An improved electrodialysis device for concentrating and purifying TMAH dilute waste liquid

Abstract

The application discloses an improved electrodialysis device for TMAH dilute waste liquid concentration and purification, which comprises cation exchange membranes, A-type electrodialysis separators, anion exchange membranes and B-type electrodialysis separators arranged alternately, wherein the A-type electrodialysis separators adopt thick separators, and the B-type electrodialysis separators adopt thin separators. Through the design of thick dilute chambers and thin concentrated chambers, higher flow and flow rate of the dilute water circulation are realized; under the ion migration distance of reasonable voltage, the high flow increases the ion density of the movable membrane surface per unit area of the dilute water chamber; the innumerable enhanced turbulence generated by the high flow rate and the microwave wave type spiral grid greatly weakens the concentration polarization phenomenon; the membrane surface current density is improved to the highest under the working condition of low ion concentration; the TMAH concentration and purification efficiency are effectively improved; the number of electrodialysis membranes, the investment cost of the supporting equipment and the pump consumption are greatly reduced; and the economic advantages of the application to the concentration and purification of TMAH dilute waste liquid and other low-salinity water are obvious.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and specifically to an improved electrodialysis device for the concentration and purification of TMAH dilute waste liquid. Background Technology

[0002] In the semiconductor and optoelectronic fields, development is a crucial step in creating patterns in photoresist on a silicon wafer surface. Soluble areas on the photoresist are dissolved by a chemical developer, leaving visible island or window patterns on the wafer surface. During development, the photoresist in non-exposed areas remains because it did not undergo a chemical reaction during exposure; while the exposed photoresist gradually dissolves. The developer solution mentioned above is usually tetramethylammonium hydroxide (hereinafter referred to as TMAH). In addition to the concentrated waste liquid with a TMAH concentration of 2-3% discharged during the first rinse of the waste developer solution, a secondary rinse waste liquid with a concentration of several tens of times that of the concentrated waste liquid will also be discharged. The concentration of TMAH in this part of the diluted waste liquid is 180-400ppm. The low concentration waste liquid must be concentrated and then purified and separated. However, according to the traditional electrodialysis device, the dilute and concentrated chambers use the same type of partition, which is only suitable for treating salt solutions with a concentration of 3% and above. If a suitable electrodialysis membrane and configuration are selected, it can be used for the recovery of concentrated waste liquid with a concentration of 2-3%. However, if electrodialysis technology is used for the concentration and purification of diluted TMAH waste liquid, its economic efficiency will be very poor.

[0003] Currently, electrodialysis is the most commonly used process for recovering concentrated TMAH waste liquid (TMAH mass concentration 2-2.5%). While electrodialysis can be used for the concentration and separation of diluted TMAH waste liquid, the demand for electrodialysis membranes and supporting facilities is enormous, resulting in significant investment and very poor economic efficiency. In some cases, the membranes reach the end of their service life before the investment is even recouped, rendering them unsuitable for application.

[0004] Currently, patent CN217676938U proposes a developer waste liquid recovery device. This device uses a bipolar membrane, a cation exchange membrane, and an anion exchange membrane. Organic matter such as photoresist in the developer waste liquid is blocked by the cation exchange membrane and remains in the raw material compartment. Anions such as hydroxide and carbonate in the developer waste liquid enter the intermediate compartment through the anion exchange membrane and combine with hydrogen ions generated by the first bipolar membrane to obtain water or carbon dioxide. Under the drive of an external electric field, TMA+ in the developer waste liquid in the raw material compartment migrates into the product compartment through the cation exchange membrane and combines with hydroxide ions generated by the second bipolar membrane to obtain pure TMAH product. The device has high equipment investment costs, and according to the provided embodiments, it is only suitable for the purification and recovery of TMAH concentrated waste liquid. Patent CN115770482A proposes an electrodialysis device for lithium extraction in salt lake brine using a two-dimensional channel membrane. This device solves the problem of swelling of two-dimensional electrodialysis membranes when exposed to water by uniformly and alternately arranging the slots of the slotted grid to compress the electrodialysis membrane. The dilute and concentrated chambers use the same type of partition, that is, the chamber thickness is the same. It is suitable for high saline (above 3% mass concentration). For low saline, the membrane current will be very low, the concentration polarization phenomenon will be severe, and the migration efficiency will be very low. Patent CN115784248A discloses a method for stacking large nanosheets into a two-dimensional thin film by assembling them on the end face. This method can effectively reduce the number of pores in the membrane and improve the transport path of ions in the two-dimensional membrane. However, it does not improve the application device of the thin film. In actual low-salt water extraction applications, when ions migrate directionally under the action of an electric field, the ion density on the membrane surface of the fresh water chamber is too low, the upper limit of the membrane current is limited, and the concentration polarization phenomenon on the membrane surface is very serious, which seriously affects the ion separation efficiency of the membrane. It can even produce a large amount of hydrogen and oxygen during water electrolysis, causing safety hazards.

