CN114570326A

CN114570326A - Adsorbent and preparation method and application thereof

Info

Publication number: CN114570326A
Application number: CN202210135489.8A
Authority: CN
Inventors: 王曼曼; 李子凌
Original assignee: North China University of Science and Technology
Current assignee: North China University of Science and Technology
Priority date: 2022-02-14
Filing date: 2022-02-14
Publication date: 2022-06-03
Anticipated expiration: 2042-02-14
Also published as: CN114570326B

Abstract

The invention particularly relates to an adsorbent and a preparation method and application thereof, belonging to the technical field of analysis and detection, wherein the method comprises the following steps: obtaining Mesoporous Carbon Nitride (MCN); dissolving the MCN in a first solvent to obtain a magnetic Mesoporous Carbon Nitride (MCN) solution; mixing the MCN solution with CoCl₂·6H₂O、FeCl₃·6H₂O, mixing, and then adjusting the pH value to obtain a mixed solution; and reacting the mixed solution to obtain the adsorbent. Preparation of MCN/CoFe by hydrothermal Synthesis₂O₄Magnetic solid phase extraction adsorbent, mixing MCN/CoFe₂O₄As an MSPE adsorbent, a novel method for analyzing bisphenol estrogens (BPs) in a water environment is established by combining high performance liquid chromatography-variable wavelength detection, the BPs in the water environment can be simply, efficiently and economically analyzed, a novel idea is provided for enriching and purifying organic pollutants in the water environment, and the bottleneck of pretreatment of BPs samples is broken through.

Description

Adsorbent and preparation method and application thereof

Technical Field

The invention belongs to the technical field of analysis and detection, and particularly relates to an adsorbent and a preparation method and application thereof.

Background

Bisphenol estrogens (BPs) are the most widely used artificial chemical substances with estrogen-like action in environmental estrogens, and are named because phenol has 2 hydroxyl groups. In industry, BPs are mainly used in the synthesis of compounds and monomers such as polycarbonate plastics, epoxy resins and polyester resins, and are also commonly used as additives for the production of chemical products such as plasticizers, flame retardants, stabilizers and coatings. BPs in water environment mainly come from industrial wastewater and domestic sewage discharged from factories, and after entering aquatic organisms and human bodies through food chains, the BPs are combined with estrogen receptors in the bodies to influence the combination of endogenous hormones and the receptors and interfere the functions of secretion systems in the bodies, so that the functions of reproduction, development, secretion, immunity and the like of the bodies are changed, for example, the reproduction function of the bodies is abnormal, the number of male sperms is reduced, and the occurrence of tumors is induced. Therefore, the establishment of the BPs detection method in the water environment has important research significance.

At present, the detection method of BPs mainly comprises high performance liquid chromatography-ultraviolet visible spectrometry, high performance liquid chromatography-fluorescence detection, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry and the like. As the concentration of the BPs in the water environment is only at a trace level (ng/L or mu g/L), and the components of the environmental sample are complex and difficult to directly and accurately quantify, the target substances in the environmental sample need to be enriched and purified by an effective pretreatment method so as to meet the detection requirements of an instrument. The sample pretreatment directly affects the accuracy, sensitivity and cost of the analysis method, and becomes a bottleneck of the detection technology.

Disclosure of Invention

The application aims to provide an adsorbent, a preparation method and an application thereof so as to break through the bottleneck of pre-treatment of BPs samples.

The embodiment of the invention provides a preparation method of an adsorbent, which comprises the following steps:

obtaining magnetic mesoporous carbon nitride;

dissolving the magnetic mesoporous carbon nitride in a first solvent to obtain a magnetic mesoporous carbon nitride solution;

the magnetic mesoporous carbon nitride solution is addedAnd CoCl₂·6H₂O、FeCl₃·6H₂Mixing the O and then adjusting the pH value to obtain a mixed solution;

and reacting the mixed solution to obtain the adsorbent.

Optionally, the obtaining of the magnetic mesoporous carbon nitride specifically includes:

dispersing the molecular sieve in a second solvent, and then centrifuging and evaporating to obtain a white solid;

heating the white solid, and then cooling to obtain dark powder;

and removing the silicon dioxide skeleton of the dark powder to obtain the magnetic mesoporous carbon nitride.

Optionally, the evaporation temperature is 45-55 ℃.

Optionally, the heating rate of the heating is 1.5-2.5 ℃/min, the end point temperature of the heating is 550-650 ℃, and the end point temperature holding time of the heating is 1.5-2.5 h.

