Electrostatic spinning and electrostatic spray method combine and prepare nanofiber-based composite separating filmTechnical field
The invention belongs to the preparation field of composite membrane for separation, particularly relate to a kind of electrostatic spinning and prepare nanofiber-based composite membrane for separation in conjunction with the electrostatic spray method.
Background technology
Shortage of water resources and environmental pollution be serious day by day in the world today, and China is a country that lack of water is serious.The freshwater resources total amount is 28000 billion cubic meters, accounts for 6% of water globe resource, has only 2300 cubic metres per capita, only is 1/4 of world average level.There are 300 urban water shortages in the whole nation, because of 1,200 hundred million yuan of the annual losses of lack of water National urban industry.Be one of 13 countries that water resource is the poorest per capita in the whole world.According to environment department monitoring, national cities and towns have 100,000,000 tons of unprocessed water bodys that directly enter of sewage every day at least.Section over half water quality is polluted in the seven big water systems of the whole nation, the water body in the whole nation 1/3 is unsuitable for fish existence, and 1/4 water body is unsuitable for irrigating, and 90% urban waters is seriously polluted, 50% water source, cities and towns does not meet drinking water standard, and oneself can not drink 40% water source.
The embrane method water technology because have the efficient height, energy consumption is low, occupation of land is little, the water that is cleaned and the harmful substance of recovery can be utilized again, can realize closed cycle, prevent advantages such as secondary pollution, brought into play enormous function [Xu is another, Xu Zhikang, macromolecule member material at aspects such as seawater and brackish water desalination, potable water, wastewater treatment and reuses, Chemical Industry Press, 2005; S.Judd, B.Jefferson, membrane technology and industrial effluent reusing, Chemical Industry Press 2006].At present China's film industry with membrane technology overall research compare with external advanced person's technology with application level bigger gap arranged, greatly develop membrane technology become social economy's sustainable development must [Guo has intelligence China film industrial development present situation. the Asia water supply and drainage, 2005,5,22-25].
The diffusion barrier of macromolecule material adopts the solution phase inversion more, yet bigger by the prepared diffusion barrier general thickness of this method, and the less and formed micropore of voidage mostly is hole-closing structure.Caused the lower filtration flux of diffusion barrier just because of this design feature by this kind method preparation.
The principle that EFI ionization techniques (Electrospray Ionization is called for short ESI) is based on high-pressure electrostatic conductor fluid generation after the match high velocity jet develops and next technology, is called the electron spray technology again.The experimentation of electron spray can be sketched and be: under the normal pressure, the solution of analyte is with high-tension capillary by one, under several kilovolts high electric field action approximately, produce the vaporific drop of altitudinal belt electric charge, in transition process, drop is because solvent evaporation or COULOMB EXPLOSION and volume reduces gradually produce the ion of complete desolventizing at last.The electron spray process can be divided into 3 stages: drop formation, drop atrophy and gas ion form.Utilize the colloidal particle of preparing nano-scale that the electrostatic spray method can be simple and efficient.
