal membrane distillation device - Google Patents

Abstract

The invention discloses a solar photo-thermal membrane distillation device, which sequentially comprises a water feeding cavity, a steam cavity and a condensation water cavity from left to right; the steam cavity is internally provided with an independent photo-thermal evaporation material, a plurality of steam channels and a hydrophobic membrane in sequence from left to right, and the bottom of the independent photo-thermal evaporation material is inserted into the water feeding cavity; the water in the water supply cavity is evaporated by the steam cavity to form steam and then enters the condensation water cavity. The solar photo-thermal membrane distillation device provided by the invention has the characteristics of simple structure and easiness in operation, avoids the membrane pollution problem caused by direct contact between water supply and a membrane, can efficiently collect condensed water, solves the problem of light blocking of the condensed water and steam, and improves the stability of a photo-thermal membrane distillation system and the solar energy utilization efficiency.

Description

A solar thermal membrane distillation device

Technical Field

The invention relates to the technical field of seawater desalination, and in particular to a solar thermal membrane distillation device.

Background technique

With climate change, population growth and economic development, the shortage and pollution of fresh water resources have become increasingly serious and have become a global problem that needs to be solved urgently. As an effective method for producing fresh water, membrane distillation has recently attracted great attention. Membrane distillation is a new membrane separation process that uses a hydrophobic microporous membrane with the vapor pressure difference on both sides of the membrane as the driving force for mass transfer. It has the advantages of low operating temperature (~70°C), relative insensitivity to the salinity of the feed water, and the ability to remove almost all non-volatile solutes. Solar energy is the most widely distributed and largest energy source on the earth. Due to its sustainable and green characteristics, the research and industrial fields have paid extensive attention to the relevant technologies of using solar energy to drive the membrane distillation process in recent years.

In traditional solar-driven water treatment systems, condensed water is difficult to collect, and condensed water and steam block incident light, which seriously weakens the evaporation efficiency and stability of the system. Therefore, the key to achieving efficient water treatment is to design a reasonable water treatment system, efficiently collect condensed water, and solve the problem of condensed water and steam blocking light. Membrane distillation uses the condensed water on the opposite side of the hydrophobic membrane to efficiently collect steam passing through the membrane and solve the problem of blocking light.

In traditional solar-driven membrane distillation systems, the heat energy provided by solar collectors is usually used to heat the feed water to achieve seawater desalination and sewage treatment. This method requires heating the entire feed water, and the heat dissipation through convection and conduction is serious, and the utilization rate of solar energy is low. In 2014, Gang Chen's research group at the Massachusetts Institute of Technology proposed the concept of localized heating, which efficiently utilized solar energy for rapid photothermal evaporation, significantly improving the utilization efficiency of solar energy [H. Ghasemi et al. Nat. Commun. 2014, 5: 4449]. Subsequently, photothermal membrane distillation based on the concept of localized heating was proposed, and the photothermal evaporation material was deposited on the membrane or incorporated into the membrane. Under light, the feed water flowing through the membrane was directly photothermally evaporated to achieve the membrane distillation process [A. Politano et al. Adv. Mater. 2017, 29; 1603504]. Subsequent related studies have further optimized the photothermal membrane distillation system, mainly focusing on the research of photothermal evaporation materials, such as optimizing the light absorption of photothermal evaporation materials [D P. Dongare et al. Proc. Natl Acad. Sci. USA 2017, 114; 6936-6941; L. Huang et al. Desalination 2018, 442; 1-7]. In actual applications, since the photothermal evaporation material is in direct contact with a large amount of feed water, the photothermal evaporation material loses heat to the entire feed water, which seriously weakens the photothermal evaporation efficiency of the system. At the same time, the direct contact between the feed water and the membrane also causes the problem of membrane pollution. Therefore, the reasonable design of the structure of both the photothermal evaporation material and the membrane is the key to achieving long-term stable and efficient water treatment. In addition, the existing solar membrane distillation system is often complex in structure and has high manufacturing cost. For example, the Chinese patent application number CN200520005444.0 discloses a solar membrane distillation device, in which a hot solar heating device is added to the hot working medium heating device, a solar cooling device is used for the cold working medium cooling device, and a solar power generation device is used for the driving device. However, the entire device is relatively large in size and has high system cost. Therefore, it is an urgent need to design a membrane distillation device with compact structure and low cost for practical application.

