Preparation method and application of pyridyl resin based on charge regulation and control

Abstract

The invention discloses a preparation method and application of pyridyl resin based on charge regulation and control, and belongs to the technical field of polymer adsorption resin. The method comprises the following steps: by increasing the proportion of monomer vinylpyridine, obtaining resin with enhanced surface Zeta positive potential, regulating and controlling the electrostatic interaction and electrostatic collapse of pyridyl resin by virtue of pH reversible switching, under an acidic condition (pH is 2-6), pyridine nitrogen atoms are protonized to form active sites with positive electricity, and PFAS is efficiently captured by virtue of electrostatic attraction; the pH is finely adjusted to be neutral, so that protonation dissociation can be realized, electrostatic interaction disappears, and green regeneration of the resin can be realized through hot water elution. Meanwhile, the poor solvent pore-foaming agent is adopted, so that the prepared resin has macropores and mesopores matched with PFAS micelles, adsorption and desorption of PFAS are more easily achieved, and the resin is suitable for treatment of high-salt, high-chlorine and other complex industrial wastewater.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high molecular adsorption resin, and particularly relates to a pyridine-based resin preparation method based on charge regulation and application. BACKGROUND

[0002] As a kind of persistent chemicals that are difficult to degrade, perfluorinated compounds (PFAS) have become a new focus of global pollution control due to their strong migration and wide toxicity. The current international convention mainly restricts the use of long-chain PFAS (carbon chain length ≥ 8, such as perfluorooctanoic acid PFOA and perfluorooctanesulfonic acid PFOS), resulting in the wide use of short-chain PFAS (carbon chain length < 8) as substitutes, and the emission of short-chain PFAS (such as perfluorohexanoic acid PFHxA) has increased sharply. However, these short-chain PFAS still have significant endocrine disruption, liver toxicity and developmental toxicity, and some countries in Europe and the United States have gradually included short-chain PFAS in the control. It is worth noting that the environmental behavior and toxicological effects of PFAS show a carbon chain length dependence, among which, short-chain PFAS have stronger water solubility and weak hydrophobicity (such as the lgKow value of PFHxA is 2.5), and the carboxyl group or sulfonic acid group in the short-chain PFAS is more likely to ionize RCOO - or RSO3 - , which can be transported over long distances through atmospheric deposition and water circulation, and the pollution range far exceeds the industrial source area.

[0003] Adsorption method has become the most widely used technology in PFAS pollution control due to its advantages of simple operation and controllable cost. Compared with activated carbon adsorption which relies on hydrophobic interaction, anion exchange resin which is dominated by electrostatic interaction is more suitable for the adsorption and removal of PFAS. It uses quaternary amine, tertiary amine, primary amine and other active groups to combine with PFAS in water through electrostatic force and hydrophobic force, and removes PFAS from aqueous solution. However, the existing resin materials still have insufficient capture efficiency for short-chain PFAS, which is specifically limited by the following problems: 1) the limited electrostatic potential of the surface of the resin material leads to limited adsorption capacity; 2) short-chain PFAS has strong hydrophilicity, and the hydrophobic interaction between the resin and the short-chain PFAS is weak; 3) wastewater often contains high concentration of inorganic salts, which is affected by the competitive adsorption of various anions and thus affects the adsorption of PFAS by the resin.

[0004] The lone pair of electrons on the pyridine nitrogen atom is located in sp 2In hybrid orbitals, the unconjugated orbitals can act as Lewis bases to bind with various electron-deficient centers. This property enables the resin material to maintain a high zeta potential on its surface through coordination with cations, thereby driving efficient capture of anions (such as perfluorocarboxylate and sulfonate ions). For example, Tao Weihua et al. prepared a poly(2-vinylpyridine) resin (WH-225) for adsorbing 5-sulfoisophthalic acid (SIPA) in water by suspension copolymerization of 2-vinylpyridine and divinylbenzene with n-heptane as a porogen. This resin showed a higher adsorption capacity for SIPA compared to commercial adsorbents. The applicant's research revealed that the proportion of 2-vinylpyridine monomer used in the synthesis of WH-225 resin was relatively low (around 60%), resulting in insufficient zeta potential strength on the resin surface. Measurements showed that the equilibrium adsorption capacity for PFHxA was only 241 mg / g. Furthermore, due to the uneven dispersion of PFAS in water, micelles of varying sizes easily form, especially in acidic environments. Therefore, the resin (WH-225) prepared using the linear porogen n-heptane has a more uniform pore size, which is not conducive to the rapid adsorption of PFAS micelles. In addition, current methods for regenerating resins, including WH-255, often involve organic reagents and high-concentration alkalis, which can easily cause secondary pollution.

[0005] In summary, there is an urgent need to develop a new resin that has a high adsorption capacity for PFAS, especially for short-chain PFAS (generally exceeding 1000 mg / g), and is easy to regenerate in a green manner. Summary of the Invention

[0006] 1. The problem to be solved To address the problems of existing resins having low saturation adsorption capacity for short-chain PFAS (below 500 mg / g) and the reliance on high-concentration alkalis and organic reagents such as alcohols for desorption and regeneration, which can easily cause secondary pollution, this invention provides a pyridine-based resin based on charge regulation. By increasing the proportion of vinylpyridine monomers, a resin with enhanced surface zeta potential is obtained. The electrostatic interaction and electrostatic collapse of the resin are controlled by reversible pH switching: when the pH is acidic (pH 2-6), the pyridine nitrogen atoms in the resin undergo protonation to form positively charged active sites, achieving efficient PFAS capture through electrostatic forces; when the pH is finely adjusted to neutral, the protons dissociate, the electrostatic interaction disappears, and the resin can be easily and greenly regenerated by hot water elution. Simultaneously, the use of a poor solvent as a porogen gives the resin macropores and mesopores suitable for PFAS micelles, further facilitating PFAS adsorption and desorption. This resin is suitable for the treatment of various high-salt PFAS industrial wastewaters.

