FIELD OF INVENTION
[001] The present disclosure relates to the field of preparing cellulose nanofibrils (CNF) / nanocellulose from waste discard of tobacco stalk. The disclosure also provides various applications and utility of said nanocellulose prepared from tobacco stalk.
BACKGROUND OF THE INVENTION
[002] Natural fibers can be used to reinforce polymers due to their renewability, biodegradability, and mechanical characteristics such as strength. Such natural fibers comprise fibrous bundles, and can be added to various polymers as both, additive or substitute. Such natural fibers from various hardwoods are known in the art. [003] Tobacco stalks are a waste by-product, which are normally discarded in land¬fills, which is an added cost. Hence, if such waste by-products can be utilized in some form and manner, it would lead to cost reduction, and reduction in waste material generation, while at the same time leading to sustainable use of biological resources. [004] Chinese patent application number 201110190553 provides a method for co-production of biogas and stem growing media by fermentation of waste tobacco stems. [005] Chinese patent application number 200910165144 provides a tobacco stalk organic fertilizer, a preparation method and a using method thereof.
SUMMARY OF THE INVENTION
[006] In an aspect of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk, said method comprising: (a) obtaining tobacco stalk; (b) contacting tobacco stalk with white liquor to obtain a digested pulp; and (c) subjecting the pulp to mechanical grinding to obtain nanocellulose.
[007] In an aspect of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk, said method comprising: (a) obtaining tobacco stalk having moisture content of 8- 20%, density of 60 - 90 kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch; (b) contacting tobacco stalk with white liquor ( 15 - 22%) to obtain a digested pulp, wherein white liquor comprises sodium

hydroxide at a concentration of 68- 84%, having sulphidity of 17 - 25%, and having active alkali concentration of 85-110 grams per litre (gpl), wherein tobacco stalk to liquid ( estimated white liquor + water) w/w ratio is 1:4, and wherein said contacting of tobacco stalk with white liquor is carried out at the holding temperature of 90-110°C, followed by increasing the holding temperature to 150 -165°C, and finally increasing the holding temperature to 155-175°C; (c) bleaching said digested pulp comprising three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp having ISO brightness in the range 75-90 ; and (d) subjecting the pulp to mechanical grinding to obtain nanocellulose, wherein grinding comprises a first step of grinding, wherein said pulp is ground between two grinding stones (deep ditch 46) having clearance in the range of 250 to -140 µm for 1-20 cycles , each cycle for 1.0 -30 minutes, and a second step of grinding, wherein the two grinding stones (deep ditch 80) have clearance of -20 to -140 µm for 1-20 cycles , each cycle for 1-35 minutes. [008] In an aspect of the present disclosure, there is provided nanocellulose obtained from tobacco stalk having mean nanofibril diameter in the range of 20-80 nm, crystallinity in the range of 59-62%, zeta potential in the range of -14 to 10.3 mV, and degree of polymerization in the range of 450-801.
[009] In an aspect of the present disclosure, there is provided a paper product incorporating nanocellulose having mean nanofibril diameter in the range of 20-80 nm, crystallinity in the range of 59-62%, zeta potential in the range of -14 to 10.3 mV, and degree of polymerization in the range of 450-801, wherein nanocellulose content is in the range of 1-20%, said paper product has enhanced tensile strength of up to 37 % compared to paper product without nanocellulose, and said paper product has enhanced burst factor of up to 33% compared to paper product without nanocellulose. [0010] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended

claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0011] The following drawings form part of the present specification and are included
to further illustrate aspects of the present disclosure. The disclosure may be better
understood by reference to the drawings in combination with the detailed description
of the specific embodiments presented herein.
[0012] Figure 1 depicts the tobacco stalk nanocellulose size distribution, in accordance
with an embodiment of the present disclosure.
[0013] Figure 2 depicts the SEM image of tobacco stalk nanocellulose, in accordance
with an embodiment of the present disclosure.
[0014] Figure 3 depicts the zeta potential of tobacco stalk nanocellulose, in accordance
with an embodiment of the present disclosure.
[0015] Figure 4 depicts the FTIR spectroscopy analysis of tobacco stalk nanocellulose,
in accordance with an embodiment of the present disclosure.
[0016] Figures 5 and 6 depict the X ray diffraction results of tobacco stalk
nanocellulose, in a graphical form, wherein the X-axis represents 2 θ Bragg angle and
the Y-axis represents intensity, and X ray diffraction data of tobacco stalk
nanocellulose, in accordance with an embodiment of the present disclosure.
[0017] Figure 7 depicts the graphical representation of the effect of presence of
tobacco stalk nanocellulose in pulp on burst factor and tensile strength, in accordance
with an embodiment of the present disclosure.
[0018] Figure 8 depicts the SEM image of hardwood (Eucalyptus) nanocellulose, in
accordance with an embodiment of the present disclosure.
[0019] Figure 9 depicts the SEM image of tobacco stalk nanocellulose, in accordance
with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION
[0020] Those skilled in the art will be aware that the present disclosure is subject to
variations and modifications other than those specifically described. It is to be
understood that the present disclosure includes all such variations and modifications.
The disclosure also includes all such steps, features, compositions and compounds
referred to or indicated in this specification, individually or collectively, and any and
all combinations of any or more of such steps or features.
Definitions
[0021] For convenience, before further description of the present disclosure, certain
terms employed in the specification, and examples are collected here. These
definitions should be read in the light of the remainder of the disclosure and
understood as by a person of skill in the art. The terms used herein have the meanings
recognized and known to those of skill in the art, however, for convenience and
completeness, particular terms and their meanings are set forth below.
[0022] The articles “a”, “an” and “the” are used to refer to one or to more than one
(i.e., to at least one) of the grammatical object of the article.
[0023] The terms “comprise” and “comprising” are used in the inclusive, open sense,
meaning that additional elements may be included. It is not intended to be construed as
“consists of only”.
[0024] Throughout this specification, unless the context requires otherwise the word
“comprise”, and variations such as “comprises” and “comprising”, will be understood
to imply the inclusion of a stated element or step or group of element or steps but not
the exclusion of any other element or step or group of element or steps.
[0025] The term “including” is used to mean “including but not limited to”.
“Including” and “including but not limited to” are used interchangeably.
[0026] The term “white liquor” refers to a strong alkaline solution comprising mainly
sodium hydroxide (68- 84 g/lit as Na2O), sodium sulfide (17-26 g/lit as Na2O), and
sodium carbonate (14-18 g/lit as Na2O). The total active alkali (sodium hydroxide +

