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Carbohydrate Polymers 127 (2015) 202–208

Contents lists available at ScienceDirect

Carbohydrate Polymers

j ourna l ho me pa g e: www.elsev ier .com/ locate /carbpol

ellulose nanocrystals isolated from oil palm trunk

unidah Lamaminga, Rokiah Hashima,∗, Othman Sulaimana, Cheu Peng Leha,omoko Sugimotob, Noor Afeefah Nordina

Division of Bioresource, Paper and Coatings Technology, School of Industrial Technology, Universiti Sains Malaysia, 11800 Minden, Penang, MalaysiaForestry and Forest Products Research Institute, I Matsunosato, Tsukuba 305-8687, Ibaraki, Japan

r t i c l e i n f o

rticle history:eceived 7 February 2015eceived in revised form 4 March 2015ccepted 8 March 2015vailable online 30 March 2015

eywords:

a b s t r a c t

In this study cellulose nanocrystals were isolated from oil palm trunk (Elaeis guineensis) using acid hydrol-ysis method. The morphology and size of the nanocrystals were characterized using scanning electronmicroscopy and transmission electron microscopy. The results showed that the nanocrystals isolatedfrom raw oil palm trunk (OPT) fibers and hot water treated OPT fibers had an average diameter of7.67 nm and 7.97 nm and length of 397.03 nm and 361.70 nm, respectively. Fourier Transform Infraredspectroscopy indicated that lignin and hemicellulose contents decreased. It seems that lignin was com-

ellulose nanocrystalsil palm trunkaw fibersot water treated fibershermal propertiesrystallinity

pletely removed from the samples during chemical treatment. Thermogravimetric analysis demonstratedthat cellulose nanocrystals after acid hydrolysis had higher thermal stability compared to the raw andhot water treated OPT fibers. The X-ray diffraction analysis increased crystallinity of the samples due tochemical treatment. The crystalline nature of the isolated nanocrystals from raw and hot water treatedOPT ranged from 68 to 70%.

© 2015 Elsevier Ltd. All rights reserved.

. Introduction

As an agricultural plant, the oil palm tree (Elaies guineensis) hasecome one of the major crops that contributes to economic growthf Malaysia. The total biomass of 95 million tons are generatednnually, this lignocellulosic material provides a continuous sup-ly for the new oil palm biomass industry (MPOB, 2012). This new

ndustry has converted such underutilized bio-fiber into promisingalue-added products such as fertilizer, mattress filling, mediumensity fiberboard, molded wares, composite material, pulp andaper, and other potential products. Oil palm bio-fibre waste is lig-ocellulosic materials, and it is rich in cellulose. The trunks becomevailable during the replanting season on a cycle of every 25 to 30ears. Holocellulose composition in oil palm trunk range from 72o 78% (Abdul Khalil, Siti Alwani, Ridzuan, Kamarudin, & Khairul,008; Hashim et al., 2010; Lamaming et al., 2013, 2014). This makeshe trunks suitable to be used as raw material for the production ofellulose nanofibers.

Cellulose is a poly �-1,4,d anhydroglucopyranose that dis-lays a regular network of inter and intramolecular hydrogenonding organized into perfect stereoregular configurations called

∗ Corresponding author. Tel.: +60 4 653 5217; fax: +60 4 6573678.E-mail addresses: hrokiah@usm.my, hrokiah1@gmail.com (R. Hashim).

ttp://dx.doi.org/10.1016/j.carbpol.2015.03.043144-8617/© 2015 Elsevier Ltd. All rights reserved.

microfibrils (Janardhanan & Sain, 2006). Naturally, cellulose com-posed of two main regions that are amorphous and crystalline. Thecrystalline regions were accessible by using strong acid hydrolysisto remove the amorphous regions. It is insoluble in water but canbe degraded by microbial and fungal enzymes (Li et al., 2009). Syn-thesizing cellulose from lignocellulosic materials is very useful invarious applications such as a potential use as reinforcing the com-ponent in high-performance composite materials (Zuluaga, Putaux,Restrepo, Mendragon, & Ganán, 2007; Faria, Cordeiro, Belgacem, &Dufresne, 2006). Research on cellulose nanofibers has been gainingmuch interest this past year with different isolation methods andraw materials. There are different methods for isolation of the cel-lulose microfibers being reported including mechanical, chemical,chemo-mechanical, and enzymatic isolation processes (Jonoobi,Khazaeian, Md Tahir, Azry, & Oksman, 2011).

