Membrane separation device, system equipment and process method for treating acidic wastewater

Abstract

This invention provides a membrane separation device, a system for treating acidic wastewater, and a process method. The membrane separation device includes a first shell and a second shell, which are opposite to each other and have interconnected internal cavities. The first shell has a limiting protrusion that can extend into the second shell and cooperate with a limiting step inside to form a limiting space. A membrane module is housed in the limiting space. The membrane module includes a stacked support frame, a high-operating-pressure separation membrane, and a support plate. The support plate has a through hole for the feed liquid to pass through. This membrane separation device, through its structural design, can support membrane separation treatment of acidic wastewater under a working pressure difference of ≥0.5 MPa, driven by both pressure and concentration differences. By simultaneously establishing and maintaining pressure and concentration differences on both sides of the membrane, and using a system consisting of at least two series-connected membrane separation devices, it is beneficial to achieve both efficient recovery of acid and enhanced retention of metal ions in the acidic wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment and relates to a membrane separation device, a system equipment and process method for treating acidic wastewater. Background Technology

[0002] In the field of acidic wastewater treatment, traditional neutralization precipitation methods, while simple to operate, consume large amounts of alkaline reagents. This not only wastes recoverable acid resources in the wastewater but also generates large amounts of hazardous sludge containing heavy metals (such as Fe, Cr, and Ni), leading to secondary pollution and disposal costs. To achieve resource recovery, diffusion dialysis technology is used for acid recovery. Relying on concentration gradients to drive proton migration, it has the advantage of low energy consumption. However, it is limited by weak mass transfer driving force, resulting in low acid flux and low recovery efficiency, making it difficult to meet industrial-scale requirements. In contrast, pressure-driven membrane separation technologies (such as nanofiltration, reverse osmosis, or special composite membrane processes) enhance mass transfer through external pressure, theoretically significantly improving acid recovery rates and treatment flux. However, this may simultaneously exacerbate concentration polarization and solute enrichment at the membrane surface, especially in complex wastewater containing high salt and high metal content.

[0003] In high-acid, high-metal-impurity systems, the solution osmotic pressure increases significantly, reducing the effective transmembrane driving force. Under high-flux conditions, this further enhances solute enrichment at the membrane surface, leading to increased local metal ion concentrations and mass transfer resistance, thus reducing separation efficiency. To maintain the target flux, it is often necessary to increase the operating pressure, thereby increasing system energy consumption. Furthermore, H... + The transport mechanism differs from that of multivalent metal ions within the membrane: the former mainly migrates via proton conduction, while the latter is limited by hydration radius and charge repulsion. With enhanced operating conditions, the intramembrane mass transfer coupling effect is strengthened, increasing H₂O levels. + While increasing flux, it may weaken the retention capacity for multivalent metal ions, thus limiting the effectiveness of achieving efficient mass transfer by simply relying on pressure increase.

[0004] Therefore, traditional pressure-driven membrane separation schemes are difficult to achieve high acid recovery rates and high metal retention rates simultaneously in actual operation, especially in complex electroplating, metallurgical or stainless steel pickling wastewater, which restricts the synergistic realization of efficient recycling of acid resources and wastewater discharge compliance. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a membrane separation device, a system equipment and process method for treating acidic wastewater. The membrane separation device, through its structural design, can support the separation membrane to achieve pressure-concentration dual-driven membrane separation treatment of acidic wastewater under a working pressure difference of greater than or equal to 0.5 MPa. Based on the simultaneous establishment and maintenance of pressure difference and concentration difference driving on both sides of the membrane, the system equipment composed of at least two series-connected membrane separation devices is conducive to achieving both efficient recovery of acid and enhanced retention of metal ions in acidic wastewater.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a membrane separation device, comprising: The first housing has a first inner cavity and is provided with a liquid inlet and a liquid circulation outlet communicating with the first inner cavity, and the first inner cavity has a first opening on the first housing; The second housing has a second inner cavity and is provided with a liquid outlet and a liquid circulation inlet communicating with the second inner cavity, and the second inner cavity has a second opening on the second housing; The first opening and the second opening are disposed opposite to each other and are detachably fixedly connected, so that the first inner cavity and the second inner cavity are connected. A limiting step is provided in the second inner cavity of the second housing, and a limiting protrusion corresponding to the limiting step is provided on the first housing at the first opening position. The limiting protrusion extends into the second inner cavity and forms a limiting space with the limiting step. A membrane module, disposed within the limiting space, includes a stacked support frame, a separation membrane, and a support plate; the working pressure difference of the separation membrane is greater than or equal to 0.5 MPa; the support frame is disposed on one side of the limiting protrusion and in contact with it, and the hollow portion of the support frame is used for the passage of liquid; the support plate is disposed on one side of the limiting step and in contact with it, and the support plate is provided with a liquid passage area corresponding to the hollow portion of the frame, and the liquid passage area is provided with several through holes for the passage of liquid.