Electrostatic spinning is the topmost simple and effective technology of super-fine fiber materials such as current preparation nanofiber.The topmost characteristics of electrostatic spinning fiber are fibers than thin many of traditional spinning process, diameter generally at tens nanometer to thousands of nanometers, formed nonwoven is a kind ofly to have nanometer micropore and the porous material hole intercommunication.Porosity can be up to about 80%, and hole can be by regulating electrospinning technological parameter and effectively regulation and control.Because of the electrostatic spinning nano fabric nonwoven cloth has the form characteristics that fibre number is thin, surface area is big, porosity is high, and having excellent mechanical intensity and lightweight light weight and absorption property, is that material is supported in extraordinary filtering material and filtration.Therefore electrostatic spinning nano fiber is in extremely various countries researcher's the concern of application study in diffusion barrier field.The electrostatic spinning non-weaving cloth is to be applied in exploitation high-efficiency air filtering material aspect as filtering material the earliest, utilize electrostatic spinning technique aspect air filtration, to develop some high performance air cleaner [Gopal R, KaurS, Ma Z 2006 Journal of Membrane Science 281581-55 :].The electrospun fibers diameter and the institute pile up formation nonwoven the aperture be the principal element that influences filtering material filtering accuracy and efficient.In filtering material.Less fibre diameter often has higher filtering accuracy and filter efficiency, and therefore in pressure loss parameter allowed bands such as (static pressure differences before and after filtering), electrostatic spinning will select to form the less diameter and the parameter in aperture, to improve filtering accuracy.But because the restriction of this processing method own characteristic of electrostatic spinning, it is very difficult less than the fiber of 100 nanometers to obtain average diameter, must just can reach below 100 nanometers by selecting specific macromolecular material, thereby also limit the further reduction that static spins the nonwoven aperture.In general, the electrostatic spinning nano fiber nonwoven be directly used in filter medium effectively the filtering diameter greater than the above particle of 30Onm [Barhate R S, Ramakrishna S 2007 Journal of Membrane science 2961-8].If utilize the high voidage of electrostatic spinning nano fiber nonwoven and open-celled structure to obtain high-throughoutly simultaneously particle, solubility organic molecule even inorganic salts less than 300nm to be carried out filtering effectively, just must be under the prerequisite that guarantees electrostatic spinning nano fiber nonwoven fabric construct characteristics select layer in the ultra-thin densification of its surface construction.[Wang X, Fang Di, YoonK, Hsiao B S and Chu Benjamin 2006 J.Membr.Sci 278 261-8 such as Wang Xuefen; Wang X, Chen X, Yoon K., Fang D, Hsiao B S and Chu B 2005 Environ.sci.﹠amp; Technol 39 7684-91] people's new membrane parting material one nano-fiber composite film of utilizing the electrostatic spinning nano fiber non-woven membrane to prepare first to form by electrostatic spinning nano fiber multihole film and functional coating, and successfully be used for emulsions wastewater and filter (Water filtration) system.But these methods that reduce the aperture adopt the surface-coated method more, and uniform high-efficiency applies on a large scale to large-area electrostatic spinning nano fiber nonwoven when being difficult in control selection layer thickness.In other words, this methods and strategies is difficult in and obtains promotion and application in the suitability for industrialized production.
Summary of the invention
Technical problem to be solved by this invention provides a kind of electrostatic spinning and the electrostatic spray method prepares nanofiber-based composite membrane for separation, this preparation method is simple, can make things convenient for and accurate control surface is selected the thickness and the uniformity of layer and easier operation of accomplishing scale production; Resulting nanofiber-based composite membrane for separation can be used widely in fields such as micro-filtration, ultrafiltration, nanofiltration, counter-infiltrations.
A kind of electrostatic spinning of the present invention and electrostatic spray method prepare nanofiber-based composite membrane for separation, comprising:
(1) the functional polymer membrane material is dissolved in the solvent, the macromolecule spinning solution A that is mixed with concentration and is 0.5-25wt% carries out electrostatic spinning, obtain nonwoven, supporting layer as composite membrane, the average diameter of supporting layer nanofiber is 200～1000nm, thickness is 50～200 μ m, and porosity is 70%～95%;
(2) the functional polymer membrane material that will be different from step (1) is dissolved in the solvent, the macromolecule spinning solution B that is mixed with concentration and is 0.1-10wt% is sprayed on above-mentioned nonwoven surface by the electrostatic spray method with it, be the selection layer of composite membrane selection layer as composite membrane, selecting the average diameter of layer colloidal solid is 20～500nm, thickness is 0.05～20 μ m, and porosity is 80%～95%;
(3) above-mentioned product is heat-treated or chemical treatment, make nanofiber-based composite membrane for separation.
Functional polymer membrane material in described step (1) and (2) is a PVAC polyvinylalcohol, polyvinyl phenol PVP, polyvinylchloride, Kynoar PVDF, cellulose acetate CA, polymethyl methacrylate, polylactic acid PLA, 3-hydroxybutyric acid and 3-hydroxypentanoic acid copolyesters PHBV, polycaprolactone (PCL), polycarbonate, polyaniline, polyacrylonitrile (PAN), polysulfones PSU, polyether sulfone PES, polystyrene PS, polyvinylcarbazole, polyethylene terephtalate, shitosan or polyamic acid.