Utilizing oil palms waste as a source for natural cellulose fiberswill significantly benefit for the agricultural use, fiber resource,food, and energy needs. It will also help the environment becausethe products are considered as sustainable green materials. Thiswill also tackle the problem of oil palm waste being left out inthe field or burned and contribute to the economy by turning itinto valuable products. The nanocellulose can be used in nanocom-

posite materials as reinforcing filler for the automotive industry,predominantly for interior applications, construction, electronics,cosmetics, packaging and also in biomedicine purposes (AbdulKhalil, Bhat, & Ireana Yusra, 2012; Tang, Du, Li, Wang, & Hu, 2009).

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pplication of nanocellulose in polymer reinforcement is still newnd further research is needed. One of the applications is incorpo-ating nanocellulose with polyvinyl alcohol (PVA), polylactic acidPLA), starch, and polycaprolactone but also with polyethylene orolypropylene (Panaitescu et al., 2011). The PVA biocomposite filmhat was produced is water soluble, biodegradable, and can be usedn manufacture medicine cachets, yarn for surgery, and controlledrug delivery systems because it has no toxic effect on the humanody (Tang et al., 2009).

Research on the cellulose nanocrystal isolation using empty fruitunch has been reported by a few researchers (Fahma, Iwamoto,ori, Iwata, & Takemura, 2010; Jonoobi et al., 2011; Mohamadaafiz, Eichhorn, Hassan, & Jawaid, 2013). Fahma et al. (2010) iso-

ated the cellulose nanocrystal from an empty fruit bunch by usingcid hydrolysis and Jonoobi et al. (2011) isolated the nanocrystalsing chemo-mechanical process. The latter researcher using acidydrolysis as described by Chuayjuljit, Su-uthai, and Charuchinda2010) with followed the original procedure of Battista (1950).owever, no studies could be found yet on the cellulose nanocrystal

solated from other parts of oil palm biomass, an especially trunk.or this reason, the aim of this study was to isolate the celluloseanocrystal from oil palm trunk using chemo-mechanical treat-ents. The morphological and structural characteristics of isolated

anocrystal were evaluated through Scanning electron microscopeSEM) and Transmission electron microscope (TEM). The chemicalomponents of the fibers were measured before and after chemi-al treatments according to TAPPI standard. The properties of theellulose nanocrystal isolated from the trunk were characterizedsing thermogravimetric analysis (TGA), Fourier transform infraredFTIR) spectroscopy, and X-ray diffraction (XRD) analysis.

. Experimental

.1. Preparation of samples

Old oil palm trunks obtained from a plantation in Kuala Selangorere harvested and sawn into discs before the bark was removed.

he trunks were then chipped and dried before being ground toarticles and pass screening process of 1000 �m using a Willeyill. Two types of materials were prepared from oil palm trunk,

amely raw fibers and water-treated fibers soaked in hot wateraving a temperature of 60 ◦C ± 3 ◦C. For water treatment, thebers were soaked with a thermostat control unit using hot dis-illed water for 6 h before they were filtered on a Buchner Funnel.his treatment was done because hot water removes a substantialmount of extractives in oil palm trunk and reduces the need to usethanol/toluene solvents in producing the cellulose nanocrystal.

.2. Isolation of the cellulose nanocrystal

The isolation of the cellulose nanocrystal was done following therocedure of Fahma et al. (2010) with a slight modification. About0 g of raw oil palm trunk fibers was weighed. Extractives of raw oilalm trunk fibers were removed by Soxhlet extraction for 4 h usingthanol/toluene (v/v 2:1). Then, the extracted fibers were bleachedour times in sodium chlorite (NaClO2) solution under acidic condi-ions (pH 4 to 5) at 70 ◦C for 1 h then washed with deionized water.emicelluloses were removed by soaking the fibers with 6 wt%otassium hydroxide (KOH) solution at 20 ◦C for 24 h and rinsingith deionized water until pH 7. Then, the cellulose fibers wereydrolyzed in 210 mL of sulfuric acid (H2SO4) solution (64%) under

trong agitation at 45 ◦C for 1 h. The hydrolysis was terminated bydding 400 mL of cold water. The precipitate was resuspended inater with strong agitation, centrifuged and dialysed for 3 daysntil the pH became constant. It was then homogenized, sonicated,

lymers 127 (2015) 202–208 203

and freeze dried. The step was repeated for water-treated fibers byskipping the Soxhlet extraction step.

