U.S. patent application number 16/522928 was filed with the patent office on 2020-02-13 for porous membrane and method for filtering fluid including particles with porous membrane.
The applicant listed for this patent is NATIONAL TAIWAN UNIVERSITY. Invention is credited to Geng-Sheng LIN, Chung-Yuan MOU, Kuo-Lun TUNG, Jingling YANG.
Application Number | 20200047133 16/522928 |
Document ID | / |
Family ID | 69405339 |
Filed Date | 2020-02-13 |
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United States Patent
Application |
20200047133 |
Kind Code |
A1 |
MOU; Chung-Yuan ; et
al. |
February 13, 2020 |
POROUS MEMBRANE AND METHOD FOR FILTERING FLUID INCLUDING PARTICLES
WITH POROUS MEMBRANE
Abstract
A porous membrane and a method for filtering a fluid including
particles with the porous membrane are disclosed. The porous
membrane includes a macroporous substrate and a mesoporous silica
thin film (MSTF) with perpendicular mesopore channels. The MSTF is
positioned on the macroporous substrate. The method includes
passing the fluid including the particles through the porous
membrane.
Inventors: |
MOU; Chung-Yuan; (TAIPEI,
TW) ; YANG; Jingling; (TAIPEI, TW) ; TUNG;
Kuo-Lun; (TAIPEI, TW) ; LIN; Geng-Sheng;
(TAIPEI, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NATIONAL TAIWAN UNIVERSITY |
TAIPEI |
|
TW |
|
|
Family ID: |
69405339 |
Appl. No.: |
16/522928 |
Filed: |
July 26, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62718355 |
Aug 13, 2018 |
|
|
|
62718382 |
Aug 14, 2018 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 71/28 20130101;
B01D 71/54 20130101; H01M 2/1653 20130101; B01D 71/34 20130101;
B01D 2325/02 20130101; H01M 4/386 20130101; B01D 69/10 20130101;
H01M 10/0525 20130101; H01M 10/0565 20130101; B01D 71/40 20130101;
B01D 71/027 20130101; B01D 71/36 20130101; B01D 69/12 20130101;
B01D 69/02 20130101; H01M 2/1646 20130101; H01M 10/0562 20130101;
B01D 2325/04 20130101; B01D 71/025 20130101; B01D 71/52 20130101;
B82Y 30/00 20130101; B01D 71/80 20130101; H01M 2/1686 20130101 |
International
Class: |
B01D 71/02 20060101
B01D071/02; B01D 71/34 20060101 B01D071/34; B01D 71/40 20060101
B01D071/40; B01D 71/36 20060101 B01D071/36; B01D 71/54 20060101
B01D071/54 |
Claims
1. A porous membrane, comprising: a macroporous substrate; and a
mesoporous silica thin film (MSTF) with perpendicular mesopore
channels, wherein the MSTF is positioned on the macroporous
substrate.
2. The porous membrane of claim 1, wherein each mesopore channel of
the MSTF has a pore size of more than or equal to about 2 nm, and
less than or equal to about 10 nm.
3. The porous membrane of claim 1, wherein the MSTF has a thickness
of more than or equal to about 10 nm, and less than or equal to
about 100 nm.
4. The porous membrane of claim 1, wherein the MSTF has an area of
more than or equal to about 0.5 cm.sup.2, and less than or equal to
about 100 cm.sup.2.
5. The porous membrane of claim 1, wherein the macroporous
substrate comprises an inorganic material, a metal, a polymer, or a
combination thereof.
6. The porous membrane of claim 5, wherein the inorganic material
is selected from the group consisting of aluminum oxide, zirconia,
titania, magnesia, spinel, calcia, cordierite, zeolite, mullite,
ferrite, zinc oxide, silicon carbide, aluminum nitride, silicon
nitride, titanium carbide, tungsten carbide, barium titanate, boron
carbide, kaolin, and hydroxyapatite.
7. The porous membrane of claim 5, wherein the inorganic material
comprises an anodic aluminum oxide (AAO).
8. The porous membrane of claim 5, wherein the polymer is selected
from the group consisting of polyvinylidene fluoride (PVDF),
polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl
methacrylate (PMMA), polyoxyethylene (PEO), polyamide (PAI),
polytetrafluoroethylene (PTFE), and rubber.
9. The porous membrane of claim 1, wherein the macroporous
substrate has macropores, and the macropores have an average pore
diameter of more than or equal to about 20 nm, and less than or
equal to about 1 .mu.m.
10. The porous membrane of claim 1, wherein the macroporous
substrate has a thickness of more than or equal to about 10 nm, and
less than or equal to about 1 mm.
11. The porous membrane of claim 1, wherein the macroporous
substrate is in direct contact with the MSTF.
