Patent Application
20230357287
The present invention belongs to the technical field of separation materials, and particularly relates to a N,O-type multidentate functional monomer, a preparation method thereof and an application thereof in ion-imprinted polymers.
As an essential trace element in all living organisms, copper is a component of several enzymes involved in electron flow and a major catalyst in redox reactions, and is irreplaceable in the life cycle. However, excessive copper may cause irreversible damage to the body. Increased copper concentration in the blood can cause symptoms such as hypotension, black stools, coma, jaundice, and gastrointestinal discomfort. Long-term exposure to copper can also damage the liver and kidneys. The maximum contaminantlevel of copper in drinking water is 1.3 mg/L. If the content exceeds the standard, it will cause harmful effects on the human body and the ecological system. Wastewater containing heavy metal ions such as copper should be properly disposed of. At present, methods adopted industrially lack selectivity. To remove or isolate specific metal ions from a mixture, selective separation methods are required.
Molecular imprinting technology (MIP) is a technique to use a target molecule as a template and make functional monomer to form a specific spatial distribution around the template through the interaction between the functional monomer and the template, and add a cross-linking agent to form a template-containing polymer through a polymerization reaction. After template molecules are removed, cavities with the same shape as the template molecules and specific distribution of recognition sites are left in the polymer. The material with these specific cavities is a molecularly imprinted material. Theoretically, there should be a specific selectivity similar to “antigen-antibody” between molecularly imprinted materials and template molecules. Although the current imprinted materials are not able to offer the desired “specificity”, their separation selectivity is still far better than that of ordinary separation materials.
Ion-imprinted polymer (IIP) refers to the imprinted polymer prepared with metal ions as templates. Although IIP can be used to separate and enrich specific metal ions, relative to MIP, the selectivity of existing IIP is generally low. The reasons are as follows: firstly, the metal ions are very similar in size and charge, making it difficult to identify; secondly, most of the existing functional monomers are monodentate ligands, and the complexes of these monomers and metal ions are not stable and the imprinting effect is not good; furthermore, the functional monomers used in the synthesis of IIP are excessive, which necessarily causes non-specific adsorption; therefore, the imprinting materials based on the existing functional monomers cannot provide a highly specific ion recognition microenvironment.
In view of the problems existing in the prior art, the object of the present invention is to provide a N,O-type multidentate functional monomer, a preparation method thereof and an application thereof in ion-imprinted polymers. In the present invention, a N,O-type multidentate functional monomer is synthesized, and on this basis, an ion-imprinted polymer with better selectivity to metal ions is synthesized. The imprinted materials obtained in the present invention have high selectivity for metal ions, for example, Cu2+, Ni2+, etc.
In order to achieve a first object, the present invention adopts the followingtechnical solutions:
A method for preparing a N,O-type multidentate functional monomer(AAPTS-COOH), specifically comprising the following steps:
The N,O-type multidentate functional monomer AAPTS-COOH is a siloxane monomer with three carboxylic acid groups and two N atoms, the structural formula being as follows:
The N,O-type multidentate functional monomer can form six-membered rings and five-membered rings simultaneously with metal ions.
Further, in the above technical solution,the acrylic esters in the step (a) can be any one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, pentyl acrylate, and hexyl acrylate. More preferably, the acrylic esters are tert-butyl acrylate.
Further, in the above technical solution, the organic solvent in the step (a) is any one of methanol or ethanol.
Further, in the above technical solution, the molar ratio of the N-aminoethyl-γ-aminopropyltrimethoxysilane to the acrylic esters in the step (a) is preferably 1:5.
Further, in the above technical solution, the reaction temperature in the step (a) is preferably 50° C., and the reaction time is preferably 24 h.
Further, in the above technical solution, the mass fraction of the trifluoroacetic acid aqueous solution in the step (b) is 1-98%, preferably 95%.
Further, in the above technical solution, the hydrolysis time in the step (b) is preferably 1 h.
A second object of the present invention is to provide a N,O-type multidentate functional monomer(AAPTS-COOH) prepared by the method for preparing N,O-type multidentate functional monomer(AAPTS-COOH).