2.3. Chemical analysis of the specimens

The chemical components of the oil palm trunks fibers beforeand after water treatments were investigated. Preparations ofextractive free samples were conducted according to TAPPI 264 cm-97 (TAPPI, 1997) with a modification of the solvent ethanol-tolueneratio of 2:1. Holocellulose content was done based on the methodof Wise, Murphy, and D’Addieco (1946). The cellulose content wasextracted from the percentage of holocellulose with 17.5% sodiumhydroxide. Lignin content of the samples was analyzed accordingto TAPPI 222 om-02 (TAPPI, 2002). Total starch content was carriedout using a total starch kit manufactured by Megazyme Interna-tional Ltd, Bray, Ireland. Measurement was conducted in triplicate,and the recorded data were found to be reproducible.

2.4. Microstructure study of the samples

An LEO Supra 50 Vp field emission scanning microscope (FESEM)with ultra-high resolution was used to study the effect of the waterand chemo-mechanical treatments on the fiber morphology. Allsamples were gold-sputtered using sputter coater model PolaronSC 515 ± 20 nm to avoid charging.

2.5. Transmission electron microscope

The structure and size of the nanocrystal were observed bytransmission electron microscopy (TEM) using a Philips CM 12 elec-tron microscope. A drop of diluted oil palm trunk nanocrystal.

A total of 10 fibers of each material were measured, and theresult was reported as the mean value of the data from each set ofmeasurements.

2.6. Spectroscopic study by Fourier transform infrared

The presence of any changes in functional groups during treat-ment in the samples was scanned by FT-IR Spectroscopy. Thesamples were pounded to made a thin pellet that is the mixture ofapproximately 5 mg of particles samples and 95 mg of finely groundKBr. Spectra were viewed using a Nicolet infrared spectropho-tometer (Avatar 360 FT-IR E.S.P) machine. The spectra producedare transmittance mode between wave numbers of 4000 cm−1 and500 cm−1.

2.7. X-ray diffraction analysis of the samples

Structural and phase analyzes of the samples were measuredby using an X-ray diffractometer with Ni-filtered CuK� radia-

tion (wavelength of 1.5406 ´A). The operating voltage and currentwere generated of 40 kV and 30 mA, respectively. The sampleswas scanned at 2◦/min with a 2� angle range from 5◦ to 50◦. Thecrystallinity index value was computed according to Segal, Creely,Martin, and Conrad (1959) to quantify the crystallinity of the sam-ples. The crystallinity index (CIr) is defined by:

CIr (%) = (I0 0 2 − Iam)I0 0 2

× 100 (1)

where I0 0 2 is the peak intensity corresponding to crystalline andIam is the peak intensity of the amorphous fraction.

2.8. Thermogravimetric analysis

Thermogravimetric analysis was performed to determine thethermal decomposition of the oil palm trunk fibers after each

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reatment. The thermal stability data were collected on a Perkinlmer TGA 7. The samples of 7–15 mg were burned under temper-ture ranging from 25 ◦C to 800 ◦C at a heating rate of 10 ◦C/minnder a nitrogen atmosphere.

. Results and discussion

.1. Chemical composition and cellulose yield of the samples

The chemical compositions of the oil palm trunk (OPT) fibersefore and after treatments and isolated cellulose microfibers are

isted in Table 1. The yield of extractives exhibited a decrease ran-ing from 8 to 19% as the fibers underwent hot water treatment. Itan be observed that the chemical composition values of oil palmrunks fibers were slightly decreased compared to those fibers thatnderwent water treatment, with an exception of the extractivesontent. This might be due to the hot water treatment tending toxtract some of the water soluble materials in the fibers (Lamamingt al., 2014). It appears that other chemical components of the sam-les were not affected since the temperature of the water treatmentas only 60 ◦C using distilled water. Using hot water treatment

an remove a substantial amount of extractives; therefore, one caneduce the use of toluene/ethanol solvents to remove the extrac-ives from the fibers to produce the cellulose nanocrystals.