[0007] The membrane separation device provided by this invention adopts a split-type structure design. Through a detachable fixed connection between the first and second housings, the cooperation of limiting protrusions and limiting steps, and the clamping of the support frame and support plate, the membrane modules can be stacked and pressure applied, which is beneficial for fixing and supporting the separation membrane and increasing its stability. The cavity connecting the first and second housings also handles the inflow and outflow of the feed liquid from the separation membrane, bears the main pressure, and provides a location for the pressure drive of the membrane separation process. Therefore, a liquid passage zone with through holes is provided on the support plate near the feed liquid outlet side. This improves the separation membrane's resistance to feed liquid impact while also allowing for flow and permeability, enabling the separation membrane to withstand higher pressures and pressure differentials and operate stably and efficiently. Furthermore, this split-type structure design facilitates the installation and replacement of new separation membranes, and facilitates cleaning, maintenance, and debugging. In addition to the feed inlet and feed outlet on both sides of the separation membrane, the membrane separation device also has a feed circulation outlet and a feed circulation inlet on both sides. This allows for the use of more interfaces to construct flow paths or circulations with different functions, thereby effectively controlling the composition, concentration and other properties of the feed liquid on both sides of the separation membrane. For example, it can realize membrane separation treatment functions with pressure drive as the main method and concentration difference drive as the auxiliary method on both sides of the separation membrane.

[0008] The working pressure difference of the separation membrane described in this invention refers to the pressure difference formed on both sides of the separation membrane when the pressure on the feed liquid side is greater than the pressure on the receiving liquid side, and this pressure difference is greater than or equal to 0.5 MPa. For example, this pressure difference can be 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, or 1.5 MPa, etc., preferably in the medium-high pressure range with a pressure difference > 0.5 MPa, and more preferably in the high pressure range with a pressure difference ≥ 1 MPa, but it is not limited to the values ​​listed above, and other unlisted values ​​within the above range are also applicable.

[0009] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0010] In some embodiments, the separation membrane includes a nanofiltration membrane and / or a reverse osmosis membrane.

[0011] In some embodiments, a first flange is provided around the outer periphery of the first housing near the first opening, and a second flange is provided around the outer periphery of the second housing near the second opening, wherein the first flange and the second flange are bolted together.

[0012] In some embodiments, a first sealing ring groove is provided on the side of the limiting protrusion facing the support frame, and a first sealing ring is provided in the first sealing ring groove.

[0013] In some embodiments, the support frame is provided with a second sealing ring groove on the side facing the separation membrane, and a second sealing ring is disposed in the second sealing ring groove.

[0014] In some embodiments, the support plate is provided with a third sealing ring groove on the side facing the limiting step, and a third sealing ring is provided in the third sealing ring groove.

[0015] In some embodiments, the limiting protrusion is an annular protrusion, which is disposed around the edge of the first opening, and the outer diameter of the annular protrusion is less than or equal to the diameter of the second opening; the limiting step is an annular step, which is disposed around the inner wall of the second housing in the second inner cavity.

[0016] In some embodiments, the diameter of the hollow portion of the support frame is less than or equal to the diameter of the first opening.

[0017] In some implementations, the support frame and support plate can be obtained by 3D printing after modeling, and the material can be acid and alkali resistant and high pressure resistant.

[0018] In some embodiments, the liquid circulation outlet of the first housing is connected to the liquid inlet via a pipeline.

[0019] In some embodiments, the liquid outlet of the second housing is connected to the liquid circulation inlet via a pipeline.

[0020] In some embodiments, the diameter of the through holes is 0.4mm to 0.8mm, for example, 0.4mm, 0.5mm, 0.6mm, 0.7mm, or 0.8mm; the spacing is 0.1mm to 0.3mm, for example, 0.1mm, 0.15mm, 0.2mm, 0.25mm, or 0.3mm; and the density is 1 hole / mm². 2 ~3 pieces / mm 2 For example, it could be 1 per mm 2 2 pieces / mm 2 Or 3 / mm 2 Therefore, the liquid passing through the several through holes can be both permeable and supportive of the separation membrane to stably withstand high operating pressure differences.

[0021] In a second aspect, the present invention provides a system for treating acidic wastewater, comprising at least two stages of the membrane separation devices described in the first aspect, and a storage tank matching each stage of the membrane separation devices, wherein: The first-stage storage tank is connected to the feed inlet of the first-stage membrane separation device through a pipeline equipped with the first pump body, and the feed circulation outlet of the first-stage membrane separation device is connected to the first-stage storage tank through a pipeline, thus forming the first-stage membrane separation loop. The feed liquid outlet of the first-stage membrane separation unit is connected to the second-stage storage tank through a pipeline; and the second-stage storage tank is connected to the feed liquid circulation inlet of the first-stage membrane separation unit through a pipeline equipped with a second pump body, thus forming the first-stage receiving liquid circulation loop. As described above, the nth stage storage tank is connected to the nth stage membrane separation device to form the nth stage membrane separation loop; at the same time, the nth stage membrane separation device is connected to the (n+1)th stage storage tank to form the nth stage receiving liquid circulation loop; n is an integer ≥ 1. The final stage of the storage tank is equipped with an acid production and outlet.

