Device for relieving reverse osmosis of forward osmosis salt and membrane pollution in situ by using capacitive deionization technology and use method

Abstract

The invention relates to a device for relieving reverse osmosis of forward osmosis salt and membrane pollution in situ by utilizing a capacitive deionization technology and a use method, and relates to the technical field of membrane filtration. Comprising a raw material liquid chamber, a draw liquid chamber, a forward osmosis membrane and a fluid circulation system, and the raw material liquid chamber and the draw liquid chamber are separated through the forward osmosis membrane; a capacitive deionization assembly is arranged in the draw solution chamber; and the fluid circulating system is respectively communicated with the raw material liquid chamber and the draw liquid chamber. In order to solve the inherent problems of salt reverse osmosis of the draw solution and membrane pollution in the forward osmosis technology, the invention proposes to carry out electrochemical adsorption on solutes in the draw solution in situ by utilizing a capacitive deionization (CDI) technology, and solves the problems of reduction of the efficiency of the draw solution caused by salt reverse osmosis and attenuation of water flux caused by membrane pollution in the existing forward osmosis technology. Salt reverse osmosis inhibition and membrane pollution alleviation are realized in situ.

Description

Technical Field

[0001] This invention relates to the field of membrane filtration technology, specifically to a device and method for using capacitive deionization technology to in-situ alleviate forward osmosis, reverse osmosis, and membrane fouling. Background Technology

[0002] Forward osmosis (FOO) is an emerging membrane filtration technology that utilizes the osmotic pressure difference generated by the concentration difference of the solutions on either side of the membrane as the driving force. On either side of the membrane, the side with the higher concentration solution is called the draw solution side, and the side with the lower concentration solution is called the feed solution side. The FAO membrane is a semi-permeable membrane, allowing water molecules from the lower-concentration feed solution side to pass through and enter the higher-concentration draw solution side. Due to its small pore size and the fact that no additional driving force is required, FAO membranes offer advantages such as low energy consumption, high-quality effluent, and low membrane fouling tendency, making them a hot research topic. The core bottlenecks of FAO filtration lie in two aspects: the unavoidable accumulation of salt from the draw solution side to the feed solution side and membrane fouling. These phenomena significantly reduce the operating performance and lifespan of the FAO membrane. Therefore, researching techniques to mitigate salt reverse osmosis and membrane fouling has become crucial for extending membrane lifespan and improving membrane performance.

[0003] In existing research, two common strategies are used to mitigate the phenomenon of salt accumulation on the feed side, decreased osmotic pressure differential, and reduced efficiency caused by back osmosis of the draw solution: First, modifying the forward osmosis membrane, such as altering the surface charge properties to utilize charge repulsion to block molecules; second, installing a microfiltration or ultrafiltration membrane system on the feed side. When salt accumulation on the feed side becomes severe, excess salt is promptly removed through microfiltration or ultrafiltration to eliminate salt accumulation caused by back osmosis of the draw solution. For the former, there are currently no technologically mature and stable modified forward osmosis membranes available, while the latter requires high pressure for salt removal, increasing energy costs. Furthermore, the large amount of back osmosis from the draw solution exacerbates inorganic fouling of the forward osmosis membrane.

[0004] Capacitive deionization (CDI) technology removes charged ions by applying a voltage (less than the theoretical electrolysis voltage of water, 1.23V) across the electrodes. Electrode regeneration and ion desorption are achieved through short-circuiting or applying a reverse voltage. It features low energy consumption and in-situ regeneration. Coupled with forward osmosis, CDI reduces solute backflow from the draw solution to the feed solution through electro-adsorption of ions and inhibits ion deposition on the membrane surface through the electric field on the electrode surface, creating a synergistic optimization effect.

[0005] Therefore, how to provide a device and method for in-situ mitigating forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to design a device and method for in-situ mitigating salt back osmosis and membrane fouling in forward osmosis using capacitive deionization (CDI) technology. Addressing the inherent problems of salt back osmosis and membrane fouling in forward osmosis technology, this invention proposes to utilize capacitive deionization (CDI) technology to electrochemically adsorb solutes in the draw solution in situ. This solves the problems of decreased draw solution efficiency due to salt back osmosis and reduced water flux due to membrane fouling in existing forward osmosis processes, thereby achieving in-situ inhibition of salt back osmosis and mitigation of membrane fouling.