Optionally, the pH value of the mixed solution is 11.5-12.5.

Optionally, the pH adjusting agent is NaOH solution.

Optionally, the reaction temperature is 170-190 ℃, and the reaction time is 20-28 h.

Based on the same inventive concept, the embodiment of the invention also provides an adsorbent, and the adsorbent is prepared by adopting the preparation method of the adsorbent.

Based on the same inventive concept, the embodiment of the invention also provides application of the adsorbent, wherein the application comprises application of the adsorbent in magnetic solid phase extraction.

Based on the same inventive concept, the embodiment of the invention also provides application of the adsorbent, and the application comprises the application of the adsorbent to the detection of the content of the bisphenol estrogen.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

the embodiment of the invention provides a suckerPreparation method of adsorbent, MCN/CoFe prepared by hydrothermal synthesis method₂O₄Magnetic solid phase extraction adsorbent, mixing MCN/CoFe₂O₄As a magnetic solid phase extraction adsorbent, a new method for analyzing the BPs in the water environment is established by combining high performance liquid chromatography-variable wavelength detection, the BPs in the water environment can be simply, efficiently and economically analyzed, a new idea is provided for enriching and purifying organic pollutants in the water environment, and the bottleneck of pretreatment of BPs samples is broken through.

The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a flow chart of a method provided by an embodiment of the present invention;

FIG. 2 is a schematic diagram of a preparation process provided by an embodiment of the present invention;

FIG. 3 is a scanning electron microscope image of an SBA-15 provided by an embodiment of the present invention;

FIG. 4 is a scanning electron microscope image of an MCN provided by an embodiment of the invention;

FIG. 5 shows MCN/CoFe provided by the embodiment of the invention₂O₄Scanning electron micrographs of (a);

FIG. 6 is a transmission electron microscope image of an SBA-15 provided by an embodiment of the present invention;

FIG. 7 is a transmission electron microscope image of an MCN provided by an embodiment of the invention;

FIG. 8 shows MCN/CoFe provided by an embodiment of the present invention₂O₄Transmission electron microscopyA mirror image;

FIG. 9 is CoFe provided by the embodiment of the present invention₂O₄MCN and MCN/CoFe₂O₄An infrared spectrum of (1);

FIG. 10 shows CoFe provided by the embodiment of the present invention₂O₄MCN and MCN/CoFe₂O₄X-ray diffraction patterns of (a);

FIG. 11 shows MCN and MCN/CoFe provided by an embodiment of the present invention₂O₄A small angle X-ray diffraction pattern of (a);

FIG. 12 shows MCN and MCN/CoFe provided by an embodiment of the invention₂O₄The nitrogen adsorption-desorption isotherm diagram of (a);

FIG. 13 shows MCN and MCN/CoFe provided by an embodiment of the invention₂O₄The aperture distribution map of (a);

FIG. 14 is CoFe provided by the embodiment of the present invention₂O₄And MCN/CoFe₂O₄The hysteresis curve of (1);

FIG. 15 is a graph showing experimental results of the effect of the amount of adsorbent used on the extraction efficiency according to the present invention;

FIG. 16 is a graph showing experimental results of the effect of adsorption time on extraction efficiency provided by the examples of the present invention;

FIG. 17 is a graph showing experimental results of pH effect of solution on extraction efficiency provided by an example of the present invention;

FIG. 18 is a graph showing experimental results of the effect of ionic strength on extraction efficiency provided by an embodiment of the present invention;

FIG. 19 is a graph showing experimental results of the influence of the kind of elution solvent on the extraction efficiency, according to an embodiment of the present invention;

FIG. 20 is a graph showing experimental results of elution volumes on extraction efficiency provided by examples of the present invention;

FIG. 21 is a graph showing experimental results of the effect of usage times on extraction efficiency provided by the present invention;