[0022] In the system equipment for treating acidic wastewater provided by this invention, the feed liquid enters the feed side (or feed liquid side) of the membrane separation device under the drive of the first pump, and the receiving liquid circulates on the receiving liquid side under the action of the second pump. The membrane module separates the feed liquid side and the receiving liquid side, thereby simultaneously forming a pressure difference and a concentration difference on both sides of the separation membrane. This causes the acid in the feed liquid to preferentially migrate to the receiving liquid side, while metal ions are mainly retained on the feed liquid side due to the membrane trapping effect. Based on this, constructing a receiving liquid circulation and renewal loop on one side of the second inner cavity can effectively form and maintain a stable concentration difference with the first inner cavity side, effectively mitigating the driving force decay caused by enrichment on the second inner cavity side and improving acid migration efficiency. Using the concentration difference as an auxiliary driving force, combined with the pressure difference under the high operating pressure of the membrane separation device as the main driving force, both mass transfer rate and selectivity can be effectively balanced. Meanwhile, the use of at least two-stage membrane separation devices (referring to the second inner cavity side) helps to disperse the load on the single-stage membrane surface, reduce concentration polarization and local osmotic pressure burden, and alleviate the constraint between acid recovery rate and metal rejection rate. This also facilitates the division of labor between rapid acid migration in the first stage and in-depth metal rejection in the second and subsequent stages. Therefore, the operation of this system helps to reduce system energy consumption.

[0023] In some embodiments, the system equipment contains ≥2 membrane separation devices, for example, 2, 3, 4, 5 or 6, preferably 2.

[0024] In some implementations, the separation membranes in different levels of membrane separation devices may be the same or different.

[0025] In some embodiments, an nth-stage feed liquid circulation branch is connected to the pipeline connecting the first pump body to the feed liquid inlet of the nth-stage membrane separation device, and the other end of the nth-stage feed liquid circulation branch is connected to the nth-stage storage tank.

[0026] In some embodiments, the system equipment further includes an nth-stage cooling circulation device matched with the nth-stage storage tank for cooling the nth-stage storage tank.

[0027] In some embodiments, the first pump body includes a water pump, such as a high-pressure centrifugal pump; the second pump body includes a peristaltic pump. In some embodiments, the peristaltic pump can control the feeding of the liquid in a continuous or intermittent manner.

[0028] In some embodiments, turbulence structures and / or information acquisition and detection devices may be installed as needed in the second inner cavity of the membrane separation device, the receiving liquid circulation loop, and the storage tanks starting from the second-stage storage tank; the turbulence structures may be baffles, spiral baffles, deflectors, or stirrers, etc., and the information acquisition and detection devices may be online pH meters, conductivity meters, or flow monitoring modules, etc.

[0029] In some embodiments, the system equipment further includes a temperature control unit, which includes a temperature control device and a temperature monitoring / device, etc. The temperature control unit is configured to heat, cool or keep warm the required membrane separation device, liquid storage tank or pipeline.

[0030] In some embodiments, the system equipment further includes an automatic control unit, which is electrically connected to at least the pump body, information acquisition and detection device, temperature control unit, valve body, etc., for the purpose of realizing automatic control.

[0031] Thirdly, the present invention provides a process method for treating acidic wastewater, wherein the process method is carried out using the system equipment described in the second aspect, and the process method includes: The system supplies acidic wastewater to be treated to the first-stage storage tank and initial receiving liquid to all subsequent storage tanks. The first pump body causes the liquid in the nth stage storage tank to flow in the nth stage membrane separation loop and enters the first inner cavity of the nth stage membrane separation device for membrane separation treatment; at the same time, the nth stage peristaltic pump causes the liquid in the (n+1)th stage storage tank to flow in the nth stage receiving liquid circulation loop and enters the second inner cavity of the nth stage membrane separation device to form a new receiving liquid, which is then circulated back to the (n+1)th stage storage tank. During the membrane separation process, the acid concentration of the feed solution in the first inner cavity is maintained to be greater than that in the second inner cavity, forming a concentration difference; at the same time, the working pressure applied to one side of the first inner cavity is maintained to be greater than that applied to one side of the second inner cavity, forming a pressure difference.

[0032] In some embodiments, the initial receiving liquid includes water or an acid solution.

[0033] In some implementations, the pH of the initial receiving liquid in the (n+1)th stage reservoir is less than or equal to the pH of the initial receiving liquid in the nth stage reservoir.

[0034] Compared with existing technical solutions, the present invention has at least the following beneficial effects: The membrane separation device provided by this invention, through its structural design, supports membrane separation treatment of acidic wastewater under a working pressure difference of ≥0.5 MPa, achieving both pressure and concentration differentials simultaneously. Furthermore, by employing a system and process consisting of at least two series-connected membrane separation units, it effectively achieves both efficient acid recovery and enhanced metal ion retention in acidic wastewater, making it particularly suitable for large-scale treatment of high-acid, high-salt, and high-heavy-metal acidic wastewater. Attached Figure Description

[0035] Figure 1 This is an exploded view of the first housing in the membrane separation device provided in Example 1.

[0036] Figure 2 This is an exploded view of the first housing in the membrane separation device provided in Example 1.

[0037] Figure 3 This is a top view of the first housing in the membrane separation device provided in Example 1.

[0038] Figure 4 This is a top view of the second housing in the membrane separation device provided in Example 1.

