Oil-water separation device based on dielectric wetting and use method

Abstract

The invention relates to an oil-water separation device based on dielectric wetting and a use method.The oil-water separation device comprises an oil-water separation module, a power supply control module, a conveying pump, a conveying pipeline, a sample box and a water tank, one end of the conveying pump is connected with the sample box through the conveying pipeline, and the other end of the conveying pump is connected with the oil-water separation module through the conveying pipeline; the oil-water separation module is connected with the power supply control module, one output end of the oil-water separation module is connected with the water tank, the other output end of the oil-water separation module is connected with the input end of the sample box, and the power supply control module is used for controlling working parameters of the oil-water separation module. And oil and water respectively flow into the water tank and the sample box after being separated in the oil-water separation module. The dielectric wetting effect is introduced, the hydrophilicity and hydrophobicity of the stainless steel mesh are regulated and controlled, the effect of washing the stainless steel mesh is achieved, and the problem that a surfactant and oil adhere to a separation membrane is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil-water separation, and in particular, to an oil-water separation device and a usage method based on electrowetting-on-dielectric. Background Art

[0002] In the past, more and more oil spill accidents and the treatment of urban sewage and industrial oily wastewater have become a global challenge that poses a serious threat to the ecosystem. This severe situation has prompted researchers to explore efficient and sustainable technologies and materials to mitigate water pollution. Researchers hope to recycle the polluted water or reduce the pollutant concentration to an acceptable level. Therefore, it is urgent to solve the problem of oil-water separation. However, traditional methods including coagulation, centrifugation, sedimentation, flotation, biodegradation, etc. cannot effectively separate oil and water, especially in oil / water emulsions. Membrane technology has great potential for treating oily wastewater. Against this background, a series of polymer membranes have been prepared using various technologies, and many researchers have also reported the feasibility of membrane-based oil-water separation processes. In the prior art, there is a method of overlapping two types of electrode plates and achieving oil-water separation by passing oily sewage through two layers of filtration respectively. This method requires treating both types of electrode plates, increasing the cost.

[0003] Although substantial progress has been made in the development of membrane materials and devices for treating oily wastewater, how to efficiently recover both oil and water from emulsions remains a challenge. Therefore, it is necessary to further develop superwetting interfaces (such as superhydrophobic or superhydrophilic interfaces) to achieve effective emulsion oil / water separation. Generally speaking, when designing a superhydrophobic interface to remove oil in oil / water separation, two common strategies have been proposed, namely reducing the surface energy and surface decoration through nano / microstructures. An interface with superhydrophilicity is superhydrophobic underwater and can remove water while retaining oil. However, during the membrane separation process, oil is likely to adhere to the membrane, thus affecting the water flux. Traditional oil-water separation membranes generally have the problem of membrane pore blockage when treating oily sewage containing surfactants. Summary of the Invention

[0004] In view of the above-mentioned technical problems, an oil-water separation device and a usage method based on electrowetting-on-dielectric are provided.

[0005] The technical means adopted by the present invention are as follows:

[0006] An oil-water separation device based on electrowetting includes an oil-water separation module, a power control module, a delivery pump, a delivery pipeline, a sample tank, and a water tank. One end of the delivery pump is connected to the sample tank through the delivery pipeline, and the other end of the delivery pump is connected to the oil-water separation module through the delivery pipeline. The oil-water separation module is connected to the power control module. One output end of the oil-water separation module is connected to the water tank, and the other output end of the oil-water separation module is connected to the input end of the sample tank. The power control module is used to control the working parameters of the oil-water separation module. After the oil and water are separated in the oil-water separation module, they flow into the water tank and the sample tank respectively.

[0007] Further, a three-way valve is provided on the pipeline where the other output end of the oil-water separation module is connected to the input end of the sample tank. The other output end of the three-way valve is connected to a collector, and the collector is used for sampling and analysis.