Comparing the findings of this work to those of previousesearch, the chemical composition of oil palm trunk determinedas within the acceptable limits (Abdul Khalil et al., 2008; Hashim

t al., 2010; Lamaming et al., 2013, 2014). Lignin content for rawnd water treated fibers was 11.7% and 13.2%, respectively. Theesults determined showed an increase in holocellulose content ofhe samples from 77.4% to 81.4% as a result of water treatment.he starch content of both raw and hot water treated oil palmrunk fibers were 16.1%, respectively. The result was similar withhe value 16.5% reported by previous research (Abe et al., 2013).fter the fibers had undergone treatment to produced celluloseanocrystal, the starch content was not detected as the chemicalsed dissolved and removed the starch during the acid hydrolysisreatment.

Fig. 1 displays the cellulose nanocrystals yield produced aftercid hydrolysis from raw and hot water treated oil palm trunkbers. Yield of cellulose nanocrystals decreased for fibers that hadndergone hot water treatment. Hot water treatment of the fibersrobably facilitated swelling and open up of the fibers during acidydrolysis and thus reducing the yield.

.2. Microstructure analysis of the samples

The SEM micrographs of the raw, hot water treated, and chemo-echanically treated fibers are displayed in Fig. 2. The chemical

reatment seems to affect the morphology of the fibers in term ofize and surface smoothness of the fibers. Fig. 2a and b shows the

orphology of the raw and hot water treated OPT fibers while theorphology of the fibers after the chemomechanical treatment is

xhibited in Fig. 2c and d. More irregularities and impurities wereound in the fibers, as shown in Fig. 2a and b.

able 1hemical composition of oil palm trunk (OPT) fibers.

Materials Extractives (%) Chemical Compo

Lignin

Raw OPT 19.15 (0.97) 11.68 (0.74)

Hot water treated OPT 8.04 (0.54) 13.19 (0.58)

Numbers in parentheses are standard deviation values.

Fig. 1. Cellulose nanocrystals yield after acid hydrolysis from raw and hot watertreat fibers from oil palm trunk.

Fig. 3 shows the TEM images of the celluloses nanocrystal afterthe chemo-mechanical treatment. The TEM images reveal the indi-vidualization of nanocrystal from the micro sizes fiber bundles.Average diameter and length of the cellulose fibers isolated fromraw and hot water treated oil palm trunk powder were of 7.67 nmand 7.97 nm and 397.03 nm and 361.70 nm, respectively.

3.3. Spectroscopic analysis

Fig. 4 illustrates the FTIR spectra of the oil palm fibers for theraw and the hot water-treated cellulose nanocrystal from raw fibersand the cellulose nanocrystal from hot water treated fibers. In gen-eral, the spectra for both raw and hot water treated were foundto be similar. All the spectra were dominated by signals in theregion I between 3380 and 3418 cm−1 due to stretching vibra-tions of OH groups. The hydrophilic tendency of the materials alsoreflected in the broad absorption band in this 3100 to 3700 cm−1

region. The existence of O-H is attributed to the moisture contentwhere hydroxyl is found in cellulose, hemicelluloses, and lignin(Hsu, 1997).

Cellulose, hemicelluloses, and lignin are the major constituentsof the natural fibers. Cellulose being a linear polymeric compoundhas some important functional group within the cellulose units. InFig. 4, region II clearly shows bands between 2900 and 2928 cm−1,which indicates the aliphatic saturated C H stretching associatedwith methylene groups in cellulose (Hsu, 1997).