[0039] Figure 5 This is a top view of the support frame in the membrane separation device provided in Example 1.

[0040] Figure 6 This is a top view of the support plate in the membrane separation device provided in Example 1.

[0041] Figure 7 This is a top view schematic diagram of the separation membrane in the membrane separation device provided in Example 1.

[0042] Figures 1 to 7 In the middle: 1-membrane separation device, 2-first shell, 3-second shell, 4-membrane module, 5-support frame, 6-separation membrane, 7-support plate, 8-feed inlet, 9-feed circulation outlet, 10-feed outlet, 11-feed circulation inlet, 12-limiting protrusion, 13-limiting step, 14-hollow part of frame, 15-through hole, 16-first flange, 17-second flange, 18-first sealing ring groove, 19-second sealing ring groove, 20-third sealing ring groove.

[0043] Figure 8 This is a structural process diagram of the system equipment for treating acidic wastewater provided in Example 2.

[0044] Figure 8 In the middle: 21-First stage membrane separation device, 22-Second stage membrane separation device, 31-First stage storage tank, 32-Second stage storage tank, 33-Third stage storage tank, 41-First stage water pump, 42-Second stage water pump, 51-First stage peristaltic pump, 52-Second stage peristaltic pump, 61-First stage circulating cooling device, 62-Second stage circulating cooling device.

[0045] Figure 9 This is a schematic diagram illustrating the principle of the process for treating acidic wastewater provided in Application Example 2. Detailed Implementation

[0046] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0047] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0048] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0049] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0050] In this invention, the order in which the steps are written in the methods described in the various embodiments does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any conflict-free order, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0051] Example 1 This embodiment provides a membrane separation device, such as... Figures 1 to 6 As shown, the membrane separation device 1 includes: The first housing 2 is a cylindrical body with a first inner cavity and a first opening at one end, i.e., the first opening is circular, and a liquid inlet 8 and a liquid circulation outlet 9 that are connected to the first inner cavity are provided on the side wall of the cylindrical body away from the first opening. The second housing 3 is a cylindrical body with a second inner cavity and a second opening at one end, i.e., the second opening is circular, and a liquid outlet 10 and a liquid circulation inlet 11 that are connected to the second inner cavity are provided on the side wall of the cylindrical body away from the second opening. The first housing 2 is provided with a first flange 16 around the outside near the first opening, and the second housing 3 is provided with a second flange 17 around the outside near the second opening. The first flange 16 and the second flange 17 are bolted together to achieve a detachable fixed connection, so that the first inner cavity and the second inner cavity are connected. A limiting step 13 is provided in the second inner cavity of the second housing 3. A limiting protrusion 12 corresponding to the limiting step 13 is provided on the first housing 2 at the first opening position. The limiting protrusion 12 extends into the second inner cavity and forms a limiting space with the limiting step 13. The limiting protrusion 12 is an annular protrusion, which is provided around the edge of the first opening, and the outer diameter of the annular protrusion is less than or equal to the diameter of the second opening. The limiting step 13 is an annular step, which is provided around the inner wall of the second housing 3 in the second inner cavity. Membrane module 4, disposed within the confining space, includes a stacked annular support frame 5, a circular separation membrane 6, and a circular support plate 7. The separation membrane 6 is a nanofiltration membrane with an operating pressure greater than 0.5 MPa. The support frame 5 is disposed on one side of the confining protrusion 12 and contacts it. The hollow portion 14 of the support frame 5 is square for the passage of liquid feed. The diameter of the circumscribed circle of the hollow portion 14 of the support frame 5 is less than or equal to the diameter of the first opening. The support plate 7 is disposed on one side of the confining step 13 and contacts it. The support plate 7 has a liquid passage area corresponding to the hollow portion 14 of the frame. The liquid passage area has a plurality of through holes 15 arranged in a 58×58 square array for the passage of liquid feed. Each through hole 15 has a diameter of approximately 0.5 mm, a spacing of 0.2 mm, and a density of 2 holes / mm. 2 ; The limiting protrusion 12 has a first sealing ring groove 18 on the side facing the support frame 5, in which a first sealing ring is disposed; the support frame 5 has a second sealing ring groove 19 on the side facing the separation membrane 6, in which a second sealing ring is disposed; the support plate 7 has a third sealing ring groove 20 on the side facing the limiting step 13, in which a third sealing ring is disposed.

