J. Nig. Soc. Phys. Sci. 4 (2022) 949

Journal of the
Nigerian Society

of Physical
Sciences

Potential of Anacardic Acid for Nanosized Cellulose Preparation
Under Different Treatment Conditions

Olugbenga O. Oluwasinaa,∗, Abiodun D. Aderibigbea,b, Damilola C. Petinrina, Adeyemi S. Adebisia,
Olayinka O. Oluwasinac, Oluwasegun J. Wahabb

aDepartment of Chemistry, Federal University of Technology Akure, P.M.B. 704 Akure, Ondo State, Nigeria
bDepartment of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom

cSchool of Chemistry and Physics, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, 4000, 7 South Africa

Abstract

Herein, anacardic acid was applied for the preparation of nanosized cellulose using three different treatment conditions including ultrasonication,
microwave irradiation, and reflux. Physico-chemical characterization was undertaken using FTIR, TEM, SEM, and XRD. FTIR, TEM, and SEM
analyses confirm the preparation of nanosized cellulose with similar chemical but different physical properties as the cellulose starting material. In
addition, calculated degrees of crystallinities from XRD data revealed crystallinities of 53.9, 54.4, and 54.7% for the nanosized cellulose prepared
by ultrasonication (UNC), microwave irradiation (MNC), and reflux (RNC) respectively, which all are higher than the 53.3% of the precursor
cellulose. Overall, the study shows that anacardic acid holds potential for the preparation of nanosized cellulose.

DOI:10.46481/jnsps.2022.949

Keywords: Anacardic acid, cellulose, nanosized cellulose, ultrasonication, reflux, microwave irradiation

Article History:
Received: 20 July 2022
Received in revised form: 15 September 2022
Accepted for publication: 28 September 2022
Published: 05 November 2022

c© 2022 The Author(s). Published by the Nigerian Society of Physical Sciences under the terms of the Creative Commons Attribution 4.0 International license

(https://creativecommons.org/licenses/by/4.0). Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Communicated by: K. Sakthipandi

1. Introduction

Nanosized cellulose, which is a material with at least one
dimension < 100 nm, is traditionally prepared using mineral
acids like sulfuric and hydrochloric acids [1-4]. However, the
use of mineral acids comes with significant problems particu-
larly operational hazards, generation of toxic wastes, and cor-
rosion of reactors [5]. Consequently, growing attention is be-
ing paid to the development of environmentally friendly meth-
ods for preparing nanosized cellulose. Some of these methods

∗Corresponding author tel. no: +234(0)8107246660
Email address: oooluwasina@futa.edu.ng (Olugbenga O. Oluwasina)

are enzymatic and organic acid-based hydrolysis. Although en-
zymatic hydrolysis is environmentally friendly, significant me-
chanical energy is often required to break down the enzymat-
ically hydrolyzed cellulose fibres into nanocrystals [6, 7]. In
addition, dispersion and chemical modification of the product
cellulose nanocrystal is challenging [5]. Consequently, signifi-
cant consideration is being paid to organic acid-based hydroly-
sis [8, 9].

Attractive features of the organic acid-based method include
ease of recovery, biodegradability, limited corrosivity, and con-
venient handling of the organic acid [10]. Fu and coinvesti-
gators reported access to highly crystalline nanosized cellulose
material in two steps using an ionic liquid and subsequently ox-

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Olugbenga et al. / J. Nig. Soc. Phys. Sci. 4 (2022) 949 2

Figure 1. The general structure of anacardic acids (R = saturated or unsaturated
alkyl chain)

alic acid under relatively mild conditions [2]. Robles’s group
described the ultrasonic-assisted hydrolysis of cellulose using
citric, oxalic, and maleic acids. Though the yields of the pre-
pared nanosized cellulose were poor to moderate (20 to 40%),
the thermal stabilities were better than those obtained using
sulfuric acid [11]. Holilah and coworkers observed that the
yields, particles sizes, and crystallinities of the nanosized cel-
lulose they prepared using organic acids (acetic, citric, and ox-
alic) were higher than that prepared using inorganic acids (hy-
drochloric, sulphuric, and phosphoric) [12].

Investigation into the discovery and development of bio-
based alternatives to petroleum-derived heavy chemicals is be-
coming increasingly popular due to the need to achieve sustain-
able development. While many bio-based reagents can be em-
ployed to prepare nanosized cellulose, our attention was drawn
to anacardic acid (Figure 1) because of the presence of the car-
boxylic acid group. In addition, the extraction of anacardic acid
from the cashew fruit is well established [13-15] and appli-
cations of the acid [15-18] including those exploiting the car-
boxylic acid group [14] are growing.