[0005] The above methods only apply when the solution has a certain concentration (3% by mass or higher). Improving migration efficiency involves optimizing membrane selection, chamber thickness, and the ion transport path within the membrane. For solutions with a concentration of 3% or higher, the number of ions is abundant. Under the influence of an electric field, ions migrate and interfere with each other due to the repulsion of like charges. Therefore, reducing the chamber thickness not only shortens the ion migration path but also reduces the ion density per unit area of ​​the membrane, thus minimizing interference. With an optimized ion transport path, saturated membrane current can be achieved at a lower voltage, improving both migration efficiency and economy. However, for dilute TMAH waste liquid, the ion quantity is sparse, resulting in almost no interference during migration. Using a thin chamber leads to an even lower ion density per unit area of ​​the membrane. Furthermore, an optimized ion transport path exacerbates concentration polarization, resulting in extremely low membrane current and consequently, very low migration efficiency and poor economy.

[0006] To address the economic challenges of applying electrodialysis technology to the concentration and purification of TMAH dilute wastewater, the technical problem that needs to be solved by those skilled in the art is how to address the concentration polarization problem on the membrane surface during the concentration and salt extraction of TMAH dilute wastewater, thereby increasing the membrane current and thus improving the migration efficiency. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an improved electrodialysis device for the concentration and purification of TMAH dilute wastewater. This improved electrodialysis device features a thick desalination chamber and a thin concentration chamber. The desalination chamber uses a thick partition, allowing for higher flow rates and velocities in the desalination circulation. Under reasonable voltage and ion migration distance, the high flow rate increases the total number of ions that can migrate in the desalination chamber, thus raising the upper limit of current density per unit area of ​​the membrane. Furthermore, the high flow rate enhances turbulence, and the numerous enhanced turbulences generated by the micro-wave spiral grid significantly reduce concentration polarization. The thin partition in the concentration chamber minimizes membrane stack resistance, reducing the overall voltage requirement of the membrane stack and thus lowering power consumption. Under low ion concentration conditions, this invention not only significantly increases the membrane current density, effectively improving the concentration and purification efficiency of TMAH, but also achieves maximum cost-effectiveness in terms of power consumption, greatly reducing the number of electrodialysis membranes, the investment cost of supporting equipment, and pump consumption. It offers significant economic advantages for the concentration and purification of low-salinity wastewater such as TMAH dilute wastewater.

[0008] An improved electrodialysis device for the concentration and purification of TMAH dilute waste liquid includes alternating cation exchange membranes, type A electrodialysis partitions, anion exchange membranes, and type B electrodialysis partitions. The type A electrodialysis partitions are thick partitions, forming a thick chamber that is a desalination chamber through which low-salt water is introduced, enabling a high flow rate and high velocity of low-salt water in the desalination chamber. The type B electrodialysis partitions are thin partitions, forming a thin chamber that is a concentrate chamber through which ultrapure water is introduced. Under the action of an electric field, ions from the low-salt water in the desalination chamber migrate to the ultrapure water in the concentrate chamber. Both type A and type B electrodialysis partitions are composed of a fixed frame and a crisscrossing spiral grid arranged in their chambers. The fixed frame is provided with liquid guiding holes and water distribution channels at both ends that are respectively connected to the liquid guiding holes and their chambers.

