Isolation and Regeneration of Cellulose Fiber from Sugarcane Bagasse

Madeline Yeo Geok Kim (23927)

A final project report submitted in the fulfillment of the requirements for the degree of

Bachelor of Science with Honours

(Resource Chemistry)

Supervisor: Dr. Chin Suk Fun

Resource Chemistry

Department of Chemistry

Faculty of Resource Science and Technology

University Malaysia Sarawak

2012

II

Declaration

I declare that this thesis entitled “Isolation and Regeneration of Cellulose Fiber from

Sugarcane Bagasse” is the result of my own research except as cited in the references. The

thesis has not been accepted for any degree and is not concurrently submitted in

candidature of any other degree.

Signature :……………………………….

Name :……………………………….

Date :……………………………….

I

Acknowledgment

First of all, I would like to thank the Department of Chemistry, Univerisiti Malaysia

Sarawak for giving me the opportunity to fulfill my Final Year Project. I really appreciate

all the materials, equipments, instruments and other facilities provided which are necessary

for the completion of my project.

I would like to express my deepest gratitude to my supervisor Dr. Chin Suk Fun for her

guidance, encouragement and concern throughout this project. She is the one who

constantly keep track on my progress and gave me a lot of precious ideas, information,

knowledge and advice on my project and report writing.

A special thank to master students of Physical Chemistry Laboratory, Kak Fiona for her

generosity in helping and give some assistance throughout the project. She easing my

burden and helping me to solve problem that arise in my project. I also like to thank my

friends, Ooi Sheue Lin and Tan Tong Ling for their assists, advice and support. This

support goes beyond academic guidance to make life enjoyable. Last but not least, I would

like to thank my family for their prayers, supports and advices when I am down and

discontentment. I appreciate the valuable experience, knowledge and laboratory skills that I

gained throughout this project.

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Table of Contents

Page

Acknowledgment………………………………………………………………………….

Declaration…………………………………………………………………………...

Table of contents………………………………………………………………………….….

List of Abbreviations…………………………………………………………............ VI

List of Tables……………………………………………………....……………….. VII

List of Figures………………………………………..………………...………….... VIII

Abstract…………………………………………………………….………….…..... 1

1.0 Introduction……………………………………………………………………... 2

1.1 Problem statement………………………………………………….... 4

1.2 Objective……………………………………………………………... 4

2.0 Literature Review………………………………………………………………. 5

2.1 Sugarcane Bagasse…………………………………………………… 5

2.2 Cellulose……………………………………………………………... 5

2.2.1 Cell wall Composition of cellulose ……………………………. 7

2.3 Solvent System Of Isolation and Regeneration Of

8

Cellulose Fiber from Sugarcane Bagasse…………………………….

