Isolation and Characterization of Microcrystalline Cellulose from

Coconut Fiber using Acid Hydrolysis Process

H. Nasution

, H. Harahap

, P. Suherman

and Kelvin

Department of Chemical Engineering, Faculty of Engineering, Universitas Sumatera Utara, Padang Bulan, Medan,

Indonesia

Keywords: Coconut fiber; microcrystalline cellulose; x-ray diffraction, Water soluble, Loss on drying.

Abstract: The object of this research was to explore the utilization of coconut fiber as a natural source for the production

of microcrystalline cellulose. Coconut fiber was treated with alkali at the first time then bleached before the

production of microcrystalline cellulose by acid hydrolysis (HCl). The produced materials were characterized

using X-ray Diffraction (XRD) and some physicochemical properties such as pH, water soluble substance

and loss on drying. XRD showed that acid hydrolysis process increase the crystallinity of microcrystalline

cellulose from α-cellulose. Meanwhile the physicochemical properties showed that the produced material was

close to British Pharmacopeia standard. The results proved that coconut fiber was a valuable source for the

production of microcrystalline cellulose.

1 INTRODUCTION

Natural fibers consist amorphous and semicrystalline

structure. Amorphous structure contain lignin and

hemicellulose while semicrystalline contain

cellulose. Cellulose fiber has better strength, stiffness

and thermal stability than natural fiber because

natural fiber still contains lignin and hemicellulose

(Melbi et al, 2018).

Cellulose is a linear chain of glucose molecules

with degree of polymerization between 10,000 to

15,000 and linked together through an oxygen

covalently bounded. During biosynthesis, van der

Waals and intermolecular hydrogen bonds between

hydroxyl groups and oxygen of adjacent molecules. It

makes cellulose relatively stable and gives high axial

stiffness. In cellulose there are regions where the

cellulose chains are arranged in a highly ordered

structure. This region is called crystalline region. On

the other side there are region that disordered. It is

known as amorphous region. Crystalline phase can be

extracted using acid catalyst hydrolysis. The result of

this extraction is microcrystalline cellulose (Robert et

al, 2011).

Microcrystalline cellulose is produced by

depolymerization of cellulose materials with

solutions of mineral acids at increased temperatures.

The acid catalyst destroys glycoside bonds mainly in

non crystalline domains. It makes cellulose lose its

degree of polymerization from 10,000-15,000

become 120 to 250. Microcrystalline cellulose is used

mainly as food products, cosmetic formulation,

inactive ingredients of tablets and special additive for

some technical applications (Michael and Alex,

2006). There are some natural resources that are used

to produce microcrystalline cellulose. That natural

resources are cassava bagasse (Panee et al,2015), corn

husk (Roshni and Yamini, 2015), rice straw (Chin et

al, 2016), empty fruit bunch palm oil (Nasution et al,

2017), cotton stalks (Hassan and El-Sakhawy, 2005).

In this study, coconut fiber was used as raw material.

The composition of coconut fiber can be seen at Table

1 (Khalil et al, 2006). Table 1 shows that the main

constituent of coconut fiber is cellulose.

Table 1: Composition of coconut fiber

Composition Percentage

Holocellulose 56.3

α – Cellulose 44.2

Lignin 20.5

Ash 2.2

There are some methods to produce

microcrystalline cellulose which is ultrasonication

222

Nasution, H., Harahap, H., Suherman, P. and Kelvin, .

Isolation and Characterization of Microcrystalline Cellulose from Coconut Fiber using Acid Hydrolysis Process.

DOI: 10.5220/0010077802220226

In Proceedings of the International Conference of Science, Technology, Engineering, Environmental and Ramiﬁcation Researches (ICOSTEERR 2018) - Research in Industry 4.0, pages

222-226

ISBN: 978-989-758-449-7

(Zailani et al, 2016), ultrafiltration membrane

(Nguyen and Rajesh, 2016), enzymatic hydrolysis

(Herman et al, 2017) and acid hydrolysis (Ravindra et

al, 2017). Acid hydrolysis was the conventional

method for produce microcrystalline cellulose.

