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Available online at www.sciencedirect.com
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Original Article
Chemical pulping of waste pineapple leaves fiber
for kraft paper production
a,∗ b
Waham Ashaier Laftah , Wan Aizan Wan Abdul Rahaman
a
Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia
b
Center for Composites, Universiti Teknologi Malaysia, Johor, Malaysia
a r t i c l e i n f o a b s t r a c t
Article history: The main objective of this study is to evaluate the implementation of acetone as a pulping
Received 29 August 2014 agent for pineapple leaves. Mixtures of water and acetone with concentration of 1%, 3%,
Accepted 15 December 2014 5%, 7%, and 10% were used. The effects of soaking and delignification time on the paper
Available online xxx properties were investigated. Thermal and physical properties of paper sheet were studied
using thermogravimetric analysis (TGA) and tearing resistance test respectively. The mor-
×
Keywords: phological properties were observed using microscope at 200 magnification. The paper
sheet produced from pulping with 3% acetone concentration shows the highest mechan-
Natural fiber
Renewable resources ical properties. Papers strength was improved by increasing the delignification time. The
◦
Pineapple leaves delignification time was reduced by cooking the pineapple leaves at a temperature of 118 C
Pineapple fiber under applied pressure of 80 kPa which has remarkable effect on paper strength.
Chemical pulping © 2014 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier
Kraft paper Editora Ltda. All rights reserved.
non-wood raw materials in papermaking industry has been
1. Introduction
given more attention due to the rising consumption of wood
resource for the paper production. From 1970 to present time,
Pulp and paper industries have been considered the main con- the non-wood plant fiber pulping capacity has increased on
sumers of natural resources (wood) and energy (electricity), a global basis two to three times as fast as the wood pulping
including water, and significant contributors of pollutant dis- capacity. It was also forecasted that during the next decade,
charges to the environment. The demand for paper and the the non-wood pulp production will annually grow at an aver-
unacceptable large ecological footprint of current paper pro- age of 6%, which is three times as fast as the production of pulp
duction requires the need for alternatives. It was reported in on wood basis [2]. Initially, non-wood fiber pulping occurred
2004 that the annual paper consumption is 52.45 kg per per- in regions where wood supply had been reduced to levels
son and was 16.32% greater than in 1991. The use of printing insufficient to sustain papermaking, and an alternative source
and writing paper grew by more than 10% from 1980 to 2000 of fiber feedstock was mandatory. Non-wood fiber resources
[1]. In many parts of the world, local supplies of wood can- have the potential to complement conventional wood sup-
not support the demand for pulp. As a result, the search for plies. This is because, they are abundant, have short cycles
∗
Corresponding author.
E-mail: [email protected] (W.A. Laftah).
http://dx.doi.org/10.1016/j.jmrt.2014.12.006
2238-7854/© 2014 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda. All rights reserved.
Please cite this article in press as: Laftah WA, Abdul Rahaman WAW. Chemical pulping of waste pineapple leaves fiber for kraft paper production.
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and rapid regeneration, and are of comparatively low price. Industrial grade acetone with 65% purity was purchased from
Therefore, non-wood fiber will play important roles in paper- Krass Instrument and Services.
making as substitutes or complements to wood. Examples of
non-wood fiber resources available for paper production are 2.2. Sample preparation
wheat-straw [3–5], rice-straw [6,7], sugarcane straw [8], reeds
[9], bamboo [10], bagasse [11,12], kenaf [13], palm oil [14], and Dried pineapple leaves were immersed in mixtures of ace-
jute [15]. Non-wood material, particularly wheat straw, was tone/water of 1%, 3%, 5%, 7%, and 10% (v/v) for 3 days to
successfully exploited as the main raw material for papermak- study the effect of acetone concentration on paper quality
ing in China because of the limited wood resource with forest and to optimize the best mixture content for farther prepara-
coverage of only 13.94% [16]. By a wide margin, the leading tion. The effect of soaking time was studied at interval times
non-wood plant fiber presently in use is straw, followed by of 3, 7, 21 and 28 days. Mixture of 3% acetone was used to
bagasse and bamboo. However, pineapple leaf fiber (PALF) is investigate the effect of cooking time on paper properties at
◦
another alternative non-wood fiber that can be used for paper 118 C under applied pressure of 80 kPa. The pineapple leaf
production. There have been numerous studies carried out by pulp was washed with water and disintegrated in a laboratory
researchers on various aspects of PALF. PALF obtained from blender. The pulp was molded using mold and deckle. The
◦
plants bearing edible fruits were examined for textile pur- paper was dried in the oven at 60 C until the pulp was fully
poses, and blends of PALF with silk and polyester fibers were dried. Finally, the paper was pressed using the compression
◦
studied [17]. PALF have also been incorporated into thermo- molding machine at 100 C and pressure of 10 MPa to get even
plastic materials such as polypropylene and polyethylene to thickness of paper sheet.