As it is well-known, lignin is a multifunctional natural poly-mer built up by oxidative coupling of three major C6–C3phenylpropanoid units, which form a randomized structure in atridimensional network by certain interunit linkages. The impor-tant functional groups of lignin include carbonyls, phenol hydroxyl,aromatic rings, and methoxyl groups (Glasser & Kelly, 1987). Thepeak at 1707 to 1723 cm−1 in the spectra (region III) of raw andwater-treated samples is assigned to the C O stretching of theacetyl. Uronic ester groups of hemicelluloses or to the ester link-age of carboxylic group of the ferulic and �-coumaric acids of lignin(Sun, Xu, Sun, Fowler, & Baird, 2005). The peak at 1640 cm−1 may

be attributed to the bending mode of the absorbed water and acontribution of some carboxylate groups. Aromatic hydrocarbonsof lignin showed absorption in the peak 1510 cm−1 and 1426 cm−1

correspond to carbon-carbon stretching vibrations in the aromatic

sition (%) Starch (%)

Holocellulose �-cellulose

77.39 (0.20) 50.74 (1.63) 16.1481.36 (0.23) 51.75 (1.10) 16.05

J. Lamaming et al. / Carbohydrate Polymers 127 (2015) 202–208 205

Fig. 2. SEM micrographs of oil palm trunk (OPT) fibers (a) raw fibers (b) hot water treated fibers (c) chemo-mechanically treated fibers of raw OPT (d) chemo-mechanicallytreated fibers of hot water-treated OPT.

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Fig. 3. Transmission electron micrographs of the cellulose nanocrystal

ing. Deformation of C H asymmetric can be found at peak around

373 cm−1. These two peaks (in region III) were found to van-

sh in the produced nanocrystal spectra indicating the removal ofignin. From Fig. 4c and d, the intensity of the peak at 1247 cm−1

region IV) sharply decreased proving that the removal of

l palm trunk (a) and (b) raw fibers (c) and (d) hot water treated fibers.

hemicelluloses. The increase of band at 897 cm−1 (region V) in

Fig. 4c and d can be attributed to the typical structure of cellulosedue to the �-glycosidic linkages of glucose ring of cellulose (Ganán,Cruz, Garbizu, Arbelaiz, & Mondragon, 2004; Kaushik, Singh, &Verma, 2010).

206 J. Lamaming et al. / Carbohydrate Polymers 127 (2015) 202–208

Fig. 4. Infrared spectra of the oil palm trunk (OPT) fibers (a) raw fibers (b) hot water treated fibers (c) cellulose nanocrystals from raw fibers (d) cellulose nanocrystals fromhot water treated fibers.

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ig. 5. XRD curve for all materials (a) raw fibers (b) hot water treated fibers (c) cellu

.4. X-ray diffraction analysis

The XRD method was used to determine the percent of crys-allinity of the produced cellulose nanocrystals isolated from raw

nd hot water treated oil palm trunk fibers. Fig. 5 show X-rayiffractograms obtained for all samples, and all samples exhibitedajor intensity at a 2� value of 22◦ related to their crystalline struc-

ure of cellulose as lignin is amorphous in nature. The cellulose

anocrystals from raw fibers (d) cellulose nanocrystals from hot water treated fibers.

nanocrystal of oil palm trunk obtained from raw and hot watertreated showed the diffraction intensity at 22◦ and a shoulder in theregion 2� = 19◦. These two peaks of diffraction intensity indicatedthat all of the nanocrystals produced were of cellulose 1 type.

The crystallinity index for the raw and hot water treated sam-ples, and the cellulose nanocrystal isolated from both raw and hotwater treated was found to be 47.18%, 50.65%, 69.61%, and 68.07%,respectively. These values had higher crystallinity characteristics

J. Lamaming et al. / Carbohydrate Po

Table 2Crystallinity index of all materials of oil palm trunk (OPT) fibers.

Materials Crystallinity index (%)

Raw OPT 47.18Hot water treated OPT 50.65

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crystallinity. Higher crystallinity values resulted in greater resis-

