CN113509793A

CN113509793A - Preparation method of composite nanofiber filtering membrane for removing formaldehyde

Info

Publication number: CN113509793A
Application number: CN202010273385.4A
Authority: CN
Inventors: 高婷婷; 郭国良
Original assignee: Ningbo Fotile Kitchen Ware Co Ltd
Current assignee: Ningbo Fotile Kitchen Ware Co Ltd
Priority date: 2020-04-09
Filing date: 2020-04-09
Publication date: 2021-10-19

Abstract

A preparation method of a composite nanofiber filtering membrane for removing formaldehyde is characterized by comprising the following steps: dissolving a polymer in an organic solvent, adding chloroplatinic acid into the solution after the polymer is completely dissolved, uniformly stirring, and filling the solution into an injector for electrostatic spinning to obtain nano fibers; secondly, putting the nano-fibers into an activating agent, taking out the activated nano-fibers for unfolding, and naturally airing or drying the nano-fibers; thirdly, the nanofiber membrane is tiled on the PET aggregate non-woven fabric, the surface of the PET aggregate non-woven fabric is covered with a layer of PP non-woven fabric, and the periphery of the PET aggregate non-woven fabric is fixed by a hot-melt net membrane through hot pressing, so that the composite nanofiber filter membrane is obtained. The formaldehyde catalyst is loaded on the nano fibers and is made into a composite filtering membrane with PET and non-woven fabrics, formaldehyde removal and particulate matter filtering are efficiently combined into a whole, two pollutants are compositely treated by one filtering screen, and the effective utilization rate of the formaldehyde catalyst can be greatly improved.

Description

Preparation method of composite nanofiber filtering membrane for removing formaldehyde

Technical Field

The invention relates to an air filtering material, in particular to a preparation method of an air filtering membrane.

Background

The current air quality safety problem has threatened people now, and the particulate matter is air pollution's main primitive and fiercely, causes the haze weather to appear in many areas, seriously threatens human health. Many households choose to purchase air purifiers to ensure daily respiratory safety. The most central part of the air purifier is a filter assembly, most of the filter assemblies on the market are high-efficiency air filters at present, the core medium of the filter assemblies is generally an ultrafine glass fiber membrane or a melt-blown fiber non-woven fabric, although the filter assemblies have higher filtering efficiency, the air resistance can be increased sharply along with the increase of dust holding capacity in the using process, and thus, a large amount of energy is consumed. In addition, glass fibers have poor folding resistance, are easily broken during processing and use, and have the possibility of causing cancer while affecting filtration efficiency. The nanofiber has excellent properties of large specific surface area, low density, high porosity, good bonding property among pores, easy combination with nano-sized active substances, low resistance, low gram weight and the like, so that the nanofiber has better intrinsic filtering effect and is widely concerned and researched in academia and industry. The method for preparing the nano-fiber has a plurality of methods, wherein the electrostatic spinning method is widely applied by the advantages of simple operation, wide application range, relatively high production efficiency and the like, and is a method capable of directly and continuously preparing the polymer nano-fiber.

In recent years, formaldehyde emitted from indoor decoration has attracted much attention as a key factor affecting the health and comfort of living environment of people, and the current methods for removing formaldehyde include physical adsorption methods, chemical methods (photocatalytic oxidation methods, plasma methods and the like) and ventilation methods. The release period of formaldehyde in the indoor air is 3-5 years, the concentration is low, the problems of energy consumption, removal rate, airspeed and the like exist by selecting a single physical or chemical method, the ventilation also needs a long-time slow action, and the traditional treatment processes are not suitable for treating indoor air pollution. The related catalytic particles are generally selected from alumina ceramics, activated carbon and the like, and have the defects of large volume and heavy weight, and meanwhile, the catalyst is not uniformly distributed and has low utilization rate.

The prior art discloses a fiber membrane capable of decomposing formaldehyde, and Chinese patent application with application number of 201811025215.3 discloses a nanofiber membrane material capable of decomposing formaldehyde at normal temperature, a preparation method and application thereof (publication number of CN 109012164A).