12. A method for filtering a fluid comprising particles with the
porous membrane of claim 1, the method comprising: passing the
fluid comprising the particles through the porous membrane of claim
1.
13. The method of claim 12, wherein the particles are
nanoparticles.
14. The method of claim 12, wherein the particles comprise
biomolecules, dyes, or a combination thereof.
15. The method of claim 14, wherein the biomolecules comprise
proteins, viruses, or a combination thereof.
16. The method of claim 12, wherein the porous membrane has a
permeation flux of more than or equal to about 300 L m.sup.-2
h.sup.-1 bar.sup.-1, and less than or equal to about 1100 L
m.sup.-2 h.sup.-1 bar.sup.-1.
17. The method of claim 12, wherein each mesopore channel of the
MSTF has a pore size of more than or equal to about 2 nm, and less
than or equal to about 10 nm.
18. The method of claim 12, wherein the macroporous substrate has
macropores, and the macropores have an average pore diameter of
more than or equal to about 20 nm, and less than or equal to about
1 .mu.m.
19. The method of claim 12, wherein the MSTF has an area of more
than or equal to about 0.5 cm.sup.2, and less than or equal to
about 100 cm.sup.2.
20. The method of claim 12, wherein the macroporous substrate
comprises an inorganic material, a metal, a polymer, or a
combination thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 62/718,355, filed Aug. 13, 2018, and U.S.
Provisional Application Ser. No. 62/718,382, filed Aug. 14, 2018,
the disclosures of which are incorporated by reference.
BACKGROUND
Field of Invention
[0002] The present disclosure relates to a porous membrane and a
method for filtering a fluid including particles with a porous
membrane. More particularly, the present disclosure relates to a
porous membrane including a macroporous substrate and a mesoporous
silica thin film (MSTF) positioned thereon and a method for
filtering a fluid including particles with the porous membrane.
Description of Related Art
[0003] Recently, well-defined mesoporous thin membranes with pore
diameters of 2 to 50 nm have attracted growing interest and wide
applications, such as membrane-based purification and
chromatography systems that require highly efficient separations.
In nanofiltration, ultrasmall nanochannels in the pore size range
of 1 to 10 nm are especially required for artificial membranes to
achieve molecule-level separation. However, the common commercial
nanoporous membranes generally exhibit random structure pores,
tortuous pore paths, wide pore size distribution, and are
relatively thick, thus with unsatisfactory liquid flux.
[0004] Therefore, membranes with large-scale perpendicular
nanochannels are eagerly demanded to achieve efficient
nanofiltration ability.
SUMMARY
[0005] The present disclosure provides a porous membrane including
a macroporous substrate and a mesoporous silica thin film (MSTF)
with perpendicular mesopore channels. The MSTF is positioned on the
macroporous substrate.
[0006] In some embodiments, each mesopore channel of the MSTF has a
pore size of more than or equal to about 2 nm, and less than or
equal to about 10 nm.
[0007] In some embodiments, the MSTF has a thickness of more than
or equal to about 10 nm, and less than or equal to about 100
nm.
[0008] In some embodiments, the MSTF has an area of more than or
equal to about 0.5 cm.sup.2, and less than or equal to about 100
cm.sup.2.
[0009] In some embodiments, the macroporous substrate includes an
inorganic material, a metal, a polymer, or a combination
thereof.
[0010] In some embodiments, the inorganic material is selected from
the group consisting of aluminum oxide, zirconia, titania,
magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite,
zinc oxide, silicon carbide, aluminum nitride, silicon nitride,
titanium carbide, tungsten carbide, barium titanate, boron carbide,
kaolin, and hydroxyapatite.
[0011] In some embodiments, the inorganic material includes an
anodic aluminum oxide (AAO).
[0012] In some embodiments, the polymer is selected from the group
consisting of polyvinylidene fluoride (PVDF), polyvinyl chloride
(PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA),
polyoxyethylene (PEO), polyamide (PAI), polytetrafluoroethylene
(PTFE), and rubber.
[0013] In some embodiments, the macroporous substrate has
macropores, and the macropores have an average pore diameter of
more than or equal to about 20 nm, and less than or equal to about
1 .mu.m.
[0014] In some embodiments, the macroporous substrate has a
thickness of more than or equal to about 10 nm, and less than or
equal to about 1 mm.
[0015] In some embodiments, the macroporous substrate is in direct
contact with the MSTF.
[0016] The present disclosure provides a method for filtering a
fluid including particles with a porous membrane. The method
includes the following step. The fluid including the particles is
passed through the porous membrane, wherein the porous membrane
comprises a macroporous substrate and a mesoporous silica thin film
(MSTF) with perpendicular mesopore channels, and the MSTF is
positioned on the macroporous substrate.
[0017] In some embodiments, the particles are nanoparticles.
