Preparation process of boron adsorption purification filter element for ultrapure water system

Abstract

The application discloses a preparation process of a boron adsorption purification filter element for an ultrapure water system, and comprises the following steps: step one, selecting PTFE nanofiber nonwoven felt as a base material; step two, performing plasma pretreatment on the PTFE nanofiber nonwoven felt; step three, placing the activated PTFE nanofiber nonwoven felt in an initiation type chemical vapor deposition device, performing vacuum pumping, selecting GMA, EGDMA and an initiator TBPO to perform initiation type chemical vapor deposition, and depositing a polymer film according to the same gradient pressure to obtain modified PTFE felt; step four, immersing the modified PTFE felt in a 5% NMG solution to perform cyclic immersion; and finally, performing multiple cyclic washing. The preparation process of the boron adsorption purification filter element for the ultrapure water system is very superior in boron removal effect, can make boron ions reach a trace level, and the prepared boron adsorption purification filter element has little TOC dissolution.

Description

Technical Field

[0001] This invention relates to the field of boron removal technology for ultrapure water, and more particularly to a process for preparing boron adsorption purification filter cartridges for ultrapure water systems. Background Technology

[0002] Boron removal has always been a key technical challenge in ultrapure water systems. Boron is present in natural water, and due to its strong affinity for other ions in water, especially boric acid and borate ions, it is difficult to remove during water treatment. Boron has a particularly significant impact on high-precision industries such as semiconductors and electronics, especially in ultrapure water reuse systems, where excessive boron levels in ultra-concentrated water can lead to a series of serious consequences.

[0003] Currently, the mainstream boron removal technologies in the industry mainly rely on boron-removing resins or traditional boron adsorption purification filter cartridges. Although both boron-removing resins and traditional boron adsorption purification filter cartridges can reduce boron content to some extent, they still have shortcomings in application: When treating high-salinity water, such as concentrated water or reclaimed water, the active sites of existing ion-exchange boron removal resins are easily occupied by background ions such as sulfate and chloride ions in the water, resulting in a significant decrease in selectivity for trace boron.

[0004] Traditional resins and filter cartridges prepared by liquid phase coating often contain unreacted monomers, solvents or pore-forming agents. During operation, these substances are continuously released into the water, leading to an increase in total organic carbon (TOC) and increasing the burden of TOC degradation in subsequent processes.

[0005] Most existing modified filter cartridges use physical impregnation, which results in extremely weak bonding between the polymer functional layer and the substrate. The polymer film is prone to peeling and delamination, which not only shortens the service life of the filter cartridge but also causes secondary pollution.

[0006] In the concentrate recovery or raw water reuse stage of ultrapure water production systems, boron content is often concentrated to thousands or even tens of thousands of ppt. If it cannot be removed by effective means, it will lead to a series of serious consequences: In the semiconductor manufacturing field, residual boron will enter the silicon wafer surface as an acceptor impurity (P-type dopant), changing the electrical properties of semiconductor materials and directly causing chip failure or a significant drop in yield; in the electronics industry, boron contamination will interfere with fine development and etching processes, causing instability in micro and nano structures; in recycling systems, long-term accumulation of boron will accelerate the failure of expensive downstream polishing resins, significantly increasing production costs and maintenance frequency. Summary of the Invention

[0007] In view of this, the present invention proposes a process for preparing boron adsorption purification filter cartridges for ultrapure water systems.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A process for preparing a boron adsorption purification filter element for an ultrapure water system includes the following steps: Step 1: Select PTFE nanofiber nonwoven felt as the substrate; Step 2: Place the PTFE nanofiber nonwoven felt in the chamber of the plasma cleaner and evacuate the chamber; then introduce a mixture of argon and oxygen into the chamber and turn on the radio frequency power supply for discharge treatment; stop evacuating and introduce nitrogen into the chamber until the pressure in the chamber rises back to 1 atmosphere; transfer the PTFE nanofiber nonwoven felt to the reaction stage in the initiation chemical vapor deposition equipment. Step 3: First, evacuate the chamber of the initiation chemical vapor deposition equipment and adjust the reaction platform temperature to 20℃~40℃; briefly open and then close the valves on the gas supply pipes between the three external vaporizers and the vacuum chamber; then heat the chamber to increase the temperature, and then heat the three vaporizers to vaporize the glycidyl methacrylate monomer, ethylene glycol dimethacrylate monomer, and tert-butyl peroxide-2-ethylhexanoate monomer respectively. Open the valves to allow the glycidyl methacrylate vapor, ethylene glycol dimethacrylate vapor, and tert-butyl peroxide-2-ethylhexanoate vapor to be introduced into the internal chamber for deposition; finally, close the valves on the gas supply pipes, stop the chamber heating, continue evacuating the chamber, and adjust the reaction platform temperature to 50~70℃. Step 4: Completely immerse the PTFE nanofiber nonwoven felt in a 5% N-methyl-D-glucamine solution for cyclic immersion; finally, wash it multiple times.

[0009] Furthermore, in step one, the PTFE nanofiber nonwoven felt has a diameter of 200–500 nm, an average pore size of 0.1–2 μm, a thickness of 80–150 μm, and a porosity of 80%–90%.