Hydrochloric acid and sulfuric acid were common

used as mineral acid for acid hydrolysis (Ravindra et

al, 2017). With sulfuric acid hydrolysis, the sulphate

group are problematic because of the thermal stability

if compared to hydrochloric acid hydrolysis. So in

this study, we choose hydrochloric acid to hydrolyzed

the cellulose because microcrystalline produce with

hydrochloric acid has better thermal stability (Birgi

and John, 2009).

The main purpose of the present paper is to

characterize microcrystalline cellulose that extracted

from coconut fiber. The microcrystalline will be used

as reinforcement agent for composites.

2 METHODS

2.1 Materials

Coconut fiber was collected from local market in

Medan, Sumatera Utara, Indonesia. Other chemicals

such as nitric acid, sodium nitric, hydrochloric acid,

sodium hydroxide and sodium hypochloride were

supplied by Merck.

2.2 Extraction of α-Cellulose from

Coconut Fiber

Coconut fibers were cleaned from impurities and cut

into small pieces. 50 gram of coconut fiber were

added with 700 ml of 3,5% nictric acid that contained

8 mg of sodium nitric, then heated on temperature 90

°C using hotplate for 2 hours. Then, coconut fiber was

washed with distilled water until its filtrate neutral.

2% of sodium hydroxide solution were add to the

fiber and heated on temperature 50 °C for 1 hour.

Clean the filtrate using distilled water till its filtrate

neutral. Then the cellulose were added with 3,5%

sodium hypochloride and then heated until boiled for

10 minutes then cleaned the filtrate using distilled

water until its filtrate neutral.

Purified the cellulose using 340 ml sodium

hydroxide solution 17,5% for 30 munites on

temperature 80 °C. Cellulose was washed using

distilled water until its filtrate neutral then bleached

again for 30 minutes using sodium hypochlorite on

temperature 60 °C then washed with water until

filtrate neutral.

2.3 Isolation of Microcrystalline

Cellulose from α-Cellulose

The α-cellulose hydrolysed with hydrochloric acid

2,5 N at temperature 75 °C for 15 minutes. Cold water

were added and stirred strongly then placed at free air

area for one night until the solution formed a

suspension. Distilled water was used to washed the

suspension until neutral and then dried using oven for

1 hour at temperature 60 °C. Then Microcrystalline

Cellulose was saved in desiccator.

2.4 Yields of α-Cellulose and

Microcrystalline Cellulose

Yields of α-cellulose and microcrystalline cellulose

were determined by the following equations:

α-cellulose yield =

α-Cellulose weight

Coconut fiber weight

x 100 % (1)

Microcrystalline cellulose yield =

microcrystalline celluloseweight

α-celluloseweight

x 100 % (2)

3 CHARACTERIZATION OF

COCONUT HUSK FIBER,

Α-CELLULOSE AND

MICROCRYSTALLINE

CELLULOSE

3.1 Crystallinity

Crystalinity of coconut husk fiber, α-cellulose and

microcrystalline cellulose was determined by X-Ray

Diffraction (XRD) and recorded in 6100 Shimadzu.

The crystallinity index was determined with Segal’s

empirical method (Larissa et al, 2015):

(%) = (I

200

– I

)/I

200

x 100 (3)

3.2 Determination of Phsycochemical

Properties of the Microcrystalline

Cellulose

Some of the properties were pH, water-soluble

substance and moisture content identification.

3.2.1 pH

Shake 1 g of microcrystalline cellulose for 5 minutes

in 50 ml of distilled water the pH was determined with

a pH meter (Achor et al, 2014).

Isolation and Characterization of Microcrystalline Cellulose from Coconut Fiber using Acid Hydrolysis Process

223

3.2.2 Water Soluble Substances

5 g of microcrystalline cellulose was shook in 80 ml

of distilled for 10 minutes, then filtered using filter

paper Whatman no.1. Then dried at 100-105 °C for 1

hour to evaporate the water and weight the

microcrystalline cellulose (Paul, 2008).

