CN110629313B

CN110629313B - Porous nanofiber material, preparation method thereof and application thereof in chemical wastewater nitrobenzene monitoring

Info

Publication number: CN110629313B
Application number: CN201810644283.1A
Authority: CN
Inventors: 杨宇斐
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2018-06-21
Filing date: 2018-06-21
Publication date: 2022-03-15
Anticipated expiration: 2038-06-21
Also published as: CN110629313A

Abstract

The present invention relates to a porous nanofibrous material comprising a polymer matrix and a fluorescent agent. The invention also relates to a preparation method of the porous nanofiber material, which is used for preparing the novel porous nanofiber material by an electrospinning technology, and the method is simple, easy, rapid, efficient, low in cost and good in universality. The prepared novel porous nanofiber material has a novel and unique nanofiber morphology with a secondary porous structure, the detection limit of monitoring p-nitrobenzene in wastewater is very low, the response time of monitoring the p-nitrobenzene in the wastewater is short, and the material has excellent regeneration performance and can be repeatedly utilized.

Description

Porous nanofiber material, preparation method thereof and application thereof in chemical wastewater nitrobenzene monitoring

Technical Field

The invention belongs to the technical field of new materials and preparation thereof, and particularly relates to a porous nanofiber material, a preparation method thereof and application thereof in monitoring of nitrobenzene in chemical wastewater.

Background

In recent years, due to its superior properties and application value, one-dimensional nanomaterials are attracting much attention of researchers. A great deal of research is devoted to the preparation and construction of nano materials with various forms, such as nano fibers, nano tubes, nano rods, nano wires, nano rings and the like. Existing methods such as melt flutter, gas phase jet, nanolithography, self-assembly, etc. are often limited by narrow material range, fiber aggregation, high cost, low yield, etc. Among various methods for preparing one-dimensional nano materials, the electrospinning technology has become a practical and efficient method for preparing nano fiber materials. Compared with common mechanical drawing, electrostatic spinning also provides a continuous preparation process, and nanofibers with smaller diameters than those obtained by common mechanical drawing can be prepared through high voltage action different from mechanical drawing. The electrospinning technology can realize high-yield production, has simple equipment and low cost, and becomes a hot spot concerned by academic circles and industrial circles.

The electrospun fiber material essentially has an inherent three-dimensional porous structure and has the advantages of long length, high specific surface area, controllable size and the like. Therefore, the electrospinning technology can be widely applied to the fields of reinforcing materials, tissue engineering, separation technology, enzyme and catalyst immobilization, electronic devices and the like. The electrospun fiber membrane with the secondary porous structure comprises a core-shell, hollow and porous microstructure, and the structures enrich the secondary morphology of the electrospun fiber and further improve the specific surface area of the material, thereby becoming one of the research hotspots of the electrospinning technology.

Monitoring and treatment of nitrobenzene in waste water discharged by petrochemical enterprises are tasks and urgent research subjects of multiple petrochemical enterprises in China. Nitrobenzene compounds are widely used in the industrial fields of medicine, pesticide, dye, paper making, textile and the like, belong to refractory substances, and can be accumulated in the environment in large quantities to pollute surface water, underground water and soil. With the rapid development of fine chemical engineering, the increase of chemical enterprises for producing aniline substances and the enlargement of the scale thereof lead the demand of nitrobenzene substances to be obviously increased and the possibility of sudden environmental pollution accidents to be increased. Nitrobenzene has been listed as an organic pollutant detected in drinking water in the united states and a priority pollutant formulated by EPA, and is also listed as a black list of environmental pollutants in our country. The development of a rapid and sensitive detection technology for nitrobenzene is of great significance. Most of the existing nitrobenzene monitoring methods are methods of chromatography, chromatography-mass spectrometry and the like. However, this method is relatively time-consuming, cumbersome, bulky, complex to pre-process, expensive to implement and maintain, and not suitable for on-site monitoring. Patent CN105363394A reports a method for preparing magnetic molecularly imprinted microspheres and synthesizing micelles/polymers, which has relatively complicated synthesis reaction, modification and enrichment processes, high cost, and yet to improve detection sensitivity. The patent CN101382550A reports an enzyme-linked immunosorbent assay for measuring nitrobenzene, and the method has harsh storage conditions and needs to further reduce the detection limit. Patent CN103257138A reports an electrospinning material based on a color sensing mechanism, however, the enrichment and color development process is relatively tedious and time-consuming, and the response sensitivity needs to be improved.