Disclosure of Invention

The first technical problem to be solved by the present invention is to provide a method for preparing a composite nanofiber filtration membrane with a good formaldehyde removal effect, aiming at the above technical current situation.

The second technical problem to be solved by the present invention is to provide a method for preparing a composite nanofiber filter membrane integrating formaldehyde removal and particulate matter filtration.

The technical scheme adopted by the invention for solving the technical problems is as follows: a preparation method of a composite nanofiber filtering membrane for removing formaldehyde is characterized by comprising the following steps:

dissolving a polymer in an organic solvent to prepare a solution with the weight percentage of 5-20%, preferably 40-80 ℃, and the viscosity of 200-2000 mPa & s, adding chloroplatinic acid with the weight percentage of 0.5-5% after complete dissolution, putting the solution into the solution, stirring uniformly, and putting the solution into an injector for electrostatic spinning to obtain nano fibers; the polymer is at least one of polyacrylonitrile, polystyrene, polyvinylidene fluoride, nylon, polycarbonate and polyether sulfone;

putting the nano-fibers into an activating agent, taking out the activated nano-fibers for unfolding, and naturally airing or drying the activated nano-fibers at a preferred temperature of 30-50 ℃;

thirdly, the nanofiber membrane is tiled on the PET aggregate non-woven fabric, the surface of the PET aggregate non-woven fabric is covered with a layer of PP non-woven fabric, and the periphery of the PET aggregate non-woven fabric is fixed by a hot-melt net membrane through hot pressing, so that the composite nanofiber filter membrane is obtained.

The organic solvent is at least one of N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide and acetone.

Preferably, the activation conditions in step (ii) are as follows: activating in water bath for 0.5-5 h at the temperature of 60-90 ℃.

Preferably, the activating agent in the step (II) is at least one of basic sodium borohydride, basic potassium borohydride, formaldehyde, formic acid and ethylene glycol.

Preferably, the activating agent is a mixed solution of alkaline sodium borohydride and alkaline potassium borohydride, the concentration of hydroxide ions is 0.01-5M/L, and the concentration of sodium borohydride is 0.01-0.5M/L; the concentration of the potassium borohydride is 0.01-0.5M/L, the molar ratio of the activating agent to the platinum is 5-100: 1.

preferably, the activating agent is at least one of formaldehyde, formic acid or ethylene glycol, and the molar ratio of the activating agent to platinum is 1: 1-50: 1.

Preferably, the hot melt net film in the third step is made of at least one of EVA ethylene vinyl acetate copolymer, PA nylon, and TPU polyurethane.

Preferably, the electrospinning conditions in step (i) are as follows: the spinning parameter voltage is adjusted to be 7-26 kv, the distance between the needle end of the injector and the collector is 5-25 cm, the injection speed is 5-200 ul/min, the rotating speed of the collector is 300-3000 rpm, the spinning temperature is 20-30 ℃, and the humidity is 40-70%.

Compared with the prior art, the invention has the advantages that: the catalyst chloroplatinic acid is added into the polymer to prepare an electrostatic spinning solution, the nanofiber membrane is obtained through electrostatic spinning, the nanofiber membrane, PET and non-woven fabric are made into a composite filtering membrane, and the chloroplatinic acid exists on the nanofiber membrane in fine dispersed platinum after subsequent reduction. The formaldehyde removal and the particulate matter filtration are efficiently combined into a whole, so that the two pollutants are treated by one filter screen.

Drawings

Fig. 1 is a schematic view of the layered structure of the composite nanofiber membrane of example 1.

FIG. 2 is a SEM photograph of example 1.

FIG. 3 is a TEM photograph of example 1.

FIG. 4 is a SEM photograph of example 2.

FIG. 5 is a TEM photograph of example 2.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

Example 1, spinning of nanofibers: adding 4.5g of polyvinylidene fluoride PVDFF into 50mLN, N-dimethylformamide DMF, stirring for 4h at 70 ℃, wherein the rotation speed is 200r/min, preparing 8% PAN solution, the solution is light yellow, then adding 0.15g of chloroplatinic acid into the solution, stirring uniformly, defoaming or standing for 12h before spinning, then injecting the prepared solution into an injector for spinning, wherein the spinning parameter temperature is 25 ℃, the humidity is 50%, the distance from a nozzle tip to a receiving end is 10cm, the rotation speed of the receiving end is 500rpm, the injection speed is 50ul/min, the voltage is 14KV, and spinning is carried out for 1h to obtain the PVDF nanofiber loaded with Pt ions.

