CN113952845B

CN113952845B - Membrane filter material, preparation method thereof and application of membrane filter material in treating aerosol

Info

Publication number: CN113952845B
Application number: CN202111305418.XA
Authority: CN
Inventors: 赵园; 曾献; 邹青; 胡宸; 罗益玮; 段承杰; 林继铭
Original assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd; CGN Power Co Ltd; Lingdong Nuclear Power Co Ltd
Current assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd; CGN Power Co Ltd; Lingdong Nuclear Power Co Ltd
Priority date: 2021-11-05
Filing date: 2021-11-05
Publication date: 2022-07-15
Anticipated expiration: 2041-11-05
Also published as: WO2023077673A1; CN113952845A

Abstract

The invention discloses a membrane filter material, a preparation method thereof and application of the membrane filter material in treating aerosol. The preparation method is based on sol-gel electrostatic spinning and heat treatment processes, firstly, polyvinyl alcohol/tetraethyl orthosilicate/ferric salt are prepared to form sol-gel precursor liquid, then, precursor fiber is obtained through electrostatic spinning, and the precursor fiber is calcined in reducing atmosphere to remove organic matters and Fe on the surface of hybrid fiber₂O₃Reducing to Fe to obtain flexible Fe/Fe₂O₃/SiO₂A hybrid nanofiber membrane. The preparation method is low in preparation cost and simple to operate, and the prepared inorganic nanofiber membrane can efficiently filter aerosol under a high-temperature condition, and particularly has the efficiency of filtering polonium aerosol up to 99%.

Description

Membrane filter material, preparation method thereof and application of membrane filter material in treating aerosol

Technical Field

The invention relates to the technical field of aerosol treatment, in particular to a membrane filter material, a preparation method thereof and application of the membrane filter material in treating aerosol.

Background

The aerosol is a multiphase system formed by the atmosphere and solid and liquid particles suspended in the atmosphere, and the harmful aerosol loaded with harmful substances can be transmitted in a long distance under the action of a wind system, so that the harmful aerosol not only causes serious harm to the living environment of human beings, but also can affect global climate change. Radioactive aerosol is a strong hazardous gas containing radioactive nuclideColloidal sols, inhaled by humans or animals, can cause serious internal radiation hazards, which can further harm the ecosystem if discharged into the atmosphere without treatment. Under some special working conditions, the filtering material for treating radioactive aerosol needs to have the characteristic of high temperature resistance, for example, when the covering gas seal of the lead-based fast reactor of the nuclear energy system fails, argon carrying polonium aerosol is rapidly released into a reactor top containing chamber in a short time, and simultaneously a large amount of heat is released, so that the common filtering material cannot be effectively purified or even melts under the temperature environment, and the purifying capacity is completely lost. CN204294017U discloses a nuclear island air filter for treating radioactive aerosol, which is fixed to a box body by an adhesive, and the adhesive is melted under high temperature conditions, so that the filter is not suitable for operating under high temperature environment. CN106128538A discloses a method for removing lead-based fast reactor or ADS subcritical system²¹⁰The device mainly comprises a ceramic filter membrane, glass fiber, filter cloth and the like, wherein the filter membrane contains rare earth components, and the filtering cost is relatively high. CN106757528B discloses an ultra-low density silica fluffy fiber and a preparation method thereof, the prepared silica fiber has the advantages of high temperature resistance and high filtration precision, the electrostatic spinning technology required by the method is simple to operate and low in cost, but the affinity of the general silica fiber and nuclide is relatively weak.

Based on this, there is a need to develop a process for preparing a high temperature-resistant, high-filtration-efficiency and low-cost membrane filter material for treating aerosols, especially for treating radioactive polonium and other nuclide aerosols at high temperature for air purification in nuclear power plants, and at the same time, the membrane filter material also has a filtration effect on other harmful aerosols for purifying the atmosphere.

Disclosure of Invention

One of the objectives of the present invention is to provide a membrane filter material with high temperature resistance, high filtering precision and high polonium affinity and a preparation process thereof. The object can be achieved by the following technical scheme.

The invention provides a preparation method of a membrane filter material, which comprises the following steps:

mixing polyvinyl alcohol with water to prepare a PVA aqueous solution;

mixing water, tetraethyl silicate and phosphoric acid, and hydrolyzing to prepare Si hydrolysate;

mixing the Si hydrolysate with ferric salt to prepare Si/Fe hydrolysate;

mixing the PVA aqueous solution and the Si/Fe hydrolysate, and aging to prepare a spinning precursor solution;

performing electrostatic spinning on the spinning precursor liquid to prepare a precursor nanofiber membrane;

drying the precursor nanofiber membrane, and calcining in a reducing atmosphere to prepare Fe/Fe₂O₃/SiO₂A hybrid nanofiber membrane.

In some embodiments of the invention, in the method of making the membrane filter material,

the PVA aqueous solution contains 5-20 wt% of polyvinyl alcohol; and/or the like, and/or,

in the step of mixing the water, the tetraethyl silicate and the phosphoric acid, the molar ratio of the water to the tetraethyl silicate to the phosphoric acid is (5-20) to 1 (0.005-0.015); and/or the hydrolysis time of the hydrolysis is 4-18 h;

in the step of mixing the Si hydrolysate and the ferric salt, the molar ratio of Si to Fe is (2-16): 1; and/or the ferric salt is ferric nitrate, ferric chloride or a combination thereof; and/or the like, and/or,

and mixing the PVA aqueous solution and the Si/Fe hydrolysate, wherein in the aging step, the mass ratio of the PVA aqueous solution to the Si/Fe hydrolysate is 1 (0.5-2.5), the aging is standing, and the aging time is 4-24 h.

the molar ratio of Si to Fe is (2-8): 1; and/or the like, and/or,

the mass ratio of the PVA aqueous solution to the Si/Fe hydrolysate is 1 (0.5-1.5).

