High-temperature-resistant resin special for condensate water fine treatment, preparation method and application thereof

Abstract

This invention belongs to the field of adsorbents, specifically relating to a high-temperature resistant resin for condensate polishing, its preparation method, and its applications. The resin has an interpenetrating polymer network structure, including a cation exchange network with a styrene-divinylbenzene copolymer backbone and sulfonic acid groups as cation exchange groups; an anion exchange network with a styrene-divinylbenzene copolymer backbone and quaternary ammonium groups as anion exchange groups; and g-C3N4 nanosheets uniformly dispersed at the interfaces of the interpenetrating polymer network. The prepared resin does not delaminate or break down during long-term operation above 80°C, exhibiting stable exchange capacity; it can withstand short-cycle ultra-high temperature shocks of 95°C; and it also possesses excellent anti-fouling and regeneration recovery capabilities, making it suitable for practical industrial applications.

Description

Technical Field

[0001] This invention relates to the field of adsorbent technology, specifically to a high-temperature resistant resin for condensate polishing, its preparation method, and its application. Background Technology

[0002] Condensate recovery from power plant boilers has been widely adopted, making a significant contribution to the full recycling of water resources. However, due to the maximum operating temperature limit of strongly basic anion exchange resins (OH- type, 60℃), the temperature of steam condensate generally needs to be cooled to around 50℃ before entering the ion exchange system for purification. This not only results in a significant loss of heat energy but also causes considerable inconvenience in water-scarce areas.

[0003] Therefore, in existing technologies, anion exchange resin and cation exchange resin are usually used together to finely treat boiler condensate, which not only saves a lot of cooling water, but also recovers a lot of heat energy, resulting in significant energy-saving and emission-reduction benefits.

[0004] However, current methods for blending anion exchange resins and cation exchange resins are merely simple physical mixing methods, which result in poor high-temperature stability, potential severe stratification after long-term use, and generally low mechanical strength and poor resistance to contamination.

[0005] Based on this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a special resin for high-temperature condensate polishing, its preparation method, and its application, so as to solve the above-mentioned problems.

[0007] In a first aspect, a high-temperature resistant resin for condensate polishing, which has an interpenetrating polymer network structure, comprising: The cation exchange network has a styrene-divinylbenzene copolymer backbone and contains sulfonic acid groups as cation exchange groups; An anion exchange network with a styrene-divinylbenzene copolymer backbone and quaternary ammonium groups as anion exchange groups; And g-C3N4 nanosheets uniformly dispersed at the interface of the interpenetrating polymer network.

[0008] Furthermore, the g-C3N4 nanosheets are aminated g-C3N4 nanosheets with exposed amino groups at their edges.

[0009] Furthermore, the mass ratio of the cation exchange network to the anion exchange network is (0.8~1.2):1.

[0010] Secondly, a method for preparing a special resin for high-temperature resistant condensate polishing includes the following steps: Step 1: Prepare g-C3N4 nanosheets; Step 2: Styrene, divinylbenzene, porogen, initiator and g-C3N4 nanosheets obtained in Step 1 are mixed and subjected to suspension polymerization to obtain cationic semi-interpenetrating network white spheres containing g-C3N4. Step 3: Mix the cationic semi-interpenetrating network white spheres containing g-C3N4 obtained in Step 2 with anionic oil phase monomers, and carry out in-situ polymerization under mega-sound assisted stirring to obtain g-C3N4 doped and modified interpenetrating polymer network double network white spheres. Step 4: The g-C3N4 doped and modified interpenetrating polymer network double network white spheres obtained in Step 3 are subjected to chloromethylation, quaternization and sulfonation treatments in sequence, and quaternary ammonium groups and sulfonic acid groups are introduced simultaneously on the g-C3N4 doped and modified interpenetrating polymer network double network white spheres. Step 5: The product obtained in Step 4 is subjected to a transformation process, converting the sulfonic acid group to the hydrogen form and the quaternary ammonium group to the hydroxide form, to obtain the special resin for high-temperature condensate polishing.