[0007] 2. Technical Solution To solve the above problems, the technical solution adopted by the present invention is as follows: This invention provides a charge-controlled pyridyl resin, which is obtained by crosslinking vinylpyridine monomer with a vinyl crosslinking agent, wherein the monomer ratio in the resin is 65% to 99%; the resin contains macropores and mesopores; the average pore size of the macropores is 820 to 860 nm; and the average pore size of the mesopores is 15 to 20 nm.

[0008] Furthermore, the monomers mentioned above include any one of 4-vinylpyridine and 2-vinylpyridine.

[0009] Furthermore, the crosslinking agent mentioned above includes any one or more of divinylbenzene and triallyl isocyanurate.

[0010] Further, the monomer ratio in the above-mentioned resin is 70%~95%, preferably 75%~95%, further preferably 85%~95%, and most preferably 90%~95%. It should be noted that the calculation of the monomer ratio in the resin in this invention is: monomer m2 / (monomer m2 + crosslinking agent m1)×100%; the corresponding calculation of the degree of crosslinking of the resin is: crosslinking agent m1 / (monomer m2 + crosslinking agent m1)×100%. Therefore, the degree of crosslinking can be obtained from the monomer ratio, and it can be seen that the degree of crosslinking of the resin in this invention is 1%~35%, preferably 5%~30%, further preferably 5%~25%, even further preferably 5%~15%, and most preferably 5%~10%.

[0011] Furthermore, the average pore size of the above resin is 844.8 nm.

[0012] Furthermore, the average pore size of the above resin is 17.7 nm.

[0013] Furthermore, the particle size of the above-mentioned resin is 50~2000 μm.

[0014] Furthermore, the resin particle size is 50~800 μm, which provides moderate resistance and good settling properties in the fluid system; preferably 20~400 μm, further preferably 20~300 μm, even more preferably 50~300 μm, and most preferably 150~300 μm.

[0015] Further, the nitrogen content in the above resin is 0.005%~14%, preferably 1%~14%, more preferably 5%~14%, even more preferably 10%~14%, and most preferably 12%~13.3%.

[0016] Furthermore, the surface zeta potential of the above-mentioned resin is 10-50 mV at pH 1-6, preferably 20-50 mV, more preferably 25-50 mV, and most preferably 30-50 mV. This invention utilizes reversible pH switching to regulate the electrostatic interaction and electrostatic collapse of pyridine resin: under acidic conditions, the pyridine nitrogen atoms in the resin are protonated, forming a high positive potential intensity on the resin surface, thereby achieving efficient adsorption of short-chain PFAS through electrostatic forces; when the pH is finely adjusted to the neutral range, the protons dissociate, the electrostatic forces on the resin surface disappear, and the green regeneration of the resin can be achieved by destroying the main weak forces of hydrogen bonding adsorption through hot water.

[0017] This invention also provides a method for preparing a charge-controlled pyridyl resin, comprising the following steps: S1. Preparation of the aqueous phase: Dispersant and salting-out agent are added sequentially to distilled water and stirred to obtain the aqueous phase, wherein the mass percentage concentrations of dispersant and salting-out agent in the aqueous phase are 0.05%~2% and 0.5%~20%, respectively; S2. Preparation of the oil phase: The monomer, crosslinking agent, porogen, and initiator are mixed and stirred to obtain a homogeneous oil phase. The monomer is vinylpyridine, the crosslinking agent is a vinyl-containing crosslinking agent, and the monomer and crosslinking agent constitute the reactants. The mass ratio of the monomer and the crosslinking agent is (7:3) to (49:1); the mass ratio of the porogen to the reactants is (4:1) to (1:4); the mass percentage concentration of the initiator in the oil phase is 0.01% to 3%. It should be noted that the order of S1 and S2 is not limited in this invention. S3. Polymerization reaction: Nitrogen gas is introduced into the aqueous phase S1 and the oil phase S2 respectively. Then the aqueous phase is poured into the reactor and the oil phase is added during stirring. The mass ratio of the aqueous phase to the oil phase is (1:1) to (4:1). The reaction is carried out at 55~80℃ for 1~3 h, and then the temperature is raised to 80~95℃ and held for 2~5 h. After cooling, extraction and drying, the charge-controlled pyridine resin is obtained.

[0018] Furthermore, the mass percentage concentration of the above-mentioned dispersant in the aqueous phase is preferably 0.3% to 1%, and most preferably 0.4% to 0.5%.

[0019] Furthermore, the dispersant mentioned above includes any one or more of gelatin, hydroxyethyl cellulose, polyvinyl alcohol, and sodium lignosulfonate.

[0020] Furthermore, the dispersant is polyvinyl alcohol, with a mass percentage concentration of 0.47% in the aqueous phase.

[0021] Furthermore, the dispersants mentioned above are polyvinyl alcohol and sodium lignosulfonate, with mass percentage concentrations of 0.3% and 0.2% respectively in the aqueous phase.

[0022] Furthermore, the mass percentage concentration of the above-mentioned salting-out agent in the aqueous phase is preferably 2% to 10%, even more preferably 3% to 7%, and most preferably 6% to 7%.

[0023] Furthermore, the salting-out agent is sodium chloride, with a mass percentage concentration of 6.5% in the aqueous phase.