[0008] Further, the oil-water separation module includes an upper electrode plate and a lower electrode plate with conductive properties. The lower electrode plate is composed of a conductive mesh membrane with hydrophobic and oleophobic properties.

[0009] Further, the lower electrode plate is a conductive material with pore meshes coated with a superhydrophobic and oleophobic dielectric material.

[0010] Further, the upper electrode plate is a conductive material.

[0011] Further, the distance between the upper electrode plate and the lower electrode plate is 2 - 20 mm.

[0012] Further, the power supply of the power control module is 20 - 100 V. The upper electrode plate is connected to the positive electrode, and the lower electrode plate is connected to the negative electrode.

[0013] The specific usage method of the present invention includes the following steps:

[0014] Prepare a conductive double-hydrophobic mesh membrane;

[0015] Use the conductive double-hydrophobic mesh membrane as the lower electrode plate, assemble the oil-water separation module, and connect and assemble the oil-water separation module, the delivery pump, the sample tank, and the water tank through the delivery pipeline;

[0016] Start the delivery pump, turn on the power of the oil-water separation module, and perform the oil-water separation operation;

[0017] Monitor the water flux of the oil-water separation in real time. When it is less than the preset value, turn off the power of the oil-water separation module. After a preset power-off time, turn on the power and continue the oil-water separation operation.

[0018] Further, the preparation of the conductive double-hydrophobic mesh membrane specifically includes the following steps:

[0019] Select a conductive material with a mesh size of 10 to 500 meshes, and spin-coat the superhydrophobic and oleophobic dielectric material on the conductive material with pores at 1000 to 2500 rpm for 10 to 100 s. After spin-coating, keep it at 80 - 150 °C for 10 - 30 minutes to make the conductive material with pores have hydrophobic and oleophobic properties.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. When traditional oil-water separation membranes are used to treat emulsified oily sewage containing surfactants, there is generally a problem of membrane pore blockage, resulting in a decrease in water flux. Disassembly and flushing are required, causing waste of time. The present invention introduces the dielectric wetting effect to regulate the hydrophilicity and hydrophobicity of the stainless steel mesh to achieve the effect of flushing the stainless steel mesh and solve the problem of adhesion of surfactants and oil to the separation membrane.

[0022] 2. The method for preparing the oil-water separation membrane of the present invention is simple and low-cost. A conductive double-hydrophobic network membrane can be prepared by means of spin-coating and heating.

[0023] 3. The method for designing the oil-water separation device of the present invention is simple and low-cost. The device involved in the present invention does not require any complex tools.

[0024] 4. The device of the present invention can be used to treat different types of oily sewage by selecting conductive mesh membranes with different mesh numbers. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is the working principle flow chart in the present invention.

[0027] Figure 2 It is the experimental device for the content of the present invention.

[0028] Figure 3 It is the experimental device for the examples of the present invention.

[0029] In the figure: 1. Oil-water separation module; 2. Power control module; 3. Delivery pump; 4. Delivery pipeline; 5. Sample box; 6. Collector; 7. Three-way valve; 8. Water tank. Detailed Embodiments

[0030] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0031] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way restricts the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0032] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless otherwise clearly specified in the context, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the convenience of description, the dimensions of the various parts shown in the drawings are not drawn according to the actual proportional relationship. Technologies, methods, and devices known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, the said technologies, methods, and devices should be regarded as part of the specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0034] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by orientation words such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal", and "top, bottom" are generally based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description. Without contrary explanations, these orientation words do not indicate and imply that the devices or elements referred to must have a specific orientation or be constructed and operated in a specific orientation, and thus cannot be construed as limiting the protection scope of the present invention. The orientation words "inside, outside" refer to the inside and outside relative to the contour of each component itself.

[0035] For ease of description, spatial relative terms, such as "above", "on top of", "on the upper surface", "upper", etc., may be used herein to describe the spatial positional relationship of one device or feature to other devices or features as shown in the figures. It should be understood that the spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, a device described as "above" or "on top of" other devices or structures will then be positioned "below" or "beneath" the other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the corresponding explanations for the spatial relative descriptions used herein will be made accordingly.

