CN113174022B - Filter material and application thereof in preparation of high-purity guanidine carbonate - Google Patents
Filter material and application thereof in preparation of high-purity guanidine carbonate Download PDFInfo
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- CN113174022B CN113174022B CN202110489085.4A CN202110489085A CN113174022B CN 113174022 B CN113174022 B CN 113174022B CN 202110489085 A CN202110489085 A CN 202110489085A CN 113174022 B CN113174022 B CN 113174022B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F292/00—Macromolecular compounds obtained by polymerising monomers on to inorganic materials
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/14—Other self-supporting filtering material ; Other filtering material
- B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
- B01J20/26—Synthetic macromolecular compounds
- B01J20/268—Polymers created by use of a template, e.g. molecularly imprinted polymers
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
- B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
- B01J20/28009—Magnetic properties
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/305—Addition of material, later completely removed, e.g. as result of heat treatment, leaching or washing, e.g. for forming pores
- B01J20/3057—Use of a templating or imprinting material ; filling pores of a substrate or matrix followed by the removal of the substrate or matrix
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C277/00—Preparation of guanidine or its derivatives, i.e. compounds containing the group, the singly-bound nitrogen atoms not being part of nitro or nitroso groups
- C07C277/06—Purification or separation of guanidine
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/0666—Polycondensates containing five-membered rings, condensed with other rings, with nitrogen atoms as the only ring hetero atoms
- C08G73/0672—Polycondensates containing five-membered rings, condensed with other rings, with nitrogen atoms as the only ring hetero atoms with only one nitrogen atom in the ring
Abstract
The invention discloses a filtering material and application thereof in preparation of high-purity guanidine carbonate, belongs to the technical field of filtering materials, and particularly relates to a magnetic molecularly imprinted polymer and a preparation method thereof, wherein the preparation method comprises the following steps: the magnetic molecularly imprinted polymer takes a compound containing modified multi-walled carbon nanotubes as a composite carrier, and polyacrylic acid is grafted on the modified multi-walled carbon nanotubes; the magnetic molecularly imprinted polymer is prepared by taking dopamine as a functional monomer and melamine as a template molecule. The magnetic molecularly imprinted polymer prepared by the invention has good adsorption performance on melamine, and the adsorption capacity is more than 25mg/g after 1 hour of adsorption; the anti-interference performance is good in melamine adsorption, and the adsorption quantity is more than 23mg/g under the interference of cyanuric acid and diamine oxazine; after the desorption of the activating agent, the repeated adsorption performance is good, and the repetition times is more than 24 when the adsorption performance is reduced by 90 percent.
Description
Technical Field
The invention belongs to the technical field of filter materials, and particularly relates to a filter material and application thereof in preparation of high-purity guanidine carbonate.
Background
Guanidine carbonate is an organic fine chemical product with wide application, and is mainly used for synthesizing flame retardants, flocculating agents, foaming agents, sulfonamides and the like. Guanidine carbonate is also used as a synergist for synthetic detergents and as a raw material for high-grade cosmetics. The production of guanidine carbonate in China mainly adopts the method that dicyandiamide and ammonium chloride are melted to generate guanidine hydrochloride, then free guanidine is generated under the action of alkali, guanidine reacts with carbon dioxide to generate guanidine carbonate, impurities such as melamine, dimer and polymer of melamine are easily generated in the process of high-temperature melting in the route, and Cl exists in the system-、Na+The purification is difficult to completely remove, and even the guanidine carbonate with the purity of more than 99 percent still has ash content of 0.2 percentTherefore, it is difficult to obtain high purity guanidine carbonate.
Disclosure of Invention
The invention aims to provide a magnetic molecularly imprinted polymer with good melamine adsorption performance, strong anti-interference capability and good repeatability.
The technical scheme adopted by the invention for realizing the purpose is as follows:
a magnetic molecularly imprinted polymer comprising:
the magnetic molecularly imprinted polymer takes a compound containing modified multi-walled carbon nanotubes as a composite carrier, and polyacrylic acid is grafted on the modified multi-walled carbon nanotubes;
the magnetic molecularly imprinted polymer is prepared by taking dopamine as a functional monomer and melamine as a template molecule.
Preferably, the composite carrier is a magnetic composite carrier; the magnetic composite carrier contains ferroferric oxide.