[0018] In some embodiments, the particles include biomolecules,
dyes, or a combination thereof.
[0019] In some embodiments, the biomolecules include proteins,
viruses, or a combination thereof.
[0020] In some embodiments, the porous membrane has a permeation
flux of more than or equal to about 300 L m.sup.-2 h.sup.-1
bar.sup.-1, and less than or equal to about 1100 L M.sup.-2
h.sup.-1 bar.sup.-1.
[0021] It is to be understood that both the foregoing general
description and the following detailed description are by examples,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The disclosure can be more fully understood by reading the
following detailed description of the embodiment, with reference
made to the accompanying drawings as follows:
[0023] FIG. 1 shows a cross-sectional view of a porous membrane
according to various embodiments of the present disclosure.
[0024] FIG. 2A shows the macroporous substrate in FIG. 1 according
to various embodiments of the present disclosure.
[0025] FIG. 2B shows the porous membrane in FIG. 1 according to
various embodiments of the present disclosure.
[0026] FIGS. 3A-3B respectively show top-view scanning electron
microscopy (SEM) images of a single-layer AAO membrane.
[0027] FIGS. 4A-4C respectively show top-view SEM images of a
dual-layer MSTF-5.91.perp.AAO membrane.
[0028] FIG. 5 shows a side-view SEM image of a dual-layer
MSTF-5.91.perp.AAO membrane.
[0029] FIGS. 6A-6D respectively show 2D grazing-incidence
small-angle X-ray scattering (GISAXS) scattering profile of
MSTF-2.2, MSTF-2.5, MSTF-3.7 and MSTF-5.9.
[0030] FIG. 7 shows 1D intensity profile plotted against q.sub.y
for the GISAXS pattern of MSTF-2.2, MSTF-2.5, MSTF-3.7 and
MSTF-5.9.
[0031] FIG. 8 shows the corresponding permeation fluxes of the
MSTF.perp.AAO membranes with different pore sizes.
[0032] FIG. 9 shows UV-vis absorption spectra before and after
filtering the mixture solution of Cyt c and BSA through the
nanofilter device with MSTF-5.9|AAO as filter membrane.
[0033] FIG. 10 shows the dye rejection by MSTF-2.2.perp.AAO
membrane as a function of dye molecular weight (M.W.).
DETAILED DESCRIPTION
[0034] Reference will now be made in detail to the present
embodiments of the, examples of which are illustrated in the
accompanying drawings. Wherever possible, the same reference
numbers are used in the drawings and the description to refer to
the same or like parts.
[0035] The following embodiments are disclosed with accompanying
diagrams for detailed description. For illustration clarity, many
details of practice are explained in the following descriptions.
However, it should be understood that these details of practice do
not intend to limit the present disclosure. That is, these details
of practice are not necessary in parts of embodiments of the
present disclosure. Furthermore, for simplifying the drawings, some
of the conventional structures and elements are shown with
schematic illustrations.
[0036] One aspect of the present disclosure provides a porous
membrane including a macroporous substrate and a mesoporous silica
thin film (MSTF) with perpendicular mesopore channels thereon. FIG.
1 shows a cross-sectional view of a porous membrane 100 according
to various embodiments of the present disclosure. The porous
membrane 100 includes a macroporous substrate 110 and a mesoporous
silica thin film (MSTF) 120 with perpendicular mesopore channels
H1. These mesopore channels H1 are through nanochannels. The
macroporous substrate 110 has macropores H2. The MSTF 120 is
positioned on the macroporous substrate 110. In some embodiments,
the macroporous substrate 110 is in direct contact with the MSTF
120. FIG. 2A shows the macroporous substrate 110 in FIG. 1
according to various embodiments of the present disclosure. FIG. 2B
shows the porous membrane 100 in FIG. 1 according to various
embodiments of the present disclosure.
[0037] In some embodiments, each mesopore channel H1 of the MSTF
120 has a pore size of more than or equal to about 2 nm, and less
than or equal to about 10 nm. For example, the pore size is 2.2 nm,
2.5 nm, 3 nm, 3.7 nm, 4 nm, 5 nm, 5.4 nm, 5.9 nm, 6 nm, 7 nm, 8 nm,
or 9 nm, but not limited thereto. In some embodiments, the MSTF 120
has a thickness of more than or equal to about 10 nm, and less than
or equal to about 100 nm. For example, the thickness of the MSTF
120 is 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, or 90 nm, but not
limited thereto. In some embodiments, the MSTF 120 has an area of
more than or equal to about 0.5 cm.sup.2, and less than or equal to
about 100 cm.sup.2. For example, the area of the MSTF 120 is 10
cm.sup.2, 20 cm.sup.2, 30 cm.sup.2, 40 cm.sup.2, 50 cm.sup.2, 60
cm.sup.2, 70 cm.sup.2, 80 cm.sup.2, or 90 cm.sup.2, but not limited
thereto.
