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Isolation and characterization of CNC from waste maize cob available in
Bangladesh as a potential candidate for the fabrication of multifunctional
bio-nanocomposites: A new approach
Shamim Dewan
b
, Md. Mahmudur Rahman
a,*
, Md. Ismail Hossain
a
, Bijoy Chandra Ghos
a
,
M Mohinur Rahman Rabby
b
, Md. Abdul Gafur
c
, Md. Al-Amin
a
, Md. Ashraful Alam
d
a
BCSIR, Rajshahi Laboratory, Bangladesh Council of Scientic and Industrial Research (BCSIR), Rajshahi 6206, Bangladesh
b
Department of Chemical Engineering, Rajshahi University of Engineering and Technology (RUET), Rajshahi 6204, Bangladesh
c
Pilot Plant and Process Development Centre, Bangladesh Council of Scientic and Industrial Research (BCSIR), Dhaka 1205, Bangladesh
d
Institute of Glass and Ceramic Research &Testing (IGCRT), Bangladesh Council of Scientic and Industrial Research (BCSIR), Dhaka 1205, Bangladesh
ARTICLE INFO
Keywords:
Maize cob
Lignocellulosic ber
Chemical modication
Sustainable environment
Bio polysaccharide
Potential reinforcement
ABSTRACT
Nano-cellulose is a biodegradable polysaccharide which has multifunctional uses due to its fascinating properties
(i.e., antibacterial, antifungal, anticarcinogenic activity) in wastewater treatment, drug design, food packaging,
etc. CNC usually extracted from primary plant (such as jute, hemp, ax, cotton, etc.) which has other signicant
uses (for example preparation of yarn, rope, tissue paper, etc.). To reduce the pressure on primary plant the use of
waste biomass of secondary plant could be an effective and economic route of CNC isolation. In this study a series
of chemical treatment i.e. scouring (5% soap solution), alkali treatment (16% NaOH solution), bleaching (2%
NaClO
2
and 2% Na
2
S
2
O
5
solution at pH =4.0), acid hydrolysis (60% H
2
SO
4
) was conducted to isolate CNC from
the waste maize cob. Characterization of the specimens were conducted by FTIR-ATR (Fourier Transform
Infrared-Attenuated Total Reection), FESEM (Field Emission Scanning Electron Microscopy), XRD (X-ray
Diffraction), EDX (Energy Dispersive X-ray), DLS (Dynamic Light Scattering), Thermal analysis (TGA/DTG/DTA),
and Zeta potential analysis. Different functional groups (>C=O, C≡C, C-O-C, C-O, -OH, etc.) were identied by
FTIR-ATR. Crystal structure, crystallite size, and crystallinity index of CNC (around 84.63±0.03%) were
observed by XRD analysis. Produced CNC showed enhanced thermal stabilities in TGA/DTG/DTA curves (about
40% residual mass at 600 ◦C) with the appearance of a peculiar 2D honey comb like void surface microstructure
in FESEM micrographs and the surface charge (around -7.09mV) was measured by zeta potential. The newly
produced CNC was perfectly nano sized (around 100 nm according to DLS analysis and FESEM micrograph).
Hence, this newly produced CNC would be benecially used to fabricate bio-nanocomposites for potential ap-
plications in various sectors such as biomedical, engineering, and industrial wastewater treatment as an
appropriate substitute of the unsafe fossil based synthetic ones to develop legitimate environment.
1. Introduction
Cellulose is a biopolymer which is very much available on earth
(Rahman et al., 2018a;Rahman et al., 2024a;Hossain et al., 2024).The
fundamental structural element of all plant bers is cellulose. The
building blocks of cellulose molecules are glucose units connected in
lengthy chains (β-1,4 glycoside linkages link the repeating units of
D-anhydro glucose C
6
H
11
O
5
), which are then connected in bundles
known as microbrils. The most abundant type of renewable organic
matter on earth is cellulose. It is a carbohydrate polymer composed of
repeating β-D-glucose units (Cheran et al., 2022).The hydrogen bonds in
cellulose control the crystallinity and consequently the physical char-
acteristics of natural bers (Komuraiah et al., 2014). Besides cellulose
other two major constituents of plant bers are hemicellulose and lignin
as illustrated in Fig. 1.CNC (Crystalline Nano Cellulose) is the nano
sized crystalline form of cellulose (length: 100 nm to 250 nm, diameter:
5 nm to 70 nm) (Teo et al., 2020) which is biodegradable, biocompat-
ible, and benecially used in bio-nanocomposites fabrication. CNCs are
biopolymer which are attractive because of some interesting properties
i.e., high thermal sustainability, insulation property (Septevani et al.,
* Corresponding author.
E-mail address: shamrat.acce@gmail.com (Md.M. Rahman).
Contents lists available at ScienceDirect
South African Journal of Chemical Engineering
journal homepage: www.elsevier.com/locate/sajce
https://doi.org/10.1016/j.sajce.2024.12.007
Received 2 June 2024; Received in revised form 11 November 2024; Accepted 27 December 2024
South African Journal of Chemical Engineering 51 (2025) 287–301
Available online 28 December 2024
1026-9185/© 2024 The Author(s). Published by Elsevier B.V. on behalf of South African Institution of Chemical Engineers. This is an open access article under the
CC BY-NC-ND license (
http://creativecommons.org/licenses/by-nc-nd/4.0/ ).
2017), large surface area (Kondor et al., 2021), excellent surface
morphology, high crystallinity (Deepa et al., 2011;Li et al., 2009), high
porosity, biodegradability (Khan et al., 2020), chemical inertness,
excellent stiffness, low density, high strength (Trache et al., 2020).CNC
is getting popular day by day due to its promising properties i.e., optical
transparency, biodegradability, environment friendly nature, low ther-
mal expansion (Liu et al., 2016). That’s why CNCs have vast applications
(Corrˆ
ea et al., 2010;Sheltami et al., 2012;Shen et al., 2013;Li et al.,
2015;Xie et al., 2019;Wang et al., 2020;Ren et al., 2022;Chaka, 2022).
Scientists are now concerned with improving the sustainability and
caliber of ecofriendly products in order to maintain the climate and
biodiversity (Shelare et al., 2023;Soudagar et al., 2024a &2024b &
2024d). Owing to their biodegradable qualities and environmentally
benecial practices, people are switching back to natural bers from
synthetic and potentially harmful materials. Having a lesser density than
glass ber they have been effectively utilized in the engineering and
construction sectors. Use of natural bers might help to reduce pollution
and greenhouse gas emissions (Karimah et al., 2021;Hassan et al., 2024;
Soudagar et al., 2024c). Different components are used in dened
amounts to create the articial bers in certain ways. Globally, the
synthetic bers are same. For this reason, they have similar mechanical
and thermal properties. Conversely, natural bers are grown in a natural
setting with the aid of soil, water, sunlight, and air that’s why they have
special qualities. Environmental circumstances differ from place to place
and from season to season, and these differences have an impact on plant
development. Therefore, they differ geographically in terms of their
mechanical and thermal properties (Komuraiah et al., 2014). Maize cob
contains a sufcient amount of cellulose (more than 40%) that can be
used as a raw material for CNC (Sartika et al., 2023).Synthetic polymers
(such as polyethylene, polyvinyl chloride, polyethylene terephthalate,
etc.) are widely used as packaging materials (Rahman et al., 2024gKabir
et al., 2018; ; Alojaly et al., 2022). They are not ecofriendly and
responsible for environment pollution due to their non-biodegradable
(Rydz, 2024) property. Synthetic polymeric materials don’t undergo
natural decomposition i.e., bacterial decomposition and sustain as per-
manent waste (Eubeler et al., 2009) in the environment which are
contaminating air, oceans, rivers, lands regularly. Combustion of the
synthetic polymeric materials generate CO
2
, CO, NO, NO
2
, SO
2
(˙
Zukowski et al., 2023) which are responsible for global warming, air
pollution, acid rain, etc. Further, they enter into the ecosystem as
microplastics resulting various desieses of human (such as cancer, car-
diovascular disease, kidney failure, etc.) and animals (Zhao et al., 2023).