produce biocomposite materials. The use of non-wood raw
materials provides several interesting advantages; specifically, 2.3. Testing
it allows wood raw materials to be saved for other more decent
uses and hence deforestation and replanting to be alleviated. It The turbidity of spent liquor from puling process was
can also reduce wood and cellulose fiber imports in countries determined using HACH Ratio/XR Turbidimeter. Thermogravi-
with a shortage of wood raw materials. Besides, users are metric analysis (TGA) was performed by using Mettler Toledo
◦
increasingly demanding papers that are obtained by using TGA/STDA851 at heating rate 10 C/min with the temperature
◦ ◦
clean technologies or made from recycled or non-wood fiber. range between 30 C and 800 C. TGA was used to determine
The current challenges of the pulp and paper industry are the the thermal stability of cellulose and lignin in pineapple leaves
achievement of affordable quality pulp while preserving the and the paper sheet. The tearing resistance test or Elmendorf
environment by using increasingly smaller amounts of water tear test was used to measure the internal tearing resistance of
and energy and gradually fewer raw materials [4]. It is also the paper rather than the edge-tear strength of paper. The test
important to minimize pollution from residual effluents that was carried out according to ASTM D1922 using the HT-8181
results from cooking and bleaching of the raw materials. The Elmendorf Tearing Strength Tester. The tearing resistance
increasing concern with the environment and its preserva- (expressed in grams-force, gf) of the paper was determined
tion have exposed the need to replace the classical pulping from the average tearing force and the number of sheets com-
process such as kraft and sulfite pulping which use sulfur con- prising the test piece using following equation:
taining reagents. This is due to the fact that the release of
sulfur to the environment can cause serious pollution problem
Tearing resistance, gf
[6]. The new pulping processes using less polluting chemicals
16 ∗ 9.81 ∗ average scale reading ∗ gf capacity
known as the “organosolv” processes have been developed by =
n
∗ 1600 gf
the researchers to resolve the problem. During the last years,
this large progress of process technology has been reported to
where gf capacity = 3200 g and number of plies, n = 1.
reduce the sulfur emissions by the pulp mills. Even though the
Inverted Microscope LEICA DMIRM equipped with a digital
ability to obtain pulp by using the organic solvents has been
camera was used to study the morphology of the paper at 200×
known for some time, pilot plants and small-scale industrial
magnification. Morphological study was used to observe the
plants exploiting them have only recently come into opera-
fibers structure and their coarseness in the paper.
tion. This has been the result of the shortage of alternatives
to traditional procedures, which leads to the expenditure of
substantial efforts in new processes. In fact, some processes 3. Results and discussion
that use organic solvents are being reconsidered in response
to the new economic and environmental order. 3.1. Turbidity
Pulp quality is identified by the good strength, bleach abil-
ity, high cellulose and hemicellulose content and low lignin
2. Methodology content. Therefore, it is desirable to have a pulp process that
gave the highest delignification efficiency and good quality of
2.1. Raw material cellulose and hemicellulose [18]. The effect of acetone con-
centration on the pineapple leaves pulping was first observed
Pineapple leaves were obtained from the plantation of by the turbidity of the spent liquor after the pulping pro-
Malaysian Pineapple Industry Board (MPIB), Johor, Malaysia. cess. In organic solvent pulping process, the removal of lignin
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400 solution decreases with the increase of the acetone concentra-
Acetone (1,3,5,7,9) %
Soaking time (3,7,21,28,35) days tion in the solution. Higher amount of acetone concentration
350
Cooking time (90,180,270,360,450) mins that is above 3% is not effective for delignification due to highly
◦
300 evaporated and low boiling point of acetone, which is 56.2 C.
Fig. 1 illustrates the effect of soaking time on the turbid-
250
ity of spent liquor. It can be seen that when the pineapple
200 leaves were soaked for a longer period of time, the turbid-
ity increases dramatically, which indicates that a significant
150 amount of lignin dissolves in the solvent. The effect of cooking ◦
Turbidity (NTU) Turbidity
time at high temperature of 118 C under applied pressure on
100
turbidity of spent liquor also shows the same trend as illus-
50 trated in Fig. 1. From the results, delignification without any
applied pressure and temperature requires much longer time.