A third object of the present invention is to provide an application of the N,O-type multidentate functional monomer(AAPTS-COOH) prepared by the above method in ion-imprinted polymers (IIP).
A method for synthesizing an ion-imprinted polymer (IIP) is provided, comprising the following steps:
Furthermore, in the above technical solution, the organic solvent described in the step (1) is methanol or ethanol.
Furthermore, in the above technical solution, the volume ratio of the organic solvent to the buffer solution in the step (1) is 1:1-10.
Furthermore, in the above technical solution, the buffer solution in the step (1) is preferably deionized water with a pH value of 3-9.
Further, in the above technical solution, the metal ion in the step (1) is any one of Cu2+ and Ni2+.
Further, in the above technical solution, the tetraalkoxysilane in the step (2) is preferably tetraethoxysilane (TEOS), and the molar ratio of the tetraethoxysilane to the N,O-type multidentate functional monomer is preferably 10:1.
Further, in the above technical solution, the dosage ratio of the ammonia waterto the cross-linking agent tetraalkoxysilane in the step (2) is (0.1-20) mL: 0.06 mol.
Furthermore, in the above technical solution, the concentration of the ammonia water solution in the step (2) is 2-28%.
Furthermore, in the above technical solution, the reaction temperature in the step (2) is preferably 90° C., and the reaction time is preferably 24 h.
Furthermore, in the above technical solution, the aging temperature in the step (3) is preferably 80° C., and the aging time is preferably 24 h.
Furthermore, in the above technical solution, the size of the solid product obtained by grinding and sieving in the step (3) is preferably 200-300 mesh.
A fourth object of the present invention is to provide an ion-imprinted polymer obtained by the above method for synthesizing the ion-imprinted polymer (IIP).
Further, in the above technical solution, the ion-imprinted polymer is preferably any one of a copper ion-imprinted polymer (Cu2+-IIP) or a nickel ion-imprinted polymer (Ni2+-IIP).
The application of the ion-imprinted polymer in the selective adsorption of metal ions described above in the present invention has high selective adsorption capacity for metal ions (for example, Cu2+, Ni2+, etc.) in water.
The usage method of theion-imprinted polymer described above in the present invention is specifically as follows:
the solution to be tested (metal ion solution) is adjusted to pH of 2-12, then the ion-imprinted polymer is added.
The present invention will be further described in detail below in conjunction with embodiments. These embodiments will be implemented on the premise of the technology of the present invention. Presently, detailed embodiments and specific operation process are given to illustrate the inventiveness of the present invention, but the protection scope of the present invention is not limited to the following embodiments.
According to the information contained herein, various changes in the precise description of the present invention will readily become apparent to those skilled in the art without departing from the spirit and scope defined in the appended claims. It should be understood that the scope of the present invention is not limited to the processes, properties or components defined, since these embodiments and other descriptions are only intended to illustrate certain aspects of the present invention. In fact, it is apparent for those skilled in the art or related arts to make changes to the embodiments of the present invention that fall within the protection scope as defined by the appended claims.
In order to better understand but not to limit the protection scope of the present invention, all figures representing dosage, percentage, and other numerical values used in this application should be understood as being modified by the term “about” in all cases. Accordingly, unless expressly indicated otherwise, the numerical parameters set forth in the specification and appended claims are approximations that may vary depending upon the desired properties sought to be obtained. At a minimum, each numerical parameter should be construed to be available in light of the reported significant digits and by applying conventional rounding methods.
The principle of the present invention is as follows:
In the present invention, through the Michael addition reaction of N-aminoethyl-γ-aminopropyltrimethoxysilane and acrylic esters, an ester group is bonded to the amino group and imine group of N-aminoethyl-γ-aminopropyltrimethoxysilane, and the ester group is hydrolyzed with a trifluoroacetic acid solution to obtain a multidentate functional monomer with a carboxyl group at the end. In the functional monomer, 2 nitrogen atoms and 3 oxygen atoms can coordinate with metal ions. When it is dissolved in methanol and then the template metal ion (copper ion or nickel ion, etc.) aqueous solution is added, the multidentate functional monomercan form a functional monomer-template metal ion complex with it through reversible chelation. Then the cross-linking agent tetraalkoxysilane (for example, tetraethoxysilane, TEOS) is added for bulk polymerization under the catalysis of ammonia water, and after aging, a solid product is obtained. The product is ground and sieved to obtain polymer particles with an appropriate particle size, and then washed with hydrochloric acid to remove template metal ions therein, finally washed to a neutral state, and dried to obtain the ion-imprinted polymer.