Use of synthetic polymers could be replaced by biopolymers which are
ecofriendly as well as easily undergo bacterial decomposition
(Babaremu et al., 2023). CNC is a biopolymer which can be used in
packaging, biomedical application like drug delivery, wound dressings,
tissue engineering, antibacterial activity, biosensor, and bioimaging
(Raghuwanshi &Garnier, 2024;Du et al., 2019;Lin &Dufresne, 2014),
bio-nanocomposites fabrication (Khatun et al., 2023;Ulaganathan et al.,
2022), etc. Wastewater treatment is one of the potential applications of
fabricated bio-nanocomposites (Noreen et al., 2021). Wastewater
treatment is a big challenge in different textile industry. Textile in-
dustries generally use different chemical treatment (Hayat et al., 2015)
method for wastewater treatment which are at the same time very much
costly and not ecofriendly (dengarous for aquatic life).
Bio-nanocomposites fabricated from CNCs are cheap, ecofriendly ma-
terial which has high efciency in textile wastewater treatment (El
Messaoudi et al., 2024;Rahman &Maniruzzaman, 2021;Rahman et al.,
2022;Rahman et al., 2023b). Plants which are not cultivated for wood
can be classied in two groups i.e., primary plants, secondary plants
(Rahman et al., 2023c). Fiber producing plants such as jute, cotton, etc.
are categorized as primary plants. On the other hand, plants which are
cultivated basically for their stem, fruits, owers while ber is found as
byproduct can be dened as secondary plants such as corn, okra,
papaya, etc. CNC generally isolated from primary plants (Dhali et al.,
2021). This is not an economic way of CNC extraction because primary
plants have other signicant uses. Isolation of CNC from the waste of
secondary plants could be an economic route which at the same time
Fig. 1. Building structure of the lignocellulosic ber of maize cob in the particular variety of maize (Zea mays) along with complex molecular structure of cellulose,
hemicellulose, and lignin.
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
288
will reduce dependency on primary plants. The literature review says
that CNCs have been extracted from different agro-industrial wastes
such as corn husk (Kampeerapappun, 2015), rice straw (Lu et al., 2012),
banana rachis (Sheikh et al., 2023;Rahman et al., 2024e), wheat straw
(Pereira et al., 2017), bamboo ber (Rasheed et al., 2020), pineapple
crown (Prado et al., 2019), cotton pulp (Chen et al., 2019), cocoa pod
husk (Akinjokun et al., 2021), sugarcane bagasse (Le˜
ao et al., 2017),
coconut husk bers (Poornachandhra et al., 2023), pea hull (Li et al.,
2020). Maize (Zea mays) is a widely cultivated cereal product of grass
family (Poaceae) (Perera, 2014). Comparison of the environmental and
economic impact focusing on its major waste called maize cob, a source
of CNC are shown in Fig. 11. Maize can broadly be classied in two
major parts i.e., edible part, waste part. Waste part can further be
classied in three parts i.e., maize shell, maize cob, silk. Waste part of
the maize is valueless and useless one which is responsible for bad smell
production during bacterial decomposition, drainage block in rainy
season, and CO
2
emission during combustion. Maize cob, an agro-waste
biomass could also be a potential source of cellulose to produce CNC due
to its high amount of cellulose, hemicellulose and low amount of lignin
as mentioned in Table 1.For why maize cob extracted ber’s application
as nanocellulose is highly encouraged as it will reduce the burden of
burning-off, resulting in environmental pollution of water and air
(Rajanna et al., 2022).
In this study, CNC would be extracted from the puried ber of waste
maize cob by H
2
SO
4
hydrolysis method. Before hydrolysis sequentially
series of chemical treatment (i.e., scouring, alkali treatment, bleaching)
to be performed for the purication of the ber. A portion of work has
been conducted to isolate CNC from the waste of secondary plant
(particularly maize) but in previous no one has performed such work
from the waste material particularly from the Bangladeshi variety maize
cob namely Z. mays which is much more available in Rajshahi region.
Additionally, the quality and the high yield of the obtained nano-
cellulose could be promising while their characterization could have
been performed by conducting a number of useful technique namely
FTIR-ATR, FESEM, XRD, EDX, DLS, TGA/DTG/DTA, and Zeta potential
analysis. Hence, in this study, maize cob of Bangladeshi variety, a
completely economically valueless and useless product has been
selected to produce very much economically valuable product like CNC
which has various potential uses. The prospects of this study are (i) to
develop a new route of production of CNC from the agrowaste biomass
of maize cob of Bangladeshi variety, and (ii) to optimize the overall
thermomechanical, physicochemical, morphological properties of the
newly produced CNC as a suitable reinforcement to fabricate bio-
nanocomposites for potential applications in various sectors as an
appropriate substitute of the unsafe fossil based synthetic ones to
develop legitimate environment.
2. Experimental
2.1. Materials
Z. mays was collected from Shaheb Bazar, Rajshahi, Bangladesh
which was the main raw material of this study. CNC was isolated
particularly from its cob. Ghari detergent manufactured by RSPL Health
BD LTD collected from a local market of Rajshahi, Bangladesh to prepare
5% soap solution. Sodium hydroxide (NaOH) pellets (with purity ≥
97%) manufactured by Merck Specialities Private Limited (India), So-
dium Chlorite (NaClO
2
) ne powder (with purity 86~94%) manufac-
tured by Research-Lab Fine Chem Industries (India), Sodium
Metabisulphite (Na
2
S
2
O
5
) ne powder (with purity 97~98%) manu-
factured by Research-Lab Fine Chem Industries (India), Hydrochloric
acid (HCl) solution purity about 37% manufactured by Merck Life Sci-
ence Private Limited (India), Sulfuric acid (H
2
SO
4
) purity about 98%
manufactured by Supelco, Merck Darmstadt, Germany (analytical
grade), distilled water and ultrapure water were prepared and collected
from Biopolymers and Sustainable Environmental Research Laboratory,
BCSIR Rajshahi.
2.2. Method
2.2.1. Collection of maize cob ber
The particular variety of maize, Z. mays was collected from Rajshahi,
Bangladesh. Then maize cob was manually separated from the maize.