[0010] Furthermore, in step two, the plasma cleaner is evacuated to 1-5 Pa; the volume ratio of argon to oxygen is 8-9:1; and the flow rate of the argon-oxygen mixture is 20-50 sccm. In step two, the plasma cleaner turns on the radio frequency power supply and discharges at 30W for 20-40 seconds.

[0011] Furthermore, in step two, the method for transferring the PTFE nanofiber nonwoven felt is as follows: the activated PTFE nanofiber nonwoven felt is quickly loaded into a nitrogen-filled sealed bag in the chamber of the plasma cleaner, the sealed bag is transferred to the chamber of the initiation chemical vapor deposition equipment, the sealed bag is removed, and the activated PTFE nanofiber nonwoven felt is placed on the reaction table in the inner chamber of the initiation chemical vapor deposition equipment.

[0012] Furthermore, in step three, the feeding ratio of the glycidyl methacrylate monomer to the PTFE nanofiber nonwoven felt substrate is 8-12 g: 1 m 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 5-6:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 2.5-3:1.

[0013] Furthermore, in step three, the flow rate of glycidyl methacrylate vapor is 1.0–1.5 sccm, the flow rate of ethylene glycol dimethacrylate vapor is 0.2–0.3 sccm, and the flow rate of tert-butyl peroxide-2-ethylhexanoate vapor is 0.8–1.2 sccm.

[0014] Furthermore, in step three, the chamber of the initiating chemical vapor deposition equipment is evacuated to 0.1–0.01 Pa; In step three, the deposition time is 20–45 min; In step three, the temperature of the vacuum chamber of the initiation chemical vapor deposition equipment is heated to 200°C to 300°C by turning on the array of electric heating filaments in the chamber. In step three, the reaction platform surface is kept at 50-70°C for 10-20 minutes.

[0015] Furthermore, in step three, the valve on the gas supply pipe is a shut-off valve, and the gas supply pipe is equipped with a flow control valve; the vacuum pipe is equipped with a vacuum throttle valve and a vacuum pump. During the deposition time of 0-5 min, the shut-off valve on the gas supply pipe is opened, the vacuum throttle valve on the vacuum pipe is adjusted to reduce the gas flow rate, the vacuum pump is turned on, the gas inlet flow rate is greater than the gas extraction flow rate, and the pressure in the chamber is 110-120 Pa. After a 5-minute deposition time, the shut-off valve on the gas supply pipe is opened, and the vacuum throttle valve on the vacuum pumping pipe is adjusted to increase the gas volume, making the pumping flow rate greater than the inlet flow rate. The vacuum pump is then turned on, and the pressure inside the chamber is 35–45 Pa.

[0016] Furthermore, in step four, the 5% N-methyl-D-glucamine solution is prepared by mixing NMG powder, ultrapure water, and anhydrous ethanol, with the mass ratio of ultrapure water to anhydrous ethanol being 8-9:1. PTFE nanofiber nonwoven felt is cyclically impregnated at 30–50°C for 4–6 hours.

[0017] Furthermore, in step four, the PTFE nanofiber nonwoven felt that has been repeatedly impregnated is washed with ultrapure water in multiple cycles until the TOC increase in the effluent is <5ppb.

[0018] Compared with existing technologies, the beneficial effects of this invention are as follows: The boron adsorption purification filter element preparation process provided by this invention for ultrapure water systems can remove 99% of the boron in the recycled water effluent. Therefore, the boron removal effect of the boron adsorption purification filter element is excellent, and the boron ions can be reduced to trace levels. Furthermore, the TOC leaching of the boron adsorption purification filter element is very low. After the recycled water is debored by the boron adsorption purification filter element, it can be applied to some fields with very strict water quality requirements, such as semiconductor manufacturing, electronics industry, and pharmaceutical industry (further deep boron removal may be required depending on the situation). It can also be directly applied to the source of ultrapure water systems for reuse. Detailed Implementation

[0019] 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.

[0020] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Example 1

[0021] A process for preparing a boron adsorption purification filter element for an ultrapure water system includes the following steps: Step 1: Select PTFE nanofiber nonwoven felt as the substrate; the PTFE nanofiber nonwoven felt has a diameter of 300nm, an average pore size of 2μm, a thickness of 100um, and a porosity of 85%.

[0022] Step 2: Place the PTFE nanofiber nonwoven felt in the chamber of the plasma cleaner and evacuate the chamber to 1 Pa; then introduce a mixture of argon and oxygen into the chamber at a volume ratio of 9:1 and a flow rate of 30 sccm; turn on the radio frequency power and discharge the mixture at 30W for 20 seconds; stop evacuating and introduce nitrogen into the chamber until the pressure inside the chamber rises back to 1 atmosphere; quickly transfer the activated PTFE nanofiber nonwoven felt into a nitrogen-filled sealed bag in the chamber of the plasma cleaner, transfer the sealed bag to the chamber of the initiation chemical vapor deposition (ICD) equipment, remove the sealed bag, and place the activated PTFE nanofiber nonwoven felt on the reaction stage inside the chamber of the ICD equipment.