0
Fig. 1 indicates that the turbidity for cooking liquor at higher
temperature is higher than the soaking liquor. This is because
Fig. 1 – The turbidity of spent liquor for various acetone of the precipitation of lignin on the surface of the fibers due
concentrations at specified soaking time. The turbidity of to the presence of most of spent liquor between the fibers and
soaking liquor for 3% acetone concentration at various the fiber walls [19].
soaking times. The turbidity of cooking liquor for 3%
acetone concentration at various cooking times, at
◦
3.2. Thermogravimetric analysis (TGA)
temperature of 118 C.
Fig. 2 shows the thermogravimetric (TG) curve for pineap-
ple leaves paper produced from pulping with various acetone
depends not only on the cleavage of ether bonds in lignin concentrations. Thermal decomposition of the samples takes
◦
macromolecules, but also on the ability of the aqueous solvent place in a programmed temperature range of 30–800 C. Dehy-
solution to dissolve lignin fragments [19]. The result in Fig. 1 dration as well as degradation of lignin for pineapple leaves
◦
indicated that when the acetone concentration is increased occurs in the temperature range 90–230 C. The cellulose
from 1% to 3% (v/v), the turbidity also increases dramatically, component starts to decompose at the temperature above
◦
which means a large amount of lignin was precipitated at 3% 230 C and most of it already decomposed at a temperature of
◦
acetone concentration. Below 3% acetone concentration, the 350 C. The paper being produced shifts toward higher values
turbidity was low, which is an indication of low content of compared to pineapple leaves indicating their increasing ther-
lignin dissolved [19]. On the other hand, the turbidity of the mal stability. Thermal stability increased corresponds to the
% 0 5 10 15 20 25 30 35 40 46 50 55 60 65 70 min
100
PALF 90 3% 5% 80 1% 7% 10% 70
60 2 **3
50
40
30
20
50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 ºC 10 0510 15 20 25 30 35 40 45 50 55 60 65 70 min
Lab: METTLER STARe SW 9.00
Fig. 2 – TG analysis for paper produced from pulping with various acetone concentrations at specified soaking time.
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% 0 5 10 15 20 25 30 35 40 46 50 55 60 65 70 min
100 3 days 7 days 21 days 90 28 days
80
70 2 **3
60
50
40
30
50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 ºC
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 min
Lab: METTLER S TARe SW 9.00
Fig. 3 – TG analysis for paper produced from pulping with 3% acetone concentration at various soaking times.
% 0 5 10 15 20 25 30 35 40 46 50 55 60 65 70 min
100 90 mins 180 mins 90 270 mins 360 mins 80 450 mins
70
60 2 **3 50
40
30
20
50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 ºC
10
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 min Lab: METTLER STA Re SW 9.00
◦
Fig. 4 – TG analysis for paper produced from pulping with 3% acetone concentration at 118 C and various cooking times.
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amount of lignin presence in the paper. The higher the lignin 10000
Acetone (1,3,5,7,9) %
the least stable the paper is thermally. Paper soaked in 10%
9000 Soaking time (3,7,21,28,35) days
acetone contains the highest lignin amounting to 27.7% com- Cooking time (90,180,270,360,450) mins
8000
pared to the pineapple leaves that consist of about 30% lignin.
The paper produced from pulping with 3% acetone concentra- 7000
tion shows the highest thermal stability, with the least amount
6000
of lignin. Major decomposition of cellulose component in the
resultant paper occurred at a temperature of approximately 5000 ◦
370 C [17]. 4000
Thermal stability of the paper sheets pulped with 3% ace- 3000
Tearing force (gf) force Tearing
tone is slightly increased with soaking time as shown in Fig. 3.
Thermal stability increases with the decrement of lignin in 2000
the paper. The amount of lignin has been slightly decreased in 1000
conjunction with the increase in delignification time. Reduc-
0
tion of lignin with delignification time indicates that the time
of soaking is an important factor in determining the quality of
paper, which means a good quality paper with good thermal Fig. 5 – Effect of acetone concentrations, soaking time and
stability and low lignin content is produced at long soaking cooking time on tearing force of the paper.
time. Twenty-eight days of delignification time at room tem-
perature results in full removal of lignin; therefore, the paper
had the highest thermal stability.
and the amount of lignin in the paper was reduced to the
Fig. 4 indicates that the time was reduced initially when
lowest level. However, as the cooking time was further pro-
temperature and pressure increased. When the cooking time
longed, the thermal stability reduced at which after 450 min,
extended to 180 min, the thermal stability was the highest
the paper being produced shows the lowest thermal stability
Fig. 6 – Light microscopic images at 200× magnifications of pineapple leaves acetone/water mixture pulp fibers: (a) 1%
acetone; (b) 3% acetone; (c) 5% acetone; (d) 7% acetone; and (d) 10% acetone concentration, at specified soaking time.