[0009] As a preferred embodiment of the above technical solution, the type A electrodialysis partition includes a type A spiral grid, type A liquid guiding holes, and type A water distribution channels. The type A spiral grid is generally wavy, and when water flows through the grid in its thick cavity, it forms micro-turbulence under the spiral and wavy turbulence.

[0010] As a preferred embodiment of the above technical solution, the thickness of the type A electrodialysis separator is 1.0-2.0 mm; The number of A-type liquid guiding holes is 3-8. When the A-type liquid guiding hole is square, the side length is 30-100mm. When the A-type liquid guiding hole is circular, the diameter is 30-100mm. When the A-type liquid guiding hole is elliptical, its major axis is 40-100mm and its minor axis is 30-80mm. The type A water distribution channel is a single type A fan-shaped water flow channel. The length of the type A fan-shaped water flow channel connected to the type A liquid guide hole is 20-100mm, and the length of the side connected to its chamber hole is 40-200mm.

[0011] As a preferred embodiment of the above technical solution, the type B electrodialysis partition includes a type B spiral grid, type B liquid guiding holes, and type B water distribution channels. The surface of the type B spiral grid is planar, and when water flows through the grid in its thin cavity, it forms micro-turbulence under the disturbance of the spiral grid strips.

[0012] As a preferred embodiment of the above technical solution, the thickness of the type B electrodialysis separator is 0.5-1.0 mm; The number of type B liquid guiding holes is 1-4. When the type B liquid guiding hole is square, the side length is 30-100mm. When the type B liquid guiding hole is circular, the diameter is 30-100mm. When the type B liquid guiding hole is elliptical, its major axis is 40-100mm and its minor axis is 30-80mm. The type B water distribution channel consists of 5-20 type B fan-shaped water flow channels. The length of the side of the type B fan-shaped water channel connected to the type B liquid guiding hole is 1-2 mm, and the length of the side connected to its chamber hole is 2-5 mm.

[0013] As a preferred embodiment of the above technical solution, the cation exchange membrane is a cation-selective permeable polymeric material thin film. Under the action of an electric field, positively charged cations can migrate directionally from the positive electrode to the negative electrode, that is, from the thick chamber to the thin chamber, thereby realizing TMAH purification.

[0014] As a preferred embodiment of the above technical solution, the anion exchange membrane is a thin film of polymer material with anion selective permeability. Under the action of an electric field, negatively charged anions can migrate directionally from the negative electrode to the positive electrode, that is, from the thick chamber to the thin chamber, thereby realizing TMAH purification.

[0015] As a preferred embodiment of the above technical solution, the A-type electrodialysis separator and the B-type electrodialysis separator have an electrical width of 110-2000mm and a length of 270-2500mm.

[0016] As a preferred embodiment of the above technical solution, all intersections between the spiral grid edge and the fixed frame are welded together.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs desalination and concentrate chambers of varying thicknesses, with the desalination chamber being a thicker cavity. This allows for high flow rates and velocities. Firstly, the high flow rate increases the total number of ions that can migrate per unit time in the desalination chamber, thus raising the upper limit of current density per unit area of ​​the membrane surface and preventing energy waste caused by sparse ions reaching migration saturation prematurely. Secondly, the high flow rate promotes turbulence and numerous enhanced local turbulences generated by the micro-wave-shaped spiral grid. This significantly reduces concentration polarization, thereby greatly reducing the number of membranes and associated facilities. Furthermore, the desalination channel can incorporate a spiral grid with larger wave peaks and valleys, which, combined with the high flow rate, creates stronger turbulence, further mitigating the impact of concentration polarization and improving ion migration efficiency. Additionally, the concentrate baffle is thin, minimizing membrane stack resistance and overall voltage requirements, thus reducing power consumption. Attached Figure Description

[0018] Figure 1 This is a layout diagram of the electrodialysis component of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the Type A electrodialysis separator of the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of the Type B electrodialysis separator of the present invention.

[0021] Figure 4 This is a schematic diagram of the structure of a single spiral grid of the present invention.