F

Cellulose nanocrystals from raw OPT 69.61Cellulose nanocrystals from hot water treated OPT 68.07

s compared to those of nanofibers isolated from oil palm emptyruit bunches having 59% and 69% carried out in two previousorks, respectively (Fahma et al., 2010; Jonoobi, Harun, Shakeri,isra, & Oksman, 2009). However, the crystallinity of the micro-

rystalline cellulose produced from the same materials was 87%igher in past study carried out by Mohamad Haafiz et al. (2013)hich was higher than what we have found in this work. After the

aw and hot water treated fibers were exposed to chemical treat-ent in order to produce the cellulose nanocrystals, it was found

hat the crystallinity of the samples was increased. This may be dueo the sulfuric acid attacking the amorphous region, thus penetrat-ng the region causing hydrolytic cleavage of glycosidic bonds andeleasing individual crystallites (Li et al., 2009). Efficient removalf non-cellulosic polysaccharides such as hemicelluloses and ligninatrix that attached to the celluloses fibers would also contribute

o an increase in crystallinity.According to Chen et al. (2009), under drastic conditions of acid

ydrolysis, amorphous and crystalline regions may be only partiallyestroyed because of erosion caused by the high concentration ofulfuric acid. From Table 2, the crystallinity of water-treated fibers

ig. 6. TGA curves of all materials (a) cellulose nanocrystals from raw fibers (b) water tre

lymers 127 (2015) 202–208 207

was higher than that of the raw fibers probably due to the fact thathot water treatment removed water soluble substances that hinderpenetrating of the acid into the amorphous region.

3.5. Thermal analysis

Fig. 6 shows the TGA curves for all the specimens. From thisfigure, the weight loss of the samples starts at temperature levelsranging from 50◦ to 150 ◦C due to the evaporation of the moisturein the materials tested. Being a lignocellulosic material, the com-position of oil palm trunks degrades below 400 ◦C. Wax, pectin andhemicellulose also degraded at a temperature of 180 ◦C while cellu-lose and lignin degraded at temperature levels of 300 ◦C and 400 ◦C,respectively (Johar, Ahmad, & Dufresne, 2012; Nazir, Wahjoedi,Yussof, & Abdullah, 2013). According to Sonia and Priya Dasan(2013), the degradation of natural fibers takes place in two stagesstarting from degradation of the amorphous phase consisting hemi-celluloses, lignin and the crystalline phase, where the cellulose isdominant in the phase.

After chemomechanical treatment, the thermal stability of thelignocellulosic materials increased due to the removal of hemicellu-loses and lignin during the treatment process. This could also be dueto the higher degree of crystallinity of the materials after mechani-cal processing (Jonoobi et al., 2009). The chemical treatments attackthe amorphous region in the cellulose and increase the degree of

tance towards heat and increase in the maximum temperature forthermal degradation. At temperature levels ranging from 300 to350 ◦C, the degradation of the �-celluloses took place. After 380 ◦C,

ated fibers (c) cellulose nanocrystals from hot water treated fibers (d) raw fibers.

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he residual decomposition products maintained leveled off andhowed a slow degradation profile (El-Sakhawy & Hassan, 2007)

Lignin, as well as ash, was found to be responsible for the charormation of the fiber at the end of the testing (Sonia & Priya Dasan,013). From Fig. 6, it can be seen that raw fibers showed higher ashontent followed by the water-treated fibers, as these specimenstill contain more lignin content compared to those of celluloseanofibers from raw fibers and water-treated fibers, where the ashontent was less indicating the removal of the lignin.

. Conclusions

Based on the findings in this work, cellulose nanocrystal wasuccessfully extracted from oil palm trunk (OPT) by acid hydrolysis.esults showed that average diameter and length of the celluloseroduced from raw and hot water treated OPT samples rangedrom 7.67 nm to 7.97 nm and from 397.03 nm to 361.70 nm, respec-ively. The FTIR spectra demonstrated the removal of lignin andemicelluloses after the chemical treatment. The TEM micrographslucidated the individualization of the fibers after the treatment.RD analysis showed that crystallinity increased after acid hydrol-sis, unfolded that the crystalline nature of the isolated nanocrystalrom raw and water treated OPT fell in the range 68 to 70%. On thether hand, thermogravimetric analysis displayed that the thermaltability increased in the materials after acid hydrolysis comparedo the raw and hot water treated OPT as removal of the ligninnd hemicelluloses as well as the increase of the crystallinity ofhe materials. The hot water treatment did not affect the sizend properties of obtained nanocrystal since there is no signifi-ant differences were observed for the reported data on the size,rystallinity, and thermal analysis.

cknowledgements

The authors acknowledge Ministry of Higher Education forcholarship awarded and Universiti Sains Malaysia for the grant1001/PTEKIND/811255) in funding for this research.

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