[0011] Furthermore, the preparation method of g-C3N4 nanosheets in step 1 is as follows: urea is calcined at 540~560℃ and ground to obtain g-C3N4 powder; the g-C3N4 powder is dispersed in water, subjected to ultrasonic treatment and centrifugation, and the supernatant is dried to obtain aminated g-C3N4 nanosheets.

[0012] Furthermore, in step 2, the degree of crosslinking of the cationic semi-interpenetrating network white spheres containing g-C3N4 is 8%~10%, and the amount of g-C3N4 nanosheets added is 1.0%~2.0% of the mass of styrene.

[0013] Furthermore, the megaphonic assisted stirring in step 3 employs two megaphonic sources and a stirring paddle located between them. The difference Δf between the megaphonic frequencies of the two sources is 0.8~0.9 MHz; the stirring paddle rotates at 80~90 rpm. Preferably, the two megaphonic frequencies are 0.75 MHz and 1.58 MHz, respectively, and the stirring paddle rotates at 80 rpm.

[0014] Furthermore, in step 4, chloromethylation and quaternization are first performed to introduce quaternary ammonium groups, followed by sulfonation to introduce sulfonic acid groups.

[0015] Furthermore, the transformation treatment described in step 5 includes: first, using hydrochloric acid to convert the sulfonic acid group to the hydrogen form, and washing with water until neutral; then, using sodium hydroxide solution to convert the quaternary ammonium group to the hydroxyl form, and washing with water until neutral.

[0016] Thirdly, a special resin for high-temperature resistant condensate polishing is used in the polishing of condensate from high back-pressure generator units in power plants. The processing temperature of the application is not lower than 80°C, and no pre-cooler is required.

[0017] The cation and anion networks constructed in this invention are interconnected and entangled at the molecular level, forming a physically interlocked structure. This structure has the following advantages: 1) Suppressing phase separation: The two networks are entangled with each other, preventing phase separation caused by differences in hydrophilicity and hydrophobicity during the functionalization process, thus ensuring the uniformity of the resin structure.

[0018] 2) Stress dissipation: When the resin is subjected to thermal shock or osmotic pressure shock, the entanglement point can serve as a stress dissipation center, preventing crack propagation and improving the resistance to breakage.

[0019] 3) Synergistic function: The two networks coexist within the same particle, and the cation and anion groups can work synergistically during ion exchange to improve the exchange efficiency.

[0020] 4) The g-C3N4 nanosheets prepared by the present invention using urea calcination combined with ultrasonic exfoliation have a large number of amino groups exposed at their edges. These amino groups can form hydrogen bonds or covalent bonds with the styrene-divinylbenzene copolymer chains during polymerization, firmly anchoring g-C3N4 to the polymer network interface.

[0021] 5) This invention employs dual-frequency megasonic spectroscopy (0.75 MHz and 1.58 MHz) and stirring-assisted in-situ polymerization of anionic networks. The megasonic spectroscopy provides microscale dispersion across different ranges, while stirring provides macroscopic mixing. Together, they ensure uniform penetration of anionic monomers within the cation network, forming a true interpenetrating structure rather than a core-shell structure. Experiments demonstrate that when the frequency difference between the two megasonic spectroscopy frequencies is 0.8–0.9 MHz, the harmonic components of the two frequencies produce a resonance enhancement effect, resulting in the most uniform sound field distribution and optimal monomer penetration depth and dispersion uniformity.

[0022] When the frequency difference Δf between the two megaphonic frequencies is within the range of 0.8–0.9 MHz, a stable three-dimensional interpenetrating network forms inside the resin, maintaining a regeneration cycle life of over 500 cycles even under harsh conditions such as high temperature (95°C) and copper ion contamination. When Δf is too small (e.g., 0 MHz) or too large (e.g., 1.5 MHz), the number of regeneration cycles decreases sharply, indicating that Δf = 0.8–0.9 MHz is the key process window for achieving optimal structural stability.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The chemically compounded high-temperature condensate polishing resin obtained can operate at temperatures above 80°C for a long time without stratification or breakage, and its exchange capacity remains stable. Furthermore, the resin of this invention can withstand short-cycle ultra-high temperature shocks of 95°C, while conventional resins have mostly failed under these conditions.