Solvent in described step (1) and (2) is water, oxolane, ethanol, n-butanol, 1,4-dioxane, isopropyl alcohol, N-methyl pyrrolidone, carrene, chloroform, acetone, N, dinethylformamide, N, N-dimethylacetylamide, formamide, concentration are the aqueous acetone solution of 70～95wt%, the acetone N that concentration is 30～95wt%, dinethylformamide solution or concentration are the carrene N of 30～95wt%, dinethylformamide solution.
Electrostatic spinning process parameter in the described step (1) is voltage 8kV～50kV, spout aperture 0.2mm～3mm, and solution flow rate 10 μ l/min～100 μ l/min, the spinning environment temperature is 10～60 ℃.
Electrostatic spray technological parameter in the described step (2) is voltage 10kV～50kV, spout aperture 0.1mm～1mm, and solution flow rate 10 μ l/min～40 μ l/min, the spraying environment temperature is 10～60 ℃.
Heat treatment process parameter in the described step (3) is 30～200 ℃ of temperature, and heat treatment time is 10～180min, and vacuum is 0～0.1MPa.
Chemical treatment in the described step (3) is immersed in the solvent that contains crosslinking agent for the product with step (2), and soak time is 0.5～24h.
Described crosslinking agent is formaldehyde, toluene di-isocyanate(TDI), pyromellitic trimethylsilyl chloride, glutaraldehyde, glycerine, acrylic acid, ethylene glycol or oxalic acid; Solvent is water, N, N-dimethylacetylamide, formamide, oxolane, ethanol, n-butanol, 1,4-dioxane, isopropyl alcohol, N-methyl pyrrolidone, carrene, chloroform, acetone, N, dinethylformamide, concentration are the water acetone soln of 1～20wt%, the carrene N that concentration is 10～45wt%, and N-dimethyl second phthalein amine aqueous solution or concentration are the formamide aqueous solution of 25～40wt%.
Beneficial effect
(1) preparation method is simple, can make things convenient for and accurate control surface is selected the thickness and the uniformity of layer and easier operation of accomplishing scale production;
(2) resulting nanofiber-based composite membrane for separation can be used widely in fields such as micro-filtration, ultrafiltration, nanofiltration, counter-infiltrations.
The specific embodiment
Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiment only to be used to the present invention is described and be not used in and limit the scope of the invention.Should be understood that in addition those skilled in the art can make various changes or modifications the present invention after the content of having read the present invention's instruction, these equivalent form of values fall within the application's appended claims institute restricted portion equally.
Embodiment 1
(1) polyether sulfone (PES) 24g is dissolved in N, among N-dimethyl methyl acetamide (DMAC) the solvent 76g, obtains the electrostatic spinning solution of transparent homogeneous;
(2) Kynoar (PVDF) 4.0g is dissolved in N, among the mixed solvent 92g of dinethylformamide (DMF)/acetone, dinethylformamide (DMF)/acetone=2/8 obtains the electrostatic spray solution of transparent homogeneous;
(3) electrostatic spinning stoste in (1) is joined in the container, extruded by micro-injection pump control, spout connects high-voltage positive electrode, and the electrostatic spinning parameter is controlled at voltage 16kv, spout aperture 0.5mm, solution flow rate 30 μ l/min, 25 ℃ of environment temperatures, relative air humidity 75%, carry out electrostatic spinning, the average diameter of the PES electrostatic spinning nano fiber that is obtained is 1.2 μ m, and deposit thickness is 500 μ m, and porosity is 72%;
(4) electrostatic spray stoste in (2) is joined in the container, extrude by micro-injection pump control, spout connects high-voltage positive electrode, the electrostatic spray numerical control is built in voltage 20kv, spout aperture 0.1mm, solution flow rate 10 μ l/min, 45 ℃ of environment temperatures, carry out electrostatic spray, the PVDF electrostatic spray deposit thickness that is obtained is 15 μ m;
(5) be 70 ℃ with the film that makes in temperature, vacuum is heat treatment 30min in the baking oven of 0.1MPa.Promptly get colloidal particle and nanofiber-based composite membrane for separation.