As part of our work on the investigation of environmen-
tally friendly methods for the preparation of bioderived mate-
rials, we wondered if anacardic acid could function as an ef-
fective hydrolyzing agent for the preparation of nanosized cel-
lulose. Anacardic acid, a yellow liquid obtained from the nut
of the cashew fruit, is composed of both saturated and unsatu-
rated molecules. Herein, we report the preparation of nanosized
cellulose by the hydrolysis of cellulose (derived from plantain
inflorescence stalk) using anacardic acid under different con-
ditions including ultrasonication, microwave irradiation, and
reflux. Following this, the nanosized cellulose products were
characterized using FTIR, TEM, SEM, and XRD. This study
shows that anacardic acid is a potential candidate for the prepa-
ration of nanosized cellulose.

2. Materials and methods

2.1. Materials

The cashew (Anacardium occidentale) seeds were purchased
from the local fruit market in Akure, Ondo State, Nigeria. Plan-
tain (Musa paradisiaca) inflorescence stalk (PIS) was obtained
from the Teaching/Demonstration Plantation of the Federal Uni-
versity of Technology Akure (FUTA). The materials were au-
thenticated at the Department of Crop, Soil, and Pest Manage-
ment, FUTA. All reagents were purchased from Sigma Aldrich
and used as received.

2.2. Instrumentation

Fourier transform infrared (FTIR) spectra were recorded on
Bruker c© Alpha Platinum-Attenuated Total Reflectance IR spec-
trometer. X-ray diffraction (XRD) data were collected on a Pan-
alytical Empyrean X-ray diffractometer employing a Co Kα ra-
diation at 40 kV and 40 mA. Transmission electron micrographs
(TEM) were captured using the JEOL 2100+ machine operat-
ing an acceleration voltage of 200 kV from samples prepared on
a copper EM grid. Scanning Electron Microscopy (SEM) char-
acterization was undertaken using LEO 1450 SEM, the samples
were attached to a brass stub and coated with gold before anal-
ysis. Ultrasonication treatment was undertaken using a Bran-
sonic ultrasonicator (Ranson 1210E- MT,USA) sonicator. Mi-
crowave irradiation was achieved using Russell Hobbs-ASDA
(Leeds) microwave operating at a frequency of 2.45 GHz.

2.3. Preparation of plantain inflorescence stalk cellulose

Plantain inflorescence stalk (PIS) cellulose was prepared
following the method reported by Oluwasina and coworkers
[19]. Briefly, PIS powder and 5% NaOH (1:30 ratio by mass)
were charged into a 15 L autoclave and heated at 140 oC under
atmospheric pressure for 1 hour. The pulp obtained was washed
with water until a neutral pH and finally dried. The dried PIS
pulp (7.5 g), hot water (375 mL), NaClO2 (4.45 g), and acetic
acid (1.03 mL) in a 1 L beaker were heated at 80 oC for 1 hour.
Next, NaClO2 (8.9 g) and acetic acid (2.06 mL) were fed into
the stirring mixture, and the whole suspension was heated for
a further 2 hours. The bleached sample obtained was washed
with water to a neutral pH and dried to give a white fibrous
material labeled as plantain inflorescence stalk (PIS) cellulose.

2.4. Anacardic acid isolation

Anacardic acid was isolated from cashew nut powder fol-
lowing the combination of the methods reported by Shobha’s
[20] and Bezerra’s [14] groups. Briefly, cashew seed nut pow-
der (average particle size of 1 mm) was extracted with n-hexane
for 12 hours to give a brown viscous liquid which was con-
centrated by distillation. A solution of the brown oil (70 g)
in aqueous MeOH (300 mL, 5%) was warmed to 50 oC, after
which Ca(OH)2 was added in portions with continuous stirring
for 3 hours. The crude product obtained was filtered and the re-
sulting residue was washed successively with MeOH (150 mL),
and water (200 mL) and stirred in concentrated HCl (400 mL,
11 M) for 1 hour. The organic component was extracted using
petroleum ether (100 mL x 3), dried over anhydrous Na2SO4,
and concentrated to furnish a dark brown liquid identified as
crude anacardic acid.

2.5. Nanosized cellulose preparation

Nanosized cellulose was prepared by ultrasonication, mi-
crowave irradiation, and reflux. Typically, a suspension of PIS
cellulose (5 g) and anacardic acid in acetone (50 mL, 80% v/v)
was treated by ultrasonication, microwave irradiation, or reflux
for 45 min. The resulting crude product was washed consecu-
tively with acetone (100 mL), EtOH (100 mL), distilled water
(100 mL), and oven dried at 60 oC for 8 hour to deliver a white

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Olugbenga et al. / J. Nig. Soc. Phys. Sci. 4 (2022) 949 3

Figure 2. FTIR spectra show that plantain inflorescence stalk (PIS) cellulose
and nanosized cellulose prepared by ultrasonication (UNC) microwave irradia-
tion (MNC) and reflux (RNC) contain identical functional groups

powder labeled as ultrasonication-prepared nanosized cellulose
(UNC), microwave irradiation-prepared nanocellulose (MNC)
or reflux-prepared nanocellulose (RNC) to represent the prepa-
ration methods.