[0038] In some embodiments, the macroporous substrate 110 includes
an inorganic material, a metal, a polymer, or a combination
thereof. In some embodiments, the inorganic material is selected
from the group consisting of aluminum oxide, zirconia, titania,
magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite,
zinc oxide, silicon carbide, aluminum nitride, silicon nitride,
titanium carbide, tungsten carbide, barium titanate, boron carbide,
kaolin, and hydroxyapatite. In some embodiments, the inorganic
material includes an anodic aluminum oxide (AAO). In some
embodiments, the macroporous substrate 110 is an AAO substrate. In
some embodiments, the polymer is selected from the group consisting
of polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC),
polyacrylonitrile (PAN), polymethyl methacrylate (PMMA),
polyoxyethylene (PEO), polyamide (PAI), polytetrafluoroethylene
(PTFE), and rubber. In some embodiments, the macropores H2 of the
macroporous substrate 110 have an average pore diameter of more
than or equal to about 20 nm, and less than or equal to about 1
.mu.m. For example, the average pore diameter of the macropores H2
is 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm,
800 nm, or 900 nm, but not limited thereto. In some embodiments,
the macroporous substrate 110 has a thickness of more than or equal
to about 20 nm, and less than or equal to about 1 mm. For example,
the thickness of the macroporous substrate 130a is 30 nm, 40 nm, 50
nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500
nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm, but not limited
thereto.
[0039] In some embodiments, the porous membrane 100 is a filter and
is used for filtration, such as nanofiltration or
ultrafiltration.
[0040] Another aspect of the present disclosure provides a method
for filtering a fluid including particles with a porous membrane.
The method includes the following step. The fluid including the
particles is passed through the porous membrane, wherein the porous
membrane comprises a macroporous substrate and a mesoporous silica
thin film (MSTF) with perpendicular mesopore channels, and the MSTF
is positioned on the macroporous substrate. The fluid may be a
liquid, a gas or a supercritical fluid. The embodiments of the
porous membrane used in this method can refer to the embodiments of
the porous membrane 100 as mentioned previously. In some
embodiments, the porous membrane has a permeation flux of more than
or equal to about 300 L m.sup.-2 h.sup.-1 bar.sup.-1, and less than
or equal to about 1100 L m.sup.-2 h.sup.-1 bar.sup.-1. For example,
the permeation flux is 400, 500, 600, 700, 800, 900, or 1000 L
m.sup.-2 h.sup.-1 bar.sup.-1. In some embodiments, the permeation
flux is 339, 413, 638, or 1027 L m.sup.-2 h.sup.-1 bar.sup.-1. The
porous membrane of the present disclosure has excellent size
exclusion ability and high molecular-sieving ability.
[0041] In some embodiments, the particles are nanoparticles. For
example, the particles are Ag nanoparticles. In some embodiments,
the particles have an average size of more than 1.5 nm. In some
embodiments, the particles include biomolecules, dyes, or a
combination thereof, but not limited thereto. In some embodiments,
the biomolecules include proteins, viruses, or a combination
thereof, but not limited thereto.
[0042] Another aspect of the present disclosure provides a method
of fabricating a porous membrane. The method includes the following
steps. (i) A polymer film is formed on a marcoporous substrate.
(ii) A mesoporous silica thin film (MSTF) with perpendicular
mesopore channels is grown on the polymer film. (iii) The polymer
film is removed to form the porous membrane. More specifically, the
porous membrane includes the marcoporous substrate and the MSTF
with perpendicular mesopore channels thereon. The MSTF fabricated
by the method is free of cracking defects and has uniform
perpendicular mesopore channels. Moreover, by this method, large
area MSTF can be produced. In some embodiments, the method is used
for fabricating a centimeter-size MSTF. In some embodiments, the
MSTF has an area of more than or equal to about 0.5 cm.sup.2, and
less than or equal to about 100 cm.sup.2.
[0043] In some embodiments, the polymer film is formed by
synthesizing the polymer film on the marcoporous substrate. For
example, the polymer film is formed by the following steps. A
solution including polymers and a photoinitiator is coated on the
marcoporous substrate. The solution is irradiated with UV light to
form crosslinked polymers to form the polymer film.
[0044] In some embodiments, the polymers comprise polystyrene (PS),
poly(ethylene oxide) poly(propylene oxide) poly(ethylene oxide)
triblock copolymer (PEO-PPO-PEO triblock copolymer, P123),
polymethyl methacrylate (PMMA), or a combination thereof. In some
embodiments, the polymer film includes cross-linked polystyrene
(PS), cross-linked poly(ethylene oxide) poly(propylene oxide)
poly(ethylene oxide) triblock copolymer (PEO-PPO-PEO triblock
copolymer, P123), cross-linked polymethyl methacrylate (PMMA), or a
combination thereof.