[0023] Step 3: First, evacuate the chamber of the initiation chemical vapor deposition equipment to 0.1 Pa using a vacuum pump, and adjust the temperature of the reaction platform to 30°C; during deposition, when the vapor encounters the relatively cold PTFE nanofiber nonwoven felt surface, it will condense and remain. The valve on the gas supply pipe connected to the chamber of the initiating chemical vapor deposition (CVD) equipment is a shut-off valve, and a flow control valve is installed on the gas supply pipe. The vacuum pipe connected to the chamber of the initiating CVD equipment is equipped with a vacuum throttle valve and a vacuum pump. The temperature of the supply pipe must be higher than the temperature inside the vaporizer to prevent vapor condensation. Briefly open and then close the shut-off valve on the gas supply pipe between the three external vaporizers and the vacuum chamber; In the vacuum chamber of the re-initiated chemical vapor deposition apparatus, the temperature of the chamber is heated to 250°C by turning on the array of electric heating filaments inside the chamber, and the temperature of the reaction platform is 30°C. Then, the monomers of glycidyl methacrylate, ethylene glycol dimethacrylate, and tert-butyl peroxide are heated to a vapor state in three vaporizers respectively. The valves are opened to allow the vapors of glycidyl methacrylate, ethylene glycol dimethacrylate, and tert-butyl peroxide (the vapors of tert-butyl peroxide are only slightly heated) to be introduced into the internal chamber for deposition for 25 minutes. The flow rate of glycidyl methacrylate vapor during introduction is 1.5 sccm, the flow rate of ethylene glycol dimethacrylate vapor is 0.25 sccm, and the flow rate of tert-butyl peroxide-2-ethylhexanoate vapor is 1.0 sccm. During the deposition time of 0-5 min, the shut-off valve on the gas supply pipe is opened, the vacuum throttle valve on the vacuum pipe is adjusted to reduce the gas flow rate, the vacuum pump is turned on, the gas inlet flow rate is greater than the gas extraction flow rate, and the pressure in the chamber is 120 Pa. After a deposition time of 5 minutes, the shut-off valve on the gas supply pipe is opened, and the vacuum throttle valve on the vacuum tube is adjusted to increase the gas volume. The gas pumping flow rate is greater than the gas inlet flow rate. The vacuum pump is then turned on, and the pressure in the chamber is 40 Pa. The feed ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 10g:1m. 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 5:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 3:1.

[0024] Finally, close the valve on the gas supply pipe and stop heating the chamber. Continue to pump gas out of the chamber using a vacuum pump, adjust the temperature of the reaction table surface to 70°C, and maintain it for 15 minutes to obtain modified PTFE nanofiber nonwoven felt. Step 4: The modified PTFE nanofiber nonwoven felt is completely impregnated in a 5% N-methyl-D-glucamine solution for cyclic impregnation; finally, it is washed multiple times to obtain the boron adsorption purification filter element.

[0025] A 5% N-methyl-D-glucamine solution (NMG) was prepared by mixing NMG powder (purity ≥99%), ultrapure water, and anhydrous ethanol, with a mass ratio of ultrapure water to anhydrous ethanol of 8.5:1. PTFE nanofiber nonwoven felt was cyclically impregnated at 45°C for 6 hours.

[0026] Ethanol, as a wetting agent, can reduce the surface tension of the solution, which is beneficial for the N-methyl-D-glucamine solution to thoroughly impregnate the PTFE nanofiber nonwoven felt.

[0027] Finally, the PTFE nanofiber nonwoven felt that has been impregnated with ultrapure water is washed multiple times until the TOC increase in the effluent is less than 5 ppb.

[0028] Plasma treatment of PTFE nanofiber nonwoven felt activates the surface energy of PTFE nanofiber nonwoven felt. High-energy particles bombard CF bonds to generate free radicals and introduce -OH polar groups, thereby improving the chemical affinity of PTFE.

[0029] The gas-phase initiator TBPO is pyrolyzed into tert-butoxy radicals by the filament. The tert-butoxy radicals descend to the surface of the PTFE nanofiber nonwoven felt substrate at 30°C, initiating the free radical copolymerization of glycidyl methacrylate and ethylene glycol dimethacrylate adsorbed on the substrate surface.

[0030] During the deposition stage, at a deposition pressure of 120 Pa, gas molecules spend more time in the chamber and collide more frequently. This high pressure forces monomer molecules into the deep voids within the PTFE nanofiber nonwoven felt. When polymerization occurs, the polymer solidifies in situ within these voids, reducing polymer film detachment. Glycidyl methacrylate, as a functional monomer, polymerizes in situ with ethylene glycol dimethacrylate, as a crosslinking agent, to form a three-dimensional network film. At a deposition pressure of 40 Pa, the resulting polymer film is denser and more uniform, which is beneficial for increasing the distribution density of boron-free functional groups, reducing the encapsulation of unreacted monomers, and lowering TOC.

[0031] A polyglycidyl methacrylate copolymer is formed by copolymerizing glycidyl methacrylate and ethylene glycol dimethacrylate on the surface of PTFE fibers.

[0032] The reason for finally adjusting the reaction table surface temperature to 70°C is that at 70°C, some unreacted residual monomers remaining in the gaps of the PTFE nanofiber nonwoven felt can volatilize and be released from the gaps of the PTFE nanofiber nonwoven felt due to the increased molecular kinetic energy after heating, thus ensuring low TOC.