[0024] Furthermore, the above-mentioned aqueous phase is prepared by first adding the dispersant to warm water at 45~55℃ and stirring to dissolve it, then adding the salting-out agent and stirring at 300~500 rpm until a homogeneous and transparent solution is formed.

[0025] Furthermore, the mass ratio of the monomer to the crosslinking agent is preferably (8:2) to (19:1), and most preferably (9:1) to (19:1).

[0026] Furthermore, the monomers mentioned above include any one of 4-vinylpyridine and 2-vinylpyridine.

[0027] Furthermore, the monomer mentioned above is 4-vinylpyridine.

[0028] Furthermore, the crosslinking agent mentioned above includes any one or more of divinylbenzene and triallyl isocyanurate.

[0029] Furthermore, the mass ratio of the reactants to the porogen is preferably (3:1) to (1:3), further preferably (2:1) to (1:2), even further preferably (1.5:1) to (1:1.5), and most preferably (1:0.7) to (1:1).

[0030] Furthermore, the aforementioned porogen includes any one or more mixed solvents selected from toluene, 200# gasoline, and xylene. It should be noted that the porogen used in this invention is a poor solvent, which has a weak ability to dissolve high molecular weight solutes. It can promote crystal nucleation by reducing the solubility of the solute in the solution, making it easier to obtain adsorption resins with different pore sizes.

[0031] Furthermore, the aforementioned pore-forming agent is toluene.

[0032] Furthermore, the aforementioned pore-forming agent is xylene.

[0033] Furthermore, the mass percentage concentration of the above-mentioned initiator in the oil phase is 0.5% to 2.5%, more preferably 1% to 2%, and most preferably 1.2% to 1.8%.

[0034] Furthermore, the aforementioned initiator includes either benzoyl peroxide (BPO) or azobisisobutyronitrile (AIBN).

[0035] Furthermore, the mass ratio of the aqueous phase to the oil phase is (2:1) to (3:1), preferably 2.5:1.

[0036] Furthermore, an oil phase is added during the above stirring process: the stirrer speed is controlled at 200~350 rpm, and the oil phase droplet size is adjusted to 1~5 mm.

[0037] Further, the above polymerization reaction is carried out at 65~75℃ for 1~3 h, more preferably at 65~70℃ for 2 h; then heated to 80~95℃ and held for 2~5 h, more preferably at 85~92℃ and held for 3~4 h, and most preferably at 85℃ and held for 4 h.

[0038] Furthermore, the above extraction includes Soxhlet extraction using any one of the solvents selected from acetone, ethanol, industrial alcohol, or low-boiling-point solvent gasoline. Furthermore, the extraction solvent is acetone, and the extraction time is 6-7 hours.

[0039] Furthermore, the extraction solvent is ethanol, and the extraction time is 7-8 hours.

[0040] Furthermore, the above drying is vacuum drying, with a temperature of 50~70℃, preferably 55~65℃, and most preferably 60℃; a time of 20~28 hours, preferably 22~26 hours, and most preferably 24 hours; and a vacuum degree of ≤0.1 MPa, preferably ≤0.09 MPa, and most preferably ≤0.08 MPa. It should be noted that before vacuum drying, the resin should be evenly spread in a corrosion-resistant tray with a thickness controlled at 1~3cm to avoid uneven heating in certain areas that could cause the resin structure to collapse.

[0041] The present invention also provides a pyridyl resin based on charge regulation prepared by the above method.

[0042] Furthermore, the above-mentioned resin contains macropores and mesopores.

[0043] Furthermore, the average pore size of the aforementioned macropores is 820~860 nm.

[0044] Furthermore, the average pore size of the aforementioned macropores is 844.8 nm.

[0045] Furthermore, the average pore size of the aforementioned mesopores is 15~20 nm.

[0046] Furthermore, the average pore size of the aforementioned mesopores is 17.7 nm.

[0047] Furthermore, the particle size of the above-mentioned resin is 50~2000 μm.

[0048] Furthermore, the resin particle size is 50~800 μm, which provides moderate resistance and good settling properties in the fluid system; preferably 20~400 μm, further preferably 20~300 μm, even more preferably 50~300 μm, and most preferably 150~300 μm.

[0049] Further, the nitrogen content in the above resin is 0.005%~14%, preferably 1%~14%, more preferably 5%~14%, even more preferably 10%~14%, and most preferably 12%~13.3%.

[0050] Furthermore, the surface zeta potential of the above resin is 10-50 mV at pH 1-6, preferably 20-50 mV, more preferably 25-50 mV, and most preferably 30-50 mV.

[0051] The present invention also provides the application of the above-described resin or the resin prepared by the above-described method in the preparation of ion exchange chromatography columns.

[0052] The present invention also provides an ion exchange chromatography column, wherein the packing material in the chromatography column is composed of the above-mentioned resin or the resin prepared by the above method and quartz sand in a volume ratio of 1:1.

[0053] This invention also provides the application of the above-mentioned resin or the resin prepared by the above-mentioned method or the above-mentioned ion chromatography column in the treatment of high-salt PFAS wastewater. The charge-controlled pyridine resin provided by this invention is prepared by suspension copolymerization of vinylpyridine and a vinyl-containing crosslinking agent. The lone pair electrons of the nitrogen atom in the pyridine group of the resin are easily protonated in the acidic region, forming a stable resin complex with a strong positive surface charge. This complex adsorbs small micelles of perfluorinated compounds with negatively charged weak acid groups (carboxylate and sulfonic acid) in the water, thereby achieving a high efficiency in PFAS removal, including a high removal rate for short-chain PFAS with a carbon chain length of 4-8. It also has the ability to resist interference from inorganic salt ions (including but not limited to chloride ions, sulfate ions, nitrate ions, etc.) in the aquatic environment. The protonation phenomenon of the pyridine group in the resin disappears under neutral conditions, and the green regeneration of the charge-controlled pyridine resin is achieved by relying on the main weak interaction forces such as hydrogen bond adsorption broken by hot water.

