[001] The present invention is related to the graphene
nanotechnology and its application in air filtration and
masks. More particularly, the present invention is
5 related to preparation of graphene nanocomposites/derivatives membrane for use in high
performance masks and air purifiers that has the
application in graphene based advanced materials in air
filtration membranes.
10
BACKGROUND OF THE INVENTION:
[002] With high-speed urbanization and industrialization,
severe air pollution shows threatening influences on
individual’s health, especially in developing countries.
15 Air pollutants in the atmosphere include mineral powder,
coal and carbon powder (which are produced by industrial
emissions), vehicle exhaust, combustion from daily life,
and smoke from forest fires, among other sources. In
addition, there are also certain natural contaminants,
20 including pollen, bacteria, and some microorganisms and
virus-carrying aerosols, that may cause allergies or
respiratory infectious diseases.
[003] Particulate matter (PM) air pollution is a severe
global issue, posing a serious threat to human health. PM
25 pollutants can be mainly classified into two kinds
according to their aerodynamic diameters: PM2.5 and PM10.
PM2.5 pollutants also possess large surface area and are
loaded with pathogenic substances, which also increase
the morbidity of the disease and imperil global public
30 health.
[004] In order to mitigate the health risks from air
pollutants, various membrane-based separation
technologies have been developed. The realm of materials
that are being tested for their feasibility as air
filters comprises of membranes derived from organic
polymers along with inorganic membranes made from glass,
metal, ceramics, etc., including hybrids such as
inorganic polymeric membranes.
[005] Graphene, unique atom-thick 2D structure with sp2
5
hybridization and large specific surface area, high
thermal conductivity, superior electron mobility, and
chemical stability have made graphene and its derivatives
extremely attractive components for nano-composite
10 membrane materials for air filtration applications. Its
anti-microbial property reduces the risk of different air
allergies, infection and diseases caused by bacteria and
viruses.
[006] The conventional air filters and air purifiers just
15 remove particulate matter from the environment. The
addition of above-mentioned membrane is suggested to
improve the PM filtration as well as adding the antimicrobial and odour removal properties as well.
20 OBJECTS OF THE INVENTION:
[007] The primary objective of the present invention is to
synthesize graphene nano-composite/derivative membrane
with a porous nano-composite fabric of predetermined
thickness sealed in between the layers of polymer
25 membrane of predefined thickness for use in high
performance masks and air purifiers.
[008] Yet another object of the present invention is to
provide graphene nano-composite/derivative membranes that
is effective barrier against particulate matter.
30 [009] Yet another object of the present invention is to
provide a graphene nano-composite/derivative membrane
that shows anti-bacterial property.
[010] Yet another object of the present invention is to
provide graphene nano- composite/derivative membrane that
35 kills the bacteria in the due course of time that comes
in contact with the membrane using antimicrobial
graphene-based composite material.
[011] Yet another object of the present invention is to
provide a graphene nano-composite/derivative membrane
5 that shows anti-viral property.
[012] Yet another object of the present invention is to
provide graphene nano-composite/derivative membrane that
kills the viruses in the due course of time that comes in
contact with the membrane using antiviral graphene-based
10 composite material.
[013] Yet another object of the present invention is to
provide graphene nano-composite/derivative membrane which
is standalone product be used for filtering /cleaning air
through air mask/ air filters/ AC vents including but not
15 limited to other air purifying equipment.
[014] Another objective of the present invention is to
provide a graphene nano-composite/derivative membrane
which comprises of highly active graphene nano-composite
layer standalone or sandwiched between other hydrophobic
20 layers/ non-hydrophobic/multiple membrane or combination
thereof.
[015] Yet another objective of the embodiments of the
present invention is to provide graphene nanocomposite/derivative membrane preparation method for
25 masks/filtration membrane wherein the modified graphene
may be in multiple layers/sheets.
[016] Yet another objective of the embodiments of the
present invention is to provide graphene nanocomposite/derivative membrane preparation method for
30 masks/filtration membrane wherein the oxygen content in
the modified graphene may vary from 1 to 60%
[017] Yet another objective of the embodiments of the
present invention is to provide a graphene nanocomposite/derivative membrane preparation method wherein
35 the use of functionalization stabilizes graphene
suspension in a complex polymer environment without
agglomeration.
SIGNIFICANCE OF THE INVENTION:
5 [018] The main significance of the present invention is to
provide graphene nano-composite/derivative membrane that
is reusable/washable more than twenty cycles without any
significant effect on its performance.
[019] Another significance of the present invention is to
10 provide graphene nano-composite/derivative membrane that
doesn’t allow to store any static charge on the surface
of the membrane.
[020] Further another significance of the present
invention is to provide graphene nano15 composite/derivative membrane that spreads heat evenly
across the multi-application area across the surface of
membrane.