[0033] During impregnation, the secondary amino group in N-methyl-D-glucamine acts as a nucleophile, nucleophilically attacking the epoxy group of glycidyl methacrylate, thereby initiating a ring-opening reaction and fixing the polyhydroxy structure onto the film via covalent bonds. The cis-diol structure of N-methyl-D-glucamine undergoes esterification chelation with neutral boric acid molecules to form a stable five-membered ring complex, thus achieving the removal of boron.

[0034] Another boron adsorption purification filter element can be manufactured using the above method. The substrate of this second boron adsorption purification filter element has an average pore size of 0.5 μm. Both the first boron adsorption purification filter element made of a substrate with an average pore size of 2 μm and the second boron adsorption purification filter element made of a substrate with an average pore size of 0.5 μm are folded into a wavy shape. The folded first boron adsorption purification filter element and the second boron adsorption purification filter element are then arranged in a ring and fixed outside the porous central tube. A support mesh is provided between the folded first boron adsorption purification filter element and the second boron adsorption purification filter element, thereby forming a composite boron adsorption purification filter element. Boric acid molecules enter the boron removal device from the side of the composite boron adsorption purification filter element along with the recycled water or the ultrapure water to be treated in the primary loop. Boric acid molecules are captured when they collide with the surface of one boron adsorption purification filter element, and then captured when they collide with another boron adsorption purification filter element. The recycled water or ultrapure water to be treated continuously changes direction in the composite boron adsorption purification filter element. After penetrating the composite boron adsorption purification filter element laterally, the boron acid molecules continuously encounter NMG groups on the surface of one boron adsorption purification filter element and the surface of another boron adsorption purification filter element during the process of penetrating the gaps of the PTFE nanofiber nonwoven felt. Finally, the boron-removed water passes through the PTFE nanofiber nonwoven felt and enters the central tube, flowing upward or downward along the central tube. Example 2

[0035] Compared with Example 1, the difference is that the feeding ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 12g:1m 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 6:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 2.5:1.

[0036] Everything else is the same as in Example 1. Example 3

[0037] Compared with Example 1, the difference is that the feeding ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 10g:1m. 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 5:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 3:1.

[0038] Everything else is the same as in Example 1. Example 4

[0039] Compared with Example 1, the difference is that the feeding ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 8g:1m. 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 5.5:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 2.5:1. Example 5

[0040] Compared with Example 1, the difference is that the feeding ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 8g:1m. 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 6:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 2.7:1.

[0041] Comparative Example 1 A process for preparing a boron adsorption purification filter element for an ultrapure water system includes the following steps: Step 1: Select PTFE nanofiber nonwoven felt as the substrate; the PTFE nanofiber nonwoven felt has a diameter of 300nm, an average pore size of 2μm, a thickness of 100um, and a porosity of 85%.

[0042] Step 2: First, evacuate the chamber of the initiation chemical vapor deposition equipment to 0.1 Pa using a vacuum pump. Place the PTFE nanofiber nonwoven felt on the reaction platform inside the chamber of the initiation chemical vapor deposition equipment and adjust the temperature of the reaction platform surface to 30°C. During deposition, when the vapor encounters the relatively cold surface of the PTFE nanofiber nonwoven felt, it will condense and remain. The valve on the gas supply pipe connected to the chamber of the initiating chemical vapor deposition (CVD) equipment is a shut-off valve, and a flow control valve is installed on the gas supply pipe. The vacuum pipe connected to the chamber of the initiating CVD equipment is equipped with a vacuum throttle valve and a vacuum pump. The temperature of the supply pipe must be higher than the temperature inside the vaporizer to prevent vapor condensation. Briefly open and then close the shut-off valve on the gas supply pipe between the three external vaporizers and the vacuum chamber; In the vacuum chamber of the re-initiated chemical vapor deposition apparatus, the temperature of the chamber is heated to 250°C by turning on the array of electric heating filaments in the chamber, and the temperature of the reaction platform is 30°C. Then, the monomers of glycidyl methacrylate, ethylene glycol dimethacrylate, and tert-butyl peroxide-2-ethylhexanoate are heated to a vapor state in the three vaporizers respectively. The valves are opened to allow the vapors of glycidyl methacrylate, ethylene glycol dimethacrylate, and tert-butyl peroxide-2-ethylhexanoate to be introduced into the internal chamber for deposition for 25 minutes. The flow rate of glycidyl methacrylate vapor during introduction is 1.5 sccm, the flow rate of ethylene glycol dimethacrylate vapor is 0.25 sccm, and the flow rate of tert-butyl peroxide-2-ethylhexanoate vapor is 1.0 sccm. During the deposition time of 0-5 min, the shut-off valve on the gas supply pipe is opened, the vacuum throttle valve on the vacuum pipe is adjusted to reduce the gas flow rate, the vacuum pump is turned on, the gas inlet flow rate is greater than the gas extraction flow rate, and the pressure in the chamber is 120 Pa. After a deposition time of 5 minutes, the shut-off valve on the gas supply pipe is opened, and the vacuum throttle valve on the vacuum tube is adjusted to increase the gas volume. The gas pumping flow rate is greater than the gas inlet flow rate. The vacuum pump is then turned on, and the pressure in the chamber is 40 Pa. The feed ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 10g:1m. 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 5:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 3:1.