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with high content of lignin. However, the amount of remaining
lignin in the paper sheet did not show any significant changes
above 360 min, which is similar to that at 90 min. Even though
the turbidity of the cooking liquor has been increased with
time, higher amount of lignin was observed in the paper Technical
Elementary fiber
produced after 450 min of cooking. This is due to the fact
fiber
that the dissolved lignin was precipitated back onto the
fibers [19].
3.3. Tearing resistance
Fig. 7 – Micrograph of pineapple leaves fiber bundles.
The result in Fig. 5 indicates that the strength of paper was
reduced at acetone concentration above 3% (v/v). It is there-
fore equivalent to the turbidity test, where less lignin has been 3.4. Morphological analysis
dissolved in the solvent. As a consequence, higher amount
of
lignin remaining in the paper sheet causes the paper to
The fibers structure and coarseness of the pineapple leaves
become brittle and hence constitutes to lower strength prop- fiber using various acetone concentrations in the ace-
erties. tone/water mixture pulping were observed by using the
When the pineapple leaves was soaked in the ace- microscope, as shown in Fig. 6. The results showed that there
tone/water mixtures at 3% acetone concentration (v/v) for were large fiber bundles in the paper sheets, being orientated
a
longer period of time, the paper strength increased as in various orientations. The large fiber bundles were made
shown in Fig. 5. The improvement in paper strength is a of a number of technical fibers that were made of even finer
result of low lignin content at longer soaking time. The elementary fibers of below 10 m diameters [17] as shown in
results in Fig. 5 show that the temperature and pressure Fig. 7. However in Fig. 6(b), larger portion of elementary fibers
have positive effect on paper strength and more lignin was was distributed throughout the paper sheets, hence introduc-
removed from pineapple leaves. Applying pressure during ing to the paper strength. This is because, the fiber extraction
the cooking increases the boiling point of cooking solvent from dried leaves proved difficult with more tissues present
◦
up to higher temperature of 118 C and enhances the lignin on the surface and fine fibers torn from the bundles [17]. Dry-
removal. These conclude that the tearing strength of the paper ing the leaves also made it almost impossible to remove the
is dependent upon the lignin content, where the reduction technical fibers from the bottom face of the leaves. Besides,
of lignin increases the tearing resistance and produced bet- delamination of elementary fibers in the solvent containing
ter paper quality. In order to produce chemical-grade pulps, more than 3% acetone concentration did not adequately occur
high temperature and long cooking time are the main factors due to acetone evaporation or due to dilution of the acetone
[20]. concentration in the spent liquor during washing [19].
Fig. 8 – Light microscopic images at 200× magnification of pineapple leaves acetone/water mixture pulp fibers: (a) 3 days; (b)
7 days; (c) 21 days; and (d) 28 days soaking time, at 3% acetone concentration.
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Fig. 9 – Light microscopic images at 200× magnification of pineapple leaves acetone/water mixture pulp fibers: (a) 90 min;
(b) 180 min; (c) 270 min; (d) 360 min; and (e) 450 min cooking time, at 3% acetone concentration.
When the soaking time was prolonged, more elementary acetone concentration must be soaked for a longer period
fibers have been delaminated from the technical fibers as of time to achieve the optimum delignification. Cooking the
shown in Fig. 8. Fig. 9 also shows the same result when pineapple leaves at high temperature and applied pressure
the pineapple leaves were cooked under pressure for up to for more than 450 min reduced delignification time. Ace-
450 min. However, the delamination of the elementary fibers tone/water mixtures can be used as alternative-pulping media
was improved when temperature and pressure were applied due to low polluted spent liquor as a result of low consump-
during the cooking. From the color of the fibers as observed in tion of acetone during the pulping process. Besides, pineapple
all Figs. 6–8, in addition to the brown color of lignin particles leaves constitute an effective alternative pulping raw mate-
on the fibers, many other parts of the paper appear brownish. rial, where paper sheets with good properties can be produced
This indicates that some lignin, although not in particle form based on pineapple leaves fibers.
or not being observed by the light microscope, exists in the
fiber wall [19]. For instance, the acetone is not nearly as strong
Conflicts of interest
as caustic, which can shorten the fiber lengths and led to poor
surface appearance of the paper sheets as can be seen from
The authors declare no conflicts of interest.
the micrographs in all figures.
r e
f e r e n c e s
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