Later the raw ber was prepared by mechanical hammer milling and
blending method. Finally, the obtained raw maize cob ber was dried in
an oven at 105 ◦C and then stored in a sealed condition for further study.
Workow of ber extraction from the waste maize cob after harvesting
its edible parts have shown in Fig. 2.
2.2.2. Scouring
Scouring was conducted to remove different dusty, waxy, gummy,
oily substances from the ber. Scouring was carried out by 5% soap
solution. The ratio of prepared maize cob ber to solution of the 5% soap
solution was 1:20 (Rahman et al., 2023c). The detergent solution with
maize cob ber then heated at a temperature of 60 ◦C. Maintaining that
temperature scouring was performed for 2 hr with moderate stirring.
After that, the ber was repeatedly cleaned on a lter cloth using
distilled water. Then the scoured ber was dried in the oven (at 105 ◦C)
and nally stored in a thumped condition (Rahman et al., 2022).
2.2.3. Alkali treatment
Alkali treatment of the scoured ber was performed to draw out
hemicellulose and lignin from the desired alpha cellulose (Sartika et al.,
2023;Rahman et al., 2024c). Alkali treatment was carried out by using
16% NaOH solution. The ratio of scoured maize cob ber to 16% NaOH
solution was maintained at 1:20. The NaOH solution with scoured maize
cob ber was heated at 70 ◦C on a hot plate. Then the treatment was
continued for 2h with moderate stirring (Rahman &Rahman, 2022;
Rahman et al., 2024d). After being alkali treated, the ber was repeat-
edly rinsed with distilled water. Washing was carried out on a lter
cloth. Ultimately, the ber that had been alkali treated was dried at 105
◦C in an electric oven and stored in a moisture free condition until
bleaching (Hassan et al., 2024;Sheikh et al., 2023).
2.2.4. Bleaching
Bleaching of the alkali treated ber was conducted to obtain com-
plete removal of the lignin of the bundle of bers. Total bleaching
process was carried out by 2% NaClO
2
solution and 2% Na
2
S
2
O
5
solu-
tion. The ratio of alkali treated maize cob ber to 2% NaClO
2
solution
was maintained at 1:20. pH of the solution was carefully maintained at 4
by using 0.1N HCl and 0.1N NaOH (Rahman et al., 2023b,Rahman et al.,
2024a). Temperature of the mixture kept at 95 ◦C. Treatment of the ber
was conducted for 2h with moderate stirring. Later the ber was
Table 1
Chemical constituents in terms of cellulose, hemicellulose, and lignin in different
source based natural bers.
Fiber source Cellulose
(%)
Hemicellulose
(%)
Lignin
(%)
References
Banana trunk 31.48 14.98 15.07 (Muthu et al.,
2020;Karimah
et al., 2021)
Kenaf 36 21 18
Rice straw 30 25 15
Wheat straw 35 28 18
Barley straw 38 33 16
Banana leaf 25.65 17.04 24.84
Rice husk 40 22 20
Sugarcane
bagasse
40 25 15
Maize cob
(Z. mays)
52 28 15 This study
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
289
repeatedly washed by using distilled water. Then the ber was further
treated with 2% Na
2
S
2
O
5
solution where ber to 2% Na
2
S
2
O
5
solution
ratio was 1:30. The ber was treated with 2% Na
2
S
2
O
5
solution at room
temperature in a dark condition for thirty minutes (Sheikh et al., 2023;
Hossain et al., 2024). After drying in the electric oven at 105 ◦C, the
bleached ber was nally rinsed several times on a lter cloth with
distilled water and kept in a thumped condition.
2.2.5. Sulfuric acid hydrolysis
For acid hydrolysis rst of all bleached alpha cellulose was taken in
small size (by cutting down as small as possible). Then CNC was
extracted by acid hydrolysis of bleached small sized maize cob ber. The
Fig. 2. Raw ber extraction procedure during the experimental session from the waste maize cob of Z. mays by applying mechanical hemmer milling and
blending process.
Fig. 3. Sequential CNC isolation processes (scouring, alkali treatment, bleaching, sulfuric acid hydrolysis, centrifugation respectively) from the extracted raw maize
cob ber, a secondary plant based agro-waste biomass.
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
290
hydrolysis was conducted by 60% H
2
SO
4
solution under nonstop stirring
with magnetic stirrer on a hot plate at 40 ◦C for 15 min (Sartika et al.,
2023;Rahman et al., 2018a). During hydrolysis the ber to 60% H
2
SO
4
solution was maintained at 1:15 ratio. After 15 min, the reaction was
quenched by ice and stirring was conducted for another 30 min. Later
the suspension was diluted by distilled water and cooled down at room
temperature. Then the suspended CNC was separated from the diluted
suspension by centrifugation process (6000 rpm, 1 ◦C, 12 min) and the
solid fraction was stored in 96% ethanol after totally neutralizing
(pH=7.0) by distilled water (Hassan et al., 2024;Kusmono et al., 2020).
Yield of CNC from maize cob typically ranges from 50–55% (Sartika
et al., 2023) of the initial biomass, depending on the efciency of the
acid hydrolysis process whereas yield of CNC from traditional sources (e.
g., jute, hemp) typically range from 60–65% (Kassab et al., 2020).
Although the yield percent is higher in traditional sources (e.g., jute,
hemp) but to achieve this high yield it is required higher quantity of
chemicals for the isolation on the other hand it is possible to isolate CNC
from maize cob in lower cost by limited chemicals use. Jute, hemp, etc.
have some signicant uses but maize cob is just an agro waste. As a
waste material maize cob is responsible for environmental pollution
that’s why it must be benecial if CNC is isolated from this waste.
Workow of CNC isolation elaborately illustrated in Fig. 3.All the ex-
periments like scouring, alkali treatment, bleaching, and acid hydrolysis
were conducted by maintaining/wearing Personal Protective Equipment
(PPE) such as head cap, safety goggles, latex gloves, face mask, apron,
safety shoes to avoid health distress since some harsh chemicals (NaOH,
NaClO
2
, Na
2
S
2
O
5
, HCl, H
2
SO
4
) were used for the experimental purpose.
3. Characterization methods
3.1. FTIR-ATR analysis
FTIR-ATR technique is often used to inspect precisely the intra-
molecular and intermolecular interaction in polymeric specimens. FTIR
spectroscopy also used to determine the presence of active sites or
functional groups, chemical structure, chemical compositions, purity of
compound, overall molecular behavior, the quantity of targeted mole-
cules, etc. (Rahman et al., 2023c). PerkinElmer, Serial Number: 115,
061, Model: L1600300 spectrum Two made in Llantrisant, UK, was used
for the functional group analysis among raw maize cob ber, alkali
treated ber, bleached ber, and maize cob CNC. The PerkinElmer was
equipped with a high linearity room temperature DTGS detector and
linked to PerkinElmer Spectrum IR software version 10.6.2. Specimen
were placed to the ATR attachment of diamond prism, and using a res-
olution of 5 cm
-1
spectra were measured from 400 cm
-1
- 4000 cm
-1
.