[0043] Finally, close the valve on the gas supply pipe and stop heating the chamber. Continue to pump gas out of the chamber using a vacuum pump, adjust the temperature of the reaction table surface to 70°C, and maintain it for 15 minutes to obtain modified PTFE nanofiber nonwoven felt. Step 3: The modified PTFE nanofiber nonwoven felt is completely impregnated in a 5% N-methyl-D-glucamine solution for cyclic impregnation; finally, it is washed multiple times to obtain the boron adsorption purification filter element.

[0044] A 5% N-methyl-D-glucamine solution was prepared by mixing NMG powder, ultrapure water, and anhydrous ethanol, with a mass ratio of ultrapure water to anhydrous ethanol of 8.5:1. PTFE nanofiber nonwoven felt was cyclically impregnated at 45°C for 6 hours.

[0045] Comparative Example 2 A process for preparing a boron adsorption purification filter element for an ultrapure water system includes the following steps: Step 1: Select PTFE nanofiber nonwoven felt as the substrate; the PTFE nanofiber nonwoven felt has a diameter of 300nm, an average pore size of 2μm, a thickness of 100um, and a porosity of 85%.

[0046] Step 2: Place the PTFE nanofiber nonwoven felt in the chamber of the plasma cleaner and evacuate the chamber to 1 Pa; then introduce a mixture of argon and oxygen into the chamber at a volume ratio of 9:1 and a flow rate of 30 sccm; turn on the radio frequency power and discharge the mixture at 30W for 20 seconds; stop evacuating and introduce nitrogen into the chamber until the pressure inside the chamber rises back to 1 atmosphere; quickly transfer the activated PTFE nanofiber nonwoven felt into a nitrogen-filled sealed bag in the chamber of the plasma cleaner, transfer the sealed bag to the chamber of the chemical vapor deposition equipment, remove the sealed bag, and place the activated PTFE nanofiber nonwoven felt on the reaction stage inside the chamber of the chemical vapor deposition equipment.

[0047] Step 3: First, evacuate the chamber of the chemical vapor deposition equipment to 0.1 Pa using a vacuum pump, and adjust the temperature of the reaction platform to 30°C; during deposition, when the vapor encounters the relatively cold PTFE nanofiber nonwoven felt surface, it will condense and remain. The valve on the gas supply pipe connected to the chamber of the chemical vapor deposition equipment is a shut-off valve, and a flow control valve is installed on the gas supply pipe; the vacuum pipe connected to the chamber of the chemical vapor deposition equipment is equipped with a vacuum throttle valve and a vacuum pump. The temperature of the supply pipe must be higher than the temperature inside the vaporizer to prevent vapor condensation; Briefly open and then close the shut-off valve on the gas supply pipe between the two external vaporizers and the vacuum chamber; In the vacuum chamber of the rechemical vapor deposition equipment, the temperature of the chamber is heated to 250°C by turning on the array of electric heating filaments in the chamber, and the temperature of the reaction table surface is 30°C. Then, the two vaporizers are heated to vapor state to glycidyl methacrylate monomer and ethylene glycol dimethacrylate monomer respectively. The valves are opened to allow glycidyl methacrylate vapor and ethylene glycol dimethacrylate vapor to be introduced into the internal chamber for deposition for 25 minutes. The flow rate of glycidyl methacrylate vapor during introduction is 1.5 sccm, and the flow rate of ethylene glycol dimethacrylate vapor is 0.25 sccm. During the deposition time of 0-5 min, the shut-off valve on the gas supply pipe is opened, the vacuum throttle valve on the vacuum pipe is adjusted to reduce the gas flow rate, the vacuum pump is turned on, the gas inlet flow rate is greater than the gas extraction flow rate, and the pressure in the chamber is 120 Pa. After a deposition time of 5 minutes, the shut-off valve on the gas supply pipe is opened, and the vacuum throttle valve on the vacuum tube is adjusted to increase the gas volume. The gas pumping flow rate is greater than the gas inlet flow rate. The vacuum pump is then turned on, and the pressure in the chamber is 40 Pa. The feed ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 10g:1m. 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 5:1.

[0048] Finally, close the valve on the gas supply pipe and stop heating the chamber. Continue to pump gas out of the chamber using a vacuum pump, adjust the temperature of the reaction table surface to 70°C, and maintain it for 15 minutes to obtain modified PTFE nanofiber nonwoven felt. Step 4: The modified PTFE nanofiber nonwoven felt is completely impregnated in a 5% N-methyl-D-glucamine solution for cyclic impregnation; finally, it is washed multiple times to obtain the boron adsorption purification filter element.

[0049] A 5% N-methyl-D-glucamine solution was prepared by mixing NMG powder, ultrapure water, and anhydrous ethanol, with a mass ratio of ultrapure water to anhydrous ethanol of 8.5:1. PTFE nanofiber nonwoven felt was cyclically impregnated at 45°C for 6 hours.