2.4 Physical Treatment of Cellulose Fibers…………………………….... 13

2.5 Biological Treatment of Cellulose Fibers……………………………. 14

2.6 Cellulose Regeneration………………………………………………. 15

I

III

II

IV

3.0 Material and Method……………………………..……………………………... 16

3.1 Material………………………………………………………………. 16

3.2 Method…………………………………………………………….…. 16

3.2.1 Pretreatment of Cellulose Material……………………………... 16

3.2.2 Dissolution of Cellulose………………………………………... 18

3.2.3 Regeneration of Cellulose………………………………………. 18

4.0 Results ……………….……………………………………………...………….. 19

4.1 Pretreatment and Isolation of Cellulose Fiber from Sugarcane

Bagasse………………………………………………………………. 19

4.2 Dissolution and Regeneration of Cellulose Fiber…………………….. 24

4.3 Percentage Yield of Regenerated Cellulose………………………...... 26

4.4 CHN analyzer………………………………………………………… 28

4.5 FTIR Spectroscopic Analysis……………………………………..….. 29

4.6 Scanning Electron Microscope (SEM) analysis……………………… 31

4.6.1 Morphology of Raw Sugarcane Bagasse……………………….. 31

4.6.2 Morphology of Isolated Cellulose………...……………………. 32

4.6.3 Morphology of Cross Section for Raw Sugarcane Bagasse

and Isolated Cellulose…………………………………...……… 34

4.6.4 Morphology of Cellulose Ultrasonicated Treated at Various

Duration………………………………………………………..... 36

4.6.5 Surface Morphology of Ultrasonic Treatmented Cellulose

Fibers ………………………………………………... …………

4.6.6 Surface Morphology of Homogenization Cellulose Fibers…….. 41

38

V

4.6.7 Morphology of Ultrasonication and Homogenization of

Cellulose ……………………….……………………………….. 44

4.6.8 Morphology of Regenerated Cellulose………………….……… 47

5.0 Discussion………………………………………………………………...…….. 48

5.1 Effects of Pretreatment of Sugarcane Bagasse with Aqueous Based

Solvent System…………………………………………………………….. 48

5.2 Effects of NaOH, Thiourea & Urea in Dissolution of Cellulose…………... 49

5.3 Gelation Behavior of Cellulose Solution…………………………………... 50

5.4 FTIR Analysis…………………………………………………………….... 50

5.5 Effects of Ultrasonication and Homogenization of Cellulose Fiber……….. 51

5.6 Comparison of cross sectional surface morphology of raw sugarcane

bagasse and isolated cellulose……………………………………………… 52

5.7 Coagulation Mechanism of Regenerated Cellulose………………………... 52

6.0 Conclusions and Recommendations………………..………….……..………… 54

7.0 References……………………...……………………………………………….. 55

Appendices……………………………………………….……………………........ 61

VI

List of Abbreviations

Calcium Thiocyanate

Ca(SCN)2

Celsius

⁰C

Fourier Transform Infrared Spectrophotometer

FTIR

Hydrochloric acid

HCI

Kilo Hertz

KHz/103Hz

Lithium Chloride

LiCl

Mass concentration : Mass/Volume

w/v

N-methylmorpholine-N-oxide

NMMO

N,N-dimethylacetamide

DMAC

Phosphoric acid

H3PO4

Revolutions per Minutes

Rmp

Scanning Electron Microscopy

SEM

Sodium Chlorite

NACIO2

Sodium Hydroxide

NaOH

Sulphuric acid

H2SO4

Zinc Chloride

ZnCl

1-butyl-3-methylimidazolium chloride

BMIMCl

1-ethyl-3-methylimidazolium acetate

EMIMoAc

1-ethyl-3-methylimiidazolum diethyl

phosphate

EMIMDEP

VII

List of Tables

Table Page

Table 1 Surface morphology studies on the different treatment of isolated

cellulose

17

Table 2 Experimental yield of regenerated cellulose by different volume of

ethanol

26

Table 3 CHN analyzer of cellulosic materials 28

List of Figures

Figures Page

Figure 1 Structure of Cellulose 6

Figure 2 Composition of cell wall and microfibrils consist of crystalline

and amorphous regions

7

Figure 3 The grounded sugarcane bagasse 19

Figure 4 Sugarcane bagasse treated with NaOH for 4h 20

Figure 5 Sugarcane bagasse after the treatment of sodium chlorite and

acetic acid mixture

21

Figure 6 Filtration of isolated cellulose 22

Figure 7 Drying of the cellulose fiber 23

Figure 8 Dissolution of isolated cellulose in NaOH: Thiourea: Urea

solution

24

Figure 9 The cellulose solution after cooled for 24h at -20°C 25

Figure 10 FTIR analysis of the raw sugarcane bagasse, isolated cellulose 29

VIII

and commercially available pure cellulose

Figure 11 SEM image of the surface of raw sugarcane bagasse 31

Figure 12 SEM image of the surface of isolated sugarcane bagasse 32

Figure 13 SEM images of cross section of sugarcane bagasse and

isolated cellulose

34

Figure 14 SEM images of the diameter of cellulose treated with

ultrasonic

36

Figure 15 SEM images of the diameter of cellulose treated with

homogenizer

Figure 16a SEM images of the surface morphology cellulose treated with

30s ultrasonic

38

Figure 16b SEM images of the surface morphology of cellulose treated

with 60s ultrasonic

38

Figure 16c SEM images of the surface morphology of cellulose treated

with 90s ultrasonic