[0007] To achieve the above objectives, the present invention provides an apparatus for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology, comprising: a feed liquid chamber, a draw liquid chamber, a forward osmosis membrane, and a fluid circulation system, wherein the feed liquid chamber and the draw liquid chamber are separated by the forward osmosis membrane; a capacitive deionization component is disposed in the draw liquid chamber; and the fluid circulation system is connected to both the feed liquid chamber and the draw liquid chamber.

[0008] Furthermore, the capacitive deionization assembly includes a CDI electrode module installed in the extraction liquid chamber.

[0009] Furthermore, the CDI electrode module includes three pairs of alternating activated carbon electrodes and titanium current collectors, spaced 3 mm apart, and fixed by an insulating support.

[0010] Furthermore, the CDI electrode module is connected to a DC power supply via a current collector titanium wire, and the output voltage is adjustable from 0 to 2V. It can achieve "adsorption-regeneration" switching by switching the positive and negative electrodes.

[0011] Furthermore, the fluid circulation system includes a raw material liquid circulation branch and a draw liquid circulation branch, wherein the raw material liquid circulation branch is connected to the raw material liquid chamber; and the draw liquid circulation branch is connected to the draw liquid chamber.

[0012] Furthermore, the raw material liquid circulation branch includes a raw material liquid storage tank and a first circulation pump; one end of the first circulation pump is connected to the raw material liquid storage tank, and the other end is connected to the raw material liquid inlet of the raw material liquid chamber, and the raw material liquid outlet of the raw material liquid chamber is connected to the raw material liquid storage tank.

[0013] Furthermore, the extraction liquid circulation branch includes an extraction liquid storage tank and a second circulation pump; one end of the second circulation pump is connected to the extraction liquid storage tank, and the other end is connected to the extraction liquid inlet of the extraction liquid chamber, and the extraction liquid outlet of the extraction liquid chamber is connected to the extraction liquid storage tank.

[0014] A method of using a device that utilizes capacitive deionization technology to in-situ mitigate forward osmosis, reverse osmosis, and membrane fouling includes:

[0015] The device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology adopts a batch operation mode, with each operating cycle lasting 24 hours. At 0 hours, the feed liquid and the second circulation pump are turned on and adjusted to the design flow rate. The adsorption voltage and desorption voltage of the CDI electrode module are set.

[0016] The conductivity of the raw material liquid and the extract liquid at the outlet is measured every hour during operation.

[0017] During operation, the current detection module and a laptop computer are used to monitor the device current at any time. When the current drops to 30% of the initial value, it is considered that the electrode adsorption is saturated. The electrode voltage is then switched to the desorption voltage -0.5V to desorb the adsorbed ions and discharge them with the concentrated water. The desorption time is 5 minutes. After desorption is completed, the two chambers of the device are thoroughly cleaned and the CDI electrode module is chemically cleaned to maintain the electrode adsorption performance.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) By drawing the electrode adsorption of ions by the CDI electrode module in the extracting solution, the reverse osmosis rate of the salt solute is reduced, and the water recovery rate and average water flux of the forward osmosis membrane are increased.

[0020] (2) By reducing salt reverse osmosis, inorganic salt fouling of the forward osmosis membrane is alleviated, which also improves the water recovery performance of the device. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention;

[0022] Figure 2 A comparison chart of water recovery rates under two operating conditions;

[0023] Figure 3 A comparison chart of the water flux of the device under two operating conditions;

[0024] Figure 4 Scanning electron microscope (SEM) image of the forward osmosis membrane after 10 cycles of operation with the CDI electrode module enabled;

[0025] Figure 5 Scanning electron microscope (SEM) results of the forward osmosis membrane after 10 cycles without enabling the CDI electrode module.

[0026] In the diagram: 1-Feed liquid chamber, 2-Draw liquid chamber, 3-Feed liquid inlet, 4-Feed liquid outlet, 5-Draw liquid outlet, 6-Draw liquid inlet, 7-Forward osmosis membrane, 8-Current collector titanium wire, 9-DC power supply, 10-CDI electrode module. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0030] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0031] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0032] See Figure 1This embodiment discloses an apparatus for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology. The apparatus includes: a feed liquid chamber, a draw liquid chamber, a forward osmosis membrane, and a fluid circulation system. The feed liquid chamber and the draw liquid chamber are separated by the forward osmosis membrane and sealed by a silicone gasket and a flange. A capacitive deionization component is installed in the draw liquid chamber. The fluid circulation system is connected to both the feed liquid chamber and the draw liquid chamber.