Additionally, for each sample, minimum four replicas were taken for
good observation (Rahman et al., 2023d).
3.2. FESEM analysis
The FESEM technique is frequently used for the morphological
analysis of a particular surface of polymeric spacemen (Orasugh et al.,
2020). FESEM micrograph of the exposed chemically modied and un-
modied natural ber provides a clear suspicion about the microstruc-
ture, surface roughness, sorption proling porosity, void structure,
particle size, pour size, spiral structure, shrinkage or wrinkle, etc. By
ImageJ and Origin Lab software, it is simple to determine the particle
size and distribution curve from the SEM image. Using a vacuum sputter
coater, a 200 Å gold coating was applied on the spacemen in each
analysis of raw ber, alkali treated ber, bleached ber, and CNC to
prevent them from charging onto the peripheral surface as well as for
good quality image. For FESEM analysis the magnication range was
kept around 10,000x - 30,000x. For this study to examine the samples a
FESEM of model number (JEOL, Model: JSM -IT800, made in Japan) was
used where accelerating voltage was 10kV to 20 kV (Rahman et al.,
2023a and 2024f).
3.3. XRD analysis
XRD is a rapid analytical technique to perceive the crystalline nature
of different polymeric spacemen. In this study, the degree of crystallinity
or crystallinity index of raw maize cob ber, alkali treated ber,
bleached ber, and maize cob CNC samples were measured by XRD
analysis. BRUKER D8 ADVANCE wide angle X-ray diffractometer with
40 mA current, and Cu K
α
radiation (
α
=0.154 nm), 50 kV voltage, was
used to inspect the specimens (Rahman and Maniruzzaman, 2024;
Uddin et al., 2024; Rahman et al., 2018b). Varying the angle from 5◦to
80◦(2θ) the crystallinity index was detected. The crystallinity index
(C
r
I) can be calculated by the following equation:
CrI=ICA
ICA +IAM ×100 (1)
Where, I
AM
and I
CA
are the amorphous area and crystalline area
respectively and they can easily be measured by the origin lab software
(Bano &Negi, 2017).
The d-spacing can be calculated by using Bragg’s equation:
nλ=2dsinθ(2)
Here, λis the X-ray wavelength, n is an integer, θis the diffraction angle,
and d is the distance between crystal lattice planes. Accurate crystallite
size (L) can be calculated by the Scherrer equation:
L=0.94 λ
H cos θ(3)
In this equation, H denotes the full width at half maximum of the
peak in radians, λis the X-ray wavelength (0.1542 nm), and θstands for
the Bragg angle (Benini et al., 2018; Hassan et al., 224).
3.4. Thermal analysis
A common method for evaluating the thermal stability brought on by
the disintegration of different polymeric materials is thermogravimetric
analysis, or TGA. The thermal analysis technique known as TGA is used
to calculate the mass of a spacecraft in relation to time as temperature
varies. Physical events like desorption and adsorption, phase transitions,
and chemical phenomena like thermal breakdown, chemisorption, and
solid gas reactions (reduction or oxidation) are all covered by this
measurement. The sample is heated in a given environment (He, N
2
, Air,
Ar, CO
2
, etc.) at constant rate in TGA analysis. As a function of tem-
perature or time the change of weight of substance is recorded. During
TGA analysis for a known initial weight of substance the temperature is
increased at a constant rate and at different time interval as a function of
temperature the changes in weights are recorded. The plot of weight
change against temperature is called thermogram. The physical and
chemical properties of polymeric spacemen, as well as composition,
melting and polymer relaxation temperatures, onset and maximum
degradation temperatures, phase changes, type of chemical reaction
occurring during the experiment, residual mass, etc. as a function of
increasing heat, can all be determined by holding the heat constant up to
1000 ◦C (Loganathan et al., 2017;Rahman et al., 2023c). For thermal
phase transitions, the rst derivative of temperature is called DTA
(Differential Thermal Analysis). The process of DTA involves monitoring
a sample’s thermal response as it is heated in order to analyze and
determine the chemical composition of various substances. The method
is based on the idea that heat causes reactions and phase changes in
substances, which might result in the emission or absorption of heat
(Wunderlich, 2001). DTG (Derivative Thermogravimetry) is the rst
derivative of TG. The rate of mass loss (dm/dT in mg/min unit) is given
by the DTG peak height at any temperature (Karak, 2012). In this study
thermal analysis of every spaceman was conducted by a Thermal
Gravimetric Analyser of model number (EXSTAR 6000 TG/DTA 6300,
Seiko). Each specimen was taken in amounts of around 25 mg for
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
291
observation. The samples were heated gradually at a rate of 20 ◦C/min
from 26 ◦C to 600 ◦C while maintaining a steady nitrogen ow rate of 60
ml/min (Rahman and Maniruzzaman, 2019;Hossain et al., 2024). To
acquire the correct outcome, several analyses were performed for every
sample.
3.5. DLS analysis
The size distribution prole of tiny particles in suspension or poly-
mers in solution may be found using the DLS method. DLS is used to
describe the size of different particles, such as micelles, vesicles, pro-
teins, carbohydrates, and nanoparticles. It measures the hydrodynamic
radius of particles. DLS is used to examine size range from a few nano-
meters to a few micrometers. The hydrodynamic radius of the nano-
particles is measured by the Stokes-Einstein equation.
D=KBT
6
πη
R(4)
Here, R is the radius of sphere, D is the diffusion constant, T is the ab-
solute temperature,
η
is the dynamic viscosity, and K
B
is the Boltzmann’s
constant. The speed at which the particles are diffusing because of
Brownian motion is basically measured in DLS by measuring the in-
tensity of the scattered light. Small particles cause the intensity to more
uctuate than larger. Main apparatuses of DLS are laser, detector. In DLS
a laser i.e., He, Ne of known wavelength passes through a dilute sample.
Using a detector intensity of scattered light is collected and based on
collected scattered light particle size is determined. Correlogram of DLS
analysis shows smooth curve in case of large particles and noisy curve in
case of small particles. DLS analysis provides accurate result addition-
ally turbid sample can be measured directly and another advantage is
after measurement complete recovery of sample is possible. Some lim-
itations of DLS analysis are it can’t identify the size of solid particles
(particles >1000 nm size are impossible to measure by this method), and
it can measure the hydrodynamic radius of the particles and can’t
measure the actual size of particles (Mao et al., 2017;Patel et al., 2024;
Loya et al., 2024). In this study, DLS analysis was conducted to identify
the particle size of the isolated maize cob CNC. For nano particle size
analysis HORIBA Scientic, nano partica, Nano Particle Analyzer,
SZ-100V2 was used.