[0024] 2. In the prior art, the exhausted resin is transported from the mixed bed to the regeneration tower, where it is subjected to air scrubbing and hydraulic separation (separating the cation and anion resins into layers), and then regenerated with sulfuric acid and alkali solution respectively.

[0025] The IPN amphoteric resin (a special resin for high-temperature condensate polishing) of this invention has "single particle dual function" and can be regenerated simultaneously without separation steps, thus simplifying the regeneration system.

[0026] 3. It can directly replace the existing "cation resin + anion resin" mixed bed, eliminating the need for resin separation and regeneration equipment. The cooler is eliminated: it can withstand temperatures above 80℃ and can directly treat condensate from the condenser outlet, resulting in significant energy savings.

[0027] 4. Reduced regenerator consumption: The simultaneous regeneration characteristics of amphoteric resins can optimize the regeneration process and reduce acid and alkali consumption.

[0028] 5. It has excellent pollution resistance and regeneration capabilities, making it suitable for practical industrial applications. Detailed Implementation

[0029] The present invention will be further described in detail below through specific embodiments.

[0030] Example 1 1. Preparation and surface modification of g-C3N4 nanosheets Analytical grade urea was placed in a crucible and sealed, then calcined in a muffle furnace at 550°C for 2 hours and allowed to cool naturally to obtain a light yellow g-C3N4 block. This block was then ground into powder to obtain g-C3N4 powder. g-C3N4 powder was added to deionized water at a concentration of 1 mg / mL, stirred and dispersed, and ultrasonically treated at a frequency of 20 kHz for 2 h. After that, it was centrifuged (centrifugation speed of 3000 rpm) for 10 min, and the supernatant was collected to obtain an aqueous dispersion of aminated g-C3N4 nanosheets. The dispersion was then vacuum dried at 60 °C for 12 h to obtain g-C3N4 nanosheet powder. 2. Synthesis of white spheres containing g-C3N4 cation semi-interpenetrating network Styrene is the backbone monomer; divinylbenzene is the crosslinking agent; the porogen is obtained by mixing toluene and liquid paraffin in a mass ratio of 1:1; benzoyl peroxide is the initiator; polyvinyl alcohol (PVA) is the dispersant; 98% concentrated sulfuric acid is the sulfonating agent; chloromethyl ether is the chloromethylating agent; and 30% trimethylamine aqueous solution is the quaternizing agent.

[0031] 92g of styrene, 8g of divinylbenzene (crosslinking degree 8%), 80g of porogen, 1g of benzoyl peroxide, and 1.5g of g-C3N4 nanosheet powder were mixed and ultrasonically dispersed at a frequency of 20kHz for 30min to obtain g-C3N4 oil phase dispersion; wherein g-C3N4 was uniformly dispersed in the oil phase without agglomeration.

[0032] Prepare 300g of a 1wt% polyvinyl alcohol aqueous solution as the aqueous phase.

[0033] The g-C3N4 oil phase dispersion was slowly added to the aqueous phase, stirred, and the oil droplet size was adjusted to 0.7-0.9 mm. The temperature was raised to 80℃ and the reaction was maintained for 6 h to complete the cationic semi-interpenetrating network polymerization. The mixture was cooled, filtered, washed with water, and the pore-forming agent was extracted with ethanol. The mixture was dried at 60℃ to obtain cationic semi-interpenetrating network white spheres containing g-C3N4.

[0034] 3. Specific megasonic-assisted in-situ interpenetrating polymerization of anion networks Add 100g of the above-mentioned cationic semi-interpenetrating network white spheres containing g-C3N4 to the reactor, add 300g of 1wt% polyvinyl alcohol aqueous solution, stir for 30min to allow the resin to fully swell, and obtain swollen resin material.