[0050] Comparative Example 3 Step 1: Glycidyl methacrylate vapor monomer and ethylene glycol dimethacrylate vapor monomer are mixed, and tert-butyl peroxide monomer is added as an initiator for bulk polymerization in tetrahydrofuran to obtain a polyglycidyl methacrylate copolymer solution; the concentration of the polyglycidyl methacrylate copolymer solution is 1.5 wt%. The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 5:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 3:1.

[0051] Step 2: Select PTFE nanofiber nonwoven felt as the substrate; the PTFE nanofiber nonwoven felt has a diameter of 300nm, an average pore size of 2μm, a thickness of 100um, and a porosity of 85%; The feed ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 10g:1m. 2 ; The PTFE nanofiber nonwoven felt was immersed in a polyglycidyl methacrylate copolymer solution for 10 minutes.

[0052] Step 3: Allow the solvent to evaporate naturally in a fume hood to initially concentrate the liquid film; then place it in an oven at 75°C under vacuum to completely remove residual solvent and cure the poly(glycidyl methacrylate) copolymer. The polymer adheres to the surface of the PTFE nanofiber nonwoven felt in a physical coating form.

[0053] Step 4: The modified PTFE nanofiber nonwoven felt is completely impregnated in a 5% N-methyl-D-glucamine solution for cyclic impregnation; finally, it is washed multiple times to obtain the boron adsorption purification filter element.

[0054] A 5% N-methyl-D-glucamine solution was prepared by mixing NMG powder, ultrapure water, and anhydrous ethanol, with a mass ratio of ultrapure water to anhydrous ethanol of 8.5:1. PTFE nanofiber nonwoven felt was cyclically impregnated at 45°C for 6 hours.

[0055] Comparative Example 4 Step 1: Select PTFE nanofiber nonwoven felt as the substrate; the PTFE nanofiber nonwoven felt has a diameter of 300nm, an average pore size of 2μm, a thickness of 100um, and a porosity of 85%.

[0056] Step 2: Place the PTFE nanofiber nonwoven felt in the chamber of the plasma cleaner and evacuate the chamber to 1 Pa; then introduce a mixture of argon and oxygen into the chamber at a volume ratio of 9:1 and a flow rate of 30 sccm; turn on the radio frequency power and discharge the mixture at 30W for 20 seconds; stop evacuating and introduce nitrogen into the chamber until the pressure inside the chamber rises back to 1 atmosphere; quickly transfer the activated PTFE nanofiber nonwoven felt into a nitrogen-filled sealed bag in the chamber of the plasma cleaner, transfer the sealed bag to the chamber of the initiation chemical vapor deposition (ICD) equipment, remove the sealed bag, and place the activated PTFE nanofiber nonwoven felt on the reaction stage inside the chamber of the ICD equipment.

[0057] Step 3: First, evacuate the chamber of the initiation chemical vapor deposition equipment to 0.1 Pa using a vacuum pump, and adjust the temperature of the reaction platform to 30°C; during deposition, when the vapor encounters the relatively cold PTFE nanofiber nonwoven felt surface, it will condense and remain. The valve on the gas supply pipe connected to the chamber of the initiating chemical vapor deposition (CVD) equipment is a shut-off valve, and a flow control valve is installed on the gas supply pipe. The vacuum pipe connected to the chamber of the initiating CVD equipment is equipped with a vacuum throttle valve and a vacuum pump. The temperature of the supply pipe must be higher than the temperature inside the vaporizer to prevent vapor condensation. Briefly open and then close the shut-off valve on the gas supply pipe between the three external vaporizers and the vacuum chamber; In the vacuum chamber of the re-initiated chemical vapor deposition apparatus, the temperature of the chamber is heated to 250°C by turning on the array of electric heating filaments in the chamber, and the temperature of the reaction platform is 30°C. Then, the monomers of glycidyl methacrylate, ethylene glycol dimethacrylate, and tert-butyl peroxide-2-ethylhexanoate are heated to a vapor state in the three vaporizers respectively. The valves are opened to allow the vapors of glycidyl methacrylate, ethylene glycol dimethacrylate, and tert-butyl peroxide-2-ethylhexanoate to be introduced into the internal chamber for deposition for 25 minutes. The flow rate of glycidyl methacrylate vapor during introduction is 1.5 sccm, the flow rate of ethylene glycol dimethacrylate vapor is 0.25 sccm, and the flow rate of tert-butyl peroxide-2-ethylhexanoate vapor is 1.0 sccm. During the deposition time of 0-5 min, the shut-off valve on the gas supply pipe is opened, the vacuum throttle valve on the vacuum pipe is adjusted to reduce the gas flow rate, the vacuum pump is turned on, the gas inlet flow rate is greater than the gas extraction flow rate, and the pressure in the chamber is 120 Pa. After a deposition time of 5 minutes, the shut-off valve on the gas supply pipe is opened, and the vacuum throttle valve on the vacuum tube is adjusted to increase the gas volume. The gas pumping flow rate is greater than the gas inlet flow rate. The vacuum pump is then turned on, and the pressure in the chamber is 40 Pa. The feed ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 10g:1m. 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 5:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 3:1.