3.6. Zeta potential analysis
The charge that is located at the slipping point of a particle in a
medium is called zeta potential. In other words, zeta potential analysis is
used to measure the surface charge (both positive and negative) over a
particle. Zeta potential is used to identify the stability of a colloid, to
understand dispersion and aggregation process in water purication,
paints and cosmetics, etc. Zeta potential is the potential which is
observed at the shear plane. Zeta potential also known as electrokinetic
potential that is basically the difference in the potential between elec-
troneutral region of the solution and shear plane. Factors affecting zeta
potential are pH, thickness, and concentration. Range of zeta potential
typically from +100 to -100 mV. Zeta potential is measured by applying
an electric eld. Particles migrate toward the electrode of opposite
charge in a particular velocity. The velocity of the particles depends on
strength of electric eld or voltage gradient. Zeta potential is associated
with the electrophoretic mobility by the Henry equation. Electropho-
retic mobility,
μ
eis calculated from the equation:
μ
e=V
E(5)
Here, V is the particle velocity, E is the electric eld strength. Once
μ
eis
calculated the zeta potential can be obtained by Henry’s equation:
μ
e=2
ε
z f(Ka)
3
η
(6)
Where, z is zeta potential,
ε
is dielectric constant,
η
is viscosity, and f(Ka)
is the Henry’s function (Bhattacharjee, 2016;Loya et al., 2024). In this
study, zeta potential was applied to measure the surface charge of the
isolated CNC. For zeta potential analysis HORIBA Scientic, nano par-
tica, Nano Particle Analyzer, SZ-100V2 was used.
3.7. EDX analysis
The components or chemical content of the surface of natural poly-
mers or biopolymeric composites have been extensively studied using
EDX. This specic approach allows for the detection of various metals
and minerals, including Pb, Cr, Cd, Zn, Na, Al, Si, Co, Cu, Mg, Ni, Ca, and
others, along with the main chemical compositions and components that
are often connected with the ber’s perimeter or structure, such as N, C,
and O. Interestingly, even though hydrogen is one of the core compo-
nents of biopolymers, this approach is unable to detect its existence or
quantity because of its small size and the lack of electrons in its remotest
shell (Ali, 2016;Moros et al., 2019;Nasrollahzadeh et al., 2019). In this
study EDX analysis was performed to determine the components and
their chemical compositions of raw maize cob ber, bleached ber, al-
kali treated ber, and maize cob CNC. The analysis was conducted by
the EDX analyzer of model QT-606 Energy dispersive X-ray uorescence
spectrometer RoHS1.0.
4. Result and discussion
4.1. FTIR-ATR analysis
FTIR spectroscopy is often used to examine the intramolecular and
intermolecular hydrogen bonding among raw maize cob ber, bleached
ber, alkali treated ber, and maize cob CNC as FTIR is the most often
used method for examining intramolecular and intermolecular in-
teractions in polymers. In other words, FTIR spectroscopy gives clear
indication about functional group. FTIR results of all the characterized
specimen are mentioned in the Table 2 analyzing the wave number of
Fig. 4.The peak at 3300 cm
-1
appeared among raw maize cob ber,
bleached ber, alkali treated ber, and maize cob CNC because of N-H
stretching of amines (Rahman et al., 2018a;Hassan et al., 2024). In case
of CNC, the peak (N-H) was sharp but raw, alkali treated, and bleached
ber provided small peak compared to CNC in FTIR analysis which in-
dicates the successful CNC isolation. Because of C-H stretching the peak
at 2850 cm
-1
–2950 cm
-1
originated in FTIR analysis amongst isolated
CNC, bleached ber, alkali treated ber, and raw ber. A band at 2928
cm
-1
in the raw maize cob ber caused by the aliphatic C-H bonds
stretching (Costa et al., 2015). A Sharp peak was generated for CNC
whereases raw, alkali treated, and bleached ber provided small in-
tensity peaks which implies successful chemical treatment during CNC
isolation. Due to S-H stretching a peak of small intensity appeared at
2540 cm
-1
only for CNC. This new innovated peak may be because of
efcacious acid hydrolysis during CNC isolation. The newly generated
peak in CNC at a wave number of 2160 cm
-1
due to stretching of C≡C
functional group. This alkyne group may be appeared because of a series
of chemical treatments during CNC isolation. The peak at 1600–1900
cm
-1
was attributed to raw maize cob ber, bleached ber, alkali treated
ber, and maize cob CNC due to C=O stretching. Comparatively small
peaks were found in that range among raw, alkali treated, and bleached
ber but the peak provided by CNC was sharp enough which species
the perfect removal of impurities. Because of the symmetric bending of
CH
2
functional group a peak at 1400–1450 cm
-1
appeared in case of raw
maize cob ber, bleached ber, alkali treated ber, and maize cob CNC.
Comparing sharp and small intensity peaks it can be said that successful
chemical treatment was conducted in each step of CNC isolation. In FTIR
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
292
analysis of alkali-treated ber between 1720–1740 cm
-1
no peak
appeared which species perfect removal of C=O group of hemicellulose
from the ber after alkali treatment (Rahman et al., 2023c). Comparing
the alkali treated ber with the raw ber it can be claimed that the alkali
treated ber was pure and hemicellulose free. A sharp peak was noticed
at 1260–1350 cm
-1
in case of maize cob CNC because of C-O stretching.
But the originated peak intensity at 1260–1350 cm
-1
was not that sharp
among raw, alkali treated, and bleached ber. The sharp peak in CNC
appeared due to its appropriate isolation. The peak attributed at
1070–1150 cm
-1
for C-O-C stretching. In case of CNC sharp peak origi-
nated due to C-O-C stretching compared to raw, alkali treated, and
bleached ber in FTIR analysis. The sharp intensity peak appeared in
CNC dictates its proper separation. The broad peak at 1020 cm
-1
in raw
ber points to the presence of the C-OH group of lignin. The peak in-
tensity reduced after alkali treatment that indicates removal of moderate
amount of lignin during alkali treatment. No peak appeared due to C-OH
group stretching of lignin in case of CNC and bleached ber that dictates
the successful removal of bundle of lignin during bleaching process
hence it can be claimed that isolated CNC was totally lignin free. Though
small intensity peaks appeared for raw, alkali treated, and bleached ber
but CNC provided a sharp peak that originated at 850 cm
-1
because of
C-H stretching of aromatics. Another peak of small intensity noticed at
800 cm
-1
for N-O stretching in case of CNC but no peak attributed at that
wave number for raw, alkali treated, and bleached ber (Rahman et al.,
2024b). This newly generated peak at 800 cm
-1
for N-O stretching in
CNC might be appeared because of chemical modication at that spe-
cic wavelength. Although no peak attributed in raw ber but a small
peak originated at 735 cm
-1
due to C-C deformation in raw maize cob
ber, bleached ber, alkali treated ber which pointing the successful
chemical treatment throughout the CNC isolation process. In CNC the
newly generated peak at 600 cm
-1
noticed due to C-Cl vibration. Raw,
alkali treated, and bleached ber didn’t provide any peak at that wave
number. A small and sharp peak also noticed at the wave number of 420
cm
-1
because of S-S vibration in raw ber and CNC respectively but
bleached and alkali treated ber did not give any vibration at that wave
number. This phenomenon indicates that in raw ber sulphur may be
appeared from the air or soil and the alkali treatment, the bleaching
process was removed that sulphur which came from soil or air. Further
generation of the peak at 420 cm
-1
due to S-S vibration in CNC might be
attributed because of chemical modication of sulphur during H
2
SO
4
hydrolysis (Sheikh et al., 2023). From the FTIR analysis, it is noticed that
many functional groups were disappeared after CNC isolation although
they were present in raw, alkali treated, and bleached ber and many
functional groups provided sharp peaks in CNC compared to raw, alkali
treated, and bleached ber again many functional groups were newly
generated in CNC after isolation. Based on these phenomena it can be
claimed that pure CNC was isolated from the raw ber of maize cob
through a series of chemical treatments.
