Electric vortex desalination chip based on joint control of transverse and longitudinal electric fields

Abstract

The invention discloses an electric vortex seawater desalination chip based on the joint control of transverse and longitudinal electric fields, comprising a microfluidic channel, wherein the microfluidic channel is composed of a main path and two branches connected together, wherein the starting end of the main path is the input end, and the end of the main path is connected to the starting ends of the two branches to form an overall "Y"-shaped structure, wherein the flow path in the first branch is upward, and the flow path in the second branch is downward; a cation selective membrane is respectively embedded on the upper wall and the lower wall of the main path, and the cation selective membrane is connected to electrodes, wherein the voltage of the upper wall electrode is set to V3, and the voltage of the lower wall electrode is set to V4, and V3 and V4 form a longitudinal electric field for controlling the chip; electrodes with a voltage of V2 are set at the ends of the two branches, and an electrode with a voltage of V1 is set at the starting end of the main path, and V1 and V2 form a transverse electric field for controlling the chip; the invention adopts a microfluidic channel with an aperture of 100 micrometers, and continuous seawater desalination and desalination treatment can be achieved by adjusting the voltage.

Description

Technical Field

[0001] The invention relates to the technical field of electric vortex type microfluidic desalination chips, and in particular to an electric vortex type seawater desalination chip based on the combined control of transverse and longitudinal electric fields. Background Art

[0002] Water purification technology is an important measure to solve the shortage and safety of drinking water. In areas with abundant seawater resources, seawater desalination technology has become an important way to supply local fresh water by effectively separating the salt from the water in the seawater. Seawater desalination technology is based on the reverse osmosis process. During the reverse osmosis process, the applied external hydrostatic pressure pushes the seawater through the semipermeable membrane system. The presence of the semipermeable membrane allows water to pass through, but at the same time prevents the salt and other impurities dissolved in the seawater. For the efficiency and cost issues of seawater desalination, improving the permeability of the membrane has become one of the key technologies. Ion exchange membranes such as nanoporous graphene membranes have a microscale porous structure that allows water to flow through faster, thus having a more efficient seawater desalination capacity.

[0003] The existing electrodialysis method further combines electrodialysis and ion exchange, adopts DC potential difference to form driving force, utilizes the selective permeability of ion exchange membrane, removes ions in water, and realizes seawater desalination. This electrodialysis method combining electric drive and ion exchange membrane technology is considered to be a new technology with potential for seawater desalination. In the existing patents of electrodialysis technology, only longitudinal electric field is used to control electroosmotic flow, so that the seawater in the microchannel composed of two cation selective membranes forms a vortex on the surface of the ion exchange membrane under the action of the longitudinal electric field, realizing seawater desalination. However, this scheme can only carry out seawater desalination based on this type of electric vortex when there is fluid pressure at the end of the channel. In addition to problems such as channel height, this scheme will also cause energy waste during seawater desalination treatment. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an electric vortex type seawater desalination chip based on the joint control of the transverse and longitudinal electric fields. The microfluidic chip adopts a microfluidic channel with a pore size of 100 microns, and can achieve continuous seawater desalination and desalination by adjusting the voltage. The new electric vortex type desalination chip can achieve seawater desalination under the condition that there is no fluid pressure at the end of the channel, which is convenient for the automatic control of the desalination process and is conducive to the promotion and application of small and medium-sized desalination plants.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The electric vortex desalination chip based on the joint control of the transverse and longitudinal electric fields includes a microfluidic channel, which is composed of a main path and two branches. Along the flow direction, the starting end of the main path is the input end, and the end of the main path is connected to the starting ends of the two branches to form an overall "Y"-shaped structure, in which the flow path in the first branch is upward, and the flow path in the second branch is downward;

[0007] A cation selective membrane is embedded in the upper wall and the lower wall of the main path respectively, and the cation selective membrane is connected to the electrode, wherein the voltage of the upper wall electrode is set to V3, and the voltage of the lower wall electrode is set to V4, V3 and V4 form a longitudinal electric field to control the chip, and under the action of the longitudinal electric field, an electric vortex will be formed on the surface of the cation selective membrane; the V3 is greater than V4;