The multidentate functional monomer provided the present invention contains five coordination atoms (two nitrogen atoms and three oxygen atoms) and can form a stable complex with the metal ions. Therefore, when the imprinted material is synthesized, the functional monomer is not necessarily excessive, and the molar ratio of the functional monomer to the metal ions is just 1: 1. Because there is no excessive functional monomer in the obtained imprinted material, it is inevitably beneficial to eliminating nonspecific adsorption induced by the functional monomer, which contributes to acquiring high-selectivity ion imprinted material.
In the ionic imprinting technology, the combining stability of the ligand (functional monomer) and the template ions is not only the key to form specific cavities, but also is of great significance on re-identification capability of the imprinted material. Compared with a conventional coordination compound, AAPTS-COOH features better coordination capability, thereby generating a better imprinted effect. The complex formed by the multidentate ligand and the metal ions usually contains more than one annular structure, which is also called a chelate. The five-membered and six-membered rings are relatively stable annular structures. The six-membered ring is more favorable to reduce the ring strain by way of single bond rotation, and thus, the six-membered ring is more stable than the fix-membered ring. The N atoms of AAPTS-COOH are connected to three propionyloxy and can form three six-membered rings and one five-membered ring with the metal ions, with better stability, and a better imprinted effect can be generated.
In the following Examples 1 to 3, N-aminoethyl-γ-aminopropyltrimethoxysilane, aliased as N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (CAS number: 1760-24-3) is used.
The synthesis route of a N,O-type multidentate functional monomer (AAPTS-COOH) of this example is shown in
(a) Synthesis of AAPTS-tBu:
Add 80 mL of methanol, 8.9 g of N-aminoethyl-γ-aminopropyltrimethoxysilane (AAPTS, 0.04 mol) and 25.6 g of tert-butyl acrylate (0.2 mol) to a three-necked flask equipped with a nitrogen tube and a stirring device sequentially, stir and mix well, introduce N2into the three-necked flask for 10 minutes to remove oxygen in the reaction system, and then heat the reaction system to 50° C. and react for 24 hours at a constant temperature. Carry out rotary evaporation to remove the excess reactant and solvent to obtain the Michael addition product AAPTS-tBu, and dry the product at 60° C. for 24 h for future use.
(b) Synthesis of AAPTS-COOH: add 5 g of the Michael addition product AAPTS-tBu obtained in the step (a) to 20 mL of trifluoroacetic acid aqueous solution (95%) and hydrolyze at room temperature for 1 hour; after filtration, carry out rotary evaporation at 40° C. under reduced pressure to obtain a viscous liquid; then add 50 mL of cold diethyl ether, filter to obtain the precipitate and then wash it with cold diethyl ether to obtain the N,O-type multidentate functional monomer AAPTS-COOH. Seal and refrigerate the product for future use.
The N,O-type multidentate functional monomer AAPTS-COOH is a siloxane monomer with three carboxylic acid groups and two N atoms, the structural formula being as follows:
The N,O-type multidentate functional monomer can form six-membered rings and five-membered rings simultaneously with metal ions.
The AAPTS-tBu obtained in the step (a) and the N,O-type multidentate functional monomer AAPTS-COOH obtained in the step (b) of this example are subjected to NMR test respectively. The NMR characterization results are as follows:
In addition, the applicant also conducts infrared tests on the raw material N-aminoethyl-γ-aminopropyltrimethoxysilane AAPTS, AAPTS-tBu obtained in the step (a) and N,O-type multidentate functional monomer AAPTS-COOH obtained in the step (b) of this example respectively. The infrared spectra (FT-IR) are shown in
Based on the above NMR characterization data and infrared characterization data, it can be concluded that the product prepared in this example is the target product N,O-type multidentate functional monomer AAPTS-COOH.