4.2. FESEM analysis
FESEM analysis was conducted to inspect the morphological changes
during different stages of purication by chemical treatment. Fig. 5 (a),
The FESEM micrograph of raw maize cob ber clearly showed the
presence of different fatty, waxy, and gummy materials. The micrograph
also demonstrated that the intercellular space of raw maize cob ber was
lled by lignin and fatty substances which hold the unit cells. Compared
to the raw maize cob ber with 16% NaOH treated ber it appears that
surface of the raw ber roughened after alkali treatment as well as
different impurities, fatty, waxy, and gummy substances successfully
removed additionally porosity on the ber surface was arrived. Fig. 5
(b), The FESEM micrograph of NaOH treated ber dictates that NaOH
treatment of the cellulose ber increased the amount of amorphous
cellulose (Rahman et al., 2022). Removal of hydrogen bond in the
network structure which was an important alteration that occurred due
to NaOH treatment according to the following reaction stoichiometry:
Fiber-OH +NaOH →Fiber-O
-
Na
+
+H
2
O+Surface impurities
…………… (7)
Table 2
The most amenable functional groups with their particular intensity and wave number in case of raw ber, alkali treated ber, bleached ber, and CNC.
Adsorption bond Intensity Raw ber peak (cm
-1
) Alkali treated ber peak (cm
-1
) Bleached ber peak (cm
-1
) CNC peak (cm
-1
)
-OH stretching Sharp &Str. 3130–3500 3150–3550 3100–3600 3000–3750
N-H of Amines Sharp &Str. …….. ……….. ..…….. 2800
C-H Sharp &Str. 2710 2700 2715 2750
S-H Broad &Str. …… …… …… 2540
C≡C Broad &Str. …….…….. …… 2160
C=O Str. 1600 1630 1670 1700
C=O of Hemicellulose Sharp &Str. 1720 …… …… …….
CH
2
Symmetric Bending 1420 1400 1433 1450
C-O Str. 1325 1310 1260 1350
C-O-C Sharp &Str. 1110 1090 1100 1150
C-OH of Lignin Symmetric str. 1020 1030 …… ………
C-H of Aromatics Sharp &Str. 848 843 845 850
N-O Str. 808 815 810 800
C-C Deformation Bending …….…… …… 735
C-Cl Sharp &Str. …….…… ……. 600
S-S Sharp &Str. …….…… ….. 420
Fig. 4. The respective spectrum (in the range of 4000 to 400 cm
-1
) of raw ber,
alkali treated ber, bleached ber, and maize cob derived CNC detected in
FTIR-ATR analysis.
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
293
Fig. 5 (c), The FESEM micrograph of bleached ber designates that
there stands a sharp difference between raw, alkali treated, and
bleached ber. Due to the presence of hydroxyl and carboxyl group
cellulose ber are negatively charged. Although in raw ber hydroxyl
and carboxyl groups were covered by lignin after bleaching process
bundle of lignin successfully removed which is clearly marked in Fig. 5
(d), the FESEM micrograph of bleached ber. Comparison of the pre-
vious two FESEM micrograph of raw and alkali treated ber with the
microgram of bleached ber prescribes that surface of bleached ber
became smooth which is undoubtedly as a result of successful removal of
lignin, hemicellulose, and impurities. Fig. 6 dictates the average particle
size of isolated CNC was at a range of around 1–100 nm which was
calculated by the help of Origin lab and ImageJ software using the
FESEM micrograph of maize cob CNC. Furthermore, there was origi-
nated a lot of crystalline structure of cellulose which were attributed due
to successful acid hydrolysis. Additionally, there was appeared lots of
honey comb structures which indicates that the CNC would provide
better capacity for reinforcement.
4.3. EDX analysis
EDX analysis result of raw ber of maize cob at Table 3 &Fig. 7 (a)
dictated the presence of 37.43% C, 61.03% O, 1.54% K. According to the
literature review main constituents of lignocellulosic bers are alpha
cellulose, hemicellulose, lignin, etc. which are consist of carbon,
hydrogen, and oxygen. That’s why presence of oxygen and carbon
molecules were detected during the elemental analysis. Although there
was presence of huage amount of hydrogen molecules in the raw
lignocellulosic ber of maize cob but EDX analysis couldn’t detect that
because EDX can’t detect small sized molecules like H, He, Li, etc. due to
the lack of electrons in their outermost shell (Rahman, 2024;Rahman
et al., 2024c;Hossain et al., 2024). Additionally, presence of K molecules
in raw ber since plants take different minerals from soil as macronu-
trient. Presence of 37.12% C, 58.26% O, 3.31% Ca, 1.31% Mg was
noticed in EDX analysis, Table 3 &Fig. 7 (b) of alkali treated ber. In
alkali treated ber composition of carbon and oxygen decreased
compared to raw ber which is due to the removal of hemicellulose
(consist of carbon, oxygen, hydrogen). Additionally, presence of Ca, Mg
Fig. 5. FESEM micrographs of the subjected (a) raw ber, (b) alkali treated ber, (c) bleached ber, and (d) maize cob derived CNC under the magnication range of
1,400x to 30,000x.
Fig. 6. Maize cob derived CNC particles size distribution prole (Histogram) in
1 to 100 nm range, determined from the FESEM micrograph of maize cob CNC
(with the help of ImageJ and Origin lab software).
Table 3
Elemental composition of raw, alkali treated, bleached ber, and maize cob CNC
found in EDX analysis.
Sample Elemental Composition (%)
C O Si K Ca Mg S
Raw ber 37.43 61.03 - 1.54 - - -
Alkali treated ber 37.12 58.26 - - 3.31 1.31 -
Bleached ber 41.85 58.15 - - - - -
CNC 39.55 42.08 3.81 - 2.78 - 11.78
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
294
may be because of impurities of NaOH which was used during alkali
treatment. Bleached ber, Fig. 7 (c) dictated the presence of 41.85% C,
58.15% O. Sample analysis of CNC, Fig. 7 (d) indicated that the
composition of C, O, Si, Ca, S in the isolated CNC was 39.55%, 42.08%,
3.81%, 2.78%, 11.78% respectively. Presence of Si in the CNC which
may be came from air. Further arrival of Ca may be due to chemical
impurities of acid which was used for hydrolysis. Furthermore, existence
of S could be because of chemical modication of sulfuric acid.