sodium sulfide) content determines the amount of white liquor to be used for kraft
pulping.
[0027] The term “white liquor concentration” refers to the concentration of NaOH +
sodium sulphide in white liquor (in terms of Na2O gm/ litre).
[0028] Tobacco stalk is a waste material which is typically discarded in landfills,
which lends to higher costs (disposal), and increases land pollution. Hence, there is a
need to develop processes which can potentially use this waste material in ways that
are commercially viable and reduce waste at the same time. Towards this, the present
disclosure provides a process of preparing nanocellulose from tobacco stalks, which
has mechanical features comparable to that of conventional nanocellulose prepared
from hardwoods such as Eucalyptus. The nanocellulose of the present disclosure can
be used to reinforce polymers, such as papers to confer superior burst factor and tensile
strength. This not only enhances the mechanical properties of the paper product, and
other contemplated polymers, but also reduces cost, and provides an alternative to
hardwood fibers.
[0029] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk, said method comprising: (a) obtaining
tobacco stalk; (b) contacting tobacco stalk with white liquor to obtain a digested pulp;
and (c) subjecting the pulp to mechanical grinding to obtain nanocellulose.
[0030] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said method
further comprises the step of bleaching said digested pulp from step (b).
[0031] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk, said method comprising: (a) obtaining
tobacco stalk; (b) contacting tobacco stalk with white liquor to obtain a digested pulp;
(c) bleaching said digested pulp; and (d) subjecting the digested pulp to mechanical
grinding to obtain nanocellulose.
[0032] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein tobacco stalk

of step (a) has moisture content in the range of 8-20 %, density in the range of 60-90
kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch.
[0033] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein tobacco stalk
of step (a) has moisture content of 12.5 %, density of 70 kg/m3, and is in the form of
chips having size in the range of 0.2-0.4 inch.
[0034] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein in step (b),
tobacco stalk to liquid w/w ratio is in the range of 1:2-1:8.
[0035] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein in step (b),
tobacco stalk to liquid w/w ratio is 1:4.
[0036] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said white
liquor comprises sodium hydroxide , sodium sulphide and sodium carbonate.
[0037] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said white
liquor concentration is in the range of 15-22 %.
[0038] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said white
liquor concentration is 18 %.
[0039] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said white
liquor sulphidity is in the range of 17-25 %.
[0040] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said white
liquor sulphidity is 20 %.

[0041] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said white
liquor active alkali concentration is in the range of 85-110 gpl.
[0042] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said white
liquor active alkali concentration is 95 gpl.
[0043] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein in step (b),
said digested pulp is obtained after contacting tobacco stalk with white liquor at the
holding temperature in the range of 90-110 °C, followed by increasing the holding
temperature to 150-165°C, and finally increasing the holding temperature to 155-175
°C.
[0044] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein in step (b),
said digested pulp is obtained after contacting tobacco stalk with white liquor at the
holding temperature of 100 °C, followed by increasing the holding temperature to
165°C, and finally holding at 165 °C.
[0045] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said digested
pulp unscreened yield is in the range of 41-45 %, reject content is in the range of 0.2-1
%, screened pulp yield is in the range of 40-44 %, pulp kappa number is in the range
of 16-21, pulp viscosity is in the range of 650-660 cm3/g, and the International
Organization for Standardization brightness (hereinafter referred to as ISO brightness)
of pulp is in the range of 25-35.
[0046] In an embodiment of the present disclosure, there is provided a method of
preparing nanocellulose from tobacco stalk as described herein, wherein said digested
pulp unscreened yield is 43.2 %, reject content is 0.41 %, screened pulp yield is 42.8
%, pulp kappa number is 16.8, pulp viscosity is 654 cm3/g, and pulp ISO brightness is
26.8.

