ISOLATION OF CELLULOSE FIBERS FROM SUGARCANE BAGASSE AND CORN COB AND PREPARATION OF CELLULOSE NANOCRYSTALS FROM A SELECTED

PURE CELLULOSE SOURCE.

Norrihan Binti sam

Bachelor of Science with Honours Resource Chemistry Programme

2008

Faculty of Resource Science and Technology

Isolation of cellulose fibers from sugarcane bagasse and corn cob and preparation cellulose nanocrystals from a selected pure cellulose source.

NORRIHAN BINTI SAM ( 14858 )

This project is submitted in partial fulfillment of the requirement for the degree of Bachelor of Science with Honours ( Resource Chemistry ).

Resource Chemistry Programme Faculty of Resource Science and Technology

Universiti Malaysia Sarawak 2008

Declaration

No portion of the work referred in this dissertation has been submitted in support of an application for another degree of qualification of this way or any other university or institution of high learning.

_____________________ Norrihan Binti Sam Programme of Resource Chemistry Faculty of Resource Science and Technology Universiti Malaysia Sarawak

Acknowledgements

First of all, I am grateful to God because I had successfully finished my final year project.

I wish to gratitude to my supervisor, Dr Pang Suh Chem for his guidanes, generosity, patience

and encouragement during my final year project. I also would like to thank my parents for their

helpful to prepare samples. Also my thanks to Mr Voon for help me to observed my samples

using SEM microscope. Finally, I would like to thank to my friends, Nurul Hidayah and Bashela

Carol for their co-operation during a year we worked together.

TABLE OF CONTENTS

Table of Contents v

Abstract vi

Chapter 1: Introduction 1

Chapter 2: Literature Reviews 5

Chapter 3: Materials and Methods

3.1 Sample Preparation 15

3.2 Isolation of cellulose 15

3.4 Preparation of cellulose nanocrystals 20

Chapter 4: Results and Discussions

4.1 Isolation of Cellulose Fibers 22

4.2 Physical Characterization 23

4.3 Percentage Yield of Cellulose 30

4.4 Characterization of Cellulose Fibers 33

Chapter 5: Conclusions 48

References 49

Abstract

Two different procedures for the isolation of cellulose from sugarcane bagasse and corn

cob were studied. These are the acetic acid - nitric acid mixture and the delignification with

acidified sodium chlorite. The treatment of sugarcane bagasse and corn cob with the 80% acetic

acid- 70% nitric acid mixture at 120 ºC yielded 38.6% and 28.6% of cellulose, respectively.

Another treatment of sugarcane bagasse and corn cob was the delignification with acidified

sodium chlorite followed by extraction with 10% NaOH gave cellulose yields of 56.80% and

57.20%, respectively. The cellulose nanocrystals were prepared by acid hydrolysis of cotton

wool. The cellulose fibers and cellulose nanocrystals were characterized using FT-IR

spectroscopy, CHN analyzer, Nikon optical microscope and Scanning Electron Microscope

( SEM ).

Keywords: Cellulose fibers; cellulose nanocrystals; Isolation; Acid Hydrolysis

Abstrak

Terdapat dua prosedur untuk pengasingan selulosa dari hampas tebu dan tongkol

jagung. Dua kaedah tersebut adalah campuran asid asetik-asid nitrik dan pembuangan lignin

dengan keasidan sodium klorit. Rawatan untuk hampas tebu dan tongkol jagung dengan

campuran 80% asid asetik dan 70% asid nitrik pada suhu 120 ºC meghasilkan 38.60% and

28.60% selulosa. Rawatan kedua untuk hampas tebu dan tongkol jagung adalah pembuangan

lignin dengan keasidan sodium klorit diikuti pengestrakan 10% NaOH menghasilkan 56.80%

and 57.20% selulosa. Nanokristal selulosa telah disediakan dengan menggunakan asid hidrolisis

( asid sulfurik ). Gentian selulosa dan nanokristal selulosa diuji dengan menggunakan FT-IR

spektroskopi, penganalisis CHN, mikroskop optikal dan Mikroskop Pengimbas Elektron ( SEM ).

