阅读说明：本技术 一种海水持续淡化装置及方法 (Continuous seawater desalination device and method ) 是由 侯旭 谢歆雯 王苗 邓文燕 熊辉 何文 于 2019-09-27 设计创作，主要内容包括：本发明涉及海水持续淡化装置及方法。本发明将碳纳米管或石墨烯等一类碳基材料复合疏水聚合物制备得到一种疏水碳基复合膜,通过激光打孔获得具有微-纳米多级孔结构的疏水碳基复合膜,进一步在其表面涂覆有光热/电热响应性的聚合物分子,增强其电焦耳热和光热效应以提高能源利用率,最终获得兼具多级孔道结构和电热、光热效应的疏水碳基复合膜。设计相应器件将该疏水碳基复合多孔膜应用于电热/光热驱动海水淡化过程,控制条件使该疏水碳基复合多孔膜发热,热量作为热源为水相变过程提供传质驱动力,冷凝回收水蒸气最终实现海水脱盐。本发明结合热相变过程和膜法,能够实现电热-光热交替24小时持续海水淡化。(The invention relates to a device and a method for continuously desalting seawater. According to the invention, a hydrophobic carbon-based composite membrane is prepared by compounding carbon-based materials such as carbon nanotubes or graphene with a hydrophobic polymer, the hydrophobic carbon-based composite membrane with a micro-nano hierarchical pore structure is obtained by laser drilling, and polymer molecules with photo-thermal/electric-thermal responsiveness are further coated on the surface of the hydrophobic carbon-based composite membrane, so that the electric joule heat and the photo-thermal effect of the hydrophobic carbon-based composite membrane are enhanced to improve the energy utilization rate, and the hydrophobic carbon-based composite membrane with a hierarchical pore structure and the electric-thermal and photo-thermal effects is finally obtained. Corresponding devices are designed to apply the hydrophobic carbon-based composite porous membrane to an electric heating/photo-thermal driving seawater desalination process, conditions are controlled to enable the hydrophobic carbon-based composite porous membrane to generate heat, heat is used as a heat source to provide a mass transfer driving force for a water phase change process, and water vapor is condensed and recovered to finally realize seawater desalination. The invention combines the thermal phase change process and the membrane method, and can realize the continuous seawater desalination of 24 hours by alternating electric heat and light heat.)

1. A continuous seawater desalination device is characterized by comprising:

carbon-based composite membrane unit: the carbon-based composite membrane unit comprises a carbon nano tube composite porous membrane, the carbon nano tube composite porous membrane is a hydrophobic carbon-based composite membrane prepared by compounding a carbon-based material with a hydrophobic polymer, and the hydrophobic carbon-based composite membrane with a micro-nano hierarchical pore structure is obtained by punching;

a power supply unit: the power supply unit is a solar power supply unit and provides electric energy for the carbon-based composite film unit;

the fresh water collecting unit is used for collecting the fresh water treated by the carbon-based composite membrane unit;

in the daytime, under the illumination condition, the carbon-based composite porous membrane performs photothermal conversion to provide heat and mass transfer driving force for a system, so that the seawater desalination process is completed, and meanwhile, the solar cell panel of the power supply unit is used for storing light energy in an electric energy form; under the condition of insufficient illumination in daytime or at night, the electric energy stored by the solar cell panel supplies power to the carbon-based composite membrane unit, so that joule heat is generated to provide heat and mass transfer driving force for the system, the seawater desalination process is carried out, and the electric heating-photo-thermal alternative continuous seawater desalination is realized in a circulating manner.

2. The continuous seawater desalination device of claim 1, wherein: the hydrophobic carbon-based composite membrane prepared by compounding the carbon-based material with the hydrophobic polymer is further coated with photo-thermal/electric-thermal responsive metal complex molecules on the surface of the hydrophobic carbon-based composite membrane so as to enhance the electric joule heat and photo-thermal effect of the hydrophobic carbon-based composite membrane.

3. The continuous seawater desalination device of claim 1, wherein: the punching area is 5mm multiplied by 5mm, the punching area is provided with 30-100 holes, and the aperture of each hole is 50-120 mu m.

4. The continuous seawater desalination device of claim 1, wherein: the carbon nanotube composite porous membrane is connected with the electrode, and the carbon-based composite porous membrane and the electrode are packaged by adopting a sandwich structure.