[0047] In an embodiment of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk as described herein, wherein said bleached pulp ISO brightness is in the range of 75-90, and pulp viscosity is in the range of 337-345 cm3/g.
[0048] In an embodiment of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk as described herein, wherein said bleached pulp ISO brightness is 79, and pulp viscosity is 341 cm3/g.
[0049] In an embodiment of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk as described herein, wherein said pulp prior to mechanical grinding is diluted in water, and pulp to water w/w ratio is in the range of 1:25-1:40.
[0050] In an embodiment of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk as described herein, wherein said pulp prior to mechanical grinding is diluted in water, and pulp to water w/w ratio is 0.3:10. [0051] In an embodiment of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk as described herein, wherein said mechanical grinding comprises: (a) a first step of grinding, wherein said pulp is ground between two grinding stones (deep ditch 46) having clearance of 250 to -140 µm for 1-20 cycles , each cycle for 1-30minutes; and (b) a second step of grinding, wherein the two grinding stones (deep ditch 80) having clearance of -20 to -140 µm for 1-20 cycles , each cycle for 1-35 minutes.
[0052] In an embodiment of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk as described herein, wherein said mechanical grinding comprises: (a) a first step of grinding, wherein said pulp is ground between two grinding stones (deep ditch 46) having clearance of 250 to -140 µm for 7 cycles of 30 minutes; and (b) a second step of grinding, wherein the two grinding stones (deep ditch 80) having clearance of -20 to -140 µm for 14 cycles of 30 minutes. [0053] In an embodiment of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk as described herein, wherein said bleaching

comprises three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp.
[0054] In an embodiment of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk, said method comprising: (a) obtaining tobacco stalk having moisture content of 12.5%, density of 70 kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch; (b) contacting tobacco stalk with 18% white liquor ( wt/ wt on OD chips) to obtain a digested pulp . Wherein white liquor having sulphidity of 20%, and having active alkali concentration of 95 gpl, wherein tobacco stalk to liquid w/w ratio is 1:4, and wherein said contacting of tobacco stalk with white liquor is carried out at the holding temperature of 100°C, followed by increasing the holding temperature to 165°C, and finally holding at 165°C; (c) bleaching said digested pulp comprising three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp; and (d) subjecting the pulp to mechanical grinding to obtain nanocellulose, wherein grinding comprises a first step of grinding, wherein said pulp is ground between two grinding stones (deep ditch 46) having clearance in the range of 250 to -140 µm for 1-20 cycles each cycle for 1-30 minutes, and a second step of grinding, wherein the two grinding stones (deep ditch 80) have clearance of -20 to -140 µm for 1-20 cycles, each cycle for 1-35 minutes. [0055] In an embodiment of the present disclosure, there is provided a method of preparing nanocellulose from tobacco stalk, said method comprising: (a) obtaining tobacco stalk having moisture content of 12.5%, density of 70 kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch; (b) contacting tobacco stalk with 18% white liquor (w /w on OD chips) to obtain a digested pulp. Wherein white liquor

having sulphidity of 20%, and having active alkali concentration of 95 gpl, wherein tobacco stalk to liquid w/w ratio is 1:4, and wherein said contacting of tobacco stalk with white liquor is carried out at the holding temperature of 100°C, followed by increasing the holding temperature to 165°C, and finally holding at 165°C; (c) bleaching digested pulp comprising three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp; and (d) subjecting the pulp to mechanical grinding to obtain nanocellulose, wherein grinding comprises a first step of grinding, wherein said pulp is ground between two grinding stones (deep ditch 46) having clearance in the range of 250 to -140 µm for 1-20 cycles, average cycle time 3 minutes, and a second step of grinding, wherein the two grinding stones (deep ditch 80) have clearance of -20 to -140 µm for 1-20 cycles average cycle time 5 minutes.
[0056] In an embodiment of the present disclosure, there is provided nanocellulose obtained from tobacco stalk having a mean nanofibril diameter in the range of 20-80 nm, crystallinity in the range of 59-62%, zeta potential in the range of -14 to 10.3 mV, and degree of polymerization in the range of 450-801.
[0057] In an embodiment of the present disclosure, there is provided nanocellulose as described herein, having mean nanofibril diameter of 68.8 nm, crystallinity of 62 %, zeta potential of -14 mV, and degree of polymerization of 801.
[0058] In an embodiment of the present disclosure, there is provided nanocellulose as described herein, wherein said nanocellulose is prepared by a method as described herein.
[0059] In an embodiment of the present disclosure, there is provided nanocellulose prepared by a method as described herein, wherein said method comprises: (a) obtaining tobacco stalk; (b) contacting tobacco stalk with white liquor to obtain a digested pulp; and (c) subjecting the pulp to mechanical grinding to obtain nanocellulose.

[0060] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said method further comprises the
step of bleaching said digested pulp from step (b).
[0061] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said method comprises: (a)
obtaining tobacco stalk; (b) contacting tobacco stalk with white liquor to obtain a
digested pulp; (c) bleaching said digested pulp; and (d) subjecting the digested pulp to
mechanical grinding to obtain nanocellulose.
[0062] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein tobacco stalk of step (a) has
moisture content in the range of 8-20 %, density in the range of 60-90 kg/m3, and is in
the form of chips having size in the range of 0.2-0.4 inch.
[0063] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein tobacco stalk of step (a) has
moisture content of 12.5 %, density of 70 kg/m3, and is in the form of chips having
size in the range of 0.2-0.4 inch.
[0064] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein in step (b), tobacco stalk to liquid
w/w ratio is in the range of 1:2-1:8.
[0065] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein in step (b), tobacco stalk to liquid
w/w ratio is 1:4.
[0066] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said white liquor comprises sodium
hydroxide, sodium sulphide and sodium carbonate.
[0067] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said white liquor concentration is
in the range of 15-22 %.