In some embodiments of the present invention, in the preparation method of the membrane filter material, the aging is normal temperature aging, the aging temperature is 20 ℃ to 30 ℃, and the aging time is 6h to 24 h; alternatively, the first and second electrodes may be,

the aging is water bath aging, the aging temperature is 40-70 ℃, and the aging time is 4-20 h.

In some embodiments of the invention, in the method for preparing a membrane filter material, the parameters for performing the electrostatic spinning include: the receiving distance is 5 cm-25 cm, and/or the injection speed is 0.8 mL/h-3 mL/h, and/or the voltage is 6 kV-15 kV.

in the step of drying and calcining the precursor nanofiber film in a reducing atmosphere,

the drying temperature is 60-100 ℃, the drying time is 4-8 h, and/or,

the reducing atmosphere is a mixed atmosphere of hydrogen and inert gas, and/or,

the calcining temperature of the calcining is 350-800 ℃, and the calcining time is 1-8 h.

In some embodiments of the present invention, in the preparation method of the membrane filter material, the concentration of the hydrogen is 5%, the inert gas is selected from nitrogen or argon, the calcination temperature is 450 ℃ to 700 ℃, and the calcination time is 2h to 8 h.

In a second aspect, the invention provides a membrane filter material prepared according to the preparation method provided in the first aspect of the invention.

A third aspect of the invention provides the use of a membrane filter material as provided in the second aspect of the invention in the treatment of an aerosol selected from a polonium aerosol, an iodine aerosol or a lead bismuth aerosol.

In some embodiments of the invention, the membrane filter material treats the aerosol at 25 ℃ to 450 ℃.

The invention provides a preparation method of a membrane filter material, which adopts the technical means of combining a sol-gel electrostatic spinning process and a heat treatment process to form a sol-gel by using polyvinyl alcohol/tetraethyl orthosilicate/ferric saltPrecursor liquid, and calcining in reducing atmosphere to remove organic matter and Fe on the surface of hybrid fiber₂O₃Reduction to Fe, Fe/Fe₂O₃/SiO₂The hybrid nanofiber membrane has an excellent combination of high temperature resistance and high affinity for polonium. Wherein, the high-efficiency filtration of more than 98 percent can be realized within the high-temperature range of 300-400 ℃, and the filtration efficiency can even reach more than 99 percent.

The inventors found that the incorporation of Fe element can improve SiO₂Nanofibers filter polonium aerosol but also result in poor spinnability of the precursor liquid and increased fiber fragility. In some preferred embodiments of the present invention, the problems of poor spinnability and increased fiber brittleness of the precursor liquid can be solved by adjusting the process conditions such as the type of iron salt, the Si/Fe ratio, the spinning parameters, and the calcination temperature.

The electrostatic spinning device is simple to operate, the spinning cost is low, the spinning process is controllable, and the electrostatic spinning device is adopted to prepare the membrane filtering material, so that the filtering cost can be reduced while the filtering requirement is met. Moreover, the fiber prepared by electrostatic spinning has the characteristics of large specific surface area, small pore size and high porosity, so that the fiber still has excellent filtering precision and lower pressure drop for the aerogel with the particle size below the submicron level.

The Fe/Fe provided by the invention₂O₃/SiO₂The hybrid nanofiber membrane is a flexible inorganic nanofiber membrane and has the characteristics of high temperature resistance, high filtering precision and high polonium affinity.

The Fe/Fe provided by the invention is applied₂O₃/SiO₂The hybrid nanofiber membrane is capable of filtering polonium aerosols in gases at high temperatures, rapidly reducing polonium concentration in a short time.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more fully understand the present application and the advantages thereof, the drawings used in the description of the embodiments will be briefly introduced below. It is obvious that the drawings in the following description are only some embodiments of the application, and that other drawings can be derived from these drawings by a person skilled in the art without inventive effort. It should also be noted that fig. 1 is drawn in a simplified form only to facilitate and clearly assist in describing the present invention. The various dimensions of each of the components shown in fig. 1 are arbitrarily illustrated, may be precise, or may not be drawn to scale. For example, the dimensions of the elements in the figures may be exaggerated where appropriate to improve clarity. The various features of the drawings are not necessarily to scale unless specifically indicated. The present invention is not limited to each size of each component.

Wherein like reference numerals refer to like parts in the following description.

FIG. 1 is a diagram of Fe/Fe production in example 1₂O₃/SiO₂Schematic illustration of an electrospinning apparatus for hybrid nanofiber membranes;

FIG. 2 is Fe/Fe prepared in example 1₂O₃/SiO₂SEM image of hybrid nanofiber membrane;

FIG. 3 shows Fe/Fe containing Pb, Bi and Te elements after filtration prepared in example 1₂O₃/SiO₂SEM image of hybrid nanofiber membrane;

FIG. 4 is Fe/Fe prepared in example 1₂O₃/SiO₂XRD patterns of the hybrid nanofiber membrane before and after filtration;

FIG. 5 is Fe/Fe prepared in example 1₂O₃/SiO₂Graph comparing the filtration efficiency of the hybrid nanofiber membrane at different filtration temperatures.