5. A continuous desalination plant of seawater as defined in claim 4, characterized in that: the packaging structure is formed by sequentially overlapping a polymethyl methacrylate plate, silica gel, a carbon-based composite porous membrane/electrode, silica gel and a polymethyl methacrylate plate.

6. A continuous desalination plant of seawater as defined in claim 4, characterized in that: the electrode connection structure includes: the titanium electrode comprises a titanium electrode anode, a titanium electrode cathode, a screw hole groove, a carbon film position area and a carbon film; and the upper and lower edges of each carbon film are tightly bonded with the upper and lower edges of the interdigital parts of the anode and the cathode of the titanium electrode respectively by using conductive silver adhesive, and the left and right edges of the carbon film are not bonded with the titanium electrode.

7. A continuous desalination plant of seawater as defined in claim 4, characterized in that: the seawater desalination device comprises a shell and a top cover, wherein a seawater storage tank is arranged at the bottom of the shell, a carbon-based composite porous membrane and electrodes which are packaged by a sandwich structure are arranged on the seawater storage tank, the carbon-based composite porous membrane is in contact with seawater, the water phase is changed by heat generated by the carbon-based composite porous membrane, vaporized water molecules pass through a micro-nano pore system in the carbon-based composite porous membrane and reach the inner surface of the top cover, and after condensation, pure water is finally gathered in a pure water collecting tank along the gradient of the inner surface and is led out from.

8. A method for continuously desalinating seawater is characterized by comprising the following steps: in the daytime, under the illumination condition, the carbon-based composite porous membrane performs photothermal conversion to provide heat and mass transfer driving force for a system, so that the seawater desalination process is completed, and meanwhile, the solar cell panel is used for storing light energy in an electric energy form; under the condition of insufficient illumination in the daytime or at night, the electric energy stored by the solar cell panel supplies power to the carbon-based composite membrane unit, so that joule heat is generated to provide heat and mass transfer driving force for the system, the seawater desalination process is carried out, and the continuous seawater desalination of 24 hours by alternating electric heating and light heating is realized through the circulation.

9. The method for continuously desalinating seawater according to claim 8, wherein: the voltage of the direct current is 5-30V.

10. The method for continuously desalinating seawater according to claim 8, wherein: use of a continuous desalination plant according to any one of claims 1 to 7.

Technical Field

The invention relates to a novel energy-saving seawater desalination method, which is based on the efficient photo-thermal conversion efficiency and the electrified Joule thermal effect of carbon-based materials such as carbon nano tubes or graphene and the like, and combines thermal phase change and evaporative mass transfer to realize the seawater desalination process.

Background

With growing population and increasing water pollution, water shortage has become one of the most serious global challenges facing human society. The seawater desalination technologies developed to date and used commercially on a large scale include Reverse Osmosis (RO), Electrodialysis (ED), multi-stage flash evaporation (MSF), low-temperature multi-effect (MED), etc., which have high efficiency desalination and cause energy consumption problems in equipment operation, while the solar seawater desalination technology is considered to be a promising technology due to its advantages of low energy consumption, low cost, high energy conversion efficiency, environmental friendliness, etc. At present, interface solar energy driven steam generation is realized in the field of solar seawater desalination through methods such as photon management, nanoscale thermal regulation and control, development of novel photo-thermal conversion materials, design of efficient light absorption solar distillers and the like, and the green and sustainable seawater desalination technology becomes a research hotspot in recent years. Carbon-based materials such as carbon nanotubes, graphene, carbon black, graphite, and the like have light absorption capability covering the entire sunlight spectrum, and are novel photothermal conversion materials.

For example, CN200910169726.7 provides a method for efficiently desalinating seawater by absorbing solar energy with carbon nanotubes: the conversion of light energy to heat energy is realized by utilizing the carbon nano tube, and the heat energy on the surface of the carbon nano tube is taken away and transferred to seawater by utilizing the carrier gas which flows circularly; the carrier gas enters the seawater storage tank to divide the seawater into an upper layer and a lower layer with different temperatures and concentrations; the upper layer seawater, the lower layer seawater and the carrier gas realize the separation of the fresh water and the concentrated seawater through the continuous heat, mass and momentum transfer process. CN201710591777.3 discloses a solar seawater desalination or sewage treatment method based on carbon nanotube film. The invention takes a carbon nano tube vertical array directly prepared by a chemical vapor deposition method as a raw material, and a carbon nano tube vertical array film with strong light absorption and surface hydrophilicity is obtained by processing; placing the hydrophilic carbon nanotube film on the surface of water to be treated; the carbon nano tube film can absorb light efficiently and perform photothermal conversion, so that water is heated to cause rapid evaporation of water, and the steam is condensed to obtain purified water.