[0033] The capacitive deionization assembly includes a CDI electrode module, which is installed in the extraction liquid chamber.

[0034] The CDI electrode module includes three pairs of alternating activated carbon electrodes (the size matches the width of the device, and the thickness is 2 mm) and titanium current collectors, with a spacing of 3 mm between them, and is fixed by an insulating bracket.

[0035] To further optimize the technical solution, the CDI electrode module is connected to a DC power supply via a current-collecting titanium wire and connected to a computer using an Altair 16-channel DAM3055N data acquisition module for real-time current monitoring. The output voltage is adjustable from 0 to 5V, and "adsorption-regeneration" switching can be achieved by switching the positive and negative electrodes.

[0036] The fluid circulation system includes a feed liquid circulation branch and a draw liquid circulation branch. The feed liquid circulation branch is connected to the feed liquid chamber; the draw liquid circulation branch is connected to the draw liquid chamber. Both branches are equipped with a flow meter (accuracy ±1%) and a pressure sensor (range 0-1MPa).

[0037] The raw material liquid circulation branch includes a raw material liquid storage tank and a first circulation pump; one end of the first circulation pump is connected to the raw material liquid storage tank, and the other end is connected to the raw material liquid inlet of the raw material liquid chamber. The raw material liquid outlet of the raw material liquid chamber is connected to the raw material liquid storage tank. The solution pipeline between the raw material liquid storage tank and the raw material liquid chamber is connected by a flange, and a sealing gasket (made of salt corrosion resistant rubber) is installed at the interface.

[0038] The extraction liquid circulation branch includes an extraction liquid storage tank and a second circulation pump; one end of the second circulation pump is connected to the extraction liquid storage tank, and the other end is connected to the extraction liquid inlet of the extraction liquid chamber, while the extraction liquid outlet of the extraction liquid chamber is connected to the extraction liquid storage tank. The solution pipeline between the extraction liquid storage tank and the extraction liquid chamber is connected by a flange, and a sealing gasket (made of salt corrosion resistant rubber) is installed at the interface.

[0039] This invention also provides a method for using a device that utilizes capacitive deionization technology to in-situ alleviate forward osmosis, reverse osmosis, and membrane fouling, comprising:

[0040] The device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology adopts a batch operation mode, with each operating cycle lasting 24 hours. At 0 hours, the feed liquid and the second circulation pump are turned on and adjusted to the designed flow rates (5 L / h for feed liquid and 3 L / h for draw liquid). The adsorption voltage (1V) and desorption voltage (-0.5V) of the CDI electrode module are set. The desorption voltage of -0.5V is achieved by rotating the electrodes. The voltage range of the DC power supply used is 0 to 5V.

[0041] The conductivity of the raw material liquid and the extract liquid at the outlet is measured every hour during operation.

[0042] During operation, the current detection module and a laptop computer are used to monitor the device current at any time. When the current drops to 30% of the initial value, it is considered that the electrode adsorption is saturated. The electrode voltage is then switched to the desorption voltage -0.5V to desorb the adsorbed ions and discharge them with the concentrated water. The desorption time is 5 minutes. After desorption is completed, the two chambers of the device are thoroughly cleaned and the CDI electrode module is chemically cleaned (soaked in 0.1mol / L hydrochloric acid solution for 30 minutes) to maintain the electrode adsorption performance.

[0043] This invention reduces the reverse osmosis rate of salt solutes and increases the water recovery rate and average water flux of the forward osmosis membrane by using the CDI electrode module in the extraction solution to adsorb ions. By reducing salt reverse osmosis, inorganic salt fouling of the forward osmosis membrane is alleviated, which also improves the water recovery performance of the device.

[0044] Example

[0045] This embodiment constructs a small-scale, laboratory-scale capacitive deionization coupled forward osmosis device, using an effective membrane area of ​​10 cm². 2 The forward osmosis membrane has a feed solution chamber and a draw solution chamber, each with a volume of 0.5L, and a feed solution storage tank and a draw solution storage tank, each with a volume of 2L. The CDI electrode module uses graphene nanoplates loaded with activated carbon, with a specific surface area of ​​1500m². 2 / g. The DC power supply is an adjustable regulated power supply with a current range of 0-1A and a voltage range of 0-5V.