Summary of the invention

The purpose of the present invention is to provide a solar thermal membrane distillation device with a simple structure and easy operation, which avoids the membrane contamination problem caused by direct contact between feed water and membrane, and significantly improves the stability and solar energy utilization efficiency of the solar thermal membrane distillation device.

The present invention provides the following technical solutions:

A solar thermal membrane distillation device comprises, from left to right, a water supply chamber, a steam chamber, and a condensing water chamber; in the steam chamber, from left to right, independent photothermal evaporation materials, a plurality of water vapor channels, and a hydrophobic membrane are arranged, and the bottom of the independent photothermal evaporation material is inserted into the water supply chamber; the water in the water supply chamber evaporates in the steam chamber to form steam and then enters the condensing water chamber.

A cold liquid tank is arranged in the condensed water chamber to collect water vapor passing through the hydrophobic membrane.

The working process of the solar thermal membrane distillation device provided by the present invention is as follows: the independent photothermal evaporation material absorbs water in the water supply chamber and generates steam, and the generated water vapor passes through the water vapor channel and the hydrophobic membrane in turn and enters the condensation water chamber, and the distillation process is completed after condensation.

The water supply chamber is provided with a light-transmitting glass plate, which is in close contact with the light-receiving side of the independent photothermal evaporation material and is used to transmit sunlight and maintain the airtightness of the device.

Preferably, the water supply chamber comprises a light-transmitting glass plate and a water supply trough. The bottom of the independent photothermal evaporation material is inserted into the water supply chamber. Preferably, the light-transmitting glass plate and the water supply trough are integrated.

The water vapor channel is formed by separating the independent photothermal evaporation material and the hydrophobic film with a spacer, and the width of the water vapor channel is 0.1-10 mm.

The water vapor channel is formed by being surrounded by the independent photothermal evaporation material and the hydrophobic membrane, and is used to enrich the steam generated by the independent photothermal evaporation material and separate the water supply and the hydrophobic membrane.

The width of the water vapor channel is the key to achieving long-term stability and high efficiency in the membrane distillation process. When the width is too large, the steam transmission resistance and the heat loss of the system will increase; when the width is too small, the processing and operation complexity of the system will increase, and there is a risk of membrane contamination.

Preferably, the width of the water vapor channel is 1-3 mm, which can reduce both heat loss and the hidden danger of membrane pollution.

A raw water inlet is provided at the upper part of the water supply chamber, and a concentrated water outlet is provided at the lower part of the water supply chamber. Raw water is input into the water supply chamber through the raw water inlet, and the raw water evaporated and concentrated by the steam chamber is discharged from the concentrated water outlet.

A condensate inlet is provided at the lower part of the condensate chamber, and a condensate outlet is provided at the upper part of the condensate chamber. The condensate input from the condensate inlet condenses the steam and is collected and then discharged from the condensate outlet.

The hydrophobic membrane is a flat membrane with or without a support, and the pore size of the hydrophobic membrane is 0.1-0.5 μm.

The material of the hydrophobic membrane is selected from polytetrafluoroethylene, polypropylene or polyvinylidene fluoride.

Preferably, the hydrophobic membrane is a flat membrane with a support, a pore size of 0.1-0.3 μm, and is made of polyvinylidene fluoride.

Preferably, the solar thermal membrane distillation device also includes a water feed pump, a condensing water pump, a liquid storage tank and a driving device, wherein the driving device drives the feed water in the water feed storage tank to flow through the water feed tank, and the driving device drives the condensed water in the condensing water storage tank to flow through the cold liquid tank.

Preferably, the driving device is a solar panel.

The independent photothermal evaporation material includes a support body and a light absorber covered on the outer surface of the support body, wherein the support body is nickel foam, the light absorber is vertically oriented graphene, and the vertically oriented graphene is covered with a hydrophilic coating; the independent photothermal evaporation material is used to absorb raw water in the water supply cavity and generate steam. The independent photothermal evaporation material captures solar energy and converts light energy into heat energy, quickly generating a local high temperature area.