39

Figure 16d SEM images of the surface morphology of cellulose treated

with 120s ultrasonic

39

Figure 17a SEM images of the surface morphology of cellulose treated

with 30s homogenizer

41

Figure 17b SEM images of the surface morphology of cellulose treated

with 60s homogenizer

41

Figure 17c SEM images of the surface morphology of cellulose treated

with 90s homogenizer

42

Figure 17d SEM images of the surface morphology of cellulose treated

with 120s homogenizer

42

IX

Figure 18a SEM images of the cellulose treated with 30s homogenization

and 30s ultrasonic

44

Figure 18b SEM images of the cellulose treated with 60s homogenization

and 60s ultrasonic

44

Figure 18c SEM images of the cellulose treated with 90s homogenization

and 90s ultrasonic

45

Figure 18d SEM images of the cellulose treated with 120s

homogenization and 120s ultrasonic

45

Figure 19 SEM image of the regenerated cellulose 47

1

Isolation and Regeneration of Cellulose Fiber from Sugarcane Bagasse

Madeline Yeo Geok Kim

Resource Chemistry Programme

Faculty of Resource Science and Technology

Universiti Malaysia Sarawak

ABSTRACT

Sugarcane bagasse is the by-product obtained after sucrose extraction from sugarcane plant. However, the

remaining bagasse is disposed and resulted in environmental pollution. Sugarcane bagasse has high

proportion of cellulose, lignin and hemicelluloses. Sodium hydroxide used to remove lignin and

hemicelluloses. Acetic acid and sodium chlorite was use to bleach the cellulose. FTIR results indicated that

lignin and hemicelluloses has removed. Mechanical treatment by ultrasonic and homogenizer on isolated

cellulose showed surface destruction on the cellulose through scanning electron microscopy (SEM) images.

Furthermore, NaOH: Thiourea: Urea with the composition (8:6.5:8) was used as aqueous based solvent

system in cellulose dissolution process. Ethanol acts as a non-solvent successfully precipitate the regenerated

cellulose. The yield of regenerated cellulose increases as volume of the added ethanol increase.

Keywords: Sugarcane bagasse, Cellulose fiber, Ultrasonic, Homogenizer, Yield.

ABSTRAK

Hampas tebu adalah produk selepas pengekstrakan sukrosa daripada tanaman tebu. Tetapi, hampas-hampas

tebu ini akan dibuang selepas pengekstrakan sukrosanya dan ia akan mencermakan alam sekitar. Hempas

tebu ini mempunyai banyak selulosa, lignin dan hemiselulosa. Natrium hidroksida digunakan untuk

menghilangkan lignin dan hemisellulosa. Asid asetik dan natrium klorida digunakan untuk melunturkan

selulosa. Keputusan FTIR menunjukkan bahawa lignin dan hemisellulosa telah disingkirkan. Rawatan

mekanikal dengan menggunakan ultrasonik dan penghomogenan pada selulosa telah menunjukkan

kemusnahan pada permukaan selulosa melalui imej SEM. Tambahan pula, NaOH: Thiourea: Urea dengan

komposisi (8:6.5:8) telah digunakan sebagai sistem akueus berasaskan pelarut dalam proses pelarutan

selulosa. Etanol bertindak sebagai bukan pelarut berjaya memendakan selulosa yang dijana semula. Hasil

daripada selulosa yang dijana semula meningkat dengan peningkatan isipadu etanol.

Kata kunci: Hampas tebu, Selulosa, Ultrasonik, Penghomogenan, Hasil.

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1.0 Introduction

Sugarcane is a green material that widely used in sugar production industry while

sugarcane bagasse is the residue of cane stalks left over after crushing and extraction of the

sugarcane juice. These wastes cause environmental pollution. Therefore, the best way to

overcome this problem is to reuse and recycle the sugarcane bagasse in terms of waste to

wealth concept (Draman et al., 2009).

Sugarcane (Saccarhum officinarum) bagasse is a residue produced in large amount by

sugar industries. Normally, 1 ton of sugarcane will generate 280 kg of bagasse, the fibrous

by-product remaining after sugar extraction from sugarcane (Sun et al., 2004). Thailand

produced nearly 70 million tons of sugarcane in 2007 and became the world third sugar

producer followed by Brazil and Australia, respectively. Nearly 600-800 million tons (dry)

of annual crop residues are available annually in China, in which sugarcane bagasse (SCB)

accounts for 70-80 million tons. In Central Asia, Middle East, and North Africa that do not

have enough supplies of wood but have an abundant supply of agricultural residues

including rice straw, sugarcane bagasses, reeds, and grass. These lignocelluloses materials

provide a low-cost feedstock for biological production of fuels and chemicals, which offer

economic, environmental, and strategic advantages (Adsul et al., 2004).