[0008] Electrodes with a voltage of V2 are set at the ends of the two branches, and an electrode with a voltage of V1 is set at the beginning of the main path. V1 and V2 form a transverse electric field for controlling the chip. Under the action of the transverse electric field, the fluid in the microfluidic channel will produce tangential electroosmotic movement under the action of the transverse electric field; V1 is greater than V2;

[0009] Each of the electrodes is connected to an adjustable DC voltage source, wherein the voltage value setting should satisfy V1>V2, V3>V4 and V2≠V3, and the voltage value range is appropriately adjusted according to the structural size parameters and chip desalination efficiency.

[0010] The cross section of the microfluidic channel is rectangular.

[0011] The cross section of the microfluidic channel is 20 μm to 1000 μm.

[0012] The microfluidic channel is made of silicon glass material.

[0013] The base channel material in the microfluidic channel is silicon or resin, and the purpose is to make the wall surface of the microfluidic channel carry negative charge to provide driving force for the fluid.

[0014] The area containing salt water is connected to the beginning of the main path of the microfluidic channel. By adjusting the voltage difference between the "Y"-shaped structure of the microfluidic channel and the beginning of the main path, a first type of electroosmotic flow is formed, thereby driving the salt water into the microfluidic channel; when the salt water enters the cation selective membrane area, the voltage difference on both sides of the cation selective membrane is adjusted, thereby forming a concentration polarization effect, triggering the second electroosmotic flow to form a low-concentration vortex; under the action of the first type of electroosmotic flow, the low-concentration vortex area will form a directional rolling; by collecting these low-concentration vortices, the continuous desalination of the salt water is completed.

[0015] The method for using an electric vortex type seawater desalination chip based on the combined control of transverse and longitudinal electric fields comprises the following steps:

[0016] Continuous seawater desalination and desalination treatment is achieved by adjusting the voltage. By adjusting the voltage difference between the beginning of the main path of the microfluidic channel and the "Y" structure (the voltage difference between V1 and V2), the double electric layer on the microchannel wall drives the fluid flow under the control of the transverse electric field, so that salt water enters the microchannel;

[0017] When salt water enters the cation selective membrane area, the voltage difference on both sides of the cation selective membrane is adjusted (the voltage difference between V3 and V4). The concentration polarization effect in the microfluidic channel triggers the appearance of electric vortices on the surface of the cation selective membrane. The area where the vortex exists is the low ion concentration area, which realizes the effective separation of salt and water.

[0018] Under the action of electroosmotic flow, the fluid in the low ion concentration area forms a lateral directional flow. Near the node at the end of the "Y"-shaped structure of the microfluidic channel, these low-concentration vortices are collected to complete the continuous desalination of the brine.

[0019] The present invention can process microfluidic channels in parallel, change the roughness of the ion membrane surface and thus increase the intensity of local eddy currents, thereby realizing large-scale desalination treatment.

[0020] The preparation method of the microfluidic channel of the present invention is to manufacture the microfluidic channel by hot molding or laser etching.

[0021] The microfluidic channel of the present invention can be used for seawater desalination equipment, electrodialysis equipment, and microfluidic equipment. The specific use process only requires adjusting the voltage according to the voltage configuration of the present invention. The voltage satisfies the conditions of V1>V2, V3>V4, and V2≠V3, and seawater desalination treatment can be achieved.

[0022] Beneficial effects of the present invention:

[0023] The silicon glass material used in the present invention is used to prepare a microchannel with a scale of about 100 to 1,000 micrometers. A cation selective membrane is embedded in the upper and lower walls of the microchannel. By adjusting the voltage values ​​of the four electrodes so that the voltages meet the conditions of V1>V2, V3>V4, and V2≠V3, seawater desalination can be achieved.

[0024] Generally speaking, in a microchannel made of silicon glass material, due to the electroosmotic effect, under the action of the transverse electric field, the electroosmotic flow drives the salt solution at the inlet end of the microchannel into the microchannel.