4.4. Thermal analysis (TGA/DTG/DTA)
Mass loss of raw maize cob ber, bleached ber, alkali treated ber,
and maize cob CNC in the temperature range of 0 ◦C to 100 ◦C was about
10% during thermal analysis which was basically evaporative loss, Fig. 8
(a). Curves are horizontal in the temperature range of 100 ◦C to 250 ◦C
which dictates that during thermal analysis moisture was released at a
constant rate of 10% at that temperature range. In the temperature
range of 250 ◦C to 340 ◦C about 65% and 30% moisture was released
from the alkali treated ber and CNC spacemen respectively whereas in
case of raw and bleached ber respectively about 55% and 60% mois-
ture was released in the temperature range of 250 ◦C to 375 ◦C according
to this comparison it can be said that CNC is better heat stable. About
10% mass loss was noticed in case of raw and bleached ber in the
temperature range of 375 ◦C to 600 ◦C, Fig. 8 (a). On the other hand, in
alkali treated ber loss of mass about 14% in the temperature range of
350 ◦C to 600 ◦C. But in CNC about 12% moisture loss observed due to
low thermal decomposition during TG analysis (residual mass of CNC
was around 40%) in the temperature range of 325 ◦C to 600 ◦C, Fig. 8 (a)
which indicates that maize cob CNC is much more thermally stable than
other bers i.e., raw maize cob ber, bleached ber, alkali treated ber.
Degradation of cellulose, which may include hydroxyl group rupture,
β-1,4 glycoside linkage breakdown, hemicellulose depolymerization,
and dehydration, was the reason for the weight loss of different spec-
imen (Rahman and Maniruzzaman, 2019;Rahman et al., 2024e). Rate of
mass loss of CNC, raw ber, bleached ber, and alkali treated ber at 75
◦C was 95
μ
g/min, 200
μ
g/min, 550
μ
g/min, 425
μ
g/min respectively,
Fig. 8 (b). In the temperature range of 200 ◦C to 400 ◦C mass loss rate
was 570
μ
g/min, 5100
μ
g/min, 690
μ
g/min, 3600
μ
g/min in case of
CNC, alkali treated ber, raw ber, and bleached ber respectively,
Fig. 8 (b). Further, mass loss with respect to time in the temperature
range of 400 ◦C to 600 ◦C for CNC, raw ber, bleached ber, and alkali
treated ber was 30
μ
g/min, 115
μ
g/min, 300
μ
g/min, 280
μ
g/min
respectively, Fig. 8 (b). According to the DTG analysis of all specimen it
can be claimed that CNC showed more thermal stability in various
temperature compared to other samples. (Kiziltas et al., 2016;Rahman,
2024;Zor et al., 2023). Heat loss due to endothermic reaction appeared
at the temperature of around 75 ◦C and 120 ◦C in case of raw ber, CNC
and alkali, bleached ber respectively which dictated in the DTA curve,
Fig. 8 (c).. Some exothermic reaction occurred at 260 ◦C, 250 ◦C, 270 ◦C,
230 ◦C, 325 ◦C in CNC, alkali treated ber, bleached ber, raw ber,
Fig. 7. Resultant images of EDX analysis (carried out for elemental analysis) in case of the (a) raw ber, (b) alkali treated ber, (c) bleached ber, and (d) maize cob
derived CNC.
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
295
alkali treated ber respectively that ensured by the sharp peak at their
respected temperature Fig. 8 (c). Furthermore, at 350 ◦C 330 ◦C, 340 ◦C
&430 ◦C, 400 ◦C, a few exothermic reactions taken place in case of CNC,
alkali treated ber, bleached ber, and raw ber respectively. CNC
sample again undergone an exothermic reaction at 500 ◦C (Rahman &
Maniruzzaman, 2021;Hossain et al., 2024). As per thermal analysis
(TGA, DTG, DTA) it could be professed that the isolated CNC is thermally
more stable compared to raw maize cob ber, bleached ber, and alkali
treated ber.
Fig. 8. Overall thermal analysis, (a) TGA, (b) DTG, and (c) DTA of the subjected specimen (raw ber, alkali treated ber, bleached ber, and maize derived cob CNC)
up to 600 ◦C.
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
296
4.5. XRD analysis
XRD patterns of raw maize cob ber, bleached ber, alkali treated
ber, and maize cob CNC shown in the Fig. 9.Peaks in XRD data at
around 2θ=12.6◦(plane 001), 21◦(plane 110), 22.5◦(plane 002), 29◦
(plane 111), 30◦(plane 220), and 35◦(plane 004) (Fig. 9.) demonstrates
that extracted nanocellulose crystals take on a crystalline structural
form. The crystallinity index (C
r
I) of all the analyzed specimen was
calculated by using the Eq. (1) and is tabulated (Table 4.). The hemi-
cellulose and lignin contents were eliminated to some extent in the
amorphous zone during the alkali process, which caused the crystallinity
index to rise gradually (N.H. Abdul-Rahman et al., 2017;Hassan et al.,
2024;Rahman et al., 2024c &2024d). The bundle of lignin was removed
during the bleaching process, which caused the crystalline spheres to
reorganize. The reduction of the amorphous area in cellulose by hy-
drolysis processes is reected by the high crystallinity index of nano-
cellulose. The amorphous area can disintegrate with acid hydrolysis,
making it less stable than the crystalline sections. Acid hydrolysis at a
high concentration removes the amorphous portion of cellulose as well
as breaks down the crystalline portion of cellulose. Hydronium ions
migrate into cellulose amorphous areas during the acid hydrolysis pro-
cess, assigning glycosidic linkages of hydrolytic cleavage that nally
issues unique crystallites. Due to the increasing of crystallinity of bers
of maize cob, rigidity, toughness, strength was also increased. In raw
ber, the proportion of crystallinity index was 38.09±0.01% and in
extracted CNC (with a JCPDS-ICDD card number (00–056–1718)), this
value risen to 84.63±0.03%, Table 5 and a comparative study of crys-
tallinity index of the CNC collect from different sources (see Table 6)
(Nagalakshmaiah et al., 2019;Marett et al., 2017;Thakur et al., 2020;
Kumar et al., 2013). Amorphous nano compounds such as hemicellulose
and lignin were successfully eliminated by using alkali treatment,
bleaching, and acid hydrolysis as a result CNC provided higher crys-
tallinity index value (Aisiyah et al., 2020;Guo et al., 2020).
4.6. Particles size and zeta potential analysis
According to the DLS analysis the nanocellulose particles belongs to
the range of 100–200 nm, Fig. 10 (a) while Fig. 10 (b) have shown the
multiple bar chart for better understanding the average particle size of
the newly produced CNCs. Whereas most of the CNC particles (about
60%) have possessed their hydrodynamic radius around 160 to 180 nm,
additionally about 22% particles have possessed below 150 nm and rest
of the particles have shown their size below 200nm but higher than 180
nm respectively. Since in DLS analysis the particles size was observed in
Fig. 9. Comparative XRD analysis of the subjected raw ber, alkali treated ber, bleached ber, and maize cob derived CNC in the range of 5◦to 60◦(2θ) with
respective crystalline planes (while CPS stand for counts per second).
Table 4
TGA, DTA, and DTG thermal analysis, mass loss, reaction mechanism, and
degradation rate of various chemically treated bers (raw ber, alkali treated
ber, bleached ber, and maize cob CNC).