[0058] Finally, close the valve on the gas supply pipe and stop heating the chamber. Continue to pump gas out of the chamber using a vacuum pump, adjust the temperature of the reaction table surface to 70°C, and maintain it for 15 minutes to obtain modified PTFE nanofiber nonwoven felt. Step 4: The modified PTFE nanofiber nonwoven felt is completely immersed in a 20% (w / w) trimethylamine aqueous solution; the PTFE nanofiber nonwoven felt is immersed at 45°C for 6 hours; finally, it is washed repeatedly to obtain the boron adsorption purification filter element.

[0059] In a conventional concentrate recovery process, the concentrate can be recovered by going through a UF ultrafiltration device, a softening device, a security filter, an antiscalant dosing point, a secondary reverse osmosis (RO) membrane device, and then using recycled water. The recycled water from the same batch flows sequentially through the boron adsorption purification filter cartridges prepared in Examples 1-5 and Comparative Examples 1-4. The water quality parameters of the recycled water from the same batch are kept consistent, specifically as follows: boron content of 80 ppb, total organic carbon of 15 ppb, resistivity of 1.2 MΩ·cm, and pH of 7.

[0060] The boron adsorption purification filter cartridges prepared in Examples 1-5 and Comparative Examples 1-4 were installed in standard industrial filter housings, and recycled water from the same batch was introduced. The water pressure was set to 0.6 MPa, and the filter was continuously flushed for 72 hours. During measurement, samples were taken at regular intervals, and the boron content of the effluent was measured using inductively coupled plasma mass spectrometry (ICP-MS), while the TOC of the effluent was monitored using a high-precision TOC analyzer. If the polymer film is unstable, organic polymer chains may detach and enter the water cycle, causing TOC fluctuations. The detection results of the effluent boron content and effluent TOC of Examples 1-5 and Comparative Examples 1-4 are shown in Table 1.

[0061] Table 1. Results of boron content and TOC in the effluent from Examples 1-5 and Comparative Examples 1-4. project Outflow TOC Boron content in effluent Boron removal rate Example 1 15ppb <50ppt >99% Example 2 15ppb <50ppt >99% Example 3 16ppb <50ppt >99% Example 4 15ppb <50ppt >99% Example 5 16ppb <50ppt >99% Comparative Example 1 20ppb 16700ppt 79.1% Comparative Example 2 16ppb 61300ppt 2.3% Comparative Example 3 72ppb 358,000ppt 55.2% Comparative Example 4 17ppb 63900ppt 20.1% As shown in Table 1, the boron adsorption purification filter cartridges prepared in Examples 1-5 can remove 99% of the boron in the effluent. Therefore, the boron adsorption purification filter cartridges are highly effective, removing boron ions to trace levels. Furthermore, the TOC leaching of the boron adsorption purification filter cartridges prepared in Examples 1-5 is minimal; only a short rinsing time is required in step four to maintain a stable TOC in the effluent. After boron removal using the boron adsorption purification filter cartridges prepared in Examples 1-5, the reclaimed water can be applied to fields with very strict water quality requirements (such as semiconductor manufacturing, the electronics industry, and the pharmaceutical industry, where further deep boron removal may be necessary). It can also be directly used at the source of ultrapure water systems for reuse.

[0062] In Comparative Example 1, the PTFE nanofiber nonwoven felt was not subjected to plasma pretreatment. Therefore, under water pressure, the polymer film experienced localized peeling due to continuous high-pressure shearing and interfacial stress mismatch, leading to an increase in TOC in the effluent. The boron removal efficiency of the boron adsorption purification filter element prepared in Comparative Example 1 was also lower than that in Examples 1-5. In Comparative Example 2, the initiator TBPO was not introduced into the chemical vapor deposition equipment. Therefore, the GMA monomer could not crosslink into a network on the surface of the PTFE nanofiber nonwoven felt, and only some unreacted oligomers were physically adsorbed, which were easily washed away under water pressure. In Comparative Example 3, the boron adsorption purification filter element was prepared using the traditional liquid-phase impregnation method. Due to the high viscosity of the polymer solution, it could not penetrate into the deep gaps of the PTFE nanofiber nonwoven felt, and only wrapped the outer layer. Therefore, under water pressure, a large amount of the polymer film peeled off, resulting in limited boron removal efficiency, while solvent residue led to a significant increase in TOC in the effluent. In Comparative Example 4, a 20% trimethylamine aqueous solution was used to replace a 5% N-methyl-D-glucamine solution. The ion exchange sites were occupied by salt ions in the recycled water, making it impossible to accurately capture boron. Therefore, the removal of boron ions was affected by other salt ions, resulting in a low boron removal rate.