[0045] In some embodiments, the polymer film is removed by a heat
treatment and an ozone clean. In some embodiments, the heating
treatment is performed at a temperature between about 300.degree.
C. and about 500.degree. C. For example, the temperature is
350.degree. C., 400.degree. C. or 450.degree. C., but not limited
thereto.
[0046] In some embodiments, step (ii) is prior to step (i). More
specifically, a mesoporous silica thin film with perpendicular
mesopore channels is grown on a polymer film. After that, the
mesoporous silica thin film and the polymer film are transferred
onto the marcoporous substrate, wherein the polymer film is
positioned between the marcoporous substrate and the mesoporous
silica thin film.
[0047] In some embodiments, the polymer film includes
polyvinylidene fluoride (PVDF). In some embodiments, the polymer
film is removed by N-methyl-pyrrolidone (NMP) and an ozone
clean.
[0048] In some embodiments, the mesoporous silica thin film with
the perpendicular mesopore channels is grown on the polymer film by
the following steps. (i) The polymer film is immersed into an
ammonia solution, wherein the ammonia solution includes a tertiary
alkyl ammonium halide, ammonium hydroxide, alcohol, and a pore
expending agent. (ii) A silica precursor is introduced into the
ammonia solution. (iii) A heating step is performed to form the
mesoporous silica thin film on the polymer film. In some
embodiments, the tertiary alkyl ammonium halide is
cetyltrimethylammonium bromide (CTAB). In some embodiments, the
pore expending agent is selected from the group consisting of
decane, ethyl acetate, hexadecane, silane polyethylene glycol,
pentyl ether and a combination thereof. In some embodiments, the
silica precursor includes tetraethyl orthosilicate, fumed silica,
zeolite beta seeds, or a combination thereof. In some embodiments,
the heating step is performed at a temperature between about
35.degree. C. and about 80.degree. C. For example, the temperature
is 40.degree. C., 45.degree. C., 50.degree. C., 55.degree. C.,
60.degree. C., 65.degree. C., 70.degree. C., or 75.degree. C., but
not limited thereto.
[0049] Hereinafter, the present disclosure will be described in
detail with reference to the embodiments and comparative examples
in the present disclosure. However, the present disclosure is not
limited to the following embodiments.
EXAMPLE 1
Synthesis of a Dual-Layer MSTF/AAO Membrane by a Polymer Interlayer
Method
[0050] Firstly, polystyrene (PS), PEO-PPO-PEO triblock copolymer
(P123) and polymethyl methacrylate (PMMA) were respectively used to
produce a smooth surface layer on aluminum oxide (AAO) membranes
with macropores for further growth of mesoporous silica thin film
(MSTF). PS and P123 were dissolved in toluene under 50.degree. C.
for 1 h, respectively. PMMA was dissolved in anisole. Subsequently,
0.1 wt %-1 wt % photoinitiator was well dispersed into the
solutions above. These solutions were used to spin-coat the AAO
membranes (2.5 cm-4.7 cm in diameter, situated on a 5.times.5
cm.sup.2 glass sheet) at 2000 rpm for 30 s, respectively. Then the
cross-linking of the polymers on AAO surface were induced by the
photoinitiator under UV light irradiation for 5 min-10 min. The
spin-coated PS/AAO support and PMMA/AAO support were cured under
100.degree. C. for 1 h-2 h afterwards, while P123/AAO support was
stabilized at room temperature for 1 h-2 h, respectively.
[0051] Further growth of a mesoporous silica thin film (MSTF) on
the top surface of each polymer film coated AAO membrane was
conducted in an oil-in-water emulsion. The oil-in-water emulsion
was prepared by mixing cetyltrimethylammonium bromide (CTAB) (0.965
g), ethanol (30.0 g) and a pore expending agent (either 3.0 mL of
decane, or 3.1 mL of pentyl ether, or 4.5 mL of hexadecane, or 1.2
mL of ethyl acetate, or 1.2 mL of ethyl acetate with the addition
of 2.2 mL of silane polyethylene glycol) at 50.degree. C. Then, the
polymer film coated AAO membranes were directly immersed into the
solution, followed by an introduction of NH.sub.3 aqueous solution
(7.5 g, 35.5 wt %), tetraethyl orthosilicate (TEOS)/ethanol
solution (8.35 mL, 20% by volumes) under stirring at 50.degree. C.
overnight. The molar ratios of
CTAB:H.sub.2O:NH.sub.3:decane:ethanol:TEOS were calculated to be
1:8400:90:5.8:250:2.8. The synthesized MSTF/polymer film/AAO
membranes were rinsed with ethanol, and then calcined in air
atmosphere by heating from room temperature at rate of 1.degree.