3.2.3 Loss on Drying

5 g of microcrystalline cellulose was dried at 100-105

°C for 1 hour then cooled in a desiccator. After then

the microcrystalline cellulose was weighed. The %

loss on drying was then determined as the ratio of

weight of mass loss to weight of sample expressed as

a percentage (Achor et al, 2014).

4 RESULT AND DISCUSSION

4.1 Yield of Process

From the process, the yield of α-cellulose was 45.44%

and the yield of microcrystalline cellulose was

42.74%. From 50 g of coconut fiber, 22.72 g of

cellulose was obtained. Then from 22.72 g of

cellulose, 9.71g of microcrystalline cellulose was

obtained. Here the results show concluded that

coconut fiber contains a lot of amorphous phase in

cellulose.

4.2 Crystallinity

Figure 1, Figure 2 and Figure 3 show the XRD

patterns of microcrystalline cellulose, α-cellulose and

coconut fiber. The sharp peak indicative the

crystallinity (Larissa et al, 2015). From fig 1(a), the

amorphous peak still high and the difference between

amorphous peak and crystalline peak still small and it

means the crystallinity still low. From fig 1(b), the

amorphous peak of cellulose was lower than coconut

fiber, it means the most of the lignin and

hemicellulose was removed from coconut fiber and

the crystallinity increased. From fig 1(c) the

amorphous peak already low and the difference peak

between amorphous and crystal peak was large, it

means most of the amorphous region already

removed from the crystal region.

From the for coconut fiber XRD characteristics, a

sharp peak is resolved which is indicative of

crystalline at 2θ = 21.80°. The α-cellulose XRD

characteristics, a sharp peak is resolved which is

indicative of crystalline at 2θ = 22.80°. Then

microcrystalline cellulose XRD characteristics, a

sharp peak is resolved which is indicative of

crystalline at 2θ = 22.80°. The index crystallinity of

coconut fiber, α-cellulose and microcrystalline

cellulose was determined by Segal empirical. The

results show that the crystalinity of coconut fiber, α-

cellulose and microcrystalline cellulose were

43.45%, 46.54% and 75%. The results show that the

crystallinity increases in the series of transformation

from coconut fiber to microcrystalline cellulose.

Some studies about microcrystalline cellullose

percent crystallinity by hydrochloric acid hydrolysis

have been report such as empty fruit bunch palm oil

is 73% (Nasution et al, 2017), cotton stalks is 77%,

bagasse is 76% and rice straw is 77% (Hassan and El-

Sakhawy, 2005).

Figure 1: XRD patterns of coconut fiber.

Figure 2: XRD patterns of α-cellulose.

Figure 3: XRD patterns of microcrystalline cellulose.

0 20406080

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4.3 Physicochemical Properties of

Microcrystalline Cellulose

By using universal pH indicator, the pH of the

microcrystalline cellulose was 7. The water soluble

substance was 0.2% and the loss on drying was 5%.

From British Pharmacopeia, the standard pH for

microcrystalline cellulose was 5-7, the water soluble

substance was <0.25% and the loss on drying was

<7% (British Pharmacopoeia, 2009). From the results

can be concluded that the microcrystalline cellulose

in accordance with British Pharmacopeia’s standard.

5 CONCLUSIONS

Microcrystalline cellulose has been isolated from

coconut fiber by acid hydrolysis, after coconut fiber

treated by alkali and bleaching process. it showed that

the crystallinity of microcrystalline cellulose has

increased because the exposure of crystalline phase

after the removal of lignin via alkaline treatment and

removal amorphous region of cellulose via acid

hydrolysis. The physicochemical properties of

microcrystalline cellulose showed that the produced

material is close to British Pharmacopeia standard.

Meanwhile XRD showed that increasing crystallinity

of microcrystalline cellulose from α-cellulose after

acid hydrolysis. The results obtained here suggest that

coconut fiber is capable of being a source for

production microcrystalline cellulose which can be

used as reinforcing fillers in various industries.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge that the present

research is supported by Directorate of Research and

Community Service Director General Strengthening

Research and Development Ministry of Research and

Technology and The Higher Education Republic of

Indonesia on year of grant 2018.

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