[0068] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said white liquor concentration is
18 %.
[0069] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said white liquor sulphidity is in
the range of 17 - 25 %.
[0070] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said white liquor sulphidity is 20
%.
[0071] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said white liquor active alkali
concentration is in the range of 85-110 gpl.
[0072] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said white liquor active alkali
concentration is 95 gpl.
[0073] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein in step (b), said digested pulp is
obtained after contacting tobacco stalk with white liquor at the holding temperature in
the range of 90-110 °C, followed by increasing the holding temperature to 150-165°C,
and finally increasing the holding temperature to 155-175 °C.
[0074] by a method as described herein, wherein in step (b), said digested pulp is
obtained after contacting tobacco stalk with white liquor at the holding temperature of
100 °C, followed by increasing the holding temperature to 165°C, and finally holding
at 165 °C.
[0075] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said digested pulp unscreened yield
is in the range of 41-45 %, reject content is in the range of 0.2-1 %, screened pulp
yield is in the range of 40-44 %, pulp kappa number is in the range of 16-21, pulp

viscosity is in the range of 650-660 cm3/g, and pulp ISO brightness is in the range of
25-35.
[0076] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said digested pulp unscreened yield
is 43.2 %, reject content is 0.41 %, screened pulp yield is 42.8 %, pulp kappa number
is 16.8, pulp viscosity is 654 cm3/g, and pulp ISO brightness is 26.8.
[0077] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said bleached pulp ISO brightness
is in the range of 75-90, and pulp viscosity is in the range of 337-345 cm3/g.
[0078] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said bleached pulp ISO brightness
is 79, and pulp viscosity is 341 cm3/g.
[0079] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said pulp prior to mechanical
grinding is diluted in water, and pulp to water w/w ratio is in the range of 1:25-1:40.
[0080] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said pulp prior to mechanical
grinding is diluted in water, and pulp to water w/w ratio is 0.3:10.
[0081] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said mechanical grinding
comprises: (a) a first step of grinding, wherein said pulp is ground between two
grinding stones (deep ditch 46) having clearance of 250 to -140 µm for 1-20 cycles,
each cycle for 1-30 minutes; and (b) a second step of grinding, wherein the two
grinding stones (deep ditch 80) having clearance of -20 to -140 µm for 1-20 cycles ,
each cycle for 1-35 minutes.
[0082] In an embodiment of the present disclosure, there is provided nanocellulose
prepared by a method as described herein, wherein said mechanical grinding
comprises: (a) a first step of grinding, wherein said pulp is ground between two
grinding stones (deep ditch 46) having clearance of 250 to -140 µm for 7 cycles of 30

minutes; and (b) a second step of grinding, wherein the two grinding stones (deep ditch 80) having clearance of -20 to -140 µm for 14 cycles of 30 minutes.
[0083] In an embodiment of the present disclosure, there is provided nanocellulose prepared by a method as described herein, wherein said bleaching comprises three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp.
[0084] In an embodiment of the present disclosure, there is provided nanocellulose prepared by a method as described herein, wherein said method comprises: (a) obtaining tobacco stalk having moisture content of 12.5%, density of 70 kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch; (b) contacting tobacco stalk with white liquor to obtain a digested pulp, wherein white liquor at a concentration of 18% ( w/w on dry basis) , having sulphidity of 20%, and having active alkali concentration of 95 gpl, wherein tobacco stalk to liquid w /w ratio is 1:4, and wherein said contacting of tobacco stalk with white liquor is carried out at the holding temperature of 100°C, followed by increasing the holding temperature to 165°C, and finally holding at 165°C; (c) bleaching said digested pulp comprising three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp; and (d) subjecting the pulp to mechanical grinding to obtain nanocellulose, wherein grinding comprises a first step of grinding, wherein said pulp is ground between two grinding stones (deep ditch 46) having clearance in the range of 250 to -140 µm for 1-20 cycles , each cycle for 1 -30minutes, and a second step of grinding, wherein the two grinding stones (deep ditch 80) have clearance of -20 to -140 µm for 1-20 cycles, each cycle for 1-35 minutes.

[0085] In an embodiment of the present disclosure, there is provided nanocellulose prepared by a method as described herein, wherein said method comprises: (a) obtaining tobacco stalk having moisture content of 12.5%, density of 70 kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch; (b) contacting tobacco stalk with white liquor to obtain a digested pulp, wherein white liquor at a concentration of 18%, having sulphidity of 20%, and having active alkali concentration of 95 gpl, wherein tobacco stalk to liquid w/w ratio is 1:4, and wherein said contacting of tobacco stalk with white liquor is carried out at the holding temperature of 100°C, followed by increasing the holding temperature to 165°C, and finally holding at 165°C; (c) bleaching said digested pulp comprising three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp; and (d) subjecting the pulp to mechanical grinding to obtain nanocellulose, wherein grinding comprises a first step of grinding, wherein said pulp is ground between two grinding stones (deep ditch 46) having clearance in the range of 250 to -140 µm for 1-20 cycles average cycle time 3 minutes, and a second step of grinding, wherein the two grinding stones (deep ditch 80) have clearance of -20 to -140 µm for 1-20 cycles average cycle time 5 minutes.
[0086] In an embodiment of the present disclosure, there is provided a paper product incorporating nanocellulose, wherein nanocellulose content is in the range of 1-20%, said paper product has enhanced tensile strength of up to 37 % compared to paper product without nanocellulose, and said paper product has enhanced burst factor of up to 33% compared to paper product without nanocellulose.
[0087] In an embodiment of the present disclosure, there is provided a paper product as described herein, wherein said nanocellulose is obtained from tobacco stalk. [0088] In an embodiment of the present disclosure, there is provided a paper product as described herein, wherein said nanocellulose obtained from tobacco stalk has mean