[0022] Figure 5 This is a schematic diagram of the structure of the Type A water distribution channel of the present invention.

[0023] Figure 6 This is a schematic diagram of the B-type water distribution channel of the present invention.

[0024] The attached diagram is labeled as follows: 1-Cation exchange membrane, 2-Type A electrodialysis partition, 201-Type A liquid guiding hole, 202-Type A water distribution channel, 203-Type A spiral grid, 3-Anion exchange membrane, 4-Type B electrodialysis partition, 401-Type B liquid guiding hole, 402-Type B water distribution channel, 403-Type B spiral grid, 5-Type B fan-shaped water flow channel. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0026] The present invention will now be described in further detail with reference to the accompanying drawings: This invention provides an improved electrodialysis device for the concentration and purification of TMAH dilute waste liquid. It can be widely used for the concentration and purification of TMAH dilute waste liquid and is widely applicable to new construction, renovation and upgrading projects, scenarios with ion concentration requirements for low-concentration solutions, scenarios with purification requirements for low-concentration materials, and scenarios with separation requirements for monovalent and divalent ions in low-concentration solutions.

[0027] refer to Figure 1 An improved electrodialysis device for the concentration and purification of TMAH dilute waste liquid includes alternating cation exchange membranes 1, type A electrodialysis partitions 2, anion exchange membranes 3, and type B electrodialysis partitions 4. Each electrodialysis partition includes a fixed frame with a central chamber and a crisscrossing spiral grid within the chamber. In this embodiment, the cation exchange membrane 1 can be an alkali-resistant separation membrane for monovalent and divalent ions, used for the separation of TMAH, monovalent and divalent ions and photoresist in the dilute TMAH waste liquid; the anion exchange membrane 3 can be an alkali-resistant organic polymer film, used to ensure the ion balance of the electrodialysis system.

[0028] The working principle of this invention is as follows: High flow rate and high velocity are used to increase the membrane surface current, thereby improving the TMAH recovery efficiency of dilute TMAH waste liquid. Generally, electrodialysis is used in scenarios with high-concentration materials. High-salt water has a very high ion quantity. Under the influence of an electric field, ions migrate and interfere with each other due to the repulsion of like charges. Reducing the thickness of the chamber not only reduces the ion migration path but also reduces the membrane surface ion density, thus reducing interference. With an optimized ion transport path, saturated membrane surface current can be achieved at a lower voltage, improving both migration efficiency and economy. However, for low-salt water, the ion quantity is sparse, and there is almost no interference during migration. Using a thin chamber results in a low membrane surface ion density. Combined with an optimized ion transport path, the ion migration rate is much greater than the mass transfer rate, exacerbating concentration polarization. The membrane surface current is very low; even with increased voltage, the current increase is not significant, and water electrolysis is intensified. Therefore, the migration efficiency is very low, and the economy is poor. This invention designs the freshwater chamber as a thick chamber, which increases the circulation flow rate and membrane surface velocity of the TMAH dilute waste liquid, increases the membrane surface ion density, and raises the upper limit of the membrane surface current. Furthermore, the grid inside the freshwater chamber is designed as a wave-shaped spiral grid with larger peak and valley values, forming numerous enhanced turbulences, which greatly reduces the influence of concentration polarization and improves the purification efficiency of TMAH.

[0029] In this embodiment, the electrodialysis separator has a width of 110-2000mm and a length of 270-2500mm.