Description of reference numerals: 1-injection pump, 2-spinning precursor liquid, 3-drawn polymer, 4-roller receiver, 5-high voltage power supply.

Detailed Description

The invention is further illustrated below with reference to the figures, embodiments and examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, it should be understood that various changes or modifications can be made by those skilled in the art after reading the teachings of the present invention, and these equivalents also fall within the scope of the appended claims of the present application.

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. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments and examples only and is not intended to be limiting of the invention.

Term(s) for

Unless otherwise stated or contradicted, terms or phrases used herein have the following meanings:

the term "and/or", "and/or" as used herein is intended to be inclusive of any one of the two or more items listed in association, and also to include any and all combinations of the items listed in association, including any two or more of the items listed in association, any more of the items listed in association, or all combinations of the items listed in association. It should be noted that when at least three items are connected by at least two conjunctive combinations selected from "and/or", "or/and", "and/or", it should be understood that, in the present application, the technical solutions definitely include the technical solutions all connected by "logic and" and also the technical solutions all connected by "logic or". For example, "A and/or B" includes A, B and A + B. For example, the embodiments of "a, and/or, B, and/or, C, and/or, D" include any of A, B, C, D (i.e., all embodiments using a "logical or" connection), any and all combinations of A, B, C, D, i.e., any two or any three of A, B, C, D, and four combinations of A, B, C, D (i.e., all embodiments using a "logical and" connection).

The terms "preferably", "better", and the like are used herein only to describe better embodiments or examples, and should not be construed as limiting the scope of the present invention.

In the present invention, the terms "first", "second", "third", etc. in the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or quantity, nor is it to be construed as implicitly indicating the importance or quantity of the technical feature indicated. Also, "first," "second," "third," etc. are for non-exhaustive enumeration description purposes only and should not be construed as constituting a closed limitation to the number.

In the present invention, the technical features described in the open type include a closed technical solution composed of the listed features, and also include an open technical solution including the listed features.

In the present invention, where a range of values (i.e., a numerical range) is recited, unless otherwise specified, alternative distributions of values within the range are considered to be continuous, and include both the numerical endpoints of the range (i.e., the minimum and maximum values), and each numerical value between the numerical endpoints. Unless otherwise specified, when a numerical range refers to integers only within the numerical range, both endpoints of the numerical range are inclusive of the integers and each integer between the endpoints is inclusive of the integer. Further, when multiple range describing features or characteristics are provided, these ranges may be combined. In other words, unless otherwise indicated, the ranges disclosed herein are to be understood to include any and all subranges subsumed therein.

The temperature parameter in the present invention is not particularly limited, and is allowed to be constant temperature treatment or to vary within a certain temperature range. It will be appreciated that the described thermostatic process allows the temperature to fluctuate within the accuracy of the instrument control.

The calcination temperature, unless otherwise specified, is referred to herein as the set temperature of the calcination apparatus.

In the present invention, "room temperature" means no temperature control operation, and mainly means 4 to 35 ℃, preferably 4 to 30 ℃, more preferably 20 ℃ ± 5 ℃, 20 to 30 ℃ and the like. Examples of "room temperature" in the present invention include 15 ℃, 16 ℃, 18 ℃, 20 ℃, 25 ℃, 26 ℃, 28 ℃, 30 ℃, 32 ℃, 35 ℃ and the like.

The percentage contents referred to in the present invention refer to volume% for a gas-gas mixture, weight% for a solid-solid phase mixture, volume% (v/v) for a liquid-liquid phase mixture, and weight% or solid-liquid% (w/v) for a solid-liquid mixture, unless otherwise specified.

In the present invention,% (w/w) and wt% each represent a weight percentage.

PVA, polyvinyl alcohol. TEOS, tetraethyl silicate.

s100: mixing polyvinyl alcohol with water to prepare a PVA aqueous solution;

s200: mixing water, tetraethyl silicate and phosphoric acid, and hydrolyzing to prepare Si hydrolysate;

s300: mixing the Si hydrolysate with ferric salt to prepare Si/Fe hydrolysate;

s400: mixing the PVA aqueous solution and the Si/Fe hydrolysate, and aging to prepare a spinning precursor solution;

s500: performing electrostatic spinning on the spinning precursor liquid to prepare a precursor nanofiber membrane;

s600: drying the precursor nanofiber membrane, and calcining in a reducing atmosphere to prepare Fe/Fe₂O₃/SiO₂A hybrid nanofiber membrane.

The preparation method provided by the invention combines the technical means of sol-gel electrostatic spinning and heat treatment process, uses polyvinyl alcohol/tetraethyl orthosilicate/ferric salt to form sol-gel precursor liquid, and calcines the sol-gel precursor liquid in a reducing atmosphere to remove organic matters and Fe on the surface of the hybrid fiber₂O₃Reduction to Fe, Fe/Fe₂O₃/SiO₂The hybrid nanofiber membrane has excellent combination properties of high temperature resistance, high filtering precision and high polonium affinity.

S100: preparation of aqueous PVA solution

In some embodiments of the invention, the polyvinyl alcohol is mixed with water by stirring. The stirring time is 2 to 12 hours, preferably 4 to 8 hours.

In some embodiments of the invention, the stirring time is 6 hours.

The aqueous PVA solution is required to have a suitable viscosity as a precursor liquid.