[0035] 90g of styrene, 10g of divinylbenzene (crosslinking degree 10%), 75g of porogen, and 1g of benzoyl peroxide were mixed to prepare an anionic oil phase monomer. The anionic oil-phase monomer and the swollen resin were first mixed and stirred for 10 minutes in a megaphon-assisted dispersion tank. Two megaphonic vibrators (purchased from Shenzhen Jiemeng Technology Co., Ltd.) were installed in the megaphonic dispersion tank, and a stirring paddle was installed between the two megaphonic vibrators. Megaphonic dispersion was used, with the megaphonic frequencies corresponding to the two megaphonic vibrators being 0.75MHz and 1.58MHz, respectively. Water bath assisted heating was used, and the reaction was carried out at 80℃, with megaphonic sound and stirring (80rpm) for 3 hours. After the reaction, the mixture was cooled, filtered, washed with water, and the pore-forming agent was extracted with ethanol. It was then dried at 60℃ to obtain g-C3N4 doped and modified IPN (interpenetrating network) double-network white spheres (two sets of polystyrene-divinylbenzene networks interpenetrated and entangled, neither of which was functionalized).

[0036] 4. Synchronization Functionality and Transformation of Dual-Network White Balls 100g of g-C3N4-doped IPN double-network white spheres were added to a reactor, along with 200g of chloromethyl ether and 30g of anhydrous ZnCl2 catalyst. The mixture was stirred at 40℃ for 8 hours to introduce chloromethyl groups onto the benzene ring. After the reaction was completed, the mixture was filtered and washed sequentially with methanol and deionized water to chloromethylate the g-C3N4-doped double-network white spheres.

[0037] 200g of 30% trimethylamine aqueous solution was added to chloromethylated g-C3N4-doped modified double-network white spheres. The pH of the system was adjusted to 9-10 with NaOH. The mixture was heated to 45℃ in a water bath and stirred for 12h to convert chloromethyl groups to quaternary ammonium groups, thus obtaining quaternized g-C3N4-doped modified double-network white spheres.

[0038] Quaternized g-C3N4 doped and modified double-network white spheres were added to the reactor, and 300 g of 98% concentrated sulfuric acid was added. The temperature was raised to 85°C, and the reaction was stirred for 6 h to complete the sulfonation of the benzene ring. The temperature was slowly lowered, and deionized water was added dropwise to dilute the sulfuric acid to avoid the resin from breaking due to sudden cooling, thus obtaining sulfonated g-C3N4 doped and modified double-network white spheres.

[0039] The sulfonated g-C3N4-doped modified double-network white spheres were repeatedly washed with deionized water until the effluent pH was 6-7 and the conductivity was ≤10μS / cm to remove residual sulfuric acid.

[0040] Subsequently, sulfonated g-C3N4 doped double-network white spheres were transformed by column chromatography using a 2wt% dilute hydrochloric acid solution to convert the sulfonic acid groups to the hydrogen form. After the transformation was completed, the resin was washed with deionized water until the effluent pH was 6-7 and the conductivity was ≤10μS / cm to remove residual hydrochloric acid.

[0041] The resin is then subjected to column chromatography using a 4wt% NaOH solution to convert the quaternary ammonium group to the hydroxyl form. Finally, it is washed with deionized water until the pH of the effluent is 7-8 and the conductivity is ≤5μS / cm. The effluent is then dehydrated to a water content of about 55% to obtain the high-temperature resistant condensate polishing resin.

[0042] Comparative Example 1 (Synthesis method of pure IPN interpenetrating network from macroporous strongly acidic + strongly basic styrene-based resin) 1. Synthesis of white spheres with a cationic semi-interpenetrating network (without g-C3N4) Oil phase: 92g styrene + 8g divinylbenzene + 80g porogen + 1g benzoyl peroxide are mixed evenly; Aqueous phase: 300g of 1wt% polyvinyl alcohol aqueous solution.

[0043] The oil phase was slowly added to the aqueous phase, stirred, and the oil droplet size was adjusted to 0.7-0.9 mm. The temperature was raised to 80°C and the reaction was maintained for 6 hours to complete the cationic semi-interpenetrating network polymerization. The mixture was cooled, filtered, washed with water, and the pore-forming agent was extracted with ethanol. The mixture was then dried at 60°C to obtain cationic semi-interpenetrating network white spheres.