Preferably, the magnetic carrier contains modified halloysite nanotubes; the modified halloysite nanotube is modified by a modifying coupling agent, and the modifying coupling agent is prepared from N-phenyl-P-phenylenediamine and a silane coupling agent. The modified multi-walled carbon nanotube and the modified halloysite nanotube form a compound, magnetic iron tetroxide is synthesized in situ to form a magnetic compound carrier in the compound, and after the magnetic molecularly imprinted polymer is finally prepared, the modified multi-walled carbon nanotube and the modified halloysite nanotube enable the stability of the magnetic molecularly imprinted polymer to be good and the shape to be uniform, enable identification points in the magnetic molecularly imprinted polymer to be more easily accessible, and enable the magnetic molecularly imprinted polymer to have strong adsorption capacity on melamine, strong anti-interference performance and good repeated performance of elution and re-adsorption.
Preferably, in the preparation of the modified multi-walled carbon nanotube, the multi-walled carbon nanotube is subjected to ultrasonic treatment in an acid solution for 0.5 to 3 hours, separated, washed to be neutral, dried, added into toluene and subjected to ultrasonic treatment for 0.5 to 3 hours, acrylic acid is added at the temperature of 50 to 70 ℃, AIBN is added, reaction is carried out for 4 to 12 hours, and the modified multi-walled carbon nanotube is obtained through suction filtration separation, deionized water washing and drying.
More preferably, the acid solution is a mixed solution of sulfuric acid and nitric acid, and the mixing ratio of sulfuric acid to nitric acid in the acid solution is 1: 0.1-0.5.
More preferably, the amount of multi-walled carbon nanotubes used is 0.1 to 0.5 wt% of the acidic solution.
More preferably, the addition amount of the multi-walled carbon nanotubes after the acid treatment is 0.05 to 0.4 wt% of toluene.
More preferably, the amount of acrylic acid added is 0.5 to 5 wt% of toluene.
More preferably, AIBN is added in an amount of 0.5 to 2% by weight based on acrylic acid.
Preferably, the modification of the halloysite nanotubes comprises: preparing a modified coupling agent, purifying the halloysite nanotube and preparing the modified halloysite nanotube.
More preferably, in the preparation of the modified coupling agent, N-phenyl-P-phenylenediamine and silane coupling agent KH-560 are mixed, heated and refluxed at the temperature of 130-150 ℃ and continuously stirred for reaction for 2-6h, after the reaction is finished, ethanol solution is added for hydrolysis, and ultrasonic treatment is carried out for 20-60min, so as to obtain the modified coupling agent.
Still more preferably, the molar ratio of N-phenyl-p-phenylene diamine to silane coupling agent KH-550 is 1: mixing at a ratio of 0.3-3.
Still more preferably, the mass fraction of ethanol in the ethanol solution is 85-95 wt%.
More preferably, in the purification of the halloysite nanotube, halloysite nanotube powder is added into ethanol, stirred for 10-30min, filtered and dried, added into a sodium hexametaphosphate solution, stirred and dispersed, centrifugally separated and dried to obtain the purified halloysite nanotube.
Still more preferably, the halloysite nanotube powder is added in an amount of 10-30 wt% of ethanol.
Still more preferably, the mass fraction of sodium hexametaphosphate in the sodium hexametaphosphate solution is 0.5 to 3%.
Still more preferably, the amount of the halloysite nanotube powder added after ethanol treatment is 10 to 30 wt% of the sodium hexametaphosphate solution.
More preferably, in the preparation of the modified halloysite nanotube, the purified halloysite nanotube is added into an ethanol solution, ultrasonic treatment is carried out for 20-60min at the temperature of 20-40 ℃, a modified coupling agent is added, stirring reaction is carried out for 2-6h at the temperature of 70-90 ℃, and after the reaction is finished, filtration, ethanol washing and drying are carried out to obtain the modified halloysite nanotube.
Still more preferably, the mass fraction of ethanol in the ethanol solution is 85-95 wt%.
Still more preferably, the purified halloysite nanotubes are added in an amount of 10-20 wt% of the ethanol solution.
Still more preferably, the modified coupling agent is added in an amount of 5 to 40 wt% based on the ethanol solution.
The invention discloses application of a magnetic molecularly imprinted polymer in preparation of high-purity guanidine carbonate.
The invention aims to provide a preparation method of a magnetic molecularly imprinted polymer with good melamine adsorption performance, strong anti-interference capability and good repeatability.
The technical scheme adopted by the invention for realizing the purpose is as follows:
a preparation method of a magnetic molecularly imprinted polymer comprises the following steps:
preparing a magnetic composite carrier from a compound containing the modified multi-walled carbon nano-tube in a solution containing an iron element through a synthesis process;
the magnetic molecularly imprinted polymer is prepared by the preparation process of the magnetic composite carrier in a solution containing melamine and dopamine.
Preferably, the iron element is ferric ion.
Preferably, the solution containing iron element contains sodium citrate and hydrazine hydrate.