In some embodiments of the invention, the aqueous PVA solution contains from 5% to 20% by weight polyvinyl alcohol (PVA).

In some preferred embodiments of the present invention, the polyvinyl alcohol is present in the aqueous PVA solution in an amount selected from the group consisting of 5wt% to 18 wt%, 5wt% to 16 wt%, 5wt% to 12 wt%, 5wt% to 10 wt%, 7 wt% to 12 wt%, 7 wt% to 15 wt%, 7 wt% to 18 t%, 10 wt% to 20wt%, 15 wt% to 20wt%, and 18 wt% to 20 wt%.

In some particular embodiments of the invention, the polyvinyl alcohol is present in the aqueous PVA solution in an amount of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 wt%.

S200: preparation of Si hydrolysate

In some embodiments of the invention, the molar ratio of water, tetraethyl silicate, and phosphoric acid is (5-20): 1 (0.005-0.015).

In some preferred embodiments of the present invention, the molar ratio of water, tetraethyl silicate and phosphoric acid is (10-20): 1 (0.01-0.015).

In some embodiments of the invention, the molar ratio of water, tetraethyl silicate, and phosphoric acid is 15:1: 0.01.

After water, tetraethyl silicate and phosphoric acid are mixed, tetraethyl silicate is hydrolyzed under the phosphoric acid condition to obtain Si hydrolysate. The hydrolysis method includes but is not limited to stirring, and the hydrolysis time is kept for a certain length to ensure sufficient hydrolysis.

In some embodiments of the invention, the hydrolysis time is between 4h and 18h, preferably between 8h and 12 h.

S300: preparation of Si/Fe hydrolysate

The metal has a higher affinity for polonium than the oxide. The inventor finds that the SiO content can be improved by doping Fe element₂The nano-fibers filter polonium sol performance, but also result in poor spinnability of the precursor solution and increased fiber brittleness.The adsorption enthalpy of polonium on metallic iron was predicted by a semi-empirical model to be-346 kJ/mol, higher than SiO₂Of-125 kJ/mol, which indicates that the incorporation of Fe can increase SiO₂The fiber has the effect of trapping and filtering polonium volatile.

The Fe element is preferably added through ferric nitrate and ferric chloride.

If the dosage of the ferric salt is too much, the spinnability of the spinning solution is poor, the spinning is difficult or the spinning fiber is more brittle and is easy to crack, and if the dosage of the ferric salt is too little, the adsorption enhancement effect of elements such as Po and the like is influenced. The mol ratio of Si and Fe is controlled within a proper range (such as (2-8): 1), so that better spinning performance can be realized, and the flexibility and the filtering effect of the spinning fiber are optimal.

In some embodiments of the invention, the molar ratio of Si to Fe is (2-16): 1.

In some preferred embodiments of the present invention, the molar ratio of Si to Fe is (2-8): 1.

In some specific embodiments of the invention, the molar ratio of Si to Fe is 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2: 1.

S400: preparation of spinning precursor liquid

In step S400, the mixing of the PVA aqueous solution and the Si/Fe hydrolysate includes, but is not limited to, stirring, and the stirring time may be adjusted according to the actual situation, based on the effect of uniform mixing.

In some embodiments of the invention, the mass ratio of the PVA aqueous solution to the Si/Fe hydrolysate is 1 (0.5-2.5), preferably 1 (1-2).

In some embodiments of the invention, the mass ratio of the aqueous PVA solution to the Si/Fe sol is 2:1, 1.5:1, 1:1.5, 1:2, 1: 2.5.

In step S400, the spinnability of the spinning solution is enhanced through aging, and meanwhile, the flexibility of the spinning fiber is enhanced. In some embodiments of the present invention, the aging mode is room temperature standing, and the aging time is 6 to 24 hours, preferably 10 to 24 hours, and further 12 to 18 hours.

In some embodiments of the present invention, the aging mode is water bath aging, the aging temperature is 40 ℃ to 70 ℃, and the aging time is 4h to 20h, preferably 6h to 16h, and further 6h to 10 h.

In some embodiments of the present invention, the aging mode is room temperature standing, and the aging time is 16 h.

S500: preparation of precursor nanofiber membranes

In some embodiments of the present invention, the spinning precursor solution prepared in step S400 is injected into an injector with a nozzle and fixed on an electrostatic spinning device mechanism, and spinning voltage, receiving distance, and injection speed are adjusted to prepare a precursor nanofiber membrane.

Parameters such as spinning voltage, receiving distance, advancing distance and the like all have certain influence on the diameter and mechanical property of the spinning film.

In some embodiments of the invention, the spinning voltage is from 6kV to 15kV, preferably from 8kV to 12 kV.

In some embodiments of the invention, the acceptance distance is from 5cm to 25cm, preferably from 10cm to 20 cm.

In some embodiments of the invention, the bolus rate is from 0.8mL/h to 3mL/h, preferably from 1mL/h to 2 mL/h.

Spinning voltage, receiving distance and injection speed need to be considered integrally, and various parameters need to be coordinated to achieve optimal material performance.

In some embodiments of the invention, the spinning voltage is from 6kV to 15kV, the acceptance distance is from 5cm to 25cm, and the bolus rate is from 0.8mL/h to 3 mL/h.

In some embodiments of the invention, the spinning voltage is 8kV to 12kV, the acceptance distance is 10cm to 20cm, and the bolus rate is 1mL/h to 2 mL/h.