Kata kunci: Gentian selulosa; nanokristal selulosa; Pengasingan; Asid Hidrolisis

1

1.0 Introduction

Biopolymers can be defined as polymers which are produced from natural sources. For

example, starch, cellulose, protein and others. Biopolymers widely been used to prepare

nanomaterials. In recent years, nanoparticles are becoming more significant and technology of

their production and uses is rapidly growing into an important industry.

Cellulose is the major constituent of all plant materials and constantly replenished by

photosynthesis (Sun et al., 2004). Cellulose is synthesized by all higher plants and various kind

of organisms. The amount of cellulose synthesized is enormous and the cellulose is the most

abundant biopolymer on earth (Colvin , 1980).

The major function of cellulose is as a structural component in plants. In higher plants and

lower plants, cellulose is a structural component of different layers and lamellas of the cell wall

which embedded with matrix polysaccharides (Lewin and Goldstein, 1991). Natural sources of

cellulose include wood pulp, cotton, hemp, jute, sugarcane bagasse , corn cob , cereal straws and

others.

Cellulose has many uses such as to make cellophane, rayon, cigarette papers ( transparent)

and textile derived from beech wood cellulose . Cellulose is insoluble in the most organic solvents

(Rose et al., 2007). Several cellulose derivatives are produced such as carboxymethylcellulose,

cellulose acetate and methylcellulose (Rose et al., 2007).

2

The hydroxyl groups on each anhydroglucose in the cellulose chain make cellulose very

hygroscopic and readily adsorb water in the amorphous regions (Lewin and Goldstein, 1991).

Reagents that interact with the hydroxyl groups must penetrate the structure and the availability of

the hydroxyl groups is an important factor in all cellulose reactions (Lewin and Goldstein, 1991).

Cellulose derivatives can be prepared by esterification, etherification, xanthation and

grafting (Lewin and Goldstein, 1991). The most important commercial materials of cellulose are

cellulose esters and cellulose ethers (Haigler and Weimer, 1991). Cellulose acetate and cellulose

triacetate are examples of cellulose esters which are film and fiber forming materials that have

variety of uses (Haigler and Weimer, 1991).

Sugarcane and maize ( corn) can be easily cultivated in Malaysia. The botanical name for

sugarcane is Saccharum officianum. It is a tropical grass native in Asia. There are many types of

corn such as dent corn, flower corn, sweet corn and popcorn. However, the residues such as

sugarcane bagasse and corn cob is not been utilized so far. So, they can be as raw material for

regenerated cellulose. Furthermore, this will make the environmentally- friendly.

In recent years, the utilization of agro-industrial residues such as sugarcane bagasse and

corn cob had been increasing . Sugarcane bagasse ( SCB ) had been used as a raw material by

several processes and products such as electricity generation, pulp and paper production and

products based on fermentation (Sun et al., 2004).

3

In the industry, the sugarcane bagasse is used in the boilers for steam production, building

materials, fuel and feedstocks. Due to the abundance and renew ability, cellulose have great deal

as feedstock and sugarcane bagasse contain 60% of cellulose and hemicellulose where their

degradability is very poor (On-line 1, 2007).

Corn cob have high potential as a raw material to produce a variety of value-added

chemicals (Rivas et al., 2004). Corn cob also used as fertilizers, soil conditioners by land

application (Tsai et al., 2001), as animal feed, as energy source by combustion (Lin et al., 1995)

and biological substrate for the production of forage protein (Perotti and Molina, 1988). In recent

years, the utilization of corn cob waste for the preparation of activated carbon has been increased

(Tsai et al., 2001).

There are many classification of nanotechnology. These include nanoparticle, nanocrystal,

nanocomposites, nanostructures, nanophase materials and others. Nanoparticle and nanostructures

have different definition. Nanoparticle is a solid particle which have size range of about 1-1000nm

and have different shape such as noncrystalline, an aggregate of crystallites or a single crystallites.

Nanostructures is a solid material which have one, two or three dimensions. In one

dimension, the material could be particles. In two dimension, the material could be thin films

whereas in three dimension, the material could be thin wire (Klabunde, 2003).