[0052] Example 2 This embodiment provides a system for treating acidic wastewater, including two stages (two) of the membrane separation devices provided in Embodiment 1, and a storage tank matching each stage of the membrane separation device, such as... Figure 8 As shown, specifically: The first-stage storage tank 31 (which may be referred to as the feed liquid tank) is connected to the feed liquid inlet of the first-stage membrane separation device 21 through a pipeline equipped with a first-stage water pump 41, and the feed liquid circulation outlet of the first-stage membrane separation device 21 is connected to the first-stage storage tank 31 through a pipeline, forming a first-stage membrane separation circuit; at the same time, a first-stage feed liquid circulation branch is connected to the pipeline connecting the first-stage water pump 41 and the feed liquid inlet of the first-stage membrane separation device 21, and the other end of the first-stage feed liquid circulation branch is connected to the first-stage storage tank 31; the first-stage storage tank 31 is also equipped with a first-stage cooling circulation device 61 for cooling the first-stage storage tank 31; The feed outlet of the first-stage membrane separation device 21 is connected to the second-stage storage tank 32 (which can be called the first-stage receiving tank or the second-stage feed tank) through a pipeline; and the second-stage storage tank 32 is connected to the feed circulation inlet of the first-stage membrane separation device 21 through a pipeline equipped with the first-stage peristaltic pump 51, thus forming the first-stage receiving liquid circulation loop. The second-stage storage tank 32 is connected to the feed inlet of the second-stage membrane separation device 22 via a pipeline equipped with a second-stage water pump 42, and the feed circulation outlet of the second-stage membrane separation device 22 is also connected to the second-stage storage tank 32 via a pipeline, forming a second-stage membrane separation circuit. Simultaneously, a second-stage feed liquid circulation branch is connected to the pipeline connecting the second-stage water pump 42 and the feed inlet of the second-stage membrane separation device 22, with the other end of the second-stage feed liquid circulation branch connected to the second-stage storage tank 32. The second-stage storage tank 32 is also equipped with a second-stage cooling circulation device 62 for cooling the second-stage storage tank 32. The feed outlet of the second-stage membrane separation device 22 is connected to the third-stage storage tank 33 (which can be called the second-stage receiving tank or the third-stage feed tank) through a pipeline; and the third-stage storage tank 33 is connected to the feed circulation inlet of the second-stage membrane separation device 22 through a pipeline equipped with the second-stage peristaltic pump 52, thus forming the second-stage receiving liquid circulation loop. The third-stage storage tank 33 is equipped with an acid production and outlet; The devices and pipelines between the first-stage storage tank 31 and the second-stage storage tank 32 constitute a primary separation unit, and the devices and pipelines between the second-stage storage tank 32 and the third-stage storage tank 33 constitute a secondary separation unit.

[0053] Application Example 1 This application example provides a process method for treating acidic wastewater. The process method uses the system equipment provided in Example 2 and includes: Acidic wastewater to be treated is supplied to the first-stage storage tank, and initial receiving liquid is supplied to the second-stage and third-stage storage tanks; The acidic wastewater to be treated in the first-stage storage tank is circulated in the first-stage membrane separation loop by the first-stage water pump and then introduced into the first inner cavity of the first-stage membrane separation device for membrane separation treatment. At the same time, the liquid in the second-stage storage tank is circulated in the first-stage receiving liquid circulation loop by the first-stage peristaltic pump and then introduced into the second inner cavity of the first-stage membrane separation device to form a new receiving liquid (acid liquid), which is then circulated back to the second-stage storage tank. Simultaneously, the acidic wastewater to be treated in the second-stage storage tank is circulated in the second-stage membrane separation loop by the second-stage water pump and then introduced into the first inner cavity of the second-stage membrane separation device for membrane separation treatment; at the same time, the liquid in the third-stage storage tank is circulated in the second-stage receiving liquid circulation loop by the second-stage peristaltic pump and then introduced into the second inner cavity of the second-stage membrane separation device to form a new receiving liquid (acid liquid), which is then circulated to the third-stage storage tank and discharged from the acid liquid production outlet in the third-stage storage tank; During the above membrane separation process, the acid concentration of the feed liquid in the first inner chamber is kept greater than that in the second inner chamber to form a concentration difference; at the same time, the working pressure applied to one side of the first inner chamber is kept greater than that applied to one side of the second inner chamber to form a pressure difference.