In some embodiments of the invention, the spinning voltage is 10kV, the acceptance distance is 15cm, and the bolus rate is 1 mL/h.

S600: preparation of Fe/Fe₂O₃/SiO₂Hybrid nanofiber membranes

In step S600, the precursor nanofiber membrane prepared in step S500 needs to be dried and then calcined to remove the residual solvent and volatile components. The higher the drying temperature, the shorter the drying time required. Drying means include, but are not limited to, drying.

In some embodiments of the invention, the drying temperature is 60 ℃ to 100 ℃, the drying time is 1h to 8h, and the drying mode is drying.

In some embodiments of the invention, the drying temperature is 60-80 ℃, the drying time is 4-8 h, and the drying mode is drying.

In some embodiments of the invention, the drying temperature is 80-100 ℃, the drying time is 1-4 h, and the drying mode is drying.

In step S600, the calcination is performed to remove organic substances from the nanofiber membrane of the precursor, and to remove Fe on the surface of the fiber³⁺Reduction to Fe further improves the adsorption capacity of the fibers to polonium, so that calcination is carried out in a reducing atmosphere. The reducing temperature is inert gas containing hydrogen, the inert gas can be other common inert gases such as nitrogen, argon and the like, and the expression form of mixing hydrogen in the inert gas is H₂/Ar、H₂/N₂、5％H₂/Ar、3％H₂/N₂. When the concentration of hydrogen is 3 to 5%, the reduction can be carried out sufficiently, and the higher the concentration of hydrogen is, the higher the reduction efficiency is, but the higher the concentration of hydrogen is, the higher the concentration of hydrogen is not suitable for safety.

In some embodiments of the invention, the reducing atmosphere is selected from H₂/Ar or H₂/N₂More preferably H₂/Ar。

In some embodiments of the invention, the reducing atmosphere is 5% H₂/Ar。

In some embodiments of the invention, the calcination temperature is 350 ℃ to 800 ℃ and the calcination time is 1h to 8h, further, the calcination temperature is 450 ℃ to 800 ℃ and the calcination time is 2h to 4h, further preferably, the calcination temperature is 450 ℃ to 700 ℃ and the calcination time is 2h to 4 h.

In some embodiments of the invention, the calcination temperature is 550 ℃, the calcination time is 2 hours, and the reducing atmosphere is 5% H₂/Ar。

In some embodiments of the invention, the calcination temperature is 500 ℃, the calcination time is 2 hours, and the reducing atmosphere is 5% H₂/Ar。

In a second aspect, the invention provides a membrane filter material obtained by the preparation method according to the first aspect. The membrane filter material is Fe/Fe₂O₃/SiO₂The hybridized nanofiber membrane is a flexible inorganic nanofiber membrane and has the characteristics of high temperature resistance, high filtering precision and high polonium affinity.

The invention tests the high-temperature filtering effect of the filtering membrane, and finds that the filtering membrane still has better filtering effect within the temperature range of 300-450 ℃, which can reach more than 97 percent, and has more than 99 percent of filtering efficiency below 400 ℃. The installation position of the membrane filtering material is not particularly limited, and the membrane filtering material conforms to the design principle of a filtering device and can achieve the purpose of filtering. The number of the membrane filter material is also not particularly limited, and may be 1, 2 or more. When the number of the membrane filter materials is more than one, the distribution thereof is not particularly limited, and the membrane filter materials may be arranged adjacently or may be installed in different modules, respectively. It will be appreciated that the quantity and distribution of the membrane filter material is also suitable to enable filtration purposes.

Fig. 1 is a schematic view of an electrospinning apparatus according to an embodiment of the present invention, including an injection pump 1, a drum receiver 3, and a high voltage power supply 5. Injecting the spinning precursor liquid 2 into an injection pump 1 for pushing, wherein under the action of an electric field, liquid drops at a needle head are changed into a conical shape (namely a Taylor cone) from a spherical shape; after spinning is started, liquid firstly enters a cone-jet area, and the diameter of jet flow is smaller and smaller under the combined action of surface charge repulsion and a strong electric field until the liquid is bent; then, the jet flow enters a whiplash unstable region, the jet flow swings like a whiplash while accelerating, the diameter of the jet flow is greatly reduced, and the solvent is volatilized; finally, the jet solidifies to form a fiber of ultra-fine diameter, i.e. drawn polymer 3 (the shape in fig. 1 is merely an example and should not be understood to constitute a limitation of the scope of the invention).

In a third aspect, the invention provides the use of a membrane filter material according to the second aspect for the treatment of aerosols. The membrane filter material (specifically Fe/Fe) provided by the invention is applied₂O₃/SiO₂Hybrid nanofiber membranes) capable of filtering aerosols, especially polonium aerosols, in high temperature environments and rapidly reducing the radioactive concentration of a nuclide in a short period of time.

In some embodiments of the invention, when the membrane filter material is applied to treatment of polonium aerosols, the effective filtration of polonium aerosols by the filter membrane is based primarily on the small pore size characteristics of the filter membrane itself, and the adsorption-binding enhancement of polonium by Fe on the surface of the filter membrane.

In some embodiments of the invention, when the membrane filter material is applied to the treatment of iodine aerosol and lead bismuth aerosol, the effective filtration of the aerosol by the filter membrane is mainly based on the small pore diameter characteristics of the filter membrane.

In some embodiments of the invention, the membrane filter material is suitable for processing the aerosol at 25 ℃ to 450 ℃.