The existing electrospinning fiber fluorescent material is mainly constructed by covalent modification and electrostatic layer-by-layer self-assembly. The construction methods have the defects of long preparation period, complicated synthesis steps, leakage of fluorescent agents and the like. The development of a new construction mode, the improvement of the stability, the reproducibility and the reproducibility of the material, and the development of a new detection material with high sensitivity and high selectivity is the development direction of the electrospun fiber fluorescent sensing material.

Therefore, there is a need to develop a porous nanofiber material with good stability, reproducibility and reproducibility, high sensitivity and selectivity, and fluorescence sensing function, and a preparation method thereof.

Disclosure of Invention

The invention aims to solve the technical problem of providing a novel porous nanofiber material and a preparation method thereof, aiming at the defects of the prior art, the method prepares raw materials into electrospinning stock solution, prepares a nanofiber film material by an electrospinning technology, is simple and quick, has good universality, and has the characteristics of good stability, reproducibility and reproducibility of the prepared porous nanofiber material, and high sensitivity and selectivity when used for monitoring the nitrobenzene in the chemical wastewater.

To this end, a first aspect of the invention provides a porous nanofibrous material comprising a polymer matrix and a fluorescent agent.

According to the porous nanofiber material disclosed by the invention, the porous nanofiber material has a one-dimensional nanofiber morphology and a secondary porous structure.

According to the porous nanofiber material disclosed by the invention, the diameter of the nanofiber is 200-600 nm.

The porous nanofiber material according to the present invention, the content of the fluorescent agent is 5 to 10 parts by weight based on 100 parts by weight of the polymer matrix.

In some preferred embodiments of the present invention, the fluorescent agent is present in an amount of 6 to 8 parts by weight, based on 100 parts by weight of the polymer matrix.

According to the porous nanofibrous material of the invention, the polymer matrix comprises cellulose organic acid ester.

In some preferred embodiments of the invention, the polymer matrix comprises at least one of cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, or cellulose acetate butyrate.

According to the porous nanofiber material of the present invention, the fluorescer comprises an anthracene-based fluorescer.

In some preferred embodiments of the present invention, the fluorescer comprises at least one of 9-chloroanthracene, 9-anthracenal, 9-anthracenemethanol, 9-methylanthracene, 9-acetylanthracene, 9-bromoanthracene, or 9-vinylanthracene.

In a second aspect, the present invention provides a method for preparing a porous nanofiber material according to the first aspect of the present invention, comprising the steps of:

s1, mixing the polymer matrix, the fluorescent agent and the solvent to prepare an electrospinning stock solution;

s2, preparing the electrospinning stock solution into electrospinning nanofibers through electrospinning;

s3, removing the solvent in the electrospun nanofiber to obtain the nanofiber;

and S4, removing the pore-foaming agent in the nanofiber to obtain the porous nanofiber material.

According to the preparation method of the porous nanofiber material, the solvent comprises a mixed solvent consisting of a solvent I and a solvent II; the solvent I comprises an amide polar solvent, and the solvent II comprises a ketone solvent.

In some preferred embodiments of the invention, the solvent I comprises at least one of N, N dimethylacetamide, N dimethylformamide, N-dimethylpropionamide, N-diethylacetamide, N-methylacetamide or N-ethylacetamide.

In some preferred embodiments of the present invention, the solvent II comprises at least one of acetone, cyclohexanone, methyl ethyl ketone, or methyl isobutyl ketone.

According to the preparation method of the porous nanofiber material, the pore-foaming agent comprises at least one of polyethylene glycol and alkylphenol polyoxyethylene ether.

In some preferred embodiments of the invention, the polyethylene glycol has a molecular weight of 2000-6000.

In some preferred embodiments of the present invention, the alkylphenol polyoxyethylene ether has a polymerization degree of 8 to 20, and the alkyl group is a C6 to C15 alkyl group.