This composite membrane can be used for ultrafiltration, adopt Wang X, Fang Di, Yoon K, the cross-current mode of Hsiao B S and Chu Benjamin 2006J.Membr.Sci 278261-8 document specifies is assessed the milipore filter performance, filtration flux to emulsions wastewater is 185L/m2h, and rejection is 99.5%.
The component of described emulsions wastewater and content is at Wang X, Fang Di, and Yoon K has detailed description in the Hsiao B S and Chu Benjamin2006 J.Membr.Sci 278 261-8 documents.Concrete component is as follows:
Soybean oil 1350ppm; Non-ionic surface active agent (Dow Coming 193 fluid) 150pmm; Water.
Embodiment 2
(1) polysulfones (PSU) 19.0g is dissolved in N, among dinethylformamide (DMF) the solvent 81g, obtains the electrostatic spinning solution of transparent homogeneous;
(2) polyvinyl alcohol (PVA) 7.0g is dissolved in the 93g deionized water, obtains the electrostatic spray solution of transparent homogeneous;
(3) electrostatic spinning stoste in (1) is joined in the container, extrude by micro-injection pump control, spout connects high-voltage positive electrode, and static spins parameter and is controlled at voltage 10kv, spout aperture 1mm, solution flow rate 40 μ l/min, 55 ℃ of environment temperatures are carried out electrostatic spinning, and the average diameter of the PSU electrostatic spinning nano fiber that is obtained is 2 μ m, deposit thickness is 250 μ m, and porosity is 86%;
(4) electrostatic spray stoste in (2) is joined in the container, extrude by micro-injection pump control, spout connects high-voltage positive electrode, and static spins parameter and is controlled at voltage 45kv, spout aperture 0.05mm, solution flow rate 8 μ l/mln, 35 ℃ of environment temperatures, relative air humidity 45% carries out electrostatic spray, the average diameter of the colloidal particle of the PVA electrostatic spray that is obtained is 80nm, and deposit thickness is 0.7 μ/m;
(5) film that makes is immersed in the acetone weight concentration is 10% in the mixed solvent of the water that contains oxalic acid and acetone, soaks 75 ℃ of heat treatment 10min after 6 hours, promptly get colloidal particle and nanofiber-based composite membrane for separation.
This composite membrane can be used for nanofiltration, in cross-current mode (seeing embodiment 1) film properties assessed, and be 58L/m2h to the filtration flux of 0.1% Adlerika, rejection is 98%.
Embodiment 3
(1) polyacrylonitrile (PAN) 13.0g is dissolved in N, among N-dimethylacetylamide (DMAC) the solvent 87g, obtains the electrostatic spinning solution of transparent homogeneous;
(2) polyamic acid 12.0g is dissolved in N, among dinethylformamide (DMF) the solvent 88g, obtains the electrostatic spray solution of transparent homogeneous;
(3) spinning solution in (1) is joined in the container, extrude by micro-injection pump control, spout connects high-voltage positive electrode, and static spins parameter and is controlled at voltage 18kv, spout aperture 1.8mm, solution flow rate 35 μ l/min, 25 ℃ of environment temperatures are carried out electrostatic spinning, and the average diameter of the PAN electrostatic spinning nano fiber that is obtained is 500nm, deposit thickness is 70 μ m, and porosity is 92%;
(4) electrostatic spray stoste in (2) is joined in the container, extrude by micro-injection pump control, spout connects high-voltage positive electrode, the electrostatic spray parameter is controlled at voltage 12kv, spout aperture 0.8mm, solution flow rate 5 μ l/min, 15 ℃ of environment temperatures, relative air humidity 25% carries out electrostatic spray, and the polyamic acid electrostatic spray deposit thickness that is obtained is 16 μ m;
(5) be heat treatment 3h in 180 ℃ the baking oven with the film that makes in temperature, promptly get nanofiber-based composite membrane for separation.
This composite membrane can be used for nanofiltration, in cross-current mode (seeing embodiment 1) film properties assessed, and be 46L/m2h to the filtration flux of 0.1% Adlerika, rejection is 99%.