Some specific examples are as follows.

Experimental parameters not described in the following specific examples are preferably referred to the guidelines given in the present application, and may be referred to experimental manuals in the art or other experimental methods known in the art, or to experimental conditions recommended by the manufacturer.

The starting materials and reagents mentioned in the following specific examples are commercially available or can be easily obtained or prepared by those skilled in the art.

Raw materials:

deionized water, made from a laboratory pure water system, water purifier model (Center-EDI 90V).

Tetraethyl silicate (TEOS), analytically pure, national pharmaceutical group chemicals, inc.

Phosphoric acid (H)₂PO₄) Sunglong chemical Co., Ltd.

Ferric nitrate nonahydrate (Fe (NO)₃)₃·9H₂O), ferric chloride hexahydrate (FeCl)₃·6H₂O), nitric acid (HNO)₃) Analytically pure, Guangdong Guanghua science and technology, Inc.

Polyvinyl alcohol (PVA), national chemical group, Inc.

Example 1

Preparing a flexible Fe/Fe2O3/SiO2 hybrid nanofiber membrane by the following operation steps:

1.1 dissolving PVA in deionized water, stirring at 80 deg.C for 6h to obtain 10 wt% PVA water solution (as precursor liquid). Deionized water, tetraethyl silicate (TEOS) and phosphoric acid as H₂O:TEOS:H₃PO₄And mixing and uniformly stirring the components at a molar ratio of 10:1:0.01 to obtain the Si hydrolysate. Mixing the obtained Si hydrolysate with nitric acid (Fe (NO) nonahydrate₃)₃·9H₂O) is evenly stirred and mixed according to the molar ratio of Si to Fe of 4:1 to obtain the Si/Fe hydrolysate. And then mixing the prepared 10 wt% PVA solution with the obtained Si/Fe hydrolysate according to the mass ratio of 1:1, and aging for 16h to obtain the spinning precursor solution.

1.2 injecting the spinning precursor liquid prepared in the step 1.1 into an injector provided with a spray head, fixing the injector on an electrostatic spinning device mechanism shown in the figure 1, setting the electrospinning parameters to be 17cm, setting the injection speed to be 1mL/h and the voltage to be 9kV, and carrying out electrostatic spinning to obtain the precursor nanofiber membrane.

1.3, putting the precursor nanofiber membrane obtained in the step 1.2 into an oven for drying. The drying temperature is 80 ℃, and the drying time is 6 h. Calcining in a tubular furnace while introducing 5% H₂In the atmosphere of/Ar, the calcining temperature is 550 ℃, and the heat preservation time is 2 hours, thus obtaining the flexible Fe/Fe₂O₃/SiO₂A hybrid nanofiber membrane.

Example 2

Preparation of Flexible Fe/Fe₂O₃/SiO₂Hybrid nanofiber membrane, differing from example 1 in that: in step 1.1, the mole ratio of Si to Fe in the preparation of Si/Fe hydrolysate was 2:1, and the rest was the same as in example 1.

Example 3

Preparation of Flexible Fe/Fe₂O₃/SiO₂Hybrid nanofiber membrane, differing from example 1 in that: in step 1.1, the mole ratio of Si to Fe in the preparation of Si/Fe hydrolysate is 8:1, and the rest is the same as in example 1.

Example 4

Preparation of Flexible Fe/Fe₂O₃/SiO₂Hybrid nanofiber membrane, differing from example 1 in that: in step 1.1, in the preparation of the Si/Fe hydrolysate, ferric chloride hexahydrate (FeCl)₃·6H₂O) instead of nitric acid nonahydrate (Fe (NO)₃)₃·9H₂O); in the preparation of the spinning precursor liquid, the mass ratio of the PVA solution to the Si/Fe hydrolysate is 1.5: 1; flexible Fe/Fe₂O₃/SiO₂The preparation of the hybrid nanofiber membrane was performed at 90 ℃ for drying and 500 ℃ for calcination, as in example 1.

Comparative example 1

A nanofiber membrane was prepared, differing from example 1 in that: in step 1.1, NO Fe was introduced (in example 1, Fe (NO)₃)₃·9H₂Introduced as O). Specifically, step 1.1: PVA is dissolved in deionized water and stirred until the solution is clear and transparent, the stirring temperature is 80 ℃, and the stirring time is 6 hours, so that 10 wt% PVA aqueous solution (as precursor solution) is obtained. Deionized water, tetraethyl silicate (TEOS) and phosphoric acid as H₂O:TEOS:H₃PO₄And mixing the components according to the molar ratio of 10:1:0.01, and uniformly stirring to obtain the Si hydrolysate. And then mixing the prepared 10 wt% PVA solution with the obtained Si hydrolysate according to the mass ratio of 1:1, and aging for 16h to obtain the spinning precursor solution. The rest is the same as example 1.

Comparative example 2

Preparation of Flexible Fe/Fe₂O₃/SiO₂A hybrid nanofiber membrane, in substantially the same manner as in example 1, except thatIs characterized in that: in step 1.1, in the preparation of the Si/Fe hydrolysate, the molar ratio of Si to Fe is 1:1, the remaining parameters were the same as in example 1.

Comparative example 3

Preparation of Flexible Fe/Fe₂O₃/SiO₂A hybrid nanofiber membrane, using essentially the same method as example 1, except that: in step 1.3, the calcination temperature was 900 ℃ and the remaining parameters were the same as in example 1.