[0054] Furthermore, the PFAS mentioned above are short-chain PFAS with a carbon chain length of 4 to 8.

[0055] 3. Beneficial effects Compared with the prior art, the advantages of this invention are as follows: (1) The present invention provides a method for preparing and applying pyridine-based resins based on charge regulation. By increasing the proportion of vinylpyridine monomers, a resin with enhanced surface zeta potential is obtained. The electrostatic interaction and electrostatic collapse of the pyridine-based resin are regulated by reversible pH switching: under acidic conditions (pH=2), the pyridine groups in the resin are highly protonated (≡N). + H), forming positively charged active sites, achieves a balanced adsorption capacity of up to 2455 mg / g for short-chain PFHxA through electrostatic attraction-hydrophobic synergy, greatly improving the adsorption performance for short-chain PFAS; when the pH is finely adjusted to neutral, proton dissociation occurs, electrostatic interaction disappears, and only hot water elution is needed to destroy the main adsorption force through hydrogen bonding, thus achieving green regeneration of the resin. The desorption rate for PFAS is >90%, effectively avoiding the use of organic solvents, making it more economical and environmentally friendly.

[0056] (2) The present invention provides a method for preparing and applying a pyridine resin based on charge regulation. Considering that PFAS is unevenly dispersed in water and easily forms micelles of different sizes, a poor solvent is used as a pore-forming agent. The prepared resin has macropores and mesopores that are suitable for PFAS micelles, which is more conducive to capturing PFAS and further improving the adsorption capacity.

[0057] (3) The present invention provides a method for preparing and applying a pyridine resin based on charge regulation. The resin has excellent salt resistance and interference resistance. Under high ionic strength (NaCl≤500 mmol / L), its removal rate for short-chain and medium-to-long-chain PFAS is still >95%, and it is suitable for the treatment of various high-salt PFSA industrial wastewater. Attached Figure Description

[0058] Figure 1 The adsorption characteristics of resin A0 prepared in Example 1 of this invention for PFAS of different chain lengths under different pH conditions are shown in the following: (a) is the result of competitive adsorption experiment of mixed PFAS solution; (b) is the comparison of equilibrium adsorption capacity of perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA).

[0059] Figure 2 The zeta potential of resin A0 and perfluorohexanoic acid (PFHxA) prepared in Example 1 of this invention is measured under different pH conditions, wherein: (a) is resin A0; (b) is PFHxA.

[0060] Figure 3 This is a graph showing the pore size distribution data of resin A0 prepared in Example 1, determined by mercury intrusion porosimetry.

[0061] Figure 4 This is a graph showing the mesopore size distribution data of resin A0 in Example 1, measured using the multi-point BET method according to the present invention.

[0062] Figure 5 This is a comparison chart of the Zeta potential and equilibrium adsorption capacity of resin A0 and resin WH-225 prepared in Example 1 of this invention under different pH conditions.

[0063] Figure 6 This is a schematic diagram of resin column filling in Example 11 of the present invention.

[0064] Figure 7 This is a graph showing the change in PFAS removal rate of actual industrial wastewater treated by resin A0 chromatography column in Example 11 of this invention. Detailed Implementation

[0065] The present invention will be further described below with reference to specific embodiments.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0067] 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.

[0068] As used herein, the term “about” is used to provide for the flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable. As used herein, the term “at least one of…” is intended to be synonymous with “one or more of…”. For example, “at least one of A, B, and C” explicitly includes only A, only B, only C, and combinations thereof. Concentration, amount, and other numerical data may be presented in range format herein. It should be understood that such range format is used solely for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly stated as the limits of the range, but also all individual values ​​or subranges encompassed within the range, as if each value and subrange were explicitly stated. For example, a range of values ​​from about 1 to about 4.5 should be interpreted to include not only the explicitly stated limits of 1 to 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that describe only a single value, such as "less than about 4.5," which should be interpreted to include all the values ​​and ranges described above. Furthermore, this interpretation should apply regardless of the breadth of the range or characteristic described.

[0069] Example 1 This embodiment provides a pyridyl resin A0 based on charge regulation and its preparation.

[0070] The monomer in resin A0 is 4-vinylpyridine:

[0071] The crosslinking agent is divinylbenzene:

[0072] Specifically, the preparation of this resin includes the following steps: S1. Preparation of the aqueous phase: Dispersant and salting-out agent are added sequentially to distilled water and stirred to obtain the aqueous phase, wherein the mass percentage concentrations of dispersant and salting-out agent in the aqueous phase are 0.47% and 6.5%, respectively. Specifically, the aqueous phase contains 100 g of distilled water, 0.5 g of dispersant polyvinyl alcohol, and 7 g of salting-out agent sodium chloride. When preparing the solution, first add the dispersant polyvinyl alcohol to warm water at 45~55℃ and stir to dissolve it. Then add the salting-out agent sodium chloride and stir to dissolve it. The stirring speed is controlled at 300~500 rpm until a homogeneous and transparent solution is formed. S2. Preparation of the oil phase: Mix the monomer, crosslinking agent, porogen, and initiator, and stir to obtain a homogeneous oil phase. The monomer and crosslinking agent constitute the reactants, with a mass ratio of 19:1 (crosslinking degree 5%); the mass ratio of the porogen to the reactants is 1:0.7; and the mass percentage concentration of the initiator in the oil phase is 1.2%. Specifically, the oil phase contains 23.75 g of monomer 4-vinylpyridine, 1.25 g of crosslinking agent divinylbenzene, 17.5 g of porogen toluene, and 0.5 g of initiator azobisisobutyronitrile (AIBN), and is stirred at 150 rpm at room temperature of 25°C until homogeneous. S3. Polymerization reaction: Nitrogen gas was introduced into the aqueous phase S1 and the oil phase S2 respectively. Then the aqueous phase was poured into the reactor and the oil phase was added during stirring. The reaction was carried out at 65℃ for 1 h and then heated to 85℃ and held for 3 h to complete the polymerization reaction. After cooling, the product was extracted with acetone soxhlet for 6 h and dried under vacuum (≤0.08 MPa) at 60℃ for 24 h to obtain the charge-controlled pyridyl resin. Specifically, nitrogen gas was first introduced into the S1 aqueous phase and S2 oil phase for 5 minutes to remove oxygen. The aqueous phase was then poured into a 500 mL Mitsui flask reactor and stirred for 10 minutes at a stirring rate of 200 rpm under nitrogen protection. The oil phase was then added, and the stirring rate was maintained at 200 rpm. The droplet size of the oil phase was controlled to be approximately 1-5 mm. After polymerization, a charge-controlled pyridinyl resin A0 was finally obtained.

[0073] Example 2 This embodiment provides a pyridyl resin A1 based on charge regulation and its preparation.

[0074] Resin A1 has the same structure as resin A0 in Example 1; In contrast to Example 1, the degree of crosslinking of resin A1 is increased from 5% in resin A0 to 10%.

[0075] Crosslinking degree calculation: crosslinking agent m1 / (monomer m2 + crosslinking agent m1) × 100%; Specifically, regarding its preparation method: The amount of crosslinking agent divinylbenzene used in Example 1 was changed from 1.25 g to 2.5 g, and the amount of monomer 4-vinylpyridine was changed from 23.75 g to 22.5 g; Change the polymerization reaction time: After the polymerization reaction is carried out at 65℃ for 2 h, the temperature is raised to 85℃ and held for 4 h.

[0076] The other preparation processes were the same as in Example 1. Finally, a charge-controlled pyridine resin A1 was obtained. Due to the decrease in the proportion of the monomer 4-vinylpyridine, the nitrogen content in resin A1 was measured by an elemental analyzer (EA, Vario Micro, Elementar, Germany) to be reduced from 11.30% in the original resin A0 to 10.65%.

[0077] Example 3 This embodiment provides a charge-controlled pyridyl resin A2 and its preparation.

[0078] Resin A2 has the same structure as resin A0 in Example 1; In terms of preparation method, the extraction method of the product obtained from the polymerization reaction is changed, unlike Example 1: Specifically, the acetone soxo-extraction method used in Example 1 for 6 hours was changed to ethanol soxo-extraction method for 7 hours.

[0079] The other preparation processes were the same as in Example 1. Finally, a charge-controlled pyridine resin A2 was obtained. The specific surface area and porosity of the resin material were measured by a multi-station extended fully automated rapid specific surface area and porosity analyzer (ASAP 2460). The change in the product extraction method in this example had no effect on the specific surface area of ​​the resin material.

[0080] Example 4 This embodiment provides a charge-controlled pyridyl resin A3 and its preparation.

[0081] Resin A3 has the same structure as resin A0 in Example 1; In terms of preparation method, the difference from Example 1 is the change in the type of pore-forming agent: Specifically, the porogen toluene used in Example 1 was replaced with xylene.

[0082] The other preparation processes are the same as in Example 1. Finally, a charge-controlled pyridyl resin A3 was obtained. The average pore size of resin A3 (18.9 nm) measured by the multi-point BET method is basically the same as that of resin A0 (17.6 nm).

[0083] Example 5 This embodiment provides a charge-controlled pyridyl resin A4 and its preparation.

[0084] The monomers in resin A4 are the same as in Example 1, except that the crosslinking agent in Example 1 is triallyl isocyanurate.

[0085] In terms of preparation method, the type of crosslinking agent is changed, unlike in Example 1: Specifically, the crosslinking agent divinylbenzene used in Example 1 was replaced with triallyl isocyanurate.

[0086] The other preparation processes are the same as in Example 1, and finally, charge-controlled pyridine resin A4 is obtained.

[0087] Example 6 This embodiment provides a charge-controlled pyridyl resin A5 and its preparation.

[0088] Resin A5 has the same structure as resin A0 in Example 1; In terms of preparation method, the dispersant type is changed, unlike in Example 1: Specifically, the dispersant polyvinyl alcohol used in Example 1 was replaced with polyvinyl alcohol with a mass percentage concentration of 0.3% and sodium lignosulfonate with 0.2%.

[0089] The other preparation processes are the same as in Example 1. Finally, a charge-controlled pyridyl resin A5 was obtained. The average particle size of resin A5 prepared by this method (500 μm) was observed to be larger than that of resin A0 (200 μm) by optical microscopy.

[0090] Example 7 This embodiment provides a charge-controlled pyridyl resin A6 and its preparation.

[0091] Resin A6 has the same structure as resin A0 in Example 1; In terms of preparation method, the difference from Example 1 is the amount of salting-out agent added: Specifically, the amount of sodium chloride added as the salting-out agent in Example 1 was changed from 7 g to 2 g.