Preferably, the solution in the solution containing melamine and dopamine is a phosphate buffer.
Preferably, in the preparation of the magnetic molecularly imprinted polymer, adding the modified multi-walled carbon nanotube and the modified halloysite nanotube into deionized water, performing ultrasonic treatment at the temperature of 20-40 ℃ for 30-180min, adding ferric chloride, adding sodium citrate, stirring for 10-30min, adding hydrazine hydrate, reacting for 6-18h in a high-temperature reaction kettle at the temperature of 160-180 ℃, separating a magnet, and washing for several times by using ethanol and deionized water in sequence to obtain the magnetic composite carrier; adding the magnetic composite carrier into phosphate buffer solution with pH of 7-8, stirring for 1-4h, performing ultrasonic treatment for 10-30min, adding melamine and dopamine, stirring and reacting at 20-40 ℃ for 8-24h, removing upper liquid, performing magnetic separation, washing with ethanol and deionized water for several times in sequence, and drying to obtain the magnetic molecularly imprinted polymer.
More preferably, the modified multi-walled carbon nanotubes are added in an amount of 0.01 to 0.05 wt% based on the weight of the deionized water.
More preferably, the modified halloysite nanotubes are added in an amount of 0.005-0.03 wt% of deionized water.
More preferably, ferric chloride is added in an amount of 0.8 to 2.5 wt% of the deionized water.
More preferably, the sodium citrate is added in an amount of 1.2-3.6 wt% of the deionized water.
More preferably, the hydrazine hydrate is added in an amount of 1-4 wt% based on the deionized water.
More preferably, the amount of the magnetic composite carrier added is 0.1 to 1 wt% of the phosphate buffer solution.
More preferably, melamine is added in an amount of 0.1-0.6 wt% of the phosphate buffer solution.
More preferably, dopamine is added in an amount of 0.1-0.9 wt% of the phosphate buffer solution.
The invention discloses a filter material, comprising: a filter screen containing the magnetic molecularly imprinted polymer.
The invention discloses a preparation method of high-purity guanidine carbonate, which comprises the following steps: a filter cartridge using the filter material.
The magnetic molecularly imprinted polymer is prepared by taking a magnetic compound containing the modified multi-walled carbon nanotube, the modified halloysite nanotube and ferroferric oxide as a carrier, dopamine as a functional monomer and melamine as a template molecule, so that the magnetic molecularly imprinted polymer has the following beneficial effects: the adsorption performance to melamine is good, and the adsorption capacity is more than 25mg/g after 1 hour of adsorption; the anti-interference performance is good in melamine adsorption, and the adsorption quantity is more than 23mg/g under the interference of cyanuric acid and diamine oxazine; after the desorption of the activating agent, the repeated adsorption performance is good, and the repetition times is more than 24 when the adsorption performance is reduced by 90 percent. Therefore, the magnetic molecularly imprinted polymer has good melamine adsorption performance, strong anti-interference capability and good repeatability, and the preparation method thereof.
Drawings
FIG. 1 is a diagram of the adsorption of a magnetic molecularly imprinted polymer to melamine;
FIG. 2 is a drawing of the anti-interference magnetic molecularly imprinted polymer;
FIG. 3 is a graph of the number of times of repeated adsorption of magnetic molecularly imprinted polymer to melamine.
Detailed Description
The technical solution of the present invention is further described in detail below with reference to the following detailed description and the accompanying drawings:
example 1:
a preparation method of a magnetic molecularly imprinted polymer,
modified multi-walled carbon nanotubes: and (2) carrying out ultrasonic treatment on the multi-walled carbon nano tube in an acid solution for 2h, separating, washing to be neutral, drying, adding the multi-walled carbon nano tube into toluene, carrying out ultrasonic treatment for 1h, adding acrylic acid at the temperature of 60 ℃, adding AIBN, reacting for 9h, carrying out suction filtration separation, washing with deionized water, and drying to obtain the modified multi-walled carbon nano tube. The acid solution is a mixed solution of sulfuric acid and nitric acid, and the mixing ratio of the sulfuric acid to the nitric acid in the acid solution is 1: 0.3; the using amount of the multi-wall carbon nano tube is 0.3 wt% of the acid solution; the addition amount of the multi-wall carbon nano-tube after the acid solution treatment is 0.2 wt% of toluene; the addition amount of acrylic acid was 1.5 wt% of toluene; AIBN was added in an amount of 1% by weight based on the weight of acrylic acid.