[0030] refer to Figure 2 , Figure 4 , Figure 5 The thickness of the A-type electrodialysis partition is generally set to 1.0-2.0mm, including a fixed frame around the perimeter and an interlaced A-type spiral grid 203 set in the chamber. The fixed frame is provided with A-type liquid guiding holes 201 on the upper and lower sides and A-type water distribution channels 202 at both ends that are connected to the liquid guiding holes and the chamber respectively. In this embodiment, all intersections between the crisscrossing spiral mesh edges of the A-type spiral mesh 203 and the fixed frame are welded together. The A-type spiral mesh 203 is composed of tightly arranged spiral mesh strips ( Figure 4 The spiral mesh is composed of crisscrossing and fixed spacing. The spiral mesh is curved in a slightly wavy shape, with the height of the crests and troughs being 0.1-0.8 mm. When water flows through the mesh in the chamber, it forms countless micro-turbulences under the spiral and wavy turbulence. In this embodiment, the type A liquid guiding holes 201 are square, circular, or elliptical, and are evenly spaced on the upper and lower sides of the fixed frame. The number of type A liquid guiding holes 201 is 3-8. When the type A liquid guiding holes 201 are square, the side length is 30-100mm. When the type A liquid guiding holes 201 are circular, the diameter is 30-100mm. When the type A liquid guiding holes 201 are elliptical, the major axis is 40-100mm and the minor axis is 30-80mm. In this embodiment, the type A water distribution channel 202 is a single type A fan-shaped water flow channel ( Figure 5 The type A fan-shaped water flow channel ( Figure 5 The length of the side connecting the liquid guiding hole is 20-100mm, and the length of the side connecting the chamber hole is 40-200mm. The A-type water distribution channel 202 has 3-8 liquid guiding holes on both sides of the fixed frame. refer to Figure 3 , Figure 4 and Figure 6 The thickness of the B-type electrodialysis partition is generally set to 0.5-1.0 mm. It includes a fixed frame around the perimeter and a crisscrossing B-type spiral grid 403 set in the chamber. The fixed frame is provided with B-type liquid guiding holes 401 on the upper and lower sides and B-type water distribution channels 402 at both ends that are connected to the B-type liquid guiding holes 401 and the chamber, respectively. In this embodiment, all intersections between the edge of the B-type spiral mesh 403 and the fixed frame are welded together. The B-type mesh 403 is composed of closely arranged spiral mesh strips. Figure 4 The grid is composed of interlaced and spaced spiral mesh strips, which are generally planar. When water flows through the thin cavity into the grid, it is within the spiral mesh strips (…). Figure 4Numerous micro-turbulences are formed under the disturbance of the flow; In this embodiment, the type B liquid guiding holes 401 are square, circular, or elliptical, and are evenly spaced on the upper and lower sides of the fixed frame. The number of type B liquid guiding holes 30 is 1-4. When the liquid guiding hole 401 is square, the side length is 30-100mm. When the type B liquid guiding hole 401 is circular, the diameter is 30-100mm. When the type B liquid guiding hole 401 is elliptical, the major axis is 40-100mm and the minor axis is 30-80mm. In this embodiment, the B-type water distribution channel 402 is composed of 5-20 B-type fan-shaped water flow channels 5. The length of the side of the B-type fan-shaped water channel 5 connected to the liquid guiding hole is 1-2mm, and the length of the side connected to the chamber hole is 2-5mm. The B-type water distribution channel 402 has 1-4 liquid guiding holes on both sides of the fixed frame.

[0031] The following is a further explanation with reference to specific embodiments: The dilute waste liquid of TMAH photolithography developer for flat panel displays is recycled. The TMAH dilute waste liquid has a conductivity of 600-800 μS / cm, a pH of 11-11.5, and contains 180-400 ppm TMAH, a small amount of carbonate, photoresist, and trace metal ions. The TMAH waste liquid is connected to type A liquid guide hole 201 and flows through type A fan-shaped water flow channel (…). Figure 5 The membrane flow rate is 20-49 cm / s in the desalination chamber, and the operating pressure is 0.02 MPa-0.12 MPa. Ultrapure water is introduced into the B-type liquid guide hole 401 and flows through the B-type fan-shaped water flow channel 5 into the concentrate chamber, with the membrane flow rate controlled at 5-15 cm / s. The operating pressure is kept in balance with the desalination chamber pressure. An inert liquid is introduced into the electrode chamber, and the operating pressure is kept in balance with the desalination and concentrate chamber pressures. The operating pressure is ≤0.2 MPa, the operating current is 30-60 A / m², the effective membrane area processing capacity is 180-240 L / (m²*h), and the TMAH recovery rate can reach up to 85%. Driven by an electric field, TMA+ passes through the cation exchange membrane 1 into the concentrate chamber, and OH- passes through the anion exchange membrane 3 into the concentrate chamber. Neutral photoresist molecules and divalent carbonate ions are retained in the desalination chamber, thus purifying TMAH. When the TMAH is purified to a mass concentration of 2.38%, it is collected and reused.