[0063] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for preparing a boron adsorption purification filter element for an ultrapure water system, characterized in that, Includes the following steps: Step 1: Select PTFE nanofiber nonwoven felt as the substrate; Step 2: Place the PTFE nanofiber nonwoven felt in the chamber of the plasma cleaner and evacuate the chamber; then introduce a mixture of argon and oxygen into the chamber and turn on the radio frequency power supply for discharge treatment; stop evacuating and introduce nitrogen into the chamber until the pressure in the chamber rises back to 1 atmosphere; transfer the PTFE nanofiber nonwoven felt to the reaction stage in the initiation chemical vapor deposition equipment. Step 3: First, evacuate the chamber of the initiation chemical vapor deposition equipment and adjust the reaction platform temperature to 20℃~40℃; briefly open and then close the valves on the gas supply pipes between the three external vaporizers and the vacuum chamber; then heat the chamber to increase the temperature, and then heat the three vaporizers to vaporize the glycidyl methacrylate monomer, ethylene glycol dimethacrylate monomer, and tert-butyl peroxide-2-ethylhexanoate monomer respectively. Open the valves to allow the glycidyl methacrylate vapor, ethylene glycol dimethacrylate vapor, and tert-butyl peroxide-2-ethylhexanoate vapor to be introduced into the internal chamber for deposition; finally, close the valves on the gas supply pipes, stop the chamber heating, continue evacuating the chamber, and adjust the reaction platform temperature to 50~70℃. Step 4: The PTFE nanofiber nonwoven felt is completely immersed in a 5% N-methyl-D-glucamine solution for cyclic immersion; finally, it is washed multiple times.

2. The process for preparing a boron adsorption purification filter element for an ultrapure water system according to claim 1, characterized in that, In step one, the PTFE nanofiber nonwoven felt has a diameter of 200-500 nm, an average pore size of 0.1-2 μm, a thickness of 80-150 μm, and a porosity of 80%-90%.

3. The preparation method of a boron adsorption purification filter element for an ultrapure water system according to claim 1, characterized in that, In step two, the plasma cleaner is evacuated to 1-5 Pa; the volume ratio of argon to oxygen is 8-9:1; and the flow rate of the argon-oxygen mixture is 20-50 sccm. In step two, the plasma cleaner turns on the radio frequency power supply and discharges at 30W for 20-40 seconds.

4. The preparation method of a boron adsorption purification filter element for an ultrapure water system according to claim 1, characterized in that, In step two, the method for transferring the PTFE nanofiber nonwoven felt is as follows: the activated PTFE nanofiber nonwoven felt is quickly loaded into a nitrogen-filled sealed bag in the chamber of the plasma cleaner, the sealed bag is transferred to the chamber of the initiation chemical vapor deposition equipment, the sealed bag is removed, and the activated PTFE nanofiber nonwoven felt is placed on the reaction table in the inner chamber of the initiation chemical vapor deposition equipment.

5. The preparation method of a boron adsorption purification filter element for an ultrapure water system according to claim 1, characterized in that, In step three, the feeding ratio of glycidyl methacrylate monomer to PTFE nanofiber nonwoven felt substrate is 8-12 g: 1 m 2 The mass ratio of glycidyl methacrylate monomer to ethylene glycol dimethacrylate monomer is 5-6:1; the mass ratio of glycidyl methacrylate monomer to tert-butyl peroxide-2-ethylhexanoate monomer is 2.5-3:

1.

6. The preparation method of a boron adsorption purification filter element for an ultrapure water system according to claim 1, characterized in that, In step three, the flow rate of glycidyl methacrylate vapor is 1.0–1.5 sccm, the flow rate of ethylene glycol dimethacrylate vapor is 0.2–0.3 sccm, and the flow rate of tert-butyl peroxide-2-ethylhexanoate vapor is 0.8–1.2 sccm.

7. The preparation method of a boron adsorption purification filter element for an ultrapure water system according to claim 1, characterized in that, In step three, the chamber of the initiating chemical vapor deposition equipment is evacuated to 0.1–0.01 Pa; In step three, the deposition time is 20–45 min; In step three, the temperature of the vacuum chamber of the initiation chemical vapor deposition equipment is heated to 200°C to 300°C by turning on the array of electric heating filaments in the chamber. In step three, the reaction platform surface is kept at 50-70°C for 10-20 minutes.

8. The preparation method of a boron adsorption purification filter element for an ultrapure water system according to claim 1, characterized in that, In step three, the valve on the gas supply pipe is a shut-off valve, and the gas supply pipe is equipped with a flow control valve; the vacuum pipe is equipped with a vacuum throttle valve and a vacuum pump. During the deposition time of 0-5 min, the shut-off valve on the gas supply pipe is opened, the vacuum throttle valve on the vacuum pipe is adjusted to reduce the gas flow rate, the vacuum pump is turned on, the gas inlet flow rate is greater than the gas extraction flow rate, and the pressure in the chamber is 110-120 Pa. After a 5-minute deposition time, the shut-off valve on the gas supply pipe is opened, and the vacuum throttle valve on the vacuum pumping pipe is adjusted to increase the gas volume, making the pumping flow rate greater than the inlet flow rate. The vacuum pump is then turned on, and the pressure inside the chamber is 35–45 Pa.

9. The preparation method of a boron adsorption purification filter element for an ultrapure water system according to claim 1, characterized in that, In step four, the 5% N-methyl-D-glucamine solution is prepared by mixing NMG powder, ultrapure water and anhydrous ethanol, with the mass ratio of ultrapure water to anhydrous ethanol being 8-9:

1. PTFE nanofiber nonwoven felt is cyclically impregnated at 30–50°C for 4–6 hours.

10. The preparation method of a boron adsorption purification filter element for an ultrapure water system according to claim 1, characterized in that, In step four, the PTFE nanofiber nonwoven felt that has been repeatedly impregnated is washed with ultrapure water in multiple cycles until the TOC increase in the effluent is less than 5 ppb.