The vertically oriented graphene covered with a hydrophilic coating is composed of a carbon nanowall array. The nickel foam is a porous structure.

The vertically oriented graphene sprayed on the surface serves as a water transport channel, which transfers the feed water to the local high-temperature area through capillary action to quickly generate photothermal steam; this solves the heat loss problem caused by the direct contact between the photothermal evaporation material and the feed water in the conventional photothermal membrane distillation system, and improves the photothermal evaporation efficiency of the system; at the same time, it realizes the separation of the feed water and the membrane, solves the membrane pollution problem caused by the direct contact between the membrane and the feed water in the conventional membrane distillation system, and improves the long-term stability of the system.

The light absorber has a light absorbency of 90-99%. Preferably, the light absorber has a light absorbency of 96.0-98.0%.

The preparation method of the independent photothermal evaporation material comprises the following steps:

(1) placing nickel foam in a plasma enhanced chemical vapor deposition reaction chamber, introducing methane or a mixture of hydrogen and methane, performing a chemical vapor deposition reaction, introducing an inert gas, and cooling to obtain vertically oriented graphene/nickel foam;

(2) washing the vertically oriented graphene/nickel foam obtained in step (1) with acetone, methanol, and deionized water, and then drying in a dry atmosphere;

(3) The vertically oriented graphene/nickel foam surface obtained in step (2) is uniformly sprayed with the solution using a spray gun, and allowed to stand in the air to dry, thereby forming an ultra-clear water coating on the vertical graphene surface to obtain a free-standing photothermal evaporation material.

In the step (1), the flow ratio of the mixed gas of hydrogen and methane is 0-20:1.

Preferably, the flow ratio of the mixed gas of hydrogen and methane in step (1) is 0-15: 1. The flow ratio of hydrogen and methane is the key to synthesizing vertically oriented graphene. When the flow ratio of the mixed gas is greater than 15: 1, the obtained product is not vertically oriented graphene.

Preferably, the flow ratio of the mixed gas in step (1) is 1-5: 1. When the flow ratio is less than 1: 1, the synthesis speed is slow; when the flow ratio is greater than 5: 1, the morphology and chemical properties of the obtained product are closer to amorphous carbon, carbon nanofibers and carbon nanotubes.

In the step (1), the reaction conditions of the chemical vapor deposition reaction are: the synthesis gas pressure is 1-1000 Pa; the synthesis temperature is 400-1000°C.

Preferably, in step (1), the synthesis temperature is 500-1000°C and the synthesis gas pressure is 10-1000Pa.

When the gas pressure is <1Pa, the process requirements for the synthesis equipment are high and difficult to achieve; when the gas pressure is >1000Pa, the energy consumption is high and it is not conducive to practical application. When the temperature is <400℃, vertically oriented graphene cannot be synthesized; when the temperature is >1000℃, the process requirements for the equipment are high and a large input power is required, which is not conducive to practical application.

Preferably, in step (1), the reaction conditions of the chemical vapor deposition reaction are: synthesis gas pressure is 50-500 Pa, and synthesis temperature is 600-800°C.

In the step (1), the plasma source in the chemical vapor deposition reaction is selected from microwave plasma, with a power of 200-400W and maintained for 10-180min.

When the time is <10 min, the amount of vertically oriented graphene synthesized is small and the light absorption rate is low; when the time is greater than >180 min, there is no obvious improvement in the light absorption rate, but the energy and raw material consumption are large.

Preferably, the microwave plasma is maintained for 30-120 min.

In the step (1), an inert gas is used as a cooling gas.

In the step (2), an inert gas is used as a drying gas.

In the step (3), the poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) solution is used as the spraying solution, and the number of spraying times is 1 to 10 times.

Preferably, the number of spraying times is 3-6 times. Within this range, the vertically oriented graphene with the coating on the surface can obtain good hydrophilicity, and the coating will not completely cover the nanosheet structure of the vertically oriented graphene.