[0032] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified electrodialysis device for concentrating and purifying TMAH dilute waste liquid, characterized in that: It includes alternating cation exchange membranes, type A electrodialysis dialysis dialysis plates, anion exchange membranes, and type B electrodialysis dialysis dialysis plates; The A-type electrodialysis partition is a thick partition with a thickness of 1.0-2.0 mm. The thick chamber formed by it is a freshwater chamber and is filled with low-salt water to achieve a high flow rate and high velocity of low-salt water in the freshwater chamber. The A-type electrodialysis partition includes an A-type spiral grid, A-type liquid guiding holes, and A-type water distribution channels. The A-type spiral grid is generally wavy. When water flows through the grid in its thick chamber, it forms micro-turbulence under the turbulence of the spiral and wavy shape. The B-type electrodialysis partition is a thin partition with a thickness of 0.5-1.0 mm. The thin chamber formed by it is a concentrate chamber and is circulated with ultrapure water. The B-type electrodialysis partition includes a B-type spiral grid, B-type liquid guiding holes, and B-type water distribution channels. The surface of the B-type spiral grid is planar. When water flows through the grid in its thin chamber, it forms micro-turbulence under the turbulence of the spiral grid strips. Under the influence of an electric field, ions from the low-salt water in the desalination chamber migrate to the ultrapure water in the concentrate chamber. The cation exchange membrane is a cation-selective permeable polymeric membrane. Under the influence of an electric field, positively charged cations can migrate directionally from the positive electrode to the negative electrode, that is, from the thick chamber to the thin chamber, thus achieving TMAH purification. The anion exchange membrane is an anion-selective permeable polymeric membrane. Under the influence of an electric field, negatively charged anions can migrate directionally from the negative electrode to the positive electrode. That is, both positively charged cations and negatively charged anions can migrate from the thick chamber to the thin chamber, thus achieving TMAH purification. Both the Type A electrodialysis partition and the Type B electrodialysis partition consist of a fixed frame and a crisscrossing spiral grid set in its chamber. The fixed frame is provided with liquid guiding holes and water distribution channels at both ends that are respectively connected to the liquid guiding holes and its chamber.

2. The improved electrodialysis device for concentrating and purifying TMAH dilute waste liquid according to claim 1, characterized in that: The number of A-type liquid guiding holes is 3-8. When the A-type liquid guiding hole is square, the side length is 30-100mm. When the A-type liquid guiding hole is circular, the diameter is 30-100mm. When the A-type liquid guiding hole is elliptical, its major axis is 40-100mm and its minor axis is 30-80mm. The type A water distribution channel is a single type A fan-shaped water flow channel. The length of the type A fan-shaped water flow channel connected to the type A liquid guide hole is 20-100mm, and the length of the side connected to its chamber hole is 40-200mm.

3. The improved electrodialysis device for concentrating and purifying TMAH dilute waste liquid according to claim 1, characterized in that: The number of type B liquid guiding holes is 1-4. When the type B liquid guiding hole is square, the side length is 30-100mm. When the type B liquid guiding hole is circular, the diameter is 30-100mm. When the type B liquid guiding hole is elliptical, its major axis is 40-100mm and its minor axis is 30-80mm. The type B water distribution channel consists of 5-20 type B fan-shaped water flow channels. The length of the side of the type B fan-shaped water channel connected to the type B liquid guiding hole is 1-2 mm, and the length of the side connected to its chamber hole is 2-5 mm.

4. The improved electrodialysis device for concentrating and purifying TMAH dilute waste liquid according to claim 1, characterized in that: The width of the type A electrodialysis separator and the length of the type B electrodialysis separator are 110-2000mm and 270-2500mm respectively.

5. The improved electrodialysis device for concentrating and purifying TMAH dilute waste liquid according to claim 1, characterized in that: All intersections between the spiral grid edge and the fixed frame are welded together.

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