In some further preferred embodiments of the present invention, the alkylphenol polyoxyethylene ether is selected from at least one of octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, or polyethylene glycol octylphenyl ether (Triton X-100).

In some further preferred embodiments of the present invention, the polyethylene glycol is selected from at least one of PEG-2000, PEG-3000, PEG-4000, PEG-6000.

In some embodiments of the present invention, the polyoxyethylene octylphenol ether is at least one member selected from the group consisting of OP-7, OP-10, and OP-15, and the polyoxyethylene nonylphenol ether is at least one member selected from the group consisting of NP-7, NP-10, and NP-15.

According to the preparation method of the porous nanofiber material, the content of the fluorescent agent in the electrospinning stock solution is 5-10 parts by weight based on 100 parts by weight of the polymer matrix; the content of the solvent is 400-1000 parts by weight; the content of the pore-foaming agent is 25-100 parts by weight.

In some further preferred embodiments of the present invention, the amount of fluorescer in the electrospinning dope is 6 to 8 parts by weight based on 100 parts by weight of the polymer matrix; the content of the solvent is 500-800 parts by weight; the content of the pore-foaming agent is 40-80 parts by weight.

In some preferred embodiments of the present invention, the mass ratio of the solvent I to the solvent II in the solvent is 1 (1-4).

In some further preferred embodiments of the present invention, the mass ratio of the solvent I to the solvent II in the solvent is 1 (1.5-3).

In some preferred embodiments of the present invention, in step S2, the electrospinning device includes a syringe and a receiver, the syringe is pushed at a speed of 0.8-1.5mL/h, and the receiver is rotated at a speed of 500-; the distance between the needle of the injector and the receiver is 12-18cm, the voltage of the electrospinning is 10-20kV, and the electrospinning time is 8-10 min.

In some preferred embodiments of the present invention, in step S3, the solvent is removed by drying, wherein the temperature of drying is 60-80 ℃; the drying time is 10-15 hours.

In some preferred embodiments of the present invention, in step S4, the fluorescence sensing nanofiber is soaked to remove the pore-forming agent, and then dried to obtain a porous nanofiber material; the soaking time is 30-40 hours; the drying temperature is 60-80 ℃; the drying time is 6-12 hours.

In a third aspect, the invention provides an application of the porous nanofiber material according to the first aspect or the porous nanofiber material obtained by the preparation method according to the second aspect in nitrobenzene monitoring of chemical wastewater, which includes that after the porous nanofiber material is immersed in the chemical wastewater for 30-60 seconds, a fluorescence emission signal of the porous nanofiber material at 420nm is detected. And (3) calculating the fluorescence quenching rate of the nitrobenzene on the porous nanofiber material through a formula (I), and calculating the concentration of the nitrobenzene in the wastewater through a formula (II).

Q＝(F₀-F)/F₀ (I)

F₀/F＝Kc+b (II)

Wherein Q is fluorescence quenchingThe ratio F is the fluorescence intensity of the porous nanofiber material in the wastewater, F₀Is the initial fluorescence intensity of the porous nanofiber material itself; c is the concentration of nitrobenzene in the wastewater and the K and b values are obtained by making a standard curve.

The manufacturing method of the standard curve comprises the following steps: measuring the influence of nitrobenzene solutions with different concentrations on the fluorescence intensity of the porous nanofiber material as F₀and/F is a vertical coordinate, c is a horizontal coordinate, a standard curve is fitted through data processing, and a standard curve equation is obtained, wherein the slope of the equation is K, and the intercept is b.

Compared with the prior art, the invention has the following beneficial effects:

the novel porous nanofiber material with the fluorescence sensing function is prepared by an electrospinning technology, and the method is simple, easy, rapid, efficient, low in cost, good in universality and suitable for polymer matrixes and fluorescent agents of different types. The prepared novel porous nanofiber material has novel and unique one-dimensional nanofiber morphology and a two-stage porous structure, the detection limit of the material for monitoring p-nitrobenzene in wastewater is very low, and the detection can be realized by 0.03 mu g/L of nitrobenzene in water; the response time to nitrobenzene in the wastewater is short, and the shortest time is only 30 s; the material has excellent regeneration performance, can be repeatedly used for more than 20 times, still keeps the fluorescence intensity at more than 96 percent, and can be repeatedly used.