[0054] Application Example 2 This application example uses the process method for treating acidic wastewater from Application Example 1, with the following differences: In the system equipment, the effective area of ​​the membrane module in the membrane separation unit is 1.764 × 10⁻⁶. -2 m 2 The separation membrane is a Lucky nanofiltration membrane, model LF NFAR-4040; Simulated acidic wastewater in a high-concentration system was prepared as the acidic wastewater to be treated, consisting of hydrochloric acid and ferric chloride, containing Fe. 3+ The concentrations were 30 g / L and 20 g / L, respectively, but the pH of the solution was 0.97; the amount added to the system equipment was 2 L; water with pH 7 was added to the primary separation unit as the initial receiving liquid, and acid solution with pH 2 was added to the secondary separation unit as the initial receiving liquid, with a pre-set initial receiving liquid volume of 0.2 L for both. During the operation of the system equipment and process, the pressure of the first-stage membrane separation unit was controlled at 1.5 MPa, the flow rate of the receiving liquid in the first-stage separation unit was 721 mL / min, and the temperature was controlled at 30℃~40℃; at the same time, the pressure of the second-stage membrane separation unit was controlled at 0.9 MPa, the flow rate of the receiving liquid in the second-stage separation unit was 498 mL / min, and the temperature was controlled at 25℃. The concentration of metal ions was measured using an atomic absorption spectrophotometer (AAS, Beijing Purkinje, AA320CRT); the pH values ​​of the receiving liquid and the feed liquid were measured using a pH meter (Mettler-Toledo, Stander-FE28); and the amount of chloride ions was titrated with AgNO3 solution on an automatic titration stage to ensure ion conservation. When evaluating membrane separation performance, the solute rejection ratio R is calculated using the following equation: The acid recovery rate W is calculated using the following equation. a : in C f 、C p Indicates the concentration of the feed liquid and the receiving liquid. V r1 、V r2 Represents the initial and final volumes (L) of the receiving liquid. pH p , pH r This represents the initial and final pH values ​​of the receiving solution. pH f 、V f Represents the pH value and volume (L) of the feed solution; In the above process, acid can migrate effectively under dual-drive action, and iron ions can be significantly retained in the separation membrane. When the feed solution containing 30 g / L of iron ions runs for approximately 211 minutes, about 1.57 L of acid solution discharged from the third-stage storage tank is collected, achieving an overall acid recovery rate of 60.74%. 3+ The overall retention rate can reach 88.3%; when the feed solution containing 20 g / L of iron runs for 267 minutes using the system equipment and process, approximately 1.81 L of acid solution discharged from the third-stage storage tank is collected, and the overall acid recovery rate can reach 67.4%. 3+ The overall rejection rate can reach 92.4%. The higher the concentration of metal ions in the feed solution, the lower the rejection rate, indicating that the metal ion rejection rate is affected by the concentration of the metal ions themselves. However, the secondary separation's cyclic design provides sufficient tolerance and a buffer mechanism, ensuring a metal ion rejection rate of no less than 88%. Verification has shown that for feed solutions with these two specific metal ion concentrations and acid concentrations, a 20 g / L feed solution can achieve a transmembrane flux of 14 L / m³ in the first-stage separation unit. 2 ·h~21L / m 2 The transmembrane flux of the second-stage separation unit can reach 41 L / m³.2 ·h~48L / m 2 •h; The transmembrane flux of a 30 g / L feed liquid in the first-stage separation unit can reach 8 L / m 2 ·h~15L / m 2 The transmembrane flux of the second-stage separation unit can reach 32 L / m³. 2 ·h~37L / m 2 ·h.

[0055] The principle of the process method for treating acidic wastewater provided by this invention will be explained in conjunction with the results of this application example, such as... Figure 9 As shown in the figure, this diagram illustrates the transmembrane migration mechanism of acid and metal ions in acidic wastewater under pressure-concentration dual-driven conditions. The orange area at the top represents the feed side (i.e., the first inner chamber side, or the raw material side), the blue area at the bottom represents the receiver side (i.e., the second inner chamber layer), and the gray area in the middle represents the membrane separation interface. Under applied pressure, the feed side flows along the membrane surface, while the receiver side maintains a lower solute concentration, thus simultaneously creating pressure-driven and concentration-driven migration on both sides of the membrane.

[0056] H + The effective migration size is much smaller than Fe 3+ The hydrated ion structure results in lower and faster transport resistance within the membrane pores; simultaneously, the separation membrane surface carries a positive charge under acidic conditions, Fe 3+ These types of multivalent metal cations are subject to stronger repulsion; even if the surface charge of the separation membrane is limited, Fe 3+ It also exhibits higher migration resistance due to the complex interaction between high charge density and the interfacial ionic environment; meanwhile, Fe 3+ It is more likely to accumulate on the membrane surface, thereby enhancing local concentration polarization and further hindering its own permeation; while the low-acid environment on the receiver side preferentially drives H₂. + Migration, without affecting Fe 3+ It provides the same strong directional driving force, and the high concentration of hydrogen ions on the receiving liquid side increases the positive charge content of the membrane, thereby improving the membrane's resistance to Fe. 3+ The repulsive effect.

[0057] Thus, the two driving forces work together to cause H in the acidic system + They migrate more easily to the receiving liquid side, while high-valence metal ions, especially Fe, are more likely to migrate. 3+Due to the charge repulsion, large ion hydration structure, and membrane surface enrichment effect of nanofiltration membranes, transmembrane migration is significantly suppressed. In the figure, the feed liquid is located above the separation membrane, and the flow direction is from right to left as indicated by the arrow, indicating that the feed liquid flows tangentially through the membrane module on the separation membrane surface. This flow mode provides external pressure, giving the liquid a transmembrane driving force, and also slows down the excessive growth of the membrane surface boundary layer. In the figure, the receiver liquid is located below the membrane, and the arrow direction is opposite to that of the feed liquid to achieve cross-flow, indicating that the receiver liquid side is also in a state of circulation and renewal. The continuous flow and renewal of the receiver liquid can reduce the local accumulation of acid and salt on the receiver liquid side of the membrane surface. On the other hand, it helps to maintain a large concentration difference across the membrane, thus ensuring the continuous existence of concentration difference driving force. Therefore, this process is a coupled mass transfer system with pressure driving from above and concentration difference pulling from below.

[0058] It should be noted that the present invention is not limited to retaining only Fe. 3+ Ions can be separated by adding more stages of membrane separation devices and separation units as needed, and / or using different separation membranes in different stages of membrane separation devices to achieve the interception effect of multiple metal ions.