Preparation of modified coupling agent: mixing N-phenyl-P-phenylene diamine and a silane coupling agent KH-560, heating and refluxing at the temperature of 140 ℃, continuously stirring for reaction for 4 hours, adding an ethanol solution for hydrolysis after the reaction is finished, and performing ultrasonic treatment for 30min to obtain the modified coupling agent. The mol ratio of the N-phenyl-p-phenylene diamine to the silane coupling agent KH-550 is 1: 1, and the mass fraction of ethanol in the ethanol solution is 95 wt%.
Purifying the halloysite nanotubes: adding halloysite nanotube powder into ethanol, stirring for 20min, filtering, drying, adding into sodium hexametaphosphate solution, stirring, dispersing, centrifuging, and drying to obtain purified halloysite nanotube. The addition amount of the halloysite nanotube powder is 20 wt% of ethanol, the mass fraction of sodium hexametaphosphate in the sodium hexametaphosphate solution is 1.5%, and the addition amount of the halloysite nanotube powder after ethanol treatment is 20 wt% of the sodium hexametaphosphate solution.
Modified halloysite nanotubes: adding the purified halloysite nanotube into an ethanol solution, performing ultrasonic treatment at 30 ℃ for 40min, adding a modified coupling agent, stirring and reacting at 80 ℃ for 4h, filtering after the reaction is finished, washing with ethanol, and drying to obtain the modified halloysite nanotube. The mass fraction of ethanol in the ethanol solution is 95 wt%, the addition amount of the purified halloysite nanotube is 20 wt% of the ethanol solution, and the addition amount of the modified coupling agent is 15 wt% of the ethanol solution.
Preparation of magnetic molecularly imprinted polymer: adding a modified multi-walled carbon nanotube and a modified halloysite nanotube into deionized water, performing ultrasonic treatment at the temperature of 30 ℃ for 60min, adding ferric chloride and sodium citrate, stirring for 20min, adding hydrazine hydrate, reacting in a high-temperature reaction kettle at the temperature of 170 ℃ for 12h, separating a magnet, and washing with ethanol and deionized water for several times in sequence to obtain a magnetic composite carrier; adding the magnetic composite carrier into phosphate buffer solution with pH of 8, stirring for 2h, then carrying out ultrasonic treatment for 20min, adding melamine and dopamine, stirring and reacting at the temperature of 30 ℃ for 12h, removing upper-layer liquid, carrying out magnet separation, washing for several times by using ethanol and deionized water in sequence, and drying to obtain the magnetic molecularly imprinted polymer. The addition amount of the modified multiwall carbon nanotube is 0.04 wt% of deionized water, the addition amount of the modified halloysite nanotube is 0.02 wt% of deionized water, the addition amount of ferric chloride is 1.8 wt% of deionized water, the addition amount of sodium citrate is 2.6 wt% of deionized water, and the addition amount of hydrazine hydrate is 3 wt% of deionized water; the addition amount of the magnetic composite carrier is 0.6 wt% of the phosphate buffer solution, the addition amount of the melamine is 0.36 wt% of the phosphate buffer solution, and the addition amount of the dopamine is 0.49 wt% of the phosphate buffer solution.
Example 2:
compared with the embodiment 1, the invention is different only in that the addition amount of acrylic acid in the preparation of the modified multi-wall carbon nanotube is 2.8 wt% of toluene, and the addition amount of the modified coupling agent in the preparation of the modified halloysite nanotube is 23 wt% of ethanol solution.
Example 3:
compared with the embodiment 1, the invention is different only in that the addition amount of acrylic acid is 4.2 wt% of toluene in the preparation of the modified multi-wall carbon nanotube, and the addition amount of the modified coupling agent is 34 wt% of ethanol solution in the preparation of the modified halloysite nanotube.
Example 4:
a preparation method of a magnetic molecularly imprinted polymer,
further, the addition of N, N-diacetyl o-phenylenediamine in the preparation of the modified coupling agent can further improve the adsorption performance of the magnetic molecularly imprinted polymer on melamine. The addition amount of the N, N-diacetyl o-phenylenediamine is 6-24 wt% of the N-phenyl-p-phenylenediamine.
Modified multi-walled carbon nanotubes: and (2) carrying out ultrasonic treatment on the multi-walled carbon nano tube in an acid solution for 2h, separating, washing to be neutral, drying, adding the multi-walled carbon nano tube into toluene, carrying out ultrasonic treatment for 1h, adding acrylic acid at the temperature of 60 ℃, adding AIBN, reacting for 9h, carrying out suction filtration separation, washing with deionized water, and drying to obtain the modified multi-walled carbon nano tube. The acid solution is a mixed solution of sulfuric acid and nitric acid, and the mixing ratio of the sulfuric acid to the nitric acid in the acid solution is 1: 0.3; the using amount of the multi-wall carbon nano tube is 0.3 wt% of the acid solution; the addition amount of the multi-wall carbon nano-tube after the acid solution treatment is 0.2 wt% of toluene; the addition amount of acrylic acid was 4.2 wt% of toluene; AIBN was added in an amount of 1% by weight based on the weight of acrylic acid.