[0036] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of differentiating the corresponding components. Without additional statements, the above terms have no special meanings, and thus should not be construed as limiting the protection scope of the present invention.

[0037] As Figures 1 to 3 shown, an oil-water separation device based on electrowetting is disclosed in an embodiment of the present invention, which includes an oil-water separation module 1, a power control module 2, a delivery pump 3, a delivery pipeline 4, a sample box 5, and a water tank 8. One end of the delivery pump is connected to the sample box through the delivery pipeline, and the other end of the delivery pump is connected to the oil-water separation module through the delivery pipeline. The oil-water separation module is connected to the power control module. One output end of the oil-water separation module is connected to the water tank, and the other output end of the oil-water separation module is connected to the input end of the sample box. The power control module is used to control the working parameters of the oil-water separation module. After the oil and water are separated in the oil-water separation module, they flow into the water tank and the sample box respectively.

[0038] A three-way valve 7 is provided on the pipeline where the other output end of the oil-water separation module is connected to the input end of the sample box. The other output end of the three-way valve is connected to a collector 6, and the collector is used for sampling and analysis.

[0039] The oil-water separation module includes an upper plate and a lower plate with conductive properties. The lower plate is composed of a conductive mesh membrane with hydrophobic and oleophobic double-hydrophobic properties.

[0040] The upper plate and the lower plate are encapsulated. During actual use, both the upper and lower plates need to be powered on. The oily wastewater flows into the oil-water separation module through a pipeline. There is a passage in the module to transport the oily wastewater to the passage formed by the upper and lower plates. Taking the illustration as an example, when the oily wastewater flows from right to left, the water phase in the oily wastewater can flow into the water tank through the lower plate with pores, while the remaining oily wastewater will be powered by a transfer pump, flow out of the passage formed by the upper and lower plates from the left, and finally flow out of the oil-water separation module.

[0041] The lower plate is a conductive material with pores coated with a superhydrophobic and oleophobic dielectric material. The superhydrophobic and oleophobic dielectric material may specifically include materials such as polytetrafluoroethylene and Teflon, and any material that can achieve the superhydrophobic and oleophobic function is acceptable. The conductive material with pores is specifically 10 - 500 mesh, including but not limited to iron, aluminum, stainless steel, copper, platinum, gold, silver, titanium and their alloys, or a combination of the above elements and alloys.

[0042] The upper plate is a conductive material. Specifically, it can be conductive glass.

[0043] The distance between the upper plate and the lower plate is 2 - 20 mm.

[0044] The power supply of the power control module is 20 - 100 V. The upper plate is connected to the positive electrode, and the lower plate is connected to the negative electrode.

[0045] In the present invention, the emulsion in the sample box is transported to the oil-water separation module through a transport pipeline. The oil-water separation module includes an upper plate and a lower plate with conductive properties. A conductive mesh membrane with hydrophobic and oleophobic properties is used as the lower plate to play the role of separating two phases. The power control module is connected to the oil-water separation module, and the dielectric wetting effect is achieved by controlling the power on and off. The conductive mesh membrane with superhydrophilicity and underwater superhydrophobicity (i.e., the double-channel conductive mesh membrane) is powered on and off to change the hydrophilic and hydrophobic properties of the double-channel conductive mesh membrane. Based on the dielectric wetting effect, after the double-channel conductive mesh membrane is powered on, the contact angles of different phases in the emulsion can be changed. The contact angle of the oil phase is greater than the original contact angle, and the hydrophilic and hydrophobic properties remain unchanged, while the contact angle of the water phase changes from greater than 90 degrees originally to less than 90 degrees, realizing the conversion of the hydrophilic and hydrophobic properties of the water phase. This causes the water phase to be able to pass through the membrane, while the oil droplets can never pass through. As the time of oil-water separation increases, the water flux of the double-channel conductive mesh membrane will gradually decrease because of the adhesion of the oil liquid and surfactant on the double-channel conductive mesh membrane. At this time, it is powered off to make the double-channel conductive mesh membrane return to the hydrophobic and oleophobic state, and the emulsion cannot leak out through the double-channel conductive mesh membrane. By increasing the pump power, the emulsion is used to wash the double-channel conductive mesh membrane to strip the oil liquid and surfactant on the membrane from the double-channel conductive mesh membrane, so as to restore its water flux. The valve is opened to make the emulsion flushing the mesh membrane flow back to the sample box again.