2.6. Determination of degree of crystallinity
The degree of crystallinity (DC) was determined using XRD

data by the method described by Neto’s group [21].

Degree o f crystallinity(%) =
crystalline band areas

(crystalline band areas + amor phous band area)
× 100 (1)

3. Results and Discussion

3.1. Chemical composition identification by FTIR
The chemical compositions of the PIS cellulose, RNC, UNC,

and MNC prepared products were identified from their FTIR
spectra (Figure 2). All the spectra show the presence of iden-
tical functional groups in all samples, an observation expected
if the PIS cellulose is cellulosic and the RNC, UNC, and MNC
are the nanosized products. Indeed, all spectra contain broad
bands at 3312 cm−1, weak/medium peaks at 2280 cm−1, weak
peaks at 1636 cm−1, and sharp peaks at 1014 cm−1 representa-
tive of O-H stretching, C-H stretching, O-H bending, and C-O
stretching vibrations respectively [22-25].

3.2. Morphology and fibre width determination by TEM and
SEM

The fibre morphology and width were determined by TEM
analysis (Figure 3). All fibres except for that prepared by re-
flux (RNC) appear as hollow tubes with thick edges. As ex-
pected, the PIS cellulose has the highest particle width of 102.4

Figure 3. TEM micrographs of (a) plantain inflorescence stalk (PIS) cellulose
and nanosized cellulose prepared by (b) ultrasonication (c) microwave irradia-
tion and (d) reflux

nm. UNC and MNC have fibre widths of 49.6 and 54.9 nm
respectively.The fibre width of RNC could not be determined
as a sizeable micrograph was not obtained. The lower fibre
width observed for UNC compared to MNC could be because
ultrasonication involves the use of microbubbles of the anac-
ardic acid solution which may be more efficient than the bulk
solution involved with microwave heating for the splitting of
PIS cellulose [26]. The observed nano sizes of the UNC and
MNC fibers widths indicate that different materials have been
successfully prepared from the PIS cellulose [27].

Further information on the morphology of the samples was
obtained after SEM analysis. The PIS cellulose appears as fibre
bundles cemented together to give a lightly rough surface (Fig-
ure 4). The nature of the PIS cellulose surface was attributed
to the presence of lignin and hemicellulose. On the other hand,
the RNC, UNC, and MNC samples appear as individual strands
loosely bound into a bunch with deep longitudinal furrows and
a higher degree of surface roughness than observed for the PIS
cellulose. The loosely bound strands in the hydrolyzed cellu-
lose samples can be attributed to the removal of the fibrous
lignin and hemicellulose from the PIS cellulose by anacardic
acid. Overall, the SEM micrographs support the TEM results
showing that the cellulose derivative (RNC, UNC, and MNC)
samples were prepared from the PIS cellulose using all methods
employed.

3.3. Degree of crystallinity determination from XRD patterns

The X-ray diffractograms displayed in Figure 5 were col-
lected to determine the degrees of crystallinity.The diffractogram
for the PIS cellulose is similar (save the absence of a peak at
2Θ values below 20 o) to the diffractograms of cellulose sam-

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Olugbenga et al. / J. Nig. Soc. Phys. Sci. 4 (2022) 949 4

Figure 4. SEM micrographs of (a) plantain inflorescence stalk cellulose and
nanosized cellulose prepared by (b) ultrasonication (c) microwave irradiation
and (d) reflux

Figure 5. X-ray diffractograms of plantain inflorescence stalk (PIS) cellulose
and nanosized cellulose prepared by ultrasonication (UNC), microwave irradi-
ation (MNC), and reflux (RNC)

ples reported by Teixeira and coauthors [27] using sugarcane
bagasseas a cellulose source. The PIS cellulose diffractogram
looks identical to those of UNC, MNC, and RNC samples. The
calculated DCs were as follows 53.3, 53.9, 54.4, and 54.7 %
for the PIS cellulose, UNC, MNC, and RNC respectively. The
DCs shows that the reflux method produced the most crystalline
nanosized cellulose material. This could be because refluxing
was most effective in the removal of non-cellulosic components
from PIS cellulose.

4. Conclusion

The preparation of nanosized cellulose using anacardic acid
under different treatment conditions including ultrasonication,
microwave irradiation, and reflux was undertaken. Results from
the physicochemical characterizations suggest that anacardic
acid was most effective for the preparation of nanosized cellu-
lose under reflux conditions. This study shows that a combina-

tion of anacardic acid as a hydrolysis agent and reflux provides
access to nanosized cellulose with higher crystallinity compared
to the precursor cellulose. Other conditions including pressure,
reaction duration, and amounts of acid for the preparation of
nanosized cellulose using anacardic acid could be investigated.

Acknowledgments

We thank the referees for the positive enlightening com-
ments and suggestions, which have greatly helped us in making
improvements to this paper.

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