The present invention optimizes the structures of both photothermal evaporation materials and hydrophobic membranes to provide a solar thermal membrane distillation device with a simple structure and easy operation, thereby avoiding the membrane contamination problem caused by direct contact between feed water and the membrane, being able to efficiently collect condensed water and solving the light blocking problem of condensed water and steam. The stability of the solar thermal membrane distillation device and the solar energy utilization efficiency are significantly improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a solar thermal membrane distillation device provided in Example 1;

FIG2 is a schematic diagram of the connection of the solar thermal membrane distillation device provided in Example 1;

FIG3 is a schematic diagram of the photothermal evaporation principle of the solar thermal membrane distillation device provided in Example 1;

FIG4 is a flow chart of the preparation of a stand-alone photothermal evaporation material for a solar photothermal membrane distillation device provided by the present invention.

Detailed ways

In order to make the present invention more clearly understood, the present invention is further described below in conjunction with specific embodiments and with reference to the accompanying drawings. The embodiments described below are only used to explain the present invention and have no limitation on the present invention in form or substance.

As shown in Figure 4, the preparation process of independent photothermal evaporation materials uses plasma enhanced chemical vapor deposition to prepare vertically oriented graphene, and spraying to prepare ultra-clear water coatings.

The following performance tests were performed on the independent photothermal evaporation material provided by the present invention:

1. Water contact angle: The contact angle of water on the surface of the stand-alone photothermal evaporation material and the membrane was measured using a contact angle meter model DropMeter A-200 to characterize the hydrophilicity of the material. A 5 μL water droplet was dropped on the surface of the material using an electric pump, and the change process of the water droplet was recorded using a high-speed camera. The water contact angle was calculated using the Young-Laplace equation.

2. Absorbance: Use UV-3150UV-VIS ultraviolet-visible spectrophotometer to measure the light reflectance and light transmittance of the independent photothermal evaporation material in the 200-2600 nanometer band. Use the formula: light absorbance = 1-light reflectance-light transmittance to calculate the average light absorbance.

Embodiment 1:

As shown in Figures 1 and 2, the solar thermal desalination device provided by the present invention includes: a transparent glass plate 1, an independent photothermal evaporation material 2, a hydrophobic membrane 3, a water vapor channel 4, a liner 5, a water supply tank 6, a cold liquid tank 7, a raw water inlet 8, a concentrated water outlet 9, a condensed water inlet 10, a condensed water outlet 11, a solar cell 12, a water supply pump 13, a condensed water pump 14, a water supply tank 15, and a condensed water tank 16. Among them, the transparent glass plate 1 and the water supply tank 6 constitute a water supply chamber, the upper part of the water supply chamber is provided with a raw water inlet 8, and the lower part of the water supply chamber is provided with a concentrated water outlet 9. The independent photothermal evaporation material 2, the hydrophobic membrane 3, the water vapor channel 4 and the liner 5 constitute an evaporation chamber. The lower part of the condensation chamber is provided with a condensed water inlet 10, and the upper part of the condensation chamber is provided with a condensed water outlet 11.

As shown in Figures 1 and 2, the electric energy provided by the solar panel 12 drives the water supply pump 13 and the condensate pump 14 to operate continuously; the water supply is injected into the water supply tank 6 through the raw water inlet 8; a water vapor channel 4 is formed by a spacer 5 between the independent photothermal evaporation material 2 and the hydrophobic membrane 3; the other side of the hydrophobic membrane 3 is a cold liquid tank 7; the condensed water is injected into the cold liquid tank 7 through the condensate inlet 10; the light-transmitting glass plate 1 is close to the light-receiving side of the independent photothermal evaporation material 2, which not only plays the role of closing the membrane distillation device, but also plays the role of guiding water vapor to the water vapor channel 4; the bottom of the independent photothermal evaporation material 2 is inserted into the water supply tank 6, absorbs solar energy, and converts light energy into heat energy to evaporate the water supply; water vapor is enriched in the water vapor channel 4, and then passes through the hydrophobic membrane 2 to condense, and the cold liquid tank 7 collects the condensed fresh water; the pore size of the hydrophobic membrane 3 is 0.3μm; the width of the water vapor channel 4 is 1mm. During the operation of the solar thermal membrane distillation device, the raw water inlet 8, the concentrated water outlet 9, the condensed water inlet 10, and the condensed water outlet 11 are all kept open; the feed water storage tank 15 and the condensed water storage tank 16 are both maintained at a certain water level. When the device stops working, the fresh water in the condensed water storage tank 16 can be transferred and used.