Parameters Raw ber (%
at ◦C)
Alkali
treated
ber (% at
◦C)
Bleached ber (%
at ◦C)
CNC (% at
◦C)
Initial loss 15 at 75 12.5 at 95 13.5 at 100 16 at 100
Maximum loss 86 at 600 82 at
600
78 at 600 60 at 600
50%
degradation (
◦C)
300 320 330 310
Highest
degradation (
◦C)
599 598 595 592
Residue at 600
◦C
13 17 23 40
Endothermic
peak at ◦C
75, 220,
420
120, 250,
330
120, 280, 330, 430 75, 270,
350, 500
Maximum rate
of mass loss
(
μ
g/min)
690 5100 3600 570
Table 5
Crystallinity index of the subjected raw ber, alkali treated ber, bleached ber,
and CNC of maize cob according to the XRD analysis of this current work.
Name of the samples Crystallinity Index (CrI %) value
Raw ber 38.09±0.01
Alkali treated ber 45.17±0.05
Bleached ber 72.39±0.07
CNC 84.63±0.03
The data are shown in Table 5 as mean ±standard deviation (SD), and there
were three trials (n =3). It has been statistically examined using analysis of
variance (ANOVA) in order to determine if the sample’s characteristics differ
substantially at the 5% (p <0.05) level.
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
297
nano range it is conrmed that the nanocellulose was isolated success-
fully. The zeta potential value of extracted maize cob CNC was found
around -7.09mV, Fig. 10 (c) which dictates that lots of negative charge
were present on the surface of nanocellulose. Notably, inside the lattice
of the subjected CNC solids, both the positive as well as negative charges
are recompensed because of the electro-neutrality of the considered
stable compounds like nanocellulose. Once reaching the peripheral
surface of the newly produced CNCs, the rhythm could be destroyed
while some charges persist unpaid, hence the electro-neutrality should
have been lost then the surface of the subjected crystalline solids are
charged (Serrano-Lotina et al., 2023). However, the sign as well as the
magnitude of the newly appeared charges that are belong to the surface
of the CNCs could be responsible to govern the endorsement of the ionic
species from the existing solutions as well as the physical properties of
distributions. Conversely, it is well known to all that with the increasing
of the value of negative surface charge/zeta potential of the subjected
CNC particles the stability of those particles have also shown an
increasing tendency this could be happened due to the electrostatic
repulsion forces among the similarly charged CNCs particles (Hossain
et al., 2024;Selvamani et al., 2019;Rahman et al., 2024b).
Table 6
Comparative study of crystallinity index of the CNC collect from different
sources and maize cob according to the XRD analysis.
Source Crystallinity Index (C
r
I)Value
(%)
Reference
Garlic straw 68.80% (Nagalakshmaiah et al.,
2019)Chili leftover 78.50%
Groundnut shells 74.00%
Pistachio shells 66.00% (Marett et al., 2017)
Rice straw 76.00% (Thakur et al., 2020)
Sugarcane
bagasse
72.50% (Kumar et al., 2013)
Keya leaf 61.31% (Hossain et al., 2024)
Okra stalks 86.09% (Rahman et al., 2024b)
Maize cob 84.63 ±0.03% This study
Fig. 10. (a) Particles size distribution (within 0 to 600 nm range) according to the DLS method, (b) Multiple bar chart addressing the different size of the CNC
particles, and (c) Zeta potential (within -500 mV to +500mV range) of the maize cob derived CNC (while a.u stand for arithmetic unit).
S. Dewan et al. South African Journal of Chemical Engineering 51 (2025) 287–301
298
5. Conclusion
In this study, useless lignocellulosic agro waste (maize cob) was
utilized to extract potentially valuable CNC via several chemical modi-
cation steps such as scouring, alkali treatment, bleaching, and acid
hydrolysis (H
2
SO
4
). Characterization of the raw maize cob ber,
bleached ber, alkali treated, and extracted maize cob CNC were carried
out by conducting a quite number of state-of-the-art equipment’s like
FTIR-ATR, FESEM, EDX, TG (TGA/DTG/DTA), DLS, Zeta potential
analysis, and XRD analysis. Effective modication was noticed in the
absorption pattern of comparative FTIR-ATR spectrum of individual -
bers. Each step of modication exposes new face look in the FESEM
micrographs (2D honeycomb like peripheral surface microstructure)
and elemental composition also altered as observed in EDX analysis.
Higher residual mass of CNC (around 40%) as observed in TGA analysis
dictated that the isolated CNC was thermally more stable compared to
all other specimens such as raw, alkali treated, and bleached maize cob
bers. Isolated CNC given lowest rate of mass loss of 40
μ
g/min which
indicates that extracted CNC was highly thermal stable due to its purity.
Analyzing the particles size it was found that the average particles size of
the newly produced CNC was around 100 nm in sized. The highest value
of crystallinity index was found at approximately around 84.63±0.03%
in case of the subjected CNC according to the XRD analysis. Due to these
outstanding properties along with negative surface charge the newly
produced CNC could be promising to fabricate a very much strength
multifunctional biopolymeric nanocomposites that should have a very
good agreement with sustainable environmental development. Hence,
they would be benecially used in various sectors including bulky in-
dustrial, engineering, as well as biomedical elds in order to maintain
the climate and biodiversity.
Funding
The authors extend their appreciation to the Ministry of Science and
Technology (MOST), the People’s Republic of Bangladesh, and the
Bangladesh Council of Scientic and Industrial Research (BCSIR), for
their joint funding to conduct this current work through Research and
Development Project under grant number of (G.
O.39.00.0000.012.02.009.23.159 and G.O. 39.02.0000.011.14.169.
2023/877).
CRediT authorship contribution statement
Shamim Dewan: Writing –original draft, Software, Methodology,
Conceptualization. Md. Mahmudur Rahman: Writing –review &
editing, Writing –original draft, Visualization, Validation, Supervision,
Software, Resources, Project administration, Methodology, Investiga-
tion, Funding acquisition, Formal analysis, Data curation, Conceptuali-
zation. Md. Ismail Hossain: Validation, Software, Investigation. Bijoy
Chandra Ghos: Investigation, Formal analysis, Data curation. M
Mohinur Rahman Rabby: Software, Resources, Methodology. Md.
Abdul Gafur: Resources, Methodology. Md. Al-Amin: Software,
Investigation. Md. Ashraful Alam: Software, Resources.
Declaration of competing interest
The authors declare that they have no known competing nancial
interests or personal relationships that could have appeared to inuence
the work reported in this paper.
Acknowledgment
All authors of this paper devoutly acknowledge the chairman of
Bangladesh Council of Scientic and Industrial Research (BCSIR), as
well as the Ministry of Science and Technology (MOST), People’s Re-
public of Bangladesh for their nancial support and for consenting us to
conduct their highly sophisticated instruments for experimentation.
Furthermore, I want to acknowledge my better-half Suriaya Naznin, lab
attendant Md. Mojul Islam and Mst. Ronjina Khatun for their cordial
help and support during the experimental session and drafting.
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