[0092] The other preparation processes are the same as in Example 1. Finally, charge-controlled pyridine resin A6 was obtained. Due to severe emulsification during the synthesis process, the product was stuck together, and the final yield of resin A6 was reduced to 10% (the yield of resin A0 was 85.2%). Yield calculation = dry weight of product / (weight of monomer and crosslinking agent) × 100%.

[0093] Example 8 This embodiment provides the equilibrium adsorption capacity and hot water desorption rate of resins A0-A6 prepared in Examples 1-7 for short-chain perfluorohexanoic acid PFHxA.

[0094] Specifically, a PFHxA solution of 500 mg / L was prepared, and the pH was adjusted to 2.00±0.01 with 1M HCl. 20 mg / 100 mL of resin was added. A blank group (without resin) and parallel experimental groups (n=3) were set up. The shaker was set at 25℃ and 150 rpm. After adsorption for 24 h, samples were collected. Pre-salting of the samples was performed using an automated solid-phase extraction system (Autotrace 280, Thermo Scientific, USA) and an Oasis® WAX solid-phase extraction column. After desalting, the samples were diluted 1000-fold and transferred to HPLC vials through a 0.22 μm PTFE-Q filter membrane for analysis. The PFHxA concentrations in the experimental and control groups were detected using ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-Class & Xevo TQ-MS, Waters, USA), and the resin equilibrium adsorption capacity was calculated. Specifically, a C18 column was used at a column temperature of 35℃. The mobile phase consisted of 5 mM ammonium acetate aqueous solution (mobile phase A) and methanol (mobile phase B), with an injection volume of 10 μL. Separation was performed at a flow rate of 0.3 mL / min using the gradient elution program in Table 1. Mass spectrometry was used for detection in positive electrospray ionization mode with multiple reaction monitoring (MRM).

[0095] Table 1. Gradient elution program

[0096] Hot water desorption: In the shake-flask experiment after adsorption equilibrium was achieved, hot water desorption was performed at 90℃. The specific process is as follows: First, the resin that had completed adsorption was separated from the adsorbent solution by suction filtration using a Buchner funnel, and the residual mother liquor on the resin surface was quickly washed with a small amount of water. Next, all the drained wet resin was transferred to an Erlenmeyer flask, and then 100 mL of distilled water (i.e., the desorption liquid volume V1) was added. The flask was immediately placed in a constant temperature shaking water bath and desorbed by constant temperature shaking at 90℃ and a certain rotation speed. The desorption process was maintained for 2 hours to ensure that desorption equilibrium was reached. Subsequently, a sample was immediately taken and filtered through a 0.22 μm PTFE-Q filter membrane, diluted 1000 times with chromatographic grade methanol, transferred to a brown liquid chromatography vial, and the PFHxA concentration C1 was determined by chromatography.

[0097] The specific calculation method for the desorption rate is as follows: First, the total adsorption capacity of the resin during the adsorption stage (M) needs to be calculated. 吸附 M), which is the difference between the total mass of the target substance in the original solution before adsorption and the total mass of the target substance in the residual solution after adsorption, is calculated using the formula M. 吸附 =(C0×V0)-(C2×V2), where C0 and V0 are the concentration and volume of the original adsorption solution, respectively, and C2 and V2 are the concentration and volume of the residual solution after adsorption equilibrium, respectively; then, calculate the total amount of target substance desorbed from the resin (M). 脱附 ), that is: M 脱附 =C1×V1, where C1 and V1 are the concentration and volume of the desorption solution, respectively; the final desorption rate (η) is calculated using the formula: Desorption rate (η) = (M 脱附 / M 吸附 The formula is calculated as follows: (C1×V1) / ((C0×V0)-(C2×V2))]×100%. This formula clearly expresses the desorption efficiency as the percentage of the total amount of target substance in the desorption solution relative to the total amount adsorbed by the resin, thus quantitatively evaluating the effect of the hot water desorption process.

[0098] The calculated results of the resin equilibrium adsorption capacity and hot water desorption rate are shown in Table 2: Table 2

[0099] As shown in the table: changing the dispersant (A5) slightly improves the resin's adsorption performance for PFHxA without affecting desorption; therefore, resin A5 should be the preferred choice for applications requiring large particle size resin. Increasing the crosslinking agent ratio (A1) and changing the crosslinking agent (A4) reduces the resin's acidic adsorption capacity, but the desorption performance remains largely unchanged; therefore, it can be considered for use in weakly acidic environments to reduce mechanical wear. Replacing the porogen with xylene (A3) has virtually no effect on adsorption or desorption; xylene can be used as a substitute for toluene as a porogen. Replacing the Soxhlet extraction solvent with ethanol (A2) has virtually no effect on adsorption or desorption; ethanol can be used as a substitute for acetone as a Soxhlet extraction solvent.

[0100] Example 9 This embodiment provides the determination of the adsorption selectivity of resin A0 prepared in Example 1 for PFAS of different chain lengths at different pH values, as well as the determination of the equilibrium adsorption capacity for short-chain perfluorohexanoic acid (PFHxA) and perfluorooctanoic acid (PFOA).

[0101] Specifically, at 25°C and within a pH range of 2–6, the effects of resin A0 on PFBA (C4), PFBS (C4), PFHpA (C7), PFOA (C8), PFOS (C8), and PFDA (C8) were determined. 10 The adsorption selectivity of ).

[0102] Prepare a mixed solution of PFBA, PFBS, PFHpA, PFOA, PFOS, and PFDA, with each PFAS concentration of 100 mg / L. Adjust the pH with 1M HCl and 1M NaOH. Add 20 mg / 100 mL of resin. Set up a blank group (without resin) and parallel experimental groups (n=3). Set the shaker to 25℃ and 150 rpm, and collect samples after 24 h of adsorption. The sample pretreatment and concentration detection methods are the same as in Example 8.