4

In nanotechnology, they give many applications in areas of chemistry, pharmacy,

cosmetics, surface coating agents, textile sizing, paper coating agriculture and biochemistry

(Nakache, 2000).

In this research, we hope to find the most cost effective method for the extraction of

cellulose from sugarcane bagasse and corn cob. Furthermore, we hope to synthesize cellulose

nanocrystals using cellulose extracted from sugarcane bagasse and corn cob or directly from a

selected pure cellulose source such as cotton wool. Cellulose nanocrystals prepared in this study

could be suitable for the preparation of cellulose / silica nanocomposites which possesses high

potential for biomedical applications.

The objectives of this research are:

• To extract and characterize cellulose from sugarcane bagasse and corn cob.

• To prepare and characterize cellulose nanocrystals from suitable cellulosic materials.

• To determine the chemical and physical properties of cellulose fibers and cellulose

nanocrystals.

5

2.0 Literature review

2.1 Cellulose

Cellulose was first isolated and recognized as a distinct chemical substance in the 1980s by

agricultural chemist, Anselme Payen (1838).Chemically, cellulose is a linear polymer and the

glucose unit in the cellulose is linked by β-1,4- glycosidic bonds. The β isomers are arranged in

parallel row and the hydroxyl groups in adjacent chains are held together by forming the hydrogen

bonds, to hydrolysis than starch. (Timberlake, 2006). Cellulose molecules are linear and have

strong tendency to form intra- and intermolecular hydrogen bonds (Sjostrom, 1993).

Primary plant cell wall contain 9-25% of cellulose microfibrils, 25-50% matrix of

hemicellulose and 10-35% of pectins (Bhatnagar and Sain, 2005). Secondary cell wall are formed

when the primary cell walls are thickening and inclusion of lignin into the cell wall matrix

(Bhatnagar and Sain, 2005). This cell walls contain 40-80% of cellulose, 10-40% of hemicellulose

and 5-25% of lignin (Bhatnagar and Sain, 2005).

Cellulose is polymorphic. Studies had been reported that there are four different forms of

cellulose (Lewin and Goldstein, 1991). The native cellulose has a parallel chain orientation and

this cellulose is called as cellulose I while the cellulose in anti-parallel chain orientation is called

as cellulose II (Lenholm, 1995). Mercerisation is the process where the cellulose I convert to

cellulose II by treatment with alkali which had been used for many years (John, 1992).

6

O

OH

OHOH

OOO

OH

OHOHO O

OO

OH

OH OHOH

OH OHO

Structure of cellulose

Natural cellulose is usually found in the form of microfibrils that they are organized in

fibres, cell walls and others. In the cellulose microfibrils, the cellulose chains are aligned parallel

to the microfibril axis while in the cellulose fibres, the cellulose chains are ultrastructural

organisation and orientation of the microfibrils which are responsible of their mechanical strength

(Malainine et al., 2002).

Cellulose commonly function as reinforcing elements and fibrous reinforcing elements of

various composition are common to biological supportive structures (Haigler and Weimer, 1991).

Cellulose chains aggregate to form long thin threads called microfibrils (Lewin and Goldstein,

1991). Cellulosic walls are natural composite structure and they consists of microfibrils that are

embedded in an amorphous matrix (Frey-Wyssling, 1976: Preston, 1986) of polysaccharide such

as hemicelluloses, pectins and protein (Haigler,1985: Delmer and Stone, 1988: Bacic et al., 1988).

Celulose microfibrils transform a gel like matrix into reinforced composite with high tensile

strength (Frey-Wssyling, 1976).

7

Studies by X-ray diffraction and electron microscopic observations indicate that the

microfibrils are much smaller units (Lewin and Goldstein, 1991). The microfibrils consists of two

regions: one area of crystallinity and another area of amorphous cellulose (Lewin and Goldstein,

1991). The microfibrils are composed of distributed crystalline and amorphous regions formed by

the transition of the cellulose chain due to the fringed micellar theory (Lewin and Goldstein,

1991). This gives an orderly arrangement in the microfibrils in the crystalline regions to a less

orderly orientation in the amorphous area (Howsman and Sisson, 1954).