C./min to 300.degree. C. -500.degree. C. and maintained at this
temperature for 30 min-6 h, followed by UV ozone clean for 15
min-30 min. The polymer film and surfactant (e.g. CTAB) were
removed by calcination and an ozone clean. After that, porous
membranes including the AAO membrane and the MSTF with
perpendicular mesopore channels freely standing on the AAO membrane
were obtained. The MSTF AAO membranes with different pore size of
MSTF are labeled as MSTF-X.perp.AAO (X corresponds to the pore
size).
EXAMPLE 2
Synthesis of a Dual-Layer MSTF/AAO Membrane by a Polyvinylidene
Fluoride (PVDF) Assistant Transfer Method
[0052] Firstly, 10.0 wt % polyvinylidene fluoride (PVDF) was
dissolve in acetone and dimethyl formamide mixed solution (acetone:
dimethyl formamide=3:1 v/v) under the ultrasonic at 30.degree. C.
for 1 h. Then, the PVDF solution was spin-coated at 2000 rpm for 30
s on a 5.times.5 cm.sup.2 glass sheet. Further solvent was
evaporated at 60.degree. C. for 1 h. Subsequently, MSTF was grown
onto the PVDF film by the same procedures as mentioned in Example
1. Then, the synthesized MSTF/PVDF film/glass sheet was rinsed with
ethanol three times. To remove the residual organic surfactants,
the samples were immersing in a hydrochloric acid/ethanol (5 mg/ml,
50 mL) solution for 12 h-16 h under constant stirring, followed by
washing the MSTF/PVDF film/glass sheet by ethanol, and peeling off
the MSTF/PVDF film from the glass sheet. Subsequently, transfer the
MSTF/PVDF film onto AAO membrane (0.1 cm-4.7 cm in diameter).
Finally, the PVDF film in MSTF/PVDF film/AAO membrane was removed
by N-methyl-pyrrolidone (NMP), follow by UV ozone clean for 15
min-30 min to remove the PVDF film and the organics. After that, a
porous membrane which includes the AAO membrane and the MSTF with
perpendicular mesopore channels freely standing on the AAO membrane
was obtained. The MSTF.perp.AAO membranes with different pore size
of MSTF are labeled as MSTF-X_AAO (X corresponds to the pore
size).
EXAMPLE 3
Characterization of a Dual-Layer MSTF.perp.AAO Membrane by Scanning
Electron Microscope (SEM)
[0053] Top-view and edge-view micrographs were taken on a field
emission scanning electron microscope (SEM) (Hitachi S-4800)
operated at accelerating voltages of 5 kV and 15 kV, respectively.
The samples were loaded onto a plate holder with conducting carbon
tape adhered at the bottom and silver paint coated at the edges of
membranes. The whole specimen was baked at 80.degree. C. overnight
prior to SEM imaging.
[0054] FIGS. 3A-3B respectively show top-view scanning electron
microscopy (SEM) images of a single-layer AAO membrane. FIGS. 4A-4C
respectively show top-view SEM images of a dual-layer MSTF-5.91_AAO
membrane. The top-view SEM images of the single-layer AAO membrane
(FIGS. 3A, 3B) and the top-view SEM images of the dual-layer
MSTF-5.91.perp.AAO membrane (FIGS. 4A-4C) confirm that the
continuous regime of the thin film of mesoporpous silica of
MSTF-5.91.perp.AAO showed no apparent defects. Centimeter-size thin
film of mesoporpous silica in MSTF-5.91.perp.AAO can be routinely
prepared with optically uniformity. A magnified top-view SEM image
(FIG. 4C) reveals the single-layer MSTF with hexagonally arranged
nanopores cover on both the wall and macrospore of AAO membrane. A
side-view SEM image (FIG. 5) of the MSTF-5.91.perp.AAO reveals AAO
with uniform perpendicular channels (thickness of 60 .mu.m), while
MSTF with uniform thickness of about 30 nm.
EXAMPLE 4
Characterization of a Dual-Layer MSTF/AAO Membrane by Grazing
Incidence Small Angle X-Ray Scattering (GISAXS)
[0055] The incidence X-ray energy of 12 keV (1.033 A) and the
sample-to-detector distance of 3.10 m result in a q-range of
0.005540-0.2853 .ANG..sup.-1 that is equivalent to real space
distance of 2.2-113 nm. The incidence angle of each X-ray beam
varied between 0.1 and 0.3.degree.. The scattering data extraction
was performed in an X-ray scattering image analysis package
(POLAR). Alternatively, in-house scattering was conducted by a
grazing-incidence geometry (Nano-Viewer, Rigaku) with a two
dimensional (2D) area detector (Rigaku, 100K PILATUS). The
instrument is equipped with a 31 kW mm.sup.-2 generator (rotating
anode X-ray source with a Cu K.alpha. radiation of .lamda.=0.154
nm). The scattering vector, q (q=4.pi./.lamda. sin .theta.), along
with the scattering angles .theta. in these patterns were
calibrated using silver behenate. The mesoporous silica thin film
with perpendicular nanochannels were mounted on a z-24 axis
goniometer with an incident angle of 0.1-0.3.degree..