However, the solar seawater desalination process is influenced by the sunlight intensity, and the four seasons and the regional limitations related to the sunlight intensity make the traditional solar seawater desalination process incapable of continuously and efficiently desalinating seawater under natural conditions.

CN201810956984.9 provides a carbon nanotube-cellulose acetate membrane for efficiently desalting seawater and a preparation method thereof. The method comprises the steps of introducing the magnetized carbon nano tubes into a cellulose acetate reverse osmosis membrane, aligning the carbon nano tubes to form a permeation channel through a magnetic field, applying a high-frequency pulse magnetic field to enable the carbon nano tubes to perform micro-oscillation when in use, weakening the interaction between water molecules and cellulose acetate, and promoting the water molecules to pass through a membrane layer. Compared with the traditional method, the carbon nanotube-cellulose acetate membrane prepared by the method can still maintain higher desalination rate and water flux after being used for a long time, and has high seawater desalination efficiency and long service life.

However, it still does not solve the technical problem of continuous desalination of seawater.

Disclosure of Invention

The invention provides an electric heating-photo-thermal alternative continuous seawater desalination system based on the electric joule heating effect and photo-thermal conversion effect of carbon-based materials such as carbon nano tubes or graphene, and the like: under the daytime illumination condition, the system can store part of solar energy in the form of electric energy on one hand, and on the other hand, the carbon-based composite porous membrane can directly absorb the energy in sunlight and complete photothermal conversion, and the heat promotes water molecules to evaporate and pass through micro-nano multistage pore channels of the composite membrane to collect the evaporated water molecules, thereby finally realizing solar seawater desalination; in the daytime, when the illumination is insufficient or at night, the system can release electric energy, the carbon-based composite porous membrane generates joule heat under the action of voltage, the joule heat drives water molecules to evaporate and collect the evaporated water molecules through micro-nano multistage pore channels, and finally the solar seawater desalination is realized. The system realizes an efficient and energy-saving seawater desalination process, solves the common technical problems of corrosion resistance, pollution resistance and the like of a membrane material, utilizes the excellent conductivity, light absorption characteristic and anti-pollution salt-blocking effect of the carbon-based composite membrane, and combines a solar cell system to realize 24-hour uninterrupted, alternate and continuous seawater desalination.

1. The carbon nano tube is used as a carbon-based material in the method, the material has light absorption capacity covering the whole sunlight spectrum and excellent photo-thermal conversion characteristic, the material shows stronger joule heat effect and electrochemical corrosion resistance under the electrified condition, and a multi-level and multi-scale pore system in the material can continuously and efficiently provide structural support for the water and salt conveying process, so that the material is a novel photoelectric double-response seawater desalination membrane material.

2. The method uses a laser drilling method to construct a micro-nano multistage pore structure, and the structure has the characteristics of high-efficiency ion interception and rapid water transportation capability.

3. In the implementation process of the method, the hydrophobic polymer is used as a structural support, and the compounded carbon-based composite membrane has better mechanical strength (no deformation after being soaked in salt water for 30 minutes).

4. In the implementation process of the method, carbon nanotubes or graphene and other carbon-based materials can still keep good hydrophobicity under a long-time electrifying condition (the contact angle between the surface of the membrane and 100g/L NaCl solution can still keep more than 120 degrees after electrifying for 1.5 hours), and the membrane wetting barrier of the traditional commercial separation membrane in practical application is broken through, referring to FIG. 5.

5. In the implementation process of the method, the interdigital electrodes are connected with the carbon-based composite porous membrane in parallel, so that each membrane can reach the highest temperature under the same voltage, as shown in fig. 3 (a).