nanofibril diameter in the range of 20-80 nm, crystallinity in the range of 59-62%, zeta
potential in the range of -14 to 10.3 mV, and degree of polymerization in the range of
450-801.
[0089] In an embodiment of the present disclosure, there is provided a paper product
as described herein, wherein said nanocellulose obtained from tobacco stalk has mean
particle size of 68.8 nm, crystallinity of 62 %, zeta potential of -14 mV, and degree of
polymerization of 801.
[0090] In an embodiment of the present disclosure, there is provided a paper product
incorporating nanocellulose from tobacco stalk having mean particle size of 68.8 nm,
crystallinity of 62 %, zeta potential of -14 mV, and degree of polymerization of 801,
wherein nanocellulose content is in the range of 1-20%, said paper product has
enhanced tensile strength of up to 37 % compared to paper product without
nanocellulose, and said paper product has enhanced burst factor of up to 33%
compared to paper product without nanocellulose.
[0091] In an embodiment of the present disclosure, there is provided a paper product
as described herein, wherein said nanocellulose is prepared by a method as described
herein.
[0092] In an embodiment of the present disclosure, there is provided a paper product
comprising nanocellulose prepared by a method as described herein, wherein said
method comprises: (a) obtaining tobacco stalk; (b) contacting tobacco stalk with white
liquor to obtain a digested pulp; and (c) subjecting the pulp to mechanical grinding to
obtain nanocellulose.
[0093] In an embodiment of the present disclosure, there is provided a paper product
comprising nanocellulose prepared by a method as described herein, wherein said
method further comprises the step of bleaching said digested pulp from step (b).
[0094] In an embodiment of the present disclosure, there is provided a paper product
comprising nanocellulose prepared by a method as described herein, wherein said
method comprises: (a) obtaining tobacco stalk; (b) contacting tobacco stalk with white

liquor to obtain a digested pulp; (c) bleaching said digested pulp; and (d) subjecting
the digested pulp to mechanical grinding to obtain nanocellulose.
[0095] In an embodiment of the present disclosure, there is provided a paper product
comprising nanocellulose prepared by a method as described herein, wherein tobacco
stalk of step (a) has moisture content in the range of 8-20 %, density in the range of
60-90 kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch.
[0096] In an embodiment of the present disclosure, there is provided a paper product
comprising nanocellulose prepared by a method as described herein, wherein tobacco
stalk of step (a) has moisture content of 12.5 %, density of 70 kg/m3, and is in the form
of chips having size in the range of 0.2-0.4 inch.
[0097] In an embodiment of the present disclosure, there is provided a paper product
comprising nanocellulose prepared by a method as described herein, wherein in step
(b), tobacco stalk to liquid w/w ratio is in the range of 1:2-1:8.
[0098] In an embodiment of the present disclosure, there is provided a paper product
comprising nanocellulose prepared by a method as described herein, wherein in step
(b), tobacco stalk to liquid w/w ratio is 1:4.
[0099] In an embodiment of the present disclosure, there is provided a paper product
comprising nanocellulose prepared by a method as described herein, wherein said
white liquor comprises sodium hydroxide, sodium sulphide and sodium carbonate.
[00100] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said white liquor concentration is in the range of 15-22 %.
[00101] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said white liquor concentration is 18 %.
[00102] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said white liquor sulphidity is in the range of 17-25 %.

[00103] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said white liquor sulphidity is 20 %.
[00104] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said white liquor active alkali concentration is in the range of 85-110 gpl.
[00105] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said white liquor active alkali concentration is 95 gpl.
[00106] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
in step (b), said digested pulp is obtained after contacting tobacco stalk with white
liquor at the holding temperature in the range of 90-110 °C, followed by increasing the
holding temperature to 150-165°C, and finally increasing the holding temperature to
155-175 °C.
[00107] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
in step (b), said digested pulp is obtained after contacting tobacco stalk with white
liquor at the holding temperature of 100 °C, followed by increasing the holding
temperature to 165°C, and finally holding at 165 °C.
[00108] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said digested pulp unscreened yield is in the range of 41-45 %, reject content is in the
range of 0.2-1 %, screened pulp yield is in the range of 40-44 %, pulp kappa number is
in the range of 16-21, pulp viscosity is in the range of 650-660 cm3/g, and pulp ISO
brightness is in the range of 25-35.
[00109] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said digested pulp unscreened yield is 43.2 %, reject content is 0.41 %, screened pulp

yield is 42.8 %, pulp kappa number is 16.8, pulp viscosity is 654 cm3/g, and pulp ISO
brightness is 26.8.
[00110] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said bleached pulp ISO brightness is in the range of 75-90, and pulp viscosity is in the
range of 337-345 cm3/g.
[00111] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said bleached pulp ISO brightness is 79, and pulp viscosity is 341 cm3/g.
[00112] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said pulp prior to mechanical grinding is diluted in water, and pulp to water w/w ratio
is in the range of 1:25-1:40.
[00113] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said pulp prior to mechanical grinding is diluted in water, and pulp to water w/w ratio
is 0.3:10.
[00114] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said mechanical grinding comprises: (a) a first step of grinding, wherein said pulp is
ground between two grinding stones (deep ditch 46) having clearance of 250 to -140
µm for 1-20 cycles, each cycle 30 minutes; and (b) a second step of grinding, wherein
the two grinding stones (deep ditch 80) having clearance of -20 to -140 µm for 1-20
cycles, each cycle 30 minutes.
[00115] In an embodiment of the present disclosure, there is provided a paper
product comprising nanocellulose prepared by a method as described herein, wherein
said mechanical grinding comprises: (a) a first step of grinding, wherein said pulp is
ground between two grinding stones (deep ditch 46) having clearance of 250 to -140
µm for 7 cycles, for 210 minutes; and (b) a second step of grinding, wherein the two