This example provides a method for preparing a N,O-type multidentate functional monomer(AAPTS-COOH), specifically comprising the following steps:
(a)Add 80 mL of methanol, 8.9 g of N-aminoethyl-γ-aminopropyltrimethoxysilane (AAPTS, 0.04 mol) and 15.5 g of methyl acrylate (0.18 mol) to a three-necked flask equipped with a nitrogen tube and a stirring device sequentially, stir and mix well, introduce N2into the three-necked flask for 10 minutes to remove oxygen in the reaction system, and then heat the reaction system to 50° C. and react for 24 hours at a constant temperature. Carry out rotary evaporation to remove the excess reactant and solvent to obtain the Michael addition product AAPTS-tBu, and dry the product at 60° C. for 24 h for future use.
(b) Synthesis of AAPTS-COOH: add 4 g of the Michael addition productobtained in the step (a) to 25 mL of trifluoroacetic acid aqueous solution (95%) and hydrolyze at room temperature for 1 hour; after filtration, carry out rotary evaporation at 40° C. under reduced pressure to obtain a viscous liquid; then add 50 mL of cold diethyl ether, filter to obtain the precipitate and then wash it with cold diethyl ether to obtain the N,O-type multidentate functional monomer AAPTS-COOH. Seal and refrigerate the product for future use.
The N,O-type multidentate functional monomer AAPTS-COOH is a siloxane monomer with three carboxylic acid groups and two N atoms, the structural formula being as follows:
The N,O-type multidentate functional monomer can form six-membered rings and five-membered rings simultaneously with metal ions.
This example provides a method for preparing a N,O-type multidentate functional monomer(AAPTS-COOH), specifically comprising the following steps:
(a)Add 80 mL of methanol, 8.9 g of N-aminoethyl-γ-aminopropyltrimethoxysilane (AAPTS, 0.04 mol) and 20.0 g of ethyl acrylate (0.2 mol) to a three-necked flask equipped with a nitrogen tube and a stirring device sequentially, stir and mix well, introduce N2 into the three-necked flask for 10 minutes to remove oxygen in the reaction system, and then heat the reaction system to 50° C. and react for 24 hours at a constant temperature. Carry out rotary evaporation to remove the excess reactant and solvent to obtain the Michael addition product, and dry the product at 60° C. for 24 h for future use.
(b) Synthesis of AAPTS-COOH: add 6 g of the Michael addition product obtained in the step (a) to 25 mL of trifluoroacetic acid aqueous solution (95%) and hydrolyze at room temperature for 1 hour; after filtration, carry out rotary evaporation at 40° C. under reduced pressure to obtain a viscous liquid; then add 60 mL of cold diethyl ether, filter to obtain the precipitate and then wash it with cold diethyl ether to obtain the N,O-type multidentate functional monomer AAPTS-COOH. Seal and refrigerate the product for future use.
The N,O-type multidentate functional monomer AAPTS-COOH is a siloxane monomer with three carboxylic acid groups and two N atoms, the structural formula being as follows:
The N,O-type multidentate functional monomer can form six-membered rings and five-membered rings simultaneously with metal ions.
This application example provides a method for synthesizing a copper ion-imprinted polymer (Cu2+-IIP), comprising the following steps:
Dissolve 2.62 g (0.006 mol) of N,O-type multidentate functional monomer AAPTS-COOH prepared in Example 1 in 6 mL of methanolcompletely, add 12.5 mL of Cu2+aqueous solution (32 g/L, pH=5) and stir for 10 minutes.Then add 12.5 g oftetraethoxysilane (TEOS, 0.06 mol) and 1.5 mL of ammonia water solution (NH3·H2O, 4.2%), mix well, heat to reflux, and react at constant temperature for 24 hours to obtain a gel-like product. Put the product in an oven at 80° C. for aging for 24 hours, then take out, grind and sieve to obtain particles of 200-300 mesh. Then wash with 1 mol/L hydrochloric acid repeatedly until no Cu2+can be detected in the washing solution (detected by flame atomic absorption spectrometry), and then wash with water until neutral, and perform vacuum drying at 60° C. for 24 h to obtain the copper ion-imprinted polymer (Cu2+-IIP).