6. In the implementation process of the method, the carbon-based composite porous membrane and the electrode are packaged by adopting a sandwich structure, namely a polymethyl methacrylate (PMMA) plate-silica gel-carbon-based composite porous membrane/electrode-silica gel-polymethyl methacrylate (PMMA) plate are sequentially superposed, and the sandwich structure can effectively reduce the electrochemical corrosion of the carbon-based composite porous membrane and the electrode material and avoid the circuit aging.

7. Compared with the traditional commercial separation membrane, the carbon-based composite porous membrane can generate heat in the implementation process of the method, and the heating temperature is controllable (the surface temperature of the membrane can be adjusted by adjusting the voltage, and the surface temperature of the membrane can reach 113.2 ℃ at 20V at most, refer to the attached figure 6 (a)).

8. In the implementation process of the method, the electric response polymer is coated on the surface of the carbon-based composite porous membrane, so that the system operation voltage is reduced, and the electrochemical reaction on the surface of the electrode is reduced. (after coating the carbon-dragon complex # 1 molecule, the film surface can reach 150 ℃ at the maximum voltage of 4V, refer to FIG. 6 (b).

9. The method has higher evaporation rate (electric heat desalination rate: 12.51 kg/m) than the traditional solar seawater desalination process in the implementation process²H, rate of photothermal desalination: 15.80kg/m²·h)。

10. The method has better desalination effect (the highest can reach 99.959%) than the traditional seawater desalination process in the implementation process.

11. The method has high energy utilization efficiency in the implementation process. (the highest efficiency of utilization of electric joule heat energy at a voltage of 10V is 92.70% under the condition of four-sheet film integration, and the highest efficiency of utilization of photo-thermal energy is 93.64% at an optical concentration Copt of 4 under the condition of four-sheet film integration).

12. The method can be operated continuously for 24 hours alternately: under the condition of illumination in the daytime, the carbon-based composite porous membrane photo-thermal conversion system provides heat and mass transfer driving force for the seawater desalination process, and meanwhile, a solar cell panel is used for converting light energy into electric energy for storage; under the condition of no illumination in the daytime or at night, the electric energy stored by the solar cell panel is utilized to electrify the carbon-based composite porous membrane, so that joule heat is generated to provide heat and mass transfer driving force for the system, the seawater desalination process is carried out, and the electric heating-photo-thermal alternating continuous seawater desalination for 24 hours is realized in a circulating manner.

13. All energy used by the method is directly or indirectly provided by the sun, and no other energy input system is provided, so that the method is a novel energy-saving seawater desalination method.

Drawings

The invention is further illustrated by the following figures and examples.

FIG. 1 is a diagram of a 24-hour continuous seawater desalination mechanism with alternating Joule heating and photothermal.

FIG. 2 is a schematic diagram of a 24-hour continuous seawater desalination plant with alternating Joule heating and photothermal heating.

Fig. 3 is a schematic diagram of electrode connection and packaging. (a) The connection part of the interdigital electrode is shown schematically; (b) a schematic drawing of a Polymethylmethacrylate (PMMA) package clip; (c) packaging the object picture by the sandwich structure; (d) an equivalent circuit diagram of the interdigital electrode.

Fig. 4 is a schematic diagram of a desalination device.

Fig. 5 is a contact angle test of the carbon nanotube composite porous membrane when energized.

Fig. 6 is an infrared thermal imaging test chart. (a) Infrared thermal imaging of the monolithic film by an external electric field; (b) coating a carbon-dragon complex 1# molecule and externally applying an electric field for infrared thermal imaging; (c) four films are integrally coated with a carbon-dragon complex 1# molecule and an external electric field infrared thermal imaging is carried out; (d) the temperature of the top cover of the device in the electric heating seawater desalination process; (e) and (4) the temperature of the top cover of the device in the photo-thermal seawater desalination process.

FIG. 7 is a diagram of (a) the side (left) and the surface (right) of a carbon nanotube composite hydrophobic membrane material object; (b) the side (left) and the surface (right) of the picture of the carbon nano tube composite hydrophobic porous membrane real object manufactured by laser drilling.

Fig. 8 is a schematic view (a) and a microscopic view (b) of laser drilling.

FIG. 9 shows a desalination apparatus and effect objects. (a) The single-film seawater desalination test device under sunlight and desalination effect; (b) a single-film electric heating seawater desalination testing device and a desalination effect; (c) four-film integrated electric heating seawater desalination testing device and desalination effect.