grinding stones (deep ditch 80) having clearance of -20 to -140 µm for 14 cycles for 420 minutes.
[00116] In an embodiment of the present disclosure, there is provided a paper product comprising nanocellulose prepared by a method as described herein, wherein said bleaching comprises three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp.
[00117] In an embodiment of the present disclosure, there is provided a paper product comprising nanocellulose prepared by a method as described herein, wherein said method comprises: (a) obtaining tobacco stalk having moisture content of 12.5%, density of 70 kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch; (b) contacting tobacco stalk with white liquor to obtain a digested pulp, wherein white liquor concentration of 18%, having sulphidity of 20%, and having active alkali concentration of 95 gpl, wherein tobacco stalk to white liquor w/v ratio is 1:4, and wherein said contacting of tobacco stalk with white liquor is carried out at the holding temperature of 100°C, followed by increasing the holding temperature to 165°C, and finally holding at165°C; (c) bleaching said digested pulp comprising three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp; and (d) subjecting the pulp to mechanical grinding to obtain nanocellulose, wherein grinding comprises a first step of grinding, wherein said pulp is ground between two grinding stones (deep ditch 46) having clearance in the range of 250 to -140 µm for 41 cycles for 27.3 minutes, and a second step of grinding, wherein the two grinding stones (deep ditch 80) have clearance of -20 to -140 µm for 29 cycles , for 122 minutes.

[00118] Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible.
EXAMPLES
[00119] The disclosure will now be illustrated with working examples, which is
5 intended to illustrate the working of disclosure and not intended to take restrictively to
imply any limitations on the scope of the present disclosure. Unless defined otherwise,
all technical and scientific terms used herein have the same meaning as commonly
understood to one of ordinary skill in the art to which this disclosure belongs.
Although methods and materials similar or equivalent to those described herein can be
0 used in the practice of the disclosed methods and compositions, the exemplary
methods, devices and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may vary.
Example 1 5 Preparation of nanocellulose from tobacco stalk
[00120] Six hundred eighty six kg tobacco stalk [equivalent to 600 kg bone dried
mass (BD)] having 12.5 % moisture, density of 70 kg/ m3 and chip size in the range of
0.2-0.4 inch was added in to a 11 m3 tumbling digester. To this, 18% white liquor
(calculated based on the chip weight) was added keeping the bath ratio (chip to liquid)
0 at 1:4. The material was digested at 165 0C for 90 minutes. The pulping conditions
used were as specified in Table 1 below. Table 1



After complete digestion, the digested pulp was removed, washed, dried and pulp yield was estimated as given in Table 2. Pulp kappa number and brightness were also measured. The pulp was subjected to bleaching to obtain clean fiber prior to conversion to nanocellulose. Bleaching conditions were as mentioned in Table 3b below. The pulp underwent an oxygen pre-treatment before it was subjected to D0EpD1 sequence. The oxygen pre-treatment conditions are as specified in Table 3a.








[00121] Bleached pulp can be converted to nanocellulose by acid hydrolysis / enzymatic hydrolysis / mechanical process like high pressure homogenization / grinding / cryocrushing. In the present instance, the bleached pulp was converted by the grinding method. The method was optimized to suit tobacco bleached / unbleached cellulose.
[00122] Throughout this Examples section, the term, “bleached pulp” refers to the pulp obtained by following the D0EpD1 procedure as described above. Further, the term “tobacco stalk nanocellulose” refers to nanocellulose obtained from bleached pulp, following the process of Example 2 below. Wherever reference have been made to nanocellulose obtained from unbleached pulp, it is to be considered to have been made from unbleached pulp using the process of Example 2.

Example 2
Nanocellulose conversion and characterization
[00123] The detailed procedure for nanocellulose conversion is provided below. The cellulose nanofibrils so obtained were characterized using standard analytical tools known in the literature (Vigneshwaran et. al., Bioresource Technology, 103, 2012, 219-226 and Tonoli et. al., Carbohydrate Polymers, 89, 2012, 80-88).
[00124] The pulp (300 g in 10 lt ), unbleached was soaked for 60 mins in water and uniformly dispersed in water prior to nanocellulose conversion. The supermasscolloider – ultra fine friction grinding machine, Model - MASUKO-MKC A6-2, was used for preparation of nanocellulose. The machine comprises two ceramic non- porous grinding stones. The clearance between these two stones can be adjusted freely. Upper grinding stone is fixed whereas the lower one is rotated at a high speed. Soaked pulp was (10 L) gradually fed into the hopper of the machine (for 30 min) into the clearance between two grinding stones by centrifugal force. The clearance between the grinding stones varied from +250 micron to -140 micron. The grinding speed was 1500 RPM. Initially coarse grinding was done with deep ditch 46 blade for 7 cycles (+ 250 micron to -140) each cycle for 30 mins. After 7 cycles the grinding was done with deep ditch 80 blade for 14 cycles (-20 to -140 micron) each cycle for 30 mins. The grinding process is as shown below in Table 4.



[00125] After 21 cycles the nanocellulose produced were characterized by XRD, Particle size analyzer, FTIR, and viscosity. A summary of the results is as provided below in Table 5.
5

[00126] Table 6 below shows the viscosity behavior showing shear thinning property, i.e., at increasing rpm, the viscosity goes down, which is expected of nanocellulose.