Drawings

The present invention will be described in further detail with reference to the accompanying drawings.

FIG. 1 is a transmission electron micrograph of the porous nanofiber material of example 1;

FIG. 2 is a transmission electron microscope image of the nanofiber material without added porogen in comparative example 4;

FIG. 3 is a standard curve chart for the calculation of nitrobenzene concentration in wastewater in test examples 1-8;

fig. 4 is a reproducibility characterization plot of the porous nanofiber material in example 1.

Detailed Description

In order that the invention may be more readily understood, the following detailed description of the invention is given, with reference to the accompanying examples and drawings, which are given by way of illustration only and are not intended to limit the scope of the invention.

In view of the problems that the method for monitoring nitrobenzene in the prior art has complicated process, higher cost and lower detection sensitivity and response sensitivity; the invention provides a method for preparing a porous nanofiber material with a fluorescence sensing function by an electrospinning technology, which is simple and rapid, has good universality, and has the characteristics of good stability, reproducibility and reproducibility, and high sensitivity and selectivity when used for monitoring nitrobenzene in chemical wastewater. The present invention has been made based on the above findings.

The test instrument employed in the present invention was as follows:

transmission electron microscopy: obtained by JEM-100CX type transmission electron microscope

Fluorescence emission signal: the measurement was carried out using a fluorescence spectrometer model F4500.

Examples

The raw material ratios in examples 1 to 6 and comparative examples 1 to 6 are shown in Table 1.

Example 1

The method for preparing the porous nanofiber material comprises the following steps:

s1, stirring a mixed solvent formed by 100 parts by weight of cellulose acetate, 8 parts by weight of 9-chloroanthracene, 50 parts by weight of PEG-4000 and 700 parts by weight of N, N-dimethylacetamide and acetone in a weight ratio of 1:2 for 30 minutes at the rotation speed of 300rpm under magnetic stirring at room temperature until the system is completely and uniformly mixed to prepare an electrospinning stock solution;

s2, placing the prepared electrospinning stock solution into a syringe of electrospinning equipment, and spraying the electrospinning stock solution onto the surface of a conductive glass substrate of a receiver to perform rotary and uniform coating under the conditions of room temperature, 15kV voltage and pushing speed of 1.0mL/h, wherein the distance between the needle of the syringe and the receiver is 15cm, the rotating speed of the receiver is 600r/min, the electrospinning time is 10min, and electrospinning nanofibers are formed on the surface of the conductive glass;

s3, placing the conductive glass attached with the electrospun nanofibers in an oven at 75 ℃ for drying for 12 hours, and removing the solvent to obtain the nanofiber material;

s4, soaking the nanofiber material in water for 25 hours to remove the pore-forming agent, and then placing the nanofiber material in an oven at 70 ℃ to dry for 9 hours to dry moisture, so as to obtain the porous nanofiber material.

The transmission electron microscope image of the prepared porous nanofiber material is shown in figure 1, and it can be seen from the image that the porous nanofiber material presents a one-dimensional nanofiber morphology and has a uniform secondary porous structure, and the fiber diameter is between 200 and 500 nm.

Example 2

The preparation method is the same as that of example 1, except that the raw material ratios listed in table 1 are adopted; the rotation speed in the step S1 is 260rpm, and the stirring time is 35 hours; the voltage in the step S2 is 20kV, the push speed is 1.2mL/h, the rotating speed of the receiver is 600r/min, the electrospinning time is 9min, the drying temperature in the step S3 is 68 ℃, and the drying time is 14 hours; the soaking time in the step S4 is 30 hours, the drying temperature is 75 ℃, and the drying time is 10 hours.

Example 3

The preparation method is the same as that of example 1, except that the raw material ratios listed in table 1 are adopted; the rotation speed in the step S1 is 320rpm, and the stirring time is 25 hours; the voltage in the step S2 is 15kV, the pushing speed is 0.8mL/h, the rotating speed of the receiver is 500r/min, the electrospinning time is 10min, the drying temperature in the step S3 is 70 ℃, and the drying time is 15 hours; the soaking time in the step S4 is 40 hours, the drying temperature is 80 ℃, and the drying time is 12 hours.