[021] Further another significance of the present
invention is to provide a graphene nano20 composite/derivative membrane where the membrane is
neither toxic nor generate any secondary contamination to
the air for defined application.
[022] Further another significance of the present
invention is to provide a graphene nano25 composite/derivative membrane where the membranes are
flexible and provides robustness for multiple
application.
[023] Further another significance of the present
invention is to provide graphene nano30 composite/derivative membrane preparation method for
masks/filtration membrane which will improve its
filtration efficiency.
[024] Further another significance of the present
invention is to provide graphene nano35 composite/derivative membrane preparation method for
masks/filtration membrane which will help in reducing
odour and humidity.
[025] Further another significance of the present
invention is to provide graphene nano5 composite/derivative membrane preparation method for
masks/filtration membrane that possess low density.
SUMMARY OF THE INVENTION:
[026] In an aspect the present disclosure provides a
graphene nano composite polymeric membrane and the method
10 of its synthesis.
[027] The preferred embodiment of the present invention is
disclosed in the drawings and the process is disclosed in
the example herein.
[028] The process involved in the synthesis of the preferred
15 embodiment includes filtration, coating, polymer mixing,
vacuum assisted filtration methods.
[029] In an embodiment, the graphene oxide is synthesized
by modified hummer’s method, doping of the graphene oxide
with sulphur element; saturation of the graphene oxide
20 with amine group, crosslinking of the silver particles
with the graphene oxide resulting in graphene nano
composite; mixing graphene nano composite with polymer
matrix (polypropylene and/or polyester) in the form of
slurry; coating of the resultant composition on the
25 polymer foam and/or fibres; adding the polymeric
foam/fibre in the solution of water and ethanol; drying
of the fibre overnight; obtained the graphene nano
composite polymeric membrane.
[030] Another embodiment of the invention, the thermal
30 reduction of Graphene Oxide is carried out in a
controlled atmosphere with the help of gases including
but not limited to nitrogen, helium, argon or a
combination thereof.
[031] Another embodiment of the invention, the chemical
reduction of Graphene Oxide is carried in solution phase
with the help of chemicals including but not limited to
Sodium borohydride, Hydrogen peroxide, Hydrazine,
5 dimethylhydrazine, NaOH, ascorbic acid or a combination
thereof.
[032] Another embodiment of the invention, the graphene
oxide may be doped with nitrogen and sulphur containing
species not limited to an amide group (—C(O)N), a nitrile
10 group (—C≡N), and an amine group (—NH2, thiol group (-SH) and thiocyanate group (-S-C≡N).
[033] Another embodiment of the invention, the graphene
oxide may be functionalized with metallic elements
including, but not limiting to Ag, Cu, Au, Fe, Ti, Ni,
15 Zn, Mg, Pt etc. and/or their combination.
[034] Another embodiment of the invention, the graphene
oxide may be functionalized with metal oxide
nanoparticles including, but not limiting to Ag2O, CuO,
Au2O3, Fe2O3, TiO2, NiO, ZnO, MgO, PtO2 etc. and/or their
20 combination.
BRIEF DESCRIPTION OF THE DRAWINGS:
[035] The drawings described herein are for illustrative
purposes only of selected embodiments and not for all
25 possible implementations and are not intended to limit
the scope of the present disclosure. The invention
itself, however, both as to organization and method of
operation, may best be understood by reference to the
detailed description which follows taken in conjunction
30 with the accompanying drawings in which:
[036] Figure 1 illustrates the two dimensional overview of
graphene silver nano-composite polymeric membrane;
[037] Figure 2 illustrates the two dimensional
representation of the graphene nano composite with silver
crosslinking.
[038] Figure 3 illustrates the two dimensional
5 representation of the coating of silver particles on the
graphene nano composite.
DETAILED DESCRIPTION OF THE INVENTION:
[039] The terms "comprises", "comprising", or any other
variations thereof, are intended to cover a non-exclusive
10 inclusion, such that a process or method that comprises a
list of steps does not include only those steps but may
include other steps not expressly listed or inherent to
such a process or method. Similarly, one or more systems
or sub-systems or elements or structures or components
15 preceded by "comprises... a" does not, without more
constraints, preclude the existence of other systems,
sub-systems, elements, structures, components, additional
systems, additional sub-systems, additional elements,
additional structures or additional components.
20 Appearances of the phrase “in an embodiment”, “in another
embodiment” and similar language throughout this
specification may, but not necessarily do, all refer to
the same embodiment.
[040] Unless otherwise defined, all technical and
25 scientific terms used herein have the same meaning as
commonly understood by those skilled in the art to which
this invention belongs. The system, methods, and examples
provided herein are only illustrative and not intended to
be limiting.