Sugarcane bagasse on a dry weight basis consists of celluloses of 43.6%, hemicelluloses of

33.8%, lignin of 18.1%, ash of 2.3% and wax of 0.8% (Sun et al., 2004). Chemically,

cellulose is a linear natural polymer of anhydroglucose units linked at the one and four

carbon atoms by β-glycosidic bonds. This is confirmed by the presence of three carboxyl

3

groups with different acidity/reactivity, secondary OH at C-2, secondary OH at C-3, and

primary OH at C-6 position, and can form various strong intermolecular and intramolecular

hydrogen bonds (Kadla & Gilbert, 2000). Cellulose cannot easily separate into readily

utilizable components due to their high crystallinity nature (Chuan et al., 2006).

Cellulose in sugarcane bagasse is isolated by celluloses dissolution of an aqueous based

solvent system. However, there are only a limited number of common solvents in which

cellulose is soluble (Heinze & Liebert, 1689); solvents include, carbon disulfide, N,N-

dimethylacetamide/lithium chloride (DMAC/LiCl), concentrated inorganic salt (ZnCl/H2O,

Ca(SCN)2/H2O) and mineral acids (H2SO4/H3PO4), or molten salt hydrates (LiClO4.3H2O,

NaSCN/KSCN/LiSCN/H2O). The efficiency of existing methods for dissolving and

derivitizing cellulose can be improved by the present of suitable solvents such as N-

methylmorpholine-N-oxide (NMMO), used as a solvent for non-derivitizing dissolution of

cellulose for the production of lyocell fibers (Swatloski et al., 2002). However, the cost,

toxicity, stability and difficulty for solvent recovery need to be taken into consideration.

Therefore, an aqueous based solvent system is preferable for cellulose dissolution.

In this study, cellulose was dissolved in the NaOH/thiourea/urea aqueous solution and

regenerated by using ethanol. The morphology and chemical structural of the cellulose

were characterized and the yields of the regenerated cellulose were calculated.

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1.1 Problem Statement

A few factors of the solvent system used to extract cellulose from sugarcane bagasse

needed to consider factor such as cost, toxicity, environmental friendly and solvent

recovery. After much consideration, the cellulose is isolated in the acidified sodium

chlorite and acetic acid. On the contrary, the condition of cellulose to dissolve in aqueous

based solvent system was carried out. Apart from this, the length of time for physical

treatment of cellulose is important in order to have better effects of destruction on the cell

wall of cellulose. Intensive washing of the regenerated cellulose was done to remove

impurities on the surface of regenerated cellulose.

1.2 Objectives

(1) To isolate cellulose from sugarcane bagasse by alkaline hydrolysis treatment.

(2) To determine the optimal condition for the dissolution of cellulose dissolved in the

aqueous solvent system.

(3) To determine the surface morphology and yield of regenerated cellulose.

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2.0 Literature Review

2.1 Sugarcane Bagasse

The use of renewable resources, such as sugarcane bagasse, as starting materials for the

production of various chemicals, has increased in recent years. Sugarcane bagasse is a

residue produced in huge amounts by the sugar and alcohol industries, which has found in

wide applications as fuel for boilers to recover energy (Sene et al., 2002). Alternative

promising application include its use as low-cost animal feedstock, as raw material for

biological production of fuels, chemicals, and food additives, such as vanillin (Mathew &

Abraham, 2005) and xylitol (Carvalho et al., 2003,2005 ; Santos et al., 2003,2005a), and

even as cell support in different bioprocesses (Pandey et al., 2000 ; Sene et al, 2002).

Sugarcane bagasse consist of approximately 51.1% fibers and 47.5% medulla. The dried

fibre containes 51.1% cellulose, 28.5% hemicelluloses, 20.2% lignin and 3% other

components (Bertoti et al., 2009).

2.2 Cellulose

Cellulose is the most abundant renewable resource in the world. The cellulose-contaning

materials and their derivatives have been widely use. Apart from the use of unmodified

cellulose-containing materials, such as rice straw and cotton, the cellulose can be extracted

from its primitive resources (for example, lignocellulosic materials) and then processed

into its derivatives via chemical, enzymatic or microbiological method (Kirk-Othmer,

1993). Many literatures describe the preparation of cellulose derivatives and their

applications. However, the full potential of cellulose not yet been exploited for four main

6

reasons: the historical shift to petroleum-based polymers from the 1940s onward, the lack

of an environmental-friendly method to extract cellulose from its primitive resources, the

difficulty in modifying cellulose properties, and the limited number of solvents that readily

dissolve cellulose.