[00127] Figure 1 depicts the mean fibril diameter, 68.8 nm, and size distribution of
the tobacco stalk nanocellulose.
[00128] Figure 2 represents scanning electron microscopy analysis of the tobacco
stalk nanocellulose which reveals the fibrillated nature of the nanocellulose.
[00129] Figure 3 depicts the zeta potential of the tobacco stalk nanocellulose
obtained by the process as described in the present disclosure. It can be inferred that
the zeta potential of the nanocellulose of the instant disclosure is very close to that of
pure cellulose (-14 mV) as there are no chemical modifications done to the tobacco
stalk nanocellulose.
[00130] Fourier Transform Infrared Spectroscopy (FTIR Spectroscopy) was also
carried out on the tobacco stalk nanocellulose to determine the organic composition of
the nanocellulose obtained. As seen in Figure 4, it can be inferred from the peaks that
the sample contained predominantly cellulose.
[00131] Figure 5 depicts the X ray diffraction (XRD) analysis of the nanocellulose
prepared from tobacco stalk. The crystallinity index (CI) was calculated using the
equation: CI (%)=[I002-Iam)/I002]x100%, where I002 is the intensity for the peak at 2θ

value of 22 and Iam is the intensity at 2θ value of 18. As inferred from the data, the
crystallinity index of tobacco stalk nanocellulose is 62%.
[00132] Degree of polymerization was calculated based on viscosity measurements.
Viscosity measurements were carried out using an Ubehlohde viscometer, at 25 °C.
Solvent used for dissolving cellulose samples was bis (ethylenediamine) copper
hydroxide (c = 1 mg/ml). The formula used to calculate degree of polymerization is as
follows.
Degree of polymerization = (2000 x ηsp) / (c x (1+(0.29 ηsp))
Where ηsp is the specific viscosity given by (η/η0 -1) and c is the concentration of the
sample in g/dl. The degree of polymerization was found to be 801, which further
indicated formation of cellulose nanofibrils.
Example 3
Tobacco stalk nanocellulose application and utility
[00133] In order to establish the application and utility of the tobacco stalk nanocellulose prepared by a process as disclosed herein. Nanocellulose prepared from unbleached tobacco stalk pulp (using same process as described in Example 1 for bleached pulp) was added to unbleached tobacco stalk pulp at varying concentrations ranging from 5-20 % (in particular, at 5, 10, and 20 %), and checked for strength properties. Table 7 below depicts the improvement in tensile strength and burst strength with increase in nanocellulose concentration.


[00134] As seen in Table 7, with increase in nanocellulose concentration, there is an increase in the burst strength and tensile strength. A visual depiction of the same can also be seen in Figure 8, where TS refers to tensile strength, while BS refers to burst strength/factor.
[00135] Tobacco stalk nanocellulose (bleached) was also added to hard wood pulp (1-2 % of bleached tobacco stalk nanocellulose) and processed into sheets. Various parameters such as burst strength, tensile strength, stiffness, etc. were measured, results of which are presented in Table 8 below. As seen in Table 8, addition of tobacco stalk nanocellulose at a concentration of 1 and 2 % resulted in an increase in burst strength and tensile strength.

[00136] In order to further establish the utility of tobacco stalk nanocellulose as a substitute for hard wood nanocellulose for use in strengthening the burst factor, and tensile strength of hard wood pulp derived paper product, tobacco stalk nanocellulose or hard wood nanocellulose at 2 % concentration was added to hard wood pulp, and

burst factor, and tensile strength in each case was ascertained. As seen in Table 9 below, it can be appreciated that even though substituting hardwood nanocellulose for tobacco stalk nanocellulose results in a slight decrease in burst factor (about 6% decrease), and tensile strength (about 1.1% decrease), tobacco stalk nanocellulose increases burst factor by about 33%, and tensile strength by about 8.2% compared to hardwood pulp alone.
Hardwood NC:EU# (hardwood nanocellulose:hardwood pulp); Tobacco stalk NC:EU^ (tobacco stalk nanocellulose:hardwood pulp)
[00137] The fiber width of tobacco stalk nanocellulose of the present disclosure was also compared with that of hard wood nanocellulose available commercially, and it was found that nanocellulose obtained by tobacco stalk has average width of 26.61 nm, while the width of commercially available nanocellulose is 32.49 nm width, both are comparable. The crystallinity index of the tobacco stalk nanocellulose (62 %) and commercial hard wood nanocellulose (61 %) is also comparable. The fibrillar similarity of hard wood (Eucalyptus) nanocellulose and tobacco stalk nanocellulose can be further visually appreciated from Figure 9 (Eucalyptus nanocellulose) and Figure 10 (tobacco stalk nanocellulose), whereby it can be seen that the microscopic nature of the two nanocelluloses is similar in nature.

[00138] These data suggest that tobacco stalk nanocellulose is suitable for enhancing strength properties of hardwood pulp, and is comparable to conventionally used nanocellulose prepared from hardwood.
[00139] Apart from the suitability of tobacco stalk nanocellulose as a viable substitute for hardwood nanocellulose, the significance of using tobacco stalk nanocellulose can also be appreciated from the fact that the total grinding time to prepare nanocellulose particles from tobacco stalk pulp is about 2.65 times less than total grinding time to prepare nanocellulose from hard wood pulp (2.5 hours for tobacco stalk nanocellulose compared to 6.6 hours for hard wood nanocellulose). Details of grinding time for each cycle is provided below in Table 10.