30 [041] The preferred embodiments will now be described more
fully with reference to the accompanying drawings. The
embodiments are provided to thoroughly describe the
disclosure and will fully convey the scope to those who
are skilled in the art.
[042] In describing the preferred embodiments of the
present invention, reference will be made herein to
Figure 1, 2 and 3 of the drawings which explains the
features of the invention.
5 [043] According to the Figure 1 the present invention is
related to the graphene nano-composite polymeric membrane
with silver crosslinking.
[044] The process for the synthesis of graphene nano
composite polymeric membrane is explained in the example
10 illustrated herewith. The process for the synthesis of
graphene nano composite comprising synthesis of graphene
oxide by modified hummers method, thermal reduction of
Graphene Oxide, silver crosslinking with the sulphur
doped amine functionalized graphene oxide.
15 [045] Figure 2 and 3 shows the composite of graphene oxide
crosslinked with metal oxide nanoparticles. The
crosslinking of metal nanoparticles with graphene layers
partially reduces the graphene oxide, further the
crosslinking improves the dispersibility of reduced
20 graphene oxide,
[046] The graphene nano-composite is mixed with polymer
matrix. The graphene nano-composite/derivative crosslink
with monomer and/or polymer matrix of the membrane.
Further the crosslinking improves the dispersibility of
25 graphene nano-composite/derivative.
[047] The graphene nano-composite/derivative is mixed with
polymer in the form of slurry containing a mixture of
graphene nano-composite/derivative and solvent and is
generally referred as graphene additive.
30 [048] The graphene nano-composite/derivative is mixed with
polymer in the form of slurry, where the graphene
additive weight ratio lies in the range of about 0.01 to
20 weight percent.
[049] The graphene additive is coated on the polymer foam
35 and/or fibres using spray coating, dip coating, also by
vacuum assisted coating or heating and are generally
referred as pre-processing. The polymer substrate coated
with the graphene additive is subjected to drying and
curing. The polymer substrate coated with the graphene
additive is compacted by calendaring to achieve the
5 desired thickness and is generally referred to as post
processing.
[050] Also, the graphene additive is coated on the natural
fibre using spray coating, dips coating, vacuum assisted
coating or heating and is generally referred as pre10 processing. The polymer substrate coated with the
graphene additive is subjected to drying and curing. The
natural fiber substrate coated with the graphene additive
is compacted by calendaring to achieve the desired
thickness and is generally referred to as post
15 processing.
[051] The invention will be more specifically illustrated
by the following Example.
Example: Synthesis of Graphene Nano Composite Polymeric
Membrane using 5gm graphite flakes
20 Synthesis of Graphene Oxide
[052] Initially graphene oxide is synthesized using 5gms
graphite flakes by modified Hummers method. H2SO4 and
NaNO3 are added in a ratio of 50:1 by volume to the
graphite flakes. KMnO4 is then added slowly to the above
25 composition slowly while stirring continuously for four
days to allow the oxidation of graphite. The completion
of oxidation is confirmed by the color change of the
solution from dark green to purplish brown.H2O2 is added
dropwise to the above composition till the sample color
30 changes to milky white and subsequently to yellow,
indicating high oxidation level of graphite. Lukewarm
water is then added slowly and the sample is left for 12h
to settle. When the layers are separated, the upper layer
is decanted and 10% HCl is added to the lower sedimented
layer which is again kept for settling. The upper layer
is again decanted to remove the acid. De ionised water is
mixed with the settled layer and left for settling. This
process is repeated 2-3 times to decrease the acid
5 content and the time for settling depends on the
precursor graphite flakes. The decanted layer is then
centrifuged at 12000 rpm for 20 minutes to remove the
remaining acid.De ionised water is added to the sediment.
NaOH solution is added to the sediment till the pH
10 reaches 6.5 while stirring continuously and vigorously.
The above composition is centrifuged at 14000 rpm for 30
minutes. The supernatant is discarded and water is added
for further centrifugation. The process is repeated 4
times to remove the sodium salts. The washed pellets are
15 dispersed in acetone water solution (30%v/v). The above
solution is sonicated at 600 W for 2h. The sonicated
solution is centrifuged at 8000 rpm for 12 minutes. The
pellet is collected and dried at 55oC (in this step
inferior quality of Graphene Oxide is obtained). To
20 obtain superior quality Graphene Oxide, the supernatant
is carefully collected and concentrated at 65oC under
constant stirring. Further the pellets obtained are kept
in a rotary evaporator and finally dried in an oven at
55oC .
25 Synthesis of sulfur doped Graphene:
[053] 100 ml of Graphene Oxide (0.25 mg/ml) dispersed in
DI water and 200 mg thiourea are placed in Teflon lined
autoclave preheated at 240°C for 5 h. The product was
washed from the reaction vessel using deionized water.