[0046] The draw solution was a 1 mol / L NaCl solution, and the feed solution was deionized water. The apparatus was operated with and without the CDI electrode module enabled, with each cycle lasting 24 hours. The results showed that under the condition of ion adsorption with the CDI electrode module enabled, the water recovery rate reached 2158.5 ± 5.2 mL, significantly higher than that without the CDI electrode module (1824.7 ± 3.3 mL, p < 0.05). Figure 2 (As shown). The FO membrane water flux with the CDI electrode module enabled ranged from 9.31 to 12.72 LMH, significantly higher than that without the CDI electrode module enabled (e.g., ...). Figure 3 (As shown).

[0047] Scanning electron microscopy analysis of the forward osmosis membrane after 10 cycles showed that, after 10 cycles of operation, the device with the CDI electrode module enabled had only a small amount of inorganic fouling on the surface of the forward osmosis membrane, such as... Figure 4 As shown. In devices where the CDI electrode module was not activated, large areas of inorganic contamination appeared on the surface of the forward osmosis membrane, such as... Figure 5 As shown, this demonstrates that the technology has a significant positive effect on mitigating inorganic fouling in forward osmosis membranes.

[0048] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology, characterized in that, include: The system includes a feed liquid chamber, a draw liquid chamber, a forward osmosis membrane, and a fluid circulation system. The feed liquid chamber and the draw liquid chamber are separated by the forward osmosis membrane. A capacitive deionization component is installed in the draw liquid chamber. The fluid circulation system is connected to both the feed liquid chamber and the draw liquid chamber.

2. The device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology as described in claim 1, characterized in that, The capacitive deionization assembly includes a CDI electrode module, which is installed in the extraction liquid chamber.

3. The device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology as described in claim 2, characterized in that... The CDI electrode module includes three pairs of alternating activated carbon electrodes and titanium current collectors, spaced 3 mm apart, and fixed by an insulating bracket.

4. The device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology as described in claim 2, characterized in that, The CDI electrode module is connected to a DC power supply via a current collector titanium wire, and the output voltage is adjustable from 0 to 2V. It can achieve "adsorption-regeneration" switching by switching the positive and negative electrodes.

5. The device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology as described in claim 1, characterized in that, The fluid circulation system includes a raw material liquid circulation branch and a draw liquid circulation branch. The raw material liquid circulation branch is connected to the raw material liquid chamber; the draw liquid circulation branch is connected to the draw liquid chamber.

6. The device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology as described in claim 5, characterized in that, The raw material circulation branch includes a raw material storage tank and a first circulation pump; one end of the first circulation pump is connected to the raw material storage tank, and the other end is connected to the raw material inlet of the raw material chamber, and the raw material outlet of the raw material chamber is connected to the raw material storage tank.

7. A device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology as described in claim 5 or 6, characterized in that, The extraction liquid circulation branch includes an extraction liquid storage tank and a second circulation pump; one end of the second circulation pump is connected to the extraction liquid storage tank, and the other end is connected to the extraction liquid inlet of the extraction liquid chamber, and the extraction liquid outlet of the extraction liquid chamber is connected to the extraction liquid storage tank.

8. A method of using the device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology as described in any one of claims 1-7, characterized in that, include: The device for in-situ mitigation of forward osmosis, reverse osmosis, and membrane fouling using capacitive deionization technology adopts a batch operation mode, with each operating cycle lasting 24 hours. At 0 hours, the feed liquid and the second circulation pump are turned on and adjusted to the design flow rate. The adsorption voltage and desorption voltage of the CDI electrode module are set. The conductivity of the raw material liquid and the extract liquid at the outlet is measured every hour during operation. During operation, the current detection module and a laptop computer are used to monitor the device current at any time. When the current drops to 30% of the initial value, it is considered that the electrode adsorption is saturated. The electrode voltage is then switched to the desorption voltage -0.5V to desorb the adsorbed ions and discharge them with the concentrated water. The desorption time is 5 minutes. After desorption is completed, the two chambers of the device are thoroughly cleaned and the CDI electrode module is chemically cleaned to maintain the electrode adsorption performance.

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