Example 5. the following is a performance test of the nanofiber membrane.

5.1. Temperature resistance test

The nanofiber membranes prepared in examples 1-4 and comparative examples 1-4 were subjected to a temperature resistance test, the test method being: and calcining the nanofiber membrane at 700 ℃ in Ar atmosphere for not less than 6 hours, and observing the material performance. The results show that: the flexibility, the surface appearance and the like of the material have no obvious change. Thus, the temperature resistance of the test specimen reached 700 ℃.

5.2. Filter accuracy testing

The nanofiber membranes prepared in examples 1 to 4 and comparative examples 1 to 4 were subjected to filtration accuracy test, and the test method was: and testing the pore size range of the nanofiber membrane by using a specific surface area and pore size analyzer (BET) to obtain the filtering precision of the filtering membrane to the aerosol.

5.3. Filtration efficiency test

The nanofiber membranes prepared in examples 1 to 4 and comparative examples 1 to 4 were subjected to filtration efficiency test.

Te and Po (radioactive nuclide) are homologous elements and have similar chemical properties, and the volatile forms of the Te and Po are consistent after the Te and Po (radioactive nuclide) are heated, so that the filtering efficiency of the nanofiber membrane on the radioactive nuclide Po can be referred to the filtering efficiency on the Te element. The volatile forms of Te and Po can also be seen in the XRD test results in example 9.

The method for testing the filtering efficiency of the Te element comprises the following steps: doping 5% of Te into the LBE alloy to prepare Te doped lead bismuth alloy, generating Te aerosol through heating, filtering by adopting a nano fiber membrane, and further filtering the filtered Te aerosol by using a high-efficiency filter membrane (capturing Te elements which are not filtered by the nano fiber membrane); the filter was dissolved in nitric acid, and the amount of trapping (Te element mass) was accurately measured by an ICP (ICAP7000, Thermo Fisher) apparatus.

The Te element filtering efficiency is calculated by adopting the following calculation formula:

wherein eta is the filtration efficiency, m₁Mass of nuclide (Te) m in tail gas when electrostatic spinning filtering membrane is not used₂The mass of nuclide (Te) in tail gas after being filtered by an electrostatic spinning filter membrane is adopted.

Flexible Fe/Fe prepared in example 1₂O₃/SiO₂The filtration efficiency of the hybrid nanofiber membrane at different temperatures is shown in fig. 5, wherein the horizontal axis represents the filtration temperature of the electrospinning filtration membrane, and the vertical axis represents the filtration efficiency of the fiber filtration membrane. Prepared flexible Fe/Fe₂O₃/SiO₂The hybrid nanofiber membrane has excellent filtering performance in a high-temperature range of 300-450 ℃, the filtering removal efficiency can reach more than 97%, and the Te element has filtering efficiency of more than 99% below 400 ℃. It can be understood that the effective filtration of aerosol by the filter membrane is mainly based on the small pore size of the filter membrane and the adsorption binding enhancement effect of Fe on nuclide on the surface of the filter membrane. Because the filter membrane has smaller pore size, the filter membrane can also realize better filtering effect on other aerosols, such as iodine aerosol and lead bismuth aerosol.

5.4. Surface topography testing

Flexible Fe/Fe before and after filtration for example 1₂O₃/SiO₂The hybrid nanofiber membrane was subjected to SEM test with instrument model SU5000, Hitachi, and the scanning results are shown in fig. 2 and fig. 3. Wherein FIG. 2 is a flexible Fe/Fe before filtration₂O₃/SiO₂SEM image of the hybrid nanofiber membrane according to fig. 2, the fibers before filtration were smooth in surface, uniform in size, and had an average diameter of 366 nm. FIG. 3 shows the flexible Fe/Fe containing Pb, Bi and Te after filtration₂O₃/SiO₂SEM image of hybrid nanofiber membrane, according to FIG. 3, highThe aerosol in the warm filtering environment is effectively captured and adhered to the fiber filtering membrane.

XRD testing

Flexible Fe/Fe before and after filtration for example 1₂O₃/SiO₂The hybrid nanofiber membrane is subjected to XRD test, the instrument model is Rigaku D/MAX 2500V, the scanning angle is 5-80 degrees, the scanning speed is 5 degrees/min, the step length is 0.02, and the diffraction result is shown in figure 4. S in FIG. 4 represents an amorphous material (Fe/Fe)₂O₃/SiO₂Hybrid nanofiber membrane), B represents amorphous Bi, T represents amorphous PbTe, horizontal axis represents 2 θ, vertical axis represents diffraction angle, 21 ° of peak-to-peak corresponds to amorphous material (Fe/Fe)₂O₃/SiO₂Hybrid nanofiber membranes). According to FIG. 4, the flexible Fe/Fe before the trapping test was performed₂O₃/SiO₂The hybrid fiber shows an amorphous peak at 21 ° in fig. 4, flexible Fe/Fe after the trapping test₂O₃/SiO₂The hybrid fiber is deposited with elements Pb, Bi and Te, and diffraction peaks of PbTe and Bi exist besides the amorphous package peak of 21 degrees, which shows that the element Te is volatilized in the form of PbTe vapor during the volatilization and filtration of PbBiTe, and the result is consistent with that Po in the lead-based reactor volatilizes in the form of PbPo vapor on the surface of a lead-bismuth pool.

5.6. Analysis of test results

The above temperature resistance, filtration accuracy, filtration efficiency and performance parameters are detailed in table 1.