As shown in FIG3 , the independent photothermal evaporation material 2 includes a support 17 and a light absorber 18 covering the outer surface of the support 17 , wherein the light absorber 18 is vertically oriented graphene with a super-hydrophilic coating sprayed on the surface, and the support 17 is nickel foam.

The light absorber 18 captures solar energy and converts it into heat energy to form a local high temperature zone; the support body 17 plays a mechanical support role, separating the light absorber 18 and the hydrophobic membrane 3. At the same time, the light absorber 18 also serves as a water supply channel 19, which transports the water supply 20 through capillary action so that it reaches the local high temperature area to achieve rapid photothermal evaporation. At the same time, the water supply channel 19 can protect the hydrophobic membrane 3, prevent the hydrophobic membrane 3 from directly contacting the water supply 20, and solve the problem of membrane contamination; in addition, the water supply channel 19 can prevent the light absorber 18 from directly transferring the heat flow to the water supply 20, thereby reducing energy loss.

The preparation method of the independent photothermal evaporation material 2 is as follows:

1. Place the nickel foam in a plasma enhanced chemical vapor deposition reaction chamber, evacuate to <10Pa, and then heat to 800°C;

2. Open the _CH4 and _H2 gas valves, and introduce a mixture of _CH4 and _H2 , where the flow rate of _H2 is 5 ml min ^-1 , the flow rate of _CH4 is 5 ml min ^-1 , and the gas pressure is adjusted to 100 Pa;

3. Turn on the inductively coupled plasma source, adjust the power to 250W, and maintain for 120 minutes;

4. Turn off the plasma source, close the _CH4 and _H2 gas valves, open the Ar gas valve, introduce Ar as a cooling gas, wait until it cools to room temperature, and take out the vertically oriented graphene/graphene foam;

5. The obtained vertically oriented graphene/nickel foam surface was sprayed three times with a spray gun, and the poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) solution was evenly sprayed on it, and it was left to dry in the air to form an ultra-clear water coating on the vertical graphene surface to obtain a free-standing photothermal evaporation material.

The prepared independent photothermal evaporation material has a black outer surface. The independent photothermal evaporation material treated by surface spraying shows strong hydrophilicity, and the water contact angle is 20.4°, indicating that the light absorber can be transferred to water through capillary action.

The microstructure of the free-standing photothermal evaporation material exhibits a three-dimensional porous structure; the vertically oriented graphene is composed of carbon nanowalls and is evenly distributed on the skeleton of nickel foam.

The average light absorption rate of the independent photothermal evaporation material in the 200-2600 nanometer band is as high as 98.0%; the vertically oriented carbon nanowall prevents the escape of incident light and has a strong light capture ability.

The bottom of the independent photothermal evaporation material 2 is inserted into the water supply tank 6 to absorb solar energy and convert light energy into heat energy to evaporate water; water vapor is enriched in the water vapor channel 4, and then condensed through the hydrophobic membrane 3, and the cold liquid tank 7 collects the condensed fresh water. Under the light intensity of 1kW m ^-2 , the solar energy utilization efficiency of the material is 69.2%.

The solar thermal membrane distillation device provided by the present invention is used to perform membrane distillation on natural seawater with a salinity of 3.25%, and the desalination rate reaches 99.5%, which meets the drinking requirements; the membrane distillation treatment of artificial salt water with a salinity of 9.85% reaches a desalination rate of 99.4%, which meets the drinking requirements; the membrane distillation treatment of artificial salt water with a salinity of 16.7% reaches a desalination rate of 99.2%, which meets the drinking requirements. The membrane distillation treatment of oil-water mixture (natural seawater: 3.25%; mineral oil: 1g L ^-1 ) reaches a desalination rate of 99.1%, and the total organic carbon content of condensed water is maintained below 5mg L ^-1 , which meets the drinking requirements.