[0046] The specific usage method of the present invention includes the following steps:

[0047] Prepare a conductive double-hydrophobic network film; clean the conductive network film to remove surface dirt, and after drying, make it have the characteristics of hydrophobicity and oleophobicity by means such as spraying specific materials.

[0048] Take the conductive double-hydrophobic network film as the lower electrode plate, assemble the oil-water separation module, and connect and assemble the oil-water separation module, transfer pump, sample box and water tank through a conveying pipeline; install a power control module to ensure that a voltage can be applied to the upper and lower electrode plates.

[0049] Start the transfer pump and supply power through the power control module. The transfer pump pumps the emulsion from the sample box into the oil-water separation device, and the power control module energizes the oil-water separation module to make the oil-water separation module have the effect of dielectric wetting. The waste liquid filtered through the oil-water separation membrane flows into the collector through a hose with the valve closed.

[0050] Monitor the water flux of the oil-water separation in real time. When it is less than the preset value, disconnect the power supply of the oil-water separation module. At this time, the oil-water separation channel no longer has the effect of dielectric wetting. At this time, the emulsion flowing through the oil-water separation module plays a role in washing away the oil droplets and surfactants attached to the double-conductive network film. After the power is cut off for a preset time, power on and continue the oil-water separation operation.

[0051] The method for judging less than the preset value can be by setting a flow sensor, or when it is observed that the water separation flux decreases significantly, and it is adjusted according to different application scenarios.

[0052] The preparation of the conductive double-hydrophobic network film specifically includes the following steps:

[0053] Select a conductive material with 10-500 meshes, and spin-coat the super-hydrophobic and oleophobic dielectric material on the conductive material with pores at 1000-2500 rpm for 10-100 s. After spin-coating, keep it at 80-150 °C for 10-30 minutes to make the conductive material with pores have the characteristics of hydrophobicity and oleophobicity.

[0054] In this embodiment, the specific method includes:

[0055] Step 1: Select an 80-mesh iron net, and spin-coat Teflon on the stainless steel iron net at 2000 rpm for 1 min. After spin-coating, dry it at 175 °C for 10 min to make the stainless steel iron net have the characteristics of hydrophobicity and oleophobicity.

[0056] Step 2: Install the treated stainless steel iron net at the position of the lower electrode plate of the oil-water separation module, install conductive glass at the upper electrode plate, and the distance between the two electrode plates is 2 cm. Install a power module that can provide a voltage of 100 V, connect the positive electrode to the upper electrode plate and the negative electrode to the lower electrode plate.

[0057] Step 3: Connect the peristaltic pump, beaker, and separation channel using a hose to complete the construction of the overall system.

[0058] Step 4: Start the peristaltic pump and pump the emulsion in the sample box into the oil-water separation module.

[0059] Step 5: Energize the upper and lower electrode plates. According to the principle of dielectric wetting, change the contact angle of the aqueous phase in the separation channel so that the aqueous phase can flow into the water tank through the stainless steel mesh, and the separated waste liquid flows out of the oil-water separation module.

[0060] Step 6: As the energization time increases, more oil phase and surfactant adhere to the stainless steel mesh, and the water flux significantly decreases. At this time, control the power supply to turn off, open the valve, and increase the flow rate of the peristaltic pump. The dielectric wetting effect disappears, and the stainless steel mesh returns to the hydrophobic and oleophobic state. The aqueous phase no longer flows into the water tank, and the unseparated emulsion flows back to the sample box, playing a role in flushing the stainless steel mesh and carrying away the oil phase and surfactant on the stainless steel mesh.