Preparation of modified coupling agent: mixing N-phenyl-P-phenylenediamine, N-diacetyl o-phenylenediamine and a silane coupling agent KH-560, heating and refluxing at the temperature of 140 ℃, continuously stirring for reacting for 4 hours, adding an ethanol solution for hydrolysis after the reaction is finished, and performing ultrasonic treatment for 30min to obtain the modified coupling agent. The mol ratio of the N-phenyl-p-phenylene diamine to the silane coupling agent KH-550 is 1: 1, the addition amount of the N, N-diacetyl o-phenylenediamine is 12 wt% of the N-phenyl-p-phenylenediamine, and the mass fraction of ethanol in the ethanol solution is 95 wt%.
Purifying the halloysite nanotubes: adding halloysite nanotube powder into ethanol, stirring for 20min, filtering, drying, adding into sodium hexametaphosphate solution, stirring, dispersing, centrifuging, and drying to obtain purified halloysite nanotube. The addition amount of the halloysite nanotube powder is 20 wt% of ethanol, the mass fraction of sodium hexametaphosphate in the sodium hexametaphosphate solution is 1.5%, and the addition amount of the halloysite nanotube powder after ethanol treatment is 20 wt% of the sodium hexametaphosphate solution.
Modified halloysite nanotubes: adding the purified halloysite nanotube into an ethanol solution, performing ultrasonic treatment at 30 ℃ for 40min, adding a modified coupling agent, stirring and reacting at 80 ℃ for 4h, filtering after the reaction is finished, washing with ethanol, and drying to obtain the modified halloysite nanotube. The mass fraction of ethanol in the ethanol solution is 95 wt%, the addition amount of the purified halloysite nanotube is 20 wt% of the ethanol solution, and the addition amount of the modified coupling agent is 34 wt% of the ethanol solution.
Preparation of magnetic molecularly imprinted polymer: adding a modified multi-walled carbon nanotube and a modified halloysite nanotube into deionized water, performing ultrasonic treatment at the temperature of 30 ℃ for 60min, adding ferric chloride and sodium citrate, stirring for 20min, adding hydrazine hydrate, reacting in a high-temperature reaction kettle at the temperature of 170 ℃ for 12h, separating a magnet, and washing with ethanol and deionized water for several times in sequence to obtain a magnetic composite carrier; adding the magnetic composite carrier into phosphate buffer solution with pH of 8, stirring for 2h, then carrying out ultrasonic treatment for 20min, adding melamine and dopamine, stirring and reacting at the temperature of 30 ℃ for 12h, removing upper-layer liquid, carrying out magnet separation, washing for several times by using ethanol and deionized water in sequence, and drying to obtain the magnetic molecularly imprinted polymer. The addition amount of the modified multiwall carbon nanotube is 0.04 wt% of deionized water, the addition amount of the modified halloysite nanotube is 0.02 wt% of deionized water, the addition amount of ferric chloride is 1.8 wt% of deionized water, the addition amount of sodium citrate is 2.6 wt% of deionized water, and the addition amount of hydrazine hydrate is 3 wt% of deionized water; the addition amount of the magnetic composite carrier is 0.6 wt% of the phosphate buffer solution, the addition amount of the melamine is 0.36 wt% of the phosphate buffer solution, and the addition amount of the dopamine is 0.49 wt% of the phosphate buffer solution.
Example 5:
this example is different from example 4 only in that the modified coupling agent was prepared in such an amount that the amount of N, N-diacetyl o-phenylenediamine added was 18 wt% based on the amount of N-phenyl-p-phenylenediamine.
Example 6:
a preparation method of a filter material, which comprises the following steps,
the magnetic molecularly imprinted polymer prepared in example 3 was dispersed in a conventional guanidine carbonate filter screen.
Example 7:
a method for preparing high-purity guanidine carbonate,
in the former reaction procedure, the aqueous solution of guanidine hydrochloride is added into a reaction kettle, then the sodium hydroxide solid is slowly added into the reaction kettle at a constant speed, the reaction temperature is controlled at 50-52 ℃, and the aqueous solution of mixed guanidine and sodium chloride is generated. The sodium chloride belongs to impurities in the technical process, and is in a supersaturated state in an aqueous solution due to high content of the sodium chloride, so most sodium chloride crystals are separated out from the generated aqueous solution in which the guanidino and the sodium chloride are mixed, the reaction kettle is naturally cooled to 30-35 ℃ to further separate out the sodium chloride crystals, and the sodium chloride impurities in the guanidino solution are removed by adopting a filter cylinder.