0.04g NaOH and 0.2g potassium borohydride are added into deionized water to prepare 100ml activating agent, and then 0.5g of the fiber membrane is put into a conical flask. Putting the conical flask into a water bath kettle, and heating for 1h at 70 ℃.

Preparing a composite nanofiber membrane: the nanofiber membrane is laid on PET (polyethylene terephthalate) aggregate non-woven fabric and dried at 50 ℃. Then covering a layer of thin PP non-woven fabric on the surface of the nanofiber membrane, and fixing the periphery of the nanofiber membrane by using an EVA (ethylene vinyl acetate) hot-melt net membrane through hot pressing to obtain the composite nanofiber membrane.

Referring to fig. 1, the obtained composite nanofiber membrane sequentially comprises a PP non-woven fabric 1, a hot-melt net film 2, a nanofiber 3, a hot-melt net film 2 and a PET aggregate 4 from top to bottom, the PP non-woven fabric plays a role of a protective layer, and the PET aggregate 4 plays a role of a support layer. The filtration efficiency and the pressure drop of the PP non-woven fabric and the PET aggregate 4 non-woven fabric are very small and can be ignored, namely, the filtration performance of the composite nanofiber membrane, namely the filtration performance of the core layer nanofiber 3.

FIG. 2 shows that the diameter of the nanofibers of the PAN in this embodiment is 50-150 nm, the fibers are flat, and the diameter distribution is narrow. The small black dots in fig. 3 are reduced Pt, and it can be seen that the Pt particles have good dispersibility, are not agglomerated into large particles, and have a high uniformly distributed loading rate.

By compositional testing EDS (X-ray spectroscopy), it was shown that the mass concentration of Pt was 2.82%, close to the theoretical calculation, indicating maximum utilization of Pt.

Element(s)	Atomic mass ratio%	The atomic number and the specific gravity%
			C	74.42	83.11
O	14.14	11.85
			Na	07.74	04.51
Cl	00.88	00.33
			Pt	02.82	00.19

And (3) performance testing:

filtration performance of composite nanofiber membrane particulate:

the filtering performance of the composite nanofiber membrane is tested by adopting a TSI 8130 type automatic filter material tester, a sample is in a circular shape with the area of 10cm2, NaCl aerosol with the mass median diameter of particle particles of 0.26um is generated, and the air flow speed is 32L/min.

The penetration rate k of the particles is obtained by testing the concentration of the particles at two ends of the membrane, and then the filtration efficiency eta is obtained

C1 for downstream aerosol concentration and C2 for upstream aerosol concentration

The formaldehyde removing capacity and formaldehyde catalysis performance of the composite nanofiber membrane are as follows:

about 0.1g of nanofiber loaded with formaldehyde catalyst is put into a sample tube, the gas flow of the system is 300ml/min, the inlet gas concentration of formaldehyde is c0, and the relative humidity is 55%. Detecting the concentration c of formaldehyde at the outlet of the pipeline by using a PMP formaldehyde analyzer, detecting the stable concentration of the outlet, and calculating the formaldehyde removal rate according to the following formula:

in this example, the efficiency of catalytic decomposition of formaldehyde in the sample was 75% when the inlet concentration was 5 ppm. The removal rate of PM0.3 particulate matter is 97.85%, and the pressure drop is 88 pa.

Example 2, spinning of nanofibers: adding polyacrylonitrile PAN6g into 50mLN, N-Dimethylacetamide (DMAC), stirring for 4 hours at 70 ℃ at the rotating speed of 200r/min to prepare a 12% PAN solution, wherein the solution is light yellow, adding 0.6g of chloroplatinic acid into the solution, stirring uniformly, defoaming or standing for 12 hours before spinning, injecting the prepared solution into an injector for spinning, wherein the spinning parameter temperature is 25 ℃, the humidity is 50%, the distance from the nozzle tip to a receiving end is 10cm, the rotating speed of the receiving end is 500rpm, the injection speed is 10ul/min, the voltage is 11KV, and spinning is carried out for 1 hour to obtain the PAN nanofiber loaded with Pt ions.