TABLE 1 Fe/Fe of examples and comparative examples₂O₃/SiO₂Performance parameters of hybrid nanofiber membranes

^aThe average pore diameter of the porous material is,^bthe filtration temperature is 400 DEG C

In Table 1, Fe/Fe prepared according to examples 1 to 4₂O₃/SiO₂The performance test result of the hybrid nanofiber membrane is that the Fe/Fe provided by the invention₂O₃/SiO₂Hybrid sodiumThe rice fiber membrane has good temperature resistance, and can resist the temperature up to 700 ℃; the aperture range is less than 15nm, and the filtering precision is high; the filtering efficiency is high, the whole is higher than 98%, and the part can reach 99%.

The results that the filtration precision (15.5nm) of comparative example 1 is slightly lower than that (10.5 nm-13.2 nm) of examples 1-4, and the filtration efficiency (93.54%) of comparative example 1 is obviously lower than that (98.45-99.61%) of examples 1-4 show that the introduction of Fe improves SiO₂Filtration accuracy and filtration efficiency of nanofiber membrane on LBE-Te. The high affinity of Fe to Po is utilized to enhance the adsorption performance of the fiber membrane to Po. According to the test results of the filtration precision and the filtration efficiency of the embodiments 1 to 3, in a certain range, the higher the Fe content in the fiber membrane is, the higher the filtration precision and the filtration efficiency are. However, too high an amount of Fe also affects spinnability. The comparative example 2 contains Fe in an excessively high amount, resulting in difficulty in controlling the viscosity of the solution, poor spinnability, difficulty in spinning fibers or poor properties of spun fibers. Comparative example 3, too high calcination temperature, hybrid nanofiber Fe and Fe₂O₃The crystal grains can grow and be bonded, the brittleness of the fiber is increased, the fiber is broken, and then the fiber film is broken.

In comparative example 1, the filter membrane still can achieve more than 90% of the filtering effect on the aerosol by only the pore size structure of the filter membrane without depending on the adsorption enhancement effect of the Fe element in the filter membrane, which indicates that the filter membrane has a better filtering effect on most aerosols, including but not limited to polonium aerosol, iodine aerosol and lead bismuth aerosol.

The technical features of the embodiments and examples described above can be combined in any suitable manner, and for the sake of brevity, all possible combinations of the technical features of the embodiments and examples described above are not described, but should be considered within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, so as to understand the technical solutions of the present invention specifically and in detail, but not to be understood as the limitation of the protection scope of the invention. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Furthermore, it should be understood that after reading the above teachings of the present invention, various changes or modifications may be made to the invention by those skilled in the art, and equivalents may be obtained and still fall within the scope of the present application. It should also be understood that the technical solutions provided by the present invention, which are obtained by logical analysis, reasoning or limited experiments, are within the scope of the present invention as set forth in the appended claims. Therefore, the protection scope of the present patent shall be subject to the content of the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. The preparation method of the membrane filter material is characterized by comprising the following steps of:

mixing polyvinyl alcohol with water to prepare a PVA aqueous solution;

mixing the Si hydrolysate with ferric salt to prepare Si/Fe hydrolysate; wherein the molar ratio of Si to Fe is (2-16): 1, and the ferric salt is ferric nitrate, ferric chloride or a combination thereof;

mixing the PVA aqueous solution and the Si/Fe hydrolysate, and aging to prepare a spinning precursor solution; wherein the mass ratio of the PVA aqueous solution to the Si/Fe hydrolysate is 1 (0.5-2.5);

drying the precursor nanofiber membrane, calcining at 350-800 ℃ for 1-8 h in a reducing atmosphere, and preparing Fe/Fe₂O₃/SiO₂A hybrid nanofiber membrane.

2. The method for producing a membrane filter material according to claim 1,

in the step of mixing the Si hydrolysate and the ferric salt, the molar ratio of Si to Fe is (2-8): 1; and/or the like, and/or,

and mixing the PVA aqueous solution and the Si/Fe hydrolysate, wherein in the aging step, the aging is standing for 4-24 hours.

3. The method for producing a membrane filter material as claimed in claim 2,

4. The method for preparing the membrane filter material according to claim 2, wherein the aging is performed at normal temperature, the aging temperature is 20 ℃ to 30 ℃, and the aging time is 6h to 24 h; alternatively, the first and second electrodes may be,

5. The method of claim 1, wherein said electrospinning is carried out under parameters comprising: the receiving distance is 5 cm-25 cm, and/or the injection speed is 0.8 mL/h-3 mL/h, and/or the voltage is 6 kV-15 kV.

6. A method of producing a membrane filter material as claimed in any one of claims 1 to 5,

the drying temperature is 60 ℃ to 100 ℃, the drying time is 4h to 8h, and/or,

the calcining temperature of the calcining is 450-800 ℃, and the calcining time is 2-4 h.

7. The method for preparing the membrane filter material according to claim 6, wherein the hydrogen gas has a volume concentration of 5%, the inert gas is selected from nitrogen or argon, and the calcination temperature is 450 ℃ to 700 ℃.

8. A membrane filtration material obtained by the production method according to any one of claims 1 to 7.

9. Use of the membrane filter material of claim 8 in the treatment of an aerosol, wherein the aerosol is a polonium aerosol.

10. Use of the film filter material of claim 9 for the treatment of an aerosol at a temperature of from 25 ℃ to 450 ℃.