Example 4

The preparation method is the same as that of example 1, except that the raw material ratios listed in table 1 are adopted; the rotating speed in the step S1 is 400rpm, and the stirring time is 20 hours; the voltage in the step S2 is 16kV, the push speed is 1.0mL/h, the rotating speed of the receiver is 600r/min, the electrospinning time is 9min, the drying temperature in the step S3 is 70 ℃, and the drying time is 12 hours; the soaking time in the step S4 is 32 hours, the drying temperature is 76 ℃, and the drying time is 10 hours.

Example 5

The preparation method is the same as that of example 1, except that the raw material ratios listed in table 1 are adopted; the rotation speed in the step S1 is 350rpm, and the stirring time is 28 hours; the voltage in the step S2 is 12kV, the push speed is 1.3mL/h, the rotating speed of the receiver is 600r/min, the electrospinning time is 8min, the drying temperature in the step S3 is 75 ℃, and the drying time is 14 hours; the soaking time in the step S4 is 35 hours, the drying temperature is 80 ℃, and the drying time is 8 hours.

Example 6

The preparation method is the same as that of example 1, except that the raw material ratios listed in table 1 are adopted; the rotation speed in the step S1 is 300rpm, and the stirring time is 33 hours; the voltage in the step S2 is 20kV, the pushing speed is 1.5mL/h, the rotating speed of the receiver is 700r/min, the electrospinning time is 10min, the drying temperature in the step S3 is 70 ℃, and the drying time is 15 hours; the soaking time in the step S4 is 40 hours, the drying temperature is 72 ℃, and the drying time is 12 hours.

Comparative example 1

The preparation method is the same as example 1, except that the raw material ratios listed in table 1 are adopted.

Comparative example 2

The preparation method is the same as example 1, except that the raw material ratios listed in table 1 are adopted. .

Comparative example 3

Comparative example 4

The preparation method of the nanofiber material without adding the pore-foaming agent comprises the following steps:

s1, stirring a mixed solvent formed by 100 parts by weight of cellulose acetate, 8 parts by weight of 9-chloroanthracene and 700 parts by weight of N, N-dimethylacetamide and acetone according to a weight ratio of 1:2 at the room temperature under the magnetic stirring of a rotating speed of 300rpm for 230 minutes until the system is completely and uniformly mixed to prepare an electrospinning stock solution;

s2, placing the prepared electrospinning stock solution into a syringe of electrospinning equipment, and spraying the electrospinning stock solution onto the surface of a conductive glass substrate of a receiver to perform rotary and uniform coating under the conditions of room temperature, 20kV voltage and pushing speed of 1.0mL/h, wherein the distance between the needle of the syringe and the receiver is 15cm, the rotating speed of the receiver is 600r/min, the electrospinning time is 10min, and electrospinning nanofibers are formed on the surface of the conductive glass;

s3, placing the conductive glass attached with the electrospun nanofibers in an oven at 70 ℃ for drying for 12 hours, and removing the solvent to obtain the nonporous nanofiber material.

The transmission electron microscope image of the prepared nanofiber material is shown in figure 2, and it can be seen from the image that the nanofiber material presents a one-dimensional nanofiber morphology, the surface is smooth, and the fiber diameter is between 200 and 500 nm.

Comparative example 5

The preparation method of the porous nanofiber material by adopting the silica gel matrix comprises the following steps:

s1, stirring 100 parts by weight of tetraethoxysilane, 8 parts by weight of 9-chloroanthracene and 700 parts by weight of a mixed solvent formed by N, N-dimethylacetamide and acetone according to a weight ratio of 1:2 at room temperature for 30 minutes under the magnetic stirring at the rotating speed of 200rpm until the system is completely and uniformly mixed; then adding 14 parts by weight of 0.3mol/L hydrochloric acid solution, heating at 75 ℃ for 30min to hydrolyze tetraethoxysilane to obtain high molecular silica gel, and continuing stirring at room temperature for 12h to prepare electrospinning stock solution;

s3, placing the conductive glass attached with the electrospun nanofibers in an oven at 70 ℃ for drying for 12 hours, and removing the solvent to obtain the silica gel matrix nanofiber material;

s4, soaking the silica gel matrix nanofiber material in water for 24 hours to remove a pore-forming agent, and then placing the material in an oven at 80 ℃ to dry for 8 hours to dry moisture, so as to prepare the porous nanofiber material.