[0044] 2. Ultrasound-assisted in-situ interpenetrating polymerization of anion networks Add 100g of the above-mentioned cationic semi-interpenetrating network white spheres to the reactor, add 300g of 1wt% polyvinyl alcohol aqueous solution, stir for 30min to allow the resin to fully swell, and obtain swollen resin material.

[0045] 90g of styrene, 10g of divinylbenzene (crosslinking degree 10%), 75g of porogen, and 1g of benzoyl peroxide were mixed to prepare an anionic oil phase monomer. Anionic oil-phase monomers and swollen resin were ultrasonically dispersed in an ultrasonic dispersion tank with an ultrasonic frequency of 40 kHz, following a cycle of 2 seconds of ultrasonication followed by 6 seconds of pause. The reaction was carried out at 80 ℃ under ultrasonic conditions for 5 hours. After the reaction was completed, the mixture was cooled, filtered, washed with water, and the pore-forming agent was extracted with ethanol. The mixture was then dried at 60 ℃ to obtain pure IPN double-network white spheres (both the anionic and ionic networks are cross-linked and interpenetrating).

[0046] 3. Synchronization Functionality and Transformation of Dual-Network White Balls 100g of double IPN double network white spheres were added to the reactor, along with 200g of chloromethyl ether and 30g of anhydrous ZnCl2 catalyst. The mixture was stirred at 40℃ for 8 hours to introduce chloromethyl groups onto the benzene ring. After the reaction was completed, the mixture was filtered and washed sequentially with methanol and deionized water to chloromethylate the double network white spheres.

[0047] 200g of 30% trimethylamine aqueous solution was added to chloromethylated double-network white spheres. The pH of the system was adjusted to 9-10 with NaOH. The mixture was heated to 45℃ in a water bath and stirred for 12h to convert chloromethyl groups into quaternary ammonium groups, thus obtaining quaternized double-network white spheres.

[0048] Quaternized double-network white spheres were added to the reactor, along with 300 g of 98% concentrated sulfuric acid. The temperature was raised to 85°C, and the mixture was stirred for 6 h to complete the sulfonation of the benzene ring. The temperature was then slowly lowered, and deionized water was gradually added dropwise to dilute the sulfuric acid, preventing the resin from breaking due to sudden cooling. This yielded sulfonated double-network white spheres.

[0049] The sulfonated double-network white spheres were repeatedly washed with deionized water until the effluent pH was 6-7 and the conductivity was ≤10μS / cm to remove residual sulfuric acid.

[0050] Subsequently, the sulfonated double-network white spheres were transformed by column chromatography using a 2wt% dilute hydrochloric acid solution to convert the sulfonic acid groups to the hydrogen form. After the transformation was completed, the resin was washed with deionized water until the effluent pH was 6-7 and the conductivity was ≤10μS / cm to remove residual hydrochloric acid.

[0051] The quaternary ammonium group was then converted to hydroxyl group by column chromatography using 4wt% NaOH solution. Finally, the effluent was washed with deionized water until the pH of the effluent was 7-8 and the conductivity was ≤5μS / cm. The effluent was then dehydrated to a water content of about 55% to obtain control resin 1.

[0052] Comparative Example 2 The difference between this example and Comparative Example 1 is that step 2 in this example uses the megasonic-assisted technique of Example 1. Specifically, the anionic oil-phase monomer and the swollen resin are mixed and stirred for 10 minutes in a megasonic-assisted dispersion tank. Two megasonic vibrators are installed in the tank, and a stirring paddle is installed between them. Megasonic-assisted dispersion is used, with the megasonic frequencies corresponding to the two vibrators being 0.75MHz and 1.58MHz, respectively. The reaction is carried out at 80℃ under megasonic conditions for 3 hours. All other parameters are the same, ultimately yielding control resin 2.

[0053] Comparative Example 3 The difference between this example and Example 1 is that in this example, commercially available graphitic carbon nitride (g-C3N4 powder, purchased from Shanghai Jichun Industrial Co., Ltd.) is used instead of the g-C3N4 nanosheet powder in Example 1. All other aspects are the same.