Frey-Wyssling and Muhlethaler had used electron microscopy studies and negative

staining techniques which to proposed a model of an elementary microfibril. This results give

highly crystalline straight-chain aggregates contain dislocations and chain ends, which there are no

true amorphous areas (Lewin and Goldstein, 1991).

There are variety types of degradation of cellulose: hydrolyic (Brown, 1978), oxidative

(Cowlin and Kirk, 1976), alkaline (Cross and Bevan, 1880), thermal (Van Beckum and Ritter,

1937), microbiological(Murphy and D’ Addieco, 1946) and mechanical (Green, 1963). Sun et al.

( 2004) stated that isolation of pure cellulose using acidified sodium chlorite are traditionally used

to delignify wood.

8

A study on isolation of cellulose had been reported by Sun et al., (2004) using sugarcane

bagasse. The cellulose fibers were characterized using FT-IR spectroscopy . There are studies that

were described the methods for chemical and physio-chemical analysis, including neutral sugar,

molecular weight measurement and alkaline nitrobenzene oxidation of residual lignin in isolated

hemicellulose and cellulose (Lawther et al., 1995; Sun et al., 1995; Sun et al., 1996).

2.2 Chemical composition of sugarcane bagasse and corn cob.

Sugarcane bagasse contains about 40-50 % of glucose polymer cellulose which is mainly

in a crystalline structure (Sun et al., 2004). Another compounds are hemicelluloses and amorphous

polymer such as xylose, arabinose, galactose and mannose (Sun et al., 2004). Lignin is mostly the

remainder and another compounds which are lesser such as mineral, wax and others (Jacobsen et

al., 2002 ; Wyman, 1999).

Corn cob consists of hemicellulose fractions and pentoses such as xylose and arabinose

which the dry weight is about 39% whereas the cellulose fractions is about 34% of the dry weight

(Rivas et al., 2003). In oven dry basis, the average composition of corn cob is : cellulose, 34.3 %;

hemicellulose, 39.0 % ; lignin, 14.4 % and others are 12.3 % (Rivas et al., 2004).

9

2.3 Cellulose nanocrystals

Nanocrystal is a solid particle that is a single crystal which the range is in the nanometer

size (Klabunde, 2001). Amorphous regions in a cellulose can be removed using acid hydrolysis

which is well known process (Bondeson et al., 2006). Over 50 years ago, studies had reported that

acid hydrolysis of cellulose fibers would produce microcrystalline cellulose (Ranby, 1951;

Battista, 1956).

The shape and size of microcrystalline cellulose are more or less fixed by the source of

cellulose (Battista, 1975) where different sources (cotton, wood pulp and others) will give

different sizes of microcrystallites although in the same experimental conditions (Marchessault et

al., 1961). Many different cellulose suspensions had been studied from varies of cellulose sources

such as bacterial cellulose (Araki and Kuga,2001: Roman and Winter, 2004) tunicate cellulose

(Favier et al., 1995), soft wood pulp (Revol et al.,1992: Araki et al., 1998) and primary cell wall

cellulose of sugar beet (Dinand et al., 1999).

Another studies also reported that the cellulose nanocrystals that result from the

degradation by acid hydrolysis are form colloidal suspensions and form aqueous suspensions

when they are stabilized (de Sousa Lima and Borsali, 2004). They contain highly crystalline rod-

like particles with a high specific area (Angles and Dufresne, 2001).

10

Nickerson and Habrle (1947) stated that cellulose crystallites is produced by using

hydrochloric and sulfuric acid hydrolysis from the cellulose materials. There are also a few

research about redispersion of nanocrystals in polar and non polar organic solvents and the

dispersions of microfibril cellulose had been prepared in DMSO or dimethylsulfoxide (Turbak et

al., 1983).

Moreover, studies also reported that nanocrystals had been dispersed in a polar organic

solvent using DMF which is without surfactants or chemical modification (Samir et al., 2004).

Dong et al. (1996) stated that microcrystalline cellulose made by acid hydrolysis of cellulose

fibers possessed properties of certain polyelectrolytes because some negative charged sulfate

groups were produced when the hydroxyl groups of cellulose reacted with sulfuric acid. In the

latest research, the cellulose nanocrystals is examined in polar aprotic organic solvents, which is

without the use of surfactants or chemical modification (Viet et al., 2006).