Fig. 10 is a responsive polymer molecular structure.

Detailed Description

1. Preparation of carbon-based composite film (taking carbon nanotube array as an example):

toluene is used as a carbon source, ferrocene is used as a catalyst,preparing 4% ferrocene/toluene solution, and adopting floating assisted catalytic method (FCCVD) to grow and prepare wide-caliber (-80 nm) and high-crystallinity (I) at 740 deg.C_G/DAbout.2.51) and high density (0.17 g/cm)³) Uniformly mixing components of Polydimethylsiloxane (PDMS) A, B in a ratio of 10:1, removing bubbles for 30min, dripping the mixture to the surface of the carbon nanotube array by using a suction pipe, standing for 30min after the array is completely soaked, setting a spin-coating program ① 500r-20s, ② 3000r-40s to remove redundant resin, curing at 70 ℃ for 3h, stripping a substrate after the curing is completely finished, polishing the surface to expose the end of the carbon nanotube, and slicing the membrane by using an ultrathin slicer to obtain the carbon nanotube array composite hydrophobic membrane, wherein the thickness of the membrane is 30 μm, and the porous membrane has high water flux.

2. Punching a carbon-based composite film:

using a laser cutting machine, setting the cutting power at 25W and the cutting speed at 2m/s, focusing to obtain the carbon nanotube array composite porous membrane with the pore diameter of 50 μm, referring to fig. 7(b), the density is 64 pores per area of 5mm × 5mm, and the preparation process and the pore size characterization are shown in fig. 8.

3. The carbon-based composite porous membrane-electrode packaging clamping piece comprises an electrode connecting part and a packaging clamping piece:

(1) an electrode connection portion: referring to fig. 3, the interdigital electrode-parallel carbon-based composite porous membrane device, and the electrode connection method, referring to fig. 3 (a): a titanium electrode anode 1, a titanium electrode cathode 2, a screw hole groove 3, a carbon film position area 4 and a carbon film 5; the upper edge and the lower edge of each carbon film are tightly bonded with the upper edge and the lower edge of an interdigital part of a titanium electrode anode 1 and a titanium electrode cathode 2 respectively by conductive silver adhesive, the left edge and the right edge of the carbon film are not bonded with the titanium electrode, so that the current flowing through the titanium electrode can flow through the carbon film, the four carbon films are bonded in a dotted line frame in a graph (a) in a graph 3(a) by the method, an equivalent circuit refers to a graph (d) in the graph 3, the carbon film does not shield a screw hole groove theoretically, the screw hole groove 3 only helps to position each carbon film in the carbon film bonding process in the graph, and the hole characteristic is kept.

(2) Polymethylmethacrylate (PMMA) package clip referring to fig. 3 (b): an electrode jack 6, a screw hole groove 7, a carbon film hole groove 8 and a polymethyl methacrylate (PMMA) plate 9; the thickness of the polymethyl methacrylate (PMMA) plate 9 is 2mm, and holes are respectively arranged in an electrode inserting hole 6, a screw hole groove 7 and a carbon-based composite porous membrane hole groove 8 of the polymethyl methacrylate (PMMA) plate in the shapes shown in the drawing, wherein the electrode inserting hole 6 allows a titanium electrode in (1) to pass through for leading out the electrode, and the carbon membrane hole groove 8 allows saline water to pass through and contact the surface of the carbon-based composite porous membrane.

(3) Referring to fig. 3(b), the silicone pad packaging clip has the same structure as the polymethyl methacrylate (PMMA) packaging clip.

(4) Sandwich structure encapsulation referring to fig. 3 (c): the structure comprises a silica gel pad packaging clamping piece 10, a screw 11, a polymethyl methacrylate (PMMA) packaging clamping piece 12 and an electrode connecting part 13;

① referring to the electrode connecting part in (1), four carbon films are bonded with the titanium electrode by the conductive silver paste in the method described in (1), namely the electrode connecting part 13 in the step, referring to fig. 3 (a);

②, secondly, adopting the silica gel pad packaging clamping piece 10 in the step (3), referring to fig. 3(c), clamping the electrode connecting part in the step (1) by two silica gel pad packaging clamping pieces in a sandwich structure, aligning the screw hole groove 7 of the silica gel pad packaging clamping piece with the screw hole groove 3 of the electrode connecting part in the step (1), respectively penetrating the positive and negative electrodes 1 and 2 of the titanium electrode of the electrode connecting part through the corresponding electrode insertion holes in the silica gel pad packaging clamping piece, and obtaining the electrode connecting part after silica gel pad packaging after the step is completed;