In the middle-stage reaction process, introducing carbon dioxide into the solution containing guanidine groups until the pH value is 9, and separating to obtain a crude guanidine carbonate product.
In the latter refining step, purified water is added into a dissolving kettle, the guanidine carbonate crude product is slowly added into the dissolving kettle at a constant speed, the dissolving temperature is controlled to be 65-68 ℃, insoluble impurities in the crude guanidine carbonate are removed by adopting a filtering process after the crude guanidine carbonate is dissolved, the crude guanidine carbonate is conveyed to a crystallization kettle to be cooled to 25-30 ℃, a high-purity guanidine carbonate product is obtained by crystallization, and the mother liquor is returned to the dissolving kettle for recycling.
The filter cartridge of the method of this example contained the filter material of example 6.
Guanidine carbonate content obtained in this example: not less than 99.4 percent.
Example 8:
a method for preparing high-purity guanidine carbonate,
in the former reaction process, firstly, adding the aqueous solution of guanidine hydrochloride into a reaction kettle, then slowly adding sodium hydroxide solid into the reaction kettle at a constant speed, controlling the reaction temperature to be 50 ℃ to generate an aqueous solution mixed with guanidine and sodium chloride, sending the aqueous solution to a concentration kettle, naturally cooling to 35 ℃ after most of water is evaporated to separate out sodium chloride crystals, and removing sodium chloride impurities in the guanidine solution by using a filter cylinder.
In the reaction process, the concentration and evaporation process comprises the following steps: the temperature is 50 ℃, the vacuum is less than or equal to-0.085 Mpa, the evaporation time is 4 hours, and the water content of the guanidino solution is less than or equal to 8 percent.
In the middle-stage reaction process, introducing carbon dioxide into the solution containing guanidine groups until the pH value is 9, and separating to obtain a crude guanidine carbonate product.
In the latter stage of refining, purified water is first added into a dissolving kettle, the guanidine carbonate crude product is slowly added into the dissolving kettle at a constant speed, the dissolving temperature is controlled to be 65 ℃, after the crude guanidine carbonate is dissolved, the aqueous solution is sent to a concentration kettle, after most of water is evaporated, insoluble impurities in the crude guanidine carbonate are removed by a filter cylinder, the crude guanidine carbonate is sent to a crystallization kettle to be cooled to 25 ℃, a high-purity guanidine carbonate product is obtained by crystallization, and mother liquor is returned to the reaction kettle for recycling.
In the refining process, the concentration and evaporation process comprises the following steps: the temperature is 65 ℃, the vacuum is less than or equal to-0.085 Mpa, the evaporation time is 5 hours, and the water content of the guanidine carbonate solution is less than or equal to 10 percent.
The filter cartridge of the method of this example contained the filter material of example 6.
The content of highly pure guanidine carbonate obtained in this example: not less than 99.7 percent.
Comparative example 1:
this comparative example is different from example 3 only in that the modified multi-walled carbon nanotubes were replaced with multi-walled carbon nanotubes in the preparation of the magnetic molecularly imprinted polymer.
Comparative example 2:
this comparative example is different from example 3 only in that the modified halloysite nanotubes were replaced with halloysite nanotubes in the preparation of the magnetic molecularly imprinted polymer.
Comparative example 3:
compared with example 3, the comparative example only differs in that in the preparation of the magnetic molecularly imprinted polymer, the modified multi-walled carbon nanotubes are replaced by multi-walled carbon nanotubes, and the modified halloysite nanotubes are replaced by halloysite nanotubes.
Test example 1:
1. adsorption test of Melamine
Test samples: the magnetic molecularly imprinted polymers prepared in examples 1 to 5 and comparative examples 1 to 3.
The test method comprises the following steps: 20mg of the test sample is weighed and dispersed in 10mL of 100mg/L melamine solution for 1h of constant temperature oscillation, a magnet is added for separation, and the supernatant is taken and filtered through a 0.2 mu m filter membrane to be detected at 236 nm.
The melamine adsorption capacity is calculated according to the following formula:
the adsorption amount is (pre-adsorption concentration-post-adsorption concentration) × solution volume/test sample mass.