Figure 1: Structure of Cellulose (Cellulose, n.d)

Cellulose is composed of β-(1 4) - linked β-glucopyranosyl units with three hydroxyl

groups, which can form strong inter- and intra- molecular hydrogen bonds (Figure 1).

Therefore, cellulose does not easily dissolve in common solvents and does not melt before

thermal degradation (Klemm et al., 2005).

7

2.2.1 Cell Wall Composition of Cellulose

The cell wall of the cellulose consists of repeated crystalline structures result from the

aggregation of microfilbrils. These microfilbrils are surrounded by hemicelluloses and

lignin. Hemicelluloses and lignin is the amorphous region of matrix in the cellulose.

Several layers can be divided in the cell wall (Figure 2) : Warty wall (W), secondary cell

wall (S) (secondary cell wall is further divided into S1, S2, S3 layer), primary cell wall (P)

and lastly is the middle lamella (ML) (Frone et al., 2011).

Figure 2: Composition of cell wall and microfibrils consist of crystalline and amorphous regions

(Frone, Panaitescu, & Donescu, 2011).

8

2.3 Solvent System of Isolation and Regeneration of Cellulose Fiber from Sugarcane

Bagasse

Generally, the pretreatment processes such as applying high temperature, pressure, acids or

bases, and organic solvents to disrupt the lignin seal and cellulose crystalline structure of

lignocellulosic material. Most of the pretreatment methods have their disadvantage in

large-scale application. For example, the dilute acid process generates toxic byproducts,

such as furfural and aldehydes, which not only significantly reduced the sugar yield, poison

enzymatic hydrolysis and biofuels fermentation. In addition, steam explosion operated at

high temperature and pressure to achieve fibrillation, requires costly capital investment for

equipments. Organosolvent method, using organic solvents at high temperature to dissolve

the lignin, requires solvent recovery and high cost of capital investment (Chia & Cheng,

2009).

According to Knauf and Moniruzzam (2004), there are several processes that can be used

to release and or/purify lignin components from biomass. However, each process uses

several chemical agents to extract materials from lignocellulosic biomass and produces

other materials with different composition and properties. There are two main chemical

processes of biomass hydrolysis, which use acids and bases, whose choice mainly depends

on the material structure and characteristics desired for the products to be recovered.

Among the many aqueous and non-aqueous cellulose solvent system reported in the past

three decades, N-methyl-morpholine-N-oxide, NMMO/H2O system is the most powerful in

obtaining high concentration solution and has been commercialized to produce Tencel or

Lyocell fibers (Jin et al., 2007). In the commercially Lyocell process, N-methyl-

9

morpholine-N-oxide (NMMO) is used as direct solvent for cellulose as a modern industrial

fiber-making technology (Fink et al., 2001). The direct dissoultion of cellulose without

chemical derivatization and the almost complete recovery of the NMMO are the main

feature of Lyocell process. NMMO is able to dissolve cellulose due to high polarity of its

N-O bond, which breaks the hydrogen bond network of the cellulose and forms hydrogen

bonds with the solute (Rosenau et al., 2002). However, this innovative technology also

produces considerable amounts of byproducts and the expensive solvent requires effective

recovery. Thus it is not suitable for replacing viscous technology completely (Fink et al.,

2001).

According to Swatloski et al (2002) as early as 1934, Graenacher discovered that molten

N-ethylpyridinium chloride, in the presence of nitrogen-containing bases, can be used to

dissolve cellulose. This is the first example of cellulose dissolution using ionic liquids.

Ionic liquids are salts with low melting point and is founded in liquid state at room

temperature (Zhu et al., 2006). They are generally thermally stable, non-volatile and non-

flammable (Hermanutz et al., 2008). Due to these properties, researchers have classified

them as green solvents attributed to their environmental amiable nature compare to the

conventional organic solvents. The regenerated cellulose from ionic liquids has founded to

be more amorphous and porous which prevent it from enzymatic attack (Li et al., 2009).