FIG. 22 is a graph showing the results of liquid chromatography-variable wavelength detection provided by an embodiment of the present invention.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are illustrative of the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, 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 belongs. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In order to solve the technical problems, the general idea of the embodiment of the application is as follows:

the applicant finds in the course of the invention that: magnetic solid-phase extraction (MSPE) is a solid-phase extraction technique that uses Magnetic or magnetizable materials as adsorbents. Different from the traditional solid phase extraction technology, the MSPE directly disperses the magnetic adsorbent in the sample solution, thereby omitting the filling process of a solid phase extraction column and avoiding the problems of column blockage and the like; in addition, the separation process does not need operations such as centrifugation or filtration, and the like, and the target and the sample solution can be quickly separated only by applying an external magnetic field. Based on this, the MSPE is widely used in the fields of environmental, biological and food analysis, etc. Among them, the adsorbent is the core of the MSPE, which determines the efficiency and cost of the pretreatment. The MSPE adsorbent consists essentially of a magnetic source (usually Fe)₃O₄) And a non-magnetic functional material, wherein the former provides magnetic action for interacting with an external magnetic field, and the latter provides an action site for adsorbing the target. At present, materials such as carbon nanotubes, graphene oxide and metal organic frameworks have been widely used as the MSPE adsorbent, and the research and development of the MSPE adsorbent which is simple, efficient and low in cost is still a current hot problem.

Mesoporous Carbon Nitride (MCN) is a carbon nitride formed from only C and N in sp²By carrying out the processAnd (3) forming a pi bond similar to a benzene ring through the interaction of lone pair electrons on the Pz orbit to form the porous material with the mesoporous size of 2-50 nm of a highly delocalized conjugated system. On one hand, MCN has good chemical stability, thermal stability and mechanical property, so that the MCN has a wide application prospect in the fields of catalytic degradation, gas adsorption, biosensing and the like. On the other hand, when MCN is used as an adsorbent, electron delocalization characteristics and abundant nitrogen-containing functional groups (-NH-and-NH) are present in the structure₂-) can interact with some ions or molecules, hydrophobic, pi-pi bonds, hydrogen bonds, and electrostatic forces, among others. It is worth noting that compared with the massive graphite carbon nitride, the introduction of the mesoporous structure enables the MCN to have regular ordered mesoporous channels, narrower pore size distribution and excellent specific surface area (not less than 100 m)²Per g) and pore volume>0.5cm³The,/g) and the like. Based on the excellent performances, MCN can become an ideal adsorbent to be applied to the field of sample pretreatment. At present, the study of MCN on the adsorption of organic matters is just started, only 3 documents report that MCN is directly used for column-assisted dispersion solid-phase extraction of 5 sulfonamides in water environment and milk samples. MCN is used as a solid phase microextraction adsorbent and is respectively used for pretreatment of polycyclic aromatic hydrocarbon and polychlorinated biphenyl of water environment and human serum samples.

Based on the above, in order to discuss the application of MCN in the field of sample pretreatment and develop a novel method for analyzing BPs in water environment with high efficiency, simplicity and low cost, the research takes MCN as an adsorbing material, CoFe for the first time₂O₄Magnetic MCN (MCN/CoFe) is constructed as a magnetic source by a simple hydrothermal synthesis method₂O₄) The adsorbent is combined with high performance liquid chromatography-variable wavelength detection to establish a high-efficiency, simple and low-cost analysis method for the BPs in the water environment.

According to an exemplary embodiment of the present invention, there is provided a method for preparing an adsorbent, the method including:

s1, obtaining MCN;

s1.1, dispersing a molecular sieve in a second solvent, and then centrifuging and evaporating to obtain a white solid;

in some embodiments, the molecular sieve may be selectedSBA-15 is used, SBA-15 belongs to a mesoporous molecular sieve, and SBA-15 has a two-dimensional hexagonal through hole structure and has a P6mm space group. In the XRD diffraction pattern, the main peak is near about 1 degree, and is a (10) crystal plane peak. The second intense peak is (11) and (20) in this order. The other peaks are weak and not easily observed. In addition, silica on the SBA-15 skeleton is generally amorphous, and no significant diffraction peak is observed in wide-angle XRD diffraction. In general, a typical synthetic procedure for SBA-15 is: dissolving a triblock surfactant P123(Aldrich, EO20PO70EO20, Ma (5800) in a proper amount of deionized water at 35-40 ℃), adding Tetraethoxysilane (TEOS) and hydrochloric acid (HCl), continuously and violently stirring for more than 24 hours, filling the mixture into a polytetrafluoroethylene bottle, crystallizing for more than 24 hours, filtering, washing and drying, finally calcining at 550 ℃ for more than 5 hours to remove a template agent or washing away the template agent by using a solvent under reflux, and then filtering, washing and drying to obtain white powder, namely SBA-15. The molar ratio of the materials used in the experiment was about 1 TEOS: 0.017P 123: 5.88 HCl: 136H₂And O. In other embodiments, other molecular sieves may be selected by those skilled in the art.

In this embodiment, the second solvent may be an aqueous solution of hexamethylenetetramine.