[0054] It should be noted that commercially available ordinary g-C3N4 powder is only calcined and ground, contains a small amount of intrinsic amino groups, is prone to agglomeration in water, has poor binding with resin, and is easily detached. In contrast, the g-C3N4 nanosheet powder used in this invention is a large amount of aminated g-C3N4 with a large number of exposed edge amino groups, which can anchor the IPN network.

[0055] Comparative Example 4 The difference between this example and Example 1 is that melamine is used in this example instead of urea in Example 1, but all other aspects are the same.

[0056] Comparative Example 5 The difference between this example and Example 1 is that when the anionic oil phase monomer and the swollen resin are dispersed in the megohm-assisted dispersion tank, the stirring paddle is not started, and dispersion is only achieved through megohm-assisted dispersion. All other aspects are the same.

[0057] Comparative Example 6 The difference between this example and Example 1 is that when the anionic oil phase monomer and the swollen resin are dispersed in the megasonic-assisted dispersion tank, the speed of the stirring paddle is 160 rpm, and all other aspects are the same.

[0058] I. Characterization Experiment 1) The total mass exchange capacity (cation fraction) shall be determined according to the method specified in GB / T 8144.

[0059] 2) Determination of strong group exchange capacity (anionic fraction) shall be performed in accordance with the method specified in GB / T 11992.

[0060] 3) Temperature resistance test ① The test shall be conducted in accordance with the method specified in DL / T 953-2018 Determination of Heat Resistance and Antioxidant Properties of Strong Basic Anion Exchange Resins for Water Treatment. The test conditions are: soaking in hot water at 85℃ for 720h and measuring the rate of decrease in exchange capacity (such as the exchange capacity of strong groups).

[0061] ② Soak in 95℃ hot water for 24 hours and measure the rate of decrease in exchange capacity (e.g., exchange capacity of strong groups).

[0062] The test results of the examples and comparative examples are shown in Tables 1-2.

[0063] Table 1

[0064] As can be seen from the above, if g-C3N4 doping modification is not used (Comparative Example 1), although the performance of resistance to conventional high temperature of 85℃ is not significantly affected, the performance of resistance to extreme high temperature short-cycle impact of 95℃ will be severely affected, which will lead to a significant decrease in the rate of exchange capacity reduction (mainly affecting the pore structure).

[0065] As shown in Comparative Example 2, even with the use of a specific megahertz field (Comparative Example 2), the resistance to short-cycle impact at extreme high temperatures of 95℃ cannot be improved without the use of g-C3N4 doping modification.

[0066] Comparative Examples 3 and 4 show that for g-C3N4 nanosheet powder, its source or degree of amination is not deep, which has little impact on its performance against conventional high temperature of 85℃ and its performance against extreme high temperature short-cycle impact of 95℃.

[0067] However, in Comparative Examples 5 and 6, it was found in the experiment that the lack of agitator to assist dispersion significantly affected the pore size of the final resin, resulting in huge differences in the total exchange capacity of the resin produced in different regions. For example, using the total exchange capacity (mmol / kg; the unit was converted here to highlight the intuitiveness of the subsequent standard deviation difference) as the test standard, 20 samples were tested and their standard deviations were calculated. The standard deviation of Example 1 was 252; while the standard deviation of Comparative Example 5 was 975; and the standard deviation of Comparative Example 6 was 633.

[0068] 4) Simulated effects of iron / copper contamination on resin properties Corrosion in thermal system pipelines (especially during start-up and shutdown). Condensate contains high levels of iron oxide and copper oxide. Iron ions adsorb onto the sulfonic acid groups of cation exchange resins, causing "iron poisoning," which significantly reduces exchange capacity and makes regeneration difficult. Copper ions catalyze the degradation reaction of anion exchange resins (Hoffmann degradation), drastically reducing the temperature resistance of the regenerated resin.

[0069] Therefore, by simulating the common iron / copper corrosion product pollution in power plant condensate, the performance changes of the resins in Example 1 and each comparative example after pollution treatment, regeneration and recovery, and high-temperature aging were investigated to comprehensively evaluate the resins' anti-pollution ability and temperature stability.