After treating the oil-water mixture (natural seawater: 3.25%; mineral oil: 1 g L ^-1 ) for 60 hours, there was no visible oil contaminant attached to the surface of the hydrophobic membrane, and the water contact angle was 128.1°, proving that the membrane still retained strong hydrophobicity.

Example 2

The solar thermal membrane distillation device used in this embodiment is as described in Example 1, wherein the pore size of the hydrophobic membrane 3 is 0.1 μm; the width of the water vapor channel 4 is 3 mm; and the preparation method of the independent photothermal evaporation material 2 is as follows:

1. Place the nickel foam in a plasma enhanced chemical vapor deposition reaction chamber, evacuate to <10Pa, and then heat to 700°C;

2. Open the CH ₄ and H ₂ gas valves, and introduce a mixture of CH ₄ and H ₂ , wherein the flow rate of H ₂ is 5 ml min ^-1 , the flow rate of CH ₄ is 5 ml min ^-1 , and the gas pressure is adjusted to 50 Pa;

3. Turn on the inductively coupled plasma source, adjust the power to 250 W, and maintain for 60 minutes;

4. Turn off the plasma source, close the _CH4 and _H2 gas valves, open the Ar gas valve, introduce Ar as a cooling gas, wait until it cools to room temperature, and take out the vertically oriented graphene/graphene foam;

5. The obtained vertically oriented graphene/nickel foam surface was sprayed 6 times with a spray gun, and the poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) solution was evenly sprayed on it, and it was left to dry in the air to form an ultra-clear water coating on the vertical graphene surface to obtain a free-standing photothermal evaporation material.

The performance test results of this embodiment are shown in Table 1.

Example 3

The solar thermal membrane distillation device used in this embodiment is as described in Example 1, wherein the pore size of the hydrophobic membrane 3 is 0.2 μm; the width of the water vapor channel 4 is 2 mm; and the preparation method of the independent photothermal evaporation material 2 is as follows:

1. Place the nickel foam in a plasma enhanced chemical vapor deposition reaction chamber, evacuate to <10Pa, and then heat to 650°C;

2. Open the _CH4 and _H2 gas valves, and introduce a mixture of _CH4 and _H2 , wherein the flow rate of _H2 is 5 ml min ^-1 , the flow rate of _CH4 is 5 ml min ^-1 , and the gas pressure is adjusted to 400 Pa;

3. Turn on the inductively coupled plasma source, adjust the power to 250W, and maintain for 30 minutes;

4. Turn off the plasma source, close the _CH4 and _H2 gas valves, open the Ar gas valve, introduce Ar as a cooling gas, wait until it cools to room temperature, and take out the vertically oriented graphene/graphene foam;

5. The obtained vertically oriented graphene/nickel foam surface was sprayed 4 times with a spray gun, and the poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) solution was evenly sprayed on it, and it was left to dry in the air to form an ultra-clear water coating on the vertical graphene surface to obtain a free-standing photothermal evaporation material.

The performance test results of this embodiment are shown in Table 1.

Example 4

The solar thermal membrane distillation device used in this embodiment is as described in Example 1, wherein the pore size of the hydrophobic membrane 3 is 0.22 μm; the width of the water vapor channel 4 is 1.5 mm; and the preparation method of the independent photothermal evaporation material 2 is as follows:

1. Place the nickel foam in a plasma enhanced chemical vapor deposition reaction chamber, evacuate to <10Pa, and then heat to 600°C;

2. Open the _CH4 and _H2 gas valves, and introduce a mixture of _CH4 and _H2 , wherein the flow rate of _H2 is 5 ml min ^-1 , the flow rate of _CH4 is 5 ml min ^-1 , and the gas pressure is adjusted to 500 Pa;

3. Turn on the inductively coupled plasma source, adjust the power to 250 W, and maintain for 90 minutes;

4. Turn off the plasma source, close the _CH4 and _H2 gas valves, open the Ar gas valve, introduce Ar as a cooling gas, wait until it cools to room temperature, and take out the vertically oriented graphene/graphene foam;

5. The obtained vertically oriented graphene/nickel foam surface was sprayed 5 times with a spray gun, and the poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) solution was evenly sprayed on it, and it was left to dry in the air to form an ultra-clear water coating on the vertical graphene surface to obtain a free-standing photothermal evaporation material.