30 The reaction mixture is directly filtered by suction
filtration on the nylon membrane and repeatedly washed
with deionized water and methanol.
Sulfur doped Graphene substitution with amine group:
[054] Sulfur doped Graphene 200 mg is added to 500 ml
35 ethylene glycol and sonicated for 5 hrs. The above
solution along with 50 ml ammonia solution is transferred
to 1 ltr Teflon line autoclave and subjected to
solvothermal reaction for 150oC for 12 h. After reaction,
the vessel is allowed to cool down and the precipitate is
separated by filtration and washed with De ionised water
and dried at 80o
5 C overnight.
Silver crosslinking
[055] 100 mg Amine functionalized Graphene is added to 400
ml solution of water and ethanol in a ratio of 95:5 and
sonicated for 2 hrs. The above solution along with 100 mg
10 silver nitrate precursor is transferred to Teflon lined
beaker and subjected to solvothermal reaction for 90oC for
12 h. After reaction, the vessel is allowed to cool down
and the precipitate is separated by filtration and washed
with De-ionized water. Dried at 80oC overnight and get the
15 silver crosslinked graphene oxide.
Membrane Preparation
[056] Silver crosslinked Graphene nanocomposite/derivative (250 mg) is added to 1 ltr solution
of water and ethanol in the ratio of 95:5 followed by
20 sonication. The above solution is transferred to Teflon
lined container and heated at 60oC while stirring
continuously. The polymeric foam/ fibre is dipped inside
the solution for 1 hr and then transferred in cold water
solution. The foam/fibre is dried at 120oC overnight and
25 finally getting the graphene silver nano composite
polymeric membrane.

We claim

1. Graphene nano composite polymeric membrane comprising
sulphur doped amine functionalized silver linked reduced
5 graphene oxide.
2. The process for the synthesis of graphene nano composite
polymeric membrane comprises:
i) Taking graphite flakes in the container;
ii) synthesis of graphene oxide by modified hummers method;
10 iii)doping of the graphene oxide with sulphur element;
iv) saturation of the graphene oxide with amine group,
v) crosslinking of the silver particles with the graphene
oxide resulting in graphene nano composite;
vi) mixing graphene nano composite with polymer matrix
15 (polypropylene and/or polyester) in the form of slurry;
vii)coating of the resultant composition on the polymer
foam and/or fibres
viii) adding the polymeric foam/fibre in the solution of
water and ethanol;
20 ix) drying of the fibre overnight;
x) obtained the graphene nano composite polymeric
membrane.
3. The process for the synthesis of graphene nano composite
25 polymeric membrane as claimed in claim 2 wherein doping of
the graphene oxide with sulphur element comprises following
steps:
i) adding Graphene Oxide (0.25 mg/ml) dispersed in
deionized water to thiourea placed in Teflon lined
30 autoclave preheated at 240°C for 5 h.
ii) washing the resultant product by deionized water;
iii) filteration of the reaction mixture suction filtration
on the nylon membrane;
iv) repeat washing with deionized water and methanol.
35
4. The process for the synthesis of graphene nano composite
polymeric membrane as claimed in claim 2 wherein
saturation of the graphene oxide with amine group
comprises following steps:
5 i) adding sulfur doped graphene oxide to ethylene glycol
and sonicated for 5 hrs;
ii) transferring the above solution along with ammonia
solution to Teflon line autoclave and subjected to
solvothermal reaction for 150oC for 12 h;
10 iii) cooling down the reaction vessel;
iv) separating the precipitate by filtration and washed
with De ionised water;
v) dried at 80oC overnight.
15 5. The process for the synthesis of graphene nano composite
polymeric membrane as claimed in claim 2 wherein
crosslinking of the silver particles with the graphene
oxide comprises following steps:
i) adding amine functionalized graphene to solution
20 of water and ethanol in a ratio of 95:5 and
sonicated for 2 hrs;
ii) reacting the above solution with silver nitrate
precursor in the vessel and subjected to
solvothermal reaction for 90oC for 12 h;
25 iii) cooling down the vessel;
iv) separating the precipitate by filtration and
washing with deionized water.
v) dried at 80oC overnight;
vi) getting the silver crosslinked graphene oxide.
30
6. The process for the synthesis of graphene nano composite
polymeric membrane as claimed in claim 2 wherein coating
of the silver nano composite on the polymeric foam/ fibre
comprises following steps:
35 i) Adding silver crosslinked graphene nano-composite
is to 1 ltr solution of water and ethanol in the
ratio of 95:5 followed by sonication in the
container;
ii) heating at 60oC while stirring continuously.
iii) dipping the polymeric foam/ fibre inside the
5 solution for 1 hr followed by cooling in cold water
solution.
iv) drying the foam/fibre at 120oC overnight;