[0070] The ferrous ion contaminated solution is prepared using ferrous sulfate and dilute sulfuric acid, with a ferrous ion concentration of 100 mg / L and a pH of 4.0 (simulating the acidic corrosion environment of a condensate system). The copper ion contaminated solution is prepared using copper sulfate and dilute sulfuric acid, with a copper ion concentration of 10 mg / L and a pH of 4.0 (simulating the acidic corrosion environment of a condensate system).

[0071] Take 100 mL of resin samples from Example 1 and each comparative example, rinse repeatedly with deionized water until the effluent is clear, drain the water, and set aside. Load the resin samples into a jacketed glass exchange column, and maintain the temperature in a constant-temperature water bath at 85 / 95℃ (simulating high-temperature condensate conditions). Introduce the working contaminant solution (ferrous ion contaminant solution or copper ion contaminant solution) for 5 hours. After contamination, rinse the resin with deionized water until the effluent conductivity is <10 μS / cm, remove the resin, and measure some parameters (post-contamination state).

[0072] The contaminated resin is then regenerated using conventional methods. The cation portion (H type) is regenerated using a 5% (w / w) HCl solution.

[0073] Anionic portion (OH type): Regenerated using a 5% (w / w) NaOH solution.

[0074] For resins contaminated with ferrous ions, after regeneration, wash with deionized water until neutral, and then measure the regenerated properties (such as total exchange capacity by mass).

[0075] For resins contaminated with copper ions, the temperature resistance was tested: resins after 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, and 600 regeneration cycles were soaked in deionized water at 85℃ for 720 h (resistant to 85℃ high temperature) or in deionized water at 95℃ for 24 h (resistant to 95℃ ultra-high temperature); the rate of decrease in total exchange capacity was measured; if the rate of decrease in total exchange capacity was less than or equal to 30%, it indicated that the resin could still be regenerated and used; the maximum number of regeneration cycles was measured until the rate of decrease in total exchange capacity was greater than 30%.

[0076] Table 2

[0077] By comparing Comparative Examples 3 and 4 with Table 2 and Example 1, it can be seen that the source of g-C3N4 nanosheet powder is not deep in amination, and its ability to resist iron contamination is limited.

[0078] Experimental Example Experiments revealed that the dual megaphonic effect utilizes a sound field generated by two specific megaphonic frequencies (one large and one small) combined with stirring to force the anion monomer to penetrate into the macropores of the cation resin, increasing the penetration depth and preventing the agglomeration of g-C3N4 nanosheets during polymerization. This ensures their uniform dispersion at the dual-network interface and simultaneously strengthens the entanglement at the dual-network interface, preventing subsequent delamination. Furthermore, under a specific megaphonic field, the anion monomer is allowed to uniformly penetrate into the cation network channels, polymerizing in situ to form the IPN dual network while ensuring that g-C3N4 does not agglomerate.

[0079] When assisting the dispersion of the two megaphonic vibrators in the megaphonic auxiliary dispersion tank of Example 1, it was found that the difference in megaphonic frequency between the two megaphonic vibrators was Δf. Among them, with the megaphonic frequency of one megaphonic vibrator being 0.75MHz, the megaphonic frequency of the other megaphonic vibrator was changed. When Δf was different, the corresponding changes are shown in Table 3.

[0080] Table 3

[0081] As shown in Table 3, when Δf is in the range of 0.8~0.9MHz, using a specific megaphonic sound field will promote the formation of a specific interwoven three-dimensional network inside the resin. This network structure is very stable, especially after regeneration. Even at a high temperature of 95℃, the specific three-dimensional network inside the resin still maintains good stability, the pore structure does not collapse over a large area, and the resin still maintains excellent ion exchange capacity. If Δf is too small, it means that both sound fields are very concentrated, which is not conducive to the formation of stable pore structures with different particle sizes; if Δf is too large, there may be severe interference between the two sound fields, which is also not conducive to the formation of stable pore structures. Therefore, preferably, Δf is 0.8~0.9MHz; such a dual-sound field megaphonic sound field will promote monomer penetration and improve interpenetration uniformity, thereby improving the stability of the three-dimensional network inside the resin even at high temperatures.