[0025] When the salt solution enters the ion selective membrane in the channel, under the action of the longitudinal electric field, the salt solution forms ion concentration polarization on the surface of the ion selective membrane. The local disturbance electric field drives the ion concentration polarization layer to form an electric vortex area, and the area has the characteristic of low ion concentration. The transverse electric field drives the electroosmosis flow, causing the electric vortex to flow in a directional manner. Collecting these electric vortices can realize seawater desalination.

[0026] The present invention can achieve seawater desalination under the condition that there is no fluid pressure at the end of the channel by directly adjusting the transverse electric field and the longitudinal electric field. Since the present invention is a microfluidic chip, it does not need external pressure drive and can be powered by two No. 5 batteries. In addition, by adjusting the vertical electric field strength on the surface of the cationic membrane, the seawater desalination efficiency can be improved. The microfluidic chip is suitable for households and small and medium-sized desalination plants in water-scarce areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0029] like Figure 1 As shown, the configuration of the present invention mainly lies in the structural configuration of the microfluidic channel and the voltage configuration. Figure 1 The basic structure of the microchannel is shown in Figure 1. First, a “Y”-shaped channel is fabricated through micro-nano processing.

[0030] Two cation selective membranes are embedded in the upper and lower walls near the nodes of the "Y"-shaped channel, and electrodes are connected to one side of the cation selective membrane, with the voltage of the upper electrode set to V3 and the voltage of the lower electrode set to V4. Then two electrodes are set at the left and right ends of the microchannel, respectively, with the voltage of the left electrode set to V1 and the voltage of the right electrode set to V2.

[0031] Since the chip is designed at a scale of hundreds of microns, only two batteries are needed to achieve the voltage setting of the electrode. By adjusting the voltage values ​​of the four electrodes, the voltage satisfies V1>V2, V3>V4 and V2≠V3. When traditional electrodialysis chips are used for seawater desalination, fluid pressure is required at the end of the channel, and the pressure is proportional to the -4th power of the pore diameter. Compared with traditional electrodialysis equipment, the present invention can desalinate seawater without external pressure at the end of the channel.

[0032] For the present invention, the surface of the cation selective membrane has an electrodynamic vortex (such as Figure 1The ion concentration of the fluid in these electric vortex regions is very low. By adjusting the voltage values ​​of the four electrodes (first adjusting the voltage V1>V2, after 1 minute, the electric vortex is fully developed; then adjusting the voltage to satisfy V3>V4 and V2≠V3), seawater desalination based on electric vortex can be achieved.

[0033] In addition, the present invention also has the effect of killing local bacteria and repelling other charged particles when desalinating seawater, thereby ensuring the safety of the produced fresh water.

[0034] The method for using an electric vortex type seawater desalination chip based on the combined control of transverse and longitudinal electric fields comprises the following steps:

[0035] Continuous seawater desalination and desalination treatment is achieved by adjusting the voltage. By adjusting the voltage difference between the left and right ends of the microfluidic channel (the voltage difference between V1 and V2), the double electric layer on the microchannel wall drives the fluid flow under the control of the transverse electric field, so that salt water enters the microchannel;

[0036] When salt water enters the cation selective membrane area, the voltage difference on both sides of the cation selective membrane is adjusted (the voltage difference between V3 and V4). The concentration polarization effect in the microfluidic channel triggers the appearance of electric vortices on the surface of the cation selective membrane. The area where the vortex exists is the low ion concentration area, which realizes the effective separation of salt and water.

[0037] Under the action of electroosmotic flow, the fluid in the low ion concentration area forms a lateral directional flow. Near the node at the end of the "Y"-shaped structure of the microfluidic channel, these low-concentration vortices are collected to complete the continuous desalination of the brine.