Meanwhile, ionic liquids could act as delignification agent in which its reduce the cellulose

crystallinity (Zhao et al., 2010). Besides that, ionic liquids have found to be recyclable and

they could be reused for several times without affecting their performances in dissolution

of cellulose (Li et al., 2008). The solubility of ionic liquids namely 1-butyl-3-

methylimidazolium chloride (BMIM Cl), 1-ethyl-3-methylimidazolium acetate (EMIM

oAc) and 1-ethyl-3-methylimidazolium diethyl phosphate (EMIM DEP) in the

10

pretreatment of sugarcane bagasse was demonstrated by Yoon et al., (2010). Initial toxicity

studies appear to suggest that small exposures to 1-butyl-3-methylimidazolium chloride

posses limited health problem (Swatloski et al., 2004). Cuprammonium technology is

another traditional technique used to prepare cellulose products in which its will generates

heavy metals residues that are difficult to dispose (Fushimi et al., 1996). The high cost of

copper and the difficulties in its economical recirculation are serious limitations to its use.

Acidified sodium chlorite frequently used to delignify wood as Green et al. (1963)

demonstrated an initial step in the isolation of cellulose. However, chlorinating agents (e.g.

NaClO2) associated with environmental concerns have led to the increased use of more

environmentally benign agents for delignification such as hydrogen peroxide or an acetic

acid-nitric acid mixture in both elemental chlorine-free (ECF) and totally chlorine-free

(TCF) in isolation sequences (Crampton et al., 1938 ; Brendel et al., 2000). Bleaching of

mechanical pulps by using hydrogen peroxide is widely used under alkaline conditions

(Allison & Graham, 1989). Currently, there is also a growing interest in the use of

hydrogen peroxide as one of the oxidants replacing chlorine-based reagents with the

development of totally chlorine-free bleaching technologies (Choudents et al., 1996). It

generally accepted that perhydroxyl anion HOO ̄ is the most important active species

involved in the suspension of chromophores in lignin macromolecules (Rutkowski, 1994).

On the other hand, radicals such as OH• and O2 •− produced at high pH levels can

participate in lignin degradation and hemicelluloses dissolution (Sun et al., 2002; Wojciak

et al., 2002 ; Sun et al., 2004). Sequential treatment of dewaxed sugarcane bagasse with

water, NaOH and H2O2 with or without ultrasonic irradiation, resulted in dissolution or

degradation of 95.5 and 94.7% of the original hemicelluloses, and 91.7 and 90.2% of the

original lignin, yielding 44.7 and 45.9% cellulose respectively. In comparison, treatment

11

with sonication time for 40 min solubilized 0.8 and 1.5% higher of the original

hemicelluloses and lignin, respectively. This slightly higher efficiency of the ultrasound-

assisted extraction can be explained by increased accessibility and extractability of the

hemicellulosic and lignin component on the cell wall by the mechanical action of the

ultrasound (Hromadkova et al., 1999; Sun & Tomkinson, 2002). Unfortunately, hydrogen

peroxide can reacts with variety of substances. Therefore, hydrogen peroxide usually

diluted during transportation. Exposure to hydrogen peroxide takes place through

inhalation of damp or mist, through food uptake and through skin and eye contact.

Hydrogen peroxide can irritate the eyes, skin and mucous membranes. Permanent eye

damage will occur if exposures of the eyes to concentration of 5% or more of hydrogen

peroxide (Peroxide, n.d.). Therefore, dissolution of cellulose by hydrogen peroxide is not

practical.

Acidified sodium chlorite was used to delignify wood as an initaial step in the isolation of

pure cellulose, and chlorine is widely used as a bleaching agent in the pulp or cellulose

industry (Kempf & Dence, 1970). However, in aqueous media their reaction with

lignocellulosic materials will results in aromatic substitution, in some cases accompanied

by displacement of side chains, and quinonoid structures will form in oxidation reaction

(Simson et al., 1978). Its reaction with lignin is fast compared with its reaction with

cellulose. However, damages to the fibres during usual conditions of chlorine bleaching

will occur due to its rate of reaction (Singh, 1990).

In recent years, the environmental risks associated with the traditional delignification and

bleaching using elemental chlorine promotes the development of new systems free from

element chlorine or totally chlorine-free. Treatment of sugarcane bagasse with 80% acetic

12

acid and 70% nitric acid (10/1,v/v) mixture at 110 and 120 °C for 20 min removed most of

the lignin, non-cellulose polysaccharides and other components, yielding 43.6 and 43.0%

pure cellulose, which equal or rather close to the value of α–cellulose in sugarcane bagasse

(43.6%). The increase in the yield reported here might be because of the use of one-step

protocol to minimize cellulose loss, since the method for two-step protocal to isolate

involves a sodium chlorite delignification as the first stage followed by extraction with

alkali to remove hemicellulose (Sun et al., 2004).