[0059] Application Example 3 This application example uses the process method for treating acidic wastewater from Application Example 1, with the following differences: In the system equipment, the effective area of ​​the membrane module in the membrane separation unit is 1.854 × 10⁻⁶. -2 m 2 The separation membrane is a Lucky nanofiltration membrane, model LF NFAR-4040; Referring to the pickling wastewater from the hydrochloric acid pickling process for stainless steel, a simulated wastewater was prepared as the acidic wastewater to be treated. Its components were hydrochloric acid, ferric chloride, chromium chloride, and nickel chloride, containing Fe. 3+ Concentration 15g / L, Cr 3+ The concentration is 4 g / L, Ni 2+ The concentration is 3 g / L, and the solution pH is 1; the amount added to the system equipment is 2 L; water with pH 7 is added to the primary separation unit as the initial receiving liquid, and acid solution with pH 3 is added to the secondary separation unit as the initial receiving liquid, with a pre-set initial receiving liquid volume of 0.2 L for each. The system equipment and process were operated for 304 minutes. During this period, the pressure of the first-stage membrane separation unit was controlled at 0.8 MPa to 0.9 MPa, the flow rate of the receiving liquid in the first-stage separation unit was 582 mL / min, and the temperature was controlled at 30℃ to 40℃. At the same time, the pressure of the second-stage membrane separation unit was controlled at 0.7 MPa to 0.8 MPa, the flow rate of the receiving liquid in the second-stage separation unit was 498 mL / min, and the temperature was controlled at 25℃. After the end time, approximately 1.93 L of acid was collected from the third-stage storage tank. The acid effectively migrated under dual-drive conditions, achieving an overall acid recovery rate of 78.8%. Fe 3+ Cr 3+ Ni 2+ The overall rejection rates were 97.4%, 99.5%, and 98.7%, respectively. Verification showed that for this specific feed solution with varying metal ion and acid concentrations, the transmembrane flux of the first-stage separation unit in the system could reach 17 L / m³. 2 ·h~20L / m 2 The transmembrane flux of the second-stage separation unit can reach 57 L / m³. 2 ·h~65L / m 2 ·h.

[0060] Application Comparative Example 1 The differences between this comparative example and Application Example 3 include: eliminating the processing in the secondary separation unit and processing only in the primary separation unit; the discharged acid solution is directly obtained from the pipeline connecting the secondary storage tank and the feed inlet of the secondary membrane separation unit; specifically, the effective area of ​​the membrane module in the membrane separation unit is 1.811 × 10⁻⁶. -2 m 2 The system equipment and process operated for 274 minutes, yielding approximately 1.79 L of discharged acid, with an acid recovery rate of 69.8%; Fe 3+ Cr 3+ Ni 2+ The rejection rates were 71.4%, 86.5%, and 81.7%, respectively. For this specific feed solution with varying metal ion and acid concentrations, the transmembrane flux in a system with only a single separation unit was 19 L / m³. 2 ·h~25L / m 2 Compared to Application Example 3, the acid recovery rate and metal rejection rate in Application Comparative Example 1 both decreased significantly.

[0061] Application Comparative Example 2 The differences between this comparative example and Comparative Example 1 include: further eliminating the initial receiving liquid, i.e., no initial receiving liquid is added to the first-stage storage tank; simultaneously, the circulation of the receiving liquid side from the first-stage storage tank to the first-stage membrane separation unit via pipeline is stopped, and the acid solution discharged from the first-stage membrane separation unit to the first-stage storage tank is directly stored and discharged in the first-stage storage tank; specifically, the effective area of ​​the membrane module of the membrane separation unit is 1.664 × 10⁻⁶. -2 m 2 The system equipment and process operated for 219 minutes, yielding approximately 1.28 L of discharged acid. Due to the lack of a receiving liquid at the membrane surface, significant concentration polarization occurred during acid migration, resulting in an overall acid recovery rate of only 55.8%. (Fe)3+ Cr 3+ Ni 2+ Due to the lack of repulsion from the receiving liquid, leakage was enhanced, resulting in rejection rates of 57.4%, 71.5%, and 69.7%, respectively. Compared to Comparative Application Example 1, both the acid recovery rate and metal rejection rate in Comparative Application Example 2 were further reduced. The transmembrane flux was validated to be 14 L / m for this specific feed solution with varying metal ion and acid concentrations. 2 ·h~20L / m 2 ·h.

[0062] In summary, the membrane separation device, system equipment, and process method for treating acidic wastewater provided by this invention can achieve membrane separation treatment by simultaneously setting up a dual driving force on the feed liquid side of the membrane separation device, with pressure as the main driving force and the concentration difference driving force of the receiving liquid as the auxiliary driving force. Under this process, the receiving liquid side can maintain a low concentration environment by continuously circulating and refreshing the receiving liquid side. By using at least two membrane separation devices to construct a multi-stage series connection of primary membrane separation unit and secondary membrane separation unit, it is beneficial to achieve both efficient recovery of acid and enhanced retention of metal ions in acidic wastewater.