The Cu2+-IIP prepared in this application example is characterized by scanning electron microscope and infrared spectrometer, and the results are shown in
The Zeta potential test results of the ion-imprinted polymer Cu2+-IIP prepared in this application example under different pH environments are shown in
Cu2+-IIP in this application example is synthesized by the sol-gel method using AAPTS-COOH as a functional monomer and TEOS as a cross-linking agent. Therefore, Cu2+-IIP is actually a type of silica gel particles containing AAPTS-COOH. Its Zeta potential is definitely related to the properties of silicon hydroxyl and AAPTS-COOH. It is believed that, silica gel is generally partially negatively charged except for electrically neutral in a strongly acidic environment. AAPTS-COOH contains three carboxyl groups and 2 amine groups, among which the acidity of the carboxyl group is weak (the pkais about 4.7); therefore, when the pH of the solution rises from 2 to 7, the carboxyl group is definitely changed from a protonated state (electrically neutral) to a deprotonated state (negatively charged); while the amine group is relatively strongly basic, so it always exists in a protonated state (positively charged) in the range of pH=2-7. As shown in
The synthesis method of a nickel ion-imprinted polymer (Ni2+-IIP) in this application example is basically the same as that of Cu2+-IIP, except that the template metal ion solution in Application Example 1 is changed to Ni2+ solution (pH=7) from Cu2+ solution (pH=5). The steps are as follows:
Dissolve 2.62 g (0.006 mol) of N,O-type multidentate functional monomer AAPTS-COOH prepared in Example 1, 2 or 3 in 6 mL of methanolcompletely, add 12.1 mL of Ni2+aqueous solution (29 g/L, pH=7) and stir for 10 minutes.Then add 12.5 g oftetraethoxysilane (TEOS, 0.06 mol) and 1.5 mL of ammonia water solution (NH3·H2O, 4.2%), mix well, heat to reflux, and react at constant temperature for 24 hours to obtain a gel-like product. Put the product in an oven at 80° C. for aging for 24 hours, then take out, grind and sieve to obtain particles of 200-300 mesh. Then wash with 1 mol/L hydrochloric acid repeatedly until no Ni2+can be detected in the washing solution (detected by flame atomic absorption spectrometry), and then wash with water until neutral, and perform vacuum drying at 60° C. for 24 h to obtain the nickelion-imprinted polymer (Ni2+-IIP).
In order to measure the selectivity of Cu2+-IIP, a non-imprinted polymer called Cu2+-NIP is synthesized in this comparative application example. Its synthesis steps are basically the same as those of Cu2+-IIP, but no Cu2+ is added during the synthesis. The specific steps are as follows:
Dissolve 2.62 g (0.006 mol) of N,O-type multidentate functional monomer AAPTS-COOH prepared in Example 1 to 6 mL of methanol completely, then add 12.5 g of tetraethoxysilane (TEOS, 0.06 mol) and 1.5 mL of ammonia water solution (NH3·H2O, 4.2%),mix well, heat to reflux, and react at constant temperature for 24 hours to obtain a gel-like product. Put the product in an oven at 80° C. for aging for 24 hours, then take out, grind and sieve to obtain particles of 200-300 mesh. Then wash with 1 mol/L hydrochloric acid repeatedly for 3 times, and then wash with water until neutral, and perform vacuum drying at 60° C. for 24 h to obtain the non-imprinted polymer (Cu2+-NIP).
In order to measure the selectivity ofNi2+-IIP, a non-imprinted polymer called Ni2+-NIP is synthesized in the present invention. Its synthesis steps are basically the same as those of Ni2+-IIP, but no template Ni2+solution is added during the synthesis. The specific steps are the same as those for the synthesis of Cu2+-NIP.
The synthesis method in this application example is basically the same as that of copper ion-imprinted polymer (Cu2+-IIP) in the Application Example 1, and the only difference is that the N,O-type multidentate functional monomer AAPTS-COOH in this application example is the N,O-type multidentate functional monomer prepared in Example 2.
The synthesis method in this application example is basically the same as that of copper ion-imprinted polymer (Cu2+-IIP) in the Application Example 1, and the only difference is that the N,O-type multidentate functional monomer AAPTS-COOH in this application example is the N,O-type multidentate functional monomer prepared in Example 3.