In some embodiments, the temperature of the evaporation is 45-55 ℃.

S1.2, heating the white solid, and then cooling to obtain dark powder;

in some embodiments, the heating rate is 1.5-2.5 ℃/min, the heating end point temperature is 550-650 ℃, and the heating end point temperature holding time is 1.5-2.5 h.

S1.3, removing the silicon dioxide framework of the dark powder to obtain MCN;

s2, dissolving the MCN in a first solvent to obtain an MCN solution;

s3, mixing the MCN solution and CoCl₂·6H₂O、FeCl₃·6H₂O, mixing, and then adjusting the pH value to obtain a mixed solution;

in some embodiments, the pH of the mixture is 11.5-12.5.

The applicant finds out in the invention process that: the pH influences the formation condition of crystal grains, the generation condition of the crystal grains is poor when the value is too small, the diffraction peak intensity is insufficient when the value is larger, impurities are generated, generally speaking, the pH value of the mixed liquid is controlled to be 11.5-12.5, and the pH value is preferably 12.

In some embodiments, the pH adjusting agent is NaOH solution.

And S4, reacting the mixed solution to obtain the adsorbent.

In some embodiments, the reaction temperature is 170-190 ℃, and the reaction time is 20-28 h.

The reaction temperature is controlled to be 170-190 ℃, the reaction time is controlled to be 20-28 h, and the prepared MCN/CoFe₂O₄The chemical property is more stable, the purity and the crystallinity of the product are higher, the temperature is preferably 180 ℃, and the time is preferably 24 h. Sufficient reaction time to favor MCN/CoFe₂O₄If the time is outside the above range, MCN/CoFe₂O₄The growth time is not sufficient and more impurities may be present.

According to another exemplary embodiment of the present invention, there is provided an adsorbent, which is prepared by the method for preparing an adsorbent according to any one of the above.

The adsorbent uses MCN as an adsorbing material and CoFe₂O₄Magnetic MCN (MCN/CoFe) is constructed as a magnetic source by a simple hydrothermal synthesis method₂O₄) The adsorbent is combined with high performance liquid chromatography-variable wavelength detection to establish a high-efficiency, simple and convenient and low-cost analysis method for BPs in a water environment. The material has high specific surface area (202.5 m)²G) and sufficient magnetic strength (55.5 emu/g). Mixing MCN/CoFe₂O₄As an MSPE adsorbent, a novel method for analyzing BPs in a water environment is established by combining high performance liquid chromatography-variable wavelength detection.

According to another exemplary embodiment of the present invention, there is provided a use of an adsorbent, comprising applying the adsorbent as described above in magnetic solid phase extraction.

MSPE is simple to operate, and the separation of a target object and a sample matrix can be realized only by applying an external magnetic field; the adsorbent has good reusability and stability, and can be used at least 16 times. The method can simply, efficiently and economically analyze the BPs in the water environment, and provides a new idea for enriching and purifying organic pollutants in the water environment.

In this embodiment, the magnetic solid phase extraction process includes: 15mL of the filtered lake water/tap water sample was measured, and 20mg of MCN/CoFe was added₂O₄Vortex and shake for 15min, separate the adsorbent from the sample solution with a magnet, and discard the supernatant. Eluting with 1mL MeOH, repeating for 3 times, mixing eluates, concentrating to dryness by nitrogen blow, redissolving with 200 μ L MeOH, filtering with 0.22 μm filter membrane, and analyzing by liquid chromatography. The liquid chromatography conditions included: the chromatographic column is Agilent Eclipse Plus-C₁₈Columns (4.6 mm. times.250 mm, 4 μm, Agilent, USA); the mobile phase is ACN and H₂O (52: 48, v/v); the flow rate is 1 mL/min; the column temperature is 30 ℃; the detection wavelength is 200 nm; the amount of sample was 20. mu.L.

According to another exemplary embodiment of the present invention, there is provided a use of the adsorbent, which includes applying the adsorbent as described above to the detection of the content of bisphenol estrogens.

The usage amount of the adsorbent is only 20mg, and the adsorption completion time is within 15 min; when the sample loading volume is 15mL, the enrichment factor reaches 60-78, and the detection limit of 3 kinds of BPs is 0.3-0.5 ng/mL.

The adsorbent of the present application, and the preparation method and application thereof will be described in detail below with reference to examples, comparative examples and experimental data.