[0061] Step 7: After a certain period of time, reconnect the power supply and close the valve. It is observed that the water flux of the stainless steel mesh recovers compared to before the power outage.

[0062] The present invention utilizes a conductive mesh membrane with a hydrophilic and hydrophobic material coating to change its surface properties, making it superhydrophilic in air and superhydrophobic underwater. The present invention uniformly loads a hydrophobic and oleophobic material onto the conductive mesh membrane. On this basis, combined with the principle of dielectric wetting, an oil-water separation membrane is obtained. This mesh membrane has underwater hydrophobic and oleophobic properties, can effectively separate oil and water, and is used for sewage treatment of lubricating oil, etc., and has a broad application prospect.

[0063] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An oil-water separation device based on electrowetting, characterized in that, It includes an oil-water separation module, a power control module, a delivery pump, a delivery pipeline, a sample box and a water tank. One end of the delivery pump is connected to the sample box through the delivery pipeline, and the other end of the delivery pump is connected to the oil-water separation module through the delivery pipeline. The oil-water separation module is connected to the power control module. One output end of the oil-water separation module is connected to the water tank, and the other output end of the oil-water separation module is connected to the input end of the sample box. The power control module is used to control the working parameters of the oil-water separation module. After the oil and water are separated in the oil-water separation module, they flow into the water tank and the sample box respectively.

2. The oil-water separation device based on dielectric wetting according to claim 1, wherein, A three-way valve is provided on the pipeline where the other output end of the oil-water separation module is connected to the input end of the sample box. The other output end of the three-way valve is connected to a collector, and the collector is used for sampling and analysis.

3. The oil-water separation device based on dielectric wetting according to claim 1, wherein The oil-water separation module includes an upper electrode plate and a lower electrode plate with conductive properties. The lower electrode plate is composed of a conductive mesh film with hydrophobic and oleophobic properties.

4. The dielectric-wetting-based oil-water separation device according to claim 1, wherein, The lower electrode plate is a conductive material with pore meshes coated with a superhydrophobic and oleophobic dielectric material.

5. The oil-water separation device based on dielectric wetting according to claim 1, characterized in that, The upper electrode plate is a conductive material.

6. The dielectric-wetting-based oil-water separation device according to claim 1, wherein The distance between the upper electrode plate and the lower electrode plate is 2 - 20 mm.

7. The oil-water separation device based on electrowetting according to claim 1, characterized in that The power supply of the power control module is 20 - 100 V. The upper electrode plate is connected to the positive electrode, and the lower electrode plate is connected to the negative electrode.

8. A method for using the dielectric wetting-based oil-water separation device according to any one of claims 1 to 7, characterized in that, It includes the following steps: Prepare a conductive double-hydrophobic and oleophobic mesh film; Use the conductive double-hydrophobic and oleophobic mesh film as the lower electrode plate, assemble the oil-water separation module, and connect and assemble the oil-water separation module, the delivery pump, the sample box and the water tank through the delivery pipeline; Start the delivery pump, turn on the power of the oil-water separation module, and perform the oil-water separation operation; Real-time monitor the water flux of the oil-water separation. When it is less than the preset value, turn off the power of the oil-water separation module. After the power-off for the preset time, turn on the power and continue the oil-water separation operation.

9. The method according to claim 8, wherein The preparation of the conductive double-hydrophobic and oleophobic mesh film specifically includes the following steps: Select a conductive material with 10 - 500 mesh. Spin-coat the superhydrophobic and oleophobic dielectric material on the conductive material with pore meshes at 1000 - 2500 rpm for 10 - 100 s. After the spin-coating is completed, keep it at 80 - 150 °C for 10 - 30 minutes to make the conductive material with pore meshes have hydrophobic and oleophobic properties.

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