In the present invention, the selectivity of copper ion-imprinted polymer (Cu2+-IIP) prepared in the Application Example 1 and non-imprinted material (Cu2+-NIP) prepared in Comparative Application Example 1 to Cu2+ is tested respectively according to the following method. The specific method is as follows.
Add 0.01 g of Cu2+-IIP and Cu2+-NIP to 5 mL of a mixed solution of Cu2+ and several other metal ions (reference ions) (Cu2+/ Zn2+, Cu2+/ Pb2+, Cu2+/ Ni2+or Cu2+/ Co2+), respectively; the concentrations of metal ions are all 20 mg/L in the mixed solution, and the pH of the mixed solution is 5. After shaking at 40° C. for 24 h, the concentrations of metal ions in the solution are measured by FAAS respectively, and then the adsorption capacity (Q, mg/g), partition coefficient (KD, L/g), selectivity coefficient (k) and imprinting factor (IF) are calculated. The results are shown in Table 1. The comparison between the selectivity coefficient (k) of Cu2+-IIP synthesized by the present invention and those in the literatures is shown in Table 2.
The calculation formulae used in the present invention are as follows:
In the formula, C0 (mg/L) and Ce (mg/L) represent the initial concentration of ions in the solution and the concentration when reaching the extraction equilibrium, respectively;
V (L) represents the volume of the solution; W (g) represents the mass of the adsorbent; KD(mL/g) represents the partition coefficientof ions in the adsorbent and solution; kIIP and kNIP represent the selectivity coefficients of ion-imprinted polymer (IIP) and non-imprinted polymer (NIP).
In order to confirm the universality of the synthesis method of Cu2+-IIP, the present invention synthesized Ni2+-IIP by a similar method (see Application Example 2), and measured its selectivity to Ni2+. The specific measurement method is as follows.
Add 0.01 g of Ni2+-IIP and Ni2+-NIP to 5 mL of Ni2+/Co2+ mixed solution respectively, the concentration of metal ions in the mixed solution is 10 mg/L, and the pH of the mixed solution is 7. After shaking at 40° C. for 24 h, the concentration of metal ions in the solution was measured by FAAS, and then the selectivity coefficient (k) was calculated and compared with the literature value. The results are shown in Table 3.
In addition, the selectivity towards Cu2+of copper ion-imprinted polymers (Cu2+-IIP) obtained in Application Example 3 and Application Example 4 of the present invention also have been measured, and the results demonstrate that the two Cu2+-IIPs offer almost the same selective adsorption capability as the copper ion-imprinted polymer obtained in Application Example 1. Thus, the copper ion-imprinted polymer synthesized by AAPTS-COOH as a functional monomer in the present invention has high selective adsorption capacity for copper ions and nickel ions. Furthermore, the Cu2+-IIP synthesis method based on AAPTS-COOH of the present invention has good universality, and is expected to be used for the imprinting of other metal ions, simultaneous imprinting of multiple metal ions and the imprinting of organic molecules.
Compared with the prior art, the present invention has the followingbeneficial effects:
The present invention provides an N,O-type multidentate functional monomer (AAPTS-COOH), and the copper ion-imprinted polymer (Cu2+-IIP) synthesized by using AAPTS-COOH as a functional monomer has significantly better selectivity to Cu2+ than those reported in the existing literatures. Based on the good universality of the Cu2+-IIP synthesis method of AAPTS-COOH, when the template metal ionCu2+ is replaced by Ni2+, the ratio of the functional monomer, the template metal ion and the cross-linking agent used in the synthesis ofCu2+-IIP can be directly used in the synthesis of Ni2+-IIP. This characteristic is not only beneficial to simplify the synthesis method of ion-imprinted polymer, but also is expected to be used for simultaneous imprinting of multiple metal ions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202010055553.2 | Jan 2020 | CN | national |
This application is a continuation of International Application No. PCT/CN2020/140732 with a filling date of Dec. 29, 2020, designating the United states, now pending, and further claims to the benefit of priority from Chinese Application No. 202010055553.2 with a filing date of Jan. 17, 2020. The content of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2020/140732 | Dec 2020 | WO |
| Child | 18353848 | US |