Last few years, much effort had been published to the use of nanocrystals obtained from

polysaccharides such as cellulose. The advantages of this natural polysaccharides are their low

density, renewable character, bidegradable and highly specific properties of nanoparticles (Samir

et al., 2004). The polysaccaharide nanocrystals reinforced polymer composites will be transparents

in well dispersed composites (Samir et al., 2004).

11

A study on preparation of cellulose nanocrystals had been reported using Whatman ashless

cotton cellulose powder. The particles size of cellulose nanocrystals were characterized using

Transmission Electron Microscopy ( TEM ) and Photon Correlation Spectroscopy ( PCS ) (Dong

et al., 1998). The surface charges were characterized using conductometric titration (Dong et al.,

1998). The function of conductometric titration is to quantify the amount of sulfate groups on the

cellulose which sulfuric acid is used (Bondeson et al., 2006) to produce cellulose nanocrystals.

The utilization of sulfuric acid to make the cellulose nanocrystals become charged at their

surface and lead to the electrostatic repulsion so that the aqueous suspension is stable (Samir et

al., 2004). The aqueous suspension display characteristic of birefringent (Marchessault et al.,

1959) and chiral nematic phase is formed (Samir et al., 2004).

2.4 Nanocomposites

For inorganic particle dispersion or suspension, most researched had focused on the phase

of gas and liquid (Ke and Stroeve, 2005). In application of photon crystals, submicron silica

particles with narrow-size distribution are self-assembled to form an ordered structure in liquid

phase (Qi et al., 1998; Zhang et al., 2001).

Organic polymers such as polymers and biomacromolecules made the fine particles to

form clusters, agglomerates or heterogenous morphology because the fine particles are not

disperse (Lu, 2000). This must be avoiding in order to obtain composite materials with good

properties.

12

Due to their high-porosity structure, aerogels are clearly an ideal starting material in

nanocomposites. Aerogels are made by sol-gel polymer of selected silica, alumina or resorcinol-

formaldehyde monomers in solution but highly porous and have nanosize pores (Ajayan et al.,

2003).

In the composites, the physical structures have dimensions at least in one phase and the

additional phases may have nanoscale dimensions or may be larger (Ajayan et al., 2003).

Composites contain a polymer matrix and synthetic filler such as glass fiber, carbon or aramid

which act as reinforcement (Bhatnagar and Sain, 2005). It have been widely used in many

applications such as automotive, packaging, construction and others (Bhatnagar and Sain, 2005).

Aerogel nanocomposites can be produced in many ways depending on when the second

phase is introduced into the aerogel material and the second component can be added during sol-

gel processing of material (Ajayan et al., 2003). A non silica material such as a soluble organic,

biopolymer, biomaterial and others is added to the silica sol before gelation ( Ajayan et al., 2003 )

.

In the previous study, highly porous aerogel were prepared from cellulose hydrogel by

improved drying methods (Jin et al., 2004). The gel are expected to be useful in various dry

processes such as particle separation or catalytic conversions in gas phase, as well as vapor-phase

( Jin et al., 2004 ). Cellulose can be regenerated as highly swollen hydrogels by immersing the

salt-cellulose in water or polar solvents (Kuga, 1980: Hattori et al., 1998). This behavior has been

utilized as an industrial process for manufacturing chromatography packing materials (Kuga,

1980).

13

A study had been reported that polymer composites reinforced with tunicin whiskers,

which an animal cellulose, display spectacularly enhanced mechanical properties although at low

content of whiskers (Samir et al., 2004). This is because the formation of rigid network resulting

from strong interactions between adjacent whiskers by hydrogen bonding which the proposed is to

explain the mechanical behavior of cellulose whiskers reinforced composites (Favier et al., 1995).

The most commonly studied is poly( oxyethylene ) or POE based polymer electrolytes due

to their cationic solvatation ability (Samir et al., 2004). POE based electrolytes must be used

above their melting temperature because they give high degree of crystallinity which strongly

restricts the ionic conductivity at room temperature (Samir et al., 2004). In the mid – 1990s, the

potential for all – organic nanocomposites are based on polymers reinforced with cellulose

nanocrystals fibrils (Favier et al., 1995).