[0103] Specifically, at 25°C and within a pH range of 2–6, the saturated adsorption capacity of resin A0 for PFHxA and PFOA was determined.

[0104] Prepare an 800 mg / L PFHxA solution, adjust the pH with 1M HCl and 1M NaOH; add 20 mg / 100 mL of resin; set up a blank group (no resin) and parallel experimental groups (n=3); set the shaker at 25℃ and 150 rpm, and collect samples after 24 hours of adsorption. Prepare a 100 mg / L PFOA solution, adjust the pH with 1M HCl and 1M NaOH; add 20 mg / 100 mL of resin; set up a blank group (no resin) and parallel experimental groups (n=3); set the shaker at 25℃ and 150 rpm, and collect samples after 24 hours of adsorption. The pretreatment and concentration detection methods for the above samples are the same as in Example 8.

[0105] Results analysis: like Figure 1 As shown in (a), in the PFAS mixed solution, resin A0 affects C4~C 10 All PFAS have adsorption capacity, which is significantly pH-dependent. In the acidic range, electrostatic adsorption of resin A0 is dominant, while in the neutral range, electrostatic adsorption disappears and hydrogen bonding becomes the dominant adsorption mechanism. Figure 1As shown in (b), resin A0 exhibits an equilibrium adsorption capacity of 3238 mg / g for PFHxA at pH=2, the highest value across the entire pH range. This is 2-3 times the equilibrium adsorption capacity of commercially available anion exchange resins (IRA910, 1124 mg / g), further demonstrating that the pyridine group is fully protonated in a strongly acidic environment, resulting in a strongly positively charged resin surface that efficiently captures short-chain PFAS anions via electrostatic interactions. For PFOA, the equilibrium adsorption capacity is 947 mg / g at pH=2. In the neutral range, protonation disappears, and the nitrogen atoms of the resin pyridine group adsorb PFOA through hydrogen bonding. At pH=6, the equilibrium adsorption capacity decreases to 547 mg / g.

[0106] Example 10 This embodiment provides the determination of the physicochemical properties of resin A0 prepared in Example 1.

[0107] Specifically, 1) The surface zeta potential of resin A0 in the pH range of 1.0 to 6.0 was measured using a particle size potentiometer (Zetasizer Nano ZS, Malvern, UK).

[0108] The results are as follows Figure 2 As shown in (a), resin A0 maintains a positive charge in the pH range of 1.0 to 4.5, but rapidly becomes negatively charged when pH > 4.5.

[0109] In addition, this embodiment also measured the surface Zeta potential changes of short-chain perfluorohexanoic acid (PFHxA) at 25°C and different pH values; the results are as follows. Figure 2 As shown in (b), PFHxA exists in solution as large micelles with no surface charge when pH < 5. When pH > 5, the micelles dissolve and form small micelles with negative surface charge.

[0110] 2) The macropore and mesopore size distribution of resin A0 was determined by mercury porosimetry and BET method.

[0111] like Figure 3 As shown, the resin A0 macropores (>50 nm) have an average pore size of 844.8 nm, which is used to accommodate large PFAS micelles, such as... Figure 4 As shown, the average pore size of the mesoporous resin A0 (2~50 nm) is 17.7 nm, which is used to contain small micelles after PFAS dissolution. Using resin A0 with different pore sizes is more conducive to capturing various types of PFAS micelles and ensuring high adsorption capacity.

[0112] Comparative Example 1 This comparative example provides the physicochemical properties of resin WH-255 and its performance in adsorbing PFAS.

[0113] The resin WH-255 is derived from the research of Tao Weihua et al. (WHTao,AMLi,C.Long,HMQian, Poly(vinylpyridine) adsorbent for the removal of SIPA from its aqueous solution,Chin. Chem. Lett.20(2009)604–607). It differs from resin A0 prepared in Example 1 in the following ways: 1) Monomer type: Resin A0 uses 4-vinylpyridine as the monomer, while resin WH-225 uses 2-vinylpyridine as the monomer; 2) Monomer content: The monomer ratio in resin A0 is 95%, while the monomer ratio in resin WH-225 is 60%. The specific monomer ratio is calculated as: monomer m2 / (monomer m2 + crosslinking agent m1)×100%; 3) Pore-forming agent: Resin A0 uses toluene as the porogen, while resin WH-225 uses n-heptane as the porogen.

[0114] Specifically, the surface zeta potential change of resin WH-225 in the pH range of 1.0 to 6.0 was measured using the same method as in Example 10, and compared with the surface positive potential of resin A0.

[0115] The results are as follows Figure 5 As shown in Figure (a), it can be seen that the positive potential of the resin surface increases with the increase of the monomer ratio. At pH 2, the positive potential of resin WH-255 is 13.8 mV, and the positive potential of resin A0 increases to 30.5 mV.

[0116] Next, the effect on the adsorption performance of PFAS was further investigated. The equilibrium adsorption capacity of resin WH-255 for short-chain PFHxA was measured in the same way as in Example 9 and compared with the equilibrium adsorption capacity of resin A0.

[0117] The results are as follows Figure 5 As shown in Figure (b), it can be observed that the adsorption capacity of the resin for PFHxA is significantly increased with the increase of the monomer ratio. At pH 2, the equilibrium adsorption capacity of resin WH-255 for PFHxA is 241 mg / g, while the equilibrium adsorption capacity of resin A0 can reach 3238 mg / g. This can be attributed to several factors, including the influence of the increased monomer ratio on the adsorption capacity. Resin A0, synthesized using toluene as a porogen, has both macropores (>50 nm) and mesopores (2~50 nm) with varying pore sizes. In contrast, resin WH-255, synthesized using the linear porogen n-heptane, has a more uniform pore size (average about 9.4 nm). For PFAS, which are unevenly dispersed in water and easily form micelles of different sizes, the former is more suitable for the adsorption of PFAS.