③, finally, using the polymethyl methacrylate (PMMA) packaging clamping piece 12 in the step (2), continuously packaging the electrode connecting part packaged by the silica gel pad by using two polymethyl methacrylate (PMMA) packaging clamping pieces with a sandwich structure referring to fig. 3(c), wherein the anode and cathode 1 and 2 of the titanium electrode reserved by the electrode connecting part packaged by the silica gel pad in the previous step respectively penetrate out of the electrode jack 6 on the polymethyl methacrylate (PMMA) packaging clamping piece;

④ obtaining polymethyl methacrylate (PMMA) plate packaging clamping piece, silica gel pad packaging clamping piece, carbon film/electrode connecting part, silica gel pad packaging clamping piece and polymethyl methacrylate (PMMA) packaging clamping piece in sequence, 5 layers of sandwich structure, inserting screw 9 into corresponding screw hole groove, and packaging the electrode connecting part by stress after screwing the screw.

4. Desalination device referring to fig. 4: electrode outlet holes 1 and 6, a heavy brine inlet 2, a heavy brine storage tank 3, a pure water collecting tank 4, a top cover 5 (detachable), a carbon-based composite porous membrane-electrode packaging clamping piece floating position 7 and a pure water outlet 8. The device structure is as follows: the electrode outlet holes 1 and 6 are respectively positioned on the left side wall and the right side wall of the device; the heavy brine inlet 2 penetrates through the left side wall of the device and is connected with the heavy brine storage tank 3 so as to maintain the level of the heavy brine in the heavy brine storage tank; the floating position 7 of the carbon-based composite porous membrane-electrode packaging clamping piece is positioned in the heavy brine storage tank 3 and is used for placing the carbon-based composite porous membrane-electrode packaging clamping piece, and the size of the floating position is consistent with that of the heavy brine storage tank, so that the carbon-based composite porous membrane-electrode packaging clamping piece can be clamped conveniently; the pure water collecting tank 4 surrounds the heavy salt water storage tank 3 in a shape of a Chinese character 'hui'; a pure water outlet 8 penetrates through the right side wall of the device and is connected with the collecting tank 4; when the device works, the heat enables water vapor to evaporate, and the water vapor is condensed on the top cover 5 of the device and slides into the pure water collecting tank 4 along the side wall of the device. The working mode of the device is as follows: and opening the top cover 5, clamping the carbon-based composite porous membrane-electrode packaging clamping piece at 7, leading out the electrodes from the holes 1 and 6, and closing the top cover 5. The heavy brine is injected from the water tank 2, so that the carbon-based composite membrane-electrode packaging clamping piece floats in the heavy brine storage tank 3, the hollow part of the clamping piece allows the carbon-based composite porous membrane to be in contact with the brine, the heat of the carbon-based composite porous membrane generates heat to change the water phase, vaporized water molecules pass through a micro-nano pore system in the carbon-based composite porous membrane and reach the inner surface of the top cover 5, and the condensed pure water is finally gathered in the pure water collecting tank 4 along the gradient of the inner surface and is led out from a pure water outlet 8 to complete seawater.

5.24 h continuous seawater desalination process referring to fig. 2, fig. 4: the system comprises a desalination device and a solar panel. The device is installed by the method in the step 4, and under the condition of illumination in the daytime, a solar panel in the system can store partial solar energy in the form of electric energy, on the other hand, the carbon-based composite porous membrane can directly absorb the energy in the sunlight and complete photothermal conversion, and the heat promotes water molecules to evaporate and pass through micro-nano composite pores of the composite membrane to collect the evaporated water molecules, thereby finally realizing the solar seawater desalination; the solar cell panel in the system can release electric energy stored in the daytime at night or under the condition of insufficient illumination in the daytime, the solar cell panel is connected with electrodes led out from holes 1 and 6 in the device in the step 4, joule heat is generated on the surface of the carbon-based composite porous membrane under the action of current, and the composite membrane can also realize electric-induced seawater desalination under the drive of the joule heat, so that 24-hour seawater desalination is realized.