Through the electronic competition scanning, the silica gel matrix porous nanofiber material presents a one-dimensional nanofiber shape and has a two-stage porous structure, and the fiber diameter is between 200 and 500 nm.

Comparative example 6

The porous material is prepared by adopting a coating technology, and the method comprises the following steps:

s1, stirring a mixed solvent formed by 100 parts by weight of cellulose acetate, 8 parts by weight of 9-chloroanthracene and 700 parts by weight of N, N-dimethylacetamide and acetone according to a weight ratio of 1:2 at room temperature for 30 minutes under the magnetic stirring at the rotating speed of 300rpm until the system is completely and uniformly mixed to prepare a coating stock solution;

s2, directly dripping the prepared coating stock solution on the conductive glass to form a film on the surface of the conductive glass;

and S3, placing the conductive glass attached with the film in an oven at 70 ℃ for drying for 12 hours, and removing the solvent to obtain the continuous and compact film material.

S4, soaking the continuous and compact fluorescence sensing film material in water for 24 hours to remove a pore-forming agent, and then placing the film material in an oven at 80 ℃ to dry for 8 hours to dry moisture, so as to prepare the porous film material.

Test example 1

The fluorescence intensity F at 420nm of the porous nanofiber material prepared in example 1 was measured₀Then, the porous nanofiber material is immersed in chemical wastewater X with the nitrobenzene content of 0.03 mu g/L for 30 seconds, and the fluorescence intensity F of the porous nanofiber material at the 420nm position is detected. The fluorescence quenching rate Q of the porous nanofiber material by the nitrobenzene is calculated by the formula (I), the concentration c of the nitrobenzene in the wastewater is calculated by the formula (II), and the calculation result is shown in Table 1.

The fluorescence intensity F at 420nm of the porous nanofiber material prepared in example 1 was measured₀And then soaking the porous nanofiber material in chemical wastewater Y with the nitrobenzene content of 0.06 mu g/L for 40 seconds, and detecting the fluorescence intensity F of the porous nanofiber material at 420 nm. The fluorescence quenching rate Q of the porous nanofiber material by the nitrobenzene is calculated by the formula (I), the concentration c of the nitrobenzene in the wastewater is calculated by the formula (II), and the calculation result is shown in Table 1.

Q＝(F₀-F)/F₀ (I)

F₀/F＝Kc+b (II)

For the porous nanofiber materials prepared in examples 1-6, K is 28.545-28.553; and b is 0.255-0.264, and the average value of K and b is taken during calculation.

Test examples 2 to 6

The test method was the same as in test example 1 except that the porous nanofiber materials prepared in examples 2 to 6 were used, respectively, and the results are shown in table 2.

Test examples 7 to 9

The test method was the same as in test example 1 except that the porous nanofiber materials prepared in comparative examples 1 to 3 were used, respectively, and the results are shown in table 2.

Test example 10

The test method was the same as in test example 1, except that the non-porous nanofiber material prepared in comparative example 4 was used, and the results are shown in table 2.

Test example 11

The test method was the same as in test example 1, except that the silica gel matrix porous nanofiber material prepared in comparative example 5 was used, and the results are shown in table 2.

Test example 12

The test method was the same as in test example 1 except that the porous film material prepared in comparative example 6 was used, and the results are shown in Table 2.

Reproducibility test of the porous nanofiber material of the present invention:

the fluorescence intensity F at 420nm of the porous nanofiber material prepared in example 1 was measured₀Then, after immersing it in chemical wastewater X having a nitrobenzene content of 0.03. mu.g/L for 30 seconds, the fluorescence intensity F at 420nm was recorded. It was then heated at 60 ℃ for 20 minutes to recover its fluorescence and its fluorescence intensity was recordedF'. This was repeated for 20 quench-regeneration cycles. The results are shown in FIG. 4.