[0118] Example 11 This embodiment provides the application of a chromatography column prepared with resin A0 in the treatment of high-salt PFAS wastewater.

[0119] Specifically, the following steps are included: 1) Take a glass chromatography column with an inner diameter of 20 mm and a height of 500 mm, fill it with 30 mL each of resin A0 and 50-mesh quartz sand (volume ratio 1:1), mix them thoroughly, and fix them on a support to obtain... Figure 6 The resin A0 chromatography column shown; 2) Fluoride plant wastewater (pH pre-adjusted to 2.3, containing PFPeA 7.89 μg / L, PFHxA 309.86 μg / L, PFHpA 5.29 μg / L, PFOA 55.40 μg / L, PFNA 8.09 μg / L, PFDA 3.08 μg / L, Na) is introduced into the column using a top-in, bottom-out method. + 477 mg / L, Ca 2+ 98.7 mg / L, F - 0.9 mg / L, Cl - 543.0 mg / L, NO3 - 367.2 mg / L), with a controlled flow rate of 2 BV / h (1 BV = 60 mL); run for 10 days.

[0120] 3) Results Analysis The results are as follows Figure 7 As shown, after 10 days of continuous operation, the A0 resin chromatography column achieved a 99.88% removal rate for short-chain PFAS: PFHxA; and a 100% removal rate for medium- and long-chain PFAS: PFOA, PFNA (perfluorononanoic acid), and PFDA (perfluorodecanoic acid). The multi-component synergistic removal rate was 74.70% for PFPeA (perfluorovaleric acid) and 92.89% for PFHpA (perfluoroheptanoic acid). This demonstrates that the chromatography column prepared with A0 resin in this invention effectively achieves broad-spectrum and efficient removal of high-concentration PFAS from high-salt wastewater.

Claims

1. A pyridyl resin based on charge regulation, characterized in that, The resin is obtained by crosslinking vinylpyridine monomer with a vinyl crosslinking agent, and the monomer ratio in the resin is 65%~99%; the resin contains macropores and mesopores; the average pore size of the macropores is 820~860 nm; and the average pore size of the mesopores is 15~20 nm.

2. The resin according to claim 1, characterized in that, The monomer includes any one of 4-vinylpyridine and 2-vinylpyridine; and / or The crosslinking agent includes any one or more of divinylbenzene and triallyl isocyanurate; and / or The resin has a particle size of 50~2000 μm; and / or The nitrogen content in the resin is 0.005% to 14%.

3. The resin according to claim 1 or 2, characterized in that, The zeta potential of the resin surface is 10-50 mV at pH 1-6.

4. A method for preparing a pyridyl resin based on charge regulation, characterized in that, Includes the following steps: S1. Preparation of the aqueous phase: Dispersant and salting-out agent are added sequentially to distilled water and stirred to obtain the aqueous phase, wherein the mass percentage concentrations of dispersant and salting-out agent in the aqueous phase are 0.05%~2% and 0.5%~20%, respectively; S2. Preparation of the oil phase: The monomer, crosslinking agent, porogen, and initiator are mixed and stirred to obtain a homogeneous oil phase. The monomer is vinylpyridine, and the crosslinking agent is a vinyl-containing crosslinking agent. The monomer and crosslinking agent constitute the reactants, and their mass ratio is (7:3) to (49:1). The mass ratio of the reactants to the porogen is (4:1) to (1:4). The mass percentage concentration of the initiator in the oil phase is 0.01% to 3%. S3. Polymerization reaction: Nitrogen gas is introduced into the aqueous phase S1 and the oil phase S2 respectively. Then the aqueous phase is poured into the reactor and the oil phase is added during stirring. The mass ratio of the aqueous phase to the oil phase is (1:1) to (4:1). The reaction is carried out at 55~80℃ for 1~3 h, and then the temperature is raised to 80~95℃ and held for 2~5 h. After cooling, extraction and drying, the charge-controlled pyridine resin is obtained.

5. The method according to claim 4, characterized in that, The dispersant includes any one or more of gelatin, hydroxyethyl cellulose, polyvinyl alcohol, and sodium lignosulfonate; and / or The salting-out agent includes sodium chloride; and / or The monomer includes any one of 4-vinylpyridine and 2-vinylpyridine; and / or The crosslinking agent includes any one or more of divinylbenzene and triallyl isocyanurate; and / or The pore-forming agent includes any one or more mixed solvents selected from toluene, 200# gasoline, and xylene; and / or The initiator includes either benzoyl peroxide or azobisisobutyronitrile.

6. The method according to claim 5, characterized in that, The extraction includes Soxhlet extraction using any one of the following solvents: acetone, ethanol, industrial alcohol, or low-boiling-point solvent gasoline.

7. A pyridyl resin based on charge regulation prepared by the method of any one of claims 4-6.

8. The use of the resin according to any one of claims 1-3 or the resin according to claim 7 in the preparation of ion exchange chromatography columns.

9. An ion exchange chromatography column, characterized in that, The packing material in the chromatography column is composed of the resin described in any one of claims 1-3 or the resin described in claim 7 and quartz sand in a volume ratio of 1:

1.

10. The application of the resin according to any one of claims 1-3, or the resin according to claim 7, or the ion exchange chromatography column according to claim 9 in the treatment of high-salt PFAS wastewater.

Images