The solubiltiy of microcrystalline cellulose and steam-exploded cellulose in aquoes NaOH

systems had been demostrated by Isogai and Atalla (1998) in which native cellulose pulps

have very limited solubility. Zhang’s group (Zhang et al., 2001 ; Zhang et al., 2004; Zhou

et al., 2004; Cai & Zhang, 2006) and Weng et al. (2008) successfully developed aqueous

NaOH solution systems with either urea or thiourea for cotton liner dissolution. The

optimal solubility was found with either 7/12/81 NaOH/urea/H2O or 9.5/4.5/86

NaOH/thiourea/H2O in compositions. Both solvent systems were inexpensive and less

toxic, but the precise structure of the solvent complex involved still not clearly understood.

Recently, Zhang et al. (2010) developed a new complex aqueous solvent consisted of

NaOH, urea and thiourea and was able to dissolve cellulose quickly when pre-cooled to

temperature between -8 and -12°C (Jin et al., 2007). The results show that the rapid

dissolution behavior and solubility of cellulose in aqueous NaOH/urea/thiourea solution at

a 8/8/6.5 mass ratio composition and pre-cooled to -10°C was aided by vigorous stirring

for 3 min and further dissolution at -2 to -0°C for 7-10 min (Zhang et al., 2010).

13

2.4 Physical Treatment of Cellulose Fibers

Physical treatment toward the cellulose was employed in this project. There are several

physical treatment used as a mechanical destruction toward the cell wall of cellulose fiber.

The most commonly used method is ultrasonication. Mason and Lorimer (2002) define that

ultrasonic is a sound that having a higher frequency that human hearing range such as >20

kHz. Ultrasound is able to degrade polymeric sequences and particularly in synthetic

materials that dissolved in various solvent (Wang & Cheng 2009). Acid hydrolysis is

combined with ultrasonic treatment had been demonstrated by Filson and Andoh (2009) in

order to obtain nano-cellulose fibers with an average diameter between 21-23nm. A few

parameters needed to achieve a high dispersion such as temperature and concentration of

the disperser, intensity at the tip of probe, pressure, volume and shape of vessel used.

Ultrasonic is widely used due to these properties and it is used in various applications such

as preservation of food, various washing processes, medicine, chemistry (degassing and

dispersion) (Wang & Cheng, 2009). Regenerated cellulose, pure cellulose, microcrystalline

cellulose and native cellulose had undergone this treatment in which resulting in a mixture

of micro and nano-cellulose fibers (Wang & Cheng, 2009).

Homogenization is another way of mechanical treatment that brings about irreversible

changes in the fibers (Herrick et al., 1982). It increases the bonding potential by modifying

of their morphology and size (Herrick et al., 1982). In the homogenization process, the

fibers were subjected to large pressure drop with shearing and impact forces (Herrick et al.,

1982). The combination of forces allowed the fiber to form a high degree of

microfibrillation of cellulose fibers and results in microfibrilated cellulose (MFC) (Herrick

14

et al., 1982). Microfibrillated cellulose is a type of lose morphology developed by Turbak

et al. (1983) in the early 1980s.

According to Frone et al. (2011), by using microwave can obtain disintegration of cellulose

fibers up to nano-scale. However, there is a disadvantage of using this method due to the

obtained material is highly degraded and the nano-fibers strength characteristics are low

(Frone, et al., 2011).

Gamma ray irradiation of cellulose fibers allowed the separation of gas mixture (25-30% H;

13-18% CO, 45-58% CO2 and 2-3% CH4) due to the depolymerisation, dehydrogenation

and glucoside chains destruction effects (Frone et al., 2011). By analyzing the molar mass

and polydispersity of the irradiated cellulose fibers with gel permeation chromatography

technique, it was concluded that the cellulose destruction by high-energy radiation affects

the molecular structure of the secondary structure and supramolecular structure of the

cellulose fibers (Frone et al., 2011).

2.5 Biological Treatment of Cellulose Fibers

Cellulose materials undergo degradation process under enzymatic action. Since cellulose

has great stability and high crystallinity, the destruction of cellulose is due to the primary

structure of chemical component. Lignin limits the availability of the cellulose material and

its act as a physical barrier in cellulose. The presence of microorganism such as bacteria