Example 1

A method of making an adsorbent, the method comprising:

the preparation method of MCN comprises the following steps: dispersing 1.0g of SBA-15 in 10.0mL of aqueous solution containing 8.0g of hexamethylenetetramine, stirring for 5h at room temperature, centrifuging at high speed to collect solid, heating and evaporating at 50 ℃, transferring the obtained white solid into a closed crucible, heating to 600 ℃ at the heating rate of 2 ℃/min, heating and keeping for 2h, and naturally cooling to room temperature. And soaking the obtained dark powder in 4mol/L ammonium bifluoride aqueous solution for 48 hours to remove the silicon dioxide framework. Finally, a dark color sample was collected by high-speed centrifugation, washed repeatedly with ultrapure water and anhydrous ethanol, and vacuum-dried at 60 ℃ for 4 hours to obtain MCN.

Preparation of MCN/CoFe by hydrothermal Synthesis₂O₄The specific method comprises the following steps: 75mg of MCN was added to 70mL of ethylene glycol, and after uniform ultrasonic dispersion, 154.7mg of CoCl was added thereto₂·6H₂O (0.65mmol) and 351.4mg FeCl₃·6H₂O (1.30mmol), stirred vigorously for 12h, adjusted to pH 12.0 with 1mol/L NaOH solution, and then stirred for 30 min. Transferring the obtained mixed solution into a reaction kettle, reacting at 180 ℃ for 24h, collecting reaction products, repeatedly washing with ultrapure water and absolute ethyl alcohol, and drying at 60 ℃ in vacuum to dryness to obtain MCN/CoFe₂O₄。

Comparative example 1

Microporous beta-cyclodextrin polymers prepared by the method provided by Talanta,2018,187: 207-.

Comparative example 2

The magnetic molecularly imprinted nanoparticles prepared by the method provided by Talanta,2017,162:57-64 were used as adsorbents.

Comparative example 3

The magnetic multi-wall carbon nano-tube prepared by the method provided by Microchem J,2020,157:104867 is used as an adsorbent.

Comparative example 4

The magnetic graphene @ polydopamine @ Zr-MOF prepared by the method provided by Talanta,2015,144:1329-1335 is used as an adsorbent.

Comparative example 5

C prepared by the method provided by J Environ Chem Eng,2016,4:4062-₁₆Silica/magnetic montmorillonite as adsorbent.

Examples of the experiments

The SBA-15 of example 1 and the MCN and MCN/CoFe constructed therefrom were measured with a Scanning Electron Microscope (SEM), a field emission Transmission Electron Microscope (TEM), a Fourier transform infrared spectrometer (FT-IR), an X-ray diffractometer (XRD), and a Vibrating Sample Magnetometer (VSM), respectively₂O₄Apparent morphology, crystal structure and composition, specific surface area and pore distributionAnd magnetic strength.

By applying the pairs of SBA-15, MCN and MCN/CoFe₂O₄The SEM appearance characterization shows that the MCN and MCN/CoFe prepared by the method are shown in figures 3-5₂O₄The shapes of the short rod-shaped structures are uniform and regular, are consistent with the shape of a template SBA-15 and are MCN/CoFe₂O₄Uniformly distributed nanoparticles were observed on the surface (fig. 5).

To further observe the internal microstructure of the material, experiments were conducted on MCN and MCN/CoFe₂O₄TEM representation is carried out, and the results are shown in FIGS. 6-8, and both the two have pore structures which are uniformly distributed, highly ordered and regularly arranged. As can be seen, MCN and MCN/CoFe₂O₄The mesoporous structure of template SBA-15 has been successfully replicated (fig. 6). Furthermore, FIG. 8 shows CoFe₂O₄The nano particles are uniformly dispersed on the surface of the MCN, which shows that the MCN and the CoFe₂O₄The compounding has been successful.

Use of FT-IR and XRD on CoFe₂O₄MCN and MCN/CoFe₂O₄The surface groups and the crystal structure of (a). FIG. 9 shows MCN/CoFe₂O₄At 1310, 1616 and 3402cm^-1Stretching vibration of C-N and C-N bond and stretching mode of N-H bond at 590.9cm^-1Has a tensile vibration peak of a metal M-O bond. MCN/CoFe₂O₄The wide angle XRD pattern of (fig. 10) shows that the diffraction peak at 25.6 ° (002) is consistent with the (002) diffraction peak of MCN and bulk carbon nitride reported in the literature; diffraction peaks at 30.1 ° (220), 35.4 ° (311), 43.1 ° (400), 53.4 ° (422), 57.0 ° (511) and 62.6 ° (440) with CoFe₂O₄The characteristic diffraction peaks of (A) are identical. Further, as shown in FIG. 11, MCN/CoFe₂O₄Has a sharp diffraction peak in a small angle range of 0.5-5 degrees, corresponds to a 0.95 (100) crystal face of a two-dimensional hexagonal structure with a space group of p6mm, and shows that MCN/CoFe₂O₄Has a typical mesoporous structure.