[0056] The perpendicular mesopore channels over the entire MSTF
membranes with different pore size were further characterized by
grazing-incidence small-angle X-ray scattering (GISAXS). FIGS.
6A-6D respectively show 2D GISAXS scattering profile of MSTF-2.2,
MSTF-2.5, MSTF-3.7 and MSTF-5.9. As shown in FIGS. 6A-6D, the 2D
GISAXS patterns show prominent spots on the left of the
grazing-incidence X-ray beam. These indicate the highly ordered
vertical nanochannel features of mesoporous thin films. FIG. 7
shows 1D intensity profile plotted against q.sub.y for the GISAXS
pattern of MSTF-2.2, MSTF-2.5, MSTF-3.7 and MSTF-5.9. The 1D
intensity profiles of these MSTF show significant peaks located at
different q.sub.y positions, and reflect the 2D hexagonal symmetry
with the space group p6mm, as well as evidence the perpendicular
orientation of MSTF above substrates. The (100) peak of MSTF-5.9 is
found to correspond with an averaged d-spacing of 6.87 nm, account
for a pore to pore center distance of 7.94 nm, which agrees with
the SEM results (FIG. 4C) with average pore size of about 5.9 nm
and pore walls sizes of about 2.0 nm. Meanwhile, the average pore
sizes of MSTF-3.7, MSTF-2.5 and MSTF-2.2 nm were about 3.7 nm, 2.5
nm, and 2.2 nm, respectively.
EXAMPLE 5
Flux Measurement of the Dual-Layer MSTF.perp.AAO Membranes
[0057] Pressure-driven separation was carried out using a dead-end
filtration device under a pressure of 7 kPa at room temperature.
The effective permeation area of the filter was 12.6 cm.sup.2. Pure
water flux (Jw, in L m.sup.-2 h.sup.-1 bar.sup.-1) was used to
evaluate the permeation performance of the MSTF.perp.AAO
membranes.
[0058] The effectiveness of the dual-layer MSTF.perp.AAO membrane
filter for separating nanosize-based proteins was evaluated using a
dead-end filtration device. FIG. 8 shows the corresponding
permeation fluxes of the MSTF.perp.AAO membranes with different
pore sizes. P represents the permeation flux. The permeation fluxes
were tested with pure water. It should be noted that all permeation
fluxes were found to be larger than 339 L m.sup.-2 h.sup.-1
bar.sup.-1 and even reached 1027 L m.sup.2 h.sup.-1 bar.sup.-1,
which is significantly higher than the permeances of reported
works.
EXAMPLE 6:
Use of a Dual-Layer MSTF-5.9.perp.AAO Membrane as a Filter for
Size-Exclusion Ultrafiltration
[0059] To demonstrate the high molecular-sieving ability of the
MSTF-5.91|AAO membrane with pore diameter of 5.9 nm,
ultrafiltration of proteins was performed using the dead-end
filtration device as mentioned in Example 5 under the same
permeation conditions. Ten milliliters of a solution was placed
into a filtration device equipped with a membrane filter. The
solution that permeated through the thin membrane was collected.
The concentration changes in the protein solutions before and after
the filtration were determined by UV-vis absorption spectroscopy
(Hitachi U-3310). The separation performance was evaluated based on
the amount of the protein present in the permeate and the original
(feed) solution. The feed solutions of proteins with different
molecular weights (MWs) and sizes were selected, such as bovine
serum albumin (BSA) (67 kDa, 7 nm), ovalbumin (OVA) (43 kDa, 5 nm),
lysozyme (LYZ) (14 kDa, 3 nm), and cytochrome c (Cyt c) (12 kDa, 2
nm). The concentration changes of the protein solutions before and
after the filtration were determined by UV-vis absorption
spectroscopy, respectively. The summary results are shown in the
following Table 1. Table 1 shows ultrafiltration results of various
proteins using MSTF-5.91.perp.AAO and bare AAO membranes.