Claims

1. Based on the joint control of transverse and longitudinal electric fields, the electric vortex type seawater desalination chip is characterized by: The microfluidic channel includes a main channel and two branches connected together. Along the flow direction, the beginning of the main channel is the input end, and the end of the main channel is connected to the beginnings of the two branches to form an overall "Y"-shaped structure, wherein the flow path in the first branch is upward, and the flow path in the second branch is downward; A cation selective membrane is embedded in the upper wall and the lower wall of the main path respectively, and the cation selective membrane is connected to the electrode, wherein the voltage of the upper wall electrode is set to V3, and the voltage of the lower wall electrode is set to V4, V3 and V4 form a longitudinal electric field to control the chip, and under the action of the longitudinal electric field, an electric vortex will be formed on the surface of the cation selective membrane; the V3 is greater than V4; Electrodes with a voltage of V2 are set at the ends of the two branches, and an electrode with a voltage of V1 is set at the beginning of the main path. V1 and V2 form a transverse electric field to control the chip. Under the action of the transverse electric field, the fluid in the microfluidic channel will produce tangential electroosmotic movement under the action of the transverse electric field; V1 is greater than V2; Each of the electrodes is connected to an adjustable DC voltage source, wherein the voltage value is set to satisfy V1>V2, V3>V4 and V2≠V3; The salt water area is connected to the beginning of the main path of the microfluidic channel. By adjusting the voltage difference between the "Y" structure of the microfluidic channel and the beginning of the main path, the first type of electroosmotic flow is formed, thereby driving the salt water into the microfluidic channel; when the salt water enters the cation selective membrane area, the voltage difference on both sides of the cation selective membrane is adjusted, thereby forming a concentration polarization effect, triggering the second electroosmotic flow to form a low-concentration vortex; under the action of the first type of electroosmotic flow, the low-concentration vortex area will form a directional rolling; by collecting these low-concentration vortices, the continuous desalination of the salt water is completed; The cross section of the microfluidic channel is 20 μm to 1000 μm; When the salt solution enters the ion selective membrane in the channel, under the action of the longitudinal electric field, the salt solution forms ion concentration polarization on the surface of the ion selective membrane. The local disturbed electric field drives the ion concentration polarization layer to form an electric vortex area, and this area has the characteristic of low ion concentration; the transverse electric field drives the electroosmosis flow, causing the electric vortex to flow in a directional manner, and these electric vortices are collected to realize seawater desalination treatment.

2. The electric vortex type seawater desalination chip based on the combined control of transverse and longitudinal electric fields according to claim 1 is characterized in that: The cross section of the microfluidic channel is rectangular.

3. The electric vortex type seawater desalination chip based on the combined control of transverse and longitudinal electric fields according to claim 1 is characterized in that: The microfluidic channel is made of silicon glass material; The base channel material in the microfluidic channel is silicon or resin.

4. The method for using the electric vortex type seawater desalination chip based on the combined control of the transverse and longitudinal electric fields according to any one of claims 1 to 3, characterized in that: The steps include: Continuous seawater desalination treatment is achieved by adjusting the voltage. By adjusting the voltage difference between the beginning of the main path of the microfluidic channel and the "Y"-shaped structure, the double electric layer on the microchannel wall drives the fluid flow under the control of the transverse electric field, allowing salt water to enter the microchannel. When salt water enters the cation selective membrane area, the voltage difference on both sides of the cation selective membrane is adjusted, and concentration polarization occurs in the microfluidic channel, triggering the appearance of electric vortices on the surface of the cation selective membrane. The area where the vortex exists is a low ion concentration area, achieving effective separation of salt and water. Under the action of electroosmotic flow, the fluid in the low ion concentration area forms a lateral directional flow. Near the node at the "Y"-shaped structure end of the microfluidic channel, these low-concentration vortices are collected to complete the continuous desalination of the brine.

5. The method for using the electric vortex type seawater desalination chip based on the combined control of the transverse and longitudinal electric fields according to claim 4 is characterized in that: The preparation method of the microfluidic channel is to manufacture the microfluidic channel by hot molding or laser etching.

6. The application of the electric vortex type seawater desalination chip based on the combined control of transverse and longitudinal electric fields according to any one of claims 1 to 3, characterized in that: The microfluidic channel can be used in seawater desalination equipment, electrodialysis equipment, and microfluidic equipment. When used, the voltage satisfies the conditions of V1>V2, V3>V4, and V2≠V3.

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