The results of the melamine adsorption amount test are shown in fig. 1, wherein the adsorption amount of the magnetic molecularly imprinted polymer prepared in example 3 to melamine is 32.06mg/g, the adsorption amount of the magnetic molecularly imprinted polymer prepared in comparative example 1 to melamine is 23.30mg/g, the adsorption amount of the magnetic molecularly imprinted polymer prepared in comparative example 2 to melamine is 24.33mg/g, the adsorption amount of the magnetic molecularly imprinted polymer prepared in comparative example 3 to melamine is 23.27mg/g, and comparative example 1 and comparative example 3 show that the adsorption amount of melamine when the unmodified multi-walled carbon nanotube and the modified halloysite nanotube are used together is not improved, and the adsorption amount of comparative example 1 is less than that of comparative example 3 but is reduced slightly; compared with the comparative example 3, the comparative example 2 shows that the modified multi-wall carbon nanotube and the unmodified halloysite nanotube have slight effect of improving the melamine adsorption when being used together, and the adsorption amount of the comparative example 2 is higher than that of the comparative example 3, but the improvement amount is not obvious; the adsorption capacity of the comparative example 1 and the adsorption capacity of the comparative example 3 to the melamine are basically consistent, which shows that the adsorption performance to the melamine is basically consistent, the adsorption capacity of the comparative example 2 to the melamine is slightly higher than that of the comparative example 1 and the comparative example 3, but the adsorption performance of the comparative example 2 to the melamine is not greatly different from that of the comparative example 1 and the comparative example 3; compared with the comparative example 3, the embodiment 3 shows that the adsorption performance of the magnetic molecularly imprinted polymer prepared by the modified multi-walled carbon nanotube and the modified halloysite nanotube on melamine is greatly enhanced; compared with the comparative examples 1 to 3, the embodiment 3 can obtain that the adsorption performance of the magnetic molecularly imprinted polymer obtained by jointly using the multi-walled carbon nanotube and the halloysite nanotube after modification on melamine is better than that of the magnetic molecularly imprinted polymer obtained by jointly using only one of the multi-walled carbon nanotube and the halloysite nanotube after modification, and compared with the embodiment 3, the embodiment 4 to 5 show that the N, N-diacetyl o-phenylenediamine used in the preparation of the modified halloysite nanotube can further improve the adsorption of the prepared magnetic molecularly imprinted polymer on melamine, but the promotion amount is not obvious.
2. Anti-interference adsorption test for melamine
Test samples: the magnetic molecularly imprinted polymers prepared in examples 1 to 5 and comparative examples 1 to 3.
The test method comprises the following steps: and (3) carrying out a selectivity experiment on cyanuric acid and diamine oxazine, adding 20mg of a test sample into 10mL of mixed solution of melamine, cyanuric acid and diamine oxazine, oscillating for 2h, and carrying out HPLC detection after magnet separation. Wherein the concentrations of melamine, cyanuric acid and diamine oxazine are all 100 mg/L.
The anti-interference adsorption test result is shown in fig. 2, wherein the anti-interference adsorption amount of the magnetic molecularly imprinted polymer prepared in example 3 to melamine is 29.88mg/g, the anti-interference adsorption amount of the magnetic molecularly imprinted polymer prepared in comparative example 1 to melamine is 21.12mg/g, the anti-interference adsorption amount of the magnetic molecularly imprinted polymer prepared in comparative example 2 to melamine is 22.16mg/g, the anti-interference adsorption amount of the magnetic molecularly imprinted polymer prepared in comparative example 3 to melamine is 21.14mg/g, and compared with comparative example 3, comparative example 1 shows that the anti-interference adsorption to melamine is not improved when the unmodified multi-walled carbon nanotube and the modified halloysite nanotube are used together, and the anti-interference adsorption amount of comparative example 1 is less than that of comparative example 3, but the anti-interference adsorption is basically consistent; compared with the comparative example 3, the comparative example 2 shows that the anti-interference adsorption of melamine is slightly improved when the modified multi-walled carbon nanotube and the unmodified halloysite nanotube are used together, and although the anti-interference adsorption capacity of the comparative example 2 is higher than that of the comparative example 3, the anti-interference adsorption improvement effect is not obvious; the anti-interference adsorption capacity of the comparative example 1 and the comparative example 3 to melamine is basically consistent, which shows that the anti-interference adsorption performance to the melamine is basically consistent, the anti-interference adsorption capacity of the comparative example 2 to the melamine is slightly higher than that of the comparative example 1 and the comparative example 3, but the anti-interference adsorption performance of the comparative example 2 to the melamine is not much different from that of the comparative example 1 and the comparative example 3; compared with the comparative example 3, the embodiment 3 shows that the anti-interference adsorption performance of the magnetic molecularly imprinted polymer prepared by the modified multi-walled carbon nanotube and the modified halloysite nanotube on melamine is greatly enhanced; compared with the comparative examples 1 to 3, the embodiment 3 can obtain that the anti-interference adsorption performance of the magnetic molecularly imprinted polymer obtained by jointly using the multi-walled carbon nanotube and the halloysite nanotube after modification is superior to that of the magnetic molecularly imprinted polymer obtained by jointly using only one of the multi-walled carbon nanotube and the halloysite nanotube after independent modification, and compared with the embodiment 3, the embodiments 4 to 5 show that the N, N-diacetyl o-phenylenediamine used in the preparation of the modified halloysite nanotube can further improve the anti-interference adsorption of the prepared magnetic molecularly imprinted polymer on melamine, but the improvement amount is not significant.