[00140] Overall, the present disclosure provides nanocellulose prepared from an otherwise waste discard, tobacco stalk, which has nanocellulose characteristics similar to that of nanocellulose prepared from hardwood sources, such as Eucalyptus, thus suggesting its utility as a cheaper and alternative source to hardwood nanocellulose. The reduced grinding time to obtain tobacco stalk nanocellulose is also a significant economic gain. The utility of the tobacco stalk nanocellulose is further exemplified by the present disclosure whereby hardwood pulp incorporated with tobacco stalk nanocellulose at concentrations of up to 2 % exhibits superior burst factor and tensile strength.

I/We Claim:
1. A method of preparing nanocellulose from tobacco stalk, said method
comprising:
a. obtaining tobacco stalk;
b. contacting tobacco stalk with white liquor to obtain a digested pulp; and
c. subjecting the pulp to mechanical grinding to obtain nanocellulose.
2. The method as claimed in claim 1, further comprising the step of bleaching said digested pulp from step (b).
3. The method as claimed in claim 1, wherein tobacco stalk of step (a) has moisture content in the range of 8-20 %, density in the range of 60-90 kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch.
4. The method as claimed in claim 1, wherein in step (b), tobacco stalk to liquid w/w ratio is in the range of 1:2-1:8.
5. The method as claimed in claim 1, wherein said white liquor comprises sodium hydroxide, sodium sulphide and sodium carbonate
6. The method as claimed in claim 1, wherein said white liquor concentration is in the range of 15-22 %.
7. The method as claimed in claim 1, wherein said white liquor sulphidity is in the range of 17-25 %.
8. The method as claimed in claim 1, wherein said white liquor active alkali concentration is in the range of 85-110 grams per litre (gpl).
9. The method as claimed in claim 1, wherein in step (b), said digested pulp is obtained after contacting tobacco stalk with white liquor at the holding temperature in the range of 90-110 °C, followed by increasing the holding temperature to 150-165°C, and finally increasing the holding temperature to 155-175 °C.
10. The method as claimed in claim 1, wherein said digested pulp unscreened yield is in the range of 41-45 %, reject content is in the range of 0.2-1 %, screened pulp yield is in the range of 40-44 %, pulp kappa number is in the range of 16-21, pulp

viscosity is in the range of 650-660 cm3/g, and pulp ISO brightness is in the range of 25-35.
11. The method as claimed in claim 2, wherein said pulp ISO brightness is in the range of 75-90, and pulp viscosity is in the range of 337-345 cm3/g.
12. The method as claimed in claim 1, wherein in step (c), said pulp is diluted in water, and pulp to water w/w ratio is in the range of 1:25-1:40.
13. The method as claimed in claim 1, wherein in step (c), said grinding comprises:
a. a first step of grinding, wherein said pulp from method of claim 12 is
ground between two grinding stones (deep ditch 46) having clearance of 250 to
-140 µm for 1-20 cycles, each cycle for 1.0-30 minutes; and
b. a second step of grinding, wherein the two grinding stones (deep ditch 80)
having clearance of -20 to -140 µm for 1-20 cycles, each cycle for 1- 35
minutes.
14. The method as claimed in claim 2, wherein said bleaching comprises three sequential steps of D0, Ep, and D1, whereby D0 step comprises contacting digested pulp with chlorine dioxide, Ep step comprises contacting the digested pulp from step D0 with alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp from step Ep with chlorine dioxide to obtain bleached digested pulp.
15. A method of preparing nanocellulose from tobacco stalk, said method comprising:
a. obtaining tobacco stalk having moisture content of 12.5%, density of 70
kg/m3, and is in the form of chips having size in the range of 0.2-0.4 inch;
b. contacting tobacco stalk with white liquor to obtain a digested pulp,
wherein white liquor concentration is 18%, having sulphidity of 20%, and
having active alkali concentration of 95 gpl, wherein tobacco stalk to liquid
w/w ratio is 1:4, and wherein said contacting of tobacco stalk with white liquor
is carried out at the holding temperature of 100°C, followed by increasing the
holding temperature to 165 °C, and finally holding at 165 °C;

c. bleaching said digested pulp comprising three sequential steps of D0, Ep,
and D1, whereby D0 step comprises contacting digested pulp with chlorine
dioxide, Ep step comprises contacting the digested pulp from step D0 with
alkaline hydrogen peroxide, and D1 step comprises contacting the digested pulp
from step Ep with chlorine dioxide to obtain bleached digested pulp; and
d. subjecting the pulp to mechanical grinding to obtain nanocellulose,
wherein grinding comprises a first step of grinding, wherein said pulp is ground
between two grinding stones (deep ditch 46) having clearance in the range of
250 to -140 µm for 1-20 cycles, each cycle for 1- 30 minutes, and a second step
of grinding, wherein the two grinding stones (deep ditch 80) have clearance of
-20 to -140 µm for 1-20 cycles, each cycle for 1-35 minutes.
16. Nanocellulose obtained from tobacco stalk having mean particle diameter in the range of 20-80 nm, crystallinity in the range of 59-62%, zeta potential in the range of -14 to 10.3 mV, and degree of polymerization in the range of 450-801.
17. Nanocellulose as claimed in claim 16 having mean particle size of 68.8 nm, crystallinity of 62 %, zeta potential of -14 mV, and degree of polymerization of 801.
18. Nanocellulose as claimed in any of the claims 16-17 prepared by a method as claimed in any of the claims 1-15.
19. A paper product incorporating nanocellulose of any of the claims 16-18, wherein nanocellulose content is in the range of 1-20%, said paper product has enhanced tensile strength of up to 37 % compared to paper product without nanocellulose, and said paper product has enhanced burst factor of up to 33% compared to paper product without nanocellulose.