TABLE 1 raw material ratios of examples and comparative examples

Table 2 results of monitoring nitrobenzene in wastewater for materials prepared in examples and comparative examples

As can be seen from the comparison of the results of the materials prepared in the examples and comparative examples in Table 2 in the monitoring of nitrobenzene in chemical wastewater, the novel porous nanofiber material prepared by the electrospinning technology has a novel and unique two-stage porous structure nanofiber morphology, so that the detection limit of nitrobenzene in wastewater is very low, and the detection of 0.03 mu g/L nitrobenzene in water can be realized. In contrast, if the polymer matrix material is replaced by a macromolecular silica gel matrix (comparative example 5), or the sensing material is prepared by a coating method instead of an electrospinning technology (comparative example 6), the detection capability of the prepared sensing material on nitrobenzene in wastewater is far inferior to that of the electrospun porous nanofiber material in the embodiment of the invention.

By comparing the test results of the example 1 and the comparative examples 1 and 2, it is found that when the amount of the fluorescent agent is too low or the amount of the mixed solvent is too large, not only the concentration of the fluorescent agent is reduced, but also the morphology of the prepared porous nanofiber material is changed, so that the detection capability of the porous nanofiber material on nitrobenzene is reduced, and the nitrobenzene of 0.03 mu g/L in the water body cannot be detected.

By comparing the test results of example 1 and comparative example 3, it is found that too little porogen causes the detection capability of the material p-nitrobenzene to be reduced; and the pore-foaming agent is used in an excessive amount, so that the detection capability of the p-nitrobenzene is not improved, and the preparation cost is increased.

Therefore, in the present invention, it is preferable that the amount of the fluorescent agent is 5 to 10 parts by weight, the amount of the mixed solvent is 400 to 1000 parts by weight, and the amount of the porogen is 25 to 100 parts by weight, relative to 100 parts by weight of the polymer matrix.

By comparing test example 1 and test example 9, it was found that the porous nanofiber material of the present application (example 1) has better flexibility density and lower detection limit of nitrobenzene in the monitoring of nitrobenzene in chemical wastewater compared with the non-porous nanofiber material (comparative example 4).

The reproducibility test of the porous nanofiber material proves that the novel porous nanofiber material prepared by the invention can be repeatedly used and has excellent reproducibility. As can be seen from the attached FIG. 4, after 20 cycles of regeneration, the fluorescence intensity is still maintained above 96%, and thus, the fluorescence intensity of the material is kept stable and can be recycled. The nitrobenzene molecules are volatile, so that target molecules can be effectively separated from the porous nanofiber material in a heating mode, and the fluorescent agent is kept stable in the process and free of leakage and dark bleaching, so that the fluorescence of the material is ideally recovered and regenerated.

It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.

Claims

1. The application of the porous nanofiber material in monitoring of nitrobenzene in chemical wastewater comprises the following steps:

i) after the porous nanofiber material is immersed in chemical wastewater for 30-60 seconds, detecting a fluorescence emission signal F of the porous nanofiber material at a 420nm position;

II) calculating the fluorescence quenching rate Q of the porous nanofiber material by using a formula (I), and calculating the concentration c of nitrobenzene in the wastewater by using a formula (II);

Q＝(F₀-F)/F₀ (I)

F₀/F＝Kc+b (II)；

wherein, F₀Is the initial fluorescence intensity of the porous nanofiber material itself; the K and b values are obtained by making a standard curve, and the making method of the standard curve comprises the following steps: measuring the influence of nitrobenzene solutions with different concentrations on the fluorescence intensity of the porous nanofiber material as F₀Fitting a standard curve through data processing to obtain a standard curve equation, wherein F is a vertical coordinate, c is a horizontal coordinate, the slope of the equation is K, and the intercept is b;

wherein the porous nanofibrous material comprises a polymer matrix and a fluorescer, the porous nanofibrous material having a one-dimensional nanofibrous morphology and a secondary porous structure, the polymer matrix comprising a cellulose organic acid ester; the phosphor comprises an anthracene-based phosphor;

in the electrospinning stock solution for preparing the porous nanofiber material, relative to 100 parts by weight of the polymer matrix, the dosage of the fluorescent agent is 5-10 parts by weight, the dosage of the mixed solvent is 400-1000 parts by weight, and the dosage of the pore-forming agent is 25-100 parts by weight.