0.1g of NaOH and 0.5g of potassium borohydride are added into deionized water to prepare 100ml of activating agent, and then 1g of the fiber membrane is placed into a conical flask. Putting the conical flask into a water bath kettle, and heating for 1h at 70 ℃.

Preparing a composite nanofiber membrane: and (3) flatly paving the nanofiber membrane on PET aggregate non-woven fabric, and drying at 50 ℃. Then covering a layer of thin PP non-woven fabric on the surface of the nanofiber membrane, and fixing the periphery of the nanofiber membrane by using an EVA (ethylene vinyl acetate) hot-melt net membrane through hot pressing to obtain the composite nanofiber membrane.

FIG. 4 shows that the diameter of the nanofibers of the PAN in this embodiment is 500-1000 nm, the fibers are flat, and the diameter distribution is narrow. The small black dots in fig. 5 are reduced Pt, and it can be seen that the Pt particles have good dispersibility, are not agglomerated into large particles, and have a high uniformly distributed loading rate.

By the composition test EDS, the mass concentration of Pt was shown to be 9.73%, which is close to the theoretical calculation, indicating that Pt is maximally utilized.

Element(s)	Atomic mass ratio%	The atomic number and the specific gravity%
			C	85.84	96.26
O	2.51	2.12
			Na	1.1	0.64
Cl	00.81	00.31
			Pt	09.73	00.67

And (3) performance testing: in this example, the efficiency of catalytic decomposition of formaldehyde in the sample is 98% when the inlet concentration is 5 ppm. The removal rate of PM0.3 particulate matter is 97.85%, and the pressure drop is 88 pa.

Claims

1. A preparation method of a composite nanofiber filtering membrane for removing formaldehyde is characterized by comprising the following steps:

dissolving a polymer in an organic solvent to prepare a solution with the viscosity of 200-2000 mPa & s of 5-20% by weight, adding chloroplatinic acid with the weight of 0.5-5% after the polymer is completely dissolved, putting the solution into the solution, uniformly stirring, and putting the solution into an injector for electrostatic spinning to obtain nano fibers; the polymer is at least one of polyacrylonitrile, polystyrene, polyvinylidene fluoride, nylon, polycarbonate and polyether sulfone;

secondly, putting the nano-fibers into an activating agent, taking out the activated nano-fibers for unfolding, and naturally airing or drying the nano-fibers;

2. The process according to claim 1, wherein the organic solvent used in the step (i) is at least one selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, and acetone.

3. The method according to claim 1, wherein the activation conditions in step (ii) are as follows: activating in water bath for 0.5-5 h at the temperature of 60-90 ℃.

4. The method according to claim 1, wherein the activating agent in step (ii) is at least one of basic sodium borohydride, basic potassium borohydride, formaldehyde, formic acid, and ethylene glycol.

5. The preparation method according to claim 4, wherein the activating agent is a mixture of alkaline sodium borohydride and alkaline potassium borohydride, the concentration of hydroxide ions is 0.01-5M/L, and the concentration of sodium borohydride is 0.01-0.5M/L; the concentration of the potassium borohydride is 0.01-0.5M/L, the molar ratio of the activating agent to the platinum is 5-100: 1.

6. the preparation method according to claim 4, wherein the activator is at least one of formaldehyde, formic acid or ethylene glycol, and the molar ratio of the activator to platinum is 1:1 to 50: 1.

7. The method according to claim 1, wherein the hot melt net film in step (c) is made of at least one of EVA-ethylene-vinyl acetate copolymer, PA nylon, and TPU polyurethane.

8. The production method according to claim 1, wherein the electrospinning conditions in step (i) are as follows: the spinning parameter voltage is adjusted to be 7-26 kv, the distance between the needle end of the injector and the collector is 5-25 cm, the injection speed is 5-200 ul/min, the rotating speed of the collector is 300-3000 rpm, the spinning temperature is 20-30 ℃, and the humidity is 40-70%.