3. Repeatability test
Test samples: the magnetic molecularly imprinted polymers prepared in examples 1 to 5 and comparative examples 1 to 3.
The test method comprises the following steps: and (3) taking 20mg of a test sample, carrying out oscillation adsorption for 1h in 10mL of 0.1mg/L melamine solution, testing the adsorption amount, then eluting with an eluent, washing with ethanol, then adding 10mL of 0.1mg/L melamine solution, repeating the test, and recording the adsorption amount and times. The eluent was 70% volume fraction acetonitrile and 30% volume fraction 20mM ammonium acetate solution.
The number of times the melamine adsorption dropped to 90% of the initial adsorption was recorded.
The repeatability is characterized by the times of elution, desorption and re-adsorption by an eluent, and the adsorption performance of the magnetic molecularly imprinted polymer is reduced by 90%, and the test result is shown in fig. 3, wherein the times of 90% reduction of the adsorption performance of the magnetic molecularly imprinted polymer prepared in example 3 on melamine is 25, the times of 90% reduction of the adsorption performance of the magnetic molecularly imprinted polymer prepared in comparative example 1 on melamine is 22, the times of 90% reduction of the adsorption performance of the magnetic molecularly imprinted polymer prepared in comparative example 2 on melamine is 22, the times of 90% reduction of the adsorption performance of the magnetic molecularly imprinted polymer prepared in comparative example 3 on melamine is 21, and compared with comparative example 3, the test result shows that the magnetic molecularly imprinted polymer prepared when the unmodified multi-walled carbon nanotube and the modified halloysite nanotube are used together has good reusability; compared with the comparative example 3, the comparative example 2 shows that the magnetic molecularly imprinted polymer prepared when the modified multi-walled carbon nanotube and the unmodified halloysite nanotube are used together has good reusability; compared with the comparative example 3, the embodiment 3 shows that the magnetic molecularly imprinted polymer prepared by the modified multi-walled carbon nanotube and the modified halloysite nanotube has enhanced reusability; compared with the comparative examples 1 to 3, the embodiment 3 can obtain that the reusability of the magnetic molecularly imprinted polymer obtained by jointly using the multi-walled carbon nanotube and the halloysite nanotube after modification on melamine adsorption is better than that of the magnetic molecularly imprinted polymer obtained by jointly using only one of the multi-walled carbon nanotube and the halloysite nanotube after modification, and compared with the embodiment 3, the embodiments 4 to 5 show that the N, N-diacetyl o-phenylenediamine is used in the preparation of the modified halloysite nanotube, so that the reusability of the prepared magnetic molecularly imprinted polymer on melamine adsorption can be further improved.
The above embodiments are merely illustrative, and not restrictive, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the protection scope of the present invention should be defined by the claims.
Claims (5)
1. A preparation method of a magnetic molecularly imprinted polymer comprises the following steps:
preparing a magnetic composite carrier from a compound containing the modified multi-walled carbon nano-tube in a solution containing an iron element through a synthesis process; polyacrylic acid is grafted on the modified multi-walled carbon nanotube, the compound contains a modified halloysite nanotube, the modified halloysite nanotube is modified by a modified coupling agent, and the modified coupling agent is obtained by mixing and processing N-phenyl-p-phenylenediamine and a silane coupling agent;
preparing a magnetic molecularly imprinted polymer by a preparation process of a magnetic composite carrier in a solution containing melamine and dopamine;
the iron element is ferric ion; the solution containing the iron element contains sodium citrate and hydrazine hydrate.
2. The method for preparing a magnetic molecularly imprinted polymer according to claim 1, wherein: the solution in the solution containing melamine and dopamine is phosphate buffer solution.
3. The method for preparing a magnetic molecularly imprinted polymer according to claim 1, wherein: the magnetic composite carrier contains ferroferric oxide.
4. A magnetic molecularly imprinted polymer prepared by the method of any one of claims 1 to 3.
5. Use of a magnetic molecularly imprinted polymer as defined in claim 4 for the preparation of high purity guanidine carbonate.
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