Using N₂Adsorption-desorption experiments on prepared MCN and MCN/CoFe₂O₄Characterization findings (FIGS. 12-13), MCN and MCN/CoFe₂O₄N of (A)₂The adsorption-desorption isotherms are all IV-type curves with H1 type hysteresis loops and accord with the typical characteristics of mesoporous materials; furthermore, MCN/CoFe₂O₄The type IV curve of (A) also confirms MCN and CoFe₂O₄The mesoporous structure of the MCN is not changed by the composition of the nanoparticles, which is consistent with the results of small-angle XRD and TEM characterization. According to calculation, MCN/CoFe₂O₄Has a specific surface area and a pore volume of 202.5m, respectively²In terms of/g and 0.8cm³(ii) in terms of/g. Furthermore, from the results of the pore size distribution curves (FIG. 13), MCN and MCN/CoFe₂O₄The average pore diameters of (a) and (b) are respectively 10.6 and 15.7nm, and are within the pore diameter range (2-50 nm) of a typical mesoporous material. From the results of FIG. 14, it is clear that CoFe₂O₄And MCN/CoFe₂O₄The saturation magnetic strengths of (A) and (B) are respectively 80.4 and 55.5emu/g, which indicates that the prepared MCN/CoFe₂O₄Has sufficient magnetic strength to enable separation of the adsorbent from the sample solution by means of an external magnet. In summary, MCN/CoFe is based on the high specific surface area and pore volume, uniform size and sufficient magnetic strength of the material₂O₄Can be used as magnetic solid phase extraction adsorbent.

Adsorption and elution conditions are key factors that affect the accuracy of the MSPE process. To obtain the best recovery, this study examined the effect of adsorbent dosage, adsorption time, solution pH, ionic strength, elution solvent type and volume (single elution volume x number of elutions) on the recovery of 3 BPs (BPAF, BPF and BPA). The test uses BPs standard water solution with the concentration of 100ng/mL as a sample solution, 15mL, and all the tests are carried out in parallel for 3 times. The results are shown in FIGS. 15-20.

Regarding the effect of adsorbent dosage and adsorption time on BPs recovery:

the appropriate adsorbent dosage and adsorption time determine the extraction efficiency and cost of the process. Experimental fixed adsorption time 15min, investigation of 10, 15, 20 and 25mg MCN/CoFe₂O₄Effect on recovery of 3 targets. From FIG. 15, it was found that when the amount of the adsorbent was increased from 10mg to 15mg, the recovery rate of BPAF increased and reached a maximum, and the recovery rates of BPF and BPA gradually increased;when the dosage of the adsorbent is increased to 20mg, the recovery rate of BPAF has no significant change, and the recovery rates of BPF and BPA reach the highest; further increase to 25mg did not significantly change the recovery of 3 BPs.

The experiment fixed adsorbent dosage of 20mg, investigation adsorption time 5 ~ 20min on 3 kinds of BPs recovery effect, the result is shown in figure 16. When the adsorption time is 5min, the recovery rate of 3 target substances reaches 75.8% -86.4%; when the adsorption time is continuously prolonged to 15min, the recovery rate reaches the best and is 82.5 to 103 percent; when the recovery rate is further increased to 20min, the recovery rate is not changed obviously. Therefore, 20mg MCN/CoFe was selected for the experiment₂O₄Adsorption for 15min was the optimum adsorption condition.

Regarding solution pH and ionic strength:

solution pH and ionic strength affect to some extent the form of BPs present, the surface active sites of the adsorbent and the degree of ionization. Therefore, experiments were conducted to examine the effect of pH 3-9 and ionic strength (0, 25, 50, 75 and 100mmol/L NaCl) on the recovery of 3 target species. From the results of fig. 17 and 18, it can be seen that the solution pH and ionic strength had no significant effect on the recovery of BPs.

Regarding elution solvent type and volume:

under optimal loading conditions, experiments were performed to examine the effect of elution solvents (acetone, ACN, ethyl acetate and MeOH) and elution volumes (1 mL. times.1, 1 mL. times.2, 1 mL. times.3 and 1 mL. times.4) and on the recovery of 3 BPs. As can be seen from FIGS. 19 and 20, the best recovery of the target product was obtained using 1mL of X3 MeOH.