2. The use according to claim 1, wherein the diameter of the nanofibers is 200-600 nm.

3. Use according to claim 2, wherein the fluorescent agent is present in an amount of 5-8 parts by weight, based on 100 parts by weight of the polymer matrix.

4. Use according to claim 3, wherein the fluorescent agent is present in an amount of 6 to 8 parts by weight, based on 100 parts by weight of the polymer matrix.

5. The use of any one of claims 1-4, wherein the polymer matrix comprises at least one of cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose acetate succinate.

6. The use according to any one of claims 1 to 4, wherein said fluorescer comprises at least one of 9-chloroanthracene, 9-anthracenal, 9-anthracenemethanol, 9-methylanthracene, 9-acetylanthracene, 9-bromoanthracene and 9-vinylanthracene.

7. The use according to any one of claims 1 to 4, wherein the porous nanofibrous material is prepared by a preparation method comprising the steps of:

s1, mixing the polymer matrix, the fluorescent agent, the pore-forming agent and the solvent to prepare an electrospinning stock solution;

s3, removing the solvent in the electrospun nanofiber to obtain the nanofiber;

8. The use according to claim 7, wherein the solvent comprises a mixed solvent of solvent I and solvent II.

9. The use according to claim 8, wherein the solvent I comprises an amide polar solvent and the solvent II comprises a ketone polar solvent.

10. The use according to claim 9, wherein the solvent I comprises at least one of N, N dimethylacetamide, N dimethylformamide, N-dimethylpropionamide, N-diethylacetamide, N-methylacetamide or N-ethylacetamide, and the solvent II comprises at least one of acetone, cyclohexanone, methyl ethyl ketone or methyl isobutyl ketone.

11. The use of claim 7, wherein the porogen comprises at least one of a polyethylene glycol and an alkylphenol polyoxyethylene ether; the polymerization degree of the alkylphenol polyoxyethylene ether is 8-20, and the alkyl is C6-C15.

12. The use as claimed in claim 11, wherein the polyethylene glycol has a molecular weight of 2000-6000; the alkylphenol polyoxyethylene ether is selected from at least one of octyl phenol polyoxyethylene ether, nonyl phenol polyoxyethylene ether or polyethylene glycol octyl phenyl ether.

13. The use according to claim 7, wherein the electrospinning dope contains 5 to 10 parts by weight of the fluorescer and 400 to 1000 parts by weight of the solvent based on 100 parts by weight of the polymer matrix; the content of the pore-foaming agent is 25-100 parts by weight.

14. The use according to claim 13, wherein the electrospinning dope contains 6 to 8 parts by weight of the fluorescer and 500 to 800 parts by weight of the solvent based on 100 parts by weight of the polymer matrix; the content of the pore-foaming agent is 40-80 parts by weight.

15. The use according to claim 14, wherein the mass ratio of the solvent I to the solvent II in the solvent is 1 (1-4).

16. The use according to claim 15, wherein the mass ratio of solvent I to solvent II in the solvent is 1: (1.5-3).

17. The application of claim 7, wherein in step S2, the electrospinning device comprises a syringe and a receiver, the syringe is pushed at a speed of 0.8-1.5mL/h, and the receiver is rotated at a speed of 500-700 r/min; the distance between the needle of the injector and the receiver is 12-18cm, the voltage of the electrospinning is 10-20kV, and the electrospinning time is 8-10 min.

18. The use according to claim 7, wherein in step S3, the solvent is removed by drying at 60-80 deg.C for 10-15 hr.

19. The use of claim 7, wherein in step S4, the nanofibers are soaked to remove the porogen, and then dried to obtain the porous nanofiber material; the soaking time is 30-40 hours, the drying temperature is 60-80 ℃, and the drying time is 6-12 hours.