Download Preparation and Characterization of Cellulose Nanocrystals from

Faculty of Resource Science and Technology
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
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
1.0 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).
1
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).
2
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).
3
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.
4
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).
5
OH
OH
HO
O
HO
O
O
O
O
OH
HO
OH
O
OH
HO
OH
O
O
O
OH
OH
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).
6
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.
7
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).
8
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 rodlike particles with a high specific area (Angles and Dufresne, 2001).
9
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).
10
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.
11
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 resorcinolformaldehyde 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 solgel 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).
12
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 ).
13
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).
14
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 acidnitric 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.
15
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%.
16
Dewaxed sample
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
Crude cellulose residue
Washed with distilled water and
95% ethanol
Dried at 60 ºC
Purified cellulose fibers
Figure 1: Isolation of cellulose from dewaxed sugarcane bagasse and corn cob samples
using the acetic acid- nitric acid mixture method.
17
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.
18