A study on cellulose nanocrystals reinforced poly (oxyethylene) had been reported by

Samir et al. ( 2004 ). The nanocomposites were characterized using Scanning Electron Microscope

( SEM ) and Differential Scanning Calorimetry ( DSC ).

14

Another study on processing of cellulose nanofiber- reinforced composites also had been

reported by Bhatnagar and Sain ( 2005 ). The raw materials that had been used were hemp fiber,

flax fiber, kraft pulp, rutabaga and polyvinyl alcohol (Bhatnagar and Sain, 2005). The composites

were characterized using Scanning Electron Microscopy ( SEM ), Fourier Transform Infrared

Spectroscopy ( FT-IR ), Transmission Electron Microscopy ( TEM ), Atomic Force Microscopy

( AFM ) and X-Ray Power Diffraction (Bhatnagar and Sain, 2005).

15

3.0 Materials and Methods

3.1 Sample Preparation

Sugarcane bagasse ( SCB ) and corn cob were obtained from Pasar Minggu, Kuching.

These samples were dried completely under sunlight and then cut into small pieces. The sugarcane

bagasse and corn cob samples were grinded using a Wiley Mill at the Timber Research and

Technical Training Centre ( TRTTC ). The powdered samples were then extracted in a Soxhlet

apparatus with 50 ml of toluene and 100 ml of ethanol ( 1: 2 v/v) for 6 h and allowed to dry in an

oven at 60 ºC ( Sun et al., 2004 ).

3.2 Isolation of cellulose

The isolation of cellulose was conducted using two different methods: the acetic acid-

nitric acid mixture reported by Crampton and Maynard ( 1938 ) and Brebdel et al. ( 2000 ) and the

delignification with acidified sodium chlorite reported by Sun et al. ( 2004 ).

3.2.1 Acetic acid – niric acid mixture method

Both the sugarcane bagasse and corn cob samples were used for the extraction of cellulose as

shown in the Figure 1. Three different extractions were made for both type of samples.

2.00 g or 5.00 g of dewaxed sample was weighed in 250 ml Erlenmeyer flask and 100 ml

80% acetic acid and 10 ml 70% nitric acid was added. The flask was then covered using

aluminium foil and heated at 120 ºC for 20 minutes or 40 minutes.

16

The sample mixture was cooled and 60 ml of distilled water was then added. Then, the

residue was filtered and washed with distilled water and 95% ethanol. Finally, the residue was

dried in an oven at 60 ºC for 19 h, 23h and 39h for sugarcane bagasse and 17h for cellulose sample

extracted from the corn cob.

For the corn cob sample, modifications were made in the composition of acetic acid-nitric

acid mixture by varying the percent concentration of nitric acid between 4, 50 and 70%.

17

Figure 1: Isolation of cellulose from dewaxed sugarcane bagasse and corn cob samples

using the acetic acid- nitric acid mixture method.

Dewaxed sample

Crude cellulose residue

Purified cellulose fibers

Add 100 ml 80% acetic acid and 10 ml 70% nitric acid

Heat in paraffin oil at 120 ºC

Cooled and 60 ml distilled water was added

Washed with distilled water and 95% ethanol

Dried at 60 ºC

18

3.2.2 Delignification with acidified sodium chlorite method

Figure 2 shows the isolation of cellulose from both sugarcane bagasse and corn cob samples

using the delignification with acidified sodium chlorite method.

5.00 g of dewaxed sample was weighed in the 250 ml beaker. The dewaxed sample was

heated with 100 ml of distilled water for 2h at 80 ºC in a water bath. The solution was then filtered

and the residue was delignified with 1.3% sodium chlorite at pH 4, adjusted with 10% acetic acid,

at 75 ºC for 2h in a water bath. After that, the solution was filtered again. The residue was

extracted with 10% NaOH for 17 h at 25 ºC. The residue obtained after filtration was washed with

distilled water and 95% ethanol and dried in an oven at 60 ºC for 17 h.