The performance test results of this embodiment are shown in Table 1.

Table 1 Performance test results of solar thermal desalination devices prepared in Examples 1-4

The above is a detailed description of the present invention in combination with the embodiments, but the implementation methods of the present invention are not limited to the above embodiments, and any other changes, replacements, combined simplifications, etc. made under the core guiding idea of the patent of the present invention are included in the protection scope of the patent of the present invention.

Claims (7)

1. The solar photo-thermal membrane distillation device is characterized by sequentially comprising a water supply cavity, a steam cavity and a condensation water cavity from left to right; the steam cavity is internally provided with an independent photo-thermal evaporation material, a plurality of steam channels and a hydrophobic membrane in sequence from left to right, and the bottom of the independent photo-thermal evaporation material is inserted into the water feeding cavity; the water supply in the water supply cavity is evaporated by the steam cavity to form steam and then enters the condensation water cavity;

the water vapor channel is formed by surrounding an independent photo-thermal evaporation material and a hydrophobic film, the water vapor channel is formed by separating the independent photo-thermal evaporation material and the hydrophobic film by a spacer, and the width of the water vapor channel is 0.1-10 mm;

The independent photo-thermal evaporation material comprises a support body and a light absorber covered on the outer surface of the support body, wherein the support body is foam nickel, the light absorber is vertically oriented graphene, and the vertically oriented graphene is covered with a hydrophilic coating; the independent photo-thermal evaporation material is used for absorbing raw water in the water feeding cavity and generating steam;

the independent photo-thermal evaporation material sequentially comprises a hydrophilic coating, vertically oriented graphene and a support body from left to right;

the preparation method of the independent photo-thermal evaporation material comprises the following steps:

(1) Placing the foam nickel in a plasma enhanced chemical vapor deposition reaction cavity, introducing methane or a mixed gas of hydrogen and methane, performing chemical vapor deposition reaction, introducing inert gas, and cooling to obtain vertically oriented graphene/foam nickel;

(2) Washing the vertically oriented graphene/foam nickel obtained in the step (1) with acetone, methanol and deionized water, and then drying in a dry atmosphere;

(3) Uniformly spraying a solution on the surface of the vertical oriented graphene/foam nickel obtained in the step (2) by using a spray gun, standing and drying in air, and forming a super-hydrophilic coating on the surface of the vertical graphene to obtain an independent photo-thermal evaporation material; wherein, the poly (3, 4-ethylenedioxythiophene) -poly (styrenesulfonic acid) solution is used as the spraying solution.

2. The solar photothermal membrane distillation apparatus according to claim 1, wherein the water supply chamber is provided with a light-transmitting glass plate, and the light-transmitting glass plate is closely attached to the light-receiving side of the independent photothermal evaporation material.

3. The solar photo-thermal membrane distillation apparatus according to claim 1, wherein the upper portion of the water supply chamber is provided with a raw water inlet, the lower portion of the water supply chamber is provided with a concentrated water outlet, raw water is input into the water supply chamber through the raw water inlet, and raw water evaporated and concentrated through the steam chamber is discharged from the concentrated water outlet.

4. The solar photo-thermal membrane distillation apparatus according to claim 1, wherein a condensate water inlet is provided at a lower portion of the condensate water chamber, a condensate water outlet is provided at an upper portion of the condensate water chamber, and condensate water inputted from the condensate water inlet condenses and collects steam and then discharges the steam from the condensate water outlet.

5. The solar photo-thermal membrane distillation apparatus according to claim 1, wherein the hydrophobic membrane is a flat membrane with or without a support, and the pore size of the hydrophobic membrane is 0.1-0.5 μm.

6. The solar photo-thermal membrane distillation apparatus according to claim 1 or 5, wherein the hydrophobic membrane is made of polytetrafluoroethylene, polypropylene or polyvinylidene fluoride.

7. The solar photothermal membrane distillation apparatus of claim 1, wherein the absorbance of the light absorber is 90-99%.