Based on MCN/CoFe₂O₄Establishment of methodology

Based on MCN/CoFe₂O₄Magnetic solid phase extraction is combined with high performance liquid chromatography-variable wavelength detection to establish an analysis method of BPs in a water environment. To verify the feasibility of the method, the experiments evaluated the linear range, detection Limits (LODs), quantitation Limits (LOQs), accuracy and precision of the method.

Regarding linear range, detection limit and quantification limit:

under the optimal experimental condition, lake water and tap water samples are selected, 7 BPs standard solutions with different concentrations are prepared for analysis, a standard curve is drawn by taking the concentration (x, ng/mL) of a target object as a horizontal coordinate and taking a corresponding peak area (y) as a vertical coordinate. The results are shown in table 1:

linear range, regression equation, correlation coefficient, detection limit, and quantitation limit for the methods of Table 1

Note:⁽¹⁾peak area;⁽²⁾target concentration, ng/mL.

In a lake water sample, 3 BPs have good linear relation (r is more than or equal to 0.9996) within the range of 1.0-300 ng/mL, and the detection limit and the quantification limit of the method are respectively 0.3-0.4 ng/mL and 1.0-1.5 ng/mL; in a tap water sample, 3 BPs are in good linear relation (r is more than or equal to 0.9996) within the range of 1.2-360 ng/mL, and the detection limit and the quantification limit of the method are respectively 0.4-0.5 ng/mL and 1.2-1.8 ng/mL, which indicates that the method has good sensitivity.

Regarding accuracy and precision:

to assess the accuracy and precision of the method, three concentration level (low, medium, high) spiking recovery experiments were performed on the blank lake water and tap water samples, respectively, as shown in table 2:

TABLE 2 recovery and precision of the process

The recovery rate of 3 kinds of BPs in the lake water sample by the method is 89.3-104 percent, the intra-day precision is 2.1-6.4 percent, and the inter-day precision is 4.1-9.5 percent; in tap water samples, the recovery rate of 3 target substances is 80.5-95.3%, and the precision in the day and the precision in the daytime are 1.5-4.1% and 2.2-8.0%, respectively. The above results show that the established method has good accuracy and precision.

Regarding MCN/CoFe2O4 reusability:

the number of times the adsorbent is used determines the cost of the pretreatment process. Under the optimal experimental conditions, MCN/CoFe was used₂O₄The adsorbent was subjected to continuous repeated adsorption-desorption experiments on 3 BPs in the lake water sample to examine the reusability of the adsorbent. The results are shown in fig. 21, with the increase of the times of the adsorption-desorption experiments, the recovery rates of the 3 targets are 84.5% -107%, the recovery rate after the 16 th experiment is still higher than 84.5%, and the RSD of the recovery rate is less than or equal to 10.8%, which indicates that the prepared adsorbent has good reusability and stability.

For MCN/CoFe₂O₄Enrichment and purification effects on BPs:

under the optimal MSPE condition, high performance liquid chromatography-variable wavelength detection is combined, and the direct sample injection and MSPE post-sample injection analysis are respectively carried out on the lake water sample with the added standard (BPF and BPA are added with standard 10ng/mL, and BPAF is added with standard 15 ng/mL). FIG. 22a is a chromatogram of 2 μ g/mL BPs standard solution, when a lake water sample is added with a standard and directly injected for analysis (FIG. 22b), the impurity peak is obvious and no target is detected; after MSPE treatment, as shown in FIG. 22c, the response signal of impurity peak is reduced obviously, and 3 targets are detected, which proves that MCN/CoFe₂O₄The adsorbent can effectively purify and enrich the BPs in the lake water sample. When the sample loading volume is 15mL, MCN/CoFe₂O₄The enrichment factor for the BPs reaches 60-78. Furthermore, comparison with the commercial C18 adsorbent revealed (FIG. 22d), C₁₈And MCN/CoFe₂O₄The adsorbents can effectively purify and enrich the BPs in the lake water, and the obtained recovery rates are 93.9-98.6 percent and 96.1-106 percent respectively, but the obtained products are subjected to MCN/CoFe₂O₄After treatment, the peak response signal of the impurities of the sample is obviously lower than that of C18, which indicates that the adsorbent has better purification capacity.