TABLE-US-00001 TABLE 1 AAO MSTF-5.9 .perp. AAO Size rejection
rejection Proteins kDa (nm) (%) (%) Bovine Serum 67 7 29.6 99.6
Albumin Ovalbumin 43 5 3.1 57.1 Lysozyme 14 3 2.6 29.1 Cytochrome c
12 2 0.6 10.4
[0060] MSTF-5.91.perp.AAO achieved 99.6% rejection of BSA, 57.1%
rejection of OVA, 29.1% rejection of LYZ, and 10.4% rejection of
Cyt c. The results indicate that more than 70.9% of LYZ and 89.6%
of Cyt c passed through the biomimetic MSTF-5.91.perp.AAO membrane,
while BSA was completely rejected. The results demonstrate that the
MSTF-5.91_AAO membrane exhibits excellent selectivity for the
separation of proteins with different MWs.
[0061] To demonstrate mixed molecular separations with the
MSTF.perp.AAO membranes, two common proteins with different
molecular size, BSA (7 nm) and Cyt c (2 nm) are applied for mixed
nanofiltration. FIG. 9 shows UV-vis absorption spectra before and
after filtering the mixture solution of Cyt c and BSA through the
nanofilter device with MSTF-5.91.perp.AAO as filter membrane. The
UV-vis spectra shows the characteristic peaks of BSA and Cyt c at
280 and 416 nm, respectively. The mesoporous silica thin membrane
with a pore size of 5.9 nm (MSTF-5.91.perp.AAO) was used as the
nanofilter. After mixing, the UV-vis spectra show two
characteristic peaks at 280 and 416 nm, which can be attributed to
the BSA and Cyt c, respectively. After filtration by the mesoporous
silica membrane nanofilter device, well-defined Cyt c peak at 416
nm can be obtained in the UV-vis spectra, where the characteristic
peak of BSA almost completely disappears (the small peak at 280 nm
was also attributed to the signal of Cyt c, as shown of the bare
initial Cyt c solution). It can be calculated that more than 89.4%
of Cyt c can pass the mesoporous silica membrane, while 99.9% of
BSA are rejected. Since the membrane with a uniform pore size of
5.9 nm, when the molecular size is larger than the pore size of the
MSTF.perp.AAO membranes, they can be blocked. While small ones can
easily pass through the MSTF.perp.AAO membranes, making the
size-selective separation and purification possible. These results
confirm that the prepared MSTF-5.91.perp.AAO can be used as an
effective nanofilter for size selective filtration at the
macroscale due to the centimeter scale size.
[0062] Base on this concept, this mesoporous matrix also can be
applied for concentrate and separate Au nanoparticles in mixed
solution, as well as the isolation of virus.
EXAMPLE 7
Use of a Dual-Layer MSTF-2.2.perp.AAO Membrane as a Filter for Dye
Nanofiltration
[0063] To demonstrate the high molecular-sieving ability of the
MSTF-2.2.perp.AAO membranes with pore diameter of 2.2 nm,
nanofiltration of dyes was performed using the dead-end filtration
device as mentioned above under the same permeation conditions.
Seven different dye solutions (reactive red, evans blue, rose
bengal, Congo red, rhodamine B safranin O, methylene blue) with
concentrations of 80 mgL.sup.-1 were chosen as feeds.
[0064] FIG. 10 shows the dye rejection by MSTF-2.2.perp.AAO
membrane as a function of dye molecular weight (M.W.). The M.W. cut
off is determined from the dashed lines shown (1 Da=1 g/mol). As
shown in FIG. 10, the MSTF-2.2.perp.AAO membrane can reject
reactive red (Mw=1469), evans blue (Mw=960), rose bengal (Mw=1017)
and Congo red (Mw=696.68) with rejection rates of 99.9%, 100%,
96.2% and 92.0%, respectively, and show poor rejection rates for
smaller dyes, rhodamine B (69.5%) (Mw=479), safranin O (79.2%)
(Mw=350), and methylene blue (68.7%) (Mw=320). The molecular weight
cutoff (MWCO) of MSTF-2.2.perp.AAO was determined to be about 690
Da for 90% dye rejection. These results confirm that the prepared
MSTF-2.2_AAO membrane can be used as an effective selective
nanofilter for dye nanofiltration at the macroscale due to its
uniform periodic vertical mesoporous channels and centimeter
size.
[0065] Based on the above, the present disclosure provides a porous
membrane including a macroporous substrate and a mesoporous silica
thin film (MSTF) with perpendicular mesopore channels, wherein the
MSTF is positioned on the macroporous substrate. The porous
membrane can be applied for filtration, such as nanofiltration or
ultrafiltration. The present disclosure provides a method for
filtering a fluid including particles by using the porous membrane
as a filter. The porous membrane has excellent size exclusion
ability and high molecular-sieving ability.
[0066] Although the present invention has been described in
considerable detail with reference to certain embodiments thereof,
other embodiments are possible. Therefore, the spirit and scope of
the appended claims should not be limited to the description of the
embodiments contained herein.
[0067] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims.
* * * * *