[0082] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0083] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A high-temperature-resistant condensate polishing resin for exclusive use, characterized by comprising a polyamine compound and a polyphenol compound. The high-temperature resistant condensate polishing resin has an interpenetrating polymer network structure, comprising: The cation exchange network has a styrene-divinylbenzene copolymer backbone and contains sulfonic acid groups as cation exchange groups; An anion exchange network with a styrene-divinylbenzene copolymer backbone and quaternary ammonium groups as anion exchange groups; And g-C3N4 nanosheets uniformly dispersed at the interface of the interpenetrating polymer network.

2. The high-temperature condensate polishing special resin according to claim 1, characterized in that, The g-C3N4 nanosheets are aminated g-C3N4 nanosheets with exposed amino groups at their edges.

3. The high-temperature condensate polishing special resin according to claim 1 or 2, characterized in that, The mass ratio of the cation exchange network to the anion exchange network is (0.8~1.2):

1.

4. A method for preparing a high-temperature resistant resin for condensate polishing as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Prepare g-C3N4 nanosheets; Step 2: Styrene, divinylbenzene, porogen, initiator and g-C3N4 nanosheets obtained in Step 1 are mixed and subjected to suspension polymerization to obtain cationic semi-interpenetrating network white spheres containing g-C3N4. Step 3: Mix the cationic semi-interpenetrating network white spheres containing g-C3N4 obtained in Step 2 with anionic oil phase monomers, and carry out in-situ polymerization under mega-sound assisted stirring to obtain g-C3N4 doped and modified interpenetrating polymer network double network white spheres. Step 4: The g-C3N4 doped and modified interpenetrating polymer network double network white spheres obtained in Step 3 are subjected to chloromethylation, quaternization and sulfonation treatments in sequence, and quaternary ammonium groups and sulfonic acid groups are introduced simultaneously on the g-C3N4 doped and modified interpenetrating polymer network double network white spheres. Step 5: The product obtained in Step 4 is subjected to a transformation process, converting the sulfonic acid group to the hydrogen form and the quaternary ammonium group to the hydroxide form, to obtain the special resin for high-temperature condensate polishing.

5. The preparation method according to claim 4, characterized in that, The preparation method of g-C3N4 nanosheets in step 1 is as follows: urea is calcined at 540~560℃ and ground to obtain g-C3N4 powder; the g-C3N4 powder is dispersed in water, ultrasonically treated, centrifuged, and the supernatant is dried to obtain aminated g-C3N4 nanosheets.

6. The preparation method according to claim 4, characterized in that, In step 2, the degree of crosslinking of the cationic semi-interpenetrating network white spheres containing g-C3N4 is 8%~10%, and the amount of g-C3N4 nanosheets added is 1.0%~2.0% of the mass of styrene.

7. The preparation method according to claim 4, characterized in that, The megaphonic assisted stirring in step 3 uses two megaphonic sources and a stirring paddle located between the two megaphonic sources. The difference Δf between the megaphonic frequencies of the two megaphonic sources is 0.8~0.9MHz; the rotation speed of the stirring paddle is 80~90rpm.

8. The preparation method according to claim 4, characterized in that, In step 4, chloromethylation and quaternization are performed first to introduce quaternary ammonium groups, and then sulfonation is performed to introduce sulfonic acid groups.

9. The preparation method according to claim 4, characterized in that, The transformation process described in step 5 includes: first, using hydrochloric acid to convert the sulfonic acid group to the hydrogen form, and washing with water until neutral; then, using sodium hydroxide solution to convert the quaternary ammonium group to the hydroxyl form, and washing with water until neutral.

10. The application of a high-temperature resistant condensate polishing resin as described in any one of claims 1 to 3, or a high-temperature resistant condensate polishing resin prepared by the preparation method described in any one of claims 4 to 9, in the polishing of condensate from high back-pressure units in power plants, characterized in that, The processing temperature of the application is not lower than 80°C.

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