Analysis of actual samples

The method was used for analysis of BPs in 10 lake and 10 tap water samples, respectively. The results are shown in Table 3:

TABLE 3 analysis results of 3 BPs in water environments

Note:⁽¹⁾mean ± standard deviation;⁽²⁾adding standard concentration of 10 ng/mL;⁽³⁾it was not detected.

BPF, BPA and BPAF are detected in lake water samples, and the concentrations are 1.4 +/-0.03-5.6 +/-0.09 ng/mL, 1.2 +/-0.02-5.9 +/-0.03 ng/mL and 3.0 +/-0.09-15.1 +/-0.1 ng/mL respectively; no 3 BPs were detected in all tap water samples. After 10ng/mL of standard is added to the lake water sample and the tap water sample, the recovery rates are 82.6 +/-6.4% -106 +/-3.5% and 80.2 +/-2.1% -94.7 +/-2.6%, respectively, and the method has good accuracy and can be used for analyzing BPs in the actual water environment sample.

The results of comparison between example 1 and comparative examples 1 to 5 are shown in Table 4, using LOD, recovery rate, adsorbent amount, adsorption time, sample volume, EF, number of times of use, and the like as evaluation indices.

TABLE 4 comparison of analysis results of BPs in water environment by combining the methods with literature methods and HPLC

As can be seen from the above table, when HPLC analysis is used, the LODs in the method is 0.3-0.5 ng/mL, and the recovery rate is 80.5% -104%, which is equivalent to or better than the method reported in the literature. In the aspect of adsorption time, the microporous beta-cyclodextrin polymer, the magnetic molecularly imprinted nano-particles, the magnetic multi-walled carbon nanotubes and the like need 20-60 min, and the research only needs 15min, so that the time is greatly saved. For adsorbent dosage, only 2 is needed for this study0mg MCN/CoFe₂O₄And the method is far lower than other methods (30-200 mg), so that the cost of the pretreatment process is saved. Furthermore, when the sample loading volume is 15mL, MCN/CoFe₂O₄The enrichment multiple of BPs reaches 60-78; the adsorbent can be used at least 16 times, further reducing the cost. Therefore, the method can efficiently, simply and economically analyze the BPs in the water environment.

One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:

(1) the method provided by the embodiment of the invention prepares MCN/CoFe by hydrothermal synthesis₂O₄Mixing MCN/CoFe₂O₄As an MSPE adsorbent, a novel method for analyzing the BPs in the water environment is established by combining high performance liquid chromatography-variable wavelength detection, the BPs in the water environment can be simply, efficiently and economically analyzed, a novel idea is provided for enriching and purifying organic pollutants in the water environment, and the bottleneck of pretreatment of BPs samples is broken through;

(2) the adsorbent MCN/CoFe provided by the embodiment of the invention₂O₄Has a high specific surface area (202.5 m)²The magnetic strength is 55.5emu/g), and the enrichment factor of the BPs reaches 60-78; the adsorbent can be used at least 16 times, so that the cost of pretreatment is saved.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A method of making an adsorbent, the method comprising:

obtaining magnetic mesoporous carbon nitride;

mixing the magnetic mesoporous carbon nitride solution with CoCl₂·6H₂O、FeCl₃·6H₂Mixing the O and then adjusting the pH value to obtain a mixed solution;

and reacting the mixed solution to obtain the adsorbent.

2. The method for preparing the adsorbent according to claim 1, wherein the obtaining of the magnetic mesoporous carbon nitride specifically comprises:

heating the white solid, and then cooling to obtain dark powder;

3. The method for preparing the adsorbent according to claim 2, wherein the temperature of the evaporation is 45 to 55 ℃.

4. The method for preparing the adsorbent according to claim 2, wherein the heating rate is 1.5 to 2.5 ℃/min, the heating end point temperature is 550 to 650 ℃, and the heating end point temperature holding time is 1.5 to 2.5 hours.

5. The method for producing the adsorbent according to claim 1, wherein the pH of the mixed solution is 11.5 to 12.5.

6. The method for producing the adsorbent according to claim 1, wherein the pH-adjusting agent is NaOH solution.

7. The method for preparing the adsorbent according to claim 1, wherein the reaction temperature is 170-190 ℃ and the reaction time is 20-28 h.

8. An adsorbent produced by the method for producing an adsorbent according to any one of claims 1 to 7.

9. Use of an adsorbent, comprising the use of the adsorbent of claim 8 in magnetic solid phase extraction.

10. Use of an adsorbent, comprising the use of the adsorbent of claim 8 for the detection of the content of bisphenol estrogens.