[0063] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0064] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0065] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A membrane separation device, characterized in that, include: The first housing has a first inner cavity and is provided with a liquid inlet and a liquid circulation outlet communicating with the first inner cavity, and the first inner cavity has a first opening on the first housing; The second housing has a second inner cavity and is provided with a liquid outlet and a liquid circulation inlet communicating with the second inner cavity, and the second inner cavity has a second opening on the second housing; The first opening and the second opening are disposed opposite to each other and are detachably fixedly connected, so that the first inner cavity and the second inner cavity are connected. A limiting step is provided in the second inner cavity of the second housing, and a limiting protrusion corresponding to the limiting step is provided on the first housing at the first opening position. The limiting protrusion extends into the second inner cavity and forms a limiting space with the limiting step. A membrane module, disposed within the limiting space, includes a stacked support frame, a separation membrane, and a support plate; the working pressure difference of the separation membrane is greater than or equal to 0.5 MPa; the support frame is disposed on one side of the limiting protrusion and in contact with it, and the hollow portion of the support frame is used for the passage of liquid; the support plate is disposed on one side of the limiting step and in contact with it, and the support plate is provided with a liquid passage area corresponding to the hollow portion of the frame, and the liquid passage area is provided with several through holes for the passage of liquid.

2. The membrane separation device according to claim 1, characterized in that, Separation membranes include nanofiltration membranes or reverse osmosis membranes.

3. The membrane separation device according to claim 1 or 2, characterized in that, The first housing is provided with a first flange around the outer periphery near the first opening, and the second housing is provided with a second flange around the outer periphery near the second opening. The first flange and the second flange are bolted together.

4. The membrane separation device according to any one of claims 1-3, characterized in that, The limiting protrusion is provided with a first sealing ring groove on the side facing the support frame, and a first sealing ring is provided in the first sealing ring groove; And / or, the support frame is provided with a second sealing ring groove on the side facing the separation membrane, and a second sealing ring is provided in the second sealing ring groove; And / or, the support plate is provided with a third sealing ring groove on the side facing the limiting step, and a third sealing ring is provided in the third sealing ring groove.

5. The membrane separation apparatus according to any one of claims 1-4, characterized in that, The limiting protrusion is an annular protrusion, which is arranged around the edge of the first opening, and the outer diameter of the annular protrusion is less than or equal to the diameter of the second opening; the limiting step is an annular step, which is arranged around the inner wall of the second housing in the second inner cavity. And / or, the diameter of the hollow portion of the support frame is less than or equal to the diameter of the first opening.

6. The membrane separation apparatus according to any one of claims 1-5, characterized in that, The liquid circulation outlet of the first housing is connected to the liquid inlet via a pipeline; And / or, the liquid outlet of the second housing is connected to the liquid circulation inlet via a pipeline.

7. A system for treating acidic wastewater, characterized in that, The membrane separation device comprises at least two stages as described in any one of claims 1-6, and a storage tank matching each stage of the membrane separation device, wherein: The first-stage storage tank is connected to the feed inlet of the first-stage membrane separation device through a pipeline equipped with the first pump body, and the feed circulation outlet of the first-stage membrane separation device is connected to the first-stage storage tank through a pipeline, thus forming the first-stage membrane separation loop. The feed liquid outlet of the first-stage membrane separation unit is connected to the second-stage storage tank through a pipeline; and the second-stage storage tank is connected to the feed liquid circulation inlet of the first-stage membrane separation unit through a pipeline equipped with a second pump body, thus forming the first-stage receiving liquid circulation loop. As described above, the nth stage storage tank is connected to the nth stage membrane separation device to form the nth stage membrane separation loop; at the same time, the nth stage membrane separation device is connected to the (n+1)th stage storage tank to form the nth stage receiving liquid circulation loop; n is an integer ≥ 1. The final stage of the storage tank is equipped with an acid production and outlet.

8. The system equipment for treating acidic wastewater according to claim 7, characterized in that, On the pipeline connecting the first pump body to the feed inlet of the nth stage membrane separation device, there is an nth stage feed liquid circulation branch, and the other end of the nth stage feed liquid circulation branch is connected to the nth stage storage tank.

9. The system equipment for treating acidic wastewater according to claim 7 or 8, characterized in that, The system equipment also includes an nth-stage cooling circulation device that matches the nth-stage liquid storage tank, used to cool the nth-stage liquid storage tank; And / or, the first pump body includes a water pump, and the second pump body includes a peristaltic pump.

10. A process for treating acidic wastewater, characterized in that, The process method is performed using the system equipment described in any one of claims 7-9, and the process method includes: The system supplies acidic wastewater to be treated to the first-stage storage tank and initial receiving liquid to all subsequent storage tanks. The first pump body causes the liquid in the nth stage storage tank to flow in the nth stage membrane separation loop and enters the first inner cavity of the nth stage membrane separation device for membrane separation treatment; at the same time, the nth stage peristaltic pump causes the liquid in the (n+1)th stage storage tank to flow in the nth stage receiving liquid circulation loop and enters the second inner cavity of the nth stage membrane separation device to form a new receiving liquid, which is then circulated back to the (n+1)th stage storage tank. During the membrane separation process, the acid concentration of the feed solution in the first inner cavity is maintained to be greater than that in the second inner cavity, forming a concentration difference; at the same time, the working pressure applied to one side of the first inner cavity is maintained to be greater than that applied to one side of the second inner cavity, forming a pressure difference.

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